lt basic handout 20051103

2005/11/3

1

E-mail: [email protected]://www.terasoft.com.tw

E-mail: [email protected]://www.opticalres.com

Gore

[email protected]

Goals

• To learn how to create and modify LightTools objects• To learn how to modify the optical properties of surfaces

associated with LightTools objects• To become familiar with the power of LightTools’ “point and shoot”

ray trace• To learn how to import and modify objects into LightTools from

CAD software• To learn how to model sources and define receivers for

illumination simulations• To understand the output options for simulation analysis and how

to interpret the results• To learn how to control the LightTools environment• To become familiar with graphical and command line entry of

LightTools commands

2005/11/3

2

What we plan to cover

How to get around and understand interface and key program concepts

How to create and modify objects

How to trace rays

How to define sources and receivers and run simple illumination analysis and view charts

How to run supplied utilities

How to make it more realistic

Content

Section 1: Illumination Fundamentals

Section 2: LightTools Introduction

Section 3: Object Geometry

Section 4: Creating Complex Objects

Section 5: Optical Properties

Section 6: Modeling Sources

Section 7: Receivers and Charts

Section 8: LightTools Utilities Library

2005/11/3

3



Section 1 Illumination Fundamentals

Primary Illumination Quantities

Basic quantities

Flux

Radiometric

Power

Photometric

Power weighted by the

human eye response

Illuminance

Intensity

Luminance

Illuminance

Area

Luminance

Area

Intensity

Solid Angle

Flux

2005/11/3

4

Radiometric/Photometric Reference

Luminance

Illuminance

Intensity

Photometry Relationships

If Distance, R, is largeI = Illuminance * R2

If L is constantIntensity = L * Projected Area

If Illuminance is constantFlux = Illuminance * Area

=A

daeIlluminancFlux

If L is constantFlux = L * Etendue

If PSA is constant over the areaEtendue = Area * PSA

If Intensity is constantFlux = Intensity * Solid Angle

)sin(IntensityFlux Ω

= φθθ dd

If Luminance is constantIlluminance = L * Projected

Solid Angle

Ω

= φθθθ ddL )sin()cos(eIlluminanc

y

x

zφ

θ

=A

daL )cos(Intensity θ

Ω

=A

ddadL φθθθ )sin()cos(FluxFlux

2005/11/3

5

!

Scattering

• No surface is perfect! Scattered light plays a crucial role in many designs.

• In general, a surface spreads the specular beam and has a diffuse component. Scatter increases Etendue

Types of Scattering Surfaces

In Out

SPECULARSnell’s Law(Ex: Mirror)

DIFFUSELambertian

(Ex: White Paper)

MIXTUREReal Life

(Ex: Glossy Paper)

Perfectly Specular or Lambertian Surfaces are only approximations of reality!

InIn OutOut



Section 2LightTools Introduction

2005/11/3

6

""

LightTools® is Modular

• Core Module

– Basis for all other modules (includes macro language support)

• Illumination Module

• Four Data Transfer Modules

– Standards: IGES, SAT, STEP

– Program-specific: CATIA

• Imaging Path Module

– Generally for use with CODE V®

– Not discussed in these training materials

"

LightTools® Applications

Design and analysis of illumination systems Light pipes, flat panel displays, automotive lighting, projection

systems, and much more

Stray light investigations Veiling glare, scattered light (BSDF), etc.

Complex opto-mechanical layout

Including native or CAD-imported optical and mechanical components

Conceptual design and proposals Excellent visualization graphics

Optical design In conjunction with CODE V and the Imaging Path module

2005/11/3

7

"

What Differentiates LightTools?

• LightTools is different from other optical/illumination software programs in several ways:– CAD-like, easy-to-use graphical user interface that is element-based

rather than surface-based– Inherent non-sequential ray trace with a uniquely powerful “Point and

Shoot” ray trace feature– Ability to create native components or to import them from CAD software– Ability to easily modify native and (most) imported components (including

Boolean operations) – Ability to model polarization, scattering, Fresnel loss, user coatings and

many other surface properties– Ability to define point, surface, volume and “ray data” sources– Ability to define multiple receivers on any surface in the model– Monte Carlo-based ray trace for irradiance, intensity, luminance, and color

calculations– COM interface allows other applications (Visual Basic, Excel/VBA, etc.) to

communicate with LightTools, allowing for powerful macros to be written in a programming environment

"

Basic Concepts for LightTools

• Element-based, not surface-based– Differs from conventional optical design approach– 3D solid objects closely simulate physical objects– All surfaces of all objects can be optically active with various

properties• Geometrical ray tracing

– Geometrical ray tracing is the basis of nearly all optical analysis software

– Non-sequential (NS) ray tracing does not require a pre-defined sequence of surfaces or elements

– NS ray tracing determines its path dynamically, closely simulating the real behavior of light

– LightTools ray tracing supports scattering, ray splitting, and other special capabilities

– LightTools does not consider diffraction effects

2005/11/3

8

"#

Views in LightTools

• LightTools is primarily a graphically oriented program, presenting the system data in the form of “views” which display in multiple windows

• 3D Design view is the main design view, supplemented by tabbed window-like dialogs for access to object properties and other data

• LightTools also provides Explorer-like navigation views (System Navigator, Window Navigator)

• Additional views for specialized use– Spreadsheet-like “Table views” provide complete LightTools model

and analysis information

– 2D Design view

– Imaging Path view (with optional Imaging Path Module)

"

Surface Properties

• Even if you start with an accurate solid model, optical analysisrequires more than object shapes and materials

• Surface properties are also important– Surface profiles can be planes, spheres, toroids, aspheres, splines,

and many other forms

– Surfaces can be smooth (“specular”), refracting or reflecting, scattering, absorbing, coated, textured, diffractive (e.g., gratings), and more

– Color coding (in shaded views) identifies the type of surface (e.g., blue for refracting, silver for reflect)

• Each surface has a basic property (“bare surface”) and can have one or many overlying “property zones” which allow properties to vary over a single surface

2005/11/3

9

"

View Preferences (3D)

• Choose File > New Model > 3D Design

• Choose View > View Preferences• Defaults OK except on Grid tab

– Check “Snap to Grid”– Enter 0.1 (mm) for both

X and Y values– Click Apply

• On Colors tab, choose a color scheme if desired

• Right click on 3D_untitled (under View Preferences) and choose Save View Environment

"

Preferences $ General, Defaults

• Choose Edit > Preferences• Assumptions for today

– General Preferences, System tab• Units: millimeters• Radius mode: Radius

– Defaults – Select photometric units on the following tabs

• Spectral Region• Receiver• Source

• Click Apply• Right click on General Preferences

header and choose Save General and Defaults

2005/11/3

10

"!

Start New 3D Model

• Launch LightTools from Windows Start menu– Starts with Console view, an always-present text window where

messages appear

– Open and close files and start new models here

– Navigation windows start out blank

• Choose File > New Model > 3D Design

%

Quick Tour of Interface Elements

2005/11/3

11

"

Quick Tour of the 3D View

The Right Mouse Button

• Left mouse button is for selection, menu picks, etc. as in most Windows software

• The right mouse button is also useful– Right click for pop-up “context” menus

– Right DRAG to rotate the 3D view

– Right DRAG with the Control key to zoom the 3D view in (move mouse cursor UP) and out (move mouse cursor DOWN)

– Right DRAG with Shift key to pan the 3D view

• This allows you to do most work with a single pane of the 3D View

• This is the only use of mouse “dragging”– Left mouse operations are always distinct clicks

– Button diagrams show you the clicks for each command

2005/11/3

12

Way to Zoom

In addition to the right mouse button view controls (rotate, zoom,

pan), there are zoom controls on the tool bar

The Zoom tool is especially useful for zooming in on a

particular feature you need to see or select (command name: Zoom)

Select the tool, then click at the opposite corners of the region you

wish to zoom

To see everything again, use Fit



Section 3 Object Geometry

2005/11/3

13

#

Command Panel

• Contains the “tools” of LightTools

• Has three tiers (palettes) of command buttons, or icons– Top palette: major category selection

• Element Entry, Ray Tracing, Modifying, etc.

– Second palette: subcategory selection• Entry of lenses, reflectors, prisms, etc.

– Third palette: actual commands• Buttons are larger than in the first two

palettes• Numbers on glyph indicate order of

point entry• Command line prompts describe next

entry

Top palette:category selection

Second palette: subcategory

Third palette:Actual commands

Entering Objects

• LightTools is solid-based

– The smallest functional unit of entry for physical entities is a complete

solid element, including its edges

– Real objects have surfaces; surfaces do not exist by themselves (with

one minor exception)

• Native LightTools geometry is created from “primitives”

– Primitive shapes include sphere, block, toroid, extruded prism,

revolved prism

– Primitives are combined to form complex objects

2005/11/3

14

Optical vs. Mechanical

• The same primitives appear as both “Elements” and “3D Objects”; difference is default settings

Add mechanical element

Add optical element

Mechanical Aluminum3D Objects

TIR, Reflect, AbsorbBK7 glassElements

Surface PropertiesMaterialCategory

Basic Primitive Shapes

• Cube– Specified along diagonal or

half-width and length

• Sphere– Specify radius or diameter

• Cylinder Toroid Ellipse

• General– Extruded Revolved

2005/11/3

15

!

Follow the Numbers and Prompts

Click forPoint 1

Click forPoint 2

Click forPoint 3

%

What Just Happened?

• Entering a block is a simple operation—3 mouse clicks—but it

opens the door to other aspects of LightTools

• Before looking at other object geometry, we’ll first consider

– Use of the command line

– Console and Error Windows

– Coordinate systems

– Point entry

2005/11/3

16

"

Command Line

• When you click on a command button, LightTools echoes this to the command line (e.g. “Block3Pt”)– You can also type the command at the command line

• Many commands require the entry of a point in space– The point can be entered via a mouse click in an appropriate pane or

by typing a command– If the point is entered by a mouse click, the equivalent command

appears in the Command Window (and in the Console Window at command completion)

• Commands can be “nested”– During the entry of a command, the command may be interrupted to

perform another command. – The first command is “put on hold” until the second command is

completed. – Up to 8 levels of nesting are possible.

Console Window (1)

The Console Window is the top level window in LightTools and is always open (you cannot dismiss it but you can iconify it)

It keeps a scrolled log of all messages (including error messages) and commands, no matter how they were generated

LightToolsmessages

Usercommands

2005/11/3

17

Console Window (2)

The Console Window must be the active window to Start a new model

Exit LightTools

The log can help you in several ways. The log Identifies selected objects

Tells you why rays failed to trace

Gives details about the status of data exchange operations, including Repair

The scrolled log is retained for the entire LightTools session

Error Window

• Error messages also appear in the error window with a time stamp

• Error window always remains in front

• Can resize, dock/undock, and close error window

– WARNING: if you close the error window, it won’t open automatically if an error occurs

Docking bar

CloseWindow

2005/11/3

18

#

Coordinate Systems

• LightTools has a global coordinate system and a user coordinate system (UCS)– By default they are coincident– Both coordinate systems are right-handed

• Rotations described by the optical Euler angles: – Order is important! For multiple angles, Alpha rotation 1st, then Beta

about the newly defined axes, then Gamma about the axes resulting from the Alpha and Beta rotations

+x

+y

+z

+z'+y'

a +x

+y

+z

+z'

+x'

b

+y

+z

+y'+x' g

+x

Alpha > 0 Beta > 0 Gamma > 0

Alpha: positive for “+Z to +Y” Beta: positive for “+X to +Z” Gamma: positive for “+X to +Y”

Example: Coordinate Rotation

a = 45 b = g = 0

a = 45 b = 30g = 0

a = 45 b = 30g = 10

X-Y plane Y-Z plane

2005/11/3

19

Surface Coordinate System

Each surface has a local coordinate system identified with it

The z-axis of each surface coordinate system points outward from the solid

Place UCS on surface to see coordinate system orientation

Global coordinateSystem(black axes)

Local coordinatesystem(colored axes)

Place UCS on surface

Return UCS to global

User Coordinate System - UCS

The UCS can be shifted and rotated with respect to the global coordinate

system with UCS Preferences View > View UCS > UCS Preferences or

UCS tab of the 3D view preferences

2005/11/3

20

!

Defining New UCS

• The UCS axes can also be aligned with the coordinate system of a surface or ray using the command palette

• Sketched objects are entered aligned with or oriented relative to the UCS Z-axis.– Useful for entering tilted

subsystems

Move origin Rotate aboutorigin

Place on surface

Use mouse clicks todefine origin and 2coordinate axes

Place on line

%

Aligning View Along UCS Planes

The currently active 3D view can be quickly aligned along the UCS X, Y, or Z axes

Front view(UCS X-Y plane)

Top view(UCS X-Z plane)

Right side view(UCS Y-Z plane)

2005/11/3

21

"

Point Entry

LightTools keeps track of the location of the current point (location

of the last point entered)

A new point can be entered in absolute terms or as a delta from

the current point

Points can be entered in global, UCS, or pane coordinates

Entering Points on the Command Line

• The basic command for entering a point globally isXYZ x,y,z

– The x, y, z coordinates are separated by commas (no white space)– White space is used before and after the coordinates

• Points can also be given in UCS (local) coordinatesLXYZ x,y,z

• Points can also given in pane coordinatesUVW u,v,w

– U is horizontal in the pane, V is vertical in the pane, W is perpendicular to the pane

• All forms are converted internally to XYZ form

2005/11/3

22

Entering Points Relative to Current Point

• A point can also be expressed as a change (delta) relative to the current point in global, local, or pane coordinates– The delta can be a linear delta or a length and an angle

• Linear delta forms are as follows

– DXYZ dx,dy,dz delta in global coordinates

– LDXYZ dx,dy,dz delta in local coordinates

– DUV du,dv,dw delta in pane coordinates

Entering Points as Angular Deltas

• Points can also be entered as length and angle from current point

• Most useful form:

– LA l,q delta length and angle (in pane)

0o

90o

θ

la 2,0 la 1,45 la 2,0 la 1,90 la 1,0

2005/11/3

23

#

Point Entry Examples

• XYZ 0,0,0 global origin

• UVW 0,0,0 origin in pane (keep depth)

• DXYZ 1,2,3 shift 1 in x, 2 in y, 3 in z (global)

• DUV 1,2,0 shift 1 right, 2 up in pane (keep depth)

• LA 2,45 shift length 2, 45 in pane

• ; repeat last entered point (global)

Point Entry for a Block

#1

#2#3

Block3Pt XYZ 0,0,0 XYZ 0,1,0 XYZ 0,0,4

Xyz 0,0,0 la 1,90 dxyz 0,-1,4

#1 #3#2

Block3Pt

2005/11/3

24

Optical Elements

• Optical elements have BK7 glass as their starting material, and surface properties that are “reasonable” for how they typically interact with light. – E.g.: singlet lens has transmissive front and rear surfaces and an

absorbing edge

2D & 3D textures(discussed later)

Prisms

Singlets Fold mirrors

3D opticalobjects

Dummy surfaces

Optical elementReflectors

Why So Many Singlet Lenses?

• Different buttons allow you to sketch in desired lens geometry more quickly

• Can adjust parameters in object’s property dialog box.

Plane parallel plate

Lens with flats on 1 or both surfaces

Mirror: front surface reflects, rear absorbs

Quick: enter numeric data (radius, thickness,glass)

Library: insert savedobject

2005/11/3

25

!

Flats and Inner Diameters

• Flats are commonly used to provide a mounting surface on concave surfaces

• Width of flat given by: (diameter – inner diameter)/2• “Calculate Inner Diameter” automatically maximizes inner diameter

as surface parameters change

Front surfaceinner diameter

Lens primitivediameter

#%

Surface Shapes for Lenses

LightTools allows the following surface shapes: Sphere (default) Conic Polynomial asphere (20th order) Anamorphic asphere (20th order) Odd polynomial asphere

(30th order) Cylinder (X or Y) Toroid (X or Y, with 20th order aspheric profile) Zernike polynomial XY polynomial Superconic Spline Patch and Spline Sweep

2005/11/3

26

#"

Surface Shape Dialog BoxCalculate Inner Diameter: LightTools automatically adjusts inner diameter as outer diameter is changed.Maximum inner diameter = 2 *(Surface Radius of curvature)

Coefficient name and current value for this surface shape Convex

Concave

#

Reflectors

• Any surface on a lens or 3D object can be converted to a reflective surface by changing desired surface to reflect surface in Optical Properties dialog box

• Common mirror geometries also available from the command palettes– Simple spherical mirror included in lens palette– Flat fold mirrors have own command button

• Common reflectors available with Place Reflector• Types: revolved (rotationally symmetric)

and trough• Reflector geometries: parabolic, elliptical

and hyperbolic• Input (depending on geometry):

– Diameter or depth– Distance to first focus– Distance between foci

2005/11/3

27

#

Workshop 3-1: Parabolic Reflector

• Enter a parabolic trough reflector with the following specifications:

– Distance to first focus = 5 mm

– Reflector diameter = 25 mm

#

Dummy Surfaces

Always rendered in wireframe mode

Two kinds Flat plane

Flat plane defined by the center point and the axis normal direction

Often used as receivers during illumination simulations

Spherical surface Spherical surface defined by the center point and

radius

Useful to add a tag point at arbitrary position on object

2005/11/3

28

##

Extruded and Revolved Solids

• Most of LightTools’ native objects are regular geometric shapes defined with a few mouse clicks

• Two objects allow you to define a complex cross section and theneither extrude it a given length or revolved it about a specified axis

• Available as both “Optical” or “Mechanical” objects

Optical:BK7 glass,TIR surfaces

Mechanical:Aluminum,Absorbing surfaces

#

Extrusiondepth

Dove prism

Face

Extruded Solids

An extruded solid is specified by the vertex locations to define the face and a depth Closing the polygon is not necessary (automatic) Depth is given in a second pane Depth is from current depth (not )

Requires point entry in two views (e.g. Right side and Isometric)

Useful for Boolean operations for unusual shapes, holes, etc. Can be tapered

taper = (dimension EndSurface2)/(dimension EndSurface1)

2005/11/3

29

#

Steps to Enter Extruded Prism

1st click

2nd click

3rd click

nth click

(n+1)st click--selects a different pane

Define faceshape ofprism

(n+1)nd click for prism depth Enter “;” on command line to finish

#

Entry of a Revolved Prism

A revolved prism is input as a profile of points defining a cross-section of the revolution, axis of revolution, and amount of revolution in degrees Closing the profile is not

necessary

Entered in one pane unlike linear extrusion

Angle of revolution

Axis of revolutionCross-SectionProfile

2005/11/3

30

#!

Steps to Enter a Revolved Prism

Step 1:Click to define prism vertices

Step 2:Double click to close prism face(or click and type “;” )

Step 3:Click to define originand direction of rotation axis

Step 4:Click to define rotation angle, or enter sweep angle in degreeson the command line

%

Editing Extruded/Revolved Prisms

• Properties dialog box lists vertices relative to the object coordinate system (not the global coordinate system) – Can edit vertices to alter face shape– Can’t insert additional vertices

• Other modifications– Extruded prisms: change length and taper– Revolved prisms: change sweep angle

2005/11/3

31

"

Workshop 3-2: Extruded Reflector

• The figures illustrate a trough reflector. The segment vertices lie on a parabola. It can be made by using the extruded prism command.

• In the right side view, the coordinates of the segment vertices are:

X Y Z

Workshop 3-2: Extruded Reflector (2)

• Use point entry or grid snap when entering the vertex points

• Extruded prisms have their profile entered in one pane, and depth in another

• You can copy and paste to the command line. Text from the console window or from a text editor can be pasted into the command line.

• Set the optical properties of the segmented surface to “Simple Mirror.”

• Trace a parallel fan of rays to the mirror. Does the mirror act like a parabola?

• Save the model after it is entered.

2005/11/3

32

Prisms

• The Optical Elements > Place Prism palette contains regular prisms in addition to the extruded and revolved prisms– Polygonal rod defined by center-to-vertex or center-to-

face distance

– Common imaging prisms

2D Objects

• Three 2-dimensional entities can be drawn in LightTools– Polyline

– Box

– Text

• Can be used to annotate drawings

• Polyline useful to create reference line for “Snap to line”operations.

2005/11/3

33

#

Library Elements

Simple or complex objects can be saved as library elements for use in other LightTools models

Useful for combining multiple LightTools models

To save a library element Select the object(s) Choose File > Save Library... Enter origin point and file name; saved as .ent file

To enter a saved library element Either

Choose File > Restore Library or Click the Library command button

Follow the Command Window prompts for scale, position, and orientation

Workshop 3-3: Mirror System

• Create the following beam deflecting mirror system:

• Trace a single ray using the icon on the toolbar– X,Y,Z=0,0,0– Alpha, Beta, Gamma=0,0,0

• Create M1 (Mirror 1)– X,Y,Z=0,0,20– Alpha,Beta,Gamma=-20,0,0– FrontSurface Shape=“Conic”– Diameter=15– Thickness=2– Conic Constant=-1– Front radius = 50 Concave– Rear radius = 50 Convex

M1

M2

M3

Image plane

Entrance slit

2005/11/3

34

Workshop 3-3: Mirror System (2)

Create M2 (Mirror 2) Flat surfaces, Height,

Width=15,15 X,Y,Z=0,13,4

Rotate M2 25 degrees relative to the incoming beam Set the UCS on the ray Rotate the UCS Alpha by 25

degrees with View > View UCS > UCS Preferences (subtract 25 from the existing value. This will give clockwise rotation)

Select M2 (tag point on the front surface), and align it along the UCS Z-axis (Edit> Align > Along UCS Z Axis)

25 deg

M1

M1

M2

M2


Create M3 (Mirror 3) Make a copy of M1

XYZ=0,-8,4

Rotate M3 20 degrees to the incoming beam (clockwise) as before using Edit > Align > Along UCS Z axis

Add a dummy plane perpendicular to the beam to see the image plane

XYZ=0,13,25.4 (approximate position)

M1

Dummy plane

M3

M2

2005/11/3

35

!


Create a diverging NSRay Fan X,Y,Z=0,0,0

Alpha, Beta, Gamma=0,0,0

Subtended angle=10 degrees

Optional: Move the dummy plane along the center ray and observe the ray print on the surface change. Select the icon at right, then click on the dummy surface



Section 4Creating Complex Objects

2005/11/3

36

"

Complex Objects

• The objects entered from the Elements and 3D Objects palettes are “building blocks” for LightTools

• These basic shapes are referred to as “primitives”

• Complex objects can be created by – Combining these primitives

– Using a Data Exchange Module to import from a CAD package

• The Modifying palette contains many commands used when creating complex objects

Make a Selection

• Before you can create a more complex object, you usually first

must select the primitive(s) you want to start with

• Can be done in:

– System navigator

– Using the Selection commands palette

– Edit menu

– 3D View—clicking when DefaultSelect is the command prompt

– Typing at the command line

2005/11/3

37

Selection in the System Navigator

• Click to select object– Left click to select one object

– Shift-left click to select a range of objects

– Ctrl-left click to select objects not in a continuous range

Selection Command Palette

Select single objectAdd single objectto current selection

Select objects based on their relationship to “fence”drawn by cursor

Remove object from current selection

2005/11/3

38

#

Selection Using the Edit Menu

• Select All selects all objects in the current model

• Invert Selection performs 2 operations

– 1. Any object that wasn’t selected at the time of the

command is now selected

– 2. Any object that was selected at the time of the

command is unselected

– Easy way to select a large number (but not all) of

objects in model

Editing Command Palette

• Now that we’ve made our selection, what can we do?

– Move or Copy the selection

– Adjust the orientation

• Align lets you align selection to a specified line

– Scale by a specified factor

– Array in rectangular or radial pattern

• Makes multiple copies of original and places them in

specified regular pattern

• Resulting copies are individual objects

• Original is not part of the array

2005/11/3

39

Array Example: Pillow Lenses

• Create single “pillow” (lens with rectangular shape)

• Rectangular array

– 5 across, 4 up

– Indicate locations for

“corner” lens and its

2 neighbors

Original lens

“Corner” lens

Specify these locations

Editing with Context Menu

When one or more objects are selected, a right click brings up a

context menu

Edit All Selected allows user to open Properties dialog box at a

specific level and make changes to multiple targets at once

2005/11/3

40

!

Grouping Command Palette

Grouping allows individual objects to be associated with each other If you move the group, all of the components maintain

their relative relationship to each other

Each component maintains all of its own properties (material, optical properties, size, etc.)

Once a group is established, you can Ungroup

Add single object

Remove single object

%

Grouped Objects Example

Coordinates of group are coordinates of the first object selected when the group was created

T1 incandescent lamp Group contains optical parts,

mechanical parts, and a source

Select the group and move entire lamp as a unit

2005/11/3

41

"

Boolean (3D) Editing

Boolean (3D) Editing

Boolean operations are used to combine basic geometries to create complex objects

2005/11/3

42

Components of a Boolean Operation

Any solid object, optical or mechanical, can be used in a Boolean operation

Some operations are simple (e.g., making a hole in a primary mirror)

Others are complex, requiring cascaded Boolean operations Dashboard lightpipes may have dozens of components

Careful positioning and sizing of Boolean components are important for useful results Extruded prisms are useful for making holes and edges

There is no limit to the number or level of Boolean operations that can be performed

Performing the Boolean Operation

• Decide on the end result, the components needed, and the Boolean operations required– There may be many ways to achieve the same result

• Form and position the component objects– Take care with position, size, and depth of components

– For example, hole forming objects should extend completely through the object to avoid jagged edges

• Choose and perform the Boolean command

• If the result does not look right, undo the Boolean operation with Unbool

2005/11/3

43

#

Lightpipe by Boolean Operations

Lightpipe Components

2005/11/3

44

Types of Boolean Operations

Union Used to combine two or more objects into oneobject

Intersect Used to keep only the overlap of selected objects

Subtract Used to remove an object from other objects

Trim Used to slice off part of an object

Unbool Used to undo a Boolean operation

Union

Used to combine two or more individual objects into one physical

object

Union is a mathematical operation

The objects do not have to be physically touching or overlapping

Different than Cement

The final object has the material of the first object selected

Select the objects to join and click on Union

2005/11/3

45

!

Union Example

3 sections joined to form pipe

!%

Intersect

Used to keep only the parts of two or more objects which

physically overlap

Useful for creating truncated objects

Select the objects and click on Intersect

The order of selection may be important

Resulting object has the material of the first object selected

Allows you to truncate an optical part with a mechanical block, leaving

an optical part

2005/11/3

46

!"

Intersect Example: Lightpipe Curve

!

Subtract

Used to physically remove the volume of one object from another

object

Useful for making holes in objects (such as primary mirrors),

creating hollow cylinders, etc.

The order of selection is important!

Select the main object first, the object to be subtracted second, and

click on Subtract

2005/11/3

47

!

Subtract Example: Ring for Lightpipe

Select

Select more

Subtract

!

Trim

Used to slice off part of the selected objects

Trim creates a plane and intersects it with the object, keeping only

the part on one side of the plane

The plane is specified by indicating a location on the plane and the

normal to the plane (perpendicular)

2005/11/3

48

!#

Trim Geometry

Object to be trimmed

Trim plane

Perpendicular (normal)

Click pointsThis side kept

Trimmed object

!

Workshop 4-1: Arrayed Reflector

• Start with the extruded reflector you created in Workshop 3-2 and use “Trim” to create a 20 degree wedge. – Center the extrusion about X=0, and use the point XYZ 0,0,0 as the

reference point for the trim operations.

– Hint: Use LA commands to perform the trim operations.

20o

Trim

2005/11/3

49

!

Workshop 4-1: Arrayed Reflector (2)

Use the Circular array command to array the segmented wedges

into a full 360o reflector.

The original object is not part of the final array.

The arrayed objects are separate entities. Union them together to

form a single reflector.

!

Unbool

The component parts of a Boolean operation are still kept in memory as well as the type of Boolean operation

The parts not displayed are not thrown away

The full descriptions of all component parts are retained

Thus, it is possible to undo a Boolean operation to restore the component parts This can be done over multiple levels of Boolean operations which

have been performed to form complex structures

Select the Boolean object and click on Unbool The component parts are restored to the model

2005/11/3

50

!!

Modifying Boolean Operations

An object that is the result of a Boolean operation can be modified

without re-performing the operation

Any component can have its size, shape, position, or orientation

changed relative to the entity

Holes can be moved, truncations can be resized, etc.

The type of Boolean operation cannot be changed without

performing an Unbool first

"%%

Boolean Edit Example

Diameter of holechanged in Propertiesdialog box withoutunBooling the object

Right click on selected entity to rename

2005/11/3

51

"%"

Boolean Tree

The System Navigator shows the resulting object, and the constituent primitives underneath it

Surfaces that do not appear in the final object are in parentheses and can not be expanded

Final Object

Primitives

Surfaces not in final object

"%

Boolean Operations in Table View

System Navigator shows the components of the Boolean solid

Table View shows the specific Boolean operations performed; all surfaces are listed

View > New > Tables > Components

2005/11/3

52

"%

Workshop 4-2: Integrating Sphere

• Create an integrating sphere– Subtract one sphere of radius 9 mm from another sphere of radius 10

mm to create a hollow shell

– Subtract a 1.0 mm radius cylinder from one of the sides as shownbelow for the exit port.

• Save the model (we’ll use it later).

sphere of radius 9mm

sphere of radius 10mm

subtract

"%

Element Editing

Element Editing palette allows modifications that are

commonly used with lenses

Stretch changes focal length of lens

Bend changes shape of lens, keeps same focal

length

Fold maintains alignment of fold mirror and

surrounding optics

Cement/Break and Immerse/Remove have wider

application as they enable light to go directly from one

material to another, without an air gap

2005/11/3

53

"%#

Cementing and Breaking

Cement is used to cement two surfaces into one, with no

intervening air gap

The second object selected moves and changes radius as necessary

NOTE: Different surface properties on the two cemented surfaces

may cause rays to behave differently depending on the ray direction

Break is used to remove a cemented interface

Click on Break and then click on the desired interface to break

The separation after Break is zero, but the objects are independent

objects

There is an infinitesimal air gap separating objects

Cement and Break operations are confirmed in Console Window

"%

Entry of a Cemented Doublet

All elements created in LightTools are singlets

To enter a cemented doublet, you must enter both component

singlets and then cement them

Select the elements such that the tag points are on the surfaces to

be cemented

The second element moves to cement its tagged surface to the

tagged surface of the first selected element

If necessary, the second tagged surface radius is changed to match

the the radius on the first tagged surface

2005/11/3

54

"%

Cementing Example

Tag points

Select First Lens + More Second Lens

Cemented grouplisted in SystemNavigator

"%

Object Immersion

Immersion allows ray tracing through objects that are completelyor partially contained within objects composed of materials other than air, or objects that are in optical contact with objects composed of materials other than air.

Objects remain individual entities; neither object moves or changes shape

Remove undoes the Immerse command

Examples:X prisms Clad fibersFlow sensorsLight emitting diodesNested volume sources

2005/11/3

55

"%!

Immersion Example

• Immersed Fiber

– Select cladding (immersing region)

– Select more core (immersed object)

– Immerse

• Immersion indicated in

Properties dialog box

on Immersion tab

""%

Data Exchange with CAD Programs

2005/11/3

56

"""

Data Exchange Modules

Many times the complex model you want to use in LightTools has

been created in another CAD package

Data Exchange Modules allow you to import/export a model in the

following formats

SAT

STEP

IGES

CATIA

""

Data Exchange Process

The more you know (and can control) the data exchange process, the better LightTools is a solid modeler; objects are solids

SAT, STEP and CATIA formats are also solid model-based Objects are solids This is good

IGES format is surface-based Objects are a collection of unrelated surfaces You must create a solid from them This can be bad

User should know what items are included in the file: physical elements, rays, reference

surface etc.

what options were used in creating the file

2005/11/3

57

""

Importing a Model

Open 3D design view

File > Import > Plain SAT/LT SAT/IGES/STEP/CATIA

Process model: If surface-based:

Flip surface normals by selecting the surface, then Edit > Imported Geometry > Flip Surface Normal

Combine surfaces into solid with Edit > Imported Geometry > Combine Imported Surfaces

Repair geometry with Edit > Imported Geometry > Repair Selected Geometry

Resulting model Material: fused silica (n=1.44524, V=67.795) Optical Properties: all surfaces set to Transmitted/TIR (100% transmitting)

""

STEP Import Dialog Box

Applicable to trimmedsurfaces only

2005/11/3

58

""#

IGES Example: Simple Lens

IGES is a surface-based modeler

Simple lens comes in as 6 separate surfaces

Surface normals may not be correct

Incorrect surfacenormal orientation

""

Surface Normals: Blue vs. Red

• Correct surface normal orientation is critical for both refractive solid objects and reflective surfaces

• Blue surface patch indicates the surface normal is pointing out of the object (the viewer is looking in the opposite direction of the normal)– Surface normal is pointing outward from the object’s material, toward

the viewer

• Red surface patch indicates the viewer is looking in the same direction as the surface normal pointing out of the object– Surface normal is pointing outward from the object’s material away

from the viewer who is now looking through the material

2005/11/3

59

""

Surface Normals

User must consider which side of surface is of importance Easier to tell which way the surface normal should point for solid

objects User knows material must be inside the object and surface normals should

point outward

For reflectors (surface-like objects) the user must determine correct direction for surface normals

Surface normals can be selected and flipped by selecting: Edit > Imported Geometry > Flip Surface Normal

Flipping surface normals only changes which side the material is on Orientation of physical surface does not change

""

Processing Imported Objects

• First, correctly orient the surface normals

• Second, select all surfaces– Do not select Polylines

• Right click in 3D view and select View Preferences. On Visibility tab, uncheck “Enable Polyline Selection”

• Third, combine the surfaces

• Fourth, repair the model

2005/11/3

60

""!

Repairing Imported Models

• Repair feature used primarily for imported objects

• Helps correct problems resulting from differences in model

precision from other CAD packages

• Converts spline surfaces into simplified analytic surfaces if

possible

– Spheres, cylinders, toroids, planes, and cones

• Main benefit is increased ray trace speed

"%

Repair Feature

Automatic Repair also available from menu

Edit > Imported Geometry > Repair Selected Geometry

Custom Repair allows user to specify which

operations are performed and tolerances for

each

Automatic Repair

Custom Repair

2005/11/3

61

""

Troubleshooting Imported Files

Place file to be imported onto a local drive, not a network drive

Directory or folder name where imported file is located should not

have any blank spaces

Check the import file in a text editor

Delete any blank lines at the beginning and end of the file

Scan the body of the file for unreadable characters or graphical

symbols

"

Troubleshooting Imported Files (2)

Monitor the LightTools console window during translation Resize design view so the console window is visible

Depending on importing file size and complexity and computer speed, importing process may take some time to complete

Cursor arrow will change to an hourglass icon to indicate LightTools is busy working

Pressing [Ctrl]-[Alt]-[Del] will bring up the Windows task manager showing the LightTools process

LightTools...Not Responding does not necessarily mean LightToolshas crashed Sometimes it means LightTools is busy and not communicating with the

Windows task manager

2005/11/3

62

"

Troubleshooting Imported Files (3)

Users need to know how the imported file was created in the

originating CAD package

Console window will display information tables with IGES and

STEP entity type and name

For IGES files, cross check entity type with Appendix of supported

entities

Console window will display tables with entity type and possible

errors

Errors listed in the table do not necessarily mean the imported model

is bad

"

Data Export

Export Selected Entities Only

User can export selected portions of model rather then the entire

model

Convert 3D Textures to Real Geometry

Changes mathematical representation of 3D textures into physical

surfaces

2005/11/3

63



Section 5 Optical Properties

"

All surfaces TIR With correct surface properties

Why Optical Properties Matter

Optical Properties determine how much the energy and direction of a ray changes

Example: H7 Automotive lamp

2005/11/3

64

"

Rendering Color of Surfaces

In Solid and Translucent rendering, the color of a surface indicates

the direction of light propagation

Can change using 3D View Preferences, Surface Color tab

Split (reflect & transmit)

Absorb (optical)

Absorb (mechanical)Reflect

"

Propagation Directions

• Transmitted: light goes through the surface

• Reflected: light remains on the same side of the surface as it started

• Split or Both: light divides at the surface; some is transmitted and some is reflected

• Absorb: light stops at the surface. “Mechanical” or “Optical” behave the same.

Transmit Reflect Split Absorb(optical)

Absorb(mechanical)

2005/11/3

65

"!

Point and Shoot Rays

We!ll use Point and Shoot (a.k.a. non-sequential or NS) rays to see how light interacts with a surface

Each ray starts with a power of 1.0

The power drops via the transmittance and reflectance values specified for each surface

A limiting energy threshold can be specified for each ray, fan, or grid When ray intensity falls below this, the ray trace stops

Default threshold is 0.01 (1%)

Fresnel losses, scattering losses, and bulk absorption are all taken into consideration

"%

Why Did They Stop?

Each of the three rays shown below stops for a different reason

Surface set to absorb

Top Surface: Max Hits = 5

Ray misses all other surfaces

5

1

4

3

2

Surface set to split

2005/11/3

66

""

Ray Termination Conditions

A point and shoot ray continues to trace until one of the following stop conditions is encountered The ray fails to hit any more optical surfaces

The ray hits an absorb or mechanical surface

The intensity of the ray falls below the threshold limit

The maximum number of hits on a surface is exceeded

The ray encounters a TIR condition on a surface specified as REFRACT mode

The ray encounters a refract condition on a surface specified asTIRONLY mode

The ray diffracts into an evanescent diffraction order (sine of the diffracted angle > 1)

"

Ray Properties

• Most properties are defined for the entire fan or grid of rays, and are read-only for the individual segments

Description of ray fan

Ray stops when its power drops below 1%

Automatic: check if the surrounding region has amaterial

2005/11/3

67

"

Accessing Ray Trace Data

Single ray trace data is very useful for troubleshooting Check details for preceding and following interfaces Check path and surface transmittance values

"

What Optical Properties to Use?

• Example: Lightpipe for an automobile radio knob

Front

Back

LightpipeLED source

2005/11/3

68

"#

Choices for Optical Properties

Optical properties for each zone of a surface are set using the following dialog box

"

Smooth Optical Raytrace Modes

Rays hitting a Smooth Optical surface follow Snell!s Law: n sin( ) = n! sin( !)

TIR = Total Internal Reflection: sin( !) = [n sin( )]/n! > 1.0 All light is reflected Light travels from higher index

material to lower index material Smooth Optical allows choice of Raytrace Mode (direction)

Transmitted/TIR: trace rays that either refract or TIR off a surface

Split (Reflect and Transmitted):both rays are traced

Transmitted Rays Only: traces only those rays which meet refract condition, terminates others

Reflected Rays Only: all rays reflect TIR Rays Only: traces only those rays which meet TIR condition,

terminates others

θ

θ

’

’

2005/11/3

69

"

Specifying Power in Given Direction

Propagation Directions and Raytrace Mode determine in which

direction the rays are traced

Power in each direction is specified by either:

Fixed percentages

Variable percentages calculated from:

Fresnel loss

Coating

Polarization

"

Fixed Power Percentages

Can specify percent Reflectance and Transmittance at surface LightTools calculates Absorption so that

R + T + A = 100% You can specify power in a direction where no rays are traced

Specifying energy in a given direction doesn!t mean that rays are traced in that direction

Example: Raytrace Mode = Reflect Reflectance = 80% Absorption = 15% Transmittance = 5%

BUT No rays are tracedin the transmitted direction!

2005/11/3

70

"!

Advanced Properties for Power

Power distribution can be calculated based on

Fresnel loss: depends on the angle of incidence and index of

refraction

Coating: User-defined or supplied coatings can specify R and T as

function of wavelength, angle of incidence or location

Polarizer: Linear polarizer specifies X and Y reflectance and

transmittance; others use standard R, T, and A

"%

Fresnel Loss

The loss of transmitted power as a function of angle of incidence of a ray at a surface is called Fresnel loss The loss is sent into the reflected ray

The calculation is for uncoated surface only If an optical coating is present, LightTools uses the coating

prescription to determine the proper transmission and reflection as a function of incident angle

In general, the steeper the angle of incidence the more energy is reflected from a surface The Fresnel loss is polarization dependent LightTools averages the polarizations, if polarization ray tracing is

disabled LightTools computes losses for both S & T polarization states if

polarization ray tracing is enabled

2005/11/3

71

""

User-Defined Coatings

Edit > User Coatings

"

Wavelengths

The coating is a function of wavelength, but how to define the wavelength for the point and shoot ray?

Use Spectral Region Preferences to enter spectrum Select desired wavelength for ray in Ray Properties dialog box list

Right click in rowto access menu

2005/11/3

72

"

Coating Example: X-Prism

X-Prism spectrally divides white light into 3 channels using 2 color coatings

"

λ #$%

"

Polarization

Polarizing properties in LightTools are Linear polarizer

Ideal retarder Jones Matrix

Mueller Matrix

Polarization only affects ray amplitude and phase, not direction

Some polarization models have reflectance and transmittance options Polarization state of transmitted and reflected rays will be the same,

magnitudes may be different

Polarizer and retarder models are defined with respect to the surface coordinate system (aligned with Y-axis of surface)

2005/11/3

73

"#

Zone_1 vs. BareSurface

The Smooth Optical setting is commonly used with lenses. Front and rear surfaces of lenses automatically have two property

zones defined Zone_1 Bare surface (everything outside of Zone_1)

Each zone can have different optical treatments Default is the same treatment

Zone_1 size, shape, location, and orientation on the surface can be specified Default is to cover the entire physical

surface

Example - if you had a lens with the center zone reflective you could set the bare surface to refract and zone_1 to reflect

"

Bare Surface Properties

Bare Surface covers everything not defined as a separate zone

Every surface has this zone

2005/11/3

74

"

Zone_1 Properties

Can adjust geometry of zone_1

Defined with respect to surface coordinate system

"

Optical Properties Options

• Simple Mirror—Smooth Optical where only the Reflectance is specified

• Absorber–Optical or Mechanical (only rendering color changes)

2005/11/3

75

"!

Scattering

• Ray Propagation Direction can be Transmitted (forward scatter),

Reflected (back scatter) or both

• Energy distribution given byReflectance + Transmittance + Absorption = 100%

• Specify scattering distribution

– Most distributions centered about the specular

(specular: direction of the ray that obeys Snell’s law)

Specular direction

"#%

Simple Scattering

Simple Scattering requires at most one parameter to describe the

scattering distribution

3 Options:

Lambertian

Gaussian

Cos Nth

2005/11/3

76

"#"

Lambertian Scattering

Random scattering surface (white paint)

Each incident ray can scatter in any direction with the same

probability

Scattering occurs about the surface normal and not the incident

angle

Each scattered ray has the same energy

Surface Normal

Specular Direction

"#

Scattering Ray Controls

The options available for Lambertian scattering appear for otherscattering models also Propagation direction:

Transmitted

Reflected

Both

Number of scattered rays E.g.: 1 ray incident,

5 rays scattered

Polarized Scattered rays have same polarization as a specular ray traveling in that

direction would have

Weighted rays

2005/11/3

77

"#

Weighted Rays

• LightTools’ default is non-weighted rays– Magnitude of each scattered ray is same

– Directions (angles) of scattered rays generated by probability distribution

– More rays generated in direction where scattered energy is high

– Efficient ray trace

• Can choose Weighted rays: Yes– Magnitude of each scattered ray determined by the probability

distribution

– Ray directions are chosen uniformly in direction cosine space

– Less efficient ray trace

"#

Workshop 5-1: Integrating Sphere

• Restore the geometry of the Integrating Sphere that you created in Workshop 4-2.

• Set the surface properties of the inner sphere to be a Lambertian reflective scatterer with a reflectance of 0.90.

• Trace a single ray from inside sphere and see what happens.

• Change the number of scattered rays to 10 and decrease the ray threshold to 0.0010 and then 0.00010.

scattered rays = 1threshold = 0.010

scattered rays = 10 scattered rays = 10threshold = 0.0010 threshold = 0.00010

2005/11/3

78

"##

• Each incident ray can scatter with the Gaussian distribution given by

where P( ) = intensity or radiance in the direction

Po = intensity or radiance in the specular direction = standard deviation of the Gaussian

distribution, in degrees

• Useful for near-specular or narrow distribution scatter

Gaussian Scattering

"#

Gaussian Scattering Settings

The Gaussian (sigma) defines the angular spread of the scatter distribution

Additional Controls

Fresnel Loss: reflectance and transmittance based on incident angle and index

Force Energy Conservation

Distribution Intensity: default

Radiance: often used for measured BSDF data

2005/11/3

79

"#

Force Energy Conservation

• Because the scatter distribution is centered on the specular ray

direction, the scattering distribution can “overlap” the surface.

• Force Energy Conservation setting accounts for this

– Yes: Energy of all scattered rays = energy of incident ray; scatter

distribution slightly distorted

– No: Energy is lost at the scattering surface

Distribution “overlaps” surfaceNo

Yes

"#

Advanced Scattering Models

Three advanced scattering models are available

Elliptical Gaussian: allows user to define different spread in

orthogonal directions

User Defined: rotationally symmetric energy distribution is described

by input file consisting of scatter angle vs. intensity or BSDF (bi-

directional scattering distribution function [radiance]) data

Complete: consists of diffuse (Lambertian) and near-specular

components to model scatter that is directional but surrounded by a

haze

2005/11/3

80

"#!

Complete Scattering

Each branch is 100% to its child branches

Available whenray propagatesas “Split” or in“Both” directions

100

Available if polarization raytracing is enabled

100100

100

"%

Probabilistic Ray Splitting

By default, both the reflected and transmitted rays are traced with power determined by transmittance and reflectance values Trace until ray power drops below ray power threshold or max hits

exceeded Can have exponential growth of rays with multiple split surfaces

Probabilistic ray splitting uses a probabilistic approach to determine whether to trace the reflected or transmitted ray at each split. Ex. Reflect/Transmit with reflectance R, transmittance T, and

absorption A. Probability for a split ray to: Transmit = T/(R + T) Reflect = R/(R + T) Power weighted by (R + T)

Complete scattering, Fresnel loss, QWAR, and User Coatings have slightly more complex probabilities

2005/11/3

81

""

Probabilistic Ray SplittingAll surfaces: Fresnel splitMax hits = 100Ray threshold = 1e-10

Reflector and source

Receiver plane

“Sawtooth” grating

Probabilistic Ray Split: NO Probabilistic Ray Split: YES

2,000 rays started277,948 rays at receiverSimulation time: 50 minError estimate: 42%

2,000 [200,000] rays started 1,247 [118,969] rays at receiverSimulation time: 19 seconds [29 min]Error estimate: 44% [6%]

1 NS ray started in each model

"

Surface Settings for Faster Raytracing

• Scattering surfaces and “split” surfaces can generate many rays in

many directions

• For faster simulations, want to reduce time tracing rays that you

don’t care about.

• 2 surface settings:

– Probabilistic ray splitting for split surfaces

• Not desirable for stray light or ghost analysis of system

– Aim areas, aim cones for scattering surfaces

2005/11/3

82

"

Importance Sampling: Aim Area, Aim Cone

Powerful tool to speed up ray tracing and increase accuracy for illumination simulations with scattered surfaces

Allows control over the direction in which rays are reflected and/or transmitted from the scatter surface

Defined by using the following icon sequence below

How does it work?

Scattered rays are generated uniformly within the projected solid angle of the aim entity then weighted by the scattering model associated with the surface.

"

Example: Aim Area

incident ray

scattered rays 1 of 100 rays traced to surface of interest

no aim area

incident ray

define aim area

incident ray

scattered rays

with aim area

all rays traced to surface of interest

2005/11/3

83

"#

Optical Property Zones

"

Optical Property Zones

• Simulate textured surfaces (“paint dots”) by defining multiple

property zones on a surface

• Can specify any LightTools optical property (scatter, grating,

coating, etc.) for each zone

• Zone geometries:

– Rectangle, circle, arcuate, ellipse

– Arrays of the above

– Monochrome bitmap image for non-periodic structures, such as

speedometer applique. “Black” has surface property of zone, “white”

has surface property of bare surface.

2005/11/3

84

"

Entering Property Zones

Place Zones palette under Optical elements

Select surface and LightTools will prompt for center of

zone, zone extent and other input (array spacing in x

and y etc.) as needed.

Can adjust with Properties dialog box for the new

zone

"

Displaying the Property Zones

• Make property zones visible using View Preferences

• Example: array of elliptical reflectors on an absorbing surface

2005/11/3

85

"!

3D Textured Surfaces $ ExampleArray of Pyramid structure

Easier and quicker to create micro-structured films such as BEFs

3D Structure converted to real geometry

"%

3D Textured Surfaces $ Bumps and Holes

Allows large regular arrays of 3D structures be applied to a surface, without slowing the ray trace time (statistical representation of the structure)

Arrays are defined on a zone by zone basis, thus an unlimited number of array patterns can be defined

Useful feature for back light applications Ray tracing speed is much faster than similar structures created

via Boolean operations The structure can be converted into real geometry using the data

exchange feature (STEP, SAT or CATIA)

2005/11/3

86

""

3D Textured Surfaces $ Bumps and Holes

Improved ray tracing performance

Model 10" x 10" x 0.25" block

1,000,000 hemispheres with R=0.01" on bottom 10"x10" surface

Computer 800 MHz PIII Dell laptop

512 MB RAM

Test results Render 1,000,000 lenslets = 21 seconds (visibility OFF by default)

Run 100,000 ray simulation = 2 minutes 1 second

Reduced file size

"

• – – – – –

2005/11/3

87

"

• – !"$#%&('– )*+(,.-

• /0• 1324• 56

"

• ! " # $ % & '

• ( ) * + , - . / 0 1 2 3 4

– 7(8:9;!<>=?@%ABDCCEFGHIJ– KLANMPOQ(ASR7T8@UVSGXWYZ

2005/11/3

88

"#

3D Texture

• 5 6 7 8 9 : ; < = > ? @AA

• 5 6 B C : D E F G H I J– +D[\@BDC^]`_!a Ctrl bdcfegT_@h>b^X] B c

• K L 3D M % N J O– i(j@k!l(+(,mnBoCpX] C c

qA r

qB r

qC r

"

3D Textures

• P Q R S T U V LightTools® W X Y 3D Texture Z [ \ ]

2005/11/3

89

"

• ^ _ 8 9 3D Texture ` W X a P – s@t!V>tu Bare surface nTv!v– w(x!y@TzD– 10x10 \R7T8

• 3D Texture 1 b Bare surface 8 c d e– KLA|@VSG~@T>

• f 9 3D Textures g h– )@@A7!

"

• i j * k– s@tJMX– (MzX> – "M!

2005/11/3

90

"!

• X,Y P l m H n o p– o UCS !

! " # ! " # ! " # ! " #

Rotation Angle

Origin X

Origin Y

Height

Wid

th

Surface OriginZone Origin

" %

$ %$ %$ %$ % &&&&I''''

¡ ¢£¡

2005/11/3

91

" "

$ %$ %$ %$ % &&&&II''''

¢¤¡ ¥f£¡¥f¤¡

"

$ % ( $ % ( $ % ( $ % (

• q r s t u v w x – ¦d§f¨©!ª« @A@¬¨!

®¯°±²³qµ´¶S·¸¹º r

2005/11/3

92

"

) * + $ % ) * + $ % ) * + $ % ) * + $ %

=

=

=

• x_coordinate » 3D Texture ¼ X ½¾$¿ÀÁ• y_coordinate » 3D Texture ¼ Y ½¾$¿ÀÁ• Normalizing radius »@ÂÃÄ$Å¿ ´¶S·$Æ¯q`Çf±²SÈSÉÊ ¿$ËSÌr

"

, - $ % , - $ % , - $ % , - $ %

1

2

3

2005/11/3

93

" #

. / ,. / ,. / ,. / ,

ÍSÎÏ Å ÍSÎÐ ¢ÎBezier´¶S·ÑSÒÓÑSÒÓ´¶S·¹º

1

2

3

"

0 1 / ,0 1 / ,0 1 / ,0 1 / ,

Spacing X

Spacing Y Offset Y

Offset X

2005/11/3

94

"

2 0 1 / ,2 0 1 / ,2 0 1 / ,2 0 1 / ,

X-A

xis

Y-Axis

"

3 4 1 / ,3 4 1 / ,3 4 1 / ,3 4 1 / ,

Spacing X

Spacing Y

Offset X

Offset Y

2005/11/3

95

" !

Bezier Curve / ,/ ,/ ,/ ,

• K L < y z x p b y p | Bezier ~ $

"!%

) * + / ,) * + / ,) * + / ,) * + / ,

• x p b y p f ] z

+

+

+

+=

+

+

+

+=

!

"

#$

X

Y

• i,j » X,Y ½¾$¿ ¯ÔqÖÕ(×ØÙÚ r• Normalizing Index »ÂÃÄÅ¿ ´¶S·$Æ¯q`Çf±²SÈÛSÜÝ¯Ô ¿$ËSÌr

2005/11/3

96

"!"

5 6 7 / ,5 6 7 / ,5 6 7 / ,5 6 7 / ,

Spacing Y

Spacing X

Center Y

Center X

Spacing along circumference

"!

5 6 7 / ,5 6 7 / ,5 6 7 / ,5 6 7 / , &&&&8888''''

Adjust for Uniform Spacing

Adjust for Uniform Spacing

2005/11/3

97

"!

5 6 7 ) * + / ,5 6 7 ) * + / ,5 6 7 ) * + / ,5 6 7 ) * + / ,

• b k m Q f ] X

iÈÕ(×ØÞßÙÚ ¿Sà ¯

% ⋅+⋅+⋅+=

"!

, - / ,, - / ,, - / ,, - / ,

• 8 9 C @x yA – á!â>ã Excel äå>æ:ç!èTéXêëoì@í@îïñðòóôõDö÷oøùúXûü>ý åSþ@ÿ

2005/11/3

98

"!#

, - 9 : ; < = > ? +, - 9 : ; < = > ? +, - 9 : ; < = > ? +, - 9 : ; < = > ? +

<value>………<value><value><y><x>

<value>………<value><value><y><x>

<paramN_label>………<param2_label><param1_label>yx

# optional Any comment



Section 6Modeling Sources

2005/11/3

99

"!

LightTools Sources

• Sources in LightTools are geometric shapes that can emit rays

from their surfaces or volume

• Similar to emitting “photons” from a real source

• Emitted rays are unpolarized

• Rays are generated randomly within the source geometry

• Can have any number of sources

"!

Source Types

Four kinds of sources

Point source

Surface emitting source

Sphere, block, cylinder, toroid

Volume emitting source

Sphere, block, cylinder, toroid

Ray Data source

Source data imported from Radiant

Imaging, or from a previous

illumination simulation Surface sources

Volumesources

2005/11/3

100

"!!

Different Types of Sources Point

Emits light from a point, angular distribution can be specified

Volume Volume sources emit from all points inside the enclosed volume of a

3D object The volume spatial distribution and the angular distribution can be

specified Uniform or user-defined

Surface Surface sources emit only from surfaces of a 3D object The user can control the emitting direction and state for each surface

(inward, outward, or both; on or off) The surface spatial distribution and the angular distribution can be

specified separately for each surface Uniform, Lambertian, user-defined

Ray data Usually measured (e.g.: Radiant Imaging) Contains XYZ, LMN, and Power for a large number of rays

%%

Source Characteristics

Sources are air-filled and do not by default shadow other sources Optical properties can be specified for surfaces Spectral properties can be specified for each source (source

spectrum) Surface, Spatial, and Angular emittance control

Can be combined for complex models

Sources can be built up by combining multiple shapes Sphere, Block, Cylinder, Toroid

Spiral (fluorescent) Tungsten (circular, bent)

2005/11/3

101

%"

Source Emittance Control

• In many cases sources do not emit to the full sphere (4p steradians)

• In many models it is necessary to limit the source emittance in one or more of the following ways:– Based on surface (only for surface sources)– Based on angular extents– Based on spatial position on the source surface or volume

• LightTools offers many different ways to control the source emission– Emission direction (inward/outward – for surface sources)– Aim Sphere control (angle of emission)– Spatial apodization (power vs position)– Angular apodization (power vs angle)– Volume apodization (power vs position)

%

Surface Emittance Control

Surfaces can emit either inward or outward

Figure illustrates a cylindrical source with different surface emittance All surfaces outward (1) End caps outward (2) Left end cap inward (3)

(1)

(2)

(3)

2005/11/3

102

%

Angular Emittance Control

• In addition to the surface emittance, the

angular emittance can also be controlled

for sources (point, surface, or volume

source) using the “Aim Sphere”

• Limiting angles are specified on an aim

sphere, which is normally oriented relative

to the z-axis of the source entity

– Can be rotated relative to the entity

• Rays are traced in an annular cone limited

by an upper angle and a lower angle A cylinder source emitting into (a) full sphere; (b) limited aim sphere

(a)

(b)

%

Aim Sphere Controls

• Lower Angle– Measured from

+Z axis to –Z axis of aim sphere

• Upper angle– Measured from

+Z axis to –Z axis of aim sphere, mainly to clip the region defined by Lower Angle

Z

Lowerangle

Upperangle

Rays emitted intothis annular zoneAim Sphere

Source

Rays not emitted inthis region

Rays not emitted inthis region

2005/11/3

103

%#

Aim Sphere Limits (1)

To cover the whole sphere:upper = 0

, lower = 180

,

alpha = any number, beta = any number

To cover the “upper” hemisphere:upper = 0

, lower = 90

,

alpha = 90, beta = 0

To cover the “lower” hemisphere: upper = 0

, lower = 90

,

alpha = -90, beta = 0

To cover the “forward” 20:

upper = 0, lower = 10

,

alpha = 0, beta = 0

%

Aim Sphere Limits (2)

Lower angle of 90 degrees, Upper angle of 20 degrees

Lower angle of 45 degrees, Upper angle of 20 degrees

2005/11/3

104

%

Apodization

%

Apodization Controls

Sources can have the surface or volume spatial distributions specified and the angular distribution specified (defaults are in italics)

Distribution type

Point source

Surface source

Volume source

Surface

—

uniform user-defined

—

Volume

—

—

uniform

user-defined

Angular uniform

user-defined

uniform Lambertian

user-defined

uniform user-defined

Spatial

2005/11/3

105

%!

Source Apodization

Used to customize spatial and angular variations of source emittance

Spatial apodization Can be applied to surface emitters on a surface-by-surface basis

Volume sources can have volume apodization specified cylindrically or in a rectangular grid

Angular apodization Can be applied to point sources

Can be applied to surface emitters on a surface-by-surface basis

Can be applied to volume emitters but is constant over entire volume

Usually the far-field distribution

"%

Source Apodization

Any source can be apodized to get the desired angular/spatial distribution Variation of source power is specified (position/angle)

Spatially apodized collimated source (Lower Angle=Upper Angle=0) tracing to a flat surface

Angular apodization applied to a spherical source to model NICHIA NSCG100A

2005/11/3

106

""

Apodization File Format

Data is applied to the source using a data file or by directly entering in the grid File name takes the form of

name. txt or name. apd Format is an ASCII text file Header line must contain the

word MESH: n m, SPHEREMESH: n m orPOLARMESH: n m, where n and m are the size of the text file

U and V directions correspond to X, Y for spatial apodization and Longitude, Latitude for angular apodization

MESH: n m

a11 a12 a13 ... a1n

a21 a22 a23 ... a2n

...

am1 am2 am3 ... amn

&'($)*

&'

('

"

Mapping Surface Apodization Data

Data are fit within the bounds as shown below

The default is for apodization bounds to fit entire surface for spatial apodizer or entire sphere for a direction apodizer

If bounds are larger than surface or full sphere extra data will be ignored

If bounds are smaller than surface or full sphere regions outside are filled with zeros

2005/11/3

107

"

Applying Apodization Data

Spatial and angular apodization

can be applied through dialog

boxes

Tree view provides an easy way

to select the desired surface, etc.

"

Surface Apodization Example

Source apodized using an interference fringe pattern Note that the data in V-direction starts at maximum latitude (Vmax-to-

Vmin) Top left corner is the Umin,Vmax

Cylinder source (collimated) with rear surface emitting on to a dummy plane

Irradiance pattern on the dummy plane

Data file used to apodize the source (41 X 41).

Vmin

Vmax

Vmin

Vmax

0 0 0 1.08620 0 0 1.23740 0 0 1.23660 0 0 1.23610 0 0 1.2261

1.2231 1.24068 1.217 1.89162.4972 2.48838 2.5169 2.47942.4789 2.51608 2.4792 2.4813

2005/11/3

108

"#

Angular Apodization Mapping

Same file format as for the surface apodization Different coordinate system [Longitude (U), Latitude (V)]

Z

X

Y

[Longitude 0, Latitude 90]

[Latitude 0]



[Latitude 180]

[Longitude 270, Latitude 90] Z

Y

X

U

V

UV coordinate (0,0)

Long. = 0

Long. = 90

"

Angular Apodization Example

• LED example: HP HSMx-C650 Surface Mount LED

2005/11/3

109

"

Angular Apodization File

spheremesh: 1 1100.220.450.60.750.860.920.950.970.991

Max ValueMin Latitude(“North Pole”)

Min Value, Max Latitude (“South Pole”)100 degrees latitude Note that the

LED intensity distribution is rotationally symmetric. Therefore, only one column of data is requiredto specify the variation in Latitude

"

Volume Apodization

Used to specify the volume distribution for volume sources

Ideal for modeling complex (arbitrary) power distributions

Arc sources

Two volume apodization options

Cylinder

Rotationally symmetric

Grid (User Defined)

Any arbitrary distribution

2005/11/3

110

"!

Volume Cylinder Source (1)

A volume cylinder source is apodized using the data shown below Aim sphere can be limited (collimated) in +Z direction and +Y direction

(or any other) to view the irradiance

#sample volume cylinder apodization filecylindermesh: 4 5rmin: 1.0rmax: 4.0lmin: 0.0lmax: 5.00 0 0.8 1.00 0 0.8 1.00.1 0.25 0.8 1.00.1 0.25 0.8 1.00.1 0.25 0.8 1.0

Radial

Leng

th

%

Volume Cylinder Source (2)

Irradiance along +Z-axis direction

Aim Sphere Lower

Angle=Upper Angle=0

Alpha=0

• Irradiance along +Y-axis direction

• Aim Sphere– Lower

Angle=Upper Angle=0

– Alpha=90 "((++$$

2005/11/3

111

"

Volume Grid Apodization

Used to model volume power distribution Any arbitrary distribution can be specified X and Y data is organized as a 2D matrix to define

slices in XY plane Number of XY matrices is equal to the number of

slices in Z direction

#sample volume grid apodization file3Dregulargridmesh: 3 4 3xmin: -1.5xmax: 1.5ymin: -2.0ymax: 2.0zmin: 0zmax: 5# xy matrix for first z layer1 0 72 1 64 5 11 1 6# xy matrix for second z layer4 5 11 2 32 2 21 2 3# xy matrix for third z layer1 8 94 5 11 2 31 2 3

Modeling D2 Arc Lamp

Volume grid apodization used to model D2 (automotive lamp) arc

Arc is a volume emitter

Can use CCD images taken from different view points

Abel Inversion

Abel Transform provides a way to create 3D data from 2D pictures

Real sources are often NOT rotationally symmetric

2005/11/3

112

D2 Arc Lamp (1)

Use two (or more) images to model the arc using volume apodization technique

Abel Inversion is typically used to compute the flux density from the projected image

Volume apodization data can be modified to model arc changes

Philips D2 lamp

Top

Side

Conversion routine provided by ORA

D2 Arc Lamp (2)

• Image resolution used for apodization ~ 100 pixels

• No de-magnification applied– Needs to account

for bulb wall refraction

• Line charts show a slice through the image (arbitrary scale)

• Absorption/scattering can be modeled using dummy geometry and a ray data source (discussed in the next section)

,-.

/

).

/

2005/11/3

113

#

Workshop 6-1: LED Modeling

Given the following LED specifications, setup the LED in LightTools

Workshop 6-1 : Spectral Characteristics

2005/11/3

114

Workshop 6-1: Angular Radiation Distribution

0.510

0.525

0.5410

0.5615

0.620

0.725

0.8530

135

0.9540

0.845

0.5550

0.3555

0.1260

0.07565

0.02570

0.0175

0.0580

085

090

Relative Intensity

Angular Displacement

(degrees)

Workshop 6-1: Total Flux

2005/11/3

115

!

Workshop 6-1

Use the Source Flux Scaler Utility to scale the power of the LED given a Peak Intensity of 11.9 Candela (you should get approximately a 25 Lumen LED)



Section 7Receivers and Charts

2005/11/3

116

"

Receivers and Charts - Overview

LightTools has several ways to record ray data information during a simulation using receivers

Charts are graphical illustrations of receiver data

Receivers are similar to light detectors Light detectors respond to photons LightTools receivers respond to rays

Receivers are like CCDs (Charged Coupled Device, a type of photo sensor array) used as light detectors CCD can count (or record) each photon that falls within its cells

known as pixels Receivers can record ray information (such as X,Y,Z, L,M,N, etc.)

within its boundaries

Receivers can be operated in radiometric (default) or photometric mode

Receivers and Charts - Overview

Receivers are usually divided into rectangular meshes to collect ray data A mesh is a rectangular grid of

cells (or bins) Each bin can record data Number of bins can be changed

Gives desired resolution

More bins gives higher spatial/angular resolution

Data can be displayed as color maps Color is proportional to the

magnitude of the data being displayed

2005/11/3

117

Receivers: Surface and Far Field

There are two types of receivers Surface Far field

Surface receivers Rectangular and planar in shape Attached to a surface (planar or

non-planar) Receiver is projected onto non-planar surfaces

Can have luminance meters Spatial or angular

Far field receivers Spherical in shape Located at infinity Only one receiver at a time Can operate in finite mode too (finite far field)

Any number of receivers allowed in this mode

Receiver Coordinate System (1)

Surface receivers use the local coordinate system of the surface

The system shown to the right has A collimated disc source

A disc with an absorbing rectangular region (a zone ) on its front surface

A Surface receiver on the rear surface of the disc

Local coordinate system of the rear surface of disc is shown

X, Y in the illuminance chart are oriented with respect to X, Y of the local coordinate system

2005/11/3

118

#


• Far field receivers use the “global” coordinate system

• The system shown below has– Three point sources in X, Y, Z directions with aim cones 20, 30, 40

degrees (same power)– Coordinates shown in (a) are “Longitudes” with respect to the global

coordinates– Longitude limits [0 at –Y, 180 at +Y, 270 at +X]– Latitude limits [0 at +Z, 90 at +Y, 180 at –Z)

(a) (b)

X

Y

Z

Y


Far field receiver coordinates are identical to the angular apodization coordinate system

Z

X

Y


[Latitude 0]



[Latitude 180]


2005/11/3

119

Receiver Meshes

Each receiver type can have several types of meshes A mesh is a rectangular grid of bins that collect data

Different meshes for different types of data

Surface receiver Illuminance mesh (Irradiance, Illuminance) Intensity mesh (Intensity)

Spatial luminance mesh (Luminance)

Angular luminance mesh (Luminance) CIE meshes (Chromaticity and CCT)

Far field receiver Intensity mesh (Intensity)

CIE meshes (Chromaticity and CCT)

Receiver Mesh Limits (1)

Mesh boundaries Usually calculated automatically

Can be user defined (important in some cases to get enough bins)

Angular limits can be defined for all meshes for a given receiver

Illuminance mesh has linear bounds, intensity mesh has angular bounds

Batwing LED with optics Very narrow distribution

LED is emitting in +Y direction

2005/11/3

120

!

Receiver Mesh Limits (2)

Higher spatial/angular resolution can be obtained by setting proper mesh boundaries

Mesh bounds in (a) Latitude Min=0 Latitude Max=180 Longitude Min=0 Longitude Max=360 41 X 41 bins

Mesh bounds in (b) Latitude Min=60 Latitude Max=120 Longitude Min=150 Longitude Max=210 41 X 41 bins

(a)

(b)

Intensity Charts – 3D Raster and Lumviewer

%

Receiver Mesh Data

Mesh data can be viewed using the receiver properties dialog box

Charts are graphical display of same data

Data can be directly copied to EXCEL (or other program)

2005/11/3

121

"

Working With Mesh Data

Any data mesh on a given receiver can be exported to an ASCII

file

The desired data must be open in a Chart View

In the desired Chart View, use File>Export

Exported file can directly be used as an

apodization file (spatial or angular)

Mesh data is usually saved with the

*.lts file

All charts are available when reopening

the file

Mesh Export

Exported data format

CHART: Intensity Chart Legend

Longitude Latitude luminous intensity

## XDim YDim minXbound minYbound maxXbound maxYbound

MESH: 91 91 90 0 270 180

## Mesh cell values

0.000003 0.000052 0.000142 0.000289 0.000474 0.000691… 0.000939 0.001205 0.001485 0.001775 0.002072

0.002374 …

…

…

2005/11/3

122

Receiver Ray Data

• LightTools saves in memory (RAM and virtual) several pieces of information about every ray which hits a receiver– Ray power– Ray position (x,y,z)– Ray direction cosines (l,m,n)– Wavelength– Optical path length

• This allows LightTools to perform some unique post-processing of the data after an illumination run– Re-binning– Best focus calculation– User-defined position calculation– Symmetry calculations

• Mesh data is the “binned” ray data for each mesh

Working With Receiver Data

Ray data is only available at design time Not saved with the *.lts file

Ray data can be exported to a file Select the desired receiver

In the 3D Design View, use Illumination>Export

Export Rays Exports X, Y, Z, L, M, N, P

Export Ray Directions Exports L, M, N, P (far field data)

This is an important feature when source(s) are very complex and simulation times are longer

Source structure is only needed for secondary effects (reflection, absorption, etc.)

2005/11/3

123

#

Ray Data Export Example

• Ray data of a receiver on a spline surface (using SplinePatch)– Surface receiver on the spline surface– Collimated disc source– Exported ray data is shown in a 3D graph

(X, Y, and Z of each ray)– Ray data resembles the actual surface

profile – neat check!

Actual data format in the exported ray data file

Save Design Time Using Ray Data

Receiver ray data files can directly be used as ray data sources in any LightTools design A very useful feature when working with

very complex systems avoids the need to repeat trace for complex geometry

A complex light pipe and a LED Usually the trace takes time, and brute

force simulations could be inefficient for quick design changes

Trace the LED to a dummy plane and use as a ray data source

2005/11/3

124

Receiver Binning

Binning during the simulation LightTools will automatically figure out the

optimum number of receiver bins to meet the desired error estimate (default is 5%, user defined) if the Auto Size Mesh=Yes

User can control the number of bins if desired (before or after simulation)

Data can be re-binned This is the process of re-distributing the rays

cells or bins across the receiver grid Allows determination of

irradiance/intensity/luminance on a given area within the receiver limits

Data in the Intensity Mesh are shown in these charts

41 X 41 bins

21 X 21 bins

Spatial and Angular Location of Bins

• X, Y or Longitudes, Latitudes usually denote the boundaries of the data mesh

• The actual coordinates of the “bin center” can be different– Important when bin sizes are

relatively large• Consider 11 X 11 intensity mesh

with Latitudes[0 to 180] and Longitudes[0 to 360]– About 16 degree error in

Longitude direction and About 8 degree error in Latitude direction due to finite bin size –if the boundaries are used

• Same applies for linear boundaries (illuminance or irradiance data)

Bin width=32.72, height=16.36 degrees

Bin center is 16.36 degrees offset from the boundary in Longitude direction and 8.18 degrees offset in Latitude direction

Actual bin coordinates are shown in the table

Long. Lat.

2005/11/3

125

!

Effect of Bin Size and Shape

Illuminance mesh Bins are always rectangular Non-planar surfaces are handled by projecting

rectangular bins on to the surface Intensity mesh

Bins at poles are non-rectangular Higher error due to fewer rays Can overcome by rotating the receiver

coordinates

#%

Receiver Binning and Accuracy

In the Monte Carlo model, accuracy is determined by the number of rays falling in each bin (ray density)

The program selects the number of bins to control the accuracy You specify the minimum and maximum number of bins in each

direction (defaults are 5 and 41) Program sets the number to try to get the peak error value of the cell

with the maximum irradiance/intensity below the required value (default 0.05 or 5%) or as close as possible

2005/11/3

126

#"

54% of 5,000 rays11 x 11 gridPeak error 16.8%

54% of 5,000 rays5x 5 gridPeak error 8.9%

54% of 240,000 rays11x 11 gridPeak error 2.9%

Binning Effects

Note the tradeoff between spatial resolution (grid size) and peak error

Larger numbers of rays must be traced to get enough rays per binfor better accuracy

#

Error Estimate

The peak error estimate is the first standard deviation of the receiver cell with the highest value and is given by the following formula:

where f = irradiance or intensity of each ray

N = total number of rays traced from one source

( )

N

N

f

f=

2

εN

=1ε

Converges when f is constant

2005/11/3

127

#

Workshop 7-1: Receiver Orientation

A lighting system has a circular beam pattern (intensity) with an angular extent of +/- 45 degrees. The optical axis of the system is along the +Z axis. We want to measure the intensity of the system with a far field receiver but want to avoid the receiver poles to prevent triangular bins

Suggest a far field receiver setup to meet the following criteria Angular resolution of intensity measurements = 5 degrees

Error estimate at peak < 5% (assume that all rays reaching the receiver have the same power)

Simulate this system and show that it meets expectations for a uniform point source with Lower Angle = 45 degrees, emitting in +Z direction

#

Receiver Setup

Use a far field receiver with Alpha=-90 Min. Latitude = 45 Max. Latitude = 135 Mesh size = 19 X 19

The first Latitude bin center is located at 47.5 degrees and the last at 132.5, with 5-degree bin width

The first Longitude bin center is located at 137.5 degrees and the last at 222.5, with 5-degree bin width

This setup is sometimes called Type A Photometer and is available in LightTools Utilities (SAE Test Point Analyzer)

45 50 55 80 85 90

47.5 52.5 82.5 87.5

2005/11/3

128

##

Simulation Results

Results shown using the 3D Intensity Raster Chart

Use the receiver dialog box to view the error, number of rays, etc. for each bin

#

Receiver Data Filtering

It is often desirable to characterize the receiver data based on

various parameters

Receiver data filtering is an excellent way to sub-sample the

entire data set

Excellent tool for variety of applications

Segmented reflector design (specially automotive exterior)

Stray light analysis

Illumination and optical system characterization

2005/11/3

129

#

Receiver Data Filtering

Ability to filter receiver ray data based on: Source (origin of rays)

Wavelength (wavelength of rays) Power/Flux (absolute or relative incident or exiting power of rays)

Hit number (of ray on receiver, or the last hit ) Incident Angle (of rays upon receiver) Exit Angle (of rays upon receiver)

Element (rays that hit the receiver and a specified element)

Surface (rays that hit the receiver and a specified surface) Property Zone (rays that hit the receiver and a specified property zone

on a surface)

Volume Interface (rays that undergo scattering in a material)

Optical Path Length (cumulative from source to receiver)

#

Adding Filters

Add filters to receivers by

Selecting the receiver in 3D view or in the

System Navigator

Right click to select Add Filter

Select the filter type using the drop down list

in the popup menu

2005/11/3

130

#!

Adding Filters

• Receiver dialog box can also be used to add filters

• Filter characteristics can be defined separately

• All the “enabled” filters will behave as “AND”

• Can combine filters to give different logic

• Filters can be enabled/disabled without retracing

%

Filtering Receiver Data

• Three sources with different wavelengths– 700 nm (Red)– 500 nm (Green)– 400 nm (Blue)

• Two “Wavelength” filters on the receiver (WaveFilter1 & WaveFilter2)

• Case (a)– WaveFilter1>550 nm– WaveFilter2=OFF

• Case (b)– WaveFilter1>450 nm– WaveFilter2<550 nm

• Case (c)– WaveFilter1=OFF– WaveFilter2<450 nm (a) (b) (c)

Illumination>Illuminace Display>CIE RGB>RGB Raster Chart

2005/11/3

131

"

Receiver Defocus

After an illumination simulation is completed, a receiver can be

moved to a user-defined position to analyze the flux distribution,

power, etc.

Also calculates Best Focus

This is the position which minimizes the area of the beam cross-

section (or the spot size ). Also known as the circle of least

confusion.

This can be done on a receiver by receiver basis

User defocus feature is important to analyze data at far field

Best Focus Example

• Elliptical reflector with semi-major axis=10, semi-minor axis=6. The corresponding distance between foci is 16 (foci are located 8 units from the center of the ellipse)

• Two receivers located at XYZ=0,0,1 and XYZ=0,0,15. Since receivers are located at same distance from the second focus theilluminance (or irradiance) distribution should be the same

• If either of the receivers set to “best focus”, then they both should move by Z=|7|

2005/11/3

132

Best Focus For Elliptical Reflector

• Elliptical receiver with a point source at one foci

• Two dummy planes with receivers at Z=1 and Z=15

• Irradiance with no defocus (a) and best focus (b)– At best focus, both

receivers move 7 units in Z

• Works only in “free space”. If there is additional absorbing media then this would not work

Symmetry Switch

Five different types of symmetry Ideal for analyzing a system

where you know the symmetry before starting

Allows the Monte Carlo algorithm to converge faster

No Symmetry Quadrant Symmetry Rotational Symmetry

2005/11/3

133

#

Symmetry Switch Example

Sun shining through the atmosphere with and without the rotational symmetry flag Simulated using Mie scattering

Clear atmosphere (with rotational

symmetry flag on)

Hazy atmosphere (with rotational

symmetry flag on)

Hazy atmosphere (without rotational symmetry flag on)

Luminance Meters

Luminance meters are parts of surface receivers When a luminance meter is defined, an additional data mesh is added

to the receiver

LightTools has two types of luminance meters Spatial luminance meter Angular luminance meter

Each surface receiver can have one of each type (total of two luminance meters/receiver at any given time)

2005/11/3

134

Adding Luminance Meters

Luminance meters are defined by selecting a surface receiver, and then using the command buttons

Controls for the luminance meter can be accessed using the properties dialog box

Distance is fixed, latitudes/longitudes control the orientation

Spatial Luminance Meter

• Measures the spatial luminance of an emitter. This is equivalent to

using a regular luminance meter, commonly known as a “spot

meter”, across the emitter surface

• The aperture should be large enough to capture sufficient number

of rays

The “aperture” and the distance defines the cone (solid angle) through which the light enters the luminance meter. It “scans” the entire surface while retaining the orientation. Luminance is computed for each bin in the spatial luminance mesh

2005/11/3

135

!

Luminance of a Graphic

• A surface with a graphic is analyzed with the spatial luminance meter– “Zone” is transmitting– “BareSurface” is absorbing

• Every position on the graphic can be measured at once– Spatial resolution depends on the number of bins

%

Angular Luminance Meter

• Measures the angular luminance of an emitter. This is equivalent

to using a regular luminance meter, commonly known as a “spot

meter”, at various angular positions around the emitter

• Luminance at all positions in one hemisphere can be measured

The “dome” represents the path of the luminance meter around the emitter in the upper hemisphere. Luminance is computed for each bin in the angular luminance mesh

2005/11/3

136

"

Luminance of a Lambertian Source

Two crossed Brightness Enhancement Films (BEF) with a Lambertian source (a) without the BEFs

(b) with BEFs

(a)

(b)

System

Dummy Plane

BEFs

Source

Receivers Summary

At least one receiver is required to run a simulation

Surface receivers are important for illuminance and luminance measurements

Also support intensity measurements, but only cover 2π steradians

Luminance meters are attached to surface receivers

Far field receivers are important for intensity measurements

Receiver data can be Re-binned

Filtered

Exported

Defocused

2005/11/3

137

Workshop 7-2: Airport Beacon

An airport beacon has the following specifications Maximum emission angle = 7.5 degrees

The cutoff point must be < 10% below the peak intensity

Height = 50 mm Diameter = 100 mm

Construction type = Fresnel

Source = Lambertian cylinder (length =10 mm, radius = 2 mm, emission angle = + 50 degrees)

"%%

#%

Step 1 $ Create the System

• Use the “Fresnel Lenses”utility to construct the beacon – This creates the top half of

the beacon– Copy and reorient to

create the lower portion– Union top & bottom to

form full beacon

• Create the source– Use a cylindrical surface

source, only the cylinder surface being the emitter

• Add the appropriate receiver type– Avoid triangular bins

2005/11/3

138

#

Step 2 $ Add Controls

Add a filter to filter out rays that do not

hit the lens

Can exclude direct light during design

phase without having to create extra

geometry

Step 3 $ Simulate

Run simulation

Look at the intensity chart

with and without the filter

Limit the receiver intensity

mesh limits so that the

region of interest is shown

with enough details

2005/11/3

139

Controlling the Simulation

Simulation Controls

Available only after setting up the simulation

Use Simulation Info Properties to control various ray trace controls Simulation parameters (Ray

Preview, Ray Report, and Update Interval)

Spectral content Random seed control

2005/11/3

140

!

Total Rays

• Total number of rays

– Total number of rays to use for the simulation

– If there is more than one source active, then the total

number of rays is distributed among all sources

according to the “source weight factor” (SWF)

– For total of 1000 rays

• (a) will emit 33% (0.5/(1+0.5))

• (b) will emit 66% (1/(1+0.5))

– No change in source power

(b) SWF=1

(a) SWF=0.5

%

Relative Threshold

Relative ray power threshold This is the energy threshold at which simulation rays are terminated.

Default is 0.01 or 1% of the starting power

Particularly important for stray light analysis where the desired power levels are well below the default 1%. A lens housing with scattering walls (reflectance = 0.5%). Analyze the first

bounce (a) threshold=1% (b) threshold=0.1%

(a) (b)

2005/11/3

141

"

Spectral Content

Spectral content controls the spectral range to include in the

simulation

Efficient way to analyze systems with broad spectral band

Consider Red, Green, and Blue LEDs in a system. By setting the

spectral range, effect of each LED can be analyzed separately without

changing their parameters

• If the system has no dispersive elements then the non-dispersive flag can increase the performance by tracing at a given wavelength

Random Seed Control

The random number generator starts at an arbitrary number and follows a certain sequence

Re-initialization resets the starting point Sometimes important for repeatability

Performance testing

Sobol (default) and Pseudo-Random algorithms allow the choice of random number generator to use The convergence depends on the nature of the model

2005/11/3

142



Section 8LightTools Utilities Library

LightTools Utilities

Utilities are programs supplied with LightTools that Perform common tasks, e.g.

Entering standard sources as ray data sets, physical models, or apodization files

Changing surface properties

Automate application-specific tasks, e.g. Generate complex geometry for backlights Analyze receiver data against SAE standards

Manage files Convert macros from old .ltb format to Visual BASIC Perform disc cleanup of .ltr and .log files

Use the JumpStart routines Source code is supplied Excellent examples for learning to write your own macros

Found under Tools > Utility Library

2005/11/3

143

#

LightTools Utility Library

Description of selected program

Utility category

Specific programs

Start program

Expand/collapseprogram list

Favorite utilities

Using the Utility Library

• The Utility Library is a separate program from LightTools

– It opens a separate task window

– It uses the COM interface to interact with LightTools

• Programs are organized in general categories

– Explore the list; it will keep growing

• User “favorites” can be attached to the LTU buttons below the

menu bar.

– Use “Set” button, then assign a utility to each button.

2005/11/3

144

Workshop 8-1: Complete LED Model

• We will create a T1-3/4 (5 mm) GaAlAs Light Emitting Diode (LED)

complete with the physical structure and appropriate spectrum.

• Create an appropriate source spectrum

– LED’s typically have a narrow spectral distribution. For AlGaAs, this is

peaked at 660 nm, and has a 20 nm half-width

– Using the Source Spectrum utility

• Create and save an appropriate Gaussian spectrum for this LED

(settings shown on next page)

• With the User Preferences for the Default Spectral Range, load this

spectral region. New sources will be created with this spectral region.

Workshop 8-1: Complete LED Model (2)

1. Enter name for saved spectrum

2. Enter Peak Wavelength (660), Full width (20), then Make Gaussian Spectral File

2005/11/3

145

!


Create the physical

structure

Use the Light Emitting

Diode (LED) utility to

create the physical

structure of the LED.

Accept the default values

for all parameters.

!%


• Run an illumination simulation with 50,000 rays.

• Using the Spectrum Viewer utility (found under Misc.), plot the spectrum at the far field receiver. – On Receiver tab, select “Initiate/Update”– Press “Get Data”. Note the progress update shown in the bottom of

the window. – View the receiver spectrum by pressing “Re-Bin + Replot”

2005/11/3

146

!"

Q & A

• If you have any further questions, please contact us.– [email protected]– [email protected]– [email protected]

lt basic handout 20051103

Documents