human eye optics

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Human Eye Optics

SOLO HERMELIN

Updated: 16.01.10http://www.solohermelin.com

http://www.solohermelin.com/

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Table of Content

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Human Eye Introduction

Human Eye Structure

RetinaRods and ConesFacts and Figures concerning the human retina

Human Eye Optics

Introduction to Lenses and Geometrical Optics Waves and Rays

Optical Aberration Common Vision Defects and Their Correction Aberrometers

Color Blindness

Microscope Optical Components- IntroductionEyepieces (Oculars)

References

The Lens

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http://www.olympusmicro.com/primer/anatomy/introduction.html

Human Eye Introduction

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SOLO Optics - EyeHuman Eye Introduction

http://www.olympusmicro.com/primer/anatomy/numaperture.html

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The visual pathway: from the eyes to the brain’s visual cortex (adapted from Gray 1918)

Human Eye Structure

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Structure of the eye from Hecht, Optics

The human eye is able to detect from about 390 to 780 nanometers, defining the visual spectrum

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1 = Iris The colored part of the eye located between the Lens and Cornea. It regulates the entrance of the light.2 = Cornea The transparent, blood-free tissue covering the central front of the eye that initially refracts or bends light rays as light enters the eye. Contact lenses are fitted over the Cornea.3 = Retina The innermost layer of the eye, a neurological tissue, which receives light rays focused on it by the Lens. This tissue contains receptor cells (Rods and Cones) that send electrical impulses to the brain via the optic nerve when the light rays are present.4 = Rods The receptor cells which are sensitive to light and are located in the Retina of the eye. They are responsible for night vision, as non-color vision in low level light.5 = Cones The receptor cells which are sensitive to light and are located in the Retina of the eye. They are responsible for color vision.6 = Lens The eye's natural Lens. Transparent, biconvex intraocular tissue that helps bring rays of light to a focus on the Retina.7 = Pupil The opening at the center of the Iris of the eye. It contracts in a high level of light and when the eye is focused on a distant object.

Human Eye Structure

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The vertebrate retina is a light sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These are sent to various visual centers of the brain through the fibers of the optic nerve.

In vertebrate embryonic development, the retina and the optic nerve originate as outgrowths of the developing brain, so the retina is considered part of the central nervous system (CNS). It is the only part of the CNS that can be imaged non-invasively in the living organism.

Retina

The retina is a complex, layered structure with several layers of neurons interconnected by synapses. The only neurons that are directly sensitive to light are the photoreceptor cells. These are mainly of two types: the rods and cones. Rods function mainly in dim light and provide black-and-white vision, while cones support daytime vision and the perception of colour. A third, much rarer type of photoreceptor, the photosensitive ganglion cell, is important for reflexive responses to bright daylight.

Neural signals from the rods and cones undergo complex processing by other neurons of the retina. The output takes the form of action potentials in retinal ganglion cells whose axons form the optic nerve. Several important features of visual perception can be traced to the retinal encoding and processing of light.

SOLO Optics - EyeRetina

Anatomy of vertebrate retina

The vertebrate retina has ten distinct layers. From innermost to outermost, they include:

1 .Inner limiting membrane - Müller cell footplates 2 .Nerve fiber layer

3 .Ganglion cell layer - Layer that contains nuclei of ganglion cells and gives rise to optic nerve fibers .

4 .Inner plexiform layer 5 .Inner nuclear layer contains bipolar cells

6 .Outer plexiform layer - In the macular region, this is known as the Fiber layer of Henle .

7 .Outer nuclear layer8 .External limiting membrane - Layer that separates

the inner segment portions of the photoreceptors from their cell nuclei .

9 .Photoreceptor layer - Rods / Cones 10 .Retinal pigment epithelium

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Retina's simplified axial organization. The retina is a stack of several neuronal layers. Light is concentrated from the eye and passes across these layers (from left to right) to hit the photoreceptors (right layer). This elicits chemical transformation mediating a propagation of signal to the bipolar and horizontal cells (middle yellow layer). The signal is then propagated to the amacrine and ganglion cells. These neurons ultimately may produce action potentials on their axons. This spatiotemporal pattern of spikes determines the raw input from the eyes to the brain. (Modified from a drawing by Ramón y Cajal.)

In adult humans the entire retina is approximately 72% of a sphere about 22 mm in diameter. The entire retina contains about 7 million cones and 75 to 150 million rods. An area of the retina is the optic disc, sometimes known as "the blind spot" because it lacks photoreceptors. It appears as an oval white area of 3 mm². Temporal (in the direction of the temples) to this disc is the macula. At its center is the fovea, a pit that is most sensitive to light and is responsible for our sharp central vision. Human and non-human primates possess one fovea as opposed to certain bird species such as hawks who actually are bifoviate and dogs and cats who possess no fovea but a central band known as the visual streak. Around the fovea extends the central retina for about 6 mm and then the peripheral retina. The edge of the retina is defined by the ora serrata. The length from one ora to the other (or macula), the most sensitive area along the horizontal meridian is about 3.2 mm.


In section the retina is no more than 0.5 mm thick. It has three layers of nerve cells and two of synapses, including the unique ribbon synapses. The optic nerve carries the ganglion cell axons to the brain and the blood vessels that open into the retina. The ganglion cells lie innermost in the retina while the photoreceptive cells lie outermost. Because of this counter-intuitive arrangement, light must first pass through and around the ganglion cells and through the thickness of the retina, (including its capillary vessels,not shown) before reaching the rods and cones. However it does not pass through the epithelium or the choroid (both of which are opaque).

The white blood cells in the capillaries in front of the photoreceptors can be perceived as tiny bright moving dots when looking into blue light. This is known as the blue field entopic phenomenon (or Scheerer's phenomenon).

Between the ganglion cell layer and the rods and cones there are two layers of neuropils where synaptic contacts are made. The neuropil layers are the outer plexiform layer and the inner plexiform layer. In the outer the rods and cones connect to the vertically running bipolar cells, and the horizontally oriented horizontal cells connect to ganglion cells.

The central retina is cone-dominated and the peripheral retina is rod-dominated. In total there are about seven million cones and a hundred million rods. At the centre of the macula is the foveal pit where the cones are smallest and in a hexagonal mosaic, the most efficient and highest density. Below the pit the other retina layers are displaced, before building up along the foveal slope until the rim of the fovea or parafovea which is the thickest portion of the retina. The macula has a yellow pigmentation from screening pigments and is known as the macula lutea. The area directly surrounding the fovea has the highest density of rods converging on single bipolars. Since the cones have a much lesser power of merging signals, the fovea allows for the sharpest vision the eye can attain.

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Light

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Left cross-section of human eye, Right cells in the human retina (adapted from Gray 1918)

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Rods and Cones

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1 .Rods The vast majority of the cells on the retina

Panchromatic -- sensitive to wide range of wavelengths .

But not energy/color-discriminating within this range: Receptors translate all light to same "signal" = amount of light.

Thus, delivers "shades of gray", like a high speed, black and white film.

The specific chemical that makes rods active is rhodopsin, a complex protein with a 40,000 amu atomic weight, which makes up as much as 35% of the cell dry weight .

Absorption curve of rhodopsin shown roughly by the curve

Absorption of the photon splits off a small, 264 amu fragment (a chromophore) called retinaldehyde (a derivative of Vitamin A), and instantaneously one of the double bonds changes from a cis to a trans type bond.

Remainder of protein is called opsin .

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1 .Rods (continue – 1)

In a process not well understood, splitting of protein changes permeability of the neuron's membrane to sodium ions, which changes the electrical potential of the cell .

Change in potential propagates through nerve cells to transmit message to brain.

Between 1 to 10 photons must be absorbed to "trigger" particular rod (similar to photographic grains in film) .

However, rods are bundled to a single nerve fiber, so act together.

Slowly (over 30 min timescale), the full rhodopsin molecule is regenerated.

Rods concentrated to outer part of retina.

Completely missing in the 0.3 mm diameter fovea centralis, in center of yellow patch called the macula.

Note the image of the full moon on retina is only 0.2 mm.

Night blindness occurs when there is damage to the outer part of the retina .

Normal vision (left and right) and night blindness (middle), from http://www.retina-international.org/nightbld.htm.

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2 .ConesAbout 5% of the retinal cells.

Probably work same way as rods, but contain slightly different iodopsin protein with the retinaldehyde group.

As a group, provide sensitivity to colors.

Translate color sensation to brain.

From three different kinds we achieve color sensitivity.

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Rod / Cone Sensitivity

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The RED sensitivity for the R-conesor the L-cones

Range from 410 to 690 nanometerPeak 580 nm

Peak range from 558 to 580 nm

The GREEN sensitivity for the G-conesor the M-cones

Range from 440 to 670 nmPeak 540 nm

Peak range from 534 to 540 nm

The BLUE sensitivity for the B-conesor the S-cones Range from 400 to 540 nanometerPeak 440 nmPeak range from 420 to 440 nm

Three Types of Cones:L, M, S

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Facts and Figures concerning the human retina

1 .Size of the retina

32 mm from ora to ora along the horizontal meridian (Van Buren, 1963; Kolb, unpublished measurements). Area of the human retina is 1094 square mm (Bernstein, personal communication) calculated from the expectations that the average dimension of the human eye is 22 mm from anterior to posterior poles, and that 72% of the inside of the globe is retina (Michels et al., 1990) .

2 .Size of optic nerve head or disc.

1.86 x 1.75 mm

3 .Degrees and distance in micometers.

One degree of visual angle is equal to 288 µm on the retina without correction for shrinkage (Drasdo and Fowler (1974).

4 .Foveal position.

11.8o or or 3.4 mm temporal to the optic disk edge

5 .Cross diameter of the macula.3 mm of intense pigmentation, surrounded by 1 mm wide zone of less pigmentation

(Polyak, 1941).

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Facts and Figures concerning the human retina (continue - 1 )

6 .Cross diameter of the central fovea from foveal rim to foveal rim.

1.5 mm (Polyak, 1941)

1.2-1.5 mm (Ahnelt and Kolb, unpublished data)

7 .Cross diameter of central rod free area.

400-600 µm (Polyak, 1941)

750 µm (Hendrickson and Youdelis, 1984)

570 µm (Yamada, 1969)

250 µm (Ahnelt et al., 1987)

8 .Vertical thickness of the fovea from ILM to ELM.

In the foveal pit 150 µm (Yamada, 1969)

foveal rim 300 µm

9 .Length of foveal axons (Henle fibers).

150-300 µm (Ahnelt and Pflug, 1986).

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10 .Vertical thickness of the retina in different areas.

The vertical extent of the retina across the horizontal meridian at different eccentricities is shown in Figure 3. This is taken from data given by Sigelman and Ozanics (1982). The small black numbers are the originals from Sigelman and Ozanics which were measured in typical histological preparations where there is a great deal of shrinkage. The figures in red are those recently measured by Ahnelt (personal communication) in well fixed EM quality material where there is little or no shrinkage. Hence the latter numbers are larger. The numbers are in mm .

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11 .Age when fovea is fully developed.

Not before 4 years of age (Hendrickson and Youdelis, 1984).

12 .Highest density of cones at center of the fovea) counted in a 50 x 50 µm square.(

147,000/mm2 (Osterberg, 1935)

178,000-238,000/mm2 (Ahnelt et al., 1987)

96,900-281,000/mm2 mean161,900/mm2 (Curcio et al., 1987).

13 .Total number of cones in fovea.

Approximately 200,000. There are 17,500 cones/degree2. Rod free area is approximately 1o thus there are 17,500 cones in the central rod-free fovea.

14 .Total number of cones in the retina.

6,400,000) Osterberg, 1935.(

15 .Total number of rods in the retina.

110,000,000 to 125,000,000 (Osterberg, 1935).

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16 .Rod distribution

Rods peak in density 18o or 5mm out from the center of the fovea in a ring around the fovea at 160,000 rods/mm2. (Fig. 5)

No rods in central 200 µm.

Average 80-100,000 rods/mm2

Rod acuity peak is at 5.2o or 1.5 mm from foveal center where there are 100,000 rods/mm2 (Mariani et al.,1984).

17 .Number of axons in the optic nerve.

564776-1,140,030) Bruesch and Arey, 1942(

800,000-1,000,000) Polyak, 1941(

1,200,000) Quigley et al., 1982; Balaszi et al., 1984.(

18 .Number of cones to ganglion cells in the fovea.

1 cone to 2 ganglion cells out to about 2.2o (Schein, 1988).

19 .Number of cones/retinal pigment epithelial cell (RPE).

30 cones/RPE in fovea (Rapaport et al., 1995).

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20 .Number of rods/retinal epithelial cell (RPE).

In periphery 22 rods/RPE cell

In rod peak (4-5 mm from foveal center) 28 rods/RPE cell (Rapaport et al.,1995).

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21 .Number of neural and glial types in the retina. The retina consists of many millions of cell types packed together in a tightly knit network spread over the surface of the back of the eye fundus as a thin film of tissue only 1/2 millimeter thick. The retina is like a three layered cake with three layers containing cell bodies of neurons and two filling layers where synapses betwen the neurons occur. There are two basic kinds of photoreceptors, rods and cones. The cones are further subdivided into two types (long and short wavelength sensitive) in the majority of mammals, i.e. most mamals are dichromats and have divariant color vision. In primates a third wavelength sensitive cone has developed closely related to the long wavelength cone type but a little more sensitive in the middle wavelength (i.e. green cone). Thus primates including man are trichromats and have trivariant color vision. Many reptiles, birds and fish have 4 or even 5 types of cone each sensitive to a slightly different peak wavelength.

The second order neurons postsynaptic to the photorecepors in the first synaptic (filling layer) (outer plexiform layer) are bipolar cells and horizontal cells. There are 9 types of bipolar cell and 2 to 4 types of horizontal cell in species from mammals to fish. The third order neurons are amacrine cells and ganglion cells that synapse in the inner synaptic filling layer (inner plexiform layer). There are two types of interplexiform cell stretching between both plexiform layers, in most vertebrate retinas.There are approximately 22 types of amacrine cell and 20 types of ganglion cell in the typical mammalian retina. There may be 30 or more amacrine cell types in fish and reptilian retinas and 22 or so ganglion cell types. The increased number of third order neurons is due to the greater information processing taking place in the non mammalian retinas that in mammalian.

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22 .Useful Units in Vision Science (Wandell, 1995).

Radiometric units represent a physical measurement e.g., radiance is measured in watts sr -1 m-2.

Calorimetric units adjust radiometric units for visual wavelength sensitivity e.g., luminance is measured in candela per square meter, cd/m2 .

Lux are units of illumination. Thus a light intensity of 1 candela produces an illumination of 1 lux at 1 meter.

Scotopic luminance units are proportional to the number of photons absorbed by rod photoreceptors to give a criterion psychophysical result.

Photopic luminance units are proportional to a weighted sum of the photons absorbed by L- and M-cones to give a criterion psychophysical result.

Typical ambient luminance levels (cd/m2).:

Starlight: 0.001

Moonlight: 0.1

Indoor lighting: 100

Sunlight: 10.000

Maximum intensity of common CRT monitors: 100

One Troland (Td) of retinal illumination is produced when an eye with a pupil size of 1 mm2 looks at a surface whose luminance is 1 cd/m2.

Lens focal length: f(meters); lens power= 1/f (diopters).

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Facts and Figures concerning the human retina (continue - 8)

23 .Image formation (Wandell, 1995).

The eyes are 6 cm apart and halfway down the head.

Visual angle of common objects (degrees, deg)The sun or moon = 0.5 deg

Thumbnail (at arm's length) = 1.5 deg

Fist (at arm's length) = 8-10 deg

Visual field (measured from central fixation)

Monocular: 160 deg (w) x 175 deg (h)

Binocular: 200 deg (w) x 135 deg (h)

Region of binocular overlap: 120 deg (w) x 135 deg (h)

Range of pupil diameters: 1-8 mm.

Refractive indices

Air: 1.000 Glass: 1.520

Water: 1.333

Cornea: 1.376

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Facts and Figures concerning the human retina (continue - 9)

23 .Image formation (Wandell, 1995) (continue – 1).

Optical power (diopters).Cornea: 43 Lens (relaxed): 20

Whole eye: 60

Change in power due to accomodation: 8

Axial chromatic aberration over the visible spectrum: 2 diopters.

Visible spectrum: 370-730 nanometers (nm)

Peak wavelength sensitivity :Scotopic: 507 nm

Photopic: 555 nm

Spectral equilibrium hues :

Blue: 475 nm

Green: 500 nm

Yellow: 575 nm

No spectral equilibrium: red

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http://www.olympusmicro.com/primer/lightandcolor/lensesintro.html

Introduction to Lenses and Geometrical Optics

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http://www.olympusmicro.com/primer/anatomy/magnification.html

Magnification

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Image Formation on the Retina

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SOLO

converging beam=

spherical wavefront

parallel beam=

plane wavefront

Image PlaneIdeal Optics

ideal wavefrontparallel beam

=plane wavefront

Image PlaneNon-ideal Optics

defocused wavefront

ideal wavefrontparallel beam=

plane wavefront


aberrated beam=

iregular wavefront

diverging beam=

spherical wavefront

aberrated beam=

irregular wavefront

Image Plane

Non-ideal Opticsideal wavefront

Optical Aberration

SOLO

converging beam=

spherical wavefront

parallel beam=

plane wavefront


P'

Optical Aberration

converging beam=

spherical wavefront


diverging beam=

spherical wavefront

PP'

An Ideal Optical System can be defined by one of the three different and equivalent ways:

All the rays emerging from a point source P, situated at a finite or infinite distance from the Optical System, will intersect at a common point P’, on the Image Plane.

3

All the rays emerging from a point source P will travel the same Optical Path to reach the image point P’.

2

The wavefront of light, focused by the Optical System on the Image Plane, has a perfectly spherical shape, with the center at the Image point P.

1

Ideal Optical System

SOLO

ideal wavefrontparallel beam=

plane wavefront


aberrated beam=

iregular wavefront

diverging beam=

spherical wavefront

aberrated beam=

irregular wavefront

Image Plane

Non-ideal Opticsideal wavefront

Optical Aberration

Real Optical System

An Aberrated Optical System can be defined by one of the three different and equivalent ways:

The rays emerging from a point source P, situated at a finite or infinite distance from the Optical System, do not intersect at a common point P’, on the Image Plane.

3

The rays emerging from a point source P will not travel the same Optical Path to reach the Image Plane

2

The wavefront of light, focused by the Optical System on the Image Plane, is not spherical.

1

Optical Aberration W (x,y) is the path deviation between the distorted and referenceWavefront.

SOLO Optical Aberration


Display of Optical Aberration W (x,y)

Rays Deviation3

Optical Path Length Difference2

wavefront shape W (x,y) 1

Red circle denotes the pupile margin.Arrows shows how each ray is deviatedas it emerges from the pupil plane.Each of the vectors indicates the thelocal slope of W (x,y).

The aberration W (x,y) is represented in x,y plane by color contours.

xy

yxW ,Wavefront Error

x

y

yxW ,

OpticalDistanceErrors

x

y

RayErrors

The Wavefront error agrees withOptical Path Length Difference, But has opposite sign because a long (short) optical path causes phase retardation (advancement).

Aberration Type:Negative vertical

coma Reference


Display of Optical Aberration W (x,y)

Advanced phase <= Short optical path

Retarded phase <= Long optical path

Reference

Ectasia

x

y

Ray Errors

y

yxW ,

x

Optical Distance Errorsx

y

yxW ,

Wavefront Error

SOLOReal Imaging Systems

Departures from the idealized conditions of Gaussian Optics in a real Optical System arecalled Aberrations

Monochromatic Aberrations

Chromatic Aberrations

• Monochromatic Aberrations

Departures from the first order theory are embodied in the five primary aberrations

1. Spherical Aberrations

2. Coma

3. Astigmatism

4. Field Curvature

5. Distortion

This classification was done in 1857 by Philipp Ludwig von Seidel (1821 – 1896)

• Chromatic Aberrations

1. Axial Chromatic Aberration

2. Lateral Chromatic Aberration

Optical Aberration

Spherical Aberations

B4

1

r

4

4

1rBW

O

W

( a )

Comacos' 3rhFW

W

'hFO

( b )

r

Astigmatism

cos' 22 rhCW

W

( c )

2'hCO

r

Curvature of Field

2'2

1hD

r

22'2

1rhDW

O

W

( d )

Distortion

3'hE

cos'3 rhEW

W

( e )

r

O

SOLO

Real Imaging Systems

Seidel Aberrations Distortions of the Wavefront

cos''cos'cos'';, 32222234 rhCrhCrhCrhCrChrW DiFCAsCoSp

Optical Aberration

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Common Optical Defects in Lens Systems (Aberrations)


SOLO Optics Zernike’s Polynomials

In 1934 Frits Zernike introduces a complete set of orthonormal polynomialsto describe aberration of any complexity.

mN

mn

mn

mnN YRaZZ ,,

,2,12

813min

N

NIntegern

oddN

evenNmsign

NnnIntegernm

1

1

4

212min2

Each polynomial of the Zernike set is a product of three terms.

where

012

01

mifn

mifna m

n

sn

mn

s

sm

n smnsmns

snR 2

2/

0 !2/!2/!

!1

oddisNandmif

evenisNandmif

mif

Y mN

0sin

0cos

01

radial index

meridional index


Properties of Zernike’s Polynomials.

n m

mn

mn ZCW ,,

W (ρ,θ) – Waveform Aberration

Cnm (ρ,θ) – Aberration coefficient (weight)

Znm (ρ,θ) – Zernike basis function (mode)

mallnallforZZMean mn

mn 00,, 1

mnallforZVariance mn ,1, 2

3 Zernike’s Polynomials are mutually orthogonal, meaning that they are independentof each other mathematically. The practical advantage of the orthogonality is that we can determine the amount of defocus, or astimagtism, or any other Zernike mode occurring in an aberration function without having to worry about the presence of the other modes.

4 The aberration coefficients of a Zernike expansion are analogous to the Fouriercoefficients of a Fourier expansion.

n m

mn

n m

mn

mn

mn CZZCMeanWVariance

22

,,,

'

1

0' 12

1nn

m

n

m

n ndRR

'0

2

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In 1934 Frits Zernike introduces a complete set of orthonormal polynomialsto describe aberration of any complexity.

Astigmatism

4,4,,2 22 ayax

Coma1

3,5,,2 2 axaxComa2

4,4,,2 2 ayax

Spherical& Defocus

3,5,,3.12 22 aa

36 Zernikes

Geounyoung Yoon, “Aberration Theory”

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Astimagtism

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“Aberation Theory”Geunyoung Yoon Ph.D.

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SOLO Optics - Eye FIGURE 127: Top left, optical power (in diopters) of the two main elements of the human eye, cornea and crystalline lens (number in brackets is corresponding f.l. if imaging in air; for the eye as a whole, assuming a single imaging element with 22.2mm f.l. effective in the aqueous medium). Top right, a graph showing approximate size of the aberrated blur relative to the diffraction blur (Airy disc diameter). Absolute blur size is at the minimum for ~2mm pupil diameter. For larger pupils, blur is enlarged due to eye aberrations, and for smaller pupils due to diffraction. At large pupil openings, dominant aberration component is roughness, as can be seen from the right-most diffraction pattern. It shows what an actual pattern at 5mm pupil may look like, not one appropriate to the ray spot. Change in the nominal size of the blur is much less pronounced than the change relative to the Airy disc.

Ray spots show axial blur for F, e and C spectral lines at 1mm, 2mm and 5mm pupil diameter (SPEC'S) of the eye model used). Longitudinal chromatism is nearly constant at about 0.3mm of axial defocus between F and C; relative to the Airy disc (black circle), transverse chromatism changes with the square of the pupil diameter. Hence, it is at the level of a 4" f/12 achromat for about 3mm pupil diameter. Both, diffraction and aberrated blurs are relatively large with respect to the cones (~2μ-10μ) and rods (~2.5μ-5μ), so it is diffraction and aberrations that determine retinal image quality.

http://www.telescope-optics.net/eye_aberrations.htm

Eye Aberration

Common Vision Defects

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Correction of Common Vision Defects Common Vision Defects

Hyperopia (Farsightedness) Myopia (Nearsightedness( Astigmatism

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Aberrometers

A number of technical and practical parameters that may be useful in choosing an aberrometer for daily clinical practice.

The main focus is on wavefront measurements, rather than on their possible application in refractive surgery. The aberrometers under study are the following:

1 .Visual Function Analyzer (VFA; Tracey): based onray tracing; can be used with the EyeSys Vista corneal topographer.

2 .OPD-scan (ARK 10000; Nidek): based on automatic retinoscopy; provides integrated corneal topography and wavefront measurement in 1 device.

3 .Zywave (Bausch & Lomb): a Hartmann-Shack system that can be combined with the Orbscan corneal topography system.

4 .WASCA (Carl Zeiss Meditec): a high-resolution Hartmann-Shack system.

5 .MultiSpot 250-AD Hartmann-Shack sensor: a custom-made Hartmann-Shack system, engineered by the Laboratory of Adaptive Optics at Moscow State University, that includes an adaptive mirror to compensate for accommodation

6 .Allegretto Wave Analyzer (WaveLight): an objective Tscherning device

SOLO OPTICSAberrometers

Figure 1. The principles of the wavefront sensors :Top: Skew ray .Center Left: Ray tracing .Center Right: Hartmann-Shack .Bottom Left: Automatic retinoscope .Bottom Right: Tscherning .

Single-head arrows indicate direction of movement for beams .

Figure 2. Reproductions of the fixation targets for the patient: A: VFA.B: OPD-scan. C: Zywave. D: WASCA.E: MultiSpot. F: Allegretto.

SOLOOPTICSAberrometers

Johannes Hartmann1865 - 1936

In 1920, an astrophysicist named Johannes Hartmann deviseda method of measuring the ray aberration of mirrors and lenses.He wanted to isolate rays of light so that they could be traced and anyimperfection in the mirror could be seen. The Harman Test consist on using metal disk in which regulary spaced holes had been drilled.

The disk or screen was then placed over the mirror that was to be testedand a photographic plate was placed near the focus of the mirror. Whenexposed to light, a perfect mirror will produce an image of regularyspaced dots. If the mirror does not produce regularly spaced dots, the irregularities, or aberrations, of the mirror can be determined.

Figure 1. Optical schematic for an early Hartmann test.

Schematic from Santa Barbara Instruments Group (SBIG) software for analysis of Hartmann tests.

1920

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Optical schematic for first Shack-Hartmann sensor.

Around 1971 , Dr. Roland Shack and Dr. Ben Platt advanced the concept replacingthe screen with a sensor based on an array of tiny lenselets. Today, this sensor is known as the Hartmann - Shack sensor. Hartmann – Shack sensors are used in a variety of industries: military, astronomy, ophthalmogy .

Schematic showing Shack-Hartmann CCD output.

Schematic of Shack-Hartmann data analysis process.

Hartmann - Shack Aberrometer

Roland Shack

1971

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Lenslet array made by Heptagon for ESO. The array has 40 x 40 lenslets, each 500 μm (0.5 mm) insize.

Part of lenslet array made by WaveFront Sciences. Each lens is 144 μm in diameter.


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Recent image from Adaptive Optics Associates (AOA) shows the optical set-up used to test the first Shack-Hartmann sensor.

Upper left) Array of images formed by the lens array from a single wavefront .

Upper right) Graphical representation of the wavefront tilt vectors .

Lower left) Zernike polynomial terms fit to the measured data .

Lower right) 3-D plot of the measured wavefront.

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Color TheorySOLO

Color Blindness

Normal Color Vision Red-Blind/Protanopia Green-Blind/Deuteranopia

Blue-Blind/Tritanopia

Blue-Weak/Tritanomaly

Red-Weak/Protanomaly Green-Weak/Deuteranomaly

Monochromacy/Achromatopsia Blue Cone Monochromacy

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Shinobu Ishihara(1879--1963)

Shinobu Ishihara created the Ishihara Color Test to detect Color Blindness.

The Ishihara Color Blindness test – named after a Japanese Professor at the University of Tokyo – is the most well known tool to test for red-green color blindness. Mr Ishihara developed this test almost 100 years ago. It was first published in 1917 and is used since then to check if someone is suffering from protanopia or deuteranopia, the two different kinds of red-green color vision deficiencies.

A collection of 38 plates filled with colored dots build the base of this test. The dots are colored in different shades of a color and a number or a line is hidden inside with different shades of an other color. But enough theory, take the color blindness test by Mr Ishihara yourself and be surprised (or not) of the result.

A plate from the Ishihara Test for color blindness. Can you see the number 74? However, whether you see the number or not, don’t take this as a final indication: it is only one plate of many plates in the full test and the colors on your computer screen might not be exactly right.

A plate from the Ishihara Test for color blindness. Can you see the number 12?

Color TheorySOLO

Color Blindness

Color TheorySOLO

Color Blindness

Types of colour visiondeficiency

MalesFemales

Overall~ 8 %~ 5%

Anomalous trichromasy

protanomaly1%< / FONT>0.01%

deutanomaly5%0.4%

tritanomalyrarerare

Dichromasy

protanopia1%0.01%

deuteranopia1.5%0.01%

tritanopia0.008%0.008%

Monochromasy

rod monochromasyrarerare

cone monochromasyrarerare

atypical monochromasyvery rarevery rare

Prevalence of congenital colour deficiencies

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Microscope Optical Components - Introduction

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Microscope Optical Components - Introduction


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http://www.olympusmicro.com/primer/anatomy/bx51cutaway.html

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http://www.olympusmicro.com/primer/anatomy/bh2cutaway.html

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http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/PageMill_Resources/PUBLICATIONS/treediag.jpg

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http://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/EVOLUTIONofEYEPIECES.pdf

SOLO OPTICSEyepieces (Oculars)


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Numerical Aperture (NA) = n (sinμ)


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References

OPTICS

1. Waldman, G., Wootton, J., “Electro-Optical Systems Performance Modeling”, Artech House, Boston, London, 1993

2. Wolfe, W.L., Zissis, G.J., “The Infrared Handbook”, IRIA Center, Environmental Research Institute of Michigan, Office of Naval Research, 1978

3. “The Infrared & Electro-Optical Systems Handbook”, Vol. 1-7

4. Spiro, I.J., Schlessinger, M., “The Infrared Technology Fundamentals”, Marcel Dekker, Inc., 1989

http://www.cs.bgu.ac.il/~icbv07/LectureNotes/ICBV-Lecture-Notes-12-Sensing-2-The-Human-Eye-1SPP.pdf


Austin Roorda, PhD, “Optics Waveform”, University of Houston, College of Optometry

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References

Foundation of Geometrical Optics

[3] E.Hecht, A. Zajac, “Optics ”, 3th Ed., Addison Wesley Publishing Company, 1997,

[4] M.V. Klein, T.E. Furtak, “Optics ”, 2nd Ed., John Wiley & Sons, 1986

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References

[1] M. Born, E. Wolf, “Principle of Optics – Electromagnetic Theory of Propagation, Interference and Diffraction of Light”, 6th Ed., Pergamon Press, 1980,

[2] C.C. Davis, “Laser and Electro-Optics”, Cambridge University Press, 1996,

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TechnionIsraeli Institute of Technology

1964 – 1968 BSc EE1968 – 1971 MSc EE

Israeli Air Force1970 – 1974

RAFAELIsraeli Armament Development Authority

1974 – 2013

Stanford University1983 – 1986 PhD AA

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