getting more precision in videoscope measurements while taking larger measurements from farther away

Getting More Precision in Videoscope Measurements

While Taking Larger Measurements from Farther Away

Charles Janecka

Long Beach, CA — October 27th, 2016

• How Stereo Measurement Works

• Applications in Industrial Endoscopy

• Measurement Environment Setup and Accuracy

• Super Wide Stereo

• More Precision From Farther Away

Agenda

How Stereo Measurement

Works

• Parallax is the apparent change in position of an object from two vantage points.

• Human vision and environmental interaction is based on this parallax.

How Stereo Measurement Works

• Lateral shift is inversely proportional to the distance from the viewer.

• While driving down a road, nearby fencing and trees move by quicker than the

mountains in the background.

• Our ability to determine distance and depth rely on having two eyes. Stereo

measurement uses two separate lenses for the same ability.

• Using the premise that lateral shift is inversely proportional to distance, we can use

this concept for stereo measurement.

How Stereo Measurement Works

Applications in Industrial

Endoscopy

• The lenses are offset from each

other a known distance.

• The brain is replaced by a CCD chip and processor.

• The eyes are replaced by dual lensing in a tip adaptor.

• The dual lensing creates

two images onto the CCD.

Applications in Industrial Endoscopy

• A relevant point exists out in the real world.

• This point transmits itself

to two positions on the

CCD chip.


• A relevant point exists out in the real world.

• This point transmits itself

to two positions on the

CCD chip.

• The user picks one point and

the scope picks the same point

on the other image.

• These points correlate to

physical pixels on the CCD chip.

• Knowing this pixel location and the physical

locations of the lenses, the videoscope calculates

the distance to the point.


There are many standards that dictate the allowable size of defects in certain

industries. With stereo measurement, the size of defects, such as the one shown

below, can be determined.

• Cracks

• Dents

• Pitting

• Corrosion

• Material lift

• Missing material

• Many more


Distance

Depth

Point to Line

Measurement point 1 (M1)

Measurement point 2 (M2)

Reference point 1 (R1)

Reference point 2 (R2)Measurement point (M1)



Measurement point (M1)



Lines

Area








Measurement point (M2)Measurement

point (M6)

- to close the area



Measurement Environment

Setup and Accuracy

The location of the lenses must be known to

precisely and accurately utilize the parallax.

The line of sight used for the parallax originates at the matched points on the CCD. They go

through the center of the lenses.

Measurement Environment Setup and Accuracy

• Even with the most advanced lens manufacturing and assembly techniques,

variances occur.

• These variances are miniscule, but have

potentially large effects on the

measurement result.

• Both the location and rotational value

must be known. x

y

z

γ

α

β


• The alignment and assembly of the CCD chip is also never perfect.

• The more precise stereo becomes, the more pronounced these differences will

be.

• One-to-one matching is performed to align individual tips to the chip.


Super Wide Stereo

• Greater field of view.

• Deeper depth of field.

• One-to-one matching.

• Multi spot ranging.

Now available

Super Wide Stereo

The range of measurable distance has increased.

• Previous standard

• 0.2 in. to 1.2 in. (5 mm to 30 mm)

• New standard

• 0.15 in. to 2.4 in. (4 mm to 60 mm)

• Field of view has increased 1.5X.

• Depth of field has increased 1.7X.a

2a

60º • The effect is a 4X wider measurement area.

Super Wide Stereo

a

Super Wide Stereo

a

2a

60º

Super Wide Stereo

90º 60º

a

2a

Super Wide Stereo

90º 60º

a

~4 times larger2a

Super Wide Stereo

• Larger defects can be measured.

• Defects previously could not be measured now can.

• Base to crack

• Measuring from twice as far makes it easier for the user.

• Two steps in taking measurement images:

• Find the defect.

• Get close enough and aligned for a proper image.

Super Wide Stereo

More Precision From Farther

Away

• Stereo measurement by way of parallax fundamentally relies on the selection of

two pixels.

• One pixel will be chosen by the user and the other by the videoscope.

• This correlates to two physical locations on the CCD.

More Precision From Farther Away

• The locations on the CCD relate to the difference in the angles of incidence at the

lensing.

• The videoscope uses many values, including:

• Position of lenses relative to each other.

• Position of lenses relative to the CCD.

• Rotational position of the lenses and the CCD relative to each other.

• Angle of line at the lens given by parallax.

• The angle of the parallax line is the only one that changes.

• Once these angles are known, all other values can be calculated to determine object

size so that it can be measured.


• In this image, the angles stay the same.

• The sides change, respectively.


• This creates a situation to be mitigated.

• Farther away means the error is bigger.

• Just like the angle, the error has not changed with

the triangle.

• There are two ways

to compensate.


• The first way is to calibrate the individual tip to the actual CCD.

• One-to-one matching reduces the error caused by miniscule variances in

assembly and manufacturing.


• The second way is to pick a better pixel.

• The margin of error increases as the resolution goes down.

• Resolution means more than the number of pixels on a chip.


• Pixel sizes have gotten so small that new variables have to be considered:

• Lens quality.

• Aperture size.

• Circle of confusion (CoC).

• Airy disk.


• Higher resolution imaging has pushed the physical bounds of what is possible.

• This has forced a dramatic redesign in optical systems.

• We now have smaller pixels, but we can also use them.

• This all equates to stereo measurements with smaller margins of error that are

also easier to take.


Thank You

getting more precision in videoscope measurements while taking larger measurements from farther away

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