The challenges that go into providing accurate and precise measurements larger and from further away.Though well established, stereo measurement is often thought of as unchanging. With measurements such as distance from root, blending profiles, corrosion and area measurements requiring a greater range of measurement and precision, it is essential to understand the evolution of stereo measurement as well as other technologies available. This presentation will focus on the basic types of measurement technologies for videoscopes, and their inherent strength and weaknesses. Reference, Shadow, Stereo, Pattern projection measurement will all be presented. In reference to stereo measurement, recent advances and factors can improve the precision of stereo measurement compared to what existed a decade ago. What goes into the hardware and the software that translate into to a greater precision to perform greater and more reliable measurements during RVI.

1. Getting More Precision in Videoscope Measurements
While Taking Larger Measurements from Farther Away
Charles Janecka
Long Beach, CA — October 27th, 2016

2. • How Stereo Measurement Works
• Applications in Industrial Endoscopy
• Measurement Environment Setup and Accuracy
• Super Wide Stereo
• More Precision From Farther Away
Agenda

3. How Stereo Measurement
Works

4. • 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

5. • 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

6. Applications in Industrial
Endoscopy

7. • 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

8. • A relevant point exists out in the real world.
• This point transmits itself
to two positions on the
CCD chip.
Applications in Industrial Endoscopy

9. • 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.
Applications in Industrial Endoscopy

10. 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
Applications in Industrial Endoscopy

11. Distance
Depth
Point to Line
Measurement point 1 (M1)
Measurement point 2 (M2)
Reference point 1 (R1)
Reference point 2 (R2)
Measurement point (M1)
Reference point 1 (R1)
Reference point 2 (R2)
Measurement point (M1)
Reference point 3 (R3)
Applications in Industrial Endoscopy

12. Lines
Area
Measurement point (M1)
Measurement point (M4)
Measurement point (M3)
Measurement point (M2)
Measurement point (M1)
Measurement point (M4)
Measurement point (M3)
Measurement point (M2)
Measurement
point (M6)
- to close the area
Measurement point (M5)
Applications in Industrial Endoscopy

13. Measurement Environment
Setup and Accuracy

14. 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

15. • 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
Measurement Environment Setup and Accuracy

16. • 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.
Measurement Environment Setup and Accuracy

17. Super Wide Stereo

18. • Greater field of view.
• Deeper depth of field.
• One-to-one matching.
• Multi spot ranging.
Now available
Super Wide Stereo

19. 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

20. a
Super Wide Stereo

21. a
2a
60º
Super Wide Stereo

22. 90º 60º
a
2a
Super Wide Stereo

23. 90º 60º
a
~4 times larger
2a
Super Wide Stereo

24. • 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

25. More Precision From Farther
Away

26. • 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

27. • 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.
More Precision From Farther Away

28. • In this image, the angles stay the same.
• The sides change, respectively.
More Precision From Farther Away

29. • 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.
More Precision From Farther Away

30. • 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.
More Precision From Farther Away

31. • 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.
More Precision From Farther Away

32. • Pixel sizes have gotten so small that new variables have to be considered:
• Lens quality.
• Aperture size.
• Circle of confusion (CoC).
• Airy disk.
More Precision From Farther Away

33. • 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.
More Precision From Farther Away

34. Thank You