CVP BASIC VISION EXAM COMBINED
PRACTICE QUESTIONS AND DETAILED
SOLUTIONS
◉ Geometric Pattern Matching.
Answer: -relies on edges and geometric features in the image for
matching
-very tolerant to: occulation(hidden), scale changes, non-uniform
lighting, background changes
◉ Aspect Ratio.
Answer: -ration of an images width to its height
-commonly expressed as two numbers separated bya colon, like 16.9
-for x:y, x-units wide and y-units high
◉ LVDS interface.
Answer: -low-voltage differential signaling
-way to communicate data using a small voltage swing
-offers very high rates - 1 Gb/s speeds - at very low power
,◉ Perspective error, Parallax.
Answer: -change in magnification with a change in working distance
-how we perceive distance with our eyes
-objects that are far away seem smallar than closer objects
-useful for perceiving distance, harmful when trying to make
measurements
◉ What specification of a lens helps me determine FOV?.
Answer: -Focal Length:
-Angular FOV:
-Magnification:
◉ Non-specular Light.
Answer: -diffuse light
-reflects light diffusly and evenly over the hemisphere surrounding
the reflective surface
◉ What are the limitations imposed by using a circular bright field
ring light geometry?.
Answer: -limited only to intensity needed on part
-not good on reflective parts or objects
,◉ What are the limitations imposed by using a circular dark field
ring light geometry?.
Answer: -light must be very close to part
-large footprint
-limited spot size
-ambient light may interfere
◉ Histogram Equalization (imaging processing).
Answer: -example of a look-up table
-alters gray scale values of pixels so that they become evenly
distributed across the full grayscale range
-associates an equal number of pixels per a constant grayscale
interval
-essentially changing the contrast of the image without altering the
spatial arrangement of pixels, meaning the overall structure of the
image (like edges and shapes) remains the same, but the intensity
values of each pixel are adjusted to create a more even distribution
across the intensity range, making details more visible in low-
contrast areas
◉ FOV calculation with fixed magnification:.
Answer: FOV = sensor size/PMAG
, ◉ A lenses ability to reproduce contrast for a given resolution is
controlled by what?.
Answer: theoretical limitations associated with laws of physics, the
actual design of the lens, and the the actual manufacturing of the
lens
◉ Gain.
Answer: -amplifies analog signal from pixel before conversion
--Pro: higher grayscale level (brighter)
--Con: introduces noise (6db gain = 2x noise)
-increases visibility of both signal and noise
-should only be used as a last resort to increase brightness
◉ Exposure Time.
Answer: -length of time that the sensor is open for collecting light.
Also, known as shutter speed and integration time.
-considerations:
--frame rate may be reduced with increase
--motion blur is greater with increase
--SNR is greatly increased with more exposure
◉ Quantization Noise.
Answer: -errors coming from the A/D conversion process
PRACTICE QUESTIONS AND DETAILED
SOLUTIONS
◉ Geometric Pattern Matching.
Answer: -relies on edges and geometric features in the image for
matching
-very tolerant to: occulation(hidden), scale changes, non-uniform
lighting, background changes
◉ Aspect Ratio.
Answer: -ration of an images width to its height
-commonly expressed as two numbers separated bya colon, like 16.9
-for x:y, x-units wide and y-units high
◉ LVDS interface.
Answer: -low-voltage differential signaling
-way to communicate data using a small voltage swing
-offers very high rates - 1 Gb/s speeds - at very low power
,◉ Perspective error, Parallax.
Answer: -change in magnification with a change in working distance
-how we perceive distance with our eyes
-objects that are far away seem smallar than closer objects
-useful for perceiving distance, harmful when trying to make
measurements
◉ What specification of a lens helps me determine FOV?.
Answer: -Focal Length:
-Angular FOV:
-Magnification:
◉ Non-specular Light.
Answer: -diffuse light
-reflects light diffusly and evenly over the hemisphere surrounding
the reflective surface
◉ What are the limitations imposed by using a circular bright field
ring light geometry?.
Answer: -limited only to intensity needed on part
-not good on reflective parts or objects
,◉ What are the limitations imposed by using a circular dark field
ring light geometry?.
Answer: -light must be very close to part
-large footprint
-limited spot size
-ambient light may interfere
◉ Histogram Equalization (imaging processing).
Answer: -example of a look-up table
-alters gray scale values of pixels so that they become evenly
distributed across the full grayscale range
-associates an equal number of pixels per a constant grayscale
interval
-essentially changing the contrast of the image without altering the
spatial arrangement of pixels, meaning the overall structure of the
image (like edges and shapes) remains the same, but the intensity
values of each pixel are adjusted to create a more even distribution
across the intensity range, making details more visible in low-
contrast areas
◉ FOV calculation with fixed magnification:.
Answer: FOV = sensor size/PMAG
, ◉ A lenses ability to reproduce contrast for a given resolution is
controlled by what?.
Answer: theoretical limitations associated with laws of physics, the
actual design of the lens, and the the actual manufacturing of the
lens
◉ Gain.
Answer: -amplifies analog signal from pixel before conversion
--Pro: higher grayscale level (brighter)
--Con: introduces noise (6db gain = 2x noise)
-increases visibility of both signal and noise
-should only be used as a last resort to increase brightness
◉ Exposure Time.
Answer: -length of time that the sensor is open for collecting light.
Also, known as shutter speed and integration time.
-considerations:
--frame rate may be reduced with increase
--motion blur is greater with increase
--SNR is greatly increased with more exposure
◉ Quantization Noise.
Answer: -errors coming from the A/D conversion process
