Cognex In-Sight 7600, Reference Manual

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Appendix
Mechanical Vignetting
All lenses are designed to cover a certain “image circle” size, which can be found in the lens manufacturer’s
specification. The image circle size is the diameter of the optical image the lens can produce. If a vision system has 2/3”
image sensor, you must use a lens that produces at least a 2/3” image circle.
Otherwise, the lens optics will not cover the image sensor, resulting in dark corners. The mismatch of image circle to
image sensor size is one cause of mechanical vignetting.
The In-Sight 7905 vision system has a 2/3” image sensor. The S-Mount/M12 lenses used in the autofocus module (ISAF-
7000-8mm) and the S-Mount/M12 adapter kit (ISLN-7000-SMNT) have a smaller image circle. Therefore, these S-Mount
lenses will cause mechanical vignetting when used with the In-Sight 7905 vision system, and the corners of the image
will be cropped to the size of the lens.
Here is an example of mechanical vignetting when using the In-Sight 7905 vision system with an 8mm S-Mount/M12
lens at a 100mm working distance:
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Appendix