From what I've seen in spec sheets for modern color sensors (as of late 2020), the optimum sensing range is generally on the scale of centimeters. I am curious about the physics that can explain this limitation. Does it have to do with ambient light saturating the photocells/diodes/transistors on the sensor?

For example, if I wanted to sense the color of an object passing no closer than 5 feet away from the receiver in a well-lit environment, what sort of problems would I run into on the sensor output? Would anything change if the object was in a poorly-lit environment?

For the sake of the argument, let's assume I cannot use a camera or image processor for my application.

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    \$\begingroup\$ The issue isn't so much what sensor you use, but if you construct a suitable optical path and put enough light on the sensor. Note that the root of "camera" is actual "chamber" - the word is really about the optical setup, not the film or semiconductor sensor. Build an artist's "camera obscura" (perhaps with actual optics) put the sensor in the right place on the image wall... \$\endgroup\$ – Chris Stratton Nov 12 '20 at 20:22
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    \$\begingroup\$ With the right lens, I'm sure that distance can be modified. \$\endgroup\$ – Reinderien Nov 12 '20 at 20:41
  • \$\begingroup\$ With a big enough lens you can be as far away as you like. Telescopes look at other planets for example. \$\endgroup\$ – user1850479 Nov 12 '20 at 20:46
  • \$\begingroup\$ A typical color sensor, like the VEML6040, has a field of view of 110 degrees. So an object 5 feet away would have to be roughly 10 feet in diameter to be seen well. A large dimly lit object could still be seen if no bright objects were within the FOV. A smaller object could be seen well if it was brighter than the surrounding view. With optics you can make the FOV much smaller. \$\endgroup\$ – Mattman944 Nov 12 '20 at 23:09
  • \$\begingroup\$ @Mattman944 The field of view is more related to how the board-level component is integrated into the grand scheme sensor, correct? As I've been looking at spec sheets, I've noticed that for chips such as the VEML6040, manufacturers don't mention specs like optimum range or FoV, while manufacturers for most integrated color sensors like the O5C500 (can be found on automation24.com) will point them out. Seeing the comments here, I imagine this is because the integrated sensors have lenses. \$\endgroup\$ – John Nov 13 '20 at 14:57

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