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It would be great if light detectors were made small enough to put close together. But say...
I seem to recall that your everyday computer scanner uses a row of infinitesimal light sensors.
Suppose you break off about a 3/8 inch long segment?
Hook up each individual sensor. Or every other one. Or every third one. Whatever suits your resolution requirements.
Shine a light down on the detector row. The light should be a point source.
Lay the pencil crosswise.
The number of dark sensors tells you the diameter of the pencil.
If you don't want to hook up all the detectors individually, you might hook up only the ones near the expected dimensions of the pencil.
Or wire them in an additive way to give an analog reading of voltage/ current. The more detectors darkened, the lower the voltage. Etc.
I seem to recall that your everyday computer scanner uses a row of infinitesimal light sensors.
Suppose you break off about a 3/8 inch long segment?
Hook up each individual sensor. Or every other one. Or every third one. Whatever suits your resolution requirements.
Shine a light down on the detector row. The light should be a point source.
Lay the pencil crosswise.
The number of dark sensors tells you the diameter of the pencil.
If you don't want to hook up all the detectors individually, you might hook up only the ones near the expected dimensions of the pencil.
Or wire them in an additive way to give an analog reading of voltage/ current. The more detectors darkened, the lower the voltage. Etc.
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