PHOTODETECTOR, ITS USAGE, AND IMAGE FORMING APPARATUS

摘要

PROBLEM TO BE SOLVED: To effectively prevent reductions in detection accuracy through the use of a dual-wavelength beam system to a mode using a lightguide between a light emission part and a light reception part.

SOLUTION: A photodetector for detecting reflected or scattered light from a surface to be measured M is provided with the light emission part 1 for irradiating two types A and B of light of different wavelengths; the light reception part 2 for sensing the two types A and B of light of different wavelengths; and a lightguide member 3 provided between the light emission part 1 and the light reception part 2. The lightguide member 3 is provided with a light transmission path separating means 7 for irradiating only the light of one wavelength A to the surface to be measured M and guiding detection light from the surface to be measured M to the light reception part 2 with the light of the other wavelength B among the two types A and B of light from the light emission part 1.

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