PURPOSE: To prevent the lowering of detection accuracy of positions and angles free from the leakage of light by arranging a plurality of photodetecting surfaces while the portion excluding the photodetecting surface in shielded from light.
CONSTITUTION: A non-photodetecting part 145 excluding the first photodetecting surface 141 to the fourth photodetecting surface 144 of a photodetector 14 is shielded from light with an aluminum-deposited film. As a result, when a light emitting part uses a relatively large light source, light passing through a slit and entering the non-photodetecting part 145 is prevented from affecting a photoelectric conversion output. Hence, a differential signal of output of a first differential amplifier, namely, outputs of the photodetecting surfaces 141 and 143 not lowered in output. And, an output as a result of a threshold processing with a first comparator, namely, a digital signal (a) is outputted stably without being affected by noises. Likewise, a digital signal (b) to be obtained from a differential signal of the outputs of the photodetecting surfaces 142 and 144 is outputted stably without being affected by noises.
TAKAMOTO KENJI
ITO MASAYA
FUKUI KOJI
MURAKAMI HIROSHI
