To miniaturize various kinds of optical sensors, etc., by installing a diffraction grating or an optical axis converting element such as a prism on the light-receiving side, equipped with a light-receiving lens and a light-receiving element, to optical-axis- convert and receive reflected light from an object to be detected.
The zero order and ± 1st order diffracted lights of outgoing infrared light have an angle of 37° with each other, and are reflected by an object at a detecting point. Light-receiving beams 32b and 32c on both sides of reflected light are incident on a light-receiving side diffraction grating 31 at an angle of 37° to a light-receiving lens 30, to have an angle of 13° by optical axis conversion to be incident on the light- receiving lens 30, and then are focused to light-receiving elements 29b and 29c on both sides. Concurrently, the center light-receiving beam 32a goes straight on to be condensed into a light-receiving element 29a. This narrows a light-receiving visual field angle in the light-receiving lens 30 to reduce off-axis aberration, thereby allowing the smallness of the light-receiving elents 29a-29c, also arranging them on the same plane.
AOYAMA SHIGERU
ITO YOSHINORI
SHINOHARA MASAYUKI
