Photoelectrical encoder employing an optical grating

Claim 1

A photoelectrical encoder employing optical gratings wherein a physical quantity is detected from brightness obtained by moving a first and a second scale each provided thereon with an optical grating relative to each other, characterized in that said first scale is constructed such that narrow belt-shaped reflecting portions and unreflecting portions are alternately arranged on a base member, said second scale is constructed such that, on a light transmitting base member, a first signal lead-out material layer made of a light shielding conductive material, a PN semiconductor layer for converting light into electricity and a second signal lead-out material layer made of a light transmitting conductive material are laminated in the described order to form a narrow belt-shaped light receiving portion and a plurality of narrow belt-shaped light receiving portions thus formed are arranged at regular pitches, as against the light from said light transmitting base member, said light receiving portions function as light shielding slits and intervals between the light receiving portions are formed into light transmitting slits, a light source is fixed to the light transmitting base member on the side opposite said light receiving portions and a reflector is fixed to the light transmitting base member for reflecting the light from said light source and radiating the light through the light transmitting base member to the side opposite the light source, said first and second scales are disposed in such a manner that said light reflecting portions and said light receiving portions face each other, and the light from said light source is adapted to be transmitted through said light transmitting slits of said second scale and radiated onto reflecting portions of said first scale.