PHOTOELECTRIC TYPE ROTARY ENCODER

PURPOSE:To enhance the S/N value of an optical signal, by respectively providing a blocking film non-forming parts to the incident surfaces and the emitting surfaces of a rotary plate and a fixed plate and forcibly correcting the radial light emitted from a light emitting element to straight light directed to a light receiving element. CONSTITUTION:Blocking films 18, 19 for blocking light are formed to the incident surfaces and the emitting surfaces of a rotary plate 17 and a fixed plate 15 and slit shaped blocking film non-forming parts 20, 21, 22, 23 each comprising three are provided to said plates 17, 15 at the same interval as the arrangement interval of photodiodes 14. By this method, radial light emitted from a light emitting element comes to straight light directed to a light receiving element and reflection between the rotary plate 17 and the fixed plate 15 is eliminated and the light from the light emitting element is passed only through the corresponding blocking film non-forming parts 21, 22 of the rotary plate 17 and the fixed plate 15 and, therefore, the S/N value of an optical signal can be enhanced and the structure can be simplified.