Rotational angle detecting device with full circumference illumination and detection

Claim 1

A rotational angle detecting device comprising: a rotatable plate adapted to be attached to a shaft of a rotatable rotor and having a surface including a plurality of windows arranged at a first angular pitch on the entire circumference around the axis of the shaft; a light source for uniformly illuminating all of said windows on said rotatable plate at the same time; a stationary detector plate having a surface opposed to said surface of said rotatable plate, said surface of said detector plate including a first photodetector comprising a plurality of first detecting segments disposed around the entire circumference at a second angular pitch for receiving light from said light source passing through said windows on said rotating plate and for generating a first electrical signal with an amplitude corresponding to the intensity of said received light, and a second photodetector comprising a plurality of second detecting segments disposed around the entire circumference at said second angular pitch for receiving light from said light source passing through said windows on said rotating plate and for generating a second electrical signal with an amplitude corresponding to the intensity of said received light wherein the spacing of said windows and said first and second detecting segments is such that light is completely interrupted by rotation of said disk; a first conductor electrically connecting said first detecting segments in parallel to generate a first combined output signal comprising the sum of each of said first electrical signals; and a second conductor electrically connecting said second detecting segments in parallel to generate a second combined output signal comprising the sum of each of said second electrical signals.