Photoelectric conversion type rotational position detector

A photoelectric conversion-type rotational position indicator for indicating the rotational position of a rotating body measuring light received from a fixed disposed light emitting member, comprising:

• a light receiving member fixedly disposed opposite the light emitting member, said light receiving member including m.times.n identically shaped light receiving portions made from a photoelectric converting material at predetermined spacings on the light receiving member, to generate n sinusoidal signals (360/(m.times.n)) degrees out of phase from each other, where m is a positive, non-zero integer equal to the number of sinusoidal signal cycles generated per revolution of a light shielding member, and n is a positive, non-zero integer equal to the number of phase separated sinusoidal signals to be generated by the light receiving portions, the identically shaped light receiving portions being disposed between a first set of two concentric circles having radii r.sub.1 and r.sub.2 on the light receiving member and divided circumferentially therein, the first set of circles being coaxial with the light receiving member;
• a light shielding member coaxially interposed between the light emitting member and said light receiving member and being operably connected to the rotating body such that the light shielding member rotates with the rotating body,
• the light shielding member having m windows disposed in a region between a second set of two concentric circles having radii r.sub.3 and r.sub.4, such that r.sub.1 .gtoreq.r.sub.3 >r.sub.2 .ltoreq.r.sub.4, the second set of circles being coaxial with the light shielding member, the windows not being superimposed upon one another when viewed in a radial direction from the center of the light shielding member,
• each of the windows being shaped with an inner curve and an outer curve such that the visible area of each light receiving portion through each of the windows varies in a sinusoidal form of one cycle as the light shielding member rotates through (2360/M) degrees;
• and,
• means for obtaining the phase separated sinusoidal signals by connecting n groups of m light receiving portions in parallel or series.