Abstract: An optical encoder apparatus is disclosed comprising a light source, a lens for focusing and collimating light emitted from the light source, a cap for receiving and aligning the light source and the lens, a scale movable relative to the cap including alternating opaque and translucent regions for blocking and transmitting light emitted from the light source, an array of a plurality of photodiodes for converting light emitted from the light source into electrical signals, a mask mounted in a fixed position between the scale and the photo transducer array, including in the mask alternating opaque and translucent regions arranged to act in concert with the movable scale to modulate the light received by the photo transducers, a mounting post for mounting the optical encoder apparatus, a receptor for attaching to the cap including a deck for receiving and aligning the photo transducer array, and including a cavity for receiving the mounting post, and a clamp for securing the receptor, and therefore the optical e

Abstract: In an optical encoder with a single light source, an array of a plurality of spaced photodetectors formed on a common substrate, a reticle disposed in fixed position relative to said photodetector array, and a scale of alternating translucent and opaque regions relatively moveable between said light source and said reticle so as to cause said array to provide a plurality of phase related analog signals whose amplitudes vary with the position of said scale, an improved digital automatic gain control is disclosed. A digital switch selects one of said analog signals and an analog to digital converter converts and puts out the selected signal as a digital value. A programmed microprocessor reads each such digitized signal, determines the signal value corresponding to maximum light transmission, compares said value with a nominal reference value, and computes a correction value therefrom.