Importance

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Abstract

An optical encoder for producing an electrical signal representative of the angular position and velocity of a rotatable shaft. A flexible code disk, which is coupled to the shaft via a hub portion, has a plurality of slots located adjacent its outer rim, for alternately blocking and permitting transmission of a light beam to each of a plurality of separate photocells, as the disk is rotated. The rim of the disc is disposed in a special low-friction seat, whereby the slots are maintained in proper alignment with the photocells, even though the shaft may have a slight angular misalignment relative to the encoder. The photocells are formed on a common silicon substrate that has a single diffusion layer, and the electrical outputs of separate photocells are connected in a push-pull circuit arrangement. This produces an electrical signal whose successive zero crossings are an accurate representation of the angular position of the rotatable shaft, regardless of variations in the intensity of the light beam or irregularities in the transducing sensitivities of the photocells. Additionally, the encoder has a control loop that includes a separate photocell segment formed on the same common silicon substrate, for regulating the intensity of the light beam so as to produce a constant peak voltage level for the electrical signal output.

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First Claim