Staas & Halsey
Optical encoder with offset adjusting means
An optical encoder, having an offset adjustment function for causing light receiving element outputs to have the same direct current component level, and capable of greatly reducing an adverse affection by noise, to thereby generate an accurate position signal. A combined signal (i10), generated in a third electric current mirror circuit (T17-T19) for receiving output currents (ia11, ia12) from light receiving elements (A11, A12) through first and second electric current mirror circuits (T11-T13, T14-T16) and serving as a feedback signal (i10', i10") for eliminating an offset between direct current components of the output currents of the light receiving elements, is superimposed through a variable resistor (VRa1) on these output currents. The light receiving element outputs, free from a direct current component offset and delivered through the first and second electric current mirror circuits, are converted into voltages by means of resistors (R11, R12) having the same resistance with each other, and are applied to a comparator (Ca1), whereby an accurate position signal (Pa1) is generated.
Fanuc Ltd.
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Mitsuyuki Hirofumi
Taniguchi Kikuchi