Opto-electronic scale reading apparatus having an array of elongate photo-sensitive elements and a periodic light pattern

摘要

Opto-electronic linear encoding apparatus includes a scale and a readhead movable relative to the scale in a direction of spacing of the scale lines. The readhead is formed of a single semi-conductor substrate, typically made of gallium arsenide. The substrate is divided into two regions, the first region including a light emitting diode having a plurality of elongate electrodes provided on its upper surface and spaced in the direction of spacing of the scale lines. The light emitting diode region, the elongate electrodes and the substrate cooperate to produce a plurality of coplanar elongate light emitting regions between the elongate electrodes which perform the combined functions of a diffused light source and an index grating. The second region is an analyzer having a plurality of elongate photosensitive elements spaced apart in the direction of spacing of the scale lines. The photosensitive elements are divided into a plurality of sets and are interleaved on the substrate in a repeating pattern with the outputs of elements of a given set being connected in common. The analyzer thus performs the combined functions of an analyzer grating and a plurality of photodetectors which generate a plurality of phase-shifted cyclically varying signals.