Increment sensing with three beam mark detection

Claim 1

In a device for digital control of a machine or movable equipment part under utilization of a drive asociated with an optical electronic increment sensor, the improvement comprising: a plurality of parallel track defining means with each track being defined by alternately translucent or transparent and opaque incremental marking sections; means defining a corresponding plurality of groups of three separate beams each, the beam of each group traversing one of each said of the increment track means, two beams of each group being close to opposite outer borders of the respective track marking and a third one of the group of beams traverses the respective center of that track; said beams of any of said groups being arranged so that projections of the beams of the respective group into a plane of the respective track result in scanning dots being arranged along a line having an oblique angle in relation to the direction of extension of the respective track marking sections; three beam combining means, respectively (i) combining the beams of all groups having traversed one border of each marking of the plurality of tracks (ii) combining the beams of all groups having traversed another border of each said marking of the plurality of tracks; and (iii) combining all beams of the groups having traversed the respective track centers; and pickup means for separately detecting illumination from the three beams as modulated by said marker tracks and as combined as per (i), (ii), and (iii) and providing separate electrical signals respectively representing passage of one border of all tracks, of another border of all tracks, and of the center of all tracks.