Photoelectric shaft angle encoder

Claim 1

A SHAFT ANGLE ENCODING SYSTEM COMPRISING CODE TRACK MEANS, ILLUMINATION MEANS FOR DIRECTING RADIATION TO SAID TRACK MEANS, TWO PHOTOCELL MEANS DIRECTED RESPECTIVELY TOWARD TWO SPACED POSITIONS OF SAID TRACK MEANS, SAID TRACK MEANS HAVING FIRST REGIONS FOR DIRECTING RADIATION TO SAID PHOTOCELL MEANS AND SECOND REGIONS FOR OBSCURING RADIATION FROM SAID PHOTOCELL MEANS, SAID FIRST REGIONS AND SAID SECOND REGIONS BEING ALTERNATELY SEQUENCED, ADJOINING ONES OF SAID FIRST MEANS AND SAID SECOND MEANS CONSTITUTING ANALOGOUS CYCLES, SAID TRACK MEANS AND SAID TWO PHOTOCELL MEANS BEING CONSTRAINED FOR RELATIVE MOTION INTO A SEQUENCE OF RELATIVE ANALOG POSITIONS, SAID SPACED POSITIONS OF SAID TRACK BEING 90* OUT-OF-PHASE IN TERMS OF SAID CYCLES SO THAT SAID TWO PHOTOCELL MEANS PRODUCE TWO SIGNALS REPRESENTING OUT-OF-PHASE VECTORS FOR SAID SEQUENCE OF RELATIVE ANALOG POSITIONS, A PHASE DIVIDING CIRCUIT A SEQUENCE OF IMPEDANCES, SAID TWO SIGNALS BEING APPLIED TO SAID SEQUENCE OF IMPEDANCES, A PLURALITY OF TAPS BETWEEN ADJACENT IMPEDANCES OF SAID SEQUENCE, A PLURALITY OF SIGNALS OF DIFFERING PHASE APPEARING AT SAID TAPS, PHASE RESPONSIVE MEANS FOR PRODUCING DIGITAL SIGNALS REPRESENTING SAID SIGNALS OF DIFFERING PHASE AND FLIP-FLOP OUTPUT MEANS FOR GENERATING AN INDICATION OF ONE OF SAID DIGITAL SIGNALS FOR ONE OF SAID RELATIVE ANALOG POSITIONS.