| 摘要 |
PROBLEM TO BE SOLVED: To obtain A/B pulse signal which linearly interpolates the amount of travel (length) of a scale, independently of level fluctuations. SOLUTION: An A-phase signal and a B-phase signal, indicating the length of travel of a main scale 2, are supplied to a digital preprocessing circuit 10, are sampled at a prescribed clock period which interpolates the inside of one pitch of a scale, and are each converted into digital signals. The digitized A- phase signal and the B-phase signal are supplied for a B/A ratio computing part 22 via a digital filter 21, and the computed value D2 of the division result of B/A is output. Output pattern data (D3 and D4) of binary values (1, 0) are read from an A/B phase pattern table 24 by the computed value for each sampling and output data (D0 and D1) from a quadrant-verifying part 23. The output pattern data D3 and D4 is outputted from an output buffer 25 as an A-phase pulse signal and a B-phase pulse signal for interpolating one pitch to become movement information, when the scale has moved.
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