JPS5618715A - Error-compensated encoder - Google Patents

Abstract

PURPOSE: To accurately compensate for the cumulative error of a scale at a low cost, by adding only small number of electronic units to a linear encoder.

CONSTITUTION: A glass-made scale 1, which has stripes at a regular spacing, is movably supported. The movement of the scale is detected by a displacement detector 2 which changes the movement into electric signals S1, S2. The outputs of the detector 2 are applied to a resistance divider 3. The output of the divider is applied to a semiconductor switch 5. The divider 3 and the switch 5 constitute a phase shifter. When signals D1, D2 from a computer 9 are varied, the phases of the outputs S4, S5 of the shifter change depending on the inputs S1, S2. The outputs S4, S5 are converted into rectangular waves by a trigger circuit 6. The rectangular waves are changed into a train of pulses by a pulse generation circuit 7. The pulses are counted by a counter circuit 8. The movement of the scale 1 can thus be converted into a digital value. The computer 9 operates the digital value to vary the signals D1, D2 to compensate for an error.

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