| 摘要 |
A laser interferometer measuring system generates a series of digital output quadrature pulses corresponding to movement of a retroreflector 18. The output pulses are intended for receipt by a master counter containing an incremental count corresponding to displacement of the retroreflector 18. Errors present in the output pulses due to environmental or geometrical error sources in the interferometer may be compensated for by scaling the output pulses in accordance with a correction factor K. The output pulses are stored in a first counter 30, 130; a series of secondary pulses, being either the output pulses as scaled, or independently generated by a signal generator 200, are sent both to the master counter and a second counter 80, 180. A processor 50, 150 continually monitors the value of the second counter, and compares this with an actual value of displacement, equal to the product of the correction factor and the instantaneous value of the first counter. The frequency of secondary pulses transmitted to the master counter and the second counter is continually controlled by the processor in order to equalize the value of the second counter with the actual displacement value.
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