This paper introduces a new measurement system using laser scanning metrology principles, which is a combination of interference encoder optics and small optical scanner. High frequency scanning of laser beam on moving scale creates harmonic signals which contain position information. High through-rate phase detection logic using PLL (Phase-Locked Loop) decodes the signals to produce position information up to 7.6pm LSB from 4 micro meter pitch grating scale. The entire signal processing logic is implemented on one FPGA chip, which also keeps the cost of the system low.
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