スキャン光学エンコーダに関する一研究 : −レーザ干渉によるスキャン光学系と位相同期検波による高分解能位置センサ−

概要

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Optical encoders are widely used in precision positioning machines today. However its resolution is limited by the optical grating pitch. In order to achieve a resolution of under 1nm, we have to use very small pitch grating which is made by special tools such as a hologram machine. This high resolution grating increases the encoder cost and complicates the installation procedure. Then this paper introduces a new low-cost measurement system with improved sensor stability and easy installation, using scanning metrology principles, which is a combination of interference laser encoder optics and small optical scanner. High frequency scanning of interference laser on moving scale creates harmonic signals which contain position information. High bandwidth phase detection logic using PLL developed by NanoWave Inc. decodes the signals to produce position information up to 7.6pm resolution 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. Furthermore, its relatively long grating pitch also realizes great robustness and provides easy installation in high precision sensing unit.
社団法人精密工学会の論文