Abstract
Optical heterodyne interferometry is a new interference technique, allowing quick and accurate measurements of dimension. A similar technique can determine the fringe phase of the moiré method as intensity is modulated by movement of the reference grating. The phase difference between certain points in the moiré pattern is detected automatically. The interference fringes generated by laser are used to measure straightness. Small displacement of fringes is detected with the heterodyne moiré method. Generally, beam flutter caused by air disturbance becomes a serious problem in systems using long beam paths, though it can be reduced by controlling the air flow.
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