Tohoku University Technology: Absolute position measurement device and measurement method: T18-501

High resolution and high accuracy absolute position measurement using diffracted light

Optical linear encoder is used as high accuracy displacement sensor for semiconductor manufacturing equipment and various absolute position detection methods have been implemented. However, complex micro-pattern combinations and detection opticsare necessary. For this purpose, an optical single-axis encoder thatuses white light source and diffraction grating with unequal tickspacing is proposed to detect the absolute position based on the spectrum of the analyzer. However, the rotational motion error of thegrating affects the position detection. 　The present invention is able to provide an optical absolute positionmeasurement device and method with high resolution and accuracyin single or double axis by analyzing the spectrum of a diffractedbunch light. An unequal spaced grating is provided to incident thebunch white light, and the absolute position is detected from the peakwavelengths detected on the optical spectrum of the analyzer.

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