Position detection apparatus

Details Position detection apparatus Position detection apparatus

1990-12-17

1992-07-28

Turner, Samuel A.

Optics: measuring and testing

By particle light scattering

With photocell detection

356356, 356363, G01B 902

Patent

active

RE0340103

ABSTRACT:
An apparatus includes a means for providing a predetermined frequency difference between two light beams and generating an optical beat with respect to interference between first and second diffracted light beams from a diffraction grating formed on a substrate, and a means for detecting a phase difference between the optical beat and a reference signal having a frequency corresponding to the frequency difference between the two light beams, and detects a position of the substrate based upon the phase difference in accordance with an optical heterodyne interference method.

REFERENCES:
patent: 3891321 (1975-06-01), Hock
patent: 4558952 (1985-12-01), Kulesh et al.
patent: 4636077 (1987-01-01), Nomura et al.

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