Diffraction-type displacement detector for alignment of mask and

Details Diffraction-type displacement detector for alignment of mask and Diffraction-type displacement detector for alignment of mask and

1991-01-17

1992-11-03

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

356401, G01N 2186

Patent

active

051608499

ABSTRACT:
A displacement detector comprises a beam irradiation device for irradiating beams almost equal in wavelength on a diffraction grating provided on an object to be measured from two directions different each other, a photoelectric detector for detecting an interference intensity of specific diffracted rays generated from the diffraction grating, and a measuring device for measuring a displacement of the object to be measured with reference to a grating pitch direction of the diffraction grating according to an outgoing signal of the photoelectric detector; the photoelectric detector is equipped with a first photoelectric detector for detecting an interference intensity of diffracted rays of an angle of diffraction running in the said direction from the diffraction grating, and a second photoelectric detector for detecting an interference intensity of diffracted rays different in angle of diffraction running in the same direction from the diffraction grating; the measuring device has a first measuring portion for measuring a value corresponding to a displacement of the object to be measured according to an outgoing signal of the first photoelectric detector, and a second measuring portion for measuring a value corresponding to a displacement of the object to be measured according to an outgoing signal of the second photoelectric detector, outputting at least one mean value of the measured value of the first measuring portion and the measured value of the second measuring portion.

REFERENCES:
patent: 4710026 (1987-12-01), Magome et al.
patent: 4828392 (1989-05-01), Nomura et al.
patent: 4870289 (1989-09-01), Sato et al.

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