Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1998-08-12
1999-12-28
Turner, Samuel A.
Optics: measuring and testing
By particle light scattering
With photocell detection
356360, G01B 902
Patent
active
060089016
ABSTRACT:
A shape measuring apparatus of this invention includes a light source for generating light beams including two different frequency components, a first optical system for extracting a reference signal from the light beams including the two frequency components, a second optical system for reflecting one of the light beams including the two frequency components by a reference surface, reflecting the other light beam by a measuring region of a surface to be measured, and causing the two reflected light beams to interfere with each other, a photodetector having a plurality of photodetecting elements to detect the interference light beam from the optical system, a housing for holding at least a part of the optical system and the photodetector, an actuator for changing a relative position of the housing and the surface to be measured, and a length measuring device for detecting position information of the housing. An element corresponding to a light beam vertically reflected by the surface to be measured is selected from the photodetector. A measured signal is detected by adding output signals from the selected element and neighboring elements thereof. A distance between the housing and the surface to be measured is controlled in an optical axis direction such that a phase difference between the reference signal and the measured signal is held constant. A shape of the surface to be measured is measured from position information of the housing when the relative position of the housing and the surface to be measured is changed in a direction perpendicular to the optical axis.
REFERENCES:
patent: 4611916 (1986-09-01), Yoshizumi
patent: 4776699 (1988-10-01), Yoshizumi
patent: 4886362 (1989-12-01), Oono
patent: 5485275 (1996-01-01), Ohtsuka
Yoshizumi, K. et al., "Precise Measuring System For Aspheric Surfaces," Optics, vol. 12, No. 6, pp 450-454 (Dec. 1983).
Canon Kabushiki Kaisha
Turner Samuel A.
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