Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1992-12-02
1999-01-19
McGraw, Vincent P.
Optics: measuring and testing
By particle light scattering
With photocell detection
356237, G01B 902, G01N 2188
Patent
active
058619526
ABSTRACT:
A light source portion having an acousto-optic element produces a laser beam of two light components having a frequency difference .DELTA.w and having registered polarization directions. The laser beam is subsequently divided by a half mirror. One of the divided laser beams is detected by a photoelectric detector as reference light, and a corresponding signal is applied to a synchronism detector. The other laser beam is projected by a scanning optical system to the surface of, e.g., an original to be examined to scan the same. At the position on the surface irradiated by the scanning light spot, the laser beam is modulated at a beat frequency .DELTA.w on the basis of optical heterodyne interference. A synchronism detector detects a signal corresponding to the scattered light from a particle or defect on the surface being examined, in synchronism with the frequency of the reference light, whereby the particle or defect can be detected with a good signal-to-noise ratio.
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Miyazaki Kyoichi
Nose Noriyuki
Takeuchi Seiji
Tsuji Toshihiko
Yoshii Minoru
Canon Kabushiki Kaisha
McGraw Vincent P.
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