System for detecting defects on an optical surface

Details System for detecting defects on an optical surface System for detecting defects on an optical surface

1982-03-29

1985-03-19

Thomas, James D.

Optics: measuring and testing

Inspection of flaws or impurities

Having predetermined light transmission regions

73432L, 356371, 364507, 364525, G01N 2132, G06F 1520, G01B 1130

Patent

active

045055858

ABSTRACT:
In a system for detecting defects on an optical surface, a disk to be inspected is mounted on a turntable, and is attracted on the surface of the turntable. On the disk is provided an optical head having an objective lens located at its focal point on the surface of the disk. A laser beam emitted from a laser unit is projected through the optical head onto the disk, is reflected on the disk, and is then directed through the optical head to a photo detector. The optical head is moved in the radial direction of the disk as the turntable is rotated, and the disk is helically scanned by the laser beam. Only a defect signal is extracted from an electrical signal generated from the photo detector in a defect signal generator. The defect signal is compared in a data processing unit, and is converted to defect information of different size. When it is judged that a prescribed region on the surface of the disk is scanned by a position signal from a position sensor for detecting the position of the optical head, the data processing unit generates an address, and the defect information is stored in each size in specific assigned locations of the RAM. The defect information thus stored is displayed on a CRT or is printed out by a printer.

REFERENCES:
patent: 3302786 (1967-02-01), Conrad
patent: 3670153 (1972-06-01), Rempert et al.
patent: 4177539 (1978-09-01), Bell et al.
patent: 4247203 (1981-01-01), Levy et al.
patent: 4314763 (1982-02-01), Steigmeier et al.
patent: 4332477 (1982-06-01), Sato
patent: 4347001 (1982-08-01), Levy et al.
patent: 4353650 (1982-10-01), Summargren
patent: 4448532 (1984-05-01), Joseph et al.

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