Detection of defects in a circular or spiral diffraction grating

Details Detection of defects in a circular or spiral diffraction grating Detection of defects in a circular or spiral diffraction grating

1983-04-15

1985-09-17

Willis, Davis L.

Optics: measuring and testing

Inspection of flaws or impurities

Having predetermined light transmission regions

356354, G01N 2100

Patent

active

045417164

ABSTRACT:
Topographical defect detecting apparatus and process for optically inspecting a circular or spiral track surface defining a diffraction grating such as exists on a video disc or optical disc record. Light from a substantially point source illuminates the track surface. Diffracted reflections from the surface are viewed by the human eye with or without the aid of a TV camera and monitor.
Non-uniformities in track spacing and deviation from average surface flatness are readily observable.

REFERENCES:
patent: 3460841 (1969-08-01), Caldwell
patent: 3915526 (1975-10-01), Taylor
patent: 4030835 (1977-06-01), Firester et al.
patent: 4300143 (1981-11-01), Bell et al.
patent: 4352564 (1982-10-01), Roach
patent: 4395122 (1983-07-01), Southgate et al.
"Technology Focus: Video Discs-a Triquetral Marketplace," Electronic Engineering, Sep. 1980, p. 129, et seq.

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