Surface roughness measuring method and apparatus utilizing trunc

Details Surface roughness measuring method and apparatus utilizing trunc Surface roughness measuring method and apparatus utilizing trunc

1990-08-15

1991-11-26

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250225, 356349, 356358, G01N 2186

Patent

active

050685414

ABSTRACT:
An apparatus for measuring surface roughness or profile of a subject, including a truncated conical lens having a central circular flat surface and a conical surface, and an objective lens disposed in series with the truncated conical lens. Parallel rays of light are transmitted through the truncated conical and objective lenses and are thereby converted into a first and a second measuring beam for irradiating respectively a minute spot on the surface of the subject and an annular spot surrounding the minute spot. An optical arrangement is provided for preparing a reference beam whose frequency is different from that of the measuring beams, and effecting interference between the reference beam with each of the first and second measuring beams, to produce two beat beams, which are converted into electrical beat signals. A height variation or roughness of the subject surface is determined based on a phase difference between the two beat signals.

REFERENCES:
patent: 3624605 (1971-11-01), Aagard
patent: 3930732 (1976-01-01), Holly
patent: 3999865 (1976-12-01), Milam et al.
patent: 4061427 (1977-12-01), Fletcher et al.
patent: 4442455 (1984-04-01), Huignard et al.
patent: 4708481 (1987-11-01), Mori et al.
patent: 4984891 (1991-01-01), Miyzaki et al.
patent: 4995726 (1991-02-01), Fujita et al.

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