Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1990-05-24
1992-06-23
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356387, G01N 2186
Patent
active
051245639
ABSTRACT:
The width of a line projecting out of or recessed on a medium such as an integrated circuit is measured. A device for that purpose includes a confocal optical assembly having a monomode light source delivering a beam having a flat wave front. An optical deflector scans the surface of the medium transversely to the line width of the beam. A separator separates the light beam directed towards the medium carrying the line from the beam reflected by the medium. A detector includes a blade placed at a position conjugate with the focal point of the optical assembly and orthogonal to the line whose width is to be measured and a differential sensor placed at a position conjugate with the pupil of the optical assembly and delivering a signal responsive to the difference of lighting on each side of the blade for comparison with a threshold.
REFERENCES:
patent: 3563665 (1971-02-01), Takahashi et al.
patent: 4112309 (1978-09-01), Nakazawa et al.
patent: 4485309 (1984-11-01), Johansson et al.
Philips Technical Review, vol. 43, No. 7, Jul. 1987, pp. 184-191, Eindhoven, NL; G. Prast: "Quantitative Measurements By The Schlieren Method", pp. 188-190.
Lee John R.
Micro-Controle
Nelms David C.
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