Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Patent
1998-06-01
2000-07-18
Allen, Stephone B.
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
3562371, G01N 2100, G01N 2188
Patent
active
060910755
ABSTRACT:
An automatic focus detection method comprises the steps of: irradiating onto a single spot of a sample a plurality of beams of illuminating light transmitted and condensed through an objective lens in a symmetrically diagonal manner with respect to an optical axis of the objective lens; branching reflected light from the same spot of the illuminated sample after transmission through the objective lens, in directions of illumination symmetrical with respect to the optical axis so as to obtain a plurality of optical images; and causing a photoelectric conversion device to receive the branched optical images for conversion to an electric signal representing light intensity distribution of the images, whereby a defocus of the sample is detected based on a discrepancy between the optical axis and the center of the light intensity distribution.
REFERENCES:
patent: 3614232 (1971-10-01), Mathisen
patent: 3970845 (1976-07-01), Hollis et al.
patent: 4953964 (1990-09-01), Anafi et al.
patent: 5235400 (1993-08-01), Terasawa et al.
Maeda Shunji
Makihara Hiroshi
Nakayama Yasuhiko
Oka Kenji
Shibata Yukihiro
Allen Stephone B.
Hitachi , Ltd.
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