The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 18, 2000
Filed:
Jun. 01, 1998
Yukihiro Shibata, Fujisawa, JP;
Shunji Maeda, Yokohama, JP;
Hiroshi Makihara, Yokohama, JP;
Minoru Yoshida, Yokohama, JP;
Yasuhiko Nakayama, Yokohama, JP;
Kenji Oka, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
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.