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:
Dec. 28, 1999
Filed:
Aug. 12, 1998
Masaru Ohtsuka, Machida, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A shape measuring apparatus of this invention includes a light source for generating light beams including two different frequency components, a first optical system for extracting a reference signal from the light beams including the two frequency components, a second optical system for reflecting one of the light beams including the two frequency components by a reference surface, reflecting the other light beam by a measuring region of a surface to be measured, and causing the two reflected light beams to interfere with each other, a photodetector having a plurality of photodetecting elements to detect the interference light beam from the optical system, a housing for holding at least a part of the optical system and the photodetector, an actuator for changing a relative position of the housing and the surface to be measured, and a length measuring device for detecting position information of the housing. An element corresponding to a light beam vertically reflected by the surface to be measured is selected from the photodetector. A measured signal is detected by adding output signals from the selected element and neighboring elements thereof. A distance between the housing and the surface to be measured is controlled in an optical axis direction such that a phase difference between the reference signal and the measured signal is held constant. A shape of the surface to be measured is measured from position information of the housing when the relative position of the housing and the surface to be measured is changed in a direction perpendicular to the optical axis.