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:
May. 27, 2003
Filed:
May. 24, 2001
Ko Ishizuka, Saitama, JP;
Takayuki Kadoshima, Utsunomiya, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A light wave measuring instrument has a small optical system. Beams from a laser light source illuminate a grating scale and plus-first-order-diffracted and minus-first-order-diffracted beams from the grating scale are diffracted and reflected so as to travel through their original optical paths. The beams are returned to a non-polarization beam splitter, transmitted through a quarter wavelength plate and converted into one straight polarized beam having a polarization direction varying with the phase difference between the two beams. The straight beam is then separated. The separate beams are separated into P and S polarized beams. The S polarized beams are reflected by a polarization film, while the P polarized beams are reflected by a parallel glass plate. These beams are transmitted through the polarization film again to become coherence signal beams having reverse phases of fringes, which are then emitted in the same direction.