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:
Feb. 25, 2020
Filed:
Aug. 31, 2018
Seiko Epson Corporation, Tokyo, JP;
Shoichiro Toyoda, Shiojiri, JP;
Koji Shiokawa, Azumino, JP;
SEIKO EPSON CORPORATION, Tokyo, JP;
Abstract
A projection system includes a first lens group that does not move when the projection magnification is changed with the aid of the zoom function, and the first lens group includes a correction lens group that is moved in the direction of the optical axis to correct worsened astigmatism. The projection system satisfies the following conditional expressions (1) and (2):|Δ20|<×√2  (1)1.5<|1/  (2)where P represents the pixel pitch in an image displayed by liquid crystal panels, FNO represents the F number of the entire lens system, ΔBF represents the amount of movement of the back focus position in a case where the correction lens group is moved by the amount of movement for correction of the aberration that changes when the temperature changes by 20° C., f represents the focal length of the entire lens system, and f1 represents the focal length of the correction lens group.