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:
Mar. 26, 1985
Filed:
Apr. 07, 1983
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A transfer apparatus comprises a projection device operable with a photomask having a semiconductor circuit pattern therein and includes a projection lens for projecting the image of the photomask to a photosensitive member sensitive to the image of the photomask projected by the projection lens. The apparatus further includes an illuminating device for illuminating the photomask, a memory circuit for storing the time characteristic .DELTA.l of a focus error occurring in the projection lens due to the exposure light from the photomask having passed through the projection lens, a history detector for detecting the illuminating history to/t of the illuminating device, a transmission signal forming device for forming a transmission signal regarding the transmission factor .tau. of the photomask used, a length measuring device for measuring the length of a part of the optical path between the photomask and the photosensitive member, an operation circuit for calculating a proper value in accordance with the output of the memory circuit, the output of the history detector and the transmission signal, and an adjusting device for adjusting the length of the optical path of the projection device until the proper value and the value measured by the length measuring device are in accord with each other.