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:
Jun. 28, 1994
Filed:
Feb. 03, 1993
Yasuhiro Yoshitake, Yokohama, JP;
Yoshitada Oshida, Fujisawa, JP;
Masataka Shiba, Yokohama, JP;
Yasuhiko Nakayama, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A novel exposure system includes a reduced-projection lens optimized for a predetermined single exposure wavelength and a chromatic aberration correction system for TTL (Through The Lens) alignment with broadband light. The correction system includes a holographic lens which dispersion has a negative number in contrast to a conventional glass lens which has a positive dispersion number. By employing a holographic lens, the total optical length of an alignment system can be made short enough to avoid the necessity of installing a mirror therein, thus realizing a highly accurate alignment system.