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. 06, 1990
Filed:
Jun. 20, 1988
Yuji Yasuda, Tokyo, JP;
Ricoh Company, Ltd., Tokyo, JP;
Abstract
A transmissive filter for correcting illuminance distribution is positioned between a lens for forming an image of an illuminated original on an image forming surface and the image forming surface, or between the original and the image forming lens, and having transparent areas for passing light therethrough and opaque areas for blocking light, for correcting illuminance irregularities on the image forming surface. The transmissive filter has lowest transmittance around an effective pupil formed by projecting an exit pupil of the lens onto the filter when the filter is disposed between the lens and the image forming surface, or lowest transmittance around an effective pupil formed by projecting an entrance pupil of the lens onto the filter when the filter is disposed between the original and the lens. The transmittance is progressively higher concentrically in a stepwise manner toward an axial center and an outer periphery of the filter.