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:
Oct. 01, 1991
Filed:
Mar. 30, 1990
Akira Arimoto, Kodaira, JP;
Hitachi, Ltd., Tokyo, JP;
Hitachi Kiki Co., Ltd., Tokyo, JP;
Abstract
A variable density scanning apparatus comprises a semiconductor laser which generates at least one laser beam, a first drive circuit which applies to said semiconductor laser a modulation drive signal having a predetermined modulation frequency in accordance with the density of dots constituting the pattern to be formed on the scanning surface, a dynamic diffraction grating which receives a laser beam from said semiconductor laser and diffracts said laser beam into a plurality of diffraction beams, a second drive circuit which applies to said dynamic diffraction grating a diffraction drive signal having a predetermined high frequency in accordance with the dot density, a polygonal mirror which receives a plurality of diffraction beams from said dynamic diffraction grating and scans said diffraction beam in the main scanning direction, a third drive circuit which applies to said polygonal mirror a rotation drive signal having a predetermined rotation frequency in accordance with the dot density, and a control unit which applies to said first, second and third drive circuits respectively a control signal that indicates an instruction to change the dot density.