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. 22, 2005
Filed:
Oct. 29, 2003
Sadao Mizuno, Ibaraki, JP;
Hiroaki Yamamoto, Kawabe-gun, JP;
Hideki Hayashi, Nara, JP;
Jouji Anzai, Suita, JP;
Tomotada Kamei, Neyagawa, JP;
Sadao Mizuno, Ibaraki, JP;
Hiroaki Yamamoto, Kawabe-gun, JP;
Hideki Hayashi, Nara, JP;
Jouji Anzai, Suita, JP;
Tomotada Kamei, Neyagawa, JP;
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
An optical head reproduces optical disks of different disk plate thickness t(0.6 mm) or t(1.2 mm) by using light beams of two wavelengths and one object lens. An converging element comprises a central portion and outer portion, wherein the central portion has optimum design plate thickness of 0.6*tto tand the outer portion has optimum design plate thickness of 0.6 mm. By providing a step difference in the converging element, information can be recorded or reproduced for an information medium of disk plate thickness tand for an information medium of disk plate thickness t, in a state having small side lobes. Alternatively, a step difference is provided in the object lens, and optical distance Lfrom a second light source to a condensing optical system is set to 80 to 95% of optical distance Lfrom a first light source to the condensing optical system. Alternatively, only light of first wavelength is shielded or diffracted in a ring-like shape.