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:
Jul. 26, 2011
Filed:
Mar. 14, 2007
Nobuhiko Takeshita, Koriyama, JP;
Tomoki Gunjima, Koriyama, JP;
Kara Yoshida, Koriyama, JP;
Asahi Glass Company, Limited, Tokyo, JP;
Abstract
An optical head device having a broadband phase plate of transforming at least three linearly polarized light beams having different wavelengths into circularly polarized light beams, is obtained. A broadband phase plate comprising two phase platesA andB laminated with e.g. an adhesive agent so that their optical axes are crossed, wherein provided that wavelengths of linearly polarized incident light beams are λ, λand λ(λ<λ<λ), at least one or both of the two phase plates has such a phase difference characteristics that a ratioR(λ)/R(λ)and a ratioR(λ)/R(λ)between retardation values of the wavelengths are smaller than 1 andR(λ)/R(λ)is smaller thanR(λ)/R(λ), is integrated in the optical head device.