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:
May. 28, 2013
Filed:
Apr. 19, 2012
Koji Miyasaka, Fukushima, JP;
Takuji Nomura, Fukushima, JP;
Mamoru Isobe, Fukushima, JP;
Asahi Glass Company, Limited, Tokyo, JP;
Abstract
A phase difference layerand a reflection layerare provided. Then, adjustment is performed such that the phase difference layerand the reflection layerimpart a predetermined phase difference to light having a particular wavelength bandwidth or plural kinds of light of different wavelengths that enter in an oblique direction relative to the normal direction of the plane of the phase difference layer. By virtue of this, the lightthat goes forward and backward through the phase difference layerand then exits the layer has an ellipticity κ of 0.7 or greater. Thus, in particular, when this wave plate is employed in an optical head device, the function of reflection and the function of a ¼-wave plate are integrated. Thus, stable recording and reproduction of an optical disk are achieved, and size reduction is achieved in the optical head device.