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:
Aug. 13, 2002
Filed:
Feb. 21, 2001
Yoshito Asoma, Saitama, JP;
Sony Corporation, , JP;
Abstract
An objective lens comprises a single objective lens adapted to a finite system having first and second aspherical surfaces and a hologram is formed on at least one of said aspherical surfaces. The light of the positive 1st order or that of the negative 1st order of the hologram is subjected to optimal correction of spherical aberration under actual operating conditions. When a semiconductor laser is used as light source, the change in the spherical aberration caused by the change in the refractive index arising as a result of the change in the environmental temperature of the medium between the first surface and the second surface is substantially offset by the change in the spherical aberration of the hologram attributable to the change in the oscillation wavelength of the semiconductor laser of the light source caused by the change in the environmental temperature so that, if the objective lens has a numerical aperture greater than 0.5, the astigmatism is favorably corrected regardless of the change in the environment particularly in terms of temperature. Such an objective lens can make it easy to downsize an optical pickup device comprising it.