Patent ID: 8116187
Filing Date: 2012-02-14
Classification: G02B,G11B

Abstract:
1. A method of designing an optical element having a diffraction function to be used for an optical disc drive in which each of a plurality of light beams having different design wavelengths passes through the optical element, the optical drive configured to record data to and/or reproduce data from each of first and second optical discs based on different standards, by selectively using a first light beam of the plurality of light beams having a first design wavelength for the first optical disc and a second light beam of the plurality of light beams having a second design wavelength, different from the first design wavelength, for the second optical disc, the method comprising: determining at least two types of optical path difference functions including first and second optical path difference functions in such a manner that: obtaining a combined shape by combining shapes respectively defined by the determined plurality of types of optical path difference functions having the same kind of function which is a function of correcting spherical aberration, and the combined shape is applied to the at least one surface of surfaces of the optical element.