Patent ID: 6611487
Filing Date: 2003-08-26
Classification: B82Y,G02B,G11B,H01S

Abstract:
An optical head including a semiconductor laser source, a condenser lens, a photodiode for detecting a laser light emitter from said semiconductor laser source, and an optical coupler means for collecting the laser light to said photodiode,wherein a chromatic aberration W of said condenser lens is satisfied by an expression W(h, NA)={(NA)3&Dgr;&lgr;/4&lgr;}h, where h is a height of incident light from an optical axis on a hologram, NA is a numerical aperture, &Dgr;&lgr; is a wavelength fluctuation, and a &lgr; is a wavelength at recording, andwherein said height h is determined so that said chromatic aberration W becomes equal to or less than &lgr;/4.