Patent ID: 7715296
Filing Date: 2010-05-11
Classification: G11B

Abstract:
1. An optical head device, comprising: a first light source for emitting a light having a first wavelength; a second light source for emitting a light having a second wavelength; a third light source for emitting a light having a third wavelength; at least one photo detector; and an objective lens, wherein: an optical system is formed by, a light emitted from said first light source is transmitted to a first optical recording medium through said objective lens, a light emitted from said second light source is transmitted to a second optical recording medium through said objective lens, a light emitted from said third light source is transmitted to a third optical recording medium through said objective lens, a light reflected from said first optical recording medium is transmitted to said photo detector through said objective lens, a light reflected from said second optical recording medium is transmitted to said photo detector through said objective lens, and a light reflected from said third optical recording medium is transmitted to said photo detector through said objective lens, wherein: recording or reproducing information is executed for said first optical recording medium by using said light having said first wavelength, recording or reproducing information is executed for said second optical recording medium by using said light having said second wavelength, and recording or reproducing information is executed for said third optical recording medium by using said light having said third wavelength, wherein: further comprising: an aperture controlling element disposed in a common optical path between said first light source and said objective lens, between said second light source and said objective lens and between said third light source and said objective lens, wherein said aperture controlling element is divided into a first region which is outside a first circle having a first diameter smaller than an effective diameter of said objective lens, a second region which is within said first circle and outside a second circle having a second diameter smaller than said first diameter, and a third region which is within said second circle, wherein: said first region transmits almost all said light having said first wavelength, and does not transmit almost all said light having said second wavelength and almost all said light having said third wavelength, said second region transmits almost all said light having said first wavelength and almost all said light having said second wavelength, and does not transmit almost all said light having said third wavelength, said third region transmits almost all said light having said first wavelength, almost all said light having said second wavelength, and almost all said light having said third wavelength, phase differences among said light having said first wavelength transmitting through said first region, said light having said first wavelength transmitting through said second region, and said light having said first wavelength transmitting through said third region are adjusted to be about integer times the value of 2π, and a phase difference between said light having said second wavelength transmitting through said second region and said light having said second wavelength transmitting through said third region is adjusted to be about integer times the value of 2π.