Patent ID: 7254107
Filing Date: 2007-08-07
Classification: G11B

Abstract:
1. An optical head which performs recording and/or reproducing of a signal to an optical recording medium, comprising: a light source; an objective lens that converges light released from the light source onto the optical recording medium; an objective-lens-use opening that determines an aperture of the objective lens; a spherical aberration correcting device that corrects spherical aberration that occurs when the optical recording medium has a base-substrate thickness that deviates from a standard base-substrate thickness; a light separation device that is placed in a light path from the spherical aberration correcting device to the optical recording medium; a light-source light-quantity controlling opening that aperture-controls light that has been separated by the light separation device; a first light detector that receives light that has been aperture-controlled by the light-source light-quantity controlling opening; and a second light detector that receives light that has been reflected by the optical recording medium; wherein: a length of an optical light path from the spherical aberration correcting device to the objective-lens-use opening is made substantially the same as a length of an optical light path from the spherical aberration correcting device to the light-source light-quantity controlling opening, and the aperture of the light-source light-quantity controlling opening substantially has the same size as the aperture of the objective-lens-use opening.