Patent ID: 7787348

Claim:
An optical head apparatus comprising: a first light source which emits light having a first wavelength; a second light source which emits light having a second wavelength; at least one photodetector which receives the light having the first wavelength and the light having the second wavelength, which have been reflected by an optical recording medium; an objective lens provided, opposed to the optical recording medium; and an optical wave synthesizing/separating system which synthesizes/separates the light having the first and second wavelengths and traveling toward the objective lens from the first and second light sources, and the light having the first and second wavelengths and traveling toward the photodetector from the objective lens, wherein the optical wave synthesizing/separating system includes at least one beam splitter including a polarizing beam splitter for the light having the first wavelength and a polarizing beam splitter for the light having the second wavelength, and a quarter-wave plate of a wide band for the different wavelengths, which is provided between the at least one beam splitter and the objective lens, and the optical wave synthesizing/separating system emits the light having the first and second wavelengths, applied from the side of the first and second light sources, to the side of the objective lens with a quantity of light larger than 50% of a quantity of incident light, emits the light having the first and second wavelengths, applied from the side of the objective lens, to the side of the photodetector with a quantity of light larger than 50% of a quantity of incident light; wherein the polarizing beam splitter for the light having the first wavelength transmits almost all of the P-polarized component and reflects almost all of the S-polarized component of light having the first wavelength, transmits almost all of both the P-polarized component and S-polarized component of incident light having the second wavelength, transmits almost all of the P-polarized component thereof and reflects almost all of the S-polarized component thereof, or reflects almost all of both the P-polarized component and S-polarized component thereof, the polarizing beam splitter for the light having the second wavelength transmits almost all of the P-polarized component of light having the second wavelength and reflects almost all of the S-polarized component thereof, transmits almost all of both the P-polarized component and S-polarized component of incident light having the first wavelength, transmits almost all of the P-polarized component thereof and reflects almost all of the S-polarized component thereof, or reflects almost all of both the P-polarized component and S-polarized component thereof.