Patent ID: 7693026

Claim:
An optical head, comprising: a first light source that emits light of a first wavelength, that at least either records onto or reproduces information from a first information recording medium; a second light source that emits light of a second wavelength, that at least either records onto or reproduces information from a second information recording medium; a third light source that emits light of a third wavelength, that at least either records onto or reproduces information from a third information recording medium; focusing means for focusing light of the first wavelength, light of the second wavelength, and light of the third wavelength; photodetecting means for detecting light of the first wavelength, light of the second wavelength, and light of the third wavelength; wherein light of the first wavelength, light of the second wavelength and light of the third wavelength are focused by the focusing means and are irradiated onto the information recording media; wherein the photodetecting means detects light that is at least either reflected or diffracted by the information recording media; and wherein, when a distance between the surface of the first information recording medium on the focusing means side, and the tip of the focusing means on the side of the first information recording medium is WD 1 when light of the first wavelength is irradiated onto the first information recording medium, and a distance between the surface of the second information recording medium on the focusing means side, and the tip of the focusing means on the side of the second information recording medium is WD 2 when light of the second wavelength is irradiated onto the second information recording medium, and a distance between the surface of the third information recording medium on the focusing means side, and the tip of the focusing means on the side of the third information recording medium is WD 3 when light of the third wavelength is irradiated onto the third information recording medium, a difference between the maximum value and the minimum value of WD 1 , WD 2 and WD 3 is smaller than the maximum value of the diameter of the focusing means.