| 摘要 |
Disclosed is an optical head device, including: a first light source which emits light with a first wavelength; a second light source which emits light with a second wavelength; first and second optical detectors; an optical coupling and dividing means in which light emitted from the first light source and light emitted from the second light source are coupled and are each respectively led to an optical recording medium having a first and a second substrate thickness, and in which the lights emitted from the first and second light sources, and reflected on the optical recording medium, are led to the first and second optical detectors, respectively; and, a lens system which is disposed between the optical coupling and dividing means and the optical recording medium, and includes an objective lens; wherein the second substrate thickness is set to be greater than the first substrate thickness, and an effective optical path length from the second light source to the lens system is set to be shorter than an effective optical path length from the first light source to the lens system, and wherein the recording or reproducing of the optical recording medium with the first and second substrate thickness is conducted by using the light emitted from the first and the second light sources, respectively.
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