Optical head device

Disclosed is an optical head device, which has: a first light source (1) which emits a light with a first wavelength; a second light source (2) which emits a light with a second wavelength; first and second optical detectors; an optical coupling and dividing means (3) in which the light emitted from the first light source and the light emitted from the second light source are coupled and are then led to an optical recording medium with a first or second substrate thickness, (7,8) and in which the light emitted from the first light source and reflected on the optical recording medium is led to the first optical detector (1) and the light emitted from the second light source and reflected on the optical recording medium is led to the second optical detector (2); and a lens system (4) 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 (8) is set to be greater than the first substrate thickness (7) 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 substrate thickness is conducted by using the light emitted from the first light source, and the recording or reproducing of the optical recording medium with the second substrate thickness is conducted by using the light emitted from the second light source.