| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical device capable of improving S/N ratio of both of a main beam and a subbeam by increasing each of the light quantities respectively even though no increase of light emitting capacity of semiconductor laser itself is made. SOLUTION: The optical device is equipped with a light emitting element 1 to emit light on an information recording medium 6, a diffraction grating 2 to branch a light beam emitted from the light emitting element 1 into a plurality of luminous fluxes, a converging means 5 to converge a plurality of luminous fluxes branched by the diffraction grating 2 on the information recording medium 6, a light deflection means 3 to deflect the light reflected from the information recording medium 6, a light receiving element 7 to receive a plurality of luminous fluxes deflected by the light deflector means 3, and a first grating region and a second grating region each having different diffraction efficiency mutually in the diffraction grating 2. |
