| 摘要 |
The optical head has a radiating light source for emitting a beam, and a finite lens for focusing the beam onto a recording medium, and a slab type waveguide for guiding light. The optical head includes a holographic coupler and a plurality of photo-detectors. The holographic coupler which lacks a lens effect is provided in the slab type waveguide between the radiating light source and the finite lens. The holographic coupler transmits the beam going from the radiating light source toward the finite lens and diffracts a beam returning from the finite lens toward the radiating light source after being reflected at the recording medium. The photo-detectors detect the beam which is diffracted by the holographic coupler and coupled to and guided by the slab type waveguide. Since the holographic coupler does not have a lens effect, even if the wavelength of the light changes, there is no deviation of the position of the focused point from the optical axis within the slab type waveguide. It is possible to make various changes in the positioning of the photo-detectors and photo-detecting sections with respect to the holographic coupler./!
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