| 摘要 |
PROBLEM TO BE SOLVED: To effectively and spatially separate a light source from a light receiving means by using a polarizing hologram having a relatively small diffraction angle. SOLUTION: Luminous flux from a semiconductor laser 1, which is a light source, illuminate the recording surface of an optical recording medium 8 through a diffraction grating 3, the returned luminous flux reflected from a recording surface is received by a light receiving mean 9 through the diffraction grating 3 to conduct an information writing and/or reproducing. The diffraction grating 3 is a polarizing hologram having different diffraction depending on the polarization condition of the transmission luminous flux and is arranged to conduct a polarization operation to the returned luminous flux. A 1/4 wavelength plate 6 is provided on the optical path of the medium 8 side of the hologram to rotate the deflected surface of the returned luminous flux by approximately 90 degrees to the light beams from the light source. A cube shaped optical element 2 is provided between the light source and the hologram so that the luminous flux from the light source 1 is totally reflected toward the hologram 3 and the diffracted returned luminous flux by the hologram are transmitted toward the means 9. The element 2 is made by combining two prisms 2a and 2b so that the tilted surfaces of the prisms are brought in close proximity to each other and the space between the tilted surfaces made by the prisms 2a and 2b becomes a region 2c having a low refractive index against the luminous flux from the light source 1. |
