Optical head device and birefringent diffraction grating polarizer and polarizing hologram element used therein

摘要

An optical head device uses a birefringent diffraction grating polarizer configured in a reflection type. The device includes a polarizing hologram element (216) which reflects the light from a light source (210) to a converging lens system and diffracts the polarized light returning from a recording medium. A total reflection film (203) is formed on a surface of a diffraction grating which is provided periodically by an ion exchange region and a dielectric film on a surface of a crystal plate (200) having optically anisotropic characteristics. A polarizing beam splitter film (218) formed on a surface of the polarizing hologram element has reflectivity and transmissivity having dependency on the polarization of the incident light. In another form, a polarizing hologram element includes a polarizing hologram which has diffractive efficiency having dependency on polarization of incident light and a polarizing beam splitter film (218) which has reflectivity and transmissivity having dependency on the polarization of the incident light. The diffracted light is received by multi-split photodetectors. The arrangements enable to make the optical head device compact, light in weight and low cost.