| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain an optical element which is efficient and has a low aspect ratio by reducing incidence of return light on a light source and having a function minimizing incident light quantity. <P>SOLUTION: S-polarized light is made incident on a polarization filter 1 from a light source 11 for DVD and a light source 12 for CD. The polarization filter 1S transmit the S-polarized light and diffracts P-polarized light. The light passing through the polarization filter 1 is diffracted by a diffraction element 2 into three beams, reflected by a polarization beam splitter 3, transmitted through a collimator lens 4, circularly polarized by a 1/4 wavelength plate 5, is made incident on an objective lens 6, and converged on an optical recording medium 7. Three beams reflected by the optical recording medium 7 is made incident on the objective lens 6, and is converted into linear p-polarized light by the 1/4 wavelength plate 5. Almost all P-polarized light is transmitted through the polarization beam splitter 3, made incident on a light receiving element 9 through a detection lens 8, while the other light travels to a light source side as return light. Since the P-polarized light is divided into three beams by the diffraction element 2 and diffracted by the polarization filter 1, incidence on the light source is reduced and an optical property is stabilized. <P>COPYRIGHT: (C)2010,JPO&INPIT |
