| 摘要 |
PURPOSE:To simplify position adjustment by providing a three-dividing photo detector arranged between focal lines with dividing in parallel with either of two orthogonal optical focuses having astigmatism. CONSTITUTION:Emitted light of a semiconductor laser 1 is converged on a disk surface 4 by a image formation lens 3. The reflected light from the disk surface 4 is image-formed by the image formation lens 3, a light path is changed by a beam splitter prism 7, the light is made into the one having the astigmatism after passing through a concave spherical lens 5 and a cylindrical lens 6, and arrives at a three-dividing photo detector 8. The three-dividing photo detector 8 is between the two orthogonal optical focal lines having the astigmatism, the detector is divided into three areas by two dividing lines 21 and 22 which is paralleled with one of the two orthogonal focal lines, and the optical beam is arranged so as to extend over the three areas. Thus, the biaxial direction of the position adjustment of the photo detector 8 is sufficient, and the position adjustment of the photo detector 8 can be simplified. |
