| 摘要 |
PURPOSE:To simplify the adjustment of the position of a photodetector by decreasing the number of the photodetectors. CONSTITUTION:An emitted light from a semiconductor laser 1 is condensed on an optical disk 13 by an image forming lens 18, a reflected light 14 from the optical disk 13 is diffracted by a diffracting element 3, and received by half-divided photodetecting parts 39, 40, 41, and 42 of a photodetector 4. The emitted light from the semiconductor laser 1 is reflected by a mirror 5 on the photodetector 4, so that both the +1 order diffracted light and -1 order diffracted light can be received by one photodetector 4 without forcedly working the photodetector 4 into a shape in which the light is not shielded. |
