| 摘要 |
PURPOSE:To miniaturize the titled device in size and to decrease the cost by using at least a couple of photodetectors provided at the left/right of a converg ing means to receive a reflected light from a disc obtained from the 0th-order diffracted light and using an output of a couple of the photodetectors to detect the tilt of the disc thereby making the optical path as the definite system. CONSTITUTION:A laser light irradiated from a light source 43 is made incident in a micro Fresnel lens 45 via a prism 44 and separated into the 0th-order diffracted light and the + or - 1st order diffracted lights through diffraction at the lens 45. One of the 1st order diffracted lights is converged on a prescribed tack of a disc 6 and the other ligh and the 0th-order diffracted light are diffused toward outside. A couple of photodetectors 47 are arranged at the left/right outside of the micro Fresnel lens 45 so as to receive the 0th-order diffracted light. When the disc 6 is tilted from a prescribed angle, the output difference of the photodetectors 47 is changed in response to the angle and direction of the tilt. Then in boosting the output signal and applying the boosted signal to a piezoelectric element 51, the lower part of the piezoelectric element 51 is turned horizontally and the entire head assembly 41 is controlled to have a prescribed angle always to the disc 6. |
