| 摘要 |
PURPOSE:To improve the read accuracy of an optical disk by detecting the radiated luminous quantity of a laser light source so as to apply feedback control and detecting the reflected luminous quantity from an optical disk to apply feedback control thereby controlling the output of a laser light source to be constant. CONSTITUTION:A light (l) from a mirror surface opposite to an output L of a laser diode 1 and a reflected light R from an optical disk 6 are received respectively by photodetectors 2, 7 and its output is converted into a voltage. The voltage in response to the light (l) and the 1st reference voltage Vref1 are compared and its error is fed back to a laser drive circuit 14 via a nonlinear circuit 13. Similarly, a voltage corresponding to the light R is compared with the 2nd reference voltage Vref2 via a low filter 23 and its error is fed back to the said circuit 14 via a nonlinear circuit 25. Thus, the output of the light source is fed back duplicatedly in this way to keep the luminous quantity of the optical disk constant thereby improving the read accuracy. |
