| 摘要 |
PURPOSE: To reduce influence of an information pit and to stabilize tracking control by detecting a high reflectance part with a tracking error signal in a peak detection circuit and detecting a low reflectance part with a tracking sum signal in a bottom detection circuit. CONSTITUTION: A photodetector of an optical head is provided with first, second light receiving areas 1a ,b constituted so as to be divided symmetrically by a directional line 50 that the direction of an information track of an optical disk is projected on a light receiving part. The peak detection circuit 3a ,b outputs envelope component signals 54a, b of the peaks of the output signals of the first, second light receiving areas 1a ,b respectively to generate the tracking error signal through a subtraction circuit 4. The bottom detection circuit 5a ,b . outputs the envelope component signals 55a, b of the bottoms of the output signals of the first, second light receiving areas 1a ,b respectively to generate the tracking sum signal through the subtraction circuit 6. Time constants of respective detection circuits 3a ,b , ba ,b , are set large for an information signal frequency. |
