43 the switch circuit 47 and the switch circuit 49 the switch circuit sw 1 43 becomes open in response to the defect identification signal of l level supplied from the slice circuit 41 when detecting a defect such as a black dot note that a delay time has been set to complete the above switch operation before supplying the error signals te and fe extracted from the read signal to the equalizer 45 the switch operation interrupts the supply of the error signals te and fe from the signal processing circuit 15 to the equalizer 45 at this time the switch circuit sw 2 47 becomes closed in response to the l level defect identification signal the drive signals td fd to the driver circuit 19 for operating the optical pickup 11 is controlled to have a constant value before detecting the defect in other words pre value hold control is executed a capacitor c 1 and resistors r 1 r 2 are provided in the loop circuit from an output of the equalizer 45 through the switch circuit sw 2 47 to an input so that a direct current component of the drive signals td fd can be taken out to the input the capacitor c 1 and the resistors r 1 r 2 are set in such values that the round gain of the loop is given 0 db the switch circuit sw 3 49 is configured to maintain an open state without responding to an l level defect identification signal furthermore the switch circuit sw 1 43 and the switch circuit sw 2 47 respectively maintain a close state and an open state when an h level defect identification.