Abstract: A disc playing apparatus having a tracking servo loop and a focus servo loop is configured such that a transfer function of at least one of the servo loops is adjustable. Disc defect detection signals are generated in response to a change in a low frequency component and a high frequency component of a read signal output from the pickup, and the transfer function of at least one of the tracking servo loop and the focus servo loop is adjusted in response to the disc defect detection signals. According to another feature of the invention, the transfer function of at least one of the tracking servo loop and the focus servo loop is gradually changed each time an erroneous jumping movement of the information reading light spot is detected by information contained in the read signal output by the pickup.

Abstract: A method for setting the loop gain in a focusing servo loop of a disc player. The loop is opened and the objective lens is moved repeatedly up and down about the focusing point while the disc is slowly rotated, thereby generating an S-shaped focusing error curve. The S-shaped error curve is sampled and a loop gain is determined based on the sampled values. If an eject instruction occurs during the loop gain setting process, a braking pulse is applied to a spindle motor for stopping the disc rotation.

Abstract: A disc player operates in a manual search mode in which play and jump operations are alternately repeated, in response to a manual search command, while maintaining the reproducing level at a level lower than the level at the initiation of the manual search command as long as no change command appears.When the change command appears the reproducing level is shifted to a level which is designated by an operator so as to adjust the reproduced sound level to a level sufficient to listen to the reproduced sound for music selection.

Abstract: A method of setting the loop gain of a tracking servo loop of a disc player. The optimum loop gain is set for each playing of a disc without being influenced by disc eccentricity. The servo loop is opened, the disc is driven at a revolving speed which is lower than that of normal playback at the current position of the information reading spot, and a tracking error signal is obtained. The loop gain is set on the basis of a plurality of the sample values.

Abstract: A loop gain setting method automatically sets the loop gain of a focus servo loop and a tracking servo loop of a disc player for playing a disc. Firstly the loop gains of the focus servo loop and the tracking servo loop are set, and subsequently the appropriateness of the set values of loop gains is judged by comparing the set values of the loop gains with each other. According to another aspect of the present invention the loop gains of the focus servo loop and the tracking servo loop are set, and subsequently the appropriateness of the set values of loop gains is judged by comparing at least one of the set values of the loop gains with a sensed value of the amplitude of the envelope of an RF signal read-out from the disc.

Abstract: A servo system for a disc player having a pickup for reading information recorded on an information recording disc, includes an A/D converter for converting an error signal produced on the basis of signals output from the pickup into a digital signal, and performs driving and control of the pick up according to the signal level of the error signal having been processed digitally. The servo system further comprises a filter circuit permitting low frequency components of the error signal to pass therethrough and supplying the low frequency components to the A/D converter, detection circuit detecting noise components having levels higher than a predetermined level, contained in the error signal, and a circuit generating a control signal for a predetermined period after an instant of detection of the noise components by the detection circuit.

Abstract: A disc player having digital processing of error signals in a servo system utilizes an A/D converter. The relatively small closed loop error signals are amplified by a predetermined amount above that for the open loop error signals prior to conversion in the A/D converter, and the converter output representing the digitized small error signals are amplified by a predetermined amount below that for the digitized open loop error signals. While the overall gain in the servo system is substantially the same for the closed loop and open loop error signals, the small closed loop error signals are greatly expanded in range at the converter input to permit the same A/D converter to faithfully convert both the open loop and the closed loop error signals.