Kabushiki Kaisha Toshiba

Tokyo Shibaura Denki Kabushiki Kaisha

Satoru Maeda

Yasuhiro Hayashi

Hiroshi Nakane

Tadashi Kojima

Takashi Inoue

Shigeru Todokoro

Masayuki Tamura

Disclosed is a track-search control circuit for performing track-search of an optical disc stably even at the time of multi-speed reproduction of the optical disc. The track search control circuit comprises a circuit for detecting the light beam having traversed the track when the light beam moves in the radial direction of the optical disc and generating a normal direction on-track signal FVACLR at the time of being on the track and a normal direction off-track signal FVBCLR at the time of being off the track, a first measurement circuit that starts time measurement at the time of generating the normal direction on-track signal, a second measurement circuit that starts time measurement at the time of generating the normal direction off-track signal, circuits which detect the error between a moving velocity of the optical beam in the radial direction of the optical disc and a target velocity based on a measurement output by the first measurement circuit and a measurement output by the second measurement circuit, and a correction circuit for correcting the moving velocity of the optical beam in the radial direction based on the detected error signal.

Track search control circuit and optical disc drive

A focus servo control system is a system for selectively applying a light beam to a disk on which data is recorded on plurally layered recording surfaces and setting the focus position of the light beam on a selected recording surface of the two-layered recording surfaces based on a signal read from reflected light from the selected recording surface of the plurally layered recording surfaces of the disk and includes a focus error detector for detecting a positional difference between the focus position of the light beam and the selected recording surface of the plurally layered recording surfaces, a sample-hold circuit for sampling and holding an output of the focus error detector, a focus position correcting circuit for correcting the focus position of the light beam based on one of the output of the focus error detector and an output of the sample-hold circuit, a data signal level detector for detecting the signal level relating to data read out from the disk, a comparator for comparing a signal level detected by the data signal level detector with a predetermined level to output the result of comparison, and a selector for selecting one of the output of the focus error detector and the output of the sample-hold circuit as an input signal of the focus position correcting circuit based on the output of the comparator.

Focus servo control system and disk reproducing system

A track jump control apparatus for a disc reproducing system having a transport unit for moving a pickup element that reads data recorded on the disc in the radial direction of the disc at a high speed. The system also has a detecting unit for detecting a moving direction of the pickup element unit based on a pick-up signal output from the pickup element while the pickup element moves in the radial direction of the disc, and a protection unit for stopping the pickup element moved by the transport unit when the pickup element is judged to be moving in a different direction from the direction moved by the transport unit. The apparatus has a measuring unit for measuring a pulse duration of the picked-up signal, which is continuously obtained from the pickup element while the pickup element moves in the radial direction of the disc at a high speed. The apparatus also has a control unit for inverting a detected result of the detecting unit when the pulse duration of the picked-up signal is beyond a specific limit based on the measured result of the measuring unit.

Track jump control apparatus for disc reproducing system

A drive speed detector for a pickup feed motor including a detector for detecting the drive speed of the optical pickup feed motor by generating an AC signal with a frequency which is proportional to the drive speed of the optical pickup feed motor and a controller for controlling the sensitivity of the detecting means in order to uniform an amplitude level of the AC signal output from the detecting means.

Drive speed detector for a motor that drives a data reproducing device

Pick-up control circuits for disc information reproducing apparatus. The apparatus includes a carriage, a source of a light beam mounted in the carriage, a focus lens for placing the light beam on a disc, the focus lens being mounted on a standard position in the carriage but movable by a prescribed range from the standard position, a circuit for detecting a tracking error signal responsive to a deviation of the light beam from a center of the track, a lens actuator for driving the focus lens to deviate from the standard position, a carriage actuator for driving the carriage to move in the radial direction in respect of the disc, a power source for applying a drive voltage to the carriage actuator, a switch connected between the power source and the carriage actuator, and a circuit for controlling the switch to apply the drive voltage intermittently to the carriage actuator, so that focus lens is moved to the standard position on or before reaching an end of the movable range.

Pick-up control circuits for disc information reproducing apparatus

A tracking control system for an optical disc information reproducing apparatus in which information stored in an optical disc as a series of recesses or pits arranged in concentric tracks or in a single spiral track is read out during rotation of the optical-disc by a scanning spot of a light beam, the system comprising a light source for generating the light beam used for scanning the track, means for applying the scanning spot of the light beam to a selected track location, a transducer for converting an optical signal detected by the scanning spot into an electric signal bearing a tracking error information, means for controlling the scanning spot applying means in response to the tracking error information signal, thereby causing the scanning spot to scan the selected track location accurately, means for transferring the tracking error information signal to the controlling means, a transfer characteristics of the transferring means being variable, means for limiting a slew rate of the tracking error information signal, means for subtracting an output of the slew rate limiting means from the tracking error information signal, and means for lowering the transfer characteristics of the controlling means in response to an output of the subtracting means, thereby causing the controlling means being irresponsive to the tracking error information signal.

Tracking control system for optical record disc information reproducing

A tracking servo system for an optical-disc information reproducing apparatus includes (a) a light source for generating a light beam to scan a target track on an optical-disc wherein the information is stored as a series of pits arranged in the form of the track; (b) four photodetectors, arranged in two pairs with each pair intersecting the other and being disposed in a direction oblique to an image of the track for converting an image of the pit into respective electric signals; (c) a circuit for comparing the phases of the electric signals and for producing a tracking error signal ranging in accordance with the phase difference between the electric signals; and (d) a motor and lens for deflecting the light beam along a path perpendicular to the target track in response to the tracking error signal, whereby the light beam accurately scans the target track.

Growing community of inventors

Kodama-gun, Japan

Satoru Maeda