Olympus Optical Company, Ltd.

Saburo Funada

Shoji Yoshikawa

Masanori Doi

Yoshiro Yoda

Kazutake Sugawara

A laser controller for an optical data recording/reproducing apparatus includes a detector for detecting an intensity of a laser beam emitted from a laser, a servo controller for comparing the detected value with a reference value and generating a feedback signal in accordance with the difference between the two values, and a drive circuit for supplying a drive signal corresponding to the feedback signal to the laser, and a modulator for modulating the drive signal during recording. Furthermore, the laser controller includes a controller connected to the servo controller, a RAM, a timer, and a temperature sensor which are connected to the controller. When reproduction and erasing are to be performed, the operation of the modulator is stopped, and the drive signal is obtained by feedback control. When erasing is to be performed, a level of the feedback signal is stored in the RAM. When recording is to be performed, the operation of the servo controller is stopped, while the level of the stored feedback signal read out from the RAM is supplied to the drive circuit. As a result, the intensity of the laser beam is not controlled by feedback control, but by open loop control based on the readout feedback signal, while the intensity of the laser beam is modulated in accordance with the data to be recorded.

Laser control circuit for optical data recording/reproduction apparatus

A focus servo control device has a focus driver for driving an optical system having an objective lens, and a servo control section for detecting that the optical system is within a focus servo control range. A focus servo control loop is formed in response to a detection signal representing that the optical system is in the focus servo control range, and the optical system is driven under servo control until the amount of light reflected by the optical disk is detected as a maximum.

Focus servo control device for optical disks having servo offset error

An optical information-recording/reproducing apparatus comprises a beam-irradiator for irradiating a beam to an optical information-recording medium having a pre-format portion containing an address signal, and a data portion including an area in which information signals are to be recorded, a reflected-beam detector for producing an electric signal corresponding to the reflected beam from the recording medium, an error-signal detector for detecting an error signal for tracking control and/or focussing control of the beam, based on the electric signal, an information signal detector for detecting an information signal to be recorded in the data portion of the recording medium, based on the electric signal, a pre-format portion detector for detecting the pre-format portion of the recording medium, based on the electric signal, an offset-canceller for overlapping the error signal from the error signal detector and a compensation signal corresponding to the substantial difference of DC offset components between the data portion and pre-format portion detected by the pre-format detector and a controller for controlling tracking and/or focussing of the beam, based on a signal which is generated when the DC offset components contained in the error signal are compensated by said offset canceller.

Optical information-recording/reproducing apparatus with cancellation

The optical recording and reproducing apparatus comprises a magnetic field applying section, a movable mechanism for moving the magnetic field applying section, a distance detecting section for detecting a distance between magnetic poles of the magnetic field applying section and the surface of a recording medium, and a distance control section for maintaining the above distance constant in response to an output of the distance detecting section. The distance between two magnetic pole ends of the magnetic field applying section can be minimized. Further, on the basis of the tracking control of either one of the recording and erasing light beams, it is possible to enable a high-precision tracking control to the other of the two light beams.

Optical recording and reproducing apparatus

The light beam from a semiconductor laser that generates laser light for recording or reproducing is irradiated onto a disk through an objective lens and the light reflected from the disk is received by a four quadrant light detector with four light receiving areas. Based on the light received by the light receiving areas, first and second feedback signals are generated and fed to servo actuators to control the objective lens in tracking and focusing. These signals are supplied to the actuators for tracking and focusing through switches to apply the tracking servo and focusing servo functions. When there is any change in the total quantity of light received by the light detector, the loop gain of the servo system is kept constant by controlling the duty ratio of opening and closing of the switches by means of control signals which have a frequency sufficiently higher than the response frequency of the feed back signals, thereby intermittently turning on and off the servos in a variable duty cycle that compensates for the change in light quantity.

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Tokyo, Japan

Saburo Funada