Abstract: A PWM pulse of a duty ratio according to a current instruction value D of a servo control section is outputted from a pulse width modulating section to a driving section, thereby current driving a load. In a calibrating process, a calibration processing section outputs a reference current instruction value Dr corresponding to a reference load current Ir and measures a drive current Is of a load. When the measurement current Is doesn't coincide with the reference load current Ir, the current instruction value is adjusted, a current instruction value Ds of the measurement current Is which coincides with the reference load current Ir is obtained, and a correction coefficient K=Ds/Dr of the current instruction value is decided. A correcting section corrects the current instruction value D which is outputted from a control section by the correction coefficient K obtained by the calibrating section and outputs to the pulse width modulating section.

Abstract: A recovery is promptly executed for a reading error of a track address in a modified constant angular velocity format. Upon seeking, when a defective reading operation of the track address occurs, a clock frequency of the zone corresponding to each detecting position is selected due to the detection of the head by a head position sensor or the movement of the head to a home position at which a detection signal of a home position sensor is obtained, and the reading operation is retried. Errors due to back talk noises upon reproduction are reduced. At the time of retry for the occurrence of errors due to the back talk noises, a modulation amount of a read beam from a laser diode is changed.

Abstract: A positioning control system for performing recording/reproducing operations by irradiating an optical beam to predetermined position on an optically recording medium, e,g., magneto-optical disk, includes a photo-detector constituted by at least two-divisional units; and a servo-error signal generating circuit which can generate at least one servo-error signal in accordance with a difference between the detection currents.

Abstract: A recovery is promptly executed for a reading error of a track address in a modified constant angular velocity format. Upon seeking, when a defective reading operation of the track address occurs, a clock frequency of the zone corresponding to each detecting position is selected due to the detection of the head by a head position sensor or the movement of the head to a home position at which a detection signal of a home position sensor is obtained, and the reading operation is retried. Errors due to back talk noises upon reproduction are reduced. At the time of retry for the occurrence of errors due to the back talk noises, a modulation amount of a read beam from a laser diode is changed.

Abstract: A track cross signal generation circuit comprises a tracking error signal generation circuit, an offset compensation circuit, a level setting circuit, and a comparator. The comparator directly receives a tracking error signal output from the tracking error signal generation circuit without passing through the offset compensation circuit and a reference level output from the level setting circuit. Further, the comparator compares the tracking error signal with the reference level, and generates a track cross signal representing the tracks formed on an optical recording medium crossed by a beam. Namely, the gain of the tracking error signal is not affected by the offset compensation circuit even within a high-speed region of the beam. Consequently, the track zero cross signal correctly indicates tracks crossed by the beam, and correctly and stably carries out a seek operation in the high-speed region of the beam.

Abstract: A laser diode having a cathode connected to the ground side of a positive power source and an anode connected to the plus voltage side of the power source through a control circuit. A maximum current to drive the laser diode is supplied to the laser diode by a disgorging type constant current source. In a reading mode operated at a frequency one or more digit higher than a frequency for writing data, a differential current between the write current and a read current is sucked from the disgorging type constant current source by a sucking type constant current source, thereby allowing the read current to flow into the diode. In a writing mode, a current switch connects the sucking type current source according to write data. The disgorging type current source and the sucking type current source are connected to a photodiode by a current switch. An APC responds to the photodiode which detects a read power, thereby reducing a laser fluctuation created from temperature change.

Abstract: In an apparatus for supplying a current for driving a laser diode, an amount of current is supplied to the laser diode. During a read mode, a read peak current modified by a high frequency signal in addition to the amount of current is supplied to the laser diode, and during a write mode, a base read current in addition to the amount of current is supplied to the laser diode so that a light output of the laser diode is equal to a base read output. The read peak current is adjusted so that a mean value of the light output of the laser diode is equal to the base read output. An automatic control is performed upon the amount of current so that the light output of the laser diode is close to or approaches the base read output.

Abstract: A power supply circuit for supplying an electric power to a laser diode which is used for reading digital data on an optical memory medium, where the laser diode emits light when a current flowing therethrough exceeds a threshold level. The power supply circuit includes: a current source for outputting a current; an automatic power control circuit for controlling the current which is output from the current source so that an average power of light which is emitted from the laser diode to be equal to a predetermined value; a high frequency signal generating circuit for generating a high frequency signal; and a high frequency current control circuit for controllng a current which is supplied from the current source to the laser diode so that the current flowing through the laser diode is modulated by the high frequency signal.

Abstract: A system for obtaining an optimum focusing position in an optical disc system. An optical beam is impinged onto a track of an optical disc, and a reflection signal having information regarding an intensity of an optical beam reflected by an optical disc is obtained. A predetermined frequency component, the frequency component being generated by a modulation caused by an existence of a pit on a track of the optical disc in a reflecting signal, is extracted from the reflection signal. Then a focus position in which a maximum intensity of the extracted frequency component is obtained is searched by changing the focus position of the optical beam. Further, the above system is incorporated in a focus servo control system for maintaining an optimum focusing position in an optical disc system during reading and writing operations, to determine an optimum offset value which is to be adjusted to compensate an error arisen from a construction of the focus servo control system, during an offset adjusting operation.

Abstract: An optical disk access system capable of varying the focus position of a beam spot illuminating the optical disk. The focus position of the beam spot is varied in accordance with a mode of operation of the optical disk system. The various focus positions are automatically selected by the optical disk access system by intentionally vibrating the beam spot in a radial direction of the optical disk and detecting the amount of light reflected from the optical disk while varying a signal that changes the focus position of the beam spot. The optical disk system automatically selects a value of the signal determining the focus position of the beam spot that corresponds to maximum values derived from the light reflected from the optical disk.

Abstract: A tracking servo control system of an optical disk system produces a tracking control output signal for control of a tracking actuator which is adjusted to enable accurate positioning of a focussed light beam spot of the optical disk system at the center of a selected groove of a disk, for a variety of optical disks having various groove shapes. The output signal of a light receiver responsive to reflected image of the light beam spot focussed on the disk is processed to produce a tracking error signal:Y and a sum signal:X which are processed by a correction circuit for calculating the value: ##EQU1## where Z is a correction factor, the value of which is adjusted, to normalize the calculated value:E, in accordance with the peak detected value of E.

Abstract: A light control circuit of an optical disc system for controlling light from a light emitting element at a read power level even if a write data operation is performed. The light control circuit includes a light control circuit, a superimposedly energizing circuit for providing a light for data write and a subtraction circuit for subtracting a predetermined current from a light sensing element. A light control circuit may further include a reference value setting circuit for automatically finding and determining reference values of a read power level, a write power level, and a subtraction value. The reference values may be defined with respect to an origin of the characteristic of the light emitting element where a current flowing through the light emitting element is substantially zero.

Abstract: A focus servomechanism control system in an optical disc is provided for controlling a light focusing unit to adjust a focus of light impinging on a track in a rotatable optical disc. The focus servomechanism control system includes: a unit for moving the light focusing unit in a direction perpendicular to a plane of the optical disc; a unit for producing a focus error signal; a unit for producing a track error signal; and a unit for controlling a position of the light focusing unit through the light focusing unit moving unit in response to the focus error signal and the offset parameter. The focus servomechanism control system further includes an offset setting unit for continuously setting, during an offset adjustment mode, a plurality of offset parameters to the position control unit, to determine a maximum amplitude of the track error signal, and to set the offset parameter producing the maximum amplitude of the track error signal to the position control unit.

Abstract: A tracking servo apparatus for controlling a position of a light beam to follow an information track on an information storage disk. In response to a drive signal, a light-deflection mechanism moves the light beam onto the disk transversely with respect to the information track. The photodetector detects the difference in the intensity of the light beam in half sections and produces a radial error signal. The radial error signal is corrected in response to the drive signal which is applied to the light-deflection mechanism, and then a new drive signal is produced depending upon the corrected radial error signal.

Abstract: A method for removing liquid from the surface of a plate-shaped material, for instance, as applied to removing surface treatment liquids from metal plates of photographic film. While the plate-shaped material is being conveyed, a larger part of the liquid is removed from its surface by a first liquid removing device having a solid scraping surface positioned adjacent the surface of the plate-shaped material. This first liquid removing device may be a scraper blade or a pair of rollers. Subsequently, liquid remaining on the surface of the plate-shaped material is removed by a second liquid removing device, specifically, an air knife. The air flow rate and air pressure used with the air knife are sufficiently low that there is no significant scattering of liquid from the surface of the plate-shaped material.

Abstract: Novel glucosaminyl muramyl peptide derivatives of the formula: ##STR1## wherein X is hydrogen atom or a group of the formula: R.sub.1 CO--, Y is hydroxy group or a group of the formula: --OR.sub.2, ##STR2## R.sub.1 is an alkyl or alkenyl group, R.sub.2 is a lower alkyl group or a phenylalkyl group, R.sub.3 and R.sub.4 are the same or different and are each hydrogen atom or an alkyl group, Y' is hydroxy group or a group of the formula: --OR.sub.2 or ##STR3## (D) and (L) mean the configuration, provided that when X is hydrogen atom, Y is a group of the formula: ##STR4## and their pharmaceutically acceptable salts. They have excellent biological activities such as potentiating activity of nonspecific resistance to microbial infections and immunostimulant activity and hence are useful in the prophylaxis and treatment of various microbial infections.