Kabushiki Kaisha Toshiba

Toyoki Taguchi

Masayuki Tazawa

Naomasa Nakamura

Naoki Morishita

Yoshinori Honguh

Tadashi Kobayashi

Hiroshi Hasegawa

Hisashi Yamada

Toshihiro Sugaya

Isao Hoshino

Masahiko Tanaka

Kei Shimura

Tetsuya Nagahama

Teruo Murakami

Hiromichi Kobori

Hiroharu Satoh

Makoto Morimoto

Masaaki Matsumaru

Sadanari Fujimoto

The semiconductor laser apparatus includes a semiconductor laser, a detection element for detecting the intensity of the output light from the semiconductor laser, an error detection circuit containing a gain controllable operation amplifying circuit and a gain-fixed type control amplifying circuit connected to a next stage to the gain controllable operation amplifying circuit, to which a semiconductor laser drive control signal is input and an output signal of the detection element is input as a negative feedback signal, for outputting an error signal corresponding to a difference between the two input signals, a high-frequency signal generating circuit for generating a high-frequency signal having a predetermined frequency, a high-frequency signal superimposing circuit for superimposing the high-frequency signal onto the output signal from the error detection circuit, and a laser drive circuit for supplying a drive current to the semiconductor laser on the basis of the output signal from the high-frequency signal superimposing circuit.

Semiconductor laser apparatus, information recording/reproduction apparatus and image recording apparatus

In a laser-driving device including a high-frequency current generating circuit generating a high-frequency current superimposed on a control current output from a light intensity control circuit for light intensity control, and supplied to a laser diode as a drive current, the high-frequency current generating circuit has a sourcing current source, a sinking current source, current switches connected between the current sources and a drive output terminal respectively, a gated oscillation circuit oscillating with a desired frequency, and switch drive circuits complementarily on/off controlling the current switches by using a drive switching signal obtained by removing a high-frequency component from an output signal of the oscillation circuit. The present invention, therefore, provides a high-frequency current generating circuit which can increase the amplitude of the high-frequency current superimposed on the control current of the laser diode and which generates less heat while suppressing power consumption.

High-frequency current generating circuit and control device for controlling light intensity of laser diode

In a laser drive circuit for use in an optical disc recording and reproducing apparatus, a P-channel MOS transistor acting as a drive current source generates a drive current I depending on a setting current Ic. A P-channel MOS transistor acting as a current switch supplies the drive current I to a semiconductor laser, in response to a drive pulse signal CP. An OP amplifier controls a setting current Ic depending on a monitor current Im and a setting voltage Vc. A capacitor removes noise generated by the transistor acting as a current switch and superposed on the drive current I .

Laser drive circuit and recording apparatus using the same

There is provided an input circuit including a current/current conversion circuit and a current change-over circuit for converting an input control current into an inside control current; a control amplification circuit for amplifying a voltage corresponding to a difference current between an output current from the input circuit and a monitor current which is fed back from the photodetector for detecting a light output of the LD; an output circuit which is controlled with an output from the control amplification circuit; an offset compensation circuit for compensating for the offset generated between the input of the current/current conversion circuit and the output of the control amplification circuit, so that the offset is detected to compensate for the offset in the state in which the output of the control amplification circuit is cut off with the switch.

Semiconductor laser driving circuit and semiconductor laser device

The semiconductor laser apparatus includes a semiconductor laser, a detection element for detecting the intensity of the output light from the semiconductor laser, an error detection circuit containing a gain controllable operation amplifying circuit and a gain-fixed type control amplifying circuit connected to a next stage to the gain controllable operation amplifying circuit, to which a semiconductor laser drive control signal is input and an output signal of the detection element is input as a negative feedback signal, for outputting an error signal corresponding to a difference between the two input signals, a high-frequency signal generating circuit for generating a high-frequency signal having a predetermined frequency, a high-frequency signal superimposing circuit for superimposing the high-frequency signal onto the output signal from the error detection circuit, and a laser drive circuit for supplying a drive current to the semiconductor laser on the basis of the output signal from the high-frequency signal superimposing circuit

Semiconductor laser control circuit, semiconductor laser apparatus, information recording/reproduction apparatus and image recording apparatus

An input signal is supplied to an adder circuit via a gain control amplifier and integrating amplifier and output signals of the gain control amplifier and the integrating circuit are added together by the adder circuit. An output signal of the adder circuit is supplied to a driving current generating circuit. The driving current generating circuit is constituted by first and second transistors whose bases and emitter are commonly connected. An externally attached resistor monitors a driving current flowing in the collector of the transistor constructing the driving current generating circuit and feeds back the current to the gain control amplifier. Therefore, the current control operation of high precision can be attained by use of a part of the driving current.

Laser driving circuit capable of stably controlling laser output

The present invention provides a peak and bottom detecting circuit including a current source for charging or discharging the capacitor, a switch for connecting the current source to the capacitor, a comparator for comparing a potential of a connection node between the switch and the capacitor, and a potential of an input signal with each other, and for turning the switch on/off in accordance with the result of the comparison, a buffer for buffering the potential of the connection node between the switch and the capacitor, and outputting an output signal, and a damper for comparing the potential of the output signal and the potential of the input signal and reducing the current allowed to flow from the current source as the potential difference becomes smaller.

Semiconductor integrated circuit device

There is provided a semiconductor laser driving circuit. The circuit has: an amplifier for receiving an emission level setting voltage, and outputting a first driving signal on the basis of the emission level setting voltage; a driving signal generation circuit for receiving a control signal for instructing a light-emission period of a semiconductor laser, and the first driving signal output from said amplifier, and outputting a second driving signal corresponding to a level of the first driving signal in accordance with a light-emission or extinction period; a driving circuit for receiving the second driving signal output from said driving signal generation circuit, and generating and outputting a driving current to be supplied to the semiconductor laser; and a control circuit for receiving the emission level setting voltage, and adjusting a level of the second driving signal during the extinction period in correspondence with the emission level setting voltage.

Semiconductor laser driving circuit, semiconductor laser device, image

A laser light control circuit with low power consumption and a small amount of heat generation by superposing a control current output from a light quantity control circuit with a high-frequency current output from a high frequency current generator on the basis of the control current, includes a bias circuit which sets a bias current of the high-frequency current in response to the operation voltage of a semiconductor laser element.

Laser light control circuit, optical pickup unit and optical pickup

An optical recording medium, which has a land and a groove on which a record mark is formed, comprises a transparent substrate, an inner protection layer formed on the substrate, a recording material layer formed on the inner protection layer and a reflection layer formed on the outer protection layer. The groove is formed to have a depth of .lambda./6 and the ratio of the thickness of the outer protection layer to the thickness of the recording material layer is set in a range between 0.8 and 1.2.

Optical recording medium and optical recording/reproducing apparatus

A primary optical disk recording apparatus comprises a first light source for recording a signal on a primary optical disk, an objective lens for converging a light beam from the first light source on the primary optical disk, a second light source for detecting a focus error between the objective lens and the primary optical disk, and a controller for detecting a reflection light beam from the first light source, which is reflected from the primary optical disk, while the signal is being recorded on the primary optical disk, and for subjecting a signal of the reflection beam to an arithmetic operation process, thereby detecting a first focus error signal and controlling the focus error on the basis of the first focus error signal.

Apparatus for recording information on a primary optical disk to

A semiconductor laser apparatus comprises a semiconductor laser, a photodetector, first and second variable gain units, a controllable amplifying unit, a driving unit, and a compensation unit. A control signal is supplied to one of input terminals of each of the first and second variable gain units and an output signal of the photodetector is negative-fed back to the other of the input terminals of each of the first and second variable gain units. A varied gain of an error between the control signal and the output signal is output independently of each of the first and second variable gain units. The controllable amplifying unit amplifies the error signal from the first variable gain unit with desired frequency characteristics. The driving unit includes a plurality of driving elements connected in parallel and supplies a driving current to the semiconductor laser in accordance with a drive control signal from the controllable amplifying unit. The compensation unit negatively feeds back a compensation current to the negative feedback terminals to compensate a phase delay on the basis of the error signal output from the second variable gain unit.

Device for driving a semiconductor laser by a plurality of driving

A semiconductor laser apparatus comprises a semiconductor laser, a photodetector, first and second variable gain units, a controllable amplifying unit, a driving unit, and a compensation unit. A control signal is supplied to one of input terminals of each of the first and second variable gain units and an output signal of the photodetector is negative-fed back to the other of the input terminals of each of the first and second variable gain units. A varied gain of an error between the control signal and the output signal is output independently from each of the first and second variable gain units. The controllable amplifying unit amplifies the error signal from the first variable gain unit with desired frequency characteristics. The driving unit supplies a driving current to the semiconductor laser in accordance with a drive control signal from the controllable amplifying unit. The compensation unit negatively feeds back a compensation current to the negative feedback terminals to compensate a phase delay on the basis of the error signal output from the second variable gain unit.

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Yokohama, Japan

Toyoki Taguchi