JPH0541567Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a semiconductor laser drive device used to write information by irradiating semiconductor laser light onto a magneto-optical recording medium or a heat mode recording medium. It is.

[Summary of the idea]

The present invention provides a semiconductor laser driving device for forming substantially uniform pits over the entire surface of a disk, which is a recording medium. That is, in a semiconductor laser driving device that has an automatic optical output control circuit section that keeps the emission power of the semiconductor laser constant regardless of temperature and a current switch section that superimposes a modulated current, the automatic optical output control circuit section Shunt electronic switch means are provided at the terminals of the operational amplifier that sets the rated light emission and at the base of the constant current transistor that constitutes the current switch section to control ON/OFF of the light emission power. Furthermore, an electronic switch means is provided to switch the reference voltage applied to the terminal for setting the rated light emission of the operational amplifier for setting the rated light emission, thereby controlling the DC light emission power and controlling the current flowing through the constant current transistor of the current switch section. Electronic switch means are provided to enable switching of the modulation current.

[Conventional technology]

In order to write information such as image signals or audio signals to a magneto-optical recording medium or a heat mode recording medium, an intensity-modulated laser beam is irradiated along a spiral or concentric track with an accuracy of several μm or less. things are being done.

Conventionally, the configuration shown in FIG. 2 is generally known as a semiconductor laser driving device that performs the above-described operation. In the figure, reference numeral 11 denotes an automatic light output control circuit for causing a constant current Idc to flow through the semiconductor laser 2 to emit rated light. The light emitting power is controlled by feeding back the current I _M flowing through the monitor photodiode 3 mounted together with the semiconductor laser 2 in the package 12 so that the light emitting power is always constant regardless of temperature changes. . When writing to an information recording medium, the intensity of the laser beam is modulated. To do this, a modulation current I _AC is applied to the current switch section 13, and this is added to Idc to drive the semiconductor laser 2. good. Current switch part 1
The input terminal 5 of No. 3 receives information to be written onto the recording medium. The above-mentioned technology was developed in Japanese Patent Application Laid-open No. 1983-
No. 129949 or Japanese Patent Application Laid-Open No. 59-94253.

Now, with the semiconductor laser drive device as described above,
It is possible to record information and reproduce the written information. However, in order to form uniform pits over the entire disk surface, which is a recording medium, additional functions must be added. That is, if the semiconductor laser drive device shown in FIG. 2 is used for a disk that rotates at a constant frequency, when writing to the outer periphery of the disk, the writing energy becomes insufficient and good writing becomes impossible.

This is because conventional devices do not have a function to control Idc and change the residual heat power to the disk. Furthermore, since I _AC cannot be controlled according to the position on the disk surface, there will be excess or deficiency in the write power.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings. In FIG. 1, reference numeral 1 denotes a slow start circuit that supplies voltage to the entire semiconductor laser drive device, and has the function of removing surge components contained in the power supply and preventing damage to the semiconductor laser. The semiconductor laser 2 is DC driven by the transistor _Q1 and emits light. A monitor photodiode 3 mounted together with the semiconductor laser 2 monitors the state of light emission, and the current flowing therein is converted into voltage by a resistor R1 and amplified by an operational amplifier OP1. The output of OP1 drives the base of transistor Q1 through an inverting integral compensation circuit constituted by OP2, so that the DC light emission always remains constant.

Transistors Q2 and Q3 are current switch sections. By alternately switching Q2 and Q3, the semiconductor laser 2 produces an optical output in which modulated light is superimposed on DC light. Switching of Q2 and Q3 is operated by applying a modulation waveform via coupling capacitors C1 and C2. 4
is a modulation circuit, and information to be written on the information recording medium is inputted from a terminal 5.

Transistor Q4 is a constant current element. Q4
By adjusting the current flowing through the collector of
The amplitude of modulated light can be changed. operational amplifier
OP3 has this function and amplifies the output of the constant voltage generating circuit 6 in the normal direction to drive the base of Q4.

Electronic switch SW1 inserted in series between the base of Q4 and the output power line of slow start circuit 1
An electronic switch SW2 inserted in series between the normal rotation terminal of OP2 and the output power line 1 is opened and closed by a switch drive circuit 7, and is operated by a command from a laser power on/off terminal 8.

Terminals of the electronic switches SW5 and SW4 are connected to a constant voltage generating circuit 9, and desired voltages are respectively set. The other terminals of SW3 and SW4 are wired in common and connected to the normal rotation terminal of OP2 via a resistor. Since the base of Q1 is configured to be driven by the voltage set by SW3 and SW4, SW3 and SW4 determine DC light emission. Note that SW3 and SW4 are not turned on or off at the same time. Electronic switch SW5 provided in the return path of OP3 performs the same opening/closing operation as SW4. SW3 is on and SW4, SW
When 5 is off, SW3 is off and SW4,
Compared to the case where SW5 is in the on state, both the DC light emission and the modulated light emission superimposed thereon are increased. Input terminal 10 of switch drive circuit 7
This controls the opening and closing of SW3, SW4, and SW5, and attempts to achieve good recording by changing the writing level of the laser beam on the inner and outer circumferences of the information recording medium.

[Effect of idea]

As explained above, the present invention enables ON/OFF control of laser emission and switching control of emission power by providing electronic switch means in the automatic light output control circuit section and current switch section of the semiconductor laser. This has the effect of making the recording pits uniform and stabilizing the quality of recording and reproducing information.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a semiconductor laser driving device according to the present invention, and FIG. 2 is a block diagram showing a conventional semiconductor laser driving device. 2... Semiconductor laser, 3... Monitor photodiode, 4... Modulation circuit, 6... Constant voltage generation circuit, 7... Switch drive circuit, 9... Constant voltage generation circuit, 11... Automatic optical output control circuit , 13...Current switch section, Q1, Q2, Q3, Q4...
Transistor, OP1, OP2, OP3...Operation amplifier, SW1, SW2, SW3, SW4, SW5...
...Electronic switch.

Claims (1)

[Claims for Utility Model Registration] In a semiconductor laser driving device having an automatic light output control circuit section for keeping the emission power of the semiconductor laser constant, and a current switch section for superimposing a modulated current on the semiconductor laser, the above-mentioned An electronic switch is provided in a terminal of an operational amplifier that sets the rated light emission of the automatic light output control circuit section and a constant current element constituting the current switch section to control intermittent light emission power, and to control the rated light emission of the operational amplifier. 1. A semiconductor laser driving device, comprising: electronic switch means for switching a reference voltage of a terminal to be set; and electronic switch means for controlling a current flowing through a constant current element of the current switch section.