JPH09161302A - Circuit and method for controlling semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a low speed and inexpensive CPU by successively setting an output current value of a current driver means among plural current driver means related to a sector. SOLUTION: A CPU 3 outputs an instruction voltage for making an output current of a current driver 9 a target value to an ALU 5 through a D/A converter 4. According to the operation result in the ALU 5, a signal (instruction value) (a') outputted from a sample-and-hold circuit to the current driver 9 is raised until it arrives at the target value, and continues to hold the value of an instant when the signal (d) is changed from an 'H' to an 'L'. In the sector n+1, the current driver 10 is turned on, and the instruction value b' outputted from the sample-and-hold circuit 7 is held, and in the sector (n+2), the current driver 11 is turned on, and the instruction value (c') outputted from the sample-and-hold circuit 8 is held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recording / reproducing information on / from an optical storage medium such as an optical disk using a semiconductor laser, and more particularly to a semiconductor laser control circuit for controlling driving of a semiconductor laser element.

[0002]

2. Description of the Related Art In general, a mark edge recording method is well known as one method for recording information on an optical disc or the like with high density. In this mark edge recording method, when recording is performed with a laser drive current having a normal pulse waveform,
There is a problem that the shape of the recording mark is distorted into a teardrop shape due to the effect of heat accumulation, and this is a cause of an increase in errors during reproduction particularly in mark edge recording using the recording mark length as data.

As a countermeasure against this, a recording waveform compensation (multi-value recording) system has been proposed in which information as shown by signal j in FIG. 3 is recorded with a waveform obtained by combining laser powers of several patterns.

As a semiconductor laser control circuit which realizes this recording waveform compensation method, Japanese Patent Laid-Open No. 2-68736 has been proposed. In this configuration, as shown in FIG. 5, the optical power control error signal voltage received by the photodetector PD and converted into a voltage is input to the input end of each one end, and the input end of each other end is First, second, and third operational amplifiers to which a reference voltage is input, a sample / hold circuit for controlling the output of each operational amplifier by a predetermined sample gate signal, and a power supply connected to the output side of each sample and hold circuit And a light emitting element (LD) that emits an output waveform formed by. FIG. 6 shows signal waveforms of these parts.

[0005]

However, according to the conventional circuit configuration described in the above-mentioned publication, the circuit configuration shown in FIG. 5 causes a gap between the preformatted area and the MO area in the sector as shown in FIG. It is necessary to perform test light emission in the provided ALPC area to set the power.

The ALPC area is an area in which the power level of light at the time of recording can be known, and is a section in which the level of light (laser) for reading is set before reading data. Hereinafter, it will be referred to as a recording power check unit.

Therefore, in order to realize the recording compensation waveform (write current waveform) as shown by the signal j in FIG. 3 with this circuit configuration, it is necessary to perform three-valued power setting in the ALPC area. .

Conventionally, it was sufficiently possible to set the power in the ALPC area as described above by the single hole recording method using the recording power of only one value. But,
High-density recording (long hole recording method and Z-
In the CAV recording), if the method shown in FIG.
2.6 GB magneto-optical disk standard with 130 mm diameter (SC23
According to / WG2N776), 6Byte (72channel bi
ts) only exists.

In such a standard, when the disk rotation speed is 3600 rpm, the channel clock frequency in the Z-CAV disk outermost zone (33Bands / 1024-bytesectors) reaches 67 [MHz] and passes the ALPC area. The time is 1.075 [μsec]
Becomes

In this ALPC area, the signal j of FIG.
In order to complete the three-value power setting as shown in, the one-value power setting is about 300 [nsec] (= 1.075 [μse
c] / 3).

In order to realize this with an accuracy of about ± 1%, in the configuration shown in FIG. 5, the bandwidth of the semiconductor laser APC (Auto Power Control) loop per channel is 17 [MHz] or more (17 [MHz] or more. ] 〓 (300
A bandwidth of [nsec] / 5) ^-1 ) is required. This corresponds to the RF band in the current optical disk recording / reproducing apparatus.

Therefore, a photodetector for a semiconductor laser monitor,
It is necessary to prepare wide-band compatible components that realize these bands in all the current / voltage conversion circuits, arithmetic circuits, and sample / hold circuits. Moreover, a circuit that realizes these widebands requires three circuits for each output value. Therefore,
It is difficult to realize the above method circuit at low cost.

Therefore, an object of the present invention is to provide a semiconductor laser control circuit capable of performing multi-value recording with a simple and low band circuit configuration by dividing power setting into a plurality of sectors.

[0014]

In order to achieve the above object, the present invention provides a photodetector for detecting the output light of a semiconductor laser and a current for converting a current signal detected by the photodetector into a voltage signal. A voltage converting means, including an instruction voltage generating means for generating a plurality of arbitrary reference voltages respectively, and an operating means for performing a comparison operation with the voltage converted by the current-voltage converting means based on each of the instruction voltages. When,
A holding means for sampling and holding the result calculated by the calculating means, a plurality of current driver means for setting an output current value for driving the semiconductor laser based on an output signal from the holding means, and a storage medium for storing the same. A semiconductor laser control circuit for sequentially setting the output current value of one current driver means of the plurality of current driver means for one sector, and a switch means for switching the driver means according to the data to be stored. I will provide a.

Further, the detected voltage signal received by the semiconductor laser and detected is compared with any one of a plurality of arbitrary instruction voltages serving as a predetermined reference, and based on the result, the semiconductor laser is driven. The setting of the output current value is performed for each sector by setting one output current value in the recording power check unit provided at the front of the sector.
Provided is a semiconductor laser control method which is sequentially performed for each sector or for each skipped sector.

The semiconductor laser control circuit and the control method therefor having the above-mentioned configuration are limited to one current driver for setting in one sector, so that the setting can be performed while being constituted by inexpensive parts operating at a relatively low speed. The time margin is increased and the current driver is set in consecutive sectors, so that the total setting time is shortened. Further, by setting the current driver every one sector, the time margin of setting is increased.

[0017]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a configuration example of a semiconductor laser control circuit as a first embodiment according to the present invention, and FIG. 2 shows a timing chart of signals of respective parts for explaining the operation, which will be described.

This semiconductor laser control circuit comprises a photodetector (PD) 1 for detecting the output light of a semiconductor laser, and a current-voltage converter 2 for converting the output current of the photodetector 1 into a voltage.
And a CPU 3 that generates a plurality of reference potentials (instruction voltage for setting an output current of a current driver, which will be described later, to a target value)
And a D / A converter 4 for converting an instruction voltage generated by the CPU 3 into an analog signal, and an operation for performing a comparison operation with the plurality of converted instruction signals and the voltage converted by the current-voltage converter 2. Unit 5, a plurality of sample / hold circuits (S / H circuits) 6, 7 and 8 for temporarily holding respective calculation results by the arithmetic unit 5, and the sample / hold circuits.
A plurality of current drivers 9, 10, whose output current values are set based on the outputs of the hold circuits 6, 7, 8, respectively.
11, a modulator 12 for controlling the timing operation of the output of each of the current drivers 9, 10, 11 and a light emitting element (LD) 13 for performing a light emitting operation based on the output of each of the current drivers 9, 10, 11. Composed of and.

Next, with reference to FIG. 2, the operation of the semiconductor laser control circuit thus constructed will be described. In FIG. 2, each signal a, b, c indicates the output waveform of the current driver 9, 10, 11, respectively, and each signal a ′, b ′,
c'shows the output waveforms of the sample / hold circuits 6, 7, and 8. Further, each of the signals d, e, f is sent to the modulator 12
Is a control signal for turning on / off the current drivers 9, 10, 11; when the signals d, e, f are "H", the current drivers are turned on, and when they are "L", they are turned off. Become.

Then, in the ALPC area of the sector n (recording power check section described above), the CPU 3 executes the D / A
Through the converter 4, an instruction voltage for setting the output current of the current driver 9 to a target value is output to the calculator 5. According to the calculation result of the calculator 5, the signal (instruction value) a ′ output from the sample / hold circuit 6 to the current driver 9 continues to increase until it reaches the target value, and the signal d changes from “H” to “H”. The value at the moment of switching to "L" is maintained.

Similarly, in the sector n + 1, the current driver 10 is turned on and the instruction value b'output from the sample / hold circuit 7 is held, and in the sector n + 2, the current driver 11 is turned on and the sample / hold circuit is turned on. The instruction value c ′ output from 8 is held.

When data is actually formed, for example, the current driver 9 controls the signal g shown in FIG. 3, the current driver 10 controls the signal h, and the current driver 1 controls by the modulator 12.
1 outputs the waveform shown by the signal i, and as a result, a multilevel signal of the combined output current like the signal j flows into the light emitting element 13 and emits light.

In FIG. 2, each current driver 9, 10,
The setting of 11 is performed in the sectors consecutive with the sectors n, n + 1, and n + 2. Next, FIG. 4 shows a timing chart for explaining the operation of the semiconductor laser control circuit according to the second embodiment. The configuration of the second embodiment is the same as that of the first embodiment described above, and the description thereof is omitted here.

In the signals d ', e', and f'shown in FIG. 4, the modulator 12 turns on / off the current drivers 9, 10 and 11, respectively.
It is a control signal for turning off, and is output every other sector in this embodiment. By these control signals, the movement of other circuits operates in the same manner as in the first embodiment.

As described above, in the semiconductor laser control circuit of this embodiment, by setting the output current value of one current driver in one sector, it is possible to control the output of the light emitting element with a low speed and inexpensive component. Becomes Further, by setting the output current value of the current driver in consecutive sectors, it becomes possible to control the output of the light emitting element (LD) at high speed with low speed and inexpensive parts.

Further, by setting the output current value of the current driver in each skipped sector, the processing time burden of the CPU controlling the entire circuit can be reduced, and the burden of program development can be reduced and the performance can be improved. Low cost CPU
It is possible to enable the use of

[0027]

As described above in detail, according to the present invention, it is possible to provide a semiconductor laser control circuit capable of performing multi-value recording with a simple and low-band circuit configuration in which power setting is divided into a plurality of sectors. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a semiconductor laser control circuit according to a first embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the semiconductor laser control circuit shown in FIG.

FIG. 3 is a diagram showing an example of a recording compensation waveform.

FIG. 4 is a diagram showing a configuration example of a semiconductor laser control circuit according to a second embodiment.

FIG. 5 is a diagram showing a configuration example of a semiconductor laser control circuit that realizes a conventional recording waveform compensation method.

FIG. 6 is a timing chart for explaining the operation of the conventional semiconductor laser control circuit.

[Explanation of symbols]

1 ... Photodetector (PD), 2 ... Current-voltage converter, 3 ... C
PU, 4 ... D / A converter, 5 ... Arithmetic unit, 6, 7, 8
... Sample / hold circuit (S / H circuit), 9, 10,
11 ... Current driver, 12 ... Modulator, 13 ... Light emitting element (LD).

Claims (3)

[Claims] 1. A light detecting means for detecting the output light of a semiconductor laser, a current-voltage converting means for converting a current signal detected by the light detecting means into a voltage signal, and a plurality of arbitrary instructions serving as references respectively. Instruction voltage generation means for generating a voltage, operation means for performing a comparison operation with the voltage converted by the current-voltage conversion means based on each of the instruction voltages, and holding means for sample-holding the result calculated by the operation means A plurality of current driver means for setting an output current value for driving the semiconductor laser based on the output signal from the holding means, and a switch means for switching the driver means according to the data stored in the recording medium. And sequentially setting the output current value of one current driver means of the plurality of current driver means per sector. The semiconductor laser control circuit, which comprises carrying out. 2. The semiconductor laser control circuit according to claim 1, wherein the setting operation of the output current value of the current driver means is performed in consecutive sectors or in every skipped sector. 3. A semiconductor laser is driven based on the result of comparison calculation of a detection voltage signal received by the semiconductor laser and detected by one of a plurality of arbitrary reference voltages serving as a predetermined reference. The setting of the output current value of 1 is set for each sector in the recording power check unit provided at the front of the sector, sequentially for each sector or for each skipped sector. A method for controlling a semiconductor laser, comprising: