KR100200819B1 - Laser diode power control method and circuit of the optical disk system - Google Patents

Abstract

The present invention relates to a laser diode power control method and circuit in an optical disc system. To this end, a laser diode is used as a light source, and an optical disc system having a photodiode as a means for sensing light emitted from the laser diode, wherein in the recording mode, the current output from the photodiode has a second predetermined recording gain. A current / voltage converter converting the voltage into a voltage by using the readout mode and converting the current output from the photodiode into a voltage by a first predetermined read gain, and rising and falling edges of data to be recorded on the optical disk. The edge detection unit for detecting the edge and the output value of the current voltage converter during the second predetermined time at the rising edge of the data detected by the edge detection unit in the recording mode and holding the sample; The electric current before the first predetermined time at the falling edge of the data. Monitors and monitors the light amount of the laser diode from a sample holding part for sampling and holding the output value of the converter, an analog / digital converter for converting the output value of the sample and hold part into a digital signal, and an output value of the analog / digital converter. A processor for controlling correction of a difference between a value and a preset value, and a recording for correcting the recording power by applying a current corresponding to a difference value of the recording power output from the processor to the laser diode Power adjusting means and read power adjusting means for correcting the read power by applying a current corresponding to a difference value of the read power output from the processor to the laser diode. Therefore, there is an advantage that can accurately compensate for the power fluctuations caused by the temperature rise of the laser diode.

Description

Laser Diode Power Control Method and Circuit in Optical Disc System

1 is a circuit diagram showing a conventional laser diode power control circuit in an optical disc system.

2 is a circuit diagram showing a laser diode power control circuit according to the present invention in an optical disc system.

3 is a diagram showing temperature characteristics of a laser diode.

4A to 4G are operational waveform diagrams of the respective parts in FIG.

* Explanation of symbols for the main parts of the drawings

31: MPU 32: laser diode means

33: current / voltage conversion unit 34: sample holding unit

35: analog / digital converter 36: edge detector

37,38: digital-to-analog converter 40: recording power correction means

50: read power correction means

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc system for optically writing and reading data, and more particularly, to a laser diode power control method and circuit for adjusting a level of a beam emitted from a light emitting element to a predetermined level.

An optical disk system used as a large capacity external memory device in an information processing apparatus has an advantage in that data can be recorded with a recording density of 10 times or more than that obtained in a conventional magnetic disk system.

In an optical disc system, data recording is performed by radiating a strong laser beam having a recording power level of about 5 to 10 dB at the laser diode, and when the emitted laser beam is applied onto the recording disc, the portion of the disc to which the light beam is applied. The magnet's magnetism changes (pits are formed) and recording is made.

When reading data recorded on the optical recording medium, a weak laser beam having a read power of about 1 kHz is applied by the reflected beam that is reflected by the disk.

In order to stably obtain the laser beam of the recording power level and the reading power level, the emission amount of the laser diode is monitored by the photodiode, and the laser control circuit controls the emission amount of the laser diode in response to the monitored current.

The laser diode has a unique characteristic, which is that the laser diode power changes as the temperature changes at the same driving current. Therefore, when a laser diode is used in an optical disk system, it must be adjusted so that a constant recording power level and a reading power level can be obtained regardless of temperature fluctuations.

FIG. 1 shows a conventional laser diode power control circuit in an optical disc system.

Referring to FIG. 1, the laser diode 1 includes a laser diode LD that emits beams of a write power level and a read power level, and a photodiode PD that monitors an amount of beams emitted from the laser diode LD. It is composed of

The photodiode current adjusting means 2 is constituted by the first variable resistor VR1 and is used to initially adjust the current flowing through the photodiode PD to a predetermined value.

The read power level detecting means 3 is composed of an operational amplifier 31, a resistor R10, a resistor R11, and a capacitor C1, and detects the photodiode voltage from the photodiode current adjusting means 2, and detects it. Compared to the photodiode voltage and the read power level set by the first digital-to-analog converters DAC1: 4, a current corresponding to a power fluctuation amount is compensated and output.

The voltage output from the first digital-to-analog converter DAC1: 4 is defined by the microprocessor unit (MPU) 21 such that the output voltage of the laser diode LD becomes a read power level.

The read power level current adjusting means 5 is composed of a transistor TR7, a coil L, and a resistor R12, and the driving current of the laser diode LD so that a beam having a read power level is emitted from the laser diode LD. Adjust it.

The recording power level current adjusting means 6 is composed of two parallel connection transistors TR8, transistors TR9 and resistors R13, so that the beam of the recording power level is emitted from the laser diode LD. Adjust the drive current. Here, the transistor TR8 and the transistor TR9 are connected to perform the differential operation to realize the high speed operation.

The second digital-to-analog converter DAC2: 7 is set to a predetermined output value by the microprocessor unit (MPU) 21 so that the laser diode LD in the laser diode means 1 emits a beam corresponding to the recording power level. have.

The recording power level setting means 8 is composed of a transistor TR12 and a resistor R15, and a laser beam whose laser diode LD corresponds to the recording power level set by the second digital-to-analog converter DAC2: 7. The reference recording power level is set in the recording power level current composition means 6 so as to emit light.

The recording power level subtraction setting means 9 is composed of a transistor TR13 and a variable resistor VR2, and is applied to a signal output from the second digital / analog converter DAC2: 7 to the recording power level subtraction setting means 9. Set the corresponding reference subtraction value.

The recording power level subtracting means 10 is composed of a transistor TR10, a transistor TR11, and a resistor R14, and is differentially connected to realize high speed operation. The recording power level current set by the recording power level subtraction setting means 9 is subtracted from the PD current in which the recording power level current and the read power level current overlap.

The level shifting means (11) is composed of an AND gate (AND), a zener diode (D1) and a zener diode (D2), a resistor (R16) and a resistor (R17), and a recording power level current forming means (6) and a recording power. The transistors TR8, transistor TR9, transistor TR10 and transistor TR of the recording power level current forming means 6 and the recording power level subtracting means 10 are operated so that the level subtracting means 10 operates in accordance with the recording data. Adjust the bias of TR11).

However, conventionally, as shown in FIG. 3, when the temperature of the laser diode is converted from C1 to C2, the laser diode power at the same driving current is also changed so that the driving current (IW, IR) must be adjusted again according to the temperature change. There is a hassle to get level read / write laser diode power.

In addition, when a video signal compressed using a technique such as data compression is to be recorded and reproduced for a long time, the laser diode power must be adjusted in the MPU without stopping recording and reproducing operations. However, since the pulse width of the recording data of the video signal is a short time of at least 80 ns to at most 320 ns, the analog-to-digital converter (ADC) 12 and the MPU 21 as shown in FIG. 1, which is a conventional optical control circuit (US Pat. No. 4,785,443). In the method of resetting the first digital-to-analog converter 4 and the second analog-to-digital converter 7 by using a), the MPU 21 needs some time to perform the calculation, so the recording and playback operations must be stopped. There is a problem. Therefore, when data is continuously recorded, the laser diode power fluctuates due to temperature. If you continue recording without correcting this, pits are not formed correctly on the recording medium. Will occur.

In addition, the read power level detecting means 3 must be inputted to the inverting input terminal of the operational amplifier 32 only by the amount of change in power on the basis of the read level of the photodiode PD, so that the laser diode predetermined by the variable resistor VR1 ( As much as the amount of change in the recording power of the LD) is compensated, the laser diode LD power is kept constant.

However, at the time of writing, the current of the photodiode PD should be subtracted by the current as much as the recording level, and therefore a subtraction circuit (transistors TR11 and TR13 and variable resistor VR2 in FIG. 1) is added. If the current is not subtracted as much as the recording level from the photodiode (PD) current at the time, the write photodiode voltage equal to the error due to the subtraction is added to the photodiode (PD) current of the read level, that is, the read level photodiode ( A voltage obtained by adding a PD level voltage to a recording level photodiode (PD) voltage and a laser diode (LD) power fluctuation amount is applied to the read power level detecting means (3), thereby affecting the read power and thus reading power level detecting means (3). Therefore, the compensation operation of the laser diode LD is different from the desired value. Therefore, the driving current of the laser diode LD of the read level different from the desired value flows to the laser diode LD. As a result, the read power of the laser diode LD does not come to the specified value, and there is a difficulty in that the fine tuning of the variable resistor VR2 is required.

Accordingly, an object of the present invention is to provide a laser diode power control method for adjusting read / write power of a laser diode even during a recording and reproducing operation using data to be recorded in an optical disc system in order to solve the above problems.

Another object of the present invention is to provide a circuit most suitable for realizing the laser diode power control method in an optical disc system.

In order to achieve the above object, the laser diode power control method according to the present invention in the optical disc system allows the output value of the photodiode to be converted into current / voltage with a first predetermined read gain in the read mode, and the converted value is A first step of setting the applied power until the first predetermined value is the read power value of the laser diode;

A second value for controlling the read power of the laser diode by sampling the output value of the photodiode at the time when the falling edge of the recording data is detected and correcting by the difference value compared with the read power value set in the first step; step ;

In the case of the recording mode, the output value of the photodiode causes current / voltage conversion to be performed by the second predetermined recording gain, and the applied power until the converted value matches the second predetermined value is used as the recording power value of the laser diode. Third step for setting to;

A fourth step for controlling the recording power of the laser diode by sampling the output value of the photodiode at the time when the rising edge of the recording data is detected and correcting by the difference value compared with the recording power value set in the third step; Characterized in that it comprises a step.

In order to achieve the above another object, a laser diode power control circuit according to the present invention uses a laser diode as a light source, and an optical disc system having a photodiode as a means for sensing light emitted from the laser diode,

In the recording mode, the current output from the photodiode is converted into a voltage by a second positive write gain, and in the read mode, the current output from the photodiode is converted into a voltage by a first predetermined read gain. Voltage conversion unit;

An edge detector for detecting a rising edge and a falling edge of data to be recorded on the optical disc;

In the recording mode, the output value of the current voltage converter is sampled and held for a second predetermined time at the rising edge of the data detected by the edge detector, and in the read mode, at the falling edge of the data detected by the edge detector. A sample holding unit sampling and holding an output value of the current voltage converting unit for one predetermined time;

An analog / digital converting unit for converting an output value of the sample holding unit into a digital signal; A processor configured to monitor an amount of light of the laser diode from an output value of the analog / digital converter and to correct a difference value between a monitor value and a preset value;

Recording power adjusting means for correcting the recording power by applying a current corresponding to a difference value of the recording power output from the processor to the laser diode; And

And a read power adjusting means for correcting the read power by applying a current corresponding to the difference value of the read power output from the processor to the laser diode.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

2 is a circuit diagram of an embodiment of a laser diode power control circuit according to the present invention in an optical disc system.

The configuration of the circuit diagram shown in FIG. 2 includes a laser diode means 32 including a laser diode LD as a light source and a photodiode PD for sensing light emitted from the laser diode LD, and in the recording mode. The current output from the photodiode PD is converted into a voltage by a second predetermined write gain, and in the read mode, the current output from the photodiode PD is converted into a voltage by a first predetermined read gain. The current / voltage converter 33, the edge detector 36 for detecting the rising edge and the falling edge of the data to be recorded on the optical disc, and the rising edge of the data detected by the edge detector 36 in the recording mode. Sampling and holding the output value of the current / voltage converter 33 during the second predetermined time, and in the read mode, the current / voltage converter 33 during the first predetermined time at the falling edge of the data detected by the edge detector 36 Of) From the sample holding unit 34 for sampling and holding the output value, the analog / digital converting unit 35 for converting the output value of the sample holding unit 34 into a digital signal, and the output values of the analog / digital converting unit 35 Corresponds to the difference between the recording power output from the processor (MPU) 31 and the processor 31 which monitors the amount of light of the laser diode LD and controls to correct the amount of difference between the monitor value and the preset value. By applying as much current as possible to the laser diode LD, a current corresponding to the difference between the recording power adjusting means 40 for correcting the recording power and the reading power output from the processor 31 is supplied to the laser diode ( Read power adjusting means 50 for correcting the read power by applying to LD).

3 is a diagram showing temperature characteristics of a laser diode.

4A to 4G are operation waveform diagrams of the respective parts in FIG. 2, and FIG. 4A is modulated write data input to the edge detector 36 at point (1), and FIG. 4B is MPU at point (2). The rising edge detection enable signal output from (31), FIG. 4C is the falling edge detection enable signal output from the MPU 31 at the point (2), and the edge detection unit 36 at the point (3) is shown in FIG. The rising edge detection signal outputted in Fig. 4e is the falling edge detection signal outputted by the edge detector 36 at point (3), and the input signal of the sample holding portion 34 at point (4) is shown in Fig. 4f. 4g shows an output signal of the sample holding section 34 at the point (5).

The operation of the present invention will now be described in detail with reference to the accompanying drawings.

Referring to FIG. 2, an initial setting process of the read / write power of the laser diode LD is as follows.

First, in the read mode, the MPU 31 turns off the switch SW1 so that the photodiode (PD) output is converted into current / voltage by the read gain by the current / voltage converter 33, and the MPU 31 is performed. ) Incrementally increases the value of the second digital-to-analog converter 38 through the analog-to-digital converter 35 until this converted value reaches a predetermined value.

When the value of the photodiode PD matches the desired read level, the MPU 31 determines and sets the value of the second digital-to-analog converter 38 at that time as the read power value of the laser diode LD. That is, this value is output from the second digital-to-analog converter 38 so that a current having a read level is supplied to the laser diode LD through the transistor TR6, and the laser diode LD corresponds to the read power. It emits light.

When the initialization of the read power is completed normally, the write power is initialized. At this time, the write power is supplied to the laser diode LD by adding a current corresponding to the write power level to the current of the read power level.

That is, in the recording mode, the MPU 31 turns on the switch SW1 to cause the photodiode PD output to perform the current / voltage conversion by the recording gain by the current / voltage conversion unit 33, and the MPU ( 31) gradually increases the value of the first digital-to-analog converter 37 through the analog-to-digital converter 35 until this converted value reaches a predetermined value. When the value of the photodiode PD matches the desired recording level, the MPU 31 determines and sets the value of the first digital-to-analog converter 37 at that time as the recording power value of the laser diode LD. That is, this value is outputted by the first digital-to-analog converter 37 so that the current of the write level through the transistor TR5 is added to the read level of the current through the transistors TR1 and TR3 to the laser diode LD. The laser diode LD is supplied to emit light corresponding to the recording power.

At the time of writing, when the recording data is 'high', the transistors TR1 and TR3 are turned on, and the transistors TR2 and TR4 are turned off, and the laser diode LD driving current at the recording level is sinked to ground. . Therefore, only the current corresponding to the read level is supplied to the laser diode LD to emit light with the read power.

The laser diode power control is performed by the edge detector 36 and the sample hold 34 during the read / write operation. The write power control is performed in the following order.

When the modulated data D _WR to be recorded is input as in 4a, the MPU 31 outputs a rising edge detection enable signal for a predetermined time, and the switch SW1 is turned on.

During the enable period, the edge detector 36 detects and outputs the rising edge of the recording data, and if the sample hold 34 detects and holds the value of the photodiode PD, the MPU 31 performs the analog / digital converter ( Through 35), the output of the photodiode PD, that is, the light amount of the laser diode LD is monitored.

If there is a difference between the monitored value and the previously set value, the first digital-to-analog converter 37 is reset by correcting the corresponding amount. Since this operation can be performed without stopping the recording operation, it can be usefully used for long time recording such as recording of a video signal.

In addition, the read power control is similar to the recording power control, and only by switching off the switch SW1 and using the falling edge instead of the rising edge, the value of the photodiode PD is monitored and compared with the previously set value. The value of the digital-to-analog converter 38 is readjusted and set.

As described above, the laser diode power control method and circuit according to the present invention in the optical disc system can keep the laser diode reading and the recording power constant even while the recording operation is in progress, thus corresponding to the modulated recording data. There is an advantage that an accurate pit can be formed on the recording medium. Therefore, there is an advantage that not only the recording error that may occur during recording but also the jitter becomes smaller during playback, thereby reducing the playback error.

In addition, there is an advantage that the recorded data can be accurately reproduced by keeping the read power of the laser diode constant while the reproducing operation is in progress.

Claims (5)

In the case of the read mode, the current / voltage conversion is performed with the first predetermined read gain of the photodiode, and the applied power is converted into the read power value of the laser diode until the converted value matches the first predetermined value. A first step for setting up; A second value for controlling the read power of the laser diode by sampling the output value of the photodiode at the time when the falling edge of the recording data is detected and correcting by the difference value compared with the read power value set in the first step; step; In the case of the recording mode, the output value of the photodiode causes current / voltage conversion to be performed by the second predetermined recording gain, and the applied power until the converted value matches the second predetermined value is used as the recording power value of the laser diode. A third step for setting to; A fourth step for controlling the recording power of the laser diode by sampling the output value of the photodiode at the time when the rising edge of the recording data is detected and correcting by the difference value compared with the recording power value set in the third step; Laser diode power control method comprising the step of. In an optical disc system including a laser diode as a light source and a photodiode as a means for sensing light emitted from the laser diode, in a recording mode, the current output from the photodiode is controlled by a second predetermined recording gain. A current / voltage converter converting the voltage into a voltage and converting the current output from the photodiode into a voltage by a first read gain in the read mode; An edge detector for detecting a rising edge and a falling edge of data to be recorded on the optical disc; In the recording mode, the output value of the current voltage converter is sampled and held for a second predetermined time at the rising edge of the data detected by the edge detector, and in the read mode, at the falling edge of the data detected by the edge detector. A sample holding unit sampling and holding an output value of the current voltage converting unit for one predetermined time; An analog / digital converting unit for converting an output value of the sample holding unit into a digital signal; A processor configured to monitor an amount of light of the laser diode from an output value of the analog / digital converter and to correct a difference value between a monitor value and a preset value; Recording power adjusting means for correcting the recording power by applying a current corresponding to a difference value of the recording power output from the processor to the laser diode; And read power adjusting means for correcting the read power by applying a current corresponding to a difference value of the read power output from the processor to the laser diode. The photodiode of claim 1, wherein the current / voltage converter is turned off in a read mode so that the output of the photodiode performs current / voltage conversion by the read gain, and is turned on in a write mode. A switch for causing the output of the diode to perform current / voltage conversion by the write gain; And a current / voltage converter for converting the output of the photodiode into a voltage with a current / voltage conversion gain set by an on / off operation of the switch. 3. The apparatus of claim 2, wherein the recording power adjusting means comprises: a digital / analog converter for converting a difference value of the recording power output from the processor into an analog signal; And a plurality of amplifying means for applying a current corresponding to the output signal of the digital-to-analog converter to the laser diode. 3. The apparatus of claim 2, wherein the read power adjusting means comprises: a digital / analog converter for converting a difference value of the recording power output from the processor into an analog signal; And an amplifying means for applying a current corresponding to the output signal of the digital to analog converter to the laser diode.