KR20080046997A - Apparatus and method for automatically controlling laser power in the optical device - Google Patents

Abstract

An automatic laser power control device in an optical recording apparatus and a method thereof are provided to generate multiplexed laser power suitable for a system using multiplexed laser power, and achieve programmable control of recording power according to changes of surroundings or temperature. An automatic laser power control device in an optical recording apparatus comprises an FPD(Front Photo Diode,360), a first sample/hold unit(300), a second sample/hold unit(310), a multiplexer(320), a DSP(Digital Signal Processor,330), and a laser diode driver(340). The FPD detects laser emitted from a laser diode(350) as an electrical signal. The first sample/hold unit is configured to perform sampling of bottom level of a detected signal of the FPD and hold the signal. The second sample/hold unit is configured to perform sampling of signal level of the detected signal of the FPD and hold the signal. The multiplexer selects one output from the first or the second sample/hold unit according to a signal of media type discriminated by a control unit. The DSP generates a reference voltage to control drive current of the laser diode by comparing the FPD signal inputted from the multiplexer with a target power level. The laser diode driver generates drive current on the basis of the reference voltage from the DSP and outputs it to the laser diode.

Description

Apparatus and Method for automatically controlling laser power in the optical device}

1 is a view showing the configuration of a conventional automatic laser power control device.

Figure 2 is a graph recording the laser diode output in a conventional ALPC device.

3 is a view showing the configuration of the present invention ALPC device.

Figure 4 is a view showing the configuration of a laser diode driver in the ALPC device of the present invention.

FIG. 5A is a diagram showing the configuration of the recording DAC of FIG. 4; FIG.

Figure 5b is a graph recording the laser diode output according to the Non-Return to Zero Inverted (NRZI) pattern in the ALPC device of the present invention.

Figure 6 is a graph recording the laser diode output in the ALPC device of the present invention.

7 is a signal flow diagram showing an automatic laser power control method of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for controlling power of a laser during recording of an optical recording device. In particular, a laser diode driver and a front photo diode capable of generating a plurality of laser intensities when recording data on a media are provided. A method and apparatus for controlling the power of a laser using only additional circuitry for signal level measurement.

The optical recording device uses a laser diode to generate a laser signal for reproducing, erasing, or recording data on the media. The optical recording apparatus uses a laser having an intensity capable of reproducing data on such media (hereinafter referred to as a reproduction intensity laser). ), An intensity laser capable of erasing data stored on the media (hereinafter referred to as erasing intensity laser), and an intensity laser capable of recording data on the media (hereinafter referred to as recording intensity laser) are fixed values for accurate recording. Should be maintained.

However, the laser diode has very sensitive input / output characteristics depending on the operating temperature. Therefore, an automatic laser power control (ALPC) device for controlling the driving of the laser diode is used in a device for recording data on the media.

1 is a view showing the configuration of a conventional ALPC device.

Typically, an ALPC device consists of three channels: VRDC, VWDC, and VWDC2.

The VRDC (Voltage Read Disk Channel) 100 includes a VRDC level sample / hold unit 101, a DDC (Digital to Analog Converter) 103 and an operational amplifier 105 for a VRDC channel. The DAC 103 converts a predetermined reproduction power reference signal into an analog signal. The sample / hold unit 101 samples and holds a signal detected by the front photo diode (FPD) in the optical pickup unit 130, and the analog output signal and the sample / hold unit 101 of the DAC 103 The operational amplifier 105 amplifies the sampled and held signal to generate a VRDC voltage.

The VWDC 110 includes a VWDC level sample / hold unit 111, a VWDC channel DAC 113, and an operational amplifier 115. The DAC 113 converts a preset erase power reference signal into an analog signal. The sample / hold unit 111 samples and holds a signal detected by the FPD in the optical pickup unit 130, and the analog output signal and the sample / hold unit 111 of the DAC 113 are sampled and held. The operational amplifier 115 amplifies the signal to generate a VWDC voltage.

The VWDC2 120 is configured as a VWDC2 channel DAC 121. The VWDC2 120 converts a preset recording power reference signal into an analog signal, and the converted analog signal is converted into a VWDC2 channel. It is output as a voltage.

On the other hand, in the case of recording data on media such as an optical disk, the laser diode in the optical pickup unit 130 generates lasers of various intensities, and generally generates lasers in the form of multi-pulse intensity.

In the recording mode for recording data, the laser intensity of the multi-pulse type is different for each media.

In the case of read-write media that can be written once, two lasers, a reproduction intensity laser and a recording intensity laser, are generated using two channels of the VRDC 100 and the VWDC2 120, and a rewritable laser is generated. In the case of a rewritable recording medium, three lasers, a reproduction intensity laser, an erasing intensity laser, and a recording intensity laser, are generated using three channels of the VRDC 100, the VWDC 110, and the VWDC2 120. .

The ALPC device detects the intensity of the laser output from the laser diode by using a front photo diode (FPD), and adjusts the driving current output to the laser diode according to the variation of the detected laser intensity to a constant intensity in the laser diode. The laser is outputting. In order to produce a laser having a constant regeneration intensity from the laser diode during reproduction, the VRDC voltage is adjusted according to the variation of the FPD signal, the VWDC voltage is adjusted during erasing, and the VWDC2 voltage is adjusted during recording.

Figure 2 is a graph recording the laser diode output in a conventional ALPC device.

Conventional laser diodes start recording at room temperature, and as the recording time elapses, heat is emitted from the laser diode, which is thus stored in the laser diode. The temperature of the laser diode is increased by the heat storage, and the intensity of the laser output from the laser diode is reduced even when the driving current of the same level is supplied to the laser diode.

Therefore, as the VWDC voltage and the VWDC2 voltage increase, the driving current supplied by the optical pickup unit 130 to the laser diode is increased to output a laser of a constant intensity from the laser diode.

In the conventional temperature compensation scheme for the laser intensity, in the case of the signal level 210 of the VWDC channel, the operational amplifier is configured to generate a signal and a preset signal detected and fed back from the FPD in the optical pickup unit 130 of FIG. 1. Although the compensation is automatically performed, the signal level 200 of the VWDC2 channel is used as an open-loop without a feedback loop from the FPD, and then the signal level 210 of the VWDC channel changes over time. We had to compensate in proportion.

As described above, a laser having two to three intensities is conventionally used when reproducing or recording data, and a feedback loop of ALPCs of the VRDC 100 and VWDC 110 channels is provided to maintain the constant laser intensity. At least two were required.

In particular, in the case of Blu-Ray discs, an optical disc standard that is capable of storing digital data of high definition video, the type of recording intensity laser is output from a laser diode during data recording. In one predetermined write strategy, there is a problem that the conventional technique cannot cope with it because the intensity of the laser can be used in three or more levels at the time of data recording.

Accordingly, an object of the present invention is to generate multiple laser intensities to cope with a system using multiple laser intensities, such as a Blu-Ray disc, and to record power in accordance with ambient environment or temperature change. To provide an automatic laser power control device and method that can control the programmable (Programmable).

The automatic laser power control apparatus of the optical recording apparatus of the present invention for achieving the above object is to sample and hold the FPD for detecting the laser emitted from the laser diode as an electrical signal, and the bottom level of the detection signal of the FPD A first sample / hold unit, a second sample / hold unit for sampling and holding the signal level of the detection signal of the FPD, and an output of the first sample / hold unit and the second sample / hold unit according to a media type signal A multiplexer for selecting one, a DSP for generating a reference voltage for controlling a driving current of a laser diode by comparing an FPD signal input from the multiplexer with a target power level, and a driving current based on a reference voltage output from the DSP The laser diode driver generates and outputs the laser diode.

A method of controlling recording power for recording data on an optical recording medium, the method comprising: calculating a target FPD signal level corresponding to a target recording power, and detecting the FPD signal by the FPD of the optical recording apparatus; The controller determines the type of media to generate an operation control signal, and the sample / hold unit samples and holds the detected FPD signal according to the presence or absence of the operation control signal, and the DSP inputs the FPD from the sample / hold unit. Computing a reference voltage by comparing the signal level with the calculated target FPD signal level, characterized in that the step of applying the calculated reference voltage to the reference DAC.

Hereinafter, with reference to the accompanying drawings will be described in more detail the objects, features and advantages of the present invention.

3 shows a schematic diagram of an ALPC circuit according to the present invention.

The ALPC circuit includes: a first sample for sampling and holding the bottom level of the detection signal of the FPD 360 and the FPD 360 for detecting the output of the laser diode driver 340, the laser diode 350; A second sample / hold unit 310 for sampling and holding a level of a specific section according to the hold unit 300 and the operation control signal WFPDSH, and a first sample / hold unit 300 and a second unit according to a media type signal A multiplexer 320 selecting any one of the outputs of the sample / hold unit 310 and a reference compensated by converting an FPD signal output from the multiplexer 320 into a digital signal and comparing it with a target power level The DSP 330 outputs a voltage to the laser diode driver 340.

In the operation of the ALPC circuit, when the optical recording apparatus writes data to the media, the controller (not shown) of the optical recording apparatus first determines the type of media, and according to the determined type of media, the operation control signal WFPDSH and Generates a media type signal.

When the media is a rewritable media that can be rewritten, the first sample / hold unit 300 samples and holds a signal detected and returned from the FPD 360 to output to the multiplexer 320. . The first sample / hold unit 300 is controlled to operate according to the presence or absence of an input signal without the operation control signal WFPDSH.

 When the media is a write-readable media, the control unit generates an operation control signal WFPDSH, and accordingly, the second sample / hold unit 310 is detected and returned from the FPD 360. The signal is sampled and held and output to the multiplexer 320.

In addition, the multiplexer 320 selects one of the outputs of the first sample / hold unit 300 and the second sample / hold unit 310 according to the media type signal generated by the controller (not shown). To provide.

The DSP 330 converts a signal input from the multiplexer into a digital signal, and compares the signal with a target power level.

For example, if the sensitivity of the FPD signal (mV / mW) is 20mV / mW, the FPD signal changes 20mV when 1mW of power is output. It can be inferred and compares the inferred optical power with a target power level.

As a result of the comparison, when the detected FPD signal is lower than the target power level, the DSP 330 increases and outputs the level of the reference voltage. When the detected FPD signal is higher, the DSP 330 decreases and outputs the reference voltage.

The reference voltage output from the DSP 330 is input to the laser diode driver 340 and is set as a reference voltage for generating a driving current of the laser diode 350. The laser diode driver 340 lasers according to a variable reference voltage. By varying the driving current of the diode, the intensity of the laser output from the laser diode is kept constant.

Figure 4 shows the configuration of a laser diode driver (Laser Dilode Driver) according to the present invention. The laser diode driver according to an exemplary embodiment of the present invention includes a reference DAC 400, a regenerative power DAC 450, a high frequency signal amplitude control DAC 430, a high frequency oscillator 440, and a recording power compensation DAC ( 420, a recording power DAC 410, an amplifier 460, and an adder 470.

The reference voltage output from the DSP is input to the reference DAC 400 and converted into an analog voltage, and then, a reproduction power DAC 450, a high frequency signal amplitude control DAC 430, a recording power compensation DAC 420, and a recording power DAC ( 410) Each of the predetermined initial voltages, the regeneration power voltage, the high frequency signal amplitude determination voltage, the recording power compensation voltage, and the recording power voltage are respectively applied as reference voltages for converting the analog signals.

Then, the analog signals output from the reproduction power DAC 450, the high frequency signal amplitude control DAC 430, the recording power compensation DAC 420, and the recording power DAC 410 are varied according to the intensity of the laser output from the laser diode. Compensated based on the reference voltage and output.

In the case of the regeneration mode, the amplifier 460 amplifies the output signal I _apc and the regeneration power DAC 450 output of the regeneration power control to the adder 470.

Meanwhile, in order to improve the reproduction performance, a high frequency signal (HFM: High Frequency Modulation) may be loaded onto the output signal of the amplifier 460 through the high frequency generator 440. In this case, the high frequency signal amplitude control DAC 430 may be used. Determine the amplitude of the frequency.

In the case of the recording mode, the laser power can be generated in multiple times using the recording power DAC 410. The reference DAC 400 serves as a reference for each of the DACs 410, 420, 430, and 450 used in the laser diode driver. For example, when the output of the reference DAC 400 is 2.0V, a maximum value is applied. The output of each of the DACs is 2.0V.

In particular, the reference DAC 400 is responsible for a reference to the recording power DAC 410. The reference DAC 400 does not directly compensate the reference voltage of the recording power DAC 410 according to a change in the surrounding environment such as temperature during data recording. By compensating for the DAC 400, the reference voltage of the recording power DAC 410 is adjusted.

On the other hand, the recording power compensation DAC 420 is for stabilizing the recording power quickly when switching from the playback mode to the recording mode, and when switching from the playback mode to the recording mode, the controller (not shown) turns off the high frequency generator 440. Let's do it. Therefore, since the laser power is insufficient in the initial stage of the recording mode, it is used to compensate for the power level by loading the DC level.

The adder 470 adds the output signals of the high frequency generator 440 and the amplifier 460 in the reproduction mode and outputs them to the laser diode, and in the recording mode, the recording power DAC 410 and the recording power compensation DAC ( The output signal of 420 is added and output to the laser diode.

Fig. 5A shows the structure of the recording power DAC 410 according to the present invention. The recording power DAC 410 is composed of a total of eight DACs (500, 510, 520, 530, 540, 550, 560, 570). When recording data, lasers having different intensities are used using the respective DACs. Up to eight can be generated.

FIG. 5B illustrates an embodiment in which recording power is managed at four levels with respect to a non-return to zero inverted (NRZI) pattern input according to the type and speed of the optical medium. Referring to FIG. 5B, the write power level 600 applies the same voltage to the first write power DAC 500, the second write power DAC 510, and the third write power DAC 520. The erase power level 610 is managed by applying the same voltage to the first erasing power DAC 550, the second erasing power DAC 560, and the third erasing power DAC 570. The cool power level 620 sets and manages a value in the power level reduction DAC 540. In addition, the read power level, that is, the bias power level 630, sets a value to the play power DAC 530.

Here, as shown in FIG. 5B, the first recording power DAC 500 is a DAC for recording power level of the first recording pulse, and the third recording power DAC 520 sets the recording power level of the last recording pulse. Is a DAC for a recording power level between the first and last recording pulses, and a regeneration power DAC 530 is a DAC for a bias power level in a mark section. .

The power level reduction DAC 540 is a DAC for the cooling power level 620 and serves to reduce the optical power level so that the mark does not invade adjacent tracks in the mark section during data recording.

In addition, the first erasing power DAC 550, the second erasing power DAC 560 is a DAC for operating the erasing power (Erase Power) level 610, the third erasing power DAC (570) is the first recording A DAC for operating an erasing power level 610 before a pulse.

On the other hand, in the case of a Blu-Ray disc, a write strategy prescribed by a Blu-Ray disc standard shows two erase powers in the space section between the pit and the pit when data is recorded. It can be managed at the level.

Therefore, when the laser diode driver according to the present invention is used, the recording power can be controlled in accordance with the standard of the Blu-Ray disc.

6 is an ALPC operation diagram according to the present invention, which shows a recording pulse output from a laser diode in a state where temperature compensation is made during long-term recording of a recording medium in an optical recording apparatus.

In the present invention, as shown in FIG. 6, the same ALPC is used for all power levels when data is written to the media, and the reference voltage of the recording power DAC 410 is directly compensated according to the change in laser intensity according to the change of the surrounding environment. It can be seen that the recording power can be controlled by compensating the reference voltage of the reference DAC 400 that determines the reference of the recording power DAC 410, rather than providing it.

7 is an operational flowchart of an ALPC according to a preferred embodiment of the present invention.

The ALPC operation routine is called by the system's periodic timer because the FPD signal needs to be measured at regular intervals to check the change in recording power. If the measurement period of the FPD signal is too short, the system may be overloaded and normally recorded. The power does not change dramatically, so the FPD signal can be measured every tens of msec.

When the ALPC circuit is operated for the first time, the controller (not shown) checks whether the optical recording device is in the recording mode (S700), if it is playing, terminates the operation of the ALPC circuit, and if recording, corresponds to the target recording power. A target FPD signal level is calculated (S705). The target FPD signal level can be obtained by multiplying the FPD signal sensitivity (mV / mW) by the recording power (mW).

After calculating the target FPD signal level, the FPD 360 detects the current laser intensity (S710). The laser intensity is detected every time by measuring the elapsed time.

The control unit then determines the type of media (S715). As a result of the determination, when the media is rewritable media, the control unit does not generate an operation control signal, and the first sample / hold unit 300 determines whether or not the detected FPD signal is input, thereby sampling and holding. (S720).

When the type of the media is a read-only media, the control unit generates an operation control signal, and the second sample / hold unit 310 samples and detects the detected FPD signal according to the presence or absence of the operation control signal. Hold (S725).

The multiplexer 320 selects one of the signals of the first sample / hold unit 300 or the second sample / hold unit 310 according to the media type signal and provides it to the DSP 330 (S730).

The DSP 330 compares the FPD signal level input from the multiplexer 320 with the calculated target FPD signal level, and if the measured value is smaller than the target FPD signal level, the DSP 330 is a unit of the measured FPD signal level. The level is added, and if the measured FPD signal level has a larger value, the unit level is subtracted from the measured value (S735).

The calculated value is applied as the reference voltage to the reference DAC 410 (S740).

In this case, the unit level is an experimentally determined value. If the convergence speed to the target FPD signal level is to be increased, the unit level may be made relatively larger. The size of the level can be reduced.

As described above, the ALPC routine may be repeatedly performed at regular intervals, thereby compensating the setting value of the reference DAC, which is a reference of each DAC of the laser diode driver, to maintain the recording power stably.

Although the present invention has been described in detail with reference to exemplary embodiments above, those skilled in the art to which the present invention pertains can make various modifications to the above-described embodiments without departing from the scope of the present invention. I will understand. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

As described so far, according to the automatic laser power control device and method of the optical recording device of the present invention, the recording power level is multipled by using a laser diode driver capable of operating the laser power level in multiple. By controlling the output voltage of the reference DAC, which is a reference of each DAC, it is possible to programmatically control the intensity of the laser output from the laser diode during data recording.

Claims (6)

A front photo diode (FPD) for detecting a laser emitted from the laser diode as an electrical signal; A first sample / hold unit configured to sample and hold a bottom level of the detection signal of the FPD; A second sample / hold unit for sampling and holding a signal level of the detection signal of the FPD; A multiplexer for selecting one of outputs of the first sample / hold unit and the second sample / hold unit according to a media type signal determined by the controller; A digital signal processor (DSP) for generating a reference voltage for controlling the driving current of the laser diode by comparing the FPD signal input from the multiplexer with a target power level; Automatic laser power control device comprising a laser diode driver for generating a driving current based on the reference voltage output from the DSP to output to the laser diode. The laser diode driver of claim 1, further comprising: a laser diode driver; A reference DAC for converting a reference voltage output from the DSP into an analog signal; A reproduction power DAC for converting a predetermined initial voltage into an analog signal based on the output voltage of the reference DAC; A recording power DAC for converting a predetermined initial voltage into an analog signal based on the output voltage of the reference DAC; A high frequency signal amplitude control DAC for converting a predetermined initial voltage into an analog signal based on an output voltage of the reference DAC; An amplifier for amplifying an output signal of the regenerative power DAC and a regenerative power control signal of a laser diode; A high frequency generator for generating a high frequency signal at an amplitude corresponding to an output voltage of the high frequency signal amplitude adjusting DAC; And an adder for adding the output signal of the amplifier, the high frequency generator and the recording power DAC to the laser diode. The method of claim 2; And a recording power compensation DAC for converting a predetermined initial voltage based on an output voltage of the reference DAC into an analog signal and outputting the same to the adder. Calculating a target FPD signal level corresponding to a target recording power, and detecting the FPD signal by the FPD of the optical recording apparatus; Determining, by the controller, a type of media to generate an operation control signal, and the sample / hold unit sampling and holding the detected FPD signal according to the presence or absence of the operation control signal; A DSP calculating a reference voltage by comparing the sampled and held FPD signal level with the calculated target FPD signal level; And applying the calculated reference voltage to a reference DAC. The method of claim 4, wherein The calculation of the reference voltage adds a unit level to the measured FPD signal level if the measured FPD signal level is lower than a target FPD signal level, and subtracts the unit level from the measured value if the measured FPD signal level is higher. Automatic laser power control method characterized in that the calculation. The method of claim 5, Automatic laser power control method characterized in that the size of the unit level can be adjusted.

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