KR100765207B1 - Auto Power Control apparatus of Laser Diode and method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control apparatus for a laser diode and a method thereof, and an object thereof is to maintain a constant power of a laser diode that determines the performance of an optical recording device in an optimal state.

To this end, the present invention is a device for controlling the power of a laser diode used in an optical recording device for recording data on an optical disk, the sample of extracting the power level of the laser diode by sampling the RF signal output during data recording & Hold part; And calculating a relational expression for the power level of the extracted laser diode and then compensating a power variation of the laser diode according to the temperature change based on the calculated relational expression.

Description

Power control device of laser diode and method thereof

1 is a block diagram illustrating a power control device of a conventional laser diode;

2 is a block diagram illustrating an apparatus for controlling power of a laser diode according to an embodiment of the present invention;

3 is a graph showing the current versus the actual light output characteristics of the laser diode with temperature changes,

4 is a graph simulating the current versus light output characteristics of a laser diode with temperature change,

5 is a graph showing the power change of the laser diode according to the temperature change,

6 shows a recording unit block recorded on an optical disc;

7 is a diagram illustrating an example of detecting an RF signal sampled in lands and grooves;

8 is a power level graph obtained by sampling and holding an RF signal.

* Description of the symbols for the main parts of the drawings *

20: optical pickup 30: I / V converter

40: ADC 42: Sample & Hold

50: compensation unit 60: DAC

70: LD drive part

The present invention relates to an optical recording apparatus for optically recording and reproducing data, and more particularly, to an apparatus and method for controlling power of a laser diode for controlling a laser diode with optimum power, which determines the performance of the optical recording apparatus. It is about.

Recently, with the development of video and audio media, recording media capable of recording and storing high-quality video data and high-quality audio data for a long time, for example, DVD Ver. R / RW (Digital Versatile Disc Recordable / Rewritable), DVD -Optical discs such as RAM (DVD Random Access Memory) have been developed and commercialized. Also, as the storage capacity of these DVDs is gradually reaching its limit, new high-density optical discs, for example, BD discs with high capacity of several tens of Gbytes or more ray Disc Recordable / Rewritable) and HD-DVD (High Density DVD) are being developed. In addition, there are recording media such as a magnetic optical disc drive (MODD) and a CD-R / RW.

An optical recording device uses a laser diode (hereinafter referred to as LD) to record data on the optical disk, and the optical recording device irradiates a laser beam having a large power to record data on the surface of the optical disk. Drive LD to make it work. This is possible because the recording of data only needs to change the physical properties of the recording layer present on the optical disc, and the physical properties are changed by a laser beam having a large power.

At this time, the optimal recording power for recording data should be kept at a constant value for accurate recording. However, LD has a characteristic that changes very sensitively with temperature, so that the LD recording power changes with temperature even under the same driving current. do. In other words, the recording power output from the LD decreases as the temperature increases, and increases as the temperature decreases. This may lead to poor recording performance or no recording in the optical recording device.

Therefore, in order to solve this problem, it is important to output a constant recording power at an optimal state regardless of temperature change when a laser diode is used in an optical recording device, and such a technology, Automatic Laser Diode Power Control ; Or hereinafter called ALPC) or Automatic Power Control (APC) function should be able to implement effectively in a short time.

In general, APC monitors the power of the LD through a separate photo diode (hereinafter referred to as PD), and feeds back the power variation of the LD so that the power of the LD is kept constant.

1 is a block diagram illustrating a power control device of a conventional laser diode for implementing such an APC function.

In FIG. 1, a conventional laser diode power control apparatus detects an output power of light emitted from an LD and converts a recording power of the detected light into a current signal, and converts a current detected from the PD into a voltage to convert the current power fed back. According to the comparison result of the comparator 3 and the comparator 3 comparing the output power of the I / V converter 1, the current output of the LD output from the I / V converter 1, and the desired reference power, An up / down counter 5 that is operated to determine the increase or decrease of current, a digital / analog converter 7 (hereinafter referred to as DAC) that converts the output of the up / down counter 5 into analog, and a DAC ( And an LD driver 9 for driving the LD to output a current corresponding to the recording control level, that is, recording power, in accordance with the output value of 7).

The operation of the conventional laser diode power control device configured as described above is as follows.

When the output power of the light emitted from the LD is detected by the PD and converted into a current signal, the current detected by the PD is converted into a voltage through the I / V converter 1 so that the fed back current power is input to the comparator 3, The comparator 3 compares the feedback current power with a desired reference power and inputs the comparison result to the up / down counter 5. That is, the current signal output from the PD is input to the up / down counter 5 via the I / V converter 1 and the comparator 3 according to the power level.

The output of the comparator 3 is input to the up / down control terminal of the up / down counter 5 to increase or decrease according to the output result of the comparator 3, and the output of each up / down counter 5 is a DAC. Via 7 is converted into an analog signal and supplied to the LD driver 9.

Accordingly, the LD driver 9 drives the LD by outputting a current corresponding to the recording control level, that is, recording power, to the LD in accordance with each power level and a control signal to control each power.

However, the conventional power control device of the laser diode compares the power level of the LD in the comparator 3 to control the recording power of the LD by comparing the reference power and the current power fed back, and then up / down according to the comparison result. Since the operation of the down counter 5 determines the increase or decrease of the current, the power control speed and the control range are limited, which causes a problem in that it cannot effectively cope with the high speed and high capacity optical recording device in the future.

In addition, since the desired power level is not compensated for during sampling, there is a problem in that it cannot quickly respond to a change in output of the LD according to a temperature change, and thus, an accurate power level cannot be obtained.

Accordingly, the present invention is to solve the above-mentioned conventional problems, an object of the present invention is to maintain a constant power of the laser diode that determines the performance of the optical recording device in an optimal state regardless of the temperature change constant The present invention provides a device for controlling a diode and a method thereof.

Another object of the present invention is to configure the sample & hold unit for sampling and holding the analog input inside the ADC to output the signal to compensate for the desired power level during sampling of the RF to maintain a constant LD power output according to temperature changes in a short time The present invention provides a laser diode power control apparatus and method thereof.

In order to achieve the above object, the present invention provides a device for controlling the power of a laser diode used in an optical recording device for recording data on an optical disc, wherein the RF signal is applied to the land area and the groove area in the recording unit block during data recording. A sample & hold unit for extracting the power level of the laser diode by sampling and holding and outputting a power voltage; And calculating the relational expression for the power level of the extracted laser diode by formulating the output characteristics of the laser diode according to the temperature change as a first function, and then compensating for the power variation of the laser diode according to the temperature change based on the calculated relational expression. It characterized in that it comprises a compensation unit.

In addition, the compensator calculates a power level of the laser diode according to the relational expression and then compensates for the difference between the calculated power level and the actual power level of the laser diode at the instant of sampling the RF signal based on the calculated value. It is characterized by.

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In addition, the compensation unit is characterized in that to calculate the power of the laser diode by fixing one of the slope and the y-intercept of the modified primary function and the other.

In addition, the present invention provides a method of controlling the power of a laser diode used in an optical recording device for recording data on an optical disc, wherein the RF signal for the land area and the groove area in the recording unit block is sampled and held during data recording. Extracting a power level of the laser diode by outputting a power voltage; And calculating the relational expression for the power level of the extracted laser diode by formulating the output characteristics of the laser diode according to the temperature change as a first function, and then compensating for the power variation of the laser diode according to the temperature change based on the calculated relational expression. Characterized in that it comprises a step.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

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2 is a block diagram illustrating an apparatus for controlling power of a laser diode according to an embodiment of the present invention, wherein the optical pickup 20, the I / V converter 30, the ADC 40, and the sample and hold unit 42 are shown in FIG. ), A compensator 50, a DAC 60, and an LD driver 70.

The optical pickup 20 records data by irradiating a predetermined light onto a recordable optical disc, LD for irradiating an optical disc with light having a recording power corresponding to a predetermined recording control level (that is, a predetermined amount of current); And a front photo diode (hereinafter referred to as PD) which detects an output power of light emitted from the LD and converts it into a current signal.

The I / V converter 30 converts the current detected from the PD into a voltage and outputs a value corresponding to the current recording power of the LD.

The ADC 40 is an analog / digital converter that receives an analog input from the I / V converter 30 and converts it to digital. The ADC 40 receives an analog signal therein, and samples and holds the analog signal. And a sample & hold section 42 for outputting an analog voltage to form a WFPDSH signal (Write) of an RF in the run-in / run-out area (land area) of a recording unit block (hereinafter referred to as RUB). The front photo diode sample and hold signal is sampled, and the EFPDSH signal (Erase Front Photo Diode Sample and Hold Signal) of RF is sampled in a physical cluster (groove region) to obtain two power data Pe1 and Pe2. At this time, the land and the groove are recorded at different powers.

The compensator 50 compensates the LD power in order to maintain the LD recording power in an optimal state even when the temperature is changed when data is written to the optical disk. The new formula is based on two power data obtained from the RF sampling signal. By compensating for the desired power level, the power change of LD according to the temperature change can be realized quickly.

In addition, the compensator 50 calculates the power change of the LD according to the temperature change into two power data to compensate for the voltage difference expected when sampling at every moment thereafter to obtain an accurate power level.

The DAC 60 is a digital / analog converter for converting the value calculated by the compensator 50 to analog.

The LD driving unit 70 drives the LD to output a current corresponding to the recording control level, that is, recording power according to the output value of the DAC 60. As the temperature increases to maintain the LD recording power constant, the LD increases. It supplies a lot of current to the LD and as the temperature decreases, it supplies less current to the LD.

Hereinafter, the operation process and the effect of the power control device and method of the laser diode configured as described above will be described.

In FIG. 2, when the output power of the light emitted from the LD is detected by the PD and converted into a current signal, the current detected by the PD is converted into a voltage through the I / V converter 30 and input to the ADC 40.

Therefore, the ADC 40 converts the analog input of the I / V converter 30 into digital and inputs the converted value at each instant into the compensator 50.

3 is a graph showing the current versus the actual optical output characteristics of the laser diode according to the temperature change, it can be seen that the output power of the LD changes even at the same driving current according to the temperature change.

FIG. 4 is a graph simulating current versus light output characteristics of a laser diode according to temperature change, and the graph of FIG. 3 is expressed as a first function. At this time, the slope and y-intercept of the linear function change according to the type of LD.

As shown in FIG. 5, the power change of LD whose current versus light output changes as the temperature changes is represented by the change in the ADC value relative to the DAC value.

FIG. 5 is a graph illustrating a change in power of a laser diode according to a temperature change. When LD is operated as shown in FIG. 5, the expression is expressed by the following Equation 1 below.

Y = αX-β ....... [Equation 1]

Where α is the slope and β is the y-intercept.

In more detail, the output characteristic of LD can be seen that the slope (α) decreases and the y-intercept (ㅣ β ㅣ) increases as the temperature increases (see FIGS. 3 and 4). α) and y-intercept (β) will vary depending on the type of LD, Figure 5 is a graph showing the power change of the LD according to the temperature change.

As can be seen in Figure 5, as the temperature changes the value of the slope (α) and y-intercept (β) is changed at the same time, at this time two values are required to obtain the slope (α) and y-intercept (β).

In the present invention, the sample & hold unit 42 is configured inside the ADC 40 to obtain these two values.

Fig. 6 shows a recording unit block recorded on an optical disc, wherein data recorded on the optical disc is recorded in RUB units of a predetermined recording size.

One RUB consists of a 40wbs run-in area, a physical cluster area that is a real power record section of 496 x 28wbs, and a run-out area of 16wbs. The sample & hold unit 42 configured inside the N-sample samples different powers in the run-in area and the run-out area.

FIG. 7 shows an example of detecting an RF signal sampled in lands and grooves. In the sample & hold section 42, the WFPDSH signal of RF is detected in the run-in / run-out area, which is a land area. Sampling is performed, and the EFPDSH signal of the RF is sampled in the physical cluster area, which is the groove area, to obtain two LD power data Pe1 and Pe2.

Accordingly, the sample & hold section 42 samples and holds the RF signal to obtain two power levels (WRLVL: Write Read Level and ERLVL: Errase Read Level) as shown in FIG.

The new equation Y = Ax + B is derived from the two power data thus obtained, and then the value calculated by the compensator 50 is converted into an analog signal through the DAC 60 and then sent to the LD driver 70 to the LD driver. Adjust the power At this time, the DAC value is changed to a DAC value corresponding to the power level calculated by the sampling instant compensation unit 50.

As described above, according to the power control apparatus and method of the laser diode according to the present invention, the LD power by the conventional counter by compensating the LD power at the sampling instant in order to keep the LD power according to the temperature change constant. The effect is that the APC function can be implemented more efficiently and faster than compensation.

In addition, by configuring the sample & hold unit for sampling and holding the analog input inside the ADC and outputting the signal, compensating for the desired power level when sampling the RF, so that it can respond quickly to the power change of the LD according to the temperature change. The effect is to get a power level.

What has been described above is just one embodiment for implementing the power control device and method of the laser diode according to the present invention, the present invention is not limited to the above-described embodiment, it is within the technical scope of the present invention Various modifications are possible by those skilled in the art.

Claims (6)

An apparatus for controlling the power of a laser diode used in an optical recording device for recording data on an optical disc, A sample & hold unit for extracting a power level of the laser diode by sampling and holding an RF signal for a land area and a groove area in a recording unit block and outputting a power voltage during data writing; And Compensation for the power change of the laser diode according to the temperature change after calculating the relational expression for the power level of the extracted laser diode by formulating the output characteristics of the laser diode according to the temperature change by the first function. To call Power control device for a laser diode comprising a. delete The method of claim 1, The compensator calculates a power level of the laser diode according to the relational expression and then compensates for the difference between the calculated power level and the actual power level of the laser diode at the instant of sampling the RF signal based on the calculated value. Power control device for laser diodes. The method of claim 1, The compensator is configured to calculate the power of the laser diode by fixing one of the slope and the y-intercept of the modified primary function and the other to calculate the power of the laser diode. A method of controlling the power of a laser diode used in an optical recording device for recording data on an optical disc, Extracting a power level of the laser diode by sampling and holding an RF signal for a land area and a groove area in a recording unit block and outputting a power voltage during data writing; And After calculating the output characteristic of the laser diode according to the temperature change by the first function, calculating the relation for the power level of the extracted laser diode, and then compensating for the power change of the laser diode according to the temperature variation based on the calculated relation. Power control method of a laser diode comprising a step. delete

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