KR100704293B1 - Automatic laser power control apparatus and method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light output control apparatus and a method thereof, which aims to control to stabilize the light output level automatically over a wide recording speed range.

To this end, the present invention provides an apparatus for controlling the light output of a laser diode emitted for recording data on an optical disc, comprising: a photodiode for detecting a power level of the light output emitted during data recording; And a control unit controlling light output levels of different recording speeds based on the detected power levels of the light outputs.

Description

Optical power control apparatus and method thereof

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

2 is a signal waveform diagram showing FPDO at a high recording speed in the conventional optical output control apparatus;

3 is a block diagram illustrating a light output control apparatus according to an embodiment of the present invention;

4 is a signal waveform diagram of the first method for the light output control (APC) for the multi-pulse write strategy (WS) in the present invention;

5 is a signal waveform diagram of a second method for optical power control (APC) in case of a multiple pulse recording strategy (WS) in the present invention;

6 is a signal waveform diagram of a first method for light output control (APC) in the case of a castle write strategy (WS) in the present invention;

7 is a signal waveform diagram of a third method for light output control (APC) in the case of a castle write strategy (WS) in the present invention;

8 is a signal waveform diagram of a third method for light output control (APC) for the L-type writing strategy (WS) in the present invention.

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

20: LD drive unit 30: sample holder adjustment unit

40: control unit 50: optical pickup

60: PD amplifier 70: peak power detector

80: middle power detector 90: bias power detector

100: ADC

The present invention relates to an optical output control apparatus and a method thereof, and more particularly, to an optical output control apparatus and a method which can automatically stabilize the optical output level in a wide recording speed range.

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.

In order to record data on such an optical disk, an optical recorder uses a laser diode (hereinafter referred to as LD), and the optical recorder 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 characteristics of the recording layer present on the optical disc, and the physical characteristics are changed by a laser beam having a large power.

At this time, the optimal recording power for recording data should be maintained at a constant value for accurate recording. However, LD has a characteristic that changes very sensitively depending on the temperature, as shown in FIG. The light output of the LD changes according to (T1 <T2 <T3). 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 improve such a problem, it is important to output constant recording power at an optimum state regardless of temperature change when the LD is used in an optical recording device, and such a technique, Automatic Laser Diode Power Control; APC) or Automatic Power Control (hereinafter referred to as APC) 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.

In order to realize this APC function, the optical recorder performs an Optimal Power Control (OPC) process to determine the correct optical output, and then has several complex time structures in the LD for accurate recording. The power level is generated as shown in FIG. This structure is called a write strategy (WS), and the APC scheme must control all emitted power levels during read and write for all conventional write strategies (WS).

Therefore, in order to implement such an APC function, an optical output device is provided with an optical output control device, which has US Patent No. 2005-0083828 (Chin-Yuan Chen).

The optical output control device disclosed in the publication detects the output power of the laser light emitted from the LD and converts it into a current signal by converting the current detected from the PD into a voltage and amplifies it in the PD amplifier to output current power. The current power of the output LD is compared with a desired reference power, and the set values in the LD driver for driving the LD are adjusted to output a current corresponding to the recording control level, that is, recording power, according to the comparison result. This operation was performed by separating all applied power levels in succession.

FIG. 2 is a signal waveform diagram showing an output (FPDO) of a front photo diode at a high writing speed in a conventional optical output control device. The relationship between the output signals is shown.

In FIG. 2, PW is the peak power of LD, PE is the erase power of LD, PB is the bias power of LD, and NRZI is the NRZI (Non) output from the encoder. Return to Zero Inverter signal.

However, such a conventional optical output control device must accurately adjust the LD power level in order to increase the recording speed. To this end, the frequency bandwidth of the PD and the PD amplifier must be improved, but increasing the PD bandwidth increases the cost of the optical recording device. There is a drawback to increase.

In addition, when the difference between the peak power and the erase power is small, the duty optical and electronic noise, and the peak detectors have a problem of starting to fix the peak noise value while the spatial and recording power cannot be properly adjusted.

Accordingly, an object of the present invention is to solve the conventional problems as described above, and an object of the present invention is to provide a light output control apparatus and method capable of automatically and stably controlling the light output level in a wide recording speed range without increasing the cost. To provide.

In order to achieve the above object, the present invention provides an apparatus for controlling the light output of a laser diode emitted for recording data on an optical disc, comprising: a photodiode for detecting a power level of the light output emitted during data recording; And a controller for controlling light output levels of different recording speeds based on the detected power levels of the light outputs.

In addition, the present invention includes a peak power detector for detecting the peak power of the detected light output; A middle power detector detecting middle power of the detected light output; And a bias power detector for detecting a bias power of the detected optical output, wherein the controller is configured to control a plurality of channels to control optical outputs having different recording speeds according to the detected peak power, middle power, or bias power level. It characterized by having a.

In addition, the present invention provides a method of controlling the light output of a laser diode emitted for recording data on an optical disc, the method comprising: detecting a power level of the light output emitted during data recording; And controlling the light output levels of different recording speeds based on the detected power levels of the light outputs.

The control step may also include a first method of controlling power level detection and adjustment of the light output for low speed recording; A second method of detecting and adjusting an erase power level of an optical output and adjusting peak power based on a result of averaging detection power of the photodiode for a multi-pulse write strategy; And a third method of detecting and adjusting middle and bias power levels of optical output, and proportional adjustment of peak power levels for different types of recording strategies; Selecting any one of the features to control the light output level.

Also, the first method is used for slow recording; The peak power, the erase power, and the bias power level of the detected light output are compared with a predetermined target value, and the light output of the laser diode is adjusted according to the comparison result.

Also, the second method is used for high speed recording in a multiple pulse recording strategy; When the error of the detected peak power becomes the duty limit of the frequency bandwidth of the photodiode amplifier, comparing the middle power level of the detected light output with a predetermined target value and adjusting the light output of the laser diode according to the comparison result It features.

Also, the third method is used when the OPC result has a large difference between the peak power and the middle power; The bias power, the middle power, and the peak power level of the detected light output are compared with a predetermined target value, and the light output of the laser diode is adjusted according to the comparison result.

In addition, the target value is characterized in that the target power data determined through the OPC process.

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

3 is a block diagram illustrating an optical output control apparatus according to an embodiment of the present invention, the encoder 10, LD drive unit 20, sample holder control unit 30, the control unit 40, optical pickup 50 ), A PD amplifier 60, a peak power detector 70, a middle power detector 80, a bias power detector 90, and an ADC 100.

The encoder 10 outputs Non Return to Zero Inverter (NRZI) data for controlling the light output level and inputs the data to the LD driver 20 and the sample holder controller 30.

The LD driving unit 20 drives the LD to output a current corresponding to the recording control level, that is, recording power, according to the NRZI data of the encoder 10 and the recording strategy of the controller 40. In order to maintain the temperature, the current is supplied to the LD as the temperature increases, and the current is supplied to the LD as the temperature decreases.

The sample holder adjusting unit 30 samples and holds the sample & holder 82 according to the NRZI data of the encoder 10 and the recording strategy WS of the controller 40 to output an analog voltage. Generates an SH signal for

The controller 40 controls the optical output level in a wide recording speed range to maintain the LD recording power in an optimal state even when the temperature changes during data recording on the optical disk. A first method for instructing adjustment, a detection and adjustment of erase power based on a signal averaged from the PD for the multi-pulse write strategy WS, a second method for instructing the adjustment of peak power, an L-type and Inputting a signal to the LD driver 20 for controlling the light output level to widely vary the transmission ratio speed by a third method instructing proportional adjustment of the peak power level for the castle type write strategy WS. do.

The optical pickup 50 irradiates a predetermined light onto a recordable optical disc to record data, and includes an LD for emitting a laser light having a recording power corresponding to a predetermined recording control level (that is, a predetermined amount of current) to the optical disc. And a front photo diode (hereinafter referred to as PD) for converting an output power of light emitted from the LD into a current signal and detecting an optical output level proportional to the lens output power LOP.

When the current detected from the PD is converted into a voltage, the PD amplifier 60 amplifies it and outputs a value corresponding to the current recording power of the LD.

The peak power detection unit 70 detects the peak power of the light output amplified by the PD amplifier 60, the peak detector 72 for detecting the maximum power level of the light output with a controlled discharge current, noise Lowpass filter 74 to minimize errors by

The middle power detector 80 detects the middle power level of the optical output amplified by the PD amplifier 60, and detects the erase power in the middle power channel according to the result of the applied write strategy WS and OPC. A first sample & holder 82 and a low pass filter 84, and a second sample & holder 86 and a low pass filter 88 for detecting a result of averaging detection data of the PD in the middle power channel. do.

The bias power detector 90 detects the bias power of the optical output amplified by the PD amplifier 60, and includes a bias detector 92 for detecting a minimum power level of the optical output having a controlled discharge current; And a low pass filter 94 to minimize errors due to noise.

The ADC 100 includes the peak power PW detected by the peak power detector 70, the erase power PE detected by the middle power detector 80, and the bias power detected by the bias power detector 90. An analog / digital converter that receives an analog input of PB and converts it into digital, and inputs the converted output value to the control unit 40.

Hereinafter, the operation process and the effect of the light output control device and the method configured as described above will be described.

In FIG. 3, the encoder 10 outputs NRZI (Non Return to Zero Inverter) data for controlling the light output level and inputs it to the LD driver 20 and the sample holder controller 30. .

Accordingly, the sample holder adjuster 30 samples and holds the light output for the sample & holder 82 according to the NRZI data of the encoder 10 and the recording strategy WS of the controller 40. Generates the SH signal of level. In this case, each light output level may be adjusted by setting values in the LD driver 20.

The LD driver 20 drives the LD to output a current corresponding to the recording control level, that is, recording power, according to the NRZI data of the encoder 10 and the recording strategy of the controller 40, and outputs the laser light emitted from the LD. Power is detected at the PD to generate a current corresponding to the light output level.

This current is converted into a voltage and input in an APC manner, which has a peak power channel, middle power channels, a bias power channel and a read power channel.

Among them, the peak power channel detects the peak power (PW) level of the light output at the controlled discharge current in the peak detector 72 and minimizes the error due to noise through the low pass filter 74.

In addition, each of the middle power channels has samples & holders 82,86 and low pass filters 84,88, and the first sample & holder 82 of the middle power channels in accordance with the result of the applied write strategy WS and OPC. ) And the low pass filter 84 detect the erase power, and the second sample & holder 86 and the low pass filter 88 among the middle power channels detect the result of averaging detection data of the PD.

The bias power channel then has a bias detector 92 and a low pass filter 94 with controlled discharge current to detect the bias power, which is the minimum power level of the light output.

Based on this scheme, the optical output control apparatus of the present invention has a first method of instructing power level detection and adjustment for low speed recording, detection of erase power based on a signal averaged from the PD for the multi-pulse write strategy WS. And three methods for instructing adjustment and peak power, and a third method for instructing the proportional adjustment of peak power level for the L-type and castle-type recording strategy (WS). Can be.

First, the control unit 40 automatically selects one from three APC algorithms according to the applied recording strategy WS and the OPC result.

In the case of the low speed recording, when the pulse time is larger than the response time of the PC amplifier 60, the control unit 40 selects the first method shown in FIG. When the peak power PW is directly detected, the bias power PB and erase power (PE or middle power) levels should be compared with a predetermined target value (peak power, bias power), and in the LD driver 20 The register settings can be adjusted according to the comparison result.

FIG. 4 is a signal waveform diagram of the first method for the light output control (APC) in the case of the multi-pulse write strategy (WS) in the present invention, wherein the pulse-shaped waveform is the emitted light output of the multi-pulse write strategy (WS). The optical discs used three power levels: peak power (PW), erase power (PE) and bias power (PB) levels. The PD signal is not proportional to the duty band pass frequency limit, and the peak target and the bias target illustrate target APC power data that can be determined during OPC performance.

In the case of multi-pulse write strategy WS and fast write, when the detected peak power error is an important duty limit of the frequency bandwidth of the PD amplifier 60, the controller 40 automatically controls the second shown in FIG. Choose a method. When the second method is applied, one channel (middle one channel) from the middle power APC channel has a continuous "sample" state of the SH of the second channel (middle two channel) only during a long magnitude interval. In this case the signal from the PD is input directly to the low pass filter 84 for averaging. The data counted from the APC middle output channel is then compared with the predetermined target values.

As a result of the comparison, according to the result of the middle 1 channel data, the erase power may be modified by adjusting a register in the corresponding LD driver 50. If the comparison result shows that the erase power is correct, the peak power can be corrected according to the result of comparing the middle 2 channel with the target value.

FIG. 5 is a signal waveform diagram of the second method for the optical output control (APC) in the case of the multi-pulse write strategy (WS) in the present invention, in which the direct detection of the peak power (PW) in the case of the fast write duty band pass frequency limitation is It becomes impossible.

③ When the OPC result has a significant difference between the peak power and the middle power, the controller 40 selects the first method shown in FIG. 6 according to the case of the mono pulse recording strategy (castle, L-type) or The third method shown in Figs. 7 and 8 should be selected. This difference depends on the system noise, PD amplifier 60 frequency response. If the magnitude of the PD signal is smaller than the sum of the PD signals, this corresponds to the standard deviation of the middle power and the registered noise, and the first and third methods may be applied.

The bias and middle power levels should then be detected and adjusted directly in this case. And the peak power register settings are modified in proportion to the middle power register modification.

FIG. 6 is a signal waveform diagram of the first method for the light output control (APC) in the case of the castle write strategy (WS) in the present invention, wherein the peak target shows target APC power data that can be determined during OPC performance. It is.

FIG. 7 is a signal waveform diagram of the third method for light output control (APC) in the case of the castle writing strategy WS in the present invention, in the case of a high speed recording and a relatively small difference between middle power and peak power. Since the first method does not control the peak power accurately, a third method of instructing proportional adjustment of the peak power level is used.

8 shows the signal waveform of the third method for the light output control APC in the case of the L-type writing strategy WS in the present invention.

As such, all of the first, second and third APC methods need to modify the target values for different power levels in accordance with the authorized write strategy WS. After determining the optimum power by Optimal Power Control (OPC), the optical recorder requires a special recording operation to confirm the OPC results. If the result of the check is positive, the controller 40 detects data from the APC channels according to the selected APC method and uses it as a future target value.

As described above, according to the light output control apparatus and method according to the present invention, it is possible to stably control the light output level over a wide recording speed range in order to widen the transmission rate speed without increasing the cost. It works.

What has been described above is only one embodiment for implementing the light output control apparatus and method thereof according to the present invention, the present invention is not limited to the above-described embodiment, it is usually within the technical spirit of the present invention Of course, various modifications are possible by those who have the knowledge of.

Claims (8)

An apparatus for controlling the light output of a laser diode emitted for recording data on an optical disc, A photodiode for detecting a power level of an optical output emitted during data writing; And A control unit for controlling light output levels of different recording speeds based on the detected power level of the light output; Light output control device comprising a. The method of claim 1, A peak power detector for detecting peak power of the detected light output; A middle power detector detecting middle power of the detected light output; And Further comprising: a bias power detector for detecting a bias power of the detected optical output, And the control unit includes a plurality of channels for controlling light output at different recording speeds according to the detected peak power, middle power, or bias power level. A method of controlling the light output of a laser diode emitted for writing data to an optical disc, Detecting a power level of an optical output emitted during data recording; And Controlling the light output levels of different recording speeds based on the detected power levels of the light outputs; Light output control method comprising a. The method of claim 3, wherein The control step, A first method of controlling power level detection and adjustment of the light output for low speed recording; A second method of detecting and adjusting an erase power level of an optical output and adjusting peak power based on a result of averaging the detected powers of the photodiodes for a multi-pulse write strategy; And A third method of controlling middle and bias power level detection and adjustment of optical output, and proportional adjustment of peak power levels for different types of recording strategies; medium The light output control method, characterized in that for selecting any one to control the light output level. The method of claim 4, wherein The first method, Used for slow recording; And comparing the detected peak power, erase power, and bias power levels with a predetermined target value and adjusting the light output of the laser diode according to the comparison result. The method of claim 4, wherein The second method is Used for high speed write with multiple pulse write strategy; When the error of the detected peak power becomes the duty limit of the frequency bandwidth of the photodiode amplifier, comparing the middle power level of the detected light output with a predetermined target value and adjusting the light output of the laser diode according to the comparison result Light output control method characterized in that. The method of claim 4, wherein The third method, Is used when the OPC results have a large difference between peak power and middle power; And comparing the bias power, middle power, and peak power level of the detected light output with a predetermined target value and adjusting the light output of the laser diode according to the comparison result. The method according to any one of claims 5 to 7, The target value is a light output control method, characterized in that the target power data determined through the OPC process.

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