KR100363173B1 - Auto output control apparatus of laser diode - Google Patents

Abstract

The present invention relates to an optical recording apparatus and method, and more particularly, to an automatic laser diode power supply control apparatus and method for controlling a laser diode in an optimal state.

An automatic laser diode power supply control apparatus according to the present invention includes a photodiode for monitoring a current power value of an optical signal output from a laser diode, comparing the current power value with a reference power value, and controlling the output of the laser diode according to the comparison result. An automatic laser diode output control apparatus, comprising: a sample holder configured to sample and hold a current power value output from the photodiode; A sample hold control signal generator for generating a sample hold control signal for controlling a sampling operation of the sample holder based on an NRZI signal; And an operation unit for comparing the current power value sampled by the sample holder with the reference power value, and adjusting the output of the laser diode according to the difference value.

According to the present invention, it is possible to improve recording and playback performance by appropriately adjusting abrupt light output changes by using different loops depending on the type and state of the disc.

Description

Automatic laser diode output control device {Auto output control apparatus of laser diode}

The present invention relates to an optical recording / reproducing apparatus, and more particularly, to an automatic laser diode output control apparatus for controlling the output of a laser diode in an optimal state.

The modern society is called the information age or the multimedia age. Therefore, this era requires high-capacity recording media, and CD-R, CD-RW, Magnetic Optical Disc Drive (MODD), and Digital Versatile Disc Random Access Memory (DVD-RAM) are used as optical recording apparatuses. . Since such optical recording devices use laser diodes, controlling the output of the laser diodes optimally will determine the performance of the device. In addition, since the types of recording pulses required for different optical recording apparatuses are different, there is a need for an effective response method for excitation.

1 is a block diagram showing the configuration of a conventional automatic laser diode output control device.

The apparatus illustrated in FIG. 1 includes an interface unit 110, a decoder 120, an address controller 130, a pulse generator 140, an ALPC block 150, an LD driver 160, and a delay unit 170. Include.

The interface unit 110 communicates with an external processor, for example, a microprocessor of a computer, to exchange recording / reproduction data, control data, information on a use mode, and the like.

The decoder 120 includes an address decoder 121, a register unit 122, and a demultiplexer 123 for selecting one of various registers provided in the register unit 122.

The address controller 130 may include sub blocks for implementing various registers and functions, and is in charge of overall control.

The laser diode driver 160 is a device capable of high-speed switching and may be included in a separate general purpose IC or ASIC.

The pulse generator 140 generates a signal for generating and controlling each recording pulse for forming a domain on the recording medium corresponding to the data to be recorded.

The delay unit 170 is for time delay, LD represents a laser diode, and PD represents a photo diode.

The ALPC block 150 detects a difference between the reference power value provided from the decoder 120 and the current power value provided from the photodiode PD, and controls the laser diode driver 160 according to the detection result.

The operation of the apparatus shown in FIG. 1 will be described. First, since the interface unit 110 is different according to the system configuration, it is assumed that it is already configured.

The decoder 120 selects and holds a target power value (read power, erase power, peak power, etc.) as a reference power value. The selected reference power value is input to the ALPC block 150, and at least three reference power values such as read power, erase power, and peak power are input.

Each reference power value is analog converted by the D / A converter 151 and provided to the comparator 152.

On the other hand, the photodiode signal output from the photodiode PD is provided to the comparator 152 via a buffer (not shown).

At this time, the comparator 152 generates a signal capable of controlling its operation from the pulse generator 140 and is provided through the delay unit 170.

The up / down counter unit 153 performs up or down counting according to the comparison result of the comparator 152.

The output of the up / down counter unit 153 is selected by the second demultiplexer unit 154, converted into an analog signal via the second D / A converter unit 155, and provided to the LD driver 160.

The LD driver 160 receives a control signal for controlling each power level provided from the ALPC block 150 and each power provided from the pulse generator 140.

The apparatus shown in FIG. 1 uses an up / down counter 153 in performing control by comparing a reference power value with a feedback current power value. However, since the playback and recording speed of the media is getting faster, the control speed and the control range are limited by the operation speed of the up / down counter 153.

In addition, as the recording speed of the media increases, the width of the recording pulse becomes shorter and more complicated, and thus countermeasures are required.

The technical problem to be achieved by the present invention is to provide an automatic laser diode output control apparatus for controlling the laser diode in an optimal state, which is devised to solve the above problems.

1 is a block diagram showing the configuration of a conventional automatic laser diode output control device.

2 is a block diagram showing the configuration of an automatic laser diode output control apparatus according to the present invention.

Figure 3 is a block diagram showing a preferred embodiment of the automatic laser diode output control apparatus according to the present invention.

FIG. 4 is a timing diagram for schematically showing the operation of the apparatus shown in FIG. 3.

5 is a timing diagram for schematically showing generating a sample hold control signal by a delayed control signal.

6 is a diagram schematically illustrating an operation mode of the operation unit illustrated in FIG. 3.

Automatic laser diode power supply control apparatus according to the present invention for solving the technical problem to be achieved by the present invention

A photodiode for monitoring a current power value of an optical signal output from a laser diode, and an automatic laser diode output control device for comparing the current power value with a reference power value and controlling the output of the laser diode according to a comparison result.

A sample holder configured to sample and hold a current power value output from the photodiode;

A sample hold control signal generator for generating a sample hold control signal for controlling a sampling operation of the sample holder based on an NRZI signal; And

And a calculation unit for comparing the current power value sampled by the sample holder with the reference power value, and adjusting the output of the laser diode according to the difference value.

Here, the automatic laser diode output control apparatus of the present invention includes a comparator for comparing the photodiode signal and the reference power value; An up / down counter for performing up or down counting according to a comparison result of the comparator; It is preferable to further include a multiplexer which selects one of the output of the up / down counter or the output of the ADC and provides it to the operation unit.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration and operation of the automatic laser diode output control apparatus of the present invention.

As shown in FIG. 1, the conventional automatic laser diode output control apparatus uses an up / down counter in performing control by comparing the reference power with the current power fed back, and thus, the media playback and recording speed is increased. Control speed and control range will be limited.

In addition, as the recording speed of the media increases, the shape of the recording pulse also becomes smaller and more complicated.

The present invention provides an automatic laser power control apparatus that includes a method for sampling an input signal at a desired location for a desired period of time.

Figure 2 is a block diagram showing the configuration of an automatic laser diode output control apparatus according to the present invention.

2 shows an amplifier 200, a sample holder 202, a calculator 204, a laser diode driver 206, a sample hold control signal generator 208, a pulse generator 210, and a controller 212. It is.

The output of the laser diode LD is controlled by the laser diode driver LD driver 206 and its output level is detected by the photodiode PD. The photodiode signal detected by the photodiode PD represents a current power value of the optical signal output from the laser diode LD.

The photodiode signal has a form in which a write pulse applied to the laser diode LD is delayed in time. The delay amount depends on the operating characteristics of the laser diode (LD), photodiode (PD), amplifier, and the like and hardly changes after the device is configured.

The write pulse is a multiple pulse consisting of a first pulse, a multi-pulse train, a last pulse, a cooling pulse, and the like. Each pulse includes a read power level, a peak power level, And any one of bias1 power level, bias2 power level, and bias3 power level. That is, the level of the write pulse changes on the time axis and is any one of the read power level, the peak power level, the bias 1 (or erase) power level, the bias 2 (or cooling ) power level, and the bias 3 (or bottom ) power level. It becomes a level.

The recording pulse is generated based on the NRZI signal (Non Return to Zero Inverted signal), and the start / end position, pulse width, and width of each pulse constituting the recording pulse according to the correlation between the spaces before and after the current mark. The power level may be changed.

The pulse generator 210 generates a power level control signal for turning on and off each power level according to the correlation between the NRZI signal and the mark and space. The power level control signal includes a read control signal, a peak control signal, a bias control signal, a bias control signal, and a bias control signal that controls read power level, peak power level, bias 1 power level, bias 2 power level, and bias 3 power levels, respectively. 3 control signals and the like.

The sample holder 202 samples the magnitude of the photodiode signal at some point in time to obtain a current power value, and provides it to the calculator 204.

The calculator 204 compares the reference power value with the sampled current power value and controls the output of the laser diode LD according to the comparison result. Specifically, the calculation unit 204 changes the level of the driving power provided to the laser diode LD according to the comparison result, and the laser diode driver LD driver 206 changes the output of the laser diode LD according to this current value. Let's do it.

The laser diode driver LD driver is provided with driving powers corresponding to each power level, and the level of the driving power is changed according to the output of the calculator 204. In addition, the laser diode driver 206 drives the laser diode LD by selectively combining each driving power source, and the selection of the driving power source is performed by a power level control signal.

Figure 3 is a block diagram showing a preferred embodiment of the automatic laser diode control device according to the present invention.

The apparatus shown in FIG. 3 includes a reference DAC 302, a switching amplifier 304, a comparator 306, an ADC 308-312, up / down counters 314-322, multiplexers 324-332, arithmetic unit. 334 to 342, DACs 344 to 352, sample holders 354 to 358, multiplexer 360, delay unit 362, pulse generator 364, NRZI detector 366, controller 368 , An interface unit 370, and a monitor unit 372.

The reference DAC 302 analog converts the reference power value provided from the controller 368 and provides it to the inverting input terminal of the comparator 306.

The reference power value varies depending on the disc format (CD, CD-R, DVD, DVD-RW, DVD + RW, etc.), the type of media, and the manufacturer, and is provided to the controller 368 through the interface unit 370. The controller 368 stores the reference power values in a table form, and reads the contents stored in the table to the reference DAC 302 according to a disc format, a type of media, a manufacturer, an operation mode, and the like.

The switching amplifier 304 amplifies the photodiode signal according to a predetermined gain and provides it to the non-inverting input terminal of the comparator 306. The output of the switching amplifier 304 will represent the current power value. In FIG. 3, the Monitor Front PD signal represents a photodiode signal which is an output of the photodiode PD.

Switching amplifier 304 is a variable gain amplifier whose gain is controlled nonlinearly. The gain of the switching amplifier 304 is set according to the operation mode, whether the land / groove or the like.

The comparator 306 compares the reference power value provided by the reference DAC 302 with the current power value provided by the switching amplifier 304 and outputs a value of 0 or 1 depending on the comparison result. The output of the comparator 306 is provided to the up / down counters 314 to 322.

The up / down counters 314 to 322 perform up count or down count according to the comparison result of the comparator 306. The initial set values of the up / down counters 314 to 322 are provided by the control unit 368, and are usually slightly different from the reference power values. It is preferable that the difference between the initial setting value and the reference power value is small so that the current power value can quickly follow the reference power value.

Multiplexers 324-332 select one of the two feedback loops as described later.

The calculation units 334 to 342 perform operations such as averaging the sampled current power value, calculating a difference value from the reference power value, adjusting the power value, and maintaining the calculated value.

The DACs 344 to 352 convert analog outputs of the calculation units 334 to 342 and provide them to a laser diode driver (not shown).

The sample holders 354 to 358 sample and hold the photodiode signal output from the switching amplifier 304. The outputs of the sample holders 354 to 358 are digitally converted through the ADCs 308 to 312 and provided to the calculation units 334 to 342 through the multiplexers 324 to 332, respectively.

The multiplexer 360 generates a sample hold control signal for controlling the sample hold operation of the sample holders 354 to 358. Although not shown, the multiplexer unit 360 includes a plurality of multiplexers 360a to 360c, and each of the multiplexers 360a, 360b, or 360c includes a multiplexer and a logic gate.

The multiplexer of the multiplexer 360 selects one or more of a delayed read control signal, a delayed peak control signal, a delayed bias 1 control signal, a delayed bias 2 control signal, and a delayed bias 3 control signal provided from the delay unit 362. The gate generates a sample hold control signal by logically combining the output of the multiplexer. The simplest form of gate can be an end gate.

The delay unit 362 includes a plurality of delay elements, and delays and outputs the read control signal, the peak control signal, the bias 1 control signal, the bias 2 control signal, and the bias 3 control signals generated by the pulse generator 364. .

By the operations of the delay unit 362 and the multiplexer unit 360, the section for sampling can be easily selected, and a desired portion of the photodiode signal fed back can be sampled by using the delay unit 362 and the multiplexer 360.

The pulse generator 364 generates a read control signal, a peak control signal, a bias 1 control signal, a bias 2 control signal, and a bias 3 control signals. The start / end positions, pulse widths, and the like of each signal are NRZI detectors 366. Determined by

The NRZI detector 366 inputs an NRZI signal to detect a correlation between the current mark and the space before and after. The detected result is provided to the pulse generator 364 to determine the start / end position, pulse width, and the like of each signal of each control signal.

The control unit 368 provides the reference power value received through the interface unit 370 to the reference DAC 302 and the calculation units 334 to 342 and sets initial values of the up / down counters 314 to 322. In addition, the gain of the switching amplifier 304, the switching positions of the multiplexers 324 to 332, and the operating modes of the calculation units 334 to 342, depending on information such as an operation mode, a type of media, a disk format, and whether or not lands or grooves are used. And so on.

The monitor unit 372 monitors the current power value output from the switching amplifier 305 and performs emergency measures.

Typically, the sample holders 354 to 358 and the ADCs 308 to 312 shown in FIG. 3 are used as one unit, but are shown separately for convenience of description.

The operation of the apparatus shown in FIG. 3 will now be described in detail.

Automatic laser diode power control refers to controlling the power of the laser during recording / playback on an optical disc. Since the output of the laser changes with temperature, it is necessary to control the laser output to be constant according to the change in operating temperature. This is called automatic laser output control. The reason why the automatic laser diode power supply control is performed is to stabilize the laser output according to the temperature change and to prevent recording deterioration due to heat accumulation in the multi-train recording method.

The automatic laser diode power supply control apparatus of the present invention is largely composed of two loops. The first loop is used when the response time of the control circuit does not need to be fast. The amplification unit 304, the reference DAC 302, the comparator 304, the up / down counters 314 to 322, and the arithmetic units 334 to 322 342, DACs 344-352, laser diode drivers (LD driver, not shown), laser diodes (LD, not shown), photodiodes (PD, not shown), and current / voltage converters (I / V). It is composed by.

The second loop is used when the response time of the control circuit needs to be fast. The amplifying unit 304, the sample holders 354 to 358, the calculating units 334 to 342, the DACs 344 to 352, and the laser diode driver LD driver, not shown), laser diode (LD, not shown), photodiode (PD, not shown), and current / voltage converters (I / V).

The selection of the first loop or the second loop is performed in the multiplexers 324 to 332 and is determined by the type of media.

1) Operation of the first loop

The switching amplifier 304 amplifies the output signal of the photodiode. The photodiode signal output from the photodiode represents a current power value and has a waveform of a delayed write pulse.

The switching amplifier 304 varies in gain depending on the operating mode of the driver of the disk, that is, the reproducing mode, the recording mode, and the erasing mode. The photodiode signal amplified by the switching amplifier 304 is input to the non-inverting input terminal (+ notation) of the comparator 22. Also, if the input of the switching amplifier 304 is a current, I / V conversion is also performed.

The reference DAC 302 is implemented as an 8-bit DAC. The reference DAC 302 receives a reference power value according to the type of media, a manufacturer, etc. from the control unit 368 and outputs an analog conversion. The reference power value output from the reference DAC 302 is input to the inverting input terminal (-notation) of the comparator 306.

The first to fifth up / down counters 314 to 322 perform up or down counting operations by one bit according to the output of the comparator 302.

The first up / down counters 314 to fifth up / down counters 322 are used to control read power, peak power, bias 1, bias 2, and bias 3, respectively.

Although not shown in detail, each of the up / down counters 314 to 322 includes two up / down counters. One is for land and the other is for groove.

The first up / down counter unit 314 to the fifth up / down counter unit 322 perform down counting when the current power value is greater than the reference power value as a result of the comparison of the comparator 306, and vice versa. If it is smaller than this reference power supply value, up counting is performed.

The initial setting values of the up / down counters 314 to 322 are provided by the control unit 368, and the difference between the initial setting value and the reference power value may be small so that the current power value can quickly follow the reference power value.

The first to fifth calculators 334 to 342 perform calculations according to a calculation mode provided by the controller 368. The first to fifth calculators 334 to 342 are used for calculating read power, peak power, bias 1 (erase erase) power, bias 2 ( cooling cooling ) power, and bias 3 ( bottom bottom ) power, respectively. Examples of the operation mode provided by the controller 368 include a sub ALPC mode (SUB-ALPC), an average ALPC (Average ALPC) mode, and a SUB-average ALPC mode.

The output signal of the first to fifth DACs 344 to 352 drives a laser diode (not shown) through a laser diode driver (LD driver, not shown), and the output of the laser diode is driven by a photodiode (not shown). It is monitored and fed back to the switching amplifier 304 shown in FIG.

2) Description of operation of the second loop

The NRZI detector 366 detects data to be recorded by inputting NRZI data. The NRZI detector 366 detects a predetermined correlation according to the size of the space before and after the current mark, and outputs the detection result to the pulse generator 364. According to the adaptive control method, the combination of the length of the current mark and the space before and after is classified into several groups according to the length of the mark and the space, and the power level, start / end position, The pulse width and the like vary. The power level of each pulse also varies depending on the energy of the NRZI signal. Here, energy refers to the number of times converted between 0 and 1 during a unit time.

The pulse generator 364 controls power levels for forming a recording pulse (FIG. 4B) suitable for the detection result of the NRZI detector 366 and the laser diode and media type and the recording speed provided from the controller 368. Signals (Figs. 4C to 4F) are generated.

The delay unit 362 delays and outputs the power level control signals output from the pulse generator 364.

The multiplexer unit 360 selects and combines delayed power level control signals provided from the delay unit 362 to output sample hold control signals for controlling the respective sample holders 354 to 358.

The sample holders 354 to 358 perform sampling on the photodiode signal while being activated by the sample hold control signal. Here, the sample holders 354 to 358 and the ADCs 308 to 312 perform sampling and digital conversion operations continuously within the activation period of the second loop and the active period of the sample hold signal.

The sample holders 354 to 358 are for sampling read power, peak power, and bias power, respectively.

The photodiode signals sampled by the sample holders 354 to 358 are digitally converted through the ADCs 308 to 312 and provided to the calculation units 334 to 342.

The calculation units 334 to 342 compare the power values sampled by the sample holders 354 to 358 with the reference power values provided by the control unit 368 according to the operation mode instructed by the control unit 368, and accordingly, Control the power level of the diode.

The monitor 372 performs a laser diode test mode (LTM) or an interrupt.

The laser diode test mode can optionally be performed and used to inspect the laser diode at initialization or during operation, and to inspect or accurately calibrate each power level. When the laser diode test mode is performed, the laser diode LD outputs an optical signal having power for recording, thereby affecting already recorded data. Therefore, when performing the laser diode test mode, the pickup (not shown) is moved to the innermost or outermost circumference of the disc, or the objective lens is maximized up or down through the focus servo (not shown). The recorded data shall be protected.

In the case of 4.7 GB DVD-RAM, since the range of the bias power level is 0 to 10 mW, the third ADC 312 may be implemented by only one.

The output signals of the first to fifth DACs 344 to 352 drive the laser diode LD, and the output level of the laser diode LD is fed back to the switching amplifier 304 through the photodiode.

In the first loop using the first to fifth up / down counters 314 to 322, the tracking speed is slow because the reference power value is followed while moving only one bit at a time. However, in the case of the second loop using the first to third ADCs 308 to 312, the following speed is fast because all bits can be changed at once without limitation.

In the case of DVD-RAM, since there is a mirror or gap area where data is not recorded, a first loop or a second loop is used, and a CD-RW or CD-RW without a mirror or gap area is used. In this case, it is preferable to use a second loop.

The embodiment of the present invention shown in FIG. 3 makes it possible to more precisely control the output of the laser diode by adopting a control structure having two loops, and the output control value is infinitely maintained in time or arbitrarily varied. It is easy.

The feedback loop using the up / down counters 314 to 322 can prevent a sudden power change due to a noise or error, but is limited in response speed since it follows only in steps. In this case, optical power can be adjusted by outputting each power in a DC form in a user data unused region (a gap region of a DVD-RAM), and a peak holder or a bottom holder is included in the comparator 306. .

In the case of media that do not have a gap area, there is no unused area, so the focus servo can be controlled in Max / Min and each power can be corrected while outputting in DC form. At this time, since the focus servo is controlled at Max / Min, the optical signal having a level less than or equal to the read power is focused on the disk, thereby protecting data. This method is possible because the photodiode PD has a structure in which a certain amount of light in the output of the laser diode LD is input regardless of the position or type of the disk.

The feedback loops using the sample holders 354 to 358 and the ADCs 308 to 312 should also be approximated because they may include some noise during sampling, but they are not limited in response speed and change width.

The apparatus shown in Fig. 3 can selectively use one of the two feedback loops, so that the laser power can be controlled efficiently according to the type of media and the recording speed.

Each feedback loop is provided with the required number of power levels, and the example shown in FIG. 2 is composed of five peak, bias1, bias2, bias3, and read levels. In this case, the ADC and the DAC may be used as long as a high-speed device is available. In other words, each high-speed ADC can be used to digitize and process each level value. At this time, since it is a high-speed ADC, each level value is sampled from a write pulse without using a peak holder or a bottom holder. In addition, when a high speed DAC is used, it is possible to change an input value in one DAC at a high speed, thereby generating a recording pulse by using one DAC.

FIG. 4 is a timing diagram for schematically showing the operation of the apparatus shown in FIG. 3.

In Fig. 4, (a) shows the input NRZI signal, and (b) shows the write pulse output from the laser diode. The shape of each recording pulse varies depending on the type of media, the recording speed, and the disc production company. This recording pulse is shown as an example of 4.7 GByte DVD-RAM, and the shape of the recording pulse is also changed depending on the correlation between the mark and the space. (c) is a control signal for controlling the peak power level, (d) is a control signal for controlling the erase power level, (e) is a control signal for controlling the cooling power level, and (f) Is a control signal for controlling the bottom power level. In this manner, a combination of the respective control signals as shown in (c), (d), (e) and (f) can generate a write pulse as shown in (b).

(g) is a signal which is fed back and a part of the optical signal output from the laser diode LD is input to the photodiode, and the current which is the output of the photodiode is converted into a voltage and amplified with an appropriate gain. Therefore, by monitoring the signal, it is possible to know the power of the light output from the laser diode LD, thereby enabling proper control. (h) is a delayed peak control signal, (i) is a delayed erase control signal, (j) is a delayed clocking control signal, and (k) is a delayed bias control signal. Each signal (h), (i), (j), and (k) has a constant time delay, which is equal to the amount of time delay in (b) and (g).

At this time, the amount of time delay is generated through the photodiode PD and the switching amplifier 302. In each of the signals (h), (i), (j), and (k), the dotted line indicates the range in which sample hold is possible, and it is possible to create a sample hold control signal having a desired position and width within the range. Thus, the generated sample hold control signal can detect the output of the laser diode LD at the correct position.

5 is a timing diagram for schematically showing generating a sample hold control signal by a delayed control signal. In Fig. 5, Q1-Q8 of (a)-(i) are examples of delayed control signals generated by the delay unit 362, and (j)-(l) are generated by the multiplexer unit 360. This is a sample hold control signal for controlling the sampling operation of the sample holders 354 to 358. The delay amount of the delayed control signals can be appropriately adjusted to the desired magnitude.

Each delayed control signal is selected by the multiplexer and uses a logic gate to produce the desired sample hold control signal.

The gain of the switching amplifier 304 is adjusted nonlinearly. Therefore, overshoot or undershoot occurs in the photodiode signal during gain switching. It is desirable to avoid these overshoot and undershoot periods in sampling the photodiode signal. Delayed power level control signals are appropriately used in combination to avoid overshoot and undershoot periods.

Sampling noise by the ADCs 308-312 causes a change in power level.

Such sampling noise can be avoided by ignoring the slight change or by averaging the sampled power value in a certain section.

FIG. 6 schematically shows the operation mode of the calculation units 334 to 342 shown in FIG. In FIG. 6A, the mirror or gap section is generated in the case of a DVD-RAM. The mirror or gap section is an unused section or a section for controlling the focus servo at Max / Min. In the case of (b), continuous control is performed, and at this time, optical power may be changed by sampling noise or disturbance. In the case of (c), the control is controlled only in a specific section (mirror or gap section) of (a), and the change is held at the last controlled value in the remaining sections, thereby reducing the optical power change (sub-ALPC mode). In the case of (d), the optical power fluctuation can be reduced by obtaining a constant average and reflecting the average value instead of simply reflecting each controlled value ( average ALPC mode). This can have the same effect as using a low pass filter. In the case of (e), the functions of (d) and (d) are used at the same time, and the change of average is reflected only in a specific section and the last value is maintained in the remaining sections to minimize the change of optical power due to sampling noise or disturbance. can do.

The present invention is not limited to the above-described embodiments and can be modified by those skilled in the art within the spirit of the invention.

As described above, according to the present invention, it is possible to improve recording and playback performance by appropriately adjusting the sudden light output change by using different loops depending on the type and state of the disc.

Claims (6)

A photodiode for monitoring a current power value of an optical signal output from a laser diode, and an automatic laser diode output control device for comparing the current power value with a reference power value and controlling the output of the laser diode according to a comparison result. A sample holder configured to sample and hold a current power value output from the photodiode; A sample hold control signal generator for generating a sample hold control signal for controlling a sampling operation of the sample holder based on an NRZI signal; And And a calculation unit for comparing the current power value sampled by the sample holder with the reference power value and adjusting the output of the laser diode according to the difference value. The method of claim 1, wherein the sample hold control signal generator A delay unit for introducing a power level control signal for forming a write pulse and delaying the power level control signal by a different delay amount to generate a plurality of delayed power level control signals; And a multiplexer unit for introducing the plurality of delayed power level control signals and combining the plurality of delayed power level control signals to generate a sample hold control signal. 3. The multiplexer of claim 2, wherein the multiplexer comprises: a multiplexer for selectively outputting the plurality of delayed power level control signals; And And a gate for logically combining the outputs of the multiplexers. The method of claim 1, wherein the calculating unit averages the sampled photodiode signals for a predetermined period, compares the average value with the reference power value, and adjusts the output power value of the laser diode according to the difference value. Automatic laser diode output control device. The apparatus of claim 1, further comprising: a comparator for comparing the photodiode signal with the reference power value; An up / down counter which performs up or down counting according to a comparison result of the comparator; And a multiplexer which selects one of an output of the up / down counter or an output of the ADC and provides the multiplexer to the operation unit. 6. The multiplexer of claim 5, wherein the multiplexer selects an output of the up / down counter when the disc driven by the disc reproducing apparatus is a DVD sequence, and selects an output of the ADC when the CD sequence is a CD sequence. Automatic laser diode output control device.