KR100267982B1 - Recording power modulation circuit - Google Patents

Abstract

PURPOSE: A modulating circuit for a recording power is provided to record data after detecting an optimum recording power of a disk through comparing an EFM(Eight to Fourteen Modulation) signal to be recorded on the disk and a reproduced EFM signal. CONSTITUTION: An encoder(71) outputs a CD encoding EFM signal after detecting a reference power. A recording/reproducing servo(72) records and reproduces the CD encoding EFM signal in a test area of a PCA area. A first comparator(73) detects a phase difference at front portions of the CD encoding EFM signal and a reproducing EFM signal from the servo. A second comparator(75) detects a phase difference at rear portions of the signals. A differential amplifier(78) amplifies a difference between signals from first and second LPF(Low Pass Filter)(74,76). An ADC(Analog/Digital Converter) converts outputs of the amplifier into digital. A microcomputer(79) records, reproduces, and compares the digital values for deciding a value having a minimum difference from the EFM signals as an optimum power.

Description

Recording power modulation circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a circuit that finds an appropriate recording power before recording when recording data on a compact disc recordable CD-R / RW. In particular, an EFM (Eight to Fourteen Modulation) signal recorded in a specific area of the disc is recorded. And a recording power modulation circuit for recording data after detecting the optimum recording power of the disc by comparison with the reproduced EFM signal.

CR-R systems typically record data by laser-forming chemicals on the disc.

In the structure of such a CD-R / RW disc, as shown in Fig. 1, a recordable user area in which data is recorded, a program area in which data is recorded, and a lead-in in which information about recorded data is recorded. Lead-In Area, Program Memory Area (PMA) with information about the data being recorded, and Power Calibration Area (PCA) to determine the appropriate laser power for the data to be recorded. Divided into

In this case, the CD-R / RW system first operates to detect an optimum recording power in the PCA area before recording data.

To this end, the PCA area is divided into a test area for testing the laser power and a count area for recording the number of tests as shown in FIG. 2.

At this time, the test can be performed up to 100 times, and if more than 100 times, the recording is no longer possible even if the recording space remains.

At this time, the method for detecting the optimal recording power reads the ATIP (Absolute Time In Pregroove) information recorded on the disk and divides the recording power in 15 steps based on the reference power recommended by the disk manufacturer. After a random or nT EFM signal is written to and played back, it is judged to be the most appropriate recording power when peak hold and bottom hold are properly balanced, and this value is used to record data in the recordable user area. Record it.

The reference power is encoded in special information of ATIP in the lead-in area, and has a wavelength of 785 nm at a single speed.

In other words, after recording random data or nT EFM signal in the test area and reproducing it, the peaks of the positive and negative parts of the Hi-Fi (HF) signal for each recording power are examined as shown in the waveforms of FIGS. 3A to 3C. The power at which the value of (β = (A1 + A2) / (A1-A2)) becomes '0' is obtained.

FIG. 3A illustrates a case where the power P recorded in the test area is smaller than the disc optimal power Po, and FIG. 3B illustrates a case where the power P recorded in the test area and the disc appropriate power Po are correctly matched. 3C is a case where the power P recorded in the test area is larger than the disc proper power Po.

Therefore, when the power recorded in the test area is the same as in Fig. 3B, the value of the parameter β (β = (A1 + A2) / (A1-A2)) becomes '0'.

However, since it is impossible to find a recording power that is exactly zero, the CD-R / RW specification recommends that a recording power of about 0.04 is obtained.

When the proper recording power is determined in the test area by this process, random EFM data is recorded in the count area of the PCA area with the appropriate recording power obtained for one ATIP frame period.

At this time, the position of the test area and the position of the count area are the same.

This is to quickly and easily find the pre-position of the test area, that is, the untested area, in the next recording.

However, the appropriate recording power may include a change in power sensitivity throughout the disk, a shift in the wavelength of the laser diode due to a change in operating temperature, a change in spot aberration due to a change in the disk skew, and optimum power control before actual data recording. It may change depending on when it is performed for a long time.

Therefore, the recording power must be continuously adjusted to the optimum power required even when data is recorded in the recordable user area with the appropriate recording power determined in the PCA area.

This is called Running Optimum Power Control (OPC).

4A and 4B show how an Incident Recording Pulse in a disc recording layer is reflected in that layer.

When the peak power of the incident pulse increases as shown in FIG. 4A, the pulse reflected at the sample timing B is proportional to the incident pulse up to the point at which physical exchange occurs in the disk as shown in FIG. 4B.

At that point, sample timing B (B-level) decreases rapidly for the pit format.

5 shows the variation of the B-level reflected as a function of incident recording power for a typical CD-WO disc 11T.

That is, the running OPC is to maintain the B-level constant by continuously adjusting the recording power.

FIG. 6 is a block diagram illustrating a running OPC process, in which the laser power recorded on the disk 61 is detected by the photodetector 62 and then the B-level is measured by the signal processor 63 so that the memory 64 is measured. And output to the subtractor 65.

At this time, the correct reference value of the B-level reflected by the normal OPC procedure for testing the recording power in the test area of the PCA area is determined and the reference value is stored in the memory 64.

Accordingly, the memory 64 outputs the corrected B-level to the subtractor 65 when the B-level output from the signal processor 63 is different from the reference value, that is, when the optimum power is changed. The subtractor 65 outputs a difference value between the measurement B-level output from the signal processing unit 63 and the correction B-level output from the memory 64 to the laser diode (LD) power control unit 66.

The LD power control section 66 drives the laser diode 67 with the adjusted optimal power to record data on the disk 61.

That is, the actual reflected B-level during recording is controlled by the control loop such that the actual value is close to the reference B-level.

As described above, the conventional CD-R / RW system divides the recording power in 15 steps based on the reference power recommended by the disc manufacturer to obtain the optimum recording power before recording the data. After the random or nT EFM signal is written and played back, the peaks of the positive and negative parts of the HF signal for each recording power are examined, and the value of parameter β (β = (A1 + A2) / (A1-A2)) is '0.04'. Power to be obtained.

However, since the value of about 0.04 is determined as the optimal power by substituting the experimental formula ((A1 + A2) / (A1-A2)), the error occurrence rate is increased.

That is, since the optimum power is roughly determined by the experimental value, the accuracy of the optimum power is lowered, and thus, when data is read from the disk, it becomes a jitter factor of the RF signal, making accurate data recovery difficult.

The present invention has been made to solve the above problems, and an object of the present invention is to write a random or nT EFM signal in a test area of the PCA area by dividing the recording power in several steps around the reference power recommended by the disc manufacturer. The present invention provides a recording power modulation circuit which compares a recording EFM signal with a reproduction EFM signal to determine the recording power having the lowest error as an optimal recording power, thereby reducing an error occurrence rate and detecting an accurate optimum power.

A characteristic of the recording power modulation circuit according to the present invention for achieving the above object is an encoder for detecting the reference power recorded on the disk and outputting the recording data by dividing the recording power in several stages based on the reference power; A recording and reproducing servo for recording and reproducing the recording data in a specific area of the disc with the recording power output from the encoder, and comparing the recording data output from the encoder with the reproducing data output from the recording and reproducing servo. A comparator for detecting a phase difference before and after the signal, an amplifier for differentially amplifying the output of the comparator after low pass filtering, an ADC for converting the output of the amplifier to a digital value, and a digital value of the ADC. After storing the data, it feeds back to the recording and reproducing servo to perform the recording and reproducing and comparing process of data in several stages. And a controller which performs all of the lock powers sequentially and determines the optimal recording power of the smallest value among the stored digital values.

1 is a view showing the structure of a typical CD-R / RW disc

FIG. 2 shows the format of the PCA, PMA, and lead-in areas on the disk of FIG.

3A to 3C are waveform diagrams showing a hi-fi signal for each recording power

4A-4B show incident recording pulses in a typical CD-R / RW disc recording layer and show how they are reflected in the layer

5 is a view showing the function of the incident recording pulse of FIGS. 4A to 4B

FIG. 6 is a block diagram illustrating an example in which data is recorded and an optimal recording power is adjusted using the optimal recording power determined in FIGS. 3A to 3C;

7 is a block diagram of a write power modulation circuit according to the present invention;

8A to 8G are operational waveform diagrams of each part of FIG.

Explanation of symbols for the main parts of the drawings

71: encoder 72: recording and playback servo

73: first comparator 74: first low pass filter

75: second comparator 76: second low pass filter

77: differential amplifier 78: analog / digital converter

79: microcomputer 80: B-level determination unit

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

7 is a block diagram of a recording power modulation circuit according to the present invention.

Referring to FIG. 7, the encoder 71 outputs a CD encoding EFM signal by dividing the recording power in 15 steps based on the reference power after detecting the reference power from the ATIP information recorded on the disk, and is output from the encoder 71. A recording and reproducing servo 72 for recording and reproducing a CD-encoding EFM signal with a recording power in a test area of the PCA area, and a CD-encoding EFM signal output from the encoder 71 and a reproducing output from the recording and reproducing servo 72. A first comparator 73 for comparing the EFM signals to detect a phase difference between two signals, and a first low pass filter (LPF) for filtering the low frequency portion of the output of the first comparator 73 ( 74, a second comparator 75 comparing the CD encoding EFM signal output from the encoder 71 with the reproduction EFM signal output from the recording and reproducing servo 72 to detect a phase difference between the two signals. Second Comparator (75) The output of the differential amplifier 78 and the differential amplifier 78 to amplify the difference between the two signals output from the second LPF 76, the first and second LPF (74, 76) filtering the low-frequency portion of the output Analog / Digital Converter (ADC) that converts to digital values, saves the digital values, and performs data recording and playback and comparison processes sequentially for 15 power stages based on the reference power. The microcomputer 79 determines the optimal value of the least error between the CD-encoding EFM signal and the reproduction EFM signal, and the B-level determination for determining the B-level with the optimum power output from the microcom 79. It is comprised including the part 80.

In the present invention configured as described above, when CD-R / RW is inserted or data for recording is input, the encoder 71 reads the reference power recommended by the disc manufacturer from the ATIP information in the lead-in area and then 15 steps centering on the reference power. 8, and outputs the random data or nT CD-encoded EFM signal to the recording and reproducing servo 72 and the first and second comparators 73 and 75 as shown in FIG. 8A.

The recording and reproducing servo 72 records the nT CD encoding EFM signal in the test area of the PCA area and reproduces the same as in FIG. 8B and outputs the same to the first and second comparators 73 and 75.

The first comparator 73 compares the CD encoding EFM signal output from the encoder 71 and the reproduction EFM signal output from the recording and reproducing servo 72 to compare the phase difference between the two parts of the signal as shown in FIG. 8C. Detect.

The second comparator 75 compares the CD encoding EFM signal output from the encoder 71 and the reproduction EFM signal output from the recording and reproducing servo 72 to compare the phase difference between the two signals as shown in FIG. 8D. Detect.

At this time, if the EFM signal recorded in the test area of the PCA area is 3T, the reproduced EFM signal will also approach 3T.

That is, if 3T is recorded at the optimum power, the EFM signal at the time of recording and the EFM signal at the time of reproduction will be 3T with little error. However, if 3T is not recorded at the proper power, the reproduction EFM signal will be larger or smaller than 3T.

Meanwhile, the first LPF 74 filters the output waveform of the first comparator 73 to output at a constant DC level as shown in FIG. 8E, and the second LPF 76 outputs the output waveform of the second comparator 75. Is filtered and output at a constant DC level as shown in FIG. 8F.

The differential amplifier 77 differentially amplifies the two DC levels output from the first and second LPFs 74 and 76 so that the state of the current pit maintains a constant voltage level as shown in FIG. 8G.

The ADC 79 converts the output of the differential amplifier 77 into a digital value and outputs it to the microcomputer 79.

The microcomputer 79 stores the digital value and feeds it back to the recording and reproducing servo 72 to record and reproduce the 3T EFM signal in the test area of the PCA area with the power of the second stage and to reproduce the first and second comparators. Output as (73,75).

The comparison results of the first and second comparators 73 and 75 are again input to the microcomputer 79 through the first and second LPFs 74 and 76, the differential amplifier 77, and the ADC 78.

The microcomputer 79 performs all of the above steps sequentially for the power of 15 steps, and then determines the smallest value among the 15 stored digital values as the appropriate recording power and outputs the power to the B-level determination unit 80.

The B-level determination section 80 determines the B-level of the appropriate recording power output.

If the outputs of the first and second LPFs 74 and 76 are the same as in g1 of FIG. 8G (a = b), the 3T recorded in the PCA area is recorded at the required power level. If the digital value input to (79) is 0 and the output a of the first LPF 74 is larger than the output b of the second LPF 76 as in g2 (a> b), In the case where 3T is recorded at a power larger than the proper power, the digital value becomes larger as it deviates.

And, as in g3, if the output a of the first LPF 74 is smaller than the output b of the second LPF 76 (a < b), the recorded 3T is recorded at a power smaller than the proper power. If it is.

In other words, if the phase difference between the front portion and the rear portion of the CD encoding EFM signal and the reproduction EFM signal is the same, it means that the recorded CD encoding EFM signal is recorded in the PCA area with the optimal recording power.

Therefore, the microcomputer 79 determines a digital value close to zero as an appropriate recording power.

As described above, the characteristic of the recording power modulation circuit according to the present invention is that the recording power is divided into several stages based on the reference power recommended by the disc manufacturer, and the random or EFM signal is written to the test area of the PCA area and then reproduced and recorded. By comparing the measured EFM signal and the reproduced EFM signal directly, the lowest error value is determined as the optimal recording power, which reduces the error occurrence rate and improves the accuracy of the optimal recording power, thereby eliminating jitter during recording and thereby recording on the disc. When data is reproduced, accurate data is restored.

Claims (4)

An encoder that detects the reference power recorded on the disc and outputs recording data by dividing the recording power in several stages based on the reference power; A recording and reproducing servo which records and reproduces the recorded data in a specific area of the disc with the recording power output from the encoder; A comparison unit which compares the recording data output from the encoder with the reproduction data output from the recording and reproducing servo, and detects phase differences before and after the two signals, An amplifier for low-pass filtering each output of the comparator and then differentially amplifying the output; An analog / digital converter for converting the output of the amplifier into a digital value; The digital value of the analog / digital converter is stored and fed back to the recording and reproducing servo to sequentially perform all recording and reproducing and comparison procedures for the recording power of several stages, and then optimize the lowest value among the stored digital values. And a control unit for determining the write power of the write power. The recording power modulation circuit of claim 1, wherein the specific area of the disk on which data output from the encoder is recorded is a test section of the PCA area. The write power modulation circuit of claim 1, wherein the data output from the encoder is an nT EFM signal. The method of claim 1, wherein the control unit A recording power modulation circuit characterized in that the optimal recording power is determined by a value having the least error between the recording data and the reproduction data.

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