KR20010035777A - Apparatus for correcting defect level and asymmetric waveform level in optical disk system - Google Patents

Abstract

PURPOSE: An apparatus for compensating a defect level and an asymmetrical waveform level of an optical disk system is provided to detect whether a digital signal is defective and whether there occurs an asymmetrical waveform and then to compensate for a defect level and an asymmetrical waveform level, when converting an RF(Radio Frequency) signal into the digital signal for generating data in an optical disk system. CONSTITUTION: An analogue-digital signal converting part (100) converts an RF(Radio Frequency) signal output from an optical disk into a digital signal. A defect level compensating part(110) detects an envelope of the converted digital signal, judges whether the digital signal is defective, and outputs the first compensating value if it is affirmative. An asymmetrical waveform level compensating part(130) detects a DSV(Digital Sum Value) of the digital signal and outputs the second compensating value if the DSV exceeds a predetermined range. An adder(140) adds one of outputs of the defect level compensating part(110) and the asymmetrical waveform level compensating part(130) to the digital signal. A switch(120) outputs the first compensating value to the adder(140) if the defect level is detected by the defect level compensating part(110), whereas outputting the second compensating value to the adder(140) if the defect level is not detected.

Description

Apparatus for correcting defect level and asymmetric waveform level in optical disk system

The present invention relates to an apparatus for correcting asymmetric waveform levels and defect levels in an optical disk system, and more particularly, to an apparatus for correcting asymmetric waveform levels and defect levels generated when converting a radio frequency (RF) signal into digital data in an optical disk system. will be.

In optical disc systems including compact discs (CDs) and digital video discs (DVDs), the asymmetric waveform phenomenon is a phenomenon in which the RF signal waveform output from the disc is broken up and down about the reference level due to errors in the disc processing process. Say. When this asymmetric waveform occurs, it becomes difficult to find the center value of the waveform, which makes it difficult to recover the data without error.

In addition, the defect phenomenon of the optical disk refers to the occurrence of defects in the RF signal due to scratches on the surface of the disk due to user's carelessness, fingerprints, dust, or dirt.

Therefore, correction of the above-described asymmetric waveform and defects is necessary.

The technical problem to be achieved by the present invention is to detect and correct the defect of the digital signal when converting the RF signal into a digital signal for data reproduction in the optical disk system, and to detect the presence or absence of an asymmetric waveform phenomenon to adjust the level of the asymmetric waveform. It is to provide a device for calibrating.

1 is a block diagram of an asymmetric waveform level and defect level correction apparatus in an optical disk system according to the present invention.

2 shows an example of a defect signal.

3 shows an example of an asymmetric waveform.

4 is a block diagram illustrating an embodiment of an envelope detector.

5 shows a block diagram of an embodiment of a defect detector and a defect level correction value calculator.

6 is a more detailed block diagram of an embodiment of the asymmetric waveform level correction unit of FIG. 1.

In order to achieve the above technical problem, the present invention provides an analog-to-digital signal converter for converting a radio frequency signal output from an optical disk into a digital signal; A defect level correction unit detecting the envelope of the converted digital signal to determine whether the digital signal is defective, and outputting a first correction value when it is determined that the defect is defective; An asymmetric waveform level correction unit detecting a DS V of the digital signal and outputting a second correction value when the DSV is out of a predetermined range; An adder for adding one of the outputs of the defect level corrector and the asymmetric waveform level corrector to the digital signal; And a switch for outputting the first correction value to the adder if a defect level is detected by the defect level correction unit, and outputting the second correction value to the adder if it is not detected.

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

1 is a block diagram of an asymmetric waveform level and defect level correction apparatus in an optical disk system according to the present invention. The apparatus according to FIG. 1 includes an A / D converter 100, a defect level correction unit 110, a switch 120, an asymmetric waveform level correction unit 130, and an adder 140.

The operation according to the configuration is as follows. The A / D converter 100 converts the RF analog signal output from the optical disk into a digital signal. The defect level correction unit 110 detects and corrects a defect from the digital signal. As described above, a defect is a phenomenon in which distortion occurs in a signal picked up from a disk by scratches on the surface of the disk, fingerprints, dust, or dirt of a user. 2 shows an example of a defect signal. As shown, the defects refer to portions indicated by reference numerals 200 and 202.

The asymmetric waveform level correction unit 130 corrects an asymmetric waveform phenomenon of the digital signal output from the A / D converter 100. As shown in FIG. 3, the asymmetric waveform phenomenon is caused by setting a reference level at a portion shown as an asymmetrical level without a reference level (dotted line) at a position where the waveform is vertically symmetrical.

The asymmetric wave phenomenon is mainly caused by errors in the disc machining, so the characteristics are similar in the whole signal output from the disc. Therefore, if the center value is corrected too frequently, it has rather unstable characteristics. In the present invention, the asymmetry level is corrected by using DSV (Digital Sum Value).

The DSV is obtained by counting the number of '0's and' 1's of the signals stored on the disk. The DSV is substantially the same as the number of '0's and' 1's for a sufficiently long section. Has a value of '0'. However, on discs with asymmetric waveforms, the error occurs in the reference level, causing the DSV to deviate from zero. At this time, if the value of the DSV is out of the value specified by the user, by adding or subtracting a certain value to all the input signal to correct the position of the reference level so that the DSV value converges to '0'.

The switch 120 corrects the defect level correction value output from the defect level correction unit 110 and the asymmetric waveform level correction unit 130 according to the defect detection signal output from the defect level correction unit 110. One of the values is selected and output to the adder 140.

The adder 140 adds the correction value output from the switch 120 and the output value of the A / D converter 100.

The defect level correction unit 110 includes an envelope detector 111, a defect detector 112, and a defect level correction value calculator 113 connected to an output terminal of the A / D converter 100. .

The operation according to the configuration is as follows. First, the envelope detector 111 detects an envelope of digital data output from the A / D converter 100. The defect detector 112 detects whether a defect is detected from the envelope detected by the envelope detector 111. If a defect is detected, the defect level correction value calculator 113 outputs the defect correction value.

4 is a block diagram illustrating an embodiment of an envelope detector 111. The envelope detector according to FIG. 4 includes a maximum and minimum envelope value detector 300 and a maximum and minimum envelope value average unit 350.

The maximum and minimum envelope value detecting unit 300 may include a first switch 302 for determining whether input digital data is greater than a first threshold value, a first switch 302 turned on by the first determiner 301, Maximum envelope storage (MAX, 303) for storing input digital data when the first switch 302 is turned on and outputting the stored value as the first threshold value, and whether the input digital data is smaller than the second threshold value. A second discriminator 304 for discriminating, a second switch 305 turned on by the second discriminator 304, and digital data input when the second switch 305 is turned on; The minimum envelope storage (MIN, 306) outputting as a threshold value, the first counter 307 for counting the input clock, the second counter 307 determines whether the counted value is equal to ENVCNT, the envelope detection period A third switch that is turned on according to the output of the third discriminator 308 and the third discriminator 308 to transfer the value stored in the MAX 303 309, the output of the fourth switch 310 and the third discriminator 308, which are turned on according to the output of the third discriminator 308 and transfer the value stored in the MIN 304, are delayed for a predetermined time. Retarders 311, 312, and 313 are output as reset signals for resetting the MAX 303, MIN 306, and counter 307, respectively.

The minimum and maximum envelope value averaging unit 350 includes a minimum value accumulator 351 and a maximum value accumulator 352 that accumulate the minimum and maximum envelope values output through the third switch 309 and the fourth switch 310, respectively. ), The minimum value accumulator 351, the maximum value accumulator 352, and the minimum value accumulator 353, the maximum value averager 354, and the ENVAVR, respectively, averaging the accumulated values in the ENVAVR determined by the user. The conversion table 355 to be converted to the second counter 356 to count the value output from the third determiner 308, the value output from the conversion table 355 and the value output from the second counter 356 And a fourth discriminator 357 which determines whether this is the same and outputs the output as a reset signal of the minimum and maximum value accumulators 351 and 352.

Operation of the envelope detector according to the configuration shown in FIG. 4 is as follows. First, when the input digital data is larger than the value stored in the MAX 303, the first determiner 301 outputs an on signal to the first switch 302. The MAX 303 stores digital data input as the first switch 302 is turned on. Similarly, the second discriminator 304 outputs an on signal to the second switch 305 when the input digital data is smaller than the value stored in the MIN 306. The MIN 306 stores the digital data input as the second switch 305 is turned on.

The first counter 307 counts the input clock, and the third determiner 308 determines the third and fourth switches 309 and 310 if the value counted by the first counter 307 is equal to a predetermined EVNCNT value. Outputs the on signal. The ON signal output from the third discriminator 308 is delayed by the delayers 311, 312, and 313 for a predetermined time, respectively, and then resets the MAX 303, the MIN 306, and the first counter 307.

Meanwhile, the minimum and maximum accumulators 351 and 352 accumulate the minimum and maximum envelope values output as the third and fourth switches 309 and 310 are turned on, respectively. Accumulation is for a period of time determined by a given ENVAVR. The minimum and maximum averages 353 and 354 average the values accumulated in the minimum and maximum value accumulators 351 and 352 using ENVAVR, respectively. For each average, a shift register that performs division by shift operation by the input ENVAVR value is appropriate. The second counter 356 receives the signal output from the third determiner 308 as a clock and counts the signal. The conversion table 355 converts the input ENVAVR into a predetermined value. For example, when the ENVAVR is 7, 3 bit data is converted into 8 bit data as in 2 ⁷ = 128. If the output value of the conversion table 355 is the same as the output value of the second counter 356, the fourth determiner 357 outputs a reset signal to the minimum value and maximum value accumulators 351 and 352.

5 shows a block diagram of an embodiment of a defect detector 112 and a defect level correction value calculator 113. The defect detector according to FIG. 5 is output from the first discriminator 401 that determines whether the value ENV_HIGH output from the maximum value averager 354 of FIG. 4 is smaller than the predetermined value DEFECTHIGH, and the minimum value averager 353 of FIG. 4. A logical arithmetic operator 403 for logically calculating the outputs of the second discriminator 402, the first discriminator 401, and the second discriminator 402, which determine whether the calculated value ENV_LOW is greater than the predetermined value DEFECTLOW. A counter 404 for counting the output value of 403 and a third discriminator 405 for determining whether the value output from the counter 404 is equal to the predetermined value DEFECTCNT are provided.

The operation is as follows. The first discriminator 401 outputs an on signal when EVN_HIGH is less than DEFECTHIGH, and the second discriminator 402 outputs an on signal when ENV_LOW is greater than DEFECTLOW. If one of the output signals of the OR operation 403, the first discriminator 401, and the second discriminator 402 is an ON signal, the ON signal is output. The counter 404 counts when the output signal of the OR operator 403 is on. If the value counted by the counter 404 is equal to DEFECTCNT, the third discriminator 405 outputs a DEFECT signal which is a defect detection signal. That is, if ENV_HIGH is smaller than DEFECTHIGH or ENVLOW is larger than DEFECTLOW, a defect condition is generated. If the defect condition is maintained by DEFECTCNT, it is finally determined as a defect and a DEFECT signal is output.

The combined level correction value calculator according to FIG. 5 includes an averager 411 that averages ENVHIGH and ENVLOW, and a defect level corrector 412 that outputs a DEFECT_DIFFER which is a correction level based on the output value and the reference level value of the averager 411. It is provided.

FIG. 6 is a more detailed block diagram of an embodiment of the asymmetric waveform level correction unit 130 of FIG. 1. The asymmetric waveform level correction unit 130 according to FIG. 6 includes a DSV detector 500 to 502 and a correction value generator 503 that detect a DSV from the input data.

The DSV detectors 500 to 502 may count up or down according to the output of the signal comparator 500 and the signal comparator 500 comparing the level of the input data to the first level or the second level. If the output value of the up / down counter 501 is outside the predetermined threshold, the determination unit outputs a reset signal to the up / down counter 501 and outputs an asymmetrical correction signal to the correction value generator 503. 502. The operation is as follows. The signal comparator 500 determines whether the signal of the input data is a first level or a second level, and outputs '1' for the first level and '0' for the second level, for example. The up / down counter 501 counts up or down according to the output of the signal comparator 500. The determination unit 502 outputs a reset signal to the up / down counter 501 when the value output from the up / down counter 501 is out of the threshold DSVTH, and increases or decreases the reference level to the correction value generator 503. A correction signal indicating a decrease is output.

The correction value generator 503 corrects by increasing or decreasing the reference level at the current position according to the correction signal.

According to the present invention, more accurate data reproduction is possible by detecting and correcting defects during data reproduction in the optical disc system and correcting asymmetric waveform levels by detecting DSV.

Claims (7)

An analog-digital signal converter for converting a radio frequency signal output from the optical disk into a digital signal; A defect level correction unit detecting the envelope of the converted digital signal to determine whether the digital signal is defective, and outputting a first correction value when it is determined that the defect is defective; An asymmetric waveform level correction unit detecting a DS V of the digital signal and outputting a second correction value when the DSV is out of a predetermined range; An adder for adding one of the outputs of the defect level corrector and the asymmetric waveform level corrector to the digital signal; And And a switch for outputting the first correction value to the adder if the defect level is detected by the defect level correction unit, and outputting the second correction value to the adder if not detected. Level and asymmetric waveform level correction device. The method of claim 1, wherein the defect level correction unit An envelope detector for detecting an envelope of the digital signal output from the analog-digital signal converter; A defect detector for determining a maximum and minimum value of the detected envelope and determining that there is a defect if the determined maximum and minimum envelope values satisfy a predetermined defect condition for a predetermined time; And And a defect level correction value calculator for outputting a correction value from the maximum and minimum envelope values determined by the defect detector and a reference level. The method of claim 2, wherein the envelope detector Maximum and minimum envelope detectors which obtain maximum and minimum envelope values of the digital signal during an envelope detection time; And And a maximum and minimum envelope average section for accumulating the detected maximum and minimum envelope values for a predetermined number of times and dividing the accumulated values by the predetermined number of times. The method of claim 3, wherein the maximum and minimum envelope detection unit A maximum envelope storage device for storing the value of the digital signal when the value is greater than a first threshold value; A minimum envelope storage unit storing a value of the digital signal when the value of the digital signal is smaller than a second threshold value smaller than the first threshold value; And And a counter for counting an input clock and resetting the maximum envelope storage and the minimum envelope storage when the envelope detection time has elapsed. 5. The method of claim 4, wherein the maximum and minimum envelope averages are A maximum envelope accumulator for accumulating the output of the maximum envelope accumulator by the number of times; A minimum envelope accumulator that accumulates the output of the minimum envelope accumulator by the number of times; And And a maximum and minimum envelope averager for averaging the outputs of the maximum and minimum envelope accumulators by the number of times, respectively. And the maximum and minimum envelope averages are shift registers which are shifted by a value input by a user and averaged by the number of times. The method of claim 2, wherein the defect detector is A first discriminating unit determining whether the maximum and minimum envelopes detected by the envelope detector satisfy a predetermined defect condition; And And a second discrimination unit for determining that the maximum and minimum envelopes are defective if the maximum and minimum envelopes satisfy the defect condition for a predetermined period of time. The method of claim 1, wherein the asymmetric waveform level correction unit A signal comparator for comparing the levels of the digital signals; An up / down counter for counting up or counting down according to the output of the signal comparator; A discriminator for outputting a reset signal to the up / down counter and outputting a correction signal if the output value of the up / down counter is outside a predetermined threshold value; And And a correction value generator for increasing and decreasing a reference level according to a correction signal output from the determination unit, and correcting the defect level and the asymmetry level in the optical disk system.