KR100272542B1 - Bit data reproduction method of digital disc - Google Patents

Abstract

PURPOSE: A method for reproducing bit data of a digital disk, is provided to reverse bits in both sides if a 3T having a biggest effect of interception between codes is detected with 1T by an error, and to reverse a wrong bit if the 3T is detected with 2T, so as to reduce error generation in digital bit data. CONSTITUTION: An RF(Radio Frequency) signal is sampled, and the present RF sample data and prior RF sample data are added, to decide and generate bit data. A reverse cycle of the generated bit data are detected. Whether the detected reverse cycle is smaller than a minimum reverse cycle corresponding to a minimum pit length of a disk is decided. If the detected reverse cycle is smaller than the minimum reverse cycle, the bit data are compensated to make the detected reverse cycle incident with the minimum reverse cycle.

Description

BIT DATA REPRODUCTION METHOD OF DIGITAL DISC}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of reproducing digital bit data from radio frequency (RF) signals read out from a digital disc, and more particularly, to a method of reproducing bit data of a digital disc which minimizes the occurrence of errors.

Digital discs, such as conventional Compact Discs (Digital Compact Discs) and Digital Versatile Discs (DVDs), convert 8-bit to 14-bit modulation (Eight-to-Eight) to the original data for servo or timing recovery. Fourteen Modulation (EMF) to record digital bit data having a value of '0' or '1' as Pits for changing the reflectance or refractive index of the light beam. That is, the digital bit data may have a logical value of '1' or '0' in order to prevent the light beam from moving off the track due to excessive DC component generation during reproduction. Case 3 to 11) is formatted so as not to be continuous beyond the range.

As a result, the RF signal picked up from the optical disc by the optical pickup should always maintain a width in a defined range, for example, 3T to 11T for CD and 3T to 14T for DVD.

In other words, in the case of CD, the length of one pit and the interval between the pit and the pit are divided into 9 steps from 3T to 11T, respectively, and the rows of the pit are arranged side by side in the circumferential direction with a track pitch of 1.6um. Is placed. Here, 'T' means the length of one clock pulse, and 3T means three clock pulses, and 11T corresponds to the length of 11 clock pulses.

At this time, the optical disc cannot be formed to have a uniform plane due to mechanical tolerances in manufacturing, but is formed to have a slightly asymmetric plane. In addition, the spot of the light beam irradiated onto the surface of the optical disk cannot always maintain a constant size and shape due to the mechanical tolerance of the optical pickup. For this reason, the width of the RF signal picked up from the optical disc by the optical pickup exceeds or falls short of the prescribed range, thereby causing an error in the digital bit data.

There is also a trend to improve the recording capacity of information by allowing the pits to be densely formed on the optical disc. Such densification of the pit causes interference between adjacent pits, thereby increasing the generation of noise components in the RF signal. Interference between these pits acts as a factor in increasing the error rate in digital bit data.

In particular, the higher the density recording on the disk, the greater the interference between the codes and 3T is most affected. The influence of the inter-symbol interference causes the size of the 3T signal to become small, leading to errors and misinterpretation as 1T or 2T.

Therefore, in order to minimize the occurrence of errors in digital bit data, a conventional bit data reproducing apparatus for adaptively interpolating an RF signal in accordance with the transmission speed of the RF signal is disclosed in Korean Patent Application No. 95-55629, filed by the present applicant. Is disclosed. According to Korean Patent Application No. 95-55629, the analog RF signal read out from the optical pickup is converted into digital RF data, and the RF data is adaptively interpolated according to the transmission speed, and then the error amount due to the asymmetry of the optical disk is corrected. The digital bit data is restored by absolute value replacement of the asymmetrically corrected RF data. That is, adaptive interpolation of RF data generates a clock signal corresponding to the transmission rate of the RF data using a digital phase locked loop (PLL) and adjusts the logic value of the RF signal for each phase value of the clock signal. Is achieved.

However, the adaptive interpolation can remove transient noise (i.e., noise component due to focus error of the light beam) by interpolating the RF data bit by bit, but can correct the distortion of the RF data due to the interference between the pit. There was no. In other words, when the width of the RF signal is less than the prescribed range, the adaptive interpolation could not correct the width of the RF data to reach the prescribed range. In addition, the asymmetry correction only removes the temporary noise component due to the tilting of the optical disk and cannot make the RF signal have a value in a prescribed range.

As a result, the conventional digital bit reproducing apparatus cannot compensate for the distortion of the RF signal due to the interference between the pit of the optical disc, and thus it is not possible to minimize the occurrence of an error in the digital bit data below a certain limit.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to invert bits on both sides when 3T having the greatest influence of inter-signal interference is detected as 1T by an error, and to detect bit when 2T is detected. By inverting the wrong bit by the bit, to provide a bit reproduction method of the digital disk to reduce the occurrence rate of the error in the digital bit data.

According to an aspect of the present invention, there is provided a method of reproducing bit data of a digital disk, the method including: reproducing an RF signal according to information pits formed on an optical disk, and after sampling the RF signal, present RF samples. Determining and generating bit data by adding data and previous RF sample data, detecting an inversion period of the generated bit data, and determining whether the inversion period detected in the step is less than 3T, the minimum inversion period. If the inversion period detected in the step is 1T, the left and right bits are inverted, and if 2T, the current RF sample data and the previous RF sample data at the left and right bit positions to be compensated are added and absolute values are taken, and then the left side is compared by two absolute values. Or compensating the bit data by inverting only the right bit.

1 is a flowchart of a method of reproducing bit data of a digital disk according to the present invention.

2 is a waveform diagram showing an example of error-produced reproduction bit data and compensated reproduction bit data applied to the present invention.

3 is a waveform diagram showing another example of error-produced reproduction bit data and compensated reproduction bit data applied to the present invention;

4 is a waveform diagram showing another example of error-produced reproduction bit data and compensated reproduction bit data applied to the present invention.

Explanation of symbols for the main parts of the drawings

101 to 107: each performing step rf0 to rf4: RF sample data

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

1 is a flowchart illustrating a reproducing method for obtaining bit data by shaping an RF signal having a sinusoidal waveform read from an optical pickup during reproduction, into a square wave having 1 or 0, in particular, abnormal bit data due to distortion of the RF waveform. It is a way to prevent the gain.

First, data read from the optical pickup during reproduction is a sinusoidal RF signal, which is sliced or sampled and shaped. In the present invention, the RF signal is sampled by a constant clock, and each sampling value is added to a sampling value before one clock, and the bit value is generated by determining that the value is '1' if it is 0 or more and '0' if it is 0 or less. Since the bit data generated in this manner is necessarily at least 3T, a signal less than 3T is compensated for and output through the reproducing step of FIG. Looking at the steps for each step for compensation, first the run-lentgh (continuous length of '1' or '0') is detected by inputting the RF signal shaped as described above (step 101).

If the detected continuous length is 1T (step 102), it is determined that the left and right bit signal is an abnormal signal, and inverts all the values of the left and right bit data of the 1T signal (step 103), and if the continuous length is 2T (step 104), the left and right bits The abnormal bit is determined (step 105), and the corresponding bit is inverted (step 106, 107). If it is not a 1T or 2T signal, it is a normal signal and outputs as it is.

Hereinafter, the bit data reproduction method of the present invention will be described in detail by taking an example of an RF waveform as shown in FIG. The input waveform from the optical pickup is sampled and has sample data such as -44, -11, 12, 23, -15, -35, -63, respectively. Each sample data is converted to bit data having the value of '1' or '0' added with the previous sample value. At the rf0 position, the bit data is '0' because -44 and -11 are less than 0. In the case of -11 and 12 plus 0 or more, bit data is' 1'.In the rf2 position, bit data is' 1 'and 12 and 23 is more than 0. Therefore, bit data is' 1' and 23 and -15 are added in rf3. Since the value is greater than or equal to 0, the bit data is determined to be '1', and at the rf4 position, the bit data is determined to be '0' since -15 and -35 are less than zero. The square wave obtained in this manner is the same as that of FIG. 2 (b). In this case, since the continuous length of '1' is 3T, the waveform is output as it is without any compensation process.

Next, the RF sample value is distorted due to defect or interference in the input RF waveform as follows. The input waveform from the optical pickup has sample data such as -44, -11, 2, 23, -15, -35, -63 after sampling as shown in FIG. Each sample data is converted to bit data having the value of '1' or '0' added to the previous sample value. At the rf0 position, the bit data is '0' because -44 and -11 are less than 0. In the rf1 position, the bit data is '0' because -11 and 2 are less than 0. In the rf2 position, the bit data is '1'. Since the sum of 15 is greater than or equal to 0, the bit data is determined to be '1', and at the rf4 position, the bit data is determined to be '0' since the sum of -15 and -35 is less than 0. The square wave obtained in this manner is the same as that of FIG. 3 (b). In this case, since the continuous length of '1' is 2T, the waveform is inverted and compensated by inverting one bit data of the left and right sides of 2T. To determine which of the bits on the left and right are wrong bits, a comparison is made to which side of the bit on the left and right sides of the 2T bit data is more likely to cause an error. Since the waveform shaping in the present invention determines whether the sum of the sampling value of the corresponding bit and the sampling value of the previous bit is equal to or greater than 0 or less, the smaller the absolute value is, the more likely the error is to occur in the bit determination. By taking advantage of this, the bit of the rf0 + rf1 value, which is a sample value for determining the left bit of the 2T signal, and the rf3 + rf4 value, which is a sample value for determining the right bit of the 2T signal, is regarded as an error and inverted. To compensate.

In the above example, since the absolute value of rf0 + rf1 for the left bit determination is 9 and the absolute value of rf3 + rf4 for the right bit determination is 50, it is determined that the left bit is distorted and the bit data '0' of the left bit is set to '1'. The inversion is compensated with 3T as shown in FIG.

Next, the RF sample value is distorted due to defect or interference in the input RF waveform as follows. The input waveform from the optical pickup has sample data such as -44, -11, 2, 13, -15, -35, -63 after sampling as shown in FIG. Each sample data is converted to bit data having the value of '1' or '0' added to the previous sample value. At the rf0 position, the bit data is '0' because -44 and -11 are less than 0. In the rf1 position, the bit data is '0' because -11 and 2 are less than 0. In the rf2 position, the bit data is '1'. Since the sum of 15 is less than 0, the bit data is determined as '0', and at the rf4 position, the bit data is determined as '0' because -15 and -35 are less than 0. The square wave obtained in this manner is the same as that of FIG. 4 (b). In this case, since the continuous length of '1' is an abnormal waveform having 1T, the left and right bit data of 1T are inverted according to the procedure of FIG. Will be compensated as follows.

As described above, according to the bit data reproduction method of the digital disk according to the present invention, an RF signal is sampled, bit data is generated by bit determination from the sampled RF data, and the continuous length of the generated bit data is detected to inter-sign. If 3T, which has the greatest influence of interference, is detected as 1T due to an error, both sides of the bit are inverted, and if 2T is detected, the current RF sample data at the left and right bit positions to be inverted and the RF sample data before the 1-bit clock are added. By taking the absolute value and converting the bit data having the smallest absolute value out of the two absolute values to 3T, noise and distortion components caused by the interference between the pits are eliminated to reduce the incidence of errors in the digital bit data. Thus, digital bit data can be accurately reproduced from the RF signal.

Claims (5)

A method for reproducing bit data from a digital disc, comprising: an optical pickup for picking up a high frequency signal according to information pits formed on the digital disc; Sampling the high frequency signal and adding current high frequency sample data and previous high frequency sample data to determine and generate bit data; Detecting an inversion period of the generated bit data; Determining whether the inversion period detected in the step is smaller than the minimum inversion period corresponding to the minimum feet length of the disc; And compensating for the bit data such that the detected inversion period is equal to the minimum inversion period if it is determined that the inversion period detected in the step is smaller than the minimum inversion period. . The method of claim 1, wherein in the determining step, the minimum inversion period is 3T. 2. The method of claim 1, wherein in the compensating step, if it is determined that the detected inversion period is 1T, bit data is compensated by inverting both left and right bits. 3. The method of claim 2, wherein if it is determined that the inversion period detected in the compensation step is 2T, only the left or right bit data is inverted by wrong bit data determination to compensate for the bit data. . The method of claim 4, wherein The wrong bit data determination and compensation of the wrong bit data, Obtaining an absolute value by adding current high frequency sample data and previous high frequency sample data at the left bit position to be compensated; Obtaining an absolute value by adding current high frequency sample data and previous high frequency sample data at the right bit position to be compensated; And comparing the magnitudes of the two absolute values obtained in the above step, and inverting the bit data of the position having a small absolute value.

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