KR100218018B1 - Optical disc reproducing apparatus - Google Patents

Abstract

end. The technical field to which the invention described in the claims belongs

The present invention relates to an optical disc reproducing apparatus.

I. The technical problem that the invention is trying to solve

The present invention improves the error correction apparatus of the optical disc reproducing apparatus which reduces the error in decoding by removing the code that does not satisfy the condition (d, k) caused by the error.

All. Summary of Solution of the Invention

According to an aspect of the present invention, there is provided an optical disc reproducing apparatus which amplifies and equalizes a reproduced signal, and then outputs the decoded signal to the outside as an audio and video signal through a decoder that decodes a signal detected by a detector into an original signal. An input terminal is connected to an output terminal of the detector, and an output terminal is connected to an input terminal of the decoder, and the error correction unit reduces error in the decoding by eliminating a part that does not satisfy a predetermined condition caused by an error.

la. Important uses of the invention

The present invention is used for an optical disc reproducing apparatus.

Description

Optical Disc Player

1 is a block diagram of an optical disc reproducing apparatus.

2 is a block diagram of an error correction apparatus according to the present invention.

3 is a detailed block diagram of an isolation pulse removing device according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reproducing an optical disc, and more particularly, to an error correction apparatus for an optical disc for correcting an error in a signal read from an optical disc system requiring high-density recording.

In general, in order to record a digital signal to a storage device such as a hard disc or an optical disc, there is a modulation method (Run Length Limited: RLL) according to the characteristics of each recording medium. In the RLL modulation, an m-bit source signal is input to output an n-bit channel signal. Therefore, the code rate R is defined as m / n. In the RLL modulation, modulation is performed so as to satisfy the d condition and the k condition, where d and k are the minimum numbers between two consecutive ones. Thus, the RLL modulation scheme can be characterized as (d, k, m, n). The d condition is a factor in determining the size of the minimum recording pit in the optical recording device, and a factor in determining the recording frequency in terms of the signal spectrum. The k condition is a factor that determines the characteristics of a phase locked loop (hereinafter referred to as a PLL) that generates a change in the DC component of the signal system and a clock used to recover data. In general, the larger the d condition, the lower the efficiency of the code and the smaller the detection window width. However, the recording density ratio is increased because the amount of information stored per minimum recording unit increases. The smaller the k condition, the lower the efficiency of the code. However, it is relatively easy to implement a PLL and has a characteristic of less DC variation. RLL modulation codes that are currently widely used commercially are (1, 7, 3) code with (d, k, m, n) of (1, 7, 3, 2), (2, 7, 1, 2) 7) codes, (2, 10, 8, 17) EFM (Eight to Fourteen Modulation) codes. EFM Plus, where (d, k, m, n) is the modulation code (d, k, m, n) for (2, 10, 8, 16) for digital video disc systems (hereinafter referred to as DVDP) that requires high density recording. (Plus) The modulation code is limited by Sony Corporation in Japan, and Matsushita uses an 8-16 modulation code with (d, k, m, n) of (2, 12, 8, 15), which has a higher recording density. It was suggested by the company. However, these codes also become a problem that detection errors occurring at the receiving side due to an increase in recording density are inevitable. In particular, errors caused by noise such as impulsive noise are mostly caused by inter-symbol interference. Inter-symbol interference increases as the recording density increases because of an increase in user density. User identity is generally defined as the number of symbols included in the full width at half maximum of a laser beam in an optical disc system. Among the errors caused by the intersymbol interference, the fact that the probability of error caused by the minimum mark length according to the d condition is the largest is known. The jitter analysis results of the jitter analyzer are most widely distributed at the minimum mark length. You can tell from the facts.

Accordingly, an object of the present invention is to provide an error correction apparatus that reduces an error in decoding by removing a code that does not satisfy the (d, k) condition caused by an error.

Another object of the present invention is to provide an error correction apparatus for limiting the condition (d, k) to (2, 10), which is a condition of an EFM modulation code which is currently commercially available and widely used.

It is still another object of the present invention to provide an error correction apparatus which is sure to be adopted even in the DVDP system, which is a high density optical disk system among the (d, k) conditions.

According to the technical idea of the present invention for achieving the above objects, the audio and video signals are decoded through an decoder that amplifies and equalizes a reproduction signal and then decodes the signal detected by the detector into an original signal. In the optical disc reproducing apparatus for outputting externally, the input terminal is connected to the output terminal of the detector and the output terminal is connected to the input terminal of the decoder to reduce the error during decoding by eliminating a code that does not satisfy a predetermined condition caused by an error. It is characterized by having an error correction means.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings.

It should be noted that like elements and parts in the figures represent the same numerals wherever possible.

Looking at the contents of the present invention, the error can occur in the code that satisfies (2, 10) can be divided into two cases as follows. First, the code does not satisfy the condition (2, 10). Codes that do not satisfy the condition (2, 10) fall under the condition that d is less than 2 or k is greater than 10. In other words, it corresponds to the following code:

Where X means any value. The following is a case where an error occurs while satisfying the condition (2, 10). In such a case, it is difficult to correct an error and cannot be determined as an error in terms of a decoder. Such an error is corrected by an error correction code (ECC) unit at the rear of the decoder of the optical disc system, but will not be dealt with in the present invention. Therefore, the error to be corrected in the present invention corresponds to the former error. The following describes the former error correction method described above. First is the removal of the isolation pulse. This case corresponds to equation (1) via d = 0. The generation of the isolation pulse is most often caused by impulsive noise resulting from damage to the disk. Therefore, these isolated pulses simply need to be eliminated. Of course, this isolated pulse may occur even if a pulse with a short time interval is located in the middle of a pulse with a long time interval, but the experimental result is that the probability is much smaller than that of an impulsive noise. The following are the results before and after correction for the isolated pulse error.

Before correction after correction

XXXXX00011000XXXXX XXXXX00000000XXXXX

The following describes the correction of errors where d is one. When d is 1 in a signal passing through a detector, a pulse having a short time interval may be located between pulses having a long time interval in encoding. In a code that satisfies the condition (2, 10), a signal having 3T having a minimum mark length is located between signals having 7T or more. The run-length is calculated based on the bit having d equal to 1, and the larger run-length is corrected. The following is an example of correction.

Before correction after correction

XXX1000000010100001XXX XXX1000000100100001XXX

XXX1000101000000001XXX XXX1000100100000001XXX

In the above example, the former is the case where the run-length of the previous bit is greater than the run-length of the subsequent bit, starting from the bit with d equal to 1, and the latter is the opposite. Detailed description of the apparatus for performing the above-described error correction function is as follows.

1 is a block diagram of an optical disc reproducing apparatus. Referring to FIG. 1, in general, an input terminal is connected to a disk 5, the disk 5, the playback player PD 15 for starting playback, and an output terminal of the playback player PD 15. A reproduction amplifier 35 for amplifying and outputting a reproduction signal, an input terminal connected to an output terminal of the reproduction amplifier 35, an equalizer 45 for equalizing the amplified signal, and an output terminal of the equalizer 45 A detector 55 for detecting and outputting an equalized signal connected to an input terminal thereof, a phase synchronization loop 65 interconnecting the detector 55 to generate a frequency according to a phase, and a detector 55 An error correction device 75 for correcting an error of data by connecting an input terminal to an output terminal, and a decoder 85 for restoring an output signal back to an original signal by connecting an input terminal to an output terminal of the error correction device 75. And input to an output terminal of the decoder 85. An error correction code section 95 for connecting an end thereof to an error correction code of the decoded decoded signal, and an input terminal connected to an output end of the error correction code section 95, for decoding audio and video signals. It consists of a video decoder 105.

The error correcting device proposed in the present invention is located between the detector and the decoder of FIG. 1 to reduce an error in decoding. 2 is a block diagram of an error correction apparatus according to the present invention. Referring to FIG. 2, the error correction apparatus first receives the output of the detector 55 and removes an isolation pulse having d equal to zero. A detailed block diagram of the isolation pulse eliminator is shown in FIG. The isolated pulse-controlled signal is stored in parallel in a 23-bit buffer. Each 9 bit is allocated to the buffer before or after the 5 bits to be corrected because the maximum run-length of the EFM code is 9. The error correcting apparatus checks whether d in the 5 bits to be corrected is 1 and corrects the method described above when d is 1. In FIG. 2, the first run-length calculator 20 is a block for obtaining a run-length starting from the eighth bit of the buffer, and the second run-length calculator 30 starts from the fourteenth bit of the buffer. To calculate the run-length. The comparator 40 outputs 1 when the run-length obtained by the first run-length calculator 20 is greater than or equal to the run-length obtained by the second run-length calculator 30. When d is 1 and the output of the comparator 40 is 1, the ninth and tenth bits of the buffer are inverted by the correction circuit 100. By using the error correction device, it is possible to reduce the detection error by correcting the error caused by the inter-symbol interference caused by the removal of the isolation pulse due to the impulsive noise and the increase in the recording density.

Although the present invention described above is limited to, for example, the drawings, the same will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the present invention.

Claims (4)

An optical disc reproducing apparatus, comprising: a detector for detecting a reproducing signal read and amplified and equalized from the optical disc, and a preset minimum number of recorded feet among run-length limited (RLL) modulation codes of the reproducing signal detected from the detector; And an error correction device for correcting and outputting an error code of the code so as to fall within a fraudulent reference range for a modulation code exceeding a range, and a decoder for decoding a reproduction signal that is code-corrected and input from the error correction device. An optical disc reproducing apparatus. 2. The error correcting apparatus according to claim 1, wherein the error correcting apparatus comprises: an isolated pulse removing unit for removing an isolated pulse from a run-length limited modulation code of the optical disc reproduction signal detected by the detector, and the run output from the isolated pulse removing unit. A first run-length calculation for calculating a run-length of a buffer storing a length-limited modulation code in units of bits and a predetermined length of a set of the run-length limited modulation codes stored in the buffer; And a second run-length calculator for calculating run-lengths of the lower bits included in a predetermined length of the run-length limited modulation codes stored in the buffer, and the first run-length calculator and the first run-length calculator. A comparator for comparing the run-lengths calculated and output from the 2-run-length calculator and outputting a predetermined value, and receiving a residual bit located between the upper and lower bits And a code correction unit for correcting and outputting an error code generated in the remaining bits according to the output signal of the comparator. 3. The method of claim 2, wherein the run-length limited modulation code has a minimum number of write feet of two, a maximum number of write feet of ten, and a maximum run length of nine bits. F. Optical disc playback device characterized in that the (EFM) modulation code. 4. An optical disc reproducing apparatus as set forth in claim 3, wherein said isolated pulse is a code sound of said minimum recording feet number of said run-length limited modulation codes being zero.