JP2001084711A - Optical disk reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical disk reproducing apparatus, in which the reliability of demodulated data is decided, which suppresses the error correction operation of an error correction circuit when the reliability is low and suppresses errors in decision and corrections. SOLUTION: A signal-processing circuit 5 which receives a signal to be read out from an optical disk 1, which executes a binary coding operation, which extracts a synchronizing signal and which performs demodulation by referring to an EFM table 6 is provided. A temporary storage device 7, which stores demodulated data, is provided. An error correction circuit 8, which transfers data between itself and the temporary storage device and which executes an error correction by using a CIRC, is provided. An error-correction suppressing circuit 10, which decides the reliability of demodulated data on the basis of a prescribed decision reference which transfers the decision information to the error correction circuit, when the reliability decided to be low and which suppresses the error correction operation of the error correction circuit is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus, and more particularly to a control circuit of an error correction circuit for correcting an error in demodulated data, for example, a CD (Compact Disk) ROM, DV for a computer system.
D (Digital Versatile Disc), CD-R, C
It is used for optical disk reproducing devices such as D-RW and DVD-RAM.

[0002]

2. Description of the Related Art In a CD recording / reproducing system, CIRC is used.
(Correction, Cross Interleaved Read-Solomon Code).

[0003] As is well known, the CIRC has a two-stage lead.
Solomon codes (Read-Solomon Code) C1 and C2 are combined by interleaving. The code C1 mainly has a role of correcting a random error, and the code C2 has a role of mainly correcting a burst error. Interleaving has a role of converting a burst error into a random error.

The above two-stage Reed-Solomon codes C1, C2
Has four units of error correction data, each having eight bits as one unit (symbol). The data length of code C1 is 32 bytes and the data length of code C2 is 28 bytes.

[0005] The error correction capability and error detection capability of a Reed-Solomon code are indicated by a minimum value d (minimum code distance) between two data.

On the other hand, in the CD recording / reproducing system, the shortest value (in other words, the minimum time width Tmin of the recording waveform) and the longest value (in other words, the maximum time width Tmax of the recording waveform) of the pit of the optical disk are defined. ing.

In order to stably reproduce the CIRC signal from the optical disk, EFM (Eight to Fourteen Modu
A modulation scheme called “lation” is adopted, and each symbol (8 bits) of a CIRC signal (32-byte data and parity) output in one frame time is converted into a pattern of 14 bits (actually, 256 bits). Select from the following patterns) and record.

FIG. 6 shows a conventional example of a reproduction data processing system including an error correction circuit in an optical disk reproducing apparatus.

In FIG. 6, an optical disk as a record carrier
Numeral 1 indicates that information data is digitally recorded on a track and is rotated by a spindle motor 2.

An optical pickup 3 serving as a signal extracting means for reading information data recorded on the optical disk 1 irradiates a track on the optical disk 1 with a laser beam. Thus, by detecting a change in the amount of light reflected from the track on the optical disc 1 and returning, the information data is read and output as an electric signal.

The head amplifier 4 includes an optical pickup 3
Amplification and waveform equalization of the output signal are performed to generate a focus error signal FE, a tracking error signal TE, an RF (high frequency) signal including information recorded on the optical disc 1, and the like, which are signals necessary for reproduction.

The signal processing circuit 5 receives the RF signal from the head amplifier 4 and binarizes it, extracts a bit clock,
The synchronization signal is extracted. Further, demodulation is performed with reference to the EFM table 6 and the demodulated data is stored in the temporary storage device 7. The error correction circuit 8 exchanges data with the temporary storage device 7 and performs error correction using CIRC. Thereafter, the corrected information data is read from the temporary storage device 7.

When the error of the demodulated data stored in the temporary storage device 7 exceeds the error correction capability, the conventional error correction circuit 8 performs a correction operation different from the original error correction, and performs erroneous determination and error correction. May be performed.

That is, in the Reed-Solomon code used in CDs and DVDs, the minimum distance d of the code between the two data is the limit of the error correction capability.
In C1 correction of D, d = 5. Therefore, if there is an error of three symbols in the demodulated data, the demodulated data is normally processed as being uncorrectable. When such an erroneous determination occurs, not only erroneous data cannot be corrected but also correct data may be destroyed.

In general, the result of the correction process is used as a reliability flag of the reproduced data. Therefore, if an erroneous determination occurs as described above, a problem that the reliability flag is not attached to the error data may occur. And the reliability of the reproduced data is impaired.

Further, there is a conventional method of detecting a code string that may cause an erroneous determination in the course of correction processing, and treating all suspicious code strings as errors to protect the reproduced data. Since correct data included in the suspicious code string is also treated as an error, reproduction performance (playability) deteriorates.

[0017]

As described above, the error correction circuit of the conventional optical disk reproducing apparatus performs a correction operation different from the original error correction when an error of demodulated data exceeds the error correction capability, and performs an erroneous determination. And there is a problem that erroneous correction may be performed.

When the error correction circuit of the conventional optical disk reproducing apparatus detects a code string that may cause an erroneous determination in the course of the correction processing, the error correction circuit treats all suspicious code strings as errors. ) Is deteriorated.

The present invention has been made in order to solve the above-mentioned problems. The present invention determines the reliability of demodulated data, and when the reliability is low, suppresses the error correction operation by an error correction circuit. It is an object of the present invention to provide an optical disc reproducing apparatus capable of suppressing correction.

[0020]

An optical disk reproducing apparatus according to the present invention receives a signal read from an optical disk, binarizes the signal, extracts a synchronization signal, and demodulates the signal by referring to an EFM table. A temporary storage device for storing data demodulated by the signal processing circuit; an error correction circuit for transmitting and receiving data between the temporary storage device and performing error correction using CIRC; The reliability of the data demodulated by the processing circuit is determined based on a predetermined criterion. If the reliability is determined to be low, the determination information is transferred to the error correction circuit, and the error correction operation of the error correction circuit is performed. And an error correction inhibiting circuit for inhibiting.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

<First Embodiment> FIG. 1 shows a main part of a CD reproducing apparatus as an example of an optical disk reproducing apparatus using an error correction circuit according to a first embodiment of the present invention.

In the CD reproducing apparatus shown in FIG. 1, a disc-shaped optical disc 1 as a record carrier usually has digitally recorded information data on a spiral track.
Rotated by spindle motor 2.

The optical pickup 3 incorporates a semiconductor laser, an objective lens, a photoelectric conversion element, and the like, and emits a laser beam to a track on the optical disk 1 while the optical disk 1 is rotating, and reflects the laser beam from the track to return. The information data is read by detecting a change in the amount of light coming or transmitted through the track, and is output as an electric signal.

The head amplifier 4 performs amplification and waveform equalization processing of the output signal of the optical pickup 3, and outputs a focus error signal FE, a tracking error signal TE, and information recorded on the optical disc 1, which are necessary for reproduction. And the like.

The signal processing circuit 5 receives the RF signal from the head amplifier 4, binarizes it, extracts a bit clock,
The synchronization signal is extracted, demodulated with reference to the EFM table 6, and the demodulated data is stored in the temporary storage device 7.

The error correction circuit 8 exchanges data with the temporary storage device 7 and performs error correction using CIRC. Thereafter, the corrected information data is read from the temporary storage device 7. This information data is appropriately processed to become reproduction data.

In the Reed-Solomon code used in the CIRC, the minimum distance d between codes of two data is the limit of the error correction capability.
= 5. Therefore, if there is an error of three symbols in the demodulated data, the demodulated data is normally processed as being uncorrectable. When such an erroneous determination occurs, not only erroneous data cannot be corrected but also correct data may be destroyed.

Therefore, as shown in FIG. 1, an error correction suppressing circuit 10 is provided, and whether or not the demodulated data is in its original form (reliability of the demodulated data) is determined based on a predetermined criterion. The error correction operation is suppressed by transferring the result of the determination and the determination that the reliability is low (determination information) to the error correction circuit 8. This makes it possible to suppress erroneous determination and erroneous correction by the error correction circuit 8.

Here, a plurality of embodiments will be described with respect to a criterion for judging the reliability of demodulated data in the error correction suppression circuit 10.

(1) First Embodiment (See FIG. 2) The signal processing circuit 5 detects whether or not demodulated data exists in the EFM table 6, and generates an EFM violation detection pulse when it does not exist. Use signals. That is,
This EFM violation detection pulse signal is counted by a counter 21 for detecting the number of EFM violations, and it is counted whether or not this count value is equal to or greater than a determination reference value (for example, 3) in data of a determination reference frame (for example, one frame). Value judgment circuit
Detect at 22. If this detection result is equal to or greater than the determination reference value (for example, if there is an EFM violation of three or more symbols in one frame of data), it is determined that the reliability of the data of the frame is low, and the determination information is determined. Output.

The output of the counter 21 when the count value of the counter 21 becomes, for example, 3 or more may be used as the judgment information.

The number of EFM violation symbols may be determined, for example, by at least one symbol according to a user's criterion, and the error correction suppression circuit 10 is configured to determine the number in accordance with the criterion. I just need.

The determination information transferred from the error correction suppression circuit 10 to the error correction circuit 8 can use error flag information for individual data, syndrome information for a corrected frame, and the like.

(2) Second Embodiment (See FIG. 3) It is detected whether the demodulated data does not violate the rules of the minimum time width Tmin to the maximum time width Tmax, and it is detected that the data violates. The demodulated data time width violation detection pulse signal generated in this case is used.

The demodulation data time width violation detection pulse signal may be generated by the signal processing circuit 5 or may be generated by the error correction suppression circuit 10.
In this case, the demodulated data transferred from the signal processing circuit 5 and the sampling clock are input to the AND gate, and the output is counted by a demodulated data time width detection counter. The count value determination circuit detects whether the count value is out of the determination reference range. If the count value is out of the determination reference range (the demodulated data violates the specification of the minimum time width Tmin to the maximum time width Tmax). Is detected), a demodulation data time width violation detection pulse signal is generated.

The demodulated data time width violation detection pulse signal is counted by a counter 31 for detecting the number of times of demodulated data time width violation, and this count value is detected by a count value judgment circuit 32, thereby affecting one frame which affects the demodulated data. Counts the number of symbols in the circuit and the number of symbols
If the data exceeds the error correction capability of No. 8, it is determined that the reliability of the data of the frame is low and the determination information is output.

The number of symbols violating the Tmin-Tmax rule may be determined by the manufacturer as, for example, three or more symbols in one frame of data. You may.

For CD and DVD, Tmin = 3T
(T is the length of one symbol), and Tmax = 11T. However, a DVD having a high correction capability is less likely to be erroneously corrected than a CD.

(3) Third Embodiment (See FIG. 4) The RF signal output from the head amplifier 4 is shown in FIG.
As shown in FIG. 4, a reproduction abnormality detection signal (defect period signal) as shown in FIG.

That is, as shown in FIG. 4C, the defect period signal and the synchronizing signal output from the signal processing circuit 5 are received by an error period determination circuit 41, and the error period determination circuit 41 It is determined that the reliability of the data of the frame including the generation period is low and the determination information is output.

It should be noted that the above-mentioned defect period signal is also present in a conventional reproducing apparatus, and during the generation period of this defect period signal, for example, the P signal in the signal processing circuit 5 is output.
Stop the operation of the LL frequency comparison circuit and phase comparison circuit,
It is used so that the frequency of the data sampling clock is not disturbed.

(4) Fourth Embodiment (see FIG. 5) The RF signal output from the head amplifier 4 is shown in FIG.
5B generated by the servo system of the CD reproducing apparatus during a period equal to or less than the predetermined level as shown in FIG. 5B, and a signal generated by the signal processing circuit 5 as shown in FIG. A synchronization signal as shown in (c) is used.

That is, as shown in FIG. 5D, the synchronization signal output from the signal processing circuit 5 is received by the synchronization signal interval measurement circuit 51, and the synchronization signal interval is measured. When the error period determination circuit 52 detects that the synchronization signal interval has returned to normal after the end of the defect period signal based on the measurement result of the synchronization signal interval measurement circuit 51 and the defect period signal, the error period signal From the beginning of the defect period signal until the interval between the synchronization signals returns to normal after the end of the defect period signal, it is determined that the reliability of the data of the frame is low, and the determination information is output.

In order to increase the accuracy of the determination by the error correction suppression circuit 10, at least two (preferably all) of the plurality of embodiments are implemented on the same chip and operated at the same time. If it is determined that the reliability of data is low in one embodiment, that data is adopted. In this case, each embodiment can be realized with a relatively simple and small-scale configuration.

In general, the result of the correction processing in the error correction circuit 8 is used as a reliability flag of the reproduced data. When the correction is suppressed, the effect that the reproduction performance (playability) is improved can be obtained.

[0047]

As described above, according to the error correction circuit of the optical disk reproducing apparatus of the present invention, the reliability of the demodulated data is determined, and if the reliability is low, the error correction operation is suppressed. Correction can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a part of an optical disk reproducing apparatus according to the present invention.

FIG. 2 is a circuit diagram showing a first embodiment of the error correction suppression circuit in FIG. 1;

FIG. 3 is a circuit diagram showing a second embodiment of the error correction suppression circuit in FIG. 1;

FIG. 4 is a waveform diagram and a circuit diagram showing a third embodiment of the error correction suppression circuit in FIG. 1;

FIG. 5 is a waveform diagram and a circuit diagram showing a fourth embodiment of the error correction suppression circuit in FIG. 1;

FIG. 6 is a block diagram showing a part of a conventional optical disc reproducing apparatus.

[Explanation of symbols]

 1 ... optical disk, 2 ... spindle motor, 3 ... optical pickup, 4 ... head amplifier, 5 ... signal processing circuit, 6 ... EFM table, 7 ... temporary storage device, 8 ... error correction circuit, 10 ... error correction suppression circuit.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Kunihiko Kodama Inventor 3-3-9, Shimbashi, Minato-ku, Tokyo F-term in TOSHIBA ABU E Corporation (reference) 5D044 BC02 CC04 DE68 DE81 FG10 GL02 GL10

Claims (6)

[Claims] 1. A signal processing circuit that receives a signal read from an optical disc, performs binarization and extraction of a synchronization signal, and performs demodulation with reference to an EFM table; and data demodulated by the signal processing circuit. A temporary storage device for storing data, an error correction circuit for transmitting and receiving data to and from the temporary storage device, and performing error correction using CIRC; and a method for determining the reliability of the data demodulated by the signal processing circuit. A determination based on the determination criterion, and when it is determined that the reliability is low, an error correction suppression circuit that transfers the determination information to the error correction circuit and suppresses an error correction operation of the error correction circuit. An optical disc reproducing apparatus characterized by the following. 2. A method for determining the reliability of demodulated data by the error correction suppression circuit, comprising: counting a pulse signal generated when the signal processing circuit detects that demodulated data does not exist in the EFM table; 2. The optical disc reproducing apparatus according to claim 1, wherein when there is an EFM violation with a number of symbols exceeding the error correction capability of the error correction circuit, the reliability of the data of the frame is determined to be low. 3. The determination of the reliability of demodulated data by the error correction suppression circuit measures the demodulated data time width, and determines whether the demodulated data has a minimum time width Tmin to a maximum time width Tmax.
The pulse signal generated when the violation of the above rule is violated is counted, and when the violation of the Tmin to Tmax rule of the number of symbols exceeding the error correction capability of the error correction circuit exists, the reliability of the data of the frame is reduced. 2. The optical disk reproducing apparatus according to claim 1, wherein it is determined that the temperature is low. 4. A method of determining the reliability of demodulated data by the error correction suppression circuit, comprising the steps of: outputting a defect period signal notifying a reproduction abnormality from a servo system of an optical disk reproducing device when a signal read from the optical disk is at or below a predetermined level. 2. The optical disc reproducing apparatus according to claim 1, wherein when received by the error correction suppressing circuit, the reliability of data of a frame including a generation period of the defect period signal is determined to be low. 5. A method for determining the reliability of demodulated data by said error correction suppression circuit, comprising: a period period signal for notifying a reproduction abnormality from a servo system of an optical disk reproducing device during a period when a signal read from said optical disk is at or below a predetermined level. When received by the error correction suppression circuit, the interval of the synchronization signal transferred from the signal processing circuit is measured, and from the start of the defect period signal until the interval of the synchronization signal returns to normal after the end of the defect period signal. 2. The optical disk reproducing apparatus according to claim 1, wherein the reliability of the data of the frame including the period is determined to be low. 6. The error correction suppression circuit simultaneously employs at least two of the determination criteria according to claim 2 and determines that data reliability is low based on at least one of the determination criteria. 2. The optical disk reproducing apparatus according to claim 1, wherein in such a case, the error correction operation of the error correction circuit is suppressed.