JP2001006180A - Binarization device for optical disc reproducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binarization device for optical disc reproducer in which a reproduced analog signal can be binarized accurately regardless of the signal length. SOLUTION: The binarization device for reproduced analog signal from the optical disc in an optical disc reproducer comprises means for comparing a reproduced analog signal with a reference voltage Vref to binarize the analog signal, and a control means 25 for switching the level of the reference voltage Vref in the binarizing means depending on the voltage of the reproduced analog signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binarizing apparatus for an optical disk reproducing apparatus for binarizing an analog signal reproduced from an optical disk.

[0002]

2. Description of the Related Art FIG. 9 shows an example of the configuration of an optical disk reproducing apparatus. In FIG. 9, 1 is an optical disk, 2 is a pickup, 3 is an I / V amplifier, 4 is an analog calculator, 5 is a servo control unit, 6 is an equalizer, 7 is a binarization circuit, and 8 is PL.
L and 9 are sampling circuits.

The optical disc 1 includes a read only type called a ROM and a writable type called a RAM or RW. FIG. 10A shows a state after data recording on a writable optical disk. When the write data is "1" on the optical disk, the recording film undergoes a phase change by the irradiation of the intense laser beam, and a low reflection area called a mark is formed. An area without a mark corresponding to data “0” is called a space, and is an area having a high reflectance.

At the time of data reproduction, a weak laser beam spot moves along a track, and data is read depending on the amount of reflected light. The length of the mark and the space is 1 to 3T, where T is the period of the read clock.
It is encoded so as to take nine discrete values up to 1T.

[0005] The ROM is the same except that the mark described above is a depression called a pit and writing is not possible. In the disk reproducing apparatus, a laser beam emitted from a semiconductor laser in the pickup 2 is reflected by the optical disk 1 and converted into an electric signal by a four-divided light receiving element in the pickup 2 to output four signals A to D. After the output signal passes through the I / V amplifier 3, the analog arithmetic unit 4 performs analog addition of (A + B + C + D), and outputs the result as a reproduction signal RF. Further, another two analog calculation results representing the track error signal TE and the focus error signal FE are output from the analog calculator 4 to the servo control circuit 5.

[0006] The reproduced RF signal is subjected to gain adjustment for the frequency by the equalizer 6 and then compared with a fixed reference voltage Vref by a binarization circuit 7 to be binarized. After this, P
In LL8, a synchronous clock component included in the reproduction signal is extracted. Using the falling edge of the extracted synchronous clock, binarized data is extracted from the reproduced signal binarized by the sampling circuit 9. Here, 1 is used as the binarization circuit.
Are provided, and a reference voltage V of a fixed voltage level is provided.
A method of binarizing by comparing with ref is used.

[0007]

When reproducing data from an optical disk on which information is recorded, a reproduced signal sometimes has a large amplitude fluctuation or amplitude asymmetry. Particularly, in a writable optical disk, the amplitude may fluctuate greatly due to fluctuations of various writing conditions, and the amplitude of the AC component of the reproduced signal may be close to 0 near the end of the mark.
In this case, accurate information cannot be reproduced by the conventional method of comparing with the fixed voltage level reference voltage Vref.

FIG. 10B shows a reproduction signal corresponding to the mark and space in FIG. 10A. Arrow b
1 and b2 are places where the above problem occurs. Further, as another conventional example, there is a method of controlling the slice level to an appropriate level with respect to the fluctuation of the envelope of the reproduction signal and the asymmetry. For example, Japanese Patent Application Laid-Open No. 9-274770 discloses a control method in which a middle point between an upper envelope and a lower envelope of a reproduction signal is set to a slice level of a binarization circuit, as shown in FIG. I have.

The method of setting the midpoint of the envelope at the slice level follows the lower limit of the data frequency band and fluctuations below it in principle, and cannot follow higher frequencies. However, in an optical disk capable of writing data of 4 GB or more, the mark and the short mark after the long space and the short space after the long mark, respectively, as shown by arrows b1 and b2 in FIG. The amplitude of the reproduced signal of the space becomes extremely small, becomes almost zero at the boundary between the mark and the space, and the frequency of erroneous detection increases. Since the frequency of such amplitude fluctuation corresponds to 1 / 6T, which is the upper limit of the data frequency band,
There is a problem that accurate information reproduction cannot be performed because the fluctuation cannot be followed.

At the short mark after the long space,
And one of the causes that the amplitude of the reproduction signal of the mark and the space becomes extremely small at the short space after the long mark, respectively, is that the amplitude of the long mark and the space is extremely large, so that the interference with the adjacent space or the mark is also caused. It is because it becomes big. Another possible cause is that the relationship between the size of the mark and the size of the beam spot during recording is not uniform, and a long mark tends to spread.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a binarizing device for an optical disk reproducing device capable of accurately binarizing a reproduced analog signal regardless of a signal length.

[0012]

According to a first aspect of the present invention, there is provided an apparatus for binarizing an analog signal reproduced from an optical disk of an optical disk reproducing apparatus. The apparatus includes a binarizing unit for comparing an analog signal with a reference voltage to binarize the analog signal, and a control unit for switching a voltage value of the reference voltage of the binarizing unit according to the voltage of the reproduced analog signal.

According to a second aspect of the present invention, there is provided A / D conversion means for converting the reproduced analog signal into a digital signal, and the binarization means and the control means are output from the A / D conversion means. Is processed by digital values.

According to a third aspect of the present invention, the control means increases or decreases the reference voltage of the binarization means by a predetermined value when the reproduced analog signal becomes equal to or more than a predetermined value from a reference value. In a state where the reference voltage of the binarization means has increased or decreased by a predetermined value,
When the reproduced analog signal changes below or above the original voltage value of the reference voltage, the voltage value of the reference voltage of the binarizing means is restored.

According to a fourth aspect of the present invention, there is provided a signal length determining means for determining a mark or space length of a signal output after being binarized, wherein the signal length determined by the signal length determining means is equal to or less than a predetermined length. At this time, the control means increases or decreases the reference voltage of the binarization means to a value larger than the predetermined value.

According to a fifth aspect of the present invention, the predetermined value for increasing or decreasing the reference voltage is increased each time the signal length determining means determines that the length is equal to or less than the predetermined length. In the invention according to claim 6, the predetermined value for increasing or decreasing the reference voltage is increased or decreased differently according to the mark and the space.

Further, in the invention according to claim 7, when the mark or space shorter than the minimum length defined by the encoding is detected by the signal length determination means, a correction means for correcting the mark or space to a predetermined minimum value is provided. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of an optical disk reproducing apparatus to which the first embodiment of the present invention is applied, and FIG. 2 is a configuration diagram of the first embodiment of the present invention. The first embodiment is according to claims 1 and 3.

In FIG. 1, an optical disk 1, a pickup 2, an I / V amplifier 3, an analog operation unit 4, a servo control unit 5, an equalizer 6, a PLL 8, and a sampling circuit 9 are the same as those described with reference to FIG. . The first embodiment differs from the conventional example in that a binarizing circuit 20 shown in FIG. 2 is used instead of the binarizing circuit 7 of the conventional example.

In the binarization circuit 20 shown in FIG.
24 to comparators, and 25 a control unit. The reference voltage Vref 0 of the comparator 24 is the same as the reference voltage of the binarizing circuit 7 described with reference to FIG. 9 of the related art, and is set to Vref 0 = AV. The voltage of the analog signal output from the equalizer 6 is "1" is output when the value is equal to or more than AV, and "0" is output when the value is equal to or less than AV.

The reference voltage Vref 1 of the comparator 22 is set to Vref 1 = (A + B) V, and is set to “1” when the voltage of the analog signal output from the equalizer 6 is equal to or more than (A + B) V, and A + B) Outputs “0” when V or less.

The reference voltage Vref of the comparator 23 is
2 is set to Vref 2 = (A−B) V, and is set to “1” when the voltage of the analog signal output from the equalizer 6 is equal to or more than (A−B) V, and to (A−B) V "0" is output in the following cases.

When the comparator 22 outputs "1" from the comparator 22, that is, when the voltage of the analog signal is determined to be (A + B) V or more, the controller 25
The first reference voltage Ref is set to Ref = (A + α) V, and the analog signal output from the equalizer 6 is binarized to output a binarized signal.

When the comparator 23 outputs "0", that is, when it is determined that the voltage of the analog signal is equal to or lower than (AB) V, the reference voltage Ref of the comparator 21
Is set to Ref = (A−β) V, and the analog signal output from the equalizer 6 is binarized and a binarized signal is output.

In the state where the reference voltage Ref = (A + α) V is being output to the comparator 21, when the comparator 24 outputs “0”, the control unit 25 sets the reference voltage Ref to the comparator 21 to Ref = (A + α) V. Change to AV.

The comparator 21 supplies a reference voltage Ref =
(A-β) When “1” is output from the comparator 24 while V is being output, the comparator 21
Is changed to Ref = AV. By changing the reference voltage Ref in this manner, it is possible to follow the amplitude fluctuation in the high frequency band and accurately reproduce data.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a configuration diagram of the second embodiment. The second embodiment is according to claims 4, 5 and 6. The difference between the configuration of the first embodiment described in FIG. 2 and the second embodiment is that a signal length determination unit 26 shown in FIG. 3 is added to the first embodiment.

The signal length determination section 26 receives the binary data output from the sampling circuit 9 shown in FIG.
In the first embodiment, a comparator 2 for outputting a binary output
The reference voltage Ref 1 is increased from the reference value A to A + α or A
Although it has been reduced to -β, in the second embodiment, it is set to an optimum value corresponding to the analog signal input to the binarization circuit 20.

That is, the signal length determining section 26 determines whether or not the binarized data output from the sampling circuit 9 includes a mark or space having a length of 1T or 2T.

If the signal length determination unit 26 determines that a mark having a length of 1T or 2T is included, the control unit 2
5 changes the reference voltage Ref of the comparator 21 to Ref = A + α. Even when the state of Ref = A + α is set, if the signal length determination unit determines that a mark having a length of 1T or 2T is included, the signal length is changed to Ref = A + 2α.

The signal length determination unit 26 determines whether the signal length is 1T or 2T.
If it is determined that it contains spaces of length
The controller 25 sets the reference voltage Ref of the comparator 21 to Ref =
Change to A-β. Even when the state of Ref = A-β is set, if the signal length determination unit determines that a space having a length of 1T or 2T is included, the signal length is changed to Ref = A−2β.

By doing so, the optical disk 1
The analog signal can be binarized in an optimal state even if is changed.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a block diagram of an optical disc reproducing apparatus to which the third embodiment of the present invention is applied, FIG. 5 is a block diagram of a third embodiment of the present invention, and FIG. 6 is an operation flowchart of the third embodiment. . The third invention is according to claims 2 and 3.

In FIG. 4, an optical disk 1, a pickup 2, an I / V amplifier 3, an analog operation unit 4, a servo control unit 5, an equalizer 6, a binarizing circuit 7, and a PLL 8 are as described with reference to FIG. Reference numeral 30 denotes a binarizing circuit according to the third embodiment.

As shown in FIG. 5, the binarization circuit 30 includes an A / D converter 31 for converting an analog signal output from the equalizer 6 into a digital value, and a digital comparison for comparing the converted digital value. And a control circuit 33. The A / D converter 31 performs A / D conversion in synchronization with the synchronization clock output from the PLL 8, and the control circuit 30 sends a reference voltage to the digital comparator 32 for comparison.

Next, the operation will be described with reference to FIG. In the figure, A, A + B and AB represent Vref 0, Vref 1 and Vref described in the first embodiment, respectively.
This is a digital value corresponding to 2. First, the reference value R
Set A as ef.

Next, the digital comparator 3
The digital value A + B is transmitted to the value 2 and compared with the value D converted by the A / D converter 31 to determine whether D> A + B. When D> A + B, the reference value Ref = A
Is changed to Ref = A + α and set.

Next, the control circuit 33 outputs the digital value AB.
To the digital comparator 32 to compare whether D <AB. If D <AB, the reference value Ref
= A is changed to Ref = A-β and set.

The last set reference value Ref is sent to the digital comparator 32 to compare whether D> Ref or not. If D> Ref, “0” is set, and if D <Ref, Outputs "1" as binary data. This series of operations is repeated in synchronization with the synchronization clock. Since the reference value is switched in accordance with the magnitude of the amplitude of the reproduced signal in this manner, the data can be accurately reproduced by following the amplitude fluctuation in the high frequency band.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The fourth embodiment relates to claims 4, 5 and 6. The fourth embodiment is different from the third embodiment in that the binarizing circuit 30 described with reference to FIG.
Is added.

In the signal length judging circuit 34, as described in the second embodiment, the binarized data output from the binarizing circuit 30 includes a mark or space of 1T or 2T in length. Is determined.

When the signal length determination circuit 34 determines that a mark having a length of 1T or 2T is included, the control circuit 25 sets the reference value Ref to Ref = A, as in the second embodiment.
Change to + α. Even if the state of Ref = A + α is set, if the signal length determination circuit determines that a mark having a length of 1T or 2T is included, the signal length is changed to Ref = A + 2α.

The signal length determination circuit 34 outputs 1T or 2T.
If it is determined that a space having a length of T is included, the control circuit 25 changes the reference value Ref to Ref = A-β, as in the second embodiment. Even if the state of Ref = A-β is set, if the signal length determination circuit determines that a space having a length of 1T or 2T is included, Ref = A−2.
Change to β.

Next, a fifth embodiment of the present invention will be described with reference to FIG. The fifth embodiment is according to claim 7. The fifth embodiment is configured by adding a correction circuit 35 to the binarization circuit 30 described in the third embodiment with reference to FIG.

The correction circuit 35 is a circuit which holds the latest digital value of the reproduced signal and the binarized data for four cycles or more, and corrects to 3T when detecting the 1T and 2T marks and spaces.

That is, when a mark having a length of 1T is detected, the binarized data in the cycles before and after that is corrected, and the mark is corrected to a 3T mark. In the case of a 2T mark, the digital value of the reproduced signal in the previous and subsequent cycles is compared, the smaller binary data is corrected, and the 3T mark is corrected.

When a space having a length of 1T is detected, the binarized data in the cycles before and after the space is corrected,
Correct to 3T space. In the case of a 2T space, the digital value of the reproduced signal in the previous and subsequent cycles is compared, and the larger binarized data is corrected, so as to be corrected to a 3T space.

In this way, in addition to switching the reference value according to the magnitude of the amplitude of the reproduced signal, the non-specified 1T, 2
Since T is corrected to 3T, data can be accurately reproduced.

[0049]

As described above, since the reference value for binarizing an analog signal is switched according to the value of the analog signal reproduced from the optical disk, binarization is performed accurately regardless of the signal length. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical disc reproducing apparatus to which a first embodiment of the present invention is applied.

FIG. 2 is a configuration diagram of a first embodiment of the present invention.

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical disc reproducing apparatus to which a third embodiment of the present invention is applied.

FIG. 5 is a configuration diagram of a third embodiment of the present invention.

FIG. 6 is an operation flowchart of a third embodiment of the present invention.

FIG. 7 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram of a fifth embodiment of the present invention.

FIG. 9 is a configuration diagram of a conventional optical disc reproducing apparatus.

FIG. 10 is an explanatory diagram of an analog signal for recording and reproducing an optical disk signal.

FIG. 11 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 20, 30 Binarization circuit 21 to 24 Comparator 25 Control unit 26 Signal length determination unit 31 A / D converter 32 Digital comparator 33 Control circuit 34 Signal length determination circuit 35 Correction circuit

Claims (7)

[Claims] 1. An apparatus for binarizing an analog signal reproduced from an optical disk of an optical disk reproducing apparatus, comprising: a binarizing means for binarizing the reproduced analog signal by comparing it with a reference voltage; Control means for switching the voltage value of the reference voltage of the binarization means in accordance with the voltage of the analog signal obtained. 2. An A / D conversion means for converting the reproduced analog signal into a digital signal, wherein the binarization means and the control means are processed by a digital value output from the A / D conversion means. 2. The binarizing device for an optical disc reproducing device according to claim 1, wherein 3. The control means increases or decreases the reference voltage of the binarization means by a predetermined value when the reproduced analog signal becomes equal to or more than a predetermined value from a reference value. In the state where the reference voltage of the binarizing means has increased or decreased by a predetermined value, the voltage value of the reference voltage of the binarizing means when the reproduced analog signal has changed below or above the original voltage value of the reference voltage 3. The binarizing device for an optical disk reproducing device according to claim 1, wherein 4. A signal length judging means for judging a mark or space length of a binarized signal to be output, wherein when the signal length judged by the signal length judging means is less than a predetermined length,
4. The binarization of an optical disk reproducing apparatus according to claim 1, wherein said control means increases or decreases said reference voltage of said binarization means to a value larger than said predetermined value. apparatus. 5. The optical disc reproducing apparatus according to claim 4, wherein a predetermined value for increasing or decreasing the reference voltage is increased each time the signal length determining means determines that the length is equal to or less than a predetermined length. Pricer. 6. The method according to claim 4, wherein a predetermined value for increasing or decreasing the reference voltage is increased or decreased by varying the reference value in accordance with a mark and a space.
Or a binarizing device of the optical disc reproducing device according to 5. 7. A correction means for correcting, when a mark or space shorter than a minimum length specified by encoding is detected by said signal length determination means, to a predetermined minimum value. Item 1. A binarizing device for an optical disk reproducing device according to item 1, 2, 3, 4, 5, or 6.