JPH01251324A - Optical disk reproducing device - Google Patents

Abstract

PURPOSE:To improve jitter and to lower error rate by correcting the amplitude and the phase of a reproducing signal by a correcting means, equalizing a pulse width to a reference pulse width and matching the phase correctly when the pulse width is different from the reference pulse width. CONSTITUTION:A reproducing signal Sp from an optical pickup is supplied to a comparator 3, which is a component of a waveform shaping means, through an RF amplifier 1 and the series circuit of an amplitude phase correcting circuit 2 and it is turned into a pulse string signal. An output signal Scmp of the comparator 3 is supplied to a length comparator 4 which is a component of a pulse width comparing means 100 and supplied also to a reference pulse generator 5. When the pulse width of a pulse outputted by the waveform shaping means by corresponding to a bit and a land of a prescribed length is different from the reference pulse width, the amplitude and the phase of the reproducing signal are corrected by the correcting means, the pulse width is equalized to the reference pulse width and the phase is correctly matched. Thus, the jitter can be improved and the error rate can be lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a reproducing apparatus for a recordable optical disc in which digital data is recorded using pits, and more particularly to a technique for reducing jitter in a reproduced signal.

``Prior Art'' Conventionally, an optical disk on which digital data such as a digital audio signal can be optically recorded has been proposed, which can be recorded only once, and is called a RAW disk. Recording of digital data on this DRAW disk is performed by forming pits using a laser beam.

And how to play this DRAW disc? A laser beam is used in this process, and digital data is reproduced from the difference in the level of reflected light when the laser beam is irradiated onto a pit and a land that is not a pit.

``Problems to be Solved by the Invention'' Edge-recorded optical discs generally include jitter in the playback signal.

One of the major causes of this jitter is considered to be the occurrence of a time lag between the recorded signal and the reproduced signal.

In the case of a DRAW disk, a material with a certain degree of high thermal conductivity is used as the disk medium in consideration of playback deterioration, and when the disk medium is irradiated with a laser beam, thermal energy quickly diffuses.

Therefore, rotate the disc and place it on the disc medium.
When forming a PT, the amount of thermal energy transmitted by diffusion increases behind the pit PT.

Therefore, short pits PT are less likely to be formed and become even shorter and smaller.On the other hand, when forming long pits PT, thermal energy increases, so the pits PT become even longer and larger.

In this manner, each PT is shorter or longer than its respective reference length, resulting in a time lag in the reproduced signal.

FIG. 1A shows the shape of the pit PT, and the broken line and solid line in FIG. 1B show the waveforms of the reproduction signal of the short pit PT and the long pit PT, respectively.

Figures 1I and 12 show that the C
This figure shows the relationship between the PT when a D signal is recorded, the reproduced signal, and the output signal of a comparator functioning as a waveform shaping means.

FIG. 11 explains a pit PT having a length of 3T (T is a reference unit).

Figure A shows the normal size, and Figure B shows the shortened one. The solid lines and broken lines in FIG.
The output signal of the comparator when compared with th is shown.

Further, FIG. 12 explains a land LD having a length of 3T.

Figure A shows the regular size, and Figure B shows the shorter one. The solid lines and broken lines in FIG.
The output signal of the comparator when compared with th is shown.

As is clear from these Figures 11 and 12,
It can be seen that as the pits PT and runts LD become shorter, the convergence of the reproduced signal becomes smaller, and the output signal of the comparator shifts in the shorter direction in both the pits and the runts, resulting in so-called jitter.

Furthermore, although the shape of the pit PT in FIGS. 11 and 121m is symmetrical, the shape of the pit PT actually becomes larger at the rear, as shown in FIG. 10A.

Therefore, the output signal of the comparator has a backward phase shift in both the pint part and the runt part, which also causes jitter.

This jitter increases the error rate and
In the case of audio signal reproduction, this leads to deterioration of sound quality.

The present invention takes the above points into consideration and aims to improve jitter and reduce the error rate.

"Means for Solving the Problems" In order to solve the above-mentioned problems, in the present invention, a reproduced signal from a recordable optical disc in which digital data is recorded using pits is waveform-shaped by a waveform-shaping means. The optical disk reproducing apparatus is configured to extract pulses corresponding to pits and lands of a predetermined length from the output signal of a waveform shaping means, and then output the pulses to a reproduction signal processing circuit, and extracts pulses corresponding to pits and lands of a predetermined length, and calculates the pulse width and the reference pulse width. and a comparison means for comparing the waveform shaping means,
and a correction means for correcting the amplitude and phase of the reproduced signal based on the comparison error signal from the comparison means.

"Function" In the above configuration, when the pulse width of the pulse output from the waveform shaping means corresponding to pits and lands of a predetermined length differs from the reference pulse width, the amplitude and phase of the reproduced signal are corrected by the correction means. Since the pulse width is made equal to the reference pulse width and properly phased, jitter is improved, thereby reducing the error rate.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to FIG. This example is an example in which the present invention is applied to a reproducing apparatus for a DRAW disc on which a CD signal is recorded.

In the figure, a reproduced signal Sp from an optical pickup (not shown) is supplied to a comparator 3 constituting waveform shaping means via a series circuit of an RF amplifier 1 and an amplitude/phase correction circuit 2, and is converted into a pulse train signal. .

In addition to the comparator 3, other waveform shaping means include a saturation tank + IJ device, a limiter, and the like.

The output signal S cmp of this comparator 3 is the reproduction 1
A word processing circuit (not shown) is supplied.

Further, the output signal S cmp of the comparator 3 is supplied to the length comparator 4 constituting the pulse width comparison means 100 and also to the reference pulse generator 5 . Reference pulse generator 5
A reference pulse P3 that rises at the falling edge of the output signal Scmp of the comparator 3 and has a pulse width of 3T is generated and supplied to the length comparator 4. The length comparator 4 calculates the pulse width of the pulse falling at the rising edge of the reference pulse P3, that is, the output signal S cmp of the comparator 3.
If the pulse width of the pulse Pa corresponding to a pit is smaller than the pulse width of the reference pulse P3, a pulse Ps corresponding to the smaller portion is output. This pulse Ps is then supplied to the inverting input terminal of the operational amplifier 7 via the low-pass filter 6.

Further, when the pulse width of the pulse Pp is larger than the pulse width of the reference pulse P3, the length comparator 4 outputs a pulse Pb corresponding to the larger portion.

This pulse pb is then supplied to a length comparator 8. Further, the output signal S cmp of the comparator 3 is supplied to a reference pulse generator 9, and from this reference pulse generator 9,
A reference pulse P3.5 that rises at the falling edge of the output signal Scmp of the comparator 3 and has a pulse width of 3.5T is generated and supplied to the length comparator 8. Then, from the length comparator 8, when the pulse Pb from the length comparator 4 falls within the reference pulses P3 and 5 (at this time, the pulse width of the pulse pp should be 3T), it is output as is. When the pulse Pb is not within the reference pulse P3.5, the pulse width of the pulse Pp is 4T~
ll'l''), the pulse pb is regulated to fall at the falling edge of the reference pulse P3.5 and is output, and this output signal is passed through the low-pass filter 10 to the non-conductor of the operational amplifier 7. Supplied to the inverting input terminal.

In the above configuration including the reference pulse generators 5 and 9, the length comparator 4°8, the low-pass filter 6.10, and the operational amplifier 7, the amount of change in the pulse width of the pulse Pp that should be 31 is detected. be done. For example, when the length of PT (pi)PT should be 3T as shown in FIG. 3A, but is formed short as shown in FIG. The same figure C
As shown in the figure, the pulse Pp corresponding to the pit PT is compared with the comparison level Vth and has a pulse width shorter than 3T, as shown in the figure. Therefore,
The length comparator 4 obtains a pulse Ps having a pulse width corresponding to the amount of decrease in the pulse width, as shown in FIG. Here, E in the figure shows the reference pulse P3.

On the other hand, when the length of the pit PT, which should originally be 3T as shown in FIG. 4A, is formed as long as shown in FIG.
is compared with the bell vth as shown in FIG. Become something. Therefore, from the length comparator 4, as shown in FIG. Supplied.

Here, E and G in the figure indicate reference pulses P3 and P3.5, respectively. In the end, when the pulse width of the pulse Pp that should be 3T becomes shorter, the output signal Spd of the operational amplifier 7 becomes smaller according to the amount of decrease, and when it becomes longer, it becomes larger depending on the amount of increase. Become.

Note that when a pulse Pp with a pulse width of 4T to IIT is supplied, a pulse having a pulse width of 0.5T is supplied from the length comparator 8 to the non-inverting input terminal of the operational amplifier 7 via the low-pass filter 10. However, this pulse is
There is no equivalent relationship with the pulse pp whose pulse width should be 3T, resulting in an erroneous detection signal. Therefore, in such a case, for example, the length comparator 8 outputs a cancellation pulse Pe having a pulse width of 0.5T, and this pulse Pe is supplied to the inverting input terminal of the operational amplifier 7 via the low-pass filter 6. False detections are prevented.

Further, in FIG. 1, the output signal Scmp of the comparator 3 is supplied to a length comparator 14 and also to a reference pulse generator 15. The reference pulse generator 15 generates a reference pulse P3' which rises at the rising edge of the output signal S cmp of the comparator 3 and has a pulse width of 3T, and is supplied to the length comparator 14. This length comparison @14
From this, the pulse width of the pulse PQ corresponding to the land LD of the pulse rising at the rising time of the reference pulse P3', that is, the output signal S cmp of the comparator 3, is the reference pulse P.
If the pulse width is smaller than the pulse width 3', a pulse Ps' corresponding to the smaller portion is output. Then, this pulse Ps' is passed through the operational amplifier 1 through the low-pass filter 16.
7 non-inverting input terminal.

Furthermore, when the pulse width of the pulse PQ is larger than the pulse width of the reference pulse P3', the length comparator 14 outputs a pulse Pb' corresponding to the larger portion. This pulse Pb' is then supplied to a length comparator 18.

Further, the output signal S cmp of the comparator 3 is supplied to a reference pulse generator 19, and the reference pulse generator 9 outputs a pulse of 3.5T that rises at the time of the rise of the output signal S cmp of the comparator 3. Reference pulse P having a width 3.
5' is generated and provided to length comparator 18. Then, from the length comparison 318, when the pulse Pb' from the length comparator 14 falls within the reference pulse P3.5' (at this time, the pulse width of the pulse P2 should be 3T), the pulse Pb' from the length comparator 14 remains unchanged. When the pulse Pb' is not within the reference pulse P3.5', the pulse width of the pulse PQ' is 4T to IIT. H1X171 is output so as to fall at the rise of P3.5', and this output signal is supplied to the inverting input terminal of the operational amplifier 17 via the low-pass filter 2o.

The above reference pulse generators 15, 19, length comparator 14.
18, low pass filter 16.20 and operational amplifier 1
In the configuration according to No. 7, the amount of change in the pulse width of the pulse PQ that should be 3T is detected. For example, when the length of the land LD, which should be 3T as shown in FIG. 5A, is shortened as shown in FIG. 5B, the reproduced signal sp supplied to the comparator a is , as shown in figure C, the comparison level Vt,
Compared with h, the pulse P2 corresponding to the land LD has a pulse width shorter than 3T, as shown in the figure. Therefore, as shown in FIG. F, the length comparator 14 obtains a pulse Ps' having a pulse width corresponding to the amount of decrease in the pulse width, and is supplied to the operational amplifier 17 via the low-pass filter 16. Here, E in the figure shows the reference pulse P3'.

On the other hand, when the length of the land LD, which should originally be 3T as shown in FIG. 6A, is formed long as shown in FIG.
is compared with the comparison level vth as shown in FIG. Become. Therefore, from the length comparator 14, the same 11:! As shown in UP, a pulse Pb' having a pulse width corresponding to the amount of increase in pulse width is obtained, and is passed through the length comparator 18 and the low-pass filter 20 to the operational amplifier 1.
7. Here, E and G in the figure indicate reference pulses P3' and P3.5', respectively. In the end, when the pulse width of the pulse PQ that should be 3T shortens, the output signal SQd of the operational amplifier 17 increases in accordance with the amount of decrease, and when it becomes longer, it decreases in accordance with the amount of increase. Become.

Note that when the pulse P9 having a pulse width of 4T to IIT is supplied, the length comparator 18 outputs a value of 0. A pulse having a pulse width of 5T is supplied to the inverting input terminal of the operation up 17 via the low-pass filter 20, but this pulse has no equivalent relation to the pulse PQ whose pulse width should be 3T, and becomes an erroneous detection signal. Therefore, in such a case, for example, the length comparator 18 outputs a cancellation pulse Pe' having a pulse width of 0.5T, and this pulse Pe'
is supplied to the non-inverting input terminal of the operational amplifier 17 via the low-pass filter 1G, thereby preventing false detection.

Further, in FIG. 1, output signals Spd and SQd of operational amplifiers 7 and 17 are supplied to a non-inverting input terminal and an inverting input terminal of operational amplifier 21, respectively. In this case, when the pulse width of the pulse Pp and PQ that should be 3T becomes shorter, the output signal Sp9 of the operational amplifier 21 becomes smaller in accordance with the amount of decrease, and when it becomes longer in the negative direction, the output signal Sp9 becomes smaller. It becomes larger according to the amount of increase. Then, the output signal S of this operational amplifier 21
The pH is supplied to the amplitude phase correction circuit 2 via the control circuit 22 as a control signal.

20fti [The correction circuit 2 is configured to have frequency characteristics as shown in FIG. That is, the output signal S
The smaller py is, the more the high-frequency component of the reproduced signal Sp is emphasized, and the WR width of the reproduced signal sp in the pit PT and land LD portion, which is about 6T to 3T in length, becomes larger, for example. Moreover, this amplitude phase correction circuit 2
The configuration is such that the smaller the output signal SpQ, the more delayed the phase of the high frequency component of the reproduced signal Sp.

FIG. 2 shows an example of this tti@ correction circuit 2. In FIG.

In the figure, an input terminal 2 to which a reproduced signal St+ is supplied.
11 is an output terminal 21 via a voltage controlled resistor 212.
Connected to 3. Further, a capacitor 214 is connected in parallel with the voltage controlled resistor 212, and a capacitor 214 is connected in parallel with the voltage controlled resistor 212.
The connection point between 2 and output terminal 213 is voltage controlled resistor 2
It is grounded via 15. Then, the output signal Spy of the operational amplifier 21 is supplied as a control signal to the voltage-controlled resistors 212 and 215 from the terminal 216, and the output signal Sp
As R becomes smaller, the amount of emphasis on the high-frequency components of the reproduced signal sp increases, and the phase thereof is delayed.

This example is configured as described above, and the output of the operational amplifier 21 (
The word SpR has a pulse width of 3T among the pulses pp and pΩ.
When the pulse width of what is supposed to be becomes shorter, it becomes smaller according to the amount of decrease, and the amplitude and phase correction circuit 2 increases the strength of the high frequency component of the reproduced signal sp. The I amount is increased, for example, the amplitude of the reproduced signal Sp in the pitch 1-PT and land portions having a length of about 6T to 3T is increased, and the phase of the high frequency component of the reproduced signal Sp is delayed. It will be done like this. As a result, the pulse width is 3 among the pulses Pp and PQ.
The pulse width of what should be T is controlled to be correctly 37, and the phases are also controlled to match correctly.

On the other hand, when the pulse width of one of the pulses Pp and PQ that should be 3T becomes longer, the pulse width is controlled to be correctly 37 by the operation opposite to the above, and the phases are matched correctly. controlled by.

In this way, according to this example, the pulse width of the pulse Pp1 corresponding to the pit PT and the pulse pH corresponding to the land LD which should be 3T is controlled to be 37, and the phases match correctly. Since the signal is controlled in this manner, jitter is improved and the error rate can be significantly reduced.

Note that FIGS. 8 and 9 show the distribution of pulse widths of pulses pp and PQ in the conventional example and in this example, and in the case of this example, a sufficient improvement effect was obtained. It will be done.

[Effects of the Invention] According to the present invention described above, when the pulse width of the pulse outputted from the waveform shaping means in response to pits and lands of a predetermined length differs from the reference pulse width, the correction means corrects the reproduced signal. The one-line width and phase are corrected to ensure that the pulse width is equal to the reference pulse width and the phases are correctly matched, improving jitter and significantly reducing error rates. .

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing one embodiment of the present invention, Figures 2 to 9
The figure is a diagram for explaining the same, and FIGS. 10 to 12 are diagrams for explaining a conventional example. 2... Amplitude phase correction circuit 3... Comparator 100... Pulse width comparison means Patent applicant Iwa Co., Ltd. Figure 2 H3T6A mouth) PT B mouth) PT C (Sp) -- -2F=Vth/1'tL2 PP/l tY'tLλ%1%/)
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Claims (1)

[Claims] (1) An optical disc playback device in which a playback signal from a recordable optical disc on which digital data is recorded using pits is waveform-shaped by a waveform shaping means and then supplied to a playback signal processing circuit. , a comparison means for extracting pulses corresponding to pits and lands of a predetermined length from the output signal of the waveform shaping means and comparing the pulse width with a reference pulse width; An optical disc reproducing apparatus comprising: a correction means for correcting the amplitude and phase of the reproduction signal based on a comparison error signal from the comparison means.