JPH1049873A - Optical disk apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical disk apparatus, which evades change in the signal level of a regenerative signal, which removes a low-frequency noise, which removes the influence of the low-frequency component of a modulation code, and which surely reproduces input data by randomizing the input data with a preset pseudorandom signal. SOLUTION: At an input-data processing circuit 21, an address detection circuit 23 generates a set pulse PR by using a regenerative address signal AND. An M-seires generation circuit 24 generates an M-series pseudorandom signal SM according to a pseudorandom signal which uses the set pulse PR as a reference. Then, an exclusive-OR (EX-OR) circuit 25 generates and outputs an exclusive-OR signal by input data DI and by the signal SM. In this manner, the input-data processing circuit 21 randomizes the input data by a preset pseudorandom signal in such a way that a DC level is not generated, and an output D11 is passed through an encoder 2 so as to output recording data D3. Thereby, the influence of the low-frequency component of a modulation code is prevented, and the input data is reproduced surely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, for example, applied to an optical disk device that modulates and records user data by RLL (Run Length Limited) modulation, and randomizes user data by a pseudo random signal in advance. This ensures that the recorded data can be reproduced.

[0002]

2. Description of the Related Art Conventionally, an optical disc apparatus is designed to improve recording density by modulating user data by an RLL (1, 7) modulation method or the like in which a modulation code has a DC component and recording the data on an optical disc. I have.

That is, as shown in FIG. 4, in this type of optical disk apparatus 1, after inputting an error correction code to user data, performing scrambling, and adding a header or the like, input data D1 to be provided for recording is generated. . In the optical disk device 1, the input data D 1 is input to the encoder 2.

[0006] As shown in FIG.
In the L (1, 7) conversion circuit 3, the input data D1
Is subjected to RLL (1, 7) modulation, followed by NRZI (Non Re
(turn-to-zero) conversion circuit 4 performs NRZI modulation.

[0005] As shown in FIG. 6 in the form of a conversion table, the RLL (1, 7) conversion circuit 3 converts the logical value of the immediately preceding channel bit consisting of the output data D2 into
The input data D1 is converted into channel bits in 2-bit units. That is, the immediately preceding channel bit is logic “0”.
And the input data D1 continues with logic “1, 1”, the RLL (1, 7) conversion circuit 3
When 1 is logic "0, 0", the channel bit of "0, 1, 0" is output (the second column from the bottom). Alternatively, when the subsequent input data D1 is other than logic “0, 0”,
The channel bit of "1, 0, 0" is output (bottom column).

The NRZI conversion circuit 4 outputs the recording data D3 whose logical level is inverted at the timing of the logical "1" with respect to the output data D2 having such a continuous channel bit. As a result, FIG.
As shown in FIG. 2, the encoder 2 is, for example, the input data D1
Is a sequence of logic "1, 1, 0, 1, 1, 0, ..." (FIG. 7A), and if the immediately preceding channel bit is logic "0", the basic cycle is At T, period 7
The recording data D3 whose logical value repeatedly switches at T and at a period of 2T is output (FIGS. 7B and 7C). In this case, in the input data D1, according to the state immediately before,
The recording data D3 whose polarity is inverted with respect to the recording data D3 shown in FIG. 7C is generated (FIG. 7D).

In the optical disk device 1, the optical pickup 5 is driven by the recording data D3 (FIG. 4) generated in this manner, whereby a pit row and the like are sequentially formed on the optical disk 7 which is driven to rotate by the spindle motor 6. To record the input data D1.

At the time of reproduction, the optical pickup 5
, A return light obtained by irradiating the optical disk 7 with a laser beam is received by a light receiving method corresponding to the optical disk 7, whereby a reproduction signal RF whose signal level changes corresponding to a pit row or the like formed on the optical disk 7. Generate

[0009] The reproduction signal detection circuit 8 outputs the reproduction signal RF.
Is input to a high-pass filter (HPF) 9 where the DC level fluctuation due to the reflectance of the optical disk 7 and the recording sensitivity and the DC level fluctuation due to residual errors in focus control and track control are removed (hereinafter, these DC levels are removed). The level fluctuation is called low-frequency noise).

An equalizer circuit (EQ) 10 receives the reproduced signal output from the high-pass filter 9, corrects the frequency characteristics and phase characteristics, and outputs the corrected signal.

The comparator 11 includes an equalizer circuit 10
Of the reproduced signal RF1 output from the multiplexing circuit is binarized by a predetermined slice level, and the resulting binarized signal S2 is output. The PLL (Phase Locked Loop) 12 is provided with an oscillation output of a built-in voltage-controlled oscillation circuit and a binary signal S2.
The reproduction clock CK is generated based on the binarized signal S2 by varying the oscillation frequency of the voltage-controlled oscillation circuit based on the result of the phase comparison with.

The decoder 13 generates reproduced data corresponding to the recording data D3 of the recording system by sequentially latching the binary signal S2 based on the reproduced clock CK. Further, the decoder 13 processes the reproduced data to decode the input data D1 of the recording system.

That is, the decoder 13 converts the reproduced data into N
After the RZI demodulation, as shown in a table format in FIG. 8, a decode bit is set by the immediately preceding two channel bits, the channel bit to be processed, and the following two next channel bits, thereby setting the input data D1. Is decrypted.

In the optical disk device 1, the decoded input data D1
Is demodulated from user data.

[0015]

When low-frequency noise is removed in the high-pass filter 9, bit errors due to low-frequency noise can be effectively avoided, but the DC level inherent in the recording data D3 is also lost. Will be.

That is, as described above with reference to FIG. 7, when the input data D1 has a predetermined fixed pattern, the recording data D3 whose logic level is switched by the periods 7T and 2T is generated. And the DC level is displaced.

In this case, as shown in FIG. 9, in the reproduction signal RF (FIG. 9B) output from the optical pickup 5, the signal level is changed corresponding to the recording data D3 (FIG. 9A). Will change. On the other hand, the reproduction signal RF1 output from the high-pass filter 9 (FIG. 9)
In (C)), since the DC level displaced toward the period 7T is lost, the entire signal level pulsates according to the frequency characteristics of the high-pass filter 9 and the DC level of the recording data D3.

As a result, in the conventional optical disk device, it is difficult to correctly reproduce the edge information of the recording data D3 in the binary signal obtained by binarizing the reproduction signal RF1. There was a problem that a bit error occurred.

The present invention has been made in view of the above points, and it is an object of the present invention to propose an optical disk apparatus capable of effectively avoiding the influence of low-frequency components in a modulation code and reliably reproducing recorded data. Is what you do.

[0020]

According to the present invention, input data is randomized and modulated in advance by a pseudo random signal.

If the input data is randomized by the pseudo-random signal, the DC component of the recording data after modulation can be reduced accordingly. Accordingly, in the reproduction signal, the change in the signal level due to the removal of the low-frequency noise can be reduced, and the edge information of the recording data can be correctly reproduced. Thereby, the error rate in the reproduction result can be improved.

[0022]

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

FIG. 1 is a block diagram showing an optical disk device according to an embodiment of the present invention. In the optical disk device 20, the input data D1 is preprocessed by the input data processing circuit 21, and then modulated by the encoder 2. Correspondingly, the output data of the decoder 13 is post-processed by the output data processing circuit 22. FIG. 1
In the configuration shown in FIG. 4, the same components as those of the optical disk device 1 described above with reference to FIG. 4 are denoted by the corresponding reference numerals, and duplicate description will be omitted.

Here, as shown in FIG. 2, in the input data processing circuit 21, the address detection circuit 23 generates a reset pulse PR from the reproduction address signal AD. Here, on the optical disk 7, an address is recorded at the head of each sector by a pre-pit.
In the optical disk device 1, at the time of recording, the light amount of the laser beam is held at the light amount at the time of reproduction, and the reproduction signal RF is signal-processed. Further, based on the reproduction address, the optical pickup 5 is driven at the timing of scanning the target sector to record the input data D1. The address detection circuit 23 outputs the reproduction address signal A
Based on D, a reset pulse PR whose signal level rises at the start of scanning of each sector is generated.

The M-sequence generation circuit 24 generates and outputs a preset M-sequence pseudo-random signal SM composed of a pseudo-random signal based on the reset pulse PR. The exclusive OR circuit (EX-OR) 25
An exclusive OR signal of the input data D1 and the pseudo random signal SM is generated and output. This allows the input data processing circuit 21 to prevent a DC level from being generated in the recording data D3 output from the subsequent encoder 2.
According to a preset M-sequence pseudo-random signal SM,
The input data D1 is randomized and output.

In the optical disk device 20, the output data D2 of the encoder 2 whose DC level is suppressed as described above is recorded on the optical disk 7. At the time of reproduction, after the reproduction signal RF is signal-processed by the reproduction signal detection circuit 8, the reproduction data is generated by the decoder 13.

As shown in FIG. 3, the reproduced data D41 is demodulated by the decoder 13, and the resulting demodulated data D42 is input to the output data processing circuit 22. In the output data processing circuit 22, the synchronization detection circuit 26 generates a reset pulse PR whose signal level rises at the timing of starting scanning of each sector from the output data of the decoder 13.

The M-sequence generation circuit 27 generates and outputs a preset M-sequence pseudo-random signal SM1 consisting of a pseudo-random signal based on the reset pulse PR. Here, the M-sequence generation circuit 27 is configured in common with the M-sequence generation circuit 24 of the recording system, and thereby outputs the same pseudo-random signal SM1 as the pseudo-random signal SM added at the time of recording.

Exclusive OR circuit (EX-OR)
28 demodulates and outputs the input data D1 of the input data processing circuit 21 by generating an exclusive OR signal of the output data D42 of the decoder 13 and the pseudo random signal SM1.

In the above configuration, the input data of the optical disk device 20 (FIG. 1) undergoes processing such as scrambling by a data processing circuit (not shown) and is input to the input data processing circuit 21 (FIG. 2). Here, the input data D1
Is an M-sequence pseudo-random signal SM output from the M-sequence generation circuit 24 and an exclusive-OR signal generated in the exclusive OR circuit 25. The resulting output data D11 is RLL in the encoder 2 that follows. After being modulated, it is NRZI-modulated and converted into recording data D3.

At this time, in the recording data D3,
By being randomized in advance by the pseudo-random signal SM, the DC level is sufficiently suppressed and generated. The recording data D3 drives the optical pickup 5 to sequentially form pits and the like on the optical disk 7 and input data D1. Is recorded.

On the other hand, at the time of reproduction, a reproduction signal RF output from the optical pickup 5 is input to the high-pass filter 9 at a signal level corresponding to the logical level of the recording data D3, where low-frequency noise is removed. . At this time, since the DC level is sufficiently suppressed in the recording data D3, a change in the signal level due to the removal of low-frequency noise is effectively avoided in the reproduction signal RF.

The reproduced signal RF1 output from the high-pass filter 9 is binarized by a comparator 11 via a subsequent equalizer circuit 10, and is converted into a binarized signal S2. In the binary signal S2, the reproduction signal RF
1, since the change in signal level is effectively avoided, the edge information of the recording data D3 is correctly reproduced, and the PL is determined with reference to the binarized signal S2.
The reproduction clock CK can be correctly generated by the L circuit 12. In the decoder 13, the binarized signal S2 is sequentially latched by the reproduction clock CK, and the reproduction data corresponding to the recording data D3 can be correctly reproduced.

The reproduced data D41 (FIG. 3) is decoded by the decoder 13, and then subjected to an exclusive OR operation in the exclusive OR circuit 28 with the M-sequence pseudo-random signal SM1 output from the M-sequence generation circuit 27. Is obtained, whereby the input data D1 is reproduced, and the input data is decoded from the reproduced data D1.

According to the above configuration, the input data D1
Is randomized by a pseudo-random signal SM, and then PL
By performing the L modulation, the DC level of the recording data D3 can be suppressed. Therefore, in the regeneration system,
Even if low-frequency noise is removed, fluctuations in the signal level of the reproduction signal can be effectively avoided, and bit errors can be reduced accordingly.

In the above-described embodiment, a case has been described in which input data is randomized in advance using an M-sequence pseudo-random signal SM. However, the present invention is not limited to this, and various pseudo-random signals are widely applied. be able to.

In the above embodiment, 1-7
Although the case where input data is modulated by RLL modulation, which is modulation, has been described, the present invention is not limited to this, and can be widely applied to the case where input data is modulated by various modulation methods.

Further, in the above-described embodiment, the case where the input data D1 is recorded / reproduced has been described. However, the present invention is not limited to this, and can be widely applied to a recording-only optical disk device, a reproduction-only optical disk device, and the like. Can be.

[0039]

According to the present invention, as described above, by pre-randomizing user data with a pseudo-random signal, it is possible to effectively avoid a change in the signal level of a reproduced signal and remove low-frequency noise. Thus, the influence of the low-frequency component of the modulation code can be effectively avoided, and the recorded data can be reliably reproduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical disk device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an input data processing circuit in the optical disk device of FIG.

FIG. 3 is a block diagram showing an output data processing circuit in the optical disk device of FIG. 1;

FIG. 4 is a block diagram showing a conventional optical disk device.

FIG. 5 is a block diagram illustrating an encoder in the optical disc device of FIG. 4;

FIG. 6 is a table for explaining the operation of a PLL (1-7) conversion circuit in the encoder of FIG. 5;

FIG. 7 is a time chart for explaining the operation of the encoder in FIG. 5;

FIG. 8 is a table provided for explaining the operation of the decoder in FIG. 5;

FIG. 9 is a signal waveform diagram for describing pulsation of a reproduction signal in the optical disc device of FIG. 4;

[Explanation of symbols]

1, 20 optical disk device, 2 encoder, 7
... Optical disk, 8... Reproduced signal detection circuit, 9... High-pass filter, 11... Comparator, 13... Decoder, 21... Input data processing circuit, 22.

Claims (2)

[Claims] 1. A random signal generation circuit for generating a pseudo-random signal, a pre-processing circuit for randomizing and outputting user data to be used for recording with the pseudo-random signal, and modulating and recording output data of the pre-processing circuit An optical disc device comprising: a modulation circuit that outputs data; and a recording system that records the recording data on an optical disc. 2. A reproduction system for detecting a reproduction signal from an optical disc and binarizing the reproduction signal to generate reproduction data; a demodulation circuit for processing the reproduction data and outputting demodulated data; An optical disc device comprising: a random signal generating circuit for generating; and a post-processing circuit for modulating the demodulated data with the pseudo-random signal to demodulate user data.