JPH07176051A - Optical disk and optical disk reproducing device reproducing the same - Google Patents

Abstract

PURPOSE:To provide an optical disk and optical disk reproducing device capable of well extracting data by partial response (1, 0, -1). CONSTITUTION:The optical disk 2 is formed by magneto-optical recording recording data or recording the recording data with pits. The recording data converted to an interleaved NRZI series in such a manner that the shortest recording length attains approximately lambda/4NA are recorded on the optical disk 2. The output signals of first and second photodetecting sections divided in the diametral direction of the spot of the reflected light corresponding to the tangential direction of the optical disk are subtracted (amplifiers 10, 11) at the time of reproduction. The transmission characteristics to the reproduced signals outputted from a changeover switch 14 are approximated to sine characteristics without depending on reproducing speeds. The data extraction by the partial response (1, 0, -l) is well executed by cL uaca extracting means consisting of comparators 15, 16 and an OR circuit 17. The shortest recording length is short and the recording density is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc and an optical disc reproducing apparatus for reproducing the same.

[0002]

2. Description of the Related Art There is an increasing number of methods for applying a partial response to data detection in response to high-density recording of data. Partial response positively uses intersymbol interference, and has the advantage of being able to detect data with sufficient phase margin even when recording at high density.

By the way, the applicant of the present invention has previously used a photodetector having two photodetection portions divided in the radial direction of a spot of reflected light corresponding to the tangential direction of the optical disc in an optical disc reproducing apparatus. It has been proposed that a reproduction data is obtained by processing the subtraction output of the output signals of these two photo-detecting sections (see Japanese Patent Application No. 5-140477).

[0004]

In such an optical disc reproducing apparatus, an MTF (Modulation Transfer Functio) is used.
n) Since the characteristics are close to the sine characteristics, it is possible to adopt partial response class 4, that is, partial response (1, 0, -1), for extracting data.

The present invention provides an optical disc and an optical disc reproducing apparatus capable of favorably extracting data by a partial response (1, 0, -1).

[0006]

The optical disc according to the invention of claim 1 is the shortest when the numerical aperture of the objective lens at the time of reproduction is NA and the wavelength of the light irradiated through the objective lens at the time of reproduction is λ. The recording data is converted into the interleaved NRZI sequence so that the recording length becomes approximately λ / 4NA.

According to a second aspect of the present invention, there is provided an optical disc reproducing apparatus for reproducing the disc according to the first aspect, in which reflected light from the optical disc is incident and reflected in the tangential direction of the optical disc. A photodetector having first and second photodetector portions divided in a radial direction of a light spot, and a first photodetector of the photodetector.
And a subtracting means for subtracting the output signal of the second photodetector, and a data extracting means for extracting the data from the output signal of the subtracting means by the partial response (1, 0, -1). .

[0008]

According to the first aspect of the present invention, the subtraction signal of the output signals of the first and second photo-detecting units divided in the radial direction of the spot of the reflected light corresponding to the tangential direction of the optical disc during reproduction is a reproduction signal. , The transmission line characteristic for the reproduced signal is sine regardless of the reproducing speed.
It is close to the characteristic, and it becomes possible to favorably extract data by the partial response (1, 0, -1). Further, the shortest recording length is approximately λ / 4NA, which can be shortened as compared with the conventional optical disc, and the recording density can be improved.

According to the second aspect of the present invention, the transmission line characteristic for the reproduction signal from the optical disk is close to the sine characteristic regardless of the reproduction speed, and the data extraction by the partial response (1, 0, -1) is good. It becomes possible to do it. Also, an equalizer or the like is not used to match the transmission line characteristic with the sine characteristic,
It is possible to avoid troublesome operations such as switching the characteristics of the equalizer according to the reproduction speed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a recording / reproducing apparatus for an optical disc. In the figure, 1 is a spindle motor, and the optical disk 2 is rotationally driven by the motor 1.

Recording data from a host computer (not shown) is stored in the controller 3 and the data buffer 4.
And is supplied to the encoder 5 via an encoder to perform encoding processing (addition of error correction code, modulation, etc.). The output data (modulation data) of the encoder 5 is supplied to the precoder 6, and in order to avoid the propagation of a code error at the time of identification, an intermediate sequence,
That is, it is converted into interleaved NRZI series data.

The recording data output from the precoder 6 is supplied to the drive circuit 7 of the magnetic head 8 for generating an external magnetic field. When the optical disk 2 is a magneto-optical disk, the magnetic head 8 generates a magnetic field according to the recording data, and the recording data is magneto-optically recorded in the data area of the optical disk 2 in cooperation with the laser light from the optical head 9. Will be recorded.

Here, the period T of the recording clock CKw supplied to the controller 3, the encoder 5, the precoder 6, etc. is set so as to satisfy the equation (1). In the equation (1), NA is the numerical aperture of the objective lens, λ is the wavelength of the laser beam, and v is the linear velocity of the optical disc 2. in this case,
Recording is performed so that the shortest recording length is λ / 4NA.

[0014]

[Equation 1]

FIG. 2 shows an example of the structure of the optical head 9. Reference numeral 101 denotes a semiconductor laser, and this semiconductor laser 1
The laser light from 01 collimator lens 102, beam cross-section shaping lens 103, polarization beam splitter 104,
The recording surface of the optical disc 2 is irradiated with light via the mirror 105 and the objective lens 106.

When the optical disc 2 is one in which recorded data is magneto-optically recorded (hereinafter referred to as "MO disc"), the reflected light from the optical disc 2 has its polarization plane rotated according to the recorded data. The optical disk 2 has recorded data recorded in pits (hereinafter referred to as "RO
In the case of “M disc”), the amount of reflected light from the optical disc 2 changes depending on the presence or absence of pits. If the optical disc 2 is a ROM disc, the same recording data as in the case of the MO disc described above,
It is preliminarily recorded so that the shortest recording length (shortest pit length) is λ / 4NA.

The reflected light from the optical disk 2 is the objective lens 106, the mirror 105 and the polarization beam splitter 10.
The light beam is incident on the polarization beam splitter 107 via No. 4.
Then, the light transmitted through the polarization beam splitter 107 is incident on the photodetector 110 via the condenser lens 108 and the cylindrical lens 109. This photo detector 110
The focus error signal and the tracking error signal are formed using the output signal of

The light reflected by the polarization beam splitter 8 has its polarization plane rotated by 45 ° by the ½ wavelength plate 111, and then enters the polarization beam splitter 113 via the condenser lens 112. This polarization beam splitter 11
The light passing through 3 (p-polarized light) is incident on the 2-split photodetector 114, and the light reflected by the polarization beam splitter 113 (s-polarized) is incident on the 2-split photodetector 115.

First and second photodetector sections 1 of photodetector 114
14a and 114b and the first and second photodetectors 115a and 115b of the photodetector 115, as shown in FIG. 3, the diameter of the spot SP of incident light (reflected light) corresponding to the tangential direction of the optical disc 2. Are arranged in the direction. Then, the photodetectors 114a, 11a of the photodetector 114
4b outputs the output signals Spa and Spb, and the photodetectors 115a and 115b of the photodetector 115 output the output signals Ssa and Ssb.

Returning to FIG. 1, the output signals Spa and Spb of the photodetectors 114a and 114b of the photodetector 114 are output by the amplifier 10.
And is subtracted. Photodetector 1 of photodetector 115
The output signals Ssa and Ssb of 15a and 115b are supplied to the amplifier 11 and subtracted. The output signals of the amplifiers 10 and 11 are supplied to the amplifier 12 and subtracted. The subtraction signal (hereinafter referred to as “MO signal”) output from the amplifier 12 is supplied to the fixed terminal on the m side of the changeover switch 14.

Further, the output signals of the amplifiers 10 and 11 are supplied to the amplifier 13 and added. The addition signal (hereinafter referred to as “RF signal”) output from the amplifier 13 is supplied to the fixed terminal on the r side of the changeover switch 14. The changeover switch 14 has a control means (not shown), but the optical disk 2 has M
When it is an O disk, it is connected to the m side and the MO signal is selected, while when the magneto-optical disk 2 is a ROM disk, it is connected to the r side and the RF signal is selected.

Output signal (reproduction signal) of the changeover switch 14
So is supplied to the positive terminal of the comparator 15 and the negative terminal of the comparator 16. The slice level SL1 is supplied to the negative side terminal of the comparator 15, and the slice level SL2 is supplied to the positive side terminal of the comparator 16. FIG. 4 shows the eye pattern of the output signal So of the changeover switch 14 and the slice level S.
The relationship between L1 and SL2 is shown. The comparator 15 outputs a high level “1” signal when So ≧ SL1 and a low level “0” signal when So <SL1. The comparator 16 outputs a high level “1” signal when So ≦ SL2 and a low level “0” signal when So> SL2. Comparator 15,1
The output signal of 6 is supplied to the OR circuit 17.

Here, the partial response (1, 0, -1) is generated by the comparators 15 and 16 and the OR circuit 17.
A data extracting means for extracting the data is configured. Extracted data output from the OR circuit 17,
That is, the reproduction data is supplied to the decoder 18. The reproduced data output from the OR circuit 17 is supplied to the clock reproducing circuit 19 having a PLL structure. Then, the reproduction clock CKr synchronized with each bit of the reproduction data reproduced by the clock reproduction circuit 19 is supplied to the decoder 18.

In the decoder 18, the reproduction data output from the OR circuit 17 is subjected to decoding processing such as demodulation and error correction. Then, the reproduction data output from the decoder 18 is supplied to the host computer via the controller 3 and the buffer memory 4.

The curve a in FIG. 5 shows the MTF characteristic of the output signal So of the changeover switch 14, which is close to the sine characteristic. Since the recording data is recorded on the optical disc 2 so that the shortest recording length is λ / 4NA as described above, the frequency characteristic frequency corresponding to the spatial frequency 2NA / λ of the MTF characteristic is that of the optical disc 2. It is always 1 / 2T (T is a bit period) regardless of the reproduction speed (rotation speed). The curve b in FIG.
It is the MTF characteristic of the output signal So when the addition processing is performed in.

6A shows the waveform response characteristic Gs corresponding to the sine characteristic, and FIG. 6B shows the waveform response characteristic Gm corresponding to the MTF characteristic of the curve a in FIG. Then, FIG. 6C shows the waveform response characteristics Gs and Gm in comparison. As is clear from FIG. 6C, the transmission line characteristic in this example is similar to the sine characteristic, and similar to the case of the sine characteristic, code interference occurs from the pulse waveform immediately before 2T.

Therefore, in this example, the data of the reproduced data is extracted by the data extracting means (in this example, the comparators 15 and 16 and the OR circuit 17) for extracting the data by the partial response (1, 0, -1). It can be extracted well.

Further, in this example, since the recording data is recorded on the optical disc 2 so that the shortest recording length is λ / 4NA, the sine characteristic is always approximated, and the reproduction speed (rotation speed) is Even if it changes, the transmission path characteristic for the reproduction signal does not change, and the reproduction data can be satisfactorily extracted by the data extraction means for extracting the data by the partial response (1, 0, -1). In this case, the transmission line characteristic is s
An equalizer or the like is not used to match the ine characteristic, and there is no troublesome operation such as switching the characteristic of the equalizer according to the reproduction speed.

Further, according to this example, the shortest recording length of the optical disc 2 is λ / 4NA, for example, λ = 0.78 μm, N
When A = 0.55, the shortest recording length is about 0.35 μm
Becomes When the conventional partial response method is not adopted, the shortest recording length is about 0.6 μm. Therefore, according to this example, the recording density of the optical disc 2 can be improved by about 40%.

Although the shortest recording length of the optical disc 2 is set to λ / 4NA in the above embodiment, the same operational effect can be obtained even when the shortest recording length is near λ / 4NA. It's clear.

[0031]

According to the first aspect of the present invention, the subtraction signal of the output signals of the first and second photodetection units divided in the radial direction of the spot of the reflected light corresponding to the tangential direction of the optical disc during reproduction. When is used as the playback signal,
The transmission line characteristic for the reproduction signal is si regardless of the reproduction speed.
It becomes close to the ne characteristic, and the data extraction by the partial response (1, 0, -1) can be satisfactorily performed. Further, the shortest recording length is λ / 4NA, which can be shortened as compared with the conventional optical disc, and the recording density can be improved.

According to the second aspect of the invention, the transmission line characteristic for the reproduction signal from the optical disk is s regardless of the reproduction speed.
It becomes close to the ine characteristic, and the data extraction by the partial response (1, 0, -1) can be satisfactorily performed. Further, an equalizer or the like is not used to match the transmission line characteristic with the sine characteristic, and the troublesome operation of switching the characteristic of the equalizer according to the reproduction speed can be avoided.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a configuration of an optical head.

FIG. 3 is a diagram showing a configuration of a two-divided detector.

FIG. 4 is a diagram showing a relationship between an eye pattern and a slice level in a data extracting unit.

FIG. 5 is a diagram for explaining an MTF characteristic of a reproduced signal according to the embodiment.

FIG. 6 is a diagram showing waveform response characteristics of a transmission line.

[Explanation of symbols]

 1 Spindle Motor 2 Optical Disc 3 Controller 4 Data Buffer 5 Encoder 6 Precoder 7 Drive Circuit 8 Magnetic Head 9 Optical Head 10-13 Amplifier 14 Changeover Switch 15, 16 Comparator 17 OR Circuit 18 Decoder 19 Clock Recovery Circuit

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[Procedure amendment]

[Submission date] December 27, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

When the optical disc 2 is one in which recorded data is magneto-optically recorded (hereinafter referred to as "MO disc"), the reflected light from the optical disc 2 has its polarization plane rotated according to the recorded data. The optical disk 2 has recorded data recorded in pits (hereinafter referred to as "RO
In the case of “M disc”), the amount of reflected light from the optical disc 2 changes depending on the presence or absence of pits. When the optical disc 2 is a ROM disc, it is assumed that the same recording data as that of the MO disc described above is recorded in advance so that the shortest recording length (shortest pit length) is λ / 4NA. .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

The light reflected by the polarization beam splitter 107 has its polarization plane rotated by 45 ° by the ½ wavelength plate 111, and then enters the polarization beam splitter 113 via the condenser lens 112. The light (p-polarized light) transmitted through the polarization beam splitter 113 is divided into two photodetectors 114.
The light (s-polarized light) that is incident on and is reflected by the polarization beam splitter 113 is incident on the two-split photodetector 115.

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (2)

[Claims] 1. Interleaving so that the minimum recording length is approximately λ / 4 NA when the numerical aperture of the objective lens during reproduction is NA and the wavelength of the light irradiated through the objective lens during reproduction is λ. An optical disc on which recording data converted into a de-NRZI series is recorded. 2. The optical disc reproducing apparatus for reproducing the optical disc according to claim 1, wherein the reflected light from the optical disc is incident and is split in the radial direction of the spot of the reflected light corresponding to the tangential direction of the optical disc. A photodetector having first and second photodetector sections, subtracting means for subtracting the output signals of the first and second photodetector sections of the photodetector, and an output signal of the subtracting means An optical disk reproducing apparatus, comprising: a data extracting means for extracting data according to a partial response (1, 0, -1).