JP2000173059A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to detect a header region with high accuracy. SOLUTION: An optical head 23 reads the data from an optical disk 21 having a header region for the recording address data and a data region for recording the user data. In the optical head 23, a laser beam reflected by the optical disk 21 is received by a plurality of separated light receiving regions in a photoelectric covering part. The sub signal comprising by level adding each signal obtained from the plurality of light receiving regions is compared with the reference level obtained by dividing the peak level of the sum signal at a prescribed ratio. Thereby, the header region is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an improvement in an optical disk device that writes and reads data to and from an optical disk such as a RAM (Random Access Memory).

[0002]

2. Description of the Related Art As is well known, a wobble land-groove system is adopted as a physical format of a DVD-RAM. In the wobble land-groove method, as shown in FIGS. 5 and 6, when viewed from the side irradiated with the laser beam, a convex groove track 101 and a concave land track 102 recorded on the optical disk surface are provided. Each is a method of recording marks.

[0003] The groove track 101 and the land track 102 are data areas in which user data is recorded. Each of the groove tracks 101 and the land track 102 has a small undulation called a wobble 103 at a predetermined frequency. The optical disk device is capable of performing a rough read channel PLL pull-in based on a frequency signal obtained by detecting the wobble 103.

The groove track 101 and the land track 102 are divided into units called sectors 104, and a header area 105 is provided at the head of each sector 104. In the header area 105, address information is recorded at the time of manufacturing in the form of a pit string. For this reason, in the wobble land / groove method, an address can be detected by reading a pit string in the header area 105.

[0005] In this header area 105, the pit row is divided into two in the track direction, and each pit row is
CAPA (Complementary Allocated Pit Address)
In other words, the tracks 101 and 102 are arranged so as to be alternately offset in the radial direction of the optical disk at intervals of half the track width (pitch).

FIG. 7 shows an optical disk apparatus for reproducing this type of optical disk. That is, the optical disk 11
Is read by the optical head 13 while being rotated by the spindle motor 12. First, in the optical head 13, the laser light generated from the laser diode 13a is
3b and the optical disk 11 through the objective lens 13c.
Is irradiated on the data recording surface of the.

[0007] The laser beam reflected from the optical disk 11 travels backward through the objective lens 13c, is reflected at a substantially right angle by the beam splitter 13b, is received by the optical detector 13d, and is photoelectrically converted. This light detector 13d is
The light receiving area is divided into two in the track row on the optical disk 11 so as to correspond to the radial direction and the tangential direction, respectively, to be divided into a total of four light receiving areas.

Each electrical signal obtained from the four light receiving areas of the photodetector 13d is I / V (current / current).
The voltage is supplied to the push-pull signal generation circuit 15 and the adder 16 via the conversion amplifiers 14a to 14d.

Here, in the optical disk apparatus, of the outputs from the four light receiving areas of the optical detector 13d, the output sums from two light receiving areas corresponding to the inside and the outside in the radial direction with respect to the track row of the optical disk 11 respectively. The address data is reproduced based on the push-pull signal obtained by taking the difference between the two, and the user data is reproduced using the sum signal obtained by fully adding the outputs of all the light receiving areas of the photodetector 13d.

As described above, in the optical disk device, different processing is performed in the header area 105 and the data area (tracks 101 and 102), so that it is important to accurately discriminate each area. Conventional discriminating means includes a header region 10
5 has been detected. That is, outputs from the four light receiving areas of the photodetector 13d are output from the I / V conversion amplifiers 14a to 14a.
After passing through 4d, it is supplied to the push-pull signal generation circuit 15 to generate the above-described push-pull signal.

When the push-pull signal is normally reproduced, as shown in FIG. 8A, the push-pull signal has a higher absolute value level on the positive side and on the negative side in the header area 105. Therefore, the level comparators 17a and 17b compare the level of the push-pull signal with the reference level L1 on the positive side and the reference level L2 on the negative side, respectively, as shown in FIGS. 8B and 8C. A header detection signal is obtained, where the detection of the header area 105 is performed.

The outputs from the four light receiving areas of the photodetector 13d are output from I / V conversion amplifiers 14a to 14d.
, And is subjected to waveform equalization processing by an equalizer circuit 18, converted into digital data clock-normalized by a data strobe circuit 19, and supplied to a data processor circuit 20.

In this data processor circuit 20, ID extraction, frame slipping processing, error correction processing, and the like are performed on the input digital data, and user data is reproduced here. Further, the data processor circuit 20 generates a timing necessary for various data processing and a data reproduction clock based on the header detection signals obtained from the level comparators 17a and 17b.

However, in the conventional header detecting means as described above, since the header is detected based on the push-pull signal, the detection accuracy greatly depends on the quality of the push-pull signal. The quality of the push-pull signal depends on whether the optical transmission characteristic of the optical head 13 is good or not, and whether there is a skew between the vertical axis of the optical disk 11 and the irradiation optical axis (this depends on the assembly accuracy at the time of manufacturing the apparatus). The optical disk 11 easily deteriorates due to various factors such as scratches, dirt, deformation and the like.

For this reason, for example, as shown in FIG. 9A, when the quality of the positive-side push-pull signal is degraded due to some factor and a sufficient amplitude exceeding the reference level L1 cannot be obtained. As shown in FIG. 3B, an erroneous header detection signal is generated, and the header area 10
5 cannot be accurately distinguished from the data areas (tracks 101 and 102).

[0016]

As described above, the conventional header detecting means uses a push-pull signal whose quality is easily deteriorated due to various factors, so that the reliability of header detection is low. Have a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an extremely good optical disk device capable of detecting a header area with high accuracy.

[0018]

According to an optical disc apparatus of the present invention, an optical disc having at least a header area in which address data is recorded and a data area in which user data is recorded by using an optical head. It is intended for reproducing data. Then, a detection means is provided for detecting the header area based on the difference in the amount of reflected light between the header area and the data area, which is determined from the output of the optical head.

According to the above configuration, the header area is detected based on the difference in the amount of reflected light between the header area and the data area, which is determined from the output of the optical head. This makes it possible to detect the header area with higher accuracy as compared with the method using.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. In FIG. 1, an optical disk 21 is driven to rotate by a spindle motor 22, and its recording data is read by an optical head 23. In the optical head 23, the laser light generated from the laser diode is transmitted to the optical disk 2 via the objective lens.
Irradiation is performed on the data recording surface of No. 1.

Then, the laser light reflected from the optical disk 21 travels backward through the objective lens and is received by the optical detector and is photoelectrically converted. This light detector has its light receiving area divided into two with respect to the track row on the optical disk 21 in the radial direction and the tangential direction, respectively, to be divided into a total of four light receiving areas.

The electric signals obtained from the four light receiving areas of the optical detector of the optical head 23 are amplified by a preamplifier circuit 24 and then supplied to a focus / tracking error detection circuit 25, where the focus error signal is output. And a tracking error signal. Then, based on the focus error signal and the tracking error signal, the focus / tracking control circuit 2
6 generates a drive signal for focus control and tracking control of the optical head 23 with respect to the objective lens, and outputs the drive signal to the optical head 23.

On the other hand, the preamplifier circuit 24 amplifies the electrical signals obtained from the four light receiving areas of the optical detector of the optical head 23, generates a sum signal obtained by level addition, and generates a sum signal. And to the level comparison circuit 28.

This sum signal is, as shown in FIG.
Header area 105 and data area (tracks 101 and 10)
Due to the difference in light reflectivity from 2), the level obtained in the header area 105 is higher in absolute value than the level obtained in the data area. This difference in level is hardly affected by the quality of the optical transmission characteristics of the optical head 23, skew, scratches, dirt, deformation, and the like of the optical disk 21.

Therefore, in the level comparison circuit 28,
The input sum signal and a reference level L3, which is higher than the peak level of the sum signal obtained in the data area and lower than the peak level of the sum signal obtained in the header area 105, output from the attenuator 29 described later. 2B, a header detection signal can be generated as shown in FIG. 2B.

The sum signal is transmitted to the optical disk 11 having a poor optical transmission characteristic of the optical head 23 and a skew.
Even if distortion occurs due to various factors such as scratches, dirt, deformation, etc., as shown in FIG. 3 (a), the level is sufficiently higher than the reference level L3. ), An accurate header detection signal can be obtained.

Also, even when the tracking servo is off, the level of the sum signal does not change, so that the header area 105 can be accurately detected, for example, even during a search.

Here, the peak level detection circuit 27
Detects the peak level of the input sum signal, and outputs the detected peak level to the attenuator 29. The attenuator 29 divides the input peak level based on a preset ratio, and is used for level comparison with the sum signal obtained in the header area 105 as shown in FIG. The reference level L3 is generated and output to the level comparison circuit 28. Therefore, a header detection signal as shown in FIG. 4B is obtained from the level comparison circuit 28.

As described above, the reference level L3 for comparing the level with the sum signal for detecting the header is generated based on the peak level of the sum signal.
Optimum reference level L3 according to data read from 1
Can be generated in real time. However, whether the reference level L3 is variable or fixed can be appropriately selected as needed.

It should be noted that the present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the spirit and scope of the present invention.

[0031]

As described in detail above, according to the present invention,
It is possible to provide an extremely good optical disk device capable of detecting the header area with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart for explaining a header detection operation in the embodiment.

FIG. 3 is a waveform chart for explaining a header detection operation when distortion occurs in the sum signal in the embodiment.

FIG. 4 is a waveform chart for explaining a reference level generation operation in the embodiment.

FIG. 5 is a view for explaining a physical format of an optical disk of a wobble land-groove system.

FIG. 6 is a view for explaining the configuration of a header area in the physical format of the wobble / land-groove optical disk.

FIG. 7 is a block diagram for explaining a header detecting means in a conventional optical disk device.

FIG. 8 is a waveform chart for explaining an operation of detecting a header in the conventional optical disk device.

FIG. 9 is a waveform chart for explaining a problem of header detection in the conventional optical disk device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Optical disk, 12 ... Spindle motor, 13 ... Optical head, 14a-14d ... I / V conversion amplifier, 15 ... Push-pull signal generation circuit, 16 ... Adder, 17a, 17b ... Level comparator, 18 ... Equalizer circuit, 19: data strobe circuit, 20: data processor circuit, 21: optical disk, 22: spindle motor, 23: optical head, 24: preamplifier circuit, 25: focus / tracking error detection circuit, 26: focus / tracking control circuit, 27: peak level detection circuit, 28: level comparison circuit, 29: attenuator.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yo Yoshioka 3-3-9, Shimbashi, Minato-ku, Tokyo Toshiba Abu E Co., Ltd. (72) Inventor Tatsuharu Ashiya 70 Yanagicho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Address F-term in Toshiba Yanagimachi Plant (reference) 5D090 AA01 BB04 CC04 CC16 CC18 DD03 DD05 EE13 EE18 FF25 GG28 HH01

Claims (5)

[Claims] 1. An optical disc device for reproducing at least data from an optical disc having a header area in which address data is recorded and a data area in which user data is recorded by using an optical head, comprising: An optical disc device comprising: a detecting unit that detects the header area based on a difference in the amount of reflected light between the header area and the data area, which is determined from an output. 2. The detection section detects the header area based on a difference between an output signal level of the optical head obtained in the header area and an output signal level of the optical head obtained in the data area. 2. The optical disk device according to claim 1, wherein: 3. An optical head comprising: a laser emitting unit; an objective lens for irradiating a laser beam generated by the laser emitting unit onto a signal recording surface of the optical disk; and a laser receiving a laser beam reflected by the optical disk. Photoelectric conversion means having a plurality of light receiving areas divided into a plurality of light receiving areas, wherein the detecting means is a header area of a sum signal obtained by level-adding signals obtained from the plurality of light receiving areas of the photoelectric conversion means. 3. The optical disk device according to claim 2, wherein the header area is detected based on a difference between a level in the data area and a level in the data area. 4. The level of the sum signal obtained in the header area is set to be higher in absolute value than the level of the sum signal obtained in the data area. Detecting the header region by comparing the level with a reference level set higher than the peak level of the sum signal obtained in the region and lower than the peak level of the sum signal obtained in the header region. 4. The optical disk device according to claim 3, wherein: 5. The detector according to claim 1, wherein the detector is configured to detect a peak level of the sum signal, and to divide the peak level detected by the peak level detector at a predetermined ratio to thereby reduce the reference level. 5. The optical disk device according to claim 4, further comprising an attenuator for generating.