JP4076646B2 - Optical disk device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in an optical disk apparatus for writing and reading data on, for example, an optical disk such as a DVD-RAM (Random Access Memory).
[0002]
[Prior art]
As is well known, the wobble land groove method is adopted as the physical format of the DVD-RAM. As shown in FIGS. 5 and 6, the wobble / land / groove method includes a convex groove track 101 and a concave land track 102 recorded on the optical disc surface as viewed from the side irradiated with the laser beam. Each is a method of recording a mark.
[0003]
The groove track 101 and the land track 102 are data areas in which user data is recorded, and a small undulation called a wobble 103 is formed at a predetermined frequency. In the optical disk apparatus, it is possible to perform rough read channel PLL pull-in based on the frequency signal obtained by detecting the wobble 103.
[0004]
Further, the groove track 101 and the land track 102 are each divided by a unit called a sector 104, and a header area 105 is provided at the head of each sector 104. In the header area 105, address information is recorded in the form of pit rows at the time of manufacture. Therefore, in the wobble / land groove method, the address can be detected by reading the pit string in the header area 105.
[0005]
In this header area 105, the pit rows are divided into two in the track direction, and each pit row is in a form called CAPA (Complementary Allocated Pit Address), that is, for each of the tracks 101 and 102, respectively. They are arranged so that they are alternately offset in the radial direction at intervals of half the track width (pitch).
[0006]
FIG. 7 shows an optical disc apparatus for reproducing this type of optical disc. That is, the recording data of 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 beam generated from the laser diode 13a goes straight through the beam splitter 13b and is irradiated onto the data recording surface of the optical disc 11 through the objective lens 13c.
[0007]
Then, the laser light 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 subjected to photoelectric conversion. The light detector 13d is divided into two light receiving areas, corresponding to the radial direction and the tangential direction, with respect to the track row on the optical disc 11, for a total of four light receiving areas.
[0008]
The electrical signals obtained from the four light receiving regions of the photodetector 13d are supplied to the push-pull signal generation circuit 15 and the adder 16 via I / V (current / voltage) conversion amplifiers 14a to 14d, respectively. .
[0009]
Here, in the optical disk device, the difference between the total output from the two light receiving areas corresponding to the inner side and the outer side in the radial direction with respect to the track row of the optical disk 11 among the outputs from the four light receiving areas of the optical detector 13d. The address data is reproduced based on the push-pull signal taken, 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.
[0010]
As described above, in the optical disk apparatus, since different processing is performed in the header area 105 and the data area (tracks 101 and 102), it is important to accurately distinguish each area. The conventional discriminating means detects the header area 105. That is, the outputs from the four light receiving regions of the photodetector 13d are supplied to the push-pull signal generation circuit 15 after passing through the I / V conversion amplifiers 14a to 14d, and the above-described push-pull signal is generated.
[0011]
This push-pull signal is a signal having a high absolute value level on the positive side and the negative side in the header area 105 as shown in FIG. Therefore, the level comparators 17a and 17b compare the push-pull signal with the positive reference level L1 and the negative reference level L2, respectively, as shown in FIGS. 8B and 8C. A header detection signal is obtained, and the header area 105 is detected here.
[0012]
The outputs from the four light receiving regions of the optical detector 13d are fully added by the adder 16 via the I / V conversion amplifiers 14a to 14d, and then subjected to waveform equalization processing by the equalizer circuit 18 to obtain a data strobe circuit. In 19, the data is converted into clock-normalized digital data and supplied to the data processor circuit 20.
[0013]
In the 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.
[0014]
However, since the conventional header detection means as described above performs header detection 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 is determined by whether the optical transmission characteristics of the optical head 13 are good or not, and the presence of a deviation (skew) between the vertical axis of the optical disk 11 and the irradiation optical axis (this also depends on the assembly accuracy when the apparatus is created) The optical disk 11 easily deteriorates due to various factors such as scratches, dirt, and deformation.
[0015]
For this reason, for example, as shown in FIG. 9A, when the quality of the positive-side push-pull signal deteriorates due to some factor and a sufficient amplitude exceeding the reference level L1 cannot be obtained, As shown in (b), an erroneous header detection signal is generated, which causes a problem that the header area 105 and the data areas (tracks 101 and 102) cannot be accurately distinguished.
[0016]
[Problems to be solved by the invention]
As described above, the conventional header detection means uses a push-pull signal whose quality easily deteriorates due to various factors, and thus has a problem that reliability of header detection is low.
[0017]
Accordingly, the present invention has been made in consideration of the above circumstances, and an object thereof is to provide an extremely good optical disc apparatus capable of detecting a header area with high accuracy.
[0018]
[Means for Solving the Problems]
In the optical disk apparatus according to the present invention, a data area composed of a groove track and a land track on which user data is recorded, and the groove track and the land track are divided in units of sectors, and are arranged at the head of each sector. And address data recorded by pit rows that are divided into two in the direction of the groove track and the land track and are alternately offset in the radial direction of the optical disc at intervals of half the track pitch. For an optical disc having a header area,
A laser light emitting means; an objective lens that irradiates the signal recording surface of the optical disk with laser light generated by the laser light emitting means; and a light receiving area for receiving the laser light reflected by the optical disk , wherein the groove In an optical disc apparatus that reproduces at least data using an optical head including a photoelectric conversion means having four light receiving areas each divided into a radial direction and a tangential direction with respect to the track and the land track ,
The four light receiving regions of the sum signal signal obtained by level adding respectively obtained, and the level in the header area according to the difference in the reflected light amount in the said header region data region of the photoelectric conversion means for the optical head has Detection means for detecting the header area based on a difference from the level in the data area is provided.
[0019]
According to the above configuration, based on the difference between the level in the header area and the level in the data area of the sum signal obtained by adding the levels of the signals obtained from the plurality of light receiving areas of the photoelectric conversion means of the optical head. Thus, since the header area is detected, the header area can be detected with higher accuracy than the conventional means using a push-pull signal.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, an optical disk 21 is rotationally driven by a spindle motor 22 and its recorded data is read by an optical head 23. The optical head 23 irradiates the laser beam generated from the laser diode onto the data recording surface of the optical disc 21 through the objective lens.
[0021]
Then, the laser light reflected from the optical disc 21 is received by the optical detector by going back through the objective lens and is photoelectrically converted. This light detector is divided into two light receiving areas, which are divided into two so that the light receiving area corresponds to the radial direction and the tangential direction with respect to the track row on the optical disc 21, respectively.
[0022]
The electrical signals respectively obtained from the four light receiving regions of the optical detector of the optical head 23 are amplified by the preamplifier circuit 24, and then supplied to the focus / tracking error detection circuit 25, where the focus error signal and tracking error are detected. It is used for signal generation. Then, based on the focus error signal and the tracking error signal, the focus / tracking control circuit 26 generates a drive signal for focus control and tracking control for the objective lens of the optical head 23 and outputs it to the optical head 23. Yes.
[0023]
On the other hand, the preamplifier circuit 24 amplifies electrical signals respectively obtained from the four light receiving areas of the optical detector of the optical head 23 and then generates a sum signal obtained by level addition. Each is output to the circuit 28.
[0024]
As shown in FIG. 2A, the level of the sum signal obtained in the header area 105 is higher in the data area due to the difference in the light reflectance between the header area 105 and the data area (tracks 101 and 102). It is higher in absolute value than the level obtained. This difference in level is less susceptible to the effects of optical transmission characteristics of the optical head 23, skew, scratches, dirt, deformation, etc. of the optical disk 21.
[0025]
Therefore, in the level comparison circuit 28, the peak of the sum signal obtained in the header area 105 is higher than the peak level of the sum signal inputted and the sum signal obtained from the attenuator 29 described later and obtained in the data area. By comparing the level with a reference level L3 set lower than the level, a header detection signal can be generated as shown in FIG.
[0026]
The sum signal is shown in FIG. 3A even when distortion occurs due to various factors such as the optical transmission characteristics of the optical head 23 being poor, the presence of skew, and scratches, dirt, and deformation of the optical disk 11. As described above, since the level sufficiently exceeds the reference level L3, an accurate header detection signal can be obtained as shown in FIG.
[0027]
Further, 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 even during a search, for example.
[0028]
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. A 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.
[0029]
Thus, by generating the reference level L3 for level comparison with the sum signal for header detection based on the peak level of the sum signal, the optimum reference level L3 corresponding to the data actually read from the optical disc 21 is obtained. Can be generated in real time. However, whether the reference level L3 is variable or fixed can be selected as appropriate.
[0030]
The present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the scope of the invention.
[0031]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide an extremely good optical disc apparatus that can detect the header area with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram for explaining an embodiment of an optical disc apparatus according to the present invention.
FIG. 2 is a waveform diagram shown for explaining a header detection operation in the embodiment;
FIG. 3 is a waveform diagram for explaining a header detection operation when distortion occurs in the sum signal in the embodiment;
FIG. 4 is a waveform diagram shown for explaining a reference level generation operation in the embodiment;
FIG. 5 is a view for explaining the physical format of an optical disk of the 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 type optical disc.
FIG. 7 is a block diagram showing a header detecting means in a conventional optical disc apparatus.
FIG. 8 is a waveform diagram for explaining the header detection operation in the conventional optical disc apparatus.
FIG. 9 is a waveform diagram for explaining a problem of header detection in the conventional optical disc apparatus.
[Explanation of symbols]
11 ... Optical disc,
12 ... Spindle motor,
13: Optical head,
14a-14d ... I / V conversion amplifier,
15 ... push-pull signal generation circuit,
16 ... adder,
17a, 17b ... level comparators,
18 ... Equalizer circuit,
19: Data strobe circuit,
20: Data processor circuit,
21 ... Optical disc,
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.

Claims (3)

A data area composed of a groove track and a land track on which user data is recorded, and the groove track and the land track are divided in units of sectors and are arranged at the head of each sector, and the groove track and the land track For an optical disc having a header area containing address data recorded by pit rows which are divided into two with respect to the track direction and are alternately offset in the radial direction of the optical disc at intervals of half the track pitch And
A laser light emitting means; an objective lens that irradiates the signal recording surface of the optical disk with laser light generated by the laser light emitting means; and a light receiving area for receiving the laser light reflected by the optical disk , wherein the groove In an optical disc apparatus that reproduces at least data using an optical head including a photoelectric conversion means having four light receiving areas each divided into a radial direction and a tangential direction with respect to the track and the land track ,
The four light receiving regions of the sum signal signal obtained by level adding respectively obtained, and the level in the header area according to the difference in the reflected light amount in the said header region data region of the photoelectric conversion means for the optical head has An optical disc apparatus comprising: a detecting means for detecting the header area based on a difference from a level in a data area. The level of the sum signal obtained in the header area is set higher in absolute value than the level of the sum signal obtained in the data area,
The detection means compares the level of the sum signal with a reference level set 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. The optical disk apparatus according to claim 1, wherein the header area is detected by doing so.   The detection means includes a peak level detection means for detecting a peak level of the sum signal, and an attenuator for generating the reference level by dividing the peak level detected by the peak level detection means at a predetermined ratio. The optical disk apparatus according to claim 2, wherein the optical disk apparatus is provided.

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