JPH1139677A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate both from each other even when a land width is nearly equal to a groove width by discrimitaning the land or the groove based on a tracking error signal and a difference signal from a light receiving means and performing tracking control. SOLUTION: An edge pulse signal EP is obtained by an edge detection circuit 12, and a SUBID is latched at the rise of the EP by a flip-flop 14, and an on track signal LG is obtained. A controller 13 imparts an instruction to a tracking control circuit 11 so as to close a tracking control loop at the rise of the LG when the tracking control is applied on the land. After a tracking error signal TES is amplified by a power amplifier 18 based on this instruction, it is fed back to a tracking actuator 19, and the tracking error control is applied on the land. Further, when the tracking control is applied on the groove, the controller 13 imparts the instruction so as to close the tracking control at the fail of the LG, and similarly, the tracking control is applied on the groove.

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, and more particularly to an optical disk device that uses an optical disk having the same land and groove width and records or reproduces data on both the land and the groove.

[0002]

2. Description of the Related Art In recent years, as various types of information such as image information and audio information have been digitized, the amount of digital information has increased dramatically. Accordingly, there has been a strong demand for information storage devices to have a large capacity and a high density. Until now, in an optical disc device, a linear recording density in a direction along a track has been increased and a track pitch has been increased. By responding to the demands for higher density, the size has been reduced.

However, in order to obtain an appropriate tracking control signal, the track pitch cannot be reduced excessively, and there is a limit to narrowing the track pitch. Therefore, an apparatus that records and reproduces information only on either a land or a groove has been proposed, but an apparatus that records and reproduces information on both a land and a groove has been proposed. Recording information on both lands and grooves in this way is called land / groove recording.

[0004] In an optical disk device, there is a problem of stabilization of pull-in of tracking control. When the tracking control is performed, it is preferable to close the tracking control loop when the light spot is near the center of the land or groove where the tracking control is to be performed.
That is, it is preferable to close the tracking control loop near the center of the land when performing tracking control on the land, and to close the tracking control loop near the center of the groove when performing tracking control on the groove. Conversely, if the tracking control loop is closed on the groove when the tracking control is to be performed on the land, the tracking control cannot be performed because the polarity of the tracking control signal is reversed. Therefore, it is necessary to determine whether the land or the groove.

Next, the operation of a conventional apparatus for generating an on-track signal for detecting the timing of crossing the center of a land or groove at the same time as discriminating the land or groove will be described with reference to FIGS. In FIG.
FIG. 10 is a block diagram of a control signal detection system of a conventional optical disk device, and FIG. 10 shows signals generated in various parts of the device of FIG. The reflected light 40 ′ from a disc (not shown) is received by the four-divided photodetector 1. The four outputs A, B, C, and D of the quadrant photodetector 1 are added to adders 2, 3, 4,
The focus error signal (FE) is calculated in accordance with the following equation by an error generation circuit composed of 5, 5 and subtracters 6 and 8.
S), a tracking error signal (TES), and a reflected light amount signal (TOTAL) are generated. FES = (A + D)-(B + C) TES = (A + C)-(B + D) TOTAL = A + B + C + D Here, a case is shown in which the astigmatism method is used for FES detection and the push-pull method is used for TES detection. The detected FES is guided to a focus control circuit 15, amplified by a power amplifier 16, and drives a focus actuator 17.

[0006] TOTAL is a binarization circuit 9 and TES is 2
The binarization is performed by the binarization circuit 10 to obtain TOTALD and TESD. Further, an edge pulse EP is obtained by an edge detection circuit 12 that generates a pulse at the rising edge and the falling edge of TESD. By latching TOTALD at the rising edge of EP by the flip-flop 14, an on-track signal LG is obtained.

Here, a light spot is formed based on the reproduced signal,
A method of determining that the center of the land or the center of the groove is crossed will be described with reference to FIG. FIG.
Shows the relationship between the position of the light spot on the disk and the reproduction signal when the groove width is larger than the land width. TE
S is 0 at each center point on the land (point L in the figure) and at each center point on the groove (point G in the figure). Further, TOTAL corresponding to the amount of reflected light from the disk becomes minimum at the center point of the land and becomes maximum at the center point of the groove. TO
The magnitude relationship of TAL differs depending on the magnitude relationship between the land width and the groove width. In this case, when there is a light spot on the land, the effect of light diffraction is the largest, and therefore, the decrease in the amount of reflected light is the largest. ing.

Next, when the signal obtained from the disk shown in FIG. 11 is made to correspond to the signal shown in FIG. 10, TOTALD
Becomes high level at the groove (point G) and low level at the land (point L) in FIG. Therefore, LG is inverted from a high level to a low level at a land center point, and is inverted from a low level to a high level at a groove center point. That is,
By detecting the rising time of LG, it is detected that the light spot passes through the center point of the groove, and conversely, L
By detecting the falling time point of G, it is detected that the light spot passes through the land center point.

Accordingly, in the apparatus shown in FIG.
3 applies LG when tracking control is performed on the land.
Is given to the tracking control circuit 11 so as to close the tracking control loop at the fall of. Based on this instruction, the tracking error signal TES is output to the power amplifier 1.
8, after the amplification, the tracking actuator 1
9 and the tracking is applied on the land. When tracking control is performed on the groove, if an instruction is given to close the tracking control loop at the rise of LG, tracking can be performed on the groove similarly.

[0010]

By the way, in the land / groove recording disk described above, the land width and the groove width are made substantially equal in order to make the width of the recording information bit the same in the land and the groove. ing. FIG. 12 shows the relationship between the position of the light spot on the disk and the reproduced signal in this case. In TES, a signal similar to that in FIG. 11 is obtained, but TOTAL has a twice cycle as in FIG. That is, the maximum value is always shown at each center point on the land (point L in FIG. 12) and at each center point on the groove (point G in FIG. 12). Therefore, at the point where TES becomes 0, TOT
AL always takes the maximum value. This is because, unlike the case of FIG. 11, the land width and the groove width are equal to the width P, so that the influence of light diffraction is substantially equal on the land and on the groove.

FIG. 13 shows such a disk.
10 shows a state of a signal when an on-track signal LG is to be obtained by the device of FIG. 9. Since a signal similar to that shown in FIG. 11 is obtained from the TES, the binary signal TES detected from the TES is obtained.
The edge pulse EP detected from the edges of D and TESD is a signal similar to that of FIG.

On the other hand, TOTAL is twice as long as that of FIG. 11, and at the point where TES becomes 0, TOTAL always has the maximum value. Therefore, TOTALD is, as shown in FIG. No matter where the light spot is located, the level becomes high. For this reason, in the conventional device, LG is always at the high level, and it is not possible to detect the on-track timing in a disc that performs land / groove recording.

As described above, when recording or reproducing data on or from a disk in which the width of the land is substantially equal to the width of the groove, the land and the groove cannot be discriminated in the prior art, and the tracking control cannot be stably performed. There was a problem.

An object of the present invention is to solve such a problem and to provide an optical disk apparatus capable of discriminating between lands and grooves even when the land width and the groove width are substantially equal.

[0015]

An optical disk device according to claim 1 is an optical disk device for recording or reproducing information on or from an optical disk in which lands and grooves have substantially the same width. An irradiating means for irradiating the optical disc with a sub-spot at a position radially separated from the optical disk by half of the width, and a light receiving area divided into two by reflecting the reflected light from the sub-spot in the radial direction. A first light receiving means, a second light receiving means for receiving reflected light from the main spot, a differential detecting means for detecting a difference signal from the first light receiving means, and a tracking error from the second light receiving means. Detecting means for detecting a signal; and performing tracking control by determining whether a land or a groove based on the tracking error signal and the difference signal. Characterized in that it comprises a control means.

According to a second aspect of the present invention, there is provided an optical disk apparatus for recording or reproducing information on or from an optical disk in which a land and a groove have substantially the same width.
Irradiating means for irradiating the optical disk with a main spot and a first sub-spot and a second sub-spot at symmetrical positions spaced radially from the main spot, and a first sub-spot A light receiving area divided into two in accordance with the radial direction of the reflected light from
Light receiving means, a second light receiving means provided with a light receiving area divided into two corresponding to the reflected light from the second sub spot in the radial direction, and a third light receiving means for receiving the reflected light from the main spot. A light receiving means, a first difference detecting means for detecting a first difference signal from the first light receiving means, a second difference detecting means for detecting a second difference signal from the second light receiving means, Detecting means for detecting a tracking error signal from the light receiving means, and control means for performing tracking control by determining whether a land or a groove based on the tracking error signal, the first difference signal, and the second difference signal. And the following.

According to a third aspect of the present invention, in the optical disk device according to the second aspect, the irradiating means is symmetrically spaced apart from the main spot by a half of the width in the radial direction with respect to the main spot. The first sub-spot and the second sub-spot are illuminated at different positions.

According to a fourth aspect of the present invention, in the optical disk device of the second aspect, a third difference detecting means for detecting a difference signal between the first difference signal and the second difference signal is provided. It is characterized by.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) This embodiment will be described with reference to FIGS. FIG. 1A shows a configuration of an optical pickup used in the optical disk device according to the present embodiment.
The optical disk will be described as an example of a magneto-optical disk capable of recording and reproduction using a magneto-optical effect.

In FIG. 1A, a light emitted from a semiconductor laser 21 is separated by a diffraction grating 22 into three beams of a zero-order light (main) and ± first-order lights (sub), and then a collimating lens. 23 converts the light into parallel light. This 3
The two parallel lights pass through the beam splitter 24,
The light is reflected by the mirror 25 and forms a focused spot on the optical disk 27 by the objective lens 26.

The reflected light from the disk 27 returns to the semiconductor laser 21 through the same optical path, but a part of the reflected light is reflected by the beam splitter 24. This reflected light is the second
Are separated into transmitted light and reflected light by the beam splitter 28, and the transmitted light passes through the beam splitter 28, and then passes through the condensing lens 35 and the cylindrical lens 36 whose generatrix is set at 45 ° to the plane of the paper. After that, the light is condensed on the photodetector 37.

On the other hand, the light reflected by the beam splitter 28 is condensed by another condensing lens 29, and the light is changed by a half-wave plate 30 to a polarization direction of 45 °.
After being rotated, they are separated by the polarizing beam splitter 31. The separated light is converted into an electric signal by the photodetectors 32 and 33, respectively, and the signal recorded on the optical disk 27 is detected by differential detection by the differential amplifier.

FIG. 1B shows the positional relationship on the optical disk 27 of the light spots of the three beams of 0-order light and ± 1st-order light. As shown in FIG. 1B, the optical disc 27 has a land (center point L) and a groove (center point G) formed with the same width (P). Two sub-spots 38 and 3 due to next light
9 is focused on the main spot 40 so as to be half the land width (groove width) P. Light reflected from the main spot 40 and the sub spots 38 and 39 passes through the above-described optical path and is condensed on the photodetector 37.

FIG. 1C shows the relationship between the diffraction patterns 38 ', 39', 40 'of each spot on the photodetector 37 and the light receiving section of the photodetector 37. The diffraction pattern received by the photodetector 37 is actually the cylindrical lens 3
6, the main spot 40 and the sub-spots 38, 39 will be described as corresponding to the diffraction patterns 40 ', 38', 39 'in FIG. 1C, respectively.

In order to detect the diffraction patterns 40 'and 39', the light receiving section of the photodetector 37 has two light receiving sections 1a and 1b.
The light receiving unit 1a is composed of a conventional FES and TES.
The light receiving portion 1b is divided into two portions corresponding to the radial direction of the optical disk 27.

Next, the signal processing of the present invention will be described with reference to FIGS. FIG. 2 is a block diagram of a control signal detection system of the optical disk device according to the present embodiment. In this figure, a light receiving section 1b and a subtractor 20 are added as compared with the conventional configuration, and the same components as those in the conventional configuration are denoted by the same reference numerals and description thereof is omitted. Here, the outputs from the light receiving unit 1a divided into four parts are A, B, C, and D, and the outputs from the light receiving part 1b divided into two parts are E and F.

The four outputs A, B, C,
D is calculated by an error generation circuit including adders 2, 3, 4, 5 and subtracters 6, 8 according to the following equation, and a focus error signal (FES) and a tracking error signal (TES) are generated. . Further, the two outputs E and F from the light receiving section 1b are subtracted by the subtractor 20, and a land / groove discrimination signal SUB1 is generated. FES = (A + D)-(B + C) TES = (A + C)-(B + D) SUB1 = EF FIG. 3 shows the relationship between TES and SUB1 of these signals and the position of the light spot. TES and SUB1 of FIG.
And TES and TOTAL of FIG.
ES indicates that the same signal is obtained, whereas SUB1
Is 周期 cycle of the conventional TOTAL, and T
A signal shifted by 90 ° from ES is obtained. This is due to the fact that SUB1 performs the same calculation as TES and that the distance between the main spot 40 and the sub-spot 39 is 配置 of the land width (groove width) P. I do.

Next, TES and SUB will be described with reference to FIGS.
The tracking pull-in control will be described with reference to signal No. 1. FIG. 4 shows signals generated in various parts of the apparatus shown in FIG.

SUB1 is binarized by a binarization circuit 9, and TES is binarized by a binarization circuit 10, to obtain SUB1D and TESD. Further, an edge pulse EP is obtained by an edge detection circuit 12 that generates a pulse at the rising edge and the falling edge of TESD. By latching SUB1D at the rising edge of EP by the flip-flop 14, an on-track signal LG is obtained.

When the tracking control is performed on the land, the controller 13 closes the tracking control loop at the rising edge of the LG.
Give instructions. Based on this instruction, the tracking error signal TES is amplified by the power amplifier 18 and then fed back to the tracking actuator 19 to perform tracking on the land. When tracking control is performed on the groove, if an instruction is given to close the tracking control loop at the fall of LG, tracking can be similarly performed on the groove.

As described above, the diffraction pattern 3 of the sub-spot 39 spaced apart from the main spot 40 by approximately の of the groove width (land width) in the radial direction of the disk.
By using the land / groove discrimination signal generated from 9 ', stable tracking control can be performed even on a disc having substantially equal land and groove widths, and recording and reproduction can be performed with high reliability.

Although the optical pickup shown in FIG. 1A uses an astigmatism method as a focus error signal detection method as described above, other known servo error signal detection methods are used. For example, even if the knife edge method or the like is used as a focus error signal detection method, a similar effect can be obtained by obtaining a land / groove discrimination signal. Further, the optical pickup shown in FIG. 1A shows an example in which a diffraction grating is used for forming a sub spot, but two semiconductor lasers may be used to form two main and sub spots. . Further, an example is shown in which a magneto-optical disk utilizing the magneto-optical effect is used as an optical disk on which recording and reproduction can be performed. For example, an optical disk utilizing a phase change effect may be used.

(Embodiment 2) Embodiment 1
In the configuration shown in FIG. 5, when the arrangement of the main spot 40 and the sub-spot 39 on the optical disk 27 deviates from half the groove width (land width), the phase difference δ becomes as shown in FIG.
Occurs. When the phase difference δ is small, there is no problem in land / groove discrimination, but when δ is large, there is a problem in that land / groove discrimination is mistaken. Further, in the first embodiment, SUB1 varies because it is affected by the disk reflectance distribution and the TES offset. Due to this effect, there is a possibility that an error may occur in the land / groove determination.

Since TES and SUB1 indicate a change in which one cycle is equal to the land width + groove width (2 × P), the phase difference δ shown in FIG. Then, δ = 2π · (y / 2P) = (π / P) · y.

Hereinafter, in this embodiment, even when the irradiation positions of the main spot 40 and the sub-spot 39 on the disk 27 are shifted, the phase difference δ does not occur and the structure is not affected by the fluctuation of the reflectance of the disk. Will be described with reference to FIGS.

FIG. 6A shows a configuration of an optical pickup used in the optical disk device according to the present embodiment, and FIG. 6B shows a light spot of three beams of 0-order light and ± 1st-order light. 6 shows a positional relationship on the optical disk 27, and FIG.
(C) shows the relationship between the diffraction patterns 38 ′, 39 ′, 40 ′ of each spot on the photodetector 37 and the light receiving section of the photodetector 37. In FIG. 6, as compared with FIG. 1, as shown in FIG.
The difference is that a light receiving section 1c is added to the photodetector 37 in order to detect 8 ', and the same reference numerals are given to other same components, and description thereof will be omitted. The light receiving section 1c is divided into two parts corresponding to the radial direction of the optical disk 27. Further, since the sub-spots 38 and 39 are formed by ± first-order light of the diffraction grating 22, they are condensed at symmetric positions with respect to the main spot 40. Therefore, as shown in FIG. 6B, if the shift amount from the original spot position is y, and the interval between the sub spots 38 with respect to the main spot 40 is (P / 2 + y), the main spot 40 is shifted. The interval between the sub spots 39 is-(P / 2 + y).

Next, the signal processing of the present invention will be described with reference to FIGS. FIG. 7 is a block diagram of a control signal detection system of the optical disk device according to the present embodiment. In this figure, the light receiving units 1b and 1c and the subtractor 41,
Reference numerals 42 and 43 are added, and the same components as those in the related art are denoted by the same reference numerals and description thereof is omitted. Here, the outputs from the light receiving unit 1a divided into four are A, B, C, and D, the outputs from the light receiving unit 1b divided into two are E and F, and the output from the light receiving unit 1c divided into two is G and H.

The four outputs A, B, C,
D is calculated by an error generating circuit including adders 2, 3, 4, 5 and subtractors 6, 8 according to the following equation.
Similarly, a focus error signal (FES) and a tracking error signal (TES) are generated. Also, the light receiving unit 1
b, the outputs E and F are subtracted by a subtractor 41 to obtain a difference signal S
UB1 is generated, and the outputs G and H from the light receiving section 1c are subtracted by a subtractor 42 to generate a difference signal SUB2, and these difference signals are subtracted by a subtractor 43 to generate a land / groove discrimination signal SUB. Is done.

FES = (A + D)-(B + C) TES = (A + C)-(B + D) SUB = SUB1-SUB2 = (EF)-(GH) Next, the irradiation positions of the main spot and the sub spot are determined. FIG. 8 shows the reason why the phase difference always becomes 90 ° due to the signals of TES and SUB even if it deviates from the original position.
This will be described with reference to FIG.

FIG. 8 shows TES and SU of these signals.
13 shows B1, SUB2, and the relationship between SUB and the position of the light spot. FIG. 8A shows the signals of SUB1 and SUB2 when the main spot and the sub spot are at their original positions (no shift), and FIG. 8B shows the signals of SUB1 when they are shifted y from the original position. The signal of SUB2 is shown in FIG.
Shows signals of the SUB.

Here, TES, SUB1, and SUB2
Is assumed to be approximated by a sine curve since it changes sinusoidally. The TES at a position shifted by x from the center of a predetermined land is set to 0, and its signal amplitude is K, and is expressed by the following equation. TES = K · sin [(π / P) · x] Similarly, the signals of SUB1 and SUB2 are, as described above, because the sub-spots formed by the diffraction grating are arranged symmetrically with respect to the main spot. , Assuming that the amount of deviation from the position of the sub spot with respect to the main spot is y, the sub spots 38, 3
9 are (P / 2 + y) and − (P / 2 +
y). Therefore, SUB1 and SUB2 are represented by the following equations, where the signal amplitude is L. SUB1 = L · sin [(π / P) · (x + (P / 2 +
y))] = L · sin [(π / P) · x] · cos
[(Π / P) · (P / 2 + y)] + L · cos [(π /
P) .x] .sin [(π / P). (P / 2 + y)] SUB2 = L.sin [(π / P). (X− (P / 2)
+ Y))] = L · sin [(π / P) · x] · cos
[(Π / P) · (P / 2 + y)] − L · cos [(π /
P) .x] .sin [(π / P). (P / 2 + y)] On the other hand, y is a value determined by the setting of the first main spot and the sub spot, and the positional relationship on the disc does not change. 2 · L · sin [(π / P) · (P / 2 +
y)] = M (M: constant), the signal SUB obtained by subtracting SUB1 and SUB2 is as follows.

SUB = M · cos [(π / P) · x] = M · sin [(π / P) · x−90 °] On the other hand, since TES is represented by the above equation, the sub-spot The distance between 38, 39 and the main spot 40 is
As shown in FIG. 8, even when the SUB deviates from the original position, the SUB always becomes a signal whose phase is shifted by 90 ° with respect to the TES, and becomes the maximum at the center point L of the land and the minimum at the center point G of the groove. Become.

The condition under which the signal SUB cannot be detected is when M = 0, and becomes 0 under the following conditions. (Π / P) · (P / 2 + y) ≠ n · πn: integer (P / 2 + y) ≠ n · Pn: integer In other words, the interval (P / 2 + y) between the sub spots with respect to the main spot is the land width (groove) If the width is an integer multiple of (width), SUB is always 0, and land / groove discrimination is impossible. However, at other intervals, M ≠ 0, and detection is possible.

On the other hand, when the following condition is satisfied, the signal amplitude of the SUB becomes maximum. (Π / P) · (P / 2 + y) = n · π + P / 2 n: integer (P / 2 + y) = n · P + P / 2 n: integer That is, the interval (P / 2 + y) between the sub spot and the main spot is If the integer multiple of the land width (groove width) +1/2 of the land width (groove width), the signal amplitude of the SUB becomes the maximum, and stable land / groove discrimination becomes possible. Further, in the present embodiment, the sub spot 3
From the difference signal between the diffraction patterns 38 'and 39' of 8, 39,
Since the SUB is obtained, it is possible to prevent the influence of the reflectivity fluctuation of the disk.

Next, the tracking pull-in control based on the TES and SUB1 signals will be described with reference to FIG.
The tracking pull-in control using the TES and SUB signals is the same as in the first embodiment except that SUB is used for the land / groove discrimination signal.
Then, the TES is binarized by the binarization circuit 10, and the SUBD,
TESD is obtained respectively. An edge pulse EP is obtained by an edge detection circuit 12 that generates a pulse at the rising edge and the falling edge of TESD. The on-track signal LG is obtained by latching the SUBD at the rising edge of the EP by the flip-flop 14.
The controller 13 gives an instruction to the tracking control circuit 11 to close the tracking control loop at the time of the fall of LG when performing tracking control on the land, and L when performing tracking control on the groove.
If an instruction is given to close the tracking control loop at the rise of G, tracking can be performed on the groove in the same manner.

As described above, the diffraction pattern by the reflected light of the pair of sub-spots arranged symmetrically with respect to the main spot is condensed on the photodetector divided into two corresponding to the radial direction of the disk, and By detecting the difference signals and using these difference signals as land / groove discrimination signals, the distance between a pair of sub-spots symmetrically arranged with respect to the main spot is １ ／ of the groove width (land width). Even in the case of deviation, the land / groove discrimination signal which is maximum at the land and minimum at the groove can be obtained, so that stable track pull-in control can be performed even on an optical disk having the same land and groove width.

Further, by arranging a pair of sub-spots symmetrically arranged with respect to the main spot at approximately half the groove width (land width), the signal amplitude of the land / groove discrimination signal is maximized. Therefore, more stable track pull-in control can be performed.

Further, since a main spot is formed by zero-order light and a pair of sub-spots is formed by ± first-order light using a diffraction grating, the diffraction angle of the first-order light with respect to the zero-order light and the
Since the diffraction angle of the −1st order light with respect to the next order light is equal, a pair of sub spots can be easily arranged symmetrically with respect to the main spot on the disk.

[0049]

According to the first and second aspects of the present invention, stable track pull-in control can be performed. According to the third aspect of the present invention, since the signal amplitude is maximized, more stable track pull-in control can be performed. According to the fourth aspect of the present invention, it is possible to prevent the influence of the fluctuation of the reflectivity of the optical disk, so that more stable track pull-in control can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical system of an optical disk device according to a first embodiment.

FIG. 2 is a block diagram of a control signal detection system of the optical disc device of the first embodiment.

FIG. 3 is a diagram showing signals TES and SUB1 when a light spot moves on an optical disc having the same land and groove width in the first embodiment.

FIG. 4 is a diagram showing signals generated in each section of the device of FIG. 2;

FIG. 5 is a diagram for explaining a problem in the first embodiment.

FIG. 6 is a diagram showing an optical system of an optical disk device according to a second embodiment.

FIG. 7 is a block diagram of a control signal detection system of the optical disc device according to the second embodiment.

FIG. 8 is a diagram showing a TE in a case where a light spot moves on an optical disk having the same land and groove widths in the second embodiment;
It is a figure showing the relation between S, SUB1, SUB2, and SUB.

FIG. 9 is a block diagram of a control signal detection system of a conventional optical disc device.

FIG. 10 is a diagram showing signals generated in each section of the device in FIG. 9;

FIG. 11 is a diagram showing signals when an optical spot moves on an optical disk having lands and grooves of different widths.

FIG. 12 is a diagram showing signals when an optical spot moves on an optical disk having the same land and groove width.

FIG. 13 is a diagram showing signals generated in each section of the apparatus of FIG. 9 for a disk having the same land and groove width.

[Explanation of symbols]

 1a, 1b, 1c Light receiving unit 2, 3, 4, 5 Adder 6, 8, 20, 41, 42, 43 Subtractor 9, 10 Binarization circuit 11 Tracking control circuit 12 Edge detection circuit 13 Controller 14 Flip-flop

Claims (4)

[Claims] 1. An optical disc apparatus for recording or reproducing information on an optical disc in which a land and a groove have substantially the same width is provided. A main spot and a position radially separated from the main spot by half of the width. Irradiating means for irradiating the optical disc with a sub-spot; first light-receiving means provided with a light-receiving area divided into two in correspondence with the reflected light from the sub-spot in the radial direction; A second light receiving means for receiving light, a differential detecting means for detecting a difference signal from the first light receiving means, a detecting means for detecting a tracking error signal from the second light receiving means; Control means for discriminating between land and groove based on the difference signal and performing tracking control. apparatus. 2. An optical disc apparatus for recording or reproducing information on or from an optical disc in which a land and a groove have substantially the same width, wherein the main spot and the main spot are symmetrically spaced apart from each other at an equal distance in a radial direction. Irradiating the optical disk with a first sub-spot and a second sub-spot at appropriate positions, and a light receiving area divided into two corresponding to the reflected light from the first sub-spot in the radial direction. A first light receiving means, a second light receiving means having a light receiving area divided into two corresponding to the reflected light from the second sub spot in the radial direction, and a second light receiving means for receiving the reflected light from the main spot. 3, a first difference detection unit that detects a first difference signal from the first light reception unit, a second difference detection unit that detects a second difference signal from the second light reception unit, Detecting means for detecting a tracking error signal from the light receiving means of No. 3, and control for performing tracking control by determining whether it is a land or a groove based on the tracking error signal, the first difference signal, and the second difference signal And an optical disk device. 3. The irradiating means irradiates a first sub-spot and a second sub-spot to a main spot and a symmetrical position radially separated from the main spot by a half of the width in a radial direction. 3. The optical disk device according to claim 2, wherein: 4. The optical disk device according to claim 2, further comprising third difference detecting means for detecting a difference signal between the first difference signal and the second difference signal.