JPH0758550B2 - Optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field B Outline of Invention C Conventional Technology D Problems to be Solved by the Invention E Means for Solving Problems (FIGS. 1 to 3) F Action G Example G ₁ 1st Example G ₂ Second Example H Effect of Invention A Field of Industrial Application The present invention relates to a disc recording / reproducing apparatus capable of optical recording on a disc.

B Outline of the Invention The present invention provides a data recording area sandwiched between a first pregroup and a second pregroup formed at a predetermined distance from the first pregroove in the tracking direction.
An optical disk device for recording or reproducing an optical disk having a sample servo area composed of a wobble pit provided between a first pre-groove and a second pre-group. Detecting means for detecting the reflected light of the detecting means, which is divided into two in the track direction, adding means for adding the respective detection outputs of the detecting means to generate a reproduction signal, and subtracting the respective detection outputs of the two-divided detecting means. A subtraction means, a timing generation means for generating a first sampling pulse corresponding to the data area and a second sampling pulse corresponding to the sample servo area based on the addition output from the addition means, and a subtraction result from the subtraction means. The first sample and hold means for sampling and holding with one sampling pulse, and the subtraction result from the subtracting means are A second sample-hold means for sample-holding with a sampling pulse, and a second subtracter means for subtracting the output signals from the first sample-hold means and the second sample-hold means and outputting the subtraction result as a tracking error signal. With this provision, a good trunking error signal is always obtained even if there is radial skew, lens movement, etc., and it is possible to perform recording or reproduction while performing good tracking by this tracking error signal. is there.

C Related Art Conventionally, various types of disk recording / reproducing devices capable of optical recording on a magneto-optical disk have been proposed. As a tracking error detecting method used in the optical recording / reproducing apparatus capable of optical recording, for example, a method shown in FIG. 10 has been proposed. In FIG. 10, (1) shows a semiconductor laser element (laser diode) as a laser light source.
Then, the divergent laser beam from this is made into a parallel beam by passing through the collimator lens (2), and after being deflected by 90 degrees by the beam splitter (3),
It is incident on the lens (4). The focused beam from the lens (4) illuminates an optical disc (5) as an optical recording medium and focuses it there. A beam emitted from the optical disk (5), that is, a reflected beam is incident on the lens (4) again to be a parallel beam, passes through the beam splicer (3) and is incident on the two-division photodetector (6).

This two-division photodetector (6) is composed of two photodetectors (6A) and (6B) as shown in FIG. 11, and the circular spot SP by the parallel beam from the lens (4) is 2 In the case where the two photodetectors (6A) and (6B) are located exactly half each, it means that the focused beam from the lens (4) scans exactly in the middle of the track of the optical disk (5). Therefore, these two photodetectors (6A), (6B)
If both detection outputs from the above are supplied to the operational amplifier (7) and the difference therebetween is taken, a tracking error signal is obtained at the output terminal (8).

However, in such a conventional tracking error detection method, when the lens (4) moves in parallel to the optical disc (5) as shown by the broken line in FIG. 10, the two-division photodetector (6) is fixed. Therefore, the position of the spot SP on it shifts as shown by a broken line in FIG. 11, and a DC fluctuation (as shown in FIG. 14A) occurs in the tracking error signal from the output terminal (8). That is, as shown in FIG. 10, when the position of the lens (4) changes, the tracking error signal changes its direct current as shown in FIG. 14B.

Further, as shown in FIG. 12, when a radial skew occurs on the optical disk (5), the two-split photodetector (6) is fixed in the same manner, and the position of the spot SP on it is shown in FIG. The tracking error signal from the output terminal (8) is deviated as shown by the broken line, and a DC fluctuation occurs. Therefore, also in this case, the DC of the tracking error signal fluctuates as shown in FIG. 14B.

In order to prevent this DC fluctuation, a disc recording / reproducing apparatus having a tracking control unit as shown in FIG. 15 has been proposed. This tracking control device is used for a recording / reproducing device of a magneto-optical disk for recording / reproducing with a semiconductor laser, and a divergent laser beam is emitted from a semiconductor laser element (1) to an optical disc (5) via a lens (4). Irradiate. Then, the reflected beam from the optical disk (5) passes through the lens (4) again, and after being polarized by 90 degrees by the beam splitter (3), it is split into two photodetectors (6).
Incident on. The two-division photodetector (6) is composed of two photodetection units (6A) and (6B) which are divided into two in the track direction. The two photodetection units (6A) and (6B) The detection output signal is supplied to the differential amplifier (7) and the difference signal (tracking error signal) is output from the differential amplifier (7), and the detection output signal is also added to the first addition circuit (9).
And the addition signal is output from the first addition circuit (9). The difference signal output from the differential amplifier (7)
To the sample and hold circuit (11) of the first adder circuit (9) and the added signal output from the first adder circuit (9) and the second and third sample and hold circuits (12) and (13) and the timing generator (1
Supply to 0). And this timing generator (10)
Detects a synchronization signal from the addition signal, forms first, second, and third sampling pulse signals based on the synchronization signal, and supplies the first sampling pulse signal to the first sample hold circuit (11) Then, the second sampling pulse signal is supplied to the second sample hold circuit (12), and the third sampling pulse signal is supplied to the third sample hold circuit (13). Then, the output signal of the first sample-hold circuit (11) is supplied to the second adding circuit (16), and the output signal of the second sample-hold circuit (12) and the third sample-hold circuit (13). The output signal and the subtraction circuit (14) are supplied to the subtraction circuit (14), and the subtraction output signal of the subtraction circuit (14) is passed through the variable gain adjuster (15) to the second addition circuit (16).
Supply to. Then, in the second adder circuit (16), the first
The output signal of the sample hold circuit (11) and the output signal of the variable gain adjuster (15) are added, and the second addition circuit (1
The output signal of 6) is supplied to the output terminal (8), and the signal obtained at this output terminal (8) is used as the tracking error signal.

Next, the configuration of each track of the optical disc (5) for obtaining the tracking error signal with this circuit configuration will be described. As shown in FIG. 16, for example, this optical disk (5) has a plurality of tracks formed in the circumferential direction within a track forming area T, and each of these tracks is divided into first to sixteenth segments S _{1 to} S ₁₆ . To divide. Each of the segments S _{1 to} S ₁₆ is divided into a sample servo area S _A and a sample servo / data area S _B for each track. The specific structure of one segment of each track is that, assuming that the track is a straight line, pregrooves g are continuously provided at every track pitch P as shown in FIG. 17A. The pre-groove g has a depth of λ / 8 where λ is the wavelength of the divergent laser beam of the semiconductor laser element (1). The predetermined length of this track is set as one segment, the front part of this one segment is set as the sample servo area S _A , and the remaining part is set as the sample servo and data area S _B. And
An area between one pre-groove g and an adjacent pre-groove g is defined as a land 1, and first and second wobble pits w _A and w _B are provided in the sample servo area S _A of the land 1. The first and second wobble pits w _A and w _B are
With a depth of λ / 4 for the above divergent laser beam wavelength λ,
The first wobble pit w _A is provided in the first half of the sample servo area S _A , and the second wobble pit w _B is provided in the second half,
_A first wobble pit w _A and a second wobble pit w _B are distributed to the left and right in the radial direction with the center line t _{C of the} track as a boundary. Data recording is performed by irradiating the land 1 of the sample servo and the data area S _{B with} a laser beam to invert the magnetism.

Writing of the pre-groove g and the wobble pits w _A and w _B configured in this manner is performed with a distance of half Q of one track pitch P in the radial direction as shown in FIG.
This is done with a laser beam of a book. That is, while writing the pre-groove g with a depth of λ / 8 with one laser beam,
Wobble pit with a depth of λ / 4 with another laser beam
Write w _A and w _B separately to the left and right. 2 in this way
A plurality of tracks are continuously formed by repeatedly writing with a laser beam of a book.

Next, the tracking performed by the apparatus of FIG. 15 on the track thus configured will be described. First, a laser beam having a wavelength λ from the semiconductor laser device (1) is irradiated onto a predetermined track of the optical disc (5),
If this irradiation completely scans the center t _C of the track, 2
The output signal voltage of the split photodetector (6) is in the state shown in FIG. 17B. That is, FIG. 17B shows the sum of the output signals of the two photodetectors (6A) and (6B). In the sample servo and data area S _B , the disc (5 ) Is a slightly smaller output signal than that of a perfect mirror surface, and in the sample servo area S _A , wobble pits w _A and w _B with a depth of λ / 4 make it approximately half the output signal of the sample servo and data area S _B. , And the output signals of the first wobble pit w _A and the second wobble pit w _B become the same. Here, the sampling timings of the respective sample-hold circuits (11), (12), (13) are as shown in FIG. 17C, when the first sample-hold circuit (11) outputs sampling pulse signals.
When the gate is opened over the entire period of the sample servo and data area S _B by p1, the second sample hold circuit (12) scans the first wobble pit w _A of the sample servo area S _A by the sampling pulse signal p2. The gate is opened (at beam spot b _{2 in} FIG. 17A), and the third sample and hold circuit (13) causes the sampling pulse signal p3
2nd wobble pit in sample servo area S _A
The gate is opened during the scanning of w _B (at the beam spot b _{3 in} FIG. 17A). In this way, the respective sample-hold circuits (11), (12), (13) perform sampling, so that the output signal of the first sample-hold circuit (11) is sampled via the differential amplifier (7). It becomes a tracking error signal in the section of the servo and data area S _B , and the output signals of the second and third sample and hold circuits (12) and (13) are the first and second wobble pits w _A and w _B , respectively. It becomes the detection signal of the detector (6) in the section. Therefore, when the beam spot scans the center t _C of the track, the output signals of the second and third sample hold circuits (12) and (13) become equal, and both output signals are subtracted by the subtraction circuit (14).
The output signal subtracted by is 0, and an output signal corresponding to the shift is obtained when scanning is performed with a shift from the center t _{C in the} radial direction. This subtraction circuit (1
The output signal of 4) and the track error signal output from the first sample hold circuit (11) are added to the second addition circuit (16).
The tracking error signal of the sample servo and the data area S _B is corrected by the output signal of the subtraction circuit (14) by the addition. At this time, in order to perform this correction favorably, the output signal of the subtraction circuit (14) is adjusted in gain by the variable gain adjuster (15) and then supplied to the second addition circuit (16). Then, the output signal of the second adder circuit (16) becomes a tracking error signal and is obtained at the output terminal (8).

In this way, the tracking error signal obtained by correcting the tracking error signal of the sample servo and data area S _B is obtained by the signal holding the detection signal of the detector (6) obtained in the section of the sample servo area S _A , and the lens ( The DC fluctuation of the tracking error signal due to the position fluctuation of 4), the radial skew of the optical disk (5), etc. is corrected.

D The problem to be solved by the present invention is that the tracking error signal is obtained as described above, but the tracking error signal of the sample servo and the data area S _B has a constant value obtained by holding the detection signal of the detector (6). because corrects the DC fluctuation by mixing signals, and when such tracking deviation within one section of the sample servo and data areas S _B occurs can no longer be removed completely DC variation I will end up. That is,
Since the output signal of the subtraction circuit (14) that does not include DC fluctuation and the output signal of the sample hold circuit (11) that includes DC fluctuation are added with a certain gain ratio, the DC fluctuation included in the obtained error signal is 1 / It is the ratio of gains and does not become zero. Further, the variable gain adjuster (15) has a difficulty in performing optimum correction at all times because the optimum adjustment state of the gain varies depending on the state of the optical disk (5).

The present invention has been made in view of the above points, and an object thereof is to provide an optical recording / reproducing apparatus capable of optical recording, which always obtains a good tracking error signal.

E Means for Solving the Problems In the optical disk device of the present invention, for example, as shown in FIGS. 1 to 3, a first pregroup g (for example, g ₂ ) and a predetermined distance from the first pregroup in the tracking direction. A data recording area SB sandwiched by a second pregroup g (for example, g ₃ ) formed apart from each other, and a wobble provided between the first pregroup and the second pregroup. An optical disk device for recording or reproducing an optical disk provided with a sample servo area SA composed of pits W, and detecting means 6A divided into two in the track direction for detecting reflected light of light irradiated on the optical disk 5. 6B, an adding means 9 for adding the respective detection outputs of the detecting means 6A, 6B to generate a reproduction signal, a subtracting means 7 for subtracting the respective detection outputs of the two detecting means 6A, 6B, and an adding means 9 Timing generating means 17 for generating a first sampling pulse corresponding to the data area and a second sampling pulse corresponding to the sample servo area on the basis of the addition output from First sample-hold means 18 for sample-holding with sampling pulse
And second sample and hold means 19 for sampling and holding the result of the subtraction from the subtracting means 7 with the second sampling pulse.
And a second subtraction means 20 for subtracting the output signals from the first sample hold means 18 and the second sample hold means 19 and outputting the subtraction result as a tracking error signal.

According to the present invention, when the beam scans the data recording area SB, the output difference between the detection means 6A and 6B is sampled, and the sampled first signal is held,
When the beam is scanning the sample servo area SA,
The disc is obtained by sampling the output difference of each detecting means 6A, 6B, holding the sampled second signal, and obtaining a tracking error signal by the difference signal between the outputs of the first signal and the second signal. It is possible to always obtain a perfect tracking error signal even if there is a skew or a change in the lens position.

G Example G ₁ First Example Hereinafter, a first example of the optical disk device of the present invention will be described with reference to FIGS. 1 to 4. 1 to 4, parts corresponding to those in FIGS. 10 to 18 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a diagram showing the configuration of the disc recording / reproducing apparatus of this example. In FIG. 1, (6) shows a two-division photodetector, and this two-division photodetector (6) is composed of two photodetection sections (6A) and (6B). The differential amplifier (7) outputs the detection output signals from the parts (6A) and (6B)
Is supplied to the differential amplifier (7) to output the difference signal (tracking error signal) to the adder circuit (9) and the adder circuit (9) outputs the added signal. . Then, the difference signal output from the differential amplifier (7) is supplied to the first and second sample hold circuits (18).
And (19). Further, the addition signal output from the addition circuit (9) is supplied to the timing generator (17), the timing generator (17) detects a synchronization signal from the addition signal, and the first and the first signals are detected based on the synchronization signal. 2 sampling pulse signals are formed, the first sampling pulse signal is supplied to the first sample-hold circuit (18), and the second sampling pulse signal is supplied to the second sample-hold circuit (19). . The first and second sampling pulse signals are signals as shown in FIG. 3C described later, for example. The output signal of the first sample and hold circuit (18) and the second sample and hold circuit (19)
And the output signal of the subtraction circuit (20)
The output signal of (0) is supplied to the output terminal (8), and the signal obtained at this output terminal (8) is used as the tracking error signal.

Next, the structure of each track of the optical disc (5) for obtaining the tracking error signal in the apparatus of this example will be described.
For example, as shown in FIG. 2, this optical disc (5) has a plurality of tracks formed in the circumferential direction within a track formation area T, and each track is divided into, for example, 1000 sections. And the sample servo area for each divided section
It is divided into S _A and sample servo and data area S _B. Therefore, 1000 sample servo areas S _A are provided for each track, S _{A1 to} S _A1000 . The specific configuration of each track is the third if the track is a straight line.
As shown in FIG. A, one track pitch P (for example, 1.6 μ
For each m), the pregroove g is first provided in the entire section of the sample servo and data area S _{B and} the section of the sample servo area S _A. This pre-groove g has the wavelength of the divergent laser beam of the semiconductor laser device (1) as λ,
The depth is λ / 8. The wobble pit w is provided only in the first half of the section of the sample servo area S _A where there is no pre-groove g. The wobble pit w is formed so as to be displaced from the pre-groove g in the radial direction by half the pitch P of one track, and has a depth of λ / 8. _A clock pit c is provided in the sample servo area S _A in front of the wobble pit w. The depth of the clock pit c is λ / 4. Then, the area between the pregrooves g adjacent to each other in the sample servo and the data area S _B is set as a land 1, and the land 1 is irradiated with a laser beam to invert the magnetism to record data.

Writing of the pre-groove g, the wobble pit w, and the clock pit c configured in this way is performed by two laser beams separated by half Q of one track pitch P in the radial direction, as shown in FIG. 4, for example. . That is,
The pre-groove g is written with one laser beam, and the clock pit c and the wobble pit w are written with the other laser beam. By doing so, the pre-groove g and the wobble pit w written in the same process by the two beams are accurately formed at the above-mentioned interval Q.

By thus repeatedly performing writing with two laser beams, a plurality of tracks are continuously formed as shown in FIG. 3A. That is, on the disc (5), for example, the pre-groove g ₂ and the wobble pit w _{2 which} are written secondly are formed adjacent to the pre-groove g ₁ which is written first, and in this way a plurality of tracks are sequentially formed. It is formed.

Next, the tracking performed by the apparatus of FIG. 1 on the track thus formed will be described. First, a laser beam having a wavelength λ from the semiconductor laser device (1) is irradiated onto a predetermined track of the optical disc (5),
If this irradiation completely scans the center of a predetermined track, that is, the center t _C between adjacent pregrooves g, the output signal voltage of the two-division photodetector (6) due to the incidence of the reflected beam obtained by this irradiation is The state shown in FIG. 3B is obtained. That is, this FIG. 3B shows two photodetectors (6A), (6A).
In the sample servo and data area S _B , the pre-groove g on both sides of the land 1 is added.
The output from the rear end of the wobble pits w until the start of the sample servo and data area S _B is the maximum output, and slightly less output signal from the maximum output. Also,
In the sample servo area S _A , the first clock pit c
There is almost no output signal in the section of wobble pit w
In the section of, the output signal of about half of the maximum output is obtained. Here, the sampling timings of the respective sample hold circuits (18) and (19) are as shown in FIG.
The sample hold circuit (18) opens the gate over the entire period of the sample servo and data area S _B by the sampling pulse signal p1, and the second sample hold circuit (19) receives the sampling servo signal S _A by the sampling pulse signal p2. When scanning the wobble pit w (see FIG. 3A
(At beam spot b ₂ of)) Open the gate. In this way, the respective sample and hold circuits (18) and (19) perform sampling, so that the output signal of the first sample and hold circuit (18) outputs the sample servo and data area through the differential amplifier (7). It becomes the tracking error signal in the section of S _B , and the output signal of the second sample hold circuit (19) is the wobble pit w through the differential amplifier (7).
It becomes a tracking error signal during scanning. Therefore, when the beam spot is scanning the center t _C between the adjacent pre-grooves g, the first sample hold circuit (1
The output signals of 8) and the second sample hold circuit (19) are in opposite phase, and the signal obtained by subtracting both output signals by the subtraction circuit (20) becomes 0, which is a subtraction signal indicating that this track has been taken. Are supplied to the output terminal (8). Also,
When scanning is shifted from the center t _{C in the} radial direction, a tracking error signal corresponding to the deviation is output from the output terminal (8).
Is supplied to.

Next, the fact that the tracking error signal obtained at the output terminal (8) has no DC fluctuation will be described using mathematical expressions.

First, the tracking error signal TE1 output from the first sample hold circuit (18) and the tracking error signal TE2 output from the second sample hold circuit (19) are
It is expressed as the following equation.

However, A is amplitude, B is DC fluctuation, X is disk (5)
The position of the upper light spot.

Therefore, the output signal of the subtraction circuit (20), that is, the tracking error signal TE obtained at the output terminal (8) is expressed by the following equation.

From this formula, Then, ΔQ = 0, and the tracking error signal obtained at the output terminal (8) in FIG. 1 does not include the DC fluctuation component B.

By thus obtaining the tracking error signal that does not include the DC fluctuation component, the shape of the pre-groove,
Even if the shape of the beam spot is not uniform, it is possible to completely remove the DC fluctuation due to the skew and lens shift. Then, the data is recorded on the land 1 and the data is reproduced from the land 1 while performing the good tracking by the good tracking error signal. It should be noted that, at the time of this reproduction, the power of the laser beam is lowered as compared with the time of recording, and the tracking servo,
Better tracking can be performed by increasing the servo gain such as focus servo.

In the present embodiment, since the tracking error signal of the sample-and-hold and data area S _B by subtracting the tracking error signal area having a pit opposite phases and good tracking error signal, resulting in a sample servo area It is not necessary to adjust the received signal with a gain adjuster or the like. Therefore, it is not necessary to adjust the adjuster or the like depending on the state of the disc, and a good tracking error signal can always be obtained regardless of the state of the disc.

In the above embodiment, the land 1 of the sample hold and data area S _B may be used as the data recording section, or the pre-groove g of the sample servo and data area S _B may be used as the data recording section as shown in FIG. In this case, for example, the clock pit c may be provided in the sample servo area S _A continuously with the pre-groove g, and the scanning with the beam spot may be performed centering on the pre-groove g.
It can be easily understood that the same action and effect as those of the above-described embodiment can be obtained in this case as well.

G ₂ Second Embodiment Next, a second embodiment of the optical disk device of the present invention will be described with reference to FIGS. 6 to 8. In FIGS. 6 to 8, parts corresponding to those in FIGS. 1 to 4 and 10 to 18 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 6 is a diagram showing the configuration of the disc recording / reproducing apparatus of this example. In FIG. 6, (6) shows a two-division photodetector, and this two-division photodetector (6) is composed of two photodetection sections (6A) and (6B). The differential amplifier (7) outputs the detection output signals from the parts (6A) and (6B)
To the differential amplifier (7) to output the difference signal (tracking error signal) to the first addition circuit (9) and to supply the addition signal to the first addition circuit (9). (9) outputs. And a differential amplifier (7)
And supplies the difference signal output by the first, second and third sample and hold circuits (22), (23) and (24). Also,
The addition signal output from the first addition circuit (9) is supplied to the timing generator (21), the timing generator (21) detects the synchronization signal from the addition signal, and the first, Forming second and third sampling pulse signals, supplying the first sampling pulse signal to the first sample-hold circuit (22), and supplying the second sampling pulse signal to the second sample-hold circuit (23). Then, the third sampling pulse signal is supplied to the third sample hold circuit (24). The first, second and third sampling pulse signals are signals as shown in FIG. 7C described later, for example. The output signal of the second sample and hold circuit (23) and the third sample and hold circuit (24)
To the second adder circuit (25), and the output signal of the second adder circuit (25) to the 1/2 voltage divider (26). Then, the output signal of the 1/2 voltage divider (26) and the output signal of the first sample hold circuit (22) are supplied to the subtraction circuit (20), and the output signal of the subtraction circuit (20) is output to the output terminal ( 8), and the signal obtained at this output terminal (8) is used as a tracking error signal.

Next, the structure of each track of the optical disc (5) for obtaining the tracking error signal in the apparatus of this example will be described.
In this optical disk (5), each track is divided into, for example, 1000 sample servo areas S _A and 1000 sample servo and data areas S _B , as shown in FIG. 2, as in the first embodiment. ing. The specific configuration of each track, the track is as shown in FIG. 7 A When a straight line, providing a pregroove g to the entire section of the sample servo and data areas S _B for each track picks P.
This pre-groove g is formed by the above-mentioned semiconductor laser device (1).
Let λ be the wavelength of the divergent laser beam of, and have a depth of λ / 8. The sample servo area S _A is provided with a clock pit C, a first wobble pit w _A , and a second wobble pit w _B in order from the beginning. The clock pit C, the first wobble pit w _A, and the second wobble pit w _B are
It is formed so as to be displaced from the pre-groove g in the radial direction by half of one track pitch P. And clock pit c
Is λ / 4, and the depths of the first and second wobble pits w _A and w _B are λ / 8. Then, the area between the pregrooves g adjacent to each other in the sample servo and the data area S _B is set as a land 1, and the land 1 is irradiated with a laser beam to invert the magnetism to record data.

Writing of the pre-groove g, the first and second wobble pits w _A and w _B, and the clock pit c thus configured is performed by distributing one laser beam, for example, as shown in FIG. That is, for example, with the pre-groove g as the center, a clock pit c and a second wobble pit w _B are formed by shifting the pre-groove g by one half of the one track pitch P in the radial direction to form a clock pit c and a second wobble pit w _B. The first wobble pit w _A is formed by shifting from g by the distance Q in the other radial direction. By doing so, the first wobble pit w _A , the pre-groove g, and the second wobble pit w _B written by the same beam
And are formed exactly at the intervals Q described above.

By thus repeatedly performing writing with one laser beam, a plurality of tracks are continuously formed as shown in FIG. 7A. That is, on the disc (5), for example, the pre-groove g1 written by the first beam is written.
Also, the pre-groove g2 written by the second beam and the first and second wobble pits w _A2 and w _B2 are formed adjacent to the first wobble pit w _A1 , and a plurality of tracks are sequentially formed in this manner. It

Next, the tracking performed by the device of FIG. 6 on the track thus formed will be described. First, a laser beam having a wavelength λ from the semiconductor laser device (1) is irradiated onto a predetermined track of the optical disc (5),
If this irradiation completely scans the center of a predetermined track, that is, the center t _C between adjacent pregrooves g, the output signal voltage of the two-division photodetector (6) due to the incidence of the reflected beam obtained by this irradiation is Then, the state becomes as shown in FIG. 7B. That is, FIG. 7B shows two photodetector sections (6A), (6A).
In the sample servo and data area S _B , the pre-groove g on both sides of the land 1 is added.
As a result, the output from the rear end of the wobble pit w _{B to} the start end of the sample servo and data area S _B becomes the maximum output, and the output signal is slightly smaller than this maximum output. Further, in the sample servo area S _A , there is almost no output signal in the section of the first clock pit c, and approximately half of the maximum output is obtained in the section of the first and second wobble pits w _A and w _B. . Here, the sampling timings of the respective sample-hold circuits (22), (23), (24) are as shown in FIG. 7C, when the first sample-hold circuit (22) performs sampling servo and sampling servo by the sampling pulse signal p1. The gate is opened over the entire period of the data area S _B , and the second sample hold circuit (23) scans the first wobble pit w _A of the sample servo area S _A by the sampling pulse signal p2 (see FIG. 7A). Beam spot of b ₂
The gate is opened, and the third sample hold circuit (24) scans the second wobble pit w _B of the sample servo area S _A by the sampling pulse signal p3 (when the beam spot b _{3 in} FIG. 7A is reached). ) Open the gate. In this way, the sample and hold circuits (22), (23),
The output signal of the first sample and hold circuit (22) is sampled by the (24), and the differential amplifier (7) outputs the signal.
Becomes a tracking error signal in the section of the sample servo and the data area S _B via the differential amplifier (7) and the output signal of the second sample hold circuit (23)
Wobble pit w _A becomes a tracking error signal during scanning, and the output signal of the third sample-hold circuit (24) becomes a tracking error signal during second wobble pit w _B scanning through the differential amplifier (7). . Therefore, after the output signal of the second sample hold circuit (23) and the output signal of the third sample hold circuit (24) are added by the second adder circuit (25), the 1/2 voltage divider (26 By dividing the voltage by 1/2, the average value of both output signals can be taken, and by taking this average value, the signal shows the true center t _C of the track. Then, when the beam spot is scanning the center t _{C of} each track, this 1/2 voltage divider (2
The output signal of 6) and the output signal of the first sample hold circuit (22) are in opposite phase, and both output signals are subtracted by the subtraction circuit (2
The signal subtracted by 0) becomes 0, and a subtraction signal indicating that tracking is achieved is supplied to the output terminal (8). Further, when scanning is performed with a shift in the radial direction from the center t _C, a tracking error signal corresponding to the shift is supplied to the output terminal (8).

Next, the fact that the tracking error signal obtained at the output terminal (8) has no DC fluctuation will be described using mathematical expressions.

First, the tracking error signal TE1 output from the first sample-hold circuit (22), the tracking error signal TE2 output from the second sample-hold circuit (23), and the tracking error signal output from the third sample-hold circuit (24). The signal TE3 is expressed by the following equation.

Therefore, the output signal of the subtraction circuit (20), that is, the tracking error signal TE obtained at the output terminal (8) is expressed by the following equation.

From this equation, it can be seen that the tracking error signal obtained at the output terminal (8) in FIG. 6 does not include the DC fluctuation component even if ΔQ ≠ 0.

By thus obtaining the tracking error signal that does not include the DC fluctuation component, it is possible to record or reproduce data while performing good tracking as in the first embodiment.

Note that the above embodiment, although a land l sample servo and data area S _B and the data recording section, of the also in the second embodiment, as shown in FIG. 9, sample servo and data areas S _B Puri The groove g may be used as the data recording section. In this case, for example, a clock pit c is provided in the sample servo area S _A continuously with the pre-groove g,
The scanning with the beam spot may be performed centering on the pre-groove g. It can be easily understood that the same action and effect as those of the above-described embodiment can be obtained in this case as well.

Furthermore, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

H Effect of the Invention According to the optical disk device of the present invention, a perfect tracking error signal can always be obtained even if there is a skew of the disk, fluctuations in the position of the lens, and the like. It is a benefit that can be recorded or played back.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the optical disk device of the present invention, FIGS. 2 to 5 are diagrams for explaining the example of FIG. 1, and FIG. 6 is a second embodiment of the present invention. FIG. 7 is a block diagram showing the configuration, FIG. 7 to FIG. 9 are diagrams for explaining the example of FIG. 6, and FIG.
FIG. 14 is a diagram for explaining a conventional tracking control device, FIG. 15 is a configuration diagram showing an example of a conventional tracking control device, and FIGS. 16 to 18 are for explaining the example of FIG. 15, respectively. It is a diagram. (1) is a semiconductor laser device, (3) is a beam splitter, (4) is a lens, (5) is an optical disk, and (6) is 2
The split photodetectors (6A) and (6B) are photodetection units, respectively.

Claims (1)

[Claims] 1. A data recording area sandwiched between a first pregroup and a second pregroup formed at a predetermined distance from the first pregroup in the tracking direction, and the first pregroup. An optical disk device for recording or reproducing an optical disk having a sample servo area composed of a wobble pit provided between the optical disk and the second pre-group, the reflected light of the light irradiated on the optical disk. Detecting means divided into two in the track direction, adding means for adding each detected output of the detecting means to generate a reproduction signal, and subtracting for subtracting each detected output of the two divided detecting means. Means and the first sampling pulse corresponding to the data area and the sample servo area corresponding to the data area based on the addition output from the adding means. A second sampling pulse that is generated and timing generating means that is generated, first subtraction means that samples and holds the subtraction result by the first sampling pulse, and second subtraction result that is obtained by the subtraction means. Second sample and hold means for sampling and holding with the sampling pulse of, and second output for outputting the subtraction result as a tracking error signal by subtracting the output signals from the first sample and hold means and the second sample and hold means. An optical disk device comprising: