JPH1131330A - Method for positioning light spot on optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform precise tracking in an optical disk device recording information on a groove part and an inter-groove part. SOLUTION: The tracking is performed using that a light quantity of reflected light is reduced when a light spot 31 is placed on a boundary between the groove part 60 and the inter-groove part 63. That is, the tracking is performed so that the intensity of the reflected light becomes maximum. Specifically, methods of three kinds of (1) the reflected light intensity of sub-spots shifted to left/right from a center of a track are compared, (2) a medium that the groove part and the inter-groove part are wobbled to left/right beforehand to be formed is used and (3) the light spot is wobbled so that the light spot is shifted to left/right delicately from the track center are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for positioning a light spot at a desired position on an optical information recording medium. Particularly, a light spot positioning method suitable for reproducing information from an optical information recording medium having information tracks in both the groove portion and the inter-groove portion using light having a wavelength approximately four times the optical depth of the groove. About.

[0002]

2. Description of the Related Art The prior art is disclosed in, for example,
No. 0330. In this example, as a recording medium, an optical recording medium having a groove portion and an inter-groove portion on a substrate and having an information recording area in both the groove portion and the inter-groove portion is used. Further, pre-pits are arranged as identification information of recording units (sectors) on a virtual extension line at the boundary between the groove and the groove. As a result, the recording information is recorded in both the groove portion and the inter-groove portion, and the identification (address) information indicating the recording area is recorded by the pre-pit, and one pre-pit is formed by a pair of the groove portion and the inter-groove portion. Is shared as address information.

[0003] When this method is applied to, for example, a phase change recording medium or a magneto-optical recording medium, information of an adjacent inter-groove portion or inter-groove portion is mixed in a groove portion due to an interference effect in a light spot. Since there is no longer any crosstalk (no crosstalk), there is a feature that the track can be narrowed and high-density recording becomes possible.

[0004] Such an effect of reducing crosstalk is as follows.
For example, as disclosed in Japanese Patent Application Laid-Open No. 5-282705, the optical depth of the groove is set to about 1/5 to 1/7 of the light wavelength.
It is known that it becomes remarkable when it is used.

On the other hand, as a method of positioning a light spot with respect to a medium, for example, Japanese Patent Application Laid-Open No.
A push-pull tracking method utilizing diffraction of light by a groove portion as disclosed in Japanese Patent Publication No. 34-34 is used.
As is well known, the push-pull tracking method is a method of detecting light reflected and diffracted by a guide groove on an optical disc and forming a tracking error signal from the distribution. In push-pull tracking, the largest tracking error signal can be obtained when the optical depth of the groove is about 1/8 wavelength, and control can be performed stably. JP-A-63-6
In the example of JP-A-6734, the polarity of the tracking error signal is switched between when the light spot follows the groove information track and when the light spot follows the inter-groove information track.

[0006]

However, an optical information recording medium having information tracks in both the groove and the inter-groove as described above will be reproduced with light having a wavelength shorter than the wavelength at which the crosstalk reduction effect can be obtained. Then, for short wavelength light, the optical depth of the groove may be about １ ／ of the light wavelength. The optical depth of the groove is 1/4 for the reproduction light
In this case, there is a problem that the tracking signal by the push-pull becomes almost zero and the light spot cannot be positioned.

FIG. 6 illustrates this problem. That is, when light having a length of five times or more the optical depth of the groove is used as the push-pull tracking signal, a sufficient push-pull signal can be obtained. However, when the wavelength is about four times the optical depth of the groove, the phase difference between the light reflected and diffracted at each of the groove and the inter-groove becomes π.
There is almost no tracking error signal (push-pull signal). Further, since the signal polarity is inverted due to a slight difference in wavelength or groove depth, substantially stable tracking cannot be performed.

For example, as shown in the example of FIG. 6, a medium designed with a red laser (wavelength: 600 to 700 nm) and an optical depth of a groove to be about １ ／ wavelength is replaced with a blue laser (wavelength: 400 to 500 nm).
This problem occurs, for example, when playback is performed in step m). Such a problem, with the shortening of the laser wavelength intended for high-density recording, a medium with a groove depth corresponding to the conventional red laser,
It becomes apparent when reproducing with a new blue laser.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a medium having an information recording track in a groove and a space between grooves.
It is to operate stably even when using light whose light wavelength is about four times the optical depth of the groove. It is another object of the present invention to provide a method of positioning a light spot on an information track without special switching operation for both the groove information track and the inter-groove information track.

[0010]

According to the present invention, the following means are used in order to achieve the above object.

(1) An optical information recording medium having a substantially spiral or concentric information track composed of both a groove portion and a groove portion interposed between the groove portions is formed on a disk-shaped substrate, and light is irradiated on the medium. When a light spot is formed by condensing light, the position of the light spot is adjusted so that the peak intensity or the average intensity of the reflected light of the light is maximized, so that the light spot follows the information track.

At this time, when light having a wavelength four times the optical depth of the groove is used, the positional relationship between the track and the spot can be detected most effectively.

Thus, even when light having a wavelength approximately four times the optical depth of the groove is used, the position of the light spot can always be positioned at the center of the information track in the groove or in the space between the grooves. Further, at this time, it is possible to position the light spot at the center of the information track without particularly switching the polarity of positioning with respect to the groove portion and the groove portion.

This is because when the light spot is located between the groove and the groove, the phase difference between the reflected light from the groove and the groove becomes 180 degrees, so that the intensity of the reflected light decreases.
Conversely, when the light spot is located at the center of the groove or the space between the grooves, the property of increasing the intensity of the reflected light is used. This change in the intensity of the reflected light appears most remarkably when the optical depth of the groove is about １ ／ of the light wavelength.

At this time, it is preferable to detect peak intensity, bottom intensity or average intensity as the reflected light.
When the peak intensity or bottom intensity of light is detected, the influence of the change in the intensity of the reflected light due to the recorded information can be removed. Suitable for recording information. On the other hand, in the case of magneto-optical recording and the like, since the intensity of reflected light does not change, it is preferable to detect the average intensity of light and improve the quality of the detection signal. More desirably, the peak intensity or the bottom intensity of the reflected light is smoothed with an appropriate time constant, and the reflected light intensity is preferably used. At this time, the appropriate time constant is preferably set to a frequency sufficiently lower than the information recording frequency and higher than the frequency band for following the light spot.

In the present invention, it is preferable to record and reproduce information on both the groove and the groove. Therefore, the relationship between the groove width, the width of the groove and the size of the light spot is determined by the light spot. The light intensity is 1 / (e (e *
The light spot can be most stably positioned when the diameter of e)) is substantially equal to or smaller than the width of the groove and the space between the grooves.

In the case of a Gaussian spot, the diameter W of the portion having an intensity of 1 / (e * e) of the center intensity is equal to the light wavelength λ and NA.
Satisfies the relationship W = kλ / NA. Here, k is a coefficient that depends on the intensity distribution of incident light on the lens, and is usually 0.8 to 0.9. Therefore, for example, when an optical lens with NA = 0.6 is used with light having a wavelength of 500 nm, the light spot diameter becomes 0.65 μm to 0.75 μm, which is 0.75 μm which is the track width of the recording medium for red laser. It is almost the same or smaller than micron.

(2) As means for adjusting the position of the light spot so that the peak intensity, the bottom intensity, or the average intensity of the reflected light is maximized, in addition to the light spot, the position in the radial direction is substantially ４ of the information track width. Forming a pair of sub-spots displaced from the light spot in opposite directions to each other, detecting the peak intensity or the average intensity of the reflected light from the two sub-spots, respectively, so that the difference between the detected intensities becomes zero. The position of the light spot was adjusted.

Since the reflected light is maximized when the light spot is at the center of the information track, the intensity of the reflected light from the two sub-spots when the two sub-spots are displaced by the same distance from the groove center. Become equal. When the difference between the reflected light from the two sub-spots becomes zero, that is, when the reflected light amounts of the two sub-spots become equal, the light spot is located at the center of the information track, and the intensity of the reflected light becomes maximum. .

In practice, even when the light spot is located between the groove and the inter-groove (boundary), the reflected light from the two sub-spots of the information track is equal. However, in this case, as shown in FIG. 1, the amount of reflected light is the lowest. Further, since the polarity with respect to the displacement of the light spot is different, it is possible to automatically position the light spot only at the center of the information track by controlling the polarity for following the light spot. In other words, the direction in which the tracking error signal changes differs from the direction in which the light spot shifts. For example, in FIG. 1, there is a light spot near the track center, and when the light spot is displaced to the right in the drawing, the tracking error signal increases in the positive direction. When there is a light spot at the track boundary and the light spot is displaced to the right in the drawing, the tracking signal increases in the negative direction. Therefore, the tracking error signal when the light spot is displaced right and left in the vicinity of the center of the track is reversed in polarity, and is fed back to the drive circuit of the light spot (lens), whereby the light spot can always be positioned at the center of the track. .

In this case, the sub-spot does not need to be radially aligned with the light spot in the radial direction, and may be formed so as to be displaced from the light spot in both the radial direction and the direction along the track. By doing so, the light spot and the sub-spot can be prevented from overlapping, and it is easy to separate only the reflected light of the sub-spot from the reflected light of the light spot and detect it.

Also in this case, by detecting the peak, bottom intensity or average intensity as the reflected light of the light, the influence of the change in the intensity of the reflected light due to the recorded information can be removed, and the quality of the detection signal can be reduced. Can be improved. Further, it is more desirable to use a value obtained by smoothing the peak intensity and the bottom intensity of the reflected light with an appropriate time constant as the intensity of the reflected light.

The diameter of the sub spot and the diameter of the main spot may be the same.

(3) It is also preferable to provide at least a diffraction grating or a hologram element in an optical system for forming a light spot as means for forming a pair of sub-spots.

Thus, by the action of the diffraction grating or the hologram element, a sub-spot can be formed from the same light source that forms the light spot. For this reason, it becomes easy to form a sub spot at a position displaced by a certain distance from the light spot.

(4) As another tracking method, the light spot is vibrated so as to be slightly displaced in the radial direction with respect to the information track, and the change in the peak intensity or the average intensity of the reflected light is the same as the vibration. By adjusting the position of the light spot so as to minimize the fluctuation component of the period, the light spot can follow the information track.

At this time, in order to obtain a large tracking signal, the amount of displacement of the light spot must be one quarter of the track width.
It is preferable to increase the vibration amplitude in the range between the two. However, in consideration of the effect on the reproduction signal in practical use, the vibration amplitude is set to an amount at which the light spot can be regarded as being at the center of the track, that is, about 1/8 or less of the track width. Is good.

When the light spot is located at the center of the information track, the amount of reflected light is reduced both when the light spot is displaced radially inward and outward from the information track by vibration. For this reason, when the light spot is located at the center of the information track, the change in the amount of reflected light mainly includes a component having a frequency twice as high as the vibration frequency.
Further, the fluctuation component of the reflected light having the same frequency as the vibration becomes almost zero. Therefore, the light spot can be positioned at the center of the information track by adjusting the position of the light spot so that the fluctuation component having the same cycle as the vibration is minimized.

The vibration of the light spot may be performed using a driving device for positioning the light spot, or may be performed using an acousto-optic device.

The light spot only needs to wobble minutely relative to the information track. That is, the light spot itself does not necessarily have to vibrate, and for example, the information track may be formed by wobbling as described later.

(5) Among the vibrations, the peak intensity, bottom intensity or average intensity of the reflected light of a half cycle in which the light spot is located radially inward relative to the information track, and the light spot is the information track It is also preferable to adjust the position of the light spot so that the difference between the peak intensity, the bottom intensity, or the average intensity of the half-period reflected light located radially outward relative to the target is zero. is there.

This makes it possible to automatically adjust the position of the light spot so as to minimize the fluctuation component having the same period as the vibration.

(6) As an optical information recording medium, a groove portion and an inter-groove portion are formed by being wobbled in a radial direction, and have at least a region formed such that the phase of the wobble is radially aligned with the phase of an adjacent track. It is also possible to adjust the position of the light spot so that the reflected light fluctuation in the same cycle as the wobble is minimized.

This makes it easy to slightly vibrate the light spot relative to the information track. At this time, since the phases of the wobbles are radially aligned in each information track, a high-quality wobble detection signal can be obtained. Further, since the cycle of the wobble signal when the optical disc is rotated at a constant rotation speed becomes substantially constant, the detection of the wobble becomes easy.

(7) It is also desirable to use an information recording medium having identification information or synchronization information in each track.

This makes it possible to easily detect the phase of the wobble, so that the light spot is located at a half cycle in which the light spot is located radially inward relative to the information track, or located in a radially outward position relative to the information track. It can be easily determined whether or not it is a half cycle.

(8) Among the wobbles, the peak intensity, bottom intensity or average intensity of the half-cycle reflected light whose light spot is located radially inward with respect to the information track, and the light spot is the information track The position of the light spot was adjusted so that the difference between the peak intensity, the bottom intensity, or the average intensity of the half-cycle reflected light positioned radially outward relative to the light intensity becomes zero.

This makes it possible to automatically adjust the position of the light spot so as to minimize the fluctuation component having the same period as the wobble.

(9) The period of the wobble is longer than four times the maximum period component determined by the recording code of the information recorded on the optical information recording medium, ie, longer than the period corresponding to eight times the longest mark length. .

This makes it easy to separate the fluctuation in the amount of reflected light synchronized with the wobble from the fluctuation in the amount of reflected light due to the recorded information. That is, separation can be easily performed by using a filter circuit having an appropriate time constant.

It should be noted that detection of information recorded on the medium,
In order to be able to ignore the influence on recording, the frequency of the wobble of the groove or the light spot should be 4 times the maximum period component determined by the recording code of the information recorded on the medium.
One criterion is to make it longer than double.

As another standard, the amplitude of the wobble of the light spot or the swing of the groove may be set to 10% or less of the track width.

As another criterion, the swing of the groove and the amplitude of the wobble of the light spot may be 10% or less of the diameter of the light spot.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 The present invention will be described below in detail with reference to the drawings.

FIG. 3 is a block diagram of the optical information reproducing apparatus of the present invention. In FIG. 3, light 12 emitted from light generation means 21 is shown.
1 is controlled to have a constant intensity by the light intensity control means 171 and is irradiated as reproduction light 122 onto the optical information recording medium 60 through the light condensing means 22 such as a lens or a mirror to form a light spot 31. The reflected light 123 from the light spot 31 is
The light is guided to the light detecting means 27 including a photodiode or the like. The optical head 20 includes a light generation unit 121, a light collection unit 22,
And light detecting means 27 and the like.

The reproduction signal from the light detection means 27 is guided to a reproduction processing means 70 comprising a light spot position shift signal generation circuit 72, a reproduction circuit 71 and the like. The details of the light spot position shift signal generation circuit 72 will be described later. The reproduction circuit 71 sends the composite information 47 such as data identification information and user data on the medium to the central control means 151 including a microcomputer or the like based on the detected reproduction signal 40.

An automatic position control means 512, a motor 511, and the like are provided by the light spot position shift signal 41 generated by the light spot position shift circuit 72 and the command signal 48 generated by the central control means 151 based on the identification information. The light spot scanning means 51 controls the relative positional relationship between the light spot 31 and the medium 60.

Here, as the optical information recording medium 60, a land / groove type recording medium having both the groove portions and the inter-groove portions as information tracks was used. The width of the groove and the space between the grooves is about 0.
The groove is designed to have a depth of about λ / 6 for red laser light of 630 nm to 680 nm at 7 μm. In this example, the depth is about 69 nm because polycarbonate having a refractive index of 1.57 is used as the medium substrate. In the present invention, the medium was reproduced using a blue (430 nm) laser beam. Therefore, the optical depth of the groove is 0.25λ, that is, λ
/ 4.

FIG. 4 shows details of the optical head 20 used in this embodiment. The light emitted from the laser diode which is the light generating means 21 is collimated by a collimator lens 22
1. The light is condensed on the optical information recording medium 60 via the beam splitter 223 and the objective lens 225. In this example, a pair of sub-spots 311 and 312 are formed in addition to the light spot 310 by the diffraction grating 224 inserted into the optical system. This diffraction grating 224 can be replaced with a hologram element or the like.

The three light spots 310 and the sub spots 3
The reflected light from 11, 312 passes through an objective lens 225, a beam splitter 223, and an imaging lens 226, and is guided to photodetectors 270, 271 and 272 corresponding to each spot.

In this case, the size of the light spot is equal to or smaller than the track width. When the light spot 310 is located at the center of the groove or the groove, the sub-spot 311.312 is illuminated so as to span the boundary between the groove and the groove.

FIG. 11 shows the data thus detected.
2 shows a circuit for processing signals corresponding to two sub-spots. 2
The signals corresponding to the two sub spots pass through a preamplifier 722, a peak detection circuit 723, and a
42 and 43, and these two signals become the differential signal 41 by the differential circuit 721. In this example, using the differential signal as a light spot position shift signal, the objective lens 25 is moved by an actuator constituting the automatic position control means 512, and the positions of the light spots 310, 311 and 312 are feedback-controlled.

The principle of obtaining a light spot position shift signal according to this embodiment will be described.

FIG. 1 shows the relationship between the position of the light spot 31 and the amount of reflected light. When the light spot 31 is located at the boundary between the groove 63 and the groove 64 (broken line), the amount of reflected light detected by the detector 27 decreases. This is because the phase difference between the reflected light from the groove portion 63 and the reflected light from the inter-groove portion 64 is about 180 degrees, that is, the phase difference is opposite. Therefore, when the light spot 31 is located exactly in the middle of the groove track 63 or the groove track 64, the amount of reflected light is maximized, and conversely, when the light spot 31 is located at the boundary between the grooves, the reflected light amount is minimized. Therefore, the light spot can be positioned at the center of the groove track 63 or the inter-groove track 64 by adjusting the light spot position so that the amount of reflected light becomes maximum.

In this embodiment, two sub-spots 311 and 312 are used to automatically adjust the position of the light spot. That is, the two sub spots are separated from the main spot 310 in the radial direction (vertical direction of the track) by about 1 /
4, that is, shifted by about 0.175 μm. The directions of displacement of the two spots 311 and 312 from the main spot 310 are opposite to each other.

FIG. 5 shows two staggered portions formed in this manner.
The relationship between the light amount difference between the reflected light amounts of two spots and the track is shown. When the (main) light spot 310 is located exactly at the center of the track, the amount of reflected light obtained from the sub spot
Since the phase between 63 and the reflected light from the inter-groove portion 64 is opposite to each other, the phase is reduced. At this time, if the shift amount of the sub spot from the main spot is set to be the same, these light amount signals should be the same (A and C in FIG. 1). Therefore, when these difference signals are formed, the difference signal becomes zero. Therefore, this difference signal can be used as a light spot position shift signal.

Here, even when the light spot is at the track boundary, the position shift signal is 0. In this example, when the light amount difference (light spot position shift signal) is positive, the light spot is shifted to the left in the figure. When the light spot is moved to the right when the light amount difference is negative, the light spot exists stably only at the center of the track. For this reason, the position of the light spot can be controlled using the light amount difference as a light spot position shift signal.

FIG. 2 shows the relationship between the tracking signal thus obtained and the wavelength of the reproduction light. In principle, the tracking signal according to the present invention has an optical depth of just one groove.
When the wavelength is / 4 wavelength, that is, when the wavelength of the light is four times the depth of the optical groove, it becomes maximum. According to the tracking signal of the present invention, the wavelength of the light is about 5 times the optical groove depth or about 4.times.
Practically good tracking signals are obtained when it is shorter than 5 times. Therefore, according to the present invention, it is possible to stably perform tracking control of an optical spot on an optical information recording medium having a groove having a depth of 1/4 wavelength, which has conventionally been difficult to obtain a tracking signal. .

Here, in this embodiment, a peak detection circuit is used to obtain a detection signal from the photodetector. The reason and effect will be described below.

As shown in FIG. 10, the amount of reflected light varies due to the presence of the recording mark 65. In the lower graph of FIG. 10, the line on the center saw represents the high-frequency signal by the recording mark, and the upper and lower lines show this envelope signal. In this example, a phase-change recording medium in which the amount of reflected light at the recording mark 65 decreases is used as the recording medium. Therefore, the upper envelope signal (thick line) corresponds to the amount of reflected light when no mark exists.

Therefore, in this embodiment, the upper envelope signal is obtained for each detector output by using the peak detection circuit 723 shown in FIG. Thus, a tracking signal can be obtained without being affected by the mark.

In the present invention, in addition to the peak detection circuit 723, a smoothing circuit (low-pass filter) 724 is used in order to remove the influence of minute scratches and dirt to realize stable tracking. Of course, it goes without saying that the effects of the present invention can be obtained without this low-pass filter.

Further, when the recording signal does not include a DC component, the peak detection circuit is not used and the smoothing circuit 724 is used.
It is also possible to use only. For example, when the present invention is applied to a magneto-optical recording medium, since the amount of reflected light hardly changes due to the recording signal, both the peak detection circuit and the smoothing circuit can be omitted. Even in this case, actually, a smoothing effect can be obtained due to the frequency response of an actuator or the like which is a component of the automatic light spot position adjusting mechanism (servo). When using a recording medium that increases the reflectance of the recording mark portion, it is preferable to use a bottom detection circuit instead of the peak detection circuit.

In the embodiment described above, the same tracking signal can be obtained in the groove portion and the inter-groove portion as shown in FIG. Of course, when the shape of the groove and the space between the grooves are different, the tracking signal is slightly different. However, since the polarity of the tracking signal is not inverted between the groove and the groove, tracking can be stably performed between the groove and the groove without changing the control method. In addition, the device configuration becomes easy.

Therefore, in the case of using the medium as in this embodiment, the tracking method of the present invention is effective even when the depth of the groove of the medium is smaller than 1/4 of the optical wavelength. That is, even when a red laser is used, the configuration of the apparatus can be greatly simplified by using the tracking method of this embodiment.

Embodiment 2 Another embodiment of the light spot positioning method of the present invention will be described below.

In this embodiment, the basic configuration of the optical information reproducing apparatus is the same as that of the above-described embodiment, and has the configuration shown in FIG. That is, the light emitted from the light generating means 21
The light intensity control means 171 controls the light intensity at a constant intensity by the light intensity control means 171, and as the reproduction light 122, the light condensing means 22
Irradiates the optical information recording medium 60 through the
Form 31. The reflected light 123 from the light spot 31 is guided to the light detecting means 27 composed of a photodiode or the like through the condensing means 22.

The optical head 20 is composed of the light generating means 121, the light collecting means 22, the light detecting means 27, and the like. The reproduction signal from the light detection unit 27 is guided to a reproduction processing unit 70 including a light spot position shift signal generation circuit 72 and a reproduction circuit 71, which are features of the present invention. The details of the light spot position shift signal generation circuit 72 will be described later.

The reproducing circuit 71 sends composite information such as data identification information and user data on the medium to the central control means 151 comprising a microcomputer or the like based on the detected reproduced signal. A light spot scanning unit 51 including an automatic position control unit 512, a motor 511, and the like, based on a light spot position deviation signal 41 generated by the light spot position deviation circuit 72 and a command signal generated by the central control unit 151 based on the identification information. Controls the relative positional relationship between the light spot 31 and the medium 60. The configuration of the medium, the used light wavelength, and the like are the same as in the above-described embodiment.

Next, in order to detect the displacement of the light spot in this embodiment, the position of the light spot is slightly vibrated in the direction perpendicular to the track without using the diffraction grating as in the above-described example. Was. For this minute vibration, an acousto-optic device provided in the optical head 20 was used. With this acousto-optic element, in the present embodiment, the light spot is set to 0.05 at a frequency of about 100 kHz.
Vibration was performed at an amplitude of μm.

The oscillation amplitude of the light spot is preferably 10% or less of the spot diameter, and more preferably 10% or less of the track width.

FIG. 12 shows a light spot position shift signal generation circuit 72 and its related circuits in this embodiment. The amount of light reflected from the light spot is detected by the photodetector 27, and the detection signal is synchronously detected by the synchronous detection circuit 1200 to obtain a light spot position shift signal and control the automatic position control means. At this time, it is desirable to use an element for compensating for a phase shift between the drive signal of the acousto-optic element and the light detection signal, and then synchronously detect the light detection signal with the drive signal of the acousto-optic element. That is, the oscillation circuit 120 that controls the acousto-optic element 1203
The signal from 1 is phase-compensated by the phase compensation circuit 1202 and input to the synchronous detection circuit 1200.

The signal obtained by such synchronous detection corresponds to a signal obtained by differentiating a signal (FIG. 1) indicating the relationship between the light spot position and the amount of reflected light. That is, a signal having a waveform similar to the waveform shown in FIG. 5 is obtained. Therefore, the light spot can be stably tracked by using the synchronous detection signal in the same manner as in the embodiment.

Also in this embodiment, as described above,
It is desirable to introduce a signal to the synchronous detection circuit after passing the output of the photodetector through the peak hold circuit 723 and the like, since the influence of the recording signal can be removed.

Embodiment 3 FIG. 9 shows the arrangement of tracks and sectors on a recording medium used in an embodiment of the present invention. In the radial direction of the disk-shaped recording medium 60, a plurality of groups 691, 692,
693 are located. The track 63 is wobbled by a minute amount in the radial direction. Each track is divided into a plurality of arc-shaped sectors (recording units) 61 aligned in the radial direction. As the length of the arc-shaped sector 61 becomes substantially constant irrespective of the group, the number of divisions of one peripheral sector is increased as the group is located at a position with a larger radius. As described above, by using the grouped recording media, the density at the inner and outer perimeters can be made substantially constant, and the surface area of the medium can be used effectively. Recording and playback control
The configuration of the device using the medium is simplified.

FIG. 7 shows an example of the arrangement of tracks in one group of the information recording medium of the present invention. About 0.7μm in width,
A groove information track 63 having a depth of about 70 nm and a width of about 0.7 μm
Are arranged alternately. The groove information track 63 and the inter-groove information track 64 are switched by a switching section 65.
Are connected to each other. That is, the groove portion 63 is configured to be connected to the adjacent groove portion 64 after one track round, and the groove portion 64 is configured to be connected to the adjacent groove portion 63 after one track round. Each track is divided into a plurality of arc-shaped recording units 61 such as sectors, and identification information 62 is arranged at the head of each information recording unit 61. In this example, the sector length is about 8-9mm
, Which is equivalent to a user capacity of 2048 bytes. The groove and the space between the grooves are wobbled in the radial direction with an amplitude of about 30 nm. The wobble period was set to 1/232 of the sector length, that is, about 37 μm. The ratio of 1: 232 was selected so that the period of the length (channel bit length) wobble of the recording data would be an integral multiple. That is, in this example, it is configured to be 186 times the recording channel bit length. As described above, by making the wobble cycle an integral multiple of the recording channel bit, it becomes easy to generate a recording clock from the wobble.

The amplitude of the swing is about 10% of the diameter of the light spot,
Alternatively, if the track width is set to 10% or less, the influence on the information signal is small.

Here, it is assumed that the wavelength of the light spot is shorter than 4.5 times the optical depth of the groove. In this embodiment, the depth of the groove is designed to be about λ / 6 with respect to 650 nm red laser light. In this example, the refractive index as the medium substrate
Because of using 1.57 polycarbonate, the depth is about 69
nm. According to the present invention, blue (430n)
m) was reproduced using the laser light. Therefore, the optical depth of the groove is 0.25λ, that is, λ / 4.

FIG. 8 is an enlarged partial plan view of each information identification information portion.

FIG. 8 shows a portion 66 where the tracks before and after the identification information are connected by the groove portion and the inter-groove portion.
In FIG. 8, the identification information is the first position 621 and the second position 622.
Radially aligned at two locations. The front and rear tracks are connected by a groove 63 and a groove 64. In the example of this figure, each piece of identification information corresponds to the recording area of the information track on the right side. Further, the identification information corresponding to the groove information track 63 on the right side of the figure is located at a first position 621, and the identification information corresponding to the inter-groove information track 64 is located at a second position 622. That is, the identification information is arranged such that the position in the direction along the information track is different between adjacent tracks and coincides with the two adjacent tracks.

Therefore, for example, when the light spot 631 scans on the inter-groove portion 64, only one of the pits is always reproduced, and there is no fear that crosstalk from an adjacent track will occur. Therefore, the address information allocated to the pre-pits can be reproduced favorably without crosstalk, and high-density recording can be realized. In this example, the prepit address information is recorded by an 8/16 modulation code (channel bit length: 0.2 μm).
Therefore, the shortest pit length is about 0.6 μm. From the viewpoint of simplification of the recording / reproducing device, it is desirable that the modulation code of the pre-pit portion and the modulation code of the recording portion of the user information be the same. In this embodiment, the modulation code and the recording linear density are the same. is there. Therefore, most of the circuits can be shared.

The identification information can be formed by small pits (pits). In this embodiment, identification information 621 is provided on both sides of a track (land portion or groove portion).
And 622 are evenly arranged, so that the influence on the tracking servo signal is cancelled. Therefore, the track offset can be kept sufficiently small. Further, for example, when the inter-groove portion 64 is reproduced, the first pre-pit portion 62
The address information of the first and second pre-pit sections 622 is reproduced continuously. For this reason, if information is arranged so that address information is obtained by combining the two, the inter-groove 6
4, address (track number) independently of groove section 63,
That is, identification information can be set. That is, by continuously reproducing the address information of the first pre-pit section 621 and the second pre-pit section 622, the land section and the groove section can be identified.

Here, a phase change type recording film (GeSbTe) was used as the recording film. Therefore, the recording mark is formed in the form of an amorphous region.

A method of performing tracking control of a light spot using the optical information recording medium of this embodiment will be described below with reference to FIG.

First, the optical detection signal obtained by the optical detector 27 is passed through a bandpass filter 1300 to extract the frequency component of the wobble and its second harmonic component. In this embodiment, since the relative linear velocity between the medium and the light spot is set to about 6 m / s, the frequency of the wobble is about 160 kHz. The filters may be digital or analog. The intensity of the wobble signal detected in this way is
It becomes 0 when the light spot is located at the center of the groove or the groove track or at the boundary between the groove and the groove. Accordingly, the light spot can be stably tracked by using the wobble detection signal in the same manner as in the above embodiment. At this time, it is necessary to switch the polarity of the tracking control depending on the phase of the wobble, but identification of the recording unit is used for detecting this phase. That is, using the identification information detected by the generation circuit 71, the polarity of the wobble detection signal is switched by the polarity inversion circuit 1302. The detection of the second harmonic component together with the fundamental wave as the wobble signal is performed when the fundamental wave component becomes 0, that is, when the light spot is located at the center of the track, the signal synchronized with the wobble signal is detected. This is for detecting That is, the generation of the timing signal using the wobble uses both the fundamental wave component and the harmonic wave component.

Also in this embodiment, as described above,
It is desirable to introduce a signal to the band-pass filter after passing the output of the photodetector through the peak hold circuit 723 or the like in that the influence of the recording signal can be removed.

When the above-described embodiment is used, the same tracking signal can be obtained in the groove portion and the inter-groove portion. Therefore, as described above, a medium having a structure in which the groove portion and the inter-groove portion are connected to each other is used. However, since the tracking can be stably performed between the groove portion and the inter-groove portion without changing the control method, the device configuration is particularly easy. Therefore, in the case of using the medium as in the present embodiment, the tracking method of the present invention (including the methods of Embodiment 1 and Embodiment 2)
This is effective even when the depth of the groove of the medium is smaller than 1/4 of the optical wavelength. That is, even when a red laser is used, the configuration of the apparatus can be greatly simplified by using the tracking method of this embodiment.

[0088]

According to the present invention, the position of the light spot is always positioned at the center of the information track in the groove or in the space between the grooves, even if light having a wavelength approximately four times the optical depth of the groove is used. Becomes possible. Furthermore, at this time, without switching the polarity of the positioning particularly with respect to the groove portion and the inter-groove portion,
The light spot can be positioned at the center of the information track.

This is because when the light spot is located between the groove and the groove, the phase difference between the light reflected from the groove and the groove becomes 180 degrees, so that the intensity of the reflected light decreases.
Conversely, when the light spot is located at the center of the groove or the space between the grooves, the property of increasing the intensity of the reflected light is used. This change in the intensity of the reflected light appears most remarkably when the optical depth of the groove is about １ ／ of the light wavelength.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating the principle of the present invention.

FIG. 2 is a graph showing a relationship between a tracking signal and a wavelength.

FIG. 3 is a configuration diagram of an apparatus according to the present invention.

FIG. 4 is a configuration diagram of one embodiment of the present invention.

FIG. 5 is a diagram illustrating the principle of an embodiment of the present invention.

FIG. 6 is a graph showing a problem of a conventional light spot positioning method.

FIG. 7 is a plan view of an optical information recording medium used in one embodiment of the present invention.

FIG. 8 is a partial plan view of an optical information recording medium used in one embodiment of the present invention.

FIG. 9 is a plan view of an optical information recording medium used in one embodiment of the present invention.

FIG. 10 is a diagram illustrating the principle of an embodiment of the present invention.

FIG. 11 is a circuit diagram of an embodiment of the present invention.

FIG. 12 is a circuit diagram of one embodiment of the present invention.

FIG. 13 is a circuit diagram of an embodiment of the present invention.

[Explanation of symbols]

 60-groove, 63-groove, 31-light spot.

Claims (27)

[Claims] An optical information recording medium having a substantially spiral or concentric information track composed of both a groove and an inter-groove portion sandwiched between the grooves is formed on a disk-shaped substrate. When a light spot having a wavelength shorter than about 4 times the light is condensed on the medium to form a light spot, the peak intensity, bottom intensity or average intensity of the reflected light of the light is maximized. A light spot positioning method for adjusting a position so that the light spot follows the information track. 2. In addition to said light spot, a pair of sub-spots displaced from said light spot in a direction opposite to each other in a radial direction by about 1/4 of said information track width are formed. The peak intensity, the bottom intensity, or the average intensity of the reflected light from the sub spot is detected, and the position of the light spot is adjusted so that the difference between the detected intensities becomes zero, so that the light spot follows the information track. The light spot positioning method according to claim 1, wherein: 3. The light spot positioning method according to claim 2, wherein at least a diffraction grating or a hologram element is used in the optical system for forming the light spot as the means for forming the pair of sub-spots. . 4. The method according to claim 1, wherein the light spot is slightly vibrated in the radial direction with respect to the information track, and a fluctuation component having the same cycle as the vibration among a change in peak intensity, bottom intensity or average intensity of the reflected light. 2. The method according to claim 1, wherein the position of the light spot is adjusted to be a minimum, and the light spot follows the information track. 5. A peak intensity, a bottom intensity or an average intensity of a half-period reflected light in which the light spot is located radially inward with respect to the information track in the vibration, and the light spot The position of the light spot is adjusted so that the difference between the peak intensity, the bottom intensity or the average intensity of the reflected light of a half cycle located relatively radially outward with respect to the information track becomes zero. The method for positioning a light spot according to claim 4, wherein: 6. The light spot positioning method according to claim 4, wherein the amplitude of the vibration is equal to or less than one tenth of the diameter of the light spot. 7. The optical information recording medium, wherein the groove and the inter-groove are wobbled in a radial direction, and the wobble is radially aligned with a phase of an adjacent track. Wherein at least the position of the light spot is adjusted such that the reflected light fluctuation in the same cycle as the wobble is minimized,
The method for positioning a light spot according to claim 1. 8. The method according to claim 7, wherein the optical information recording medium has at least one piece of identification information or synchronization information in a radial direction. 9. A peak intensity, a bottom intensity, or an average intensity of a half-period reflected light in which the light spot is located radially inward relative to the information track in the wobble; The position of the light spot is adjusted so that the difference between the peak intensity, the bottom intensity or the average intensity of the reflected light of a half cycle located relatively radially outward with respect to the information track becomes zero. The method for positioning a light spot according to claim 7 or 8, wherein: 10. The vibration cycle of the wobble or light spot is longer than four times a maximum cycle component determined by a recording code of information recorded on an optical information recording medium. 10. The method for positioning a light spot according to any one of 10 above. 11. The light spot positioning method according to claim 1, wherein the width of the groove and the width of the space between the grooves are substantially equal. 12. The light spot positioning method according to claim 1, wherein a wavelength of the light is 500 nm or less. 13. The light spot positioning method according to claim 1, wherein the diameter of the light spot is smaller than the width of the groove. 14. The light spot positioning method according to claim 1, wherein the diameter of the light spot is smaller than the width of the gap. 15. The light spot positioning method according to claim 4, wherein the amplitude of the wobble or light spot vibration is smaller than 10% of the diameter of the light spot. 16. An apparatus according to claim 4, wherein the amplitude of said wobble or light spot vibration is smaller than 10% of a track width.
0. The method for positioning a light spot according to any one of [0]. 17. A method for positioning a light spot on an optical information recording medium having information tracks in both a groove and a groove between the grooves, the light spot being positioned and the irradiation position of the light spot Irradiates the optical information recording medium with two sub-light spots displaced by an integral multiple of 1/4 of the width of the groove or the inter-groove portion, and detects reflected light from the two sub-light spots, respectively. Forming a detection signal, forming a difference signal of the detection signal, forming a track shift signal indicating a position shift between the light spot and the information track from the formed difference signal, based on the track shift signal; A light spot positioning method for controlling an irradiation position of the light spot. 18. A method for positioning a light spot on an optical information recording medium having information tracks in both a groove portion and an inter-groove portion sandwiched between the groove portions, wherein the positioned light spot is positioned in the width direction of the information track. Irradiating to oscillate, to detect the reflected light from the light spot to form a detection signal, from the detection signal to detect the fluctuation component of the cycle of the vibration and an integral multiple of the cycle to form an extraction signal, A light spot positioning method for forming a track shift signal indicating a position shift between the light spot and the information track from the extracted signal, and controlling an irradiation position of the light spot based on the track shift signal. 19. A method for positioning a light spot on an optical information recording medium having information tracks in both a groove and a groove between the grooves, wherein the position groove is vibrated in the width direction of the information track. Forming a detection signal by detecting reflected light from the light spot, detecting a variation component having a cycle that is an integral multiple of the cycle of the vibration from the detection signal to form an extraction signal, A light spot positioning method for forming a track shift signal indicating a position shift between the light spot and the information track from the extracted signal, and controlling an irradiation position of the light spot based on the track shift signal. 20. An optical information recording medium having a track constituted by both a groove and a groove interposed between the grooves, wherein light having a wavelength shorter than 4.5 d with respect to the optical depth d of the groove is used. When the light spot is formed by condensing the light spot on the medium, the position of the light spot is adjusted so that one of the peak intensity, the bottom intensity, and the average intensity of the reflected light of the light spot is increased. An optical recording / reproducing method in which the light spot is made to follow the track and information is recorded or reproduced by the light spot. 21. When an optical information recording medium having a track formed by both a groove and a groove interposed between the grooves is used, light of a predetermined wavelength is converged on the medium to form a light spot. In addition to the light spot, a pair of sub-spots which are opposite to each other in the track width direction and are displaced from the light spot by the same amount are formed, and the peak intensity of the reflected light from the two sub-spots, Detecting at least one of the intensity and the average intensity for each sub-spot, adjusting the position of the light spot so that the difference between the detected intensities becomes zero, causing the light spot to follow the track, An optical recording / reproducing method for recording or reproducing information using spots. 22. When an optical information recording medium having a track constituted by both a groove and a groove interposed between the grooves is used, light of a predetermined wavelength is focused on the medium to form a light spot. The light spot is vibrated in the radial direction with respect to the track, and the position of the light spot is changed so that a fluctuation component having the same period as the vibration among the changes in the peak intensity, the bottom intensity and the average intensity of the reflected light is minimized. An optical recording / reproducing method in which a light spot is made to follow the above-mentioned track so that information is recorded or reproduced by the light spot. 23. Among the vibrations, at least one of a peak intensity, a bottom intensity and an average intensity of reflected light of a half cycle of the vibration in which the light spot is located radially inward with respect to the track. The difference between one and at least one of the peak intensity, the bottom intensity, and the average intensity of the reflected light in a half cycle of the vibration in which the light spot is positioned radially outward relative to the track is zero. 21. The optical recording / reproducing method according to claim 19, wherein the position of the light spot is adjusted so as to be as follows. 24. When an optical information recording medium having a track formed by both a groove and a groove interposed between the grooves is used, light of a predetermined wavelength is focused on the medium to form a light spot. The optical information recording medium, wherein the groove portion and the inter-groove portion are formed by being wobbled in the radial direction, and have at least a region formed such that the phase of the wobble is radially aligned with the phase of an adjacent track. A method for adjusting the position of the light spot, wherein the position of the light spot is adjusted so that reflected light fluctuations in the same cycle as the wobble are minimized. 25. A method for positioning a light spot on an optical information recording medium having information tracks in both a groove portion and a groove portion interposed between the groove portions, the light spot being positioned and the irradiation position of the light spot. Irradiates the optical information recording medium with two sub-light spots displaced by an integral multiple of 1/4 of the width of the groove or the inter-groove portion, and detects reflected light from the two sub-light spots, respectively. Forming a detection signal, forming a difference signal of the detection signal, forming a track shift signal indicating a position shift between the light spot and the information track from the formed difference signal, based on the track shift signal; A light spot positioning method for controlling an irradiation position of the light spot. 26. A method for positioning a light spot on an optical information recording medium having information tracks in both a groove and a groove between the grooves, wherein the positioned light spot is positioned in the width direction of the information track. Irradiating to oscillate, to detect the reflected light from the light spot to form a detection signal, from the detection signal to detect the fluctuation component of the cycle of the vibration and an integral multiple of the cycle to form an extraction signal, A light spot positioning method for forming a track shift signal indicating a position shift between the light spot and the information track from the extracted signal, and controlling an irradiation position of the light spot based on the track shift signal. 27. A method of positioning an optical spot on an optical information recording medium having information tracks in both a groove and a groove between the grooves, wherein the position groove is vibrated in the width direction of the information track. Forming a detection signal by detecting reflected light from the light spot, detecting a variation component having a cycle that is an integral multiple of the cycle of the vibration from the detection signal to form an extraction signal, A light spot positioning method for forming a track shift signal indicating a position shift between the light spot and the information track from the extracted signal, and controlling an irradiation position of the light spot based on the track shift signal.