JP3050969B2 - Optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus such as an optical disk and an optical card, and more particularly to an optical recording / reproducing apparatus having improved multi-value recording for improving recording density and data transfer speed. Things.

[0002]

2. Description of the Related Art In conventional optical recording, one bit of information is stored in one bit.
It is expressed by the presence or absence of two recording pits. On the other hand, multi-value recording in which multi-level information is added to one recording area has been proposed. As an example of such multi-value recording,
i) multi-level information by changing the reflectivity stepwise by a phase change type medium or the like; ii) multi-level information by changing the depth and width of pits; iii) multi-level information by using a multilayer film. There are those that record information and make it multi-valued. These represent multi-value information by variously changing the state of one pit.

[0003] As another example, iv) a set of information is converted into a pattern (optical interference, diffraction pattern) of a certain area having a different surface shape and recorded, and is illuminated by a light source during reproduction. In some cases, a set of information is obtained by optical interference from a pattern or a diffraction pattern.

Further, as a similar technique, information of a fixed length is encoded and converted into two or three pit intervals, and a mark set composed of a set of these pits is recorded in the track width direction. There has been proposed a method of reproducing information using optical interference and diffraction patterns obtained by illuminating a set of mark sets with laser light.

[0005] An optical system and a detection system for reproducing information from optical interference and a diffraction pattern by this method will be described. The reflection interference pattern from the recording pits recorded on the disk is guided to a detector by a beam splitter. Then, the peak position of the primary lobe of the interference pattern corresponding to the interval of the recording pitch is obtained by the linear array, and the information is reproduced.

[0006]

By the way, multi-value recording is performed by changing the reflectivity, depth and width of one pit, and the state of the multilayer film in the thickness direction in a stepwise manner. Then, it is difficult to control the above values stepwise,
Multi-value of ~ 4 values is the limit.

The method iV) can be used for a simple system that does not require tracking or focusing servo. However, since the recording area becomes large, it is not suitable for high-density recording.

Further, the method of recording a pit pair in the track width direction can be multivalued in multiple steps, and high density recording can be realized. However, since information is reproduced by detecting an analog optical interference pattern corresponding to the interval between the pit pairs, the pattern is distorted when various disturbances are applied, and high-precision detection cannot be performed. To this end, a correction is made for the disturbance. The main causes of the disturbance include surface runout of the disk, eccentricity, inclination of the pit pair, and the like. As these correction methods, focus servo is applied to the surface deflection, and track servo is applied to the eccentricity.

These servos are performed by causing the objective lens to follow the displacement of the disk. FIG.
When there is no lens shift, the track servo moves the objective lens 3 following the displacement of the disk 2 on which the recording pits 1 are recorded. Then
Since the linear array detector 4 is fixed, the interference pattern 5 is moved on the linear array detector 4 in synchronization with the movement of the objective lens 3. This means that the peak of the primary lobe of the interference pattern 5 to be detected is shifted, and the detection accuracy is reduced.

When the pit pair is tilted, if there is no mark tilt, as shown in FIG. 9, the interference pattern 5 also tilts in the direction of the pit pair tilt, and the position of the primary lobe cannot be accurately detected. Thus, the correction for the inclination of the pit pair is
It was not proposed until now.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it has been found that, with respect to multi-value recording due to a change in the interval between pit pairs in the track width direction, a pattern shift due to an objective lens shift, a pattern inclination due to a pit pair inclination, and the like. It is an object of the present invention to provide an optical recording / reproducing apparatus capable of performing a stable and highly accurate reproduction by correcting external disturbance.

[0012]

That is, according to the present invention, multi-valued information is recorded by writing a plurality of pits arranged substantially in the width direction of a track while changing the intervals according to the information, thereby obtaining a lens. An optical recording / reproducing apparatus that irradiates the plurality of pits with the laser light collected by the laser beam and detects the interference light obtained from the plurality of pits by an array-shaped detector to reproduce information. Means for detecting the amount of movement of the lens, and means for changing the detection start position of the array of detectors according to the amount of movement of the lens detected by the detection means. .

According to the present invention, multi-valued information is recorded by writing a plurality of pits arranged substantially in the width direction of the track while changing the intervals according to the information, and the laser light converged by the lens is written. In an optical recording / reproducing apparatus that irradiates the plurality of pits and detects the interference light obtained from the plurality of pits using an area detector to reproduce information, one of the interference light Means for detecting the inclination of the interference light from the track width direction using all or all of the sections, and means for changing the detected transfer position of the area-like detector according to the inclination of the interference light detected by the detection means And characterized in that:

[0014]

In the optical recording / reproducing apparatus of the present invention, the shift amount and the tilt amount are detected to correct the shift of the interference pattern due to the shift of the objective lens and the tilt of the interference pattern due to the tilt of the pit pair. Try to counter them. In order to electrically cancel the fluctuation of the detection value with respect to disturbance fluctuation, an array sensor or an area sensor capable of addressing and reading is used.
An image sensor such as I, SIT, or CMD is used.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

[0016] In this invention, for a disturbance fluctuation, in order to cancel the variation of the detection value electrically, the addressable readable sensor, not been lifting the amplifying action at the time of reading the MOS type imaging device Since it is vulnerable to blooming, blooming poses a problem in the detection of interference patterns due to a large difference in light amount distribution in the sensor.
An amplifying image sensor such as an MD is used. First, the lens shift correcting means will be described.

As shown in FIG. 2, the interference pattern 5
Is shifted by an amount shifted by the tracking servo with respect to the fixed linear array detector 4. Therefore, in order to detect the shift amount, the movement amount of the objective lens 3 may be measured. As a measuring method, a method in which a capacitance displacement meter is provided in an objective lens actuator system to directly measure a displacement amount, an objective lens 3
That measures the amount of displacement by a current flowing through a coil (not shown) that drives the motor. In the method of measuring from the coil current, the phase is delayed because the objective lens 3 moves mechanically compared to the phase of the drive current. Therefore,
It is necessary to correct the phase.

If the shift amount of the objective lens 3 can be detected, if the transfer start address of the shift register (not shown) of the linear array detector 4 is shifted by the amount corresponding to the shift amount, the interference is caused by the lens shift. Pattern shifts are corrected. Next, the means for correcting the inclination of the interference pattern will be described.

As shown in FIG. 3, in order to correct the inclination of the interference pattern 5, the direction and amount of the inclination may be measured. FIG. 5 is a sectional view of the optical path of the detection light having passed through the beam splitter 6 divided by the beam splitter 7 for detecting the inclination.
This shows a configuration in which an interference pattern is incident on the divided PD 8.

FIG. 6 shows the principle of detecting the inclination by the two-divided PD 8. When there is no inclination ((a) in the figure), the difference signal of the two divisions P8 is zero. on the other hand,
When the pattern is tilted (FIG. 10B), the difference signal of the two-divided PD 8 becomes positive or negative. The direction of the inclination is determined by the sign of the left and right divided PD8, and the amount of the inclination is determined by the magnitude. The inclination correction uses an area sensor instead of a linear sensor.

The difference and the sum of the outputs of the two-divided PD 8 are obtained, and the two are divided. This is performed for normalization because the interference pattern 5 changes depending on the interval between the pit pairs. This output is AD-converted and R for gradient correction is obtained.
Fill in the OM table. The transfer start address of the shift register in the Y direction is determined based on the ROM output. Furthermore,
In synchronization with the transfer clock of the shift register in the X direction, Y
If the transfer address in the direction is designated according to the inclination of the pattern, a detection value obtained by correcting the inclination of the pattern in the area sensor can be obtained.

Next, FIG. 1 shows an entire block of lens shift correction. The tracking drive signal 9 of the lens actuator is supplied to the transfer start address designation ROM 13 of the CMD transfer shift register 12 via the phase correction circuit 10 and the A / D conversion circuit 11. Further, the tracking drive signal 9 is supplied to the objective lens 3 via the coil 15 via the amplifier 14.

FIG. 4 shows a reproducing optical system used in the present invention. In the figure, in the track width direction of the disk 2, 1.5 to 3 μm
A mark set (recording pit) 1 of pits having a diameter of 1 μm and having different intervals in the range is formed. Mark set 1
Λ = 600 to 800 nm via the collimator lens 16
When the light of the semiconductor laser 17 is irradiated, the interference pattern 5
Is reflected and enters the linear array detector 4.

From the photoelectrically converted signal, the peak position of the primary lobe of the interference pattern 5 is obtained by electrical processing.
Demodulate the data. The linear array detector 5 that detects the interference pattern 5 uses a linear sensor for correcting a lens shift. Although any of SIT, AMI, and CMD image sensors may be used, a small unit element is desirable in order to perform high resolution and fine correction of lens shift. Here, a CMD that can easily reduce the element size is used, and 5 μm, 8
A device with 00 elements is used.

Then, an actual shift amount of the lens is obtained by performing phase correction on the tracking drive signal 9 of the lens actuator. This is A / D converted, and the transfer is performed by shifting the transfer start address by the transfer start address designation ROM 13 of the transfer shift register 12. Since the maximum amount of lens shift due to tracking is about ± 30 μm, the use of CMD in units of 5 μm shifts ± 6 element transfer addresses. By performing the above-described correction, the shift of the pattern of ± 30 μm can be suppressed to 5 μm or less.

Next, a second embodiment of the present invention will be described with reference to the entire block diagram of the inclination correction shown in FIG.
The configuration of the optical system is almost the same as that of the first embodiment described above. However, in order to detect the tilt of the pit pair, a part of the detected light beam is split by a beam splitter 7 (not shown) for tilt detection.
The light enters the divided PD 8.

The output of the two-divided PD 8 for detecting inclination is supplied to a divider 20 via operational amplifiers 18 and 19.
The output of the divider 20 is supplied to the A / D conversion circuit 11
Are supplied to the transfer start address and the gradient determination ROM 21 via the. This transfer start address, gradient determination ROM 21
Specifies the addresses of the X-direction shift register 22 and the Y-direction shift register 23 according to the inclination.

In this embodiment, the area sensor 24 is used to correct the inclination. This area sensor 24 is capable of performing XY addressing readout, has a high resolution,
High-speed reading needs to be possible. Here, 5 μm
A CMD area sensor of 800 × 800 elements is used.

The operation of the second embodiment will be described. The direction and amount of inclination are detected by the two-part PD 8 for detecting inclination. The two-divided PD 8 may be provided only on one side. However, when the pattern is shifted and the symmetry is deteriorated, the outputs of the two-divided PD 8 on both sides are averaged to cancel. When the inclination of the pattern is detected, the operational amplifiers 18 and 1
9. The output through the divider 20 is converted to an A / D
Is converted. Further, a transfer start address and a gradient determination ROM
According to 21, the address of the X-direction shift register 22 and the address of the Y-direction shift register 23 are transferred in synchronization with the inclination in order to designate the transfer start address of the CMD area sensor 24.

Here, 800 × 800 in 5 μm units.
Since the element CMD area sensor 24 is used, tan θ =
The inclination is corrected in units of n / 400 (n = 0, 1, 2, 3,...: shift amount of the transfer start address). By performing the above-described correction, the inclination can be changed to tan θ = ± 1/40.
0 = ± 0.14 ° or less, and high-precision detection became possible.

As described above, the deterioration of the detection accuracy due to the shift and the inclination of the interference pattern is electrically corrected on the detector, so that the correction can be performed at higher speed and with higher accuracy than in the case where the detection is performed mechanically. It is possible to reproduce multi-valued recorded information stably.

[0032]

As described above, according to the present invention, for multi-valued recording due to a change in the interval between pit pairs in the track width direction, a pattern shift due to an objective lens shift, a pattern inclination due to a pit pair inclination, and the like are performed. It is possible to provide an optical recording / reproducing device capable of performing a reproduction stably and with high accuracy by correcting disturbance.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the entirety of lens shift correction in a first embodiment of an optical recording / reproducing apparatus according to the present invention.

FIG. 2 is a diagram illustrating correction of a lens shift.

FIG. 3 is a diagram illustrating inclination correction of an interference pattern.

FIG. 4 is a diagram showing a reproducing optical system of the optical recording / reproducing apparatus of the present invention.

FIG. 5 is a schematic diagram showing a configuration in which an interference pattern is incident on a two-segment PD for tilt detection.

FIG. 6 is a diagram illustrating a principle of detecting a tilt by the two-divided PD in FIG. 5;

FIG. 7 is an overall block configuration diagram of tilt correction according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating detection accuracy in the case where there is no conventional lens shift.

FIG. 9 is a diagram for explaining detection accuracy in the case where there is no tilt of a conventional interference pattern.

[Explanation of symbols]

1. Recording pit, 2. Disk, 3. Objective lens, 4.
Linear array detector, 5: interference pattern, 6, 7: beam splitter, 8: split PD, 9: lens actuator tracking drive signal, 12: shift register, 1
3 ... Transfer start address designation ROM, 21 ... Transfer start address, gradient determination ROM, 22 ... X direction shift register,
23 ... Y direction shift register, 24 ... Area sensor.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-169732 (JP, A) JP-A-63-211123 (JP, A) JP-A-63-273218 (JP, A) 141033 (JP, A) JP-A-4-315820 (JP, A) JP-A-63-281227 (JP, A) JP-A-63-281228 (JP, A) (58) Fields investigated (Int. G11B ^7/ 00-7/013 G11B 7/09 G11B 7/13

Claims (4)

(57) [Claims] 1. A multi-value information is recorded by writing a plurality of pits arranged in a substantially width direction of a track while changing an interval thereof according to the information, and the laser beam collected by a lens is written. In an optical recording / reproducing apparatus that irradiates a plurality of pits and detects the interference light obtained from the plurality of pits with an array detector to reproduce information, the amount of movement of the lens is detected. An optical recording / reproducing apparatus comprising: means for changing a detection start position of the array-shaped detector according to a movement amount of a lens detected by the detection means. 2. A multi-value information is recorded by writing a plurality of pits arranged substantially in the width direction of a track while changing the interval according to the information, and the laser light converged by a lens is written to the plurality of pits. In the optical recording and reproducing apparatus for irradiating the pits and detecting the interference light obtained from the plurality of pits using an area detector and reproducing the information, a part or all of the interference light Means for detecting the inclination of the interference light from the track width direction using the method, and means for changing the detection transfer position of the area-like detector according to the inclination of the interference light detected by the detection means. An optical recording and reproducing apparatus. 3. The optical recording / reproducing apparatus according to claim 1, wherein the array-like detector is a charge modulation device (CMD). 4. The optical recording and reproducing apparatus according to claim 2, wherein the area detector is a charge modulation device (CMD).