JPH11161987A - Skew detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a skew detector of an optical disk device capable of detecting an exact skew amount even when the disk is a rewritable optical disk by the simple constitution. SOLUTION: This skew detector 33 includes a variation amount detecting means 34 for detecting the varying amount of a skewing amount for the moving distance of an optical pickup from a difference signal Sd from the divided light receiving part of a skew sensor, a comparing means 35 for comparing the varying amount detected by the variation amount detecting means 34 with a reference value, an integrating means 36 for integrating the varying amount and outputting it as a compensated skew amount only when the varying amount is equal to or below the reference value based on the compared result of the comparing means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for recording or reproducing data on or from an optical disk, and more particularly to an optical disk skew detecting apparatus.

[0002]

2. Description of the Related Art Conventionally, an optical pickup for reproducing an optical disk is constructed, for example, as shown in FIG. FIG.
, The optical pickup 1 comprises a lens holder 3 having an objective lens 2 attached to a tip thereof, and a fixing portion 4 for supporting the lens holder 3 movably in two axial directions.
And a biaxial base 5 to which the fixing part 4 is attached, and a driving means (not shown) for driving the lens holder 3 in biaxial directions.
It is composed of

Here, the lens holder 3 is, for example, provided by two pairs of elastic support members 6 having one end fixed to both sides of the lens holder 3 and the other end fixed to the fixing portion 4.
It is supported so as to be movable in two directions perpendicular to the fixed part 4, that is, in a tracking direction perpendicular to the paper surface and a focusing direction indicated by reference symbol Fcs. Also, the objective lens 2
A light beam from a light emitting unit (not shown) is focused on a signal recording surface of the optical disk, and return light from the optical disk 7 is imaged as a spot on a light receiving surface of a photodetector via an optical system (not shown).

Thus, based on the detection signal from the photodetector, a reproduction signal of the optical disk is detected, and a tracking error signal and a focus error signal are detected. Thus, the driving of the driving unit is controlled based on the tracking error signal and the focus error signal.

[0005] The optical pickup 1 configured as described above.
According to the above, the lens holder 3 is moved in the tracking direction and the focusing direction Fcs by being externally driven and controlled by the driving means by the tracking servo and the focus servo as described above. Thus, the objective lens 2 attached to the lens holder 3 is appropriately moved in the focusing direction and the tracking direction. As a result, the return light from the optical disk accurately forms a spot on the light receiving surface of the photodetector, and a reproduction signal of the optical disk is detected based on the detection signal from the photodetector.

[0006] In recent years, the density of optical discs has been increasing in recent years, for example, for recording image information and for storing huge data. When reproducing high-density optical discs, conventional optical discs are ignored. Radial skew of the resulting optical disk has become a problem in terms of reliability of the detection signal and securing of a system margin.

Therefore, as shown in FIG. 8, for example, by mounting a skew sensor 8 for detecting skew on the two-axis base 5, the skew is detected by the skew sensor 8. As shown in FIG. 9, the skew sensor 8 includes an LED (light emitting diode) 8a as a light emitting element and a photodetector 8b as a light receiving element. As shown in FIG. 10, the photodetector 8b includes two light receiving sections A and B divided in the radial direction of the optical disk 7.

Accordingly, the light emitted from the LED 8a is reflected on the optical disk and enters the photodetector 8b, so that the reflected light spot from the optical disk 7 can be detected when the optical disk 7 has no radial skew. Table 8
It falls on the dividing line b, but if there is a radial skew, it deviates from this dividing line. Accordingly, the difference signal Sd (Sd) between the output signals of the light receiving portions A and B divided into two parts of the photodetector 8b.
By taking d = SA-SB), the radial skew of the optical disk 7 is detected. The difference signal Sd is, for example, a sum signal S, which is the total output signal of the two light receiving units, so as not to fluctuate due to the reflectance of the optical disk 7.
By dividing by (S = SA + SB), normalization is performed.

[0009]

By the way, rewritable optical disks have recently been widely used as optical disks. However, in such rewritable optical disks, when unrecorded, the surface of the optical disk is not used. Is substantially constant, the sum signal S1 of the photodetector 8b is substantially constant and the difference signal Sd1 changes slowly as shown in FIG.

On the other hand, when there is a recorded portion on a part of the optical disk, the reflectance of the recorded portion becomes smaller than the reflectance of the unrecorded portion.
As shown in FIG. 2, the sum signal S2 of the photodetector 8b drops and the difference signal Sd2 also changes greatly (this large change is called an offset). This is so that when moving from the unrecorded portion to the recorded portion or from the recorded portion to the unrecorded portion, the return light from the optical disc 7 is incident on the photodetector 8b divided in the radial direction of the optical disc. Because it is.

Therefore, the difference signal Sd between the case where there is no recording portion shown in FIG. 11 and the case where there is a recording portion shown in FIG.
13 is superimposed and compared as shown in FIG.
It can be seen that the offset of the difference signal Sd2 is due to the traversal from the unrecorded portion to the recorded portion or from the recorded portion to the unrecorded portion. Thus, in the case of a rewritable optical disc, when an unrecorded portion and a recorded portion are mixed,
During the traversal from the unrecorded portion to the recorded portion or from the recorded portion to the unrecorded portion, the output signal of the skew sensor causes a large offset. Therefore,
There is a problem that an error occurs in the detection of the skew amount, and the accurate skew amount cannot be detected. Also, when there is a flaw, dust, or the like on the optical disc, the difference signal Sd1 greatly fluctuates as shown in the vicinity of the center in FIG. 11, and similarly, an error occurs in the detection of the skew amount. .

The present invention has been made in view of the above points, and has a simple structure so that an accurate skew amount can be detected even in the case of a rewritable optical disk, or even if there is a scratch or dust on the optical disk. An object of the present invention is to provide a skew detection device for an optical disk device.

[0013]

According to the present invention, there is provided an optical pickup for irradiating an optical disk with light through a light focusing means and detecting return light from a signal recording surface of the optical disk. On the other hand, the skew sensor includes a skew sensor that is fixedly arranged and detects the inclination of the optical disc. The skew sensor includes a light emitting unit that irradiates light to the surface of the optical disc, and a skew sensor that detects reflected light from the optical disc. A light detector comprising a divided light receiving unit, based on a difference signal between the two divided light receiving unit, configured to detect the skew amount of the optical disk,
Further, a fluctuation amount detecting means for detecting a fluctuation amount of the skew amount with respect to the movement distance of the optical pickup from the difference signal of the skew sensor, and a fluctuation amount detected by the fluctuation amount detecting means, a predetermined reference value and A skew detection device comprising: a comparing unit for comparing, and an integrating unit that integrates the amount of variation and outputs the corrected amount as a corrected skew amount only when the amount of variation is equal to or less than a reference value based on a comparison result of the comparing unit. Is achieved by

According to the above arrangement, the fluctuation detecting means detects the fluctuation of the skew based on the skew detected by the skew sensor, and when the fluctuation is equal to or smaller than the reference value, the integrating means detects the fluctuation. By accumulating the fluctuation amount, the output is output as a correction skew amount. On the other hand, when the variation exceeds the reference value, the integrating means does not perform the integration of the variation and holds the corrected skew amount integrated up to that time.

Therefore, for example, in the case of a rewritable optical disk, the above-mentioned fluctuation amount is reduced when traversing from an unrecorded portion to a recorded portion or traversing from a recorded portion to an unrecorded portion due to a decrease in the reflectance at the recorded portion. When the value suddenly increases, the integrating means holds the integrated skew amount without performing the integration of the fluctuation amount. In addition, since the fluctuation amount is equal to or less than the reference value in the unrecorded portion or the recorded portion, the integrating means obtains a new correction skew amount by integrating the fluctuation amount.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows an embodiment of an optical disk device incorporating a skew detecting device according to an embodiment of the present invention. In FIG. 1, an optical disk device 10 includes a spindle motor 12 as a driving unit that rotationally drives an optical disk 11, and an optical pickup 13. Here, the spindle motor 12 is driven and controlled by the optical disk drive controller 14, and is rotated at a predetermined rotation speed. The optical disc 11 can select and reproduce a plurality of types of optical discs.

The optical pickup 13 irradiates the signal recording surface of the rotating optical disk 11 with light to record a signal or to detect return light from the signal recording surface. A reproduced signal based on the return light is output to the signal demodulator 15.

As a result, the recording signal demodulated by the signal demodulator 15 is subjected to error correction through an error correction circuit 16, and is transmitted to an external computer or the like via an interface 17. With this, the external computer etc.
A signal recorded on the optical disk 11 can be received as a reproduction signal.

The optical pickup 13 is connected to a head access control section 18 for moving the optical pickup 13 to a predetermined recording track on the optical disk 11 by a track jump or the like. Further, at the moved predetermined position, a biaxial actuator that holds an objective lens as a light focusing unit of the optical pickup 13 is provided.
A servo circuit 19 for moving the objective lens in the focusing direction and the tracking direction is connected.

FIG. 2 shows a configuration example of the optical pickup 13. In FIG. 2, the optical pickup 13
A lens holder 22 having an objective lens 21 as a light focusing means attached to the tip thereof;
Fixing part 23 supporting movably in two axial directions
And a biaxial base 24 to which the fixing portion 23 is attached, a driving unit (not shown) for driving the lens holder 22 in the biaxial directions, and a skew sensor 30.

Here, the lens holder 22 is, for example,
Two directions perpendicular to the fixed part 23, that is, a tracking direction perpendicular to the paper surface, by two pairs of elastic support members 25 having one end on both sides of the lens holder 22 and the other end fixed to the fixed part 23. And is supported so as to be movable in a focusing direction indicated by reference symbol Fcs. The objective lens 21 condenses a light beam from a light emitting unit (not shown) on a signal recording surface of the optical disk, and returns light from the optical disk 11 to a light receiving surface of a photodetector via an optical system (not shown). To form an image as a spot.

Thus, based on the detection signal from the photodetector, a reproduction signal of the optical disk is detected, and a tracking error signal and a focus error signal are detected. Thus, the tracking servo and the focus servo are performed by the driving unit based on the tracking error signal and the focus error signal.

Further, a skew sensor 30 for detecting a radial skew amount of the optical disk 11 is provided on the optical pickup 13. The skew sensor 30 has the same configuration as the skew sensor 8 in the conventional optical pickup 1 shown in FIG.
As shown in FIG. 3, the light-receiving element is composed of an LED 31 as a light-emitting element and a photodetector 32 as a light-receiving element divided into two parts in the radial direction of the optical disk 11, and outputs from the respective light-receiving portions A and B of the photodetector 32. The skew amount of the optical disk 11 is generated by a skew detection device according to an embodiment of the present invention described later based on the signal difference signal.

FIG. 5 shows the configuration of the skew detecting device. In FIG. 5, the skew detecting device 33 includes a fluctuation detecting circuit 34 as fluctuation detecting means, a comparing circuit 35 as comparing means, and an integrating circuit 36 as integrating means. The fluctuation amount detection circuit 34 detects the difference signal Sd between the output signals Sa and Sb from the light receiving portions A and B of the photodetector 32 of the skew sensor 30 as the optical pickup 13 moves in the radial direction of the optical disk 11. Is input, the amount of change in the difference signal Sd with respect to the moving distance of the optical pickup 13 in the radial direction is detected.

The comparison circuit 35 includes a variation detection circuit 34
Is compared with a reference value set in advance, and when the variation is smaller than the reference value, an integration command is output to the integration circuit 36. Note that the reference value is set in advance based on measurement so as to sufficiently cover a normal fluctuation amount of the skew amount. The integration circuit 36 integrates the variation from the variation detection circuit 34 based on the integration command from the comparison circuit 35, and does not integrate the variation when there is no integration command from the comparison circuit 35. It is configured to hold the integrated value. The fluctuation amount detecting circuit 34 as the fluctuation amount detecting means, the comparing circuit 35 as the comparing means, and the integrating circuit 36 as the integrating means are constituted by predetermined software which performs the same functions, for example, mainly using a CPU. May be.

The optical disk device 10 according to the present embodiment
The skew detection signal is configured as described above, and is detected as follows. First, when an optical disk is loaded into the optical disk device 10, the optical disk device 10 performs the first disk tilt adjustment by adjusting to a position where the jitter of the reproduction signal becomes the best without using the skew sensor 30.

Using the position at this time as the origin, the skew detecting device 33 detects the moving distance of the optical pickup 13 in the radial direction of the optical disk 11 in step ST1, and detects the skew sensor 30 in step ST2. Skew measurement is performed based on the output signal of the photodetector 30. That is, the skew detection device 33 obtains the above-described difference signal Sd by an arithmetic circuit (not shown).
Next, in step ST3, the skew detecting device 33
The fluctuation amount detection circuit 34 detects a fluctuation amount ΔSd of the difference signal Sd with respect to the moving distance of the optical pickup 13.

Then, in step ST4, the skew detecting device 33 uses the comparison circuit 35 to detect the variation Δ
Sd is compared with Sd0, which is a reference value. Here, when the variation ΔSd does not exceed the reference value Sd0, the comparison circuit 35 outputs an integration command to the integration circuit 36, and the integration circuit 36 determines in step ST5 based on the integration command. , The variation ΔSd is integrated. On the other hand, the variation ΔS
When d exceeds the reference value Sd0, the comparison circuit 35 does not output the integration command. Thus, the integrating circuit 36 does not perform the integration of the variation ΔSd in step ST6, and retains the integrated value up to that time. Thus, in step ST7, the integrating circuit 36 outputs the obtained integrated value as a correction skew amount. As shown in FIG. 7, the correction skew amount obtained by the skew detection device 33 is more accurately detected without abrupt fluctuation even when a rewritable optical disk has a recording portion. Will be.

The correction skew amount thus obtained is input as a skew error signal to a driver for driving a radial skew adjustment mechanism, so that the radial skew is adjusted so as to cancel the radial skew. The mechanism will be controlled appropriately.

In this case, when the skew amount changes slowly, since the above-mentioned fluctuation amount is smaller than the reference value, the fluctuation amount is integrated by the integrating circuit 36. When the skew amount fluctuates greatly, for example, when there is a crossing between the portion and the unrecorded portion, or when a scratch, dust, or the like is attached, the integrating circuit 3
6 is not performed, and the previous integrated value is held. Then, when the fluctuation amount becomes smaller again, the accumulation of the fluctuation amount by the integrating circuit 36 is restarted.

Thus, instead of ignoring a portion where the reflectivity drops, such as a recorded portion of a rewritable optical disk, only an area where the amount of change at the boundary between a recorded portion and an unrecorded portion greatly changes is ignored. Then, in an area where the amount of variation is small in the recording portion, the radial skew amount is detected with high accuracy by integrating the amount of variation by the integrating circuit 36.

In particular, when an unrecorded portion sequentially changes to a recorded portion, such as when writing on a rewritable optical disk, the skew sensor 30 always generates a skew at the boundary area between the unrecorded portion and the recorded portion. Since the measurement is performed, the skew detection device 33 detects the radial skew amount more accurately than the conventional skew detection. Also, the optical disk 1
If there is a scratch, dust or fingerprints on the surface of 1, an accurate amount of skew will be detected even if the amount of change in the amount of skew changes abruptly.

In the above embodiment, the skew sensor 30 is configured to detect the radial skew of the optical disk 11. However, the present invention is not limited to this. It is obvious that the present invention can be applied. In this case, if the surface of the optical disc is scratched or dust or fingerprints are attached, the tangential skew is detected with higher accuracy.

[0035]

As described above, according to the present invention, an accurate skew amount can be detected with a simple structure even in the case of a rewritable optical disk, or even if the optical disk has scratches or dust. Thus, it is possible to provide a skew detection device for an optical disk device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical disc device incorporating an optical pickup provided with a skew detection device according to the present invention.

FIG. 2 is a schematic side view showing a configuration of an optical pickup in the optical disk device of FIG.

FIG. 3 is a schematic perspective view showing a configuration of a skew sensor in the optical pickup of FIG.

FIG. 4 is a schematic plan view showing a configuration of a photodetector of the skew sensor of FIG.

FIG. 5 is a block diagram showing a configuration of an embodiment of a skew detection device in the optical pickup of FIG. 2;

FIG. 6 is a flowchart illustrating an operation of the skew detection device of FIG. 5;

7 is a graph showing a skew detection signal of a rewritable optical disk by the skew detection device of FIG.

FIG. 8 is a schematic sectional view showing an example of a conventional optical pickup.

9 is a schematic perspective view showing a configuration of a skew sensor in the optical pickup of FIG.

FIG. 10 is a schematic plan view showing a configuration of a photodetector of the skew sensor of FIG.

FIG. 11 is a graph showing a skew detection signal in an unrecorded portion of a rewritable optical disk by a conventional skew detection device.

FIG. 12 is a graph showing a skew detection signal in a recording portion of a rewritable optical disk by a conventional skew detection device.

FIG. 13 is a graph showing the skew detection signals of FIGS. 11 and 12 in an overlapping manner.

[Brief description of reference numerals]

10 optical disk device, 11 optical disk, 1
2 ... Spindle motor, 13 ... Optical pickup, 14 ... Optical disk drive controller, 15
... Signal demodulator, 16 ... Error correction circuit, 17 ...
Interface, 18 Head access control unit, 19 Servo circuit, 21 Objective lens, 2
2 ... Lens holder, 23 ... Fixed part, 24 ...
· Biaxial base, 25 ··· Elastic support member, 30 ··· Skew sensor, 31 ··· LED, 32 ··· Photodetector, 33 ··· Skew detector, 34 ··· Fluctuation detection circuit , 35 ... comparison circuit, 36 ... accumulator circuit.

Claims (2)

[Claims] 1. An optical disc, which is irradiated with light through an optical focusing means and detects return light from a signal recording surface from the optical disc, and is fixedly disposed to detect an inclination of the optical disc. The skew sensor includes a light emitting unit that irradiates light to the surface of the optical disc, and a photodetector that includes a light receiving unit that is divided into two to detect reflected light from the optical disc. hand,
A skew amount of the optical disc is detected based on the difference signal between the light receiving portions divided into two, and a variation amount of the skew amount with respect to the moving distance of the optical pickup is determined from the difference signal of the skew sensor. A fluctuation amount detecting means for detecting the fluctuation amount, a comparing means for comparing the fluctuation amount detected by the fluctuation amount detecting means with a predetermined reference value, and a fluctuation amount equal to or less than a reference value based on a comparison result of the comparing means. A skew detection device comprising: an integration unit that integrates the variation amount and outputs the corrected amount as a corrected skew amount only when. 2. An optical pickup for irradiating an optical disk with light through a light focusing means and detecting return light from a signal recording surface from the optical disk, and supporting the light focusing means movably in two axial directions. A two-axis actuator, a signal processing circuit that generates a reproduction signal based on a detection signal from the optical pickup, and a servo circuit that moves the light focusing unit in two-axis directions based on the detection signal from the optical pickup. A skew sensor fixedly arranged with respect to the optical pickup and detecting a tilt of the optical disk, wherein the skew sensor irradiates the surface of the optical disk with light, and detects reflected light from the optical disk. And a photodetector comprising a light receiving unit divided into two,
A skew amount of the optical disc is detected based on the difference signal between the light receiving portions divided into two, and a variation amount of the skew amount with respect to the moving distance of the optical pickup is determined from the difference signal of the skew sensor. A fluctuation amount detecting means for detecting the fluctuation amount, a comparing means for comparing the fluctuation amount detected by the fluctuation amount detecting means with a predetermined reference value, and a fluctuation amount equal to or less than a reference value based on a comparison result of the comparing means. An optical disc device comprising an integrating means for integrating the variation and outputting the corrected skew only when.