JP2006172525A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device for saving power consumption, while preventing deterioration in recording/reproducing quality owing to tilt. <P>SOLUTION: The optical disk device comprises: a tilt detecting means 114 for detecting the correlative tilt between an optical pickup 101 and an optical disk; a tilt control means 109 for controlling the tilt, based on the detection result of the tilt detecting means 114; and tilt correcting means 103, 113 for adjusting at least the inclination of an objective lens in response to the output of the tilt control means 109 and correcting the correlative tilt with the optical disk. When a value detected by the tilt detecting means 114 is not more than a prescribed value, the operations of the tilt correcting means 103, 113 are stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus equipped with an optical pickup (PU) for recording / reproducing information and having an information recording medium and a PU tilt correction mechanism, and more particularly to a tilt correction mechanism.

FIG. 18 is a block diagram of a general optical disc apparatus. Although a recording / reproducing optical disc drive will be described, for example, a reproducing optical disc drive in which the recording compensation circuit 2 in FIG. 18 is omitted may be used.
An audio circuit, a modulation / demodulation circuit (image compression / decompression circuit) 1 or an interface for connection with a computer is connected to the signal input / output depending on the purpose of use of the signal. The recording compensation circuit 2 includes circuits such as laser modulation by a recording signal, and the RF signal processing circuit 3 includes circuits such as waveform shaping of a read signal.
The servo 4 detects an error component from the read signal and feeds it back to the optical pickup (PU) 5 or the spindle motor 6 to control the rotation of the focus servo, tracking servo and spindle motor 6.
Further, in addition to this servo system, there may be a tilt servo mechanism for removing the inclination of the recording surface of the optical disc 7 and the optical system of the optical pickup 5. In the information reproducing operation, the information signal recorded on the optical disk (information recording medium or medium) 7 is read by the optical pickup 5 and the signal is input to the RF signal processing circuit 3.
The RF signal processing circuit 3 shapes the waveform of the input signal, and then inputs the signal to the demodulation circuit 1. After demodulation, the signal is output to a host computer or the like (not shown). Reference numeral 8 denotes a CPU.
In the information recording operation, first, when a signal to be recorded is input, the modulation circuit 1 modulates the signal into a signal that can be easily recorded on the optical disc 7. Next, the modulated signal is input to the recording compensation circuit 2 to perform laser modulation or the like, and a laser driving current corresponding to the signal is supplied to the optical pickup 5.
Generally, the current that flows during information recording is larger than that during information reproduction. The semiconductor laser emits light based on the input signal, and information is recorded by irradiating the recording surface of the optical disc 7 with the laser from the optical pickup 5.

FIG. 19 is a block diagram of an optical pickup. The light beam (linearly polarized light) emitted from the semiconductor laser 11 as divergent light is converted into parallel light by the collimator lens 12 and enters the polarization beam splitter 13. The beam splitter 13 functions to transmit or reflect light on the bonding surface depending on the polarization direction of light. The incident light is parallel light and is transmitted because it oscillates parallel to the incident surface of the beam splitter 13.
The transmitted light beam is changed in direction by the rising mirror 14 and then incident on the quarter-wave plate 15. The quarter wave plate 15 converts linearly polarized light into circularly polarized light. Thereafter, the light beam enters the objective lens 16. The light incident on the objective lens 16 is collected on the recording surface of the optical disc 7. The light reflected from the recording surface is incident on the objective lens 16 and the quarter wavelength plate 15 again.
At this time, the circularly polarized light is converted again to linearly polarized light, but the phase is shifted by 90 degrees with respect to the light incident on the quarter-wave plate 15 first, and the light vibrates vertically. This light is reflected by the beam splitter 13 in a direction perpendicular to the incident direction. Then, after being condensed by the condenser lens 17, it is received by the light receiving element 18.
The amount of light received by the light receiving element 18 is converted into an electric signal, and information recorded on the optical disc 7 is reproduced. Further, the light receiving element 18 is divided, and a tracking error signal and a focus error signal are generated according to the amount of light received by each of the divided light receiving elements. Based on these signals, current is passed through the tracking coil 19 and the focusing coil 21 to perform tracking servo and focusing servo.
In recent years, such optical disk drives have been increased in density, and for this reason, an apparatus having an information recording medium and a means for correcting the tilt of the optical system, which is a factor that increases aberration of the optical system, has increased. ing. There are various types of tilt correction means, and there is a type in which a tilt coil 20 is mounted on an objective lens driving device as a type that has been widely used in recent years. In this form, the objective lens driving device is suspended by six wires, and each of the six also serves as a feed line for the track coil, the focus coil, and the tilt coil.

FIG. 20 is a configuration diagram of the objective lens driving device. An objective lens 31, a lens holder 32, a magnet 33, and various coils 34 to 36 are shown. For example, consider the case where such a tilt correction means is operated.
In a mechanism that performs tilt correction by a wire suspension type actuator as shown in FIG. 20, it is necessary to always supply current to the tilt correction mechanism during operation. On the other hand, there is a strong demand for power saving particularly in an optical disk drive mounted on a notebook PC.
To deal with these problems, for example, Japanese Patent Application Laid-Open No. 2003-228561 discloses a technique for taking a focus drive current into a tilt control circuit and operating / stopping the tilt correction mechanism with the focus drive current.
Further, in Patent Document 2, only a mechanism that does not need to supply current after settling by combining a tilt correction mechanism that always needs to supply current and a tilt correction mechanism that does not need to supply current after operation. It is proposed to perform tilt correction with.
JP 2001-023212 A JP 2001-126284 A

However, the technique proposed in Patent Document 1 has a problem that it can cope with the deterioration of the recording / reproduction quality due to the warp of the disk and the surface blur but cannot cope with other factors. In addition, there is a problem that it is not possible to appropriately deal with information recording media having different margins for tilt.
In addition, the technique proposed in Patent Document 2 requires the use of two types of tilt correction mechanisms, and there is a problem that the mechanism is complicated and expensive.
An object of the present invention is to provide an optical disc apparatus capable of solving these problems by a simple control logic change and realizing low power consumption while preventing deterioration in recording / reproduction quality due to tilt. .

In order to achieve the above object, the invention according to claim 1 is a tilt detection means for detecting a relative tilt between the optical pickup and the optical disc, and a tilt control means for performing tilt control based on a detection result of the tilt detection means. And a tilt correction unit that corrects a relative tilt with respect to the optical disk by adjusting at least the tilt of the objective lens according to the output of the tilt control unit, and a value detected by the tilt detection unit is equal to or less than a predetermined value In this case, the operation of the tilt correction means is stopped.
The invention according to claim 2 is characterized in that the shape data of the optical disk is stored in a memory in advance, and it is determined whether or not to stop the operation of the tilt correction means based on the value of the shape data stored in the memory. And
According to a third aspect of the present invention, when the value detected by the tilt detecting means is less than or equal to a predetermined value due to a difference in recording density of the optical disc, the operation of the tilt correcting means is stopped or the shape data stored in the memory It is determined whether to stop the operation of the tilt correction means based on the value of.
The invention described in claim 4 is characterized in that a predetermined value for stopping the operation of the tilt correcting means is changed according to a difference in recording density of the optical disc.
According to a fifth aspect of the present invention, when the value detected by the tilt detecting means is less than or equal to a predetermined value according to information recorded in advance on the optical disc, the operation of the tilt correcting means is stopped or stored in the memory It is determined whether to stop the operation of the tilt correction means based on the value of the shape data.
The invention described in claim 6 is characterized in that a predetermined value for stopping the operation of the tilt correction means is changed according to information recorded in advance on the optical disc.

According to the seventh aspect of the present invention, the operation of the tilt correction unit is performed by combining a servo signal obtained when operating one or both of the focus servo and the track servo with respect to the optical disc and the value detected by the tilt detection unit. A predetermined value for stopping the operation is determined.
The invention according to claim 8 is characterized in that a servo signal for determining a predetermined value for stopping the operation of the tilt correction means is a defocus amount.
The invention according to claim 9 is characterized in that the servo signal for determining a predetermined value for stopping the operation of the tilt correction means is a drive signal for the focus actuator.
The invention according to claim 10 is characterized in that the servo signal for determining a predetermined value for stopping the operation of the tilt correcting means is the number of tracks straddling in the on-focus / off-track.
The invention described in claim 11 is characterized in that the servo signal for determining a predetermined value for stopping the operation of the tilt correcting means is a lens shift amount representing the displacement amount of the objective lens.
The invention described in claim 12 is characterized in that a predetermined value for stopping the operation of the tilt correcting means is individually set.
In a thirteenth aspect of the present invention, the predetermined value for stopping the operation of the tilt correction means is determined by a manufacturing process of the product.

  According to the present invention, power saving can be achieved by avoiding unnecessary tilt correction operation while ensuring sufficient recording / reproduction quality.

Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.
As a first embodiment, FIG. 1 is a configuration diagram of a tilt control apparatus in an optical disc apparatus according to a first embodiment of the present invention, and FIG. 2 is a configuration of a tilt control apparatus in an optical disc apparatus according to a second embodiment of the present invention. FIG. The tilt control apparatus shown in FIG. 1 includes an optical pickup 101, a spindle motor (SPM) 102, a motor driver 103, a seek motor 104, a DSP 105, a CPU 106, an RF amplifier 107, an EQPLL 108, and a tilt control circuit 109.
The optical pickup 101 includes a focus coil 111, a tracking coil 112, a tilt coil 113, and a photodetector 114. In addition, the optical pickup 101 shown in FIG.
As a method often used as a tilt detection means, there are a method of generating a tilt error signal based on a signal obtained from the photodetector 114 and a method of generating a tilt error signal by mounting the tilt sensor 115. These differences are differences in the tilt error signal generation method, and the present invention can be applied to both control apparatuses.
FIG. 3 is a characteristic diagram showing the relationship between tilt and jitter. The vertical axis represents the jitter amount, and the horizontal axis represents the tilt amount. When tilt (relative tilt angle with respect to the information recording medium) occurs during recording / reproducing with respect to the information recording medium (optical disc), aberration is generated, which deteriorates recording / reproducing quality. A typical index of recording / reproduction quality is jitter, and the relationship between jitter and tilt is as shown in FIG.
At this time, when the tilt is within the allowable range A, the recording / reproduction quality can be sufficiently ensured, so that the convenience of the user is not impaired. However, when the allowable range is exceeded, there is a problem in reproduction compatibility. Phenomena such as sound / images appearing / playing out are disturbed and the user's convenience is impaired.
FIG. 4 is a characteristic diagram showing the relationship between the radius and tilt of the information recording medium. The vertical axis represents the jitter amount, and the horizontal axis represents the radius. As shown in FIG. 4, the tilt of the information recording medium changes in the radial direction, and it is not always necessary to perform tilt correction at all locations on the disc. For example, recording / playback is possible without operating the tilt correction mechanism inside the radius a in FIG.
The present invention is characterized in that the operation / stop of the tilt correction mechanism is switched according to a value obtained from the tilt detection means. For example, as shown in S1 to S4 in FIG. 5, the current tilt is acquired (S1), the tilt is detected at an appropriate period (S2), and the tilt correction mechanism is stopped when the detected tilt is equal to or less than a predetermined value. (S3). If the detected tilt is greater than or equal to a predetermined value, the tilt correction mechanism is operated (S4). The predetermined value used at this time is appropriately set in consideration of the detection error of the tilt detection means. By performing such control, power saving can be measured by removing unnecessary tilt correction operation while ensuring sufficient recording / reproduction quality.

In the second embodiment, the tilt of the information recording medium changes in the radial direction, but it may be difficult to obtain these during operation, or the performance may be degraded. In such a case, there is a method of acquiring a tilt at a predetermined position and controlling the tilt correction mechanism based on the value.
For example, as shown in S1 and S2 of FIG. 6 (1), the tilt is acquired at several points when the information recording medium is inserted or immediately before the actual operation (S1), and the radius or the address and tilt of the information recording medium are obtained. A function representing the relationship is obtained in advance and stored in the memory (S2). At this time, an appropriate smooth function is used.
In the actual operation shown in (2), the current tilt is obtained based on the current radius or the address of the information recording medium and the function stored in the memory, and the tilt correction mechanism is stopped when the tilt is less than a predetermined value. The predetermined value used at this time is appropriately set in consideration of the detection error of the tilt detection means and the error due to approximation.
By controlling in this way, it is possible to measure power saving by removing unnecessary tilt correction operation while ensuring sufficient recording / reproduction quality.

As a third embodiment, FIG. 7 is a characteristic diagram showing the relationship between tilt and jitter of different information recording media, and FIG. 8 is a characteristic diagram showing a range where tilt correction is required for different information recording media. As shown in FIG. 7, the vertical axis represents the jitter amount, and the horizontal axis represents the tilt amount. The influence of the tilt on the recording / reproducing jitter varies depending on the recording density of the information recording medium. Further, as shown in FIG. 7, in an apparatus for recording / reproducing with lasers of different wavelengths, there are a plurality of optical systems, and therefore the amount of tilt at which the jitter is the best differs.
In this embodiment, power is reduced by using the control of the first embodiment or the second embodiment for a medium in which the change in jitter due to tilt is small, and the medium in which the change in jitter is large and the margin is small. The conventional tilt control is performed.
Consider the case where the tilt of the disk changes as shown in FIG. It is assumed that the information recording media A and B have the same disk shape. As shown in the figure, since the margin for tilt varies depending on the medium, the range in which tilt control is required varies.

As the fourth embodiment, the threshold for stopping the tilt correction mechanism is changed by the information recording medium. In FIG. 8, the information recording medium B can be made smaller in the range where tilt correction is required than the information recording medium A, and power saving can be measured as compared with the case where only one threshold is provided.
According to the third and fourth embodiments, it is possible to measure power saving by removing unnecessary tilt correction operation while ensuring sufficient recording / reproduction quality.
As a fifth embodiment, FIG. 9 is a characteristic diagram showing the relationship between tilt and jitter on information recording media having different prerecorded information. The vertical axis represents the jitter amount, and the horizontal axis represents the tilt amount. As shown in FIG. 9, even if the information recording medium is the same type, the allowable amount of tilt varies depending on the vendor that manufactured the information recording medium, the corresponding linear velocity, and the like.
These allowable amounts are governed by the matching between the light emission pulse and the information recording medium and the physical characteristics of the information recording medium. In FIG. 9, a medium having a small allowable tilt and a large change in jitter with respect to the tilt is represented as C, and a medium having a large allowable tilt and a small change in jitter with respect to the tilt is represented as D.

In the fifth embodiment, for the medium in which the change in jitter due to tilt is predicted to be small from the information recorded in advance on the information recording medium, the power is reduced using the control method of Example 1 or 2, Conventionally, tilt control is performed on a medium which is predicted to have a large jitter change and a small margin. In the example of FIG. 9, the control method of the first or second embodiment is used for the medium D, and the conventional control method is used for the medium C.
As the sixth embodiment, the threshold for stopping the tilt correction mechanism is changed from information recorded in advance on the information recording medium. Similarly to the case shown in FIG. 8, the range in which the tilt correction operation is required is different between the medium in which the change in jitter due to tilt is predicted to be small and the medium in which the change in jitter due to tilt is predicted to be large. For this reason, it is possible to save power by appropriately setting the threshold as compared with the case where only one threshold is provided.
According to the fifth and sixth embodiments, power saving can be measured by removing unnecessary tilt correction operation while ensuring sufficient recording / reproduction quality.
FIG. 10 is a characteristic diagram showing the relationship between tilt and jitter when servo signal states are different on the same type of information recording medium. As shown in FIG. 10, the jitter of the optical disk drive increases not only due to the tilt but also due to various factors. If characteristics other than the tilt are undesirable, the margin for the tilt is apparently reduced even when recording is performed with the same drive and the same medium. End up.
This may be caused by other factors causing aberrations or when the writing power is not appropriate. Considering such a case, it is not preferable that the operation / stop of the tilt control is necessarily generated only from the tilt error signal.
As a seventh embodiment, FIG. 11 is a configuration diagram of a tilt control device in the optical disc apparatus of the present invention, and FIG. 12 is a configuration diagram of a tilt control device in the optical disc device of the present invention. The same components will be described with the same reference numerals. In the seventh embodiment, the tilt correction mechanism is operated / stopped using a servo signal in addition to the tilt error signal.
As a method for obtaining a servo signal at this time, a method of calculating a signal obtained from a photodetector as shown in FIG. 1, a method of obtaining from a DSP 105 as shown in FIG. 1, and a result of computation at the CPU 106 as shown in FIG. The method of doing etc. can be considered.
The flowcharts of this embodiment are as shown in FIGS. 13, 14, and 15, for example. In S1 to S4 in FIG. 13, the operation / stop of the tilt correction mechanism is determined from the current tilt amount and the current servo signal state, and learning is performed in advance in S1 and S2 in FIG. 14 (1) and S1 to S6 in (2). The operation / stop of the tilt correction mechanism is determined from the tilt amount and the current servo signal. The function g (Tilt, y) at this time is appropriately set in consideration of the relationship between jitter and the servo signal and the relationship between jitter and tilt.

In the eighth embodiment, the Defocus amount is used as the servo signal. Since the Defocus amount directly affects the focusing of the laser, both recording and reproduction have a great influence on jitter. Such a physical quantity is a dominant factor for jitter, and is suitable for estimating a tilt margin.
As shown in S1 to S6 in FIG. 15 and S1 to S6 in FIG. 16, in a medium in which the amount of Defocus considered to be optimally fluctuates in the medium surface, there is a high possibility that the amount of Defocus is shifted. A Defocus amount that seems to be optimal in advance is acquired at a predetermined address, and the tilt correction mechanism is always operated when the amount of fluctuation at that time is large. In the case of being small, a method is conceivable in which g (Tilt, y) is appropriately set based on the amount of fluctuation and the like is determined again during operation.
In the ninth embodiment, a focus actuator drive signal is used as a servo signal. As disclosed in Japanese Patent Laid-Open No. 2001-023212, the drive signal of the focus actuator represents the warp and the surface shake of the disc, and these differential values correspond to the tilt.
For this reason, it is considered that a disc with a large driving signal for the focus actuator has a large tangential or radial tilt and a small margin for tilt. Therefore, it is suitable for estimating the tilt margin.
In the tenth embodiment, the number of tracks straddling in the on-focus / off-track is used as the servo signal. The number of tracks straddling is highly correlated with the eccentricity of the information recording medium, and in a medium with a large amount of eccentricity, the track following accuracy is deteriorated, thereby deteriorating jitter. As a result, the tilt margin is reduced, which is suitable for estimating the tilt margin.

In the eleventh embodiment, a signal indicating the amount of displacement of the objective lens (lens shift amount) is used. The lens shift amount has a high correlation with the eccentric centroid of the information recording medium, and in a medium with a large eccentric centroid, the track following accuracy deteriorates due to self-excited vibration, thereby deteriorating jitter. As a result, the tilt margin is reduced, which is suitable for estimating the tilt margin. According to the present embodiment, power saving can be measured by removing unnecessary tilt correction operation while ensuring sufficient recording / reproduction quality.
FIG. 17 is a characteristic diagram showing the relationship between tilt and jitter in different drives. Even for the same medium, the allowable tilt amount differs depending on the drive. This is caused by an assembly error of the optical system and a variation of components such as LSI. Here, in order to prevent a problem from occurring in any drive, it is necessary to determine a threshold based on a drive having the smallest allowable tilt amount. In the twelfth embodiment, the threshold is individually set in consideration of the variation for each apparatus.
In the thirteenth embodiment, thresholds set individually are set in the manufacturing process. According to the present embodiment, power saving can be measured by removing unnecessary tilt correction operation while ensuring sufficient recording / reproduction quality.

1 is a configuration diagram of a tilt control device in an optical disc device according to a first embodiment of the present invention. FIG. It is a block diagram of the tilt control apparatus in the optical disk apparatus based on the 2nd Embodiment of this invention. It is a characteristic view showing the relationship between tilt and jitter. It is a characteristic view showing the relationship between the radius and tilt of an information recording medium. It is a flowchart which shows the control action of this invention (the 1). It is a flowchart which shows the control action of this invention (the 2). It is a characteristic view which shows the relationship between the tilt and jitter of a different information recording medium. It is a characteristic view which shows the range which needs tilt correction with a different information recording medium. FIG. 11 is a characteristic diagram showing a relationship between tilt and jitter on information recording media having different pre-recorded information. FIG. 11 is a characteristic diagram showing a relationship between tilt and jitter when servo signal states are different on the same type of information recording medium. It is a block diagram of the tilt control apparatus in the optical disk apparatus based on the 3rd Embodiment of this invention. It is a block diagram of the tilt control apparatus in the optical disk apparatus based on the 4th Embodiment of this invention. It is a flowchart (the 3) which shows the control action of this invention. It is a flowchart (the 4) which shows the control action of this invention. It is a flowchart (the 5) which shows the control action of this invention. It is a flowchart (the 6) which shows the control action of this invention. It is a characteristic view showing the relationship between tilt and jitter in different drives. It is a block diagram of a general optical disc device. It is a block diagram of an optical pick-up. It is a block diagram of an objective lens drive device.

Explanation of symbols

101 Optical Pickup 102 Spindle Motor 103 Motor Driver (Tilt Correction Unit Component)
104 seek motor 105 DSP
106 CPU
107 RF amplifier 108 EQPLL
109 Tilt control circuit (tilt control means)
111 Focus coil 112 Tracking coil 113 Tilt coil (Tilt correction means component)
114 Photodetector (tilt detection means)

Claims (13)

  Tilt detection means for detecting the relative tilt between the optical pickup and the optical disc, tilt control means for performing tilt control based on the detection result of the tilt detection means, and at least the inclination of the objective lens according to the output of the tilt control means And a tilt correction means for correcting a relative tilt with respect to the optical disc, and when the value detected by the tilt detection means is a predetermined value or less, the operation of the tilt correction means is stopped. Optical disk device.   2. The optical disk according to claim 1, wherein shape data of the optical disk is previously stored in a memory, and it is determined whether or not to stop the operation of the tilt correcting means based on the value of the shape data stored in the memory. apparatus.   If the value detected by the tilt detection means is less than or equal to a predetermined value due to the difference in recording density of the optical disk, the operation of the tilt correction means is stopped or the tilt correction is performed based on the value of the shape data stored in the memory 2. The optical disk apparatus according to claim 1, wherein it is determined whether or not to stop the operation of the means.   2. The optical disk apparatus according to claim 1, wherein a predetermined value for stopping the operation of the tilt correcting means is changed according to a difference in recording density of the optical disk.   When the value detected by the tilt detection means is less than or equal to a predetermined value according to information recorded in advance on the optical disc, the operation of the tilt correction means is stopped or the value based on the value of the shape data stored in the memory 2. The optical disk apparatus according to claim 1, wherein it is determined whether or not to stop the operation of the tilt correcting means.   2. The optical disc apparatus according to claim 1, wherein a predetermined value for stopping the operation of the tilt correction means is changed according to information recorded in advance on the optical disc.   A predetermined value for stopping the operation of the tilt correcting unit is determined by combining a servo signal obtained when operating one or both of the focus servo and the track servo with respect to the optical disc and a value detected by the tilt detecting unit. 2. The optical disk apparatus according to claim 1, wherein   8. The optical disk apparatus according to claim 7, wherein the servo signal for determining a predetermined value for stopping the operation of the tilt correction means is a defocus amount.   8. The optical disk apparatus according to claim 7, wherein the servo signal for determining a predetermined value for stopping the operation of the tilt correction means is a drive signal for the focus actuator.   8. The optical disk apparatus according to claim 7, wherein the servo signal for determining a predetermined value for stopping the operation of the tilt correcting means is the number of tracks straddling in on-focus / off-track.   8. The optical disk apparatus according to claim 7, wherein the servo signal for determining a predetermined value for stopping the operation of the tilt correcting means is a lens shift amount representing a displacement amount of the objective lens.   12. The optical disc apparatus according to claim 1, wherein predetermined values for stopping the operation of the tilt correction means are individually set.   13. The optical disc apparatus according to claim 12, wherein the predetermined value for stopping the operation of the tilt correction means is determined by a product manufacturing process.

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