JP2009193641A - Optical recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately obtain optimal recording power by suppressing the effect of laser power variation caused at a disk revolution cycle due to the effect of lens shift caused immediately after an optical pickup seek, or by case attitude difference. <P>SOLUTION: An optical recording and reproducing device has an objective lens position detection means and a lens shift determination means, and carries out OPC (optical power control) after the objective lens position is moved within a predetermined area from the optical axis center. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical recording / reproducing apparatus that records or reproduces information on a disk-shaped medium using a laser beam, and in particular, includes a recording power adjustment process to obtain an optimum recording power, and to record or record good information. The present invention relates to an apparatus for performing a reproduction operation.

  In recent years, an environment in which disk media are inexpensively supplied in large quantities has been reached, and the optical recording / reproducing apparatus needs to sufficiently cover the composition and solid variation of the disk medium. The composition of the medium mainly depends on the specifications and manufacturing processes of each manufacturer, such as track width and pitch, groove shape, recording film material, and radial film uniformity. In addition, even if the same manufacturer has different solids in the medium, a characteristic difference appears due to a difference in manufacturing lots. In a mobile device such as a video camera, high definition video (HD; High Definition) must be recorded on a medium in real time. In other words, a recording laser power optimization technique is extremely important in order to maintain good recording quality with respect to the use environment as a mobile device and the variation in solids of disk media.

  In the known recording power optimization process, first, test recording is attempted in a predetermined area of the disk medium by changing the recording laser power stepwise. Next, the data recorded by trial recording is reproduced to obtain a recording power at which the best reproduction signal can be obtained. Such processing is called OPC (Optimum Power Control), and is performed for each disk medium, each ambient temperature change, and each disk radial position, etc., and a recording power that always optimizes the recording quality is set. Yes.

  By the way, it is known that the optical beam spot quality deteriorates due to the optical axis center of the laser beam and the center shift of the objective lens (hereinafter referred to as “lens shift”) in the optical pickup for recording and reproducing on the disk medium. Yes.

  FIG. 4 is a graph illustrating the relationship between the objective lens output light amount (4-1) and the total wavefront circumferential difference (4-2) in an optical pickup corresponding to the objective lens NA = 0.6 and the laser wavelength λ = 660 nm. . In (4-1), the horizontal axis indicates the objective lens position [um], and the vertical axis indicates the amount of light emitted from the objective lens. When the objective lens position is 0, that is, the light quantity when the objective lens center and the optical axis center coincide with each other, the light quantity becomes 0.8 when the objective lens position is shifted by +300 [um], which is about 20 % Reduction in light intensity is observed. On the other hand, in (4-2), the horizontal axis represents the objective lens position [um], and the vertical axis represents the total wavefront aberration [mλrms] indicating the optical spot quality on the disk surface. Assuming that the aberration when the objective lens position is 0, that is, when the objective lens center and the optical axis center coincide with each other, is 30 [mλrms], when the objective lens position is shifted by +300 [um], the aberration is 50 [mλrms]. It is shown that the light spot quality deteriorates.

  Thus, the objective lens position of the optical pickup is related to the objective lens output power intensity and the light beam spot quality. That is, it affects the accuracy of OPC for obtaining the optimum recording power.

Conventionally, JP-A-2001-60320 (Patent Document 1) and JP-A-2002-352426 (Patent Document 2) are known as recording laser power optimization techniques that eliminate the influence of the lens shift described above. . Japanese Patent Application Laid-Open No. 2001-60320 discloses a technique for ensuring the accuracy of OPC in a reproduction process for a recording power that fluctuates with a disk rotation period. Specifically, after performing OPC test recording, an attempt is made to obtain an OPC result in which power fluctuation components in the circumference are suppressed by averaging reproduction signal characteristic values of a plurality of regions from different angular positions on the disc. Is. Japanese Patent Laid-Open No. 2002-352426 discloses a technique for detecting the periodic fluctuation component of the light beam return light and correcting the output of the recording power so as to cancel the periodic fluctuation component. .
JP 2001-60320 A JP 2002-352426 A

  However, the above prior art has the following problems. In the technique described in Japanese Patent Application Laid-Open No. 2001-60320, since the reproduction signal fluctuation component within the circumference of the disk is averaged, data recorded by test recording at each power at a plurality of positions on the track is required. That is, a large OPC test area is required. As described above, the mobile device frequently performs the optimum adjustment of the recording power. On the other hand, a predetermined OPC use area on the disk is limited. Therefore, write-once media (write-once) may run out of OPC usage area as the number of OPC increases.

  Further, the technique described in Japanese Patent Laid-Open No. 2002-352426 changes the recording power intensity so that fluctuations in the disk reflection light amount during recording are suppressed. Therefore, even if aberration occurs in the light beam spot, it is corrected only by the recording power intensity, so it is difficult to improve the recording quality, in other words, to secure a margin for various fluctuation factors.

  That is, the above-described conventional techniques 1 and 2 do not take measures against lens shift that causes an increase in aberrations in the light beam spot. More specifically, a seek operation is indispensable in the OPC process, but a lens shift occurs immediately after the seek. Further, when there is a posture difference in the apparatus, a lens shift occurs due to the influence of gravity. An essential solution is desired for the problem of ensuring the accuracy of OPC by lens shift.

  Therefore, an object of the present invention is to provide an optical recording / reproducing apparatus that appropriately performs a recording power optimization process even when there is an influence of a lens shift.

An optical recording / reproducing apparatus according to the present invention includes a light source, an objective lens for condensing a light beam from the light source on a disk-shaped recording medium to be arranged, and an actuator for driving the objective lens. With an optical pickup,
Feed control means for transporting the optical pickup in the radial direction of the recording medium;
Detecting means for detecting a relative position of the objective lens in the radial direction with respect to the optical pickup;
Determination means for determining whether or not the relative position obtained by the detection means is within a predetermined range;
An optical recording / reproducing apparatus having adjustment means for adjusting the amount of light flux for recording information on the recording medium,
An optical recording / reproducing apparatus in which the adjustment unit is performed when the determination unit determines that the relative position is within the predetermined range.

  As described above, according to the present invention, it is possible to obtain the optimum recording power with high accuracy by suppressing the rotational period fluctuation of the recording power and the increase in aberration of the light beam spot caused by the lens shift. In particular, the reliability of the recording power adjustment process, which greatly affects recording quality, against seek operations that are indispensable for OPC processing caused by ultra-miniaturization of the device and use of the mobile environment, or severe dynamic fluctuation factors that occur due to device posture differences Contributes to improved performance. If checked, the effect of ensuring good recording quality can be obtained.

(First embodiment)
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  The laser power adjustment according to the present invention is applied to, for example, an optical recording / reproducing apparatus 100 as shown in FIG.

<Components and Series of Operations of Optical Recording / Reproducing Device 100>
An optical recording / reproducing apparatus 100 includes an optical disc (hereinafter referred to as “disc”) 101, an optical pickup (hereinafter referred to as “OPU”) 120, and a spindle motor (hereinafter referred to as “SPM”) 110, which are disc-shaped recording media. Prepare. Further, a spindle motor driver (hereinafter referred to as “SPM driver”) 109, an LD power control circuit 111, an actuator driver 113, a feed mechanism 112, a servo recording / reproducing processor 114, and a disk controller (CPU) 115 are provided.

The overall configuration and basic operation of FIG. 1 will be described.
The disk controller 115 includes a CPU (Central Processing Unit). The overall operation of the optical recording / reproducing apparatus 100 is controlled by executing a user instruction command or a predetermined program from an operation system (not shown) via the external interface 116. The recording or reproducing operation on the disc is performed with a known shock proof (intermittent drive) control via the memory 117.

  The disk 101 is, for example, a phase change type disk, and the recording layer is made of a phase change material such as Ge—Sb—Te. When the light beam intensity is modulated and irradiated while rotating the disk, the amorphous state and the crystalline state change reversibly. In order to change the recording layer from the crystalline state to the amorphous state, the light beam is irradiated onto the pulse, once melted, and then rapidly cooled. On the other hand, in order to change the crystalline state from the amorphous state, annealing is performed at a temperature equal to or higher than the crystallization temperature by irradiation with a laser beam having a relatively weak light beam intensity. Utilizing such a phase change characteristic, it has a characteristic capable of accumulating 1 or 0 of information by a state change. The disk 101 may be a write-once (write-once) type disk having an organic dye in the recording layer. In the write-once type, the intense light beam irradiated at the time of recording is absorbed by the dye film and is thermally altered, whereby the reflectance of the medium changes. Although this type of disc can be recorded only once, the demand for it is rapidly expanding because the player is compatible with reproduction and relatively inexpensive.

  Next, servo / recording / reproducing processing by the disk controller 115 and the servo recording / reproducing processor 114 will be described. The processor 114 performs rotational drive control of the spindle motor (SPM) 110 by a spindle motor driver (hereinafter “SPM” control). Here, the rotation control of the spindle motor is so-called CLV (Constant Linear Velocity). The disk 101 has meandering sidewalls called wobbles along the track grooves. The disk rotation speed is controlled so that the frequency of the wobble becomes a target value.

  The OPU 120 includes an objective lens 102, an actuator 103, an optical system 104, an LD / driver 105, a reproduction signal sensor 106, an LD power monitor sensor 107, and a temperature sensor 108. The OPU 103 is connected to the servo recording / reproducing processor 114 or a motor / actuator driver system by a flexible cable or the like.

  The LD / driver 105 is a semiconductor laser element (hereinafter referred to as “LD”) used as a light source and a laser driver. Laser light emitted from the LD is condensed on the disk 101 via the optical system 104 and the objective lens 102. The LD power monitor sensor 107 includes a semiconductor light receiving sensor and a photoelectric conversion amplifier. Part of the laser light emitted from the LD constitutes an APC (Auto Power Control) loop by the servo recording / reproducing processor 114 and the LD power control circuit 111 via the LD power monitor sensor 107. In other words, the LD emission power is feedback controlled so that the LD power monitor sensor output and the target power set by the disk controller 115 coincide.

  The reproduction signal sensor 106 includes a semiconductor light receiving sensor and a photoelectric conversion amplifier. Here, a lens position (Lens Position; hereinafter abbreviated as “LP”) signal will be described with reference to FIG. By using this LP signal, the relative position of the objective lens 102 with respect to the OPU 120 can be detected. FIG. 6 shows a light spot arrangement on a track, a sensor configuration, and a matrix portion of the DPP method (differential push-pull method) using three beams.

  The position of the main beam Main is controlled at the track center. The positions of the sub-beams SUB1 and SUB2 are shifted in the 1/2 track radial direction with respect to Main.

  The sensor unit corresponds to each of three beams, and a quadrant sensor (A to D) is disposed on the main beam Main, and a two-segment sensor (E to F, G to H) is disposed on the sub beams SUB1 and SUB2. . The reproduction signal sensor output is transmitted from the OPU 120 to the arithmetic processing unit of the servo recording / reproducing processor 114 via a flexible cable or the like. In the arithmetic processing section, gain control (Auto Gain Control), filter processing (Pre Filter), and digitization (Analog / Digital Converter) are performed, and the A to H channel signals are subjected to matrix arithmetic processing.

  In the matrix portion, functional blocks for calculating the sensor output signals are shown. Reference numerals 601 to 604 denote calculators, 605 to 606 denote adders, and 607 denotes a coefficient calculator. The reflected light of the main beam Main is applied to the four-divided sensors A to D. As the sensor output signal, first, an (A + D) signal and a (B + C) signal are generated. Next, it is input to the calculator 602 and (A + D) − (B + C) is calculated and output. Further, the reflected light of the sub beam SUB1 is applied to the two-divided sensors E and F. The sensor output signal is input to the calculator 601 and an (EF) signal is output. On the other hand, the reflected light of the sub beam SUB2 is applied to the sensors G and H. The sensor output signal is input to the calculator 603, and a (GH) signal is output. The (EF) signal and the (GH) signal are input to the adder 605, and the (E + G)-(F + H) signal is output. Subsequently, the coefficient calculator 607 multiplies the predetermined coefficient k and outputs k {(E + G)-(F + H)}.

Here, the track error signal TE is obtained by the output of the calculator 604.
TE = (A + D)-(B + C) -k {(E + G)-(F + H)}
The push-pull signal of the main beam is obtained as an output signal (A + D) − (B + C) of the calculator 602, but includes an offset due to the objective lens shift in the disk radial direction. Therefore, after the push-pull component (E + G) − (F + H) of the sub beam is multiplied by a predetermined coefficient k, a difference calculation is performed to generate a track error signal TE in which the offset component is canceled.

The LP signal is obtained by the output of the adder 606.
LP signal = (A + D)-(B + C) + k {(E + G)-(F + H)}
The LP signal is extracted as a lens shift component in the disc radial direction by the sum of the main push-pull signal and the sub push-pull signal. The predetermined coefficient k is a constant determined according to the divided light amount ratio between the main beam and the sub beam.

  From the above, based on the tracking error TE signal and the LP signal, the light beam spot is subjected to tracking control in the information track groove direction. The tracking control is controlled by fine adjustment in the actuator 103 and rough adjustment by the feed mechanism 112.

  FIG. 7 is a diagram showing an outline of lens position control (fine adjustment) by an actuator. In FIG. 7, reference numeral 701 denotes a disk surface, reference numerals 702 and 703 denote objective lens positions, and reference numeral 704 denotes a light beam. At the objective lens position 702, the tracking of the disc surface 701 is performed by matching the center of the objective lens with the optical axis. Recording or reproduction is performed while the objective lens position is shifted by an actuator like 703 (lens position ΔLP only) and the light beam spot is traced to the target track. That is, while the objective lens is in the movable range of the actuator, the thread feeding mechanism is stopped and the objective lens is shifted in the disk radial direction only by the actuator control to perform tracking tracking. At this time, when it is detected by the LP signal that the actuator is positioned at the end of the movable range of the actuator, the sled feeding mechanism is activated to move the entire optical pickup in the disk radial direction (coarse adjustment). As described above, the objective lens is controlled to follow a predetermined track of the disk by combining fine adjustment by the actuator and rough adjustment by the thread feeding mechanism. Further, the feed mechanism 112 transports the OPU 120 in the disk radial direction (traverse control) and performs a seek operation to a predetermined address.

  Next, the digitized reproduction signal is subjected to data processing by generating a clock synchronized with the edge of the reproduction signal by a PLL (Phase Locked Loop) (not shown). Further, predetermined decoding processing such as data detection by PRML (Partial-Response Maximum-Likelihood), ECC (Error Correction Code) is performed.

  On the other hand, for recording on the disk, the servo recording / reproducing processor 114 generates a recording pattern by modulation processing conforming to the disk format. The LD / driver 105 performs waveform shaping and timing control of the laser emission pulse in accordance with the recording pattern, and takes a so-called write strategy operation.

  The disk controller 115 performs recording by a shock proof operation. Specifically, the disk access is operated intermittently by utilizing the difference between the rate of data input to and output from the apparatus (low speed) and the rate of recording to the disk (high speed). In other words, while the signal from the external interface is accumulated in the memory 117, the disk access is put in a dormant state. The hibernation state is to turn off the LD with high power consumption and stop the operation of the related electric circuit block. When a predetermined amount of data is stored in the memory 117, disk access is started, and recording from the memory 117 to the disk 101 is performed. When recording to the disc is completed, the disc access is again set to the hibernation state. By intermittently accessing the disk in this manner, the LD can be turned off at the time of a pause, so that average power consumption can be reduced. Further, even if vibration or impact is applied from the outside of the apparatus, the memory 117 serves as a buffer, and servo return processing (retry processing) can be performed, so that an effect of improving seismic reliability can be obtained.

  Further, a temperature sensor 108 is provided inside the OPU 120 and has a function of detecting the temperature near the LD by the disk controller 115.

<Recording Power Adjustment Flow of Optical Recording / Reproducing Device 100>
FIG. 2 is a flowchart showing recording power adjustment according to the present invention. A specific flow will be described with reference to FIG.

Step S201: Seek to OPC area This step transfers the OPU 120 to a predetermined disk area PCA (Power Calibration Area) in order to obtain the optimum recording power to the disk. The disk controller 115 activates the servo operation and performs address seek. The PCA is assigned to a predetermined address on the innermost or outermost periphery of the disk. After being transferred to the PCA area, the OPU 120 performs a wait jump (standby operation) near the address.

Step S202: Lens Shift Determination The disk controller acquires the LP signal and compares it with a predetermined threshold value (Th value).
If LP <Th, the process proceeds to step S204.
If LP> Th, the process proceeds to step S203.

Step S203: Feed Control The servo recording / reproducing processor controls the feed mechanism 112 so that the position of the objective lens 102 in the OPU 120 is at the center. Since the light beam spot is weighted to a predetermined address, the lens shift component LP is reduced by the feed control. When the feed control is performed, the process returns to step S202 again to determine lens shift.

Step S204: Perform OPC When it is determined in step S202 that the lens shift is equal to or less than the predetermined value, the disk controller 115 performs OPC (Optimum Power Control) for determining the recording laser power. Specifically, trial recording is performed in the PCA area to evaluate the reproduction signal. During trial recording, recording is performed while changing the recording laser power in multiple stages. During reproduction, the trial-recorded data is reproduced, and the reproduction data is acquired for each recording laser power to determine the signal quality. In determining the signal quality, for example, an asymmetry (β value) indicating the objectivity of the amplitude of the reproduction signal, a jitter value indicating the fluctuation of the edge, or an error rate indicating the reliability of the reproduction data is used as an index. Then, the laser power value that provides the best recording quality, that is, the optimum recording power is obtained.

  The obtained optimum recording power is stored in a predetermined register. At the same time, conditions such as time and temperature at which OPC is performed are also stored as attribute information. This attribute information is used, for example, when a predetermined time elapses or when a certain temperature change is detected and the optimum recording power is searched for.

  Here, the recording power adjustment sequence based on the present embodiment will be described in detail with reference to FIGS. FIG. 3 shows the time transition of the objective lens position, with the horizontal axis representing time and the vertical axis representing the objective lens position. A displacement 303 (inner circumference side) to 304 (outer circumference side) shown on the vertical axis is a physical movable limit of the objective lens in the actuator. Further, the displacement 301 to the displacement 302 is a margin range that does not hinder the quality of recording / reproduction even if there is a decrease in light amount or an increase in aberration caused by the lens shift. The displacements Th1 to Th2 are in the vicinity of the lens shift zero, and are a range in which the OPC is permitted to be performed.

  Assume that the objective lens is positioned at point A0 when seeking to the PCA area. The A0 point does not interfere with normal recording / reproduction, but the OPC for obtaining the recording power is not permitted (step S202). Therefore, feed control is performed in a state where the relative position of the objective lens 102 with respect to the optical disc 101 in the disc radial direction is maintained, and the relative position of the objective lens is shifted from the A0 point to the A1 point (step S203). If it is determined that the lens shift is smaller than the threshold value Th1 (step S202), the execution of OPC is permitted (step S204). As described above, the OPC is permitted only when the lens position is within a predetermined range from Th1 to Th2, that is, only from the A1 to A2 section and from the B1 to B2 section in FIG. After that, when the disc tracing operation is continued, the feed control is moved again at the point A3, the objective lens is shifted to the point B0, and this operation is repeated.

  Here, the relationship between the threshold value of the objective lens position and the amount of light is shown in FIG. If the light emitted from the objective lens at the point where the lens shift is zero is 1.0, the relative light amounts of the threshold values Th1 (A1 point) and Th2 (A2 point) are 0.96, 301 (A0 point), and 302 (A3 point). The relative amount of light is 0.8. The rotation period variation of the amount of light emitted from the objective lens varies depending on the amount of eccentricity of the disk. However, if the lens shift is within the interval from Th1 to Th2, the average light amount variation is approximately ± 3%, and recording power adjustment (OPC) ) The margin is sufficient to ensure accuracy. Further, the average light amount fluctuation in the section 301 to 302 is ± 10% or less, which is an allowable range of lens shift in which information can be recorded. The same applies to playback. As described above, the predetermined range in which the OPC from Th1 to Th2 is permitted to be executed is set to be narrower than the allowable lens shift range from 301 to 302. The threshold value is set based on the average amount of fluctuation in light quantity based on disk eccentricity.

  The implementation flow according to the present invention has been described in detail above. Since the lens shift amount is monitored before the OPC is performed (step S202), the recording power adjustment error can be suppressed, which contributes to the improvement of the recording quality.

(Second embodiment)
A second embodiment according to the present invention will be described with reference to FIG. FIG. 8 shows the time transition of the objective lens position with the horizontal axis representing time and the vertical axis representing the objective lens position. A displacement 303 (inner circumference side) to 304 (outer circumference side) shown on the vertical axis is a physical movable limit of the objective lens in the actuator. Further, the displacement 301 to the displacement 302 is a margin range that does not hinder the quality of recording / reproduction even if there is a decrease in light amount or an increase in aberration caused by the lens shift. The displacements Th1 to Th2 are in the vicinity of the lens shift zero, and are a range in which the OPC is permitted to be performed.

  In this embodiment, the drive range of the actuator is limited based on the LP signal. In the normal recording operation, the position of the objective lens is controlled by the actuator in the section 301 to 302. On the other hand, during OPC, the movable range of the actuator is limited only to the section from Th1 to Th2.

  As described above, the threshold value is not changed, and the movable range of the actuator is limited, thereby suppressing an average light amount fluctuation based on the disk eccentricity and obtaining the optimum recording power with high accuracy during the OPC operation. it can.

  The LP signal is not limited to the matrix calculation output described above. You may monitor the average level of the actuator drive signal which drives an objective lens. An LP signal can be obtained from the actuator drive signal by averaging fluctuations in the rotation period such as disk surface blurring and eccentricity.

  In addition, the preferred embodiment of the present invention has been described with respect to the configuration based on hardware, but the gist of the present invention is not limited to this, and can of course be realized by software program processing. .

It is a functional block diagram of an optical recording / reproducing apparatus. It is a flowchart which shows the operation | movement in connection with the 1st Embodiment of this invention. It is a figure explaining the whole sequence of the 1st Embodiment of this invention. It is a figure explaining the light quantity fluctuation | variation by a lens shift, and an aberration fluctuation | variation. It is a figure explaining the predetermined value setting of the lens shift determination means of this invention. It is a figure explaining the lens position control signal of embodiment by this invention. It is a figure explaining lens shift. It is a figure explaining the whole sequence of the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Optical disk 102 Objective lens 103 Actuator 104 Optical system 105 LD / driver 106 Playback signal sensor 107 LD power monitor sensor 108 Temperature sensor 109 SPM driver 110 SPM
111 LD power control circuit 112 Feed mechanism 113 Actuator driver 114 Servo recording / reproducing processor 115 Disk controller 116 External interface 117 Memory

Claims (4)

An optical pickup including a light source, an objective lens for condensing a light beam from the light source on a disk-shaped recording medium disposed, and an actuator for driving the objective lens;
Feed control means for transporting the optical pickup in the radial direction of the recording medium;
Detecting means for detecting a relative position of the objective lens in the radial direction with respect to the optical pickup;
Determination means for determining whether or not the relative position obtained by the detection means is within a predetermined range;
An optical recording / reproducing apparatus having adjustment means for adjusting the amount of light flux for recording information on the recording medium,
The optical recording / reproducing apparatus, wherein the adjusting means is performed when the determining means determines that the relative position is within the predetermined range.   2. The optical recording / reproducing apparatus according to claim 1, wherein the predetermined range is set narrower than an allowable range of the relative position in which the information can be recorded on the recording medium.   In order to make the relative position of the objective lens within the predetermined range, the optical pickup is transported by the feed control means while maintaining the relative position of the objective lens with respect to the recording medium. The optical recording / reproducing apparatus according to claim 2.   3. The optical recording / reproducing apparatus according to claim 2, further comprising a control unit that limits a range of driving of the objective lens by the actuator so that the relative position of the objective lens is within the predetermined range. .

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