WO2006001424A1 - 情報記録再生装置、情報記録再生方法及びフォーカス位置調整プログラム - Google Patents
情報記録再生装置、情報記録再生方法及びフォーカス位置調整プログラム Download PDFInfo
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- WO2006001424A1 WO2006001424A1 PCT/JP2005/011742 JP2005011742W WO2006001424A1 WO 2006001424 A1 WO2006001424 A1 WO 2006001424A1 JP 2005011742 W JP2005011742 W JP 2005011742W WO 2006001424 A1 WO2006001424 A1 WO 2006001424A1
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- focus
- offset amount
- signal
- information recording
- focus offset
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/094—Methods and circuits for servo offset compensation
Definitions
- the present invention relates to a technique for recording information on an information recording medium such as an optical disc, and a technique for reproducing recorded information.
- an optical pickup In an information recording / reproducing apparatus that records information on an information recording medium such as an optical disc, an optical pickup is used to record and reproduce information.
- the optical pickup includes a laser light source, an objective lens for condensing the laser light emitted from the laser light source on the optical disk, and an actuator for supporting the objective lens movably.
- the actuator controls the position of the objective lens so that the laser beam is correctly focused on the optical disk based on the error signal of the objective lens position with respect to the optical disk.
- the laser beam is correctly focused on the optical disc.
- the focal point of the laser beam may be shifted due to variations in optical design or misalignment of electrical offset. Therefore, at the time of recording and reproducing information, by applying an appropriate offset current corresponding to the above-mentioned shift amount to the focus control current, it is possible to eliminate in-focus shift due to optical design variation or electrical offset. There is a need to.
- Examples of problems to be solved by the present invention include the above. According to the present invention, by determining an appropriate focus offset amount with high accuracy, it is possible to remove a focal point shift caused by variation in optical design or electrical offset, and improve recording / reproduction characteristics. Let it be an issue.
- the information recording / reproducing apparatus moves the objective lens based on the focus control signal including the focus offset amount, and changes the focus state of the laser light with respect to the information recording medium.
- the information recording / reproducing apparatus records information and reproduces the recorded information by irradiating the optical disc with laser light. To record and play back good information
- the focus control unit moves the objective lens based on the focus control signal to bring the laser beam into focus on the optical disc.
- the focus control signal includes a focus offset amount in order to correct the focus deviation. That is, if an appropriate focus offset amount is determined and a focus control signal including the amount is used, the laser beam can be accurately focused on the optical disc.
- an optimum focus offset amount is determined by detecting a feature point of a detection signal obtained when the focus offset amount is changed within a predetermined change range.
- the detection signal is a signal obtained by reproducing the information recorded on the optical disc and having a correlation with the in-focus position.
- the detection signal is based on the amplitude of the RF signal and the RF signal.
- 8 values, asymmetry, modulation depth, etc. can be used.
- These detection signals each have characteristic values when the laser beam is in focus. For example, when the laser beam is in focus, the RF signal amplitude takes the maximum value. Therefore, by detecting the feature point of the detection signal, it is possible to determine the focus offset amount that provides an accurate focus state, that is, the appropriate focus offset amount.
- the focus offset signal in a predetermined change range. Change the signal and measure the detection signal. Therefore, the wider the change range, the longer it takes to determine the appropriate force offset amount. Therefore, the predetermined change range of the focus offset amount should be limited on the condition that the focus position is included. Is effective for shortening the processing time.
- the predetermined change range can be a range of a predetermined focus error amount centered on the zero cross point of the focus error signal. In another preferred example, the predetermined change range may be a range of a predetermined focus error amount within a focus loop lock range.
- the predetermined change range may be a range in which a parameter value indicating a predetermined recording / reproduction characteristic is within an allowable value.
- Range focus error The range including the zero cross point of the signal, the predetermined range within the lock range of the focus loop, the range where the recording / playback characteristics parameter value is within the allowable range value, etc. all include the in-focus position.
- a prediction characteristic of the detection signal is generated based on a value of the detection signal corresponding to a plurality of focus offset amounts, and the characteristic point of the prediction characteristic is included.
- a change range determining means for determining a range as the predetermined change range can be further provided.
- the detection signal may be an amplitude value of a reproduction RF signal of recorded information
- the feature point may be a point where the amplitude value is a maximum value. Since the amplitude value of the reproduced RF signal takes the maximum value at the focal point of the laser beam, it is possible to determine the appropriate focus offset amount by detecting the maximum value of the amplitude value of the RF signal as a feature point.
- the detection signal can be a 13-value of a reproduction RF signal of recorded information
- the feature point can be a change point of the ⁇ value.
- the ⁇ value of the reproduction RF signal takes a changing point at the focal point of the laser beam.
- the change point is the point where the tangential component of the j8 value changes greatly. Therefore, an appropriate focus offset amount can be determined by detecting a change point of the value of the reproduction RF signal as a feature point.
- the detection signal can be an asymmetry value of a reproduction RF signal of recorded information
- the feature point can be a change point of the asymmetry value.
- the asymmetry value of the reproduction RF signal takes a change point at the focal point of the laser beam.
- the change point is a point where the tangent component of the asymmetry value changes greatly. Therefore, an appropriate focus offset amount can be determined by detecting a change point of the asymmetry value of the reproduction RF signal as a feature point.
- the detection signal may be a modulation degree of a reproduction RF signal of recorded information
- the feature point may be a point at which the modulation degree is a maximum value. Since the modulation degree of the reproduction RF signal takes the maximum value at the focal point of the laser beam, an appropriate focus offset amount can be determined by detecting the maximum value of the modulation degree of the RF signal as a feature point. It is out.
- an information recording / reproducing method executed in an information recording / reproducing apparatus including a focus control unit having an objective lens changes a focus offset amount within a predetermined change range.
- the objective lens is moved based on a determination step for determining an optimum focus offset amount by detecting a feature point of the detection signal obtained at the time of detection, and a focus control signal including the optimum focus offset amount.
- a focus control step for controlling the focus state of the laser beam with respect to the information recording medium. Also with this method, an appropriate focus offset amount can be determined with high accuracy, as in the information recording / reproducing apparatus.
- a focus position adjustment program executed by an information recording / reproducing apparatus including a focus control unit having an objective lens and a computer includes a focus control including a focus offset amount.
- the above-described information recording / reproducing apparatus can be realized by executing this focus position adjustment program on an information recording / reproducing apparatus including a computer and controlling a focus control unit having an objective lens.
- FIG. 1 is a block diagram showing a schematic configuration of an information recording / reproducing apparatus according to an embodiment of the present invention.
- FIG. 2 is a graph showing the relationship between the RF signal amplitude and the playback RF signal ⁇ value and the focus offset amount.
- FIG. 3 is a diagram schematically showing the definition of ⁇ value.
- FIG. 4 is a graph showing the relationship between recording power and ⁇ value.
- FIG. 5 is a graph showing the relationship between the RF signal amplitude and the playback RF signal ⁇ value and the focus offset amount.
- FIG. 6 is a flowchart of focus offset amount determination processing.
- FIG. 7 is a diagram illustrating an example of a change range of a focus offset amount.
- FIG. 8 is a diagram for explaining the definitions of asymmetry and modulation degree.
- FIG. 9 is a graph showing the relationship between the degree of modulation as a detection signal, the ⁇ value of the reproduction RF signal, and the focus offset amount.
- FIG. 10 is a graph showing a relationship between a ⁇ value as a detection signal, a ⁇ value of a reproduction RF signal, and a focus offset amount.
- FIG. 11 is a graph showing the relationship between the asymmetry as a detection signal and the ⁇ value of the reproduction RF signal and the focus offset amount.
- FIG. 1 shows a schematic configuration of an information recording / reproducing apparatus according to an embodiment of the present invention.
- an information recording / reproducing apparatus 1 includes an optical pickup 2, an objective lens position control unit 4, a detection signal measurement unit 5, a system control unit 6, a memory 7, and a spindle motor 8.
- FIG. 1 mainly shows a configuration related to the focus position adjustment of the present invention, among the components of the information recording / reproducing apparatus.
- the information recording / reproducing apparatus 1 records information on the optical disc D and reproduces information from the optical disc D.
- Optical disc D is, for example, CD—RZRW (Compact Disc-Recordable / Rewri table), DVD—R / RW (Digital Versatile Disc—Recordable / Re—recordable, DVD + R / RW (Digital Versatile Disc + Recordable / Rewritable) ⁇ Blu ⁇ Ray (Blu-ray Disc), AOD (Advanced Optical Disc), etc. can be an optical disc that can record information only once or multiple times.
- the spindle motor 8 rotates the optical disc D at a predetermined speed.
- the optical pickup 2 irradiates the optical disk D with the laser light 9 and receives the return light from the information recording surface of the optical disk D.
- the optical pickup 2 includes a light source such as a laser diode (not shown), an objective lens 21, an actuator 22, a light receiving unit 23, and a calculation unit 24.
- the objective lens 21 condenses the laser beam emitted from a light source (not shown) such as a laser diode on the disk D.
- the actuator 22 supports the objective lens 21 so as to be movable in a direction 25 perpendicular to the recording surface (lower surface in the figure) of the optical disk D.
- the light receiving unit 23 is configured by, for example, a four-divided photodetector, receives the return light from the optical disc D, generates an electric signal corresponding to the amount of received light, and supplies the electric signal to the calculation unit 24.
- Performance The arithmetic unit 24 generates a reproduction signal of recorded information and a servo error signal for various servo controls by performing a predetermined operation on the electric signal output from each of the four divided photodetectors. .
- the calculation unit 24 generates an objective lens position error signal (focus error signal) S1 by a known astigmatism method based on the output signals of the four photodetectors, and the objective lens position control unit Supply to 4.
- the calculation unit 24 calculates the sum of the output signals of the four photodetectors and supplies the sum to the detection signal measurement unit 5 as the reproduction RF signal S2.
- the objective lens position control unit 4 supplies a control signal Iv to the actuator 22 of the optical pickup 2 based on the focus error signal S1 supplied from the calculation unit 24. Based on the control current Iv from the objective lens position controller 4, the actuator 22 controls the objective lens 21 in the focus direction 25 so that the laser light 9 is in focus on the recording surface of the optical disc D. Control the position. Ideally, if there is no electrical offset in the focus error signal S1 or the control current Iv, the laser light 9 should be controlled to focus on the optical disc D. The focal point may shift due to variations or misalignment of the electrical offset. At this time, the control current Iv is supplied to the optical pickup 2 after adding an offset current described later. In the following description, this offset current amount is also referred to as “focus offset amount”.
- the detection signal measuring unit 5 measures the amplitude of an RF signal, which is an example of a detection signal, based on the reproduction RF signal S 2 and sends it to the system control unit 6.
- the detection signal is a signal obtained by reproducing the information recorded on the optical disc and having a correlation with the in-focus position.
- the RF signal is an RF signal. In addition to the signal amplitude, it can be the j8 value, asymmetry, modulation depth, etc. obtained based on the RF signal.
- the system control unit 6 is configured by, for example, a microcomputer and executes a focus offset amount determination process in the present invention. Specifically, the control signal S3 for controlling the focus offset amount is supplied to the objective lens position control unit 4 to change the focus offset amount.
- the system control unit 6 is connected to the memory 7.
- the memory 7 stores the maximum value of the reproduction RF signal read during the focus offset amount determination process (hereinafter referred to as “detection signal level maximum value”) and the focus offset amount (hereinafter referred to as “adjustment”). An area for storing the “adjusting focus offset amount”) is provided.
- the optical pickup 2, the objective lens position control unit 4, the detection signal measurement unit 5, and the system control unit 6 constitute a focus control unit in the present invention, and the system control unit 6 and the memory are determined in the present invention. It constitutes the means.
- the system control unit 6 changes the focus offset amount by a predetermined amount within a predetermined change range from the minimum value force to the maximum value, Each time, the RF signal amplitude as a detection signal is measured. Then, the maximum value of the RF signal amplitude and the focus offset amount at that time are obtained. As described above, when the laser beam is in focus, the RF signal amplitude is maximum, so the focus offset amount force when the RF signal amplitude reaches the maximum value corresponds to an appropriate focus offset amount. .
- FIG. 2 shows an example of measurement data obtained by this peak search method.
- the RF signal amplitude obtained when the information already recorded on the optical disk is read out while changing the focus offset amount by a predetermined amount is shown as a number of plot points 110.
- the horizontal axis indicates the focus offset amount
- the vertical axis (left) indicates the RF signal amplitude.
- the focus offset amount “a” when the RF signal amplitude reaches the maximum value is determined as an appropriate focus offset amount.
- FIG. 2 the ⁇ value of the RF signal obtained by recording the information after fixing the recording power and changing the focus offset amount and reproducing it is shown as graph 113.
- the vertical axis (right) shows the measured ⁇ value of the reproduced RF signal after fixed power recording.
- FIG. 3 schematically shows the definition of the ⁇ value.
- the ⁇ value is a parameter indicating the amount of deviation between the average level of the RF signal and the center value of the amplitude level of the RF signal (center value of all marks).
- the average level of the RF signal can be obtained, for example, by passing the RF signal through an LPF (Low-Pass Filter).
- the center value of the amplitude level of the RF signal can be obtained by calculating the minimum level and the maximum level force of the RF signal corresponding to the reproduced recording data. For example, the j8 value is closer to “0”, that is, the smaller the difference between the average level of the RF signal and the center value of the amplitude level of the RF signal, the better.
- FIG. 4 shows the correlation between the recording power and the ⁇ value. Specifically, Fig. 4 shows the
- the energy of the laser beam is most concentrated at the irradiation point on the optical disc D, so that the recording power efficiency is the best.
- the optical disc is irradiated with the laser beam blurred, resulting in a large recording power loss and the recording power applied to the optical disc. Is substantially reduced. Therefore, the relationship between the focused state of the laser beam and the j8 value is maximized when the laser beam is focused on the optical disk. Therefore, when the laser beam is in focus, that is, when an appropriate focus offset amount is set, the j8 value takes the maximum value.
- the 13-value graph 113 shows the ⁇ value of the reproduction RF signal after fixed power recording in FIG. 2, in the focus offset amount “a” obtained by the above-described peak search method, the 13-value graph 113 is almost the same. The value near the maximum value is shown. Therefore, it is possible to evaluate that the focus offset amount “a” when the RF signal amplitude obtained by the peak search method becomes the maximum value is an appropriate force offset amount. Also, by adjusting the focus offset amount as an adjustment value to the control current Iv, it is possible to correct the focus deviation during recording / reproducing, and the recording characteristics and reproducing characteristics can be improved.
- FIG. 2 shows RF signal amplitude prediction characteristics 112 obtained by second-order parabolic approximation.
- This prediction characteristic 112 sets the focus offset amount to three different values, detects the RF signal amplitude at that time, obtains three plot points 111, and based on these three plot points 111! /, (This method is also referred to as the “parabolic approximation method”).
- the RF signal amplitude prediction characteristic 1 12 obtained by the parabolic approximation method when the focus offset amount at the point where the RF signal amplitude becomes the maximum value is obtained, the value is “b”.
- the actual RF signal amplitude is detected at a number of points by changing the focus offset amount by a predetermined amount to obtain the RF signal amplitude characteristics. That is, in the peak search method, an actual RF signal amplitude characteristic (a set of plot points 110) is acquired, and an optimum focus offset amount is obtained based thereon.
- the parabolic approximation method detects only a few representative focus offset values (three plot points 111 in the above example), and based on them, predicts the RF signal amplitude by parabolic approximation. Is getting. That is, the acquired RF signal amplitude characteristic 112 is just a prediction characteristic.
- the parabolic approximation method can determine an appropriate focus offset amount with the same accuracy as the peak search method when the actual RF signal amplitude characteristics are close to the characteristics predicted by the parabolic approximation. If the RF signal amplitude characteristics are different from those predicted by parabolic approximation, an error will be included.
- the RF signal amplitude prediction characteristic 112 obtained by the parabolic approximation method has an actual RF signal amplitude characteristic (that is, a set of plot points 111 obtained by the peak search method). This is an example when there is a deviation, and therefore the accuracy of the appropriate focus offset amount “b” obtained by the parabolic approximation method is low!
- FIG. 5 the actual RF signal amplitude characteristics obtained by changing the focus offset amount by the peak search method are shown as a plurality of plot points 120.
- a graph 122 shows prediction characteristics of the RF signal amplitude obtained by the parabolic approximation method using the three points 121.
- the appropriate focus offset amount obtained by any method is “d”. In this way, if the actual RF signal amplitude characteristics do not substantially match the prediction characteristics obtained by parabolic approximation, the parabolic approximation method can determine an appropriate focus offset with high accuracy. Absent.
- the peak search method measures the actual RF signal characteristics, detects the maximum value thereof, and determines an appropriate focus offset amount, so that the actual RF signal characteristics are significantly different. Even in such a case, there is an advantage that an appropriate focus offset amount can be determined with high accuracy.
- the case where the actual RF signal amplitude characteristics cannot be predicted by parabolic approximation generally means that the actual RF signal amplitude characteristics are distorted or do not have symmetry around the peak position. Can be given.
- one specific example of such a case is a case where recording or reproduction is performed on one layer of a two-layer optical disc. In the case of a two-layer optical disk, even if the laser beam is focused on one layer, the reflected light from the other layer is also incident on the light receiving unit 23 of the same optical pickup 2. Distortion occurs In many cases, parabolic approximation is a difficult characteristic.
- the maximum value of the RF signal amplitude obtained by the prediction by the second-order parabolic approximation is compared with the maximum value of the RF signal amplitude obtained by the peak search method that actually obtains the maximum value of the RF signal. Deviations as shown in 2 occur.
- the peak search method actually detects the maximum value of the RF signal amplitude characteristics, so the focus offset amount can be adjusted more accurately even in such a double-layer optical disc or optical disc with optical design variations. The value can be obtained.
- FIG. 6 is a flowchart showing an example of the focus offset amount determination process by the peak search method. This process is executed when adjusting the focus position of the laser beam, for example, immediately before the actual information recording when the optical disc D is set in the information recording / reproducing apparatus 1. This process itself is realized by the system control unit 6 shown in FIG. 1 executing a program prepared in advance and controlling each component.
- the RF signal measured during this processing is preferably already recorded on the optical disc D.
- the system control unit 6 records the RF signal on the PCA (Power Calibration Area) etc. of the optical disc D before performing the focus offset amount determination process. Is also possible.
- the system control unit 6 first secures an area for storing “maximum detection signal level value” and “adjustment focus offset amount” in the memory 7.
- the focus offset amount determination processing of the present invention performs peak search and change points of signals other than the RF signal amplitude as described later. It can also be performed by a search (these are called “feature points”). Therefore, in the flowchart of FIG. 6, the “detection signal” will be described as a representative example.
- the system control unit 6 determines a change range of the focus offset amount (step S1). For example, by determining the maximum and minimum values of the focus offset amount to be changed Thus, the range of change can be determined.
- the system control unit 6 sets the focus offset amount to the minimum value in the change range (step S2). More specifically, this is realized by the system control unit 6 covering the control current Iv with an offset current corresponding to the minimum value of the focus offset amount.
- the detection signal measurement unit 5 measures the detection signal level (RF signal amplitude in the above example) when the focus offset amount is the minimum value (step S3). Then, the system control unit 6 stores the focus offset amount in the memory 7 as the adjustment focus offset amount and the detected signal level measured at that time as the maximum detection signal level value (step S4).
- the minimum value of the focus offset and the value of the RF signal at that time are the initial values of the adjustment focus offset and the maximum detection signal level.
- the system control unit 6 sends a control current S3 for increasing the focus offset amount by a predetermined amount, including the minimum value force, to the objective lens position control unit 4.
- the objective lens position control unit 4 sends a control current Iv obtained by increasing the focus offset amount by a predetermined amount to the optical pickup 2 (step S5).
- the detection signal measurement unit 5 measures the level of the detection signal at that time (step S6), and the system control unit 6 calculates the measured RF signal and the maximum detection signal level stored in the memory 7. Compare (step S7). If the measured RF signal is smaller than the maximum detection signal level (step S7: No), the process proceeds to step S9.
- step S7 when the measured RF signal is larger than the maximum detection signal level (step S7: Yes), the system control unit 6 sets the maximum detection signal level currently stored in the memory 7, After updating with the measured detection signal level and further updating the adjustment focus offset amount with the current focus offset amount (step S8), the process proceeds to step S9.
- step S9 the system control unit 6 determines whether or not the current focus offset amount force reaches the maximum value set in step S1, and determines whether or not the force has reached the maximum value. (Step S9: No), return to Step S5, further increase the current focus offset amount by a predetermined amount, and repeat the operations from Step S5 to Step S9.
- the current focus offset amount force reaches the maximum value set in step S1.
- the maximum detection signal level held in memory 7 at that time is the maximum value of the detection signal (RF signal amplitude in the above example). It is stored and determined as an adjustment value for the appropriate focus offset amount for adjusting the focus offset amount (step S10).
- the focus offset amount determination process ends with the end of step S10.
- the system control unit 6 supplies the focus offset amount determined in step S10 to the objective lens position control unit 4 as an appropriate focus offset amount.
- information is recorded or reproduced using an appropriate focus offset amount.
- the focus offset amount is set to the minimum value in step S2, and then the peak search is performed by increasing the focus offset amount by a predetermined amount in step S5.
- the peak search may be performed by decreasing the value by a predetermined amount.
- step S1 the focus offset amount change range determined in step S1 is wide, and the focus offset amount determination processing takes time. Therefore, it is preferable to determine the change range narrowly on condition that the maximum value of the detection signal level is included. Limiting the variable range in this way can increase the adjustment time if the number of detection signal measurements is large, and one way to do this is to limit the range for peak search. It is an effective force to do.
- the change range of the focus offset amount can be set to a predetermined range of the focus error signal.
- the focus error signal exhibits a substantially S-shaped characteristic.
- Figure 7 shows an example.
- the horizontal axis indicates the objective lens position (distance of the objective lens from the optical disk), and the vertical axis indicates the amplitude of the focus error signal.
- the focus error signal 130 is basically in focus at the point where its amplitude becomes zero (referred to as “zero cross point”). Therefore, if the change range of the focus offset amount is set to a predetermined range including the zero cross point of the focus error signal, the maximum value of the detection signal level is included in the range. Should be turned.
- the change range should be set within the range of ⁇ 50% of the amplitude L of the focus error signal 130 (—LZ2 ⁇ force error signal ⁇ LZ2), for example, centered on the zero-cross point of the focus error signal. Can do.
- the system control unit 6 needs to acquire a focus error signal as illustrated in FIG. 7 to determine the change range.
- the change range can be a predetermined range within the lock range of the focus servo.
- the focus servo device mounted on the information recording / reproducing device has a lock range determined in advance according to its capability, and the maximum detection signal level corresponding to the focus position is located near the center of the lock range. It should be. Therefore, it is also possible to set a predetermined amplitude range from the center of the lock range of the focus servo loop as a change range of the focus offset amount.
- the change range can be set to a range in which deterioration of recording and reproduction characteristics can be tolerated.
- the range in which various parameters indicating recording and playback characteristics for example, jitter, asymmetry, eight values, modulation factor, error rate, etc.
- the range of change in the focus offset amount can be determined as the range of change in the focus offset amount. It is.
- the change range of the focus offset amount can be obtained by the parabolic approximation method described above.
- the parabolic approximation method has a characteristic that the characteristics of the detection signal are difficult to approximate to a parabola, and in some cases the accuracy decreases, but a certain degree of accuracy can be secured. Therefore, the prediction characteristic of the detection signal can be calculated by the parabolic approximation method, and the peak value of the detection signal can be set to the change range of the focus offset amount by the peak search method according to the present invention.
- the number of detection signal level measurements can be reduced, and the focus offset amount determination process can be performed quickly. It becomes possible.
- the predetermined amount for changing the focus offset amount in step S5 of the focus offset amount determination process does not necessarily need to be the variable minimum resolution of the focus offset.
- the number of measurements is reduced by providing an interval for acquiring the detection signal level within a range in which desired accuracy can be ensured. May be.
- the detection signal level such as the RF signal amplitude is actually measured over the predetermined change range of the focus offset amount. Therefore, the focus offset amount that maximizes the measured detection signal is determined as the appropriate focus offset amount. Therefore, compared to the parabolic approximation method in which the detection signal level is measured at a small number of points such as three points and the maximum value of the detection signal is obtained by predicting the measured signal force by parabolic approximation, the peak of this embodiment Since the search method actually determines the characteristics of the detection signal, the maximum value of the detection signal level can be determined more accurately. Therefore, according to the information recording / reproducing apparatus in the embodiment, it is possible to obtain the focus offset amount as a more appropriate adjustment value.
- the RF signal amplitude is sequentially measured as the detection signal, and the focus offset amount that maximizes the RF signal amplitude is obtained by the peak search method, thereby obtaining the focus offset amount as the adjustment value.
- the focus offset amount that becomes the adjustment value using the eight values, asymmetry, modulation degree, etc. as the detection signal. is there. This is because, as the RF signal amplitude shows the maximum value near the in-focus point, these characteristic values are also forces that show characteristic values near the in-focus point with respect to the focus offset amount.
- FIG. 8 conceptually shows the modulation factor and asymmetry.
- “Modulation” refers to the ratio between the RF signal amplitude obtained by reading the data recorded on the recording medium and the difference between the RF signal zero level and the peta level.
- FIG. 8 shows an example of an RF signal waveform obtained by reproducing a recording medium. That is, the modulation degree is a ratio of the RF signal amplitude 114 and the difference II 4H between the zero level and the peak level, and is given by the following equation.
- Asymmetry refers to the position of the shortest mark with respect to a predetermined long mark that gives the maximum amplitude in the RF signal in which the recording medium force is also reproduced.
- Asymmetry ⁇ (I14H + I14D / 2- (l3H + I3L) / 2 ⁇ / ll4 (2) That is, as shown in FIG. 8, the RF signal level I14H and I14L corresponding to a predetermined long mark (14T mark), the RF signal level I3H and I3L intermediate level corresponding to the shortest mark, Show the positional relationship of
- Fig. 9 shows a graph 150 of the modulation factor of the RF signal obtained when the focus offset amount is changed, and / / of the RF signal reproduced after recording with the focus offset amount changed with the recording power fixed
- a ternary graph 151 is shown.
- the horizontal axis represents the focus offset amount
- the vertical axis represents the measured modulation degree of the RF signal and the ⁇ value of the reproduced RF signal after fixed power recording.
- the focus offset amount when the measured modulation degree of the RF signal reaches the maximum value is located near the peak position of the j8 value, that is, near the focal point. The Therefore, by using the peak search method and obtaining the maximum value of the modulation degree of the RF signal as a detection signal instead of the RF signal amplitude, an appropriate focus offset adjustment value can be obtained.
- Fig. 10 shows a graph of 13 values of the RF signal measured when the focus offset amount is changed 152 and ⁇ of the RF signal reproduced after recording while changing the focus offset amount while fixing the recording power.
- a value graph 151 is shown.
- the horizontal axis shows the focus offset, and the vertical axis shows the measured RF signal ⁇ value and the reproduced RF signal ⁇ value after fixed power recording.
- the ⁇ value 152 of the measured RF signal indicates the changing point by the value X of the focus offset amount that is in the vicinity of the in-focus point.
- the change point is a position on the graph where the change in the slope of the tangential component of the ⁇ value corresponding to each focus offset amount becomes large.
- the ⁇ value of the RF signal is measured for each predetermined amount up to the minimum value force maximum value of the focus offset amount, and a graph is created based on the measured RF signal value. For each measured point on the graph, by finding the point where the slope of the tangent of the ⁇ value of the RF signal is the maximum, that is, the change point, the focus offset amount at that time, that is, the adjustment value can be obtained. .
- This method is not the peak search method itself, but the RF signal
- the advantage of the present invention is founded in that the ⁇ value of is actually measured and the adjustment value is obtained by detecting the feature point corresponding to the in-focus position.
- this method is referred to as “change point search method”.
- FIG. 11 shows a graph 153 of the RF signal asymmetry measured when the focus offset amount was changed, and / 3 of the RF signal reproduced after recording with the recording offset fixed and the focus offset amount changed.
- a value graph 151 is shown.
- the horizontal axis represents the focus offset amount
- the vertical axis represents the measured RF signal asymmetry and the ⁇ value of the reproduced RF signal after fixed power recording.
- the asymmetry of the measured RF signal indicates the changing point with the force offset amount value X in the vicinity of the in-focus point. Therefore, the change point search method is used to find the slope of the tangent line of the RF signal asymmetry on the graph, and by finding the point where the slope of the tangent line of the asymmetry is the maximum value as the change point, the focus offset amount that becomes the adjustment value You can ask for it.
- the RF signal amplitude may be used as detection signals.
- other characteristic values based on the RF signal such as j8 value, asymmetry, modulation degree, etc.
- the present invention can be used for information recording on an optical disc such as a DVD-R / RW, DVD + R / RW, Blu-ray disc, AOD (Advanced Optical Disc), or CD-RZRW. it can.
- an optical disc such as a DVD-R / RW, DVD + R / RW, Blu-ray disc, AOD (Advanced Optical Disc), or CD-RZRW. it can.
Landscapes
- Optical Recording Or Reproduction (AREA)
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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JP2006528670A JP4234759B2 (ja) | 2004-06-29 | 2005-06-27 | 情報記録再生装置、情報記録再生方法及びフォーカス位置調整プログラム |
JP2006528670D JP4328877B2 (ja) | 2004-06-29 | 2005-06-27 | 情報記録再生装置、情報記録再生方法及びフォーカス位置調整プログラム |
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JP2004-192027 | 2004-06-29 | ||
JP2004192027 | 2004-06-29 |
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WO2006001424A1 true WO2006001424A1 (ja) | 2006-01-05 |
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PCT/JP2005/011742 WO2006001424A1 (ja) | 2004-06-29 | 2005-06-27 | 情報記録再生装置、情報記録再生方法及びフォーカス位置調整プログラム |
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JP (2) | JP4234759B2 (ja) |
WO (1) | WO2006001424A1 (ja) |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0449533A (ja) * | 1990-06-18 | 1992-02-18 | Ricoh Co Ltd | フオーカスオフセット補正方法 |
JPH06162529A (ja) * | 1992-11-18 | 1994-06-10 | Canon Inc | 光学的情報記録再生装置 |
JPH10228652A (ja) * | 1997-02-13 | 1998-08-25 | Funai Electric Co Ltd | 光ディスク読取装置 |
JPH11191225A (ja) * | 1997-12-25 | 1999-07-13 | Mitsubishi Electric Corp | 光ディスク装置 |
JP2002342963A (ja) * | 2001-05-17 | 2002-11-29 | Matsushita Electric Ind Co Ltd | 光ディスク装置及びその制御方法 |
-
2005
- 2005-06-27 WO PCT/JP2005/011742 patent/WO2006001424A1/ja active Application Filing
- 2005-06-27 JP JP2006528670A patent/JP4234759B2/ja not_active Expired - Fee Related
- 2005-06-27 JP JP2006528670D patent/JP4328877B2/ja active Active
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0449533A (ja) * | 1990-06-18 | 1992-02-18 | Ricoh Co Ltd | フオーカスオフセット補正方法 |
JPH06162529A (ja) * | 1992-11-18 | 1994-06-10 | Canon Inc | 光学的情報記録再生装置 |
JPH10228652A (ja) * | 1997-02-13 | 1998-08-25 | Funai Electric Co Ltd | 光ディスク読取装置 |
JPH11191225A (ja) * | 1997-12-25 | 1999-07-13 | Mitsubishi Electric Corp | 光ディスク装置 |
JP2002342963A (ja) * | 2001-05-17 | 2002-11-29 | Matsushita Electric Ind Co Ltd | 光ディスク装置及びその制御方法 |
Also Published As
Publication number | Publication date |
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JP4234759B2 (ja) | 2009-03-04 |
JPWO2006001424A1 (ja) | 2008-04-17 |
JP4328877B2 (ja) | 2009-09-09 |
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