JP4968753B2 - Information recording / reproducing apparatus and method - Google Patents

Description

  The present invention relates to a technical field of an information recording / reproducing apparatus and method for recording or reproducing information using, for example, an optical information recording disk (hereinafter, simply referred to as a disk) having surface wobbling.

  In this type of information recording / reproducing apparatus, a light beam converged on the recording surface of the disk by the objective lens is irradiated, and information is recorded or reproduced using the reflected light (or transmitted light). It is necessary to always accurately focus the light beam on the recording surface of the disk (ie, just focus). Therefore, focus servo control for controlling the position of the objective lens in the optical axis direction is indispensable. In the focus servo control, the objective lens is driven in the optical axis direction (that is, the focus direction) so that the focus error signal corresponding to the separation distance between the objective lens and the recording surface becomes a reference level (for example, zero level). Control the focus actuator.

  By the way, even after trying to turn on focus servo control again after turning focus servo control from on to off, if the position of the objective lens is outside the focus pull-in range, a valid focus error signal cannot be obtained. In addition, the focus servo control may not be turned on. In such a case, it is necessary to carry out focus pull-in control after the position of the objective lens is brought close to the focus pull-in range by focus search.

  Then, for example, if the focus is lost while the disc with surface blurring is rotated at high speed (that is, if the position of the objective lens is out of the focus retractable range), the focus is refocused. A search needs to be performed. Further, when calibrating the recording power of the light beam, the focus servo control is once turned off to remove the focus, so that it is necessary to perform the focus search again.

  However, when a disc such as a BD (Blu-Ray: BD) is used as an information recording medium, it is downsized to improve the frequency characteristics of the light receiving element that receives reflected light, so that the focus pull-in range (in other words, The capture range is extremely narrow. Therefore, it can be said that it is extremely difficult to perform the focus pull-in control again while rotating the disc with surface blur at a high speed.

  In order to solve this problem, techniques related to the following patent documents are disclosed.

  Japanese Patent Application Laid-Open No. 2004-133260 discloses a technique for reducing the number of rotations of a disk to the vicinity of the number of rotations corresponding to a standard linear velocity defined by the standard when focus is lost, and then performing focus pull-in control.

  Patent Document 2 captures the rise of the S-curve of the focus error signal, applies a brake signal, and decelerates to match the speed of the focus actuator after approaching the in-focus point, and then performs focus pull-in control Techniques to do this are disclosed.

  In Patent Document 3, the speed of the focus actuator is adjusted after approaching the in-focus point by detecting the relative speed of the objective lens and the disc that moves up and down due to the focus error signal and surface blurring detected in each layer in the multilayer disc. Then, a technique for performing focus pull-in control is disclosed.

  Patent Document 4 discloses a technique for generating an approximate signal of the relative distance between the objective lens and the disc, adjusting the speed of the focus actuator after approaching the vicinity of the focal point, and then performing focus pull-in control.

  However, for example, the following problems may occur in the techniques disclosed in the above-mentioned patent documents. That is, in the technique according to Patent Document 1, since the focus pull-in control is performed after the disk rotation speed is lowered, it takes time to increase the disk rotation speed to the original rotation speed thereafter. In the technique according to Patent Document 2, the relative speed between the focus actuator and the disk depends on variations in the surface blurring of the disk and the focus actuator sensitivity. The technique according to Patent Document 3 cannot be applied to a single-layer disc. The technique according to Patent Document 4 results in a complicated system.

Japanese Patent Laid-Open No. 10-143874 JP-A-11-353657 Japanese Patent Laid-Open No. 2001-243637 Japanese Patent Laid-Open No. 2004-046925

  The present invention has been made in view of, for example, the above-described problems. For example, when focus is lost while a disc with surface blurring is rotated at a high speed, a focus search is performed again and focus pull-in control is performed. Information recording / reproducing apparatus and method for carrying out recording, especially for a disc having a single-layer or multi-layer recording layer, although the configuration is relatively simple, the number of rotations of the disc is not reduced, and the disc Provided is an information recording / reproducing apparatus and method capable of performing focus search again and performing focus pull-in control in a stable and reliable manner almost without being influenced by variations in surface blur amount and focus actuator sensitivity. This is the issue.

  In order to solve the above-described problem, the information recording / reproducing apparatus according to the present invention is configured to support a focus actuator that drives the objective lens in the optical axis direction of the light beam in accordance with a separation distance between the objective lens and the recording surface of the rotating disk. Control based on a focus error signal to perform focus servo control for converging the light beam on the recording surface, so that information is recorded on the recording surface by the light beam, or recorded on the recording surface. An information recording / reproducing apparatus for reproducing recorded information, wherein an AC component for following surface rotation of the rotating disk in a focus drive signal as a drive signal for the focus actuator in a period in which the focus servo control is on Is stored in advance in association with the rotation angle of the rotating disk, The duration of Okasusabo control is turned off, the stored AC components, in association with the rotation angle of the disk to the rotating, an adding means for adding the focus drive signal.

  According to the information recording / reproducing apparatus of the present invention, focus servo control is first performed as follows. That is, when the focus servo control is turned on, a focus error signal corresponding to the separation distance between the objective lens and the recording surface of the rotating disk is obtained by, for example, a four-divided light receiving element, and the focus actuator is controlled based on this signal, Accordingly, the objective lens is driven in the optical axis direction of the light beam so that the light beam is converged on the recording surface.

  Here, when the rotating disk has surface shake, an AC component (that is, an AC component) for following the face shake is generated in the focus drive signal during the period when the focus servo control is on as described above. Therefore, the storage means including a memory or the like stores the AC component in advance in association with the rotation angle of the rotating disk.

  After that, when the focus servo control is switched from on to off, focus search is performed again, and focus pull-in control is performed, for example, an adding unit composed of an adder circuit or the like uses the AC component stored in the storage unit as follows: It is added to the focus drive signal in association with the rotation angle of the rotating disk. Then, the relative speed between the focus actuator and the disk can be maintained substantially constant in a feed forward manner.

  In this case, it does not matter whether the disk is a single layer or a multilayer. In addition, since only the storage means and the addition means need be added, the configuration is relatively simple. Furthermore, since the relative speed between the focus actuator and the disk is kept substantially constant, it is not necessary to reduce the number of rotations of the disk, and it is hardly affected by variations in the surface blurring of the disk and the focus actuator sensitivity. Therefore, according to the information recording / reproducing apparatus of the present invention, the focus search can be performed again and the focus pull-in control can be performed stably and reliably, which is very effective in practice.

  In one aspect of the information recording / reproducing apparatus according to the present invention, the adding means corresponds to the rotation angle of the rotating disk while fading in the stored AC component during the period when the focus servo control is off. In addition, it is added to the focus drive signal.

  According to this aspect, it is possible to avoid adding an abrupt step response to the focus drive signal. Note that “while fading in” includes not only literally the meaning of fading in but also broadly includes the meaning of gradually increasing the level of the stored AC component to the correct level in at least two stages. .

  In another aspect of the information recording / reproducing apparatus according to the present invention, the adding means is configured such that, among the stored AC components, an AC component corresponding to a rotation angle of the rotating disk is within a predetermined AC component level. Then, it starts adding the stored AC component to the focus drive signal.

  According to this aspect, it is possible to avoid adding an abrupt step response to the focus drive signal. Note that “within a predetermined AC component level” means a range determined in advance by experiment, experience, or simulation as an AC component level in which the behavior of the focus actuator has no practical problem when the AC components of the level are added. And is typically zero.

  In another aspect of the information recording / reproducing apparatus according to the present invention, when the stored AC component is added to the focus drive signal, the vibration amplitude of the focus actuator that vibrates at a frequency different from the added AC component. The information recording / reproducing apparatus starts the focus pull-in control after a sufficient time that the vibration amplitude is attenuated. To do.

  According to this aspect, depending on the AC component addition start time due to disc surface vibration, the focus actuator generates unnecessary vibrations. Therefore, for example, the first time measuring means including an electronic clock circuit or the like does not need to be generated at the start of addition. It is monitored whether sufficient time has passed that would dampen any vibrations. Then, after the sufficient time has elapsed, the focus pull-in control is started. As a result, unnecessary vibrations of the focus actuator and AC components are mixed, so that the relative speed between the focus actuator and the disk cannot be maintained substantially constant, and failure of focus pull-in control can be avoided. The “sufficient time” is a range determined in advance by experiment, experience, or simulation as the time that the unnecessary vibration will be sufficiently attenuated when unnecessary vibration of the focus actuator of the amplitude is mixed. is there. The first time measuring means is, for example, a circuit that detects the vibration amplitude of the unnecessary vibration over time, or a circuit that determines whether or not the vibration amplitude falls within a predetermined vibration amplitude threshold that can be said to be sufficiently attenuated. And an electronic clock circuit or the like. Here, the “predetermined vibration amplitude threshold” is a range determined in advance by experiment, experience, or simulation as a vibration amplitude value that is low enough to say that unnecessary vibration is sufficiently attenuated.

  In another aspect of the information recording / reproducing apparatus according to the present invention, after the focus servo control is turned off, the light beam converges on the recording surface from a predetermined time while the focus search is performed again. A second time measuring means for measuring an arrival time required to reach the in-focus position, and the adding means performs the focus search again so that the light beam is moved to the in-focus position. When reaching, in addition to the stored AC component, a brake pulse of a level proportional to the measured arrival time is added to the focus drive signal.

  According to this aspect, when the focus servo control is performed again, when the light beam reaches the in-focus position, it is reached by the second time measuring means including, for example, a focus error signal threshold determination circuit and an electronic clock circuit. Time is measured, a brake pulse is set to a level proportional to the arrival time, and this brake pulse is added to the focus drive signal in addition to the AC component stored as described above. Thereby, even if the disk rotates at high speed, the relative speed between the focus actuator and the disk can be quickly suppressed in a feedback manner. In addition, the focus search can be stabilized. In particular, it is practically advantageous because it can cope with vibrations caused by disturbances other than surface blurring.

  In this aspect, the time measuring means uses the time when the signal level of the focus error signal reaches the minimum value in the S-curve as the predetermined time.

  According to this aspect, since the time is measured within the capture range starting from the time when the focus error signal reaches the minimum value in the S-curve, the measurement accuracy is relatively good. However, it is necessary to check whether or not the focus error signal has reached the minimum value in the S-curve. For example, after that, it is necessary to detect the signal level of the focus error signal several times and sequentially compare with the minimum candidate value. The “minimum value in the S curve” is not limited to the literal minimum value, and a slight margin may be allowed.

  Alternatively, in this aspect, the time measuring means uses a time when the focus error signal reaches a predetermined focus error signal level threshold as the predetermined time.

  According to this aspect, the time measurement accuracy is somewhat sacrificed because the time is measured outside the capture range, but it is necessary to confirm whether or not the signal level of the focus error signal has reached the minimum value in the S-curve. This is relatively easy to implement.

  In order to solve the above-described problem, the information recording / reproducing method according to the present invention is configured to allow a focus actuator that drives the objective lens in the optical axis direction of the light beam to correspond to a separation distance between the objective lens and the recording surface of the rotating disk. Control based on a focus error signal to perform focus servo control for converging the light beam on the recording surface, so that information is recorded on the recording surface by the light beam, or recorded on the recording surface. An information recording / reproducing method for reproducing recorded information, wherein an AC component for following a surface shake of the rotating disk in a focus drive signal as a drive signal for the focus actuator during a period in which the focus servo control is on Is stored in advance in association with the rotation angle of the rotating disk, and The duration of Okasusabo control is turned off, the stored AC components, in association with the rotation angle of the disk to the rotating, an adding step for adding to the focus drive signal.

  According to the information recording / reproducing method of the present invention, as in the information recording / reproducing apparatus of the present invention described above, the focus search can be performed again and the focus pull-in control can be performed stably and reliably.

  Note that the information recording / reproducing method of the present invention can also cope with various aspects of the above-described information recording / reproducing apparatus of the present invention.

  As described above, according to the information recording / reproducing apparatus of the present invention, the storage means and the adding means are provided, and according to the information recording / reproducing method of the present invention, the storage process and the adding process are provided. It is possible to perform focus search again and perform focus pull-in control stably and reliably.

  The operation and other advantages of the present invention will become apparent from the embodiments described below.

It is a side view which shows a mode that focus pull-in control is implemented in the information recording / reproducing apparatus which concerns on a comparative example, and its subject. It is a side view which shows a mode that focus pull-in control is implemented in the information recording / reproducing apparatus which concerns on another comparative example, and its subject. 4A is a characteristic view showing a focus error signal capture range obtained by the light receiving element 10 and a top view after the light receiving element 10 is downsized and FIG. It is a block diagram which partially shows the especially required location among the information recording / reproducing apparatuses 1 which concern on 1st Example. Numbers assigned according to the rotation angle of the disk 100 to be recorded or reproduced by the information recording / reproducing apparatus 1 according to the first embodiment (in other words, the rotation angle of the rotation shaft of the spindle motor 200 that rotates the disk 100). FIG. FIG. 6 is a characteristic diagram showing a relationship between a focus drive signal FOD following a surface blur and a rotation angle of the disc 100, which is stored in the storage unit 232 of the information recording / reproducing apparatus 1 in the first example. 6 is a time chart showing a focus drive signal FOD and other signals when performing a focus search again in the information recording / reproducing apparatus 1 in the first example. 6 is a time chart for explaining conditions for starting to add a stored AC component to a focus drive signal FOD when performing a focus search again in the information recording / reproducing apparatus 1 in the first example. In the information recording / reproducing apparatus 1 which concerns on the modification of 1st Example, (a) It is a time chart which shows a mode that the stored AC component is added to the focus drive signal FOD, fading in. In the information recording / reproducing apparatus 1 according to the modification of the first embodiment, the AC component stored in advance, the unnecessary vibration of the focus actuator 12 caused by the addition of the AC component, and the AC component and the unnecessary vibration component are combined. 5 is a time chart showing a focus drive signal FOD added in the step. It is a block diagram which shows a part especially required among the information recording / reproducing apparatuses 1 based on 2nd Example. In the information recording / reproducing apparatus 1 which concerns on 2nd Example, it is a time chart which shows a mode that the brake pulse of the level proportional to the measurement specification of arrival time Time A and the arrival time Time A is further added to the focus drive signal FOD. . In the information recording / reproducing apparatus 1 which concerns on 2nd Example, it is a time chart which expands and shows a mode that the brake pulse of the level proportional to arrival time Time A is further added to the focus drive signal FOD.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Information recording / reproducing apparatus 10 Light receiving element 2 Control part 232 Storage part 24 Calculator 25 Low pass filter 26 Switch 20 A / D conversion part 281 Time measurement part

  Hereinafter, the best mode for carrying out the present invention will be described for each embodiment in order with reference to the drawings.

(1) First Example The configuration and operation of an information recording / reproducing apparatus according to a first example will be described with reference to FIGS.

  FIG. 1 is a side view showing how focus pull-in control is performed in an information recording / reproducing apparatus according to a comparative example and the problem thereof. FIG. 2 is a side view showing how focus pull-in control is performed and its problems in an information recording / reproducing apparatus according to another comparative example.

  As shown in FIG. 1, when a focus search is performed while the disc 100 with surface blurring is rotating at a high rotation speed of, for example, 9400 rpm, the moving speed Vdisc in the focus direction of the disc 100 causes the objective lens 11 to pass through the light beam. The movement speed Vsweep in the focus direction by the focus actuator 12 driven in the optical axis direction exceeds and reverses back (see the focus error signal FE and the focus drive signal FOD in the lower right in FIG. 1), and the focus is pulled in at an inappropriate position. There is a risk of starting control. Therefore, it is necessary to increase the moving speed Vsweep of the focus actuator 12 or increase the level of the threshold voltage fe_threshold1 related to the focus error signal FE.

  However, as shown in FIG. 2, simply increasing the moving speed Vsweep of the focus actuator 12 causes the disk 100 and the focus actuator 12 to move when the moving speed Vdisc of the disk 100 approaches the objective lens 11. The relative speed of the lens becomes too high, and the focus pull-in may fail. Therefore, it is necessary to improve the focus search that enables stable focus pull-in even when the relative speed between the disc 100 and the focus actuator 12 is high.

  In addition, the optical pickup 15 of the information recording / reproducing apparatus incorporates a light receiving element (OEIC: Opto-Electronic Integrated Circuit) 10 that receives the reflected light of the light beam on the disk 100 together with the focus actuator 12. Here, when BD is used as the disk 100, it is known that a method of reducing the size of the light receiving element 10 and improving various signal qualities is effective for increasing the speed.

  However, when the light receiving element 10 is downsized, there is a possibility that the difficulty of pulling in the focus may further increase as will be described in detail below. FIG. 3 is a characteristic diagram showing (a) a top view before the light receiving element 10 is downsized, and (b) a top view after the downsizing, and a capture error signal capture range obtained by the light receiving element 10.

  As shown in the left diagrams of FIGS. 3A and 3B, the light receiving element 10 is a quadrant detector, and the reflected light forms a beam spot BS. The focus error signal FE at this time is calculated by the adder 42 when calculated by the adder 41 (S1 + S3) using the received light amounts (S1 to S4) of the reflected light detected by the respective detection elements 10a to 10d. From (S2 + S4), the subtractor 43 calculates (S1 + S3) − (S2 + S4). The focus position at which the focus error signal FE obtained in this way becomes 0 is the focus servo control close position. At this time, if the capture range CR is defined as the distance of the focus position corresponding to P-P (Peak to Peak) of the S-shaped curve amplitude, as shown in the right diagrams in FIGS. 3 (a) and 3 (b). It can be seen that the capture range CR is narrowed as the light receiving element 10 is downsized. For this reason, the difficulty of pulling in the focus further increases. For example, if the focus is lost while the disk 100 with surface blurring is rotated at high speed, it is not easy to perform focus search again and perform focus pull-in control.

  Therefore, in the first embodiment, as described in detail below with reference to FIGS. 4 to 7, even if the relative speed between the disk 100 and the focus actuator 12 is high, this value is substantially constant in a feedforward manner. The focus search can be performed again stably and reliably.

  FIG. 4 is a block diagram partially showing particularly necessary portions in the information recording / reproducing apparatus 1 according to the first embodiment. In FIG. 4, other known components necessary for the information recording / reproducing apparatus 1 are omitted as appropriate. For example, a tracking servo system, a spindle servo system, a recording / reproducing signal processing system, Of course, a signal input / output system or the like is provided.

  As shown in FIG. 4, the information recording / reproducing apparatus 1 according to the first embodiment records information on a recording surface of a disc 100 such as a CD (Compact Disc), a DVD, a BD or the like, or is recorded on the recording surface. A device for reproducing information.

  A spindle motor (SPDL) 200 has a turntable fixed to its output rotation shaft, and clamps the disk 100 on the disk mounting surface of the turntable and rotates it at a predetermined rotational speed. Further, the spindle motor 200 is provided with an FG detection unit 201. Here, FIG. 5 shows the rotation angle of the disk 100 to be recorded or reproduced by the information recording / reproducing apparatus 1 in the first embodiment (in other words, the rotation angle of the rotation shaft of the spindle motor 200 that rotates the disk 100). FIG. 3 is a plan view of the disc 100 showing numbers assigned according to

  As shown in FIG. 5, the FG (FG: Frequency Generator) detection unit 201 emits one pulse as an FG pulse signal for each predetermined rotation angle (for example, 10 °) of the disk 100. The generated FG pulse signal is stored in a storage unit (MEM) 232 in a control unit (DSP: digital signal processor) 2. Thereby, the control part 2 can grasp | ascertain the rotation angle of the disc 100 to rotate.

  On the other hand, the information recording / reproducing apparatus 1 includes an optical pickup 15. The optical pickup 15 includes an objective lens 11 that condenses the light beam, a focus actuator 12 that drives and controls the objective lens 11 in the focus direction based on the focus error signal FE, and a light receiving element 10 as shown in FIG. Is provided. In addition, of course, a light source for emitting a light beam and other optical systems are provided.

  Based on the amount of reflected light received by the light receiving element 10, a focus error signal FE is generated and input to the control unit 2 via the arithmetic unit 4 including the adder 41 shown in FIG. The Therefore, the focus error signal FE is converted from an analog signal to a digital signal in the A / D conversion unit 20, subjected to predetermined phase compensation in an equalizer (EQ) circuit 21, and then swept from a later-described sweep unit 27. After the instruction and the selective addition of the AC component, the D / A converter 29 converts the signal again into an analog signal, and inputs it to the focus actuator 12 as the focus drive signal FOD via the driver 9.

  By the way, when there is a surface shake in the rotating disk, an AC component for following the surface shake is generated in the focus drive signal FOD during the period when the focus servo control is on. Therefore, the storage unit 232 performs a filtering process on the focus error signal FE including the AC component (in other words, the focus drive signal FOD before D / A conversion) by a low-pass filter (LPF) 231, It is stored in advance in association with the rotation angle of the disk 100 detected by the FG detection unit 201. FIG. 6 shows a relationship between the focus drive signal FOD following the surface blur and the rotation angle of the disc 100, which are stored in the storage unit 232 of the information recording / reproducing apparatus 1 in the first example.

  As described above, the AC component of the focus drive signal FOD, which is stored in the storage unit 232 in advance and follows the surface shake, can be obtained by turning on the switch 26 even when the focus servo control is turned off. It is selectively added to FOD. Specifically, the AC component is obtained by subtracting the DC component from the focus drive signal FOD in which the AC component and the DC component are mixed in the arithmetic unit 24, and is switched via the low-pass filter 25. It is added when 26 is on. The AC component and the DC component are input to the computing unit 24 via the amplifier 224. On the other hand, the DC component is input to the calculator 24 via the adder 233 and the amplifier 234.

  Next, an operation when the AC component stored in advance as described above is selectively added to the focus drive signal FOD will be described with reference to FIG. FIG. 7 is a time chart showing the focus drive signal FOD and other signals when performing the focus search again in the information recording / reproducing apparatus 1 in the first example.

  In FIG. 7, when the focus servo control is switched from on to off, the focus search is again performed (in the case of FIG. 7, it is an up search, but a down search may be performed), the focus pull-in control is performed, and the focus servo control is again performed. A series of situations is shown until it is turned on. That is, during time t1 to t2, the focus actuator 12 moves the objective lens 11 to a position far from the disk 100 in preparation for the up search. During the time t2 to t3, the focus drive signal FOD is maintained at the minimum value fe_min, and the objective lens 11 is made to stand by at that position. Thereafter, during time t3 to t6, the focus actuator 12 moves the objective lens 11 in a direction to approach the disc 100. In the process, the point where the focus error signal FE intersects the predetermined threshold fe_threshold1 is searched, and focus pull-in control is performed. Will be. However, since the disk 100 is rotated at a high speed while having surface blurring, and there are circumstances as shown in FIGS. 1 to 3, the relative speed between the focus actuator 12 and the disk 100 is relatively high. Or, it is very difficult to perform the focus pull-in control again late.

  However, in this embodiment, an AC component for following the surface shake of the disk 100 is stored in advance in the storage unit 223 during the period in which the focus servo control is on. Therefore, for example, during time t3 to t6, the switch 26 is turned on, and the AC component stored in advance is selectively added to the focus drive signal FOD in association with the rotation angle of the rotating disk 100. As a result, the relative speed between the focus actuator 12 and the disk 100 is maintained substantially constant in a feed-forward manner.

  Thereby, according to the information recording / reproducing apparatus 1 which concerns on 1st Example, it becomes possible to perform a focus search again stably and reliably and to implement focus pull-in control.

  However, such addition of AC components can be a steep step response as the focus drive signal FOD. Therefore, as a condition for starting to add the stored AC components, among the stored AC components, the AC component corresponding to the rotation angle of the rotating disk 100 falls within a predetermined AC component level (including its boundary value). In some cases, it is preferable to begin adding the stored AC component to the focus drive signal FOD. In this case, in the example of FIG. 7, when the AC component corresponding to the rotation angle of the rotating disk 100 is substantially zero, addition to the focus drive signal FOD starts, but the AC component falls within a predetermined AC component level. In some cases, the addition start time may be shifted as shown in FIG. FIG. 8 is a time chart for explaining conditions for starting to add the stored AC component to the focus drive signal FOD when performing the focus search again in the information recording / reproducing apparatus 1 in the first example. For example, as shown in the upper part of FIG. 8, when the AC component corresponding to the rotation angle of the rotating disk 100 is at the upper limit value of a predetermined AC component level, the addition of the AC component may be started. Alternatively, as shown in the lower part of FIG. 8, when the AC component corresponding to the rotation angle of the rotating disk 100 is at the lower limit value of the predetermined AC component level, the addition of the AC component may be started. In any case, since the AC component corresponding to the rotation angle of the rotating disk 100 is within a predetermined AC component level, it is possible to avoid adding a sudden step response to the focus drive signal FOD.

  Further, if the AC component stored in advance as described above is suddenly added to the focus drive signal FOD, a sudden step response is added. This countermeasure will be described with reference to FIG. FIG. 9 is a time chart showing how the stored AC component is added to the focus drive signal FOD while fading in the information recording / reproducing apparatus 1 according to the modification of the first embodiment.

  As shown in FIG. 9, when the stored AC component is added to the focus drive signal FOD, it is added while fading in. Thereby, it is possible to avoid adding an abrupt step response to the focus drive signal FOD.

  Further, when the AC component stored in advance as described above is added to the focus drive signal FOD, the focus actuator 12 may vibrate unnecessarily depending on the addition start timing or the like. This countermeasure will be described with reference to FIG. FIG. 10 shows an AC component stored in advance in the information recording / reproducing apparatus 1 according to the modification of the first embodiment, unnecessary vibration of the focus actuator 12 caused by addition of the AC component, and this AC component and unnecessary vibration. It is a time chart which shows the focus drive signal FOD which the component synthesize | combined and added.

  As shown in FIG. 10, the relative speed between the focus actuator 12 and the disk 100 is maintained substantially constant during a period in which unnecessary vibration of the focus actuator 12 and an AC component corresponding to the rotation angle of the rotating disk 100 are mixed. Since it is not possible, even if focus pull-in control is started, there is a high possibility of failure. Therefore, the control unit 2 starts focus pull-in control after a sufficient time has elapsed when unnecessary vibrations generated at the start of addition will attenuate. Thereby, failure of focus pull-in control can be avoided.

(2) Second Example Next, the configuration and operation process of the information recording / reproducing apparatus 1 according to the second example will be described with reference to FIGS. Note that in the second embodiment, the same components as those in the first embodiment shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

  FIG. 11 is a block diagram partially showing a particularly necessary part of the information recording / reproducing apparatus 1 according to the second embodiment.

  As shown in FIG. 11, the information recording / reproducing apparatus 1 according to the second embodiment is different from the information recording / reproducing apparatus 1 according to the first embodiment in terms of a time measuring unit 281 and an amplifier having a brake pulse voltage coefficient K times. 282 is further provided, and a brake pulse is further added to the focus drive signal FOD.

  The time measuring unit 281 includes a circuit capable of detecting the threshold value of the focus error signal FE and measuring the detection time. For example, while the focus search is being performed again, the light beam converges on the recording surface from a predetermined time. The arrival time Time A required to reach the in-focus position is measured. There are two possible measurement specifications for the arrival time Time A. This specification will be described with reference to FIG. Here, FIG. 12 shows that in the information recording / reproducing apparatus 1 in the second example, a measurement specification of the arrival time Time A and a brake pulse having a level proportional to the arrival time Time A are further added to the focus drive signal FOD. It is a time chart which shows a mode.

  In the first measurement specification, as shown in the first row from the top in FIG. 12, the signal level of the focus error signal FE reaches the minimum value in the S-curve as a predetermined time as the measurement start time of the arrival time Time A. Time cap is used. According to this aspect, since the time is measured within the capture range, the measurement accuracy is relatively good. However, it is necessary to check whether the minimum value is truly the minimum value. For example, when the signal level of the focus error signal FE becomes equal to or lower than a predetermined focus error signal level threshold fe_threshold0, the value is assumed to be the minimum value, and then the predetermined number of confirmations Count is determined at a predetermined sampling period Ts. Meanwhile, it is necessary to confirm that the minimum value has not been updated. At this time, in order to identify the time Time cap, it is necessary to go back by the time corresponding to Ts × Count from the point of confirmation, and therefore, a relatively complicated process is required.

  On the other hand, as shown in the second stage of FIG. 12, the second measurement specification indicates the time when the focus error signal FE reaches a predetermined focus error signal level threshold as the predetermined time as the measurement start time of the arrival time Time A. Use. According to this aspect, the time measurement accuracy is somewhat sacrificed because the time is measured outside the capture range, but it is not necessary to confirm the minimum value as described above, and therefore it can be realized relatively easily.

Then, the arrival time Time A obtained according to the first or second measurement specification is amplified K times by the amplifier 282, and a brake pulse having a level of Volt B is obtained as shown in the third stage of FIG. It is done. That is, the level of the brake pulse is
“Volt B = Time A × K”.

  FIG. 13 shows an enlarged time chart of how the brake pulse is further added to the focus drive signal FOD. As shown in FIG. 13, the brake pulse application time Time B is shorter than the surface blurring period T_men related to the focus drive signal FOD. The brake pulse set in this way is added to the focus drive signal in addition to the AC component stored as described above. Thereby, even if the disk 100 rotates at high speed, the relative speed between the focus actuator 12 and the disk 100 can be quickly suppressed in a feedback manner. In addition, the focus search can be stabilized. In particular, it is practically advantageous because it can cope with vibrations caused by disturbances other than the surface shake of the disk 100.

  In the above-described embodiment, the “information recording / reproducing apparatus 1” is a specific example of the subject that implements the “information recording / reproducing apparatus” and the “information recording / reproducing method” according to the present invention. 201 ”,“ light receiving element 10 ”, and“ storage unit 232 ”are specific examples of“ storage unit ”according to the present invention, and“ calculator 24 ”,“ low-pass filter 25 ”, and“ switch 26 ” It is a specific example of the “adding unit” according to the present invention, and the “light receiving element 10”, the “A / D conversion unit 20”, and the “control unit 2” are included in the “first time measuring unit” according to the present invention. This is a specific example, and the “time measuring unit 281” is a specific example of “second time measuring means” according to the present invention.

  It should be noted that the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and is accompanied by such changes. Moreover, it is included in the technical scope of the present invention.

  The present invention can be used in the technical field of an information recording / reproducing apparatus and method for performing a focus search when information is recorded or reproduced using, for example, a BD, DVD, or other disk-shaped recording medium.

Claims (8)

A focus actuator that drives the objective lens in the direction of the optical axis of the light beam is controlled based on a focus error signal corresponding to a separation distance between the objective lens and the recording surface of the rotating disk. An information recording / reproducing apparatus that performs focus servo control for converging a light beam, records information on the recording surface by the light beam, or reproduces information recorded on the recording surface,
In a period during which the focus servo control is on, an AC component for following the surface shake of the rotating disk in the focus drive signal, which is a drive signal for the focus actuator, is associated with the rotation angle of the rotating disk in advance. Storage means for storing;
When focus pull-in control is performed by performing focus search again after the focus servo control is turned off from on , so that the relative speed between the disk and the focus actuator is kept constant, An information recording / reproducing apparatus comprising: an adding unit that adds the stored AC component to the focus drive signal in association with a rotation angle of the rotating disk. When the focus servo control is turned on by performing a focus search again after the focus servo control is turned from on to off , the adding means fades in the stored AC component while rotating the focus servo control. in association with the rotation angle of the disc to the information recording and reproducing apparatus according to claim 1, characterized in adding to the focus drive signal. The adding means converts the stored AC component into the focus drive signal when an AC component corresponding to a rotation angle of the rotating disk is within a predetermined AC component level among the stored AC components. information recording and reproducing apparatus according to claim 1, characterized in that start and added to. When the stored AC component is added to the focus drive signal, a sufficient time is measured during which the vibration amplitude of the focus actuator that vibrates at a frequency different from that of the added AC component will be sufficiently attenuated. A first time measuring means for performing
The information recording and reproducing apparatus, after the elapse the vibration amplitude at will if sufficient time to decay, the information recording and reproducing apparatus according to claim 1, characterized in that initiating the focus pull-in control. After the focus servo control is turned off, while the focus search is performed again, required from a predetermined time, until such time as the light beam onto the recording surface reaches the focus position has converged A second time measuring means for measuring the arrival time;
When the light beam reaches the in-focus position by performing the focus search again, the adding means performs braking at a level proportional to the measured arrival time in addition to the stored AC component. The information recording / reproducing apparatus according to claim 1 , wherein a pulse is added to the focus drive signal. The second time measuring means, the information recording and reproducing apparatus according to claim 5, characterized by using the time at which the signal level of the focus error signal as the predetermined time has reached a minimum value at the S-shaped curve. The second time measuring means, the information recording and reproducing apparatus according to claim 5, wherein the focus error signal as the predetermined timing is characterized by using a time that has reached the predetermined focus error signal level threshold. A focus actuator that drives the objective lens in the direction of the optical axis of the light beam is controlled based on a focus error signal corresponding to a separation distance between the objective lens and the recording surface of the rotating disk. An information recording / reproducing method for performing focus servo control for converging a light beam and recording information on the recording surface by the light beam or reproducing information recorded on the recording surface,
In a period during which the focus servo control is on, an AC component for following the surface shake of the rotating disk in the focus drive signal, which is a drive signal for the focus actuator, is associated with the rotation angle of the rotating disk in advance. The memory process to remember,
When focus pull-in control is performed by performing focus search again after the focus servo control is turned off from on , so that the relative speed between the disk and the focus actuator is kept constant, An information recording / reproducing method comprising: an addition step of adding the stored AC component to the focus drive signal in association with a rotation angle of the rotating disk.

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