JP4229130B2 - Optical disk device - Google Patents

Description

  The present invention relates to an optical disc apparatus that sets tracking servo control and focusing servo control to a hold state when a beam spot of an optical pickup passes through an address area.

  One of a plurality of types of DVD is a DVD-RAM. In this DVD-RAM, as shown in FIG. 4, data is recorded in both the groove G and land L constituting the data area. It has become. In addition, a CAPA (Complementary Allocated Pit Addressing) area, which is an address area indicating a sector physical address, is provided at the head of each data area. The tracks in the CAPA area are formed so as to be shifted by 1/2 with respect to the tracks (grooves and lands) in the data area in terms of the track width. For this reason, in the track-on state, when the beam spot passes through the CAPA region, a large amplitude level change appears in the tracking error signal. Therefore, the tracking actuator is driven greatly in the radial direction, and tracking is likely to be shifted. . For this reason, the tracking servo gain is reduced to prevent the tracking error. However, when the servo gain is reduced, the followability to the track deteriorates, and the mounted DVD- When the amount of eccentricity of the RAM is large, track deviation tends to occur.

  For this reason, the following technique has been proposed (the first conventional technique). That is, in this technique, the servo gain is set to a small value at the start of tracking servo control, and the servo gain is increased when it is first detected that the beam spot has passed through the CAPA region with the servo gain set small. ing. Thereafter, it is detected whether the beam spot is passing through the CAPA region by counting clocks indicating wobbles formed on the track. When the beam spot starts to pass through the CAPA region, tracking servo control is held, and when the beam spot finishes passing through the CAPA region, the servo control hold is released. For this reason, even when the servo gain is increased to prevent the tracking followability from being deteriorated, the influence of the large amplitude level change that occurs when the beam spot passes through the CAPA region is eliminated, and the beam spot becomes CAPA. The effect of preventing the occurrence of track deviation when passing the area or after passing the CAPA area is obtained (for example, see Patent Document 1).

Further, the following technique has been proposed (referred to as a second conventional technique). In other words, a recordable optical disc has an unrecorded area and a recorded area. The unrecorded area has a higher reflectance, and the recorded area has a lower reflectance than the unrecorded area. For this reason, when the focusing servo gain is optimized in the unrecorded area, the servo gain is insufficient in the recorded area, and when optimized in the recorded area, the servo gain becomes excessive in the unrecorded area. For this reason, the focusing servo gain is first optimized for the ID portion provided at the head of the data area and in which data is always recorded. Thereafter, the beginning of the data portion is detected based on the sector mark recorded in the ID portion, and it is detected whether the data portion is unrecorded or recorded. The servo gain is optimized based on the detection result (see, for example, Patent Document 2).
JP 2000-163766 A JP 61-45420 A

FIG. 3 is an explanatory diagram showing a waveform of an actuator drive signal and a change in servo gain in servo control of focusing (81 in FIG. 3B is a driving signal of a focusing actuator (hereinafter referred to as “for focusing”). ) 82 is a tracking actuator drive signal (hereinafter referred to as a “tracking drive signal”) , and 83 is a focusing servo gain ). With reference to FIG. 3B, a problem that occurs when the first prior art is used will be described.

  That is, after the tracking servo control is started and the track is turned on (time T51), the hold control for holding the tracking servo when passing through the CAPA area may be started immediately. However, after the track is turned on, it is necessary to perform a predetermined setting. In some cases, the hold control cannot be started during the period until the predetermined setting is completed. More specifically, because of variations in the characteristics of the optical pickup, it is necessary to adjust the focus balance so that the amplitude of the RF signal becomes maximum after the track is turned on. May fail. Further, when the front-end control IC is given an address read command, it starts hold control for reading the address, but there is a command for executing only hold control without reading the address. It has no composition. In such a case, if the hold control is started by giving an address read command after the track is turned on, the address read may fail. Therefore, the focus balance adjustment must be performed before the address read command is given. Necessary.

On the other hand, although the track is on, the period before the hold control is started, that is, the sector asynchronous period, is caused by a large level change in the amplitude of the tracking error signal when the beam spot passes through the CAPA region. As a result, a large amplitude change also appears in the focus error signal. Such a phenomenon becomes more prominent in the case of an optical pickup in which the crosstalk between the tracking error signal and the focus error signal is deteriorated. Therefore, when the beam spot passes through the CAPA region, a large amplitude level change 91 also appears in the focusing drive signal, and the focal position of the beam spot is greatly swung in the optical axis direction. As a result, the focusing servo control becomes unstable. However, due to this influence, the tracking servo control becomes more unstable, and the track may shift.

  According to the second conventional technique, the focusing servo gain in the unrecorded area is optimized by changing the focusing servo gain in the unrecorded area and the recorded area, and the focusing servo gain in the recorded area is optimized. It has become a technology to do. For this reason, it is difficult to apply from the viewpoint of solving the problem caused in the first prior art.

  The present invention was devised to solve the above-described problems. The purpose of the present invention is to start the control to hold the servo control when passing through the address area after the tracking servo control is started and the track is turned on. In the period up to this time, by setting the focusing servo gain to a servo gain lower than the servo gain after starting the hold control and higher than the servo gain at the time of track off, the address area track becomes the data area track. On the other hand, when playing back an optical disc positioned in the radial direction, the occurrence of track deviation in the period from when the track is turned on to when the control for holding the servo control is started is preferably performed without causing defocusing. An object of the present invention is to provide an optical disc apparatus capable of preventing the above.

  In order to solve the above-described problems, an optical disc apparatus according to the present invention performs an RF signal processing unit that generates a focus error signal and a tracking error signal from an output of an optical pickup, and performs servo control of focusing based on the focus error signal. At the same time, servo control means for performing tracking servo control based on the tracking error signal, and after the tracking servo control is started and the track is turned on, the focusing servo gain is the first servo gain before the track is turned on. The gain setting means for setting the second servo gain, which is higher than the servo gain, and the tracking servo control and the focusing servo control are held during the period when the beam spot of the optical pickup passes through the address area. It is applied to an optical disc apparatus provided with a holding means for performing a control for a hold control and. The gain setting means sets the focusing servo gain higher than the first servo gain in a period (sector asynchronous period) after the tracking servo control is started and the track is turned on until the hold control is started. The servo gain is set to a third servo gain that is lower than the second servo gain.

  According to the present invention, after the tracking servo control is started and the track is turned on, the focusing servo gain in the period from the start of the hold control to the third servo gain that is lower than the second servo gain is set. The gain is set. For this reason, even when the level change of the tracking error signal leaks to the focus error signal due to the crosstalk in the optical pickup, the level change of the driving signal for the focusing actuator becomes a suppressed level change. Therefore, the amount by which the focusing actuator is shaken in the optical axis direction is also suppressed. For this reason, the level change of the drive signal for the tracking actuator is also suppressed. Further, since the third servo gain is higher than the first servo gain, the occurrence of defocusing is suppressed. For this reason, when playing an optical disc in which the track in the address area is shifted in the radial direction with respect to the track in the data area, the track is shifted in the period from when the track is turned on until the control for holding the servo control is started. This can be suitably prevented without causing a focus shift.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an electrical configuration of a front end of a DVD recorder which is an embodiment of an optical disc apparatus according to the present invention.

  In the figure, an optical pickup 3 is placed on an optical disk (CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD-RW, DVD-RAM, etc.) 1 that is rotationally driven by a spindle motor 2. While irradiating a laser beam having a wavelength corresponding to the optical disc 1, the reflected light from the optical disc 1 is detected. The detected signal is output to the RF signal processing means 6. Further, data is written to the optical disc 1 in accordance with the recording signal output from the recording signal generating means 4.

  The data encoding unit 5 encodes the compressed video / audio information output from the compression / expansion unit (not shown) by performing a predetermined process, and outputs the encoded information to the recording signal generation unit 4. The recording signal generating unit 4 generates a recording signal based on the encoded video / audio information output from the data encoding unit 5 and drives the optical pickup 3.

The RF signal processing means 6 generates a focus error signal (hereinafter referred to as “FE signal” ) 31 and a tracking error signal (hereinafter referred to as “TE signal” ) 32 from the output of the optical pickup 3, and servo servo The data is output to the control means 10 and the microcomputer 9 (hereinafter referred to as “microcomputer” ). Further, the RF signal 33 is generated and output to the data decoding means 7 and the amplitude detecting means 8. The CAPA detection means 20 will be described in detail later.

  The data decoding unit 7 generates a reproduction clock from the RF signal 33 and outputs the generated clock 34 to the servo control unit 10. Further, the digital data is demodulated using the reproduction clock, and the data recorded on the optical disc 1 is reproduced by decoding the demodulated digital data and correcting the error. Then, the reproduced data is output to compression / expansion means (not shown).

  The servo control means 10 servo-controls the focusing of the optical pickup 3 based on the FE signal 31. For this reason, the FE signal 31 is amplified at an amplification factor instructed from the microcomputer 9, and the focusing drive signal 41 is generated by adding the offset voltage 311 output from the microcomputer 9 to the FE signal 31. Further, the tracking of the optical pickup 3 is servo-controlled based on the TE signal 32. For this reason, the TE signal 32 is amplified at the amplification factor instructed from the microcomputer 9 and the tracking drive signal 42 is generated by adding the offset voltage 321 output from the microcomputer 9 to the TE signal 32. Further, the rotation of the spindle motor 2 is servo-controlled based on the clock 34.

The drive circuit 11 amplifies the focusing drive signal 41 and drives a focusing actuator (not shown) in the optical pickup 3. Further, the tracking drive signal 42 is amplified to drive a tracking actuator (not shown) in the optical pickup 3. The spindle motor drive signal 44 output from the microcomputer 9 is amplified to drive the spindle motor 2. The amplitude detector 8 detects the peak level and the bottom level of the RF signal 33, calculates the difference between the detected peak level and the bottom level, and uses the calculation result as a signal indicating the amplitude of the RF signal 33. Output to.

  The microcomputer 9 controls main operations as a front end. That is, when the optical disc 1 is loaded, the type of the loaded optical disc 1 is determined. In addition, the servo control of focusing and tracking is started and stopped, and the spindle motor 2 is started and stopped. Also, focus balance adjustment, defocus adjustment, TE balance adjustment, and the like are performed. Also, servo gain setting in focusing servo control and control for holding tracking servo control and focusing servo control are performed. For this reason, a focus balance adjusting unit 21, a defocus adjusting unit 22, a TE balance adjusting unit 23, a gain setting unit 24, and a holding unit 25 are configured by a part of the functions.

  The focus balance adjusting unit 21 uses the center voltage of the FE signal 31 as a reference voltage (for example, 1.65 V, which is 1/2 of the power supply voltage, 3.3 V) based on the level change of the FE signal 31 when the focusing actuator is driven. ) To detect the offset voltage necessary for the above. Then, the detected offset voltage 311 is output to the servo control means 10 (the offset voltage 311 is added to the FE signal 31 in the servo control means 10).

  The offset voltage 311 at this time is an offset voltage at which the focusing servo control can be most stably performed. However, since the characteristics of the optical pickup 3 vary, the focal position of the beam spot is determined. The offset voltage for accurately positioning the track on the recording surface may not match.

  The defocus adjustment unit 22 detects the offset voltage having the maximum amplitude from the change in the amplitude of the RF signal 33 when the offset voltage 311 added to the FE signal 31 is changed. The detected offset voltage 311 is output to the servo control means 10. Note that the offset voltage 311 at this time is an offset voltage for accurately positioning the focal position of the beam spot on the recording surface of the track in the servo control of focusing (the offset voltage that provides the best signal quality of the output of the optical pickup 3). ).

  The TE balance adjusting means 23 determines the center voltage of the TE signal 32 based on the level change of the TE signal 32 when the beam spot crosses the track as a reference voltage (for example, 1.65 V which is 1/2 of 3.3 V which is the power supply voltage). Etc.) (offset voltage required for setting the TE balance deviation amount to 0) is detected. Further, the detected offset voltage 321 is output to the servo control means 10 (the offset voltage 321 is added to the TE signal 32 in the servo control means 10). Also, if necessary, an offset voltage for accurately positioning the beam spot at the center of the track is detected, and detrack adjustment is performed to output the detected offset voltage 321 to the servo control means 10.

  The gain setting means 24 sets the focusing servo gain to a predetermined servo gain before the focus is turned on, and sets the focusing servo gain to the first servo gain lower than the predetermined servo gain after the focus is turned on. To do. After the tracking servo control is started and the track is turned on, the focusing servo gain is equal to the second servo gain that is higher than the first servo gain (the predetermined servo gain before the focus is turned on). ).

  Further, the gain setting means 24 is configured so that the track of the CAPA area (address area) provided at the head of the data area composed of the groove G and the land L as shown in FIG. In the case of an optical disc positioned in the radial direction with respect to the track in the data area), focusing is performed during the period from when tracking servo control is started and track is turned on until hold control (described in detail later) is started. Is set to a third servo gain that is higher than the first servo gain and lower than the second servo gain.

  When the optical disc 1 is a DVD-RAM, the holding means 25 is in a period in which the beam spot of the optical pickup 3 passes through the CAPA area (period in which the CAPA detection means 20 outputs a CAPA detection signal 36 indicating the detection of the CAPA area). The tracking servo control and the focusing servo control are set to the hold state.

  Below, the CAPA detection means 20 is demonstrated.

  When the optical disc 1 is a DVD-RAM, the CAPA detection means 20 is a wobble indicating a large level change in the amplitude of the TE signal 32 resulting from the beam spot passing through the CAPA region and a wobble formed in the groove G. The period during which the beam spot passes through the CAPA region is detected from the count value of the clock. The detected period is notified to the holding means 25 as a CAPA detection signal 36.

  FIG. 2 is a flowchart showing the main operation of the embodiment in the initial setting when the mounted optical disk is a DVD-RAM, and FIG. 3A is a waveform of the actuator drive signal and the focusing servo in the embodiment. It is explanatory drawing which shows the change of the gain in control. The operation of the embodiment will be described with reference to FIG.

When detecting that the optical disk (DVD-RAM) 1 is loaded, the gain setting means 24 gives an instruction to the servo control means 10 to set the focusing servo gain 43 to 0 dB which is the second servo gain. (Steps S1, S2). The focus balance control means 21 drives the focusing actuator to detect an offset voltage that makes the focus balance deviation amount 0, and outputs the detected offset voltage 311, thereby adding the offset voltage 311 to the FE signal 31. To do. Then, the servo control of the focusing by the servo control means 10 is started and the focus is turned on (step S3) (time T1).

  Note that the focus balance at this time is the balance that stabilizes the servo control of focusing most, but due to variations in the characteristics of the optical pickup 3, it does not match the offset voltage that maximizes the amplitude of the RF signal. There is.

When the focus is turned on at time T1, the gain setting unit 24 sets the focusing servo gain 43 to -6 dB, which is the first servo gain, as in the prior art (step S4). In this state, tracking balance adjustment is performed (step S5), and then tracking servo control is started to turn on the track (step S6) (time T2).

Even after the track is turned on, if the focusing servo gain 43 is kept at the first servo gain (−6 dB), the focus may be lost due to insufficient servo gain. On the other hand, when the focusing servo gain 43 after the track-on (after time T2) is set to the second servo gain (0 dB), the level change on the TE signal 32 side leaks to the FE signal 31 side. As a result, the level change of the focusing drive signal 41 is increased (see 91 in FIG. 3B), and the focusing actuator is greatly shaken. Since the influence also appears on the TE signal 32 side, the level change of the tracking drive signal 42 becomes large (see 92 in FIG. 3B), and there is a possibility of deviation from tracking.

From the above, when the track is turned on (time T2), the gain setting unit 24 sets the focusing servo gain 43 to be lower than the second servo gain (0 dB) and lower than the first servo gain (−6 dB). The third servo gain (−3 dB), which is a high gain, is set (step S7).

When the focusing servo gain 43 is set to the third servo gain, even when the level change of the TE signal 32 leaks to the FE signal 31 due to crosstalk, as shown by 61 in FIG. In addition, the level change of the focusing drive signal 41 is suppressed to about 0.7 times the level change of the prior art (indicated by 91). Therefore, the amount by which the focusing actuator is shaken in the optical axis direction is also suppressed. For this reason, the level change of the tracking drive signal 42 is also suppressed (see 62), and the probability of occurrence of tracking deviation is greatly reduced.

  As described above, the defocus adjustment unit 22 detects and outputs an offset voltage at which the level of the RF signal is maximum based on the output of the amplitude detection unit 8 in a state where the probability of occurrence of tracking deviation is small. . The output offset voltage 311 is added to the FE signal 31 in the servo control means 10. That is, defocus adjustment is performed (step S8). As a result, thereafter, focusing servo control is performed so as to maximize the amplitude of the RF signal. That is, focusing servo control is performed without fear of failure in reading the address in the CAPA area. For this reason, when the address recorded in the CAPA area is read, the address recorded in the CAPA area can be read without failing in reading.

From the above, the microcomputer 9 shifts to the control for reading the address after the defocus adjustment is completed (after time T3). That is, based on the CAPA detection signal 36, the hold unit 25 starts hold control for holding the focusing servo control and the tracking servo control during the period in which the beam spot passes through the CAPA region. Also, reading of the address recorded in the CAPA area is started (step S9) (time T3). At the same time, the gain setting means 24 sets the focusing servo gain 43 to 0 dB as the second servo gain (step S10).

  Therefore, hereinafter, the address reading and the data reading are performed in a state in which focusing servo control is performed in which the probability of occurrence of tracking error is small and there is no risk of address reading failure. Become.

In addition, this invention is not limited to the said embodiment . Although the case where the present invention is applied to a DVD recorder has been described in the above embodiment , the same applies to other apparatuses including a DVD-RAM playback function (for example, a DVD player, a hard disk drive integrated DVD recorder, etc.). The present invention can be applied to.

In the above embodiment, the difference between the first servo gain and the second servo gain 6 dB, a case has been described in which the difference between the second servo gain and the third servo gain and 3 dB, third In the case where the servo gain is smaller than the second servo gain and larger than the first servo gain, the same applies to the case where the difference between the first to third servo gains becomes other values. The present invention can be applied to.

In the above-described embodiment, the case where the defocus adjustment is performed based on the amplitude of the RF signal has been described. However, in the present invention, the defocus adjustment may be performed based on the jitter amount.

It is a block diagram which shows the electric constitution of the front end of the DVD recorder which is one Embodiment of the optical disk device based on this invention. It is a flowchart which shows the main operation | movement of embodiment in the initial setting when the mounted optical disk is DVD-RAM. It is explanatory drawing which shows the change of the servo gain in the servo control of the actuator drive signal, and focusing servo. It is explanatory drawing which shows the track | truck and CAPA area | region (address area | region) of DVD-RAM.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 3 Optical pick-up 6 RF signal processing means 10 Servo control means 24 Gain setting means 25 Hold means 31 Focus error signal 32 Tracking error signal 33 RF signal 34 Reproduced clock 36 CAPA detection signal 41 Focusing drive signal 42 Tracking drive Signal A1, A2 CAPA area G Groove L Land

Claims (1)

RF signal processing means for generating a focus error signal and a tracking error signal from the output of the optical pickup;
Servo control means for performing focusing servo control based on the focus error signal and performing tracking servo control based on the tracking error signal;
After tracking servo control is started and the track is turned on, the servo setting for focusing is set to a second servo gain that is higher than the first servo gain that is the servo gain before the track is turned on. Means,
In a period during which the beam spot of the optical pickup passes through the address area, the optical disc apparatus includes hold means for performing hold control, which is control for setting tracking servo control and focusing servo control to a hold state.
The gain setting means sets the focusing servo gain higher than the first servo gain and lower than the second servo gain during a period from when tracking servo control is started and track-on is started until hold control is started. An optical disc apparatus, wherein a third servo gain, which is a servo gain, is set.

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