JP2006221816A - Focus position adjustment device and recording and reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus position adjustment method capable of obtaining good recording/reproducing characteristics together with a land track and groove track. <P>SOLUTION: While discerning whether the laser beam spot is positioned on the land track or the groove track according to the L/G switch signal LGS from the land groove detection unit 34, the focus position rough detection unit 50 and the focus position precise detection unit 60 detect two new focus positions (for the land and the groove) so that the bit error rate BER that is measured in the error rate measurement unit 33 and the envelope of and the jitter in the reproduction signal RF would improve, and output two control signals (FBAL and FOFF) for changing the control target position into the new two focus position to the focus error detection unit 36. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a focus position adjustment method for adjusting the focus position of an optical disc that can be recorded and reproduced, and a recording / reproduction apparatus that is an optical disc drive apparatus including a focus position adjustment device that adjusts the focus position.

  With the spread of multimedia technology in recent years, optical disk drive devices are widely used as large-capacity auxiliary storage devices in personal computers and audiovisual systems. An optical disc drive device uses an optical disc such as a compact disc (CD) or a digital video disc (DVD) as a recording medium, reproduces information such as computer data and video / audio data recorded on the optical disc, and stores such information. Or recording on an optical disc.

Conventionally, in such an optical disk drive apparatus, focus servo and tracking servo are performed in order to correctly record and reproduce information.
Here, the focus servo is control so that the light beam applied to the optical disk is always in a predetermined convergence state, and indicates a deviation of the position of the light beam with respect to the optical disk (hereinafter referred to as “focus position”). This is performed based on a focus error signal (a signal generated from reflected light at a light beam spot on the optical disk). The tracking servo is control for causing a light beam to follow a spiral track formed on an optical disk.

  The optical disk loaded in the optical disk drive device is rotated by a spindle motor, and a light beam is irradiated when a certain number of rotations is reached. Then, with the focus servo and tracking servo operating, information recorded on the optical disk is reproduced and information is recorded on the optical disk.

However, the conventional optical disk drive apparatus that performs such focus servo and tracking servo has the following problems.
First, a conventional optical disk drive device uses a groove track (a groove portion of a guide groove of a spirally formed track) and a land track (between the grooves) for an optical disk of a single spiral land groove format (SS-L / GFMT). Since the focus servo is performed without distinguishing between the first and second portions, there is a problem that it cannot be said that focus servo with sufficiently high accuracy is performed particularly for a high-density optical disc. Here, the SS-L / GFMT optical disc is formed with a recordable / reproducible groove track and a land track alternately for every round of the optical disc, and from the inner circumference to the outer circumference to the land track and the groove track. An optical disc having a structure capable of continuous recording and reproduction.

In this type of optical disc, when the reflected light from the optical disc passes through the objective lens and is diffracted, it is affected by aberrations at the objective lens and the distribution of the diffracted light differs between the land track and the groove track. As a result, the relationship between the zero level (control target position for the focus position) of the focus error signal and the focus position differs between the land track and the groove track. In other words, in the conventional focus servo, the focus position is controlled to converge to the same control target position, but different focus positions can be obtained for the land track and the groove track. On the other hand, even if the focus position is adjusted so that the reproduction (including recording in a recordable optical disk) is optimal, the optimum reproduction (including recording in the recording optical disk) cannot be obtained on the other side.

  Further, the conventional optical disc drive apparatus has a problem that a reproduction error is large because it is not considered that the zero level of the focus error signal is not necessarily the optimum focus position. That is, the control target position corresponding to the zero level of the focus error signal and the focus position at which the amplitude of the reproduction signal detected by the optical head is optimal (maximum) or the focus position at which the jitter of the reproduction signal is optimal (minimum) ( (Hereinafter referred to as “focus optimum position”) may not necessarily match. In such a case, even if the focus servo is performed with reference to the control target position, the reproduction error is increased because the amplitude of the obtained reproduction signal is small or the reproduction jitter is large. Therefore, sufficient recording / reproducing performance cannot be ensured.

Further, in the case of an SS-L / GFMT optical disk, even if an attempt is made to adjust the focus position so that the amplitude of the reproduction signal is maximized or the reproduction jitter is minimized, the amplitude and reproduction jitter of the reproduction signal in the address area and the data area. There is a problem that an error occurs in the adjustment of the focus position due to the difference in size of the lens.
In an SS-L / GFMT optical disc, there is an address area in which track numbers and sector numbers for identifying the sectors are recorded in advance with concave and convex pits between sectors where data is recorded. The address area is formed with pits in a manner different from that of the data area. For this purpose, a conventional method of adjusting the focus position using the amplitude of the reproduction signal or the magnitude of the reproduction jitter as focus position information (information indicating the current focus position, ie, information indicating the shift state of the position of the light beam with respect to the optical disk). Then, since the value indicated by the focus position information is different between the data area and the address area, an adjustment error occurs.

In addition, when the optical disc is rotated, the optical disc has a surface shake with a constant frequency. However, when the displacement of the surface shake is large, an error occurs in the focus position information due to the influence of the surface shake. As a result, there is a problem that adjustment of the focus position with high accuracy is hindered.
Further, in the SS-L / GFMT optical disc, (1) when the focus position is greatly deviated from the optimum focus position, the acquisition of address information which is a precondition for carrying out the focus position adjustment is normally performed. (2) Although the data area of the optical disk is unrecorded at the time of shipment, focus position information cannot be obtained from the data area in the first place. (3) Therefore, a test pattern is previously recorded on the unrecorded optical disk. Even if recording is attempted, recording may no longer be normal when the focus position is greatly deviated from the optimum focus position. For this reason, when the focus position is shifted so much that the address information cannot be read, the SS-L / GFMT optical disc can no longer search for the optimum focus position. .

Further, in the SS-L / GFMT optical disc, when the data area is not recorded, even if an attempt is made to record a temporary test pattern on the optical disc in advance, the method can no longer be adopted in the write-protected optical disc. There's a problem.
Further, even when recording / reproducing operation is normally performed on an SS-L / GFMT optical disc, the characteristics of the optical head change due to the influence of the environmental temperature, and the focus error signal detected by the optical head is changed. The zero level, that is, the control target position of the focus servo may change depending on the temperature. As a result, even when the optimum focus position is searched and the recording / reproducing operation is normally performed at the time of starting the optical disk drive device, the recording / reproducing is performed due to the subsequent characteristic change of the optical head or the like or the temporal change. If the error rate at the time exceeds the allowable value or the light beam power at the time of recording reaches the upper limit value, it is no longer possible to start searching for the focus position. is there.

In view of the above problems, it is a first object of the present invention to provide a focus position adjustment device and an optical disc drive device that can obtain good recording / reproduction characteristics for both land tracks and groove tracks.
A second object of the present invention is a focus position adjustment that performs high-precision focus position adjustment in consideration of the deviation even when the zero level of the focus error signal is not necessarily the optimum focus position for recording and reproduction. It is to provide a device or the like. Specifically, the problem of occurrence of a reproduction error due to sacrifice of either the amplitude or jitter of the reproduction signal is avoided.

The third object of the present invention is to provide a highly accurate avoidance of disturbance of focus position information due to such an address area even for an optical disk having an address area in which pits are formed in a manner different from that of the data area. It is to provide a focus position adjusting device that performs focus position adjustment.
A fourth object of the present invention is to provide a focus position adjusting device and the like for performing a focus position adjustment in which an adjustment error due to surface wobbling of an optical disk is unlikely to occur.

A fifth object of the present invention is to provide a focus position adjustment device or the like that can perform the focus position search again even when the focus position is shifted so much that the address information cannot be read. That is.
A sixth object of the present invention is to provide a focus position adjustment device and the like that can search for an optimum focus position even with an unrecorded and write-protected optical disk. It is.

  The seventh object of the present invention is that the error rate at the time of recording / reproduction exceeds an allowable range or the light beam power at the time of recording reaches the upper limit due to a change in the temperature characteristics of the optical element. Even if it exists, it is providing the focus position adjustment apparatus etc. which can start the search of an optimal focus position again.

  In order to achieve the first object, the present invention provides a focus position adjusting device for an optical disc having first and second shaped tracks, and an optical disc drive apparatus having such a focus position adjusting device. A focus error detecting means for detecting a convergence state of the light beam applied to the optical disc and outputting a focus error signal indicating the convergence state; and so that the convergence state becomes a predetermined state based on the focus error signal. Focus control means for changing the focus position of the light beam, reproduction state detection means for detecting the reproduction state of the optical disk based on a reproduction signal when information recorded on the optical disk is read, and a light beam spot is the optical disk Detecting which of the first and second shaped tracks of Track detecting means for outputting a track identification signal indicating the track of the track, and focus position searching means for changing the focus position of the light beam so that the reproduction state is better, the focus position searching means comprising the track Based on the reproduction state when the identification signal indicates the first shape track, a first update focus position where the reproduction state is better is determined, and the track identification signal indicates the second shape track. A focus position update unit that determines a second update focus position where the reproduction state is better based on the reproduction state at the time of display, and a focus position when the track identification signal indicates a track of the first shape Change the focus error signal so that is at the first update focus position. A focus error signal changing unit that changes the focus error signal so that a focus position becomes the second update focus position when the track identification signal indicates a second-shaped track; The focus position of the light beam is changed based on the focus error signal changed by the focus error signal changing unit.

  In order to achieve the second object, the present invention provides the focus position adjusting device or the like, wherein the reproduction state detecting means considers the focus error signal in addition to the reproduction signal. Detect state. The reproduction state detection means includes an envelope detection unit that detects an envelope of the reproduction signal, and a jitter detection unit that detects jitter of the reproduction signal, and detects the detected envelope, jitter, and focus error signal. Based on this, the playback state is detected.

  In order to achieve the third object, the present invention provides the focus position adjustment device or the like, and further, an area detection for detecting whether the light beam spot is located in a data area or an address area of the optical disk. The reproduction state detection unit extracts a part of the reproduction signal based on the detection by the region detection unit, and detects the reproduction state from a part of the extracted reproduction signal. The reproduction state detection means detects the reproduction state only for the reproduction signal when the area detection means detects that the light beam spot is located in the data area.

  In order to achieve the fourth object, the present invention is the focus position adjusting device or the like, and further includes a surface shake component removal filter that removes a frequency component indicating the surface shake of the optical disc from the focus error signal. The reproduction state detection means detects the reproduction state from the focus error signal from which the frequency component has been removed and the reproduction signal. The focus position adjusting device further includes sector specifying means for specifying a sector at a position where surface acceleration of the optical disc is reduced, and the playback state detecting means is the playback signal obtained only from the specified sector. And the reproduction state is detected from the focus error signal.

Further, in order to achieve the fifth object, the present invention provides the focus position adjusting device or the like, wherein the focus position update unit is configured such that the reproduction state is more improved when the focus position is shifted by a predetermined movement amount. The first update focus position and the second update focus position are determined by determining whether or not the image quality is good.
In order to achieve the sixth object, the present invention provides the focus position adjusting device or the like, and further includes test data in a test area provided in at least one of a lead-in area and a lead-out area of the optical disc. The reproduction state detection unit detects the reproduction state based on a reproduction signal when the test data is read out.

  Further, in order to achieve the seventh object, the present invention provides the focus position adjusting device or the like, and further, a failure state for determining whether or not the reproduction state is a failure state exceeding a predetermined allowable range. And determining that the focus position update unit determines new first and second update focus positions when the determination unit determines that the defect state is present, and changes the focus error signal to the focus error signal change unit. Re-exploration means.

  In order to achieve the above object, the present invention provides a focus position adjusting device for an optical disc having first and second shaped tracks, and an optical disc drive apparatus having such a focus position adjusting device, wherein the optical disc A focus error detecting means for detecting a convergence state of the light beam applied to the light beam and outputting a focus error signal indicating the convergence state; and based on the focus error signal, the light beam Focus control means for changing the focus position, reproduction state detection means for detecting the reproduction state of the optical disk based on a reproduction signal when information recorded on the optical disk is read, and a light beam spot is the first of the optical disk And whether the track is located on the second shape track. A track detection means for outputting a track identification signal indicating a track, and a focus position search means for changing the focus position of the light beam so that the reproduction state is improved, wherein the focus position search means comprises the track Based on the reproduction state when the identification signal indicates the first shape track, a first update focus position where the reproduction state is better is determined, and the track identification signal indicates the second shape track. A focus position update unit that determines a second update focus position where the reproduction state is better based on the reproduction state at the time of display, and a focus position when the track identification signal indicates a track of the first shape The focus error signal is changed so that becomes the first update focus position, and the traffic is A focus error signal changing unit that changes the focus error signal so that a focus position becomes the second update focus position when the mark identification signal indicates a second shape track, and the focus control means The focus position of the light beam is changed based on the focus error signal changed by the focus error signal changing unit.

  According to this configuration, a distinction is made between when the light beam spot is located on the first shape track and when the light beam spot is located on the second shape track, and independently, a new reproduction state is improved. The focus positions for the land track and the groove track are searched. Then, the focus position is controlled by distinguishing between the land track and the groove track so that these new focus positions become control targets. Therefore, the conventional problem that one of the land track and the groove track is in a good reproduction state but the other is not good is avoided, and the first object is achieved.

  Here, the reproduction state detection means may detect the reproduction state in consideration of the focus error signal in addition to the reproduction signal. The reproduction state detection means includes an envelope detection unit that detects an envelope of the reproduction signal, and a jitter detection unit that detects jitter of the reproduction signal. The reproduction state may be detected based on the above.

  According to this configuration, the reproduction information includes both the envelope and jitter information of the reproduction signal, and the focus position is searched by the focus position searching means based on such a reproduction state. Position adjustment is realized. In other words, when the focus position is controlled by focusing only on the amplitude of the reproduction signal as in the prior art, or when the focus position is controlled by focusing only on the jitter of the reproduction signal, the problem of an increase in reproduction error is avoided, The second object is achieved.

  The focus position adjusting device further includes area detecting means for detecting whether the light beam spot is located in a data area or an address area of the optical disc, and the reproduction state detecting means is used for detection by the area detecting means. A part of the reproduction signal may be extracted based on the reproduction signal, and the reproduction state may be detected from a part of the extracted reproduction signal. The reproduction state detection unit may detect the reproduction state only for a reproduction signal when the region detection unit detects that the light beam spot is located in the data region.

According to this configuration, since the address position of the optical disc is excluded and the focus position is adjusted, even in an optical disc in which pits are formed in different manners in the address region and the data region, Disturbance of focus position adjustment based on the difference is avoided, and the third object is realized.
Further, the focus position adjusting device further includes a surface shake component removing filter for removing a frequency component indicating surface shake of the optical disc from the focus error signal, and the reproduction state detecting means is a focus from which the frequency component has been removed. The reproduction state may be detected from the error signal and the reproduction signal. The focus position adjusting device further includes sector specifying means for specifying a sector at a position where surface acceleration of the optical disc is reduced, and the playback state detecting means is the playback signal obtained only from the specified sector. The reproduction state may be detected from the focus error signal.

According to this configuration, a reproduction state in which the surface shake component of the optical disk is removed is obtained, and the focus position is adjusted based on such a reproduction state. The focus position adjustment is realized, and the fourth object is achieved.
Further, the focus position update unit determines whether the reproduction state becomes better when the focus position is shifted by a predetermined movement amount, thereby determining the first update focus position and the second update focus. The position may be determined.

  According to this configuration, the focus position searching means forcibly shifts the focus position by a predetermined fixed amount of movement, and determines a new target focus position from the reproduction state obtained as a result. For this reason, even if precise adjustment is impossible, the focus position can be restored so that it can be adjusted again. Therefore, the fifth object is achieved.

The focus position adjusting device further includes recording means for recording test data in a test area provided in at least one of a lead-in area and a lead-out area of the optical disc, and the reproduction state detecting means includes the test data The reproduction state may be detected on the basis of a reproduction signal at the time of reading.
According to this configuration, the test data is recorded in an area that is not subject to write protection, and the focus position is adjusted using the test data. Even in the case of an optical disc, the search for the focus position can be executed. Therefore, the sixth object is achieved.

  Further, the focus position adjusting device further includes a failure state determination means for determining whether or not the reproduction state is a failure state exceeding a predetermined allowable range, and when it is determined that the reproduction state is in the failure state, the focus position adjustment device Re-exploring means for causing the position update unit to determine new first and second update focus positions and for causing the focus error signal changing unit to change the focus error signal may be included.

  According to this configuration, since the adjustment of the focus position is started not only when the rotation of the optical disk starts but also when a certain defective state occurs, the defective state is eliminated and the seventh object is achieved. Is done.

Hereinafter, an optical disk drive device 100 according to the present invention will be specifically described with reference to the drawings.
[Configuration of Entire Optical Disk Drive Device 100]
FIG. 1 is a block diagram showing the overall configuration of the optical disc drive apparatus 100.
The optical disc drive apparatus 100 is roughly composed of a mechanism and optical system components 1 to 13, a signal processing unit 40, an optical head control unit 20, and a drive controller 14.

The mechanism and optical system components are an optical disk 1, an optical head 7 (actuator 2, objective lens 3, reproduction signal detector 4, photodetector 5, leaf spring 6, optical head 7, semiconductor laser 8), optical head support member 9. , A coarse motion motor 10, a seek control unit 11, a spindle motor 12, and a rotation control unit 13.
The signal processing unit 40 is a circuit for processing a write signal to the optical disc 1 and a read signal from the optical disc 1, and includes a laser power driving unit 41, a modulation unit 42, an addition amplifier 43, an addition amplifier 44, a difference amplifier 45, and an addition. It comprises an amplifier 46 and a demodulator 47.

The optical head control unit 20 is a circuit that controls the tracking servo and the focus servo of the optical head 7 using various control signals from the signal processing unit 40, and includes a focus driving unit 21, a tracking driving unit 22, and a tracking control unit 23. , An adder 24, a disturbance signal generator 25, a focus controller 26, and a focus position adjuster 30.
The optical disc 1 is a rewritable information recording medium and is mounted on a spindle motor 12. The rotation control unit 13 drives and controls the spindle motor 12 under the control of the drive controller 14. The optical head support member 9 is a member that supports the optical head 7, and is slid in the radial direction of the optical disk 1 by the coarse motion motor 10. The seek control unit 11 controls the seek operation of the optical head 7 by driving the coarse motion motor 10 under the control of the drive controller 14.

  The modulator 42 performs a certain conversion on the signal pattern sent from the drive controller 14 and outputs the obtained signal to the laser power driver 41 later. The laser power driver 41 modulates the output power of the semiconductor laser 8 based on the signal from the modulator 42. As a result, the signal pattern from the drive controller 14 is recorded on the optical disc 1.

  The optical head 7 is a set of a support member 6 such as a semiconductor laser 8, an objective lens 3, a photodetector 5, a reproduction signal detector 4, an actuator 2, and a leaf spring. The light beam emitted from the semiconductor laser 8 passes through the optical system in the optical head 7, is condensed by the objective lens 3, and is irradiated onto the optical disk 1. The light beam reflected by the optical disk 1 passes through the objective lens 3 and the optical system in the optical head 7, and then enters the photodetector 5, the reproduction signal detector 4, and the like.

  The photodetector 5 is a four-divided photodiode that indicates the focus position of the light beam irradiated on the optical disk. Each of the adding amplifiers 43 and 44 outputs the focus signals VFS1 and VFS2 by adding and amplifying two of the four optical signals from the photodetector 5. These focus signals VFS1 and VFS2 are used to generate a focus error signal FES indicating a deviation from a predetermined convergence state of the light beam. That is, here, a focus error detection method based on the astigmatism method is employed.

The reproduction signal detector 4 is a broadband two-division photodiode that detects the amount of reflected light from the optical disc 1 and outputs two reflected light amount signals. Since information (signal pattern) is recorded on the optical disc 1 with a change in reflectance, the information recorded on the optical disc 1 can be read by these two reflected light quantity signals.
The difference amplifier 45 calculates the difference between the two reflected light amount signals from the reproduction signal detector 4 and outputs the difference to the tracking control unit 23 and the focus position adjustment unit 30 as a wideband tracking error signal RFTE. The broadband tracking error signal RFTE is a signal including a reproduction signal (hereinafter referred to as an “address signal”) of an address portion formed on the optical disc 1 with uneven pits. The address pits formed on the optical disc 1 are formed at positions shifted by 1/4 track pitch from the center of the groove track and the center of the land track, respectively, and the broadband tracking error signal RFTE indicating the state of these pits is: This is used for detection of an address area of the optical disc 1, detection of land tracks and groove tracks, tracking servo, and the like.

  The summing amplifier 46 adds the two light quantity signals from the reproduction signal detector 4 and outputs them to the demodulator 47 as a reproduction signal RF. The reproduction signal RF is a wideband signal indicating all information recorded on the optical disc 1. The demodulator 47 binarizes the reproduction signal RF from the summing amplifier 46 with a predetermined threshold value and performs inverse conversion corresponding to the conversion at the modulator 42 to indicate information recorded on the optical disc 1. An RF pulse signal PRF is generated and sent to the focus position adjustment unit 30 and the drive controller 14.

  The focus position adjustment unit 30 has a basic function of generating a focus error signal FES from the two focus signals VFS1 and VFS2, but at this time, by using various control signals RFTE, RF, and PRF, The search for the optimum focus position depending on the position of the beam spot (whether it is located on the land track or the groove track of the optical disc 1) is executed, and the result is reflected in the focus error signal FES. Further, based on the broadband tracking error signal RFTE, a land (L) / groove (G) switching signal LGS indicating whether the current light beam spot is located on a land track or a groove track, and the light beam spot is an address. A gate signal IDGATE indicating the timing at which the region is located is generated.

  The focus position searching by the focus position adjusting unit 30 can be roughly divided into two types, that is, a rough search performed after the optical disk 1 reaches a certain number of revolutions, and immediately after the rough search is completed. There is precision exploration to be performed. And in precision exploration, two functions (optional function) for further improving the accuracy, that is, a function for excluding the surface shake component from the focus error signal FES or for exploring only a specific data area. Can be operated. These two search modes and two optional functions are selected or added under the control of the drive controller 14.

  The focus driving unit 21 and the tracking driving unit 22 supply the actuator 2 with a driving current for changing the position of the objective lens 3 based on signals from the adding unit 24 and the tracking control unit 23, respectively. The actuator 2 is composed of a magnet, a coil, and the like, and moves the objective lens 3 against the reaction force of the leaf spring 6, thereby converging the light beam irradiated onto the optical disk 1 (the light beam and the surface of the optical disk 1 between Relative positional deviation) and positional deviation of the light beam spot from the track) are changed.

  The tracking control unit 23 is a circuit that performs control for tracking servo, and performs feedback control so that the light beam follows the track on the optical disc 1 based on the broadband tracking error signal RFTE from the differential amplifier 45. Further, the tracking control unit 23 always follows only the land track or the groove track based on the L / G switching signal LGS sent from the focus position adjusting unit 30 according to an instruction from the drive controller 14. Such control, that is, control for causing the light beam to jump back (still jump) to the inner peripheral side of the optical disk 1 is performed for each rotation of the optical disk 1.

The focus control unit 26 includes a loop filter for phase compensation and the like. Based on the focus error signal FES from the focus position adjustment unit 30, the focus control unit 26 calculates an error between the focus position indicated by the signal FES and the control target position of the focus servo. A signal that makes zero is generated and output to the adder 24.
Note that the focus control unit 26 and the tracking control unit 23 are based on the gate signal IDGATE sent from the focus position adjustment unit 30 for a time during which the light beam converged and irradiated on the optical disc 1 is located in the address area. The output signal just before entering the area is held. As described above, the address pits formed on the optical disc 1 are formed at positions shifted by 1/4 track pitch from the center of the groove track and the center of the land track. This is because unnecessary areas are excluded from the focus servo and tracking servo targets.

  The disturbance signal generation unit 25 adds a signal necessary for the focus position adjustment unit 30 to perform a precise search of the focus position, specifically, a 1 kHz sine wave signal or the like that changes the focus position by ± 0.4 μm. To the unit 24. The addition unit 24 adds the signal from the focus control unit 26 and the signal from the disturbance signal generation unit 25 under the control from the drive controller 14 (instruction of coarse search or fine search), and the focus drive unit 21. Or the signal from the focus control unit 26 is passed as it is and is output to the focus drive unit 21.

  The drive controller 14 includes a microprocessor, a ROM in which a control program is recorded, and a RAM as a work area. The drive controller 14 controls the rotation control unit 13, the seek control unit 11, the signal processing unit 40, and the optical head control unit 20 in an integrated manner. For example, when a certain condition is detected, various conditions for searching for a specific type of focus position are set for the focus position adjusting unit 30 and the like, and the search is executed.

  2 (a) and 2 (b) are diagrams showing the physical structure of the optical disc 1, FIG. 2 (a) is a schematic view when the optical disc 1 is viewed from above, and FIG. It is an enlarged view near the / G switching point. This optical disc 1 is an SS-L / GFMT optical disc. That is, both the groove (G) and the land (L) of the track formed in a spiral shape can be recorded and reproduced, and the land and the groove are alternately formed for each round of the optical disc 1. Thus, the land and groove can be used continuously for reproduction or recording from the inner periphery to the outer periphery.

As shown in FIG. 2 (a), in this optical disc 1, a land track (indicated by a white line in the figure) and a groove track (indicated by a solid black line in the figure) are connected every rotation, and one spiral is formed. It is composed.
As shown in FIG. 2B, the optical disc 1 has an address area composed of an uneven pit structure for identifying a sector between the data area. Further, the L / G switching point exists for every rotation of the optical disk, and the land and the groove are switched just in the address area. There are 17 address areas per circumference on the inner circumference side of the optical disc 1, one of which is an L / G switching point. A data sector is composed of one set of an address area and a data area. Therefore, for example, one round (= 1 track) on the inner circumference side of the disk is divided into 17 sectors.

  Also, as shown in FIG. 2B, the address area of the optical disc 1 has a pit (hereinafter “ CAPA (Complementary Allocated Pit Address) ”). More specifically, at the end of the data area other than the first data sector including the L / G switching point, the first address is arranged at a position shifted by 1/2 track pitch toward the outer periphery of the optical disc 1 with respect to the groove track. The second address is arranged at a position shifted by 1/2 track pitch toward the inner periphery after the first address. On the other hand, in the first data sector including the L / G switching point, at the end of the data section located in front of the first data sector, the track is shifted by 1/2 track pitch toward the inner circumference side of the optical disc 1 with respect to the groove track. The first address is arranged at the position, and the second address is arranged at a position shifted by 1/2 track pitch to the outer peripheral side after the first address.

2C is a cross-sectional view of the optical disc 1 and the objective lens 3 when a light beam is irradiated on the land of the SS-L / GFMT optical disc 1, and FIG. 2D is a diagram of the SS-L / GFMT. FIG. 4 is a cross-sectional view of the optical disc 1 and the objective lens 3 when a light beam is irradiated on the groove of the optical disc 1. As can be seen from FIGS. 2C and 2D, since the land and the groove of the optical disk 1 are different in shape, when the reflected light from the optical disk 1 passes through the objective lens 3 and is diffracted by the optical head 7, The distribution of diffracted light differs between the land track and the groove track. As a result, the relationship between the zero level of the focus error signal (control target position for the focus position) and the actual focus position is different between the land track and the groove track. For this purpose, the optical disc drive apparatus 100 adjusts the focus position which differs depending on whether the light beam is located on the land track or the groove track. That is, the control target position when the light beam is located on the land track and the control target position when located on the groove track are independent.
[Configuration of Focus Position Adjustment Unit 30]
FIG. 3 is a block diagram showing a detailed configuration of the focus position adjusting unit 30 shown in FIG. The focus position adjustment unit 30 is roughly divided into components for coarse focus position search (error rate measurement unit 33, focus position rough search unit 50) and components for precise search (lead gate detection unit). 32, surface shake component removing unit 35, switching unit 39, focus position precise search unit 60) and components common to them (address signal detecting unit 31, land groove detecting unit 34, two switching units 37, 38, focus) Error detector 36).

  The land / groove detection unit 34 indicates whether the current position of the light beam spot is located on the groove or on the land based on the broadband tracking error signal RFTE output from the differential amplifier 45 of the signal processing unit 40. / G switching signal LGS is generated. Specifically, the land / groove detection unit 34 binarizes a signal obtained by binarizing the peak envelope of the wideband tracking error signal RFTE (hereinafter referred to as “peak envelope signal PEPS”) and the bottom envelope of the wideband tracking error signal RFTE. Signal (hereinafter referred to as “bottom envelope signal BEPS”), and the bottom envelope signal after the logical level of the peak envelope signal PEPS changes when the light beam follows the track on the optical disc 1 and passes through the address area. If the logic level of BEPS changes, it is determined as a groove. Conversely, if the peak envelope signal PEPS changes after the logic level of the bottom envelope signal BEPS changes, it is determined as a land, and a signal indicating the determination result is an L / G switching signal. LGS and To output Te. The L / G switching signal LGS is used for distinguishing lands and grooves in the search for the focus position, or used for causing the tracking control unit 23 to perform a still jump.

  4A to 4C are diagrams illustrating timings of the input / output signals RFTE and LGS of the land / groove detection unit 34. FIG. FIG. 4A shows an outline of the track structure on the optical disc 1 and the locus of the light beam spot moving from the groove track to the land track through the L / G switching point. FIG. 4B shows the light beam spot. FIG. 4C shows the waveform of the wideband tracking error signal RFTE when the track follows the track as shown in the locus shown in FIG. 4A, and FIG. 4C shows the waveform of the L / G switching signal LGS.

  As shown in FIG. 4 (a), the address area of the optical disc 1 is composed of pits (CAPA) which are complementarily arranged at positions shifted from the track center by 1/2 track pitch in the radial direction of the optical disc 1 at the head of the sector. ing. Note that by forming such CAPA, it is possible to reproduce the address information formed by the pits by the broadband tracking error signal RFTE when the light beam passes through the address area.

  Assume that the light beam spot passes through the address area shown in FIG. 4A while following the groove track. Then, as shown on the left side of the timing chart of FIG. 4B, the wideband tracking error signal RFTE has a waveform such that the address signal first appears on the positive side and then appears on the negative side with respect to the zero level. . Subsequently, when the light beam spot passes through the L / G switching point, as shown on the right side of the timing chart of FIG. 4B, the broadband tracking error signal RFTE is first set to the negative side with respect to the zero level. Appears and then appears on the positive side. Since the land / groove detection unit 34 detects the L / G switching point from the polarity inversion sequence as shown in FIG. 4B, the L / G switching signal LGS (light) as shown in FIG. (A signal that becomes “Hi” level when the beam spot is located in the groove and becomes “Low” level when the beam spot is located in the land)).

  The address signal detector 31 receives the wideband tracking error signal RFTE from the differential amplifier 45 of the signal processor 40, outputs an address pulse signal PADR obtained by binarizing the signal RFTE with a predetermined threshold, A gate signal IDGATE (a gate signal which becomes “Low” in the data area and becomes “Hi” in the address area) indicating the timing at which the spot is located in the address area is output. Specifically, a signal obtained by binarizing the peak envelope of the wideband tracking error signal RFTE and a signal obtained by inverting the signal obtained by binarizing the bottom envelope of the wideband tracking error signal RFTE are generated. A gate signal IDGATE is generated.

FIG. 5 is a block diagram showing a detailed configuration of the address signal detection unit 31. The address signal detection unit 31 is roughly composed of components 3101 to 3106 for generating the gate signal IDGATE and a component 3107 for generating the address pulse signal PADR.
The peak envelope detector 3101 detects the peak side envelope of the broadband tracking error signal RFTE) from the reproduction signal detector 4. The bottom envelope detector 3102 detects the bottom envelope of the wideband tracking error signal RFTE. The binarization circuit 3103 binarizes the signal from the peak envelope detector 3101 (a signal indicating the peak envelope of the wideband tracking error signal RFTE) with a predetermined threshold value. The binarization circuit 3104 binarizes the signal from the bottom envelope detection unit 3102 (a signal indicating the bottom envelope of the wideband tracking error signal RFTE) with a predetermined threshold value. The NOT circuit 3105 inverts the output signal from the binarization circuit 3104 and outputs it. The OR circuit 3106 outputs a gate signal IDGATE obtained by ORing the output signal from the binarization circuit 3103 and the output signal from the NOT circuit 3105. The binarization circuit 3107 is an address reproduction signal that appears on the negative side with a positive threshold value that is centered on the amplitude of the address reproduction signal that appears on the positive side with respect to the zero level of the broadband tracking error signal RFTE. In contrast, an address pulse signal PADR obtained by binarization is output at a negative threshold value that becomes the center of the amplitude.

  FIGS. 6A to 6D are timing charts for illustrating a process in which the gate signal IDGATE is generated in the address signal detection unit 31, and FIG. 6A is a broadband signal input to the address signal detection unit 31. The tracking error signal RFTE, FIG. 6B is output from the binarization circuit 3103, FIG. 6C is output from the binarization circuit 3104, and FIG. 6D is output from the address signal detection unit 31. The gate signal IDGATE is shown.

  When a broadband tracking error signal RFTE as shown in FIG. 6A is input to the address signal detection unit 31, the output of the binarization circuit 3103 is as shown in FIG. 6B. The waveform becomes “Hi” when the address signal appears on the positive side with respect to the zero level of the signal RFTE, and becomes “Low” otherwise. On the other hand, the output of the binarization circuit 3104 becomes “Low” when an address signal appears on the negative side with respect to the zero level of the wideband tracking error signal RFTE, as shown in FIG. In other cases, the waveform becomes “Hi”. Therefore, the output of the OR circuit 3106, that is, the gate signal IDGATE becomes “Hi” when the address signal appears in the wideband tracking error signal RFTE as shown in FIG. The waveform becomes “Low”.

  The error rate measurement unit 33 is a signal (evaluation information used for coarse search of the focus position, that is, a signal (error occurrence rate of information recorded in the address area of the optical disc 1) or an error occurrence rate of information recorded in the data area ( Bit error rate BER). Specifically, the error rate measuring unit 33 is based on the gate signal IDGATE from the address signal detecting unit 31 and the error rate of the RF pulse signal PRF from the demodulating unit 47 (for example, the parity of the RF pulse signal PRF per unit time). The number of bit errors) and the error rate of the address pulse signal PADR from the address signal detector 31 (for example, the number of parity bit errors of the address pulse signal PADR per unit time) are selected and measured, and the result Is output as a bit error rate BER to the focus position rough search unit 50.

  FIG. 7 is a block diagram showing a detailed configuration of the error rate measuring unit 33. The selection circuit 3301 is a 2-input 1-output selector. When the gate signal IDGATE from the address signal detection unit 31 is “Hi”, the selection circuit 3301 selects and outputs the RF pulse signal PRF from the demodulation unit 47, and the gate signal IDGATE When “Low”, the address pulse signal PADR from the address signal detector 31 is selected and output.

  The parity error detector 3302 detects the occurrence of a parity error for each symbol data in the RF pulse signal PRF or the address pulse signal PADR output from the selection circuit 3301, and sets it to “Hi” level each time an error is detected. Number of pulse signals (parity error signal PE) are output. Since parity data is added to each symbol data in the data recorded on the optical disc 1, the parity error detector 3302 includes data bits and parity bits included in each symbol data. And parity error is detected.

The cycle counter 3303 outputs a clock signal with a fixed cycle to the bit error detection unit 3304. The bit error detection unit 3304 counts the number of parity error signals PE input during one cycle of the clock signal from the cycle counter 3303 and outputs the result as a bit error rate BER.
The focus error detection unit 36 corresponds to the difference between the two focus signals VFS1 and VFS2 input from the photodetector 5 through the addition amplifiers 43 and 44, as expressed by the following Expression 1. Information is calculated and output as a focus error signal FES to the focus control unit 26, the surface shake component removal unit 35, and the switch 39.

FES = k1 * VFS1-k2 * VFS2 + OFFSET (Formula 1)
That is, after a certain weight is applied to each of the focus signals VFS1 and VFS2, a difference between them is calculated, and a value obtained by adding a certain offset value is output as the focus error signal FES. At this time, the ratio (focus balance) of the weights (k1 and k2) is determined according to the balance control signal FBAL input from the switch 37, and the offset value OFFSET (focus) is determined according to the offset control signal FOFF input from the switch 38. Determine the offset. As can be seen from the fact that the focus error signal FES is input to the focus control unit 26, the focus error detection unit 36 changes the focus balance and the focus offset in accordance with the two control signals FBAL and FOFF, thereby generating a focus error signal. The zero level of (the difference between VFS1 and VFS2), that is, the control target position of the focus servo is changed (set).

  FIG. 8 is a block diagram illustrating a detailed configuration of the focus error detection unit 36. The preceding stage of the focus error detector 36 is a differential amplifier circuit including a differential amplifier 3613, a feedback resistor 3612, a focus balance circuit 3611, and a D / A converter 3618. The focus balance circuit 3611 includes a voltage-controlled variable resistance component (two transistors are complementarily connected). This differential amplifier circuit changes the gain ratio (focus balance) when calculating the difference between the two input signals VFS1 and VFS2 according to the balance control signal FBAL (analog value thereof) sent from the switch 37. Yes. The subsequent stage is an offset adjustment circuit including three resistors 3614 to 3616, a differential amplifier 3617, and a D / A converter 3619. A constant offset value (focus offset) based on the offset control signal FOFF (analog value) sent from the switch 38 is added to the difference signal from the preceding stage.

  The selectors 37 and 38 are two-input and one-output selectors controlled by the drive controller 14, respectively. When the control signals FBAL1 and FOFF1 from the rough search unit 50 are selected and output and an instruction to the effect that fine search is being performed is received, the control signals FBAL2 and FOFF2 from the focus position precise search unit 60 are selected. Output.

  The focus position rough search unit 50 is a control circuit that performs a focus position search at the initial stage of focus pull-in, that is, a rough search. Are forcibly moved by a certain distance, two control signals FBAL1 and FOFF1 are output to the switches 37 and 38. At this time, the focus position rough search unit 50 refers to the L / G switching signal LGS from the land / groove detection unit 34 according to a pre-programmed procedure, and the case where the light beam spot is positioned on the land track. Different control is performed depending on the case of the upper position. This means that even if the focus position is adjusted so that the playback state is optimal for only one of the land track and the groove track, the optimal playback state is not necessarily obtained for the other track. This is because of consideration. In other words, by searching for the target value of the focus control while distinguishing each of the land track and the groove track, comprehensively (for both the land track and the groove track) good reproduction characteristics can be obtained.

  FIG. 9 is a block diagram showing a detailed configuration of the focus position rough search unit 50. The first storage unit 52 is a rewritable nonvolatile memory having an area for recording a plurality of focus balance values (numerical values corresponding to the magnitude of the balance control signal FBAL1), and assembles the optical disk drive device 100. One focus balance value indicating the adjustment value of the focus position in the groove track of the optical disk 1 obtained at the time of adjustment is stored in advance. Similarly, the second storage unit 53 is a rewritable nonvolatile memory having an area for recording a plurality of focus offset values (a numerical value corresponding to the magnitude of the offset control signal FOFF1). One focus offset value indicating the adjustment value of the focus position in the land track of the optical disc 1 obtained when the 100 is assembled and adjusted is stored in advance.

  The DSP 51 is a digital signal processor having a control program therein, and performs software processing for focus position search. Specifically, when the light beam spot is positioned on the groove track on the optical disc 1, the balance control signal FBAL1 is output while referring to the focus balance value stored in the first storage unit 52, thereby generating an error. The optimum focus balance value at which the bit error rate BER from the rate measuring unit 33 is equal to or less than a predetermined value is searched. Subsequently, when the output of the balance control signal FBAL1 is maintained and the light beam spot is positioned on the land track on the optical disc 1, the offset control is performed with reference to the focus offset value stored in the second storage unit 53. By outputting the signal FOFF1, an optimum focus offset value at which the bit error rate BER from the error rate measuring unit 33 is equal to or less than a predetermined value is searched.

  When the DSP 51 obtains a more optimal focus balance value and focus offset value by such exploration, the DSP 51 distinguishes them for the land track and the blue track and distinguishes them from the first and second storage units. The control signals FBAl1 and FOFF1 corresponding to the focus balance value and the focus offset value are switched while distinguishing the land track and the groove track as new control reference positions of the focus position after the search. To the devices 37 and 38.

The read gate detection unit 32 is a circuit that is optionally used to further improve accuracy when performing precise focus position search. The read gate detection unit 32 includes an address area on the optical disc 1 and a data area previously designated by the drive controller 14. A gate signal RDGT that becomes “Hi” at is output to the focus position precise search unit 60.
Specifically, the drive controller 14 detects the surface shake (AC signal) generated when the optical disk 1 is rotated by taking in the focus error signal FES and performing A / D conversion in advance, and the change amount of the AC signal is small. The read gate detector 32 is notified of the sectors in the data areas so that the gate signal RDGT becomes “Hi” in the data area corresponding to the position. Then, the read gate detection unit 32 discriminates the address region and the data region (sector) from the broadband tracking error signal RFTE from the signal processing unit 40, and in the address region and the data region (sector) designated in advance by the drive controller 14. The gate signal RDGT is generated so as to be “Hi”. The gate signal RDGT is used to eliminate a problem that the accuracy of focus control is deteriorated due to the influence of surface shake in precise focus position search.

  FIG. 10 is a timing chart of the input signal RFTE of the read gate detector 32, the gate signal IDGATE indicating the address area, and the output signal RDGT from the read gate detector 32. The gate signal RDGT indicates an address area and a previously designated data sector (read data sector). Note that if high accuracy is not required in precise focus position search, the drive controller 14 can stop the function by instructing the read gate detection unit 32. At this time, the read gate detector 32 always sets the gate signal RDGT to “Hi”.

  The surface shake component removing unit 35 is an optional circuit used for precise focus position search, and removes the surface shake component of the optical disc 1 included in the focus error signal FES from the focus error detection unit 36. It is a filter that allows other frequency components (such as a 1 kHz signal applied from the disturbance signal generator 25) to pass through, and outputs the passed signal to the focus position precise search unit 60 via the switch 39. This is the same as the role of the read gate detection unit 32, and it is for performing more accurate focus position control by eliminating the influence of surface deflection in precise focus position search.

  The switch 39 is a 2-input 1-output selector controlled by the drive controller 14 and bypasses the input / output of the surface shake component removing unit 35 based on an instruction from the drive controller 14. Specifically, in the case of performing a rough search of the focus position, one of the output signal from the surface shake component removal unit 35 and the output signal FES from the focus error detection unit 36 is determined based on an instruction from the drive controller 14. After selection, the focus error signal FESS is output to the focus position precise search unit 60 as a focus error signal FESS. The switch 39 has a function of determining whether or not the surface shake component removing unit 35 is to function in the precise search of the focus position, that is, whether or not the precise search of the focus position is to be performed with higher accuracy.

  The focus position precise search unit 60 is a circuit that performs control for fine focus position search performed after the coarse focus position search by the focus position rough search unit 50 is completed. Specifically, the disturbance signal component (disturbance signal output from the disturbance signal generation unit 25) included in the focus error signal FESS sent from the switch 39 and the reproduction signal RF sent from the signal processing unit 40. Based on this, an optimum focus position is searched so that the envelope of the reproduction signal RF becomes large and the jitter of the reproduction signal RF becomes small, and such focus position is maintained by the focus servo by the focus control unit 26. The two control signals FBAL2 and FOFF2 are output to the switchers 37 and 38 as shown in FIG. This is to obtain a comprehensively good reproduction state by performing focus control in consideration of both the envelope and jitter of the reproduction signal RF.

Similarly to the focus position coarse search unit 50, the focus position precise search unit 60 uses the L / G switching signal LGS from the land / groove detection unit 34 to determine whether the light beam spot is positioned on the land track or on the groove track. Different control is performed depending on the case of the position. This is to obtain good reproduction characteristics comprehensively (for both the land track and the groove track) by searching for the target value of the focus control by distinguishing the land track and the groove track.
[Coarse focus position search]
Next, an operation when the optical disc drive apparatus 100 configured as described above performs a rough focus position search during recording / reproduction will be described.

  First, the overall operation of the optical disc drive apparatus 100 will be described with reference to FIGS. In this coarse focus position search, the switches 37 and 38 select and pass the control signals FBAL1 and FOFF1 from the focus position rough search unit 50 according to an instruction from the drive controller 14, and the adder unit 24 performs focus control. Since only the signal from the unit 26 is passed, the components used only for precise focus search (disturbance signal generation unit 25, read gate detection unit 32, surface shake component removal unit 35, focus position precision search unit 60) operate. No (not directly related).

First, the drive controller 14 instructs the rotation control unit 13 to rotate the spindle motor 12 at a constant rotational speed, and then issues a rough seek operation by the coarse motor 10 by issuing an instruction to the seek control unit 11. Let Subsequently, the modulation unit 42 and the laser power driving unit 41 are controlled to irradiate the optical beam 1 from the semiconductor laser 8 toward the optical disc 1.
The photodetector 5 detects the light beam reflected by the light beam spot on the optical disc 1 with a lens divided into four parts, and then converts it into an electrical signal. The summing amplifiers 43 and 44 add two of these four signals. By adding, two focus signals VFS1 and VFS2 used to generate the focus error signal FES are generated.

  The focus error detection unit 36 performs the calculation of the above formula 1 on the two focus signals VFS1 and VFS2 based on the two control signals FBAL and FOFF input from the focus position rough search unit 50 via the switches 37 and 38. As a result, a focus error signal FES is generated. That is, the focus error zero level, that is, the focus servo control target position is changed.

The focus control unit 26 moves the actuator 2 via the addition unit 24 and the focus drive unit 21 based on the focus error signal FES from the focus error detection unit 36, so that the focus error signal FES and the control target position of the focus servo are Focus servo is performed so that the difference between is zero.
Next, the tracking servo is started in such a state that the focus servo is operated. That is, the difference amplifier 45 generates a wideband tracking error signal RFTE indicating the positional deviation between the track center on the optical disc 1 and the light beam spot by taking the difference between the two signals from the reproduction signal detector 4. The tracking control unit 23 performs feedback control by moving the actuator 2 via the tracking drive unit 22 so that the light beam follows the track on the optical disc 1 based on the broadband tracking error signal RFTE.

In a state where the focus control and tracking control are operated, the reproduction signal RF obtained from the reproduction signal detector 4 through the addition amplifier 46 next becomes a constant amplitude with a moderate amplitude if not the maximum. Thereby, stable and good reproduction is possible.
Next, the relationship between the focus position and the reproduction characteristics will be described. FIG. 11 is a general graph showing the bit error rate BER of the RF pulse signal PRF with respect to the change of the focus position. The horizontal axis indicates the focus position, and the vertical axis indicates the bit error rate BER. Now, assuming that the optimum focus position is 0 μm, the bit error rate BER at this optimum focus position is about 1e-4. As the focus position deviates from the focus optimum position, the bit error rate BER increases in a quadratic function manner. When the focus position deviates from the optimum position by ± 0.6 μm, the bit error rate BER is about 1e-3.

  The focus position rough search unit 50 intentionally changes the convergence state of the light beam on the optical disc 1 by changing the focus balance or the focus offset in the focus error detection unit 36. That is, the focus position rough search unit 50 sequentially adjusts the focus balance or the focus offset until the error rate of the RF pulse signal PRF measured by the error rate measurement unit 33 is a predetermined value or less, for example, the bit error rate is 5e-4 or less. The optimum focus position is searched for by repeating the change. As can be seen from FIG. 11, when the reproduction state in which the bit error rate BER is 5e-4 or less is converted into the shift of the focus position, it corresponds to a range of ± 0.3 μm with respect to the optimum focus position. In other words, the focus position rough search unit 50 corrects the two control signals FBAL1 and FOFF1 to the focus error detection unit 36 so that the deviation from the optimum focus position is not more than a predetermined value based on the bit error rate.

Now, the rough focus position search will be described in more detail. FIG. 12 is a flowchart showing a detailed operation of the focus position rough search unit 50.
As shown in FIG. 9, the focus position rough search unit 50 is realized by software by a DSP 51 or the like having a built-in control program. Further, the rough search of the focus position is performed in a state where the tracking control for causing the light beam to follow a specific land track or groove track is operated by the drive controller 14 instructing the tracking control unit 23. That is, each time the optical disc 1 makes one turn, a still jump that jumps back to the inner circumference side of the optical disc 1 is performed, and the light beam follows a specific land track or a specific groove track on the optical disc 1 in the following manner. The procedure is executed.

  Now, it is assumed that there is a need for a rough focus position search because a reproduction error has occurred over a certain value. That is, the DSP 51 of the focus position rough search unit 50 sends the focus balance value and the focus offset value stored in advance in the first storage unit 52 and the second storage unit 53 to the focus error detection unit 36 as the control signals FBAL1 and FOFF1. In this state, it is assumed that the bit error rate BER measured by the error rate measuring unit 33 exceeds a certain value (5e-4).

  First, the focus position rough search unit 50 determines whether the light beam is positioned on the land track or the groove track based on the logic level of the L / G switching signal LGS from the land / groove detection unit 34 ( Step S10). Specifically, the L / G switching signal LGS is observed, and this determination is made based on whether the signal is at the “Low” level or the “Hi” level for a certain time or more.

  As a result, when it is determined that the position is on the groove track, the focus balance value (current FBAL value) stored in the first storage unit 52 is read, and the value is A (A = current FBAL value). (Step S11). Next, a new focus balance value (updated FBAL value) is calculated (step S12). Specifically, the calculation shown in Expression 2 is performed with the change amount of the FBAL value as B (a focus balance value converted to a focus position, for example, 0.6 μm) and the updated FBAL value as X.

X = A + B (Formula 2)
The obtained updated FBAL value (X) is output as a balance control signal FBAL1 to the focus error detection unit 36 via the switch 37 (step S13). This means that the focus balance in the focus error detection unit 36 has been changed so that the focus position changes by +0.6 μm with respect to the focus position before the change.

  With the focus balance changed in this way, the bit error rate BER is received from the error rate measuring unit 33 (step S14), and it is determined whether the bit error rate BER is 5e-4 or less (step S15). As a result, if the bit error rate BER is 5e-4 or less, as described above with reference to FIG. 11, the deviation between the focus position after changing the focus balance and the optimum focus position is within 0.3 μm. After determining and storing the updated FBAL value (X) in the first storage unit 52, the focus position search is normally terminated (step S28).

On the other hand, if the bit error rate BER is greater than 5e-4, it is determined how many times the FBAL value changing process has been performed (step S16). As a result, when the number of times is the first time, the second updated FBAL value is calculated (step S17). Specifically, the calculation shown in Expression 3 is performed.
X = A−B (Formula 3)
Then, the obtained FBAL value (X) is output as a balance control signal FBAL1 to the focus error detection unit 36 via the switch 37. This means that the focus balance in the focus error detection unit 36 is changed so that the focus position changes by −0.6 μm with respect to the focus position before the change.

  Then, steps S14 and S15 are repeated with the focus balance changed in this way. That is, the bit error rate BER is received from the error rate measuring unit 33 (step S14), it is determined whether the bit error rate BER is 5e-4 or less (step S15), and the bit error rate BER is 5e-4 or less. If so, the focus position search is normally terminated after the updated FBAL value (X) is stored in the first storage unit 52 (step S28).

On the other hand, if the bit error rate BER is greater than 5e-4, it is determined how many times the FBAL value change process has been performed (step S16). If the number of times is the second time, the focus position search can be completed normally. The focus position exploration is terminated assuming that there has not been any (step S29).
When the focus position rough search unit 50 determines that the light beam is located on the land track in the determination in step S10, the focus offset value (current FOFT value) stored in the second storage unit 53 is determined. ) And set the value as C (C = current FOFT value) (step S21). Next, a new focus offset value (updated FOFT value) is calculated (step S22). Specifically, the calculation shown in Expression 4 is performed assuming that the change amount of the FOFT value is D (a focus offset value converted to a focus position, for example, 0.6 μm), and the updated FOFT value is Y.

Y = C + D (Formula 4)
Next, the obtained FOFT value (Y) is output as an offset control signal FOFF1 to the focus error detection unit 36 via the switch 38 (step S23). This means that the focus offset in the focus error detection unit 36 is changed so that the focus position changes by +0.6 μm with respect to the focus position before the change.

  With the focus offset changed in this way, the bit error rate BER is received from the error rate measuring unit 33 (step S24), and it is determined whether the bit error rate BER is 5e-4 or less (step S25). As a result, if the bit error rate BER is 5e-4 or less, it is determined that the deviation between the focus position after the focus offset change and the optimum focus position is within 0.3 μm, and the FOFF value (Y) is After the data is stored in the storage unit 53, the focus position search is normally terminated (step S28).

On the other hand, if the bit error rate BER is greater than 5e-4, it is determined how many times the FOFF value changing process has been performed (step S26). As a result, when the number of times is the first time, a second updated FOFF value is calculated (step S27). Specifically, the calculation shown in Equation 5 is performed.
Y = C−D (Formula 5)
Then, the obtained FOFF value (Y) is output as a balance control signal FOFF1 to the focus error detection unit 36 via the switch 37. This means that the focus offset in the focus error detection unit 36 is changed so that the focus position changes by −0.6 μm with respect to the focus position before the change.

  Then, steps S24 and S25 are repeated with the focus offset changed in this way. That is, the bit error rate BER is received from the error rate measuring unit 33 (step S24), it is determined whether the bit error rate BER is 5e-4 or less (step S25), and the bit error rate BER is 5e-4 or less. If so, after the FOFF value (Y) is stored in the second storage unit 53, the focus position search is normally terminated (step S28).

On the other hand, if the bit error rate BER is greater than 5e-4, it is determined how many times the FOFF value changing process has been performed (step S26). If the number of times is the second time, the focus position search can be completed normally. The focus position exploration is terminated assuming that there has not been any (step S29).
When a new focus balance value and / or focus offset value is searched in step S15 and step S25, the focus position rough search unit 50 performs the new focus balance until the search is performed again. The value and / or the focus offset value are continuously output to the focus error detection unit 36 as the control signals FBAL1 and FOFF1. That is, when the light beam spot is positioned on the groove track, the focus position rough search unit 50 outputs the balance control signal FBAL1 using the latest focus balance value stored in the first storage unit 52 (offset control signal). On the other hand, when the light beam spot is located on the land track, the balance control signal FBAL1 is output using the latest focus balance value stored in the first storage unit 52, and the second The offset control signal FOFF1 is output using the latest focus offset value stored in the storage unit 53. Accordingly, the focus position search by the focus position rough search unit 50 is reflected as a decrease in the bit error rate BER in the subsequent recording / reproduction.

  The reason why the amount of change of the focus position in this embodiment is 0.6 μm is as follows. In other words, the initial focus position of the optical disk drive device is adjusted so that the signal recorded in the address or the data area on the optical disk can be reproduced satisfactorily during assembly adjustment. However, the reproduction error may increase or the recording characteristics may deteriorate due to a change in the focus position indicated by the focus error signal due to a temperature characteristic of the optical head or a change with time. Regarding the temperature characteristics of the optical head, a change characteristic of 0.0114 μm / ° C. is shown depending on the configuration of the optical head. That is, when the temperature around the optical head increases from 25 ° C. at the time of starting the apparatus to 60 ° C., the focus position changes by 0.4 μm. In addition to the temperature characteristic of the optical head, if there is a change with time of the optical head characteristic, the signal recorded in the address or the data area on the optical disk may not be reproduced.

  In particular, in the address area, if the focus position deviates by more than ± 0.6 μm from the focus position where the bit error rate BER of the address pulse signal is minimum, the address reading becomes worse. Therefore, for example, when the focus position deviates from the focus position where the bit error rate BER is minimum within the range of +0.6 μm to +1.0 μm, the focus position is 0 μm if the focus position is forcibly moved by −0.6 μm. Since it is in the range of ~ + 0.4 μm, the address can be read normally. Further, for example, when the focus position is deviated from the focus position where the bit error rate BER is minimum in the range of −0.6 μm to −1.0 μm, the focus position is changed by forcibly moving +0.6 μm. Since it falls within the range of 0 μm to −0.4 μm, the address can be read normally.

For the above reason, in this embodiment, the focus position change amount is 0.6 μm, and the focus position where the bit error rate BER is 5e−4 or less is searched.
As described above, the focus position rough search unit 50 adjusts the focus balance in the focus error detection unit 36 so that the bit error rate BER is equal to or less than a certain value for only the groove track, while only the land track is detected. By adjusting the focus offset in the focus error detection unit 36 so that the bit error rate BER becomes a certain value or less as a target, the zero level of the focus error, that is, the control target of the focus servo was determined. As described above, since the focus position is searched by using both the groove track and the land track in the focus position rough search in the present embodiment, the conventional method in which only one of the tracks is used is searched. In contrast, the problem that the reproduction characteristics of one of the tracks is extremely bad is avoided. That is, focus control capable of obtaining good reproduction characteristics for both tracks, that is, focus control in which reproduction errors are comprehensively suppressed is realized.

In the present embodiment, the focus position rough search unit 50 adjusts the focus balance for only the groove track, and then adjusts the focus offset for only the land track, so that the optimum focus for both tracks is obtained. Although the location has been explored, the present invention is not limited to such track types and procedures.
FIG. 13 shows a modification of the rough focus position search of this embodiment. This figure shows a total of eight different exploration method numbers. 1 to 8 are shown, and control parameters (control signals FBAL1, FOFF1 output from the focus position rough search unit 50 to the focus error detection unit 36) used for each search method are shown. In the figure, a control parameter surrounded by squares means that it is a target obtained by exploration based on the procedure shown in FIG. 12, and a dotted arrow indicates that the control parameter thus obtained is It means that it is used as the other control parameter as it is.

In all of these eight methods, the focus position is separately searched in consideration of both the groove track and the land track, and the search procedure is basically the same as the flowchart shown in FIG. (It is determined whether the bit error rate BER is equal to or less than a certain value).
In FIG. Reference numeral 1 denotes the present embodiment (procedure shown in FIG. 12). That is, when the light beam spot is located on the groove track, the focus position rough search unit 50 outputs only the balance control signal FBAL1 corresponding to the latest FBAL value stored in the first storage unit 52, and the land track. If the offset control signal FOFF1 corresponding to the latest FOFF value stored in the second storage unit 53 is output together with the balance control signal FBAL1, the FBAL value is adjusted for the groove track. While maintaining the FBAL value, the FOFF value is adjusted for the land track.

Search Example No. No. 2 corresponds to a change in the type of track in this embodiment (Exploration Example No. 1).
Search Example No. A method 3 uses different FBAL values (first and second FBAL values) for the groove track and the land track, and does not adjust the focus offset. That is, when the light beam spot is positioned on the groove track, the focus position rough search unit 50 outputs only the balance control signal FBAL1 corresponding to the latest first FBAL value stored in the first storage unit 52, In the case where only the balance control signal FBAL1 corresponding to the latest second FBAL value stored in the first storage unit 52 is output when positioned on the track, the first FBAL value is adjusted for the groove track, and then the next The second FBAL value is adjusted for the land track.

  In this manner, by configuring the land track and the groove track to change the focus control target position based on the focus balance, the focus position can be set without giving an offset to the target value of the focus control unit. Therefore, the trouble that the dynamic range of the focus control system is narrowed by the offset is avoided. For example, if disturbance vibration is applied to the device during recording / reproducing operation, a malfunction when the focus position is adjusted by offset (the focus control system is likely to be saturated, and the tracking performance to the focus control target position is degraded. However, according to this method, it is possible to improve the playability of the apparatus by avoiding the problem.

  Search example No. 4 is a method of using different FOFF values (first and second FOFF values) for the groove track and the land track, and the focus balance is not adjusted. That is, when the light beam spot is positioned on the groove track, the focus position rough search unit 50 outputs only the offset control signal FOFF1 corresponding to the latest first FOFF value stored in the second storage unit 53, In the case where only the offset control signal FOFF1 corresponding to the latest second FOFF value stored in the second storage unit 53 is output when positioned on the track, the first FOFF value is adjusted for the groove track and then the next The second FOFF value is adjusted for the land track.

In general, the focus offset adjustment circuit can be realized with a simpler configuration than the focus balance adjustment circuit.Furthermore, the focus servo response due to the focus balance change is less responsive than the focus offset change. According to this search example, a simple and high-speed focus servo control circuit is realized.
Search Example No. 5, the basic control method is the search example No. Same as 1. That is, when the light beam spot is located on the groove track, the focus position rough search unit 50 outputs only the balance control signal FBAL1 corresponding to the latest FBAL value stored in the first storage unit 52, and the land track. In the case of being located, the offset control signal FOFF1 corresponding to the latest FOFF value stored in the second storage unit 53 is output together with the balance control signal FBAL1.

  However, this exploration example No. 5, the focus position rough search unit 50 first searches the search example No. 5 described above. By executing the procedure 1 and the like, the FOFF value corresponding to the difference between the optimum focus position for the groove track and the optimum focus position for the land track, that is, substantially the same for both the groove track and the land track ( The FOFF value that can obtain the focus state is obtained and stored in the second storage unit 53 in advance. Then, the focus position rough search unit 50 adjusts the FBAL value only for the groove track.

  Search example No. 6 is the above-mentioned search example No. This corresponds to the type of track 5 in FIG. These exploration examples No. 5 and 6, it is possible to automatically obtain an optimum focus position for the other track even though the focus balance is adjusted for only one track. That is, the focus position search in one of the groove track and the land track optimizes the focus position of the other track, and the focus position adjustment time is shortened.

  Search example No. 7 is a method using different FBAL values (first and second FBAL values) and a common FOFF value for each of the groove track and the land track, and the focus balance is not adjusted. That is, when the light beam spot is located on the groove track, the focus position rough search unit 50 controls the control signals FBAL1, FOFF1 corresponding to the latest first FBAL value and FOFF value stored in the two storage units 52, 53, respectively. When the balance control signal FBAL1 corresponding to the latest second FBAL value stored in the first storage unit 52 is output together with the offset control signal FOFF1 First, the exploration unit No. The first FBAL value and the second FBAL value are obtained by executing the procedure 3 and the like so that a substantially similar (not necessarily optimum) focus state can be obtained for both the groove track and the land track. Stored in the first storage unit 52 in advance. Then, the focus position rough search unit 50 adjusts the FOFF value only for the groove track.

Search Example No. 8 is the above-mentioned exploration example No. 7 corresponds to the type in which the types of tracks are replaced. These exploration examples No. Also in 7 and 8, if the focus position search in one of the groove track and the land track is performed, the focus position of the other track is also optimized, so the focus position adjustment time is shortened.
In this embodiment, the optical head output power differs between reproduction and recording, so that the focus position during recording may deviate from the optimum focus position even when the focus position during reproduction is optimized. In this case, the processing for correcting the difference in focus position between playback and recording is performed by correcting the focus position during recording with the same focus offset with respect to the focus position during playback for both the groove track and the land track. Can be easy.

  In this embodiment, the error rate measuring unit 33 detects a parity error. However, in addition to this, for example, a method for detecting a reproduction error using an error correction code called CRCC (Cyclic Redundancy Check Code), etc. It may be adopted. In order to obtain CRCC, data to be recorded on the optical disc 1 is divided into blocks, data bits are expressed by a polynomial, and this formula is divided by a predetermined value called a generator polynomial. The result of the division is added as a check bit after the data bit and recorded. In order to detect errors during reproduction, the data including the data bits and the check bits is again divided by the generator polynomial. At this time, if there is no code error, the result of division and division is zero, and when there is a code error, the result of division is not zero and it is possible to determine whether there is an error. Therefore, the error rate measuring unit 33 can be configured using an error detector based on CRCC instead of the parity error detector 3302 of this embodiment.

  Further, in the present embodiment, as shown in FIG. 12, the focus position rough exploration section 50 focuses on only two places shifted by +0.6 μm and −0.6 μm with respect to the adjustment value stored in advance. Although the position search is attempted, the focus position may be searched by setting the change amount of the focus position to be finer than 0.6 μm (for example, the change amount = 0.1 μm). As a result, the focus position where the bit error rate BER is minimized can be searched with higher accuracy.

  In addition, when the focus position is searched based on the RF pulse signal PRF, the focus position rough search unit 50 of this embodiment searches the focus position so that the error rate of the RF pulse signal PRF is a predetermined value or less, and the address When the focus position is searched based on the pulse signal PADR, the focus position where the error rate of the address pulse signal PADR is equal to or less than a predetermined value is searched. However, the reproduction signal is generated according to the respective positions in the address area and the data area. The focus position where the jitter of the playback signal is minimized, or the focus position where the amplitude of the playback signal is maximum and the focus position where the jitter of the playback signal is the minimum, or playback. A focus position where the error rate of the signal is minimized may be searched.

For example, when only the address pulse signal PADR is directly input to the parity error detector 3302 of the error rate measuring unit 33, the bit error rate BER output from the error rate measuring unit 33 is generated only in the address area of the optical disc 1. This indicates a bit error rate. This makes it possible to search the focus position based on the error rate only in the address area. For example, as in a rewritable optical disk immediately after formatting, the data area is not recorded, but information is recorded in the address area. An optical disc drive apparatus that can perform a focus position search even for an optical disc is realized.
[Precise focus position search]
Next, in the case where the optical disc drive apparatus 100 performs a precise focus position search during recording / reproduction, related components will be described in more detail. For convenience of explanation, the case where the read gate detection unit 32 and the surface shake component removal unit 35 are not operated will be described first.

  For precise focus position search, the drive controller 14 first controls the recording position, the start of recording, or the stop of recording in order to record the focus position searching test signal in the drive test area on the optical disc 1. A test recording control signal TWCNT is output to the modulator 42. After the recording, the focus position precise search control signal FPSON for controlling the start or stop of the focus position precise search is output to the focus position precise search unit 60.

  Further, the drive controller 14 receives the binarized address pulse signal PADR from the address signal detector 31 and recognizes the current position of the light beam converged and irradiated on the track on the optical disc 1 from the optical head 7. In addition, by instructing the tracking controller 23 based on the address pulse signal PADR, the light beam can be moved to an arbitrary track on the optical disc 1.

  The reason why the focus position search test signal is recorded in advance on the optical disc 1 prior to the start of the precise search for the focus position is as follows. That is, the optical disk 1 of this embodiment is a recordable disk, and when not recorded, no data is recorded in a data area other than a preformat area such as an address area where an address signal is recorded in advance. When such an optical disc 1 is loaded in the optical disc drive apparatus 100, the focus position precise search unit 60 that performs a precise search for the focus position based on the reproduction signal RF in the data area can start the focus search. Can not. Therefore, a focus position search test signal is recorded in advance in the drive test area of the unrecorded optical disc 1 prior to the focus position search.

  That is, the drive controller 14 determines whether or not the optical disk 1 loaded in the optical disk drive device 100 is unrecorded prior to the focus position search. A focus position search test signal is recorded in advance, and information for specifying the drive test area (track) is stored for later reuse. When it is determined that the mounted optical disk 1 has been recorded, the optical head 7 is sought to the recording location (track) and the focus position search is started.

  FIG. 14 is a diagram for explaining a drive test area of the optical disc 1 and shows an information area layout of the SS-L / GFMT optical disc 1. As shown in the figure, a sector number indicating a physical address of the optical disc 1 is assigned according to the position of the optical disc 1, and the lead-in area (sector number 27AB0hex to 30FFFhex) on the inner periphery of the disc is embossed data. An area (sector number 27AB0hex to 2FFFhex), a mirror area (an address is not assigned and an intermediate area between the embossed data area and the rewritable data area), and a rewritable data area (sector number 30000 hex to 30FFFhex) are included in the rewritable data. There is a drive test area in the area. Further, the lead-out area (sector numbers 16B480hex to 17966Fhex) on the outer periphery of the disk is a rewritable data area, which includes a drive test area. The lead-in area and lead-out area of the optical disc 1 have a disk test area and a drive test area as test areas. The focus test is used for a drive test area (hereinafter referred to simply as “test area”). "). Thus, this SS-L / GFMT type optical disc 1 is provided with test areas in the lead-in area on the inner periphery of the disk and the lead-out area on the outer periphery of the disk.

  The drive controller 14 instructs the modulation unit 42 to record the focus position search test signal in the test area before operating the focus position precision search, particularly every time the optical disk drive device 100 is activated. Further, if recording is always repeated only on the track having the same address, the recording / reproduction characteristics of the track become remarkably deteriorated. Therefore, the track to be recorded is randomly changed in the test area for each learning. Further, since the reproduction signal RF from the optical disk 1 necessary for precise focus position search needs to be recorded on the land track and the groove track on the optical disk 1 continuously one or more times, the drive controller 14 A groove track is randomly determined from the test area on the inner periphery and the test area on the outer periphery of the disk, and one track (= 1 rotation) is recorded continuously from the determined head address of the groove track. The modulation unit 42 is instructed to record one track (= 1 rotation).

  A specific procedure for determining the test area by the drive controller 14 is as follows. Now, the test area start track address of the lead-in area is TNh, the test area end track address of the lead-in area is TNie, the test area start track address of the lead-out area is TNoh, and the test area end track address of the lead-out area is Assuming TNoe, recording in the test area is performed on two tracks (= 2 rotations) from the beginning of the groove track to the end of the next land track. In other words, the recording symmetrical tracks are the tracks from TNich to TNie-1 and from TNoh to TNee-1. In terms of actual sector numbers, TNh = 30600h, TNie-1 = 30CDDh, TNoh = 16BE80h, TNee-1 = 16C52Fh. The sector numbers of the zero sectors included in the sector numbers 30600h to 30CDDh and 16BE80h to 16C5Fh are determined at random.

Next, the overall operation when the optical disc drive apparatus 100 performs a precise focus position search will be described with reference to FIGS.
Under the control of the drive controller 14, after the optical disk 1 has been rotated at a predetermined rotational speed, the optical beam 1 is irradiated onto the optical disk 1 from the semiconductor laser 8. The focus error detection unit 36 generates and outputs a focus error signal FES from the two focus signals VFS1 and VFS2 based on the light beam reflected from the optical disc 1. At this time, the focus error detection unit 36 changes the focus balance and the focus offset based on the control signals FBAL2 and FOFF2 from the focus position precise search unit 60, so that the focus error zero level, that is, the control target position of the focus servo. To change.

  The focus control unit 26 responds to the focus error signal FES from the focus error detection unit 36 by moving the actuator 2 via the addition unit 24 and the focus drive unit 21 based on the focus error signal FES from the focus error detection unit 36. Focus servo is performed so that the difference between the focus position to be focused and the target position for focus control becomes zero. The adding unit 24 adds the disturbance signal from the disturbance signal generating unit 25 and the signal from the focus control unit 26 only when a precise search for the focus position is performed according to an instruction from the drive controller 14. The added signal is output to the focus drive unit 21, but when the focus position is not precisely searched, the signal from the focus control unit 26 is output to the focus drive unit 21 as it is.

  In a state where the focus servo is operated by the focus control unit 26, the reproduction signal detector 4 and the differential amplifier 45 can obtain a wide-band tracking error signal RFTE indicating the positional deviation between the track center on the optical disc 1 and the light beam. The tracking control unit 23 performs feedback control so that the light beam follows the track on the optical disc 1 based on the broadband tracking error signal RFTE. When the focus control and tracking control are activated, the reproduction signal detector 4 can obtain a reproduction signal having a constant amplitude and a constant amplitude, if not the maximum.

  The drive controller 14 can read the address on the optical disc 1 where the light beam is currently located via the demodulator 47 in a state where the focus control and the tracking control are operating as described above. Then, the drive controller 14 searches for a groove track in the test area on the optical disc 1 at random. When the drive controller 14 searches for a target groove track in the test area, it is preferable to search for a track one track inner side from the target groove track, and the light beam is the first sector of the target groove track. When (= sector zero) is reached, a command for generating a recording signal (hereinafter referred to as “test recording command”) and a test signal for focus position precise search are sent to the modulation unit 42.

The modulation unit 42 outputs a test signal for focus position precision search to the laser power driving unit 41 based on the test recording command from the drive controller 14. The laser power driver 41 receives the test signal from the modulator 42 and modulates the laser power with the test signal.
The drive controller 14 records the test signal continuously in two tracks from the randomly determined groove track, that is, in the order of the groove track and the land track from the inner circumference side of the optical disc 1, and ends the recording operation.

  Next, the drive controller 14 moves the optical head 7 to the groove track in the test area recorded as described above. Also in this case, it is preferable that the still jump is performed so that the light beam always follows the groove track when the light beam is positioned on the target groove track after moving to the inner circumference side of the target groove track. Is sent to the tracking control unit 23. The tracking control unit 23 performs a still jump for each rotation of the optical disc 1 and controls the tracking drive unit 22 so that the light beam always follows only one groove track in the test area searched at random.

  In this way, the focus control and tracking control are operated, and a still jump is performed for each rotation of the optical disc 1, and after the light beam always follows the groove track in the test area, the drive controller 14 A disturbance signal is generated from the signal generator 25, and the disturbance is applied to the focus control system. By this application, the focus position is forcibly changed, and the frequency component (disturbance component) of the disturbance signal is included in the focus error signal FES. Then, the focus position precise search unit 60 uses the disturbance component included in the focus error signal FESS sent from the switch 39 and the envelope and jitter of the reproduction signal RF sent from the signal processing unit 40 to transmit light to the optical disc 1. Information indicating the beam position deviation, that is, focus position information FPIS is obtained, and a focus position optimum for both the amplitude and jitter of the reproduction signal RF, that is, the optimum focus position is searched based on the obtained focus position information FPIS. Further, the focus position precise search unit 60 is based on the gate signal IDGATE from the address signal detection unit 31 and the gate signal RDGT from the read gate detection unit 32, or a specific data region specified by the drive controller 14 By searching for focus position information FPIS only for the target, a more accurate focus optimum position is searched.

  FIG. 15 is a diagram for explaining the optimum focus position in the precise search of the focus position, and shows the envelope RFENV of the reproduction signal RF and the magnitude of the reproduction jitter with respect to the focus position. As shown in this figure, with respect to the focus position (horizontal axis), the envelope is a convex curve that shows the maximum at a certain focus position (in this figure, -0.50 μm), and the jitter is The concave curve is minimized at a focus position (0 μm in the figure) different from the position where the envelope is maximized. That is, the focus position at which the envelope of the reproduction signal RF is maximized (envelope maximum position) is deviated from the focus position at which the jitter of the reproduction signal RF is minimum (jitter minimum position). In this embodiment, the optimum focus position is searched based on a value (focus position information FPIS) obtained by multiplying the envelope and the reproduction jitter of the reproduction signal by a coefficient and adding them. Specifically, the focus position precise search unit 60 adjusts the coefficient to be multiplied by the envelope and the coefficient to be multiplied by the jitter, thereby adjusting the focus optimum position to a predetermined position between the envelope maximum position and the jitter minimum position (for example, -0.25 μm).

  FIG. 16 is a block diagram showing a detailed configuration of the focus position precise search unit 60. The envelope detector 61 detects the envelope of the reproduction signal RF from the signal processor 40. The first high-pass filter 63 cuts off the frequency component of the reproduction signal envelope output from the envelope detection unit 61 that is equal to or lower than the rotation frequency (for example, 39.78 Hz) of the optical disc 1, and has a frequency equal to or higher than a predetermined frequency, that is, This is a filter that allows signal components having a frequency (1 kHz) or more of the disturbance signal output from the disturbance signal generator 25 to pass therethrough. The first gain adjustment unit 66 adjusts the gain of the output signal of the first high-pass filter 63 to a predetermined value.

  The jitter detector 62 binarizes the reproduction signal RF with a predetermined threshold value to generate an RF pulse signal PRF, and detects jitter from the RF pulse signal PRF and a reference clock signal generated internally. The second high-pass filter 64 has the same characteristics as the first high-pass filter 63, and allows the disturbance signal frequency (1 kHz) component of the reproduced signal detected by the jitter detector 62 to pass through the optical disc 1. The component below the rotation frequency (for example, 39.78 Hz) is cut off. The second gain adjustment unit 67 adjusts the gain of the output signal of the second high-pass filter 64 to a predetermined value.

  The subtractor 69 subtracts the output signal of the second gain adjustment unit 67 from the output signal of the first gain adjustment unit 66. The subtraction in this way is that the envelope signal output from the envelope detector 61 becomes smaller and the jitter signal output from the jitter detector 62 becomes larger when the focus position deviates from the optimum focus position. This is because the difference in polarity of each signal is taken into consideration.

  The third high-pass filter 65 has the same characteristics as the first high-pass filter 63, and allows the frequency (1 kHz) component of the disturbance signal to pass through the focus error signal FESS output from the switch 39. Thus, the component below the rotation frequency (for example, 39.78 Hz) of the optical disc 1 is blocked. The third gain adjustment unit 68 adjusts the gain of the output signal of the third high-pass filter 65 to a predetermined value. The multiplier 70 multiplies the output signal from the subtracter 69 and the output signal from the third gain adjustment unit 68 and outputs the result to the averaging processing unit 71 as focus position information FPIS.

  The third storage unit 72 is a rewritable nonvolatile memory for storing the latest focus balance value obtained for the groove track in the precise search of the focus position. The fourth storage unit 73 is a rewritable nonvolatile memory for storing the latest focus offset value obtained for the land track in the precise search of the focus position.

  The averaging processing unit 71 focuses on the period from the multiplier 70 only for the period specified by the gate signal IDGATE sent from the address signal detection unit 31 and the gate signal RDGT sent from the read gate detection unit 32. The position information FPIS is averaged, the obtained average value is stored, and control signals FBAL2 and FOFF2 corresponding to the average value are output to the focus error detection unit 36 via the switches 37 and 38. At this time, as in the case of the rough exploration described above, the control signals FBAL2 and FOFF2 are changed based on the L / G switching signal LGS from the land / groove detection unit 34 while distinguishing the groove track from the land track. Specifically, when the L / G switching signal LGS indicates a groove track, the averaging processing unit 71 uses a control signal (focus balance value) for setting a more optimal focus position based on the obtained average value. ) And is stored in the third storage unit 72, and the focus balance value is output as the control signal FBAL2. On the other hand, if the L / G switching signal LGS indicates a land track, the averaging processing unit 71 While maintaining the output of the control signal FBAL2, based on the obtained average value, a control signal (focus offset value) for obtaining a more optimal focus position is determined and stored in the fourth storage unit 73, and The focus offset value is output as the control signal FOFF2.

  FIG. 17 is a block diagram showing a detailed configuration of the averaging processing unit 71. The time measuring device 7101 starts time measurement after a predetermined wait time (200 μs) from the rising edge of the gate signal IDGATE from the address signal detection unit 31, and measures time (1 ms) for one period of disturbance. The timer signal TMS indicating the time is output to the AND circuit 7109. The AND circuit 7109 calculates the logical product of the timer signal TMS from the time measuring device 7101 and the gate signal RDGT from the read gate detector 32, and uses the result as the data acquisition timing signal DGTS and the first averaging circuit 7102 and the first signal. 3 to the averaging circuit 7104. That is, averaging is performed in the first averaging circuit 7102 and the third averaging circuit 7104 only when the gate signal RDGT is “Hi” and the timer signal TMS from the time measuring device 7101 is “Hi”. Allow.

The first selection circuit 7106 outputs the focus position information FPIS from the multiplier 70 to the first averaging circuit 7102 when the L / G switching signal LGS is “Hi” (groove track), and “Low” ( This selector outputs to the third averaging circuit 7104 at the time of a land track).
The first averaging circuit 7102 averages the focus position information FPIS from the first selection circuit 7106 only during a period when the timing signal DGTS from the AND circuit 7109 is “Hi”. If the read gate detector 32 is not operating (when the gate signal RDGT is always “Hi”), the average value of the focus position information FPIS in one cycle of the disturbance signal is calculated. It will be. The second averaging circuit 7103 is composed of a DSP or the like incorporating a control program, and further averages the average value obtained by the first averaging circuit 7102 for a predetermined number of times (for example, 24 periods of disturbance signal). And a new focus target position M11 (focus balance value) for the groove track determined in accordance with the average value is output. The relationship between the focus position information here and the new focus target position (a specific procedure for precise exploration) will be described later.

  The third averaging circuit 7104 and the fourth averaging circuit 7105 have the same functions as the first averaging circuit 7102 and the second averaging circuit 7103, respectively. The only difference is that it functions when “Low” (land track). Accordingly, the fourth averaging circuit 7105 outputs the focus target position Ml2 (focus offset value) for the land track.

The second selection circuit 7107 selects the second averaging circuit 7103 when the L / G switching signal LGS is “Hi” (groove track), and the fourth average when it is “Low” (land track). This selector is a selector that selects the output circuit 7105 and outputs each output signal to the third selection circuit 7108.
The third selection circuit 7108 outputs the focus target position Ml1 (focus balance value) in the groove track to the third storage unit 72 when the L / G switching signal LGS is “Hi”, and the L / G switching signal LGSLGS. When “Low” is set, the focus target position Ml2 (focus offset value) in the land track is output to the fourth storage unit 73. Further, when reproducing the signal from the groove track, the third selection circuit 7108 reads the latest focus target position Ml1 (focus balance value) stored in the third storage unit 72 and reads it from the land track. When reproducing the signal, the focus target position Ml2 (focus offset value) in the latest land track stored in the fourth storage unit 73 is read out and output to the focus error detection unit 36 via the switches 37 and 38. .

  FIG. 18 is a timing chart of the disturbance signal, the gate signal IDGATE, and the timer signal TMS when the read gate detection unit 32 is not operating. Here, since the read gate detector 32 is not operating (the gate signal RDGT is always “Hi”), the timer signal TMS is equal to the timing signal DGTS. In this figure, the time measuring instrument 7101 starts measurement after a predetermined wait time (200 μs) from the falling edge of the gate signal IDGATE from the address signal detection unit 31, and when the time corresponding to one period of the disturbance signal has elapsed. Is shown to stop. In this way, the data acquisition timing signal DGTS for averaging the focus position information FPIS for one period of disturbance in the data area is obtained.

  FIGS. 19A and 19B show the gate signal IDGATE, the data acquisition timing signal DGTS, and the L / G switching signal in the groove and land during the focus position precise search when the read gate detection unit 32 is not operating. FIG. 19A is a timing chart in the groove, and FIG. 19B is a timing chart in the land.

  Note that the drive controller 14 controls the tracking control unit 23 during the precise focus position search so as to perform a still jump every rotation of the optical disc 1 so that the light beam on the optical disc 1 always has a groove track or a land track. Controls to follow the track. Therefore, when the light beam on the optical disc 1 follows the groove track, the L / G switching signal LGS is “Hi” level indicating the groove at the L / G switching point as shown in FIG. The waveform changes from “1” to “Low” level indicating a land, and when the data sector 1 performs a still jump, the waveform changes to “Hi” level indicating a groove again. That is, after the light beam on the optical disc 1 changes from following the groove track to following the land track, the data sector 1 performs a still jump to return to the previously following groove track.

  At this L / G switching point, as shown in FIG. 19A, the data acquisition timing signal DGTS is 1 “Low” during and before and after the period when the gate signal IDGATE is “Hi” level, and between the data sector 0 and the data sector. The waveform shows the level. When the data acquisition timing signal DGTS indicates the “Low” level, the first averaging circuit 7102 does not acquire the focus position information FPIS from the first selection circuit 7106 (the averaging is interrupted).

  On the other hand, when the light beam on the optical disk 1 follows the land track, the L / G switching signal LGS signal is “Low” indicating the land at the L / G switching point as shown in FIG. The waveform changes from the level to the “Hi” level indicating the groove, and when the data sector 1 performs the still jump, the waveform changes to the “Low” level indicating the land again. That is, after the light beam on the optical disk 1 changes from following the land track to following the groove track, the data sector 1 performs a still jump to return to the land track that followed earlier.

  At this L / G switching point, as shown in FIG. 19B, the data acquisition timing signal DGTS is “Low” in the period when the gate signal IDGATE is “Hi”, before and after it, and in the data sector 0 and the data sector 1. The waveform shows the level. When the data acquisition timing signal DGTS indicates “Low” level, the third averaging circuit 7104 does not acquire the focus position information FPIS from the first selection circuit 7106 (the averaging is interrupted).

  As can be seen from these timing charts, the averaging processing unit 71 distinguishes the groove track from the land track while discarding the focus position information FPIS in the address area based on the gate signal IDGATE from the address signal detection unit 31. The information FPIS is averaged. In other words, the focus position information FPIS acquired only in the data area of the groove track and the focus position information FPIS acquired only in the data area of the land track are averaged independently.

Next, the focusing operation of the focus position precise search by the focus position precise search unit 60 will be described with reference to FIG.
The focus position precise search unit 60 uses the focus signal information FBAL2 and FOFF2 corresponding to the focus control target position obtained by averaging the focus position information FPIS from the multiplier 70 by the averaging processing unit 71 to the focus error detecting unit 36. Output to. At this time, ideally, an exploration that an optimum focus position is always obtained if the target position of the focus control is changed by the focus position information FPIS so that the reproduction state obtained by one precise focus position exploration is optimized. Is preferred. If this is expressed by an equation, it becomes as shown in Equation 6.

Focus position information FPIS × K = target position change amount (Expression 6)
Here, K is a constant (hereinafter referred to as “correction gain constant”) that relates the amount of deviation from the optimum focus position and the amount of change in the control target position. If the focus control target position is changed based on Equation 6, when the correction gain constant K = 1, it can be ideally set to the focus control target position at which the focus position is optimized by one change.

  However, since the detection sensitivity of the envelope signal and the jitter signal that change in response to the disturbance signal from the disturbance signal generation unit 25 varies during the precise focus position search, in this embodiment, the focus position information FPIS and the target value of the focus control are changed. Is set to be smaller than 1 and the focus position search and the update of the target value of the focus control are repeated a predetermined number of times, so that the convergence operation is performed to the focus control target position where the focus position is optimal. I am doing so. Here, if the value of the correction gain constant K when the focus position precision search is converged in this embodiment is preferably set to 0.7, and the focus position precision search is converged in four times, For example, even when the deviation from the initial optimum focus position is 1 μm, the optimum focus position can be searched with an accuracy of ± 0.05 μm or less.

As described above, the focus position precise search unit 60 acquires the focus position information FPIS only for the data area in which the focus position information FPIS of the address area is discarded separately for the land track and the groove track, and the track for each of the land track and the groove track. A focus target position where the focus position corresponding to the position is optimal is obtained.
Next, the jitter detector 62 will be described with reference to FIGS. 20, 21, and 22. FIG. 20 is a block diagram showing a detailed configuration of the jitter detector 62. The binarization circuit 6201 receives the reproduction signal RF from the signal processing unit 40 and outputs an RF pulse signal PRF binarized with a predetermined threshold value. The phase comparison circuit 6202 detects a phase shift between the RF pulse signal PRF and the clock signal CLK output from the VCO (voltage controlled oscillator) 6205. Specifically, a pulse having a pulse width corresponding to the phase shift is output from the output terminals UP and DN depending on whether the phase of the RF pulse signal PRF is advanced or delayed with respect to the phase of the clock signal CLK. . The differential circuit 6203 calculates the difference between the pulse signals UP and DN output from the phase comparison circuit 6202 and outputs the difference to the integration circuit 6204. The integration circuit 6204 integrates the output signal of the differential circuit 6203 and outputs it to the VCO 6205. VCO 6205 outputs a clock signal CLK having a frequency corresponding to the output of integration circuit 6204 to phase comparison circuit 6202. The adder circuit 6206 calculates the sum of the pulse signals UP and DN output from the phase comparison circuit 6202 and outputs the sum to an LPF (low-pass filter) 6207 described later. The LPF 6207 outputs a low frequency component of the output signal from the adder circuit 6206 as the pulse width variation signal PD. The pulse width variation signal PD generated in this way represents the jitter between the RF pulse signal PRF and the clock signal CLK.

  FIG. 21 is a diagram showing the timing of the RF pulse signal PRF, the clock signal CLK, and the phase comparison circuit output pulse signals UP and DN in the jitter detector 62. The relationship between the clock signal CLK output from the VCO 6205 and the RF pulse signal PRF is, for example, output from the VCO 6205 to the pulse of the RF pulse signal PRF having the shortest pulse width in the case of EFM (eight to fourteen modulation), for example. In general, the relationship is such that three pulses of the clock signal CLK are included. In this figure, for simplicity, it is assumed that the pulse widths of the RF pulse signal PRF and the clock signal CLK are equal.

  The phase comparison circuit 6202, the differential circuit 6203, the integration circuit 6204, and the VCO 6205 constitute a PLL (phase locked loop). First, the phase comparison circuit 6202 outputs pulse signals UP and DN corresponding to the phase difference between the RF pulse signal PRF and the clock signal CLK as shown in FIG. That is, when the RF pulse signal PRF is advanced from the clock signal CLK at the rising edge and the falling edge, the pulse signal UP having a width corresponding to the advance is output (see A in FIG. 21). On the other hand, if it is delayed, a pulse signal DN having a width corresponding to the delay is output (see B in FIG. 21). The phase advance / delay becomes a positive / negative pulse signal by the differential circuit 6203 and further becomes a signal cumulatively added by the integration circuit 6204. The VCO 6205 generates a clock signal CLK having a frequency corresponding to the voltage of the added signal and feeds it back to the phase comparison circuit 6202. As a result, the clock signal CLK is controlled such that the average of the phase difference is zero with respect to the RF pulse signal PRF.

  If there is no variation in pulse width, as a result of feedback, the pulse signals UP and DN do not have a pulse relative to the phase difference (ie remain at zero level). Here, it is assumed that the pulse width of the RF pulse signal PRF is narrower than that of the clock signal CLK (see C in FIG. 21). At this time, the pulse signal DN is generated at the rising edge of the clock signal CLK, and the pulse signal UP is generated at the falling edge of the RF pulse signal PRF. On the other hand, it is assumed that the RF pulse signal PRF has a wider pulse width than the clock signal CLK (see D in FIG. 21). At this time, the pulse signal UP is generated at the rising edge of the RF pulse signal PRF, and the pulse signal DN is generated at the falling edge of the clock signal CLK.

  As described above, the frequency and phase of the clock signal CLK are controlled by the PLL so that the average phase difference between the inputs U and V of the phase comparison circuit 6202 becomes zero. Therefore, when the pulse width of the RF pulse signal PRF varies, pulses having the same width are output as the pulse signals UP and DN, respectively. As a result, the adding circuit 6206 outputs only the fluctuation component of the pulse width. The LPF 6207 outputs a DC voltage signal as a pulse width fluctuation signal PD by smoothing the fluctuation component of the pulse width. In this way, the jitter detector 62 outputs the pulse width variation detection signal PD as the jitter of the reproduction signal RF in the data area.

  FIG. 22 is a block diagram showing a detailed configuration of the phase comparison circuit 6202 shown in FIG. As shown in the figure, the rising edge of the RF pulse signal PRF is detected by the monomulti 6202A. The falling edge of the RF pulse signal PRF becomes a rising edge by the inverting circuit 6202C, and the rising edge is detected by the monomulti 6202B. The outputs of the respective mono-multis 6202A and 6202B are input to the OR circuit 6202D, and the OR circuit 6202D sends the output to the CK input of the flip-flop 6202E. The clock signal CLK from the VCO 6205 is input to the CK input of the flip-flop 6202F. The pulse signal UP from the flip-flop 6202E and the pulse signal DN from the flip-flop 6202F are input to the NAND circuit 6202G. The output signal of the NAND circuit 6202G is the reset (R) terminal of the flip-flop 6202E and the reset of the flip-flop 6202F. The signal is input to the (R) terminal. The D input of the flip-flop 6202E and the D input of the flip-flop 6202F are connected to the power supply voltage Vcc (for example, + 5V). The phase comparison circuit 6202 configured as described above operates so as to set the flip-flop at the earlier signal edge and reset at the later one of the edge signal from the OR circuit 6202D and the edge of the clock signal CLK. .

  Note that the configuration of the phase comparison circuit 6202 is not limited to the configuration shown in this figure, and as a result, a circuit having differential outputs and addition outputs of the pulse signals UP and DN, that is, (UP−DN) and (UP + DN). May be provided as an output terminal. If only (UP + DN), for example, it can be directly realized by exclusive OR (exclusive OR). However, in order to obtain (UP−DN) and (UP + DN) with a relatively simple configuration, a circuit that can output the pulse signals UP and DN independently is preferable. Further, the internal configuration of the phase comparison circuit 6202 only needs to have the above-described function, and can be realized by other circuit configurations.

  The focus position precise search unit 60 configured in this way has the jitter, envelope, and focus error signal of the reproduction signal RF when the disturbance signal from the disturbance signal generator 25 is applied to the focus control system via the adder 24. A focus target position is obtained from the FES. Control signals FBAL2 and FOFF2 for changing the control target position of the focus servo based on the obtained focus target position are output to the focus error detection unit 36. The focus error detection unit 36 outputs the focus error signal FES by changing the focus balance and the focus offset based on the control signals FBAL2 and FOFF2 from the focus position precise search unit 60, and is output from the signal processing unit 40. The zero level of the focus error based on the focus signals VFS1 and VFS2, that is, the control target position of the focus servo is set.

  Regarding the setting of the control target position, as already explained in the explanation of the convergence operation of the focus position precise search, the correction gain constant relating the deviation amount from the focus optimum position and the change amount of the control target position is one time. If the gain for completely correcting the deviation from the optimum focus position in the correction operation is 1, the variation in the detection sensitivity of the envelope signal and jitter signal of the reproduction signal that changes in response to the disturbance signal from the disturbance signal generator 25 is taken into consideration. Thus, it is set to a value (0.7) smaller than 1. Then, if the correction of the focus position based on the control signals FBAL2 and FOFF2 corresponding to the average value obtained by averaging the focus position information FPIS for 24 periods of the disturbance signal is performed once, this correction is preferably performed about 4 times. By repeating the operation, the focus position at which the amplitude or jitter of the reproduction signal is optimized, that is, the deviation from the optimum focus position can be reduced to a predetermined value (for example, ± 0.05 μm in terms of the focus position) or less. . That is, it is possible to converge to the focus optimum position with accuracy of a convergence error of ± 0.05 μm or less by four correction operations.

Next, the significance of the focus position precise search unit 60 and the focus control unit 26 performing processing based on the gate signal IDGATE from the address signal detection unit 31 will be described.
The SS-L / GFMT optical disc 1 has an address area between data sectors (see FIG. 4A). Further, as shown in the figure, there is a land / groove switching point after the address area for each round of the optical disk 1. As shown in the figure, the physical structure of the data area is different from the physical structure of the address area. As a result, the state of the light beam reflected from the optical disk 1 incident on the detectors 4 and 5 that detect the focus error signal FES and the broadband tracking error signal RFTE is different between the data area and the address area. Then, both the focus error signal FES and the broadband tracking error signal RFTE cause an offset. That is, in the address area, the focus position and tracking position detected together with the focus error signal FES and the broadband tracking error signal RFTE include an error.

  Therefore, in a state in which the focus servo that controls the light beam irradiated on the optical disc 1 to be always in a predetermined convergence state and the tracking servo that controls the light beam to follow the track on the optical disc 1 are operated. When the light beam spot enters the address area from the data area, both the focus servo and the tracking servo are disturbed. In order to prevent this disturbance, it is necessary to prevent the focus servo and tracking servo from following when the light beam passes through the address area. Therefore, both servos hold the servo in the address area based on the gate signal IDGATE (as shown in FIG. 6D detected by the address signal detector 31).

  As described above, in the SS-L / GFMT optical disc 1, single spiral recording / reproduction is performed while alternately switching the track following each rotation of the optical disc 1 from the land track to the groove track or from the groove track to the land track. Operation is realized. Since the tracking polarity is reversed between the land track and the groove track, it is necessary to switch the polarity. A signal used for switching the tracking polarity to follow the track is an L / G switching signal LGS as shown in FIG.

  In the focus position precise search in the present embodiment, focus control and tracking control are operated, and a still jump is performed every rotation of the optical disc 1 so that the focus of the groove track is in a state where the light beam spot always follows the groove track. Performs precise position search, moves to the next land track after the focus position precise search of the groove track, and performs a focus position precise search of the land track with the light beam spot always following the land track. . Further, since the envelope and jitter of the reproduction signal are used as the focus position information FPIS for calculating the deviation of the current focus position from the optimum focus position, the focus position search by the focus position precise search unit 60 is performed on the optical disc 1. It is necessary to do in the already finished area.

  Next, the relationship between the surface shake component appearing as the focus servo residual in the focus error signal FES, the disturbance signal from the disturbance signal generator 25 and the data sector will be described with reference to FIGS. FIG. 23A is a waveform diagram per one rotation of the disk of the surface shake component that appears as the focus servo residual in the focus error signal FES. FIG. 23B shows the waveform of the disturbance signal output from the disturbance signal generator 25. FIG. 23C is a schematic diagram of the data sector of one rotation of the disk, that is, one track (for example, the inner circumference side of the optical disk 1).

  As shown in FIG. 23 (a), the surface shake component is the residual of the focus servo in synchronization with the rotation of the optical disk 1, and here, as the sine wave signal that changes for two cycles with one rotation of the optical disk, the focus error signal FES. Appear in As shown in FIG. 23C, the number of sectors in one rotation of the optical disk, that is, in one track is, for example, 17 sectors from data sector 0 (DS0) to data sector 16 (DS16) in the innermost circumference. Here, the rotation frequency of the optical disc 1 is 39.78 Hz in the innermost circumference of the optical disc 1 and there are 17 data sectors in one rotation of the optical disc. Therefore, the frequency of one data sector including the address area is 676 Hz.

  In the focus position precise search of the present embodiment, the focus position information FPIS in the address area is discarded based on the gate signal (gate signal IDGATE) in the address area, and the focus position information FPIS is acquired only in the data area. If the focus position information FPIS is acquired only in the data area, the focus position information FPIS is acquired intermittently. Therefore, the disturbance signal applied from the disturbance signal generator 25 to the focus control system when performing the focus position precise search by the focus position precise search unit 60 is preferably included in the data area of one data sector for one period or more. Is required. That is, by making sure that a disturbance signal is always included in one period in the data area of one data sector, the focus position information FPIS corresponding to the disturbance can be acquired in units of one data sector. Accordingly, in consideration of conditions such as the number of revolutions of the optical disc 1, the number of data sectors per revolution, and the presence of disturbance signals in the data area of one data sector, the focus position precise search is performed in this embodiment. Sometimes the frequency of the disturbance signal applied to the focus control system is 1 kHz.

Next, the search principle of the optimum focus position will be described with reference to FIGS. 24, 25, 26, and 27. FIG. FIG. 24 is a diagram showing the relationship between the focus position and the envelope of the reproduction signal RF detected by the envelope detector 61, and the relationship between the disturbance signal and the envelope of the reproduction signal RF at each focus position.
When a disturbance signal is applied from the disturbance signal generator 25 to the focus control system with reference to the point A with the focus control being operated, the direction in which the objective lens 3 approaches the optical disk 1 is the positive direction, and the objective lens 3 is from the optical disk 1. If the direction of separation is the negative direction, the envelope of the reproduction signal RF becomes small when the focus position is changed in the positive direction, and the envelope of the reproduction signal RF becomes large when the focus position is changed in the negative direction. On the other hand, when a disturbance signal is applied with reference to point B and the focus position is changed in the positive direction, the envelope of the reproduction signal RF becomes large, and when the focus position is changed in the negative direction, the envelope of the reproduction signal RF becomes small. Become. Furthermore, when a disturbance signal is applied with reference to point C, that is, the maximum envelope point of the reproduction signal RF, the envelope of the reproduction signal RF changes so as to decrease in accordance with the disturbance signal regardless of whether the focus position is changed to positive or negative. To do.

  Thus, when the disturbance signal from the disturbance signal generator 25 is applied to the focus control system, the focus servo changes in response to the applied disturbance signal, so that the envelope of the reproduction signal RF also changes. Therefore, the amount of defocus with respect to the focus position is obtained by multiplying the disturbance component of the focus error signal FES when the disturbance signal from the disturbance signal generator 25 is applied to the focus control system via the adder 24 and the envelope of the reproduction signal RF. And polarity, that is, focus position information FPIS indicating a deviation between the focus position and the optimum focus position can be obtained.

  Here, the principle of obtaining a deviation from the optimum focus position from the disturbance component of the focus error signal and the envelope of the reproduction signal RF will be described with reference to FIGS. 24 and 25A to 25C. 25A to 25C show the disturbance signal, the envelope of the reproduction signal RF at points A, B, and C in FIG. 24, respectively, and the disturbance signal and points A and B in FIG. A waveform obtained by multiplying the envelope of the reproduction signal RF at each of the points C and C is shown. For convenience of explanation, it is assumed that a waveform obtained by multiplying the disturbance signal and the envelope of the reproduction signal RF by the disturbance signal is obtained continuously. When a continuous sinusoidal disturbance signal as shown in FIG. 25 (a) is applied to the focus control system at point A in FIG. 24, the envelope waveform of the reproduction signal RF becomes the waveform at point A in FIG. 25 (b). As shown, the waveform is a sinusoidal waveform whose phase is 180 degrees out of phase with the disturbance signal. Then, the waveform obtained by multiplying the envelope of the reproduction signal RF and the disturbance signal becomes a waveform that changes on the negative side from the zero level as shown by the waveform at point A in FIG. That is, the focus position information FPIS obtained by multiplying the envelope of the reproduction signal RF and the disturbance signal (hereinafter referred to as “focus position information FPIS by the envelope”) has a waveform that always changes to the negative side with respect to the disturbance signal. Become. If the waveform at point A shown in FIG. 25C is smoothed by a low-pass filter or the like, the deviation amount and polarity from the optimum focus position at point A in FIG. 24 can be obtained.

  Similarly, when a sinusoidal disturbance signal is applied to the focus control system at point B in FIG. 24, the envelope waveform of the reproduction signal RF has the same phase as that of the disturbance signal as shown by the point B waveform in FIG. It becomes a sinusoidal waveform. Then, the waveform obtained by multiplying the envelope of the reproduction signal RF and the disturbance signal becomes a waveform that changes on the positive side of the zero level as shown by a point B waveform shown in FIG. That is, the focus position information FPIS by the envelope has a waveform that always changes to the positive side with respect to the disturbance signal. If the point B waveform shown in FIG. 25C is smoothed by a low-pass filter or the like, it is possible to obtain the deviation amount and polarity from the optimum focus position at point B in FIG.

  Similarly, when a sinusoidal disturbance signal is applied to the focus control system at point C in FIG. 24, the envelope waveform of the reproduction signal RF is negative with respect to the zero level as shown by the point C waveform in FIG. The waveform turns back to the side. Then, the waveform obtained by multiplying the envelope of the reproduction signal RF and the disturbance signal becomes a sine wave waveform whose phase is shifted by 180 degrees from the disturbance signal, as shown by a point C waveform shown in FIG. That is, the focus position information FPIS based on the envelope has a waveform that is inverted between positive and negative with respect to the disturbance signal. If the waveform at point C shown in FIG. 25C is smoothed by a low-pass filter or the like, the shift amount and polarity from the optimum focus position at point C in FIG. 24 can be obtained.

  Next, the relationship between the focus position and the jitter of the reproduction signal RF will be described with reference to FIG. FIG. 26 is a diagram showing the relationship between the focus position and the jitter of the reproduction signal RF from the jitter detector 62, and the relationship between the disturbance signal and the jitter of the reproduction signal RF at each focus position. When a disturbance signal is applied from the disturbance signal generator 25 to the focus control system based on point A with the focus control activated, the direction in which the objective lens 3 approaches the optical disk 1 is the positive direction, and the objective lens 3 is separated from the optical disk 1. If the direction is a negative direction, the jitter of the reproduction signal RF increases when the focus position is changed in the positive direction, and the jitter of the reproduction signal RF decreases when the focus position is changed in the negative direction. When the disturbance signal is applied with reference to point B and the focus position is changed in the positive direction, the jitter of the reproduction signal RF becomes small, and when the focus position is changed in the negative direction, the jitter of the reproduction signal RF becomes large. When a disturbance signal is applied with reference to point C, that is, the jitter minimum point of the reproduction signal RF, the jitter of the reproduction signal RF changes so as to increase regardless of whether the focus position is changed to positive or negative.

  Thus, when the disturbance signal from the disturbance signal generator 25 is applied to the focus control system, the focus servo changes in response to the applied disturbance signal, so that the jitter of the reproduction signal RF also changes. Therefore, if the disturbance component of the focus error signal FES when the disturbance signal from the disturbance signal generator 25 is applied to the focus control system via the adder 24 is multiplied by the jitter of the reproduction signal RF, the amount of defocus with respect to the focus position is calculated. The focus position information FPIS indicating the polarity, that is, the deviation between the focus position and the optimum focus position can be obtained.

  However, the envelope response characteristic of the reproduction signal RF from the envelope detection unit 61 and the jitter response characteristic of the reproduction signal RF from the jitter detection unit 62 with respect to the disturbance signal are the envelope waveform shown in FIG. 24 and the jitter waveform shown in FIG. As is clear from FIG. 2, the response characteristics are reversed. Therefore, when the focus position precise search is performed based on the focus position information FPIS based on the envelope of the reproduction signal RF from the envelope detection unit 61 and the focus position information FPIS based on the jitter of the reproduction signal RF from the jitter detection unit 62, for example, It is necessary to match the polarity of the envelope and the jitter such as matching the polarity of the jitter to the polarity of the envelope. In this embodiment, as shown in FIG. 16, the subtractor 69 performs polarity adjustment by calculating the difference between the jitter signal from the second gain adjustment unit 67 from the envelope signal from the first gain adjustment unit 66. ing. Note that the procedure for calculating the deviation from the optimum focus position from the disturbance component of the focus error signal and the jitter of the reproduction signal RF is obtained by the same principle as the principle for detecting deviation from the optimum focus position by the envelope. Description of the principle of detecting the deviation from the optimum focus position is omitted.

Next, the deviation detection characteristic from the optimum focus position obtained by the focus position precise search unit 60 will be described with reference to FIG. FIG. 27 is a diagram showing the relationship between the focus position and the detected deviation value from the optimum focus position.
When the focus position is searched by the focus position precise search unit 60, for example, the gain of the second gain adjustment unit 67 is set to zero, and the first gain adjustment unit 66 is appropriately adjusted so that only the envelope of the reproduction signal RF is obtained. If the deviation from the optimum focus position is detected based on the focus position where the envelope of the reproduction signal RF is maximum (for example, for example, the curve 7120 shown in FIG. 27), the deviation from the optimum focus position becomes zero. −0.50 μm). When the focus position shifts in the positive direction around the focus position where the envelope is maximum, the shift from the optimal focus position increases in the positive direction, and when the focus position shifts in the negative direction, the shift from the optimal focus position. Has a characteristic of increasing in the negative direction.

  On the other hand, when the gain of the first gain adjustment unit 66 is set to zero and the second gain adjustment unit 67 is appropriately adjusted to detect a deviation from the optimum focus position based only on the jitter of the reproduction signal RF, FIG. As shown by the curve 7122 shown, the deviation from the optimum focus position becomes zero at the focus position (for example, 0 μm) at which the jitter is minimized. When the focus position shifts in the positive direction around the center of the focus position where the jitter is minimized, the deviation from the optimal focus position increases in the positive direction, and when the focus position shifts in the negative direction, the deviation from the optimal focus position The characteristic increases in the negative direction.

  Further, when the gain of the first gain adjusting unit 66 is set to an appropriate coefficient, for example, α, and the gain of the second gain adjusting unit 67 is set to an appropriate coefficient, for example, β, detection sensitivity and jitter from the optimum focus position by the envelope are set. If the adjustment is made so that the deviation detection sensitivity from the optimum focus position becomes equal, the deviation detection characteristic from the optimum focus position becomes zero from the optimum focus position as shown by a curve 7121 shown in FIG. This is an intermediate position (for example, 0.25 μm) between the focus position where the envelope is maximum and the focus optimal position where jitter is minimum. In this case, the deviation detection characteristic from the optimum focus position is an intermediate characteristic between the deviation detection characteristic from the optimum focus position by the envelope and the deviation detection characteristic from the optimum focus position by jitter. In other words, if the focus position shifts in the positive direction around the middle position between the focus position where the envelope is maximum and the focus position where jitter is minimum, the deviation from the optimum focus position increases in the positive direction, and the focus position is negative. The deviation from the optimum focus position increases in the negative direction when it is deviated in the negative direction.

  For this reason, the present embodiment employs a curve 7121 that takes into account both the envelope and jitter of the reproduction signal RF. Specifically, the averaging processing unit 71 of the focus position precise search unit 60 obtains a deviation amount corresponding to the focus position information obtained by the averaging from the curve 7121 shown in FIG. New focus target positions Ml1 and Ml2 are obtained by shifting the current focus positions (Ml1 and Ml2) by an amount obtained by performing the correction according to Expression 6.

  Next, the relationship between the convergence position error and the influence of the address area when searching for the optimum focus position by the focus position precise search unit 60 will be described. In the SS-L / GFMT optical disc 1 in this embodiment, there is an address area between sectors. The focus position precise search is performed in a state where the focus control and the tracking control are operated. However, as described above, the correct focus error signal FES and the broadband tracking error signal RFTE cannot be obtained in the address region. Therefore, when both the focus servo and the tracking servo pass through the address area, the focus control unit 26 and the tracking control unit 23 are placed on the optical disc 1 based on the gate signal IDGATE from the address signal detection unit 31. Each output signal immediately before the converged light beam enters the address area is held. When the light beam converged and irradiated on the optical disk 1 passes through the address area and enters the data area, the hold is released based on the gate signal IDGATE from the address signal detection unit 31, and the operations of the focus servo and tracking servo are performed. To resume.

  Even in the focus position search, if the focus optimal position is searched using the focus position information FPIS including the envelope and jitter of the reproduction signal RF acquired in the address area, the search result includes an error from the optimal position. That is, the convergence error to the optimum focus position increases due to the influence of the address area. Therefore, in this embodiment, a disturbance signal having a frequency that is included in the data area of one data sector in one or more periods of disturbance is applied to the focus control system, and the address is determined based on the gate signal IDGATE from the address signal detection unit 31. The focus position information FPIS is detected only in the data area excluding the area. As a result, high-accuracy focus optimum position search that is not affected by the address area is realized even for the optical disc 1 having an address area that causes a detection error in the focus position information FPIS.

  As described above, the focus position precise search unit 60 of the embodiment controls the focus position optimal position between the maximum envelope of the reproduction signal RF and the minimum jitter of the reproduction signal RF. Even when the focus position is changed due to a follow-up residual to surface shake or the like, the margin for defocus is optimized and good reproduction characteristics can be obtained. In other words, as shown in FIG. 15, when the focus position is adjusted to the minimum jitter position, the jitter margin for defocusing decreases when the focus position shifts in the positive direction. When the focus position is adjusted to the envelope maximum position of the reproduction signal RF, if the focus position is shifted in the negative direction, the envelope of the reproduction signal RF becomes extremely small with respect to defocusing. Deteriorate. Therefore, since the optimum focus position is adjusted to an intermediate point between the focus position where the amplitude of the reproduction signal RF is maximum and the focus position where the jitter is minimum, the focus position where the envelope of the reproduction signal RF is maximum and the reproduction signal RF When the focus position at which the jitter is minimized is different, good reproduction characteristics can be obtained even when the focus position is changed due to a follow-up residual to the disc surface fluctuation of the focus servo.

  The focus position precise search unit 60 of this embodiment searches for a focus position intermediate between the focus position where the amplitude of the reproduction signal RF is maximum and the focus position where the jitter of the reproduction signal RF is minimum. The focus position where the RF error rate is below a predetermined value, the focus position where the amplitude of the reproduction signal RF is maximum, the focus position where the jitter of the reproduction signal RF is minimum, or the error rate of the reproduction signal RF is minimum The focus position may be searched.

  In the focus position precise exploration of the present embodiment, first, the focus position is finely explored in a state where the light beam spot follows the groove track, and then moved to a land track on the outer periphery of one track. Although the focus position precision search was performed with the still jump, the focus position precision search procedure is not limited to this. Well.

That is, as for the change of the focus control target position (focus balance value and focus offset value) in the precise search of the focus position of the present embodiment, the modification examples in the coarse focus position search (eight kinds of search methods shown in FIG. 13) are used. Can be adopted.
[Optional function for precise focus position search]
Next, two optional functions in the precise search for the focus position will be described. First, the first optional function for carrying out the precise search of the focus position by paying attention to only a specific data area of the optical disc 1, that is, the function of the read gate detector 32 will be described.

  As described above, the read gate detection unit 32 performs the focus position precise search for the gate signal RDGT that becomes “Hi” in the address area on the optical disc 1 and the data sector (read data sector) designated in advance by the drive controller 14. To the unit 60. In the present embodiment, the drive controller 14 detects the surface shake (AC signal) generated when the optical disk 1 is rotated by taking in the focus error signal FES and performing A / D conversion in advance, and the change amount of the AC signal is small. These data sectors are designated as read data sectors so that the gate signal RDGT becomes “Hi” in the data area corresponding to the position.

Then, the focus position precise search unit 60 acquires focus position information FPIS only for a data area designated in advance based on such a gate signal RDGT, and performs a precise search for the focus position. The significance of operating the first optional function is as follows.
When performing the focus position precise search, the focus control unit 26 irradiates the optical disc 1 by driving the actuator 2 via the addition unit 24 and the focus drive unit 21 based on a signal from the focus error detection unit 36. The controlled light beam is controlled so as to always be in a predetermined convergence state. However, when the surface shake of the optical disc 1 increases, a control residual of the surface shake component of the optical disc 1 appears in the focus error signal FES. Accordingly, when the surface shake of the optical disc 1 is large, the focus position detection error increases unless processing such as averaging the influence of the surface shake is performed by continuously detecting the focus position information FPIS. become. However, in the SS-L / GFMT optical disc 1, since the data area is discontinuous, the focus position information FPIS is also detected discontinuously, and is easily affected by the surface shake component. Therefore, in the first optional function, the focus position search accuracy is further improved by detecting the focus position information FPIS in a state where the influence of the surface shake of the optical disc 1 is reduced.

  28A to 28E are timing charts for explaining the function of the read gate detection unit 32. FIG. 28A is a waveform of the surface shake component of the optical disc 1, and FIG. Read data sectors (hatched data sectors) set in the gate detection unit 32, FIG. 28C shows the gate signal RDGT output from the read gate detection unit 32, and FIG. 28D shows the averaging processing unit 71. FIG. 28E shows the data acquisition timing signal DGTS output from the AND circuit 7109 of the averaging processing unit 71. Here, for convenience of explanation, it is assumed that the disturbance signal from the disturbance signal generation unit 25 is applied with an AC signal of one cycle synchronously applied to the data area of one data sector.

  In the detection of the focus position information FPIS, t (0), t (1), t (2), and t (3) shown in FIG. , T (4), that is, the vicinity where the change in the control residual of the surface shake component is maximized. Then, as shown in FIG. 28 (b), the read gate detecting unit 32 is a data sector excluding a data sector located at a position where the change amount of the surface shake component is small, that is, at a timing at which the polarity of the surface shake component is reversed. Are designated as read data sectors only. In such designation, the read gate detection unit 32 determines “Hi” only in the gate signal RDGT as shown in FIG. 28C, that is, in the address area and the read data sector, based on an instruction from the drive controller 14. Is output.

  Such a signal RDGT is input to the averaging processing unit 71 of the focus position precise search unit 60, more specifically, to the AND circuit 7109 shown in FIG. The timer signal TMS from the time measuring device 7101 is input to the other input terminal of the AND circuit 7109. As shown in FIG. 18, the time measuring unit 7101 starts time measurement after a predetermined wait time (200 μs) from the rising edge of the gate signal IDGATE from the address signal detection unit 31, and takes time corresponding to one period of disturbance ( Here, a time corresponding to one data sector) is measured, and a timer signal TMS indicating the time during the measurement is output. Such a timer signal TMS is as shown in FIG.

  The gate signal RDGT and the timer signal TMS are ANDed in the AND circuit 7109, and the result is output to the first averaging circuit 7102 and the third averaging circuit 7104 as the data acquisition timing signal DGTS. The As shown in FIG. 28 (e), the data acquisition timing signal DGTS includes a pulse train that becomes “Hi” for only one period of the disturbance signal only in the data region at the timing when the change in the surface shake component is small. Become. The first averaging circuit 7102 and the third averaging circuit 7104 average the focus position information FPIS from the multiplier 70 during the period in which the data acquisition timing signal DGTS is “Hi”. As a result, stable data other than the address area and only in the area designated as the read data sector, that is, the address area that causes an error in the focus position information FPIS and the area where the change in the surface shake component is large are excluded. Focus position information FPIS is acquired and averaged only for the area, and is used for precise search of the focus position.

In this way, the first optional function realizes a precise search of the focus position with high accuracy while avoiding control disturbance due to the surface shake component.
Next, a second optional function for performing a precise search of the focus position based on the focus error signal FESS obtained by directly removing the surface shake component from the focus error signal FES, that is, the function of the surface shake component removing unit 35 Will be described.

As described above, the surface shake component removing unit 35 removes the surface shake component of the optical disc 1 included in the focus error signal FES from the focus error detecting unit 36 and applies other frequency components (applied from the disturbance signal generating unit 25). The 1 kHz signal and the like are passed through, and the passed signal is output to the switch 39.
FIG. 29 is a block diagram illustrating a detailed configuration of the surface shake component removing unit 35. The surface shake component removing unit 35 includes a band pass filter 3501 and a subtractor 3502 that pass only a frequency band of a known surface shake component. The focus error signal FES is input to the plus terminal of the subtractor 3502, and the surface shake component signal that has passed through the band pass filter 3501 is input to the minus terminal. Therefore, the output signal from the subtractor 3502 is a signal obtained by removing only the surface shake component from the focus error signal FES.

  When the second optional function is operated, the switch 39 switches the signal from the surface shake component removing unit 35 to be input to the focus position precise search unit 60 according to an instruction from the drive controller 14. . Therefore, the focus position precise search unit 60 performs a precise search for the focus position based on the signal output from the surface shake component removal unit 35.

  As a result, occurrence of detection error of the focus position information FPIS due to unnecessary disturbance such as surface vibration of the optical disc 1 is reduced. That is, in the focus position precise search unit 60, the focus error signal FESS obtained by removing the surface shake component of the optical disc 1 from the focus error signal FES by the surface shake component removal unit 35 and the envelope of the reproduction signal RF and so on From the focus error signal FESS and the jitter of the reproduction signal RF, the focus position information FPIS is obtained, and the focus position is precisely searched based on the focus position information FPIS. Realized.

The surface shake component removing unit 35 in the present embodiment is a filter that removes the surface shake component generated in the rotating optical disc 1, but also removes unnecessary low frequency signal components such as a power supply frequency, for example. Such characteristics may be used.
[Re-exploration of focus position]
Next, the timing at which the optical disc drive apparatus 100 starts the focus position search (rough search and precise search) again will be described separately for recording and playback. In other words, in the present optical disc drive apparatus 100, when starting up, that is, after the rotation of the optical disc 1 is started and reaches a certain number of rotations, a rough focus position search and a subsequent precise search are executed. . However, these explorations are not limited to such cases. In other words, the drive controller 14 also detects the focus position coarse search unit 50 and the focus position precise search unit when detecting a state where the following certain conditions are satisfied during recording and playback in accordance with a built-in control program. 60 starts the focus position search (coarse search and fine search). Here, the conditions and operation | movement are demonstrated.

First, a description will be given of the start condition for re-searching the focus position during recording.
When recording information on the optical disc 1, the drive controller 14 modulates the laser power in accordance with the signal pattern to be recorded on the optical disc 1 and controls the laser power drive unit 41 and the like so as to record information on the optical disc 1. To do. After recording, a verify operation for verifying whether or not desired recording is performed is performed. The verify operation is to record information on the optical disc 1 and immediately reproduce it to determine whether or not the information has been recorded correctly. As a result of the verify operation, when it is found that desired recording characteristics (bit error rate BER or the like) are not obtained, the recording power is increased and the recording and verify operations are performed again. Thus, the drive controller 14 controls the recording power to increase until a desired recording characteristic is obtained. However, there is an upper limit value of the recording power that does not improve the reproduction characteristics even when the recording power is increased. The upper limit value of the recording power is a value determined from the power margin in recording and erasing, the performance of the semiconductor laser, etc., even if the recording power is increased too much and cannot be completely erased in the next erasing.

  For this reason, an upper limit of recording power is set in the laser power driving unit 41. Further, when desired recording characteristics cannot be obtained even if the recording power is increased, a case other than the recording power may be considered. Therefore, as a condition for starting re-exploration of the focus position at the time of recording, it is assumed that the recording power reaches the upper limit value. As a result, even if the bit error rate BER is not improved even when the recording power is increased as described above, a recording characteristic is obtained such that the bit error rate BER becomes equal to or less than a predetermined value by re-examining the focus position. be able to.

FIG. 30 is a flowchart showing a specific procedure for re-searching the focus position during such recording. When recording information on the optical disc 1, the drive controller 14 sends a power setting value for recording and a recording signal pattern to the modulation unit 42 (step S40).
The modulation unit 42 receives the recording power setting value and the recording signal pattern from the drive controller 14 and sends a signal for modulating the laser power to the laser power driving unit 41. The laser power driving unit 41 receives the signal from the modulation unit 42. Based on the above, the laser power is modulated to record information on the optical disc 1 (step S41). Note that, as a normal recording power setting value, a recording power obtained when the apparatus is assembled (hereinafter referred to as a “recording power process value”) is used. The recording power range is 11 mW to 14 mW, and the normal recording power is about 12 mW. Therefore, here, when information is recorded on the optical disc 1, the drive controller 14 records information on the optical disc 1 by setting a process value of the recording power.

  After the end of the recording operation, the drive controller 14 performs verification to verify whether recording has been performed correctly (step S42). The drive controller 14 determines whether or not the verification has been correctly completed (step S43). If the verification has not been correctly completed, the recording power is increased by a predetermined unit (for example, 0.5 mW unit) and recording is performed again. (Step S44). However, before recording, the upper limit value of the recording power is compared with the updated recording power (step S45), and if the recording power does not exceed the recording power upper limit value, the recording operation is performed (step S41) and the verification is performed (step S41). Step S42).

  If the verification is not properly completed (step S43), the above operations (steps S44, S45, S41 to S43) are repeated. In this manner, recording (step S41), verification (step S42) and recording power increase (steps S44, S45) are repeated. As a result, when the recording power exceeds the upper limit value (step S45), the drive controller 14 By instructing the focus position rough search unit 50 and the focus position precise search unit 60, the focus position is re-searched (steps S46 and S47). When the re-exploration is completed, the drive controller 14 sets the process value of the recording power again (step S40), and performs the above-described recording operation and bay validation (steps S41 and S42). When the verification is correctly completed (step S43), the recording operation is normally ended (step S49). On the other hand, if the verification is not properly completed (step S43), the recording power is increased (steps S44 and S45), the recording (step S41) and the verification (step S42) are repeated.

If the recording power exceeds the upper limit value (step S45) and the recording power exceeds the upper limit value twice or more in succession (step S46), the processing when the recording operation does not end normally is performed. This is performed (step S48). As processing when the recording operation does not end normally, processing such as restarting the apparatus is performed.
The drive controller 14 stores the address of the test area used for searching for the focus position at the time of activation, and when re-exploring, by referring to the address, The focus position is re-examined using the same track as the (track).

Next, a description will be given of conditions for starting re-exploration of the focus position during reproduction.
In some cases, the information recorded on the optical disc 1 cannot be reproduced because the bit error rate BER has increased while the information already recorded on the optical disc 1 is being reproduced. This occurs when the focus position is shifted due to the temperature characteristics of the optical head, etc., even though the focus position has been searched once. When the bit error rate BER increases, the optical disc 1 playback device performs playback retry in order to play back desired recording information. This retry of reproduction is continuously repeated up to a predetermined number of times until it can be correctly reproduced. However, when the bit error rate BER greatly increases, there are cases where the reproduction cannot be performed correctly even if the reproduction retry is repeated a predetermined number of times.

Therefore, another condition for starting the re-exploration of the focus position at the time of reproduction is that the reproduction retries are continuously generated a predetermined number of times or more. As a result, even if the reproduction is not performed even if the reproduction retry is repeated a predetermined number of times, it is possible to reproduce within the predetermined number of times during the next reproduction by re-examining the focus position.
FIG. 31 is a flowchart showing a specific procedure for re-examining the focus position during such reproduction. When reproducing the signal from the optical disc 1, the drive controller 14 receives the RF pulse signal PRF from the demodulator 47 (step S60) and performs a reproduction error check every 16 sectors (step S61). As a result of the reproduction error check, when the reproduction is not completed normally (step S62), the reproduction operation is retried (steps S63, S60 to S62). When the retry of the reproduction operation exceeds 50 times (step S63), the focus position is re-searched by instructing the focus position rough search unit 50 and the focus position precision search unit 60 (steps S64 and S65).

  When the re-exploration is completed, the drive controller 14 performs the above-described reproduction operation (steps S60 and S61). If the reproduction error check is correctly completed (step S62), the reproduction operation is normally terminated (step S67). On the other hand, when the reproduction error check is not properly completed (step S62), the reproduction retry is repeated (steps S63, S60 to S62).

If the number of retries exceeds 50 (step S63), and if the number of playback retries exceeds 50 consecutive times (step S64), the processing when the playback operation does not end normally is performed. This is performed (step S66). As a process when the reproduction operation does not end normally, a process such as restarting the apparatus is performed.
Further, the drive controller 14 stores the address of the test area used when searching for the focus position at the time of activation, and moves to the address of the test area used at the time of activation to re-examine the focus position.

By such re-exploration of the focus position, the focus position is deviated from the optimum position while the optical disk drive device is operating even though the focus position is once searched at the time of startup, and the recording operation or the reproduction operation is normally performed. Even if it is in a state where it does not end, it returns to a state where normal recording operation and reproduction operation can be performed again.
As described above, the optical disc drive apparatus 100 according to the present invention has been described based on the embodiment, but the present invention is not limited to this embodiment.

That is, the optical disc drive apparatus 100 according to the present embodiment has two types of modes (coarse search and precise search) as a focus position search method. Although the detection unit 32 and the surface shake component removal unit 35) are provided, the present invention may not have all these modes and optional functions.
For example, a simple optical disk drive device that does not have a function for performing a precise search for a focus position, that is, an optical disk drive device that performs only a rough search for a focus position may be used. FIG. 32 is a block diagram showing only the components related to the focus position search of the optical disc drive apparatus 110 that executes only the search for the coarse focus position. As can be seen from this figure, this optical disk drive device 110 has a component 50 or the like for performing a coarse focus position search, but does not have a component 60 or the like for performing a precise focus position search. .

  Further, a simple optical disk drive device that does not have a function of performing a rough search of the focus position, that is, an optical disk drive device that executes only a precise search of the focus position can be provided. FIG. 33 is a block diagram showing only components related to the focus position search of the optical disc drive apparatus 120 that performs only the precise search of the focus position. As can be seen from this figure, this optical disk drive device 120 has components 25, 600 and the like for executing a precise focus position search, but includes a component 50 and the like for executing a coarse focus position search. , It does not have the components 32, 35, etc. relating to optional functions. FIG. 34 is a block diagram showing a detailed configuration of the focus position precise search unit 600 of the optical disk drive device 120 shown in FIG. 33, as can be seen by comparing with the focus position precise search unit 60 shown in FIG. Further, the gate signal RDGT is not input to the averaging processing unit 710. FIG. 35 is a block diagram showing a detailed configuration of the averaging processing unit 710 shown in FIG. 34. As can be seen from comparison with the averaging processing unit 71 shown in FIG. 17, it relates to the gate signal RDGT. There is no component to perform (AND circuit 7109 in FIG. 17).

  In addition, an optical disk drive apparatus that performs only the precise search of the focus position including the first optional function (read gate detection unit 32) described above may be used. FIG. 36 is a block diagram showing only the components related to the focus position search of the optical disc drive device 130 that executes only the focus position precise search having the first optional function (read gate detection unit 32). As can be seen from this figure, this optical disk drive device 130 has components 25, 60 and the like for executing a precise focus position search and a read gate detection unit 32, but in order to execute a coarse focus position search. The component 50 or the like or the component 35 or the like related to the second optional function is not included.

  Furthermore, an optical disk drive apparatus that performs only the precise search for the focus position, which includes the above-described second optional function (surface shake component removal unit 35), may be used. FIG. 37 is a block diagram showing only components related to the focus position search of the optical disc drive apparatus 140 that executes only the focus position precise search having the second optional function (surface shake component removing unit 35). As can be seen from this figure, the optical disk drive device 140 includes the components 25, 60, etc. and the surface shake component removing unit 35 for executing a precise focus position search, but performs a rough focus position search. Therefore, the component 50 or the like for the first optional function is not included.

  Further, in the rough search and the precise search of the focus position in this embodiment, the focus control and tracking control are operated, and the light beam spot is always set to the groove track (or the land track) by performing the still jump for each rotation of the optical disc 1. Although the coarse search and the precise search of the focus position with respect to the groove track (or land track) are performed in a state of following the track), the present invention is not limited to the method using such a still jump. For example, the focus position rough search unit 50 (or the focus position precision search unit 60) does not make a still jump, but simply follows the track along the spiral. The bit error rate BER (or focus position information FPIS) in each track is continuously measured while alternately switching the land track and the groove track every rotation based on LGS, and the focus control target position (focus) for each track is measured. The balance value and the focus offset value) may be constantly updated. As a result, it is possible to continuously repeat the coarse search (or fine search) of the focus position without performing complicated tracking control like a still jump.

  The recording / reproducing apparatus according to the present invention is useful as an optical disk drive apparatus or the like, and the focus position adjusting method according to the present invention is for adjusting the focus position of an optical disk that can be recorded and reproduced in the optical disk drive apparatus. Useful.

1 is a block diagram showing the overall configuration of an optical disc drive apparatus 100 according to the present invention. (A) is a schematic view when the SS-L / GFMT optical disc 1 is viewed from above, (b) is an enlarged top view of the optical disc 1 near the L / G switching point, and (c) is a land of the optical disc 1. FIG. 4D is a cross-sectional view of the optical disc 1 and the objective lens 3 when the optical beam is irradiated to the optical disk 1, and FIG. 4D is a cross-sectional view of the optical disc 1 and the objective lens 3 when the groove of the optical disc 1 is irradiated with the light beam. . 3 is a block diagram illustrating a detailed configuration of a focus position adjustment unit 30. FIG. (A) is a schematic configuration of a track on the optical disc 1, (b) is a broadband tracking error signal RFTE, and (c) is an L / G switching signal LGS. 3 is a block diagram showing a detailed configuration of an address signal detection unit 31. FIG. (A) is a broadband tracking error signal RFTE input to the address signal detector 31, (b) is an output signal of the binarization circuit 3103, (c) is an output signal of the binarization circuit 3104, and (d) is an address. The gate signal IDGATE output from the signal detection part 31 is shown. 3 is a block diagram showing a detailed configuration of an error rate measuring unit 33. FIG. 4 is a block diagram illustrating a detailed configuration of a focus error detection unit 36. FIG. 3 is a block diagram illustrating a detailed configuration of a focus position rough search unit 50. FIG. An input signal RFTE of the read gate detector 32, a gate signal IDGATE indicating an address area, and an output signal RDGT from the read gate detector 32 are shown. It is a graph which shows the bit error rate BER of RF pulse signal PRF with respect to the change of a focus position. 4 is a flowchart showing a detailed operation of a focus position rough search unit 50. A modified example of the rough focus position search of this embodiment will be described. An information area layout of the SS-L / GFMT optical disc 1 is shown. It is a graph which shows the relationship between a focus position, envelope RFENV of reproduction | regeneration signal RF, and the magnitude | size of reproduction | regeneration jitter. FIG. 3 is a block diagram showing a detailed configuration of a focus position precise search unit 60. 3 is a block diagram showing a detailed configuration of an averaging processing unit 71. FIG. The disturbance signal, the gate signal IDGATE, and the timer signal TMS when the read gate detection unit 32 is not operating are shown. (A) is a timing chart of the gate signal IDGATE, the data acquisition timing signal DGTS, and the L / G switching signal LGS in the groove at the time of focus position precise search when the read gate detection unit 32 is not operating, (b) ) Is the same figure in the land. 3 is a block diagram showing a detailed configuration of a jitter detector 62. FIG. An RF pulse signal PRF, a clock signal CLK, and pulse signals UP and DN output from the phase comparison circuit in the jitter detector 62 are shown. 5 is a block diagram showing a detailed configuration of a phase comparison circuit 6202. FIG. (A) is a waveform per one rotation of a disc of a surface shake component appearing as a focus servo residual in the focus error signal FES, (b) is a waveform of a disturbance signal output from the disturbance signal generator 25, (c). Indicates an outline of a data sector for one rotation of the disk (one track). The relationship between the focus position and the envelope of the reproduction signal RF detected by the envelope detector 61 and the relationship between the disturbance signal and the envelope of the reproduction signal RF at each focus position are shown. (A) is a disturbance signal, (b) is the envelope of the reproduction signal RF at points A, B and C in FIG. 24, (c) is the disturbance signal and points A, B and C in FIG. The waveform obtained by multiplying the envelope of the reproduction signal RF at each point is shown. It is a figure which shows the relationship between a focus position and the jitter of reproduction signal RF from the jitter detection part 62, and the relationship between the disturbance signal in each focus position, and the jitter of reproduction signal RF. It is a figure which shows the relationship between a focus position and the deviation detection value from a focus optimal position. (A) is a waveform of the surface shake component of the optical disc 1, (b) is a read data sector set in the read gate detector 32, (c) is a gate signal RDGT output from the read gate detector 32, (d ) Indicates the timer signal TMS output from the time measuring unit 7101 of the averaging processing unit 71, and (e) indicates the data acquisition timing signal DGTS output from the AND circuit 7109 of the averaging processing unit 71. 3 is a block diagram showing a detailed configuration of a surface shake component removing unit 35. FIG. It is a flowchart which shows the specific procedure of the re-exploration of the focus position in recording. It is a flowchart which shows the specific procedure of the re-exploration of the focus position at the time of reproduction | regeneration. It is a block diagram which shows the structure of the optical disk drive device 110 which performs only a search with a rough focus position. It is a block diagram which shows the structure of the optical disk drive device 120 which performs only the precise search of a focus position. FIG. 34 is a block diagram showing a detailed configuration of a focus position precise search unit 600 of the optical disc drive device 120 shown in FIG. 33. FIG. 35 is a block diagram showing a detailed configuration of an averaging processing unit 710 shown in FIG. 34. It is a block diagram which shows the structure of the optical disk drive device 130 which performs only the precise search of a focus position provided with the 1st option function (read gate detection part 32). It is a block diagram which shows the structure of the optical disk drive device 140 which performs only the precise search of a focus position provided with the 2nd option function (surface shake component removal part 35).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Actuator 3 Objective lens 4 Reproduction | regeneration signal detector 5 Photodetector 6 Leaf spring 7 Optical head 8 Semiconductor laser 9 Optical head support member 10 Coarse motion motor 11 Seek control part 12 Spindle motor 13 Rotation control part 14 Drive controller 20 Light Head control unit 21 Focus drive unit 22 Tracking drive unit 23 Tracking control unit 24 Addition unit 25 Disturbance signal generation unit 26 Focus control unit 30 Focus position adjustment unit 31 Address signal detection unit 32 Read gate detection unit 33 Error rate measurement unit 34 Land groove Detection unit 35 Surface shake component removal unit 36 Focus error detection unit 37 to 39 Switcher 40 Signal processing unit 41 Laser power drive unit 42 Modulation unit 43, 44 Addition amplifier 45 Difference amplifier 46 Addition amplifier 47 Demodulation unit 5 Focus position rough search unit 51 DSP
52 First storage unit 53 Second storage unit 60 Focus position precise search unit 61 Envelope detection unit 62 Jitter detection unit 63 First high-pass filter 64 Second high-pass filter 65 Third high-pass filter 66 First gain adjustment unit 67 Second gain adjustment unit 68 Third gain adjustment unit 69 Subtractor 70 Multiplier 71 Averaging processing unit 72 Third storage unit 73 Fourth storage unit 100 Optical disc drive device 110 Optical disc Drive device 120 Optical disk drive device 130 Optical disk drive device 140 Optical disk drive device 600 Focus position precise search unit

Claims (6)

A recording / reproducing apparatus for an optical disc,
A focus error detecting means for detecting a convergence state of the light beam irradiated on the optical disc and outputting a focus error signal indicating the convergence state;
A focus control means for changing a focus position of the light beam so that the convergence state becomes a predetermined state based on the focus error signal;
Reproduction state detection means for detecting a reproduction state of the optical disk based on a reproduction signal when information recorded on the optical disk is read;
A focus position searching means for changing a focus position of the light beam so that the reproduction state becomes better,
The focus position searching means searches for the focus position so that the reproduction state detected from the reproduction signal and the focus error signal at a position where disturbance to the focus control system is small is good. .   2. The recording / reproducing apparatus according to claim 1, wherein the position where the disturbance to the focus control system is small is a position where acceleration of surface vibration of the optical disc is small.   2. The recording / reproducing apparatus according to claim 1, wherein the position where the disturbance to the focus control system is small is specified in units of sectors formed on the optical disc. A focus position adjusting method in a recording / reproducing apparatus for an optical disc,
A focus error detection step of detecting a convergence state of the light beam irradiated on the optical disc and outputting a focus error signal indicating the convergence state;
A focus control step of changing a focus position of the light beam so that the convergence state becomes a predetermined state based on the focus error signal;
A reproduction state detection step of detecting a reproduction state of the optical disc based on a reproduction signal when information recorded on the optical disc is read;
A focus position search step for changing a focus position of the light beam so that the reproduction state becomes better,
The focus position search step searches the focus position so that the reproduction state detected from the reproduction signal and the focus error signal at a position where disturbance to the focus control system is small is good. Method.   5. The focus position adjusting method according to claim 4, wherein the position where the disturbance to the focus control system is small is a position where acceleration of surface vibration of the optical disk is small.   5. The focus position adjusting method according to claim 4, wherein the position where the disturbance to the focus control system is small is specified in units of sectors formed on the optical disc.

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