JP2004152381A - Method of acquiring tilt information, apparatus for acquiring tilt information, optical pickup device and optical disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for acquiring inclination information capable of acquiring the information relating to the inclination of an information recording medium with high sensitivity. <P>SOLUTION: An optical pickup is moved in a prescribed scanning direction orthogonally crossing a focusing direction (step 409) and at least one section where a variation in a distance between a recording surface and the optical pickup reaches a prescribed amount is detected on the basis of information related to the position in the scanning direction of the optical pickup and information related to the above distance corresponding to the above information (steps 413 and 415) and further the information related to the tilt of the information recording medium is acquired on the basis of the moving quantity in the scanning direction of the optical pickup in the detected section (steps 419 and 421). As a result, the length of the section includes the information related to the tilt of the information recording medium and since a change in the tilt of the information recording medium is enlarged, the change in the slight tilt of the information recording medium can be detected. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tilt information acquisition method, a tilt information acquisition device, an optical pickup device, and an optical disc device. More specifically, the present invention relates to a tilt information acquisition method for acquiring tilt information of an information recording medium, and is suitable for implementing the tilt information acquisition method. The present invention relates to a tilt information acquisition device, an optical pickup device including the tilt information acquisition device, and an optical disk device including the optical pickup device.
[0002]
[Prior art]
In an optical disc device, an information recording medium such as an optical disc is used, and recording and erasing of data are performed by irradiating a recording surface with a laser beam, and data is reproduced based on light reflected from the recording surface. . The optical disc device includes an optical pickup device as a device for irradiating a recording surface of the information recording medium with a laser beam to form a light spot and receiving reflected light from the recording surface.
[0003]
Usually, an optical pickup device includes an objective lens, an optical system that guides a light beam emitted from a light source to a recording surface of an information recording medium, and guides a return light beam reflected by the recording surface to a predetermined light receiving position, and a light receiving position. And a light-receiving element arranged in the first position. The light receiving element outputs a signal including not only reproduction information of data recorded on the recording surface but also information (servo information) necessary for controlling the position of the optical pickup device itself and the objective lens.
[0004]
In order to accurately form a predetermined light spot at a predetermined position on the recording surface, and to accurately detect reproduction information, servo information, and the like, it is desirable that the recording surface and the optical axis of the objective lens be substantially orthogonal to each other. . However, for example, the recording surface may be inclined with respect to a plane perpendicular to the optical axis of the objective lens due to, for example, warpage or eccentricity of the information recording medium. There is a possibility that a signal including servo information or the like may be deteriorated.
[0005]
Therefore, various methods and apparatuses for detecting the inclination of the information recording medium with respect to a plane perpendicular to the optical axis of the objective lens (hereinafter, abbreviated as “the inclination of the information recording medium” for convenience) have been proposed (for example, Patent Document 1). And Patent Document 2).
[0006]
[Patent Document 1]
JP-A-8-171733
[Patent Document 2]
JP-A-10-177729
[0007]
[Problems to be solved by the invention]
However, in the devices disclosed in Patent Document 1 and Patent Document 2, when the information recording medium is a large disk having a diameter of about 300 mm like a laser disk and the tilt amount of the information recording medium is large to some extent, Although it is possible to obtain effective tilt information to some extent, in the case of a small disc having a diameter of about 120 mm such as a CD (compact disc) or a DVD (digital versatile disc), the tilt amount is small. There is an inconvenience that it is difficult to detect information.
[0008]
The present invention has been made under such circumstances, and a first object of the present invention is to provide a tilt information obtaining method and a tilt information obtaining apparatus capable of obtaining information on tilt of an information recording medium with high sensitivity. It is in.
[0009]
A second object of the present invention is to provide an optical pickup device capable of outputting a signal including information on the tilt of an information recording medium with high accuracy.
[0010]
Further, a third object of the present invention is to provide an optical disk device capable of performing high-speed access to an information recording medium with high accuracy and stability.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, information on an inclination of the information recording medium with respect to an optical pickup having an objective lens for forming a light spot on a recording surface of the information recording medium on which a spiral or concentric track is formed is obtained. A first step of moving the optical pickup in a predetermined scanning direction orthogonal to the focus direction; information on the position of the optical pickup in the scanning direction, and the recording surface corresponding thereto. Detecting at least one section in which the amount of change in the distance is a predetermined amount based on information on the distance between the optical pickup and the optical pickup; and detecting the information based on the amount of movement of the optical pickup in the scanning direction in that section. A second step of acquiring information relating to the inclination of the recording medium. In the present specification, the “information about the tilt” includes not only the tilt itself but also information that changes in response to a change in the tilt, information that can be converted into a tilt, and the like. In addition, the “information about the position” includes not only the position itself, but also information that changes in response to a change in the position, information that can be converted into the position, and the like. Further, the “information about the interval” includes not only the interval itself but also information that changes in response to a change in the interval, information that can be converted into the interval, and the like.
[0012]
According to this, the optical pickup is moved in a predetermined scanning direction orthogonal to the focus direction (first step), and information on the position of the optical pickup in the scanning direction and information on the corresponding gap between the recording surface and the optical pickup. , At least one section in which the amount of change in the interval is a predetermined amount is detected, and information on the tilt of the information recording medium is acquired based on the amount of movement of the optical pickup in the scanning direction in that section (second). Process). That is, since the length of the section includes the information on the inclination of the information recording medium, and the change in the inclination of the information recording medium is enlarged, a slight change in the inclination of the information recording medium can be detected. Therefore, it is possible to obtain information on the inclination of the information recording medium with high sensitivity.
[0013]
In this case, as in the tilt information acquisition method according to claim 2, in the first step, while controlling the position of the objective lens with respect to a focus direction such that a predetermined light spot is formed on the recording surface, The optical pickup may be moved in the scanning direction, and in the second step, information on the interval may be obtained based on information on a position of the objective lens in the focus direction.
[0014]
In each of the tilt information obtaining methods according to the first and second aspects, as in the tilt information obtaining method according to the third aspect, in the second step, the movement amount is divided by the predetermined amount, and a result of the division or The arc tangent of the result of the division can be used as the average inclination amount in the section.
[0015]
4. The tilt information acquiring method according to claim 1, wherein the moving range in the scanning direction includes a plurality of sections, and the plurality of sections include a section in which the change amount is less than the predetermined amount. In this case, various estimated amounts can be considered as the amount of inclination in the section, but in the second step, for example, as in the inclination information acquisition method according to claim 4, the amount of change is less than the predetermined amount. The average inclination amount in the section may be equal to 0 or the same as the average inclination amount in the section closest to the area.
[0016]
5. The tilt information acquisition method according to claim 1, wherein a plurality of sections are included in the moving range in the scanning direction, and a plurality of sections include a section in which the error of the change amount exceeds an allowable value. In the second step, in the second step, for example, as in the tilt information acquisition method according to claim 5, an error of the change amount is included in the plurality of sections. If a section exceeding the allowable value is included, the average inclination amount in that section may be set to 0 or the same as the average inclination amount in the section closest to the section.
[0017]
In each of the tilt information obtaining methods according to the first to fifth aspects, various directions can be considered as the scanning direction. However, as in the tilt information obtaining method according to the sixth aspect, the scanning direction is the same as the track direction. May be a direction orthogonal to the tangential direction of In such a case, a so-called radial tilt can be accurately obtained.
[0018]
In each of the tilt information obtaining methods according to the first to sixth aspects, as in the tilt information obtaining method according to the seventh aspect, the tilt of the information recording medium with respect to the optical pickup is corrected based on the information regarding the tilt. The method may further include a third step.
[0019]
According to an eighth aspect of the present invention, information on an inclination of the information recording medium with respect to an optical pickup having an objective lens for forming a light spot on a recording surface of the information recording medium on which a spiral or concentric track is formed is obtained. Moving means for moving the optical pickup in a predetermined scanning direction orthogonal to the focus direction; information on the position of the optical pickup in the scanning direction and the recording surface corresponding thereto. At least one section in which the amount of change in the distance is a predetermined amount is detected based on information on the distance from the optical pickup, and the information recording is performed based on the amount of movement of the optical pickup in the scanning direction in that section. A tilt information obtaining unit that obtains information on the tilt of the medium.
[0020]
According to this, the optical pickup is moved in the predetermined scanning direction orthogonal to the focus direction by the moving means, and the information on the position of the optical pickup in the scanning direction and the recording surface and the optical surface corresponding to the information are related by the tilt information acquiring means. At least one section in which the amount of change in the distance becomes a predetermined amount is detected based on the information about the distance between the optical pickup and the information about the tilt of the information recording medium is acquired based on the amount of movement of the optical pickup in the scanning direction in that section. Is done. That is, since the length of the section includes the information on the inclination of the information recording medium, and the change in the inclination of the information recording medium is enlarged, a slight change in the inclination of the information recording medium can be detected. Therefore, it is possible to obtain information on the inclination of the information recording medium with high sensitivity.
[0021]
In this case, as in the tilt information acquisition device according to claim 9, the moving unit controls the position of the objective lens with respect to a focus direction such that a predetermined light spot is formed on the recording surface, The optical pickup may be moved in the scanning direction, and the tilt information obtaining means may obtain information on the interval based on a drive signal for driving the objective lens in the focus direction.
[0022]
In each of the tilt information obtaining apparatuses according to the eighth and ninth aspects, there are various methods for the tilt information obtaining means obtaining the information on the position. As described above, the tilt information acquiring means may acquire information on the position based on a drive signal output from the moving means for moving the optical pickup in the scanning direction. In addition, as in the tilt information obtaining apparatus according to claim 11, the tilt information obtaining means may obtain information on the position based on the number of tracks traversed by the objective lens, or As described in the tilt information obtaining device described in the above, the tilt information obtaining means may obtain the information on the position based on the address information recorded on the recording surface.
[0023]
In each of the inclination information acquisition devices according to claims 8 to 12, as in the inclination information acquisition device according to claim 13, the inclination information acquisition means divides the movement amount by the predetermined amount, and a result of the division. Alternatively, the arc tangent of the result of the division may be used as the average slope amount in the section.
[0024]
14. The tilt information acquisition device according to claim 8, wherein the moving range in the scanning direction includes a plurality of sections, and the plurality of sections include a section in which the change amount is less than the predetermined amount. In this case, various estimated amounts can be considered as the amount of inclination in the section. For example, as in the inclination information acquisition device according to claim 14, the inclination information acquisition unit determines that the amount of change is less than the predetermined amount. The average amount of inclination in a section that is equal to 0 or the same as the average amount of inclination in a section closest to the area may be set.
[0025]
15. The tilt information acquisition device according to claim 8, wherein a plurality of the sections are included in the moving range in the scanning direction, and a plurality of the sections include a section in which the error of the change amount exceeds an allowable value. In the section, various estimation amounts are conceivable as the inclination amount in the section. For example, as in the inclination information acquisition device according to claim 15, the inclination information acquisition unit determines that the error in the change amount is an allowable value. When a section exceeding the section is included, the average inclination amount in the section may be set to 0 or the same as the average inclination amount in the section closest to the section.
[0026]
In each of the tilt information acquiring apparatuses according to the eighth to fifteenth aspects, various directions can be considered as the scanning direction. However, as in the tilt information acquiring apparatus according to the sixteenth aspect, the scanning direction is the same as the track direction. May be a direction orthogonal to the tangential direction of In such a case, a so-called radial tilt can be accurately obtained.
[0027]
In each of the tilt information acquiring apparatuses according to the eighth to sixteenth aspects, the tilt of the information recording medium with respect to the optical pickup is corrected based on the information regarding the tilt, as in the tilt information acquiring apparatus according to the seventeenth aspect. The apparatus may further include a tilt correction unit.
[0028]
An invention according to claim 18 is an optical pickup device that irradiates a recording surface of an information recording medium with light and receives reflected light from the recording surface, wherein a light source and a light flux emitted from the light source are used as information. An optical system including an objective lens for condensing light on the recording surface of the recording medium and guiding the return light beam reflected on the recording surface to a predetermined light receiving position, and a photodetector disposed at the light receiving position and receiving the return light beam An optical pickup device comprising: an optical pickup including: a tilt information acquisition device according to any one of claims 8 to 17;
[0029]
According to this, since the tilt information acquiring device according to any one of claims 8 to 17 is provided, it is possible to acquire information on the tilt of the information recording medium with respect to the objective lens with high sensitivity. Therefore, it is possible to output a signal including information on the inclination of the information recording medium with high accuracy.
[0030]
According to a nineteenth aspect of the present invention, there is provided an optical disc apparatus for irradiating light onto a recording surface of an information recording medium to perform at least reproduction among information recording, reproduction, and erasure, and the optical pickup according to claim 18. An optical disc device comprising: a device; and a processing device that performs at least reproduction among recording, reproduction, and erasure of the information by using an output signal from the optical pickup device.
[0031]
According to this, information on the inclination of the information recording medium can be detected with high accuracy based on the output signal of the optical pickup device according to claim 18, and as a result, the information recording medium can be accessed at a high speed. Can be performed accurately and stably.
[0032]
In this case, as in the optical disk device according to the twentieth aspect, it is possible to further include a light emission power correction unit that corrects the light emission power of the light source based on the information regarding the tilt. In such a case, it is possible to suppress a decrease in the irradiation light amount on the recording surface due to the inclination of the information recording medium.
[0033]
In each of the optical disk devices according to the nineteenth and twentieth aspects, a track error signal detected from the output signal of the photodetector is corrected based on the information regarding the tilt, as in the optical disk apparatus according to the twenty-first aspect. A track error signal correction means may be further provided. In such a case, the offset component caused by the inclination of the information recording medium can be removed, and the tracking control can be performed with high accuracy.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an optical disk device according to an embodiment of the present invention.
[0035]
The optical disk device 20 shown in FIG. 1 includes a spindle motor 22 for rotating and driving the optical disk 15, an optical pickup device 23, a laser control circuit 24, an encoder 25, a driver 27, a reproduction signal processing circuit 28, a servo controller 33, and a buffer. A RAM 34, a buffer manager 37, an interface 38, a ROM 39, a CPU 40, a RAM 41, and the like are provided. Note that the arrows in FIG. 1 indicate typical flows of signals and information, and do not indicate all of the connection relationships of the respective blocks. As an example, an information recording medium conforming to the DVD standard is used as the optical disc 15.
[0036]
The optical pickup device 23 is a device for irradiating a predetermined position on a recording surface of the optical disk 15 on which a spiral or concentric track is formed with laser light and receiving reflected light from the recording surface. The configuration and the like of the optical pickup device 23 will be described later in detail.
[0037]
As shown in FIG. 2, the reproduction signal processing circuit 28 includes an I / V amplifier 28a, a servo signal detection circuit 28b, a wobble signal detection circuit 28c, an RF signal detection circuit 28d, a decoder 28e, and a track error signal correction unit. , And the like. The I / V amplifier 28a converts a current signal, which is an output signal of the optical pickup device 23, into a voltage signal and amplifies the voltage signal with a predetermined gain. The servo signal detection circuit 28b detects a servo signal (such as a focus error signal and a track error signal) based on the voltage signal from the I / V amplifier 28a. The focus error signal detected here is output to the servo controller 33, and the track error signal is output to the TE signal correction circuit 28f. The TE signal correction circuit 28f corrects the track error signal based on the later-described inclination distribution information from the CPU 40, and outputs the signal to the servo controller 33. The wobble signal detection circuit 28c detects a wobble signal based on a voltage signal from the I / V amplifier 28a. The RF signal detection circuit 28d detects an RF signal based on a voltage signal from the I / V amplifier 28a. The decoder 28e extracts address information, a synchronization signal, and the like from the wobble signal detected by the wobble signal detection circuit 28c. The address information extracted here is output to the CPU 40, and the synchronization signal is output to the encoder 25. The decoder 28e performs demodulation processing, error correction processing, and the like on the RF signal detected by the RF signal detection circuit 28d, and then stores the result in the buffer RAM 34 via the buffer manager 37. If the reproduction data is music data, it is output to an external audio device or the like.
[0038]
Returning to FIG. 1, the servo controller 33 generates various control signals for controlling the optical pickup device 23 based on the servo signals from the reproduction signal processing circuit 28 and outputs the generated signals to the driver 27.
[0039]
The buffer manager 37 manages the input and output of data to and from the buffer RAM 34, and notifies the CPU 40 when the amount of accumulated data reaches a predetermined amount.
[0040]
The driver 27 controls the optical pickup device 23 and the spindle motor 22 based on a control signal from the servo controller 33 and an instruction from the CPU 40.
[0041]
The encoder 25 fetches the data stored in the buffer RAM 34 via the buffer manager 37 based on an instruction from the CPU 40, performs data modulation processing, error correction code addition processing, and the like, and writes a write signal to the optical disk 15. And outputs a write signal to the laser control circuit 24 in synchronization with a synchronization signal from the reproduction signal processing circuit 28.
[0042]
The laser control circuit 24 controls the emission power of the laser light emitted from the optical pickup device 23 based on a write signal from the encoder 25 and an instruction from the CPU 40. Further, the laser control circuit 24 performs feedback control of the emission power of the laser light based on the emission light signal from the monitor (not shown) of the optical pickup device 23 during emission of the laser light.
[0043]
The interface 38 is a two-way communication interface with a host (for example, a personal computer), and conforms to a standard interface such as ATAPI (AT Attachment Packet Interface) and SCSI (Small Computer System Interface).
[0044]
The ROM 39 stores a program described in a code decodable by the CPU 40. Then, the CPU 40 controls the operation of each unit according to the program stored in the ROM 39, and temporarily stores data and the like necessary for the control in the RAM 41.
[0045]
Next, the configuration and the like of the optical pickup device 23 will be described with reference to FIGS. As shown in FIGS. 3A and 3B, the optical pickup device 23 irradiates the recording surface of the optical disk 15 rotated by the spindle motor 22 with laser light, and reflects light reflected from the recording surface. Main body 101 that receives the light, two seek shafts 102 that hold the main body 101 and guide the movement of the main body 101 in the X-axis direction (left-right direction in the drawing), and a rod-shaped rod extending in the X-axis direction. A lead screw 103 having a shape and a spiral groove formed on the surface thereof; a seek motor 104 for rotating the lead screw 103; and a measuring device for measuring the amount of movement of the pickup body 101 in the X-axis direction. It is configured to include a rotary encoder RE, a signal processing circuit 115, and the like.
[0046]
As shown in FIG. 3B, a protrusion TB formed on the pickup main body 101 is in contact with the groove of the lead screw 103, and when the lead screw 103 rotates, the pickup main body depends on the rotation angle. 101 moves in the X-axis direction.
[0047]
The rotary encoder RE generates a pulse each time the rotation axis of the seek motor 104 rotates by a predetermined angle.
[0048]
As shown in FIG. 4 and FIG. 5 which is a cross-sectional view taken along line AA in FIG. 4, the pickup main body 101 transfers a light beam having a wavelength of The emitted light beam emitting system 12 (not shown in FIG. 4, see FIG. 5), a light collecting system 11 for collecting the light beam from the light beam emitting system 12 at a predetermined position on the recording surface of the optical disk 15, and a light collecting system 11 It is composed of a supporting system for supporting, a magnetic circuit system, and the like. The condensing system 11 can be slightly moved in the X-axis direction and the Z-axis direction with respect to the light beam emitting system 12.
[0049]
As shown in FIG. 5, the light beam emitting system 12 includes a light receiving / emitting module 51, a housing 71, a polarization hologram 53, a coupling lens 52, a rising mirror 57, and the like. Note that the polarization hologram 53, the coupling lens 52, and the rising mirror 57 are arranged at predetermined positions inside the housing 71, respectively.
[0050]
The light receiving / emitting module 51 includes a laser diode 51a as a light source, and a light receiver 51b as a photodetector that receives reflected light (return light flux) from the recording surface of the optical disk 15. The light receiving / emitting module 51 is fixed to the housing 71 such that the maximum intensity emission direction of a light beam (hereinafter also referred to as “emission light beam”) emitted from the laser diode 51a is in the −Y direction. In the present embodiment, as an example, the outgoing light beam is set to be a P-polarized light beam with respect to the polarization hologram 53. The light receiver 51b includes a plurality of light receiving elements that output signals optimal for detecting a wobble signal, an RF signal, a servo signal, and the like in the reproduction signal processing circuit 28.
[0051]
The polarization hologram 53 is arranged in the −Y direction of the light receiving / emitting module 51. This polarization hologram 53 is a hologram having a different diffraction efficiency depending on the polarization state of the incident light beam. That is, of two light beams whose polarization directions are orthogonal to each other, the light beam acts as a hologram for one light beam and diffracts the light beam with high diffraction efficiency, but does not act as a hologram for the other light beam. Most of it is transmitted as it is. In this embodiment, since the output light beam is a P-polarized light beam, the polarization hologram 53 acts as a hologram for the S-polarized light beam, and does not act as a hologram for the P-polarized light beam. Is set. Therefore, most of the emitted light flux passes through the polarization hologram 53. The polarization hologram 53 is integrated with the light receiving / emitting module 51.
[0052]
The coupling lens 52 is disposed on the −Y side of the polarization hologram 53, and makes the outgoing light flux transmitted through the polarization hologram 53 into substantially parallel light.
[0053]
The rising mirror 57 is disposed on the −Y side of the coupling lens 52, and changes the maximum intensity emission direction of the emitted light beam that has been made substantially parallel by the coupling lens 52 to the + Z direction. The emitted light beam enters the light condensing system 11 through an opening provided in the housing 71. That is, inside the housing 71, an optical path for guiding the light beam emitted from the laser diode 51a to the light condensing system 11 and guiding the return light beam to the light receiver 51b is formed.
[0054]
The magnetic circuit system includes a base plate 85, a first yoke 86a, a second yoke 86b, a first magnet 91a, a second magnet 91b, and the like.
[0055]
The base plate 85 is fitted into a rectangular recess formed on the + Z side surface of the housing 71. The base plate 85 is provided with an opening having substantially the same shape so as not to block the opening provided in the housing 71. The base plate 85 has a role as a yoke for forming a magnetic circuit.
[0056]
On the + Z side surface of the base plate 85, the first yoke 86a and the second yoke 86b are arranged in a predetermined positional relationship. The first yoke 86a and the second yoke 86b are plate members having substantially the same shape. Here, the second yoke 86b is located near the + Y side end of the base plate 85, and the first yoke 86a is located on the -Y side of the second yoke 86b. The first yoke 86a and the second yoke 86b are opposed to each other with the optical path of the light beam emitted from the housing 71 interposed therebetween.
[0057]
The first magnet 91a and the second magnet 91b are plate-like permanent magnets having substantially the same shape. The first magnet 91a is attached to the + Y-side surface of the first yoke 86a, and the second magnet 91b is attached to the -Y-side surface of the second yoke 86b.
[0058]
Therefore, a magnetic circuit is formed by the first magnet 91a, the second magnet 91b, the first yoke 86a, the second yoke 86b, and the base plate 85.
[0059]
As shown in FIGS. 5 and 6, the condensing system 11 includes a lens holder 81, an objective lens 60 fixed to a predetermined position of the lens holder 81, a λ / 4 plate 55, a first tracking It includes a coil 82a, a second tracking coil 82b, and a focusing coil 84.
[0060]
The lens holder 81 is disposed between the first magnet 91a and the second magnet 91b and at a predetermined distance from the base plate 85 in the + Z direction. In the center of the lens holder 81, a stepped through-hole extending in the Z-axis direction, which is an optical path of a light beam emitted from the housing 71, is formed. The objective lens 60 is disposed at the end of the through hole on the + Z side such that the optical axis thereof substantially coincides with the center axis of the through hole. The λ / 4 plate 55 is disposed inside the through-hole such that the optical axis of the λ / 4 plate 55 substantially coincides with the optical axis of the objective lens 60.
[0061]
The first tracking coil 82a is composed of two coils, and each coil is attached to the −Y side surface of the lens holder 81 at a predetermined distance from each other in the X-axis direction. Similarly, the second tracking coil 82b is composed of two coils, and each coil is attached to the + Y side surface of the lens holder 81 at a predetermined distance from each other in the X-axis direction. The tracking coils are connected so that currents (drive currents) of the same magnitude flow.
[0062]
Each of the tracking coils is set to generate a thrust in the + X direction or the -X direction according to the direction of the drive current when the drive current is supplied. Therefore, it is possible to drive the light collection system 11 in the + X direction or the −X direction. Then, since the thrust changes according to the magnitude of the drive current, the shift amount of the condensing system 11 in the X-axis direction, that is, the shift amount of the objective lens 60 can be controlled by the drive current. Each of the tracking coils has a size and a shape corresponding to a required thrust.
[0063]
The focus coil 84 is set to generate a thrust in the + Z direction or the −Z direction according to the direction of the drive current when the drive current is supplied. Therefore, it is possible to drive the light condensing system 11 in the + Z direction or the −Z direction. Then, since the thrust changes according to the magnitude of the drive current, the shift amount of the light focusing system 11 in the Z-axis direction, that is, the shift amount of the objective lens 60 can be controlled by the drive current. The focus coil 84 has a size and a shape according to a required thrust.
[0064]
The lens holder 81 has two input terminals (not shown) for supplying a drive current to the respective tracking coils at an end on the −X side, and a focusing coil 84 at an end on the + X side. It has two input terminals (not shown) for supplying a drive current.
[0065]
The support system includes a stem 87 and an elastic member. The stem 87 is a block-shaped member, and is fixed near the end on the −Y side of the base plate 85. The stem 87 has a plurality of input terminals (not shown) for inputting drive currents for focus control and tracking control from the motor driver 27, and a drive current for each of the tracking coil and the focus coil 84. It has a plurality of output terminals (not shown) for outputting.
[0066]
The elastic member includes four conductive wire springs (59a). ₁ , 59a ₂ , 59b ₁ , 59b ₂ ). The four wire springs are divided into two groups of two, and the first group of wire springs (59a ₁ , 59a ₂ ) Have one end connected to two input terminals provided on the −X side of the lens holder 81 by soldering, and the other end connected to two output terminals provided on the stem 87 by soldering. . The second group of wire springs (59b ₁ , 59b ₂ One end is connected to two input terminals provided on the + X side of the lens holder 81 by soldering, and the other end is connected to two output terminals provided on the stem 87 by soldering. Therefore, the lens holder 81 is supported by the stem 87 via each wire spring. The drive current from the motor driver 27 is supplied to the first group of wire springs (59a). ₁ , 59a ₂ ) Is supplied to each of the tracking coils, and the second group of wire springs (59b ₁ , 59b ₂ ) Is supplied to the focusing coil 84.
[0067]
The signal processing circuit 115 counts pulses from the rotary encoder RE. Here, the signal processing circuit 115 has a pulse counter m for counting the pulses from the rotary encoder RE, and each time a pulse from the rotary encoder RE is input, 1 is added to the value of the pulse counter m. It has become. Further, the signal processing circuit 115 determines a position of the objective lens 60 with respect to the base plate 85 in the Z-axis direction (hereinafter, referred to as “Z-direction position” for convenience) based on the drive current supplied from the motor driver 27 to the focusing coil 84. (Described later) is detected at predetermined time intervals. Specifically, a drive current is obtained via a low-pass filter, and the current value is converted into a drive amount of the objective lens. Then, an average value of the detection results is obtained for each predetermined number of detections (for example, every 10 times). When the difference between the reference value and the average value becomes 0.03 mm or more, the value of the pulse counter m at that time is obtained. To the CPU 40 and the average value is used as a new reference value. If a current value corresponding to 0.03 mm is obtained in advance, it is not necessary to convert the current value into a driving amount of the objective lens. The pulse from the rotary encoder RE is also output to the CPU 40.
[0068]
Here, the operation of the optical pickup device 23 configured as described above will be described. It is assumed that the optical pickup device 23 is mounted on the optical disk device 20 such that the direction perpendicular to the recording surface of the optical disk 15 coincides with the Z-axis direction and the tangential direction of the track coincides with the Y-axis direction. That is, the X-axis direction is the tracking direction, and the Z-axis direction is the focus direction.
[0069]
The linearly polarized light (here, P-polarized light) emitted from the laser diode 51 a in the −Y direction enters the polarization hologram 53. The polarization hologram 53 transmits most of the light beam without acting as a hologram because the incident light beam is a P-polarized light beam. The light beam transmitted through the polarization hologram 53 is converted into substantially parallel light by the coupling lens 52, reflected by the rising mirror 57 in the + Z direction, and condensed through the opening of the housing 71 and the opening of the base plate 85. The light enters the system 11. The light beam incident on the light condensing system 11 becomes circularly polarized light with an optical phase difference added by the λ / 4 plate 55, and is condensed as a minute spot on the recording surface of the optical disk 15 via the objective lens 60.
[0070]
The reflected light reflected on the recording surface of the optical disc 15 becomes circularly polarized light in the opposite direction to the outward path, is converted into substantially parallel light again by the objective lens 60 as a return light beam, and is linearly polarized by the λ / 4 plate 55 at right angles to the forward path. Here, S-polarized light is used. Then, the return light beam enters the housing 71 through the opening of the base plate 85. The return light beam that has entered the housing 71 is reflected in the + Y direction by the rising mirror 57, and enters the polarization hologram 53 via the coupling lens 52. The polarization hologram 53 acts as a hologram because the returning light beam is an S-polarized light beam, and diffracts the returning light beam. The diffracted light from the polarization hologram 53 is received by the light receiver 51b, and each light receiving element constituting the light receiver 51b outputs a current signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0071]
Here, position control of the objective lens 60 with respect to the focus direction in the optical disc device 20, that is, focus control will be described.
[0072]
1. The reproduction signal processing circuit 28 converts the output signal of the light receiver 51b into a voltage signal with the I / V amplifier 28a, detects the focus error signal with the servo signal detection circuit 28b, and outputs it to the servo controller 33.
2. The servo controller 33 generates a focus control signal for correcting a focus shift based on the focus error signal, and outputs the focus control signal to the motor driver 27.
3. The motor driver 27 outputs a drive current for focus control corresponding to the focus control signal to the optical pickup device 23.
4. The drive current for focus control from the motor driver 27 is input to a predetermined input terminal of the stem 87, and the second group of wire springs (59b ₁ , 59b ₂ ) Is supplied to the focusing coil 84.
5. When a drive current flows through the focusing coil 84, a thrust corresponding to the magnitude and direction of the current is generated in the focus direction, and the light condensing system 11 moves in the focus direction. As a result, the objective lens 60 shifts to a predetermined position in the focus direction.
[0073]
Next, a process of acquiring the tilt information of the optical disc 15 will be described with reference to FIGS. For example, when a request for acquiring tilt information is received from the host, the start address of the program corresponding to the flowchart of FIG. 7 is set in the program counter of the CPU 40, and the process starts. Note that the flowchart in FIG. 7 corresponds to a series of processing algorithms executed by the CPU 40.
[0074]
In the first step 401, the seek motor 104 is driven to move the pickup main body 101 to the end on the -X side. The position on the recording surface where the light spot is formed at this time is defined as a start position As. Here, the start position As is, for example, a position where the distance from the rotation center of the optical disk 15 (hereinafter also referred to as “distance in the X direction” for convenience) is 20 mm.
[0075]
In the next step 403, the signal processing circuit 115 is instructed to initialize the pulse counter m. As a result, in the signal processing circuit 115, 0 is set in the pulse counter m.
[0076]
In the next step 405, focus control is performed as described above in order to correct the focus shift of the light spot formed on the recording surface of the optical disk 15.
[0077]
In the next step 407, the signal processing circuit 115 is instructed to start detecting the Z-direction position of the objective lens. Accordingly, in the signal processing circuit 115, the Z direction position at the start position As is set to the reference value.
[0078]
In the next step 409, the drive of the seek motor 104 is started in order to move the pickup main body 101 to the outer peripheral side of the optical disk 15 at a preset moving speed. As a result, the objective lens 60 moves to the outer peripheral side of the optical disc 15 at the same moving speed as the pickup main body 101. That is, the + X direction is the scanning direction. Further, counting of pulses from the rotary encoder RE is started.
[0079]
In the next step 411, focus control is performed.
[0080]
In the next step 413, it is determined whether or not the amount of change in the Z-direction position of the objective lens is 0.03 mm or more based on the presence or absence of a notification from the signal processing circuit 115. If there is no notification from the signal processing circuit 115, the determination here is denied, and the process proceeds to step 417.
[0081]
In step 417, it is determined whether or not the light spot formation position has reached a predetermined position on the outer peripheral side of the optical disk 15 (hereinafter, referred to as “end position Ae”) based on the integrated value of the pulse from the rotary encoder RE. I do. Here, as an example, a position where the distance in the X direction is 60 mm is defined as an end position Ae. That is, the scanning area (moving range) from the start position As to the end position Ae. If the light spot formation position has not reached the end position Ae, the determination here is denied, and the process returns to step 411.
[0082]
Hereinafter, the processing and determination of steps 411 → 413 → 417 are repeated until the determination in step 413 or step 417 is affirmed.
[0083]
On the other hand, in step 413, if there is a notification from the signal processing circuit 115, the determination here is affirmed, and the process proceeds to step 415.
[0084]
In this step 415, after the value of the pulse counter m received from the signal processing circuit 115 is stored in the RAM 41, the process proceeds to step 417.
[0085]
In this step 417, it is determined whether or not the light spot formation position has reached the end position Ae. If the light spot formation position has not reached the end position Ae, the determination here is denied, and the process returns to step 411. On the other hand, if the formation position of the light spot has reached the end position Ae, the determination here is affirmative, the detection end is notified to the signal processing circuit 115, and after the seek motor 104 is stopped, step 419 is performed. Move to
[0086]
In step 419, the tilt amount of the optical disk 15 is obtained based on the value of the pulse counter m stored in the RAM 41. Here, as an example, assume that the values of the pulse counter m stored in the RAM 41 are a1, a2, a3, a4, and a5. In this case, the tilt amounts of the optical disc 15 (T1, T2, T3, and T4) are obtained based on the following equations (1) to (4). Here, h is the detection resolution of the Z-direction position of the objective lens, and is 0.03 mm in the present embodiment. K is the amount of movement of the pickup main body 101 when the rotary encoder RE outputs one pulse.
[0087]
T1 = [h / {k (a2-a1)}] × 180 / π (1)
[0088]
T2 = [h / {k (a3-a2)}] × 180 / π (2)
[0089]
T3 = [h / {k (a4-a3)}] × 180 / π (3)
[0090]
T4 = [h / {k (a5-a4)}] × 180 / π (4)
[0091]
In the next step 421, inclination distribution information is obtained based on the inclination amount of the optical disk 15 obtained as described above, and stored in the RAM 41 and output to the TE signal correction circuit 28f. Here, as shown in FIG. 8A, when the distance in the X direction is between A1 (= k × a1 + 20) and A2 (= k × a2 + 20) (hereinafter, referred to as “first section”), the inclination amount is T1, when the distance in the X direction is between A2 and A3 (= k × a3 + 20) (hereinafter referred to as “second section”), the amount of inclination is between T2 and the distance in the X direction is between A3 and A4 (= k × a4 + 20) In the following (hereinafter referred to as “third section”), the inclination amount is T3, and in the X direction distance between A4 and A5 (= k × a5 + 20) (hereinafter referred to as “fourth section”), the inclination amount is T4. In this case, when the distance in the X direction is between As and A1 (hereinafter referred to as “head section”), the error in the amount of change in the Z direction position exceeds the allowable value. Cannot be calculated. Further, when the distance in the X direction is between A5 and Ae (hereinafter, referred to as “final section”), the amount of change in the Z direction position is less than 0.03 mm, so that the amount of tilt in the final section cannot be calculated. . Therefore, in the present embodiment, as shown in FIG. 8B, the amount of inclination in the first section is regarded as being the same as the amount of inclination T1 in the first section, and the amount of inclination in the last section is determined in the fourth section. Is assumed to be the same as the amount of inclination T4 in. Then, the inclination information acquisition process ends.
[0092]
When the tilt distribution information obtained in this way is compared with the measured value of the tilt amount of the optical disk 15 measured using the dedicated tilt measuring device, as shown in FIG. Good agreement is shown in each case.
[0093]
For comparison with the present invention, FIGS. 9B to 10B show the results of obtaining the tilt distribution information of the optical disk 15 using the above-described conventional tilt detection method. FIG. 9B shows tilt distribution information obtained by detecting the Z-direction position of the objective lens every time the pickup main body 101 moves by 1 mm and obtaining the tilt of the recording surface during that time. Obviously, both the amount of inclination and the inclination tendency are considerably different from the actually measured values. FIG. 10A shows tilt distribution information obtained by detecting the Z-direction position of the objective lens every time the pickup main body 101 moves by 5 mm and obtaining the tilt of the recording surface during that time. Although slightly improved compared to the case of FIG. 9B, both the amount of inclination and the inclination tendency are still different from the actually measured values. FIG. 10B shows tilt distribution information obtained by detecting the Z-direction position of the objective lens every time the pickup main body 101 moves by 10 mm and obtaining the tilt of the recording surface during that time. Although the inclination tendency substantially matches the actual inclination, an error of 0.1 degree or more exists in the inclination amount. This means, for example, that the angle is θ ₀ From θ ₁ 11A, according to the conventional method, as shown in FIG. 11A, the length of the base (namely, the moving distance of the objective lens) is made the same, and the height (namely, the position of the objective lens in the Z direction) is changed. While the variation Δh is detected, in the present invention, as shown in FIG. 11B, the variation Δr in the length of the base is detected with the same height. Therefore, in the present invention, the detection sensitivity is higher than in the related art, and it is possible to detect even a slight change in angle.
[0094]
Next, tracking control in the optical disc device 20 will be described. It is assumed that the inclination distribution information of the optical disk 15 has already been obtained as described above.
[0095]
1. The reproduction signal processing circuit 28 converts the output signal of the light receiver 51b into a voltage signal by the I / V amplifier 28a, detects a track error signal by the servo signal detection circuit 28b, and outputs the signal to the TE signal correction circuit 28f. .
2. The TE signal correction circuit 28f removes an offset component included in the track error signal based on the inclination distribution information from the CPU 40, and outputs the signal to the servo controller 33.
3. The servo controller 33 generates a tracking control signal for correcting a track shift based on the track error signal from the TE signal correction circuit 28f, and outputs the tracking control signal to the motor driver 27.
4. The motor driver 27 outputs a drive current for tracking control corresponding to the tracking control signal to the optical pickup device 23.
5. The drive current for tracking control from the motor driver 27 is input to a predetermined input terminal of the stem 87, and the first group of wire springs (59a ₁ , 59a ₂ ) Is supplied to each tracking coil.
6. When a drive current flows through each tracking coil, a thrust corresponding to the magnitude and direction of the current is generated in the tracking direction, and the light condensing system 11 moves in the tracking direction. As a result, the objective lens 60 shifts to a predetermined position in the tracking direction.
[0096]
Next, a processing operation for recording data on the optical disk 15 using the above-described optical disk device 20 will be briefly described. It is assumed that the inclination distribution information of the optical disk 15 has already been obtained as described above.
[0097]
Upon receiving the recording request command from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the motor driver 27 based on the specified recording speed, and indicates that the recording request command has been received. To the reproduction signal processing circuit 28. Further, the CPU 40 instructs the buffer manager 37 to store the user data received from the host in the buffer RAM 34.
[0098]
When the rotation of the optical disk 15 reaches a predetermined linear velocity, focus control and tracking control are performed as described above. The focus control and the tracking control are performed as needed until the recording process is completed. Then, the reproduction signal processing circuit 28 acquires the address information based on the output signal of the light receiver 51b, and notifies the CPU 40 of the address information. Note that the reproduction signal processing circuit 28 acquires address information at predetermined timings until the recording process ends, and notifies the CPU 40 of the address information.
[0099]
The CPU 40 outputs a signal for controlling the seek motor 104 to the motor driver 27 based on the address information so that the optical pickup device 23 is located at the writing start position.
[0100]
When receiving from the buffer manager 37 that the amount of user data accumulated in the buffer RAM 34 has exceeded a predetermined value, the CPU 40 instructs the encoder 25 to generate a write signal. At this time, the CPU 40 corrects the light emission power based on the inclination distribution information and notifies the laser control circuit 24 of the correction.
[0101]
When the CPU 40 determines that the position of the optical pickup device 23 is the writing start position based on the address information, it notifies the encoder 25. Thus, the user data is recorded on the optical disk 15 via the encoder 25, the laser control circuit 24, and the optical pickup device 23. Note that the CPU 40 corrects the light emission power as needed based on the slope distribution information until the recording process ends.
[0102]
Next, a processing operation for reproducing data recorded on the optical disk 15 using the above-described optical disk device 20 will be briefly described. It is assumed that the inclination distribution information of the optical disk 15 has already been obtained as described above.
[0103]
When receiving the command of the reproduction request from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the motor driver 27 based on the reproduction speed, and also notifies the motor driver 27 of the reception of the command of the reproduction request. The processing circuit 28 is notified.
[0104]
When the rotation of the optical disk 15 reaches a predetermined linear velocity, focus control and tracking control are performed as described above. The focus control and the tracking control are performed at any time until the reproduction processing ends. Then, the reproduction signal processing circuit 28 acquires the address information based on the output signal of the light receiver 51b, and notifies the CPU 40 of the address information. Note that the reproduction signal processing circuit 28 acquires address information at predetermined timings until the reproduction processing ends, and notifies the CPU 40 of the address information.
[0105]
The CPU 40 outputs a signal for controlling the seek motor 104 to the motor driver 27 based on the address information so that the optical pickup device 23 is located at the reading start position. When the CPU 40 determines that the position of the optical pickup device 23 is the read start position based on the address information, it notifies the reproduction signal processing circuit 28.
[0106]
Then, the reproduction signal processing circuit 28 detects the RF signal based on the output signal of the light receiver 51b, performs demodulation processing, error correction processing, and the like, and then stores the signal in the buffer RAM 34. The buffer manager 37 transfers the reproduced data stored in the buffer RAM 34 to the host via the interface 38 when the data is prepared as sector data.
[0107]
As is clear from the above description, in the optical disk device according to the present embodiment, the TE signal correction circuit 28f configures a track error signal correction unit, the signal processing circuit 115 and the CPU 40 configure a tilt information acquisition unit, A processing device is configured by the processing circuit and the CPU 40, and the moving unit and the emission power correction unit are configured by the CPU 40. However, it goes without saying that the present invention is not limited to this. That is, the above-described embodiment is merely an example, and at least a part of each component realized by the processing according to the program by the CPU 40 may be configured by hardware, or all components may be configured by hardware. It is good.
[0108]
As described above, according to the tilt information acquisition method and the tilt information acquisition device according to the present embodiment, the Z direction of the objective lens with respect to the base plate is determined based on the drive information of the objective lens in the optical axis direction acquired at regular intervals. The position is detected, and inclination information of the optical disk is obtained based on the amount of movement in the scanning direction when the amount of change substantially matches the detection limit. As a result, it is possible to detect the effect of the change in the tilt by expanding it, and it is also possible to detect a slight change in the tilt of the optical disk. That is, it is possible to acquire information on the tilt of the optical disc with high sensitivity.
[0109]
Further, according to the optical pickup device of the present embodiment, since information on the tilt of the optical disk with respect to the objective lens is obtained with high sensitivity using the tilt information obtaining device, a signal including information on the tilt of the optical disk is output with high accuracy. It is possible to do.
[0110]
Further, according to the optical disk device of the present embodiment, the inclination information of the optical disk with respect to the objective lens can be obtained with high accuracy, and as a result, it is possible to perform high-speed access to the optical disk with high accuracy and stability. Become.
[0111]
In the above embodiment, the case where the position where the distance in the X direction is 20 mm is the start position As and the position where the distance in the X direction is 60 mm is the end position Ae, but the present invention is not limited to this. A position where the distance is 60 mm may be set as the start position As, and a position where the distance in the X direction is 20 mm may be set as the end position Ae. In this case, the −X direction is the scanning direction. Further, for example, the inclination amount of only an area to be accessed from now on or the inclination amount of only an area that may adversely affect recording quality and signal quality may be obtained. Furthermore, the present invention may be applied only to a region where the inclination amount needs to be obtained with high sensitivity.
[0112]
Further, in the above embodiment, the case where the cumulative value of the number of pulses from the start position As is set in the pulse counter m of the signal processing circuit 115 has been described. However, the present invention is not limited to this. After the change amount becomes 0.03 mm or more and the value of the pulse counter m is received from the signal processing circuit 115, the initialization of the pulse counter m may be instructed. In this case, in step 419, the inclination amount is calculated based on the following equations (5) to (8) instead of the equations (1) to (4). Note that r1, r2, r3, and r4 are the values of the pulse counter m received from the signal processing circuit 115, respectively.
[0113]
T1 = {h / (k × r1)} × 180 / π (5)
[0114]
T2 = {h / (k × r2)} × 180 / π (6)
[0115]
T3 = {h / (k × r3)} × 180 / π (7)
[0116]
T4 = {h / (k × r4)} × 180 / π (8)
[0117]
Further, in the above embodiment, the processing of the above steps 411 and 413 may be performed at fixed time intervals or at fixed movement amounts of the pickup main body 101.
[0118]
In the above embodiment, the signal processing circuit 115 detects the position of the objective lens in the Z direction at predetermined time intervals, and notifies the CPU 40 of the value of the pulse counter m when the average change amount becomes 0.03 mm or more. However, the present invention is not limited to this. The position in the Z direction of the objective lens and the value of the pulse counter m at that time are associated with each other and sequentially stored as detection data in a memory (not shown), and the X-direction distance becomes the end position. Later, all the detection data may be notified to the CPU 40. At this time, the CPU 40 analyzes the detection data and obtains a section where the amount of change is approximately 0.03 mm.
[0119]
Further, in the above embodiment, the case where the movement amount of the pickup main body 101 is obtained based on the pulse count value from the rotary encoder RE has been described. However, the present invention is not limited to this. For example, a track error detected from the output signal of the light receiver 51b is detected. The number of tracks crossed by the objective lens 60 may be counted based on the frequency of the signal, and the movement amount of the pickup main body 101 may be obtained from the number of tracks and the track pitch. In addition, when a counting error occurs, the moving speed of the pickup main body 101 may be reduced. In this case, the rotary encoder RE becomes unnecessary.
[0120]
In the above embodiment, when a pulse motor is used as the seek motor, the amount of movement of the pickup main body 101 can be obtained by counting the number of drive pulses of the seek motor, and the rotary encoder RE becomes unnecessary.
[0121]
Further, in the above embodiment, the case where the movement amount of the pickup main body 101 is obtained by the signal processing circuit 115 has been described. However, the present invention is not limited to this. For example, the movement amount of the pickup main body 101 is obtained by the CPU 40. Is also good.
[0122]
In the above embodiment, the movement amount of the pickup main body 101 may be obtained by using the address information recorded on the optical disc. This case will be described with reference to FIG. The flowchart in FIG. 12 corresponds to a series of processing algorithms executed by the CPU 40 as in FIG.
[0123]
In the first step 501, the same processing as in the above step 401 is performed.
[0124]
In the next steps 503 to 509, the same processing as in the above steps 405 to 411 is performed.
[0125]
In the next step 511, it is determined whether or not the amount of change in the Z-direction position of the objective lens is 0.03 mm or more based on the presence or absence of the notification from the signal processing circuit 115. If there is no notification from the signal processing circuit 115, the determination here is denied, and the routine proceeds to step 519.
[0126]
In this step 519, it is determined whether or not the formation position of the light spot has reached the end position Ae. If the light spot formation position has not reached the end position Ae, the determination here is denied, and the process returns to step 509.
[0127]
On the other hand, if there is a notification from the signal processing circuit 115 in step 511, the determination here is affirmed, and the process proceeds to step 513.
[0128]
In step 513, the movement of the pickup main body 101 is interrupted.
[0129]
In the next step 515, a wobble signal formed on the optical disc is detected via the reproduction signal processing circuit 28, and address information is extracted. Then, the address information is stored in the RAM 41.
[0130]
In the next step 517, the movement of the pickup main body 101 is restarted. Then, control goes to a step 519.
[0131]
In this step 519, it is determined whether or not the formation position of the light spot has reached the end position Ae. If the light spot formation position has not reached the end position Ae, the determination here is denied, and the process returns to step 509. On the other hand, if the formation position of the light spot has reached the end position Ae, the determination here is affirmed, and the process proceeds to step 521.
[0132]
In step 521, the address information stored in the RAM 41 is converted into a distance in the X direction, and the tilt amount of the optical disk 15 is obtained in the same manner as in step 419.
[0133]
In the next step 523, the same processing as in the above step 421 is performed to obtain the inclination distribution information of the optical disk.
[0134]
As a result, although the processing time becomes longer, the distance in the X direction can be obtained with high accuracy, and as a result, the accuracy of the inclination distribution information is improved. In this case, if the drive current supplied from the motor driver 27 to the focusing coil 84 is set to be output to the CPU 40, the signal processing circuit 115 becomes unnecessary.
[0135]
Further, in the above-described embodiment, the case where the Z direction position of the objective lens is detected using the drive current of the focusing coil 84 has been described. However, the present invention is not limited to this. The direction position may be detected.
[0136]
Further, in the above-described embodiment, a case has been described in which the inclination amount in the first section is considered to be the same as the inclination amount T1 in the first section. However, the present invention is not limited to this. good. In this case, as shown in FIG. 13A, the difference from the actually measured value is large. On the inner circumference side, among the various factors related to the recording and reproducing quality, other than the tilt of the optical disk, Since the influence of the factors (for example, variation in the optimum recording power, variation in the groove shape of the track, etc.) is relatively small as compared with the outer peripheral side, there is no problem even if the inclination amount in the leading section is set to zero.
[0137]
Alternatively, the inclination amount in the head section may be estimated from the inclination amount T1 in the first section and the inclination amount T2 in the second section. For example, assuming that the rate of change in the amount of inclination is constant, the amount of inclination Ts in the head section may be estimated based on the following equation (9). Thereby, as shown in FIG. 13B, the difference from the actually measured value can be reduced.
[0138]
Ts = 2 × T1−T2 (9)
[0139]
Similarly, the inclination amount in the final section may be estimated from the inclination amount T3 in the third section and the inclination amount T4 in the fourth section. For example, the inclination amount Te in the last section may be estimated based on the following equation (10). Thereby, as shown in FIG. 13B, the difference from the actually measured value can be reduced.
[0140]
Te = 2 × T4-T3 (10)
[0141]
In the above embodiment, the case where the detection resolution of the Z direction position of the objective lens is 0.03 mm has been described, but the present invention is not limited to this.
[0142]
Further, in the above embodiment, the case where the TE signal correction circuit for correcting the track error signal based on the inclination distribution information from the CPU 40 is provided in the reproduction signal processing circuit, but the present invention is not limited to this. For example, a correction circuit for correcting a track error signal component included in an output signal from the light receiver 51b may be provided in the optical pickup device.
[0143]
Further, in the above-described embodiment, the case has been described where the amount of change in the distance between the base plate and the recording surface is determined based on the position of the objective lens in the focus direction. However, the present invention is not limited to this. Alternatively, the distance from the recording surface may be directly measured.
[0144]
Further, in the above embodiment, a coil for tilting the lens holder in the YZ plane is added to the focusing system as tilt correction means, and the coma aberration component included in the wavefront aberration of the light spot is determined based on the tilt distribution information. The attitude of the objective lens 60 with respect to the optical disk 15 may be controlled so as to reduce the size. In this case, it is not necessary to correct the track error signal and the light emission power of the laser diode.
[0145]
Further, in the above-described embodiment, an optical element for canceling a wavefront aberration (particularly, a coma aberration component) due to the tilt of the optical disc may be disposed between the objective lens 60 and the coupling lens 52 as a tilt correction unit. . As this optical element, for example, a liquid crystal element whose optical anisotropy changes according to an applied voltage is suitable. In this case, the CPU 40 controls the voltage applied to the liquid crystal element based on the inclination distribution information, and adds a wavefront aberration opposite to the wavefront aberration of the light spot on the recording surface to the emitted light beam. Therefore, it is not necessary to correct the track error signal and the light emission power of the laser diode.
[0146]
In the above embodiment, the case where the radial tilt is obtained has been described, but the present invention is not limited to this.
[0147]
Further, in the above embodiment, the case where the information recording medium conforming to the DVD standard is used as the optical disc 15 is described. However, the present invention is not limited to this. For example, the information recording medium or the laser disc conforms to the CD standard. May be.
[0148]
Further, in the above-described embodiment, the case where the number of the light sources is one has been described. In this case, for example, a plurality of light sources including at least one of a light source emitting a light beam having a wavelength of 405 nm, a light source emitting a light beam having a wavelength of 660 nm, and a light source emitting a light beam having a wavelength of 780 nm may be provided.
[0149]
Further, in the above embodiment, the optical disk device capable of recording and reproducing information has been described. However, the present invention is not limited to this, and any optical disk device capable of at least reproducing, among recording, reproducing, and erasing information, may be used.
[0150]
【The invention's effect】
As described above, according to the tilt information obtaining method and the tilt information obtaining apparatus according to the present invention, there is an effect that information on the tilt of the information recording medium can be obtained with high sensitivity.
[0151]
Further, according to the optical pickup device of the present invention, there is an effect that a signal including information on the tilt of the information recording medium can be output with high accuracy.
[0152]
Further, according to the optical disc device of the present invention, there is an effect that high-speed access to the information recording medium can be performed accurately and stably.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an optical disc device according to an embodiment of the present invention.
FIG. 2 is a block diagram for explaining a configuration of a reproduction signal processing circuit in FIG. 1;
FIGS. 3A and 3B are diagrams for explaining the configuration of the optical pickup device in FIG. 1;
FIG. 4 is a view for explaining a detailed configuration of a pickup main body in FIG. 3;
FIG. 5 is a sectional view taken along line AA of FIG. 4;
FIG. 6 is a perspective view of the light collection system in FIGS. 4 and 5;
FIG. 7 is a flowchart illustrating a process of acquiring tilt information of the optical disc in the optical disc apparatus according to the embodiment of the present invention.
FIGS. 8A and 8B are diagrams for explaining inclination distribution information acquired by the optical disc device according to one embodiment of the present invention;
FIG. 9A is a diagram for comparing inclination distribution information acquired by an optical disk device according to an embodiment of the present invention with an actual measured value of inclination distribution measured by a measurement device; FIG. 9B is a diagram for explaining the slope distribution information (part 1) obtained by using the conventional method.
FIG. 10A is a diagram for explaining inclination distribution information (part 2) acquired using a conventional method, and FIG. 10B is a diagram illustrating the inclination distribution information acquired using a conventional method. It is a figure for explaining inclination distribution information (the 3).
FIGS. 11A and 11B are diagrams for explaining the difference between the present invention and the conventional method.
FIG. 12 is a flowchart illustrating a modified example of a process of acquiring tilt information in an optical disc device according to an embodiment of the present invention.
FIGS. 13A and 13B are diagrams for explaining a method of estimating the amount of tilt in the first section and the last section, respectively.
[Explanation of symbols]
Reference numeral 15: optical disk (information recording medium), 20: optical disk device, 23: optical pickup device, 28: reproduction signal processing circuit (part of the processing device), 28f: TE signal correction circuit (track error signal correction means), 40 ... CPU (part of processing device, moving means, part of inclination information obtaining means, emission power correction means), 51a laser diode (light source), 51b light receiver (photodetector), 60 objective lens, 115 Signal processing circuit (part of inclination information acquisition means).

Claims (21)

A tilt information obtaining method for obtaining information on the tilt of the information recording medium with respect to an optical pickup including an objective lens that forms an optical spot on a recording surface of an information recording medium on which a spiral or concentric track is formed,
A first step of moving the optical pickup in a predetermined scanning direction orthogonal to the focus direction;
Based on information on the position of the optical pickup in the scanning direction and information on the distance between the recording surface and the optical pickup corresponding to the information, at least one section where the amount of change in the distance is a predetermined amount is detected. A second step of acquiring information on an inclination of the information recording medium based on a movement amount of the optical pickup in the scanning direction in the section. In the first step, the optical pickup is moved in the scanning direction while controlling a position of the objective lens with respect to a focus direction so that a predetermined light spot is formed on the recording surface;
2. The tilt information acquisition method according to claim 1, wherein, in the second step, information on the interval is obtained based on information on a position of the objective lens in the focus direction. 3. The method according to claim 1, wherein in the second step, the movement amount is divided by the predetermined amount, and a result of the division or an arc tangent of the result of the division is set as an average inclination amount in the section. 4. How to get tilt information. The moving range in the scanning direction includes a plurality of sections,
The said 2nd process WHEREIN: The average inclination amount in the area | region where the said change amount is less than the said predetermined amount is set to 0 or the same as the average inclination amount in the area | region closest to the area | region. The tilt information acquisition method according to any one of the above. The movement range in the scanning direction includes a plurality of the sections,
In the second step, when the plurality of sections include a section in which the error of the change amount exceeds an allowable value, the average slope amount in the section is set to 0 or the average slope amount in the section closest to the section. The tilt information acquisition method according to any one of claims 1 to 4, wherein the inclination information acquisition method is the same as: The tilt information acquiring method according to claim 1, wherein the scanning direction is a direction orthogonal to a tangential direction of the track. The tilt information acquiring method according to claim 1, further comprising: a third step of correcting a tilt of the information recording medium with respect to the optical pickup based on the information regarding the tilt. A tilt information acquisition device that acquires information about the tilt of the information recording medium with respect to an optical pickup including an objective lens that forms an optical spot on a recording surface of an information recording medium on which a spiral or concentric track is formed,
Moving means for moving the optical pickup in a predetermined scanning direction orthogonal to the focus direction;
Based on information on the position of the optical pickup in the scanning direction and information on the distance between the recording surface and the optical pickup corresponding to the information, at least one section where the amount of change in the distance is a predetermined amount is detected. Tilt information obtaining means for obtaining information on the tilt of the information recording medium based on the amount of movement of the optical pickup in the scanning direction in that section. The moving means moves the optical pickup in the scanning direction while controlling the position of the objective lens with respect to a focus direction such that a predetermined light spot is formed on the recording surface,
9. The tilt information obtaining apparatus according to claim 8, wherein the tilt information obtaining unit obtains information on the interval based on a drive signal for driving the objective lens in the focus direction. 10. The apparatus according to claim 8, wherein the tilt information obtaining unit obtains information on the position based on a driving signal output from the moving unit for moving the optical pickup in the scanning direction. The described tilt information acquisition device. The tilt information obtaining apparatus according to claim 8, wherein the tilt information obtaining unit obtains information on the position based on the number of tracks traversed by the objective lens. The tilt information obtaining apparatus according to claim 8, wherein the tilt information obtaining unit obtains information on the position based on address information recorded on the recording surface. 13. The tilt information acquiring unit according to claim 8, wherein the movement amount is divided by the predetermined amount, and a result of the division or an arc tangent of the result of the division is set as an average inclination amount in the section. The tilt information acquisition device according to claim 1. The moving range in the scanning direction includes a plurality of sections,
The method according to claim 8, wherein the inclination information acquiring unit sets an average inclination amount in a section where the change amount is smaller than the predetermined amount to be equal to 0 or an average inclination amount in a section closest to the area. 13. The tilt information acquisition device according to any one of 13. The movement range in the scanning direction includes a plurality of the sections,
When the plurality of sections include a section in which the error in the amount of change exceeds an allowable value, the slope information acquiring unit sets the average slope amount in the section to 0 or an average slope in a section closest to the section. The inclination information acquisition device according to claim 8, wherein the inclination information is equal to the amount. 16. The tilt information acquisition device according to claim 8, wherein the scanning direction is a direction orthogonal to a tangential direction of the track. 17. The tilt information acquisition device according to claim 8, further comprising a tilt correction unit configured to correct a tilt of the information recording medium with respect to the optical pickup based on the information regarding the tilt. An optical pickup device that irradiates light to a recording surface of an information recording medium and receives reflected light from the recording surface,
A light source, an optical system including an objective lens for condensing a light beam emitted from the light source on a recording surface of an information recording medium, and an optical system for guiding a return light beam reflected on the recording surface to a predetermined light receiving position; An optical pickup including a photodetector receiving the return light beam;
An optical pickup device comprising: the inclination information acquisition device according to any one of claims 8 to 17. An optical disc device that irradiates light onto a recording surface of an information recording medium and performs at least reproduction of information recording, reproduction, and erasing,
An optical pickup device according to claim 18,
An optical disk device comprising: a processing device that performs at least reproduction among recording, reproduction, and erasure of the information by using an output signal from the optical pickup device. 20. The optical disk device according to claim 19, further comprising a light emission power correction unit that corrects light emission power of the light source based on the information on the tilt. 21. The optical disk device according to claim 19, further comprising a track error signal correction unit that corrects a track error signal detected from an output signal of the photodetector based on the information on the tilt.

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