JP2007234168A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive capable of utilizing optical disks of a plurality of kinds as recording media, preventing contact of the optical disk with an objective lens due to an individual difference irrespective of the kind of the inserted optical disk, and precisely performing a focus pull-in operation. <P>SOLUTION: The optical disk drive includes a laser light source 1, a collimator lens 2, a beam splitter 3, the objective lens 4, an actuator 5, a cylindrical lens 6, a light reception part 7, a focus position detection means 8, a lens driving means 9, a control means 10, and a signal value storage means 11 in which a CD lens driving signal value fd31 estimated on the basis of a BD lens driving signal measured value fd11 is stored. When performing focus control of a CD medium, the control means 10 controls the lens driving means so that the focus pull-in is started from the CD lens driving signal value fd31. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention reproduces information from an optical disk or records information on an optical disk, and performs an accurate focus control on a plurality of optical disks having different working distances so that each optical disk and an objective lens do not contact each other. It relates to the device.

  An optical disk capable of reproducing information by irradiating a laser beam is used as a recording medium for information such as video and audio. An optical disc apparatus using these optical discs as recording media reproduces or records the optical disc by rotating the optical disc and irradiating the recording surface of the optical disc with laser light.

  In such an optical disc apparatus, when the optical disc is reproduced or recorded, the focused spot of the laser beam condensed by the objective lens is just focused (focused state) with respect to the recording surface of the optical disc. Focus control is performed to maintain the distance to the optical disc. The distance between the optical disk and the objective lens is detected as a focus error signal.

  In this focus control, first, the objective lens is brought close to the optical disc in a state in which laser light is irradiated from the optical head. During this time, a focus error signal is detected. When the amplitude of the focus error signal exceeds a predetermined threshold and then intersects with 0, a focus pull-in operation for stopping the approach of the objective lens to the optical disk is performed. After the focus pull-in operation, the position of the objective lens is controlled based on the focus error signal so that the focused spot is in focus.

  As the optical disk, a CD (Compact Disc) and a high-density (large storage capacity) DVD (Digital Versatile Disc) are used, and in recent years, a higher density (large storage capacity) BD (Blu-ray) than DVD. Disc) has also appeared and has been commercialized.

  In general, optical disk devices that support recording or reproduction of BD media, DVD media, and CD media often use one optical head due to space and cost constraints. Usually, the objective lens is designed for one type of optical disk (mostly BD). An objective lens corresponding to the BD has a high NA (aperture ratio: 0.85), and an objective lens having a large NA has a short focal length. Further, the thickness of the substrate, which is the thickness from the surface of the optical disk to the recording surface, is 0.1 mm for BD media, and is as thick as 0.6 mm for DVD media and 1.2 mm for CD media.

  The distance (so-called working distance) between the optical disk and the objective lens at the focus pull-in position becomes small. In addition, in order to reduce the size of the entire apparatus, the objective lens is designed to have a smaller incident beam diameter. As a result, the working distance becomes smaller.

  In the case of an optical disc apparatus capable of reproducing or recording BD, DVD, and CD as described above, the working distance for BD media is about 1.4 mm, the working distance for DVD media is about 0.9 mm, The working distance is about 0.4 mm. In general, when the working distance is 0.5 mm or less, the possibility of contact between the objective lens and the optical disk increases rapidly, and measures for avoiding contact are necessary.

  In order to avoid the contact between the optical disk and the objective lens as described above, for example, as in the invention described in Japanese Patent Laid-Open No. 5-182206, driving that flows through an objective lens driving means (actuator) that drives the objective lens A smoothed drive current signal having an amplitude level substantially proportional to the current is detected to exceed a predetermined amplitude level (threshold), and the drive current signal is detected to exceed a predetermined amplitude level. In some cases, the objective lens driving means outputs a signal for the objective lens to leave the optical disk.

In the invention described in Japanese Patent Laid-Open No. 5-182206, the predetermined amplitude level is set to a value at which the objective lens does not contact the optical disc, thereby suppressing the objective lens from contacting the optical disc. it can.
JP-A-5-182206

  However, in an actual optical disk apparatus and optical disk medium, there are many cases where an assembly error of a turntable for mounting and rotating an optical disk, a substrate thickness error due to variations of individual optical disks, and the like occur. Further, even when the same drive current is supplied to another actuator of the same configuration, that is, the sensitivity error of the actuator, the objective lens is caused by the variation of the magnetic flux of the permanent magnet and the variation of the winding density of the coil. There are many cases where an error occurs in the amount of movement.

  As described above, even an optical disc apparatus having the same configuration includes a plurality of errors, and there is an error in the shape and movement amount depending on each individual. When an actuator having an error is driven within a predetermined threshold, it takes a very long time to reach a just focus state, or it does not become a just focus, or an optical disk and an objective lens come into contact. . As described above, it is very difficult to effectively avoid contact between the optical disk and the objective lens by giving a predetermined threshold value to a plurality of optical disk apparatuses having a common design.

  Therefore, the present invention can use a plurality of types of optical discs as a recording medium. Regardless of the type of the inserted optical disc, the present invention suppresses contact between the optical disc and the objective lens due to individual differences and accurately performs a focus pull-in operation. Provided is an optical disc apparatus capable of

  In order to achieve the above object, the present invention provides an objective lens for irradiating a recording surface of an optical disc such as a CD, a DVD, or a BD to receive reflected light from the optical disc, and the objective lens as a recording surface of the optical disc. An actuator that approaches and separates in the vertical direction, a light receiving unit that receives reflected light from the optical disk and converts it into an electrical signal, and a laser emitted from the objective lens based on the electrical signal converted by the light receiving unit Focus position detection means for outputting a focus position signal of light, lens drive means for generating a lens drive signal for driving the actuator, and control means for controlling the lens drive means based on the focus position signal The laser beam emitted from the objective lens is focused on the recording surface of an optical disc having a different working distance. An optical disc apparatus for performing focus control, wherein a first lens drive signal reference value and a laser beam are preliminarily given as the lens drive signal for bringing a laser beam into focus on a recording surface of a BD medium. The lens drive for bringing the laser beam into focus on the recording surface of the DVD medium by using a difference from a second lens drive signal reference value given in advance as the lens drive signal to be brought into focus in step 1 as a first offset value When the difference between the third lens drive signal reference value given in advance as a signal and the first lens drive signal reference value is set as the second offset value, the recording surface of the BD medium is rotated an integer number of times in a focused state. Measured when the first lens drive signal measured value, which is an average value of the actually measured lens drive signals, and the DVD medium recording surface are rotated an integer number of times in a focused state. A value obtained by multiplying the first offset value by the ratio of the third offset value to the second offset value, when the difference from the third lens drive signal actual measurement value, which is an average value of the lens drive signals, is used as the third offset value. And a signal value storage means for storing a second lens drive signal value obtained by adding the first lens drive signal measured value to the actual measured value of the first lens drive signal. The lens driving means is controlled so as to start focus pull-in from the second lens driving signal value stored in.

  According to this configuration, the lens drive signal value for starting the focus pull-in of the CD with a small working distance that is easy to contact the objective lens and the medium is obtained based on the lens drive signal at the time of focus control of the BD having a large working distance. Since the estimation is performed, it is possible to solve the problem that the objective lens comes into contact with the optical disk or that it takes a long time to pull the focus.

  Thereby, the accuracy of focus control in each of the BD, DVD, and CD optical discs can be increased, and the accuracy of reproduction and / or recording of the optical discs can be increased. In addition, since the focus pull-in operation can be shortened, the time required for the operation of the optical disk apparatus can be shortened, and an optical disk apparatus with less stress for the user can be provided.

  In order to achieve the above object, the present invention provides an objective lens that irradiates a recording surface of an optical disc with laser light and receives reflected light from the optical disc, and the objective lens approaches and separates in a direction perpendicular to the recording surface of the optical disc. And an actuator for receiving the reflected light from the optical disk and converting it into an electrical signal, and outputting a focal position signal of the laser light emitted from the objective lens based on the electrical signal converted by the light receiving unit A focus position detecting means, a lens driving means for generating a lens driving signal for driving the actuator, and a control means for controlling the lens driving means based on the focus position signal. Light that performs focus control so that the laser light emitted from the objective lens is focused on the recording surface of an optical disc of a different size A disk drive device based on a first lens driving signal actual measurement value that is an average value of lens driving signals actually measured when the recording surface of the first optical disk having a large working distance is rotated an integer number of times in a focused state. Signal value storage means for storing the estimated second lens drive signal value is provided, and the control means stores the signal value when the focus control of the second optical disk having a working distance smaller than that of the first optical disk is performed. The lens driving means is controlled to start focus pull-in from the second lens driving signal value stored in the means.

  According to this configuration, the lens driving signal value at the start of pulling in the focus of the second optical disk having a small working distance and the object lens and the medium being in contact with each other can be obtained. In addition, since the estimation is performed, it is possible to solve the problem that the objective lens comes into contact with the optical disk or that it takes a long time to pull the focus.

  Thereby, the accuracy of focus control in each optical disc having a different working distance can be improved, and the accuracy of reproduction and / or recording of the optical disc can be increased. In addition, since the focus pull-in operation can be shortened, the time required for the operation of the optical disk apparatus can be shortened, and an optical disk apparatus with less stress for the user can be provided.

  In the above configuration, the signal value storage means is a first lens drive signal reference value given in advance as a lens drive signal value for bringing the laser beam into focus on the recording surface of the first optical disc as the second lens drive signal value. The first lens drive signal is actually measured as a first offset value which is a difference between a second lens drive signal reference value given in advance as a lens drive signal value for bringing the laser beam into focus on the recording surface of the second optical disk. What added to the value may be memorize | stored.

  In the above configuration, the signal value storage means has a predetermined upper limit value of the lens driving signal and a second lens driving signal reference value given in advance as a lens driving signal value to be brought into focus on the recording surface of the second optical disc. And a limit drive signal value obtained by adding a limit offset value, which is a difference between the second lens drive signal value and the control unit, to store the upper limit of the lens drive signal generated by the lens drive unit. The lens driving unit may be controlled to be equal to or less than a driving signal value. When the lens driving signal generated by the lens driving unit is equal to or higher than the limit driving signal value, the objective lens is Alternatively, the lens driving unit may be controlled so as to generate a forced retraction signal that moves the actuator so as to be separated from the second optical disk.

  According to this configuration, since the upper limit of the lens drive signal is determined for each individual optical disk apparatus, the lens drive signal comes into contact with the optical disk before reaching the upper limit, or is far from the focus pull-in position even if the upper limit is reached. It is possible to suppress the occurrence of problems such as being present.

  In the above configuration, the laser light is focused on the recording surface of the first optical disk. The first lens driving signal reference value given in advance as the lens driving signal and the laser light are focused on the recording surface of the second optical disk. A difference from a second lens driving signal reference value given in advance as the lens driving signal is set as a first offset value, and the working distance of the laser beam is smaller than that of the first optical disc than that of the second optical disc. The difference between the third lens drive signal reference value given in advance as the lens drive signal to be brought into focus on the recording surface of the large third optical disc and the first lens drive signal reference value is set as a second offset value, and The first lens driving signal actual which is an average value of lens driving signals actually measured when the recording surface of the first optical disk is rotated an integer number of times in a focused state. When the third offset value is the difference between the measured value and the third lens driving signal measured value that is the average value of the lens driving signals measured when the recording surface of the third optical disc is rotated an integer number of times in a focused state, In the signal value storage means, a value obtained by multiplying the first offset value by the ratio of the third offset value to the second offset value as the second lens driving signal value is added to the first lens driving signal actual measurement value. A value may be stored.

  According to this configuration, the individual difference of the optical disk device can be corrected not only for errors due to simple assembly, but also for errors due to variations in sensitivity of electronic members such as control means, light receiving units, actuators, etc. Even when reproducing or recording a plurality of types of optical disks having a working distance, it is possible to suppress the occurrence of problems such as the objective lens being in contact with the optical disk or the focus being not pulled in.

  Further, in the above-described configuration, the signal value storage means is a second lens driving signal given in advance as a lens driving signal value to be brought into focus on the recording surface of the second optical disk and a predetermined upper limit value of the lens driving signal. A limit drive signal value obtained by multiplying a limit offset value, which is a difference from a reference value, by a ratio of a third offset value to the second offset value, is added to the second lens drive signal value, and the control is stored. The means may control the lens driving means so that an upper limit of the lens driving signal generated by the lens driving means is equal to or less than the limit driving signal value. The means generated by the lens driving means When the lens drive signal is equal to or greater than the limit drive signal value, the objective lens is moved away from the first, second, or third optical disc. The lens driving means may be one that controls so as to generate a forced evacuation signal to move the actuator.

  According to this configuration, since the upper limit of the lens drive signal is determined for each individual optical disk apparatus, the lens drive signal comes into contact with the optical disk before reaching the upper limit, or is far from the focus pull-in position even if the upper limit is reached. It is possible to suppress the occurrence of problems such as being present.

  According to the present invention, a plurality of types of optical discs can be used as a recording medium. Regardless of the type of the inserted optical disc, the contact between the optical disc and the objective lens due to individual differences is suppressed and the focus pull-in operation is performed accurately. It is possible to provide an optical disc device that can be used.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a configuration of an example of an optical disc apparatus according to the present invention. The optical disc apparatus A shown in FIG. 1 is capable of playing back three types of optical discs: CD (Compact Disc) media, DVD (Digital Versatile Disc) media, and BD (Blu-ray Disc) media.

  The optical disc Ds includes a recording layer Ds1 on which data is recorded, and a transparent base material Ds2. The recording layer Ds1 and the base material Ds2 are pasted, and the border between the recording layer Ds1 and the base material Ds2 forms the recording surface Ds3.

  The optical disc apparatus A includes at least a laser light source 1, a collimator lens 2, a beam splitter 3, an objective lens 4, an actuator 5, a cylindrical lens 6, a light receiving unit 7, a focus position detecting unit 8, and a lens driving unit. 9, a control unit 10, and a signal value storage unit 11. Further, the order in which the laser beams are incident is not limited to that shown in FIG. 1, and can be changed or replaced as long as there is no problem in reproducing or recording the optical disc.

  The laser light source 1 emits laser light. Laser light that can be emitted from the laser light source 1 is an optical disk among blue laser light for BD (wavelength 405 nm), red laser light for DVD (wavelength 650 nm), and infrared laser light for CD (wavelength 780 nm). This is a laser light source device that can selectively emit laser light corresponding to a medium.

  The collimator lens 2 is a lens that converts laser light emitted from the laser light source 1 from divergent light into parallel light. The laser beam that has been transmitted through the collimator lens 2 and converted into parallel light is incident on the beam splitter 3.

  The beam splitter 3 is a prism that transmits part of the laser light and reflects the rest. Half of the laser beam input to the beam splitter 3 is reflected and enters the objective lens 4.

  The objective lens 4 focuses the laser beam reflected by the beam splitter 3 on the recording surface Ds3 of the optical disc Ds. Although the objective lens 4 is not limited to this, here, it is an objective lens corresponding to BD media. The laser beam reflected by the recording surface Ds3 of the optical disc Ds passes through the objective lens 4, is converted into parallel light by the objective lens 4, and enters the beam splitter 3 as a backward laser beam.

  The actuator 5 can move the objective lens 4 so as to approach and separate from the optical disc Ds in accordance with a lens driving signal generated and output by a lens driving means 9 described later. The actuator 5 is not limited thereto, but here, a drive current (lens drive signal) is passed through a coil (not shown) in a magnetic field formed by a permanent magnet (not shown), and the objective lens 4 is driven by Lorentz force. It may be something that can be done.

  In the present invention, the actuator 5 performs a focusing operation to move the objective lens 4 so as to approach and separate from the optical disc Ds. In addition, the actuator 5 moves the objective lens 4 along the recording surface Ds3 of the optical disc Ds. A tracking operation for moving the objective lens 4 and a tilt operation for moving the objective lens 4 so that the optical axis of the laser light emitted from the objective lens 4 can be swung as required.

  Half of the return laser light incident on the beam splitter 3 is transmitted and incident on the cylindrical lens 6. The cylindrical lens 6 is a lens having an arcuate cross section obtained by cutting a cylindrical lens along the central axis. As the laser light passes through the cylindrical lens 6, aberration occurs in the laser light.

  The laser beam that has passed through the cylindrical lens 6 is applied to the light receiving unit 7. The laser light applied to the light receiving unit 7 is converted into an electrical signal. The light receiving unit 7 is not limited to this, but may be one using a photoelectric element that converts light into electricity.

  This electrical signal is input to the focus position detecting means 8. The focus position detection means 8 outputs a focus error signal (FE signal) by performing arithmetic processing on the input electrical signal. This FE signal is input to the control means 10.

  The lens driving unit 9 generates a lens driving signal that is a driving current for driving the actuator 5 and inputs the lens driving signal to the actuator 5. The lens driving means 9 is controlled by a control means 10 described later.

  Although the control means 10 is not limited to this, here, it is a processing device using a CPU, a microcomputer or the like. The control means 10 performs control to cause the lens driving means 9 to generate a lens driving signal that is a driving current for driving the actuator 5. The control unit 10 monitors the value of the lens driving signal generated by the lens driving unit 9 and input to the actuator 5.

  Further, after the objective lens 4 is just focused on the recording surface Ds3 of the optical disc Ds, the control means 10 controls the lens driving means 9 so as to keep the just focus based on the FE signal output from the focus position detecting means 8. To do. Details of the control method will be described later.

  Examples of the focus position detection unit 8, the lens driving unit 9, and the control unit 10 include an independent device, a device in which a plurality of units are integrated, and a computer program. Moreover, it is not limited to these.

  The signal value storage unit 11 is a memory device including a memory element such as a read-only ROM (Read Only Memory) and a writable RAM (Random Access Memory). The signal value storage means 11 is connected to the control means 10 and includes a database therein. The signal value stored in the database is output to the control means 10 in response to a request from the control means 10.

  The signal value stored in the database is not limited to this, but here, the lens drive signal value at the focus pull-in position corresponding to each of the BD, DVD, and CD optical disks, the limit drive signal value of the lens drive signal, and the like are listed. be able to. In addition to these, lens drive signal values necessary for the control of the control means 10 may be stored.

  FIG. 2 is a diagram showing the timing of the focus error signal and the lens drive signal. When focus control is performed by the optical disc apparatus A, first, a focus pull-in operation is performed so that the laser light is just focused on the recording surface Ds3. When performing the focus pull-in operation, the control unit 10 controls the lens driving unit 9 to generate the lens driving signal fd and operate the actuator 5.

  At this time, the control unit 10 controls the lens driving unit 9 so as to generate a lens driving signal fd whose signal value increases regardless of the FE signal. When the value of the lens driving signal fd generated by the lens driving means 9 increases, the objective lens 4 is moved closer to the optical disk Ds by the actuator 5.

  At this time, the objective lens 4 continues to emit while condensing the laser beam, and the laser beam reflected by the recording surface Ds3 of the optical disc Ds enters the light receiving unit 7 and is converted into an electric signal. Based on the converted electrical signal, the focus position detecting means 8 outputs an FE signal (see FIG. 2).

  When the objective lens 4 is moved while emitting laser light, the FE signal may output an S-shaped waveform as shown in FIG. The control means 10 adjusts the point where the amplitude of the S-shaped waveform of the FE signal exceeds a predetermined threshold (line L1 shown in FIG. 2) and further crosses 0 (point P1 shown in FIG. 2). By setting the focus position (focus pull-in position), the focus pull-in operation ends. After that, the control unit 10 causes the lens driving unit 9 to generate the lens driving signal fd based on the FE signal output from the focus position detecting unit 8, and causes the lens driving signal fd to be input to the actuator 5. 4 is made to follow the recording surface Ds3 of the optical disc Ds to perform control for maintaining just focus.

  FIG. 3 shows a schematic diagram of the relative positions of the objective lens and the optical disc when the laser beam is just focused on the recording surface of the optical disc, and FIG. 4 shows a list of main specifications of each of the BD, DVD, and CD. . Here, the optical disk Ds shown in FIG. 3 is a BD medium. As described above, the optical disc Ds includes the recording layer Ds1 and the base material Ds2, and the recording surface Ds3 is formed at the boundary between the recording layer Ds1 and the base material Ds2.

  The optical disk Ds rotates while being placed on the turntable Tr, and is irradiated with laser light from the objective lens 4. When the lens drive signal is not input to the actuator 5 (in the neutral state), the objective lens 4 stands by at a neutral position Np indicated by a two-dot chain line in the drawing. When focus control (focus pull-in operation) is performed and the laser light emitted from the objective lens 4 is just focused on the recording surface Ds3 of the optical disk Ds, the objective lens 4 moves to a position closer to the optical disk Ds than the neutral position Np. ing.

  As shown in FIG. 3, the shortest distance between the optical disk Ds and the objective lens 4 when the laser light is just focused on the recording surface Ds3 is called a working distance Wd (working distance Wd). The working distance Wd varies depending on the type of the optical disk (the thickness of the optical disk substrate) and the aperture ratio of the objective lens 4.

  The substrate thicknesses of the BD media, DVD media, and CD media are as shown in FIG. That is, it is 0.1 mm for BD media, 0.6 mm for DVD media, and 1.2 mm for CD. Furthermore, the wavelength of the corresponding laser and the numerical aperture (NA) of the objective lens are also 405 nm for BD media, 0.85 for NA, 650 nm for DVD media, 0.6 for NA, and 780 nm for CD media. , NA has different specifications such as 0.45.

  The objective lens 4 used in the optical disc apparatus A has an aperture ratio corresponding to BD media and has a short focal length. When this objective lens 4 is used, the working distance Wd1 of the BD media is about 1.4 mm, the working distance Wd2 of the DVD media is about 0.9 mm, and the working distance Wd3 of the CD media is about 0.4 mm ( (See FIG. 4).

  FIG. 5 is a graph showing an example of the relationship between the working distance and the lens driving signal when focus control is performed using the optical disc apparatus shown in FIG. In the graph shown in FIG. 5, the horizontal axis represents the working distance Wd (mm), and the vertical axis represents the lens drive signal fd (A).

  A graph G1 shown on the upper side of FIG. 5 shows the relationship between the working distance and the lens drive signal when the BD, DVD, and CD media are just focused in the optical disc apparatus A. This graph G1 is commonly used in the optical disc apparatus A having the same member and shape.

  That is, the working distance and lens drive signal reference values of BD media, DVD media, and CD media are given by (Wd1, fd1: plot PL1), (Wd2, fd2: plot PL2), and (Wd3, fd3: plot 3), respectively. It is done. These Wd1, Wd2, Wd3, fd1, fd2, and fd3 may be theoretical values when the focus control of each medium is performed by an optical disk apparatus that does not include manufacturing errors. It may be an average value of values obtained when focus control is performed.

  The plots PL1, PL2, and PL3 shown in the graph G1 are reference values when the optical disc apparatus A performs focus control on each of the BD media, the DVD media, and the CD media. That is, when the lens drive signal reference values fd1, fd2, and fd3 are output from the lens drive means 9 in the reference optical disk apparatus (not including an error), the objective lens 4 is moved from the neutral position Np to the BD media and DVD media, respectively. The laser beam can be moved to a position where the laser beam is just focused on the recording surface of the CD medium or a focus pull-in position in the vicinity thereof.

  As shown in FIG. 5, the relationship between the working distance of the optical disc and the lens drive signal can be approximated linearly.

  An optical disc such as a BD, DVD, or CD is placed on the turntable Tr as shown in FIG. Mechanical errors such as errors in manufacturing the members constituting the turntable Tr and errors in assembling occur. Due to this error, in the optical disc apparatus, the distance between the objective lens 4 and the optical disc Ds when the objective lens 4 is in the neutral position varies depending on each individual.

  When focus control of BD media is performed with an optical disc apparatus having a mechanical error, the distance from the neutral position to the just focus becomes different from the reference value. That is, even if the lens drive signal reference value fd1 is input to the actuator 5, it is not possible to just focus on the recording surface of the BD medium. Similarly, the lens drive signal reference value fd2 cannot be just focused on the recording surface of the DVD medium, and the lens drive signal reference value fd3 cannot be just focused on the recording surface of the CD medium. Further, when the lens drive signal reference value fd3 is input by an optical disk apparatus in which the neutral position Np of the objective lens 4 and the recording surface Ds3 of the optical disk are separated from each other, the limit value is reached without being just focused on the recording surface of the CD medium. In addition, when the lens drive signal reference value fd3 is input in the optical disc apparatus in which the neutral position Np of the objective lens 4 and the recording surface Ds3 of the optical disc are approaching, the optical disc Ds and the objective lens 4 may be in contact with each other.

  Therefore, the lens driving signal is corrected by the following method. As shown in the graph of FIG. 5, since the relationship between the working distance of the optical disc and the lens drive signal can be approximated linearly, first, the difference between the lens drive signal reference value fd1 of the BD media and the lens drive signal reference value fd3 of the CD media. The first offset value Δfd1 is calculated in advance.

  Next, a BD medium is inserted into the optical disc apparatus in which a mechanical error may occur, and focus control is started. The control means 10 controls the lens driving means 9 so as to maintain the just focus after performing the focus pull-in operation as described above when performing the focus control. At this time, the control means 10 detects the lens drive signal output from the lens drive means 9, and obtains a lens drive signal actual measurement value fd11 of the BD media, which is a smooth value thereof.

  Taking the optical disk from which the lens drive signal actual measurement value fd11 of the BD medium is obtained as an example, the lens drive signal actual measurement value fd11 having a smaller value than the lens drive signal reference value fd1 of the BD media is obtained. This indicates that the amount of movement of the objective lens 4 is small and just focus has been reached, and the distance from the neutral position Np of the objective lens 4 to the recording surface of the optical disc is shorter than the reference optical disc apparatus. I understand.

  The smoothing value of this lens drive signal is obtained by focusing the laser light emitted from the objective lens 4 on the recording surface of the BD medium, and maintaining the state to rotate the BD medium an integer number of times (including one rotation). The average value of the lens driving signal at this time can be used. According to this method, since the BD medium rotates an integer number of times, it is possible to suppress the occurrence of an error due to blurring due to the rotation of the medium.

  Here, the reason why the BD medium is used is that the working lens is large and the possibility that the objective lens 4 comes into contact with the optical disk Ds during the focus pull-in operation is low even if some errors occur. On the other hand, since the working distance of CD media is small and the risk of contact is high, the lens driving signal value of CD is estimated from the actual lens driving signal value fd11 of BD media.

誤差を有する光ディスク装置の信号値記憶手段１１にはこのＣＤのレンズ駆動信号値ｆｄ３１の値が記憶される。 As the lens drive signal value fd31 for CD, the laser beam emitted from the objective lens 4 is just focused on the recording surface of the CD, which is obtained by adding the first offset value Δfd1 to the measured lens drive signal value fd11 for BD. That is, it is expressed by the following formula.

The value of the lens drive signal value fd31 of the CD is stored in the signal value storage means 11 of the optical disc apparatus having an error.

  When performing CD media focus control using an optical disc apparatus having an error, the lens drive means 9 is configured so that the control means 10 performs focus pull-in with the lens drive signal value fd31 of the CD media stored in the signal value storage means 11. To control. For example, when the distance between the objective lens 4 in the neutral position and the optical disk is short as in the optical disk apparatus of the graph G2 shown in FIG. 5, when the reference value fd3 of the CD medium lens drive signal is input to the actuator 5, Although the objective lens 4 and the optical disk come into contact with each other, the lens drive signal value is set to fd31 at the time of the CD media focus pull-in operation, and the quick pull-in operation is performed while suppressing the contact between the optical disk Ds and the objective lens 4. Is possible.

(Second Embodiment)
FIG. 6 is a graph showing another example of the relationship between the working distance and the lens driving signal when focus control is performed using the optical disc apparatus shown in FIG. Graphs G1 and G2 shown in FIG. 6 are the same graphs as the graphs G1 and G2 shown in FIG. 5, and the same reference numerals are used. Further, it is assumed that the grab G3 has an error that the objective lens 4 is far away when the objective lens 4 is in the neutral position.

  Further, when the focus control is performed by the reference optical disc apparatus, the lens drive signal fda is obtained when the objective lens 4 is at the bottom surface of each optical disc (the distance between the bottom surface of the optical disc and the objective lens 4 is at the neutral position). This is a reference value for the upper limit of the lens drive signal that is set so as not to be in constant contact regardless of the type of lens.

  In an optical disc apparatus having an error (for example, as indicated by a grab G2 or a graph G3), when the upper limit value fda of a constant lens drive signal is employed, for example, in the case of an optical disc apparatus indicated by a graph G2, the lens drive signal fda is supplied to the actuator 5. When entered, the working distance reaches a negative value (not shown). That is, the objective lens 4 comes into contact with the optical disc Ds. Further, in the case of the optical disc apparatus shown by the graph G3, when the lens drive signal fda is input to the actuator 5, the working distance is larger than Wd3 and cannot be approached. That is, the optical disk apparatus shown in the graph G3 has a problem that accurate focus control of CD media is not performed.

  Therefore, a limit offset value Δfda, which is a difference between the reference value fd3 of the lens drive signal value of the CD in the reference optical disc apparatus A and the upper limit reference value fda of the lens drive signal, is calculated in advance. That is, the lens drive signal value fd31 for CD is calculated from the actual measured lens drive signal value fd11 for BD and the first offset value Δfd1 using Equation 1, and stored in the signal value storage means 11.

誤差を有する光ディスク装置の信号値記憶手段１１にはこのレンズ駆動信号リミット値ｆｄａ２の値が記憶される。 Thereafter, a lens drive signal limit value fda2 is calculated by adding the limit offset value Δfda to the lens drive signal value fd31 of the CD.

The value of the lens driving signal limit value fda2 is stored in the signal value storage means 11 of the optical disc apparatus having an error.

  When performing CD media focus control using an optical disc apparatus having an error, the lens drive means 9 is configured so that the control means 10 performs focus pull-in with the lens drive signal value fd31 of the CD media stored in the signal value storage means 11. To control. At this time, the control means 10 controls the lens driving means 9 so that the lens driving signal generated by the lens driving means 9 becomes a value equal to or smaller than the lens driving signal limit value fda2.

  The control method is not limited to this, but the control means 10 monitors the lens drive signal generated by the lens drive means 9 and input to the actuator 5 so that the lens drive signal is below the lens drive signal limit value fda2. An example of controlling the lens driving means 9 can be mentioned.

  Further, when the lens driving signal exceeds the lens driving signal limit value fda2, the control unit 10 causes the lens driving unit 9 to generate a forced retraction signal that moves the objective lens 4 away from the optical disk Ds. May be controlled to be retracted from the optical disk Ds. Needless to say, the forced retraction signal at this time is smaller than the lens drive signal limit value fda2, but may be 0 (returning the objective lens 4 to the neutral position Np).

  Also, when using an optical disc apparatus having an error in the direction in which the objective lens 4 is farther from the optical disc Ds, the lens drive signal limit value is calculated using Equations 1 and 2 and stored in the signal value storage unit 11. Thus, it is possible to perform focus control with high accuracy.

  In the second embodiment, the lens drive signal is controlled by adopting the lens drive signal limit value fda2 when performing the CD media focus control. However, in the focus control of the BD media and the DVD media. Also, it is possible to execute the same control by adopting the lens drive signal limit value fda2.

  Further, the lens drive signal limit value of the optical disk apparatus shown by the graph G3 can be estimated by the same method.

  In the first embodiment and the second embodiment described above, the lens driving signal value of the CD is estimated based on the actual measured value of the BD lens driving signal, and stored in the signal value storage means. However, the present invention is not limited to this, and the lens driving signal value of the CD and the lens driving signal limit value fda2 may be estimated based on the actual lens driving signal value of the DVD. Further, the lens drive signal value for DVD and the lens drive signal value for CD may be estimated from the actual measured value of the BD lens drive signal.

(Third embodiment)
In the first and second embodiments described above, the optical disk apparatus has been described as an example including a mechanical error of the optical disk apparatus A, but in this embodiment, in addition to the mechanical error, the actuator 5 An optical disc apparatus including variations in sensitivity will be described.

  The actuator 5 is used to drive a current through a coil arranged in a magnetic field formed by a permanent magnet, and drive the objective lens 4 with a Lorentz force generated at that time. However, the magnetic flux density and magnetic force of the permanent magnet, the winding method of the coil, and the number of windings are likely to cause unevenness and error, and the same current is passed through the coil of the actuator 5 using the permanent magnet and the coil having the same configuration. However, individual differences may occur in the amount of movement of the objective lens 4.

  FIG. 7 is a graph showing another example of the relationship between the working distance and the lens driving signal when focus control is performed using the optical disc apparatus shown in FIG. The graph G1 shown in FIG. 7 is the same graph as the graph G1 shown in FIG. 5, and uses the same reference numerals. A grab G4 shows the relationship between the working distance of the optical disc apparatus having an error and the lens drive signal.

  As shown in the graph of FIG. 7, the relationship between the working distance of the optical disc and the lens driving signal can be approximated linearly. As shown in FIG. 7, the slope of the graph G4 indicating the relationship between the working distance of the optical disc apparatus including the error and the lens drive signal is different from the slope of the reference graph G1. This is because there is a difference in the amount of movement of the objective lens 4 by the lens driving signal because the sensitivity of the actuator 5 is different. Thus, if there is a change in the amount of movement of the objective lens 4 due to the lens drive signal, the risk of contact increases in the case of a CD with a small working distance when determining the lens drive signal at the time of focus pull-in.

  Therefore, the first offset value Δfd1 which is the difference between the lens drive signal reference value fd1 for BD media and the lens drive signal reference value fd3 for CD media, the lens drive signal value reference value fd1 for BD media, and the lens drive signal reference value for DVD media. A second offset value Δfd11 that is a difference from fd2 is calculated in advance.

  Next, the BD medium is inserted in the optical disk apparatus including the error, and focus control is started. The control means 10 controls the lens driving means 9 so as to maintain the just focus after performing the focus pull-in operation as described above when performing the focus control. At this time, the control means 10 detects the lens drive signal output from the lens drive means 9, and obtains a lens drive signal actual measurement value fd12 of the BD media, which is a smooth value thereof. Similarly, the lens drive signal actual measurement value fd22 of the DVD medium is obtained. A third offset value Δfd21 that is the difference between the lens drive signal actual measurement value fd12 of the BD media and the lens drive signal actual measurement value fd22 of the DVD media is calculated.

で求められる。このΔｆｄ３をＢＤのレンズ駆動信号実測値に加算したものがＣＤのレンズ駆動信号値ｆｄ３２となる。すなわち以下の式で示される。

誤差を有する光ディスク装置の信号値記憶手段１１にはこのＣＤのレンズ駆動信号値ｆｄ３２の値が記憶される。 If the difference between the lens driving signal value fd32 for CD and the lens driving signal actual measurement value fd12 for BD is Δfd3, the graph G1 and the graph G4 are linear with each other.

Is required. A value obtained by adding Δfd3 to the actual measured value of the BD lens drive signal is a lens drive signal value fd32 of the CD. That is, it is shown by the following formula.

The signal value storage means 11 of the optical disc apparatus having an error stores the value of the lens drive signal value fd32 of the CD.

  When performing CD media focus control using an optical disc apparatus having an error, the lens drive means 9 is configured so that the control means 10 performs focus pull-in with the CD media lens drive signal value fd32 stored in the signal value storage means 11. To control. By setting the lens drive signal value to fd32 during the focus pull-in operation of the CD medium, it is possible to perform the pull-in operation quickly while suppressing contact between the optical disc Ds and the objective lens 4.

(Fourth embodiment)
FIG. 8 is a graph showing another example of the relationship between the working distance and the lens drive signal when focus control is performed using the optical disc apparatus shown in FIG. Graphs G1 and G4 shown in FIG. 8 are the same as the graphs G1 and G4 shown in FIG. 7, and the same reference numerals are used.

  Further, when the focus control is performed by the reference optical disc apparatus, the lens drive signal fda is obtained when the objective lens 4 is at the bottom surface of each optical disc (the distance between the bottom surface of the optical disc and the objective lens 4 is at the neutral position). This is a reference value for the upper limit of the lens drive signal that is set so as not to be in constant contact regardless of the type of lens.

  When an upper limit value fda of a fixed lens driving signal is employed in an optical disc apparatus having an error (for example, as shown by the graph G4), for example, in the case of the optical disc apparatus shown by the graph G4, when the lens driving signal fda is input to the actuator 5, As shown in the graph G4, the working distance reaches a negative value (not shown). That is, the objective lens 4 comes into contact with the optical disc Ds.

  Therefore, a limit offset value Δfda, which is a difference between the reference value fd3 of the lens drive signal value of the CD in the reference optical disc apparatus A and the upper limit reference value fda of the lens drive signal, is calculated in advance. BD lens drive signal actual measurement value fd12, DVD lens drive signal actual measurement value fd22, first offset value Δfd1, second offset value Δfd11, third offset value Δfd21, and Equations 3 and 4 are used. The lens drive signal value fd32 of the CD is calculated from the signal value and stored in the signal value storage means 11.

ＣＤのレンズ駆動信号値ｆｄ３２に第２リミットオフセット値Δｆｄａ２を加えて第２レンズ駆動リミット値ｆｄａ３を算出する。

誤差を有する光ディスク装置の信号値記憶手段１１にはこの第２レンズ駆動信号リミット値ｆｄａ３が記憶される。 Further, a second limit offset value Δfda2 is calculated by multiplying the limit offset value fda by the ratio of the second offset value Δfd11 and the third offset value Δfd21.

The second lens drive limit value fda3 is calculated by adding the second limit offset value Δfda2 to the lens drive signal value fd32 of the CD.

The second lens drive signal limit value fda3 is stored in the signal value storage means 11 of the optical disc apparatus having an error.

  When performing CD media focus control using an optical disc apparatus having an error, the lens drive means 9 is configured so that the control means 10 performs focus pull-in with the CD media lens drive signal value fd32 stored in the signal value storage means 11. To control. At this time, the control unit 10 controls the lens driving unit 9 so that the lens driving signal generated by the lens driving unit 9 is equal to or less than the second lens driving signal limit value fda3.

  The control method is not limited to this, but the control means 10 monitors the lens drive signal generated by the lens drive means 9 and input to the actuator 5, and the lens drive signal is the second lens drive signal limit value fda3. Examples of controlling the lens driving means 9 are as follows.

  In addition, when the lens driving signal exceeds the second lens driving signal limit value fda3, the control unit 10 causes the lens driving unit 9 to generate a forced retraction signal that moves the objective lens 4 away from the optical disk Ds. The lens 4 may be controlled to be retracted from the optical disk Ds. Needless to say, the forced retraction signal at this time is smaller than the second lens drive signal limit value fda3, but may be 0 (returning the objective lens 4 to the neutral position Np).

  In the third and fourth embodiments, description of the optical disk including an error in which the distance between the objective lens and the optical disk at the neutral position is long is omitted, but Expressions 3, 4, 5, and 6 are used. Thus, the lens drive signal value and the second lens drive signal limit value of the CD media can be obtained, and by storing these values in the signal value storage means 11, the limit value is obtained when performing the CD media focus control. Can be prevented from becoming smaller than the lens drive signal value at which just focus is achieved, and accordingly, accurate focus control can be performed in a short time.

  In the third and fourth embodiments, the control using the second lens drive signal limit value fda3 when performing the focus control of the CD media is exemplified. However, in the focus control of the BD media and the DVD media. Also, it is possible to execute the same control by adopting the second lens drive signal limit value fda3.

  In each of the embodiments described above, the lens drive signal value, the first lens drive signal limit value, and the second lens drive signal limit value of the CD media are calculated by the control means 10 and stored in the signal value storage means 11. The signal value storage means 11 may store what is calculated by an external device when the optical disk apparatus A is assembled.

  In the above embodiment, BD media, DVD media, and CD media have been described as examples of the optical disc media. However, the present invention is not limited to this, and an optical disc apparatus that can record or reproduce by irradiating laser light. Can be widely adopted.

  The present invention can be applied to an optical disc apparatus that uses an optical disc such as a BD, DVD, or CD as a recording medium.

It is a figure which shows the structure of an example of the optical disk apparatus concerning this invention. It is a table | surface which shows a timing of a focus error signal and a lens drive signal. It is the schematic of the relative position of an objective lens and an optical disk when just-focusing on the recording surface of an optical disk. It is a list of main specifications of BD, DVD, and CD. 6 is a graph showing an example of a relationship between a working distance and a lens driving signal when focus control is performed using the optical disc apparatus shown in FIG. 1. 6 is a graph showing another example of a relationship between a working distance and a lens drive signal when focus control is performed using the optical disc apparatus shown in FIG. 1. 6 is a graph showing another example of a relationship between a working distance and a lens drive signal when focus control is performed using the optical disc apparatus shown in FIG. 1. 6 is a graph showing another example of a relationship between a working distance and a lens drive signal when focus control is performed using the optical disc apparatus shown in FIG. 1.

Explanation of symbols

A Optical disk device 1 Laser light source 2 Collimator lens 3 Beam splitter 4 Objective lens 5 Actuator 6 Cylindrical lens 7 Light receiving part 8 Focus position detecting means 9 Lens driving means 10 Control means 11 Signal value storage means Ds Optical disk Ds1 Recording layer Ds2 Base material Ds3 Recording surface

Claims (8)

An objective lens for irradiating a recording surface of an optical disc such as CD, DVD, BD, etc., and receiving reflected light from the optical disc;
An actuator for moving the objective lens toward and away from the recording surface of the optical disc in a vertical direction;
A light receiving unit that receives reflected light from the optical disc and converts it into an electrical signal;
A focus position detecting means for outputting a focal position signal of the laser beam emitted from the objective lens based on the electrical signal converted by the light receiving unit;
Lens driving means for generating a lens driving signal for driving the actuator;
Control means for controlling the lens driving means based on the focus position signal, and performing focus control so that the recording surface of the optical disk having a different working distance is focused on the laser light emitted from the objective lens. An optical disk device,
The first lens drive signal reference value given in advance as the lens drive signal for bringing the laser light into focus on the recording surface of the BD medium and the lens drive signal for bringing the laser light into focus on the recording surface of the CD media The difference from the second lens drive signal reference value given in advance as the first offset value,
The difference between the third lens drive signal reference value given in advance as the lens drive signal for bringing the laser beam into focus on the recording surface of the DVD medium and the first lens drive signal reference value is set as the second offset value,
The first lens driving signal actual measurement value, which is an average value of the lens driving signals actually measured when the recording surface of the BD medium is rotated an integer number of times in a focused state, and an integer number of times in the focused state of the DVD medium recording surface When a difference from a third lens driving signal actual measurement value, which is an average value of lens driving signals actually measured when rotating, is set as a third offset value,
Signal value storage means for storing a second lens driving signal value obtained by adding a value obtained by multiplying the first offset value by the ratio of the third offset value to the second offset value to the first lens driving signal actual measurement value. Have
The control means controls the lens driving means so as to start focus pull-in from the second lens drive signal value stored in the signal value storage means when performing CD media focus control. Optical disk device. An objective lens for irradiating a recording surface of the optical disc with laser light and receiving reflected light from the optical disc;
An actuator for moving the objective lens toward and away from the recording surface of the optical disc in a vertical direction;
A light receiving unit that receives reflected light from the optical disc and converts it into an electrical signal;
A focus position detecting means for outputting a focal position signal of the laser beam emitted from the objective lens based on the electrical signal converted by the light receiving unit;
Lens driving means for generating a lens driving signal for driving the actuator;
Control means for controlling the lens driving means based on the focus position signal, and performing focus control so that the recording surface of the optical disk having a different working distance is focused on the laser light emitted from the objective lens. An optical disk device,
The second lens estimated on the basis of the first lens driving signal measured value that is the average value of the lens driving signals actually measured when the recording surface of the first optical disc having a large working distance is rotated an integer number of times in focus. Having signal value storage means for storing drive signal values;
The control means starts the focus pull-in from the second lens drive signal value stored in the signal value storage means when performing the focus control of the second optical disk whose working distance is smaller than that of the first optical disk. An optical disc apparatus for controlling lens driving means.   The signal value storage means includes a first lens drive signal reference value and a laser beam which are given in advance as a lens drive signal value for bringing the laser beam into focus on the recording surface of the first optical disc as the second lens drive signal value. Is added to the first lens driving signal actual measurement value as a difference from a second lens driving signal reference value given in advance as a lens driving signal value for bringing the lens into focus on the recording surface of the second optical disk. The optical disk apparatus according to claim 2, wherein the recorded information is stored. The signal value storage means is a difference between an upper limit value of a lens driving signal given in advance and a second lens driving signal reference value given in advance as a lens driving signal value to be brought into focus on the recording surface of the second optical disc. A limit drive signal value obtained by adding the limit offset value to the second lens drive signal value is stored,
The said control means controls this lens drive means so that the upper limit of the said lens drive signal produced | generated by the said lens drive means becomes below the said limit drive signal value, The Claim 2 or Claim 3 characterized by the above-mentioned. Optical disk device. The signal value storage means is a difference between an upper limit value of a lens driving signal given in advance and a second lens driving signal reference value given in advance as a lens driving signal value to be brought into focus on the recording surface of the second optical disc. The limit drive signal value obtained by adding the limit offset value to the second lens drive signal value is stored,
The control means forcibly moves the actuator so that the objective lens moves away from the first or second optical disk when the lens driving signal generated by the lens driving means becomes equal to or greater than the limit driving signal value. 4. The optical disk apparatus according to claim 2, wherein the lens driving unit is controlled so as to generate a retract signal. The laser light is focused on the recording surface of the first optical disk. The first lens driving signal reference value given in advance as the lens driving signal and the laser light are focused on the recording surface of the second optical disk. A difference from a second lens drive signal reference value given in advance as a lens drive signal is set as a first offset value,
A third lens driving signal reference given in advance as the lens driving signal for bringing the laser light into a focused state on a recording surface of a third optical disk having a working distance smaller than that of the first optical disk and larger than that of the second optical disk. The difference between the value and the first lens drive signal reference value is the second offset value,
The first lens driving signal actual measurement value, which is an average value of the lens driving signals actually measured when the recording surface of the first optical disk is rotated in an integral number of times in a focused state, and the recording surface of the third optical disc are in focus. When a difference from a third lens driving signal actual measurement value, which is an average value of lens driving signals actually measured when rotating an integer number of times, is set as a third offset value,
In the signal value storage means, a value obtained by multiplying the first offset value by the ratio of the third offset value to the second offset value as the second lens driving signal value is added to the first lens driving signal actual measurement value. 3. The optical disk apparatus according to claim 2, wherein a value is stored. The signal value storage means is a difference between an upper limit value of a lens driving signal given in advance and a second lens driving signal reference value given in advance as a lens driving signal value to be brought into focus on the recording surface of the second optical disc. A limit drive signal value obtained by multiplying the second offset value by a ratio of the third offset value to the second offset value is stored in the limit offset value.
7. The optical disc apparatus according to claim 6, wherein the control unit controls the lens driving unit so that an upper limit of the lens driving signal generated by the lens driving unit is equal to or less than the limit driving signal value. The signal value storage means is a difference between an upper limit value of a lens driving signal given in advance and a second lens driving signal reference value given in advance as a lens driving signal value to be brought into focus on the recording surface of the second optical disc. A limit drive signal value obtained by multiplying the second offset value by a ratio of the third offset value to the second offset value is stored in the limit offset value.
The control means controls the actuator so that the objective lens is separated from the first, second, or third optical disk when the lens drive signal generated by the lens drive means becomes equal to or greater than the limit drive signal value. The optical disk apparatus according to claim 6, wherein the lens driving unit is controlled to generate a forced retraction signal to be moved.

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