JP2004206869A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device in which the seek time for an object address is shortened. <P>SOLUTION: A DSP 55 outputs a digital signal for controlling focus jumping to a D/A converter 58. The D/A converter 58 converts the digital signal into an analog signal and provides the analog signal to a driver 59. The driver 59 controls a pickup 60 by an acceleration signal and a deceleration signal. In addition, the DSP 55 outputs a PWM signal to make the pickup 60 seek and provides the PWM signal to an integrator 11. The integrator 11 integrates the PWM signal to form a thread driving signal and provides the thread driving signal to a driver 12. The driver 12 drives a feed mechanism 13 by the thread driving signal to make the pickup 60 seek. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an optical disk device, and more particularly, to an optical disk device for reproducing or recording information from a multilayer optical disk having a plurality of signal recording layers.

  The recording capacity of a general CD (compact disc) or CD-ROM (compact disc read-only memory) currently provided is 640 Mbytes, but recently, the recording capacity of 4.7 Gbytes has been increased with the increase in density. DVDs (digital video discs) are also provided. The thickness of the CD or CD-ROM is 1.2 mm and the diameter is 12 cm. The thickness of a DVD is 0.6 mm, half that of a CD or CD-ROM, and the diameter is 12 cm, the same as a CD or CD-ROM. Further, a two-layer DVD having a recording capacity of 8.5 Gbytes by using a two-layer signal recording surface has also been proposed (Non-Patent Document 1).

  In order to reproduce a two-layer optical disk having two recording layers (signal recording surfaces), a method of reproducing two signal recording surfaces from one surface of the disk, a method of reproducing one signal recording surface from both surfaces of the disk, respectively. Can be considered. However, the method of reproducing one signal recording surface from both surfaces is complicated since it is necessary to turn over the disc when reproducing one signal recording surface after reproducing the other signal recording surface. It is. Further, it is impossible to immediately reproduce another signal recording surface while reproducing one signal recording surface. For this reason, a method of reproducing two signal recording surfaces from one surface has become mainstream.

  As shown in FIG. 14, a single-sided reading dual-layer optical disc has a reflective recording layer 101 made of aluminum or the like and having a reflectance of 70% or more, and a reflectance of about 30% made of gold or the like. And an ultraviolet curable resin having a thickness of about 40 μm is sandwiched between the two recording layers 1 and 2 as an intermediate layer 103. Here, information as shown in FIG. 15 is recorded on each of the reflective recording layer 101 and the translucent recording layer 102. That is, the information includes data and ID, and the ID includes an address (track number), layer information (layer number), and track information (track format information, area information, track method, reflectance).

  As described above, in a two-layer optical disc, one of the recording layers is of a translucent type. Therefore, by irradiating a laser beam from one side direction to focus on each of the recording layers, the information recorded on the recording layer is optically reflected. It can be read through a pickup device.

In the case of a two-layer optical disc, the objective lens is moved in the direction of the optical axis in order to refocus the laser beam on the other recording layer during reproduction of one recording layer and start reproduction of the other recording layer. A so-called focus jump is performed (Patent Document 1).
JP-A-8-171731 Kishi Shunno et al., "Single-sided reading double-layer optical disk", National Technical Report Vol. 41, No. Pages 6, 10-16, December 1995

  However, in the conventional focus jump method, a target address is sought after a focus jump, so that there is a problem that an access time becomes long.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk device capable of shortening a seek time to a target address.

  According to an aspect of the present invention, an optical disc apparatus for reproducing an optical disc having information recorded on a plurality of signal recording surfaces of a plurality of layers includes an information reading means for irradiating the optical disc with a beam and detecting the reflected light to read the information. Driving means for moving the information reading means along the signal recording surface; and, when the information reading means is focused on one of the signal recording surfaces of the plurality of layers, the signal recording surface of another layer. An accelerating means for generating an accelerating signal for focusing on a target address and information of a current address and a layer from which the information reading means is reading information in response to information of a target address and a target layer Calculating means for calculating the amount of movement of the information reading means from the information reading means, and driving the driving means so that the information reading means moves by the calculated amount of movement, and generating an acceleration signal from the accelerating means. It constituted a control means for focusing on the signal recording surface of the layer of interest given to.

  In the optical disk device according to the present invention, in response to the target address and layer information being given, the movement amount is calculated from the current address and layer information, and the information reading means is moved by the calculated movement amount. Since the driving means is driven as described above, the acceleration signal is generated to focus on the signal recording surface of the target layer, so that the access time can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions have the same reference characters allotted, and description thereof will not be repeated.

  In order to reproduce information from two signal recording surfaces by irradiating a laser beam from one surface of an optical disc, focus on an objective lens during optical pickup during reproduction of one signal recording surface or after reproduction on another signal recording surface Need to be redone. In the conventional method, when refocusing from one signal recording surface to another signal recording surface, the objective lens is decelerated when a focus error signal from another signal recording surface starts to be observed. However, as shown in FIG. 1, the transition period Ttran from one signal recording surface to another signal recording surface includes approximately 10% noise when the difference is larger than the difference between the peak values of the focus error signal FE. Have been. Therefore, it is difficult to accurately determine whether or not the detected signal is the focus error signal FE from the signal recording surface to be reproduced, and an accurate focus jump cannot be performed.

  Therefore, the embodiment of the present invention is mainly used for reproducing information from a two-layer optical disk having two signal recording surfaces using an optical pickup capable of compatible reproduction of optical disks having different substrate thicknesses. It is an object of the present invention to provide an optical disk device capable of accurately switching a focal position from one signal recording surface to another signal recording surface.

  Referring to FIG. 2, double-layer DVD 1 has two signal recording surfaces 5, 9 at a position of 0.6 (allowable error ± 0.05) mm from the substrate surface. The two-layer DVD 1 is formed by bonding substrates 2 and 10 made of transparent polycarbonate or the like and having a thickness of 0.6 (tolerance error ± 0.05) mm with an ultraviolet curing resin 6. The signal recording surface 5 includes pits 3 formed inside the substrate 2 and a metal reflection film 4 formed so as to cover the pits 3. The signal recording surface 9 includes pits 7 formed inside the substrate 10 and a metal reflection film 8 formed so as to cover the pits 7. Since the thickness of the ultraviolet curing resin 6 is 40 to 70 μm, the signal recording surface 5 is separated from the signal recording surface 9 by a distance of 40 to 70 μm.

  Referring to FIG. 3, CD 20 has one signal recording surface 24 at a position of 1.2 (allowable error ± 0.1) mm from the substrate surface. The signal recording surface 24 includes pits 22 formed on one side of a substrate 21 made of transparent polycarbonate or the like, and a metal reflection film 23 formed so as to cover the pits 22. On the signal recording surface 24, a protective film 25 is formed.

  Table 1 below shows the rated values and reproduction conditions of CDs and double-layer DVDs.

  The substrate thickness on the signal reading surface side of the CD is 1.2 (allowable range: 1.1 to 1.3) mm, and the shortest pit length is 0.90 (allowable range: 0.80 to 1.0) μm. The track pitch is 1.6 (allowable range: 1.5 to 1.7) μm, and the reflectance is 70% or more. On the other hand, the substrate thickness on the signal reading surface side of the dual-layer DVD is 0.6 (allowable range: 0.55 to 0.65) mm, and the shortest pit length is 0.40 (allowable range: 0.30 to 0.35 mm). 50) μm, the track pitch is 0.74 (allowable range: 0.73 to 0.75) μm, and the reflectivity is 20 to 40%.

  In the reproduction condition, the wavelength of the laser beam is 635 (allowable range: 620 to 650) nm, and the spot diameter of the laser beam on the CD is 1.5 (allowable range: 1.4 to 1.6) μm. The effective numerical aperture of the objective lens is 0.35 (allowable range: 0.30 to 0.40), and the spot diameter of the laser beam in the dual-layer DVD is 0.9 (allowable range: 0.85 to 0.95). ) Μm, and the effective numerical aperture of the objective lens is 0.60 (allowable range: 0.55 to 0.65).

  4 and 5 show a configuration of an optical pickup capable of compatible reproduction of a CD and a double-layer DVD. 4 and 5, an optical pickup 60 includes a semiconductor laser 31 that generates a laser beam having a wavelength of 635 nm, a polarization plane rotation element 32 that rotates the polarization plane of the laser beam, a diffraction grating 35, and a half mirror. 36, a collimator lens 37, a polarization selection element 38 for selectively blocking a laser beam, an objective lens 42, and a photodetector 43. The laser beam from the semiconductor laser 31 reaches the half mirror 36 via the polarization plane rotating element 32 and the diffraction grating 35, is half-reflected by the half mirror 36, is converted into parallel light by the collimator lens 37, and is raised by the rising mirror 144. Then, the light passes through the polarization selection element 38, is condensed by the objective lens 42, and irradiates the signal recording surface 5 through the substrate of the optical disk. The laser beam reflected by the signal recording surface 5 returns to the half mirror 36 via the objective lens 42, the polarization selection element 38, and the collimator lens 37, is transmitted half by the half mirror 36, and is focused on the photodetector 43. , Will be detected.

  The photodetector 43 is divided into four light receiving surfaces a to d, a + b + c + d is output as a reproduction signal, and (a + c)-(b + d) is output as a focus error signal.

  The objective lens 42 is designed to be able to collect light on the signal recording surface of an optical disk having a substrate thickness of 0.6 mm, and has a numerical aperture of 0.6 (allowable range: 0.55 to 0.65). The polarization plane rotation element 32 has a structure in which a TN type liquid crystal 34 is sandwiched between two sheets of glass with transparent electrodes 33 and 33. When a voltage is applied to the transparent electrode, a voltage is applied to the TN type liquid crystal 34 and a laser beam is applied. Transmits through the TN type liquid crystal 34 without rotating its polarization plane. When no voltage is applied to the transparent electrode, the laser beam has its polarization plane rotated by 90 ° and passes through the TN liquid crystal.

  The polarization selection element 38 has a structure in which a polarization filter 40 provided at a portion corresponding to the outer periphery of a laser beam is sandwiched between two glasses 39 and 39. Are provided. The polarizing filter 40 has a property of transmitting only a laser beam in a predetermined polarization direction, and in FIG. 4, transmits only a laser beam polarized in a direction parallel to the paper. Therefore, the polarization selection element 38 has characteristics as shown in FIG. In other words, the outer peripheral portion 38a of the polarization selecting element 38 allows the polarization filter 40 to transmit only the laser beam polarized in the horizontal direction in the drawing, and the inner peripheral portion 38b transmits the laser beam regardless of the polarization direction of the laser beam. The polarizing filter 40 transmits a laser beam polarized in a horizontal direction, and its transmittance is about 70 to 90%. Therefore, if no filter is provided in the inner peripheral portion 38b, the transmittance is different between the inner peripheral portion and the outer peripheral portion of the laser beam, which is a factor of deteriorating the reproduction characteristics. Therefore, it is necessary to provide the filter 41 on the inner periphery of the polarization selection element 38.

  A reproduction operation of a dual-layer DVD having a substrate thickness of 0.6 mm on the signal reading surface side will be described. When a two-layer DVD is reproduced, a voltage is applied to the polarization plane rotation element 32 from the liquid crystal drive circuit 44. As a result, the laser beam having a wavelength of 635 nm from the semiconductor laser 31 and polarized in a direction parallel to the plane of the drawing is transmitted as it is without rotating the polarization plane by the polarization plane rotation element 32, and the half mirror 36 is transmitted through the diffraction grating 35. Incident on. The incident laser beam is half-reflected by the half mirror 36, converted into parallel light by the collimator lens 37, transmitted through the entire surface without being shielded by the polarization selecting element 38, and condensed by the objective lens 42. Irradiate the signal recording surface 5 through the substrate 2 of the dual-layer DVD 1. The spot diameter of the laser beam applied to the signal recording surface 5 is 0.9 μm (allowable range: 0.80 to 1.0) μm. Subsequent operations are the same as those described with reference to FIG. 3, and thus description thereof will not be repeated.

  Next, a reproducing operation of a CD having a substrate thickness of 1.2 mm on the signal reading side will be described. When a CD is reproduced, no voltage is applied to the polarization plane rotating element 32. As a result, the laser beam having a wavelength of 635 nm from the semiconductor laser 31 and polarized in a direction parallel to the plane of the paper is transmitted with the polarization plane rotated by 90 ° by the polarization plane rotation element 32 and transmitted through the diffraction grating. Incident on. The incident laser beam is half-reflected by the half mirror 36, converted into parallel light by the collimator lens 37, only the outer periphery is shielded by the polarization selecting element 38, condensed by the objective lens 42, and passes through the substrate 21 of the CD 20. The signal recording surface 24 is irradiated. The diameter of the inner peripheral portion 38b of the polarization selecting element 38 has a numerical aperture of 0.6 (permissible range: 0.55 to 0.65). In the case of an objective lens having an effective light beam diameter of 4 mm, the effective numerical aperture is 0.35 (permissible). The range is set to 2.3 (allowable error ± 0.2) mm so that the range is 0.30 to 0.40). When the effective light beam diameter is other than 4 mm, the diameter of the inner peripheral portion 38b is determined so that the effective numerical aperture becomes 0.35 in proportion to this. The spot diameter of the laser beam applied to the signal recording surface 24 is 1.5 μm (permissible range: 1.4 to 1.6). Subsequent operations are the same as those described with reference to FIG. 3, and thus description thereof will not be repeated.

  With reference to FIG. 7, an optical disk device capable of compatible reproduction of optical disks having different substrate thicknesses will be described. The objective lens 42 in the optical pickup 60 is controlled so that the signal to be reproduced by the actuator 47 is focused on a track formed as a pit row, and the laser beam is focused by the objective lens 42. The signal is irradiated on the signal recording surface 5 through the substrate 2 of the optical disk. The laser beam reflected by the signal recording surface 5 is detected by the photodetector 43 and detected as a reproduction signal. The reproduced signal detected by the photodetector 43 is sent to a head amplifier 45, and after a predetermined amplification, sent to a discrimination circuit 48, an RF demodulation circuit 53, and a servo circuit 46. The servo circuit 46 controls the actuator 47 based on the sent tracking error signal. Further, the discrimination circuit 48 identifies the type of the optical disc mounted on the reproducing apparatus based on the transmitted signal, and sends the identification result to the command circuit 49. The command circuit 49 issues a command to the NA switching circuit 50 based on the identification result sent to switch the numerical aperture of the objective lens 42 so as to match the identified optical disk. In addition, the command circuit 49 also issues a command to the characteristic switching circuit 51 based on the received identification result in order to switch to a demodulation circuit suitable for reproducing the identified optical disc. The NA switching circuit 50 switches the effective numerical aperture of the objective lens 42 via the liquid crystal driving circuit 44, and the characteristic switching circuit 51 switches the RF demodulation circuit 53.

  FIG. 8 is a block diagram showing the overall configuration of the optical disk device according to the present embodiment centering on the focus jump circuit 46a in the servo circuit 46 shown in FIG. Referring to FIG. 8, single-sided reading dual-layer DVD 1 is driven to rotate by spindle motor 16, and information recorded on disc 1 is read by pickup 60. A signal such as a focus error signal FE is output from the pickup 60, amplified by the head amplifier 45, supplied to the A / D converter 54, and converted from an analog signal to a digital signal. This digital signal is provided to a DSP (digital signal processor) 55.

  A ROM 56 and a RAM 57 are connected to the DSP 55. The ROM 56 stores a program for controlling the DSP 55, and the RAM 57 stores information obtained from the disk 1. The DSP 55 executes a program stored in the ROM 56, performs control for performing focus servo of the pickup 60 with an acceleration signal or a deceleration signal based on information stored in the RAM 57, and controls for seeking the pickup 60. Perform The DSP 55 outputs a digital signal for controlling the focus jump to the D / A converter 58, and the D / A converter 58 converts the digital signal into an analog signal and supplies the analog signal to the driver 59. The driver 59 controls the pickup 60 based on the acceleration signal and the deceleration signal.

  Further, the DSP 55 outputs a PWM (Pulse Wide Modulation) signal for seeking the pickup 60 and supplies the PWM signal to the integrator 11. The integrator 11 integrates the PWM signal and supplies it to the driver 12 as a thread drive signal. The driver 12 drives the feed mechanism 13 by the thread drive signal to cause the pickup 60 to seek.

  As shown in FIG. 9, the actuator 47 is attached to a lens holder 701 for holding the objective lens 42, a focus coil 702 wound around the lens holder 701, and both end surfaces of the focus coil 702 in the Y direction. Tracking coils 703a and 703b, four leaf springs 704 attached to both end surfaces in the X direction of the lens holder 701, a fixing base 705 supporting the leaf spring 704, and two concave portions 706 of the lens holder 701, respectively. A yoke 707, a permanent magnet 708 for applying a magnetic field perpendicular to the focus coil 702 and the tracking coils 703a and 703b, a yoke 709 for supporting the permanent magnet 708, and a yoke base 710 for supporting the yokes 707 and 709. Including.

  The driver 59 shown in FIG. 8 generates a focus drive voltage in response to the focus error signal, and the generated focus drive voltage is applied to the focus coil 702. Thereby, the lens holder 701 moves in the Z (optical axis) direction so that the laser beam is focused on the first recording layer 5 or the second recording layer 9 of the two-layer optical disc 1. The driver 59 further generates a tracking drive voltage in response to the tracking error signal TE, and the generated tracking drive voltage is applied to the tracking coils 703a and 703b. Thus, the lens holder 701 moves in the X (tracking) direction so that the laser beam is always irradiated on the track of the optical disc 1.

  The driver 59 includes a resistor 61, a capacitor 63, a switch 65, and an amplifier 62, as shown in FIG. When performing the focusing servo control, the switch 65 is on the terminal 66 side, and the focus error signal FE is directly supplied to the non-inverting input terminal of the amplifier 62. Therefore, the amplifier 62 supplies the focus drive voltage to the focus coil 702 in response to the focus error signal FE, and moves the objective lens 42 in the Z direction by the actuator 47. On the other hand, when performing a focus jump, the switch 65 is on the terminal 67 side, and the voltage of the connection node between the resistor 61 and the capacitor 63 is applied to the non-inverting input terminal of the amplifier 62. At the same time, a focus jump instruction signal JP for instructing to perform a focus jump is applied to the inverting input terminal of the amplifier 62.

  In a conventional optical disk device, when an address of a target destination and target layer information are given, a focus jump is first performed from a current layer to a target layer, and then a target address is sought by a pickup feed mechanism. Is controlled.

  However, since DVDs are capable of high-density recording, they are likely to be used as computer memories in the future, and it is necessary to access target addresses as soon as possible. However, in the conventional method, since the control is performed so as to seek the target address after the focus jump, there is a problem that the time for access becomes long.

  Therefore, an embodiment of the present invention aims to provide an optical disk apparatus which can shorten the access time by simultaneously performing a focus jump and a seek to a target address.

  FIG. 11 is a flowchart for explaining the operation of the optical disk apparatus shown in FIG. 8, and FIGS. 12 and 13 are diagrams for explaining an operation for seeking a focus jump and a target address in the embodiment of the present invention. It is. Note that the ROM 56 shown in FIG. 8 stores a focus jump routine program as shown in FIG.

  Next, a specific operation of the embodiment of the present invention will be described with reference to FIGS. 8, 11, 12, and 13. FIG. When the destination address of the disk 1 and the target layer information are given from the outside, the DSP 55 obtains the position and layer information addressed by the pickup 60 and calculates the movement amount from the current position to the destination. For example, as shown in FIG. 12, when the pickup 60 focuses on the point a2 of the translucent recording layer 102, and a command for focusing on the point a1 of the reflective recording layer 101 is given by an external command. , The movement amount from the point a2 to the point a1 is calculated, and the DSP 55 turns off the power supply to the tracking coils 703a and 703b shown in FIG. 9, and then outputs a PWM signal to the integrator 11, which outputs the PWM signal to the integrator 11. The PWM signal is integrated, and a thread drive signal as shown in FIG. The driver 12 drives the feed mechanism 13 according to the thread drive signal. Thereby, the pickup 60 starts moving by the feed mechanism 13.

  The DSP outputs a focus error signal FE to the D / A converter 58 simultaneously with the output of the PWM signal. The focus error signal FE is converted into an analog signal by the D / A converter 58 and is provided to the driver 59. The driver 59 starts the focus jump start of the pickup 60 by the focus error signal FE of the analog signal. As a result, the pickup 60 moves from the translucent recording layer 102 as the first layer to the reflective recording layer 101 as the second layer, and ends the focus jump.

  At this time, the DSP 55 determines whether or not the pickup 60 has reached the point a1 of the reflective recording layer 101. If not, the DSP 55 continues to output the thread drive signal. Then, when the pickup 60 reaches the vicinity of the target address, the movement by the feed mechanism 13 is terminated, the track jumps to the designated track of the reflective recording layer 101, and the tracking is turned on to reach the target address. I do.

  As described above, according to this embodiment, the pickup jumps from the first layer to the second layer based on the focus error signal FE while seeking the target of the pickup 60 by the sled drive signal. As a result, the access time can be reduced, and the value of the computer as a memory can be increased.

  As described above, according to this embodiment, in response to the target address and layer information being given, the movement amount is calculated from the current address and layer information, and the information is calculated by the calculated movement amount. Since the driving means is driven to move the reading means and the acceleration signal is generated to focus on the signal recording surface of the target layer, the access time can be reduced.

  The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description of the embodiments, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  INDUSTRIAL APPLICABILITY The present invention is applied to an optical disk device capable of reducing a seek time to a target address.

FIG. 9 is a waveform diagram of a focus error signal obtained when the focal point of the objective lens is moved over two signal recording surfaces. It is sectional drawing which shows the structure of a two-layer DVD. It is sectional drawing which shows the structure of CD. FIG. 2 is a diagram illustrating a configuration of an optical pickup capable of compatible reproduction of optical disks having different substrate thicknesses. FIG. 5 is a perspective view illustrating a structure of the optical pickup illustrated in FIG. 4. FIG. 6 is a plan view illustrating polarization characteristics of the polarization selection element illustrated in FIG. 5. FIG. 6 is a block diagram illustrating an overall configuration of an optical disc device including the optical pickup illustrated in FIGS. 4 and 5. FIG. 2 is a block diagram showing the overall configuration of the optical disc device according to the embodiment. FIG. 8 is an exploded perspective view illustrating a structure of the actuator illustrated in FIG. 7. FIG. 8 is a circuit diagram illustrating a focus jump circuit illustrated in FIG. 7. 9 is a flowchart for explaining the operation of the optical disk device shown in FIG. FIG. 9 is a diagram for explaining a focus jump and a seek operation of a target address in the optical disc device shown in FIG. 8. FIG. 13 is a timing chart showing a focus error signal and a sled drive signal during the operation shown in FIG. 12. FIG. 2 is a cross-sectional view showing a schematic structure of a single-sided reading dual-layer disc. FIG. 15 is a diagram showing information recorded on the single-sided reading dual-layer disc shown in FIG. 14.

Explanation of reference numerals

  1 Double-layer DVD, 2, 10, 21 substrate, 3, 7, 22 pits, 4, 8, 23 metal reflection film, 5, 9, 24 signal recording surface, 6 UV curable resin, 11 integrator, 12, 59 driver , 13 feed mechanism, 16 spindle motor, 20 CD, 25 protective film, 31 semiconductor laser, 32 polarization plane rotation element, 33 glass with transparent electrode, 34 TN type liquid crystal, 35 diffraction grating, 36 half mirror, 37 collimator lens, 38 Polarization selection element, 38a outer circumference, 38b inner circumference, 39 glass, 40 polarization filter, 41 filter, 42 objective lens, 43 photodetector, 44 liquid crystal drive circuit, 45 head amplifier, 46 servo circuit, 46a focus jump circuit, 47 actuator, 48 discriminating circuit, 49 command circuit, 50 NA switching circuit, 51 characteristics off Circuit, 53 RF demodulation circuit, 54 A / D converter, 55 DSP, 56 ROM, 57 RAM, 58 D / A converter, 60 optical pickup, 61 resistor, 62 amplifier, 63 capacitor, 65 switch, 66, 67 Terminal, 101 reflective recording layer, 102 translucent recording layer, 103 intermediate layer, 144 rising mirror, 701 lens holder, 702 focus coil, 703a, 703b tracking coil, 704 leaf spring, 705 fixing base, 706 recess, 707 , 709 yoke, 708 permanent magnet, 710 yoke base.

Claims (1)

An optical disc device for reproducing an optical disc having information recorded on signal recording surfaces of a plurality of layers,
Irradiating the optical disk with a beam, and information reading means for reading the information by detecting reflected light thereof;
Driving means for moving the information reading means along the signal recording surface;
When the information readout unit is focused on any one of the signal recording surfaces of the plurality of layers, an acceleration unit that generates an acceleration signal for focusing on the signal recording surface of another layer,
Arithmetic means for calculating the amount of movement of the information reading means from the current address and the information of the layer from which the information reading means is reading information, in response to the target address and the information of the target layer being given. When,
The driving means is driven so that the information reading means moves by the movement amount calculated by the calculating means, and an acceleration signal is generated from the acceleration means and given to the information reading means to provide a signal of a target layer. An optical disc device comprising: a control unit for focusing on a recording surface.

Images