JP2008226317A - Optical disk reproducing device and disk discriminating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disk reproducing device which accurately detects the number of layers of a recording surface in a multilayer disk with a predetermined specification. <P>SOLUTION: The disk reproducing device for reproducing an optical disk medium 90 including: a plurality of recording layers with one and the same specification; and an optical system 11, counts the number of S-shaped curves of an FE (Focus Error) signal while reducing the influence of spherical aberration that changes in accordance with the position of an objective lens 11h by controlling a liquid crystal shutter 11g for moving the objective lens 11h from one side of its movable limit to the other. The number of layers of the recording surface provided in the optical disk medium 90 is detected according to the counted number of S-shaped curves of the FE signal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a disc playback apparatus and a disc discrimination method.

  At present, in order to increase the capacity of the disk medium, the recording layer is multilayered and the laser wavelength is shortened along with the improvement of the recording density. Under such circumstances, there is a BD (Blue-ray Disc) standard as a next-generation optical disk standard, and commercialization of a BD standard disk playback device and optical disk medium is being promoted.

The disk reproducing device needs to determine the type when reproducing the optical disk medium. As an example of this discrimination method, the objective lens is raised and lowered in the laser irradiation state, a focus error signal (hereinafter referred to as FE signal) obtained from the return light from the optical disk medium is detected, and the laser focus passes through the recording surface of the optical disk medium. Thus, there is a method for detecting an S-shaped curve appearing in the FE signal. (For example, see Patent Document 1)
JP 2004-146016 A

  The objective lens of a BD disc reproducing apparatus has a large NA (Numerical Aperture) and is likely to generate spherical aberration. For this reason, in the technique of Patent Document 1, there is a layer in which the amplitude of the S-curve appearing in the FE signal is small, and the number of layers on the recording surface cannot be accurately detected.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a disc reproducing apparatus and disc discriminating method capable of accurately detecting the number of layers of a recording surface in a multilayer disc of a predetermined standard.

In order to achieve the above object, a disc playback apparatus according to the first aspect of the present invention provides:
A disc playback apparatus for playing back an optical disc medium including a plurality of recording surfaces,
Irradiating means for irradiating laser light;
Electrical signal conversion means for receiving laser light and converting it into an electrical signal;
An optical system that includes an objective lens, condenses the laser light emitted by the irradiating means onto the optical disc medium via the objective lens, and guides reflected light from the optical disc medium to the electrical signal converting means via the objective lens The system,
Error signal conversion means for converting the electric signal converted by the electric signal conversion means into a focus error signal;
S-curve detection means for detecting the S-curve of the signal level of the focus error signal converted by the error signal conversion means;
An objective lens moving means for moving an objective lens included in the optical system in a focus direction;
Numerical aperture changing means for changing the numerical aperture of the optical system by reducing the beam diameter of the laser light incident on the objective lens;
By controlling the numerical aperture changing means, the beam diameter of the laser beam is reduced to control the numerical aperture of the optical system, and by controlling the objective lens moving means, the objective lens is moved within a predetermined range. Counting control means for determining the number of layers of the recording surface of the mounted optical disk medium by counting the number of S-curves detected by the S-curve detection means in between;
It is characterized by comprising.

  For example, the counting control means controls the irradiating means, the objective lens moving means, and the numerical aperture changing means so that the irradiating means irradiates the objective lens with a predetermined range. By moving and changing the numerical aperture of the optical system by reducing the beam diameter of the laser light according to the position of the objective lens, and counting the number of S-curves detected by the S-curve detecting means, The number of layers on the recording surface of the mounted optical disk medium is obtained.

  For example, the counting control unit controls the numerical aperture changing unit to reduce the beam diameter of the laser light, thereby changing the beam diameter to a numerical aperture that can be detected by all recording surfaces of the optical disc medium to be detected. The objective lens is moved within a predetermined range by controlling the objective lens moving means, and the number of S-curves detected by the S-curve detecting means is counted during the recording of the mounted optical disk medium. Find the number of layers on the face.

  For example, the numerical aperture changing means includes shutter driving means for changing the beam diameter of the laser light incident on the objective lens by driving the liquid crystal shutter according to the control of the liquid crystal shutter and the counting control means.

  For example, the numerical aperture changing means controls the open / close shutter to change the numerical aperture of the optical system by changing the beam diameter of the laser light incident on the objective lens.

In order to achieve the above object, a disc discrimination method according to a second aspect of the present invention includes:
An optical system including an objective lens is provided. Laser light is irradiated by the optical system, and is condensed on an optical disk medium including a plurality of recording surfaces via the objective lens. A disc discriminating method of a disc reproducing apparatus for collecting the reflected light from the disc and reproducing the optical disc medium,
An electrical signal converting step of receiving the reflected light and converting it into an electrical signal;
An error signal conversion step of converting the electric signal converted in the electric signal conversion step into a focus error signal;
An S-curve detection step for detecting an S-curve of the signal level of the focus error signal converted in the error signal conversion step;
An objective lens moving step of moving the objective lens included in the optical system in the focus direction;
A numerical aperture control step for controlling the numerical aperture of the optical system by narrowing the beam diameter of the laser light incident on the objective lens by a diaphragm;
While the laser beam is irradiated in the irradiation step, the numerical aperture is controlled by reducing the beam diameter of the laser beam by the aperture in the numerical aperture control step, and the objective lens is moved in a predetermined range by the movable lens moving step. A counting control step for determining the total number of recording surfaces of the optical disc mounted by counting the number of S-curves detected in the S-curve detection step during the movement;
Comprising
It is characterized by that.

  According to the present invention, the number of layers on the recording surface can be accurately detected in a multilayer disc of a predetermined standard.

(First embodiment)
Hereinafter, a disc playback apparatus 100 according to an embodiment of the present invention will be described. As shown in FIG. 1, the disk reproducing apparatus 100 includes an optical pickup 10, a signal generation circuit 20, a signal processing circuit 30, a control unit 40, a focus / tracking driver circuit 50, a spindle motor driver circuit 60, and a liquid crystal shutter driver circuit 70. And a spindle motor 80. However, an APC (Automatic Power Control) circuit for controlling the laser beam is omitted for simplicity. Further, the disc playback apparatus 100 loads the optical disc medium 90 and reads the recorded information.

  The optical pickup 10 irradiates the optical disk medium 90 with laser light, converts the reflected signal into an electric signal, and supplies the electric signal to the signal generation circuit 20. As shown in FIG. 1, the optical pickup 10 includes an optical system 11 and a focus / tracking actuator 12.

  As shown in FIG. 2, the optical system 11 includes an LD (Laser Diode) 11a, a collimator lens 11b, a beam shaping prism 11c, a polarizing beam splitter 11d, and a light receiving element for APC (Automatic Power Control) arranged on the optical axis. 11e, a quarter-wave plate 11f, a liquid crystal shutter 11g, an objective lens 11h, a polarizing beam splitter 11i, a light receiving element 11j, and a light receiving element 11k.

  The LD (Laser Diode) 11a is a light source that irradiates a blue-violet semiconductor laser for BD having a wavelength of 405 nm.

  The collimator lens 11b collimates the laser light emitted from the LD 11a.

  The beam shaping prism 11c shapes the laser beam collimated by the collimator lens 11b from an elliptical beam to a circular beam.

  The polarization beam splitter 11d transmits a part of the laser light emitted from the LD 11a, supplies it to the quarter-wave plate 11f, reflects a part thereof, and supplies it to the APC light receiving element 11e. The polarization beam splitter 11d reflects part of the laser light reflected by the optical disk medium 90 and supplies the reflected laser beam to the polarization beam splitter 11k.

  The APC light receiving element 11e collects the laser beam reflected by the polarization beam splitter 11d and converts it into an electrical signal. The converted electrical signal is used to adjust the laser output of the LD 11a. Here, the mechanism for adjusting the laser output is omitted.

  The quarter wavelength plate 11f converts the laser light transmitted through the polarization beam splitter 11d from linearly polarized light to circularly polarized light.

  As shown in FIG. 3E, the liquid crystal shutter 11g includes four shutters 111a to 111d formed concentrically with outer diameters d1 to d4. Each of the four shutters 111a to 111d has a normally-off configuration (light blocking when no voltage is applied), and when a predetermined voltage is applied between the transparent electrodes facing each other across the liquid crystal layer (liquid crystal layer), It changes to a light transmission state. As shown in FIGS. 3A to 3D, a reference (common) voltage Vr is applied to one of the electrodes facing each other across the liquid crystal layer, and the other electrode corresponds to the on / off state of the shutter. A voltage is applied.

More specifically, as shown in FIG. 3A, the liquid crystal shutter driver circuit 70 applies the voltages Vr and V1 + Vr to the electrodes constituting the shutter 111a, applies the voltage V1 to the liquid crystal, and the shutter 111b. When the voltages Vr and Vr are applied to the electrodes constituting .about.111d and the voltage “0” is applied to the liquid crystal layer, the shutter 111a is opened and the shutters 111b to 111d are closed. For this reason, the liquid crystal shutter 11g narrows the incident laser beam to the beam diameter d1. The laser beam focused to the beam diameter d1 is condensed by the objective lens 11h and focused. At this time, the beam diameter d1 is selected and designed so that the numerical aperture NA is 0.45 which is the same value as the numerical aperture of the CD standard.
That is, the light beam diameter d1 is selected and designed so that NA = n × sin θ ₁ = 0.45.
Here, n is 1 which is the refractive index of air, and θ ₁ is the maximum angle with respect to the optical axis of the incident light beam.

Next, as shown in FIG. 3B, the liquid crystal shutter driver circuit 70 applies the voltage V1 to the liquid crystal constituting the shutter 111a, applies the voltage V2 to the liquid crystal constituting the shutter 111b, and the shutters 111c, 111d. When a voltage “0” is applied to the liquid crystal forming the shutter, the shutters 111a and 111b are opened, and the shutters 111c and 111d are closed. For this reason, the liquid crystal shutter 11g narrows the incident laser light to the light beam diameter d2. The laser beam focused to the beam diameter d2 is condensed by the objective lens 11h and focused. At this time, the light beam diameter d1 is selected and designed so that the numerical aperture NA is 0.6, which is the same as the numerical aperture of the DVD standard.
That is, the beam diameter d2 is designed so that NA = n × sin θ ₂ = 0.6. As described above, n is 1 which is the refractive index of air, and θ ₂ is the maximum angle with respect to the optical axis of the incident light beam.

Next, as shown in FIG. 3C, the liquid crystal shutter driver circuit 70 applies the voltage V1 to the liquid crystal composing the shutter 111a, and applies the voltage V2 to the liquid crystal composing the shutter 111b, thereby constructing the shutter 111c. When the voltage V3 is applied to the liquid crystal to be applied and the voltage “0” is applied to the liquid crystal constituting the shutter 111d, the shutters 111a to 111c are opened and the shutter 111d is closed. For this reason, the liquid crystal shutter 11g restricts the incident laser light to the light beam diameter d3. The laser beam focused to the beam diameter d3 is condensed by the objective lens 11h and focused. At this time, the light beam diameter d3 is selected and designed so that the numerical aperture NA is 0.7, which is the same as the numerical aperture of the DVD standard.
That is, the beam diameter d3 is designed so that NA = n × sin θ ₃ = 0.7. As described above, n is 1 which is the refractive index of air, and θ ₃ is the maximum angle with respect to the optical axis of the incident light beam.

Further, as shown in FIG. 3D, when the liquid crystal shutter driver circuit 70 applies voltages V1 to V4 to the liquid crystals constituting the shutters 111a to 111d, the shutters 111a to 111d are opened. For this reason, the liquid crystal shutter 11g transmits all the incident laser light. The light beam diameter at this time is the light beam diameter d4. The laser beam is focused by the objective lens 11h and focused. At this time, the light beam diameter d4 is selected and designed so that the numerical aperture NA is 0.85 which is the same value as the numerical aperture of the BD standard.
That is, the beam diameter d4 is designed so that NA = n × sin θ ₄ = 0.85. As described above, n is the refractive index of air 1, and θ ₄ is the maximum angle with respect to the optical axis of the incident light beam.

  The objective lens 11h condenses the laser light emitted from the LD 11a on the recording surface of the optical disc medium 90. The objective lens 11h is moved in the focus direction and the tracking direction by the focus / tracking actuator 12, and adjusts the focal position of the laser beam.

  The polarization beam splitter 11i transmits a part of the laser beam supplied from the polarization beam splitter 11d, supplies it to the light receiving element 11k, reflects a part thereof, and supplies it to the light receiving element 11j.

  The light receiving element 11j condenses the laser beam reflected by the polarization beam splitter 11i and converts it into an electric signal. The electrical signal converted by the light receiving element 11j is used to detect an FE (Focus Error) signal by the knife edge method.

  The light receiving element 11k condenses the laser light transmitted through the polarization beam splitter 11k and converts it into an electric signal. The electrical signal converted by the light receiving element 11m is used to detect an RF (Radio Frequency) signal and a push-pull TE (Tracking Error) signal.

  As the APC light receiving element 11e and the light receiving elements 11j and 11k, silicon PIN photodiodes optimized for receiving light with a wavelength of 405 nm and converting them into electrical signals are used.

  The focus / tracking actuator 12 moves the focal position of the laser light by driving the objective lens 11j in the focus direction and the tracking direction by the voltage supplied from the focus / tracking driver circuit 50.

  The signal generation circuit 20 decodes the electrical signal supplied from the optical pickup 10 and generates an RF signal, an FE signal, and a TE signal. Then, the RF signal is supplied to the demodulation circuit 32 of the signal processing circuit 30, and the FE signal and the TE signal are supplied to the phase compensation circuit 31 of the signal processing circuit 30.

  The signal processing circuit 30 performs processing on the RF signal, the FE signal, and the TE signal based on the control of the control unit 40. The signal processing circuit 30 includes a phase compensation circuit 31, a demodulation circuit 32, and a PLL (Phase Locked Loop) circuit 33.

  The phase compensation circuit 31 performs phase compensation on the FE signal and the TE signal supplied from the signal generation circuit 20 and generates an actuator control signal that controls the focal position of the laser light emitted from the optical pickup 10.

  The demodulation circuit 32 decodes the RF signal supplied from the signal generation circuit 20 and supplies the digital signal recorded on the optical disc medium 90 to the control unit 40. In addition, the demodulation circuit 32 extracts a synchronization signal included in the RF signal and supplies it to the PLL circuit 33.

  The PLL circuit 33 generates a spindle motor control signal corresponding to the phase difference between the synchronization signal supplied from the demodulation circuit 32 and the reference signal determined by the control unit 40.

  The control unit 40 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls the entire disk reproducing apparatus 100. For example, the control unit 40 supplies an aperture control signal to the liquid crystal shutter driver circuit 70 to control the opening of the liquid crystal shutter 11g in order to control the numerical aperture of the optical system by controlling the beam diameter of the laser light. . Further, the control unit 40 generates a stepping motor control signal and supplies it to the stepping motor driver circuit 60.

  The focus / tracking driver circuit 50 applies a voltage corresponding to the actuator control signal supplied from the phase compensation circuit 31 to operate the focus / tracking actuator 12 that drives the objective lens 11j of the optical pickup 10. To supply.

  The spindle motor driver circuit 60 supplies the spindle motor 80 with a voltage corresponding to the spindle motor control signal supplied from the PLL circuit 33 in order to drive the spindle motor 80.

  The liquid crystal shutter driver circuit 70 supplies a voltage corresponding to the liquid crystal shutter control signal supplied from the control unit 40 to the liquid crystal shutter 11g in order to control the liquid crystal shutter 11g.

  The spindle motor 80 is driven by the voltage supplied from the spindle motor driver circuit 70, and rotates the optical disk medium 90.

  The optical disk medium 90 is a BD standard disk, a DVD standard disk, a CD standard disk, or a hybrid disk thereof. Further, the recording surfaces of the BD standard and the DVD standard may be multilayered instead of one layer.

  For example, in the BD standard optical disc medium 90 (1) having a single layer structure shown in FIG. 4A, the distance from the disc surface 92 (1) to the BD recording surface 91 (1) is 0.1 mm. The thickness of itself is 1.2 mm. An BD standard optical disc medium 90 (2) having an eight-layer structure shown in FIG. 4B includes eight layers of BD recording surfaces L0 to L7 in a region 91 (2) from 75 μm to 100 μm from the disc surface 92 (2). . Further, like the other disks, the thickness of the disk is 1.2 mm.

  For example, FIG. 5A is a schematic diagram of a CD (Compact Disc) standard disc. In a CD disc, the distance from the disc surface 92 (3) to the recording surface 91 (3) is 1.2 mm, and the thickness of the disc itself is also 1.2 mm. FIG. 5B is a schematic diagram of a DVD (Digital Versatile Disc) standard disc. In a DVD disc, the distance from the disc surface 92 (4) to the recording surface 91 (4) is 0.6 mm, and the thickness of the disc itself is 1.2 mm. FIG. 5C is a schematic diagram of a hybrid disc having a BD layer, a DVD layer, and a CD layer. In this hybrid disc, the distance from the disc surface 92 (5) to the recording surface 91 (5a) of the BD layer is 0.1 mm, and from the surface 92 (5) to the recording surface 91 (5b) of the DVD layer. The distance is 0.6 mm, the distance from the surface 92 (5) to the recording surface 91 (5 c) of the CD layer is 1.2 mm, and the thickness of the disc itself is 1.2 mm. Further, the hybrid disk may have a plurality of BD layers and DVD layers.

  Next, with reference to FIG. 6, an outline of a mechanism for the disc reproducing apparatus 100 according to the first embodiment to detect the number of layers on the recording surface of the optical disc medium 90 will be described.

  The disc reproducing apparatus 100 irradiates the optical disc medium 90 with laser light while moving the objective lens 11h from the lower drive limit to the upper drive limit, generates an FE signal from the reflected light, and detects an S-curve from the FE signal. . This operation is called up search. (Conversely, the operation of detecting the S-curve while the objective lens 11h is moved from the upper drive limit to the lower drive limit is referred to as a down search.)

The disc reproducing apparatus 100 moves the objective lens 11h at a constant speed, performs an up search, and controls the optimal liquid crystal shutter 11g in order to suppress the influence of spherical aberration that changes with the up search. More specifically, the disc reproducing apparatus 100 controls the liquid crystal shutter 11g to set the numerical aperture to 0.70 at the time (time) t1 after the start of the up-search, and the liquid crystal during the period from the time t2 to the time t2. The shutter 11g is controlled to set the numerical aperture to 0.60, and the liquid crystal shutter 11g is controlled to set the numerical aperture to 0.45 from time t2 to time t3, which is the time for completing the up search. As a result, the disc reproducing apparatus 100 can detect the S-curve of the FE signal while reducing the influence of spherical aberration that changes with the up-search, and therefore can accurately count the number of layers on the recording surface.
Note that the times t1, t2, and t3 relate to the start position of the up-search and the moving speed of the objective lens so that any recording surface can be appropriately detected with respect to a plurality of types (standards) of the optical disc medium 90 to be detected. This is a value obtained in advance based on an experiment or the like.

  Here, the disk layer counting process performed by the disk reproducing apparatus 100 according to the first embodiment of the present invention will be described in detail with reference to the flowchart shown in FIG.

  First, when the optical disk medium 90 is loaded into the disk reproducing apparatus 100, the control unit 40 controls the spindle motor driver circuit 60 to start rotating the optical disk medium 90 at a predetermined rotation speed (step S101).

  The control unit 40 controls the focus / tracking driver circuit 50 to start the down sweep of the objective lens 11h (step S102).

  The control unit 40 determines whether or not the objective lens 11h has reached the drive lower limit (step S103).

  If it is determined that the objective lens 11h has not reached the drive lower limit (step S103; NO), the down sweep is continued and the process returns to step S103.

  When it is determined that the objective lens 11h has reached the drive lower limit (step S103; YES), the control unit 40 stops the down sweep of the objective lens 11h (step S104).

  The controller 40 irradiates the LD 11a with blue-violet laser light (step S105).

  The control unit 40 controls the liquid crystal shutter driver circuit 70 to set the numerical aperture to “0.70” (step S106), and sets “0” to the counter n in order to specify the number of layers on the recording surface of the optical disc medium 90. Substitute (step S107).

  The control unit 40 controls the focus / tracking driver circuit 50 to start up sweeping the objective lens 11h at a constant speed (step S108).

  The controller 40 determines whether or not the time t1 has elapsed since the start of the up sweep (step S109).

  If it is determined in step S109 that the time t1 has not elapsed since the start of the up sweep (step S109; NO), the control unit 40 determines whether or not a new S-curve has been detected in the FE signal. (Step S111).

  If it is determined in step S111 that an S-curve has been detected (step S111; YES), the control unit 40 adds “1” to the counter n (step S112), and the process returns to step S109.

  If it is determined in step S111 that no S-curve has been detected (step S111; NO), the process returns to step S109.

  If it is determined in step S109 that the time t1 has elapsed since the start of the up sweep (step S109; YES), the control unit 40 controls the liquid crystal shutter driver circuit 70 to set the numerical aperture to “0.60”. (Step S110).

  The control unit 40 determines whether or not the time t2 has elapsed since the start of the up sweep (step S113).

  If it is determined in step S113 that the time t2 has not elapsed since the start of the up sweep (step S113; NO), it is determined whether or not a new S-curve has been detected in the FE signal (step S115).

  If it is determined in step S115 that an S-curve has been detected (step S115; YES), the control unit 40 adds “1” to the counter n (step S116), and the process returns to step S113.

  If it is determined in step S115 that no S-curve has been detected (step S111; NO), the process returns to step S113.

  If it is determined in step S113 that the time t2 has elapsed since the start of the up sweep (step S113; YES), the control unit 40 controls the liquid crystal shutter driver circuit 70 to set the numerical aperture to “0.45”. (Step S114).

  The controller 40 determines whether or not a new S-curve has been detected in the FE signal (step S117).

  If it is determined in step S117 that an S-curve has not been detected (step S117; NO), the control unit 40 determines whether or not the objective lens 11h has reached the drive upper limit (step S121).

  If it is determined in step S121 that the objective lens 11h has reached the upper drive limit (step S121; YES), the disk layer counting process is terminated.

  If it is determined in step S121 that the objective lens 11h has not reached the upper drive limit (step S121; NO), the process returns to step S117.

  If it is determined in step S117 that an S-curve has been detected (step S117; YES), “1” is added to the counter n (step S118).

  The controller 40 determines whether or not a new S-curve has been detected in the FE signal (step S119).

  If it is determined in step S119 that an S-curve has been detected (step S119; YES), the process returns to step S118.

  If it is determined in step S119 that an S-curve has not been detected (step S119; NO), the control unit 40 determines whether or not the objective lens 11h has reached the upper drive limit (step S120).

  If it is determined in step S120 that the objective lens 11h has not reached the upper drive limit (step S120; NO), the process returns to step S119.

  If it is determined in step S120 that the objective lens 11h has reached the upper drive limit (step S120; YES), the disk layer counting process is terminated.

  According to the disk layer counting process of the first embodiment, the disk reproducing apparatus 100 compensates for spherical aberration by changing the numerical aperture in a stepwise manner in accordance with the focal position of the laser beam, and ensures the FE signal. The S-curve can be detected at, and the number of recording layers of the optical disk medium 90 can be accurately counted.

  Note that the numerical aperture may not only be changed stepwise, but may be changed continuously. For example, a dot matrix type liquid crystal panel is used as the liquid crystal shutter, and a transparent circle centering on the position of the optical axis of the optical system (area through which the laser beam can be transmitted) is displayed. Accordingly, display control may be performed so as to decrease gradually (continuously).

(Second Embodiment)
In the first embodiment, the disc reproducing apparatus 100 changes the numerical aperture stepwise according to the position of the objective lens 11h when performing an up search. However, depending on the recording surface of all the standards when performing the up search. The numerical aperture may be changed to a predetermined numerical aperture of 0.85 or less so that the S-curve of the FE signal can be detected, and the numerical aperture may be maintained regardless of the position of the objective lens 11h. The configuration of the second embodiment is the same as the configuration of the first embodiment.

  Next, a disk layer counting process performed by the disk playback apparatus 100 according to the second embodiment of the present invention will be described with reference to the flowchart shown in FIG.

  First, when the optical disk medium 90 is loaded in the disk reproducing apparatus 100, the control unit 40 controls the spindle motor driver circuit 60 to start rotating the optical disk medium 90 at a predetermined rotation speed (step S201).

  The control unit 40 controls the focus / tracking driver circuit 50 to start a down sweep of the objective lens 11h (step S202).

  The control unit 40 determines whether or not the objective lens 11h has reached the drive lower limit (step S203).

  If it is determined that the objective lens 11h has not reached the drive lower limit (step S203; NO), the down sweep is continued and the process returns to step S203.

  When it is determined that the objective lens 11h has reached the drive lower limit (step S203; YES), the control unit 40 stops the down sweep of the objective lens 11h (step S204).

  The control unit 40 irradiates the LD 11a with blue-violet laser light (step S205).

  The control unit 40 controls the liquid crystal shutter driver circuit 70 to set the numerical aperture to “0.60” (step S206).

  The control unit 40 assigns “0” to the counter n in order to specify the number of layers on the recording surface of the optical disc medium 90 (step S207).

  The control unit 40 controls the focus / tracking driver circuit 50 to start up sweeping of the objective lens 11h at a constant speed (step S208).

  The control unit 40 determines whether or not an S-curve has been detected in the FE signal (step S209).

  If it is determined in step S209 that an S-curve has not been detected (step S209; NO), the control unit 40 determines whether or not the objective lens 11h has reached the upper drive limit (step S213).

  If it is determined in step S213 that the objective lens 11h has reached the upper drive limit (step S213; YES), the disk layer counting process is terminated.

  If it is determined in step S213 that the objective lens 11h has not reached the upper drive limit (step S213; NO), the process returns to step S209.

  If it is determined in step S209 that an S-curve has been detected (step S209; YES), the control unit 40 adds “1” to the counter n (step S210).

  The controller 40 determines whether or not an S-curve has been detected in the FE signal (step S211).

  If it is determined in step S211 that an S-curve has been detected (step S211; YES), the process returns to step S210.

  If it is determined in step S211 that an S-shaped curve has not been detected (step S211; NO), the control unit 40 determines whether or not the objective lens 11h has reached the drive upper limit (step S212).

  If it is determined in step S212 that the objective lens 11h has not reached the upper drive limit (step S212; NO), the process returns to step S211.

  If it is determined in step S212 that the objective lens 11h has reached the upper drive limit (step S212; YES), the disk layer counting process is terminated.

  According to the disk layer counting process of the second embodiment, the disk reproducing apparatus 100 changes the numerical aperture to be able to detect the S-shaped curve by the recording surface of all the standards when performing an up search, and uses the numerical aperture for the FE. An S-curve can be detected in the signal, and the number of layers on the recording surface of the optical disk medium 90 can be accurately counted. Since it is not necessary to change the numerical aperture at the time of up-search, processing can be performed efficiently.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation and application are possible.

  In the first and second embodiments, the disk layer counting process is performed by the up search, but may be performed by the down search.

  In the first embodiment, the numerical aperture of the liquid crystal shutter 11g is changed to “0.45”, “0.60”, “0.70”, and “0.85”. However, the numerical aperture may be changed to another numerical aperture, or the numerical aperture may be changed more finely.

  In the first and second embodiments, the numerical aperture is changed using the liquid crystal shutter, but the numerical aperture may be changed using an open / close shutter.

  As described above, according to the present invention, it is possible to provide a disc reproducing apparatus suitable for detecting the number of layers of a multilayer disc.

It is a figure which shows the structure of the disc reproducing | regenerating apparatus concerning embodiment of this invention. It is a figure which shows the structure of the optical system of the optical pick-up shown in FIG. It is a figure which shows the structure and operation | movement of the liquid-crystal shutter of the optical system shown in FIG. (A) It is a schematic diagram of the liquid-crystal shutter when a numerical aperture is 0.45. (B) It is a schematic diagram of a liquid-crystal shutter when a numerical aperture is 0.60. (C) is a schematic diagram of a liquid crystal shutter when the numerical aperture is 0.70. (D) It is a schematic diagram of the liquid-crystal shutter in case a numerical aperture is 0.85. (E) It is a schematic diagram which shows the planar structure of a liquid-crystal shutter. (A) It is a figure which shows the structure of the BD disc of one layer. (B) It is a figure which shows an example of the structure of BD disc of 8 layers. (A) It is a figure which shows the structure of CD disk. (B) It is a figure which shows the structure of a DVD disc. (C) It is a figure which shows the structure of a BD / DVD / CD hybrid disc. It is the figure which showed the relationship between a focus position, the S curve in a FE signal, and a numerical aperture. It is a flowchart for demonstrating the disk layer count process of 1st Embodiment. It is a flowchart for demonstrating the disk layer count process of 2nd Embodiment.

Explanation of symbols

10 Optical Pickup 11 Optical System 11a LD (Laser Diode)
11b Collimator lens 11c Beam shaping prism 11d Polarizing beam splitter 11e APC light receiving element 11f 1/4 wavelength plate 11g Liquid crystal shutter 11h Objective lens 11i Polarizing beam splitter 11j Light receiving element 11k Light receiving element 12 Focus tracking actuator 20 Signal generation circuit 30 Signal processing Circuit 31 Phase compensation circuit 32 Demodulation circuit 33 PLL circuit 40 Control unit 50 Focus / tracking driver circuit 60 Spindle motor driver circuit 70 Liquid crystal shutter driver circuit 80 Spindle motor 90 Optical disc medium 100 Disc playback device

Claims (6)

A disc playback apparatus for playing back an optical disc medium including a plurality of recording surfaces,
Irradiating means for irradiating laser light;
Electrical signal conversion means for receiving laser light and converting it into an electrical signal;
An optical system that includes an objective lens, condenses the laser light emitted by the irradiating means onto the optical disc medium via the objective lens, and guides reflected light from the optical disc medium to the electrical signal converting means via the objective lens The system,
Error signal conversion means for converting the electric signal converted by the electric signal conversion means into a focus error signal;
S-curve detection means for detecting the S-curve of the signal level of the focus error signal converted by the error signal conversion means;
An objective lens moving means for moving an objective lens included in the optical system in a focus direction;
Numerical aperture changing means for changing the numerical aperture of the optical system by reducing the beam diameter of the laser light incident on the objective lens;
By controlling the numerical aperture changing means, the beam diameter of the laser beam is reduced to control the numerical aperture of the optical system, and by controlling the objective lens moving means, the objective lens is moved within a predetermined range. Counting control means for determining the number of layers of the recording surface of the mounted optical disk medium by counting the number of S-curves detected by the S-curve detection means in between;
A disc playback apparatus comprising: The counting control unit controls the irradiation unit, the objective lens moving unit, and the numerical aperture changing unit to move the objective lens within a predetermined range in a state where the irradiation unit is irradiated with laser light. At the same time, the diameter of the optical system is changed according to the position of the objective lens to change the numerical aperture of the optical system, and the number of S-curves detected by the S-curve detecting means is counted. The number of layers on the recording surface of an optical disc medium
2. The disc reproducing apparatus according to claim 1, wherein The counting control unit controls the numerical aperture changing unit to reduce the beam diameter of the laser light, thereby changing the beam diameter to a numerical aperture that can be detected by all recording surfaces of the optical disc medium to be detected, By controlling the objective lens moving means, the objective lens is moved within a predetermined range, and the number of S-curves detected by the S-curve detecting means during that time is counted to determine the recording surface of the mounted optical disk medium. Find the number of layers,
2. The disc reproducing apparatus according to claim 1, wherein The numerical aperture changing means includes shutter driving means for changing the beam diameter of the laser light incident on the objective lens by driving the liquid crystal shutter according to the control of the liquid crystal shutter and the counting control means.
4. The disc reproducing apparatus according to claim 1, wherein the disc reproducing apparatus is a disc reproducing apparatus. The numerical aperture changing means controls the open / close shutter and changes the numerical aperture of the optical system by changing the beam diameter of the laser light incident on the objective lens.
The disk reproducing apparatus according to claim 1, wherein the disk reproducing apparatus is a disk reproducing apparatus. An optical system including an objective lens is provided. Laser light is irradiated by the optical system, and is condensed on an optical disk medium including a plurality of recording surfaces via the objective lens. A disc discriminating method of a disc reproducing apparatus for collecting the reflected light from the disc and reproducing the optical disc medium,
An electrical signal converting step of receiving the reflected light and converting it into an electrical signal;
An error signal conversion step of converting the electric signal converted in the electric signal conversion step into a focus error signal;
An S-curve detection step for detecting an S-curve of the signal level of the focus error signal converted in the error signal conversion step;
An objective lens moving step of moving the objective lens included in the optical system in the focus direction;
A numerical aperture control step for controlling the numerical aperture of the optical system by narrowing the beam diameter of the laser light incident on the objective lens by a diaphragm;
While the laser beam is irradiated in the irradiation step, the numerical aperture is controlled by reducing the beam diameter of the laser beam by the aperture in the numerical aperture control step, and the objective lens is moved in a predetermined range by the movable lens moving step. A counting control step for determining the total number of recording surfaces of the optical disc mounted by counting the number of S-curves detected in the S-curve detection step during the movement;
Comprising
Disc discriminating method characterized by the above.

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