JP4296216B2 - FOCUS CONTROL DEVICE, FOCUS CONTROL METHOD, FOCUS CONTROL PROGRAM, AND RECORDING MEDIUM CONTAINING FOCUS CONTROL PROGRAM - Google Patents

Description

【Technical field】
[0001]
  The present application relates to a focus control field of an optical disc information recording / reproducing apparatus.
[Background]
[0002]
  Conventionally, as an optical disc such as a DVD (Digital Versatile Disc), an optical disc having two information layers such as an information recording layer for recording information or an information reproducing layer for reproducing information is known.
[0003]
  In these two-layer discs, when information is written to or read from the information layer, when the focus is drawn in the information layer, the focus is drawn from the information layer close to the position where the pickup exists. Therefore, even when information is written to or read from an information layer far from the position where the pickup is present, the focus is first drawn into the information layer near the position where the pickup is present, and the focus servo circuit is closed and the pickup is closed. The focus jump is performed to the information layer far from the position where the.
[0004]
  In this method, when the reflectances of the two information layers are greatly different, the focus jump between the two layers may fail. Further, even when the focus is drawn to the information layer near the position where the pickup exists, the reflectivity between the two layers is greatly different, and the focus may not be drawn well in the information layer.
[0005]
  As described above, when the focus cannot be satisfactorily drawn, there is a case where the movement direction of the pickup is changed and the focus is pulled back from the opposite side (for example, Patent Document 1).
[0006]
  In addition, when the focus jump has failed a predetermined number of times, there is a case in which an operation of newly pulling the focus into the information layer of the focus jump destination is performed (for example, Patent Document 2).
[Patent Document 1]
JP 2001-325734 A
[Patent Document 2]
JP 2002-74685 A
Disclosure of the invention
[0007]
  However, in any of the above cases, if the focus cannot be satisfactorily pulled in the desired information layer, the focus pull-in operation is performed again after the objective lens of the pickup is moved to another position. For this reason, since refocusing (recovery) of the focus is required, there is a problem that it takes extra time to focus on the desired information layer.
Means for solving the problem
[0008]
  Therefore, the present application has been made in view of the above inconveniences, and an example of the problem is that an optical recording medium having a large number of information layers can stably produce a desired layer even when the reflectance of each information layer is different. Is to provide a focus control device, a focus control method, a focus control program, and an information recording medium on which the focus control program is recorded.
  The focus control apparatus according to claim 1 of the present invention is a focus control apparatus for reproducing the information from a recording medium having a plurality of information layers on which information to be reproduced is formed, and is incident on the recording medium. A light emitting means for emitting light, a light receiving means for collecting the light emitted from the light emitting means on the information layer, a light receiving means for receiving the light reflected from the information layer, and a light reflected from the information layer. An electric signal generating means for generating an electric signal from the light received by the light receiving means, and a reflectance measuring means for measuring the reflectance in the information layer based on the electric signal generated by the electric signal generating means. And when the difference in reflectance between any one of the plurality of information layers measured by the reflectance measuring means and the other information layer is a predetermined value or more, the one information layer And a moving means for moving the light receiving means to adjust the focus from a direction in which the number of other information layers is smaller than that of the other information layers when moving the focus position of the focus to the other information layers. It is characterized by providing.
[0009]
  A focus control method according to claim 9 of the present invention is a focus control method for reproducing the information from a recording medium having a plurality of information layers on which information to be reproduced is formed, and is incident on the recording medium. A light emitting step for emitting light, a light receiving step for condensing the light emitted to the recording medium in the light emitting step on the information layer, and receiving light reflected from the information layer, An electrical signal generating step for generating an electrical signal from the light reflected from the information layer and received in the light receiving step, and the reflectance in the information layer is measured based on the electrical signal generated in the electrical signal generation. When the reflectance difference between the reflectance measurement step and the reflectance of one of the plurality of information layers measured in the reflectance measurement step and the other information layer is a predetermined value or more, When moving the focal position of the focus from one information layer to the other information layer, the light receiving means is moved to adjust the focus from the direction in which the number of other information layers is smaller than the other information layer. And a moving step.
[0010]
  According to a tenth aspect of the present invention, there is provided a focus control program comprising: a computer included in a focus control device for reproducing the information from a recording medium having a plurality of information layers on which information to be reproduced is formed; A light emitting means for emitting light incident on the medium; a light receiving means for collecting the light emitted from the light emitting means to the recording medium on the information layer and receiving the light reflected from the information layer; An electrical signal generating means for generating an electrical signal from light reflected from the information layer and received by the light receiving means, and a reflectance in the information layer is measured based on the electrical signal generated by the electrical signal generating means And a difference in reflectance between one of the plurality of information layers measured by the reflectance measuring means and the other information layer is predetermined. If the value is equal to or greater than the value, when moving the focal position of the focus from the one information layer to the other information layer, the focus is changed from the direction in which the number of other information layers is smaller than the other information layer. It is characterized by functioning as a moving means for moving the light receiving means for matching.
[Brief description of the drawings]
[0011]
FIG. 1 is a block diagram showing a schematic configuration example of an optical disc playback apparatus according to an embodiment.
FIG. 2 is a diagram showing a schematic internal configuration of the pickup according to the embodiment and a positional relationship between the pickup and the optical disc.
FIG. 3 is a flowchart showing a focus control operation in the double-layer optical disc of the first embodiment.
FIG. 4 is a flowchart showing an operation of focus control in the four-layer optical disc of the second embodiment.
FIG. 5 is a flowchart showing a focus control operation in the four-layer optical disc of the third embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
[0012]
  Next, an embodiment best suited for the present application will be described with reference to the drawings.
[0013]
  In the following embodiment, an operation for focusing an information layer when there are a plurality of information layers on which information is written or information is written on an optical disc such as a DVD is described. is there.
[0014]
  (I) Overall configuration and operation
  First, the overall configuration of the information recording / reproducing apparatus including the optical disc focus control apparatus according to the embodiment will be described with reference to FIG. A schematic configuration of the optical pickup used in the embodiment will be described with reference to FIG.
  Therefore, the present application has been made in view of the above inconveniences, and an example of the problem is that an optical recording medium having a large number of information layers can stably produce a desired layer even when the reflectance of each information layer is different. Is to provide a focus control device, a focus control method, a focus control program, and an information recording medium on which the focus control program is recorded.
[0015]
  FIG. 1 is a block diagram illustrating a schematic configuration example of the optical disc playback apparatus according to the embodiment. FIG. 2 is a block diagram illustrating a schematic configuration example of the optical pickup.
[0016]
  An outline operation of the optical disc reproducing apparatus S according to the embodiment will be described with reference to FIG. As shown in FIG. 1, the laser beam LB irradiated from the pickup 2 is reflected on the information layer of the optical disc 1, and the reflected laser beam LB changes according to the information on the information layer of the optical disc 1, and the change Is converted into an electric signal Si in the pickup 2. Based on the converted electric signal Si, the microcomputer 8 analyzes focus servo information and the like. Depending on the type of the optical disk, the converted electrical signal Si may contain information on the number of information layers recorded on the optical disk and reflectivity information, and the microcomputer unit 8 analyzes the information. . The pickup 2 (or the objective lens inside the pickup 2) is moved to a desired position based on the focus servo information or the analysis result of the number of information layers and the reflectance information.
[0017]
  Next, the detailed operation of the optical disc reproducing apparatus S according to the embodiment will be described with reference to FIG.
[0018]
  This optical disc recording / reproducing apparatus S irradiates an information layer of the optical disc 1 with a laser beam LB, converts the laser beam LB reflected on the optical disc 1 into an electric signal Si, a light emitting means, a light receiving means, an electric signal generating means, Further, the pickup 2 as the moving means, the amplification unit 5 that amplifies the input electric signal Si and outputs the amplified signal Sa, and the digital video / audio signal Sda and the focus by processing the input amplified signal Sa. A signal processing unit 6 that outputs a signal Spm including information such as servo information and outputs a driver signal Sdp and Sdm by processing the input control signal Smp, and a signal processing unit 6 as an amplification factor setting unit; The digital video / audio signal is based on the input digital video / audio signal Sda and the control signal Scd. A digital-to-analog conversion unit 7 (hereinafter referred to as a DAC unit) that converts Sda into a digital signal and outputs an analog video / audio signal So, a control signal Scd that performs calculation based on the signal Spm and controls the DAC unit 7 and Microcomputer unit 8 serving as a reflectance measurement unit, an amplification factor setting unit, a control unit and a recognition unit that outputs a control signal Smp for controlling the pickup 2 and the motor unit 3, and an input motor driver signal Sdm and a pickup driver signal A driver unit 4 that amplifies Sdp and outputs a motor control signal Sm and a pickup control signal Sp, and a motor unit 3 that rotates the optical disc 1 based on the input motor control signal Sm.
[0019]
  Note that the output signal So output from the DAC unit 7 is viewed by the user through a display device such as a liquid crystal display device or a loudspeaker such as a speaker via a power amplifier (not shown).
[0020]
  Next, each component will be specifically described.
[0021]
  The electrical signal Si includes information recorded on the information layer of the optical disc 1 and focus servo information regarding the condensing position of the laser beam LB.
[0022]
  For example, the electric signal Si includes a focus error signal and a focus search signal, and information for determining whether or not the pickup 2 is in an appropriate position for reading information in the information layer of the optical disc 1 is included. include.
[0023]
  An electric signal Si representing information recorded on the optical disc 1 and focus servo information is input to the amplifying unit 5. The electric signal Si is a weak signal, but is amplified in the amplifying unit 5 to be output as an amplified signal Sa that can be easily handled in the subsequent signal processing unit 6.
[0024]
  The signal processor 6 receives the amplified signal Sa and the control signal Smp. The signal processing unit 6 performs arithmetic processing on various types of information included in the amplified signal Sa, and outputs a processing signal Spm including information such as a digital video / audio signal Sda and focus servo information.
[0025]
  For example, the signal processing unit 6 generates and outputs a digital video / audio signal Sda by performing a decoding process on the amplified signal Sa representing information encoded and recorded on the optical disc. Further, based on the control signal Smp, the focus servo signal included in the amplified signal Sa is set to an appropriate amplification factor, and a focus servo circuit (described later) is opened and closed.
[0026]
  Further, the signal processing unit 6 moves the motor driver signal Sdm and the pickup 2 (or the objective lens inside the pickup 2) for rotating the motor unit 3 at a predetermined number of rotations from the input control signal Smp. A pickup driver signal Sdp that is a signal for generating the signal is generated and output to the driver unit 4.
[0027]
  The driver unit 4 amplifies the input motor driver signal Sdm to a voltage necessary for driving the motor unit 3 and then outputs the motor control signal Sm. Further, the driver unit 4 amplifies the input pickup driver signal Sdp to a current necessary for driving the pickup 2 (or an objective lens inside the pickup), and then outputs the pickup control signal Sp.
[0028]
  The motor unit 3 rotates the optical disc 1 based on the input motor control signal Sm.
[0029]
  A digital video / audio signal Sda and a control signal Scd are input to the DAC unit 7. The DAC unit 7 converts the digital video / audio signal Sda from a digital signal to an analog signal to generate an analog video / audio signal So, and outputs the analog video / audio signal So based on the control signal Scd.
[0030]
  For example, the control signal Scd is a signal for controlling to stop or start the output of the analog video / audio signal So to be output from the DAC unit 7.
[0031]
  The microcomputer 8 receives the processing signal Spm.
[0032]
  As described above, the processing signal Spm includes information such as the digital video / audio signal Sda and the focus servo information.
[0033]
  The focus servo information includes information indicating the reflected light intensity of the optical disk for measuring the reflectance of the information layer of the optical disk, focus error signal information indicating the state of the focus search when the pickup 2 is moved, and recording in the information layer. Information representing the number of information layers that have been recorded, or optical disc reflectivity information representing the reflectivity of each information layer, and the like.
[0034]
  The information representing the reflected light intensity includes, for example, an electric signal level corresponding to the reflected light intensity. The microcomputer unit 8 determines the amplification factor of the electric signal of the focus servo circuit configured by the pickup 2, the amplification unit 5, the signal processing unit 6, and the driver unit 4 in accordance with information representing the reflected light intensity. This amplification factor is determined for each information layer if the intensity of reflected light differs for each information layer. As described above, the microcomputer unit 8 changes the amplification factor of the electric signal in the focus servo circuit according to the light reflectance of the information layer on which the laser beam LB is focused. A focus servo circuit with an appropriately set amplification factor can operate stably.
[0035]
  The focus error signal is information representing the positional relationship between the focal position of the light beam LB emitted from the pickup 2 and the information layer of the optical disc. For example, when the focus error signal is represented by a so-called push-pull method, the closer the focus error signal is to zero, the closer the focus position of the light beam LB is to the information layer of the optical disc (optical system). Excluding electrical offset).
[0036]
  When reading information recorded on the information layer from the information layer of the optical disc, the microcomputer unit 8 detects a focus error signal and moves the pickup 2 or an objective lens inside the pickup 2 as a pickup driver. The pickup 2 drive control information for controlling the signal and servo opening / closing information indicating information indicating that the focus servo circuit is closed at an appropriate timing are output.
[0037]
  In this embodiment, when the focus position of the focus is moved from one information layer to another information layer, servo opening / closing information indicating information indicating that the focus servo circuit is opened is output. That is, when the focus of the laser beam LB is moved from one information layer to another information layer, the focus servo circuit is once opened, and then the servo circuit is closed to focus the laser beam LB on the other information layer. To work.
[0038]
  On the other hand, the control signal Smp output from the microcomputer unit 8 includes the pickup 2 drive control information for driving the pickup 2 (or the objective lens in the pickup 2) and a desired information layer for performing a focus search. In order to adjust the focus, amplification factor determination information for determining the amplification factor of the signal of the focus servo circuit included in the signal processing unit 6, servo opening / closing information indicating that the focus servo circuit is opened and closed, and the like are included. ing.
[0039]
  For example, the pickup 2 drive control information is information used for recognizing the position of the information layer of the optical disc. By generating a pickup driver signal Sdp based on the pickup 2 drive control information, the focal position of the laser beam LB of the pickup 2 is brought close to and away from the information layer of the optical disc. Then, since a so-called S-characteristic appears in the focus servo signal included in the electrical signal Si obtained from the pickup 2, a focus search operation can be performed.
[0040]
  The amplification factor determination information is information that determines the magnitude of an electrical signal in a focus servo circuit configured by the pickup 2, the amplification unit 5, the signal processing unit 6 and the driver unit 4. The magnitude of the electric signal Si output from the pickup 2 varies depending on the reflectance of the information layer of the optical disc. Therefore, the microcomputer unit 8 determines the amplification factor of the focus servo circuit based on the reflected light intensity of the information layer representing the reflectance of the information layer included in the electric signal Si. Using the amplification factor determination information included in the control signal Smp corresponding to the amplification factor determined in the microcomputer unit 8, the signal processing unit 6 determines the amplification factor of the focus servo circuit. For example, by changing the resistance value of the amplifier included in the focus servo circuit using an analog switch circuit, the amplification factor of the focus servo circuit can be changed and determined. Therefore, the amplification factor of the focus servo circuit is set to be different for each information layer having a different reflectance.
[0041]
  Servo opening / closing information indicating that the focus servo circuit is opened and closed is a state in which the focus servo circuit configured by the pickup 2, the amplification unit 5, the signal processing unit 6, and the driver unit 4 is opened, or This is information for determining whether to close the focus servo circuit when performing an operation of writing information to the information layer using the light beam LB and an operation of reading information from the information layer.
[0042]
  In the case of information for opening the focus servo circuit, the signal processing unit 6 sets, for example, an analog switch circuit included in the focus servo circuit to an open state in order to open the focus servo circuit. In the case of information for closing the focus servo circuit, the signal processing unit 6 sets, for example, an analog switch circuit included in the focus servo circuit in a closed state in order to close the focus servo circuit.
[0043]
  (II)First embodiment of the present application
  Next, the present embodiment will be described with reference to FIGS. This embodiment is an embodiment for explaining the operation of the focus control apparatus when there are two information layers on the optical disc.
[0044]
  FIG. 2 is a diagram showing the positional relationship of the double-layer optical disc 1, the pickup 2 and the focal point F1 of the laser beam LB, and the schematic configuration inside the pickup 2. As shown in FIG. FIG. 3 is a flowchart showing the focus control operation in the dual-layer optical disc.
[0045]
  FIG. 2 shows a schematic configuration inside the pickup 2. Hereinafter, a schematic configuration inside the pickup 2 will be described with reference to the drawings.
[0046]
  The laser beam LB1 emitted from the semiconductor laser LS as the light emitting means passes through the beam splitter BS and enters the objective lens OB as the condensing means. The light incident on the objective lens OB becomes the laser beam 2 condensed after passing through the objective lens OB, and is focused at the focal point F1. Since the position of the focal point F1 is in the first layer JS1 which is the information layer of the optical disc 1 in FIG. 2, the focused laser beam 2 is reflected by the first layer JS1 of the optical disc 1 and enters the objective lens OB. . The laser beam LB3 that has passed through the objective lens OB is changed in direction by the beam splitter BS and is input to the photodetector PD as an electric signal generating means. In the photodetector, an electric signal Si is generated corresponding to the light intensity of the laser beam LB3. An actuator AC as a moving unit is attached to the objective lens OB so as to be wound, and a current flows through the actuator AC by an actuator control signal Sfa that is a part of the pickup control signal Sf output from the driver unit 4. Thus, the objective lens OB moves in the direction of the arrow D1 or the direction of the arrow D2 in FIG. When the magnetic field generated by the current flowing through the actuator AC repels or attracts the magnetic fields of the magnets MG1 and MG2, the objective lens OB moves as described above. The objective lens OB moves in the moving direction of the pickup 2 even when the pickup 2 is moved by the pickup control signal Sf.
[0047]
  Further, when the objective lens OB moves in the direction of the arrow D1 in FIG. 2, the focal point F1 similarly moves in the direction of the arrow D1 in FIG. In this case, if the objective lens OB continues to move in the direction of the arrow D1 in FIG. 2, the focal point F1 moves in the direction of the optical disc surface SF1 after moving to the second layer JS2. When the objective lens OB moves in the direction of the arrow D2 in FIG. 2, the focal point F1 similarly moves in the direction of the arrow D2 in FIG. In this case, when the objective lens OB continues to move in the direction of the arrow D2 in FIG. 2, the focal point F1 moves from the first layer JS1 to the direction of the optical disc back surface SF2.
[0048]
  Thus, the focal point F1 moves in the moving direction of the objective lens OB. Further, when the pickup 2 is moved, if the objective lens OB is moved together with the pickup 2, the focal point F1 is also moved in the direction in which the pickup 2 is moved (same as the moving direction of the objective lens OB). Become.
[0049]
  Next, the two-layer optical disk in the present embodiment will be described with reference to FIG. The optical disc 1 is provided with a first layer JS1 and a second layer JS2 as information layers. Each information layer is formed with a space substantially parallel to the optical disc front surface SF1 and the optical disc back surface SF2. The reflectances of the first layer JS1 and the second layer JS2 may be different values or may be substantially the same value, and each will be described with reference to a flowchart representing the focus control operation in FIG.
[0050]
  Next, the focus control operation in the two-layer optical disc will be described with reference to FIG.
[0051]
  First, the outline of the focus control operation in the two-layer optical disc in FIG. 3 will be described. The case where the reflectances of the two information layers are almost the same is the same as the conventional case, and the description thereof is omitted. When the reflectances of the two information layers are different, an amplification factor corresponding to the reflectance of the desired information layer to which focus servo is to be applied is set in the focus servo circuit in the signal processing unit 6.
[0052]
  Then, the focus search is performed while bringing the pickup 2 close to the desired information layer from the side opposite to the direction in which the other information layer adjacent to the desired information layer to which the focus servo is to be applied. By closing the focus servo circuit when the pickup 2 or the objective lens included in the pickup 2 reaches the vicinity of the zero cross near the center of the so-called S-shaped characteristic corresponding to the desired information layer during the focus search , Focus on the desired information layer stably (the focus servo circuit is closed with the focus on the desired information layer so that the residual of the focus error signal becomes zero) Can work).
[0053]
  Furthermore, when focusing from the focused information layer to another information layer, an amplification factor corresponding to the reflectance of the desired information layer to which focus servo is to be applied is set in the focus servo circuit in the signal processing unit 6. .
[0054]
  Then, the focus search is performed while bringing the pickup 2 close to the desired information layer from the side opposite to the direction in which the other information layer adjacent to the desired information layer to which the focus servo is to be applied. A focus servo circuit when the pickup 2 or the objective lens included in the pickup 2 arrives near the zero cross near the center of the so-called S-shaped characteristic of the focus error signal corresponding to the desired information layer during the focus search By closing, a desired information layer can be focused stably.
[0055]
  Next, the operation of each step will be described.
[0056]
  In step S1, the microcomputer unit 8 calculates the reflectance of the two information layers (the first layer and the second layer), and stores the reflectance for each information layer in the storage unit in the microcomputer unit 8. To do. Here, the reflectivity is a focus error signal, a total addition signal of the photodetector in the pickup 2, or an RF (Radio Frequency) signal corresponding to information in the information layer or an RF ENV (Radio Frequency Envelope) signal that is an envelope signal of the RF signal. At least one signal level is measured and calculated in the microcomputer unit 8.
[0057]
  Next, in step S <b> 2, the microcomputer unit 8 calculates a value (difference in reflectance or reflectance ratio) representing a difference in reflectance between the two information layers. As a result, when the absolute value of the value representing the difference in reflectance is equal to or larger than a value (for example, 20 to 30 percent, more preferably 25 percent) stored in advance in the storage unit (step S2: YES) (when the reflectance between the two layers differs by 25% or more), the process proceeds to step S3. In this case, the difference in reflectance between the two information layers is large. When the absolute value of the value representing the difference in reflectance is smaller than a value stored in advance in the storage unit (for example, 20 to 30 percent, more preferably 25 percent) (step S2: NO), step S10 Proceed to In this case, the difference in reflectance between the two information layers is small.
[0058]
  Next, in step S3, it is determined whether the layer to be focused on is the first layer (information layer on the side close to the pickup 2) or the second layer (information layer on the side far from the disc). To do.
[0059]
  If it is desired to focus on the first layer (step S3: YES), the process proceeds to step S4. When it is desired to focus on the second layer (step S3: NO), the process proceeds to step S7.
[0060]
  Next, in step S4, the microcomputer unit 8 controls the signal processing unit 6 to open the focus servo circuit. Then, the microcomputer unit 8 sets the amplification factor in the focus servo circuit of the signal processing unit 6 based on the reflectance of the first layer measured in step S1.
[0061]
  Then, the microcomputer unit 8 moves the pickup 2 or the objective lens of the pickup 2 so that the focal position of the focus approaches the information layer 1 from the position where the pickup 2 exists.
[0062]
  When the microcomputer 8 detects that the pickup 2 or the objective lens included in the pickup 2 has reached the vicinity of the zero cross in the center of the so-called S-shaped characteristic of the focus error signal, the movement of the objective lens of the pickup 2 or the pickup 2 is moved. The driver unit 4 is controlled to stop the operation. Accordingly, the focus servo circuit of the signal processing unit 6 in which the amplification factor is set is closed based on the reflectance of the first layer.
[0063]
  Then, the focus is stably applied to the first layer (the focus servo circuit is closed with the focus on the first information layer so that the residual of the focus error signal becomes zero). The focus servo circuit is operating.)
[0064]
  In step S5, it is determined whether or not a command is given to the microcomputer unit 8 to move the focus position of the focus to the second layer. If there is a command to move the focus position from the first layer to the second layer (step S5: YES), the process proceeds to step S6. If there is no command to move the focal position of the focus from the first layer to the second layer (step S5: NO), the process proceeds to step S5.
[0065]
  In step S6, the microcomputer unit 8 controls the signal processing unit 6 to open the focus servo circuit. The microcomputer unit 8 sets the amplification factor in the focus servo circuit of the signal processing unit 6 based on the reflectance of the second layer measured in step S1.
[0066]
  Then, the microcomputer unit 8 positions the focus on the opposite side of the optical disk 1 from the position where the pickup 2 is present, and the position where the pickup 2 exists further than the position where the second layer exists. Move to the opposite side. Thereafter, the focus position of the focus is stopped. Then, the microcomputer unit 8 moves the pickup 2 or the objective lens of the pickup 2 so that the focal position of the focus approaches the second layer.
[0067]
  When the microcomputer 8 detects that the pickup 2 or the objective lens included in the pickup 2 has reached the vicinity of the zero cross in the center of the so-called S-shaped characteristic of the focus error signal, the movement of the objective lens of the pickup 2 or the pickup 2 is moved. The driver unit 4 is controlled to stop the operation. Accordingly, the focus servo circuit of the signal processing unit 6 for which the amplification factor is set is closed based on the reflectance of the second layer.
[0068]
  Then, the focus is stably applied to the second layer (the focus servo circuit is closed with the focus on the second layer, and the focus servo is set so that the residual of the focus error signal becomes zero. Circuit is working).
[0069]
  In step S7, the microcomputer unit 8 controls the signal processing unit 6 to open the focus servo circuit. Then, the microcomputer unit 8 sets the amplification factor in the focus servo circuit of the signal processing unit 6 based on the reflectance of the second layer measured in step S1.
[0070]
  Then, the microcomputer unit 8 positions the focus on the opposite side of the optical disk 1 from the position where the pickup 2 is present, and the position where the pickup 2 exists further than the position where the second layer exists. From the opposite side, the pickup 2 or the objective lens of the pickup 2 is moved so as to approach the second layer.
[0071]
  When the microcomputer 8 detects that the pickup 2 or the objective lens included in the pickup 2 has reached the vicinity of the zero cross in the center of the so-called S-shaped characteristic of the focus error signal, the movement of the objective lens of the pickup 2 or the pickup 2 is moved. The driver unit 4 is controlled to stop the operation. Accordingly, the focus servo circuit of the signal processing unit 6 for which the amplification factor is set is closed based on the reflectance of the second layer.
[0072]
  Then, the focus is stably applied to the second layer (the focus servo circuit is closed with the focus on the second layer, and the focus servo is set so that the residual of the focus error signal becomes zero. Circuit is working).
[0073]
  In step S8, it is determined whether or not an instruction has been given to the microcomputer unit 8 to move the focus position of the focus to the first layer. If there is a command to move the focal position of the focus from the second layer to the first layer (step S8: YES), the process proceeds to step S9. If there is no command to move the focus position from the second layer to the first layer (step S8: NO), the process proceeds to step S8.
[0074]
  Next, in step S9, the microcomputer unit 8 activates the focus servo circuit.
The signal processing unit 6 is controlled to open. Then, the microcomputer unit 8 sets the amplification factor in the focus servo circuit of the signal processing unit 6 based on the reflectance of the first layer measured in step S1.
[0075]
  Then, the microcomputer unit 8 sets the focal position of the focus to the same side as the position where the pickup 2 is present, with respect to the optical disc 1 on the side where the pickup 2 is present and where the first layer is present Move. Thereafter, the focus position of the focus is stopped. Then, the microcomputer unit 8 moves the pickup 2 or the objective lens of the pickup 2 so that the focus position of the focus approaches the first layer.
[0076]
  When the microcomputer 8 detects that the pickup 2 or the objective lens included in the pickup 2 has reached the vicinity of the zero cross in the center of the so-called S-shaped characteristic of the focus error signal, the movement of the objective lens of the pickup 2 or the pickup 2 is moved. The driver unit 4 is controlled to stop the operation. Accordingly, the focus servo circuit of the signal processing unit 6 in which the amplification factor is set is closed based on the reflectance of the first layer.
[0077]
  Then, the focus is stably applied to the first layer (the focus servo circuit is closed with the focus on the first information layer so that the residual of the focus error signal becomes zero). The focus servo circuit is operating.)
[0078]
  In step S10, the microcomputer unit 8 controls the signal processing unit 6 to open the focus servo circuit. Then, the microcomputer unit 8 sets the amplification factor in the focus servo circuit of the signal processing unit 6 based on the reflectance of the first layer measured in step S1.
[0079]
  Then, the microcomputer unit 8 moves the pickup 2 or the objective lens of the pickup 2 so that the focal position of the focus approaches the information layer 1 from the position where the pickup 2 exists.
[0080]
  When the microcomputer 8 detects that the pickup 2 or the objective lens included in the pickup 2 has reached the vicinity of the zero cross in the center of the so-called S-shaped characteristic of the focus error signal, the movement of the objective lens of the pickup 2 or the pickup 2 is moved. The driver unit 4 is controlled to stop the operation. Accordingly, the focus servo circuit of the signal processing unit 6 in which the amplification factor is set is closed based on the reflectance of the first layer.
[0081]
  Then, the focus is stably applied to the first layer (the focus servo circuit is closed with the focus on the first information layer so that the residual of the focus error signal becomes zero). The focus servo circuit is operating.)
[0082]
  In step S11, it is determined whether or not a command is given to the microcomputer unit 8 to move the focus position of the focus to the second layer. If there is a command to move the focus position of the focus from the first layer to the second layer (step S11: YES), the process proceeds to step S12. If there is no command to move the focal position of the focus from the first layer to the second layer (step S11: NO), the process proceeds to step S11.
[0083]
  Next, in step S12, the microcomputer unit 8 moves the focal position of the focus from the first layer to the second layer while keeping the focus servo circuit of the signal processing circuit closed (while keeping the focus servo applied). Thus, the driver unit 4 is controlled. Specifically, the microcomputer unit 8 controls the driver 4 so that a pulse signal for moving the pickup 2 or the objective lens included in the pickup 2 from the first layer to the second layer is output to the actuator.
[0084]
  When the microcomputer 8 detects that the pickup 2 or the objective lens included in the pickup 2 has reached the vicinity of the zero cross in the center of the so-called S-shaped characteristic of the focus error signal, the movement of the objective lens of the pickup 2 or the pickup 2 is moved. The driver unit 4 is controlled to stop the operation. Accordingly, the focus servo circuit of the signal processing unit 6 for which the amplification factor is set is closed based on the reflectance of the second layer.
[0085]
  Then, the focus is stably applied to the second layer (the focus servo circuit is closed with the focus on the second layer, and the focus servo is set so that the residual of the focus error signal becomes zero. Circuit is working).
[0086]
  In this embodiment, two recording / reproducing layers are used. However, the present invention is not limited to this, and the present invention can be applied to a case where there are three or more recording / reproducing layers.
[0087]
  In addition, a program corresponding to the flowchart of FIG. 2 is recorded in advance on a flexible disk or recorded in advance via a network such as the Internet, and is read and executed by a general-purpose microcomputer or the like. It is possible to cause the general-purpose microcomputer or the like to function as a CPU according to the embodiment.
[0088]
  (III)Second embodiment of the present application
  Next, the present embodiment will be described with reference to FIG. This embodiment is an explanation of the operation of the focus control apparatus when there are four information layers on the optical disc.
[0089]
  4, the same members as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
[0090]
  The optical disc 1 in FIG. 4 is an optical disc having four information layers. From the objective lens OB side, the first layer JS41 having a high reflectivity, the second layer JS42 having the same high reflectivity as the first layer JS41, the third layer JS43 having a low reflectivity, and the same low reflectivity as the third layer JS43. The information layers are stacked in the order of the fourth layer JS44 having a rate.
[0091]
  In the case of the present embodiment, the reflectance of the first layer JS41 and the second layer JS42 and the reflectance of the third layer JS43 and the fourth layer JS44 are greater than predetermined values. That is, the difference between the reflectance of the first layer JS41 and the second layer JS42 and the reflectance of the third layer JS43 and the fourth layer JS44 is greater than a predetermined value. Alternatively, the ratio between the reflectance of the first layer JS41 and the second layer JS42 and the reflectance of the third layer JS43 and the fourth layer JS44 is greater than a predetermined value.
[0092]
  In this case, when the focus F1 is moved between the second layer JS42 and the third layer JS43, the focus servo circuit remains closed and does not move.
[0093]
  First, when the focus F1 is adjusted to the first layer JS41 or the second layer JS42, the focus is drawn while moving the objective lens OB from the back surface SF2 of the optical disc in the direction of the front surface SF1 of the optical disc.
[0094]
  First, when the focus F1 is adjusted to the third layer JS43 or the fourth layer JS44, the focus is drawn while moving the objective lens OB from the front surface SF1 of the optical disk to the back surface SF2 of the optical disk.
[0095]
  Next, a case where the focus F1 is moved between the information layers after the focus F1 is set to any of the information layers will be described.
[0096]
  When the focal point F1 is moved between the first layer JS41 and the second layer JS42 (when the objective lens OB is moved), the focus servo circuit is moved while being closed. In addition, when the focus F1 is moved between the third layer JS43 and the fourth layer JS44 (when the objective lens OB is moved), the focus servo circuit is moved while being closed (focus jump).
[0097]
  When the focal point F1 is moved from the second layer JS42 to the third layer JS43 (when the objective lens OB is moved), the focus servo circuit is opened once and the objective lens OB is moved from the back surface SF2 of the optical disc to the front surface SF1 of the optical disc. The focal point F1 is moved from the fourth layer JS44 to the surface SF1 side of the optical disc. After that, the focus is drawn into the fourth layer JS44 while moving the objective lens OB from the front surface SF1 of the optical disk to the back surface SF2 of the optical disk. Thereafter, the focus jump is performed from the fourth layer JS44 to the third layer JS43 while the focus servo circuit is closed.
[0098]
  When the focal point F1 is moved from the third layer JS43 to the second layer JS42 (when the objective lens OB is moved), the focus servo circuit is opened once, and then the objective lens OB is moved from the front surface SF1 of the optical disc to the rear surface of the optical disc. The focal point F1 is moved from the first layer JS41 to the back surface SF2 side of the optical disc. Thereafter, the focus is drawn into the first layer JS41 while moving the objective lens OB from the back surface SF2 of the optical disc in the direction of the front surface SF1 of the optical disc. Thereafter, the focus jump is performed from the first layer JS41 to the second layer JS42 while the focus servo circuit is closed.
[0099]
  (IV)Third embodiment of the present application
  Next, the present embodiment will be described with reference to FIG. This embodiment is an explanation of the operation of the focus control apparatus when there are four information layers on the optical disc.
[0100]
  In FIG. 5, the same members as those in FIG.
[0101]
  The optical disc 1 in FIG. 5 is an optical disc having four information layers. From the objective lens OB side, the first layer JS51 having a high reflectivity, the second layer JS52 having a low reflectivity, the third layer JS53 having the same high reflectivity as the first layer JS51, and the same low reflectivity as the second layer JS52. The information layers are stacked in the order of the fourth layer JS54 having a rate.
[0102]
  In the case of the present embodiment, the reflectivity of the first layer JS51 and the third layer JS53 and the reflectivity of the second layer JS52 and the fourth layer JS54 are larger than predetermined values. That is, when the difference between the reflectance of the first layer JS51 and the third layer JS53 and the reflectance of the second layer JS52 and the fourth layer JS54 is larger than a predetermined value. Alternatively, the ratio between the reflectance of the first layer JS51 and the third layer JS53 and the reflectance of the second layer JS52 and the fourth layer JS54 is greater than a predetermined value.
[0103]
  In this case, the focal point F1 is set between the first layer JS51 and the second layer JS52, between the third layer JS53 and the fourth layer JS54, and between the first layer JS51 and the fourth layer JS54. When the focus servo circuit is moved, it is not moved with the focus servo circuit closed.
[0104]
  First, when the focus F1 is adjusted to the first layer JS51 or the third layer JS53, the focus is drawn while moving the objective lens OB from the back surface SF2 of the optical disc in the direction of the front surface SF1 of the optical disc.
[0105]
  First, when the focal point F1 is set to the second layer JS52 or the fourth layer JS54, the objective lens OB is moved from the front surface SF1 of the optical disc in the direction of the rear surface SF2 of the optical disc, while the second layer JS52 or the fourth layer JS52 is moved. Focus is pulled in layer JS54.
[0106]
  Next, the case where the focal point F1 is moved between the information layers after the focal point F1 is set to any one of the information layers will be described.
[0107]
  When the focus F1 is moved between the first layer JS51 and the third layer JS53 and between the second layer JS52 and the fourth layer JS54, the focus jump is performed with the focus servo circuit closed.
[0108]
  When moving the focus F1 from the first layer JS51 to the second layer JS52, after opening the focus servo circuit, the objective lens OB is moved in the direction from the back surface SF2 of the optical disk to the front surface SF1 of the optical disk, and the focus F1 is moved. It is moved from the fourth layer JS54 to the surface SF1 side of the optical disk. Thereafter, the focus is drawn in the fourth layer JS54 while moving the objective lens OB in the direction from the front surface SF1 of the optical disk to the back surface SF2 of the optical disk. Thereafter, a focus jump is performed from the fourth layer JS54 to the second layer JS52 while the focus servo circuit is closed.
[0109]
  When moving the focus F1 from the fourth layer JS54 to the third layer JS53, after opening the focus servo circuit, the objective lens OB is moved in the direction from the front surface SF1 of the optical disk to the back surface SF2 of the optical disk, and the focus F1 is moved. It is moved from the first layer JS51 to the back surface SF2 side of the optical disk. After that, the focus is drawn in the first layer JS51 while moving the objective lens OB from the back surface SF2 of the optical disc in the direction of the front surface SF1 of the optical disc. Thereafter, a focus jump is performed from the first layer JS51 to the third layer JS53 while the focus servo circuit is closed.
[0110]
  When moving the focus F1 from the first layer JS51 to the fourth layer JS54, after opening the focus servo circuit, the objective lens OB is moved from the back surface SF2 of the optical disc in the direction of the front surface SF1 of the optical disc, and the focus F1 is moved. It is moved from the fourth layer JS54 to the surface SF1 side of the optical disk. After that, the focus is drawn in the fourth layer JS54 while moving the objective lens OB from the front surface SF1 of the optical disk to the back surface SF2 of the optical disk.
[0111]
  When moving the focus F1 from the fourth layer JS54 to the first layer JS51, after opening the focus servo circuit, the objective lens OB is moved in the direction from the front surface SF1 of the optical disk to the back surface SF2 of the optical disk, and the focus F1 is moved. It is moved from the first layer JS51 to the back surface SF2 side of the optical disk. After that, the focus is drawn in the first layer JS51 while moving the objective lens OB from the back surface SF2 of the optical disc in the direction of the front surface SF1 of the optical disc.
[0112]
  As described above, the focus control device described in the present embodiment has a semiconductor laser that emits light incident on a recording medium such as an optical disk having two information reproducing recording layers, and a semiconductor laser that is emitted to the optical disk. An objective lens that collects the reflected light on the information layer and receives the light reflected from the information layer; a photodetector that generates an electrical signal from the light reflected from the information layer and received by the objective lens; If the reflectance of the information layer measured by the microcomputer differs from that of the microcomputer that measures the reflectance in the information layer based on the electrical signal generated by the detector, each information layer with a different reflectance A microcomputer or servo signal that sets the amplification factor of the electrical signal generated by the photodetector When combining and processing unit, the focus on the desired information layer, the number of the other information layers from the less direction to the information layer, and an actuator for moving the objective lens to adjust the focus.
[0113]
  According to this configuration, even when there are a plurality of information layers having different reflectivities on a single optical disc, an amplification factor suitable for the reflectivity of the information layer is set for each information layer, and the focus servo circuit is Since it can be operated, the focus servo is stably applied to each information layer.
[0114]
  Further, the focus control device described in this embodiment is measured by a signal processing unit that generates an electric signal for moving the objective lens according to the intensity of the electric signal generated from the photodetector based on the converted light, and a microcomputer. When the reflectivity of the plurality of information layers is different, the generation of the electric signal generated from the signal processing unit is stopped, the objective lens is moved to a desired position, and then the electric signal of the electric signal is generated in the signal processing unit. And a microcomputer for restarting the generation.
[0115]
  According to this configuration, when a plurality of information layers having different reflectivities exist on one optical disk, when the focus servo is applied by moving between the information layers, the focus servo circuit is temporarily opened and the pickup objective is Move the lens position. Since the focus servo circuit can be operated by setting an amplification factor suitable for the reflectivity of the information layer for each information layer, the focus servo can be stably applied to each information layer.
[0116]
  Furthermore, the focus control device described in the present embodiment includes a plurality of information provided in the recording medium based on information obtained by converting information formed in the information layer of the recording medium from an optical signal to an electrical signal by a photodetector. If the microcomputer that recognizes the reflectance of the information layer and the microcomputer determines that the reflectance of the information layers is different, the microcomputer or the signal processing unit sets the amplification factor corresponding to the information layer And a microcomputer for moving the objective lens to a desired position.
[0117]
  According to this configuration, even when there are a plurality of information layers having different reflectivities on a single optical disc, there are a plurality of information layers having different reflectivities from the disc information recorded on the optical disc in advance. Therefore, an amplification factor suitable for the reflectance of the information layer is set for each information layer, and the focus servo is stably applied to each information layer.
[0118]
  Furthermore, the focus control device described in this embodiment includes a servo signal processing unit that generates an electrical signal for moving the objective lens according to the intensity of reflected light reflected from the information layer, and a microcomputer. When the information layer is determined to have different reflectivities, the generation of the electrical signal from the signal processing unit is stopped, the objective lens is moved to a desired position, and then the signal processing unit And a microcomputer for restarting generation.
[0119]
  According to this configuration, even when a plurality of information layers having different reflectivities exist on a single optical disc, there are a plurality of information layers having different reflectivities from disc information recorded in advance on the optical disc. Therefore, an amplification factor suitable for the reflectance of the information layer can be set for each information layer.
[0120]
  When the focus servo is applied by moving between the information layers, the focus servo circuit is once opened and the objective lens position of the pickup is moved. Thereafter, an amplification factor suitable for the reflectance of the information layer can be set for each information layer and the focus servo circuit can be operated, so that the focus servo is stably applied to each information layer.
[0121]
  Further, in the focus control device described in the present embodiment, the information layer that is desired to be reproduced is the information layer that is present at the position closest to the laser semiconductor or the information layer that is present at the position farthest from the laser semiconductor. A microcomputer for determining that the information layer desired to be reproduced is focused, and an information layer having a reflectance approximate to the information layer desired to be reproduced when the information layer desired to be reproduced is not the information layer. When there are a plurality of the distances from the information layer located closest to the semiconductor laser to the information layer having an approximate reflectance, and the approximate reflectance from the information layer located farthest from the semiconductor laser. A microcomputer that compares the distance to the information layer, and an approximate reflectance corresponding to a small value of the compared distance. In order to adjust the focus to that information layer, and a microcomputer for moving the control by using an actuator of the objective lens.
[0122]
  According to this configuration, when information layers having different reflectivities exist in a laminated state on a single optical disc, there are a plurality of information layers having reflectivities that approximate the information layer to be focused. In some cases, the information layer on the surface in the laminated state or the information layer having an approximate reflectance closest to the information layer on the back surface in the laminated state is focused.
[0123]
  Therefore, when the desired information layer to be focused exists in a portion close to the center of the laminated information layer in the laminated state, the desired information layer positioned as far as possible in the laminated state And focus on the information layer having the approximate reflectance. After that, the focus lens is repeatedly moved by moving the objective lens to the information layer closer to the center having an approximate reflectance and focusing, so that the desired information layer near the center of the information layer is focused. Matching can be done stably.
[0124]
  Further, when the information layer to be focused is an information layer on the surface in the laminated state or an information layer on the back surface in the laminated state, the information layer is focused. In this case, focusing can be performed in a short time without complicated operations.
[0125]
  Furthermore, in the focus control device described in the present embodiment, the information layer that is desired to be reproduced is the information layer that exists at the position closest to the semiconductor laser or the information layer that exists at the position farthest from the semiconductor laser. If there are a plurality of information layers that have a reflectance that approximates the information layer that is desired to be reproduced and a microcomputer that determines that the information layer that is desired to be reproduced is in focus, the microcomputer is positioned closest to the semiconductor laser. Compared to a microcomputer that compares the distance from an existing information layer to an information layer having an approximate reflectance and the distance from the information layer that is farthest from the semiconductor laser to an information layer having an approximate reflectance. In order to focus on an information layer having an approximate reflectance corresponding to a small value of the distance, the objective lens is While moving using the actuator, the generation of the electric signal generated from the signal processing unit is stopped, the objective lens is moved to a desired position, and then the generation of the electric signal is resumed in the signal processing unit. And a microcomputer.
[0126]
  According to this configuration, when the desired information layer to be focused exists in a portion near the center of the laminated information layer that is in the laminated state, the information layer is positioned as far as possible in the laminated state. Focus is placed on an information layer having a reflectivity approximate to that of the desired information layer. After that, the focus lens is repeatedly moved by moving the objective lens to the information layer closer to the center having an approximate reflectance and focusing, so that the desired information layer near the center of the information layer is focused. Matching can be done stably.
[0127]
  Also, when multiple information layers with different reflectivities exist on one optical disc, when moving the information layer and applying focus servo, the focus servo circuit is opened once and the objective lens position of the pickup is moved Let Since the focus servo circuit can be operated by setting an amplification factor suitable for the reflectivity of the information layer for each information layer, the focus servo can be stably applied to each information layer.
[0128]
  When the information layer to be focused is the information layer on the surface in the stacked state or the information layer on the back surface in the stacked state, the information layer is focused. In this case, focusing can be performed in a short time without complicated operations.
[0129]
  Furthermore, the focus control device described in the present embodiment has an information layer that is desired to be reproduced when the microcomputer recognizes that there are a plurality of information layers having a reflectance approximate to the information layer that is desired to be reproduced. When the information layer is located closest to the semiconductor laser or the information layer located farthest from the semiconductor laser, the microcomputer determines that the information layer desired to be reproduced is focused. And the distance from the information layer closest to the semiconductor laser to the information layer having the approximate reflectance, and the information layer existing farthest from the semiconductor laser to the information layer having the approximate reflectance. A microcomputer that compares the distance and information having an approximate reflectance corresponding to a small distance value. To adjust the focus in the layer, and a microcomputer for moving the control by using an actuator of the objective lens.
[0130]
  According to this configuration, even when there are a plurality of information layers having different reflectivities on a single optical disc, there are a plurality of information layers having different reflectivities from the disc information recorded on the optical disc in advance. Therefore, an amplification factor suitable for the reflectance of the information layer is set for each information layer, and the focus servo is stably applied to each information layer.
[0131]
  In addition, when the desired information layer to be focused exists in a portion close to the center of the laminated information layer that is in the laminated state, the desired information layer that is located as far as possible in the laminated state And focus on the information layer having the approximate reflectance. After that, the focus lens is repeatedly moved by moving the objective lens to the information layer closer to the center having an approximate reflectance and focusing, so that the desired information layer near the center of the information layer is focused. Matching can be done stably.
[0132]
  Further, when the information layer to be focused is the information layer on the surface in the laminated state or the information layer on the back surface in the laminated state, the information layer is focused. In this case, focusing can be performed in a short time without complicated operations.
[0133]
  Further, the focus control device described in the present embodiment has an information layer that is desired to be reproduced when the microcomputer recognizes that there are a plurality of information layers having a reflectance approximate to the information layer that is desired to be reproduced. When the information layer is located closest to the semiconductor laser or the information layer located farthest from the semiconductor laser, the microcomputer determines that the information layer desired to be reproduced is focused. And the distance from the information layer closest to the semiconductor laser to the information layer having the approximate reflectance, and the information layer existing farthest from the semiconductor laser to the information layer having the approximate reflectance. A microcomputer for comparing distance and an information layer having an approximate reflectance corresponding to a small distance value While the objective lens is moved using an actuator to adjust the focus, the generation of the electrical signal generated from the processing circuit unit is stopped, and the objective lens is moved to a desired position. And a microcomputer for restarting the generation of the electric signal.
[0134]
  According to this configuration, even when a plurality of information layers having different reflectivities exist on a single optical disc, there are a plurality of information layers having different reflectivities from disc information recorded in advance on the optical disc. Therefore, an amplification factor suitable for the reflectance of the information layer can be set for each information layer.
[0135]
  When the focus servo is applied by moving between the information layers, the focus servo circuit is once opened and the objective lens position of the pickup is moved. Thereafter, an amplification factor suitable for the reflectance of the information layer can be set for each information layer and the focus servo circuit can be operated, so that the focus servo is stably applied to each information layer.
[0136]
  In addition, when the desired information layer to be focused exists in a portion close to the center of the laminated information layer that is in the laminated state, the desired information layer that is located as far as possible in the laminated state And focus on the information layer having the approximate reflectance. Subsequently, focus jump is repeated by sequentially moving the objective lens to the information layer closer to the center having approximate reflectance and focusing, thereby focusing on the desired information layer near the center of the information layer. Matching can be done stably.
[0137]
  Further, when the information layer to be focused is the information layer on the surface in the laminated state or the information layer on the back surface in the laminated state, the information layer is focused. In this case, focusing can be performed in a short time without complicated operations.

Claims (11)

In a focus control device for reproducing the information from a recording medium having a plurality of information layers on which information to be reproduced is formed, light emitting means for emitting light incident on the recording medium;
A light receiving means for condensing the light emitted from the light emitting means on the information layer and receiving the light reflected from the information layer;
An electric signal generating means for generating an electric signal from the light reflected from the information layer and received by the light receiving means;
A reflectance measuring means for measuring the reflectance in the information layer based on the electrical signal generated by the electrical signal generating means;
When the difference in reflectance between any one of the plurality of information layers and the other information layer measured by the reflectance measurement unit is equal to or greater than a predetermined value, the other information from the one information layer A moving means for moving the light receiving means to adjust the focus from a direction in which the number of other information layers is smaller than the other information layers when moving the focus position of the focus to the layers;
A focus control device comprising: The focus control device according to claim 1,
A movement signal generating means for generating an electric signal for moving the light receiving means according to the intensity of the electric signal generated from the electric signal generating means based on the converted light;
When the reflectances of the plurality of information layers measured by the reflectance measuring unit are different, the generation of the electric signal generated from the movement signal generating unit is stopped and the light receiving unit is moved to a desired position. Control means for restarting the generation of the electric signal in the movement signal generating means after
A focus control device comprising: The focus control device according to claim 1,
The information formed in the information layer of the recording medium is a plurality of information layers provided in the recording medium based on information converted from an optical signal to an electric signal by the electric signal generation unit. A recognition means for recognizing the reflectance,
When it is determined by the pre-recognition means that the reflectances of the plurality of information layers are different, the amplification factor corresponding to the desired information layer is set by the amplification factor setting means, and the light receiving means is moved to the desired position. Control means to move to,
A focus control device comprising: The focus control device according to claim 3.
A movement signal generating means for generating an electric signal for moving the light receiving means according to the intensity of the reflected light reflected from the information layer;
When it is determined by the identification means that the reflectances of the plurality of information layers are different, the generation of the electric signal from the movement signal generation means is stopped and the light receiving means is moved to a desired position. After that, the control means for restarting the generation of the electric signal in the movement signal generation means,
A focus control device comprising: The focus control device according to claim 1,
If the information layer that is desired to be reproduced is the information layer that is closest to the light emitting means, or the information layer that is located farthest from the light emitting means, the information that is desired to be reproduced A determination means for determining whether to focus the layer;
When the information layer that is desired to be reproduced is not the target of the determination means, and there are a plurality of information layers having reflectances approximate to the information layer that is desired to be reproduced, the information layer is located closest to the light emitting means. The distance from the existing information layer to the information layer having the approximate reflectance is compared with the distance from the information layer existing farthest from the light emitting means to the information layer having the approximate reflectance. A comparison means;
A movement control means for controlling the movement of the light receiving means using the moving means in order to focus on the information layer having the approximate reflectance corresponding to a small value of the distance compared by the comparing means;
A focus control device comprising: The focus control device according to claim 2,
If the information layer that is desired to be reproduced is the information layer that is closest to the light emitting means, or the information layer that is located farthest from the light emitting means, the information that is desired to be reproduced A determination means for determining whether to focus the layer;
When the information layer that is desired to be reproduced is not the target of the determination means, and there are a plurality of information layers having reflectances approximate to the information layer that is desired to be reproduced, the information layer is located closest to the light emitting means. The distance from the existing information layer to the information layer having the approximate reflectance is compared with the distance from the information layer existing farthest from the light emitting means to the information layer having the approximate reflectance. A comparison means;
While moving the light receiving means using the moving means in order to focus on the information layer having the approximate reflectance corresponding to a small value of the distance compared by the comparing means, The control means for stopping the generation of the electric signal generated from the movement signal generation means and moving the light receiving means to a desired position and then restarting the generation of the electric signal in the movement signal generation means;
A focus control device comprising: The focus control device according to claim 3.
In the case where the recognition means recognizes that there are a plurality of information layers having a reflectance approximate to the information layer desired to be reproduced,
If the information layer that is desired to be reproduced is the information layer that is closest to the light emitting means, or the information layer that is located farthest from the light emitting means, the information that is desired to be reproduced A determination means for determining whether to focus the layer;
In the case where the information layer desired to be reproduced is not the target of the determination means, the distance from the information layer present at the closest position to the light emitting means to the information layer having the approximate reflectance, and the light emitting means A comparison means for comparing the distance from the information layer located farthest from the information layer to the information layer having the approximate reflectance,
A movement control means for controlling the movement of the light receiving means using the moving means in order to focus on the information layer having the approximate reflectance corresponding to a small value of the distance compared by the comparing means;
A focus control device comprising: The focus control device according to claim 4,
In the case where the recognition means recognizes that there are a plurality of information layers having a reflectance approximate to the information layer desired to be reproduced,
If the information layer that is desired to be reproduced is the information layer that is closest to the light emitting means, or the information layer that is located farthest from the light emitting means, the information that is desired to be reproduced A determination means for determining whether to focus the layer;
When the information layer that is desired to be reproduced is not the target of the determination means, the distance from the information layer that is closest to the light emitting means to the information layer having the approximate reflectance, and the light emitting means Comparison means for comparing the distance from the information layer present at the farthest position to the information layer having the approximate reflectance, and the approximation in which the value of the distance compared by the comparison means corresponds to a small value While the light receiving means is moved using the moving means in order to focus on the information layer having the reflectance, the generation of the electric signal generated from the movement signal generating means is stopped to The control means for restarting the generation of the electrical signal in the movement signal generation means after moving the means to a desired position;
A focus control device comprising: In a focus control method for reproducing the information from a recording medium having a plurality of information layers on which information to be reproduced is formed,
A light emitting step for emitting light incident on the recording medium;
A light receiving step for condensing the light emitted to the recording medium in the light emitting step on the information layer and receiving the light reflected from the information layer;
An electric signal generating step of generating an electric signal from the light reflected from the information layer and received in the light receiving step;
A reflectance measurement step of measuring the reflectance in the information layer based on the electrical signal generated in the electrical signal generation;
When the difference in reflectance between any one of the plurality of information layers measured in the reflectance measurement step and the other information layer is a predetermined value or more, the other information from the one information layer A moving step of moving the light receiving means to adjust the focus from a direction in which the number of other information layers is smaller than the other information layers when moving the focus position of the focus to the layers;
A focus control method comprising: A computer included in a focus control device for reproducing the information from a recording medium having a plurality of information layers on which information to be reproduced is formed;
Light emitting means for emitting light incident on the recording medium;
A light receiving means for condensing the light emitted from the light emitting means to the recording medium on the information layer and receiving the light reflected from the information layer;
An electric signal generating means for generating an electric signal from the light reflected from the information layer and received by the light receiving means;
One of the plurality of information layers measured by the reflectance measuring means, and the reflectance measuring means for measuring the reflectance in the information layer based on the electrical signal generated by the electrical signal generating means. When the difference in reflectance between the information layer and the other information layer is equal to or greater than a predetermined value, the focus position of the focus is moved from the one information layer to the other information layer with respect to the other information layer. Moving means for moving the light receiving means to focus from a direction in which the number of other information layers is small,
Focus control program characterized by functioning as   A recording medium in which the focus control program according to claim 10 is recorded in a computer-readable manner.