WO2006106664A1

WO2006106664A1 - Focus control device, focus control method, focus control program, and recording medium containing the focus control program

Info

Publication number: WO2006106664A1
Application number: PCT/JP2006/306272
Authority: WO
Inventors: Yoshimichi Nishio; Hiroyuki Kobayashi; Takaaki Ujiie; Hidetaka Urabe; Hiroshi Someya; Yoshihiro Hashizuka; Hiroki Goto; Hideaki Tsurumi; Manabu Shimodaira
Original assignee: Pioneer Corporation
Priority date: 2005-03-30
Filing date: 2006-03-28
Publication date: 2006-10-12
Also published as: JPWO2006106664A1; JP4296216B2

Abstract

There are provided a focus control device, a focus control method, and a focus control program capable of stably reaching a desired layer for performing focus serve even when an optical recording medium has a plurality of information layers having different reflection factors. An information recording medium containing the focus control program is also provided. The focus control device includes: a microcomputer for measuring a reflection factor in the information layer according to an electric signal generated by a photo-detector; a microcomputer or a servo signal processing unit used when the reflection factors of the information layers measured by the microcomputer are different, for setting an amplification ratio of the electric signal generated by a photo detector for each of the information layers having different reflection factors; and an actuator used when focusing in a desired information layer by moving an objective lens for focusing in the direction having less number of other information layers.

Description

Specification

FOCUS CONTROL DEVICE, FOCUS CONTROL METHOD, FOCUS CONTROL PROGRAM, AND RECORDING MEDIUM CONTAINING FOCUS CONTROL PROGRAM

Technical field

[0001] The present application relates to a focus control field of an optical disc information recording / reproducing apparatus.

Background art

Conventionally, an optical disc such as a DVD (Digital Versatile Disc) is known as an optical disc having two information layers such as an information recording layer for recording information or an information reproducing layer for reproducing information. ing.

[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 information layer force close to the position where the pick-up exists is also focused. I'm pulling in. Therefore, even when information is written to or read from a distant information layer where there is a pick-up, the focus servo circuit is closed while the focus is drawn close to the position where the pickup first exists, and the focus servo circuit is closed. In addition, the position force where the pickup is located performs a focus jump to an information layer that is far away.

[0004] In this method, if the reflectivity of the two information layers is significantly different, the force jump between the two layers may fail. In addition, even when the focus is pulled into the information layer close to the position where the pickup exists, the reflectivity between the two layers is greatly different, so that there is a case where the focus cannot be properly bowed into the information layer! .

[0005] As described above, when the focus cannot be satisfactorily pulled, the movement direction of the pickup may be changed, and the opposite side force may also be pulled back (for example, Patent Document 1).

[0006] Further, when the focus jump fails a predetermined number of times, there is a case where 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: Japanese Patent Laid-Open No. 2001-325734 Patent Document 2: Japanese Patent Laid-Open No. 2002-74685

Disclosure of the invention

Problems to be solved by 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 the focus pull-in (recovery) is required again, there is a problem that it takes an extra time to pull the focus into the desired information layer.

[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 many information layers is stable even when the reflectance of each information layer is different. It is another object of the present invention to provide a focus control apparatus, a focus control method, a focus control program, and an information recording medium on which the focus control program is recorded.

The focus control device according to claim 1 of the present invention is 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 the emitted light, light emitted from the light emitting means for condensing on the information layer, light receiving means for receiving the light reflected from the information layer, and reflection from the information layer And measuring the reflectance in the information layer based on the electrical signal generated by the electrical signal generating means and the electrical signal generated by the electrical signal generating means. In the case where the reflectivity of the information layers measured by the reflectivity measuring means and the reflectivity measuring means is different, the signal generating means for each information layer having a different reflectivity. When focusing on the desired information layer with an amplification factor setting means for setting the amplification factor of the generated electrical signal, the number of other information layers is smaller than the! / 情報 direction from the information layer. And a moving means for moving the light receiving means to adjust the focus.

[0009] The focus control method according to claim 9 of the present invention provides focus control for reproducing the information from a recording medium having a plurality of information layers on which information to be reproduced is formed. In the method, a light emitting step for emitting light incident on the recording medium, a light emitting step! /, Condensing the light emitted to the recording medium on the information layer, and the information layer A light receiving step for receiving the light reflected from the information layer, an electric signal generating step for generating an electric signal from the light reflected from the information layer and received in the light receiving step, and the electric signal generation. The reflectance measurement step for measuring the reflectance in the information layer based on the generated electrical signal, and the reflection of the plurality of information layers measured in the reflectance measurement step. When the ratio is different, an amplification factor setting step for setting an amplification factor of the electrical signal generated in the signal generation step for each information layer having a different reflectance, and when focusing on the desired information layer Other information for the information layer From a small number direction, characterized in that and a moving step carried out while moving the operation in the light receiving step to adjust the focus.

[0010] The focus control program according to claim 10 of the present invention is included in a recording medium force having a plurality of information layers on which information to be reproduced is formed, and included in a force control device for reproducing the information. A light emitting means for emitting light incident on the recording medium; condensing the light emitted from the light emitting means to the recording medium on the information layer; and reflecting the light reflected from the information layer. A light receiving means for receiving light, an electric signal generating means for generating an electric signal from light reflected from the information layer and received by the light receiving means, and the information based on the electric signal generated by the electric signal generating means. If the reflectance of the plurality of information layers measured by the reflectance measuring means for measuring the reflectance in the layers is different, the information with different reflectance is used. Amplification rate setting means for setting the amplification factor of the electrical signal generated by the signal generation means for each layer, and when focusing on the desired information layer, the information layer It is characterized by functioning as a moving means for moving the light receiving means in order to adjust the focus from the direction where the number is small.

Brief Description of Drawings

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 disk. FIG. 3 is a flowchart showing the focus control operation in the double-layer optical disc of the first embodiment.

FIG. 4 is a flowchart showing the focus control operation in the four-layer optical disk of the second embodiment.

FIG. 5 is a flowchart showing the focus control operation in the four-layer optical disk of the third embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment that is most suitable for the present application will be described with reference to the drawings.

[0013] It should be noted that the following embodiments focus on the information layer in the case where there are a plurality of information layers on which information is written on an optical disc such as a DVD or information layers on which information is written. Is described.

[0014] m Overall composition and appreciation

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. Further, 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, in an optical recording medium having many information layers, even if the reflectance of each information layer is different, it is stably desired. The object 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 showing a schematic configuration example of the optical disc reproducing apparatus according to the embodiment. FIG. 2 is a block diagram showing a schematic configuration example of the optical pickup.

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 emitted from the pickup 2 is reflected by the information layer of the optical disc 1, and the reflected laser beam LB changes according to the information in the information layer of the optical disc 1. This change is converted to electrical signal Si in pickup 2. Based on the converted electrical signal Si, the microcomputer section 8 analyzes the force servo information. Also, depending on the type of optical disc, Since the signal Si is recorded on the optical disc and includes the number of information layers and reflectivity information, the information is analyzed by the microcomputer unit 8. The pickup 2 (or the objective lens inside the pickup 2) is moved to a desired position based on the force servo information or the analysis result of the number of information layers and the reflectance information.

Next, the detailed operation of the optical disc reproducing apparatus S according to the embodiment will be described with reference to FIG.

This optical disc recording / reproducing apparatus S irradiates an information layer of the optical disc 1 with a laser beam LB, and converts the laser beam LB reflected on the optical disc 1 into an electric signal Si. A pickup 2 as an electric signal generating means and a moving means, an amplifying section 5 for amplifying an inputted electric signal Si and outputting an amplified signal Sa, and a digital image by processing the inputted amplified signal Sa. Z voice signal Sda and force signal A signal Spm containing information such as servo information is output, and a driver signal Sdp and Sdm are output by processing the input control signal Smp. The digital video Z audio signal Sda is converted from digital to analog based on the signal processing unit 6 and the input digital video Z audio signal Sda and the control signal Scd. Digital video conversion unit 7 (hereinafter referred to as DAC unit) that outputs audio signal So, control signal S cd and pickup 2 that controls DAC unit 7 and performs calculation based on signal Spm, and motor unit 3 A microcomputer 8 as a reflectance measuring means, an amplification factor setting means, a control means and a recognition means, and an input motor driver signal Sdm and pickup driver signal Sdp are amplified. The driver unit 4 outputs a motor control signal Sm and a pickup control signal Sp, and the motor unit 3 rotates the optical disc 1 based on the input motor control signal Sm.

Note that the output signal So output from the DAC unit 7 is viewed by the user through a power amplifier (not shown) or the like, using a display device such as a liquid crystal display device or a loudspeaker such as a speaker.

Next, each component will be specifically described.

[0021] The electric signal Si includes information recorded in the information layer of the optical disc 1 and a laser beam LB. Focus servo information regarding the light condensing position is included.

[0022] For example, the electric signal Si includes a focus error signal and a focus search signal, and it is determined whether the pickup 2 is in an appropriate position for reading information in the information layer of the optical disc 1. Contains information to do.

[0023] The amplification unit 5 receives an electric signal Si representing information recorded on the optical disc 1 and focus servo information. The electric signal Si is amplified in the force amplifying unit 5 which is a weak signal, and is output as an amplified signal Sa that can be easily handled in the signal processing unit 6 in the subsequent stage.

[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 the digital video Z audio signal Sda and focus servo information.

[0025] For example, the signal processing unit 6 generates a digital video Z audio signal Sda by performing a decoding process on the amplified signal Sa representing the information encoded and recorded on the optical disc, Output. Based on the control signal Smp, the focus servo signal included in the amplified signal Sa is set to an appropriate amplification factor, and the focus servo circuit (described later) is opened and closed.

[0026] Further, the signal processing unit 6 receives the motor driver signal Sdm and the pickup 2 (or the inside of the pickup 2) for rotating the motor unit 3 at a predetermined rotational speed from the input control signal Smp. The pickup driver signal Sdp, which is a signal for moving the objective lens), is generated and output to the driver unit 4.

The driver unit 4 amplifies the input motor driver signal Sdm to a voltage necessary for driving the motor unit 3 and outputs a motor control signal Sm with a force. 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 outputs a force pickup control signal SP.

[0028] The motor unit 3 rotates the optical disc 1 based on the input motor control signal Sm.

[0029] The digital video Z audio signal Sda and the control signal Scd are input to the DAC unit 7. The DAC unit 7 converts the digital video Z audio signal Sda into an analog signal from the digital signal, generates an analog video Z audio signal So, and outputs the analog video Z audio signal So based on the control signal Scd. .

[0030] For example, the control signal Scd is a signal for performing stop or start control of the output of the analog video Z audio signal So to be output from the DAC unit 7.

[0031] The microcomputer 8 receives the processing signal Spm.

As described above, the processing signal Spm includes information such as the digital video Z audio signal Sda and force 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, and focus error signal information indicating the state of the focus search when the pickup 2 is moved. In addition, information indicating the number of information layers recorded in the information layer, or optical disc reflectivity information indicating the reflectivity of each information layer is included.

[0034] The information indicating 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 constituted by the pickup 2, the amplification unit 5, the signal processing unit 6, and the driver unit 4 in accordance with the 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 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.

The focus error signal is information indicating 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 expressed by the so-called push-pull method, the closer the focus error signal is to zero, the closer the focus position of the light beam LB and the information layer of the optical disk are. Represents (excluding optical and electrical offsets).

[0036] When reading information recorded on the information layer from the information layer of the optical disc, the microcomputer unit 8 detects the focus error signal while detecting the focus error signal. Outputs pickup 2 drive control information for controlling the pickup driver signal, which is a signal to move the objective lens inside, and servo open / close information indicating information indicating that the force servo circuit is closed at an appropriate timing. .

[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 moving the focus of the laser beam LB from one information layer to another information layer, open the focus servo circuit and then adjust the servo circuit to focus the laser beam LB on the other information layer. To close.

[0038] On the other hand, the control signal Smp output from the microcomputer unit 8 includes pickup 2 drive control information for driving the pickup 2 (or an objective lens in the pickup 2) in order to perform a focus search. In order to focus on a desired information layer, amplification factor determination information for determining the amplification factor of the signal of the focus servo circuit included in the signal processing unit 6, and a servo indicating that the focus servo circuit is opened and closed Includes opening and closing information.

[0039] For example, the pickup 2 drive control information is information used to recognize the position of the information layer of the optical disc. Based on the pickup 2 drive control information, the pickup driver signal Sdp is generated to bring the focal position of the laser beam LB of the pickup 2 closer to and away from the information layer of the optical disc. Then, since the focus servo signal included in the electrical signal Si obtained from Pickup 2 has a so-called S-characteristic, a focus search operation can be performed.

The amplification factor determination information is information that determines the magnitude of an electric signal in the 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 electrical 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 that represents 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 amplification factor of the focus servo circuit is determined in the signal processing unit 6. For example, included in the focus servo circuit By changing the resistance value of the amplifier 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 opening and closing of the focus servo circuit is used to open a force servo circuit including the pickup 2, the amplification unit 5, the signal processing unit 6, and the driver unit 4. Alternatively, it is information for determining whether to close the focus servo circuit when performing the operation of writing information to the information layer using the light beam LB and the operation of reading information from the information layer.

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 to a closed state in order to close the focus servo circuit.

Next, the present embodiment will be described with reference to FIG. 2 and FIG. The present embodiment is an embodiment for explaining the operation of the focus control device when the optical disk has two information layers.

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.

FIG. 2 shows a schematic configuration inside the pickup 2. Hereinafter, the schematic internal configuration of 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 collected after passing through the objective lens OB, and is focused at the focal point F1. In FIG. 2, the focal point F1 is located on the first layer JS1, which is the information layer of the optical disc 1. Therefore, the focused laser beam 2 is reflected by the first layer JS1 of the optical disc 1 and enters the objective lens OB. To do. The laser beam LB3 that passed through the objective lens OB The direction is changed by the 1-splitter BS and input to the photo detector 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. The objective lens OB is mounted so that the actuator AC as a moving means is wound, and an electric current flows to the actuator AC by the actuator control signal Sfa which is a part of the pickup control signal Sf output from the driver unit 4. As a result, the objective lens OB moves in the direction of the arrow D1 or the direction of the arrow D2 in FIG. The actuator OB moves as described above when the magnetic field generated by the current flowing through the AC repels or attracts the magnetic fields of the magnets MG1 and MG2. The object 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. Further, 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, if the object lens OB continues to move in the direction of the arrow D2 in FIG. 2, the focus F1 also moves the first layer JS1 force in the direction of the back surface SF2 of the optical disk.

[0048] Thus, the focal point F1 moves in the moving direction of the objective lens OB. If the objective lens OB is moved together with the pickup 2 when the pickup 2 is moved, 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.

Next, the two-layer optical disc 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 surface SF1 and the optical disc back surface SF2. The reflectivity of the first layer JS1 and the second layer JS2 may be different values or may be almost the same value, and each will be described in the flow chart showing the focus control operation in FIG.

Next, the focus control operation in the two-layer optical disc will be described with reference to FIG. First, the outline of the focus control operation in the two-layer optical disc in FIG. 3 will be described. When the reflectances of the two information layers are almost the same, the explanation is omitted because it is the same as the conventional one. 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, a focus search is performed while bringing the pickup 2 close to the desired information layer from the side opposite to the direction in which another information layer adjacent to the desired information layer to which focus servo is to be applied. During the focus search, the focus servo circuit is activated 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 corresponding to the desired information layer. By closing, 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. The focus servo circuit can be operated.

[0053] Further, when the information layer force is focused, when focusing on other information layers, the focus servo circuit in the signal processing unit 6 calculates the amplification factor corresponding to the reflectance of the desired information layer to which the focus servo is to be applied. Set to.

[0054] Then, a focus search is performed while bringing the pickup 2 close to the desired information layer from the side opposite to the direction in which another information layer adjacent to the desired information layer to which focus servo is to be applied. During a focus search, when the objective lens included in Pickup 2 or 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. By closing the focus servo circuit, the desired information layer can be stably focused.

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 reflectivity for each information layer in the storage unit in the microcomputer unit 8. Memorize the reflectance. Here, the reflectivity is RFENV (Radio Frequency Envelop, which is the focus error signal, the full addition signal of the photo detector in pickup 2, or the RF (Radio Frequency) signal corresponding to information in the information layer or the envelope signal of the RF signal. e) At least one signal level of the signal is measured and calculated in the microcomputer section 8.

Next, in step S 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, the absolute value of the value representing the difference in reflectance is preliminarily calculated and is equal to or larger than the value stored in the storage unit (for example, 20 to 30 percent, more preferably 25 percent). If this is the case (step S2: YES) (if the reflectivity between the two layers differs by more than 25%), proceed 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 less than the value stored in the memory (e.g., 20 to 30 percent, more preferably 25 percent) (step S2: NO) Proceed to step S10. In this case, the difference in reflectance between the two information layers is small.

[0058] Next, in step S3, the layer to be focused on is the first layer (information layer on the side closer to the pickup 2) or the second layer (information layer on the side far from the disc force). Determine if it exists.

[0059] If it is desired to focus on the first layer (step S3: YES), the process proceeds to step S4. If you want to focus on the second layer (step S3: NO), go 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] 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 positional force information layer 1 where the pickup 2 exists.

[0062] When the microcomputer unit 8 detects that the objective lens included in the pickup 2 or 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 microcomputer 8 The driver unit 4 is controlled to stop the movement of the objective lens. Accordingly, the gain is based on the reflectivity of the first layer. Close the focus servo circuit of the signal processor 6 where is set.

[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 and the residual of the focus error signal is zero). The focus servo circuit operates so that

[0064] In step S5, it is determined whether or not the microcomputer unit 8 is instructed to move the focus position of the focus in the second layer. First layer force If there is a command to move the focus position on the second layer (step S5: YES), proceed to step S6. 1st layer force If there is no command to move the focus position on the 2nd layer (step S5: NO), proceed to step S5.

[0065] In step S6, 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.

[0066] Then, the microcomputer 8 picks up the focal position of the focus with respect to the optical disc 1 on the side opposite to the position where the pickup 2 is present, and further from the position where the second layer is present. Move to the side opposite to where 2 is. Then stop the focus position. 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] The microcomputer unit 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 driver unit 4 is controlled to stop the movement of the objective lens. Along with this, 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 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 residual of the focus error signal becomes zero). The focus servo circuit is activated.

[0069] In step S7, the microcomputer unit 8 opens the focus servo circuit. The signal processing unit 6 is controlled. 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 8 picks up the focal position of the focus on the side opposite to the position where the pickup 2 is present with respect to the optical disc 1 and more than the position where the second layer is present. Move the objective lens of Pickup 2 or Pickup 2 so that it approaches the second layer from the side opposite to where 2 is located.

[0071] When the microcomputer unit 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 microcomputer 8 The driver unit 4 is controlled to stop the movement of the objective lens. Along with this, 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 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 residual of the focus error signal becomes zero. The focus servo circuit is activated.

[0073] In step S8, 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 first layer. Second layer force If there is a command to move the focus position on the first layer (step S8: YES), proceed to step S9. Second layer force If there is no command to move the focus position on the first layer (step S8: NO), the process proceeds to step S8.

[0074] Next, in step S9, 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.

[0075] Then, the microcomputer unit 8 sets the focal position of the focus on the optical disc 1 on the side where the pickup 2 is present and the position where the pickup 2 is present further than the position where the first layer is present. Move to the same side. Then stop the focus position. The microcomputer unit 8 brings the focus position closer to the first layer. Move the pickup 2 or the pickup 2 objective lens.

[0076] When the microcomputer unit 8 detects that the objective lens included in the pickup 2 or 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 microcomputer 8 The driver unit 4 is controlled to stop the movement of the objective lens. Along with this, 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.

Then, the focus is stably applied to the first layer (the focus servo circuit is closed with the focus on the first information layer, and the residual of the focus error signal is zero). The focus servo circuit operates so that

[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 reflectivity 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 positional force information layer 1 where the pickup 2 exists.

[0080] The microcomputer unit 8 detects that the pickup 2 or the objective lens included in the pickup 2 has arrived near the zero cross in the center of the so-called S-shaped characteristic of the focus error signal. The driver unit 4 is controlled to stop the movement of the objective lens. Along with this, 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.

Then, the focus is stably applied to the first layer (the focus servo circuit is closed with the focus on the first information layer and the residual of the focus error signal is reduced). The focus servo circuit operates to zero.

In step S 11, it is determined whether or not a command is given to the microphone mouth computer unit 8 to move the focal position of the focus to the second layer. If there is a command to move the focal position of the focus in the second layer (step Sl 1: YES), the process proceeds to step S12. First layer force There is no command to move the focus position on the second layer In the case (step S11: NO), the process proceeds to step S11.

[0083] Next, in step S12, the microcomputer unit 8 keeps the focus servo circuit of the signal processing circuit closed (with the focus servo applied), changes the focus position of the focus, and also applies the second layer force to the second layer. The driver unit 4 is controlled so as to move to the layer. 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 to the first layer force and 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 arrived near the zero cross in the center of the so-called S-characteristic of the focus error signal, the microcomputer 8 The driver unit 4 is controlled to stop the movement of the objective lens. Along with this, 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 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 residual of the focus error signal becomes zero). The focus servo circuit is activated.

It should be noted that the present embodiment is not limited to this, and the present invention can be applied to the case where the number of recording / reproducing layers is three or more.

[0087] In addition, the 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. By doing so, it is possible to make the general-purpose microcomputer or the like function as the CPU according to the embodiment.

(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 the optical disc has four information layers.

In FIG. 4, the same members as those in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.

An optical disc 1 in FIG. 4 is an optical disc having four information layers. From the objective lens OB side, the first layer JS41 with high reflectivity, the second layer JS42 with the same high reflectivity as the first layer JS41, low The information layers are stacked in the order of the third layer JS43 having reflectivity and the fourth layer JS44 having the same low reflectivity as the third layer JS43.

[0091] In the case of this embodiment, the reflectivity of the first layer JS41 and the second layer JS42 and the reflectivity of the third layer JS43 and the fourth layer JS44 are larger than the predetermined values. is there. That is, when the difference between the reflectivity of the first layer JS41 and the second layer JS42 and the reflectivity of the third layer JS43 and the fourth layer JS44 is larger than a predetermined value. Or first layer JS41 and second layer JS4

This is the case where the ratio of the reflectivity of 2 to the reflectivities of the third layer JS43 and the fourth layer JS44 is greater than the value determined by daring.

[0092] In this case, when the focal point F1 is moved between the second layer JS42 and the third layer JS43,

When the focus servo circuit is closed, it does not move.

[0093] First, when the focus F1 is set to the first layer JS41 or the second layer JS42, the objective lens

Pull the focus while moving the OB from the back surface SF2 of the optical disk to the front surface SF1 of the optical disk.

[0094] When the focus F1 is first adjusted to the third layer JS43 or the fourth layer JS44, the objective lens OB is moved from the front surface SF1 of the optical disc to the rear surface SF2 of the optical disc, and the focus is drawn. .

Next, the case where the focus F1 is moved between the information layers after the focus F1 is set on any of the information layers will be described.

[0096] When the focus 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 in a closed state. Also, 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 (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 and the objective lens OB is moved to the rear surface SF2 of the optical disk. From the 4th layer JS44 to the surface SF1 side of the optical disk. 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. Then, close the focus servo circuit from the 4th layer JS44 to the 3rd layer JS43. Well focus jump.

[0098] When moving the focal point F1 from the third layer JS43 to the second layer JS42 (when moving the objective lens OB), open the focus servo circuit and then move the objective lens OB to the optical disk. Is moved from the front surface SF1 to the back surface SF2 of the optical disk, and the focal point F1 is moved from the first layer JS41 to the back surface SF2 side of the optical disk. After that, the focus is drawn into the first layer JS41 while moving the objective lens OB from the back surface SF2 of the optical disc toward the front surface SF1 of the optical disc. After that, the focus jump is made from the first layer JS41 to the second layer JS42 with the focus servo circuit closed.

[0099] (IV) Third embodiment of the present application

[0100] In FIG. 5, the same members as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.

[0101] The optical disc 1 in FIG. 5 is an optical disc having four information layers. From the OB side, the first layer JS51 with high reflectivity, the second layer JS52 with low reflectivity, the third layer JS53 with the same high reflectivity as the first layer JS51, the same low reflectivity as the second layer JS52 The information layers are stacked in the order of the fourth layer JS54 having the 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 the predetermined values. is there. That is, when the difference between 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 is greater 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 larger than a predetermined value.

[0103] In this case, 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 moving the focal point F1, the focus servo circuit should not be 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 objective lens OB is moved from the back surface SF2 of the optical disc toward the front surface SF1 of the optical disc while moving the lens. Pull in the orcas.

[0105] When the focus F1 is first adjusted 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 to the back surface SF2 of the optical disc, and the second Focus is pulled in layer JS52 or fourth layer JS54.

[0106] Next, the case where the focus F1 is moved between the information layers after the focus F1 is set on any of the information layers will be described.

When the focus F 1 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 from the back surface SF2 of the optical disk to the front surface SF1 of the optical disk. The focal point F1 is moved from the fourth layer JS54 to the surface SF1 side of the optical disk. After that, the focus is pulled 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. After that, the 4th layer J S54 force and the 2nd layer JS52 force the focus jump with the focus servo circuit 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 from the front surface SF1 of the optical disk to the rear surface SF2 of the optical disk. The focal point F1 is moved from the first layer JS51 to the back surface SF2 side of the optical disc. After that, the focus is pulled in the first layer JS51 while moving the objective lens OB from the back surface SF2 of the optical disk to the front surface SF1 of the optical disk. After that, perform the focus jump while closing the focus servo circuit from the first layer J S51 force to the third layer JS53.

[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 disk to the front surface SF1 of the optical disk. The focal point F1 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 from the front surface SF1 of the optical disk to the rear surface SF2 of the optical disk. The focal point F1 is moved from the first layer JS51 to the back surface SF2 side of the optical disc. 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 according to the present embodiment includes a semiconductor laser that emits light incident on a recording medium such as an optical disc having two information reproducing and recording layers, and a semiconductor laser power. The light emitted to the optical disc is condensed on the information layer, and the objective lens that receives the light reflected from the information layer, and the photodetector that is reflected from the information layer and received by the objective lens also generates an electric signal. And based on the electrical signal generated by the photo detector! / If the reflectance of the information layer measured by the microcomputer differs from that of the microphone computer that measures the reflectance in the information layer, it is generated by the photo detector for each information layer with a different reflectance. When focusing on the desired information layer and the microcomputer or servo signal processing unit that sets the amplification factor of the electrical signal, focus is from the direction where the number of other information layers is smaller than the information layer. And an actuator for moving the objective lens to match.

[0113] According to this configuration, even when there are a plurality of information layers having different reflectivities on one optical disc, an amplification factor suitable for the reflectivity of the information layer is set for each information layer, so Since the cus servo circuit can be operated, the focus servo can be used stably for each information layer.

[0114] Further, the focus control device according to the present embodiment generates a signal processing unit that generates an electric signal for moving the objective lens in accordance with the intensity of the electric signal generated from the photodetector based on the converted light. When the reflectance of the plurality of information layers measured by the microcomputer is different, the generation of the electric signal generated by the signal processing unit force is stopped and the object lens is moved to a desired position. And a microcomputer for restarting the generation of the electric signal in the signal processing unit.

[0115] According to this configuration, a plurality of information layers having different reflectivities exist on one optical disc. In some cases, when the focus servo is applied by moving between the information layers, the focus servo circuit is opened and the objective lens position of the pickup is moved. Since the focus servo circuit can be operated by setting an amplification factor suitable for the reflectance of the information layer for each information layer, the focus servo can be stably applied to each information layer.

[0116] Further, the focus control device described in the present embodiment is based on information obtained by converting information formed in the information layer of the recording medium into an optical signal force electric signal by a photodetector. If the microcomputer recognizes the reflectance of the plurality of information layers and the microcomputer determines that the reflectance of the plurality of information layers is different, the amplification factor corresponding to the information layer Is set by a microcomputer or a signal processing unit, and a microcomputer for moving the objective lens to a desired position is provided.

[0117] According to this configuration, even when there are a plurality of information layers having different reflectivities on one optical disc, it is necessary to comprehend a plurality of reflectivities from the disc information recorded on the optical disc. Since it is possible to identify the presence of different information layers, 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. .

Furthermore, the focus control device described in the present embodiment includes a servo signal processing unit that generates an electric signal for moving the objective lens according to the intensity of reflected light reflected from the information layer, and a microcomputer. If it is determined that the reflectance of the plurality of information layers is different, 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 the generation of the electric signal.

[0119] According to this configuration, even when there are a plurality of information layers having different reflectivities on one optical disc, a plurality of reflectivities are obtained from disc information recorded on the optical disc. Since it is possible to identify that there is a different information layer, 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 opened and the objective lens position of the pickup is moved. Then the information layer Since the focus servo circuit can be operated by setting an amplification factor suitable for the reflectivity of the information layer every time, the focus servo is stably applied to each information layer.

[0121] 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 laser semiconductor force, or exists at the position that is farthest from the laser semiconductor force. In the case of the information layer, the microcomputer that determines that the force is matched to the information layer that is desired to be reproduced and the information layer that is desired to be reproduced are not the information layer! If there are multiple information layers with reflectivity approximate to the desired information layer, the distance from the information layer that is closest to the semiconductor laser power to the information layer with approximate reflectivity and the distance from the semiconductor laser Information layer force existing at a far-away position Microcomputer comparing the distance to the information layer having the approximate reflectance and the approximate reflection corresponding to a smaller value of the compared distance In order to adjust the focus on the information layer having, and a microcomputer for moving control using Akuchiyueta the objective lens.

[0122] According to this configuration, when information layers having different reflectivities exist in a laminated state on a single optical disc, the information layer approximates the information layer to be focused! If there is more than one information layer with the reflectivity, the focus is on the information layer with the approximate reflectance that is closest to the information layer on the front surface of the stacked state or the information layer on the back surface of the stacked state. I tried to match.

[0123] Therefore, the desired information layer force to be focused is in a laminated state. If the information layer force exists in the vicinity of the center of the laminated information layer, the outermost layer in the laminated state Focus is placed on the information layer having a reflectivity approximate to that of the desired information layer. After that, the focus jump is repeated by sequentially moving the object lens to the information layer closer to the center having an approximate reflectance and adjusting the focus.

Therefore, it is possible to stably adjust the focus to a desired information layer near the center of the information layer.

[0124] Also, 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, focus can be achieved in a short time without complicated operations. You can let them.

[0125] Furthermore, the focus control apparatus described in the present embodiment is configured so that the information layer that is desired to be reproduced is an information layer that is present at the position closest to the semiconductor laser force or information that is present at the position farthest from the semiconductor laser. If there are multiple information layers that have a reflectance close to that of the information layer that is desired to be reproduced, and a microcomputer that determines that the force is matched to the information layer that is desired to be reproduced, Semiconductor laser power The distance from the information layer present at the closest position to the information layer having the approximate reflectance, and the distance from the information layer present at the position farthest from the semiconductor laser to the information layer having the approximate reflectance In order to focus on an information layer having a similar reflectance corresponding to a small value of the compared distance value and a microcomputer for comparing While moving the sensor using the actuator, the generation of the electric signal generated by the signal processing unit is stopped, the objective lens is moved to a desired position, and then the electric signal is generated by the signal processing unit. And a microcomputer for restarting.

[0126] According to this configuration, in the case where the desired information layer force to be focused exists in a portion close to the center of the laminated information layer that is in the laminated state, the outer side where the laminated state is to be formed The focus is adjusted to the information layer having a reflectance approximate to that of the desired information layer. Subsequently, the focus jump is repeated by sequentially 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 obtained. It will be possible to stably combine the furcas.

[0127] Further, when there are a plurality of information layers having different reflectivities on one optical disc, when the focus servo is applied by moving between the information layers, the focus servo circuit is opened and opened. Move the objective lens position. Since the focus servo circuit can be operated by setting an amplification factor suitable for the reflectance of the information layer for each information layer, the focus servo can be stably applied to each information layer.

[0128] The information layer force 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, and the information layer is focused. In this case, focus in a short time without complicated movements. Can be matched.

[0129] Furthermore, the focus control device described in the present embodiment is desired to be reproduced when the microcomputer recognizes that there are a plurality of information layers having reflectance similar to the information layer desired to be reproduced. If the information layer to be reproduced is an information layer that is present at the position closest to the semiconductor laser power or is located at the position farthest from the semiconductor laser power, the information layer that is desired to be reproduced should be focused. The distance from the information layer present at the closest position to the information layer having an approximate reflectance, and the information layer force present at the position farthest from the semiconductor laser. A microcomputer for comparing the distance to the information layer having the reflectance, and an approximate reflectance corresponding to a small distance value. And a microphone computer that controls the movement of the objective lens using an actuator in order to match the focus to the information layer.

[0130] According to this configuration, even when there are a plurality of information layers having different reflectivities on one optical disc, a plurality of reflectivities are obtained from the disc information recorded on the optical disc. Since it is possible to identify the presence of different information layers, 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 the vicinity of the center of the laminated information layer in the laminated state, the outer side of the laminated state should be as outer as possible. Focus is placed on the information layer having a reflectance approximate to that of the desired information layer. After that, by sequentially moving the objective lens to the information layer closer to the center having an approximate reflectance and focusing, the focus jump is repeated to move closer to the center of the information layer and move to the desired information layer. The ability to match the furcas will be stable.

[0132] 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, the focus can be adjusted in a short time without complicated operations. [0133] Further, the focus control device described in the present embodiment is desired to be reproduced when the microcomputer recognizes that there are a plurality of information layers having reflectivity approximate to the information layer desired to be reproduced. If the information layer is an information layer that is located closest to the semiconductor laser cover, or is an information layer that is located farthest from the semiconductor laser force, focus on the information layer that is desired to be reproduced. The information layer force that exists at the closest position to the semiconductor laser force and the distance to the information layer that has an approximate reflectance, the distance farthest from the semiconductor laser, and the approximation from the information layer that exists at the position A microcomputer that compares the distance to the information layer with the measured reflectance and an approximate reflectance corresponding to a smaller distance value While the objective lens is moved using an actuator to focus on the information layer, 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 in the processing circuit unit.

[0134] According to this configuration, even when a plurality of information layers having different reflectivities exist on a single optical disc, a plurality of reflectivities are obtained from the disc information recorded on the optical disc. Since it is possible to identify that there is a different information layer, 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 opened and the objective lens position of the pickup is moved. After that, since the focus servo circuit can be operated by setting an amplification factor suitable for the reflectance of the information layer for each information layer, the focus servo can be stably applied to each information layer.

[0136] Further, when the desired information layer to be focused exists in the vicinity of the central portion of the laminated information layer that is in the laminated state, the outer side of the laminated state should be as far as possible. Focus is placed on the information layer having a reflectance approximate to that of the desired information layer. After that, by sequentially moving the objective lens to the information layer closer to the center having an approximate reflectance and focusing, the focus jump is repeated to move closer to the center of the information layer and move to the desired information layer. The focus can be adjusted stably. Furthermore, when the information layer to be focused is an information layer on the front surface of the laminated state or an information layer on the back surface of the laminated state, the information layer is focused. In this case, the focus can be adjusted in a short time without complicated operations.

Claims

The scope of the claims

[1] Recording medium force having a plurality of information layers on which information to be reproduced is formed In the focus control apparatus for reproducing the information, 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 reflectance of the plurality of information layers measured by the reflectance measuring means is different, an amplification factor of the electric signal generated by the signal generating means is set for each information layer having a different reflectance. An amplification factor setting means for

When focusing on the desired information layer, moving means for moving the light receiving means to focus from a direction in which the number of other information layers relative to the information layer is small; and

A focus control device comprising:

[2] In 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, and a plurality of signals measured by the reflectance measuring means. When the reflectance of the information layer is different, the generation of the electric signal generated from the movement signal generation unit is stopped, the light reception unit is moved to a desired position, and then the movement signal generation unit Control means for restarting the generation of electrical signals in

A focus control device comprising:

[3] In the focus control device according to claim 1,

The information formed in the information layer of the recording medium is provided in the recording medium based on the information in which the optical signal force is also converted into an electric signal by the electric signal generating means. Recognizing means for recognizing the reflectance of the plurality of information layers;

When it is determined by the prior recognition means that the reflectance of the plurality of information layers is different

A control means for setting an amplification factor corresponding to a desired information layer by the amplification factor setting means, and for moving the light receiving means to a desired position;

A focus control device comprising:

[4] In 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 electrical signal from the movement signal generation means is stopped and the light receiving means is moved to a desired position. Control means for restarting the generation of the electrical signal in the movement signal generation means,

A focus control device comprising:

[5] In the focus control device according to claim 1,

If the information layer that is desired to be reproduced is the information layer that is located closest to the light emitting means or the information layer that is located farthest from the light emitting means force, the information that is desired to be reproduced A plurality of information layers having reflectivity approximate to the information layer that is desired to be reproduced when the information layer that is desired to be reproduced is not the target of the determination means; In this case, the distance from the information layer present at the nearest position to the information layer having the approximate reflectance and the approximation from the information layer located farthest from the light emitting means. A comparison means for comparing the distance to the information layer having the reflectance,

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 reflectivity corresponding to the value of the distance compared by the comparison means. When,

A focus control device comprising:

[6] In the focus control device according to claim 2,

An information layer that is desired to be reproduced is an information layer that is located closest to the light emitting means. If there is an information layer that is present at the farthest position or the light emission means force, a judgment means that determines whether to focus on the information layer that is desired to be reproduced, and an information layer that is desired to be reproduced are the information layer When there is a plurality of information layers having reflectances approximate to those of information layers that are desired to be reproduced when not being the target of the determination means, the light emission means force is approximated from the information layer existing at the closest position. A comparison means for comparing the distance to the information layer having the reflectance and the distance from the information layer located farthest from the light emitting means to the information layer having the approximate reflectance;

While the light receiving means is moved by using the moving means in order to focus on the information layer having the approximate reflectance corresponding to the distance value and the 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, moving the light receiving means to a desired position, and then restarting the generation of the electric signal in the movement signal generation means. When,

A focus control device comprising:

[7] 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 close to that of the information layer desired to be reproduced,

If the information layer that is desired to be reproduced is the information layer that is located closest to the light emitting means or the information layer that is located farthest from the light emitting means force, the information that is desired to be reproduced Determining means for determining that the layer is in focus; and when the information layer that is desired to be reproduced is not the target of the determining means, the light emission means force is approximated from the information layer that is present at the closest position. A comparison means for comparing the distance to the information layer having a distance from the information layer located farthest from the light emitting means to the information layer having the similar reflectance;

A focus control device comprising:

[8] 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 close to that of the information layer desired to be reproduced,

If the information layer that is desired to be reproduced is the information layer that is located closest to the light emitting means or the information layer that is located farthest from the light emitting means force, the information that is desired to be reproduced Determining means for determining that the layer is focused; and when the information layer desired to be reproduced is not the target of the determining means, the light emitting means force is approximated from the information layer present at the closest position. The comparison means for comparing the distance to the information layer having a distance from the information layer that is farthest from the light emitting means to the information layer having the approximate reflectance is compared by the comparison means. In order to focus on the information layer having the approximate reflectance corresponding to a small value of the measured distance, the light receiving means is moved using the moving means. The generation of the electric signal generated by the movement signal generation unit is stopped while the light reception unit is moved to a desired position, and then the generation of the electric signal is resumed by the movement signal generation unit. Control means;

A focus control device comprising:

In a focus control method for reproducing the information, the recording medium has 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 for 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 reflectance of the plurality of information layers measured in the reflectance measurement step is different, an amplification factor of the electrical signal generated in the signal generation step is set for each information layer having a different reflectance. An amplification factor setting step;

When focusing on the desired information layer, other information is given to the information layer. A moving step for moving the operation in the light receiving step to adjust the focus from the direction in which the number of layers is small;

A focus control method comprising:

[10] A recording medium having a plurality of information layers on which information to be reproduced is formed. A computer included in a focus control device for reproducing the information,

Light emitting means for emitting light incident on the recording medium;

Light receiving means for condensing the light emitted from the light emitting means onto the recording medium and receiving the light reflected from the information layer;

When the reflectance of the plurality of information layers measured by the reflectance measuring means is different, an amplification factor of the electric signal generated by the signal generating means is set for each information layer having a different reflectance. Gain setting means to

When focusing on the desired information layer, moving means for moving the light receiving means to adjust the focus from a direction in which the number of other information layers relative to the information layer is small,

Focus control program characterized by functioning as

[11] A recording medium in which the focus control program according to claim 10 is recorded in a computer-readable manner.