JP2011040130A - Optical drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain the vicinity of a track center even in an unrecorded area even while performing tracking servo by a DPD method using a code of a recording layer when an optical disk having a servo dedicated layer is reproduced. <P>SOLUTION: The optical drive device includes: an optical disk having a recording layer and a servo dedicated layer; a tracking error signal generation part 61-1 for generating a tracking error signal TE<SB>R</SB>from the received light amount of a photodetector 5-1 for receiving reflected light of a recording layer optical beam; a tracking error signal generation part 61-2 for generating a tracking error signal TE<SB>S-P</SB>from the received light amount of a photodetector 5-2 for receiving reflected light of a servo dedicated layer optical beam; a tracking servo part 62; and a determination part 63 for detecting that the irradiation position of the recording layer optical beam is an unrecorded area of the recording layer. The tracking servo part 62 is switched to control based on the tracking error signal TE<SB>R</SB>to control based on the tracking error signal TE<SB>S-P</SB>according to the result of ongoing detection of the determination part 63. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical drive device, and more particularly to an optical drive device that performs tracking servo.

  In order to increase the recording capacity of the optical disk, it is necessary to increase the number of recording layers. If a land groove is provided for each recording layer, a stamper is required for each layer, which increases costs. Therefore, in recent years, an optical disk provided with a servo dedicated layer different from the recording layer has appeared (see, for example, Patent Documents 1 and 2). In such an optical disc, a land groove (differential push-pull method: DPP method) necessary for tracking servo is provided in the servo dedicated layer, and the tracking servo is performed using the servo dedicated layer in principle. A land groove is not provided in the recording layer.

JP 2001-176117 A

  By the way, for example, when the optical disc is tilted, tracking servo in a layer different from the recording layer itself causes a servo shift. Therefore, recently, it is also considered to perform tracking servo by the DPD method using the code of the recording layer only during reproduction when the code (pit or recording mark) has already been formed in the recording layer.

  However, even during reproduction, codes are not necessarily formed in all areas, and there are unrecorded areas without codes. When performing tracking servo during playback using the code of the recording layer, the optical beam irradiation position is not recorded during playback of the optical disc in the on-track state (the tracking servo is turned on and controlled to be at the center of the track). When the region is crossed, tracking servo cannot be performed during that time, and the on-track state cannot be maintained.

  Accordingly, one of the objects of the present invention is to maintain the vicinity of the track center even in an unrecorded area while performing tracking servo by the DPD method using the code of the recording layer when reproducing an optical disc provided with a servo dedicated layer. An optical drive device is provided.

  In order to achieve the above object, an optical drive device according to the present invention controls a recording surface of an optical disc having a recording layer and a servo-dedicated layer so as to have the same optical axis at least in the vicinity of the recording surface. An optical system for irradiating the recording layer and the servo dedicated layer with the first and second light beams, respectively, and a first photodetector for receiving the reflected light from the recording surface of the first light beam; And a second photodetector that receives reflected light from the recording surface of the second light beam, and a first tracking error signal that is generated based on the amount of light received by the first photodetector. 1 tracking error signal generating means, second tracking error signal generating means for generating a second tracking error signal based on the amount of light received by the second photodetector, and the first and second tracking errors. Signal Tracking servo means for controlling the optical system based on one of them, and determination means for determining that the irradiation position of the first light beam is an unrecorded area of the recording layer, the tracking servo means The control is switched to the control based on the second tracking error signal according to the determination result of the determination means that is executing the control based on the first tracking error signal.

  According to the present invention, when reproducing an optical disc provided with a servo-dedicated layer, it is possible to maintain the vicinity of the track center even in an unrecorded area of the recording layer while performing tracking servo by the DPD method using the code of the recording layer. Become.

  In the optical drive device, the determination unit determines that the irradiation position of the light beam is an unrecorded area depending on whether or not the second tracking error signal has changed beyond a first predetermined range. It is good to do. According to this, it can be appropriately determined that the irradiation position of the light beam has reached the unrecorded area of the recording layer.

  In the optical drive device, the determination unit includes a sample-and-hold circuit that holds the second tracking error signal, and the second tracking error signal is generated based on a value held by the sample-and-hold circuit. It may be determined whether or not it has changed beyond the first predetermined range. According to this, even when the optical disk is tilted, it can be appropriately determined that the irradiation position of the light beam has reached the unrecorded area.

  In these optical drive apparatuses, the tracking servo means further determines that the irradiation position of the first light beam is an unrecorded area by the determination means during execution of control based on the first tracking error signal. When the control is switched to the control based on the second tracking error signal, the second tracking error signal is narrower than the first predetermined range during execution of the control based on the second tracking error signal. The control may be switched to the control based on the first tracking error signal according to whether or not the signal falls within the predetermined range, or RF that generates an RF signal based on the amount of light received by the first photodetector. A signal generation unit, wherein the determination unit determines that the irradiation position of the light beam is a recording area according to the RF signal; The tracking servo means outputs the second tracking error signal when the irradiation position of the light beam is determined to be an unrecorded area by the determination means during execution of control based on the first tracking error signal. And when the determination unit determines that the irradiation position of the light beam is a recording area during execution of the control based on the second tracking error signal, the first tracking error signal is changed to the first tracking error signal. It is good also as switching to the control based on. According to these, the tracking servo means can perform control switching stably between the recording layer and the servo dedicated layer.

  In the optical drive device, the servo dedicated layer has a land groove, and the tracking servo means detects whether the irradiation position of the second light beam is a land or a groove, and according to the result The direction of position control of the objective lens included in the optical system may be controlled.

  In the optical drive device, the servo dedicated layer may have a land groove, and the second tracking error signal generation unit may generate the second tracking error signal using a DPP method. The servo dedicated layer may have a dummy code, and the second tracking error signal generation unit may generate the second tracking error signal using a DPD method.

  The optical drive device may further include an RF signal generation unit configured to generate an RF signal based on an amount of light received by the first photodetector, and the determination unit may determine the first signal according to the RF signal. The irradiation position of the light beam may be determined to be an unrecorded area of the recording layer. This also makes it possible to appropriately determine that the irradiation position of the light beam has reached the unrecorded area of the recording layer.

  Further, in this optical drive device, the determination means determines whether the irradiation position of the first light beam is an unrecorded area or a recording area according to the RF signal, and the tracking servo means When the determination means determines that the irradiation position of the first light beam is an unrecorded area during execution of the control based on the first tracking error signal, the control is based on the second tracking error signal. The first tracking error is detected when the irradiation position of the first light beam is determined to be a recording area by the determination means during execution of control based on the second tracking error signal. It is good also as switching to control based on a signal.

  According to the present invention, when reproducing an optical disc provided with a servo-dedicated layer, it is possible to maintain the vicinity of the track center even in an unrecorded area while performing tracking servo by the DPD method using the code of the recording layer.

1 is a schematic diagram of an optical drive device according to a first embodiment of the present invention. (A) is a top view of the recording surface of the optical disk by the 1st Embodiment of this invention. (B) is the sectional view on the A-A 'line of (a). It is explanatory drawing of the astigmatism provided by the sensor lens by the 1st Embodiment of this invention. It is a top view of the photodetector by the 1st Embodiment of this invention. It is a top view of the photodetector by the 1st Embodiment of this invention. It is a figure which shows the functional block of the process part by the 1st Embodiment of this invention. In the optical drive apparatus according to a first embodiment of the present invention, when performing the reproducing and writing while maintaining near the center of the track, a diagram showing the time variation of the tracking error signal TE _R and TE _S-P. It is a figure which shows the internal circuit of the determination part by the 1st Embodiment of this invention. In the optical drive apparatus according to a first embodiment of the present invention, the time variation of the output signal V _OUT of the comparator upon playing back and write while maintaining near the center of the track, the time variation of the tracking error signal TE _S-P Are listed side by side. In the optical drive device according to the modification of the first embodiment of the present invention, the time variation of the output signal _VOUT of the determination unit when performing reproduction or writing while maintaining the vicinity of the track center is represented by the tracking error signal _TES-. These are listed side by side with the time variation of _P. It is explanatory drawing of how the light beam hits each layer when the optical disk by the 1st Embodiment of this invention inclines. (A) shows the case where the optical disc is not tilted, and (b) shows the case where the optical disc is tilted. The time variation of the tracking error signal TE _R and TE _S-P when performing reproduction and writing while maintaining near the center of the track, a diagram showing the case where the optical disc is tilted. It is a figure which shows the internal circuit of the determination part which considered the tilt of the optical disk. Tracking error signal TE R according to the first embodiment of the present _invention, a diagram drawing the TE _S-P. In the lower part, a plan view of the recording surface is shown for reference. Tracking error signal TE R according to the first embodiment of the present _invention, a diagram drawing the TE _S-P. In the lower part, a plan view of the recording surface is shown for reference. Tracking error signal TE R according to the first embodiment of the present _invention, a diagram drawing the TE _S-P. In the lower part, a plan view of the recording surface is shown for reference. Tracking error signal TE R according to the first embodiment of the present _invention, a diagram drawing the TE _S-P. In the lower part, a plan view of the recording surface is shown for reference. First mode by the tracking error signal TE R of the present _invention, the TE _S-P, is a diagram drawn for the inclination of the triplicate optical disk 11. Tracking error signal TE R according to the first embodiment of the present _invention, a diagram drawing the TE _S-P. Tracking error signal TE R according to the first embodiment of the present _invention, a diagram drawing the TE _S-P, which is an illustration of a method of obtaining the maximum value of .DELTA.1. First mode by the tracking error signal TE R of the present _invention, a diagram drawing the TE _S-P, problems that always the same direction control direction of the objective lens in the tracking servo in servo-only layer mode It is a figure explaining a point. It is a figure which shows the functional block of the process part of the optical drive apparatus by the 2nd Embodiment of this invention. It is a figure which shows the time change of the various signals which the determination part by the 2nd Embodiment of this invention utilizes when performing reproduction | regeneration and writing, maintaining track center vicinity. In the optical drive device according to the modification of the embodiment of the present invention, the time change of the output signal _VOUT of the determination unit when reproducing or writing is performed while maintaining the vicinity of the track center, the time of the tracking error signal TE _S-P It is listed side by side with changes. Tracking error signal TE R according to a modification of the embodiment of the present _invention, a diagram drawing the TE _S-D, which is an illustration of a method of obtaining the maximum value of .DELTA.1. Tracking error signal TE R according to a modification of the embodiment of the present _invention, a diagram drawing the TE _S-P, which is an illustration of a method of obtaining the maximum value of .DELTA.1. Tracking error signal TE R according to a modification of the embodiment of the present _invention, a diagram drawing the TE _S-D, which is an illustration of a method of obtaining the maximum value of .DELTA.1. Tracking error signal TE R according to a modification of the embodiment of the present _invention, a diagram drawing the TE _S-P, which is an illustration of a method of obtaining the maximum value of .DELTA.1. Tracking error signal according to a modification of the embodiment of the present invention TE _R, diagrams drawn the TE _S-D. Tracking error signal TE R according to a modification of the embodiment of the present _invention, a diagram drawing the TE _S-P. Tracking error signal according to a modification of the embodiment of the present invention TE _R, diagrams drawn the TE _S-D. Tracking error signal TE R according to a modification of the embodiment of the present _invention, a diagram drawing the TE _S-D, which is an illustration of a method of obtaining the maximum value of .DELTA.1.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram of an optical drive device 1 according to a first embodiment of the present invention.

  The optical drive device 1 performs reproduction and recording of the optical disk 11. Various optical recording media such as CD, DVD, and BD can be used as the optical disc 11, but in this embodiment, the recording layer 12 and the servo dedicated layer 13 are provided on the recording surface, and the recording layer 12 is provided. A disk-shaped optical disk that is multilayered by a multilayer film is used. In addition, the optical disc includes a reproduction-only type (DVD-ROM, BD-ROM, etc.), a write-once type (DVD-R, DVD + R, BD-R, etc.), and a rewritable type (DVD-RAM, DVD-RW, DVD + RW, etc.). There are several types classified according to the recording method, such as BD-RE.) In this embodiment, a write-once type or a rewritable type is used.

  FIG. 2A is a plan view of the recording surface of the optical disc 11. FIG. 2B shows a cross-sectional view taken along line A-A ′ of FIG.

  As shown in FIG. 2, a plurality of recording layers 12 and one servo dedicated layer 13 are provided on the recording surface of the optical disc 11. The servo-dedicated layer 13 is periodically provided with grooves, and the convex portion of the groove is called a land L and the concave portion is called a groove G. However, the convex portion and the concave portion of the groove are relative, and which of the convex portion and the concave portion is referred to as the land L depends on which of the front surface and the rear surface of the optical disk 11 is on the bottom. In FIG. 2, the land L and the groove G are drawn in a straight line, but in actuality, they slightly meander (wobble) in the radial direction.

  In the example of FIG. 2, the land L is an information writing line, and each recording layer 12 is provided with a code (pit or recording mark) M for storing information at a position corresponding to the land L. In FIG. 2, the width of the code M is drawn so as to be considerably smaller than the width of the land. This is because priority is given to the visibility of the drawing, and the actual width of the code M is the land width. A little smaller than the width. The code M is recorded or erased by irradiation with a light beam. The unrecorded area of each recording layer 12 is an area where the code M is not recorded. On the other hand, the recording area is an area where the code M is recorded. Note that the information writing line may be provided at a position corresponding to the groove G, or may be provided at a position corresponding to each of the land L and the groove G.

  Returning to FIG. As shown in FIG. 1, the optical drive device 1 includes laser light sources 2-1, 2-2, an optical system 3, a photodetector 5-1 (first photodetector), and a photodetector 5-2 (first). 2 photodetectors) and a processing unit 6. Of these, the laser light source 2, the optical system 3, and the photodetector 5 constitute an optical pickup.

  The optical system 3 includes a collimator lens 21, a polarizing beam splitter 22, a dichroic prism 23, a quarter wavelength plate 24, a collimator lens 25, a sensor lens (cylindrical lens) 26, a diffraction grating 27, a collimator lens 28, a beam splitter 29, and a collimator. The lens 30, the sensor lens (cylindrical lens) 31, and the objective lens 4 are provided. The optical system 3 functions as an outward optical system that guides the light beams emitted from the laser light sources 2-1 and 2-2 to the optical disk 11, and returns the return beam from the optical disk 11 to the photodetectors 5-1 and 5-2. It also functions as a return optical system that leads to

  First, in the forward optical system of a light beam (first light beam; hereinafter referred to as a recording layer light beam) emitted from the laser light source 2-1, the collimator lens 21 first converts the recording layer light beam into parallel light. Then, the light is incident on the polarization beam splitter 22. The polarization beam splitter 22 passes the incident parallel light and makes it incident on the dichroic prism 23. The dichroic prism 23 reflects the incident parallel light, bends its path in the direction of the optical disk 11, and makes it incident on the quarter-wave plate 24. The quarter-wave plate 24 converts the incident parallel light into circularly polarized light and makes it incident on the objective lens 4.

  On the other hand, in the forward optical system of the light beam emitted from the laser light source 2-2 (second light beam; hereinafter referred to as the servo layer light beam), first, the diffraction grating 27 generates three servo layer light beams ( 0-order diffracted light and ± 1st-order diffracted light) and enter the collimator lens 28. The collimator lens 28 converts the incident servo layer light beam into parallel light and makes it incident on the beam splitter 29. The beam splitter 29 passes the incident parallel light and makes it incident on the dichroic prism 23. The dichroic prism 23 passes the incident parallel light and makes it incident on the quarter-wave plate 24. The quarter-wave plate 24 converts the incident parallel light into circularly polarized light and makes it incident on the objective lens 4.

  The optical system 3 is configured so that the optical axes of two types of light beams (parallel light beams) incident on the objective lens 4 coincide. The objective lens 4 condenses these two types of light beams having the same optical axis on the optical disc 11 and returns the return light beam reflected by the recording surface of the optical disc 11 to parallel light.

  Here, the collimator lens 28 is configured to be driven in the focus direction (direction perpendicular to the recording surface). The objective lens 4 is configured to be driven in a focus direction and a direction parallel to the surface of the optical disc 11. In the optical drive device 1, the position control of the collimator lens 28 and the objective lens 4 is performed so that the servo layer light beam is focused on the servo dedicated layer and the recording layer light beam is focused on the access target layer. (Focus servo).

  The return light beam of the servo layer light beam is diffracted by the land group of the servo dedicated layer 13 and is decomposed into zero-order diffracted light and ± first-order diffracted light. The 0th order diffracted light and the ± 1st order diffracted light are different from the 0th order diffracted light and the ± 1st order diffracted light generated by the diffraction grating 27 and are confusing. The −1st order diffracted light is referred to as main beam MB, sub beam SB1, and sub beam SB2, respectively. In the case of 0th order diffracted light and ± 1st order diffracted light, it refers to diffracted light generated by diffraction in the land group of servo dedicated layer 13. To do. The main beam MB, sub beam SB1, and sub beam SB2 each independently generate reflected light.

  In the return path optical system for the recording layer light beam, the recording layer light beam that has passed through the objective lens 4 is incident on the dichroic prism 23 via the quarter-wave plate 24, bent by the dichroic prism 23, and polarized beam splitter. 22 is incident. The polarization beam splitter 22 further folds the recording layer light beam and makes it incident on the collimator lens 25. The recording layer light beam that has passed through the collimator lens 25 is incident on the sensor lens 26 (cylindrical lens) while being condensed. The sensor lens 26 provides astigmatism to the incident recording layer light beam. The recording layer light beam provided with astigmatism is incident on the photodetector 5-1.

  In the return optical system for the servo layer light beam, the servo layer light beam that has passed through the objective lens 4 enters the beam splitter 29 via the quarter-wave plate 24 and the dichroic prism 23. The beam splitter 29 bends the path of the incident light beam and makes it incident on the collimator lens 30. The servo layer light beam that has passed through the collimator lens 30 is incident on the sensor lens 31 (cylindrical lens) while being condensed. Similar to the sensor lens 26, the sensor lens 31 gives astigmatism to the incident servo layer light beam. The servo layer light beam provided with astigmatism is incident on the photodetector 5-2.

  FIG. 3 is an explanatory diagram of astigmatism imparted by the sensor lenses 26 and 31. As shown in the figure, the sensor lens has a lens effect only in one direction (MY axis direction = subordinate direction). Therefore, the focal position of the optical system constituted by the collimator lens and the sensor lens differs between the MY axis direction and the MX axis direction (bus line direction) which is a direction perpendicular to the MY axis direction (shown in FIG. 3). MY axis focus and MX axis focus). A point where the lengths of the light beams in the MY axis direction and the MX axis direction are equal is referred to as a focal point.

  In the focus servo described above, the converging point of the recording layer light beam (signal light) reflected by the access target layer is positioned just on the photodetector 5-1 and the servo layer light beam (signal signal reflected by the servo layer). The position control of the collimator lens 28 and the objective lens 4 is performed so that the hand-shaping point of (light) is positioned on the photodetector 5-2. The joint point of the light beam (stray light) reflected by the other layers is not located on the photodetectors 5-1 and 5-2, and the spots (strays formed on the photodetectors 5-1 and 5-2 ( The stray light spot) has a shape that spreads in at least one of the MY axis direction and the MX axis direction as compared with spots (signal light spots) formed by signal light on the photodetectors 5-1 and 5-2. .

Returning to FIG. The photodetector 5-1 is installed on a plane that intersects the optical path of the return light beam of the recording layer light beam emitted from the optical system 3. On the other hand, the photodetector 5-2 is installed on a plane that intersects the optical path of the return light beam of the servo layer light beam emitted from the optical system 3. The light detector 5-1 includes one light receiving surface, and the light detector 5-2 includes three light receiving surfaces, and each light receiving surface is divided into a plurality of light receiving regions. In the optical drive device 1, these light receiving areas are used in appropriate combinations, so that the servo layer focus error signal FE _S , the recording layer focus error signal FE _R , the full addition signal (recording layer pull-in signal PI _R , servo dedicated layer) pull-in signal _PI S, RF signals RF), a servo-only layer for tracking error signal TE _S, it is possible to generate various signals such as a recording layer for tracking error TE _R. The specific contents will be described later.

As an example, the processing unit 6 includes a DSP (Digital Signal Processor) having an A / D conversion function that converts analog signals for multiple channels into digital data. accepts the output signal, a focus error signal _FE R, FE _S, full addition signal (pull-in signal _PI R, _PI S, RF signals RF), the tracking error signal _TE R, generates a TE _S. Details of the processing of the processing unit 6 will also be described later.

  The CPU 7 is a processing device incorporated in a computer, a DVD recorder, or the like, and transmits an instruction signal for specifying an access position on the optical disc 11 to the processing unit 6 via an interface (not shown). Receiving this instruction signal, the processing unit 6 controls the objective lens 4 and moves it parallel to the surface of the optical disk 11 (this movement is called “lens shift”) to realize an on-track state (tracking servo). . In the on-track state, the CPU 7 acquires the RF signal generated by the processing unit 6 as a data signal.

  From here, the detail of the structure of the photodetector 5 and the detail of the process of the process part 6 are demonstrated.

  FIG. 4 is a top view of the photodetector 5-1 according to the present embodiment. FIG. 5 is a top view of the photodetector 5-2 according to the present embodiment. 4 and 5 also show examples of spots formed on the light receiving surface by signal light. The X and Y directions shown in FIGS. 4 and 5 correspond to the optical disc tangential direction and the optical disc radial direction, respectively.

  As shown in FIG. 4, the photodetector 5-1 includes a square light receiving surface 51. The light receiving surface 51 is divided into four squares (light receiving regions 51A to 51D) having the same area, and is disposed at a position where the return light beam of the recording layer light beam can be received.

  As shown in FIG. 5, the photodetector 5-2 includes three square light receiving surfaces 52 to 54. Among these, the light receiving surface 52 is divided into four squares (light receiving regions 52A to 52D) having the same area. The light receiving surfaces 53 and 54 are divided into two upper and lower portions with the same area (light receiving regions 53A and 53B and light receiving regions 54A and 54B). The light receiving surfaces 52 to 54 are arranged at positions where the main beam MB, the sub beam SB1, and the sub beam SB2 can be received.

The photodetectors 5-1 and 5-2 that have received the light beam output a signal having an amplitude of a value (light reception amount) obtained by dividing the intensity of the light beam by the area of the light receiving surface for each light receiving region. Hereinafter, an output signal corresponding to the light receiving region _X is represented as I _X.

  FIG. 6 is a diagram illustrating functional blocks of the processing unit 6. As shown in the figure, the processing unit 6 includes a tracking error signal generation unit 61-1 (first tracking error signal generation unit), a tracking error signal generation unit 61-2 (second tracking error signal generation unit), and a tracking. A servo unit 62 (tracking servo unit), a determination unit 63 (determination unit), a full addition signal generation unit 64 (RF signal generation unit), a focus error signal generation unit 65, and a focus servo unit 66 are provided.

The tracking error signal generation unit 61-1 generates a recording layer tracking error signal TE _R (first tracking error signal) using the DPD method based on the output signal of the photodetector 5-1. It will be described in detail how to generate a tracking error signal TE _R.

Upon generation of the tracking error signal TE _R, the tracking error signal generator 61-1, the output signal of the light detector 5-1, two phase difference signals _{S1p = P (I 51A, I} 51B) and S2p = P ( I _51C , I _51D ). P (X, Y) is a function indicating the phase difference between the signal X and the signal Y. Then, the phase difference signals S1p, the S2p added, is output as the tracking error signal TE _R.

The phase difference indicated by the phase difference signals S1p and S2p is 0 when the light beam is diffracted by the code M and the incident light is incident on the recording surface when the focal position of the incident light on the recording surface is at the center of the track. The focal position of the light increases as it moves away from the track center. Thus, by the sum of the phase difference indicated by the tracking error signal TE _R controls the objective lens 4 so as to be zero, it is possible to realize the on-track state.

  However, the phase difference indicated by the phase difference signals S1p and S2p becomes 0 not only when the on-track state is applied but also when the light beam is irradiated on the area without the code M (unrecorded area). Therefore, an on-track state cannot be realized in the unrecorded area by the DPD method.

The tracking error signal generation unit 61-2 generates a servo-dedicated layer tracking error signal TE _S (second tracking error signal) using the DPP method based on the output signal of the photodetector 5-2. Hereinafter, in some cases particularly referred to as a tracking error signal TE _S-P the tracking error signal TE _S servo-only layer using a DPP method. Hereinafter, a method for generating the tracking error signal TE _S-P will be described in detail.

In the generation of the tracking error signal TE _S-P , the tracking error signal generation unit 61-2 calculates the differential push-pull signal DPP by the following equation (1). Then, this differential push-pull signal DPP is output as a tracking error signal TES _-P . However, MPP and SPP are a main push-pull signal and a sub push-pull signal, respectively, and are represented by equations (2) and (3), respectively. Further, k is a positive constant and is determined so as to cancel out the lens shift offset (offset caused by the above-described lens shift) generated in each of the main push-pull signal MPP and the sub push-pull signal SPP.

  As shown in FIG. 5, each beam MB, SB1, SB2 has push-pull regions P1 and P2. These are areas where the above-described 0th-order diffracted light and ± 1st-order diffracted light interfere with each other. As shown in FIG. 5, in the main beam MB and the sub-beams SB1 and SB2, the push-pull area P1 and the push-pull area P2 The positional relationship is reversed.

The relative intensities of the push-pull areas P1 and P2 change as the focal position of the incident light on the recording surface moves in the radial direction of the optical disc (that is, moves in the direction crossing the track). When the focal position of the incident light on the recording surface is at the center of the track, the intensities of the push-pull areas P1 and P2 are equal. Therefore, the value of the main push-pull signal MPP is 0 when the focal position of the incident light on the recording surface is at the center of the track, and other than 0 otherwise. The same applies to the sub push-pull signal SPP. However, as described above, since the positional relationship between the push-pull region P1 and the push-pull region P2 is reversed between the main beam MB and the sub beams SB1 and SB2, the main push-pull signal MPP and the sub push-pull signal SPP are The phase is 180 ° different and the sign is reversed. For this reason, the value of the differential push-pull signal DPP represented by the equation (1) is also 0 when the focal position of the incident light on the recording surface is at the center of the track, and other than 0 otherwise. Thus, the on-track state can be realized by controlling the objective lens 4 so that the tracking error signal TE _S-P becomes zero.

Tracking servo section 62, the tracking error signal TE _R and on the basis of either of the TE _S, (more specifically the objective lens 4) optical system 3 for controlling the (tracking servo). Hereinafter referred to as the tracking error signal TE recording layer mode mode for controlling the optical system 3 based on the _R, the tracking error signal TE servo-only layer mode mode for controlling the optical system 3 based on the _S.

  When the above-described instruction signal is input from the CPU 7, the tracking servo unit 62 first starts tracking servo in the recording layer mode to realize an on-track state. When the determination result that the irradiation position of the light beam for the recording layer is an unrecorded area is notified from the determination unit 63 during the tracking servo in the recording layer mode, the tracking servo is switched to the servo dedicated layer mode. I do. Conversely, when the determination unit 63 notifies the determination result that the irradiation position of the light beam for the recording layer is the recording area during tracking servo in the servo dedicated layer mode, the recording layer mode is switched to the tracking. Servo is performed. These switching processes will be described in more detail later together with the description of the determination unit 63.

The determination unit 63 determines whether the irradiation position (focal position) of the recording layer light beam is in an unrecorded area or a recorded area in the access target layer. Specifically, it monitors the tracking error signal TE _S tracking error signal generator 61-2 generates, depending on whether changes beyond a predetermined range, performs the above determination. Details will be described below.

7, when performing reproduction and writing while maintaining near the center of the track, a diagram showing the time variation of the tracking error signal TE _R and TE _S-P. The solid line of the tracking error signal TES _-P indicates the case where the mode is switched according to the present embodiment, and the dotted line indicates the case where the switching to the servo dedicated layer mode is not performed according to the present embodiment. Here, a case is considered in which there is no tilt or optical axis deviation described later, and the focal position of the light beam is at the track center of the servo dedicated layer and the recording layer, respectively.

Located focal position recording area, and when the focal position is in the track center, the value of the tracking error signal TE _R becomes zero. On the other hand, when in the position where the focus position is slightly deviated from the track center, the value of the tracking error signal TE _R becomes non-zero. Therefore, the tracking servo unit 62, by controlling the objective lens 4 so that the value of the tracking error signal TE _R becomes 0, suitably on-track state is achieved. As a result, as shown in FIG. 7, the value of the tracking error signal TE _S-P is also maintained at zero.

On the other hand, when the focal position is in the unrecorded region, the irradiation position of the recording layer for light beam because there is no code M, the values of the tracking error signal TE _R be shifted focal position from the track center remain 0 is there. Therefore, when the tracking servo unit 62 is performing the control based on the tracking error signal TE _R, the irradiation position of the recording layer for light beam gradually deviated from the track. Along with this deviation, the value of the tracking error signal TES _-P gradually moves away from 0 as shown in FIG. 7, and finally the same as at the time of track jump unless mode switching is performed according to the present embodiment. Will repeat the vibration.

The determination unit 63 detects such a change in the value of the tracking error signal TE _S-P to determine whether the irradiation position of the recording layer light beam is in an unrecorded area or a recorded area in the access target layer. Determine. That is, the determination unit 63 in advance predetermined threshold .DELTA.1, stores the Δ2 (0 ≦ Δ2 <Δ1) , running control tracking servo unit 62 based on the tracking error signal TE _R, the tracking error signal TE _{S When} the value of _−P exceeds the range of −Δ1 to Δ1, it is determined that the irradiation position of the recording layer light beam has entered an unrecorded area in the access target layer (the determination unit 63 only determines so). And it is not guaranteed 100% that it has entered the unrecorded area.) On the other hand, if it falls within the range of -Δ2 to Δ2, it is determined that the irradiation position of the recording layer light beam has entered the recording area in the access target layer (the determination unit 63 only determines so). Yes, it is not 100% guaranteed that the recording area in the access target layer has been entered.)

  The determination unit 63 notifies the tracking servo unit 62 of the result of the above determination. When the tracking servo unit 62 is notified of the determination result that the irradiation position of the light beam for the recording layer has entered the unrecorded area in the access target layer, the tracking servo unit 62 stops the tracking servo in the recording layer mode, and the servo dedicated layer mode Switch to tracking servo at. On the other hand, when the determination result that the irradiation position of the light beam for the recording layer has entered the recording area in the access target layer is notified, the tracking servo in the servo dedicated layer mode is stopped and the tracking in the recording layer mode is stopped. Switch to servo.

FIG. 8 is a diagram specifically illustrating an internal circuit of the determination unit 63. As shown in the figure, the determination unit 63 includes comparators 70 and 71 and an output signal generation unit 72. Comparator 70 and 71 each have two input terminals, the tracking error signal TE _S and the reference potential _{V ref} are input, respectively. The reference potential V _ref, the focal position of the light beam is the potential of the tracking error signal TE _S when in the track center is arbitrarily determined in consideration of the operating point of the circuit. That is, the tracking error signal _TE S, TE _R is the value of the included reference potential _{V ref.} The output signal generator 72 receives the output signals V ₁ and V ₂ from the comparators 70 and 71 and generates an output signal _VOUT .

FIG. 9 shows the time changes of the signals V ₁ , V ₂ , and V _OUT when performing reproduction and writing while maintaining the vicinity of the track center side by side with the time change of the tracking error signal TE _S-P. . Note that the time scale in FIG. 9 is shorter than that in FIG. As understood from FIG. 9, the comparator 70 sets the value of the signal V ₁ to low when the value of the tracking error signal TE _S-P is in the range of −Δ1 to Δ1, and otherwise sets the signal V _{1 Let} the value of _{1 be} high. On the other hand, the comparator 71 sets the value of the signal V ₂ to low when the value of the tracking error signal TE _S-P is in the range of −Δ2 to Δ2, and sets the value of the signal V ₂ to high otherwise. . The output signal generator 72, a high signal _{V OUT} at the rising edge of the signal _{V 1,} and a low signal _{V OUT} at the falling edge of the signal _{V 2.} The determination unit 63 notifies the tracking servo unit 62 of this signal _VOUT as a determination result of whether the irradiation position of the light beam for the storage layer is in an unrecorded area or a recorded area in the access target layer.

The tracking servo unit 62 performs mode switching according to the output signal _VOUT . That is, when _VOUT is low, the recording layer mode is selected, and when _VOUT is high, the servo dedicated layer mode is selected. As a result, the tracking error signal TE _S-P changes as shown in FIG.

It should be noted here that when the irradiation position of the recording layer light beam is in an unrecorded area, the output signal _VOUT becomes a signal that vibrates violently as shown in FIG. Due to this vibration, if the tracking servo unit 62 is sensitive to the output signal _VOUT and performs mode switching, mode switching frequently occurs in an unrecorded area, and the tracking servo may become unstable. is there. Therefore, when switching from the servo-only layer mode to the recording layer mode, it is preferable to perform processing with a certain delay. Specifically, the tracking servo unit 62 may delay the process, or the determination unit 63 may delay the output timing of the determination result.

FIG. 10 shows a specific example of the delay process. In FIG. 10, similarly to FIG. 9, the time changes of the signals V ₁ , V ₂ , and V _OUT when performing reproduction and writing while maintaining the vicinity of the track center are arranged in time changes of the tracking error signal TE _S-P. Although those described in this example, the timing at which the output signal V _OUT by the output signal generation unit 72 of the determination unit 63 is low, rather than immediately after the falling edge of the signal V _2, from the fall of the signal V ₂ It is after the elapse of a predetermined delay time d. For example, the delay time d is a time for TE _S-P to return to zero. According to this example, as shown in FIG. 10, since TE _S-P can return to near zero, the oscillation cycle of the output signal _VOUT is long. Accordingly, since the frequency of switching between the servo dedicated layer and the tracking servo of the recording layer can be reduced, the tracking servo can be performed relatively stably.

  As described above, according to the optical drive device 1 according to the present embodiment, when the optical disk 11 provided with the servo dedicated layer 13 is reproduced, the tracking servo is performed by the DPD method using the code of the recording layer 12. Thus, the vicinity of the track center can be maintained even in an unrecorded area.

  The description so far has been made on the assumption that the servo dedicated layer 13 has a land / groove. However, the servo dedicated layer 13 has a dummy code instead of a land / groove. Even in this case, it is possible to maintain the vicinity of the track center in the unrecorded area by the same processing. This will be described in detail below.

If the servo-only layer 13 has a dummy code, the tracking error signal generator 61-2, the tracking error signal TE _S-D by using the DPD method by the same processing as the tracking error signal generator 61-1 Generate. The determination unit 63 monitors the tracking error signal TES _-D generated using the DPD method, and the irradiation position (focal position) of the light beam is accessed depending on whether or not it has changed beyond a predetermined range. It is detected whether it is in an unrecorded area or a recorded area in the target layer. This detection processing can also be realized by the same processing as that in the case of using the tracking error signal TE _S-P made by using the DPP method. Thus, even when the servo dedicated layer 13 has a dummy code, it is possible to perform the same processing as when the land / groove is provided. Accordingly, even when the servo dedicated layer 13 has a dummy code instead of a land / groove, the vicinity of the track center in the unrecorded area can be maintained as in the case of having the land / groove. It becomes possible.

Returning to FIG. Total sum signal generator 64, based on the received light amount of the light receiving regions 51A~51D constituting the light receiving surface 51 for receiving the light beam recording layer, generates an RF signal RF and the recording layer the pull-in signal PI _R . Further, based on the received light amount of the light receiving regions 52A~52D constituting the light receiving surface 52 for receiving the servo-only layer for light beam, to produce a servo-only layer pull-in signal PI _S. Specifically, these signals are generated by performing calculations of the following equations (4-1) and (4-2). As is clear from the equation (4-1), the RF signal RF and the pull-in signal PI are the same signal. However, the recording layer pull-in signal PI _R is usually band-limited is output in a state of being made by passing the low-pass filter. The band is limited in order to remove fluctuations and noise according to the presence or absence of the code M.

Recording layer pull-in signal PI _R and the servo-only layer pull-in signal PI S _(hereinafter collectively referred to as pull-in signal PI.) Is a signal used for the layer recognized in the focus servo unit 66. That is, the pull-in signal PI has a property that when the focal position of the light beam moves between layers, the pull-in signal PI becomes maximum when the surface of the layer is in focus. Therefore, the focus servo unit 66 compares the value of the pull-in signal PI with a predetermined threshold value, and detects a portion that is higher than the threshold value, so that the focal position of the light beam becomes the recording layer or the servo. Detect that it is in the vicinity of the dedicated layer.

  The RF signal RF is input to the CPU 7 as a data signal. The CPU 7 acquires information written on the optical disc 11 based on the RF signal RF.

Focus error signal generating unit 65, and generates a focus error signal FE _R recording layer based on the received light amount of the light receiving regions 51A~51D constituting the light receiving surface 51 for receiving the light beam recording layer, servo generating a focus error signal FE _S servo layer based on the received light amount of the light receiving regions 52A~52D constituting the light receiving surface 52 for receiving the main beam MB of dedicated layer for light beam. Specifically, by calculating the following equation (5) and (6), to generate these focus error signal _FE R, FE _S.

Focus servo unit 66 controls the position of the collimator lens 28 and the objective lens 4 to the recording surface perpendicular direction of the optical disc 11, that the value of each focus error signal FE _R, FE _S is made to be 0 Then, the recording layer light beam is focused on the recording layer, and the servo dedicated layer light beam is focused on the dedicated servo layer (focus servo).

  Finally, processing that takes into account the tilt (tilt) of the optical disk 11 will be described. In the description so far, the tilt of the optical disk 11 has been ignored, but the optical disk 11 may actually be tilted. In this case, the recording layer light beam and the servo-dedicated layer light beam are simultaneously irradiated to the track center. Becomes difficult.

  FIG. 11 is an explanatory diagram of how the light beam strikes each layer when the optical disc 11 is tilted. FIG. 11A shows a case where the optical disc 11 is not tilted, and FIG. 11B shows a case where the optical disc 11 is tilted. If the optical disk 11 is not tilted, as shown in FIG. 11A, when the recording layer 12 is in an on-track state, the servo dedicated layer 13 is also in an on-track state. However, as shown in FIG. 11B, when the optical disk 11 is tilted, even if the recording layer 12 is in an on-track state, the servo dedicated layer 13 does not become the track center.

This also affects the value of the tracking error signal TE _R and _{TE S-P.} Figure 12 is a time change of the tracking error signal TE _R and TE _S-P when performing reproduction and writing while maintaining near the center of the track, a diagram illustrating a case where the optical disk 11 is tilted. In the figure, it is assumed that mode switching according to the present embodiment is not performed.

As is apparent from comparison between FIGS. 12 and 7, the tracking error signal TE _R is not the same as the tracking error signal TE _R in FIG. 7, the value of the tracking error signal TE _S-P, the tracking error signal in FIG. 7 Compared with TES _-P , when the focal position is within the recording area, there is an offset by α (hereinafter referred to as tilt offset). This tilt offset occurs because the optical disk 11 is tilted.

FIG. 13 is a diagram illustrating an internal circuit of the determination unit 63 in consideration of the tilt of the optical disc 11. As shown in the figure, in the determination unit 63 in this case, a sample hold circuit 73 is provided at the input terminals of the comparators 70 and 71 described above. The sample hold circuit 73 is a circuit that samples the tracking error signal TE _S-P generated by the tracking error signal generation unit 61-2 and holds it for a predetermined time. As a result, the comparators 70 and 71 output signals V ₁ and V _{2 based on} the potential V _ref + α of the tracking error signal TE _S-P held when the irradiation position of the recording layer light beam is in the recording area. Will be generated. That is, the comparator 70 sets the value of the signal V ₁ to low when the value of the tracking error signal TE _S-P is within the range of α−Δ1 to α + Δ1, and sets the value of the signal V ₁ to high otherwise. To do. On the other hand, the comparator 71, a low value of the signal V ₂ if the value of the tracking error signal TE _S-P is in the range of α-Δ2~α + Δ2, and high values of the signal V ₂ Otherwise To do.

  In this way, even when the optical disk 11 is tilted, it is possible to appropriately determine that the irradiation position of the recording light beam has reached the unrecorded area, and it is possible to perform mode switching appropriately.

  By the way, when the tilt of the optical disk 11 must be taken into account, after switching from the servo-only layer mode to the recording layer mode, Δ1 needs to be determined by a special determination method so that it can return to the on-track state normally. . Further, it is necessary to switch the control direction of the objective lens 4 in the tracking servo in the servo dedicated layer mode between the land and the groove. This will be described in detail below.

First, a case where the optical disc 11 is not tilted will be described. Figure 14 is a diagram drawn with the tracking error signal TE _R of the tracking error signal generating unit 61-1 generates a tracking error signal _{TE S-P} in which the tracking error signal generator 61-2 generates the horizontal axis Is the optical disc radial direction (track jump direction). For reference, a plan view of a recording surface (including a recording layer code M, a servo dedicated layer land L and a groove G) is shown at the bottom of the figure. Further, in FIG line segment C _R indicating a track center of the recording layer, the line segment indicating a track center of the servo-only layer C _{S (land} L of the center only) depicts. In FIG. 14, the horizontal width of the symbol M is drawn so as to be considerably smaller than the width of the land. This is because priority is given to the visibility of the drawing, and the actual horizontal width of the symbol M is larger than the width of the land. It is a little small. The same applies to other drawings to be described later.

FIG. 14 shows a case where an optical disk 11 that can be reproduced by a red laser (optical disk 11 whose track pitch is determined according to the spot diameter of the red laser) is used, and a blue laser is used as a recording layer light beam. Show. This case, as shown in the figure, the tracking error signal TE _R generated based on the recording layer for light beam of the reflected light is near the irradiation position of the recording layer for light beam code M (the land L) In some cases, it has a maximum value, and when it is in the groove G, it is always zero. In contrast, as shown in such FIG. 28 to be described later, the tracking error signal TE _R when light beam recording layer is red laser has a maximum value near the center of the groove G. This difference is due to the difference in spot size between the red laser and the blue laser.

FIG. 14 shows signals when the irradiation position of the recording layer light beam is in the recording area. In this case, the irradiation position of the recording layer for light beam is temporarily displaced from the track center C _R in the arrow A1 direction in FIG. Then, the tracking error signal TE _R varies in the arrow B1 direction in the drawing, by the tracking servo in the recording layer mode immediately returns. Thus, the irradiation position of the recording layer for light beam returns to the track center C _R. At this time, the tracking error signal TES _-P also changes in the direction of the arrow C1 in the figure. However, since the tracking servo in the recording layer mode is performed, the threshold value Δ1 is not normally exceeded. The mode 62 is not switched to the servo dedicated layer mode.

FIG. 15 is the same as FIG. 14 except that the irradiation position of the recording layer light beam is in the unrecorded area. In this case, the code M does not exist in the recording layer as shown in FIG. Therefore, the tracking error signal TE _R is always 0, not the tracking servo functions of the irradiation position of the recording layer for light beam in the recording layer mode even when deviated in the direction indicated by the arrow A2 in FIG from the track center C _R As shown by the arrow C2 in the figure, the tracking error signal TE _S-P eventually exceeds the threshold value Δ1. After that, tracking servo is performed in the servo dedicated layer mode.

FIG. 16 shows an example where the irradiation position of the recording layer light beam returns to the recording area once the state of FIG. 15 is reached. In this case, the irradiation position of the recording layer light beam first moves along the arrow A3 in the figure by tracking servo in the servo-only layer mode. At this time, the tracking error signal TES _-P changes along the arrow C3 in the figure. The value of the tracking error signal TE _S-P at the tip of the arrow C3 is Delta] 2, when exceeding this Delta] 2, the mode of the tracking servo unit 62 is switched to the recording layer mode. Thereafter the tracking servo in the recording layer mode, the irradiation position of the recording layer for light beam returns to the track center C _R (arrow B4, A4).

  Next, a case where the optical disk 11 is tilted will be described. FIG. 17 is the same as FIG. 16 except that the optical disk 11 is tilted.

If the optical disc 11 is tilted, as shown in FIG. 17, as viewed from the irradiation direction of the light beam, the track center C _S of the track center C _R and the servo-only layer of the recording layer do not match. As a result, if the irradiation position of the recording layer for light beam is at the track center C _R, the value of the tracking error signal TE _S-P is a tilt offset α as described above (≠ 0). Since the value of the tilt offset α is held by the sample hold circuit 73 described above, the mode of the tracking servo section 62 is dedicated to the servo when the value of the tracking error signal TE _S-P exceeds the range of α−Δ1 to α + Δ1. The mode is switched to the layer mode, and the mode is switched to the recording layer mode when the value of the tracking error signal TES _-P falls within the range of α−Δ2 to α + Δ2.

Here, assuming that the irradiation position of the recording layer light beam returns to the recording area after the mode of the tracking servo section 62 is once switched to the servo dedicated layer mode, the irradiation position of the recording layer light beam is first set to the servo-only layer mode. It moves along the arrow A5 shown in FIG. 17 by the tracking servo in the layer mode. At this time, the tracking error signal TE _S-P changes along the arrow C5 in the drawing. The value of the tracking error signal TE _S-P at the tip of the arrow C5 is alpha + Delta] 2, at the time of exceeding the alpha + Delta] 2, the mode of the tracking servo unit 62 is switched to the recording layer mode. Thereafter the tracking servo in the recording layer mode, the irradiation position of the recording layer for light beam returns to the track center C _R (arrow B6, A6).

In the example of FIG. 17, after switching from the servo-only layer mode to the recording layer mode, it was possible, especially returning the irradiation position of the recording layer for light beam without problems in track center C _R. However, depending on the irradiation position of the recording layer light beam when the value of the tracking error signal TE _S-P is α−Δ2, it may not be returned. Hereinafter, such a case will be described.

FIG. 18 is a diagram showing tracking error signals TE _S-P (1) to TE _S-P (3) in each case with respect to three types of inclinations of the optical disc 11. Distance X (> A. A from the light beam irradiation position initially track center C _R of the when the value of the tracking error signal TE _R is the maximum, from the track center C _R of the irradiation position of the recording layer for light beam ), And the mode of the tracking servo unit 62 at that time is the servo dedicated layer mode. Due to the tracking servo in the servo dedicated layer mode, the values of the tracking error signals TE _S-P (1) to TE _S-P (3) are respectively indicated by arrows R (1) to R (3) shown in the figure. Change along. Then, when each value becomes a value α (1) −Δ2−α (3) −Δ2 obtained by subtracting Δ2 from each tilt offset α (1) to α (3), the tracking servo unit 62 The mode switches to the recording layer mode. 18, the position of the tracking error signal TE _R at the time of switching to the recording layer mode indicates (hereinafter, referred to as switching position.) At the point P (1) to P (3).

As understood from FIG. 18, when the switching positions are the points P (1) and P (2), the recording is performed by the tracking servo in the recording layer mode as in the case described with reference to FIGS. it is possible to return the irradiation position of the layer light beam to track the center C _R. In contrast, when the switching position is a point P (3), since the value of the tracking error signal TE _R is 0, the tracking servo does not function in the recording layer mode, the irradiation position of the recording layer for light beam It can not be returned to the track center C _R.

In order to prevent the case where this manner the irradiation position of the recording layer for light beam can not be returned to the track center C _R occurs, in this embodiment utilizes .DELTA.1. In other words, the switching position, the recording layer position of limit tracking servo functions in mode (point P (2 in Fig. 18). A position spaced a distance a from the track center C _R.) Away from the track center C _R than In this case, the upper threshold value α + Δ1 is prevented from exceeding the maximum value of the tracking error signal TE _S-P .

Figure 19 is a diagram an extracted only the tracking error signal _{TE S-P} (3) of the three tracking error signal _{TE S-P (1) ~TE} S-P (3) shown in FIG. 18 . The figure also shows the upper threshold value α (3) + Δ1 and the lower threshold value α (3) −Δ1 determined as described above. As shown in the figure, when the upper threshold value α (3) + Δ1 does not exceed the maximum value of the tracking error signal TE _S-P, the irradiation position of the recording layer for light beam deviates from the track center C _R when went, upon reaching at a distance Y (<a) from the track center C _R, mode of the tracking servo unit 62 is switched to the servo-only layer mode. That is, it ends up distance X (> a) the irradiation position of the recording layer for light beam position to the from the track center C _R is moved as shown in FIG. 18, not originally occur obtained. Therefore, it is possible to prevent the case where it is impossible to return the irradiation position of the recording layer for light beam to the track center C _R occurs.

The maximum value that Δ1 can take varies depending on the inclination of the optical disk 11. That is, as the inclination of the optical disk 11 is smaller (in the example of FIG. 18, the tracking error signal TE _S-P is shifted to the right), the value of Δ1 can be increased. The maximum value of Δ1 is the smallest in the case of the tracking error signal TE _S-P (2) shown in FIG. 18 (strictly speaking, a small distance from the tracking error signal TE _S-P (2) to the right. Is the case. Conversely, determining the specific values of .DELTA.1, as the tracking error signal TE _S-P is equal to or smaller than the maximum value of .DELTA.1 when the tracking error signal TE _{S-P (2)} shown in FIG. 18 If it is possible to prevent the case where the inclination of the optical disk 11 be any value, it is impossible to return the irradiation position of the recording layer for light beam to the track center C _R occurs. Therefore, hereinafter, a description will be given of how to obtain the maximum value of Δ1 when the tracking error signal TE _S-P becomes the tracking error signal TE _S-P (2).

FIG. 20 shows only the tracking error signal TE _S-P (2) extracted from the three tracking error signals TE _S-P (1) to TE _S-P (3) shown in FIG. . In the following description, it is assumed that the slope (gradient) of the tracking error signal TE _S-P is g ₁ as shown in FIG.

Length c shown in the figure is expressed as c = Δ2 / _{g 1.} Therefore, d = a-c = a -Δ2 / g 1 becomes further expressed as _{Δ1 = (1/2) × (ag} 1 -Δ2). This Δ1 is the maximum value of Δ1 when the tracking error signal TE _S-P becomes the tracking error signal TE _S-P (2). For example, in the case of TE _S-P (1) (FIG. 18), the distance in the track radial direction between α (1) −Δ2 and α (1) is smaller than a. Therefore, when the control is performed in the servo dedicated layer, the distance from the track center CR in the recording layer does not become larger than a. Therefore, when the tracking control is switched (when switched from α (1) −Δ2), the recording is performed. Layer control is possible. On the other hand, in the case of the tracking error signal TE _S-P (3) (FIG. 18), since α (3) <α (2), the position where the sign of the slope changes is not reached in Δ1. Therefore, when the control is performed in the servo dedicated layer, the distance from the track center CR in the recording layer does not become larger than a. Therefore, when the tracking control is switched (when switched by α (3) + Δ2), the recording layer Can be controlled. Therefore, by setting Δ1 ≦ (1/2) × (ag 1 -Δ2), also the inclination of the optical disk 11 is of any value, to return the irradiation position of the recording layer for light beam to the track center C _R It can prevent the case where it cannot be done.

When determining Δ1 as described above, for example, in the tracking error signal TE _S-P (1) shown in FIG. 18, the upper threshold value α (1) + Δ1 is the maximum of the tracking error signal TE _S-P . It becomes larger than the value and does not function as a threshold for switching to the servo-only layer mode. In such a case, there is a problem if the control direction of the objective lens 4 in the tracking servo in the servo dedicated layer mode is always the same direction. Details will be described below.

21, three of the tracking error signal _TE S-P _{(1) ~TE} tracking error signal in the _{S-P (3) TE S} -P (1) shown in FIG. 18, similar to FIGS. 14 to 17 FIG. If the irradiation position of the recording layer for light beam is shifted in the arrow A7 direction in FIG from the track center C _R, after the irradiation position of the recording layer for light beam properly to track center C _R when returning to the recording layer mode In order to return, it is necessary to change the tracking error signal TES _-P along the arrow C7 in the figure in the tracking servo in the servo dedicated layer mode. On the other hand, if the irradiation position of the recording layer for light beam is shifted to (the opposite direction to the A7 direction) arrow A8 direction in FIG from the track center C _R, after the recording layer for light beam when returning to the recording layer mode to return the irradiation position of the appropriately the track center C _R, in the tracking servo in servo-only layer mode, it is necessary to change the tracking error signal TE _S-P along the arrow C8 of FIG.

In the arrows C7 and C8, the control direction of the objective lens 4 is opposite. Assuming that that only the control direction of the objective lens 4 only in the arrow C8 direction, if the irradiation position of the recording layer for light beam is shifted in the arrow A7 direction in FIG from the track center C _R, tracking servo only layer mode tracking error signal TE _S-P by a servo will change in the direction of the arrow C9 in FIG. In that case, after returning to the recording layer mode, the mobile since the tracking servo tracking error signal TE _R will vary along the arrow B9 in Figure, the track irradiation position next to the recording layer for light beam Result. This is an undesirable result.

  In order to prevent this, the tracking servo unit 62 according to the present embodiment performs the tracking servo in the servo dedicated layer mode depending on whether the irradiation position of the servo dedicated layer light beam is in the land L or in the groove G. The control direction of the objective lens 4 is reversed. As a result, after switching from the servo dedicated layer mode to the recording layer mode, it is possible to return to the on-track state normally.

  The detection of whether the irradiation position of the servo-dedicated layer light beam is in the land L or the groove G is preferably performed based on the received light amounts of the light receiving regions 52A to 52D constituting the light receiving surface 52. Specifically, the RF signal RF is generated by the following equation (7), and the above detection is performed based on the value.

  Since the reflectance differs between the land L and the groove G, the value of the RF signal RF shown in the equation (7) is different depending on whether the irradiation position of the servo dedicated layer light beam is in the land L or in the groove G. Different. The tracking servo unit 62 stores the intermediate value as a threshold value, and the irradiation position of the servo dedicated layer light beam is the land L depending on whether the value of the RF signal RF is higher or lower than the threshold value. Which of the grooves G is present is detected.

  FIG. 22 is a diagram showing functional blocks of the processing unit 6 of the optical drive device 1 according to the second embodiment of the present invention. The optical drive device 1 according to the present embodiment is the same as the optical drive device 1 according to the first embodiment, except that the processing of the determination unit 63 is partially different. Below, it demonstrates paying attention only to the process of the determination part 63. FIG.

As illustrated in FIG. 22, the RF signal RF is input to the determination unit 63 according to the present embodiment instead of the tracking error signal TE _S-P . The determination unit 63 detects whether the irradiation position of the recording layer light beam is in an unrecorded area or a recorded area in the access target layer in accordance with the RF signal RF. Details will be described below.

  FIG. 23 is a diagram illustrating temporal changes of various signals used by the determination unit 63 when performing reproduction or writing while maintaining the vicinity of the track center.

  First, as shown in FIG. 23, the RF signal RF is a signal that vibrates violently in a short period in the recording area. Since this vibration corresponds to a change in reflectance due to the symbol M, the RF signal RF does not vibrate in the unrecorded area. Although an example is shown in FIG. 23, the absolute value of the RF signal RF varies due to non-uniform reflectance of the recording layer and confocal crosstalk. Therefore, the determination unit 63 first performs bottom clamp processing for aligning the lower values of the RF signal RF to obtain the clamp signal RFC shown in FIG.

  When the clamp signal RFC is obtained, the determination unit 63 then obtains a top envelope signal ENV that envelops the maximum value of the clamp signal RFC with a predetermined droop plate (generally the vibration period of the RF signal RF). The slice signal SS is obtained by slicing the top envelope signal ENV with a predetermined slice level SL stored in advance. Note that the slice level SL is preferably set to a value approximately between the maximum value and the minimum value of the clamp signal RFC.

  Finally, the determination unit 63 generates an unrecorded area detection signal NR based on the slice signal SS. Specifically, the unrecorded area detection signal NR is set high when the high level of the slice signal SS continues for a certain time D or more, and immediately when the slice signal SS becomes low, the unrecorded area detection signal NR is set low. Thus, the unrecorded area detection signal NR is generated. The reason why the rising delay process is performed in this manner is to prevent erroneous detection of an unrecorded area due to noise because the RF signal RF has a property that is greatly influenced by noise.

  The unrecorded area detection signal NR indicates that the irradiation position of the recording layer light beam has entered the recording area in the access target layer when low, and the irradiation position of the recording layer light beam when high. This signal indicates that an unrecorded area in the access target layer has been entered. The determination unit 63 notifies the tracking servo unit 62 of the detection result by outputting the unrecorded area detection signal NR. The tracking servo unit 62 switches modes according to the input unrecorded area detection signal NR.

  As described above, even with the optical drive device 1 according to the present embodiment, when performing reproduction or writing while maintaining the on-track state by performing tracking servo in the recording layer mode, the irradiation position of the light beam Can be switched to the tracking servo in the servo-only layer mode.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to such embodiment at all, and this invention can be implemented in various aspects in the range which does not deviate from the summary. Of course.

For example, the determination unit 63 generates both the output signal _VOUT and the unrecorded area detection signal NR, and the detection and notification that the irradiation position of the recording layer light beam has entered the recording area is the unrecorded area detection signal NR. The detection and notification that the recording layer light beam irradiation position has entered the unrecorded area may be performed based on the output signal _VOUT . As described above, the output signal _VOUT vibrates violently when the irradiation position of the light beam is in an unrecorded area. Therefore, it has been described that it is preferable to perform processing with a certain delay when switching from the servo-only layer mode to the recording layer mode. However, this delay is caused by an unrecorded area in the output signal _VOUT. This can also be realized by combining the detection signals NR. That is, as described above, the determination unit 63 performs detection and notification that the irradiation position of the recording layer light beam has entered the recording area based on the unrecorded area detection signal NR, and the irradiation of the recording layer light beam. The detection and notification that the position has entered the unrecorded area may be performed based on the output signal _VOUT . By doing so, the tracking servo section 62 can switch modes at a more appropriate timing. That is, the tracking servo unit 62 performs tracking control in the recording layer when the unrecorded area detection signal NR is low, and performs tracking control in the servo dedicated layer when the signal is high. FIG. 23 shows an example of generating the unrecorded area detection signal NR by processing the RF signal RF.

FIG. 24 assumes that the determination unit 63 performs the above processing, and similarly to FIGS. 9 and 10, the signals V ₁ , NR, and V when performing reproduction and writing while maintaining the vicinity of the track center. The time variation of _OUT is described side by side with the time variation of the tracking error signal TES _-P . According to this example, as shown in FIG. 24, the value of the output signal _VOUT is high while the focal position of the light beam enters the unrecorded area and once becomes high, and then remains within the unrecorded area. Maintained in a state. Accordingly, since the frequency of switching the tracking control in the recording layer and the servo dedicated layer can be greatly reduced, tracking servo can be performed more stably.

14 to 21, the optical disk 11 that can be reproduced by the red laser (the optical disk 11 whose track pitch is determined according to the spot diameter of the red laser) is used, and the blue laser is used as the recording layer light beam. Although the case is shown, the combination of the type of the optical disk 11 and the color of the light beam for the recording layer is not limited to this. Also, for the servo dedicated layer light beam, either a red laser or a blue laser can be used. As described above, the tracking error signal TE _S, can be any of the tracking error signal _{TE S-D} which is generated by the tracking error signal _{TE S-P} and DPD method generated by the DPP method. These differences all affect the value of Δ1. Therefore, several examples will be described below and a method for determining Δ1 will be described.

Figure 25 is a servo-only layer for light beam and the red laser is a diagram showing an example of using a tracking error signal TE _S-D generated by the DPD method as a tracking error signal TE _S. Other conditions are the same as in the case of FIG. Since use of the red laser, the maximum value of the tracking error signal TE _S-D is located near the center of the groove G. Further, a code M (dummy code) is also provided in the servo dedicated layer. However, when the DPD method is used in the servo dedicated layer, the land / groove is not necessary.

The tracking error signal TE _S-D shown in FIG. 25 is such that the irradiation position of the recording layer light beam when the value of the tracking error signal TE _S-D is α−Δ2 functions as a tracking servo in the recording layer mode. position limit, i.e. shows a case where a position apart a distance a from the track center C _R. At this time, since the maximum value of .DELTA.1 is smallest, the specific values of .DELTA.1, less than or equal to the maximum value of .DELTA.1 when the tracking error signal TE _S-D is the tracking error signal TE _S-D shown in FIG. 25 If determined to be possible to prevent the case where the inclination of the optical disk 11 be any value, it is impossible to return the irradiation position of the recording layer for light beam to the track center C _R occurs. In the following, the tracking error signal TE _S-D is explained how to determine the maximum value of Δ1 when the tracking error signal TE _S-D shown in FIG. 25.

In the following, the gradient of the change of the tracking error signal TE _S-D when the irradiation position of the servo-only layer for light beam moves in a direction away from the center C _S of the land and g _1, the tracking in the vicinity of the center of the groove G Let g _{2 be} the absolute value of the gradient of the change in the error signal TES _-D . The length c shown in the figure is expressed as c = Δ2 / g ₂ . Therefore, d = a−c = a−Δ2 / g ₂ and d = Δ1 / g ₁ + Δ1 / g ₂ , so that Δ1 = (ag ₁ g ₂ −Δ2g ₁ ) / (g ₁ + g ₂ ) It is expressed. The Δ1 is the maximum value of Δ1 when the tracking error signal _{TE S-D} is the tracking error signal _{TE S-D} shown in FIG. 25. _{Accordingly, Δ1 ≦ (ag 1 g 2} -Δ2g 1) / (g 1 + g 2) With, also the inclination of the optical disk 11 is of any value, the track center of the irradiation position of the recording layer for light beam _{C R} It is possible to prevent the case where it cannot be returned to the state. Note that g ₂ can be approximated to infinity. In this case, Δ1 ≦ ag _{1 is} satisfied, and the maximum value of Δ1 is a value that does not depend on Δ2.

  In FIG. 26, an optical disk 11 having a track pitch determined according to the spot diameter of the blue laser (optical disk 11 that cannot be reproduced by a red laser) is used, and both the recording layer light beam and the servo dedicated layer light beam are combined with the blue laser. It is a figure which shows the example in the case of doing. Other conditions are the same as in the case of FIG.

The tracking error signal TE _S-P shown in FIG. 26 indicates that the irradiation position of the recording layer light beam when the value of the tracking error signal TE _S-P is α−Δ2 corresponds to the tracking servo in the recording layer mode. position limit, that is, the case where a position apart a distance a from the track center C _R. At this time, since the maximum value of .DELTA.1 is smallest, the specific values of .DELTA.1, less than or equal to the maximum value of .DELTA.1 when the tracking error signal TE _S-P is the tracking error signal TE _S-P shown in FIG. 26 If determined to be possible to prevent the case where the inclination of the optical disk 11 be any value, it is impossible to return the irradiation position of the recording layer for light beam to the track center C _R occurs. In the following, a description will be given tracking error signal TE _S-P is how to determine the maximum value of Δ1 when the tracking error signal TE _S-P shown in FIG. 26.

Hereinafter, the gradient of the change in the tracking error signal TE _S-P is assumed to be g ₁ . Length c shown in the figure is expressed as c = Δ2 / _{g 1.} Therefore, since d = ac = a−Δ2 / g ₁ and d = 2Δ1 / g ₁ , Δ1 = (1/2) × (ag ₁ −Δ2). This result is the same as the example of FIG. This .DELTA.1 becomes the maximum value of .DELTA.1 when the tracking error signal _{TE S-P} is the tracking error signal _{TE S-P} shown in FIG. 26, Δ1 ≦ (1/2) × (ag 1 -Δ2) and doing, even inclination any value of the optical disk 11, so that the irradiation position of the recording layer for light beam can be prevented not be able to return to the track center C _R occurs.

Figure 27 is a diagram showing an example of using a tracking error signal _{TE S-D} generated by the DPD method as a tracking error signal TE _S. Other conditions are the same as in the case of FIG.

In the tracking error signal TE _SD shown in FIG. 27, the irradiation position of the recording layer light beam when the value of the tracking error signal TE _SD is α−Δ2 functions as the tracking servo in the recording layer mode. position limit, that is, the case where a position apart a distance a from the track center C _R. At this time, since the maximum value of .DELTA.1 is smallest, the specific values of .DELTA.1, less than or equal to the maximum value of .DELTA.1 when the tracking error signal TE _S-D is the tracking error signal TE _S-D shown in FIG. 27 If determined to be possible to prevent the case where the inclination of the optical disk 11 be any value, it is impossible to return the irradiation position of the recording layer for light beam to the track center C _R occurs. In the following, the tracking error signal TE _S-D is explained how to determine the maximum value of Δ1 when the tracking error signal TE _S-D shown in FIG. 27.

In the following, the gradient of the change of the tracking error signal TE _S-D when the irradiation position of the servo-only layer for light beam moves in a direction away from the center C _R of the lands and g _1, the tracking in the vicinity of the center of the groove G Let g _{2 be} the absolute value of the gradient of the change in the error signal TES _-D . The length c shown in the figure is expressed as c = Δ2 / g ₂ . Therefore, d = a−c = a−Δ2 / g ₂ and d = Δ1 / g ₁ + Δ1 / g ₂ , so that Δ1 = (ag ₁ g ₂ −Δ2g ₁ ) / (g ₁ + g ₂ ) It is expressed. This result is the same as the example of FIG. The Δ1 is the maximum value of Δ1 when the tracking error signal _{TE S-D} is the tracking error signal _{TE S-D} shown in FIG. 27. _{Accordingly, Δ1 ≦ (ag 1 g 2} -Δ2g 1) / (g 1 + g 2) With, also the inclination of the optical disk 11 is of any value, the track center of the irradiation position of the recording layer for light beam _{C R} It is possible to prevent the case where it cannot be returned to the state. Note that g ₂ can be approximated to infinity. In this case, Δ1 ≦ ag _{1 is} satisfied, and the maximum value of Δ1 is a value that does not depend on Δ2.

FIG. 28 is a diagram showing an example in which the optical disc 11 (the optical disc 11 that can be reproduced by the red laser) whose track pitch is determined according to the spot diameter of the red laser is used and the recording layer light beam is a red laser. It is. Other conditions are the same as in the case of FIG. Since it will be repeated, detailed description will be omitted, but Δ1 in this case becomes Δ1 ≦ (1/2) × (ag ₁ −Δ2) by the same calculation as in FIG.

Figure 29 is a diagram showing an example of using a tracking error signal _{TE S-D} generated by the DPD method as a tracking error signal TE _S. Other conditions are the same as in the case of FIG. Since it will be repeated, detailed description will be omitted, but Δ1 in this case becomes Δ1 ≦ (ag ₁ g ₂ −Δ2 g ₁ ) / (g ₁ + g ₂ ) by the same calculation as in FIG.

30 and 31 use an optical disc 11 (optical disc 11 that can be reproduced by a red laser) whose track pitch is determined according to the spot diameter of the red laser, and the recording layer light beam is used for the red laser and the servo dedicated layer. It is a figure which shows the example in the case of making a light beam into a blue laser. FIG. 30 shows the tracking error signal TE _S-P and FIG. 31 shows the tracking error signal TE _S-D . In this case, the tracking error signals TE _S-P and TE _S-D are always 0, and there is a region where the tracking mode in the servo dedicated layer mode cannot be performed (a region corresponding to the section Z shown in the figure). Therefore, as a problem before the method of determining Δ1, it is preferable not to use such a method.

  In the description so far, the description has been made on the assumption that the code in the recording layer is provided corresponding to only one of the land and groove in the servo dedicated layer. It may be done. In this case, tracking servo in the servo dedicated layer mode is preferably performed by the DPD method. This will be described in detail below.

FIG. 32 shows an example in which tracking servo in the servo dedicated layer mode is performed by the DPD method. The figure is a diagram drawn with the tracking error signal TE _R of the tracking error signal generating unit 61-1 generates a tracking error signal TE _S-D tracking error signal generator 61-2 generates the horizontal axis Is the optical disc radial direction (track jump direction). In the lower part of the figure, a plan view of the recording layer and the servo dedicated layer is shown. In the figure, an optical disk 11 (optical disk 11 that can be reproduced by a red laser) whose track pitch is determined in accordance with the spot diameter of the red laser is used, and the servo dedicated layer light beam is a red laser and recording layer light. The beam is a blue laser, and the optical disk 11 is not tilted.

A signal TE _SD (L) indicated by a broken line in FIG. 32 indicates a component generated by the dummy code M in the land L in the tracking error signal TE _SD . Similarly, the signal TE _S-D (G) indicates a component generated by the dummy code M in the land G in the tracking error signal TE _S-D . The waveform of the tracking error signal TE _S-D is the sum of the signal TE _S-D (L) and the signal TE _S-D (G). Since the waveform of the tracking error signal TE _S-D is formed in this way, the tracking error signal TE _S-D, as shown in FIG. 32, a relatively gentle across the boundaries of the land L and the group G It has a constant slope, and its value becomes zero near the boundary.

As shown in FIG. 32, the slope in the vicinity of the boundary of the land L and the group G of the tracking error signal TE _S-D is always the same direction. Therefore, the control direction of the objective lens 4 in the tracking servo in the servo dedicated layer mode may always be the same direction. That is, it is not necessary to change the polarity of the tracking servo every other dummy code M.

On the other hand, if the tracking servo in the servo dedicated layer mode is performed by the DPP method, the waveform of the tracking error signal TE _S-P generated by the DPP method is as shown in FIG. Therefore, it is necessary to change the polarity of the tracking servo every other row of the dummy code M. Therefore, when the code in the recording layer is provided corresponding to both the land and groove in the servo dedicated layer, the tracking servo in the servo dedicated layer mode should be performed by the DPD method that does not require changing the polarity of the tracking servo. Is preferred.

  Note that the recording density of the recording layer does not change between the case of using the DPD method and the case of using the DPP method for tracking servo in the servo dedicated layer mode, but the position of the code M of the recording layer is different. That is, when using the DPD method, as shown in FIG. 32, the code M of the recording layer is provided at a position corresponding to the boundary between the land L and the group G of the servo dedicated layer (position between the dummy code strings). On the other hand, the code M of the recording layer when using the DPP method is provided at a position corresponding to the center of each of the land L and the group G of the servo dedicated layer.

In addition, Δ1 in the example of FIG. 32, that is, Δ1 when the DPD method is used for tracking servo in the servo dedicated layer mode is obtained by performing the same calculation as in FIG. 25 and the like, and Δ1 ≦ (ag ₁ g ₂₋ Δ2g ₁ ) / (g ₁ + g ₂ ). On the other hand, Δ1 when the DPP method is used for tracking servo in the servo dedicated layer mode is obtained by performing the same calculation as in the case of FIG. 20 and the like, and Δ1 ≦ (1/2) × (ag ₁ −Δ2) It becomes.

DESCRIPTION OF SYMBOLS 1 Optical drive device 2-1, 2-2 Laser light source 3 Optical system 4 Objective lens 5-1, 5-2 Photo detector 6 Processing part 11 Optical disk 12 Recording layer 13 Servo exclusive layers 21, 25, 28, 30 Collimator lens 22 Polarizing beam splitter 23 1/4 wavelength plate 24 Dichroic prism 26, 31 Sensor lens 27 Diffraction grating 29 Beam splitters 51-54 Light receiving surfaces 51A-51D, 52A-52D, 53A, 53B, 54A, 54B Light receiving region 61-1, 61-2 Tracking error signal generation unit 62 Tracking servo unit 63 Determination unit 64 Full addition signal generation unit 65 Focus error signal generation unit 66 Focus servo unit 70, 71 Comparator 72 Output signal generation unit 73 Sample hold circuit

Claims (10)

The first and second light beams controlled to have the same optical axis at least in the vicinity of the recording surface with respect to the recording surface of the optical disc having the recording layer and the servo dedicated layer are respectively used for the recording layer and the servo only. An optical system for irradiating the layer in focus;
A first photodetector for receiving reflected light from the recording surface of the first light beam;
A second photodetector for receiving reflected light from the recording surface of the second light beam;
First tracking error signal generating means for generating a first tracking error signal based on the amount of light received by the first photodetector;
Second tracking error signal generation means for generating a second tracking error signal based on the amount of light received by the second photodetector;
Tracking servo means for controlling the optical system based on one of the first and second tracking error signals;
Determining means for determining that the irradiation position of the first light beam is an unrecorded area of the recording layer;
The optical drive apparatus characterized in that the tracking servo means switches to control based on the second tracking error signal according to a determination result of the determination means that is executing control based on the first tracking error signal. .   The determination means determines that the irradiation position of the first light beam is an unrecorded area according to whether or not the second tracking error signal has changed beyond a first predetermined range. The optical drive device according to claim 1, wherein:   The determination means has a sample hold circuit for holding the second tracking error signal, and the second tracking error signal is in the first predetermined range with reference to a value held by the sample hold circuit. The optical drive device according to claim 2, wherein it is determined whether or not the change has occurred beyond the threshold.   The tracking servo means, when performing the control based on the first tracking error signal, when the irradiation position of the first light beam is determined to be an unrecorded area by the determination means. The control is switched to the control based on the tracking error signal, and whether or not the second tracking error signal falls within the second predetermined range narrower than the first predetermined range during the control based on the second tracking error signal. 4. The optical drive device according to claim 2, wherein the control is switched to control based on the first tracking error signal. RF signal generation means for generating an RF signal based on the amount of light received by the first photodetector is further provided,
The determination unit determines that the irradiation position of the first light beam is a recording area according to the RF signal,
The tracking servo means, when performing the control based on the first tracking error signal, when the irradiation position of the first light beam is determined to be an unrecorded area by the determination means. When switching to control based on a tracking error signal, and when the determination unit determines that the irradiation position of the first light beam is a recording area during execution of control based on the second tracking error signal, 4. The optical drive device according to claim 2, wherein the control is switched to control based on the first tracking error signal. The servo dedicated layer has a land groove,
The tracking servo means detects whether the irradiation position of the second light beam is a land or a groove, and controls the position control direction of the objective lens included in the optical system according to the result. The optical drive device according to claim 3, wherein the optical drive device is an optical drive device.   7. The servo dedicated layer has a land groove, and the second tracking error signal generation means generates the second tracking error signal using a DPP method. The optical drive device according to one item.   8. The servo dedicated layer has a dummy code, and the second tracking error signal generation means generates the second tracking error signal using a DPD method. The optical drive device according to Item. RF signal generation means for generating an RF signal based on the amount of light received by the first photodetector is further provided,
The optical drive apparatus according to claim 1, wherein the determination unit determines that the irradiation position of the first light beam is an unrecorded area of the recording layer according to the RF signal. The determination unit determines whether the irradiation position of the first light beam is an unrecorded area or a recorded area according to the RF signal,
The tracking servo means, when performing the control based on the first tracking error signal, when the irradiation position of the first light beam is determined to be an unrecorded area by the determination means. When switching to control based on a tracking error signal, and when the determination unit determines that the irradiation position of the first light beam is a recording area during execution of control based on the second tracking error signal, The optical drive device according to claim 9, wherein the control is switched to control based on the first tracking error signal.

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