JP2011076671A - Optical drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce influence of noise generated in an RF signal when generating an instruction signal which instructs a timing of sample-holding a tracking error signal, based on the RF signal. <P>SOLUTION: A determination part 63 of an optical drive device includes: a recording determination signal generation part 74 which generates a recording determination signal NR which shows whether a recording area or a non-recording area is irradiated with a light beam for recording layer, based on the RF signal; an instruction signal generation part 75 which generates an instruction signal SHT to indicate a timing of sampling a tracking error signal TE<SB>S</SB>based on the RF signal and the recording determination signal NR; and a sample-hold circuit 73 which sample-holds the tracking error signal TE<SB>S</SB>according to the instruction signal SHT. <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.

  At the time of recording / reproducing of the optical disc, tracking servo for following the track is performed. As a specific technique of tracking servo, a differential push-pull method (DPP method) and a phase difference detection method (DPD method) are known. When the DPP method is used, a land groove is provided on the optical disc, and tracking servo is performed using diffraction of a light beam at the boundary between the land and the groove. On the other hand, when the DPD method is used, no land groove is required, and diffraction by a code (recording mark) on the recording layer is used.

  In recent years, multilayered optical disks have been put into practical use in order to increase the recording capacity of the optical disk. However, when tracking servo is performed using the DPP method, if a land groove is provided for each recording layer, a stamper is provided for each layer. Therefore, it is necessary to perform land groove forming processing. Since this is an increase factor of cost, in recent years, an optical disk provided with a servo dedicated layer different from the recording layer has appeared (for example, see Patent Document 1). In such an optical disc, a land groove 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 playback, codes are not necessarily formed in all areas, and there may be unrecorded areas without codes. When performing tracking servo during playback using the code of the recording layer, the optical beam (light for the recording layer) is being played back during playback of the optical disk in the on-track state (the tracking servo is on and controlled to be centered on the track). If the irradiation position of the beam) straddles an unrecorded area, tracking servo cannot be performed during that time, and the on-track state cannot be maintained.

As one method for solving this problem, it is conceivable to perform tracking servo using the servo dedicated layer only when the irradiation position of the light beam is in an unrecorded area. The irradiation position of the light beam is in the unrecorded area, the tracking error signal using a servo-only layer (hereinafter, referred to as the tracking error signal T _S.) Performs generation of constantly around the reference value is the value It is possible to make a determination according to whether or not it is within a predetermined range. The reference value is zero when the optical disc is not tilted, and is a value corresponding to the magnitude of the tilt when tilted.

The reference value, in short, when the on-track state is maintained by the tracking servo using the recording layer, the value of the tracking error signal T _S. This value, while playing an optical disc in the on-track state is obtained by sampling and holding the value of the tracking error signal T _S.

  However, in the conventional sample and hold technique, the reference value may not be an appropriate value due to the influence of noise or the like. This will be described in detail below.

  FIG. 18 is a diagram for explaining a conventional sample-and-hold technique, and shows an ideal case where there is no influence of noise. In the figure, two examples of the instruction signals SHT1 and SHT2 are given as examples of the instruction signal SHT for instructing the sample and hold timing, and their generation methods will be described.

  As shown in FIG. 18, in the conventional sample and hold technique, an RF signal indicating the presence or absence of a code in the recording layer is used to generate the instruction signal SHT. Here, the RF signal is described as a signal that is high when there is a sign at the irradiation position of the light beam and low when there is no sign.

  First, a top envelope signal ENV obtained by enveloping the maximum value of the RF signal with a predetermined droop plate is obtained. The slice signal SS is obtained by slicing the top envelope signal ENV with a predetermined slice level SL stored in advance.

  Next, the non-recorded determination signal NR is generated by delaying the slice signal SS over a predetermined time D. The recording / non-recording determination signal NR is a signal that becomes low when the irradiation position of the light beam is an unrecorded area and becomes high when the irradiation position is a recording area. The reason for delaying is to prevent the determination of the recording area and the unrecorded area from being erroneously determined due to the influence of noise by monitoring whether the slice signal SS is changed during the predetermined time D.

Finally, a pulse signal indicating the rise of the recording / unrecording determination signal NR is generated and used as the instruction signal SHT1. Similarly, a pulse signal indicating the fall of the recording / unrecording determination signal NR is generated and used as the instruction signal SHT2. These instruction signals SHT1 and SHT2 become high when the irradiation position of the light beam enters the recording area or shortly after entering the non-recording area. Therefore, the instruction signals SHT1 and SHT2 are high. samples the value of the tracking error signal T _S in time, by holding at a low, generally appropriate reference values are obtained.

  FIG. 19 shows a case where noise occurs in the RF signal when the irradiation position of the light beam is an unrecorded area.

As shown in FIG. 19, when noise N is generated in the RF signal, a high interval in which the noise N is reflected also occurs in the recording / unrecorded determination signal NR. For this reason, as shown in FIG. 19, the pulses of the instruction signals SHT1 and SHT2 stand at a position that is not originally a sample hold timing. The reference value obtained by sampling and holding the value of the tracking error signal T _S in accordance with this pulse becomes incorrect value.

  As described above, when noise occurs in the RF signal when the irradiation position of the light beam is an unrecorded area, the instruction signals SHT1 and SHT2 are pulsed in spite of the unrecorded area. As a result, an inappropriate value will be acquired.

Accordingly, one object of the present invention, when generating the instruction signal instructing the sample hold timing of the tracking error signal T _S based on the RF signal, the optical drive device capable of reducing the influence of noise generated in the RF signal It is to provide.

  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 irradiation position of the first light beam Of the recording layer A determination means for determining that the recording area is present, a tracking servo means for controlling the optical system based on one of the first and second tracking error signals, and a received light amount of the first photodetector. Based on the RF signal generating means for generating an RF signal indicating the presence or absence of a code in the recording layer, whether the irradiation position of the first light beam is a recording area or an unrecorded area based on the RF signal A recording / unrecorded determination signal generating means for generating a recorded / unrecorded determination signal, and an instruction for generating an instruction signal for instructing a sample timing of the second tracking error signal based on the RF signal and the recorded / unrecorded determination signal Signal generating means; and sample and hold means for sampling and holding the second tracking error signal in accordance with the instruction signal; Depending on whether or not the second tracking error signal has changed beyond a first predetermined range based on the value sampled and held by the sample and hold means. It is determined that the irradiation position is an unrecorded area, and the tracking servo means outputs the second tracking error signal according to the determination result of the determining means that is executing control based on the first tracking error signal. It is characterized by switching to the control based on.

  According to the present invention, it is possible to reduce the influence of noise generated in an RF signal when generating an instruction signal that indicates the sample hold timing of the second tracking error signal based on the RF signal.

  In the optical drive device, a period in which the irradiation position of the first light beam is indicated as an unrecorded area by the recording / non-recording determination signal, and a period in which the recording layer has no code by the RF signal. , And at the beginning of a period in which the value of the RF signal continuously indicates that the recording layer has a code, the recording non-recording determination signal indicates that the irradiation position of the first light beam is an unrecorded area. The signal may be a value indicating sample timing in a period not corresponding to any of the periods, and may be a value indicating non-sample timing in a period other than the period. Is a timing at which the RF signal changes from a value indicating that the recording layer has no sign to a value indicating that the recording layer has a sign. It generates a pulse signal indicating, based on said recording unrecorded determination signal and the pulse signal, it is also possible to generate the indication signal. In the latter case, the instruction signal further includes a period in which the irradiation position of the first light beam is indicated as an unrecorded area by the recording / non-recording determination signal, a period in which the pulse signal does not exist, and the At the sample timing, when the recording / unrecording determination signal indicates that the irradiation position of the first light beam is an unrecorded area at the rising edge of the pulse signal, it does not correspond to any of the lifetime of the pulse signal. It is good also as a signal which becomes a value which shows that there is, and becomes a value which shows that it is not a sample timing when that is not right.

  Further, in each of the optical drive devices, the recording / unrecording determination signal generation means irradiates the first light beam with the recording / non-recording determination signal when the value of the RF signal continues for a predetermined time. The position may be an unrecorded area.

  In each of the above optical drive devices, the first photodetector is divided into first to fourth light receiving regions, and the RF signal generation unit is configured to receive light received in the first to fourth light receiving regions. The RF signal may be generated according to whether or not all are equal to or greater than a predetermined value.

  In this optical drive device, the RF signal generation means indicates that the value of the RF signal has a sign in the recording layer when the amounts of light received in the first to fourth light receiving areas are all equal to or greater than a predetermined value. The RF signal value may be a value indicating that there is no sign in the recording layer when any of the received light amounts of the first to fourth light receiving regions is less than a predetermined value.

According to the present invention, when generating the instruction signal instructing the sample hold timing of the tracking error signal T _S based on the RF signal, it is possible to reduce the influence of noise generated in the RF signal.

1 is a schematic diagram of an optical drive device according to an embodiment of the present invention. (A) is a top view of the recording surface of the optical disk by 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 embodiment of this invention. It is a top view of the photodetector by embodiment of this invention. It is a top view of the photodetector by embodiment of this invention. It is a figure which shows the functional block of the process part by embodiment of this invention. In the optical drive apparatus according to an 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. This figure shows a case where the optical disc is not tilted. It is a figure which shows the internal circuit of the determination part by embodiment of this invention. In the optical drive apparatus according to an 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, wherein arranged in the time variation of the tracking error signal TE _S-P It is a thing. In the optical drive apparatus according to an embodiment of the present invention, the time variation of the output signal V _OUT of the determination unit when performing reproduction and writing while maintaining near the center of the track, are arranged in time change of the tracking error signal TE _S-P It is described. It is explanatory drawing of how the light beam hits each layer when the optical disk by 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 by embodiment of this invention. It is a figure which shows the time change of the various signals relevant to the production | generation of the instruction | indication signal SHT by embodiment of this invention. (A) illustrates what value the instruction signal SHT1 has depending on the relationship between the RF signal RF and the recording / unrecording determination signal NR. (B) illustrates what value the instruction signal SHT2 has depending on the relationship between the pulse signal PS and the recording / unrecording determination signal NR. It is a figure which shows the example of the process for reducing more reliably the influence of the noise with respect to the instruction | indication signal SHT by embodiment of this invention. It is a figure which shows the example of the process for reducing more reliably the influence of the noise with respect to the instruction | indication signal SHT by embodiment of this invention. It is a figure for demonstrating the conventional sample hold technique. It is a figure for demonstrating the conventional sample hold technique.

  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 an 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 polarizing beam splitter 21, a collimator lens 22, a dichroic prism 23, a quarter wavelength plate 24, a sensor lens (cylindrical lens) 26, a diffraction grating 27, a beam splitter 28, a collimator lens 29, and a sensor lens (cylindrical lens). ) 31 and the objective lens 4. 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 recording layer light beam first enters the polarization beam splitter 21. . The polarization beam splitter 21 passes the incident recording layer light beam and makes it incident on the collimator lens 22. The collimator lens 22 converts the recording layer light beam into parallel light and makes it incident on the dichroic prism 23. The dichroic prism 23 reflects the incident parallel light 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 a servo-dedicated layer light beam), the diffraction grating 27 first converts the servo-dedicated layer light beam into three. The beam is decomposed into beams (0th order diffracted light and ± 1st order diffracted light) and is incident on the beam splitter 28. The beam splitter 28 passes the incident light beam and makes it incident on the collimator lens 29. The collimator lens 29 converts the incident servo dedicated layer light beam into 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 29 is configured to be drivable 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 of the collimator lens 29 and the objective lens 4 is controlled so that the servo-dedicated 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-dedicated 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 collimator lens 22. Is incident on. The light beam that has passed through the collimator lens 22 is reflected by the polarization beam splitter 21 while condensing, and enters the sensor lens 26 (cylindrical lens). 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-dedicated layer light beam, the servo-dedicated layer light beam that has passed through the objective lens 4 enters the collimator lens 29 via the quarter-wave plate 24 and the dichroic prism 23. The light beam that has passed through the collimator lens 29 is reflected by the beam splitter 28 while condensing, and enters the sensor lens 31 (cylindrical lens). Similar to the sensor lens 26, the sensor lens 31 gives astigmatism to the incident servo dedicated layer light beam. The servo dedicated 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 joint point of the recording layer light beam (signal light) reflected by the access target layer is located just on the photodetector 5-1 and the servo dedicated layer light beam reflected by the servo dedicated layer. Position control of the collimator lens 29 and the objective lens 4 is performed so that the joint point of (signal light) is located 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 dedicated 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 focus error signal FE _S for the servo layer, the focus error signal FE _R for the recording layer, the full addition signal (the recording layer pull-in signal PI _R , the servo only) 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 photodetector 5-1 and 5-2 and the detail of the process of the process part 6 are demonstrated. In the following description, a description will be given first ignoring the tilt of the optical disc, and then a configuration considering the tilt of the optical disc will be described. In the description of the configuration in consideration of the tilt of the optical disk, when generating an instruction signal for instructing the sample hold timing of the tracking error signal based on the RF signal, it is possible to reduce the influence of noise generated in the RF signal. The configuration will be described.

  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 for generating 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.

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.

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. Accordingly, under the assumption that the optical disk is not tilted, the value of the tracking error signal TE _S-P is also maintained at 0 as shown in FIG.

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 TE _S-P gradually moves away from 0 as shown in FIG. 7, and finally the track jump (recording surface) is performed unless the mode is switched according to the present embodiment. The focus position of the incident light on the optical disk moves in the radial direction of the optical disk, that is, moves in the direction crossing the track.

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.

  Even if 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 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, the following equations (4) and (5) are calculated to generate these signals. As is clear from Equation (4), 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 indicates that there is a code in the recording layer when it is high, and indicates that there is no code in the recording layer when it is low. 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. The RF signal RF is also input to the determination unit 63. This point will be described later.

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-only layer on the basis of 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 (6) and (7), to generate these focus error signal _FE R, FE _S.

Focus servo unit 66 controls the position of the collimator lens 29 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).

  Now, a configuration considering the 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 may be simultaneously irradiated to the track center. It becomes difficult. The same applies to the case where a deviation occurs between the two optical axes in the optical system.

  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. When the optical disk 11 is tilted, an offset due to tilt occurs as in the case of lens shift, and the midpoint of the tracking error signal is not zero. However, in FIG. 12, the offset due to tilt is cancelled. As a result, the middle point is zero.

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 (the reference value described above, hereinafter referred to as “reference value deviation”). This deviation of the reference value 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 inclination of the optical disc. As shown in the figure, in addition to the configuration shown in FIG. 8, the actual determination unit 63 includes a sample hold circuit 73 (sample hold unit), a recording / unrecorded determination signal generation unit 74 (recorded / unrecorded determination signal generation unit). ) And an instruction signal generation unit 75 (instruction signal generation means).

The sample hold circuit 73 is provided at the input terminals of the comparators 70 and 71, and samples (samples) the tracking error signal TE _S-P generated by the tracking error signal generation unit 61-2 at a timing according to an instruction signal SHT described later. And hold it. 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.

The recording / non-recording determination signal generation unit 74 is based on the RF signal RF generated by the full addition signal generation unit 64 and indicates whether the irradiation position of the recording layer light beam is a recording region or an unrecorded region. A recording determination signal NR is generated. The instruction signal generation unit 74 performs tracking by the sample and hold circuit 73 based on the RF signal RF generated by the full addition signal generation unit 64 and the recording / non-recording determination signal NR generated by the recording / non-recording determination signal generation unit 74. An instruction signal SHT for instructing the sample timing (sample timing) of the error signal TE _S-P is generated.

  The recording / non-recording determination signal generation unit 74 and the instruction signal generation unit 75 perform processing for reducing the influence of noise generated in the RF signal when the instruction signal SHT is generated. Hereinafter, this process will be described in detail with specific examples.

  FIG. 14 is a diagram showing temporal changes of various signals related to generation of the instruction signal SHT. In the figure, as a specific example of the instruction signal SHT, an instruction signal SHT1 that uses the waveform of the RF signal RF as it is and an instruction signal SHT2 that is a pulse signal indicating the timing when the RF signal RF becomes high are shown. Cite.

  First, the recording / unrecording determination signal generation unit 74 first generates a top envelope signal ENV of the RF signal RF that vibrates vigorously in a short cycle according to the presence or absence of a code. The top envelope signal ENV is an envelope signal that envelops the maximum value of the RF signal RF with a predetermined droop plate (generally the vibration period of the RF signal RF).

  The period during which the RF signal RF maintains the same value is determined by the standard. For example, in a Blu-ray disc, the shortest is 2T and the longest is 8T. However, 1T is a time corresponding to a half cycle of a channel data transfer rate (66 Mbps in the case of BD). Here, the period in which the same value is maintained is a period in each case where the RF signal RF is high or low continues.

  Next, the recording / unrecording determination signal generator 74 slices the top envelope signal ENV at a predetermined slice level SL stored in advance, so that the high level is obtained when the value of the top envelope signal ENV is equal to or higher than the slice level SL. If not, the slice signal SS that is low is acquired. Note that the slice level SL is preferably set to a value approximately between the maximum value and the minimum value of the top envelope signal ENV.

  Then, the recording / unrecording determination signal generation unit 74 generates a recording / non-recording determination signal NR based on the slice signal SS. Specifically, a signal obtained by delaying the slice signal SS by a predetermined time D is set as a recording / unrecording determination signal NR.

  When the instruction signal SHT1 is used as the instruction signal SHT, the instruction signal generation unit 75 is a period during which the recording / non-recording determination signal NR is low (the irradiation position of the recording layer light beam in the unrecorded area is determined by the recording / non-recording determination signal NR). A period during which the RF signal RF is low (a period during which the RF signal RF indicates that there is no sign in the recording layer), and a period during which the value of the RF signal RF is continuously high (recording). When the recorded / unrecorded determination signal NR is low at the beginning of the period (a period indicating that there is a code in the layer), it is high (a value indicating sample timing) in a period not corresponding to any of the periods, and is not so A signal that is low (a value indicating that it is not a sample timing) in a period is generated and used as an instruction signal SHT1.

  Specifically, the instruction signal generation unit 75 first sets the instruction signal SHT1 to low and simultaneously starts monitoring the RF signal. Then, when the RF signal rises, it is determined whether the recording / unrecording determination signal NR is high or low. If the determination result is high, the instruction signal SHT1 is changed to high according to the rising. When the RF signal returns to low, the instruction signal SHT1 also returns to low. On the other hand, if the determination result is low, the instruction signal SHT1 remains low. The instruction signal generator 75 also monitors the recording / unrecording determination signal NR. If the recording / non-recording determination signal NR changes to low when the instruction signal SHT1 is high, the instruction signal SHT1 also changes to low. The instruction signal generation unit 75 generates the instruction signal SHT1 as described above.

  FIG. 15 (a) illustrates in an easy-to-understand manner what value the instruction signal SHT1 has depending on the relationship between the RF signal RF and the recording / unrecording determination signal NR. As shown in the figure, in the period P1 in which the RF signal RF is high, the recording / non-recording determination signal NR is high over the entire period. In this case, the instruction signal SHT1 is also high over the entire period P1. In the period P2 in which the RF signal RF is high, the recording / unrecording determination signal NR changes from high to low during the period. In this case, the instruction signal SHT1 becomes high at the beginning of the period P2, but changes to low when the recording / unrecording determination signal NR changes to low. Further, in the period P3 in which the RF signal RF is high, the recording / unrecording determination signal NR is low over the entire period. In this case, the instruction signal SHT1 is also low over the entire period P3. In the period P4 when the RF signal RF is high, the recording / unrecording determination signal NR changes from low to high during the period. In this case, the instruction signal SHT1 becomes low over the entire period P4.

  By configuring the instruction signal SHT1 as described above, at least a part of the noise N can be prevented from appearing in the instruction signal SHT1 as shown in FIG. That is, the influence of the noise N on the instruction signal SHT1 can be reduced.

  When the instruction signal SHT2 is used as the instruction signal SHT, the instruction signal generator 75 first indicates that the recording layer has a sign from the timing when the RF signal RF becomes high (a value indicating that the recording layer has no sign). A pulse signal PS indicating the timing at which the value changes) is generated. For generating the pulse signal PS, for example, it is preferable to use a method of generating a delay signal DRF of the RF signal RF and generating a signal that becomes high at the rising edge of the RF signal RF and becomes low at the rising edge of the delay signal DRF. It is. Similarly, the pulse signal PS indicating the timing when the RF signal RF becomes low (timing that changes from a value indicating that the recording layer has a code to a value indicating that the recording layer has no code) may be generated. . That is, a delay signal DRF of the RF signal RF may be generated, and a signal that becomes high at the falling edge of the RF signal RF and becomes low at the falling edge of the delay signal DRF may be generated.

  Then, the instruction signal generation unit 75 has a period in which the recording / unrecording determination signal NR is low (a period in which the recording layer recording beam irradiating position is indicated by the recording / non-recording determination signal NR), a pulse A period in which the signal PS is low (a period in which the pulse signal PS does not exist) and a period that does not correspond to any of the lifetimes of the pulse signal PS when the recording / unrecorded determination signal NR is low at the rising edge of the pulse signal PS A signal that becomes high (a value indicating that it is a sample timing) and becomes low (a value that indicates that it is not a sample timing) in a period other than that is generated as an instruction signal SHT2. A specific generation method is the same as that in the case of the instruction signal SHT1 described above.

  FIG. 15 (b) shows in an easy-to-understand manner what value the instruction signal SHT 2 has depending on the relationship between the pulse signal PS and the recording / unrecording determination signal NR. As shown in the figure, since it is the same as the case of the instruction signal SHT1 shown in FIG.

  By configuring the instruction signal SHT2 as described above, at least a part of the noise N can be prevented from appearing in the instruction signal SHT2 as shown in FIG. That is, the influence of the noise N on the instruction signal SHT2 can be reduced.

As described above, according to the above processing of the recording / unrecorded determination signal generation unit 74 and the instruction signal generation unit 74, the influence of noise generated in the RF signal RF is reduced when the instruction signals SHT1 and SHT2 are generated. Yes. Accordingly, by the sample hold circuit 73 samples the tracking error signal TE _S at a timing according to the command signal SHT1, SHT2, the deviation α is hold appropriate reference value, the tracking servo unit 62 perform the mode switching properly It becomes like this.

  16 and 17 show an example of processing for further reliably reducing the influence of the noise N on the instruction signal SHT.

In the example of FIG. 16, when the full addition signal generation unit 64 (FIG. 6) generates the RF signal RF, the light reception amounts of the light reception regions 51 </ b> A to 51 </ b> D (FIG. 4) of the photodetector 5-1 are all greater than or equal to a predetermined value. Depending on whether or not, the RF signal RF is generated. That is, the RF signal RF is generated using the following equation (8) instead of the above equation (4). Here, in Expression (8), it is assumed that the signals I _{51A to} I _51D are binary signals that take either high (1) or low (0) values by a comparator (not shown). That is, Expression (8) represents an AND operation of I _{51A to} I _51D .

  By adopting the equation (8), the RF signal RF is high (the sign is in the recording layer) when the light receiving amounts of the respective light receiving areas 51A to 51D are all equal to or larger than a predetermined value (when it is high). And a signal that becomes low (a value indicating that there is no sign in the recording layer) when any of the light receiving amounts of the light receiving regions 51A to 51D is less than a predetermined value (if it is low). It becomes.

As shown in FIG. 16, even when noise N is generated in the RF signal RF, the noise N is not always generated in the same manner in all the light receiving regions 51A to 51D. That is, the RF signal RF, which is calculated by the equation (4) is a total sum signal of the signals _I 51A _{~I 51D,} the noise N, the noise generated in the three following of the signals _I 51A _{~I 51D,} optical disc And noise generated in all of the signals I _{51A to} I _51D due to scratches, dust, dirt, and the like on the surface. Therefore, by calculating the RF signal RF using Equation (8), as shown in FIG. 16, if no noise N occurs in at least one light receiving region, noise is generated in the RF signal RF. You can avoid it. Thereby, the influence of noise on the instruction signal SHT can be more reliably reduced.

More specifically, since the recording / unrecording determination signal NR rises behind the RF signal RF, when noise continuously occurs in a short period as shown in FIG. 14, a part of the noise remains without being removed. There is. Since the noise continuously generated in such a short cycle is mostly generated in three or less of the signals I _{51A to} I _51D , the instruction signal SHT is obtained by adopting the equation (8). The influence of noise on the can be more reliably reduced.

  The full addition signal generator 64 outputs the RF signal RF calculated by the equation (4) to the CPU 7 and outputs the RF signal RF calculated by the equation (8) to the determination unit 63. Also good. By doing so, it is possible to reduce the influence of noise on the instruction signal SHT while outputting the conventional RF signal RF to the CPU 7.

  In the example of FIG. 17A, the recording / unrecording determination signal generation unit 74 determines a predetermined time (a period during which the RF signal RF maintains the same value) in which the value (high or low) of the RF signal RF is determined according to the standard. (In the example of a Blu-ray disc, it is 8T as described above.) When the recording is continued, the recording / unrecording determination signal NR is forcibly set to low (a value indicating that the irradiation position of the recording layer light beam is an unrecorded area). If the value of the RF signal RF continues beyond the period indicated by the maximum value, some noise is suspected. Therefore, by doing so, it is possible to reduce the influence of the noise on the instruction signal SHT.

  FIG. 17A shows an example in which the recording / unrecording determination signal NR is forcibly set to low when the value of the RF signal RF continues for 9T. FIG. 17B shows an example in which the process of forcibly changing the recording / unrecording determination signal NR to low is not performed as a comparative example. In FIG. 17A and FIG. 17B, the waveform of the RF signal RF is assumed to be the same. When the processing for forcibly changing the recording / unrecording determination signal NR to low is performed by comparing the instruction signal SHT1 in FIG. 17A and the instruction signal SHT1 in FIG. It can be seen that the probability that the signal SHT goes high is reduced. This example is particularly effective when noise over a relatively long period of time such as the noise N shown in FIG.

  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, it is needless to say that the value (high or low) of each signal indicating each state described in the above embodiment may not be the one described in the above embodiment. As an example, the RF signal RF may indicate that there is no sign when it is high, and may indicate that there is a sign when it is low. Thus, when the value of the signal which shows a state is replaced, the process of each part is also suitably changed according to replacement.

  In addition, when writing by appending, first, DPD control is performed in the written area of the recording layer, and then the tracking error signal of the servo dedicated layer is sampled and held, and this value is used as a reference value for tracking servo control in the servo dedicated layer. By performing the above, even when tilt occurs, it is possible to write in order immediately after the previous recording area without creating a useless empty area on the disc. An area where DPD control can be performed in advance is preferably provided on the disc so that it can be done in this way even when writing for the first time.

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 Units 70 and 71 Comparator 72 Output Signal Generation Unit 73 Sample Hold Circuit 74 Recorded / Unrecorded Determination Signal Generator 75 Instruction signal generator

Claims (7)

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;
Determination means for determining that the irradiation position of the first light beam is an unrecorded area of the recording layer;
Tracking servo means for controlling the optical system based on one of the first and second tracking error signals;
RF signal generating means for generating an RF signal indicating the presence or absence of a code in the recording layer based on the amount of light received by the first photodetector;
A recorded / unrecorded determination signal generating means for generating a recorded / unrecorded determination signal indicating whether the irradiation position of the first light beam is a recorded area or an unrecorded area based on the RF signal;
Instruction signal generating means for generating an instruction signal for instructing a sample timing of the second tracking error signal based on the RF signal and the recording / unrecording determination signal;
Sample hold means for sample-holding the second tracking error signal according to the instruction signal,
The determination means determines whether the second tracking error signal has changed beyond a first predetermined range based on a value sampled and held by the sample and hold means. Determine that the irradiation position of the light beam is an unrecorded area,
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 instruction signal is a period in which the irradiation position of the first light beam is indicated as an unrecorded area by the recording / non-recording determination signal, and a period in which the RF signal indicates that there is no code in the recording layer, And at the beginning of a period in which the value of the RF signal continuously indicates that the recording layer has a code, the recording / non-recording determination signal indicates that the irradiation position of the first light beam is an unrecorded area. 2. The optical signal according to claim 1, wherein the optical signal is a signal indicating a sample timing in a period not corresponding to any of the periods, and a value indicating a non-sample timing in a period other than the period. Drive device.   The instruction signal generating means generates a pulse signal indicating a timing at which the RF signal changes from a value indicating that the recording layer has no sign to a value indicating that the recording layer has a sign, and the pulse signal The optical drive apparatus according to claim 2, wherein the instruction signal is generated based on the recording unrecorded determination signal.   The instruction signal is recorded in a period in which the irradiation position of the first light beam is indicated by an unrecorded area, a period in which the pulse signal does not exist, and a rising edge of the pulse signal. When the unrecorded determination signal indicates that the irradiation position of the first light beam is an unrecorded area, it is a value indicating sample timing when it does not correspond to any of the lifetime of the pulse signal, 4. The optical drive device according to claim 3, wherein the signal is a value indicating that the sample timing is not reached otherwise.   The recording / non-recording determination signal generating means determines that the irradiation position of the first light beam is in an unrecorded area when the value of the RF signal continues beyond a predetermined time. The optical drive device according to claim 1, wherein the optical drive device is changed to a value indicated. The first photodetector is divided into first to fourth light receiving regions;
6. The RF signal generation unit according to claim 1, wherein the RF signal generation unit generates the RF signal in accordance with whether or not all the received light amounts of the first to fourth light receiving regions are equal to or greater than a predetermined value. The optical drive device according to any one of the above.   The RF signal generation means sets the value of the RF signal as a value indicating that the recording layer has a sign when the light receiving amounts of the first to fourth light receiving regions are all equal to or greater than a predetermined value, The value of the RF signal is set to a value indicating that the recording layer has no sign when any of the received light amounts of the fourth to fourth light receiving areas is less than a predetermined value. Optical drive device.

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