JP4998250B2 - Optical drive device - Google Patents

Description

  The present invention relates to an optical drive device, and more particularly to an optical drive device suitable for an optical disc having a multilayered recording layer.

  An optical drive device for reproducing or recording an optical disc such as a CD (Compact Disc), a DVD, an HD-DVD, or a BD (Blu-ray Disc) is irradiated with a light beam on the recording layer of the optical disc and returned. The light beam is received by a photodetector. Information is reproduced using the output signal (RF signal) of the photodetector.

  By the way, an optical disc other than a ROM (CD-ROM, DVD-ROM, etc.) has two types of lines, land and groove, prepared beforehand, and information is either one or both lines (hereinafter, information writing). Written in the center of the line). When the focus is at the center of the information writing line, the track is on, and when the focus is off, the track is off. The RF signal becomes a signal reflecting the information recorded on the recording layer when the track is on. Therefore, the optical drive apparatus performs processing for determining whether or not the focal point of the light beam is on the information writing line.

  In the above determination process when only one of the land and the groove is an information write line, the optical drive device uses an RF signal and a tracking error signal. The tracking error signal is 0 when the focal point is at the center of the land or groove, and takes a value other than 0 otherwise. The RF signal vibrates as the focal point moves across the track (this movement is referred to as track jump), and the minimum value of this vibration differs depending on whether the focal point is in the groove or the land. Therefore, the optical drive apparatus monitors the minimum value of the RF signal and the tracking error signal, and indicates that the focal point is on the information writing line by the minimum value of the RF signal and the tracking error signal becomes zero. It is determined that the track is on.

Patent Document 1 discloses a differential push-pull method that is a technique for radial position control (tracking servo) that follows an optical disk recording track.
JP-A-4-34212

  However, the RF signal has fluctuations due to non-uniform reflectance of the recording surface and confocal crosstalk in addition to the vibration and the change in the minimum value, and the accuracy of the determination processing deteriorates due to the fluctuation. Sometimes.

  Note that the non-uniformity of the reflectance of the recording surface means that the film thickness of the optical disk is non-uniform due to a manufacturing problem, and therefore the reflectance of the recording surface becomes non-uniform. As a result, a periodic variation substantially equal to the rotation period of the optical disk appears in the RF signal. In addition, confocal crosstalk is that the reflected light of each layer interferes when the interlayer distance is the same in an optical disc having three or more recording layers. As a result, periodic fluctuations appearing in the RF signal with a period shorter than the period of periodic fluctuations due to non-uniform reflectance of the recording surface.

  Accordingly, one of the objects of the present invention is to provide an optical drive device that can improve the accuracy of the determination processing when there is non-uniform reflectance on the recording surface or confocal crosstalk.

An optical drive device according to the present invention for solving the above-mentioned problems occurs in the RF signal acquisition means for acquiring the RF signal RF ₂ indicating the intensity of the light beam reflected by the optical recording medium, and the maximum value of the RF signal RF ₂ Amplitude indication signal acquisition means for acquiring amplitude indication signal SI = RF ₂ te−RF ₂ eth indicating the amplitude of periodic variation (variation due to confocal crosstalk), and periodic variation caused in the maximum value of RF signal RF ₂ And amplitude difference information acquisition means for acquiring amplitude ratio information k = RF ₂ bebh / RF ₂ tebh indicating the amplitude ratio between the periodic fluctuation occurring in the minimum value of the RF signal RF ₂ , the amplitude indication signal SI, and the amplitude ratio 'a slice signal generating means for generating a RF signal RF ₂ and the slice signal d' slice signal d on the basis of the information k determining means for determining whether or not the track-on state with a free It is characterized in. The determination means compares the minimum value of the vibration of the RF signal RF ₂ and the slice signal d 'and, it is also possible to determine whether the track-on state on the basis of the results.

  According to the present invention, the determination process can be performed using a slice signal reflecting non-uniform reflectivity and confocal crosstalk on the recording surface. Therefore, non-uniform reflectivity and confocal crosstalk exist on the recording surface. In this case, the accuracy of the determination process can be improved.

  According to the present invention, it is possible to improve the accuracy of the track-on state determination process when there is nonuniform reflectance on the recording surface or confocal crosstalk.

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

  In the following, a general track-on state determination process will be described first, and then a track-on state determination process that can be applied even when the recording surface has non-uniform reflectance or confocal crosstalk will be described.

  FIG. 1A is a plan view of the optical disc, and FIG. 1B is a cross-sectional view of the optical disc taken along the line AA ′ in FIG.

  As shown in FIG. 1, the optical disk is provided with a number of 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 part and the concave part of the groove are relative, and differ depending on which of the front and back surfaces of the optical disk is down. Therefore, it may be called differently from the above.

  In the example of FIG. 1, the land L is an information writing line, and a mark M for storing information is provided in the land L. The mark M is recorded or erased by irradiation with a light beam.

  Next, FIG. 2 is a diagram showing the appearance of the photodetector 5 for receiving the light beam reflected by the optical disk recording surface.

  As shown in FIG. 2, the photodetector 5 includes a main beam light receiving unit M, a first sub beam light receiving unit S1, and a second sub beam light receiving unit S2. The light beam is irradiated onto the recording surface in a state of being separated into three beams (0th order diffracted light and ± 1st order diffracted light) by the diffraction grating, and the first sub beam light receiving unit S1, the main beam light receiving unit M, and the second sub beam light receiving unit. S2 receives the return light beam of the + 1st order diffracted light (first sub beam SB1), the return light beam of the 0th order diffracted light (main beam MB), and the return light beam of the −1st order diffracted light (second sub beam SB2), respectively.

  Each light receiving unit is a four-divided light receiving unit in which four light receiving regions each having a square light receiving surface of a predetermined size are arranged in a square shape. Specifically, the main beam light receiving unit M includes light receiving areas a, b, c, and d clockwise from the upper right of the drawing. The first sub-beam light receiving unit S1 includes light receiving regions e1, e2, e3, e4 clockwise from the upper right of the drawing. The second sub-beam light receiving unit S2 includes light receiving regions f1, f2, f3, and f4 clockwise from the upper right of the drawing.

Each light receiving unit that receives the light beam outputs a signal having an amplitude of a value (amount of received light) obtained by dividing the intensity of the light beam by the area of the light receiving surface for each light receiving region. Hereinafter, output signals corresponding to the respective light receiving regions a, b, c, d, e1, e2, e3, e4, f1, f2, f3, and f4 are respectively represented as I _a , I _b , I _c , I _d , I _e1, and _{I e2, I e3, I e4} , I f1, I f2, I f3, I f4.

The tracking error signal TE is defined by the following equation (1). MPP and SPP are a main push-pull signal and a sub push-pull signal, respectively, and are defined by equations (2) and (3). k _t is a correction coefficient, and is determined in advance so that an offset (lens shift offset) generated in the MPP and SPP due to the movement of the objective lens can be canceled exactly.
TE = MPP-k _t SPP (1)
MPP = (I _a + I _d ) − (I _b + I _c ) (2)
SPP = (I _e1 + I _f1 ) + (I _e4 + I _f4 ) − (I _e2 + I _f2 ) − (I _e3 + I _f3 ) (3)

FIG. 3A shows a change in the tracking error signal TE when the focus of the light beam is moved along the line AA ′ in FIG. As shown in FIG. 3A, when the focal point of the light beam is at the center of the land L and the groove G, the value of the tracking error signal TE becomes 0 (points C _L and C _{G in} FIG. 3A). ).

The RF signal RF is defined by the following equation (4).
RF = I _a + I _b + I _c + I _d (4)

  FIG. 3B shows a change in the RF signal RF when the focal point of the light beam is moved along the line AA ′ in FIG. Note that the RF signal RF is a signal that vibrates violently due to the unevenness of the mark on the recording surface as shown in FIG. 4 later. In FIG. 4, the top envelope signal RFte that envelops the maximum value for each period of the vibration Similarly, only the bottom envelope signal RFbe enveloping the minimum value is shown.

  As shown in FIG. 3B, the bottom envelope signal RFbe has a property that it becomes smaller when the focus of the light beam is on the land L and becomes larger when it is on the groove G. Therefore, the optical drive device determines whether the focus of the light beam is currently in the land L or in the groove G using the bottom envelope signal RFbe.

  Specifically, the optical drive device has a slice signal d having a constant value between the maximum value and the minimum value of the bottom envelope signal RFbe (d = (V1−V0) × x / 100 + V0 in the example of FIG. 4 described later). ) And is compared with the bottom envelope signal RFbe. Then, a mirror signal is generated that becomes high when the bottom envelope signal RFbe is larger and becomes low when the bottom envelope signal RFbe is smaller. FIG. 3C shows an example of this mirror signal. The optical drive device uses this mirror signal to determine whether the focus of the light beam is currently in the land L or in the groove G. The frequency of the mirror signal is several kHz to several tens kHz in the case of BD.

  The optical drive apparatus performs the track-on state determination process as described above. This process is performed as follows. That is, the optical drive apparatus monitors the mirror signal, and further monitors the tracking error signal TE when the mirror signal indicates that the focal point of the light beam is currently on the land L. When the tracking error signal TE becomes 0, it is determined that the focus of the light beam is in the track-on state.

  The above processing is the track-on state determination processing that has been generally used until now, but due to this processing, sufficient accuracy cannot be obtained if the recording surface has uneven reflectance or confocal crosstalk. . Therefore, in the following, the track-on according to this embodiment in which sufficient accuracy can be obtained even when there is a non-uniform reflectance of the recording surface or confocal crosstalk while giving a specific example of the RF signal RF. The state determination process will be described in detail.

First, FIG. 4 is a diagram showing an example of the RF signal RF at the time of track jump. The RF signal RF _{0 in} the figure is for the case where there is no nonuniform reflectance on the recording surface and no confocal crosstalk. As shown in the figure, the actual RF signal RF is a signal that oscillates violently between the voltage values V0 and V1, the envelope of the minimum value is Botomuenbe signal RF 0 _BE. In the figure, the bottom envelope signal RF ₀ be is drawn to be a rectangular wave.

Next, FIG. 5 shows the RF signal RF ₁ in a state in which periodic variation is caused by reflection unevenness of the recording surface in the RF signal RF _0. The periodic fluctuation due to the non-uniform reflectance of the recording surface is proportional to the voltage value before the fluctuation, and as shown in the figure, the voltage value before the fluctuation × (1 + X1) and the voltage value before the fluctuation × (1−Y1). ).

Assuming that the amount of fluctuation caused by the non-uniform reflectance is represented by the signal S ₁ (maximum value X1, minimum value−Y1), the RF signal RF ₁ is represented by the following equation (5). Note that the RF signal RF ₁ in FIG. 5 is obtained by approximating the signal S ₁ with a sine wave in Equation (5). About when the frequency of the signals _{S 1} is 1x BD 13.5~27Hz, approximately 162~324Hz in the case of 12 times speed BD.
RF ₁ = RF ₀ (1 + S ₁ ) (5)

The signal V0r shown in FIG. 5 is a signal given periodic variation due to reflectivity uneven recording surface into a DC signal V0, it does not follow the frequency component of just the RF signal RF ₁ of Botomuenbe signal (mirror signal Signal). The signal V1r shown in FIG. 5 is a signal given periodic variation due to reflectivity uneven recording surface into a DC signal V1, is just a top Embedded signal of the RF signal RF _1. These are expressed by the following formulas (6) and (7), respectively.
V0r = V0 × (1 + S ₁ ) (6)
V1r = V1 × (1 + S ₁ ) (7)

Next, FIG. 6, the periodic variation indicates an RF signal RF ₂ in the state caused by further confocal crosstalk in the RF signal RF _1. The periodic fluctuation due to confocal crosstalk is also proportional to the voltage value before the fluctuation, and as shown in the figure, the voltage value before the fluctuation × (1 + X2) and the voltage value before the fluctuation × (1−Y2). It can be expressed as the variation between.

Assuming that the amount of fluctuation caused by confocal crosstalk is represented by a signal S ₂ (maximum value X2, minimum value −Y2), the RF signal RF ₂ is represented by the following equation (8). Note that the RF signal RF ₂ in FIG. 6 is obtained by using the signal drawn in FIG. 5 as the RF signal RF ₁ in Equation (8) and approximating the signal S ₂ with a sine wave. The frequency of the signal _{S 2,} for example when the in one cycle of the signals _{S 1} there are 30 pieces of the confocal crosstalk component, about 0.405~0.81kHz in the case of 1 × speed BD, in case of a 12-speed BD About 4.86 to 9.72 kHz.
RF ₂ = RF ₁ × (1 + S ₂ ) (8)

Generally, the period of the signal S ₂ also becomes shorter tens times than the period of the signal S _1. Since the frequency band of the mirror signal and the frequency band of the signal S ₂ overlap (frequency band of frequency fluctuation caused by confocal crosstalk), it is difficult to directly separate these components from the RF signal RF _2. It is possible to separate the S ₁ component from the mirror signal and the signal S ₂ component.

When trying to determine the track-on state, the optical drive device needs to generate a slice signal as described above. However, if the RF signal varies as the RF signal RF ₂ in FIG. 6, a slice signal d as described above is not a suitable slice signal. Therefore, the optical drive device generates the slice signal d ′ as follows. Hereinafter, this generation process will be described in detail.

Optical drive apparatus first obtains an amplitude instruction signal SI indicating the amplitude of the component due to out confocal crosstalk periodic variation occurring in the maximum value of the RF signal RF _2. Specifically, a top hold signal RF ₂ te which envelops the maximum value of the top envelope signal RF ₂ te is generated for each period of periodic fluctuation caused by confocal crosstalk. Then, the amplitude instruction signal SI is generated by Expression (9).
SI = RF ₂ te−RF ₂ teth (9)

Next, the optical drive apparatus, and amplitude of the component due to out confocal crosstalk periodic variation occurring in the maximum value of the RF signal RF _2, of the periodic variation occurring in the minimum value of the RF signal RF ₂ Amplitude ratio information (hereinafter referred to as “k”) indicating a ratio with the amplitude of the component caused by confocal crosstalk is acquired. As described above, since the amount of fluctuation caused by confocal crosstalk is proportional to the voltage value before the fluctuation, the amplitude ratio information k is equal to V0r / V1r.

In order to calculate the amplitude ratio information k = V0r / V1r, the optical drive apparatus firstly forms a bottom that envelops the minimum value of the top envelope signal RF ₂ te for each period of periodic fluctuation caused by confocal crosstalk. A hold signal RF ₂ tebh and a bottom hold signal RF ₂ bebh that envelops the minimum value of the bottom envelope signal RF ₂ be for each period of periodic fluctuation caused by confocal crosstalk are generated. The bottom hold signal RF ₂ tebh is represented by V1r × (1-Y2), and the bottom hold signal RFbeb h is represented by V0r × (1-Y2). Therefore, the optical drive device uses these signals to calculate the amplitude ratio information k using equation (10).
k ₌ the RF 2 bebh amplitude _/ RF 2 _tebh amplitude = (V0r × (1-Y2 )) / (V1r × (1-Y2)) = V0r / V1r ··· (10)

  If the amplitude ratio information k is a constant, it can be calculated and stored in advance. Therefore, for example, when the optical disk is inserted, the above calculation may be performed over a predetermined period, and an average value of the obtained numerical values may be used as the amplitude ratio information k. In this case, k≈V0 / V1.

The optical drive device generates the temporary signal g by the equation (11) using the amplitude instruction signal SI and the amplitude ratio information k acquired as described above. FIG. 6 also shows this temporary signal g.
g = RF ₂ bebh + k × SI (11)

Then, as shown in Expression (12), the slice signal d ′ is generated by shifting the temporary signal g upward by the shift amount Δ. FIG. 6 also shows an example of this slice signal d ′. The shift amount Δ is expressed by the equation (13). δ is a constant value.
d ′ = g + Δ (12)
Δ = (RF ₂ teth−RF ₂ tebh) × k + δ (13)

Note that the signal obtained by adding only the first term on the right side of the equation (13) to the temporary signal g is almost the bottom envelope signal of the RF signal RF ₂ when it is assumed that there is no change in the RF signal RF ₂ caused by the difference between land / groove. equal (since the frequency band of the frequency variation due to the frequency band and the confocal crosstalk mirror signal overlap, it is difficult to obtain this Botomuenbe signal directly from the RF signal RF _2.). The constant δ means that the bottom envelope signal is shifted upward by a constant value.

  As shown in FIG. 6, since the slice signal d ′ follows the periodic fluctuation caused by non-uniform reflectance of the recording surface and confocal crosstalk, the use of the slice signal d ′ enables accurate track-on state. Judgment processing can be realized.

  Next, the configuration of the optical drive device 1 that realizes the processing described above will be described.

  FIG. 7 is an example of a schematic diagram of the optical drive device 1 according to the present embodiment.

  The optical drive device 1 performs reproduction and recording of the optical disk 11. As the optical disc 11, various optical recording media such as CD, DVD, HD-DVD, and BD can be used. In this embodiment, in particular, the optical disc 11 has a recording surface multi-layered into three or more layers by a multilayer film. A disc-shaped optical disk is used.

  As shown in FIG. 7, the optical drive device 1 includes a laser light source 2, an optical system 3, an objective lens 4, a photodetector 5, and a processing unit 6. Among these, the laser light source 2, the optical system 3, the objective lens 4, and the photodetector 5 constitute an optical pickup.

  The optical system 3 includes a diffraction grating 21, a beam splitter 22, a collimator lens 23, a quarter wavelength plate 24, and a sensor lens (cylindrical lens) 25. The optical system 3 functions as an outward optical system that guides the light beam emitted from the laser light source 2 to the optical disk 11, and also functions as a backward optical system that guides the return beam from the optical disk 11 to the photodetector 5.

  First, in the forward optical system, the diffraction grating 21 decomposes the light beam emitted from the laser light source 2 into three beams (0th-order diffracted light and ± 1st-order diffracted light) and enters the beam splitter 22 as P-polarized light. The beam splitter 22 reflects the incident P-polarized light and bends its path in the direction of the optical disk 11. The collimator lens 23 converts the light beam incident from the beam splitter 22 into parallel light. The quarter wavelength plate 24 converts the light beam that has passed through the collimator lens 23 into circularly polarized light. The light beam that has passed through the quarter-wave plate 24 enters the objective lens 4.

  Next, in the return path optical system, the beam splitter 22 transmits 100% of the light beam reflected on the recording surface and converted into S-polarized light by reciprocating the quarter wavelength plate 24 and traveling backward through the return path optical system. The light enters the sensor lens 25. The sensor lens 25 gives astigmatism to the light beam incident from the beam splitter 22. The light beam provided with astigmatism enters the photodetector 5.

  The objective lens 4 has a function of condensing a light beam incident from the optical system 3 (a light beam in a parallel light state) on the optical disk 11 and returning a return light beam from the optical disk 11 to parallel light.

  The photodetector 5 is installed on a plane that intersects the optical path of the return light beam emitted from the optical system 3 as shown in FIG. The detailed configuration is as shown in FIG.

  The processing unit 6 is configured by a DSP (Digital Signal Processor) having an A / D conversion function that converts analog signals for multiple channels into digital data as an example, and receives an output signal from the photodetector 5, An RF signal RF and a tracking error signal TE are generated. Then, a track-on state determination process is performed using each of these signals.

  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). The processing unit 6 that has received this instruction signal controls the objective lens 4 to perform a track jump to the instructed access position, and when it is finally determined that the track is on, the determination result is sent to the CPU 7. Output. Receiving this determination result, the CPU 7 acquires the output signal of the photodetector 5 as a data signal.

  FIG. 8 is a functional block diagram showing functional blocks of the processing unit 6 relating to the track jump control process and the track-on state determination process.

  As shown in FIG. 8, the processing unit 6 functionally includes a track jump control unit 61, an RF signal acquisition unit 62, an amplitude instruction signal acquisition unit 63, an amplitude ratio information acquisition unit 64, a slice signal generation unit 65, and a TE signal acquisition unit. 66, and includes a track-on state determination unit 67.

  The track jump control unit 61 receives an instruction signal from the CPU 7 and transmits a control signal to the objective lens 4 to start track jump. After the objective lens 4 is moved to the vicinity of the instructed access position, the track jump is stopped at the position determined by the track-on state determination unit 67 as the track-on state, and the determination result of the track-on state is sent to the CPU 7. Output.

The RF signal acquisition unit 62 receives the input of the output signals I _a , I _b , I _c , and I _d from the main beam light receiving unit M of the photodetector 5 and generates the RF signal RF ₂ by Expression (4).

The amplitude instruction signal acquisition unit 63 generates a top envelope signal RF ₂ te of the RF signal generated by the RF signal acquisition unit 62, and further calculates the maximum value of this top envelope signal for each period of periodic fluctuation caused by confocal crosstalk. The top hold signal RF ₂ tes enveloping the signal is generated. Then, the amplitude instruction signal SI is generated by Expression (9).

The amplitude ratio information acquisition unit 64 generates a top envelope signal RF ₂ te and a bottom envelope signal RF ₂ be of the RF signal generated by the RF signal acquisition unit 62, and further generates a top for every period of periodic fluctuation caused by confocal crosstalk. A bottom hold signal RF ₂ tebh that envelops the minimum value of the envelope signal RF ₂ te and a bottom hold signal that envelops the minimum value of the bottom envelope signal RF ₂ be for each period of periodic variation caused by confocal crosstalk. RF ₂ bebh is generated. Then, using these, the amplitude ratio information k is calculated by the equation (10). As described above, the calculation of the amplitude ratio information k may be performed in advance.

  The slice signal generation unit 65 generates the slice signal d ′ by Expression (12) using each signal generated as described above and the amplitude ratio information k.

The TE signal acquisition unit 66 outputs output signals I _a , I _b , I _c , I _d , I _{e 1} , I _{e 2} , I _{e 3} , I _{e 4} , I _f 1, I _f from the main beam receiving unit M and the sub beam receiving units S 1 and S 2. The input of _f2 , _If3 , _If4 is received, and the tracking error signal TE is generated by the equation (1).

The track-on state determination unit 67 compares the bottom envelope signal RF ₂ be and the slice signal d ′, and generates a mirror signal that is high when the bottom envelope signal RF ₂ be is larger and is low when the bottom envelope signal RF ₂ be is smaller. The track-on state determination unit 67 uses this mirror signal to determine whether the focus of the light beam is currently in the land L or in the groove G.

  The track-on state determination unit 67 monitors the mirror signal, and further monitors the tracking error signal TE when the mirror signal indicates that the focal point of the light beam is currently on the land L. When the tracking error signal TE becomes 0, it is determined that the focus of the light beam is in the track-on state, and the determination result is output to the track jump control unit 61. The processing of the track jump control unit 61 that has received this determination result is as described above.

  As described above, according to the optical drive device 1, the track-on state determination process can be performed using the slice signal d ′ reflecting the nonuniform reflectance of the recording surface and the confocal crosstalk. The accuracy of the track-on state determination process when there is a non-uniform reflectance or confocal crosstalk can be improved.

  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, an actual RF signal may drop sharply due to dirt or dust on the surface of the optical disk. FIG 9 shows an RF signal RF ₃ as an example of the RF signal in such a case. The RF signal RF ₃ is obtained by adding a drop due to a defect (a drop within a given period from the drop point P) to the RF signal RF ₂ in FIG.

As shown in FIG. 9, when comparing the (same. As that shown in FIG. 6) and the bottom hold signal _RF 2 Bebh bottom hold signal _RF 3 Bebh the RF signal RF ₂ of the RF signal RF _3, bottom hold signal RF ₃ bebh becomes smaller than the bottom hold signal RF ₂ bebh not only during the drop period but for a while after that. Then, during that period, the value of the slice signal d ′ calculated by the equation (12) also becomes small, and a correct mirror signal cannot be generated.

Therefore, instead of the bottom hold signal RF ₃ bebh (a signal formed by enveloping the minimum value of the bottom envelope signal RF ₃ be for each period of periodic fluctuation caused by confocal crosstalk), a longer period, for example, reflection on the recording surface. The bottom hold signal RF ₂ bebhbh that envelops the minimum value of the bottom envelope signal RF ₂ be for each period of periodic fluctuation caused by the rate nonuniformity may be used. In this way, the signal level difference at the drop point P is reduced, so that the influence of the Defect on the slice signal d ′ can be reduced. Therefore, even if the RF signal moves as shown in FIG. 9, the accuracy of the track-on state determination process can be improved.

  In the above embodiment, the tracking error signal obtained by Equation (1) (differential push-pull method) is used. However, in the present invention, tracking obtained by various methods such as the 3-beam method and the 1-beam method is also used. An error signal can be used.

It should be noted that the slice signal d used in the general track-on state determination process is learned from the formula d = (V1−V0) × x / 100 + V0, for example, the slice signal d ′ = (RF ₂ te−RF ₂ bebh) × x. Although it is conceivable to set it to / 100 + RF ₂ bebh, the slice signal d ′ obtained in this way does not have a sufficient fluctuation range, and the accuracy of the track-on state determination processing may not be sufficiently improved.

(A) is a top view of the optical disk by embodiment of this invention, (b) is sectional drawing of the optical disk in the AA 'line in Fig.1 (a). It is an external view at the time of seeing the photodetector by embodiment of this invention from the irradiation direction of a light beam. (A) is a figure which shows the change of the tracking error signal TE when the focus of a light beam is moved along line 1A-A '. (B) shows the change of the RF signal RF when the focal point of the light beam is moved along the line AA ′ in FIG. (C) is a mirror signal created using the bottom envelope signal and slice signal of FIG. 3 (b). It is a figure which shows an example of the RF signal at the time of a track jump. An RF signal is shown in a state where periodic fluctuations are caused by non-uniform reflectance of the recording surface. An RF signal is shown in a state where periodic fluctuations occur due to non-uniform reflectance of the recording surface and confocal crosstalk. 1 is a schematic diagram of an optical drive device according to an embodiment of the present invention. It is a functional block diagram which shows the functional block of the process part regarding the track jump control process and track-on state determination process by embodiment of this invention. An RF signal in a state where a drop due to Defect has occurred is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical drive apparatus 2 Laser light source 3 Optical system 4 Objective lens 5 Photodetector 6 Processing part 7 CPU
DESCRIPTION OF SYMBOLS 11 Optical disk 21 Diffraction grating 22 Beam splitter 23 Collimator lens 24 1/4 wavelength plate 25 Sensor lens 61 Track jump control part 62 RF signal acquisition part 63 Amplitude instruction | indication signal acquisition part 64 Amplitude ratio information acquisition part 65 Slice signal generation part 66 TE signal Acquisition unit 67 Track on state determination unit M Main beam light receiving unit S1 First sub beam light receiving unit S2 Second sub beam light receiving unit

Claims (6)

An RF signal acquisition means for acquiring an RF signal indicating the intensity of the light beam reflected by the optical recording medium multi-layered into three or more layers ;
An amplitude indication signal acquisition means for acquiring an amplitude indication signal indicating the amplitude of the periodic fluctuation occurring in the maximum value of the RF signal;
Every second period longer than the first period of the top envelope signal that envelops the maximum value of the RF signal for each first period, which is the period of vibration generated by the unevenness of the recording surface of the optical recording medium Enveloping the minimum value for each second period of the first bottom hold signal enveloping the minimum value of the signal and the bottom envelope signal enclosing the minimum value of the RF signal for each of the first period The amplitude for obtaining amplitude ratio information indicating the amplitude ratio between the periodic fluctuation occurring in the maximum value of the RF signal and the periodic fluctuation occurring in the minimum value of the RF signal based on the second bottom hold signal Ratio information acquisition means;
Slice signal generating means for generating a slice signal based on the amplitude instruction signal and the amplitude ratio information;
Determining means for determining whether or not a track is on using the RF signal and the slice signal;
An optical drive device comprising: The amplitude instruction signal acquisition means acquires the amplitude instruction signal based on the top envelope signal and a top hold signal enveloping the maximum value of the top envelope signal for each second period. The optical drive device according to claim 1. The optical drive apparatus according to claim 1, wherein the second period is a period of periodic fluctuation due to confocal crosstalk. The slice information generating means shifts the amplitude of a temporary signal obtained by adding a product of the amplitude instruction signal and the amplitude ratio information to the second bottom hold signal by a predetermined shift amount, thereby causing the slice signal to be The optical drive device according to claim 1, wherein the optical drive device is generated. The top envelope signal is RF ₂ te, the top hold signal is RF ₂ teth, the first bottom hold signal is RF ₂ tebh, the second bottom hold signal is RF ₂ bebh, where the shift amount is Δ, the slice signal d ′ is
d ′ = RF ₂ bebh + (RF ₂ bebh / RF ₂ tebh) x (RF ₂ te-RF ₂ teth) + Δ
The optical drive device according to claim 4, wherein Said determining means, said minimum value of the vibration of the RF signal and comparing the slice signal, any one of claims 1 to 5, characterized in that determining whether the track-on state on the basis of the result The optical drive device according to Item .

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