JP4867913B2 - Photodetector, optical pickup, and optical drive device - Google Patents

Description

  The present invention relates to a photodetector, an optical pickup, and an optical drive device, and more particularly to a photodetector, an optical pickup, and an optical drive device that are 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 used to irradiate a recording layer of the optical disc with an optical beam. Write. At the same time, the return light beam reflected by the recording surface is received by the photodetector, and the irradiation power of the light beam to the recording surface is adjusted based on the output signal (RF signal). This adjustment processing is performed while actually writing information on the optical disc, and is called ROPC (Running Optimum Write Power Control).

ROPC is a technique for preventing writing on an optical disk from failing due to obstacles such as dirt and dust (see, for example, Patent Document 1). That is, when the amount of the light beam reaching the recording surface decreases due to an obstacle, the temperature of the recording layer can be sufficiently increased in an optical disc that stores information using the phase change of the recording layer such as a DVD-RAM. The phase change cannot be caused and jitter (fluctuation in writing accuracy) is deteriorated. In ROPC, in order to prevent the occurrence of such a situation, the irradiation power of the light beam is increased as the RF signal is weaker, that is, as there are more obstacles.
JP 2006-127593 A

  However, the RF signal may fluctuate due to factors other than the obstacle of the optical disk. One of them is non-uniform reflectance of the recording layer, and the other is confocal crosstalk. If the RF signal includes fluctuations caused by these factors, the accuracy of ROPC deteriorates.

  Accordingly, one of the objects of the present invention is to provide an optical drive device that can prevent ROPC accuracy deterioration due to non-uniform reflectance of the recording layer and the presence of confocal crosstalk.

  An optical drive device according to a first aspect of the present invention for solving the above-described problems includes an RF signal acquisition means for acquiring an RF signal RF indicating the intensity of a light beam reflected by an optical recording medium, and an A maximum value envelope means for enveloping the maximum value with a given droop plate, a minimum value envelope means for enclosing the minimum value of a given signal with a given droop plate, and taking out fluctuations occurring in the RF signal RF A top signal d obtained by giving a fluctuation signal acquisition means for acquiring a fluctuation signal and a first droop plate corresponding to a period of fluctuation caused by confocal crosstalk to the maximum value envelope means. A top envelope signal obtaining means to obtain, and a bottom envelope obtained by giving the fluctuation signal and the first droop plate to the minimum value envelope means. The bottom envelope signal acquisition means for acquiring the signal e, and the maximum value envelope means correspond to the period of the reflectivity-induced fluctuation that occurs in the RF signal RF due to the nonuniformity of the reflectance of the bottom envelope signal e and the optical recording medium. A first top hold signal a1 that obtains a first top hold signal a1 obtained by providing the second droop plate, and the top envelope signal d and the second droop plate to the minimum value envelope means A first bottom hold signal obtaining means for obtaining a first bottom hold signal b1 obtained by the operation, and a second top hold obtained by applying the top envelope signal d and the second droop plate to the maximum value envelope means. A second top hold signal acquisition means for acquiring a signal a2, and the bottom value encoder in the maximum value envelope means; A corrected second bottom hold signal b2 ′ obtained by giving a corrected bottom envelope signal e ′ obtained by giving a signal e and the first droop plate together with the second droop plate to the minimum value envelope means is obtained. Based on the modified second bottom hold signal acquisition means, the first top hold signal a1, the first bottom hold signal b1, the second top hold signal a2, and the modified second bottom hold signal b2 ′, Fluctuation center signal acquisition means for acquiring a fluctuation center signal SC indicating the fluctuation center of fluctuations occurring in the RF signal RF, and corrected RF signal generation means for generating a correction RF signal CRF using the fluctuation center signal SC. It is characterized by.

According to the present invention, the modified RF signal CRF is less affected by the nonuniformity of the reflectivity of the recording layer and the fluctuation due to confocal crosstalk than the uncorrected RF signal RF. Deterioration of ROPC accuracy due to the presence of focal crosstalk can be prevented.
The optical drive device according to a second aspect of the present invention is the optical drive device according to the first aspect, wherein the fluctuation signal acquisition means includes the RF signal and a period of vibration of the RF signal in the maximum value envelope means. An envelope signal obtained by providing a third droop plate corresponding to is obtained as the fluctuation signal.

  The optical drive device according to a third aspect of the present invention is the optical drive device according to the second aspect, wherein the fluctuation center signal acquisition means includes the first top hold signal a1, the first bottom hold signal b1, The fluctuation center signal SC is acquired based on an average value signal of the second top hold signal a2 and the modified second bottom hold signal b2 ′.

  An optical drive device according to a fourth aspect of the present invention is the optical drive device according to the third aspect, wherein a decrease detecting means for detecting a decrease in the RF signal RF and the decrease detected by the decrease detecting means. Reduction amount acquisition means for acquiring a reduction amount of the correction RF signal generation means, wherein the correction RF signal generation means acquires a signal obtained by subtracting the reduction amount from the average value signal as the correction RF signal CRF. And

  The optical drive device according to a fifth aspect of the present invention is the optical drive device according to the fourth aspect, further comprising a corrected bottom envelope signal acquisition means for acquiring the corrected bottom envelope signal e ′, wherein the decrease detection means is The lowering of the RF signal RF is detected using the bottom envelope signal e and the modified bottom envelope signal e ′.

  The optical drive device according to a sixth aspect of the present invention is the optical drive device according to the fourth aspect, further comprising a corrected bottom envelope signal acquisition means for acquiring the corrected bottom envelope signal e ′, and the reduction amount acquisition means. Is characterized in that a difference e′−e between the corrected bottom envelope signal e ′ and the bottom envelope signal e is acquired as the amount of decrease.

  An optical drive device according to a seventh aspect of the present invention is the optical drive device according to the fourth aspect, wherein the lowering detection means uses the top envelope signal d and the bottom envelope signal e to generate the RF signal RF. It is characterized by detecting a decrease.

  An optical drive device according to an eighth invention of the present invention is the optical drive device according to the fourth or seventh invention, wherein the fluctuation signal and the first droop plate are supplied to the maximum value envelope means, Obtaining a drop top envelope signal d 'obtained by temporarily enlarging a droop plate applied to the maximum value envelope means in response to detection of a drop in the RF signal RF by a drop detection means And a decrease amount acquisition unit that acquires a difference dd ′ between the top envelope signal d and the reduced top envelope signal d ′ as the decrease amount.

Further, an optical drive device according to a ninth aspect of the present invention is the optical drive device according to the eighth aspect, wherein a decrease time point indication signal C indicating a time point when the decrease of the RF signal RF is detected by the decrease detection means is provided. A lowering point instruction signal acquiring unit for acquiring, and the lowering top envelope signal acquiring unit temporarily enlarges a droop plate to be supplied to the maximum value envelope unit according to the lowering point instruction signal C. And
An optical drive device according to a tenth aspect of the present invention is the optical drive device according to the first aspect, wherein the fluctuation signal acquisition means includes the RF signal and a period of vibration of the RF signal in the minimum value envelope means. An envelope signal obtained by providing a third droop plate corresponding to is obtained as the fluctuation signal.
An optical drive apparatus according to an eleventh aspect of the present invention is the optical drive apparatus according to the first aspect, wherein the fluctuation signal acquisition means passes a signal that vibrates the RF signal at least at the oscillation period of the RF signal. A signal obtained by passing through a low-pass filter is obtained as the fluctuation signal.

  An optical drive device according to a twelfth aspect of the present invention is the optical drive device according to the first, second, third, tenth, or eleventh aspect of the present invention, wherein the first top hold signal a1, the first Based on the bottom hold signal b1, the second top hold signal a2, and the modified second bottom hold signal b2 ′, an instruction signal acquisition for acquiring an instruction signal SI indicating the amount of periodic fluctuation occurring in the envelope signal The modified RF signal generating means generates the modified RF signal CRF using the instruction signal SI.

  An optical drive device according to a thirteenth aspect of the present invention is the optical drive device according to the twelfth aspect, wherein the instruction signal acquisition means includes the second top hold signal a2 and the modified second bottom hold signal b2 ′. A signal obtained by subtracting the average value signal of the first top hold signal a1 and the first bottom hold signal b1 from the average value signal is obtained as the instruction signal SI.

  An optical drive device according to a fourteenth aspect of the present invention is the optical drive device according to the twelfth or thirteenth aspect, wherein the corrected bottom envelope signal acquisition means acquires the corrected bottom envelope signal e ′, and the second top hold. Correction value determining means for determining a correction value k of the instruction signal SI based on the signal a2, the first bottom hold signal b1, the top envelope signal d, and the modified bottom envelope signal e ′; The RF signal generating means generates the modified RF signal CRF using the instruction signal SI corrected using the correction value k determined by the correction value determining means.

  An optical drive device according to a fifteenth aspect of the present invention is the optical drive device according to the fourteenth aspect, wherein a decrease detection means for detecting a decrease in the RF signal RF and the decrease detected by the decrease detection means. A reduction amount acquisition means for acquiring a reduction amount of the correction signal, wherein the modified RF signal generation means subtracts the instruction signal SI corrected using the correction value k and the reduction amount from the fluctuation center signal SC. The signal obtained in this way is the modified RF signal CRF.

  An optical drive device according to a sixteenth aspect of the present invention is the optical drive device according to the fifteenth aspect, wherein the decrease amount acquisition means is a difference e′−e between the corrected bottom envelope signal e ′ and the bottom envelope signal e. Is acquired as the amount of decrease.

  An optical drive device according to a seventeenth aspect of the present invention is the optical drive device according to the fifteenth or sixteenth aspect, wherein the drop detecting means uses the bottom envelope signal e and the modified bottom envelope signal e ′. It is characterized by detecting a decrease in the RF signal RF.

  An optical drive device according to an eighteenth aspect of the present invention is the optical drive device according to the twelfth or thirteenth aspect of the present invention, wherein the decrease detection means for detecting a decrease in the RF signal RF, and the maximum value envelope means When a reduction is obtained by enlarging a droop plate that is temporarily supplied to the maximum value envelope means in response to detection of a drop in the RF signal RF by the drop detection means while giving a fluctuation signal and the first droop plate. Based on the lower top envelope signal acquisition means for acquiring the top envelope signal d ′, the second top hold signal a2, the first bottom hold signal b1, the lower top envelope signal d ′, and the bottom envelope signal e. Correction value determining means for determining a correction value k of the instruction signal SI, and the corrected RF signal generating means And generating said modified RF signal CRF with the instruction signal SI which is corrected using the correction value k, which is determined by the value determination means.

  An optical drive device according to a nineteenth aspect of the present invention is the optical drive device according to the eighteenth aspect, further comprising a reduction amount acquisition means for acquiring the reduction amount of the reduction detected by the reduction detection means. The modified RF signal generation means includes a signal obtained by subtracting the instruction signal SI corrected using the correction value k and the amount of decrease from the fluctuation center signal SC as the modified RF signal CRF. It is characterized by.

  An optical drive apparatus according to a twentieth aspect of the present invention is the optical drive apparatus according to the nineteenth aspect, wherein the decrease amount acquisition means is a difference d between the top envelope signal d and the reduced top envelope signal d ′. The optical drive apparatus according to claim 16, wherein −d ′ is acquired as the reduction amount.

  An optical drive device according to a twenty-first aspect of the present invention is the optical drive device according to any one of the eighteenth to twentieth inventions, wherein the decrease indicates the time point when the decrease of the RF signal RF is detected by the decrease detection means. A lowering point instruction signal acquiring unit for acquiring a time point indicating signal C, wherein the lowering top envelope signal acquiring unit temporarily includes a droop plate to be supplied to the maximum value envelope unit according to the lowering point instruction signal C. It is characterized by being enlarged.

  An optical drive device according to a twenty-second invention of the present invention is the optical drive device according to any one of the eighteenth to twenty-first inventions, wherein the lowering detection means uses the top envelope signal d and the bottom envelope signal e. A decrease in the RF signal RF is detected.

  An optical drive device according to a twenty-third aspect of the present invention is the optical drive device according to the first, second, third, tenth, eleventh, twelfth or thirteenth aspect of the present invention, wherein the corrected RF signal CRF Based on the output control means for controlling the irradiation power of the light beam based on the detection result, a decrease in the RF signal RF is detected, and at least the processing of the optical drive device including the processing by the output control means is executed according to the detection result. And a lowering detection means for limiting.

  An optical drive device according to a twenty-fourth aspect of the present invention is the optical drive device according to the twenty-third aspect, further comprising a modified bottom envelope signal acquisition means for acquiring the corrected bottom envelope signal e ′, wherein the decrease detection means is The lowering of the RF signal RF is detected using the bottom envelope signal e and the modified bottom envelope signal e ′.

  An optical drive device according to a twenty-fifth aspect of the present invention is the optical drive device according to the twenty-third aspect, wherein the drop detecting means uses the top envelope signal d and the bottom envelope signal e to generate the RF signal RF. It is characterized by detecting a decrease.

  An optical drive device according to a twenty-sixth aspect of the present invention is the optical drive device according to any one of the first to twenty-fifth aspects, wherein the bottom envelope signal e and the second droop plate are provided in the minimum value envelope means. A second bottom hold signal acquisition unit that acquires a second bottom hold signal b2 obtained by applying the second bottom hold signal b2. The modified second bottom hold signal acquisition unit includes the second bottom hold signal b2 in the maximum value envelope unit. And the second droop plate are provided to obtain the modified second bottom hold signal b2 ′.

  An optical drive device according to a twenty-seventh aspect of the present invention is the optical drive device according to any one of the first to twenty-fifth aspects, wherein the modified second bottom hold signal acquisition means is connected to the minimum value envelope means. The modified second bottom hold signal b2 ′ is obtained by providing the modified bottom envelope signal e ′ and the second droop plate.

  An optical drive device according to a twenty-eighth aspect of the present invention is the optical drive device according to any one of the first to twenty-fifth aspects, wherein the modified second bottom hold signal acquisition means is the first top hold signal a1. The modified second bottom hold signal b2 ′ is obtained by calculation from the first bottom hold signal b1 and the second top hold signal a2.

  An optical drive device according to a twenty-ninth aspect of the present invention according to another aspect includes an RF signal acquisition means for acquiring an RF signal RF indicating the intensity of the light beam reflected by the optical recording medium, and an RF signal RF. Based on the output control means for controlling the irradiation power of the light beam based on the detection result, a decrease in the RF signal RF is detected, and at least the processing of the optical drive device including the processing by the output control means is executed according to the detection result. And a drop detecting means for limiting.

  An optical drive device according to a thirtieth aspect of the present invention according to another aspect of the present invention is the optical drive device according to the twenty-ninth aspect of the present invention, wherein a maximum value of a given signal is enveloped by a given droop plate. A value envelope means, a minimum value envelope means for enveloping a minimum value of a given signal with a given droop plate, a fluctuation signal obtaining means for obtaining a fluctuation signal obtained by taking out fluctuations occurring in the RF signal, Bottom envelope signal acquisition means for acquiring a bottom envelope signal e obtained by applying the fluctuation signal and the first droop plate to the minimum value envelope means, and the bottom envelope signal e and the first droop plate to the maximum value envelope means. And a modified bottom envelope signal acquisition means for acquiring a corrected bottom envelope signal e ′ obtained by giving The decrease detecting means detects a decrease in the RF signal RF using the bottom envelope signal e and the modified bottom envelope signal e ′.

  According to a thirty-first aspect of the present invention, there is provided an optical drive device according to the thirty-first aspect of the present invention, wherein the maximum value of a given signal is enveloped by a given droop plate. A value envelope means, a minimum value envelope means for enveloping a minimum value of a given signal with a given droop plate, a fluctuation signal obtaining means for obtaining a fluctuation signal obtained by taking out fluctuations occurring in the RF signal, Top envelope signal acquisition means for acquiring a top envelope signal d obtained by providing the maximum value envelope means with the fluctuation signal and a first droop plate corresponding to a period of fluctuation caused by confocal crosstalk; and the minimum value envelope. Obtaining a bottom envelope signal e obtained by applying the fluctuation signal and the first droop plate to the means; Further comprising a step, wherein the drop detecting means, and detects the deterioration of the RF signal RF with reference to the top Embedded signal d and the Botomuenbe signal e.

  According to the present invention, it is possible to prevent the accuracy of ROPC from deteriorating due to the non-uniform reflectance of the recording layer and the presence of confocal crosstalk.

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

  Hereinafter, the overall configuration of the optical drive device will be described first, and then the details of the ROPC unit for performing the ROPC process will be described.

[Overall configuration of optical drive device]
FIG. 1 is an example of a schematic diagram of an optical drive device 1 according to the present embodiment.

  As shown in FIG. 1, the optical drive device 1 includes a laser light source 2, an optical system 3, an objective lens 4, a lens driving unit 5, a photodetector 6, a processing unit 7, and an ROPC unit 8. 11 playback and recording.

  Various optical recording media such as CD, DVD, HD-DVD, and BD can be used for the optical disc 11, but in this embodiment, in particular, a disc shape having a recording surface multi-layered into three or more layers by a multilayer film. The optical disc is used.

  The film thickness of each layer is preferably uniform originally, but in reality, the film thickness near the center of the disk is often larger than the film thickness near the periphery. Also, the film thickness may be non-uniform even within the same circumference. As a result, the reflectance of the recording surface becomes non-uniform, and for this reason, a periodic variation (reflectance-induced variation) substantially equal to the rotation period of the optical disk 11 appears in the RF signal.

  Further, in the optical disc 11, when the layer spacing is equal, the reflected light of each layer interferes (confocal crosstalk), so that the RF signal has a period of periodic fluctuation due to nonuniform reflectance of the recording surface. In addition, periodic fluctuations with short periods (confocal crosstalk-induced fluctuations) appear.

  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 disc 11, and also functions as a return optical system that guides the return beam from the optical disc 11 to the photodetector 6.

  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 optical system, the beam splitter 22 transmits 100% of the light beam reflected by the recording surface and further passing through the quarter wavelength plate 24 to become S-polarized light and traveling backward through the return 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 6.

  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 lens driving unit 5 moves the objective lens 4 in the radial direction of the optical disk 11 based on the tracking error signal TE output from the processing unit 7, thereby positioning the spot formed on the recording surface by the light beam on the optical disk 11. Move in the radial direction (tracking servo). Further, the lens driving unit 5 moves the objective lens 4 in a direction perpendicular to the recording surface of the optical disk 11 based on the focus error signal FE output from the processing unit 7, thereby forming a light beam on the recording surface. The position of the spot to be moved is moved toward and away from the recording surface (focus servo).

  The photodetector 6 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.

  FIG. 2 is a view showing the appearance of the photodetector 6.

  As shown in FIG. 2, the photodetector 6 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. As described above, the light beam is irradiated onto the recording surface in a state of being decomposed 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, The second sub-beam light receiving unit S2 respectively returns the return light beam of the + 1st order diffracted light (first subbeam 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 subbeam SB2). Is received. Although an example using three beams will be described here, the present invention is also applicable to the case where only the main beam MB is used.

  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.

  Returning to FIG. As an example, the processing unit 7 is configured by a DSP (Digital Signal Processor) having an A / D conversion function that converts analog signals for multiple channels into digital data, and receives an input of an output signal of the photodetector 6. Thus, three types of signals, that is, an RF signal RF, a focus error signal FE, and a tracking error signal TE are generated.

The RF signal RF is defined by the following equation (1) using the output signals I _a , I _b , I _c , I _d of the main beam light receiving unit M.
RF = I _a + I _b + I _c + I _d (1)

Further, the focus error signal FE is defined by Expression (2). However, the main beam focusing error signal FE _M and the sub-beam focusing error signal FE _S is defined by each of formulas (3) and (4). The k _f is a correction factor, previously determined to allow just cancel noise (track cross noise) appearing on the FE _M and FE _S when the objective lens 4 crosses the tracks.
FE = FE _M + k _f FE _S (2)
FE _M = (I _a + I _c ) − (I _b + I _d ) (3)
FE _S = {(I _e1 + I _f1 ) + (I _e3 + I _f3 )} − {(I _e2 + I _f2 ) + (I _e4 + I _f4 )} (4)

The tracking error signal TE is defined by the equation (5). However, the main push-pull signal MPP and the sub push-pull signal SPP are defined by Expression (6) and Expression (7), respectively. k _t is a correction coefficient, and is determined in advance so that an offset (lens shift offset) generated in the MPP and SPP by the movement of the objective lens 4 can be canceled exactly.
TE = MPP-k _t SPP (5)
MPP = (I _a + I _d ) − (I _b + I _c ) (6)
SPP = (I _e1 + I _f1 ) + (I _e4 + I _f4 ) − (I _e2 + I _f2 ) − (I _e3 + I _f3 ) (7)

  The processing unit 7 outputs the focus error signal FE and the tracking error signal TE among the generated signals to the lens driving unit 5. The processing of the lens driving unit 5 receiving this output is as described above.

  Further, the processing unit 7 outputs the RF signal RF among the generated signals to the ROPC unit 8.

  FIG. 3 is a diagram illustrating an example of the RF signal RF output from the processing unit 7. As shown in the figure, the RF signal RF is a signal that vibrates violently with a short cycle (hereinafter referred to as a vibration cycle). This vibration is due to the unevenness of the mark on the recording surface.

  Further, as described above, the RF signal RF also fluctuates due to non-uniform reflectance of the recording layer and confocal crosstalk. FIG. 3 also shows a top envelope signal RFte that envelops the maximum value for each vibration period of the RF signal RF, and a bottom envelope signal RFbe that also envelops the minimum value, as shown in FIG. In addition, each of these signals includes fluctuations in two types of periods, long and short. Of these variations, the longer variation represents the reflectance-induced variation of the recording layer, and the shorter variation represents the confocal crosstalk-induced variation.

  FIG. 4 is an explanatory diagram of the reflectance-induced variation and the confocal crosstalk-induced variation. A signal RFte ′ in the figure shows a signal obtained by removing the confocal crosstalk-induced variation component from the top envelope signal RFte. The voltage value c0 indicates a signal obtained by removing both the reflectance-induced variation and the confocal crosstalk-induced variation from the top envelope signal RFte.

As shown in FIG. 4, the voltage value of the signal fluctuated due to the reflectance-induced fluctuation is proportional to the voltage value c0 before the fluctuation, and the voltage value before the fluctuation × (1 + X1) and the voltage value before the fluctuation × (1−Y1). Take a value between and. Similarly, the voltage value of the signal that has fluctuated due to the confocal crosstalk variation is proportional to the voltage value before the fluctuation, and is between the voltage value before the fluctuation × (1 + X2) and the voltage value before the fluctuation × (1−Y2). Take the value of Therefore, assuming that the reflectivity-induced variation is represented by the signal S ₁ , the confocal crosstalk-induced variation is represented by the signal S ₂ , and X1 = Y1, X2 = Y2, the RF signal RF can be represented by the following equation (8). . However, RF ₀ is an RF signal before being subjected to fluctuation. Incidentally, FIG. 4 is a depicting signals S ₁ and the signal S ₂ both as a sine wave.
RF = RF ₀ × (1 + X1 × S ₁ ) × (1 + X2 × S ₂ ) (8)

  Note that the RF signal RF may drop sharply due to obstacles (defects) such as dirt and dust on the surface of the optical disk 11. FIG. 5 shows an example of the RF signal RF in such a case.

  The ROPC unit 8 controls the output of the laser light source 2 based on the RF signal RF input from the processing unit 7 and adjusts the irradiation power of the light beam onto the recording surface (ROPC). However, the ROPC unit 8 acquires a fluctuation center signal indicating the fluctuation center of fluctuation in order to minimize the influence of fluctuation due to non-uniform reflectance of the recording layer and confocal crosstalk. Further, when the fluctuation center signal has changed due to confocal crosstalk-induced fluctuation, an instruction signal for canceling the amount of change is acquired. Then, a corrected RF signal is generated based on the fluctuation center signal and the instruction signal, and the output of the laser light source 2 is controlled based on the generated corrected RF signal.

  Further, as will be described in detail later, the ROPC unit 8 calculates the fluctuation center signal and the instruction signal using the average value signal for a certain period, and therefore the fluctuation center signal and the instruction signal are abruptly generated by the RF signal RF due to the defect. Does not follow the decline. Therefore, the ROPC unit 8 acquires a decrease in the RF signal RF and an amount of the decrease (a decrease amount) in order to perform appropriate ROPC even during the decrease period, and generates a corrected RF signal based on the decrease amount.

  Further, the ROPC unit 8 performs ROPC only during the period when the RF signal RF is lowered due to the defect in principle.

  Hereinafter, nine specific embodiments of the ROPC unit 8 will be described.

[First Embodiment]
FIG. 6 is a diagram showing functional blocks of the ROPC unit 8 according to the first embodiment.

  As shown in FIG. 6, the ROPC unit 8 includes a fluctuation signal acquisition unit 81, a bottom envelope signal acquisition unit 82, a modified bottom envelope signal acquisition unit 83, a top envelope signal acquisition unit 85, a first top hold signal acquisition unit 88, 1 bottom hold signal acquisition unit 87, second top hold signal acquisition unit 88, second bottom hold signal acquisition unit 89, modified second bottom hold signal acquisition unit 90a, correction value determination unit 91a, fluctuation center signal acquisition unit 92, instruction A signal acquisition unit 93, a decrease amount acquisition unit 94a, a modified RF signal generation unit 95a, an output control unit 96a, and a decrease detection unit 97a are configured.

  Among the functional blocks, the fluctuation signal acquisition unit 81, the bottom envelope signal acquisition unit 82, the modified bottom envelope signal acquisition unit 83, the top envelope signal acquisition unit 85, the first top hold signal acquisition unit 88, and the first bottom hold signal. The acquisition unit 87, the second top hold signal acquisition unit 88, the second bottom hold signal acquisition unit 89, and the modified second bottom hold signal acquisition unit 90a each envelope the maximum value of the given signal with the given droop plate. At least one of the maximum value envelope means and the minimum value envelope means for enveloping the minimum value of a given signal with a given droop plate is provided. Hereinafter, each of these means will be described first.

  The maximum value envelope means holds a signal (envelope signal) whose voltage value decreases at a given droop plate and constantly compares the given signal with the envelope signal. If the voltage value of the given signal is larger, the voltage value of the envelope signal is set as the voltage value of the given signal. As a result, the envelope signal held by the maximum value envelope means becomes a signal that envelops the maximum value of a given signal for each period corresponding to the droop plate.

  Similarly, the minimum value envelope means holds a signal (envelope signal) whose voltage value increases at a given droop plate, and always compares the given signal with the envelope signal. If the voltage value of the given signal is smaller, the voltage value of the envelope signal is set as the voltage value of the given signal. As a result, the envelope signal held by the minimum value envelope means becomes a signal that envelops the minimum value of a given signal for each period corresponding to the droop plate.

  Now, the fluctuation signal acquisition part 81 acquires the fluctuation signal which extracts the fluctuation | variation which has arisen in RF signal RF. More specifically, the RF signal RF and the third droop plate corresponding to the vibration period of the RF signal RF are provided to the maximum value envelope means, thereby enclosing the maximum value for each vibration period of the RF signal RF. The envelope signal RFte is acquired and used as the fluctuation signal (FIGS. 3 and 5).

  Here, although the top envelope signal RFte is used as the fluctuation signal, the vibration of the RF signal RF is provided by giving the RF signal RF and the third droop plate corresponding to the vibration period of the RF signal RF to the minimum value envelope means. The bottom envelope signal RFbe obtained by enveloping the minimum value for each period may be acquired and used as the fluctuation signal. In addition, a signal (for example, an intermediate signal between the top envelope signal RFte and the bottom envelope signal RFbe) obtained by passing the RF signal RF through a low-pass filter that does not pass a signal that vibrates at least with the vibration period of the RF signal RF is obtained, and the fluctuations described above are obtained. It may be a signal.

  The bottom envelope signal acquisition unit 82 provides the minimum envelope device with the top envelope signal RFte acquired by the variation signal acquisition unit 81 and the first droop plate corresponding to the confocal crosstalk-induced variation period (> vibration period). Thus, the bottom envelope signal e obtained by enveloping the minimum value for each period of the confocal crosstalk-induced variation of the top envelope signal RFte is acquired. FIG. 7 shows an example of the top envelope signal RFte and the bottom envelope signal e.

  Here, FIG. 8 shows an example of the bottom envelope signal e when there is a defect. As shown in the figure, when there is a defect, the bottom envelope signal e follows the decrease in the top envelope signal RFte due to the defect. Therefore, the corrected bottom envelope signal acquisition unit 83 acquires the corrected bottom envelope signal e ′ by giving the bottom envelope signal e and the first droop plate to the maximum value envelope means. The modified bottom envelope signal e ′ is slightly similar to the bottom envelope signal e (FIG. 7) when there is no defect, although it slightly decreases during the decrease period due to the defect. Note that the modified bottom envelope signal e ′ shown in FIG. 8 is shown for explanation and is exactly the same as the bottom envelope signal e in FIG. Actually, as described above, it slightly decreases in the decrease period due to the defect.

  The top envelope signal acquisition unit 85 gives the maximum envelope signal RFte acquired by the variation signal acquisition unit 81 and the first droop plate to the maximum value envelope means, thereby changing the period of the confocal crosstalk caused variation of the top envelope signal RFte. A top envelope signal d that envelops the maximum value of each is obtained. FIG. 7 also shows an example of the top envelope signal d.

  The first top hold signal acquisition unit 86 maximizes the bottom envelope signal e acquired by the bottom envelope signal acquisition unit 82 and the second droop plate corresponding to the reflectance-induced variation period (> confocal crosstalk-induced variation period). By giving to the value envelope means, the top hold signal a1 that envelops the maximum value for each period of the reflectance-induced variation of the bottom envelope signal e is obtained. FIG. 7 also shows an example of the top hold signal a1.

  The first bottom hold signal acquisition unit 87 gives the top envelope signal d acquired by the top envelope signal acquisition unit 85 and the second droop plate to the minimum value envelope means, thereby reducing the reflectance-induced variation of the top envelope signal d. A bottom hold signal b1 formed by enveloping the minimum value for each period is acquired. FIG. 7 also shows an example of the bottom hold signal b1.

  The second top hold signal acquisition unit 88 gives the top envelope signal d acquired by the top envelope signal acquisition unit 85 and the second droop plate to the maximum value envelope means, thereby reducing the reflectance-induced variation of the top envelope signal d. A top hold signal a2 enveloping the maximum value for each period is acquired. FIG. 7 also shows an example of the top hold signal a2.

  The second bottom hold signal acquisition unit 89 gives the bottom envelope signal e acquired by the bottom envelope signal acquisition unit 82 and the second droop plate to the minimum value envelope means, so that the reflectance of the bottom envelope signal e varies every period. A bottom hold signal b2 obtained by enveloping the minimum value is acquired. FIG. 7 also shows an example of the bottom hold signal b2.

  Here, as described above with reference to FIG. 8, when there is a defect, the bottom envelope signal e decreases following the decrease in the top envelope signal RFte due to the defect. For this reason, the bottom hold signal b2 also follows and decreases. FIG. 8 also shows an example of the bottom hold signal b2 thus lowered. Therefore, the corrected second bottom hold signal acquisition unit 90a gives the corrected bottom hold signal b2 by giving the bottom hold signal b2 acquired by the second bottom hold signal acquisition unit 89 and the second droop plate to the maximum value envelope means. 'Get. The corrected bottom hold signal b2 ′ is substantially the same signal as the bottom hold signal b2 (FIG. 7) when there is no defect. FIG. 8 also shows an example of the modified bottom envelope signal b2 ′.

  The fluctuation center signal acquisition unit 92 generates fluctuations in the RF signal RF based on the top hold signal a1, the bottom hold signal b1, the top hold signal a2, and the modified second bottom hold signal b2 ′ acquired as described above. The fluctuation center signal SC indicating the fluctuation center is obtained. More specifically, an average value signal of the four signals is set as a fluctuation center signal SC.

When the fluctuation center signal SC is expressed by a mathematical formula, the formula (9) is obtained.
SC = (a1 + b1 + a2 + b2 ′) / 4 (9)

Here, if the voltage value at the center of the fluctuation of the RF signal RF is c0, the top hold signal a1, the bottom hold signal b1, the top hold signal a2, and the modified second bottom hold signal b2 are respectively the above-described X1, Y1. , X2, Y2 can be expressed as the following formulas (10) to (13). Note that it is assumed that the reflectance-induced variation that occurs in light (stray light) reflected by layers other than the focused layer has been removed by other techniques.
a1 = c0 × (1 + X1) × (1-Y2) (10)
b1 = c0 × (1-Y1) × (1 + X2) (11)
a2 = c0 × (1 + X1) × (1 + X2) (12)
b2 ′ = c0 × (1-Y1) × (1-Y2) (13)

Using Expressions (10) to (13), the fluctuation center signal SC of Expression (9) can be expressed as Expression (14) using X1, Y1, X2, and Y2.
SC = c0 * {2 + X1-Y1 + X2-Y2 + (X1-Y1) * (X2-Y2) / 2} / 2 (14)

  Among the terms on the right side of Equation (14), c0 × (2 + X1−Y1) / 2 represents the center voltage of the reflectance-induced variation, and the other terms are caused by the reflectance due to confocal crosstalk. The amount of change occurring in the fluctuation center voltage (hereinafter referred to as confocal crosstalk-induced change amount) is shown.

  The instruction signal acquisition unit 93 acquires an instruction signal SI indicating the amount of confocal crosstalk-induced variation generated in the top envelope signal RFte in order to cancel the confocal crosstalk-induced variation amount from the variation center signal SC. Specifically, a signal obtained by subtracting the average value signal of the first top hold signal a1 and the first bottom hold signal b1 from the average value signal of the top hold signal a2 and the modified second bottom hold signal b2 ′ is designated as the instruction signal SI. Get as.

When the instruction signal SI is expressed by a mathematical formula, the formula (15) is obtained.
SI = (a2 + b2′−a1−b1) / 2 (15)

Further, when Expression (10) to Expression (13) are used, the instruction signal SI of Expression (15) can be expressed as Expression (16) using X1, Y1, X2, and Y2.
SI = c0 × (X1 + Y1) × (X2 + Y2) / 2 (16)

Here, the relationship of the following formula (17) is established between X2 and Y2.
(X2 + Y2) ² = 2 × (X2−Y2) (17)

  Equation (17) is derived as follows.

  First, FIG. 9 shows the path of a light beam when confocal crosstalk occurs. This figure shows an example in which the optical disk 11 is composed of three layers L0, L1, and L2, and the layer spacing is equal. As shown in the figure, when the focus of the light beam is on the layer L0, the optical IC emitted from the recording surface is not only the signal light I0 that is the reflected light on the layer L0, but also the layers L1 and L2. The reflected light I1 reflected between the two becomes the interference light.

When the electric field vector of the signal light I0 is E0, and the electric field vector of the reflected light I1 from the other layer is E1, the intensity of the interference light IC is expressed by Expression (18). However, ΔΦ represents a phase difference between the signal light I0 and the reflected light I1.
| E0 + E1 | ² = | E0 | ² + | E1 | ² + | E0 || E1 | cosΔΦ
= I0 + I1 + (I0 × I1) ^0.5 × cosΔΦ (18)

When cos ΔΦ takes the maximum value 1 in Equation (18), the intensity of the interference light IC is I0 × (1 + X2). Therefore, X2 is obtained as in the following equation (19).
X2 = [I0 + I1 + (I0 × I1) ^0.5 ] / I0-1 = [I1 + (I0 × I1) ^0.5 ] / I0 (19)

Similarly, when cos ΔΦ takes the minimum value −1 in equation (18), the intensity of the interference light IC is I0 × (1−Y2). Therefore, Y2 is obtained as in the following equation (20).
Y2 = 1− [I0 + I1− (I0 × I1) ^0.5 ] / I0 = [− I1 + (I0 × I1) ^0.5 ] / I0 (20)

Therefore, Equation (21) and Equation (22) hold, and the above Equation (17) is obtained from these.
X2-Y2 = 2 × I1 / I0 (21)
X2 + Y2 = 2 × (I1 / I0) ^0.5 (22)

From equation (14), the confocal crosstalk-induced change amount of the fluctuation center signal is c0 × {X2−Y2 + (X1−Y1) × (X2−Y2) / 2} / 2, of which (X1 If -Y1) * (X2-Y2) / 2 is small and ignored, it is necessary to use a signal equal to c0 * {X2-Y2} / 2 in order to cancel the confocal crosstalk-induced change amount from the fluctuation center signal SC. There is. This c0 × {X2-Y2} / 2 is equal to than ^{c0 × (X2 + Y2) 2} /4 Equation (17), the correction value k as shown in the instruction signal SI represented by the formula (16) in equation (23) The multiplied signal is exactly equal to c0 * {X2-Y2} / 2.
k = (X2 + Y2) / (X1 + Y1) / 2 (23)

Expression (23) can be rewritten as Expression (24) by Expression (25) and Expression (26). Equations (25) and (26) indicate the magnitudes of reflectance-induced variation and confocal crosstalk-induced variation, respectively.
k≈ (1-e ′ / d) / {2 × (1-b1 / a2)} (24)
{C0 * (1 + X1) -c0 * (1-Y1)} / {c0 * (1 + X1)}
= (X1 + Y1) / (1 + X1)
= (A2-b1) / a2 (25)
{C0 * (1 + X1) * (1 + X2) -c0 * (1 + X1) * (1-Y2)} / {c0 * (1 + X1) * (1 + X2)}
= (X2 + Y2) / (1 + X2)
= (D−e ′) / d (26)

  The correction value determination unit 91a obtains the top hold signal a2, the first bottom hold signal b1, the modified bottom envelope signal e ′, and the top envelope signal d from each unit, and calculates the correction value k based on Expression (24).

  The instruction signal acquisition unit 93 multiplies the instruction signal SI acquired as described above by the correction value k calculated by the correction value determination unit 91a. The instruction signal acquisition unit 93 outputs the corrected instruction signal kSI thus obtained to the modified RF signal generation unit 95a.

  Next, the decrease amount acquisition unit 94a acquires the decrease amount of the RF signal RF due to the defect. Specifically, the difference e′−e between the modified bottom envelope signal e ′ and the bottom envelope signal e is acquired as the reduction amount. FIG. 10 illustrates this difference e′−e.

The corrected RF signal generation unit 95a uses the fluctuation center signal SC acquired by the fluctuation center signal acquisition unit 92, the corrected instruction signal kSI acquired by the instruction signal acquisition unit 93, and the reduction amount acquired by the reduction amount acquisition unit 94a. A modified RF signal CRF is generated. Specifically, the corrected RF signal CRF is obtained by the following equation (27).
CRF = SC-kSI-reduction amount (27)

  The output control unit 96 a has a function of transmitting a control signal for controlling the light beam irradiation power to the laser light source 2. The output control unit 96a adjusts a control signal to be transmitted to the laser light source 2 based on the modified RF signal CRF. Thereby, ROPC based on the modified RF signal CRF is realized.

  In addition, the decrease detection unit 97a has a function of detecting a decrease in the RF signal RF. Specifically, the decrease in the RF signal RF is detected based on whether or not the difference between the modified bottom envelope signal e ′ and the bottom envelope signal e is greater than or equal to a predetermined amount. That is, if the difference between the modified bottom envelope signal e ′ and the bottom envelope signal e is greater than or equal to a predetermined amount, it is determined that the RF signal RF has decreased, and otherwise, it is determined that it has not decreased. As a result, the drop detection unit 97a detects a drop in the RF signal RF (a drop due to a defect) that is not a drop caused by confocal crosstalk or nonuniform reflectance.

  The decrease detection unit 97a restricts execution of processing of each unit of the optical drive device 1 including at least the output control unit 96a according to the detection result of the decrease in the RF signal RF. Specifically, only when the RF signal RF is lowered, the above-described units are caused to execute processing, and in other cases, the above-described units are not subjected to processing. Note that it is preferable that the above-described units to be restricted are functional blocks that are not directly involved in detection of a decrease in the RF signal RF among the functional blocks of the ROPC unit 8 shown in FIG. In FIG. 6, these functional blocks are surrounded by a one-dot chain line. Specifically, the top envelope signal acquisition unit 85, the first top hold signal acquisition unit 88, the first bottom hold signal acquisition unit 87, the second top hold signal acquisition unit 88, the second bottom hold signal acquisition unit 89, the correction The second bottom hold signal acquisition unit 90a, the correction value determination unit 91a, the fluctuation center signal acquisition unit 92, the instruction signal acquisition unit 93, the decrease amount acquisition unit 94a, the modified RF signal generation unit 95a, and the output control unit 96a correspond to this.

  As described above, according to the present embodiment, the modified RF signal CRF is less affected by variations in the reflectance of the recording layer and variations due to confocal crosstalk than the unmodified RF signal RF. It is possible to prevent deterioration of ROPC accuracy due to non-uniform reflectance of layers and presence of confocal crosstalk. In particular, when the fluctuation center signal SC has changed due to the confocal crosstalk-induced fluctuation, the change can be canceled by the instruction signal SI.

  Further, when the RF signal RF is not lowered, the execution of the processing of each part of the optical drive device 1 is restricted, so that the power consumption of the optical drive device 1 can be reduced.

[Second Embodiment]
FIG. 11 is a functional block diagram of the ROPC unit 8 according to the second embodiment.

  This embodiment differs from the first embodiment in the method of obtaining the modified second bottom hold signal b2 ′, and the other parts are the same. Therefore, only the part relating to the method of obtaining the corrected second bottom hold signal b2 ′ will be described below.

  The ROPC unit 8 according to the present embodiment does not have the second bottom hold signal acquisition unit 89, and instead of the corrected second bottom hold signal acquisition unit 90a, a modified second bottom hold signal acquisition unit 90b is provided. Have.

  FIG. 12 shows the top envelope signal RFte and the modified bottom envelope signal e ′ when there is a defect. As described above, the modified bottom envelope signal e ′ is substantially the same signal as the bottom envelope signal e (FIG. 7) when there is no defect. Therefore, the corrected second bottom hold signal acquisition unit 90b acquires the corrected bottom hold signal b2 ′ by giving the corrected bottom envelope signal e ′ and the second droop plate to the minimum value envelope means. FIG. 12 also shows an example of the corrected bottom hold signal b2 ′ thus obtained.

  As described above, according to the present embodiment, the corrected bottom hold signal b2 ′ that is substantially the same as the bottom hold signal b2 (FIG. 7) when there is no defect is obtained.

[Third Embodiment]
FIG. 13 is a diagram showing functional blocks of the ROPC unit 8 according to the third embodiment.

  This embodiment is different from the first and second embodiments in the method of obtaining the modified second bottom hold signal b2 ′, and the other parts are the same. Therefore, only the part relating to the method of obtaining the corrected second bottom hold signal b2 ′ will be described below.

  The ROPC unit 8 according to the present embodiment has a modified second bottom hold signal acquisition unit 90c instead of the modified second bottom hold signal acquisition unit 90b in the ROPC unit 8 according to the second embodiment. .

The modified second bottom hold signal acquisition unit 90c acquires a modified second bottom hold signal b2 ′ by calculation from the top hold signal a1, the first bottom hold signal b1, and the second top hold signal a2. Specifically, the corrected second bottom hold signal b2 ′ is obtained by Expression (28).
b2 ′ = b1− (a2−a1) × b1 / a2 (28)

  Even in this case, a modified bottom hold signal b2 ′ substantially similar to the bottom hold signal b2 (FIG. 7) in the case of no defect is obtained.

[Fourth Embodiment]
FIG. 14 is a diagram showing functional blocks of the ROPC unit 8 according to the fourth embodiment.

  This embodiment is different from the first embodiment in that the instruction signal SI is not used when generating the corrected RF signal, and the other parts are the same as those of the first embodiment. Therefore, only the part relating to the generation of the modified RF signal will be described below.

  The ROPC unit 8 according to the present embodiment has a modified RF signal generation unit 95b instead of the modified RF signal generation unit 95a in the ROPC unit 8 according to the first embodiment.

The corrected RF signal generation unit 95b calculates the corrected RF signal CRF not by the equation (27) but by the equation (29).
CRF = SC-reduction amount (29)

  When X2-Y2 is small (equation (21)), that is, when the confocal crosstalk intensity I1 (FIG. 9) is small, sufficient ROPC accuracy can be obtained even if the corrected RF signal CRF is obtained in this way. It is.

[Fifth Embodiment]
FIG. 15 is a diagram illustrating functional blocks of the ROPC unit 8 according to the fifth embodiment.

  The present embodiment is different from the first embodiment in that the modified bottom envelope signal e ′ is not used, and the other parts are the same as those in the first embodiment. Therefore, only the part regarding the difference will be described below.

  The ROPC unit 8 according to the present embodiment has a lowered top envelope signal acquisition unit 99 instead of the modified bottom envelope signal acquisition unit 83 in the ROPC unit 8 according to the first embodiment. Along with this, a decrease time point instruction signal acquisition unit 98 is newly provided, and instead of the decrease detection unit 97a, the correction value determination unit 91a, and the decrease amount acquisition unit 94a, a decrease detection unit 97b, a correction value determination unit 91b, And a decrease amount acquisition unit 94b.

  FIGS. 16 and 17 are explanatory diagrams of processing of the decrease detection unit 97b and the decrease time point instruction signal acquisition unit 98. The drop detection unit 97b has a function of detecting a drop in the RF signal RF, similar to the drop detection unit 97a, but uses the top envelope signal d and the bottom envelope signal e instead of the modified bottom envelope signal e ′ and the bottom envelope signal e to generate the RF signal RF. Detecting a drop in

  Specifically, the lowering detection unit 97b first shifts the top envelope signal d downward by a predetermined value (“shifted d” in FIG. 16). As this predetermined value, a value slightly larger than the maximum width of the confocal crosstalk amplitude is set in advance. Next, the decrease detection unit 97b compares the shifted top envelope signal d and the bottom envelope signal e, and determines that the RF signal RF is decreased if the shifted top envelope signal d is larger. If not, it is determined that it has not decreased.

  Further, the decrease detection unit 97b generates a decrease period instruction signal A (FIG. 17) that becomes high only during a period when it is determined that the RF signal RF is decreasing and becomes low during other periods. The decrease point instruction signal acquisition unit 98 acquires the decrease period instruction signal A from the decrease detection unit 97b, and generates a delay signal B (FIG. 17) obtained by delaying the decrease period instruction signal A by a minute time. Further, a lowering point instruction signal C (FIG. 17) is generated which becomes high only during different periods of the lowering period instruction signal A and the delay signal B and becomes low in other periods.

Returning to FIG. The drop-time top envelope signal acquisition unit 99 normally acquires the top envelope signal d in the same manner as the top envelope signal acquisition unit 85, but temporarily supplies it to the maximum value envelope means in accordance with the decrease point indication signal C. Increase the droop rate. Specifically, the drop top envelope signal acquisition unit 99 monitors the drop point indication signal C, and when high appears after low for a predetermined period or longer, the droop plate to be temporarily supplied to the maximum value envelope means is selected. Enlarge. The signal obtained as a result (lower top envelope signal d ′) follows the lowering of the top envelope signal RFte due to the defect. FIG. 18 shows an example of the drop-down top envelope signal d ′.
As shown in FIG. 15, the lowering point instruction signal C may be input also to the bottom envelope signal acquisition unit 82 and the second bottom hold signal acquisition unit 89. In this case, each of the bottom envelope signal acquisition unit 82 and the second bottom hold signal acquisition unit 89 monitors the lowering point instruction signal C, and a high appears after low for a first predetermined period or more, and then a second predetermined signal. When high appears again within a period (<first predetermined period), the droop plate applied to the minimum value envelope means is temporarily increased. As a result, the bottom envelope signal e and the bottom hold signal b2 (FIG. 8) can be made to quickly follow the rise of the top envelope signal RFte due to the defect. Needless to say, this may be applied to the other embodiments described above.

  The decrease amount acquisition unit 94b acquires the difference dd ′ between the top envelope signal d and the reduced top envelope signal d ′ as the decrease amount of the RF signal RF due to the defect. FIG. 19 illustrates this difference dd ′.

In addition, the correction value determination unit 91b obtains the correction value k using the equation (30) instead of the equation (24).
k = (1-e / d ′) / {2 × (1-b1 / a2)} (30)

  As described above, since the amount of decrease and the correction value k can be obtained also in this embodiment, the accuracy of ROPC due to the non-uniformity of the reflectance of the recording layer and the presence of confocal crosstalk as in the first embodiment. Deterioration can be prevented.

[Sixth Embodiment]
FIG. 20 is a diagram showing functional blocks of the ROPC unit 8 according to the sixth embodiment.

  The present embodiment is different from the fifth embodiment in that the instruction signal SI is not used when the corrected RF signal is generated, and the other parts are the same as those of the fifth embodiment. Therefore, only the part relating to the generation of the modified RF signal will be described below.

  The ROPC unit 8 according to the present embodiment has a modified RF signal generation unit 95b instead of the modified RF signal generation unit 95a in the ROPC unit 8 according to the fifth embodiment. The details of the modified RF signal generation unit 95b are as described in the fourth embodiment.

  When X2-Y2 is small (equation (21)), that is, when the confocal crosstalk intensity I1 (FIG. 9) is small, sufficient ROPC accuracy can be obtained even if the corrected RF signal CRF is obtained in this way. It is.

[Seventh Embodiment]
FIG. 21 is a diagram showing functional blocks of the ROPC unit 8 according to the seventh embodiment.

  This embodiment is different from the first embodiment in that it does not include the drop detection unit 97a, and the other parts are the same as those of the first embodiment.

  In this way, even without using the drop detection unit 97a, as in the first embodiment, it is possible to prevent the deterioration of ROPC accuracy due to the non-uniform reflectance of the recording layer and the presence of confocal crosstalk.

[Eighth Embodiment]
FIG. 22 is a diagram showing functional blocks of the ROPC unit 8 according to the eighth embodiment.

  This embodiment is different from the first embodiment in that the modified RF signal CRF is not used, and the other parts are the same as those in the first embodiment. Therefore, only the part relating to the difference from the first embodiment will be described below.

  The ROPC unit 8 according to this embodiment has an output control unit 96b instead of the output control unit 96a in the ROPC unit 8 according to the first embodiment. Accordingly, in the ROPC unit 8 according to the present embodiment, the top envelope signal acquisition unit 85, the first top hold signal acquisition unit 88, the first bottom hold signal acquisition unit 87, the second top hold signal acquisition unit 88, the first 2 bottom hold signal acquisition unit 89, corrected second bottom hold signal acquisition unit 90a, correction value determination unit 91a, fluctuation center signal acquisition unit 92, instruction signal acquisition unit 93, reduction amount acquisition unit 94a, and correction RF signal generation unit 95a Is no longer needed.

  The output control unit 96b has a function of transmitting a control signal for controlling the light beam irradiation power to the laser light source 2 similarly to the output control unit 96a. However, unlike the output control unit 96a, the RF signal RF The control signal transmitted to the laser light source 2 is adjusted based on the above. This is ROPC similar to the background art.

  The decrease detection unit 97a causes the output control unit 96b to execute processing only when the RF signal RF is decreasing, and does not cause the output control unit 96b to perform processing in other cases. Therefore, according to the present embodiment, the power consumption of the optical drive device 1 can be reduced.

[Ninth Embodiment]
FIG. 23 is a diagram showing functional blocks of the ROPC unit 8 according to the ninth embodiment.

  This embodiment is different from the eighth embodiment in that the modified bottom envelope signal e ′ is not used. The specific processing for detecting the drop without using the modified bottom envelope signal e ′ is the same as that described in the fifth embodiment. Therefore, the ROPC unit 8 according to the present embodiment is the same as the ROPC unit 8 according to the eighth embodiment, instead of the modified bottom envelope signal acquisition unit 83 and the decrease detection unit 97a. The detector 97b is provided.

  Even in this case, the power consumption of the optical drive device 1 can be reduced.

  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.

It is an example of the schematic diagram of the optical drive device by embodiment of this invention. It is a figure which shows the external appearance of the photodetector by embodiment of this invention. It is a figure which shows the example of the RF signal which the process part by embodiment of this invention outputs. It is explanatory drawing of the reflectivity variation by the embodiment of this invention, and the confocal crosstalk variation. It is a figure which shows the example of the RF signal which fell rapidly by obstructions (defects), such as dirt on the surface of an optical disk, and dust. It is a figure which shows the functional block of the ROPC part by the 1st Embodiment of this invention. It is a figure which shows the example of the top envelope signal d, the bottom envelope signal e, the top hold signal a1, the bottom hold signal b1, the top hold signal a2, and the bottom hold signal b2 by embodiment of this invention. It is a figure which shows the example of the bottom envelope signal e and the bottom hold signal b2 in case there exists a defect by embodiment of this invention. It is a figure which shows the course of the light beam in case confocal crosstalk generate | occur | produces by embodiment of this invention. It is a figure which shows the difference e'-e of the correction bottom envelope signal e 'and the bottom envelope signal e by embodiment of this invention. It is a figure which shows the functional block of the ROPC part by the 2nd Embodiment of this invention. It is a figure which shows correction | amendment bottom envelope signal e 'and correction | amendment bottom hold signal b2' when there exists a defect by embodiment of this invention. It is a figure which shows the functional block of the ROPC part by the 3rd Embodiment of this invention. It is a figure which shows the functional block of the ROPC part by the 4th Embodiment of this invention. It is a figure which shows the functional block of the ROPC part by the 5th Embodiment of this invention. It is explanatory drawing of the process of the fall detection part by the 5th Embodiment of this invention, and a fall time instruction | indication signal acquisition part. It is explanatory drawing of the process of the fall detection part by the 5th Embodiment of this invention, and a fall time instruction | indication signal acquisition part. It is a figure which shows the example of the fall top envelope signal d 'by the 5th Embodiment of this invention. It is a figure which shows the difference dd 'of the top envelope signal d and the fall top envelope signal d' by the 5th Embodiment of this invention. It is a figure which shows the functional block of the ROPC part by the 6th Embodiment of this invention. It is a figure which shows the functional block of the ROPC part by the 7th Embodiment of this invention. It is a figure which shows the functional block of the ROPC part by the 8th Embodiment of this invention. It is a figure which shows the functional block of the ROPC part by the 9th Embodiment of this invention.

Explanation of symbols

A Decreasing period instruction signal B Delay signal C Decreasing point instruction signal CRF Correction RF signal FE Focus error signal TE Tracking error signal I0 Signal light I1 Reflected light IC Interference light M Main beam light receiving part S1 First sub beam light receiving part S2 Second sub beam light receiving Part a, b, c, d, e1, e2, e3, e4, f1, f2, f3, f4 Light receiving area MB Main beam SB1 First sub beam SB2 Second sub beam a1 Top hold signal a2 Top hold signal b1 Bottom hold signal b2 Bottom hold signal d Top envelope signal d ′ Decreasing top envelope signal e Bottom envelope signal e ′ Modified bottom envelope signal RF RF signal RFbe Bottom envelope signal RFte Top envelope signal SC Fluctuation center signal SI Instruction signal 1 Optical drive device 2 Laser light source 3 Optical system 4 Objective lens Lens drive unit 6 Optical detector 7 Processing unit 11 Optical disk 21 Diffraction grating 22 Beam splitter 23 Collimator lens 24 1/4 wavelength plate 25 Sensor lens 81 Fluctuation signal acquisition unit 82 Bottom envelope signal acquisition unit 83 Modified bottom envelope signal acquisition unit 85 Top envelope signal Acquisition unit 86 First top hold signal acquisition unit 87 First bottom hold signal acquisition unit 88 Second top hold signal acquisition unit 89 Second bottom hold signal acquisition units 90a, 90b, 90c Bottom hold signal acquisition units 91a, 91b Correction value determination Unit 92 Fluctuation center signal acquisition unit 93 Instruction signal acquisition units 94a and 94b Reduction amount acquisition units 95a and 95b Signal generation units 96a and 96b Output control units 97a and 97b Decrease detection unit 98 Decreasing point indication signal acquisition unit 99 Decreasing top envelope signal Acquisition department

Claims (28)

RF signal acquisition means for acquiring an RF signal indicating the intensity of the light beam reflected by the optical recording medium;
A maximum value envelope means for enveloping the maximum value of a given signal with a given droop plate;
A minimum value envelope means for enveloping a minimum value of a given signal with a given droop plate;
Fluctuation signal acquisition means for acquiring a fluctuation signal obtained by taking out fluctuations occurring in the RF signal;
Top envelope signal acquisition means for acquiring a top envelope signal obtained by giving the maximum value envelope means the fluctuation signal and a first droop plate corresponding to the period of confocal crosstalk-induced fluctuation;
Bottom envelope signal acquisition means for acquiring a bottom envelope signal obtained by applying the fluctuation signal and the first droop plate to the minimum value envelope means;
A first envelope obtained by providing the maximum envelope means with the bottom envelope signal and a second droop plate corresponding to the period of the reflectivity-induced variation that occurs in the RF signal due to non-uniform reflectivity of the optical recording medium. First top hold signal acquisition means for acquiring one top hold signal;
First bottom hold signal acquisition means for acquiring a first bottom hold signal obtained by applying the top envelope signal and the second droop plate to the minimum value envelope means;
Second top hold signal acquisition means for acquiring a second top hold signal obtained by applying the top envelope signal and the second droop plate to the maximum value envelope means;
A modified second bottom hold obtained by applying a corrected bottom envelope signal obtained by applying the bottom envelope signal and the first droop plate to the maximum value envelope means together with the second droop plate to the minimum value envelope means. Modified second bottom hold signal acquisition means for acquiring a signal;
Based on the first top hold signal, the first bottom hold signal, the second top hold signal, and the modified second bottom hold signal, a fluctuation center signal indicating a fluctuation center of fluctuation occurring in the RF signal is acquired. A fluctuation center signal acquisition means;
Modified RF signal generating means for generating a modified RF signal using the fluctuation center signal;
An optical drive device comprising:   The fluctuation signal acquisition means acquires, as the fluctuation signal, an envelope signal obtained by providing the maximum value envelope means with the RF signal and a third droop plate corresponding to a vibration period of the RF signal. The optical drive device according to claim 1, wherein:   The fluctuation center signal acquisition means acquires the fluctuation center signal based on an average value signal of the first top hold signal, the first bottom hold signal, the second top hold signal, and the modified second bottom hold signal. The optical drive device according to claim 2, wherein: A drop detecting means for detecting a drop in the RF signal;
A reduction amount acquisition means for acquiring a reduction amount of the reduction detected by the reduction detection means;
Further comprising
The optical drive apparatus according to claim 3, wherein the corrected RF signal generation unit acquires a signal obtained by subtracting the decrease amount from the average value signal as the corrected RF signal. Corrected bottom envelope signal acquisition means for acquiring the corrected bottom envelope signal;
Further comprising
5. The optical drive device according to claim 4, wherein the lowering detection unit detects the lowering of the RF signal using the bottom envelope signal and the modified bottom envelope signal. Corrected bottom envelope signal acquisition means for acquiring the corrected bottom envelope signal;
Further comprising
The optical drive apparatus according to claim 4, wherein the decrease amount acquisition unit acquires a difference between the corrected bottom envelope signal and the bottom envelope signal as the decrease amount.   The optical drive apparatus according to claim 4, wherein the decrease detection unit detects a decrease in the RF signal by using the top envelope signal and the bottom envelope signal. While giving the fluctuation signal and the first droop plate to the maximum value envelope means, the droop plate to be temporarily given to the maximum value envelope means is enlarged in accordance with the detection of the decrease in the RF signal by the drop detection means. A lower top envelope signal acquisition means for acquiring a lower top envelope signal obtained by
Further comprising
The optical drive apparatus according to claim 4, wherein the decrease amount acquisition unit acquires a difference between the top envelope signal and the reduced top envelope signal as the decrease amount. A lowering point instruction signal acquiring unit for acquiring a lowering point instruction signal indicating a point in time when the lowering of the RF signal is detected by the lowering detection unit;
Further comprising
9. The optical drive apparatus according to claim 8, wherein the lower-time top envelope signal acquisition unit temporarily enlarges a droop plate to be supplied to the maximum value envelope unit in accordance with the lowering point indication signal.   The fluctuation signal acquisition means acquires, as the fluctuation signal, an envelope signal obtained by providing the minimum value envelope means with the RF signal and a third droop plate corresponding to a vibration period of the RF signal. The optical drive device according to claim 1, wherein:   2. The fluctuation signal acquisition unit acquires a signal obtained by passing the RF signal through a low-pass filter that does not pass a signal that vibrates at least at the vibration period of the RF signal as the fluctuation signal. The optical drive device described. Based on the first top hold signal, the first bottom hold signal, the second top hold signal, and the modified second bottom hold signal, an instruction signal indicating an amount of periodic fluctuation generated in the fluctuation signal is obtained. Instruction signal acquisition means for
Further comprising
The optical drive apparatus according to claim 1, wherein the correction RF signal generation unit generates the correction RF signal also using the instruction signal.   The instruction signal acquisition means subtracts an average value signal of the first top hold signal and the first bottom hold signal from an average value signal of the second top hold signal and the modified second bottom hold signal. The optical drive device according to claim 12, wherein the optical drive device is acquired as the instruction signal. Modified bottom envelope signal acquisition means for acquiring the corrected bottom envelope signal;
Correction value determining means for determining a correction value of the instruction signal based on the second top hold signal, the first bottom hold signal, the top envelope signal, and the modified bottom envelope signal;
Further comprising
14. The corrected RF signal generation unit generates the corrected RF signal using the instruction signal corrected using the correction value determined by the correction value determination unit. Optical drive device. A drop detecting means for detecting a drop in the RF signal;
A reduction amount acquisition means for acquiring a reduction amount of the reduction detected by the reduction detection means;
Further comprising
The corrected RF signal generating means uses the signal obtained by subtracting the instruction signal corrected using the correction value and the amount of decrease from the fluctuation center signal as the corrected RF signal. 14. The optical drive device according to 14.   The optical drive apparatus according to claim 15, wherein the decrease amount acquisition unit acquires a difference between the corrected bottom envelope signal and the bottom envelope signal as the decrease amount.   The optical drive apparatus according to claim 15 or 16, wherein the lowering detection unit detects the lowering of the RF signal using the bottom envelope signal and the modified bottom envelope signal. A drop detecting means for detecting a drop in the RF signal;
While giving the fluctuation signal and the first droop plate to the maximum value envelope means, the droop plate to be temporarily given to the maximum value envelope means is enlarged in accordance with the detection of the decrease in the RF signal by the drop detection means. A drop top envelope signal acquisition means for acquiring a drop top envelope signal obtained by
Correction value determining means for determining a correction value of the instruction signal based on the second top hold signal, the first bottom hold signal, the lowered top envelope signal, and the bottom envelope signal;
Further comprising
14. The corrected RF signal generation unit generates the corrected RF signal using the instruction signal corrected using the correction value determined by the correction value determination unit. Optical drive device. A reduction amount acquisition means for acquiring a reduction amount of the reduction detected by the reduction detection means;
Further comprising
The corrected RF signal generating means uses the signal obtained by subtracting the instruction signal corrected using the correction value and the amount of decrease from the fluctuation center signal as the corrected RF signal. 18. An optical drive device according to 18.   The optical drive apparatus according to claim 19, wherein the decrease amount acquisition unit acquires a difference between the top envelope signal and the reduced top envelope signal as the decrease amount. A lowering point instruction signal acquiring unit for acquiring a lowering point instruction signal indicating a point in time when the lowering of the RF signal is detected by the lowering detection unit;
Further comprising
21. The lower-end top envelope signal acquisition unit temporarily enlarges a droop plate to be supplied to the maximum value envelope unit in accordance with the lowering point indication signal. Optical drive device.   The optical drive device according to any one of claims 18 to 21, wherein the lowering detection unit detects the lowering of the RF signal using the top envelope signal and the bottom envelope signal. Output control means for controlling the irradiation power of the light beam based on the modified RF signal;
A drop detecting means for detecting a drop in the RF signal and limiting the execution of the processing of the optical drive device including at least the processing by the output control means according to a detection result;
The optical drive device according to any one of claims 1, 2, 3, 9, 12, 13, and 14, further comprising: Corrected bottom envelope signal acquisition means for acquiring the corrected bottom envelope signal;
Further comprising
24. The optical drive apparatus according to claim 23, wherein the lowering detection means detects the lowering of the RF signal using the bottom envelope signal and the modified bottom envelope signal.   24. The optical drive device according to claim 23, wherein the lowering detection means detects the lowering of the RF signal using the top envelope signal and the bottom envelope signal. Second bottom hold signal acquisition means for acquiring a second bottom hold signal obtained by applying the bottom envelope signal and the second droop plate to the minimum value envelope means;
Further comprising
The modified second bottom hold signal acquisition means acquires the corrected second bottom hold signal by giving the second bottom hold signal and the second droop plate to the maximum value envelope means. Item 26. The optical drive device according to any one of Items 1 to 25.   2. The modified second bottom hold signal obtaining unit obtains the modified second bottom hold signal by giving the modified bottom envelope signal and the second droop plate to the minimum value envelope unit. 26. The optical drive device according to any one of items 1 to 25.   The modified second bottom hold signal acquisition means acquires the modified second bottom hold signal by calculation from the first top hold signal, the first bottom hold signal, and the second top hold signal. The optical drive device according to any one of claims 1 to 25.

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