JP2008287776A - Recording layer detecting device of optical disk, and recording layer detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a specified recording layer highly accurately in an optical disk having a plurality of recording layers. <P>SOLUTION: A controller 60 performs displacement of an objective lens 21, obtains the number of detections of sigmoid waveform signals by a sigmoid detecting circuit 37 for each of a plurality of reference levels, discriminates relation of magnitude of the plurality of reference levels and amplitude values of sigmoid signals on the basis of the number of detection for each of a plurality of reference levels, and sets sigmoid detection levels of a sigmoid detecting circuit 37 using a plurality of reference levels and slice levels of a binarization circuit for detecting sigmoid signals of a signal extracting circuit 40. Then the controller 60 counts the number of sigmoid signals detected by the sigmoid detecting circuit 37 and the signal extracting circuit 40, and detects the specified recording layer on condition that the number of the counted sigmoid signals becomes a value corresponding to the specified recording layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disc recording layer detection apparatus and a recording layer detection method for detecting a designated recording layer in an optical disc having a plurality of recording layers.

  2. Description of the Related Art Conventionally, an optical disc recording / reproducing apparatus that irradiates a recording layer of an optical disc with laser light, records data on the optical disc, or reproduces data recorded on the optical disc is well known. In recent years, in order to increase the amount of data that can be recorded on an optical disc, the number of optical discs on which a plurality of recording layers are formed tends to increase, and the number of recording layers formed in the future is expected to increase. In order to record or reproduce data on an optical disc on which a plurality of recording layers are formed, focus pull-in is performed so that the laser beam is accurately focused on the designated recording layer at the start of recording or reproduction. There is a need to do.

The method of focusing the laser beam on the designated recording layer is generated based on the reflected light from the optical disk by displacing the objective lens in the optical axis direction of the laser beam, as shown in Patent Document 1 below, for example. The S-shaped waveform signal in the focus error signal is detected and counted, and when the count value becomes a value corresponding to the designated recording layer, the laser beam is focused on the designated recording layer, and the focus is drawn. The method of doing is used. Specifically, when the objective lens is displaced in the direction of the optical axis of the laser light as shown in FIGS. 13A and 13B, the focal position of the laser light becomes the recording layer as shown in FIG. An S-shaped waveform signal appears when it coincides with the position and the surface of the cover layer. Then, as shown in FIG. 13C, the S-shaped waveform signal is detected when the instantaneous value of the S-shaped waveform signal exceeds a predetermined detection level and then crosses the predetermined detection level again. . When the predetermined detection level is set to a level at which an S-shaped waveform signal from the cover layer is detected in addition to the recording layer (see the dashed line in FIG. 13C), the S-shaped waveform signal from the cover layer is There is a case where the level is set so that only the S-shaped waveform signal from the recording layer is detected without being detected (see the broken line in FIG. 13C).
JP-A-8-185633

However, as the number of recording layers increases and as the numerical aperture (NA) of the objective lens is increased to reduce the diameter of the light spot, the amplitudes of the plurality of S-shaped waveform signals from the plurality of recording layers differ from each other. become. The amplitude of the S-shaped waveform signal by the cover layer and the recording layer varies greatly depending on the type of optical disk, the structure of the optical pickup, and the like. For this reason, there are the following problems (1) to (4).
(1) Even if the detection level is set high so that the S-shaped waveform signal from the cover layer is not detected, the S-shaped waveform signal from the cover layer is detected because the amplitude of the S-shaped waveform signal from the cover layer is large. Thus, the designated recording layer is erroneously detected (see FIG. 17A).
(2) Since the amplitude of the S-shaped waveform signal by the recording layer does not exceed the detection level, the S-shaped waveform signal by the recording layer is not detected, and the designated recording layer is erroneously detected (FIGS. 17B and 17C). reference).
(3) Even if the detection level is set low so that the S-shaped waveform signal by the cover layer is detected, the amplitude of the S-shaped waveform signal by the cover layer does not exceed the detection level. The waveform signal is not detected and the designated recording layer is erroneously detected (see FIG. 17D).
(4) When the detection level is set low so that the S-shaped waveform signal from the cover layer is detected, the instantaneous noise value exceeds the detection level and is not detected as the S-shaped waveform signal. Incorrect layer detection (see FIG. 17E).

Conventionally, an S-shaped waveform signal in a focus error signal is also evaluated in an inspection of an optical disc and an optical pickup. In this case, as shown in Patent Document 2 below, digital data relating to all S-shaped waveform signals is taken into a computer, and the taken digital data is evaluated. However, in this conventional apparatus, even when it is desired to evaluate the S-shaped waveform signal of a specific recording layer, digital data relating to all the S-shaped waveform signals is taken into the computer, and a long time is required for the evaluation. Necessary. Also in such a conventional apparatus, when a specific recording layer is to be designated, the problems (1) to (4) occur.
JP 2006-79698 A

  The present invention has been made to cope with the above-described problems, and an object thereof is based on the magnitude of the amplitude of the S-shaped waveform signal by the recording layer and the amplitude of the S-shaped waveform signal by the cover layer in an optical disc having a plurality of recording layers. First, an object of the present invention is to provide a recording layer detection apparatus and a recording layer detection method for an optical disc that can detect a designated recording layer with high accuracy.

  In order to achieve the above object, the present invention includes a laser light source (21) for emitting laser light and an objective lens (25) for focusing the laser light emitted from the laser light source on the recording layer of the optical disc. Optical means (22 to 27) for deriving reflected light from the recording layer of the optical disc, and a photodetector (28) for receiving the reflected light derived by the optical means and outputting a detection signal corresponding to the received reflected light In the recording layer detection apparatus for an optical disc provided with an actuator (29) for driving the objective lens and displacing the objective lens in the optical axis direction of the laser beam, a focus error signal is generated based on the detection signal output from the photodetector. Focus error signal generation means (34) for generating the focus error signal when the objective lens is displaced in the optical axis direction S-shaped detection means (37, 41 to 45) for detecting an S-shaped waveform signal in the focus error signal on condition that the instantaneous value of the focus error signal generated by the stage exceeds the detection level; and S-shaped detection means Are sequentially set to a plurality of reference levels, and the actuator is driven and controlled to displace the objective lens from the lowest point position to the highest point position for each of the set reference levels, or from the highest point position to the highest point. Level-corresponding S-curve detecting means (36, S400 to S417) for detecting the number of S-curve signals detected by the S-curve detecting means for each reference level and level-corresponding S-curve detecting means Based on the number of S-shaped waveform signals respectively detected by the plurality of reference levels and the amplitude values of the S-shaped waveform signals Detection level setting means (S601 to S619, S641 to S652, S701 to S721, S730 to S740) for determining the relationship and setting the detection level of the S-shaped detection means using a plurality of reference levels according to the determination result; In a state where the detection level of the S-shaped detection means is set by the detection level setting means, the actuator is driven and controlled to displace the objective lens from the lowest point position toward the highest point position, or from the highest point position to the lowest point. The number of S-shaped waveform signals detected by the S-shaped detecting means was counted while being displaced toward the position, and the counted number of S-shaped waveform signals became a value corresponding to the designated recording layer. , Designated recording layer detection means (36, S621 to S626, S655 to S661, S801 to S809, S82) for detecting the designated recording layer. 0 to S824).

  In the present invention configured as described above, the level-corresponding S-shaped detecting means detects the number of S-shaped waveform signals detected by the S-shaped detecting means for each of a plurality of reference levels, and detects level setting means. However, the detection level of the S-shaped detector is set using a plurality of reference levels based on the number of S-shaped waveform signals corresponding to the plurality of reference levels. Then, the designated recording layer detection means detects S by the S-character detection means while displacing the objective lens from the lowest point position toward the highest point position or from the highest point position toward the lowest point position. The number of letter waveform signals is counted, and the designated recording layer is detected on the condition that the counted number of S-shaped waveform signals becomes a value corresponding to the designated recording layer. Thereby, the detection level of the S-shaped detection means is set to an appropriate value according to the amplitude of the S-shaped waveform signal by the cover layer and the plurality of recording layers, and the designated recording layer is detected with high accuracy.

  Further, in this case, the detection level setting means is such that, for example, the number of S-shaped waveform signals detected by the level-corresponding S-shaped detection means with respect to a predetermined one of the plurality of reference levels is the recording layer of the optical disc. The number of S-shaped waveform signals detected by the level-corresponding S-shaped detecting means is smaller than the maximum reference level that is larger by “1” than the number of recording layers of the optical disc. For example, the half of the maximum reference level) is set as the detection level of the S-shaped detection means, and the designated recording layer detection means is a value indicating the recording layer in which the number of counted S-shaped waveform signals is designated. The designated recording layer is detected on the condition that the value is larger by “1” than that. This relates to setting of the detection level when the amplitude of the S-shaped waveform signal by the cover layer and the plurality of recording layers is larger than a predetermined reference level, and in this case, the detection level for detection of the designated recording layer Is set to be smaller than the amplitude of the S-shaped waveform signal by the cover layer and the plurality of recording layers, but this detection level is set as large as possible, so that it is not affected by noise and the designated recording is performed. The layer is reliably detected.

  Further, the detection level setting means includes, for example, a maximum reference level in which the number of S-shaped waveform signals detected by the level-corresponding S-character detecting means is “1” larger than the number of recording layers of the optical disc, When the level difference from the maximum reference level in which the number of S-shaped waveform signals detected by the detection means is equal to the number of recording layers of the optical disc is equal to or greater than a predetermined value (for example, 2 or more), An intermediate value (for example, a value slightly larger than the intermediate value between the two maximum reference levels) is set as the detection level of the S-shaped detection means, and the designated recording layer detection means counts the number of the counted S-shaped waveform signals. The designated recording layer is detected on the condition that becomes a value indicating the designated recording layer. This is related to the case where the amplitude of the S-shaped waveform signal by the cover layer is smaller than the amplitude of the S-shaped waveform signal by the plurality of recording layers, and also in this case, the detection level is set as large as possible. The comparison between the amplitude of the S-shaped waveform signal and the detection level by the cover layer and the recording layer is not wrong, and at the same time, the designated recording layer is reliably detected without being affected by noise.

  Further, in the configuration of the present invention, the actuator is further driven and controlled to displace the objective lens from the lowest point position toward the uppermost point position or from the uppermost point position toward the lowest point position. A maximum reference for detecting the maximum amplitude value of the S-shaped waveform signal included in the focus error signal generated by the signal generation means or a value near the maximum value and setting the detected maximum amplitude value or the vicinity thereof as a maximum reference level Level setting means (S200 to S233) and a plurality of reference level setting means (S300 to S306) for setting a plurality of reference levels by dividing the maximum reference level set by the maximum reference level setting means by a predetermined number It is good to provide. According to this, it is not necessary to prepare a plurality of reference levels in advance, and at the same time, the plurality of reference levels are appropriately set according to the maximum amplitude value of the S-shaped waveform signal included in the focus error signal. become.

  Further, in the configuration of the present invention, an S-shape corresponding to the plurality of reference levels is further based on a change in the number of S-shaped waveform signals corresponding to the plurality of reference levels detected by the level-corresponding S-shape detection means. If recording layer number detection means (S500 to S519) is provided for determining whether the number of waveform signals includes an S-shaped waveform signal from the cover layer of the optical disk and detecting the number of recording layers of the optical disk according to the determination result. Good. According to this, even if the number of recording layers is unknown because the user cannot input without knowing the number of recording layers of the optical disk, or the number of recording layers is not included in the identification code of the optical disk, The number of recording layers is automatically detected. As a result, even if the number of recording layers is unknown, the designated recording layer can be accurately detected.

  Further, in the configuration of the present invention, the actuator is driven and controlled so that the laser beam continues to be focused on any one of the plurality of recording layers of the optical disk based on the focus error signal generated by the focus error signal generator. When the recording layer designated by the focus servo means (35) and the designated recording layer detection means is detected, the drive control of the actuator by the designated recording layer detection means is stopped and the focus servo means is operated to operate the above-mentioned optical disc of the optical disc. A focus pull-in means (S627, S628, S662, S663) that keeps the laser beam focused on the designated recording layer may be provided. According to this, since the focus is automatically drawn into the recording layer after the designated recording layer is detected, the data recording to the designated recording layer or the data recorded on the recording layer is performed. In reproduction, the recording layer for recording or reproduction is not mistaken.

  Further, in the configuration of the present invention, when a designated recording layer is detected by the designated recording layer detecting means, the S-shaped waveform signal by the designated recording layer is analyzed for the S-shaped waveform signal. S-shaped waveform signal output means (45 to 47, S810 to S812, S825 to S827) for outputting to the signal analyzer (50) may be provided. In this case, for example, when the objective lens is displaced in the direction of the optical axis, the S-shaped detector detects the focus error on the condition that the instantaneous value of the focus error signal generated by the focus error signal generator exceeds the detection level. It comprises first and second S-shaped detecting means for detecting S-shaped waveform signals in the signal, and the level-corresponding S-shaped detecting means sequentially sets the detection level in the first S-shaped detecting means to a plurality of reference levels. In addition, by driving and controlling the actuator, the objective lens is displaced from the lowest point position to the highest point position for each of the set reference levels, or from the highest point position to the lowest point position, and for each reference level. The number of S-shaped waveform signals detected by the first S-shaped detecting means is detected, and the detection level setting means is detected by the level corresponding S-shaped detecting means. Based on the number of character waveform signals, the detection level of the second S-shaped detector is set using a plurality of reference levels, and the designated recording layer detector is configured to detect the second S-shaped detector by the detection level setting unit. While the detection level is set, the actuator is driven and controlled to displace the objective lens from the lowermost point position toward the uppermost point position, or from the uppermost point position toward the lowermost point position. The number of S-shaped waveform signals detected by the S-shaped detecting means is counted. According to this, after the designated recording layer is detected, the S-shaped waveform signal from the recording layer is automatically input to the signal analyzing apparatus, so that the S-shaped waveform signal from the designated recording layer is evaluated. It becomes convenient.

  Furthermore, the embodiment of the present invention is not limited to the invention of the recording layer detection device for optical disks, but can also be implemented as an invention of a recording layer detection method and a computer program applied to an optical disk recording layer detection device. is there.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall schematic diagram of an optical disk inspection apparatus including an optical disk recording layer detection apparatus of the present invention. This inspection apparatus is particularly suitable for inspecting an optical disc DK having a plurality of recording layers. The optical disk DK has a plurality of recording layers N1 to Nz, as shown in a sectional view in FIG. In this optical disc DK, the laser light incident side surface and back surface are covered with a transparent protective layer, and a transparent protective layer is also provided between each of the recording layers N1 to Nz. In the following description, the laser light incident side surface is referred to as the cover layer N0, the direction from the cover layer N0 toward the recording layer Nz is referred to as the lower layer side, and the opposite is referred to as the upper layer side. In the present embodiment, the number of recording layers N1 to Nz, that is, the recording layer number LNO is “4”, but this recording layer number LNO may be any integer as long as it is an integer equal to or greater than “2”.

a. Configuration Example Hereinafter, a configuration example of the optical disk DK inspection device will be described. The inspection apparatus includes a rotating device 10 that rotates the optical disc DK, and an optical pickup 20 that irradiates the optical disc DK with laser light and receives reflected light from the optical disc DK. The rotating device 10 includes a spindle motor 11 that rotates a rotating shaft 11a to rotate a turntable 12. An optical disk DK is detachably assembled to the top surface of the turntable 12. This inspection apparatus also includes a radial drive device that drives the optical disc DK in the radial direction. However, since the radial movement of the optical disc DK is not directly related to the present invention, in FIG. The radial feed control circuit is omitted. Further, a rotation control circuit that controls the rotation of the optical disk DK is also omitted. In this case, the optical disk DK is rotated at a constant linear velocity. In addition, there are a tracking servo control circuit for aligning the laser beam irradiation position with the recording location and recording groove of the optical disk DK, a reproduction signal generation circuit for reproducing a signal recorded on the optical disk DK, a data decoding circuit, etc. Since it is not directly related to the present invention, it is omitted.

  The optical pickup 20 includes a laser light source 21 that is driven by a laser drive circuit 31. The laser drive circuit 31 is controlled by a controller 60 described later in detail. Laser light emitted from the laser light source 21 is condensed on the recording layers N1 to Nz of the optical disc DK via the collimating lens 22, the polarization beam splitter 23, the quarter wavelength plate 24, and the objective lens 25. The laser light reflected by the recording layers N1 to Nz of the optical disc DK enters the polarization beam splitter 23 via the objective lens 25 and the quarter wavelength plate 24 and is reflected by the polarization beam splitter 23. The laser light reflected by the polarization beam splitter 23 is condensed on the photodetector 28 via the condenser lens 26 and the cylindrical lens 27. In this case, the cylindrical lens 27 causes astigmatism in the transmitted reflected light. The photodetector 28 is composed of four divided light receiving elements made up of four identical square light receiving elements separated by a dividing line, and each light receiving element receives electric signals A to D proportional to the amount of received light as detection signals. Output to the amplifier circuit 32.

  The optical pickup 20 is also provided with a focus actuator 29. The focus actuator 29 is controlled by a drive signal output from the drive circuit 33, and drives the objective lens 25 in the optical axis direction of the laser light (perpendicular to the surface of the optical disk DK) to thereby adjust the focal position of the laser light to the optical axis. Displace in the direction.

  The signal amplification circuit 32 amplifies the detection signals A to D output from the photodetector 28 and outputs them to the focus error signal generation circuit 34. The focus error signal generation circuit 34 calculates using the detection signals A to D from the photodetector 28 via the signal amplification circuit 32 (specifically, calculation of (A + C) − (B + D) in the case of the astigmatism method). ) To generate a focus error signal and output it to the focus servo circuit 35. The detection signals A to D represent the amounts of light received by the four light receiving elements positioned in the clockwise direction in the photodetector 28. In this case, the focus error signal (A + C) − (B + D) represents the amount of defocus of the laser beam by the objective lens 25 with respect to the cover layer N0 and the recording layers N1 to Nz. The focus servo circuit 35 is controlled by the controller 60 to generate a focus servo signal based on the focus error signal and output it to the drive circuit 33.

  A reciprocating signal generating circuit 36 is also connected to the drive circuit 33. The reciprocating signal generation circuit 36 is controlled by the controller 60 and outputs a reciprocating signal for reciprocating the objective lens 27 to the drive circuit 33. As shown in FIG. 13A, the reciprocating signal is a control signal for reciprocating the objective lens 25 between the lowest point position and the highest point position. FIG. 13B shows the state of displacement of the objective lens 25 by this reciprocating signal. The drive circuit 33 applies a voltage proportional to the reciprocating signal to the focus actuator 29 to reciprocate the objective lens 27. In addition, the reciprocating signal generation circuit 36 outputs signals representing the lowest point position and the highest point position of the objective lens 27 at the timing when the objective lens 27 passes the lowest point position and the highest point position. 60.

  The inspection apparatus includes an S-shaped detection circuit 37, a signal extraction circuit 40, a signal analysis apparatus 50, and a controller 60. The S-shaped detection circuit 37 is set with the detection level and the polarity of the input signal according to an instruction from the controller 60, starts operating according to the instruction from the controller 60, and instantaneously outputs the focus error signal input from the focus error signal generation circuit 34. After the value exceeds the detection level, an S-shaped detection signal is output to the controller 60 when crossing the detection level again. As shown in FIG. 13C, the focus error signal is an S-shaped waveform signal that changes from positive to negative when the reciprocating signal increases (that is, when the objective lens 25 is displaced to the lower layer side) Is referred to as a positive S-shaped waveform signal). On the other hand, the focus error signal is an inverted S-shaped waveform signal (hereinafter referred to as a negative S-shaped waveform signal) that changes from negative to positive when the reciprocating signal decreases (that is, when the objective lens 25 is displaced upward). It becomes). Therefore, when the S-shaped detection circuit 37 is set to be positive, the detection signal is output at a timing when the focus error signal crosses the detection level from the bottom to the top and then crosses the detection level from the top to the bottom. . On the other hand, when the S-shaped detection circuit 37 is set to the negative polarity, after the focus error signal crosses the detection level from the top to the bottom, the detection signal is output at a timing crossing the detection level from the bottom to the top. .

  The signal extraction circuit 40 extracts only positive and negative S-shaped waveform signals from the designated recording layer from the input focus error signal, and outputs them to the signal analysis device 50. As shown in FIG. 2, the signal extraction circuit 40 includes a positive-side binarization circuit 41, a negative-side binarization circuit 42, a positive-side extraction signal generation circuit 43, a negative-side extraction signal generation circuit 44, and an extraction signal. The circuit includes a generation circuit 45, an output instruction circuit 46, and a gate circuit 47. When the positive slice level SLh is set by the controller 60 and the focus error signal (see FIG. 14B) is smaller than the slice level SLh, the positive binarization circuit 41 becomes low level and the focus error signal is sliced. When the level is equal to or higher than the level SLh, a positive-side binarized signal (see FIG. 14C) that becomes a high level is output. The negative side binarization circuit 42 becomes low level when the negative slice level SLl is set by the controller 60 and the focus error signal (see FIG. 14B) is larger than the slice level SLl, and the focus error signal is sliced. When the level is equal to or lower than the level SL1, a negative side binarized signal (see FIG. 14D) that becomes a high level is output.

  The positive-side extraction signal generation circuit 43 is composed of a flip-flop circuit, and is set when the positive-side binarization signal changes from low level to high level, and the negative-side binarization signal changes from high level to low level. It is reset when Then, the positive-side extraction signal generation circuit 43 becomes a high level from when the focus error signal crosses the positive slice level SLh from the bottom to the top until it crosses the negative slice level SLl from the bottom to the top. An extraction signal (see FIG. 14E) for generating an S-shaped waveform signal in the focus error signal when the objective lens 25 moves from the upper layer side to the lower layer side is generated. The negative-side extraction signal generation circuit 44 is also composed of a flip-flop circuit, and is set when the negative-side binarization signal changes from low level to high level, and the positive-side binarization signal changes from high level to low level. It is reset when Then, the negative-side extraction signal generation circuit 44 becomes a high level from when the focus error signal crosses the negative slice level SLl from the top to the bottom until it crosses the positive slice level SLh from the top to the bottom. A negative side extraction signal (see FIG. 14F) is generated for extracting an S-shaped waveform signal in the focus error signal when the objective lens 25 moves from the lower layer side to the upper layer side. The positive side and negative side extraction signal generation circuits 43 and 44 are connected to the lowest point position and the highest point of the objective lens 27 from the reciprocation signal generation circuit 36 regardless of the positive side and negative side binary signals. It is reset when a signal representing the position is input.

  The take-out signal generation circuit 45 receives a signal representing the lowest point position of the objective lens 27 from the reciprocation signal generation circuit 36 and then receives a signal representing the highest point position of the objective lens 27 from the reciprocation signal generation circuit 36. Until the positive side extraction signal generation circuit 43 outputs the positive side extraction signal to the output instruction circuit 46, and after the signal indicating the uppermost point position is input, the signal indicating the lowermost point position. Is input to the output instruction circuit 46 (see FIG. 14G) until the negative side extraction signal generation circuit 44 inputs the negative side extraction signal. The take-out signal generation circuit 45 outputs a positive-side and a negative-side take-out signal relating to the designated recording layer as a gate signal for outputting an S-shaped waveform signal (FIG. 14 (H)). To the gate circuit 47. The output instruction circuit 46 includes a computer device including a CPU, a ROM, a RAM, and the like, and executes an S-shaped waveform extraction program shown in FIGS. 11A and 11B described later according to an instruction from the controller 60. By executing this S-shaped waveform extraction program, the output instruction circuit 46 controls the extraction signal generation circuit 45 so that the extraction signal generation circuit 45 outputs the gate signal to the gate circuit 47.

  The gate circuit 47 is conductively controlled when the gate signal is at a high level, and outputs the focus error signal from the focus error signal generation circuit 34 to the signal analysis device 50. That is, an S-shaped waveform signal (see FIG. 14I) corresponding to the designated recording layer is input to the signal analysis device 50. FIG. 14 shows the case where the S-shaped waveform signal of the second recording layer N2 is extracted and supplied to the signal analyzing device 50. The signal analysis device 50 is constituted by an oscilloscope, for example, and an operator analyzes the input S-shaped waveform signal. In this signal extraction circuit 40, the positive side binarization circuit 41, the negative side binarization circuit 42, the positive side extraction signal generation circuit 43, the negative side extraction signal generation circuit 44, and the extraction signal generation circuit 45 Since it has a function of detecting an S-shaped waveform signal, it corresponds to the S-shaped detecting means of the present invention together with the S-shaped detecting circuit 37 described above. Further, since the extraction signal generation circuit 45, the output instruction circuit 46 and the gate circuit 47 extract and output the S-shaped waveform signal from the designated recording layer, it corresponds to the S-shaped waveform signal output means of the present invention.

  The controller 60 is configured by a computer including a CPU, a ROM, a RAM, a hard disk, and the like, and executes a main program shown in FIGS. 3 to 10B in accordance with instructions from the input device 61 including a keyboard and a mouse. The controller 60 is also connected with a display device 62 for visually informing the operator of the operation instructions and the operation status.

b. Overall Operation The operation of the optical disk inspection apparatus configured as described above will be described. The operator sets the optical disk DK on the turntable 12 and starts the operation of the inspection apparatus. First, when an operator turns on a power switch (not shown), the controller 60 starts execution of the main program in step S10 in FIG. 3 and then executes initialization processing in step S11. Execute. First, the operation of the entire apparatus will be schematically described. In the user setting process routine of step S12, the following information input by the operator is input using the input device 61.
(1) Is it a mode for recording or reproducing data (a mode for performing focus pull-in) or a mode for evaluating an S-shaped waveform signal?
(2) Number of recording layers LNO of optical disk DK
(3) Designated recording layer number LNO (number of recording layers from the recording layer N1 to the lower layer side)

  Next, in step S13, the controller 60 executes an S-shaped amplitude vicinity level setting routine. This S-shaped amplitude vicinity level setting routine has the maximum absolute value among the plurality of S-shaped waveform signals respectively corresponding to the plurality of recording layers N1 to N4 on both the positive side and the negative side of the S-shaped waveform signal. A level whose absolute value is slightly larger than the positive and negative amplitude values (a level value slightly larger than the positive maximum amplitude value on the positive polarity side and a slightly smaller level value than the negative maximum amplitude value on the negative polarity side) ) Are set as the positive S-shaped amplitude vicinity level F (8) and the negative S-shaped amplitude vicinity level G (8), respectively. FIG. 15A shows the S-side amplitude vicinity level F (8) on the positive side.

  Next, the controller 60 executes a reference level setting routine in step S14. In this reference level setting routine, the positive S-shaped amplitude vicinity level F (8) and the negative S-shaped amplitude vicinity level G (8) are each divided into 8 parts, and both S-shaped amplitude vicinity levels F (8). , G (8) is a routine for setting positive and negative reference levels F (1) to F (8) and G (1) to G (8), respectively, with positive and negative maximum levels. FIG. 15B shows the positive reference levels F (1) to F (8).

  Next, the controller 60 executes a level-corresponding S-character detection number routine in step S15. This level-corresponding S-curve detection number routine is the S-curve signal generated by the S-curve detection circuit 37 for each of the reference levels F (1) to F (8) and G (1) to G (8) in the positive polarity and the negative polarity. This is a routine for detecting the number of detections (numbers of positive and negative peak values of the S-shaped waveform signal exceeding the reference levels F (1) to F (8) and G (1) to G (8), respectively). Then, the detection results are set as positive level corresponding S-character detection numbers H (1) to H (8) and negative level corresponding S-character detection numbers L (1) to L (8), respectively.

  Next, the controller 60 determines whether or not the recording layer number LNO is larger than “0” in step S16. Although details will be described later, in the user setting routine in step S12, the operator inputs the number of recording layers LNO or data recorded in a BCA (Burst Cutting Area) of the optical disc DK (hereinafter referred to as a BCA code). If the number of recording layers in the recording layer can be read, the recording layer number LNO is set to a value larger than “0”, so the controller 60 determines “No” in step S16. Then, the process after step S18 is performed. On the other hand, in the user setting routine, when the recording layer number LNO is not input by the operator or the recording layer number in the BCA code of the optical disc DK cannot be read, the recording layer number LNO is “0”. Is set to Therefore, in this case, the controller 60 determines “No” in step S16, and executes the recording layer number determination routine in step S17. This recording layer number determination routine uses the detected positive side level corresponding S-shaped detection numbers H (1) to H (8) and negative side level corresponding S-shaped detection numbers L (1) to L (8). This is a routine for automatically detecting the recording layer number LNO on the basis of changes in these detection numbers H (1) to H (8) and L (1) to L (8).

Next, in Step S18, the controller 60 determines whether or not the focus pull-in mode is selected by the user setting process in Step S12. If the focus pull-in mode is selected, the controller 60 executes a focus pull-in routine in step S19. In the focus pull-in routine, the detection level of the S-shaped waveform signal (S-shaped detection level) in the S-shaped detection circuit 37 is set, and this S-shaped detection level is used to specify by the user in the user setting process in step S12. In this routine, the focus is drawn into the recorded recording layer N _DLN . After execution of the focus routine, data is recorded on the recording layer with the focus drawn or data recorded on the recording layer is reproduced by executing a program (not shown).

On the other hand, if the S-shaped waveform evaluation mode is selected by the user setting process in step S12, the controller 60 executes an S-shaped waveform evaluation routine in step S20. The S-shaped waveform evaluation routine sets positive and negative slice levels for the focus error signal to the signal extraction circuit 40, and uses the S-level for the designated recording layer N _DLN extracted from the focus error signal. In this routine, the waveform signal is extracted by the signal extraction circuit 40 and output to the signal analysis device 50. The signal analyzer 50 displays the S-shaped waveform signal on an oscilloscope or the like, and allows the operator to evaluate the S-shaped waveform signal.
Next, the various routines will be described in detail.

c. User Setting Routine The user setting routine is shown in detail in FIG. 4 and its execution is started in step S100. After starting the execution, the controller 60 prompts the operator to input in step S101 whether the mode is for recording or reproducing data (that is, the focus pull-in mode) or the mode for evaluating the S-shaped waveform signal. The instruction is displayed on the display device 62. When the operator inputs one of the modes using the input device 61 in accordance with this display, the controller 60 inputs and stores the input mode in step S101.

  Next, in step S102, the controller 60 displays an instruction for prompting the operator to input the number of recording layers of the optical disk DK on the display device 62, and waits for the operator to input the number of recording layers. When the operator inputs the number of recording layers of the optical disc DK using the input device 61, the controller 60 determines “YES” in step S102, and uses the number input in step S103 as the number of recording layers. Store as LNO. On the other hand, when the operator inputs using the input device 61 that the number of recording layers cannot be input without knowing the number of recording layers of the optical disc DK, the controller 60 determines “No” in step S102. In step S104, the number of recording layers included in the BCA code of the optical disc DK is read through a signal reproduction circuit (not shown). If the recording layer number is successfully read, the controller 60 determines “YES” in step S105, and stores the read number as the recording layer number LNO in step S106. If the number of recording layers is not included in the BCA code or if the recording is not possible, the controller 60 determines “No” in step S105, and in step S107. The recording total number LNO is set to “0”.

  Next, in step S108, the controller 60 displays on the display device 62 an instruction for prompting the operator to specify a recording layer related to the optical disc inspection. When the operator inputs a recording layer number related to the inspection using the input device 61, the controller 60 stores the number input in step S108 as the designated recording layer number DLN. In step S109, the execution of this user setting routine is terminated.

d. S-shaped amplitude vicinity level setting routine The S-shaped amplitude vicinity level setting routine is shown in detail in FIGS. 5A and 5B, and its execution is started in step S200. After starting the execution, in step S201, the controller 60 clears the S-curve detection count values p and m and the level changing variables u and d to “0”, and sets the positive side level setting flag USF and the negative value setting flag USF. The side level setting flag DSF is cleared to “0”. The S-shaped detection frequency count value p is a variable for counting the number of times the S-shaped waveform signal is detected when the objective lens 25 is moved upward (lower layer side). The S-curve detection count value m is a variable for counting the number of detections of the S-curve signal when the objective lens 25 is moved downward (upper layer side). The level changing variable u is a variable for changing the S-shaped detection level A + u · ΔA to a large positive value when the objective lens 25 moves upward (lower layer side). The level changing variable d is a variable for changing the S-shaped detection level − (A + d · ΔA) to a negative value having a large absolute value when the objective lens 25 moves downward (upper layer side). Here, A is an appropriate value determined in advance, and ΔA is a predetermined positive small value (see FIG. 15A). The positive-side level setting flag USF is a flag used in the setting process of the positive-side S-shaped amplitude vicinity level F (8), and the negative-side level setting flag DSF is the negative-side S-shaped amplitude vicinity level G (8 ) Is a flag used in the setting process.

  Next, the controller 60 starts the operation of the reciprocating signal generation circuit 36 and the S-shaped detection circuit 37 in step S202. The reciprocating signal generation circuit 36 outputs a reciprocating signal to the drive circuit 33, and the drive circuit 33 drives and controls the focus actuator 29 to reciprocate the objective lens 25. After the processing in step S202, the controller 60 sets the detection polarity of the S-shaped waveform signal in the S-shaped detection circuit 37 to positive polarity in step S203, and in step S204, the controller 60 sets the S-shaped waveform signal in the S-shaped waveform signal. The S-curve detection level is set to A + u · ΔA. In this case, since the level changing variable u is initially set to “0”, the S-shaped detection level of the S-shaped waveform signal in the S-shaped detecting circuit 37 is set to a predetermined value A. In this state, the S-shaped detection circuit 37 starts detecting the S-shaped waveform signal in the positive focus error signal with the S-shaped detection level as A + u · ΔA.

  Next, the controller 60 waits for input of a signal representing the lowest point position from the reciprocating signal generation circuit 36 in step S205, and when the signal is input, starts to execute the cyclic processing of steps S206 to S208. The circulation process of steps S206 to S208 is repeatedly executed until a signal representing the uppermost point position is input from the reciprocating signal generation circuit 36. This is a process of increasing the detection count value p by “1”. By the processing in steps S206 to S208, the number of positive S-shaped waveform signals exceeding the S-shaped detection level A + u · ΔA is counted until the objective lens 25 reaches the highest point position from the lowest point position. That is, the number of S-shaped waveform signals having a positive amplitude exceeding the S-shaped detection level A + u · ΔA is counted.

  After the processes in steps S206 to S208, the controller S60 sets the detection polarity of the S-shaped waveform signal in the S-shaped detection circuit 37 to negative polarity in step S209, and the S-shaped waveform in the S-shaped detection circuit 37 in step S210. The S-curve detection level of the signal is set to-(A + d · ΔA). Also in this case, since the level changing variable u is initially set to “0”, the S-shaped detection level of the S-shaped waveform signal in the S-shaped detecting circuit 37 is set to a predetermined value −A. . In this state, the S-shaped detection circuit 37 sets the S-shaped detection level to − (A + d · ΔA) and starts to detect the S-shaped waveform signal (reverse S-shaped waveform signal) in the negative focus error signal. Then, the controller 60 repeats the processing of steps S211 to S213 corresponding to the processing of steps S206 to S208 described above until the objective lens 25 reaches the lowest point position from the highest point position-(A + d · The number of negative S-shaped waveform signals exceeding ΔA) is counted as the count value m. That is, the number of S-shaped waveform signals having a negative amplitude exceeding the S-shaped detection level − (A + d · ΔA) is counted.

  After the processing of Steps S211 to S213, the controller 60 determines whether or not the positive side level setting flag USF is “2” in Step S214 of FIG. 5B. The positive side level setting flag USF is initially set to “0” by the process of step S201. In this case, the controller 60 determines “No” in step S214, and the program is transferred to step S215. Proceed. In step S215, it is determined whether or not the S-shaped detection frequency count value p on the positive polarity side (that is, when the objective lens 25 is moved upward (lower layer side)) is larger than “0”. If even one S-shaped waveform signal is detected when the objective lens 25 is moved upward (lower layer side), the controller 60 determines “Yes” in step S215, and performs the processing in steps S216 and S217. Execute. In step S216, the positive level setting flag USF is set to “1”, and in step S217, the level changing variable u is incremented by “1”. Next, after the processing of steps S222 to S225, the processing of steps S222, S223, S226 to S228, and S232, the processing of steps S222, S223, S226, and S229, or the processing of steps S222 and S232, the controller 60 proceeds to step S230. The S-curve detection count value p on the positive side is cleared to “0”, and the program is returned to step S203 of FIG. 5A through the process of step S231.

  Then, the controller 60 increases the S-shaped detection level A by the predetermined value ΔA and moves the objective lens 25 from the lowest point position to the highest point position by the processing of the above-described steps S203 to S208. The S-curve detection count value p on the positive side exceeding A + u · ΔA is detected again. After the processing of these steps S203 to 208, the controller 60 starts executing the processing after step S214 of FIG. 5B again through the processing of steps S209 to S213 described above. In this case, the positive side level setting flag USF is set to “1”, and the controller 60 makes a “No” determination at step S214, so the determination process at step S215 is executed. Then, as long as the S-curve detection count value p is larger than “0”, the above-described steps S216, S217, S230, and S203 to S208 are repeatedly executed to set the S-curve detection level A of the S-curve detection circuit 37. Increasing the predetermined value ΔA continues to detect the S-curve detection count value p.

  When the S-curve detection count value p becomes “0”, the controller 60 determines “No” in step S215, and determines whether the positive side level setting flag USF is “1” in step S218. To do. In this case, since the positive level setting flag USF is set to “1” by the process of step S216, the controller 60 determines “Yes” in step S218, and in step S219, the positive side S The character amplitude vicinity level F (8) is set to the S-character detection level A + u · ΔA. As shown in FIG. 15A, the S-shaped detection level A + u · ΔA is a level at which the S-shaped waveform signal is not detected for the first time as a result of increasing the S-shaped detected level, that is, the positive of the S-shaped waveform signal. The level value is slightly larger than the peak value.

  Next, a case where the predetermined value A determined in advance is too large and the peak value of the positive S-shaped waveform signal never exceeds the S-shaped detection level A + u · ΔA will be described. In this case, in the state where the positive side level setting flag USF is set to “0”, the positive S-character detection count value p detected by the processing of steps S203 to S208 in FIG. 5A is “0”. Therefore, the controller 60 determines “No” in steps S214, S215, and S218 in FIG. 5B, and subtracts “1” from the level changing variable u in step S221. After the process of step S221, the S-curve detection level of the S-curve detection circuit 37 is decreased by a predetermined value ΔA and the S-curve detection count value p is detected by the processes of steps S203 to S208 of FIG. 5A described above. To do. In this case, the S-curve detection level of the S-curve detection circuit 37 is successively lowered by a predetermined value ΔA by the processing of step S221 until the S-curve detection count value p becomes larger than “0”. As a result of lowering the S-curve detection level of the S-curve detection circuit 37, if the S-curve detection count value p becomes larger than "0", the positive S-curve amplitude neighborhood level F (8) is obtained by the above-described processing. Is set.

  On the other hand, the processes in steps S222 to S229 and S231 in FIG. 5B correspond to the processes in steps S214 to S221 and 230 in FIG. 5B described above for setting the negative S-shaped amplitude vicinity level G (8). It is. In this case, the level at which the S-shaped waveform signal is not detected for the first time while reducing the S-shaped detection level of the S-shaped detection circuit 37 by the predetermined value ΔA, that is, a level slightly smaller than the negative peak value of the S-shaped waveform signal. A value is detected. The detected negative value is set as the negative S-shaped amplitude vicinity level G (8).

  Such a setting process of the positive S-shaped amplitude vicinity level F (8) composed of steps S214 to S221 and S230 and the setting of the negative S-shaped amplitude vicinity level G (8) composed of steps S222 to S229 and S231. The process is performed until the S-shaped amplitude vicinity level F (8) and the S-shaped amplitude vicinity level G (8) are set. When both of the neighborhood levels F (8) and G (8) are set and the positive and negative level setting flags USF and DSF are both set to “2”, the controller 60 In S214, S222, and S232, “Yes” is determined, and in step S233, the execution of the S-shaped amplitude vicinity level setting routine is ended.

e. Reference Level Setting Routine The reference level setting routine is shown in detail in FIG. 6, and its execution is started in step S300. After starting the execution, the controller 60 repeatedly executes the processes of steps S302 and S303 by sequentially increasing the variable n from “1” to “7” by the processes of steps S301, S304, and S305, thereby performing the reference level F ( 1) to F (7) and G (1) to G (7) are set, respectively. In step S302, the value n · (F (8) / 8) is set as the reference level F (n). In step S303, the value n · (G (8) / 8) is set as the reference level G (n).

  Thus, the positive S-shaped amplitude vicinity level F (8) is divided into eight, and eight positive reference levels F (1) to F (8) including the S-shaped amplitude vicinity level F (8) are obtained. It is set (see FIG. 15B). Further, the negative-side S-shaped amplitude vicinity level G (8) is divided into eight, and eight negative-side reference levels G (1) to G (8) including the S-shaped amplitude vicinity level G (8) are set. Is done. When the setting processing of the reference levels F (1) to F (8) and G (1) to G (8) is completed, the controller 60 determines that “Yes”, that is, the variable n is “7” or more in step S304. If it is determined that there is, the execution of the reference level setting routine is terminated in step S306.

f. Level Corresponding S-Circuit Detection Number Routine The level-corresponding S-curve detection number routine is shown in detail in FIG. 7, and its execution is started in step S400. After starting the execution, the controller 60 initially sets the variable n to “1” and the variables p and m to “0” in step S401. The variable n is the number of S-shaped detections H (n), L corresponding to the positive and negative levels for each of the positive and negative reference levels F (1) to F (8) and G (1) to G (8). (n) (n = 1 to 8) is designated. The variables p and m are count values used for counting the positive and negative level corresponding S-shaped detection numbers H (n) and L (n).

  After the initial setting in step S401, the controller 60 sets the detection polarity of the S-shaped waveform signal in the S-shaped detection circuit 37 to positive polarity in step S402, and the S-shaped detection level of the S-shaped detection circuit 37 in step S403. Is set to the reference level F (n). Note that the variable n is initially “1”, and the S-shaped detection level of the S-shaped detection circuit 37 is set to the reference level F (1). Next, the controller 60 detects the input of the S-shaped detection signal from the S-shaped detection circuit 37 in step S404 until the signal representing the uppermost point position is input from the reciprocating signal generation circuit 36 in step S406. In step S405, the count value p is incremented by “1”. In this case, at the end of the aforementioned S-shaped amplitude vicinity level setting routine of FIGS. 5A and 5B and the reference level setting routine of FIG. 6, the reciprocation signal represents the position near the lowest point position, that is, the objective lens 25. Is near the lowest point position. Therefore, in the processing of steps S404 to S406, the number of S-shaped waveform signals exceeding the reference level F (n) to the positive side while raising the objective lens 25 from the lowest point position to the highest point position is used as the count value p. Will be detected.

  Next, the controller 60 corresponds to steps S402 to S406 described above, and a step for detecting the number of negative S-shaped waveform signals (inverse S-shaped waveform signals) exceeding the reference level G (n) on the negative side. The processing of S407 to 411 is executed. In this case, since it is immediately after the detection of the highest point position in step S406, the reference level G (n) is set while lowering the objective lens 25 from the highest point position to the lowest point position in the processing of steps S407 to S411. The number of S-shaped waveform signals exceeding the negative side is detected as the count value m. When the processing in steps S407 to S411 is completed, the controller 60, in steps S412 and S413, determines the number of positive and negative level corresponding S-shaped detections H (n) and L (n) specified by the variable n. Are respectively set to count values p and m representing the number of detected S-shaped waveform signals.

  Next, the controller 60 determines whether or not the variable n is “8” or more in step S414. If the variable n is less than “8”, the controller 60 determines “No” in step S414, and sets the count values p and m for counting the number of detected S-shaped waveform signals to “0” in step S415. "1" is added to the variable n for designating the reference levels F (n) and G (n) in step S416, and the processes of steps S402 to S414 described above are repeatedly executed. . When the variable n reaches “8”, the controller 60 determines “Yes” in step S414, and ends the execution of the level-corresponding S-character detection number routine in step S417. In this state, the number of S-shaped waveform signals detected by the S-shaped detection circuit 37 is determined for each of the positive and negative reference levels F (1) to F (8) and G (1) to G (8). The positive level corresponding S-character detection number H (n) and the negative level corresponding S-character detection number L (n) are set.

g. Recording Layer Number Determination Routine The recording layer number determination routine is shown in detail in FIG. 8, and its execution is started in step S500. In the recording layer number determination routine and the processing of the focus pull-in routine and the S-shaped waveform evaluation routine described later, the following conditions 1 to 3 are predicated on the S-shaped waveform signal and noise. Incidentally, these conditions 1 to 3 are conditions that are sufficiently satisfied in a normal multilayer optical disc.
(Condition 1) The absolute value of the amplitude level of the S-shaped waveform signal relating to the recording layers N1 to Nz is larger than the absolute value of the reference levels F (3) and G (3). In other words, the positive and negative level corresponding S-shaped detection numbers H (3) and L (3) are each equal to or greater than the recording layer number LNO.
(Condition 2) The absolute value of the amplitude level of the S-shaped waveform signal related to the cover layer N0 is larger than the absolute values of the reference levels F (1) and G (1). In other words, the numbers S (1) and L (1) of S-shaped detection corresponding to the positive and negative levels are equal to or greater than the value LNO + 1 obtained by adding “1” to the recording layer number LNO.
(Condition 3) The absolute value of the noise is an intermediate value (= {F (1) + F (2)} / 2) between the reference levels F (1) and F (2) and the reference levels G (1) and G (2 ) Is less than the absolute value of the intermediate value (= {G (1) + G (2)} / 2).

  After starting the execution of step S500, the controller 60 subtracts the positive side level-corresponding S-character detection number H (2) from the positive-side level-corresponding S-character detection number H (3) in step S501. It is determined whether or not −H (3) is “1” or more. If the subtraction value H (2) −H (3) is equal to or greater than “1” (actually “1”), the controller 60 determines “Yes” in step S501 and records in step S502. The layer number LNO is set to the positive level corresponding S-character detection number H (3). This is due to the following reason. The fact that the subtraction value H (2) −H (3) is “1” or more means that there is no influence of noise on the positive-level level-corresponding S-character detection number H (2) from the condition 3, so The amplitude level of the positive S-shaped waveform signal is at the reference level H (2) and the reference level H (3). Therefore, the recording layer number LNO of the optical disc DK is equal to the positive side level corresponding S-character detection number H (3).

  If the subtraction value H (2) −H (3) is not “1” or more, in other words, if the subtraction value H (2) −H (3) is “0”, the controller 60 proceeds to step S501. It is determined as “No”, and in step S503, a value H (1) −H (2) obtained by subtracting the positive side level-corresponding S-character detection number H (2) from the positive-side level-corresponding S-character detection number H (1). ) Is “1” or more. If the subtraction value H (1) −H (2) is not “1” or more (actually “0”), the controller 60 determines “No” in step S503, and step S504. The recording layer number LNO is set to a value H (3) -1 which is smaller by “1” than the positive side level-corresponding S-character detection number H (3). This is due to the following reason. The fact that the subtraction value H (2) −H (3) is “0” and the subtraction value H (1) −H (2) is “0” means that the number of detected S-characters corresponding to the positive side level H ( 1), H (2), and H (3) are all equal, and from the condition 2, the detected number H (1) corresponding to the positive side level includes the detected portion of the S-shaped waveform signal by the cover layer N0. Since there is no influence of noise from the condition 3, the positive S-shaped amplitude level by the cover layer N0 is equal to or higher than the reference level H (3). Therefore, the recording layer number LNO of the optical disk DK is a value H (3) −1 obtained by subtracting “1”, which is a detected amount of the S-shaped waveform signal by the cover layer N0, from the positive-side level corresponding S-shaped detection number H (3). Is equal to

  If the subtraction value H (2) −H (3) is “0” and the subtraction value H (1) −H (2) is “1” or more, the controller 60 determines “ It determines with "No", determines with "Yes" in step S503, and performs the process after step S505. This is because the subtraction value H (1) −H (2) is equal to or greater than “1” due to the conditions 2 and 3, and the positive amplitude value of the S-shaped waveform signal of the cover layer N0 is the reference level. Is it because it is between F (1) and F (2), or the positive side amplitude value of the S-shaped waveform signal of the cover layer N0 is above the reference level F (3) and is due to the influence of noise? This is because it is not possible to determine which of these is. Then, if the cover layer N0 is used, the number of recording layers should be the positive level corresponding S-character detection number H (3). On the other hand, if it is due to the influence of noise, the number of recording layers should be the value H (3) −1 obtained by subtracting “1” from the positive side level-corresponding S-character detection number H (3). In determining the recording layer number LNO, if the cause of the subtraction value H (1) −H (2) being “1” or more is due to the influence of noise, the subtraction value H (1) −H. Focusing on the point that (2) is not always "1" or more, the recording layer number LNO is determined based on the detection results of the S-shaped waveform signal for a plurality of times with respect to the reference level F (1). Yes.

  For this reason, after the determination processing of “Yes” in the step S503, the controller 60 detects a number of times that the S-shaped waveform signal exceeds the reference level F (1) on the positive side in step S505. The variable n representing the number of inspections is initially set to “1”, the detection polarity of the S-shaped waveform signal in the S-shaped detection circuit 37 is set to positive polarity in step S506, and the S-shaped detection circuit 37 in step S507 Set the S-curve detection level to the reference level F (1). Next, in step S508, the controller 60 initially sets a count value p for counting the number of S-shaped waveform signals exceeding the reference level F (1) to the positive side to “0”. Then, the controller 60 inputs the S-character detection signal from the S-character detection circuit 37 in step S509 until the signal indicating the uppermost point position or the lowermost point position is input from the reciprocation signal generation circuit 36 in step S511. In step S510, the count value p is incremented by “1”. In this case, at the end of the level-corresponding S-shaped detection number routine of FIG. 7 described above, the reciprocating signal represents the position near the lowest point position, that is, the objective lens 25 is near the lowest point position. Therefore, in the processing of steps S509 to S511, the number of S-shaped waveform signals exceeding the reference level F (1) to the positive side is first counted while raising the objective lens 25 from the lowest point position to the highest point position. It will be detected as p. When a signal representing the uppermost point position is input from the reciprocating signal generation circuit 36, the controller 60 determines “Yes” in step S511, and in step S512, determines the count value p for the first inspection. Is set as the number of detections J (n) (= J (1)) of the S-shaped waveform signal.

  After the process of step S512, the controller 60 determines whether or not the variable n is “6” or more in step S513. If the variable n is not “6” or more, the controller 60 determines “No” in step S513, adds “1” to the variable n in step S514, and performs the processing in steps S508 to S512 described above. Execute. In this case, the state in which the variable n is switched from “1” to “2” is a state in which the objective lens 25 has reached the uppermost point position. In the second inspection, the control of the reciprocating signal generation circuit 36 The objective lens 25 is lowered from the highest point position to the lowest point position. Then, when the number of detections p of the S-shaped waveform signal (reverse S-shaped waveform signal) with respect to the reference level F (1) is detected during the descent and the objective lens 25 reaches the lowest point position, in step S512 This is set as the number of detections J (2) of the S-shaped waveform signal in the second inspection. Then, the objective lens 25 rises again from the lowest point position, and the variable n is updated by the processes of steps S513 and S514, and the processes of steps S508 to S512 are executed.

  When the circulation process consisting of steps S508 to S514 is performed six times, the variable n becomes “6”, the controller 60 determines “Yes” in step S513, and the number of detections for six times in step S515. The average value Jave (= {J (1) + J (2) +... + J (6)} / 6) of J (n) (n = 1 to 6) is calculated. Thereby, the objective lens 25 is reciprocated three times, and the average value Jave of the detection times J (n) for six times with respect to the reference level F (1) is calculated. In the present embodiment, the number of inspections is six, but other numbers may be performed.

  Next, in Step S516, the controller 60 determines whether or not a subtraction value Jave−H (2) obtained by subtracting the positive level corresponding S-character detection number H (2) from the calculated average value Jave is “1” or more. Determine whether or not. The subtraction value Jave−H (2) is “1” or more means that the number of detection times J (1) to J (6) in the six inspections is the number of detected S-curve H (2) corresponding to the positive level. In this case, it is considered that the positive amplitude value of the S-shaped waveform signal by the cover layer N0 is between the reference level F (1) and the reference level F (2). Therefore, in this case, the controller 60 determines “Yes” in step S516, and sets the recording layer number LNO to the positive level corresponding S-character detection number H (3) in step S517.

  On the other hand, when the subtraction value Jave−H (2) is less than “1”, only a part of the detection times J (1) to J (6) in the six inspections is the number of detected S-characters corresponding to the positive side level. This is the same as H (2). In this case, the influence of noise appears in the positive-level-corresponding S-shaped detection number H (1), and the positive-side amplitude value of the S-shaped waveform signal by the cover layer N0 is the reference level. It is considered that F (3) is exceeded. Therefore, in this case, the controller 60 determines “No” in step S516, and in step S518, the recording layer number LNO is smaller by “1” than the positive side level corresponding S-character detection number H (3). Set to the value H (3) -1. By such processing for determining the number of recording layers, even when the number of recording layers of the optical disc DK is not input and the number of recording layers in the BCA code cannot be read, the number of recording layers of the optical disc DK is automatically estimated. Is done.

h. Focus Retraction Routine The focus retraction routine is shown in detail in FIGS. 9A-9C, and its execution is started in step S600. After starting the execution, in step S601, the controller 60 determines whether the positive side level-corresponding S-character detection number H (3) is greater than the recording layer number LNO by “1” or more (H (3) ≧ LNO + 1). . If the positive side level-corresponding S-character detection number H (3) is larger than the recording layer number LNO by “1” or more, the controller 60 determines “Yes” in step S601 and executes the processes of steps S602 to S605. To do. Note that the positive level corresponding S-character detection number H (3) is larger than the recording layer number LNO by “1” or more means that the amplitude of the S-shaped waveform signal by the cover layer N0 is larger than the reference level F (3). It means that. In the processing of these steps S602 to S605, the variable n for designating any of the positive side level corresponding detection numbers H (1) to H (8) by the processing of steps S602 and S604 is changed from “4” to “1”. As long as the detected number H (n) corresponding to the positive side level is “1” or more than the number LNO of recording layers, the designation of the reference level H (8) with the maximum variable n is completed. Until it is determined as “No” in step S605, the circulation processing of steps S603 to S605 is repeatedly executed. If the positive side level-corresponding S-character detection number H (n) is not “1” or more than the recording layer number LNO, the controller 60 determines “No” in step S603 and advances the program to step S606. . If the variable n is “9” or more, the controller 60 determines “Yes” in step S605 and advances the program to step S606.

  In step S606, the controller 60 sets the S-curve detection level of the S-curve detection circuit 37 to a value F (n-1) / 2 that is half the reference level F (n-1). This reference level F (n-1) is the maximum reference from which the number of S-shaped waveform signals larger by “1” than the number of recording layers LNO is detected among the reference levels F (3) to F (8). Is a level. When the S-shaped waveform signal is as shown in FIG. 16A, the variable n is “5”, and the amplitude of the S-shaped waveform signal by the cover layer N0 and the recording layers N1 to N4 is from the reference level F (4). And one or more S-shaped waveform signals are below the reference level F (5). In this case, as indicated by a thick broken line in the figure, the reference level F (2) that is half of the reference level F (4) is set as the S-shaped detection level. The S-curve detection level set by the processing in steps S601 to S606 is always set to a value equal to or higher than the intermediate value of the reference levels F (1) and F (2), and is affected by noise due to the condition 3. There is nothing.

After the process of step S606, the controller 60 sets the variable k used for detection of the designated recording layer N _{DLN to} a value DLN + 1 that is larger by “1” than the designated recording layer number DLN in step S607. This is because the detection of the S-shaped waveform signal by the cover layer N0 is also used for detection of the designated recording layer _NDLN described later because the amplitude of the S-shaped waveform signal by the cover layer N0 is large.

  On the other hand, if the positive level corresponding S-character detection number H (3) is not equal to or greater than the value LNO + 1 obtained by adding “1” to the recording layer number LNO, the controller 60 determines “No” in step S601, The determination process of S608 is executed. Note that the positive side level-corresponding S-character detection number H (3) is not equal to or greater than the value LNO + 1 obtained by adding “1” to the recording layer number LNO. This means that the amplitude of the S-shaped waveform signal by the cover layer N0 is the reference level F (3 ) Means the following. In step S608, the controller 60 determines whether or not the positive side level-corresponding S-character detection number H (3) is equal to or greater than the recording layer number LNO. If the positive side level-corresponding S-character detection number H (3) is equal to or greater than the recording layer number LNO, the controller 60 determines “Yes” in step S608, and the positive-side level-corresponding S-character detection number H in step S609. It is determined whether (4) is equal to or greater than the recording layer number LNO. If the positive side level-corresponding S-character detection number H (4) is equal to or greater than the recording layer number LNO, the controller 60 determines “Yes” in step S609, and executes the processes of steps S610 to S613. In the processing of these steps S610 to S613, the variable n for designating any one of the reference levels H (1) to H (8) is sequentially increased from “5” by “1” by the processing of steps S610 and S612. Thus, as long as the positive side level-corresponding S-character detection number H (n) is equal to or greater than the recording layer number LNO, “No” is determined in step S613 until the variable n is designated as the maximum reference level H (8). And the circulation process of steps S611 to S613 is repeatedly executed. If the positive side level-corresponding S-character detection number H (n) is not greater than or equal to the recording layer number LNO, the controller 60 determines “No” in step S611 and advances the program to step S614. If the variable n is “9” or more, the controller 60 determines “Yes” in step S613 and advances the program to step S614.

  In step S614, the controller 60 determines whether or not the positive side level-corresponding S-character detection number H (2) is larger than the recording layer number LNO. If the amplitude of the S-shaped waveform signal by the cover layer N0 is larger than the reference level F (2) and the positive side level-corresponding S-shaped detection number H (2) is larger than the recording layer number LNO, the controller 60 proceeds to step S614. The determination is “Yes” and the program proceeds to step S615. In step S615, the controller 60 sets the S-shaped detection level of the S-shaped detection circuit 37 to an intermediate value {F (n) + F (2)} / 2 between the reference level F (n) and the reference level F (2). Set. In this case, the amplitude value of the S-shaped waveform signal by the cover layer N0 is between the reference level F (2) and the reference level F (3).

  On the other hand, if it is determined in step S614 that “No”, that is, the positive side level-corresponding S-character detection number H (2) is not greater than the recording layer number LNO, the controller 60 determines in step S616 that the S-character detection circuit. The S-shaped detection level of 37 is set to an intermediate value {F (n) + F (1)} / 2 between the reference level F (n) and the reference level F (1). In this case, the cover layer is based on the premise that the absolute value of the S-shaped amplitude level related to the cover layer N0 is larger than the absolute values of the reference levels F (1) and G (1), which is the condition 2. The amplitude value of the S-shaped waveform signal by N0 is between the reference level F (1) and the reference level F (2).

  In the processing of these steps S615 and S616, as shown in FIG. 16B, the maximum reference level F (n-1) in which the number of S-shaped waveform signals equal to the number of recording layers LNO is detected is determined as the reference level A. And the maximum reference level F (2) or F (1) at which the S-shaped waveform signal is detected by the cover layer N0 (that is, the number of detected S-characters corresponding to the positive side level adds “1” to the recording layer number LNO). If the maximum reference level F (2) or F (1)) that is equal to or greater than the value LNO + 1 is the reference level B, the S-shaped detection level is the reference level A + 1 and the reference level B that are “1” higher than the reference level A. Is set to an intermediate value (A + 1 + B) / 2. In FIG. 16B, the maximum reference level for detecting the number of S-shaped waveform signals equal to the number of recording layers LNO is the reference level F (5), and the S-shaped waveform signal is detected by the cover layer N0. The maximum reference level is the reference level F (2). The S-curve detection level set by the processing in steps S608 to S616 is always set to a value equal to or higher than the reference level F (3), and is not affected by noise due to the condition 3. Further, there is a level difference of “2” or more between the reference level A and the reference level B, and the S-shaped detection level is set to an intermediate value (A + 1 + B) / 2 between the reference level A + 1 and the reference level B. Since a difference larger than at least half of the reference level interval occurs between the S-shaped detection level and the reference level A and the reference level B, the S-shaped waveform due to the cover layer N0 and the recording layers N1 to N4. There is no error in comparing the amplitude of the signal and the S-shaped detection level.

  If the positive side level-corresponding S-character detection number H (3) is equal to or greater than the recording layer number LNO and the positive-side level-corresponding S-character detection number H (4) is less than the recording layer number LNO, the controller 60 Determines “Yes” and “No” in steps S608 and S609, respectively, and advances the program to step S617. In step S617, the controller 60 determines whether or not the positive level corresponding S-character detection number H (2) is equal to or less than the recording layer number LNO. The amplitude of the S-shaped waveform signal by the cover layer N0 is equal to or less than the reference level F (2), and the number of detected S-characters corresponding to the positive level H (2) is equal to or less than the number of recording layers LNO (actually equal to the number of recording layers LNO). If so, the controller 60 determines “Yes” in step S617, and sets the S-curve detection level of the S-curve detection circuit 37 to an intermediate level between the reference level F (3) and the reference level F (2) in step S618. Set the value {F (3) + F (2)} / 2. Also in this case, the cover layer N0 is based on the premise that the absolute value of the S-shaped amplitude level related to the cover layer N0 is larger than the absolute value of the reference levels F (1) and G (1), which is the condition 2. The amplitude value of the S-shaped waveform signal is between the reference level F (1) and the reference level F (2). The maximum reference level that exceeds all the amplitude values of the S-shaped waveform signals of the recording layers N1 to N4 is the reference level F (3).

  As described above, as a result of setting the S-shaped reference level to the value {F (3) + F (2)} / 2, there is no influence of noise due to the condition 3. In addition, since there is a difference of at least half the reference level interval between the S-shaped detection level and the reference level F (3) and the reference level F (2), the cover layer N0 and the recording layer N1. There is no error in comparing the amplitude of the S-shaped waveform signal by .about.N4 and the S-shaped detection level.

After the processing of steps S615, S616, and S618, the controller 60 sets the variable k used for detection of the designated recording layer N _DLN to the designated recording layer number DLN in step S619. This is because the detection of the S-shaped waveform signal by the cover layer N0 is not used for detection of the designated recording layer _NDLN described later because the amplitude of the S-shaped waveform signal by the cover layer N0 is small.

  Further, when the positive side level-corresponding S-shaped detection number H (3) is smaller than the recording layer number LNO, that is, the maximum reference level exceeding the amplitude of all S-shaped waveform signals by the recording layers N1 to N4 is the reference level F ( 3) In the case of the following, the controller 60 determines “No” in steps S601 and S608, and advances the program to step S640 and subsequent steps in FIG. 9C. In addition, the positive level-corresponding S-character detection number H (3) is equal to or greater than the recording layer number LNO, and the positive-side level-corresponding S-character detection number H (4) is smaller than the recording layer number LNO (that is, the recording layers N1 to N1). The maximum reference level that exceeds the amplitude of all the S-shaped waveform signals by N4 is F (3)), and the positive level corresponding S-shaped detection number H (2) is larger than the recording layer number LNO (ie, the cover). When the amplitude of the S-shaped waveform signal by the layer N0 is larger than the reference level F (2)), the controller 60 performs “No”, “Yes”, “No”, “No” in steps S601, S608, S609, and S617. Each determination is “No”, and the program proceeds to step S640 and thereafter in FIG. 9C. The processing after step S640 in FIG. 9C is when there is a possibility of erroneous detection of the designated recording layer if the S-shaped detection level is determined using the positive-level-corresponding S-shaped detection numbers H (1) to H (8). This will be described in detail later.

  After the processes in steps S607 and S619, the controller 60 executes the processes after step S620 in FIG. 9B. In step S620, an error count value ECT for counting the number of times when focus pull-in has failed is set to “0”. Next, the controller 60 clears the count value p for counting the number of S-shaped detections to “0” in step S621, and sets the detection polarity of the S-shaped waveform signal in the S-shaped detection circuit 37 to the positive polarity in step S622. The circulation processing of steps S623 to S626 is executed. In this circulation process, the controller 60 detects that the count value p is equal to the set variable k in step S626, or represents the highest point position from the reciprocating signal generation circuit 36 in step S624. Until the input of the signal is detected, the count value p is incremented by “1” in step S625 each time the input of the S-shaped detection signal from the S-shaped detection circuit 37 is detected in step S623. In this case, immediately after the above-described recording layer number determination routine of FIG. 8 ends, the reciprocating signal represents the position near the lowest point position, that is, the objective lens 25 is near the lowest point position. It is in. Therefore, in the circulation process of steps S623 to S626, the number of S-shaped waveform signals exceeding the set S-shaped detection level to the positive side while raising the objective lens 25 from the lowest point position to the uppermost position is counted. It will be detected as p.

  If the count value p becomes equal to the variable k during the cyclic processing of steps S623 to S626, the controller 60 determines “Yes” in step S626, executes the processing of steps S627 and S628, and then proceeds to step S670. This completes the execution of the focus pull-in routine. In step S627, the controller 60 stops the operations of the reciprocating signal generation circuit 36 and the S-shaped detection circuit 37. In step S628, the controller 60 starts the operation of the focus servo circuit 35. The drive circuit 33 starts driving the focus actuator 29 by using the focus servo signal from the focus servo circuit 35 instead of the reciprocation signal from the reciprocation signal generation circuit 36 by the processing of these steps S627 and S628. Thereby, the laser beam continues to be focused on the detection recording layer. That is, the focus is drawn into the detection recording layer. After the focus pull-in, as described above, by executing a program (not shown), data is recorded on the focus-recorded recording layer, or data recorded on the recording layer is reproduced.

  On the other hand, if a signal representing the position of the uppermost point is input from the reciprocation signal generation circuit 36 before the count value p becomes equal to the variable k during the cyclic processing consisting of the steps S623 to S626, the controller 60 causes the step S624. The determination is “Yes” and the program proceeds to step S629. In step S629, the controller 60 adds “1” to the error count value ECT. Next, in step S630, the controller 60 determines whether the error count value ECT is “3” or more. Wait for the input of a signal indicating. While waiting for the signal representing the lowest point position, the objective lens 25 is controlled by the reciprocating signal and moves from the highest point position toward the lowest point position. When the objective lens 25 reaches the lowest point position and a signal indicating the lowest point position is input from the reciprocating signal generation circuit 36 to the controller 60, the controller 60 determines “Yes” in step S631. Then, the processes of steps S621 to S626 described above are executed, and the recording layer corresponding to the variable k is started to be detected again. When the recording layer corresponding to the variable k is detected, that is, when the variable k is equal to the count value p, the focus pull-in in steps S627 and S628 described above is executed.

In such focus pull-in, in order to detect the designated recording layer N _DLN , the S-shaped detection level of the S-shaped detection circuit 37 is accurately set by the processing of steps S601 to S619 in FIG. 9A described above. The variable k to be used is also set accurately. Therefore, the focus pull-in control is appropriately performed on the designated recording layer N _DLN by the processing of steps S620 to S631 in FIG. 9B.

  On the other hand, when the error count value ECT is “3” or more, the controller 60 determines “Yes” in step S630, and executes the processes of steps S632 and S633. In step S632, the controller 60 displays an error on the display device 62 and notifies the operator of the failure of focus pull-in. In step S633, the controller 60 stops the operation of the entire apparatus. In this case, the controller 60 stops the execution of the program in step S671.

Next, the process of FIG. 9C will be described. In this process, when the positive S level detection level is set in the S detection circuit 37 using the positive level corresponding S detection numbers H (1) to H (8), the designated recording layer N _DLN is erroneously detected. If there is a possibility, the negative S level detection number L (1) to L (8) is used to set the negative S detection level in the S detection circuit 37, and the set S This is a process for executing the focus pull-in process using the character detection level.

In this case, the controller 60 clears the error count value ECT to “0” in step S640, and executes the S-curve detection level setting process in steps S641 to S652. The processing of steps S641 to S646 corresponds to the processing of steps S601 to S606 of FIG. 9A, and the negative level corresponding S-character detection number L (3) is greater than the value LNO + 1 by “1” larger than the recording layer number LNO. At a certain time, the controller 60 determines the S-curve detection level of the S-curve detection circuit 37 from the recording layer number LNO among the negative reference levels G (3) to G (8) by the processing of steps S641 to S646. Is also set to a value G (n−1) / 2 which is half of the minimum reference level (reference level at which the absolute value is maximum) G (n−1) at which a large number of S-shaped waveform signals by “1” is detected. . Further, the processing in step S647 corresponds to step S607 in FIG. 9A. In step S647, the controller 60 sets the variable k used for detection of the designated recording layer N _DLN to “1” in the recording layer number LNO. Is added to the value LNO + 1−DLN by subtracting the designated recording layer number DLN. Contrary to the case of FIG. 9B, the bottom recording is performed by moving the focus of the laser beam from the lower layer side to the upper layer side (cover layer N0 side), as described later. This is for counting from the layer.

  On the other hand, if the negative level corresponding S-character detection number L (3) is not equal to or greater than the value LNO + 1, the controller 60 determines “No” in step S641 and advances the program to step S648. In step S648, it is determined whether or not the negative level corresponding S-character detection number L (3) is equal to or greater than the recording layer number LNO. If the negative-level-corresponding S-character detection number L (3) is equal to or greater than the recording layer number LNO, the controller 60 determines “Yes” in step S648 and executes the processes of steps S649 to S652. The processing in steps S649 to S652 corresponds to the processing in steps S610 to S613 in FIG. 9A, and the controller 60 performs the negative reference levels G (4) to G (G) by the circulation processing in steps S649 to S652. 8), the first reference level G (n) at which the S-shaped waveform signal having the recording layer number LNO is no longer detected is detected, that is, the minimum reference level (absolutely) at which the S-shaped waveform signal having the recording layer number LNO is detected. A reference level G (n) which is smaller by “1” than the negative reference level (G (n−1) having the maximum value) is detected. Then, the S-curve detection level is set to a value G (n−1) / 2 that is half of the minimum reference level G (n−1) by the process of step S646 described above. Further, the variable k is also set to the same value LNO + 1−DLN as described above by the processing in step S647 described above. Contrary to the case of FIG. 9B, the same value is set so that the count of the number of S-shaped detections that will be described later will be changed from the lower layer side to the upper layer side (cover layer N0 side). This is because the detection of the S-shaped waveform signal by the cover layer N0 is not performed first because it is performed while moving.

  Further, when the negative level corresponding S-character detection number L (3) is smaller than the recording layer number LNO, the controller 60 determines “No” in step S648, and the above-described step S632 in FIG. 9B. Similar error display processing in step S653 and operation stop processing for the entire apparatus in step S654 similar to step S633 in FIG. 9B described above are executed, and execution of the program is stopped in step S671. This is because the negative-side level-corresponding S-shaped detection number L (3) is smaller than the recording layer number LNO. This is because it is determined that some abnormality not corresponding to “3), which is larger than the absolute value of G (3)” has occurred.

When the setting of the S-curve detection level and the variable k is completed, the controller 60 clears the count value m for counting the negative S-curve detection count to “0” in step S655, and in step S656. Waiting for input of a signal representing the position of the uppermost point from the reciprocating signal generation circuit 36. When the objective lens 25 reaches the uppermost point position and a signal representing the uppermost point position from the reciprocating signal generation circuit 36 is input to the controller 60, the controller 60 determines “Yes” in step S656, In step S657, the detection polarity of the S-shaped waveform signal in the S-shaped detection circuit 37 is set to negative polarity, and the circulation processing of steps S658 to S661 is executed. This circulation process corresponds to the above-described circulation process of steps S623 to S626 of FIG. 9B, and the signal indicating the position of the lowest point from the point where the count value m is used and the reciprocation signal generation circuit 46 is input. This is different from the circulation process of steps S623 to S626 in FIG. By the processing of steps S658 to S661, the S-shaped waveform signal (inverted S-shaped waveform signal) exceeding the set S-shaped detection level to the negative side while lowering the objective lens 25 from the highest point position to the lowest point position. The laser beam is focused on the designated recording layer N _DLN on condition that the count value m representing the number is equal to the set variable k.

When the laser beam is focused on the designated recording layer N _DLN , the controller 60 stops the operations of the reciprocating signal generation circuit 36 and the S-shaped detection circuit 37 by the process of step S662 similar to step S627. The operation of the focus servo circuit 35 is started by the process of step S663 similar to step S628, and the execution of the focus pull-in routine is ended in step S670. Accordingly, in this case as well, the focus is drawn into the designated recording layer N _DLN as in the case described above. Even after this focus pull-in, data is recorded on the focus-drawn recording layer or data recorded on the recording layer is reproduced by executing a program (not shown) as described above.

  On the other hand, if a signal indicating the lowest point position is input from the reciprocation signal generation circuit 36 before the count value m becomes equal to the variable k during the cyclic processing including the steps S658 to S661, the controller 60 In S659, “Yes” is determined, and the processes of steps S664 to S667 and S671 are executed. The processing of these steps S664 to S667, S671 is the same as the processing of steps S629, S630, S632, S633, S671 of FIG. 9B, and the error count is incremented for each input of the signal representing the lowest point position. When the value ECT becomes “3”, the controller 60 performs error display processing and operation stop processing of the entire apparatus by the processing of steps S666, S667, and S671, and stops the execution of the program. Until the error count value ECT reaches “3”, the controller 60 determines “No” in step S665, and the objective lens 25 reaches the uppermost position by the processing in step S656 described above and moves down. At the beginning, the circulation process of steps S658 to S661 is executed.

i. S-shaped waveform evaluation routine The S-shaped waveform evaluation routine is shown in detail in FIGS. 10A and 10B, and its execution is started in step S700. After the start of execution, when the positive-level-corresponding S-character detection number H (3) is larger than the recording layer number LNO by “1” or more (H (3) ≧ LNO + 1), the controller 60 performs steps S701 to S706. The slice level of the positive side binarization circuit 41 in the signal extraction circuit 40 is set. The processes in steps S701 to S706 are the same as those in steps S601 to S606 in FIG. 9A, and the process in step S706 is replaced with the setting of the S-character detection level of the S-character detection circuit 37 by the process in step S606. The only difference is that the slice level (corresponding to the S-shaped detection level) of the positive-side binarization circuit 41 is set. As a result, the slice level of the positive-side binarization circuit 41 is detected as many S-shaped waveform signals by “1” larger than the recording layer number LNO among the reference levels F (3) to F (8). Is set to a value F (n-1) / 2 which is half of the maximum reference level. After the process of step S706, the controller 60 includes, in step S707, the output instruction circuit 46 of the signal extraction circuit 40 including the S-shaped waveform signal from the cover layer N0 in the detected count value of the S-shaped waveform signal. The instruction information to represent is output. The output instruction circuit 46 stores the output instruction information.

  On the other hand, if the amplitude of the S-shaped waveform signal by the cover layer N0 is equal to or lower than the reference level F (3) and the positive side level-corresponding S-shaped detection number H (4) is equal to or larger than the recording layer number LNO, the controller 60 The slice level of the positive binarization circuit 41 in the signal extraction circuit 40 is set by the processing of S701, S708 to S716. The processes in steps S701 and S708 to S716 are the same as those in steps S601 and S608 to S616 in FIG. 9A, and the processes in steps S715 and S716 are performed in S of the S-character detection circuit 37 by the processes in steps S615 and S616. The only difference is that the slice level of the positive binarization circuit 41 is set instead of setting the character detection level. Therefore, as in the case of the focus pull-in routine of FIG. 9A described above, if the positive side level-corresponding S-character detection number H (2) is larger than the recording layer number LNO, the slice level of the positive side binarization circuit 41 is An intermediate value between the reference level F (n) that is one level higher than the maximum detected reference level F (n-1) of the number of S-shaped waveform signals equal to the number of recording layers LNO and the reference level F (2) {F (n) + F (2)} / 2 is set. On the other hand, if the positive level corresponding S-character detection number H (2) is not larger than the recording layer number LNO, an intermediate value {F (n) + F between the reference level F (n) and the reference level F (1). (1)} / 2 is set. Then, after the processing of steps S715 and S716, the controller 60 sends the S-shaped waveform signal from the cover layer N0 to the detected count value of the S-shaped waveform signal to the output instruction circuit 46 of the signal extraction circuit 40 in step S719. The instruction information indicating that it is not included is output. The output instruction circuit 46 stores the output instruction information.

  Further, the amplitude of the S-shaped waveform signal by the cover layer N0 is equal to or lower than the reference level F (3), the positive-side level-corresponding S-character detection number H (3) is greater than or equal to the recording layer number LNO, and the positive-side level-corresponding S-character detection. If the number H (4) is not equal to or greater than the recording layer number LNO, the controller 60 slices the positive-side binarization circuit 41 in the signal extraction circuit 40 by the processing in steps S701, S708, S709, S717, S718, and S720. Set the level. The processes of steps S701, S708, S709, S717, and S718 except for step S720 are the same as the processes of steps S601, S608, S609, S617, and S618 in FIG. 9A. The only difference is that the slice level of the positive binarization circuit 41 is set instead of the setting of the S-character detection level of the character detection circuit 37. Therefore, if the positive side level-corresponding S-character detection number H (2) is equal to or smaller than the recording layer number LNO, the slice level of the positive side binarization circuit 41 is the reference level F (3) as in the case of the focus pull-in. And the reference value F (2) is set to an intermediate value {F (3) + F (2)} / 2. After the process of step S718, the controller 60 outputs the S-shaped waveform signal from the cover layer N0 to the detected count value of the S-shaped waveform signal to the output instruction circuit 46 of the signal extraction circuit 40 in the step S719. Outputs instruction information indicating that it is not included. The output instruction circuit 46 stores the output instruction information.

  Further, even when the positive side level-corresponding S-character detection number H (4) is not greater than or equal to the recording layer number LNO, the controller 60 determines that the positive-side level-corresponding S-character detection number H (2) is not less than or equal to the recording layer number LNO. In step S717, “No” is determined, and the process of step S720 is executed. In this step S720, the slice level of the positive binarization circuit 41 is set to an intermediate value {F (2) + F (1)} / 2 between the reference level F (2) and the reference level F (1). The This is because, in the evaluation of the S-shaped waveform signal, the extraction of the S-shaped waveform signal is prioritized over the influence of noise, unlike the case of the focus pull-in. In this state, as shown in FIG. 16C, the maximum reference level A in which the number of S-shaped waveform signals equal to the number of recording layers LNO is detected is the reference level F (3), and the cover layer N0 This is the case where the maximum reference level B in which the S-shaped waveform signal is detected is the reference level F (2). As shown by the thick broken line, the amplitude value of the S-shaped waveform signal by the cover layer N0 is set as the slice level. Exceeds the value {F (2) + F (1)} / 2. Therefore, in this case, in step S721, the controller 60 indicates that the detection instruction value of the S-shaped waveform signal includes the S-shaped waveform signal from the cover layer N0 with respect to the output instruction circuit 46 of the signal extraction circuit 40. The instruction information to represent is output. The output instruction circuit 46 stores the output instruction information.

  Also, in this S-shaped waveform evaluation routine, when the number of detected S-shaped H corresponding to the positive side level H (3) is smaller than the number of recording layers LNO, the controller 60 determines “No” in step S708. The error display process in step S722 similar to step S632 in FIG. 9B described above, the operation stop process for the entire apparatus in step S723 similar to step S633 in FIG. 9B described above are executed, and the program is executed in step S751. Stop. This is because the positive side level-corresponding S-curve detection number H (3) is smaller than the recording layer number LNO, “the absolute value of the S-curve amplitude level relating to the recording layers N1 to N4 is the reference level F ( 3) is larger than the absolute value of G (3) ”, and it is determined that some abnormality has occurred.

  After the processes in steps S707, S719, and S721, the controller 60 executes the processes after step S730 in FIG. 10B. When the negative-level-corresponding S-character detection number L (3) is larger than the recording layer number LNO by “1” or more (L (3) ≧ LNO + 1), the controller 60 performs the signal extraction circuit 40 through the processing of steps S730 to S735. The slice level of the negative side binarization circuit 42 is set. The processes in steps S730 to S735 are the same as those in steps S641 to S646 in FIG. 9C, and the process in step S735 replaces the setting of the S-character detection level of the S-character detection circuit 37 by the process in step S646. The only difference is that the slice level of the negative side binarization circuit 42 is set. As a result, the slice level of the negative-side binarization circuit 42 is detected as a number of S-shaped waveform signals that are larger by “1” than the recording layer number LNO among the reference levels G (3) to G (8). The value G (n−1) / 2 is half of the minimum (maximum absolute value) reference level.

  Further, if the negative side level-corresponding S-shaped detection number L (3) is not “1” or more larger than the recording layer number LNO and the negative-side level-corresponding S-shaped detection number L (3) is equal to or larger than the recording layer number LNO. The controller 60 sets the slice level of the negative-side binarization circuit 42 in the signal extraction circuit 40 by the processes of steps S730, S736 to S740, and S735. The processes in steps SS730, S736 to S740, and S735 are the same as those in steps S641, S648 to S652, and S646 in FIG. 9C. The only difference is that the slice level of the negative side binarization circuit 42 is set instead of setting the character detection level. Thus, the slice level of the negative-side binarization circuit 42 is the minimum (absolute value) in which the number of S-shaped waveform signals equal to the recording layer number LNO is detected among the reference levels G (3) to G (8). Is a value G (n-1) / 2 which is half of the reference level.

In this case, instruction information indicating whether or not the S-shaped waveform signal from the cover layer N0 is included in the detection count value of the S-shaped waveform signal is output to the output instruction circuit 46 of the signal extraction circuit 40. Absent. This is because when the designated recording layer N _DLN is detected while the objective lens 25 is moved from the lowermost layer N4 side to the uppermost layer N1 side (that is, the cover layer N0 side), the S-shaped waveform signal from the cover layer N0 is all This is because there is no problem because it occurs last in the S-shaped waveform signal.

  In the S-shaped waveform evaluation routine of FIG. 10B, if the negative level-corresponding S-shaped detection number L (3) is smaller than the recording layer number LNO, the controller 60 returns “No” in step S736. Then, the error display process in step S741 similar to step S632 in FIG. 9B described above, and the operation stop process for the entire apparatus in step S742 similar to step S633 in FIG. 9B described above are executed, and the program is executed in step S751. Stop running. This is because the negative-side level-corresponding S-shaped detection number L (3) is smaller than the recording layer number LNO, the absolute value of the S-shaped amplitude level for the recording layers N1 to N4 in the condition 1 3) is larger than the absolute value of G (3) ”, and it is determined that some abnormality has occurred.

  After the processing in step S735, the controller 60 stops the operation of the S-shaped detection circuit 37 in step S743, and outputs the designated recording layer number DLN and the recording layer number LNO to the output instruction circuit 46 in step S744. The output instruction circuit 46 stores the output designated recording layer number DLN and the number LNO of recording layers. Next, the controller 60 instructs the output instruction circuit 46 to start operation in step S745, instructs the signal analysis device 50 to take in the signal in step S746, and executes the S-shaped waveform signal evaluation routine in step S750. End execution.

g. S-shaped Waveform Extraction Program The output instruction circuit 46 starts executing the S-shaped waveform signal extraction program shown in FIGS. 11A and 11B in response to an operation instruction from the controller 60. After starting the execution, in step S801, the output instruction circuit 46 determines whether or not the stored instruction information indicates that the detection count value of the S-shaped waveform signal includes the cover layer N0. If the determination is affirmative, the output instruction circuit 46 determines “Yes” in step S801, and sets the variable m to “1” in step S802. If the determination is negative, the output instruction circuit 46 determines “No” in step S801, and sets the count value m to “0” in step S803. That is, when the objective lens 25 is moved upward from the lowest point position and the S-shaped waveform signal by the cover layer N0 exceeds the set slice level in the positive-side binarization circuit 41, the variable m is set to “1”, otherwise it is set to “0”. After the processes in steps S802 and S803, the output instruction circuit 46 waits until the objective lens 25 reciprocating in step S804 reaches the lowest point position.

  When the objective lens 25 reaches the lowest point position and a signal indicating the lowest point position is input from the reciprocating signal generation circuit 36 to the output instruction circuit 46, the output instruction circuit 46 returns “Yes” in step S804. In step S805, the count value n is cleared to “0”. The count value n is the number of S-shaped waveform signals that exceed the slice level set by the positive-side binarization circuit 41 when the objective lens 25 is moved upward from the lowest point position, that is, taken out. This is a count value for counting the number of positive pulses output from the signal generation circuit 45.

  After the process of step S805, the output instruction circuit 46 executes the circulation process of steps S806 to S809. In this cyclic processing, the output instruction circuit 46 detects that the count value n is equal to the value DLN + m obtained by adding the variable m to the designated recording layer number DLN in step S809, or the reciprocating signal in step S807. Every time a change from the low level to the high level of the positive side extraction signal input from the extraction signal generation circuit 45 is detected in step S806 until the input of the signal representing the highest point position from the generation circuit 36 is detected. In step S808, the count value n is incremented by "1". The change from the low level to the high level of the positive side extraction signal corresponds to the detection of the S-shaped waveform signal when the objective lens 25 is moved from the upper layer side to the lower layer side. Therefore, in the circulation process of steps S806 to S809, the number of S-shaped waveform signals exceeding the set slice level to the positive side while raising the objective lens 25 from the lowest point position to the highest point position is used as the count value n. Will be detected.

If the count value n becomes equal to the value DLN + m during the cyclic processing in steps S806 to S809, the output instruction circuit 46 determines “Yes” in step S809 and advances the program to step S810 and subsequent steps. Note that the count value n being equal to the value DLN + m means that an S-shaped waveform signal is being output by the designated recording layer N _DLN . In step S810, the output instruction circuit 46 instructs the extraction signal generation circuit 45 to start generating a positive side extraction signal. In step S811, the output instruction circuit 46 outputs a high level of the positive side extraction signal input from the extraction signal generation circuit 45. Wait for a change from level to low level. If there is a change, the output instruction circuit 46 determines “Yes” in step S811, and instructs the extraction signal generation circuit 45 to end generation of the positive-side extraction signal in step S812. As a result, the extraction signal generation circuit 45 outputs the gate signal shown on the left side of FIG. 14H to the gate circuit 47, and the gate circuit 47 uses the focus error signal from the focus error signal generation circuit 34, that is, the designated recording layer N _DLN . The S-shaped waveform signal is output to the signal analysis device 50.

After the processing of step S812, the output instruction circuit 46 supplies the output instruction circuit 46 with a signal representing the uppermost point position from the reciprocation signal generation circuit 36 when the objective lens 25 reaches the uppermost point position in step S813. Wait until. In this case, the objective lens 25 is moving from the upper layer side to the lower layer side, and in the next process, the designated recording layer N _DLN is detected while moving the objective lens 25 from the lower layer side to the upper layer side. When the signal indicating the uppermost point position is supplied from the reciprocating signal generating circuit 36 to the output instruction circuit 46, the output instruction circuit 46 determines “Yes” in step S813, and the program is executed in the step of FIG. 11B. Proceed to S820. When the detection signal indicating the uppermost point position is input from the reciprocating signal generation circuit 36 during the circulation processing of the steps S806 to S809, the output instruction circuit 46 determines “Yes” in step S807, The program proceeds to step S820 in FIG. 11B. In this case, the gate signal is not output from the extraction signal generation circuit 45 to the gate circuit 47, and the focus error signal, that is, the S-shaped waveform signal is not output to the signal analysis device 50.

Next, the process of FIG. 11B will be described. In this case, since the number of detections of the S-shaped waveform signal is counted while moving the objective lens 25 from the lower layer side to the upper layer side, whether or not the S-shaped waveform signal is detected by the cover layer N0 is the detection of the designated recording layer _NDLN. Regardless, the setting process of the variable m in steps S801 to S803 in FIG. 11A described above is not necessary. First, the output instruction circuit 46 clears the count value n to “0” in step S820. The count value n in this case is the number of S-shaped waveform signals exceeding the slice level set by the negative side binarization circuit 42 when the objective lens 25 is moved downward from the uppermost position. That is, it is a count value for counting the number of positive pulses output from the extraction signal generation circuit 45.

  After the process of step S820, the output instruction circuit 46 executes the circulation process of steps S821 to S824. In this cyclic processing, the output instruction circuit 46 detects that the count value n is equal to the value LNO + 1−DLN obtained by subtracting the designated recording layer number DLN from the value obtained by adding “1” to the recording layer number NLO in step S824. Until the input of the signal representing the lowest point position from the reciprocating signal generation circuit 36 is detected in step S822, or the negative side extraction signal input from the extraction signal generation circuit 45 in step S821. Every time a change from the low level to the high level is detected, the count value n is incremented by “1” in step S823. The change of the negative side extraction signal from the low level to the high level corresponds to the detection of the S-shaped waveform signal when the objective lens 25 is moved from the lower layer side to the upper layer side. Therefore, in the circulation processing of steps S821 to S824, the count value n is the number of S-shaped waveform signals that exceed the set slice level to the negative side while lowering the objective lens 25 from the highest point position to the lowest point position. Will be detected.

If the count value n becomes equal to the value LNO + 1−DLN during the cyclic processing in steps S821 to S824, the output instruction circuit 46 determines “Yes” in step S824 and advances the program to step S825 and subsequent steps. Note that the count value n being equal to the value LNO + 1−DLN means that the S-shaped waveform signal from the designated recording layer N _DLN is being output. The output instruction circuit 46 instructs the extraction signal generation circuit 45 to start generating a negative side extraction signal in step S825, and the high level of the negative side extraction signal input from the extraction signal generation circuit 45 in step S826. Wait for the change from low to low. If there is a change, the output instruction circuit 46 determines “Yes” in step S826, and instructs the extraction signal generation circuit 45 to end generation of the negative side extraction signal in step S827. As a result, the extraction signal generation circuit 45 outputs the gate signal shown on the right side of FIG. 14 (H) to the gate circuit 47. The gate circuit 47 uses the focus error signal from the focus error signal generation circuit 34, that is, the designated recording layer N _DLN . The S-shaped waveform signal is output to the signal analysis device 50.

  After the process of step S827, the output instruction circuit 46 supplies the output instruction circuit 46 with a signal representing the lowest point position from the reciprocation signal generation circuit 36 when the objective lens 25 reaches the lowest point position in step S828. Wait until When a signal indicating the lowest point position is supplied from the reciprocating signal generating circuit 36 to the output instruction circuit 46, the output instruction circuit 46 determines “Yes” in step S828, and the program is transferred to step S829. Proceed. When the input of the signal representing the lowest point position from the reciprocating signal generation circuit 36 is detected during the circulation processing in steps S821 to S824, the output instruction circuit 46 determines “Yes” in step S822. Then, the program proceeds to step S829. In this case, the gate signal is not output from the extraction signal generation circuit 45 to the gate circuit 47, and the focus error signal, that is, the S-shaped waveform signal is not output to the signal analysis device 50.

In step S829, the output instruction circuit 46 determines whether or not the user has instructed the end of the evaluation of the S-shaped waveform signal. This instruction is given by the user using the input device 61 and is supplied from the controller 60. If there is no instruction to end the evaluation of the S-shaped waveform signal, the output instruction circuit 46 determines “No” in step S829 and returns the program to step S805 of FIG. 11A. As a result, the positive and negative S-shaped waveform signals relating to the designated recording layer N _DLN are extracted again from the focus error signal and supplied to the signal analysis device 50.

When the user instructs the end of the evaluation of the S-shaped waveform signal, the output instruction circuit 46 ends the extraction of the S-shaped waveform signal by the extraction signal generation circuit 45. The S-shaped waveform signal supplied to the signal analysis device 50 as described above is used for evaluation using an oscilloscope or the like as described above. In this case, since the designated recording layer N _DLN is accurately designated, the S-shaped waveform signal related to the designated recording layer N _DLN is also accurately evaluated.

h. In addition, the implementation of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  In the above embodiment, in determining the positive and negative S-shaped amplitude vicinity levels (maximum and minimum reference levels) F (8) and L (8), the S-shaped amplitude vicinity level setting in FIGS. 5A and 5B is set. In the routine, while changing the S-shaped detection level, the S-shaped detection level when the number of detected S-shaped waveform signals changes from “1” to “0” is set to the maximum and minimum reference levels F (8), L (8). However, instead of this, as indicated by a broken line in FIG. 1, the maximum amplitude for detecting the positive and negative maximum peak values (maximum and minimum instantaneous values) of the focus error signal from the focus error signal generation circuit 34, respectively. The measurement circuit 71 is connected between the focus error signal generation circuit 34 and the controller 60, and the maximum peak values on the positive side and the negative side detected by the maximum amplitude measurement circuit 71 are set to the maximum and minimum reference levels F (8), It may be L (8).

  In this case, the maximum amplitude measuring circuit 71 includes a general peak hold circuit including an operational amplifier, a resistor, a diode, a capacitor, and the like, and an A / D conversion circuit. The maximum amplitude measuring circuit 71 is set so that the polarity of the input signal is set to positive polarity by the controller 60 and its operation is started and controlled so that the objective lens 25 is moved from the lowest point position to the highest point position (or from the highest point position to the lowest point). After changing to the lower point position), the voltage (that is, the maximum peak value on the positive side) held in the peak hold circuit is A / D converted and supplied to the controller 60. Next, in the maximum amplitude measurement circuit 71, the polarity of the input signal is set to the negative polarity by the controller 60, and the objective lens 25 is changed from the highest point position to the lowest point position (or from the lowest point position to the highest point position). Then, the voltage (that is, the negative peak value on the negative side) held in the peak hold circuit is A / D converted and supplied to the controller 60. Then, the controller 60 may set the supplied positive and negative maximum peak values as the maximum and minimum reference levels F (8) and L (8), respectively. According to this, the maximum and minimum reference levels F (8) and L (8) are set only by reciprocating the objective lens 25 once, and the maximum and minimum reference levels F (8) and L (8) are set in a short time. Can be set.

  Further, in the above embodiment, a value slightly larger than the maximum amplitude value of all the S-shaped waveform signals (that is, the S-shaped amplitude vicinity level) is maximized by the processing of the S-shaped amplitude vicinity level setting routine of FIGS. 5A and 5B. And the minimum reference levels F (8) and L (8) are set, and then the maximum and minimum reference levels F (8) and L (8) are divided into a plurality by the processing of the reference level setting routine of FIG. The reference levels F (1) to F (7) and L (1) to L (7) are set. However, these processes may be omitted, and a plurality of reference levels having a predetermined interval may be prepared in advance. In this case, in the level-corresponding S-character detection number routine of FIG. 7, the recording layer number determination routine of FIG. 8, the focus pull-in routines of FIGS. 9A to 9C, and the S-shaped waveform evaluation routines of FIGS. Instead of 1) to F (8) and L (1) to L (8), a plurality of reference levels prepared in advance may be used.

  In the above embodiment, when the detected number H (3) of the S-shaped waveform signal based on the reference level F (3) is the recording layer number LNO, the processing in steps S608 to S618 in FIG. When the level difference between the reference level at which an equal number of S-shaped waveform signals are detected and the reference level at which a number of S-shaped waveform signals larger by “1” than the number of recording layers LNO is detected is “1” or less. In addition, the focus pull-in is performed by detecting the negative S-shaped waveform signal in steps S641 to S663 in FIG. 9C. However, instead of this, the condition of focus pull-in by detecting the negative S-shaped waveform signal is relaxed, and the reference level at which the number of S-shaped waveform signals equal to the number of recording layers LNO is detected, and the number of recording layers LNO. When the level difference from the reference level where a number of S-shaped waveform signals larger by “1” is detected is “2” or less, and / or the number of detected S-shaped waveform signals H (3 by the reference level F (3) ) Is the recording layer number LNO, focus pull-in by detecting the negative S-shaped waveform signal in steps S641 to S663 in FIG. 9C may be performed. According to this, the possibility of erroneous detection of the S-shaped waveform signal by the cover layer N0 can be reduced, and more accurate focus pull-in can be performed.

Further, in the above embodiment, the positive level corresponding S-character detection numbers H (1) to H (n) are determined by the processing of the level-corresponding S-character detection number routine of FIG. L (1) to L (8) are determined, and the S level detection level using the positive side level corresponding S-shaped detection numbers H (1) to H (n) by the processing of the focus pull-in routine of FIGS. 9A and 9B. And the focus is _drawn into the designated recording layer N _DLN . 9A and 9B, when focus pull-in is impossible, the S-shaped detection level is determined by using the negative-level-corresponding S-shaped detection numbers L (1) to L (n), and the designated recording layer N _Added focus _pull to _DLN . However, the optical disk DK is limited, and any one of the positive side level corresponding S-shaped detection numbers H (1) to H (n) and the negative side level corresponding S-shaped detection numbers L (1) to L (8). When the focus pull-in using one of the level-corresponding detection numbers is sufficient, only the level-corresponding S-character detection number on either the positive side or the negative side is detected, and the one level-corresponding S-character detection number is detected. Focus pull-in may be performed using only. According to this, the setting of the S-shaped amplitude vicinity level (maximum and minimum reference levels) F (8), L (8), the level corresponding S-shaped detection numbers H (1) to H (n), L (1) to In the detection of L (8) and the focus pull-in, the number of reciprocations of the objective lens 25 can be reduced to half, and the time until the focus pull-in can be shortened.

  In the above embodiment, the reference levels F (1) to F (n), G (1) are obtained by equally dividing the S-shaped amplitude vicinity levels (maximum and minimum reference levels) F (8) and L (8). ) To G (n) are calculated, but they are not necessarily equally divided. For example, the interval between the S-shaped amplitude vicinity levels (maximum and minimum reference levels) F (8) and G (8) may be widened and narrowed toward the reference levels F (1) and G (1). . Also, the number of these reference levels is not limited to “8”, and may be larger or smaller than “8” depending on the type of the optical disk DK.

  In the above embodiment, the S-curve detection level and the slice level in the focus pull-in routines of FIGS. 9A to 9C and the S-curve waveform evaluation routines of FIGS. 10A and 10B are half the values of one specific reference level. Or an intermediate value between two specific reference levels. However, instead of the half value or the intermediate value, an appropriate value within a predetermined range from the half value or the intermediate value may be set.

  Further, in the above embodiment, the controller 60 utilizes the detection of the S-shaped waveform signal by the S-shaped detection circuit 37, the S-shaped amplitude neighborhood level setting routine of FIGS. 5A and 5B, and the level-corresponding S-shaped of FIG. The detection number routine, the recording layer number determination routine of FIG. 8, and the focus pull-in routines of FIGS. 9A to 9C are executed. Further, an S-shape by the signal extraction circuit 40 (positive side binarization circuit 41, negative side binarization circuit 42, positive side extraction signal generation circuit 43, negative side extraction signal generation circuit 44, and extraction signal generation circuit 45). Using the detection of the waveform signal, the controller 60 executes the processing of the S-shaped waveform evaluation routine of FIGS. 10A and 10B. However, instead of this, the S-shaped amplitude vicinity level setting routine of FIGS. 5A and 5B, the level-corresponding S-shaped detection number routine of FIG. 7, the recording layer number determination routine of FIG. 8, and the focus pull-in routines of FIGS. 9A to 9C In this process, the signal extraction circuit 40 (positive side binarization circuit 41, negative side binarization circuit 42, positive side extraction signal generation circuit 43, negative side extraction signal generation circuit 44, and extraction signal generation circuit 45). You may make it utilize the detection of an S-shaped waveform signal. Further, the detection of the S-shaped waveform signal by the S-shaped detection circuit 37 may be used for the processing of the S-shaped waveform evaluation routine of FIGS. 10A and 10B.

  Furthermore, in the above-described embodiment, an example in which the present invention is applied to an apparatus for inspecting the recording layers N1 to Nz of the multilayer optical disc DK has been described. However, the present invention can be applied to an inspection apparatus for inspecting the optical pickup 20 in addition to the inspection apparatus. Regarding the focus pull-in process, a laser beam is applied to a designated recording layer when data is written to or read from a designated recording layer of a multilayer optical disc DK in a normal optical disc apparatus. It can also be applied when focusing.

1 is a block diagram schematically showing an entire optical disk inspection apparatus according to an embodiment of the present invention. It is a block diagram which shows the detail of the signal extraction circuit of FIG. It is a flowchart which shows the main program performed by the controller of FIG. It is a flowchart which shows the user setting routine of FIG. It is a flowchart which shows the first half part of the S-shaped amplitude vicinity level setting routine of FIG. It is a flowchart which shows the second half part of the said S-shaped amplitude vicinity level setting routine. It is a flowchart which shows the reference | standard level setting routine of FIG. 4 is a flowchart showing a level-corresponding S-character detection number routine of FIG. 4 is a flowchart showing a recording layer number determination routine of FIG. 3. FIG. 4 is a flowchart showing a front part of a focus pull-in routine of FIG. 3. It is a flowchart which shows the intermediate part of the said focus drawing-in routine. It is a flowchart which shows the rear part of the said focus drawing-in routine. It is a flowchart which shows the first half part of the S-shaped waveform evaluation routine of FIG. It is a flowchart which shows the second half part of the said S-shaped waveform evaluation routine. It is a flowchart which shows the first half part of the S-shaped waveform extraction program performed by the output instruction | indication circuit of FIG. It is a flowchart which shows the second half part of the said S-shaped waveform extraction program. It is a schematic sectional drawing of a multilayer optical disk. It is a figure for demonstrating the relationship between the reciprocating motion of an objective lens, and a focus error signal. It is a signal waveform diagram for demonstrating the action | operation of a signal extraction circuit. It is a waveform diagram of a focus error signal for explaining the setting operation of the S-shaped amplitude vicinity level (maximum reference level F (8)). It is a waveform diagram of a focus error signal for explaining a reference level setting operation. It is a wave form diagram which shows the relationship between the focus error signal and detection level for demonstrating the conventional problem.

Explanation of symbols

DK: optical disk, 10: rotating device, 20: optical pickup, 34: focus error signal generation circuit, 35: focus servo circuit, 36: reciprocating signal generation circuit, 37: S-shaped detection circuit, 40: signal extraction circuit, 50 ... Signal analysis device, 60 ... Controller, 71 ... Maximum amplitude measurement circuit

Claims (12)

A laser light source for emitting laser light;
An optical means including an objective lens for focusing the laser light emitted from the laser light source on the recording layer of the optical disc and deriving reflected light from the recording layer of the optical disc;
A photodetector that receives the reflected light derived by the optical means and outputs a detection signal corresponding to the received reflected light;
In an optical disk recording layer detection device comprising an actuator that drives the objective lens to displace the objective lens in the optical axis direction of the laser beam.
A focus error signal generating means for generating a focus error signal based on the detection signal output from the photodetector;
When the objective lens is displaced in the optical axis direction, an S-shaped waveform signal in the focus error signal is detected on condition that the instantaneous value of the focus error signal generated by the focus error signal generation means exceeds the detection level. S-shaped detecting means for
The detection level in the S-shaped detection means is sequentially set to a plurality of reference levels, and the actuator is driven and controlled so that the objective lens is displaced from the lowest point position to the highest point position for each set reference level. Or a level-corresponding S-curve detecting means for detecting the number of S-curve waveform signals detected by the S-curve detecting means for each of the reference levels.
A magnitude relationship between the plurality of reference levels and the amplitude value of the S-shaped waveform signal is determined based on the number of S-shaped waveform signals respectively detected by the level-corresponding S-shaped detecting means and corresponding to the plurality of reference levels. Detecting level setting means for setting a detection level of the S-shaped detecting means using the plurality of reference levels according to the determination result;
In a state where the detection level of the S-shaped detection means is set by the detection level setting means, the actuator is driven and controlled to displace the objective lens from the lowest point position toward the highest point position or from the highest point position. While displacing toward the lowest point position, the number of S-shaped waveform signals detected by the S-shaped detecting means is counted, and the counted number of S-shaped waveform signals corresponds to the designated recording layer. A recording layer detection apparatus for an optical disc, comprising: a designated recording layer detection unit that detects a designated recording layer on the condition that In the optical disk recording layer detection device according to claim 1,
In the detection level setting means, the number of S-shaped waveform signals detected by the level-corresponding S-shaped detection means with respect to a predetermined one of the plurality of reference levels is greater than the number of recording layers of the optical disc. When the value is larger by “1”, the number of S-shaped waveform signals detected by the level-corresponding S-shaped detection means is smaller than the maximum reference level larger by “1” than the number of recording layers of the optical disc. The detection level is set as a detection level of the detection means, and the designated recording layer detection means confirms that the counted number of S-shaped waveform signals is larger by “1” than a value indicating the designated recording layer. An optical disk recording layer detection device that detects a recording layer specified by a condition. In the recording layer detection device for an optical disc according to claim 1 or 2,
The detection level setting means detects the maximum reference level in which the number of S-shaped waveform signals detected by the level-corresponding S-character detecting means is “1” larger than the number of recording layers of the optical disc, and the level-corresponding S-character detection. When the level difference from the maximum reference level in which the number of S-shaped waveform signals detected by the means is equal to the number of recording layers of the optical disc is greater than or equal to a predetermined value, the value between the two maximum reference levels is determined as the S-shape. The specified recording layer is set on the condition that the specified recording layer detecting means sets the number of the counted S-shaped waveform signals to a value indicating the specified recording layer. Detecting recording layer of optical disc. The optical disk recording layer detection apparatus according to any one of claims 1 to 3, further comprising:
The focus is generated by the focus error signal generating means by driving the actuator to displace the objective lens from the lowest point position toward the highest point position or from the highest point position toward the lowest point position. Maximum reference level setting means for detecting a maximum amplitude value of the S-shaped waveform signal included in the error signal or a value near the maximum amplitude value and setting the detected maximum amplitude value or the vicinity value as a maximum reference level;
An optical disk recording layer detecting apparatus comprising: a plurality of reference level setting means for setting the plurality of reference levels by dividing the maximum reference level set by the maximum reference level setting means by a predetermined number. The optical disk recording layer detection apparatus according to any one of claims 1 to 4, further comprising:
Based on the change in the number of S-shaped waveform signals corresponding to the plurality of reference levels detected by the level-corresponding S-shaped detecting means, the number of S-shaped waveform signals corresponding to the plurality of reference levels is changed to the cover layer of the optical disc. An optical disk recording layer detecting device provided with recording layer number detecting means for determining whether or not an S-shaped waveform signal is included and detecting the number of recording layers of the optical disk according to the determination result. The optical disk recording layer detection device according to any one of claims 1 to 5, further comprising:
Focus servo means for driving and controlling the actuator so that the laser beam continues to be focused on one of the plurality of recording layers of the optical disk based on the focus error signal generated by the focus error signal generating means;
When a designated recording layer is detected by the designated recording layer detection means, drive control of the actuator by the designated recording layer detection means is stopped, and the focus servo means is operated so that the designated recording layer of the optical disc An optical disk recording layer detecting device comprising: a focus pull-in means for continuously focusing the laser beam on the optical disk. The optical disk recording layer detection device according to any one of claims 1 to 5, further comprising:
When a designated recording layer is detected by the designated recording layer detection means, an S-shaped waveform signal is outputted to a signal analyzer for analyzing the S-shaped waveform signal, by outputting the S-shaped waveform signal from the designated recording layer. An optical disk recording layer detection apparatus comprising output means. In the optical disk recording layer detection device according to claim 7,
The S-shaped detection means includes a condition in which the instantaneous value of the focus error signal generated by the focus error signal generation means exceeds a detection level when the objective lens is displaced in the optical axis direction. Comprising first and second S-shaped detecting means for detecting an S-shaped waveform signal;
The level-corresponding S-curve detection means sequentially sets the detection level in the first S-curve detection means to a plurality of reference levels, and controls the actuator to drive the objective for each of the set reference levels. The number of S-shaped waveform signals detected by the first S-shaped detector for each reference level by displacing the lens from the lowest point position to the highest point position or from the highest point position to the lowest point position. Detect
The detection level setting means sets the detection level of the second S-shaped detection means using the plurality of reference levels based on the number of S-shaped waveform signals detected by the level corresponding S-shaped detection means. And the designated recording layer detecting means controls the actuator to drive the objective lens from the lowest point position while the detection level of the second S-shaped detecting means is set by the detection level setting means. Recording layer detection of an optical disc that counts the number of S-shaped waveform signals detected by the second S-shaped detecting means while being displaced toward the highest point position or displaced from the highest point position toward the lowest point position apparatus. A laser light source for emitting laser light;
An optical means including an objective lens for focusing the laser light emitted from the laser light source on the recording layer of the optical disc and deriving reflected light from the recording layer of the optical disc;
A photodetector that receives the reflected light derived by the optical means and outputs a detection signal corresponding to the received reflected light;
An actuator that drives the objective lens to displace the objective lens in the optical axis direction of the laser beam;
A focus error signal generating means for generating a focus error signal based on the detection signal output from the photodetector;
When the objective lens is displaced in the optical axis direction, an S-shaped waveform signal in the focus error signal is detected on condition that the instantaneous value of the focus error signal generated by the focus error signal generation means exceeds the detection level. An optical disk recording layer detection method applied to an apparatus comprising S-shaped detection means for
The detection level in the S-shaped detection means is sequentially set to a plurality of reference levels, and the actuator is driven and controlled so that the objective lens is displaced from the lowest point position to the highest point position for each set reference level. Or a level-corresponding S-curve detection process for detecting the number of S-curve signals detected by the S-curve detection means for each reference level,
A magnitude relationship between the plurality of reference levels and the amplitude value of the S-shaped waveform signal is determined based on the number of S-shaped waveform signals detected by the level-corresponding S-shaped detection process and corresponding to the plurality of reference levels. A detection level setting process for setting a detection level of the S-shaped detection means using the plurality of reference levels according to the determination result;
With the detection level of the S-shaped detection means set by the detection level setting process, the actuator is driven and controlled to displace the objective lens from the lowest point position to the highest point position, or from the highest point position. While displacing toward the lowest point position, the number of S-shaped waveform signals detected by the S-shaped detecting means is counted, and the counted number of S-shaped waveform signals corresponds to the designated recording layer. A recording layer detection method for an optical disc, comprising: a designated recording layer detection process for detecting a designated recording layer on the condition that In the optical disk recording layer detection method according to claim 9,
In the detection level setting process, the number of S-shaped waveform signals detected by the level-corresponding S-shaped detection process with respect to a predetermined one of the plurality of reference levels is greater than the number of recording layers of the optical disc. When the value is larger by “1”, the number of S-shaped waveform signals detected by the level-corresponding S-shaped detection process is smaller than the maximum reference level which is larger by “1” than the number of recording layers of the optical disc. The detection level is set as a detection level of the detection means, and the designated recording layer detection process is such that the number of counted S-shaped waveform signals is larger by “1” than a value indicating the designated recording layer. An optical disk recording layer detection method for detecting a recording layer specified by a condition. In the optical disk recording layer detection method according to claim 9 or 10,
In the detection level setting process, the maximum reference level in which the number of S-shaped waveform signals detected by the level-corresponding S-character detection process is larger by “1” than the number of recording layers of the optical disc and the level-corresponding S-character detection When the level difference from the maximum reference level in which the number of S-shaped waveform signals detected by the process is equal to the number of recording layers of the optical disc is greater than or equal to a predetermined value, the value between the maximum reference levels is determined as the S-shaped signal. The designated recording layer is set on the condition that the designated recording layer detection process sets the number of the counted S-shaped waveform signals to a value indicating the designated recording layer. Detecting recording layer of optical disc. The optical disk recording layer detection method according to any one of claims 9 to 11, further comprising:
The focus is generated by the focus error signal generating means by driving the actuator to displace the objective lens from the lowest point position toward the highest point position or from the highest point position toward the lowest point position. A maximum reference level setting process for detecting the maximum amplitude value of the S-shaped waveform signal included in the error signal or a value near the maximum amplitude value and setting the detected maximum amplitude value or the vicinity value as a maximum reference level;
A method for detecting a recording layer of an optical disc, comprising: a plurality of reference level setting steps for dividing the maximum reference level set by the maximum reference level setting step by a predetermined number to set the plurality of reference levels.

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