JP2006134515A - Device and method for measuring ar value of optical disk, and optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately inspect LPP of an optical disk using an AR value. <P>SOLUTION: Inspection data are recorded into a groove track of an optical disk, so that an AR value of an LPP component included in a push-pull signal 70 of a reproduction signal is calculated. The AR value is calculated from a maximum peak value and a minimum peak value of a superposed waveform of the first LPP100 not of the superposed waveform of the third LPP300. The calculated AR value is compared with a standard value, and when it is not less than the standard value, AR of the third LPP is also regarded to satisfy the standard value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disk inspection apparatus, and more particularly to measurement of an AR value.

  Conventionally, in an optical disc having land pre-pits (LPP) formed on lands adjacent to a groove track, which is an information recording track, such as DVD-R and DVD-RW, the AR (Aperture Ratio) value has a predetermined standard. It is required to meet. Here, the AR value is obtained by repeatedly sampling an LPP signal (see FIG. 6: the LPP signal itself can be extracted by the threshold component in the figure) included in the radial push-pull signal of the reproduction signal over a predetermined period. The superposed waveform obtained in this way is observed with an oscilloscope or the like, the maximum value max and the minimum value min of the peak value are measured as shown in FIG. 7, and the ratio AR = min / max is defined. Since the AR value is required to be 15% or more and the third LPP of the 3-bit LPP is the LPP corresponding to the sector address, the maximum value and the minimum value of the LPP signal corresponding to the third LPP Is measured to calculate the AR value.

  Hereinafter, a conventional AR value measuring apparatus disclosed in the following Patent Document 1 will be described. In addition, since the structure itself which produces | generates a push pull signal is common with this invention, it demonstrates in detail for convenience of description of this invention.

  FIG. 8 shows a conventional AR measurement apparatus. The AR value measuring apparatus is provided with a recording / reproducing head 2 capable of writing information to and reading information from an optical disc 1 to be inspected. The recording / reproducing head 2 includes a recording beam light generator for recording information data on a write-once or rewritable optical disc 1 having a recording surface, and a reading beam for reading recorded information (including information data) from the optical disc 1. A light generator and a quadrant photodetector are mounted. The reading beam light generator irradiates the optical disk 1 rotated by a spindle motor 9 with reading beam light, and forms an information reading spot on the recording surface. The four-divided photodetector 20 includes a photoelectric conversion element having a light-receiving surface that is divided into four by a direction along a tangent to an information recording track (groove track) of the optical disc 1 and a direction perpendicular to the tangent to the recording track. The photoelectric conversion element receives the reflected light from the optical disc 1 by the information reading spot by each of the four light receiving surfaces, and outputs light signals Ra to Rd which are individually converted into electric signals.

  The servo control device 4 generates a focus error signal, a tracking error signal, and a slider drive signal based on these light reception signals Ra to Rd. The focus error signal is supplied to a focusing actuator mounted on the recording / reproducing head 2. The focusing actuator adjusts the focus of the information reading spot based on the focus error signal. The tracking error signal is supplied to a tracking actuator mounted on the recording / reproducing head 2. The tracking actuator adjusts the formation position of the information reading spot in the disc radial direction based on the tracking error signal. The slider drive signal is supplied to the slider 10. The slider 10 moves the recording / reproducing head 2 in the radial direction of the disk at a speed corresponding to the slider drive signal.

The received light signals Ra to Rd are supplied to a head amplifier 25 having adders 21 to 23 and a subtractor 24. The adder 21 adds the light reception signals Ra and Rd, and the adder 22 adds the light reception signals Rb and Rc. That is, the adder 21 adds the received light signals Ra and Rd obtained by receiving the light from the light receiving surfaces 20a and 20d of the quadrant photodetector 20, and outputs an added received light signal Ra _{+ d} . Further, the adder 22 adds the light reception signals Rb and Rc obtained by receiving the light by the light receiving surfaces 20b and 20c of the quadrant photodetector 20, and outputs an added light reception signal Rb _{+ c} .

The adder 23 adds the output signals R _{a + d} and R _{b + c} of the adders 21 and 22. The output signal of the adder 23 is a read signal, that is, an RF signal, and is supplied to the information data reproduction circuit 30. The information data reproduction circuit 30 binarizes the read signal, and then sequentially performs demodulation processing, error correction processing, and various information decoding processing, thereby performing information data (video data, audio data) recorded on the optical disc 1. Data, computer data) is output and output.

The subtracter 24 subtracts the output signal R _{b + c} of the adder 22 from the output signal R _{a + d} of the adder 21. The output signal of the subtracter 24 becomes a signal indicating the frequency due to the wobbling of the groove track, and is supplied to the spindle servo device 26 of the spindle motor 9. The spindle servo device 26 rotationally drives the spindle motor 9 so that the frequency obtained from the output signal of the subtracter 24 becomes a frequency corresponding to a predetermined rotational speed.

Prepit detecting circuit 5, based on the output signals of the adders 21 and 22, the pre-pit detecting the land pre-pits formed on the land track of the optical disk 1 (LPP) detection signal PP _D recording processing circuit 7 To supply. Recording processing circuit 7, based on the pre-pit detection signal PP _D, the position where the recording and reproducing head 2 recording is performed at the present time, i.e., to recognize a position on the groove track, to a desired recording position from the recording position A control signal for causing the recording / reproducing head 2 to make a track jump is supplied to the servo controller 4. Further, the recording processing circuit 7 performs desired recording modulation processing on the information data to be recorded (information data for inspection) to generate a recording modulation data signal, and supplies this to the recording / reproducing head 2. A recording beam light generator mounted on the recording / reproducing head 2 generates a recording beam light corresponding to the recording modulation data signal and irradiates the recording beam light on the groove track on the optical disc 1. At this time, heat is transmitted to an area on the groove track irradiated with the recording beam, and information pits are formed in the area.

As shown in FIG. 9, the prepit detection circuit 5 includes an amplifier 31 that amplifies the output signal R _{a + d} of the adder 21, an amplifier 32 that amplifies the output signal R _{b + c} of the adder 22, and an amplifier 31. The subtracter 33 that subtracts the output signal of the amplifier 32 from the output signal and outputs the result as a radial push-pull signal (groove wobble signal) PP, and binarizes the output push-pull signal PP of the subtractor 33 with a threshold value TH. consisting binarization circuit 34 for generating a pre-pit detection signal PP _D. The gain G1 of the amplifier 31 and the gain G2 of the amplifier 32 are set to G1 = G2. The push-pull signal PP output from the subtracter 33 is supplied to the oscilloscope 61. The oscilloscope 61 samples the push-pull signal PP and displays, for example, a portion corresponding to the LPP in the push-pull signal PP. A personal computer (personal computer) 62 is connected to the oscilloscope 61. The personal computer 62 calculates the threshold value TH using the level data of the push-pull signal PP stored in the internal memory of the oscilloscope 61 (for example, a sample memory 93 described later). The personal computer 62 includes a CPU 65 and an internal memory 66. A D / A converter 63 is connected to the output port of the personal computer 62. The D / A converter 63 converts the slice level calculated by the personal computer 62 into an analog signal. The output signal of the D / A converter 63 is supplied to the binarization circuit 34 as a threshold signal for binarization. The signal (pre-pit detection signal PP _D ) output from the binarization circuit 34 is supplied to an error rate detection circuit, where an error rate corresponding to the supplied signal is detected.

  The oscilloscope 61 includes an A / D converter, a control circuit, a sample memory, a display memory, an X and Y driver, a display panel, an operation unit, and an interface. The A / D converter converts an input analog signal into a digital signal. The control circuit sequentially writes the digital signal sample data obtained by the A / D converter into the sample memory, reads out the data to be displayed from the sample memory, writes it into the display memory, and develops it. The X and Y drivers drive the display panel according to the data written in the display memory to display the waveform of the input analog signal on the display panel.

  In the AR measurement, the push-pull signal PP output from the subtractor 33 is supplied to the oscilloscope 61. In the oscilloscope 61, the push-pull signal PP is sampled by the A / D converter according to the high frequency clock, and the control circuit The sampling data is sequentially stored in the memory. The control circuit detects a peak value greater than or equal to a predetermined value in the sampling data supplied from the A / D converter. When the peak value is detected, the sampling data is stored in the memory over a predetermined period using the peak value as a trigger. This peak value corresponds to the synchronization LPP which is the first LPP. Writing to the memory over a predetermined period is repeated a plurality of times. The control circuit reads the data stored in the memory, supplies it to the display memory, and displays the waveform on the display panel. The read timing is set according to a command from the operation unit, and thereby, an overlapping waveform of the push-pull signal PP including the third LPP component to be inspected, that is, an AR waveform is displayed. In this display, the time axis is adjusted so that the peak value position of the push-pull signal PP becomes the display center line (time axis center line).

  The personal computer 62 can read out and take in the sample data stored in the sample memory by instructing the control circuit of the oscilloscope 61 via the interface. The CPU 65 of the personal computer 62 detects the maximum value max and the minimum value min of the peak value, calculates the ratio thereof, and calculates the AR value.

JP 2002-251727 A

  As described above, the conventional AR measurement apparatus is configured to detect the synchronization LPP, which is the first LPP, and detect the max and min of the third LPP using this as a trigger. Affects the detection accuracy of the AR value, and there is a problem that it is difficult to calculate an accurate AR value if the trigger timing is shifted.

  That is, when recording inspection data on a groove track which is an information recording track, synchronization information (the longest 14T that does not exist in the data length) is formed in synchronization with the synchronization LPP. In the case of (that is, pits are formed on the recording film by irradiating laser light of recording power), the LPP is affected by the formation of the mark, and the amplitude of the LPP component included in the push-pull signal is reduced. As described above, the amplitude of the LPP component fluctuates due to the influence of the 14T synchronization information. Therefore, when the trigger is set based on the detection of the synchronization LPP, a time lag occurs in the timing of triggering, and the AR value is calculated. Deviation occurs in the measurement of the minimum value of the third LPP, and an accurate AR value cannot be calculated. For example, considering the trigger timing when the polarity of the synchronization information is a mark and when the polarity of the synchronization information is a space, when the polarity of the synchronization information is a space, the amplitude of the synchronization LPP is large (the synchronization information is a space (no pit formation)). Therefore, when the polarity of the synchronization information is a mark, the amplitude of the synchronization LPP is small. Therefore, if the trigger is applied at a predetermined threshold, if the polarity of the synchronization information is a mark, The trigger timing is delayed compared to the space. Then, since the sampling timing is also delayed in time, the minimum value of the third LPP superimposed waveform is lower than the original value, and as a result, the AR value is calculated to be smaller than the original value. Will be. This means that a situation may occur in which an optical disc that satisfies the standard value (15%) is erroneously determined to be out of standard.

  An object of the present invention is to provide an apparatus and a method capable of detecting an AR value with higher accuracy than before and preventing an erroneous determination of an optical disc.

  The present invention is an AR value measuring apparatus for an optical disc in which an LPP is formed on a land adjacent to a groove track which is an information recording track, and synchronization information is transmitted to the groove track in synchronization with the synchronization LPP of the LPP. Means for recording, means for irradiating the groove track with light and generating a push-pull signal from the reflected light, and among the push-pull signals, a signal in the vicinity of the synchronization LPP is repeatedly sampled a plurality of times to generate a superimposed waveform. Means for generating, and means for calculating a ratio between the maximum peak value and the minimum peak value of the superimposed waveform as an AR value. Here, the synchronization information includes synchronization information whose polarity is a mark and synchronization information whose space is a space. That is, all the polarities of the synchronization information are set not to be spaces or marks.

  The present invention is also an AR value measurement method for an optical disc in which an LPP is formed on a land adjacent to a groove track, which is an information recording track, and the synchronization LPP is the first LPP of a plurality of LPPs. Synchronously recording on the groove track the synchronization information whose polarity is a mark and the synchronization information being a space, irradiating the groove track with light and generating a radial push-pull signal from the reflected light; Of the radial push-pull signal, a step of repeatedly sampling a signal in the vicinity of the LPP for synchronization to generate a superimposed waveform and calculating a ratio between the maximum peak value and the minimum peak value of the superimposed waveform as an AR value. Determining whether or not the AR value is equal to or greater than a predetermined threshold value. AR value corresponding to the third LPP of the number of LPP also has a determining that it is above the threshold.

  In the present invention, the AR value is not calculated for the third LPP as in the conventional case, but the AR value is calculated for the first LPP, that is, the synchronization LPP. By targeting the synchronization LPP, it is possible to prevent erroneous calculation of the AR value due to a sampling timing shift. Further, since the synchronization information is formed in the groove track adjacent to the synchronization LPP, and the synchronization information always includes synchronization information whose polarity is a mark (pit formation), the AR value of the synchronization LPP is the first value. The AR value of the third LPP can be evaluated by evaluating the AR value of the first LPP by evaluating the AR value of the first LPP. That is, if the AR of the synchronization LPP is equal to or greater than the threshold, it can be determined that it is equal to or greater than the threshold even if the AR value of the third LPP is not directly calculated.

  Further, the present invention is an optical disc in which an LPP is formed on a land adjacent to a groove track which is an information recording track, and synchronization information is recorded on the groove track in synchronization with the synchronization LPP of the LPP. The polarity of the synchronization information includes both marks and spaces, and the AR value corresponding to the synchronization LPP satisfies 10% or more, or 15% or more.

  As described above, the AR value of the synchronization LPP is equal to or less than the AR value of the third LPP, and the AR value of the third LPP can also be evaluated by evaluating the AR value of the synchronization LPP. Therefore, an optical disk satisfying the synchronization LPP of 10% or more, or 15% or more is an optical disk on which LPP is formed without any problem, and is an optical disk capable of performing data recording or reproduction with high accuracy.

  According to the present invention, since the AR value can be evaluated with higher accuracy than before, it is possible to surely check whether or not the LPP of the optical disc is normal (whether it is within the standard range). Further, it is possible to provide an optical disc capable of reliably performing data recording / reproduction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The overall configuration of the optical disk AR value measuring apparatus according to this embodiment is substantially the same as that of the conventional AR value measuring apparatus shown in FIGS. 8 and 9, and is used as it is in this embodiment. The difference from the conventional apparatus is that the measurement object of the AR value is not the third LPP but the first, that is, the synchronization LPP as in the conventional case. More specifically, in the prior art, when the synchronization LPP, which is the first LPP, is detected, the third LPP is sampled a plurality of times using this as a trigger, and the superimposed waveform (AR waveform) is generated by the oscilloscope 61. However, in this embodiment, the first LPP for synchronization LPP is detected, the vicinity of the synchronization LPP is sampled a plurality of times, and the overlapping waveform (AR waveform) is created by the oscilloscope 61. The personal computer 62 does not detect the maximum value and the minimum value in the AR waveform of the third LPP, but detects the maximum value and the minimum value in the AR waveform of the first LPP.

  FIG. 1 schematically shows the concept of AR value measurement in the present embodiment. The push-pull signal (radial push-pull signal) PP70 from the subtracter 33 includes the three LPP signals 100, 200, and 300 as described above. The first LPP signal 100 (in the figure, shown as a superimposed waveform (AR waveform) repeatedly sampled and superimposed over a predetermined period) is a synchronization LPP signal, and this synchronization LPP signal is used when recording data. In synchronization with the LPP signal, 14T synchronization information is recorded on the groove track. That is, the data recorded on the groove track is divided in advance for each synchronization frame which is an information unit, and one sector is composed of 26 synchronization frames, and one ECC block is composed of 16 sectors. Then, synchronization information (SYNC) for synchronizing each synchronization frame is inserted at the head of each synchronization frame. As the synchronization information, 14T that is sufficiently longer than the longest 11T that appears in the data modulation portion is used so that frame synchronization can be reliably obtained. In a standard such as DVD-R, the polarity of either mark or space can be selected as 14T synchronization information.

  Here, if all the polarities of the synchronization information are spaces, the adjacent tracks of the synchronization LPP 100 are not affected by the space, that is, pits are not formed, so the LPP is not affected, and the LPP signal 100 included in the PP signal 70 is not affected. The amplitude is also large. However, in general, the polarity of the synchronization information is selected so that the DSV (Digital Sum Value) value is minimized and the DC component is suppressed, or the polarity of the synchronization information is always once at a plurality of times in order to reliably execute ROPC. Since it is selected to be a mark, the synchronization information includes not only a space but also a mark. When the polarity of the synchronization information becomes a mark, a mark, that is, a pit is formed on the track adjacent to the synchronization LPP, so that the LPP itself is affected by the thermal effect and the pit reflectivity is lowered during reproduction. , The amplitude of the LPP signal 100 included in the PP signal 70 is reduced.

  When attention is paid to the third LPP signal 300, 3T to 11T data other than the synchronization information is recorded on the groove track adjacent to the third LPP, and the polarity thereof is either a mark or a space. However, the maximum value in the superimposed waveform over a predetermined period corresponds to the case where a space is located in the groove, and the minimum value corresponds to the case where a mark is located in the groove. Since the AR value is defined by AR = min (minimum peak value) / max (maximum peak value), the AR value decreases when a mark exists in the groove, and if the AR value is 15% or more at that time Satisfies the standard.

On the other hand, as described above, the synchronization information of 14T is formed in the groove adjacent to the synchronization LPP and is selected so that the polarity becomes a mark once every plural times. Therefore, the minimum peak of the synchronization LPP signal 100 is selected. The value will always be reserved. The maximum and minimum peak values of the synchronization LPP signal 100 are max (1) and min (1), respectively, and the maximum and minimum peak values of the third LPP signal 300 are max (3) and min (3, respectively. ) Generally holds the following relationship.
max (1) ≈max (3)
min (1) ≦ min (3)
Here, min (1) ≦ min (3) is because the longest 14T mark always exists at a constant frequency in the synchronization LPP, so that the influence on the LPP is maximized (amplitude reduction width is small). Because it is the largest).

Therefore, the magnitude relationship between AR (1) which is the AR value of the synchronization LPP signal 100 and AR (3) which is the AR value of the third LPP signal 300 is generally AR (1) ≦ AR (3).
Therefore, if AR (1) satisfies the standard of 15% or more, AR (3) always satisfies 15% or more. In the present embodiment, in view of such a principle, as shown in FIG. 1, an oscilloscope 61 generates a synchronization LPP signal 100 that is the first LPP signal, instead of the third LPP signal 300. The AR value is calculated by the personal computer 62 to determine whether or not the standard is satisfied.

  In FIG. 2, test data is recorded on the groove track at 8 × speed, and the data is reproduced to generate a push-pull signal. The vicinity of the synchronization LPP, which is the first LPP included in this push-pull signal, is shown. A superimposed waveform (AR waveform) on the oscilloscope 61 obtained by repeatedly sampling over a predetermined period is shown. The sign of the AR waveform shown in FIG. 7 is inverted, but it goes without saying that the AR value measurement is not affected at all. In the figure, the maximum peak value corresponds to the case where the polarity of the synchronization information is a space, and the minimum value corresponds to the case where the polarity of the synchronization information is a mark. FIG. 3 also shows inspection data recorded on the groove track at 8 × speed, and the data is reproduced to generate a push-pull signal. The vicinity of the third LPP included in this push-pull signal is passed over a predetermined period. A superimposed waveform (AR waveform) on the oscilloscope 61 obtained by repeated sampling is shown. The third LPP is sampled by detecting the synchronization LPP which is the first LPP and applying a trigger. However, since the minimum value of the peak also shifts when the trigger timing is shifted, the minimum value in the superimposed waveform is the original value. It will be lower than the value. However, in the present embodiment, since the AR value is calculated for the synchronization LPP, the AR value can always be accurately calculated without being affected by such a shift in trigger timing. AR (1) It is possible to determine whether or not AR (3) satisfies the standard value without directly calculating AR (3) based on the above relationship between and AR (3).

  FIG. 4 schematically shows a process for calculating the AR value from the synchronization LPP signal 100 (superimposed waveform) created by the oscilloscope 61. The synchronization LPP is detected at a predetermined threshold level and sampled to include the synchronization LPP. Sampling is repeated a plurality of times to obtain the synchronization LPP signal 100 (superimposed waveform). Assuming a line (dashed line in the figure) connecting the timing when the waveform rises from the bottom level (point X in the figure) and the timing when the waveform falls to the bottom level (point Y in the figure), the minimum peak value (point W in the figure) ) Measure A and maximum value B respectively. In more detail, it is as follows. That is, the push-pull signal is supplied to the oscilloscope 61, sampled by the A / D converter of the oscilloscope 61, and sequentially stored in the memory. In the vicinity of the synchronization LPP, a positive peak value greater than or equal to a predetermined value is detected from the sampling data, and the sampling data is stored in the memory over a predetermined period (a period sufficient to include only the synchronization LPP) as a trigger. Sampling data is stored in the memory. This storage in the memory is repeated a plurality of times. The control circuit of the oscilloscope 61 reads the data stored in the memory, supplies it to the display memory, and displays the waveform on the display panel. The personal computer 62 reads the sampling data stored in the memory of the oscilloscope 61, extracts the maximum value and the minimum value of the peak value, and calculates AR = min / max.

  FIG. 5 shows an overall process flowchart of the present embodiment. First, an inspection optical disk is loaded, and inspection data is recorded on a groove track which is the information recording track (S101). At this time, the synchronization information of 14T is recorded so that the synchronization LPP is detected and synchronized therewith. The synchronization information polarity setting algorithm is arbitrary. For example, the polarity of the synchronization information is set so that marks and spaces are alternately arranged so that ROPC can be executed at predetermined time intervals. ROPC detects the reflected light level when pits are formed by irradiating laser light of recording power as is well known, and dynamically adjusts the recording power so that the reflected light level matches a predetermined value. is there. In order to execute ROPC with certainty, it is convenient to execute it at the formation timing of the longest synchronization information of 14T. If the polarity of the synchronization information is set to be alternately a mark and a space, the synchronization information can be performed twice. ROPC can always be executed once, and fine power adjustment can be performed.

  After recording the inspection data, the data is reproduced to generate the push-pull signal (S102), and the synchronization LPP that is the first LPP included in the push-pull signal is extracted (S103). The extracted synchronization LPP (and signals in the vicinity thereof) is stored in the memory of the oscilloscope 61. Next, it is determined whether or not it has been repeatedly executed a predetermined number of times (S104). If the predetermined number of times has not yet been reached, the extraction of the synchronization LPP is repeated. After the extraction process is repeated a predetermined number of times, it is read from the memory and displayed as a superimposed waveform (S105). Note that the superimposed waveform display is for the convenience of the user, and is not necessarily essential for calculating the AR value, and the display step may be omitted.

  After displaying the superimposed waveform, the personal computer 62 reads data from the memory of the oscilloscope 61, detects the maximum and minimum values of the peak from the superimposed waveform of the synchronization LPP, and calculates the AR value (S106). The standard value (15%) of AR is stored in the memory of the personal computer 62 in advance, and the obtained AR value is compared with this standard value (S107). If AR is greater than or equal to the standard value, it means that the AR of the third LPP indicating the sector address is also greater than or equal to the standard value, so it is determined that the LPP of the inspection optical disk is formed normally (S108). . On the other hand, if AR is smaller than the standard value, it is highly likely that the AR of the third LPP indicating the sector address will not reach the standard value, so it is determined that the LPP of the inspection optical disk is abnormal (S109). .

  As described above, in the present embodiment, the AR value is calculated using the synchronization LPP that is the first LPP, and the optical disk is inspected according to whether the AR value satisfies the standard. An optical disc can be inspected with high accuracy without being affected by a shift in trigger timing for sampling LPP.

  In this embodiment, the AR of the synchronization LPP is compared with the standard value (15%). However, considering that AR (1) ≦ AR (3), the standard value is reduced by a minute amount from 15%. You may change to In the data area of the optical disc, a mark of 11T at the maximum is recorded and the synchronization information is 14T. Therefore, the ratio is 11/14 = 0.79, and when this is used, the standard value 15% in AR (3) is 15% × 0.79 = 11.85%. Therefore, the condition that AR (1) should satisfy is AR (1) ≧ 11.85%. As another condition to be satisfied by AR (3), for example, AR (3) ≧ 12% (double-layer structure optical disc, etc.), it is preferable that AR (1) ≧ 9.48% using the above ratio. Become. From these facts, if the condition of AR (1) ≧ 10% is generally satisfied, it can be determined that the LPP of the optical disc is normal. To summarize the conditions to be satisfied by the optical disc, AR (1) ≧ 10%, or AR (1) ≧ 15%. The condition that AR (1) should satisfy may be changed according to the type of the optical disk. For a single layer, AR (1) ≧ 15%, for a double layer, AR (1) ≧ 10%, and so on. In the present embodiment, since it is possible to inspect the optical disk with only AR (1) without detecting AR (3), AR (3) is also detected, and AR (1) is 10% or more. Even if AR (3) is less than 12%, it can be determined that the optical disc is normal as AR (3) is erroneously detected. In other words, an optical disc in which AR (1) ≧ 10% and AR (3) <12% is an optical disc that can perform data recording and reproduction without any problem. The same applies to an optical disc in which AR (1) ≧ 15% and AR (3) <15%.

  In this embodiment, the AR of the synchronization LPP is calculated and compared with the standard value. As described above, both the AR of the synchronization LPP and the AR of the third LPP are calculated, and both of them are calculated. It may be used to inspect the LPP of the optical disc. That is, after calculating AR (1) and AR (3), first, AR (3) is compared with the standard value in the same manner as in the prior art. If AR (3) ≧ standard value, the optical disc is determined to be normal and the inspection is terminated. On the other hand, if AR (3) <standard value, it is not determined that there is an abnormality at that time, but AR (1) is compared with the standard value. If AR (1) ≧ standard value, it is determined that the optical disc is normal. As described above, the peak minimum value of the third LPP may be measured smaller than the original value due to a shift in trigger timing, and therefore AR (3) may be erroneously calculated smaller than the original value. In this case, however, AR (1) and the standard value are compared in magnitude, and if AR (1) satisfies the standard, it is determined to be normal, so that the erroneous calculation of AR (3) can be compensated. In other words, when both AR (3) and AR (1) are smaller than the standard value, it can be determined that the LPP of the optical disc is abnormal.

  In the present embodiment, the polarity of the synchronization information of 14T is set by a predetermined algorithm. In short, the polarity of the synchronization information is not all marks or all spaces, but marks and spaces exist at an appropriate frequency. Therefore, the polarity can be set at random.

It is a conceptual explanatory view of AR calculation of an embodiment. It is a superimposed waveform explanatory diagram of the synchronization LPP displayed on the oscilloscope. It is explanatory drawing of the 3rd LPP superimposition waveform displayed on an oscilloscope. It is explanatory drawing of AR value calculation from the LPP signal for a synchronization (superimposition waveform). It is an AR value calculation processing flowchart of the embodiment. It is a figure which shows the relationship between a radial push pull signal and an LPP signal. It is a superposition waveform explanatory view of LPP. It is a block diagram of a conventional apparatus. It is a block diagram of the prepit detection circuit of the conventional apparatus.

Explanation of symbols

  70 Push-pull signal (radial push-pull signal), 100 1st LPP signal (superimposed waveform), 200 2nd LPP signal (superimposed waveform), 300 3rd LPP signal (superimposed waveform).

Claims (4)

An AR value measuring device for an optical disc in which land prepits are formed on lands adjacent to a groove track which is an information recording track,
Means for recording synchronization information on the groove track in synchronization with a synchronization land prepit of the land prepits;
Means for irradiating the groove track with light and generating a push-pull signal from the reflected light;
Means for generating a superimposed waveform by repeatedly sampling a signal in the vicinity of the synchronization land pre-pit among the push-pull signals a plurality of times;
Means for calculating a ratio between the maximum peak value and the minimum peak value of the superimposed waveform as an AR value;
The AR information measuring apparatus is characterized in that the synchronization information includes synchronization information whose polarity is a mark and synchronization information whose space is a space. An AR value measurement method for an optical disc in which a land pre-pit is formed on a land adjacent to a groove track which is an information recording track,
Recording synchronization information whose polarity is a mark and synchronization information whose space is a space on the groove track in synchronization with a synchronization land prepit which is a first land prepit among a plurality of land prepits; ,
Irradiating the groove track with light and generating a radial push-pull signal from the reflected light;
Among the radial push-pull signals, a step of repeatedly sampling a signal in the vicinity of the synchronizing land pre-pit multiple times to generate a superimposed waveform;
Calculating a ratio between the maximum peak value and the minimum peak value of the superimposed waveform as an AR value;
It is determined whether or not the AR value is equal to or greater than a predetermined threshold value. If the AR value is equal to or greater than the threshold value, an AR value corresponding to a third land prepit among the plurality of land prepits is also a threshold. Determining to be greater than or equal to a value;
A method for measuring an AR value of an optical disc, comprising: An optical disc having land pre-pits formed on lands adjacent to a groove track that is an information recording track,
Synchronous information is recorded on the groove track in synchronization with the synchronous land prepit of the land prepits, and the polarity of the synchronous information includes both marks and spaces. An optical disc characterized in that an AR value corresponding to a land pre-pit satisfies 15% or more. An optical disc having land pre-pits formed on lands adjacent to a groove track that is an information recording track,
Synchronous information is recorded on the groove track in synchronization with the synchronous land prepit of the land prepits, and the polarity of the synchronous information includes both marks and spaces. An optical disc characterized in that an AR value corresponding to a land pre-pit satisfies 10% or more.

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