JP2000260110A - Method and device for information reproduction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and properly decide the kinds of both a reproduction-only optical disk and a recordable optical disk by deciding that an object optical disk is the reproduction-only optical disk when its value is smaller than a previously set specific reference value and the recordable optical disk when larger. SOLUTION: A disk kind decision means 13 is composed of a comparator 14 which compares the level signal of a normalized push-pull amplitude voltage inputted through an AD converter with a reference voltage V1 as the previously set specific reference value. This comparator 14 is used to compare the 1st normalized push-pull amplitude with the reference voltage V1 as the specific reference value for decision making and the kind of an optical disk is decided according to whether its output is at H or L level. It is decided that the optical disk is the recordable optical disk which is an R or RW disk when the output is at the H level or a ROM disk when at the L level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reproducing method and an information reproducing apparatus capable of discriminating between a ROM disk (read-only optical disk) and a recordable optical disk.

[0002]

2. Description of the Related Art Generally, discrimination between a recorded optical disk and a ROM disk is performed by reproducing recognition information recorded on the optical disk. However, illegally RO
The recorded optical disk on which the M information is duplicated uses this recognition information as a “ROM disk” instead of a “recordable optical disk”.
Can be tampered with. When the illegally duplicated recorded optical disk is further illegally duplicated, a large number of illegally duplicated optical disks can be manufactured. This is a serious problem in the copyright of software, and it is necessary to take measures to protect the copyright.

In this regard, for example, Japanese Patent Application Laid-Open No. Hei 6-267181 proposes discriminating the type of optical disk by utilizing the characteristic that the reflectivity of a light beam varies depending on the type of optical disk. That is, by comparing the information signal from the optical pickup unit with the reference value, the reflectance of the light beam by the optical disk is compared with the reference reflectance, and the comparison result is output. Also, considering that the amount of reflected light of the light beam is slightly different depending on whether or not the light beam is in focus, it is detected whether or not the light beam is in focus. Then, the discriminator discriminates the type of the optical disc based on the result of the comparison of the reflectance and the focus detection signal.

[0004]

The reflectance of an optical disk cannot be falsified even if it is illegally copied.
The 67181 publication method is an effective method.

However, in the case of a recordable optical disc characterized by being compatible with a ROM disc, for example, a DVD (Digital Video or Versatile Disk) -R
OM and DVD-R (Recordable) or DVD-RW
(Rewritable), the difference between the reflectances of these two types of optical disks is small, and in such a situation, the two types of optical disks cannot be accurately distinguished. As a result, a recordable optical disk that is illegally copied, that is, an optical disk on which identification information of a ROM disk is falsely recorded, may be recognized as a ROM disk.

Accordingly, the present invention provides an information reproducing method and an information reproducing apparatus capable of easily and properly determining the type of a read-only optical disk and a recordable optical disk and effectively coping with illegal duplication and the like. The purpose is to do.

Another object of the present invention is to provide an effective reference value for achieving the above object.

[0008]

According to a first aspect of the present invention, there is provided an information reproducing method, comprising: a read-only optical disk in which information is formed by a series of phase pits, or information is recorded on a land, on a groove, or on both a land and a groove. For a recordable optical disc on which recording pits are formed by laser light, any one of the target optical discs is rotated to focus the reproduction laser light on its recording surface, and the reflected light is directed at least in the pit row direction. A push-pull signal, which is a difference signal of reflected light, and an RF signal, which is a sum signal of the reflected light, are detected by performing current-voltage conversion by the light-receiving element divided into two, and divided in the pit row direction.
Calculate a normalized push-pull amplitude obtained by dividing the push-pull signal by the DC component of the RF signal, and when the magnitude of the normalized push-pull amplitude is smaller than a predetermined reference value set in advance. The target optical disk is determined as the read-only optical disk, and when the target optical disk is larger than the reference value, the target optical disk is determined as the recordable optical disk.

According to a seventh aspect of the present invention, there is provided a read-only optical disk in which information is formed by a series of phase pits, or information is recorded on a land or a groove or on both a land and a groove by a laser beam. For a recordable optical disc on which recording pits are formed, one of the target optical discs is rotated to focus a reproduction laser beam on its recording surface, and the reflected light is directed at least two times in the pit row direction.
In an information reproducing apparatus having an optical pickup for detecting reflected light by performing current-voltage conversion by a divided light receiving element, a push-pull signal as a difference signal obtained as reflected light divided from the light receiving element in a pit row direction is detected. Push-pull signal detecting means, RF signal detecting means for detecting an RF signal which is a sum signal of reflected light obtained from the light receiving element, DC component detecting means for detecting a DC component of the RF signal, and the push-pull signal Is divided by the DC component of the RF signal to generate a normalized push-pull signal, and a normalizing unit includes an amplitude calculating unit that calculates a normalized push-pull amplitude of the normalized push-pull signal. Push-pull processing means, a predetermined reference value set in advance and calculated by the normalized push-pull processing means Comprises a determination unit for the type of the target optical discs to determine whether that is the recordable optical disc or a said read-only optical disc according to the magnitude relationship between the size of-normalized push-pull amplitude, a.

Therefore, the type of the optical disc is determined by using a predetermined reference value for the magnitude of the normalized push-pull amplitude which is a characteristic peculiar to the optical disc and greatly different between the read-only optical disc and the recordable optical disc. Therefore, a recordable optical disk that was illegally copied, that is,
An optical disc in which the recognition information of the read-only optical disc is falsely recorded is not recognized as a read-only optical disc, but can be recognized as a recordable optical disc, and measures such as making reproduction impossible are taken.

According to a second aspect of the present invention, in the information reproducing method of the first aspect, the predetermined reference value is set to a value in a range of 0.15 to 0.25.

Therefore, the predetermined reference value is set to a value in the range of 0.15 to 0.25 from the distribution of the normalized push-pull amplitude between the actual read-only optical disk and the recordable optical disk. The recordable optical disk duplicated in is not recognized as a read-only optical disk,
It is possible to easily and accurately recognize the optical disk as a recordable optical disk and to make it impossible to reproduce the optical disk.

According to a third aspect of the present invention, there is provided the information reproducing method according to the first aspect of the present invention, wherein the information is recorded on a land or a groove, or on both a land and a groove by a laser beam. A light-receiving element in which a laser beam for reproduction is focused on its recording surface by rotating any one of the target optical disks with respect to the recordable optical disk on which is formed, and the reflected light is divided into at least two in the pit row direction. And a push-pull signal, which is a difference signal of reflected light, divided in the pit row direction and an RF signal, which is a sum signal of reflected light, are detected, and the push-pull signal is divided by a DC component of the RF signal. The normalized push-pull amplitude of the normalized push-pull signal obtained as described above is calculated, and a track cross signal as a low-frequency component is generated from the RF signal. Calculating the amplitude value of the track cross signal from the maximum level and the minimum level of the track cross signal, calculating the track cross modulation degree by dividing the amplitude value by the maximum level of the track cross signal, A new normalized push-pull amplitude is calculated by dividing the pull amplitude by the track cross modulation factor, and when the magnitude of the new normalized push-pull amplitude is smaller than a predetermined reference value, the target optical disc Is determined to be the read-only optical disk, and when it is larger than the reference value, the target optical disk is determined to be the recordable optical disk.

According to an eighth aspect of the present invention, there is provided a read-only optical disk in which information is formed by a series of phase pits, or information is recorded on a land or a groove or on both a land and a groove by a laser beam. For a recordable optical disc on which recording pits are formed, one of the target optical discs is rotated to focus a reproduction laser beam on its recording surface, and the reflected light is directed at least two times in the pit row direction.
In an information reproducing apparatus having an optical pickup for detecting reflected light by performing current-voltage conversion by a divided light receiving element, a push-pull signal as a difference signal obtained as reflected light divided from the light receiving element in a pit row direction is detected. Push-pull signal detecting means, RF signal detecting means for detecting an RF signal which is a sum signal of reflected light obtained from the light receiving element, DC component detecting means for detecting a DC component of the RF signal, and the push-pull signal Is divided by the DC component of the RF signal to generate a normalized push-pull signal, and a normalizing unit includes an amplitude calculating unit that calculates a normalized push-pull amplitude of the normalized push-pull signal. Push-pull processing means, and the RF
A track cross signal detecting means for detecting a low-frequency component of the signal to generate a track cross signal; an amplitude value calculating means for detecting a maximum level and a minimum level of the track cross signal and calculating an amplitude value thereof; A modulation degree detecting means having a modulation degree calculating means for calculating a track cross modulation degree by dividing an amplitude value of the cross signal by an upper limit value of the track cross signal; and a normalization calculated by the normalization push-pull processing means. Normalized push-pull amplitude changing means for calculating a new normalized push-pull amplitude by dividing the push-pull amplitude by the track cross modulation degree calculated by the modulation degree detecting means, and a predetermined reference value set in advance. According to the magnitude relation with the magnitude of the new normalized push-pull amplitude calculated by the normalized push-pull amplitude changing means, Comprises a determination unit for the type of optical disc to determine whether it is the recordable optical disc or a said read-only optical disc, a.

Therefore, the characteristic characteristic of the optical disc, that is, a new normalized push-pull amplitude obtained by dividing the normalized push-pull amplitude, which is greatly different between the read-only optical disc and the recordable optical disc, by the track cross modulation degree. Since the type of the optical disk is determined by using a predetermined reference value, the determination accuracy is further improved under a situation where the level is further different, and the recognition of an illegally duplicated recordable optical disk, that is, a read-only optical disk is recognized. An optical disc on which information is falsely recorded is not recognized as a read-only optical disc, but can be recognized as a recordable optical disc, and measures such as making reproduction impossible are taken.

According to a fourth aspect of the present invention, in the information reproducing method of the third aspect, the predetermined reference value is set to a value in a range of 0.5 or more and 2.0 or less.

Therefore, from the distribution of the normalized push-pull amplitude in consideration of the degree of track cross modulation between the actual read-only optical disk and the recordable optical disk, the predetermined reference value is set to 0.
Since the value is set in the range of 5 or more and 2.0 or less, even a recordable optical disk illegally duplicated is not recognized as a read-only optical disk, and is easily and accurately recognized as a recordable optical disk. The reproduction can be disabled.

According to a fifth aspect of the present invention, there is provided the information reproducing method, wherein the information is recorded on a land or a groove, or on both a land and a groove by a laser beam. A light-receiving element in which a laser beam for reproduction is focused on its recording surface by rotating any one of the target optical disks with respect to the recordable optical disk on which is formed, and the reflected light is divided into at least two in the pit row direction. And a push-pull signal, which is a difference signal of reflected light, divided in the pit row direction and an RF signal, which is a sum signal of reflected light, are detected, and the push-pull signal is divided by a DC component of the RF signal. Calculating the normalized push-pull amplitude of the normalized push-pull signal obtained as described above, and the maximum level indicated by the low-frequency data included in the RF signal. An amplitude value obtained from the minimum level is divided by the maximum level to calculate an RF modulation degree, and the normalized push-pull amplitude is divided by the RF modulation degree to calculate a new normalized push-pull amplitude. When the magnitude of the new normalized push-pull amplitude is smaller than a predetermined reference value, the target optical disc is determined to be the read-only optical disc, and when larger than the reference value, the target optical disc is referred to as the recordable optical disc. I decided to judge.

According to a ninth aspect of the present invention, there is provided a read-only optical disk in which information is formed by a series of phase pits, or information is recorded on a land or a groove or on both a land and a groove by a laser beam. For a recordable optical disc on which recording pits are formed, one of the target optical discs is rotated to focus a reproduction laser beam on its recording surface, and the reflected light is directed at least two times in the pit row direction.
In an information reproducing apparatus having an optical pickup for detecting reflected light by performing current-voltage conversion by a divided light receiving element, a push-pull signal as a difference signal obtained as reflected light divided from the light receiving element in a pit row direction is detected. Push-pull signal detecting means, RF signal detecting means for detecting an RF signal which is a sum signal of reflected light obtained from the light receiving element, DC component detecting means for detecting a DC component of the RF signal, and the push-pull signal Is divided by the DC component of the RF signal to generate a normalized push-pull signal, and a normalizing unit includes an amplitude calculating unit that calculates a normalized push-pull amplitude of the normalized push-pull signal. Push-pull processing means, and the RF
Amplitude value calculating means for detecting a maximum level and a minimum level indicated by data on the low frequency side included in the signal and calculating the amplitude value, and dividing the amplitude value of the RF signal by the maximum level to obtain an RF modulation factor A modulation factor calculating means for calculating the modulation factor calculating means, and a normalized push-pull amplitude calculated by the normalized push-pull processing means divided by the RF modulation factor calculated by the modulation factor detecting means to newly calculate the modulation factor. Normalized push-pull amplitude changing means for calculating the normalized push-pull amplitude, and a predetermined reference value set in advance and the magnitude of the new normalized push-pull amplitude calculated by the normalized push-pull amplitude changing means. Determining means for determining whether the type of the target optical disk is the read-only optical disk or the recordable optical disk in accordance with the magnitude relation.

Therefore, it is a characteristic inherent to the optical disk, and is a predetermined characteristic for a new normalized push-pull amplitude obtained by dividing the normalized push-pull amplitude, which is greatly different between the read-only optical disk and the recordable optical disk, by the RF modulation factor. The type of the optical disk is determined using the reference value of, so that the determination accuracy can be further improved under the situation where the level is further different, and the recognition information of the illegally duplicated recordable optical disk, that is, the read-only optical disk The optical disk recorded falsely is not recognized as a read-only optical disk, but can be recognized as a recordable optical disk, and measures such as making reproduction impossible are taken.

According to a sixth aspect of the present invention, in the information reproducing method of the fifth aspect, the predetermined reference value is set to a value in a range of 0.18 to 0.40. Is provided.

Therefore, the predetermined reference value is set to a value in the range of 0.18 to 0.40 from the distribution of the normalized push-pull amplitude in consideration of the RF modulation degree between the actual read-only optical disk and the recordable optical disk. Therefore, even if a recordable optical disk is illegally copied, it cannot be recognized as a read-only optical disk, but can be easily and accurately recognized as a recordable optical disk, and its reproduction cannot be performed. Can be taken.

[0023]

FIG. 1 shows a first embodiment of the present invention.
A description will be given with reference to FIG. In the present embodiment, the RO
The difference between characteristic values between optical disks is used by the magnitude of a normalized push-pull amplitude derived from a push-pull signal as a difference signal and an RF signal as a sum signal between an M disk (read-only optical disk) and a recordable optical disk. Then, it relates to an example in which the type of the optical disc is determined.

First, the information is formed by the R formed by the phase pit train.
FIG. 1 shows waveforms of a normalized push-pull (PP) signal and a track cross signal TC obtained from an OM disk (read-only optical disk). Also, an R disk (recordable optical disk) having a dye material in the recording layer or an Ag-I
Similar signal waveforms are obtained for a normalized push-pull (PP) signal and a track cross signal obtained from an RW disk (recordable optical disk) having an n-Sb-Te alloy. In these recordable optical disks, information is formed as recording pits on a land, on a groove, or on both a land and a groove by a laser beam.

Since the amplitude of the push-pull signal (not shown) itself varies depending on the reflectivity of the optical disk, it must be normalized. Therefore, the DC component of the RF signal is extracted by an LPF (low-pass filter) to generate a DC component signal RFdc, and a dividing means obtains a normalized push-pull signal obtained by dividing the push-pull signal by the DC component signal RFdc. . The normalized push-pull signal is input to each of a peak hold circuit and a bottom hold circuit, and a peak hold value (maximum level) PPp and a bottom level value (minimum level value) PPb are detected.
-b = PPp-PPb normalized push-pull amplitude PPp-b
Get. Since the magnitude of the normalized push-pull amplitude PPp-b is very different depending on the type of the optical disk, a reference value for determining the type of the optical disk is set in advance, and the unknown disk (target optical disk) is determined by the disk type determining means. The normalized push-pull amplitude PPp-b is compared with this reference value. If the amplitude is larger than the reference value, it is determined that the disk is a recordable optical disk such as an R or RW disk, and if it is smaller than the reference value, it is determined that the disk is a ROM disk. .

FIG. 2 is a block diagram showing a more specific configuration example of the information reproducing apparatus with such a determination process.
First, a semiconductor laser (LD) 1, a light receiving element (PD) 2, and an objective lens (not shown) as a light source are tracked /
An optical pickup 4 having an actuator 3 for focusing and the like is provided. The light receiving element 2 is at least divided into two in the pit row direction as shown in the drawing, and here, the light receiving areas A, B,.
The light receiving element 2 having C and D is used.
For each of the light receiving areas A,
An I / V conversion and matrix amplifier 5, which converts light receiving signals (currents) from B, C, and D into voltages and outputs the voltages, is connected.

A normalized push-pull processing means 6 is connected to the I / V conversion and matrix amplifier 5. This normalized push-pull processing means 6 is an RFdc detection means 7 functioning as an RF signal detection means and a DC component detection means.
A normalized push-pull detecting means 8 functioning as a push-pull signal detecting means and a normalized push-pull signal detecting means, a peak hold circuit 9, a bottom hold circuit 10, and a first normalized PP as an amplitude calculating means. It comprises an amplitude calculating means 11 and an AD converter 12. The disc type discriminating means 1 serving as discriminating means is provided to the first normalized PP amplitude calculating means 11 via an AD converter 12.
3 are connected.

As shown in FIG. 3, for example, the disc type discriminating means 13 includes a reference voltage V1 as a predetermined reference value and a normalized push-pull amplitude voltage input through the AD converter 12. It comprises a comparator 14 for comparing the level signal.

In such a configuration, first, the laser light reflected from the target optical disk is subjected to current-voltage conversion by the light receiving element 2 having a four-part structure. At this time, the difference signal (A + B)-(C + D) from the area divided into two in the pit row direction, that is, the track direction, is a push-pull signal, and is detected by the normalized push-pull detecting means 8. Since the amplitude of the push-pull signal varies depending on the reflectance of the optical disk, it is necessary to normalize the amplitude. That is, the sum signal A + B + C + D of the light receiving element 2 is RF
This signal is a signal which is detected by the RFdc detecting means 7 and which has an LPF with a sufficiently low cutoff frequency in the RFdc detecting means 7 in order to remove the components of the recording data (pit information) contained in the signal and the fluctuation of the light quantity when crossing the track.
(Not shown), the DC component of the RF signal is extracted to generate a DC component signal RFdc. Next, the normalized push-pull detection means 8 divides the push-pull signal by the DC component signal RFdc using a divider (not shown) to generate a normalized push-pull signal. The normalized push-pull signal thus generated is input to a peak hold circuit 9 and a bottom hold circuit 10 adjusted to hold a predetermined time constant, respectively, and the maximum level PPp which is an upper limit value is input. And the minimum level PPb which is the lower limit. The maximum level PPp value and the minimum level PPb value obtained in this way are used as the first normalized PP amplitude calculating means 11.
PPp-b = PPp-PP using a subtractor (not shown) in
The normalized push-pull amplitude is calculated by the operation b.
In this embodiment, the normalized push-pull amplitude is
Is input to the comparator 14 in the disc type discriminating means 13 to determine the type of the optical disc. That is, the comparator 14 compares the first normalized push-pull amplitude with a reference voltage V1 which is a predetermined reference value for determination, and determines whether the output is at H level or L level. The type of the optical disc is determined. If it is at the H level, it is determined that the disk is a recordable optical disk such as an R or RW disk, and if it is at the L level, it is determined that it is a ROM disk.

In addition, the maximum level PPp and the minimum level PPb, or the value of the normalized push-pull amplitude
The digital processing is performed by the converter 12 and input to the CPU.
Within, the value of the normalized push-pull amplitude obtained by subtraction and division or the value of the input normalized push-pull amplitude,
The type of the optical disk may be determined by comparing with a predetermined reference value.

Next, a ROM disk (DVD-ROM)
FIG. 4 shows the magnitude of the normalized push-pull amplitude of each of the recordable optical disks (DVD-R, DVD-RW). Since the DVD-ROM is designed to have a pit depth at which the DPD tracking error signal is maximized, the magnitude of the normalized push-pull amplitude is a small value, and the variation between the discs is very small. In the illustrated example, the magnitude of the normalized push-pull amplitude is 0.12 ± 0.03.
It is about. Conversely, DVD-R and DVD-RW are designed on the premise of tracking using a push-pull signal as a recording device, so that the normalized push-pull amplitude has a sufficiently large value. Due to the balance, the variation between disks increases depending on the design. For an optical disk designed in an appropriate range, the magnitude of the normalized push-pull amplitude of the DVD-R is about 0.45 ± 0.10, and the DVD-RW is 0.3
It is about 3 ± 0.07. As shown in FIG. 4, by setting the predetermined reference value in the range of 0.15 or more and 0.25 or less (preferably 0.20) from the difference between the optical disks, R can be easily determined.
It is possible to distinguish between an OM disk (DVD-ROM) and a recordable optical disk (DVD-R, DVD-RW).

As a result, for example, an illegally copied recordable optical disc, that is, an optical disc in which identification information of a DVD-ROM is recorded in a false manner, is not recognized as a DVD-ROM, but is recognized as a recordable optical disc. The reproduction can be disabled.

The normalized push-pull signal may be such that the amplitude value of the push-pull signal is normalized by an RF signal, and is normalized by a reflectance equivalent value or a different RF signal detection value, or by sampling, division, and subtraction. Needless to say, even if the order or circuit method is different, the same characteristic value may be used.

The variation of the normalized push-pull amplitude in the present embodiment is obtained by summing up the values of many commercially available samples in the case of a ROM disk, and is based on various design methods in the case of a recordable optical disk. It is a total value including various optical disks manufactured based on the above and commercially available samples, and although it is a reasonable value, the optical system (optical pickup 3)
Depending on the wavelength λ of the semiconductor laser 1 and the numerical aperture NA of the objective lens, the respective characteristic values may shift to large or small, but the reference value for determination may be shifted accordingly.

The detection of the maximum level PPp value and the minimum level PPb value of the normalized push-pull signal may be performed by the following method. As shown in FIG. 5, a track cross signal and a push-pull signal described later are signals whose phases are shifted by 90 degrees due to a difference between a sum signal and a difference signal from a groove (pit). A signal TC is used to generate a track cross TC binarized signal by a zero cross comparator. Since the rising and falling timings correspond to the upper limit = maximum level PPp and the lower limit = minimum level PPb of the normalized push-pull signal, as shown in FIG. Activate, peak maximum level P
What is necessary is just to hold Pp and hold the minimum level PPb which is the bottom. For this reason, in FIG. 6, the LPF 15, the track cross signal detecting means 16 and the AC
A coupling + binarization unit 17 and a sampling pulse generation unit 18 are provided, and the operation timing of the peak hold circuit 9 and the bottom hold circuit 10 is controlled by the sampling pulse from the sampling pulse generation unit 18.

A second embodiment of the present invention will be described with reference to FIGS. 1, 7, and 8. The same portions as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments). This embodiment is derived from a normalized push-pull amplitude and an RF signal derived from a push-pull signal as a difference signal and an RF signal as a sum signal in a ROM disk (read-only optical disk) and a recordable optical disk. The present invention relates to an example in which the type of an optical disc is determined by utilizing a difference in characteristic values between optical discs according to a track cross modulation degree.

First, the information is formed by the R formed by the phase pit train.
FIG. 1 shows the waveform of the track cross signal TC obtained from the OM disk (read-only optical disk). The same signal is used for a track cross signal obtained from an R disk (recordable optical disk) having a dye material in the recording layer or an RW disk (recordable optical disk) having an Ag-In-Sb-Te alloy in the recording layer. It is a waveform. In these recordable optical disks, information is formed as recording pits on a land, on a groove, or on both a land and a groove by a laser beam.

The track cross signal TC is generated by the LPF by passing only a low-frequency component which is a change in an RF signal when a light beam crosses a track on an optical disk. In the present embodiment, the track cross signal TC is input to a peak hold circuit and a bottom hold circuit, respectively, and a peak hold value (maximum level) TCp and a bottom level value (minimum level value) obtained by sampling each of them are sampled. From TCb, TCp-b = TCp-
An amplitude value TCp-b of the track cross signal TCb is obtained.
Next, an operation of TCp-b / TCp is performed by the dividing means to obtain a track cross modulation degree. This value normalizes the track cross amplitude according to the reflectance of each optical disk. Next, a new normalized push-pull amplitude (second normalized push-pull amplitude) is obtained by dividing the first normalized push-pull amplitude obtained by the dividing means by the method of the first embodiment by the track cross modulation factor. Push-pull amplitude). Since the second normalized push-pull amplitude is very different depending on the type of the optical disk, a reference value for determining the type of the optical disk is set in advance, and the second type of the unknown disk (the target optical disk) is determined by the disk type determining means. Compare the normalized push-pull amplitude with this reference value,
If it is smaller than the reference value, it is determined that the disk is a recordable optical disk such as an R or RW disk, and if it is larger than the reference value, it is determined that it is a ROM disk.

FIG. 7 is a block diagram showing a more specific configuration example of an information reproducing apparatus with such a determination process.
In this configuration example, a modulation degree detecting unit 21 is provided in addition to the configuration of FIG. 2 described above. First, the LPF 22 is connected to the I / V conversion and matrix amplifier 5.
The LPF 22 includes a track cross signal detecting means 2
3. The amplitude value calculating means 24 and the track cross modulation degree calculating means 25 as the modulation degree calculating means are connected in order. The amplitude value calculating means 24 has a peak hold circuit 26 and a bottom hold circuit 27 for detecting the maximum level and the minimum level of the track cross signal, respectively. The track cross modulation degree calculating means 25 is connected to the disc type discriminating means 1 through the AD converter 28 as the discriminating means.
3 are connected.

The disc type discriminating means 13 includes, for example, a comparator 14 as described above with reference to FIG.
A normalized push-pull amplitude change in which the first normalized push-pull amplitude calculated by the above-described normalized push-pull amplitude calculating means 11 is calculated again as a new second normalized push-pull amplitude using the track cross modulation. It has the function of means.

In such a configuration, first, the laser beam reflected from the target optical disk is subjected to current-voltage conversion by the light receiving element 2 having a four-part structure. At this time, A + B
The sum signal represented by + C + D is an RF signal, and this RF signal
The component of the recording data (pit information) included in the signal is LP
By cutting by F22, a track cross signal TC is generated by passing a change in light amount when the laser beam crosses a track on the optical disk. The track cross signal TC is input to a peak hold circuit 26 and a bottom hold circuit 27 which are adjusted so as to have a predetermined time constant, and a maximum level TCp and a minimum level TCb are detected. The maximum level TCp value and the minimum level TCb value obtained in this way are calculated using the subtractor (not shown) in the amplitude value calculating means 24 by the operation of TCp-b = TCp-TCb to obtain the amplitude of the track cross signal. Calculate the value. Further, the divider in the track cross modulation degree calculating means 25
(Not shown), an operation of TCp-b / TCp is performed to obtain a track cross modulation degree.

The track cross modulation degree calculated in this way is used as described above for the normalized push-pull amplitude calculating means 1.
Along with the first normalized push-pull amplitude calculated in step 1, the first normalized push-pull amplitude is input to the disc type discriminating means 13, and the normalized push-pull amplitude changing means divides the first normalized push-pull amplitude by the degree of track cross modulation. Thus, a new second normalized push-pull amplitude is calculated.
This second normalized push-pull amplitude is applied to comparator 1
4 to determine the type of the optical disk. That is, the comparator 14 compares the second normalized push-pull amplitude with the reference voltage V1, which is a predetermined reference value for determination, and determines whether the output is at the H level or the L level. The type of the optical disc is determined. If it is at the H level, it is determined that the disk is a recordable optical disk such as an R or RW disk, and if it is at the L level, it is determined that it is a ROM disk.

In addition, the maximum level TCp and the minimum level TCb, or the track cross signal modulation degree are digitally processed by the AD converter 12 and input to the CPU, and the track cross obtained by subtraction and division in the CPU. The second normalized push-pull amplitude is calculated from the modulation degree or the input track cross modulation degree and the input first normalized push-pull amplitude, and is compared with a predetermined reference value to determine the type of the optical disc. May be determined.

The second normalized push-pull amplitude used in the present embodiment reflects the difference between the ROM disk and the recordable optical disk for each of the push-pull signal and the track cross signal, and has a large level. Shows different values. In other words, when the normalized push-pull amplitude and the track cross modulation degree are used alone, there is a possibility that the judgment accuracy may not be sufficiently obtained depending on the variation of the optical disc, but the characteristic value of the recordable optical disc is established by these balances. The difference from the ROM disk is sufficiently secured.

Next, a ROM disk (DVD-ROM)
FIG. 8 shows the second normalized push-pull amplitude of each of the recordable optical disks (DVD-R and DVD-RW).
DVD with small push-pull and large track cross
The second normalized push-pull amplitude in ROM is 0.40
It is about ± 0.04. Conversely, for DVD-Rs and DVD-RWs having a large push-pull and a small track cross, the second normalized push-pull amplitude of the DVD-R is 4.
DVD ± RW is 2.4 ± 0.5.
It is about. From the difference between the optical disks as shown in FIG. 8, by setting the predetermined reference value in the range of 0.5 or more and 1.9 or less (preferably 1.2), the ROM disk (DV
D-ROM) and recordable optical disks (DVD-R, DV)
D-RW). In particular, in the case of the present embodiment, the width of the reference value that can be used for discrimination is further expanded, so that the type of the optical disc can be determined very accurately.

As a result, for example, a recordable optical disk illegally copied, that is, an optical disk in which identification information of a DVD-ROM is falsely recorded, is not recognized as a DVD-ROM, but is recognized as a recordable optical disk. The reproduction can be disabled.

Also, the second normalized push-pull amplitude is
The difference between the ROM disk and the recordable optical disk having the normalized push-pull amplitude only needs to be emphasized by the track cross modulation degree. Even if the sampling means and the order of calculation or the calculation method are different, the same characteristic value can be obtained. It goes without saying that it is good.

The variation of the second normalized push-pull amplitude in this embodiment is a reasonable value as in the case of the first embodiment. However, depending on the optical system, each characteristic value may vary. May shift to large or small, but the reference value for determination may be shifted accordingly.

Also, the maximum level T of the track cross signal
The detection of Cp and the minimum level TCb may be performed by the following method. As shown in FIG. 9, since the track cross signal and the track error signal are signals whose phases are shifted by 90 degrees,
The phase difference error (D
A tracking error signal such as a PD (PD) signal or a push-pull signal is generated by a zero-cross comparator to generate a tracking error TE binary signal. Since the rising and falling timings correspond to the upper limit = maximum level TCp and the lower limit = minimum level TCb of the track cross signal TC, as shown in FIG. Then, the maximum level TCp, which is the peak, is held, and the minimum level TCb, which is the bottom, is held. Therefore, FIG.
In the apparatus, a track error signal detecting means 29 for detecting a track error signal such as a phase difference error (DPD) signal or a push-pull signal based on the light receiving element 2, an AC coupling + binarizing means 30, and a sampling pulse generating means 31 are provided. The operation timing of the amplitude value calculating means 24 is controlled by the sampling pulse from the pulse generating means 31.

A third embodiment of the present invention will be described with reference to FIGS. The present embodiment is based on a normalized push-pull amplitude and an RF signal derived from a push-pull signal as a difference signal and an RF signal as a sum signal in a ROM disk (read-only optical disk) and a recordable optical disk. The present invention relates to an example in which the type of an optical disc is determined by utilizing a difference in characteristic values between optical discs according to the RF modulation degree.

In the RF signal shown in FIG. 11, pits and spaces having a plurality of lengths are continuously reproduced, and long pits and long spaces on the low frequency side of the pit (recording) data included in the RF signal are included. From the indicated maximum level RFp value and minimum level RFb value, the maximum amplitude (amplitude value) RFp-b = RFp-R
Fb is obtained. Therefore, the RF signal is input to each of the peak hold circuit and the bottom hold circuit, and the obtained R signal is input.
An RF modulation factor is obtained from the Fp value and the RFb value by an operation of (RFp-RFb) / RFp. Next, a new normalized push-pull amplitude (third normalized push-pull amplitude) is obtained by dividing the first normalized push-pull amplitude obtained by the dividing means by the method of the first embodiment by this RF modulation factor. Pull amplitude). Since the third normalized push-pull amplitude is very different depending on the type of the optical disc,
A reference value for discriminating the type of the optical disc is set in advance,
The disc type discriminating means compares the RF modulation degree of the unknown disc (target optical disc) with this reference value. If the RF modulation degree is smaller than the reference value, it is discriminated that the disc is a recordable optical disc such as an R or RW disc. It is determined that the disc is a disc.

FIG. 12 is a block diagram showing a more specific configuration example of an information reproducing apparatus with such a determination process. In this configuration example, a modulation degree detecting means 41 is provided in addition to the configuration shown in FIG. That is, the light receiving element 2
Via the I / V conversion and the matrix amplifier 5,
The RF signal detecting means 42, the amplitude value calculating means 43, and the RF modulation degree calculating means 44 as the modulation degree calculating means are connected in order. The amplitude value calculating means 43 includes a peak hold circuit 45 for detecting the maximum level and the minimum level of the RF signal, respectively.
And a bottom hold circuit 46. Further, a disc type discriminating means 48 as discriminating means is connected to the RF modulation degree calculating means 44 via an AD converter 47.

The disc type discriminating means 48 includes, for example, the comparator 14 described above with reference to FIG.
Normalized push-pull amplitude changing means for recalculating the first normalized push-pull amplitude calculated by the above-described normalized push-pull amplitude calculating means 11 as a new third normalized push-pull amplitude using the RF modulation factor. It has the function of

In such a configuration, first, the laser light reflected from the target optical disk is subjected to current-voltage conversion by the light receiving element 2 having a four-part structure. At this time, A + B
The sum signal represented by + C + D is an RF signal, and this RF signal
In the signal, pits and spaces having a plurality of lengths are continuously reproduced. Maximum level RFp value and minimum level R indicated by long pits and long spaces on the low frequency side included in the RF signal
Maximum amplitude (amplitude value of RF signal) from Fb value RFp-b = RF
p-RFb is obtained. To obtain this, the RF signal is input to a peak hold circuit 45 and a bottom hold circuit 46 adjusted to hold the RF signal with a predetermined time constant, respectively.
A maximum level RFp, which is the upper limit of the RF signal, and a minimum level RFb, which is the lower limit, are detected. Using the maximum level RFp value and the minimum level RFb value obtained in this way, a subtractor (not shown) in the amplitude value calculating means 43 uses RFp-
An RF amplitude value b = RFp−RFb is calculated. Next, R
The calculation of RFp-b / RFp is performed by a divider (not shown) in the F modulation factor calculating means 44 to obtain the RF modulation factor.

The calculated RF modulation degree is input to the disc type discriminating means 48 together with the first normalized push-pull amplitude calculated by the normalized push-pull amplitude calculating means 11 as described above. Then, a new third normalized push-pull amplitude is calculated by dividing the first normalized push-pull amplitude by the RF modulation factor by the normalized push-pull amplitude changing means. The third normalized push-pull amplitude is input to the comparator 14 to determine the type of the optical disk. That is, the comparator 14 compares the third normalized push-pull amplitude with a reference voltage V1 which is a predetermined reference value for determination, and the output is H
The type of the optical disc is determined based on whether the level is the L level or the L level. If it is at the H level, it is determined that the disc is a recordable optical disc such as an R or RW disc, and
If it is at the level, it is determined that the disk is a ROM disk.

In addition, the maximum level RFp and the minimum RFb
The level or the RF amplitude value is digitally processed by the AD converter 47 and input to the CPU, and the RF modulation factor obtained by subtraction and division or the input RF modulation factor and the first normalized push-pull are input to the CPU. The type of the optical disc may be determined by calculating a third normalized push-pull amplitude from the amplitude and comparing it with a predetermined reference value.

The third normalized push-pull amplitude used in the present embodiment reflects the difference between the ROM disk and the recordable optical disk with respect to each of the push-pull signal and the RF signal, and the level greatly differs. The value is shown. In other words, when the normalized push-pull amplitude and the RF modulation degree are used alone, there is a possibility that the judgment accuracy may not be sufficiently obtained depending on the variation of the optical disc. However, since the characteristic value of the recordable optical disc is satisfied by these balances,
The difference from the ROM disk is sufficiently secured.

Next, a ROM disk (DVD-ROM)
FIG. 13 shows the second normalized push-pull amplitude of each of the recordable optical disks (DVD-R, DVD-RW). DVD with small push-pull and large RF modulation
The third normalized push-pull amplitude in ROM is 0.12
It is about ± 0.04. Conversely, push-pull is large and RF
For DVD-R and DVD-RW with a small modulation factor,
The third normalized push-pull amplitude of the DVD-R is 0.72
It is about ± 0.12, and the DVD-RW is about 0.50 ± 0.
It is about 10. From the difference between the optical disks as shown in FIG. 13, the ROM can be easily set by setting the predetermined reference value to a range of 0.16 or more and 0.40 or less (preferably 0.28).
Disc (DVD-ROM) and recordable optical disc (D
VD-R, DVD-RW). In particular, in the case of the present embodiment, the width of the reference value that can be used for discrimination is further expanded, so that the type of the optical disc can be determined very accurately.

As a result, for example, an illegally copied recordable optical disc, that is, an optical disc in which identification information of a DVD-ROM is recorded in a false manner, is not recognized as a DVD-ROM, but is recognized as a recordable optical disc. The reproduction can be disabled.

The third normalized push-pull amplitude is
It is sufficient that the difference between the ROM disk and the recordable optical disk having the normalized push-pull amplitude is emphasized by the degree of RF modulation. Even if the sampling means or the order of calculation or the calculation method is different, the same characteristic value may be used. Needless to say.

The variation of the third normalized push-pull amplitude in this embodiment is a reasonable value as in the case of the first embodiment. However, depending on the optical system, each characteristic value may vary. May shift to large or small, but the reference value for determination may be shifted accordingly.

The detection of the maximum level RFp and the minimum level RFb of the RF signal may be performed by the following method. As shown in FIG. 11, EFM (Eight-Fourteen Mo
The sync pattern inserted in the data recorded by the modulation method is the longest (14T) pit and space. After generating a clock from the RF signal by the PLL and recognizing the recording data, the pit portion and the space portion of the Sync pattern are predicted, and as shown in FIG. 14, sampling pulses are generated at predetermined timings (arrows in FIG. 11). That is, the sample and hold circuit may be operated to hold the peak maximum level RFp and hold the bottom minimum level RFb. For this reason, in FIG. 14, the PLL circuit 49, the clock generation circuit 50, and the S
The sync detection / EFM decoder 51 is provided in order, and the operation timing of the amplitude value calculation means 43 is controlled by the sampling pulse from the Sync detection / EFM decoder 51.

[0063]

According to the first and seventh aspects of the present invention, the characteristic is a characteristic inherent to an optical disk, and is a predetermined characteristic with respect to the magnitude of the normalized push-pull amplitude which is greatly different between a read-only optical disk and a recordable optical disk. Since the type of the optical disc is determined using the reference value, the recordable optical disc illegally copied, that is, the optical disc on which the recognition information of the read-only optical disc is falsely recorded is recognized as the read-only optical disc. However, it can be recognized as a recordable optical disk, and measures such as disabling reproduction can be taken.

According to a second aspect of the present invention, in the information reproducing method according to the first aspect, the predetermined reference value is set to 0.15 from the distribution of the normalized push-pull amplitude between the actual read-only optical disc and the recordable optical disc. Since the value is set to a value within the range of 0.25 or less, the illegally duplicated recordable optical disk is not recognized as a read-only optical disk, but can be easily and accurately recognized as a recordable optical disk. It is possible to take measures such as making reproduction impossible.

According to the third and eighth aspects of the present invention, a characteristic characteristic of an optical disk, which is obtained by dividing a normalized push-pull amplitude, which is greatly different between a read-only optical disk and a recordable optical disk, by a track cross modulation degree. Since the type of the optical disc is determined by using a predetermined reference value for the new normalized push-pull amplitude, the determination accuracy is further improved under a situation where the level is further different, and illegally copied recording is performed. A recordable optical disk, that is, an optical disk on which recognition information of a read-only optical disk is falsely recorded, is not recognized as a read-only optical disk, but can be recognized as a recordable optical disk and its reproduction cannot be performed. Can be taken.

According to a fourth aspect of the present invention, in the information reproducing method according to the third aspect, the distribution of the normalized push-pull amplitude in consideration of the degree of track cross modulation between the actual read-only optical disc and the recordable optical disc is represented by: Since the predetermined reference value is set to a value in the range of 0.5 or more and 2.0 or less, even a recordable optical disk that is illegally duplicated is not recognized as a read-only optical disk, and it is easy and accurate.
It can be recognized as a recordable optical disk, and measures such as disabling reproduction can be taken.

According to the fifth and ninth aspects of the present invention, a characteristic characteristic of an optical disk, which is obtained by dividing a normalized push-pull amplitude, which is greatly different between a read-only optical disk and a recordable optical disk, by the RF modulation factor. The discrimination of the type of optical disc using a predetermined reference value for the normalized push-pull amplitude is further improved, so that the discrimination accuracy can be further improved in situations with even larger levels, and illegally copied recording is possible. An optical disc, that is, an optical disc in which recognition information of a read-only optical disc is falsely recorded, is not recognized as a read-only optical disc, but can be recognized as a recordable optical disc, and its reproduction cannot be performed. Can be taken.

According to a sixth aspect of the present invention, in the information reproducing method according to the fifth aspect, the predetermined push-pull amplitude distribution is determined from the distribution of the normalized push-pull amplitude in consideration of the RF modulation degree between the actual read-only optical disc and the recordable optical disc. The reference value of 0.18
Since the value is set in the range of 0.40 or less, even a recordable optical disk illegally duplicated is not recognized as a read-only optical disk, and can be easily and accurately recognized as a recordable optical disk. Yes, it is possible to take measures such as making the reproduction impossible.

[Brief description of the drawings]

FIG. 1 is a waveform chart showing the principle of an information reproducing method according to first and second embodiments of the present invention.

FIG. 2 is a block diagram showing a configuration example of a signal processing system for that purpose.

FIG. 3 is a block diagram showing a configuration of the disc type discriminating means.

FIG. 4 is a characteristic diagram showing a difference in normalized push-pull amplitude according to a disc type.

FIG. 5 is a waveform diagram showing a modification.

FIG. 6 is a block diagram showing a configuration example of a signal processing system for that purpose.

FIG. 7 is a block diagram illustrating a configuration example of a signal processing system according to a second embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a difference in normalized push-pull amplitude according to a disc type.

FIG. 9 is a waveform diagram showing a modification.

FIG. 10 is a block diagram showing a configuration example of a signal processing system for that purpose.

FIG. 11 is a waveform chart showing the principle of an information reproducing method according to a third embodiment of the present invention.

FIG. 12 is a block diagram illustrating a configuration example of a signal processing system for that purpose.

FIG. 13 is a characteristic diagram showing a difference in normalized push-pull amplitude according to a disc type.

FIG. 14 is a block diagram illustrating a configuration example of a signal processing system according to a modification.

[Explanation of symbols]

Reference Signs List 2 light receiving element 4 optical pickup 6 normalized push-pull processing means 7 RF signal detecting means, DC component detecting means 8 push-pull signal detecting means, normalized push-pull signal detecting means 11 amplitude calculating means 13 discriminating means 21 modulation degree detecting means 23 Track cross signal detecting means 24 amplitude value calculating means 25 modulation degree calculating means 41 modulation degree detecting means 42 RF signal detecting means 43 amplitude value calculating means 44 modulation degree calculating means 48 discriminating means

Claims (9)

[Claims] 1. A read-only optical disk in which information is formed by a series of phase pits, or a recordable optical disk in which information is formed on a land or a groove, or on both a land and a groove by a laser beam. Any of the target optical discs is rotated to focus a reproduction laser beam on its recording surface, and the reflected light is subjected to current-voltage conversion by a light receiving element divided at least into two in the pit row direction to perform a pit row direction conversion. Detects a push-pull signal that is a difference signal of the reflected light and an RF signal that is a sum signal of the reflected light,
A normalized push-pull amplitude of the normalized push-pull signal obtained by dividing the push-pull signal by the DC component of the RF signal is calculated, and the magnitude of the normalized push-pull amplitude is set to a predetermined predetermined value. An information reproducing method, wherein the target optical disk is determined as the read-only optical disk when the target optical disk is smaller than the reference value, and the target optical disk is determined as the recordable optical disk when the target optical disk is larger than the reference value. 2. The method according to claim 1, wherein the predetermined reference value is not less than 0.15 and not more than 0.15.
2. The information reproducing method according to claim 1, wherein the value is set to a value within a range of 25 or less. 3. A read-only optical disk in which information is formed by a series of phase pits, or a recordable optical disk in which information is formed on a land or a groove or on both a land and a groove by a laser beam. Any of the target optical discs is rotated to focus a reproduction laser beam on its recording surface, and the reflected light is subjected to current-voltage conversion by a light receiving element divided at least into two in the pit row direction to perform a pit row direction conversion. Detects a push-pull signal that is a difference signal of the reflected light and an RF signal that is a sum signal of the reflected light,
While calculating the normalized push-pull amplitude of the normalized push-pull signal obtained by dividing the push-pull signal by the DC component of the RF signal, a track cross signal that is a low-frequency component is generated from the RF signal, The amplitude value of the track cross signal is calculated from the maximum level and the minimum level of the track cross signal, and the amplitude value is divided by the maximum level of the track cross signal to calculate the degree of track cross modulation. A new normalized push-pull amplitude is calculated by dividing the amplitude by the track cross modulation factor. When the magnitude of the new normalized push-pull amplitude is smaller than a predetermined reference value, the target optical disc is read. The optical disk is determined to be the read-only optical disk, and when the value is larger than the reference value, the target optical disk is determined to be the recordable optical disk. Information reproducing method so as to. 4. The method according to claim 1, wherein the predetermined reference value is 0.5 or more and 2.0 or more.
4. The information reproducing method according to claim 3, wherein the information is set to a value in the following range. 5. A read-only optical disk in which information is formed by a series of phase pits, or a recordable optical disk in which information is formed on a land or a groove, or on both a land and a groove by a laser beam. Any of the target optical discs is rotated to focus a reproduction laser beam on its recording surface, and the reflected light is subjected to current-voltage conversion by a light receiving element divided at least into two in the pit row direction to perform a pit row direction conversion. Detects a push-pull signal that is a difference signal of the reflected light and an RF signal that is a sum signal of the reflected light,
While calculating the normalized push-pull amplitude of the normalized push-pull signal obtained by dividing the push-pull signal by the DC component of the RF signal, the maximum level indicated by the data on the low frequency side included in the RF signal and Calculate the RF modulation degree by dividing the amplitude value obtained from the minimum level by the maximum level, calculate a new normalized push-pull amplitude by dividing the normalized push-pull amplitude by the RF modulation degree,
When the magnitude of the new normalized push-pull amplitude is smaller than a predetermined reference value, the target optical disc is determined to be the read-only optical disc. When the magnitude is larger than the reference value, the target optical disc is referred to as the recordable optical disc. An information reproducing method which is determined as follows. 6. The predetermined reference value is 0.18 or more and 0.1.
6. The information reproducing method according to claim 5, wherein the value is set to a value within a range of 40 or less. 7. A read-only optical disk in which information is formed by a series of phase pits, or a recordable optical disk in which information is formed on a land or a groove or on both a land and a groove by a laser beam. By rotating any one of the target optical discs, the reproducing laser beam is focused on its recording surface, and the reflected light is subjected to current-voltage conversion by a light receiving element divided at least into two in the pit row direction to convert the reflected light. An information reproducing apparatus having an optical pickup for detecting, a push-pull signal detecting means for detecting a push-pull signal as a difference signal obtained as reflected light divided in a pit row direction from the light receiving element, and a reflection obtained from the light receiving element. RF signal detecting means for detecting an RF signal that is a sum signal of light; DC component detecting means for detecting a DC component of the RF signal; Normalized push-pull signal detecting means for dividing the push-pull signal by the DC component of the RF signal to generate a normalized push-pull signal, and amplitude calculating means for calculating a normalized push-pull amplitude of the normalized push-pull signal And a type of the target optical disc in accordance with a magnitude relationship between a predetermined reference value set in advance and a magnitude of the normalized push-pull amplitude calculated by the normalized push-pull processing means. A discriminating means for discriminating whether the disc is the read-only optical disc or the recordable optical disc. 8. A read-only optical disk in which information is formed by a series of phase pits, or a recordable optical disk in which information is formed on a land or a groove or on both a land and a groove by a laser beam. By rotating any one of the target optical discs, the reproducing laser beam is focused on its recording surface, and the reflected light is subjected to current-voltage conversion by a light receiving element divided at least into two in the pit row direction to convert the reflected light. An information reproducing apparatus having an optical pickup for detecting, a push-pull signal detecting means for detecting a push-pull signal as a difference signal obtained as reflected light divided in a pit row direction from the light receiving element, and a reflection obtained from the light receiving element. RF signal detecting means for detecting an RF signal that is a sum signal of light; DC component detecting means for detecting a DC component of the RF signal; Normalized push-pull signal detecting means for dividing the push-pull signal by the DC component of the RF signal to generate a normalized push-pull signal, and amplitude calculating means for calculating a normalized push-pull amplitude of the normalized push-pull signal Normalized push-pull processing means having: a track cross signal detecting means for detecting a low-frequency component of the RF signal to generate a track cross signal; detecting a maximum level and a minimum level of the track cross signal to detect An amplitude value calculating means for calculating an amplitude value, a modulation degree detecting means having a modulation degree calculating means for calculating a track cross modulation degree by dividing an amplitude value of the track cross signal by an upper limit value of the track cross signal, The normalized push-pull amplitude calculated by the normalized push-pull processing means was calculated by the modulation degree detecting means. Normalized push-pull amplitude changing means for calculating a new normalized push-pull amplitude by dividing by the rack cross modulation degree, and a predetermined normalized reference value and a new normalized push-pull calculated by the amplitude changing means An information reproducing apparatus comprising: a determination unit configured to determine whether the type of the target optical disk is the read-only optical disk or the recordable optical disk in accordance with the magnitude relationship with the amplitude. 9. A read-only optical disk in which information is formed by a series of phase pits, or a recordable optical disk in which information is formed on a land or a groove, or on both a land and a groove by a laser beam. By rotating any one of the target optical discs, the reproducing laser beam is focused on its recording surface, and the reflected light is subjected to current-voltage conversion by a light receiving element divided at least into two in the pit row direction to convert the reflected light. An information reproducing apparatus having an optical pickup for detecting, a push-pull signal detecting means for detecting a push-pull signal as a difference signal obtained as reflected light divided in a pit row direction from the light receiving element, and a reflection obtained from the light receiving element. RF signal detecting means for detecting an RF signal that is a sum signal of light; DC component detecting means for detecting a DC component of the RF signal; Normalized push-pull signal detecting means for dividing the push-pull signal by the DC component of the RF signal to generate a normalized push-pull signal, and amplitude calculating means for calculating a normalized push-pull amplitude of the normalized push-pull signal Normalized push-pull processing means having; and an amplitude value calculating means for detecting a maximum level and a minimum level indicated by data on the low frequency side included in the RF signal and calculating an amplitude value thereof; A modulation factor detecting unit having a modulation factor calculating unit for calculating an RF modulation factor by dividing the amplitude value by the maximum level; and a modulation factor detecting unit that calculates a normalized push-pull amplitude calculated by the normalized push-pull processing unit. A normalized push-pull amplitude changing means for calculating a new normalized push-pull amplitude by dividing by the RF modulation degree calculated by the means; Whether the type of the target optical disc is the read-only optical disc or the recordable optical disc according to the magnitude relationship between the predetermined reference value and the magnitude of the new normalized push-pull amplitude calculated by the amplitude changing means. An information reproducing apparatus, comprising: a determination unit configured to determine the information.