JP3459864B2 - Off-center disk detection method, disk reproducing apparatus and reproducing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc reproducing apparatus capable of reproducing a disc at a high speed by using a light beam, and more particularly, to a method for detecting an eccentric disc which causes the disc reproducing device to vibrate at high speed rotation. The present invention relates to a disc reproducing apparatus and a reproducing method capable of detecting the amount of eccentricity of a disc.

[0002]

2. Description of the Related Art Although a CD (Compact Disc) player has been in practical use for a long time, in recent years, a so-called CD-ROM in which a CD is further applied as a peripheral device of a personal computer has been rapidly spread. The demand for high-speed data transfer in such CD-ROM devices has tended to increase the speed of reproduction, and recently 8 × speed has become the mainstream, but it is expected that high-speed data transfer of 12 × speed or higher will be essential in the future. It

FIG. 6 is a block diagram showing an example of a conventional disk reproducing apparatus for reproducing a CD or a CD-ROM according to FIG. 5, in which 1 is a disk, 2 is a track, 3 is a light beam, and 4 is a light beam.
Is a disk motor, 5 is a disk motor control circuit, 6 is an information reading unit, 7 is a preamplifier circuit, 8 is a tracking control circuit, 9 is a signal processing circuit, 10 is a CPU, 11 is an audio circuit, and 12 is an output terminal of an audio signal. , 13 are CD-ROM decoders, and 14 are output terminals for CD-ROM signals.

In the figure, in this disc reproducing apparatus, as a disc 1, a C in which audio information is recorded is recorded.
Various discs such as a CD-ROM in which D and computer information (hereinafter referred to as CD-ROM information) are recorded can be reproduced. If the disc 1 is a CD,
The rotation speed is uniquely determined by what is specified, but when the disc 1 is a CD-ROM, for example, 1.2 m / s
It also enables high-speed playback of n times the specified rotation speed such as ec. As described above, recently, 8 × speed reproduction has become the mainstream.

The CPU 10 receives an external request from a device such as a user or a host, sends a rotation speed command A according to this request to the disk motor control circuit 5, and based on this, sets and controls the rotation speed of the disk motor 4. By doing so, the rotation speed of the disk 1 is set to the rotation speed requested from the outside.

The disc 1 is formed with a spiral or concentric track 2 on which information is recorded. When the information reading section 6 irradiates the track 2 with a light beam 3, the audio is recorded from the track 2. Information and CD-R
The OM information is read and these are output as a read signal. The read signal is subjected to processing such as amplification and waveform shaping in the preamplifier circuit 7, and then supplied to the signal processing circuit 9 for predetermined processing. When the read signal is an audio information signal, further, If it is processed by the audio circuit 11 and is a CD-ROM information signal, C
Processed by the D-ROM decoder 13 and output terminals 1 respectively
It is output from 2 and 13.

The information reading unit 6 is composed of an optical pickup and a slider for moving the optical pickup in the radial direction of the disc 1. With this slider, the optical beam 3 from the optical pickup makes a series as the disc 1 rotates. The tracks 2 can be sequentially irradiated. Further, the optical pickup, in order to focus the light beam 3 on the track 2 of the disk 1, in order to make the light beam 3 follow the track 2 together with focusing means for controlling the position of the condenser lens in the optical axis direction thereof, This condensing lens is track 2
It also has tracking means for controlling the position in the width direction. Then, a part of the read signal amplified by the preamplifier circuit 7 is supplied to the tracking control circuit 8. The tracking control circuit 8 detects the tracking state of the light beam 3 on the track 2 from the supplied read signal, and generates the tracking control signal B according to the detection result. The tracking control signal B causes the information reading unit 6 to ensure that the light beam 3 always follows the track 2 accurately.
The tracking means in the optical pickup is controlled.

When the desired track 2 is accessed, the CPU 10 outputs the inhibition signal C to stop the operation of the tracking control circuit 8 so that the tracking control signal B is not output, and the slider reads the information reading unit. The optical pickup 6 is moved in the radial direction of the disk 1 at a high speed so that the light beam 3 is quickly sent to the desired track 2. As a result, the light beam 3 crosses a plurality of tracks, and thus the read signal output from the information reading unit 6 becomes a pulsed signal whose amplitude increases every time it crosses a track. This is referred to as a track crossing pulse here, but this track crossing pulse D is supplied from the preamplifier circuit 7 to the CPU 10. The CPU 10 recognizes the number of tracks crossed by the light beam 3 by counting the track crossing pulse D, and determines whether or not the light beam 3 has reached a desired track.

As the disc 1 rotates, the tracking control circuit 8 supplies the tracking control signal B to the information reading section 6, whereby the tracking means is controlled in the information reading section 6 and the optical beam is kept while the optical pickup is stopped. Although 3 follows the track 2, there is a limit to the amount of displacement of the light beam 3 by the tracking means. Therefore, when such tracking control is performed to some extent, the slider moves the optical pickup in the radial direction of the disk,
Then, this tracking control is performed again. In this way, the optical pickup intermittently moves in the radial direction of the disc 1.

By the way, in a disc which is reproduced by such a disc reproducing apparatus, there is a deviation between the center point of the structure, which is the rotation center of the disc, and the center of gravity of the disc, more or less. A disc with a large deviation is called an eccentric disc. As a factor causing such an eccentric center of gravity, there is a factor in manufacturing due to nonuniform pressure of the disc itself, but it is also caused by attaching an index label to the disc.

When such an eccentric center disc is rotated at the specified rotation speed as described above, the rotation speed is low,
Although almost no vibration occurs, when the rotation speed increases due to high-speed reproduction or the like, vibration occurs in the disc reproducing device. This vibration tends to increase as the rotation speed increases. Although it depends on the amount of eccentricity, according to experiments, at high-speed reproduction of approximately 6 times or more, vibration undesirably increases and noise is generated. Therefore, in the case of octuple speed reproduction, which has recently become the mainstream, vibration and noise are large, and an undesired vibration is given to a device installed in the vicinity of the disc reproducing device, or a work performed near the disc device is performed. There is also a case where it impairs.

[0012]

In order to prevent such vibration, the vibration of the disc reproducing apparatus is detected, and if the vibration is large, the reproducing speed of the disc used at this time is lowered or It is conceivable that the amount of eccentricity of the disc, which is the amount of deviation of the center of rotation with respect to the center of gravity of the disc, is detected and the reproduction speed is not set to a high value for a disc with a large amount of eccentricity.

For this purpose, however, it is necessary to newly add a device for detecting the vibration of the disc reproducing device, a device for detecting the eccentricity amount of the disc, etc. to the disc reproducing device as a separate device. There are problems that the number of parts of the device and the circuit scale are significantly increased, and the cost of the disc reproducing device is increased.

The present invention has been made in view of the above problems, and an object thereof is to accurately detect the amount of eccentricity of a disk by eliminating the need for vibration detecting means and disk eccentricity amount detecting means as separate devices. And a disc reproducing apparatus and a reproducing method for controlling the rotation speed of the disc to an optimum one according to the amount of eccentricity when the eccentricity of the disc is detected. To do.

[0015]

In order to achieve the above object, the present invention rotates a disc at a first rotation speed and a second rotation speed higher than the first rotation speed while tracking control is stopped. , Each time the light beam crosses a track on the disk, a pulse crossing signal is obtained each time the light beam crosses a track on the disk, and the eccentricity of the disk is calculated from the information of the track crossing signals at the first and second rotation speeds. Detects quantity information.

In an optical pickup, normally, a condenser lens is held by an elastic member, and a tracking control signal is supplied to a tracking means, so that the position of the condenser lens is regulated according to the tracking control signal. The beam follows the track (ie, tracking).

However, when the tracking control is stopped, the condenser lens is held by the elastic member, but is in a free state and vibrates in response to external vibration. Therefore, when vibration occurs in the disc reproducing apparatus due to the rotation of the eccentric disc, the rotation speed is low. When this vibration is small, the vibration of the condenser lens due to this vibration is also small, and the vibration frequency is also low. The condensing lens in this state vibrates slightly in the same phase as this disc reproducing device, but when the disc rotation speed increases and the vibration generated in the disc reproducing device also increases in amplitude and frequency, the The optical lens vibrates at a frequency according to the transfer function peculiar to the elastic member that indicates this, and does not follow the vibration of the rotating disk.

Therefore, since the force that causes the vibration caused by the rotation of the eccentric center disk is proportional to the square of the rotational speed of the disk and the eccentricity amount of the disk, the disk is proportional to the rotational speed of the disk. Although the vibration of the reproducing device increases, the first rotation speed is set to a low rotation speed so that the vibration is hardly generated in the disc reproducing device, and the second rotation speed is set to the eccentric disc at this speed. At this time, if the rotation speed is high such that the disk reproducing device vibrates, tracking control is not performed and the condenser lens is in a free state. Therefore, as shown in FIG. The scanning locus of the beam on the disk is a substantially circular locus 23 shown by the dotted line. In the latter case, the condenser lens vibrates at the natural frequency of the elastic member holding it. Becomes, for example, the locus 24 of elliptical shape indicated by a broken line.

When the circular locus 23 and the elliptical locus 24 are compared with each other, in the former case, the track 2 has a spiral shape or a circular shape, and therefore the locus 23 is substantially along the track 2. In the latter case, as compared with the former case, more tracks 2 are crossed, and the read signal obtained from the optical pickup is a pulse signal having a high frequency or a shortest cycle. Therefore, it is possible to obtain information indicating the magnitude of the eccentric center of gravity of the disc from the difference between the two.

Therefore, according to the present invention, as a concrete method for detecting the information on the amount of eccentricity of the disk, the number of pulses at a predetermined number of revolutions of the pulse signal, that is, the track crossing signal, is counted, or The cycle of the track crossing signal is detected, and the ratio or difference of the count numbers or cycles applied at the first and second rotation speeds is obtained. These ratios or differences represent the degree of eccentricity of the disc.

Further, according to the present invention, it is determined whether or not the disc is an eccentric center disc based on the eccentricity amount detected as described above, and the allowable maximum rotation speed of the disc is detected. Limit the rotation speed according to the amount. As a result, the disc reproducing apparatus can prevent the occurrence of vibration.

Further, according to the present invention, the information corresponding to the detected amount of eccentricity is displayed on the display means to inform the outside whether or not the disk used is an eccentricity disk.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of an eccentric center disc detecting method , a disc reproducing apparatus and a reproducing method according to the present invention.
Reference numeral 7 is a storage element, and 18 is a comparison circuit. The same reference numerals are given to the portions corresponding to those in FIG.

In this embodiment, in this embodiment, a counter 15, storage elements 16 and 17 and a comparison circuit 18 are provided in the conventional disk reproducing apparatus shown in FIG.
Is used to detect the information about the amount of eccentricity of the disk 1 using the track crossing pulse D from.

That is, for example, before the disc 1 is loaded and the information signal is reproduced, the CPU 10 generates the inhibition signal C to stop the operation of the tracking control circuit 8, and the information reading unit 6 is operated. The optical pickup is stopped, and a command A is generated so that the disk motor control circuit 5 causes the disk 1 to rotate at about 1 or 2 times the specified rotation speed or about twice the rotation speed. Set. This rotation speed will be referred to as the first
The first rotation speed is a rotation speed that does not cause vibration in the disc reproducing apparatus even if the disc 1 is an eccentric disc.
It is not limited to the above-mentioned 1x speed or 2x speed.

In the rotating state in which the disk 1 rotates at the first rotation speed, that is, in the low speed rotating state, the information reading section 6 reproduces the disk 1, and the reproduced signal is amplified by the preamplifier circuit 7 and the waveform is shaped. After performing processing such as the above, it is supplied to the CPU 10 and the counter 15 as a track crossing pulse D. The CPU 10 uses the track crossing pulse D when accessing a desired track 2 on the disk 1 as in the above-mentioned conventional technique.

On the other hand, the counter 15 counts one edge of the track crossing pulse D and is reset by the reset pulse E supplied from the disc motor control circuit 5 every one revolution of the disc 1. Therefore, the counter 15 obtains the pulse number N ₁ of the track crossing pulse D for each rotation of the disk 1, and the count value N ₁ is stored in the storage element 16.

Next, the CPU 10 sends a command A to the disk motor control circuit 5 to rotate the disk 1 at a high speed. In this case, if the disc 1 is an eccentric disc, the rotation speed is a rotation speed (hereinafter, referred to as a second rotation speed) such that the disk reproducing device always vibrates. The rotation speed.

In the high-speed rotation state of rotating at the second rotation speed, after the reproduction signal output from the information reading section 6 is processed by the preamplifier circuit 7 such as amplification and waveform shaping, as described above, It is supplied to the counter 15 as a track crossing pulse D. The counter 15 counts one edge of the track crossing pulse D and is reset by a reset pulse E supplied from the disc motor control circuit 5 every one revolution of the disc 1. Therefore,
The counter 15 obtains the pulse number N ₂ of the track crossing pulse D for each rotation of the disk 1, and the count value N ₂ is stored in the storage element 17.

In this way, when the track crossing pulse number N ₁ at low speed rotation is stored in the storage element 16 and the track crossing pulse number N ₂ at high speed rotation is stored in the storage element 17, the comparison circuit 18 , The number of these pulses N ₁ , N ₂
Are compared to obtain these ratios or differences. The comparison result F is fetched by the CPU 10.

When the disc 1 is an eccentric disc, as described with reference to FIG. 6, when the disc 1 is rotated at the first rotation speed, the scanning locus of the light beam 3 becomes a substantially circular locus 23 and the second locus. When rotating at the rotation speed, the scanning locus of the light beam 3 becomes a substantially elliptical locus 24. Therefore, the number of track crossing pulses N ₂ stored in the storage element 17 for one rotation of the disk 1 is larger than the number of track crossing pulses N ₁ stored in the storage element 16 for one rotation of the disk 1. Therefore, the ratio N ₂ / N ₁ that is the comparison result F of the comparison circuit 18 becomes larger than 1, and the difference (N ₂ −N ₁ ) becomes positive, and these are relative to them. When it is equal to or more than the preset threshold value, it means that the disk is an eccentric center of gravity.

Here, the change in the number of track crossing pulses per rotation with respect to the rotational speed of the disk is shown as follows.
Generally, as shown in FIG.

In the figure, the characteristic 19 shows the characteristic of the disk in which both the eccentricity amount and the eccentricity amount are small.
The number of track crossing pulses per one rotation of the disk is sufficiently small, and is almost constant regardless of the change in the rotation speed. Characteristic 20 shows a characteristic of a disc having a large eccentricity amount but a small eccentricity amount. The number of track crossing pulses per rotation of the disc 1 is large, but it is almost constant regardless of the change of the rotation speed. .

Characteristic 21 is a characteristic of a disc having a small eccentricity but a large eccentricity, and the number of track traversing pulses per one revolution of the disc changes as the rotational speed changes. As described above, the change increases as the rotational speed of the disc sequentially increases and the vibration frequency generated in the disc reproducing device approaches the natural frequency of the transfer function of the elastic member holding the optical pickup. Then, the rotational speed of the disc further increases, and the frequency generated in the disc reproducing device decreases as the natural frequency of the transfer function of the elastic member holding the optical pickup increases.

In FIG. 2, f ₁ is the above-mentioned first rotation speed, and f ₂ is the above-mentioned second rotation speed. From FIG. 2, the number N ₁ of track crossing pulses stored in the storage element 16 at the first rotation speed f ₁ and the number of pulse crossing pulses stored in the storage element 17 at the second rotation speed f ₂ It is possible to determine whether or not the disc 1 is an eccentric disc by comparing N ₂ with the comparison result F and determining whether or not the comparison result F is equal to or more than a preset threshold value. In the case of an eccentric center disc, this comparison result F becomes information indicating the degree of the eccentric center amount, and the CPU 10 can recognize the degree of the eccentric center amount.

Based on the comparison result F of the comparison circuit 18, the CPU 10 determines whether or not the disk 1 currently mounted is an eccentricity disk, and if it is not an eccentricity disk, reproduces the information signal. When the disk 1 is rotated, the disc 1 is rotated at a rotation speed according to a request from the outside. However, when the disc is an eccentric center of gravity disk, the maximum rotation speed of the disc 1 is according to the comparison result F regardless of the request from the outside. To limit. For example, the disc 1 is a CD-ROM
However, even if high-speed reproduction of 8 × speed is possible, it is limited to high-speed reproduction up to 6 × speed.

In this way, it is possible to easily and surely determine whether or not the disk 1 is an eccentric center disk without separately providing vibration detecting means, and the eccentricity amount of the disk 1 can be determined. The information indicating the degree can be detected, the maximum rotation speed can be limited according to the amount of eccentricity, and the vibration of the disk reproducing device can be prevented.

Further, as a method of more accurately detecting the maximum allowable rotation speed of the disk 1, a comparison result F is obtained when the second rotation speed is set to f ₂ in FIG. When it is determined that the disc 1 is an eccentric disc, the number of track crossing pulses N ₂ obtained for each second rotation speed is further reduced while sequentially lowering the second rotation speed from f _2. The first rotation speed f ₁ rewritten by the storage element 17 and stored in the storage element 16
The number of crossing pulses N ₁ of the track is compared with that of the disk 1 and the second rotation speed when the ratio or difference which is the comparison result F becomes equal to or less than a preset threshold value for each disk 1
The maximum allowable rotation speed of

FIG. 3 is a block diagram showing a second embodiment of the eccentric center-of-gravity disc detecting method , disc reproducing apparatus and reproducing method according to the present invention, in which 22 is a shortest period detecting circuit and corresponds to FIG. Are denoted by the same reference symbols and redundant description will be omitted.

In this figure, this embodiment uses a shortest cycle detection circuit 22 instead of the counter 15 in FIG.

The track crossing pulse D is a signal having a coarse and fine waveform as shown in FIG. 4, and its shortest period t is determined by the number of track crossing pulses per one rotation of the disk and the rotation speed of the disk. Therefore, when the rotational speed of the disc 1 changes twice, if the number of track crossing pulses per one revolution of the disc does not change, the shortest period t changes to 1/2, but the disc reproducing apparatus vibrates. Occurs, and the number of track crossing pulses per one rotation of the disk increases, the shortest period t changes to be smaller than 1/2.

Therefore, in the second embodiment shown in FIG.
For each of the first rotation speed f ₁ and the second rotation speed f ₂ of the disk 1, the disk 1 is read by the shortest cycle detection circuit 22.
The shortest period t of the track crossing pulse D in one rotation period of
₁ and t ₂ are detected and stored in the storage elements 16 and 17, respectively. Then, in the comparison circuit 18, these shortest periods t
The ratio t ₁ / t ₂ or the difference (t ₁ −t ₂ ) of ₁ and t ₂ is calculated, and the CPU
In step 10, whether or not the disc 1 is an eccentric center disc is determined from the comparison result F and the degree of the eccentricity is detected, and the allowable maximum rotation speed of the disc 1 is set.

When the second rotation speed f ₂ is n times the _first rotation speed f ₁ , the ratio t ₁ / t ₂ is approximately n when the disk 1 is not an eccentric disk. Further, the difference (t ₁ −t ₂ ) is approximately t ₁ · (n−1) / n, but when the disc 1 is an eccentric disc, it should be different from the preset threshold value from this value. become. As a result, it can be determined that the disc is an eccentric center of gravity disc, and the degree of the eccentric center of gravity can be known from the magnitude of this ratio or difference.

The shortest cycle detection circuit 22 is, for example, a circuit which counts a clock of a constant cycle for each cycle of the track crossing pulse D and detects each cycle as a count value. The value is set as a provisional shortest cycle, the second count value is compared with this value, and the smaller count value is set as a new provisional shortest cycle. The provisional shortest period is compared with the set count value, the smaller count value is selected and held as a new provisional shortest period, and such an operation is performed for one revolution of the disk 1 to finally obtain the value. The count value of the shortest cycle is temporarily stored in the storage element 16 or 17 as the true count value of the shortest cycle.

As described above, also in the second embodiment, the same effect as that of the first embodiment can be obtained.

In the above description of the embodiments, numerical values are specifically shown, but these are merely shown for convenience of description, and the present invention is not limited thereby.

Further, in the first embodiment shown in FIG.
The CPU 10 can be provided with the function of the circuit including the counter 15, the storage elements 16 and 17, and the comparison circuit 18, and also in the second embodiment shown in FIG. 3, the shortest cycle detection circuit 22 and the storage element are provided. 16,17, comparison circuit 1
It goes without saying that the function of the circuit composed of 8 can be provided to the CPU 10. This further simplifies the circuit configuration.

Although not shown in FIGS. 1 and 3, it is also possible to provide a display means for displaying the determination result of the CPU 10 so that the determination result can be known to the user. For example, as the display means, a visual display means for displaying information indicating whether the disc 1 is an eccentric disc or information indicating the maximum permissible double speed reproduction set on the disc 1, or in addition to this, , When it is determined that the disc is an eccentric center of gravity,
It can be a display means for issuing an alarm or the like.

[0049]

As described above, according to the present invention,
The disc is rotated without tracking control, and the information of the eccentricity of the disc is detected according to the comparison result of the number of track crossing pulses by reading the disc at different rotation speeds. Since the eccentricity disc is detected without adding a new means, it is possible to expand the scale of the disc reproducing device, avoid the cost increase, and perform the detection with high precision. Since the allowable maximum rotation speed of the eccentric center disc is regulated according to the detected eccentric center amount, it is possible to effectively suppress the occurrence of vibration in the disc reproducing device due to the eccentric center disc.

[Brief description of drawings]

[1] unbalance disk detection how according to the present invention, is a block diagram showing a first embodiment of the de office <br/> click reproducing apparatus and reproducing method.

FIG. 2 is a graph showing a characteristic of the number of track crossing pulses per one rotation of the disk with respect to the rotation speed of the disk.

FIG. 3 is a block diagram showing a second embodiment of an eccentric center-of-gravity disc detecting method , a disc reproducing apparatus and a reproducing method according to the present invention.

FIG. 4 is a waveform diagram showing a specific example of a track crossing pulse.

FIG. 5 is a block diagram showing an example of a conventional disc reproducing apparatus.

FIG. 6 is a diagram showing a scanning locus of a light beam on a disk according to the amount of eccentricity of the disk when tracking control is not performed.

[Explanation of symbols]

1 disc Two tracks 3 light beams 4 disk motor 5 Disc motor control circuit 6 Information reading section 7 Preamplifier circuit 8 Tracking control circuit 9 Signal processing circuit 10 CPU 11 Audio circuit 12 Audio signal output terminal 13 CD-ROM decoder 14 CD-ROM signal output terminal 15 counter 16,17 Storage element 18 Comparison circuit 22 Cycle detection circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiro Matsunaga               292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa               Hitachi Image Information System Co., Ltd. (72) Inventor Kazunari Narita               292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa               Hitachi, Ltd. Video information media               A business division (72) Inventor Masato Sano               292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa               Hitachi, Ltd. Video information media               A business division                (56) Reference JP-A-8-55422 (JP, A)                 JP-A-9-204741 (JP, A)

Claims (6)

(57) [Claims] 1. A disk motor drive circuit for driving a disk motor for rotating a disk, an information reading section configured to be movable in a direction traversing a track on the disk and reading information on the disk with a light beam, Tracking error detecting means for outputting a tracking error signal which is a signal corresponding to the position of the track and the light beam on the disk, and the information reading so that the light beam on the disk is always on the track by using the tracking error signal. In a disc reproducing apparatus provided with a tracking control means for controlling the position of a part and a track crossing signal creating means for creating a track crossing signal which is a signal for identifying that a light beam has crossed a track, When the tracking control means is not operated by rotating the From the first track crossing signal information which is information obtained from the track crossing signal and the track crossing signal when the disk is rotated at the second rotation speed higher than the first rotation speed and the tracking control means is not operated. A method for detecting an eccentric center disk, wherein information on the amount of eccentricity, which is the amount of deviation of the center of gravity from the center of rotation of the disk, is detected using the obtained second track crossing signal information. 2. The first track crossing signal information according to claim 1, wherein the first track crossing signal information is a total number of tracks crossed by a light beam when the disk rotates a predetermined number of times at the first rotation speed. And the second track crossing signal information is the total number of tracks crossed by the light beam when the disk has rotated a predetermined number of times at the second rotation speed.
The number of tracks of the eccentricity disc is detected by using the ratio or the difference between the number of the first tracks and the number of the second tracks. . 3. The first track crossing signal according to claim 1, wherein the first track crossing signal information is a cycle of the track crossing signal when the rotation speed of the disk is the first rotation speed. And the second track crossing signal information is
A second track crossing signal cycle, which is a cycle of the track crossing signal when the rotation speed of the disk is the second rotation speed, the first track crossing signal cycle and the second track crossing signal cycle. An eccentricity disc detection method, characterized in that the eccentricity center information of the disc is detected by using a ratio or a difference from a cycle. 4. A disk motor drive circuit for driving a disk motor for rotating a disk, an information reading section configured to be movable in a direction traversing a track on the disk and reading information on the disk with a light beam, Tracking error detection means for outputting a tracking error signal which is a signal according to the position of the track and the light beam on the disk, and the information so that the light beam on the disk is always on the track by using the tracking error signal. In a disc reproducing apparatus provided with a tracking control means for controlling the position of the reading section and a track crossing signal creating means for creating a track crossing signal which is a signal for identifying that the light beam has crossed a track, When rotating at the first rotation speed and the tracking control means is not operated First track crossing signal information, which is information obtained from the track crossing signal, and the track crossing signal when the disk is rotated at a second rotation speed higher than the first rotation speed and the tracking control means is not operated. Using the second track crossing signal information which is the information obtained from the above, arithmetic processing means for detecting information on the amount of eccentricity of the center of gravity of the disc with respect to the center of rotation of the disc, and reproduction for switching the reproduction speed of the disc A disc reproducing apparatus, which is provided with a speed switching means and reproduces the disc at a reproducing speed according to the amount of eccentricity of the disc. 5. The track-crossing signal information according to claim 4, wherein the first track crossing signal information is a total number of tracks crossed by the light beam when the disk rotates a predetermined number of times at the first rotation speed. The second track crossing signal information is a total number of tracks crossed by the light beam when the disk has rotated a predetermined number of times at the second rotation speed. The number of tracks, wherein the arithmetic processing means is configured to detect the information of the eccentricity amount of the disk by calculating the ratio or difference between the first number of tracks and the second number of tracks. A disc reproducing device characterized by. 6. The first track crossing signal according to claim 4, wherein the first track crossing signal information is a cycle of the track crossing signal when the rotation speed of the disk is the first rotation speed. And the second track crossing signal information is
A second track crossing signal cycle, which is a cycle of the track crossing signal when the rotation speed of the disk is the second rotation speed, wherein the arithmetic processing unit is configured to detect the first track crossing signal cycle. A disc reproducing apparatus, characterized in that a ratio or a difference from the second track crossing signal period is calculated to detect information on the amount of eccentricity of the disc.