JPH11353787A - Method and device for discriminating number of layers of optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate the number of recording layers of a disk in an optical disk device for reproducing an optical disk having plural recording layers. SOLUTION: A comparator for comparing a focus error signal FE with reference voltage levels Va, Vb is provided, the area of the FE signal in a range where the FE signal exceeds Va between a point a1 where the FE signal exceeds a first level Va and a point b1 where it exceeds a second level Vb during focus search in defined as a first measurement value (S1), and the area of the FE signal in a range where the FE signal exceeds Vb is defined as a second measurement value (S2). This processing is repeated whenever the FE signal crosses the Va, Vb levels, and measuring is performed until Sn. The number of recording layers is discriminated by using parameters calculated by dividing measured total area by one area Sx.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a method and apparatus for reliably determining the number of layers of an optical disc to be reproduced when reproducing a multilayer optical disc such as a VD drive.

[0002]

2. Description of the Related Art Discrimination of the number of recording layers in a conventional optical disk device will be described by taking a DVD as an example. DVD is a single-sided reading system, and single-layer and double-layer discs are permitted by the standard. These two disks have a higher reflectivity in a single layer than in a two-layer disk. By measuring the amount of return light when this disk is irradiated with a certain amount of laser beam, the disk has a single layer or two layers. Can be determined.

[0003]

However, it is assumed that the amount of reflected light is reduced due to deterioration of the laser diode or dust, or that another medium such as a CD or CD-R is inserted. If the discrimination is performed only based on the difference in reflectance, there is a possibility that the discrimination is erroneous, and a more accurate discrimination method has been required.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a method and an apparatus capable of reliably and accurately determining the number of layers of an optical disk.

[0005]

In order to achieve the above object, the present invention provides a focus error signal (hereinafter referred to as FE) when an objective lens is moved near a focal point with a disk.
Signal is sampled over a certain period of time and integrated, thereby measuring the area of the vertical axis: FE signal and the horizontal axis: the function of time, and multiplying the result by the conventional disc discriminating condition to improve discrimination accuracy. It is enhanced.

Further, the area is measured separately for each peak of the S-shaped waveform generated in each recording layer of the focus error signal, and the sum of the areas is divided by the area of one peak to obtain
Without being affected by the reflectance or the moving speed of the objective lens,
The number of recording layers is determined.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Claims 1 and 4 of the present invention
In the method and the apparatus for discriminating the number of optical disc layers described in (1), the objective lens is moved for a certain section, and the F
E level is sampled at fixed time intervals, and the integrated value of the absolute value is used to determine the disc type,
Or change the servo constants,
It is possible to add a new discrimination parameter called the area difference of the FE signal during disc discrimination, and this value depends not only on the number of recording layers but also on the reflectivity. By multiplying by the parameter such as the RF amplitude difference used in the prior art, the accuracy of the discriminant can be increased.

According to a second aspect of the present invention, there is provided a method and apparatus for determining the number of optical disc layers according to the first and fourth aspects, wherein two different voltage levels are set and a focus error signal is sampled. However, in the range between the two voltage levels, integration is not performed, and noise such as noise generated near the reference voltage of the FE signal, offset, and pseudo S-shape generated on the surface of the base material of the disk are considered. Since the influence can be eliminated, it is possible to perform the determination with higher accuracy.

According to a third aspect of the present invention, there is provided a method and apparatus for discriminating the number of optical disc layers, wherein an objective lens is moved for a certain section, and a focus error signal level detected during the section is sampled at a certain time interval. The integrated value of the focus error signal in the range exceeding Va from when the focus error signal exceeds the first level Va to when the focus error signal exceeds the second level Vb is defined as S1, and after the focus error signal exceeds Vb. The integrated value of the focus error signal in the range exceeding Vb before exceeding Va is represented by S2
The number of times the above condition is satisfied during the movement of the objective lens is repeatedly measured, and the sum of all these integrated values is divided by the maximum value of the individual integrated values to determine the disc type, Alternatively, the servo constant is changed, and the area of the FE signal is measured for each S-shaped peak, and the total area is divided by one peak, so that the reflectance and the moving speed of the objective lens are calculated. Without being affected, this value alone serves as a highly accurate discrimination parameter for discriminating the number of recording layers, and thus has the effect of performing more accurate discrimination.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 shows the configuration of an optical disk apparatus according to Embodiment 1 of the present invention. The optical disc 1 has a multilayer structure having a plurality of recording surfaces, and reflects a laser beam output from a laser diode (not shown) mounted on the optical pickup 4. The optical pickup 4 has an optical element (not shown) and an objective lens 2 mounted thereon, and converts the light reflected on the data surface of the optical disc 1 into an electric signal by a photodetector (not shown) and outputs the electric signal. An FE signal is generated by the FE signal generation means 5 from a signal from the photodetector. The FE signal is taken into the servo controller 6 as digital data at a constant sampling period (Ts). The servo controller 6
At the time of disc discrimination, a ramp-shaped signal is output by the search drive commanding means 9 and the vertical position of the objective lens 2 is gradually changed via the focus actuator driving means 11 and the focus actuator 3 to focus the laser light. Move a fixed section. The servo controller 6 has an FE for integrating the absolute value of the sampled FE signal.
The integrating means 7 is mounted, and the FE signal level is measured on the vertical axis and the area of the curve on time is measured on the horizontal axis while the objective lens 2 moves for a certain section, and the result is stored in the memory 8.

After the disc discriminating operation is completed, the value of the memory 8 is read by the system controller 10 which controls the entire apparatus, and the disc type is judged based on the value.

As described above, according to the first embodiment,
It is possible to add a new discrimination parameter called the area difference of the FE signal during disc discrimination, and this value depends not only on the number of recording layers but also on the reflectivity. The accuracy of the discriminant can be increased by multiplying the parameter such as the RF amplitude difference used in the prior art.

(Embodiment 2) FIG. 2 shows Embodiment 2 of the present invention, in which a window comparator 12 is provided in a servo controller 6 so that an FE signal falls within a range between two reference voltage levels Va and Vb. Indicates that the measurement by the FE integrating means 7 is stopped. FIG. 4 is a diagram showing an FE signal generated during disc discrimination in the second embodiment. The FE signal waveforms of a single-layer disc (left diagram in FIG. 4) and a double-layer disc (right diagram in FIG. 4) are shown. , The area to be measured is shaded. This shows that the area at the portion between Va and Vb is not measured.

As described above, according to the second embodiment,
Since effects such as noise and offset generated near the reference voltage of the FE signal and pseudo S-shaped generated on the surface of the disk substrate can be eliminated, more accurate determination can be performed.

(Embodiment 3) FIG. 3 shows the configuration of Embodiment 3 of the present invention.
A comparator 13 for comparing the E signal with the reference voltage levels Va and Vb is provided, the result is monitored by the FE integrating means 7, and the memory 8 is expanded so that a plurality of results can be stored. FIG. 5 shows an FE signal and an area to be measured in the third embodiment. When the servo controller 6 is instructed by the system controller 10 to perform the disc discriminating operation, the servo controller 6 moves the objective lens 3 in a ramp shape for a certain section. At this time, the area of the FE signal exceeding Va in a range from the point a1 exceeding the first level Va to the point b1 exceeding the second level Vb is determined by the first measurement value (S1 ), And the area of the FE signal in the range exceeding Vb between the point b1 and the point a2 is set as the second measurement value (S2). Similarly, the area of the FE signal exceeding the Va from the point a2 to the point b2 is exceeded. The area of the FE signal in the range is set as a third measurement value (S3). The fourth measurement value (S4) is
An attempt is made to measure the area of the FE signal in the range exceeding Vb from the point b2 to the next point a3 exceeding Va. However, since the point a3 does not exist in the last FE peak, the objective lens in a certain section is measured. Is completed, and the measured values up to the time when the disc discrimination operation ends are stored in S4. Therefore, the measured areas S1, S2, S3, S4
The number of recording layers is determined using a parameter calculated by dividing the sum of the data by one area Sx.

As described above, according to the third embodiment,
Since the area of the FE signal is measured for each S-shaped peak and the sum of the areas is divided by one peak, the value of the number of recording layers is determined by this value alone without being affected by the reflectance or the moving speed of the objective lens. Is determined with a high degree of certainty, so that a more accurate determination can be performed.

[0017]

As is apparent from the above embodiment, the present invention samples a focus error signal (hereinafter referred to as an FE signal) at a fixed time when the objective lens is moved near the focal point with the disk. By integrating these, the vertical axis: the FE signal, the horizontal axis: the area of the function of time are measured, and the result is multiplied by a conventional disc discriminating condition to improve discrimination accuracy. High discrimination can be performed.

According to the present invention, the area of each ridge of the S-shaped waveform generated in each recording layer of the focus error signal is measured separately, and the sum of the areas is divided by the area of one ridge to obtain the reflection. The number of recording layers is determined without being affected by the rate or the moving speed of the objective lens.
A more accurate determination can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an optical disk device according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an optical disk device according to a third embodiment of the present invention.

FIG. 4 is a waveform chart illustrating a FE signal and a part whose area is measured according to the second embodiment of the present invention.

FIG. 5 is a waveform diagram illustrating a FE signal and a part whose area is measured according to Embodiment 3 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk 2 Objective lens 3 Focus actuator 4 Optical pickup 5 FE signal generation means 6 Servo controller 7 FE integration means 8 Memory 9 Search drive command means 10 System controller 11 Focus actuator drive means 12 Window comparator 13 FE signal comparator

Claims (6)

[Claims] In an optical disc apparatus for reproducing an optical disc having a plurality of recording layers, an objective lens is moved for a certain section, and a focus error signal level detected during the sampling is sampled at a certain time interval, and the absolute value is integrated. A discrimination method for discriminating the number of optical disc layers, comprising discriminating a disc type using a value or changing a servo constant. 2. The optical disc layer according to claim 1, wherein two different voltage levels are set, and integration is not performed when a value obtained by sampling a focus error signal is in a range between the two voltage levels. Number determination method. 3. An optical disk apparatus for reproducing an optical disk having a plurality of recording layers, wherein an objective lens is moved for a certain section, and a focus error signal level detected during the movement is sampled at a certain time interval. The integrated value of the focus error signal in a range exceeding Va from the first level Va to exceeding the second level Vb is defined as S1. The integrated value of the focus error signal in the range exceeding Vb is defined as S2, and repeatedly measured as many times as the above condition is satisfied during the movement of the objective lens. The sum of all the integrated values is calculated as the sum of the individual integrated values. 1
A discriminating method for discriminating a disc type or changing a servo constant based on a result obtained by dividing the number of discs. 4. An optical disk apparatus for reproducing an optical disk having a plurality of recording layers, irradiating the optical disk with a laser beam through an objective lens, moving the objective lens for a fixed section, receiving a laser beam reflected from the optical disk, and electrically receiving the laser beam. Number of optical disc layers comprising: means for converting a signal into a signal; means for generating a focus error signal from the obtained electric signal; and means for sampling the level of the focus error signal at regular time intervals and integrating the absolute value thereof Discriminator. 5. The optical disk according to claim 1, further comprising means for setting two different voltage levels and determining whether a value obtained by sampling the focus error signal falls within a range between the two voltage levels. Layer number discrimination device. 6. An optical disk apparatus for reproducing an optical disk having a plurality of recording layers, irradiating the optical disk with a laser beam through an objective lens, moving the objective lens for a predetermined section, receiving a laser beam reflected from the optical disk, and electrically receiving the laser beam. Means for converting into a signal, means for generating a focus error signal from the obtained electric signal, means for comparing the focus error signal with reference voltage levels Va and Vb, , And the integrated value of the focus error signal in the range exceeding Va between the time when the focus error signal exceeds the first level Va and the time when the focus error signal exceeds the second level Vb is S1; Va after crossing
The accumulated value of the focus error signal in the range exceeding Vb until the value exceeds Vb is defined as S2, and repeatedly measured as many times as the above condition is satisfied during the movement of the objective lens. An optical disc layer number discriminating device comprising means for dividing by one of the integrated values of the optical discs.