JPH11176072A - Optical disk classification discrimination method and optical disk drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate the classification of an optical disk by receiving reflection light from the optical disk, obtaining a read signal, detecting the cross talk amount from the read signal amplitude change caused by a fact that a light beam traverses an optical disk track, and estimating the recording density in the track pitch direction. SOLUTION: The reflection light of a main beam is received by a four division photodetector 30 and the all are added by an RF amplifier 5 to be an RF signal. The RF signal is supplied to a peak detection part 51 and a bottom detection part 52 and a peak detection signal PD and a bottom detection signal BD are supplied to an inversion amplifier 53 based on a reference level VC. An inversion signal based on a mirror level ML is outputted from the inversion amplifier 53 to be supplied to a peak hold part 54 and a bottom hold part 55 and the respective parts hold a peak value A and a bottom value B. The peak value A and the bottom value B are calculated by an arithmetic part 56, the cross talk amount CT is obtained to be supplied to a discrimination part 57 and the disk classification is discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a CD, a CD-R
OM, CD-R, CD-RW, CD-I, MD, DVD
More particularly, the present invention relates to an optical disk type determining method and an optical disk drive device for identifying the types of a plurality of optical disks having different recording densities and adjusting an optical system.

[0002]

2. Description of the Related Art In recent years, optical disks having various recording densities have been developed, and optical disks having different recording densities have been used in the same optical disk drive. On this occasion,
Optical system parameters such as laser wavelength and numerical aperture (N
It is necessary to adjust A) according to the recording density of the optical disc to be recorded or reproduced, and the function of determining the type of the optical disc based on such a difference in recording density is required as an essential function of the optical disc drive device.

Conventionally, as a technique for determining the type of an optical disc, a technique disclosed in Japanese Patent Application Laid-Open No. 9-270167 is known. That is, when a light beam irradiating the optical disk periodically crosses a track, a read signal (RF signal)
Causes a change in the amplitude of the cycle corresponding to the change, and the change in the amplitude changes depending on the relationship between the spot diameter of the light beam and the track pitch. In other words, when the beam spot diameter is smaller than the track pitch, the amplitude increases,
When the beam spot diameter is larger than the track pitch, the amplitude becomes smaller due to crosstalk from an adjacent track. On the other hand, the beam spot diameter changes under the influence of aberration depending on the thickness of the transparent substrate on the optical disk.
The amplitude of the F signal also changes. By detecting the change in the amplitude, the thickness of the transparent substrate of the optical disk is detected, and the type of the optical disk is determined.

[0004]

However, in this method, in the case of a low-reflectivity disk such as a CD-RW (rewritable), the amplitude of the RF signal becomes small, so that the recording density is the same as that of a single-density CD. Nevertheless, there is a problem that the disc cannot be determined as a high-density disc and erroneous discrimination occurs.

The present invention has been made to solve such a problem, and provides an optical disk type determining method and an optical disk drive device capable of accurately identifying a difference in recording density and determining an optical disk type. The purpose is to do.

[0006]

According to the present invention, there is provided an optical disk type determining method for receiving a reflected light of an optical beam irradiated on an optical disk from the optical disk to obtain a read signal, and obtaining the read signal. A crosstalk amount of the read signal is detected from an amplitude change of the read signal generated by crossing a track of the optical disk, and a recording density in a track pitch direction is estimated based on the crosstalk amount to determine a type of the optical disk. It is characterized by doing.

An optical disk drive apparatus according to the present invention includes a light beam irradiating means for irradiating an optical disk with a light beam, and detecting light irradiated on the optical disk by the light beam irradiating means and reflected from the optical disk. A light detecting means for outputting a read signal; an envelope detecting means for detecting an envelope of the read signal, the amplitude of which changes when the light beam crosses a track of the optical disc; and an envelope detecting means for detecting the envelope. Peak hold means and bottom hold means for respectively holding the peak value and the bottom value of the envelope, and crosstalk detection for detecting the amount of crosstalk from the peak value and the bottom value held by the peak hold means and the bottom hold means, respectively. Means and a seed of the optical disc based on the amount of crosstalk. A disk discrimination means for discriminating, characterized in that an adjusting means for adjusting the optical system based on the determination result by the disc discrimination means.

According to the present invention, the recording density in the track pitch direction is estimated by detecting not the amplitude of the periodic change of the read signal but the crosstalk amount specified from the amplitude change,
The type of the optical disk is determined. Since the amount of crosstalk is determined by the ratio between the peak value and the bottom value of the envelope including the information on the change in the amplitude of the read signal, for example,
The influence due to the difference in the reflectance of the optical disk can be eliminated, and the track pitch can be accurately estimated.

Further, according to the present invention, in addition to calculating the ratio between the peak value and the bottom value of the envelope of the read signal as the amount of crosstalk, for example, the read signal is amplified by a gain control amplifier and the envelope detector is used for the amplification. In addition to the output, the gain of the gain control amplification means may be controlled on one of the peak hold value and the bottom hold value, and the other of the peak hold value and the bottom hold value may be output as the crosstalk amount.
In this case, the comparator may compare the amount of crosstalk with a predetermined value and output information indicating the type of the optical disk.

[0010]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of an optical disk drive according to one embodiment of the present invention. The optical disc 1 is rotationally driven by a spindle motor 2 at a constant linear velocity, for example.
At a position facing the recording surface of the optical disk 1, an optical pickup 3 as a light beam irradiation unit and a light detection unit is arranged. The drive of the optical pickup 3 is controlled by the feed motor 4 in the radial direction of the optical disc 1. A read signal (RF signal) from the optical pickup 3 is amplified by an RF (high frequency) amplifier 5 and is subjected to EFM / CIRC (Cross In).
terleaved Reed-Solomon Code) decoder 6. The decoder 6 performs EFM demodulation, CIRC
Decoding is performed, and data is temporarily stored in a buffer memory 8 under the control of a memory controller 7, and control information is supplied to a system controller 9. The data stored in the buffer memory 8 is sequentially read from the buffer memory 8 under the control of the memory controller 7,
The data is output to a host system (not shown). The servo controller 10 controls the focus and tracking of the optical pickup 3 based on the output of the RF amplifier 5 and also controls the spindle motor 2 and the feed motor 4 according to a command from the system controller 9. The servo control unit 10
Includes an optical disk type determination circuit to be described later.

FIG. 2 is a diagram showing a specific configuration of the optical pickup 3. Semiconductor laser 21a and semiconductor laser 21
b means that the oscillation wavelength is, for example, 780 nm and 635 nm, respectively.
nm, and one of them is selected according to the recording density of the optical disc 1. The laser beam emitted from the semiconductor laser 21a or 21b is collimated by a collimator lens 22 via a beam splitter 27, is divided into three of a main beam and two sub-beams by a diffraction grating 23, and is split into a beam splitter 24 and a diaphragm 2.
An image is formed as a three-beam spot on the optical disk 1 via the optical disk 8 and the objective lens 25. These constitute light beam irradiation means. Light reflected by the three-beam spot from the optical disc 1 is reflected by the beam splitter 24, passes through the lens 26, and forms images on three photodetectors 30, 31, and 32, which are light detecting means.

FIG. 3 shows a relationship between a main beam 40 for generating an RF signal and a track pitch TP and an obtained RF among three beams generated by the optical pickup 3.
It is a figure showing a signal. Now, when the main beam 40 is positioned on the track 41, the pit portions 42 and the mirror portions 43 alternately appear due to the rotation of the optical disk 1, so that the pit portions 42 have the lowest level and the mirror portions 43 have the highest level. A high frequency RF signal is obtained. When the main beam 40 moves in a direction orthogonal to the track 41, the main beam 40 gradually deviates from the pit portion 42, so that the lower level of the high-frequency signal approaches the mirror level. An RF signal whose envelope has a period corresponding to the track pitch TP is obtained.

As shown in FIG. 1A, the track pitch TP
When 1 is large, the pit portion 42 is hardly detected when the main beam 40 is in the off-track state, so that the amplitude of the bottom envelope becomes large, and when the track pitch TP2 is small as shown in FIG. Detects the adjacent pit portion 42 with a considerable area when off-tracking, and the signal level is almost the same as in the on-track state, so that the amplitude of the envelope on the bottom side becomes small. Further, the RF signal waveform changes depending on the thickness of the transparent medium of the optical disc 1. This is because when the thickness of the transparent substrate is different, the spot diameter of the main beam 40 changes due to the influence of aberration.

On the other hand, the reflectivity of the optical disc 1 itself is low only by the amplitude of the bottom envelope of the RF signal.
Discrimination between the RW and the high-density disk becomes impossible. Therefore, the present invention focuses on the crosstalk amount CT obtained from the RF signal.

FIG. 4 is a diagram showing the relationship between various optical disks and the crosstalk amount CT. Here, when the bottom level of the bottom envelope relative to the mirror level (ML) is A and the peak level of the bottom envelope relative to the mirror level is B, the crosstalk amount CT = B /
A is defined. According to measurements by the inventors, when a main beam corresponding to the beam spot diameter for CD is used,
In the case of a single-density optical disk having a transparent substrate thickness t = 1.2 mm as shown in FIG. 7A, CT1 <30%. Such an optical disc 1 includes a CD, a CD-ROM,
CD-R and the like. In the case of a double-density optical disk having a transparent substrate thickness t = 1.2 mm as shown in FIG.
T2 <75%, greater than CT1. Examples of such an optical disk include a double density CD, a CD-ROM, and the like. As shown in FIG.
In the case of a 0.6 mm high density optical disc, CT3> CT
It was 2. As such an optical disk, there is a DVD. In the case of CD-RW having the same recording density and substrate thickness as CD as shown in FIG. 3D, the amplitude of the RF signal itself was small, but CT4 was almost the same as CT1. The above is summarized as follows.

[0016]

[Table 1]

From the above, it can be understood that the recording density of the optical disk can be accurately estimated by measuring the crosstalk amount CT.

FIG. 5 is a circuit diagram of the optical disk type discriminating circuit 50 constructed based on such points. The reflected light of the main beam 40 is received by the photodetector 30 divided into four parts, and when these are all added by the RF amplifier 5, R
It becomes the F signal. The RF signal is supplied to an optical disk type discriminating circuit 5
The peak detection signal 51 is supplied to the peak detection unit 51 and the bottom detection unit 52, and the mirror level ML is detected as the peak detection signal PD and the bottom envelope is detected as the bottom detection signal BD with reference to the reference level VC. These are supplied to the inverting amplifier 53. The inverting amplifier 53 outputs a signal obtained by inverting the bottom envelope with respect to the mirror level ML, and supplies the inverted signal to the peak hold unit 54 and the bottom hold unit 55. The peak hold unit 54 holds the peak value A, and the bottom hold unit 5
At 5, the bottom value B is held. The peak value A and the bottom value B are supplied to the calculation unit 56, where B / A is calculated, and the crosstalk amount CT is obtained. The crosstalk amount CT is supplied to the discriminating unit 57, and the disc type is obtained based on the above-described reference.

FIG. 6 shows the optical disk type discriminating circuit 50.
5 is a flowchart at the time of starting the optical disc drive device using the method. First, the focus servo is turned on (S1), and a track scan is performed (S2). The envelope of the obtained RF signal is detected (S3),
Peak value B (based on VC) and bottom value A
(When VC is used as a reference) is held (S4). From the obtained peak value B and bottom value A, the crosstalk amount C
T is determined (S5), and the type of the optical disc is determined from the result (S6). Here, in the case of the single density, the operation proceeds to the next operation as it is (S7), but in the case of the double density, adjustment of the signal processing system such as switching to an equalizer level and double firmware is performed (S8). If the density is high, the optical system is changed such as the NA and the laser wavelength (S9). That is, the semiconductor laser shown in FIG.
b and the aperture 28 is narrowed down. Then, adjustment of the signal processing system such as switching to the equalizer level and high-density firmware is also performed (S10).

By the above processing, an optical disk of an arbitrary type can be set in the optical disk drive device without worrying about the type of the optical disk 1. Even in this case, the disk type is automatically determined and the disk type is determined. Various adjustments applicable to the optical disc can be performed.

The present invention is not limited to the embodiment described above. In the above-described embodiment, the optical disc type discriminating circuit 50 calculates the crosstalk amount CT by calculating the B / A in the calculation unit. However, the optical disc type discriminating circuit 60 may be configured as shown in FIG.

In this circuit, instead of arithmetic processing, RF
A variable gain amplifier 61 for amplifying a signal is provided, and the gain of the variable gain amplifier 61 is controlled so that the peak value A of the inverted bottom envelope output from the peak hold unit 54 is always constant. For this purpose, the peak value A is fed back as a gain control amount of the variable gain amplifier 61. When the optical disk type determination circuit 60 is configured as described above, the disk type can be determined only by comparing the level with the comparator 62 with the bottom value B held by the bottom hold unit 55 as the crosstalk value CT. This circuit has an advantage that the circuit and the processing are simplified because there is no arithmetic unit.

[0023]

As described above, according to the present invention,
Instead of detecting the amplitude of the periodic change of the read signal, the amount of crosstalk specified from the amplitude change is detected to estimate the recording density in the track pitch direction, and the type of the optical disk is determined. The influence of the difference can be eliminated, the track pitch can be accurately estimated, and the disc type can be accurately determined.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical disk drive device according to the present invention.

FIG. 2 is a diagram showing a configuration of an optical pickup of the device.

FIG. 3 is a diagram showing a beam spot and an RF signal waveform on an optical disc.

FIG. 4 is a diagram showing the relationship between the type of optical disc and the amount of crosstalk.

FIG. 5 is a block diagram of an optical disk type determination circuit of the same device.

FIG. 6 is a flowchart showing processing at the time of starting the apparatus.

FIG. 7 is a block diagram of an optical disk type determination circuit according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Spindle motor, 3 ... Optical pickup, 4 ... Feed motor, 5 ... RF amplifier, 6 ... EFM
CIRC decoder, 7: memory controller, 8: buffer memory, 9: system controller, 10: servo controller.

Claims (5)

[Claims] 1. An optical disk receives reflected light of a light beam applied to an optical disk from the optical disk to obtain a read signal, and an amplitude of the read signal generated when the light beam crosses a track of the optical disk. An optical disc type discriminating method, wherein a crosstalk amount of the read signal is detected from the change, and a recording density in a track pitch direction is estimated based on the crosstalk amount to discriminate the type of the optical disc. 2. The method according to claim 1, wherein a peak value and a bottom value of an envelope including information on the amplitude change of the read signal are detected, and the crosstalk amount is calculated from a ratio of the obtained peak value and bottom value. 2. The method according to claim 1, wherein the type of the optical disk is determined. 3. A light beam irradiating means for irradiating an optical disk with a light beam, and a light detecting means for detecting light reflected on the optical disk by the light beam irradiating means and reflected from the optical disk and outputting a read signal. Means, an envelope detection means for detecting an envelope of the read signal, the amplitude of which changes as the light beam traverses the track of the optical disc; and a peak value of an envelope detected by the envelope detection means; Peak hold means and bottom hold means for respectively holding the bottom value; crosstalk detection means for detecting the amount of crosstalk from the peak value and bottom value respectively held by the peak hold means and bottom hold means; Disc discriminating means for discriminating the type of the optical disc based on Optical disk apparatus characterized by comprising an adjustment means for adjusting the optical system based on the determination result by the disc discrimination means. 4. The optical disk apparatus according to claim 3, wherein said crosstalk detecting means is an arithmetic means for calculating a ratio between said peak value and bottom value as a crosstalk amount. 5. The crosstalk detecting means amplifies the read signal and outputs the amplified read signal to the envelope detection means.
A gain control amplifier for changing a gain according to one of the hold values of the peak hold means and the bottom hold means, and the other hold value of the peak hold means and the bottom hold means is output as the crosstalk amount. 4. The optical disk device according to claim 3, wherein the disk determination unit is a comparator that compares the amount of crosstalk with a predetermined value and outputs information indicating a type of the optical disk.