JPH09320180A - Device and method for discriminating optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate optical disks with different reference thickness and the optical disks with near detection signal characteristicks by using plural kinds of control signals used for reproducing the optical disk and discriminating the kind of the optical disk. SOLUTION: A preamplifier 11 in an optical disk discrimination units 3 amplifies regenerative signal RF, focus error signal FE and tracking error signal TE detected by an optical pickup 2. A discrimination part 12 stores the data becoming a reference for discriminating the optical disk 5 and discriminates the kind of optical disk 5, based on the data showing the characteristics of stored respective optical disks by using signal levels of at least two control signals among the signal RF, the signal FE and the signal TE. Further, plural optical disks contain the optical disks with different substrate thicknesses, and the optical disk discrimination unit 3 is to contain the signal optical pickup 2, detecting the control signal from the optical disk with different substrate thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc discriminating apparatus and method for automatically discriminating a plurality of optical discs, and more particularly to an optical disc discriminating apparatus and method for surely discriminating optical discs.

[0002]

2. Description of the Related Art In recent years, CD (Compact Disc), C
There is provided an optical disk reproducing device for reading information recorded on an optical disk having a thickness of about 1.2 mm such as a D-ROM by using a semiconductor laser. In such an optical disc reproducing apparatus, focus servo and tracking servo are controlled for an objective lens for an optical pickup, and a pit train on a recording surface is irradiated with a laser beam, which causes signals such as audio, video, and data. Is played.

Recently, the recording density has been increased in order to record a moving image on such an optical disc for a long time. For example, a DVD (digital video disc) standard has been proposed in which information of about 5 Gbytes per side is recorded on an optical disc having a diameter of 12 cm, which is the same as a CD-ROM. According to the DVD standard, the thickness of the optical disk is about 0.6 mm, and one optical disk including two disk substrates according to the DVD standard, which are attached to each other on their back surfaces, can record about 10 Gbytes of information. it can.

By the way, conventionally, a method for discriminating such an optical disk device has been disclosed. JP 61-
According to Japanese Patent No. 283035, the optical disc is discriminated by discriminating the optical reflectance of the optical disc from the focus error signal obtained by the focus servo and the peak value obtained based on the signal.

Further, Japanese Laid-Open Patent Publication No. 62-76061 discloses a method of discriminating the type of a disc based on the level of a signal obtained from an optical pickup in a state where the disc has reached the vicinity of the in-focus position of the optical disc.

[0006]

Discrimination of conventional optical discs has been performed as described above.

Generally, an objective lens for an optical pickup for reproducing an optical disc is designed in consideration of the thickness of the substrate of the target optical disc and the wavelength of the semiconductor laser used. Therefore, even if an optical disc having a thickness different from the designed one is to be reproduced, the spot of the laser beam is not focused on the recording surface of the optical disc, and the reproduction cannot be performed. For example, an objective lens designed to fit an optical disc having a 1.2 mm thick substrate has a size of 0.6 mm.
The spot of the laser beam cannot be focused on the recording surface of an optical disc having a thick substrate, and such an optical disc cannot be reproduced.

Therefore, the conventional method for discriminating optical discs as described above has a problem in that discs having different thicknesses cannot be discriminated.

Further, in the conventional optical disc discriminating method, since only one of the detection signals for reproducing the optical disc is used, it is impossible to discriminate clearly when the outputs of the detected signals are similar. There was a problem.

The present invention has been made to solve the above problems and has the following objects.

(1) To provide an optical disc discriminating apparatus capable of discriminating optical discs having different substrate thicknesses.

(2) To provide an optical disc discriminating apparatus capable of discriminating an optical disc surely even when the detection signal characteristics are close to each other.

[0013]

An optical disc discriminating apparatus for discriminating the types of a plurality of optical discs according to a first aspect of the present invention comprises first and second detecting means for respectively detecting at least two control signals obtained from the optical disc, It includes a discriminating means for discriminating the type of the optical disc according to the detection results of the first detecting means and the second detecting means.

Since the optical disc is discriminated using a plurality of control signals used for reproducing the optical disc, the disc can be surely discriminated even when the characteristics of the detection signal are close.

In the optical disc discriminating apparatus according to a second aspect, the plurality of optical discs according to the first aspect include optical discs having different substrate thicknesses, and the optical disc discriminating apparatus detects control signals from the optical discs having different substrate thicknesses. Includes a single optical pickup.

In the optical disc discriminating apparatus according to a third aspect, the single optical pickup according to the first aspect includes an objective lens and a changer for changing the numerical aperture of the objective lens.

In the optical disc discriminating apparatus according to a fourth aspect, the changer for changing the numerical aperture according to the first aspect includes a liquid crystal shutter.

In the optical disc discriminating apparatus according to a fifth aspect, the liquid crystal shutter according to the fourth aspect is composed of a TN type liquid crystal.

In the optical disc discriminating apparatus according to a sixth aspect, the liquid crystal shutter according to the fourth aspect is composed of STN type liquid crystal.

In the optical disc discriminating apparatus according to the seventh aspect, the liquid crystal shutter according to the fourth aspect is composed of a ferroelectric liquid crystal.

In the optical disc discriminating apparatus according to an eighth aspect, the control signal of the optical disc discriminating apparatus according to the first aspect includes a reproduction signal and a focus error signal.

In the optical disc discriminating apparatus according to the ninth aspect, the control signal of the optical disc discriminating apparatus according to the first aspect includes a reproduction signal and a tracking error signal.

In the optical disc discriminating apparatus according to the tenth aspect, the control signal of the optical disc discriminating apparatus according to the first aspect includes a focus error signal and a tracking error signal.

In the optical disc discriminating apparatus according to the eleventh aspect, the control signal of the optical disc discriminating apparatus according to the first aspect includes the level of the focus error signal and the number of S curves of the focus error signal.

In the optical disc discriminating apparatus according to the twelfth aspect, the control signal of the optical disc discriminating apparatus according to the first aspect includes a focus-on signal and a tracking error signal.

In the optical disc discriminating apparatus according to the thirteenth aspect, the control signal of the optical disc discriminating apparatus according to the first aspect includes the offset amount of the tracking error signal and the level of the tracking error signal.

In the optical disc discriminating apparatus according to the fourteenth aspect, the control signal of the optical disc discriminating apparatus according to the first aspect is detected by using a lens having a predetermined numerical aperture.

In the optical disc discriminating apparatus according to the fifteenth aspect, the optical disc discriminating apparatus according to the fourteenth aspect has a plurality of numerical apertures, and further includes a switching means for switching the plurality of numerical apertures. Since the optical disc discriminating apparatus detects the first and second control signals by switching the numerical aperture of the lens, the focus position of the optical pickup can be changed. As a result, it becomes possible to discriminate optical disks having different substrate thicknesses.

In the optical disc discriminating apparatus according to the sixteenth aspect, the two control signals of the optical disc discriminating apparatus according to the first aspect are obtained by using lenses having different numerical apertures.

An optical disc discriminating method for discriminating the types of a plurality of optical discs according to a seventeenth aspect is the step of detecting a first control signal from the optical disc and the step of detecting a second control signal different from the first control signal from the optical disc. And the first
And determining the types of the plurality of optical disks according to the second control signal.

Since the optical disc is discriminated by using a plurality of control signals used for reproducing the optical disc, it is possible to surely discriminate the optical disc even when the characteristics of the detection signal are close to each other.

In the optical disc discriminating method according to the eighteenth aspect, the first and second control signals include a reproduction signal and a focus error signal.

In the optical disc discriminating method according to the nineteenth aspect, the control signal includes a reproduction signal and a tracking error signal.

In the optical disc discriminating method according to the twentieth aspect, the control signal includes a focus error signal and a tracking error signal.

In the optical disc discriminating method according to the twenty-first aspect, the control signal includes the level of the focus error signal and the number of S curves of the focus error signal.

In the optical disc discriminating method according to the twenty-second aspect, the control signal focus-on signal and the tracking error signal are included.

In the optical disc discriminating method according to the twenty-third aspect, the control signal includes the offset amount of the tracking error signal and the level of the tracking error signal.

In the optical disc discriminating method according to the twenty-fourth aspect, the detection of the first and second control signals is performed by using a lens having a predetermined numerical aperture.

In the optical disc discriminating method according to the twenty-fifth aspect, there are a plurality of specific numerical apertures, and in the step of detecting the first and second control signals, the plurality of numerical apertures are switched to switch the first and second control signals. And detecting.

In the optical disc discriminating method according to the twenty-sixth aspect, the step of detecting the two control signals includes the step of detecting using the lenses having different numerical apertures.

Since the numerical aperture of the lens is switched to detect the first and second control signals, the focus position of the optical pickup can be changed. As a result, it is possible to provide an optical disc discriminating method capable of discriminating optical discs having different substrate thicknesses.

[0042]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the overall structure of an optical disc reproducing apparatus 1 including an optical disc discriminating apparatus according to the present invention. Referring to FIG. 1, the optical disc reproducing apparatus 1 is
Depending on the optical pickup 2 for picking up the information recorded on the optical disc 5, the optical disc discriminating unit 3 for discriminating the type of the optical disc 5 based on the signal detected by the optical pickup 2, and the result discriminated by the optical disc discriminating unit 3. And an RF demodulation circuit 4 for reproducing the optical disc 5.

The optical disc discriminating unit 3 includes a preamplifier 11 for amplifying the detection signal from the optical pickup 2. The preamplifier 11 amplifies the reproduction signal RF detected by the optical pickup 2, the focus error signal FE, and the tracking error signal TE. The focus error signal FE and the tracking error signal TE are input to the discriminating unit 12 and the servo circuit 13, and are controlled so that the optical disc is normally reproduced. The reproduction signal RF is sent to the determination unit 12 and the RF demodulation circuit 4, and the reproduction signal RF is reproduced by the RF demodulation circuit 4. The discriminating unit 12 discriminates the type of the optical disc by the device and method described later using the reproduction signal RF, the focus error signal FE and the tracking error signal TE. The command unit 14 switches the numerical aperture NA of the objective lens forming the optical pickup according to the type of the optical disc discriminated by the discriminating unit 12 according to the type of the optical disc discriminated by the discriminating unit 12 using the NA switching unit 15. Alternatively, the circuits are switched by using the circuit switching unit 16 so that the reproduction is performed by each dedicated reproduction circuit.

Next, details of the optical pickup 2 will be described. In the optical disc discriminating apparatus according to the present invention,
The optical pickup 2 is configured so that two types of optical disks having different substrate thicknesses can be reproduced by a single pickup. FIG. 2 is a configuration diagram of the optical pickup 2. Referring to FIG. 2, the optical pickup 2 has a 635 (permissible error ±
15) a semiconductor laser 25 for generating a laser beam having a wavelength of nm, a diffraction grating 24 for generating a beam for detecting the tracking error signal TE, a polarization plane rotation unit 23, and incident light from the semiconductor laser 25. Half mirror 2 that reflects and transmits the signal from the optical disk 5
2, a collimator lens 26, a polarization filter 29,
It includes an objective lens 28 for focusing a laser beam on a predetermined surface of the optical disc 5 and a photodetector 21 for detecting reflected light from the optical disc 5 through a half mirror 22.

Therefore, the laser beam from the semiconductor laser 25 is reflected by the half mirror 22 through the diffraction grating 24 and the polarization plane rotation unit 23, and the collimator lens 26.
And are made parallel to each other, and enter the optical disk 5 through the polarization filter 29 and the objective lens 28. The objective lens 28 is changed in the tracking direction, and is changed in the optical axis direction (focus direction) by a focus control mechanism (not shown). Therefore, the laser beam that has passed through the objective lens 28 is condensed, passes through the polycarbonate substrate, and is irradiated onto the recording surface of the optical disc 5. The laser beam reflected by the recording surface is the substrate, the objective lens 28, and the polarization filter 2.
The light enters the photodetector 21 through the collimator lens 26 and the half mirror 22. The photodetector 21 generates a reproduction signal RF and a tracking error signal TE in response to the irradiated laser beam. Here, the objective lens 28 is preferably designed to reduce aberrations that occur when the substrates of the optical disc 5 have different thicknesses.

The polarization plane rotating unit 23 includes a TN (twisted nematic) type liquid crystal and two transparent electrode plates sandwiching the liquid crystal. Since no voltage is applied to the transparent electrode plate during reproduction of the digital video disk, the polarization plane rotation unit 23 rotates the polarization plane of the laser beam by 90 °. On the other hand, at the time of reproducing the compact disc, since the predetermined voltage is applied to the transparent electrode plate, the polarization plane rotation unit 23 does not rotate the polarization plane of the laser beam. Therefore, the incident laser beam passes through the polarization plane rotation unit 23 as it is. Here, the liquid crystal is not limited to the TN type, but may be the STN (super twisted nematic) type or the ferroelectric type.

The objective lens 28 for a digital video disk having a substrate thickness of 0.6 mm has a numerical aperture NA = 0.6 suitable for the semiconductor laser 25 having a reproduction wavelength of 635 nm. On the other hand, when reproducing a compact disc having a substrate thickness of 1.2 mm, the polarization plane rotation unit 23 rotates the polarization plane of the laser beam, and the polarization filter 29 shields the outer peripheral portion of the laser beam, so that the effective numerical aperture of the objective lens is increased. The NA is adjusted to 0.35 (tolerance ± 0.05).

As shown in FIG. 3, the polarizing filter 29 is attached to a donut-shaped polarizing film 31, two glass plates 32 sandwiching the film 31, and the surface of the glass plate 32 on the objective lens 28 side. And a filter 33 having no polarization property. The polarizing film 31 blocks a plane of polarization perpendicular to the main surface. Therefore, the polarizing film 3
No. 1 transmits a plane of polarization parallel to the main surface, the transmittance of which is about 70-90%. If a laser beam having a plane of polarization parallel to the main surface is irradiated, if the filter 33
If is not provided, a difference may occur between the central portion and the outer peripheral portion of the polarization filter 29 during transmission. Therefore, the filter 33 has a transmittance of about 70 to 90% and makes the transmittance of the polarizing filter 5 uniform over the entire surface when a laser beam having a polarization plane parallel to the main surface is irradiated. The glass plate 32 may be made of any material as long as it is transparent and has excellent optical characteristics, and a resin such as polycarbonate or PMMA may be used instead of glass. Since the polarization filter 29 is fixed to the objective lens 28, the lighter the polarization filter 29 is, the objective lens 2
The tracking control and focus control of 8 can be stably performed.

The polarization characteristic of the polarization filter 29 is shown in FIG. Only the laser beam polarized vertically in the overhead direction is transmitted through the outer peripheral portion 29a of the polarization filter 29. The central portion (light transmitting portion) 29b of the polarization filter 29 transmits a laser beam polarized in either direction. When the numerical aperture NA of the objective lens 28 is 0.6 (tolerance ± 0.05) and the effective aperture is 4 mm, the effective numerical aperture NA of the objective lens 28 is 0.35 (tolerance ± 0.05). ), The diameter of the central portion 29b of the polarization filter 29 is set to 2.3 (permissible error ± 0.2) mm. When the effective aperture of the objective lens 28 is other than 4 mm, the effective numerical aperture NA of the objective lens 28
The central part 29b of the polarization filter 29 so that
It is sufficient to set the diameter of.

Next, an example in which the liquid crystal shutter 35 is used instead of the polarization filter 29 will be described with reference to FIG.
The liquid crystal shutter 35 includes a doughnut-shaped guest-host type liquid crystal 36 and a transparent electrode plate 37 sandwiching the liquid crystal 36. The liquid crystal shutter 35 is fixed to the objective lens 28 by a lens holder 38.

As shown in FIG. 6A, when the guest-host type liquid crystal 36 is in the off state (during reproduction of the digital video disc), the liquid crystal shutter 35 allows the laser beam to pass through as it is. On the other hand, as shown in FIG. 6B, when the guest-host type liquid crystal 36 is in the ON state (during reproduction of the compact disc), the liquid crystal shutter 35 transmits only the laser beam in the central portion thereof and the laser beam in the outer portion thereof. Are blocked by being scattered by the guest-host type liquid crystal 36.

The liquid crystal shutter 35 transmits the entire laser beam when reproducing the digital video disc, and transmits only the central portion of the laser beam when reproducing the compact disc. Therefore, the polarization filter 29 in the case of the above-described embodiment is not necessary.

In the optical pickup 2, as shown in FIG. 7, the positional relationship between the diffraction grating 24 and the polarization plane rotation unit 23 may be reversed.

FIG. 8 is a diagram showing a first modification of the optical pickup 2. Here, the polarization filter 29 and the polarization plane rotation unit 23 are integrated and provided between the semiconductor laser 25 and the diffraction grating 24.

Next, a second modification of the optical pickup 2 will be described. In this modified example, the optical pickup 2 is not single as in the previous embodiment, but two types are provided according to each substrate thickness.

FIG. 9 and FIG. 10 are a plan view and an elevation view showing one pickup in the second modification of the optical pickup 2. Basically, it is the same as that shown in FIG. 2, but the raising mirror 27 is used to make the whole compact.
Is different. Since the other parts are the same, the same reference numerals are given to the same parts and the description thereof will be omitted.

The disc discriminating apparatus according to the present invention can be applied to any of the above optical pickup configurations.

Next, the discriminating section 12 for discriminating the optical disc will be described. FIG. 11 shows the discrimination unit 1 shown in FIG.
It is a block diagram which shows the content of 2. Referring to FIG.
The determination unit 12 is a CPU 21 that controls the entire determination unit 12.
A ROM 22 that stores the operation of the discriminating unit 12 and a RAM 23 that stores data for discriminating a plurality of optical disks and a discriminating procedure, which will be described later. Discrimination unit 12
Determines the type of the optical disc based on the data representing the characteristics of each optical disc stored in the RAM 23.

Next, Table 1 shows data as a reference for identifying the optical disk stored in the RAM 23. Table 1
(A) is the data when the numerical aperture is 0.6, and Table 1
(B) is a value when the numerical aperture is 0.35.

[0061]

[Table 1]

In the embodiment of the present invention, a single-layer digital video disc (hereinafter abbreviated as “DVD-S”) and a double-layer digital video disc (hereinafter referred to as “DVD”).
-D "), compact disc (hereinafter abbreviated as" CD "), recordable compact disc having a reflectance of 10% (hereinafter abbreviated as" CD-R "), and reflectance 3%
Recordable compact disc (hereinafter referred to as "CD-R
(Abbreviated as “”) are focus error signal FE, reproduction signal RF, and tracking error signal T, which are control signals necessary for reproducing each of the five types of optical disks.
It is determined using E and the offset signal. In DVD-D, different signals are detected from the first layer and the second layer of the recording surface, and in this case, the average value of both signals is used as data.

Focus error signal FE and reproduction signal RF
As shown in FIG. 12, the relationship between and is such that the level of the reproduction signal RF becomes maximum when the focus error signal FE is in the “0” level state, that is, when the objective lens is at the in-focus position.

Here, the curve of the focus error signal FE (FIG. 12A) is called the S curve. Objective lens 28
DV when the distance from or near the optical disk 5
Two S curves appear on D-D, and one S curve appears on other optical disks. Further, the values of peak-to-peak A1 are adopted for all data used below as shown in FIG.

The offset signal in the table is obtained as follows. FIG. 13 is a diagram for explaining the offset signal. Referring to FIG. 13, the case where the tracking of the tracking error signal TE passes through the central reference point is defined as te1,
The signal actually obtained on each optical disk is te2. Here, the amplitude of the tracking error signal TE is set to A2
And the deviation amount between the reference signal and the actual signal is a,
The offset signal is represented by a2.

In the present invention, Tables 1 (A) and 1 (B)
When the detection level of the focus error signal FE, the detection level of the reproduction signal RF, and the detection level of the tracking error TE shown in FIG. Each optical disc is discriminated based on the data.

A specific determination method will be described below. FIG. 14 is a flowchart showing the operation of the optical disc reproducing apparatus 1. Referring to FIG. 14, the optical disc reproducing apparatus 1 performs a focus search so as to focus on the recording surface of the optical disc 5 (step S11, the following steps are omitted). Next, the discriminating unit 12 discriminates the disc according to the procedure described later (S12). After that, a motor (not shown) is started according to the disc discrimination result, and tracking servo is performed to reproduce various optical discs using the RF demodulation circuit 4 (S13 to S15).

FIG. 15 is a subroutine showing the details of the disc discriminating step shown in FIG. In disc discrimination, it is first judged by the optical pickup 2 whether or not the focus of the recording surface is obtained. When the focus is obtained, the three detection signals of the above-mentioned focus error signal FE, reproduction signal RF and tracking error signal TE are detected. The signal level of one of them is detected (S22).
Depending on the determination result, any one of the two signals except one of the above three signals or the number of S curves of the focus error signal FE is detected as the second signal level (S23). Disc discrimination is performed based on the detection result of the first signal level and the result of the second signal level (S24). When the focus signal is not obtained in S21, the reproduction of the optical disc is ended. In this flowchart, the detection ends at the second signal level, but the third signal is also detected if necessary.

FIGS. 16 and 17 are flowcharts showing a modification of the disc discrimination subroutine shown in S12 of FIG. In FIG. 16 and FIG. 17, the determination position of whether or not the focus is obtained is shown in FIG.
It is only different from. That is, in the embodiment described in detail below, the focus pull-in operation is required, so the focus detection performed in S21 is essential.
Therefore, in order to detect the signal relating to the focus pull-in as the first signal level, it is necessary to always follow the processing of FIG. 15, and when detecting the signal relating to the focus pull-in as the second signal level, the processing of FIG. 16 must be performed. When the signal relating to the focus pull-in is not used, the subroutine of FIG. 17 should be used.

Next, a specific discrimination method using the first signal level and the second signal level described in the above flow will be described. In the following embodiments, an objective lens having a numerical aperture NA of 0.6, an objective lens of 0.35, and three cases using both of them will be described.

(A) When numerical aperture NA = 0.6 (1) When the first signal level is the reproduction signal RF and the second signal is the S curve of the focus error signal FE. FIG. It is a figure which shows a discrimination procedure. Referring to FIG. 18, first, the reproduction signal RF at the in-focus position
Compare the levels of. Referring to Table 1 (A), DVD-
DVD-D when the RF level of the reproduction signal of S is 100%
About 35%, CD 36%, CD-R 9%, CD-
Since R is 3%, as shown in FIG. 18, a group of high-level DVD-S and a medium-level DVD-D
And CD and three groups of low level CD-R and CD-R. For the middle level group, the number of S curves of the focus error signal is 2 in the case of DVD-D and 1 in the case of CD.
Therefore, it is determined using it.

Since CD-R and CD-R have a large wavelength dependency during reproduction and reproduction is not considered, no particular discrimination is made. However, as described later, it is possible to make a determination by using, for example, the level of the tracking error signal.

In this example, the reproduction signal R at the in-focus position is also used.
After comparing the F levels, the number of S curves of the focus error signal FE was compared.
The reproduction signal RF level at the in-focus position may be compared after the comparison is performed using the number of S curves.

(2) After the comparison of the focus error signal level, the S curve of the focus error signal is compared.

FIG. 19 shows the discriminating procedure of each disk in this case.
Shown in As shown in FIG. 19, the focus error signal F
Referring to the level of E, first, DVD-S and DVD-D
And CD and CD-R and CD-R. After making the above determination, by comparing the number of S curves of the focus error signal FE, D
It is possible to distinguish between VD-D and CD.

It should be noted that the above embodiment may be reversed and the number of S curves of the focus error signal may be compared before the level of the focus error signal is compared.

(3) After the comparison with the level of the focus error signal FE, the comparison is performed with the level of the tracking error signal TE.

The discriminating procedure of each disk in this case is shown in FIG.
Shown in Referring to FIG. 20, the focus error signal FE
When compared at the level of (2), it is divided into three groups as in the case of (2). After this, DVD-D and CD can be discriminated by comparing the levels of the tracking error signal TE. Since the CD-R and the CD-R have different tracking error signal levels, this can also be determined by comparing the levels of the tracking error signal TE.

(4) After comparing the levels of the tracking error signal TE, the levels of the focus error signal FE are compared.

FIG. 21 shows the procedure for discriminating each disk in this case.
Shown in Referring to FIG. 21, the tracking error signal T
Comparing the levels of E, DVD-S, CD and CD
-Groups with high signal level such as R and DVD-
It is divided into three groups, one with an intermediate level such as D and one with a lower level such as CD-R.

Next, in the case where the tracking error signal TE has a high level, the respective focus error signals FE have different levels, and therefore it is possible to discriminate between DVD-S, CD and CD-R by comparing them.

(5) After the comparison with the level of the focus error signal FE, the S curve of the focus error signal FE and the level of the tracking error signal TE are compared.

FIG. 22 shows the discriminating procedure of each disk in this case.
Shown in Referring to FIG. 22, in the comparison of (2),
No distinction was made between CD-R and CD-R, but (3)
As shown in, the two can be discriminated by comparing the levels of the tracking error signals.

It is also possible to compare the numbers of S curves of the focus error signal and then compare the levels of the reproduction signal RF at the in-focus position.

(6) After the reproduction signal RF level is compared, the level of the tracking error signal TE is compared.

FIG. 23 shows the discriminating procedure of each disk in this case.
Shown in Referring to FIG. 23, the reproduction signal R at the focus level
By comparing the F levels, DVD-S and DVD
-D and CD groups and CD-R and CD-R
Can be classified into three groups. After this, DVD-D
And CD-R and CD-R and CD-R are compared at the level of the tracking error signal TE.

(7) After the comparison is made at the level of the tracking error signal TE, the comparison is made at the level of the reproduction signal RF.

FIG. 24 shows the procedure for discriminating each disk in this case.
Shown in Referring to FIG. 24, the tracking error signal T
It can be divided into three groups by comparing the levels of E. It is possible to discriminate between DVD-S, CD and CD-R by comparing the levels of the reproduction signal RF for the group having the highest level.

(8) After comparing the tracking error signal TE with the offset amount, the tracking error signal TE
Compare at the level of.

FIG. 25 shows the discriminating procedure of each disk in this case.
Shown in Referring to FIG. 25, the tracking error signal T
Comparing the offset amounts of E, a group with a low signal level such as DVD-S, CD, CD-R, and DV
It is divided into a group having a high signal level such as DD and a group having a CD-R having almost no signal. Of these, the two groups in which the signal levels can be obtained can be identified by comparing the level of the tracking error signal TE, the level of the focus error signal FE, or the level of the reproduction signal RF.

(B) When Numerical Aperture NA = 0.35 Next, the case where the numerical aperture NA is 0.35 will be described. Also in this case, the determination is performed in the same manner as in the case of the numerical aperture NA = 0.6.

(1) When the first signal level is the focus error signal FE and the second signal is the tracking error signal TE FIG. 26 is a diagram showing a discrimination method based on the output signal of each disk in this case.

Referring to FIG. 26, by using the level of focus error signal FE, DVD-S and C
DVD-D with a relatively high level group such as D
And a medium level group such as CD-R and a group such as CD-R which is almost undetectable. Among them, the group having a relatively high level and the medium group are discriminated by comparing the levels of the tracking error signals.

(2) The first signal level is the tracking error signal TE and the second signal is the focus error signal FE.
27. FIG. 27 shows the discrimination procedure in this case. Referring to FIG. 27, the DVD-
It is divided into high level groups such as S, CD and CD-R, medium level groups such as DVD-D and hardly detectable groups such as CD-R. After that, a high level group is discriminated using the focus error signal FE.

(3) The first signal level is the reproduction signal RF
Then, in the case where the second signal level is the tracking error signal TE The discrimination procedure in this case is shown in FIG. Referring to FIG. 28, by comparing the levels of the reproduction signal RF, a high level group (DVD-S and CD) and a medium level group (D
VD-D) and low group (CD-R and CD-R
) And After that, the high level group and the low level group are discriminated using the level of the tracking error signal TE.

(4) When the first signal is the tracking error signal TE and the second signal is the reproduction signal RF FIG. 29 shows the discrimination procedure in this case. The levels of the tracking error TE are compared with each other with reference to FIG. 29 and divided into a high level group (CD and CD-R) and a low level group (DVD-S, DVD-D and CD-R). After that, the reproduction signal RF for each group
Use the level of to determine.

(5) When the first signal is the focus error signal FE and the second signal is the number of S curves of the tracking error signal TE or the focus error signal FIG. 30 shows the determination procedure in this case. Referring to FIG. 30, the levels of the focus error signal FE are compared and a high level group (DVD-S and CD), a middle level group (DVD-D and CD-R) and a low level group (C
D-R). After that, the high group is determined using the level of the tracking error signal TE, and the middle group is determined using the number of S curves of the focus error signal FE.

(6) When the first signal is the focus-on signal, the second signal is the tracking error signal TE, and the third signal is the reproduction signal RF. The discrimination procedure in this case is shown in FIG. In this case, three steps are used for discriminating the optical disc. Here, the focus-on signal means that the focus pull-in can be performed when the optical pickup 2 is used to perform the focus pull-in while the optical disc 5 is rotated. If not, the disc is discriminated as a CD-R. After that, the remaining four types of optical disks are discriminated. Since this determination method is the same as the above-mentioned case, its explanation is omitted. The level of the reproduction signal RF in the third stage may be determined by using the level of the reproduction signal after the tracking servo of the signal which is normally obtained by actually turning on the tracking servo.

(7) When the first signal is the focus-on signal, the second signal is the reproduction signal RF, and the third signal is the tracking error signal TE. FIG. 32 is a diagram showing a determination method in this case. . In the case of the above (6), the second signal and the third signal are exchanged for determination.

(8) When the first signal is the focus-on signal, the second signal is the focus gain signal, and the third signal is the tracking error signal TE. The discrimination procedure in this case is shown in FIG. Here, the magnitude of the gain is the gain when the focus pull-in is performed, and specifically, it is determined by providing a gain switching circuit. The gain switching circuit is provided in the preamplifier 11, and its configuration is shown in FIG.
Shown in

The third stage is the same as the other cases, and therefore its explanation is omitted. (C) When making a determination by switching the numerical aperture NA (1) When making a predetermined determination at the numerical aperture NA = 0.35 and then switching to the numerical aperture NA = 0.6 FIG. 34 shows the determination method in this case. . Referring to FIG. 34, first, with the numerical aperture NA = 0.35, the focus pull-in is performed as in (B) and (6), and the CD-R is first discriminated. Next, the levels of the tracking error signal TE are compared and divided into those with a high level (CD and CD-R) and those with a low level (DVD-S and DVD-D). The high level group discriminates between CD and CD-R by comparing the levels of the reproduction signal RF. The group with a low level is discriminated by switching the numerical aperture NA to 0.6 for DVD-S and DVD-D. This is because the difference in signal level becomes larger when the numerical aperture NA is switched to 0.6. Switching of the numerical aperture NA is performed using the liquid crystal shutter 35 shown in FIG. The level of the reproduction signal RF in the third stage may be determined by using the level of the reproduction signal after the tracking servo of the signal which is normally obtained by actually turning on the tracking servo.

(2) Numerical aperture NA = 0.6 and NA
When the reproduced signal RF in the case of = 0.35 is compared FIG. 35 shows the determination method in this case. Referring to FIG. 35, the optical discs (CD, CD-) having substantially the same reproduction signals RF when the numerical aperture NA = 0.6 and NA = 0.35.
R and CD-R) and optical discs (DVD-S and D) having different levels of the reproduction signal RF when the numerical aperture NA = 0.6 and when the numerical aperture NA = 0.35.
VD-D). Then, by comparing the levels of the reproduction signal RF at the numerical aperture NA = 0.6, C
D and CD-R and CD-R, DVD-S and DVD
-D is determined. In this case, the reproduction signal RF at each numerical aperture NA is temporarily stored in the RAM 23 of the discriminating unit 12 and its value is compared.

(3) Numerical aperture NA = 0.6 and NA = 0.
When comparing the focus error signal FE in 35, the discrimination method in this case is shown in FIG. First, the numerical aperture NA
= 0.6 and the level of the focus error signal FE at NA = 0.35 are compared. Here, an optical disc (CD, CD-R and CD-R) having almost the same signal level, and an optical disc (DVD-S which has a clear difference in signal level at numerical apertures NA = 0.6 and NA = 0.35). And DVD-D).
After that, the respective optical disks are discriminated by comparing the respective groups with each other at the level of the focus error signal at the in-focus position at the numerical aperture NA = 0.6.

(4) Numerical aperture NA = 0.6 and NA
= 0.35 tracking error signal TE
37. Comparison using Level Difference of FIG. 37 FIG. 37 shows a discrimination method in this case. Referring to FIG. 37, first, the levels of the tracking error signal TE with numerical apertures NA = 0.6 and NA = 0.35 are compared. Then, a group of optical discs (CD and CD-R) having almost the same signal level in both, and a group of optical discs (DVD-S and VDV-
D) and a group of optical disks (CD-R) that cannot be compared because they are almost zero. Then, the optical discs are discriminated by comparing the level of the reproduction signal RF at the in-focus position and the tracking error level for the former two.

Next, the numerical aperture is set to NA = 0.6 and NA
A switching pattern for switching to 0.35 using the NA switching unit 15 will be described. FIG. 38 is a diagram showing such a switching pattern. (A) is a focus error signal FE
Is a pattern in which the numerical aperture NA is switched for each cycle of obtaining, and (B) is a pattern in which it is switched for every half cycle. FIG. 9C is a diagram showing a case where the switching positions of the patterns shown in FIG. In (D), first half cycle is performed with numerical aperture NA = 0.6, next one cycle is performed with NA = 0.35, and the remaining half cycle is performed with NA = 0.6. Is. (E) is (D)
This is the case where the switching position of is shifted.

Referring to FIG. 38, focusing is performed so as to pass through the in-focus position halfway in each cycle.

In the above-described embodiment, the numerical aperture NA = 0.6 or 0.35 suitable for reproduction of each optical disk is used, but in actuality there is no problem even if a deviation of about ± 0.05 occurs. .

In the above embodiment, the objective lens having the numerical aperture NA = 0.6 is mainly used for the discrimination.
Not limited to this, if the data shown in Table 1 is used, it is possible to discriminate the optical disc by other combinations.

Further, in the above embodiment, the output of the laser beam is made constant and the discriminating data of the optical disc is obtained. However, the present invention is not limited to this. And the optical disc may be discriminated based on the required laser light output.
The reflectance data of the optical disk used here is as follows.

(A) DVD-S, CD: 70% or more (b) DVD-D: 20-40% (c) CD-R: 7-10% (d) CD-R: 3-5% The ratio of each detection signal may change by about ± 5%, but such a change does not particularly affect the determination result.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an optical disc reproducing apparatus according to the present invention.

FIG. 2 is a diagram showing details of an optical pickup.

FIG. 3 is a diagram showing a polarization filter.

FIG. 4 is a diagram showing polarization characteristics of a polarization filter.

FIG. 5 is a diagram showing a configuration of an optical pickup incorporating a liquid crystal shutter.

FIG. 6 is a diagram showing an operation of a liquid crystal shutter.

FIG. 7 is a diagram showing details of an optical pickup.

FIG. 8 is a diagram showing a modification of the optical pickup.

FIG. 9 is a plan view showing a modified example of the optical pickup.

FIG. 10 is an elevational view showing a modified example of the optical pickup.

FIG. 11 is a block diagram showing a configuration of a determination unit.

FIG. 12 is a diagram showing a relationship between a focus error signal and a reproduction signal.

FIG. 13 is a diagram showing an offset signal.

FIG. 14 is a flowchart showing the overall operation of the optical disc reproducing apparatus.

FIG. 15 is a flowchart showing the contents of a disc discrimination subroutine.

FIG. 16 is a flowchart showing the contents of a disc discrimination subroutine.

FIG. 17 is a flowchart showing the contents of a disc discrimination subroutine.

FIG. 18 is a diagram showing a disc discriminating method when a numerical aperture NA = 0.6 is used.

FIG. 19 is a diagram showing a disc discriminating method when a numerical aperture NA = 0.6 is used.

FIG. 20 is a diagram showing a disc discriminating method when a numerical aperture NA = 0.6 is used.

FIG. 21 is a diagram showing a disc discriminating method when a numerical aperture NA = 0.6 is used.

FIG. 22 is a diagram showing a disc discriminating method when a numerical aperture NA = 0.6 is used.

FIG. 23 is a diagram showing a disc discriminating method when a numerical aperture NA = 0.6 is used.

FIG. 24 is a diagram showing a disc discriminating method when a numerical aperture NA = 0.6 is used.

FIG. 25 is a diagram showing a disc discriminating method when a numerical aperture NA = 0.6 is used.

FIG. 26 is a diagram showing a disc discriminating method when the numerical aperture NA = 0.35.

FIG. 27 is a diagram showing a disc discriminating method when the numerical aperture NA = 0.35.

FIG. 28 is a diagram showing a disc discriminating method when the numerical aperture NA = 0.35.

FIG. 29 is a diagram showing a disc discriminating method when the numerical aperture NA = 0.35.

FIG. 30 is a diagram showing a disc discriminating method when the numerical aperture NA = 0.35.

FIG. 31 is a diagram showing a disc discriminating method when the numerical aperture NA = 0.35.

FIG. 32 is a diagram showing a disc discriminating method when the numerical aperture NA = 0.35.

FIG. 33 is a diagram showing a disc discriminating method when the numerical aperture NA = 0.35.

FIG. 34 is a diagram showing a disc discriminating method using numerical apertures NA = 0.35 and 0.6.

FIG. 35 is a diagram showing a disc discriminating method using numerical apertures NA = 0.35 and 0.6.

FIG. 36 is a diagram showing a disc discriminating method using numerical apertures NA = 0.35 and 0.6.

FIG. 37 is a diagram showing a disc discriminating method using numerical apertures NA = 0.35 and 0.6.

FIG. 38 is a diagram showing a pattern for converting the numerical aperture NA.

FIG. 39 is a diagram showing a gain switching circuit replacement.

[Explanation of symbols]

 1 Optical Disc Playback Device 2 Optical Pickup 3 Optical Disc Discrimination Unit 4 RF Demodulation Circuit 5 Optical Disc 11 Preamplifier 12 Discrimination Section 13 Servo Circuit 14 Command Section 15 NA Switching Section 16 Circuit Switching Section 21 Photodetector 22 Half Mirror 23 Polarization Plane Rotating Unit 24 Diffraction Lattice 25 Semiconductor laser 26 Collimator lens 27 Standing mirror 28 Objective lens 29 Polarizing filter 35 Liquid crystal shutter

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shuichi Ichiura 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (26)

[Claims] 1. An optical disc discriminating apparatus for discriminating a plurality of types of optical discs, comprising first and second signal detecting means for respectively detecting at least two control signals obtained from the optical disc, and the first and second signal detecting means. A discriminating means for discriminating the types of the plurality of optical discs according to the detection result of the second detecting means
Optical disc discriminating apparatus. 2. The plurality of optical discs include optical discs having different substrate thicknesses, and the optical disc discriminating apparatus includes a single optical pickup for detecting the control signals from the optical discs having different substrate thicknesses. Item 1. The optical disc discriminating apparatus according to Item 1. 3. The single optical pickup includes an objective lens, and means for changing a numerical aperture of the objective lens.
The optical disc discriminating apparatus according to claim 2. 4. The optical disc discriminating apparatus according to claim 3, wherein the means for changing the numerical aperture includes a liquid crystal shutter. 5. The optical disc discriminating apparatus according to claim 4, wherein the liquid crystal shutter is made of TN type liquid crystal. 6. The optical disc discriminating apparatus according to claim 4, wherein the liquid crystal shutter is made of STN type liquid crystal. 7. The optical disc discriminating apparatus according to claim 4, wherein the liquid crystal shutter is made of a ferroelectric liquid crystal. 8. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a reproduction signal and a focus error signal. 9. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a reproduction signal and a tracking error signal. 10. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a focus error signal and a tracking error signal. 11. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a level of the focus error signal and the number of S curves of the focus error signal. 12. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a focus-on signal and a tracking error signal. 13. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes an offset amount of a tracking error signal and a level of the tracking error signal. 14. The control signal is detected by using an optical pickup using a lens having a predetermined numerical aperture.
The optical disc discriminating apparatus according to. 15. The specific numerical aperture is plural, and a switching means for switching the plural numerical apertures is further included.
4. The optical disc discriminating apparatus according to item 4. 16. The at least two control signals are obtained using lenses of different numerical apertures.
The optical disc discriminating apparatus according to. 17. An optical disc discriminating method for discriminating a plurality of types of optical discs, the step of detecting a first control signal from the optical disc, and detecting a second control signal different from the first control signal from the optical disc. An optical disc discriminating method comprising: a step; and a step of discriminating the types of the plurality of optical discs according to the first and second control signals. 18. The optical disc discriminating method according to claim 17, wherein the control signal includes a reproduction signal and a focus error signal. 19. The optical disc discriminating method according to claim 17, wherein the control signal includes a reproduction signal and a tracking error signal. 20. The optical disc discriminating method according to claim 17, wherein the control signal includes a focus error signal and a tracking error signal. 21. The optical disc discriminating method according to claim 17, wherein the control signal includes a level of the focus error signal and the number of S curves of the focus error signal. 22. The optical disc discriminating method according to claim 17, wherein the control signal includes a focus-on signal and a tracking error signal. 23. The optical disc discriminating method according to claim 17, wherein the control signal includes an offset amount of the tracking error signal and a level of the tracking error signal. 24. The detection of the first and second control signals is performed by using a lens having a predetermined numerical aperture.
7. The optical disc discriminating method described in 7. 25. The optical disc discrimination according to claim 24, wherein the specific numerical aperture is plural, and the step of detecting the first and second control signals further includes the step of switching the plural numerical apertures. Method. 26. The optical disc discriminating method according to claim 17, wherein the step of detecting the two control signals includes the step of detecting by using lenses having different numerical apertures.