JP3203183B2 - Optical disc discriminating apparatus and method - Google Patents

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 for automatically discriminating a plurality of optical discs and a method thereof, and more particularly to an optical disc discriminating apparatus and a discriminating method capable of reliably distinguishing optical discs.

[0002]

2. Description of the Related Art In recent years, CDs (compact discs), C
2. Description of the Related Art An optical disk reproducing apparatus for reading information recorded on an optical disk having a thickness of about 1.2 mm such as a D-ROM using a semiconductor laser has been provided. 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 array on a recording surface is irradiated with a laser beam. Is played.

In recent years, the recording density has been increasing in order to record a long moving image on such an optical disk. For example, a DVD (Digital Video Disc) standard for recording information of about 5 GB on one side on an optical disc having a diameter of 12 cm, which is the same as a CD-ROM, has been proposed. 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 adhered to each other at the back thereof can record about 10 GB of information. it can.

[0004] By the way, a method of discriminating such an optical disk apparatus has been disclosed. JP-A-61-
According to Japanese Patent No. 283035, the optical disk is determined by determining the optical reflectance of the optical disk from a focus error signal obtained by a focus servo and a peak value obtained based on the signal.

Japanese Patent Application Laid-Open 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 a position near a focal point of the optical disc.

[0006]

The discrimination of the conventional optical disk has been performed as described above.

In general, an objective lens for an optical pickup for reproducing an optical disk is designed in consideration of the thickness of the substrate of the target optical disk and the wavelength of the semiconductor laser used. Therefore, even if an optical disk having a thickness different from the design is to be reproduced, the laser beam spot does not converge on the recording surface of the optical disk and cannot be reproduced. For example, an objective lens designed to fit an optical disc with a 1.2 mm thick substrate has a 0.6 mm thickness.
A laser beam spot cannot be focused on the recording surface of an optical disk having a thick substrate, and such an optical disk cannot be reproduced.

Therefore, in the above-described conventional method for determining an optical disk, there is a problem that it is not possible to determine an optical disk having a different thickness.

Further, in the conventional optical disc discriminating method, only one of the detection signals for reproducing the optical disc is used. Therefore, when the output of the detected signals is similar, it cannot be clearly discriminated. There was a problem.

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

(1) An optical disc discriminating apparatus capable of discriminating optical discs having different substrate thicknesses is provided.

(2) To provide an optical disk discriminating apparatus capable of reliably discriminating an optical disk even when the detection signal characteristics are close.

[0013]

According to a first aspect of the present invention, there is provided an optical disc discriminating apparatus for discriminating the types of a plurality of optical discs, wherein the focus error signal, the tracking error signal, the RF First and second signal detecting means for respectively detecting at least two signals of the signal そ れ ぞ れ;
Determining means for determining the type of the plurality of optical disks according to the detection result of the detecting means.

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

According to a second aspect of the present invention, the plurality of optical disks of the first aspect include optical disks having different substrate thicknesses, and the optical disk determining device detects control signals from the optical disks having different substrate thicknesses. Includes a single optical pickup.

According to a third aspect of the present invention, a single optical pickup according to the first aspect includes an objective lens and a changer for changing a numerical aperture of the objective lens.

[0017]

[0018]

[0019]

[0020]

According to a fourth aspect of the present invention, a control signal of the optical disk determining apparatus of the first aspect includes a reproduction signal and a focus error signal.

In the optical disc discriminating apparatus according to the fifth 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 claim 6, the control signal of the optical disc discriminating apparatus of claim 1 includes a focus error signal and a tracking error signal.

In the optical disc discriminating apparatus according to the present invention, the control signal of the optical disc discriminating apparatus according to the first aspect is the level of the focus error signal and the S of the focus error signal.
Including the number of curves.

In the optical disc discriminating apparatus according to the eighth 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 ninth aspect, the control signal of the optical disc discriminating apparatus according to the first aspect includes an offset amount of the tracking error signal and a level of the 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 is detected using a lens having a predetermined numerical aperture.

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

In the optical disc discriminating apparatus according to the twelfth 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 thirteenth aspect includes a step of detecting a first control signal from the optical disc and a step of detecting a second control signal different from the first from the optical disc. And the first
And determining the type of the plurality of optical disks in response to the second control signal.

Since the discrimination of the optical disc is performed using a plurality of control signals used for reproducing the optical disc, the discrimination of the optical disc can be made reliably even when the characteristics of the detection signals are close.

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

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

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

[0036] The optical disc discriminating method according to claim 18 includes a control signal focus-on signal and a tracking error signal.

In the optical disk discriminating method according to the nineteenth aspect, the control signal includes an offset amount of the tracking error signal and a level of the tracking error signal.

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

In the optical disk discriminating method according to the twenty-first aspect, there are a plurality of specific numerical apertures, and the step of detecting the first and second control signals includes switching the plurality of numerical apertures to control the first and second control signals. .

In the optical disc discriminating method according to the present invention, the step of detecting the two control signals includes a step of detecting the two control signals using lenses having different numerical apertures.

Since the first and second control signals are detected by switching the numerical aperture of the lens, 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 configuration of an optical disk reproducing apparatus 1 including an optical disk discriminating apparatus according to the present invention. With reference to FIG. 1, an optical disc reproducing device 1
An optical pickup 2 for picking up information recorded on the optical disk 5, an optical disk identification unit 3 for identifying the type of the optical disk 5 based on a signal detected by the optical pickup 2, and a result determined by the optical disk identification unit 3. And an RF demodulation circuit 4 for reproducing the optical disk 5 from the optical disk.

The optical disc discrimination unit 3 includes a preamplifier 11 for amplifying a 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 discrimination unit 12 discriminates the type of the optical disc by using the reproduction signal RF, the focus error signal FE, and the tracking error signal TE by an apparatus and a method described later. The command unit 14 switches the numerical aperture NA of the objective lens constituting the optical pickup using the NA switching unit 15 according to the type of the optical disc determined by the determination unit 12 according to the type of the optical disc determined by the determination unit 12. Alternatively, the circuits are switched using the circuit switching unit 16 so that the playback is performed by the dedicated playback circuits.

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 635 (tolerance ±
15) A semiconductor laser 25 that generates a laser beam having a wavelength of nm, a diffraction grating 24 that generates a beam for detecting the tracking error signal TE, a polarization plane rotation unit 23, and a semiconductor laser 25. Half mirror 2 that reflects and transmits signals from optical disk 5
2, a collimator lens 26, a polarizing filter 29,
It includes an objective lens 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 via the diffraction grating 24 and the polarization plane rotation unit 23, and is reflected by the collimator lens 26.
And enters the optical disk 5 via the polarizing filter 29 and the objective lens 28. The objective lens 28 is moved in the tracking direction, and is moved 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, and irradiates the recording surface of the optical disk 5 through the polycarbonate substrate. The laser beam reflected by the recording surface is applied to the substrate, objective lens 28, polarizing filter 2
9. 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 the aberration that occurs when the thickness of the substrate of the optical disc 5 is different.

The polarization plane rotation unit 23 includes a TN (twisted nematic) type liquid crystal and two transparent electrode plates sandwiching the liquid crystal. At the time of reproduction of the digital video disc, no voltage is applied to the transparent electrode plate, so that the polarization plane rotation unit 23 rotates the polarization plane of the laser beam by 90 °. On the other hand, during reproduction of the compact disk, a predetermined voltage is applied to the transparent electrode plate, so that 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 an STN (super twisted nematic) type or a 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 of the laser beam is rotated by the polarization plane rotation unit 23, the outer periphery of the laser beam is shielded by the polarization filter 29, and the effective numerical aperture of the objective lens is adjusted. It is adjusted so that NA becomes 0.35 (allowable error ± 0.05).

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

FIG. 4 shows the polarization characteristics of the polarization filter 29. At the outer peripheral portion 29a of the polarizing filter 29, only the laser beam polarized in the overhead vertical direction is transmitted. A laser beam polarized in any direction is transmitted through the central portion (light transmitting portion) 29b of the polarizing filter 29. When the numerical aperture NA of the objective lens 28 is 0.6 (allowable error ± 0.05) and the effective aperture is 4 mm, the effective numerical aperture NA of the objective lens 28 is 0.35 (allowable error ± 0.05). ), The diameter of the central portion 29b of the polarizing filter 29 is set to 2.3 (allowable 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
Part 29b of the polarizing filter 29 so that
The caliber of may be set.

Next, an example in which a liquid crystal shutter 35 is used in place of the polarizing filter 29 will be described with reference to FIG.
The liquid crystal shutter 35 includes a donut-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 off (during reproduction of a digital video disk), the liquid crystal shutter 35 transmits the laser beam 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 a compact disc), the liquid crystal shutter 35 transmits only the laser beam in the central portion, and transmits the laser beam in the outer portion. Is scattered by the guest-host type liquid crystal 36 to block the light.

The liquid crystal shutter 35 transmits all of the laser beam during reproduction of the digital video disk, and transmits only the central portion of the laser beam during reproduction of the compact disk. Therefore, the polarizing filter 29 in the case of the above-described embodiment is not required.

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

FIG. 8 is a view 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 modification, two types of optical pickups 2 are provided according to the thickness of each substrate, instead of being single as in the previous embodiment.

FIGS. 9 and 10 are a plan view and an elevation view showing one pickup in a second modified example of the optical pickup 2. Basically, it is the same as that shown in FIG. 2, but in order to make the whole compact,
Is different. The other parts are the same, and the same parts are denoted by the same reference characters and description thereof will be omitted.

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

Next, the discriminating section 12 for discriminating an optical disk will be described. FIG. 11 shows the determination unit 1 shown in FIG.
2 is a block diagram showing the contents of FIG. Referring to FIG.
The determination unit 12 is a CPU 21 that controls the entirety of the determination unit 12.
And a ROM 22 for storing the operation of the discrimination unit 12 and a RAM 23 for storing data for discriminating a plurality of optical discs and a discrimination procedure, which will be described later. Discriminator 12
Determines the type of the optical disk based on the data representing the characteristics of each optical disk stored in the RAM 23.

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

[0061]

[Table 1]

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

The focus error signal FE and the reproduction signal RF
12, the level of the reproduction signal RF becomes maximum when the focus error signal FE is at 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 an S curve. Objective lens 28
When the distance from or near the optical disk 5 is DV
Two S curves appear in DD and one S curve appears in other optical discs. In addition, all the data used below adopt the peak-to-peak value A1 as shown in FIG.

The offset signal in the table is obtained as follows. FIG. 13 is a diagram for explaining an offset signal. Referring to FIG. 13, a case where tracking of tracking error signal TE passes through a central reference point is defined as te1,
Let te2 be the signal actually obtained on each optical disc. Here, the amplitude of the tracking error signal TE is A2
And the amount of deviation 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 (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 of the DVD shown in FIG. Discrimination of each optical disk is performed based on the data.

The 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, optical disc reproducing apparatus 1 performs a focus search so that the recording surface of optical disc 5 is focused (step S11, steps will be abbreviated below). Next, the discriminating unit 12 discriminates the disc according to a procedure described later (S12). Thereafter, a motor (not shown) is started according to the disc discrimination result, tracking servo is performed, and various optical discs are reproduced using the RF demodulation circuit 4 (S13 to S15).

FIG. 15 is a subroutine showing details of the disc discriminating step shown in FIG. In disc discrimination, it is first determined whether or not the focus is obtained on the recording surface by the optical pickup 2. When the focus is obtained, the three detection signals of the focus error signal FE, the reproduction signal RF, and the tracking error signal TE are detected. One of the signal levels is detected (S22).
According to the determination result, one of the two signals excluding one of the three signals described above or the number of S curves of the focus error signal FE is detected as the second signal level (S23). The disc is determined 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 disk 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 modified example of the disc determination subroutine shown in S12 of FIG. In FIGS. 16 and 17, the determination positions for determining whether or not focus has been obtained are shown in FIG.
The only difference is the case. That is, in the embodiment described in detail below, since a focus pull-in operation is required, the focus detection performed in S21 is indispensable.
Therefore, in order to detect a signal related to focus pull-in as the first signal level, it is necessary to always follow the processing in FIG. 15, and to detect a signal related to focus pull-in as the second signal level, it is necessary to perform the processing in FIG. When a signal relating to focus pull-in is not used, the subroutine of FIG. 17 may be used.

Next, a specific determination method using the first signal level and the second signal level described in the above flow will be described. In the following embodiments, three objective lenses having a numerical aperture NA = 0.6, a numerical aperture of 0.35, and a combination of both objective lenses will be described.

(A) When the numerical aperture NA is 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 showing a discrimination procedure. Referring to FIG. 18, first, the reproduction signal RF at the in-focus position
Compare levels. Referring to Table 1 (A), DVD-
Assuming that the reproduction signal RF level of S is 100%, DVD-D
About 35%, CD 36%, CD-R 9%, CD-R
Since R is 3%, as shown in FIG. 18, the DVD-S group having a high level and the DVD-D having a medium level
And CD groups, and three groups of low-level CD-Rs and CD-Rs. For a medium level group, the number of S curves of the focus error signal is 2 for DVD-D and 1 for CD.
Therefore, the determination is made using this.

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

In this example, the reproduction signal R at the in-focus position is
After comparing the levels of F, the number of S curves of the focus error signal FE was compared.
And then compare the reproduction signal RF level at the in-focus position.

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

The discriminating procedure for each disk in this case is shown in FIG.
Shown in As shown in FIG. 19, the focus error signal F
Referring to level E, DVD-S and DVD-D
And CD and CD-R and CD-R. After such determination, the number of S curves of the focus error signal FE is compared to obtain the D value.
It is possible to distinguish between VD-D and CD.

It should be noted that the above-described embodiment may be reversed, and the comparison may be performed using the number of S curves of the focus error signal, and then the comparison may be performed using the level of the focus error signal.

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

The discriminating procedure for each disk in this case is shown in FIG.
Shown in Referring to FIG. 20, focus error signal FE
Are divided into three groups as in the case of (2). Thereafter, the DVD-D and the CD can be determined by comparing the level of the tracking error signal TE. Also, since the level of the tracking error signal is different between the CD-R and the CD-R, this can also be determined by comparing the level of the tracking error signal TE.

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

The discriminating procedure of each disk in this case is shown in FIG.
Shown in Referring to FIG. 21, tracking error signal T
Comparing the levels of E, DVD-S, CD and CD
-A group with high signal level such as R and DVD-
Intermediate levels such as D and lower levels such as CD-R are divided into three groups.

Next, since the level of the focus error signal FE is different when the level of the tracking error signal TE is high, DVD-S, CD and CD-R can be discriminated by comparing the levels.

(5) After comparing at the level of the focus error signal FE, the comparison is made at the level of the S curve of the focus error signal FE and the level of the tracking error signal TE.

The discriminating procedure for each disk in this case is shown in FIG.
Shown in Referring to FIG. 22, in the comparison of (2),
Although CD-R and CD-R were not discriminated, (3)
As shown in (1), the two can be determined by comparing the levels of the tracking error signals.

The level of the reproduction signal RF at the in-focus position may be compared after comparing the number of S curves of the focus error signal.

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

The discriminating procedure for each disk in this case is shown in FIG.
Shown in Referring to FIG. 23, the reproduced signal R at the in-focus level
DVD-S and DVD-S
-D and CD groups and CD-R and CD-R
The three groups can be determined. After this, DVD-D
And CD group and CD-R and CD-R at the level of the tracking error signal TE.

(7) After comparing at the level of the tracking error signal TE, the comparison is performed 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, tracking error signal T
By comparing the levels of E, it can be divided into three groups. The DVD-S, CD and CD-R can be discriminated by comparing the level of the reproduction signal RF for the group having the highest level among them.

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

The discriminating procedure for each disk in this case is shown in FIG.
Shown in Referring to FIG. 25, tracking error signal T
Comparing the offset amounts of E, a group having a low signal level such as DVD-S, a CD and a CD-R or a DV.
They are divided into groups such as those having a large signal level such as DD and CD-Rs having almost no signal. Of these, the two groups whose signal levels are obtained can be determined 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) The case where the numerical aperture NA = 0.35 Next, the case where the numerical aperture NA is 0.35 will be described. In this case, the determination is made in the same manner as in the case where 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-
D-D and DVD-D
And a medium level group such as CD-R and a group such as CD-R which is hardly detectable. Of these, the group having a relatively high level and the group having a medium level are determined 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.
FIG. 27 shows a determination procedure in this case. Referring to FIG. 27, first, a DVD-
It is divided into a high level group such as S, CD and CD-R, a medium level group such as DVD-D, and a hardly detectable group such as CD-R. Thereafter, a group having a higher level is determined using the focus error signal FE.

(3) The first signal level is the reproduction signal RF
When the second signal level is the tracking error signal TE, the determination procedure in this case is shown in FIG. Referring to FIG. 28, the level of the reproduction signal RF is compared, and the group with the higher level (DVD-S and CD) and the group with the middle level (D
VD-D) and low groups (CD-R and CD-R
). Thereafter, the high and low level groups are determined using the level of the tracking error signal TE.

(4) The case where the first signal is the tracking error signal TE and the second signal is the reproduction signal RF FIG. 29 shows the determination procedure in this case. Referring to FIG. 29, the level of the tracking error TE is compared, and the level is divided into a high level group (CD and CD-R) and a low level group (DVD-S, DVD-D and CD-R). Then, the reproduction signal RF for each group
Is determined using the level of

(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 level of focus error signal FE is compared, and the group of high level (DVD-S and CD), the group of middle level (DVD-D and CD-R) and the group of low level (C
DR). Thereafter, the higher 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 a focus-on signal, the second signal is a tracking error signal TE, and the third signal is a reproduction signal RF. FIG. 31 shows a determination procedure in this case. In this case, three steps are used for discriminating the optical disk. Here, the focus-on signal means that the focus pull-in can be performed when the focus pull-in is performed using the optical pickup 2 while the optical disk 5 is rotated. If this is not possible, the disc is identified as a CD-R. Thereafter, the remaining four types of optical disks are determined. This determination method is the same as that described above, and a description thereof will be 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 normally obtained by actually turning on the tracking servo.

(7) When the first signal is a focus-on signal, the second signal is a reproduction signal RF, and the third signal is a tracking error signal TE. FIG. 32 is a diagram showing a discrimination method in this case. . The determination is made by exchanging the second signal and the third signal in the case (6).

(8) When the first signal is a focus-on signal, the second signal is a focus gain signal, and the third signal is a tracking error signal TE. FIG. 33 shows a determination procedure in this case. Here, the magnitude of the gain is the gain in the case where the focus pull-in is performed, and specifically, the gain 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

Since the third stage is the same as the other cases, the description is omitted. (C) When the numerical aperture NA is switched to make a determination (1) When a predetermined determination is made at the numerical aperture NA = 0.35 and then the numerical aperture NA is switched to NA = 0.6 The determination method in this case is shown in FIG. . Referring to FIG. 34, first, focusing is performed at numerical aperture NA = 0.35 in the same manner as in (B) and (6), and CD-R is determined first. Next, the level of the tracking error signal TE is compared, and the level is divided into a high level (CD and CD-R) and a low level (DVD-S and DVD-D). The group with the higher level compares the level of the reproduction signal RF to discriminate between CD and CD-R. A group with a low level discriminates between DVD-S and DVD-D by switching the numerical aperture NA to 0.6. This is because the difference increases the signal level 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 normally obtained by actually turning on the tracking servo.

(2) When the numerical aperture NA = 0.6 and NA
Comparison of reproduced signal RF in case of = 0.35 FIG. 35 shows a determination method in this case. Referring to FIG. 35, the optical discs (CD, CD-CD) having substantially the same reproduction signal RF when the numerical aperture NA = 0.6 and when the numerical aperture NA = 0.35 are set.
R and CD-R) and an optical disc (DVD-S and D) having different levels of the reproduction signal RF when the numerical aperture NA is 0.6 and when the numerical aperture NA is 0.35.
VD-D). After that, by comparing the level 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 determination unit 12, and the values are compared.

(3) Numerical aperture NA = 0.6 and NA = 0.
Case of Comparing Focus Error Signal FE in 35 A determination 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 disk (CD, CD-R, and CD-R) having substantially the same signal level in both optical disks (DVD-S and DVD-S) in which the signal level is clearly different when the numerical apertures are NA = 0.6 and NA = 0.35. And DVD-D).
Thereafter, each group is compared by the level of the focus error signal at the in-focus position at the numerical aperture NA = 0.6 to determine each optical disk.

(4) The case where numerical aperture NA = 0.6 and NA
= 0.35 when tracking error signal TE
FIG. 37 shows a determination method in this case. Referring to FIG. 37, first, the levels of tracking error signal TE with numerical apertures NA = 0.6 and NA = 0.35 are compared. Then, the optical disk groups (CD and CD-R) having substantially the same signal level in both, and the optical disk groups (DVD-S and VDV-
D) and an optical disk (CD-R) of a group that cannot be compared because it is almost zero. Thereafter, each optical disc is determined by comparing the level of the reproduction signal RF and the tracking error level at the in-focus position for the former two.

Next, when the above numerical aperture is 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
(B) is a pattern in which the numerical aperture NA is switched every half cycle. (C) is a diagram showing a case where the switching position of the pattern shown in (B) is shifted. (D) is a case where a half cycle is first performed with a numerical aperture NA = 0.6, the next one cycle is performed with a numerical aperture NA = 0.35, and the remaining half cycle is performed with a numerical aperture NA = 0.6. It is. (E) is (D)
Are shifted.

Referring to FIG. 38, focusing is performed in each cycle so as to pass through the focal point on the way.

In the above embodiment, a numerical aperture NA = 0.6 or 0.35 suitable for reproducing each optical disk is used. However, there is no problem even if a deviation of about ± 0.05 actually occurs. .

In the above embodiment, the discrimination was performed mainly using the objective lens having a numerical aperture NA = 0.6.
However, the present invention is not limited to this, and using the data shown in Table 1, it is also possible to discriminate an optical disk by another combination.

In the above embodiment, the discrimination data of the optical disk is obtained by keeping the output of the laser beam constant. However, the present invention is not limited to this. For example, the output of the laser beam is made to have the same reflectance from the optical disk. And the optical disk may be determined 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 to 40% (c) CD-R: 7 to 10% (d) CD-R: 3 to 5% Although the ratio of each detection signal may change by about ± 5%, such a change does not particularly affect the determination result.

[Brief description of the 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 polarizing filter.

FIG. 4 is a diagram illustrating 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 illustrating 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 modification of the optical pickup.

FIG. 10 is an elevation view showing a modification of the optical pickup.

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

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

FIG. 13 is a diagram illustrating an offset signal.

FIG. 14 is a flowchart showing the overall operation of the optical disk reproducing device.

FIG. 15 is a flowchart showing the contents of a disk determination subroutine.

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

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

FIG. 18 is a diagram illustrating a disc identification method when a numerical aperture NA = 0.6.

FIG. 19 is a diagram showing a disc determination method when the numerical aperture NA = 0.6.

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

FIG. 21 is a diagram illustrating a disc identification method when a numerical aperture NA = 0.6.

FIG. 22 is a diagram illustrating a disc determination method when a numerical aperture NA = 0.6.

FIG. 23 is a diagram showing a disc determination method when the numerical aperture NA = 0.6.

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

FIG. 25 is a diagram showing a method of discriminating a disk when the numerical aperture NA = 0.6.

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

FIG. 27 is a diagram illustrating a method of discriminating a disk when the numerical aperture NA is set to 0.35.

FIG. 28 is a diagram showing a method of discriminating a disk when the numerical aperture NA is set to 0.35.

FIG. 29 is a diagram illustrating a method for discriminating a disk when the numerical aperture NA is set to 0.35.

FIG. 30 is a diagram showing a disc determination method when the numerical aperture NA is set to 0.35.

FIG. 31 is a diagram showing a method of discriminating a disk when the numerical aperture NA is set to 0.35.

FIG. 32 is a diagram illustrating a method of discriminating a disk when the numerical aperture NA is set to 0.35.

FIG. 33 is a diagram illustrating a method of discriminating a disk when the numerical aperture NA is set to 0.35.

FIG. 34 is a diagram illustrating a method for discriminating a disk using numerical apertures NA = 0.35 and 0.6.

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

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

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

FIG. 38 is a diagram showing a pattern when the numerical aperture NA is converted.

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical disk reproducing device 2 optical pickup 3 optical disk determination unit 4 RF demodulation circuit 5 optical disk 11 preamplifier 12 determination unit 13 servo circuit 14 command unit 15 NA switching unit 16 circuit switching unit 21 photodetector 22 half mirror 23 polarization plane rotation unit 24 diffraction Grating 25 semiconductor laser 26 collimator lens 27 rising mirror 28 objective lens 29 polarizing filter 35 liquid crystal shutter

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Shuichi Ichiura 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-4-311874 (JP, A) Hei 7-287860 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 19/00 G11B 7/00

Claims (22)

(57) [Claims] An optical disc discriminating apparatus for discriminating types of a plurality of optical discs, comprising : a focus error signal, a tracking error signal, and a focus error signal obtained based on light reflected from a recording surface of the optical disc .
First and second signal detection means for respectively detecting at least two signals of the RF signal と , and discrimination for discriminating types of the plurality of optical discs in accordance with detection results of the first and second detection means. Means,
Optical disc identification device. 2. The plurality of optical disks include optical disks having different substrate thicknesses, and the optical disk determination device includes a single optical pickup that detects the control signal from the optical disks having different substrate thicknesses. Item 2. An optical disk 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.
An optical disc discriminating apparatus according to claim 2. 4. The optical disc discriminating apparatus according to claim 1, wherein said control signal includes a reproduction signal and a focus error signal. 5. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a reproduction signal and a tracking error signal. 6. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a focus error signal and a tracking error signal. 7. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a level of a focus error signal and the number of S curves of the focus error signal. 8. The optical disc discriminating apparatus according to claim 1, wherein the control signal includes a focus-on signal and a tracking error signal. 9. 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. 10. The control signal is detected by using an optical pickup using a lens with a predetermined numerical aperture.
An optical disc discriminating apparatus according to claim 1. 11. The apparatus according to claim 1, wherein the specific numerical aperture is plural, and further includes switching means for switching the plural numerical apertures.
0. The optical disk discriminating apparatus according to 0. 12. The control signal according to claim 1, wherein the at least two control signals are obtained using lenses having different numerical apertures.
An optical disc discriminating apparatus according to claim 1. 13. An optical disc discriminating method for discriminating types of a plurality of optical discs, comprising: detecting a first control signal from the optical disc; and detecting a second control signal different from the first from the optical disc. An optical disc discriminating method, comprising: determining a type of the plurality of optical discs in response to the first and second control signals. 14. The method according to claim 13, wherein the control signal includes a reproduction signal and a focus error signal. 15. The method according to claim 13, wherein the control signal includes a reproduction signal and a tracking error signal. 16. The method according to claim 13, wherein the control signal includes a focus error signal and a tracking error signal. 17. The method according to claim 13, wherein the control signal includes a level of a focus error signal and the number of S curves of the focus error signal. 18. The method according to claim 13, wherein the control signal includes a focus-on signal and a tracking error signal. 19. The method according to claim 13, wherein the control signal includes an offset amount of the tracking error signal and a level of the tracking error signal. 20. The detection of the first and second control signals is performed using a lens having a predetermined numerical aperture.
3. The optical disc discriminating method according to 3. 21. The optical disk discriminating apparatus according to claim 20, wherein the specific numerical aperture is plural, and the step of detecting the first and second control signals further includes a step of switching the plural numerical apertures. Method. 22. The optical disc discriminating method according to claim 13, wherein the step of detecting the two control signals includes the step of detecting using two lenses having different numerical apertures.