JP3157460B2 - Optical recording medium identification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for identifying a plurality of types of optical disks having different substrate thicknesses.

[0002]

2. Description of the Related Art An optical disk having a thickness of about 1.2 mm, such as a CD-ROM, from which information is read using a semiconductor laser is provided. In this type of optical disk, focus servo and tracking servo are performed on a pickup objective lens to irradiate a pit row on a signal recording surface with a laser beam to reproduce a signal. Recently, the recording density for recording a long moving image has been increasing.

[0003] For example, the same 12 cm diameter as a CD-ROM
An SD standard for recording about 5 Gbytes of information on one side of an optical disc has been proposed. The SD disc has a thickness of about 0.6 mm, and by laminating the discs, information of about 10 Gbytes can be recorded by one disc. Therefore, Japanese Patent Application Laid-Open No. Hei 5-303766 discloses that the thickness is 0.6 m.
high-density optical disk having a thin substrate of thickness m.
There has been proposed an apparatus that can reproduce a standard-density optical disk having a standard-thickness substrate of 2 mm with a single optical pickup.

This technique uses an objective lens having a numerical aperture of 0.6 designed to reproduce a high-density disk with a short-wavelength laser beam, and corrects aberrations when reproducing a standard-density optical disk with a standard thickness. This is an apparatus in which an aperture for reducing the effective numerical aperture by shielding the outer peripheral side of the laser beam from light is added to the light source side of the objective lens. S
To play D and CD with one pickup, first,
It is important to identify the type of the optical disc set in the playback device. This type of technology is disclosed in Japanese Unexamined Patent Application Publication No.
There is a method disclosed in Japanese Patent No. 59804. That is,
This method is a method of irradiating an optical disk with light using an optical pickup and detecting a difference in a detection position of reflected light from the optical disk to identify the optical disk.

[0005]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. 6-25980
According to the technology disclosed in Japanese Patent Publication No. 4 (1993) -207, a beam emitted from a semiconductor laser having a built-in optical pickup is irradiated onto an optical disc through an objective lens, the position of the reflected light is detected, and the mounted optical disc is detected. Since the identification is performed, an operation called “optical disk identification” is required before the reproduction operation of the optical disk is started. Therefore, there was a problem that quick identification was not possible. In addition, since the position of the reflected light is detected, if the optical disk is warped, it is affected by the warp.
There was a problem that it could not be accurately identified.

An object of the present invention is to solve the above problems and to provide an apparatus and a method for quickly and accurately identifying a mounted optical disk.

[0007]

SUMMARY OF THE INVENTION The present invention provides a first optical recording medium having a first substrate thickness and a second optical recording medium having a second substrate thickness greater than the first substrate thickness. In an identification device for identifying the first optical recording medium, an objective lens capable of focusing a laser beam on a recording surface of a first optical recording medium is used.
Detecting means for detecting a focus error signal from the optical recording medium or the second optical recording medium, and discriminating the optical recording medium based on at least the peak value or the number of peaks of the focus error signal at the time of focusing. And determining means for performing the determination.

Further, the present invention distinguishes between a first optical recording medium having a first substrate thickness and a second optical recording medium having a second substrate thickness larger than the first substrate thickness. In the identification device, a focus error signal from the first optical recording medium or the second optical recording medium is detected using an objective lens capable of focusing a laser beam on the recording surface of the second optical recording medium. And a discriminating means for discriminating the optical recording medium based on at least the peak value or the number of peaks of the focus error signal at the time of focus pull-in.

Further, the present invention provides an objective lens having a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a small substrate thickness by arranging two optical pickups having different numerical apertures of the objective lens. Using an optical pickup comprising a, detecting means for detecting a focus error signal from the optical recording medium, at the time of focus pull-in,
Determining means for determining an optical recording medium based on at least a peak value or the number of peaks of the focus error signal.

Further, the present invention comprises one optical pickup having two objective lenses having different numerical apertures,
Using an objective lens having a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a small substrate thickness, detecting means for detecting a focus error signal from the optical recording medium, Determining means for determining an optical recording medium based on a peak value or the number of peaks of the focus error signal.

The present invention further comprises an optical pickup having a numerical aperture changing means, wherein the numerical aperture is set to a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a thin substrate. Detecting means for detecting a focus error signal from a selective recording medium, and determining means for determining an optical recording medium based on at least a peak value or the number of peaks of the focus error signal during focus pull-in. And

Further, the present invention comprises two optical pickups having different numerical apertures of an objective lens, and has a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a standard thickness substrate. Detecting means for detecting a focus error signal from an optical recording medium using an optical pickup provided with an objective lens, and optically controlling the optical pickup based on at least a peak value or the number of peaks of the focus error signal during focusing. And a determination means for determining a target recording medium.

Further, the present invention comprises one optical pickup having two objective lenses having different numerical apertures,
Using an objective lens having a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a standard thickness substrate, detecting means for detecting a focus error signal from the optical recording medium, Determining means for determining an optical recording medium based on at least the peak value or the number of peaks of the focus error signal.

Further, the present invention comprises one optical pickup having a numerical aperture changing means, and is set to a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a standard thickness substrate. Detecting means for detecting a focus error signal from the optical recording medium, and determining means for determining the optical recording medium based on at least the peak value or the number of peaks of the focus error signal at the time of focusing. It is characterized by.

Further, the present invention is characterized in that the number of peaks of the focus error signal is one or two.

Further, the present invention is characterized in that the shape of the laser beam incident on the objective lens is circular or elliptical.

Further, the present invention is characterized in that the shape of the laser beam incident on the objective lens is polygonal.

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to the identification of a plurality of optical disks having different substrate thicknesses, track pitches and reflectivities from recording surfaces. FIG. 1 shows a wavelength of 350 to 450 n.
m (typical wavelength: 415 to 445 nm, the same applies hereinafter) when the thickness is 1.2 (tolerance ± 0.1,
A standard density optical disk having a standard thickness substrate of the same (hereinafter the same) mm, that is, a CD or CD-ROM (hereinafter, referred to as a first optical disk), and a substrate thickness of 0.6 (tolerance ± 0.05, the same applies hereinafter) mm High-density optical disk having a thin substrate of
That is, an ultra-high-density optical disk having an SD (hereinafter, referred to as a second optical disk) and a thin substrate having a substrate thickness of 0.6 (tolerance ± 0.05, the same applies hereinafter) mm, that is, a high-density SD (hereinafter, referred to as a third optical disk) The shortest pit length, track pitch, beam spot diameter and numerical aperture of the objective lens are shown.
FIG. 2 shows wavelengths of 450 to 550 nm (typical wavelength: 51
7 shows the shortest pit length, track pitch, beam spot diameter, and numerical aperture of the objective lens of the first, second, and third optical disks when a laser beam of 7 to 547 nm (hereinafter the same) is used. 3 and 4 show wavelengths 585 to 6 respectively.
90 nm (typical wavelength: 620 to 650 nm, the same applies hereinafter), wavelength 600 to 700 nm (typical wavelength: 635 to 6
The table shows the shortest pit length, track pitch, beam spot diameter, and numerical aperture of the objective lens of the first, second, and third optical disks when a laser beam of 65 nm (hereinafter the same) is used. Here, each of the second and third optical disks includes a single-sided recording optical disk and a double-sided recording / single-sided reading optical disk. The pit depths (physical depths) of the first, second, and third optical disks are 110 (90 to 13), respectively.
0) nm, 105 (95-115) nm, 72 (62-
82) nm.

The size of the substrate is 40 to 12 in diameter.
It is an optical disk of 0 mm. The present invention is directed to these optical disks. FIG. 5 shows a flowchart from the start of the reproducing operation of the optical disk to the reproducing operation in the present invention and the conventional example. The operation of reproducing an optical disk using an optical pickup is performed as follows. Conventionally, when an optical disk is loaded, a reproducing operation starts, first, a focus search is performed, and a focus servo is performed. If the focus servo is not OK, the reproduction operation ends. When the focus servo becomes OK, the motor starts, performs tracking control, and normal reproduction operation starts. According to the present invention, at the time of a focus search, the focus error signal S
The optical disk is identified by detecting the peak value of the character curve, and reproduction or recording is performed according to the identified optical disk. Further, in the present invention, a procedure for performing a focus search after starting the motor may be used. Therefore, in the flowchart of the present invention, as shown in FIG. 5, a discrimination function of the optical disk is added before the focus becomes OK compared to the related art. Even if this discriminating function is added, the time until the reproducing operation of the optical disk does not become longer than before. That is, in the conventional optical disk reproducing operation, the type of the mounted optical disk is identified during the period from the mounting of the optical disk until the focus servo is performed. The S of the focus error signal at the time of the focus search in the above optical disc to which the present invention is directed
The character curves can be classified into three types as shown in FIG. In FIG. 7, numerical aperture (NA): 0.6 (permissible error: ±
5 shows an S-shaped curve measured using an objective lens for a substrate thickness of 0.6 mm (0.05, the same applies hereinafter). When the S-curve of a CD is measured with this objective lens, the amount of light that can be effectively used is reduced. Therefore, the peak value of the S-curve is smaller than the peak value of the S-curve of the single-sided recording SD as shown in FIG. About half. In the case of double-sided recording / single-sided reading SD, the peak value of the S-shaped curve is reduced by an amount of about 30% as compared with the case of single-sided recording SD, but the peak appears twice because there are two recording surfaces. Therefore, even when it is necessary to identify the single-sided recording SD and the double-sided recording / single-sided reading SD, the identification can be performed. The same can be said for the single-sided recording optical disk of the high-density SD and the double-sided recording / single-sided reading optical disk. Double-sided recording / single-sided reading optical disk (SD and high density SD) and C
D can be identified by the difference in the peak value of the S-shaped curve. That is, when the peak value of the S-shaped curve is large, S
D or high-density SD, and if smaller, CD.

Therefore, the reproducing apparatus used for reproducing the optical disk only needs to have a function of reproducing a plurality of target optical disks. FIG. 6 shows an optical pickup 10 used in the present invention. The beam emitted from the semiconductor laser 9 passes through the diffraction grating 8, the collimating lens 7, the polarizing beam splitter 4, the quarter-wave plate 20, and the aperture 3, is condensed by the objective lens 2, and is irradiated on the optical disc 1. The beam reflected by the optical disk 1 returns through the objective lens 2, the aperture 3, the quarter-wave plate 20, and is reflected by the polarization beam splitter 4 in a direction forming an angle of 90 degrees with the direction of the incident beam, and condensed. The light passes through the lens group 5 and is detected by the photodetector 6. In the optical pickup 10, the aperture 3 inserted between the objective lens 2 and the polarizing beam splitter 4 can change the effective NA in order to enable compatible reproduction of CD and SD. That is, the distance from the substrate surface to the signal recording surface is 1.2 m for CD and SD, respectively.
m and 0.6 mm, one objective lens cannot focus on a signal recording surface at these different distances. Therefore, by changing the effective NA according to the distance to the signal recording surface, two types of distances can be obtained. It is designed to be able to focus on a certain signal recording surface. The effective NA is mechanical, electrical,
It can be changed by a magnetic method.

As a method of electrically changing the effective NA, a polarization plane switching means for rotating the polarization plane of the laser beam, and a polarization selection means for selectively shielding the outside of the laser beam passing through the polarization plane switching means. There is a method in which a unit is applied to the aperture 3 and a liquid crystal is used for the polarization plane switching unit and the polarization selection unit. An example of the liquid crystal used for the polarization selecting means is a guest-host type liquid crystal, and examples of the liquid crystal used for the polarization plane switching means include a TN type liquid crystal, an STN type liquid crystal, and a ferroelectric type liquid crystal. A Pockels cell can be used for the polarization plane switching means other than the liquid crystal.

As an example using a mechanical method, there is an example using a half-wave plate for the polarization plane switching means, and a polarization filter, a polarization selective hologram, and a polarizing glass are used as the polarization selecting means. As a magnetic method, there is an example in which a Faraday element is used for the polarization plane switching means. Further, a half mirror may be used instead of the polarizing beam splitter 4 and the quarter-wave plate 20. Further, the aperture 3 is not limited to between the quarter-wave plate 20 (half mirror) and the objective lens 2 but may be between the semiconductor laser 9 and the objective lens 2. Each optical disc is identified by detecting the peak value of the S-curve of the focus error signal by the photodetector 6 using the optical pickup having the above configuration. First Embodiment Discrimination between a CD and single-sided recording SD will be described.

When the focus search is started after loading the optical disk, the objective lens 2 of the optical pickup 10 starts to move up and down, as shown in FIG.
The S-shaped curve shown in (c) is detected by the photodetector 6. At this time, the effective NA of the objective lens 2 is set to 0.6 by the aperture 3. Substrate thickness 0.6
In the case of single-sided recording SD of mm, the total light amount of the laser beam to be irradiated can be used, but in the case of CD, the total light amount is used because the effective NA of the objective lens 2 is set to 0.6. Because the reflectance of the recording surface is SD
Even if it is 70% or more, the peak value of the S-shaped curve becomes small. Therefore, if the detected peak value of the S-shaped curve is large, it is identified as single-sided recording SD, and if it is small, it is identified as CD. Second Embodiment Discrimination between a CD and a double-sided recording / single-sided reading SD will be described.

When the focus search is started after loading the optical disk, the objective lens 2 of the optical pickup 10 starts to move up and down, as shown in FIG.
The S-shaped curve shown in (c) is detected by the photodetector 6. Also in this case, the effective NA of the objective lens 2 is set to 0.6 by the aperture 3. In the case of double-sided recording / single-sided reading SD with a substrate thickness of 0.6 mm, the entire light amount of the irradiated laser beam can be used, but the reflectance is as low as about 30%, so the S-shaped curve detected by the photodetector 6 is used. Is smaller than the SD of the single-sided recording,
Since the recording surface has two layers, two S-shaped curves are detected. Further, in the case of a CD, since the total amount of light cannot be used for the above reason, the peak value of the S-shaped curve becomes small,
This is almost the same as the case of double-sided recording / single-sided reading SD. Therefore, in this case, both optical discs can be identified by the number of detected S-shaped curves.
A single-sided reading SD can be identified as a CD if it is performed once. That is, in the case of double-sided recording / single-sided reading SD, the peak value is detected twice in the process of the objective lens 2 approaching the optical disk 1, but only once in the case of CD. Therefore, both optical discs can be identified by the number of detected peak values.

As described above, it is possible to identify optical disks having different substrate thicknesses by detecting the number of peak values of the S-shaped curve. Third Embodiment Discrimination between single-sided recording SD and double-sided recording / single-sided reading SD will be described. When the focus search is started after loading the optical disk, the objective lens 2 of the optical pickup 10 starts moving up and down, and FIG.
The S-shaped curve shown in (b) is detected by the photodetector 6. In this case, the peak values of the detected S-curve are different because the reflectivity of the optical disc is different. In the double-sided recording / single-sided reading SD, the peak value of the S-shaped curve is small since the reflectance is about 30% smaller than that of the single-sided recording SD. Therefore,
If the peak value of the S-shaped curve is large, it can be identified as single-sided recording SD, and if it is small, it can be identified as double-sided recording / single-sided reading SD.
In this case, since the number of times of the detected S-shaped curve is also different, it can be identified by the number of times of the peak value of the S-shaped curve. That is, in the case of double-sided recording / single-sided reading SD, the peak is 2 when the objective lens 2 approaches the optical disc 1.
Since it is detected twice, it can be identified as double-sided recording / single-sided reading SD if the number of peak values detected by the detector 6 is two, and CD if it is one time. Fourth Embodiment Discrimination between a CD and a high-density SD for single-sided recording will be described.

When the focus search is started after loading the optical disk, the objective lens 2 of the optical pickup 10 starts to move up and down, as shown in FIG.
The S-shaped curve shown in (c) is detected by the photodetector 6. At this time, the effective NA of the objective lens 2 is set to 0.6 by the aperture 3. Substrate thickness 0.6
In the case of a single-sided recording high-density SD having a diameter of 0.1 mm, the total light amount of the laser beam to be irradiated can be used. However, in the case of a CD, the effective NA of the objective lens 2 is set to 0.6. Since the total amount of light cannot be used, the peak value of the S-shaped curve becomes small even if the reflectance of the recording surface is 70% or more, which is the same as SD. Therefore, if the peak value of the detected S-shaped curve is large, the high-density SD of single-sided recording is obtained,
If smaller, it is identified as a CD. Fifth Embodiment Discrimination between a CD and a high-density SD for double-sided recording / single-sided reading will be described.

When the focus search is started after loading the optical disk, the objective lens 2 of the optical pickup 10 starts to move up and down, as shown in FIG.
The S-shaped curve shown in (c) is detected by the photodetector 6. Also in this case, the effective NA of the objective lens 2 is set to 0.6 by the aperture 3. In the case of a high-density SD for double-sided recording / single-sided reading with a substrate thickness of 0.6 mm, the total light amount of the irradiated laser beam can be used.
Since the reflectivity is as low as about 30%, the magnitude of the S-curve detected by the photodetector 6 is smaller than the SD for single-sided recording, but since the recording surface has two layers, two S-curves are provided. A curve is detected. Further, in the case of a CD, since the total amount of light cannot be used for the above reason, the peak value of the S-shaped curve becomes small, which is almost the same as in the case of the high-density SD of double-sided recording and single-sided reading. Accordingly, in this case, both optical discs can be identified by the number of detected S-shaped curves. If the S-shaped curve is twice, it is possible to identify a high-density SD for double-sided recording and single-sided reading, and if it is once, it is possible to identify a CD. Sixth Embodiment High-density SD for single-sided recording and high-density S for double-sided recording / single-sided reading
The identification from D will be described.

When the focus search is started after the optical disk is loaded, the objective lens 2 of the optical pickup 10 starts to move up and down, as shown in FIG.
The S-shaped curve shown in (b) is detected by the photodetector 6. In this case, the peak value of the S-shaped curve is higher in the single-sided recording high-density SD than in the double-sided recording / single-sided reading high-density SD because of the difference in the recording surface because the entire amount of the irradiated laser beam can be used. growing. Therefore, if the peak value of the S-curve detected by the photodetector 6 is large, it is identified as a high-density SD for single-sided recording, and if the peak value is small, it is identified as a high-density SD for double-sided recording / single-sided reading. In this case, since the number of peak values of the detected S-shaped curve is different, it can be identified also by the number of peak values. That is, in the case of high-density SD of double-sided recording / single-sided reading, a peak is detected twice during the process in which the objective lens 2 approaches the optical disk 1, so that the peak value detected by the detector 6 is twice. If it is, it can be identified as a high-density SD for double-sided recording / single-sided reading, and once if it is a high-density SD for single-sided recording.

The identification of the single-sided recording SD and the double-sided recording / single-sided reading high-density SD, and the single-sided recording high-density SD and the double-sided recording / single-sided reading SD are also performed by detecting the magnitude or number of peak values of the S-shaped curve. It is possible by doing. As described above, the CD and the single-sided recording SD and C are obtained by using the peak value of the S-curve of the focus error signal or the number of times of the peak value.
D and double-sided recording and single-sided reading SD, CD and single-sided recording high-density SD, CD and double-sided recording and single-sided reading high-density SD, single-sided recording SD and double-sided recording and single-sided reading SD, and single-sided recording high-density S
D, high-density SD for double-sided recording / single-sided reading, single-sided recording SD, high-density SD for double-sided recording / single-sided reading, high-density SD for single-sided recording, and double-sided recording / single-sided reading SD are possible.

In the first to sixth embodiments, 350
An optical disc can be identified by using a laser beam having a wavelength of from 700 to 700 nm.
00) nm or 635 (585-690) nm or 500 (450-550) nm or 400 (3
50 to 450) nm, and more preferably 415 to 445 nm or 517 to 547 nm or 620 to 650 nm or 635 to 665 nm.
It is.

The shape of the beam is not limited to a circle but may be an ellipse or a polygon as shown in FIG. Seventh Embodiment FIG. 8 illustrates an operation from identification of an optical disc to reproduction. Effective NA: 0.6 using pickup 10
Irradiates the optical disk 1 with a laser beam by the
The S-shaped curve of the focus error signal detected from is sent to the preamplifier 12, amplified by the preamplifier 12, and then sent to the discriminating unit 13. The determination unit 13 detects the peak value of the S-curve of the sent focus error signal, and determines the optical disk based on the magnitude relationship (or the number of times) of the detected peak values. For example, if the peak value of the detected S-shaped curve is large, the double-sided recording / single-sided reading S
D or a high-density SD for double-sided recording / single-sided reading, a single-sided recording SD, or a single-sided recording high-density SD. If the detected peak value of the S-shaped curve is small, it is determined to be CD. Here, the preamplifier 12 may be built in the pickup 10. The signal determined by the determination unit 13 is sent to the command unit 15, and the command unit 15 transmits N signals necessary for reproducing the determined optical disc.
A command for switching A and circuit switching
It outputs to the switching means 16 and the circuit switching means 17. The NA switching means 16 changes the effective NA of the pickup 10 according to a command from the command unit 15 so as to be suitable for reproducing the identified optical disc. That is, for a laser beam having a wavelength of 350 to 450 nm, the NA is set to 0.30 to 0.55 to reproduce a single-sided recording SD or a double-sided recording / single-sided reading SD, and the NA is set to 0.20 to 0.2. Set to 30 and play the CD. For a laser beam having a wavelength of 450 to 550 nm, the NA is set to 0.40 to 0.55 to reproduce a single-sided recording SD or a double-sided recording / single-sided reading SD, and the NA is set to 0.2.
Set the value to 5 to 0.40 and play the CD. 585-69
For a laser beam with a wavelength of 0 nm, NA is 0.5.
Single-sided recording SD or double-sided recording / single-sided reading SD is reproduced by setting the value to 5 to 0.65, and the CD is reproduced by setting the NA to 0.30 to 0.55. For a laser beam having a wavelength of 600 to 700 nm, NA is set to 0.55 to 0.65 to reproduce single-sided recording SD or double-sided recording / single-sided reading SD, and the NA is set to 0.30 to 0.55. Set and play the CD. Further, the circuit switching means controls the RF demodulation circuit 18
An instruction is given to switch the circuit so that demodulation according to the optical disk to be reproduced can be performed. After the NA is set according to the determined optical disc, the focus servo is OK.
Then, the motor is started, the rotation of the optical disk is started, and tracking control is performed. Thereafter, reproduction of each optical disk is performed.

In the seventh embodiment, the determination unit 13
In the above, the size of the sent S-shaped curve is determined as it is, but the present invention is not limited to this. A reference value is set in the determination unit 13 in advance, and the determination is made based on whether or not the reference value is exceeded. May be. Next, a case where discrimination between single-sided recording SD or high-density SD for single-sided recording and double-sided recording / single-sided reading SD or high-density SD for double-sided recording / single-side reading is performed, and reproduction in accordance with each optical disc will be described. In this case, since the peak value of the S-curve detected by the photodetector 6 of the optical pickup 10 has the same magnitude, both optical discs are identified by the number of detected peaks. A single peak indicates a single-sided recording SD or a single-sided recording high-density SD, and a peak twice indicates a double-sided recording / single-sided reading SD or a double-sided recording / single-sided reading high density S.
D. In this case, the NA for each optical disk is set as follows, and each optical disk is reproduced. That is, 350
For a laser beam having a wavelength of 450 nm to 450 nm, the NA is set to 0.30 to 0.55 to reproduce single-sided recording SD or double-sided recording / single-sided reading SD, and the NA is set to 0.55 to 0.65.
To reproduce the high-density SD for single-sided recording or the high-density SD for double-sided recording / single-sided reading. For a laser beam having a wavelength of 450 to 550 nm, NA is set to 0.40 to 0.5.
Set to 5 to reproduce single-sided recording SD or double-sided recording / single-sided reading SD, and set NA to 0.55 to 0.65 to reproduce single-sided recording high-density SD or double-sided recording / single-sided reading high-density SD I do. For a laser beam having a wavelength of 585 to 690 nm, the NA is set to 0.55 to 0.65, and single-sided recording SD or double-sided recording / single-sided reading SD or single-sided recording high-density SD or double-sided recording / single-sided reading is performed. Play high density SD. For a laser beam having a wavelength of 600 to 700 nm, the NA is set to 0.55 to 0.65, and single-sided recording SD or double-sided recording / single-sided reading SD or single-sided recording high-density SD or double-sided recording / single-sided reading is performed. Play high density SD. The operation after setting the NA is the same as above. However, in the reproduction of the double-sided recording / single-sided reading SD and the double-sided recording / single-sided reading high-density SD, it is necessary to amplify the detected signal since the reflectance of the recording surface on the laser beam incident side is as low as about 30%. . Otherwise, the operation is the same as the above operation.

In the above-described embodiment, it is necessary to switch three types of NA. However, the present invention is not necessarily limited to this. For a laser beam having a wavelength of 350 to 450 nm, the NA is set to 0.30. Set and play back CD, single-sided recording SD and double-sided recording / single-sided reading SD, and set NA to 0.
It may be set to 60 to reproduce a high-density SD for single-sided recording and a high-density SD for double-sided recording / single-sided reading. Also, set NA to 0.
CD is reproduced by setting to 25, and NA is set to 0.55 to reproduce single-sided recording SD, double-sided recording / single-sided reading SD, single-sided recording high-density SD and double-sided recording / single-sided reading high-density SD Is also good. That is, if the first optical disc is reproduced with a single NA, the second and third discs are reproduced with a common NA, or if the first and second optical discs are reproduced with a common NA,
The third optical disc is reproduced with a single NA. This can be applied to laser beams of other wavelengths.

Although the seventh embodiment has been described from identification to reproduction of each optical disk, each optical disk can be identified and recorded by the above-described method for recording on the optical disk targeted by the present invention. That is,
The wavelength of the laser beam is 650 (600 to 700) nm or 635 (585 to 690) nm or 500
(450-550) nm or 400 (350-45)
0) If a semiconductor laser having a power of 30 mW at nm is used, the optical pickup described in the first to sixth embodiments is used, and the effective numerical aperture of the objective lens in the pickup is suitable for each optical disc and each wavelength. By setting the effective numerical aperture, recording on the first, second and third optical disks is possible. The second and third optical disks include a single-sided recording optical disk and a double-sided recording / single-sided reading optical disk, respectively.

An optical pickup and a recording or reproducing apparatus according to the present invention will be described. In the present invention, after discrimination of optical discs having different substrate thicknesses, track pitches, pit depths (physical depths), and shortest pit lengths, recording or reproduction according to each optical disc is performed. An optical pickup used in a reproducing apparatus requires at least two objective lenses having different effective NAs. In this case, the following cases can be considered as the optical pickup.

(1) Two optical pickups having NA objective lenses corresponding to each substrate thickness. (2) One optical pickup provided with two objective lenses having NA corresponding to each substrate thickness. (3) One optical pickup provided with one objective lens whose effective NA can be changed according to each substrate thickness.

In the present invention, it is possible to use these three types of optical pickups. In each of these three optical pickups, when discriminating an optical disk, recording is performed on an NA of 0.55 to 0.65. Or during playback,
For an optical disk with a substrate thickness of 0.55 to 0.65 mm,
0.30 to 0.55 or 0.55 to 0.65 (wavelength: 3
50-450 nm) or 0.40-0.55 or 0.5.
55 to 0.65 (wavelength: 450 to 550 nm) or 0.5
5 to 0.65 (wavelength: 585 to 690 nm or 60
0-700 nm), the substrate thickness is 1.1-1.3 mm
0.20 to 0.30 (wavelength: 35
0 to 450 nm) or 0.25 to 0.40 (wavelength: 450)
~ 550 nm) or 0.30 ~ 0.55 (wavelength: 585 ~
690 nm or 600-700 nm), and the optical disk can be identified and recorded or reproduced.
However, in the case of the pickups (1) and (2), since the NA of each of the two objective lenses is fixed, the NA of one of the objective lenses is set to 0.55 to 0.65 (for each of the above wavelengths). And the NA of the other objective lens is 0.30.
(Wavelength: 350 to 450 nm) or 0.40 (wavelength: 4
50-550 nm) or 0.55 (wavelength: 585-69)
0 nm or 600 to 700 nm). Thus, the first, second, and third optical disks can be identified, recorded, or reproduced using the optical pickups (1) and (2). In the optical pickup of (3), if the effective NA is switched to three types, the above N
Identification, recording or reproduction is possible in the range of A. Also,
In the optical pickup of (3), it is possible not only to switch the effective NA to three types, but also to set it freely in the range of 0.25 to 0.65.

The wavelength of the laser beam is 350
７００700 nm is possible, preferably 650 (60
0-700) nm or 635 (585-690) n
m or 500 (450-550) nm or 40
The wavelength is 0 (350 to 450) nm, and more preferably 415 to 445 nm or 517 nm, or 620 to 650 nm, or 635 to 665 nm. .

When each optical disc is identified using the above three types of optical pickups, the S-shaped curve of the focus error signal can be used in any of the optical pickups. Eighth Embodiment In the first to sixth embodiments, the CD, single-sided recording S
D, double-sided recording / single-sided reading SD, single-sided recording high-density SD,
The identification of the high-density SD of double-sided recording / single-sided reading has been described, but the present invention is not limited to this, and the present invention includes a CD-R which is a write-once optical disk having a substrate thickness of 1.2 mm. Identification is also possible. This CD-R has a minimum pit length of 0.83 μm (0.80 to 0.8 μm).
90 μm) and a track pitch of 1.6 μm (1.5 to 1.5 μm).
7 μm), and the reflectance is 635 nm (585
６８685 nm) or 650 nm (600-700 nm)
10 to 50% of the optical disk with respect to the laser beam.

FIG. 10 shows a CD, CD-R, single-sided recording SD, high-density SD for single-sided recording, double-sided recording / single-sided reading SD, and high-density for double-sided recording and single-sided reading when the numerical aperture of the objective lens is 0.6. This shows the SD focus error signal. C
D, single-sided recording SD, single-sided recording high-density SD, double-sided recording
The single-sided reading SD and the double-sided recording / single-sided reading high-density SD exhibit the same focus error signal strength as described in the first to sixth embodiments. The focus error signal strength of the CD-R is 5 to 40% of the focus error signal strength of the CD. This is due to the fact that the numerical aperture of the objective lens is designed for a substrate thickness of 0.6 mm, making it impossible to use the entire light amount of the irradiated laser beam, and the reflectance of the optical disk is as low as 10 to 50%. Therefore, by detecting the focus error signal of the optical disc at the time of focusing, CD-R and CD, single-sided recording SD, single-sided recording high-density SD, double-sided recording / single-sided reading SD, and double-sided recording / single-sided reading high-density SD are obtained. Can be identified. The discrimination of the optical disk based on the focus error signal intensity is performed when the wavelength is 635 nm (585 to 690 nm).
m) or 650 nm (600-700 nm) laser beam.

As the pickups, the three types of pickups described in the seventh embodiment, namely, (1) two optical pickups having an objective lens having an NA corresponding to each substrate thickness, (2) each substrate thickness One optical pickup provided with two objective lenses having corresponding NAs (3) One optical pickup provided with one objective lens whose effective NA can be changed according to each substrate thickness can be used.

The shape of the beam is not limited to a circle but may be an ellipse or a polygon as shown in FIG. Ninth Embodiment In the first to sixth embodiments and the eighth embodiment described above, the numerical aperture of the objective lens is set to 0.6, that is, the numerical aperture capable of focusing on the recording surface of an optical disk having a substrate thickness of 0.6 mm. The case where the focus error signal is detected at the time of focusing and the optical disc is identified has been described. However, the numerical aperture of the objective lens is not limited to 0.35, that is, the substrate thickness is 1.2.
It is also possible to identify the optical disk by detecting a focus error signal at the time of pulling in the focus with a numerical aperture capable of focusing on the recording surface of the optical disk of mm.

FIG. 11 shows a CD, CD-R, single-sided recording SD, single-sided recording high-density SD, double-sided recording / single-sided reading SD and double-sided recording when the numerical aperture of the objective lens is 0.35.
7 shows a focus error signal of a high-density SD for single-sided reading.
Both the single-sided recording SD and the single-sided recording high-density SD have the same focus error signal intensity because the substrate thickness is 0.6 mm and the reflectance is 70% or more. The double-sided recording / single-sided reading SD and the double-sided recording / single-sided reading high density SD both have the same focus error signal intensity because the substrate thickness is 0.6 mm and the reflectivity is 20 to 40%. Compared with the SD and the high-density SD of the single-sided recording, the intensity is less than half. The focus error signal intensity of the CD is the same as that of the single-sided recording SD or the high-density SD of the single-sided recording. Further, the focus error signal intensity of the CD-R is about half or less of that of the CD, and is almost the same as the double-sided recording / single-sided reading SD or the double-sided recording / single-sided reading high density SD. Therefore, it is possible to discriminate a CD-R from a single-sided recording SD or a single-sided recording high-density SD or CD depending on the magnitude of the focus error signal intensity. The discrimination between the CD-R and the double-sided recording / single-sided reading SD or the double-sided recording / single-sided reading high-density SD can be made not by the intensity of the focus error signal but by the difference in the number of peaks of the focus error signal.
That is, in the case of double-sided recording / single-sided reading SD or the case of double-sided recording / single-sided reading high-density SD, the peak of the focus error signal appears twice, but in the case of CD-R, the peak is one. By detecting the number of times, it is possible to discriminate between a double-sided recording / single-sided reading SD or a double-sided recording / single-sided reading high density SD and a CD-R.

Further, discrimination between CD, single-sided recording SD or single-sided recording high-density SD and double-sided recording / single-sided reading SD or double-sided recording / single-sided reading high-density SD can be made by detecting the focus error signal intensity or the number of peaks. Become. Also in the ninth embodiment, the wavelength is 635 nm (585
690 nm) or 650 nm (600-700 nm)
The above-mentioned discrimination is possible using the laser beam described above. As the pickups, the three kinds of pickups described in the seventh embodiment, namely, (1) two pickups having NA objective lenses corresponding to respective substrate thicknesses are used. Optical pickup (2) One optical pickup provided with two objective lenses having NA according to each substrate thickness (3) One light provided with one objective lens whose effective NA can be changed according to each substrate thickness Pickups can be used.

The shape of the beam is not limited to a circle but may be an ellipse or a polygon as shown in FIG. Tenth Embodiment In the first to ninth embodiments, the description has been made on the optical disc having the reading surface side substrate thickness, the shortest pit length, the track pitch, and the reflectivity shown in FIGS.
The present invention is not limited to this, and may be an optical disc having the rated values and the reproduction conditions shown in FIGS. That is, FIG. 12 shows a wavelength of 350 to 450 nm (typical wavelength: 415 to 445 n).
The following shows other examples of the shortest pit length, track pitch, beam spot diameter, and numerical aperture of the objective lens of the first optical disk, the second optical disk, and the third optical disk when a laser beam (m, the same applies hereinafter) is used. FIG. 13 shows wavelengths of 450 to
First, second and third laser beams of 550 nm (typical wavelength: 517 to 547 nm, the same applies hereinafter) are used.
Another example of the shortest pit length, track pitch, beam spot diameter, and numerical aperture of an objective lens of an optical disc is shown. 3 and 4 show wavelengths of 585 to 690 nm (typical wavelengths: 620 to 650 nm, the same applies hereinafter) and wavelengths of 600 to 600 nm, respectively.
1st, 2nd, and 3rd when using a laser beam of 700 nm (typical wavelength: 635 to 665 nm, the same applies hereinafter).
Another example of the shortest pit length, track pitch, beam spot diameter, and numerical aperture of an objective lens of an optical disc is shown. Here, each of the second and third optical disks includes a single-sided recording optical disk and a double-sided recording / single-sided reading optical disk. The pit depths (physical depths) of the first, second, and third optical disks are 110 (90 to 130) n, respectively.
m, 105 (95-115) nm, 72 (62-82)
nm, which is the same as the case described above with reference to FIGS.

Optical disks having the rated values shown in FIGS. 12 to 15 can be identified and reproduced according to the identified optical disks in the same manner as in the first to ninth embodiments.

[0068]

According to the present invention, a CD and a single-sided recording S can be recorded by using an optical pickup used for recording or reproducing data on or from an optical disc.
D, CD and double-sided recording / single-sided reading SD, CD and single-sided recording high-density SD, CD and double-sided recording / single-sided reading high-density SD,
Single-sided recording and double-sided recording / single-sided reading SD, single-sided recording high-density SD and double-sided recording / single-sided reading high-density SD, single-sided recording SD and double-sided recording / single-sided reading high-density SD, and single-sided recording high-density SD and double-sided The discrimination of the recording / single-sided reading SD can be performed accurately and quickly in the process of performing the focus servo.

According to the present invention, CD and single-sided recording SD, CD and double-sided recording / single-sided reading SD, CD and single-sided recording high-density SD and CD are obtained by using two pickups having objective lenses having different numerical apertures. High-density SD for double-sided recording / single-sided reading, single-sided recording SD and double-sided recording / single-sided reading SD, high-density SD for single-sided recording and high-density SD for double-sided recording / single-sided reading,
It is possible to discriminate between single-sided recording SD, double-sided recording / single-sided reading high-density SD, and single-sided recording high-density SD and double-sided recording / single-sided reading SD.

Further, according to the present invention, two numerical apertures are different.
C using one pickup with two objectives
D and single-sided recording SD, CD and double-sided recording / simplex reading SD, C
D and high-density SD for single-sided recording, CD and high-density SD for double-sided recording and single-sided reading, single-sided recording SD and double-sided recording and single-sided reading S
D, high-density SD for single-sided recording and high-density SD for double-sided recording / single-sided reading, high-density S for single-sided recording SD and double-sided recording / single-sided reading
D and single-sided recording high-density SD and double-sided recording / single-sided reading SD
Can be determined.

Further, according to the present invention, C pickup can be achieved by using one pickup having an objective lens whose effective numerical aperture is variable.
D and single-sided recording SD, CD and double-sided recording / simplex reading SD, C
D and high-density SD for single-sided recording, CD and high-density SD for double-sided recording and single-sided reading, single-sided recording SD and double-sided recording and single-sided reading S
D, high-density SD for single-sided recording and high-density SD for double-sided recording / single-sided reading, high-density S for single-sided recording SD and double-sided recording / single-sided reading
D and single-sided recording high-density SD and double-sided recording / single-sided reading SD
Can be determined.

Further, according to the present invention, the wavelengths of 350 to 45
CD and single-sided recording SD, C using 0 nm laser beam
D and double-sided recording and single-sided reading SD, CD and single-sided recording high-density SD, CD and double-sided recording and single-sided reading high-density SD, single-sided recording SD and double-sided recording and single-sided reading SD, and single-sided recording high-density S
D, high-density SD for double-sided recording / single-sided reading, single-sided recording SD, high-density SD for double-sided recording / single-sided reading, high-density SD for single-sided recording, and double-sided recording / single-sided reading SD can be discriminated. According to the present invention, a CD and a single-sided recording SD, a CD and a double-sided recording / single-sided reading SD, a CD and a single-sided recording high-density SD, C
D and high-density SD for double-sided recording and single-sided reading, single-sided recording SD and double-sided recording and single-sided reading SD, high-density SD for single-sided recording and high-density SD for double-sided recording and single-sided reading, single-sided recording SD and double-sided recording and single-sided reading It is possible to discriminate between a high-density SD, a high-density SD for single-sided recording, and a double-sided recording / single-sided reading SD.

According to the present invention, the wavelengths 585 to 69
CD and single-sided recording SD, C using 0 nm laser beam
D and double-sided recording and single-sided reading SD, CD and single-sided recording high-density SD, CD and double-sided recording and single-sided reading high-density SD, single-sided recording SD and double-sided recording and single-sided reading SD, and single-sided recording high-density S
D, high-density SD for double-sided recording / single-sided reading, single-sided recording SD, high-density SD for double-sided recording / single-sided reading, high-density SD for single-sided recording, and double-sided recording / single-sided reading SD can be discriminated.

Further, according to the present invention, wavelengths of 600 to 70
CD and single-sided recording SD, C using 0 nm laser beam
D and double-sided recording and single-sided reading SD, CD and single-sided recording high-density SD, CD and double-sided recording and single-sided reading high-density SD, single-sided recording SD and double-sided recording and single-sided reading SD, and single-sided recording high-density S
D, high-density SD for double-sided recording / single-sided reading, single-sided recording SD, high-density SD for double-sided recording / single-sided reading, high-density SD for single-sided recording, and double-sided recording / single-sided reading SD can be discriminated.

[Brief description of the drawings]

FIG. 1 shows rated values and reproduction conditions of various optical disks when a laser beam having a wavelength of 350 to 450 nm is used.

FIG. 2 shows rated values and reproduction conditions of various optical disks when a laser beam having a wavelength of 450 to 550 nm is used.

FIG. 3 shows rated values and reproduction conditions of various optical disks when a laser beam having a wavelength of 585 to 685 nm is used.

FIG. 4 shows rated values and reproduction conditions of various optical disks when a laser beam having a wavelength of 600 to 700 nm is used.

FIG. 5 is a comparison of the flowcharts in the present invention and the conventional optical disk reproduction.

FIG. 6 is a schematic diagram showing a compatible playable pickup used in the present invention.

FIG. 7 is a diagram showing an S-shaped curve of a focus error signal of various optical disks.

FIG. 8 is a block diagram of a playback device according to the present invention.

FIG. 9 is a diagram showing a shape of a laser beam in the present invention.

FIG. 10 shows S of a focus error signal of various optical disks.
It is a figure showing a character curve.

FIG. 11 shows S of a focus error signal of various optical disks.
It is a figure showing a character curve.

FIG. 12 shows other rated values and reproduction conditions of various optical disks when a laser beam having a wavelength of 350 to 450 nm is used.

FIG. 13 shows other rated values and reproduction conditions of various optical disks when a laser beam having a wavelength of 450 to 550 nm is used.

FIG. 14 shows other rated values and reproduction conditions of various optical disks when a laser beam having a wavelength of 585 to 685 nm is used.

FIG. 15 shows other rated values and reproduction conditions of various optical disks when a laser beam having a wavelength of 600 to 700 nm is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Objective lens 3 ... NA variable aperture 4 ... Polarization beam splitter 5 ... Objective lens group 6 ... Photodetector 7 ... Collimator lens 8 ... Diffraction Lattice 9: Semiconductor laser 10: Optical pickup

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shuichi Ichiura 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-5-54406 (JP, A) JP-A-6-333255 (JP, A) JP-A-9-102129 (JP, A) JP-A-9-270167 (JP, A) JP-A-62-76061 (JP, A) JP-A-59-38931 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 19/00-19/18 G11B ^7/ 00-7/22

Claims (11)

(57) [Claims] 1. An identification device for distinguishing between a first optical recording medium having a first substrate thickness and a second optical recording medium having a second substrate thickness larger than the first substrate thickness. Detecting a focus error signal from the first optical recording medium or the second optical recording medium by using an objective lens capable of focusing a laser beam on a recording surface of the first optical recording medium; Detecting means for detecting a focus error signal based on at least a peak value or the number of peaks of the focus error signal.
There identification device of an optical recording medium characterized in that it consists of a discriminating means for discriminating an optical recording medium. 2. An identification apparatus for distinguishing between a first optical recording medium having a first substrate thickness and a second optical recording medium having a second substrate thickness greater than the first substrate thickness. Detecting a focus error signal from the first optical recording medium or the second optical recording medium using an objective lens capable of focusing a laser beam on a recording surface of the second optical recording medium. Detecting means for detecting a focus error signal based on at least a peak value or the number of peaks of the focus error signal.
There identification device of an optical recording medium characterized in that it consists of a discriminating means for discriminating an optical recording medium. 3. An objective lens comprising two optical pickups having different numerical apertures of an objective lens, and an objective lens having a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a thin substrate. Detecting means for detecting a focus error signal from an optical recording medium using an optical pickup comprising: a focus error signal based on at least a peak value or the number of peaks at the time of focus pull-in ;
There identification device of an optical recording medium characterized in that it consists of a discriminating means for discriminating an optical recording medium. 4. An objective lens having a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a small substrate thickness, comprising an optical pickup having two objective lenses having different numerical apertures. Detecting means for detecting a focus error signal from the optical recording medium, and at the time of focusing , based on at least a peak value or the number of peaks of the focus error signal.
There identification device of an optical recording medium characterized in that it consists of a discriminating means for discriminating an optical recording medium. 5. An optical pickup having a numerical aperture changing means, wherein the numerical aperture is set to a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a small substrate thickness. Detecting means for detecting the focus error signal of the focus error signal based on at least the peak value or the number of peaks of the focus error signal at the time of focusing.
There identification device of an optical recording medium characterized in that it consists of a discriminating means for discriminating an optical recording medium. 6. An objective lens comprising two optical pickups having different numerical apertures of an objective lens, and an objective lens having a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a standard thickness substrate. Detecting means for detecting a focus error signal from an optical recording medium using the optical pickup comprising: a focus error signal based on at least a peak value or the number of peaks at the time of focus pull-in ;
There identification device of an optical recording medium characterized in that it consists of a discriminating means for discriminating an optical recording medium. 7. An object having a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a substrate having a standard thickness, comprising an optical pickup having two objective lenses having different numerical apertures. Detecting means for detecting a focus error signal from an optical recording medium using a lens ; and at least focusing on the peak value or the number of peaks of the focus error signal at the time of focusing.
There identification device of an optical recording medium characterized in that it consists of a discriminating means for discriminating an optical recording medium. 8. An optical recording apparatus comprising one optical pickup having a numerical aperture changing means, wherein the numerical aperture is set to a numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a standard thickness substrate. Detecting means for detecting a focus error signal from a medium; and, at the time of focus pull-in , based on at least a peak value or the number of peaks of the focus error signal.
There identification device of an optical recording medium characterized in that it consists of a discriminating means for discriminating an optical recording medium. 9. The optical recording medium identification apparatus according to claim 1, wherein the number of peaks of the focus error signal is one or two. 10. The apparatus according to claim 9, wherein the shape of the laser beam incident on the objective lens is circular or elliptical. 11. The apparatus according to claim 9, wherein the shape of the laser beam incident on the objective lens is a polygon.