JPH09204703A - Discrimination device of optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the device in which rapid and simple discrimination is made for the optical disks different in substrate thickness, track pitch, shortest pit lengthe and reflectivity. SOLUTION: The optical pickup has an objective lens having the effective numerical aperture of 0.55 to 0.65 and can alternately reproduce a CD and an SD. During a focus servo process, various kinds of optical disks are discriminated by discriminating the presence or the absence of the variations in the waveforms of two focus error signals detected when the effective numerical aperture is set 0.55 to 0.65 and 0.20 to 0.45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of discriminating 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. In addition, recently, high density recording for recording a moving image for a long time is progressing.

[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 optical disc set in the playback device. As this type of technology, Japanese Patent Laid-Open No. 6-2
There is a method disclosed in Japanese Patent No. 59804. That is,
This method is a method of irradiating the optical disc with light using an optical pickup and detecting the difference in the detection position of the reflected light from the optical disc to identify the optical disc.

[0005]

Problems to be Solved by the Invention JP-A-6-25980
In the technique disclosed in Japanese Patent Publication No. 4, 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 mounted. Since the identification is performed, an operation called "identification of optical disc" is required before starting the reproduction operation of the optical disc. Therefore, there is a problem that quick identification cannot be performed. Also, since the position of the reflected light is detected, if the optical disk has a warp, it will be affected by it,
There was a problem that it could not be accurately identified.

The present invention solves the above problems and provides a method for quickly and accurately identifying the mounted optical disk.

[0007]

The present invention provides a first optical pickup having an objective lens having a first numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a thin substrate. A second optical pickup including an objective lens having a second numerical aperture different from the first numerical aperture, a first focus error signal detected by the first optical pickup, and a second optical pickup detected by the second optical pickup. It is characterized by comprising a discriminating means for discriminating the focus error signal when the focus is pulled.

Further, according to the present invention, a first objective lens having a first numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a thin substrate and a second numerical aperture different from the first numerical aperture are provided. A second objective lens which is provided, and one optical pickup capable of selectively switching between the first objective lens and the second objective lens; a first focus error signal detected through the first objective lens; The second focus error signal detected via the two objective lenses and the determination means for determining when the focus is pulled in.

Further, according to the present invention, an objective lens having a first numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a thin substrate, and an effective numerical aperture of the objective lens are first
An optical pickup including a numerical aperture changing unit that can be set to a second numerical aperture different from the numerical aperture, a first focus error signal detected when the numerical aperture of the objective lens is set to the first numerical aperture, and an objective. The effective numerical aperture of the lens is configured to determine the second focus error signal when the focus is pulled in.

Further, the present invention is characterized in that the first focus error signal and the second focus error signal are S-shaped waveforms. Further, the present invention is characterized in that the first focus error signal and the second focus error signal determined by the determination means have the same S-shaped waveform or different S-shaped waveforms.

The present invention is also characterized in that the S-shaped waveform comprises one S-shaped curve or two S-shaped curves. Also, the present invention provides a first focus error signal and a second focus error signal.
If the focus error signals have different S-shaped waveforms,
The first focus error signal is an S-shaped curve smaller than the second focus error signal.

Further, according to the present invention, when the first focus error signal and the second focus error signal have different S-shaped waveforms, the second focus error signal is an S-shaped curve smaller than the first focus error signal. Characterize. Further, the present invention is characterized in that the first numerical aperture is 0.55 to 0.65 and the second numerical aperture is 0.20 to 0.50.

Further, according to the present invention, the first numerical aperture is 0.55 to 0.55.
It is characterized by being 0.65 and having a second numerical aperture of 0.30 to 0.45. The present invention also has a substrate thickness of 0.55.
~ 0.65mm optical recording medium and substrate thickness 1.1 ~
It is characterized in that it can distinguish from an optical recording medium of 1.3 mm. Further, the present invention has a substrate thickness of 0.55 to 0.65 m.
optical recording medium having a minimum pit length of 0.38 to 0.42 μm or a substrate thickness of 0.55 to 0.65 mm and a minimum pit length of 0.20 to 0.30 μm. The recording medium and the optical recording medium having a substrate thickness of 1.1 to 1.3 mm and a shortest pit length of 0.80 to 0.90 μm can be distinguished from each other.

Further, according to the present invention, the substrate thickness is 0.55 to 0.6.
5 mm and the shortest pit length is 0.38 to 0.42 μm
An optical recording medium having a reflectance of 70% or more or a substrate having a thickness of 0.55 to 0.65 mm, a minimum pit length of 0.38 to 0.42 μm, and a reflectance of 20 to 40%.
Discriminating between the optical recording medium having a substrate thickness of 1.1 to 1.3 mm, the shortest pit length of 0.80 to 0.90 μm, and a reflectance of 70% or more. Is characterized by.

In the present invention, the substrate thickness is 0.55-0.6.
5 mm and the shortest pit length is 0.20 to 0.30 μm
The optical recording medium or the substrate having a reflectance of 70% or more has a thickness of 0.55 to 0.65 mm, the shortest pit length is 0.20 to 0.30 μm, and the reflectance is 20 to 40%.
Discriminating between the optical recording medium having a substrate thickness of 1.1 to 1.3 mm, the shortest pit length of 0.80 to 0.90 μm, and a reflectance of 70% or more. Is characterized by.

Further, according to the present invention, the substrate thickness is 0.55 to 0.6.
5 mm and the shortest pit length is 0.38 to 0.42 μm
And an optical recording medium having a reflectance of 70% or more, a substrate thickness of 0.55 to 0.65 mm, a shortest pit length of 0.20 to 0.30 μm, and a reflectance of 20 to 40. % Optical recording medium can be identified. The present invention also provides an optical recording medium having a substrate thickness of 0.55 to 0.65 mm, a shortest pit length of 0.38 to 0.42 μm, a reflectance of 20 to 40%, and a substrate thickness. Is 0.5
5 ~ 0.65mm, the shortest pit length is 0.20 ~
It is characterized in that it is 0.30 μm and can be distinguished from an optical recording medium having a reflectance of 70% or more.

Further, the present invention is characterized in that the shape of the laser beam is circular or elliptical. Further, the present invention is characterized in that the laser beam has a polygonal shape. Further, in the present invention, the wavelength of the laser beam is 350 to 7
It is characterized in that it is in the range of 00 nm.

Further, according to the present invention, the wavelength of the laser beam is 3
It is characterized in that it is in the range of 50 to 450 nm. Further, in the present invention, the wavelength of the laser beam is 415 to 445n.
It is characterized in that it is in the range of m. Further, the present invention is characterized in that the wavelength of the laser beam is in the range of 450 to 550 nm.

Further, according to the present invention, the wavelength of the laser beam is 5
It is characterized by being in the range of 17 to 547 nm. Further, according to the present invention, the wavelength of the laser beam is 585 to 690n.
It is characterized in that it is in the range of m. Further, the invention is characterized in that the wavelength of the laser beam is in a range of 620 to 650 nm.

Further, according to the present invention, the wavelength of the laser beam is 6
It is characterized in that it is in the range of 00 to 700 nm. Further, according to the present invention, the wavelength of the laser beam is 635 to 665n.
It is characterized in that it is in the range of m.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. The present invention relates to identification of a plurality of optical discs having different substrate thicknesses, track pitches, and reflectivities from recording surfaces. FIG. 1 has a substrate having a standard thickness of 1.2 mm (tolerance ± 0.1, the same applies hereinafter) when a laser beam having a wavelength of 350 to 450 nm (typical wavelength: 415 to 445 nm, the same applies below) is used. A high density optical disc having a standard density optical disc, that is, a CD, a CD-ROM (hereinafter, referred to as a first optical disc), and a thin substrate having a substrate thickness of 0.6 (tolerance ± 0.05, the same applies hereinafter). That is, SD (hereinafter referred to as the second optical disk) and substrate thickness 0.6
(Tolerance: ± 0.05, same hereafter) Ultra-high-density optical disk having a thin substrate of mm,
3) shows the shortest pit length, track pitch, beam spot diameter, reflectivity, and numerical aperture (NA) of the objective lens. Further, in FIG. 2, the wavelength is 450 to 550 nm.
The table shows the shortest pit length, track pitch, beam spot diameter, reflectivity, and numerical aperture of the objective lens of the first, second, and third optical disks when a laser beam (typical wavelength: 517 to 547 nm, the same applies hereinafter) is used. . 3 and 4
585-690 nm (typical wavelength: 620
650 nm, the same applies hereinafter), wavelength 600-700 nm
The table shows the shortest pit length, track pitch, beam spot diameter, reflectivity, and numerical aperture of the objective lens of the first, second, and third optical disks when a laser beam (typical wavelength: 635 to 665 nm, the same applies hereinafter) 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. In addition, the first and second
And the pit depth (physical depth) of the third optical disc
110 (90-130) nm and 105 (95, respectively)
To 115) nm and 72 (62 to 82) nm.

The substrate has a diameter of 40 to 12
It is an optical disk of 0 mm. The present invention is directed to these optical disks. FIG. 5 shows a flowchart from the reproduction operation start to the reproduction operation of the optical disk according to the present invention and the conventional example. The operation of reproducing an optical disc by using the optical pickup is performed as follows. Conventionally, when an optical disc is loaded, a reproduction operation starts, and first, focus search is performed and focus servo is performed. If the focus servo is not OK, the reproducing operation ends. When the focus servo is OK, the motor is started, tracking control is performed, and normal reproduction operation is started. On the other hand, according to the present invention, the mounted optical disc is identified based on whether or not the focus error signal waveform changes when the objective lens of the optical pickup makes two reciprocations up and down during focus search, and reproduction or recording according to the discriminated optical disc is performed. It is something to do. Therefore, in the flowchart of the present invention, as shown in FIG. 5, an optical disc identification function is added before the focus becomes OK as compared with the conventional one. Even if this identification function is added, the time until the reproduction operation of the optical disk does not become longer than before. That is, in the conventional reproducing operation of the optical disc, the type of the optical disc mounted from the mounting of the optical disc to the execution of the focus servo is identified. After the optical disc identification, the numerical aperture of the objective lens is set according to the identified optical disc, and focus servo is performed. The subsequent operation is similar to that of the conventional example. Further, in FIG. 5, the motor starts after the focus becomes OK, but the present invention is not limited to this, and the focus search may be performed after the motor is used as a star.

Discrimination of the optical disc in the present invention will be described. The optical disc is identified by using an optical pickup capable of changing the effective numerical aperture of the objective lens during focus search. FIG. 6 shows an optical pickup 10 used in the present invention. The laser beam emitted from the semiconductor laser 9 has a diffraction grating 8, a collimating lens 7,
After passing through the polarization beam splitter 4, the quarter-wave plate 20 and the aperture 3, it is condensed by the objective lens 2 and
Is irradiated. The laser beam reflected by the optical disk 1 returns through the objective lens 2, the aperture 3, and 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. It is detected by the photodetector 6 through the optical lens group 5.

The optical pickup 10 has an aperture 3 inserted between the objective lens 2 and the polarization beam splitter 4 in order to enable reproduction compatible with CD and SD.
Can change the effective numerical aperture. That is,
In CD and SD, the distance from the substrate surface to the signal recording surface is different from 1.2 mm and 0.6 mm, respectively, and it is not possible to focus on the signal recording surfaces at different distances with one objective lens. By changing the effective numerical aperture according to the distance, it is possible to focus on the signal recording surface at two kinds of distances. The effective numerical aperture is
It can be changed by electrical, mechanical or magnetic methods.

As a method for electrically changing the effective numerical aperture, a polarization plane switching means for rotating the polarization plane of the laser beam, and a polarization for selectively shielding the outside of the laser beam passing through the polarization plane switching means. The selection means is the aperture 3
And a liquid crystal is used for the polarization plane switching means and the polarization selecting means. In this method, the polarization plane switching means rotates the polarization plane of the laser beam in a certain direction, and the outer side portion of the laser beam having the polarization plane after rotation is shielded by the liquid crystal applied to the polarization selection means. A guest-host type liquid crystal is a specific example of the liquid crystal used for the polarization selecting means, and a TN type liquid crystal, an STN is a specific example of the polarization plane switching means.
Type liquid crystal and ferroelectric type liquid crystal. A Pockels cell can be used as the polarization plane switching means other than the liquid crystal.

As an example of using a mechanical method, there is an example in which a 1/2 wavelength plate is used for the polarization plane switching means, and a polarization filter, a polarization selective hologram, and a polarization glass are used for 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. A half mirror may be used instead of the polarization beam splitter 4 and the quarter wavelength plate 20. Further, the aperture 3 is not limited to be provided between the quarter wavelength plate 20 (half mirror) and the objective lens 2, but may be provided between the semiconductor laser 9 and the objective lens 2.

By the above method, the effective numerical aperture of the objective lens 2 can be changed. In the present invention,
At the time of focus search, the objective lens 2 of the optical pickup 10 is reciprocated twice (meaning two vertical movements),
Two focus error signals detected during these two round trips are detected and identified. That is, in the present invention, an objective lens capable of focusing is arranged on the signal recording surface of an optical disc having a numerical aperture of 0.6 (tolerance of ± 0.05, the same applies hereinafter) having a substrate thickness of 0.6 mm. The optical pickup 10 capable of changing the effective numerical aperture of the lens by the above method.
At the time of the first round trip, the numerical aperture of the objective lens is set to 0.6 and the first focus error signal is detected. Next, the effective numerical aperture of the objective lens is 0.35.
(Permissible error ± 0.05, the same applies hereinafter), the second round trip is performed, and the second focus error signal is detected. Then, the optical disc is identified by the presence or absence of a change in the waveform of the detected first and second focus error signals. First Embodiment (Identification of CD from Single-sided Recording SD or Double-sided Recording / Single-sided Reading SD) First optical disc and second optical disc, specifically, identification of CD from single-sided recording SD or double-sided recording / single-sided reading SD To do.

FIG. 7 shows focus error signals during two reciprocations of a single-sided recording SD, a double-sided recording / single-sided reading SD, and a CD. When the focus search is started after mounting the optical disc, the objective lens 2 of the optical pickup 10 is
First, the effective numerical aperture is set to 0.6 for the first round trip, and then the effective numerical aperture is set to 0.35 for the second round trip. Therefore, in the case of single-sided recording SD, the first focus error signal 100 obtained at the first round trip and the second focus error signal 1 obtained at the second round trip.
Reference numeral 10 is an S-shaped curve as shown in FIG. 7A, and the waveform of the second focus error signal 110 is a waveform obtained by halving the waveform of the first focus error signal 100 in the signal strength direction. In a single-sided recording SD having a substrate thickness of 0.6 mm, the effective numerical aperture of the objective lens 2 is 0.35.
Then, since the outer side of the laser beam is shielded, the amount of reflected light from the optical disc 1 is reduced, and the signal intensity of the second focus error signal 110 is about half that of the first focus error signal 100. In the case of the double-sided recording / single-sided reading SD, the first focus error signal 200 is about half of the first focus error signal 100 of the single-sided recording SD in terms of strength as shown in FIG. Has two S-shaped curves. In double-sided recording / single-sided reading SD, this is the first on the laser beam incident side.
This is because the reflectance of the recording surface is about 30%, which is lower than the reflectance of 70% or more on the recording surface of the single-sided recording SD, and two signal recording surfaces are present. The second focus error signal 210 of the double-sided recording / single-sided reading SD is the first focus error signal 2
The strength is about half that of 00. This is the above single-sided recording SD
For the same reason as above. In the case of a CD, as shown in FIG. 7C, the first focus error signal 300 has a waveform in which the first focus error signal 100 of the single-sided recording SD is approximately halved in intensity, and the first focus error signal and the second focus error signal
The focus error signal consists of one S-curve. The signal strength is the first focus error signal 10 of the single-sided recording SD.
The thickness of the CD is about half that of 0.2 because the CD substrate thickness is 1.2 mm, which is about twice the SD substrate thickness of 0.6 mm. Therefore, when the effective numerical aperture of the objective lens 2 is 0.6. Since the laser beam is focused before the signal recording surface of the CD, the CD
This is because the light intensity is weak on the signal recording surface. Also, the second focus error signal 310 of the CD becomes the same as the first focus error signal 300.

Therefore, if there is no change in the waveforms of the S-shaped first focus error signal and second focus error signal detected by the photodetector 6 during focus search, it can be discriminated as a CD, and the first focus error signal When the waveform of the second focus error signal is different, it can be discriminated as single-sided recording SD or double-sided recording / single-sided reading SD. Therefore,
It is possible to distinguish between a CD and a single-sided recording SD or a CD and a double-sided recording / single-sided reading SD. In the first embodiment,
The effective numerical aperture was set to 0.6 when the objective lens 2 was reciprocated the first time, and 0.35 when the objective lens 2 was reciprocated the second time. In this case, the waveforms of the first and second focus error signals in the single-sided recording SD and the double-sided recording / single-sided reading SD are only opposite to those in the case described above. Further, FIG. 7 shows a signal of only one of the up and down movements of the lens in the focus search (close to or away from). Second embodiment (discrimination between CD and high-density SD for single-sided recording or high-density SD for double-sided recording / single-sided reading) First optical disk and third optical disk, specifically CD and high-density SD for single-sided recording or double-sided recording Discrimination from single-sided read and high-density SD will be described.

FIG. 8 shows single-sided recording high-density SD, double-sided recording.
The focus error signal at the time of two round trips of high-density SD and CD for single-sided reading is shown. Also in the second embodiment, the effective numerical aperture of the objective lens 2 is set to 0.6 at the first round trip and 0.35 at the second round trip. High-density SD for single-sided recording and high-density SD for double-sided recording / single-sided reading
Are single-sided recording SD, double-sided recording / single-sided reading SD, respectively.
Since the reflectance, the substrate thickness, and the number of signal recording surfaces are the same,
High-density SD for single-sided recording, high-density S for double-sided recording / single-sided reading
The first and second focus error signals obtained in D and CD are the first and second focus error signals (single-sided recording SD, double-sided recording / single-sided reading SD, CD obtained in the first embodiment, respectively. 100, 1
10, 200, 210, 300, 310).

Therefore, in the second embodiment, it is possible to distinguish between a CD and a high-density SD for single-sided recording, and a CD and a high-density SD for double-sided recording / single-sided reading. In the second embodiment, as in the first embodiment, the effective numerical aperture of the objective lens 2 during the first and second reciprocations may be reversed. Third embodiment (identification of single-sided recording SD and high-density SD for double-sided recording / single-sided reading or high-density SD for single-sided recording and double-sided recording / single-sided reading SD) Second optical disk and third optical disk, specifically, single-sided Discrimination between recording SD and high-density SD for double-sided recording / single-sided reading or high-density SD for single-sided recording and double-sided recording / single-sided reading SD will be described.

FIG. 9 shows focus error signals during two reciprocations of a single-sided recording SD and a high-density SD for double-sided recording / single-sided reading. The first focus error signal 100, the second focus error signal 110, and the first focus error signal 20 in the single-sided recording SD and the high-density SD for double-sided recording / single-sided reading are respectively the first focus error signal 100, the second focus error signal 110, and the first focus error signal 20.
0, the second focus error signal 210. Therefore,
Single-sided recording SD when both the first and second focus error signals are composed of one S-shaped curve, and double-sided recording when both the first and second focus error signals are composed of two S-shaped curves. -High density SD for single-sided reading. Further, in this case, since the waveform of the focus error signal obtained by reciprocating the objective lens once is different, it is not necessary to reciprocate the objective lens twice, and it may be once.

FIG. 10 shows focus error signals during two reciprocations of high-density SD for single-sided recording and double-sided recording / single-sided reading SD. The first and second focus error signals in high-density SD for single-sided recording and double-sided recording / single-sided reading SD are the first focus error signal 100, the second focus error signal 110, and the first focus error signal 20, respectively.
0, the second focus error signal 210. Therefore,
When both the first and second focus error signals consist of one S-shaped curve, it means high-density SD for single-sided recording, and both the first and second focus error signals have two S-shaped curves.
Double-sided recording / single-sided reading SD if it consists of a curved line
It is. Also in this case, since the waveform of the focus error signal obtained by reciprocating the objective lens once is different, it is not necessary to reciprocate the objective lens twice, and the objective lens may be reciprocated once.

In the third embodiment as well, when the objective lens is reciprocated twice, the same as in the first embodiment,
The effective numerical aperture of the objective lens 2 during the second and second round trips may be reversed. Fourth Embodiment In the first, second and third embodiments, the case where the optical disc is identified by using one optical pickup having one objective lens has been described. In the fourth embodiment, identification of an optical disk when one optical pickup including two objective lenses having different effective numerical apertures is used will be described.

FIG. 12 shows an optical pickup 30 used in the fourth embodiment. The semiconductor laser, the diffraction grating, the collimator lens, the polarization beam splitter, the quarter-wave plate, the condenser lens group, and the photodetector are the same as those in the optical pickup 10, and thus the same reference numerals are used. The optical pickup 30
An objective lens 2a having an effective numerical aperture of 0.6 and an objective lens 2b having an effective numerical aperture of 0.35 are arranged on a signal recording surface of an optical recording medium having a substrate thickness of 0.6 mm. Consists of Therefore, the objective lens 2a having an effective numerical aperture of 0.6 is set and the first focus error signal is detected during the first round trip in the focus search after the optical disc is mounted. Next, before shifting to the second round trip, the objective lens 2b having a numerical aperture of 0.35 is switched to, and the second focus error signal is detected.
Further, the objective lens used for the first time and the second time may be the reverse of the above.

The first and second focus error signals obtained in the CD, the single-sided recording SD, the double-sided recording / single-sided reading SD, the single-sided recording high-density SD, and the double-sided recording / single-sided reading high-density SD are the above-mentioned first and second focus error signals. Since it is the same as the focus error signal described in the second and third embodiments, the identification of each optical disk is performed in the same manner as in the first, second and third embodiments. Fifth Example In the fifth example, identification of an optical disk when two optical pickups are used will be described.

FIG. 13 shows two optical pickups used in the fifth embodiment. The substrate thickness of the optical pickup 40 is 0.
The optical pickup 50 comprises an objective lens 2a having an effective numerical aperture of 0.6 capable of focusing a laser beam on a signal recording surface of a 6 mm optical recording medium. The optical pickup 50 has an effective numerical aperture of 0.35.
The objective lens 2b is arranged. Since the two optical pickups 40 and 50 have the same structure, corresponding parts are given the same numbers, and the optical pickups 40 and 50 are provided for identification.
Is attached to the optical pickup 50 and “b” is attached to the optical pickup 50 as a subscript.

In the fifth embodiment, when an optical disk is mounted, focus search operation starts, and the objective lenses 2a and 2b of the two optical pickups 40 and 50 simultaneously start the first round trip and the respective optical beams are started. The pickup detects the focus error signal. Therefore, in the fifth embodiment, the focus error signal obtained from the optical pickup 40 is the first focus error signal, and the optical pickup 50
The focus error signal obtained from the above is used as the second focus error signal. Therefore, in the fifth embodiment, each objective lens 2a, 2b needs only one round trip.

FIG. 14 shows the first and second focus error signals of single-sided recording SD, double-sided recording / single-sided reading SD and CD. The first and second focus error signals obtained from these optical disks are respectively the first and second focus error signals 100 and 11 in the first embodiment.
Since it is the same as 0, 200, 210, 300, 310, the CD and the single-sided recording SD depending on whether the waveforms of the first focus error signal and the second focus error signal on each optical disk are changed, as in the first embodiment. Alternatively, the CD and the double-sided recording / single-sided reading SD can be identified.

FIG. 15 shows the first and second focus error signals of high-density SD for single-sided recording, high-density SD for double-sided recording / single-sided reading, and CD. The first and second focus error signals obtained from these optical discs are also the same as the first and second focus error signals 100, 110, 200, 210, 300 and 310 in the second embodiment, respectively. Similar to the second embodiment, CD and single-sided recording high-density SD or CD and double-sided recording / single-sided reading high-density SD depending on whether the waveforms of the first focus error signal and the second focus error signal on each optical disc are changed.
Can be identified.

FIG. 16 shows the first and second focus error signals for high-density SD for single-sided recording and double-sided recording / single-sided reading SD. The first and second focus error signals obtained from these optical disks are the first and second focus error signals 100, 110, 200 in the third embodiment.
Since it is the same as 210, the high density SD for single-sided recording and the double-sided recording / single-sided reading SD can be discriminated by the presence / absence of changes in the waveforms of the first and second focus error signals in each optical disk, as in the third embodiment. can do.

FIG. 17 shows the first and second focus error signals of single-sided recording SD and double-sided recording / single-sided reading high-density SD. The first and second focus error signals obtained from these optical disks are the first and second focus error signals 100, 110, 200 in the third embodiment.
Since it is the same as 210, the single-sided recording SD and the double-sided recording / single-sided reading high-density SD can be discriminated by the presence or absence of the change of the waveforms of the first and second focus error signals in each optical disk, as in the third embodiment. can do.

In the fifth embodiment, the optical pickups 40 and 50 do not have to reciprocate at the same time.
After the reciprocation of one optical pickup is completed, the reciprocation of the other optical pickup may be started.
In the first, second, third, fourth and fifth embodiments, the optical disc can be discriminated by using the laser beam having a wavelength of 350 to 700 nm, preferably 350 to 700 nm.
450 nm or 450 to 550 nm or 585
To 690 nm or 600 to 700 nm, and more preferably 415 to 445 n.
m or 517 to 547 nm or 620 to 650 nm
nm or a laser beam having a wavelength of 635 to 665 nm.

Further, 0.35 is shown as an effective numerical aperture different from 0.6 in which the laser beam can be focused on the signal recording surface of the optical recording medium having the substrate thickness of 0.6 mm. However, it may be 0.2 to 0.45. Further, the shape of the beam is not limited to a circular shape, but may be an elliptical shape, or may be a polygonal shape as shown in FIG. Sixth Embodiment FIG. 11 shows a block diagram of an apparatus for performing identification to reproduction of an optical disc. The first, second, third, fourth and fifth
The first and second focus error signals obtained from the optical pickup 10 by the method disclosed in the embodiment are sent to the preamplifier 12, are IV converted by the preamplifier 12, and then are sent to the determination unit 13. The discriminating unit 13 detects the waveforms of the first and second focus error signals sent thereto, and discriminates the optical disc based on whether or not the detected waveforms change. For example, the detected first and second focus error signals are the first focus error signal 100 and the second focus error signal 100, respectively.
If the focus error signal 110 is a single-sided recording SD or a single-sided recording high-density SD, the first focus error signal 200 and the second focus error signal 210.
If it is a double-sided recording / single-sided reading SD or a double-sided recording / single-sided reading high-density SD, and if the first focus error signal 300 and the second focus error signal 310 are identified as a CD. The signal discriminated by the discriminating unit 13 is sent to the commanding unit 15, and the commanding unit 15 issues a command for switching to the effective numerical aperture necessary for reproducing the identified optical disc and a circuit switching command to the NA switching unit 16, respectively. It is sent to the circuit switching means 17. The NA switching means 16 switches in accordance with a command from the command unit 15 so as to be suitable for reproduction of an optical disc in which the effective aperture of the objective lens 2 in the optical pickup 10 is identified. That is, for a laser beam having a wavelength of 350 to 450 nm, the effective numerical aperture is 0.30 to 0.5.
5 is set to reproduce single-sided recording SD or double-sided recording / single-sided reading SD, and the effective numerical aperture is set to 0.20 to 0.30 to reproduce a CD. For a laser beam with a wavelength of 450 to 550 nm, the effective numerical aperture is 0.40 to 0.55.
Set to and single-sided recording SD or double-sided recording / single-sided reading S
Play D, set the effective numerical aperture to 0.25 to 0.40 and play the CD. For a laser beam with a wavelength of 585 to 690 nm, the effective numerical aperture is set to 0.55 to 0.65 and single-sided recording SD or double-sided recording / single-sided reading SD is performed.
Is played, and the CD is played with the effective numerical aperture set to 0.30 to 0.55. For a laser beam having a wavelength of 600 to 700 nm, the effective numerical aperture is set to 0.55 to 0.65 to reproduce single-sided recording SD or double-sided recording / single-sided reading SD, and the effective numerical aperture is set to 0.5. Set to 30-0.55 and C
Play D. Further, the circuit switching means 17 instructs the RF demodulation circuit 18 to switch the circuit so that demodulation according to the optical disc to be reproduced can be performed. After setting the effective numerical aperture according to the identified optical disc,
If the focus servo is OK, start the motor,
The rotation of the optical disc is started and tracking control is performed. After that, reproduction of each optical disk is performed. Here, the preamplifier 12 may be built in the pickup 10.

Next, single-sided recording SD or high-density SD for single-sided recording and double-sided recording / single-sided reading SD or double-sided recording
A case will be described in which the high-density SD for single-sided reading is determined and reproduction is performed according to each optical disc. In this case, since the peak values of the S-shaped curve detected by the photodetector 6 of the optical pickup 10 have the same magnitude, both optical disks are identified by the number of detected peaks. If the peak is once, single-sided recording SD or single-sided recording high density S
If it is D and the peak is twice, double-sided recording / single-sided reading S
D or high-density SD for double-sided recording / single-sided reading. In this case, the NA for each optical disc is set as follows, and each optical disc is reproduced. That is, 350 to 450n
NA is 0.30 ~ for the laser beam of wavelength m.
Set to 0.55 to play back single-sided recording SD or double-sided recording / single-sided reading SD and set NA to 0.55 to 0.65 to single-sided recording high-density SD or double-sided recording / single-sided reading high-density SD. To play. For a laser beam with a wavelength of 450 to 550 nm, NA is set to 0.40 to 0.55 and single side recording SD or double side recording / single side reading SD is reproduced, and NA is set to 0.55 to 0.65. A high density SD for single-sided recording or a high density SD for double-sided recording / single-sided reading is set and reproduced. For a laser beam with a wavelength of 585 to 690 nm, the NA is set to 0.55 to 0.65 and the single-sided recording S
D or double-sided recording / single-sided reading SD or single-sided recording high-density SD or double-sided recording / single-sided reading high-density SD is reproduced. Even for a laser beam having a wavelength of 600 to 700 nm, the NA is set to 0.55 to 0.65 and high density SD of single side recording SD or double side recording / single side reading SD or single side recording or double side recording / single side reading is performed. High density SD
To play. The operation after setting the NA is the same as above. However, in reproduction of double-sided recording / single-sided reading SD and double-sided recording / single-sided reading high-density SD, since the reflectance of the recording surface on the laser beam incident side is as low as about 30%, it is necessary to amplify the detected signal. . Other than that, the operation is the same as the above.

Further, in the above-mentioned embodiment, it is necessary to switch three kinds of NA, but it is not necessarily limited to this, and NA is set to 0.30 for a laser beam having a wavelength of 350 to 450 nm. Set and play 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 high-density SD for single-sided recording and high-density SD for double-sided recording / single-sided reading. Also, set NA to 0.
Set to 25 to play CD, set NA to 0.55 to play 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. Good. That is, if the first optical disk is reproduced with a single NA, the second and third disks are reproduced with a common NA, or if the first and second optical disks are reproduced with a common NA,
The third optical disk is played back by a single NA. This is also applicable to laser beams of other wavelengths.

In the sixth embodiment, the description has been made from the identification of each optical disk to the reproduction thereof. However, with respect to the recording on the optical disk which is the object of the present invention, each optical disk can be identified and recorded by the above method. That is,
The wavelength of the laser beam is 600 to 700 nm or 58
5 to 690 nm or 450 to 550 nm or 3
If a semiconductor laser of 50 to 450 nm and a power of 30 mW is used, the effective numerical aperture of the objective lens in the pickup is suitable for each optical disc and each wavelength by using the optical pickup described in the first to sixth embodiments. Recording on the first, second, and third optical disks is possible by setting the effective numerical aperture. The second and third optical disks include a single-sided recording optical disk and a double-sided recording / single-sided reading optical disk, respectively. When the wavelength of the laser beam is 635 (permissible error ± 50) nm, the reflectance of the optical disc to be recorded is 20% to 55%.

[0048]

According to the present invention, a CD and a single-sided recording S are recorded by using an optical pickup used for recording or reproducing 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 SD 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 recording Recording / single-sided read SD can be discriminated accurately and quickly in the process of performing 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 used by using two pickups having objective lenses having different numerical apertures. And 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 double-sided recording / single-sided reading,
It is possible to discriminate between single-sided recording SD and high-density SD for double-sided recording / single-sided reading, and high-density SD for single-sided recording 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 / single-sided reading SD and C
D and high-density SD for single-sided recording, CD and high-density SD for double-sided recording / single-sided reading, single-sided recording SD and double-sided recording / single-sided reading S
D, high-density SD for single-sided recording and high-density SD for double-sided recording / single-sided reading, single-sided recording SD and high-density S for 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 is obtained 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 / single-sided reading SD and C
D and high-density SD for single-sided recording, CD and high-density SD for double-sided recording / single-sided reading, single-sided recording SD and double-sided recording / single-sided reading S
D, high-density SD for single-sided recording and high-density SD for double-sided recording / single-sided reading, single-sided recording SD and high-density S for 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, wavelengths of 350 to 45
CD and single-sided recording SD, C using 0 nm laser beam
D and double side recording / single side reading SD, CD and single side recording high density SD, CD and double side recording / single side reading high density SD, single side recording SD and double side recording / single side reading SD, single side recording high density S
It is possible to discriminate between D 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 recording / single-sided reading SD.

Further, according to the present invention, wavelengths of 450 to 55
CD and single-sided recording SD, C using 0 nm laser beam
D and double side recording / single side reading SD, CD and single side recording high density SD, CD and double side recording / single side reading high density SD, single side recording SD and double side recording / single side reading SD, single side recording high density S
It is possible to discriminate between D 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 recording / single-sided reading SD.

Further, according to the present invention, wavelengths of 585 to 69
CD and single-sided recording SD, C using 0 nm laser beam
D and double side recording / single side reading SD, CD and single side recording high density SD, CD and double side recording / single side reading high density SD, single side recording SD and double side recording / single side reading SD, single side recording high density S
It is possible to discriminate between D 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 recording / single-sided reading SD.

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 side recording / single side reading SD, CD and single side recording high density SD, CD and double side recording / single side reading high density SD, single side recording SD and double side recording / single side reading SD, single side recording high density S
It is possible to discriminate between D 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 recording / single-sided reading SD.

[Brief description of 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 discs when a laser beam having a wavelength of 5850 to 690 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 flowcharts for reproducing the present invention and a conventional optical disc.

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

FIG. 7 is a diagram showing S-curve waveforms of focus error signals of various optical disks.

FIG. 8 is a diagram showing S-curve waveforms of focus error signals of various optical disks.

FIG. 9 is a diagram showing S-curve waveforms of focus error signals of various optical disks.

FIG. 10: S of focus error signals of various optical disks
It is a figure which shows a character curve waveform.

FIG. 11 is a block diagram of a playback device according to the present invention.

FIG. 12 is a schematic diagram showing a pickup having two objective lenses capable of compatible reproduction used in the present invention.

FIG. 13 is a schematic diagram showing two pickups compatible with each other used in the present invention.

FIG. 14 S of focus error signals of various optical disks
It is a figure which shows a character curve waveform.

FIG. 15 S of focus error signals of various optical disks
It is a figure which shows a character curve waveform.

FIG. 16: S of focus error signals of various optical disks
It is a figure which shows a character curve waveform.

FIG. 17 S of focus error signal of various optical disks
It is a figure which shows a character curve waveform.

FIG. 18 is a diagram showing a shape of a laser beam.

[Explanation of symbols]

 1 ... Optical disc 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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Ichiura 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Masami Shimizu 2-5 Keihanhondori, Moriguchi City, Osaka Prefecture No. 5 Sanyo Electric Co., Ltd.

Claims (27)

[Claims] 1. A first optical pickup having an objective lens having a first numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a thin substrate, and a first optical pickup different from the first numerical aperture. A second optical pickup including an objective lens having a second numerical aperture, a first focus error signal detected by the first optical pickup, and a second focus error signal detected by the second optical pickup. And a discriminating means for discriminating when the focus is pulled in. 2. A first objective lens having a first numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a thin substrate, and a second objective lens having a second numerical aperture different from the first numerical aperture. An objective lens is arranged, and the first objective lens and the second objective lens are arranged.
One optical pickup capable of selectively switching between an objective lens, a first focus error signal detected via the first objective lens, and a second focus error signal detected via the second objective lens. And a discriminating means for discriminating between and when the focus is pulled in. 3. An objective lens having a first numerical aperture capable of focusing a laser beam on a recording surface of an optical recording medium having a thin substrate, and an effective numerical aperture of the objective lens different from the first numerical aperture. An optical pickup including a numerical aperture changing unit that can be set to a second numerical aperture, a first focus error signal detected when the numerical aperture of the objective lens is set to the first numerical aperture, and the objective lens A discriminating device for discriminating an effective numerical aperture, the discriminating device discriminating an effective numerical aperture from the second focus error signal when pulling in a focus. 4. The optical recording medium identification device according to claim 1, wherein the first focus error signal and the second focus error signal are S-shaped waveforms. 5. The optical system according to claim 4, wherein the first focus error signal and the second focus error signal determined by the determination means have the same S-shaped waveform or different S-shaped waveforms. Recording medium identification device. 6. The apparatus for identifying an optical recording medium according to claim 5, wherein the S-shaped waveform comprises one S-shaped curve or two S-shaped curves. 7. The fifth focus error signal according to claim 5, wherein the first focus error signal is different from the second focus error signal when the first focus error signal and the second focus error signal have different S-shaped waveforms. An apparatus for identifying an optical recording medium, which has a small S-shaped curve. 8. The second focus error signal according to claim 5, wherein when the first focus error signal and the second focus error signal have different S-shaped waveforms, the second focus error signal is more than the first focus error signal. An apparatus for identifying an optical recording medium, which has a small S-shaped curve. 9. The method according to claim 5, wherein the first numerical aperture is 0.55 to 0.65 and the second numerical aperture is 0.20 to 0.50. Optical recording medium identification device. 10. The method according to claim 5, wherein the first numerical aperture is 0.55 to 0.65 and the second numerical aperture is 0.30 to 0.45. Optical recording medium identification device. 11. The optical recording medium according to claim 9, wherein the optical recording medium having a substrate thickness of 0.55 to 0.65 mm and the optical recording medium having a substrate thickness of 1.1 to 1.3 mm can be distinguished. A characteristic optical recording medium identification device. 12. The optical recording medium according to claim 9, wherein the substrate thickness is 0.55 to 0.65 mm and the shortest pit length is 0.38 to 0.42 μm, or the substrate thickness is 0.55 to 0.55. An optical recording medium of 0.65 mm and a shortest pit length of 0.20 to 0.30 μm, and a substrate thickness of 1.1 to 1.3 mm, and a shortest pit length of 0.80 to 0.90 μm. The optical recording medium identification device is characterized by being able to identify the optical recording medium. 13. The optical recording according to claim 9, wherein the substrate thickness is 0.55 to 0.65 mm, the shortest pit length is 0.38 to 0.42 μm, and the reflectance is 70% or more. Medium or substrate thickness is 0.55-0.65mm
And the shortest pit length is 0.38 to 0.42 μm, the reflectance is 20 to 40%, and the substrate thickness is 1.1 to 1.3 mm. An optical recording medium identification device characterized by being able to identify an optical recording medium having a reflectance of 70% or more with a thickness of 0.80 to 0.90 μm. 14. The optical recording according to claim 9, wherein the substrate thickness is 0.55 to 0.65 mm, the shortest pit length is 0.20 to 0.30 μm, and the reflectance is 70% or more. Medium or substrate thickness is 0.55-0.65mm
And the shortest pit length is 0.20 to 0.30 μm, the reflectance is 20 to 40%, and the substrate thickness is 1.1 to 1.3 mm. An optical recording medium identification device characterized by being able to identify an optical recording medium having a reflectance of 70% or more with a thickness of 0.80 to 0.90 μm. 15. The optical recording according to claim 9, wherein the substrate thickness is 0.55 to 0.65 mm, the shortest pit length is 0.38 to 0.42 μm, and the reflectance is 70% or more. Medium, substrate thickness is 0.55-0.65mm, shortest pit length is 0.20-0.30μm, reflectance is 20-40%
The optical recording medium identification device is characterized by being able to identify the optical recording medium. 16. The substrate thickness according to claim 9 or 10, the substrate thickness is 0.55 to 0.65 mm, the shortest pit length is 0.38 to 0.42 μm, and the reflectance is 20 to 40%.
Discriminating between the optical recording medium having a substrate thickness of 0.55 to 0.65 mm, the shortest pit length of 0.20 to 0.30 μm, and a reflectance of 70% or more. An apparatus for identifying an optical recording medium, which is characterized by being capable of. 17. The optical recording medium identification device according to claim 11, wherein the shape of the laser beam is circular or elliptical. 18. The optical recording medium identification device according to claim 11, wherein the laser beam has a polygonal shape. 19. The optical recording medium identification device according to claim 17, wherein the laser beam has a wavelength in the range of 350 to 700 nm. 20. The optical recording medium identification device according to claim 17, wherein the wavelength of the laser beam is in the range of 350 to 450 nm. 21. The optical recording medium identification device according to claim 20, wherein the wavelength of the laser beam is in the range of 415 to 445 nm. 22. The optical recording medium identification device according to claim 17, wherein the laser beam has a wavelength in the range of 450 to 550 nm. 23. The optical recording medium identification device according to claim 22, wherein the wavelength of the laser beam is in the range of 517 to 547 nm. 24. The optical recording medium identification device according to claim 17, wherein the wavelength of the laser beam is in the range of 585 to 690 nm. 25. The optical recording medium identification device according to claim 24, wherein the wavelength of the laser beam is in the range of 620 to 650 nm. 26. The optical recording medium identification device according to claim 17, wherein the wavelength of the laser beam is in the range of 600 to 700 nm. 27. The optical recording medium identification device according to claim 26, wherein the wavelength of the laser beam is in the range of 635 to 665 nm.