JP3244442B2 - Optical regeneration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for reproducing 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
A DVD standard for recording 4.7 Gbyte information on one side of an optical disc has been proposed. The thickness of a DVD disk is about 0.6 mm, and 9.4 Gbyte information can be recorded on a single disc by bonding both sides. There is also a CD-R as a recordable optical disc having the same diameter, substrate thickness and recording density as a CD.

[0004] Since it is conceivable that these three types of optical disks coexist, a device capable of compatible reproduction of three types of optical disks is required. DVD, CD, and CD-R have different thicknesses of disk substrates, and cannot be reproduced by one optical pickup. Japanese Patent Application Laid-Open No. 5-303766 discloses that a high-density optical disk having a thin substrate having a thickness of 0.6 mm and a standard-density optical disk having a standard-thick substrate having a thickness of 1.2 mm are combined into one. An apparatus has been proposed that enables reproduction by an optical pickup.

This technique uses an objective lens having a numerical aperture of 0.6 designed to reproduce a high-density disc with a short-wavelength laser beam, and corrects aberrations when reproducing a standard-thickness standard-density optical disc. 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. As a method of changing the effective numerical aperture of an objective lens for condensing a laser beam by selectively shielding the outer peripheral portion of a laser beam emitted from a semiconductor laser, the applicant has disclosed in Japanese Patent Application No. 8-84307. We propose a method that combines a liquid crystal that selectively rotates the plane of polarization of a laser beam and a polarization filter that transmits only a laser beam that is polarized in a specific direction, and discloses a technology that enables compatible playback of optical disks with different substrate thicknesses using this method. are doing.

[0006]

Problems to be Solved by the Invention Japanese Patent Application No. 8-84307
In the method disclosed in US Pat.
Is compatible with the above, but since a laser beam with a wavelength of 635 nm is used, a CD having a substrate thickness of 1.2 mm and a reflectance of 10% or less for a laser beam with a wavelength of 635 nm on a signal recording surface is used. -R cannot be reproduced.

Accordingly, the present invention solves such a problem, and is compatible with a DVD having a substrate thickness of 0.6 mm and a CD-R having a substrate thickness of 1.2 mm and a signal recording surface having a reflectance of 10% or less. An object of the present invention is to provide an optical reproducing device capable of reproducing.

[0008]

According to the present invention, there is provided an optical system which irradiates a laser beam onto a recording surface of an optical disk having different reproduction conditions by an objective lens and guides a laser beam reflected from the recording surface to a photodetector. An optical reproducing device comprising:
Generating a first laser beam having a first wavelength;
A laser beam generating means comprising a light emitting element, a second light emitting element for generating a second laser beam having a second wavelength different from the first wavelength, and the first light emitting element of the laser beam generating means The generated first laser beam is guided to the objective lens without diffracting, and the second laser beam generated by the second light emitting element of the laser beam generating means is diffracted and guided to the objective lens. First diffraction means, and light detection means for detecting a first reflection light of the first laser beam on the recording surface and a second reflection light of the second laser beam on the recording surface. Wherein the first light emitting element and the second light emitting element are arranged such that an optical axis shift between the first laser beam and the second laser beam occurs in the tracking direction of the optical disc, Sa The light detecting means includes a first light detector for detecting the first reflected light, and a second light detector for detecting the second reflected light, and is provided in front of the light detecting means. And the first reflected light is diffracted without diffracting the first reflected light.
The second reflected light is diffracted into the second
A second diffraction means for guiding to the photodetector is provided.

Further, in the present invention, the second diffraction means is a polarization-selective diffraction grating that selectively diffracts the laser beam due to the polarization plane of the laser beam.

In the present invention, the second diffraction means is a wavelength-selective diffraction grating for selectively diffracting the laser beam due to the wavelength of the laser beam.

In the present invention, the polarization selective diffraction grating is a Wollaston prism.

In the present invention, the polarization-selective diffraction grating is a polarization-selective hologram.

In the present invention, the wavelength-selective diffraction grating is a wavelength-selective hologram.

Further, the present invention provides an optical system comprising: an optical system for irradiating a recording surface of an optical disk having different reproduction conditions with an objective lens with a laser beam, and guiding the laser beam reflected from the recording surface to a photodetector. A reproducing apparatus, comprising: a first light emitting element that generates a first laser beam having a first wavelength; and a second light emitting element that generates a second laser beam having a second wavelength different from the first wavelength. A first laser beam generated by the first light-emitting element of the laser beam generating means and guided to the objective lens without diffracting the laser beam. (2) first diffracting means for diffracting the second laser beam generated by the light emitting element and guiding the diffracted light to the objective lens; first reflected light of the first laser beam on the recording surface; Light detecting means for detecting a second reflected light of the second laser beam on the recording surface, wherein a deviation of an optical axis between the first laser beam and the second laser beam is reduced. The first light emitting element and the second light emitting element are arranged so as to be generated in a tracking direction of the optical disc, and the light detecting means further includes the first reflected light,
And one photodetector for detecting the second reflected light is provided before the photodetecting means, and the first reflected light is guided to the one photodetector without diffracting, and 2
And a third diffracting means for diffracting the reflected light and guiding the reflected light to the one photodetector.

Further, in the present invention, the third diffraction means is a polarization selective diffraction grating for selectively diffracting the laser beam due to the polarization plane of the laser beam.

In the present invention, the third diffraction means is a wavelength-selective diffraction grating that selectively diffracts the laser beam due to the wavelength of the laser beam.

In the present invention, the polarization-selective diffraction grating is a Wollaston prism.

In the present invention, the polarization selective diffraction grating is a polarization selective hologram.

In the present invention, the wavelength-selective diffraction grating is a wavelength-selective hologram.

[0020]

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment An embodiment of the present invention will be described with reference to the drawings. FIG.
The following shows the rated values and playback conditions of CD-Rs and DVDs that are compatible playback targets of the present invention. The substrate thickness of the CD-R is 1.2 (tolerance ± 0.1) mm, the shortest pit length is 0.90 (tolerance ± 0.1) μm, and the track pitch is 1.6 (tolerance ±).
0.1) μm, reflectivity to a laser beam having a wavelength of 780 nm is 60%, the spot diameter of the laser beam during reproduction is 1.5 (tolerance ± 0.1) μm, and the numerical aperture of the objective lens is 0.1. 45 (tolerance ± 0.05), and the reproduction laser beam wavelength is 780 (tolerance ± 15) nm. on the other hand,
The DVD substrate thickness is 0.6 (tolerance ± 0.05) mm, the shortest pit length is 0.40 (tolerance ± 0.1) μm, and the track pitch is 0.74 (tolerance ± 0.01) μm. , Wavelength 6
The reflectivity for a 35 nm laser beam is 70% or more (in the case of a single signal recording surface) or 20 to 40% (in the case of two signal recording surfaces), and the spot diameter of the laser beam during reproduction is 0.9. (Allowable error ± 0.5) μm, the numerical aperture of the objective lens is 0.6 (allowable error ± 0.05), and the reproduction laser beam wavelength is 635 (allowable error ± 15) nm.

FIG. 2 shows the configuration of an optical pickup 10 for performing compatible reproduction between a CD-R and a DVD. The laser beam emitted from the semiconductor laser 1 enters the collimator lens 3 via the diffraction grating 2, is converted into parallel light by the collimator lens 3, and is condensed by the objective lens 6 via the half mirror 4 and the hologram element 5. The signal is irradiated onto the signal recording surface 7a of the optical disk through the transparent polycarbonate substrate 7. The laser beam reflected by the signal recording surface 7a returns to the half mirror 4 via the substrate 7, the objective lens 6, and the hologram element 5, and the half of the half mirror 4 shifts the incident direction of the laser beam by 90 degrees. The light is reflected in the forming direction and is detected by the photodetector 9 via the condenser lens 8.
The objective lens 6 is designed for an optical disk having a substrate thickness of 0.6 mm, and has a numerical aperture of 0.6 (allowable error ± 0.05).
It is. The hologram element 5 is made of a wavelength-selective hologram. When the wavelength of the laser beam is 780 nm, the outer peripheral portion of the laser beam is outwardly focused on the signal recording surface of an optical disk having a substrate thickness of 1.2 mm. It has the function of scattering light. In this case, 0.
The objective lens 6 having a numerical aperture of 6 is designed so that the effective numerical aperture is 0.45 (allowable error ± 0.05).

In the present invention, the semiconductor laser 1 comprises a semiconductor laser chip 1a for emitting a laser beam with a wavelength of 780 nm and a semiconductor laser chip 1b for emitting a laser beam with a wavelength of 635 nm, and a CD-R is reproduced. In this case, the semiconductor laser chip 1a is used, and when DVD is reproduced, the semiconductor laser chip 1b is used.

Referring to FIG. 3, a DV having a substrate thickness of 0.6 mm is used.
The reproduction operation of D will be described. When a DVD is reproduced, the semiconductor laser drive circuit 19 selectively drives the semiconductor laser chip 1b. As a result, the laser beam having a wavelength of 635 nm emitted from the semiconductor laser chip 1b is converted into parallel light by the collimator lens 3 via the diffraction grating 2, passes through the half mirror 4, the hologram element 5, and Focused by lens 6,
The signal is irradiated onto the signal recording surface 7a through the substrate 7 having a thickness of 0.6 mm. Subsequent operations are the same as those described with reference to FIG. The spot diameter of the laser beam applied to the signal recording surface 7a is 0.9 (allowable error ± 0.1) μm.

Next, referring to FIG. 4, the substrate thickness is 1.2 mm.
Of the CD-R will be described. When a CD-R is reproduced, the semiconductor laser chip 1a is selectively driven by the semiconductor laser drive circuit 19. As a result, the wavelength 7 emitted from the semiconductor laser chip 1a
The laser beam of 80 nm is collimated by the collimator lens 3 through the diffraction grating 2, passes through the half mirror 4, and enters the hologram element 5. The outer peripheral portion of the laser beam is scattered outward by the hologram element 5 and is incident on the objective lens 6. The laser beam is condensed by the objective lens 6 and irradiates a signal recording surface 77 a through a 1.2 mm thick substrate 77. Subsequent operations are the same as those described with reference to FIG. The spot diameter of the laser beam applied to the signal recording surface 77a is 1.5 (allowable error ± 0.1).
μm.

Referring to FIG. 5, the mounting of the semiconductor laser chips 1a and 1b on the semiconductor laser 1 will be described. FIG. 5 is a cross-sectional view of the semiconductor laser 1 shown in FIGS. 2, 3, and 4 as viewed from the diffraction grating 2 side, and the direction of the cuts k1-k2 is a direction parallel to the paper. The semiconductor laser chips 1a and 1b are mounted side by side in a direction parallel to the direction of the cuts k1-k2. In this case, the light emitting point A of the semiconductor laser chip 1a and the semiconductor laser chip 1b
Is approximately 300 μm from the light emitting point B, and a direction perpendicular to the direction of the cut k1-k2 from each light emitting point A, B;
That is, a laser beam having a plane of polarization in a direction perpendicular to the plane of the paper is emitted. Further, the light emitting points A and B are cut at k1-k2.
The semiconductor laser chips 1a, 1a
b is arranged.

In the above description, the distance between the semiconductor laser chip 1a and the semiconductor laser chip 1b is 3
Although described as 00 μm, the present invention is not limited to this.
It may be in the range of 00 μm, preferably 150 μm
It is. The details of the photodetector 9 will be described with reference to FIG. The light detector 9 is the semiconductor laser chip 1a
And a light detecting element 9b for detecting a laser beam having a wavelength of 635 nm emitted from the semiconductor laser chip 1b. The light detecting element 9a is divided into five parts. The element and the light detection element 9b are four-divided elements. The semiconductor laser 1 according to the present invention is composed of two semiconductor laser chips that emit laser beams of different wavelengths, and the light emitting points of each semiconductor laser chip are separated by about 300 μm as described above. In view of the fact that it is difficult to detect reflected light from the signal recording surface of the optical disc, two detection elements are provided. From this point of view, the photodetector 9a used at the time of CD-R reproduction is formed to be horizontally long, and can detect even if the laser beam is shifted in the horizontal direction.

The light detecting element 9a includes the areas 99A, 99B,
It is divided into 99C, 99D, and 99E.
The tracking servo is performed by detecting the laser beam in A and 99E, and if the light intensities detected in the areas 99A and 99E become equal, it means that the laser beam has been irradiated following the track. Also, the areas 99B, 99C, 99D
To perform focus servo by detecting a laser beam. Based on the light intensity detected in the areas 99B, 99C, and 99D, (99B + 99D) and 99C are compared, and control is performed so that they are equal.

The photodetector 9b includes the regions 9A, 9B, 9C,
It is divided into 9D, and based on the light intensity detected in each area, (9A + 9C) and (9B + 9D) are compared, and control is performed so that both are equal. If they are equal, the focus is in focus. Also, (9A + 9C) and (9B
The phase difference of (+ 9D) is used as a tracking error signal, and control is performed so that the two phases match. If the phase difference disappears, the laser beam is emitted following the track.

In the present invention, since the photodetector 9a for 780 nm is made horizontally long, variations in the distance between the semiconductor laser chips can be absorbed. With reference to FIG. 7, a description will be given of a reproducing apparatus for compatible reproduction of a DVD having a substrate thickness of 0.6 mm and a CD-R having a substrate thickness of 1.2 mm. The objective lens 6 in the optical pickup 10 is controlled so that the signal to be reproduced by the servo mechanism 13 focuses the laser beam on a track formed as a pit row.
The laser beam is condensed by the objective lens 6 and passes through the substrate 7 (or 77) of the optical disk to record the signal on the signal recording surface 7a.
(Or 77a). The laser beam reflected by the signal recording surface 7a (or 77a) is detected by the photodetector 9 and detected as a reproduction signal. The reproduction signal detected by the photodetector 9 is sent to a preamplifier 11 and, after a predetermined amplification, sent to a discrimination circuit 14, an RF demodulation circuit 16 and a servo circuit 12. The servo circuit 12 sends the servo mechanism 1 based on the received tracking error signal.
3 is controlled. The discrimination circuit 14 identifies the type of the optical disc mounted on the reproducing apparatus based on the transmitted signal, and sends the identification result to the command circuit 15. The command circuit 1
Reference numeral 5 denotes a semiconductor laser switching circuit based on the identification result sent to switch the semiconductor laser chip of the semiconductor laser 1 so as to match the identified optical disk.
Command 7 Further, the command circuit 15 switches a characteristic switching circuit 18 based on the received identification result to switch to a demodulation circuit suitable for reproducing the identified optical disk.
Also issue a command. The semiconductor laser switching circuit 17 switches a semiconductor laser chip via a semiconductor laser drive circuit 19 based on a command from the command circuit 15, and the characteristic switching circuit 18 based on a command from the command circuit 15, The RF demodulation circuit 16 is switched. This allows
Playback suitable for the optical disc mounted on the playback device is performed.

In the present invention, the structure of the optical pickup is not limited to the structure shown in FIG. 2, but may be the structure shown in FIG. Optical pickup 20 shown in FIG.
Has a wavelength of 635n without using a wavelength selective hologram.
When reproducing using a laser beam of m
Using an objective lens 6b having a numerical aperture of 0.6 (allowable error ± 0.05) designed for a 6 mm optical disc, and having a wavelength of 780
In the case of reproducing using a laser beam of nm, a numerical aperture of 0.45 designed for an optical disk having a substrate thickness of 1.2 mm is used.
The objective lens 6a having a tolerance (± 0.05) is used. The other components are the same as those of the optical pickup 10, and the same components are denoted by the same reference numerals.
When a DVD having a substrate thickness of 0.6 mm is reproduced, the semiconductor laser chip 1b is driven by the semiconductor laser driving circuit 19.
Is selectively driven, and the objective lens 6 b is selectively inserted into the optical path of the optical pickup 20 by the lens switching circuit 21.
As a result, the laser beam having a wavelength of 635 nm emitted from the semiconductor laser chip 1b is converted into parallel light by the collimator lens 3 via the diffraction grating 2, and enters the objective lens 6b having a numerical aperture of 0.6 through the half mirror 4. The light is condensed by the objective lens 6b, passes through the optical disk substrate 7 having a thickness of 0.6 mm, and is irradiated on the signal recording surface 7a. The signal recording surface 7
The laser beam reflected by a is returned via the substrate 7 and the objective lens 6b, and half of the laser beam is reflected by the half mirror 4 in a direction at an angle of 90 degrees to the incident direction.
Is detected by the photodetector 9 via the. The signal recording surface 7a
The spot diameter of the laser beam applied to the substrate is 0.9 (allowable error ± 0.1) μm.

Next, when a CD-R having a substrate thickness of 1.2 mm is reproduced, the semiconductor laser chip 1a is selectively driven by the semiconductor laser driving circuit 19 and the lens switching circuit 2 is driven.
By means of 1, the objective lens 6a is selectively inserted into the optical path of the optical pickup 20. As a result, the semiconductor laser chip 1a
The laser beam having a wavelength of 780 nm emitted from the laser beam is collimated by a collimator lens 3 through a diffraction grating 2, passes through a half mirror 4, enters an objective lens 6 a having a numerical aperture of 0.45, and is collected by the objective lens 6 a. The light is irradiated onto a signal recording surface 77a through a substrate 77 of a 1.2 mm thick optical disk. Subsequent operations are the same as those in the case where the DVD is reproduced, and thus the description thereof is omitted. The signal recording surface 77a
The spot diameter of the laser beam to be irradiated is 1.5 (allowable error ± 0.1) μm.

With reference to FIG. 9, a description will be given of compatible playback of DVD and CD-R in a playback apparatus using the optical pickup 20. Objective lens 6a in optical pickup 20
(Or 6b) is controlled so that the signal to be reproduced by the servo mechanism 13 focuses the laser beam on a track formed as a pit row, and the laser beam is collected by the objective lens 6a (or 6b). The light is emitted and irradiates the signal recording surface 77a (or 7a) through the substrate 77 (or 7) of the optical disk. The signal recording surface 77
a (or 7a) is reflected by the light detector 9
And detected as a reproduction signal. The reproduction signal detected by the photodetector 9 is sent to a preamplifier 11 and, after a predetermined amplification is performed, a discrimination circuit 14 and an RF demodulation circuit 1
6 and the servo circuit 12. The servo circuit 12 controls the servo mechanism 13 based on the sent tracking error signal. The discrimination circuit 14 identifies the type of the optical disc mounted on the reproducing apparatus based on the transmitted signal, and sends the identification result to the command circuit 15. The command circuit 15 controls the control circuit 22 based on the identification result to switch the semiconductor laser chip of the semiconductor laser 1 and the objective lens so as to be compatible with the identified optical disk.
Command. Further, the command circuit 15 switches a characteristic switching circuit 18 based on the received identification result to switch to a demodulation circuit suitable for reproducing the identified optical disk.
Also issue a command. The control circuit 22 is connected to the command circuit 15
The semiconductor laser chip is switched via the semiconductor laser drive circuit 19 based on a command from the
The objective lens is switched via. Further, the characteristic switching circuit 18 is configured to output a signal based on a command from the command circuit 15,
The RF demodulation circuit 16 is switched. Thereby, reproduction suitable for the optical disk mounted on the reproduction device is performed.

As described above, the position of the laser beam emitted from the semiconductor laser chip 1a and the semiconductor laser chip 1b is shifted about 300 μm in the horizontal direction, that is, in the tracking direction of the optical disk, so that the DVD
And a reproduction signal reproduced from the CD-R, a DC component shift occurs. The present invention is characterized in that it is a reproducing apparatus using an optical system in which a DC component shift occurs when reproducing optical disks having different reproducing conditions. The present invention is not limited to the means for arranging the semiconductor laser chips in the horizontal direction, but may be other means. Second Embodiment In the first embodiment, the laser beams emitted from the semiconductor laser chip 1a and the semiconductor laser chip 1b are detected by photodetectors 9a and 9b, respectively. The light detecting element 9a for detecting the laser beam emitted from the semiconductor laser chip 1a is made horizontally long so as to absorb the deviation of the optical axis. In the second embodiment, in order to improve this point, the light detecting element 9b is set in accordance with the optical axis of the laser beam emitted from the semiconductor laser chip 1b, and the light emitted from the semiconductor laser chip 1a is provided. The light detecting element 9a for detecting the laser beam is provided at a fixed distance from the light detecting element 9b, and reflects the reflected light of the laser beam emitted from the semiconductor laser chip 1a on the signal recording surface 77a.
a means for converging light onto the light detector 9 and the condensing lens 8
And provided between them.

An optical pickup 30 according to the second embodiment will be described with reference to FIG. The structure of the optical pickup 30 is the same as that of the first embodiment shown in FIG.
The only difference is that the diffraction means 31 is added to the optical pickup shown in FIG. 1 and the installation interval between the photodetectors 9a and 9b constituting the photodetector 9 is different. Therefore, the same reference numerals are given to other components. The diffraction means 31 has a wavelength of 635n emitted from the semiconductor laser chip 1b.
The laser beam of m is reflected by the signal recording surface 7a without being diffracted and transmitted as it is to the photodetector 9b, and the signal recording surface of the laser beam emitted from the semiconductor laser chip 1a. The reflected light at 77a is diffracted,
The light is guided to the light detecting element 9a installed at a position separated by a certain distance from the light detecting element 9b. Diffraction means 31
May be any as long as it selectively diffracts the laser beam due to the difference in the polarization direction of the laser beam. Further, the diffraction means 31 may selectively diffract the laser beam due to a difference in the wavelength of the laser beam. Specifically, a Wollaston prism, a polarization selective hologram, and a wavelength selective hologram are used. Thereby, the reflected light of the laser beam emitted from the semiconductor laser chip 1a on the signal recording surface 77a can be focused on an arbitrary point. Note that the Wollaston prism is excellent in that it can diffract the entire laser beam in a certain direction without reducing the intensity of the laser beam.
In the second embodiment, the distance between the light detecting element 9a and the light detecting element 9b is set in a range of 0.3 to 1.0 mm. When a polarization-selective hologram or a wavelength-selective hologram is used as the diffraction means 31, the light is determined by the wavelength of the laser beam to be diffracted, the distance between the diffraction means 31 and the photodetector 9, and the pitch of the holograms constituting the hologram element. The distance between the detection element 9a and the light detection element 9b is determined. In the second embodiment, the distance between the diffraction means 31 and the photodetector 9 is set in the range of 2 to 12 mm, and the pitch of the hologram is set in the range of 2 to 60 μm. The distance between the light detecting element 9a and the light detecting element 9b is 0.3 to 1.0 m.
m.

Referring to FIG. 11, the operation of reproducing a DVD which is an optical disk having a substrate thickness of 0.6 mm will be described. D
When VD is reproduced, the semiconductor laser drive circuit 19 selectively drives the semiconductor laser chip 1b. As a result, the laser beam having a wavelength of 635 nm emitted from the semiconductor laser chip 1b is converted into parallel light by the collimator lens 3 via the diffraction grating 2, passes through the half mirror 4, the hologram element 5, and The light is condensed by a lens 6 and passes through a substrate 7 having a thickness of 0.6 mm to irradiate a signal recording surface 7a. The laser beam reflected by the signal recording surface 7a returns to the half mirror 4 via the substrate 7, the objective lens 6, and the hologram element 5,
Half of the light is reflected by the half mirror 4 in a direction forming an angle of 90 degrees with the incident direction, and is condensed by the condensing lens 8.
It is detected by the light detection element 9b in the middle. The signal recording surface 7a
The spot diameter of the laser beam applied to the substrate is 0.9 (allowable error ± 0.1) μm.

Next, referring to FIG. 12, the substrate thickness is 1.2 m.
The playback operation of the m-CD-R will be described. When a CD-R is reproduced, the semiconductor laser chip 1a is selectively driven by the semiconductor laser drive circuit 19. As a result, the wavelength 7 emitted from the semiconductor laser chip 1a
The laser beam of 80 nm is collimated by the collimator lens 3 through the diffraction grating 2, passes through the half mirror 4, and enters the hologram element 5. The outer peripheral portion of the laser beam is scattered outward by the hologram element 5 and is incident on the objective lens 6. The laser beam is condensed by the objective lens 6 and irradiates a signal recording surface 77 a through a 1.2 mm thick substrate 77. The laser beam reflected by the signal recording surface 77a is applied to the substrate 77, the objective lens 6, the hologram element 5
To the half mirror 4 via the
Is reflected in a direction that forms an angle of 90 degrees with the incident direction, is condensed by the condensing lens 8, is diffracted by the diffracting means 31, passes through, and is detected by the photodetector 9a in the photodetector 9. Is done. The spot diameter of the laser beam applied to the signal recording surface 77a is 1.5 (allowable error ± 0.1) μm.

The diffraction means 31 shown in the second embodiment
Is applied to the optical pickup shown in FIG. 8 in the first embodiment, and has the same function as the optical pickup shown in FIG. The optical pickup described above can be used by applying to the reproducing apparatus shown in FIGS. 7 and 9 described in the first embodiment. Third Embodiment In the second embodiment, the reflected light of the laser beam emitted from the semiconductor laser chip 1a and the laser beam emitted from the semiconductor laser chip 1b on the signal recording surfaces 7a and 77a are different from each other in the light detection. Detected by the element, but preferably,
It is better to detect with one light detecting element.

An optical pickup 40 according to the third embodiment will be described with reference to FIG. The optical pickup 40 includes the condenser lens 8 and the photodetector 9 of the optical pickup shown in FIG. 2 according to the first embodiment.
And a diffraction means 32 inserted between them. The other components are the same as those in FIG. 2 and are denoted by the same reference numerals. The diffracting means 32 does not diffract a laser beam having a wavelength of 635 nm emitted from the semiconductor laser chip 1b, but diffracts a laser beam having a wavelength of 780 nm emitted from the semiconductor laser chip 1a in the second embodiment. The diffraction means 31
But the diffraction direction is the same as that of the light detecting element 9a.
In the direction of the photodetector 9b, not in the direction of. That is, the diffracting means 32 transmits the laser beam having a wavelength of 635 nm as it is without diffracting it,
The laser beam having a wavelength of 780 nm is diffracted and guided to the photodetector 9b. Therefore, the diffraction means 32
Is used, the laser beam emitted from the semiconductor laser chip 1a and the semiconductor laser chip 1b, whose optical axis is shifted, can be detected by one photodetector 9b, and it is not necessary to provide two photodetectors. The diffracting means 32 may be anything as long as it selectively diffracts the laser beam due to the difference in the polarization direction of the laser beam. The diffraction means 32
May selectively diffract the laser beam due to the difference in the wavelength of the laser beam. Specifically, a Wollaston prism, a polarization selective hologram, and a wavelength selective hologram are used.

The distance between the diffraction means 32 and the photodetector 9 is such that the hologram pitch is in the range of 10 to 50 μm, and the distance between the semiconductor laser chips 1a and 1b is in the range of 0.1 to 0.3 mm. If set, 2-12mm
Range. With reference to FIG. 14, a description will be given of a reproducing operation of a DVD which is an optical disk having a substrate thickness of 0.6 mm.
When a DVD is reproduced, the semiconductor laser drive circuit 19 selectively drives the semiconductor laser chip 1b. As a result, the laser beam with a wavelength of 635 nm emitted from the semiconductor laser chip 1b is
Is collimated by the collimator lens 3 through the half mirror 4 and the hologram element 5, condensed by the objective lens 6, and passes through a 0.6 mm thick substrate 7 to a signal recording surface 7 a. Irradiated. The laser beam reflected by the signal recording surface 7a is applied to the substrate 7, the objective lens 6,
After returning to the half mirror 4 via the hologram element 5, half of the light is reflected by the half mirror 4 in a direction forming an angle of 90 degrees with the incident direction, and after being condensed by the condenser lens 8, diffracted by the diffraction means 32. The light is transmitted as it is and detected by the light detection element 9b in the light detector 9. The spot diameter of the laser beam applied to the signal recording surface 7a is 0.9.
(Allowable error ± 0.1) μm.

Next, referring to FIG. 15, the substrate thickness is 1.2 m.
The playback operation of the m-CD-R will be described. When a CD-R is reproduced, the semiconductor laser chip 1a is selectively driven by the semiconductor laser drive circuit 19. As a result, the wavelength 7 emitted from the semiconductor laser chip 1a
The laser beam of 80 nm is collimated by the collimator lens 3 through the diffraction grating 2, passes through the half mirror 4, and enters the hologram element 5. The outer peripheral portion of the laser beam is scattered outward by the hologram element 5 and is incident on the objective lens 6. The laser beam is condensed by the objective lens 6 and irradiates a signal recording surface 77 a through a 1.2 mm thick substrate 77. The laser beam reflected by the signal recording surface 77a is applied to the substrate 77, the objective lens 6, the hologram element 5
To the half mirror 4 via the
Is reflected in a direction forming an angle of 90 degrees with the incident direction, and is condensed by the condenser lens 8, then diffracted by the diffracting means 32 and transmitted, and detected by the light detection element 9 b in the photodetector 9. Is done. The spot diameter of the laser beam applied to the signal recording surface 77a is 1.5 (allowable error ± 0.1) μm.

The diffraction means 32 shown in the second embodiment
Is applied to the optical pickup shown in FIG. 8 in the first embodiment, and has the same function as the optical pickup shown in FIG. The optical pickup described above can be used by applying to the reproducing apparatus shown in FIGS. 7 and 9 described in the first embodiment.

[0043]

According to the present invention, light sources having different wavelengths are used.
Since two semiconductor laser chips are used, it is possible to perform compatible reproduction between a thin optical disk and an optical disk having a reflectance of 10% or less for a laser beam having a standard thickness of 635 nm. Further, according to the present invention, since the photodetector is provided for each of the laser beams emitted from the two semiconductor laser chips, it is possible to prevent the reproduction characteristics from deteriorating due to the displacement of the laser beams.

Further, according to the present invention, it is possible to realize an optical pickup capable of reproducing a CD-R with substantially the same configuration as the conventional optical system. Further, according to the present invention, the wavelength of 635 nm
If the optical axis of the laser beam is adjusted, the wavelength is 780n
The optical axis can be adjusted for the m laser beam. Also,
According to the present invention, the reflected lights of the two laser beams on the signal recording surface can be respectively detected at arbitrary points, and it becomes easy to manufacture a photodetector.

Further, according to the present invention, since laser beams emitted from different light emitting points can be detected by one photodetector, the present invention can be used as a photodetector used in an optical pickup for compatible reproduction between DVD and CD-R. In particular, there is no need to make special ones.

[Brief description of the drawings]

FIG. 1 is a table showing rated values and reproduction conditions of DVD and CD-R.

FIG. 2 is a diagram illustrating a configuration of an optical pickup according to the first embodiment.

FIG. 3 is a diagram illustrating a DVD reproducing operation according to the first embodiment.

FIG. 4 is a diagram for explaining a CD-R reproducing operation according to the first embodiment.

FIG. 5 is a diagram illustrating a method of mounting a semiconductor laser chip according to the present invention.

FIG. 6 is a diagram illustrating a configuration of a photodetector according to the present invention.

FIG. 7 is a block diagram of an optical reproducing apparatus according to the present invention.

FIG. 8 is a diagram illustrating another configuration of the optical pickup according to the first embodiment.

FIG. 9 is another block diagram of the optical reproducing apparatus according to the present invention.

FIG. 10 is a diagram illustrating a configuration of an optical pickup according to a second embodiment.

FIG. 11 is a diagram illustrating a DVD reproducing operation according to the second embodiment.

FIG. 12 is a diagram for explaining a CD-R reproducing operation according to the second embodiment.

FIG. 13 is a diagram illustrating a configuration of an optical pickup according to a third embodiment.

FIG. 14 is a diagram illustrating a DVD reproducing operation according to the third embodiment.

FIG. 15 is a diagram for explaining a CD-R reproducing operation according to the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser 1a, 1b ... Semiconductor laser chip 2 ... Diffraction grating 3 ... Collimator lens 4 ... Half mirror 5 ... Wavelength selective hologram 6 ... Objective lens 7 ... · Substrate 7a ··· Signal recording surface 8 ··· Condensing lens 9 ··· Photodetector 9a ··· 5 split photodetection element 9b ··· 4 split photodetection element 10 ··· Optical pickup

Continuation of the front page (72) Inventor Shuichi Ichiura 2-5-1-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-8-55363 (JP, A) JP-A-6-55 259804 (JP, A) JP-A-8-45105 (JP, A) JP-A-7-98431 (JP, A) JP-A-9-288837 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B ^7/ 12-7/22

Claims (12)

(57) [Claims] 1. An optical reproducing apparatus comprising: an optical system that irradiates a laser beam onto a recording surface of an optical disk having different reproduction conditions by an objective lens and guides a laser beam reflected from the recording surface to a photodetector. Generating a first laser beam having a first wavelength.
A laser beam generating means comprising a light emitting element, a second light emitting element for generating a second laser beam having a second wavelength different from the first wavelength, and the first light emitting element of the laser beam generating means The generated first laser beam is guided to the objective lens without diffracting, and the second laser beam generated by the second light emitting element of the laser beam generating means is diffracted and guided to the objective lens. First diffractive means; light detecting means for detecting first reflected light of the first laser beam on the recording surface and second reflected light of the second laser beam on the recording surface; the provided consists, arranged with the first laser beam, the deviation of the optical axis of said second laser beam from the first light emitting element as occurs in the tracking direction of the optical disk and the second light emitting element, Luo, said light detecting means, to detect the first reflected light
A first light detector, and a second light for detecting the second reflected light
And a detector provided before the light detecting means,
The first reflected light is guided to the first photodetector without being diffracted.
The second reflected light is diffracted and guided to the second photodetector.
An optical reproducing device comprising a second diffraction means . 2. The apparatus according to claim 1, wherein said second diffraction means is formed by a plane of polarization of a laser beam.
-Selective diffraction grating for selectively and selectively diffracting a laser beam
An optical reproducing device, characterized in that: 3. The apparatus according to claim 1, wherein said second diffracting means is provided for generating a laser beam based on a wavelength of the laser beam.
With a wavelength-selective diffraction grating that selectively diffracts a laser beam
An optical reproducing apparatus, comprising: 4. The polarization selective diffraction grating according to claim 2, wherein the polarization selective diffraction grating is a Wollaston prism.
An optical reproducing apparatus, comprising: 5. A polarization selective hologram according to claim 2, wherein said polarization selective diffraction grating is a polarization selective hologram.
An optical regenerating apparatus characterized in that: 6. A wavelength selective hologram according to claim 3, wherein said wavelength selective diffraction grating is a wavelength selective hologram.
An optical regenerating apparatus characterized in that: 7. An optical disk having different reproduction conditions depending on an objective lens.
The recording surface of the disk is irradiated with a laser beam, and
An optical system for guiding the reflected laser beam to the photodetector is provided.
An optical reproducing apparatus comprising: a first laser beam generating a first laser beam having a first wavelength;
A light emitting device, having a second wavelength different from the first wavelength
And a second light emitting element for generating a second laser beam.
Laser beam generating means, and the first light emitting element of the laser beam generating means.
The first laser beam formed is not diffracted by the objective
Guides the lens to the second beam of the laser beam generating means.
The second laser beam generated by the optical element is diffracted
First diffraction means for guiding the laser beam to the objective lens, and first reflection of the first laser beam on the recording surface.
Light and the second laser beam on the recording surface
And a light detecting means for detecting the reflected light of the second laser beam , wherein the first laser beam and the second laser beam
Optical axis shift occurs in the tracking direction of the optical disk
The first light emitting element and the second light emitting element
And the light detecting means further comprises: the first reflected light;
It comprises one photodetector for detecting the second reflected light,
The first reflected light is provided in front of the light detecting means.
Lead to the one photodetector without diffracting the second reflection
Third diffracting means for diffracting light and leading the light to the one photodetector
An optical reproducing apparatus, comprising: 8. The apparatus according to claim 7, wherein said third diffraction means is based on a plane of polarization of the laser beam.
-Selective diffraction grating for selectively and selectively diffracting a laser beam
An optical reproducing device, characterized in that: 9. The apparatus according to claim 7, wherein said third diffracting means is adapted to generate a laser beam based on a wavelength of the laser beam.
With a wavelength-selective diffraction grating that selectively diffracts a laser beam
An optical reproducing apparatus, comprising: 10. The polarization selective diffraction grating according to claim 8, wherein said polarization selective diffraction grating is a Wollaston prism.
An optical reproducing apparatus, comprising: 11. The polarization selective hologram according to claim 8, wherein said polarization selective diffraction grating is a polarization selective hologram.
An optical regenerating apparatus characterized in that: 12. The hologram according to claim 9, wherein said wavelength-selective diffraction grating is a wavelength-selective hologram.
An optical regenerating apparatus characterized in that: