JP2000076689A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device which is compatible with plural recording and reproducing optical disks to different standards by using light beams of different wavelengths, easy to assemble and adjust, and moreover suitable for miniaturization and integration. SOLUTION: 1st semiconductor laser 1 oscillating in a 650 nm band and 2nd semiconductor laser 2 oscillating in a 780 nm band are arranged proximately. A 3-beam purpose diffraction grating 3 for generating three beams for tracking control, a two-splitting 2nd hologram element 11 diffracting only the 2nd semiconductor laser light, and a four-splitting 1st hologram element 12 diffracting only the laser light of the 1st semiconductor laser are arranged in the optical axes of the 1st semiconductor laser 1 and the 2nd semiconductor laser 2. The light emitted from the 1st semiconductor laser 1 is focused on a disk 7, and the reflected light is diffracted by the hologram element 12 and guided to a photodetector 14. After the light emitted from the semiconductor 2 is separated into three beams through the diffraction grating 3, they are focused on the disk 7, and the reflected return light is diffracted by the hologram element 11 and guided to the photodetector 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for optically recording and reproducing information on an information recording medium such as an optical disk and an optical card. In particular, the present invention provides a compatible optical pickup that can support a plurality of optical discs of different standards for recording and reproducing using light beams of different wavelengths.

[0002]

2. Description of the Related Art In recent years, optical discs are capable of recording a large amount of information signals at high density, and have been used in many fields such as audio, video, and computers.

[0003] In particular, in the case of optical discs,
Discs of various different standards such as -R and DVD are commercially available, and compatibility for recording or reproducing such discs of different standards with a single optical pickup is required. For a CD or CD-R, the characteristics of a substrate and a recording medium are optimized with respect to an infrared light beam having a wavelength of 780 nm.
The DVD is optimized for a red light beam having a wavelength of about 650 nm. Further, in the future, development of a recording or reproducing disk using a blue light beam of about 400 nm is underway.

[0004] As an optical pickup compatible with such a disk recorded or reproduced at different wavelengths, for example, an optical pickup described in Japanese Patent Application Laid-Open No. 9-128794 has been proposed.

FIG. 12 is a diagram showing a configuration of an optical pickup described in Japanese Patent Application Laid-Open No. 9-128794. This optical pickup comprises a first semiconductor laser 1 oscillating in a 635 nm band, a second semiconductor laser 2 oscillating in a 780 nm band, and a three-beam diffraction grating 3 for generating three beams for tracking control from the light beam of each light source. A grating lens 5 having a concave lens function according to the polarization direction of the light beam; an objective lens 6; a hologram element 8 for diffracting light reflected from the disk 7 to guide the light to a light receiving element; Further, the first semiconductor laser 1 and the second semiconductor laser 2 are arranged so that the polarization directions are orthogonal to each other.

First, the operation when reproducing an optical disk having a substrate thickness of 0.6 mm with the first semiconductor laser 1 in the 635 nm band will be described. The light emitted from the semiconductor laser 1 is split into three beams by the diffraction grating 3, transmitted through the hologram element 8, and then focused on the recording surface 7 a of the disk 7 by the objective lens 6 without being affected by the grating lens 5. You. The light reflected and returned is diffracted by the hologram element 8 and guided to the light receiving element 9. A grating pattern is formed such that the polarization direction of the light beam is not affected by the grating lens 5.

Next, a description will be given of an operation when reproducing an optical disk having a substrate thickness of 1.2 mm with the second semiconductor laser 2 in the 780 nm band. The light emitted from the semiconductor laser 2 is similarly split into three beams by the diffraction grating 3 and transmitted through the hologram element 8, then condensed on the recording surface 7 b of the disk 7 by the objective lens 6 under the action of a concave lens in the grating lens 5. Is done. The reflected light is also diffracted by the hologram element 8 and guided to the light receiving element 9. A grating pattern is formed such that the polarization direction of the light beam is affected by the grating lens 5.

[0008] The concave lens action of the grating lens 5 is as follows.
It is designed to correct spherical aberration that occurs when the disk thickness increases from 0.6 mm to 1.2 mm.

In such a configuration, for example, the diffracted light of the disk reflected light is applied to the first semiconductor laser 1.
The hologram element 8 is designed to be guided to the light receiving element 9. For the second semiconductor laser 2 of the other wavelength, the semiconductor laser 2 is positioned such that the difference in position on the light receiving element 9 caused by the difference in the diffraction angle of the disk reflected light due to the difference in wavelength is canceled. Is set. Also, the light from the first semiconductor laser is
The light from the second semiconductor laser is also 3
Beams are separated into beams, and a tracking error signal is detected by the same light receiving element by the three-beam method.

With such an arrangement, two light receiving elements are originally required, but one light receiving element can be used in common, and the number of parts and the number of assembly steps can be reduced.

[0011]

In the above-described conventional optical pickup, when recording / reproducing on / from a plurality of types of optical discs using light from a plurality of semiconductor lasers having different wavelengths, both wavelengths of light are commonly used. It is necessary to arrange the positional relationship of the light source (semiconductor laser) in a predetermined positional relationship determined in advance so as to guide the light receiving element.

However, when the semiconductor laser and the light receiving element are integrated in one package, the semiconductor laser and the light receiving element are usually positioned and fixed on the stem in the package. In many cases, position and rotation cannot be adjusted. That is, in many cases, offset adjustment of, for example, a focus error signal or a tracking error signal caused by a mounting error of a semiconductor laser or a light receiving element or a shape tolerance of a hologram element mounting surface is performed only by adjusting the hologram element. In such a case, if the hologram element is adjusted to match one of the semiconductor laser light sources, there is a high possibility that the hologram element will deviate from the optimal state when used with another semiconductor laser light source. That is, the servo error signal cannot be optimally adjusted only by adjusting the position of the hologram element at the time of assembling, or the mounting tolerance of the semiconductor laser and the light receiving element, the processing tolerance of the package, and the like need to be extremely strict, resulting in an increase in cost.

The hologram element often includes an aberration correction function in order to obtain a desired light-collecting characteristic on the light receiving element. However, the hologram element performs optimal aberration correction for a plurality of different wavelengths. Pattern design is also difficult.

Further, in the above-mentioned conventional optical pickup,
Any of the semiconductor laser beams of a plurality of wavelengths can detect only a tracking error signal by the three-beam method, and cannot be applied to optical disks of different standards using different tracking error signals.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a compatible optical pickup which can cope with a plurality of optical discs of different standards for recording and reproducing by using light beams of different wavelengths, is easy to assemble and adjust, and is suitable for compact integration. It is assumed that.

[0016]

According to the first aspect of the present invention, there is provided an optical pickup device which emits a light beam having a first wavelength.
And a second light source that emits a light beam of a second wavelength different from the first wavelength, diffracts the light beam of the first wavelength to the light receiving element, and A first hologram element that does not substantially diffract the light beam, a second hologram element that diffracts the light beam of the second wavelength and guides the light beam to the light receiving element, and that does not substantially diffract the light beam of the first wavelength; It is provided with.

An optical pickup device according to claim 2 is
A first light source that generates a light beam of a first wavelength, a second light source that generates a light beam of a second wavelength different from the first wavelength, and at least one of a first light source and a second light source A beam splitting diffraction grating arranged in an optical path of light emitted from one side to the optical disk and splitting light of at least one of the first wavelength and the second wavelength into three beams; The light emitted from the second light source is arranged in the optical path to the optical disk, and the light of the first wavelength reflected from the optical disk is diffracted and guided to the light receiving element, and the light of the second wavelength that is not diffracted is diffracted. A first hologram element, and light of a second wavelength, which is disposed in an optical path to the optical disc of light emitted from the first light source and the second light source, reflected from the optical disc, and transmitted through the first hologram element. Is diffracted to the light receiving element and the first wavelength A second hologram element which does not diffract, those having a.

An optical pickup device according to claim 3 is
3. The optical pickup device according to claim 1, wherein the first and second hologram elements have a 0th-order diffraction efficiency and a 1st-order diffraction efficiency with respect to the first and second wavelengths, respectively.
It is formed so that the product of the first-order or the first-order diffraction efficiency is maximized.

An optical pickup device according to claim 4 is
4. The optical pickup device according to claim 1, wherein the first hologram element and the second hologram element are formed on the first substrate and the second substrate so as to be independently adjustable. Is what is being done.

According to a fifth aspect of the present invention, there is provided an optical pickup device comprising:
4. The optical pickup device according to claim 1, wherein the first and second hologram elements are respectively formed on a first substrate and a second substrate that are stacked on substantially the same optical axis. The hologram element formed on the surfaces of the first substrate and the second substrate that are in contact with each other has a hologram formation portion formed lower than the surrounding substrate surface.

The optical pickup device according to claim 6 is
4. The optical pickup device according to claim 1, wherein the first and second hologram elements are respectively formed on a first substrate and a second substrate that are stacked on substantially the same optical axis. One of the first hologram element and the second hologram element is formed on a surface of the first substrate and the second substrate that are in contact with each other, and the other of the first hologram element and the second hologram element on the substrate on which the other hologram element is formed. A concave portion is formed at a portion facing the hologram element.

According to a seventh aspect of the present invention, there is provided an optical pickup device comprising:
4. The optical pickup device according to claim 1, wherein the first and second hologram elements are respectively formed on a first substrate and a second substrate arranged on substantially the same optical axis. In this case, the first substrate and the second substrate are stacked via a spacer.

The optical pickup device according to claim 8 is
3. The optical pickup device according to claim 2, wherein the first and second hologram elements are respectively formed on a first substrate and a second substrate arranged on substantially the same optical axis. The beam splitting diffraction grating is formed on the surface opposite to the surface on which the second hologram element is formed.

According to a ninth aspect of the present invention, in the optical pickup device,
The optical pickup device according to any one of claims 1 to 8, wherein the first light source is a red laser in a 650 nm band, the second light source is an infrared laser in a 780 nm band,
The groove depth of the first hologram element is 1.7 to 1.8 μm
And the groove depth of the second hologram element is 1.3 to 1.4 μm.
m.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. The same components as those in the conventional example are denoted by the same reference numerals.

In the following embodiment, 650 nm
An optical pickup device that has two light sources (semiconductor lasers) that emit light beams in a band and a 780 nm band, and divides only the light in the 780 nm band into three beams and irradiates the optical disk with the light will be described. However, the present invention is not limited to this, and the irradiation wavelength, the number of light beams, and the like can be appropriately changed.

<First Embodiment> FIG. 1 is a schematic diagram showing a configuration of an optical pickup device according to a first embodiment of the present invention. This pickup has basically the same configuration as that of FIG. 12, and the same components as those of FIG. 12 are denoted by the same reference numerals.

In this optical pickup, a first semiconductor laser 1 oscillating in a 650 nm band and a second semiconductor laser 2 oscillating in a 780 nm band are arranged close to each other to generate three beams for tracking control. A diffraction grating 3, a first hologram element 12 that diffracts only the light of the first semiconductor laser, a second hologram element 11 that diffracts only the light of the second semiconductor laser, a collimator lens 13,
An objective lens 6 and a light receiving element 14 are provided.

The three-beam diffraction grating 3, the first hologram element 12, and the second hologram element 11 are arranged as follows. That is, the diffraction grating 3 is formed below the transparent substrate 16 and the hologram element 11 is formed above. The hologram element 12 is formed above another transparent substrate 17. And the laser package 15
The transparent substrate 16 is adjusted and fixed on the laser emission surface of the above, and the transparent substrate 17 is adjusted and fixed thereon. Here, one hologram element and a diffraction grating are formed on both surfaces of one substrate, and the other hologram element is formed on one surface of the other substrate.
The number of parts can be reduced.

FIG. 2A is a diagram showing an operation when reproducing an optical disk with the first semiconductor laser 1 in the 650 nm band. The light emitted from the semiconductor laser 1 passes through the diffraction grating 3 and the hologram elements 11 and 12, is converted into parallel light by the collimator lens 13, then is condensed on the optical disk 7 by the objective lens 6, reflected, and returned. The light is diffracted by the hologram element 12 and guided to the light receiving element 14.

FIG. 2B is a diagram showing an operation when reproducing an optical disk with the second semiconductor laser 2 in the 780 nm band. The light emitted from the semiconductor laser 2 is a diffraction grating 3
Are divided into three beams, transmitted through the hologram elements 11 and 12, collimated by a collimator lens 13, then condensed on a disk 7 by an objective lens 6, reflected by the hologram element 11, and returned. Is diffracted by the light receiving element 14
It is led to.

The hologram elements 11 and 12 are designed so that return light to the light beams from the semiconductor lasers 2 and 1 can obtain desired light-collecting characteristics on the light receiving element 14.

Next, the hologram element 1 of the present embodiment
1 and 12 will be described. Wavelength selectivity of hologram element The diffraction efficiency of a rectangular hologram element was measured by using FIGS.
Shown in The diffraction efficiency of a rectangular hologram having the same groove width and land width as the groove depth t, the wavelength λ, and the refractive index n of the transparent substrate is: 0th-order diffraction efficiency (transmittance) η ₀ = (cos △ φ) ² ± First-order diffraction efficiency η ₁ = (2 / π × sin △ φ) ² (where △ φ = πt (n−1) / λ).

FIG. 3 shows the relationship between the 0th-order and ± 1st-order diffraction efficiencies and the groove depth at wavelengths of 650 nm and 780 nm. FIG. 4 shows the relationship between the product of the 0th-order diffraction efficiency and the ± 1st-order diffraction efficiency (reciprocation efficiency) and the groove depth. In addition,
Here, the hologram glass is made of quartz n = 1.457 (λ =
650 nm) and n = 1.454 (λ = 780 nm).

In this embodiment, one of the hologram elements diffracts as much light as possible with respect to the light beam of each wavelength and guides it to the light receiving element so as to increase the light utilization efficiency, and the other hologram. It is necessary to set the groove depth so that the element hardly diffracts light (that is, minimizes stray light).

Accordingly, for example, the depth of the groove of the hologram element 12 for diffracting only the light of the first semiconductor laser 1 having a wavelength of 650 nm is set to be approximately zero when the diffraction efficiency at 650 nm becomes almost zero and the diffraction efficiency becomes large at 780 nm in FIG. 1.
4 μm, the groove depth of the hologram element 11 for diffracting only the light of the second semiconductor laser 2 having a wavelength of 780 nm is shown in FIG.
At 780 nm, the diffraction efficiency at 780 nm becomes almost 0 and 650 n
It is sufficient to set the thickness to about 1.4 μm, where the diffraction efficiency increases with m.

At this time, the reciprocating use efficiency of the light beam of the first semiconductor laser 1 having the wavelength of 650 nm by the hologram element 12 is about 9%, and the wavelength of 780 nm by the hologram element 11 is used.
The reciprocal use efficiency of the light beam of the second semiconductor laser 2 of about 8 nm is about 8%, and the diffraction efficiency at the other wavelength in each of the hologram elements 11 and 12 is almost 0, so that loss of light amount and generation of stray light do not occur. . Even if processing tolerances are taken into consideration, if the groove depth of the hologram element 12 is set to 1.7 to 1.8 μm and the groove depth of the hologram element 11 is set to 1.3 to 1.4 μm, practical-level characteristics can be obtained. Is obtained.

The diffraction grating 3 for three beams has a groove depth of 1.4 μm, so that the light having a wavelength of 780 nm has a main beam (0-order transmittance) of 72% and a sub-beam (± 1 order diffraction). With an efficiency of 12%, an appropriate three-beam light amount ratio can be obtained. At this time, the diffraction efficiency for light of 650 nm is almost zero, and is hardly affected.

FIG. 5 shows a division pattern of the hologram element 12 for diffracting only the light of the first semiconductor laser 1 and a division pattern of the light receiving element 14. .

The hologram element 12 is divided into four cruciform parts 12a with the substantial center of the return light beam as the origin.
There are four divided areas 12b, 12c and 12d. Further, the light receiving element 14 has two divided light receiving areas (1
4a, 14b), (14c, 14d) and other areas 1
There are six regions 4e and 14f.

As shown in FIG. 5 (a), when in the focused state,
The return light diffracted by the divided region 12a of the hologram element 12 forms a beam P1 on a division line 141 extending in the x direction of the two divided light receiving regions (14a, 14b), and the divided region 1
The return light diffracted by 2d is divided into two light receiving areas (14c, 1c).
The beam P2 is formed on the dividing line 14m extending in the x direction of 4d), and the divided regions 12c and 12b form the beams P3 and P4 on the light receiving regions 14f and 14e, respectively.

When the optical disk 7 relatively approaches the objective lens 6 from the in-focus state, the beams P1 and P2 respectively receive the light receiving areas 14a or 14a as shown in FIG.
Increases to the c side. On the other hand, on the other hand, if you move away relatively,
(C) As shown in FIG.
Become larger on the side. Utilizing this property, the focus error signal FES can be detected by the knife edge method by calculating FES = (Sa + Sc)-(Sb + Sd).

On the other hand, the tracking error signal TES indicates that Sa and S on a read-only disc on which uneven pits are formed.
By comparing the phase of the sum signal of b and Sf with the phase of the sum signal of Sc, Sd and Se, it can be detected by the phase difference method. In addition, (Sa + Sb + Se)-(Sc
TES by the push-pull method can also be detected by the operation of + Sd + Sf). Further, one side of the beam, that is, the divided regions 12b and 12c or the divided region 12b
It is also possible to generate a TES by a phase difference method or a push-pull method using only one of the light beams a and 12d.

The information reproduction signal is obtained from the sum of all output signals.

Next, a division pattern of the hologram element 11 for diffracting only the light of the second semiconductor laser and a signal detection method thereof will be described with reference to FIG. The light receiving element 1
4 is the same.

The hologram element 11 has two divided areas 11a and 11b which are divided into two by a dividing line in the X direction. Further, since the diffraction grating 3 for three beams is provided below the hologram element 11 as described with reference to FIG.
The outward beam from the laser to the disk is split into three substantially along the Y direction, and the return light also returns at an angle in the Y direction.

As shown in FIG. 6A, as for the return light of the main beam, the light diffracted by the divided area 11a of the hologram element 11 in the focused state is divided into two divided light receiving areas (14).
a, 14b), a beam P1 is formed on a division line 141 extending in the x direction, and the light diffracted in the division region 11b is divided into two division light receiving regions (14c, 14d) extending in the x direction.
A beam P2 is formed 4 m above. As for the return light of the + 1-order sub-beam, the light diffracted by the divided areas 11a and 11b of the hologram element 11 is the light receiving area 1
Beams P3 and P4 are formed on the light receiving area 14e, and the light diffracted by the divided areas 11a and 11b of the hologram element 11 is returned to the -1st order sub-beam.
The beams P5 and P6 are formed on f.

When the optical disk 7 is in focus and the objective lens 6
When approaching relatively to the side, beams P1 and P2
As shown in (b), the light receiving area 14b or 14c
Become larger on the side. Conversely, when the distance increases, FIG.
(C) As shown in FIG.
Become larger on the side.

Therefore, the focus error signal FES can be detected by the calculation of FES = Sa-Sb or FES = Sc-Sd when the single knife edge method is used by utilizing the above-mentioned property.

When the double knife edge method is used, it can be detected by the calculation of FES = (Sb + Sc)-(Sa + Sd).

The tracking error signal TES is expressed by S
The TES by the three-beam method can be detected by the calculation of e-Sf.

Adjustment of Hologram Elements 11 and 12 An adjustment of the FES offset which is important in the adjustment of the hologram element 12 will be described. FIGS. 7A and 7B show the hologram element 12 and the light receiving elements 14a and 14 for FES detection.
Only the parts b, 14c and 14d are displayed. At the time of design, as shown in FIG. 5A, in the focused state, the light diffracted by the divided region 12a of the hologram element 12 is split on the dividing line 141 extending in the x direction of the two-divided light receiving regions (14a, 14b). A beam P1 is formed so as to be focused on the light receiving area (14c, 1c).
The beam P2 is formed so as to converge on a division line 14m extending in the x direction of 4d).

However, in an actual hologram / laser integrated package, the relative position between the hologram, the laser chip, and the light receiving element is more than a designed value due to a mounting error of the laser chip or the light receiving element or a processing error of the package or the stem. It is out of range. Therefore, FIG.
As shown in (a), the condensed beams P1 and P2 deviate from the division line, or deviate from the condensed state and become larger. Therefore, FES = (Sa + Sc) − (Sb +
The FES calculated in Sd) causes an offset even when the objective lens is in focus.

Therefore, as shown in FIG. 7B, the hologram element 12 is rotated in a plane perpendicular to the optical axis to move the beams P1 and P2 on the dividing line, thereby obtaining the FES.
Is adjusted so that the offset of is zero.

The same adjustment is performed for the hologram element 11. FIGS. 8A and 8B show the hologram element 11.
And FES detection light receiving elements 14a, 14b, 14c, 1
Only the portion of 4d is displayed. This is FES 14a
This is an example in the case of using the single knife edge method of detecting the difference between the output of the hologram 12 and the output 14b.

In this embodiment, 650 nm and 7
Two 80 nm laser chips are arranged close to each other. When this is fixed to a stem (not shown), the position of each chip is shifted with a certain tolerance range, or the position of the laser emission point or the emission angle varies, but each hologram element (11, 12) is different. ), The FES offset adjustment is performed, so that the optimum adjustment can be performed independently for each semiconductor laser (1, 2).

Shape of Hologram Element In the above optical system, as shown in FIG. 9A, two transparent substrates on which the hologram elements 11, 12 and the diffraction grating 3 are formed are mounted on top of each other, and the position and rotation are adjusted. FIG. When a hologram is formed on a glass substrate by etching or the like, the upper surface of the land portion of the hologram element 11 and the portion 11 'where the hologram is not formed, and the upper surface of the land portion of the diffraction grating 3 and the portion 3' where the hologram is not formed are on the same plane. It has become. Although the upper surface of the laser package 15 to which the transparent substrate 16 is attached, that is, the emission surface of the laser beam, does not normally contact the portion where the diffraction grating 3 is located as shown in FIG. 9A, there is no problem. 1
The microstructure of the hologram element 11 formed on the upper surface of 6 may be damaged when the transparent substrate 17 is overlaid. The following is an example of taking measures against this.

FIG. 9B shows a case where the hologram element 11 is formed on the transparent substrate 16. In the case of a glass substrate, the hologram formation portion is first dug down by etching or the like, and then the hologram is formed, or the land portion is made the same. They are further removed from the surface and dug down. Also, in the case of molding using a plastic or glass material, it is only necessary to form the mold so that the peripheral portion is higher than the hologram element portion.

FIG. 9C shows an example in which the lower side of the transparent substrate 17 is dug down. This is because it is not necessary to change a complicated manufacturing method of the hologram element 11, so that highly accurate processing can be easily performed.

FIG. 9D shows a state where the two transparent substrates 16 and 17 are fixed with a spacer interposed therebetween. Thus, even when the transparent substrate on which the two hologram elements are formed is overlaid and fixed, the hologram formed on the portion sandwiched between them is not damaged during adjustment.

As described above, in the optical pickup device of this embodiment, the first semiconductor laser 1 that oscillates in the 650 nm band and the second semiconductor laser 2 that oscillates in the 780 nm band are arranged close to each other. A three-beam diffraction grating 3 for generating three beams for tracking control, a hologram element 11 for diffracting only the light of the second semiconductor laser,
The hologram element 12, which diffracts only the light of the first semiconductor laser, is arranged in this order. However, the arrangement is not particularly required, and the hologram elements 11 and 12 may be formed on separate substrates. However, the three-beam diffraction grating 3 that generates three beams for tracking control that diffracts only the light of the second semiconductor laser 2 and the hologram element 11 are positioned and formed on both sides of one transparent substrate, and are adjusted. This is advantageous because there is no necessity.

Further, the TES is not used by using the three-beam
When a signal is detected by a beam, a three-beam diffraction grating is not required.

<Second Embodiment> FIG. 10 is a schematic diagram showing a configuration of a second embodiment. The configuration of the optical pickup is basically the same as that of the first embodiment (FIG. 1), but the mounting method of the semiconductor laser chip is different. This part will be described with reference to FIG. The same components are denoted by the same reference numerals.

In the first embodiment, two different wavelength laser chips are mounted close to each other. However, the laser chip has a width of 10 in the direction perpendicular to the optical axis.
Since the distance is about 0 to 300 μm, the distance between the light emitting points is further increased, and in the optical system shown in FIG. 1, the optical axis is inclined by two different wavelength laser beams. The aberration generated due to the tilt of the optical axis is designed to be reduced to some extent by the collimator lens and the objective lens. However, if the distance between the light emitting points is increased, the characteristics of the pickup become a problem.

Therefore, in the present embodiment, a prism is used to match the optical axes of the light beams from different laser chips. As shown in FIG.
6, a first semiconductor laser 1 and a second semiconductor laser 2 are attached at a distance d1 from each other.
Beam splitter 21 consisting of three members b and 21c
Is provided. It has two reflecting surfaces 19 and 20, and the separating surface 19 has a structure that reflects the light of the second semiconductor laser and transmits the light of the first semiconductor laser. Although the characteristics of the separation surface have wavelength selectivity, when the polarization directions of the two are different, a polarization beam splitter may be used. Each reflecting surface is inclined by 45 ° with respect to the optical axis, and d1
The member 2 has a distance in the optical axis direction between the reflecting surfaces corresponding to
By setting the plate thickness of 1b, two light beams emitted from the first and second semiconductor lasers can coincide with the same optical axis.

The first semiconductor laser 1 and the second semiconductor laser 2 can be arranged at any positions on the stem as long as they are on the first optical axis 22 and the second optical axis 23, respectively. After being combined by the beam splitter 21, the beam becomes the same optical axis. Therefore, it is possible to shift one laser from the focal position of the collimator lens and use it as divergent light or convergent light.

As a result, it is possible to support a plurality of optical discs of different standards for recording and reproducing using light beams of different wavelengths, and to realize a compatible optical pickup which is easy to assemble and adjust and suitable for compact integration.

<Third Embodiment> FIG. 11 shows a third embodiment.
FIG. 3 is a schematic diagram showing a main part of the optical pickup device of FIG. The configuration of the optical pickup is basically the same as that of the first embodiment (FIG. 1), except for the method of attaching the semiconductor laser chip and the configuration of the combining prism of the two semiconductor laser beams. In FIG. 11, the same components as those in FIG. 1 are denoted by the same reference numerals.

In the first and second embodiments, since the two hologram elements 11 and 12 are arranged substantially on the same optical axis, the three-beam diffraction grating 3 and the hologram are used to improve light use efficiency and remove stray light. It is necessary to set the groove depth of the element 11 so as to diffract only the light of the second semiconductor laser 2 and the hologram element 12 so as to diffract only the light of the first semiconductor laser 1. there were. In this case, there are problems that the groove depth becomes deeper than usual and the processing tolerance becomes strict.

The present embodiment solves the above-mentioned problem, that is, two-dimensionally without using a wavelength-selective hologram.
The present invention relates to an optical pickup device capable of detecting light beams from two different lasers with a common light receiving element and making the optical axes coincide with each other. As shown in FIG. Second semiconductor laser 2
Are mounted separately, and the light receiving element 14 is arranged therebetween.

In this embodiment, the transparent substrate 1
6, 17 are arranged separately on each laser chip,
Therefore, each of the hologram elements 11 and 12 can be configured so that only one light beam passes. Then, the zero-order transmitted light transmitted through each hologram element is combined on the same optical axis by the prism 25 having the reflection mirror surface 25a and the beam splitter 24 having the separation surface 24a. The light beams reflected and returned from the disk are individually and independently adjusted in position and rotation of the hologram element 11,
At 12, the light is guided to a common light receiving element 14.

With this configuration, it is possible to cope with a plurality of optical discs of different standards for recording and reproducing using light beams of different wavelengths without using a wavelength-selective hologram element, which is difficult to manufacture, and it is easy to assemble and adjust, and small in size. It is possible to realize a compatible optical pickup suitable for realization.

[0073]

According to the present invention, in an optical pickup device capable of compatible recording or reproduction of an optical disk having different irradiation light beam wavelengths, the hologram element can be adjusted independently for each wavelength light beam. Because it is possible,
Optimal assembly adjustment for the light of each light source can be easily realized. As a result, there is a margin in the mounting tolerance of the laser and the light receiving element and the processing tolerance of the package, so that the cost can be reduced. In addition, with the same light receiving element shape, 3
Different tracking error signals of the beam method and the phase difference method or the push-pull method can be detected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an optical system of an optical pickup device according to a first embodiment of the present invention.

FIG. 2 is a reproduction optical system in which a first or second semiconductor laser is used in the optical pickup device of FIG. 1;

FIG. 3 shows the hologram groove depth and diffraction efficiency (0 order and ±
It is a calculation result showing the relationship of (primary).

FIG. 4 is a calculation result showing a relationship between a groove depth of a hologram and diffraction efficiency (product of 0th order and ± 1st order).

FIG. 5 is a diagram illustrating a division pattern of a first hologram element and a light receiving element.

FIG. 6 is a diagram illustrating a division pattern of a second hologram element and a light receiving element.

FIG. 7 is a diagram illustrating adjustment of a first hologram element.

FIG. 8 is a diagram illustrating adjustment of a second hologram element.

FIG. 9 is a diagram illustrating the shapes of two hologram element substrates.

FIG. 10 is a schematic configuration diagram illustrating an optical system of an optical pickup device according to a second embodiment of the present invention.

FIG. 11 is a schematic configuration diagram illustrating an optical system of an optical pickup device according to a third embodiment of the present invention.

FIG. 12 is a schematic configuration diagram showing an optical system of a conventional optical pickup device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first semiconductor laser 2 second semiconductor laser 3 3 beam diffraction grating 5 grating lens 6 objective lens 7 disk 8 hologram element 9 light receiving element 11 second hologram element 12 first hologram element 13 collimator lens 14 light receiving element 15 Laser package 16 Transparent substrate 17 Transparent substrate 18 Spacer

Claims (9)

[Claims] A first light source that emits a light beam having a first wavelength; a second light source that emits a light beam having a second wavelength different from the first wavelength; and light having a first wavelength. A first hologram element that diffracts the light beam and guides the light beam of the second wavelength and does not substantially diffract the light beam of the second wavelength; and diffracts the light beam of the second wavelength and guides the light beam to the light receiving element. An optical pickup device, comprising: a second hologram element that does not substantially diffract a light beam of one wavelength. 2. A first light source for generating a light beam of a first wavelength, a second light source for generating a light beam of a second wavelength different from the first wavelength, a first light source and a second light source. A beam splitting diffraction grating that is disposed in an optical path of at least one of the two light sources to the optical disc and splits light of at least one of the first wavelength and the second wavelength into three beams; The light emitted from the second light source and the light emitted from the second light source are arranged in the optical path to the optical disk. The light having the first wavelength reflected from the optical disk is diffracted and guided to the light receiving element. A first hologram element that does not diffract light, and a second hologram element that is disposed in the optical path of the light emitted from the first light source and the second light source to the optical disk, is reflected from the optical disk, and transmits through the first hologram element. While diffracting light of the wavelength and guiding it to the light receiving element, Optical pickup apparatus comprising: the second holographic element which does not diffract light of a wavelength, the. 3. The optical pickup device according to claim 1, wherein the first and second hologram elements respectively have a 0th-order diffraction efficiency and a 1st-order diffraction efficiency for light of the first and second wavelengths. An optical pickup device characterized in that the product is formed so as to maximize the product of first-order or -1st-order diffraction efficiency. 4. The optical pickup device according to claim 1, wherein the first hologram element and the second hologram element are independently provided on the first substrate and the second substrate, respectively. An optical pickup device, which is formed so as to be adjustable. 5. The optical pickup device according to claim 1, wherein the first and second hologram elements are a first substrate, a second hologram element, and a second hologram element that are stacked on substantially the same optical axis. The hologram element formed on each of the substrates and formed on the surfaces of the first and second substrates that are in contact with each other is characterized in that the hologram formation portion is formed lower than the surrounding substrate surface. Optical pickup device. 6. The optical pickup device according to claim 1, wherein the first and second hologram elements are composed of a first substrate, a second substrate, and a second hologram element that are stacked on substantially the same optical axis. One of the first hologram element and the second hologram element is formed on a surface of the first substrate and the second substrate that are in contact with each other, and the other hologram element is formed on the first substrate and the second substrate. An optical pickup, wherein a concave portion is formed in a portion of the substrate facing the one hologram element. 7. The optical pickup device according to claim 1, wherein the first and second hologram elements are a first substrate and a second hologram element which are arranged on substantially the same optical axis. An optical pickup formed on each of substrates, wherein the first substrate and the second substrate are laminated via a spacer. 8. The optical pickup device according to claim 2, wherein the first and second hologram elements are respectively formed on a first substrate and a second substrate arranged on substantially the same optical axis. An optical pickup device, wherein the beam splitting diffraction grating is formed on a surface of a second substrate opposite to a surface on which a second hologram element is formed. 9. The optical pickup device according to claim 1, wherein the first light source is a red laser of 650 nm band, the second light source is an infrared laser of 780 nm band, An optical pickup wherein the groove depth of the first hologram element is set to 1.7 to 1.8 μm and the groove depth of the second hologram element is set to 1.3 to 1.4 μm.