JPH11185282A - Optical pickup and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a small-sized, light and inexpensive optical pickup with simple constitution and to record/reproduce correctly two kinds of optical disks with e.g. wavelengths and strength, etc., different from each other. SOLUTION: A light source 21 is provided with first, second light emitting elements 21a-21b arranged side by side at minute intervals on a semiconductor substrate and emitting light beams with the wavelengths different from each other, and a photodetector 25 is provided with light receiving parts respectively answering to the light beams from respective light emitting elements 21a-21b. Together with that, a light division means (phase diffraction grating) 22 diffracting only the light from one side light emitting element is provided between the light source 21 and an objective lens 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device for irradiating different types of light to the surface of a rotating optical disk corresponding to two types of optical disks and detecting return light, and a light emitting / receiving device. The present invention relates to an element, an optical pickup and an optical disk device using the same.

[0002]

2. Description of the Related Art Conventionally, in an optical pickup for reproducing two types of optical disks, for example, a compact disk (CD) and a high-density optical disk, in order to cope with the reproduction of a CD-R, for example, 650 nm and 7 nm.
There is a need for a two-wavelength optical pickup with two wavelengths of 80 nm. Such a two-wavelength optical pickup is configured, for example, as shown in FIG.

In FIG. 7, an optical pickup 1 is actually composed of two sets of optical pickups, and in the case shown in the figure, a first optical pickup 2 for reproducing a first type of optical disc D1 such as a CD. Is, for example, a wavelength of 780 n
It comprises a semiconductor laser element 2a that emits m light, a grating 2b, a beam splitter 2c, an objective lens 2d, and a photodetector 2e. A second optical pickup 3 for reproducing a second type of optical disk D2 such as a high-density optical disk includes a semiconductor laser element 3a that emits light having a wavelength of 650 nm, a beam splitter 3b, an objective lens 3c, and a photodetector 3d. It is configured.

First, with respect to the first optical pickup 2, the grating 2b is a diffraction grating, and converts a light beam from the semiconductor laser element 2a into a main beam which is a zero-order light and a secondary beam which is a ± first-order light. Split into two side beams. The beam splitter 2c is disposed with its reflection surface inclined at 45 degrees with respect to the optical axis, and separates the light beam emitted from the semiconductor laser element 2a from the return light from the signal recording surface of the optical disc D1. That is, the light beam from the semiconductor laser element 2a is reflected by the reflection surface of the beam splitter 2c, and the return light from the optical disc D1 passes through the beam splitter 2c.

[0005] The objective lens 2d is a convex lens, and forms an image of the light beam reflected by the beam splitter 2c on a desired track on the signal recording surface of the optical disk D1 that is driven to rotate. Further, the objective lens 2d is supported by a biaxial actuator (not shown) so as to be movable in a biaxial direction, that is, a focusing direction and a tracking direction. The photodetector 2e includes a light receiving unit for the return light beam that passes through and enters the beam splitter 2c.

According to the first optical pickup 2 having such a configuration, the light beam emitted from the semiconductor laser element 2a is split into a main beam and two side beams by the grating 2b, and then is split into the beam splitter 2c.
After being reflected by the reflecting surface, an image is formed at a certain point on the signal recording surface of the first type optical disc D1 via the objective lens 2d. The return light beam reflected on the signal recording surface of the optical disc D1 again enters the beam splitter 2c via the objective lens 2d. Where the return light beam is
The light passes through the beam splitter 2c and enters the light receiving portion of the photodetector 2d. Thereby, based on the detection signal output from each light receiving section of the photodetector 2d, the information recorded on the signal recording surface of the optical disc D1 is reproduced, and
A focus error signal and a tracking error signal are detected. In this case, the tracking error signal is detected by a so-called three spot method.

The second optical pickup 3 has a configuration in which the grating 2b is omitted as compared with the first optical pickup 2, and the light emitted from the semiconductor laser element 3a as a light source is The wavelengths are different.

According to the optical pickup 3, the light beam emitted from the semiconductor laser element 3a is reflected by the reflecting surface of the beam splitter 3b, and passes through the objective lens 3c to the signal recording surface of the second type optical disk D2. An image is formed at a certain point above. The return light beam reflected on the signal recording surface of the optical disk D2 again passes through the objective lens 3c.
The light enters the beam splitter 3b. Here, the return light beam is transmitted through the beam splitter 3b and is detected by the photodetector 3c.
Incident on the light-receiving part of. Thereby, based on the detection signal output from each light receiving section of the photodetector 3c, the optical disc D
The information recorded on the signal recording surface 2 is reproduced, and the focus error signal and the tracking error signal are detected. In this case, the tracking error signal is obtained by a push-pull method using one spot or a DPD.
Method.

[0009]

By the way, in the optical pickup 1 described above, two types of optical discs D are used.
Since dedicated optical pickups 2 and 3 are required to reproduce the signals D1 and D2, two sets of optical pickups 2 and 3 are incorporated, and the beam splitters 2c and 3b and the objective lenses 2d and 3c are assembled. For example, the number of parts is increased, and the size and weight of the optical pickup 1 as a whole are increased, resulting in an increase in cost.

The present invention has been made in view of the above points, and has a simple structure that is small in size, light in weight, and low in cost. In addition, recording and reproduction of two types of optical disks having different wavelengths and intensities are performed correctly. , An optical pickup and an optical disk device.

[0011]

According to the present invention, there is provided a light source for irradiating a light beam emitted from the light source so as to be focused on a signal recording surface of a rotationally driven optical disk. Focusing means, a photodetector on which a return light beam from the signal recording surface of the optical disk is incident, and light separation means for separating the return light beam from the light beam from the light source, wherein the light source is a semiconductor substrate. The first and the second light emitting element that are formed side by side at a minute interval from each other and emit light beams of different wavelengths from each other, the photodetector,
A light receiving unit corresponding to the light beam from each light emitting element is provided, and a light splitting means for diffracting only light from one light emitting element, preferably a phase diffraction grating, is provided between the light source and the objective lens. This is achieved by an optical pickup provided.

According to the above arrangement, when reproducing an optical disk of the first kind, a light beam emitted from one of the light emitting elements of the light source is split into three beams by the light splitting means. , Focuses on the signal recording surface of the first type of optical disk, and the return light beam from this optical disk again enters the photodetector via the objective lens and the light separating means. Thus, the reproduction signal, the tracking error signal, and the focus error signal of the first type optical disk are detected by the so-called three spot method based on the detection signal from the photodetector.

Similarly, when reproducing the second type of optical disk, the light beam emitted from the other light emitting element of the light source passes through the light splitting means and passes through the light separating means and the objective lens. Focuses on the signal recording surface of the second type of optical disc, and the return light beam from this optical disc is
The light again enters the photodetector via the objective lens and the light separating means. As a result, based on the detection signal from the light receiving unit, the reproduction signal, the tracking error signal, and the focus error signal of the second type optical disc are detected by the so-called differential push-pull method.

In this case, in both types of optical discs, a common light separating means, a light focusing means, and a photodetector are used, so that the two types of optical discs can be reproduced with a simple configuration. In addition, the light source is substantially the same size as a conventional light source having only one light-emitting element, and is provided with two light-emitting elements. The whole device is configured to be small and lightweight. Further, for reproducing two types of optical discs, the light sources are provided with corresponding light emitting elements, and the other optical systems are commonly used. As a result, it is configured to be small and lightweight.

In the case where the first and second light emitting elements are constituted by a single package, and the light dividing means is mounted on the package, the light source and the light dividing means are constituted by one component. As a result, mutual optical adjustment of these optical elements becomes unnecessary, and assembly is facilitated.

As the light source, a light emitting / receiving element having two light emitting elements is provided, and a light receiving portion of the light receiving / emitting element is configured to receive a return light beam of one of the light emitting elements. When the light separating means is configured to transmit the return light beam for one light emitting element and reflect the return light beam for the other light emitting element, Since the emitted light beam is not diffracted by the light splitting means, even if the returned light passes through the light splitting means again via the light splitting means, it is incident on the light receiving portion of the light receiving and emitting element without being diffracted. Therefore, accurate reproduction with a small amount of light loss can be performed with a simple configuration.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows the configuration of an optical disk device incorporating an optical pickup according to an embodiment of the present invention. In FIG. 1, an optical disk device 10 includes a spindle motor 12 as a driving unit that rotationally drives an optical disk 11, and an optical pickup 13. here,
The spindle motor 12 is driven and controlled by an optical disk drive controller 14 and is rotated at a predetermined rotation speed. The optical disc 11 can select and reproduce a plurality of types of optical discs.

The optical pickup 13 irradiates the signal recording surface of the rotating optical disk 11 with light to record a signal or to detect return light from the signal recording surface. A reproduced signal based on the return light is output to the signal demodulator 15.

As a result, the recording signal demodulated by the signal demodulator 15 is subjected to error correction through an error correction circuit 16 and sent to an external computer or the like via an interface 17. With this, the external computer etc.
A signal recorded on the optical disk 11 can be received as a reproduction signal.

The optical pickup 13 is connected to a head access control unit 18 for moving the optical pickup 13 to a predetermined recording track on the optical disk 11 by a track jump or the like. Further, a servo circuit 19 for moving the objective lens in the focusing direction and the tracking direction is connected to the biaxial actuator holding the objective lens of the optical pickup 13 at the moved predetermined position.

FIG. 2 shows a first embodiment of the optical pickup according to the present invention. In FIG. 2, an optical pickup 13 is an optical pickup corresponding to two wavelengths, and includes a light source 21, a phase diffraction grating 22 as a light splitting unit, and a beam splitter 23 as a light separating unit.
And an objective lens 24 as a light focusing means, and a photodetector 2
5 is provided.

The light source 21 is integrally formed so that two semiconductor laser elements 21a and 21b as light emitting elements are arranged close to each other and substantially on the same optical axis. Each of the semiconductor laser elements 21a and 21b is a light-emitting element using recombination light emission of a semiconductor, and one of the semiconductor laser elements 21a is, for example, a CD or a CD-R.
A laser beam having a wavelength of 780 nm for reproduction is emitted, and the other semiconductor laser element 21b emits a laser beam having a wavelength of 650 nm for reproduction of a high-density recording optical disk, for example.

As shown in FIG. 3, the phase diffraction grating 22 is formed by forming a grating 22b on one surface of a substrate 22a, and serves as a diffraction grating for light from one semiconductor laser element 21a. It is configured to act and transmit light from the other semiconductor laser element 21b as it is, preferably, for example, to have a phase of 2π for light having a short wavelength (light of 650 nm). Here, specifically, when the refractive index of the material of the grating is N and the depth of the grating is d, the phase diffraction grating is N × d
= 650 nm, the refractive index N and the depth d are selected. For example, the refractive index N =
In the case of 1.5, the depth d of the grating 22b is 433 nm. In this case, the phase difference is 780 nm for the light from one semiconductor laser element 21a.

(Equation 1) When the grating 22b is a rectangular grating, the diffraction efficiency of the plus or minus first-order light is

(Equation 2) Therefore, it is a sufficient value.

The objective lens 24 is a convex lens, and converts the light beam from each of the semiconductor laser elements 21a and 21b into a signal of the optical disk 11 that is rotationally driven, that is, the optical disk D1 of the first type or the optical disk D2 of the second type. An image is formed on a desired track on the recording surface. Further, the objective lens 23 is supported by a biaxial actuator (not shown) so as to be movable in biaxial directions, that is, in a tracking direction and a focusing direction.

The photodetector 25 has a light receiving portion for each of the return light beams from the signal recording surface of the optical disk 11. That is, the photodetector 2
Numeral 5 includes a light receiving portion appropriately divided so as to detect a tracking error signal by the three-spot method with respect to return light from one semiconductor laser element 21a, and returns light from the other semiconductor laser element 21b. In order to detect a tracking error signal by the one-beam method, a light receiving unit divided appropriately is provided.

Optical pickup 13 according to the present embodiment
Are configured as described above, and first, CD, CD-R
A case where reproduction of the first type of optical disc D1 is performed will be described. In this case, the first semiconductor laser element 21a of the light source 21 emits light.

Thus, the light beam having a wavelength of 780 nm from the semiconductor laser element 21a is split into a main beam and two side beams by the phase diffraction grating 22, and then is reflected by the reflecting surface of the beam splitter 23, so that the objective lens The optical signal is focused on the signal recording surface of the optical disk D1 via 24. The return light from the optical disk D1 again enters the beam splitter 23 via the objective lens 24, passes through the beam splitter 23, and enters the photodetector 25. Thereby, the spots of the main beam and the two side beams are incident on the corresponding light receiving portions formed on the photodetector 25, and based on the detection signals from the respective light receiving portions of the photodetector 25, The reproduction signal RF1, the focus error signal FE1, and the tracking error signal TE1 relating to the optical disk D1 are detected, and the recording signal of the optical disk D1 is correctly reproduced. At this time, the tracking error signal TE1 is detected by a so-called three spot method.

Next, when reproducing a second type of optical disk D2 such as a high density recording optical disk, for example, the light source 2
The one second semiconductor laser element 21b emits light.

As a result, the light beam having a wavelength of 650 nm from the semiconductor laser device 21b passes through the phase diffraction grating 22 and is reflected by the reflecting surface of the beam splitter 23.
Focuses on the optical disc D2 via the objective lens 24.
At this time, the light beam having a wavelength of 650 nm from the semiconductor laser element 21b is substantially unaffected by the phase diffraction grating 22, that is, transmitted substantially without being diffracted. The return light from the optical disc D2 again enters the beam splitter 23 via the objective lens 24, passes through the beam splitter 23, and enters the photodetector 25. Thereby, based on the detection signal from the photodetector 25, the reproduction signal RF2, the focus error signal FE2, and the tracking error signal TE2 regarding the optical disk D2 are detected, and the recording signal of the optical disk D2 is correctly reproduced. At this time, the tracking error signal TE2 is detected by a so-called one-beam method, for example, a push-pull method or a DPD method.

In this case, in addition to the conventional optical pickup 1, a second semiconductor laser element 21b is added to the semiconductor laser element 21a as a light source for reproducing two types of optical discs, and the wavelength is changed. With a configuration in which only the selective phase diffraction grating 22 is provided, the beam splitter 23, the objective lens 24, and the photodetector 25 are commonly used. As a result, the optical pickup 13 according to the embodiment of the present invention can be manufactured with a simple configuration at low cost and with a small number of components.
Is reduced in size and weight.

FIG. 4 shows a second embodiment of the optical pickup according to the present invention. In FIG. 4, an optical pickup 30 is an optical pickup corresponding to two wavelengths, and includes a light receiving / emitting element 31, a phase diffraction grating 32 as a light splitting unit, a beam splitter 33 as a light separating unit, and a light focusing unit. An objective lens 34 as a means and a photodetector 35 are provided.

The light emitting / receiving element 31 is, as described later,
Two semiconductor laser elements 31a and 31 as light emitting elements
b and the light receiving element are integrally formed. Here, each of the semiconductor laser elements 31a and 31b is a light emitting element utilizing recombination light emission of a semiconductor, and one semiconductor laser element 31a emits a laser beam having a wavelength of 780 nm for CD, CD-R reproduction, for example. The other semiconductor laser element 31b emits a laser beam having a wavelength of 650 nm for reproducing a high-density recording optical disk, for example.

The phase diffraction grating 32 has the same structure as the phase diffraction grating 22 shown in FIG. 3, and functions as a diffraction grating for the light from one semiconductor laser element 31a and the other semiconductor laser element. The light from 31b is transmitted as it is.

The beam splitter 33 reflects the light from each of the semiconductor laser elements 31a and 31b of the light emitting / receiving element 31 and transmits the return light from one of the semiconductor laser elements 31a among the return light from the optical disk. At the same time, the configuration is such that the return light from the other semiconductor laser element 31b is reflected at a reflectance of about 50%.

The objective lens 34 is a convex lens, and converts the light beam from each of the semiconductor laser elements 31a and 31b into a signal of the optical disk 11 that is rotationally driven, that is, the optical disk D1 of the first type or the optical disk D2 of the second type. An image is formed on a desired track on the recording surface. Further, the objective lens 34 is supported by a biaxial actuator (not shown) so as to be movable in the biaxial directions, that is, in the tracking direction and the focusing direction.

The photodetector 35 has a light receiving portion for the return light beam from one of the semiconductor laser elements 31a that passes through the beam splitter 33 among the return light beams from the signal recording surface of the optical disk 11. It is configured as follows. That is, the photodetector 25 determines that the return light from the one semiconductor laser element 21a is 3
It is configured to include a light receiving unit that is appropriately divided so as to detect a tracking error signal by the spot method.

The light receiving / emitting element 31 is configured as shown in FIGS. That is, in FIG. 5 and FIG. 6, the light emitting / receiving element 31 has a second semiconductor substrate 31d mounted on a first semiconductor substrate 31c, and two semiconductor laser elements 31a on the second semiconductor substrate 31d. , 31b
Are mounted side by side at minute intervals.

Then, the two semiconductor laser elements 31a, 31a,
A trapezoidal prism 31e having an inclined surface (an optical path branch surface) on the side of the semiconductor laser elements 31a and 31b is disposed on the first semiconductor substrate 31c in front of the first semiconductor substrate 31c. Has a semi-transmissive film (not shown) as a beam splitter. The prism 31e has a total reflection film (not shown) formed on its upper surface, and a semi-transmissive film (not shown) formed on its lower surface. The prism 31e is a semiconductor laser element 31
a, 31b, the light beam splitting surface 3
The light beam is reflected upward by 1f to emit a light beam to the outside. The light beam emitted from the light receiving / emitting element 31 enters the objective lens 34 via the phase diffraction grating 32 and the beam splitter 33 as shown in FIG.
Focuses and focuses on the signal recording surface of the optical disk D (for example, CD).

The return light beam reflected by the optical disk D enters the beam splitter 33 via the objective lens 34. Here, one semiconductor laser element 31
The return light of the light beam from a is transmitted through the reflection surface of the beam splitter 33 and is incident on the photodetector 35, and the return light of the light beam from the other semiconductor laser element 31b is reflected by the beam splitter 33. The light is reflected by about 50% on the surface, enters the prism 31e of the light receiving / emitting element 31 via the phase diffraction grating 32, and is sequentially reflected on the bottom surface and the top surface of the prism 31e. At several points, the light exits below the prism 31e.

On the upper surface of the first semiconductor substrate 31c, light receiving portions 31g and 31h (see FIG. 6) are formed at positions for receiving light emitted from two places on the bottom surface of the prism 31e. Each of the photodetectors 31g and 31h has a light receiving unit appropriately divided with respect to the return light beam, detects an information signal read by the optical disc D, and based on a detection signal from each light receiving unit. A focus error signal and a tracking error signal are detected.

According to the optical pickup 30 having such a configuration, when the first type optical disc D1 such as a CD or CD-R is reproduced first, one semiconductor laser element 31a of the light emitting / receiving element 31 is used. Will emit light.

As a result, the light beam having a wavelength of 780 nm from the semiconductor laser element 31a is split into a main beam and two side beams by the phase diffraction grating 32, and then is reflected by the reflecting surface of the beam splitter 33, so that the objective lens The optical signal is focused on the signal recording surface of the optical disk D1 via. The return light from the optical disk D1 again enters the beam splitter 33 via the objective lens 34, passes through the beam splitter 33, and enters the photodetector 35. Thereby, the spots of the main beam and the two side beams are incident on the corresponding light receiving units formed on the photodetector 35, and based on the detection signals from the respective light receiving units of the photodetector 35, The reproduction signal RF1, the focus error signal FE1, and the tracking error signal TE1 relating to the optical disk D1 are detected, and the recording signal of the optical disk D1 is correctly reproduced. At this time, the tracking error signal TE1 is detected by a so-called three spot method.

Next, when reproducing the second type of optical disc D2 such as a high density recording optical disc, the other semiconductor laser element 31b of the light emitting / receiving element 31 emits light.

As a result, the light beam having a wavelength of 650 nm from the semiconductor laser element 31b passes through the phase diffraction grating 32 and is reflected by the reflection surface of the beam splitter 33.
Focuses on the optical disc D2 via the objective lens.
At this time, the light beam having a wavelength of 650 nm from the semiconductor laser element 21b is substantially unaffected by the phase diffraction grating 32, that is, transmitted substantially without being diffracted. The return light from the optical disk D2 again enters the beam splitter 33 via the objective lens 34, is reflected by the reflection surface of the beam splitter 33, and then passes through the phase diffraction grating 32,
The light enters the light receiving sections 31g and 31h of the light receiving / emitting element 31. Thus, the reproduction signal RF2, the focus error signal FE2, and the tracking error signal TE2 relating to the optical disk D2 are detected based on the detection signals from the respective light receiving portions 31g, 31h of the light receiving / emitting element 31, and the recording signal of the optical disk D2 is correctly reproduced. Will be done. At this time, the tracking error signal TE2 is detected by a so-called one-beam method, for example, a push-pull method or a DPD method.

In this case, since the laser beam from the semiconductor laser element 31b is not affected by the phase grating 22, the return light beam is not affected by the phase grating 22. Therefore, the diffracted light of the phase diffraction grating 22 does not enter the light receiving sections 31g and 31h of the light receiving / emitting element 31, and accurate signal reproduction is performed. As a result, a smaller optical pickup with less light loss can be configured.

As described above, according to the above-described embodiment, a common light separating means, a light focusing means, and a photodetector are used for all types of optical discs. While the two types of optical discs are reproduced, the light source is almost the same size as a conventional light source having only one light emitting element, and is provided with two light emitting elements. In addition to being manufactured, the optical pickup and the entire optical disk device are configured to be small and lightweight.

Further, for reproducing two types of optical discs, the above-mentioned light sources are provided with corresponding light emitting elements, and the other optical systems are commonly used. Is reduced, and the overall configuration is small and lightweight.

In the above embodiment, the objective lens 2
When the hologram elements 4 and 34 are designed for optical disks having different thicknesses or have a hologram element having an aperture limiting function depending on the wavelength, the reproduction performance of different types of optical disks is further improved.

In the above embodiment, the phase diffraction gratings 22 and 32 are used as the light splitting means. However, the present invention is not limited to this, and the light beam from one light emitting element is diffracted.
Obviously, the light splitting means may have another configuration as long as it has a property of transmitting the light beam from the other light emitting element substantially as it is. In the above embodiment, the optical disk is a CD or a CD-ROM.
The case of R and high-density optical disk has been described, but it is apparent that the present invention is not limited to this and can be applied to other types of optical disk for recording or reproduction.

[0051]

As described above, according to the present invention, it is possible to reduce the size and weight of the optical disk with a simple structure at a low cost, and to correctly perform recording and reproduction of two types of optical disks having different wavelengths and intensities. Thus, an optical pickup and an optical disk device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical disk device incorporating an optical pickup according to the present invention.

FIG. 2 is a schematic side view showing a configuration of a first embodiment of an optical pickup in the optical disk device of FIG. 1;

FIG. 3 is an enlarged sectional view showing a phase diffraction grating in the optical pickup of FIG.

FIG. 4 is a schematic side view showing a second embodiment of the optical pickup according to the present invention.

FIG. 5 is an enlarged side view showing a configuration of a light emitting / receiving element in the optical pickup of FIG. 4;

FIG. 6 is an enlarged plan view showing a configuration of a light emitting / receiving element in the optical pickup of FIG. 4;

FIG. 7 is a schematic side view showing an example of a conventional two-wavelength optical pickup.

[Explanation of symbols]

10 optical disk device, 11 optical disk, 1
2 ... Spindle motor, 13, 30 ... Optical pickup, 14 ... Optical disk drive controller, 15 ... Signal demodulator, 16 ... Error correction circuit,
Reference numeral 17: interface, 18: head access control unit, 19: servo circuit, 21: light source, 2
1a, 31a ... one semiconductor laser element (light emitting element), 21b, 31b ... the other semiconductor laser element (light emitting element), 22 ... phase diffraction grating (light splitting means), 23 ... beam Splitter (light separating means), 2
4 ... Objective lens (light focusing means), 25 ... Photodetector, 31 ... Light emitting / receiving element.

Claims (7)

[Claims] 1. A light source; a light converging means for irradiating a light beam emitted from the light source so as to be focused on a signal recording surface of a rotationally driven optical disk; and a return light beam from the signal recording surface of the optical disk And a light separating means for separating a light beam from the light source and a return light beam, wherein the light sources are formed on a semiconductor substrate at minute intervals and have different wavelengths. First and second light-emitting elements that emit light beams of the light-emitting device, and the photodetector includes light-receiving units respectively corresponding to light beams from the respective light-emitting elements, and between the light source and the objective lens. An optical pickup, further comprising a light splitting means for diffracting only light from one of the light emitting elements. 2. The optical pickup according to claim 1, wherein said light splitting means is a phase diffraction grating. 3. The phase diffraction grating according to claim 1, wherein, of the light beams emitted from the first and second light emitting elements, a light beam having a long wavelength is diffracted and a light beam having a short wavelength is transmitted as it is. The optical pickup according to claim 2. 4. The optical pickup according to claim 3, wherein the phase of the phase diffraction grating is set to 2π for a light beam having a short wavelength. 5. The optical device according to claim 1, wherein the first and second light emitting elements are formed in a single package, and the light splitting means is attached to the package. pick up. 6. A light receiving and emitting element having two light emitting elements is provided as the light source, and a light receiving section of the light receiving and emitting element is configured to receive a return light beam of one of the light emitting elements. The light separating means is configured to transmit a return light beam for one light emitting element and reflect a return light beam for the other light emitting element. An optical pickup according to item 1. 7. An optical pickup for irradiating a rotating optical disk with light through an objective lens and detecting return light from a signal recording surface from the optical disk through the objective lens. A biaxial actuator that supports the objective lens movably in two axial directions; a signal processing circuit that generates a reproduction signal based on a detection signal from the optical pickup; and an objective based on a detection signal from the optical pickup. A servo circuit for moving a lens in two axial directions, wherein the optical pickup irradiates a light source and a light beam emitted from the light source so as to be focused on a signal recording surface of a rotationally driven optical disc. A light converging means, a light detector on which a return light beam from the signal recording surface of the optical disk is incident, a light beam from the light source and a return light beam. Light separating means for separating light beams, wherein the light source includes first and second light emitting elements formed side by side on the semiconductor substrate at minute intervals and emitting light beams of mutually different wavelengths, The photodetector includes a light receiving unit corresponding to a light beam from each light emitting element, and a light splitting unit that diffracts only light from one light emitting element between the light source and the objective lens. An optical disk device, comprising: