JPH0954976A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the whole of a device and to miniaturize the device by using a wedge prism having a diffraction function and a polarizer function to reduce the number of optical components, to simplify the alignment at the time of setting of optical arrangements. SOLUTION: A wedge prism 20 is constituted of material showing a double refractivity phenomenon by a uniaxial crystal or a biaxial crystal. A wedge prism 20 is stuck to an optical element 17 by filling the gap between a semiconductor laser LD and a reflection mirror 13 with adhesive having the same refractive index as that of the prism 20 and the wedge prism 20 is arranged so that an exit light LF becomes perpendicular to a light-emitting surface. The exit light LF is passed through an objective lens 18 from the prism 20 to be reflected at an irradiated part 12 and becomes a returned light LR to form an image at the light emitting position on the element 17. At this time, tracking servo signals are detected by bisected photodetectors arranged on a confocal surface S. Moreover, a focusing servo signal is detected by using a diffracted light due to a grating 19 being on the surface of the prism 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device, such as a compact disc (CD), a write-once compact disc (CD-R), and an optical disc such as a magneto-optical disc, which is irradiated with light for reproduction. Further, the present invention relates to an optical device for recording and reproducing, for example, an optical pickup.

[0002]

2. Description of the Related Art A conventional optical pickup for optically reading a recording on an optical recording medium is, for example, a semiconductor laser, a collimator lens, a beam splitter, a polarization beam splitter, a quarter wavelength plate, a focus lens, a focus lens driving device, It is configured by individually disposing discrete optical components such as a split-type photodetector and the like in a predetermined positional relationship with each other with high accuracy.

FIG. 9 shows a conventional compact disc (CD).
FIG. 1 shows a configuration diagram of an example of a read-only optical pickup.
The optical pickup 81 includes a semiconductor laser 82, a diffraction grating 83, a beam splitter plate 84, an objective lens 85, and a light receiving element 86 including a photodiode. Laser light L from the semiconductor laser 82 is reflected by the beam splitter plate 84. The light is converged by the objective lens 85 and irradiated onto the optical disc 90.
The return light reflected by the beam splitter plate 84
And is detected by the light receiving element 86.

However, such an optical pickup 81 not only has a large number of components and is very large, but also requires high precision in its arrangement and has low productivity.

In recent years, in response to demands for portable CD players and the like, research and development for reducing the size of optical pickups and reducing the number of components have been actively pursued. The functions of optical elements are compounded, laser couplers (emitter / receiver unit are integrated), holograms. The use of elements is progressing. However, even in these developments, it is not necessary to sufficiently adjust the arrangement of the optical elements.

[0006]

As a method for reducing the size of the optical pickup as a whole, for example, instead of a polarization beam splitter in the middle of the optical path, an optical component such as a mirror plate having a reflective film having a high reflectance on its back surface is formed. There is also proposed a method in which light is reflected by disposing the light source so that the light receiving portion such as a light receiving element can be arranged on the same side as the light emitting portion including a semiconductor laser or the like (Japanese Patent Laid-Open No. 162541/1990).

However, in this case, since the light emitting portion and the light receiving portion are arranged on the same side, the size of the entire device is reduced, but the light emitting portion and the light receiving portion are separately configured and are arranged at predetermined positions. However, the number of parts does not decrease so much, and the adjustment of the arrangement of the optical elements is required to the same extent as in the conventional case.

As a solution to these problems, an optical pickup using a hologram element as shown in FIG. 10 has been proposed. The optical pickup 110 shown in FIG. 10 includes a semiconductor laser 101, a photodetector 102, a hologram element 103, and an objective lens 104.
It is composed of each optical component. In this case, the light emitted from the semiconductor laser 101 passes through the hologram element 103, is converged by the objective lens 104, is irradiated on the disk 105 which is the irradiated portion, and the return light reflected here is converged again by the objective lens 104. Later, the hologram element 103
In this case, the focus servo signal is detected using the ± 1st-order diffracted light of the returned light.

Here, it is necessary that the ± 1st-order diffracted light of the returning light has different powers for the ± 1st-order light rays (+ 1st-order diffracted light and −1st-order diffracted light), and the positions of the focal points of the respective light rays are shifted. is there. At this time, since the ± 1st-order diffracted light and the focal position are displaced, the diffraction pattern of the hologram element 103 becomes complicated, which causes further problems such as mass productivity and reduction in yield.

The present invention has been made in consideration of the above points, and in an optical device such as an optical pickup, the number of optical components is reduced and the alignment at the time of optical arrangement setting is simplified, and the entire device is manufactured. The present invention aims at simplification, downsizing, and facilitation of manufacture, and also enables easy and reliable detection of tracking servo signals, focus servo signals, and magneto-optical signals.

[0011]

According to the present invention, a light emitting portion and a light receiving portion are formed on a common semiconductor substrate, and light emitted from the light emitting portion is converged and irradiated by a converging means to an irradiated portion. The light receiving section is disposed including the vicinity of the focal point, and the optical element is configured to receive and detect the return light from the irradiated section by the light receiving section, and a wedge prism made of a birefringent material and having a diffraction function and a polarizer function. Configure an optical device.

Here, the vicinity of the confocal point by the converging means is
An area within the depth of focus of the converging means is meant in the optical axis direction, and an area within the diffraction limit of light by the converging means is meant in the direction orthogonal to the optical axis. On the other hand, the position away from the confocal point by the converging means described later means a region other than these regions.

The optical device according to the present invention uses the optical principle that the light emitted from the light emitting portion is always returned to the confocal position when the light is irradiated to the irradiated portion. Then, in the present invention, since the optical element in which the light receiving section is arranged in the vicinity of the confocal point by the converging means, that is, the area within the diffraction limit of the light by the converging means is configured, as described above, When the light emitted from the subject is focused on the irradiated area, the return light from the irradiated area will be surely close to the confocal point even if there is some problem in the position accuracy of the optical components attached to this optical element. This makes it possible to detect the return light which is incident on the light receiving section arranged at.

In the structure of the present invention, a wedge prism made of a birefringent material and having a diffractive function and a polarizer function is arranged, so that a part of the return light from the irradiated portion is partially confocal. Form a return path toward the portion arranged in the vicinity, and form a return path in a direction different from the return path toward this confocal position by the diffracted light in the wedge prism, and arrange it at a position away from the confocal position of the light receiving part In this way, each light is surely detected by each light receiving section, and a desired signal utilizing these lights is obtained.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The optical device of the present invention, as shown in the schematic block diagram of one example in FIG. 1, is composed of a light emitting portion 14 composed of a semiconductor laser LD and a photodetector PD composed of a photodiode or the like. Light receiving unit 15
And an optical element 17 formed on a common semiconductor substrate 16. In this optical element 17, the emitted light L _F from the light emitting section 14 is converged and irradiated onto the irradiated section 12 via the converging means 18, and the light receiving section 15 is disposed including the vicinity of the confocal point by the converging means 18, and the irradiated section is irradiated. It is configured to receive and detect the return light L _R reflected from 12, that is, a CLC (confocal laser coupler) configuration.

On the other hand, on the optical element 17, a diffraction grating having a polarization function on the surface, that is, a wedge prism 20 having a grating 19 is arranged on the optical element 17. The grating 19 and the wedge prism 20 are configured to diffract the return light L _R reflected from the irradiated portion 12.

The optical device according to the present invention shown in FIG. 1 is an example applied to an optical pickup. In FIG. 1, 11 indicates an optical pickup as a whole, and 12 indicates an optical recording medium, for example, an optical disc, which is an irradiated portion.
The optical pickup 11 includes an optical element 17 in which a semiconductor laser LD and a light emitting unit 14 including a reflecting mirror 13 and a light receiving unit 15 including a photodetector PD are integrated on the same semiconductor substrate 16, a converging unit 18, and an objective in this example. It comprises a lens and a wedge prism 20 in which a grating (diffraction grating) 19 is arranged on the wedge prism surface. The wedge prism 20 has the optical element 17
The optical element 17 is disposed so as to cover the surface on the side where the light emitting portion 14, the light receiving portion 15 and the like of the optical element 17 are disposed.

The light emitting section 14 comprises a semiconductor laser LD having a horizontal resonator structure and a reflecting mirror 13. The reflecting mirror 13 is a crystal plane of the semiconductor substrate that constitutes the optical element 17,
By selecting the crystal axis in the extension direction of the etching end face when forming the semiconductor laser LD, a specific crystal face, for example, {111}, is formed when the epitaxial growth is selectively performed.
The surface can be formed as an inclined surface having a good morphology due to the atomic surface, or as a surface having a certain angle of inclination with the horizontal resonator surface. In this example, assuming that this specific crystal plane is the {111} plane, the optical element 17 shown in FIG.
As shown in the enlarged view of the side surface of the light emitting unit 14, the rising angle of the reflecting mirror 13 is 54.7 °.

The light receiving section 15 includes a plurality of photo detectors P.
The photodetector PD is configured by D, except for the portion where the light emitting portion 14 near the light emitting portion 14 on the surface of the optical element 17, that is, near the confocal point is arranged, and includes the inside of the diffraction limit region and its peripheral portion. To be done.

The emitted light L _F from the light emitting section 14 is transmitted through the wedge prism 20 and converged by the objective lens 18 onto the irradiated section 12, and the return light L _R reflected from the irradiated section 12 is reflected by the wedge prism 20. Surface grating 1
The light passes through the wedge prism 20 through 9 and is focused on the surface of the optical element 17. A part of the light receiving unit 15 is located in the vicinity of this focus and receives and detects the return light L _R. That is, this optical element has the CLC configuration described above.

This CLC structure has a structure in which the returning light L _R is close to the diffraction limit of the objective lens, as described in Japanese Patent Application No. 5-21691 “Optical device”, which is a prior application by the applicant of the present invention. When the light is converged and the light receiving section 15 is within the light diffraction limit, that is, when the wavelength of the emitted light is λ and the numerical aperture of the converging means 18 on the optical element 17 side is NA, the distance of the emitted light from the optical axis is 1.22λ. Within / NA (in Airy disk)
It is to be placed in. In addition, the light receiving unit 15
The diameter of the emitted light L _F of the light emitting section 14 on the confocal position surface S of the light receiving surface is smaller than the diameter of the light diffraction limit, and the light receiving section 15 is located outside the emitted light L _F. .

In the optical device of this embodiment, an optical element having a CLC structure is arranged, and the optical path of the return light L _R from the irradiated portion 12 is changed to a transmitted light Lt by a wedge prism 20 and a grating 19 on the surface thereof. Diffracted light Ld (±
The transmitted light Lt and the diffracted light Ld are respectively detected by splitting into the first-order light). This transmitted light Lt corresponds to the 0th-order diffracted light described later.

In the above-mentioned CLC structure, the output light L _F and the return light L _R on the same axis are received and detected by the light receiving portion 15 arranged near the confocal point, so that it is possible to detect a focus servo signal or a magneto-optical signal. I need some ingenuity.

Therefore, as the wedge prism 20, for example, quartz, LN (LiNbO ₃ ), KTP (KTiOP) is used.
O ₄ ) .YVO ₄ or other birefringent material composed of a uniaxial crystal or a biaxial crystal, that is, a material exhibiting a birefringence phenomenon, and separates the return light L _R into an ordinary ray Lo and an extraordinary ray Le, and Can be detected by the light receiving unit 15 to detect various signals.

As the light receiving section 15 for detecting the above-mentioned various signals, as shown in the plan view of the optical element 17 in FIG. 3, the two-divided photodetectors PD ₁ , PD ₂ , near the confocal point on the surface of the optical element 17, Two 3-divided photodetectors PD _{3 to} PD ₅ and PD _{6 to} PD ₈ are formed at positions apart from the confocal point, respectively. Between the surface on which these photodetectors PD are formed and the light emitting point of the semiconductor laser LD, a semiconductor layer having a thickness of several μm, such as a clad layer forming a pn junction, is only formed. The vertical distance is only about several μm. Therefore, the surface on which the photodetector PD is formed is within the depth of focus and can be considered to be the in-focus position, that is, the confocal position surface S. Therefore, even if the lateral displacement of the lens occurs, the position of the spot on the PD does not change, which is convenient for detecting the tracking servo signal.

The emitted light L _F from the light emitting section 14 is 70.degree. In the horizontal direction as shown in FIG. 2 because the mirror angle of the reflecting mirror 13 is 54.7 ° as described above in this example.
Emit at 6 °. Therefore, in this case, the wedge prism 20 having a wedge angle of 19.4 ° is used as the semiconductor laser L.
The optical element 17 is bonded so that the gap between D and the mirror surface of the reflecting mirror 13 is filled with an adhesive having the same refractive index as the wedge prism 20, and the outgoing light L _F that has passed through the wedge prism 20 is output ( It is arranged so as to be perpendicular to the surface of the wedge prism 20. This allows
The wedge prism 20 does not cause aberration in the emitted light L _F.

The emitted light L _F passes from the wedge prism 20 through the objective lens of the converging means 18, is reflected by the disk surface which is the irradiated portion 12, becomes return light L _R , passes through the objective lens again, and then the wedge prism 20. Through the optical element 17
An image is formed at the upper light emitting position.

Then, the tracking servo signals are detected by the two-divided photodetectors PD ₁ and PD ₂ arranged on the confocal position surface S as described above. Further, the focus servo signal is detected using the diffracted light from the grating 19.

Detection of various signals in the optical element 17 is performed as follows.

The tracking servo signal is detected by the push-pull method. For example, PD ₁ -PD ₂ is used as a detection signal by using the above-mentioned two-divided photodetectors PD ₁ and PD ₂ .

The focus servo signal is detected as follows. Diffracted by the above-mentioned grating 19 ±
The first-order diffracted light Ld has a schematic optical path as shown in FIG.
The light is propagated through the wedge prism 20 through a path different from the original optical axis while being multiple-reflected in the wedge prism 20.

Here, when the propagation direction of the diffracted light Ld and the wedge direction of the wedge prism 20 have a relationship as shown in FIG. 4, the wedge angle of the wedge prism 20 is considered,
By selecting a predetermined diffraction angle θg as described below,
The focal positions of the ± first-order diffracted lights Ld can be arranged and set outside the focal position of the transmitted light Lt on the surface of the optical element 17 so as to face each other.

Therefore, the above-mentioned confocal position surface S (optical element
17 surface), at two irradiation positions of each first-order diffracted light Ld,
As shown in FIG. 3, the photo detector is divided into three parts.
PD _Three~ PD_FiveAnd PD₆~ PD₈And place
The focus servo signal can be detected by the tosizing method.
You. This three-part photo detector is a photo detector in the center.
Detector PD_Four, PD₇Is centered on the optical axis of each diffracted light,
The photodetectors on both sides are the photodetectors in the center.
Are arranged so as to be symmetric with respect to each other.

Further, when each 1st-order diffracted light Ld is focused, the signal intensity of the photodetector at the center and 2 on both sides.
So that the signal strengths of the two photodetectors are equal,
That is, PD ₃ + PD ₅ = PD ₄ , PD ₆ + PD ₈ = P
Various conditions such as the diffraction grating interval of the grating 19 and the positions of the three-divided photodetectors are set so as to be D ₇ . Then, for example, (PD ₃ + PD ₅ −PD ₄ ) − (P
The focus servo signal is detected by using D ₆ + PD ₈ −PD ₇ ) as a detection signal.

As a result, it is possible to easily detect the focus servo signal, which was difficult with the optical element having only the CLC structure described above.

The above-mentioned grating 19 has a predetermined ± 1
It is designed to obtain the next-order diffracted light and is formed by a method such as vapor deposition.

Therefore, according to the optical device of this example, a simpler diffraction pattern can be formed as compared with the optical device for detecting the focus servo signal using the hologram element 103 shown in FIG. The optical device can be manufactured at low cost without any difficulty in manufacturing.

Specific numerical examples of the optical device for detecting signals as described above will be shown below. First, the allowable range of the diffraction angle θg of the first-order diffracted light and the defocus amount (shift amount of the focus position) will be described with reference to FIGS. 5 and 6.

FIG. 5 shows the refractive index n of the wedge prism 20.
Is 1.519, the wedge prism 20 has
The thickness (T in FIG. 4) of the outgoing light L _F and the transmitted light Lt on the optical axis, and the diffraction angle of the ± first-order diffracted light Ld (the optical axis of the diffracted light Ld and the light of the outgoing light L _F and the transmitted light Lt). It shows the relationship between the allowable range of the angle θg formed by the axis and θg. In FIG.
The short side shown by the solid line shows the case where the focal point is in front of the confocal position surface S, and the long side shown by the broken line shows the case where the focal point comes before the confocal position surface S, and is shown by the hatching between them. The area indicates the allowable range of the diffraction angle θg of the ± first-order diffracted lights Ld.

The diffraction angle θg of this ± first-order diffracted light Ld is
Allowable range is the outgoing light L_FLaunch angle (in this example
70.6 °) of the crystals that make up the wedge prism 20.
The refractive index n and the focus position of each ± first-order light Ld are the predetermined three-divided frames.
Photodetector PD_Three~ PD _Five, PD₆~ PD₈Within
It is set according to the above conditions. And
Set the grating so that the diffraction angle θg is within the allowable range.
The pitch of the grid of the groove 19 is selected.

The grating pitch of the grating 19 is p,
The wavelength of the laser is λ, and the refractive index of the wedge prism 20 is n.
Then, the following equation 1 holds.

[0042]

## EQU1 ## p = Nλ / (n × sin θg) (where N is an integer)

Thus, the size of the pitch p of the grating of the grating 19 is set.

Here, the wedge prism 20 may also be used as a heat sink.

As shown in FIG. 5, the thickness T is 1 mm (10
The allowable range of the diffraction angle θg of the first-order diffracted light in the case of (00 μm) is 1.3 ° to 26.5 °. The thickness T is 1
In the case of mm, the left and right defocus amounts with respect to the diffracted light (focus shift amount; distance between the confocal position plane S and the focus of the diffracted light) were calculated. As a result, the first-order diffracted light shown in FIG. The relationship between the diffraction angle θg and the defocus amount (μm) was obtained. In FIG. 6, the meanings of the short side indicated by the solid line and the long side indicated by the broken line are the same as in FIG.

In order to secure a sufficient defocus amount, it is understood that the diffraction angle is preferably around 15 degrees in consideration of the short side. 29μ when θg = 13 ° and T = 1mm
Since a defocus amount of 53 μm is obtained when m and T = 2 mm (both are on the short side), the pull-in width of each focus servo signal is about 4.8 (in the system where the magnification of the objective lens is 3.5 times). μm), about 8.6 (μm)
Are obtained respectively. Actually, the left and right defocus amounts are different, and the spot size is different accordingly.
It is necessary to take measures such as matching the shape.

Next, an example of further detecting a magneto-optical signal (MO signal) based on the configuration of the optical device and the signal detection system of the above example will be shown.

In this example, in an optical device having the same configuration as the previous example, for example, an optical pickup, the wedge prism 20 formed of a birefringent material and the light receiving portion 15 on the surface of the optical element 17, that is, the confocal position surface S described above are provided. An analyzer (polarizer) is provided between the photo detector PD and a part of the constituent photo detector PD.
Is added.

The c-axis (optical axis) of the birefringent material forming the wedge prism 20 is set according to the pattern of the photodetector PD of the light receiving section 15, and the ordinary ray (transmitted light Lt) of the 0th-order diffracted light is set at the confocal position. An extraordinary ray of the 0th-order diffracted light is detected by another photodetector PD. Of these, the ordinary ray of the 0th-order diffracted light is used for detecting the tracking servo signal by the push-pull method as in the first embodiment, and correspondingly, as a part of the light receiving unit 15 as in the first embodiment. , Two-divided photodetectors PD ₁ and PD ₂ are arranged near the confocal position.

In the magneto-optical signal, the ordinary ray and the extraordinary ray of the 0th-order diffracted light are detected by the corresponding photodetectors PD. It is arranged so that any light beam reaches the photodetector PD through the analyzer. The analyzer is
It is composed of wire grids arranged in a certain direction, and the polarized light of the direction component is extracted. These photodetectors PD are arranged on the opposite side of the reflecting mirror 13 from the above-mentioned two-divided PD for tracking servo signal detection.

As described above, the crystal forming the wedge prism 20 is made to have anisotropy and the optical axis is set in an appropriate direction to separate the ordinary ray and the extraordinary ray with respect to the 0th order light. A magneto-optical signal can be detected using an analyzer having a predetermined azimuth.

Since the optical axis of the crystal forming the wedge prism 20 can be arbitrarily selected, the position of the photodetector PD used for detecting the extraordinary ray can also be freely selected.

From the above, for example, FIG. 7A is a side view, and FIG.
The optical elements 17 shown in the plan views are
You. The photodetector PD forming the light receiving unit 15 is
A photodetector divided into two in the vicinity of the reflecting mirror 13 of the light section 14.
PD₁, PD₂, 2 minutes on the opposite side of the reflector 13
Photo detector PD_Three, PD_FourPlace this 2
Split photo detector PD_Three, PD_FourOn the analyzer 2
1 is arranged. Further, similar to the first embodiment on the outside of these.
The photo data of 3 divisions for detecting the focus servo signal
Detector PD _Five~ PD₇, PD₈~ PD_TenEach
Place.

Detection of various signals in the optical element 17 is performed as follows.

The tracking servo signal is detected by the push-pull method in the two-divided photodetectors PD ₁ and PD ₂ near the light emitting section 14. And, for example, PD ₁
-Detect the tracking servo signal with PD ₂ as the detection signal.

The focus servo signal is detected by two 3
Same as the first embodiment using the divided photo detector PD
To spot size method. And, for example (PD_Five+
PD ₇-PD₆)-(PD₈+ PD_Ten-PD₉) Detected
Signal.

The detection of the magneto-optical signal is performed in
Split photo detector PD_Three, PD _FourAnd place it on it
It is performed using the analyzer 21 thus prepared. The light is in the analyzer 21
When the light is received by the
The light reaches the detector and is detected. Ordinary ray L of 0th order light
PD for t_Three, Extraordinary ray Le PD_FourRespectively received with,
For example PD_Three-PD_FourIs used as the detection signal,
-The direction of the rotation angle due to the effect can be detected, and the
The air signal can be detected.

FIG. 8 shows the setting direction of the optical axis of the wedge prism 20 and the extraordinary ray Le with respect to the optical element 17 of FIG. 7A.
2 is a schematic configuration diagram showing the relationship with the propagation path of the. The extraordinary ray Le forms an angle θ ′ with the optical axis of the emitted light L _F , and is received by the photodetector PD through the analyzer 21.

Although the propagation angle of the extraordinary ray depends on the incident angle of the crystal boundary surface, in the optical device of the present invention, since the return light is incident perpendicularly on the incident surface, that is, the surface of the wedge prism 20, for example, a wedge. When the prism 20 is made of crystal and the angle formed by the optical axis (C-axis) of the crystal and the optical axis of the emitted light L _F is 10 °, the propagation angle of this extraordinary ray is 9.9 °.

This value is merely an example, but the diffraction angle θ
The PD arrangement condition is determined by g = 13 ° and the thickness T of the crystal (quartz in this example) of the birefringent material forming the wedge prism 20.

As described above, the arrangement of the photodetector PD can be set arbitrarily, and the optical axis of the crystal, the thickness / refractive index of the wedge prism, and the diffraction grating interval can be set so that the occupied portion of the photodetector can be saved. It is possible to downsize the optical element and further downsize the entire optical device.

Also, in the example of this optical device, similarly to the above-mentioned example, a simpler diffraction pattern is obtained as compared with the optical device for detecting the focus servo signal using the hologram element as shown in FIG. A diffraction grating can be constructed with. Further, a conventional optical pickup that constitutes a conventional magneto-optical signal detection system and records / reproduces the signal is shown in FIG.
As shown in FIG. 1 of the structure of an optical pickup 91 for a mini disk (MD), a semiconductor laser 92, a diffraction grating 93,
A polarization beam splitter 94, a collimator lens 95, an objective lens 96, a Wollaston prism 97, a multi-lens 98 for generating astigmatism, a photodetector 99, a disc 100 and the like. According to the example of the optical device shown in FIGS. 7A and 7B, the magneto-optical signal can be detected with a remarkably smaller number of parts as compared with the conventional example of FIG.

As described above, in each of the embodiments, it is possible to manufacture an optical device, such as an optical pickup, in which the entire device is compact, the diffraction grating pattern is simple, and precise adjustment is unnecessary.

Further, since the semiconductor laser beam can be efficiently irradiated onto the optical disk, it can be used as an optical pickup for a super-resolution reproduction-only disk or a recording / reproduction disk. In particular, since the size and weight can be remarkably reduced, an optimum optical pickup can be configured for a data disc that requires a high random access speed.

Further, the irradiated portion 12 is not only an optical disk having concave and convex recording pits like a normal CD, a magneto-optical disk or a micro disk for recording by light and magnetic field applying means, but also an optical characteristic such as reflection due to a phase change. It can also be applied to an optical pickup of a phase-change disk according to a recording mode in which the rate is changed. That is, recording is performed by using the emitted light L _F , and reproduction is configured such that the return light L _R is received and detected by the photodetector PD, so that these disks can be applied as the irradiated portion 12. .

It should be noted that each of the above-described embodiments is an example of the present invention, and various other configurations are possible without departing from the gist of the present invention.

[0067]

According to the present invention, since the number of parts can be reduced and a simple optical system can be constructed, the assembling and adjusting steps can be simplified and the optical device can be easily manufactured at low cost.

Further, even when the magneto-optical signal (MO signal) is detected, the position of the light receiving element can be arbitrarily set, so that the entire light receiving element can be compacted and the optical element formed by this light receiving element can be integrated. Can be downsized. Thereby, the response speed can be improved.

When the optical device according to the present invention is compared with the optical device using the conventional hologram element, the diffraction pattern of the diffraction grating can be simplified, and the diffraction grating can be easily manufactured at low cost. Become.

Therefore, the size of the entire optical device can be made smaller, and by using this, a recording / reproducing device smaller than the conventional one can be constructed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an optical device of the present invention.

FIG. 2 is an enlarged view of a side surface of a light emitting unit of the optical element of FIG.

FIG. 3 is a plan view of the optical element of FIG.

FIG. 4 is a schematic view of an optical path in a wedge prism.

FIG. 5 is a graph showing the relationship between the range of possible diffraction angles of first-order diffracted light and the crystal thickness of the wedge prism.

FIG. 6 is a graph showing the relationship between the diffraction angle of the first-order diffracted light and the defocus amount of the diffracted light.

FIG. 7 is a diagram showing another example of the optical device of the present invention. It is a side view of an A optical element. B is a plan view of the optical element.

FIG. 8 is a schematic configuration diagram showing a relationship between a setting direction of an optical axis of a wedge prism and a propagation path of an extraordinary ray.

FIG. 9 is a configuration diagram of a conventional optical pickup.

FIG. 10 is a configuration diagram of a conventional optical pickup using a hologram element.

FIG. 11 is a configuration diagram of a conventional optical pickup for a mini disc (MD).

[Explanation of symbols]

11 Optical Pickup 12 Irradiated Part (Optical Disk) 13 Reflector 14 Light Emitting Part 15 Light Receiving Part 16 Semiconductor Substrate 17 Optical Element 19 Grating 20 Wedge Prism 21 Analyzer LD Semiconductor Laser PD [PD ₁ , PD ₂ , PD ₃ , PD ₄ , PD ₅ , PD
₆ , PD ₇ , PD ₈ , PD ₉ , PD ₁₀ ] Photodetector L _F Emitted light L _R Return light

Claims (4)

[Claims] 1. A light emitting portion and a light receiving portion are formed on a common semiconductor substrate, and light emitted from the light emitting portion is converged and irradiated by a converging means onto an irradiated portion, including a confocal vicinity by the converging means. The light receiving portion is arranged, and the light receiving portion includes an optical element configured to receive and detect return light from the irradiated portion, and a wedge prism made of a birefringent material and having a diffraction function and a polarizer function. Characterized optical device. 2. The optical device according to claim 1, wherein a portion of the light receiving portion near the confocal point has a plurality of light receiving elements, and the tracking servo signal is extracted by the light receiving elements. 3. The return light is diffracted by a diffraction grating formed on the wedge prism surface of the wedge prism.
The light receiving section for receiving the ± 1st order diffracted light with respect to the 1st order diffracted light includes a light receiving element, and a focus servo signal is extracted from the ± 1st order diffracted light by these light receiving elements. The optical device according to. 4. The return light is diffracted by a diffraction grating formed on the wedge prism surface of the wedge prism.
With respect to the second-order diffracted light, the light-receiving section that receives the 0th-order diffracted light has a plurality of light-receiving elements, and the plurality of light-receiving elements and the analyzer formed on the plurality of light-receiving elements are used to The optical device according to claim 1, wherein a magneto-optical signal is extracted from an ordinary ray and an extraordinary ray of the second-order diffracted light.