JPH0954975A - 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 hologram 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: The wedge angle of a wedge prism 20 is selected so that the exit light LF from a semiconductor laser LD and a returned light LR become perpenticular to the surface of the prism 20. The returned light LR from an irradiated part 12 is made incident on the surface of the prism 20 at right angles to be converged at the vicinity of a confocal and is reflected at the reflection mirror 21 arranged in a diffraction limit area to be introduced to the surface of the prism 20. A hologram element 19 is arranged at the position of the surface of the prism 20 where this reflected light reaches to diffract the reflected light. Focusing servo signal or the like are detected by receiving the diffracted light with light receiving parts 15 arranged on the surface of an optical element 17. By this constitution, assembly processes and position adjusting processes of optical axis, etc., are simplified.

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. 8 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. 9 has been proposed. The optical pickup 110 shown in FIG. 9 is composed of optical components such as a semiconductor laser 101, a photodetector 102, a hologram element 103, and an objective lens 104. In this case, the light emitted from the semiconductor laser 101 passes through the hologram element 103, is converged by the objective lens 104, and is the irradiated portion of the disk 1
The return light that is irradiated on the beam No. 05 and reflected here is converged again by the objective lens 104, is then diffracted by the hologram element 103, and the focus servo signal is detected using the ± first-order diffracted light of the return light. .

At this time, diffracted light is generated in the hologram element 103 even in outgoing light on the outward path, but this diffracted light is almost discarded without being used. for that reason,
The amount of return light is greatly reduced compared to the amount of emitted light. In order to compensate for this decrease in the amount of light, it is necessary to increase the output of the semiconductor laser LD, which increases power consumption.

On the other hand, a magneto-optical signal (M
In an optical device for recording / reproducing, such as an optical pickup having a detection system for (O signal) or an optical pickup using a phase change, as shown in FIG. 10 as an example of an optical pickup for a mini disk (MD), The configuration is such that components for polarization detection are added. The optical pickup 91 shown in FIG. 10 includes a semiconductor laser 92, an objective lens 96, a photodetector 99, a diffraction grating 93 used for detecting a tracking servo signal, a polarization beam splitter 94, a collimator lens 95, a Wollaston prism 97, and a focus servo. It comprises a multi-lens 98 for signal detection. In order to detect the polarized light in this way, the number of parts is very large, the optical device is complicated, and a large power is required for recording. Therefore, it is necessary to increase the LD output of the light source. After all, power consumption will increase.

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, alignment for setting an optical arrangement is simplified, and the entire device is manufactured. It simplifies and downsizes, and facilitates fabrication. Furthermore, it enables easy and reliable detection of tracking servo signals, focus servo signals, and magneto-optical signals, and makes effective use of the amount of light. Then, an optical device with low power consumption is proposed.

[0012]

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. A light receiving unit is arranged including the vicinity of the focal point, and an optical device having an optical element configured to receive and detect the return light from the irradiated unit by the light receiving unit and a wedge prism having a hologram function and a polarizer function is configured.

Here, the confocal vicinity 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.

Further, in the configuration of the present invention, by disposing the wedge prism having the hologram function and the polarizer function, the hologram function of the wedge prism diffracts the return light from the irradiated portion, and this is used for the focus servo. Signal detection can be performed.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The optical device of the present invention, as shown in the schematic configuration diagram of one example in FIG. 1, includes a light emitting portion 14 constituted by a semiconductor laser LD and a first reflecting mirror 13.
An optical element 17 is formed by forming a common semiconductor substrate 16 with a light receiving portion 15 formed of a photo detector PD such as a photodiode. 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 this light receiving section A configuration for receiving and detecting the return light L _R reflected from the irradiated portion 12 by 15, namely, CLC (confocal
Laser coupler) configuration.

A second reflecting mirror 21 is arranged near the confocal point, apart from the light receiving section 15, and the second reflecting mirror 21 is provided.
Will reflect the return light L _R as described later. Further, the wedge prism 20 is arranged on the optical element 17. A hologram element 19 having a polarization function is formed on the surface of the wedge prism 20.

The wedge prism 20, the hologram element 19 and the second reflecting mirror 21 are used to obtain diffracted light from the return light L _R 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, a light receiving unit 15 including a plurality of photodetectors PD, and a second reflecting mirror 21 are integrated on the same semiconductor substrate 16. Converging means 18 In this example, it comprises an objective lens and a wedge prism 20 on the surface of which a hologram element 19 is arranged. And wedge prism 2
0 is on the optical element 17, the light emitting portion 14 of the optical element 17,
It is arranged so as to cover the surface on the side where the light receiving portion 15 and the like are arranged.

The wedge prism 20 selects the wedge angle so that the emitted light L _F and the return light L _R from the irradiated portion are perpendicular to the surface of the wedge prism 20.

The light emitting section 14 comprises a semiconductor laser LD having a horizontal cavity structure and a first reflecting mirror 13. When the first reflecting mirror 13 is selectively epitaxially grown by selecting the crystal plane of the semiconductor substrate forming the optical element 17 and the crystal axis in the extension direction of the etching end face when forming the semiconductor laser LD. In addition, it is possible to form a specific crystal plane, for example, a {111} plane, as an inclined plane having a good morphology by an atomic plane, and as a plane having a certain angle of inclination with the horizontal resonator plane. In this example, assuming that this specific crystal plane is the {111} plane, as shown in the enlarged view of the light emitting section 14 of the optical element 17 in FIG.
The rising angle of the reflecting mirror 13 is 54.7 °.

The light receiving portion 15 is composed of 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 outgoing light L _F from the light emitting section 14 is transmitted through the wedge prism 20, is converged on the irradiated section 12 by the objective lens of the converging means 18, and the return light L _R reflected from the irradiated section 12 is the wedge. The light passes through the prism 20 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.

The return light L _R from the irradiated portion is vertically incident on the surface of the wedge prism 20 and is converged in the vicinity of the confocal point. At this time, it is reflected by the second reflecting mirror 21 arranged in the diffraction limit region. , Toward the surface of the wedge prism 20. Then, the hologram element 19 is arranged on the surface of the wedge prism 20 at a position where the light reflected by the second reflecting mirror 21 reaches. Thereby, the hologram element 19
The reflected light is diffracted by, and diffracted light is obtained. Light receiving part 1
As a part of 5, the photodetector PD that receives this diffracted light can be arranged on the surface of the optical element 17 to detect the focus servo signal and the like.

From the above, as shown in a side view of the optical element 17 in FIG. 3A and a plan view of the optical element 17 in FIG. 3B, a part of the light receiving portion 15 is provided in the vicinity of the light emitting portion 14 on the surface of the optical element 17. Split photodetectors PD ₁ and P
D ₂ and the second reflecting mirror 21 are formed. In addition, the light receiving unit 1
As a part of 5, the three-divided photodetectors PD _{3 to} PD ₅ and PD _{6 to} PD ₈ are formed on the surface of the optical element 17 at positions apart from the light emitting section 14 (outside of the above Airy disk). The two 3-division photo detectors detect the focus servo signal by the spot size method as will be described later, and the photo detectors PD ₄ , P in the center are detected.
The photodetectors on both outer sides are symmetrical with respect to D ₇ .

Between the surface of the optical element 17 forming the photodetector and the second reflecting mirror 21 and the light emitting point of the semiconductor laser LD, for example, a clad layer forming a pn junction or the like having a thickness of several μm. Only the semiconductor layer is formed, and the vertical distance between them is only about several μm. Therefore, the surface on which the photodetector PD is formed is
It may be considered as the in-focus position, that is, the confocal position surface S that is within the depth of focus. Therefore, even if the lateral displacement of the lens occurs, the spot position on the photodetector does not change, which is convenient for detecting the tracking servo signal.

The mirror surface of the second reflecting mirror 21 is the optical element 17
Is grown by, for example, growing along the {111} plane of the crystal to form a flat surface with good crystallinity.

Thus, the mirror surface of the second reflecting mirror 21 is
Since it is the growth surface of the crystal, the flatness is extremely good, and it becomes a mirror surface as it is. Since a part of the spot on the mirror surface is highly reflected, it is possible to detect a focus servo signal or a magneto-optical signal (MO signal) by using the light reflected by this mirror surface. In addition, this second
The reflecting mirror 21 may be formed by vapor-depositing a metal having a high reflectance.

As described above, in this example, the first reflecting mirror 1
As shown in Fig. 2, the rising angle of 3 is 54.7 °.
As described above, the emitted light L from the light emitting unit 14_FAre paired horizontally
And emits at an angle of 70.6 °. So in this case, the figure
As shown in 3A, it has a wedge angle of 19.4 °
The wedge prism 20 is placed on the optical element 17 to emit light.
Between the semiconductor laser LD of the portion 14 and the first reflecting mirror 13
The gap has the same refractive index as the wedge prism 20.
Wedge prism, glued together to fill with adhesive
Outgoing light L from 20 _FIs perpendicular to the exit surface
To place. As a result, the light L emitted from the prism surface_F
Aberration does not occur.

The emitted light L _F is irradiated onto the irradiated portion 12, and the reflected return light L _R is incident on the wedge prism 20 again perpendicularly. A part of the return light L _R is reflected by the second reflecting mirror 21, and the other part of the return light L _R is received by the two-divided photodetectors PD ₁ and PD ₂ . Of these, the second reflecting mirror 2
The light reflected by 1 enters the hologram element 19 on the surface of the wedge prism 20 and is diffracted there to obtain ± 1st order diffracted light. The diffraction pattern of the hologram element 19 is set so that the focus servo signal can be detected as described later. It is also possible to prevent the loss of light quantity by setting the proportion of 0th-order light to 0 as much as possible.

Then, the two-divided photo detector PD ₁ ,
The tracking servo signal is detected from the return light L _R received by PD ₂ . In addition, ± 1 by the hologram element 19
The focus servo signal is detected using the secondary diffracted light.

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

The tracking servo signal is detected by the push-pull method using the two-divided photo detectors PD ₁ and PD ₂ . Then, the tracking servo signal is detected by using, for example, PD ₁ -PD ₂ as a detection signal.

The focus servo signal is detected by two 3
Split photo detector PD_Three~ PD _Five, PD₆~ PD₈
Using the spot size method. At this time
At the center of the photo detector in the center, on the hologram element 19.
The optical axis of the diffracted light by
Are symmetric to each other with respect to the central photodetector
Place it like this. Also, the diffraction pattern of the hologram element 19
The focus position of both spots when focusing is the photodetector.
It is set to move forward and backward with respect to the PD surface.

Further, when each first-order diffracted light is focused, the signal intensity of the central photodetector and the signal intensity of the two photodetectors on both sides are equal, that is, PD ₃ + PD ₅ = PD ₄ , PD ₆ + PD ₈ = PD ₇
The diffraction pattern of the hologram element 19 and the positions of the three-divided photodetectors are set so that Then, for example, (PD ₃ + PD ₅ −PD ₄ ) − (PD ₆ + P
To detect a focus servo signal as a detection signal D ₈ -PD _7).

The light reflected by the above-mentioned second reflecting mirror 21 is
As shown in FIG. 3A, the wedge prism 2 passes through an optical path different from the optical axis of the outgoing light L _F in the wedge prism 20.
Propagate in 0. Therefore, the light propagates while being multiply reflected in the prism without interfering with the emitted light L _F. Therefore, as described above, if the hologram element 19 is arranged on the surface of the wedge prism 20 and at the position where the light reflected by the second reflecting mirror reaches, it is irrelevant to the propagation path of the emitted light in the wedge prism 20. It is possible to set a propagation path of reflected light at a position and use this reflected light to configure a focus servo signal detection system.

According to the optical device of the present invention, the outgoing light L
_F does not go through the hologram element, the wedge prism 20
Since it goes directly to the converging means and the irradiated portion,
Unlike the conventional optical pickup using a hologram element, the emitted light is diffracted to generate ± first-order diffracted light, and the loss of the light amount does not occur accordingly. Therefore, the output of the laser LD of the light source can be set lower than before, and the amount of heat generated in the light emitting section can be suppressed.

Further, when first-order diffracted light is generated from the normally emitted light, it is necessary to design the diffracted light to propagate out of the pupil plane of the objective lens so that the diffracted light does not enter the objective lens and cause interference. According to the optical device of the present invention, this design restriction is eliminated, and it is possible to preferentially deal with problems such as suppression of heat generated due to the output of the semiconductor laser LD and miniaturization of the optical system.

In each of the above-mentioned examples, the focus servo signal is detected by the spot size method, but it is also possible to detect the signal by the Foucault method by using a two-divided photodetector instead of the three-divided photodetector. In this case, the diffraction pattern of the hologram element 19 focuses the PD surface when the two spots are in focus, and when the two spots are not in focus, as in the case of the normal Foucault method, the inner PD
Alternatively, the pattern is set so that only the outer PD is irradiated with the spot.

At this time, an example of the structure of the photo detector is
Side view of optical element 17 of FIG. 4A and optical element of FIG. 4B
Shown by a plan view of 17. Two-part photo detector
PD _ThreeAnd PD_Four, PD_FiveAnd PD₆Is formed,
These receive the diffracted light from the hologram element 19 and combine them.
The center of the spot of the diffracted light at the time of focusing is divided into two photo detectors.
Arrange it so that it is in the center of.

As shown in FIG. 4A, at the time of focusing, the spot center of the diffracted light comes to the center of two two-divided photodetectors, but when the focus is deviated as shown by the broken line, one of the two ( In this case, only the photodetectors PD ₄ and PD ₅ (inside the optical path) are irradiated with the diffracted light. When the focus is deviated in the opposite direction, conversely, only the outer photodetectors PD ₃ and PD ₆ are irradiated with the diffracted light. Therefore, for example, (PD ₃ −PD ₄ ) + (PD ₆
-The focus servo signal is detected by using PD ₅ ) as a detection signal.

According to the optical device of the present invention, the spot size method, the Foucault method, and the like can be used as they are as in the conventional focus servo signal detection system as described above. Therefore, the diffraction grating of the hologram element 19 can be used. The pattern need only be optimized for this signal detection.

In the case of further detecting a magneto-optical signal based on the above-mentioned signal detection system, the wedge prism 20
A magneto-optical signal can be detected by adding an analyzer (polarizer) between the photo detector PD and the photo detector PD on the confocal position plane. An example is shown below.

FIG. 5A is a side view of the optical element, and FIG. 5B is an optical view.
As shown in the plan view of the device, the optical device shown in FIGS.
Of the optical element 17 having the same configuration as that of the above-mentioned example.
Photodetector PD₁, PD₂And 3 split photo
Tecta PD_Three~ PD_Five, PD ₆~ PD₈On top of each
The analyzer 22 (22a, 22b, 22c) is arranged.

Similar to the above-mentioned example of the optical device, the wedge prism 20 and the hologram element 19 on the surface thereof are provided as the optical element 1.
Place on 7. The wedge prism 20 is made of a birefringent material such as quartz.

The return light L _R from the irradiated portion 12 is reflected by the second reflecting mirror 21, irradiated on the hologram element 19, and then diffracted by the hologram element 19. The diffracted light obtained at this time travels in a predetermined direction by the diffraction pattern of the hologram element 19 and enters the photodetector PD through the analyzer 22.

The detection of the tracking servo signal and the focus servo signal is carried out in the photodetector PD in the same manner as in the example of the above optical device.

The detection of the magneto-optical signal is performed by the three-division photo detector used for detecting the focus servo signal.
At this time, the analyzer 22a on the two-divided photodetectors PD ₁ and PD ₂ and the three-divided photodetectors PD _{3 to} PD.
₅ , with respect to the analyzers 22b and 22c on PD _{6 to} PD ₈ , the directions of the respective analyzers 22 form 90 ° with each other, and make an angle of 45 ° opposite to the main polarization direction of the return light. To place. For example, the direction of the analyzer 22a is 45 ° counterclockwise with respect to the polarization direction of the return light,
The analyzers 22b and 22c are arranged so that the directions thereof are clockwise and form an angle of 45 °. In addition, the analyzer 22a is set to PD ₁
The PD of the analyzer 22a is divided into two parts, the upper part and the PD _{2 part.}
45 ° in the counterclockwise direction of _one on the part and the analyzer 22c relative to the return light of the polarization direction, PD of the analyzer 22a ₂
The direction of the upper portion and the analyzer 22b may also be configured to make an angle of 45 ° in the clockwise direction.

[0051]

EXAMPLE FIG. 6 shows an example of the optical device of the present invention and the shape of the beam irradiated. FIG. 6 shows the wedge prism 2.
0 is BK7 or the like, and the thickness X on the optical axis of the confocal system is 1.
mm, the refractive index is 1.52, the numerical aperture NA (o) on the optical element 17 side of the objective lens is 0.086, and the numerical aperture NA (i) on the irradiated portion side is 0.45. 2 is a design example of the optical device of FIG. The light intensity distribution is assumed to be a Gaussian beam distribution. Further, the position of the light emitting unit 14 and the rising angle of the first reflecting mirror 13 are set as shown in FIG.

In FIG. 6, the spot diameter t is (1
/ E) ² (diameter corresponding to 86.5% of the total amount of light). Beam diameter t of emitted light L _F (56.98 μm)
In comparison, the irradiation position of the reflected light of the return light L _{R on} the confocal surface to the wedge prism 20 is a sufficient distance t ′.
Since (804.02 μm) is set (t ′ >> t), it can be seen that the emitted light L _F and the reflected light do not interfere with each other.

Beam spot S received at confocal position plane
Since the return light L _R is obliquely irradiated to this surface of C, it becomes an ellipse as shown in FIG. 6, of which the first reflecting mirror 21
The portion R of the beam reflected by is the shaded portion R. When the spots R are received by the photodetector PD via the hologram element 19, they are obliquely incident on each other, so that the shape of the spot spreads laterally.

The spot SH on the surface of the hologram element 19 has a shape in which an ellipse is elongated in the major axis direction with the minor axis as a boundary and one is contracted. The minor axis diameter T1 of this spot SH is 72.41 μm and the major axis right side T1.
′ Is 97.35 μm, and T1 ″ on the left side of the major axis is 88.86 μ
m. Spot S received by photodetector PD
P also has the same shape as the spot SH on the surface of the hologram element 19, with the minor axis diameter T2 of 202.57 μm, the major axis right side T2 ″ of 352.22 μm, and the major axis left side T2 ′ of 423.08 μm. The PD from the light emitting part to the light receiving part
The horizontal moving distance lb of the beam up to is 2378.20 μm in the case of the above numerical value.

Further, since the spot diameter of the return light L _{R on} the confocal position plane depends on the magnification of the optical system, the light intensity and light quantity used for the detection of the focus servo signal and the magneto-optical signal are also the same. It depends on the magnification of the system.

7A and 7B show the relationship between the numerical aperture on the optical element side of the converging means in this embodiment and the light intensity used for the detection of the focus servo signal and the detection of the magneto-optical signal. In these figures, when the numerical aperture NA (i) of the converging means on the irradiated portion side is 0.45 and the numerical aperture NA (o) of the converging means on the optical element 17 side is changed, the above-mentioned values for the emitted light are shown. Ratio of light quantity used for signal detection (Fig. 7
7A shows changes in the spot diameter of the return light (FIG. 7B).

For example, the magnification of an optical pickup used for a compact disc is usually 5 to 6 times, and the numerical aperture NA (i) on the irradiated portion side of the converging means is 0.45 as a typical value. . Considering these, the numerical aperture NA (o) of the converging means on the optical element side is about 0.08 to 0.1, and it is understood that about 5 to 10% of the returned light can be used for the focus servo signal.

As described above, in the optical device of each example, 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 applied to 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-convex recording pits like a normal CD, a magneto-optical disk or a microdisk 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 examples is an example of the present invention, and various other configurations are possible without departing from the scope of the present invention.

[0062]

According to the optical device of the present invention, since the number of parts can be reduced and a simple optical device can be constructed, the assembling process and the process of adjusting the position of the optical axis and the like can be simplified. The optical device can be easily manufactured at low cost. Further, the size and weight of the optical device can be reduced, and the response speed can be improved. Since the emitted light can be effectively used, reproduction and recording can be performed with a lower laser output as compared with a similar system using a conventional hologram element, thereby reducing power consumption and thermally stabilizing. .
Further, along with the decrease in power consumption, the linear velocity in recording / reproducing can be made higher with the same power consumption as in the past.

[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.

3A is a side view of the optical element of FIG. 1. FIG. B is a plan view of the optical element of FIG. 1. C is a diagram showing a beam shape reflected by a second reflecting mirror.

FIG. 4 is a configuration diagram of an optical element when a focus servo signal is detected by the Foucault method. It is a side view of an A optical element. B is a plan view of the optical element.

FIG. 5 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. 6 is a design example of the optical device of the present invention.

FIG. 7 is a diagram showing the relationship between the numerical aperture on the optical element side of the A irradiated portion and the amount of light used for detection of a focus servo signal. B is a diagram showing the relationship between the numerical aperture on the optical element side of the irradiated portion and the spot diameter.

FIG. 8 is a configuration diagram of a conventional optical pickup.

FIG. 9 is a configuration diagram of a conventional optical pickup using a hologram element.

FIG. 10 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 First Reflector 14 Light Emitting Part 15 Light Receiving Part 16 Semiconductor Substrate 17 Optical Element 18 Converging Means 19 Hologram Element 20 Wedge Prism 21 Second Reflector 22 Analyzer LD Semiconductor Laser PD [PD ₁ , PD ₂ , PD ₃ , PD ₄ , PD ₅ , PD
₆ , PD ₇ , PD ₈ ] Photodetector L _F Emitted light L _R Return light

Claims (3)

[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. An optical device comprising: an optical element in which the light receiving section is arranged, the optical element configured to receive and detect return light from the irradiated section by the light receiving section, and a wedge prism having a hologram function and a polarizer function. 2. The optical device according to claim 1, wherein the light receiving section arranged in the vicinity of the confocal point has a plurality of light receiving elements, and the tracking servo signal is extracted by these light receiving elements. 3. The light emitting unit has a first reflecting mirror, a second reflecting mirror is arranged in the vicinity of the confocal point, and a focus servo signal and a magneto-optical signal are generated by using the reflected light from the second reflecting mirror. The optical device according to claim 1, wherein a signal is extracted.