JPH07192301A - Optical device - Google Patents

Abstract

PURPOSE:To simplify the device constitution, to reduce the overall size and facilitate the manufacture, and to improve the reliability and increase the quantity of light reception by making return light to the light reception surface of a light reception part astigmatic. CONSTITUTION:This optical device has a light emission part 1 and a light reception part 4 arranged closely on a common substrate 9 and is provided with an optical element 21 which receives and detects the return light LR itself to the light emission part 1, which is generated when the light L emitted by the light emission part 1 is cast on a to be irradiated part 2 and is reflected by the irradiated part 2, by the light reception part 4, and the return light to the light reception surface of the light reception part 4 is made astigmatic. This element 21 receives the return light by the light reception part 4 in an area other than the projection part of the light emission part 1, so the projection part of the light emission part 1 becomes an ineffective area regarding the light reception. The return light to the light reception part 4, however, is made astigmatic, so the spot of the return light has the center of its intensity deviating from the center of the ineffective area of the light emission part 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates an irradiated portion, for example, an optical recording medium such as an optical disk or a magneto-optical disk,
The present invention relates to an optical device suitable for application when receiving and detecting return light due to reflection from this.

[0002]

2. Description of the Related Art In a conventional optical device, for example, an optical pickup for an optical disc drive such as a compact disc (CD) player or a magneto-optical disc drive, optical components such as a grating and a beam splitter are individually assembled, so that the entire device is constructed. There is a problem in that it becomes complicated, and the optical arrangement setting is complicated, resulting in poor mass productivity.

For example, in an optical pickup device for an optical recording medium, for example, an optical disc, light emitted from a light source 51 such as a semiconductor laser diode is transmitted through a grating 52 as shown in FIG. The light is introduced into the beam splitter 53 via the beam splitter 53 and transmitted therethrough, and then is condensed by the objective lens 55 via the collimator lens 54 onto the recording portion of the optical disc of the optical recording medium 56.
In FIG. 9, an alternate long and short dash line c indicates from the light source 51 to the optical recording medium 56.
Shows the optical axis to.

The light reflected from the optical recording medium 56 is reflected by the beam splitter 53 via the objective lens 55 and the collimator lens 54, separated from the optical axis c, and the concave lens 57 and the cylindrical lens provided on the side. The light is focused on a detector 59 such as a photodiode (PD) through the lens 58 and detected.

As another optical device, for example, as shown in FIG. 10 showing an example of the structure of an optical pickup section of a reflection type optical scanning microscope, light emitted from a light source 51 is reflected by a beam splitter 53, The surface of the sample 60 is condensed and illuminated by the objective lens 55. 61 denotes a focal plane. Then, the light reflected by the sample 60 is transmitted through the beam splitter 53 through the objective lens 55 and a detector is arranged at the confocal position, or a pinhole 62 is arranged and the light passing therethrough is arranged behind it. Detector 5
9 to detect. At this time, as shown by the arrow s, the state of the sample surface can be detected by relatively scanning the stage (mounting table) on which the sample 60 is placed or the irradiation beam.

In the above-mentioned conventional optical system of the pickup system, the reflected light is prevented from returning to the emission position, that is, the light source, and the beam splitter is arranged between the light source and the irradiated portion as described above. As disclosed in Japanese Unexamined Patent Publication No. 1-303638, a configuration such as arranging holograms is adopted, and reflected light, that is, return light to a light source is separated from an optical path toward an irradiated portion and received and detected. It is configured to lead to the light receiving portion. However, in this case, the amount of light received by the light receiving element becomes small, and further there is a problem in that the alignment is complicated, the accuracy is problematic, and the assembly and manufacturing are complicated.

Further, as disclosed in, for example, Japanese Unexamined Patent Publication No. 2-278779, when the above optical pickup device is hybridly assembled on the same semiconductor substrate such as Si, strict alignment accuracy is required. Become.

[0008]

SUMMARY OF THE INVENTION The present invention seeks to simplify the structure of an optical device such as an optical device of an optical pickup system, downsize the entire device, simplify manufacturing, and improve reliability. Further, the amount of light returned to the light receiving element, that is, the amount of received light, can be increased to improve the output, and thus to reduce the power of the light emitting light source and thus the power consumption.

Further, particularly in the present invention, it is possible to easily take out a signal for detecting the distance to the irradiated portion, for example, a servo signal for focusing control of light irradiation to the irradiated portion. The optical device according to the present invention can be obtained.

According to a first aspect of the present invention, a light emitting portion and a light receiving portion are arranged in proximity to each other, and the return light of the emitted light from the light emitting portion toward the light emitting portion from the irradiated portion is received. And an optical element for receiving and detecting light, and the return light to the light receiving surface of the light receiving unit has astigmatism.

The second aspect of the present invention, as shown in the schematic configuration diagram of FIG. 1, shows that the light emitting section 1 and the light receiving section 4 are arranged close to each other, and the irradiated section 2 of the emitted light L from the light emitting section 1 is irradiated. The light emitting section 1 has an optical element 21 for detecting the return light L _R from the light emitting section 1 received by the light receiving section 4, and the emitted light L from the light emitting section 1 has astigmatism. And the irradiated part 2
The astigmatism correction / addition means CR for correcting the astigmatism of the light emitted from the light emitting section 1 toward the head and applying the astigmatism to the return light from the irradiated section 2 is arranged.

In a third aspect of the present invention, the light emitting section 1 has a semiconductor laser having astigmatism in its emitted light in the above-mentioned configuration.

In a fourth aspect of the present invention, in the above-mentioned configuration, the light emitting section 1 is provided with a reflecting mirror that imparts astigmatism to the light emitted from the light source.

[0013]

As described above, in the structure of the present invention, the irradiated portion 2
The return light itself from the light emitting section 1 toward the light emitting section 1 is received and detected by the light receiving section 4. In this case, the return light received by the light receiving section 4 is received in an area other than the emitting section of the light emitting section 1. Therefore, the emitting part of the light emitting part 1 becomes an ineffective region for receiving light. However, according to the invention,
Since the astigmatic difference is generated in the returning light to the light receiving section 4, the spot of the returning light is
The center of the intensity distribution deviates from the center of the ineffective region formed by the light emitting unit 1, and the reduction in the amount of light received due to the existence of the ineffective region can be reduced.

According to the above-mentioned optical element 21, for example, in the light receiving section 4, by dividing the light receiving surface into a plurality of light receiving elements, that is, by forming a plurality of light receiving elements, for example, detection of a focusing state by a so-called astigmatism method,
That is, it is possible to detect the position with respect to the light irradiation portion, and it is possible to perform focusing servo of the emitted light from the light emitting portion 1 with respect to the irradiated portion 2 by this detection signal, for example, a focusing signal.

By increasing the amount of received light,
Since the number of detection signals can be increased, it is possible to reduce the light amount of the light emitting unit 1 and thus save power consumption.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention, as shown in FIG. 1, has a structure in which a light emitting section 1 and a light receiving section 4 are arranged in proximity to each other, for example, on a common substrate 9, and the emitted light L from the light emitting section 1 is irradiated. 2 is provided with an optical element 21 for receiving and detecting the return light L _R itself to the light emitting unit 1 due to the reflection at the irradiated portion 2 by the light receiving unit 4, and the return light to the light receiving surface of the light receiving unit 4 is The configuration has astigmatism.

In this case, with respect to the light traveling from the light emitting portion 1 to the irradiated portion 2, light having no astigmatism or having astigmatism can be used depending on the use mode and purpose. When the irradiation unit 2 is an optical recording medium and is applied to a reproducing pickup for reading a record on the optical recording medium, the light traveling toward the irradiated unit 2 is generally light without astigmatism.

According to the above-mentioned optical element 21, the return light received by the light receiving section 4 is received in the area other than the emitting section of the light emitting section 1, so that the emitting section of the light emitting section 1 is ineffective for receiving light. It becomes an area. However, according to the present invention, since the astigmatic difference is generated in the return light to the light receiving unit 4, the spot of the return light has the center of its intensity distribution as compared with the case of no aberration. The deviation from the center of the invalid area by the portion 1 can reduce the reduction in the amount of received light due to the existence of the invalid area.

In the example shown in FIG. 1, the irradiated portion 2 is an optical recording medium such as an optical disk, and the recording information recorded on the irradiated portion 2 as, for example, concave and convex pits is recorded by the light at this pit. This is a case where the present invention is applied to a reproducing pickup that reads recorded information depending on the intensity of reflected light due to diffraction.

As described above, when an astigmatic difference is generated in the detection of the return light L _{R in} the light receiving unit 4, the position sensor of the light receiving unit 4, particularly the irradiated portion 2 thereof, specifically, the focusing state Detection can be performed, and this detection signal is used as a focusing servo signal, for example.

In this case, the converging means 3 is provided between the optical element 21 having the light emitting section 1 and the light receiving section 4 and the irradiated section 2 made of the above-mentioned optical disk. Then, the light emitted from the light emitting section 1 is irradiated by the converging means 3 with the irradiated section 2.
Then, the return light reflected from the irradiated portion 2 is converged, and the light receiving portion 4 is arranged in the vicinity of the confocal point of the returned light from the irradiated portion 2 of the converging means 3. With this configuration, before and after the light emitted from the light emitting section 1 is reflected by the irradiated section 2, the light receiving section 4 receives the light passing through coaxial paths as shown by the optical axis of the chain line a. It will be configured.

The light received by the light receiving section 4 is to be converged to near the light diffraction limit of the optical system.
At least part of its light receiving surface is within this optical diffraction limit,
When the wavelength of the light emitted from the light emitting portion 1 is λ and the numerical aperture of the converging means 3 is NA, the distance from the optical axis a of the light emitted from the light emitting portion 1 across the arrangement reference plane S of the light receiving surface is 1.22λ
It should be provided within a position within / NA.

Further, in this case, as shown in FIG. 1, the diameter φs of the light emitted from the light emitting portion 1 on the arrangement reference plane S of the light receiving surface of the light receiving portion 4 is set to be smaller than the diameter φd of the light diffraction limit, and the light receiving is performed. The effective light receiving surface of the portion 1 is located outside the diameter φs of light emission. When a semiconductor laser is used as the light source of the light emitting unit 1, the diameter φs of the emitted light can be set to about 1 to 2 μm. On the other hand, when the numerical aperture NA of the converging means 3 is 0.09 to 0.1 and the wavelength λ of the emitted light is about 780 nm, the diffraction limit, that is, φd is 1.22λ / NA≈.
It becomes about 10 μm.

Then, the light emitting portion 1 is arranged at one confocal position of the converging means 3. Specifically, the waist of the light emitted from the semiconductor laser is located at this focus position. Then, the irradiated portion 2 is positioned at the other focus of the converging means 3.

In this case, as described above, the optical element 2 in which the light emitting portion 1 and the light receiving portion 4 are arranged close to each other on the common substrate 9.
1 is configured. In this optical element 21, for example, a compound semiconductor substrate is used as the substrate 9, a semiconductor laser is formed monolithically as the light source of the light emitting section 1, and a photodiode, for example, is formed as the light receiving section 4.

In the illustrated example, the light emitting section 1 is constituted by a horizontal cavity type semiconductor laser 8 as a light source and a reflecting mirror 7 for directing light emitted from the horizontal cavity type semiconductor laser 8 in a predetermined direction.

In order to generate an astigmatic difference in the direction orthogonal to the optical axis a and the directions orthogonal to each other with respect to the return light from the irradiated portion 2, that is, the optical recording medium to the light receiving portion 4 in this example, the light emitting portion is used. 1 is a semiconductor laser having astigmatism, for example, a gain guide structure, or the resonator end face (emission light end face) of the semiconductor laser is a curved surface asymmetric with respect to a predetermined direction orthogonal to each other, For example, the mirror 7 may have a curved surface that is asymmetric with respect to a direction orthogonal to the predetermined direction.

On the other hand, astigmatism correction means for correcting astigmatism of light from the light emitting section 1 having astigmatism is provided between the light emitting section 1 and the irradiated section 2. As this astigmatism correction means, known means can be used. For example, as schematically shown in FIG. 2 and FIG. 3 in the shape of cross sections orthogonal to each other, only one of them is, for example, a concave lens or a cylindrical lens having a convex lens effect, or a lens having different lens effects in mutually orthogonal directions. Although not shown, a transparent parallel plate is tilted in one axis direction. When such astigmatism correction means is used, astigmatism is corrected for the light on the outward path from the light emitting unit 1 to the irradiated portion 2, but the return light from the irradiated portion 2 is By passing through the correcting means in the opposite direction again, the light having the astigmatism is obtained again. That is, the above-mentioned astigmatism correction means becomes the astigmatism correction / addition means CR.

The light receiving section 4 is, for example, as shown in FIG.
It is configured by the light receiving elements 4A, 4B, 4C and 4D having a divided configuration. These light receiving elements 4A, 4B, 4C and 4D are symmetrically arranged around the optical axis of the return light, that is, the emission center from the light emitting unit 1. Then, for example, when the emitted light L from the light emitting section 1 is in the so-called just focus state with respect to the irradiated section 2, the returning light spot SP is changed to the respective light receiving elements 4A, 4B, 4C and 4D as shown in FIG. 4B.
If a uniform light receiving amount is given to each of the light receiving elements 4A, 4B, 4C and 4D due to underfocus or overfocus, the returning light spot SP becomes an ellipse or an ellipse as shown in FIG. 4A or 4B.
A change occurs in the amount of received light for. Therefore, as shown in FIG. 5, the respective detection outputs A ...
A signal having a relationship between the focus position and the output as shown in FIG. 6 is obtained by performing an operation of summing B with respect to elements that are diagonal to each other and subtracting them, that is, an operation of (A + B)-(C + D). That is, the focus servo signal can be taken out.

Therefore, for example, in the above-mentioned pickup device, an actuator capable of making a minute movement with respect to the irradiated portion 2 along the axis a is provided, and the position adjustment of the converging means 3, that is, the focusing adjustment is performed by using this servo signal. it can.

With the focusing control performed in this manner, the signal is read from the optical disk of the irradiated portion 2 by the sum of the outputs of the entire light receiving portion, that is, for example, the entire light receiving elements 4A, 4B, 4C and 4D. To do.

In the above-mentioned example, the case where the irradiated portion 2 is, for example, an optical disk has been described, but the optical device to which the present invention is applied is not limited to the above-mentioned example, and is, for example, a magneto-optical disk. It is also possible to use an optical pickup device that reads out a signal magnetically recorded on the disk by the Kerr effect. In this case, although not shown, for example, the polarizer is provided between the light emitting section 1 and the irradiated section 2, that is, on the optical path from the light emitting section 1 to the irradiated section 2 and the optical path reflected back from the irradiated section 2. On the other hand, a configuration is adopted in which the analyzer is disposed on the one side and the analyzer is disposed so as to face the light receiving section 4 at a position avoiding the optical path of the light emitted from the light emitting section 1.

According to this structure, the light applied to the magneto-optical disk of the irradiated portion 2 becomes the return light whose polarization plane is rotated by the Kerr effect according to the recorded information, so that it depends on the Kerr rotation angle. The amount of light passing through the light detecting means 6 changes.
Therefore, if this is detected by the light receiving unit 4, the recording on the magneto-optical disk can be reproduced.

Further, the converging means 3 can have various structures such as a collimator lens structure.

Next, an example of the optical element 21 in which the light emitting portion 1 and the light receiving portion 4 are monolithically integrated on the common substrate 9 will be described with reference to FIGS. 7 and 8 together with an example of a manufacturing method thereof. To do.

In this case, as shown in FIG. 7A, a substrate 9 made of GaAs of the first conductivity type, for example, n-type, or an InP compound semiconductor substrate is prepared, and, for example, MOC is formed thereon.
By the VD (metalorganic chemical vapor deposition) method, for example, Al
First conductivity type n-type first cladding layer 2 made of GaAs
2, an active layer 23 made of, for example, GaAs or AlGaAs having a lower Al concentration than the cladding layer 22,
A cap layer 25 of p-type AlGaAs of conductivity type is sequentially epitaxially grown.

As shown in FIG. 7B, the current blocking region 26 and the impurity of the first conductivity type, for example, n type, are selected so as to sandwich the region which finally constitutes the resonator of the semiconductor laser from above the cap layer 25. The region is formed by ion implantation.

As shown in FIG. 7C, oblique grooves 27a are formed on the cap layer 25 at a depth of, for example, about 45 ° so as to cross the active layer 23 by anisotropic etching such as RIE (reactive etching). Further, for example, the cylindrical surface groove 27b is formed on one side surface side by similar anisotropic etching.
To form.

As shown in FIG. 7D, a vertical groove 27c is formed by anisotropic etching such as RIE so that the side surface of the groove 27b opposite to the side having the cylindrical surface groove 27b is vertically cut off.

As shown in FIG. 8A, if necessary, the cylindrical surface groove 2 is formed by oblique vapor deposition, CVD (chemical vapor deposition) or the like.
Cylindrical surface groove 27b is formed on the inclined side surface of inclined groove 27a having 7b.
A reflection film is deposited including the inside to form the reflection mirror 7.

In this way, the semiconductor laser LD is provided on the side opposite to the side where the cylindrical surface groove 27b is formed with the groove 27c interposed therebetween.
And the cladding layer 22, on the opposite side across the groove 27c.
The photodiode PD is formed of each part of the active layer 23 and the cladding layer 24.

As shown in FIG. 8B, the photodiode P
A part of the cap layer 25 on D is removed to form a light receiving window 28.

As shown in FIG. 8C, the photodiode P
The electrode 30 of D and the electrode 31 of the semiconductor laser LD are ohmic-contacted on the cap layer 25, and the common electrode 30 is ohmic-contacted on the back surface of the substrate 9.

In this way, the semiconductor laser LD as a light source is formed on the common substrate 9, and the laser light generated from the semiconductor laser LD is reflected by the reflecting mirror 7 and directed in a predetermined direction, and the photo diode. The optical element 21 including the diode PD is formed. In this case, since the reflecting mirror 7 is a reflecting mirror having a cylindrical surface formed by the cylindrical groove 27b, the light emitted from the light emitting unit 1 becomes light having astigmatism.

In the above-mentioned example, the astigmatism is generated by the reflecting mirror 7. However, the reflecting mirror 7 that generates such astigmatism is used, or a plane that does not generate astigmatism. Laser diode L using a circular reflector
Regarding D, this may be a semiconductor laser structure having a large astigmatism.

When the photodiodes 4A, 4B, 4C and 4D having the above-mentioned four-division structure are formed as the optical element 21, the semiconductor laser is formed on the semiconductor laser on the side where the groove 27c is sandwiched. A photodiode may be formed.

In the optical element 21 of the device of the present invention, the light emitting portion 1 and the light receiving portion 4 are monolithically formed on the common substrate 9 so that the distance between them can be made sufficiently small, for example, about several μm. Therefore, the return light traveling toward the light emitting unit 1 can be efficiently received, and the positional relationship between the respective units such as the alignment of the optical axis and the light receiving unit can be set accurately, reliably and in mass production.

[0048]

In the device of the present invention, since the return light of the light emitted from the light emitting section 1 to the light emitting section 1 is received by the light receiving section 4, at least as compared with the case where the return light is branched and received. In the light receiving unit 4, the amount of received light can be increased. In this case, however, this light reception is received in a region other than the emitting unit of the light emitting unit 1. Therefore, the emitting unit of the light emitting unit 1 is ineffective for receiving light. It becomes an area. However, according to the present invention, since the astigmatic difference is generated in the return light to the light receiving unit 4, the spot of the return light has the center of its intensity distribution as compared with the case of no aberration. By deviating from the center of the ineffective region by the portion 1, it is possible to reduce the decrease in the amount of received light due to the existence of the ineffective region, and as described above, the return light is incident on the light receiving surface with an inclination. By doing so, it is possible to reduce the effective dead region by the light emitting unit 1, and thus it is possible to further improve the amount of received light.

Further, according to the above-described configuration of the present invention, since the return light itself to the light emitting section 1 is received by the light receiving section 4, the optical axes a of the irradiated section 2 are aligned before and after the irradiated section 2. Since the light emitting unit 1 and the light receiving unit 4 are arranged close to each other, the light receiving unit 4 can be arranged substantially at the confocal position with the light emitting unit, whereby efficient light reception can be performed and the return When the light is separated and directed to the light receiving unit 4, it is possible to avoid alignment such as axial alignment of the light path separating unit and the light receiving unit, thereby improving accuracy,
Assembling and manufacturing can be simplified and reliability can be improved.

As described above, since the amount of light received by the light receiving section 4 can be improved, the intensity of light and light can be reduced, and the power consumption can be reduced. It is possible to improve the S / N because it is possible to improve the S / N ratio.

Further, according to the configuration of the present invention, it is possible to obtain an effect such as position detection by the astigmatism method, for example, focusing servo can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an optical device according to the present invention.

FIG. 2 is a schematic configuration diagram in one cross section of an example of an optical device according to the present invention.

FIG. 3 is a schematic configuration diagram in another cross section of an example of the optical device according to the present invention.

FIG. 4 is an explanatory diagram of a method of detecting a focusing servo signal by an astigmatism method of an example of the optical device of the present invention. FIG. 8A is a diagram showing a relationship between a returning light spot and a light receiving section in a state where focusing is deviated. FIG. 6B is a diagram showing the relationship between the returning light spot and the light receiving section in the just focusing state. FIG. 6C is a diagram showing the relationship between the returning light spot and the light receiving section in a state where focusing is deviated.

FIG. 5 is an explanatory diagram of a method of detecting a focusing servo signal of the device of the present invention.

FIG. 6 is a focus signal output curve diagram of the device of the present invention.

FIG. 7 is a process diagram (1) of an example of the manufacturing method of the device of the present invention. A is the one process drawing. B is the one process drawing. C is the one process drawing. D is the one process drawing.

FIG. 8 is a process diagram (2) of the method of manufacturing an example of the device of the present invention. A is the one process drawing. B is the one process drawing. C is the one process drawing.

FIG. 9 is a schematic configuration diagram of an example of an optical device.

FIG. 10 is a schematic configuration diagram of another example of the optical device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting part 2 Irradiated part 3 Converging means 7 Reflecting mirror CR Astigmatism correction / addition means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Matsuda 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (4)

[Claims] 1. A light emitting unit and a light receiving unit are arranged in proximity to each other, and an optical element is provided for detecting, by the light receiving unit, return light of the emitted light from the light emitting unit, which is directed to the light emitting unit from the irradiated portion, An optical device, wherein the return light to the light receiving surface of the light receiving section has astigmatism. 2. A light emitting part and a light receiving part are arranged in close proximity to each other, and an optical element is provided for detecting, by the light receiving part, return light of the emitted light from the light emitting part, which is returned from the irradiated part toward the light emitting part, The light emitted from the light emitting section has astigmatism, and the astigmatism of the light emitted from the light emitting section toward the irradiated section is corrected between the light emitting section and the irradiated section. An optical device characterized in that an astigmatism correction / applying means for providing astigmatism to the return light from the irradiated portion is arranged. 3. The light emitting section comprises a semiconductor laser having astigmatism in emitted light.
Or the optical device according to 2. 4. The optical device according to claim 1, wherein the light emitting unit includes a reflecting mirror that imparts astigmatism to the light emitted from the light source.