JPH01229437A - Optical pickup device and semiconductor device applied to pickup device - Google Patents

Abstract

PURPOSE:To obtain a compact optical pickup device by using the photodetecting element set linearly and a lens Fourier transform hologram element in combination with other optical elements. CONSTITUTION:The title device consist of a semiconductor laser 1 of the short wavelength a condenser lens 5, an optical disk (optical recording medium) 7, a lens Fourier transform type hologram diffraction element 2, and two pairs of photodetecting elements 611-614. The laser beams radiated from the laser 1 are condensed at the medium 7 through the lens 5. The reflected light including the recording information, etc., is diffracted into two directions by the element 2 after passing through the lens 5 again. These diffracted beams are condensed at the point near the middle part between both pairs of elements 611, 612 and 613, 614. Thus the stable detection of signals is possible by connecting the minute spots to the focusing and tracking beam control optical systems for example. In such a constitution, an optical system is simplified and a compact optical pickup device is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical pickup device for recording and reproducing optical information stored on an optical or magneto-optical medium such as an optical disk or an optical card, and a semiconductor device used in the pickup device. It relates to a light receiving and emitting device.

Conventional technology Optical memory technology that uses pit-like patterns as a high-density, large-capacity storage medium is being put into practical use with its applications expanding to include digital audio discs, video discs, document file discs, and even data files. . The mechanism by which information is recorded and reproduced successfully with high reliability through a light beam focused on the micron order lies in the structure for picking up the optical information, especially the optical system. The basic functions of an optical pickup device (hereinafter abbreviated as OPU) are (1) light focusing to form a diffraction-limited minute spot, (11) focus control and pit signal detection of the optical system, and (iiD tracking). It is roughly divided into three types of control.

These can be realized by combining various optical systems and photoelectric conversion detection methods depending on the purpose and application. 13th
The figure is a schematic diagram showing an example of a conventional OPU. Normal T
A diverging wavefront (electric field: horizontally polarized wave) from a semiconductor laser light source 1 oscillating in E0° mode is selected as a parallel beam by a collimating lens 12 and a left quarter-wave plate (2λ plate) 4 by a polarizing beam splitter 3. reflect. The circularly polarized wavefront that has passed through the %λ plate 4 is narrowed down to a spot of about 1 μm by the condenser lens system 5, reaches the optical disk medium surface 7, and irradiates a pit-like pattern. The light beam reflected and diffracted by the medium surface 7 travels in the opposite direction through the condensing lens system 6 again, passes through the λ plate 4, becomes a vertically polarized parallel beam, and passes through the polarizing beam splitter 3 to form a prism half mirror. 17 and is divided into two directions. The negative reflected light passes through the condensing lens 9 and the cylindrical lens 1o that imparts astigmatism, enters the four-part photodetector 11, and is converted into a focus control signal. The other transmitted light enters the two-split photodetector 8 for tracking control signal detection with the far field pattern intact.

Here, by combining the Arashi λ plate 4 with the polarization beam splinter 3, it increases the efficiency of using the amount of light and at the same time suppresses the light returned to the semiconductor laser, so that unnecessary noise does not increase in the signal light component. However, the OPU for read-only discs has some leeway in light quantity design, and it is possible to omit the λ plate and polarizing beam splitter.

Problems to be Solved by the Invention However, even in a read-only OPU, it is necessary to construct a beam splitting means, a focus control means using astigmatism or the Knifezi method, and a tracking control means independently or in combination. The optical components conventionally used for this purpose, such as beam splitters, lenses, and prisms, are difficult to manufacture, assemble, and adjust in large quantities, and it is difficult to manufacture, assemble, and adjust them in large quantities. There was a problem.

These problems can be solved by introducing an optical element having multiple functions, and an attempt has recently been reported to place a hologram element 21 close to the condenser lens 5 as shown in FIG.

((1) Mokuzai, Ono, Sugama, Ota; Autumn 1961 Proceedings of Japan Society of Applied Physics, 30P'2ZE-1, P, 227 (19
86). (2) Same; 22nd Micro-Optics Research Conference Lecture Paper; vol, + (1986) P, 3B) Conventionally, elements were created in the wavelength range suitable for hologram recording (λ1: 4oo to 500 nm) and used as OPU light sources. When reproduced with a suitable near-infrared or red laser (λ2: ~800 nm, 633 nm), significant aberrations occur in the lens action of the hologram, and it is difficult to correct them.

Therefore, the hologram element 21 is designed based on the concept of a so-called lensless Fourier transform hologram system, and the hologram element 21 is designed to have an effect equivalent to the "wedge prism method" or the "double knife method".
It is realized by electron beam lithography in the form of two parts, 212 and 212.

In this way, it is possible to create a hologram lens 21 that is free of aberration only for the design wavelength λ2 of the light source 1 used, and moreover, the aberration caused by slight variations in the spectral width of the light source is suppressed by the photodetector of the beam detector (photodetector) 22. Even if it appears on the conversion surface, the 4-division photoelectric conversion surface 221.222.22
The push-pull method using 3.224 makes it possible to suppress fluctuations within a range that does not pose a practical problem.

However, in this method, the beam splitter, prism, and cylindrical lens are replaced with a single hologram element, so although it is possible to reduce the number of parts and downsize the pickup, it still requires a light-receiving element with a constant area divided into four parts. In order to use the laser, it is necessary to install the light receiving element at a large distance from the laser light source, which requires adjusting the optical axis, which limits the ability to achieve miniaturization and cost reduction. Furthermore, as mentioned above, since the semiconductor laser and the light receiving element need to be installed at a distance of about the size of each element, that is, a distance of about several U, the hologram period of the hologram element described above is made small, and the diffraction angle of the light is In this case, the effect of wavelength dispersion becomes large. Therefore, if wavelength fluctuations of the semiconductor laser occur due to temperature changes, the focusing position of the diffracted light will deviate greatly from the center of the photodetector, making it difficult to accurately This has the disadvantage that signal detection becomes impossible.

The present invention realizes miniaturization of the OPU, and also uses a hologram element based on more general optical principles to stably and To make a simplified optical system configurable.

In this case, in the present invention, a hologram element can be designed and manufactured at any wavelength as a lens Fourier transform type that does not impart focusing power to the hologram element, and the above-mentioned position adjustment in the optical axis direction is not necessary.

Further, in the present invention, a chirping diffraction grating (off-axis one-dimensional Fresnel zone plate) whose spatial period changes continuously is used as the above-mentioned hologram element.

Furthermore, the present invention provides a semiconductor light receiving/emitting element that reduces the effect of wavelength dispersion mentioned above and enables accurate signal detection even when wavelength fluctuation occurs in an optical pickup device using a hologram element. It is something.

Means for Solving the Problems The first invention, in order to solve the above-mentioned problems, provides a semiconductor laser and an optical system that focuses the laser beam emitted from the semiconductor laser onto a predetermined storage medium in the form of a minute spot. By using two pairs of light-receiving elements arranged in a straight line with a guiding and diffraction element and connecting them to, for example, a focusing and tracking beam control optical system for the minute spot, stable signal detection becomes possible, simplifying the optical system. This allows the device to be made smaller.

The second invention focuses a laser beam from a semiconductor laser onto an optical storage medium in the form of a minute spot using an optical system, and also installs a one-dimensional Fresnel zone plate-like diffraction element between the laser and the optical system. This is an optical pickup in which two or more light-receiving elements are arranged on a straight line passing through the light emitting part of the laser. That is, the present invention guides a semiconductor laser and a laser beam emitted from the semiconductor laser to an optical system that converges it into a minute spot onto a predetermined storage medium, and uses a light receiving element arranged in a straight line with the diffraction element. By connecting it to a micro-spot focusing beam control optical system, stable signal detection becomes possible, simplifying the optical system and downsizing the device.

In the third invention, a semiconductor laser and a plurality of light receiving elements are formed on a semiconductor substrate, a laser beam emitted from the semiconductor laser is irradiated onto a predetermined medium, and the laser beam reflected or diffracted by the medium is This semiconductor device is characterized in that the intensity of a laser beam that is incident on the light receiving element and reflected or diffracted by a medium is detected.

Regarding the characteristics of working lens Fourier transform holograms, please refer to the literature ("Kanji Memory by Holography").

Kato, Fujito, Sato; Proceedings of the Institute of Image Electronics Engineers of Japan 79-0
4-1 (1979,-+1,) (4) 5peakl
erCduction in holography-
”, M, Kat.

etal; Applied Optics (Appl, Op
t,).

14 (1975) 1093), etc., it has been applied to optical systems for recording and reproducing general images ("Optical Kanji Editing Processing System" by Sato et al.; Institute of Electronics and Communication Engineers Study Group Materials, EC78). -53 (1978) 4
7) However, in the first invention, as long as there is no practical problem as a beam control means, it is sufficient that Fourier transform is established for the wavefront near the optical axis of the reproducing optical system, and the lens used for reproducing the wavefront from the hologram element is , a collimating lens can be used instead, or simply by irradiating the hologram element with a convergent spherical wave, it is possible to obtain a desired reconstructed image on the condensing surface.

The second invention uses a diffraction grating with a chirping structure (one-dimensional Fresnel zone plate) in the optical path of the condensing reflected light that contains the signal from the optical disk. In addition to condensing light with astigmatism of a predetermined spot size in the vicinity of two points shifted in the horizontal direction, the condensing distances that form the minimum spot diameter in each diffraction direction are different from each other, and in the direction perpendicular to the diffraction direction. This takes advantage of the fact that the condensing distance is constant. Therefore,
For example, in a completely focused state, the +1st order diffracted light is focused at a predetermined position in front of the light receiving element, and the other 11th order diffracted light is focused at a predetermined position behind the light receiving element. If the design is designed so that when the focusing shifts, the length of the oval focused image will expand or contract, and the amount of light detected by the light receiving element with a sufficiently small light receiving surface will increase or decrease in opposite directions. be.

The third invention is to improve the diffraction angle of light by the hologram diffraction element by forming the semiconductor laser and the light-receiving element on the same substrate, and by arranging the light-emitting point of the semiconductor laser and the light-receiving element close to each other. This is based on the idea that it is possible to easily detect an accurate signal even when wavelength fluctuations occur by reducing fluctuations in the focusing position of diffracted light due to wavelength fluctuations, and also by reducing the distance between the semiconductor laser and the photodetector. Since is the distance between stripes, it is based on the fact that it is completely determined by the precision of photolithography.

Example The details of the present invention will be explained using examples.

FIG. 1 shows a schematic configuration of an optical pickup device according to an embodiment of the first invention. 1 is a short wavelength semiconductor laser (λ
= 800 nm), 5 is the condensing V''/s, 7 is the optical disc (
optical recording medium), 2 is a lens Fourier transform type hologram diffraction element that generates astigmatism, 611 , 612 , 6
13 and 614 are two pairs of light receiving elements.

A laser beam emitted from the semiconductor laser 1 is focused onto an optical recording medium 7 by a condenser lens 6 .

The reflected light containing recorded information etc. passes through the condensing lens 5 again,
The light is diffracted in two directions by the diffraction element 2 and focused near the openings of the light receiving elements 611 and 612 and 613 and 614, respectively.

Further, in this embodiment, the semiconductor laser 1 and the light receiving element group are formed on the same substrate as schematically shown in FIG. 2, and the light receiving element also has the same structure as the laser. 620 is an electrode, 621 is an n-type GaAs substrate, 622 is an n-type cladding layer of Al - p-type cladding layer of Air A8, θ26 is Ga As cap layer, 261, 26
2°263, 264, and 265 are electrodes, and by injecting a forward current between the electrodes 263 and 620, laser oscillation occurs in the central active layer 1.

Also, when the light is emitted from the laser 1, reflected on the surface of the optical disk, diffracted and focused by the lens system and the diffraction element, and enters the elements 611, 612, 613, 614, the electrodes 620, 261, 282゜264.26
A photocurrent or photovoltaic force is generated during the period 5, and it functions as a light receiving element.

In the above configuration, the operation and characteristics of the OPU of the present invention will become completely clear by explaining the optical system for manufacturing the hologram element 2. FIG. 3a is a conceptual diagram of an optical system realized as a hologram that can accurately record and reproduce an astigmatic wavefront.

A cylindrical lens 10 is disposed in an optical path in which a coherent parallel beam 13 with a wavelength λ1 is condensed by a condensing lens 61, and linear converged beams 101. A substantially circular beam 102 is obtained at f03 and its intermediate position.

Assume now that the beam 102 is on the Xl-Y coordinate plane. This optical system is similar to that conventionally used to generate astigmatism in optical pickup optical systems, but what is important here is that the Fourier transform lens 6
(focal length !1) through the circular beam 10
A so-called lens Fourier transform type hologram element 313 is created by attaching the Fourier transform wavefront of No. 2 to the rear Fourier transform surface (indicated by ξ-η coordinates) of the lens 6o and superimposing it with another plane wave that does not contain aberrations. create.

It is a well-known technique that the above reference wave can be easily obtained using an aberration-free spherical wave that diverges from a predetermined position 16 on the front focal plane of the Fourier transform lens 50. Here, the reference wave is easily obtained by converging the parallel beam 13 and the parallel beam 14, which are mutually coherent, with the lens 15. Of course, the reference wave may be a plane wave directly guided to the hologram surface without passing through the lens 50.

Now, the hologram element 313 recorded in this way
When is placed in an optical system as shown in Figure 3 and irradiated with a parallel beam of wavelength λ2, on the back focal plane (indicated by x2-Y2 coordinates) of the Fourier transform lens 5 (focal length f),
Reconstructed image 1021 of a wavefront including astigmatism and its conjugate image 1
o22 are reproduced in a mutually symmetrical positional relationship with respect to the x2-Y2 coordinate point, and horizontal or vertical linear patterns 1011.1031 and 1012.1032 are obtained in the front and rear directions of each spot image. Since they are conjugate wavefronts, the linear image 1031 in the vertical direction is located close to the lens 5 on one side, and the horizontal images 1o12 appear side by side on the other side.

FIG. 4 illustrates the principle of operation of the optical system shown in FIG. 1 by explaining the principle of operation of the optical system shown in FIG. This is explained from the perspective of the shape of L2.

That is, in FIG. 4a, when the beam focused by the condensing lens 5 is separated from the pit surface 7o of the optical disk by a minute distance Δf in the front and rear directions (causing a focusing error), the hologram element 2 is The beams 1o21 and 1022, which are diffracted through them, are shown on the photodetector.

It will have a shape like C or d. However, in this embodiment, it is arranged on the light receiving surface x2 of the photodetector. Part C of the figure shows the situation when the image is brought into focus. The focus control signal ε is applied to each sector 61 of the photodetector.
The signal output components corresponding to numbers 1 to 614 are respectively S1. S2.
S3. As S4, the command can be executed.

Considering the stability of the servo, the tracking signal I is
A method of detecting from another photodetector using a far field pattern is more desirable.

In the above explanation, astigmatism was solved using a cylindrical lens, but another optical system, for example, inserting a parallel plate obliquely into the optical axis of the convergent spherical wave, or using another appropriate aberration. A spherical element may also be used.

In the above, the method that includes astigmatism as a beam control wavefront has been mainly explained with reference to the recording optical system of the lens Fourier transform hologram and the wavefront reproducing optical system of the information pickup optical system.The present invention is based on these principles. The present invention is not limited to a device that stands on a bench, and it is also possible to replace the conventional optical system of a more general pickup with a single hologram element.

That is, in addition to the beam control optical system described above, it is possible to record the wavefront of various conventionally developed optical systems or a beam control optical system that is more suitable for the purpose as a lens Fourier transform hologram element in advance. .

- The lattice pattern of the recorded elements can be transferred to a mold that can be easily reproduced, and a large number of uniform elements can be obtained at low cost by manufacturing replicas using resin or glass materials. This has a great effect on the design and production of. Since the replicated pattern is of the Fourier transform type, it is possible to blaze the mold by ion beam processing, etc., and the Fresnel zone plate glazing technology (Natsuai, Kubota, Nishida; 18th Micro-Optics Research Conference lecture paper; vo13 (1985) P, 3
Compared to 3), the diffraction efficiency of the replica element can be easily blazed.

That is, it is possible to obliquely illuminate the entire surface of the hologram consisting of a substantially parallel grid pattern.

The details of the second invention will be explained using examples.

FIG. 5 shows a schematic configuration of an optical pickup device according to an embodiment of the second invention. 1 is a short wavelength semiconductor laser (λ
= 800 nm), 5 is a condensing lens, 7 is an optical recording medium, 2
615 and 616 are a diffraction grating having a chirping structure, that is, a structure in which the spatial period changes continuously, and a light receiving element.

A laser beam emitted from the semiconductor laser 1 is focused by a condensing lens 5 onto an optical recording medium γ.

The reflected light containing recorded information etc. passes through the condensing lens 5 again,
The light is diffracted by the diffraction grating 2 in the υ2 direction and focused near the light receiving elements 615 and 616, respectively.

Further, in this embodiment, the semiconductor laser 1 and the light receiving element are formed on the same substrate as shown in a schematic cross-sectional view in FIG. 6, and the light receiving element also has the same structure as the laser. 620 is an electrode, 621 is an n-type GaAs substrate, and 622 is AdxGal-! As n-type cladding layer,
623 is A ly G a 1-y As (y<x
<1) active layer, 624 is a p-type cladding layer of AlxGa1-Air AS, 625 is a p-type GaAs cap layer, 266, 263, 267 are electrodes, 26
By injecting a forward current between 3 and 620, the active layer 1 in the center oscillates as a laser. When light is emitted from 1, reflected on the surface of the optical disk, diffracted and focused by the lens system and diffraction element, and incident on 615 and 616, a photocurrent or photovoltaic force is generated between the electrode 820 and 266.26γ. is generated and acts as a light receiving element. S indicates the distance between the semiconductor laser and the light receiving element.

The operation of the OPU of the present invention in the above configuration will be explained using FIG. That is, in FIG. 4a, when the beam focused by the condenser lens 5 is separated from the focal plane To of the optical disk by a minute distance Δf in the front and back (causing a focusing error), the diffraction element 2 is The diffracted beams 1o21 and 1o22 have a shape on the photodetector as shown in FIG. 7a or c. The figure shows what happens when the image is brought into focus. The focus control signal ε is applied to each sector θ15 and 61 of the 7-point detector.
The signal output components corresponding to S1. As S2, ε=S1-32, (1)
> , and focal side control is possible according to the condition ε=O.

FIG. 8 shows a schematic cross-sectional view of a semiconductor laser and a light receiving element used in the second embodiment of the present invention, and the principle of signal detection. The optical system of this embodiment is the same as the optical system shown in FIG. The major difference from the above embodiment is as shown in Fig. 8.
There are two pairs of light receiving elements with a three stripe structure, and each sector 614, 61j, 616, 817, 618
, 619 as Sl, S2 . S3.
S4. As S5゜S, the focusing signal is εF,
) If the racking signal is εT and the recording signal is εR, then ε
F=(S2+s4+36)-(S5+S,+S3) or S2-86εT=(S1+84)-(S3+86)εR
= (S1+S2+S3+S4+S6+S6), focus control can be executed according to the condition of εFmi0, and tracking control can be executed according to the condition of εTmio. In the embodiments described above, an optical path is formed in which the light beam emitted from the light source travels back and forth through the diffraction element, and a light spot is always focused on the light-emitting surface of the light-emitting element when the light beam is focused. Therefore, it is extremely easy to adjust the position of the light-receiving element, and by fixing the diffraction element in a pre-designed arrangement, it is possible to correctly receive light at a predetermined position on the light-receiving element. Regarding the fluctuation of the semiconductor laser light source wavelength,
This effect can be sufficiently avoided by setting the element spacing S in FIGS. 2 and 3 to several hundred microns.

The diffraction grating, semiconductor laser, and light receiving element of the present invention can be easily produced and have great effects in designing and manufacturing optical information pickup devices.

Although the embodiments of the present invention have been mainly described as beam control systems for optical disk optical systems, it is also possible to apply the present invention to optical systems with both recording and reproducing functions, as well as optical information pickup devices in magneto-optical storage and reproducing systems. Of course.

Details of the third invention will be explained using examples.

FIG. 9 shows a schematic diagram of a semiconductor device according to an embodiment of the present invention suitable for an optical pickup. The semiconductor laser 1 and the light receiving elements 615 and 616 are formed on the same substrate, and the light receiving element also has the same structure as the laser. In this embodiment, an n-type A substrate 621 is provided with an n-type A
l x Ga 1-x As layer 822, undoped AlyGa 1-As (y(x(1) active layer 6
23. p-type Al x Ga 1-x Asri?
7d layer 624, p-type GaAs cap layer 626
is epitaxially grown, and an electrode is formed thereon by vacuum vapor deposition. Then, by removing part of the electrode, cap layer, and cladding layer by etching, 266.267
．． A three-stripe laser structure or light-receiving element structure is formed under the 263 striped electrode portions.

Further, 620 is a common electrode. By injecting a forward current between the electrodes 262 and 620, laser oscillation occurs in the central active layer 1. Further, the light emitted from 1 is reflected by an optical storage medium etc., diffracted in two directions by the hologram element, and when it enters the active layer portions 611 and 812, the light emitted from the electrode 62
A photocurrent or photovoltaic force is generated between 0 and 261.263,
Works as a light receiving element. S indicates the distance between the semiconductor laser and the light receiving element.

FIG. 10 shows a schematic configuration of an optical pickup device to which the semiconductor device of the present invention is applied. 13 is a semiconductor device of the present invention, among which 1 is a semiconductor laser (λ ~ 780 nm);
611 and 612 indicate light receiving elements. Further, 6 is a condensing lens, 2 is an optical recording medium, and 2 is a one-dimensional 7-Resnel zone plate-shaped diffraction element (hologram element).

A laser beam emitted from the semiconductor laser 1 is focused by a condensing lens 5 onto an optical recording medium 7 and reflected. The reflected light including the recording information signal and focusing and tracking signals passes through the condenser lens 5 again, is diffracted in two directions by the diffraction grating 2, and is transmitted to light receiving elements 612 and 612, respectively.
The light is focused near the , and the signal is detected. The light detection principle in the above configuration is exactly the same as in the second invention.

The semiconductor device according to the present invention can be easily manufactured,
This has great effects in designing and manufacturing optical pickup devices.

FIG. 11 schematically shows a semiconductor device according to a second embodiment of the present invention. The principle of photodetection is exactly the same as the second invention.

Effects of the Invention As is clear from the above description, the first invention provides a compact optical pickup using a linearly arranged light receiving element and a lens Fourier transform hologram element in combination with other optical elements. The device can be realized. In addition, (11) a hologram records an astigmatic wavefront or a diffracted wavefront from a knife, but (1) even if the wavefront is reproduced at a wavelength λ2 different from the hologram creation wavelength λ, the hologram itself will not generate aberrations. (2) Using an inverse Fourier transform lens, beams for focus control and tracking control can be effectively divided and used from hologram diffracted light.

(3) Similar to optical disks, hologram elements can be easily produced in large quantities as replicas through a transfer process from a mold that serves as a mask.

(4) Since a lens-Fourier transform hologram is used that records a substantially parallel grating pattern, blaze processing using an ion beam or the like can be performed simultaneously on the entire surface in order to improve the diffraction efficiency of the element. A mask hologram mold can be manufactured.

(5) Another feature is that the detection error caused by the tilt of the light receiving element is small.

Furthermore, the second aspect of the invention can realize a compact optical pickup with an extremely simple configuration of a normal arrayed semiconductor laser, a chirping-shaped diffraction grating, and a condenser lens.

Furthermore, similar to optical disks, diffraction elements can be easily produced in large quantities through a transfer process from a mold that serves as a mask, and it is also possible to realize an inexpensive optical pickup.

In particular, in the present invention, since the positional relationship between the laser light source and the light receiving element is realized with an accuracy of 7 otolithography, there is no need for alignment of these, and the optical axis adjustment is mainly performed by adjusting the grating direction angle in the plane of the diffraction grating element. Since it can be done with only adjustments, it is highly suitable for mass production. Furthermore, compared to conventional detection systems, in the present invention, the light source and photodetector can be monolithically integrated, so the distance between the pixel elements can be designed on the order of several hundred microns. It's bearable enough.

For example, in the configuration shown in Figure 1, L = 20 Mll, grating pitch 1,000 Bottm, wavelength λ = 800 nmK, and the wavelength difference ±
At 20 nm, the spot movement amount on the photodetector is ±5 at most.
It can be designed to be around μ.

Further, the third aspect of the present invention has a structure similar to that of a normal arrayed semiconductor laser, and furthermore, a compact optical pickup can be realized with a simple structure of a diffraction grating having a chirping shape and a condensing lens. In particular, in the present invention, the positional relationship between the laser light source and the light receiving element is realized with the precision of photolithography, so when the above-mentioned 0PUK is applied, there is no need to align them, and the optical axis adjustment is mainly performed on the diffraction element surface. This can be done by simply adjusting the internal grating direction angle, making it highly suitable for mass production. Furthermore, compared to conventional detection systems, in the present invention, the light source and photodetector are monolithically integrated, so the distance between the pixel elements can be designed on the order of several hundred microns, and the diffraction angle of the diffraction grating changes due to wavelength fluctuations of the light source. can withstand enough. For example, in the configuration shown in Figure 2, L = 20 tm,
Grid pitch 8oμm.

When the wavelength difference is ±20 nm with respect to a wavelength of 800 nm, the amount of spot movement on the light receiving element can be designed to be approximately ±5 μm at most.

In addition, as an example of the present invention, a semiconductor device in which a light receiving element having a structure similar to that of a striped semiconductor laser is integrated has been shown. There is no problem even if it is a semiconductor device.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an optical information pickup device showing an embodiment of the present invention, Fig. 2 is a perspective view of a laser and a light receiving element section in an embodiment of the invention, and Fig. 3 is a recording of an astigmatic wavefront.・A principle diagram of the present invention explaining an example of reproduction, FIG. 4 is a conceptual diagram explaining the state of a beam reproduced on a photoelectric conversion surface regarding an embodiment of the present invention that records and reproduces an astigmatic wavefront, and FIG. 6 6 is a schematic diagram of an optical information pickup device showing another embodiment of the present invention, FIG. 6 is a perspective view of a semiconductor laser and a light receiving element of this embodiment, and FIG. 7 explains still another operation of the second invention. 8 is a schematic diagram of a semiconductor laser and a light receiving element according to an embodiment of the present invention, FIG. 9 is a schematic diagram of a semiconductor device according to an embodiment of the present invention, and FIG. 10 is a schematic diagram of a semiconductor device according to an embodiment of the present invention. FIG. 11 is a schematic cross-sectional view of a semiconductor device according to an embodiment of the present invention, FIG. 12 is a schematic diagram of an optical pickup optical system using a conventional hologram element, and FIG. 13 is a schematic diagram of a conventional optical pickup device. FIG. 2 is a schematic diagram showing an example of the configuration of an optical pickup optical system. DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 2... Hologram element, 3... Diffraction element that also serves as a polarizing beam splitter, 4... Quarter wavelength plate, 5...・・・・・・
Condensing optical system, 7... Optical disk, 8...
・Photodetector, 11...Photodetector, 1o...Cylindrical lens. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4 rOF! 1. l022- Diffraction beam Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 6/9

Claims (8)

[Claims] (1) A semiconductor laser, an optical system that focuses the laser beam emitted from the semiconductor laser onto a predetermined optical storage medium in the form of a minute spot, and a lens Fourier transform of a predetermined wavefront as means for controlling the focusing and tracking of the minute spot. An optical pickup device comprising a diffraction element recorded in a type hologram and two pairs of two-part light receiving elements arranged linearly. (2) The optical pickup device according to claim 1, wherein the diffraction grating is a hologram element that diffracts the light beam reflected on the surface of the optical disk in two directions and generates astigmatism. (3) A semiconductor laser, an optical system that focuses the laser beam emitted from the semiconductor laser onto a predetermined optical storage medium in the form of a minute spot, and a one-dimensional Fresnel zone plate placed between the laser and the optical system. An optical pickup device comprising a diffraction grating or a diffraction element whose spatial period changes continuously, and two or more light receiving elements arranged on a straight line passing through the light emitting part of the semiconductor laser. (4) The optical pickup device according to claim 1 or 3, wherein the light detection surface of the light receiving element is formed on an end surface of a semiconductor substrate on which a semiconductor laser is formed. (5) Claim 1 or 3, characterized in that the semiconductor laser is a stripe type semiconductor laser, and the light receiving element has a stripe structure arranged parallel to the semiconductor laser and having a similar configuration. The optical pickup device described in . (6) A semiconductor laser and a plurality of light receiving elements are formed on a semiconductor substrate, a laser beam emitted from this semiconductor laser is irradiated onto a predetermined medium, and the intensity of the laser beam reflected or diffracted by this medium is A semiconductor device characterized by being detected by a light receiving element. (7) The semiconductor device according to claim 6, wherein a light detection surface of the light receiving element is formed on an end surface of the semiconductor substrate. (8) The semiconductor laser according to claim 6, wherein the semiconductor laser is a semiconductor laser with a stripe structure, and the light receiving element has a stripe structure with a similar structure arranged in parallel to the semiconductor laser. Device.