JPS63167431A - Optical pickup device - Google Patents

Abstract

PURPOSE:To reduce the number of parts and to miniaturize a device, by forming a stable and simplified optical system by providing a hologram device having a composite function in an optical pickup device. CONSTITUTION:An optical beam from a semiconductor laser 1 is diffracted by a diffraction element 30, and a part of it is reflected and returned to the laser 1 as a feedback beam. A non-feedback beam passes through the optical system, and performs the recording and the reproduction of a recording medium by a micro spot, and also, performs focusing and tracking control. At this time, on one side of the diffraction element 30, a diffraction grating and a polarization selection reflecting film are provided, and it functions as an optical device having the composite function. Also, on the end face on one side of the laser 1, a reflection preventing film 100 for an oscillation wavelength is provided. In such way, it is possible to suppress noise by simplifying the optical system by attaching the composite function on the optical device, and stabilizing the oscillation mode of the laser. Thereby, the number of the parts can be reduced, and the optical system can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a 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.

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 depends solely on the structure that picks up the optical information, and in particular, on the optical system. There is. 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 of the optical system and bit signal detection, and oij) tracking of the optical system. It is roughly divided into three types of control. These are the purposes,
Depending on the application, it is realized by combining various optical systems and photoelectric conversion detection methods. Figure 7 shows the conventional O
It is a schematic diagram showing an example of PU. A diverging wavefront (electric field: horizontally polarized wave) from a semiconductor laser light source 1 that normally oscillates in TEoo mode is converted into a parallel beam by a collimator lens 2, and a left quarter-wave plate (114λ
Selective reflection to plate) 4. The elliptical polarized light wavefront passing through the Aλ plate is narrowed down to a spot of about 1 μm by a condenser lens system 6, reaches the optical disk medium surface 6, and irradiates a pit-like pattern. The light beam reflected and diffracted by the medium surface 6 travels in the opposite direction through the condensing lens system 6 again, passes through the quarter-wave plate 4, becomes a vertically polarized parallel beam, passes through the polarizing beam splitter 3, and enters the prism. It is divided into two directions by a half mirror 7.

One reflected light passes through a condensing lens 9 and a cylindrical lens 10 imparting astigmatism, enters a 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 unchanged.

Here, the λ plate 4 is used in combination with the polarizing beam splitter 3 to increase the efficiency of using the amount of light, and at the same time suppresses the return to the semiconductor laser, so that unnecessary noise does not increase in the signal light component. This is a device for this purpose. but,
In the OPU for read-only discs, there is a lot of leeway in the light intensity design, and it is possible to omit the μλ plate and polarizing beam splitter, and in particular, parts can be omitted for downsizing and cost reduction.

Compounding is being planned.

Problems to be Solved by the Invention However, even in a read-only OPH, it is necessary to construct a beam splitting means, a focus control means based on K such as astigmatism or the Knifezi method, and a tracking control means either 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.

The common reasons for these problems are: First, optical parts that require highly accurate flat or aspherical surfaces require many processes to achieve the desired processing, so production using pressing means is generally not possible. Second, it requires a lot of time and complicated inspection and measurement equipment to assemble and adjust a large number of parts to achieve a desired overall performance. Third, the parts are small. Since there are limits to the size of the optical system, there were also major constraints on the miniaturization of the entire optical system.

As a method to partially solve these problems, a technique has been developed in which, for example, the collimating lens 2 (or 9) shown in FIG. 7 is constructed of a Fresnel lens, and the lens is press-molded using a mold.

However, this does not reduce the number of parts, and components with a large number of surfaces, such as the prism beam splinter, remain unreplaced.

The above-mentioned reason 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.

(0) Mokuzai, Ono, Sugama, Ota; Autumn 1961 Proceedings of the Japan Society of Applied Physics, 30P-ZE-1, P, 227(1)
986) o (2) same; Lecture paper of the 22nd Micro-Optics Research Group; TOI, 4 (1986) P, 38) Conventionally, the wavelength range suitable for hologram recording (λ1: 400-500n
m), and use a near-infrared or red laser (λ2: ~800nm, 633nm) suitable as an OPU light source.
When reproduced with a hologram, significant aberrations occurred due to the lens action of the hologram, and it was difficult to correct them.

Therefore, the hologram element is constructed at two points P1 and 2 using an optical system as shown in FIG. Interference fringes between P2 and the reference light source R (actually, there are wavefronts 230 and 231 on one half of the hologram surface)
．． On the remaining side, the interference fringes between wavefronts 230 and 232) are expressed as ξ−η
The hologram element 21 is designed based on the idea of a so-called lensless Fourier transform hologram system, which is formed by a plane, and the hologram element 21 has parts 211 and 212 so as 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. By doing this, you can be sure that the design wavelength λ2 of the light source 1 to be used
In this case, it is possible to create an aberration-free hologram lens 21, and even if aberrations due to slight fluctuations in the spectral width of the light source appear on the photoelectric conversion surface of the beam detector (7 photodetector) 22, the 4-split photoelectric conversion is possible. Surface 221.222.
223.

The push-pull method using H.224 makes it possible to suppress fluctuations within a range that does not pose a practical problem. However, in FIG. 11, the pattern of the element 21 that can be written with an electron beam is
The technique is limited to simple patterns such as gratings and hyperbolic shapes, and no technique for forming more general hologram systems with high precision is disclosed at all. Furthermore, conventional hologram elements are
Although it was constructed as a "lensless Fourier transform hologram" that minimizes the lens function as a focusing power, it is possible that there is a slight wavelength deviation from the design wavelength λ of the pickup light source (
Δλ=±2 onm), a focus offset occurs, and it is necessary to provide a troublesome process of adjusting the position of the photodetector in the optical axis direction in order to adjust the wavelength shift due to the loft of the semiconductor laser.

First, the present invention provides a multifunctional hologram element that stably realizes OPH focusing and tracking control, and without imposing restrictions such as electron beam writing or recording and reproducing at a specific wavelength. It becomes possible to construct a stable and simplified optical system using a hologram element based on general optical principles. In that 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.

Second, the present invention provides an optical system that suppresses coherence fluctuations of a light source, which are necessary for stable operation of thin film elements such as hologram elements or Fresnel lenses, to a range that does not pose a practical problem. As a basis, the desired coherent beam and high signal-to-noise ratio can be obtained without making the optical system complex and expensive.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention (i) configures a light source optical system having optical feedback with a semiconductor laser, a collimating optical system, and a diffraction element, and (11) guiding the non-returning beam of the diffracted light from the diffraction element to an optical system that converges it into a minute spot on a predetermined storage medium, and controlling the minute spot, for example, by a focusing and tracking beam control optical system; Stable signal detection is possible by connecting with (
ill) Preferably, by using a maple wave plate and a diffraction element with a polarization selective reflection film, the light source system and the beam control optical system can be optically completely separated to realize more stable signal detection. The optical system can be simplified by using a Fourier transform hologram element.

Regarding the characteristics of the working lens Fourier transform hologram, please refer to the literature ((3) Kanji memory using r-holography).

Kato, Fujito, Sato; Proceedings of the Institute of Image Electronics Engineers of Japan 9-0
4-1 (1979, 11,) (4) 5peckle
As reported and analyzed in detail in (5) Optical Kanji Editing Processing System for general images, as reported and analyzed in detail in Sato et al.; IEICE Study Group Materials,
EC7B-53 (1978) 47) However, in the present 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 wavefront reproducing from the hologram element is The lens used for this can be replaced by a collimating lens, or by simply irradiating the hologram element with a convergent spherical wave, it is possible to obtain a desired reconstructed image on the condensing surface.

The present invention solves the following problems by providing the above-described configuration.

(1) In the process of creating a hologram element, a lens Fourier transform type hologram recording system with a predetermined wavefront such as an astigmatism wavefront or a Naifetsu optical system is used using a wavelength λ1 of a coherent light source suitable for hologram recording. 2) The optical system of the OPU uses a converging lens with almost no aberration for a given light source wavelength λ2 such as a semiconductor laser, or irradiates the hologram element with an equivalent convergent wavefront to achieve the desired focus and tracking control. (3) Furthermore, as a countermeasure against coherent fluctuations in the semiconductor laser light source, the diffraction grating surface of the diffraction element is tilted with respect to the collimated beam, so that the diffracted wave can be formed on the photoelectric conversion surface (7 photodetectors). By constructing an optical system in which a part of the light is returned to the semiconductor laser, and the non-returning light component, for example, the zero-order diffracted light, is guided to the converging optical system, if necessary, a strong wavelength can be placed on the input side of the converging optical system. By providing the plate, it is possible to suppress the generation of return light noise. Here, the diffraction grating also plays the role of a beam splitting means, and in order to perform the composite function, (4) one reconstructed image from the hologram element, for example, a convergent beam with astigmatism, is used for focus control,
The Q-order transmitted light component from the hologram can be used for direct tracking control at the far-field position,
In addition, (6) the back surface of the hologram element substrate can also be used as a reflective surface, and it is easy to form a multilayer dielectric thin film for polarization plane selection, so a polarization plane selection film can be formed on the diffraction element described in (3). By applying this, a single composite diffraction element can produce
Polarizing beam splitter.

It can function as an optical feedback beam vector separation and a beam control optical element.

Embodiment FIG. 1a shows a schematic configuration of an OPU device according to an embodiment of the present invention. 1 is a short wavelength semiconductor laser (wavelength λ2=8
00nm), 2 is a collimating lens (focal length f2=2
0mm), 30 is the lattice spacing d=λ2/5in45°== for the wavelength λ2 of the semiconductor laser in a general calculation example.
It is a diffraction element (diffraction grating) with a diameter of 1.131μ, and its surface is coated with a polarization selective reflection film. The polarization selective film is a coating of a dielectric multilayer film used in a polarizing beam splitter, but it may be substituted by coating MuU, Muβ, etc. in a semitransparent state. In that case, the collimated light is transmitted to the diffraction element 30 at an angle close to the total reflection angle.
It is advantageous in terms of diffraction efficiency to make the light incident on the

The parallel beam that enters through the collimating lens 2 is diffracted by the diffraction element 30, but a portion of the first-order diffracted light (or higher-order diffracted light) is reflected by the polarization selective film and travels backward through the collimating optical system to the semiconductor laser. 1 as a return beam. On the other hand, the non-returning beam, for example, the 0th order diffracted light, continues as it is, passes through the wave plate 4, and becomes a circularly polarized beam through the condenser lens 6 (numerical aperture N = 0.5, focal length f =
4 mm) and a minute spot of about 1 μmφ is formed on the bit surface (for example, above the pit 60) on the optical disk θ. The light beam reflected and diffracted by the pit surface passes through the lens 5 and the Aλ plate 4 again, and passes straight through the polarizing beam splitter (diffraction element) 30 with the plane of polarization rotated by 90' from the previous optical path. Then, the split beam is split by a beam splinter 7, and one beam is directed onto the micro spot far field putter/all photodetectors 8, and the other split beam is sent via a condenser lens 9 and a cylindrical lens 10 to a photodetector 11. An astigmatic aberration pattern is formed on the image plane and converted into tracking and focusing control signals, respectively. At this time, the diffraction element 30
As shown in the figure, a diffraction grating 301 and a polarization selective reflection film 302 are provided on one side of a substrate 300, including (i) a wavelength selective optical feedback optical element (diffraction grating) and (ii) a polarization selective reflection film (
It plays the role of a multifunctional device that also functions as a polarizing beam splitter (polarizing beam splitter). Furthermore, an anti-reflection film 100 for the oscillation wavelength is provided on one end facet of the semiconductor laser, and the semiconductor laser is of an external cavity type, with a resonator system configured between the end face 101 and the diffraction grating surface 301 to emit narrow band oscillation. do. Although an antireflection film is not necessarily required, more stable oscillation can be obtained by desirably designing the reflectance to be less than a few. Regarding external cavity type semiconductor lasers, refer to the literature ((s) ” 0
scillation center frequency
eyTuning, Quantum FM No.
1se, and DirectFrequency
Modulation Characteristics
cs 1nQuant, Elect,) vol
, Q K-18 (1982) 961.

(7) "External cavity type semiconductor laser using holographic grating", Breakfast, Hagiwara, Nagaoka; reported at the 1986 National Conference of the Optical and Radio Division of the Institute of Electronics and Communication Engineers, 194), etc. In the present invention, (i) the number of parts and elements is reduced by adding multiple functions to the optical elements necessary for the configuration of the optical pickup optical system, and at the same time (11) stabilization of the oscillation mode of the semiconductor laser and noise suppression are achieved. Therefore, (iii) it is possible to apply a technique of recording and reproducing a desired beam control wavefront using a hologram. In FIG. 1, one side end face 101 of the semiconductor laser 1 may be a completely reflective surface, but the beam 1010 can be used for monitoring current feedback to the laser 1. In addition, in this example,
Although the pickup optical system for the reflective optical disk 6 has been shown, for a transmissive optical storage medium, it is simply a matter of design that the beam control optical system should be configured on the side of the transmitted light from the medium. .

FIG. 2 shows a schematic configuration of an OPU device according to another embodiment of the present invention. Compared to the case shown in FIG. 1, the light source optical system performs similar optical feedback through one side 301 and 302 of the composite diffraction element 31, but the beam control optical system performs a hologram on the back surface 313 of the composite diffraction element 31. By incorporating it, the number of parts and elements is further reduced. In addition, in the embodiment shown in FIG. 1, the collimating optical system 2. Although a lens system is used for the condensing optical system 5, in this embodiment, thin film Fresnel lenses 20, 50, and 90 are each replaced, thereby making it possible to further reduce the size and weight.

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 12. FIG. 4a is a conceptual diagram of an optical system realized as a hologram that can accurately record and reproduce an astigmatic wavefront. A cylindrical lens 1° is arranged in the optical path in which a coherent parallel beam 13 with a wavelength λ1 is condensed by a condensing lens 51, and linear converged beams 101 and 103 oriented perpendicular to each other and a substantially circular shape are formed at an intermediate position between them. A beam of 1o2 is obtained. Now, the beam 102 is X, -y
, is assumed to be on the 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 60 (focal length f+) is By extracting the Fourier transform wavefront of the circular beam 102 onto the rear Fourier transform surface (indicated by ξ-η coordinates) of the lens 6o and superimposing it with another plane wave that does not include aberration, the so-called lens Fourier transform is performed. A mold hologram element 313 is created. 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 5o. 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 4 and irradiated with a parallel beam of wavelength λ2, the rear focal plane (indicated by X2-Y2 coordinates) of the Fourier transform lens 5 (in terms of focal length) has the following:
Reconstructed image 1021 of a wavefront including astigmatism and its conjugate image 1
022 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. 6 explains the operating principle of the optical system shown in FIG. 2 from the perspective of the beam shape generated on the focus control photoelectric conversion element 11. That is, in FIG. 5a, the condenser lens 6
The focused beam is directed to the pit surface 60 of the optical disc.
When the beam 1021 or 1022 is diffracted through the hologram element 313 and is separated by a very small distance Δf in front and back from the hologram element 313, the beam 1021 or 1022 has a shape as shown in the figure or d on the photodetector. .

C in the same figure shows the situation when the image is brought into focus.

The focus control signal ε is a signal output component corresponding to each sector 111 to 114 of the quadrant photodetector in step S13.
As S21"5 + 84, ε=(S1+35)
(S2+34), (1)>, and focus control can be performed according to the condition ε≧0.

The tracking signal J is 1, r=s2-s4. (2), but considering the stability of the servo, Fig. 2.8
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 be used.0 Above, we have explained systems that include astigmatism as the wavefront for beam control, focusing on the recording optical system of the lens Fourier transform hologram and the wavefront reproducing optical system of the information pickup optical system. However, the present invention is not limited to devices based on these principles, 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 suitable for the purpose in advance as a lens Fourier transform hologram element.

Once recorded, the lattice pattern of the elements can be transferred to a mold that can be easily replicated, and by making replicas using resin or glass materials, a large number of uniform elements can be obtained at low cost, making it possible to use optical information pickup devices. This has great effects in terms of design and manufacturing. Since the pattern to be replicated is of the Fourier transform type, it is possible to blaze the mold by ion beam processing, etc., and the Fresnel zone plate blaze technology (Kawai, Kubota, Nishida; 18th Micro-Optics Research Group) Lecture paper; Ma013 (1985) P, 3
Compared to 3), the diffraction efficiency of the replica element can be easily blazed. That is, the beam can be irradiated obliquely over the entire surface of the hologram consisting of a substantially parallel lattice pattern.

Although the embodiments of the present invention have been mainly described as beam control systems for optical disk optical systems, they can also be applied to optical systems with both recording and reproducing functions, and furthermore to optical information pickup devices in magneto-optical storage and reproducing systems. Of course it can be done.

FIG. 3 explains, as another embodiment of the present invention, the principle of recording and reproducing a diffraction grating using a hologram element, which is equally applicable to the optical systems shown in FIGS. 1 and 2. In FIG.
1, and the width δ1. A micro aperture 1002 having a spread of δ2 is illuminated, the other light beams are condensed by a condenser lens 150 as a reference light source 160, and a 7-Lie transformation lens 50
are superimposed on the rear focal plane ξ-η of the same lens via , and recorded as a hologram 3o11. Here, the minute aperture 1002 is provided with some kind of diffusion surface, for example, a diffraction grating 1o03 as shown in FIG. 3C, so that the diffraction efficiency of the hologram 3011 can be sufficiently increased.

After the diffraction grating 3o11 thus obtained is coated with a polarization selective film, it is provided on a plane ξ-η' rotated by an angle θ from the Miegh plane, as shown in the figure. When the beam 161 emitted from a point light source (semiconductor laser active layer) is converted into a parallel beam by the collimating lens 2 and irradiated onto the hologram 3011, a part of the diffracted light travels backwards to the collimating lens 2 and returns to the point light source. This beam is the reproduced minute aperture 1 from the hologram 3011.
0o2 reproduced image 1003, with a predetermined width λ1
= 442 nm, λ2=soonm.

becomes. This beam spread width has the effect of reducing the mechanical precision (~1 μm or less) required for adjusting and holding the diffraction element 30 in the optical feedback optical system by about one order of magnitude.

The grating pitch (average) of the diffraction element 3o11 is P = 1.1
3 pm and the aperture D = 8 mm, the number of gratings N = -7000, which is equivalent to a diffraction grating. The actual oscillation wavelength can be selectively oscillated in a single mode within the gain width of the semiconductor laser 1 by finely adjusting the tilt angle of the diffraction element 3o.

Minute opening width δ1. If δ2 is increased more than necessary, the optical power returned to the vicinity of the semiconductor laser active layer will decrease, and
Since the spectral width included in the feedback light is expanded proportionally, it is necessary to set it within an appropriate range.

Effects of the Invention As is clear from the above explanation, the present invention provides an OPH optical system with (1) a light source system that provides stable single mode oscillation by providing optical feedback to the semiconductor laser using a diffraction element, and has a high signal-to-noise ratio; (11) A lens Fourier transform hologram element is used in combination with other optical elements, and the hologram records the astigmatism wavefront or the diffracted wavefront from the naifetsu. ) The hologram itself does not generate aberrations even if the wavefront is reproduced at a wavelength λ2 different from the hologram creation wavelength λ1. (2) Using an inverse Fourier transform lens, beams for focus control and tracking control are converted from hologram diffracted light. It is possible to divide and use effectively.

(3) Furthermore, the back surface of the hologram element substrate can be used as a reflection/diffraction surface for optical return beam diffraction and beam splitting, which minimizes the number of parts and makes the optical system smaller, cheaper, and more reliable. You can make significant progress.

4) 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.

(5) 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. Mask hologram gold can be made.

Also, (iii) since the light source oscillates in a single mode,
In addition to holograms, it is possible to make thin-film optical elements such as Fresnel lenses exhibit high performance.
V) Since the optical feedback optical system extracts the diffracted light that does not contribute to feedback and forms the beam for the optical pickup optical system, the optical power can be used effectively.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an optical information pickup device showing one embodiment of the present invention, FIG. 2 is a principle explanatory diagram explaining another embodiment of the present invention, and FIG. 3 is a detailed explanation of the present invention. A schematic configuration diagram, Fig. 4 is a principle diagram of the present invention explaining an example of recording and reproducing an astigmatic wavefront, and Fig. 5 relates to an embodiment of the present invention for recording and reproducing an astigmatic wavefront. FIG. 6 is a conceptual diagram of a conventional optical pickup optical system using a hologram element, and FIG. 7 is a diagram showing an example of the configuration of a conventional optical pickup optical system. DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 2... Collimating lens, 3o... Diffraction element that also serves as a polarizing beam splitter, 4... Quarter wavelength plate, 6... ...
...Condensing optical system, 6... Optical disk, 313.
Mountain... Lens Fourier transform hologram element, 8...
...Photodetector, 11...River photodetector, 10...Cylindrical lens, 20...7 Renel lens, 302...Polarization selective reflection surface, 10
0...Antireflection film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure Jθ2. Ore A section rebuttal - 2nd figure (magazine JliE3 figure (噌4th figure 5 (included) //J foil 6 figure (η)

Claims (5)

[Claims] (1) A semiconductor laser, a collimating optical system, a diffraction element as means for returning light to the semiconductor laser and splitting the beam, and converging a non-returning beam diffracted from the diffraction element into a minute spot on a predetermined storage medium. 1. An optical pickup device comprising: an optical system for controlling the microspot; and means for controlling focusing and tracking of the minute spot. (2) The optical pickup device according to claim 1, wherein the semiconductor laser is coated with an anti-reflection film on the end face from which light is returned. (3) The optical pickup device according to claim 1, comprising a diffraction element in which a predetermined wavefront is recorded in a lens-Fourier transform hologram as focusing and tracking control means. (4) The optical pickup device according to claim 1, wherein the diffraction element serving as the optical feedback and beam splitting means is formed of a Fourier transform hologram with a minute aperture. (5) A semiconductor laser whose end surface to which light is returned is coated with an antireflection film, a collimating optical system, a diffraction element coated with a polarization selective reflection film as means for returning light to the semiconductor laser and splitting the beam; It is characterized by comprising a half-wave plate, an optical system for converging the non-returning beam diffracted from the diffraction element in the form of a minute spot on a predetermined storage medium, and means for controlling focusing and tracking of the minute spot. Optical pickup device.