WO2019159650A1

WO2019159650A1 - Method for manufacturing microporous optical element and microporous optical element

Info

Publication number: WO2019159650A1
Application number: PCT/JP2019/002421
Authority: WO
Inventors: 憲太郎野本
Original assignee: ウシオ電機株式会社
Priority date: 2018-02-15
Filing date: 2019-01-25
Publication date: 2019-08-22
Also published as: JP2019139190A

Abstract

The present invention provides a lightweight microporous optical element that has a large effective area and high light-gathering capability. One aspect of the present invention is a method for manufacturing a microporous optical element provided with a plurality of slits along the surface of a transparent substrate that is formed singly or formed by combining a plurality of parts while the angle of each slit relative to the surface of the transparent substrate changes from a first angle to a second angle at some midpoint in the series of slits from the front surface to the rear surface of the transparent substrate, the method comprising a slit formation step of forming the plurality of slits on the transparent substrate, and a reflective layer formation step of forming a reflective layer on the inner wall of each of the plurality of slits.

Description

Method for manufacturing fine hole optical element and fine hole optical element

The present invention relates to a method for manufacturing a fine hole optical element and a fine hole optical element.

Unlike visible light, X-rays are difficult to use with a direct incidence optical system. For this reason, an oblique incidence optical system using total reflection of a metal surface utilizing the fact that the refractive index of metal with respect to X-rays is smaller than 1 is used. In this case, since the critical angle of total reflection is as small as about 1 degree, in order to increase the effective area of the reflecting surface, a method of arranging a large number of metallic cylindrical reflecting mirrors having different diameters coaxially is known. ing. However, this method increases the weight of the entire X-ray reflection device (weight of 1 ton or more per 1 m ² ), and thus has a problem of hindering transportation from the ground when used in outer space.

Patent Document 1 (Japanese Patent No. 4025779) discloses an X-ray optical system base that uses a silicon wafer wall surface by anisotropic etching as an X-ray reflector as an X-ray optical base material that is lightweight and relatively easy to manufacture. Materials have been proposed. This is because a fine hole is made in a thin wafer, so that it becomes a mirror that is one digit or more lighter than the conventional one, and there is an advantage that a large number of mirrors can be produced by one etching. However, since holes that can be formed by anisotropic etching are limited to straight slit-like holes, when creating an X-ray optical system, it is necessary to approximate the ideal curved surface as a reflecting mirror with a straight line. Light performance is limited. Further, since the X-ray optical system is made smaller and disposed along the ideal curved surface in order to approach the ideal curved surface, a large number of X-ray optical systems are required, and the labor and cost required for production are large.

Patent Document 2 (Japanese Patent No. 5540305) discloses a fine curved hole manufactured by silicon dry etching or X-ray LIGA as a new X-ray optical system base material in order to improve light collecting performance while maintaining light weight. An X-ray optical base material that uses the wall surface of the structure as an X-ray optical system has been proposed.

Japanese Patent No. 4025779 Japanese Patent No. 5540305

However, since the X-ray optical system base material proposed in Patent Document 2 (Japanese Patent No. 5540305) needs to be subjected to high-temperature plastic deformation or elastic deformation for each substrate, the reflection surface is effective. If fine curved holes are formed at a high density to increase the area, the wall surface may be distorted during deformation. Such distortion causes a reduction in light collecting performance.

That is, in the conventionally proposed X-ray optical system substrate, although the weight can be reduced, the effective area of the reflecting surface and the light collecting performance are in a trade-off relationship. For this reason, a new technology that can achieve both a large effective area and high light collection performance is desired.
It is an object of the present invention to provide a fine hole optical element that is lightweight and has a large effective area and high light collection performance.

In order to solve the above-described problems, one aspect of the method for manufacturing a microscopic optical element according to the present invention is a plurality of extending along the surface of a transparent substrate that is formed as a single unit or a plurality of units are integrated. Are provided, and in the middle from the front surface to the back surface of the transparent substrate, the angle of each slit with respect to the front surface changes from the first angle to the second angle. A slit forming step of forming the plurality of slits on the transparent substrate, and a reflecting layer forming step of forming a reflecting layer on the inner wall of each of the plurality of slits.

According to such a method for manufacturing a microscopic optical element, slits having a high aspect ratio can be formed with high density and high accuracy by a known processing method for a transparent substrate. As a result, a fine hole optical element that is lightweight and has a large effective area and high light collecting performance is realized.

In the method for manufacturing the microscopic hole optical element, the slit forming step further modifies the transparent substrate with respect to a portion where the slit is formed, and removes the portion modified in the reforming step. And a removing step for forming the slit. By providing the reforming step and the removing step, it is easy to form a slit with a high aspect ratio.

In addition, it is preferable that the modifying step is a step of modifying the transparent substrate by irradiating a beam to cause multiphoton absorption. Multiphoton absorption by beam irradiation has a high position resolution in a transparent substrate, so that a fine slit shape can be easily realized.

In the method of manufacturing the microscopic hole optical element, the transparent substrate is formed by joining a plurality of small substrates corresponding to the plurality of portions arranged along the surface of the transparent substrate, You may provide the joining process which joins the end surfaces of a several small board | substrate after the said slit formation process.

Further, in the method of manufacturing the microscopic hole optical element, the transparent substrate is formed by bonding a plurality of thin substrates corresponding to the plurality of portions overlapping in the thickness direction of the transparent substrate, You may provide the joining process which joins the front and back of several thin substrates after the said slit formation process.
As described above, by joining the plurality of portions in the direction along the surface or in the thickness direction, the size of the microscopic hole optical element can be easily increased.

Furthermore, it is preferable that the joining step is a step of joining the plurality of portions by modifying the joining surface by irradiation with ultraviolet rays. In bonding by ultraviolet irradiation, an adhesive or the like is not required, and the bonding surfaces are firmly adhered to each other.

In the method for manufacturing the microscopic hole optical element, the reflective layer forming step is preferably a step of forming the reflective layer by an atomic layer deposition method. In the atomic layer deposition method, the reflective layer is formed to have a uniform thickness even for slits having a high aspect ratio.

In order to solve the above-described problems, one aspect of the microscopic hole optical element according to the present invention includes a transparent substrate formed in a single unit or formed by integrating a plurality of parts, and a surface along the surface of the transparent substrate. Extending in an arc shape and being arranged concentrically with each other, and a plurality of slits whose angle with respect to the front surface changes from the first angle to the second angle on the way from the front surface to the back surface of the transparent substrate, A reflective layer provided on the inner wall of the slit.

According to such a fine hole optical element, slits having a high aspect ratio can be formed with high density and high accuracy by a known processing method for a transparent substrate. As a result, a fine hole optical element that is lightweight and has a large effective area and high light collection performance is realized.

In the fine hole optical element, it is desirable that the plurality of slits be formed at a density of 10 or more per 1 mm. By forming slits at such a density, an increase in effective area is realized while avoiding an increase in weight.

Moreover, in the microscopic hole optical element, the plurality of slits may be closer to the angle perpendicular to the surface of the transparent substrate as the slits located on the inner peripheral side arranged concentrically with each other. According to such a fine hole optical element, X-rays or vacuum ultraviolet rays reflected by the reflective layer are focused.

In the microhole optical element, the transparent substrate may be formed by bonding a plurality of small substrates corresponding to the plurality of portions arranged along the surface of the transparent substrate.

In the microhole optical element, the transparent substrate may be formed by bonding a plurality of thin substrates corresponding to the plurality of portions overlapping in the thickness direction of the transparent substrate.
As described above, by joining the plurality of portions in the direction along the surface or in the thickness direction, the size of the microscopic hole optical element can be easily increased.

Furthermore, it is preferable that the transparent substrate in which such a plurality of portions are bonded is a substrate in which the plurality of portions are bonded by hydrogen bonds formed on the bonding surface. Such hydrogen bonds are formed on the bonding surfaces by, for example, irradiation with ultraviolet rays, and the bonding surfaces are firmly bonded to each other without using an adhesive.

According to the present invention, a microscopic optical element that is lightweight and has a large effective area and high light collection performance is realized.
The above-described objects, aspects, and advantages of the present invention, and objects, aspects, and effects of the present invention that have not been described above will be understood by those skilled in the art to implement the following invention by referring to the attached drawings and the claims. This will be understood from the following description (detailed description of the invention).

FIG. 1 is a diagram conceptually showing a first embodiment of the microscopic hole optical element of the present invention. FIG. 2 is an enlarged cross-sectional view of a portion P in FIG. FIG. 3 is a diagram showing the shape of the reflecting surface of the Walter optical system. FIG. 4 is a diagram showing a condensing state in the microscopic hole optical element. FIG. 5 is a diagram showing a manufacturing process of the microscopic hole optical element. FIG. 6 is a view showing the structure of a laser reforming apparatus that executes the reforming step (A) shown in FIG. FIG. 7 is a diagram showing a procedure example of the reforming step (A) executed by the laser reforming apparatus. FIG. 8 is a view showing a second embodiment of the microscopic hole optical element of the present invention. FIG. 9 is a diagram schematically showing a cross-sectional structure of the microscopic hole optical element of the second embodiment. FIG. 10 is a diagram illustrating a first alignment step in the second embodiment. FIG. 11 is a diagram illustrating a second alignment step in the second embodiment. FIG. 12 is a diagram schematically showing a cross-sectional structure of the microscopic hole optical element of the third embodiment. FIG. 13 is a view showing the microscopic hole optical element of the fourth embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram conceptually showing a first embodiment of the microscopic hole optical element of the present invention. FIG. 1 shows a front view (A) and a side view (B).

The microhole optical element 1 has a large number of arc-shaped slits 3 arranged concentrically on a transparent substrate 2 having a disk-like outer shape with a diameter of, for example, 200 mm or less and a thickness of, for example, 0.5 mm to 1 mm. It has a structure. The transparent substrate 2 is made of, for example, glass, transparent resin, or the like. Particularly, when the glass is fused quartz, the slit 3 in the manufacturing method described later can be easily processed.

In FIG. 1, the density of the slits 3 is depicted to be coarser than the actual, and the actual slits 3 are formed with a slit width of, for example, 10 μm or more, and the width of the glass or resin portion located between the slits 3 is For example, it is formed to 20 μm or more. Here, the density of the slits 3 is measured in the width direction of the slits. For example, when a plurality of slits are arranged concentrically, per 1 mm on a straight line passing through each slit through the center of the concentric arrangement, for example The density is as high as about 33. A large number of slits 3 such as 2000 are formed in the entire microscopic hole optical element 1.
FIG. 2 is an enlarged cross-sectional view of a portion P in FIG.

Each slit 3 of the minute hole optical element 1 is bent on the way from the front side (upper side in FIG. 1) to the back side (lower side in FIG. 1) of the minute hole optical element 1. Light L such as X-rays or vacuum ultraviolet rays enters from the front side. The ratio h1 / h2 between the length h1 of each slit 3 in the traveling direction of the light L and the slit width h2 where the light L is emitted from the slit 3 is a large value of 50 to 100, for example.
A metal reflection layer 4 is formed on the inner wall of each slit 3. The reflective layer 4 is a single layer film or a multilayer film made of a heavy metal such as hafnium oxide.

Examples of the material of the reflective layer 4 include the above-described hafnium oxide, oxides such as tantalum oxide, titanium oxide, lanthanum oxide, and zinc oxide, nitrides such as titanium nitride, tantalum nitride, and hafnium nitride, and metals. , Rubidium, copper, tungsten, molybdenum, platinum, iridium, and gold. The single-layer reflective layer 4 is formed with a film thickness of, for example, several hundred to several thousand Å.

The reflective layer 4 may be a multilayer film composed of a thin film made of heavy metal and a thin film made of light metal. In this case, the outermost layer is composed of a thin film made of heavy metal. For example, aluminum oxide is used as the thin film made of light metal, but silicon oxide may also be used. Further, the reflective layer 4 may be a multilayer film of a pair material such as platinum / carbon, molybdenum / silicon, tungsten / silicon and the like. In the case of a multilayer film made of these pair materials, for example, several pairs of several tens to several hundreds of layers having a film thickness of several tens of millimeters are stacked.

The angle of the slit 3 with respect to the front and back surfaces of the microhole optical element 1 is such that the slit portion 3a on the side where the light L is incident (the upper portion in FIG. 1) is the slit portion 3b on the side where the light L is emitted (see FIG. 1). The light L is reflected twice by the reflective layer 4 of each slit 3.
The shape of the reflective layer 4 in the fine hole optical element 1 is a so-called Walter optical system, and the light L can be collected at the focal point.
FIG. 3 is a diagram showing the shape of the reflecting surface of the Walter optical system.

The Walter optical system is an optical system that focuses light by reflecting light on two aspherical surfaces or conical approximate surfaces thereof. In the microscopic hole optical element 1 of the present embodiment, an optical system called type 1 is used among the Walter optical systems, and the paraboloid S1 and the hyperboloid S2 are combined. The light L reflected twice by the reflective layer 4 is collected at the focal point F.
FIG. 4 is a diagram showing a light collection state in the microscopic hole optical element 1.

The angle of each slit 3 (see FIG. 1) in the fine hole optical element 1 is closer to the optical axis L0 of the fine hole optical element 1 which is the center in the concentric arrangement of the slits 3, and the front and back surfaces of the fine hole optical element 1 The angle is nearly perpendicular to the angle. For this reason, the light L reflected by the reflection layer 4 of the outer slit 3 in the concentric arrangement has a larger reflection angle, and the light L reflected by the reflection layer 4 of the inner slit 3 has a smaller reflection angle. Then, all of the light L reflected by the reflective layer 4 at various locations of the microscopic hole optical element 1 is collected at the focal point F and forms an image. For example, in the case of X-rays, since the reflection angle is about 1 degree, the focal length of the fine hole optical element 1 is a value of, for example, 500 mm or more and 1000 mm or less.

In such a fine hole optical element 1, as described above, since the slits 3 are formed with a high density, the effective area of the reflecting surface for the light L is large. When the density of the slits 3 is, for example, 10 or more per 1 mm, a sufficiently large effective area is obtained, and high illuminance at the focal position is achieved. When considering the number of slits 3, for example, when 100 or more slits 3 are formed, a sufficiently large effective area can be obtained.

Further, as described above, since the diameter of the microhole optical element 1 is 200 mm or less and the thickness in the light traveling direction is 0.5 mm or more and 1 mm or less, the microhole optical element 1 is reflective. Compared to the large effective area of the surface, the weight is light. Such a fine hole optical element 1 is used in, for example, an observation device that performs X-ray observation in outer space, an observation device that performs radiation observation on the ground, a microanalyzer, an X-ray microscope, a nondestructive inspection device, and the like. It is suitable as an element for line reflection. Further, the fine hole optical element 1 may be used as a reflection mirror for vacuum ultraviolet rays.
Next, a method for manufacturing such a fine hole optical element 1 will be described.
FIG. 5 is a diagram showing a manufacturing process of the microscopic hole optical element 1.
The manufacturing process shown in FIG. 5 includes a modifying process (A), an etching process (B), a polishing process (C), and a reflective layer forming process (D).

In the modification step (A), the transparent substrate 2 is irradiated with the pulse laser beam PL, and the transparent substrate 2 is modified by the pulse laser beam PL. The shape, position, and angle of the irradiation area of the pulse laser beam PL are determined based on CAD data.

In the present embodiment, the modification of the transparent substrate 2 is realized by multiphoton absorption in the pulsed laser light PL. When multiphoton absorption occurs in the transparent substrate 2, the portion where multiphoton absorption occurs is specifically modified. When the transparent substrate 2 is, for example, a glass substrate, the local structure due to the bond between silicon (Si) atoms and oxygen (O) atoms is divided by multiphoton absorption, resulting in a structural change and the like, which is easily chemically reacted It becomes. Further, the energy required for the modification may be less than the energy required for laser processing that causes a destructive action such as ablation. The reforming step (A) will be described in detail later.

In the etching step (B), the transparent substrate 2 is immersed in the etchant 5, and the modified region 2a is selectively removed by the etching process. When the transparent substrate 2 is, for example, a glass substrate, a hydrofluoric acid (HF) solution or a potassium hydroxide solution is used as the etchant 5.

In this embodiment, wet etching that requires less labor is employed as the etching process, but dry etching using a fluorine (F ₂ ) -based gas can also be employed as the etching process. In this embodiment, ultrasonic cleaning that applies ultrasonic waves W to the transparent substrate 2 in the etchant 5 is also used in order to stabilize and speed up the processing. The etching conditions are such that the HF concentration is 2.5 to 5%, for example, and varies depending on the size of the transparent substrate 2, but the etching time is 1 hour to several hours, for example.

In the etching step (B), the etchant 5 and the transparent substrate 2 react also in portions other than the modified region 2a, but the etching rate differs greatly between the modified region 2a and the region 2b other than the modified region 2a. For this reason, immediately after the start of the etching step (B), the modified region 2a is completely removed and the slit 3 is formed. In the example shown here, since the through slit is formed in the transparent substrate 2, the modified region 2 a is formed through the transparent substrate 2, but the bottomed slit (non-through hole) is formed in the transparent substrate 2. If so, the modified region 2 a is formed so that only one end reaches the surface of the transparent substrate 2.

In the polishing step (C), a mixed liquid 6 of magnetic fluid and abrasive is used to smooth the side walls of the slits 3. A magnetic fluid is a fluid whose viscosity changes when a magnetic field is applied, and has already been put into practical use for polishing optical components. Specifically, a mixed liquid 6 of a magnetic fluid having an average particle diameter of about 0.01 μm and a diamond slurry having a particle diameter of, for example, 1 μm is poured into each slit 3, and a varying magnetic field is applied perpendicularly to the transparent substrate 2. The

The mixed liquid 6 moves randomly in the slit 3 according to the fluctuation of the magnetic field. It is also possible to rotate the transparent substrate 2 around the central axis to promote the relative movement between the mixed liquid 6 and the side wall of the slit 3. The mixed liquid 6 polishes the side wall surface of each slit 3 to smooth the side wall surface roughness, for example, to achieve a surface roughness of 1 to 2 nm.

In the reflective layer forming step (D), the transparent substrate 2 is placed in a mixed gas 7 of metal vapor and a reactant, and the metallic reflective layer 4 is formed on the inner wall of the slit 3 by atomic layer deposition (ALD). . In the atomic layer deposition method, an atomic layer is formed on the entire inner wall of the slit 3, so that the reflective layer 4 is evenly formed even with the slit 3 having a high aspect ratio.

The combination of the modifying step (A), the etching step (B), and the polishing step (C) corresponds to an example of the slit forming step in the present invention, and the reflective layer forming step (D) This corresponds to an example of the reflective layer forming step in the invention. The modification step (A) corresponds to an example of the modification step according to the present invention, and the etching step (B) corresponds to an example of the removal step according to the present invention.
With such a manufacturing method, the microscopic hole optical element 1 shown in FIG. 1 is realized.
Next, the above-described reforming step (A) will be described in more detail.
FIG. 6 is a view showing the structure of the laser reforming apparatus 10 that executes the reforming step (A) shown in FIG.

The laser reforming apparatus 10 includes a laser oscillator 101 that emits pulsed laser light. As the laser oscillator 101, one having a pulse width of 200 fs or more and 500 fs or less, a pulse energy of 1 μJ or less, and a repetition frequency of 5 MHz or less is used. Since such a laser oscillator 101 emits an ultrashort pulse laser beam having a high peak power, the pulsed laser beam is easily condensed on a transparent substrate 2 such as glass so that nonlinearity such as multiphoton absorption can be easily performed. Produces an effect.

The laser reforming apparatus 10 includes an attenuator 103 for dimming pulsed laser light to energy suitable for reforming. Further, a beam expansion system 104 and a diaphragm lens (fθ lens) 106 are provided so that a necessary spot size can be obtained on the transparent substrate 2 that is a workpiece (workpiece). As a result, the NA value of the condensing system becomes a large value such as 0.26.

The laser modifying apparatus 10 includes an XYZ axis stage 108 that moves the transparent substrate 2 in a three-dimensional manner so as to form a through-hole or a non-through-hole with a designated angle at a designated location on the transparent substrate 2. A biaxial galvanometer mirror 105 that scans the pulse laser beam is also provided. By these XYZ axis stage 108 and galvanometer mirror 105, the pulse laser beam is condensed at a designated position in the transparent substrate 2 to form a condensed spot.
FIG. 7 is a diagram illustrating a procedure example of the reforming step (A) executed by the laser reforming apparatus 10.

FIG. 7 schematically shows a procedure from step (A) to step (E) as an example of a procedure for forming the modified region 2a in the transparent substrate 2 in the modification step (A). . In the lower right of FIG. 7, a vector representing the movement of the XYZ axis stage 108 based on CAD data in the procedure from the stage (A) to the stage (E) is shown.

In stage (A), the XYZ axis stage 108 is positioned at the start position based on the CAD data, so that the focus of the pulse laser PL is focused immediately below the surface of the transparent substrate 2, and the formation of the modified region 2a is started. Is done.

In the step (B), the XYZ axis stage 108 moves upward in the drawing to move the focal point of the pulse laser PL to the inside of the transparent substrate 2, and as a result, the modified region 2 a is inside the transparent substrate 2. Extend to the side.

In step (C), the XYZ axis stage 108 further moves, and the modified region 2a further extends to the inside of the transparent substrate 2. Here, the boundary portion between the

portions

3a and 3b of the slit 3 shown in FIG. 2 is reached.

In stage (D), the movement direction of the XYZ axis stage 108 changes as indicated by a vector in the lower right in FIG. As a result, the direction of the modified region 2a is bent and further extended.

In stage (E), the XYZ axis stage 108 moves to the end position, and the focal point of the pulse laser PL reaches just above the back surface of the transparent substrate 2. Thereby, the modified region 2a extending from the front surface to the back surface of the transparent substrate 2 is formed.

Through the above procedure, a portion corresponding to one place on the transparent substrate 2 is modified in the slit 3 extending in an arc shape as shown in FIG. Therefore, the procedure shown in FIG. 7 is repeated at each point connected in a circular arc shape on the transparent substrate 2, thereby having an arc-shaped planar shape as shown in FIG. 1 and a cross-sectional shape as shown in FIG. The modified region 2a corresponding to the slit 3 thus formed is formed.

Thus, in the microscopic hole optical element 1 of the present embodiment, the slit 3 (and the reflective layer 4) having an ideal reflective surface shape is formed on the transparent substrate 2 with high accuracy, and the slit 3 (and the reflective layer 4). No stress or the like is applied to the transparent substrate 2 when forming. For this reason, the fine hole optical element 1 has a large effective area and high imaging performance.
Next, a second embodiment of the microscopic hole optical element of the present invention will be described.
FIG. 8 is a view showing a second embodiment of the microscopic hole optical element of the present invention. FIG. 8 shows a front view (A) and a side view (B).

The fine hole optical element 21 of the second embodiment has a large number of arc-shaped slits 23 with respect to a transparent substrate 22 having a square outer shape with a side length of, for example, 100 mm and a thickness of, for example, 4.0 mm. It has a concentric arrangement. The material of the transparent substrate 22 is made of, for example, glass or transparent resin as in the first embodiment. Further, the transparent substrate 22 in the microscopic hole optical element 21 of the second embodiment is formed by laminating so that the two sub-substrates 22a and 22b overlap in the thickness direction. Each of the sub-boards 22a and 22b is formed with an alignment mark 24 used at the time of stacking.

Each slit 23 in the second embodiment has a slit width of 20 μm, for example, and a glass or resin portion located between the slits 23 has a width of 20 μm, for example. Therefore, the density of the slits 23 is as high as 25 per mm, and the aspect ratio of the slits 23 is a large value of about 200.

Also in the second embodiment, as in the first embodiment, a reflective layer (not shown) is formed on the inner wall of each slit 23, and the shape of each reflective layer (that is, the inner wall shape of each slit 23) is shown in FIG. This is a type of the Walter optical system described in FIG.
FIG. 9 is a diagram schematically showing a cross-sectional structure of the microscopic hole optical element 21 according to the second embodiment.

In the micro hole optical element 21 of the second embodiment, the surface of the micro hole optical element 21 is placed on the sub substrate 22a located on the light incident side (upper side in FIG. 9) of the two

sub boards

22a and 22b. A slit portion 23a having a _first angle θ1 with respect to the perpendicular is formed. Of the two sub-substrates 22a and 22b, the sub-substrate 22b positioned on the light emitting side (the lower side in FIG. 9) has a second angle with respect to the normal to the surface of the microscopic hole optical element 21. slit portion 23b having a theta ₂ is formed. Then, the two

sub-substrates

22 a and 22 b are stacked to connect the

slit portions

23 a and 23 b, thereby forming a slit 23 whose angle changes in the transparent substrate 22.

In the second embodiment, for example, 826 slits 23 are formed as a whole of the microscopic hole optical element 21, and these slits 23 are divided into seven groups.

The first group, the radius _{R 1in} the innermost slit 23 is 15 mm, the radius _{R 1out} is included the outermost periphery of the slit 23 to 114 slits 23 are 19.52Mm, the first All the slits 23 included in one group have a first angle θ ₁ of 0.175 degrees and a second angle θ ₂ of 0.525 degrees.

The second group includes 122 slits 23 from the innermost circumferential slit 23 having a radius R _2in of 19.56 mm to the outermost circumferential slit 23 having a radius R _2out of 24.4 mm. All the slits 23 included in the second group have a first angle θ ₁ of 0.225 degrees and a second angle θ ₂ of 0.675 degrees.

The third group, from the innermost slit 23 with radius _{R 3in} is in 24.44Mm, radius _{R 3out} are included for the outermost periphery of the slit 23 to 123 slits 23 are 29.32Mm, All the slits 23 included in the third group have a first angle θ ₁ of 0.275 degrees and a second angle θ ₂ of 0.825 degrees.

The fourth group includes 122 slits 23 from the innermost slit 23 having a radius R _4in of 29.36 mm to the outermost slit 23 having a radius R _4out of 34.2 mm. all the slits 23 included in the fourth group, the first angle theta ₁ is at 0.325 ° second angle theta ₂ is a 0.975 degrees.

The fifth group includes 122 slits 23 from the innermost slit 23 having a radius R _5in of 34.24 mm to the outermost slit 23 having a radius R _5out of 39.08 mm. All the slits 23 included in the fifth group have the first angle θ ₁ of 0.375 degrees and the second angle θ ₂ of 1.125 degrees.

The sixth group includes 122 slits 23 from the innermost slit 23 having a radius R _6in of 39.12 mm to the outermost slit 23 having a radius R _6out of 43.96 mm. All the slits 23 included in the sixth group have a first angle θ ₁ of 0.425 degrees and a second angle θ ₂ of 1.275 degrees.

The seventh group of radius _{R 7in} from innermost slit 23 is 44 mm, the radius _{R 7 out} is included the 101 slits 23 to the slit 23 of the outermost periphery is 48 mm, the seventh All the slits 23 included in the group have a first angle θ ₁ of 0.475 degrees and a second angle θ ₂ of 1.425 degrees.
Thus, in 2nd Embodiment, the angle of the slit 23 changes in steps as it goes to an outer peripheral side.

Thus, according to the fine hole optical element 21 in which the slits 23 are divided into groups, although the imaging performance is inferior to that of the fine hole optical element 1 of the first embodiment, sufficient condensing performance can be obtained.

The microscopic hole optical element 21 of the second embodiment is manufactured by the same manufacturing method as the manufacturing method of the first embodiment shown in FIG. With respect to the fine hole optical element 21 of the second embodiment, each step shown in FIG. 5 is performed individually for each of the sub-boards 22a and 22b, and then the sub-boards 22a and 22b are aligned and bonded to each other. The process is executed. This alignment process includes a first alignment process and a second alignment process.
FIG. 10 is a diagram illustrating a first alignment step in the second embodiment.

In the first alignment step, the

sub substrates

22a and 22b are aligned so that the positions of the alignment marks 24 formed on the

sub substrates

22a and 22b coincide with each other. By such alignment, a relatively coarse alignment is realized such that

slit portions

23a and 23b (see FIG. 9) that should originally be connected as one slit 23 communicate with each other and other slits 23 do not communicate with each other.
FIG. 11 is a diagram illustrating a second alignment step in the second embodiment.

In the second alignment step, high-precision alignment is performed so that high condensing performance can be obtained with the fine hole optical element 21. Specifically, the He—Ne laser beam LB is expanded by the beam expander 110 and irradiated onto the sub-substrates 22a and 22b in parallel.

The beam LB is condensed at the focal position by the sub-boards 22a and 22b, and a condensed image is taken by the CCD camera 120 provided at the focal position. The captured condensed image 140 is confirmed on the monitor 130.

One of the two sub-boards 22a and 22b is provided with a push-pull mechanism 150, and the position of the sub-boards 22a and 22b is finely adjusted by the push-pull mechanism 150, so that the diameter of the condensed image 140 is minimized. Alignment is performed so that the luminance is maximized.
With such an alignment, high-accuracy alignment is achieved so that high condensing performance can be obtained with the fine hole optical element 21.

After such alignment, the sub-boards 22a and 22b are bonded to each other. The bonding method between the sub-boards 22a and 22b may be a bonding method using an adhesive, but in this embodiment, a bonding method using vacuum ultraviolet irradiation is used. In the bonding method using vacuum ultraviolet irradiation, the bonding surfaces are modified by irradiating the sub-substrates 22a and 22b with vacuum ultraviolet rays to form hydrogen bonds between the bonding surfaces. Be joined. It is preferable to use such a joining method by vacuum ultraviolet irradiation because there is no possibility that the slit and the reflective layer are contaminated with the adhesive.

Next, a third embodiment of the microscopic hole optical element of the present invention will be described. Since the micro hole optical element of the third embodiment is the same as the micro hole optical element of the second embodiment except that the number of laminated sub-substrates is different, the duplicate description is omitted.
FIG. 12 is a diagram schematically showing a cross-sectional structure of the microscopic hole optical element 31 of the third embodiment.

In the microhole optical element 31 of the third embodiment, a transparent substrate 32 is used in which eight

sub-substrates

32a, 32b, 32c, 32d, 32e, 32f, 32g, and 32h are laminated so as to overlap in the thickness direction. By using such a large number of sub-substrates 32a,..., 32h, the aspect ratio when the slits 33 are formed in the sub-substrates 32a,. Become.
Next, a fourth embodiment of the microscopic hole optical element of the present invention will be described.
FIG. 13 is a view showing the microscopic hole optical element 41 of the fourth embodiment.

In the microhole optical element 41 of the fourth embodiment, a large number of arc-shaped slits 43 are concentrically formed with respect to the transparent substrate 42 having a square-shaped outer shape with a side of, for example, 400 mm and a thickness of, for example, 2.0 mm. It has a deployed structure. The material of the transparent substrate 42 is made of, for example, glass or transparent resin as in the first embodiment. The transparent substrate 42 in the microscopic hole optical element 41 of the fourth embodiment is formed by joining four

small substrates

42a, 42b, 42c, and 42d in a matrix.

The fine hole optical element 41 of the fourth embodiment is an element having a large diameter compared to the fine hole optical element 1 of the first embodiment, the fine hole optical element 21 of the second embodiment, and the like, and further at the focal position. High illuminance is achieved. Such a large-diameter element is easily realized by joining a plurality of (for example, four)

small substrates

42a, 42b, 42c, and 42d arranged along the surface of the transparent substrate 42 at their end faces.

In the above description, as an example of the slit forming process according to the present invention, a slit forming process including a reforming process and a removing process is shown, but the slit forming process according to the present invention is performed on a transparent substrate. It may be a step by other means for directly forming the slit without undergoing the reforming step.

Although specific embodiments have been described above, the embodiments are merely examples and are not intended to limit the scope of the present invention. The devices and methods described herein can be embodied in forms other than those described above. In addition, omissions, substitutions, and changes can be made as appropriate to the above-described embodiments without departing from the scope of the present invention. Such omissions, substitutions, and modifications are included in the scope of the claims and their equivalents, and belong to the technical scope of the present invention.

1, 2, 31, 41 ... fine hole optical element, 2, 22, 32, 42 ... transparent substrate, 22a, 22b, 32a, ..., 32h ... sub-substrate 3, 23, 33, 43 ... slit, 4 ... reflection layer , 42a, 42b, 42c, 42d ... small substrate

Claims

A plurality of slits are provided along the surface of the transparent substrate formed as a single unit or formed by integrating a plurality of parts, and each slit with respect to the surface is performed on the way from the surface of the transparent substrate to the back surface. Is a method for manufacturing a microscopic hole optical element in which the angle from the first angle changes to the second angle,
A slit forming step of forming the plurality of slits on the transparent substrate;
A reflective layer forming step of forming a reflective layer on the inner wall of each of the plurality of slits;
A method for producing a microscopic hole optical element, comprising:
The slit forming step further includes
A reforming step of modifying the transparent substrate at a location where the slit is formed;
The method for manufacturing a microscopic hole optical element according to claim 1, further comprising: a removing step of forming the slit by removing the portion modified in the modifying step.
3. The method for manufacturing a microscopic hole optical element according to claim 2, wherein the modifying step is a step of modifying the transparent substrate by irradiating a beam to cause multiphoton absorption.
The transparent substrate is formed by bonding a plurality of small substrates corresponding to the plurality of portions arranged along the surface of the transparent substrate,
4. The method for manufacturing a microscopic hole optical element according to claim 1, further comprising a joining step of joining end faces of the plurality of small substrates after the slit forming step. 5.
The transparent substrate is formed by bonding a plurality of thin substrates corresponding to the plurality of portions overlapping in the thickness direction of the transparent substrate,
The method for manufacturing a microscopic hole optical element according to any one of claims 1 to 4, further comprising a joining step for joining the front and back surfaces of the plurality of thin substrates after the slit forming step.
The method for manufacturing a microscopic hole optical element according to claim 4 or 5, wherein the bonding step is a step of bonding the plurality of portions by modification of a bonding surface by irradiation with ultraviolet rays.
The method for manufacturing a microscopic hole optical element according to any one of claims 1 to 6, wherein the reflective layer forming step is a step of forming the reflective layer by an atomic layer deposition method.
A transparent substrate formed as a single unit or formed by integrating a plurality of parts;
A plurality of slits that are arranged along the surface of the transparent substrate and that change from the first angle to the second angle on the way from the front surface to the back surface of the transparent substrate;
A reflective layer provided on the inner wall of the slit;
A fine hole optical element comprising:
The micro-hole optical element according to claim 8, wherein the plurality of slits are formed at a density of 10 or more per 1 mm.
The plurality of slits are characterized in that slits located on the inner circumferential side arranged concentrically with each other are at an angle close to perpendicular to the surface of the transparent substrate, compared to slits located on the outer circumferential side. The fine hole optical element according to claim 8 or 9.
11. The transparent substrate is formed by bonding a plurality of small substrates corresponding to the plurality of portions arranged along the surface of the transparent substrate to each other. The fine hole optical element according to item.
12. The transparent substrate according to any one of claims 8 to 11, wherein the transparent substrate is formed by bonding a plurality of thin substrates corresponding to the plurality of portions overlapping in the thickness direction of the transparent substrate. The fine hole optical element according to item.
The micro-hole optical element according to claim 11 or 12, wherein the transparent substrate is formed by bonding the plurality of portions by hydrogen bonds formed on a bonding surface.