JPH06167605A - Optical element - Google Patents

Abstract

PURPOSE:To obtain an optical element which has excellent light convergence characteristics and obtains the uniformity of the wavelength of reflected rays. CONSTITUTION:A flat plate type element material M3 which is fixed at its one end side is held in a curved state by applying a force F3 to the other end side of the element material M3 in a direction wherein the material M3 deflects, and the thickness of the element material M3 is gradually decreased from the one end side to the other end side so that a crystal monochromator A3 which causes optical reflection on the concave surface side of the curved element material M3 forms part of an elliptic curved surface on the concave surface side of the element material M3. Consequently, the optical element which has the excellent light convergence characteristics and obtains the uniformity of the wavelength of the reflected rays is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element, and more particularly, to an optical element having an elliptic curved surface such as a mirror or a monochromator used for condensing X-rays or monochromatization.

[0002]

2. Description of the Related Art In order to analyze a sample using X-rays, it is necessary to collect divergent X-rays generated from an X-ray source, which is regarded as a point light source, on the sample or to make the sample monochromatic. Among the optical elements used for that purpose, there is an optical element having an elliptic curved surface such as a mirror or a monochromator. The optical element having these elliptic curved surfaces has a feature that the X-ray generated from the X-ray source can be focused on a single point again. In addition, when using a monochromator with an elliptic curve,
It also has a feature that X-rays of a wider range of wavelengths can be extracted as compared with the case of monochromaticization with a flat monochromator. That is, in the monochromator, only wavelengths whose incident angle satisfies the diffraction condition of black are reflected, but when the surface of the monochromator is curved, the incident angle continuously changes, and as a result, a wide range of wavelengths is obtained. X-rays are reflected. Methods of forming an elliptic curved surface include a method of forming by elaboration and a method of mechanically bending a flat plate-shaped element material into an elliptic curved surface. However, in the case of a crystal monochromator, the latter method is usually used because it is necessary to unify the crystal plane indices of the surface. Also, in the case of a mirror, the latter method is used because processing is difficult when the radius of curvature of the ellipse is large. Hereinafter, the structure and operation of the crystal monochromator when the method of deforming it into an elliptic curved surface is applied will be described with reference to FIGS.

FIG. 2 shows an X incorporating a crystal monochromator.
Schematic diagram showing a schematic configuration of a linear absorption characteristic measurement apparatus, a plan view FIG. 3 showing a shape in the use state in the first example A ₁ of the crystal graph showing the curvature curve of the monochromator, 5 conventional monochromator 6A and 6B are a plan view and a side view, respectively, showing the shape of the conventional crystal monochromator in the second example A ₂ in use.
As shown in FIGS. 5A and 5B, in the first example A ₁ of the conventional crystal monochromator, the element material M ₁ is bent on the other end side of the flat plate-shaped element material M ₁ whose one end side is fixed. Force F in all directions
By adding ₁ , the element material M ₁ is held in a curved state, and optical reflection is performed on the concave surface side of the curved element material M ₁ . The element material M ₁ has a rectangular parallelepiped shape (both width and thickness are constant) before bending. The crystal monochromator A ₁ operates as follows when incorporated in a measuring device B for measuring X-ray absorption characteristics, for example.

As shown in FIG. 2, an X-ray generated by an X-ray tube 1 placed at one focal point P ₁ of an ellipse 5 is optically converted by a crystal monochromator 2 (A ₁ ) which is transformed into a part of an elliptic curved surface. When the light is reflected, it is converted into a single color and condensed at the same time. Focused X
The line illuminates the sample 3 located at another focus P ₂ of the ellipse 5. The X-rays that have passed through the irradiated sample 3 are incident on the detector 4 having a positional resolution with a divergence angle that differs depending on the wavelength. The detector 4 measures the X-ray intensity with and without the sample 3 and measures the X-ray absorption characteristics of the sample 3 from the ratio of the two. At this time, since X-rays of different wavelengths are incident on different positions of the detector 4, the X-ray absorption characteristics can be measured as a function of wavelength. The first problem with this device B is the light condensing property on the surface of the sample 3. In order to focus light on one point on the sample 3, the curved curved surface of the crystal monochromator A ₁ needs to be accurately deformed into an ellipse. However, in this crystal monochromator A ₁ , the curved curved surface is not exactly elliptical as shown by the solid line in FIG. Therefore, the focusing condition is not satisfied, and the X-ray cannot be focused at one point. In order to solve this problem,
As shown in (a) and (b), there is a method of bending a triangular columnar element material M ₂ (Summer School Textbook, High Energy Physics Institute, OHO '88, IV-16). In the case of this crystal monochromator A ₂ , the curved curved surface is exactly elliptical. The basic principle will be briefly described below.

First, the equation of the ellipse is expressed by the following equation, as is well known. (X ² / a ² ) + (y ² / b ² ) = 1 (1) where a is 1/2 the axial length in the x direction and b is 1/2 the axial length in the y direction. is there. Next, y in the above equation (1) is expressed as a function of x, and the coordinate system is re-arranged so that y (0) = 0. ^{y = (b 2 -x 2 b} 2 / a 2) 1/2 -b ··· (2) which is elliptical curve on FIG. The displacement y of the element material M ₂ when one end (x = 0) of the element material M ₂ is fixed (that is, the displacement and the inclination are 0) and an external force F is applied to the other end (x = L) is It is given by the following equations (3) and (4). ^{d 2 y / dx 2 = 12F} · (L-x) / {E · b (x) · h (x) 3} ··· (3) y (0) = dy / dx (0) = 0 ·· (4) where E is the Young's modulus of the element material M ₂ , b (x) is the width,
h (x) is the thickness. In the crystal monochromator A ₂ , the width b (x) is linearly changed as in the following equation and the thickness h (x) is constant. b (x) = Cb · (L−x) / L (5) Here, Cb is a constant. By substituting this into the above equation (3) and solving it with the initial conditions of equation (4), an elliptic curved surface represented by equation (2) is obtained. Therefore, according to the crystal monochromator A ₂ , an accurate elliptic curved surface can be obtained, so that an optical element satisfying the condensing condition can be obtained.

[0006]

Among the conventional optical elements as described above, the crystal monochromator A ₂ is said to have good light condensing characteristics by satisfying the light condensing condition which is difficult for A _1. can do. However, the X-ray absorption characteristic measuring device in which the crystal monochromator A ₂ is incorporated instead of A ₁ causes a new problem that the wavelength uniformity cannot be obtained. That is, in order to obtain wavelength uniformity, in the case of a so-called white light source in which the distribution of X-ray intensity according to wavelength is uniform,
The uniformity of the reflection area of the crystal monochromator A ₂ is required, but the reflection surface shape of the crystal monochromator A ₂ is shown in FIG.
It is a triangle as shown in (a) and does not satisfy this requirement. Therefore, the above problem occurs. SUMMARY OF THE INVENTION In order to solve the problems in the conventional technique, the present invention aims to provide an optical element that improves the optical element, has good light-collecting characteristics, and is capable of obtaining wavelength uniformity. It is a thing.

[0007]

In order to achieve the above object, the present invention provides the above-mentioned element by applying a force in the direction of bending the element material to the other end of a flat plate-like element material having one end fixed. In an optical element that holds a material in a curved state and performs optical reflection on the concave side of the curved element material, the concave side of the element material forms a part of an elliptical curved surface. The optical element is characterized in that the thickness is gradually reduced from the one end side to the other end side. Furthermore, h (x) = C · {(L−x) /
b (x)} ⁿ , where 0.1 ≦ n ≦ 0.5, where h (x): thickness of element material at position x b (x): width of element material at position x L: of element material Length x: an optical element having a position in the length direction of the element material C: a constant.

[0008]

According to the present invention, a force is applied to the other end of a flat plate-shaped element material having one end fixed to keep the element material in a curved state,
The thickness of the element material is changed from the one end side to the other end side so that the concave side of the element material forms a part of an elliptic curved surface of the optical element which performs optical reflection on the concave side of the curved element material. Gradually reduce toward. Therefore, it is possible to secure the uniformity of the reflection area while keeping the optical reflection surface as an accurate elliptic curved surface. As a result, it is possible to obtain an optical element that has good light condensing characteristics and can obtain wavelength uniformity.

[0009]

Embodiments of the present invention will now be described with reference to the accompanying drawings.
The examples will be described to provide an understanding of the present invention. still,
The following example is an example embodying the present invention.
It does not limit the technical scope of Ming. here
1 is a crystal monochromator according to an embodiment of the present invention.
A₃Plan view (a) and side view showing the shape in the use state of
(B), Figure 2 shows X-ray absorption with a crystal monochromator.
Schematic diagram showing the schematic structure of the collection characteristics measuring device
Fig. 3 is a graph showing the curve of the crystal monochromator.
F (shared with conventional example), Fig. 4 shows focusing of crystal monochromator
It is a graph which shows a characteristic. As shown in FIG.
Crystal monochromator A₃Is a flat plate with one end fixed
Element material M₃On the other end side of the element material M₃Bend
Directional force F₃By adding the element material M₃Curved
The element material M which is held in a bent state and curved ₃On the concave side of
This is the same as the conventional example in that optical reflection is performed. However,
In this embodiment, the element material M₃The concave side of
Element material M to be formed₃From the one end side to the other
This is different from the conventional example in that it is gradually reduced toward the end face.

The basic principle of the present invention will be briefly described below. The displacement y of the element material M ₃ when one end (x = 0) of the element material M ₃ is fixed (displacement and inclination are 0) and an external force F ₃ is applied to the other end (x = L) is Similar to the above, it is given by the following equation. ^{d 2 y / dx 2 = 12F} · (L-x) / {E · b (x) · h (x) 3} ··· (3) y (0) = dy / dx (0) = 0 ·· (4) In the present invention, the thickness h (x) is continuously changed so that the mechanically deformed shape becomes a part of the elliptic curved surface. The method of changing the thickness h (x) is given by the following equation. h (x) ³ · b (x) = C · (L−x) (6) Here, C is a constant. When the width b (x) is constant,
The thickness h (x) is expressed by the following equation. h (x) = C ′ · (L−x) ^1/3 (7) Here, C ′ is a constant. By substituting the equation (6) into the equation (3) and solving it with the initial condition of the equation (4), the above equation (2) becomes a solution and the deformation of the elliptic curved surface is obtained. The above equation (7) is, so to speak, an ideal thickness shape. Furthermore, as a result of examining various h (x) curves, h (x) = C · {(L−x) / b (x)} ⁿ (8) where 0.1 ≦ n ≦ 0.5 When the width b (x) is constant, even if the thickness is h (x) = C ′ · (L−x) ⁿ ... It turned out to be obtained.

The crystal monochromator A ₃ using this basic principle will be described in more detail below. First, Figure 1
The width b (x) is 25 mm (constant) and the length L is
Is 100 mm, and the thickness h (x) is a silicon crystal having a shape according to the above formula (7). Thickness h (x) is fixed end (x
= 0), it becomes 5 mm and becomes thinner toward the tip. By the way, in the case of a monochromator, it is necessary to align the lattice plane intervals of the X-ray reflecting surface. Therefore, when processing the element material M _{3 to have} a thickness of h (x), the X-ray reflecting surface is made flat and the opposite side is cut. This tip (x =
L) is applied with an external force F ₃ of about 10.7 kgf to bend it.
At this time, the tip is bent by about 2.2 mm, and the curved shape of the crystal matches the elliptic curve shown in FIG. At this time, the half major axis a of the ellipse is 350 mm and the half minor axis b is 50 mm.
mm. By holding the element material M ₃ in this curved state, an X-ray reflection surface is formed, and the X-rays reflected here are
The light can be focused on one point on the sample 3 in FIG. The above is an ideal case where the thickness h (x) is represented by the above equation (7). Next, in the equation (9), n = 0.
Curved curves for 1 and n = 0.5 are shown by dotted lines in FIG. 3, respectively. From FIG. 3, in any case, the conventional example A ₁
It can be seen that it is closer to an elliptic curve than a rectangular parallelepiped (width and thickness are constant) curved curve. X when the parameter n is changed
The light condensing characteristics of the line are shown in FIG. As the condensing characteristics took defocus amount of the focus P ₂ in FIG. This is a shift in the position where the X-ray reflected at each point of the crystal monochromator 2 (A ₃ ) passes on the sample 3. In FIG. 4, n = 0
The point is the characteristic of the rectangular parallelepiped of Conventional Example A _{1 in} which both width and thickness are constant. It can be seen that the curved line shows a better condensing characteristic than the characteristic of the conventional example A ₁ .
If the light source has a wavelength intensity distribution instead of white light,
In addition, the width b (x) of the crystal monochromator can be adjusted so that the reflected wavelength intensity becomes constant. In that case, the crystal thickness distribution h (x) must be adjusted so as to satisfy the above expression (8) (ideally it should be adjusted so as to satisfy the above expression (6)). As described above, according to the present invention, it is possible to secure the uniformity of the reflection area while keeping the optical reflection surface as an accurate elliptic curved surface.

As a result, it is possible to obtain an optical element having a good light-collecting characteristic and a uniform wavelength of the reflection line. In particular, since the monochromator can obtain the wavelength uniformity of the reflected wave, when applied to an analyzer, high precision analysis becomes possible, and the effect becomes remarkable. Further, since some crystals are hard and brittle, it may be difficult to process them by changing the thickness h (x) as shown in FIG. In that case, the thickness of the crystal is made thin and constant, and the thickness of another material with high rigidity (for example, stainless steel) is processed as shown in Fig. 1, and then both are bonded with an adhesive.
A method of bending after that may be adopted. In this way, it is possible to have a wide selection range as the element material M ₃ . Although the crystal monochromator is exemplified as the optical element in the above embodiment, it may be applied to other optical elements such as a mirror in actual use without any problem.

[0013]

Since the optical element according to the present invention is configured as described above, it is possible to secure the uniformity of the reflection area while keeping the optical reflection surface as an accurate elliptic curved surface. As a result, it is possible to obtain an optical element having good light condensing characteristics and obtaining the uniformity of the wavelength of the reflection line. In particular, since the monochromator can obtain the wavelength uniformity of the reflected wave, it becomes possible to perform highly accurate analysis when applied to an analyzer, and the effect becomes remarkable. Further, by bonding a material having high rigidity to the element material, it is possible to use a hard and brittle element material, so that a wide selection range can be given as the element material.

[Brief description of drawings]

FIG. 1 is a plan view (a) and a side view (b) showing a shape of a crystal monochromator A _{3 according} to an embodiment of the present invention in use.

FIG. 2 is a schematic diagram showing a schematic configuration of an X-ray absorption characteristic measuring device incorporating a crystal monochromator (shared with a conventional example).

FIG. 3 is a graph showing a curve of a crystal monochromator (shared with a conventional example).

FIG. 4 is a graph showing the condensing characteristics of a crystal monochromator.

FIG. 5 is a plan view (a) and a side view (b) showing a shape of a conventional crystal monochromator in a first example A ₁ in use.

FIG. 6 is a plan view (a) and a side view (b) showing a shape of a conventional crystal monochromator in a used state of a second example A ₂ .

[Explanation of symbols]

A ₃ ... Crystal monochromator (equivalent to optical element) M ₃ ... Element material F ₃ ... Force

Claims (2)

[Claims] 1. A flat element material having one end fixed to the other end of the element material by applying a force in a direction of bending the element material to hold the element material in a curved state, and the curved element. In an optical element that performs optical reflection on the concave side of the material, the thickness of the element material is gradually reduced from the one end side to the other end side so that the concave side of the element material forms a part of an elliptic curved surface. An optical element characterized in that 2. The thickness of the element material is h (x) = C · {(L−x) / b (x)} ⁿ , where
0.1 ≦ n ≦ 0.5 where h (x): thickness of element material at position x b (x): width of element material at position x L: length of element material x: length of element material The optical element according to claim 1, wherein the position C in the direction is a constant.