JPH05142400A - Soft x-ray microscope - Google Patents

Abstract

PURPOSE:To provide a soft X-ray microscope which can easily select accurate wavelength, and is simple in device and structure. CONSTITUTION:There are disposed a condensing member 3 which converts soft X-rays transmitted from a radiation source 1 into convergent rays, and a dispersion member 5 which disperses the convergent rays into rays by wavelength in a space interspaced with the focus 4 of the convergent rays. The dispersion member 5 is rotated around an axis W normal to a plane of XY which passes through the center of the dispersion member while being formed by the optical axis 2 of the convergent rays and the dispersion direction of the flux of rays, and the flux of rays with a desired wavelength is thereby irradiated onto a specimen 6, so that transmitted ray flux is detected by a detector 8.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a soft X-ray microscope.

[0002]

2. Description of the Related Art Conventionally, a zone plate or a mirror has been used as a focusing optical system of a soft X-ray microscope. The former uses the diffraction effect of light, and as shown in FIG. 5, the light emitted from the light source is diffracted by the zone plate,
The wavelengths are condensed at different positions on the same axis. The zone plate shown in FIG. 5 is a Fresnel zone plate in which transparent portions and shielding portions are concentrically provided alternately. As an example of the latter, there is the toroidal mirror shown in FIG. 6, which is designed so that lights of all wavelengths are focused on the same focal point.

[0003]

By the way, when observing a biological specimen, it is necessary to observe the specimen for each element constituting the organism. Therefore, there is a demand for a condensing optical system in which soft X-rays having a wavelength corresponding to the absorptance peculiar to the element to be observed can be accurately and simply selected, that is, excellent in wavelength selectivity.

In the above-mentioned conventional example, when a zone plate is used for the condensing optical system, the light beam is condensed on the same optical axis. Therefore, it is necessary to give it wavelength selectivity as described above. For example, means such as placing a pinhole at the focal position can be considered. However, in reality, zero-order light (transmitted light) and higher-order light are incident on the pinhole at the same time, so that sufficient wavelength selectivity cannot be obtained. Further, in this case, since the focal position is different for each wavelength, a mechanism for aligning the focal position of the wavelength to be selected with the pinhole position is required. This is not preferable because it complicates the configuration of the entire microscope apparatus. On the other hand,
When a mirror is used, light of all wavelengths is condensed at the same focal point, so there is no need to provide a mechanism for adjusting the position of the pinhole to the focal position, and the configuration of the microscope device is simple, but There is no wavelength selectivity as in the zone plate, and therefore the element cannot be identified.

The present invention has been made in view of the above problems of the prior art. The object of the present invention is that accurate wavelength selection can be easily performed and the device structure is simple. It is to provide a soft X-ray microscope.

[0006]

A soft X-ray microscope according to the present invention comprises a soft X-ray light source, a light condensing member for converting soft X-rays emitted from the light source into convergent light, the light condensing member and the light condensing member. It has a dispersion member arranged between the focal point of the convergent light and for dispersing the convergent light into light of each wavelength, and a detector, and the dispersive member passes through the center of the dispersive member and It is characterized in that it rotates about an axis perpendicular to a plane formed by the optical axis of the converged light and the light beam dispersion direction of the dispersion member.

[0007]

By arranging the dispersion member between the condensing member and its focal point, the diffraction angle varies depending on the wavelength of the converged light incident on the dispersion member, and the condensing position of the diffracted light on the diffractive surface varies depending on the wavelength. It can be dispersed. This allows easy wavelength selection. Further, if the dispersion member is rotated so that the incident angle and the diffraction angle are adjusted in accordance with the wavelength, the order, and the diffraction condition of the dispersion member to be selected, the positions of the light source and the sample are fixed and different. The diffracted light of the wavelength can be selected.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below with reference to the drawings. Example 1 FIG. 1 shows an optical system when the present invention is applied to a scanning optical microscope. In the figure, 1 is a soft X-ray light source, 2 is an optical axis, 3 is a toroidal mirror for collecting light, 4 is a focal point of the toroidal mirror 3, and 5 is disposed between the toroidal mirror 3 and its focal point 4. A zone plate for diffracting incident light to disperse the condensing position for each light flux of each wavelength, 6 is a sample to be measured, 7 is a scanning stage for scanning the sample 6, and 8 is transmitted light of the sample 6. Is a detector and 9 is a detector. In the figure, for the sake of explanation, a point where the optical axis 2 intersects with the toroidal mirror 3 is set as an origin o, and the x axis and the y axis are arranged so that the optical axis 2 is on the xy plane, and z is arranged so as to be orthogonal to this plane. The axes are set and illustrated.
The zone plate 5 is of an axially offset type in which the center of the plate and the center of the lattice are offset so that the center of the plate has a groove density so that the center of the plate coincides with the optical axis 2. And the light incident on the plate is x
It is arranged so as to be diffracted on the y plane.

Since the present embodiment is configured as described above, the divergent light emitted from the light source 1 is condensed and reflected by the toroidal mirror 3 and enters the zone plate 5 as converged light. Then, in the zone plate 5, each wavelength is diffracted at different diffraction angles on the xy plane, and the light of each wavelength is condensed at different positions on the plane. Therefore, if the sample 6 is placed in the traveling direction of light of a desired wavelength to be condensed on the xy plane and the transmitted light from the sample 6 is detected by the detector 8,
It becomes possible to selectively observe the element with light having a wavelength corresponding to the inherent absorptance.

Next, the wavelength selection function of the present invention will be described in more detail with reference to FIG. Figure 2 shows the zone plate 5
The optical system in FIG. For the sake of explanation, in the drawing, the center of the zone plate 5 is defined as an origin o ', the origin is an o', the w axis is parallel to the z axis, and the normal line of the exit surface of the zone plate 5 is parallel to the xy plane. The u-axis is taken in the direction, and the v-axis is set so that they are right-handed. A light beam having a wavelength λ entering the zone plate 5 has an angle θi between the optical axis 2 and the u axis of the light beam, and an angle between the optical axis 2'of the diffracted light and the u axis, that is, a diffraction angle. Is defined as θo, the light is diffracted by satisfying the diffraction condition represented by the following expression (1), and focused on the focus 10 of the diffracted light. sin θi + sin θo = Nmλ (1) where N is the groove density at the center of the zone plate 5, and m is the diffraction order.

As is clear from the equation (1), since the diffraction angle θo is different depending on the wavelength λ, the diffracted light focus is dispersed for each wavelength in the diffractive surface, and thus wavelength selectivity can be provided. In addition, the zone plate 5 is defined by the following equation (2)
The optical axis 2 of the diffracted light to be selected is fixed while the light source 1 is fixed by rotating the w-axis in the direction indicated by arrow A in FIGS. 1 and 2 so as to satisfy the condition shown in FIG. The direction of ', that is, the focus position of the diffracted light to be selected can always be matched with the focal point 10. θi −θo = 2K --- Equation (2) where K is a constant.

From the above equations (1) and (2), the following equation (3-
The relationships shown in 1) and (3-2) are derived. θi = K + arcsin {Nmλ / (2cosK)} ──Equation (3-1) θo = arcsin {Nmλ / (2cosK)} − K ──Equation (3-2) Therefore, the relation shown in the above equation holds. By rotating the zone plate 5 about the w axis as a rotation axis and adjusting the incident angle θi and the diffraction angle θo respectively, the desired wavelength λ and the order m can be fixed in a certain direction with the incident direction of the optical axis 2 fixed. The light can be diffracted and condensed. The sample 6 is installed in this diffraction direction to irradiate the diffracted light, and the scanning stage 7 scans the sample 6 in a plane perpendicular to the diffracted light axis 2 ', and the transmitted light at this time is detected by the detector 8. In this case, the sample 6 can be observed in a plane. Therefore, the absorption spectrum and the like of the sample 6 can be easily obtained two-dimensionally, and analysis such as EXAFS can be performed with high spatial resolution. Further, by detecting photoelectrons emitted by irradiating the sample 6 with soft X-rays by the detector 9, element identification of the substance can be performed.

As described above, according to this embodiment, it is possible to easily select and obtain light having a desired wavelength, and even if the wavelength of light to be selected in the condensing optical system is different, Since the zone plate 5 can be rotated and the rotation angle can be adjusted without changing the relative position of the microscope, the microscope device can be simply constructed.

Embodiment 2 FIG. 3 shows an optical system when the present invention is applied to an imaging type soft X-ray microscope. In this embodiment, the optical system shown in the first embodiment is used as a condenser to irradiate the sample 6 with soft X-rays, and the soft X-rays transmitted through the sample 6 are collected by the Walter mirror 11 on the multi-channel plate 12. Light is emitted, the soft X-ray is detected by the plate 12, and the image is observed by the CCD camera 13.

In the present embodiment, as in the case of the first embodiment, even if the wavelength of the light to be selected in the condenser lens optical system is different, the desired value can be obtained by rotating the zone plate 5 and adjusting the rotation angle. The light of the wavelength can be accurately selected and obtained, and the sample 6 can be observed without changing the relative position of the light source and the microscope. Furthermore, the imaging soft X of this embodiment
Since the line microscope does not scan the sample 6 unlike a scanning microscope, there is no deterioration of pixels due to a detection error that tends to occur during scanning, and therefore a clear observation image can be obtained as compared with a scanning microscope.

As design values of the optical system of the above embodiment,
The diffraction condition of the zone plate 5 is N = 1000 (pieces / m
m), K = 179.6 (degrees) is set, light of each wavelength is made incident, and the calculation result of the rotation angle of the zone plate 5 when the primary light is focused on the focal point 10 is It shows in Table 1. In addition, in the value shown in the item of "wavelength (nm)" in Table 1, 2.33 (nm) is the absorption edge of water, and 3.55 (nm).
Is the absorption edge of calcium, and 4.37 (nm) is the absorption edge of protein.

[0017]

[Table 1]

As is clear from Table 1, by using the microscope according to the present invention, it is possible to observe only a desired element by selectively obtaining light having a wavelength necessary for biological observation.

The diffraction direction of the zone plate 5 may be set parallel to the z-axis so that the focal point 10 of the diffracted light is located in the wu plane, as shown in FIG. It may be selected in an appropriate direction depending on the structural conditions and restrictions of the device. In this case, the zone plate 5 rotates about the v-axis in the direction shown by the arrow B in the figure, thereby enabling wavelength selection in the focusing optical system.

Actually, the focal position of the diffracted light slightly shifts in the diffraction direction depending on the wavelength, but the displacement can be corrected by providing a simple position adjusting mechanism for moving the position of the sample corresponding to this displacement. It is possible. Further, in the focusing optical system, the shape of the mirror for focusing is corrected or the number of mirrors is increased to correct the aberration, or the groove shape of the zone plate is changed to correct the aberration, or the diffracted light By setting a pinhole at the focal position to reduce the spot size of the light focused on the sample, the resolution of the observed image can be increased.

[0021]

As described above, in the soft X-ray microscope of the present invention, since the wavelength can be selected by a simple operation of rotating the dispersion member, it is not necessary to adjust the positions of the light source and the detector for each observation of different wavelengths. The desired wavelength can always be selected with stable accuracy, which is extremely effective in improving the observation accuracy. or,
Since the movable part is only the rotating shaft of the dispersion member, it has excellent operability, and is structurally simple and easy to maintain.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a soft X-ray microscope according to the present invention.

FIG. 2 is a diagram showing an optical system in a zone plate in an embodiment of a soft X-ray microscope according to the present invention.

FIG. 3 is a diagram showing the configuration of another embodiment of the soft X-ray microscope according to the present invention.

FIG. 4 is a diagram showing an optical system in a zone plate in another embodiment of the soft X-ray microscope according to the present invention.

FIG. 5 is a diagram showing a condensing optical system of a zone plate.

FIG. 6 is a diagram showing a condensing optical system of a toroidal mirror.

[Explanation of symbols]

 1 Soft X-ray Light Source 3 Toroidal Mirror 5 Zone Plate 6 Sample 8 Detector 11 Walter Mirror 12 Multi-Channel Plate 13 CCD Camera

Claims (1)

[Claims] 1. A soft X-ray light source, a light-collecting member for converting soft X-rays emitted from the light source into convergent light, and a light-collecting member arranged between the light-collecting member and the focal point of the convergent light. A dispersion member for dispersing the converged light into lights of respective wavelengths and a detector, wherein the dispersion member passes through the center of the dispersion member and the optical axis of the converged light and the light beam dispersion of the dispersion member. The soft X is characterized by rotating about an axis perpendicular to the plane formed by the direction and the axis of rotation.
Line microscope.