X-ray analysis apparatus and method

This invention provides an X-ray analysis apparatus and method capable of simply and accurately determining the position of analysis in a sample from an optical image of it without lowering the sensitivity and/or the spatial resolution in light element analysis. The X-ray analysis apparatus of the present invention irradiates a sample with X-rays narrowed down by means of an X-ray guide member from above the sample in which said sample is directly irradiated with X-rays from said X-ray guide member and an optical image of said sample is obtained in the direction coaxial with said X-ray guide member.

FIELD OF INVENTION

The present invention relates to an X-ray analysis apparatus and method used for examining samples. More particularly, the invention relates to a method and apparatus for analyzing the kind, amount and distribution state of elements contained in a sample.

BACKGROUND OF THE INVENTION

An X-ray analysis apparatus irradiates a sample mounted on a sample stage with primary X-rays, detects secondary X-rays such as fluorescent X-rays, scattering X-rays and the like generated at that time by means of an X-ray detector, processes properly the detected output, and thereby makes it possible to analyze constituent elements of the sample or its internal structure.

Recently a demand for analyzing in more detail a microscopic part of a sample, using the X-ray analysis apparatus as described above, has been increased. To perform this more detailed analysis, a microscopic part of the sample is irradiated with X-rays narrowed down by means of an X-ray guide member such as an X-ray guide tube and the like. In this case it is desirable to observe what position of the sample is irradiated with the narrow-diameter X-ray beam by means of an observing means such as a CCD camera and the like, and display the observed image on the display screen of a display device attached to an arithmetic and control device such as a personal computer and the like for controlling the whole apparatus.

Exemplary conventional X-ray analysis apparatus are described in Japanese Patent Laid-Open Publication No. Hei 4-175648 and Japanese Patent Laid-Open Publication No. Hei 6-288941.FIG. 6shows schematically an X-ray analysis apparatus disclosed in Japanese Patent Laid-Open Publication No. Hei 4-175648, and in this X-ray analysis apparatus there are provided an X-ray tube42and an X-ray detector43so as to be opposite to each other obliquely above a sample41, so that characteristic X-rays (fluorescent X-rays for example)46generated when the sample41is irradiated with X-rays (primary X-rays)44which have been emitted from the X-ray tube42and narrowed down by an X-ray guide member45A are detected by means of the X-ray detector43, and a CCD camera47as a sample observing means is provided directly above the sample41so as to observe an optical image (visible light image) of the sample41in a different direction (inclined direction) from the direction of irradiation of the X-rays44(the X-ray irradiation axis).

FIG. 7shows schematically an X-ray analysis apparatus disclosed in Japanese Patent Laid-Open Publication No. Hei 6-288941 and this X-ray analysis apparatus provides an X-ray tube42and an X-ray guide member45B, such as a collimator, directly above a sample41, further provides a half mirror48made of beryllium leaf being low in X-ray absorptivity below the X-ray guide member45B so that it makes an angle of 45° with the direction of X-ray irradiation, provides a CCD camera47at the reflecting surface side of it, and thereby makes it possible to observe an optical image (visible light image) of the sample41coaxially with the axis of X-ray irradiation. InFIGS. 6 and 7, number49refers to a tank containing a cooling medium for cooling the X-ray detector43.

As shown inFIG. 6described above, however, in an X-ray analysis apparatus made to observe an optical image at an angle with the direction of X-ray irradiation, when the height of a sample is changed, a difference (discrepancy) arises between the position of observing an optical image and the position of X-ray irradiation in the sample41, and if the surface of the sample is uneven it is not possible to exactly determine the position of analysis. And even in case that the surface of a sample is not uneven, since the position of analysis is determined depending on the accuracy of determining the height of the sample41, a mechanism for accurately setting the height is required, requiring thereby an apparatus that is complex in structure.

On the other hand, in the X-ray analysis apparatus shown inFIG. 7, since an optical image (visible light image) of a sample41is observed coaxially with the axis of X-ray irradiation, a disadvantage as described above in connection with the apparatus illustrated inFIG. 6does not occur, but since the sample41is irradiated with X-rays44through the half mirror48, even in case of using a material being low in X-ray absorptivity like beryllium leaf, at least some of the X-rays44are absorbed. Particularly, the lower the low-energy X-rays effective for exciting light elements are in energy, the more likely the X-rays are to be absorbed; it is not possible to avoid the lowering of analysis sensitivity in light element analysis. And it is unavoidable that the distance between the X-ray output end (the lower end45bof the X-ray guide member45B in this example) and the sample41is made larger by arranging the half mirror48, and thereby the spatial resolution of the apparatus is lowered.

The present invention addresses the above-mentioned deficiencies, and an object of the invention is to provide an X-ray analysis apparatus and method being capable of simply and accurately determining the position of analysis in a sample from an optical image of it without lowering the sensitivity and the spatial resolution in light element analysis.

SUMMARY OF THE INVENTION

In order to attain the above-mentioned object, the present invention forms an X-ray analysis apparatus made to irradiate a sample with X-rays narrowed down by means of an X-ray guide member from above the sample in which said sample is directly irradiated with X-rays from said X-ray guide member and an optical image of said sample is obtained in the direction coaxial with said X-ray guide member.

Using the above-described apparatus, it is possible to obtain an optical image of a sample coaxially with the axis of irradiating the sample with X-rays and perform at the same time the irradiation of the sample with X-rays and the confirmation of an optical image (visible light image) of the sample to be irradiated with X-rays in X-ray analysis of the sample. Therefore, it is possible to confirm, for example, visually the state (situation) of the sample while irradiating the sample with X-rays, and accurately determine the position of analysis even in case that the surface of the sample is uneven. Since a sample is directly irradiated with X-rays for X-ray analysis, the X-rays are not absorbed by a mirror and the analysis sensitivity is not lowered even in light element analysis. Further, since it is possible to make the X-ray output end of an X-ray guide member as close as possible to a sample, it is also possible to prevent the spatial resolution from lowering.

More concretely, the present invention provides an X-ray analysis apparatus for irradiating a sample with X-rays narrowed down by means of an X-ray guide member from above the sample, being provided with a mirror having an X-ray guide member through-insertion portion above said sample so that the reflecting surface of it faces the sample side and makes a specified angle with the direction of irradiating X-rays, making the lower end side of said X-ray guide member be inserted into said X-ray guide member through-insertion portion, and being provided with a collective lens having a large numerical aperture (e.g., greater than about 0.1) for converging the light reflected by said reflecting surface in a direction making a specified angle with said reflecting surface on a sample observing means.

Hereupon, a through hole may be formed in a reflecting surface as an X-ray guide member through-insertion portion generated in the reflecting surface of a mirror so as to make the lower end side of the X-ray guide member be inserted through it. Alternatively, a depression shallow (small) in cut or a depression deep (large) in cut may be provided in the reflecting surface, and it is acceptable also that the mirror is formed out of plural (two for example) mirror members and a specified gap is formed between these mirror members.

In accordance with one embodiment of the invention, the X-ray analysis apparatus includes a paraboloid mirror, having its focus at the position of a sample, that is provided around the X-ray guide member between the mirror and the sample. In such a case, it is possible to optionally select the height of a mirror relative to a sample.

In an X-ray analysis apparatus made to irradiate a sample with X-rays narrowed down by means of an X-ray guide member from above the sample, it is acceptable also to irradiate directly said sample with X-rays from said X-ray guide member and provide an optical fiber along said X-ray guide member. In such a case, a mirror for reflecting visible light and a collective lens are made unnecessary and thereby the structure is more simplified.

Further, in an X-ray analysis apparatus made to irradiate a sample with X-rays narrowed down by means of an X-ray guide member from above the sample, it is also acceptable to provide a concave mirror having an X-ray guide member through-insertion portion in its reflecting surface above said sample so that the reflecting surface of it faces the sample side, make the lower end of said X-ray guide member be inserted through into said X-ray guide member through-insertion portion, and provide a sample observing means in which the light reflected by said reflecting surface enters at the focus position of said reflecting surface. In such a case, a collective lens is made unnecessary.

In an X-ray analysis method made to irradiate a sample with X-rays narrowed down by means of an X-ray guide member from above the sample, it is also acceptable to irradiate directly said sample with X-rays from said X-ray guide member and obtain an optical image of said sample in a direction coaxial with said X-ray guide member. The action and effect of such an X-ray analysis method are the same as those of the X-ray analysis apparatus described above, in which the sample is directly irradiated from an X-ray guide member and an image of said sample is obtained in a direction co-axial with said X-ray guide member.

DETAILED DESCRIPTION

The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the general principles of the present invention have been defined herein.

Details of the present invention are described with reference to the drawings in the following.FIGS. 1 and 2show an embodiment of the present invention.FIG. 1shows schematically an example of a main composition of an analysis part of an X-ray analysis apparatus of the present invention, andFIG. 2is a diagram showing schematically an optical portion of said analysis part. In these figures, number1refers to a main body block of an X-ray analysis apparatus, above which there is provided an X-ray generator4containing an X-ray tube3, a power source part (not illustrated) through a seal portion2. The main body block1has a through-insertion hole6for allowing an X-ray guide tube5to be inserted as an X-ray guide member for guiding a primary X-ray beam emitted by the X-ray generator4as narrowing it down into a narrow beam diameter (about 10 to 100 μm in diameter) and irradiating a sample12(described later) with this narrow primary X-ray beam a, and a lower space7communicating with this through-insertion hole6. The X-ray guide tube5is made gradually narrower from the top end to the lower end5a, for example.

Reference number8corresponds to an X-ray shielding wall provided in the lower part of the main body block1, more concretely, provided below the lower end5aof the X-ray guide tube5, and at a position in it corresponding to the X-ray output end (lower end)5aof the lowest end of the X-ray guide tube5an opening9being proper in size is formed. Below this X-ray shielding wall8, a space11being in the atmospheric pressure and air-tightly partitioned from the space7in the main body block1side by a thin diaphragm10made of a material transparent to X-rays, for example, polyethylene resin, is formed. The space7over the diaphragm10is referred to as an X-ray irradiation chamber, and the space11under the diaphragm10is referred to as a sample chamber11.

In the sample chamber11, a sample stage13having a sample12mounted on it is provided so that it can be moved straight respectively in the X direction (perpendicularly to the paper face), Y direction (horizontally in the paper face) and Z direction (vertically in the paper face) by a drive mechanism not illustrated. A door (not illustrated) used for inserting and taking out a sample12is provided at a proper position at the left side in the Y direction of sample chamber11.

The inside of said X-ray irradiation chamber7is kept in a proper vacuum state together with the through-insertion hole6, and has an X-ray output end5aof the X-ray guide tube5and an X-ray detector14composed of a semiconductor detector for detecting fluorescent X-rays b (seeFIG. 2) generated by irradiating a sample12with a primary X-ray beam a (seeFIG. 2). InFIG. 1, number15corresponds to a tank containing a cooling medium for cooling the X-ray detector14. The analysis components described above can be the same as the components of an analysis part in a conventional X-ray analysis apparatus of this kind. The present invention forms a means for observing a sample12and confirming an irradiated position of the sample12as described below.

Number16refers to a plane mirror provided in the X-ray irradiation chamber7above the sample12, and its plan view is a rectangle for example and the plane mirror has a through hole17as a through-insertion part for having the X-ray guide tube5inserted as an X-ray guide member formed nearly in the middle of its reflecting surface16a. Mirror16is provided so that its reflecting surface16afaces the sample12side and makes an angle of about 45° with the direction of irradiating X-rays (the perpendicular direction in this case) and said through hole17is formed so as to be necessary and sufficient in size to have the lower end of the X-ray guide tube5perpendicularly inserted through it. Reflecting surface16ais polish-finished so as to be capable of efficiently reflecting visible light. Although the lower end side of the X-ray guide tube5penetrates the through hole17, it is preferable that the X-ray output end5aof the lower end side is made as close as possible to the surface12aof the sample12. Further, in this case, it is preferable to form the outer circumferential surface5bof the X-ray guide tube5projecting downward from the through hole17into a stray light preventing surface by applying an antireflection coating or the like to it. Although not illustrated inFIGS. 1 and 2, the apparatus is composed so that the sample12is irradiated with visible light.

Reference number18corresponds to a collective lens, which is provided so that the optical axis of it makes an angle of about 45° with the reflecting surface16aof the mirror16, and converges the visible light c which has emanated from the sample12and is reflected by the reflecting surface16aof the periphery of the through hole17on the light receiving surface19aof the CCD camera19as a sample observing means provided at a proper position in the light output side, and is composed of a lens of a high numerical aperture. The reason why a high-numerical aperture lens is used as the collective lens18is that it reflects the visible light c from the sample12by the mirror16, particularly, by the reflecting surface16aaround (in the periphery of) the through hole17of the mirror16, and ensures that a complete or substantially complete visible light image is obtained, rather than eclipsing the image due to using a small numerical aperture lens.

InFIG. 1, number20is an arithmetic and control unit such as a personal computer or the like provided with an image processing function, and has a function of controlling the whole apparatus, performing an arithmetic operation on the basis of output signals of the X-ray detector14, the CCD camera19and the like, and image-displaying the result of arithmetic operation or the result of image processing on the display screen21aof a display device21.

In an X-ray analysis apparatus composed as described above, it is possible to obtain an optical image of a sample coaxially with the axis of irradiating the sample12with a primary X-ray beam a, and particularly perform at the same time the irradiation of the sample12with a primary X-ray beam a and the confirmation of an optical image of the sample12to be irradiated with X-rays in X-ray analysis of the sample12. Therefore, it is possible to confirm the state (situation) of the sample12visually for example, while irradiating the sample12with a primary X-ray beam a, and determine the position of analysis in the sample12even when the sample is uneven in surface. And since a primary X-ray beam a to the sample12is irradiated to the sample12from a position as close as possible to the sample12by the X-ray guide tube5penetrating the though hole17of the mirror16, even in case that a primary X- ray beam a used in a light element analysis is low in energy, absorption of the primary X-rays a by the mirror16is prevented and a light element analysis can be performed with high sensitivity. Furthermore, since the X-ray output end5aof the X-ray guide tube5can be made as close as possible to the sample12, the lowering of the spatial resolution can be prevented. Further, stray light of visible light c can be also prevented by forming the outer circumferential surface5bof the X-ray guide tube5located below the mirror16into a stray light preventing surface through applying an antireflection coating or the like to it and thereby a clear optical image can be obtained.

Although the above-described embodiment uses an X-ray guide tube5as an X-ray guide member for guiding a primary X-ray beam a emitted by an X-ray generator14as narrowing it down into a narrow beam diameter, in place of this X-ray guide tube5, as shown inFIG. 3, it is acceptable to use a collimator24of a double-pinhole type having a collimator cylinder22which is formed narrower in the lower end side22bthan the upper end side22aand which has pinholes23aand23brespectively at the upper and lower ends and make the lower end side22bbe inserted through the through hole17of the mirror16. In this case, it is preferable to form the outer circumferential surface of the lower end side22bprojecting downward from the through hole17into a stray light preventing surface.

Although each of the above-mentioned embodiments forms the through hole17in the reflecting surface16aof the mirror16and makes the lower end side of an X-ray guide member such as an X-ray guide tube5, a collimator24and the like be inserted through into this through hole17, various forms, as shown inFIGS. 4(A) to 4(C), are conceivable as a through-insertion portion having the lower end side of said X-ray guide member inserted into it without being limited to said through hole17. That is to say, for example, in order to make the lower end side of an X-ray guide tube5be inserted through the mirror, it is acceptable also to form a shallow (small) cut17ain a part of the reflecting surface16of a mirror16as shown inFIG. 4(A), form a deep (large) cut17bas shown inFIG. 4(B), or form a mirror16by arranging plural (two for example) mirror members16A and16B in a row and then form a specified gap17cbetween these mirror members16A and16B as shown inFIG. 4(C). The invention is not limited to these specific examples.

By way of particular example, in the case in which an X-ray guide tube5is made gradually narrower as going toward the lower end part and the outer diameter of the lower end part5ais 0.5 mm and the outer diameter of a portion close to the through-insertion part is 3 mm and a mirror16is 20 mm×30 mm in size, the length of said cut17ais about 4 mm. In case of alternately using plural X-ray guide tubes5or collimators24, the alternating operation can be easily performed, for example, by using a through-insertion part17a,17bor17cshown inFIGS. 4(A) to 4(C).

Although each of the above-mentioned embodiments uses a plane mirror16in order to obtain an optical image of a sample12coaxially with an X-ray guide member5or24, it is possible to adopt various means as shown inFIG. 5for example, in place of the plane mirror16. That is to say, as shown inFIG. 5(A), in order to obtain an optical image of the sample12, it is possible to arrange an optical fiber25to be used in, for example, an endoscope or the like along an X-ray guide tube5as an X-ray guide member so that the lower end of it is nearly equal in height to the lower end of the X-ray guide tube5and the upper end of it is connected to a CCD camera19. In the case of using such an optical fiber, an arrangement as shown inFIG. 5(B)may be also adopted. That is to say, inFIG. 5(B), an optical fiber26obtained by bundling a plurality of optical fibers26aeach being in a single-fiber state is used in which these optical fibers26aare provided near and around the lower end of the X-ray guide tube5, as shown in a magnified view ofFIG. 5(B). Any of the compositions shown inFIGS. 5(A) and 5(B)does not need a mirror16for reflecting visible light and/or a collective lens18, and thereby makes the structure of the apparatus simpler.

Furthermore, as shown inFIG. 5(C), it is acceptable also to provide a concave mirror (elliptical mirror)27whose reflecting surface27ais concave (elliptical) as a mirror for collecting visible rays above a sample12, form a through-insertion portion28for allowing an X-ray guide tube5to be inserted through the reflecting surface27aof this mirror27, make the lower end of the X-ray guide tube5be inserted through said through-insertion portion28., and arrange a CCD camera19at the focus position of said reflecting surface27a. According to this composition, since the mirror27serves as both a reflecting member and a collective member, a collective lens18is made unnecessary and thereby the apparatus is simplified.

In an embodiment shown inFIG. 5(D), a paraboloidal mirror29is provided in the structure shown inFIG. 2, and in more detail said paraboloidal mirror29is provided around an X-ray guide tube5between a mirror16and a sample12, and has the focus of it at the sample position; and according to this composition, since the reflected light c from the surface12aof the sample12is incident on the mirror16as a light beam parallel with a vertical line, the height of the mirror16relative to the sample12can be optionally determined.

In the above-mentioned embodiments, a CCD camera is used as a sample observing means, but in place of this, another sample observing means such as an optical microscope and the like may be used and in this case it is enough to make the light such as visible light c and the like from the collective lens18form an optical image on the sample observing means. It is not always necessary to provide a thin diaphragm10under the main body block1, and in case of omitting this, the X-ray output end5aof an X-ray guide tube5can be made closer to the surface12aof a sample12.

As described above, in case of irradiating a sample with X-rays narrowed down by means of an X-ray guide member from above the sample, since the present invention irradiates directly said sample with X-rays from said X-ray guide member and obtains an optical image of the sample coaxially with said X-ray guide member, it is possible to obtain an optical image of the sample coaxially with the axis of irradiating the sample with the X-rays and perform at the same time the irradiation of a sample with X-rays and the confirmation of an optical image (visible image) of a sample to be irradiated with X-rays. Therefore, it is possible to confirm, for example, visually the state (situation) of a sample while irradiating the sample with X-rays and accurately determine the analysis position in a sample even when the surface of the sample is uneven. And since a sample is directly irradiated with X-rays for X-ray analysis, the X-rays are not absorbed by a mirror and the analysis sensitivity is not lowered, even in light element analysis. Furthermore, since it is possible to make the X-ray output end of an X-ray guide member as close as possible to a sample, it is possible also to prevent the spatial resolution from lowering.

According to an X-ray analysis apparatus and method of the present invention, therefore, it is possible to simply and accurately determine the position of analysis in a sample from an optical image without lowering the sensitivity and the spatial resolution in light element analysis and make high precision X-ray analysis.

Although the present invention is set forth herein in the context of the appended drawing figures, it should be appreciated that the invention is not limited to the specific form shown. For example, while various forms of mirror16and guide tube5have been illustrated, the invention is not so limited. Various other modifications, variations, and enhancements in the design and arrangement of the method and apparatus set forth herein, may be made without departing from the spirit and scope of the present invention as set forth in the appended claims.