JP2010190777A - X-ray imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray imaging apparatus capable of obtaining highly accurate and high-contrast photographed images even if an X-ray source is used which divergently emits X-rays. <P>SOLUTION: The X-ray imaging apparatus comprises: the X-ray source; a first diffraction grating for the development of Talbot's effects which generate a streaked intensity distribution of the first period; a second diffraction grating for repeatedly arranging shielding parts and transmission parts in a prescribed direction in a streaked way in the second period and further diffracting X-rays diffracted by the first diffraction grating; and an X-ray detection means for obtaining image information indicating the two-dimensional distribution of X-ray intensity. The second period is approximately double the first period. A ratio of the area occupied by the shielding parts in a surface in the second diffraction grating irradiated with X-rays diffracted by the first diffraction grating is 13 to 41%. The second diffraction grating generates Moire fringes related to image information. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an X-ray imaging apparatus using an X-ray source that emits X-rays so as to diverge.

  X-rays have high transmission power and are used in various fields such as the medical field and non-destructive inspection in order to see through the inside of an object nondestructively. The contrast (shading) in an image (X-ray fluoroscopic image) obtained by X-ray transmission appears depending on the difference in the degree of X-ray absorption of the object. For this reason, for example, sufficient contrast cannot be obtained for a low-density object composed of light elements such as a soft tissue of a living body.

  Therefore, in recent years, an attempt has been made to obtain an X-ray fluoroscopic image having high contrast and resolution by detecting the phase of the X-ray transmitted through the subject using the property as an X-ray wave. One of such attempts is an imaging method using X-ray Talbot interference (for example, Non-Patent Document 1).

  Talbot interference is the following phenomenon. When a first diffraction grating having a period sufficiently larger than the wavelength of the light emitted from the light source is placed between the light source and the subject or behind the subject when viewed from the light source, a predetermined distance (Talbot) from the first diffraction grating. It is possible to detect a striped pattern image reflecting the phase information of the light transmitted through the subject at a position separated by a distance. This light phase information is determined by the refractive index of the subject and the distance of the optical path through which the light passes through the subject (transmitted optical path length). Then, by obtaining the phase information of the light that passes through the subject from the striped pattern, it is possible to obtain the internal information of the subject.

  By the way, the striped pattern obtained by Talbot interference (hereinafter referred to as “Talbot image”) is substantially the same as the pitch of the diffraction grating for Talbot interference, so it has a very high spatial resolution in order to accurately capture the Talbot image. It is necessary to prepare an X-ray image detector having In particular, a method of taking an image with an electronic image pickup device such as a CCD after converting X-rays into visible light via a phosphor (X-ray scintillator) can be used, but a Talbot image can be taken accurately. Until now, it is not practical to make the pixels of the electronic image sensor finer from the viewpoint of cost and manufacturing yield.

  In order to solve these problems, a method using so-called moire fringes is generally performed. Specifically, a diffraction grating (hereinafter referred to as “second diffraction grating”) in which an absorbing member (or reflecting member) and a transmitting member are repeatedly arranged at a place where a Talbot image is obtained at substantially the same period as the Talbot image. ) Are slightly inclined with respect to the Talbot image, and moire fringes can be generated. The interval between the moire fringes is much larger than the period of the Talbot image. For this reason, even if a general X-ray image detector is used, it is possible to accurately capture moire fringes (for example, Non-Patent Document 2).

  In this method, a pattern having the same period is generally used in the first diffraction grating and the second diffraction grating (for example, Patent Document 1).

  Here, in order to obtain an image with high contrast, it is desirable that the second diffraction grating shields X-rays as much as possible. For this reason, even when a metal material having a high shielding effect is used for the shielding part of the second diffraction grating, it is necessary to increase the thickness of the second diffraction grating. When the X-ray to be used is perfectly parallel light, there is no problem even if the thickness of the second diffraction grating is large. However, when the X-ray to be used is divergent light, the second diffraction grating is used. So-called vignetting occurs depending on the thickness of the film, and the transmittance is extremely deteriorated. In particular, when a compact X-ray source such as that used in an X-ray imaging apparatus is used, only divergent X-rays can be obtained, and therefore, an improvement in transmittance at the second diffraction grating is required.

Phase Tomography by X-ray Talbot Interferometry for Biological Imaging ', Atsusi Momose at al.Japanese Journal of Applied Physics, Vol. 45, No. 6A, 2006 "Recent development of X-ray phase imaging", Kaoru Hyakusei, Medical Imaging Technology, Vol.24, No.5, November 2006

JP 2006-359264 A

  However, although Non-Patent Document 1 describes a problem in the case of using divergent X-rays, for example, a specific example for the problem that the transmittance of X-rays decreases when the incident angle increases. There is no mention of any corrective measures.

  The present invention has been made in view of the above problems, and even when an X-ray source that emits X-rays is emitted, X-rays that can obtain a high-accuracy and high-contrast captured image. An object is to provide a photographing apparatus.

  In order to solve the above-described problem, the invention according to claim 1 is directed to an X-ray source that emits X-rays and a stripe-like intensity distribution of a first period in the X-rays emitted from the X-ray source. A first diffraction grating that produces a Talbot effect, a shielding part that shields X-rays, and a transmission part that transmits X-rays are repeatedly arranged in a predetermined direction in a second period in a striped manner, and the first diffraction grating A second diffraction grating for further diffracting the X-rays diffracted by the first diffraction grating, and image information indicating a two-dimensional distribution of the intensity of the X-rays disposed near the second diffraction grating and diffracted by the second diffraction grating. X-ray detection means for obtaining, wherein the second period is about twice the first period, out of the second diffraction grating, emitted from the X-ray source, and at the first diffraction grating On the surface irradiated with the diffracted X-ray, the ratio of the area occupied by the shielding portion is 1 % Or more and not more than 41%, the second diffraction grating, the image according to the image information, an X-ray imaging apparatus characterized by generating moire fringes.

  A second aspect of the present invention is the X-ray imaging apparatus according to the first aspect, wherein the ratio is 14% or more and 40% or less.

  According to the first aspect of the present invention, the period of the second diffraction grating is twice the period of the first diffraction grating, and the area occupied by the shielding portion on the surface of the second diffraction grating irradiated with X-rays is further increased. Since the ratio is 13% or more and 41% or less, even when an X-ray source that emits X-rays is emitted, a high-accuracy and high-contrast image can be obtained.

  According to the second aspect of the present invention, the period of the second diffraction grating is twice that of the first diffraction grating, and the area occupied by the shielding portion on the surface of the second diffraction grating irradiated with X-rays Since the ratio is 14% or more and 40% or less, even when an X-ray source that emits X-rays is emitted, an image with higher accuracy and higher contrast can be obtained.

It is a schematic diagram which shows the structure of 50 A of X-ray imaging apparatuses which concern on one Embodiment of this invention using Talbot interference. It is a schematic diagram showing a relative angular relationship between the second diffraction grating 7A and the first diffraction grating 6. It is the schematic diagram which looked at the structure from the X-ray source 1 to the X-ray detector 8 from upper direction (+ Z direction). It is a figure which shows an example of the form of the 1st diffraction grating 6 and the 2nd diffraction grating 7A. It is the schematic which shows a mode that X-ray permeate | transmits a 2nd diffraction grating. It is a figure which shows the form of the 2nd diffraction grating 7B which does not have an X-ray transmissive layer. It is a figure which illustrates schematic structure of X-ray imaging apparatus 50B using Talboro interference.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing a configuration of an X-ray imaging apparatus 50A according to an embodiment of the present invention using Talbot interference.

  As shown in FIG. 1, an X-ray imaging apparatus 50A includes an X-ray source 1, an X-ray source control unit 2, a first diffraction grating 6, a second diffraction grating 7A, an X-ray detector 8, and a control for controlling the entire apparatus. Unit 9, storage unit 12, operation unit 13, and display unit 14. Here, the subject 4 is provided in the vicinity of the second diffraction grating 7A.

  The X-ray source 1 emits toward the X-ray detector 8 so as to diverge the X-rays.

  The X-ray source control unit 2 controls the emission of X-rays by the X-ray source 1 in accordance with a signal from the control unit 9 described later. In FIG. 1, an outer edge of a space region (X-ray passage region) through which X-rays emitted from the X-ray source 1 pass is indicated by an arrow 16.

  Then, X-rays emitted from the X-ray source 1 are emitted toward the first diffraction grating 6.

  The first diffraction grating 6 diffracts the X-rays emitted from the X-ray source 1. The first diffraction grating 6 has a plurality of layers arranged in a striped pattern at a predetermined period, and the X-ray intensity distribution irradiated to the first diffraction grating 6 has a striped intensity distribution, that is, a Talbot effect. Interference fringes are generated.

  The second diffraction grating 7 </ b> A is disposed along a surface where interference fringes related to the Talbot effect generated by the first diffraction grating 6 are generated, and further diffracts the X-rays diffracted by the first diffraction grating 6. Similarly to the first diffraction grating 6, the second diffraction grating 7A has a plurality of layers arranged in a striped pattern with a predetermined period, and image information obtained by the X-ray detector 8 (two-dimensional X-ray intensity). Moire fringes are generated in the image related to the image information indicating the distribution.

  As described above, in order to generate moire fringes having a period much larger than the period of the Talbot image, the second diffraction grating 7A is arranged at a place where the Talbot image is obtained. Specifically, the relative angle relationship of the second diffraction grating 7 </ b> A is changed while maintaining a parallel state with the first diffraction grating 6, and the second diffraction grating 7 </ b> A is arranged along the plane on which the Talbot image generated by the first diffraction grating 6 is generated. Is done. FIG. 2 is a schematic diagram showing a relative angular relationship between the second diffraction grating 7A and the first diffraction grating 6. As shown in FIG. Here, the degree of inclination of the second diffraction grating 7A (degree of inclination) can be expressed by a rotation angle θ with respect to the first diffraction grating 6, and the rotation angle θ is greater than 0 degree and not more than 5 degrees. It is preferable that When the rotation angle θ exceeds 5 degrees, the clarity of moire fringes tends to deteriorate.

  FIG. 3 is a schematic view of the configuration from the X-ray source 1 to the X-ray detector 8 as viewed from above (+ Z direction). FIG. 4 is a diagram showing an example of the form of the first diffraction grating 6 and the second diffraction grating 7A. In the drawings after FIG. 3, three orthogonal axes of XYZ are appropriately attached in order to clarify the orientation relationship.

  The first diffraction grating 6 and the second diffraction grating 7A shown in FIG. 4 are X-rays made of a material having a high X-ray absorption rate (for example, heavy metals such as gold, platinum, lead, gallium, titanium, and tungsten). A layer (X-ray shielding layer) 22A, and a layer (X-ray transmission layer) 23 that transmits X-rays made of a material having a low X-ray absorption rate (for example, silicon, glass, resin, etc.) They are formed alternately.

  As shown in FIGS. 3 and 4, of the first diffraction grating 6 and the second diffraction grating 7 </ b> A, from the −Y side end face to the + Y side end face of the diffraction grating facing the emission side of the X-ray source 1. Each distance is referred to as “thickness”. Here, the period in which the X-ray shielding layer 22A and the X-ray transmission layer 23 are repeatedly arranged, that is, the “period” is the thickness of one X-ray shielding layer 22A and the thickness of one X-ray transmission layer 23. It becomes the thickness which added and.

  The thickness of the second diffraction grating 7A is set in the range of 5 times or more the period of the first diffraction grating 6 and 10 times or less. The thickness of the second diffraction grating 7A is particularly preferably about 5 times the period of the first diffraction grating 6. When the thickness of the second diffraction grating 7A exceeds 10 times the period of the first diffraction grating 6, the second diffraction grating 7A has a fine period, making it difficult to manufacture, When the thickness of the grating 7A is less than 5 times the period of the first diffraction grating 6, the contrast of the obtained image deteriorates.

  Further, in FIG. 3, the distance R1 represents the distance from the X-ray source 1 to the first diffraction grating 6, and the distance R2 represents the distance from the first diffraction grating 6 to the second diffraction grating 7A.

  Returning to FIG. 1, the description will be continued.

  The X-ray detector 8 is arranged close to the second diffraction grating 7A, and converts the two-dimensional distribution of the intensity of the X-ray diffracted by the second diffraction grating 7A into an electric signal. Specifically, an image of moire fringes corresponding to the intensity distribution of the striped X-rays generated by the second diffraction grating 7A is obtained by the X-ray detector 8. The X-ray detector 8 is configured using a so-called X-ray scintillator and an image sensor, and samples the intensity of X-rays on a two-dimensional plane by a plurality of pixels arranged in a matrix on the plane. The X-ray detector 8 converts a charge value proportional to the X-ray dose for each pixel into an electric signal, and converts the electric signal from an analog signal to a digital signal while sequentially outputting the electric signal by scanning (A / D conversion) and output to the storage unit 12 as image information.

  As shown in FIG. 1, when an object (subject 4) giving a phase difference exists on the optical path of the X-rays emitted from the X-ray source 1, the Talbot image relating to the place where the subject 4 exists is distorted. By detecting this distortion from the image of moire fringes generated by the second diffraction grating 7A, the internal form of the subject 4 can be detected.

  The control unit 9 is configured by, for example, a CPU, and controls the overall operation of the X-ray imaging apparatus 50A by executing a control program stored in the storage unit 12. Specifically, the control unit 9 gives various commands to the entire X-ray imaging apparatus 50A, and issues a display instruction to the display unit 14 to be described later. The control unit 9 also realizes the function of the detector control unit 10 described later.

  The detector control unit 10 controls the operation of the X-ray detector 8.

  The storage unit 12 is constituted by a storage device such as a semiconductor memory or a hard disk, for example. A program executed by the control unit 9, data necessary for executing the program, and image information obtained by the X-ray detector 8 Memorize etc.

  The operation unit 13 includes a keyboard, a touch panel, a mouse, or the like, and transmits various command signals to the control unit 9 in accordance with various user operations.

  The display unit 14 includes, for example, a liquid crystal display, and visually outputs moving image data generated by the control unit 9.

  In order for the X-ray imaging apparatus 50A to obtain an image with high contrast, it is desirable that the second diffraction grating 7A shields X-rays as much as possible. For this reason, even when a metal material having a high X-ray absorption rate is used for the X-ray shielding layer 22A of the second diffraction grating 7A, it is necessary to increase the thickness of the second diffraction grating 7A. When the X-ray to be used is completely parallel light, the transmittance is not affected even when the thickness of the second diffraction grating 7A is large, but the X-ray emitted from the X-ray source 1 is not affected. In the case of divergence, so-called vignetting occurs due to the thickness of the second diffraction grating 7A, and the X-ray transmittance is extremely deteriorated.

  FIG. 5 is a schematic diagram showing how X-rays pass through the second diffraction grating 7A. FIG. 5A is a diagram showing a case where X-rays are emitted substantially in parallel, and FIG. 5B is a diagram showing a case where X-rays are emitted so as to diverge. In particular, when a compact X-ray source such as that used in an X-ray imaging apparatus is used, X-rays are emitted while being diverged, and thus an improvement in transmittance at the second diffraction grating 7A is required.

  In the case where X-rays are emitted while diverging, if the X-ray shielding layer 22A is simply made thin, the amount of light passing through the second diffraction grating 7A increases, but the contrast of the moire fringe image decreases. When the second diffraction grating 7A having the same period as that of the first diffraction grating 6 is used, the X-ray emitted from the X-ray source 1 and diffracted by the first diffraction grating 6 out of the second diffraction grating 7A. When the ratio of the area occupied by the X-ray shielding layer 22A (hereinafter referred to as “shielding area ratio”) is 40% on the surface irradiated with X-rays, the X-rays diverge as compared to the case where the shielding area ratio is 50%. The transmittance is improved by about 1.3. However, for divergent X-rays, the angle at which the X-rays travel differs between the vicinity of the central axis of the region where the X-rays travel and the periphery thereof.

  Therefore, when the shielding area ratio is 40%, the influence of the incident angle of X-rays appears, and the contrast of the image of the moire fringes of the image related to the image information obtained by the X-ray detector 8 is the same as that of the emitted X-rays. X-ray incident angle with respect to the central axis of X-rays in the irradiation field outside region (outer region of the opening contour of the irradiation field stop that limits the irradiation region so that the radiation is irradiated only on the necessary part of the subject 4) As the value increases, it decreases. For example, when the angle at which X-rays enter the second diffraction grating 7A (incident angle) is 4 degrees, the contrast of the image of moire fringes is reduced by about 12% compared to the case where the incident angle is 0 degrees.

  When the incident angle is 4 degrees, it is conceivable to increase the X-ray absorption rate (shielding rate) of the X-ray shielding layer 22A by increasing the thickness of the second diffraction grating 7A. However, in general, the second diffraction grating 7A has the same fine period as that of the first diffraction grating 6 that is manufactured with a fine period to the limit that can be manufactured in order to increase the resolution of the obtained image as much as possible. Yes. Therefore, it is not easy to increase the thickness of the second diffraction grating 7A having a small period.

  By the way, it is known that moire interference occurs when the period of the second diffraction grating 7A is set to be an integer around the period of the Talbot image. It is conceivable to improve the contrast of the moire fringe image by changing the period of the second diffraction grating 7A. However, if the period of the second diffraction grating 7A is about three times the period of the Talbot image, the incident angle is 0. A moiré fringe with a desired contrast cannot be obtained between 5 degrees and 5 degrees. Therefore, in order to obtain moire fringes with sufficient contrast, the period of the second diffraction grating 7A is preferably about twice the period of the Talbot image. Specifically, the period of the second diffraction grating 7A is more preferably 1.7 times or more and 2.3 times or less of the period of the Talbot image. As the range is exceeded, the moire fringe spacing becomes narrower, and resolution tends to be difficult with a general X-ray imaging device.

  Further, the shielding area ratio of the second diffraction grating 7A is desirably set to 13% to 41%, more preferably 14% to 40%.

(Example)
For the examples (Examples 1 to 5) and the comparative examples (Comparative Examples 1 to 6) of the X-ray imaging apparatus 50A of the present invention, the X-ray transmittance and the contrast of moire fringe images were measured. In the embodiment, the shielding area ratio of the second diffraction grating 7A is set in a range of 13% to 41%, and in the comparative example, the shielding area ratio of the second diffraction grating 7A is less than 13% or more than 41%. Set to the above range.

  In Table 1, the ratio between the period of the second diffraction grating 7A and the period of the Talbot image (period ratio, ie, the value obtained by dividing the period of the second diffraction grating 7A by the period of the Talbot image) and the shielding of the second diffraction grating 7A. The results obtained by measuring the transmittance of the second diffraction grating 7A and the contrast of the image of moire fringes when the area ratio is variously changed are shown.

  In the measurement, for the first diffraction grating 6, the period was 4 μm, the ratio of the area occupied by the X-ray shielding layer 22A in the surface irradiated with X-rays was 50%, and the thickness was 4 μm. X-rays emitted from the X-ray source 1 are mainly those having a wavelength around 10 nm, and the intensity is about 30 keV.

  The second diffraction grating 7A has a thickness of 20 μm and a tilt angle of the second diffraction grating 7A with respect to the first diffraction grating 6 is 5 degrees in order to sufficiently shield X-rays.

  Further, the distance R1 was 2 m, and R2 was 1600 μm (minimum Talbot distance). The distance R2 may be an integer multiple of 1600 μm (Talbot distance). The X-ray shielding layer 22A of the first and second diffraction gratings 6 and 7A is made of gold, and the X-ray transmission layer 23 is made of silicon.

  “Transmissivity of the second diffraction grating 7A” shown in Table 1 is the transmittance of Comparative Example 1, that is, the period of the second diffraction grating 7A is the same as the period of the Talbot image, and the shielding area ratio is 50%. This is the value when the X-ray dose transmitted through the second diffraction grating 7A is 1 as the reference value when the X-ray incident angle is 0 degree.

  Similarly, the contrast of the image of the moire fringes is the same as the contrast of the image of Comparative Example 1, that is, the period of the second diffraction grating 7A is the same as the period of the Talbot image, the shielding area ratio is 50%, and the X-ray This is a value when the contrast of the image when the incident angle is 0 degree is set to 1, which is a reference value.

  As for the incident angle of the X-ray, since the transmittance becomes zero when the incident angle of the X-ray to the second diffraction grating 7A becomes 5 degrees under the conditions of Comparative Example 1, the incident angle is measured. The range was set to three levels of 0 degree, 2 degrees, and 4 degrees.

  As shown in Table 1, for example, in Example 1, the value (period ratio) obtained by dividing the period of the second diffraction grating 7A by the period of the Talbot image is 2, and the shielding area ratio of the second diffraction grating 7A Is 25%, the transmittance of the second diffraction grating 7A is 1.00 if the X-ray incident angle is 0 degree, and 1.00 if the X-ray incident angle is 2 degrees. If the incident angle of the line is 4 degrees, it becomes 0.99. Further, the contrast of the image of the moire fringe is 0.574 when the X-ray incident angle is 0 degree, and 0.574 when the X-ray incident angle is 2 degrees, and the X-ray incident angle is 0.574. If it is 4 degrees, it will be 0.570.

  From the measurement results shown in Table 1, as shown in Example 1, when the period ratio between the second diffraction grating 7A and the Talbot image is 2, and the shielding area ratio of the second diffraction grating 7A is 25%, the X-ray Even if the incident angle is increased, the contrast of the moire fringe image is hardly lowered and the transmittance is improved as compared with Comparative Example 1. In particular, as shown in Examples 2 and 3, when the shielding area ratio of the second diffraction grating 7A is 14.0% or more and 40% or less, even if the X-ray incident angle is 4 degrees, Compared to the case where the incident angle is 0 degree, the decrease in transmittance is 15% or less, and the decrease rate of the contrast of the image of moire fringes is also 5 compared to the case where the incident angle of X-ray is 0 degree. Within%. Further, if the incident angle of the X-rays on the second diffraction grating 7A is within 4 degrees, the contrast of the moire fringe image is 0.55 or more, and the moire fringe can be easily analyzed by calculation.

  Further, as shown in Examples 4 and 5, if the shielding area ratio of the second diffraction grating 7A is 13% or 41%, the contrast of the image of the moire fringes that can be analyzed by the calculation moire fringes is about. 0.300 was obtained.

  Furthermore, if the period ratio between the second diffraction grating 7A and the Talbot image is 2, and the shielding area ratio of the second diffraction grating 7A is 13.0% or more, the ratio of the thickness to the pitch of the X-ray shielding layer 22A (thickness / The pitch of the X-ray shielding layer 22A) is not increased, and the production of the second diffraction grating 7A does not become difficult. When the period ratio of the second diffraction grating 7A and the Talbot image is 2, and the shielding area ratio of the second diffraction grating 7A is 13.0%, the ratio of the thickness to the pitch of the X-ray shielding layer 22A is the second diffraction When the period of the grating 7A is equal to that of the Talbot image and the shielding area ratio of the second diffraction grating 7A is 40.0%, it substantially corresponds to the ratio of the thickness to the pitch of the X-ray shielding layer 22A.

  Although not shown in Table 1, regarding Example 1, the X-ray transmittance is 0.80 or more even when the X-ray incident angle on the second diffraction grating 7A is about 12 degrees ( Specifically, it was 0.84), and it was confirmed that the contrast reduction rate of the moire fringe image was within 5% as compared with the case where the incident angle was 0 degree.

  In Comparative Example 2, the shielding area ratio of the second diffraction grating 7A is 40%. In addition, when the period of the second diffraction grating 7A is the same as the period of the Talbot image, the period of the second diffraction grating 7A becomes small, and it is not easy in manufacturing to make the shielding area ratio less than 40%. In Comparative Example 2, the shielding area ratio is set to 40%. Further, in Comparative Example 2, the contrast of the image of the moire fringes when the X-ray incident angle is 0 degrees is higher than that in Examples 1 and 2, but according to the increase in the X-ray incident angle. The reduction rate of the contrast of the moire fringe image is large.

  Furthermore, as shown in Comparative Examples 5 and 6, when the periodic ratio between the second diffraction grating 7A and the Talbot image is 2, and the shielding area ratio of the second diffraction grating 7A is less than 13% or higher than 41%, The contrast of the moire fringe image is less than 0.300, and the analysis of the moire fringe by calculation becomes difficult due to noise or the like. Furthermore, in Comparative Example 4 in which the shielding area ratio is lower than that in Comparative Example 5 and in Comparative Example 3 in which the shielding area ratio is higher than that in Comparative Example 6, the contrast of the moire fringe image is very poor. It becomes impossible to observe.

  When the period ratio between the second diffraction grating 7A and the Talbot image is 3, the contrast of the moire fringe image is 0.50 or less when the incident angle is between 0 and 5 degrees, and the contrast is sufficient. Cannot be obtained.

  As described above, the period of the second diffraction grating 7A is approximately twice the period of the Talbot image, and the shielding area ratio of the second diffraction grating 7A is 13% or more and 41% or less, more preferably 14% or more and By setting it to 40% or less, it is possible to increase the X-ray transmittance in the X-ray shielding layer 22A while suppressing a decrease in the contrast of the image of moire fringes. That is, the second diffraction grating 7A can be configured to easily transmit X-rays incident from an oblique direction by increasing the period without greatly changing the thickness. For this reason, even when the X-ray source 1 that emits X-rays as diverging light is used, it is possible to obtain a captured image with high accuracy and high contrast.

<Modification>
As mentioned above, although embodiment of this invention was described, this invention is not limited to the thing of the content demonstrated above.

  For example, in the above embodiment, the second diffraction grating 7A is formed by alternately arranging the X-ray shielding layers 22A and the X-ray transmission layers 23. You may comprise only the X-ray shielding layer which consists of material with high mechanical rigidity. FIG. 6 is a diagram showing a form of the second diffraction grating 7B having no X-ray transmission layer. In the second diffraction grating 7B, an X-ray shielding layer 22B is formed on a substrate 24 made of, for example, silicon. Specifically, the X-ray shielding layer 22B is formed in close contact with the -Y side end surface of the substrate 24 so that the thickness of the X-ray shielding layer 22B is parallel to the normal direction of the -Y side end surface. Has been.

  In the above embodiment, the X-ray imaging apparatus 50A uses Talbot interference, and the Talbot image is generated by directly diffracting the X-rays emitted from the X-ray source 1 by the first diffraction grating 6. However, it is not limited to this. For example, an X-ray imaging apparatus using Talboro interference that is configured to arrange an X-ray source diffraction grating in the vicinity of the X-ray source 1 and emit X-rays from the X-ray source 1 through the X-ray source diffraction grating. But you can.

  For example, FIG. 7 is a diagram illustrating a schematic configuration of an X-ray imaging apparatus 50B using Talborough interference. Since the functional configuration of this modification is similar to that of the above-described embodiment, the same components are denoted by the same reference numerals.

  The X-ray source diffraction grating 15 is provided in the vicinity of the X-ray source 1 on the side from which X-rays are emitted, and is configured by arranging a multi-slit diffraction grating. With this X-ray source diffraction grating 15, the X-ray source 1 is in a state in which point-like X-ray sources are arranged in a matrix. The slits of the X-ray source diffraction grating 15 are set so that the contrast is enhanced by overlapping the captured images obtained by the X-rays emitted from the slits.

DESCRIPTION OF SYMBOLS 1 X-ray source 2 X-ray source control part 6 1st diffraction grating 7A, 7B 2nd diffraction grating 8 X-ray detector 9 Control part 12 Storage part 13 Operation part 14 Display part 15 X-ray source diffraction grating 50A, 50B X X-ray equipment

Claims (2)

An X-ray source emitting X-rays;
A first diffraction grating that exhibits a Talbot effect that produces a striped intensity distribution of a first period in the X-rays emitted from the X-ray source;
A shielding part that shields X-rays and a transmission part that transmits X-rays are repeatedly arranged in a predetermined direction at a second period in a striped pattern, and a second part that further diffracts the X-rays diffracted by the first diffraction grating. A diffraction grating,
X-ray detection means that is arranged close to the second diffraction grating and obtains image information indicating a two-dimensional distribution of the intensity of X-rays diffracted by the second diffraction grating;
With
The second period is approximately twice the first period;
Of the second diffraction grating, the ratio of the area occupied by the shielding portion on the surface irradiated with the X-rays emitted from the X-ray source and diffracted by the first diffraction grating is 13% or more and 41 % Or less,
An X-ray imaging apparatus, wherein the second diffraction grating generates an image related to the image information. The X-ray imaging apparatus according to claim 1,
An X-ray imaging apparatus characterized in that the ratio is 14% or more and 40% or less.

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