JP2002139459A - Method and apparatus for x-ray imaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase contrast-type X-ray imaging method in which a phase image of satisfactory accuracy can be acquired without using a phase shifter by a method wherein the phase image of a subject is obtained on the basis of a plurality of images measured by changing the relative position of a dividing element to a coupling element. SOLUTION: The element which divides incident X-rays and the element which couples the divided X-rays are horizontally moved relatively or turned. A difference (phase difference) in an optical path length inside an interferometer is changed. On the basis of a plurality of interference images measured in each phase difference, the phase image is calculated and found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an X-ray imaging method, and more particularly to an imaging method for non-destructively inspecting the inside of an object.

[0002]

2. Description of the Related Art When an X-ray passes through a sample, the amplitude and the phase of the X-ray change. Generally, the change in phase is more remarkable than the change in absorption, so by capturing this change,
The inside of the object can be observed with high sensitivity. Examples of a phase contrast type X-ray imaging apparatus utilizing this phase change include those described in JP-A-4-348262 and those described in JP-A-10-248833. With these imaging apparatuses, it is possible to observe soft tissue of a living body or the like that cannot be observed with a conventional X-ray imaging apparatus using a change in amplitude without contrast.

In each of the above publications, a phase change is detected using an X-ray interferometer. Among them, the patent described in Japanese Patent Application Laid-Open No. 4-348262 discloses a Bonze-Hart interferometer (Appl. Phys. Let) as shown in FIG.
t. 6,155 (1965)). This interferometer is composed of a crystal block 4 having a splitter 1, a mirror 2, and an analyzer 3 arranged in parallel at equal intervals. The incident X-ray 5 is split by the splitter 1 into a first beam 6a and a second beam 7a by X-ray diffraction in a Laue case. The first beam 6a incident on the mirror 2 is split again into a third beam 6b and a fourth beam 6c, and the second beam 7a is split again into a fifth beam 7b and a sixth beam 7c. Splitter 1, mirror 2 and analyzer 3
Of the fourth beam 6c and the fifth beam
The beam 7b is incident on the same point on the analyzer 3 and is combined by diffraction to form a first interference beam 8a and a second interference beam 8b.

In the invention described in Japanese Patent Application Laid-Open No. Hei 10-248833, a first crystal block 9 having a splitter 11 and a mirror 12, a mirror 13 and an analyzer as shown in FIG. 14
An interferometer composed of the second crystal block 10 having the following is used. The incident X-ray 15 is split by the splitter 11 of the first crystal block 9 into a first beam 16a and a second beam 17a by Laue-case X-ray diffraction. 1st beam 1
6a is a mirror 12 of the first crystal block 9 and a third beam 1
The second beam 17a is added to the fifth beam 17b and the sixth beam by the mirror 13 of the second crystal block 10 to the 6b and the fourth beam 16c.
It is split again into beams 17c. Fourth beam 1
6c and the fifth beam 17b are incident on the same point of the analyzer 14 of the second crystal block 10 and are combined to form a first interference beam 18a and a second interference beam 18b.

In the above interferometer, when a subject is set on one optical path of the split beams, for example, beams 6c and 16c, the phase of the beam is shifted according to the phase distribution of the subject, and the other beams (7b and 17b) When it is combined with the interference beam, the phase change due to the interference causes interference beams (8a, 8b, 18).
a, 18b). Therefore,
From this intensity change, phase distribution information of the subject can be obtained.

However, an accurate phase image of a subject cannot be obtained from only the intensity change distribution image (interference image) of one interference beam. Therefore, in each of the above publications, a phase image is obtained by using a measurement technique called a fringe scanning method as described in J. Opt. Soc. Am., 156, 72 (1982). In this method, a phase shifter is installed in the other split optical path, for example, beams 7b and 17b, and the M phase images are measured by changing the phase difference between the split beams from 0 to 2π / M at a time. . Then, a phase image is obtained by calculation from the plurality of measured interference images.

A wedge-shaped acrylic 19 as shown in FIG. 3A is inserted into or taken out of the optical path as shown by an arrow, or a flat plate as shown in FIG. The acryl 20 has a structure of rotating as shown by the arrow. The phase image φ (x, y) of the subject can be obtained from Expression (1) using the measured intensity Ik (x, y) of the interference image. Here, arg indicates the calculation of the argument.

[0008]

(Equation 1)

As described above, in the phase contrast imaging method, in order to obtain a high-accuracy phase image, the phase contrast is calculated from a plurality of interference images measured by changing the phase difference between the divided beams. A fringe scanning method for obtaining an image is indispensable. However, there is a problem that a new phase shifter must be provided to change the phase difference. Further, the installation of the phase shifter causes not only a change in phase but also a decrease in intensity due to absorption. Therefore, there is a problem that the measurement time is extended or the visibility of the interference image is reduced.

An object of the present invention is to provide a phase-contrast X-ray imaging method capable of acquiring an accurate phase image without using a phase shifter.

[0010]

A description will be given with reference to the schematic diagram of the X-ray interferometer shown in FIG. In this X-ray interferometer,
The incident X-ray beam 23 is split into a first beam 24 and a second beam 25 by the splitting element 21, and then is split into one beam again by the splitting element 22. By the way, as shown in the figure, when the coupling element 22 is relatively translated with respect to the splitting element 21 as shown by the arrow a, or is relatively rotated as shown by the arrow b, the interferometer , The phase difference between the split beams 24 and 25 changes. Therefore, by controlling the relative translation or rotation of the splitting element 21 and the coupling element 22, the phase difference between the split beams can be set to an arbitrary value without using a phase shifter. Therefore, the above-described problem is solved by the fringe scanning method in which the phase is changed by relatively moving or rotating the splitting element 21 and the coupling element 22 to measure a plurality of interference images and obtain a phase image from the obtained interference images. Will be resolved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings shown below, portions having the same functions are denoted by the same reference numerals, and redundant description will be omitted. (Embodiment 1) FIG. 5 is a configuration diagram of an example of a phase contrast type X-ray imaging apparatus used in the present invention. Reference numeral 26 denotes an X-ray interferometer, which comprises a splitter 1, a mirror 2, and a crystal block 4 having an analyzer 3, which are arranged in parallel at equal intervals as described with reference to FIG. Most of the portion connecting the analyzer 2 and the analyzer 3 is cut out and connected by a connecting piece. Reference numeral 27 denotes a rotation angle adjusting mechanism, which controls the incident X-rays 36 and X
The relative angle of incidence of the line interferometer 26 is adjusted. 100 is a substrate 100 mounted on the rotation angle adjusting mechanism 27,
It becomes a support base of the X-ray interferometer 26. 101 and 102
Denotes a support plate 101 and a support plate 102 mounted on a substrate 100, on which a portion of the splitter 1, a mirror 2, and a portion of the analyzer 3 are mounted, respectively. 2
Reference numeral 8 denotes a sample holder of the X-ray interferometer 26, and reference numeral 29 denotes a sample holder positioning mechanism. 30 is an X-ray detector, 31 is a control device, 32 is a computer for image processing, and 33 and 33 'are display devices. Reference numeral 34 denotes a moving mechanism that moves the support plate 102 in the direction of arrow a shown in FIG. Reference numeral 35 denotes a position detecting mechanism,
Is detected and fed back to the control device 31.
Here, strictly speaking, the displacement of the support plate 102 by the moving mechanism 34 is performed because the crystal block 4 at the base of the analyzer 3 is substantially connected to the crystal block 4 at the mirror 2 at one point. Movement, but the error is 10
^-8 , which means that there is no problem in terms of parallel movement in terms of the accuracy required for the X-ray interferometer 26.

The X-ray 36 incident on the X-ray interferometer 26 is split, reflected, and combined in the interferometer in the same manner as the Bonze-Hart interferometer shown in FIG. 1, and the first interference beam 37a and the second
An interference beam 37b is formed. When an object is set using the sample holder 28 positioned by the sample holder positioning mechanism 29 on the optical path of one of the split beams,
The phase distribution of the beam shifts according to the phase distribution of the subject, and the interference beams 37a and 37b change in intensity (interference image).
Appears as. This interference image is detected by the X-ray detector 30.

FIG. 6 is a detailed view of the X-ray interferometer 26.
In the Bonse-Hart interferometer shown in FIG. 1, since the splitting element for splitting the incident X-ray and the coupling element for coupling the split beams are formed by an integral crystal block, the splitting element and the coupling element are relatively Could not be translated or rotated. Therefore, in the first embodiment, as shown in the drawing, a cut is made in the block 4 of the interferometer 26, and the block 4 is divided into a divided block 41 composed of the splitter 38 and the mirror 39 and a divided block 42 composed of the analyzer 40. However, instead of being completely separated, they are connected by a thin connecting piece 44 left uncut, and if the blocks 41 and 42 are placed on a flat surface without applying external force, Bonse- It is designed to maintain the basic shape of a heart-shaped interferometer. The substrate 100 functions as a solid support base for this purpose, and the support plates 101 and 102
1. It functions as a support plate for the divided block 42. In this structure, the support plate 102 on which the divided block 42 is mounted is
When the side surface is pressed by the block moving mechanism 34, the uncut thin connecting piece 44 is elastically deformed, and the divided block 42 moves along the x-axis relative to the divided block 41 as indicated by an arrow a. Translate in parallel.

In the interferometer having this configuration, the relative movement x of the divided block 41 and the divided block 42 on the x-axis.
Changes the phase difference between the split beams. Δx required to change the phase difference by ΔΦ is given by equation (2). Here, d is the surface interval between the diffraction grating surfaces.

[0015]

(Equation 2) In the first embodiment, the measurement of the phase image by the fringe scanning method with the number of scans M is performed in the following order. (1) The block moving mechanism 34 and the position detector 35 so that the phase difference Φ between the split beams becomes 2π · m / M.
Is adjusted to Δx = mdd / M corresponding to the above phase difference Φ. (2) The interference image Im is measured using the detector 30. (3) The above (1) and (2) are repeated until m = 0,..., M−1, and M interference images are measured. (4) The image processing computer 32 calculates a phase image from the interference image Im according to the equation (1), and displays the phase image on the display device 33.

The control of each device in the above measurement is performed by the control device 31. However, when measuring the interference image Im using the block moving mechanism 34 and the position detector 35, the display device 3
The operation can be facilitated by referring to the monitor image by 3 '.

X for splitting, reflecting and combining an incident X-ray beam
Any diffraction grating surface may be used for line diffraction,
In this embodiment, diffraction of the Si (220) plane having a wide diffraction angle width and small intensity loss during diffraction is used. Therefore, as shown in the figure, the crystal orientation is <1,1,
0> and the Y axis are <0, 0, 1>. Since the lattice spacing d of Si (220) is 0.192 nm, Δx is 38 pm when the number of scans M in the fringe scanning method is 5, for example.
And an extremely small value. Therefore, a drive element having extremely high positioning accuracy, such as a piezoelectric element, is used for the block drive mechanism 34. Further, it is preferable to use a length measuring device having extremely high length measuring accuracy such as a laser interferometer for heterodyne detection as the position detecting mechanism 35.

The angle width at which X-rays can be incident on the interferometer is extremely narrow, on the order of several seconds. Therefore, the X-ray interferometer position adjustment mechanism 27 that adjusts the incident angle of the incident X-ray 36 to the X-ray interferometer has extremely high rotational positioning accuracy (about 1/100 second).
Use a stage with.

As described above, according to the present embodiment, the splitting element and the coupling element can be relatively moved in parallel to shift the phase between the split beams. Therefore, a phase image with high phase determination accuracy can be obtained by using the fringe scanning method without installing a phase shifter. (Second Embodiment) In the first embodiment, the relative parallel movement amount Δx of the x-axis of the divided block and the combined block is detected by the position detection mechanism 35. However, as described above, Δx that causes a necessary phase difference in the measurement by the fringe scanning method is several tens of p.
m, which is an extremely small value. For this reason, it is difficult to accurately detect Δx even with a length measuring device having a high resolution.
It is difficult to accurately adjust the phase difference. Here, an embodiment in which the phase difference is adjusted using the intensity change of the interfering beam instead of the position detection mechanism 35 will be described.

FIG. 7 shows an example of a device configuration near the detector in the second embodiment. Other device configurations are the same as those of the first embodiment. In this embodiment, as shown in the drawing, one of the two interference beams is detected by the detector 30 and the other interference beam is detected by the beam intensity detector 45. Detector 4
The phase difference is adjusted using the intensity of the interference beam detected in step 5. A slit 46 whose opening width and position can be adjusted is provided on the front surface of the detector so that the intensity of an arbitrary region in the interference beam can be detected.

As shown in the first embodiment, the divided block 4
1 and the relative translation Δx of the x-axis of the coupling block 42
Changes the phase difference between the split beams. This change ΔΦ in phase difference appears as a drift of interference fringes on the interference image. Therefore, if the opening width of the slit 46 is set smaller than the interval between the interference fringes, the beam intensity detector 4
5, that is, the intensity I of the interference beam fluctuates as shown in FIG. 8 with a change in Δx, that is, ΔΦ. At this time, the relationship between the output I of the beam intensity detector 45 and the phase difference Φ is given by equation (3).

[0022]

(Equation 3) Here, Ia is the intensity of the background and Ib is the amplitude of the intensity, which can be obtained from FIG.

Therefore, the value of the phase difference Φ can be obtained from the intensity I by using the equation (3). In addition, by adjusting the parallel movement amount Δx between blocks relatively appropriately so that the intensity I becomes a value corresponding to the target phase difference, the target phase difference Φ can be set without measuring the length of Δx. can do.

The measurement of the phase image using the fringe scanning method in this embodiment is as follows: (1) Sweep an appropriate amount of Δx to obtain a graph corresponding to FIG. (2) The intensity Im corresponding to Φm = 2π · m / M is
It is obtained from the graph obtained in (1). (3) The block is moved in parallel between the blocks using the block moving mechanism 34, and adjusted so as to have the intensity Im corresponding to the target phase difference Φm. (4) The detector 30 measures the interference image Im at each phase difference Φm. (5) The above (2) to (4) are repeated until m = 0,..., M−1, and M interference images are measured. In order. (5) The subsequent measurement procedure is performed in the same manner as in Example 1.

As described above, according to the present embodiment, it is possible to accurately control the amount of phase shift between the divided beams using the intensity fluctuation of the interference beam. Therefore, a highly accurate phase image can be obtained. (Embodiment 3) In Embodiment 2, the phase difference is adjusted using the intensity I of an arbitrary area on the interference beam. In this case, there is no problem if the intensity of the incident X-ray is constant over time. However, if the intensity is temporally fluctuating, the intensity I naturally also fluctuates. It cannot be distinguished whether it is due to a change in phase difference. For this reason, the phase difference cannot be adjusted accurately. Further, as can be seen from the equation (3), in the phase difference where the intensity I is close to the maximum value or the minimum value, the change in the intensity I becomes insensitive to the change in the phase difference, so that the phase difference is adjusted with high accuracy. Can not do it. Here, an example of an embodiment that solves the above-described problem by detecting the intensity of the interference beam in a plurality of regions will be described.

FIG. 9 shows an example of the device configuration near the detector in this embodiment. Here, the detector corresponds to the beam intensity detector 45 in the second embodiment, and the configuration of the other devices is the same as in the first and second embodiments. As shown in this figure, the detectors 47, 48 and 49 are composed of an X-ray intensity detector, slits provided on the front of each detector, and an intensity detector positioning mechanism for holding and positioning each slit. . The relationship between each X-ray intensity detector and the slit provided in front of each detector is the same as the relationship between the X-ray intensity detector 45 and the slit 46 described with reference to FIG. If a subject or an appropriate phase object is placed on one optical path of the split beam, the phase of each point on the interference beam shifts according to the phase distribution of the subject and becomes non-uniform. For this reason, by appropriately adjusting the area detected by each detector using the intensity detector positioning mechanism and the slit, the output of each detector, that is, the beam between the beams in the area detected by each detector is adjusted. The phase difference can be shifted by an appropriate amount. That is, the output from each detector according to the change in Δx can be adjusted as shown in FIG.

In such an adjustment, as can be seen from FIG. 10, when the phase changes, the ratio of the output from each detector changes. On the other hand, when the incident X-ray intensity decreases, the output from each detector decreases together with the ratio kept constant. Therefore, by utilizing the difference between these changes, it is possible to distinguish between the fluctuation of the intensity of the incident X-ray and the fluctuation of ΔΦ.

The control of the phase difference ΔΦ in the third embodiment is as follows: (1) Sweep Δx to obtain in advance the phase difference between the detectors, the intensity of the background Ia of each detector, and the vibration amplitude Ib. . (2) Using the result of the above (1), calculate the output from each detector corresponding to the target phase Φ. (3) Adjust Δx so that the output from each detector becomes the value obtained in (2). At this time, in the detector in which the intensity I is near the maximum value or the minimum value, the contribution (feedback amount) to the adjustment of Δx is reduced. For example, this is performed as in equation (4).

[0029]

(Equation 4) Here, km is the contribution ratio of the detector m, and ΔΦm is the phase difference of the detector m. Do as. The procedure for measuring the phase image by the fringe scanning method is the same as in the second embodiment.

In the third embodiment, a plurality of detectors are used. However, a two-dimensional detector is used instead, and even if a change in the intensity ratio of a plurality of appropriate pixels is used, the intensity fluctuation of the incident X-rays is used. And the variation of ΔΦ, and the phase difference can be adjusted with high accuracy.

As described above, according to the third embodiment, by detecting the intensities of a plurality of regions on the interference beam, the intensity fluctuation of the incident X-ray and the fluctuation of the phase difference of the interference beam are distinguished, and the interference beam is more accurately detected. Can be adjusted. Therefore, a highly accurate phase image can be obtained even when the intensity of incident X-rays fluctuates. (Embodiment 4) Since the X-ray interferometer used in Embodiments 1 to 3 is constituted by an integral crystal block, the size of the interferometer is limited by the diameter of the crystal ingot serving as the base material. The observation visual field (size of the sample) could not be secured to several cm or more. Here, an example in which an observation visual field of 2 cm or more can be secured by using the crystal separation type X-ray interferometer shown in FIG. 2 will be described.

In the X-ray interferometer of the present embodiment, as shown in FIG. 11, the relative rotation of the first crystal block 51 and the second crystal block 52 around the z axis changes the phase between the divided beams. Change. The phase change amount ΔΦ is a relative rotation amount Δθ, an interval between diffraction grating surfaces is d, an interval between teeth is L,
When the thickness of the tooth is x, it is given by equation (5) that B
Ecker et al. (J. Appl. Cryst.,
7,593 (1974)).

[0033]

(Equation 5) Therefore, by controlling the rotation amount Δθ between crystal blocks by an appropriate amount, the phase between the divided beams can be set to an arbitrary value.

FIG. 11 shows a configuration diagram of an example of the apparatus according to the present embodiment. Except for the X-ray interferometer and the positioning mechanism for the X-ray interferometer equipped with the interferometer, the configuration is substantially the same as that of the first embodiment. In the present embodiment, the second crystal block 52 mounted on the second θ stage 54 is rotated around the Z axis relative to the first crystal block 51 to change the phase between the divided beams. . From equation (5), the amount of rotation between crystal blocks corresponding to a phase change of 2π is Si (22
0) L = 63 using diffraction of (d = 0.192 nm)
mm, x = 1 mm for an X-ray interferometer, about 2 nrad. For this reason, for example, in the measurement of a phase image by the fringe scanning method with five scans, it is necessary to control the rotation between crystal blocks with extremely high accuracy of 0.4 nrad.

Therefore, the adjustment of the phase difference ΔΦ is performed using the intensity of the interference beam detected by the beam detector 55 as in the third embodiment. In addition, as the position control mechanism 34 of the second θ stage 54, a mechanism such as a piezoelectric element that can perform ultra-high-precision positioning is used.

As in the above embodiment, the phase image is obtained by rotating the crystal blocks to adjust the phase difference, and measuring the interference image at each phase difference. After that, the phase image is calculated by the image processing mechanism 32 and the calculation result is displayed on the display device 33.

Also in this separation type X-ray interferometer, the angle width at which X-rays can enter the interferometer is extremely narrow, about several seconds. For this reason, the first θ stage 27 for adjusting the rotational position of the entire X-ray interferometer also has extremely high rotational positioning accuracy (1/1).
(About 00 seconds). Insufficient adjustment of the rotation of the crystal blocks 51 and 52 around the y-axis appears as moire fringes in the interference image. Therefore, the rotation of the crystal blocks 51 and 52 around the y-axis is adjusted using the tilt stage 101.

As described above, according to this embodiment, the observation field of view can be increased by using the crystal separation type interferometer as shown in FIG.
cm or more can be obtained.

[0039]

According to the present invention, a phase image with high phase determination accuracy can be obtained without using a phase shifter.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a Bonze-Hart interferometer as an example of an integrated X-ray interferometer.

FIG. 2 is a perspective view showing an example of the configuration of a crystal separation type X-ray interferometer.

FIG. 3 is a diagram illustrating an example of a phase shifter.

FIG. 4 is a view showing the concept of an X-ray interferometer.

FIG. 5 is a diagram illustrating an overall configuration of the X-ray imaging apparatus according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an interferometer of the X-ray imaging apparatus according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of an interferometer of an X-ray imaging apparatus according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating a change in the intensity of an interference beam, which is an output of the beam intensity detector according to the second embodiment, according to a change in a phase difference.

FIG. 9 is a diagram illustrating a configuration of a part of a beam intensity detector of an X-ray imaging apparatus according to a third embodiment of the present invention.

FIG. 10 is a diagram illustrating a change in the intensity of an interference beam, which is an output of each detector according to the third embodiment, according to a change in a phase difference.

FIG. 11 is a diagram illustrating an overall configuration of an X-ray imaging apparatus according to a fourth embodiment of the present invention, which is a configuration example of a crystal separation type X-ray interferometer.

[Explanation of symbols]

1: splitter, 2: mirror, 3: analyzer, 4:
Crystal block, 5: incident X-ray, 6a: first beam, 6
b: third beam, 6c: fourth beam, 7a: second beam, 7b: fifth beam, 7c: sixth beam, 8a: first beam
Interference beam, 8b: second interference beam, 9: first crystal block, 10: second crystal block, 11: first tooth, 12:
Second tooth, 13: Third tooth, 14: Fourth tooth, 15: Incident X
Line, 16a: first beam, 16b: third beam 2, 16
c: fourth beam, 17a: second beam, 17b: fifth beam, 17c: sixth beam, 18a: first interference beam,
18b: second interference beam, 19: wedge-shaped acrylic, 2
0: flat acrylic, 21: split element, 22: coupling element,
23: incident X-ray, 24: first beam, 25: second beam, 26: X-ray interferometer, 27: position adjusting mechanism for X-ray interferometer, 28: sample holder, 29: sample holder positioning mechanism, 30: X-ray detector, 31: control device, 32: image processing mechanism, 33, 33 ': display device, 34: block moving mechanism, 35: position detection mechanism, 36: incident X-ray, 37
a: first interference beam, 37b: second interference beam, 38:
Splitter, 39: mirror, 41: analyzer, 4
1: division block, 42: connection block, 43: X stage, 44: cutout portion, 45 beam detector, 46:
Slit, 47: detector, 48: detector, 49: detector, 51: first crystal block, 52: second crystal block, 53: tilt stage, 54: 2θ stage, 5
5: beam detector, 56: position control mechanism, 57: first θ
stage.

Claims (6)

[Claims] 1. An incident X-ray is split by a splitting element into two beams that interfere with each other, and a beam obtained by inserting a subject into one of the two beams and another beam are combined. In the X-ray imaging method for obtaining the image of the subject, the phase image of the subject is obtained from a plurality of images measured by changing the relative position of the splitting element and the coupling element. X-ray imaging method. 2. The X-ray imaging method according to claim 1, wherein the relative positions of the splitting element and the coupling element are adjusted using the intensity of the beam combined by the coupling element. 3. The X-ray imaging method according to claim 2, wherein the adjustment using the combined beam intensity is performed using the intensities of arbitrary plural regions of the combined beam. 4. The device according to claim 1, wherein each of the splitting element and the coupling element is composed of two half mirrors, each of which is integrally cut out from a single crystal ingot and processed, and a base thereof. X-ray imaging method described in 1. 5. A splitter for splitting an incident X-ray into two beams that interfere with each other by a splitting element. The splitter further splits the split beam into two beams, each of which interferes with each other. An interferometer consisting of a mirror and an analyzer for forming an interference image by two interfering beams, means for inserting a subject into one of the two beams, means for changing the relative position of the mirror and the analyzer, An X-ray imaging apparatus, wherein a phase image of the subject is obtained from a plurality of measured interference images. 6. An interferometer comprising said splitter, mirror and analyzer is constituted by a block in which a splitter and a mirror are integrated, and a block in which a mirror and an analyzer are integrated, and a sample is placed on a beam path between each block. The X-ray imaging apparatus according to claim 5, wherein the X-ray imaging apparatus is arranged.