JPH0862159A - Tomographic apparatus - Google Patents

Abstract

PURPOSE: To correct the axial deviation indicating the deviation of the rotating center of a sample base from the center of a detector by detecting the axial deviation without replacing the sample with an axis regulating jig. CONSTITUTION: An X-ray 3 emitted from an X-ray source 1 is shaped by a slit 2, and then made monochromatic by a spectroscope 4. The monochromatic X-ray 3 is transmitted through a shaft regulating jig 8 provided near a sample 5, and the transmitted image is measured by an X-ray detector 7. In the case of conducting such a measurement, a sample base measures the transmitted image at the position of '0' degrees. Thereafter, the jig 8 is rotated at 180 deg. by the drive of a sample base driver 10 together with the sample 5, and the transmitted image of the jig 8 at this time is measured. The difference of both the transmitted images is obtained as the deviation amount indicating the deviation of the rotating center of the base from the center of the detector 7. Then, in order to set the deviation amount to zero, the base 6 or the detector 7 is moved in y direction by the drive of the driver 10 or a detector driver 11 to correct the deviation amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tomography apparatus,
Especially in tomography for the purpose of observing damage such as defects and peeling in industrial materials such as metals and ceramics used for structural materials in advanced technology fields such as automobiles and aerospace, The present invention relates to a tomography apparatus suitable for suppressing an axis shift from the center of a detector.

[0002]

2. Description of the Related Art The use of tomography is widespread because it allows nondestructive observation and inspection of the inside of a subject. For example, observing the inside of the human body using X-rays as electromagnetic waves for irradiating a subject is a powerful method for medical diagnosis.
Widely used in medical institutions. Furthermore, this method is attracting attention for its wide technical potential, such as improvement in the positional resolution of the detector and application to inspection of defects and foreign substances in industrial materials by increasing the intensity of the light source.

Conventionally, in an X-ray tomography apparatus using X-rays as electromagnetic waves, X-rays from an X-ray source are appropriately shaped by slits, and then the sample is irradiated, and an X-ray transmission image transmitted through the sample is detected. Then, after the sample is rotated by a predetermined angle, an X-ray transmission image transmitted through the sample is detected. This method is repeatedly measured until the rotation angle of the sample reaches 180 ° or 360 °. Then, from the series of measured X-ray transmission images, for example, IEEETrans. Nucl. Sci. NS21 (1974)
By the tomographic image reconstruction algorithm described on page 21,
A tomographic image of the sample through which the X-ray is transmitted can be obtained. Furthermore, a high-resolution X-ray tomography device using a two-dimensional position-sensitive CCD (Charge Coupled Device) as a detector is described in Science 237 (1987).
Year) Page 1439. Further, as a high resolution tomography apparatus using an X-ray image pickup tube as a similar detector, the one described in JP-A-62-228416 can be mentioned.

[0004]

By the way, mechanical properties are important in utilizing industrial materials such as metal composite materials and ceramics as structural materials. This property strongly depends on the interfacial separation between the matrix and the reinforcing fibers and particles inside the material, the breaking of the reinforcing fibers, the stress concentration at the ends of the broken fibers and the subsequent crack growth process. It is important to perform non-destructive and high-resolution measurement on the spot where stress is applied. This is expected to not only help optimize the manufacturing process of industrial materials, but also enable more reliable strength design of materials. Therefore, measurement of these industrial materials by tomography is important. Then, when a tomographic image of an industrial material is tomographically acquired, it is required by the image reproduction algorithm of the tomographic image that the rotation center of the sample stage driving unit that rotates the sample and the center of the detector match. Become. In order to reconstruct a more accurate tomographic image, it is desirable to match the rotation axis of the sample with the center of the detector with an accuracy of about 1/5 or less of the positional resolution of the detector. If for some reason the axis of rotation of this sample does not coincide with the center of the detector, misalignment will occur. If a tomographic image is generated with the axis misaligned, a correct tomographic image cannot be obtained.

Therefore, in the conventional tomography apparatus, in order to correct the axis deviation, an axis adjusting jig is arranged on the sample table instead of the sample, and the tip of the axis adjusting jig is mounted on the sample. The position of the axis adjusting jig is adjusted so as to coincide with the rotation axis of the table driving unit. In this case, the detector is used to detect the transmitted image of the X-axis adjustment jig by the irradiated X-rays, and the sample table is driven so that the projection position of the tip of the axis adjustment tool matches the center of the detector. The detector may be moved by a unit, or the detector may be moved by a detector driving unit.

However, in the conventional tomography apparatus, the axis adjusting jig is installed instead of the sample, and therefore the axis deviation cannot be detected unless the sample and the axis adjusting jig are exchanged. In addition, when stress or temperature is applied to the sample, when tomography is measured under different stresses or temperatures, if axis misalignment occurs due to the stress or temperature applied to the sample There is a problem that the deviation cannot be corrected.

Further, in the conventional tomography apparatus, since the correction of the axis deviation for a series of transmission images measured once the axis deviation has occurred is not taken into consideration, the temperature of the sample is continuously changed, for example. When observing the internal state of the sample in this state, it is not possible to reconstruct a correct tomographic image from the transmission image measured in the axially offset state. Therefore, there is a problem that the tomographic image at the temperature where the axis shift occurs occurs.

A first object of the present invention is to provide a tomography apparatus capable of detecting an axis shift without exchanging a sample with an axis adjusting jig.

A second object of the present invention is to provide a tomography apparatus capable of detecting an axis deviation in a state where a sample is fixed without using an axis adjusting jig.

A third object of the present invention is to provide a tomography apparatus capable of correcting the axis deviation.

[0011]

In order to achieve the first object, the present invention provides a sample stand for fixing a sample and an electromagnetic wave irradiating means for irradiating the sample fixed on the sample stand with electromagnetic waves. An electromagnetic wave detecting means for receiving an electromagnetic wave transmitted through the sample on an electromagnetic wave detecting surface and outputting a signal of a transmitted image corresponding to an incident position of the electromagnetic wave; and an electromagnetic wave irradiating means fixed at least on the sample table. An axis adjusting jig that is inserted on an electromagnetic wave transmission path connecting the electromagnetic wave detecting means to form a transmission image on an electromagnetic wave detecting surface of the electromagnetic wave detecting means, a rotation driving means that rotationally drives the sample stage, and the electromagnetic wave detecting means. From the signals relating to the transmission images at different rotation positions of the sample stage among the transmission images of the axis adjusting jig detected by the means, the rotation center of the rotation drive means and the center of the electromagnetic wave detection surface of the electromagnetic wave detection means are not aligned. It is obtained by constituting the tomograph and a shift amount calculating means for calculating the amount.

A drive command generating means for generating a drive command for reducing the displacement amount calculated by the displacement amount calculating means to zero, and the sample stage can be moved along the electromagnetic wave detecting surface to the elements of the tomography apparatus. And a sample table moving means for moving the sample table in accordance with the drive command generated by the drive command generating means are added to the device for achieving the third object.

In constructing each of the tomographic imaging apparatus, the following elements can be added.

(1) A jig driving means fixed to the sample table and movably supporting the axis adjusting jig is provided, and the jig driving means is used for the axis adjusting jig except at the time of tomography of the sample. Is moved to the electromagnetic wave transmission path, and when the tomographic image of the sample is taken, the jig for axis adjustment is retracted to the area outside the electromagnetic wave transmission path.

(2) In the axis adjusting jig, the tip portion, which is the main portion of the transmitted image, is formed in a sharpened shape, and the width of the tip portion is set to at least about the position resolution of the electromagnetic wave detecting means or less. What you have.

(3) In the axis adjusting jig, the main part of the transmission image is composed of a fine wire that absorbs an electromagnetic wave, and the diameter of this fine wire is at least equal to or less than the positional resolution of the electromagnetic wave detecting means. What is set.

Further, in order to achieve the second object,
The present invention provides a sample stage for fixing a sample, an electromagnetic wave irradiating means for irradiating the sample fixed on the sample stage with an electromagnetic wave, and an electromagnetic wave detecting surface for receiving the electromagnetic wave transmitted through the sample at an incident position of the electromagnetic wave. An electromagnetic wave detecting means for outputting a signal of a transmitted image corresponding thereto, a rotation driving means for rotationally driving the sample stage, and a transmitted image at different rotational positions of the sample stage among the transmitted images of the sample detected by the electromagnetic wave detecting means. The amount of deviation between the rotation center of the rotation driving means and the center of the electromagnetic wave detecting surface of the electromagnetic wave detecting means is calculated from a signal relating to the inverted transmitted image generated by inverting the detected transmission image at the center of the electromagnetic wave detecting surface. And a deviation amount calculating means for performing the tomography apparatus.

In constructing the tomography apparatus, instead of the shift amount calculating means, a transmission image at a rotation angle of 0 ° and a rotation angle of 180 ° of the sample stage among the transmission images of the sample detected by the electromagnetic wave detecting means. The rotation center of the rotation drive means and the center of the electromagnetic wave detection surface of the electromagnetic wave detection means are detected from a signal related to the inverted transmission image generated by inverting the detected transmission image at the rotation angle of 0 degree at the center of the electromagnetic wave detection surface. A deviation amount calculating means for calculating the deviation amount can be used.

Further, drive command generating means for generating a drive command for reducing the displacement amount calculated by the displacement amount calculating means to each element of each tomographic imaging device, and the sample stage along the electromagnetic wave detection surface. And a sample table moving means for moving the sample table in accordance with a drive command generated by the drive command generating means, thereby achieving the third object.

Further, a transmission image storage means for sequentially storing the data of the transmission image detected by the electromagnetic wave detection means in association with the rotational position of the sample stage from the read start address in the elements of each of the tomographic imaging devices, and the shift amount calculation Address changing means for changing the address of the read start position by an address corresponding to the shift amount calculated by the means, and the address changed by the address changing means as the read start address,
It is possible to configure a device in which a tomographic image generating device that sequentially reads out data of a transmitted image from the transmitted image storage device to generate a tomographic image is added.

[0021]

According to the above-mentioned means, when the jig for axis adjustment is installed on the sample table, the transmission image of the jig for axis adjustment is detected with the sample table fixed at a certain position, and then the sample table is removed. By detecting the transmission image of the axis adjustment jig at the position rotated by the specified angle and comparing the detection results of both, the axis deviation can be detected without exchanging the sample and the axis adjustment jig. be able to. For example, if the transmission image of the axis adjusting jig is detected at the position where the sample stage is fixed at 0 degree, and then the transmission image of the axis adjusting jig is detected at the position where the sample stage is rotated by 180 degrees,
1 / the difference between the position of the former transmission image and the position of the latter transmission image
The position 2 indicates the center of rotation of the sample table. Therefore, the deviation amount of the axis deviation can be obtained from the difference between the center of the electromagnetic wave detection surface (center of the detector) set in advance and the detected rotation center of the sample stage. Then, when the sample stage is moved to a position where the detected deviation amount becomes zero, the axis deviation can be corrected.

On the other hand, when the jig for axis adjustment is not used, the transmission image of the sample is detected with the sample table fixed at a certain position,
An inverted transmission image is generated by inverting this transmission image, then the transmission image of the sample is detected at the position where the sample stage is rotated by a specified angle, and this transmission image and the reverse transmission image are compared to adjust the axis. The axis deviation can be detected without using a jig for use. For example, a transmission image of the sample is detected at a position where the sample stage is fixed at 0 degree, and an inverted transmission image is generated by inverting this transmission image. Then, the transmission image of the sample is detected at the position where the sample table is rotated by 180 degrees. This transmission image corresponds to the transmission image formed when the transmission image of 0 degree is inverted about the center of rotation of the sample table. Therefore, when there is no axis deviation, it coincides with the inverted transmission image (both transmission images are Overlap.) Do. Then, when there is a disagreement between the two transmission images, the disagreement indicates a double shift amount. For this reason,
Even without using a jig for axis adjustment, it is possible to detect an axis deviation indicating a difference between the center of the electromagnetic wave detection surface (center of the detector) and the rotation center of the sample table. Also in this case, the axis deviation can be corrected by moving the sample table to a position where the detected deviation amount becomes zero.

[0023]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows, as an embodiment of the present invention, an X-ray tomography apparatus having an axis deviation correcting function. In FIG. 1, the X-ray tomography apparatus includes an X-ray source 1, a slit 2, a spectroscope 4, a stress loading device 6, an X-ray detector 7, an axis adjusting jig 8, a drive unit 9, and a sample table drive unit 10. , The detector drive unit 11,
The control unit 12 is provided.

The X-ray source 1 is constructed by using an X-ray light source capable of emitting X-rays 3 of high intensity and continuous wavelength among electromagnetic waves, and the X-rays 3 emitted from the X-ray source 1 are slits. 2. The sample 5 is irradiated through the spectroscope 4. That is, the X-ray source 1 is configured as an electromagnetic wave irradiating means for irradiating the sample 5 with the X-rays 3 through the electromagnetic wave transmission path including the slit 2 and the spectroscope 4. The slit 2 is configured as a 4-quadrant slit, and the X-ray passing through the slit 2 is 2 mm (y direction) ×
It is shaped into a beam of 1 mm (z direction). A two-crystal spectroscopic method is used for the spectroscope 4, Si (111) is used for the crystal, and the X-ray 3 with an X-ray energy of 23 keV is extracted.

The stress loading sample stage 6 constitutes a sample stage for fixing the sample 5 and also constitutes a stress loading device capable of applying a tensile stress in the z direction to the sample 5. Further, the stress-loaded sample table 6 is rotated once by the drive of a sample table driving unit 10 having a translation mechanism in the y and z directions and a rotation mechanism about the z axis. Further, an axis adjusting jig 8 is arranged on the stress-loaded sample table 6 so as to be movable in y and z directions. The axis adjusting jig 8 is provided with a translation mechanism in y and z directions. When the tomography is not performed by driving the driving unit 9, the electromagnetic wave is inserted into the electromagnetic wave transmission path.
It is designed to be retracted from the electromagnetic wave transmission path. The axis adjusting jig 8 is composed of a W / SiC fiber in which SiC is vapor-deposited to a diameter of 120 μm around a W line having a diameter of 7 μm, as a fine wire that absorbs the X-ray 3. A tip portion, which is a main portion of the transmission image, is formed in a sharpened shape, and the width of the tip portion is set to be at least about the position resolution of the detector 7 or less.

The X-ray detector 7 is constituted by using a high resolution X-ray image pickup tube which is a two-dimensional position sensitive type detector as an electromagnetic wave detection means, and one element of the X-ray image pickup tube forming the electromagnetic wave detection surface. Is set to 7 μm (y direction) × 4.4 μm (z direction), and 1024 (y direction) × 960 (z direction) pixels can be captured. That is, elements for 1024 channels are arranged in 960 columns in the z direction. And 51 located in the middle
A 3-channel element is set at the center of the detector, that is, the center of the electromagnetic wave detection surface. In addition, the X-ray detector 7 is x, y, z
By driving the detector driving unit 11 having a directional translation mechanism, x, y, and z directions can be obtained. That is, the position of the X-ray detector 7 with respect to the X-ray 3 can be adjusted by driving the detector driving unit 11.

The controller 12 drives the sample stage drive unit 10, the drive unit 9, and the detector drive unit 11 to drive the driver, driver control, X-ray source controller,
Spectrometer controller, stress sample stand controller, X
The detector 7 is equipped with a line imaging tube controller.
An image processing unit that processes an image related to the transmission image detected by
It is composed of a computer or the like having a frame memory for storing data relating to images.

Next, the operation when the axis adjusting jig 8 is installed on the sample table will be described. Here, the case where X-rays are used as electromagnetic waves will be described.

First, when the X-ray source 1 emits X-rays 3 with the sample stage fixed at a position of 0 ° and the axis adjusting jig 8 inserted in the electromagnetic wave transmission path, X-ray 3
After being molded by the slit 2, the spectroscope 4 disperses only the X-ray 3 having a specific wavelength. The dispersed X-rays 3 are applied to the axis adjusting jig 8 and the sample 5. Then, the transmission image by the transmission X-ray transmitted through the axis adjusting jig 8 and the sample 5 is X-ray.
It is detected by the line detector 7. At this time, the transmission image of the axis adjusting jig 8 becomes an image as shown in FIG.

Next, the sample stage is rotated 180 degrees, and at this position, the dispersed X-rays 3 irradiate the axis adjusting jig 8 and the sample 5, so that the axis adjusting jig 8 and the sample 5 are moved. Transparent X
The X-ray detector 7 detects the transmission image of the rays. At this time, the transmission image of the axis adjusting jig 8 becomes an image as shown in FIG.

FIG. 2 shows the rotation angles 0 and 1 of the jig 8 for adjusting the axis.
An X-ray transmission image at 80 degrees is shown. In FIG. 2, c indicates the center of the detector 7 (center of the electromagnetic wave detection surface), and c ′ indicates the center of rotation of the sample table. In this case, since the axis adjusting jig 8 is rotated from the 0 ° position to the 180 ° position as the sample table rotates, the axis adjusting jig 8 at 0 ° is rotated.
The position c ′, which is an intermediate position between the projection position c1 of FIG. 2 and the projection position c2 of the axis adjusting jig 8 at 180 °, corresponds to the projection position of the rotation axis of the drive unit 9. That is, the position of c ′ which is an intermediate position between the transmission image 81 of the axis adjusting jig 8 at 0 degree and the transmission image 82 of the axis adjusting jig 8 at 180 ° corresponds to the center of the detector 7. become. For this reason,
When there is no axis deviation, the positions of c and c ′ match, and when the positions of c and c ′ do not match, the distance δ, which indicates the difference between the two, is the amount of deviation. Then, when the shift amount δ is detected, the shift amount δ is suppressed to zero.
The displacement amount δ can be corrected to zero by moving the sample stage in the y direction by driving the sample stage driving unit 10 or by moving the X-ray detector 7 in the y direction by driving the detector driving unit 11. .

As described above, according to this embodiment, the axis deviation can be detected while the sample 5 is fixed without exchanging the sample 5 and the axis adjusting jig 8. Furthermore, the shift amount can be corrected to zero by moving the sample table so that the detected shift amount becomes zero. Therefore, it is possible to capture a tomographic image of the sample 5 with the displacement amount corrected to zero. The tomographic image of the sample 5 is obtained by repeatedly reconstructing the transmitted X-ray of the sample 5 as the sample 5 rotates and reconstructing the image from a series of transmitted X-rays obtained.

Next, the operation of detecting the axis deviation without using the axis adjusting jig 8 will be described with reference to FIG.

First, when X-rays 3 are emitted from the X-ray source 1 with the sample stage fixed at a position of 0 degree, the X-rays 3
After being molded by the slit 2, the spectroscope 4 disperses only the X-ray 3 having a specific wavelength. The sample 5 is irradiated with the X-rays 3 which are spectrally separated and are made monochromatic. Then, an X-ray detector 7 detects a transmission image of the transmission X-rays that have passed through the sample 5. At this time, the transmission image of the sample 5 becomes the image P0 shown in the position at the rotation angle of 0 degree in FIG.

Next, the sample stage is rotated by 180 degrees, and when the dispersed X-rays 3 irradiate the sample 5 at this position, a transmission image by the transmitted X-rays transmitted through the sample 5 is detected by the X-ray detector 7. Detected by. At this time, the transmission image of the sample 5 becomes the image P180 shown at the position of the rotation angle of 180 degrees in FIG.

Next, an inverted transmission image P0R is generated by inverting the transmission image at the position where the rotation angle is 0 degree, and the generated inverted transmission image P0R and the transmission image P at the position where the rotation angle is 180 degrees.
The image coincidence with 180 (image overlap) is determined.

That is, since the sample 5 is rotated around the rotation center c'of the sample table, the inverted transmission image P0R obtained by inverting the transmission image P0 at the position of the rotation angle 0 ° is the rotation angle 1
This corresponds to the transmission image P180 at the position of 80 degrees. Therefore, when there is no axis deviation, the inverted transmission image P
The 0R and the transmitted image P180 match (overlap).

On the other hand, as shown in FIG. 3, the inverted transmission image P0
When R and the transmitted image P180 do not match, the difference between the two images shows a value 2δ (μm) which is twice the shift amount δ (μm). That is, when there is a shift amount δ (difference between the center c of the detector 7 and the rotation center c ′ of the sample table) at the position of the rotation angle of 0 degree, when the inverted transmission image P0R and the transmission image P180 are compared, The quantity δ doubles to 2δ. When the shift amount δ is detected, the shift amount δ can be eliminated by moving the sample stage in the y direction by driving the sample stage drive unit 10 so that the shift amount δ is suppressed to zero.

As described above, according to the present embodiment, the axis deviation can be detected without using the axis adjusting jig 8 while the sample 5 is fixed. Further, the shift amount can be corrected to zero by moving the sample table or the detector 7 in the y direction so that the detected shift amount becomes zero. Therefore, it is possible to capture a tomographic image of the sample 5 with the displacement amount corrected to zero.

Next, the reverse transmission image P0R and the transmission image P180
A method of calculating the deviation amount 2δ will be described.

The transmission image P180 and the reverse transmission image P0R are Δ
The correlation coefficient C indicating the product with the transmission image when shifted by one (for example, one channel of the detector 7) is expressed by the following equation.

[0043]

[Equation 1]

Here, i is the position (channel) of the detector 7.
Is.

In the above equation, the value of C (Δ) becomes maximum when the transmission image P180 and the inverted transmission image P0R are displaced by Δ and the profiles of the transmission images coincide with each other.
Δ giving the maximum value of C is twice the difference δ between c ′ and c.

For example, when the 513 channel is used as a reference, the values of the transmission image P180 and the inverted transmission image P0R are multiplied. Next, only the channel of the inverted transmission image P0R is shifted by one channel, and the value of this channel is multiplied by the value of the transmission image 180. Similarly, only the channel of the inverted transmission image P0R is shifted by one channel, and the value of this channel and the transmission image 180
And the value of. By repeating such calculation, the channel having the maximum value shows a deviation from the center of the detector 7 (channel 513).

Further, the reverse transmission image P0R and the transmission image P180
As shown in the following equation, the amount of deviation 2δ from and may be calculated by the least squares method that minimizes A (Δ).

[0048]

[Equation 2]

Here, i is the position (channel) of the detector 7.
Is.

In the above equation, when the value obtained by squaring the difference between the transmission image P180 and the transmission image obtained by shifting the inverted transmission image P0R by Δ shows the minimum value, the channel deviates from the center of the detector 7. Will be shown.

Next, when the shift amount is calculated by any of the above methods, this shift amount can be corrected according to the following equation.

[0052]

(Equation 3)

Here, if the corrected projection image is P ′,
The projection image Pj of the sample 5 at the rotation angle j can be corrected according to the above equation. For example, as shown in FIG. 4, when Δ showing the maximum value of C (Δ) is 4 channels, the center is 2
Assuming that there is a channel shift, the value of 511 channels is set to 51
The values of channel 513 and channel 513 are shifted to channel 515, and the values of the other channels are similarly shifted by two channels.

Next, a tomography method for non-destructively observing the inside of a sample under a stress by using the tomography apparatus having the above-described structure and an axial deviation adjusting method for the tomography will be described.

Sample 5 is a SiC short fiber (length 1 mm, diameter 140 μm).
(including C fiber with a diameter of 30 μm in m) and Al alloy powder, and extruded. The size is 1 mm in diameter and 3 in length.
It is 0 mm. The spectroscope 4 is adjusted so as to disperse the X-rays 3 passing through the slit 2 into a predetermined energy. The detector driving unit 11 is adjusted so that the separated X-rays 3 can be directly detected by the X-ray detector (X-ray image pickup tube) 7. Further, an axis adjusting jig 8 is installed on the sample table instead of the sample 5, so that the z-axis rotation center of the sample table driving part 10 coincides with the center of the X-ray detector 7 or the sample table driving part 10 or The positions of the stress-loaded sample stage 6 and the X-ray detector 7 are adjusted by driving the detector driving unit 11. This adjustment is performed by the method described above.

Next, the sample 5 was placed on the stress-loaded sample table 6, and in the vicinity of the stress of 0, according to the stress-strain curve shown in FIG.
Sample 5 near 0.2% proof stress, near maximum tensile stress and after fracture
Tomographic images are sequentially taken. In the tomography near the stress of 0, the axis deviation was adjusted using the axis adjusting jig 8, the axis adjusting jig 8 was retracted from the electromagnetic wave transmission path, and the measurement was immediately started. Then, the transmission X transmitted through the sample 5
The line image is detected by the X-ray detector 7. The signal from the X-ray detector 7 is temporarily recorded in a 2-byte frame memory (1024 × 960 elements) via the controller of the controller 12.
The recorded numerical value on the memory is recorded in a recording area on the computer after adding a predetermined slice width in the z direction. This is repeated for a predetermined number of slices at a predetermined slice interval. Further, after rotating the sample once, the transmitted X-ray image is measured. This is repeated until the rotation angle of the sample reaches 180 degrees. After the X-ray transmission amount was obtained from the transmitted X-ray intensity for each angle thus obtained, a tomographic image at each tomographic position was obtained using the image reproduction algorithm.

Next, stress is applied to the sample 5 to 0.2%.
The stress applied near the proof stress is stopped, and a tomographic image is taken under the stress. Here, it is conceivable that an axis deviation occurs due to the stress applied or the instability of the X-ray detector 7 and the X-ray source 1. Therefore, the axis deviation is corrected by using the axis deviation adjusting method and the axis deviation correcting method described above. In this case, the W / SiC fiber as the axis adjusting jig 8 which has been retracted from the electromagnetic wave transmission line (X-ray optical path) is driven by the axis adjusting jig drive unit 9 so that the fiber sufficiently blocks the X-ray 3. Move to position.

Next, the transmission X-ray image of the fiber is detected at the same position as the tomographic position of the sample 5 to be measured later, and the element number (channel number) of the detector 7 corresponding to the center position of the fiber is recorded. Next, the fiber with sample 5 180
After being rotated by a degree, the element number of the detector 7 corresponding to the center position of the fiber is obtained in the same manner as above. Half of the difference between this element number and the element number measured before is the sample table drive unit 10.
It is the amount of deviation between the rotation axis of and the center of the detector 7. This displacement amount is obtained at each slice position, and the average value at each slice position is taken as the average displacement amount, and the rotation axis of the sample table drive unit 10 is moved by the translation mechanism unit (y direction) therebelow to cause axial displacement. Was corrected. Finally, the W / SiC fiber was retracted from the X-ray optical path, and tomography of the sample near the 0.2% proof stress was measured by the same method as described above. The same correction was performed during tomography near the maximum tensile stress. Further, after taking a tomographic image near the maximum tensile stress, the sample was fractured by continuously applying stress until the sample fractured. After fracture of the sample, a tomographic image was taken without correcting the axis deviation. FIG. 6 shows an example of a tomographic image obtained by these measurements.

The tomographic image shown in FIG. 6 (a) shows that a semicircular object flows, but this is due to axial misalignment. Therefore, in the present embodiment, when a tomographic image due to axis deviation is obtained, the axis deviation correction method for the transmission image measured in the axis deviation state is applied to correct the axis deviation as described with reference to FIG. There is.

For example, the X-ray absorption amount (projection image P180) obtained from the transmitted X-ray image of the sample 5 at the rotation angle of 180 degrees and the projection image P0 of the sample 5 at the rotation angle of 0 degrees are set at the center of the detector 7. When the shift amount Δ on the projection image that maximizes the correlation coefficient C of the equation (1) is 46 elements, the actual shift amount δ is Δ Since it is / 2, the projection image Pj at each rotation angle of the sample 5 is 23 elements,
It was corrected by the equation (3). That is, the data of the detector 7 was shifted by 23 channels. A tomographic image obtained from this corrected projection image group is shown in FIG. 6 (b).

From FIG. 6 (b), it can be clearly observed that SiC short fibers are present in the Al alloy matrix. Moreover, it is possible to identify C fibers in SiC short fibers. From the comparison with FIG. 6 (a), it was found that the axis deviation correction is very effective.

Here, the following two methods were attempted to obtain the projection image P'j whose axis deviation was corrected from the projection image Pj by the equation (3). One is a method of reading each Pj from the recording area of the computer, generating P'j shifted by 23 elements according to the equation (3), and then recording P'j. The data for one element is 4 bytes, and one Pj is for 1024 elements.
Since it measures 180 Pj, 7 per tomographic image
Reading and writing of 37,280 bytes are required. Therefore, there is a problem that the processing time of data becomes long.

Therefore, as a second method, since Pj is continuously recorded in the recording area, an address obtained by shifting the recording start address of Pj by 23 elements (92 bytes) is P'j.
I made the computer recognize the recording start address. This method does not require reading or writing data, so
The processing speed of the data has improved significantly. Further, the above-described processing is performed by the transmission image storage unit that sequentially stores the data of the transmission image detected by the detector 7 in association with the rotation position of the sample stage from the read start address, and the shift amount calculated by the shift amount calculation unit. Address changing means for changing the address of the read start position by the corresponding address, and the address by the change of the address changing means as the read start address,
This is achieved by providing the controller 12 with a tomographic image generation unit that sequentially reads out data of a transmitted image from the transmitted image storage unit to generate a tomographic image.

In this embodiment, since the X-ray 3 incident on the sample 5 is monochromatic by the spectroscope 4, the obtained tomographic image has a high S / N and a beam hardening effect (outside the sample 5). This is a phenomenon in which the amount of absorbed X-rays becomes pseudo smaller than that of the inside, and there is an effect that there is no effect due to the spectrum of the X-rays 3 passing through the sample 5 changing depending on the position of the sample 5. Further, by using monochromatic X-rays, it is possible to obtain a tomographic image of only the specific element inside the sample 5 by the difference method (a method of subtracting the tomographic images taken before and after the absorption edge of the element). There is an effect.

In the present embodiment, the axis adjusting jig 8 has X
Since the W line having a high linear absorption amount and a diameter substantially the same as the size of the element of the X-ray detector 7 in the y direction is used, the center of the rotation axis of the sample stage drive unit 10 and the center of the detector 7 are highly accurate. There is an effect that can be matched with. Further, by depositing SiC around the W line to increase the diameter of the W / SiC fiber, there is an effect that the axis adjusting jig 8 can be handled easily.

In the present embodiment, since the X-ray detector 7 uses a high-resolution and two-dimensional position-sensitive X-ray image pickup tube, there is an effect that a plurality of tomographic images can be simultaneously measured with high resolution. Furthermore, there is an effect that a three-dimensional image that three-dimensionally grasps the inside of the sample can be constructed from a plurality of tomographic images, and the measurement time of those data can be shortened. Moreover, the X-ray image pickup tube can measure an X-ray image by two-dimensionally reading the electron-hole pair generated on the X-ray photosensitive surface by the incident X-ray by the electron beam from the electron gun. Has become. With this structure, the scanning range of the readout electron beam can be arbitrarily changed, so that the position resolution of the read X-ray image can be easily changed in accordance with the measurement. From this, there is an effect that a tomographic image can be measured with a position resolution optimum for the size of the sample. That is, the above effect can be obtained by providing the X-ray detector 7 with a mechanism for varying the detection position resolution.

In this embodiment, since a generally used computer tomography algorithm and a hard processor dedicated to fast Fourier transform are used, there is an effect that the calculation for constructing a tomographic image can be processed at high speed.

In the present embodiment, since the axis adjusting jig driving section 9 which can be driven in the y and z directions is used, the axis adjusting jig 8 is retracted from the X-ray optical path when measuring the tomographic image. It is possible to prevent the adjustment jig 8 from interfering with the measurement and to change the position of the axis adjustment jig 8 according to the size of the sample 5.

Next, some modifications of the embodiment shown in FIG. 1 will be described.

First, the X-ray source 1 may be a normal X-ray tube using Mo as a target. in this case,
The spectroscope 4 is not used, and the characteristic X-ray of Mo having a high intensity emitted from the X-ray tube is used. By inserting an Nb filter between the X-ray source 1 and the slit 2, Mo-Kβ rays can be suppressed and quasi-monochromaticization by Mo-Kα rays can be realized.

The axis adjustment and tomographic image measurement in this case can be performed in the same manner as in the embodiment of FIG. Therefore, in the present embodiment, a normal X-ray tube can be used, and since it is not necessary to use a spectroscope, there is an effect that the device can be downsized and the usage is simplified. .

Next, the tip of the axis adjusting jig 8 is set to 10 μm.
A tapered needle cut to m can be used. Also in this case, axis adjustment and tomographic image measurement can be performed in the same manner as in the embodiment of FIG.

In this embodiment, since the tapered needle is used, there is an effect that the axis adjusting jig 8 can be easily manufactured. In addition, the tip of the needle is connected to the element of the X-ray detector 7.
Since the size is substantially the same as the size in the y direction, there is an effect that the center of the rotation axis of the sample stage drive unit 10 and the center of the detector 7 can be aligned with high accuracy. further,
The axis adjusting jig 8 in this case is the same as the first adjusting method when the rotation centers of the stress-loaded sample stage 6 and the sample stage drive unit 10 shown in the embodiment of FIG.
It can also be used as a jig for axis adjustment by a conventional method. Therefore, there is an effect that it is not necessary to prepare a plurality of axis adjusting jigs.

Next, as the X-ray detector 7, a photodiode array (PDA) which is a one-dimensional position sensitive detector can be used. In this case, it can be used as an X-ray detector by using an X-ray-visible light fluorescent film for the entrance window of the PDA.

Also in this case, the axis adjustment and one tomographic image measurement can be performed in the same manner as in the embodiment of FIG.

In this embodiment, the one-dimensional detector is used as the X-ray detector 7, which has the effect of simplifying the structure of the signal processing system for processing the signal from the detector 7. Further, since the PDA has a wide X-ray detection band, it has an effect of enabling tomographic image measurement with a high S / N.

Finally, in the embodiment of FIG. 1, instead of the method of obtaining the amount of axis deviation from the transmission image measured in the state where the axis deviation has occurred according to the equation (1), the method of least squares with P180 is used. Can be used. This is (2) above
This is a method for obtaining Δ (= 2δ) that minimizes A (Δ) in the equation.

When the above method is used, the calculation code of the least squares method which is usually used can be used, so that there is an effect that the data processing can be speeded up and simplified.

In each of the embodiments described above, X-rays are used as the electromagnetic waves, but the present invention is based on the axial misalignment of tomography by electromagnetic waves such as radio waves, infrared rays, visible light, ultraviolet rays, soft X-rays and γ rays. It can also be applied to the adjustment method.

[0080]

As described above, according to the present invention,
The transmission images of the jig for axis adjustment are detected at different rotation positions, and the axis shift, which indicates the shift between the rotation center of the sample stage and the center of the detector, is detected based on the detected transmission images. Therefore, the axis deviation can be detected without replacing the sample with the axis adjusting jig.

Further, the transmission images of the sample are detected at different rotational positions, and the axis deviation is detected based on the detected transmission images. Therefore, the sample can be detected without using an axis adjusting jig. Axis deviation can be detected in a fixed state. Furthermore, based on the detected axis deviation, the sample or detector is moved to a position where the axis deviation is zero, so the axis deviation between the rotation center of the sample stage and the center of the detector can be done without replacing the sample. Can be corrected. Therefore, in the case of tomographic measurement in a state where the sample cannot be exchanged, for example, when measuring a tomographic image while changing the load stress on the spot, or in the tomographic image measurement in the heating or cooling state of the sample, There is an effect that a correct tomographic image can be reconstructed.

Further, according to the present invention, it is possible to construct the correct tomographic image by obtaining the axis deviation amount using the transmission image measured in the state where the axis deviation occurs and correcting the transmission image measured at each angle. Even in an incorrect tomographic imaging due to the axis deviation acquired up to now, there is an effect that a correct tomographic image can be reconstructed and the already acquired data can be utilized.

Further, according to the present invention, since it is only necessary to assemble the axis adjusting jig and the axis adjusting jig driving section on the sample table and correct the measured transmitted image, the present invention can be easily applied to the existing apparatus. The effect is that it can be installed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a tomography apparatus having an axis deviation correction function according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of correcting an axis deviation using the axis adjusting jig according to the present invention.

FIG. 3 is a diagram illustrating a method of obtaining an amount of axis deviation from a transmission image measured in a state where an axis deviation occurs according to the present invention.

FIG. 4 is a diagram illustrating a method of correcting a transmission image at each angle measured based on an amount of axis deviation obtained from a transmission image measured with an axis deviation according to the present invention.

5 is a diagram showing a stress-strain curve of a sample used in the example of FIG. 1. FIG.

FIG. 6 is a diagram showing a tomographic image of a sample measured in a state where an axis deviation has occurred after fracture of the sample using the apparatus of FIG. 1, and (a) is a diagram showing a tomographic image before axis deviation correction. , (B) are diagrams showing a tomographic image after the axis deviation is corrected.

[Explanation of symbols]

 1 X-ray source (electromagnetic wave generator) 2 Slit 3 X-ray (electromagnetic wave) 4 Spectroscope 5 Sample 6 Stress-loaded sample stand 7 X-ray detector 8 Axis adjustment jig 9 Axis adjustment jig drive unit 10 Sample stand drive Part 11 Detector drive part 12 Controller

Claims (10)

[Claims] 1. A sample stage for fixing a sample, an electromagnetic wave irradiating means for irradiating the sample fixed on the sample stage with an electromagnetic wave, and an electromagnetic wave incident position where the electromagnetic wave transmitted through the sample is received by an electromagnetic wave detection surface. An electromagnetic wave detecting means for outputting a signal of a transmission image according to the electromagnetic wave detecting means, and at least a part of the electromagnetic wave detecting means fixed to the sample table is inserted in an electromagnetic wave transmitting path connecting the electromagnetic wave irradiating means and the electromagnetic wave detecting means. The axis adjustment jig for forming a transmission image on the electromagnetic wave detection surface, the rotation driving means for rotationally driving the sample stage, and the transmission table of the axis adjustment jig detected by the electromagnetic wave detection means have different sample stages. A tomography apparatus comprising: a deviation amount calculating means for calculating a deviation amount between a rotation center of the rotation driving means and a center of an electromagnetic wave detecting surface of the electromagnetic wave detecting means from a signal relating to a transmission image at a rotation position. 2. A sample stage for fixing the sample, an electromagnetic wave irradiating means for irradiating the sample fixed on the sample stage with an electromagnetic wave, and an electromagnetic wave incident position where the electromagnetic wave transmitted through the sample is received by an electromagnetic wave detecting surface. An electromagnetic wave detecting means for outputting a signal of a transmission image according to the electromagnetic wave detecting means, and at least a part of the electromagnetic wave detecting means fixed to the sample table is inserted in an electromagnetic wave transmitting path connecting the electromagnetic wave irradiating means and the electromagnetic wave detecting means. The axis adjustment jig for forming a transmission image on the electromagnetic wave detection surface, the rotation driving means for rotationally driving the sample stage, and the transmission table of the axis adjustment jig detected by the electromagnetic wave detection means have different sample stages. A deviation amount calculation means for calculating a deviation amount between the rotation center of the rotation driving means and the center of the electromagnetic wave detection surface of the electromagnetic wave detection means from a signal relating to a transmission image at a rotational position, and for calculating the deviation amount calculation means. Drive command generating means for generating a drive command for making the amount of deviation due to zero, and the sample table according to the drive command generated by the drive command generating means for supporting the sample table so as to be movable along the electromagnetic wave detection surface. And a sample stage moving means for moving the tomography apparatus. 3. A jig driving means fixed to a sample table and movably supporting an axis adjusting jig, wherein the jig driving means comprises:
2. The axis adjusting jig is moved onto the electromagnetic wave transmission path except when the tomography of the sample is performed, and the axis adjusting jig is retracted to an area outside the electromagnetic wave transmission path during the tomography of the sample. The tomography apparatus according to 2. 4. The axis adjusting jig is such that a tip portion, which is a main portion of a transmission image, is formed in a sharpened shape, and a width of the tip portion is set to at least a position resolution of the electromagnetic wave detecting means or less. The tomography apparatus according to claim 1 or 2. 5. The axis adjusting jig is composed of a fine wire that absorbs an electromagnetic wave at a main part of a transmission image, and the diameter of the fine wire is set to be at least equal to or less than the positional resolution of the electromagnetic wave detecting means. The tomographic apparatus according to claim 1 or 2, which is provided. 6. A sample stage for fixing a sample, an electromagnetic wave irradiating means for irradiating the sample fixed on the sample stage with an electromagnetic wave, and an electromagnetic wave incident position where the electromagnetic wave transmitted through the sample is received by an electromagnetic wave detecting surface. Electromagnetic wave detecting means for outputting a signal of a transmitted image according to the above, rotation driving means for rotationally driving the sample stage, and transmission at different rotational positions of the sample stage in the transmitted image of the sample detected by the electromagnetic wave detecting means. The amount of deviation between the rotation center of the rotation drive means and the center of the electromagnetic wave detection surface of the electromagnetic wave detection means is calculated from the signal relating to the image and the inverted transmission image generated by reversing the detected transmission image at the center of the electromagnetic wave detection surface. A tomography apparatus comprising: a deviation amount calculating means for calculating. 7. A sample table for fixing a sample, an electromagnetic wave irradiating means for irradiating the sample fixed on the sample table with an electromagnetic wave, and an electromagnetic wave incident position where an electromagnetic wave transmitted through the sample is received by an electromagnetic wave detecting surface. Electromagnetic wave detecting means for outputting a signal of a transmitted image according to the above, rotation driving means for rotationally driving the sample stage, and transmission at different rotational positions of the sample stage in the transmitted image of the sample detected by the electromagnetic wave detecting means. The amount of deviation between the rotation center of the rotation drive means and the center of the electromagnetic wave detection surface of the electromagnetic wave detection means is calculated from the signal relating to the image and the inverted transmission image generated by reversing the detected transmission image at the center of the electromagnetic wave detection surface. A deviation amount calculating means for calculating, a driving command generating means for generating a driving command for making the deviation amount calculated by the deviation amount calculating means zero, and the sample table movably supported along the electromagnetic wave detecting surface. And a sample stage moving unit that moves the sample stage according to a drive command generated by the drive command generating unit. 8. A sample stage for fixing a sample, an electromagnetic wave irradiating means for irradiating the sample fixed on the sample stage with an electromagnetic wave, and an electromagnetic wave incident position where the electromagnetic wave transmitted through the sample is received by an electromagnetic wave detecting surface. Electromagnetic wave detecting means for outputting a signal of a transmission image corresponding to the rotation angle, rotation driving means for rotationally driving the sample stage, and a rotation angle of 0 ° and a rotation angle of the sample stage in the transmission image of the sample detected by the electromagnetic wave detecting means. The rotation center of the rotation driving means and the electromagnetic wave detecting means are obtained from the signals relating to the transmitted image at 180 degrees and the inverted transmitted image generated by inverting the transmitted image at the detected rotation angle of 0 degree at the center of the electromagnetic wave detection surface. A tomography apparatus comprising: a deviation amount calculating means for calculating a deviation amount from the center of the electromagnetic wave detection surface. 9. A sample stage for fixing a sample, an electromagnetic wave irradiating means for irradiating the sample fixed on the sample stage with an electromagnetic wave, and an electromagnetic wave incident position where the electromagnetic wave transmitted through the sample is received by an electromagnetic wave detecting surface. Electromagnetic wave detecting means for outputting a signal of a transmission image corresponding to the rotation angle, rotation driving means for rotationally driving the sample stage, and a rotation angle of 0 ° and a rotation angle of the sample stage in the transmission image of the sample detected by the electromagnetic wave detecting means. The rotation center of the rotation driving means and the electromagnetic wave detecting means are obtained from the signals relating to the transmitted image at 180 degrees and the inverted transmitted image generated by inverting the transmitted image at the detected rotation angle of 0 degree at the center of the electromagnetic wave detection surface. A deviation amount calculation means for calculating a deviation amount from the center of the electromagnetic wave detection surface, and a drive command generation means for generating a drive command for making the deviation amount calculated by the deviation amount calculation means zero.
A tomography apparatus comprising: a sample stage moving unit that supports the sample stage so as to be movable along the electromagnetic wave detection surface and moves the sample stage according to a drive command generated by the drive command generating unit. 10. A transmission image storage means for sequentially storing transmission image data detected by an electromagnetic wave detection means in association with a read start address in association with a rotation position of a sample table, and a shift amount calculated by a shift amount calculation means. Address changing means for changing the address of the read start position by the address, and tomographic image generation for sequentially reading the data of the transmitted image from the transmitted image storage means by using the address by the change of the address changing means as the read start address. The tomography apparatus according to claim 6, 7, 8 or 9, further comprising: