JPH05312733A - X-ray inspection - Google Patents

Abstract

(57) [Abstract] [Purpose] The purpose of the X-ray inspection method is to eliminate the influence of scattered X-rays and improve the detection accuracy. [Structure] 1) A mask having an X-ray transmitting region and an X-ray blocking region is provided between an X-ray source and an object to be inspected, and a scattered X-ray dose of the X-ray transmitting region is provided in the X-ray transmitting region. The X-ray fluoroscopic image of the X-ray transmission area is formed by deducing from the X-ray transmission area of the adjacent X-ray blocking area and subtracting the scattering X-ray dose of the X-ray transmission area from the X-ray transmission area of the X-ray transmission area. 2) As the mask, a mask in which an X-ray transmitting region and an X-ray blocking region are alternately arranged in a grid shape having a size corresponding to one pixel of the X-ray detection device, and the mask is used for one pixel It is configured to move so as to form a complete two-dimensional X-ray fluoroscopic image from two images in which the X-ray transparent region and the X-ray blocking region are interchanged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray inspection method for nondestructively inspecting internal structures and defects. With the higher density and higher integration of systems such as electronic computers, the internal inspection that cannot be seen from the outside is required in the inspection of the printed boards used for them. Therefore, an X-ray inspecting device having high penetrating ability and capable of nondestructively inspecting internal defects is used.

[0002]

2. Description of the Related Art FIG. 8 is an explanatory view of a conventional X-ray inspection method. In the figure, 11 is an X-ray source, 12 is a detector (fluorescent plate),
13 is an object to be inspected.

In the conventional X-ray inspection method, not only the X-ray a transmitted from the portion to be inspected of the object to be inspected,
Since the X-rays b scattered from other parts of the object to be inspected are also detected, the detection accuracy of the X-rays is reduced accordingly.

[0004]

In the conventional example, there is a problem that the detection accuracy is lowered due to the influence of scattered X-rays from outside the inspection target area of the inspection object.

An object of the present invention is to eliminate the influence of scattered X-rays and improve the detection accuracy.

[0006]

To solve the above problems, 1) a mask having an X-ray transmitting region and an X-ray blocking region is provided between the X-ray source and the object to be inspected, and the X-ray transmitting region is provided. Of the scattered X-ray dose of the X-ray transmission region is estimated from the scattered X-ray dose of the X-ray transmission region adjacent to the X-ray transmission region, and the X-ray transmission region is subtracted from the transmission X-ray dose of the X-ray transmission region, An X-ray inspection method for forming an X-ray fluoroscopic image of the X-ray transmissive region, or 2) As the mask, the X-ray transmissive region and the X-ray blocking region have a size corresponding to one pixel of the X-ray detection device. Using a mask arranged alternately in a grid pattern, the mask is moved by one pixel to form a complete two-dimensional X-ray fluoroscopic image from two images in which the X-ray transmission region and the X-ray blocking region are interchanged. This is achieved by the X-ray inspection method described in 1).

[0007]

In the present invention, an X-ray is provided between the X-ray source and the inspected object.
A mask having an X-ray transmission region and an X-ray cutoff region is provided, and the scattered X-ray dose of the X-ray transmission region is estimated from the scattered X-ray dose of the X-ray transmission region adjacent to this region to determine the transmission X-ray transmission of the X-ray transmission region.
By subtracting this scattering X dose from the dose, the scattering X
The effects of lines are eliminated.

1, FIG. 2 and FIG. 3 are explanatory views of the principle of the present invention. FIG. 1 is a schematic diagram showing the structure of the present invention. 12 is a detector, which is a two-dimensional sensor, and 14 is a region 1 and X that completely transmit X-rays.
This is a checkerboard-shaped mask in which areas 2 that completely cut off lines are alternately arranged in the vertical and horizontal directions (grid shape), and the size of this grid shape is made to correspond to one pixel of the two-dimensional sensor.

FIG. 2 is a sectional view for explaining the principle of the present invention in detail. For simplicity, the incident X-rays are assumed to be parallel. Here, the areas of the mask, the object to be inspected, and the detector, which are alternately opened and closed by the mask, are 1, 2
And (1) When mask area 1 is opened and area 2 is closed Total X-ray dose of detector area 1 = 1 transmitted X-ray + 1 own scattered X-ray + scattered X-ray from another 1 Scattered X-rays from total X-ray dose = 1 in area 2 (2) When mask area 2 is opened and area 1 is closed Scattered X-rays from total X-ray dose = 2 in detector area 1 Detector area 2 Total X-ray dose = 2 own transmitted X-rays + 2 own scattered X-rays + scattered X-rays from other 2 (3) When mask areas 1 and 2 are opened (without mask) Detector area 1 Total X-ray dose = 1 own transmitted X-ray + 1 own scattered X-ray + other 1 scattered X-ray + 2 scattered X-ray Total X-ray dose in detector region 2 = 2 own transmitted X-ray + 2 itself Scattered X-rays + Scattered X-rays from the other 2 + Scattered X-rays from 1 The purpose here is, when either mask is opened, the X-ray dose in the opened area. To obtain the transmitted X-ray dose by subtracting the scattered X-ray dose from.

Comparing the above (1) and (2) with the conventional example (3), by closing either one of the mask areas 1 and 2, X which was scattered from the closed area to the other area was detected. You can see that the line has already been deleted.

Next, a method of calculating scattered X-rays of the area 1 or 2 itself and scattered X-rays from the other areas 1 or 2 will be described with reference to FIG. Since the exact amount of scattered X-ray cannot be detected, it is estimated from the X-ray amount detected by the detector.

FIG. 3A shows an example in which a mask in which one minute portion dx is opened is used. Due to the mask, only the minute part dx X
The line is transparent. At this time, a part of the X-rays irradiated on the inspection object is scattered. At this time, when the detector is brought close to the object to be inspected, a symmetrical scattered X-ray distribution (a) with the minute portion dx as the peak center is obtained. When the detector is moved away from the object to be inspected, the scattered X-ray distribution (b) becomes gentle. This is because the path of X-rays is bent due to scattering.

FIG. 3B shows an example of using a mask in which two minute portions dx are opened adjacent to each other. FIG. 3C is an enlarged view when the detector of FIG. 3A is far. In the figure, assuming that the mask grid interval is small and the distance between the object to be inspected and the detector is large, the scattering distribution becomes gentle as described above, and the amount of scattering by dx ₁ itself incident on the minute portion dx ₁ Can be approximated by the X-ray dose in the small area dx ₂ in the vicinity.

When the scattering distribution is gentle, the scattered X-ray amount scattered from the minute portion dx ₁ and incident on the adjacent dx _{1 ′} can be estimated from the amount of scattering of the minute portion dx _{2 in} the vicinity. As a concrete example of estimating the scattered X-ray dose of the minute portion dx ₁ from the nearby minute portion dx ₂ , the detector is sufficiently far from the inspected object and the scattered X-rays are gently distributed. If it can be assumed that, the average value of the X-ray dose of the minute portion dx _{2 in} the vicinity can be used as the scattering amount of the minute portion dx ₁ . Also, when the detector is close to the object to be inspected, the value obtained by multiplying the average value of the X-ray dose of the minute portion dx _{2 in} the vicinity by the correction function f (x) may be used as the scattering amount of the minute portion dx _1. it can.

Therefore, in FIG. 1, the scattered X-ray dose in the region 1 that transmits X-rays is calculated by taking the average of the region 2 that blocks X-rays in the vicinity and subtracting the average from the total X-ray dose. It is possible to obtain a transmission X-ray image from which is removed.

However, since the image of only the region 1 which transmits X-rays is left as it is, by moving the mask 1 pixel to the left and right as shown in FIG. 4A, the region 1 which transmits X-rays and the X-rays are transmitted. The area 2 for shutting off is replaced. A complete two-dimensional transmission image can be obtained by adding the previously created image to the image created by subtracting scattered X-rays in the same manner as described above.

In FIG. 1, a mask in which regions that transmit X-rays and regions that block X-rays are alternately arranged in rows and columns is used, but any mask can be used as long as it is adapted to the distribution of scattered X-rays. It can be anything. For example, as shown in FIG. 4 (B), a mask that transmits X-rays may be moved 9 times and used only in one of 9 areas. In this case, the scattering X is larger than that in the case of FIG.
The accuracy of dose calculation is improved.

As described above, according to the present invention, the influence of scattered X-rays in an X-ray transmission image can be suppressed, and transmitted X-rays can be converted into S / S.
N can be detected well.

[0019]

FIG. 5 is a block diagram for explaining an embodiment of the present invention. This figure shows an example of the configuration of a nondestructive inspection apparatus using the present invention.

In the figure, 15 is a stage on which a mask is placed, 16 is a stage controller, 17 is I / O, 18 is a CPU,
19, 20 and 21 are memory, 22 is image input, 23 is bus, 24 is 2
It is a dimensional sensor camera.

Here, the same mask as that shown in FIG. 1 is used as the mask, and the scattered X-ray dose in the X-ray transmission area is averaged over the scattered X-ray doses in the X-ray shielding area in the vicinity of the mask. By subtracting, it is possible to obtain an X-ray transmission image with the influence of scattered X-rays removed.

Further, as described above, a complete two-dimensional transmission image can be obtained by moving the mask left and right by one pixel. FIG. 6 is a flow chart of an embodiment of the present invention.

When the mask is placed at the first position, the image 1 obtained by subtracting the average of the scattered X-ray dose of the mask portion from the transmitted X-ray dose is stored in the memory 1 as the image input 1. Next, the mask is moved by one pixel, and as the image input 2, the image 2 obtained by subtracting the average of the scattered X-ray dose of the mask portion from the transmitted X-ray dose
Are stored in the memory 2.

Then, the memory 1 and the memory 2 are ANDed and stored in the memory 3. 7A to 7D are explanatory views of the image processing procedure of the embodiment. In the figure, the horizontal axis represents distance and the vertical axis represents signal strength.

In FIG. 7A, the solid line shows the image input signal when there is no mask and the dotted line shows only the desired transmitted X-ray signal. FIG. 7B shows the scattering component contained in the transmitted X-ray.

FIG. 7C shows a signal when the mask of the embodiment is used, and a value obtained by subtracting a scattering component from an image input signal when there is no mask is shown for each pixel. Figure 7 (D)
In, if the lower ends of the signals are corrected and aligned, the input signal of only the transmitted X-ray shown by the dotted line in FIG. 6 (A) can be obtained.

[0027]

According to the present invention, the influence of scattered X-rays can be eliminated in the X-ray transmission image, and the X-ray detection accuracy can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention (1)

FIG. 2 is an explanatory view of the principle of the present invention (2)

FIG. 3 is an explanatory diagram of the principle of the present invention (3)

FIG. 4 is an explanatory diagram of a mask of the present invention.

FIG. 5 is a configuration diagram illustrating an embodiment of the present invention.

FIG. 6 is a flow chart of an embodiment of the present invention.

FIG. 7 is an explanatory diagram of an image processing procedure of the embodiment.

FIG. 8 is an explanatory diagram of a conventional X-ray inspection method.

[Explanation of symbols]

 11 X-ray source 12 Detector (fluorescent plate) 13 Object to be inspected 14 Mask of the present invention 15 Stage on which mask is placed 16 Stage controller 17 I / O 18 CPU 19, 20, 21 Memory 22 Image input 23 Bus 24 Two-dimensional sensor camera

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoji Nishiyama 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (2)

[Claims] 1. A mask having an X-ray transmission region and an X-ray blocking region is provided between an X-ray source and an object to be inspected, and a scattered X-ray amount of the X-ray transmission region is set in the X-ray transmission region. The X-ray fluoroscopic image of the X-ray transmission area is formed by deducing from the X-ray transmission area of the adjacent X-ray blocking area and subtracting the scattering X-ray dose of the X-ray transmission area from the X-ray transmission area of the X-ray transmission area. An X-ray inspection method comprising: 2. A mask in which an X-ray transmission region and an X-ray blocking region are alternately arranged in a grid shape having a size corresponding to one pixel of an X-ray detection device, and the mask is one pixel. The X-ray inspection method according to claim 1, wherein a complete two-dimensional X-ray fluoroscopic image is formed from two images in which the X-ray transmissive region and the X-ray blocking region are interchanged by moving by a distance.