JPS6034700B2 - Depth detection method for the detection part inside the test object - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the depth position of a portion such as an internal defect in a test object using electromagnetic waves such as X-rays and D-rays.

The method of transmitting an object using X-rays or radiation projects the internal arrangement of a three-dimensional object onto a two-dimensional surface, and non-destructively detects the inside of an unknown opaque object. Widely used in cases.

However, the image obtained here is a superimposed image that does not include information about the depth in the traveling direction of X-rays, etc., and it is impossible to determine the depth of the internal exploration site. Therefore, the depth of the probe is detected by placing the object near the intersection of the orthogonal coordinate system and taking images from all directions along the two axes. Can not. Recently, a method of taking images from multiple angles, processing the data using a computer, and duplicating it as a cross-sectional image has become known, but this method requires large-scale equipment and is expensive. If the subject to be examined is a living body, it may cause problems such as radiation damage, so it is limited to special cases.For example, it is simple and inexpensive for early detection of habitual lesions. It is desired to develop a method that is easy to operate. Such requirements are not limited to living organisms, but also apply to industrial applications such as non-destructive testing.

For example, when examining the location of cracks in a material using an X-ray photograph or when taking an X-ray transmission photograph of an unknown internal structure, it is necessary to know the depth position. An object of the present invention is to provide a method that satisfies the above-mentioned requirements and detects the depth of a probe within a test object in a short time without moving the test object. The object to be examined is placed stationary between a point-like source of radiation and an imaging plane that forms a two-dimensional image of the object through electromagnetic waves generated from this radiation source. The depth position of the probe is detected based on the change in the size of the image of the side of the object to be inspected formed by the image plane by relatively changing the distance between the probe and the imaging plane. It is characterized by this.

The method according to the invention will be explained in detail below on the basis of illustrated embodiments. FIG. 1 is a diagram for explaining the method of the present invention.

When a point source 1 that emits y-rays is first placed at a position P and a chain radiation east is irradiated to the detection part 3 in the object 2, the radiation imaging plane is shown by a solid line 4 by an appropriate detection plane. A two-dimensional image like this can be obtained. Next, when the radiation source 1 is moved along the straight line 5 connecting it and the probe section 3 to position Q as shown by the dotted line, the angle of the conical radiation east of the radiation source 1 to the probe section 3 becomes larger. , the image obtained on the imaging plane will be enlarged as shown by the dotted line 6. By moving the radiation source 1 relative to the detector 3 in this way, the size of the image obtained on the imaging plane changes. As described later, the rate of this change is related to the depth position of the probe 3 within the object 2, so it is possible to know the depth position of the probe 3 by knowing the change in the size of the image. Become. FIG. 2 is a diagram for explaining a method for determining the relationship between the change in image size and the depth position of the probe 3. In FIG.

Now, the distance between the point P and the imaging line R is h, the distance between the point Q and the imaging plane R is h2, the size of the probe 3 is 3, and the point source 1 is Let b be the size of the image obtained on the imaging plane R when placed at point P, and let a be the increase in the image obtained on the imaging plane R when the radiation source 1 is moved to Q. As can be understood from Fig. 2, two similar triangles are obtained, with point P as the apex and point P as the base, respectively, and b as the base, and similarly,
2 with point Q as the vertex and a + b as the base, respectively
Similar triangles are obtained. By correlating these triangles, the following two equations are obtained. Evening-2
…[1} h, 1d-h, so -a+b …[21h2-d
h2 By eliminating evening from these 'U, ■ formulas and finding the depth d, the 醔 formula is obtained.

h, similar...'3la+
h2) b In this '3' formula, h, , h2 and b are known, so by finding a, the probe unit 3
The distance d between the image plane R and the imaging plane R, that is, the depth position of the probe 3 can be determined.

Furthermore, FIG. 3 shows a specific embodiment, in which the point source 1 is housed in a shielding box 7 having a radiation window for obtaining cone-shaped radiation and a shield that can be operated remotely. To make the distance to the imaging plane R variable.

The arm 8 is moved by rotating a screw punch 9 via an electric motor 10, and the moving distance of the radiation source 1 is measured by a rotational pulse transmitter 11 which is pivoted on the screw 9. An image intensifier tube 12 consisting of a channel-type secondary electron intensifier surface is provided on the imaging surface R as a detector. This image intensifier tube 1
2 is vacuum-sealed with glass, and inside it is an imaging plane R.
From the side, a fiber-like scintillator 13 and a photoelectric conversion film 14
, a secondary electron multiplier surface 15 for multiplying electrons for each individual electron tube by using minute secondary electron multiplier tubes, and a fluorescent film 16
is provided. The y-rays reaching the imaging plane R from the radiation source 1 are converted into photoelectrons in the scintillator 13, and further converted into a corresponding electron image in the photoelectric conversion film 14, and each electron of this electron image is transferred to the secondary electron multiplication surface 15. The y-ray image is multiplied by , further accelerated by a DC power source, collides with the fluorescent film 16 , and is formed on the imaging plane R. The y-ray image is then imaged on the fluorescent film 16 as a visible image with the brightness enhanced at the same magnification. Become. Especially scintillator 13
Since the secondary electron multiplication surface 15 is composed of fine fibers and thin tubes, it can be easily disassembled, and is suitable for measuring the increase in image with high precision as in the method of the present invention. Therefore, the object 2 is placed at a certain position between the radiation source 1 and the detector 12, for example, the outer contour of the object 2 is brought into contact with the imaging surface R of the detector 12, and then Y-rays are irradiated onto the fluorescent film 16. A point on the outline of the specific part 3 in the object 2 to be imaged and distinguishable from the surroundings is set on the glass surface at the rear of the detector 12, which is integrated with the fluorescent film 16 and has scale lines as shown in FIG. 4, for example. 17, it is stored as point x.

Next, while keeping the object 2 stationary, the radiation source 1 is moved from point P to point Q and the y-ray is irradiated again in the same way, and the image point x of the detector 3 moves on the glass surface 17 and is imaged as x'. Ru. In this case, the moving distance of the image points x to x' is determined as the increase a, and the depth d of the probe section can be obtained using the formula. Therefore, this glue relational expression is converted into a circuit in the arithmetic unit 18 shown in FIG. The moving distance a of the calculation device 18 is calculated by
When inputting , the depth d of the exploration section 3 can be immediately displayed on the display 20 .

In actual operation, the position of the radiation source 1 is adjusted so that one point on the outline of the probe section 3 is projected onto a fixed position on the glass surface 17 by the first y-ray irradiation, and then the position of the radiation source 1 is adjusted while continuing the irradiation. The radiation source 1 is moved until the image point x moves a certain distance on 17, and the moving distance is measured and
The depth d may also be determined by

Furthermore, if the moving distance of the radiation source 1 is determined in advance and can be controlled, the depth d can be immediately read directly without using the arithmetic device 18 if the scale on the glass surface 17 is a conversion scale obtained by converting formula '3}. become. Furthermore, as shown in FIG. 5, if an image pickup tube 21, such as a vidicon, is installed on the rear surface of the detector 12 and connected to a video tube 22, images can be viewed remotely and recorded on a videotape or the like. You can also.

Furthermore, if a light ben is used on the video tube 22 to mark the image positions of the two image points x and x' of the probe section 3,
It is also possible to directly calculate the depth d using the arithmetic unit 18'. The above description is an example of the present invention, and the present invention is not limited to the above example. For example, the green source 1 does not necessarily have to move on the straight line 5, and the green source 1 does not necessarily have to move on the straight line 5.
may be fixed and the imaging plane R may be moved.Furthermore, the radiation source 1 or the imaging surface R may be moved in a direction such that the image becomes smaller, that is, the radiation source 1 is moved from point Q to point P. Of course, there is no problem.

Furthermore, images 4 and 6 of the exploration unit 3 projected on the imaging plane R'
The depth d can also be calculated from the area ratio of . In order to extract the image of the exploration unit 3 at a predetermined depth position, by using an appropriate image processing device such as an image storage tube,
This can be easily realized by making a line drawing with the outline thickness a and erasing the others.

In this way, a complicated perspective image is reduced to only an outline, and a line drawing with depth correspondence obtained by the thickness a becomes easy and accurate to measure the increase amount a. In the embodiment, a radioactive isotope that emits Y-rays was used as a radiation source, but there is no problem in using X-rays, which are the same electromagnetic waves. As for the detector, the image intensifier tube using the channel type secondary electron intensifier surface shown in the example is advantageous in light weight, resolution, detection sensitivity, and image processing, but there are also scintillation cameras, semiconductor type Examples include the use of a position detector, a position detector using a spark chamber, a proportional counter type position counter using a high resistance anode wire, or an imaging film. It goes without saying that the type of radiation source, energy intensity, type of detector, etc. need to be selected and roughly adjusted as appropriate depending on the type of object to be examined, the properties of the probe section, etc. Examples of the test object include living bodies and general industrial materials, and the detection part is useful for detecting internal defects in organs and the like in living organisms, and internal defects in industrial materials.

As described above, according to the method of the present invention, the depth position of the probe inside the object can be determined from images stacked on a two-dimensional surface by an extremely simple operation of moving the point source or the imaging plane. This allows accurate positioning to be obtained in a short time without moving the object.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the depth detection method of the probe section inside the object according to the present invention, Fig. 2 is an explanatory diagram of the principle of the detection method, Fig. 3 is an explanatory diagram showing a concrete example, and Fig. 4 5 is a front view of a glass surface onto which a visible image of the rear part of the detector is projected, and FIG. 5 is a configuration diagram in which an image pickup tube and a video tube are connected to the rear part of the detector. 1 is a point source, 2 is a test object, 3 is a probe, 4 and 6 are transmitted images, 12 is an image intensifier tube, P and Q are source positions,
R is the imaging plane and d is the depth. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 The object to be examined is placed stationary between a point source of X-rays or γ-rays and an imaging plane that forms a two-dimensional image of the area to be examined through electromagnetic waves generated from this source. Then, the distance between the radiation source and the imaging plane is changed relatively, and the depth position of the detection part is determined based on the change in the size of the image of the detection part inside the object formed by the imaging plane. A method for detecting depth in a probe inside an object, characterized by detecting.