JPS60500271A - A method for obtaining a radiographic image of an object, preferably used for material inspection, and an apparatus for performing it - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Method of radiographic photography of objects, preferably used for material inspection and the device to run it The present invention utilizes methods according to the prior art, including /conventional radiography. I can't check the features accurately enough? c. Testing to fully determine the state and structure of an object. Radiography and radioscopy can be successfully applied as positive modalities. It concerns how to

The present invention is a technology for material inspection, that is, inspecting the fabrication and/or condition of industrial materials. Preferably used for power. In the following, we will focus on this preferred field of application. The present invention will be explained below. However, the application of the present invention is limited to this field. It will be readily apparent to those skilled in the art from the following description that this is not the case. Main departure q By making the necessary changes to the test subject, the test subject can be used as a test subject in the future. Recording of radiographic images as a result of absorption of radiation ice particles passing through When the display image is created, it is done using the so-called fluoroscopy method. The present invention can be applied when the spatial shape and structure of the object can also be determined. .

Among the special advantages of the present invention, the following points should be mentioned.

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Claims (1)

[Claims] 1. A method for obtaining a radiographic image of an object, the method comprising: It is preferably used for hyperphotographic inspection, and includes radiation/X-rays, γ-rays, isotope radiation/transmission. Place the sample to be inspected (hereinafter referred to as the inspection object) in the Recording a bright photographic image on a film or transmitting said radiographic image to an image screen. (hereinafter referred to as radiation receptor); transmitting a radiation beam to said examination position; and transmitting said image thus obtained, if necessary, to said examination position. The evaluation method also takes into account the known properties of the object to be inspected, and the new feature is that a correction object is placed in the radiation path between the object to be inspected and the radiation receptor. and that the correction object is laminated with thin plate/foil/gold on top of each other. The axis of the radiation path is perpendicular to the surface of the thin plate and 0°f! , preferably the axis and the perpendicular line are mutually aligned so as to have an angle of 600 degrees. said correction object is arranged so as to be very parallel, and that the substantive and geometrical properties of said correction object are also taken into account during the evaluation of said radiographic image. 2. In claim 1, a homogeneous compensating object (hereinafter referred to as a compensator) is The compensator is arranged in a radiation path between a radiation source and a radiation receptor, that is, in a radiation path in front of or behind the object under examination, and the obliquely cut portion of the outer surface of the compensator is connected to the radiation source. facing and at the same time with the vertical plane of the axis of the radiation path 97 mouth 〈ψ〈? 0 In claim 2, a cylindrical body or a cylindrical tube is examined and radiates D'. Let L' be the maximum length of the test object along the plane perpendicular to the axis of the line, and let L' be the angle ψ of the path of the radiation as it passes through the integrated medium constituting the test object. the way in which said compensator is arranged. 4. A method according to claim 2, in which a non-cylindrical object is examined and the compensator is arranged such that the angle ψ is in the range 60°≦ψ≦60°. 5. A correction object for use in radiographic examination, preferably material inspection, in order to influence the composition of the radiographic image, said correction object comprising a stack of six or more thin plates. , each of said laminae is a substantially homogeneous structure and has a density equal to or preferably greater than the density of the object to be inspected, said laminae are laminated to each other and are adhesively bonded, glued, thermocompressed or 6. In claim 5, each of the thin plates is attached to the top of the carrier. and the thin layer body is made by laminating and integrating the composite layers. Description: Method and apparatus for carrying out radiographic images of objects, preferably used for material inspection. A person who is able to successfully apply radiography and radionuclides as a secondary examination method to determine the condition and structure of objects whose characteristics have not been examined with sufficient accuracy. The present invention relates to the technology of materials inspection, i.e., it is preferably used for inspecting the structure and/or condition of industrial materials. While explaining the invention, it is important to note that It will be clear to those skilled in the art from the following description that the application is not limited to this field. You'll soon understand. By making the necessary changes to the present invention, the subject to be examined When a recorded or displayed radiographic image is produced as a result of the absorption of radiation particles passing through the body, hereafter referred to as the examined body, the so-called transparent The present invention applies when the spatial shape and structure of an object can be determined by hypermorphic radiography. The third point out of the first and third special points of the present invention to which the invention can be applied is as follows. I want to come. - The measurement result is not influenced by the working temperature of the object being tested; - distortions due to the presence of other media around or inside the object being tested can be sufficiently compensated for. Therefore, the present invention is particularly suitable for industrial applications when measuring the thickness of the side walls of tubes or objects that are components/components/of equipment used in chemistry. Sidewall thickness measurements carried out in this way are useful when determining the condition of the material. Tests for the presence of corrosion, the presence of deposits, the presence of scale, drift media, and the like, performed in routine diagnostic tests, are sufficiently accurate when processed in accordance with the present invention. It can also be carried out. A particularly preferred field of application is the determination of features in hidden locations, i.e. Inspection of separated objects, folds, objects covered with protective coatings, objects embedded in walls such as distillation tubes, and the like. Prior art methods such as ultrasonic inspection, thermovision, and nuclear measurements are inadequate and problematic if applied to objects in such locations. I know that. In some cases, these methods are almost impossible to perform. 5 The method according to the invention can also be applied to such locations and ensures that the fine points being searched for are reproduced with sufficient accuracy and that the disturbance sources are Compensation for children can also be carried out on a case-by-case basis. The main features of the invention are that it is suitable for applications such as 9, for example the measurement of side wall thickness, 5 or the determination of other points characterizing the condition of the specimen under test. Akira It is clear. Transmission radiography is used to create an iXX image (d), which is applied to detect gamma-ray images. It can be played directly or indirectly on the screen or on the image screen. Gamma rays can be obtained from radioactive isotopes or generated in particle accelerators. These examples are not meant to limit the invention to these examples and will be explained specifically. this place The composite film image is reconstructed from the radiographic image, and then this film is The image of the person is evaluated. If this film image is obtained by a so-called projection method, it is possible to observe and evaluate the projection of one or more cross sections of the specimen. Wear. The projection can be measured immediately, taking into account the magnification factor, or given The thickness belonging to the obtained projection can be determined using suitable equipment. Although this method belongs to the prior art in itself, if it is carried out in a conventional manner, it is not possible to obtain the necessary accuracy, i.e., the various sections of the cross section should represent sections of the material. However, these values vary considerably depending on the position within the cross section. Take the first example. If the object is a tube with a diameter of 624 mm and the thickness of the tube wall is 1 cJmm, then the thickness of the material is represented on the film by a linear section of the cross section. These straight lines represent a certain depth within the tube, i.e. from the tube surface to the tube axis, i.e. from inside the tube. It represents a certain distance on the radius towards the heart. The projection of a point on the surface of the tube is a "cut" of 0,00 It is clear to give "pieces". If we move towards the center, we can change the value of the next intercept along each straight line representing a constant depth. Depth Section 0.5 mm 25.44 Stret 1.0 m + 1155.94 mm 1.5 mm 44.00 mm 2.0 mm 5 [1.7b mm So, 5 mm 1 03.32 mm 1 0.0 mm 1 1 2.07 mm 25.0 mm 41.23 mm Center 20.00 mm The section for depth Q, 4 mm is approximately the same as the section for the center. Based on this image reconstructed according to the prior art, the thickness of the tube wall is approximately 3 mm and Only the rollers are actually visible; the other parts cannot be determined. Furthermore, the well-known phenomenon of divergence further affects accuracy. If there is a deviation from the main beam axis along the tube axis, As the distance increases, the length of the section increases. In the example given above, for example, a 60° deviation at a depth of 10 mm would change the length of the corresponding section from 112.07 mm to 129.0 mm. This well-known method, which would increase to 4 Lmm, has been proven incorrect in the international practice of measuring tube wall thickness. This is based on the corresponding standard provisions and It is not included in the recommendations. It has been proposed to perform correction of erroneous values by comparison with a reference object also reproduced on film. If the compensating object/tin/wedge is Used in conventional inspection of joints. This is because such structures cannot be controlled arbitrarily. This is because the calculation of the intercept found on the film cannot be performed with sufficient speed and accuracy. In other applications, reproduction of substrates on film has been carried out by drilling holes of various depths in flat plates. This is before The degree of blackening obtained by projecting a hole is proportional to the depth of a given hole. However, this assumption is likely to be incorrect. This is because the scattered radiation reflected by the walls of the hole increased the degree of blackening. This way Among the various reference objects for such purposes, the one that appears to be the most important is the one published by Kralicki in Materials Eva, 1977, in February 1977. In addition to the test object, the author also reproduced several precisely calibrated standards/leads/blocks on film, and measured the wall shape of the test object and the corresponding shadow of the reference object, and Find the correct value for the tube wall thickness from Tatsuko's method is limited to tubes [with dimensions in the range of approximately 250-300 x m in diameter and tube wall thickness of no more than 20 mm], and so far has The distance between the tubes is taken to be as large as possible.Considering this advanced method, radiography is the only method that can reproduce a truly proportional projection on a single sheet of film, no matter what the dimensions of the tube. does not exist in the prior art The improvement according to the present invention is that in addition to the transversely strained tube, a combination substrate system is also provided with a filter. The reference body system that is to be reproduced on the specimen comprises a plurality of thin metal plates/foils/that are superimposed on each other.Suitably, the density of the metal foil is significantly greater than the density of the specimen under test. Although it is not necessary that the thickness of each foil layered on top of the other be the same, it is advantageous for calculations and data processing to use foils of the same thickness. If this foil is stackable, it may be convenient to mount the foil on top of a carrier layer such as paper. A reference object according to the invention comprises a plurality of foils stacked on top of each other. In the following, we will refer to this as the ``correction object'' to correct the radiographic image. It is not necessary to make the foil of the same material as the test object. The evaluation The individual foils that together constitute the correction object can also be made of different metals, provided that no interfering factors arise that cannot be taken into account. Although the influence of the modifying object on the film image can be calculated in conventional ways, e.g. by considering the surface density, the values obtained in this way are not immediately accurate. It should not be assumed that the modified object is affected by scattered radiation and For this reason, a series of tests were carried out and, on average, the number of foils per unit of tube wall thickness was determined, since under such conditions the effect of secondary radiation would also change. 'For example, 'Inn/' has the same effect and therefore gives the film the same degree of darkening. We know that the number of layers exerting this same effect does not increase linearly with thickness. The number of layers that is equivalent to a total thickness of 20 mm is not, for example, twice the corresponding number that is equivalent to a thickness of 10 mm. If you accurately calculate the required number of foils. When a reference object of known thickness is reproduced on film, it modifies the contrast conditions and therefore not only has the advantage of a comparable reference image, but also extends the visibility range. make it big In actual industrial applications, an accuracy of ±0.1 to ±0.5 is usually sufficient. Ru. During the inspection process, the required visibility/thickness range/lower and upper limits will be established taking into account the relative position of the sample of selected thickness with respect to the inner and outer surfaces of the tube. Let us consider again the example discussed above, ie, a diameter of 324 mm and a tube wall thickness of 10 mm. For example, if ±0. ．． If an accuracy of 5 mm is required, a visibility range of 25 mm to 103 mm is required. That is, a material thickness of 25 mm is already visible at the outer surface of the tube, while a tube wall thickness of 103+ nm is still visible at the inner surface of the tube. If this condition is met , the projected image of the tube wall can be determined with an accuracy of ±0.5+++ m. Ru. The /25° to 115° part of the thickness of the tube wall being examined is already visible. i.e., if the combination of reference object and correction object is properly designed and used,/depending on the properties of the radiation source/can be measured. The projected image of the tube wall can be reproduced not only by the projection method described above, but also by using the so-called 52-wall method. In this case, the film is applied to the cylindrical outer surface of the selected tube. surface, thus attached to the cylindrical jacket. The fact that the projected image of the tube wall is transformed geometrically does not mean that it cannot be determined. Accuracy is affected somewhat by this, but it is only useful for You don't have to stick to a projection you don't need, so the visibility range can be quite large. Therefore, the distance between the radiation source and the film can be selected more freely. In addition to the reconstruction of the projected image of the tube wall on film and its evaluation, it is also reasonable to determine the intercept of the cross-sectional area of the tube. It is. This means that all the data for calculations are available. If it is, it can be evaluated taking into consideration the degree of blackening of the film. this place In this case, it is not necessary to know the values of the visible tube wall projection image; in order to computationally recover the intercept belonging to any point of the film image, the coordinates of the reconstruction, the exposure data, the data for transforming the correction object, and It is sufficient to know the diameter of the tube. If you know the characteristic diagram of the section, you will be able to proceed further with the analysis. 44, the thickness of the tube wall is different from that of the radiation source and the filter. If one side of the line connecting the tube has a thin tube wall and the other side has a thick tube wall, and the projections of the thicknesses of both tube walls on the film are the same, then This confirms that the analysis of the section diagrams shows which parts have thin tube walls and which This determination, which also clearly indicates whether the section is a thick tube wall, is different from prior art methods. So I couldn't get it. If the correction object itself cannot reliably reproduce the complete projection with sufficient accuracy, additional equipment may be used to compensate for the disturbing factors. I can be there. The compensator is a homogeneous object whose practical properties, or rather its density, are equal to or at least close to the density of the test object. If the object is a tube, then of course the density is that of the tube wall/this compensator is effectively a marker wedge. That is, it is actually shaped like a wedge, or has an outer surface with two opposing faces parallel, but with less It can be a board cut so that at least one side is inclined. The thickness of this plate, and thus the height of the wedge, is of a suitable size if it is equal to the length of the longest possible section of a given specimen. This compensator is placed on the film in such a way that the longitudinal projection of its slope is perpendicular to the projection of the axis of the tube. If possible, it is equal to the distance between the axis of the tube and its outer surface. Therefore, the film image of the oblique sidewall of the compensator can be obtained independently of the film image of the brass wall. The film image obtained in this way differs from the film image according to the prior art in that the thickness of the inner wall appears at the edge of the wedge, while the thickness of the outer wall The image on the side wall will be towed on the opposite side, the thick end of the wedge. The compensator is a homogeneous body with a density comparable to that of the object to be examined, and one of its outer surfaces facing the radiation source lies at an angle ψ10°〈ψ〈9 with respect to the vertical plane of the axis of the radiation path. Only 00/ is around 1. If a non-cylindrical object is examined, the value of the angle ψ lies between/inclusive of a limit value of 300 and 60°, and if a cylindrical object or a cylindrical tube is examined, then The angle ゛ψ is according to the following formula: where D/ is the maximum length of the object under examination along the plane perpendicular to the axis of the radiation path and L' is the integral medium of which the radiation constitutes the object under examination. is the maximum length of the path through . The visible length of the outer wall corresponds to the width measured between the parallel outer faces of the compensator, while the visible length of the inner wall extends from the end of the wedge to the edge of the fill. The projection of the other parts of the tube can be seen in the area covered by the projection of the inclined side of the compensator, and its Each selected blackening value follows the intercept curve of the tube being examined.In fact, the intercept curve can be traced on the fill, or the thickness of the compensator or the ideal dimensions That is, if the dimensions are not chosen to be equivalent to the longest possible intercept, the intercept curve will be incomplete; Although there is some inaccuracy as far as the resulting scattering is concerned, even the smallest part of the intercept curve can be evaluated/if only this part is accurate/. A clear representation of the numerical proportionality between the diameter of the tube being examined and the thickness of the tube wall. The oblique part of the compensator / in its capacity as a standard wedge / for the measurement of intermediate thicknesses. It is also used for This part of the compensator, reproduced as a film image independent of the film image of the tube, also has all the darkening conditions that appear in the film image of the tube, while on the image of the tube, and On the other hand, all positions of the same degree of darkening that appear mutually comparable on the wedge image can be considered to be positions of the same thickness. The corresponding thickness value can be easily determined on a standard wedge.If the angle ψ is chosen, for example, 45°, then the thickness value of the material 5 is the distance from the end of the compensator. is a linear function of The value thus obtained can then be used to calculate the effective thickness of the tube wall. The film image created according to the present invention can be used after being enlarged several times. For example, in the case of bearings, the values of the bows and gaps can also be estimated from them. Therefore, the present invention provides an overview or insight into the internal structure of an object, e.g. make it possible to In this case, the density at different positions of this internal structure is However, blurring due to the movement of an object is a well-known phenomenon in radiographic photography. Ru. 2 is usually preferred, although movement of the object during the examination/movement that affects the projection to be reproduced may increase the blurring of the image and, in some cases, render the film unusable. not/often harmful/this situation This measurement is advantageously carried out in combination with magnification. Therefore, the present invention plays the role of disassembling and inspecting a structure that senses abnormal changes in acceleration/sway. However, if there are defects in the internal structure such as the shaft angle or failures in the gear teeth, etc. Let's consider a case where the acceleration constant is fluctuating. If the film is placed with a correction object associated with the rotation axes/or a cylindrical jacket/rotating with them, and the radiation is directed towards the film and across the width of the film. This phenomenon can be detected if the distance is as wide and parallel as possible. When there is a fluctuation in acceleration, a black band and a white band appear on the film. In the absence of acceleration fluctuations, the darkening would be uniformly distributed. The nature of the anomaly can be estimated from the location and number of such bands. It may not be possible to calculate with sufficient accuracy the appropriate number of layers to form a combined correction object.In this case, five compensators may be placed in the radiation path between the radiation source and the film. It is advantageous to arrange the degree of blackening to be progressive across the width of the film, ie from one edge of the film to the opposite edge. In such a case, there will be a greater chance that parallel bands will appear and a suitable area available for testing. The anomaly detection presented above can be used when known/easier/methods such as audio frequency rattling analysis are not applicable. The subject of the invention is An improved method for obtaining radiographic images of industrial materials. Preferably used for radiographic inspection, this method involves placing the sample/object/to be inspected at a fixed position/inspection position/in the inspection area in front of the radioreceptor. and sending radiation towards the examination position, thus selecting and, if necessary, evaluating the image obtained by taking into account the known properties of the object to be examined. The improvement is the placement of a correction object in the radiation path between the object under examination and the radiation receptor. The correction object consists of thin flat plates/foils/stacked on top of each other. It consists of a thin layered laminate obtained by This is arranged such that the axis of the radiation path has an angle of 0 to 60' with respect to the normal to the surface of the thin layer, and preferably the axis and the normal are parallel to each other, and In a preferred embodiment in which the material and superficial features of the modified object are also taken into account during the evaluation of the radiographic image, the homogeneous object/compensator/ It is arranged in the radiation path between the radiation source and the radiation receptor, ie in the radiation path in front of or behind the object under examination. The compensator is cut obliquely, and the inclined part of its outer surface faces the radiation source and at the same time has an angle ψ100<ψ>90°/ with the perpendicular plane of the axis of the radiation path. , where if the sample is a non-cylindrical object If 30°≦ψ≦600, and if a cylindrical object/tube/ is examined then tgψ−D′/L′. /D' is the maximum length of the body under examination along the perpendicular to the axis of the radiation path5, and L' is the integral medium in which the radiation constitutes the body under examination. The maximum length of the path through the body is the maximum length of the path through the body. It is also related to the body. Each lamina is in fact a homogeneous structure 5 and their density is equal to or preferably/greater than the density of the object to be examined. The thin plates are laminated together 5 and then integrated by adhesion, adhesion, thermocompression, etc. to form a thin plate laminate. The implementation of the present invention can be better understood with reference to the accompanying drawings. child The symbols in these drawings represent the following: Examples of modified projections of fi-, B, C images F radiation receptor/film/K correction object representing the reference size H compensator/standard wedge representing the reference size/L sample representing the length value M, Ml the length value Path of gamma rays passing through section, object, and H /i = 1, 2, ... /S Thickness of tube wall U Axis correction of rotating object Holding to fix the object and film on top of the rotating object Belt for Q・Q Nakagami+(i=1.2.・−) etc. Position of radiation source ω Angular velocity of steady rotation /4− Ideal position of peak of intercept X Total thickness of tube wall through which radiation passes X ′ Thickness of the correction object ab Number of thin plates composing the correction object Door millimeters Position on the outer surface of the tube (ε=1.2...) Lm Height of the correction object according to the prior art Lml According to the invention Height of the Modified Object Although the drawings can be easily understood by those skilled in the art after careful study of the description given above, it is difficult to explain. For the sake of clarity, we will provide some necessary outlines: Fig. 1: Nonlinear equivalent diagram of the pb correction object for the Fe sample Fig. 2: Intersection M and plowing of a tube with radius R1 and tube wall thickness S Their envelope/cut Piece curve / Figure 6: Intersection and intercept curve /envelope of a homogeneous planar object with a certain density, like the tube in Figure 2. have Figure 5: Shape of intercept M and intercept curve as a function of radiation source distance / A is far, B is close / in the case of concentric tube walls Figure 6: Non-concentric tube walls Modified view of Fig. 5 in case of concentric tube wall, Fig. 7: Sample plate and tube wall in case of 6 different projections / Modified projection examples of A, B and C / with ridge as the position of the radiation source. The relative position of the thickness S5 compensator H1 to the correction object and the film F FIG. 8: The arrangement is the same as in FIG. The intercept curve/envelope/ which represents the position of the same degree of blackening is shown in Figure 3. When a compensator H is used, the modified example B is an image obtained using a smaller compensator H, and the modified example C is obtained when a larger compensator H is used. 9N: Conditions are as shown in Figure 8. Figure 10: The same conditions as in Figure 8, but with a higher exposure. Figure 11: Rotation arranged as shown in Figure 12. A reconstructed image of the radiographic image obtained when inspecting an object; band changes/black and white/are shown: In case A, this is the image obtained without using a compensator, and in case B, Figure 12: An object rotating with a nominal angular acceleration ω is examined; the holding base is A sample sample to be inspected together with a film F fixed by a bolt and a correction object is provided at an axis U. Which position is the radiation? Collimation in the form of a narrow groove is created by the collimator P placed facing the radiation source. / This collimator is shown with enlarged dimensions for practical reasons. ru/. If a compensator H is used, as shown in case B of FIG. If no compensator is used, the image will appear as shown in case A. Figure 1 shows the effect of the thickness of a given material in trial 1 on the film image. In other words, whether to give the same blackened points. The curves illustrated in Figure 1 are for the case where the sample is made of iron; In the example given, where the tube wall is made of lead and it is mounted on paper as a separate carrier, one division of the tube wall thickness on the horizontal axis represents 20 mm. , and each division of the number of lead foils on the vertical axis represents 10 foils. Each 10 mm tube wall thickness is equal to 100 foil laminates, 20 mm is equal to 2 40 foils, and 30+nm is equal to 480 foil laminates, respectively. equal Of course, this is just one example; the practical properties may vary from application to application, even for iron and lead); This is because it is also possible to have different thicknesses. In devices already in practical use, the corresponding data for F'e -Pb is They are 44 foils, 112 foils, and 192 foils, respectively. Compare Figure 5 and Figure 2. As you can see from Figure 5, gamma rays cross the tube through different routes. If the radiation source is far away, as in side A of Figure 5, these paths will be nearly parallel to each other, but if the radiation source is close, such as at position γ1, For example, the effect of the deviation discussed above occurs, and the paths become deviated from each other by being categorized along the circle centered on the ridge./See side B in Figure 5/Thus, the radiation source If it is far away, the reproduction diagram shown on the side of A in FIG. 5/shown above the tube is changed. In this case, section M1 is the longest section. It means that the path of the γ rays across the tube wall is at point ε on the outer surface of the tube. From the point ε3 to the point ε2, it is one continuous path, so if we proceed towards the outer surface of the main pipe, the intercept M6 between the five points ε3 and ε4 will be regenerated along one continuous path, but, It can be seen that it is considerably shorter than the intercept M1. On the other hand, if the axis/middle of the tube If we proceed towards the center Q/, for example in a plane containing points ε5 and ε6, then the path in the integral medium forming the tube consists of two parts. So, one is the path between point ε5 and point ε7, and the other is the path between point ε8 and point ε6, and the sum of the two parts of this path is the intercept M5. However, this is much shorter than M and is approximately equal to the intercept M6. Therefore, the reproduced view shown on the A side of Figure 5 is the main beam from the distant radiation source. This is a film image obtained by a camera, and there is no distortion due to misalignment. In this case, This is shown in Figure 2. If we place a correction object in the radiation path that is a solid planar object, which has already been done in the prior art, then the reproduction view will be modified as shown in FIG. Dew. In this case, the intercept M of the tube reconstruction map and the intercept of the modified object reconstruction diagram are simply added. Therefore, the case shown in Figure 2 No further useful information can be obtained regarding the situation. However, if the correction object according to the invention is used, the reproduced figure will actually be corrected. cormorant. As can be seen from FIG. 4, the parts of the correction object lying outside the outer wall of the tube appear in the same manner as the corresponding parts of the prior art correction object of FIG. If the sample and correction object are reproduced together, the resulting intercept M in Figure 6 is a linear addition of the sample thickness and the combined correction object thickness. In contrast, the intercept obtained in Figure 4 represents the sum of individual values added nonlinearly. If so, does the sum of the sample section and the correction object section have a nonlinear relationship at different positions of the tube, as shown in Figure 1? It is et al. If the path of a gamma ray in the sample, a larger thickness value means that the equivalent of this thickness can only be obtained with a larger number of foils than for a shorter path. However, the modified object remains unchanged. The longer the effective length in the medium that has been The amount of addition made becomes smaller and smaller. Therefore, the resulting intercept becomes smaller depending on the path within the sample, according to the curve shown in FIG. As can also be seen from FIG. 5, the effective position of the radiation source also determines the position of any section along the horizontal axis, so that the section on side A of FIG. Intercepts distributed along the same radius shown on the side also have shorter bases along the horizontal axis. occupies an area with a line. Let us consider the case where the position of the radiation source is the same, that is, at the edge, but the center of the inner tube wall surface and the center of the outer tube wall surface of the sample are different. The reproduction diagram in this case changes, but it changes as if the radiation source had moved a little. See Figure 6. Moreover, not only the position will change, but also the length of the intercept will become smaller, as if obtained by a different degree of offset. Therefore, not only can it be observed that the centers of the tube walls are different. You can determine which side's walls are thicker and which side's walls are thinner. FIG. 7 is a diagram illustrating the standard wedge mechanism previously described in this specification of the invention. In case A of Fig. 7, the arrangement is considered from the direction perpendicular to the axis of the radiation path, and in case C, the only difference is that the axis is rotated by 90'. Case B is a projection view of the arrangement considered from behind the radiation path in the direction of said axis. These projections are A in Figure 8. The same is true for B and C. In FIG. 8, the film image obtained with this arrangement is shown in a schematic diagram showing the important features. In the film image, the section curve is Lines represent positions of the same darkening degree. In the ditch exposure 〈IJl Figure 91 Atsushi 12. Seki Procedural amendment (method) % formula % Relationship to case Patent applicant November 27, 1981 6. Number of inventions increased by amendment 7. Subject of amendment