JPH06265488A - Nondestructive inspection unit - Google Patents

Abstract

PURPOSE:To secure an optimum contrast easily even in the case of a complex inspected work by calculating the extent of perpendicular transmitted damping in the inspected work, and determining an optimum inspecting condition after searching the contrast (damping degree) so as to become as large (small) value as possible. CONSTITUTION:An input part 1 inputs structure, composition or the like of an inspected work, for example, thickness of each layer and layer numbers through an input unit 2. A contrast operational part 3 calculates a wavelength pair contrast characteristic of the inspected work on the basis of mass absorption coefficient, density, thickness inherent in a composition of each layer from data out of the input part 1. In addition, a transmitted intensity operational part 7 operates the extent of transmitted intensity in the inspected work, and from the contrast and X-ray transmitted intensity calculated (3, 7), a condition searching part 8 searches that the contrast is large but the damping degree is small as far as possible, thereby determining the optimum inspection condition. X-rays controlled on the basis of this optimum inspection condition is generated (12), irradiating it to the inspected work 13, and it is picked up (14) by a camera. With this constitution, an optimum contrast is easily securable even to such an inspected work as having complex form and composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nondestructive inspection apparatus using an electromagnetic wave having a property of transmitting a substance.

[0002]

2. Description of the Related Art When a microdefect inside an object to be inspected is viewed as a television image by a nondestructive inspection apparatus, the material transmission characteristics of electromagnetic waves represented by X-rays are the constituent elements of the object to be inspected, the thickness, and the size of the defect. The problem was how to set the optimum inspection conditions for inspected objects that differed depending on the wavelength.
Here, X-rays will be described as a typical electromagnetic wave. First, the characteristics of the continuous X-ray generating tube will be briefly described. Approximately 0.04Å (angstrom) in the wavelength band
Taking a non-destructive inspection device using X-rays of up to 2.0 Å as an example, the conditions for determining the intensity of X-rays to be irradiated are determined by the voltage and current applied to the X-ray tube. FIG. 4 is a diagram showing the relationship between the applied voltage and the X-ray intensity and wavelength. When the voltage is increased as described above, the X-ray intensity increases and the X-ray wavelength range extends to the short wavelength side. Further, when the voltage is lowered, the X-ray intensity is lowered as a whole, and the X-ray generation wavelength range shifts to the long wavelength side. On the other hand, when the current is changed (not shown), the generated X-ray wavelength range does not change and the X-ray intensity changes. That is, increasing the current increases the strength, and decreasing the current decreases the strength. By the way, each substance has its degree of absorption (mass absorption coefficient) according to the wavelength of X-rays. FIG. 2 shows the relationship between the wavelength of X-rays and the degree of absorption, that is, the mass absorption coefficient. As shown in FIG. 2, generally, the longer the wavelength, the higher the absorption. There is a point that the degree of absorption is greatly reduced. This is called the absorption edge. If the wavelength is long, the degree of absorption is large and the contrast is good, but the transmitted X-ray intensity becomes small, and sufficient transmitted X-ray intensity cannot be obtained depending on the thickness of the inspection object. However, if conditions can be set such that the maximum intensity of the irradiated X-rays is set to the wavelength a before falling to the absorption edge, good results can be expected in terms of contrast as well as in terms of transmission ability because the wavelength is short. That is,
Both contrast and transmitted X-ray intensity are compatible. However, if the object to be inspected has a single-element / single-layer structure, it is possible to take the absorption edge into consideration and set the X-ray intensity to inspect even with the conventional empirical setting method, but the object to be inspected is different. If it is a compound or mixture of elements, or if layers with such composition are stacked, it will be difficult to estimate the total absorption coefficient including the absorption edge, and do not overlook the optimum inspection conditions. You need to be careful. Therefore, the conventional nondestructive inspection device
In order to visually recognize minute defects in the object to be inspected, the voltage and current of the X-ray generating tube have been adjusted empirically while looking at the screen or by trial and error so as to obtain the optimum contrast.

[0003]

As described above, conventionally, the optimum inspection condition was empirically sought while looking at the screen. However, it is necessary to set the condition for the inspection object having a complicated shape and composition. It has a drawback that it takes time and misses a singular point such as an absorption edge. SUMMARY OF THE INVENTION In order to solve these drawbacks, the present invention has an object to obtain a point that satisfies both conditions of good contrast and transmission attenuation as small as possible as an optimum inspection condition even in a complicated object to be inspected. .

[0004]

In order to solve such a problem, the present invention models an object to be inspected and its expected internal defects, inputs the number of layers, the thickness and the composition, and detects defects. Calculate the difference in the intensity of electromagnetic waves transmitted through the part and the part that does not exist, that is, the contrast, and further calculate the transmission attenuation in the thickness direction of the inspection object so that the contrast is as large as possible and the attenuation is as small as possible. The search is performed to determine the optimum inspection conditions. That is, the present invention is a device for inputting and storing information about an object to be inspected (for example, structure, composition and atomic number of each element, data such as atomic weight and mass absorption coefficient at each wavelength).
A contrast calculation means, a simulation means for an electromagnetic wave spectrum that can be generated in the electromagnetic wave generation tube, a transmission intensity calculation means for calculating the transmission intensity of the object to be inspected from the simulation result by the simulation means, and a calculation result of the transmission intensity calculation means. It is composed of condition search means for searching the optimum inspection condition from the calculation result of the contrast calculation means.

[0005]

When the structure / composition of the object to be inspected is input from the object information input means, the data such as the mass absorption coefficient is taken into the contrast calculating means from the information storage means based on this information, and the contrast for each wavelength is calculated. Then, the simulation calculation means calculates the electromagnetic wave spectrum waveform data that can be generated in the electromagnetic wave generation tube of the present apparatus, and the transmission intensity calculation means calculates the attenuation degree. Search the optimum inspection condition from the attenuation,
An electromagnetic wave is generated by this condition data (for example, applied voltage and current), and the inspection object is irradiated with the electromagnetic wave.

[0006]

EXAMPLES Examples of the present invention will be described below by taking a nondestructive inspection apparatus using a continuous X-ray generation tube as an example. FIG. 1 is a block diagram showing an example of the overall configuration of the present invention. In the figure, reference numeral 1 is an input unit for the structure and composition of the object to be inspected.
As the information of the object to be inspected, the thickness of each layer and the number of layers are input as shown in FIG. For the composition of each layer, enter the atomic number and molecular weight of each element of each layer. Also, enter the density of each layer. An input device 2 for these data is a keyboard, for example. If the atomic weight and mass absorption coefficient are saved as program data, these data are automatically selected as long as the atomic number is entered, and there is no need to newly enter them. A contrast calculator 3 calculates the wavelength-contrast characteristic of the object to be inspected (laminated state) from the mass absorption coefficient, density and thickness peculiar to the composition of each layer. Four
Is a data storage unit of the atomic number of each element, atomic weight and mass absorption coefficient at each wavelength, 6 is a simulation calculation unit of the electromagnetic spectrum that can be generated by this device, 7 is a transmission intensity calculation unit of the inspection object, and 8 is a contrast. A condition search unit for setting the optimum inspection condition from the contrast calculated by the calculation unit 3 and the transmission intensity of the X-ray calculated by the transmission intensity calculation unit 5, and 5 is a dedicated or combined use for displaying the calculation results 3 to 8. Display unit 9, an interface for transferring the conditions determined by the condition search unit 8 as data, 10 an X-ray generation control unit for controlling X-rays based on the optimum inspection conditions, and 11 an X-ray generation control unit.
A cabin for preventing leakage of electromagnetic waves such as rays, 12 is an X-ray generator, 13 is an object to be inspected, 14 is a TV camera imaging device using direct image capturing or an image intensifier tube, and 15 is an imaging device. It is a display device such as a television monitor for displaying an image. The above is the configuration of the entire apparatus. Next, the operation peculiar to the present invention will be described with reference to a block diagram of main parts.
FIG. 3 is a block diagram showing details of main parts of the present invention. First, each part of the figure will be described. In the input unit 1, 16 is a data input unit regarding the number of layers of the object to be inspected and the thickness of each layer, 17 is a data input unit regarding the composition and density of each layer,
Reference numeral 18 is a portion (the number of layers in which the defect is present) in which it is presumed that micro defects are present, and an estimated size data input portion of the defect portion, and 19 is a data input portion regarding the composition and density of the defect. Each of these blocks temporarily stores respective data. The block shown in the transmission intensity calculation unit 7 is an operation flowchart, and 20 is a distinction whether the transmission intensity calculation is executed in the manual mode or the automatic mode. In the manual case, the flow proceeds to 21. In the automatic case, 25 is entered. Reference numeral 22 is a condition for manual operation, for example, setting input of a voltage value, and 23 is to calculate the transmission attenuation of the defective portion and the defective portion according to the designated condition. Reference numeral 24 is a function for determining whether or not the manual setting is completed. The display unit 5 displays these series of operating conditions. Reference numeral 26 is a setting function for automatically updating the condition, for example, the voltage value in a predetermined width. 27 calculates the transmission attenuation of the defective portion and the non-defective portion according to the designated conditions. FIG. 6 is a display example of contrast data, in which the vertical axis represents contrast and the horizontal axis represents wavelength. FIG. 7 is a display example of the transmission attenuation degree. This operation will be described below. Information on the object to be inspected is modeled and input as shown in FIG. FIG. 5 shows an example of the case of three layers, and the thicknesses L ₁ , L ₂ and L ₃ of each layer and the number of laminated layers 3 are input. Regarding the composition of each layer, for example, if the first layer is a substance of Al ₂ O ₃ , the atomic number of each element,
The molecular weight is input from the input device 2. Further, the densities ρ ₁ , ρ ₂ , ρ ₃ of each layer are input, and these data are stored in 16 and 17 of the input unit 1. For the defect, the stacking number and size expected to exist are given, and for the composition, the atomic number, the molecular weight, and the estimated density are input as described above. These data are stored in 18 and 19 of the input unit 1. The contrast calculator 3 obtains the contrast as follows based on these data. For example, when the object to be inspected has a configuration as shown in FIG. 5, the contrast calculation unit 3 calculates the contrast C with respect to the wavelength by the following equations (1) and (2).
To calculate. I ₁ = I _o exp {-(μ ₁ · ρ ₁ · L ₁ + μ ₂ · ρ ₂ · L ₂ + μ ₃ · ρ ₃ · L ₃ )} I ₂ = I _o exp {-(μ ₁ · ρ ₁ · L ₁ + μ ₂ · ρ ₂ · L ₂ + μ ₃ · ρ ₃ (L ₃ −Δx) + μ · ρ · Δx)} (1) I ₁ : Transmission X-ray intensity of defect-free portion I ₂ : Defect portion Transmitted X-ray intensity I _o : Irradiated X-ray intensity ρ: Density of defect part ρ ₁ , ρ ₂ , ρ ₃ : Density of each layer μ ₁ , μ ₂ , μ ₃ : Mass absorption coefficient of each layer μ: Mass of defect part Absorption coefficient L ₁ , L ₂ , L ₃ : Thickness of each layer C = I ₂ / I ₁ = exp {(μ ₃ · ρ ₃ −μ · ρ) Δx} (2) C: Contrast Inspected against wavelength The mass absorption coefficient of each element of the object is already stored in the data storage unit 4, but all of these data are for a single element. In the case of the substance Al ₂ O ₃ as the above example, the mass absorption coefficient is Because of the additivity of It is obtained by the formula (3). μAL × MAL / MALO + μO × MO / MALO (3) where μAL: mass absorption coefficient of Al at a specific wavelength MAL: molecular weight of Al MALO: molecular weight of Al ₂ O ₃ mass absorption of μO: O at a specific wavelength Coefficient MO: molecular weight of O By calculating this for each wavelength, the data of wavelength vs. contrast (contrast of the X-ray relative intensity passing through the defect portion and the X-ray relative intensity passing through the non-defect portion) as shown in FIG. can get. Also, this data naturally includes the above-mentioned absorption edge information. The calculation result of the contrast calculation unit 3 of FIG. 6 is displayed on the display unit 5 in the form as shown in FIG. The simulation calculator 6 has a function of calculating the X-ray spectrum waveform condition of the relative intensity, that is, the spectrum of the X-ray relative intensity when the voltage applied to the X-ray generating tube is variously changed. This X-ray relative intensity spectrum is represented by relative intensity with respect to wavelength as shown in FIG. Next, the transmission intensity calculator 7
The operation of will be described. By associating the wavelength of the contrast data with this X-ray relative intensity spectrum,
It is possible to read the voltage value that produces the spectrum in which the relative intensity of X-rays is maximum at the wavelength where the maximum contrast is obtained. For example, in the case of a substance to be inspected having a contrast characteristic as shown in FIG. 6, it is understood that the wavelength a is preferably used because the absorption edge described above is located on the slightly longer wavelength side than the wavelength a. From the frequency spectrum of relative intensities when the applied voltage is changed, it can be seen that the applied voltage A that produces the spectrum having the maximum intensity at the wavelength a is the optimum applied voltage. That is, even if the condition (voltage) that maximizes the contrast is set, if the attenuation is large, it is usually not possible to obtain sufficient brightness for an image. In this embodiment, there are a manual mode and an automatic mode as a voltage setting method. In the manual mode, the operator judges from the contrast data (shown in FIG. 6) and the X-ray spectrum waveform (shown in FIG. 4) displayed on the display unit 5. Set the condition (voltage) that seems to be appropriate. The transmission attenuation calculator 23 calculates the transmission attenuation in the thickness direction for the wavelength having the maximum intensity in the spectrum generated by the voltage. FIG. 7 shows the result of this calculation. In the case of the automatic mode, the operator automatically sets the condition (voltage) instead of setting the condition (voltage). In this case, the calculation result is sent to the condition search unit 8. The condition search unit 8 searches for wavelengths that satisfy the two conditions of the contrast being as large as possible and the attenuation being as small as possible, based on the data of the contrast calculating unit 3 and the transmission intensity calculating unit 7. This operation is shown in the flowchart of FIG. Here, first, the wavelength a that gives a large contrast is obtained at the shortest possible wavelength (see FIG. 6).
Next, the voltage A having the peak of the wavelength a is obtained (see FIG. 4). Next, the degree of attenuation of the defective portion and the non-defect portion corresponding to the thickness of the object to be inspected is obtained, and whether the intensity of the X-ray transmitted at the voltage A is sufficient (that is, is not excessively attenuated).
Is determined. If the result of determination is that attenuation is excessive, wavelength a'is set to a wavelength shorter than wavelength a (that is, in the direction of increasing the X-ray intensity), and as described above, search is performed until the transmission attenuation becomes appropriate. In this way, the condition (voltage) value obtained in either manual or automatic is set in the X-ray generation controller 10 via the interface 9 to irradiate the object to be inspected. The configuration after the X-ray generation control unit 10 is a well-known X-ray generation image pickup device, and thus detailed description thereof will be omitted. Although a plurality of display units 5 are provided in the above description of the embodiment, one display unit 5 may be shared or divided display may be performed.

[0007]

EFFECT OF THE INVENTION When the object to be inspected is a compound or mixture of a plurality of different elements, or when layers having such a composition are stacked, it becomes difficult to estimate the total absorption coefficient, which is optimum. Care must be taken not to overlook the inspection conditions. Therefore, conventionally, while looking at the screen, we empirically searched for the optimum inspection conditions, but this takes time to set the conditions for the inspection object having a complicated shape and composition.
Moreover, a singular point such as an absorption edge may be missed. However, according to the present invention, it is possible to realize a non-destructive inspection apparatus having a complicated shape / composition and easily obtaining an optimum contrast even for an object to be inspected, and it is possible to significantly improve the inspection efficiency.

[Brief description of drawings]

FIG. 1 is an overall configuration block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of mass absorption characteristics.

FIG. 3 is a detailed block diagram showing an embodiment of the present invention.

FIG. 4 is a diagram showing an example of relative intensity characteristics.

FIG. 5 is a diagram showing an example of a modeled inspection object.

FIG. 6 is a diagram showing an example of contrast-wavelength characteristics.

FIG. 7 is a diagram showing a relationship between transmission intensity and thickness.

FIG. 8 is an operation flowchart of a condition search unit.

[Explanation of symbols]

 1 Structure / Composition Input Section of Inspected Object 3 Contrast Operation Section 6 X-Ray Spectral Waveform Simulation Section 7 Transmission Intensity Operation Section 8 Condition Search Section 10 X-Ray Generation Control Section 12 X-Ray Generator 13 Inspected Object

Claims (3)

[Claims] 1. The characteristics of the substance to be inspected are input, the transmission attenuation in the thickness direction of the inspected substance is calculated, and the conditions under which the contrast is as large as possible and the attenuation is as small as possible are searched, and the optimum inspection is carried out. Nondestructive inspection device characterized by defining conditions 2. The characteristics of the substance to be inspected are inputted, the difference in the intensity of electromagnetic waves transmitted through a portion with and without defects is calculated, the transmission attenuation in the thickness direction of the object to be inspected is calculated, and the contrast is as large as possible. A non-destructive inspection device characterized by searching for conditions where the value and attenuation are as small as possible and determining the optimum inspection conditions. 3. A non-destructive inspection apparatus for observing defects and shapes inside an object to be inspected by using an electromagnetic wave having a property of transmitting a substance, means for inputting characteristics of the object to be inspected, and the inspection device. Means for calculating a transmitted electromagnetic wave intensity contrast between a defective portion and a non-defective portion corresponding to a possible electromagnetic wave wavelength band, a means for simulating a spectrum of a wavelength versus relative intensity of an electromagnetic wave that can be generated by the inspection device, A means for setting condition data for determining an electromagnetic wave spectrum for generating an electromagnetic wave, a means for calculating a transmission attenuation characteristic in the thickness direction of a sample to be inspected, a contrast and an attenuation degree from the contrast data and the transmission attenuation characteristic data. Non-destructive inspection device consisting of means for searching wavelengths that satisfy both optimum values of