Measurement device, measurement method, and measurement program

Abstract

To clarify the allowable deviation between the irradiation center of X-rays before attenuation by an object to be measured and the irradiation center of X-rays after attenuation by the object to be measured, in accordance with the required accuracy in a measurement device using X-rays.SOLUTION: The measurement device comprises an irradiation unit, a detection unit, and a processing unit. The processing unit calculates thickness on the basis of the difference in brightness at a measurement point between a background image of the brightness distribution of irradiated X-rays and a target image of the brightness distribution of transmitted X-rays, obtains the required accuracy for thickness measurement, calculates a tolerance value that meets the required accuracy for the difference in X-ray brightness between the background image and the target image at the measurement point, which occurs due to a misalignment of the irradiation center of the irradiated X-rays between the background image and the target image, derives an allowable range of brightness at the measurement point in the background image that meets the required accuracy on the basis of the tolerance value, and derives an allowable range for the pixels of the background image on the basis of the allowable range of brightness at the measurement point.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a measuring device, a measuring method, and a measuring program, and more particularly to a measuring device, a measuring method, and a measuring program that are suitable for measuring the thickness of an object to be measured. [Background technology]

[0002] For example, adhesives are used to join two parts made of materials such as metal or plastic. To check whether the adhesive is used to the required thickness, destructive testing was the mainstream method, where the joined parts are extracted and destroyed. This destructive testing is a cause of the work load, increased costs, and waste associated with the destruction.

[0003] Therefore, a measuring device that measures adhesive thickness non-destructively has been proposed (see, for example, Patent Document 1). The measuring device disclosed in Patent Document 1 is capable of measuring the thickness of an object by irradiating the object with X-rays and measuring the X-ray brightness absorbed and attenuated by the object. The measuring device disclosed in Patent Document 1 obtains the difference between the X-ray brightness before and after attenuation by the object at the thickness measurement point, and calculates the thickness at the measurement point based on this difference.

[0004] Generally, the brightness of the X-rays emitted from the X-ray irradiation unit is not uniform, and the X-ray brightness at the measurement point changes depending on the distance between the thickness measurement point and the center of the X-ray irradiation. For this reason, if the center of the X-ray irradiation before attenuation by the object and the center of the X-ray irradiation after attenuation by the object are misaligned and do not match, it is known that this misalignment can cause errors in the measured thickness of the object. Therefore, there has been a demand for a measuring device that uses X-rays and that takes into consideration the tolerance for deviation of the irradiation center described above according to the required accuracy of the measurement. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-182140 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a measurement device, a measurement method, and a measurement program that can clarify the tolerance for the deviation between the irradiation center of X-rays before attenuation by the object being measured and the irradiation center of X-rays after attenuation by the object being measured, in accordance with the required accuracy of the measurement, in a measurement device using X-rays. [Means for solving the problem]

[0007] That is, the measuring device of the first aspect is a measuring device used for measuring the thickness of an object to be measured, and the measuring device comprises: an irradiation unit that irradiates X-rays onto the object to be measured; a detection unit that detects X-rays that have passed through the object to be measured; and a processing unit that estimates the thickness of the object to be measured based on the attenuation of the X-rays that have passed through the object to be measured. The processing unit is characterized by comprising: a calculation unit that calculates the thickness at the measurement point based on the difference in brightness at the measurement point of the object to be measured between a background image of the brightness distribution of X-rays irradiated from the irradiation unit and a target image of the brightness distribution of X-rays that have passed through the object to be measured; a required accuracy acquisition unit that acquires the required accuracy for measuring the thickness of the object to be measured; a tolerance calculation unit that calculates a tolerance that satisfies the required accuracy of the difference in brightness of X-rays between the background image and the target image at the measurement point, which occurs due to a misalignment of the irradiation center of the X-rays irradiated from the irradiation unit between the background image and the target image; a brightness tolerance range derivation unit that derives an allowable range of brightness at the measurement point in the background image to satisfy the required accuracy based on the tolerance; and a pixel tolerance range derivation unit that derives an allowable range for the pixels of the background image based on the allowable range of brightness at the measurement point.

[0008] In a second aspect, in the measurement device according to the first aspect, the tolerance calculation unit may calculate the tolerance based on the brightness of the measurement point in the background image, the required accuracy, and the brightness absorption coefficient of the object to be measured.

[0009] A measurement method according to a third aspect is a measurement method used in a measurement device used to measure the thickness of an object to be measured, the measurement device comprising an irradiation unit that irradiates X-rays onto the object to be measured, a detection unit that detects the X-rays that have passed through the object to be measured, and a processing unit that estimates the thickness of the object to be measured based on the attenuation of the X-rays that have passed through the object to be measured, wherein the processing unit executes the following steps: a calculation step that calculates the thickness at the measurement point based on the difference in brightness between a background image of the brightness distribution of X-rays irradiated from the irradiation unit and a target image of the brightness distribution of X-rays that have passed through the object to be measured; a required accuracy acquisition step that acquires the required accuracy for measuring the thickness of the object to be measured; a tolerance calculation step that calculates a tolerance that satisfies the required accuracy for the difference in X-ray brightness between the background image and the target image at the measurement point, which occurs due to a positional shift of the irradiation center of the X-rays irradiated from the irradiation unit between the background image and the target image; a brightness tolerance area derivation step that derives an allowable range of brightness at the measurement point in the background image to satisfy the required accuracy based on the tolerance; and a pixel tolerance range derivation step that derives an allowable range for pixels in the background image based on the allowable range of brightness at the measurement point.

[0010] A measurement program according to a fourth aspect is a measurement program used in a measurement device used to measure the thickness of an object to be measured, the measurement device comprising an irradiation unit that irradiates X-rays onto the object to be measured, a detection unit that detects X-rays that have passed through the object to be measured, and a processing unit that estimates the thickness of the object to be measured based on the attenuation of the X-rays that have passed through the object to be measured, and the processing unit is characterized by realizing: a calculation function that calculates the thickness at the measurement point based on the difference in brightness at the measurement point on the object to be measured between a background image of the brightness distribution of X-rays irradiated from the irradiation unit and a target image of the brightness distribution of X-rays that have passed through the object to be measured; a required accuracy acquisition function that acquires the required accuracy for measuring the thickness of the object to be measured; a tolerance calculation function that calculates a tolerance that satisfies the required accuracy of the difference in brightness of X-rays between the background image and the target image at the measurement point, which occurs due to a misalignment of the irradiation center of the X-rays irradiated from the irradiation unit between the background image and the target image; a brightness tolerance area derivation function that derives an allowable range of brightness at the measurement point in the background image to satisfy the required accuracy based on the tolerance; and a pixel tolerance range derivation function that derives an allowable range for the pixels of the background image based on the allowable range of brightness at the measurement point. [Effects of the Invention]

[0011] The measuring device etc. according to the present invention is a measuring device used for measuring the thickness of an object to be measured, and the measuring device includes an irradiation unit that irradiates the object with X-rays, a detection unit that detects the X-rays that have passed through the object to be measured, and a processing unit that estimates the thickness of the object to be measured based on the attenuation of the X-rays that have passed through the object to be measured, and the processing unit includes a calculation unit that calculates the thickness at the measurement point based on the difference in brightness between a background image of the brightness distribution of the X-rays irradiated from the irradiation unit and a target image of the brightness distribution of the X-rays that have passed through the object to be measured, a required accuracy acquisition unit that acquires the required accuracy for measuring the thickness of the object to be measured, and a difference in brightness between the background image and the target image of the X-rays irradiated from the irradiation unit. The measurement device is characterized by comprising a tolerance calculation unit that calculates a tolerance that satisfies the required accuracy of the X-ray brightness difference between a background image and an object image at a measurement point, which occurs due to a positional shift of the irradiation center of the X-ray; a brightness tolerance range derivation unit that derives an allowable range of brightness at the measurement point in the background image that satisfies the required accuracy based on the tolerance; and a pixel tolerance range derivation unit that derives an allowable range for pixels in the background image based on the allowable range of brightness at the measurement point.Therefore, in a measurement device using X-rays, it is possible to clarify the allowable amount of deviation between the irradiation center of X-rays before attenuation by the object to be measured and the irradiation center of X-rays after attenuation by the object to be measured, according to the required accuracy imposed on the measurement. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram for explaining the characteristics of X-rays used by the measurement device of this embodiment. [Figure 2] FIG. 2 is a diagram for explaining a background image of the measurement device of this embodiment. [Figure 3] FIG. 3 is a diagram for explaining the target image of the measurement device of this embodiment. [Figure 4] FIG. 4 is a diagram for explaining the positional deviation of the irradiation center of the measurement device of this embodiment. [Figure 5] FIG. 5 is a graph for explaining the positional deviation of the irradiation center of the measurement device of this embodiment. [Figure 6] FIG. 6 is a block diagram for explaining an example of the hardware configuration of the measurement device of this embodiment. [Figure 7] FIG. 7 is a block diagram for explaining an example of the functional configuration of the measurement device of this embodiment. [Figure 8] FIG. 8 is a diagram for explaining the allowable range of brightness and the allowable range of pixels of the measurement device of this embodiment. [Figure 9] FIG. 9 is a graph for explaining the brightness gradient of X-rays in the measurement device of this embodiment. [Figure 10] FIG. 10 is a flowchart of the measurement program of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Overview of the measuring device 10 and X-ray 2) With reference to FIG. 1, the characteristics of X-rays 2 used by a measurement device 10 according to an embodiment of the present disclosure will be described. The measuring device 10 is used to measure the thickness of an object 1 to be measured. The measuring device 10 includes an irradiation unit 10j, a detection unit 10h, and a processing unit 10e (see FIG. 6). The irradiation unit 10j irradiates the object 1 to be measured with X-rays 2. The detection unit 10h detects the X-rays 2 that have passed through the object 1 to be measured. The processing unit 10e estimates the thickness of the object 1 to be measured based on the amount of attenuation of the X-rays 2 that have passed through the object 1 to be measured. The attenuation (decay) of X-rays 2 refers to the phenomenon in which the intensity (also called energy or brightness) of X-rays 2 decreases as they pass through a material and interact with the material.

[0014] The irradiation unit 10j includes an X-ray source for generating X-rays 2. An X-ray tube is used as the X-ray source, and the X-ray tube includes an anode, a cathode, and a vacuum envelope that houses them. By applying a high voltage between the anode and the cathode, high-speed electrons emitted from the cathode collide with the anode, generating X-rays 2. Because X-rays 2 are attenuated by air as they pass through it, the longer the optical path length 3 (3a, 3b) of the X-rays 2, the greater the amount of attenuation of the X-rays 2. Therefore, the optical path length 3a between the irradiation center 21 of the X-rays 2 on the detection unit 10h and the irradiation unit 10j is the shortest, so the brightness of the X-rays 2 detected by the detection unit 10h is highest at the irradiation center 21. Furthermore, because the optical path length 3b on the detection unit 10h becomes longer the farther away from the irradiation center 21, the brightness of the X-rays 2 detected by the detection unit 10h is distributed so that it decreases radially the farther away from the irradiation center 21, and the brightness of the X-rays 2 on concentric circles at a certain distance from the irradiation center 21 is equal.

[0015] The detector 10h has a scintillator on its detection surface. When X-rays 2 enter the scintillator, atoms in the scintillator are excited and emit photons. The detector 10h detects the X-rays 2 by amplifying the emitted photons and converting them into an electrical signal. A scintillator is a phosphor material that has the property of absorbing high-energy radiation such as X-rays2 and instantly emitting fluorescence.

[0016] As shown in FIGS. 2 and 3, the irradiation unit 10j is attached to the tip of the first arm robot 100, and the detection unit 10h is attached to the tip of the second arm robot 110. The measuring device 10 is used to measure the thickness of an internal component 23 (see FIG. 4), such as an adhesive used to bond steel plates together, for example, in an automobile door as the object 1 to be measured. It can also be used to measure the thickness of ribs formed in a casting such as a die-cast. The internal component 23 is not limited to an adhesive, and may be an organic material such as plastic or rubber. The object 1 to be measured is not limited to a car door, but may be any material that has the property of transmitting X-rays 2, such as a metallic, non-metallic, or organic material. As shown in FIGS. 2 and 3, the DUT 1 is placed on the mounting table 120 while being supported by a jig 130 .

[0017] First, as shown in FIG. 2, the measuring device 10 irradiates X-rays 2 from the irradiation unit 10j toward the detection unit 10h in a location where there is no object to be measured 1, and acquires a background image 20 showing the brightness distribution of the X-rays 2 detected by the detection unit 10h. The background image 20 (see Figure 4) shows the brightness distribution of the X-rays 2 irradiated from the irradiation unit 10j, and is an image of the brightness distribution of the X-rays 2 detected by the detection unit 10h when there is nothing (such as the object to be measured 1) that attenuates the X-rays 2 other than air between the irradiation unit 10j and the detection unit 10h.

[0018] Next, as shown in Figure 3, the measuring device 10 operates the first arm robot 100 and the second arm robot 110 to irradiate the object 1 with X-rays 2 and obtain an object image 19 showing the brightness distribution of the X-rays 2 that have passed through the object 1. The first-arm robot 100 and the second-arm robot 110 are controlled to move from the state in Fig. 2 to the state in Fig. 3 while maintaining the relative positional relationship between the irradiation unit 10j and the detection unit 10h. That is, the robots are controlled so that there is no positional deviation between the irradiation center 21 on the detection unit 10h in the state in Fig. 2 and the irradiation center 21 on the detection unit 10h in the state in Fig. 3.

[0019] In reality, there may be a positional deviation of several millimeters between the irradiation center 21 on the detection unit 10h in the state of Fig. 2 and the irradiation center 21 on the detection unit 10h in the state of Fig. 3. This positional deviation occurs due to a combination of factors such as the weight of the first-arm robot 100 and the second-arm robot 110, the weight of the irradiation unit 10j and the detection unit 10h, in addition to the positioning accuracy of the first-arm robot 100 and the second-arm robot 110 being approximately ±0.01 mm. This positional deviation of the irradiation center 21 affects the measurement error of the measurement device 10, and this disclosure clarifies the tolerance for the positional deviation of the irradiation center 21 in relation to the required accuracy imposed on the measurement device 10. In addition to the positional shift described above, the relative shift between the irradiation unit 10j and the detection unit 10h also causes distance shift and angle shift, but it is the positional shift that affects the measurement error of the measuring device 10, which is more dominant than the distance shift and angle shift.

[0020] The target image 19 (see FIG. 4) shows the brightness distribution of X-rays 2 that have passed through the object 1, and is an image of the brightness distribution of X-rays 2 that have been attenuated by passing through air and the object 1. The physical quantity that indicates the degree to which the energy of X-rays 2 is attenuated by passing through air is called the mass absorption coefficient of air. In contrast, the physical quantity that indicates the degree to which the energy of X-rays 2 is attenuated by passing through the object 1 is called the brightness absorption coefficient of the object 1. The calculation unit 12 of the processing unit 10e described below regards the difference between the brightness of the X-rays 2 in the background image 20 and the brightness of the X-rays 2 in the target image 19 at the measurement point 22 (see Figure 4) on the detection unit 10h as the brightness of the X-rays 2 absorbed when passing through the object to be measured 1, and calculates the thickness of the object to be measured 1 at the measurement point 22 from the relationship between this difference and the brightness absorption coefficient of the object to be measured 1.

[0021] Next, the positional deviation between the illumination center 21 of the background image 20 and the illumination center 21 of the target image 19 will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a diagram for explaining the positional deviation of the illumination center 21 of the measurement device 10, and Fig. 5 is a graph for explaining the positional deviation of the illumination center 21 of the measurement device 10. FIG. 5 shows the X-ray brightness distribution of the background image 20 and the actual object image 19, with the horizontal axis representing the positions on the background image 20 and the object image 19, and the vertical axis representing the X-ray brightness.

[0022] Figure 4(a) shows a background image 20. There are an irradiation center 21 and a measurement point 22 on the background image 20. The measurement point 22 is the position where the thickness of the object 1 is to be measured. As shown in Figure 5, the luminance of the measurement point 22 on the background image 20 is C026. Fig. 4(b) shows an ideal object image 19. In an ideal object image 19, the irradiation center 21 coincides with the irradiation center 21 of the background image 20 shown in Fig. 4(a) without any positional deviation. The object image 19 shown in Fig. 4(b) is an image of the distribution of brightness of X-rays 2 that have passed through the object to be measured 1. When the object to be measured 1 in the object image 19 shown in Fig. 4(b) is removed, the brightness of the X-rays 2 at the measurement point 22 is the same as the brightness at the measurement point 22 in the background image 20 shown in Fig. 4(a). FIG. 4(c) shows an actual target image 19. The actual target image 19 has a misaligned irradiation center 21 that does not match the irradiation center 21 of the background image 20 shown in FIG. 4(a). Similar to FIG. 4(b), the target image 19 shown in FIG. 4(c) is an image of the luminance distribution of X-rays 2 transmitted through the object 1. When the object 1 is removed from the target image 19 shown in FIG. 4(c), the luminance of the X-rays 2 at the measurement point 22 differs from the luminance at the measurement point 22 in the background image 20 shown in FIG. 4(a). This difference results in an error when the calculation unit 12 of the processing unit 10e calculates the luminance of the X-rays 2 absorbed as they pass through the object 1. ΔC0 shown in FIG. 5 represents the difference in luminance between the background image 20 before and after the misalignment at the measurement point 22.

[0023] The calculation unit 12 of the processing unit 10e determines the difference between the luminance of the X-rays 2 in the background image 20 and the luminance of the X-rays 2 in the target image 19 at the measurement point 22 on the detection unit 10h as the luminance of the X-rays 2 absorbed when passing through the object 1. Therefore, when the calculation unit 12 calculates the luminance of the X-rays 2 absorbed when passing through the object 1 using the luminance of the measurement point 22 in the actual target image 19 shown in FIG. 4(c), the luminance error of the X-rays 2 absorbed when passing through the object 1 will be included.

[0024] (Hardware configuration of the measuring device 10) The hardware configuration of the measurement device 10 will be described with reference to Fig. 6. Fig. 6 is a block diagram for explaining an example of the hardware configuration of the measurement device 10. The measuring device 10 includes a communication interface 10a, a read-only memory (ROM) 10b, a random access memory (RAM) 10c, a storage unit 10d, a processing unit 10e, and an input / output interface 10f.

[0025] The communication interface 10 a has a function of transmitting and receiving data and the like to and from other devices via the information communication network 11 . The processing unit 10e is typically a processor, and may include a central processing unit (CPU), a micro processing unit (MPU), a graphics processing unit (GPU), etc., and may be realized by a logic circuit (hardware) or a dedicated circuit formed in an integrated circuit (an integrated circuit (IC) chip, a large scale integration (LSI)), etc.) The processing unit 10e may execute the functions and methods described in each embodiment by reading a program stored in the storage unit 10d and executing code or instructions included in the read program.

[0026] The storage unit 10d can be used as a recording device, and stores a measurement program (described later), an OS (Operating System) required for the operation of the measurement device 10, various applications, and various data used by the applications. The storage unit 10d may include, for example, a hard disk drive (HDD), a solid state drive (SSD), flash memory, etc. The storage unit 10d may also include memory (random access memory (RAM), read only memory (ROM), etc.) that provides a working area for the processing unit 10e.

[0027] The measuring device 10 stores the measurement program in the storage unit 10d and loads the measurement program into a main memory configured by the RAM 10c etc. The processing unit 10e accesses the main memory into which the measurement program has been loaded and executes the measurement program. The input / output interface 10f transmits and receives data to and from devices external to the measurement device 10. The external devices are an input device 10g and an output device 10i that input and output data to and from the measurement device 10. The input device 10g includes the detection unit 10h, a keyboard, a mouse, etc., and the output device 10i includes the irradiation unit 10j, an external monitor, a printer, an external speaker, etc.

[0028] (Functional configuration of the measuring device 10) Next, the functional configuration of the measurement device 10 will be described with reference to Fig. 7. Fig. 7 is a block diagram for explaining an example of the functional configuration of the measurement device 10. By executing the measurement program described below, the measurement device 10 has functional units such as a calculation unit 12, a required accuracy acquisition unit 13, a tolerance calculation unit 14, a brightness tolerance area derivation unit 15, and a pixel tolerance range derivation unit 16 in the processing unit 10e.

[0029] The calculation unit 12 calculates the thickness at the measurement point 22 of the object 1 based on the difference in brightness at the measurement point 22 between the background image 20 of the brightness distribution of the X-rays 2 irradiated from the irradiation unit 10j and the target image 19 of the brightness distribution of the X-rays 2 that have passed through the object 1.

[0030] The target image 19 is the actual target image shown in FIG. 4( c ), in which the illumination center 21 is displaced from the illumination center 21 of the background image 20 . This difference indicates the amount of attenuation of the X-rays 2 absorbed by the object 1, and the calculation unit 12 calculates the thickness of the object 1 at the measurement point 22 in relation to the brightness absorption coefficient of the object 1. The thickness of the object 1 calculated by the calculation unit 12 includes an error caused by the above-mentioned positional shift of the irradiation center 21 between the background image 20 and the object image 19, and the measuring device 10 according to this embodiment clarifies the allowable amount of positional shift of the irradiation center 21 between the background image 20 and the object image 19, which satisfies the required accuracy imposed on the measuring device 10, which will be described later.

[0031] The required accuracy acquisition unit 13 acquires the required accuracy for measuring the thickness of the object 1 to be measured. The required accuracy refers to the tolerance for the thickness of the object 1 calculated by the calculation unit 12. A single required accuracy may be set for the object 1, or may be set according to the position of the measurement point 22 on the object 1. For example, a stricter required accuracy may be set for measurement points 22 within a predetermined range on the object 1 than for other ranges. The required accuracy may be expressed as an allowable range for the calculated thickness of the object 1, or may be expressed by a lower limit tolerance value expressed by subtracting a tolerance from the reference dimension and an upper limit tolerance value expressed by adding a tolerance to the reference dimension. The reference dimension is a standard dimension set by the designer among the numerical values ​​representing the dimensions of a part in a design drawing. The required accuracy acquisition unit 13 may acquire the required accuracy from an input by the user of the measurement device 10, or may acquire the required accuracy set by a measurement program described below.

[0032] The tolerance calculation unit 14 calculates a tolerance for satisfying the required accuracy of the difference in brightness of the X-rays 2 between the background image 20 and the target image 19 at the measurement point 22, which occurs due to a positional shift of the irradiation center 21 of the X-rays 2 irradiated from the irradiation unit 10j between the background image 20 and the target image 19. The tolerance calculation unit 14 calculates the tolerance based on the luminance of the measurement point 22 in the background image 20, the required accuracy, and the luminance absorption coefficient of the object 1 to be measured.

[0033] The tolerance calculation unit 14 calculates the tolerance of the luminance difference at the measurement point 22 using the following formula (1). It should be noted that ΔC0 is the tolerance of the luminance difference calculated by the tolerance calculation unit 14, and is the tolerance for satisfying the required accuracy of the luminance difference between the measurement points 22 of the background image 20 before and after the positional displacement of the irradiation center 21. C0 is the luminance of the measurement point 22 in the background image 20. Δt is the required accuracy, and is the tolerance of the thickness of the measurement point 22 calculated by the calculation unit 12 due to misalignment of the irradiation center 21. The tolerance range of the thickness of the measurement point 22 calculated by the calculation unit 12 that satisfies the required accuracy is indicated by a lower tolerance expressed by subtracting Δt from the reference dimension, and an upper tolerance expressed by adding Δt to the reference dimension. μ is the luminance absorption coefficient of the object 1 to be measured.

[0034]

number

[0035] The method for deriving equation (1) will be explained below. Generally, the intensity I of X-rays passing through a medium follows the Beer-Lambert law of equation (2). I0 is the X-ray intensity before it enters the medium, and corresponds to the brightness C0 of background image 20 in this embodiment. Note that the intensity I corresponds to the brightness C of target image 19, and t is the thickness of the medium, which indicates the length through which the X-rays pass through the medium and corresponds to the thickness of the object 1 to be measured. Transforming equation (2) and solving for t gives equation (3). In the case of an actual target image 19 (see FIG. 4(c)), the measurement point 22 on the target image 19 is photographed at a brightness that is ΔC0 lower. If the resulting error in the thickness calculated by the calculation unit 12 is denoted as Δt, then equation (4) is obtained. C in equation (4) is the X-ray brightness of the target image 19 at the measurement point 22, which has been affected by the positional shift. Furthermore, since it is recognized that the correct thickness t can be calculated by subtracting ΔC0 from the background luminance C0 of the target image 19, equation (5) is obtained. By substituting equation (5) into equation (4) and solving for ΔC0, equation (1) is obtained.

[0036]

number

[0037] The luminance allowable range deriving unit 15 derives an allowable range 24 of the luminance of the measurement point 22 in the background image 20 to satisfy the required accuracy based on the allowable value ΔC0 calculated by the allowable value calculating unit 14 (see FIG. 8).

[0038] The luminance allowable range 24 will be described with reference to Fig. 8. Fig. 8 is a diagram for explaining the luminance allowable range 24 of the measurement device 10 and the pixel allowable range 24a. The tolerance ΔC0 is calculated by the tolerance calculation unit 14 based on the luminance C0 of the measurement point 22 in the background image 20, the required accuracy Δt, and the luminance absorption coefficient μ of the object to be measured 1, using equation (1). If the measurement point 22 is placed at a pixel on the background image 20 that corresponds to the position to be evaluated (measurement point 22) on the target image 19 obtained by capturing the object to be measured 1, and its luminance is C0, then the required accuracy will be met if C0 ± ΔC0. Because the background image 20 is distributed so that the luminance decreases radially with increasing distance from the illumination center 21, the tolerance region 24, which is the region in the background image 20 with luminance that satisfies the required accuracy, is a concentric range of circles with a width of C0 ± ΔC0 centered on the illumination center 21. The brightness allowable area derivation unit 15 draws a circle of radius C0-ΔC0 centered on the irradiation center 21 and a circle of radius C0+ΔC0 centered on the irradiation center 21 in the background image 20, and derives the area sandwiched between these two circles as the area of ​​C0±ΔC0 (brightness allowable area) 24 of the measurement point 22.

[0039] The pixel allowable range deriving unit 16 derives an allowable range 24 a for pixels of the background image 20 based on an allowable region 24 of luminance at the measurement point 22 . The required accuracy can be met if the brightness of measurement point 22 is within brightness tolerance range 24. The required accuracy of the dimensions of required equipment such as first-arm robot 100, second-arm robot 110, mounting table 120, and jig 130 is expressed based on the pixels of background image 20 and displayed as dimensions based on pixel size. Tolerance range 24a, which is the required accuracy of the equipment's dimensional accuracy, is expressed as the shortest width in the radial direction of the concentric circle that indicates brightness tolerance range 24 of measurement point 22, which is the strictest positional deviation direction within the range of the concentric circle. That is, the pixel tolerance range derivation unit 16 derives the distance in the radial direction of the circle centered on the irradiation center 21 from a circle with a radius of C0-ΔC0 centered on the irradiation center 21 to a circle with a radius of C0+ΔC0 centered on the irradiation center 21 as the tolerance range 24a for pixels of the background image 20. A picture element, also called a pixel, is the smallest unit of a digital image and can be used as a unit of size. For example, if one picture element is 0.085 mm, then 10 picture elements are 0.85 mm.

[0040] Next, the brightness gradient of the X-rays 2 will be described with reference to Fig. 9. Fig. 9 is a graph for explaining the brightness gradient of the X-rays 2 in the measurement device 10. As shown in FIG. 9, the brightness gradient of the X-rays 2 increases as the distance from the irradiation center 21 increases. For example, measurement point A is located farther from the irradiation center 21 than measurement point B. Even if the brightness tolerance areas of measurement point A and measurement point B are equal at ΔC0, the tolerance range 24a in the pixel of measurement point A is smaller than that of measurement point B. This is because the brightness gradient of the X-ray 2 is larger at measurement point A than at measurement point B. Therefore, when there are multiple measurement points on the target image 19, it is necessary to set the dimensional accuracy of the equipment based on the measurement point 22 that is farthest from the irradiation center 21.

[0041] (Measurement method and measurement program) Next, a measurement program according to one embodiment of the present invention will be described together with a measurement method with reference to Fig. 10. Fig. 10 is a flowchart of the measurement program according to one embodiment of the present invention. The measurement method is executed by the processing unit 10e of the measurement device 10 based on the measurement program.

[0042] The measurement program includes a calculation step S12, a required accuracy acquisition step S13, a tolerance calculation step S14, a brightness tolerance area derivation step S15, and a pixel tolerance range derivation step S16.

[0043] The measurement program causes the processing unit 10e of the measurement device 10 to perform various functions, such as a calculation function, a required accuracy acquisition function, a tolerance value calculation function, a brightness tolerance area derivation function, and a pixel tolerance range derivation function. These functions are executed in the order shown in the flowchart of Fig. 10, but the order can also be changed as appropriate. Note that each function overlaps with the description of the various functional units of the measurement device 10 described above, and therefore detailed description thereof will be omitted.

[0044] The calculation function calculates the thickness at the measurement point 22 of the object to be measured 1 based on the difference in brightness between the background image 20 of the brightness distribution of the X-rays 2 irradiated from the irradiation unit 10j and the target image 19 of the brightness distribution of the X-rays 2 that have passed through the object to be measured 1 (S12: calculation step).

[0045] The required accuracy acquisition function acquires the required accuracy for measuring the thickness of the object 1 (S13: required accuracy acquisition step).

[0046] The tolerance calculation function calculates a tolerance that satisfies the required accuracy of the difference in brightness of the X-rays 2 between the background image 20 and the target image 19 at the measurement point 22, which occurs due to a positional shift of the irradiation center 21 of the X-rays 2 irradiated from the irradiation unit 10j between the background image 20 and the target image 19 (S14: tolerance calculation step).

[0047] The brightness allowable area deriving function derives, based on the allowable value, an allowable area of ​​the brightness of the measurement point 22 in the background image 20 that satisfies the required accuracy (S15: brightness allowable area deriving step).

[0048] The pixel tolerance range deriving function derives a tolerance range for pixels of the background image 20 based on the tolerance range of the luminance of the measurement point 22 (S16: pixel tolerance range deriving step).

[0049] According to the measuring device 10 of this embodiment described above, it is possible to clarify the allowable amount of positional deviation of the irradiation center 21 between the background image 20 and the target image 19 that satisfies the required accuracy imposed on the measuring device 10, and therefore it is possible to clarify the accuracy required for necessary equipment such as the first arm robot 100 and the second arm robot 110. Furthermore, according to the measuring device 10 of this embodiment described above, the tolerance for the positional deviation of the illumination center 21 between the background image 20 and the target image 19 is made clear, so that measurements performed by the measuring device 10 within the range of this tolerance can satisfy the required accuracy. Furthermore, according to the measuring device 10 of this embodiment described above, measurements that meet the required accuracy can be performed using the first arm robot 100 and the second arm robot 110, and it becomes possible to perform full inspection based on non-destructive thickness measurement on objects 1 to be measured of various sizes and complex shapes. Furthermore, according to the measuring device 10 of this embodiment described above, it becomes possible to quickly and non-destructively determine at the production site whether the internal component 23 present inside the object to be measured 1 has an appropriate thickness. For example, by measuring the thickness of adhesive present inside the object to be measured 1, it becomes possible to quickly and safely determine at the production site whether the amount of adhesive applied is appropriate. Furthermore, according to the measuring device 10 of this embodiment described above, the allowable amount of positional deviation of the irradiation center 21 between the background image 20 and the target image 19 becomes clear, which makes it possible to reduce the complexity of determining the specifications of the necessary equipment such as the first arm robot 100 and the second arm robot 110. Furthermore, according to the measuring device 10 of this embodiment described above, when there are multiple measurement points on one target image 19, it is only necessary to clarify the tolerance for the positional deviation of the illumination center 21 between the background image 20 and the target image 19 using the measurement point farthest from the illumination center 21 as a reference, and if measurements are performed by the measuring device 10 within the range of this tolerance, measurements at other measurement points can satisfy the required accuracy. Furthermore, according to the measurement method and measurement program of this embodiment, similar to the measurement device 10, measurements performed within the range of the allowable amount can satisfy the required accuracy.

[0050] The present invention is not limited to the measuring device 10, the measuring method, and the measuring program according to the above-described embodiments, and can be implemented by various other modified examples or application examples as long as they do not deviate from the gist of the present invention as set forth in the claims. [Explanation of symbols]

[0051] 1 Object to be measured 2 X-ray 3 Optical path length 3a Optical path length 3b Optical path length 10. Measuring equipment 10a Communication Interface 10b ROM 10c RAM 10d storage section 10e Processing section 10f Input / Output Interface 10g input device 10h detection unit 10i output device 10j Irradiation section 11 Information and Communications Networks 12 Calculation section 13 Required accuracy acquisition section 14 Tolerance calculation section 15. Luminance tolerance area derivation section 16 Pixel tolerance calculation part 19 Target image 20 background images 21 Irradiation center 22 measurement points 22A measurement point 22B measurement point 23 Internal components 24 Measurement point C0±ΔC0 area (allowable brightness area) 24a Pixel tolerance of measurement point 100 First Arm Robot 110 Second Arm Robot 120 Mounting table 130 Jig

Claims

1. A measuring device used to measure the thickness of an object to be measured, The measuring device is an irradiation unit that irradiates the object to be measured with X-rays; a detection unit that detects X-rays that have passed through the object; a processing unit that estimates a thickness of the object based on an attenuation amount of X-rays that have passed through the object; Equipped with The processing unit a calculation unit that calculates a thickness at a measurement point of the object to be measured based on a difference in brightness at the measurement point between a background image of brightness distribution of X-rays irradiated from the irradiation unit and a target image of brightness distribution of X-rays that have transmitted through the object to be measured; a required accuracy acquisition unit that acquires a required accuracy for measuring the thickness of the object to be measured; a tolerance calculation unit that calculates a tolerance that satisfies the required accuracy for a difference in luminance of the X-rays at the measurement point between the background image and the target image, the difference being caused by a positional deviation of the irradiation center of the X-rays irradiated from the irradiation unit between the background image and the target image; a brightness allowable range deriving unit that derives a brightness allowable range of the measurement point in the background image that satisfies the required accuracy based on the allowable value; a pixel allowable range deriving unit that derives an allowable range for a pixel of the background image based on an allowable range of the luminance of the measurement point; A measuring device comprising:

2. The measurement device according to claim 1 , wherein the tolerance calculation unit calculates the tolerance based on the luminance of the measurement point in the background image, the required accuracy, and the luminance absorption coefficient of the object to be measured.

3. A measurement method used in a measurement device used to measure the thickness of an object to be measured, comprising: The measuring device is an irradiation unit that irradiates the object to be measured with X-rays; a detection unit that detects X-rays that have passed through the object; a processing unit that estimates a thickness of the object based on an attenuation amount of X-rays that have passed through the object; Equipped with The processing unit a calculation step of calculating a thickness at the measurement point of the object to be measured based on a difference in brightness at the measurement point between a background image of brightness distribution of X-rays irradiated from the irradiation unit and a target image of brightness distribution of X-rays transmitted through the object to be measured; a required accuracy acquisition step of acquiring a required accuracy for measuring the thickness of the object to be measured; a tolerance calculation step of calculating a tolerance that satisfies the required accuracy for a difference in luminance of the X-rays between the background image and the target image at the measurement point, the difference being caused by a positional deviation of the irradiation center of the X-rays irradiated from the irradiation unit between the background image and the target image; a brightness allowable area derivation step of deriving an allowable area of ​​brightness of the measurement point in the background image that satisfies the required accuracy based on the allowable value; a pixel tolerance range deriving step of deriving a tolerance range for pixels of the background image based on a tolerance range of the luminance of the measurement point; A measuring method characterized by carrying out the steps of:

4. A measurement program used in a measurement device used to measure the thickness of an object to be measured, The measuring device is an irradiation unit that irradiates the object to be measured with X-rays; a detection unit that detects X-rays that have passed through the object; a processing unit that estimates a thickness of the object based on an attenuation amount of X-rays that have passed through the object; Equipped with The processing unit a calculation function for calculating a thickness at a measurement point on the object to be measured based on a difference in brightness at the measurement point between a background image of the brightness distribution of X-rays irradiated from the irradiation unit and a target image of the brightness distribution of X-rays transmitted through the object to be measured; a required accuracy acquisition function for acquiring the required accuracy for measuring the thickness of the object to be measured; a tolerance calculation function that calculates a tolerance that satisfies the required accuracy for a difference in luminance of the X-rays between the background image and the target image at the measurement point, which occurs due to a positional deviation of the irradiation center of the X-rays irradiated from the irradiation unit between the background image and the target image; a brightness tolerance area derivation function that derives a brightness tolerance area of ​​the measurement point in the background image that satisfies the required accuracy based on the tolerance value; a pixel tolerance range deriving function that derives a tolerance range for pixels of the background image based on a tolerance range of the luminance of the measurement point; A measurement program characterized by realizing the above.

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