Depth measurement device, depth measurement method and depth measurement program

Abstract

To improve measurement precision of depth of an object existing inside an analyte by improving the specific precision at a position where the rate of change of a luminance value of a picked-up image obtained as a result of the irradiation of radiation on the object reaches an extreme value.SOLUTION: A depth measurement device includes a detector having a radiation source and a detection surface, and a controller. The controller: controls the movement of the radiation source or an object so that the object located at a first position moves to a second position; images the object moving from the first position to the second position by making the radiation source continue to radiate radiation to the object while the object moves from the first position to the second position, and acquires a single picked-up image; acquires the luminance value distribution of the picked-up image on a linear line; acquires luminance value change rate distribution; acquires a moving average line for the luminance value change rate distribution; identifies the distance between the position of an extreme value on a moving average line where the object is at the first position and the position of an extreme value on a moving average line where the object is at the second position as a deviation amount of the object; and calculates the depth of the object.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a depth measurement device, a depth measurement method, and a depth measurement program, and more particularly to a depth measurement device, a depth measurement method, and a depth measurement program that measure using radiation. [Background technology]

[0002] Conventionally, technologies have been used to obtain internal information of an object through images using radiation. Among these, the use of tomosynthesis technology is becoming increasingly widespread. Tomosynthesis technology is a technology that obtains desired internal information of an object (e.g., tomographic images or the depth of an object inside the object) with high accuracy based on multiple captured images obtained by irradiating the object with radiation. For example, the tomographic image generating device disclosed in Patent Document 1 moves a radiation source to irradiate the subject with radiation from multiple radiation source positions to take images, and adds up the multiple captured images thus obtained to generate a tomographic image that emphasizes the desired tomographic plane.

[0003] The application of tomosynthesis technology has also been proposed in depth measurement devices that measure the depth of an object present inside a subject. When measuring the depth of an object inside a subject using tomosynthesis technology, the amount of shift in the image of the object caused by radiation irradiated onto the object is measured while a radiation source is slid. This shift amount is obtained by measuring the distance traveled by a predetermined position on the boundary (contour) of the image of the object as the radiation source moves from one end of the slide to the other. The position on this boundary is identified as the position where the rate of change in brightness value of the image obtained by irradiating the object with radiation reaches an extreme value (maximum or minimum).

[0004] When attempting to identify the position of the extreme value (maximum or minimum value) of the rate of change of the brightness value of the captured image based on information obtained from the captured image, it is only possible to identify it as the smallest unit, the pixel that makes up the captured image, and in some cases it is not possible to accurately identify the position on the boundary of the image of the object obtained by irradiating it with radiation. As a result, the amount of shift in the image of the object measured based on the position on the boundary of the image of the object identified on a pixel-by-pixel basis in the captured image may not be obtained accurately, which could lead to a decrease in the accuracy of measuring the depth of the object. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Re-tabled publication No. 2020-067475 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present invention aims to provide a depth measurement device, a depth measurement method, and a depth measurement program that can improve the accuracy of identifying the positions where the rate of change of the brightness value of an image obtained by irradiating an object with radiation becomes an extreme value (maximum value or minimum value), thereby improving the accuracy of measuring the depth of an object located inside a subject. [Means for solving the problem]

[0007] That is, a depth measurement device according to a first aspect is a depth measurement device that includes a radiation source that emits radiation, a detector that has a detection surface that directly faces the radiation source and detects the radiation emitted by the radiation source, and maintains a fixed distance between the detection surface and the radiation source, and a control unit, and that measures the depth of an object present inside a subject by irradiating radiation, wherein the control unit controls the movement of the radiation source or the object so that, in terms of the relative position of the object with the radiation source as a reference, the object, which is located at a first position where the distance from the radiation source in a direction perpendicular to the detection surface is a first distance and the distance from the radiation source in a direction parallel to the detection surface is a second distance, moves to a second position where the distance from the radiation source in the perpendicular direction is the first distance and the distance from the radiation source in the parallel direction is a third distance different from the second distance; and a movement control unit that controls the movement of the radiation source or the object so that the object, which is located at a first position where the distance from the radiation source in a direction perpendicular to the detection surface is a first distance and the distance from the radiation source in a direction parallel to the detection surface is a second distance, the object moving from the first position to the second position is imaged as a single captured image by continuing to project a line; a brightness value distribution acquisition unit that acquires the brightness values ​​of the captured image on a straight line that extends in the same direction as the movement from the first position to the second position and passes through the captured image as a brightness value distribution; a change rate distribution acquisition unit that acquires the rate of change of the brightness values ​​of the brightness value distribution at positions on the line as a brightness value change rate distribution; a moving average line acquisition unit that acquires a moving average line that graphs the average value of the change rates at predetermined intervals on the brightness value change rate distribution line; an identification unit that identifies, on the moving average line, the distance between the position on the line of the extreme value of the moving average line when the object is at the first position and the position on the line of the extreme value of the moving average line when the object is at the second position as the amount of displacement of the object in the captured image; and a calculation unit that calculates the first distance as depth based on the fixed distance, the difference between the second distance and the third distance, and the amount of displacement.

[0008] A second aspect is a depth measurement device according to the first aspect, which includes a movement mechanism that holds an object stationary between a radiation source and a detection surface and moves the object a fixed distance in a direction parallel to the radiation source and the detection surface while maintaining the distance between the radiation source and the detection surface, and the movement control unit may control the movement mechanism.

[0009] A third aspect may be a depth measurement device according to the first aspect, further comprising a movement mechanism that keeps the radiation source and the detection surface stationary and moves the object between the radiation source and the detection surface in a direction parallel to the detection surface, and the movement control unit may control the movement mechanism.

[0010] A fourth aspect is a depth measurement device according to the first aspect, which includes a movement mechanism that moves the radiation source in a direction parallel to the detection surface while keeping the detection surface and the object stationary and maintaining a fixed distance between the radiation source and the detection surface, and the movement control unit may control the movement mechanism.

[0011] As for a fifth aspect, in the depth measurement device according to the first aspect, the extreme value may be a maximum value or a minimum value.

[0012] According to a sixth aspect, in the depth measurement device according to the second to fourth aspects, the movement mechanism may include a robot arm.

[0013] According to a seventh aspect, the depth measurement device according to the first aspect may further include an output unit that outputs the first distance as the depth of the object.

[0014] A depth measurement method according to an eighth aspect is a depth measurement method used in a depth measurement device that irradiates radiation, the depth measurement device comprising: a radiation source that emits radiation; a detector that has a detection surface that directly faces the radiation source and detects radiation emitted by the radiation source, and maintains a fixed distance between the detection surface and the radiation source; and a control unit, and that measures the depth of an object present inside a subject by irradiating radiation, the control unit including: a movement control step of controlling movement of the radiation source or the object so that, in a relative position of the object with the radiation source as a reference, the object, which is located at a first position where the distance from the radiation source in a direction perpendicular to the detection surface is a first distance and the distance from the radiation source in a direction parallel to the detection surface is a second distance, to a second position where the distance from the radiation source in the perpendicular direction is the first distance and the distance from the radiation source in the parallel direction is a third distance different from the second distance; and a control step of continuing to irradiate radiation from the radiation source to the object while the object moves from the first position to the second position. a brightness value distribution acquisition step of acquiring brightness values ​​of the captured image on a straight line extending in the same direction as the movement from the first position to the second position and passing through the captured image as a brightness value distribution; a change rate distribution acquisition step of acquiring the change rate of brightness values ​​of the brightness value distribution at positions on the line as a brightness value change rate distribution; a moving average line acquisition step of acquiring a moving average line that graphs the average value of the change rate at a predetermined interval on the brightness value change rate distribution line; an identification step of identifying the distance between the position on the line of the extreme value of the moving average line when the object is at the first position and the position on the line of the extreme value of the moving average line when the object is at the second position as the displacement amount of the object in the captured image; and a calculation step of calculating the first distance as the depth based on the fixed distance, the difference between the second distance and the third distance, and the displacement amount.

[0015] A depth measurement program according to a ninth aspect is a depth measurement program used in a depth measurement device that irradiates radiation and measures the depth of an object present inside a subject, the depth measurement program comprising: a radiation source that emits radiation; a detector that has a detection surface that directly faces the radiation source and detects the radiation emitted by the radiation source, and maintains a fixed distance between the detection surface and the radiation source; and a control unit, the depth measurement program comprising: a movement control function that controls movement of the radiation source or the object so that, in a relative position of the object with the radiation source as a reference, the object located at a first position where the distance from the radiation source in a direction perpendicular to the detection surface is a first distance and the distance from the radiation source in a direction parallel to the detection surface is a second distance, to a second position where the distance from the radiation source in the perpendicular direction is the first distance and the distance from the radiation source in a parallel direction is a third distance different from the second distance; and a movement control function that controls the radiation source relative to the object while the object is moving from the first position to the second position. The system is characterized by realizing an acquisition function that continues irradiating radiation to capture an image of an object moving from a first position to a second position and acquire it as a single captured image; a brightness value distribution acquisition function that acquires the brightness values ​​of the captured image on a straight line that extends in the same direction as the movement from the first position to the second position and passes through the captured image as a brightness value distribution; a change rate distribution acquisition function that acquires the rate of change of the brightness values ​​of the brightness value distribution at positions on the line as a brightness value change rate distribution; a moving average line acquisition function that acquires a moving average line that graphs the average value of the change rates at predetermined intervals on the brightness value change rate distribution line; an identification function that identifies the distance on the moving average line between the position on the line of the extreme value of the moving average line when the object is at the first position and the position on the line of the extreme value of the moving average line when the object is at the second position as the amount of displacement of the object in the captured image; and a calculation function that calculates the first distance as depth based on a fixed distance, the difference between the second distance and the third distance, and the amount of displacement. [Effects of the Invention]

[0016] The depth measurement device according to the present invention is a depth measurement device that measures the depth of an object present inside a subject by irradiating radiation, the depth measurement device comprising: a radiation source that emits radiation; a detector that has a detection surface that directly faces the radiation source and detects radiation emitted by the radiation source, and maintains a fixed distance between the detection surface and the radiation source; and a control unit, wherein the control unit controls the movement of the radiation source or the object so that, in terms of the relative position of the object with the radiation source as a reference, the object located at a first position where the distance from the radiation source in a direction perpendicular to the detection surface is a first distance and the distance from the radiation source in a direction parallel to the detection surface is a second distance, to a second position where the distance from the radiation source in the perpendicular direction is the first distance and the distance from the radiation source in the parallel direction is a third distance different from the second distance; an acquisition unit that causes the radiation source to continue irradiating the object with radiation while the object is moving from the first position to the second position, and captures an image of the object moving from the first position to the second position and acquires it as a single captured image; the distance between the position on the moving average line where the moving average line has an extreme value when the object is at the first position and the position on the moving average line where the object is at the second position is the extreme value when the object is at the second position; and a calculation unit that calculates the first distance as the depth based on the fixed distance, the difference between the second distance and the third distance, and the deviation amount. This improves the accuracy of identifying the position where the extreme value (maximum or minimum value) of the change rate of the brightness value of the image obtained by irradiating the object with radiation occurs, thereby improving the accuracy of measuring the depth of an object inside the subject. The depth measurement method and depth measurement program of the present invention, like the depth measurement device of the present invention, can improve the accuracy of identifying the position where the rate of change of the brightness value of an image obtained by irradiating an object with radiation becomes an extreme value (maximum or minimum value), thereby improving the accuracy of measuring the depth of an object located inside a subject. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram for explaining a mathematical formula for calculating the depth (first distance L1) used by the depth measurement device according to this embodiment. [Figure 2] FIG. 2 is a diagram for explaining various states of the positional relationship between the radiation source and detector of the depth measurement device according to this embodiment and the subject, and shows captured images captured in each state. [Figure 3] FIG. 3 shows an image captured by the depth measurement device according to this embodiment. [Figure 4] FIG. 4 is a graph showing the distribution of brightness values ​​and brightness value change rates on a straight line passing through the captured image shown in FIG. [Figure 5] FIG. 5 is a graph showing the correspondence between the amount of displacement of an image of an object shown in an image captured by the depth measurement device according to this embodiment and the resolution of the captured image. [Figure 6] Figure 6 is a graph showing an enlarged view of the area around the maximum value of the rate of change of brightness value when the object is at the first position in the graph shown in Figure 4, comparing a conventional depth measurement device with the depth measurement device of this embodiment. [Figure 7] Figure 7 is a graph showing an enlarged view of the area around the maximum value of the rate of change of brightness value when the object is at the second position in the graph shown in Figure 4, comparing a conventional depth measurement device with the depth measurement device of this embodiment. [Figure 8] FIG. 8 is a graph showing the error in the measurement results of the depth of an object by the depth measurement device according to this embodiment in comparison with that by a conventional depth measurement device. [Figure 9]FIG. 9 is a block diagram for explaining an example of the hardware configuration of the depth measurement device according to this embodiment. [Figure 10] FIG. 10 is a block diagram for explaining an example of the functional configuration of the depth measurement device according to this embodiment. [Figure 11] Figure 11 is a graph comparing a graph line of the brightness value distribution on a straight line passing through the captured image acquired by the depth measurement device of this embodiment with a graph line of the "moving average -3σ (standard deviation)" of the brightness value distribution. [Figure 12] FIG. 12 is an example of a flowchart of the depth measurement program according to this embodiment. [Figure 13] FIG. 13 is an example of a flowchart of a depth measurement program according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Overview of the depth measurement device 10) A depth measurement device 10 according to one embodiment of the present disclosure will be described with reference to FIGS. First, with reference to FIG. 1, an overview of a depth measurement device 10 according to this embodiment will be described. FIG. 1 is a diagram for explaining the mathematical formula used by the depth measurement device 10 to calculate the depth (first distance L1). The depth measurement device 10 is a device that measures the depth of the object 9 (9a, 9b) present inside the subject 1 by irradiating the subject 1 and the object 9 (9a, 9b) with radiation 4 (see Figure 2), and is a type of information processing device, electronic calculator, computer, etc. The depth refers to the depth of the position of the object 9 (9a, 9b) inside the subject 1, and refers to the distance from the radiation source 7 (7a, 7b) to the object 9 (9a, 9b) in the depth direction from the radiation source 7 (7a, 7b) toward the detection surface 8c, in a direction perpendicular to the detection surface 8c (the Y direction in FIG. 1), and refers to the first distance L1 shown in FIG. 1. The X direction in FIG. 1 refers to the direction along the detection surface 8c and parallel to the detection surface 8c. The specimen 1 may include components made of metal, non-metallic material, organic material, etc. Non-metallic materials include, for example, ceramics, glass, cement, stone, clay, manganese, graphite, etc. Organic materials include, for example, plastic, rubber, wood, paper, oil, and fat. The object 9 (9a, 9b) is a member or space that exists inside the subject 1 and has a different radiation transmittance than the subject 1. The space includes gaps, cracks, bubbles, etc. that occur inside the subject 1. The object 9 (9a, 9b) in this embodiment is a space that exists inside the subject 1, but is not limited to this.

[0019] The depth measurement device 10 comprises a radiation source 7 (7a, 7b) and a detector 8. The radiation source 7 (7a, 7b) emits radiation 4 (see FIG. 2). The detector 8 has a detection surface 8c that faces the radiation source 7 (7a, 7b) and detects the radiation 4 emitted by the radiation source 7 (7a, 7b), and the distance between the detection surface 8c and the radiation source 7 (7a, 7b) is kept at a fixed distance L. The fixed distance L is the distance between the radiation source 7 (7a, 7b) and the detection surface 8c, and is a known value that is measured in advance. The radiation 4 irradiated onto the subject 1 from the radiation source 7 (7a, 7b) passes through the subject 1 and the object 9 and reaches the detection surface 8c. The detector 8 converts the two-dimensional distribution of the luminance values ​​(amount of transmitted radiation) of the radiation 4 that has reached the detection surface 8c into a captured image. The detector 8 that is used is one that can be exposed continuously for a predetermined period of time, as described below, i.e., a detector 8 that is capable of long-term exposure. Directly facing refers to a state in which the radiation source 7 (7a, 7b) and the detection surface 8c face each other directly, and a line drawn straight down from the radiation source 7 (7a, 7b) to the detection surface 8c is perpendicular to the detection surface 8c. Note that, because the radiation 4 spreads radially, it is desirable that a line drawn straight down from the radiation source 7 (7a, 7b) to the detection surface 8c intersect at the center of the detection surface 8c in the X direction. Radiation 4 refers to particle radiation, which is material particles flowing with high kinetic energy, and electromagnetic radiation, which is high-energy electromagnetic waves. Particle radiation includes, for example, alpha rays, beta rays, neutron rays, and proton rays. Electromagnetic radiation includes, for example, gamma rays and X-rays.

[0020] The depth measurement device 10 measures the depth (first distance L1) by capturing images while moving any of the radiation source 7 (7a, 7b), the detector 8, and the object 9 (9a, 9b). There are three ways to move the radiation source 7 (7a, 7b), the detector 8, and the object 9 (9a, 9b). In the first pattern, the object 9 is placed stationary between the radiation source 7 and the detection surface 8c, and while the distance between the radiation source 7 and the detection surface 8c is maintained at a fixed distance L, the radiation source 7 and the detection surface 8c are moved the same distance in a direction parallel to the detection surface 8c. In the second pattern, the radiation source 7 and the detection surface 8c are kept stationary, and the object 9 (9a, 9b) is moved between the radiation source 7 and the detection surface 8c in a direction parallel to the detection surface 8c. In the third pattern, the detection surface 8c and the object 9 are kept stationary, and the distance between the radiation source 7 (7a, 7b) and the detection surface 8c is kept at a fixed distance L, while the radiation source 7 (7a, 7b) is moved in a direction parallel to the detection surface 8c. The first pattern and the second pattern can be treated as being the same in that the object 9 (9a, 9b) is moved relative to the radiation source 7 and the detection surface 8c without changing the relative positional relationship between the radiation source 7 and the detection surface 8c. On the other hand, the third pattern differs from the first and second patterns in that the radiation source 7 (7a, 7b) is moved relative to the detection surface 8c and the object 9 without changing the relative positional relationship between the detection surface 8c and the object 9.

[0021] The mathematical formula used to calculate the depth (first distance L1) of the depth measurement device 10 will be described with reference to FIG. In the case of the first pattern and the second pattern, that is, when the object 9 (9a, 9b) moves relative to the radiation source 7 and the detection surface 8c without changing the relative positional relationship between the radiation source 7 and the detection surface 8c, the depth measurement device 10 calculates the depth (first distance L1) using the following formula (1). In the case of the third pattern, that is, when the radiation source 7 (7a, 7b) moves relative to the detection surface 8c and the object 9 without changing the relative positional relationship between the detection surface 8c and the object 9, the depth measurement device 10 calculates the depth (first distance L1) using the following formula (2). In both equations (1) and (2), the fixed distance L, the difference d, and the deviation amount Z are all known values, so the depth measurement device 10 can calculate the first distance L1 (depth) from the radiation source 7 (7a, 7b) to the target object 9 (9a, 9b). As described above, the fixed distance L is the distance between the detection surface 8c and the radiation source 7 (7a, 7b). The difference d is the difference between the second distance L2 and the third distance L3, as will be described later. As will be described later, the deviation amount Z is the distance traveled by the image of the object 9 projected onto the detection surface 8c when the object 9 moves from the first position to the second position, in terms of the relative position of the object 9 (9a, 9b) with respect to the radiation source 7 (7a, 7b). In the case of the first pattern and the second pattern, the first position (point P1 relative to point P0) refers to a position of the object 9a relative to the radiation source 7, where the distance from the radiation source 7 in a direction perpendicular to the detection surface 8c (the Y direction shown in FIG. 1) is a first distance L1 and the distance from the radiation source 7 in a direction parallel to the detection surface 8c (the X direction shown in FIG. 1) is a second distance L2 (see FIG. 1(a)). In the case of the first pattern and the second pattern, the second position (point P2 relative to point P0) refers to a position of the object 9b relative to the radiation source 7, where the distance from the radiation source 7 in a direction perpendicular to the detection surface 8c (the Y direction shown in FIG. 1) is a first distance L1 and the distance from the radiation source 7 in a direction parallel to the detection surface 8c (the X direction shown in FIG. 1) is a third distance L3 (see FIG. 1(a)). In the third pattern, the first position (point Q0 relative to point Q1) refers to a position of the object 9 relative to the radiation source 7a, where the distance from the radiation source 7a in a direction perpendicular to the detection surface 8c (the Y direction shown in FIG. 1) is a first distance L1 and the distance from the radiation source 7a in a direction parallel to the detection surface 8c (the X direction shown in FIG. 1) is a second distance L2 (see FIG. 1(b)). In the third pattern, the second position (point Q0 relative to point Q2) refers to a position where, in the relative position of the object 9 with respect to the radiation source 7b, the distance from the radiation source 7b in a direction perpendicular to the detection surface 8c (the Y direction shown in FIG. 1) is a first distance L1, and the distance from the radiation source 7b in a direction parallel to the detection surface 8c (the X direction shown in FIG. 1) is a third distance L3 (see FIG. 1(b)).

[0022]

number

[0023] (Derivation of Equation (1)) The derivation of equation (1) will be described with reference to FIG. 1(a). 1(a) shows a state in which the radiation source 7 and the detection surface 8c are relatively stationary, while the object 9 (9a, 9b) moves relative to the radiation source 7 and the detection surface 8c, and illustrates both the first and second patterns. In FIG. 1(a), the object 9 before and after movement is distinguished as the object 9a before movement and the object 9b after movement. In FIG. 1(a), the position of the radiation source 7 is indicated by point P0. 1(a), the position of the object 9a before movement is indicated by point P1, and the position of the object 9b after movement is indicated by point P2. Note that the positions of the objects 9 (9a, 9b) refer to the center positions of the objects 9 (9a, 9b). The point P1 is at a first distance L1 from the point P0 in the Y direction, and at a second distance L2 from the point P0 in the X direction. The point P2 is at a first distance L1 from the point P0 in the Y direction, and at a third distance L3 from the point P0 in the X direction, which is different from the second distance L2. The difference d is the difference between the third distance L3 and the second distance L2, and is therefore expressed as (L3-L2).

[0024] The image of the object 9a before movement projected by the radiation 4 from the radiation source 7 appears at the position of point P3 on the detection surface 8c in Figure 1(a), and the image of the object 9b after movement projected by the radiation 4 appears at the position of point P4 on the detection surface 8c in Figure 1(a). The deviation amount Z is the distance between point P3 and point P4.

[0025] As shown in Figure 1(a), the first triangle with vertices P0, P1, and P2 and the second triangle with vertices P0, P3, and P4 are similar to each other, so the following formula (3) holds. Rearranging both sides of formula (3) gives formula (4). Converting formula (4) into a formula with L1 as the solution gives formula (1) above.

[0026]

number

[0027] (Derivation of Equation (2)) The derivation of equation (2) will be described with reference to FIG. 1(b) shows a state in which the detection surface 8c and the object 9 are relatively stationary, and the radiation source 7 (7a, 7b) moves relatively to the detection surface 8c and the object 9, which is the third pattern. In FIG. 1(b), the radiation source 7 before and after the movement are distinguished as the radiation source 7a before the movement and the radiation source 7b after the movement. In FIG. 1(b), the position of the object 9 is indicated by point Q0. In FIG. 1(b), the position of the radiation source 7a before movement is indicated by point Q1, and the position of the radiation source 7b after movement is indicated by point Q2. The position of the object 9 (point Q0) relative to the position of the radiation source 7a before movement (point Q1) is a first distance L1 in the Y direction and a second distance L2 in the X direction from point Q1. The position of the object 9 (point Q0) based on the position of the radiation source 7b after movement (point Q2) is at a first distance L1 in the Y direction from point Q2, and at a third distance L3 in the X direction from point Q2, which is different from the second distance L2. The difference d is the difference between the third distance L3 and the second distance L2, and is therefore expressed as (L3-L2) in the same manner as in FIG. 1(a). In the case of the third pattern, the first position of the object 9 is a position (point Q0) based on the position (point Q1) of the radiation source 7a before movement, and the second position of the object 9 is a position (point Q0) based on the position (point Q2) of the radiation source 7b after movement.

[0028] The image of the object 9 projected by the radiation 4 of the radiation source 7a before movement appears at the position of point Q3 on the detection surface 8c in Figure 1(b), and the image of the object 9 projected by the radiation 4 of the radiation source 7b after movement appears at the position of point Q4 on the detection surface 8c in Figure 1(b). The deviation amount Z is the distance between point Q3 and point Q4.

[0029] As shown in Figure 1(b), the third triangle with vertices Q0, Q1, and Q2 and the fourth triangle with vertices Q0, Q3, and Q4 are similar to each other, so the following formula (5) holds. Rearranging both sides of formula (5) gives formula (6). Converting formula (6) into a formula with L1 as the solution gives formula (2) above.

[0030]

number

[0031] (Method for determining the amount of deviation Z of the depth measurement device 10) Next, a method for determining the amount of deviation Z of the depth measurement device 10 will be described with reference to FIGS. 2 is a diagram for explaining each state of the positional relationship between the radiation source 7 and detector 8 of the depth measurement device 10 and the subject 1 (object 9), and shows a captured image 20 captured in each state. FIG. 3 shows the captured image 20 captured by the depth measurement device 10. FIG. 4 is a graph showing the distribution of brightness values ​​and brightness value change rates on a line 25 passing through the captured image 20 shown in FIG. 3. FIG. 5 is a graph showing the correspondence between the amount of shift Z of the image of the object 9 shown in the captured image 20 acquired by the depth measurement device 10 and the resolution of the captured image 20. FIG. 6 is a graph showing the relationship between the amount of shift Z of the image of the object 9 shown in the graph shown in FIG. Figure 7 is a graph showing an enlarged view of the area around maximum value 26a of the rate of change of brightness values ​​when object 9 is in the first position, comparing a conventional depth measurement device with the depth measurement device 10 of this embodiment; Figure 8 is a graph showing an enlarged view of the area around maximum value 26b of the rate of change of brightness values ​​when object 9 is in the second position in the graph shown in Figure 4, comparing a conventional depth measurement device with the depth measurement device 10 of this embodiment; and Figure 9 is a graph showing the error in the measurement results of the depth of object 9 by the depth measurement device 10 of this embodiment, comparing it with that of a conventional depth measurement device. Hereinafter, with reference to FIGS. 2 to 8, a method for determining the amount of deviation Z of the depth measurement device 10 will be described using the above-described first and second patterns as examples. In the case of the third pattern, the depth measurement device 10 can also determine the amount of deviation Z using the captured image 20 obtained, in the same way as in the cases of the first and second patterns.

[0032] The depth measurement device 10 causes the radiation source 7 to continue irradiating the object 9 (subject 1) with radiation 4 while the object 9 (subject 1) moves from the first position to the second position, and captures an image of the object 9 (subject 1) moving from the first position to the second position, obtaining a single captured image 20. As shown in FIG. 2(a), the object 1 includes an object 9c and an object 9d as the objects 9. Figure 2(a) shows the process of irradiating radiation 4 onto a moving object 9 (subject 1) and acquiring an image 20, divided into various states, and Figure 2(b) shows the acquired image 20 of the moving object 9 (subject 1), divided into various states in Figure 2(a). The left side of Figure 2(a) shows the state of the object 9 (subject 1) at the start of its movement, and the left side of Figure 2(b) shows an image 20 captured of the object 9 (subject 1) in the state shown in the left side of Figure 2(a) (i.e., the state of the object 9 (subject 1) at the start of its movement). The central figure in Figure 2(a) shows the state of the object 9 (subject 1) during movement, and the central figure in Figure 2(b) shows an image 20 captured from the state of the object 9 (subject 1) in the left figure in Figure 2(a) to the state in the central figure in Figure 2(a) (i.e., from the state at the start of movement of the object 9 (subject 1) to the state during movement). The right-hand diagram of Figure 2(a) shows the state of the object 9 (subject 1) at the end of its movement, i.e., the state when the distance traveled by the object 9 (subject 1) reaches the difference d, and the right-hand diagram of Figure 2(b) shows an image 20 captured from the state of the object 9 (subject 1) shown in the left-hand diagram of Figure 2(a) to the state shown in the right-hand diagram of Figure 2(a) (i.e., from the state when the object 9 (subject 1) starts moving to the state when it finishes moving). The left side of Figure 2(a) shows the object 9 (subject 1) at a first position (point P1), the center of Figure 2(a) shows the object 9 (subject 1) moving from the first position (point P1) to a second position (point P2), and the right side of Figure 2(a) shows the object 9 (subject 1) at the second position (point P2). The subject 1 includes two objects 9 (object 9c, object 9d), and to find the depth (first distance L1) of each, it is necessary to acquire known values ​​of the fixed distance L, difference d, and displacement amount Z for each of object 9c and object 9d and calculate using formula (1) or formula (2). In other words, the depths (first distance L1) of object 9c and object 9d must be measured individually, and the depths (first distance L1) of object 9c and object 9d cannot be measured simultaneously.

[0033] FIG. 2(b) shows the change over time of an image 20 acquired by the depth measurement device 10, with time progressing from the left side to the right side of FIG. 2(b). The left side of FIG. 2(b) shows an image 20 acquired when the object 9 (subject 1) starts moving, i.e., when the detector 8 starts exposing. The center of FIG. 2(b) shows an image 20 acquired by continuing the exposure of the detector 8 from the start of the object 9 (subject 1) movement until it reaches a moving state. The right side of FIG. 2(b) shows an image 20 acquired by continuing the exposure of the detector 8 from the start of the object 9 (subject 1) movement until it reaches a state where it stops moving. As shown in FIG. 2(b), the image 20 includes an image 21 of the object 1, an image 23 of the object 9c, and an image 22 of the object 9d. The depth measurement device 10 exposes the detector 8 from the start of movement of the object 9 (subject 1) to the end of movement. Therefore, the captured image 20 on the right side of FIG. 2(b) includes images of the object 9 (subject 1) from the start of movement to the end of movement. In other words, the image 23 of the object 9c and the image 22 of the object 9d shown in the right diagram of Fig. 2(b) represent the amount of deviation Z between the image 23 of the object 9c and the image 22 of the object 9d when the subject 1 moves a distance (difference d) from the first position (point P1) to the second position (point P2). Therefore, the amount of deviation Z is calculated using the captured image 20 shown in the right diagram of Fig. 2(b). Furthermore, the captured image 20 on the right side of Figure 2(b) may include an image of the object 9 (subject 1) in a stationary state before it starts moving, or may include an image of the object 9 (subject 1) in a stationary state after it has finished moving. In Figure 2(b), the amount of stretching of the image 23 of object 9c and the image 22 of object 9d increases as we move from the left side to the right side. This is because the exposure time becomes longer and the amount of image lag increases as we move from the left side to the right side. In Figure 2(b), the image 23 of object 9c and the image 22 of object 9d in the right side are most stretched when captured. 2(b), the image 22 of the object 9d is elongated longer than the image 23 of the object 9c because the first distance L1 (depth) of the object 9d is smaller than that of the object 9c. The smaller the first distance L1 (depth), the longer the image of the object 9 captured in the captured image 20 is elongated.

[0034] On the other hand, in the case of the third pattern, unlike the state shown in FIG. 2(a) for the first and second patterns, the detection surface 8c and the object 9 are stationary, and the radiation source 7 moves from right to left in the X direction, which is a direction parallel to the detection surface 8c, while irradiating the object 9 (subject 1) with radiation 4. In the case of the third pattern, when the travel distance of the radiation source 7 reaches the difference d, that is, in the state shown in the right diagram of FIG. 2(a), the captured image 20 shown in the right diagram of FIG. 2(b) is obtained. In the case of the third pattern, the depth measurement device 10 exposes the detector 8 from the state at the start of movement of the radiation source 7 to the state at the end of movement. Therefore, the captured image 20 on the right side of FIG. 2(b) includes images of the object 9 (subject 1) from the state at the start of movement of the radiation source 7 to the state at the end of movement. In other words, the image 23 of the object 9c and the image 22 of the object 9d shown in the right diagram of Fig. 2(b) represent the amount of deviation Z between the image 23 of the object 9c and the image 22 of the object 9d when the radiation source 7 moves the distance (difference d) from the first position (point Q1) to the second position (point Q2). Therefore, in the case of the third pattern, as in the cases of the first and second patterns, the captured image 20 shown in the right diagram of Fig. 2(b) is used to calculate the amount of deviation Z. Furthermore, the captured image 20 on the right side of Figure 2(b) may include an image of the object 9 (subject 1) in a stationary state before the radiation source 7 starts to move, or may include an image of the object 9 (subject 1) in a stationary state after the movement of the radiation source 7 has finished.

[0035] 3 to 7, the method for measuring the amount of deviation Z will be described below by taking as an example a method for measuring the amount of deviation Z of the image of object 9d out of two objects 9 (9c, 9d) present in the subject 1. The method for measuring the amount of deviation of the image of object 9c is also the same as the method for measuring the amount of deviation Z described below.

[0036] FIG. 3 is a captured image 20 in which the image of the object 9d in the captured image 20 shown on the right side of FIG. 2(b) is enlarged. The captured image 20 shown in FIG. 3 includes an image 60 of the object 9d at a first position and a boundary (contour) 60a of the image 60, and an image 61 of the object 9d at a second position and a boundary (contour) 61a of the image 61. The image 60 of the object 9d at the first position refers to an image projected onto the position of point P3 on the detection surface 8c by the radiation 4 (see FIG. 2) irradiated from the radiation source 7 when the object 9d is at the position of point P1 as shown in FIG. 1(a), or an image projected onto the position of point Q3 on the detection surface 8c by the radiation 4 (see FIG. 2) irradiated from the radiation source 7a when the object 9d is at the position of point Q0 as shown in FIG. 1(b). The boundary (contour) 60 a of the image 60 refers to the line that forms the periphery of the image 60 . The image 61 of the object 9d at the second position refers to an image projected onto the position of point P4 on the detection surface 8c by the radiation 4 (see FIG. 2) irradiated from the radiation source 7 when the object 9d is at the position of point P2 as shown in FIG. 1(a), or an image projected onto the position of point Q4 on the detection surface 8c by the radiation 4 (see FIG. 2) irradiated from the radiation source 7b when the object 9d is at the position of point Q0 as shown in FIG. 1(b). The boundary (contour) 61 a of the image 61 refers to the line that forms the periphery of the image 61 .

[0037] Furthermore, the captured image 20 shown in FIG. The straight line 25 refers to a straight line that extends in the same direction as the movement of the object 9d (subject 1) from the first position to the second position and passes through the captured image 20.

[0038] Furthermore, the captured image 20 shown in FIG. 3 includes an intersection 60b, an intersection 60c, an intersection 61b, and an intersection 61c. The intersection 60b is the intersection of the straight line 25 and the boundary (contour) 60a, and is the point where the distribution of the rate of change in brightness value on the straight line 25 becomes a maximum value, as will be described later. The intersection 60c is the intersection of the straight line 25 and the boundary (contour) 60a, and is the point where the distribution of the rate of change in luminance value on the straight line 25 becomes a minimum value, as will be described later. The intersection 61b is the intersection of the straight line 25 and the boundary (contour) 61a, and is the point where the distribution of the rate of change in brightness value on the straight line 25 becomes a maximum value, as will be described later. The intersection 61c is the intersection of the straight line 25 and the boundary (contour) 61a, and is the point where the distribution of the rate of change in luminance value on the straight line 25 becomes the minimum value, as will be described later.

[0039] The deviation amount Z refers to the distance from the intersection point 60b to the intersection point 61b or the distance from the intersection point 60c to the intersection point 61c. The distance from intersection point 60b to intersection point 61b refers to the distance between two positions on line 25 that correspond to two maximum values ​​(26a, 26b) in the distribution of the rate of change of brightness values ​​on line 25, as shown in Figure 4. The distance from intersection 60c to intersection 61c refers to the distance between two positions on line 25 that correspond to two minimum values ​​(27a, 27b) in the distribution of the rate of change of brightness values ​​on line 25, as shown in Figure 4.

[0040] In the following, the deviation amount Z will be described as the distance from intersection point 60b to intersection point 61b, i.e., the distance between two positions on line 25 where the distribution of the rate of change of brightness values ​​on line 25 has two maximum values ​​(26a, 26b). However, this is not limited to this, and the deviation amount Z may also be the distance from intersection point 60c to intersection point 61c, i.e., the distance between two positions on line 25 where the distribution of the rate of change of brightness values ​​on line 25 has two minimum values ​​(27a, 27b). In the method for determining the deviation amount Z of the depth measurement device 10, first, two positions on the line 25 where the distribution of the rate of change in brightness value on the line 25 has two maximum values ​​(26a, 26b) are determined. The following describes the drawbacks of identifying the position on the line 25 where the distribution of the rate of change in brightness value on the line 25 becomes the maximum value (26a, 26b) based on the pixel, which is the smallest unit constituting the captured image 20, with reference to Fig. 5. Fig. 5 is a graph showing the correspondence between the amount of shift Z of the image of the object 9 shown in the captured image 20 acquired by the depth measurement device 10 and the resolution of the captured image 20. The resolution of the captured image 20 refers to the size of one pixel of the captured image 20. As shown in Figure 5, for example, if the displacement amount Z of the image of the object 9 is 400 mm, a change of just one pixel will result in a change of 2.00 mm in the depth measured by the depth measurement device 10. In other words, if the displacement amount Z of the image of the object 9 is managed in pixel units, it is not possible to require precision greater than this (for example, a depth of 0.5 mm when the displacement amount is 200 mm, a depth of 2.00 mm when the displacement amount is 400 mm, and a depth of 4.7 mm when the displacement amount is 600 mm). Therefore, it is necessary to improve the resolution of the displacement amount of the image of the object 9. Furthermore, since the brightness values ​​detected by the detector 8 contain inherent noise originating from the X-ray energy and the detector 8, when the brightness values ​​detected by the detector 8 are converted into brightness value change rates, these noises are included, which could potentially cause a decrease in the accuracy of the measurement results of the depth measurement device 10. Specifically, in addition to the influence of the inherent noise described above, when determining the position on line 25 where the maximum value (26a, 26b) of the distribution of the rate of change of brightness values ​​on line 25 is reached, it can only be determined in units of pixels (resolution) of captured image 20, which could result in a decrease in the accuracy of the measurement results of depth measurement device 10 when determining based on the pixels of captured image 20. Therefore, in order to suppress the influence of the above-mentioned inherent noise and to interpolate the numerical values ​​that should be between the values ​​of each pixel in the distribution of the brightness value change rate on the line 25, the depth measurement device 10 uses an approximation curve (moving average line) based on the moving average value of the distribution of the brightness value change rate to identify the position on the line 25 where the distribution of the brightness value change rate on the line 25 has the maximum value (26a, 26b). In other words, the depth measurement device 10 can identify the position on the line 25 at which the distribution of the rate of change in brightness value on the line 25 reaches its maximum value (26a, 26b) more precisely (finely) than the position of each pixel in the captured image 20, thereby making it possible to improve the resolution of the amount of shift in the image of the object 9. In this embodiment, the moving average refers to a simple moving average. A simple moving average (SMA) refers to a simple, unweighted average of the most recent n pieces of data. The specific value of n is determined appropriately in consideration of the accuracy of the depth measurement results of the depth measurement device 10. Furthermore, the most recent may include not only past data (to the left of the position of the desired average value on the line 25) but also future data (to the right of the position of the desired average value on the line 25).

[0041] FIG. 4 is a graph showing the distribution of luminance values ​​and the rate of change of luminance values ​​on a line 25 passing through the captured image 20 shown in FIG. 3. The horizontal axis of FIG. 4 represents the position (unit: mm) on the line 25, and the left vertical axis represents the luminance value (unit: candela per square meter (cd / m 2 )), and the right vertical axis represents the rate of change in brightness value (unit: percent (%)). The distribution of brightness values ​​on the line 25 of the captured image 20 is shown as the graph line 30 of brightness values ​​in Figure 4, and the distribution of brightness value change rates on the line 25 of the captured image 20 is shown as the graph line 31 of brightness value change rates in Figure 4.

[0042] Figure 6 is an enlarged graph of the vicinity of the maximum value 26a of the brightness value change rate when the object 9 is at the first position in the graph shown in Figure 4, and shows an enlarged view of the frame 32 shown in Figure 4. The upper part of Figure 6 shows an enlarged view of the graph line 31 of the distribution of the brightness value change rate obtained based on the captured image 20 acquired by the depth measurement device 10 (conventional method), and the lower part of Figure 6 shows an enlarged view of the moving average line 36 of the graph line 31 of the distribution of the brightness value change rate obtained based on the captured image 20 acquired by the depth measurement device 10 (method of this embodiment). The graph 34 of the distribution of the rate of change of brightness values ​​(a scatter plot with ●, discrete data for each pixel) in the upper part of FIG. 6 according to the conventional method has a maximum value 34a at position 34b on the line 25. 6 (a scatter plot with crosses, discrete data for each pixel) 35 of the distribution of the luminance value change rate according to the method of this embodiment was obtained by simple moving average processing of graph (a scatter plot with black dots, discrete data for each pixel) 34. A moving average line 36 of graph 35 is shown by a quadratic curve regression equation obtained by quadratic regression analysis of graph (a scatter plot with crosses, discrete data for each pixel) 35, and is expressed by the following mathematical formula (7).

[0043]

number

[0044] R in Equation (7) 2 The value is 0.947287996259236, and it can be said that formula (7) fits graph 35 well. R 2 This value is also called the coefficient of determination or contribution rate, and represents the goodness of fit of the regression equation derived through regression analysis; the closer it is to 1, the better the fit. 6 obtained by the conventional method and position 36b in the lower part of Fig. 6 obtained by the method of this embodiment do not match, with a difference A. This is an indication of the effect of improving the resolution of the displacement amount Z of the image of the object 9 and suppressing the influence of the inherent noise, as a result of the above-described moving average processing.

[0045] Figure 7 is an enlarged graph of the vicinity of maximum value 26b of the brightness value change rate when object 9 is at the second position in the graph shown in Figure 4, and shows an enlarged view of frame 33 shown in Figure 4. The upper part of Figure 7 shows an enlarged view of graph line 31 of the distribution of brightness value change rate obtained based on captured image 20 acquired by depth measurement device 10 (conventional method), and the lower part of Figure 7 shows an enlarged view of the moving average line of graph line 31 of the distribution of brightness value change rate obtained based on captured image 20 acquired by depth measurement device 10 (method of this embodiment). The graph 37 of the distribution of the rate of change of brightness values ​​(a scatter plot with ●, discrete data for each pixel) in the upper part of FIG. 7 according to the conventional method has a maximum value 37a at position 37b on the line 25. Graph 38 of the distribution of the rate of change in brightness values ​​(scatter plot with x's, discrete data for each pixel) in the lower part of Fig. 7 according to the method of this embodiment was obtained by simple moving average processing of graph (scatter plot with ●'s, discrete data for each pixel) 37. The moving average line of graph 39 can be expressed by a quadratic curve regression equation obtained by quadratic regression analysis of graph 38 (scatter plot with x's, discrete data for each pixel), and is expressed by the following mathematical formula (8).

[0046]

number

[0047] R in formula (8) 2 The value is 0.954592688154133, and it can be said that equation (8) fits graph 38 well. 7 obtained by the conventional method does not match with position 37b in the upper part of Fig. 7 obtained by the method of this embodiment, and there is a difference B. This is an indication of the effect of improving the resolution of the displacement amount Z of the image of the object 9 and suppressing the influence of the inherent noise described above, by the moving average processing described above.

[0048] Referring to FIG. 8, the results of measuring the depth of the object 9 by the depth measurement device 10 will be compared between the conventional method and the method of this embodiment. It can be seen that the measurement result 41 of the depth measurement device 10 of this embodiment is located at a location closer to an error of 0.0 mm than the conventional measurement result 40. In other words, by using the method for measuring the deviation amount Z adopted as the method of this embodiment, it can be seen that the error in the measurement result of the depth measurement device 10 is reduced and accuracy is improved.

[0049] (Hardware configuration of depth measurement device 10) Next, an example of the hardware configuration of the depth measurement device 10 will be described with reference to FIG. FIG. 9 is a block diagram for explaining an example of the hardware configuration of the depth measurement device according to this embodiment. The depth measurement device 10 includes a communication interface 10a, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, a storage unit 10d, a control unit 10e, and an input / output interface 10f. Furthermore, the depth measurement device 10 includes an input device 10g and an output device 10h that input and output data via an input / output interface 10f. The input device 10g is an external device that inputs data to the depth measurement device 10, and includes, for example, the detector 8, the keyboard 11, and the mouse 12. The output device 10h is an external device that outputs data generated by the depth measurement device 10, and includes the moving mechanism 5 equipped with a robot arm, the radiation source 7, the monitor 14, the printer 15, the speaker 16, and the like.

[0050] The radiation source 7 irradiates the subject 1 with radiation 4, and the detector 8 detects the radiation 4 that has passed through the subject 1. An example of the detector 8 may be an X-ray detector that detects X-rays, which are the radiation 4. More specifically, the detector 8 may be a photographic plate, photographic film, an imaging plate (IP), a flat panel detector (FPD), or the like. The radiation 4 detected by the detector 8 is displayed as a captured image, which is a two-dimensional distribution of the brightness of the radiation 4. The keyboard 11 is a type of computer input device, and is a device for transmitting data to the depth measurement device 10 by pressing keys for inputting characters and performing operations. The mouse 12 is a type of computer input device, and is a device for selecting desktop icons and the like displayed on the screen of the monitor 14 of the depth measurement device 10 with a mouse pointer. The moving mechanism 5 equipped with a robot arm moves different objects depending on the first, second, and third patterns. The robot arm is a type of industrial robot that functions like a human arm, and the operation of the movement mechanism 5 equipped with the robot arm is controlled by a movement control unit 50 (see FIG. 10) described below of the depth measurement device 10. Examples of the robot arm include a vertical articulated robot, a horizontal articulated robot, a parallel link robot, and an orthogonal robot. In the first pattern, the moving mechanism 5 equipped with a robot arm, under the control of the movement control unit 50, holds the object 9 (9a, 9b) between the radiation source 7 and the detection surface 8c at a fixed distance L, and moves the radiation source 7 and the detection surface 8c by the same distance in a direction parallel to the detection surface 8c while maintaining the distance between the radiation source 7 and the detection surface 8c at a fixed distance L. In the second pattern, the moving mechanism 5 equipped with a robot arm is controlled by the movement control unit 50 to keep the radiation source 7 and the detection surface 8c stationary and move the object 9 (9a, 9b) between the radiation source 7 and the detection surface 8c in a direction parallel to the detection surface 8c. In the third pattern, the moving mechanism 5 equipped with a robot arm is controlled by the movement control unit 50 to keep the detection surface 8c and the object 9 stationary, and move the radiation source 7 (7a, 7b) in a direction parallel to the detection surface 8c while maintaining the distance between the radiation source 7 (7a, 7b) and the detection surface 8c at a fixed distance L.

[0051] The radiation source 7 is a radiation generating device for irradiating the subject 1 with radiation 4, and the operation of the radiation source 7, such as the timing of irradiation of the radiation 4, is controlled by a depth measurement device 10. The monitor 14 is a device that displays and visualizes the data generated by the depth measurement device 10 on a screen. The printer 15 is a printing machine that prints the data generated by the depth measurement device 10 onto a paper medium or the like. The speaker 16 is a device that converts an electrical signal based on the data generated by the depth measurement device 10 into sound and emits it into the surrounding space.

[0052] The communication interface 10a has a function of performing two-way communication with other information processing devices via the information communication network 19. The depth measurement device 10 may transmit and receive data to and from the detector 8, the moving mechanism 5 including the robot arm, and the radiation source 7 via the communication interface 10a instead of the input / output interface 10f. In this case, the communication interface 10a may perform bidirectional communication with the detector 8, the moving mechanism 5 including the robot arm, and the radiation source 7 by either wired communication or wireless communication. The wireless communication method is not particularly limited, and may be Wi-Fi (registered trademark), LoRa (registered trademark), Bluetooth (registered trademark), Zigbee (registered trademark), infrared wireless communication, microwave wireless, broadcast wireless, satellite communication, or the like.

[0053] The ROM 10b can be used as a recording device, and stores a BIOS (Basic Input Output System) required for controlling the operation of each functional unit of the depth measurement device 10, various data used by the BIOS, and the like. The RAM 10c is used to configure the main memory accessed by the control unit 10e, and is also used to temporarily store various data acquired or generated by the depth measurement device 10 before storing it in the memory unit 10d. The storage unit 10d is realized by an HDD (Hard Disk Drive), an SSD (Solid State Drive), online storage, etc., and stores the OS, a depth measurement program (described later), other application software, various data used by these programs, etc. The storage unit 10d also stores various data acquired or generated by the depth measurement device 10.

[0054] The control unit 10e includes a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), etc., and is realized by a logic circuit (hardware) formed by an integrated circuit (IC (Integrated Circuit) chip, LSI (Large Scale Integration)), etc., a dedicated circuit, etc. The input / output interface 10f is an interface for transmitting and receiving data to and from the input device 10g and the output device 10h. The input / output interface 10f may use different standards depending on the data being handled, and may be compatible with multiple standards, such as HDMI (registered trademark), USB 2.0, USB 3.0, RS-232C, IEEE 1394, SCSI, and SASI.

[0055] (Functional configuration of depth measurement device 10) Next, the functional configuration of the depth measurement device 10 will be described with reference to FIG. FIG. 10 is a block diagram for explaining an example of the functional configuration of the depth measurement device 10. As shown in FIG. The depth measurement device 10 loads a depth measurement program (described later) stored in the storage unit 10d into a main memory configured with a RAM 10c, etc. The control unit 10e accesses the main memory into which the depth measurement program has been loaded and executes the depth measurement program. By executing the depth measurement program, the depth measurement device 10 has functional units such as a movement control unit 50, an acquisition unit 51, a brightness value distribution acquisition unit 52, a change rate distribution acquisition unit 53, a moving average line acquisition unit 54, an identification unit 55, a calculation unit 56, and an output unit 57 in the control unit 10e.

[0056] The movement control unit 50 controls the movement of the radiation source 7 (7a, 7b) or the object 9 (9a, 9b) so that the object 9 (9a, 9b) located at a first position (point P1 relative to point P0, point Q0 relative to point Q1) where the distance from the radiation source 7 (7a, 7b) in a direction (Y direction) perpendicular to the detection surface 8c is a first distance L1 and the distance from the radiation source 7 (7a, 7b) in a direction (X direction) parallel to the detection surface 8c is a second distance L2, moves to a second position (point P2 relative to point P0, point Q0 relative to point Q2) where the distance from the radiation source 7 (7a, 7b) in the perpendicular direction (Y direction) is the first distance L1 and the distance from the radiation source 7 (7a, 7b) in the parallel direction (X direction) is a third distance L3 different from the second distance L2.

[0057] In the case of the first pattern, the movement control unit 50 controls the movement mechanism 5 equipped with a robot arm to hold the object 9 stationary between the radiation source 7 and the detection surface 8c, and move the radiation source 7 and the detection surface 8c by the same distance in a direction parallel to the detection surface 8c while maintaining the distance between the radiation source 7 and the detection surface 8c at a fixed distance L. In the second pattern, the movement control unit 50 controls the movement mechanism 5 equipped with a robot arm to keep the radiation source 7 and the detection surface 8c stationary and move the object 9 (9a, 9b) between the radiation source 7 and the detection surface 8c in a direction parallel to the detection surface 8c. In the third pattern, the movement control unit 50 controls the movement mechanism 5 equipped with a robot arm to keep the detection surface 8c and the object 9 stationary, and move the radiation source 7 (7a, 7b) in a direction parallel to the detection surface 8c while maintaining the distance between the radiation source 7 (7a, 7b) and the detection surface 8c at a fixed distance L.

[0058] The acquisition unit 51 causes the radiation source 7 (7a, 7b) to continue irradiating the object 9 (9a, 9b) with radiation 4 while the object 9 (9a, 9b) moves from the first position to the second position, and captures an image of the object 9 (9a, 9b) moving from the first position to the second position and acquires it as a single captured image 20. The first position is a relative position, and as shown in FIG. 1, in the first and second patterns, it refers to point P1 relative to point P0, and in the third pattern, it refers to point Q0 relative to point Q1. The second position is a relative position, and as shown in FIG. 1, in the first and second patterns, it refers to point P2 relative to point P0, and in the third pattern, it refers to point Q0 relative to point Q2. The acquisition unit 51 acquires the captured image 20 from the detector 8 .

[0059] The luminance value distribution acquisition unit 52 acquires, as the luminance value distribution, the luminance values ​​of the captured image 20 on a line 25 that extends in the same direction as the movement from the first position to the second position and passes through the captured image 20. The brightness value distribution acquisition unit 52 acquires the brightness values ​​of the captured image 20 shown in Fig. 3 as a brightness value distribution on the line 25. An example of the brightness value distribution on the line 25 acquired by the brightness value distribution acquisition unit 52 is shown as a graph line 30 of brightness values ​​in Fig. 4.

[0060] The change rate distribution acquisition unit 53 acquires the change rates of the luminance values ​​in the luminance value distribution at positions on the line 25 as the luminance value change rate distribution. An example of the brightness value change rate distribution on the line 25 acquired by the change rate distribution acquisition unit 53 is shown as a graph line 31 of the brightness value change rate in FIG. The maximum value 26a of the graph line 31 is the brightness value at the intersection of the boundary (contour) 60a of the image 60 of the object 9 at the first position and the line 25. The minimum value 27a of the graph line 31 is the brightness value at the intersection of the boundary (contour) 60a of the image 60 of the object 9 at the first position and the line 25. The maximum value 26b of the graph line 31 is the brightness value at the intersection of the boundary (contour) 61a of the image 61 of the object 9 at the second position and the line 25. The minimum value 27b of the graph line 31 is the brightness value of the intersection between the boundary (contour) 61a of the image 61 of the object 9 at the second position and the line 25. The brightness value change rate distribution reaches its maximum value when passing through the boundaries (contours) 60a, 61a of the images 60, 61 of the object 9 from the outside to the inside, and reaches its minimum value when passing through the boundaries (contours) 60a, 61a of the images 60, 61 of the object 9 from the inside to the outside.

[0061] The moving average line acquisition unit 54 acquires a moving average line by graphing the average values ​​of the change rates at predetermined intervals on the straight line 25 of the brightness value change rate distribution. The predetermined interval refers to the most recent n pieces of data used to calculate the average of the simple moving average, and refers to the number of pieces of data (interval) used to calculate the average of the simple moving average. The predetermined interval is determined appropriately in consideration of the accuracy of the depth measurement results of the depth measurement device 10.

[0062] The identification unit 55 identifies the distance between the position on the line 25 of the extreme value of the moving average line when the object 9 (9a, 9b) is at the first position and the position on the line 25 of the extreme value of the moving average line when the object 9 is at the second position as the deviation amount Z of the object 9 (9a, 9b) in the captured image 20. An extreme value is a local maximum or minimum. The moving average line is a line graph represented by a regression equation derived by regression analysis of the dots that make up graph 35 of the distribution of the rate of change of brightness values ​​shown in FIG. 6 and graph 38 of the distribution of the rate of change of brightness values ​​shown in FIG. 7. The moving average line 36 shown in FIG. 6 is expressed by a quadratic curve regression equation (Equation (7)) derived by performing quadratic regression analysis on the dots that make up the graph 35. The moving average line 39 shown in FIG. 7 is expressed by a quadratic curve regression equation (Equation (8)) derived by performing quadratic regression analysis on the dots that make up the graph 38. The determination unit 55 determines, as the deviation amount Z, the distance between the position 36b on the line 25 where the maximum value 36a of the formula (7) is obtained and the position 39b on the line 25 where the maximum value 39a of the formula (8) is obtained.

[0063] The calculation unit 56 calculates the first distance L1 as the depth based on the fixed distance L, the difference d between the second distance L2 and the third distance L3, and the deviation amount Z. In the case of the first pattern and the second pattern, the calculation unit 56 uses formula (1) to calculate the depth (first distance L1) using the fixed distance L, the difference d between the second distance L2 and the third distance L3, and the deviation amount Z identified by the identification unit 55 as known values. In the case of the third pattern, the calculation unit 56 uses formula (2) to calculate the depth (first distance L1) using the fixed distance L, the difference d between the second distance L2 and the third distance L3, and the deviation amount Z identified by the identification unit 55 as known values.

[0064] The output unit 57 outputs the first distance L1 as the depth of the object 9. That is, the output unit 57 outputs the first distance L1 calculated by the calculation unit 56 as the depth of the object 9 via the monitor 14, the printer 15, the speaker 16, and the like.

[0065] Figure 11 is a graph comparing a graph line 42 of the brightness value distribution on a straight line 25 passing through the captured image 20 acquired by the depth measurement device 10 with a graph line 43 of the "moving average -3σ (standard deviation)" of the brightness value distribution. The probability that the brightness value distribution 42 on the line 25 falls within the range of the Bollinger band between "moving average - 3σ (standard deviation)" 43 and "moving average + 3σ (standard deviation)" is 99.73%. As shown in FIG. 11, it can be seen that the variation between the two maximum values ​​of the luminance value distribution 42 on the line 25 is extremely small.

[0066] (Depth measurement method and depth measurement program) Next, a depth measurement program according to one embodiment of the present invention will be described together with a depth measurement method with reference to Fig. 12. Fig. 12 is a flowchart of the depth measurement program according to this embodiment. The depth measurement method is executed by the control unit 10e of the depth measurement device 10 based on the depth measurement program. The depth measurement program includes a movement control step S50, an acquisition step S51, a brightness value distribution acquisition step S52, a change rate distribution acquisition step S53, a moving average line acquisition step S54, a specification step S55, a calculation step S56, and the like. The depth measurement program causes the control unit 10e of the depth measurement device 10 to perform a movement control function, an acquisition function, a brightness value distribution acquisition function, a change rate distribution acquisition function, a moving average line acquisition function, a specification function, a calculation function, etc. These functions are executed in the order shown in the flowchart of Fig. 12, but the order can also be changed as appropriate. Note that each function overlaps with the description of the various functional units of the depth measurement device 10 described above, and therefore detailed description thereof will be omitted.

[0067] The movement control function controls the movement of the radiation source 7 or the object 9 so that the object 9, which is located at a first position where the distance from the radiation source 7 in a direction perpendicular to the detection surface 8c (Y direction) is a first distance L1 and the distance from the radiation source 7 in a direction parallel to the detection surface 8c (X direction) is a second distance L2, relative to the radiation source 7, moves to a second position where the distance from the radiation source 7 in the perpendicular direction (Y direction) is the first distance L1 and the distance from the radiation source 7 in the parallel direction (X direction) is a third distance L3 different from the second distance L2 (S50: movement control step). The first position is a relative position, and as shown in FIG. 1, in the first and second patterns, it refers to point P1 relative to point P0, and in the third pattern, it refers to point Q0 relative to point Q1. The second position is a relative position, and as shown in FIG. 1, in the first and second patterns, it refers to point P2 relative to point P0, and in the third pattern, it refers to point Q0 relative to point Q2.

[0068] The acquisition function causes the radiation source 7 to continue irradiating the object 9 with radiation 4 while the object 9 moves from the first position to the second position, and captures an image of the object 9 moving from the first position to the second position and acquires it as a single captured image 20 (S51: acquisition step).

[0069] The brightness value distribution acquisition function acquires the brightness values ​​of the captured image 20 on a line 25 that extends in the same direction as the movement from the first position to the second position and passes through the captured image 20 as a brightness value distribution (S52: brightness value distribution acquisition step).

[0070] The change rate distribution acquisition function acquires the change rates of the luminance values ​​in the luminance value distribution at positions on the line 25 as the luminance value change rate distribution (S53: change rate distribution acquisition step).

[0071] The moving average line acquisition function acquires a moving average line that is a graph of the average value of the rate of change at a predetermined interval on the line 25 of the brightness value change rate distribution (S54: Acquire moving average line).

[0072] The identification function identifies the distance between the position on the moving average line of the extreme value of the moving average line when the object is at the first position and the position on the line of the extreme value of the moving average line when the object is at the second position as the amount of deviation of the object in the captured image (S55: identification step).

[0073] The calculation function calculates the first distance L1 as the depth based on the fixed distance L, the difference d between the second distance L2 and the third distance L3, and the deviation amount Z (S56: calculation step).

[0074] (Other embodiments of the depth measurement method and depth measurement program) Next, a depth measurement program according to another embodiment of the present invention will be described together with a depth measurement method according to another embodiment with reference to Fig. 13. Fig. 13 is an example of a flowchart of the depth measurement program according to another embodiment. The flowchart of the depth measurement program according to another embodiment shown in FIG. 13 differs from the flowchart of the depth measurement program shown in FIG. 12 in that an output step S57 is added. The depth measurement method according to the other embodiment is executed by the control unit 10e of the depth measurement device 10 based on the depth measurement program according to the other embodiment shown in FIG. The depth measurement program of another embodiment shown in Figure 13 includes a movement control step S50, an acquisition step S51, a brightness value distribution acquisition step S52, a change rate distribution acquisition step S53, a moving average line acquisition step S54, an identification step S55, a calculation step S56, and an output step S57.

[0075] 13 causes the control unit 10e of the depth measurement device 10 to realize a movement control function, an acquisition function, a brightness value distribution acquisition function, a change rate distribution acquisition function, a moving average line acquisition function, a specification function, a calculation function, an output function, etc. These functions are executed in the order shown in the flowchart of FIG. 13, but the order can also be changed as appropriate. Hereinafter, the depth measurement method and depth measurement program according to another embodiment shown in FIG. 13 will be described, focusing only on the differences from the depth measurement method and depth measurement program shown in FIG. Furthermore, since each function overlaps with the description of the various functional parts of the depth measurement device 10 described above, detailed description thereof will be omitted. The output function outputs the first distance L1 as the depth of the object 9 (S57: output step).

[0076] (Effects of the embodiment) According to the depth measurement device 10 of the above-described embodiment, the resolution in identifying the position on the straight line 25 where the distribution of the rate of change in brightness value of the captured image 20 takes the maximum value, and further the resolution in measuring the amount of shift Z of the image of the object 9, can be improved, thereby improving the accuracy of measuring the depth of the object 9 in the subject 1.

[0077] Furthermore, according to the depth measurement device 10 of the above-described embodiment, by performing moving average processing of the distribution of the rate of change of brightness values ​​of the captured image 20, the influence of the X-ray energy irradiated by the radiation source 7 and the inherent noise originating from the detector 8 can be suppressed, and the measurement accuracy of the depth of the object 9 in the subject 1 can be improved.

[0078] Furthermore, according to the depth measurement device 10 of the above-described embodiment, the accuracy of measuring the depth of the object 9 in the subject 1 can be improved regardless of whether the relative relationship between the radiation source 7, the detection surface 8c, and the object 9 is the first pattern, the second pattern, or the third pattern.

[0079] The present invention is not limited to the depth measurement device 10, depth measurement method, and depth measurement 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 described in the claims. Furthermore, in the above embodiment, the term "data" is used, but the term "data" can be replaced with "information" and the term "information" can be replaced with "data." Furthermore, in the above-described embodiment, the word "when" may be replaced with "state," and the word "state" may be replaced with "when." For example, "when in the first position" may be replaced with "state of being in the first position," and "state of being in the first position" may be replaced with "when in the first position." [Explanation of symbols]

[0080] 1. Subject 4. Radiation 5 Moving mechanism 7 Radiation source 7a Radiation source before moving 7b Radiation source after transfer 8 Detectors 8c Detection surface 9 Objects 9a Object before movement 9b Object after movement 9c Object 9d Object 10 Depth measuring device 10a Communication Interface 10b ROM 10c RAM 10d storage section 10e Control Unit 10f Input / Output Interface 10g input device 10h output device 11 Keyboard 12 Mouse 14 monitors 15 Printers 16 speakers 19 Information and Communications Networks 20 Captured images 21 Image of the subject 22 Image of object 9d 23 Image of Object 9c 25 straight line 26a Maximum 26b Maximum 27a Minimum value 27b Local minimum 30 Brightness value graph lines 31 Graph of the rate of change of brightness value 32 slots 33 slots 34 Graph of the rate of change of brightness value of frame 32 34a Maximum value of the rate of change of brightness value 34b Position on line 25 35 Graph of the distribution of brightness value change rate 36 Moving average of the graph line of the rate of change of the brightness value in box 32 36a Maximum value of the rate of change of brightness value 36b Position on line 25 where the rate of change of brightness value is the maximum 37 Graph of the rate of change of brightness value in frame 33 37a Maximum value of the rate of change of brightness value 37b Position on line 25 38 Graph of the distribution of brightness value change rate 39 Moving average of the graph line of the rate of change of the brightness value in box 33 39a Maximum value of the rate of change of brightness value 39b Position on line 25 where the rate of change of brightness value is the maximum 40 Conventional measurement results 41 Measurement results of this embodiment 50 Movement control unit 51 Acquisition Department 52 Brightness value distribution acquisition unit 53 Change rate distribution acquisition unit 54 Moving average line acquisition part 55 Specific part 56 Calculation section 57 Output section 60 Image of object at first position 60a Boundary (Outline) 60b Intersection (intersection of the line 25 and the boundary (contour) 60a) 60c Intersection (intersection of line 25 and boundary (contour) 60a) 61 Image of object at second position 61a Boundary (Contour) 61b Intersection (intersection of the line 25 and the boundary (contour) 61a) 61c Intersection (intersection of the line 25 and the boundary (contour) 61a) d Difference (travel distance) L fixed distance L1 1st distance (depth) L2 2nd distance L3 Third distance Point P0 (position of radiation source 7) Point P1 (position of object 9a before movement) Point P2 (position of object 9b after movement) Point P3 (position of the image of object 9a before movement) Point P4 (position of the image of object 9b after movement) Point Q0 (position of object 9) Point Q1 (position of radiation source 7a before movement) Point Q2 (position of radiation source 7b after movement) Point Q3 (position of the image of radiation source 7a before movement) Q4 point (position of the image of radiation source 7b after movement) A difference B difference X: Parallel to the detection surface Y: Orthogonal to the detection surface Z deviation amount

Claims

1. 1. A depth measurement device comprising: a radiation source that emits radiation; a detector that has a detection surface that faces the radiation source and detects the radiation emitted by the radiation source, and maintains a fixed distance between the detection surface and the radiation source; and a control unit, wherein the depth measurement device measures the depth of an object present inside a subject by irradiating radiation, The control unit a movement control unit that controls movement of the radiation source or the object so that the object, which is located at a first position where the distance from the radiation source in a direction perpendicular to the detection surface is a first distance and the distance from the radiation source in a direction parallel to the detection surface is a second distance, moves to a second position where the distance from the radiation source in the perpendicular direction is the first distance and the distance from the radiation source in the parallel direction is a third distance different from the second distance; an acquisition unit that causes the radiation source to continue irradiating the object with radiation while the object is moving from the first position to the second position, and captures an image of the object moving from the first position to the second position and acquires the image as a single captured image; a luminance value distribution acquisition unit that acquires, as a luminance value distribution, luminance values ​​of the captured image on a straight line that extends in the same direction as the movement from the first position to the second position and passes through the captured image; a change rate distribution acquisition unit that acquires a change rate of the luminance value in the luminance value distribution at a position on the line as a luminance value change rate distribution; a moving average line acquisition unit that acquires a moving average line by graphing an average value of the change rates at predetermined intervals on the line of the brightness value change rate distribution; an identification unit that identifies, on the moving average line, a position on the line of an extreme value of the moving average line when the object is at the first position and a position on the line of the extreme value of the moving average line when the object is at the second position as a displacement amount of the object in the captured image; a calculation unit that calculates the first distance as the depth based on the fixed distance, a difference between the second distance and the third distance, and the deviation amount; A depth measurement device comprising:

2. a moving mechanism that moves the radiation source and the detection surface by the same distance in a direction parallel to the detection surface while keeping the object stationary between the radiation source and the detection surface and maintaining the distance between the radiation source and the detection surface at the fixed distance, The depth measurement device according to claim 1 , wherein the movement control unit controls the movement mechanism.

3. a moving mechanism that moves the object between the radiation source and the detection surface in a direction parallel to the detection surface while keeping the radiation source and the detection surface stationary; The depth measurement device according to claim 1 , wherein the movement control unit controls the movement mechanism.

4. a moving mechanism that moves the radiation source in a direction parallel to the detection surface while keeping the detection surface and the object stationary and maintaining the distance between the radiation source and the detection surface at the fixed distance, The depth measurement device according to claim 1 , wherein the movement control unit controls the movement mechanism.

5. The depth measurement device according to claim 1 , wherein the extreme value is a maximum value or a minimum value.

6. 5. The depth measurement device according to claim 2, wherein the movement mechanism comprises a robot arm.

7. The depth measurement device according to claim 1 , further comprising an output unit that outputs the first distance as the depth of the object.

8. 1. A depth measurement method for use in a depth measurement device that measures the depth of an object present inside a subject by irradiating radiation, the depth measurement method comprising: a radiation source that emits radiation; a detector that has a detection surface that faces the radiation source and detects the radiation emitted by the radiation source, and maintains a fixed distance between the detection surface and the radiation source; and a control unit, The control unit a movement control step of controlling movement of the radiation source or the object so that the object, which is present at a first position where the distance from the radiation source in a direction perpendicular to the detection surface is a first distance and the distance from the radiation source in a direction parallel to the detection surface is a second distance, relative to the radiation source, moves to a second position where the distance from the radiation source in the perpendicular direction is the first distance and the distance from the radiation source in the parallel direction is a third distance different from the second distance; an acquiring step of causing the radiation source to continue irradiating the object with radiation while the object is moving from the first position to the second position, and acquiring an image of the object moving from the first position to the second position as a single captured image; a brightness value distribution acquisition step of acquiring, as a brightness value distribution, brightness values ​​of the captured image on a straight line that extends in the same direction as the movement from the first position to the second position and passes through the captured image; a change rate distribution acquisition step of acquiring a change rate of the luminance value in the luminance value distribution at positions on the line as a luminance value change rate distribution; a moving average line acquisition step of acquiring a moving average line by graphing the average value of the change rate at a predetermined interval on the line of the brightness value change rate distribution; an identifying step of identifying, as a displacement amount of the object in the captured image, a distance between a position on the moving average line of an extreme value of the moving average line when the object is at the first position and a position on the moving average line of an extreme value of the moving average line when the object is at the second position; a calculation step of calculating the first distance as the depth based on the fixed distance, a difference between the second distance and the third distance, and the deviation amount; A depth measurement method comprising:

9. 1. A depth measurement program for use in a depth measurement device that measures the depth of an object present inside a subject by irradiating radiation, the depth measurement program comprising: a radiation source that emits radiation; a detector that has a detection surface that faces the radiation source and detects the radiation emitted by the radiation source, and maintains a fixed distance between the detection surface and the radiation source; and a control unit, The control unit a movement control function that controls movement of the radiation source or the object so that the object, which is located at a first position where the distance from the radiation source in a direction perpendicular to the detection surface is a first distance and the distance from the radiation source in a direction parallel to the detection surface is a second distance, moves to a second position where the distance from the radiation source in the perpendicular direction is the first distance and the distance from the radiation source in the parallel direction is a third distance different from the second distance; an acquisition function of causing the radiation source to continue irradiating the object with radiation while the object is moving from the first position to the second position, and capturing an image of the object moving from the first position to the second position and acquiring the image as a single captured image; a brightness value distribution acquisition function that acquires, as a brightness value distribution, brightness values ​​of the captured image on a straight line that extends in the same direction as the movement from the first position to the second position and passes through the captured image; a change rate distribution acquisition function that acquires the change rates of the luminance values ​​in the luminance value distribution at positions on the line as a luminance value change rate distribution; a moving average line acquisition function for acquiring a moving average line obtained by graphing the average value of the change rate at a predetermined interval on the line of the brightness value change rate distribution; an identifying function that identifies, on the moving average line, a position on the line of an extreme value of the moving average line when the object is at the first position and a position on the line of the extreme value of the moving average line when the object is at the second position as a displacement amount of the object in the captured image; a calculation function that calculates the first distance as the depth based on the fixed distance, a difference between the second distance and the third distance, and the deviation amount; A depth measurement program characterized by realizing the above.

Images