JP2020046231A - Method and device for three-dimensional display of radiation distribution - Google Patents

Abstract

To detect the position of a radioactive material in a wide range of a ground surface with high accuracy and displays it in three-dimensions.SOLUTION: The present invention measures radiation using a radiation detector (Compton camera 20) mounted in a moving vehicle (drone 10) capable of detecting a three-dimensional position; creates a three-dimensional map of radiation distribution by using the result of measurement by the radiation detector (20) at a plurality of positions obtained along with the movement of the moving vehicle (10) and the three-dimensional position information of the moving vehicle (10); and corrects a radiation measured value by the radiation detector (20) for time according to the time taken for measurement per unit area of a ground surface (6) when stacking the three-dimensional map of radiation distribution on top of three-dimensional topographic data or aerial photograph. Furthermore, it is possible to correct the radiation measured value for distance according to the distance between the radiation detector (20) and the ground surface (6), or correct the same for angle according to the incident angle of radiation relative to the radiation detector (20).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and apparatus for displaying a three-dimensional radiation distribution, and more particularly, to a three-dimensional display method of a radiation distribution capable of detecting a position of a radioactive material over a wide area on the ground surface with high accuracy and displaying the three-dimensional image. And an apparatus.

  When a large amount of radioactive material diffuses into the environment due to an accident and causes pollution over a wide area, the radioactive material accumulates to determine high-dose rate spots (hot spots), and the radioactive material or radioactive material is attached Must be removed or shielded for decontamination. When performing such decontamination work, it is necessary to monitor radiation over a wide area. As methods for monitoring radiation over a wide area, Patent Documents 1 and 2 disclose a method of mounting a Compton camera on a moving object such as an aircraft or a radio-controlled helicopter and detecting radioactive substances on the ground.

JP 2014-145628 A JP-A-2006-20832

  However, conventionally, three-dimensional terrain data and measurement time by a Compton camera were not taken into account, so that it was difficult to detect and display with high accuracy.

  The present invention has been made in order to solve the above-mentioned conventional problems. By taking into account three-dimensional terrain data and the time taken for measurement, the position of a radioactive material in a wide area on the ground can be detected with high accuracy. To enable three-dimensional display.

  The present invention measures radiation using a radiation detector mounted on a movable body capable of detecting a three-dimensional position, and the measurement results by the radiation detector at a plurality of positions obtained with the movement of the movable body. When a three-dimensional map of the radiation distribution is created by using the three-dimensional position information of the moving object and the three-dimensional map of the radiation distribution is displayed by being superimposed on three-dimensional topographic data or aerial photograph, The object of the present invention is to solve the problem by time-correcting a radiation measurement value by the radiation detector in accordance with a time required for measurement per unit area of the ground surface.

  Here, the radiation measurement value by the radiation detector can be distance-corrected according to the distance between the radiation detector and the ground surface.

  Further, the radiation measurement value of the radiation detector can be angle-corrected in accordance with the incident angle of radiation on the radiation detector.

  Further, the moving body may be a drone, and the radiation detector may be a Compton camera.

  The present invention also provides a moving body capable of detecting a three-dimensional position, a radiation detector mounted on the moving body, and measurement results obtained by the radiation detector at a plurality of positions obtained as the moving body moves. Means for creating a three-dimensional map of the radiation distribution by using the information and the three-dimensional position information of the moving object; means for acquiring three-dimensional topographic data or aerial photograph; Means for superimposing and displaying dimensional topographic data or aerial photograph, and means for time-correcting the radiation measurement value by the radiation detector according to the time required for measurement per unit area of the ground surface. It is another object of the present invention to provide a three-dimensional display device for radiation distribution.

  Here, it is possible to further include a unit for correcting a distance measured by the radiation detector according to a distance between the radiation detector and the ground surface.

  The apparatus may further include means for correcting the angle of the radiation measured by the radiation detector according to the incident angle of the radiation to the radiation detector.

  According to the present invention, a three-dimensional map of the radiation distribution is created in consideration of the time required for measurement per unit area of the ground surface, and the three-dimensional map of the radiation distribution is superimposed on the three-dimensional topographic data or the aerial photograph. Since they are displayed together, it is possible to detect the position of the radioactive substance over a wide area of the ground surface with high accuracy and display the three-dimensional display. In particular, when the radiation measurement value by the radiation detector is corrected for the distance according to the distance between the radiation detector and the ground surface or when the angle is corrected according to the incident angle of the radiation to the radiation detector, an even higher value is obtained. Accuracy can be detected and displayed.

FIG. 2 is a perspective view illustrating a state in which radiation data is acquired according to the first embodiment of the present invention. FIG. 2 is a perspective view illustrating a configuration of a drone equipped with a Compton camera used in the first embodiment. Similarly, (A) a configuration diagram of the Compton camera for explaining the principle of the Compton camera, and (B) a plan view showing the relationship between the Compton cone and the source position. Similarly, (A) is a perspective view for explaining distance correction at the time of Compton cone reconstruction, and (B) is a diagram showing an example of a correction coefficient. Similarly, (A) an angle characteristic image diagram, (B) a diagram showing an example of a correction coefficient, and (C) a diagram showing an example of an angle-corrected Compton cone for explaining angle correction at the time of reconstruction of a Compton cone. FIG. 9A is a view showing an example of a photographed image, FIG. 8B is a view showing an example of a measurement time distribution, and FIG. 5 is a flowchart illustrating a processing procedure according to the first embodiment. FIG. 4 is a diagram illustrating an example of topographic data acquired in the first embodiment. Diagram showing an example of radiation distribution FIG. 6 is a diagram showing an example of combining radiation distribution and topographic data in the first embodiment. Diagram showing an example of combining radiation distribution and aerial photography A perspective view showing a configuration of a drone equipped with a Compton camera and an optical camera used in a second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments and examples. In addition, constituent elements in the embodiments and examples described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are in a so-called equivalent range. Furthermore, the constituent elements disclosed in the embodiments and examples described below may be appropriately combined, or may be appropriately selected and used.

  In the first embodiment of the present invention, as schematically shown in FIG. 1, radiation data is acquired while moving (flighting) a drone 10 equipped with a Compton camera 20.

  As shown in detail in FIG. 2, the drone 10 has a propeller 14 attached to a frame 12, a Compton camera 20 attached to the frame 12 via a stay 16 and a gimbal 18, and a drone 10 mounted on the frame 12. A small computer (PC) 32 for information preprocessing, a communication device 34 for communication with the ground, and a battery 36 for power supply are provided.

  In FIG. 1, 40 is a communication device on the ground side, 42 is a computer (PC) for information main processing, and 44 is a display for display.

  The Compton camera 20 is attached to the stay 16 via a gimbal 18 so that the camera shooting direction can be stabilized regardless of the flying state of the drone 10.

  As shown in FIG. 3A, the Compton camera 20 includes a scintillator array 22A and a silicon photomultiplier (SiPM) array 22B, and a scatterer detector 22 for detecting a scattering position and energy; An absorber detector 24 for detecting an absorption position and energy, which is constituted by the scintillator array 24A and the SiPM array 24B, can be provided.

Then, the energy E _γ of the radiation source 8 and the scattering angle θ of the Compton scattering are calculated using the positions X ₁ , X ₂ and the energies E ₁ , E ₂ measured by the scatterer detector 22 and the absorber detector 24. Is calculated based on the following equation.
Here, _me is the mass of the electron, C is the speed of light, and _me C ² represents the resting energy of the electron.

  By superposing the obtained Compton cones 26 as shown in FIG. 3B, the position of the radiation source 8 can be specified.

  Therefore, from the drone 10, posture information such as azimuth, roll, and pitch, and position information such as latitude, longitude, and altitude are acquired. From the Compton camera 20, the scattering angle θ and the direction of the Compton cone 26 are acquired.

  The information acquired from the drone 10 and the Compton camera 20 is recorded and integrated, and the Compton cone 26 is drawn on a separately acquired three-dimensional terrain model, thereby reconstructing the radiation distribution.

  When acquiring the radiation data with the Compton camera 20, the radiation distribution is multiplied by the correction coefficient of the distance correction and the angle correction at the time of the reconstruction of the Compton cone 26 in consideration of the characteristic of the radiation and the directional characteristic of the Compton camera 20. It is displayed correctly.

That is, as shown in FIG. 4A, the distance between the Compton camera 20 and the ground surface 6 has a large effect at a small distance and a small effect at a large distance. 4B, the distance L between the Compton cone 26 and the Compton camera 20 drawn on the terrain model is calculated. As shown in FIG. 4B, the distance L is smaller than 1 when the distance is 0, and larger than 1 when the distance is large. A distance correction coefficient A that is proportional to the square of the distance L is calculated as shown in the following formula, and the Compton cone 26 is drawn after being corrected by multiplying by the radiation measurement value.
A = a × L ² (3)
Here, a is an arbitrary number.

  Further, as shown in FIG. 5A, the characteristics differ depending on the incident angle of the radiation from the radiation source 8 to the radiation detector (the Compton camera 20 in the present embodiment), and the radiation source 8 faces the Compton camera 20 directly. 5B, and the influence of the position oblique to the Compton camera 20 is reduced, so that the angle correction which is set for each angle and becomes the minimum value 1 when the angle is 0 as shown in FIG. The coefficient is corrected by multiplying the radiation measurement value to draw the Compton cone 26 in which a portion far from the center is emphasized as shown in FIG. Since the angle characteristics differ depending on the Compton camera 20 to be used, the angle correction coefficient can be obtained by actual measurement or simulation.

  Further, when reconstructing the radiation distribution from the radiation data obtained by moving flight imaging, the time in the imaging field of view of the Compton camera 20, that is, the measurement time, differs for each location in the imaging range. Therefore, the overlapping time of the field of view on the ground surface is integrated from the flight information of the drone 10 and the viewing angle of the Compton camera 20 as illustrated in FIG. 6 (A), and as illustrated in FIG. 6 (B). The distribution of the measurement time t per unit area of the ground surface is calculated. In FIG. 6B, a bright place has a long measurement time, and a dark place has a short measurement time.

Then, for example, the radiation measurement value is corrected by multiplying the radiation measurement value by a measurement time correction coefficient B which becomes a maximum value when the measurement time is minimum, for example, as shown in the following equation, a measurement time correction coefficient B proportional to the reciprocal of the measurement time t. , And a radiation distribution as illustrated in FIG.
Here, b is an arbitrary number.

  Accordingly, it is possible to prevent an error due to the fact that radiation detected when the measurement time is short is smaller than when the measurement time is long.

  The flight information of the drone 10 and the radiation data acquired by the Compton camera 20 are projected onto a terrain model to perform a three-dimensional reconstruction of the radiation distribution. FIG. 7 shows the procedure of radiation distribution reconstruction.

  First, in step 100, a three-dimensional model of the terrain as illustrated in FIG. 8 is created. For example, a three-dimensional model can be created by separately performing aerial photography to acquire terrain data. The radiation distribution acquired by the Compton camera 20 is reconstructed on the three-dimensional model. If a three-dimensional model of the terrain can be obtained separately, this may be used.

  Next, in step 110, distance correction as described with reference to FIG. 4 is performed according to the distance between the Compton camera 20 and the ground surface 6.

  Next, in step 120, the angle correction as described with reference to FIG. 5 is performed according to the angle between the Compton camera 20 and the radiation source 8.

  Next, at step 130, a measurement time distribution correction coefficient as described with reference to FIG. 6 is obtained according to the measurement time.

  Then, in step 140, the measurement time distribution is corrected, the radiation distribution is reconstructed, and the radiation distribution as illustrated in FIG. 9 is obtained.

  Next, in step 150, the terrain data as illustrated in FIG. 8 and the acquired image of the radiation distribution as illustrated in FIG. 9 are combined to obtain a combined image of the radiation distribution and terrain data as illustrated in FIG. To be displayed on the display 44.

  In the present embodiment, since not only the correction based on the measurement time but also the angle correction and the distance correction are performed, it is possible to obtain a particularly highly accurate radiation distribution. Note that angle correction and distance correction can be omitted as necessary.

  Further, instead of combining with the topographical data, combining with the aerial photograph taken from an oblique direction capable of three-dimensional display, a combined image of the radiation distribution and the aerial photograph is displayed on the display 44 as shown in FIG. Is also possible.

  The terrain data can also be created from an image acquired by the optical camera 50 by mounting the optical camera 50 on the same drone 10 as in the first embodiment, as in the second embodiment shown in FIG. is there. Also, an aerial photograph as shown in FIG.

  In the above-described embodiment, since the measurement data is transmitted from the communication device 34 on the drone 10 side to the communication device 40 on the ground side, quick processing is possible. Note that a memory may be provided on the drone 10 side to store the measurement data and read out later after the drone 10 returns to the ground.

  In the above embodiment, since a Compton camera having directivity is used as the radiation detector, a detailed radiation distribution can be obtained. Note that the configuration of the Compton camera is not limited to the combination of the scintillator array and the SiPM array of the embodiment. It can also be configured using.

  In addition, since a drone is used as a moving body, simple, inexpensive and stable flight is possible.

  Note that the types of the radiation detector and the moving body are not limited to these, and for example, a pinhole camera can be mounted on an unmanned or manned helicopter or automobile.

6 ... ground surface 8 ... radiation source 10 ... drone 20 ... Compton camera 42 ... computer (PC)
44 ... Display 50 ... Optical camera

Claims (7)

Measuring radiation using a radiation detector mounted on a moving object capable of detecting a three-dimensional position,
By using the measurement results of the radiation detector at a plurality of positions obtained with the movement of the moving body and the three-dimensional position information of the moving body, a three-dimensional map of the radiation distribution is created,
When displaying the three-dimensional map of the radiation distribution by superimposing it on three-dimensional terrain data or aerial photograph,
3. A three-dimensional display method of a radiation distribution, wherein the radiation measurement value by the radiation detector is time-corrected in accordance with the time required for measurement per unit area of the ground surface.   The three-dimensional radiation distribution display method according to claim 1, wherein the radiation measurement value of the radiation detector is corrected in accordance with a distance between the radiation detector and the ground surface.   3. The method according to claim 1, wherein the radiation measurement value of the radiation detector is corrected in accordance with an incident angle of radiation to the radiation detector.   4. The method according to claim 1, wherein the moving body is a drone, and the radiation detector is a Compton camera. A moving body capable of detecting a three-dimensional position,
A radiation detector mounted on the moving body;
Means for creating a three-dimensional map of radiation distribution by using measurement results of the radiation detector at a plurality of positions obtained with the movement of the moving body and three-dimensional position information of the moving body,
Means for acquiring three-dimensional terrain data or aerial photographs;
Means for superimposing and displaying the three-dimensional map of the radiation distribution with the three-dimensional terrain data or the aerial photograph;
A means for correcting the radiation measurement value by the radiation detector according to the time taken for measurement per unit area of the ground surface,
A three-dimensional display device for radiation distribution, comprising:   The three-dimensional display device for radiation distribution according to claim 5, further comprising: means for correcting a distance measured by the radiation detector according to a distance between the radiation detector and the ground surface.   7. The three-dimensional radiation distribution display device according to claim 5, further comprising: means for correcting an angle of the radiation measured by the radiation detector in accordance with an incident angle of the radiation to the radiation detector. .