Radar cross section rendering system and radar cross section rendering method

Abstract

To provide a rendering system for a radar cross section and a rendering method for a radar cross section that can perform a radar cross section analysis on a structure easily and inexpensively to display a high radar cross section domain simply in an easy-to-see way.SOLUTION: A rendering system 1 for a radar cross section comprises: a model formation device 6 which forms a model 10 simulating a structure so that frequency characteristics of a reflection ratio R of visible light in each region of the model 10 when the model 10 is irradiated with the visible light, are made to correspond to frequency characteristics of a reflection ratio r of a radar wave in said region of the model 10 when the model 10 is irradiated with the radar wave; and a rendering device 3 which computes and displays on a screen 4 frequency characteristics of reflected light in each region of the model 10 viewed from a view point 12 when the model 10 is irradiated with white light from a light source 11 based upon the frequency characteristics of the reflection ratio R of the visible light in the model 10 in a virtual space.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a radar cross section rendering system and a method for rendering a radar cross section. [Background technology]

[0002] In order to improve the stealth capability (radio stealth) of aircraft, ships, and other structures against radar, it is necessary to suppress the reflection of radar waves. In other words, it is necessary to reduce the radar cross section (hereinafter sometimes referred to as RCS). Then, at the design stage of a structure, the RCS of each part of the structure is simulated using a model that mimics the structure, and analysis is often performed on parts of the structure that have a high RCS (hereinafter sometimes referred to as high RCS parts) (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-181153 A [Patent Document 2] JP 2019-096240 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when analyzing the RCS of a structure, the analysis time is roughly proportional to the volume of the model, so if the structure is large, such as an aircraft or ship, the analysis time often takes several days to several weeks. In addition, software for analyzing RCS is generally expensive, and it is not always easy to identify high RCS areas from the analysis results.

[0005] The present invention has been made in consideration of the above-mentioned points, and has an object to provide a radar cross section rendering system and a radar cross section rendering method that are capable of easily and inexpensively performing RCS analysis on a structure and displaying high RCS areas in a simple and easy-to-understand manner. [Means for solving the problem]

[0006] To solve the above problems, one embodiment of the present invention provides a radar cross section rendering system comprising: 、 a model forming device that forms a model simulating a structure such that when visible light is irradiated onto the model, frequency characteristics of the reflectance of the visible light at each portion of the model correspond to frequency characteristics of the reflectance of the radar wave at the corresponding portion of the model when the model is irradiated with a radar wave; a direction and orientation setting device that sets, in a virtual space, a direction in which the visible light is irradiated from a light source onto the model, a direction in which the model is viewed from a viewpoint, and an orientation of the model; Based on the frequency characteristics of the reflectance of the visible light on the model, the model is illuminated with white light from the light source. anti a rendering device that calculates the frequency characteristics of the incident light and displays it on a screen; The present invention is characterized by comprising:

[0007] The reflectivity of the radar wave can be calculated as a value obtained by subtracting the attenuation rate of the radar wave from 1.

[0008] In addition, in the method of rendering the radar cross section 、 a model forming step of forming a model simulating a structure such that a frequency characteristic of a reflectance of visible light at each portion of the model when the model is irradiated with visible light corresponds to a frequency characteristic of a reflectance of a radar wave at the corresponding portion of the model when the model is irradiated with a radar wave; a direction and attitude setting step of setting, in a virtual space, a direction in which the visible light is irradiated from a light source onto the model, a direction in which the model is viewed from a viewpoint, and an attitude of the model; Based on the frequency characteristics of the reflectance of the visible light on the model, the model is illuminated with white light from the light source. anti a rendering process for calculating the frequency characteristics of the incident light and displaying it on a screen; The present invention is characterized by comprising: Effect of the Invention

[0009] According to the present invention, it is possible to easily and inexpensively perform RCS analysis on a structure and display high RCS portions in a simple and easy-to-understand manner. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a radar cross section rendering system according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart illustrating steps in a method for rendering a radar cross section according to an embodiment of the present invention. [Diagram 3] FIG. 2A is a diagram showing an example of frequency characteristics of the attenuation rate of a radar wave, and FIG. 2B is a diagram showing an example of frequency characteristics of the reflectance of a radar wave converted from the frequency characteristics of the attenuation rate of the radar wave. [Figure 4] FIG. 13 is a diagram illustrating an example of frequency characteristics of reflectance of visible light created from frequency characteristics of reflectance of radar waves. [Diagram 5] 1A and 1B are diagrams illustrating a model, a light source, and a viewpoint set in a virtual space. [Figure 6] FIG. 1 is a diagram for explaining a drawing method in the ray tracing method. [Figure 7] 1A and 1B are diagrams illustrating examples of sensors that are attached to a headset worn by a user, a finger, or the like. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a radar cross section rendering system and a radar cross section rendering method according to the present invention will be described with reference to the drawings. In the following, the description will be given on the assumption that the structure is an aircraft, but the structure does not necessarily have to be an aircraft and may be a ship, a vehicle, etc.

[0012] As shown in FIG. 1, the radar cross section rendering system 1 according to this embodiment can be configured with a computer 5 having an input device 2, a calculation device 3 and a display screen 4, and another computer 6 connected to the computer 5 via a communication network or the like. The input device 2 is composed of a keyboard, a mouse, a touch panel, etc. The arithmetic device 3 is composed of a CPU (Central Processing Unit), a memory, etc. The display screen 4 is composed of a liquid crystal display, etc.

[0013] The processes performed by each device in the radar cross section rendering system 1 will be described below. Additionally, a method for rendering a radar cross section according to this embodiment will be described with reference to the flowchart shown in FIG.

[0014] In the following, a case will be described in which a model simulating a structure is formed by the other computer 6 and the formed model is transmitted to the computer 5. Therefore, in the following, the other computer 6 will be referred to as a model forming device 6. It is also possible to configure the system so that information about the model formed by the model forming device 6 is stored in a storage medium, and the storage medium is connected to the computer 5 so that the information about the model can be input to the computer 5 . It is also possible to configure the computer 5 itself to form a model (that is, the computer 5 itself to function as a model forming device).

[0015] [Model formation process: Step S1] The model forming device 6 can be configured to create a model that simulates the shape of a structure that is to be analyzed for RCS, using a technique such as 3D CAD (Computer-Aided Design). In this case, it is possible to create a model that precisely reproduces the shape of the structure. It is also possible to create a model that approximates the shape of the structure by dividing the structure into a plurality of polygon regions, for example, and the method of creating the model can be determined appropriately.

[0016] In this embodiment, the material of the model is designed based on specular reflection (specular reflection is equivalent to total reflection by metal in terms of the characteristics of radar waves). Then, the model forming device 6 forms a model such that the frequency characteristics of the reflectance of visible light at each part of the model when visible light is irradiated onto the model correspond to the frequency characteristics of the reflectance of radar waves at that part of the model when radar waves are irradiated onto the model.

[0017] That is, in this embodiment, the frequency characteristics of the reflectance of visible light at each portion of the model are made to correspond to the frequency characteristics of the reflectance of radar waves at each portion of the structure. The specific details will be explained below.

[0018] For example, in order to maintain stealth performance in aircraft, the surface of the aircraft may be made of a radio wave absorber (i.e., the structural material of the surface may be given the function of a radio wave absorber), or a radio wave absorber may be attached or applied to the surface of the aircraft. Even if the structural material is given the function of a radio wave absorber, the attenuation rate of radar waves will vary in frequency characteristics depending on the structure (e.g., single-layer structure, multi-layer structure, etc.). Taking the example of a two-layer (two-frequency) radio wave absorber, the attenuation rate d [%] of the radar wave by the radio wave absorber may be configured to be minimal at two frequencies f1 and f2 depending on the frequency f [Hz] of the radar wave, as shown in Figure 3(a).

[0019] In this case, the frequency characteristic of the attenuation rate d of the radar wave shown in FIG. 3(a) is converted to the frequency characteristic of the reflectance rate r of the radar wave as shown in FIG. 3(b) based on the reflectance rate r=1-attenuation rate d. Then, as shown in FIG. 4, the frequency characteristic of the reflectance r of the radar wave shown in FIG. 3(b) is directly applied to the frequency characteristic of the reflectance R of visible light.

[0020] The lower limit value fmin and upper limit value fmax of the frequency of the radar wave that can be irradiated to the structure (see FIGS. 3(a) and 3(b)) are associated with the lower limit value Fmin and upper limit value Fmax of visible light (see FIG. 4), respectively. In this manner, the frequency characteristic of the reflectance R of visible light shown in FIG. 4 is calculated from the frequency characteristic of the attenuation rate d of the radar wave shown in FIG. 3(a).

[0021] In this way, the frequency characteristics of the reflectance R of visible light at a part of the model where a radio wave absorber is used can be associated with the frequency characteristics of the reflectance r (attenuation rate d) of radar waves at that radio wave absorber. The model forming device 6 performs this association process for each radio wave absorber used in the structure, and calculates the frequency characteristic of the reflectance R of visible light for each radio wave absorber.

[0022] In addition, the model forming device 6 calculates the frequency characteristics of the visible light reflectance R for each radio wave absorber in the same manner as described above for the structural materials constituting each part of the structure in which no radio wave absorber is used. That is, the frequency characteristics of the attenuation rate d of the radar wave in each structural material are obtained. Then, in the same manner as above, the frequency characteristics of the attenuation rate d of the radar wave are converted to the frequency characteristics of the reflectivity r of the radar wave based on the reflectivity r = 1 - attenuation rate d. The frequency characteristics of the reflectivity r of the radar wave are then directly applied to the frequency characteristics of the reflectivity R of visible light, and the lower limit fmin and upper limit fmax of the radar wave frequency are associated with the lower limit Fmin and upper limit Fmax of visible light, respectively.

[0023] In this manner, even for structural materials that are not radio wave absorbers, the frequency characteristics of the reflectance R of visible light are calculated from the frequency characteristics of the attenuation rate d of radar waves. In addition, for structural materials such as glass that transmit a portion of the incident radar waves, it is possible to configure the calculation of the reflectance R taking into account the transmittance of the radar waves in addition to the attenuation rate of the radar waves.

[0024] Also, for example, in the Japanese Industrial Standards (JIS Z 8120), the lower limit Fmin of visible light is set to about 360 to 400 [nm], and the upper limit Fmax is set to about 760 to 830 [nm], with a range between the lower and upper limits. However, the lower limit value Fmin and the upper limit value Fmax of visible light used here may be the lower limit value Fmin and the upper limit value Fmax defined in the analysis software or the like used in the rendering step (step S3) described later. Also, it is possible to configure so that the user sets the lower limit value Fmin and the upper limit value Fmax of visible light.

[0025] It is also possible to configure the material of the model so that it is designed to take into account not only specular reflection but also diffuse reflection (also called irregular reflection). In this case, for example, if the surface roughness, etc. can be set using analysis software used in the rendering process (step S3) described below, it may be possible to incorporate the element of diffuse reflection by setting the surface roughness, etc.

[0026] Then, the model forming device 6 assigns to each part of the model the frequency characteristic of the reflectance R of visible light of the structural material (including the case where it is a radio wave absorber; the same applies below) constituting the part of the structure corresponding to that part. In this way, the model forming device 6 forms a model such that the frequency characteristics of the reflectance R of visible light at each part of the model correspond to the frequency characteristics of the reflectance r (attenuation rate d) of radar waves at the part of the structure corresponding to that part of the model.

[0027] [Direction and attitude setting process: Step S2] Next, when the information on the model formed by the model forming device 6 is transmitted to the arithmetic device 3 of the computer 5 (see FIG. 1), the arithmetic device 3 places the model in the virtual space. Then, in response to user operation via the input device 2, the calculation device 3 sets, in the virtual space, the direction in which visible light is irradiated from the light source 11 to the model 10, the direction in which the model 10 is viewed from the viewpoint 12, and the posture of the model 10, as shown in FIG.

[0028] That is, in this embodiment, the arithmetic unit 3 of the computer 5 functions as a direction and attitude setting device of the present invention. In this case, model 10 simulates a structure (aircraft), light source 11 corresponds to a radar wave radiation source that irradiates radar waves onto the structure, and viewpoint 12 corresponds to an antenna and receiver that captures the radar waves reflected from the structure.

[0029] 5 shows a case where the light source 11 is one point light source, the light source 11 may be a plurality of point light sources, a surface light source, or a combination thereof. The direction in which visible light is irradiated from light source 11 to model 10 and the direction in which model 10 is viewed from viewpoint 12 can be set by determining the azimuth angle and elevation angle with respect to a reference direction in virtual space. Alternatively, as shown in Fig. 5, the configuration may be such that the light source 11 and viewpoint 12 are set by determining the positions (coordinates) in virtual space. Additionally, the attitude of the model 10 can be configured to set the pitch, roll and yaw of the structure (aircraft).

[0030] [Rendering process: Step S3] Next, the arithmetic unit 3 of the computer 5 calculates the frequency characteristics of the reflected light of each part of the model 10 that is visible from the viewpoint 12 when the model 10 is irradiated with white light from the light source 11, based on the frequency characteristics of the reflectance R of visible light on the model 10. Then, rendering is performed in which the frequency characteristics of the reflected light calculated for each part are attached to the corresponding part of the model 10 and displayed on the display screen 4. That is, in this embodiment, the arithmetic device 3 of the computer 5 functions as the rendering device of the present invention.

[0031] When performing the above-mentioned calculation process, the radar cross section rendering system and the radar cross section rendering method according to the present embodiment do not analyze the RCS of the model itself, but analyze the reflected light of visible light using a model that simulates the RCS. Analysis software for analyzing the reflected light of visible light and displaying the analysis results, i.e., rendering, can be downloaded from the Internet, for example, at low cost or free of charge. Therefore, in this embodiment, it is possible to easily obtain analysis software at low cost and to easily calculate the frequency characteristics of reflected visible light that simulates RCS.

[0032] As a method for rendering the frequency characteristics of reflected visible light simulating the RCS, a known method can be adopted. For example, in the ray tracing method, as shown in Fig. 6, the intersection of a ray Ra emitted from a viewpoint 12 and a model 10 is projected onto a projection surface S. Then, this process is performed while changing the direction of the ray Ra from the viewpoint 12 and scanning, so that the model 10 is projected onto the projection surface S.

[0033] Therefore, first, it is determined whether or not the ray Ra intersects with the model 10. Then, if the ray Ra intersects with the model 10, the reflected light that reflects the frequency characteristics of the reflectance R of visible light at the intersection point of the model 10 is displayed on the projection surface S with color and brightness. This process is then performed for each intersection on model 10 where ray Ra intersects, so that the reflected light from each part of model 10 is displayed in color and brightness on projection surface S (i.e., display screen 4). The rendering method is not limited to the ray tracing method.

[0034] Then, if the direction of the light source 11 or the viewpoint 12 in the virtual space or the posture of the model 10 is changed by the user via the input device 2 (step S4; YES), the arithmetic device 3 of the computer 5 performs the processes of steps S2 and S3 again. Each time the direction of the light source 11 or the viewpoint 12 or the posture of the model 10 is changed, the corresponding analysis results, that is, the color and brightness of the reflected light from each part of the model 10, are displayed on the display screen 4.

[0035] [Effect] Next, the operation of the radar cross section rendering system 1 and the radar cross section rendering method according to this embodiment will be described. In this embodiment, as described above, the RCS of the model itself is not analyzed, but the visible light reflectance R of the simulated model 10 is analyzed and rendering is performed. Therefore, as described above, analysis software that can be downloaded cheaply or free of charge from the Internet, etc., can be used. Therefore, analysis software can be easily and inexpensively obtained, and the frequency characteristics of the visible light reflectance R simulating the RCS can be easily calculated.

[0036] Furthermore, as a result of rendering, the reflected light at each part of the model 10 is displayed in color and brightness on the display screen 4. Parts with high brightness of reflected light correspond to high RCS parts in the structure. Therefore, when a user looks at the model 10 displayed on the display screen 4, it becomes possible for the user to visually and easily recognize areas where the luminance of reflected light is high as areas of high RCS in the structure.

[0037] Furthermore, areas that tend to reflect high-frequency visible light (corresponding to high-frequency radar waves) are displayed in a bluish color, and areas that tend to reflect low-frequency visible light (corresponding to low-frequency radar waves) are displayed in a reddish color. Therefore, by looking at the color of the reflected light, the user can easily visually recognize what frequency of radar waves a particular part is likely to reflect.

[0038] For example, when a part of the model 10 is specified by touching it on the display screen 4, the frequency characteristics of the reflectance R of visible light at that part (see, for example, FIG. 3(b)) or the frequency characteristics of the attenuation rate d of the radar wave (see, for example, FIG. 3(a)) can be displayed. Furthermore, the display screen 4 can be configured to display other information as appropriate.

[0039] On the other hand, as described above, in this embodiment, the light source 11 (see FIG. 5) corresponds to a radar wave emission source that irradiates a structure (such as an aircraft) with radar waves, and the viewpoint 12 corresponds to an antenna and receiver that captures the reflected waves of the radar waves from the structure. In the virtual space, the direction in which visible light is irradiated from the light source 11 onto the model 10 and the direction in which the model 10 is viewed from the viewpoint 12 can be freely set.

[0040] Therefore, in this embodiment, when the directions of the light source 11 and the viewpoint 12 with respect to the model 10 are the same, the analysis becomes equivalent to a monostatic RCS analysis. Moreover, if the direction of the light source 11 and the direction of the viewpoint 12 with respect to the model 10 are different directions, this becomes equivalent to a bistatic RCS analysis.

[0041] Furthermore, in this embodiment, when a plurality of light sources 11 are used, the analysis becomes equivalent to a multi-static RCS analysis. In this manner, the present embodiment has the feature that it is possible to easily realize monostatic, bistatic, and multistatic RCS analysis.

[0042] As described above, according to the radar cross section rendering system 1 and the radar cross section rendering method of the present embodiment, instead of performing an RCS analysis on a model simulating a structure, an analysis of reflected visible light from the model is performed. At that time, a model is formed so that the frequency characteristics of the reflectance of visible light at each part of the model when visible light is irradiated onto the model correspond to the frequency characteristics of the reflectance of radar waves at that part of the model when radar waves are irradiated onto the model. Then, based on the frequency characteristics of the reflectance of visible light on the model, the frequency characteristics of the reflected light from each part of the model that is visible from the viewpoint when white light is irradiated onto the model from a light source are calculated and displayed on the screen.

[0043] In this way, in this embodiment, the RCS of the model itself is not analyzed, but the visible light reflectance is analyzed using a model that simulates the RCS, and rendering is performed. Therefore, rendering can be performed using analysis software that can be downloaded cheaply or for free from the Internet, etc. Therefore, in this embodiment, it is possible to easily and inexpensively perform an RCS analysis of a structure (model) (actually, an analysis of reflected visible light that simulates the RCS analysis).

[0044] Furthermore, once the model has been created, the reflected visible light can be analyzed using the above-mentioned visible light analysis software, and since time-consuming RCS analysis is not required, the analysis can be completed in a shorter time than if an RCS analysis of a model were to be performed. Therefore, in this embodiment, it is possible to easily perform an RCS analysis of a structure (model) (actually, an analysis of reflected visible light that simulates the RCS analysis).

[0045] Furthermore, in this embodiment, the analysis result of reflected visible light simulating an RCS analysis of a structure (model) is displayed, and a part of the structure with a high RCS, i.e., a high RCS part, is displayed on the screen as a part with high luminance of reflected light. Therefore, according to this embodiment, it is possible to visually display high RCS areas (areas where the luminance of reflected visible light is high) in a structure (model) in an easily understandable manner.

[0046] It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, instead of displaying the analysis results on the display screen 4 of the computer 5 as described above, it is also possible to configure it so that the results are displayed as a virtual reality image on a display built into a headset 21 worn by a user 20, as shown in FIG. 7.

[0047] In this case, for example, a sensor 22 that detects the orientation of headset 21 is attached to headset 21. Then, it is possible to configure so that the direction in which model 10 is viewed from viewpoint 12 in the virtual space (see FIG. 5) can be changed according to the orientation of headset 21 detected by sensor 22. With this configuration, the user can easily change the direction in which the model 10 is viewed from the viewpoint 12 in the virtual space by simply changing the direction of his or her head and the direction of the headset 21.

[0048] Also, as shown in FIG. 7, for example, a sensor 23 is attached to the fingers of a user 20 to detect the movement of those fingers. It is possible to configure the direction in which visible light is irradiated from light source 11 in the virtual space onto model 10 and the posture of model 10 (see Figure 5) to be changed depending on the movement of fingers or the like detected by sensor 23.

[0049] In addition, as long as it is possible to detect the user's intention to change the direction of the light source 11 or the posture of the model 10 in the virtual space, it may be in the form of, for example, a controller operated by the user 20, rather than a sensor 23 attached to a finger or the like. With this configuration, the user can easily change the direction in which visible light is irradiated onto model 10 in the virtual space and the posture of model 10 by moving his or her fingers or operating a controller, etc. [Explanation of symbols]

[0050] 1. Radar Cross Section Rendering System 3 Calculation device (direction and attitude setting device, rendering device) 4 Display screen (screen) 6 Model forming device 10 Models 11 Light source 12 Viewpoints d Radar wave attenuation rate R Visible light reflectance r Radar wave reflectivity

Claims

1. a model forming device that forms a model simulating a structure such that when visible light is irradiated onto the model, frequency characteristics of the reflectance of the visible light at each portion of the model correspond to frequency characteristics of the reflectance of the radar wave at the corresponding portion of the model when the model is irradiated with a radar wave; a direction and orientation setting device that sets, in a virtual space, a direction in which the visible light is irradiated from a light source onto the model, a direction in which the model is viewed from a viewpoint, and an orientation of the model; a rendering device that calculates, based on the frequency characteristics of the reflectance of the visible light on the model, a frequency characteristic of the reflected light of each part of the model that is visible at the viewpoint when the model is irradiated with white light from the light source, and displays the frequency characteristic on a screen; 1. A radar cross section rendering system comprising:

2. 2. The radar cross section rendering system according to claim 1, wherein the reflectivity of the radar wave is calculated as a value obtained by subtracting an attenuation rate of the radar wave from 1.

3. a model forming step of forming a model simulating a structure such that a frequency characteristic of a reflectance of visible light at each portion of the model when the model is irradiated with visible light corresponds to a frequency characteristic of a reflectance of a radar wave at the corresponding portion of the model when the model is irradiated with a radar wave; a direction and attitude setting step of setting, in a virtual space, a direction in which the visible light is irradiated from a light source onto the model, a direction in which the model is viewed from a viewpoint, and an attitude of the model; a rendering step of calculating a frequency characteristic of reflected light of each part of the model that is visible at the viewpoint when the model is irradiated with white light from the light source based on a frequency characteristic of the reflectance of the visible light on the model, and displaying the calculated frequency characteristic on a screen; 16. A method for rendering a radar cross section comprising:

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