JPS61178678A - Display apparatus of image radar - Google Patents

Abstract

PURPOSE:To facilitate the discrimination of a target, by applying luminance conversion optimum to the image of an indicated part on the basis of the average luminance of the image of the indicated part. CONSTITUTION:Image intensities before and after the conversion of an image are stored in memory means 30a, 30b and the image in the means 30b is displayed on a display means CRT 18. An observer 19 indicates a specific image region to be subjected to luminance conversion by using a processing range input means 36 and a processing range display means 37 processes the range to be displayed on CRT on the basis of indication. Only the image luminance of the indicated specific region is read from the means 30b in order to convert an image and the image luminance after amplified by an amplifying means 31 and a clip means 32 is controlled so as not to exceed the max. luminance capable of being displayed by CRT 18. The amplifying ratio in this case is determined by an amplifying ratio calculation means 35 and the amplifying ratio of the means 35 is further determined by the calculation result of an average value calculation means 34. By this method, the image of the indicated part is subjected to optimum luminance conversion.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a display device for displaying a signal having an extremely wide dynamic range of signal level as an image on a cathode ray tube, and in particular for displaying radar images acquired by a video radar. It is related to the device.

[Conventional technology]

FIG. 8 is a block diagram showing the configuration of a conventional video radar. In the figure, 1 is a video radar, 2 is an antenna, 6 is a transmitter, 4 is a receiver, 5 is a signal processing device, and 6 is a video radar. A display device (hereinafter referred to as a display device), 7 is an antenna beam, 8 is an image object, 9a and 9b are pixels (pixels),
10 is a transmission radio wave, and 11 is a reception radio wave.

The video radar 1 is generally operated in either real aperture mode or synthetic aperture mode, and the display device according to the present invention is commonly applied to both modes.

In the following explanation, for the sake of simplicity, the video
is assumed to be operated in real aperture mode.

The video radar 1 radiates transmitted radio waves 10 generated by a transmitter 3 toward a video target 8 via an antenna 2. Normally, the antenna beam 7 radiated from the antenna 2 has extremely high directivity, and the transmitted radio wave 10 scans within an angle such that it hits only a portion of the image object 8. The antenna footprint created by the antenna beam 7 on the image object 8 is
This corresponds to one pixel of the radar image displayed on the cathode ray tube display device 6. The transmitted radio wave 10 is diffusely reflected on the surface of the image object 8, and is normally scattered in all directions to generate waves. Among the scattered waves, radio waves traveling in the direction of the video radar 1 are transmitted as received radio waves 11 to the receiver 4 via the antenna 2.
will be received. Receiver 4 detects received radio waves 11, extracts received power P indicating the strength of received radio waves 11, and transfers this to signal processing device 5. The signal processing device 5 receives the received power P
After converting into a digital quantity, it is stored on an internal storage means (not shown). Stored received power P
has a size corresponding to the brightness of the radar image displayed on the display device lt6, and will hereinafter be referred to as image brightness. The address on this storage means is antenna beam 7.
It was set in response to the orientation of

The video radar 1 repeats the above operations while scanning the antenna beam 7 over the video target 8 in a two-dimensional manner. However, scanning by the antenna beam 7 is performed sequentially without overlapping each pixel, for example, pixel 9a and pixel 9b.

As a result, pixels are arranged two-dimensionally on the storage means as shown in FIG. 8, and each pixel has the image brightness of the corresponding radar image. Since each address of the storage means corresponds to the directional direction of the antenna beam 7, the geometrical relationship of each image luminance P matches that represented by each pixel.

The scanning of the image object 8 by the antenna beam 7 continues until at least the entire image brightness P thereof is stored in the storage means. When all the image luminances P of the image object 8 are stored in the storage means, the signal processing device 5 transfers all the image brightnesses stored in the storage means to the storage means in the display device f116. The transferred image brightness P is converted into a video signal inside the display device 6 and then displayed on the cathode ray tube as a radar image.

However, the range of brightness values that can be achieved by the image brightness P is extremely large, hundreds of times the dynamic range of brightness that can be temporarily displayed by a normal cathode ray tube in the display device 60. The video brightness P transferred from No. 5 is compressed (brightness conversion) so that it falls within the display range of a normal cathode ray tube.

FIG. 9 is a block diagram showing the configuration of the display device 6. In the figure, 12 is a computer in the display/display device 6, 16 is a main memory of the computer 12, 14 is a central processing unit (CPU) of the computer 12, 15 is an input/output circuit of the computer 12. 16a is a display screen memory for storing the image luminance P before luminance conversion transferred from the signal processing device 5 via the input/output circuit 15, and 16b is a display screen memory for storing the luminance-converted data in the original picture memory 16a; 17 is a scan converter that converts the image brightness P of the display screen memory 16b into a video signal; 18 is a display means using a cathode ray tube (
CRT), 19 is an observer who observes the radar image displayed on the screen of the CRT 18, and 20 is an input for the observer 19 to enter data into the computer 12, including parameters necessary for a series of calculations executed by CPU 4. part (volume). On the display screen of the CRT 18, a is a radar image of the image object 8, and b and c are targets to be recognized by the observer 1'9.

FIG. 10 shows that the CPU 14 is the main memory 1 of the computer 12.
6 is a flowchart of a radar image brightness conversion processing program stored in FIG. First, in step 21, input processing of video luminance is started. Data transferred from the signal processing device 5, that is, video luminance P, is stored in both the original image memory 16a and the display screen memory 16b via the input/output circuit 15. Both the original picture memory 16a and the display screen memory 16b have a logical two-dimensional array structure, and are represented by addresses ei and j. The contents stored at address ttj can be expressed as A(i,j). Here, the contents at addresses i and j of the original picture memory 16A are written as A (1? J
), and the content 1s(i,
j). Therefore, when the transfer of the image luminance P from the signal processing device t5 is completed, the original image memo +316
Exactly the same video brightness P is stored in & and display video memo IJ 16 b.

On the other hand, Scan Gomberta 17 is a display screen memo! J1
6b constantly converts the video luminance P stored in the memory into digital/analog (D/A) to generate a video signal,
Is this t? It is displayed on the screen of cRT18. Therefore,
Initially, the radar image S displayed on the screen of the CRTlB is based on the image brightness P before brightness conversion acquired by the video radar.

At this time, in most cases, the radar image S that is first displayed is extremely bright or dark, and the probability that the observer 19 will be able to recognize the target or target C is extremely low. For this reason, the following processing is executed.

That is, the process proceeds to step 22, where the amplification coefficient α is read. Here, the amplification coefficient α is appropriately set in the input section 20 according to the state of the radar image S displayed on the CRTlB. In step 23, the content A of the video luminance P before luminance conversion is obtained from the reading addresses i and j of the original image memory 165L.
Read out (l I J ). In step 24, the content A(i, j) of the video luminance P is amplified by the calculation shown in the following equation.

R=A(i*j)・PW! IL/α・・・・・・
(1) However, P is the maximum brightness that the CRTlB can display, and R is the image brightness after amplification.

Step 25 is a process of clipping the amplified video luminance R, as shown by the following equation.

The determination of the magnitude comparison in the above equation is executed at step 26, and the process expressed by equation (2b) is executed at step 27. Here, ■ is the image luminance after luminance conversion.

In this way, in step 25, the image brightness R after amplification is
Only when lB is greater than the maximum displayable brightness Pm,
This is to update the maximum brightness Pw. In step 28, the image brightness after the brightness conversion is displayed.Screen memo IJ 16 b
Transfer to. Display screen memory 16 where image brightness ■ is written
The address b is specified by the CPU 14. CPU14
indicates the same address xtJ where the content A(i, j) of the video luminance V was read. Therefore, the content B(t, j) of address ttj in the display screen memory 16b becomes the image brightness ■. In step 29, it is determined whether the operation of converting the video luminance V consisting of steps 26 to 28 has been performed for all video luminances P stored in the original image memory 16a. Here, the original image memory 16a must be
If the radar image S in , i==M and j=N, the processing of steps 26 to 28 is repeated MN times.

Through the video brightness conversion described above, the pixel displayed at the maximum brightness Pw on the CRT 113 has its video brightness V
A (i?' J ) satisfies the following equation.

A(i,j)〉α ・・・・・・・・・(
3) As is clear from equation (3), if the amplification coefficient α is made smaller, the image brightness ■ that satisfies equation (3) increases, and the entire radar image appears visually brighter. On the other hand, when the amplification coefficient α is increased, the opposite occurs, and the entire radar image appears visually dark. In many cases when the observer 19 uses radar images, it is to detect a relatively bright target from a relatively dark background of the radar image S, and in such a usage method, the value of the amplification coefficient α is This greatly influences the probability that the observer 19 can recognize the target. For example, if the value of the amplification coefficient α is too small, the image brightness corresponding to most of the pixels
satisfies equation (3), and as a result, most of the pixels of the image object 80 are displayed with the same maximum brightness, significantly reducing the probability that the observer 19 can recognize the target. In order to maintain a high probability of target detection, it is necessary to always set the value of the amplification coefficient α to the optimum value.In the American display device, as shown in Figure 5, an observer 19 pays attention to the radar image on the CRTlB. However, the value of the amplification coefficient α was manually set by the observer 19 so that the target could be most easily recognized.

[Problem that the invention seeks to solve]

Conventional image radar optical display devices are configured as described above, so it takes trial and error operations by radar image observers to obtain the optimal brightness settings for recognizing targets on radar images. In addition, when there are multiple targets with different brightness in the radar image, in order to correctly recognize them, it is best to use a method for each image brightness of the target. This poses a problem in that it is necessary to set a certain brightness, which places a great burden on the observer, and requires a huge amount of calculation to obtain such a brightness, which also impairs the real-time nature of the display.

This invention was made to solve these problems, and even when there are multiple targets, it maximizes the probability of recognition for each target without losing real-time performance. It is an object of the present invention to provide a display device for a video radar that can perform brightness conversion as described above.

[Means for solving problems]

The video radar display device according to the present invention calculates the average value of a plurality of video brightnesses in a specific area designated by the observer among the video brightnesses stored in the storage means, and displays the calculated result. The amplification factor of the image brightness is calculated using the average value, and the specific area is displayed on the display screen with the optimum image brightness.

[Effect]

In this invention, when an observer specifies a part of the displayed radar image that he/she is particularly interested in, the image of the specified part is displayed based on the average brightness of the image of the specified part. Displayed with optimal brightness conversion to facilitate target identification.

〔Example〕

FIG. 1 is a functional block diagram of a display device for a video radar according to the present invention. This display device has a first storage means 30a for storing image brightness before brightness conversion acquired by a video radar, and a second storage means 30b for storing image brightness after brightness conversion. It is provided with a CRT 18 for displaying a video image being displayed, and a processing range input means 36 for the observer 19 to specify a specific video area for performing brightness conversion. Further, a processing range display means 67 for displaying a designated specific area on the CRT 18 and a memory access control means 68 for controlling memory access to the storage means 30a and 30b are provided, and the processing for brightness conversion is , read only the image luminance in a specific area specified by the observer 19 from the storage means 30a, transfer these to the amplification means 61 and amplify them, and then use the clip means 32 to transfer the amplified image luminance R to the CRT 18. It is configured so that the maximum display brightness is not exceeded. Furthermore, the amplification factor in the amplification means 61 is calculated by the amplification factor calculation means 35.
Furthermore, the amplification factor calculation means 65 determines the amplification factor α based on the calculation result of the average value calculation means 64. The average value calculation means 34 calculates C specified by the observer 19.
It is configured to calculate the average value of video luminance P for a specific portion of the display screen of RT18.

FIG. 2 shows a block diagram of the display device shown in FIG. 1, and corresponds to FIG. 1 as follows. An original image memory 16a corresponding to the storage means 30a, a display screen memo IJ 16b corresponding to the storage means Sob, a scan converter 17 that converts the image brightness P stored in the display screen memo 1J16b into a video signal, and a processing A tablet 39 corresponding to the range input means 66, an amplification means 61, and a clip means 62
, an average value calculation means 34 , an amplification factor calculation means 65 , a processing range display means 37 , and a combinator 12 having the functions of a memory access control means 68 . Therefore, the computer 12 uses cpul to obtain such functionality.
4, a main memory 16, and an input/output circuit 15. CR
wl and w2 shown on the screen of T18 are rectangular marks indicating the processing range.

FIG. 3 is a flowchart showing the processing executed by the CPU 14, which is the processing of the radar image brightness conversion program stored in the main memory 16.

First, step 21 is executed to input the image brightness P, and the image brightness P is stored in both the original image memo IJ 16 a and the display screen memo IJ 16 b. Along with such processing, the function of the scan converter 17 changes the image brightness P stored in the display screen memory 16b to CKTjs.
The radar image before the brightness conversion is displayed above for observer 1.
Provided on 9th. Next, the process of specifying the processing range in step 40 is started. This process instructs the computer 12 to specify an area of particular interest in the radar image being displayed on the screen of the CRT 18, and converts the brightness of only the radar image in that area. That is, by specifying this area, two coordinates x1 .゛y1 and x2
*y2 is input to the CPU 14 via the tablet 69 and the input/output circuit 15.

Next, in step 41, processing for displaying the processing range is executed. A detailed flowchart of this display processing is shown in FIG.

Step 41a is the coordinate x inputted in step 40.
1 s y 1, x 2 v y 2 is original image memory 1
6a and the display screen memory 16b, the addresses are calculated according to the following equation.

I 1 = (xl xO)/jx = (5
a) J 1 = (yl-yO)/Δy...
... (5b) I 2 = (x2 xO)/j
x −−−−・−(5c) J 2 = (y2−
yO)/Δy (5d) However, 11. Jl, I2. J2 is the calculated address and x
o, yO are constants determined from the characteristics of the tablet 69, ΔX
, Δy are constants determined by the pixel size. In step 41b, the processing range designated by the observer 19 is
This is a process for displaying on the RT18. Here, the processing range is a rectangular mark W surrounded by white bright lines on the CRT 18.
1 is displayed. For this purpose, the display screen memory 16b
Of the contents, the one at the address shown in equation (7) is (6)
It is rewritten to the maximum brightness Pm according to the formula.

B(i*j)ePm ・・・・・・・・・(
6) J=J2es='1~■2 Next, the process of determining the average brightness in step 43 is started. A detailed flowchart of this process is shown in FIG. This process calculates the average luminance AYE of 66 video luminances P at addresses i and j shown in equation (8) among the video luminances P before luminance conversion stored in the original picture memory 16g.

11 I2. JlkujkuJ2 ・・・・・・・・・
(8) The processing shown in steps 43a to 43h in FIG. 5 is to calculate the average brightness (AVE) shown in equation (9).

The process to do so will begin. This process is performed using the amplification factor α given by 190 observers in the same way as in conventional devices of this type.
The amplification factor α is calculated from the following equation 01 using the average luminance AYE obtained by the process in step 46.

However, K is a preset constant and is usually 2 to 3.

Next, the brightness conversion operation consisting of steps 23 to 29 is started.

Here, the image luminance P to be processed is limited to those whose addresses satisfy equation (8), and this series of processing would have to be repeated MN times for the image object in the conventional device. On the other hand, in the device according to the present invention, (I2-11+1)(
J2-J1+1) times. As a result, the number of calculations necessary for brightness conversion is significantly reduced, the load on the CPU 14 can be greatly reduced, and the processing time can be shortened.

When the above processing is completed, the CRTi
Of the images displayed on Q, only the portion of the image surrounded by the rectangular mark W1 is optimally converted in brightness, and the observer 19 can recognize the target T1t with a high probability. Subsequently, the observer 19 can further point out the video portion of interest with the rectangular mark W2 and recognize the target T2 in the same manner.

Now, the principle by which a target can be recognized with high probability by brightness conversion of the display device according to the present invention will be explained using the drawings.

FIG. 6 is a one-dimensional representation of the radar image brightness P stored in addresses "I1" to "I2" of the original image memory 16a, where the horizontal axis shows the memory address and the vertical axis shows the brightness. As shown in FIG. 6, large fluctuations in the image brightness P are called speckles, and are known as 1F [development that occurs because the radar is a coherent system.

In Figure 6, A is the optimal α value, the mouth is the average value of the image brightness P,
Ha is an inappropriate α value. Radar images are generally two-dimensional information, but in order to simplify the following explanation, FIG. 6 shows the image brightness distribution in only one of two orthogonal directions. The one-dimensional handling of video information in the following explanation can be easily extended to two-dimensional, without overriding the generality of the explanation.

If the image brightness obtained by radar images can be displayed as is without converting the brightness, it is obvious that there is a goal for the image brightness P to be larger than the background image brightness P, as shown in Figure 6. be. However, as mentioned above, the dynamic range of the brightness of the CRT 18 is narrower than the range of image brightness P of the radar image, so it is necessary to perform brightness conversion and compress the image brightness range of the radar image using the method described above. If we now set the value of the amplification factor α to the level of Ha, all image brightness greater than the level of Ha will be rounded to the level of Ha from the relationship of Equation 31, and the probability of recognizing the target will decrease. That is clear.

In order to automatically avoid the above-mentioned situation, the display device according to the present invention is configured to be able to set the optimum clip level (A) from the average value of the target image luminance P.

That is, the amplification factor α shown in equation 01 is determined to be inversely proportional to a constant multiple of the target average brightness. Based on the el1 equation, the optimal value of the amplification factor α can be determined from the results of visual experiments.

FIG. 7 shows the relationship between the target detection probability and a constant based on the results of a visual experiment, where the horizontal axis shows the constant K and the vertical axis shows the target detection probability.

According to the visual experiment results, the relationship shown in FIG. 7 can be obtained regardless of the size of the target or the difference in average luminance between the background and the target. If the coefficient K is larger than 2, the target detection probability will not change significantly, so by setting the coefficient Kt-2 or more, the signal processing according to the present invention can perform brightness conversion that maximizes the observer's target detection probability. Can be executed automatically.

〔Effect of the invention〕

As described above, according to the present invention, the brightness conversion is performed only in the area designated by the observer so that the observer's target detection probability is maximized, so when multiple targets exist in the same radar image, In addition, each target can be partially transformed in brightness so that it can be detected by the observer with the highest probability. As a result, the calculation time required for brightness conversion can be shortened, which is highly effective when used in video radars that require an observer to detect targets in real time.

[Brief explanation of drawings]

FIG. 1 is a functional diagram of a display device of a video radar according to an embodiment of the present invention, FIG. 2 is a block diagram of the display device shown in FIG. 1, and FIGS. 3 to 5 are a functional diagram of the display device shown in FIG. 1. 6 and 7 are characteristic diagrams explaining the principle of brightness conversion. FIG. 8 is a block diagram of a conventional video radar.
The figure is a block diagram of the display device of the video radar shown in FIG.
FIG. 10 is a flowchart showing the operation of a conventional video radar display device. 1 is a video radar, 18 is a display means (CRT), 19 is an observer, 30a and 30b are storage means, 61 is an amplification means,
32 is a clip means, 33 is an average value calculation means, 34 is an amplification factor calculation means, and 36 is a processing range input means. In addition, in the figures, the same reference numerals indicate the same parts. Patent applicant: Mitsubishi Electric Corporation Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 2 3 4. 5 Figure 8 Figure 10

Claims (1)

[Claims] The first one stores the brightness of the radar image acquired by the video radar.
storage means, amplification means for amplifying the brightness of the image stored in the first storage means, and only when the brightness of the image from the amplification means exceeds a predetermined value, the brightness of the image is set to the predetermined value. A clipping means to set, a second storage means for storing the brightness of the image from the clipping means, and a plurality of brightnesses of the image stored in the first storage means in a designated specific area. average value calculation means for determining the average value of the luminance of the video image; amplification factor calculation means for determining the amplification factor of the amplification means using the average value from the average value calculation means; A display device for a video radar, comprising a processing range specifying means specified by an operation of an observer, and a display means reading out from the second storage means and displaying the brightness of the area specified by the processing range specifying means.