JP3575971B2 - Target detection device and target detection method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a target detection device and a detection method suitable for detecting and tracking other aircraft or the like mounted on, for example, guided missiles or military aircraft.
[0002]
[Prior art]
Conventionally, when a guided missile tracks a moving aircraft, the guided missile is equipped with an imaging device such as a CCD camera, obtains a still image of a spatial region including the target aircraft, and converts the entire still image into pixels. The presence or absence of the moving target and the position of the moving target are detected by performing the scanning (scanning).
[0003]
For capturing a target such as an aircraft, for example, the average brightness of a still image obtained by shooting is calculated, the brightness is compared for each pixel in the image, and a video of a target having a large difference from the average brightness level is identified. Extraction has been performed to detect a target excluding a background such as a cloud or land from a captured image.
[0004]
At this time, in order to improve the processing speed, a processing gate is provided around the once extracted target, and the average luminance limited within the processing gate is obtained to adjust the input signal level to the image processor.
[0005]
[Problems to be solved by the invention]
As described above, since the conventional target detection apparatus processes each still photographed image on a pixel-by-pixel basis and extracts an image pattern of a target such as an aircraft or a background object, there is nothing other than the target, for example. When only the target exists alone in the spatial region, the moving target and the like can be identified and detected relatively clearly and easily from the difference from the average luminance.
[0006]
However, in the captured image, in addition to the target image, in addition to the target image, there is a confusing luminance image pattern similar to the target, such as a land and cloud image, and if the image enters the processing gate, the average luminance value is inappropriate. It was not easy to identify only the target among them, accurately exclude the background, and quickly detect it.
[0007]
[Means for Solving the Problems]
The present invention has been made in view of the above circumstances. First, a target detecting apparatus according to the present invention includes an imaging unit for obtaining a first captured image of a target area, and a subdivision of the area of the captured image obtained by the imaging unit. First area dividing means for converting the first area dividing means, first target detecting means for detecting a target based on the image feature value of each small area formed by subdivision of the first area dividing means, First target capturing area setting means for setting an area including the target detected by the target detecting means as a first target capturing area; and first target capturing area setting by the first target capturing area setting means. A second target capture area setting unit that sets a second target capture area corresponding to the first target capture area with respect to an area of a second captured image captured later by the imaging unit; Set by the target capture area setting means Second area dividing means for subdivision differentiate second target acquisition area, the subdivision differentiated second target acquisition region in the second area division unit, the first target acquisition region And a second target detecting means for correcting an image feature value of a different portion of the background and detecting a target based on the image feature value in the second target capture area when a background different from the background is detected. It is characterized by having.
[0008]
In addition, the target detection method of the present invention includes a first imaging step of obtaining a first captured image of an imaging target area, and a first area dividing step of subdividing the captured image obtained in the first imaging step. A first target detection step of detecting a target based on the image feature value of each small area formed by the subdivision of the first area division step; and a target detected by the first target detection step. A first target capture region setting step of setting a region including the first target capture region as a first target capture region, and a second captured image of the imaging target region obtained after the first target capture region setting step. 2, a second target capture area setting step of setting a second target capture area corresponding to the first target capture area on an image captured by the second image capture step; The second target set in the second target capture area setting step Different target capture region and a second region dividing step of differentiating subdivision, the second target acquisition region differentiated subdivision in this second area dividing step, and the first background target acquisition region When a background is detected, a second target detection step of correcting an image feature value of a different portion of the background and detecting a target based on the image feature value is provided.
[0009]
As described above, the target detection device and the target detection method according to the present invention reduce the amount of processing data by subdividing (blocking) the captured image prior to the target detection. Has become possible.
[0010]
In particular, since a second target capture area is set for the second captured image and subdivision is performed within the limited area, the amount of processed data can be further reduced, and a quick target can be achieved. The detection rate can be improved together with the detection.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a target detecting apparatus according to the present invention will be described in detail with reference to FIGS.
[0012]
As shown in FIG. 1, in the target detection device according to the embodiment of the present invention, an imaging device 1 such as a CCD camera mounted on a guided missile or the like first moves a spatial region including a moving target 2 to an arbitrary time (t). (Seconds). The digital video signal obtained by the photographing of the imaging device 1 is supplied to a luminance detector 3 for detecting an image feature value. Here, the image feature value indicates a luminance, a luminance average, a luminance variance, a differential value, or the like. In the embodiment described below, the description will be made assuming that the luminance and the average luminance are handled.
[0013]
The luminance detector 3 is configured as shown in FIG. 2, and an image feature value of a spatial region including the moving target 2 captured first from the imaging device 1, that is, for example, a digital luminance signal is temporarily stored in the memory 31. After that, first, the data is sequentially read out and supplied to the identification circuit 4 and also supplied to the first average luminance detection circuit 32.
[0014]
A first area division setting circuit 33 is connected to the first average luminance calculation circuit 32, and the first area division setting circuit 33 converts a captured image into a first image as shown in FIG. A first divided signal that is divided into q and p signals at predetermined intervals in the horizontal axis (x-axis) direction and the vertical axis (y-axis) direction is set in advance.
[0015]
Therefore, the first average luminance calculation circuit 32 receives the supply of the q × p first divided signal from the first region division setting circuit 33 and, as shown in FIG. Xp sub-divisions (blocks) are performed, the average luminance of the entire screen is calculated together with the average luminance signal in each sub-division region, and supplied to the first target capture region setting circuit 34 and the identification circuit 4, respectively. . Note that the average luminance of the entire screen is calculated based on each average luminance of each subdivision area. In addition, the average luminance value can be represented by, for example, 256 gradations of light and shade.
[0016]
Note that the target image and the images of the clouds and the land are captured as a pattern composed of a series of divided areas whose average luminance levels are approximately similar to each other. Therefore, in this embodiment, the identification circuit 4 is different from the conventional pixel unit, and as shown in FIG. 3B, the target 2 area and the area area of each of the backgrounds 2a and 2b are subdivided. Are respectively identified to derive respective position signals.
[0017]
Among the outputs of the identification circuit 4, the position signal 4a of the target 2 is supplied to a first target capture area setting circuit 34 of the luminance detector 3, and the first target capture area setting circuit 34 is configured as shown in FIG. As shown, a first target capture area 2A of a rectangular frame including the target 2 substantially at the center is set, and a target capture area 2A signal is sent to a second target capture area setting circuit 35 as shown in FIG. The average luminance value of each subdivided area in the area 2A is supplied to the comparison circuit 36 together with the target capture area 2A signal.
[0018]
Next, after a lapse of time t seconds from the first photographing, the target device 2 is photographed again by the imaging device 1, and the digital video signal is similarly stored in the memory 31 and supplied to the identification circuit 4. As shown in FIG. 4A, the digital luminance signals in the spatial region including the moving target 2 are sequentially read out from the digital video signals thus obtained, and supplied to the second average luminance detection circuit 37 shown in FIG. You.
[0019]
The second target acquisition area setting circuit 35 and the second area division setting circuit 38 are connected to the average luminance calculation circuit 37, and the second target acquisition area setting circuit 35 is connected to the first target acquisition area setting circuit 35. Upon receiving the target capture area 2A signal from the circuit 34, as shown in FIG. 4A, the new second target capture area 2A 'corresponding to the target capture area 2A signal capturing the target 2 at the center of the screen is averaged. It is supplied to the luminance calculation circuit 37. Of course, if the target 2 is captured at the center, the first target capture area 2A signal itself may be supplied instead of the second target capture area 2A '.
[0020]
Further, as shown in FIG. 4A, the second area division setting circuit 38 moves the inside of the second target acquisition area 2A ′ in the horizontal axis (x-axis) direction and the vertical axis (y-axis) direction. A second divided signal to be divided into n and m signals is set in advance. In this case, the coarseness of the fine division is made finer than the fineness of the fine division in the first area division setting circuit 33, and the detection accuracy of the position of the target 2 described later or the resolution of the detection is increased. You may do it.
[0021]
Therefore, like the first average luminance detection circuit 32, the second average luminance detection circuit 37 moves the area 2A 'including the moving target set by the second target capture area setting circuit 35 into the second average luminance detection circuit 32. Is divided into n × m sub-regions by the region division signal from the region division circuit 38, and the average luminance in each of the n × m sub-regions, and the average The average luminance of the area 2A ′ calculated based on the luminance is supplied to the identification circuit 4 via the correction circuit 39, and the average luminance signal in each of the n × m sub-areas is compared with the position information thereof with the comparison circuit 36. To supply.
[0022]
The identification circuit 4 receiving the average luminance signal in each of the n × m sub-regions and the average luminance signal in the region 2A ′ via the correction circuit 39 introduces the signal from the first average luminance detection circuit 32. The processing is performed in the same manner as when the processing operation is performed, and the target and the background in the area 2A ′ set by the second target capture area setting circuit 35 in the captured image are identified, and the imaging device 1 Is detected and displayed on a display device (not shown).
[0023]
As described above, according to this embodiment, the identification circuit 4 performs the comparison operation of the luminance signal with respect to the limited area 2A ′ and with the n × m pieces of the limited data. It is possible to speed up the position detection process.
[0024]
In general, similarly to the related art, the imaging device 1 is controlled based on the output signal of the identification circuit 4 and is configured to always track the target captured by the imaging device 1, so that the target temporarily moves at a high speed. However, if the imaging interval (t seconds) is small, the first target capture region setting circuit 34 or the second target capture region setting circuit 35 also determines that the target 2 is substantially in each of the regions 2A and 2A '. It is controlled to be located at the center.
[0025]
However, when tracking a high-speed moving target, the relative positional relationship between the moving target and the background cloud or land changes relatively quickly. Therefore, after a few steps from the first imaging time shown in FIGS. 3A and 3B, for example, as shown in FIG. 4A and FIG. Since the positional relationship of 2b also changes, a part of the background 2a may newly enter the target capture area 2A 'in the state of FIG.
[0026]
In particular, when the luminance level of the image of the background 2a is close to the luminance level of the image of the target 2, the average luminance in the target capture area 2A 'shown in FIG. 4B is higher than that in the case shown in FIG. The brightness level of the target 2 is approached. As described above, the identification circuit 4 identifies the target 2 using the average luminance of the area 2A 'as the reference value. Therefore, the reference luminance level changes, and the identification of the target 2 is clearly detected. It becomes difficult. Therefore, in this embodiment, as shown in FIG. 2, a comparison circuit 36 is provided, and the in-region luminance signal in the region 2A from the first target capture region setting circuit 34 and the second average luminance detection circuit 37 And a comparison is made between the luminance signal in the area 2A ′ and the detected luminance component of the background portion 2a ′ newly entering the area 2A ′ is supplied to the correction circuit 39 as a correction signal.
[0027]
Therefore, the correction circuit 39 corrects the level of the average luminance of the area 2A 'from the second average luminance detection circuit 35 based on the correction signal from the comparison circuit 36. When the section enters anew and the average luminance level approaches the luminance of the target 2, it is possible to avoid a decrease in the detection probability of the target 2 and capture an image of the target 2 with high resolution.
[0028]
As described above, the configuration of the comparison circuit 36 and the correction circuit 39 is such that the average luminance level approaches the luminance level of the target 2 due to the relative movement of the background, and the average luminance level in the target capture area 2A and the luminance level of the target 2 This avoids a decrease in the difference from the target 2 and a decrease in the target 2 detection probability.
[0029]
In the above description, the process of calculating the average luminance of each divided region in the first and second average luminance detection circuits 32 and 37 of the luminance detector 3 is performed by a simple addition operation of digital image signals. Therefore, the processing can be performed in a short time by the high-speed calculation, and the calculation of the average luminance and the target capture area setting 35 greatly reduce the data amount in the identification circuit 4, and the processing can be performed quickly. The position of the target 2 can be detected and tracked in a timely manner.
[0030]
In the description of the above-described embodiment, the luminance detector 3 and the identification circuit 4 perform the luminance averaging process performed based on the digital video signal from the imaging device 1 by using a combination of hardware configurations. However, these processing operations can be performed on software of a computer.
[0031]
As described above, according to the apparatus and method of the present invention, the imaging screen is divided, a target capture area is set, and image feature values such as average luminance, luminance variance, or differential values in each divided area are time-series. By performing the correspondence comparison, even when the contrast between the target and the background is small or the variance of the luminance of the background or the like is large, the moving target or the like can be accurately detected with good resolution.
[0032]
【The invention's effect】
As described above, the target detecting device and the detecting method according to the present invention can shorten the arithmetic processing time with a simple configuration and can detect a moving target or the like in a short time and reliably. The effect is great.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of a target detection device and a detection method according to the present invention.
FIG. 2 is a configuration diagram showing a luminance detector of the device shown in FIG.
3A is an imaging area set by a first area division setting circuit shown in FIG. 2, and FIG. 3B is set by a first target capture area setting circuit shown in FIG. 2; It is explanatory drawing which shows each imaging area including the area | region 2A which was shown.
FIGS. 4A and 4B are explanatory diagrams each showing an image pickup area in the second average luminance detection circuit shown in FIG. 2;
FIG. 5 is an enlarged view of a region 2A ′ shown in FIG.
[Explanation of symbols]
Reference Signs List 1 imaging device 2 target 3 brightness detector 31 memory 32 first average brightness detection circuit 33 first area division setting circuit 34 first target capture area setting circuit 35 second target capture area setting circuit 36 comparison circuit 37 2 average luminance detection circuit 38 second area division setting circuit 39 correction circuit 4 identification circuit

Claims (4)

Imaging means for obtaining a first captured image of the target area;
First area dividing means for subdividing the area of the photographed image obtained by the imaging means;
First target detection means for detecting a target based on the image feature value of each small area formed by the subdivision of the first area division means;
First target capture area setting means for setting an area including the target detected by the first target detection means as a first target capture area;
After setting the first target capture area by the first target capture area setting means, a second target capture corresponding to the first target capture area is performed for the area of the second captured image captured by the imaging means. Second target capture area setting means for setting an area;
Second area dividing means for subdividing the second target capturing area set by the second target capturing area setting means;
When a background different from the background in the first target capturing area is detected in the second target capturing area subdivided by the second area dividing means, image characteristics of a different portion of the background are detected. A second target detection unit for correcting a value and detecting a target based on an image feature value in a second target capture area. The target detection apparatus according to claim 1, wherein the image feature value includes one of luminance, luminance average, luminance variance, and a differential value . A first imaging step of obtaining a first captured image of the imaging target area;
A first region division step of subdividing the captured image obtained in the first imaging step;
A first target detection step of detecting a target based on the image feature value of each small area formed by the subdivision in the first area division step;
A first target capture area setting step of setting an area including the target detected by the first target detection step as a first target capture area;
A second imaging step of obtaining a second captured image of the imaging target area after the first target capturing area setting step;
A second target capture area setting step of setting a second target capture area corresponding to the first target capture area on an image captured by the second imaging step;
A second area division step of subdividing the second target acquisition area set in the second target acquisition area setting step;
When a background different from the background in the first target capturing area is detected in the second target capturing area subdivided in the second area dividing step, the image feature value of a different portion of the background is detected. A second target detecting step of correcting the target and detecting a target based on the image feature value;
A target detection method, comprising: 4. The target detection method according to claim 3, wherein the image feature value includes one of luminance, luminance average, luminance variance, and a differential value .

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