JP6602606B2 - Representative still image determining device for determining representative still image, program, radar device, and aircraft equipped with radar device - Google Patents

Description

  Embodiments described herein relate generally to a representative still image determination device for determining a representative still image from a plurality of still images, a program, a radar device, and an aircraft equipped with the radar device.

  Conventionally, when classifying a target type such as a ship captured in an ISAR moving image from an ISAR moving image obtained from a reflected echo of a radar transmitted from a radar apparatus, a representative still image determined from the ISAR moving image The type of target is categorized using.

  In an ISAR movie, generally, the target shape is difficult to see, and sometimes the target shape may be clearly seen. Conventionally, when a human operator finds a target shape that is sometimes clearly visible, a representative still image for classification processing is determined, and the type of target is classified using the representative still image.

JP 2012-063280 A JP 2011-247777 A

  Thus, the conventional representative still image determination process is performed by a human operator and is not automated.

  For this reason, there is a problem that not only the work load of the operator becomes very high but also the risk of overlooking the target even though the target is photographed in the ISAR video because it is a human work.

  Furthermore, there is a problem that the time required for determining the representative still image and the reliability of whether or not the determined representative still image is appropriate depends on the skill level of the operator.

  As described above, there are a number of problems in the conventional representative still image determination process performed by human work, and it is desired to develop an automated processing technique for solving these problems.

  The present invention has been made in view of such circumstances, and a first object of the present invention is to use a plurality of ISAR still images extracted from an ISAR moving image to classify targets captured in the ISAR moving image. It is an object to provide a representative still image determining device, a program, and a radar device capable of automatically determining a representative still image to be performed.

  A second object of the present invention is to provide an aircraft equipped with the radar apparatus so that a representative still image can be automatically determined while shooting a target ISAR moving image from the aircraft.

The representative still image determining apparatus according to the embodiment is an apparatus for determining a representative still image used for classifying targets captured in an ISAR moving image from a plurality of ISAR moving images extracted from the ISAR moving image. In addition, for all pixels of the ISAR still image, counting means for counting the number of boundaries where the luminance difference between adjacent pixels is equal to or greater than a predetermined threshold with respect to the boundary between adjacent pixels, and a plurality of ISARs Among still images, representative still image determining means for determining an ISAR still image having the largest number of counted boundaries as a representative still image, and a predetermined threshold value, the average of the luminance values of all pixels of the ISAR still image Threshold value determining means for determining based on the above .

  The radar apparatus of the embodiment is received by such a representative still image determining apparatus, a transmitter that transmits radar to a target, a receiver that receives a reflected echo reflected by the radar at the target, and a receiver. ISAR moving image generating means for generating an ISAR moving image provided to the representative still image determining device based on the reflected echo.

  The aircraft of the embodiment is equipped with such a radar device.

It is a block diagram which shows the structural example of the radar apparatus with which the representative still image determination apparatus of embodiment was applied. It is a block diagram which shows the structural example of the representative still image determination apparatus of embodiment. (A) a conceptual diagram showing an arrangement example of pixels constituting an ISAR still image; (b) an arbitrary pixel P _{n, m} and four adjacent pixels P _{n−1, m} , P _{n, m−1} , It is a figure which shows _{Pn, m + 1} , _{Pn + 1, m} . It is a flowchart which shows the operation example of the radar apparatus to which the representative still image determination apparatus of embodiment was applied.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram illustrating a configuration example of a radar apparatus 10 to which a representative still image determining apparatus 50 according to an embodiment of the present invention is applied.

  A radar apparatus 10 in FIG. 1 is an ISAR type radar apparatus, and includes a transmitter 15, a circulator 20, an antenna 30, a receiver 40, an ISAR video generation unit 45, a representative still image determination device 50, a storage unit 60, and an input unit 70. And a display unit 80.

  Such a radar apparatus 10 is preferably mounted on an aircraft. Moreover, you may make it arrange | position on the ground.

  The transmitter 15 generates an RF signal at a predetermined transmission cycle, and transmits the generated RF signal from the antenna 30 via the circulator 20 toward a target such as a ship. A part of the RF signal transmitted from the antenna 30 is reflected at the target and received by the antenna 30 as a reflected echo.

  The circulator 20 is a circulation circuit for separating transmission / reception signals. That is, the circulator 20 supplies the RF signal generated by the transmitter 15 to the antenna 30 and supplies the reflected echo received by the antenna 30 to the receiver 40 as a received signal.

  The receiver 40 discriminates the reflected echo based on the transmission cycle in which the transmitter 15 generates the RF signal, and generates a radar video signal. For example, 10-20 sets of this radar video signal are generated per second. The receiver 40 continuously outputs the set of radar video signals generated in this way to the ISAR video generation unit 45.

  In the ISAR moving image generating unit 45, this set of radar video signals is continuously displayed to become an ISAR moving image. The ISAR moving image generating unit 45 outputs the ISAR moving image to the representative still image determining device 50.

  The storage unit 60 stores in advance information on various target shapes assumed to be classified by the radar device 10, for example, when the target is a ship (hereinafter referred to as target shape information). . The ship target shape information includes data such as the total length of the ship and position information of structures such as bridges and masts. The target is not necessarily limited to a ship, and may be a moving body other than a ship, such as an aircraft or a vehicle.

  The input unit 70 receives an operation instruction from the user of the radar apparatus 10. The operation instruction input from the input unit 70 can be provided to each part (described later with reference to FIG. 2) of the representative still image determination device 50. The display unit 80 includes an LCD (Liquid Crystal Display) and the like, and displays the representative still image determined by the representative still image determining device 50. The user classifies the target based on the representative still image displayed on the display unit 80 and the target shape information stored in the storage unit 60. Alternatively, this classification process may be automatically performed using a target classification program as disclosed in Patent Document 2.

  FIG. 2 is a block diagram illustrating a configuration example of the representative still image determination device 50 according to the embodiment. The representative still image determining device 50 in FIG. 2 is a device for determining a representative still image used to classify targets captured in the ISAR moving image from a plurality of ISAR moving images extracted from the ISAR moving image. For example, it includes not only a CPU (Central Processing Unit) but also a ROM (Read Only Memory), a RAM (Random Access Memory), and other programs for the CPU to execute processing, a data storage area, and the like. The representative still image determination device 50 has the following configuration by executing a representative still image determination program stored in the storage area by the CPU. That is, the representative still image determining device 50 includes an ISAR still image generating unit 51, a still image correcting unit 52, a luminance difference calculating unit 53, a threshold determining unit 54, a counting unit 55, and a representative still image determining unit 56.

  The ISAR still image generating unit 51 receives the ISAR moving image output from the ISAR moving image generating unit 45 and extracts the ISAR still image. As described above, when 10 to 20 sets of radar video signals are generated per second, an ISAR moving image in which each set of radar video signals is continuously displayed includes 10 to 20 ISAR still images per second. include. Therefore, the ISAR still image generation unit 51 sequentially extracts ISAR still images from the ISAR moving image, and sequentially outputs the extracted ISAR still images to the still image correction unit 52.

  The still image correction unit 52 performs correction processing for clarification on each ISAR still image sequentially output from the ISAR still image generation unit 51, and sequentially applies the corrected ISAR still image to the luminance difference calculation unit 53. Output to. This process can be performed by, for example, a known rotational momentum estimation process. Note that the still image correction unit 52 is an option, and the representative still image determination device 50 of the embodiment may have a configuration in which the still image correction unit 52 is omitted.

  The brightness difference calculation unit 53 is sequentially output from the still image correction unit 52 (or in the case where there is no still image correction unit 52, the ISAR still image generation unit 51 sequentially outputs) for each ISAR still image. Know the brightness values of all pixels. The result is held and output to the threshold value determination unit 54.

  The luminance difference calculation unit 53 further calculates the luminance difference between adjacent pixels for each ISAR still image for all pixels. This will be described with reference to FIG.

  FIG. 3A shows an example of the ISAR still image 100 input to the luminance difference calculation unit 53. P represents a pixel, and the subscript after P represents a two-dimensional position determined from the X and Y directions.

FIG. 3B shows an arbitrary pixel P _{n, m} (n is an integer of 1 or more and the maximum number of pixels N in the X direction is N or less, and m is 1 or more and the Y direction. shows the maximum number of pixels M is an integer), the pixel _{P n,} 4 single pixel _{P n-1,} m adjacent to _{m, P n, m-1} , P n, and _{m + 1, P n + 1} , m FIG. Numerical values in parentheses described under each P indicate examples of luminance values (0 to 255) in the pixel P, respectively.

Pixel _{P n,} around the _m, then the adjacent four pixels _{P n-1, m, P} n, m-1, P n, m + 1, 4 one boundary between the _{P n + 1, m,} i.e., the boundary c _{n-1, m} , bn _{, m-1} , cn _{, m + 1} , bn _{, m} . The numerical value in parentheses shown after b and c represents the luminance difference between adjacent pixels at the boundaries b and c. For example, _since the luminance value of the pixel P _{n, m} is 150 while the luminance value of the pixel P _{n, m−1} is 250, the pixel P _n is indicated by b _{n, m−1} (100). _{, M} and the pixel P _{n, m−1} is 100. Further, by indicating c _{n, m} (2), it is indicated that the luminance difference between the pixel P _{n, m} and the pixel P _{n, m + 1} is 2.

  In this way, the luminance difference calculation unit 53 calculates the luminance difference between adjacent pixels P for all the pixels P of the ISAR still image 100.

The four pixels P _1,1 , P _{N, 1} , P _{1, M} , P _{N, M} located at the four corners of the ISAR still image 100 are two boundaries between two adjacent pixels. As a target, the luminance difference between adjacent pixels P is calculated. In addition, among the pixels located on the outermost periphery of the ISAR still image 100, the pixels excluding the four pixels located at the four corners described above are adjacent with respect to three boundaries between the three adjacent pixels. The luminance difference between the pixels P to be calculated is calculated.

  The luminance difference calculation unit 53 outputs the calculation result of the luminance difference at all the boundaries b and c of the single ISAR still image 100 together with the corresponding ISAR still image 100 to the counting unit 55. The same processing is performed for the next ISAR still image 100, and similarly, the calculation result of the luminance difference is output to the counting unit 55 together with the next ISAR still image 100.

  In this way, the luminance difference calculation unit 53 sequentially acquires such luminance difference calculation results for each of the ISAR still images 100 continuously output from the ISAR still image generation unit 51 side. The calculation result is sequentially output to the counting unit 55 together with the corresponding ISAR still image 100.

  The counting unit 55 uses the calculation result output from the luminance difference calculating unit 53 to count the number of boundaries where the luminance difference between adjacent pixels is equal to or greater than a predetermined threshold. This threshold is determined by the threshold determination unit 54.

  The threshold value determination unit 54 determines the threshold value by performing the following processing, for example. That is, the threshold value determination unit 54 calculates an average value of luminance values for all pixels of one ISAR still image output from the luminance difference calculation unit 53. Then, the threshold value is determined by multiplying this average value by an appropriate constant.

  For example, if the average value of the luminance values for all the pixels of the corresponding ISAR still image 100 is 80 and the appropriate constant is 1.2, the threshold value determination unit 54 sets the luminance difference 96 as the threshold value.

In this case, the counting unit 55 counts the number of boundaries larger than the luminance difference 96 that is a threshold among the luminance difference calculation results. In the example of FIG. 3B, the boundary b _{n, m−1} having a luminance difference of 100 and c _{n−1, m} having a luminance difference of 145 are counted. In this way, the boundary to be counted is counted over the entire corresponding one ISAR still image 100. Then, the count result is output to the representative still image determination unit 56 together with the corresponding ISAR still image 100.

  Thus, when the process for one ISAR still image 100 is completed, the threshold value determination unit 54 and the count unit 55 perform the same process for the next ISAR still image 100. Then, the count unit 55 outputs the count result to the representative still image determination unit 56 together with the corresponding ISAR still image 100.

  Note that the threshold value is not limited to being determined by the threshold value determination unit 54 as described above, but may be set by being input by the user via the input unit 70 instead. . In this case, the threshold value determination unit 54 can be omitted.

  In this way, the representative still image determining unit 56 is sequentially input from the counting unit 55 with the set of the ISAR still image 100 and the corresponding count value.

  The representative still image determination unit 56 determines the ISAR still image 100 having the largest count value as the representative still image.

  The representative still image should be a still image in which a target shape such as a ship can be seen most clearly. The fact that the target shape looks the clearest is that the boundary between the target and the background is the sharpest. If the boundary between the target and the background is sharp, the number of boundaries having a luminance difference larger than the threshold inevitably increases. Therefore, the representative still image determination unit 56 determines the ISAR still image 100 having the largest count value among the plurality of ISAR still images 100 in which the same target is captured as the representative still image. Then, the determined representative still image is output to the display unit 80.

  The user classifies the target based on the representative still image displayed from the display unit 80 and the target shape information stored in the storage unit 60. Alternatively, this classification process may be automatically performed using a target classification program as disclosed in Patent Document 2.

  Next, the operation of the radar apparatus 10 to which the representative still image determining apparatus 50 according to the embodiment configured as described above is applied will be described.

  FIG. 4 is a flowchart illustrating an operation example of the radar apparatus 10 to which the representative still image determination apparatus 50 of the embodiment is applied.

  For example, the radar apparatus 10 that can be mounted not only on the ground but also on an aircraft is suitably applied to classify the type of ship such as a suspicious ship. Moreover, it is also possible to apply not only to ships but also to other types of mobile objects such as vehicles and aircraft.

  When performing such target classification, the radar apparatus 10 first generates an RF signal at a predetermined transmission period in the transmitter 15, and the generated RF signal is transmitted from the antenna 30 via the circulator 20. For example, it is transmitted toward a target such as a ship (S1).

  Part of the transmitted RF signal is reflected at the target and received by the antenna 30 as a reflected echo (S2).

  The reflected echo received by the antenna 30 is supplied to the receiver 40 via the circulator 20. In the receiver 40, the reflected echo is detected based on the transmission cycle in which the transmitter 15 generates the RF signal, and a radar video signal is generated (S3). For example, 10-20 sets of this radar video signal are generated per second.

  Each set of radar video signals generated in this way is continuously output from the receiver 40 to the ISAR video generation unit 45.

  In the ISAR moving image generation unit 45, the radar video signal is continuously displayed to become an ISAR moving image (S4). The ISAR moving image is output from the ISAR moving image generating unit 45 to the ISAR still image generating unit 51 of the representative still image determining device 50.

  The ISAR still image generation unit 51 extracts an ISAR still image from the ISAR moving image output from the ISAR moving image generation unit 45 (S5). As described above, when 10 to 20 sets of radar video signals are generated per second, the ISAR moving image includes 10 to 20 ISAR still images per second. In the ISAR still image generation unit 51, these ISAR still images are sequentially extracted from the ISAR moving image. The extracted ISAR still images are sequentially output from the ISAR still image generation unit 51 to the still image correction unit 52.

  In the still image correction unit 52, correction processing for clarification is performed on each ISAR still image sequentially output from the ISAR still image generation unit 51 (S6). The ISAR still images corrected in this way are sequentially output from the still image correction unit 52 to the luminance difference calculation unit 53. This correction process can be performed by, for example, a known rotational momentum estimation process. Note that this correction process is an optional process, and can be omitted if it is deemed unnecessary, for example, the ISAR still image is clear.

  In the luminance difference calculation unit 53, for each ISAR still image sequentially output from the still image correction unit 52 (or in the case where there is no still image correction unit 52, it is sequentially output from the ISAR still image generation unit 51). The luminance values (0 to 255) of all the pixels are grasped (S7). This result is held in the luminance difference calculation unit 53 and also output to the threshold value determination unit 54.

  The luminance difference calculation unit 53 further calculates the luminance difference between the adjacent pixels P for all the pixels for each ISAR still image (S8). This is as described with reference to FIG. Then, the calculation result is output from the luminance difference calculation unit 53 to the counting unit 55 together with the corresponding ISAR still image 100. In the luminance difference calculation unit 53, the processing of step S7 and step S8 is performed for the next ISAR still image 100, and similarly, the calculation result of the luminance difference is output to the counting unit 55 together with the next ISAR still image 100. Is done.

  In this way, the luminance difference calculation unit 53 sequentially obtains a luminance difference calculation result for each of the ISAR still images 100 continuously output from the ISAR still image generation unit 51 side. Are sequentially output to the counting unit 55 together with the corresponding ISAR still image 100.

  Next, the threshold value determination unit 54 determines the threshold value based on the luminance values of all the pixels P of one ISAR still image output from the luminance difference calculation unit 53 in step S7 (S9). The threshold value is determined by, for example, multiplying an average value of luminance values for all pixels P of the target ISAR still image by an appropriate constant, but is not limited to this method, and other methods are used. It is also possible to decide. For example, the user may input and set a desired threshold value from the input unit 70. Alternatively, it may be automatically set from the average value and standard deviation of the luminance values of a certain ISAR still image.

  In the counting unit 55, the calculation result output from the luminance difference calculating unit 53 in step S8 is used, and the number of boundaries where the luminance difference between adjacent pixels is equal to or greater than the threshold value determined in step S9 is counted ( S10). This count result is output to the representative still image determination unit 56 together with the corresponding ISAR still image 100.

  In this way, each ISAR still image 100 generated by the ISAR still image generation unit 51 is accumulated in the representative still image determination unit 56 together with the count result.

  In the representative still image determination unit 56, a still image in which the target shape is most clearly seen is determined as a representative still image from the accumulated ISAR still images 100. The fact that the target shape looks the clearest means that the boundary between the target and the background is the sharpest. If the boundary between the target and the background is sharp, the number of boundaries having a luminance difference larger than the threshold inevitably increases. Therefore, the representative still image determination unit 56 determines the ISAR still image 100 having the largest count value among the plurality of ISAR still images 100 in which the same target is photographed as the representative still image (S11).

  The representative still image determined in this way is used for target classification processing. This categorization process may be performed manually by the user, or may be performed automatically by using a target categorization program as disclosed in Patent Document 2. When classification is performed by manual processing, the user compares the target shape with the target shape information stored in the storage unit 60 while displaying the representative still image from the display unit 80, and the type having the highest degree of coincidence. Is determined to be of this target type.

  As described above, the radar apparatus 10 to which the representative still image determining device 50 according to the embodiment is applied is photographed in the ISAR moving image from the plurality of ISAR still images 100 extracted from the ISAR moving image by the above-described operation. It is possible to automatically determine the representative still image used to classify the target.

  As described above, the automation of the representative still image determination process has made it possible not only to eliminate the work conventionally performed by the operator, but also to appropriately perform the operation without depending on the skill of the operator. The representative still image can be determined with high accuracy and in a shorter time.

  In addition, since the representative still image is determined based on a quantitative index of the number of boundaries where the luminance difference is larger than the threshold, there is a risk that the target may be overlooked even though the target is captured in an ISAR video. Therefore, it is possible to improve the reliability of the target classification process performed subsequently.

  Furthermore, according to the aircraft on which such a radar apparatus 10 is mounted, the representative still image can be automatically determined as described above while photographing the target ISAR moving image from the aircraft. Therefore, even if the target is a moving object such as a ship, a vehicle, or another aircraft, it is possible to shoot while following the target and classify the target with high accuracy on the spot.

  Although the embodiment of the present invention has been described, the above embodiment is presented as an example, and is not intended to limit the scope of the invention. The above-described embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. The above-described embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof, as long as they are included in the scope and gist of the invention.

DESCRIPTION OF SYMBOLS 10 Radar apparatus, 15 Transmitter, 20 Circulator, 30 Antenna, 40 Receiver, 45 Movie production | generation part, 50 Representative still image determination apparatus, 51 Still image production | generation part, 52 Still image correction part, 53 Luminance difference calculation part, 54 Threshold value Determination unit, 55 count unit, 56 representative still image determination unit, 60 storage unit, 70 input unit, 80 display unit, 100 still image

Claims (6)

An apparatus for determining a representative still image used to classify targets captured in the ISAR moving image from a plurality of ISAR still images extracted from the ISAR moving image,
Counting means for counting the number of boundaries where the luminance difference between the adjacent pixels is equal to or greater than a predetermined threshold for all the pixels of the ISAR still image, with respect to the boundary between the adjacent pixels;
Representative still image determining means for determining, as the representative still image, an ISAR still image having the largest number of counted boundaries among the plurality of ISAR still images;
Threshold determination means for determining the predetermined threshold based on an average of luminance values of all pixels of the ISAR still image;
A representative still image determination device. The representative still image determination device according to claim 1, wherein the target is a ship. The representative still image determination device according to claim 1, further comprising a radar device for acquiring the ISAR moving image. The representative still image determination device according to claim 1 or 2 ,
A transmitter for transmitting radar to the target;
A receiver for receiving a reflected echo reflected by the radar at the target;
ISAR moving image generating means for generating an ISAR moving image provided to the representative still image determining device based on the reflected echo received by the receiver;
A radar apparatus comprising: An aircraft equipped with the radar device according to claim 4 . A program for determining a representative still image used to classify targets captured in the ISAR moving image from a plurality of ISAR still images extracted from the ISAR moving image.
A function of counting the number of boundaries where the luminance difference between the adjacent pixels is equal to or greater than a predetermined threshold for all the pixels of the ISAR still image, with respect to the boundary between adjacent pixels;
A function of determining, as the representative still image, an ISAR still image having the largest number of counted boundaries among the plurality of ISAR still images;
A function of determining the predetermined threshold based on an average of luminance values of all pixels of the ISAR still image;
A program that realizes