Search device and search method

Abstract

To reduce a processing load.SOLUTION: A search device 100 includes: a wave-length variable filter 110 for varying a transmission wave length; an imaging device 120 for receiving light transmitted through the wave-length variable filter 110 to form an image; and a control device 150 for controlling the wave-length variable filter 110 and the imaging device 120. The control device 150 includes: a determination part for determining a plurality of imaging wave lengths on the basis of a first upward radiance at a reference height determined in a predetermined range based on a water surface and a second upward radiance at the estimated depth of an object to be searched for existing in water; a filter control part for controlling the wave-length variable filter 110 so as to transmit lights having the plurality of determined imaging wave lengths; an imaging control part for controlling the imaging device 120 so as to receive the lights having the plurality of imaging wave lengths transmitted through the wave-length variable filter 110 to form a plurality of wave-length images; and a determination part for determining the existence of the object to be searched for on the basis of the plurality of wave-length images.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a search device and a search method. [Background technology]

[0002] Conventionally, sonars installed on ships have been used to search for underwater objects such as marine life, but sonars can only search for objects that exist in a small area, such as the periphery of the ship.

[0003] Therefore, a technology has been developed to search for search targets on the sea by capturing images of the sea surface from the sky using a hyperspectral camera mounted on an aircraft and analyzing the resulting data cube (for example, Patent Document 1). The technology disclosed in Patent Document 1 searches for search targets by analyzing the data cube generated by the hyperspectral camera. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5668157 Summary of the Invention [Problem to be solved by the invention]

[0005] The data cube is a collection of hundreds of images captured with a wavelength resolution of a few nanometers, which means that analyzing the data cube imposes a huge processing load.

[0006] In view of the above problems, the present disclosure aims to provide a search device and a search method that can reduce the processing load. [Means for solving the problem]

[0007] In order to solve the above problem, a search device according to one embodiment of the present disclosure includes a tunable filter capable of changing the transmission wavelength, an imaging device that receives light transmitted through the tunable filter and generates an image, and a control device that controls the tunable filter and the imaging device. The control device includes: a determination unit that determines multiple imaging wavelengths based on a first upward radiance at a reference height defined within a predetermined range based on the water surface and a second upward radiance at an estimated depth of a search target present in water; a filter control unit that controls the tunable filter to transmit light of each of the determined multiple imaging wavelengths; an imaging control unit that controls the imaging device to receive light of each of the multiple imaging wavelengths transmitted through the tunable filter and generate multiple wavelength images; and a determination unit that determines the presence or absence of a search target based on the multiple wavelength images.

[0008] The determiner may also determine the multiple imaging wavelengths based on a ratio of the second upward radiance to the first upward radiance.

[0009] The determiner may also determine, as the imaging wavelength, the wavelength at which the division value obtained by dividing the second upward radiance by the first upward radiance is the largest and the wavelength at which the division value is the smallest.

[0010] The tunable filter and the imaging device may be provided on an aircraft, and the imaging device may capture images of the underwater world from the sky.

[0011] The determination unit may also determine the presence or absence of the search target object based on the difference between a plurality of wavelength images.

[0012] In order to solve the above problem, a search method according to one embodiment of the present disclosure includes determining multiple imaging wavelengths based on a first upward radiance at a reference height defined within a predetermined range based on the water surface and a second upward radiance at an estimated depth of a search target present in water, receiving light of each of the determined multiple imaging wavelengths to generate multiple wavelength images, and determining the presence or absence of the search target based on the multiple wavelength images. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to reduce the processing load. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a usage mode of a search device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating a searching device according to the embodiment. [Figure 3] FIG. 3 is a block diagram illustrating an example of a functional configuration of the control device according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating upward radiance. [Figure 5] FIG. 5 is a diagram illustrating an example of upward radiance information. [Figure 6] FIG. 6 is a flowchart showing the processing flow of the search method according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating a process performed by the determination unit according to the embodiment. [Figure 8] FIG. 8 is a diagram illustrating a first wavelength image, a second wavelength image, and a specific image according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation. Elements not directly related to the present disclosure are not shown.

[0016] [Search device 100] FIG. 1 is a diagram illustrating a usage mode of a search device 100 according to an embodiment of the present disclosure. The search device 100 according to this embodiment searches for a search object S in water. Underwater refers to the sea, rivers, lakes, dam lakes, ponds, reservoirs, and the like. In this embodiment, an example is given in which the search device 100 searches for a search object S in the sea (hereinafter referred to as "underwater"). The search object S is, for example, a marine organism or an artificial object. Examples of marine organisms include marine animals such as whales and dolphins, or fish such as tuna. Examples of artificial objects are sunken ships and artificial coral reefs.

[0017] 1, a search device 100 according to this embodiment is provided in, for example, an aircraft 10. The aircraft 10 is, for example, an unmanned aerial vehicle (drone), an airplane, a helicopter, a glider, an airship, a balloon, or an artificial satellite.

[0018] As will be described in detail later, the searching device 100 includes an imaging device 120. In this embodiment, the imaging device 120 captures images of underwater from above, for example.

[0019] 2 is a diagram illustrating a searching device 100 according to this embodiment. In FIG. 2, dashed arrows indicate the flow of signals. As shown in FIG. 2, the searching device 100 according to this embodiment includes a tunable filter 110, an imaging device 120, a receiving device 130, a transmitting device 140, and a control device 150.

[0020] The tunable filter 110 is a filter that can change the transmission wavelength. The tunable filter 110 includes, for example, a liquid crystal filter or an optical acoustic element. In this embodiment, the transmission wavelength of the tunable filter 110 is controlled by a filter control unit 216 of the control device 150, which will be described later.

[0021] The imaging device 120 receives the light that has passed through the tunable filter 110 and generates an image.

[0022] The receiving device 130 receives, for example, GPS signals output by GPS satellites, and also receives, for example, signals transmitted by a management device 20 installed on the ground.

[0023] The transmission device 140 transmits, for example, a specific image, a determination result, and the like, which will be described later, to the management device 20.

[0024] The control device 150 has one or more processors 152 and one or more memories 154 connected to the processors 152. The processor 152 includes, for example, a CPU (Central Processing Unit). The memory 154 includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM is a storage element that stores programs used by the CPU, calculation parameters, etc. The RAM is a storage element that temporarily stores data such as variables and parameters used in processing executed by the CPU.

[0025] The control device 150 communicates with each device provided in the searching device 100, such as the tunable filter 110, the image capturing device 120, the receiving device 130, and the transmitting device 140. In this embodiment, the control device 150 controls the tunable filter 110 and the image capturing device 120.

[0026] 3 is a block diagram showing an example of the functional configuration of the control device 150 according to this embodiment. For example, as shown in FIG. 3, the control device 150 also functions as a storage unit 210, an acquisition unit 212, a determination unit 214, a filter control unit 216, an imaging control unit 218, and a determination unit 220.

[0027] Note that various processes, including the processes described below, performed by one or more selected from the group consisting of the acquisition unit 212, the determination unit 214, the filter control unit 216, the imaging control unit 218, and the judgment unit 220, may be executed by the processor 152. In detail, the various processes are executed by the processor 152 executing programs stored in the memory 154. The function of the storage unit 210 is realized by the memory 154. However, the functions of the control device 150 may be divided among multiple devices, or multiple functions may be realized by a single device.

[0028] The storage unit 210 stores, for example, upward radiance information in advance. The upward radiance information is information that associates water depth with the spectrum of upward radiance. Water depth is a depth based on sea level. In other words, a water depth of 0 [m] is 0 [m] above sea level. The spectrum of upward radiance is the intensity distribution of upward radiance for each wavelength.

[0029] FIG. 4 is a diagram illustrating upward radiance. As shown in FIG. 4, upward radiance is measured by lowering a photodetector 50 into the sea from a vessel or the like. The light-receiving surface of the photodetector 50 faces downward (toward the seabed). The upward radiance is the radiance of light (visible light) that reaches the photodetector 50 from the seabed. The measured upward radiance differs depending on the water depth at which the photodetector 50 is installed. For example, when the photodetector 50 is installed at a water depth of 0 [m] (sea surface), the upward radiance is the radiance of light indicated by arrow a in FIG. 4. Furthermore, when the photodetector 50 is installed at a water depth of 60 [m], the upward radiance is, for example, the radiance of light indicated by arrow b in FIG. 4.

[0030] The upward radiance information is measured in a plurality of sea areas and is acquired from, for example, an external server provided in a country, a local government, a research institute, etc. In this embodiment, the storage unit 210 stores the upward radiance information for each sea area in advance.

[0031] 5 is a diagram illustrating an example of upward radiance information. In FIG. 5, the vertical axis represents upward radiance [μW / cm2 / nm / str], and the horizontal axis represents wavelength [nm]. In Figure 5, the thick line represents the upward radiance spectrum at a depth of 120m, the dashed line represents the upward radiance spectrum at a depth of 90m, the dashed line represents the upward radiance spectrum at a depth of 60m, the dashed line represents the upward radiance spectrum at a depth of 30m, and the thin line represents the upward radiance spectrum at a depth of -0.5m. Note that a depth of -0.5m is 0.5m above the sea surface. The sea surface is 0m above sea level.

[0032] For example, in the upward radiance information, the spectrum of upward radiance is associated with each water depth, as shown in Figure 5. The upward radiance decreases as the water depth increases, regardless of the wavelength.

[0033] 5 shows the upward radiance spectrum for every 30 [m] of water depth except for a water depth of -0.5 [m], but the upward radiance information may include, for example, the upward radiance spectrum for every 5 [m] of water depth. Furthermore, the upward radiance information may associate the upward radiance spectrum for every arbitrary water depth, such as every 1 [m] of water depth or every 10 [m] of water depth.

[0034] Returning to FIG. 3, the acquisition unit 212 acquires the GPS signal received by the receiving device 130.

[0035] The determination unit 214 determines the multiple imaging wavelengths based on the first upward radiance at a reference height defined within a predetermined range based on the water surface and the second upward radiance at an estimated depth of the search target S present in the water. For example, the determination unit 214 may determine the multiple imaging wavelengths based on the ratio of the second upward radiance to the first upward radiance. Furthermore, for example, the determination unit 214 may determine, as the imaging wavelengths, the wavelength at which the division value obtained by dividing the second upward radiance by the first upward radiance is maximum and the wavelength at which the division value is minimum.

[0036] In this embodiment, the reference height is a height determined within a predetermined range with respect to the sea surface. The distance between the image capture device 120 and the reference height is shorter than the distance between the image capture device 120 and the estimated depth. The reference height may be a predetermined height in the sky or a predetermined depth in the sea. In this embodiment, the reference height is, for example, the water depth -0.5 [m], that is, a height 0.5 [m] above the sea surface.

[0037] The imaging wavelength is the wavelength of light that is transmitted by the tunable filter 110 and received by the imaging device 120. The process of determining the imaging wavelength by the determination unit 214 will be described in detail later.

[0038] The filter control unit 216 controls the tunable filter 110 to transmit light of each of the multiple imaging wavelengths determined by the determination unit 214. For example, if the tunable filter 110 includes a liquid crystal filter, the filter control unit 216 controls the voltage applied to the liquid crystal filter to change the refractive index of the liquid crystal filter and change the transmission wavelength of the tunable filter 110 to the imaging wavelength.

[0039] The imaging control unit 218 controls the imaging device 120 to receive light of each of the multiple imaging wavelengths that has passed through the tunable filter 110 and generate multiple wavelength images. A wavelength image is an image obtained by receiving light of the imaging wavelengths. The wavelength image is, for example, a monochrome image.

[0040] The determination unit 220 determines the presence or absence of the search object S based on the multiple wavelength images. The determination unit 220 may determine the presence or absence of the search object S based on, for example, the difference between the multiple wavelength images. The process of determining the presence or absence of the search object S by the determination unit 220 will be described in detail later.

[0041] [Search method] Next, a search method using the above-described search device 100 will be described. Fig. 6 is a flowchart showing the processing flow of the search method according to this embodiment. As shown in Fig. 6, the search method according to this embodiment includes a position information calculation process S110, an upward radiance information selection process S120, a ratio spectrum calculation process S130, an imaging wavelength determination process S140, an imaging process S150, a specific image generation process S160, and a judgment process S170. Each process will be described below.

[0042] [Location information calculation process S110] In the position information calculation process S110, the determination unit 214 calculates position information indicating the position of the image capture device 120 based on the GPS signal acquired by the acquisition unit 212, for example.

[0043] [Upward radiance information selection process S120] In the upward radiance information selection process S120, first, the determination unit 214 identifies the target sea area to be imaged by the imaging device 120 based on the position information calculated in the position information calculation process S110. Then, the determination unit 214 selects the upward radiance information of the target sea area as a reference from the multiple pieces of upward radiance information stored in the storage unit 210.

[0044] [Ratio spectrum calculation process S130] In the ratio spectrum calculation process S130, the determination unit 214 refers to the upward radiance information of the target sea area selected in the upward radiance information selection process S120 and calculates the ratio of the second upward radiance to the first upward radiance for each wavelength. In this embodiment, the determination unit 214 divides the second upward radiance by the first upward radiance for each wavelength. In this embodiment, the determination unit 214 uses, for example, the upward radiance at a water depth of −0.5 m as the first upward radiance. Furthermore, the determination unit 214 regards, for example, the habitat depth of the search target S as the estimated depth and uses the upward radiance of the habitat depth of the search target S as the second upward radiance.

[0045] For example, if the estimated depth is 60 m, the determination unit 214 calculates the divided value for each wavelength by dividing the upward radiance at a depth of 60 m (second upward radiance) by the upward radiance at a depth of -0.5 m (first upward radiance).

[0046] Fig. 7 is a diagram for explaining the processing by the determining unit 214 according to this embodiment. In Fig. 7, the vertical axis represents the division value, and the horizontal axis represents the wavelength [nm].

[0047] When the determining unit 214 divides the second upward radiance by the first upward radiance for each wavelength, the ratio spectrum shown in FIG. 7 is obtained.

[0048] [Imaging wavelength determination process S140] In the imaging wavelength determination process S140, the determination unit 214 refers to the ratio spectrum created in the ratio spectrum calculation process S130, and determines the first wavelength with the largest division value and the second wavelength with the smallest division value as the imaging wavelengths.

[0049] 7, for example, the division value is smallest at 480 [nm] and largest at 630 [nm]. Therefore, in the example shown in Fig. 7, the determination unit 214 determines 630 [nm] and 480 [nm] as the imaging wavelengths.

[0050] [Image capture process S150] In the imaging process S150, the filter control unit 216 controls the tunable filter 110 to transmit light of each of the multiple imaging wavelengths determined in the imaging wavelength determination process S140. Then, the imaging control unit 218 controls the imaging device 120 to receive light of each of the multiple imaging wavelengths that has passed through the tunable filter 110 and generate multiple wavelength images.

[0051] [Specific image generation process S160] In the specific image generation process S160, for example, the determination unit 220 generates a specific image from the multiple wavelength images generated in the imaging process S150.

[0052] 8 is a diagram illustrating a first wavelength image P1, a second wavelength image P2, and a specific image P according to this embodiment. As shown in FIG. 8, the first wavelength image P1 is an image generated by receiving light of a first wavelength (here, 630 [nm]) that produces the largest division value. The second wavelength image P2 is an image generated by receiving light of a second wavelength (here, 480 [nm]) that produces the smallest division value.

[0053] In this embodiment, the determination unit 220 creates a specific image P based on the difference between the first wavelength image P1 and the second wavelength image P2. For example, the determination unit 220 calculates the difference between the light intensity of the first wavelength image P1 and the light intensity of the second wavelength image P2 for each pixel to create the specific image P.

[0054] [Determination process S170] In the determination process S170, the determination unit 220 determines the presence or absence of a search target S based on a plurality of wavelength images. In this embodiment, the determination unit 220 determines the presence or absence of a search target S based on a specific image P. For example, the determination unit 220 performs image analysis on the specific image P and determines whether or not the target T is a search target S based on the shape and size of the target T in the specific image P. If the determination unit 220 determines that the target T is a search target S, it determines that the search target S is present in the target sea area. On the other hand, if the determination unit 220 determines that the target T is not a search target S, it determines that the search target S is not present in the target sea area.

[0055] Then, the transmitting device 140 transmits the specific image P and the determination result to the management device 20, for example, in association with the target sea area.

[0056] As described above, the searching device 100 according to this embodiment includes a tunable filter 110 capable of changing the transmission wavelength, an imaging device 120 that receives light transmitted through the tunable filter 110 and generates an image, and a control device 150 that controls the tunable filter 110 and the imaging device 120. The control device 150 includes a determination unit 214 that determines multiple imaging wavelengths based on a first upward radiance at a reference height defined within a predetermined range based on the water surface and a second upward radiance at an estimated depth of a search target S present in water, a filter control unit 216 that controls the tunable filter 110 to transmit light of each of the determined multiple imaging wavelengths, an imaging control unit 218 that controls the imaging device 120 to receive light of each of the multiple imaging wavelengths transmitted through the tunable filter 110 and generate multiple wavelength images P1, P2, and a determination unit 220 that determines the presence or absence of the search target S based on the multiple wavelength images P1, P2.

[0057] In addition, the search method of this embodiment includes determining multiple imaging wavelengths based on a first upward radiance at a reference height defined within a predetermined range based on the water surface and a second upward radiance at an estimated depth of the search object present in the water, receiving light of each of the determined multiple imaging wavelengths to generate multiple wavelength images P1, P2, and determining the presence or absence of the search object S based on the multiple wavelength images P1, P2.

[0058] In this way, the searching device 100 and searching method according to this embodiment receive light of multiple imaging wavelengths determined based on the first upward radiance and the second upward radiance, and generate multiple wavelength images P1 and P2. The searching device 100 and searching method according to this embodiment then determine the presence or absence of a search target S based on the multiple wavelength images P1 and P2. Therefore, the searching device 100 and searching method according to this embodiment can determine the presence or absence of a search target S based on a far smaller number of wavelength images P1 and P2, compared to analyzing hundreds of images obtained by a hyperspectral camera. Therefore, the searching device 100 and searching method according to this embodiment can significantly reduce the processing load when searching for a search target S in water.

[0059] Furthermore, the searching device 100 according to this embodiment includes a tunable filter 110 instead of a spectrometer provided in the hyperspectral camera. The tunable filter 110 has higher durability against shock and vibration compared to a spectrometer. Therefore, the searching device 100 according to this embodiment can avoid damage even when mounted on the aircraft 10.

[0060] In the searching device 100 according to this embodiment, the determining unit 214 may determine the multiple imaging wavelengths based on the ratio of the second upward radiance to the first upward radiance.

[0061] As a result, the searching device 100 according to this embodiment can determine with high accuracy whether or not there is a search object S in the water.

[0062] Furthermore, in the searching device 100 according to this embodiment, the determination unit 214 may determine, as the imaging wavelength, the wavelength at which the division value obtained by dividing the second upward radiance by the first upward radiance is the largest, and the wavelength at which the division value is the smallest.

[0063] In the wavelength image P2 obtained by using the second wavelength at which the division value is smallest as the imaging wavelength, the contrast between the object T and the background of the object T (for example, the seabed) is strongest. Therefore, the searching device 100 according to this embodiment can obtain the second wavelength image P2 including the object T having a clear outer edge by determining the second wavelength at which the division value is smallest as the imaging wavelength.

[0064] Furthermore, in the wavelength image P1 obtained using the first wavelength at which the division value is greatest as the imaging wavelength, the contrast between the object T and the background of the object T is weakest. Therefore, by determining the first wavelength at which the division value is greatest as the imaging wavelength, the searching device 100 according to this embodiment can obtain a first wavelength image P1 that represents disturbances such as waves other than the object T and the background.

[0065] In the searching device 100 according to this embodiment, the determining section 220 may determine the presence or absence of the search target S based on the difference between the multiple wavelength images P1 and P2.

[0066] As a result, the search device 100 according to this embodiment can determine the presence or absence of the search object S by using the specific image P from which disturbances such as waves have been removed. Therefore, the search device 100 according to this embodiment can determine the presence or absence of the search object S in the water with even higher accuracy.

[0067] In the searching device 100 according to this embodiment, the tunable filter 110 and the imaging device 120 may be provided on the flying object 10, and the imaging device 120 may capture images of the underwater environment from the sky.

[0068] This allows the searching device 100 according to this embodiment to search a wide area with a single image capture.

[0069] Although the embodiments have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to the above-described embodiments. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0070] For example, in the above embodiment, the determination unit 220 determines the presence or absence of the search target S based on the difference between the multiple wavelength images P1 and P2. However, the determination unit 220 is not limited to any particular process as long as it can determine the presence or absence of the search target S based on the multiple wavelength images. The determination unit 220 may determine the presence or absence of the search target S based on, for example, the ratio of the multiple wavelength images. Alternatively, the determination unit 220 may perform multiple regression analysis or PLS (Partial Least Squares Regression) regression analysis on the ratio spectrum to determine a weighting coefficient, and multiply the multiple wavelength images by the weighting coefficient to determine the presence or absence of the search target S. Alternatively, the determination unit 220 may perform predetermined image processing on the multiple wavelength images to determine the presence or absence of the search target S.

[0071] In the above embodiment, the search device 100 is provided in the aircraft 10. However, at least the tunable filter 110 and the image capture device 120 of the search device 100 may be provided in the aircraft 10. In this case, the receiving device 130 and the transmitting device 140 may also be provided in the aircraft 10, and the control device 150 may be provided in, for example, a management device 20 on the ground. In this case, the transmitting device 140 may transmit multiple wavelength images to the management device 20. This allows the aircraft 10 to be miniaturized. In this case, compared to transferring hundreds of images obtained by a hyperspectral camera, only a much smaller number of wavelength images need to be transmitted to the control device 150, thereby significantly reducing the data transfer volume.

[0072] In the above embodiment, the tunable filter 110 and the image capturing device 120 are provided in the aircraft 10, and the image capturing device 120 captures images underwater from the sky. However, the tunable filter 110 and the image capturing device 120 may be provided on a ship or the like, and the image capturing device 120 may capture images on the water surface or underwater.

[0073] In the above embodiment, the determination unit 214 determines, as the imaging wavelength, the wavelength at which the division value obtained by dividing the second upward radiance by the first upward radiance is maximum and the wavelength at which the division value is minimum. However, the determination unit 214 may determine, as the imaging wavelength, a wavelength determined based on the wavelength at which the division value obtained by dividing the second upward radiance by the first upward radiance is maximum and a wavelength determined based on the wavelength at which the division value is minimum. For example, the determination unit 214 may determine, as the imaging wavelength, a wavelength near the wavelength at which the division value is maximum and a wavelength near the wavelength at which the division value is minimum.

[0074] The determination unit 214 may also determine three or more wavelengths as the imaging wavelengths. For example, the determination unit 214 may determine, as the imaging wavelengths, wavelengths for which the division value is equal to or greater than a predetermined value and wavelengths for which the division value is less than the predetermined value. The determination unit 220 may then determine the presence or absence of the search target S based on a wavelength image with the weakest contrast among wavelength images for which the division value is equal to or greater than the predetermined value and a wavelength image with the strongest contrast among wavelength images for which the division value is less than the predetermined value. The determination unit 214 may also determine, as the imaging wavelengths, wavelengths within a predetermined range (e.g., ±10 nm, ±20 nm, ±50 nm, etc.) based on the wavelength for which the division value is smallest and a wavelength for which the division value is largest. For example, if the wavelength for which the division value is smallest is 480 [nm], the determination unit 214 may determine, as the imaging wavelengths, multiple wavelengths within a range of 470 [nm] to 490 [nm]. In this case, the determination unit 220 may determine whether or not the search target object S is present based on the wavelength image with the strongest contrast among wavelength images within a predetermined range based on the wavelength with the smallest division value, and the first wavelength image P1.

[0075] In the above embodiment, the determination unit 214 determines multiple imaging wavelengths based on the ratio of the second upward radiance to the first upward radiance. However, the determination unit 214 may determine multiple imaging wavelengths based on the difference between the first upward radiance and the second upward radiance. In this case, the determination unit 214 may determine, for example, the wavelength at which the difference between the first upward radiance and the second upward radiance is largest and the wavelength at which this difference is smallest as the imaging wavelengths. The determination unit 214 may also determine, for example, wavelengths determined based on the wavelength at which the difference between the first upward radiance and the second upward radiance is largest and wavelengths determined based on the wavelength at which this difference is smallest as the imaging wavelengths. For example, the determination unit 214 may determine, as the imaging wavelengths, wavelengths near the wavelength at which the difference is largest and wavelengths near the wavelength at which the difference is smallest.

[0076] The determiner 214 may also determine the multiple imaging wavelengths based on, for example, the first upward radiance and the upward radiance at an arbitrary water depth deeper than the reference height. For example, the determiner 214 may determine the multiple imaging wavelengths based on the first upward radiance and the upward radiance of the seabed.

[0077] Furthermore, the determination unit 214 may determine a plurality of imaging wavelengths by taking into account, for example, upward radiance in the atmosphere from the water surface to the imaging device 120 in addition to the first upward radiance and the second upward radiance. For example, the determination unit 214 may determine, as the imaging wavelengths, the wavelength at which the divided value obtained by dividing (second upward radiance + upward radiance in the atmosphere) by (first upward radiance + upward radiance in the atmosphere) is the largest, and the wavelength at which the divided value obtained by dividing (second upward radiance + upward radiance in the atmosphere) by (first upward radiance + upward radiance in the atmosphere) is the smallest.

[0078] The determination unit 214 may determine the imaging wavelength while the aircraft 10 is flying, that is, immediately before the imaging device 120 captures an image, or may determine the imaging wavelength in advance before the aircraft 10 takes flight.

[0079] This disclosure can contribute, for example, to Goal 14 of the Sustainable Development Goals (SDGs), "Conserve and sustainably use the oceans, seas and marine resources." [Explanation of symbols]

[0080] S Search object 10 Flying Objects 100 Search device 110 Tunable wavelength filter 120 Imaging device 150 control device 216 Filter control section 218 Imaging control unit 220 Judgment section

Claims

1. a tunable filter capable of changing a transmission wavelength; an imaging device that receives light transmitted through the wavelength tunable filter and generates an image; a control device that controls the wavelength tunable filter and the imaging device; Equipped with The control device a determination unit that determines a plurality of imaging wavelengths based on a first upward radiance at a reference height that is determined within a predetermined range with respect to the water surface and a second upward radiance at an estimated depth of a search target that exists in the water; and a filter control unit that controls the wavelength-variable filter so as to transmit light having each of the determined imaging wavelengths; an imaging control unit that controls the imaging device to receive light of the plurality of imaging wavelengths that has passed through the wavelength-variable filter and generate a plurality of wavelength images; a determination unit that determines whether or not the search target object exists based on the plurality of wavelength images; A search device comprising:

2. The searching device according to claim 1 , wherein the determination unit determines the plurality of imaging wavelengths based on a ratio of the second upward radiance to the first upward radiance.

3. 3. The searching device according to claim 2, wherein the determiner determines, as the imaging wavelength, a wavelength at which a division value obtained by dividing the second upward radiance by the first upward radiance is maximum, and a wavelength at which the division value is minimum.

4. the tunable filter and the imaging device are provided on an aircraft, The search device according to claim 1 , wherein the imaging device images the underwater environment from above.

5. The searching device according to claim 1 , wherein the determining unit determines whether or not the search target is present based on a difference between the plurality of wavelength images.

6. determining a plurality of imaging wavelengths based on a first upward radiance at a reference height determined within a predetermined range with respect to the water surface and a second upward radiance at an estimated depth of a search target present in the water; receiving light of each of the determined plurality of imaging wavelengths to generate a plurality of wavelength images; determining whether or not the search target object is present based on the plurality of wavelength images; A search method including:

Images