Silhouette imaging system

Abstract

A silhouette imaging system (1) is a system (1-4) that images the silhouette of an observation target (40) in water (30), said system comprising: a planar light source (10) that has a light-emitting surface (11) which emits light (12); an imaging device (20, 70, 80) that has a detection unit which is disposed facing the light-emitting surface (11) with the water (30) therebetween, and that outputs an imaging signal on the basis of light which is part of the light (12) emitted from the light-emitting surface (11) and which has passed through the water (30) and reached the detection unit without being blocked by the observation target (40); and a control unit (50) that controls the planar light source (10) and the imaging device (20, 70, 80).

Description

Silhouette Photography System

[0001] The present disclosure relates to a silhouette photographing system that photographs the silhouette of an object underwater.

[0002] There has been proposed a monitoring device that consists of a camera, a lighting device placed on the opposite side of the aquarium from the camera, and a light-scattering plate (e.g., frosted glass) placed between the lighting device and the aquarium, and that enables the aquatic animal (e.g., fish) being observed to be recognized as a black silhouette (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 63-66460 (see, for example, claims 1 and 2, page 2, lower left to lower right columns, and Figures 1 and 12)

[0004] The above-mentioned conventional device photographs the silhouette of an aquatic animal illuminated by light emitted from a lighting device and passed through frosted glass, but there is a problem in that the image of the silhouette of the object being observed is likely to become unclear due to turbidity of the water in the aquarium.

[0005] An object of the present disclosure is to provide a silhouette photography system that can capture a clear silhouette of an object to be observed even when the water becomes turbid.

[0006] The silhouette photography system disclosed herein is a system for photographing the silhouette of an object being observed in water, and is characterized by comprising a surface light source having a light-emitting surface that emits light, and a detection unit arranged facing the light-emitting surface across the water, a photography device that outputs a photography signal based on light that is emitted from the light-emitting surface and travels through the water without being blocked by the object being observed and reaches the detection unit, and a control unit that controls the surface light source and the photography device.

[0007] According to the silhouette photography system of the present disclosure, it is possible to photograph a clear silhouette of an object to be observed even when the water becomes turbid.

[0008] 1 is a side view schematically showing the configuration of a silhouette photography system according to embodiment 1. FIG. 2 is a plan view schematically showing the configuration of the silhouette photography system according to embodiment 1. FIG. 3 is a block diagram showing the configuration of a control system of the silhouette photography system according to embodiment 1. FIG. 4 is a perspective view schematically showing a surface light source of a silhouette photography system according to a second variation of embodiment 1. FIG. 5 is a side view schematically showing the configuration of a silhouette photography system according to embodiment 2. FIG. 6 is a block diagram showing the configuration of a control system of the silhouette photography system according to embodiment 2. FIG. 7 is a side view schematically showing the configuration of a silhouette photography system according to embodiment 3. FIG. 8 is a perspective view schematically showing the configuration of a silhouette photography system according to embodiment 3. FIG. 9 is a block diagram showing the configuration of a control system of the silhouette photography system according to embodiment 3. FIG. 10 is a side view schematically showing the configuration of a silhouette photography system according to embodiment 4. FIG. 11 is a perspective view schematically showing the configuration of a silhouette photography system according to embodiment 4. FIG. 12 is a block diagram showing the configuration of a control system of the silhouette photography system according to embodiment 4. FIG. 13 is a perspective view schematically showing the configuration of a silhouette photography system according to a variation of embodiment 4. FIG. 14 is a block diagram showing the configuration of a control system of the silhouette photography system according to a variation of embodiment 4.

[0009] A silhouette photography system according to an embodiment will be described below with reference to the drawings. The following embodiments are merely examples, and the embodiments can be appropriately combined and modified.

[0010] <<Embodiment 1>> Fig. 1 is a side view that schematically shows the configuration of a silhouette photography system 1 according to embodiment 1. Fig. 2 is a plan view that schematically shows the configuration of the silhouette photography system 1. The silhouette photography system 1 is a system for photographing the silhouette of an observation target 40 in water 30.

[0011] 1 and 2, the water 30 is contained in an aquarium 31, but the water 30 may be seawater or freshwater in an aquaculture farm separated by a net or the like for cultivating aquatic organisms (e.g., fish, shellfish, crustaceans, etc.), or water in a pond provided in a facility for spawning, hatching, etc. A typical example of the observation object 40 in the water 30 in the aquarium 31 is, for example, a fish kept as an ornamental animal.

[0012] The observation target 40 may be a living organism (for example, an animal or a plant) other than fish, shellfish, or crustaceans. Note that the observation target 40 may also be an object other than a living organism.

[0013] The silhouette photography system 1 has a surface light source 10 and a camera 20 as a photography device. In Figures 1 and 2, the surface light source 10 is placed under the bottom of an aquarium 31, and the camera 20 is placed in the water 30 of the aquarium 31. However, the surface light source 10 may be provided with a waterproof function so that it is placed in the water 30. The camera 20 may also be placed above the water surface 32 of the water 30. The surface light source 10 and the camera 20 may also be placed near the outside or inside of the side of the aquarium 31, with the water 30 sandwiched between them.

[0014] The surface light source 10 has a light-emitting surface 11 that emits light 12. The surface light source 10 emits light of uniform intensity from the light-emitting surface 11. The light-emitting surface 11 is flat, but may also be curved. The surface light source 10 is, for example, an edge-light type lighting device configured with a plurality of light-emitting diodes (LEDs) that are a plurality of light-emitting elements and a plate-shaped light-guiding member that guides and emits the light emitted from the plurality of LEDs. The surface light source 10 may also be a lighting device equipped with a plurality of LEDs arranged in a matrix. By providing the plurality of LEDs with different types of LEDs that emit light of different colors (i.e., wavelengths of the emitted light), the surface light source 10 can emit light of a plurality of colors with different wavelengths. Furthermore, by providing the surface light source 10 with a plurality of LEDs arranged in a matrix, a portion of the light-emitting surface 11 can be used as a light-emitting region, and the light-emitting region can be moved.

[0015] The camera 20 is equipped with a detection unit 21 consisting of an imaging element such as a CCD (Charge-Coupled Device) sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor and an optical lens, and outputs light input to the imaging element as an imaging signal (i.e., video data). The detection unit 21 of the camera 20 is disposed facing the light-emitting surface 11 across the water 30. The camera 20 outputs an imaging signal based on the light 12 emitted from the light-emitting surface 11 that travels through the water 30 without being blocked by the object of observation 40 and reaches the detection unit 21. The camera 20 can be either an area sensor or a line sensor.

[0016] 3 is a block diagram showing the configuration of a control system of silhouette photography system 1. Silhouette photography system 1 has control unit 50 as a control circuit that controls surface light source 10 and camera 20, and display device 90 such as a liquid crystal display. In embodiment 1, control unit 50 controls the wavelength of light 12 emitted from surface light source 10. For example, in embodiment 1, control unit 50 controls the wavelength of light 12 emitted from surface light source 10 based on the image captured by camera 20.

[0017] The control circuit has, for example, a processor such as a CPU (Central Processing Unit), a memory as a storage device, and an interface. The control circuit may be a dedicated processing circuit, or may be a processor that executes a program stored in the memory. The control circuit may be a mixture of components made up of a processing circuit and components made up of a processor. Furthermore, the control unit 50 may be a computer (e.g., a desktop personal computer, a smartphone, a tablet terminal, etc.) that can communicate with the surface light source 10 and the camera 20.

[0018] Light 12 emitted from the light-emitting surface 11 of the surface light source 10 toward the water 30 travels through the water 30 toward the water surface 32 and is incident on the camera 20, which has the detection unit 21 facing downward. At this time, the camera 20 captures an image in which the object of observation 40 is not present. When the object of observation 40 (e.g., a pet) is present between the surface light source 10 and the camera 20, part of the light 12 emitted from the surface light source 10 is blocked, and the silhouette of the object of observation 40 appears in the image captured by the camera 20.

[0019] By placing the camera 20 in the water 30, the distance from the observation target 40 to the detection unit 21 of the camera 20 can be shortened. In this case, the influence of light scattering due to turbidity of the water 30 can be suppressed, making it easier to acquire clear images. By placing the camera 20 in the water 30, for example, if the observation target 40 is a creature that prefers to be on the bottom of the aquarium 31 or a creature that moves around the bottom of the aquarium 31 in search of food that sinks in the water 30, it is possible to acquire clear images of the silhouette.

[0020] The control unit 50 can also select the wavelength of the light 12 emitted from the surface light source 10 from two or more options. When the water 30 is not very turbid (i.e., when the turbidity is low), the clarity of the silhouette is determined by the light transmittance of the water 30 itself. Therefore, it is desirable to use light 12 emitted from the light-emitting surface 11 of the surface light source 10 with a wavelength that has the highest light transmittance through the water (e.g., light in the range of approximately 450 nm to 500 nm). An example of a case where the water 30 is not very turbid is water with a turbidity equal to or lower than that of seawater far from land. Furthermore, "using light in the range of 450 nm to 500 nm" means light whose wavelength distribution peaks in the range of 450 nm to 500 nm.

[0021] Furthermore, when the water 30 is highly turbid (i.e., when the turbidity is high), it is desirable that the light 12 emitted from the light-emitting surface 11 of the surface light source 10 be long-wavelength light that is less susceptible to the influence of turbidity (for example, light in the range of approximately 800 nm to 900 nm) in terms of the wavelength sensitivity of the imaging element of the detection unit 21 of the camera 20. Furthermore, "light in the range of 800 nm to 900 nm" means light whose wavelength distribution peak is in the range of 800 nm to 900 nm.

[0022] Furthermore, when the water 30 is moderately turbid, it is desirable that the light 12 emitted from the surface light source 10 have a wavelength with the highest light transmittance when the transmission characteristics of the water 30 and the turbidity particles are combined. For example, when the water 30 is coastal seawater close to land, it is desirable that the light 12 emitted from the surface light source 10 have a wavelength in the range of approximately 500 nm to 550 nm. "Light in the range of 500 nm to 550 nm" means light whose wavelength distribution peaks in the range of 500 nm to 550 nm. The wavelength range of the light 12 described above is merely an example of the wavelengths that can be used, and is not limited to these ranges.

[0023] The level of turbidity of the water 30, the type of turbidity of the water 30 (e.g., particle size and type of substances causing turbidity), and the light transmittance per wavelength of the raised object (the observation target 40) change depending on the number of days elapsed and the growth status of the raised object (the observation target 40), and accordingly, the wavelength of the surface light source 10 that produces the clearest image changes. Generally, the longer the wavelength of light, the greater its ability to penetrate matter. Therefore, if the observation target 40 is a highly transparent fish, for example, using light with a long wavelength as the light 12 will hardly capture the silhouette of the fish, making it difficult to detect. Therefore, there is a trade-off between measures to prevent turbidity of the water 30 and the light transmittance of the observation target 40. The control unit 50 selects light of an optimal wavelength as the light 12, taking this trade-off into consideration. Note that the control unit 50 may select the optimal wavelength using a trained model obtained by a machine learning technique using artificial intelligence (AI).

[0024] As described above, by using the silhouette photography system 1 according to embodiment 1, it is possible to use the surface light source 10 and the camera 20 as a photography device, so that even if the water 30 becomes turbid, a clear silhouette image of the object of observation 40 can be obtained.

[0025] Furthermore, by using the silhouette photography system 1 according to embodiment 1, it is possible to adjust the wavelength of the light 12 emitted from the surface light source 10, so that even if the water 30 becomes turbid, a clear silhouette image of the object of observation 40 can be obtained by adjusting the wavelength of the light 12.

[0026] <<First Variation of First Embodiment>> The silhouette photography system according to the first variation of the first embodiment differs from the silhouette photography system 1 described using Figures 1 to 3 in that the control unit 50 performs light emission intensity control, which periodically changes the intensity of the light 12 emitted from the light-emitting surface 11, or blinking control, which periodically turns the surface light source 10 on and off.

[0027] For example, in the silhouette photography system according to the first modification, blinking control is performed to periodically repeat extremely short flashes of light, for example, 1 / 100 of a second, in synchronization with the exposure timing of the camera 20, thereby reducing the intensity of light felt by the animal being kept, which is the observation subject 40. This control can reduce stress on the animal being kept.

[0028] Alternatively, in the silhouette photography system according to variant example 1, light emission intensity control is performed to gradually increase the intensity of light emitted from the light-emitting surface 11 before photography by the camera 20 begins, and gradually decrease the intensity of light emitted from the light-emitting surface 11 after photography by the camera 20 has finished, thereby reducing stress on the animals being kept due to sudden changes in the amount of light.

[0029] By performing the above-mentioned light emission intensity control or the above-mentioned blinking control, it is possible to set a change in brightness of the light-emitting surface 11 or a lighting time of the surface light source 10 so that the animal being raised as the observation subject 40 cannot recognize it or does not have much of an effect on the animal being raised, thereby reducing the stress experienced by the animal being raised.

[0030] Other than the above, the silhouette photography system according to the first modification of the first embodiment is the same as the silhouette photography system 1 described with reference to FIGS.

[0031] <<Second Modification of First Embodiment>> Figure 4 is a perspective view schematically showing a surface light source of a silhouette photography system according to a second modification of the first embodiment. The silhouette photography system according to the second modification of the first embodiment differs from the silhouette photography system 1 described using Figures 1 to 3 in that the light-emitting surface 11 of the surface light source 10 further has marker patterns 13 which are predetermined marks. The second modification of the first embodiment shows an example in which four marker patterns 13 are provided near the corners of the light-emitting surface 11 of the surface light source 10 within the photography range 22 of the camera 20. However, the number, shape, and position of the marker patterns 13 are not limited to the example of Figure 4.

[0032] In variant example 2 of embodiment 1, the emission wavelength of the surface light source 10 is changed, and the marker pattern 13 is photographed for each emission wavelength, and the images of the marker pattern 13 obtained are compared, so that the wavelength that produces the clearest image can be selected as the optimal wavelength.

[0033] In the second modification of the first embodiment, the type of image processing or various parameters used in the image processing can be selected based on the captured image of the marker pattern 13. For example, in the second modification of the first embodiment, the radius or intensity of an unsharp mask, which is a filter that has the effect of emphasizing the contours of the entire image or the subject to make them appear clearer, can be adjusted depending on the blurring of the boundaries of the marker pattern 13. Furthermore, the control unit 50 in the second modification of the first embodiment may use a trained model obtained by a machine learning technique using AI to select the optimal wavelength of the light 12 to be used for image processing such as sharpening processing (e.g., processing using an unsharp mask), contrast correction processing, color correction processing, and pet detection processing.

[0034] Furthermore, using the position and shape of the marker pattern 13 on the image, camera parameters consisting of external parameters such as the relative position and attitude of the camera 20 and the surface light source 10 and internal parameters such as the focal length and distortion of the lens of the camera 20 can be estimated and used for correction processing of various images. As a result, even if the camera parameters change during operation, images with the same angle of view can be acquired.

[0035] Other than the above, the silhouette photography system according to the second modification of the first embodiment is the same as the silhouette photography system 1 described with reference to FIGS.

[0036] <<Embodiment 2>> Fig. 5 is a side view schematically showing the configuration of a silhouette photography system 2 according to embodiment 2. In Fig. 5, components that are the same as or correspond to those shown in Fig. 1 are assigned the same reference numerals as those shown in Fig. 1. Fig. 6 is a block diagram showing the configuration of a control system of the silhouette photography system 2. In Fig. 6, components that are the same as or correspond to those shown in Fig. 3 are assigned the same reference numerals as those shown in Fig. 3.

[0037] The silhouette photography system 2 according to the second embodiment differs from the silhouette photography system 1 according to the first embodiment in that it has at least one of a turbidity measuring device 60 that measures the turbidity of the water 30 and a particle size measuring device 61 that measures the particle size distribution of the particles dispersed in the water 30, and in that the control unit 50 changes (i.e., selects) the wavelength of the light 12 emitted from the surface light source 10 based on at least one of the measured turbidity (amount of particles per unit volume) and particle size distribution (distribution of particle sizes).

[0038] By using the silhouette photography system 2 according to the second embodiment, it is possible to adjust the wavelength of the light 12 emitted from the surface light source 10, so that even if the water 30 becomes turbid, a clear silhouette image of the object of observation 40 can be obtained by adjusting the wavelength of the light 12.

[0039] Furthermore, by using the silhouette photography system 2 according to the second embodiment, it is possible to adjust the wavelength of the light 12 emitted from the surface light source 10 based on the detection value of at least one of the turbidity measuring instrument 60 and the particle size measuring instrument 61 (i.e., at least one of the values ​​of turbidity and particle size distribution), so that the amount of information processing by the control unit 50 can be reduced compared to the first embodiment.

[0040] Furthermore, when the silhouette photography system 2 according to the second embodiment is equipped with the particle size measuring device 61, the cause of the turbidity (turbidity due to leftover food, turbidity due to excrement, turbidity due to bacterial products, etc.) can be inferred from the size of the particles that cause the turbidity of the water 30, and therefore the wavelength of the light 12 emitted from the surface light source 10 can be adjusted to a wavelength appropriate for the type of turbidity. As a result, a clear silhouette image of the observation target 40 can be acquired.

[0041] <<Embodiment 3>> Fig. 7 is a side view schematically showing the configuration of a silhouette photography system 3 according to embodiment 3. In Fig. 7, components that are the same as or correspond to those shown in Fig. 1 are assigned the same reference numerals as those shown in Fig. 1. Fig. 8 is a perspective view schematically showing the configuration of the silhouette photography system 3.

[0042] Fig. 9 is a block diagram showing the configuration of a control system of the silhouette photography system 3. In Fig. 9, components that are the same as or correspond to those shown in Fig. 3 are assigned the same reference numerals as those shown in Fig. 3.

[0043] The silhouette photography system 3 according to the third embodiment differs from the silhouette photography system 1 according to the first embodiment in that the control unit 50 estimates the position of the observation target 40 based on the photography signal, causes the light-emitting surface 11 to partially emit light, and moves the light-emitting area 14 that partially emits light based on the position of the observation target 40, and in that the silhouette photography system 3 according to the third embodiment includes a camera 70 as a photography device that captures the silhouette of the observation target 40. The camera 70 is the same as the camera 20 according to the first or second embodiment. In other words, as shown in FIGS. 7 and 8 , in the third embodiment, the control unit 50 moves the light-emitting area 14 according to the position of the observation target 40, irradiates the observation target 40 with light, and projects a silhouette image 73 onto the camera 70 through the lens 71. The camera 70 and the lens 71 may be housed in a waterproof container 72. A transparent window made of glass, acrylic, or the like is formed on the surface of the waterproof container 72 facing the light-emitting surface 11.

[0044] When using the silhouette photography system 3 according to embodiment 3, only a portion of the surface light source 10 is selected to emit light, thereby suppressing the effects of reflected light and scattered light in the water 30, and the camera 70 can capture clear images.

[0045] Other than the above, the silhouette photography system 3 according to the third embodiment is the same as the silhouette photography system according to the first or second embodiment.

[0046] <<Embodiment 4>> Fig. 10 is a side view schematically showing the configuration of a silhouette photography system 4 according to embodiment 4. In Fig. 10, components that are the same as or correspond to those shown in Fig. 1 are assigned the same reference numerals as those shown in Fig. 1. Fig. 11 is a perspective view schematically showing the configuration of the silhouette photography system 4.

[0047] Fig. 12 is a block diagram showing the configuration of a control system of the silhouette photography system 4. In Fig. 12, components that are the same as or correspond to those shown in Fig. 3 are assigned the same reference numerals as those shown in Fig. 3.

[0048] The silhouette photography system 4 according to the fourth embodiment differs from the silhouette photography system 1 according to the first embodiment in that the photography device includes an area sensor or a line sensor 80 having a plurality of photoelectric conversion elements linearly arranged, and a line sensor moving unit 83 that moves the line sensor 80 in a predetermined direction 84, and in that the control unit 50 causes the light-emitting surface 11 to partially emit light and moves the partially emitting light-emitting region 14 in a direction 85 that is the same as the direction 84. In other words, in the fourth embodiment, as shown in FIGS. 10 and 11 , a waterproof container 82 that houses the line sensor 80 and the optical lens 81 is moved in a direction 84 perpendicular to the longitudinal direction of the line sensor 80, and the partially emitting light-emitting region (a linear region corresponding to the line sensor 80) is moved in the same direction 85 as the direction 84 according to the position of the moving line sensor 80, thereby photographing the silhouette of the observation target 40. It is also possible to emit light only in the region currently being exposed by synchronizing with the scanning of the line sensor or the exposure timing of the rolling shutter of the area sensor. In summary, the control unit 50 synchronizes the scanning by the line sensor 80 with the movement of the light emitting area on the light emitting surface 11 .

[0049] When using the silhouette photography system 4 according to the fourth embodiment, only a portion of the surface light source 10 is selected to emit light, so that the effects of reflected light and scattered light in the water 30 are suppressed, and the line sensor 80 can acquire a clear image.

[0050] Fig. 13 is a perspective view showing a schematic configuration of a silhouette photography system 4a according to a modification of Embodiment 4. Fig. 14 is a block diagram showing the configuration of a control system of silhouette photography system 4a according to a modification of Embodiment 4. Silhouette photography system 4a has a surface light source 10, an area sensor 80a as a photography device with a rolling shutter function, and a control unit 50a. Surface light source 10 and area sensor 80a may be arranged near the outside or inside of the side of aquarium 31, with water 30 sandwiched between them.

[0051] The area sensor 80a is an imaging device having a plurality of photoelectric conversion elements arranged two-dimensionally and having a rolling shutter exposure function. The control unit 50a is a control device that controls the light-emitting surface 11 to partially emit light and moves the partially emitting light-emitting area 15 in the direction of the arrow (direction 85) in accordance with the movement of the position of the area being exposed by the area sensor 80a (direction 86).

[0052] 12 and 13, the silhouette photography system 4a performs rolling shutter control by moving the light-emitting area 15 of the light-emitting surface 11 in the direction of the arrow (direction 85) and, in synchronization with this movement, moving the position of the exposed area of ​​the area sensor 80a in the direction of the arrow 86. When the silhouette photography system 4a is used, only a portion of the surface light source 10 is selected to emit light, thereby suppressing the effects of reflected light and scattered light from the water 30 and allowing the area sensor 80a to capture a clear image.

[0053] Other than the above, the silhouette photography system 4 according to the fourth embodiment and the silhouette photography system 4a according to the modified example of the fourth embodiment are the same as the silhouette photography system according to any one of the first to third embodiments.

[0054] 1 to 4, 4a Silhouette photography system, 10 Surface light source, 11 Light-emitting surface, 12 Light, 13 Marker pattern, 20 Camera (photography device), 21 Detection unit, 22 Photography range, 30 Water, 31 Aquarium, 32 Water surface, 40 Observation object, 50 Control unit, 60 Turbidity meter, 61 Particle size meter, 70 Camera (photography device), 80 Line sensor (photography device), 80a Area sensor (photography device), 90 Display device.

Claims

1. A silhouette imaging system for photographing a silhouette of an observation object in water, comprising: a surface light source having a light emitting surface that emits light; an imaging device having a detection unit disposed so as to face the light emitting surface with the water therebetween, and outputting an imaging signal based on light that has traveled through the water without being blocked by the observation object among the light emitted from the light emitting surface and has reached the detection unit; a control unit that controls the surface light source and the imaging device; wherein the control unit changes the wavelength of the light emitted from the light emitting surface based on the imaging signal characterizing the silhouette imaging system.

2. A silhouette imaging system for photographing a silhouette of an observation object in water, comprising: a surface light source having a light emitting surface that emits light; an imaging device having a detection unit disposed so as to face the light emitting surface with the water therebetween, and outputting an imaging signal based on light that has traveled through the water without being blocked by the observation object among the light emitted from the light emitting surface and has reached the detection unit; a control unit that controls the surface light source and the imaging device; a marker pattern provided within the imaging range of the imaging device; wherein the control unit changes the wavelength of the light emitted from the light emitting surface based on the imaging signal obtained by photographing the marker pattern characterizing the silhouette imaging system.

3. A silhouette imaging system for photographing a silhouette of an observation object in water, comprising: a surface light source having a light emitting surface that emits light; an imaging device having a detection unit disposed so as to face the light emitting surface with the water therebetween, and outputting an imaging signal based on light that has traveled through the water without being blocked by the observation object among the light emitted from the light emitting surface and has reached the detection unit; a control unit that controls the surface light source and the imaging device; wherein the control unit estimates the position of the observation object based on the imaging signal, causes partial light emission of the light emitting surface, and moves a light emitting region that emits partial light based on the position of the observation object characterizing the silhouette imaging system.

4. The imaging device is an area sensor having a plurality of two-dimensionally arranged photoelectric conversion elements characterizing the silhouette imaging system according to any one of claims 1 to 3.

5. A silhouette imaging system for photographing a silhouette of an observation object in water, comprising: a surface light source having a light emitting surface that emits light; A photographing apparatus having a detection unit arranged to face the light emitting surface with the water in between, and outputting a photographing signal based on the light that has traveled through the water without being blocked by the observation target among the light emitted from the light emitting surface and reached the detection unit. A control unit for controlling the surface light source and the photographing apparatus. The photographing apparatus includes a line sensor having a plurality of one-dimensionally arranged photoelectric conversion elements, and a line sensor moving unit for moving the line sensor in a predetermined direction. The control unit Causes partial light emission of the light emitting surface. Moves the light emitting region that emits partial light according to the position of the moving line sensor. A silhouette photographing system characterized by the above.

6. A silhouette photographing system for photographing a silhouette of an observation target in water, A surface light source having a light emitting surface that emits light, A photographing apparatus having a detection unit arranged to face the light emitting surface with the water in between, and outputting a photographing signal based on the light that has traveled through the water without being blocked by the observation target among the light emitted from the light emitting surface and reached the detection unit. A control unit for controlling the surface light source and the photographing apparatus. The photographing apparatus is an area sensor having a plurality of two-dimensionally arranged photoelectric conversion elements and having a rolling shutter exposure function. The control unit Causes partial light emission of the light emitting surface. Moves the light emitting region that emits partial light according to the position of the region during the exposure of the area sensor. A silhouette photographing system characterized by the above.

7. The control unit performs light emission intensity control for periodically changing the intensity of the light emitted from the light emitting surface, or flicker control for periodically repeating turning on and off of the surface light source. The silhouette photographing system according to any one of claims 1 to 3 and 5 to 6, characterized by the above.

8. The surface light source is arranged with the light emitting surface facing upward. The photographing apparatus is arranged with the detection unit facing downward. The silhouette photographing system according to any one of claims 1 to 3 and 5 to 6, characterized by the above.

9. Further includes a water tank for storing the water. The surface light source is arranged with the light emitting surface facing upward under the bottom surface of the water tank. The photographing apparatus is arranged with the detection unit facing downward above the water tank. The silhouette photographing system according to any one of claims 1 to 3 and 5 to 6, characterized by the above.

10. The water is fresh water or seawater. The object to be observed is an animal or a plant in the water The silhouette imaging system according to any one of claims 1 to 3 and 5 to 6, characterized in that

11. further comprising a display device for displaying an image based on the imaging signal The silhouette imaging system according to any one of claims 1 to 3 and 5 to 6, characterized in that