Sensing system

Abstract

This sensing system 400 is provided with an image sensor 420 and a calculation processing device 440. The calculation processing device 440 processes image data IMG generated by the image sensor 420. Upon detecting reduction in the contrast in the same determination region but between two successive image frames, the calculation processing device 440 determines that water droplets have been adhered.

Description

Sensing System

[0001] The present disclosure relates to sensing systems for automobiles.

[0002] For autonomous driving and automatic control of headlamp light distribution, an object identification system is used to sense the position and type of objects around the vehicle. The object identification system includes a sensor and a processing unit that analyzes the sensor output. The sensor is selected from among cameras, LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging), millimeter-wave radar, ultrasonic sonar, etc., taking into account the application, required accuracy, and cost.

[0003] Optical sensors (hereinafter simply referred to as sensors) can be broadly divided into passive sensors and active sensors. Passive sensors detect light emitted by an object or light reflected from the environment by an object; the sensor itself does not emit light. On the other hand, active sensors irradiate an object with illumination light and detect the reflected light. Active sensors primarily comprise a light projector (lighting) that irradiates the object with light, and an optical sensor that detects the reflected light from the object. Active sensors have the advantage of being more resistant to disturbances than passive sensors by matching the wavelength of the illumination light with the sensor's sensitivity wavelength range.

[0004] When water droplets adhere to the cover glass surface of an image sensor, detection accuracy decreases. Therefore, sensing systems that must ensure detection accuracy even in bad weather require measures such as adding a water droplet removal mechanism such as a wiper. In this case, it is necessary to detect the adhesion of water droplets in order to appropriately trigger the water droplet removal mechanism to remove raindrops.

[0005] Raindrop sensors are a well-known technology for detecting water droplets, but adding a raindrop sensor to a sensing system increases costs. Also, raindrop sensors cannot be installed on the optical axis of the image sensor because they interfere with sensing.

[0006] Furthermore, even if a water droplet removal mechanism is not provided, if water droplets can be detected, it is possible to predict a decrease in the accuracy of the sensing system, which is preferable from the perspective of functional safety.

[0007] The present disclosure has been made in view of the above-mentioned problems, and one exemplary purpose of an embodiment thereof is to provide a sensing system capable of detecting raindrops through image processing.

[0008] A sensing system according to an embodiment of the present disclosure includes an image sensor and a processing unit that processes images generated by the image sensor, and the processing unit determines the presence or absence of water droplets based on changes in the same determination region between two consecutive frames of the image.

[0009] Any combination of the above elements, or mutual substitution of elements or expressions between methods, devices, systems, etc., are also valid aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention.

[0010] According to one aspect of the present disclosure, water droplets can be detected.

[0011] FIG. 1 is a block diagram of a sensing system according to an embodiment. FIG. 2 is a diagram illustrating the influence of water droplets on image data. FIG. 3(a) and (b) are diagrams illustrating water droplet detection by the sensing system of FIG. 1. FIG. 4(a) and (b) are diagrams illustrating an example of a determination area A. FIG. 4(a) and (b) are diagrams illustrating another example of the determination area A. FIG. 5 is a block diagram of a sensing system. FIG. 6(a) and (b) are diagrams illustrating an image obtained by a ToF camera. FIG. 7(a) and (b) are diagrams illustrating the detection of water droplets based on range images. FIG. 8 is a diagram illustrating a sensing system equipped with a water droplet removal device. FIG. 9 is a diagram illustrating a vehicle lamp incorporating a sensing system. FIG. 10 is a block diagram illustrating a vehicle lamp equipped with a sensing system.

[0012] (Summary of the Embodiments) A summary of some exemplary embodiments of the present disclosure will be provided. This summary is intended to provide a basic understanding of one or more embodiments as a prelude to the detailed description that follows, and is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not intended to be a comprehensive overview of all possible embodiments, nor does it limit essential elements of the embodiments. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0013] According to one embodiment, the sensing system includes an image sensor and a processor that processes images generated by the image sensor, and determines the presence or absence of water droplets based on changes in the same determination region between two consecutive frames of the image.

[0014] The inventors recognized that when water droplets adhere to a cover glass on the optical axis (field of view) of an image sensor, scattering by the water droplets reduces the contrast of the image. When comparing two temporally adjacent frames, the position of the same object in the image rarely differs significantly, and the brightness of the object rarely differs significantly. Therefore, when comparing the same determination area in two frames, the contrast is likely to be substantially the same. In other words, if a significant decrease in contrast is detected within the same determination area, it can be assumed that this is due to the adhesion of water droplets. Thus, with the above configuration, the adhesion of water droplets can be determined through image processing.

[0015] Whether or not "contrast has decreased" can be determined by generating a judgment value that serves as an index of contrast for the judgment area of ​​each frame and determining based on the relative or absolute relationship between the two judgment values.

[0016] In one embodiment, the determination area may be set at a predetermined position. The predetermined position may be set to an area where the same object is always captured, or where nothing is captured. Such an area is suitable for the determination area because it can be said that there are few factors that change the contrast other than the presence of water droplets. For example, the upper part of the image corresponds to an empty space (sky), and the lower part of the image corresponds to the road surface. By setting the determination area to an area where the same object is always captured, it becomes easier to detect the contrast caused by the presence of water droplets.

[0017] In one embodiment, the arithmetic processing device may divide each of the two frames into a plurality of determination regions and determine whether or not water droplets are attached for each determination region.

[0018] In one embodiment, the arithmetic processing device may detect an object included in the image and define a determination region to include the detected object. This allows water droplets to be detected within a range in which a target object such as a person or vehicle is captured. Furthermore, since the contrast of an image in which a person or vehicle is captured changes more significantly depending on whether or not water droplets are present, this is expected to improve the accuracy of water droplet detection.

[0019] In one embodiment, the processor may generate two histograms for the determination regions of the two frames, so that changes in contrast can be detected.

[0020] In one embodiment, the processing unit may determine that water droplets have been present when the frequency of a predetermined section on the low-luminance side of the histogram for a given frame is lower than the frequency of the same section in the histogram for the previous frame. When water droplets are present, the pixel values ​​of areas where no objects are present increase due to scattered light from the water droplets. Therefore, water droplets can be detected based on the frequency of the section on the low-luminance side.

[0021] In one embodiment, the processing unit may determine that water droplets have been attached when the median value of a predetermined section of the histogram for a given frame increases compared to the median value of the predetermined section of the histogram for the previous frame. When water droplets are attached, the pixel values ​​of areas where no objects are present increase due to scattered light from the water droplets, causing the median value to shift toward higher brightness. Therefore, water droplets can be detected based on changes in the median value of the histogram.

[0022] In one embodiment, the processing unit may determine that water droplets have been attached when the spatial frequency of a determination region in a frame is lower than the spatial frequency of the determination region in the previous frame. When scattering occurs due to water droplets, the contours of the image of the object become blurred and the contrast decreases. This blurred contour appears as a decrease in spatial frequency. Therefore, the attachment of water droplets can be detected by monitoring the spatial frequency.

[0023] In one embodiment, the sensing system may further include an illumination device that irradiates the field of view with illumination light. The sensing system may be a Time of Flight (ToF) camera that divides the field of view into a plurality of ranges in the depth direction and generates a plurality of range images corresponding to the plurality of ranges by changing the time difference between light emission and image capture for each range.

[0024] In one embodiment, the arithmetic processing device may compare the determination area of ​​each of multiple range images of a given frame with the determination area of ​​each of multiple range images of a subsequent frame, and determine that water droplets have adhered if a decrease in contrast is detected in two or more range images. The effect of water droplets appears in multiple range images corresponding to multiple ranges. Therefore, detection accuracy can be improved by setting the condition for water droplet determination as being that a decrease in contrast is detected in two or more range images.

[0025] Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and redundant explanations will be omitted as appropriate. Furthermore, the embodiments are examples rather than limitations on the disclosure, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure.

[0026] 1 is a block diagram of a sensing system 400 according to an embodiment. The sensing system 400 may be a visible light camera, an infrared camera, a stereo camera, a ToF camera, a LIDAR, or the like. In this embodiment, the sensing system 400 is an active sensor and includes an illumination device 410, an image sensor 420, a sensing controller 430, and a processing unit 440.

[0027] The illumination device 410 includes a semiconductor light-emitting element such as a laser diode or a light-emitting diode (LED), and irradiates the field of view with illumination light L1. The wavelength of the illumination light L1 is not particularly limited, and it may be infrared light, visible light, or white light.

[0028] The image sensor 420 has sensitivity to the same wavelength as the illumination light L1. The image sensor 420 receives reflected light L2 that is the illumination light L1 reflected by an object OBJ within the sensing range (field of view) of the sensing system 400, and generates image data IMG.

[0029] The sensing controller 430 comprehensively controls the sensing system 400. Specifically, the sensing controller 430 controls the light emission of the lighting device 410 and the sensing by the image sensor 420 in a synchronized manner.

[0030] The processing unit 440 processes the image data IMG generated by the image sensor 420 .

[0031] A cover glass 422 is provided on the optical axis of the image sensor 420. The cover glass 422 is a member that is directly exposed to the external environment, and may be a part of the image sensor 420 or may be a separate member independent of the image sensor 420.

[0032] The arithmetic processing device 440 has a function of detecting water droplets WD adhering to the cover glass 422 by processing the image data IMG.

[0033] The arithmetic processing unit 440 calculates two temporally consecutive frames F of the image data IMG. ｉ , F ｉ＋１ When a decrease in contrast is detected in the same area (called a determination area), it is determined that a water droplet WD is present.

[0034] The above is the configuration of the sensing system 400. Next, its operation will be explained. FIG. 2 is a diagram illustrating the effect of water droplets on image data. FIG. 2 shows two pieces of image data captured of the same scene. The image on the left is the image data before water droplets were attached, and the image on the right is the image data after water droplets were attached. When water droplets are attached, the water droplets scatter the light reflected from or emitted by an object, making the brightness of areas where no object is present brighter. In other words, the water droplets reduce the contrast of the image compared to when there are no water droplets.

[0035] Water droplets also blur the contours of objects, meaning that when focusing on a small area containing an object, the water droplets reduce the contrast of the image compared to when there are no water droplets.

[0036] 3A and 3B are diagrams illustrating water droplet detection by the sensing system 400 of FIG. 3A. Two temporally consecutive frames F ｉ , F ｉ＋１ Each frame F ｉ , F ｉ＋１ The same size and position of the judgment area A ｉ , A ｉ＋１ is shown. ｉ Now, judgment area A ｉ There are no water droplets on the frame F behind the ｉ＋１ Judgment area A ｉ＋１ However, since the water droplets WD are transparent, they do not appear in the image itself.

[0037] In FIG. 3(b), two frames F ｉ, F ｉ＋１ Judgment area A ｉ , A ｉ＋１ A histogram of is shown.

[0038] The processing unit 440 calculates two frames F ｉ , F ｉ＋１ Judgment area A ｉ , A ｉ＋１ For ｉ , HIST ｉ＋１ When light is scattered by water droplets, the amount of light incident on pixels that were originally receiving strong light decreases, and the amount of light incident on pixels that were not originally receiving light increases. As a result, the histogram shows a decrease in the frequency of the low gradation section (dark area) with low brightness values, and an increase in the frequency of the high gradation section (bright area) with high brightness values, or the frequency of the intermediate gradation section. This causes the frequency distribution to transition to a flat distribution or one biased toward the high brightness side, reducing contrast.

[0039] The arithmetic processing unit 440 detects a change in the histogram, that is, a decrease in contrast, to determine whether or not water droplets WD are present.

[0040] For example, the arithmetic processing unit 440 may monitor the histogram of the low gradation section DARK and detect the presence of water droplets based on the change in the histogram.

[0041] For example, a plurality of adjacent bins in the low gradation section DARK, for example, three adjacent bins, are set as a monitoring section, and the adhesion of water droplets is detected by comparing the total frequency of the monitoring section. ｉ＋１ The total value of the frequency of the monitoring section and the histogram HIST ｉ It may be determined that water droplets have adhered when the difference between the total values ​​of the frequencies of the monitoring sections exceeds a threshold value.

[0042] Alternatively, the arithmetic processing unit 440 may detect the presence of water droplets by comparing the median values ​​of the monitoring intervals.

[0043] The presence of water droplets may be determined based on the high gradation section BRIGHT, rather than the low gradation section DARK. For example, a plurality of adjacent bins in the high gradation section BRIGHT are set as a monitoring section, and the adhesion of water droplets is detected by comparing the total frequency of the monitoring section. For example, a histogram HIST ｉ＋１ The total value of the frequency of the monitoring section and the histogram HIST ｉ Alternatively, the arithmetic processing unit 440 may detect the presence of water droplets by comparing the median values ​​within the monitoring intervals.

[0044] Next, a description will be given of the determination region A. Figures 4(a) and 4(b) are diagrams showing examples of the determination region A.

[0045] As shown in FIG. 4A, the determination area A may be fixed at a predetermined position within the frame. The predetermined position may be set to a range where the same object is always captured, or where nothing is captured at all. For example, the upper portion Ax of the image corresponds to empty space (sky), where there is little possibility of a car or pedestrian being captured. Therefore, it can be said that there are few factors that change the contrast other than the presence of water droplets. Therefore, it can be said that this is suitable as a determination area.

[0046] The lower part of the image, Ay, corresponds to the road surface, and is unlikely to include cars or pedestrians. Therefore, there are few factors that change the contrast other than the presence of water droplets. Therefore, this area is suitable for the judgment region.

[0047] In this way, by using the range in which the same subject is always photographed as the determination region, it becomes easier to detect the contrast caused by the adhesion of water droplets.

[0048] Conversely, the determination area A may be dynamically changed. Fig. 4B shows a dynamically changing determination area Az. The calculation processing unit 440 calculates the object OBJ included in the frame. １ , OBJ ２ Detect the detected object OBJ １ , OBJ ２ The judgment area Az １ , Az ２This allows water droplets to be detected within the range in which objects of interest such as people and vehicles are captured. In addition, the contrast of areas in which people and vehicles are captured changes more significantly depending on whether water droplets are present, which is expected to improve the accuracy of water droplet detection.

[0049] 5 is a diagram illustrating another example of the determination area A. The arithmetic processing unit 440 divides the image data IMG (frame) into a plurality of areas, and defines each of the divided areas as the determination area A. １ ~A ｎ The calculation processing unit 440 calculates the number of determination regions A １ ~A ｎ For example, if a decrease in contrast is detected in more than a predetermined number of regions, it may be finally determined that water droplets are present.

[0050] A specific example of the sensing system 400 will be described. One of the suitable applications of the sensing system 400 is a ToF camera.

[0051] 6 is a block diagram of the ToF camera 400B. The ToF camera 400B has a field of view that is divided into a plurality of N (N≧2) range RNGs in the depth direction. １ ~RNG Ｎ The image is captured in separate sections.

[0052] The ToF camera 400B includes an illumination device 410, an image sensor 420, a camera controller 430, and a processing unit 440.

[0053] The lighting device 410 irradiates a pulse of illumination light L1 ahead of the vehicle in synchronization with a light emission timing signal S1 provided by the camera controller 430. The illumination light L1 is preferably infrared light, but is not limited to this and may be visible light having a predetermined wavelength.

[0054] The image sensor 420 is configured to be capable of controlling exposure in synchronization with an image capturing timing signal S2 provided by the camera controller 430 and to be capable of generating a range image IMG. The image sensor 420 is sensitive to the same wavelength as the illumination light L1, and captures reflected light (return light) L2 reflected by the object OBJ.

[0055] The camera controller 430 holds predetermined light emission timing and exposure timing for each range RNG. ｉ When capturing an image, the ToF camera 400B generates a light emission timing signal S1 and a photographing timing signal S2 based on the light emission timing and exposure timing corresponding to the range, and then captures the image. １ ~RNG Ｎ A plurality of range images IMG corresponding to １ ~IMG Ｎ The i-th range image IMG ｉ The corresponding range RNG ｉ The object contained in the image will be captured.

[0056] FIG. 7 is a diagram illustrating the operation of the ToF camera 400B. ｉ The illumination device 410 is synchronized with the light emission timing signal S1 and measures the time t ０ ~t １ The light emission period τ １ The top row shows a diagram of light rays with time on the horizontal axis and distance on the vertical axis. ｉ The distance to the boundary in front of ＭＩＮｉ、 Range RNG ｉ The distance to the inner boundary of ＭＡＸｉ Let's say.

[0057] Light that leaves the lighting device 410 at a certain time travels a distance d ＭＩＮｉ and the round trip time T ＭＩＮｉ is T ＭＩＮｉ = 2 × d ＭＩＮｉ / c, where c is the speed of light.

[0058] Similarly, light that leaves the lighting device 410 at a certain time travels a distance d ＭＡＸｉ and the round trip time T ＭＡＸｉ is T ＭＡＸｉ = 2 × dＭＡＸｉ / c.

[0059] Range RNG ｉ When an object OBJ included in the image is to be photographed, the camera controller 430 ２ = t ０ +T ＭＩＮｉ Exposure begins at time t ３ = t １ +T ＭＡＸｉ The image capturing timing signal S2 is generated so that the exposure is completed at this timing. This is one exposure operation.

[0060] i-th range RNG ｉ When capturing an image, light emission and exposure are repeated multiple times, and the image sensor 420 accumulates the measurement results.

[0061] 8A and 8B are diagrams illustrating images obtained by the ToF camera 400B. In the example of FIG. 8A, the range RNG １ Object (pedestrian) OBJ １ exists and the range RNG ３ Object (vehicle) OBJ ３ FIG. 8(b) shows a plurality of range images IMG obtained in the situation of FIG. 8(a). １ ~IMG ３ is shown. Range image IMG １ When taking a picture, the image sensor is in the range RNG １ Since the range image IMG is exposed only by the reflected light from １ There are pedestrians １ Object image OBJ １ is captured.

[0062] Range image IMG ２ When taking a picture, the image sensor is in the range RNG ２ , and thus the range image IMG ２ No object image is captured on the

[0063] Similarly, range image IMG ３ When taking a picture, the image sensor is in the range RNG ３ Since the range image IMG is exposed by the reflected light from ３In the ３ In this way, the ToF camera 400B can capture images of objects separately for each range.

[0064] Returning to FIG. 6, the arithmetic processing unit 440 processes a plurality of range images IMG １ ~IMG Ｎ Based on this, adhesion of water droplets is detected.

[0065] 9 is a diagram illustrating the detection of water droplets based on range images. The arithmetic processing unit 440 detects a plurality of range images IMG of a certain frame. １ ~IMG Ｎ Each judgment area and multiple range images (IMG) of the following frames １ ~IMG Ｎ Each determination area is compared and referenced. Then, multiple range images IMG １ ~IMG Ｎ If a decrease in contrast is detected in the determination area in two or more of the images, it is determined that water droplets have adhered.

[0066] The effect of water droplets is not a range image of a specific range, but multiple range images IMG １ ~IMG Ｎ Therefore, by setting the condition for determining water droplets as being that a drop in contrast has been detected in two or more range images, it is possible to improve the detection accuracy.

[0067] The detection result by the arithmetic processing unit 440 can be used as a trigger to start the operation of the water droplet removal device.

[0068] 10 is a diagram showing a sensing system including a water droplet removal device. The sensing system 400 includes a water droplet removal device 460. The water droplet removal device 460 is a blower type device that removes water droplets by blowing air onto the cover glass 422. The water droplet removal device 460 includes an air blower 462 and a duct 464. The air blower 462 may be positioned so that the airflow generated by the air blower 462 is blown directly onto the cover glass 422.

[0069] When the arithmetic processing device 440 detects water droplets through image processing, it outputs a trigger TRIG to the water droplet removal device 460. In response to this trigger TRIG, the water droplet removal device 460 blows air onto the cover glass 422. Note that the configuration of the water droplet removal device 460 is not limited to a blower type, and other means such as a wiper may also be used.

[0070] 10 , the sensing system 400 is attached to the underside of the headlamp 600 body, but the camera of the sensing system 400 may be built into the headlamp 600. In this case, water droplets adhering to the cover glass 602 of the headlamp 600 become the detection target of the sensing system 400.

[0071] 11 is a diagram showing a vehicle lamp 200 incorporating a sensing system 400. The vehicle lamp 200 includes a housing 210, an outer lens 220, high beam and low beam lamp units 230H / 230L, and a sensing system 400. The lamp units 230H / 230L and the sensing system 400 are housed in the housing 210.

[0072] Note that a part of the sensing system 400, such as the image sensor 420 and the processing unit 440, may be installed outside the vehicle lamp 200, for example, behind the rearview mirror.

[0073] 12 is a block diagram showing a vehicle lamp 200 equipped with a sensing system 400. The vehicle lamp 200, together with a vehicle-side ECU 304, constitutes a lighting system 310. The vehicle lamp 200 includes a light source 202, a lighting circuit 204, and an optical system 206.

[0074] The processing unit 40 is configured to be able to identify the type of object based on the image obtained by the sensing system 400.

[0075] The arithmetic processing device 40 can be implemented as a combination of a processor (hardware) such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), or microcomputer, and a software program executed by the processor (hardware). The arithmetic processing device 40 may also be a combination of multiple processors. Alternatively, the arithmetic processing device 40 may be configured solely as hardware.

[0076] Information about the object OBJ detected by the arithmetic processing device 40 may be used for light distribution control of the vehicle lamp 200. Specifically, the lamp-side ECU 208 generates an appropriate light distribution pattern based on the information about the type and position of the object OBJ generated by the arithmetic processing device 40. The lighting circuit 204 and the optical system 206 operate to obtain the light distribution pattern generated by the lamp-side ECU 208.

[0077] Furthermore, information relating to the object OBJ detected by the arithmetic processing device 40 may be transmitted to the vehicle-side ECU 304. The vehicle-side ECU may perform automatic driving based on this information.

[0078] The above-described embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of the components and the processing steps. Such modifications will be described below.

[0079] (Variation 1) The sensing system 400 is not limited to a ToF camera and may be a LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) or a single-pixel imaging device (quantum radar) that uses correlation calculations.

[0080] (Variation 2) In the embodiment, a decrease in contrast is detected by a change in the histogram, but the means for determining the decrease in contrast is not limited to this. The calculation processing device 440 may determine that water droplets have adhered when the spatial frequency of the determination region in a certain frame is lower than the spatial frequency of the determination region in the previous frame.

[0081] (Modification 3) In the embodiment, a part of the image data is set as the determination region, but the entire image data may be set as the determination region.

[0082] The embodiments are merely examples, and it will be understood by those skilled in the art that there are various variations in the combination of each component and each treatment process, and that such variations are also included within the scope of this disclosure or the present invention.

[0083] The present disclosure relates to sensing systems for automobiles.

[0084] OBJ...object, S1...light emission timing signal, S2...photography timing signal, 200...vehicle lamp, 202...light source, 204...lighting circuit, 206...optical system, 310...lighting system, 304...vehicle-side ECU, 400...sensing system, 410...illumination device, 420...image sensor, 430...sensing controller, 440...arithmetic processing device, 460...water droplet removal device.

Claims

1. An image sensor; a processor for processing images generated by the image sensor; Equipped with The sensing system is characterized in that the arithmetic processing device determines the presence or absence of water droplets based on changes in the same determination area in two consecutive frames of the image.

2. The sensing system according to claim 1 , wherein the determination region is set at a predetermined position.

3. 2. The sensing system according to claim 1, wherein the arithmetic processing unit divides each of the two frames into a plurality of determination regions and determines whether water droplets are attached to each determination region.

4. The sensing system according to claim 1 , wherein the arithmetic processing unit detects an object included in the image and defines the determination region so as to include the detected object.

5. 5. The sensing system according to claim 1, wherein the arithmetic processing unit generates two histograms for the determination regions of the two frames.

6. The sensing system according to claim 5, wherein the arithmetic processing unit determines that water droplets have adhered when the frequency of a predetermined section on the low-luminance side of the histogram of a frame becomes lower than the frequency of the same section in the histogram of the previous frame.

7. The sensing system according to claim 5, wherein the arithmetic processing unit determines that water droplets have adhered when the median value of a predetermined section of the histogram of a frame increases compared to the median value of a predetermined section of the histogram of the previous frame.

8. The sensing system according to any one of claims 1 to 4, characterized in that the processing unit determines that water droplets have adhered when the spatial frequency of the judgment area in a frame is lower than the spatial frequency of the judgment area in the previous frame.

9. Further comprising an illumination device that irradiates the field of view with illumination light; The sensing system according to any one of claims 1 to 4, characterized in that the sensing system is a ToF camera capable of dividing the field of view into a plurality of ranges in the depth direction and generating a plurality of range images corresponding to the plurality of ranges by changing the time difference between light emission and image capture for each range.

10. The sensing system of claim 9, wherein the arithmetic processing device compares the judgment area of ​​each of the plurality of range images of a certain frame with the judgment area of ​​each of the plurality of range images of a subsequent frame, and if a decrease in contrast is detected in two or more range images, determines that water droplets have adhered.