Hydrogen flame visualization device

Abstract

To provide a hydrogen flame visualization device capable of appropriately grasping a distance to a hydrogen flame.SOLUTION: A hydrogen flame visualization device includes: a first visualization camera 11 and a second visualization camera 21 that detect light of a hydrogen flame; one or more difference cameras 12 and 22; an image processing part 30 that generates a visible image of the hydrogen flame and calculates a distance to the hydrogen flame; and a display device 50 that displays the visible image of the hydrogen flame and the distance to the hydrogen flame. A first difference image is generated from an image captured by the first visualization camera 11 and the image captured by a difference camera 12, a hydrogen flame image is detected based on the first difference image. A second difference image is generated from the image captured by the second visualization camera 21 and the image captured by the difference camera 22, the hydrogen flame image is detected based on the second difference image, and the distance to the hydrogen flame is calculated based on a parallax between the hydrogen flame image detected based on the first difference image and the hydrogen flame image detected based on the second difference image.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen flame visualization device that visualizes a colorless hydrogen flame produced by the combustion of hydrogen. [Background technology]

[0002] In recent years, opportunities to use hydrogen have been increasing, such as in fuel cell vehicles and hydrogen stations that supply hydrogen gas to fuel cell vehicles. However, the hydrogen flame generated when hydrogen is burned is colorless and transparent, and there has been a problem in that when a hydrogen flame occurs due to a hydrogen gas leak or other reasons, it is impossible for humans to visually determine where the hydrogen flame is occurring. To address this issue, the applicant has proposed a hydrogen flame monitoring device that can detect and visualize small hydrogen flames with low luminous intensity with high accuracy even in environments with a lot of sunlight.The device creates flame images using near-infrared light in the 1340 to 1500 nm wavelength range, which is only present in small amounts in sunlight, making it possible to visualize even small hydrogen flames with low luminous intensity (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-205180 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the invention described in Patent Document 1 had the problem that, although it was possible to visualize hydrogen flames, it was unable to properly grasp the distance to the hydrogen flames. In order to safely handle hydrogen flames, there was a need for a hydrogen flame visualization device that could properly grasp the distance to the hydrogen flames.

[0005] An object of the present invention is to provide a hydrogen flame visualization device that can appropriately grasp the distance to a hydrogen flame. [Means for solving the problem]

[0006] The hydrogen flame visualization device according to the present invention comprises a first visualization camera and a second visualization camera that detect light of a wavelength whose emission intensity is equal to or greater than a predetermined value in the emission spectrum of the hydrogen flame, one or more difference cameras that detect light of a wavelength whose emission intensity is less than the predetermined value in the emission spectrum of the hydrogen flame, an image processing unit that generates a visible image of the hydrogen flame based on images received from the first visualization camera, the second visualization camera, and the difference camera, and calculates the distance to the hydrogen flame, and the visible image of the hydrogen flame and the distance to the hydrogen flame generated by the image processing unit. and a display device that displays the distance to the hydrogen flame, wherein the image processing unit generates a first difference image from the image captured by the first visualization camera and the image captured by the subtraction camera, detects an image of the hydrogen flame based on the first difference image, generates a second difference image from the image captured by the second visualization camera and the image captured by the subtraction camera, detects the image of the hydrogen flame based on the second difference image, and calculates the distance to the hydrogen flame based on the parallax between the image of the hydrogen flame detected based on the first difference image and the image of the hydrogen flame detected based on the second difference image. In the above-mentioned hydrogen flame visualization device, the differential camera has a first differential camera and a second differential camera, and includes a first camera unit in which the first visualization camera and the first differential camera are arranged in close proximity, and a second camera unit in which the second visualization camera and the second differential camera are arranged in close proximity, and the image processing unit can be configured to calculate the distance to the hydrogen flame based on the parallax between the image of the hydrogen flame detected by the first camera unit and the image of the hydrogen flame detected by the second camera unit. In the above-mentioned hydrogen flame visualization device, the image processing unit can be configured to determine erroneous detection of a hydrogen flame by comparing the detection result of a hydrogen flame based on the image captured by the first visualization camera with the detection result of a hydrogen flame based on the image captured by the second visualization camera. In the hydrogen flame visualization device, the differential camera can be configured to detect light of wavelengths outside the visible range. The hydrogen flame visualization device is a wearable device having a transparent lens, and can be configured to have a projection unit that projects onto the transparent lens an image of a hydrogen flame detected by the image processing unit, warning information indicating the occurrence of a hydrogen flame, and / or information about the distance to the hydrogen flame. The hydrogen flame visualization device is a wearable device and can be configured to include a case that houses the image processing unit, a transmission lens that is arranged below the case and functions as the display device, the first camera unit that is arranged on one side of the case, the second camera unit that is arranged on the other side of the case, an attachment unit that attaches the case to the wearer's head or helmet, and a projection unit that is housed in the case and projects onto the transmission lens an image of a hydrogen flame detected by the image processing unit, warning information that indicates the occurrence of a hydrogen flame, and / or information about the distance to the hydrogen flame. In the above-described hydrogen flame visualization device, the projection unit projects the image of the hydrogen flame detected by the image processing unit onto the transmission lens, and the image processing unit images a checkerboard at a predetermined calibration distance with the first visualization camera and the second visualization camera, and performs calibration in advance to determine the relationship between the image coordinate system and the real-space coordinate system at the calibration distance from the relationship between the size of each square of the checkerboard in real space and the size of the captured image.When the hydrogen flame is imaged with the first visualization camera and the second visualization camera, the image processing unit determines the position of the hydrogen flame in the real-space coordinate system when it is at the calibration distance from the position of the image of the hydrogen flame in the captured image coordinate system based on the relationship, and determines the position of the hydrogen flame in the real-space coordinate system based on the positions of the first visualization camera and the second visualization camera in the real-space coordinate system and the position of the hydrogen flame as seen from the first visualization camera and the second visualization camera, respectively, when it is at the calibration distance. The hydrogen flame detection method of the present invention detects a hydrogen flame using a first image captured by two or more visualization cameras that detect light of a wavelength whose emission intensity is equal to or greater than a predetermined value in the emission spectrum of the hydrogen flame, and a second image captured by one or more difference cameras that detect light of a wavelength whose emission intensity is less than the predetermined value in the emission spectrum of the hydrogen flame.The method generates a difference image between the image captured by the visualization cameras and the image captured by the difference camera, detects an image of the hydrogen flame based on the difference image, and calculates the distance to the hydrogen flame based on the parallax of each hydrogen flame image detected based on the difference image which is based on the images captured by the two or more visualization cameras. [Effects of the Invention]

[0007] According to the present invention, the distance to the hydrogen flame can be calculated appropriately. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a front view showing a hydrogen flame visualization device according to an embodiment of the present invention. [Figure 2] (A) is an example of an image captured by the visualization camera, and (B) is an example of an image captured by the difference camera. [Figure 3] FIG. 1 is a diagram for explaining the mechanism for visualizing a hydrogen flame. [Figure 4] (A) is a diagram of a checkerboard, and (B) is a diagram to explain the calibration mechanism. [Figure 5] (A) is an example of a screen when no hydrogen flame is present in the field of view, and (B) is an example of a screen when a hydrogen flame is present in the field of view. [Figure 6] FIG. 10 is a diagram showing a hydrogen flame visualization device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of a hydrogen flame visualization device according to the present invention will be described below with reference to the drawings. Fig. 1 is a diagram for explaining the hydrogen flame visualization device according to this embodiment. As shown in Fig. 1, the hydrogen flame visualization device 1 according to this embodiment is a wearable device that is worn on the head.

[0010] As shown in FIG. 1, the hydrogen flame visualization device 1 according to this embodiment includes a first camera unit 10, a second camera unit 20, an image processing unit 30, a projection unit 40, a transmission lens 50, and an attachment unit 60. The helmet 100 is not particularly limited and can be attached to any commercially available helmet via the attachment unit 60, which has an elastic band. A battery (not shown) is located on the rear side of the head of the device and supplies power to the first camera unit 10, the second camera unit 20, and the image processing unit 30 and projection unit 40 housed in a case. By locating the battery on the rear side of the head, the device maintains a good weight balance between the front and rear. The attachment unit 60 may be configured to be attached directly to the wearer's head rather than to the helmet.

[0011] In this embodiment, as shown in FIG. 1 , the first camera unit 10 is disposed on the right side of the case housing the image processing unit 30 and the projection unit 40, and the second camera unit 20 is disposed on the left side of the case. Increasing the horizontal distance between the first camera unit 10 and the second camera unit 20 in this way improves the accuracy of calculating the distance to the hydrogen flame using the principle of triangulation, which will be described later. The first camera unit 10 and the second camera unit 20 are preferably disposed at a height approximately equal to the eye height of the worker wearing the hydrogen flame visualization device 1. The case housing the image processing unit 30 and the projection unit 40 is curved to follow the curves of the face and is connected to the mounting unit 60 via a connector 61. The connector 61 is equipped with a mechanism for adjusting the vertical position of the case.

[0012] The first camera unit 10 has a first visualization camera 11 and a first difference camera 12. The first visualization camera 11 is equipped with a lens, a bandpass filter, and an image sensor, and receives light in a wavelength region (e.g., light of 278 to 320 nm, 925 to 1000 nm, or 1350 to 1500 nm) whose emission intensity is equal to or greater than a predetermined value (e.g., 600 a.u. or greater) in the emission spectrum of the hydrogen flame, and outputs a two-dimensional image signal according to the intensity of the received light, thereby obtaining an image in which the hydrogen flame is emphasized.

[0013] In particular, in this embodiment, the bandpass filter of the first visualization camera 11 can be a filter that transmits light in a wavelength range where the emission intensity in the emission spectrum of the hydrogen flame is equal to or greater than a predetermined value and blocks most of the light of other wavelengths in order to visualize the hydrogen flame. For example, in this embodiment, a filter that transmits light in the wavelength range of 925 to 940 nm can be used as the bandpass filter of the first visualization camera 11. Furthermore, in order to collect light in the wavelength range of 925 to 940 nm, the lens of the first visualization camera 11 can be a near-infrared mount lens, for example, a lens that collects light with a peak wavelength around 900 nm. Note that image information captured by the first visualization camera 11 is transmitted to the image processing unit 30.

[0014] The first differential camera 12 has a lens, a bandpass filter, and an image sensor, and receives light in a wavelength range (e.g., wavelength ranges other than 278 to 320 nm, 925 to 1000 nm, and 1350 to 1500 nm) where the emission intensity in the emission spectrum of the hydrogen flame is less than a predetermined value (e.g., less than 600 a.u.), and outputs a two-dimensional image signal according to the intensity of the received light, thereby obtaining an image in which the hydrogen flame is invisible or where the emission of the hydrogen flame is suppressed. Furthermore, in this embodiment, the first differential camera 12 is configured to receive light outside the visible light range in addition to light in a wavelength range where the emission intensity in the emission spectrum of the hydrogen flame is less than a predetermined value, in order to suppress the influence of sunlight.

[0015] Therefore, in this embodiment, in order to prevent visualization of the hydrogen flame, a filter that transmits light in the wavelength range of 895 to 910 nm, for example, can be used as the bandpass filter of the first differential camera 12. Furthermore, in order to collect light in the wavelength range of 895 to 910 nm, a near-infrared compatible mount lens can be used for the lens of the first differential camera 12, and for example, a lens similar to the lens of the first visualization camera 11 can be used. Note that image information captured by the first differential camera 12 is also transmitted to the image processing unit 30.

[0016] Similar to the first camera unit 10, the second camera unit 20 has a second visualization camera 21 and a second difference camera 22. The second visualization camera 21 has a configuration similar to that of the first visualization camera 11, and receives light in a wavelength region (e.g., light from 278 to 320 nm, 925 to 1000 nm, or 1350 to 1500 nm) whose emission intensity is equal to or greater than a predetermined value (e.g., 600 a.u. or greater) in the emission spectrum of the hydrogen flame, and transmits a two-dimensional image signal corresponding to the intensity of the received light to the image processing unit 30. The second differential camera 22 has a configuration similar to that of the first differential camera 12, and receives light in a wavelength range (e.g., wavelength ranges other than 278 to 320 nm, 925 to 1000 nm, and 1350 to 1500 nm) in which the emission intensity in the emission spectrum of a hydrogen flame is less than a predetermined value (e.g., less than 600 a.u.), and outside the visible light range, and transmits a two-dimensional image signal corresponding to the intensity of the received light to the image processing unit 30.

[0017] The image processing unit 30 acquires image information from the first visualization camera 11 and the first differential camera 12 of the first camera unit 10 and the second visualization camera 21 and the second differential camera 22 of the second camera unit 20, and identifies the location of the hydrogen flame based on the acquired image information. Here, FIG. 2(A) is an example of an image captured by the first visualization camera 11 or the second visualization camera 21, and FIG. 2(B) is an example of an image captured by the first differential camera 12 or the second differential camera 22. As shown in FIG. 2(A), in the image captured by the first visualization camera 11 or the second visualization camera 21, the hydrogen flame is captured as an image with a certain brightness. In contrast, as shown in FIG. 2(B), in the image captured by the first differential camera 12 or the second differential camera 22, an image in which the hydrogen flame is hardly captured is captured.

[0018] The image processing unit 30 then detects a hydrogen flame based on the images captured by the first visualization camera 11, the first difference camera 12, the second visualization camera 21, and the second difference camera 22. FIG. 3 is a diagram for explaining a method for visualizing a hydrogen flame. As shown in FIG. 3, the image processing unit 30 generates a difference image consisting of the difference between the image captured by the first visualization camera 11 and the image captured by the first difference camera 12, and similarly generates a difference image consisting of the difference between the image captured by the second visualization camera 21 and the image captured by the second difference camera 22. Note that, hereinafter, the difference image between the image captured by the first visualization camera 11 and the image captured by the first difference camera 12 will be referred to as a first difference image, and the difference image between the image captured by the second visualization camera 21 and the image captured by the second difference camera 22 will be referred to as a second difference image.

[0019] The image processing unit 30 also generates a binary image by binarizing the first difference image and the second difference image based on a predetermined reference brightness value. In particular, in this embodiment, by conducting a test in advance and setting a reference brightness value that can appropriately distinguish between pixels derived from the hydrogen flame and pixels not derived from the hydrogen flame, a binary image that provides an image corresponding to the hydrogen flame can be obtained. Hereinafter, the binary image of the first difference image will be referred to as the first binary image, and the binary image of the second difference image will be referred to as the second binary image.

[0020] The image processing unit 30 then performs an AND process (logical product) on the first binarized image based on the first difference image and the second binarized image based on the second difference image to generate a composite image consisting of images that match between the first binarized image and the second binarized image. By performing the AND process on the first binarized image and the second binarized image in this way, even if the first camera unit 10 erroneously detects a hydrogen flame, for example, the hydrogen flame image is present only in the first binarized image of the first camera unit 10, but not in the second binarized image of the second camera unit 20. Therefore, the hydrogen flame image is not detected by the AND process, thereby preventing erroneous detection of the hydrogen flame. Furthermore, the image processing unit 30 calculates the center position of the hydrogen flame image in the composite image in order to project the hydrogen flame image using the projection unit 40, which will be described later.

[0021] Furthermore, the image processing unit 30 calculates the distance to the hydrogen flame based on the first binarized image and the second binarized image. Specifically, the image processing unit 30 calculates the distance to the hydrogen flame using the principle of triangulation from the parallax between the image of the hydrogen flame in the first binarized image based on the image captured by the first visualization camera 11 and the image of the hydrogen flame in the second binarized image based on the image captured by the second visualization camera 21. For example, the distance Z to the hydrogen flame can be calculated by Z = B × f / D, where D is the parallax D between the image of the hydrogen flame in the first binarized image and the image of the hydrogen flame in the second binarized image, f is the focal length of the cameras 11, 12, 21, and 22 (which is assumed to be the same in this embodiment), and B is the distance between the first visualization camera 11 and the second visualization camera 21. The image processing unit 30 then transmits the calculated information about the distance B to the hydrogen flame to the projection unit 40 so that the user can understand it. The transmission lens 50 functions as a display device that displays the distance to the hydrogen flame projected by the projection unit.

[0022] Furthermore, in this embodiment, the image processing unit 30 also calculates the position of the projection surface of the transmission lens 50 onto which the projection unit 40 projects an image of the hydrogen flame (hereinafter referred to as the projection position). Here, the position of the hydrogen flame image detected by the first camera unit 10 and the second camera unit 20 is a position on the image sensor of each camera (a position in the image coordinate system), and the projection position onto which the hydrogen flame image is projected by the projection unit 40 is a position in the real space coordinate system in the real world. Therefore, the position of the hydrogen flame in the image coordinate system detected by the first camera unit 10 and the second camera unit 20 must be converted to a position in the real space coordinate system. In this embodiment, calibration is performed in advance during the initial setup of the hydrogen flame visualization device 1 to obtain parameters for converting the position in the image coordinate system to a position in the real space coordinate system. The calibration according to this embodiment is described below.

[0023] Calibration is performed using a checkerboard as shown in FIG. 4(A). The checkerboard can be prepared, for example, by printing out a checkerboard with black and white grids and attaching it to a board or the like. The size of the grids on the checkerboard is fixed, such as 35 mm, which allows the number of pixels per grid (per 35 mm in real space) to be known, making it possible to adjust the relationship between the image coordinate system (x-coordinate and y-coordinate shown in FIG. 4(A)) in the first visualization camera 11 and the second visualization camera 21 and the real space coordinate system in the real world (u-coordinate and v-coordinate shown in FIG. 4(A)).

[0024] Specifically, if the center position of the checkerboard shown in Fig. 4(A) on the image coordinate system is c, the vector from center position c in the u-axis direction is nu, and the vector from center position c in the v-axis direction is nv, the relationship between the x- and y-coordinates in the image coordinate system and the u- and v-coordinates in the real space coordinate system can be expressed by the following formula 1. Note that the magnitude of "1" in the vector quantity in the u-axis direction corresponds to the amount of one square in the u-axis direction on the checkerboard shown in Fig. 4(A), and similarly, the magnitude of "1" in the vector quantity in the v-axis direction corresponds to the amount of one square in the v-axis direction on the checkerboard shown in Fig. 4(A).

number

[0025] Furthermore, from the above equation 1, the x and y coordinates of the image coordinate system and the u and v coordinates of the real space coordinate system can be expressed as the following equations 2 and 3 using the transformation matrix T of the homogeneous coordinate system.

number

number

[0026] Here, the transformation matrix T is a variable obtained based on the correspondence between the size of one square on the checkerboard (e.g., 35 mm) and the number of pixels capturing an image of that square when a checkerboard that is a predetermined calibration distance (e.g., 3500 mm) away from the hydrogen flame visualization device 1 is used during calibration; if the hydrogen flame is not at a predetermined distance (e.g., 3500 mm) from the hydrogen flame visualization device 1 during calibration, the number of pixels per square will also change, and therefore this transformation matrix T cannot be used to convert the center position of the hydrogen flame image represented in the image coordinate system into a position (u coordinate and v coordinate) in the real space coordinate system.

[0027] Therefore, in this embodiment, the image processing unit 30 assumes that the images of the hydrogen flame captured by the first visualization camera 11 and the second visualization camera 21 are on a checkerboard, and converts the position of the hydrogen flame on the checkerboard as viewed by the first visualization camera 11 from the image coordinate system to the real space coordinate system, and converts the position of the hydrogen flame on the checkerboard as viewed by the second visualization camera 21 from the image coordinate system to the real space coordinate system. Then, in the real space coordinate system, as shown in Fig. 4(B), the intersection of a line A connecting the position of the first visualization camera 11 and the position of the hydrogen flame on the checkerboard as viewed by the first visualization camera 11 and a line B connecting the position of the second visualization camera 21 and the position of the hydrogen flame on the checkerboard as viewed by the second visualization camera 21 is calculated as the position of the hydrogen flame in the real space coordinate system. Even if the hydrogen flame does not exist at the checkerboard position (z = 3500 mm), when viewed from the first visualization camera 11, the hydrogen flame exists on line A, and when viewed from the second visualization camera 21, the hydrogen flame exists on line B, so it can be said that the hydrogen flame exists at the intersection of lines A and B.

[0028] Here, if the center position of the hydrogen flame in the image coordinate system in the first binarized image generated based on the image captured by the first visualization camera 11 is defined as x0, y0, the image processing unit 30 uses the transformation matrix T to convert the coordinates x0, y0 in the image coordinate system into coordinates u0, v0 in the real space coordinate system. As described above, the coordinates u0, v0 in the real space coordinate system are coordinates in which the width of one square of a checkerboard a predetermined calibration distance away from the hydrogen flame visualization device 1 is set to "1." Therefore, the image processing unit 30 can calculate the actual position of the center position of the hydrogen flame in the real space coordinate system when it is assumed that the hydrogen flame is at the calibration distance, as vector k0 in Equation 4 below, when the distance to the checkerboard in calibration is 3500 mm and the width of one checkerboard square is 35 mm. Similarly, if the center position of the hydrogen flame in the image coordinate system in the second binarized image generated based on the image captured by the second visualization camera 21 is taken as x0, y0, the image processing unit 30 uses the transformation matrix T to convert the coordinates x1, y1 in the image coordinate system into coordinates u1, v1 in the real space coordinate system, and can determine the center position of the hydrogen flame in the real space coordinate system, assuming that the hydrogen flame is at the calibration distance, as shown by vector k1 in Equation 4 below. For example, if the center position of the hydrogen flame in the image coordinate system in the first binarized image is coordinate x0, which is shifted two squares to the right from center position c of the checkerboard, then coordinate u0 in the real space coordinate system will be "2," and can be determined as a position shifted 35 mm × 2 = 70 mm to the right in real space.

number

[0029] Furthermore, as shown in FIG. 4(B), the position (vector p0) of the first visualization camera 11 in the real space coordinate system and the position (vector p1) of the second visualization camera 21 in the real space coordinate system can be expressed as shown in the following equation 5.

number

[0030] Therefore, line A, which connects the position of the first visualization camera 11 in real space (vector p0) and the position of the hydrogen flame in the real space coordinate system on the checkerboard as seen from the first visualization camera 11 (vector k0), can be expressed by the following equation 6, and line B, which connects the position of the second visualization camera 21 (vector p1) and the position of the hydrogen flame in the real space coordinate system on the checkerboard as seen from the second visualization camera 21 (vector k1), can be expressed by the following equation 7.

number

number

[0031] Thus, logically, the intersection of lines A and B is the position of the hydrogen flame in the real space coordinate system, so it would be sufficient to find the intersection of lines A and B. However, there are cases where it is not possible to find the intersection of lines A and B due to a detection error in the center position of the hydrogen flame image, etc. Therefore, based on lines A and B in equations 6 and 7 above, image processing unit 30 calculates the point where the two lines A and B are closest as the position x1 of the hydrogen flame in the real space coordinate system using equation 8 below.

number

[0032] As described above, in this embodiment, the image processing unit 30 converts the position (u0, v0) of the hydrogen flame image captured by the first visualization camera 11 into a position (vector k0) in the real space coordinate system assuming that the image is located at a distance of the calibration distance, and converts the position (u1, v1) of the hydrogen flame image captured by the second visualization camera 21 into a position (vector k1) in the real space coordinate system assuming that the image is located at a distance of the calibration distance. Then, it obtains a line A connecting the first visualization camera 11 (vector p0) in the real space coordinate system to the position (vector k0) of the hydrogen flame on the checkerboard as seen from the first visualization camera 11, and a line B connecting the position (vector p1) of the second visualization camera 21 to the position (vector k1) of the hydrogen flame in the real space coordinate system on the checkerboard as seen from the second visualization camera 21, and determines the point at which the lines A and B are closest to each other as the position of the hydrogen flame.

[0033] Note that due to lens aberration and distortion, differences in the parallax of the subject image may occur depending on the position on the imaging surface, even for subjects at the same distance. Calibration can adjust the relationship between the parallax and distance for each position on the imaging surface, thereby suppressing distance errors caused by such aberration and distortion.

[0034] The transmission lens 50 is a transmission-type lens that transmits visible light, and the projection unit 40 projects an image onto this transmission-type lens 50, thereby superimposing and displaying the image generated by the image processing unit 30 on the real image of real space that passes through the transmission lens 50. The shape of the transmission lens 50 is not limited to the illustrated shape, and the transmission lens 50 may be configured as a pair of transmission lenses. In this embodiment, the projection unit 40 projects the image of the hydrogen flame generated by the image processing unit 30 based on the images captured by the first camera unit 10 and the second camera unit 20 onto the projection position calculated by the image processing unit 30, thereby allowing the operator to grasp the position in real space where the hydrogen flame is occurring.

[0035] Furthermore, in this embodiment, the projection unit 40 can be configured to project information about the distance to the hydrogen flame onto the transmission lens 50. In this embodiment, the image processing unit 30 calculates the distance to the hydrogen flame and transmits it to the projection unit 40, which can then project the information about the distance to the hydrogen flame onto the transmission lens 50.

[0036] Here, Fig. 5(A) is an example of a screen when a hydrogen flame is not present in the field of view, and Fig. 5(B) is an example of a screen when a hydrogen flame is present in the field of view. Compared to when a hydrogen flame is not present in the field of view as shown in Fig. 5(A), when a hydrogen flame is present in the field of view, as shown in Fig. 5(B), the projection unit 40 superimposes an image of the hydrogen flame at the position where the hydrogen flame is occurring and displays an image to warn that a hydrogen flame is occurring (in the example shown in Fig. 5(B), the outer frame of the image is highlighted in red or the like, and an image indicating danger is displayed). Furthermore, as shown in Fig. 5(B), the projection unit 40 can project distance information to the hydrogen flame as a numerical value onto the transmission lens 50.

[0037] 5(B) is a diagram showing an example of a projection surface on which the hydrogen flame image, warning information, and distance information to the hydrogen flame are projected, but the hydrogen flame image, warning information, and distance information to the hydrogen flame can be displayed using other display methods. For example, the color, brightness, size, etc. of the hydrogen flame image can be changed depending on the distance to the hydrogen flame. Furthermore, the warning information can be displayed not only on a screen but also as an alarm sound or voice.

[0038] The prototype not only detected a hydrogen flame about 4 cm in diameter from a distance of 15 to 20 m, but also accurately calculated the distance to the hydrogen flame. Furthermore, the distance to the hydrogen flame could be accurately determined even outdoors in sunlight. In other words, the hydrogen flame visualization device 1 of the present invention is also suitable for use outdoors, such as in hydrogen stations.

[0039] Visible light camera 70 is a camera that detects light in a wavelength range similar to that discernible by the human eye, and information about the image captured by visible light camera 70 is sent to image processing unit 30. Image processing unit 30 generates an image such as that shown in Fig. 5(B) by superimposing an image of the hydrogen flame, warning information, and information about the distance to the hydrogen flame on the image received from visible light camera 70, and sends this image to the display of an external device such as a computer, thereby making it possible to display an image on the display of the external device that is similar to the field of view of an operator wearing hydrogen flame visualization device 1 according to this embodiment.

[0040] As described above, the hydrogen flame visualization device 1 of this embodiment comprises a first visualization camera 11 and a second visualization camera 21 that detect light of wavelengths in the emission spectrum of the hydrogen flame where the emission intensity is equal to or greater than a predetermined value; difference cameras 12 and 22 that detect light of wavelengths in the emission spectrum of the hydrogen flame where the emission intensity is less than a predetermined value; and an image processing unit 30 that generates a first difference image from the image captured by the first visualization camera 11 and the image captured by the first difference camera 12 and detects an image of the hydrogen flame based on the first difference image, generates a second difference image from the image captured by the second visualization camera 21 and the image captured by the second difference camera 22 and detects the image of the hydrogen flame based on the second difference image, and calculates the distance to the hydrogen flame based on the parallax between the image of the hydrogen flame detected based on the first difference image and the image of the hydrogen flame detected based on the second difference image. As a result, the hydrogen flame visualization device 1 according to this embodiment can appropriately calculate the distance to the hydrogen flame using the principle of triangulation, based on the parallax between the images of the hydrogen flame detected from the images captured by the first visualization camera 11 and the second visualization camera 21. Furthermore, the hydrogen flame visualization device 1 according to this embodiment achieves mixed reality (MR) in which calculated distance information to the hydrogen flame is superimposed on the actual image transmitted through the transmission lens 50, as shown in Fig. 5(B), allowing the operator to intuitively grasp the distance to the hydrogen flame.

[0041] Furthermore, in this embodiment, by performing an AND process (logical product) on the first binarized image based on the image captured by the first visualization camera 11 and the second binarized image based on the image captured by the second visualization camera 21, for example, even if the first camera unit 10 erroneously detects a hydrogen flame, an image of the hydrogen flame will be present in only the first difference image of the first camera unit 10 and will not be present in the second difference image, so that no image of the hydrogen flame will be present when the AND process is performed, making it possible to prevent erroneous detection of a hydrogen flame. Furthermore, in this embodiment, the first difference camera 12 and the second difference camera 22 are configured to receive light outside the visible light range, making it possible to suppress disturbances caused by sunlight.

[0042] Furthermore, in this embodiment, the hydrogen flame visualization device 1 is a wearable device having a transmission lens 50 and a projection unit 40 that projects onto the transmission lens 50 an image of a hydrogen flame detected by the image processing unit 30, warning information indicating the occurrence of a hydrogen flame, and / or information about the distance to the hydrogen flame. This allows the hydrogen flame visualization device 1 of this embodiment to intuitively grasp the position of the hydrogen flame and the distance to the hydrogen flame freehand. Furthermore, in this embodiment, by performing calibration in advance, the image processing unit 30 can appropriately calculate the projection position onto the transmission lens 50 from the coordinate position of the hydrogen flame in the image coordinate system captured by the first and second visualization cameras, and can cause the projection unit 40 to appropriately project the hydrogen flame image onto the projection position.

[0043] Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments. Various modifications and improvements can be made to the above-described embodiments, and such modifications and improvements are also included in the technical scope of the present invention.

[0044] For example, in the above-described embodiment, a wearable hydrogen flame visualization device 1 that is worn on the head is exemplified, but the present invention is not limited to this configuration and may be a handheld hydrogen flame visualization device 1a that an operator can carry by hand using a handle 90, as shown in Fig. 6(A), or a stationary hydrogen flame visualization device 1b, as shown in Fig. 6(B). Note that such portable or stationary hydrogen flame visualization devices 1a and 1b may be configured to generate an image as shown in Fig. 5(B), in which an image of the hydrogen flame, warning information, and information about the distance to the hydrogen flame are superimposed on an image captured by a visible light camera 70, and display the image on a display device 80.

[0045] Furthermore, in the above-described embodiment, a configuration was exemplified in which visualization cameras 11, 21 detect light in the 900 nm range (925 to 1000 nm) of the wavelengths of hydrogen flames, but this configuration is not limited to this, and it is also possible to configure the cameras to detect, for example, light in the 1400 nm range (1350 to 1500 nm) of the wavelengths of hydrogen flames, or light in the UV range (278 to 320 nm) of the wavelengths of hydrogen flames.

[0046] Furthermore, in the above-described embodiment, a configuration having two visualization cameras 11, 21 and two difference cameras 12, 22 has been exemplified, but the present invention is not limited to this configuration, and a configuration having three or more visualization cameras or difference cameras may also be used. Furthermore, a configuration having only one difference camera may also be used.

[0047] Additionally, in the above-described embodiment, the first visualization camera 11 and the first difference camera 12 are arranged vertically in the first camera unit 10, and the second visualization camera 21 and the second difference camera 22 are similarly arranged vertically in the second camera unit 20. However, the present invention is not limited to this configuration, and the first visualization camera 11 and the first difference camera 12 may be arranged horizontally in the first camera unit 10, and the second visualization camera 21 and the second difference camera 22 may be arranged horizontally in the second camera unit 20. However, when determining the distance to a hydrogen flame, the accuracy of distance calculation is higher when the first visualization camera 11 and the first difference camera 12, and the second visualization camera 21 and the second difference camera 22 are arranged vertically than when they are arranged horizontally.

[0048] Furthermore, in the above-described embodiment, an example was given of a configuration in which calibration is performed during initial setup of the hydrogen flame visualization device 1, but in addition to during initial setup, calibration can also be performed again after transport of the hydrogen flame visualization device 1 or when a certain period of time has passed since the previous calibration. Also, various sensors (for example, temperature sensors and radiation sensors) can be combined with the hydrogen flame visualization device 1 of the embodiment, and information acquired by the sensors can be projected on the projection unit. [Explanation of symbols]

[0049] 1, 1a, 1b...Hydrogen flame visualization device 10...First camera unit 11...First visualization camera 12...First differential camera 20...Second camera unit 21...Second visualization camera 22...Second differential camera 30...Image processing unit 40…Projection section 50...Transmitting lens (display device) 60...Mounting part 61...Connector 70...Visible light camera 80...Display 90...Handle 100…Helmet

Claims

1. a first visualization camera and a second visualization camera that detect light of a wavelength whose emission intensity is equal to or greater than a predetermined value in the emission spectrum of a hydrogen flame; one or more differential cameras that detect light of wavelengths whose emission intensity is less than the predetermined value in the emission spectrum of a hydrogen flame; an image processing unit that generates a visible image of the hydrogen flame based on the images received from the first visualization camera, the second visualization camera, and the difference camera, and calculates the distance to the hydrogen flame; a display device that displays the visible image of the hydrogen flame generated by the image processing unit and the distance to the hydrogen flame, the image processing unit generates a first difference image from the image taken by the first visualization camera and the image taken by the subtraction camera, detects an image of the hydrogen flame based on the first difference image, generates a second difference image from the image taken by the second visualization camera and the image taken by the subtraction camera, detects the image of the hydrogen flame based on the second difference image, and calculates the distance to the hydrogen flame based on the parallax between the image of the hydrogen flame detected based on the first difference image and the image of the hydrogen flame detected based on the second difference image.

2. the differential camera includes a first differential camera and a second differential camera, a first camera unit in which the first visualization camera and the first difference camera are arranged close to each other; a second camera unit in which the second visualization camera and the second difference camera are disposed close to each other, 2. The hydrogen flame visualization device according to claim 1, wherein the image processing unit calculates a distance to the hydrogen flame based on a parallax between an image of the hydrogen flame detected by the first camera unit and an image of the hydrogen flame detected by the second camera unit.

3. 2. The hydrogen flame visualization device according to claim 1, wherein the image processing unit determines whether a hydrogen flame has been erroneously detected by comparing a detection result of a hydrogen flame based on the image captured by the first visualization camera with a detection result of a hydrogen flame based on the image captured by the second visualization camera.

4. 2. The hydrogen flame visualization device according to claim 1, wherein the differential camera detects light of wavelengths outside the visible region.

5. the hydrogen flame visualization device is a wearable device having a transmission lens that functions as the display device, 2. The hydrogen flame visualization device according to claim 1, further comprising a projection unit that projects onto the transmission lens an image of the hydrogen flame detected by the image processing unit, warning information indicating the occurrence of a hydrogen flame, and / or information about a distance to the hydrogen flame.

6. the hydrogen flame visualization device is a wearable device, a case that houses the image processing unit; a transmission lens disposed below the case and functioning as the display device; the first camera unit disposed on one side of the case; the second camera unit disposed on the other side of the case; an attachment portion for attaching the case to a wearer's head or helmet; 3. The hydrogen flame visualization device according to claim 2, further comprising: a projection unit housed in the case and configured to project onto the transmission lens an image of the hydrogen flame detected by the image processing unit, warning information indicating the occurrence of a hydrogen flame, and / or information about a distance to the hydrogen flame.

7. the projection unit projects an image of the hydrogen flame detected by the image processing unit onto the transmission lens; 6. The hydrogen flame visualization device according to claim 5, wherein the image processing unit captures an image of a checkerboard at a predetermined calibration distance with the first visualization camera and the second visualization camera, and performs in advance a calibration to determine a relationship between the image coordinate system and the real space coordinate system at the calibration distance from the relationship between the size of each square of the checkerboard in real space and the size of the captured image; when a hydrogen flame is captured with the first visualization camera and the second visualization camera, the image processing unit determines a position in the real space coordinate system when the hydrogen flame is at the calibration distance from the position of the image of the hydrogen flame in the captured image coordinate system based on the relationship; and determines the position in the real space coordinate system of the hydrogen flame based on the positions of the first visualization camera and the second visualization camera in the real space coordinate system and the positions of the hydrogen flame as seen from the first visualization camera and the second visualization camera, respectively, in the real space coordinate system when the hydrogen flame is at the calibration distance.

8. A method for detecting a hydrogen flame, comprising: detecting a hydrogen flame using a first image captured by two or more visualization cameras that detect light of a wavelength whose emission intensity is equal to or greater than a predetermined value in the emission spectrum of the hydrogen flame; and a second image captured by one or more difference cameras that detect light of a wavelength whose emission intensity is less than the predetermined value in the emission spectrum of the hydrogen flame, generating a difference image between the image captured by the visualization camera and the image captured by the difference camera, and detecting an image of a hydrogen flame based on the difference image; A hydrogen flame detection method, which calculates the distance to the hydrogen flame based on the parallax between the images of each hydrogen flame detected based on the difference image that is based on the images captured by the two or more visualization cameras.

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