Visual field calibration method of flame detector

Abstract

The invention discloses a visual field calibration method of a flame detector, the device is installed on an instrument of the flame detector, and the method comprises the following steps: S1, placing a camera in the center, placing a laser range finder at a position A, the inclination angle between the position A and the vertical direction is alpha, the angle of alpha is adjustable, A can rotate 360 degrees around a central shaft, and the camera is located at a position B in the center; s2, the laser range finder is controlled to rotate by a fixed angle, the laser range finder can emit a beam of laser to the ground every beta angle, the current distance value is measured, at the moment, a camera is used for taking a picture, and a picture with laser points is taken; the method comprises the following steps: acquiring laser points of a circle, synthesizing the acquired laser points of the circle on a picture, marking acquired distance values on coordinates of the laser points, generating a visual field range of the flame detector, and adjusting an elevation angle, a depression angle and a horizontal angle of instrument installation by field operators through a generated visual field graph, so that a dangerous area is covered by the visual field of the flame detector.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame detectors, and more specifically, particularly relates to a method for calibrating the field of view of a flame detector. Background Art

[0002] Each flame detector has a certain range of detection angles. Beyond this detection angle, a field of view blind area may be formed. In a space, there is often a lack of clear indication of how many flame detectors need to be installed and at what angles. This can lead to some dangerous areas not being within the field of view of the flame detectors, or there being blind areas in a space, affecting people's lives and property safety. This requires that when our instrument is installed, there can be a clear indication of the field of view for installation, which can guide the instrument to be installed at an appropriate angle, and then guide the installation of an appropriate number of flame detectors in the entire area.

[0003] Currently, there is a lack of relevant device and method for guiding installation in the domestic market. In the foreign market, there are devices for guiding installation, but there is a lack of a clear viewable range diagram. In the prior art, the method for calibrating the field of view and detection of the flame detector with the publication number CN114155674A describes that "a camera and a laser rangefinder can be installed on the same turntable and placed together at the position where the flame detector is to be installed; or the camera can be placed alone at the position where the flame detector is to be installed first; after the camera takes a viewable image, then the laser rangefinder and the turntable carrying the laser rangefinder are placed at the position where the flame detector is to be installed; when the maximum angle of view of the camera is less than the maximum angle of view of the flame detector, it is necessary to splice more than two images taken by the camera to form a viewable image that meets the maximum angle of view of the flame detector;", however, this device is fixedly installed on the turntable, with a relatively fixed position, and is not as accurate as being installed on the instrument, with the sensor as the central axis, and simulating the actual instrument field of view more precisely on both sides, and the detection effect is more direct. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for calibrating the field of view of a flame detector to solve the problems raised in the above background art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: S1. Place the camera in the middle, and place the laser rangefinder at point A. The inclination angle of point A with respect to the vertical direction is α, and the angle of α is adjustable. Among them, A can rotate 360° around the central axis, and the camera is located at the center point B; S2. Control the laser rangefinder to rotate by a fixed angle. Every β angle, the laser rangefinder will emit a laser beam towards the ground, measure the current distance value, and at this time, use the camera to take a photo to take a photo with a laser dot; S3. After rotating the laser rangefinder one full circle, N photos with laser dots and N sets of distance values L measured at different angles are obtained. S4. Combine the laser dots of the N photos onto the same picture and mark the corresponding distance values at different laser dots, including the following steps: S4-1: Take a photo before the laser rangefinder rotates to obtain a background photo. Then, the laser rangefinder rotates once every 360 / n degrees. It needs to rotate n times to complete one full circle. Each time it rotates, a photo with the background photo and laser dots is taken. There are a total of n such photos, denoted here as P1. S4-2: Subtract the background photo from these n photos to obtain n photos of the change amount compared to the background picture, denoted here as P2. S4-3: Binarize the n photos of the change amount, denoted here as P3. S4-4: In addition to the change amount of the laser dots, there will be some noise of the background change amount in the above binarized picture. Next, use the opening operation of the image, erode first and then dilate, to obtain the processed picture, denoted here as P4. S4-5: Delete small-area objects in the picture of the previous step, denoted here as P5. S4-6: Mark the information of each connected region on the basis of the previous step, obtain the bounding box and area of the largest connected region, and get the coordinates of the laser dots. S4-7: Add the picture of the change amount in S4-4 to the background picture to obtain the view picture of the laser pen rotating one full circle. Median filter this view picture to remove the light noise during the shooting process and obtain a clear view picture. S4-8: Mark the coordinates of the laser dots obtained in S4-6 on the view picture. S4-9: Combine with the actual detection view of the flame detector and the taken view picture to adjust the installation angle and direction of the instrument so that the dangerous area is within the detection range of the instrument. S5. Compare the obtained distance values with the view picture of the flame detector. It can be seen from the picture the range that the actual instrument can cover, and then guide the installation of the instrument so that the dangerous area is within the view coverage range of the instrument.

[0006] As an optional solution of the present invention, the ranging value of the laser rangefinder is higher than the view detection distance value of the flame detector.

[0007] As an optional solution of the present invention, the camera and the laser rangefinder are connected to an embedded device.

[0008] As an alternative solution of the present invention, the camera and the laser rangefinder are programmed by a host computer to implement the functions of capturing and data reading respectively.

[0009] The present invention provides a method for calibrating the field of view of a flame detector, which has the following beneficial effects: By combining a laser rangefinder and a camera, while the laser rangefinder rotates, the camera takes pictures. One picture is taken at each angle, and the pictures containing the laser during one full rotation are synthesized into one image, and the distance information is marked on the laser points, and compared with the field of view map of the detector, and then the installation angle of the instrument is adjusted so that the dangerous area is within the field of view coverage of the instrument. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the field of view calibration device of the present invention; Figure 2 It is an installation schematic diagram of the field of view calibration device of the present invention; Figure 3 It is a schematic diagram of the S4 process of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0011] The following further describes in detail the embodiments of the present invention in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0012] In the description of the present invention, unless otherwise specified, "a plurality of" means two or more; the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0013] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0014] Please refer to Figures 1 to 3 , the present invention provides a technical solution: a method for calibrating the field of view of a flame detector, including: S1. Place the camera in the center, and place the laser rangefinder at point A. The inclination angle of point A with respect to the vertical direction is α, and the angle of α is adjustable. Here, A can rotate 360° around the central axis. The camera is located at the center point B. The camera uses a 2.7 mm distortion-free lens, and the pixel of the camera is 2 million; S2. Control the laser rangefinder to rotate by a fixed angle. Every β angle, the laser rangefinder will emit a laser beam to the ground to measure the current distance value. At this time, use the camera to take a picture to take a picture with a laser point; the ranging value of the laser rangefinder is 100 meters, and the camera and the laser rangefinder are connected to the Raspberry Pi; S3. After rotating the laser rangefinder one week, obtain N pictures with laser points and N groups of distance values L measured at different angles; S4. Synthesize the laser points of the N pictures on the same picture, and mark the corresponding distance values on different laser points; It includes the following steps: As Figure 3 shown, S4-1: Take a picture before the laser rangefinder rotates to obtain a background picture. Then, the laser rangefinder rotates once every 30 degrees, and a total of 12 rotations are required to complete one week. Take a picture with the background picture and the laser point every time it rotates. There are a total of 12 such pictures. Divide the image B into non-overlapping connected regions {C1, C2,..., Cn}, where each Ci is a connected pixel set (default use 8-neighborhood connectivity), denoted here as P1; S4-2: Subtract the background picture from these 12 pictures to obtain 12 pictures of the change amount compared to the background picture, that is, area filtering: retain all regions that satisfy |Ci|≥P, and remove regions where |Ci|<P, that is , denoted here as P2; S4-3: Binarize the 12 pictures of the change amount (merge the retained connected regions to generate a new binary image B′), denoted here as P3; S4-4: In addition to the change amount of the laser point, there will be some noise in the background change amount in the above binarized picture. Next, use the opening operation of the image, erode first and then dilate to obtain the processed picture, denoted here as P4; S4-5: On the picture of the previous step, according to the threshold selected for the actual laser point, delete the objects with an area smaller than the threshold, denoted here as P5, and the formula is defined as follows: Let the input binary image be B⊆ℤ², the output image be B′, and the threshold P = 10. Then:

[0015] S4-6: Based on the previous step, mark the information of each connected region, obtain the bounding box and area of the largest connected region, and get the coordinates of the laser points; S4-7: Add the background image to the image of the change amount in S4-4 to obtain the view image of the laser pointer rotating one week. Perform median filtering on this view image to remove the light noise during the shooting process and obtain a clear view image; S4-8: Mark the coordinates of the laser points obtained in S4-6 on the view image; S4-9: Combine with the actual detection view of the flame detector and the captured view image, and adjust the installation angle and direction of the instrument so that the dangerous area is within the detection range of the instrument.

[0016] S5: Compare the obtained distance values with the view image of the flame detector, and the coverage range that the actual instrument can cover can be seen in the picture, thereby guiding the installation of the instrument so that the dangerous area is within the view coverage range of the instrument.

[0017] The specific usage mode and function of this embodiment are as follows: Figure 1 As shown in the figure, place a laser rangefinder at A. The angle between the laser rangefinder and the vertical direction is α, where the angle of α is adjustable. Place a camera at B, which is at the center of the device. Among them, A rotates around the central rotating guide rail C. The entire device is installed on the outer diameter D of the instrument. The installation schematic diagram of the view calibration device is as shown in Figure 2 As shown in the figure, place the camera in the middle, place the laser rangefinder at A, and the inclination angle between A and the vertical direction is α, and the angle of α is adjustable. Among them, A can rotate 360° around the central axis, and the camera is located at the center B; control the laser rangefinder to rotate a fixed angle. Every β angle, the laser rangefinder will emit a laser beam to the ground to measure the current distance value. At this time, use the camera to take a picture and take a picture with a laser point; after the laser rangefinder rotates one week, N pictures with laser points and N groups of distance values L measured at different angles are obtained; synthesize the laser points of the N pictures on the same picture, and mark the corresponding distance values on different laser points; compare the obtained distance values with the view image of the flame detector, and the coverage range that the actual instrument can cover can be seen in the picture, thereby guiding the installation of the instrument so that the dangerous area is within the view coverage range of the instrument. Compared with the traditional flame detector installed on the cloud platform, this device is directly installed on the instrument, and the actual instrument view is simulated on both sides with the sensor as the central axis, and the data is more accurate.

[0018] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0019] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or equivalently replace some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for field of view calibration of a flame detector, characterized in that, Including: S1. Place the camera in the center, and place the laser rangefinder at point A. The inclination angle of point A with respect to the vertical direction is α, and the angle of α is adjustable. Here, A can rotate 360° around the central axis, and the camera is located at the center point B. S2. Control the laser rangefinder to rotate by a fixed angle. Every β angle, the laser rangefinder will emit a laser beam towards the ground to measure the current distance value. At this time, use the camera to take a photo to obtain a photo with a laser point. S3. After rotating the laser rangefinder for one week, obtain N photos with laser points and N sets of distance values L measured at different angles. S4. Synthesize the laser points of the N photos onto the same picture and mark the corresponding distance values on different laser points, including the following steps: S4-1. Take a photo before the laser rangefinder rotates to obtain a background photo. Then, the laser rangefinder rotates once every 360 / n degrees. It needs to rotate n times to complete one week. Each time it rotates, take a photo with the background photo and laser points. There are a total of n such photos, denoted as P1 here. S4-2. Subtract the background photo from these n photos to obtain n photos of the change amount compared to the background picture, denoted as P2 here. S4-3. Binarize the n photos of the change amount, denoted as P3 here. S4-4. In addition to the change amount of the laser points, there will be some noise of the background change amount in the above binarized picture. Next, use the opening operation of the image, first erode and then dilate to obtain the processed picture, denoted as P4 here. S4-5. Delete small-area objects in the picture of the previous step, denoted as P5 here. S4-6. Mark the information of each connected region on the basis of the previous step, obtain the bounding box and area of the largest connected region, and get the coordinates of the laser points. S4-7. Add the picture of the change amount in S4-4 to the background picture to obtain the field of view picture of the laser pen rotating for one week. Perform median filtering on this field of view picture to remove the light noise during the shooting process and obtain a clear field of view picture. S4-8. Mark the coordinates of the laser points obtained in S4-6 on the field of view picture. S4-9. Combine with the actual detection field of view of the flame detector and the taken field of view picture, and adjust the installation angle and direction of the instrument so that the dangerous area is within the detection range of the instrument. S5. Compare the obtained distance value with the field of view picture of the flame detector, and the coverage range that the actual instrument can cover can be seen in the picture, thereby guiding the installation of the instrument so that the dangerous area is within the field of view coverage range of the instrument.

2. The method for calibrating the field of view of a flame detector according to claim 1, wherein: The ranging value of the laser rangefinder is higher than the field of view detection distance value of the flame detector.

3. A method for field of view calibration of a flame detector according to claim 1, characterized in that: The camera and the laser rangefinder are connected to an embedded device.

4. A method for calibrating the field of view of a flame detector according to claim 1, characterized in that: The camera and the laser rangefinder respectively implement the capture function and the data reading function through programming by a host computer.

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