Thermal image positioning method based on heat source array

Abstract

The invention belongs to the technical field of thermal image positioning, and particularly relates to a thermal image positioning method based on a heat source array. The method comprises the following steps: step 1, constructing a triangular right pyramid type heat source array; step 2, arranging the heat source array in an aero-engine area, adjusting each heat source point in the heat source array to a target temperature according to an instrument range, and collecting thermal images of different positions and different ranges through an instrument; and step 3, according to the heat source array, splicing and matching the thermal images with different ranges. According to the invention, the heat source array is used as a reference system, the coordinate position of each thermal image is positioned, and an accurate positioning basis is provided for thermal image correction.

Description

Technical Field

[0001] This application belongs to the field of thermal image localization technology, and specifically relates to a thermal image localization method based on a heat source array. Background Technology

[0002] During aero-engine testing, the exhaust jet and hot-end components within the cavity exhibit large local temperature gradients. Since the detector's energy response range is fixed, excessive energy reception leads to saturation, while insufficient energy reception results in cutoff. Data from saturated or cutoff detectors is inaccurate. Therefore, multiple attenuators or filters need to be added in front of the detector to effectively test targets with different energy ranges. In actual testing, switching attenuators or filters is mechanically controlled, requiring a certain amount of time. Test results for targets with different energy ranges are not acquired simultaneously. During switching, the instrument is susceptible to displacement due to vibration and focusing operations, resulting in offsets in the acquired thermal images, making accurate positioning impossible. Because the radiation characteristics of targets differ at various angles, measurements must be taken at various azimuth angles. During testing, the instrument needs to be continuously moved to different angles, resulting in deviations from predetermined values. Accurate remeasurement is required after each movement. Furthermore, misalignment easily occurs when stitching thermal images from different ranges, significantly affecting data accuracy. Therefore, research into positioning methods for thermal images with different ranges is urgently needed.

[0003] Current technology utilizes total stations for measurement. Angles and distances are marked on the ground, the instrument is placed in a designated location for testing, and the target's position in the field of view is adjusted using a pan-tilt unit. After removing invalid data from each measurement range's thermal images, the data is stitched together by comparing the outline dimensions of the thermal images from different ranges, based on pixel positions, to uniformly locate the target's position in the thermal image. While total stations can accurately measure angles and distances, precise measurements need to be repeated after each movement of the measuring point, which is time-consuming and labor-intensive. Data from each range is only valid within its defined range; data outside the range is affected by saturation or cutoff phenomena, making it difficult to distinguish the target. Furthermore, a target's position is only clearly distinguishable within a specific range; it is difficult to distinguish in other ranges, making it difficult to use a common reference position. Stitching thermal images from different ranges requires manual pixel-by-pixel comparison and layering of each range. Inconsistent standards for the positioning of the junction surface during comparison further complicate the process, leading to time-consuming, labor-intensive, and inaccurate results. Different operators may produce varying thermal image processing results, affecting the overall analysis.

[0004] Therefore, there is an urgent need for a technical solution to overcome or mitigate at least one of the aforementioned defects in the existing technology. Summary of the Invention

[0005] The purpose of this application is to provide a thermal image localization method based on a heat source array to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is:

[0007] A thermal image localization method based on a heat source array includes:

[0008] Step 1: Construct a triangular right pyramidal heat source array;

[0009] Step 2: Arrange the heat source array in the aero-engine area, adjust each heat source point in the heat source array to the target temperature according to the instrument range, and collect thermal images of different locations and ranges through the instrument.

[0010] Step 3: Perform thermal image stitching and matching for different ranges based on the heat source array.

[0011] In at least one embodiment of this application, in step one, the heat source array includes:

[0012] Four heat source points r1, r2, r3, and r4; among them,

[0013] The four heat sources r1, r2, r3, and r4 are distributed in a triangular right pyramid shape with heat source r1 as the center;

[0014] The connecting edge between heat source point r1 and heat source point r2 is a;

[0015] The connecting edge between heat source point r1 and heat source point r3 is b;

[0016] The connecting edge between heat source point r1 and heat source point r4 is c;

[0017] The connecting edges a, b, and c are of equal length and are perpendicular to each other.

[0018] In at least one embodiment of this application, step two, arranging the heat source array in the aircraft engine region, includes:

[0019] The heat source array reference frame is arranged in the aero-engine region, wherein connecting edge b is parallel to the aero-engine axis, connecting edge a and connecting edge b are on the same horizontal plane and connecting edge a is perpendicular to the aero-engine axis, connecting edge c and connecting edge b are on the same vertical plane and connecting edge c is perpendicular to the aero-engine axis.

[0020] In at least one embodiment of this application, step three, which involves stitching and matching thermal images of different ranges based on the heat source array, includes:

[0021] The horizontal azimuth and elevation angles are calculated based on the heat source array, and the offset between thermal images of different ranges is calculated based on the horizontal azimuth and elevation angles.

[0022] Using the heat source array as a reference system, the correspondence between heat sources is determined, and the stitching information between thermal images of different ranges is determined based on the correspondence between heat sources.

[0023] Calculate the center point coordinates of the heat source points at the pixel level in each thermal image;

[0024] Using the center point coordinates as a reference, thermal image stitching and matching of different ranges are performed based on the offset and the stitching information.

[0025] In at least one embodiment of this application, calculating the horizontal azimuth angle based on the heat source array includes:

[0026] Obtain the projected length a1 of connecting edge a, the projected length b1 of connecting edge b, and calculate the horizontal azimuth angle observed by the instrument:

[0027] ;

[0028] Where θ is the horizontal azimuth angle.

[0029] In at least one embodiment of this application, calculating the pitch angle based on the heat source array includes:

[0030] Obtain the projected length c1 of the connecting edge c, and calculate the pitch angle between the instrument and the target:

[0031] ;

[0032] Where γ is the pitch angle.

[0033] In at least one embodiment of this application, the heat source correspondence is determined using the heat source array as a reference frame, and stitching information between thermal images of different ranges is determined based on the heat source correspondence, including:

[0034] Using the heat source array as a reference system, the heat source points in each thermal image are matched one by one;

[0035] By extracting the coordinate information of each heat source point from the pixels of the thermal image, the position of each heat source point in the thermal image is determined, and the correspondence between heat sources is obtained.

[0036] Based on the heat source correspondence, the stitching information between thermal images of different ranges is determined, and the stitching information includes translation and rotation.

[0037] In at least one embodiment of this application, calculating the center point coordinates of the heat source points at the pixel level in each thermal image includes:

[0038] Define the pixel coordinates in the thermal image as (a i b j );

[0039] Based on the intensity of heat source radiation, a threshold for voltage response is set, and the voltage response of each pixel is compared to determine the heat source pixel region, thus obtaining the pixel coordinate numbers of several heat source pixel regions.

[0040] Calculate the center point coordinates (a0, b0) of the heat source pixel region:

[0041] ;

[0042] Where m is the total number of rows within the threshold range, n is the total number of columns within the threshold range, and x is the total number of pixels within the threshold range.

[0043] The invention has at least the following beneficial technical effects:

[0044] The thermal image localization method based on a heat source array in this application uses the heat source array as a reference system to locate the coordinate position of each thermal image, providing a precise location basis for thermal image correction. Attached Figure Description

[0045] Figure 1 This is a flowchart of a thermal image localization method based on a heat source array according to one embodiment of this application;

[0046] Figure 2 This is an axial view of a heat source array according to one embodiment of this application;

[0047] Figure 3 This is a top view of a heat source array according to one embodiment of this application;

[0048] Figure 4 This is a rear view of a heat source array according to one embodiment of this application;

[0049] Figure 5 This is a diagram showing the correspondence between different range heat source arrays in one embodiment of this application;

[0050] Figure 6 This is a schematic diagram of the heat source pixel region according to one embodiment of this application. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0052] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this application.

[0053] The following is in conjunction with the appendix Figures 1 to 6 This application will be described in further detail.

[0054] This application addresses the following problems existing in the prior art:

[0055] When testing the same target, if the instrument's field of view shifts after switching ranges, the overall coordinates of the two acquired thermal images will shift, resulting in misalignment when stitching thermal images from different ranges. In practice, it is difficult to find the same reference coordinates for different ranges.

[0056] The thermal image localization method based on a heat source array in this application solves the following problems:

[0057] 1) Different measurement ranges cannot be positioned using the same reference position, making it impossible to uniformly correct the position of the thermal images for each range;

[0058] 2) It cannot quickly and accurately calculate information such as the horizontal deflection angle, pitch angle, and offset distance between the testing instrument and the target being tested;

[0059] 3) For the same target, it is impossible to quickly locate the offset between thermal images of different ranges, and the calculation of thermal image offset is inaccurate;

[0060] 4) It can only compare pixels one by one, resulting in low efficiency in thermal image processing and large random errors.

[0061] This application provides a thermal image localization method based on a heat source array, such as... Figure 1 As shown, it includes the following steps:

[0062] Step 1: Construct a triangular right pyramidal heat source array;

[0063] Step 2: Arrange the heat source array in the aero-engine area, adjust each heat source point in the heat source array to the target temperature according to the instrument range, and collect thermal images of different locations and ranges through the instrument.

[0064] Step 3: Perform thermal image stitching and matching for different ranges based on the heat source array.

[0065] The thermal image localization method based on a heat source array in this application, firstly, in step one, as follows... Figure 2 As shown, the heat source array includes:

[0066] Four heat source points r1, r2, r3, and r4; among them,

[0067] The four heat sources r1, r2, r3, and r4 are distributed in a triangular right pyramid shape with heat source r1 as the center;

[0068] The connecting edge between heat source point r1 and heat source point r2 is a;

[0069] The connecting edge between heat source point r1 and heat source point r3 is b;

[0070] The connecting edge between heat source point r1 and heat source point r4 is c;

[0071] The connecting edges a, b, and c are of equal length and are perpendicular to each other.

[0072] The lengths of the three connecting sides can be set to known quantities, and the heat source temperature can be adaptively adjusted according to the instrument's measurement range.

[0073] In a preferred embodiment of this application, step two, arranging the heat source array in the aero-engine region, includes:

[0074] The heat source array reference frame is arranged in the aero-engine region, wherein connecting edge b is parallel to the aero-engine axis, connecting edge a and connecting edge b are on the same horizontal plane and connecting edge a is perpendicular to the aero-engine axis, connecting edge c and connecting edge b are on the same vertical plane and connecting edge c is perpendicular to the aero-engine axis.

[0075] During actual testing, the heat source array is placed near the aircraft engine target without interfering with normal testing. The heat source array can be used as a feature point array of the aircraft engine to achieve three-dimensional localization of thermal images.

[0076] In a preferred embodiment of this application, step three, which involves stitching and matching thermal images of different ranges based on the heat source array, includes:

[0077] The horizontal azimuth and elevation angles are calculated based on the heat source array, and the offset between thermal images of different ranges is calculated based on the horizontal azimuth and elevation angles.

[0078] The heat source array is used as a reference to determine the correspondence between heat sources, and the stitching information between thermal images of different ranges is determined based on the correspondence between heat sources.

[0079] Calculate the center point coordinates of the heat source points at the pixel level in each thermal image;

[0080] Using the center point coordinates as a reference, thermal images of different ranges are stitched and matched according to the offset and stitching information.

[0081] In this embodiment, the calculation of the horizontal azimuth angle based on the heat source array includes:

[0082] Obtain the projected length a1 of connecting edge a, the projected length b1 of connecting edge b, and calculate the horizontal azimuth angle observed by the instrument:

[0083] ;

[0084] Where θ is the horizontal azimuth angle.

[0085] Figure 3 The diagram shows a top-down view of the heat source array arrangement. When the instrument observes the target at a horizontal azimuth angle θ (the angle between the observation position and the axis directly behind the target), the projected length of the connecting side a (in meters) of the heat source array within the instrument's field of view is a1 (in meters), and the projected length of the connecting side b (in meters) is b1 (in meters). The horizontal azimuth angle θ is calculated based on the relationship between these two projected lengths and the horizontal azimuth angle θ. The projected length can be calculated from the focal length, pixel size, and test distance. By calculating the ratio between the projected lengths b1 and a1 based on the position of the heat source pixels in the thermal image, the horizontal azimuth angle can be accurately calculated.

[0086] In this embodiment, the calculation of the pitch angle based on the heat source array includes:

[0087] Obtain the projected length c1 (in meters) of the connecting edge c (in meters), and calculate the pitch angle between the instrument and the target:

[0088] ;

[0089] Where γ is the pitch angle.

[0090] Figure 4The rear view shows the arrangement of the heat source array. Observed from the instrument test position, the projected length of the side between heat source points r1 and r4 is c1. Therefore, the pitch angle between the instrument and the target can be calculated using the formula.

[0091] Furthermore, in a preferred embodiment of this application, the heat source correspondence is determined using the heat source array as a reference system, and the stitching information between thermal images of different ranges is determined based on the heat source correspondence, including:

[0092] Using the heat source array as a reference system, the heat source points in each thermal image are mapped one by one;

[0093] By extracting the coordinate information of each heat source point from the pixels of the thermal image, the position of each heat source point in the thermal image is determined, and the correspondence between heat sources is obtained.

[0094] The stitching information between thermal images of different ranges is determined based on the correspondence of heat sources. The stitching information includes translation and rotation.

[0095] like Figure 5 As shown, the thermal images of different ranges are obtained by using the thermal source array as a reference system to obtain the correspondence of the thermal sources. Based on the correspondence of the thermal sources, information such as the translation and rotation between thermal images of different ranges is determined, so as to achieve the matching accuracy of thermal images of different ranges at the pixel level.

[0096] like Figure 6 As shown, each heat source point in the heat source array is not displayed on just one pixel in the thermal image, but in a small pixel area. In order to improve the accuracy of thermal image correction, it is necessary to accurately determine the center point of the heat source point at the pixel level.

[0097] In this embodiment, calculating the center point coordinates of the heat source points at the pixel level in each thermal image includes:

[0098] Define the pixel coordinates in the thermal image as (a i b j );

[0099] Based on the intensity of heat source radiation, a threshold for voltage response is set, and the voltage response of each pixel is compared to determine the heat source pixel region, thus obtaining the pixel coordinate numbers of several heat source pixel regions.

[0100] Calculate the center point coordinates (a0, b0) of the heat source pixel region:

[0101] ;

[0102] Where m is the total number of rows within the threshold range, n is the total number of columns within the threshold range, and x is the total number of pixels within the threshold range.

[0103] Different range thermal images can be translated, rotated, etc., based on the center point number of each heat source and the stitching information to achieve precise and unified positioning of each range thermal image.

[0104] The thermal image localization method based on heat source array of this application has the following beneficial effects:

[0105] 1) The heat source array can be used as the same reference position for each test range. The heat source array is distributed in a triangular right pyramid shape. The heat source temperature can be adaptively adjusted according to the instrument's range. The heat source array is used as a feature point array of the aero-engine to realize three-dimensional positioning of thermal images.

[0106] 2) Based on the positional relationship of the heat sources in the thermal image, the instrument can quickly calculate information such as the horizontal deflection angle, pitch angle, and offset distance between itself and the target being measured.

[0107] 3) Utilize direct analysis of thermal images to achieve precise location calculations between thermal images of different ranges at the pixel level;

[0108] 4) By stitching and matching thermal images of different ranges based on the thermal source array, the target coordinate position can be effectively extracted and calculated, which greatly improves the efficiency of thermal image processing and reduces random errors.

[0109] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A thermal image localization method based on a heat source array, characterized in that, include: Step 1: Construct a triangular right pyramidal heat source array; Step 2: Arrange the heat source array in the aero-engine area, adjust each heat source point in the heat source array to the target temperature according to the instrument range, and collect thermal images of different locations and ranges through the instrument. Step 3: Perform thermal image stitching and matching for different ranges based on the heat source array.

2. The thermal image localization method based on a heat source array according to claim 1, characterized in that, In step one, the heat source array includes: Four heat source points r1, r2, r3, and r4; among them, The four heat sources r1, r2, r3, and r4 are distributed in a triangular right pyramid shape with heat source r1 as the center; The connecting edge between heat source point r1 and heat source point r2 is a; The connecting edge between heat source point r1 and heat source point r3 is b; The connecting edge between heat source point r1 and heat source point r4 is c; The connecting edges a, b, and c are of equal length and are perpendicular to each other.

3. The thermal image localization method based on a heat source array according to claim 2, characterized in that, Step two involves arranging the heat source array in the aero-engine area, including: The heat source array reference frame is arranged in the aero-engine region, wherein connecting edge b is parallel to the aero-engine axis, connecting edge a and connecting edge b are on the same horizontal plane and connecting edge a is perpendicular to the aero-engine axis, connecting edge c and connecting edge b are on the same vertical plane and connecting edge c is perpendicular to the aero-engine axis.

4. The thermal image localization method based on a heat source array according to claim 3, characterized in that, Step three involves stitching and matching thermal images of different ranges based on the heat source array, including: The horizontal azimuth and elevation angles are calculated based on the heat source array, and the offset between thermal images of different ranges is calculated based on the horizontal azimuth and elevation angles. Using the heat source array as a reference system, the correspondence between heat sources is determined, and the stitching information between thermal images of different ranges is determined based on the correspondence between heat sources. Calculate the center point coordinates of the heat source points at the pixel level in each thermal image; Using the center point coordinates as a reference, thermal image stitching and matching of different ranges are performed based on the offset and the stitching information.

5. The thermal image localization method based on a heat source array according to claim 4, characterized in that, Calculating the horizontal azimuth angle based on the heat source array includes: Obtain the projected length a1 of connecting edge a, the projected length b1 of connecting edge b, and calculate the horizontal azimuth angle observed by the instrument: ； Where θ is the horizontal azimuth angle.

6. The thermal image localization method based on a heat source array according to claim 5, characterized in that, Calculating the pitch angle based on the heat source array includes: Obtain the projected length c1 of the connecting edge c, and calculate the pitch angle between the instrument and the target: ； Where γ is the pitch angle.

7. The thermal image localization method based on a heat source array according to claim 6, characterized in that, Using the heat source array as a reference frame, the correspondence between heat sources is determined, and stitching information between thermal images of different ranges is determined based on the correspondence between heat sources, including: Using the heat source array as a reference system, the heat source points in each thermal image are matched one by one; By extracting the coordinate information of each heat source point from the pixels of the thermal image, the position of each heat source point in the thermal image is determined, and the correspondence between heat sources is obtained. Based on the heat source correspondence, the stitching information between thermal images of different ranges is determined, and the stitching information includes translation and rotation.

8. The thermal image localization method based on a heat source array according to claim 7, characterized in that, Calculate the center point coordinates of the heat source points at the pixel level in each thermal image, including: Define the pixel coordinates in the thermal image as (a i b j ); Based on the intensity of heat source radiation, a threshold for voltage response is set, and the voltage response of each pixel is compared to determine the heat source pixel region, thus obtaining the pixel coordinate numbers of several heat source pixel regions. Calculate the center point coordinates (a0, b0) of the heat source pixel region: ； Where m is the total number of rows within the threshold range, n is the total number of columns within the threshold range, and x is the total number of pixels within the threshold range.

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