Building facade glass thermal image test system based on infrared polarization and compensation method

Abstract

The invention relates to a building facade glass thermal image test system and compensation method based on infrared polarization, the building facade glass thermal image test system comprises a mounting bracket, an infrared thermal imager and a polarization assembly, the polarization assembly comprises a polaroid and a polaroid frame, the polaroid frame is mounted on the mounting bracket, and the polaroid is centered with a lens of the infrared thermal imager. According to the method, a polarizing film is rotated to a preset angle to eliminate part of interference light entering a lens of the thermal infrared imager, then thermal imaging pictures are shot, the polarizing film is adjusted to a plurality of preset angles for many times to correspondingly shoot the thermal imaging pictures at different polarizing film angles, and then the obtained thermal imaging pictures are spliced again to obtain a plurality of thermal imaging pictures. Therefore, a complete thermal imaging picture which eliminates ambient light reflection in all directions is obtained. According to the system and the method, the interference influence of glass reflected light on thermal imaging can be avoided, the purpose of accurately measuring the temperature of the building facade is achieved, and the applicability and the convenience of a thermal imaging technology are improved.

Description

Technical Field

[0001] The invention relates to the technical field of thermal imaging, and in particular to a thermal imaging test system and a compensation method for building facade glass based on infrared polarization. Background Art

[0002] Using a thermal imager to conduct thermal imaging tests on the building facade can intuitively present the temperature distribution of the building facade. The glass directly exchanges heat with the indoor environment, and the temperature difference of the glass can more objectively reflect the indoor temperature. It has broad application prospects in the field of heating for rapid and extensive evaluation of room temperature.

[0003] However, ordinary infrared thermal imagers are usually suitable for long-wave infrared with a wavelength of 8-14μm, and glass is a good specular reflector. Therefore, when using a thermal imager to obtain a temperature image of a building's facade, it is often affected by the infrared reflection of the glass to the surrounding environment, and thus it is impossible to obtain a true temperature image of the building's facade, especially the glass part. The existing technical solution can only objectively reflect the actual temperature of the glass when shooting directly at the glass. When the optical axis of the thermal imager does not coincide with the normal of the glass surface, the thermal radiation of the glass itself is covered by other thermal radiation reflected by it, resulting in inaccurate results. The larger the angle between the optical axis and the normal, the more serious the on-site error.

[0004] like Figure 2 As shown, when the thermal imaging test of the building's exterior glass is not performed using this solution, when the thermal imager 204 is used to measure the temperature of the building's exterior glass 201 or to take thermal imaging photos, the surrounding environment will radiate infrared light, forming interference light 203 in other directions, which will be converted into polarized light after being reflected by the glass, and combined with the infrared light emitted by the glass itself to form a total light beam 202 that is incident on the thermal imager. Therefore, the temperature or thermal imaging finally measured is not only based on the actual glass temperature information, but also interfered by the radiation of the surrounding environment.

[0005] At present, the method to solve this problem is to use tape to cover the glass surface to eliminate the reflection. However, the method of using tape to eliminate the reflection is obviously not convenient enough, the operation is cumbersome, the applicability is narrow, and it cannot be promoted. Summary of the invention

[0006] The technical problem to be solved by the present invention is generally to provide a building facade glass thermal imaging test system and compensation method based on infrared polarization, which can avoid the interference of glass reflected light on thermal imaging, achieve the purpose of accurately measuring the temperature of the building facade itself, and at the same time increase the applicability and convenience of thermal imaging technology, which is conducive to the promotion and application of this technology in related fields.

[0007] In order to achieve the above-mentioned object, the present invention discloses, on one hand, a thermal imaging test system for building facade glass based on infrared polarization, comprising:

[0008] Mounting bracket;

[0009] Infrared thermal imager, used to image the temperature distribution of the facade, the infrared thermal imager is installed on the mounting bracket; and

[0010] The polarization assembly includes a polarizer and a polarizer frame. The polarizer frame is used to allow the polarizer to rotate 360 ​​degrees around its optical axis. The polarizer frame is installed on a mounting bracket, and the polarizer is aligned with the lens of the infrared thermal imager (that is, the optical axis of the infrared thermal imager coincides with the optical axis of the polarizer).

[0011] Preferably, the polarizer is a metal wire grid infrared polarizer.

[0012] Preferably, the operating frequency band of the polarizer can cover the operating frequency band of the infrared thermal imager.

[0013] Preferably, the mounting bracket includes a pan / tilt fixture.

[0014] On the other hand, the present invention discloses a thermal imaging compensation method for building facade glass based on infrared polarization. Using the above-mentioned test system, the method rotates the polarizer to a preset angle to eliminate part of the interference light entering the lens of the infrared thermal imager and then takes a thermal imaging picture. The polarizer is adjusted to multiple preset angles multiple times to correspondingly take thermal imaging pictures at different polarizer angles, and then the multiple thermal imaging pictures obtained are re-spliced ​​to obtain a complete thermal imaging picture that eliminates the reflection of ambient light in all directions.

[0015] Preferably, the compensation method comprises the following steps:

[0016] S1: When photographing the temperature of the glass on the building's facade, place the optical axis of the polarizer perpendicular to the facade and the thermal imager facing the building to place the test system;

[0017] S2: Taking the vertical projection point of the infrared thermal imager on the facade as the origin, the measurement area is divided into 2n measurement sub-areas in the axial direction according to the measurement accuracy requirements, marked as 1, 2, 3, 4...2n respectively. The angle interval occupied by the axial direction of each measurement sub-area is 180° / n, and the outer boundary is the imaging boundary of the thermal imager;

[0018] S3: After the measurement sub-area division is completed, the two diagonal measurement sub-areas are merged into one group to form n sub-area groups, and the polarizer angle is rotated in sequence to each sub-area group in order to eliminate the influence of the polarized light reflected by the glass on the infrared thermal imager in the sub-area group, and then a thermal imaging picture is taken for each sub-area group and saved, and a total of n shots are taken;

[0019] S4: splicing all obtained thermal imaging pictures according to the corresponding sub-region groups to form a complete thermal imaging picture of the building facade, wherein the temperature displayed on the facade glass is the actual temperature after compensation.

[0020] Preferably, the polarizer is a metal wire grid type infrared polarizer. In step S3, before each shooting, the polarizer is rotated to a direction perpendicular to the metal wire grid and the angular bisector of the boundary of the area, so as to eliminate the influence of the polarized light reflected by the glass on the infrared thermal imager in the sub-area group; the polarizer is rotated 180° / n around its optical axis for each shooting.

[0021] Compared with the prior art, the present invention first adjusts the thermal imager and polarizer angles according to the actual needs of the building imaging area during actual measurement, and then divides the imaging area into n equal sub-area groups under polar coordinates, each sub-area group corresponds to an independent polarizer rotation angle, and realizes the special elimination of the infrared reflection signal of the glass in the area, so as to realize the compensation of the actual temperature of the glass in the area, and finally re-joins the sub-area groups to form a complete thermal imaging photo of the building facade. The system and method can effectively eliminate the temperature measurement error caused by the reflection phenomenon of the glass, thereby reflecting the actual temperature of the building exterior wall glass, and provide an effective means for using the glass temperature to reflect the actual indoor temperature. At the same time, the applicability and convenience of thermal imaging technology are increased, which is conducive to the promotion and application of this technology in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of the thermal imaging test system for building facade glass.

[0023] Figure 2 This is a schematic diagram of the test process of a common infrared thermal imager.

[0024] Figure 3 This is a schematic diagram of the process in which environmental radiation is reflected by the measured glass to form polarized light interference.

[0025] Figure 4 Schematic diagram of the process of eliminating polarized light parallel to the wire grid using a metal wire grid polarizer.

[0026] Figure 5 is a flow chart of the compensation method of this embodiment.

[0027] Figure 6 Schematic diagram of the measurement sub-area division method of Example 1.

[0028] Figure 7 This is a schematic diagram of the position of the first sub-region group in Example 1.

[0029] Figure 8 This is a schematic diagram of the position of the second sub-region group in Example 1.

[0030] Fig. 9 This is another schematic diagram of the position of the second sub-region group in Example 1.

[0031] Among them, 103 is a mounting bracket; 102 is a polarization component; and 101 is an infrared thermal imager. DETAILED DESCRIPTION

[0032] like Figure 1-9 As shown, a building facade glass thermal imaging test system based on infrared polarization includes: a mounting bracket 103; an infrared thermal imager 101 is arranged at one end of the mounting bracket 103;

[0033] A longitudinally movable polarization component 102 is disposed on the mounting bracket 103 , and the polarization component 102 is disposed close to or away from the infrared thermal imager 101 .

[0034] Infrared thermal imager 101, used to image the temperature distribution of the facade;

[0035] The polarization assembly 102 includes a polarizing plate frame mounted on a mounting bracket 103 and a polarizing plate 402 disposed in the polarizing plate frame; the polarizing plate frame is used to allow the polarizing plate 402 to rotate 360° around its own optical axis direction; Figure 4 As shown in the figure, the metal wire grid polarizer is composed of metal wires arranged parallel to each other. Such a polarizer only allows light perpendicular to the polarization wire to pass completely, and almost completely reflects the light parallel to the polarization wire. Figure 4 The middle line represents the light perpendicular to the polarizer, and the black dot represents the light parallel to the polarizer. Fig. 9 As shown, when the polarizer 402 rotates a certain angle, the light passing through the sub-area is the light in the direction perpendicular to the polarizer. Therefore, the light 403 passing through the metal wire grid infrared polarizer 402 and reaching the infrared lens can only reflect the light passing through the polarizer, that is, the temperature effect of the glass.

[0036] The polarizing plate 402 is aligned with the lens of the infrared thermal imager 101 , that is, the optical axis of the infrared thermal imager 101 coincides with the optical axis of the polarizing plate.

[0037] As a further improvement, the infrared polarization-based thermal image compensation method for building facade glass of the above test system is used. The method uses the polarizer 402 to rotate to a preset angle to eliminate part of the interference light entering the lens of the infrared thermal imager 101 and take a thermal imaging picture. Fig. 9As shown in , the metal wire grid polarizer 402 is composed of metal wires arranged in parallel to each other. By rotating the polarizer so that the directions of the metal wires are different, multiple angles can be formed, corresponding to the thermal imaging pictures taken at different polarizer angles. The imaging area is divided into n equal sub-areas under polar coordinates, each area will correspond to an independent polarizer rotation angle, and finally the n sub-areas are re-joined to realize a complete thermal imaging picture. Then, the obtained multiple thermal imaging pictures are re-joined to obtain a complete thermal imaging picture that eliminates the reflection of ambient light in all directions.

[0038] Among them, eliminating the interference of ambient radiation is the key to accurately obtain the temperature information of the building facade glass itself. The principle of the process of ambient radiation reflecting from the measured glass to form polarized light interference is as follows Figure 3 As shown, the infrared light 301 from the surrounding environment of the building being tested and the solar radiation has a complex polarization state, which is a superposition of various circularly polarized lights and linearly polarized lights. After being reflected by the glass 303, especially at the Brewster angle θ b When the reflected light beam 302 is near the glass 303 , the generated reflected light beam 302 basically presents a single polarization direction and has the maximum intensity. The polarization direction is perpendicular to the propagation direction of the reflected light beam 302 and parallel to the reflection plane of the glass 303 .

[0039] The test system and compensation method of this embodiment can avoid the interference of part of the glass reflected light on the thermal imaging through the polarizer 402 before each shooting, so as to realize the compensation for the actual temperature of the glass in a specific area, and take multiple thermal imaging pictures by adjusting different angles of the polarizer 402, such as Fig. 9 As shown, the imaging area is divided into n equal sub-areas under polar coordinates, each area will correspond to an independent polarizer rotation angle, and finally the n sub-areas are re-joined to form a complete thermal imaging photo of the building facade, so as to achieve the purpose of accurately measuring the temperature of the building facade itself, and at the same time increase the applicability and convenience of thermal imaging technology, which is conducive to the promotion and application of this technology in related fields.

[0040] The polarizer 402 is a metal wire grid infrared polarizer. Figure 4 As shown, the metal wire grid infrared polarizer 402 can eliminate the reflection angle of the glass reflected by the Brewster angle θ bThe reflected light beam 401 incident on the test system of this embodiment has a propagation direction parallel to the optical axis of the metal wire grid infrared polarizer 402 and the optical axis of the thermal imager, and is a superposition of the reflected linear polarized light and the circularly polarized light radiated by the glass itself. Since the metal wire grid polarizer can eliminate the polarized light parallel to the wire grid direction, the angle of the metal wire grid infrared polarizer 402 is adjusted to make the wire grid direction of the polarizer parallel to the linear polarized light direction of the reflected light. Since the direction of the linear polarized light entering the polarizer is perpendicular to the propagation direction of the light, this part of the polarized light parallel to the wire grid direction of the polarizer will all be reflected or absorbed by the metal wire grid infrared polarizer 402. Therefore, the light 403 that passes through the metal wire grid infrared polarizer 402 and reaches the infrared lens can only reflect the temperature effect of the glass.

[0041] To ensure the test effect, the operating frequency band of the polarizer may cover the operating frequency band of the infrared thermal imager 101 .

[0042] The mounting bracket 103 includes a pan-tilt fixture, which is used to fix the infrared thermal imager 101 and the polarizing plate holder at the same time to ensure that the optical axis of the infrared thermal imager 101 is perpendicular to the polarizing plate.

[0043] Among them, Figure 5 As shown, the above compensation method includes the following steps:

[0044] S1: When photographing the temperature of the glass on the building's facade, place the optical axis of the polarizer perpendicular to the facade and the thermal imager facing the building to place the test system;

[0045] S2: Taking the vertical projection point of the infrared thermal imager on the facade as the origin, the measurement area is equally divided into 2n measurement sub-areas (n≥1) according to the measurement accuracy requirements, marked as 1, 2, 3, 4...2n respectively. The angle interval occupied by the axial direction of each measurement sub-area is 180° / n, and the outer boundary is the imaging boundary of the thermal imager;

[0046] S3: After the measurement sub-area division is completed, the two diagonal measurement sub-areas are merged into one group to form n sub-area groups, and the polarizer angle is rotated in sequence to each sub-area group in order to eliminate the influence of the polarized light reflected by the glass on the infrared thermal imager in the sub-area group, and then a thermal imaging picture is taken for each sub-area group and saved, and a total of n shots are taken;

[0047] S4: splicing all obtained thermal imaging pictures according to the corresponding sub-region groups to form a complete thermal imaging picture of the building facade, wherein the temperature displayed on the facade glass is the actual temperature after compensation.

[0048] In actual measurement, the more groups n of measurement sub-areas are delineated, the better the effect of filtering out interference light is, and the more accurate the photographed measurement results are, but the number of operations required also increases, and the complexity of the process increases.

[0049] In actual measurement, the above method first adjusts the thermal imager and polarizer angles according to the actual needs of the building imaging area, and then divides the imaging area into n equal sub-area groups under polar coordinates. Each sub-area group corresponds to an independent polarizer rotation angle, so as to specifically eliminate the infrared reflection signal of the glass in the area, so as to achieve compensation for the actual temperature of the glass in the area. Finally, each sub-area group is re-joined to form a complete thermal imaging photo of the building facade. The system and method can effectively eliminate the temperature measurement error caused by the reflection phenomenon of the glass, thereby reflecting the actual temperature of the building exterior wall glass, and provide an effective means for using the glass temperature to reflect the actual indoor temperature.

[0050] Specifically, the polarizer is a metal wire grid type infrared polarizer. In step S3, before each shooting, the polarizer is rotated to a direction perpendicular to the metal wire grid and the angular bisector of the boundary of the area, so as to eliminate the influence of the polarized light reflected by the glass on the infrared thermal imager in the sub-area group; each time shooting is performed, the polarizer is rotated 180° / n around its optical axis.

[0051] Example 1

[0052] like Figure 1 , Figures 6 to 8 As shown, a thermal image compensation method for building facade glass based on infrared polarization includes the following steps:

[0053] S1: Assemble as Figure 1 In the test system shown, the polarization component 102 and the infrared thermal imager 101 are mounted on a mounting bracket 103, and the optical axis of the infrared thermal imager 101 is kept perpendicular to the polarizer, so that the polarizer can rotate 360 ​​degrees in a plane perpendicular to the optical axis, so that the direction of the polarizer wire grid can be adjusted to be parallel to the polarization direction of the reflected light; when photographing the temperature of the glass on the facade of a building, the optical axis of the polarizer is perpendicular to the facade, and the thermal imager is placed facing the building to place the test system;

[0054] S2: Taking the vertical projection point (observation point) of the infrared thermal imager 101 on the facade as the origin, set n=4, and divide the measurement area into 8 measurement sub-areas in the axial direction. Establish the following Figure 6 In the coordinate system shown, the angle θ of each measurement sub-area is 180° / n=45°;

[0055] S3: After the measurement sub-area division is completed, the two diagonal measurement sub-areas are merged into one group to form four sub-area groups. Figure 7 and Figure 8The shadows represent the first sub-region group and the second sub-region group respectively; firstly, the metal wire grid of the polarizer is rotated to the direction perpendicular to the angular bisector of the boundary of the first sub-region group to eliminate the influence of the polarized light reflected by the glass on the infrared thermal imager in the first sub-region group, and the infrared thermal imager 101 is used to take pictures and save them, and the process is completed as shown in FIG. Figure 7 The first sub-region group measurement area corresponds to the shooting of the thermal imaging picture; the polarizer is rotated 45° clockwise to eliminate the influence of the polarized light reflected by the glass on the infrared thermal imager in the second sub-region group, and the second thermal imaging picture is taken and saved, and the process is completed as shown in FIG. Figure 8 The thermal imaging picture corresponding to the measurement area of ​​the second sub-area group is shown; the polarizing plate is rotated 45° clockwise to take the third thermal imaging picture, and then the polarizing plate is rotated 45° clockwise to take the fourth thermal imaging picture, thus completing the shooting of all measurement areas, and taking n=4 pictures in total;

[0056] S4: All thermal imaging pictures are spliced ​​according to the corresponding areas to form a complete thermal imaging photo, and the accurate measurement value of the glass temperature of the building facade in the example can be obtained, and the measurement is completed.

[0057] The present invention is fully described for a clearer disclosure, and the prior art is not listed one by one.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some of the technical features therein with equivalents; it is obvious for those skilled in the art to combine multiple technical solutions of the present invention. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention. The technical contents not described in detail in the present invention are all known technologies.

Claims

1. A building facade glass thermal imaging test system based on infrared polarization, characterized in that: include: Mounting bracket; Infrared thermal imager, used to image the temperature distribution of the facade, the infrared thermal imager is installed on the mounting bracket; and The polarization component comprises a polarizer and a polarizer frame. The polarizer frame is used to enable the polarizer to rotate 360 ​​degrees around its optical axis. The polarizer frame is installed on a mounting bracket, and the polarizer is aligned with the lens of the infrared thermal imager.

2. The building facade glass thermal imaging test system based on infrared polarization according to claim 1 is characterized in that: The polarizer is a metal wire grid type infrared polarizer.

3. The building facade glass thermal imaging test system based on infrared polarization according to claim 1 is characterized in that: The operating frequency band of the polarizer can cover the operating frequency band of the infrared thermal imager.

4. The building facade glass thermal imaging test system based on infrared polarization according to claim 1 is characterized in that: The mounting bracket includes a pan / tilt clamp.

5. A thermal image compensation method for building facade glass based on infrared polarization, characterized in that: A test system as described in any one of claims 1 to 4 is used in the method, wherein a polarizing plate is rotated to a preset angle to eliminate part of the interfering light incident on the lens of the infrared thermal imager and then a thermal imaging picture is taken, the polarizing plate is adjusted to multiple preset angles multiple times to correspondingly take thermal imaging pictures at different polarizing plate angles, and then the multiple thermal imaging pictures obtained are re-stitched to obtain a complete thermal imaging picture that eliminates the reflection of ambient light in all directions.

6. The method for compensating thermal images of building facade glass based on infrared polarization according to claim 5, characterized in that: The following steps are involved: S1: When photographing the temperature of the glass on the building's facade, place the optical axis of the polarizer perpendicular to the facade and the thermal imager facing the building to place the test system; S2: Taking the vertical projection point of the infrared thermal imager on the facade as the origin, the measurement area is divided into 2n measurement sub-areas in the axial direction according to the measurement accuracy requirements, marked as 1, 2, 3, 4...2n respectively. The angle interval occupied by the axial direction of each measurement sub-area is 180° / n, and the outer boundary is the imaging boundary of the thermal imager; S3: After the measurement sub-area division is completed, the two diagonal measurement sub-areas are merged into one group to form n sub-area groups, and the polarizer angle is rotated in sequence to each sub-area group in order to eliminate the influence of the polarized light reflected by the glass on the infrared thermal imager in the sub-area group, and then a thermal imaging picture is taken for each sub-area group and saved, and a total of n shots are taken; S4: splicing all obtained thermal imaging pictures according to the corresponding sub-region groups to form a complete thermal imaging picture of the building facade, wherein the temperature displayed on the facade glass is the actual temperature after compensation.

7. The method for compensating thermal images of building facade glass based on infrared polarization according to claim 6, characterized in that: The polarizer is a metal wire grid type infrared polarizer. In step S3, before each shooting, the polarizer is rotated to a direction perpendicular to the metal wire grid and the angular bisector of the boundary of the area, so as to eliminate the influence of polarized light reflected by the glass on the infrared thermal imager in the sub-area group; each time shooting is performed, the polarizer is rotated 180° / n around its optical axis.

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