Thermal imaging equipment and temperature calibration method for thermal imager

Abstract

A thermal imaging device for measuring the temperature of at least one target within a monitored area comprises a thermal imager, an optical camera, and a processing unit, wherein the processing unit is connected to the thermal imager and the optical camera. The thermal imager is used to capture a thermal image of the monitored area. The optical camera is used to capture multiple optical images of the monitored area. The processing unit is configured to determine, based on the thermal image and the location of regions corresponding to the target in the multiple optical images, whether one of the multiple optical images is synchronized with the thermal image; perform a calculation based on the thermal image and the determined optical image to obtain a measured distance between the target and the thermal imaging device; and perform a calibration calculation based on the measured distance and the thermal image to obtain a calibrated temperature value for the target.

Description

Technical Field

[0001] The present invention relates to a thermal imaging device, and in particular to a thermal imaging device with a temperature correction function. Background Art

[0002] In response to the global COVID-19 pandemic, airports and other public places around the world have implemented temperature screening measures to prevent the spread of the virus. Compared to manual measurement, thermal imaging screening can effectively reduce the time required to perform measurements due to excessive crowding. However, due to the attenuation of thermal radiation within a medium, the temperature of an object measured by a thermal imager can vary depending on its distance from the camera, leading to errors in temperature measurements. Summary of the Invention

[0003] In view of the above, the present invention provides a thermal imaging device and a temperature calibration method for a thermal imager.

[0004] According to one embodiment of the present invention, a thermal imaging device is used to measure the temperature of at least one target within a monitoring area and includes a thermal imager, an optical camera, and a processing unit, wherein the processing unit is connected to the thermal imager and the optical camera. The thermal imager is used to capture a thermal image of the monitoring area. The optical camera is used to capture multiple optical images of the monitoring area. The processing unit is configured to determine, based on the thermal image and the location of a region corresponding to the target in the multiple optical images, whether one of the multiple optical images is synchronized with the thermal image, perform a calculation based on the thermal image and the determined optical image to obtain a measured distance between the target and the thermal imaging device, and perform a calibration calculation based on the measured distance and the thermal image to obtain a calibrated temperature value for the target.

[0005] A temperature calibration method for a thermal imager according to one embodiment of the present invention is applicable to a thermal imaging device for obtaining the temperature of at least one target within a monitored area. The temperature calibration method includes: obtaining a thermal image of the monitored area; obtaining multiple optical images of the monitored area; determining, based on the thermal image and the location of a region corresponding to the target in the multiple optical images, that one of the multiple optical images is synchronized with the thermal image; performing a calculation based on the thermal image and the determined optical image to obtain a measured distance between the target and the thermal imaging device; and performing a calibration calculation based on the measured distance and the thermal image to obtain a calibrated temperature value for the target.

[0006] Through the above-described structure, the thermal imaging device and temperature calibration method disclosed herein utilize a thermal imager and an optical camera, combined with specialized computations, to determine the distance between the object under test and the thermal imaging device for temperature calibration without requiring a rangefinder, thereby reducing equipment costs. By utilizing a unique method for synchronizing thermal and optical images, the disclosed thermal imaging device and temperature calibration method utilizes thermal and optical images captured at the closest time points for subsequent distance calculation and temperature calibration, thereby improving temperature estimation accuracy.

[0007] The above description of the disclosed contents and the following description of the embodiments are intended to demonstrate and explain the spirit and principles of the present invention, and to provide further explanation of the claims of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 FIG. 4 is a functional block diagram of a thermal imaging device according to an embodiment of the present invention.

[0009] Figure 2A FIG. 1 is a front view schematic diagram of a thermal imaging device according to an embodiment of the present invention.

[0010] Figure 2B FIG2 is a front view schematic diagram of a thermal imaging device according to another embodiment of the present invention.

[0011] Figure 3 FIG. 4 is a flow chart of a temperature calibration method for a thermal imager according to an embodiment of the present invention.

[0012] Figure 4A FIG. 1 is a schematic diagram illustrating an operation of determining an optical image synchronized with a thermal image in a temperature calibration method for a thermal imager according to an embodiment of the present invention.

[0013] Figure 4B FIG. 4 is a schematic diagram illustrating an operation of determining an optical image synchronized with a thermal image in a temperature calibration method for a thermal imager according to another embodiment of the present invention.

[0014] Figure 5 FIG. 1 is a schematic diagram illustrating the calculation principle for obtaining the measured distance between the object to be measured and the thermal imaging device in a temperature calibration method for a thermal imager according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The following detailed description of the features and advantages of the present invention is provided in the following embodiments. This description is sufficient to enable anyone skilled in the relevant art to understand the technical content of the present invention and implement it accordingly. Furthermore, based on the disclosure of this specification, the claims, and the accompanying drawings, anyone skilled in the relevant art can readily understand the relevant objectives and advantages of the present invention. The following examples further illustrate the concepts of the present invention and are not intended to limit the scope of the present invention in any way.

[0016] The present invention provides a thermal imaging device that can measure the temperature of at least one target object within a monitoring area, such as a living body or other specific object, and can calculate the distance between the thermal imaging device and the target object to correct the measured temperature, thereby obtaining a value closer to the actual temperature. Figure 1 , Figure 1 FIG. 1 is a functional block diagram of a thermal imaging device 1 according to an embodiment of the present invention. Figure 1 As shown, thermal imaging device 1 includes a thermal imager 11, an optical camera 13, and a processing unit 15. Processing unit 15 is connected to thermal imager 11 and optical camera 13 via wired or wireless communication. Thermal imager 11, also known as an infrared thermal imager, is used to capture thermal images of the monitored area. Optical camera 13, for example, a color (RGB) camera, is used to capture multiple optical images of the monitored area.

[0017] The computational processing device 15 includes processing elements such as a central processing unit (CPU), a microcontroller, and a programmable logic controller (PLC). The processing device 15 can be configured to: determine, based on the thermal image and the location of the region corresponding to the target object in the multiple optical images, whether one of the multiple optical images is synchronized with the thermal image; perform computations based on the thermal image and the determined optical image to determine the distance between the target object and the thermal imaging device (measured distance); and perform calibration computations based on the measured distance and the thermal image to determine a calibrated temperature value for the target object. The detailed computations will be described later. Furthermore, after obtaining the calibrated temperature value, the computational processing device 15 can output the calibrated temperature value via a user interface or communication interface, or compare the calibrated temperature value with a preset threshold indicating an abnormal body temperature, and then output the comparison result via the user interface or communication interface.

[0018] Specifically, through the coordinated operation of the thermal imager 11 and the optical camera 13, and the special calculations performed by the processing unit 15 based on the thermal and optical images, the thermal imaging device 1 can determine the distance between the target and the thermal imaging device for subsequent temperature calibration calculations without requiring a rangefinder, thereby reducing equipment costs. Furthermore, generally speaking, the frame rate (FPS) of the thermal imager 11 is lower than that of the optical camera 13 (e.g., 1:6). This means that there is a one-to-many mapping relationship between the image data of the two hardware devices, and optical images captured within the same time period may be out of sync with the thermal images. If the target moves during the time between the thermal and optical images used to calculate the distance between the target and the thermal imaging device, the distance calculation will be inaccurate, resulting in errors in the subsequent temperature calibration. By determining the optical image corresponding to the thermal image based on the position of the target object in the image by the processing device 15, the thermal imaging device 1 can obtain the most synchronized thermal image and optical image for subsequent distance calculation and temperature correction calculation, thereby avoiding the problem caused by the above-mentioned imaging asynchrony and thereby improving the accuracy of temperature estimation.

[0019] Figure 1 The following is an exemplary functional block diagram of the thermal imaging device 1. Furthermore, the present invention also proposes a special arrangement of the imaging elements of the thermal imaging device 1 in space. Please refer to Figure 1 、 Figure 2A and Figure 2B ,in Figure 2A FIG2 is a front view schematic diagram of a thermal imaging device 1 according to an embodiment of the present invention. Figure 2B FIG1 is a front view schematic diagram of a thermal imaging device 1 according to another embodiment of the present invention. Figure 2A In the embodiment of the present invention, the thermal imager 11 and the optical camera 13 are arranged vertically. Specifically, the sensor of the thermal imager 11 and the lens of the optical camera 13 are arranged vertically. The so-called vertical arrangement means that the center line of the sensor of the thermal imager 11 and the lens of the optical camera 13 is roughly parallel to the direction of gravity. Specifically, the center line of the sensor of the thermal imager 11 and the lens of the optical camera 13 can have a tolerance angle difference of within ±45 degrees with the direction of gravity. Figure 2B In the embodiment, the thermal imager 11 and the optical camera 13 are arranged horizontally. Specifically, the sensor of the thermal imager 11 and the lens of the optical camera 13 are arranged horizontally. The so-called horizontal arrangement means that the center line connecting the sensor of the thermal imager 11 and the lens of the optical camera 13 is approximately perpendicular to the direction of gravity. Specifically, the center line connecting the sensor of the thermal imager 11 and the lens of the optical camera 13 can have a tolerance angle difference of within ±45 degrees from the horizontal line perpendicular to the direction of gravity.

[0020] By means of the above arrangement, the processing device 15 can calculate the position of the target object on the thermal image and the corresponding optical image based on the parallax between the thermal imager 11 and the optical camera 13 to obtain the distance between the target object and the thermal imaging device 1. The detailed calculation content will be described later. It should be noted that Figure 2A and Figure 2B The thermal imager 11 and the optical camera 13 of the thermal imaging device 1 are shown as being arranged vertically or horizontally for illustrative purposes only. This does not limit the vertical or horizontal relationship between the thermal imager 11 and the optical camera 13 , nor does it limit the size or shape of the thermal imager 11 and the optical camera 13 .

[0021] The present invention also provides a temperature calibration method for a thermal imager, which is applicable to the thermal imaging device 1. Figure 1 and Figure 3 ,in Figure 3 FIG. 1 is a flow chart of a temperature calibration method for a thermal imager according to an embodiment of the present invention. Figure 3 As shown, the temperature calibration method includes step S1, obtaining a thermal image and multiple optical images of a monitored area; step S3, determining whether one of the multiple optical images is synchronized with the thermal image based on the positions of the blocks corresponding to the target object in the thermal image and the multiple optical images; step S5, performing a calculation based on the thermal image and the determined optical image to obtain a measured distance between the target object and the thermal imaging device; and step S7, performing a calibration calculation based on the measured distance and the thermal image to obtain a calibrated temperature value of the target object.

[0022] In step S1, the processing unit 15 of the thermal imaging device 1 acquires a thermal image from the thermal imager 11 and multiple optical images from the optical camera 13. Specifically, during operation, the thermal imager 11 continuously captures thermal images of the monitored area at a first frame rate, while the optical camera 13 continuously captures optical images of the monitored area at a second frame rate. The processing unit 15 determines the ratio of thermal images to optical images based on the ratio of the first frame rate to the second frame rate. For example, if the first frame rate is 5 fps and the second frame rate is 30 fps, the processing unit 15 will capture six optical images for each thermal image captured to determine the corresponding relationship in the subsequent step S3.

[0023] In addition, the time point of generation of the thermal image taken by the processing device 15 (i.e., the time point when the thermal image is generated by the thermal imager 11) can be the same as or similar to the time point when the first optical image is generated in the optical image taken (i.e., the time point when the optical camera 13 is used to generate the optical image), can be the same as or similar to the time point when the last optical image is generated in the optical image taken, or can be between the time points when the first optical image is generated and the time point when the last optical image is generated, among which the middle time point is preferred.

[0024] In step S3, the processing device 15 determines whether one of the multiple optical images is synchronized with the thermal image based on the location of the block corresponding to the target object in the thermal image and the multiple optical images. It should be noted that synchronization refers to the thermal image and the optical image being generated at the same time or at the closest time. For further explanation of the implementation of step S3, please refer to Figure 4A and 4B ,in Figure 4A FIG. 1 is a schematic diagram illustrating an operation of determining an optical image synchronized with a thermal image in a temperature calibration method for a thermal imager according to an embodiment of the present invention. Figure 4B FIG. 4 is a schematic diagram illustrating an operation of determining an optical image synchronized with a thermal image in a temperature calibration method for a thermal imager according to another embodiment of the present invention.

[0025] At Figure 4A In the embodiment shown, the processing device 15 performs the step of determining whether one of the plurality of optical images is synchronized with the thermal image based on the thermal image and the position of the block corresponding to the target object in the plurality of optical images ( Figure 3 Step S3) includes calculating the distance between the coordinates of the block corresponding to the target object in each of the optical images RGB1-RGB3 and the coordinates of the block corresponding to the target object in the thermal image TH1, and determining that the optical image and thermal image TH1 with the smallest distance among the optical images RGB1-RGB3 are synchronized, wherein the distance is calculated along the x-axis direction or the y-axis direction. Figure 4A As an example, a living body is depicted as a target object, and the distance is calculated using the coordinates of the geometric center of the block corresponding to the head of the living body in the image. Specifically, the processing device 15 can obtain the coordinates of the geometric center P0 of the block corresponding to the head of the living body in the thermal image TH1, and obtain the coordinates of the geometric centers P1 to P3 of the blocks corresponding to the head of the living body in the optical images RGB1 to RGB3, wherein the coordinates of the geometric centers P0 and P1 to P3 have the same coordinate system, and respectively calculate the distance between the coordinates of the geometric centers P1 to P3 and the coordinates of the geometric center P0. Further, for Figure 2A For the thermal imaging device 1 shown in FIG. 1 , where the imaging element is arranged vertically, the distance between the coordinates is calculated along the x-axis direction, that is, the difference between the x-coordinates of the geometric centers P1 to P3 and the x-coordinate of the geometric center P0 is calculated, which is the aforementioned distance. Figure 2BFor the horizontally arranged thermal imaging device 1 shown, the distance between coordinates is calculated along the y-axis. Specifically, the difference between the y-coordinates of geometric centers P1-P3 and P0 is calculated, representing the aforementioned distance. Next, the processing unit 15 determines that the optical image with the smallest distance between the optical images RGB1-RGB3 (i.e., optical image RGB2) and the thermal image TH1 are synchronized.

[0026] For example, the processing unit 15 can identify a heat mass with a common living body temperature (e.g., 34-40 degrees Celsius) in the thermal image TH1, and regard the top portion of the heat mass as a block corresponding to the living body's head, and can identify the block corresponding to the living body's head in the optical image RGB1-RGB3 by facial positioning (e.g., skin color recognition, facial feature recognition, or other AI recognition). In other embodiments, the processing unit 15 can also be configured to calculate the distance using the coordinates of blocks corresponding to other parts of the living body. In addition, it should be noted that, Figure 4A Three optical images RGB1 to RGB3 are shown as examples, but this is not intended to limit the number of optical images that the processing device 15 may use to compare with the thermal image.

[0027] At Figure 4B In the embodiment shown, the processing device 15 performs the step of determining whether one of the plurality of optical images is synchronized with the thermal image based on the thermal image and the position of the block corresponding to the target object in the plurality of optical images ( Figure 3 Step S3) includes: obtaining the coordinates (first coordinates) corresponding to the head of the living subject in the thermal image TH2, obtaining the coordinates (second coordinates) corresponding to the head of the living subject in each optical image RGB4, calculating the error value between the two coordinates, and determining that the optical image with the smallest error value in the optical image RGB4 is synchronized with the thermal image TH2, wherein the error value is calculated along the x-axis direction or the y-axis direction. In detail, the processing device 15 can first perform a capture process on the thermal image TH2 for thermal blobs within a specific temperature range (e.g., 34 to 40 degrees Celsius) to generate a thermal image TH2' containing multiple thermal blobs (with geometric centers A1 to A6), and then filter out the coordinates of the thermal blobs (with geometric centers A1 to A3) corresponding to the head of the living subject. For example, the processing device 15 can use the y-coordinate of the living subject's head that is usually presented in the picture as a filtering condition. Next, the processing device calculates the error value between the coordinates of the thermal mass (with geometric centers A1-A3) corresponding to the head of the living person in the thermal image TH2' and the coordinates of the block (with geometric centers B1-B3) corresponding to the head of the living person in the optical image RGB4.

[0028] Furthermore, for Figure 2AFor the thermal imaging device 1 in which the imaging element is arranged vertically, the error value is calculated along the x-axis direction, where the error value can be expressed as:

[0029]

[0030] Among them, B ix A represents the x-coordinate of the geometric center of the head on the optical image RGB4; jx represents the x-coordinate of the geometric center of the thermal mass on the thermal image TH2'; k represents the number of the geometric center of the head on the optical image RGB4; t represents the number of the candidate optical image; T represents the number of the candidate optical image determined to be synchronized; r i represents the area within the appropriate radius of the i-th head in the optical image RGB4. In addition, for Figure 2B For the horizontally arranged thermal imaging device 1, the error value is calculated along the y-axis, that is, the parameters associated with the x-coordinate in the above expression are changed to be associated with the y-coordinate. Figure 4B One of the optical images RGB4 among the multiple optical images used for comparison with the thermal image is shown as an example, and is not intended to limit the number of optical images that the processing device 15 may obtain for comparison with the thermal image.

[0031] In execution Figure 3 After obtaining synchronized thermal and optical images in step S3, the processing device 15 proceeds to step S5 to calculate the distance between the living subject and the thermal imaging device 1. As previously described, in step S5, the processing device 15 performs calculations based on the thermal and optical images to obtain the measured distance between the target object and the thermal imaging device. Specifically, the processing device 15 can calculate the measured distance between the target object and the thermal imaging device based on the target object's image position in the thermal image, the x or y coordinate of the target object's image position in the optical image, the focal length of the thermal imager 11, the focal length of the optical camera 13, and the distance between the sensor of the thermal imager 11 and the lens of the optical camera 13.

[0032] Furthermore, the y-coordinate of the imaging position of the target object in the image can be calculated by the processing device 15 by calculating the distance between the position corresponding to the top of the target object's head or the geometric center of the head and the upper edge of the image. The x-coordinate of the imaging position of the target object in the image can be calculated by the processing device 15 by calculating the distance between the position corresponding to the top of the target object's head or the geometric center of the head and the side edge of the image. The focal length of the thermal imager 11 / optical camera 13 can be pre-stored in the memory of the processing device 15 or in an external database, or obtained by the processing device 15 performing image correction on the thermal image / optical image. The distance between the sensor of the thermal imager 11 and the lens of the optical camera 13 can be pre-stored in the memory of the processing device 15 or in an external database. The expression used to calculate the measured distance can be:

[0033]

[0034] Where Z represents the measurement distance; y T Indicates the y coordinate of the imaging position of the target in the thermal image; RGB represents the y coordinate of the imaging position of the target object in the optical image; f T represents the focal length of the thermal imager 11; f RGB represents the focal length of the optical camera 13; B represents the distance between the sensor of the thermal imager 11 and the lens of the optical camera 13. In particular, represents the parallax between the sensor of thermal imager 11 and the lens of optical camera 13. Therefore, the above expression can be considered a parallax model. Because the above expression is computationally simple, the processing unit 15 of thermal imaging device 1 does not need to have high computing power and can therefore be configured with a lower-cost processor, thereby reducing equipment costs.

[0035] The above expression can be derived based on the principle of similar triangles. Please refer to Figure 5 , Figure 5 FIG. 1 is a schematic diagram illustrating the calculation principle for obtaining the measured distance between the object to be measured and the thermal imaging device in a temperature calibration method for a thermal imager according to an embodiment of the present invention. Figure 5 The thermal imager lens center O is shown as an example. T (Sensor center), optical camera lens center O RGB 、Thermal imager lens center O T With optical camera lens O RGB The distance B between the target and the thermal imager, the actual position Y of the target in the monitoring area, and the vertical distance y between the target and the thermal imager ⊥ , measurement distance Z, thermal imager focal length f T , optical camera focal length f RGB , the imaging position y of the target in the thermal image T and the imaging position y of the target in the optical imageRGB The relationship on the z-axis plane. Based on Figure 5 And the principle of similar triangles, we can get the following two equations:

[0036]

[0037]

[0038] Based on the above equation, we can derive the expression used in the previous column to calculate the measured distance.

[0039] above Figure 5 The distance calculation method shown is applicable to Figure 2A The imaging element shown is a vertically arranged thermal imaging device 1. For a thermal imaging device 1 in which the angle difference between the line connecting the sensor of the thermal imager 11 and the lens of the optical camera 13 and the vertical line is less than the tolerance angle difference, the processing unit 15 can first perform image correction on the thermal image and the optical image to compensate for the angle difference, and then perform the distance calculation described in the above embodiments. Figure 2B The imaging element shown is a horizontally arranged thermal imaging device 1, and the distance calculation method applicable thereto is similar to that of Figure 5 The difference is that the distance calculation based on the original y coordinate is changed to the distance calculation based on the x coordinate. Further, the expression used to calculate the measured distance can be:

[0040]

[0041] Where Z represents the measurement distance; x T Indicates the x-coordinate of the imaging position of the target in the thermal image; RGB represents the x-coordinate of the imaging position of the target object in the optical image; f T represents the focal length of the thermal imager 11; f RGB represents the focal length of the optical camera 13 ; and B represents the distance between the sensor of the thermal imager 11 and the lens of the optical camera 13 .

[0042] In step S7, the processing device 15 performs a calibration operation based on the measured distance and the thermal image to obtain a calibrated temperature value for the target object. Specifically, the processing device 15 determines whether the thermal image has a sensed temperature value corresponding to the target object, searches a distance-temperature calibration table based on the measured distance to obtain a compensated temperature value, and then performs a calculation (e.g., addition) on the sensed temperature value and the compensated temperature value to obtain the calibrated temperature value. The distance-temperature calibration table can be stored in the memory of the processing device 15 or obtained from an external database. Table 1 below presents an exemplary distance-temperature calibration table. For example, if the sensed temperature value corresponding to the target object in the thermal image is 36.1 degrees Celsius and the distance between the target and the thermal imaging device 1 is 1.5 meters, the calibrated temperature value obtained by the calibration operation performed by the processing device 15 is 36.6 degrees Celsius.

[0043] Table 1

[0044]

[0045]

[0046] Through the above-described structure, the thermal imaging device and temperature calibration method disclosed herein utilize a thermal imager and an optical camera, along with specialized algorithms. This eliminates the need for a rangefinder to determine the distance between the object under test and the thermal imaging device for temperature calibration, thereby reducing costs. By utilizing a unique method for synchronizing thermal and optical images, the thermal imaging device and temperature calibration method disclosed herein utilizes thermal and optical images captured at the closest time points for subsequent distance calculation and temperature calibration, thereby improving temperature estimation accuracy.

[0047]

Explanation of symbols

[0048] 1 Thermal imaging equipment

[0049] 11 Thermal Imager

[0050] 13 Optical camera

[0051] 15. Processing unit

[0052] Steps S1 to S7

[0053] TH1, TH2, TH2' thermal images

[0054] RGB1~RGB4 optical image

[0055] P0, P1~P3, A1~A6, B1~B3 geometric center

[0056] r1~r3 radius

[0057] OT Thermal imager lens

[0058] O RGB Optical camera lens core

[0059] B distance

[0060] Y actual position of the target

[0061] y ⊥ The vertical distance between the target and the thermal imager

[0062] Z measurement distance

[0063] f T Thermal imager focal length

[0064] f RGB Optical camera focal length

[0065] y T 、y RGB y coordinate of the imaging position

[0066] x T 、x RGB x-coordinate of the imaging position

Claims

1. A thermal imaging device for measuring the temperature of at least one target object within a monitoring area, comprising: A thermal imager, used to capture a thermal image of the monitored area; an optical camera for capturing a plurality of optical images of the monitored area; and A processing device connected to the thermal imager and the optical camera, and configured to execute: determining, based on the thermal image and a position of a block in the plurality of optical images corresponding to the at least one target object, that one of the plurality of optical images is synchronized with the thermal image; performing a calculation based on the thermal image and the determined optical image to obtain a measured distance between the at least one target object and the thermal imaging device; and Performing a calibration operation based on the measured distance and the thermal image to obtain a calibrated temperature value of the at least one target object, Wherein, determining that one of the plurality of optical images is synchronized with the thermal image based on the thermal image and the position of the block corresponding to the at least one target object in the plurality of optical images comprises: The distance between the coordinates of the block corresponding to the at least one target object in each of the plurality of optical images and the coordinates of the block corresponding to the at least one target object in the thermal image is calculated respectively, and the optical image with the smallest distance among the plurality of optical images is determined to be synchronized with the thermal image, wherein The distance is calculated along the x-axis direction or the y-axis direction. 2 . The thermal imaging device as claimed in claim 1 , wherein the sensor of the thermal imager and the lens of the optical camera are arranged horizontally. 3 . The thermal imaging device as claimed in claim 1 , wherein the sensor of the thermal imager and the lens of the optical camera are arranged vertically.

4. The thermal imaging device of claim 1 , wherein the at least one target object is at least one living body, and the processing device is configured to calculate the distance between the coordinates of the block corresponding to the at least one target object in each of the plurality of optical images and the coordinates of the block corresponding to the at least one target object in the thermal image, comprising: obtaining a first coordinate corresponding to a head of the at least one living body in the thermal image, obtaining a second coordinate corresponding to the head of the at least one living body in each of the plurality of optical images, and calculating the distance between the second coordinate and the first coordinate of each optical image.

5. The thermal imaging device of claim 2 , wherein the processing device is configured to perform a calculation based on the thermal image and the determined optical image to obtain the measured distance between the at least one target and the thermal imaging device, comprising: performing a calculation based on an expression to obtain the measured distance, and the expression is: in, Z represents the measured distance, x T represents the x-coordinate of the imaging position of the at least one target object in the thermal image, x RGB represents the determined x-coordinate of the imaging position of the at least one target object in the optical image, f T Indicates the focal length of the thermal imager, f RGB represents the focal length of the optical camera, and B represents the distance between the thermal imager and the optical camera.

6. The thermal imaging device of claim 3 , wherein the processing device is configured to perform a calculation based on the thermal image and the determined optical image to obtain the measured distance between the at least one target and the thermal imaging device, comprising: performing a calculation based on an expression to obtain the measured distance, and the expression is: in, Z represents the measured distance, y T represents the y coordinate of the imaging position of the at least one target object in the thermal image, y RGB represents the determined y coordinate of the imaging position of the at least one target object in the optical image, f T Indicates the focal length of the thermal imager, f RGB represents the focal length of the optical camera, and B represents the distance between the thermal imager and the optical camera.

7. The thermal imaging device of claim 1 , wherein the thermal image has a sensed temperature value corresponding to the at least one target object, and the processing device is configured to perform a calibration operation based on the measured distance and the thermal image to obtain the calibrated temperature value of the at least one target object, comprising performing a calibration operation on the sensed temperature value based on a distance-temperature calibration table and the measured distance to obtain the calibrated temperature value of the at least one target object.

8. A temperature calibration method for a thermal imager, applicable to a thermal imaging device for obtaining the temperature of at least one target object within a monitoring area, comprising: obtaining a thermal image of the monitored area; Acquire multiple optical images of the monitored area; determining, based on the thermal image and a position of a block in the plurality of optical images corresponding to the at least one target object, that one of the plurality of optical images is synchronized with the thermal image; performing a calculation based on the thermal image and the determined optical image to obtain a measured distance between the at least one target object and the thermal imaging device; and Performing a calibration operation based on the measured distance and the thermal image to obtain a calibrated temperature value of the at least one target object, Wherein, determining that one of the plurality of optical images is synchronized with the thermal image based on the thermal image and the position of the block corresponding to the at least one target object in the plurality of optical images comprises: A distance between the coordinates of the block corresponding to the at least one target in each of the plurality of optical images and the coordinates of the block corresponding to the at least one target in the thermal image is calculated, and an optical image with a minimum distance between the plurality of optical images and the thermal image is determined to be synchronized, wherein the distance is calculated along the x-axis or the y-axis. 9 . The temperature calibration method as claimed in claim 8 , wherein the sensor of the thermal imager and the lens of the optical camera are arranged horizontally. 10 . The temperature calibration method as claimed in claim 8 , wherein the sensor of the thermal imager and the lens of the optical camera are arranged vertically.

11. The temperature calibration method according to claim 8, wherein the at least one target object is at least one living body, and Calculating the distance between the coordinates of the block corresponding to the at least one target object in each of the plurality of optical images and the coordinates of the block corresponding to the at least one target object in the thermal image comprises: Obtaining a first coordinate corresponding to a head of the at least one living body in the thermal image; Obtaining a second coordinate corresponding to the head of the at least one living body in each of the plurality of optical images; and The distance between the second coordinate and the first coordinate of each optical image is calculated respectively.

12. The temperature calibration method of claim 9, wherein performing a calculation based on the thermal image and the determined optical image to obtain the measured distance between the at least one target object and the thermal imaging device comprises: The measured distance is obtained by performing an operation according to an expression, and the expression is: in, Z represents the measured distance, x T represents the x-coordinate of the imaging position of the at least one target object in the thermal image, x RGB represents the determined x-coordinate of the imaging position of the at least one target object in the optical image, f T Indicates the focal length of the thermal imager, f RGB represents the focal length of the optical camera, and B represents the distance between the thermal imager and the optical camera.

13. The temperature calibration method of claim 10 , wherein performing a calculation based on the thermal image and the determined optical image to obtain the measured distance between the at least one target object and the thermal imaging device comprises: The measured distance is obtained by performing an operation according to an expression, and the expression is: in, Z represents the measured distance, y T Indicates the y coordinate of the imaging position of the living body in the thermal image, y RGB represents the y coordinate of the imaging position of the living body in the determined optical image, f T Indicates the focal length of the thermal imager, f RGB represents the focal length of the optical camera, and B represents the distance between the thermal imager and the optical camera.

14. The temperature calibration method of claim 8 , wherein the thermal image has a sensed temperature value corresponding to the at least one target object, and performing a calibration operation to obtain the calibrated temperature value of the at least one target object based on the measured distance and the thermal image comprises: A calibration operation is performed on the sensed temperature value according to a distance-temperature calibration table and the measured distance to obtain the calibrated temperature value of the at least one target object.

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