Temperature measurement device and control method

Abstract

To provide a temperature measurement device capable of accurately measuring a temperature, and a control method.SOLUTION: A temperature measurement device 10 includes: a far-infrared camera 1 for photographing a subject SB so as to generate a thermal image TM; a temperature reference body 6 included in a photographing field angle of the far-infrared camera 1 and installed apart from the far-infrared camera 1; a distance measurement section for measuring a distance L1 from the far-infrared camera 1 to the subject SB; and a control section 4 for determining whether or not a temperature of the subject SB is proper based on a difference between the temperature of the subject SB photographed by the far-infrared camera 1 and a temperature of the temperature reference body 6 when the distance L1 from the far-infrared camera 1 to the subject SB is nearly the same as a distance from the far-infrared camera 1 to the temperature reference body 6.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a temperature measuring device and a control method. [Background technology]

[0002] The temperature measuring system disclosed in Patent Document 1 includes a thermal camera and an appropriate reference body. The appropriate reference body is arranged within the angle of view of the thermal camera and has technical characteristics that make it easy to follow changes in the ambient temperature acquired by the temperature acquisition application. The thermal camera detects the body temperature of a person based on the pixel values ​​of the appropriate reference body and the person captured in the captured image and the temperature of the appropriate reference body corresponding to the ambient temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-178253 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have found the following problems. In such a temperature measuring system, the accuracy of body temperature detection may decrease depending on the subject distance, for example, the distance between the thermal camera and a person or the distance between the thermal camera and an appropriate reference body.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and provides a temperature measuring device and a control method that are capable of measuring temperature with high accuracy. [Means for solving the problem]

[0006] The temperature measuring device according to the present disclosure comprises: A far-infrared camera that captures an object and generates a thermal image; A temperature reference body that is included in the photographing angle of the far-infrared camera and is installed away from the far-infrared camera; A distance measurement unit that measures a distance from the far-infrared camera to the subject; and a control unit that, when the distance from the far-infrared camera to the subject and the distance from the far-infrared camera to the temperature reference body are approximately the same, determines whether the temperature of the subject is appropriate based on the difference between the temperature of the subject photographed by the far-infrared camera and the temperature of the temperature reference body.

[0007] A method for controlling a temperature measuring device according to the present disclosure includes: Taking a photograph of an object using a far-infrared camera to obtain a thermal image; Measuring a distance from the far-infrared camera to a subject; and when a distance from the far-infrared camera to the subject is substantially the same as a distance to a temperature reference body that is included in the imaging angle of the far-infrared camera and installed at a distance from the far-infrared camera, determining whether or not the temperature of the subject is appropriate based on a difference between the temperature of the subject photographed by the far-infrared camera and the temperature of the temperature reference body. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a temperature measuring device and a control method capable of measuring temperature with high accuracy. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a configuration example of a temperature measuring device according to a first embodiment. [Diagram 2] 2 is a schematic diagram showing the relationship between a part of a temperature measuring device and a subject; [Diagram 3] 5 is a flowchart showing an example of a control method for the temperature measuring device according to the first embodiment. [Figure 4] 5 is a flowchart showing a specific example of a control method for the temperature measuring device according to the first embodiment. [Diagram 5] FIG. 2 is a block diagram showing an example of a thermal image captured by a far-infrared camera. [Figure 6] FIG. 4 is a schematic diagram showing an example of a screen displayed by a display unit. [Figure 7] FIG. 4 is a schematic diagram showing an example of a screen displayed by a display unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings are appropriately simplified for clarity of explanation.

[0011] First embodiment <Example of a temperature measuring device> An example of the configuration of the temperature measuring device according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing an example of the configuration of the temperature measuring device according to the first embodiment.

[0012] 1, the temperature measuring device 10 includes a far-infrared camera 1, a visible camera 2, a distance measuring unit 3, a control unit 4, a display unit 5, and a temperature reference body 6. The temperature measuring device 10 may further include a reflecting unit 7 shown in FIG.

[0013] The far-infrared camera 1 photographs a subject and generates a thermal image. The far-infrared camera 1 is communicably connected to the control unit 4, receives a predetermined instruction signal from the control unit 4, and operates according to the received instruction signal. The far-infrared camera 1 also supplies the control unit 4 with thermal imaging data showing a thermal image. The far-infrared camera 1 may be installed in a location where it can photograph a subject. The subject may be, for example, a person. The location where the far-infrared camera 1 is installed is not particularly limited, but may be, for example, a fixed location outdoors or indoors, and may be a wide variety of locations, such as an office building area or an elevator. The far-infrared camera 1 includes, for example, an objective lens, a far-infrared light sensor, and the like. The far-infrared light sensor is, for example, composed of a microbolometer having a plurality of pixels arranged in a two-dimensional array, receives far-infrared light incident through an objective lens, and generates thermal imaging data.

[0014] The visible camera 2 captures an image of a subject and generates a visible image. The visible camera 2 is communicably connected to the control unit 4, receives a predetermined instruction signal from the control unit 4, and operates according to the received instruction signal. The visible camera 2 also supplies visible image data indicating the visible image to the control unit 4. The visible camera 2 includes an imaging element such as a CMOS (Complementary Metal-Oxide Semiconductor) sensor or a CCD (Charge Coupled Devices) sensor.

[0015] The distance measurement unit 3 measures the distance to the subject, which is the distance measurement target. The distance measurement unit 3 is communicably connected to the control unit 4 and outputs the measured distance to the distance measurement target to the control unit 4. The distance measurement unit 3 is, for example, a distance measurement sensor. The distance measurement unit 3 measures the distance to the subject based on the position of the distance measurement sensor. Therefore, when the position of the distance measurement sensor in the shooting direction of the far-infrared camera 1 matches the position of the far-infrared camera, the distance from the distance measurement sensor to the subject measured by the distance measurement unit 3 can be rephrased as the distance from the far-infrared camera 1 to the subject.

[0016] The subject to be measured by the distance measurement unit 3, the subject of the far-infrared camera 1, and the subject of the visible camera 2 are the same. Therefore, it is preferable that the visible camera 2 and the distance measurement unit 3 are provided in the same place as the far-infrared camera 1. It is also preferable that the photographing by the far-infrared camera 1 and the visible camera 2 and the measurement by the distance measurement unit 3 are performed at the same time.

[0017] The control unit 4 can be configured with a processor such as a CPU (Central Processing Unit). In other words, the control unit 4 can have a function as a computer. The control unit 4 can execute a program stored in a storage device such as an internal memory (not shown) to perform various processes.

[0018] Moreover, the control unit 4 executes this program to realize the functions of the components for performing the necessary operations of the temperature measuring device 10 as appropriate. For example, the control unit 4 stores various information in the storage device. The various information includes, for example, the distance from the far-infrared camera 1 to the temperature reference body 6, the distance L2 from the temperature reference body 6 to the far-infrared camera 1 via the reflector 7 shown in FIG. 2, and the temperature threshold value of the temperature reference body 6 (described later). The control unit 4 also outputs the image generated by the visible camera 2 to the display unit 5. When the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 are the same or approximately the same, the control unit 4 judges whether the temperature of the subject is appropriate or not based on the difference between the temperature of the subject photographed by the far-infrared camera 1 and the temperature of the temperature reference body 6. When the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 are approximately the same, the intensity of the far-infrared light received by the far-infrared camera 1 from the subject and the temperature reference body 6 is constant. This ensures the measurement accuracy of the temperature of the temperature measuring device 10.

[0019] The control unit 4 has an image processing function for the thermal image captured by the far-infrared camera 1. Examples of the image processing function by the control unit 4 include a process for complementing defective pixels in the thermal image captured by the far-infrared camera 1 and a NUC (Non-Uniformity Correction) process for calibrating the variation of pixel values.

[0020] The display unit 5 includes a screen 5a. The display unit 5 includes, for example, a liquid crystal panel or an organic electroluminescence panel. The display unit 5 may be provided at a position where the subject can view the screen 5a. The display unit 5 displays the visible image generated by the visible camera 2 on the screen 5a via the control unit 4. The display unit 5 may superimpose an image showing information such as the temperature of the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 on the visible image generated by the visible camera 2 and display them on the screen 5a.

[0021] The temperature reference body 6 is included in the photographing angle of the far-infrared camera 1 and is installed at a distance from the far-infrared camera 1. The temperature of the temperature reference body 6 may be held at an arbitrary temperature threshold. The magnitude of this temperature threshold may be determined to determine whether the temperature of the subject is appropriate or not. When the purpose of using the temperature measuring device 10 is to determine whether a person's body temperature is feverish above normal temperature due to disease, inflammation, or the like, and the subject is a person, the temperature threshold is set to, for example, about 37°C as a threshold for whether the body temperature of a general person is normal or feverish. The value of the temperature threshold is adjustable. The temperature reference body is, for example, a black body furnace. The material and temperature holding method of the temperature reference body 6 are arbitrary as long as it is an object that can be held at an arbitrary temperature threshold.

[0022] As shown in Fig. 2, the reflecting part 7 may be any part that totally reflects far-infrared rays. The reflecting part 7 is, for example, a member made of a metal material such as aluminum or stainless steel. The reflecting part 7 is included in the photographing angle of view of the far-infrared camera 1 and is installed apart from the far-infrared camera 1. The reflecting part 7 is preferably installed at a position that reflects far-infrared rays from the temperature reference body 6 and allows the far-infrared camera 1 to receive the far-infrared rays reflected by the reflecting part 7.

[0023] The far-infrared camera 1 receives far-infrared rays emitted by the subject and the temperature reference body 6. In the example shown in FIG. 2, the far-infrared rays emitted by the subject SB travel along an optical path P1. The optical path P1 extends along a straight line from the subject SB to the far-infrared camera 1. The length of the optical path P1 is the distance L1 from the subject SB to the far-infrared camera 1. The far-infrared rays emitted by the temperature reference body 6 travel along an optical path P2. The optical path P2 first extends in a straight line from the temperature reference body 6 to the reflecting unit 7. Then, the direction of the optical path P2 changes at the reflecting unit 7, and the optical path P2 extends in a straight line from the reflecting unit 7 to the far-infrared camera 1. The length of the optical path P2 is the distance L2 from the temperature reference body 6 to the far-infrared camera 1 via the reflecting unit 7. The distance L2 is the sum of the distance L2a from the temperature reference body 6 to the reflecting unit 7 and the distance L2b from the reflecting unit 7 to the far-infrared camera 1. The far-infrared camera 1 can capture an image of the temperature reference body 6 through the reflecting part 7 .

[0024] <An example of a method for controlling a temperature measuring device> Next, an example of a method for controlling the temperature measuring device 10 will be described with reference to FIGS.

[0025] The control unit 4 uses the far-infrared camera 1 to capture an image of a subject and obtain a thermal image (step ST1). Then, the control unit 4 measures the distance from the far-infrared camera 1 to the subject (step ST2). In other words, the control unit 4 measures the distance from the far-infrared camera 1 to the subject based on the measurement result of the distance measurement unit 3.

[0026] Next, the control unit 4 judges whether the temperature of the subject is appropriate or not (step ST3). Specifically, the control unit 4 confirms that the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 are approximately the same. If the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 are values ​​that ensure the measurement accuracy of the temperature of the subject, it is preferable to judge that both distances are approximately the same. For example, if the ratio of the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 is 0.95 or more and 1.05 or less, it may be judged that the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 are approximately the same. After the confirmation, the control unit 4 judges whether the temperature of the subject is appropriate or not based on the difference between the temperature of the subject photographed by the far-infrared camera 1 and the temperature reference body 6.

[0027] According to the above-mentioned example of the control method of the temperature measuring device 10, when the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 are approximately the same, it is determined whether the temperature of the subject is appropriate or not based on the difference between the temperature of the subject photographed by the far-infrared camera 1 and the temperature of the temperature reference body 6. This reduces the influence of the difference between the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6, and enables accurate temperature measurement.

[0028] Next, a specific example of a method for controlling the temperature measuring device 10 will be described with reference to Figs. 1, 2, and 4 to 6. The flowchart shown in Fig. 4 specifically describes each process in the flowchart shown in Fig. 3. Steps ST11 and ST12 shown in Fig. 4 specifically describe the process of step ST1 shown in Fig. 3. Steps S21 to S24 shown in Fig. 4 specifically describe the process of step ST2 shown in Fig. 3. Similarly, steps ST31 to ST35 shown in Fig. 4 specifically describe the process of step ST3 shown in Fig. 3. In a specific example of a method for controlling the temperature measuring device 10, the temperature measuring device 10 includes a reflecting unit 7 shown in Fig. 2.

[0029] 4 is started based on the start of operation of the temperature measuring device 10. With the start of operation of the temperature measuring device 10, the control unit 4 starts capturing images with the far-infrared camera 1 and the visible camera 2 (step ST11).

[0030] Next, the control unit 4 judges whether or not a subject is present within the shooting range of the far-infrared camera 1 (step ST12). The process of step ST12 is judged based on the thermal image captured by the far-infrared camera 1 or the image captured by the visible camera 2. Specifically, the control unit 4 judges whether or not a subject is present within the shooting range of the far-infrared camera 1 by performing a person recognition process, in particular a process of recognizing a person's face, on the thermal image captured by the far-infrared camera 1 or the image captured by the visible camera 2. The process of step ST12 may be performed based on the detection result of the distance measurement unit 3, judging that some object is present within a predetermined distance.

[0031] In step ST12, if it is determined that a subject is present within the shooting range of the far-infrared camera 1 (step ST12: YES), the control unit 4 measures the distance from the far-infrared camera 1 to the subject (step S21). Specifically, the control unit 4 measures the distance L1 from the far-infrared camera 1 to the subject based on the output value of the distance measurement unit 3.

[0032] At this time, a thermal image TM as shown in Fig. 5 is obtained as a thermal image obtained by photographing with the far-infrared camera 1. The thermal image TM includes the subject SB, which is a person, and the temperature reference body 6 via the reflector 7. In other words, the subject SB and the temperature reference body 6 are included in the photographing angle of view of the far-infrared camera 1. The thermal image TM includes a pixel area 11 and a pixel area 12. The pixel area 11 is the range in which the temperature reference body 6 is photographed. The pixel area 12 is the range in which the subject SB is photographed. The brightness value of each pixel in the thermal image TM is proportional to the temperature of the object that each pixel reflects.

[0033] Next, the control unit 4 determines whether or not the distance L1 and the distance L2 are the same, in other words, whether or not they are substantially the same (step ST22).

[0034] When the control unit 4 determines that the distance L1 and the distance L2 are not substantially the same (step ST22: NO), the control unit 4 displays an instruction to guide the subject SB to an appropriate position on the display unit 5 (step ST23). For example, when the distance L1 is longer than the distance L2 and the difference between the distance L1 and the distance L2 is 10 cm, the control unit 4 displays an instruction "10 cm forward" in the guidance display area 13 of the screen 5a as shown in FIG. 6. The control unit 4 repeats step ST22 until it determines that the distance L1 and the distance L2 are substantially the same (step ST22: NO, step ST23). Although the determination result display area 14 is set in FIG. 6, it is appropriate that the determination result is not displayed until step ST22 becomes YES. Note that a face frame 15 is displayed on the screen 5a as shown in FIG. 6. The face frame 15 is a frame for guiding the subject SB to move his / her face into the face frame 15. This allows the imaging angle of the far-infrared camera 1 to include the face of the person of the subject SB, and the thermal image TM can show a large image of the face of the person of the subject SB.

[0035] When the control unit 4 determines that the distance L1 and the distance L2 are substantially the same (step ST22: YES), the control unit 4 displays on the screen 5a a message indicating that the position of the subject SB is appropriate (step ST24), as shown in Fig. 7. The control unit 4 displays instructions such as "The position is appropriate" or "Please stop" in the guidance display area 13 on the screen 5a.

[0036] Next, the control unit 4 judges whether the temperature of the subject SB is higher than the temperature of the temperature reference body 6 (step ST31). Specifically, the control unit 4 compares the luminance of the pixel indicated by the pixel area 11 in the thermal image TM shown in FIG. 5 with the luminance of the pixel indicated by the pixel area 12. More specifically, the control unit 4 compares the temperature indicated by the luminance of the pixel in the pixel area 11 with the temperature indicated by the luminance of the pixel indicating the maximum luminance in the pixel area 12, thereby comparing the temperature of the subject SB with the temperature of the temperature reference body 6. The pixel indicated by the maximum luminance in the pixel area 12 is often the inner corner of the eye, the nose, or the surroundings of these on the face of the person of the subject SB. The luminance of a pixel is often proportional to the temperature of the part indicated by that pixel. For example, when the temperature of the pixel indicated by the maximum luminance in the pixel area 12 is higher than the temperature indicated by the luminance of the pixel area 11, the control unit 4 judges that the temperature of the subject SB is higher than the temperature of the temperature reference body 6.

[0037] When the control unit 4 determines that the temperature of the subject SB is not high compared to the temperature of the temperature reference body 6 (step ST31: NO), the control unit 4 determines that the temperature of the subject SB is appropriate (step ST34). In this case, as shown in Fig. 7, the control unit 4 displays a notification content indicating that the person of the subject SB does not have a fever, such as the temperature determination result of the subject SB being "normal body temperature", in the determination result display area 14 of the screen 5a (step ST35).

[0038] When the control unit 4 determines that the temperature of the subject SB is higher than the temperature of the temperature reference body 6 (step ST31: YES), the control unit 4 determines that the temperature of the subject SB is not appropriate (step ST32). In this case, the control unit 4 displays a notification content indicating that the person of the subject SB has a fever above a general normal body temperature, such as a temperature determination result of the subject SB of "Fever" in the determination result display area 14 of the screen 5a (step ST33).

[0039] After steps ST33 and ST34, the control unit 4 determines whether or not to end the process (step ST40). Ending the process means ending the operation of the temperature measuring device 10, ending the measurement of the temperature of the subject, etc. If it is determined that the process should be ended (step ST40: YES), the process shown in Fig. 4 is ended. If it is determined that the process should not be ended (step ST40: NO), the process proceeds to step ST12 and waits for the process for the next subject.

[0040] As a result, the temperature of the subject SB can be measured with high accuracy. As in the example of the control method of the temperature measuring device 10 shown in Fig. 3, the influence of the difference between the distance from the far-infrared camera 1 to the subject and the distance from the far-infrared camera 1 to the temperature reference body 6 is reduced, and the temperature can be measured with high accuracy.

[0041] According to a specific example of the control method of the temperature measuring device 10, the reflecting section 7 is included in the photographing angle of view of the far-infrared camera 1 and is installed away from the far-infrared camera 1. The temperature reference body 6 is installed at a predetermined position so that the reflecting section 7 reflects far-infrared rays from the temperature reference body 6 and the far-infrared camera 1 can receive the far-infrared rays reflected by the reflecting section 7. This allows the temperature reference body 6 to be easily installed at a position away from the subject. In other words, the distance from the far-infrared camera 1 to the subject can be easily adjusted to the distance from the far-infrared camera 1 to the temperature reference body 6. Therefore, the distance from the far-infrared camera 1 to the subject can be easily corrected to an appropriate value, and temperature can be measured with high accuracy.

[0042] However, for example, the temperature of the far-infrared camera 1 may change suddenly or locally when the far-infrared camera 1 is exposed to wind. In such a case, the brightness of the pixel of the thermal image may vary greatly. According to a specific example of a control method for the temperature measuring device 10 shown in FIG. 4, even in such a case, the control unit 4 compares the temperature indicated by the brightness of the pixel area 11 with the temperature of the pixel indicated by the maximum brightness in the pixel area 12. In this way, the control unit 4 compares the temperature of the subject SB with the temperature of the temperature reference body 6. The pixel indicated by the maximum brightness in the pixel area 12 is often the inner corner of the eye, the nose, or the surroundings of the subject SB's face. Therefore, the guidance display area 13 and the face frame 15 may guide the subject SB to an appropriate position to ensure the accuracy of the temperature measurement.

[0043] (Other embodiments, etc.) The temperature measuring device 10 according to the above embodiment can be expressed as a program executed by the control unit 4. The control unit 4 of the above-mentioned temperature measuring device 10 includes a processor and a memory, not shown. The configuration of the temperature measuring device 10 described in the above embodiment (see FIG. 1) is realized by the processor reading and executing a program stored in the memory. In other words, this program is a control program for causing the processor to function as the temperature measuring device 10 or a part thereof.

[0044] The above-mentioned program includes a set of instructions (or software code) for making the computer perform one or more functions described in the embodiment when the program is loaded into the computer. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, the computer-readable medium or the tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, optical disk storage, and magnetic storage device. The program may be transmitted on a transitory computer-readable medium or a communication medium. By way of example and not limitation, the transitory computer-readable medium or the communication medium includes electrical, optical, or other forms of propagating signals.

[0045] Furthermore, as described in the above-mentioned various embodiments regarding the processing procedures in the temperature measuring device 10, the present disclosure may also be embodied as a control method for the temperature measuring device 10. Also, the above-mentioned program can be said to be a control program for causing the temperature measuring device 10 to execute such a control method.

[0046] The present invention is not limited to the above-mentioned embodiment, and can be appropriately modified without departing from the spirit of the present invention. The present invention may be implemented by appropriately combining the above-mentioned embodiment and examples thereof. For example, the example of the temperature reference body 6 shown in Figs. 2 and 3 is located below the far-infrared camera 1, but the temperature reference body 6 may be located in front of the far-infrared camera 1. The thermal image TM shown in Fig. 5 and the visible image shown on the screen 5a shown in Figs. 6 and 7 are long in the vertical direction, but may be long in the horizontal direction. [Explanation of symbols]

[0047] 10 Temperature measuring device 1. Far-infrared camera 2 Visible light camera 3 Distance measurement section 4. Control Unit 5 Display section 5a screen 6 Temperature reference body 7 Reflector 11, 12 Pixel area 13 Guidance display area 14 Judgment result display area 15 Face Frame SB Subject TM Thermal Image P1, P2 optical path L1, L2, L2a, L2b distance

Claims

1. A far-infrared camera that captures an object and generates a thermal image; A temperature reference body that is included in the photographing angle of the far-infrared camera and is installed away from the far-infrared camera; A distance measurement unit that measures a distance from the far-infrared camera to the subject; and a control unit that, when a distance from the far-infrared camera to the subject and a distance from the far-infrared camera to the temperature reference body are approximately the same, determines whether or not the temperature of the subject is appropriate based on a difference between the temperature of the subject photographed by the far-infrared camera and the temperature of the temperature reference body.

2. When the distance from the far-infrared camera to the subject and the distance from the far-infrared camera to the temperature reference body are substantially the same, When the temperature of the object photographed by the far-infrared camera is higher than the temperature of the temperature reference body, it is determined that the temperature of the object is not appropriate; When the temperature of the object photographed by the far-infrared camera is lower than the temperature of the temperature reference body, the temperature of the object is determined to be appropriate. The temperature measuring device of claim 1 .

3. The control unit compares the temperature of the subject photographed by the far-infrared camera with the temperature of the temperature reference body based on a difference between the temperature indicated by a pixel with the maximum brightness in the range indicating the subject in the thermal image and the temperature of the temperature reference body.

3. The temperature measuring device according to claim 2.

4. The infrared camera further includes a reflector that is included in the imaging angle of the infrared camera and is installed away from the infrared camera, the temperature reference body is provided at a position where the reflecting portion can reflect far-infrared rays from the temperature reference body and the far-infrared camera can receive the reflected far-infrared rays, the control unit, when a distance from the far-infrared camera to the temperature reference body via the reflecting unit and a distance from the far-infrared camera to the subject are substantially the same, determines whether or not the temperature of the subject is appropriate based on a difference between a temperature of the subject photographed by the far-infrared camera and a temperature of the temperature reference body.

3. The temperature measuring device according to claim 1 or 2.

5. Taking a photograph of an object using a far-infrared camera to obtain a thermal image; Measuring a distance from the far-infrared camera to a subject; a step of determining whether or not the temperature of the subject is appropriate based on a difference between the temperature of the subject photographed by the far-infrared camera and the temperature of the temperature reference body, when a distance from the far-infrared camera to the subject is approximately the same as a distance to a temperature reference body that is included in the photographing angle of the far-infrared camera and installed at a distance from the far-infrared camera.

Images