KR102593382B1 - Method for measuring temperature of infrared radiator for thermal camera calibration - Google Patents

Abstract

According to an embodiment of the present invention, a method of measuring the temperature of an infrared emitter for temperature correction of a thermal camera by an image processing device, wherein the image processing device determines the temperature in a thermal image taken by a temperature calibrator equipped with an infrared emitter. Identifying the corrector; and calculating, by the image processing device, the temperature of the infrared emitter of the identified temperature calibrator.

Description

{Method for measuring temperature of infrared radiator for thermal camera calibration}

The present invention relates to a thermal camera, and more specifically, to a method of performing temperature calibration of a thermal camera by automatically identifying a temperature calibrator in a thermal image taken by a thermal camera and measuring the temperature of an infrared emitter. .

Recently, respiratory infectious diseases such as SARS (Severe Acute Respiratory Syndrome), new flu, MERS, and coronavirus have been occurring frequently, and equipment that measures body temperature using a thermal camera is being developed to detect and track people with symptoms of these infectious diseases. It is widely used.

A conventional method of measuring body temperature using a thermal camera includes installing a thermal camera in a passageway and measuring the body temperature of passengers passing through the passageway to identify people with high fever. In addition, a real camera and a thermal camera are used simultaneously to photograph passersby and the real image and/or thermal image are displayed on the screen to easily display and identify each passerby and their body temperature.

In order to accurately measure body temperature using a thermal camera, it is necessary to output an accurate temperature value corresponding to the amount of infrared light emitted from the measurement object. To this end, an infrared emitter that emits infrared rays while maintaining a constant temperature like a black body is used. There are cases where it happens. However, whenever an infrared emitter is installed, a preparation process is required to recognize the infrared emitter in advance within the thermal image captured by the thermal camera, and also, if the infrared emitter is installed in a passageway where many people walk, the emitter may hit a person and lose its original position. If it deviates, the thermal camera cannot recognize it and temperature correction cannot be performed.

Patent Document 1: Korean Patent Publication No. 10-2018-0123900 (published on November 20, 2018) Patent Document 2: Korean Patent No. 10-1729327 (announced on April 17, 2017)

The present invention is intended to solve the above problems, and its purpose is to provide a technology that allows a thermal camera to automatically recognize a temperature correction means and perform temperature correction.

According to an embodiment of the present invention, a method of measuring the temperature of an infrared emitter for temperature correction of a thermal camera by an image processing device, wherein the image processing device determines the temperature in a thermal image taken by a temperature calibrator equipped with an infrared emitter. Identifying the corrector; and calculating, by the image processing device, the temperature of the infrared emitter of the identified temperature calibrator.

According to one embodiment of the present invention, at every predetermined period or when a predetermined event occurs, the thermal camera can automatically recognize the temperature correction means and perform a temperature correction procedure, so that the body temperature of the measurement target can be accurately measured and displayed, and thus the abnormal body temperature It has the advantage of being able to accurately and easily identify and track people with fever.

1 is a diagram for explaining a thermal camera system according to an embodiment of the present invention;
Figure 2 is a block diagram of a thermal camera system according to one embodiment;
Figure 3 is a block diagram of a thermal camera according to one embodiment;
4 is a diagram illustrating an exemplary shape of a temperature calibrator according to one embodiment;
Figure 5 is a flowchart of a method for detecting a face in a real/thermal image according to an embodiment;
Figure 6 is a flowchart of a temperature calibration method for a thermal camera according to an embodiment;
7 is a flow diagram of a method for automatically identifying a temperature calibrator according to one embodiment;
Figure 8 is a graph to explain the relationship between the detector output of a thermal camera and temperature;
9 is a flowchart of a temperature calibration method of a thermal camera according to another embodiment;
Figure 10 is a graph to explain the relationship between the detector output of a thermal camera and temperature.

The above objects, other objects, features and advantages of the present invention will be easily understood through the following preferred embodiments related to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure will be thorough and complete and so that the spirit of the invention can be sufficiently conveyed to those skilled in the art.

In this specification, when an element is referred to as being on another element, it means that it may be formed directly on the other element or that a third element may be interposed between them. Similarly, when this specification refers to a component being connected (or coupled, fastened, attached, etc.) to another component, it is either directly connected (or coupled, fastened, attached, etc.) to the other component, or between them. This means that it can be indirectly connected (or combined, fastened, attached, etc.) through a third component. Additionally, the thickness of components in the drawings of this specification are exaggerated for effective explanation of technical content. Additionally, in the drawings of this specification, the length, width, volume, size, or thickness of components are exaggerated for effective explanation of technical content.

In this specification, when terms such as first, second, etc. are used to describe components, these components should not be limited by these terms. These terms are merely used to distinguish one component from another. Embodiments described and illustrated herein also include complementary embodiments thereof.

As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. The expressions 'including', 'consisting of', and 'consisting of' used in the specification do not exclude the presence or addition of one or more other components in addition to the mentioned components.

In this specification, the term 'software' refers to technology that moves hardware in a computer, and the term 'hardware' refers to the tangible devices or devices that make up a computer (CPU, memory, input device, output device, peripheral device, etc.) , the term 'step' refers to a series of processing or manipulation connected in time series to achieve a predetermined goal, the term 'computer program' or 'program' refers to a set of instructions combined to be processed by a computer, and the term ' ‘Program recording medium’ refers to a computer-readable recording medium that records programs used to install, run, or distribute programs.

Terms such as '~unit', '~module', '~unit', '~block', and '~board' used in this specification to refer to the components of the invention refer to processing at least one function or operation. It may refer to a physical, functional, or logical unit, which may be implemented as one or more hardware, software, or firmware, or as a combination of one or more hardware, software, and/or firmware.

As used herein, 'processing unit', 'computer', or 'computing device' refers to an operating system such as Windows, Mac, or Linux, a computer processor, memory, applications, storage devices (e.g., HDD, SDD), and It can be implemented as a device equipped with a monitor. The computer may be, for example, a desktop computer or a laptop, but these are examples and the present invention is not limited to the desktop computer or laptop. The mobile terminal may be one of mobile wireless communication devices such as a smartphone, tablet PC, or PDA.

The present invention will be described in detail below with reference to the drawings. In describing the specific embodiments below, various specific details have been written to explain the invention in more detail and to aid understanding. However, a reader with sufficient knowledge in the field to understand the present invention can recognize that it can be used without these various specific details. In some cases, it is mentioned in advance that parts that are commonly known but are not significantly related to the invention are not described in order to prevent confusion in describing the invention.

Figure 1 schematically shows a thermal camera system according to an embodiment of the present invention. Referring to the drawings, a thermal camera system according to an embodiment includes a camera module 10, an image processing device 20, and a display 30. The thermal camera system of the present invention can be used to measure and display the temperature of an arbitrary subject (S), and in this specification, the present invention will be described assuming the case of measuring a person's body temperature as an example. .

In one embodiment, the camera module 10 includes a real camera and a thermal camera. In an alternative embodiment, camera module 10 may include only a thermal camera. A real camera is a camera that generates image data by capturing images in the visible light range of the subject, while a thermal camera detects infrared rays naturally emitted from the subject and converts the amount of infrared rays into heat to generate temperature data of the subject. It is a camera that does. In the drawing, both a real camera and a thermal camera are shown as being provided within the camera module 10, but the real camera and the thermal camera may be installed independently.

The image processing device 20 processes image data captured by the camera module 10. For example, the image processing device 20 performs preprocessing (e.g., noise removal, filtering, synchronization, registration, etc.) on the real image and/or thermal image received from the camera module 10 and performs one or more of the real image or thermal image. It is possible to perform image processing such as detecting the face of a photographing target (S) and overlapping the temperature information for each photographing target (S) with a real or thermal image, and the processed real image data, thermal image data, and/ Alternatively, composite data of real images and thermal images can be output to the display 30. The specific operation of the image processing device 20 will be described later with reference to FIG. 2.

The display 30 is a device that displays image data processed by the image processing device 20 to the user, and may be implemented as any image output device, such as an LCD display or an LED display. In one embodiment, the image processing device 20 may output real images and thermal images to the display 30 in various ways. For example, only one of the real image or the thermal image can be output to the display 30, or a composite image that overlaps the real image and the thermal image can be output, for example, through the PIP (Picture-In-Picture) function. You can also split and output the real image and thermal image in parallel.

In one embodiment, the thermal camera system of the present invention may further include a temperature calibrator 40. The temperature calibrator 40 is equipment used for temperature correction of a thermal camera, and in one embodiment, an infrared radiator 42 is accommodated in the case 41 of the temperature calibrator 40. The infrared emitter 42 is an object that emits infrared rays and is preferably a black body. An ideal black body is an object that absorbs and does not reflect all light coming from the outside and emits only light of the wavelength corresponding to the energy it has. Therefore, a black body can be used for temperature correction of an infrared camera (thermal camera) that takes infrared images of an object and measures the exact temperature of the object. In one embodiment, the black body can be made of a carbon material such as carbon black. The infrared emitter 42 is connected to an optional heating/cooling device and is configured to be maintained at a preset temperature.

The infrared emitter 42 is accommodated in the case 41 and is configured to be visible from the outside through a through hole on one side of the case 41. In one embodiment of the present invention, the case 41 has a predetermined shape, such as a hexahedron, and is configured to allow the infrared emitter 42 to be viewed through the front surface of the case.

In one embodiment, the temperature calibrator 40 is arranged to be located within the camera viewing angle for photographing the object S, and thus the thermal camera of the camera module 10 simultaneously photographs the object S while the temperature calibrator 40 ) can also be taken. Temperature calibration of the thermal camera using the temperature calibrator 40 will be described later with reference to FIG. 6 and the like.

Meanwhile, the image captured with a thermal camera above is referred to as a 'thermal image', but in this specification, it is also called a 'thermal image', 'thermal image', or 'infrared image' with the same meaning. Additionally, in this specification, 'image data' is simply called 'video' or 'image'.

Figure 2 is a block diagram of a thermal camera system according to one embodiment. In FIG. 2, the camera module 10, the image processing device 20, and the display 30 correspond to the camera module 10, the image processing device 20, and the display 30 in FIG. 1, respectively.

The camera module 10 may include a thermal camera 11 and a real image camera 12. The thermal camera 11 can detect infrared rays naturally emitted from the subject S and convert the amount of infrared rays into heat to generate temperature data of the subject S. In one embodiment, the thermal camera 11 includes an infrared lens that passes infrared rays, a detector (detection element array) that detects infrared rays incident on the infrared lens and converts them into electrical signals, and a device that converts the electrical signals into temperature data, which is a digital signal. It includes an analog-to-digital (A/D) converter, etc., and the specific configuration of the thermal camera 11 will be described later with reference to FIG. 3. In addition, the thermal camera 11 can additionally perform temperature correction, non-uniformity correction (NUC), dead pixel processing, etc. on the temperature data converted from the A/D converter. Temperature correction will be described later with reference to FIG. 6, etc. Do this.

The real camera 12 can generate image data by capturing an image in the visible light region of the subject S. In one embodiment, the real camera 12 is implemented with hardware and/or software, such as a lens, a CCD, and an analog-to-digital (A/D) converter. The light coming through the lens is converted into an electrical signal by the CCD, and this signal is converted into image data, a digital signal, by the A/D converter. Since the configuration and operation of the real camera 12 are known technologies, detailed description will be omitted below.

The thermal image and the real image generated by the thermal camera 11 and the real image camera 12 of the camera module 10 are transmitted to the image processing device 20 and processed. In one embodiment, the image processing device 20 may include an image processing unit 21, a face detection unit 22, and a temperature correction unit 23.

The image processing unit 21 performs image processing operations such as noise removal, filtering, synchronization, image registration and synthesis on the thermal image and/or real image received from the camera module 10, and includes the following functions, for example: It may include one or more of:

(1) Noise removal and image improvement: The image processing unit 21 may perform processing for image improvement, such as image quality improvement and contrast improvement of thermal images and/or real images. For example, the image processing unit 21 may remove noise or unevenness by performing processes such as low-pass filtering, image blurring, and image smoothing.

Additionally, the image processing unit 21 can also perform high-pass filtering on the image. For example, high-pass filtering can be performed on a real image using a spatial filter to extract the high spatial frequency component of the real image (i.e., the outline or borderline portion of the photographed object). As another method of extracting high spatial frequency components from an image, the image processing unit 21 may use a method of extracting the difference between two temporally consecutive images. That is, by obtaining the difference between the image at the first time and the image at the second time in the continuous image sequence, high spatial frequency components representing the edge or outline of the photographed object can be extracted.

(2) Image synchronization: The image processing unit 21 temporally synchronizes the thermal images and real images taken at the same time by the thermal camera 11 and the real image camera 12, respectively, so that the thermal images and real images corresponding to the same time can be obtained. In general, the thermal image camera 11 and the real image camera 12 have different image capture speeds due to differences in hardware/software such as CCD, detection element array, and A/D converter, so they cannot acquire thermal images and real images at the same time. Output synchronization of the thermal camera 11 and the real image camera 12 may be necessary.

(3) Image matching: The image processing unit 21 can match the thermal image and the real image so that the thermal image camera 11 and the real image camera 12 photograph the same subject at the same viewing angle and output the image in the same size. Additionally, in order to match the thermal image and the real image, the image processing unit 21 may change the resolution of one of the two images to have the same resolution.

(4) Color thermal image conversion: The image processing unit 21 can convert each pixel of the thermal image into a color according to the temperature data of the corresponding pixel and output it. In other words, the temperature data of each pixel is converted into a color matched according to the temperature band to generate colored thermal image data. For example, the image processing unit 21 generates a color thermal image by applying RGB values matched to each temperature value of the temperature data of each pixel. Accordingly, for example, a color thermal image can be generated in which high temperatures are displayed in red and low temperatures are displayed in blue.

Additionally, the image processing unit 21 can detect the temperature of a specific pixel and perform application processing accordingly. For example, a pixel with the highest temperature among all pixels can be detected, or pixels with a temperature within a preset temperature range can be detected.

(5) Image synthesis: The image processing unit 21 can generate one composite image by combining thermal and real images taken by the thermal camera 11 and the real image camera 12 for the same shooting target. For image synthesis, the above-described image synchronization and matching processing may first be performed, and then, for example, a composite image may be generated by overlapping part or all of the thermal image with the real image. Alternatively, a composite image can be created by overlapping information indicating the temperature of a specific pixel or specific pixel area on a real image or thermal image.

In the image processing device 20, the face detection unit 22 may detect the face area of the subject to be photographed from a thermal image and/or a real image and calculate detection area information including the coordinates of the detected face area. In one embodiment, the face detection unit 22 may detect a face using predefined facial features. For example, a face can be detected using the size, shape, and correlation of facial feature components (e.g., eyes, nose, mouth, outline, brightness, etc.), and facial color and texture information. Alternatively, the face detection unit 22 may use not only facial feature points but also non-face feature points. For example, in a case where the subject of the photo is wearing a hat, sunglasses, or a mask, specific points about various types and sizes of hats, sunglasses, and masks can be defined in advance and used. Additionally, to first detect a person in an image and then detect the face area, feature points on the entire human body or upper body (for example, each joint and skeleton of the human body, etc.) can be used. The face detection unit 22 can detect faces from thermal and/or real images using various known methods and algorithms in addition to the above-described face detection method using feature points.

The temperature correction unit 23 is a functional unit that recognizes the temperature calibrator 40 in the captured image and corrects the temperature of the object to be photographed based on this. An exemplary embodiment of recognizing the temperature calibrator 40 and performing a temperature calibration operation will be described later with reference to FIG. 7 .

In one embodiment, the image processing unit 21, face detection unit 22, and temperature correction unit 23, which are each functional unit of the image processing device 20 described above, include software programmed to perform the corresponding function and support it as necessary. It may be composed of hardware that In addition, these functional units 21, 22, and 23 may each be implemented as independent software or may be implemented as one integrated software, and at least some of these functional units may be implemented in any processing device outside the image processing device 20. It can also be installed and run.

Figure 3 is a block diagram of a thermal camera 11 according to an embodiment. In one embodiment, the thermal camera 11 may include an infrared lens 111, a shutter 112, a detector 113, and an analog-to-digital converter (ADC) 114. The infrared lens 111 is a lens that passes infrared rays, and the shutter 112 blocks light coming from the outside as necessary, such as performing temperature correction or non-uniformity correction (NUC). In one embodiment, the shutter 112 is used to block infrared rays incident on the detector 113 to update a correction table used for non-uniformity (NUC) correction of temperature data. Therefore, if the NUC table is updated in a shutterless manner, the shutter 112 may not be needed.

The detector 113 is a detection element array that detects infrared rays that have passed through the lens 111 and converts them into electrical signals. For example, it has a focal plane array (FPA) structure composed of a two-dimensional array of multiple pixels. It may have a structure, but is not limited to this structure. The ADC 114 is a converter that converts an electrical signal into a digital signal, and converts the electrical signal, which is an analog signal generated by the detector 113, into a digital signal. The digital signal converted in this way is transmitted to the image processing device 20 and processed as an image in the image processing device 20.

For example, the temperature correction unit 23 of the image processing device 20 performs correction processing such as temperature correction, non-uniformity correction, and/or dead pixel processing on the detector signal received from the thermal camera 11, and performs correction processing on the detector signal received from the thermal camera 11. The signal can be converted to temperature data. Additionally, the image processing unit 21 of the image processing device 20 may receive temperature data from the temperature correction unit 23 and convert it into thermal image (or “thermal image” or “thermal image”) data. For example, temperature data that has been temperature-corrected, non-uniformity-corrected, and/or dead-pixel-processed is converted into colors matched to each temperature band to generate thermal image data. For example, a thermal image is generated by applying RGB values matched to each temperature value of the temperature data, and accordingly, for example, a color thermal image is generated in which high temperatures are displayed in red and low temperatures are displayed in blue, or high temperatures are displayed in blue. It can produce a black-and-white thermal image that displays low temperatures close to white and low temperatures close to black.

Figure 4 shows an exemplary shape of the temperature calibrator 40 according to an embodiment, and schematically shows the front view when photographed with a thermal camera 11. Referring to Figure 4(a), in one embodiment, the temperature calibrator 40 includes a rectangular case 41a and a circular infrared radiator 42a installed therein. That is, in the thermal image taken with the thermal camera 11, the temperature calibrator 40 is identified by a case 41a with a square border and a circular infrared radiator 42a disposed therein.

Figure 4(b) shows a temperature calibrator 40 according to an alternative embodiment. In this embodiment, the temperature calibrator consists of a square-shaped case 41b and a square-shaped infrared radiator 42b installed therein. 4(c) is another embodiment in which the temperature calibrator may be composed of a pentagon-shaped case 41c and a circular infrared radiator 42c installed therein.

In the embodiment of Figure 4(d), the temperature calibrator 40 consists of a square case 41d and a plurality of circular infrared radiators 42d installed therein, and in the embodiment of Figure 4(e), the temperature calibrator ( 40) includes a square case 41e and a plurality of infrared radiators 42e arranged in a cross shape.

As such, in the present invention, the case 41 and the infrared radiator 42 of the temperature calibrator 40 may each be implemented in various shapes, and not only one infrared radiator 42 but also a plurality of infrared radiators 42 may be installed. When a plurality of infrared radiators 42 are provided, the temperatures of all infrared radiators 42 may be set to the same temperature, but may also be set to different temperatures. For example, in Figure 4(d), the three infrared emitters 42d can be set to 35 degrees, 36 degrees, and 37 degrees Celsius, respectively, and in Figure 4(e), the five infrared emitters 42e can each be set to 35 degrees Celsius. , can be set to 36 degrees, 37 degrees, 38 degrees, and 39 degrees, and by setting the infrared emitter 42 to two or more temperatures at the same time, temperature correction of the thermal camera can be performed more accurately, especially in the example above. Likewise, by setting multiple reference temperatures across a person's body temperature range, body temperature can be measured more accurately.

Figure 5 is a flowchart of an example method for detecting a face in a real/thermal image and displaying body temperature information according to an embodiment. Referring to the drawing, first, in step S110, the subject S is photographed with the thermal camera 11 and the real image camera 12 to generate a thermal image and a real image, respectively, and transmit them to the image processing device 20. . In step S120, the image processing device 20 may perform preprocessing on the received thermal image and real image. For example, image noise can be removed, high-band/low-band filtering, etc. can be used to improve images, and thermal and real images can be synchronized and matched.

Then, in step S130, the face detection unit 22 of the image processing device 20 detects one or more faces from the thermal image and/or the real image. The method for identifying and detecting faces in images is a known technology, so detailed descriptions are omitted. In one embodiment, the face may be detected in only one of the thermal image or the real image, or the face may be detected in both the real image and the thermal image.

Next, in step S140, the thermal image and the real image can be synthesized. In one embodiment, a composite image may be created by adding body temperature information to only one of the thermal image or the real image. In this case, if there is no need to composite the thermal image and the real image, step S140 may be omitted. However, if at least part of the thermal image and at least part of the real image need to be synthesized and output, step S140 can be performed. Additionally, even when only thermal images are output to the display, part of the real image can be composited into the thermal image to improve the thermal image. Thereafter, in step S150, body temperature information is added to the thermal image and/or real image and transmitted to the display 30 for output. For example, in a black-and-white or color real image or thermal image, the body temperature information of the measurement object (S) can be overlapped with the face or displayed in an area adjacent to the face.

Now, a temperature calibration method of a thermal camera according to an embodiment will be described with reference to FIGS. 6 to 10.

Figure 6 is an exemplary flowchart of a method of calibrating the temperature of a thermal camera using the image processing device 20 according to an embodiment. In this embodiment, temperature correction is to correct each pixel of the detector (detector array) 113 of the thermal camera 11 to output the same output value (temperature value) for a subject of the same temperature, and includes non-uniformity correction (NUC). can do.

Referring to Figure 6, in step S210, the temperature calibrator 40 is automatically identified in the thermal image captured by the thermal camera 11. In this regard, Figure 7 illustrates an example method for automatically identifying a temperature calibrator 40 according to one embodiment. In step S211 of Figure 7, the temperature calibrator 40 is installed at a random location within the camera capturing area. That is, the temperature calibrator 40 is installed so as to be located within the viewing angle of the thermal camera 11. The temperature calibrator 40 may be installed anywhere within the viewing angle of the thermal camera 11, and the installation location is not particularly limited. For example, the temperature calibrator 40 can be installed on one side of a passageway where many people to be measured travel.

Also, at this time, the infrared emitter 42 of the temperature calibrator 40 is set to maintain a predetermined temperature. When the temperature calibrator 40 includes a plurality of infrared radiators 42d or 42e, as in the embodiments of FIGS. 4(d) and 4(e), the infrared radiators can be set to two or more temperatures at the same time. For example, some of the plurality of infrared radiators may be set to a first temperature and others may be set to a second temperature.

Thereafter, in step S212, the identification information of the temperature calibrator 40 is registered in the image processing device 20. Here, the 'identification information' of the temperature calibrator is data that allows the temperature calibrator 40 to be recognized within the thermal image and may include, for example, the external shape or temperature information of the temperature calibrator 40.

In one embodiment, the identification information of the temperature calibrator may include data regarding the shape of the case 41 of the temperature calibrator 40. For example, as shown in FIG. 4, the case 41 of the temperature calibrator 40 may have various shapes such as a square or a pentagon, and information regarding the external shape of the case 41 may be included in the identification information. At this time, information about the shape of the case 41 may include, for example, the width to height or length ratio (in the case of a square), the length or ratio between the lengths of each side (in the case of a polygon), and the diameter or radius (in the case of a circle). You can.

In one embodiment, the identification information of the temperature calibrator may include data regarding the shape of the infrared emitter 42 of the temperature calibrator 40. For example, as shown in FIG. 4, the infrared emitter 42 may also have various shapes such as circular and square, and for these various shapes, data on values such as width and height, radius, diameter, and length ratio are included. can do. In addition, when a plurality of infrared radiators are provided as shown in FIGS. 4(d) and 4(e), the identification information of the temperature calibrator is the arrangement pattern of the infrared radiators (e.g., 3 infrared radiators in the vertical direction in FIG. 4(d)). is arranged in the form of an array, and Figure 4(e) shows five infrared radiators arranged in a cross shape).

In one embodiment, the identification information of the temperature calibrator may further include information about the temperature range including the current temperature of the infrared emitter 42 when the temperature calibrator is photographed with the thermal camera 11. For example, assuming that the infrared emitter 42 is set to 35 degrees Celsius, the identification information of the temperature calibrator further includes the temperature range (e.g., 33 to 37 degrees Celsius) including this temperature (35 degrees Celsius) as identification information. It can be included. Therefore, for example, even if an unused temperature calibrator of the same shape other than the temperature calibrator 40 currently in use is placed nearby, or an object of the same shape as the temperature calibrator accidentally passes nearby, this temperature range is additionally considered as identification information. By doing this, you can accurately recognize the temperature calibrator currently in use.

Additionally, in one embodiment, when the temperature calibrator 40 is provided with a plurality of infrared radiators 42, the temperature range may include two or more temperature ranges. For example, assuming that the plurality of infrared emitters 42 are set to 30 degrees Celsius and 40 degrees Celsius, a first temperature range (e.g., 28 degrees Celsius to 32 degrees Celsius) and a second temperature range (e.g., 38 degrees Celsius) are used as identification information of the temperature calibrator. degrees to 42 degrees) may be further included.

Registration of identification information of the temperature calibrator may be performed automatically or manually. For example, if the temperature calibrator 40 is photographed with the thermal camera 11 and the user selects a pixel area including the temperature calibrator 40 in the captured image, the image processing device 20 Recognizing the edge line (contour line) of the case 41 of the temperature calibrator 40, the boundary line between the case 41 and the infrared emitter 42, and the temperature of the infrared emitter 42, the recognized edge line and boundary line Information such as , temperature, etc. can be registered in the image processing device 20 as identification information of the temperature calibrator 40. At this time, the order of installing the temperature calibrator 40 (S211) and registering identification information (S212) may be changed. That is, the identification information of the temperature calibrator 40 may be registered first (S212), and then the temperature calibrator 40 may be installed at an arbitrary location within the viewing angle of the thermal camera (S211).

As an alternative embodiment, when manually registering the identification information of the temperature calibrator, for example, the user may select the three-dimensional shape (e.g., cube, cylinder, polygonal prism, etc.) or frontal shape (e.g., square, polygon, etc.) of the temperature calibrator case 41. The identification information of the temperature calibrator can be registered by inputting the shape (circle, etc.) and directly inputting the length, diameter, or radius of each side of the input shape into the image processing device 20.

Afterwards, when performing temperature calibration, the temperature calibrator 40 is recognized in the thermal image captured by the thermal camera 11 in step S213. That is, the temperature calibrator 40 can be identified by recognizing the outline, shape, and temperature of the temperature calibrator 40 in the thermal image and comparing it with the identification information of the previously registered temperature calibrator. For example, the temperature calibrator 40 can be identified by recognizing the outline, color, or pattern of the case 42 of the temperature calibrator 40 in the real image. At this time, the temperature calibrator ( It will be appreciated that the temperature calibrator can be identified even if the temperature calibrator 40) is not placed at a specific distance from the thermal camera 11 but is installed anywhere within the field of view.

Referring again to FIG. 6, when the image processing device 20 automatically identifies the temperature calibrator 40 in the thermal image as described above (S210), the temperature of the infrared emitter 42 of the temperature calibrator 40 is measured. And this temperature is obtained from the reference temperature data (S210). For example, if the infrared emitter 42 of the temperature calibrator 40 is set to maintain 35 degrees Celsius, the temperature data of the infrared emitter 42 obtained through steps S210 and S220 becomes the reference temperature data of 35 degrees Celsius. will be.

Next, temperature correction of the thermal camera 11 is performed based on this reference temperature (S230). In this regard, Figure 8 schematically shows the relationship between the detector output of the thermal camera 11 and temperature. In Figure 8, the vertical axis represents the output value from any one pixel of the detector (detection element array) 113 when the measurement object is photographed with the thermal camera 11, and the horizontal axis represents the temperature corresponding to each output value. The first graph (G1) is a graph showing the detector output value-temperature relationship before performing temperature correction. According to this, for example, when the corresponding pixel of the detector 113 of the thermal camera 11 captures the measurement object and generates an output value of d1, the image processing device 20 determines the temperature corresponding to this output value based on the first graph G1. Outputs the value (t1). The first graph (G1) may be a straight line or a curve, and is shown as a straight line in FIG. 8 for convenience of explanation.

This relationship between the detector output value and the temperature value may be stored, for example, as a temperature correction table in the image processing device 20. The temperature compensation table is a table that represents the relationship between the detector output value and temperature value in the measurable temperature range for all pixels of the detector. For example, the detector output value - temperature value as shown in the graph of Figure 8 in the measurable temperature range for each pixel. It may include parameters that define relationships (e.g., gain and offset), and may also include a correspondence table (e.g., lookup table) recording the detector output value and temperature value at predetermined temperature intervals (e.g., at 0.1 degree intervals).

However, for example, if the thermal camera 11 photographs the infrared emitter 42 set at 35 degrees Celsius, and the temperature value (t1) according to the first graph (G1) is output as 36 degrees Celsius, the relationship between the detector output value and the temperature value Since an error has occurred, it must be corrected. That is, since the detector output value (d1) at this time must indicate a temperature value (tb1) of 35 degrees Celsius, the first graph (G1) passes the intersection (P) of the detector output value (d1) and the temperature value (tb1). Move the graph horizontally and/or vertically to correct it to become the second graph (G2). Temperature correction at this time is offset correction. That is, by moving vertically or horizontally while maintaining the slope (gain) of the first graph (G1), only the intercept (offset) with respect to the vertical axis changes, so it is a correction that changes only the offset of the temperature data.

Also, at this time, the above-described first graph (G1) is for one pixel of the detector (detection element array) 113, and each pixel of the detection element array has this graph (i.e., detector output value-temperature relational equation). Therefore, by performing the above correction for all pixels, all pixels in the detection element array can be corrected to output the same temperature value for the same temperature. If the offset is calculated for all pixels of the detector 113 in this way, the temperature correction table can be updated by inputting it into the existing temperature correction table (S240), and then the image processing device 20 uses this updated table. Using this, it is possible to calculate and output the accurate temperature of the measurement target from the detector output value.

The automatic recognition and temperature correction operation of the temperature calibrator 40 as described above may be performed at predetermined time periods. Alternatively, the image processing device 20 may automatically determine whether to perform temperature correction and execute it. there is. For example, if the thermal camera 11 calculates the average value of the body temperature of the subject measured by shooting for a predetermined period of time, and this average value is outside the preset temperature range, the image processing device 20 executes the temperature correction method described above. It can be configured to do so.

Additionally, in one embodiment, the temperature calibrator recognition and temperature calibration operations may be performed simultaneously with the photographing, face detection, and body temperature measurement operations of the photographing subject (S). That is, when the object S and the temperature calibrator 40 are simultaneously exposed to the viewing angle of the thermal camera 11 and the thermal camera 11 photographs them, the image processing device 20 measures the body temperature of the object S. Temperature calibration using the and temperature calibrator 40 may be performed simultaneously.

Figure 9 is a flowchart of a temperature calibration method of a thermal camera according to another embodiment. As shown in Figure 4(d) or Figure 4(e), the temperature calibrator 40 is provided with a plurality of infrared emitters and has two or more reference temperatures. Indicates the temperature correction method when set to .

Referring to Figure 9, the temperature calibrator 40 is automatically identified in the thermal image captured by the thermal camera 11 in step S310. This step (S310) is the same or similar to step (S210) of FIG. 6, and the temperature calibrator 40 can be identified according to the specific identification method described with reference to FIG. 7.

When the temperature calibrator 40 is automatically identified in the thermal image (S310), the temperature of the infrared emitter 42 of the temperature calibrator 40 is measured and this temperature is obtained from the reference temperature data (S310). At this time, since the infrared emitter 42 is set to have two or more reference temperatures, the image processing device 20 can acquire two or more reference temperatures from the thermal image.

Next, temperature correction of the thermal camera 11 is performed based on this reference temperature (S330). In this regard, Figure 10 schematically shows the relationship between the detector output of the thermal camera 11 and temperature. As in Figure 8, in Figure 10, the vertical axis represents the output value from any one pixel of the detector 113, and the horizontal axis represents the temperature corresponding to each output value. The first graph (G1) is a graph showing the detector output value-temperature relationship before temperature correction.

For example, if the thermal camera 11 photographs the infrared emitter 42 set at 30 degrees Celsius and 40 degrees Celsius, and the temperature values (t1, t2) according to the first graph (G1) are output as 31 degrees Celsius and 41 degrees Celsius, respectively, the detector output value - Since an error has occurred in the relationship between temperature values, this must be corrected. That is, since the detector output values (d1, d2) at this time must correspond to temperature values (tb1, tb2) of 30 degrees Celsius and 40 degrees Celsius, respectively, the first graph (G1) shows the corresponding detector output values (d1, d2) and temperature values ( It is corrected with the second graph (G2) so that it passes the intersection (P1, P2) of tb1, tb2). The temperature correction at this time is a correction that changes both the slope (gain) and the intercept (offset) of the first graph (G1) with respect to the vertical axis.

The above-described first graph (G1) is for one pixel of the detector (detection element array) 113, and each pixel of the detection element array has this graph (i.e., detector output value-temperature relational expression), so all pixels By performing the above correction, all pixels of the detection element array can be corrected to output the same temperature value for the same temperature.

In this way, the temperature correction table can be updated by correcting the gain and offset for all pixels of the detector 113 and inputting this into the existing temperature correction table (S340). For example, parameters (eg, gain and offset) defining the corrected detector output value-temperature value relationship (ie, the second graph (G2)) can be updated in the temperature correction table. As another example, the detector output value-temperature value correspondence table (e.g., lookup table) may be updated by calculating the detector output value-temperature value at every predetermined temperature interval (e.g., 0.1 degrees) according to the corrected detector output value-temperature value relational expression.

As described above, those of ordinary skill in the field to which the present invention pertains can understand that various modifications and variations are possible from the description of this specification. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the claims and equivalents thereof as well as the claims described later.

10: camera module 11: real camera
12: thermal camera 20: image processing device
30: Display 40: Temperature calibrator
41: case 42: infrared emitter
111: Lens 112: Shutter
113: detector 114: ADC

Claims (6)

An image processing unit that processes thermal images taken with a thermal camera, a black recognition unit that recognizes a plurality of infrared radiators in the thermal image, and a temperature correction unit that corrects the temperature of the thermal image based on the temperature of the infrared radiators. A method of correcting the temperature of a thermal camera by a device, comprising:
registering identification information of a temperature calibrator having a plurality of infrared radiators emitting at least two predetermined temperatures in the image processing device;
Receiving, by the image processing device, a thermal image of the temperature calibrator and identifying the temperature calibrator in the thermal image based on the registered identification information;
calculating, by the image processing device, temperatures of at least two infrared emitters of the identified temperature calibrator;
Correcting, by the image processing device, the gain and offset of each pixel of the detector of the thermal camera by using the at least two calculated temperatures as reference temperatures; and
A temperature correction method for a thermal imaging camera, comprising: updating a temperature correction table storing gains and offsets for each pixel with the corrected gains and offsets for each pixel. delete In clause 1
A temperature correction method for a thermal imaging camera, wherein the identification information of the temperature calibrator includes information about the shape of the case of the temperature calibrator and the shape of the infrared emitter installed in the temperature calibrator. According to claim 1,
A temperature correction method for a thermal imaging camera, wherein the identification information of the temperature calibrator includes an array pattern of a plurality of infrared radiators installed in the temperature calibrator. According to claim 3 or 4,
The temperature correction method of a thermal imaging camera, wherein the identification information of the temperature calibrator further includes a predetermined temperature range including the temperature of the infrared radiator when photographing the temperature calibrator with a thermal imaging camera. According to claim 4,
The plurality of infrared radiators are set to have at least two preset temperatures,
The temperature correction method of a thermal imaging camera, wherein the identification information of the temperature calibrator further includes a predetermined temperature range including the preset temperature of the infrared radiators when photographing the temperature calibrator with a thermal imaging camera.

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