System and method for two-dimensional temperature measurement

Abstract

A two-dimensional (2D) temperature measurement system comprises a half-mirror (101) designed to split light incident from a measurement target (100) into two paths by reflecting 50% of the incident light and transmitting the remaining 50%, a first CCD camera (103a) equipped with a first bandpass filter (102a), and a second CCD camera (103b) equipped with a second bandpass filter (102b) that transmits a wavelength different from that of the first bandpass filter, wherein the half-mirror splits the light incident from the measurement target into the two paths for photographic recording by directing the light in real time to the first CCD camera equipped with the first bandpass filter and to the second CCD camera equipped with the second bandpass filter.and whereby, based on output data corresponding to photographic recording in real time, 2D temperature distribution data are generated.

Description

[0001] The invention relates to a system and a method for 2D temperature measurement (two-dimensional temperature measurement) using CCD cameras (charge-coupled device cameras). This application is based on Korean patent application No. 10-2024-0183318, which was filed with the Korean Intellectual Property Office on December 11, 2024. The entire contents of that application are hereby incorporated into the present application by reference.

[0002] According to current technology, infrared cameras are frequently used to measure two-dimensional (2D) temperature distributions. Infrared camera measurement technology employs a method in which the surface temperature of an object is determined by measuring the intensity of the infrared light emitted from that surface. However, when infrared cameras are used for 2D temperature measurement as they have been until now, the emissivity of an object—that is, the efficiency with which the object emits heat—must be precisely determined to enable accurate temperature measurement, since the emissivity of an object can vary depending on its material and surface properties.

[0003] Furthermore, in a non-contact temperature measurement method using an existing pyrometer, specifically a bicolor pyrometer that measures temperature based on the ratio of output values ​​from two photodiodes receiving different wavelengths, the bicolor pyrometer is less affected by emissivity due to the use of the ratio of radiation emitted at two wavelengths. However, temperature measurement is only possible for a single point. Therefore, such existing methods are unsuitable for real-time inspection of the entire high-temperature area.

[0004] The invention is based on the technical problem of providing a system and a method of the type mentioned above for 2D temperature measurement, which offer improvements compared to the prior art mentioned above, particularly with regard to the efficiency of temperature measurement.

[0005] The invention solves this problem by providing a system with the features of claim 1 and a method with the features of claim 6. Furthermore, the invention provides a computer-readable recording medium in which a method-executing computer program is stored. Advantageous embodiments of the invention are specified in the dependent claims, the wording of which is hereby incorporated by reference into the description. This includes, in particular, all embodiments of the invention resulting from the combinations of features defined by the cross-references in the dependent claims.

[0006] The invention improves the efficiency of temperature measurement by enabling real-time 2D temperature distribution measurement. The invention also aims to improve the accuracy of temperature measurement by minimizing the influence of emissivity or the emissivity ratio. The technical problems solved by the invention are not limited to those mentioned above; other solved technical problems will be clear to those skilled in the art from the description below. Further aspects of the invention are partly explained in the following description and partly evident from the description or become apparent through the practical implementation of the presented embodiments of the invention.

[0007] The 2D temperature measurement system according to the invention comprises a half-mirror configured to split light incident from a measurement target into two paths by reflecting approximately half (i.e., approximately 50%) of the incident light and reflecting the other half (i.e., approximately 50%).the remaining 50%) of the incident light passes through, a first CCD camera equipped with a first bandpass filter, and a second CCD camera equipped with a second bandpass filter that transmits a wavelength different from that transmitted by the first bandpass filter, wherein the half-mirror splits the light incident from the measurement target into the two paths for photographic recording by the CCD cameras, in order to transmit the light in real time to the first CCD camera equipped with the first bandpass filter and the second CCD camera equipped with the second bandpass filter, and to generate 2D temperature distribution data in real time based on output data corresponding to the recording.

[0008] In a further development of the invention, the 2D temperature measurement system can acquire radiation intensity data for each pixel with respect to the wavelengths used in the first bandpass filter and in the second bandpass filter based on the output data and generate 2D temperature distribution data for the measurement target by calculating a temperature for each pixel using the following formula: T={C2(λ1−λ2)} / {λ1λ2}ln[(Iλ1(T)Iλ2(T))k(ελ1λ15ελ1λ25)]

[0009] Here, T denotes the absolute temperature, λ1 and λ2 the wavelengths used in the first bandpass filter and the second bandpass filter respectively, ε λ1 and ε λ2 in each case the emissivity at the wavelengths of the corresponding filters, I λ1 (T) and I λ2(T) are the spectral radiation intensities of the radiation energy emitted by an object with a temperature T at the wavelengths of the corresponding filters, C2 is a secondary radiation constant with a value of 1.4388 × 10 -2 mK and k are a temperature calibration variable.

[0010] The 2D temperature measurement method according to the invention comprises the incident of light of a wavelength, which is emitted from a surface of a measurement target, onto a half-mirror, a reflection of approx.50% of the incident light is transmitted to a first CCD camera equipped with a first bandpass filter; the remaining 50% of the incident light is transmitted to a second CCD camera equipped with a second bandpass filter that transmits a wavelength different from that transmitted by the first bandpass filter; real-time output of data with respect to a wavelength used in the first bandpass filter based on an image captured by the first CCD camera; real-time output of data with respect to a wavelength used in the second bandpass filter based on an image captured by the second CCD camera; and calculation of a temperature for each pixel based on the output data to generate 2D temperature distribution data in real time.

[0011] Advantageous embodiments of the invention are illustrated in the drawings. These and further embodiments of the invention are explained in more detail below. The drawings show: Fig. 1 a schematic representation of a 2D temperature measurement system according to one embodiment, Fig. 2 a characteristic curve diagram of relative response data of a 2D temperature measurement system of Fig. 1 usable CCD camera depending on the wavelength, Fig. 3 a block diagram of a 2D temperature measurement system according to an embodiment, Fig. 4 a flowchart of each step of a 2D temperature measurement procedure using the 2D temperature measurement system according to one embodiment and Fig. Figure 5 is a characteristic curve diagram showing a Planckian blackbody radiation curve as a function of temperature to illustrate a wavelength band limiting of a bandpass filter used in the 2D temperature measurement system according to one embodiment.

[0012] Detailed reference is now made to embodiments, examples of which are shown in the accompanying drawings, where the same reference numerals consistently denote the same elements. In this respect, the actual embodiments may differ in form and are not to be interpreted as being limited to the explanations set forth herein. Accordingly, the embodiments are described below with reference to the figures only to illustrate aspects of the present description.

[0013] The following describes embodiments of the invention in detail with reference to the accompanying drawings. However, the invention is not limited to the embodiments described below. Identical components in the drawings are designated by the same reference numerals and are not described repeatedly.

[0014] Fig. Figure 1 shows a conceptual diagram of a two-dimensional (2D) temperature measurement system according to one embodiment. Accordingly, the 2D temperature measurement system comprises a half-mirror 101, which splits incident light into two paths, and two CCD cameras 103a and 103b, each having a first and a second bandpass filter 102a and 102b, respectively, which transmit different wavelengths. The half-mirror 101 is configured to reflect 50% of the incident light and transmit the remaining 50%. It splits the light incident from a measurement target 100 into two paths and directs them to the first CCD camera 103a, which is equipped with the first bandpass filter 102a, and to the second CCD camera 103b, which is equipped with the second bandpass filter 102b, for photographic recording.Based on data output according to the recording by the first CCD camera 103a and the second CCD camera 103b, a radiation ratio of each pixel point can be calculated to measure the real-time 2D temperature distribution of the measurement target 100.

[0015] Fig. Figure 2 is a diagram of relative response data from a CCD camera as a function of wavelength, used in the real-time 2D temperature measurement system of Fig. 1 can be used. The 2D temperature measurement system of Fig. The CCD camera used typically requires adjustment, and any deviation should be minimized taking into account the camera's characteristics. This means that by normalizing the actual radiation intensity for each wavelength based on the relative response data as a function of wavelength, which varies depending on the camera manufacturer, the error in the measured temperature can be minimized. Fig. 2 is an actual radiation intensity I real normalized for each wavelength using equation 1 below: Ireal=I / (Relative response)

[0016] Fig. Figure 3 is a block diagram of a 2D temperature measurement system according to one embodiment. With reference to Fig. 3 A real-time 2D temperature measurement system 300 according to an embodiment can be configured to include a photographic recording unit 310, a data acquisition unit 320 and an evaluation unit 330.

[0017] The recording unit 310 can photographically capture a measurement target using the first CCD camera 103a, equipped with the first bandpass filter 102a, and the second CCD camera 103b, equipped with the second bandpass filter 102b, to generate camera output data. According to one embodiment, the first bandpass filter 102a and the second bandpass filter 102b can be configured to measure wavelengths from approximately 1200 nm to approximately 1400 nm.

[0018] The data acquisition unit 320 can acquire and store radiation intensity data for each pixel in relation to the wavelength used in the respective bandpass filter, based on the camera output data belonging to the wavelength used in the corresponding bandpass filter.

[0019] The evaluation unit 330 can generate 2D temperature distribution data for the measurement target by calculating a temperature for each pixel using equation 2 below, based on data stored in the data acquisition unit 320: T={C2(λ1−λ2)} / {λ1λ2}ln[(Iλ1(T)Iλ2(T))k(ελ1λ15ελ1λ25)]

[0020] Here, T denotes the absolute temperature, λ1 and λ2 the wavelengths used in the first bandpass filter and the second bandpass filter respectively, ε λ1 and ε λ2 the respective emissivity at the wavelengths of the corresponding filters, I λ1 (T) and I λ2(T) the respective spectral radiation intensities of the radiation energy emitted by an object with a temperature T at the wavelengths of the corresponding filters and C2 a secondary radiation constant with a value of 1.4388 × 10 -2 mK. k is a temperature calibration variable that corrects a temperature difference measured across two bandpass filters by adjusting a light intensity value for a wavelength (e.g. λ1) with a relatively larger light intensity.

[0021] For your information: Emissivity represents the ratio of the energy actually emitted to the energy emitted by an ideal black body and can have a value between 0 and 1. Equation 2 is an expression that corrects the temperature calibration using a value k after dividing radiation intensities for wavelengths and then providing a result as a value with respect to temperature, as shown in Equation 3 below: Iλ1(T)Iλ2(T)=ελ1λ15ελ1λ25(eC2λ2T−1)(eC2λ1T−1)

[0022] Equation 3 is obtained by substituting Wein's equation into the radiation intensities I according to Equation 4 below, i.e., an equation which describes the wavelength-specific distribution of the radiation energy emitted by an object. λ1 (T) and I λ2 (T) for each wavelength: I(λ1T)=ε(λ)⋅C1λ5⋅1eC2λT−1

[0023] Here, I(λ,T) denotes the spectral radiation intensity of the radiation energy emitted by an object with a temperature T at a wavelength λ, λ represents the wavelength, T the absolute temperature, ε(λ) the emissivity at a wavelength of λ, and C1 is a primary radiation constant, which is calculated as C1 = 2πhc 2 is calculated and has a value of 3.74177 × 10 -16 World Cup 2 C2 is a secondary radiation constant, which corresponds to C2 = hc / k B is calculated and has a value of 1.4388 × 10 -2 mK has. Here, h is Planck's constant with a value of 6.62607015 × 10 -34 Js, c is the speed of light with a value of 2.99792458 × 10 8 m / s, and k B Boltzmann's constant has a value of 1.380649 × 10 -23 J / K.

[0024] Fig. Figure 4 is a flowchart of the individual steps of a 2D temperature measurement procedure using the 2D temperature measurement system according to one embodiment. With reference to Fig. 4 In the 2D temperature measurement method according to one embodiment, light of a certain wavelength emitted from the surface of a measurement object can be incident on a half-mirror in step S410. Subsequently, in step S420, 50% of the incident light can be reflected in the half-mirror and transmitted to a first CCD camera equipped with a first bandpass filter, and the remaining 50% of the incident light can be transmitted in step S430 and transmitted to a second CCD camera equipped with a second bandpass filter.

[0025] Next, data regarding the wavelength used in the first bandpass filter can be output based on the image acquired with the first CCD camera in step S440, and data regarding the wavelength used in the second bandpass filter can be output based on the image acquired with the second CCD camera in step S450. Based on the output data, a temperature can be calculated for each pixel in step S460 to generate 2D temperature distribution data.

[0026] Fig. Figure 5 is a diagram showing a Planck blackbody radiation curve as a function of temperature to describe the wavelength bandlimiting of a bandpass filter used in the real-time 2D temperature measurement system according to one embodiment. In the diagram of Fig. 5 can be, if two points lie to the left of the maximum slope of λ maxwith the best SNR, as wavelengths λ1 and λ2 are taken for the first and second bandpass filters respectively, the difference between λ1 and λ2 is reduced if it is assumed that the ratio ελ2 / ελ1 of the emissivity is close to one, which is advantageous for error reduction.

[0027] In this context, Wein's equation can be differentiated from equation 4 to yield zero, which leads to λ max as determined as 2898 / T. To measure up to 2898 K, for example, the wavelength band limit can therefore lie between 0.7 µm and 1 µm. To improve the SNR, a wavelength band range just below 1 µm, particularly between 0.8 µm and 0.9 µm, can be advantageous.

[0028] The method described above can be provided as a computer program stored on a computer-readable recording medium for execution on a computer. The medium can permanently store an executable program or temporarily store it for execution or download. The medium can include various recording or storage devices in the form of a single piece of hardware or a combination of several hardware components and can be distributed over a network without being limited to a medium directly connected to a particular computer system. Examples of the medium include a magnetic medium such as a hard disk, floppy disk, and magnetic tape; an optical recording medium such as a compact disc (CD), read-only memory (ROM), and a digital versatile disc (DVD); a magneto-optical medium such as a floppy disk; a ROM; random access memory (RAM); flash memory; and so on.for storing a program command. Other examples of the medium could be a recording medium or a storage medium managed by an app store that distributes applications, a website that provides or distributes various software, a server, etc.

[0029] The methods, processes, or techniques disclosed herein can be implemented in various ways. For example, these techniques can be implemented in hardware, firmware, software, or a combination thereof. Those skilled in the art understand that the various exemplary algorithmic processes described in connection with the invention can be implemented using electronic hardware, computer software, or a combination thereof. To clearly explain this mutual substitution between hardware and software, various example processes have been described above in general terms from their functional perspective. Whether such a function is implemented as hardware or software depends on the design requirements imposed by the specific application and the overall system.Experts can implement the described features in various ways for specific applications, but such implementations should not be interpreted as being outside the scope of the disclosure.

[0030] In hardware implementation, a processing unit used to perform the techniques may be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), a processor, a controller, a microcontroller, a microprocessor, an electronic device, another electronic unit designed to perform the functions described herein, a computer, or a combination thereof.

[0031] Therefore, the various example operations described in connection with the invention can be implemented or performed by any combination of a general-purpose processor, DSP, ASIC, FPGA or other PLS, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. A general-purpose processor can be a microprocessor, but alternatively, the processor can be any other existing processor, controller, microcontroller, or state machine. The processor can also be implemented as a combination of computing devices, such as a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors coupled to a DSP core, or any other combination of components.

[0032] When implemented in firmware and / or software, techniques can be implemented as instructions stored on a computer-readable recording medium, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable PROM (EEPROM), flash memory, compact discs (CDs), magnetic or optical data storage devices, etc. The instructions can be executed by one or more processors or cause the processor(s) to perform certain aspects of the functions described herein.

[0033] When implemented in software, the foregoing operations can be stored on or transmitted via a computer-readable medium as one or more instructions or as code. Computer-readable media can include both computer storage media and communication media, including any media that facilitate the transfer of computer programs from one location to another. Storage media can be any available media accessible to a computer. Non-limiting examples of such computer-readable media include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to transmit or store desired program code in the form of instructions or data structures and that a computer can access.Furthermore, each connection is appropriately designated as a computer-readable medium.

[0034] For example, when software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted-pair cable, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted-pair cable, DSL, or wireless technologies such as infrared, radio, and microwave fall under the definition of the medium. The terms "disk" and "disc" as used here can include CDs, laserdiscs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs. "Disk" typically reproduces data magnetically, while "disc" reproduces data optically using lasers. Combinations of these are included in the category of computer-readable media.

[0035] Software modules can reside in RAM, flash memory, ROM, EPROM, EEPROM, registers, on hard disks, removable media, CD-ROMs, or any other known form of storage medium. A storage medium can be connected to a processor so that the processor can read information from or write information to the storage medium. Alternatively, the storage medium can be integrated into the processor. The processor and storage medium can reside within the ASIC. The ASIC can also reside within a user terminal. Alternatively, the processor and storage media can reside as separate components within the user terminal.

[0036] Although the embodiments described above have been described using aspects of the subject matter disclosed herein in one or more stand-alone computer systems, the disclosure is not limited thereto and can also be implemented in connection with any computing environment, such as a network or a distributed computing environment. Furthermore, the aspects of the subject matter of the disclosure can be implemented in a variety of processor chips or devices, and storage can similarly be provided across a variety of devices. These devices can include PCs, network servers, and portable devices.

[0037] The embodiments of the invention are not limited to those described above, and various alternatives, modifications and changes can be made within the scope that is obvious to a person skilled in the art in the field of the invention.

[0038] The real-time 2D temperature measurement system and method according to the invention can offer the advantages described below.

[0039] Limitations of single-point measurement that occur with existing two-color non-contact pyrometers can be overcome, and the temperature distribution of the entire surface of the object being measured can be monitored two-dimensionally in real time.

[0040] By using a bandpass filter instead of an infrared camera for a CCD camera, it is possible to improve inaccuracies regarding emissivity values ​​and to increase the accuracy of temperature measurement through mathematical calculation.

[0041] It is understood that the embodiments described here are to be considered only in a descriptive sense and not for the purpose of limitation. Descriptions of features or aspects within each embodiment should generally be considered as being available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it is clear to those skilled in the art that various changes in form and details can be made to them without departing from the teaching and scope of the invention as defined by the following claims. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] KR 10-2024-0183318

[0001]

Claims

[1] System for two-dimensional (2D) temperature measurement, comprising: - a half-mirror (101) designed to split light incident from a measuring target (100) into two paths by reflecting approximately 50% of the incident light and transmitting the remaining 50% of the incident light, - a first CCD camera (103a) equipped with a first bandpass filter (102a), and - a second CCD camera (103b) equipped with a second bandpass filter (102b) that transmits a wavelength different from the wavelength of the first bandpass filter, - wherein the half-mirror (101) splits the light incident from the measurement target (100) into the two paths in order to photographically record it, by directing the light in real time to the first CCD camera (103a) equipped with the first bandpass filter (102a) and to the second CCD camera (103b) equipped with the second bandpass filter (102b), and wherein 2D temperature distribution data are generated based on output data corresponding to the photographic recording in real time. [2] System according to claim 1, wherein an error of a measured temperature is minimized by normalizing an actual radiant light intensity for each wavelength on the basis of relative response data with respect to wavelengths of the first CCD camera and the second CCD camera. [3] System according to claim 1 or 2, wherein the first bandpass filter and the second bandpass filter are configured to measure a wavelength range from 1200 nm to 1400 nm. [4] System according to one of claims 1 to 3, wherein two points which have a maximum slope to the left of λ max in a Planck blackbody radiation curve, as wavelengths of the first and second bandpass filters are used. [5] System according to any one of claims 1 to 4, wherein the 2D temperature measurement system acquires radiation intensity data for each pixel with wavelengths used in the first bandpass filter and in the second bandpass filter based on the output data and generates 2D temperature distribution data for the object (100) by calculating a temperature for each pixel using the following formula: T={C2(λ1−λ2)} / {λ1λ2}ln[(Iλ1(T)Iλ2(T))k(ελ1λ15ελ1λ25)] where T denotes the absolute temperature, λ1 and λ2 denote the wavelengths used in the first bandpass filter and the second bandpass filter respectively, ε λ1 and ε λ2denote the respective emissivity at the wavelengths of the corresponding filters, I λ1 (T) and I λ2 (T) denotes the respective spectral radiation intensities of the radiation energy emitted by an object with a temperature T at the wavelengths of the corresponding filters, C2 a secondary radiation constant with a value of 1.4388 × 10 -2 mK is and k is a temperature calibration variable. [6] Methods for two-dimensional (2D) temperature measurement, comprising: - Light of a specific wavelength, emitted from a surface of a measurement target, strikes a half-mirror, - Reflecting approximately 50% of the incident light at the half-mirror to transmit the light to a first CCD camera equipped with a first bandpass filter, and transmitting the remaining 50% of the incident light to transmit the light to a second CCD camera equipped with a second bandpass filter that transmits a wavelength different from a wavelength of the first bandpass filter, - Outputting real-time data with respect to a wavelength used in the first bandpass filter based on the recording by the first CCD camera, - Outputting real-time data regarding a wavelength used in the second bandpass filter based on the recording by the second CCD camera and - Calculating a temperature for each pixel based on the output data to generate real-time 2D temperature distribution data. [7] Method according to claim 6, further comprising normalizing an actual radiant light intensity for each wavelength based on relative response data with respect to wavelengths of the first CCD camera and the second CCD camera in order to minimize an error of a measured temperature. [8] Method according to claim 6 or 7, wherein the first bandpass filter and the second bandpass filter are configured to measure a wavelength range from 1200 nm to 1400 nm. [9] Method according to any one of claims 6 to 8, wherein two points which have a maximum slope to the left of λ max in a Planck blackbody radiation curve, as wavelengths of the first and second bandpass filters are used. [10] Method according to any one of claims 6 to 9, wherein calculating the temperature for each pixel based on the output data comprises collecting radiation intensity data with respect to the wavelengths used in the first bandpass filter and in the second bandpass filter for each pixel based on the output data and generating 2D temperature distribution data for the measurement target by calculating a temperature for each pixel using the following formula: T={C2(λ1−λ2)} / {λ1λ2}ln[(Iλ1(T)Iλ2(T))k(ελ1λ15ελ1λ25)] where T denotes the absolute temperature, λ1 and λ2 denote the wavelengths used in the first bandpass filter and the second bandpass filter respectively, ε λ1 and ε λ2 denote the respective emissivity at the wavelengths of the corresponding filters, I λ1 (T) and I λ2(T) denotes the respective spectral radiation intensities of the radiation energy emitted by an object with a temperature T at the wavelengths of the corresponding filters, C2 a secondary radiation constant with a value of 1.4388 × 10 -2 mK is and k is a temperature calibration variable. [11] Computer-readable recording medium on which a computer program is stored to perform the 2D temperature measurement method according to any one of claims 6 to 10 on a computer system.

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