Field infrared calibration emitter with automatic ambient temperature compensation

Abstract

FIELD: measurement technology.SUBSTANCE: invention concerns a field infrared calibration emitter with automatic compensation of the ambient temperature. The emitter comprises a radiating plate, a thermoelectric element, ambient and radiating surface temperature sensors, a control unit and user interface, a cooling system and a power source. The optical axis of the lens of the calibrated product coincides with the geometric axis of the emitting plate. The emitting plate is equipped with a thin-walled metal cylinder, eliminating lateral illumination. The control unit is implemented on a microcontroller with a PID controller, which ensures automatic measurement of the current ambient temperature and stabilization of the radiating surface temperature at levels relative to the measured temperature. The internal diameter of the cylinder and the size of the emitting plate exceed the diameter of the lens of the calibrated device by at least 5%.EFFECT: increasing the accuracy and repeatability of calibration in field conditions.5 cl, 1 dwg

Description

[0001] The invention relates to measuring equipment and thermal imaging equipment, in particular to external calibration radiation sources for calibrating thermal imaging devices, and can be used in metrological support, adjustment and verification of thermal imagers and thermographic systems in laboratory and field conditions.

[0002] A technical solution is known for an extended infrared calibration emitter (Russian Federation Patent for Utility Model No. 223444, dated December 14, 2023). The emitter comprises a housing with a fixed emitting surface based on thermoelectric modules, a temperature sensor attached to the outer surface of the emitting surface, a cooling radiator attached to the inner surface of the emitting surface, and tubes supplying coolant to the radiator. The emitting surface is designed to generate a dynamic thermal image and is divided into independently controlled sections.

[0003] The disadvantage is that this technical solution uses a bulky liquid cooling system with supply pipes, which significantly increases the device's size, reduces its mobility, and complicates field use directly at the operating site. Furthermore, there is no automatic ambient temperature compensation, requiring additional adjustments as operating conditions change.

[0004] A technical solution is known for a method of calibrating a thermal imaging device on a microbolometric matrix and a device for its implementation (Russian Federation Patent for Invention No. 2569170C1 dated 05 / 29 / 2014), containing a method of calibration directly during the operation of the device on a microbolometric matrix for the accurate determination of the temperature of the observed object using an internal calibration device.

[0005] The disadvantage is that this method leads to a decrease in the size of the observed scene during the operation of the device and requires interruption of the observation process for calibration, which is unacceptable in a number of practical applications that require continuous monitoring.

[0006] A technical solution is known for a black body simulator (RU Patent for Invention No. 497482 dated 06.02.1973), containing a first cavity with an outlet opening and a second hollow body with openings on opposite walls, coaxial with the opening of the first cavity, and a modulator located inside it, with the purpose of obtaining calibrated radiation flows corresponding to small temperature contrasts.

[0007] The disadvantage of this device is the presence of several similar devices for the purpose of forming temperature fields of different levels, which leads to a significant increase in the weight and size of the calibration complex and introduces additional errors due to the need to coordinate the operation of several emitters.

[0008] The closest technical solution to the proposed solution is a two-point, long-surface radiation source for field use (China Patent for Invention CN102680108A dated 05 / 09 / 2012), which contains two structurally combined infrared radiation sources that are used to calibrate and test thermographic equipment in positive and negative temperature ranges relative to the ambient temperature.

[0009] The disadvantage of this solution is the use of two separate radiation sources for calibration in the positive and negative temperature ranges, which increases the device's size, complexity, and hardware requirements. Furthermore, it lacks the ability to automatically compensate for ambient temperature and generate dynamic thermal scenes, which are necessary for fully verifying calibration quality directly in the field. This solution also does not provide the ability to construct a multi-point response curve for the matrix near operating temperature without the use of thermal chambers or a stationary workstation.

[0010] The technical objective of this invention is to create a compact and mobile external IR calibrator that provides two-point calibration of thermal imaging devices directly at the place of operation without liquid cooling, with automatic compensation for the current ambient temperature and the ability to generate dynamic thermal scenes.

[0011] The technical result consists of increasing the accuracy and repeatability of calibration in field conditions due to automatic compensation of the ambient temperature; reducing the weight, size and power consumption due to the elimination of liquid cooling; ensuring two-point calibration with a single source (hot / cold frames) at specified temperature contrasts relative to the ambient temperature; eliminating lateral parasitic illumination during calibration; ensuring uniform filling of the field of view of the device being calibrated.

[0012] The stated problem is solved due to the fact that the field infrared calibration emitter with automatic compensation of the ambient temperature, containing a emitting plate, a thermoelectric element, ambient and emitting surface temperature sensors, a control unit and a user interface, a cooling system and a power source, the optical axis of the lens of the product being calibrated coincides with the geometric axis of the emitting plate, while the emitting plate is equipped with a thin-walled metal cylinder that eliminates lateral illumination, while the control unit is implemented on a microcontroller with a PID controller that provides automatic measurement of the current ambient temperature and stabilization of the emitting surface temperature at levels relative to the measured temperature, with the formation of an indication of the readiness of "hot" and "cold" frames on the user interface, and the cooling system is implemented without a liquid circuit,The internal diameter of the cylinder and the size of the emitting plate exceed the diameter of the lens of the device being calibrated by at least 5%. The device contains a keypad and indicator unit for entering and displaying temperature sensor parameters and operating modes. The device contains a thermoelectric element capable of reversing the polarity of the current for rapid transition between heating and cooling modes. The power supply unit contains a battery pack with a control board for charging, discharging, and balancing the battery cells. In the automatic calibration mode of the thermal imaging device, the ambient temperature is measured, the emitting surface temperature is stabilized relative to the measured temperature, "hot" and "cold" frames are sequentially recorded by the calibrated device, and the data is transmitted for calculating corrections.

[0013] The essence of the proposed technical solution is explained by the following diagram in Fig. 1.

[0014] This device contains:

[0015] 1 - plate

[0016] 2 - cylinder-screen

[0017] 3 - keyboard and indicator unit

[0018] 4 - Environmental Sensors

[0019] 5 - radiating surface sensors

[0020] 6 - microcontroller

[0021] 7 - PID controller

[0022] 8 - thermoelectric element

[0023] 9 - cooling system

[0024] 10 - power supply

[0025] 11 - body

[0026] The body 11 is made of aluminum alloy.

[0027] The housing of the field infrared calibration emitter with automatic ambient temperature compensation includes the following parts.

[0028] The radiating plate 1 is made of aluminum alloy with a surface coating that makes its emissivity approach that of a black body.

[0029] Screen cylinder 2 is made of thin-walled metal, eliminating lateral parasitic illumination of the photodetector during the calibration process with the ability to form a uniform field, while the inner diameter of the cylinder and the size of the emitting plate exceed the diameter of the lens of the device being calibrated by at least 5%.

[0030] Keyboard and indicator unit 3 consists of a keyboard and a display with the ability to enter and display temperature sensor parameters and operating modes.

[0031] The environment sensors 4 and the radiating surface sensors 5 measure the temperature and transmit its values ​​to the microcontroller 6.

[0032] PID controller 7 sets the required polarity and magnitude of current to thermoelectric element 8.

[0033] The thermoelectric element 8 Peltier is installed on the inner side of the radiating plate 1 and is connected to the cooling system 9.

[0034] The thermoelectric element 8 is designed with the ability to reverse the polarity of the current for rapid transition between heating and cooling modes.

[0035] The cooling system 9 is equipped with a radiator and a fan to effectively dissipate heat and ensures the removal or drive of thermal energy on the back side of the thermoelectric element 8, the cooling system 9 is designed without a liquid circuit.

[0036] The power supply 10 is a power supply unit containing a battery pack with a control board for charging, discharging and balancing battery cells.

[0037] The device works as follows:

[0038] Turn on the PC (not shown in Fig. 1), launch specialized software.

[0039] An infrared calibration emitter is installed in front of the calibrated item so that the optical axis of the calibrated item's lens (not shown in the figure) coincides with the geometric axis of emitting plate 1. Emitting plate 1 is equipped with a thin-walled metal cylinder 2, which eliminates lateral stray illumination of the photodetector during calibration. The lens diameter of the calibrated device must be at least 5% smaller than the size of emitting plate 1 and the inner diameter of thin-walled metal cylinder 2, respectively, to ensure uniform filling of the calibrated device's field of view.

[0040] Before calibration, the required temperature parameters are set using the interface, which includes the keypad and indicator unit 3. Ambient temperature sensors 4 and radiating surface temperature sensors 5 transmit data to the microcontroller board 6, which controls the PID controller 7.

[0041] PID controller 7 sets the required polarity and magnitude of current to thermoelectric element 8. Cooling system 9 ensures the removal or supply of thermal energy on the back side of thermoelectric element 8.

[0042] The device is powered by a 10-volt power supply with a battery pack, with a control board for charging, discharging and balancing batteries.

[0043] The device automatically measures the ambient temperature at the location where the calibrated instrument is operating. The emitting plate 1 is then heated relative to the ambient temperature by +5°C under the control of ambient temperature sensor 4 and emitting surface sensors 5. The image ("hot frame") is then recorded in the calibrated instrument's memory for subsequent data transfer to a PC (not shown in the figure) with specialized software via a wireless or wired interface. The message "hot frame generated" is displayed on the keypad and indicator unit 3.

[0044] Then, emitting plate 1 is cooled relative to the ambient temperature by -5°C under continuous monitoring by ambient temperature sensor 4 and emitting surface sensor 5. Upon reaching the specified temperature, the image ("cold frame") is recorded in the memory of the calibrated device for subsequent data transfer to a PC with specialized software and adjustment of the calibrated device's parameters in accordance with the received data. The message "cold frame generated" is displayed on keyboard and indicator unit 3.

[0045] Emitting plate 1 is equipped with a thin-walled metal cylinder 2, which prevents lateral illumination of the photodetector during calibration and is designed to align the optical axis of the lens of the calibrated device with the geometric axis of the plate. To ensure uniform field of view, the lens diameter of the calibrated device is selected to be at least 5% smaller than the size of emitting plate 1 and the inner diameter of cylinder 2.

[0046] The temperature parameters are set from the keypad and indicator unit. Ambient temperature sensors 4 and radiating surface temperature sensors 5 send signals to microcontroller 6, which implements a PID control algorithm 7 and determines the polarity and magnitude of the current through thermoelectric element 8. Cooling system 9 provides heat transfer to the back of the Peltier element without the use of a liquid circuit. Power is supplied by a standalone power supply 10 with a battery pack and a control board for charging, discharging, and balancing the batteries.

[0047] This achieves the following technical and operational benefits: automatic compensation for ambient temperature, resulting in improved field calibration accuracy; two-point calibration with a single source without interrupting observations or using liquid cooling circuits; elimination of side illumination and improved field uniformity thanks to a thin-walled cylinder screen; portability and autonomy thanks to a battery powered device with an intelligent control system; the ability to implement dynamic thermal scenes and construct a multi-point response characteristic near the operating temperature.

[0048] Based on the above, it follows that the problem of creating a compact device for field two-point calibration of thermal imaging devices, providing automatic compensation for ambient temperature and high stability of temperature levels, has been solved.

Claims

1. A field infrared calibration emitter with automatic compensation of the ambient temperature, comprising a emitting plate, a thermoelectric element, ambient and emitting surface temperature sensors, a control unit and a user interface, a cooling system and a power source, characterized in that the optical axis of the lens of the product being calibrated coincides with the geometric axis of the emitting plate, wherein the emitting plate is provided with a thin-walled metal cylinder that eliminates lateral illumination, wherein the control unit is implemented on a microcontroller with a PID controller that ensures automatic measurement of the current ambient temperature and stabilization of the emitting surface temperature at levels relative to the measured temperature, with the formation of an indication of the readiness of "hot" and "cold" frames on the user interface, wherein the cooling system is implemented without a liquid circuit,and the internal diameter of the cylinder and the size of the emitting plate exceed the diameter of the lens of the calibrated device by at least 5%.

2. The device according to paragraph 1, characterized in that it contains a keyboard-indicator unit for entering and displaying the parameters of temperature sensors and operating modes.

3. The device according to paragraph 1, characterized in that the thermoelectric element is designed with the possibility of reversing the polarity of the current for a quick transition between heating and cooling modes.

4. The device according to paragraph 1, characterized in that the power supply unit contains a battery pack with a board for controlling the charge, discharge, and balancing of battery cells.

5. The device according to paragraph 1, characterized in that in the automatic calibration mode of the thermal imaging device, the ambient temperature is measured, the temperature of the emitting surface is stabilized relative to the measured temperature, “hot” and “cold” frames are sequentially recorded by the device being calibrated, and data is transmitted for calculating corrections.

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