Temperature continuously variable infrared thermal imager shutter correction system and method

Abstract

This invention provides a temperature-variable infrared thermal imager baffle calibration system and method. The system includes a rotating base connected to a rotating mechanism, an infrared light window disposed on the rotating base, one side of the infrared light window facing the optical path of the infrared thermal imager, and the other side connected to a cooling component with a temperature sensor mounted on it. A heat dissipation component is disposed on the rotating base and mates with the cooling component. This invention enables highly reliable single-point and two-point calibration at a specific location on the infrared thermal imager's optical path, achieving non-uniform calibration of the infrared thermal imager without opening the cover, effectively reducing the maintenance cost of the infrared thermal imager and improving its calibration efficiency. This invention can achieve internal single-point and two-point calibration of the infrared thermal imager at different operating temperatures, solving the image non-uniformity problem caused by performance degradation of the infrared thermal imager after prolonged operation and long-term storage.

Description

Technical Field

[0001] This invention relates to a calibration system and method, particularly a temperature-variable infrared thermal imager baffle calibration system and method, belonging to the field of infrared thermal imaging technology. Background Technology

[0002] Cooled infrared detectors are the core components of infrared thermal imagers and are widely used in military, high-end civilian products, and other fields. Due to issues such as manufacturing processes and differences in readout circuit channels, infrared thermal imagers exhibit severe non-uniformity in their imaging. Therefore, non-uniformity correction is required under various conditions, including before leaving the factory, long-term storage, and after prolonged operation, to maintain the high-performance working condition of the infrared thermal imager.

[0003] Currently, in various infrared imaging applications, a calibration method combining two-point and single-point calibration is commonly used. Two-point calibration primarily utilizes two reference sources with different radiation intensities to ensure that the linear gain rate of change and bias of each pixel on the focal plane with respect to the same incident radiation intensity are consistent. Single-point calibration, on the other hand, uses a uniform radiation background as a reference source to update the bias. Two-point calibration typically uses a blackbody for calibration and requires removing the infrared thermal imager from the original equipment and calibrating the objective lens close to the blackbody target surface. Single-point calibration generally uses an internal baffle as a reference source for calibration.

[0004] With the diversified development of infrared thermal imager applications, traditional two-point and single-point calibration methods are struggling to meet the high-efficiency, high-implementability, and high-reliability non-uniform calibration requirements of modern products. For example, the longer storage time requirements of infrared thermal imagers are incompatible with the manufacturing processes of domestically produced infrared detectors, leading to deterioration in the photoelectric conversion performance of detector chips after long-term storage. This makes recalibrating the equipment without opening the cover significantly difficult. Furthermore, with the increasing integration of optoelectronic systems, the cost of separately removing the infrared component for maintenance or returning it to the factory for recalibration is high and impractical. The increasing operating temperature requirements of infrared thermal imagers mean that if the temperature is above or below the linear region of the two-point calibration coefficient when the single-point calibration baffle is inserted, it will severely affect the single-point calibration effect. Therefore, it is necessary to improve existing technologies. Summary of the Invention

[0005] To address the problems of high difficulty in non-uniformity correction, high maintenance costs, and low feasibility in existing infrared thermal imager correction systems and methods, this invention provides an infrared thermal imager baffle correction system and method with continuously variable temperature.

[0006] This invention is achieved through the following technical solution: a continuously variable temperature infrared thermal imager baffle calibration system, characterized in that it includes a rotating base connected to a rotating mechanism, an infrared light window disposed on the rotating base, one side of the infrared light window being opposite to the optical path of the infrared thermal imager, and the other side being connected to a cooling component with a temperature sensor mounted on it. The rotating base is provided with a heat dissipation component that mates with the cooling component, so that the temperature information detected by the temperature sensor is fed back to the controller, thereby controlling the cooling component to cool or heat. When the cooling component reaches the target temperature, the rotating mechanism drives the rotating base to rotate, causing the infrared light window on it to insert into or cut out of the optical path of the infrared thermal imager, so as to achieve non-uniform calibration of the infrared thermal imager without opening the cover, effectively reducing the maintenance cost of the infrared thermal imager and improving the calibration efficiency of the infrared thermal imager.

[0007] The rotating base is configured as a flat plate base with a large end and a small end. An infrared light window is located at the large end of the flat plate base, and the small end of the flat plate base is connected to the rotating mechanism so that various components can be installed through the rotating base and rotated under the drive of the rotating mechanism.

[0008] The infrared window includes a circular window located at the large end of the rotating base. The outer side of the circular window is provided with an infrared window plate, and the inner side is provided with inner and outer heat insulation rings. A cooling component is provided between the inner and outer heat insulation rings so that the cooling component can be inserted into the optical path of the infrared thermal imager as needed through the infrared window.

[0009] The cooling component includes a circular temperature equalization baffle with a rectangular window. The inner side of the temperature equalization baffle is set inside the circular window through an inner heat insulation ring, and the outer side is connected to an outer heat insulation ring. A semiconductor cooling chip is set inside the rectangular window and sandwiched between inner and outer thermal conductive silicone grease. The semiconductor cooling chip is electrically connected to the existing controller. A slot for placing a temperature sensor is provided on one side of the rectangular window of the temperature equalization baffle so that cooling or heating can be performed through the semiconductor cooling chip. The temperature sensor detects whether the temperature data of cooling or heating meets the requirements, and the controller decides whether to insert or cut out the infrared thermal imager optical path.

[0010] The temperature sensor is a thermistor.

[0011] The heat dissipation assembly includes a cover plate located inside the rotating base. A cooling fan is provided between the cover plate and the small end of the rotating base. The cover plate is provided with heat dissipation fins at the position where it connects with the cooling fan and with a number of heat dissipation holes at the position where it connects with the cooling assembly. This allows the heat dissipation assembly to heat the non-working surface of the cooling assembly on the rotating base, thereby ensuring the temperature control accuracy of the cooling assembly.

[0012] The rotating mechanism includes a DC motor and a motor mount connected to the DC motor. The main shaft of the DC motor passes through the motor mount and is connected to the rotating seat. The DC motor is electrically connected to a controller so that the rotating mechanism can be controlled by the controller to drive the rotating seat to rotate.

[0013] A limiting piece is provided between the rotating mechanism and the rotating seat to limit the rotation angle of the rotating seat.

[0014] This invention provides a method for correcting the baffle of an infrared thermal imager with continuously variable temperature, characterized by comprising the following steps:

[0015] (1) Set the target temperature Td based on the single-point correction temperature Ts, the two-point correction low temperature TL, or the two-point correction high temperature TH;

[0016] (2) Set the sampling frequency Fs, and calculate the time interval Sr between two adjacent sampling times k and k-1 using the following formula:

[0017]

[0018] (3) Based on the current resistance value R0(k) of the thermistor, calculate the temperature T of the temperature equalizing baffle at the current moment using the following formula. n (k) is:

[0019]

[0020] In the formula, T0 and R0 are the reference temperature and the resistance value corresponding to the reference temperature of the thermistor, respectively, which are usually obtained by testing at 25℃; β is the thermistor exponential variation coefficient, which is determined by the selection of the thermistor.

[0021] (4) The discrete PID temperature control quantity Y(k) is calculated using the following formula:

[0022] Y(k)=K p e(k)+K i Σe(k)+K d [e(k)-e(k-1)]

[0023] In the formula, K p K i K d These are the proportional coefficient, integral coefficient, and differential coefficient, respectively. For semiconductor refrigeration chips, the empirical coefficients obtained after multiple experiments are: 1, 4, and 8; e(k) is the difference between the current temperature of the temperature equalization baffle Tn(k) and the desired temperature Td.

[0024] (5) Calculate the driving voltage U of the semiconductor cooling chip using the following formula. T (k):

[0025]

[0026] In the formula, Y NT The normalized threshold for temperature control parameters affects the temperature rise and fall rates of the thermoelectric cooler and is determined by the designer; Umax This is the maximum driving voltage of the thermoelectric cooler, which is determined by the thermoelectric cooler model.

[0027] (6) The driving voltage U of the semiconductor cooling chip is controlled by the controller. T (k) outputs to a semiconductor cooling chip, driving it to heat or cool the temperature equalization baffle to the target temperature Td.

[0028] This invention also provides a method for correcting non-uniformity of infrared thermal imager baffles with continuously variable temperature, characterized by comprising the following steps:

[0029] (1) When a serial port command is received from the computer, the serial port command is decoded to obtain the calibration method and calibration temperature information, and the following single-point calibration mode or two-point calibration mode is selected.

[0030] (1-1) When the single-point calibration mode is selected, the controller drives the DC motor to rotate the rotating seat and insert it into the optical path of the infrared thermal imager to complete the baffle insertion. The controller controls the semiconductor cooling chip to cool or heat the thermoelectric baffle by the temperature information fed back by the temperature sensor, so as to heat or cool the thermoelectric baffle to reach the single-point calibration temperature Ts. Then, the controller synchronously controls the infrared thermal imager to perform single-point calibration.

[0031] (1-11) Synchronously control the infrared thermal imager to determine whether the single-point calibration result is valid. When the single-point calibration completion instruction is returned by the infrared thermal imager, drive the DC motor to rotate the rotating seat and leave the optical path of the infrared thermal imager to complete the baffle cutting out and stop the semiconductor cooling chip from working. When the single-point calibration invalid instruction is returned by the infrared thermal imager, the single-point calibration is performed again. If the result is still invalid after three single-point calibrations, report to the system and issue a fault instruction.

[0032] (1-2) When the two-point calibration mode is selected, the low-temperature calibration is completed first. The controller drives the DC motor to rotate the rotating seat and insert it into the optical path of the infrared thermal imager to complete the baffle insertion. The controller controls the semiconductor cooling chip to cool or heat the temperature equalization baffle based on the temperature information fed back by the temperature sensor, so as to heat or cool the temperature equalization baffle to make it reach the two-point calibration low-temperature temperature TL. Then, the infrared thermal imager is controlled to perform two-point calibration low-temperature calibration. After receiving the low-temperature acquisition completion command returned by the infrared thermal imager, the two-point calibration low-temperature calibration continues.

[0033] (1-3) After the two-point calibration low temperature is completed, the high temperature calibration is performed; the controller controls the semiconductor cooling chip to cool or heat the thermoelectric baffle by the temperature information fed back by the temperature sensor, so as to heat or cool the temperature equalization baffle and make it reach the two-point calibration high temperature TH; after the temperature is reached, the infrared thermal imager is synchronously controlled to perform two-point calibration high temperature calibration.

[0034] (1-4) Synchronously control the infrared thermal imager to determine whether the two-point correction result is valid. When the infrared thermal imager returns a two-point correction completion instruction, drive the DC motor to rotate the rotating seat and leave the infrared thermal imager optical path to complete the baffle cutting out and stop the semiconductor cooling chip from working. When the infrared thermal imager returns a two-point correction invalid instruction, repeat the two-point correction operation. If the result is still invalid after three single-point corrections, report to the system and issue a fault instruction.

[0035] This invention has the following advantages and effects: Using the above scheme, highly reliable single-point and two-point calibration can be achieved at a specific location on the optical path of the infrared thermal imager. Non-uniform calibration of the infrared thermal imager can be achieved without opening the cover, effectively reducing the maintenance cost of the infrared thermal imager and improving its calibration efficiency. This invention can achieve internal single-point and two-point calibration of the infrared thermal imager at different operating temperatures, solving the image non-uniformity problem caused by performance degradation after prolonged operation and storage. Attached Figure Description

[0036] Figure 1 This is a system structure diagram of the present invention;

[0037] Figure 2 for Figure 1 Cross-sectional view;

[0038] Figure 3 This is a system principle block diagram of the present invention;

[0039] Figure 4 This is a flowchart of the correction method of the present invention;

[0040] Figure 5 This is an application effect diagram of Embodiment 1 of the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] Example 1

[0043] The temperature-variable infrared thermal imager baffle correction system provided by the present invention includes: a rotating base 4 connected to a rotating mechanism, an infrared light window provided on the rotating base 4, one side of the infrared light window being opposite to the optical path of the infrared thermal imager, and the other side being connected to a cooling component with a temperature sensor 13 on it, and a heat dissipation component mating with the cooling component on the rotating base 4.

[0044] The rotating base 4 is configured as a flat plate base with one large end and the other small end. The infrared light window is located at the large end of the flat plate base, and the small end of the flat plate base is connected to the rotating mechanism so that various parts can be installed through the rotating base 4 and rotate under the drive of the rotating mechanism.

[0045] The infrared light window includes a circular window 14 located at the large end of the rotating base 4. The outer side of the circular window 14 is provided with an infrared window plate 15, and the inner side is provided with inner and outer heat insulation rings 6 and 11. A cooling component is provided between the inner and outer heat insulation rings 6 and 11 so that the cooling component can be inserted into the optical path of the infrared thermal imager as needed through the infrared light window.

[0046] The cooling component includes a circular temperature equalization baffle 7 with a rectangular window. The inner side of the temperature equalization baffle 7 is set inside the circular window 14 through an inner heat insulation ring 6. The outer side of the temperature equalization baffle 7 is connected to an outer heat insulation ring 11. The rectangular window on the temperature equalization baffle 7 is provided with a semiconductor cooling chip 9 sandwiched by inner and outer thermal conductive silicone greases 8 and 10. The semiconductor cooling chip 9 is electrically connected to the existing controller. A slot for placing a temperature sensor 13 is provided on one side of the rectangular window of the temperature equalization baffle 7 so that the semiconductor cooling chip 9 can perform cooling or heating. The temperature sensor 13 sends the detected cooling or heating temperature data to the controller to determine whether the requirements are met. Then, under the control of the controller, the cooling component is inserted into or cut out of the infrared thermal imager optical path.

[0047] The temperature sensor 13 is configured as a thermistor;

[0048] The heat dissipation assembly includes a cover plate 12 located inside the rotating base 4. A heat dissipation fan 5 is provided between the cover plate 12 and the small end of the rotating base 4. Heat dissipation fins are provided at the position where the cover plate 12 is in contact with the heat dissipation fan 5, and a number of heat dissipation holes and slots are provided at the position where the cover plate 12 is in contact with the cooling assembly, so as to dissipate heat from the non-working surface of the cooling assembly on the rotating base 4 through the heat dissipation assembly, thereby ensuring the temperature control accuracy of the cooling assembly.

[0049] The rotating mechanism includes a DC motor 1 and a motor base 2 connected to the DC motor 1. The main shaft of the DC motor 1 passes through the motor base 2 and is connected to the rotating base 4. The DC motor 1 is electrically connected to the controller so that the rotating mechanism can be controlled by the controller to drive the rotating base to rotate.

[0050] A limiting piece 3 is provided between the rotating mechanism and the rotating seat 4 to limit the rotation angle of the rotating seat 4.

[0051] Example 2

[0052] The present invention provides a method for correcting the baffle of an infrared thermal imager with continuously variable temperature, comprising the following steps:

[0053] (1) Set the target temperature Td based on the single-point correction temperature Ts, the two-point correction low temperature TL, or the two-point correction high temperature TH;

[0054] (2) Set the sampling frequency Fs, and calculate the time interval Sr between two adjacent sampling times k and k-1 using the following formula:

[0055]

[0056] (3) Based on the current resistance value R0(k) of the thermistor, calculate the temperature T of the temperature equalizing baffle at the current moment using the following formula. n (k) is:

[0057]

[0058] In the formula, T0 and R0 are the reference temperature and the resistance value corresponding to the reference temperature of the thermistor, respectively, which are usually obtained by testing at 25℃; β is the thermistor exponential variation coefficient, which is determined by the selection of the thermistor.

[0059] (4) The discrete PID temperature control quantity Y(k) is calculated using the following formula:

[0060] Y(k)=K p e(k)+K i Σe(k)+K d [e(k)-e(k-1)]

[0061] In the formula, K p K i K d These are the proportional coefficient, integral coefficient, and differential coefficient, respectively. For semiconductor refrigeration chips, the empirical coefficients obtained after multiple experiments are: 1, 4, and 8; e(k) is the difference between the current temperature of the temperature equalization baffle Tn(k) and the desired temperature Td.

[0062] (5) Calculate the driving voltage U of the semiconductor cooling chip using the following formula. T (k):

[0063]

[0064] In the formula, Y NT The normalized threshold for temperature control parameters affects the temperature rise and fall rates of the thermoelectric cooler and is determined by the designer; U max This is the maximum driving voltage of the thermoelectric cooler, which is determined by the thermoelectric cooler model.

[0065] (6) The driving voltage U of the semiconductor cooling chip is controlled by the controller. T (k) outputs to a semiconductor cooling chip, driving it to heat or cool the temperature equalization baffle to the target temperature Td.

[0066] The present invention provides a method for correcting non-uniformity of the baffle in an infrared thermal imager with continuously variable temperature, comprising the following steps:

[0067] (1) When a serial port command is received from the computer, the serial port command is decoded to obtain the calibration method and calibration temperature information, and the following single-point calibration mode or two-point calibration mode is selected.

[0068] (1-1) When the single-point correction mode is selected, the controller drives the DC motor 1 to rotate the rotating seat 4 and insert it into the optical path of the infrared thermal imager to complete the baffle insertion. The controller controls the semiconductor cooling chip 9 to cool or heat through the temperature information fed back by the temperature sensor 13, and transmits the heating or cooling temperature to the uniform temperature baffle 7 so that it reaches the single-point correction temperature Ts. Then, the controller synchronously controls the infrared thermal imager to perform single-point correction.

[0069] (1-11) Synchronous control of the infrared thermal imager to determine whether the single-point calibration result is valid: When a single-point calibration completion instruction is received from the infrared thermal imager, the DC motor 1 is driven to rotate the rotating seat 4 and leave the optical path of the infrared thermal imager to complete the baffle cutting out and stop the semiconductor cooling chip 9 from working; when a single-point calibration invalid instruction is received from the infrared thermal imager, the single-point calibration is re-performed; if the result is still invalid after three single-point calibrations, the system is reported and a fault instruction is issued.

[0070] (1-2) When the two-point calibration mode is selected, the low-temperature calibration is completed first. The controller drives the DC motor 1 to rotate the rotating seat 4 and insert it into the optical path of the infrared thermal imager to complete the baffle insertion. The controller controls the semiconductor cooling chip 9 to cool or heat based on the temperature information fed back by the temperature sensor 13, and transmits the heating or cooling temperature to the temperature equalization baffle 7 to make it reach the two-point calibration low-temperature temperature TL. Then, the infrared thermal imager is synchronously controlled to perform two-point calibration low-temperature calibration. After receiving the low-temperature acquisition completion instruction returned by the infrared thermal imager, the two-point calibration low-temperature calibration continues.

[0071] (1-3) After the two-point calibration low temperature is completed, the high temperature calibration is performed. The controller controls the semiconductor cooling chip 9 to cool or heat through the temperature information fed back by the temperature sensor 13, and transmits the heating or cooling temperature to the uniform temperature baffle 7 so that it reaches the two-point calibration high temperature TH. Then, the infrared thermal imager is synchronously controlled to perform two-point calibration high temperature.

[0072] (1-4) Synchronous control of the infrared thermal imager to determine whether the two-point correction result is valid: When the infrared thermal imager returns a two-point correction completion instruction, the DC motor 1 is driven to rotate the rotating seat 4 and leave the infrared thermal imager optical path to complete the baffle cutting out and stop the semiconductor cooling chip 9 from working; when the infrared thermal imager returns a two-point correction invalid instruction, the two-point correction operation is repeated; when the result is still invalid after three single-point corrections, the system is reported and a fault instruction is issued.

[0073] Application Examples

[0074] The continuously variable temperature infrared thermal imager baffle correction system of the present invention was applied to a mid-wave 640×512 cooled infrared optoelectronic system. The baffle was installed 1 mm in front of the infrared detector window. The infrared thermal imager was turned on, and baffle correction was performed according to the steps of Examples 2 and 3, specifically two-point correction. After the two-point correction was completed, the non-uniformity of the output image was reduced, significantly improving the quality of the infrared image. Figure 5 The comparison before and after correction is shown.

Claims

1. A method for infrared thermal imager baffle correction based on a continuously variable temperature infrared thermal imager baffle correction system, characterized in that: The continuously variable temperature infrared thermal imager baffle correction system includes: a rotating base connected to a rotating mechanism, an infrared light window provided on the rotating base, one side of the infrared light window being opposite to the optical path of the infrared thermal imager, and the other side being connected to a cooling component with a temperature sensor on it, and a heat dissipation component mating with the cooling component provided on the rotating base. The infrared thermal imager baffle correction method includes the following steps: (1) Set the target temperature Td based on the single-point correction temperature Ts, the two-point correction low temperature TL, or the two-point correction high temperature TH; (2) Set the sampling frequency Fs, and calculate the time interval S between the adjacent two samples at time k and k-1 according to the following formula T is: ； (3) Based on the current thermistor resistance value R n (k), calculate the temperature T of the temperature-averaging baffle at the current moment using the following formula. n (k) is: ； In the formula, T0 and R0 are the reference temperature and the resistance value corresponding to the reference temperature of the thermistor, respectively, which are usually obtained by testing at 25℃; β is the thermistor exponential variation coefficient, which is determined by the selection of the thermistor. (4) The discrete PID temperature control quantity Y(k) is calculated using the following formula: ； In the formula, Kp, Ki, and Kd are the proportional coefficient, integral coefficient, and differential coefficient, respectively. For semiconductor refrigeration chips, the empirical coefficients obtained after multiple experiments are: 1, 4, and 8; e(k) is the difference between the current temperature of the temperature equalization baffle Tn(k) and the target temperature Td. (5) Calculate the semiconductor cooling chip driving voltage UT(k) using the following formula: ； In the formula, YNT is the normalized threshold of the temperature control quantity, which affects the temperature rise and fall rate of the thermoelectric cooler and is determined by the designer; Umax is the maximum driving voltage of the thermoelectric cooler, which is determined by the model of the thermoelectric cooler. (6) The controller outputs the semiconductor cooling chip driving voltage UT(k) to the semiconductor cooling chip, driving it to heat or cool the temperature equalization baffle to the target temperature Td.

2. The method for infrared thermal imager baffle correction based on a continuously variable temperature infrared thermal imager baffle correction system according to claim 1, characterized in that: The rotating base is configured as a flat plate base with one large end and the other small end. An infrared light window is located at the large end of the flat plate base, and the small end of the flat plate base is connected to the rotating mechanism.

3. The method for infrared thermal imager baffle correction based on a continuously variable temperature infrared thermal imager baffle correction system according to claim 1, characterized in that: The infrared window includes a circular window located at the large end of the rotating base. The outer side of the circular window is provided with an infrared window plate, and the inner side is fitted with inner and outer heat insulation rings. A cooling component is provided between the inner and outer heat insulation rings.

4. The method for infrared thermal imager baffle correction based on a continuously variable temperature infrared thermal imager baffle correction system according to claim 1, characterized in that: The cooling component includes a circular temperature equalization baffle with a rectangular window. The inner side of the temperature equalization baffle is set inside the circular window through an inner heat insulation ring, and the outer side is connected to an outer heat insulation ring. A semiconductor cooling chip is set inside the rectangular window and sandwiched between inner and outer thermal conductive silicone grease. The semiconductor cooling chip is electrically connected to the existing controller, and a slot for placing a temperature sensor is provided on one side of the rectangular window of the temperature equalization baffle.

5. The method for infrared thermal imager baffle correction based on a continuously variable temperature infrared thermal imager baffle correction system according to claim 1, characterized in that: The heat dissipation assembly includes a cover plate located inside the rotating base. A heat dissipation fan is provided between the cover plate and the small end of the rotating base. Heat dissipation fins are provided at the position where the cover plate connects with the heat dissipation fan, and several heat dissipation holes are provided at the position where the cover plate connects with the cooling assembly.

6. The method for infrared thermal imager baffle correction based on a continuously variable temperature infrared thermal imager baffle correction system according to claim 1, characterized in that: The rotating mechanism includes a DC motor and a motor mount connected to the DC motor. The main shaft of the DC motor passes through the motor mount and is connected to the rotating base. The DC motor is electrically connected to the controller.

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