Continuous self-adaptive range infrared temperature measuring device based on polarization attenuation

Abstract

The invention provides a continuous self-adaptive range infrared temperature measuring device based on polarization attenuation, which relates to the technical field of infrared temperature measurement and imaging and comprises a polarizing film, a polarization analyzing film, a film angle controller, a thermal infrared imager and an industrial personal computer. The polarizing polaroid is fixedly arranged in front of a lens of the thermal infrared imager or in an internal light path, and the polarization analyzing polaroid is arranged behind the polarizing polaroid, so that a variable infrared light attenuator is formed; the polaroid angle controller is connected with the polarization analyzing polaroid and used for driving the polarization analyzing polaroid to rotate around the optical axis and feeding back angle information; the thermal infrared imager is placed behind the variable infrared light attenuator, is connected with the polaroid angle controller and sends a control instruction, and the thermal infrared imager is in communication connection with the industrial personal computer; and the industrial personal computer stores the transmittance-angle calibration curve and calculates the transmittance according to the angle information so as to compensate the temperature value. According to the invention, dynamic continuous adjustment of the temperature measurement range is realized, and infrared image saturation is prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of infrared temperature measurement and imaging technology, and particularly relates to a continuous self-adaptive range infrared temperature measurement device based on polarization attenuation. BACKGROUND

[0002] Infrared thermal imaging temperature measurement technology has been widely applied in extreme environments such as monitoring of the first wall of a nuclear fusion device, high-temperature material experiments, industrial furnaces and flame diagnosis. In these application scenarios, the temperature of the measured target often needs to be dynamically changed in a very wide range, for example, the temperature of the first wall material of a nuclear fusion device can rise from room temperature (about 20°C) to several thousand degrees Celsius.

[0003] However, the effective temperature measurement range of the traditional infrared thermal imager is usually narrow (generally less than 1000°C) due to the inherent dynamic range of the infrared detector. When the temperature of the measured target rises to the saturation threshold of the detector, excessive infrared radiation will cause the pixels of the detector to saturate, resulting in image overexposure, loss of details and distortion of temperature measurement data, and the temperature distribution of the high-temperature region cannot be accurately obtained.

[0004] To solve the above problems, the existing technology mainly adopts the following two schemes:

[0005] 1. Adjusting the exposure time (integration time): by shortening the exposure time of the infrared thermal imager to reduce the number of photons received by the detector, so as to avoid high-temperature saturation. However, too short exposure time will significantly reduce the image signal-to-noise ratio, resulting in a decrease in the imaging quality of low-temperature targets and a decrease in the temperature measurement accuracy, and the clear imaging of high- and low-temperature targets cannot be simultaneously considered.

[0006] 2. Neutral density filter switching: using an internal switchable fixed transmittance filter (such as transmittance 65%, 10% discrete gears) to attenuate the radiation intensity entering the detector. Although this method can extend the upper limit of temperature measurement to a certain extent, it has obvious defects: the attenuation ratio of the filter is fixed and discrete, and cannot realize continuous and smooth adjustment of the transmittance, and when facing intermediate temperature scenes, only the closest fixed gear can be selected, and the optimal transmittance cannot be accurately matched; in addition, there is a time delay (usually > 50 ms) and mechanical vibration in the switching process of the mechanical filter wheel, which is easy to introduce transient errors and image discontinuity, and the difference in optical path of different filters may cause radiation correction deviation.

[0007] Another prior art (such as CN111623885B) calibrates the power supply voltage and the ambient temperature through an electronic compensation algorithm, which can improve the measurement stability, but belongs to the rear-end signal processing and cannot solve the physical saturation problem of the front-end optical system; another prior art (such as CN111947786A) adjusts the optical distance through a mechanical step, which only changes the focusing position and does not have the dynamic range adjustment capability; another prior art (such as CN116448249B) suppresses stray light through a light guide cylinder and a light shield plate, which can improve the signal-to-noise ratio, but cannot expand the temperature measurement range or prevent high-temperature saturation.

[0008] Therefore, there is currently a lack of a solution in the field of infrared temperature measurement that can continuously adjust the infrared transmittance, adapt to the wide range in real time, and does not require mechanical switching, which is difficult to meet the demand for seamless continuous monitoring from room temperature to thousands of degrees Celsius. SUMMARY

[0009] To solve the problems that the temperature measurement range of the infrared temperature measurement system cannot be adaptively and continuously expanded, the transmittance jumps and the measurement is discontinuous caused by the traditional discrete gear switching, the detector cannot maintain the low-temperature measurement accuracy while being saturated at high temperature, and the real-time continuity and data accuracy of wide-range temperature measurement cannot be achieved, the present application provides a continuous adaptive range infrared temperature measurement device based on polarization attenuation. The present application can achieve adaptive and continuous expansion of the temperature measurement range of the infrared temperature measurement system, and balance high-temperature unsaturation and low-temperature high signal-to-noise ratio. When the temperature of the measured object changes in a very wide range, the infrared thermal imager can neither be saturated and distorted due to high-temperature strong signals nor provide sufficient signal-to-noise ratio at low-temperature weak signals. The present application can automatically adjust the infrared transmittance of the variable infrared light attenuator according to the temperature of the measured object, realize dynamic and continuous adjustment of the temperature measurement range, and prevent the infrared image from being saturated.

[0010] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0011] A continuous adaptive range infrared temperature measurement device based on polarization attenuation, comprising a polarizing polarizer, an analyzing polarizer, a polarizer angle controller, an infrared thermal imager, and an industrial computer. The polarizing polarizer is fixedly installed in front of the lens of the infrared thermal imager or in the internal light path, the analyzing polarizer is installed behind the polarizing polarizer and placed coaxially with the polarizing polarizer, and the polarizing polarizer and the analyzing polarizer constitute a variable infrared light attenuator. The polarizer angle controller is connected to the analyzing polarizer and is used to drive the analyzing polarizer to rotate around the optical axis and feed back the angle information. The infrared thermal imager is placed behind the variable infrared light attenuator, the infrared thermal imager is connected to the polarizer angle controller and sends control instructions, and the infrared thermal imager is in communication connection with the industrial computer. The industrial computer stores the transmittance-angle calibration curve and calculates the transmittance according to the angle information to compensate the temperature value.

[0012] Advantages:

[0013] 1. This invention utilizes Malus's law to achieve continuous and smooth adjustment of infrared light transmittance within the range of 0% to 50% through a variable infrared light attenuator composed of two polarizers. Compared to existing discrete filter switching schemes, this invention achieves precise stepless adjustment of transmittance without mechanical switching, avoiding measurement discontinuities, transient errors, and image blurring caused by transmittance jumps. It allows setting the optimal transmittance for any intermediate temperature scenario, achieving seamless range coverage from room temperature to thousands of degrees Celsius.

[0014] 2. When the temperature of the analyte increases, leading to enhanced infrared radiation, this invention automatically increases the polarizer angle through closed-loop control, introducing optical attenuation to reduce the radiation intensity entering the detector, thereby effectively preventing sensor saturation. Compared to existing technologies that only shorten the exposure time (leading to a decrease in signal-to-noise ratio) or fix the filter (which cannot be continuously adjusted), this invention, without changing the detector integration time, uses purely optical means to raise the effective temperature measurement upper limit to a level far exceeding the detector's original saturation temperature, meeting the monitoring needs of extreme high-temperature environments such as the first wall of nuclear fusion.

[0015] 3. When the temperature of the target being measured is low, the system sets the polarizer angle to close to 0° (parallel state). At this point, the transmittance is close to 50%, maximizing the passage of infrared signals. This ensures high signal-to-noise ratio imaging at low temperatures without shortening the exposure time. Compared to existing technologies that generally shorten the exposure time to avoid high-temperature saturation (leading to deterioration in low-temperature performance), this invention achieves a dynamic balance of "high-temperature attenuation fidelity preservation and low-temperature full-pass sensitivity preservation," obtaining clear and accurate infrared images across the entire measurement range.

[0016] 4. This invention forms a closed-loop feedback control system through an infrared thermal imager and a polarizer angle control mechanism. It monitors image grayscale in real time and automatically adjusts the polarizer angle, adapting to rapid changes in target temperature without manual intervention. Compared to mechanical filter switching schemes (which involve delays exceeding 50ms and mechanical vibration), the continuous rotation adjustment of the polarizer has no transient interruptions, resulting in a smoother and faster response. It can handle millisecond-level brightness changes, ensuring the continuity and stability of the temperature measurement process.

[0017] 5. This invention integrates an angle sensor on the controller to read the polarizer angle in real time. The industrial control computer calculates the current attenuator transmittance in real time based on a pre-stored transmittance-angle calibration curve, and performs radiation correction compensation on the output temperature of the infrared thermal imager in conjunction with the emissivity of the object being measured, eliminating temperature measurement deviations caused by the introduction of the attenuator. This invention achieves real-time quantitative compensation for optical attenuation, ensuring temperature measurement accuracy under dynamic attenuation conditions.

[0018] 6. The polarization attenuator of this invention consists of two polarizers and a rotation controller. Its structure is simple and compact, and it can be easily integrated as an independent module into the front end of existing infrared thermal imagers, achieving range extension without replacing the core detection equipment. The polarizers can be made of high-temperature resistant substrate materials such as zinc sulfide and zinc selenide, making them suitable for high-radiation, high-temperature, and complex environments such as fusion reactors, and exhibiting good electromagnetic compatibility and long-term stability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a continuous adaptive range infrared temperature measurement device based on polarization attenuation according to the present invention.

[0020] The attached diagram is labeled as follows: 1-Object under test; 2-Polarizing filter; 3-Polarizing filter analyzer; 4-Polarizing filter angle controller; 5-Infrared thermal imager; 6-Industrial control computer. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0022] like Figure 1 As shown, the present invention provides a continuous adaptive range infrared temperature measurement device based on polarization attenuation, comprising a polarizing polarizer 2, a polarizing analyzer 3, a polarizer angle controller 4, an infrared thermal imager 5, and an industrial control computer 6. The polarizing polarizer 2 and the polarizing analyzer 3 form a variable infrared light attenuator, placed in the optical path of the infrared thermal imager 5, with the polarizing polarizer 2 closer to the object being measured 1. By controlling the angle between the polarizing polarizer 2 and the polarizing analyzer 3, the infrared light transmittance is continuously adjustable. The infrared thermal imager 5 monitors the image exposure status in real time and automatically adjusts the angle between the polarizing polarizer 2 and the polarizing analyzer 3 to avoid overexposure or underexposure. The industrial control computer 6 calculates the transmittance of the variable infrared light attenuator based on the angle between the polarizing polarizer 2 and the polarizing analyzer 3, and corrects and compensates the temperature value measured by the infrared thermal imager 5 to obtain the true temperature of the object being measured 1. When the temperature of the object being measured changes dynamically, the system's temperature measurement range is also dynamically adjusted accordingly, always maintaining accurate temperature measurement. The polarizer angle controller 4 is mechanically connected to the polarizer 3 and is driven by electromagnetic force. First, a permanent magnet is installed on the edge of the polarizer 3, and a stator is set around the polarizer 3 to generate a magnetic field. At this time, the polarizer 3 is equivalent to the rotor of the motor. The infrared thermal imager 5 sends the preset angle of the polarizer to the polarizer angle controller 4 through the signal line. The polarizer angle controller 4 drives the polarizer 3 to rotate to the preset angle by controlling the direction of the magnetic field in the armature.

[0023] Specifically, the object under test 1 serves as the temperature measurement target; it is an object that emits infrared radiation, and its surface temperature needs to be measured. The object under test 1 is positioned in front of the polarizing filter 2.

[0024] Specifically, the polarizing filter 2 is fixedly installed in front of the lens or in the internal optical path of the infrared thermal imager 5. Its function is to convert the unpolarized infrared thermal radiation emitted by the object under test 1 into linearly polarized light with a specific polarization direction. Ideally, the light intensity after passing through the polarizing filter 2 is about half of the incident light intensity, which is a characteristic of natural light after passing through a polarizer.

[0025] Specifically, the polarizer 3 is mounted behind the polarizer 2 and placed coaxially. The polarizer 3 can rotate around the optical axis, and the angle between it and the transmission axis of the polarizer 2 is denoted as θ. The polarizer 2 and the polarizer 3 together constitute a variable infrared light attenuator. According to Malus's law, the light intensity I after passing through the polarizer 3 satisfies the following condition relative to the light intensity I0 after polarization: In other words, when the polarizing polarizer 2 and the analyzing polarizer 3 are parallel (θ≈0°), light transmission is maximized; when they are perpendicular (θ=90°), ideally the light intensity approaches zero (actual polarizers have non-ideal extinction ratios, resulting in very weak light leakage). By adjusting θ within the range of 0° to 90°, the transmitted light intensity can be continuously controlled between 100% and near 0%. Therefore, the polarizing polarizer 2 and the analyzing polarizer 3 act as continuously adjustable infrared neutral density filters.

[0026] Specifically, the polarizer angle controller 4 is connected to the polarizer 3, used to drive it to rotate around the optical axis, and can accurately feedback the current angle value. The polarizer angle controller 4 can use a stepper motor or servo motor linked with an encoder to achieve high-resolution angle control (e.g., 0.1° or finer), and transmit the angle information to the infrared thermal imager 5 or industrial control computer 6 in real time. The polarizer angle controller 4 receives control commands from the data processing unit of the infrared thermal imager 5 to achieve closed-loop adjustment.

[0027] Specifically, the infrared thermal imager 5 is placed after a variable infrared light attenuator for direct imaging and temperature measurement. The infrared thermal imager 5 itself has a certain temperature measurement range and exposure control capability. When the temperature of the object being measured 1 is low, the infrared thermal imager 5 can use a longer exposure time to obtain a clear image with a high signal-to-noise ratio; as the temperature of the object increases, traditional infrared thermal imagers may experience pixel saturation or overexposure if no measures are taken. In this invention, the data processing unit built into the infrared thermal imager 5 continuously monitors the image signal. If it is found that the highest grayscale value in the image is close to the saturation threshold or a large number of pixels have reached saturation, the infrared thermal imager 5 immediately sends a command to the polarizer angle controller 4 through the interface, requesting an increase in the θ angle (for example, gradually rotating the polarizer 2 and the analyzer 3 from parallel to cross) to increase attenuation and reduce the energy entering the infrared thermal imager 5. Similarly, if the scene darkens and moves away from saturation, the infrared thermal imager 5 can issue a command to decrease θ to improve transmittance. During this dynamic adjustment process, the infrared thermal imager 5 associates the measurement results of each frame of the image (such as the brightness of each pixel or the calculated temperature value) with the corresponding polarizer angle information and transmits them to the industrial control computer 6 through the data link.

[0028] Specifically, the industrial control computer 6 is connected to the infrared thermal imager 5 via wired or wireless high-speed communication (e.g., GigE Ethernet). The industrial control computer 6 runs data acquisition and processing software, controlling the operating mode and acquisition parameters of the infrared thermal imager 5, and receiving image data and polarizer angle data sent by the infrared thermal imager 5. The industrial control computer 6 pre-stores the transmittance-angle calibration curve of the variable infrared light attenuator. This curve can be obtained through experimental calibration, that is, the actual transmittance τ corresponding to different polarizer angles θ at a certain wavelength (or band). Due to the limited material properties and extinction ratio of the polarizer in the infrared band, the actual transmittance differs from the ideal cosine wave ratio. 2 θ may have slight deviations, but precise relationship tables or formulas can be obtained through calibration. The industrial control computer 6 calculates the current attenuator transmittance τ(t) based on the real-time received θ value through interpolation or table lookup, where t represents time. Simultaneously, the industrial control computer 6 acquires raw temperature measurement data from the infrared thermal imager 5, such as the apparent temperature calculated by the infrared thermal imager 5 itself. (Value without transmittance compensation).

[0029] Industrial computer 6 executes a temperature compensation algorithm: Based on the principle of radiative transfer, the infrared thermal imager 5 receives radiation... ,in The actual radiance of the object under test. Considering the surface emissivity ε of object 1 (preset by the user or obtained through calibration), the industrial control computer 6 will... Converted to the true temperature of the measured object 1 The specific steps include: measuring the apparent temperature using the infrared thermal imager 5. Inverse calculation of apparent radiance Then use the current transmittance τ for compensation ( Finally, utilize The true temperature of the measured object is calculated by combining the surface emissivity ε of the measured object 1. After this compensation, even if the large-angle attenuation of the polarizer causes the original reading of the infrared thermal imager to be lower, the true temperature can still be reproduced. The industrial control computer will... This will be the final temperature measurement result output.

[0030] The working process of the continuous adaptive range infrared temperature measurement device based on polarization attenuation according to the present invention is as follows:

[0031] Initially, the temperature of the object being measured is low or moderate (low temperature refers to a temperature between approximately 20°C room temperature and the lower limit of the normal range of the infrared thermal imager; moderate temperature refers to a temperature between low temperature and close to the saturation threshold of the infrared thermal imager), and the transmission axes of the polarizing filter 2 and the analyzing polarizing filter 3 remain nearly parallel. The transmittance of the variable infrared light attenuator is close to its maximum value, allowing as much infrared radiation as possible to enter the infrared thermal imager lens. The infrared thermal imager 5 acquires a clear thermal image with normal exposure, and the industrial control computer 6 records the θ angle and the temperature measurement data of the infrared thermal imager at this time.

[0032] When the temperature of the object being measured rises and infrared radiation intensifies, the infrared thermal imager 5 detects an overall brightening of the image, even showing signs of saturation. To avoid overexposure, the infrared thermal imager 5 sends a control signal to drive the polarizer angle controller 4 to increase the rotation angle θ of the polarizer 3. As θ increases, according to Malus's law, the light intensity entering the infrared thermal imager decreases. The infrared thermal imager thus avoids saturation and can continue imaging within its existing high signal-to-noise ratio integration time. Simultaneously, the infrared thermal imager can also shorten the exposure time accordingly to further prevent saturation in high-temperature areas—these two adjustments work together to ensure dynamic range.

[0033] Throughout the temperature rise process, the polarizer angle θ is continuously adjusted as needed to dynamically compress the infrared signal intensity. If the temperature of the object being measured 1 decreases during use, the infrared thermal imager 5 operates in the opposite direction: gradually reducing θ to allow more light to pass through and improve the signal. Throughout the process, the industrial control computer 6 continuously receives θ and infrared thermal imager data, and performs temperature field compensation calculations for each frame of the image. The final output is a curve or image showing the actual temperature change over time.

[0034] In applications such as monitoring the first wall temperature of a nuclear fusion experimental reactor, this invention can be installed outside the observation window of the vacuum chamber. Faced with a sudden temperature increase from room temperature (approximately 20°C) to several thousand degrees Celsius, it automatically adjusts the angles of the polarizer 2 and the analyzer 3 for matching. For example, initially... To obtain detailed information about the low-temperature distribution on the wall surface, when the plasma heats the first wall surface temperature to near the conventional upper limit of the infrared thermal imager, θ increases, thus significantly attenuating the thermal radiation intensity and preventing the infrared thermal imager from saturating. When the plasma extinguishes and the wall temperature drops, the high transmittance at a small angle is restored, ensuring the accuracy of low-temperature measurements. Throughout the entire process, the temperature measurement range dynamically changes and adapts to the target temperature, and the temperature measurement data is continuous and reliable, greatly improving the dynamic adaptability and reliability of the measurement.

[0035] In summary, this invention innovatively applies an optical attenuator composed of two polarizers to infrared thermometry. By rotating the polarizers, the transmittance is continuously adjustable, resulting in a simple structure and smooth adjustment. Real-time monitoring of the infrared thermal imager's pixel exposure status and feedback control of the polarization attenuator achieves automatic anti-saturation, allowing the dynamic temperature measurement range to adaptively expand with the measured temperature, covering the entire range without switching equipment. Simultaneously, integrated angle sensing feedback, combined with the emissivity of the measured object, performs dynamic transmittance compensation correction on each frame of data, ensuring temperature measurement accuracy under dynamic attenuation conditions. This invention can increase the highest measurable temperature, significantly improving high-temperature measurement capabilities while maintaining low-temperature measurement performance. Continuous change in polarization angle avoids abrupt filter switching, achieving a seamless dynamic transition. The modular design allows it to be added as an independent component to the front end of existing infrared thermal imagers, facilitating integration across multiple models via standard interface communication.

[0036] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A continuous adaptive range infrared temperature measurement device based on polarization attenuation, characterized in that, The system includes a polarizing filter, an analyzing polarizing filter, a polarizing filter angle controller, an infrared thermal imager, and an industrial control computer. The polarizing filter is fixedly installed in front of the lens or in the internal optical path of the infrared thermal imager. The analyzing polarizing filter is installed behind the polarizing filter and placed coaxially with it. The polarizing filter and the analyzing polarizing filter constitute a variable infrared light attenuator. The polarizing filter angle controller is connected to the analyzing polarizing filter and is used to drive the analyzing polarizing filter to rotate around the optical axis and provide feedback on the angle information. The infrared thermal imager is placed behind the variable infrared light attenuator. The infrared thermal imager is connected to the polarizing filter angle controller and sends control commands. The infrared thermal imager is also communicatively connected to the industrial control computer. The industrial control computer stores the transmittance-angle calibration curve and calculates the transmittance based on the angle information to compensate for the temperature value.

2. The continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 1, characterized in that, A polarizer converts the unpolarized infrared thermal radiation emitted by the object under test into linearly polarized light.

3. The continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 1, characterized in that, The analyzer polarizer rotates about the optical axis relative to the polarizer, and the infrared light transmittance is continuously adjusted by adjusting the angle between the transmission axes of the two polarizers.

4. The continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 1, characterized in that, The polarizer angle controller receives control commands from the infrared thermal imager, drives the polarizer to rotate to the target angle according to the control commands, and feeds back the angle information to the infrared thermal imager in real time.

5. The continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 1, characterized in that, The infrared thermal imager has a built-in data processing unit that monitors the image grayscale value in real time. When the image is detected to be close to saturation, the unit sends a command to increase the included angle to the polarizer angle controller. When the image is detected to be far from saturation, the unit sends a command to decrease the included angle.

6. The continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 1, characterized in that, The industrial control computer receives image data and angle information from the infrared thermal imager and calculates the current transmittance based on the transmittance-angle calibration curve.

7. The continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 6, characterized in that, The infrared thermal imager, polarizer angle controller, and polarizer analyzer form a closed-loop feedback control system. The infrared thermal imager adjusts the rotation angle of the polarizer analyzer in real time according to the image exposure status; the infrared thermal imager outputs the apparent temperature.

8. The continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 7, characterized in that, The industrial control computer converts the apparent temperature into apparent radiance, calculates the actual radiance using the current transmittance, and converts the actual radiance into the true temperature by combining the emissivity of the surface of the object being measured.

9. The continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 1, characterized in that, In the initial state, the transmission axes of the polarizing filter and the analyzing polarizing filter remain parallel, and the transmittance of the variable infrared light attenuator is close to its maximum value.

10. A continuous adaptive range infrared temperature measurement device based on polarization attenuation according to claim 6, characterized in that, The industrial control computer performs radiation correction compensation on the apparent temperature measured by the infrared thermal imager based on the current transmittance to obtain the true temperature of the object being measured.

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