Medium-wave infrared polarization imaging system, laser beam calibration system, and image restoration method

Abstract

The present invention provides a medium-wave infrared polarization imaging system, a laser beam calibration system, and an image restoration method. The medium-wave infrared polarization imaging system requires no complex optical path debugging or microstructure design. Instead, it directly couples a liquid crystal micro-nanopolarization device with a medium-wave focal plane detector. Based on the liquid crystal micro-nanopolarization device's modulation of the polarization state of incident light from a target scene under the action of an external voltage, and through calibration data obtained by rotating the incident light from the liquid crystal micro-nanopolarization device using a controllable power supply in a laser environment, a corresponding relationship between the polarization rotation angle and the external voltage is derived. Finally, a linear polarization degree image of the target scene is inverted, thereby enabling the target scene to be analyzed using the polarization rotation angle instead of the traditional polarization angle. The medium-wave infrared polarization imaging system uses the polarization rotation angle instead of the polarization angle for parametric analysis, enabling the acquired polarization image to reflect polarization information with higher energy efficiency and achieving electrically controlled polarization detection of the target scene without sacrificing resolution.

Description

Technical Field

[0001] The present invention relates to the field of infrared detection technology, and in particular to a medium-wave infrared polarization imaging system, a laser beam calibration system and an image restoration method. Background Art

[0002] Light, as a transverse wave, transmits or reflects polarization information from its interactions with a target object during propagation, which can be used to infer the target's physical properties, such as refractive index, surface roughness, humidity, dielectric constant, and other specific parameters. The development of polarization imaging technology can provide more multi-dimensional information support for target detection, building upon traditional intensity imaging. This technology overcomes the issues of blurred imaging and unclear detection in scenes like rain, snow, and sea surfaces, significantly improving target detection accuracy. The mid-wave infrared band is widely used in industrial manufacturing, military, atmospheric exploration, and environmental monitoring, and the development of new multi-dimensional detection technologies in this band is essential.

[0003] Currently developed mid-wave infrared polarization detection technologies are primarily categorized into time-sharing, amplitude-sharing, aperture-sharing, and focal-plane polarization imaging techniques, as well as snapshot polarization imaging. The former generally requires rotating polarization elements (which results in high energy loss, computational complexity, poor real-time performance, and the need for mechanical rotation), or multi-channel imaging (which results in complex optical paths, high component precision requirements, and difficult assembly and alignment), or multi-detector clusters (which result in high cost and large system size), or microlenses (which, despite their compact size, sacrifice spatial resolution). Snapshot polarization imaging, however, requires the design of microstructured gratings containing different polarization angles. While this method can achieve a single snapshot, the actual fabrication is complex, costly, and yield-poor, requiring extensive computation and challenging alignment.

[0004] Therefore, there is an urgent need for a medium-wave infrared polarization imaging system, a laser beam calibration system and an image restoration method to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a medium-wave infrared polarization imaging system, a laser beam calibration system and an image restoration method, which are used to solve the technical problems of existing medium-wave infrared polarization detection technology, such as large energy loss, poor real-time performance, complex optical path and high cost.

[0006] To solve the above technical problems, the present invention provides a medium-wave infrared polarization imaging system, comprising:

[0007] A controllable power supply for outputting external voltage;

[0008] A liquid crystal micro-nano polarization control device, electrically connected to a controllable power supply, for adjusting the polarization rotation angle of outgoing light relative to incident light in a target scene after an external voltage is applied;

[0009] The medium-wave focal plane detector is placed close to the light-emitting side of the liquid crystal micro-nano controlled polarization device to obtain the measured target image under different external voltages corresponding to the target scene;

[0010] The data storage and analysis module is electrically connected to the medium-wave focal plane detector and is used to invert the linear polarization degree image of the target scene based on the calibration data of the correspondence between the external voltage and the polarization rotation angle stored in advance, the external voltage and the light intensity data of the target measured image.

[0011] Preferably, the controllable power supply is a square wave power supply with a frequency of 1 kHz and a duty cycle of 1:1.

[0012] Preferably, the liquid crystal micro-nano controlled polarization device includes, in sequence along the propagation direction of the incident light, a first substrate, a first electrode layer, a first alignment layer, a liquid crystal layer, a second alignment layer, a second electrode layer and a second substrate.

[0013] Preferably, the medium-wave focal plane detector includes a medium-wave infrared band adapter lens, a medium-wave infrared detection CMOS focal plane array, and an electronic component in sequence along the propagation direction of the incident light, one end of the electronic component is electrically connected to the medium-wave infrared detection CMOS focal plane array, and the other end of the electronic component is electrically connected to the data storage and analysis module;

[0014] Among them, the medium-wave infrared detection CMOS focal plane array is a HgCdTe infrared focal plane array, and the medium-wave infrared detection band is 3.7μm~4.8μm.

[0015] Preferably, the medium-wave infrared polarization imaging system further includes a device support frame and a precision gimbal stabilizer, one end of the device support frame is fixedly connected to the medium-wave infrared band adapter lens, and the precision gimbal stabilizer is used to carry the medium-wave focal plane detector.

[0016] Preferably, the device support frame has an accommodating cavity, in which a liquid crystal micro-nano polarization control device is arranged, and the angle between the liquid crystal micro-nano polarization control device and the medium-wave infrared band adapter lens is 10°~45°.

[0017] Accordingly, the present invention further provides a laser beam calibration system for calibrating calibration data of any of the above medium-wave infrared polarization imaging systems, wherein the laser beam calibration system comprises, from the optical signal input end to the optical signal output end, a medium-infrared optical parametric oscillator laser, a polarizer, a liquid crystal micro-nano polarization control device, an analyzer, an objective lens, an attenuator, and an optical quality analyzer;

[0018] The laser beam calibration system further includes a controllable power supply, which is electrically connected to the liquid crystal micro-nano bias control device.

[0019] Preferably, the polarization direction of the output light of the mid-infrared optical parametric oscillation laser and the orientation direction of the liquid crystal micro-nano controlled polarization component on the side close to the incident light are both along the X-axis.

[0020] Preferably, when the polarizer transmission direction is along the X axis, the pixel light intensity of the CMOS surface of the light quality analyzer under different external voltages is recorded within the X direction voltage adjustment range, and the average surface light intensity is taken as Ix Vn When the polarizer transmission direction is along the Y axis, the pixel light intensity of the CMOS surface of the light quality analyzer under different external voltages is recorded within the Y direction voltage adjustment range, and the average surface light intensity is taken as Iy Vn ; Polarization rotation angle AOP of liquid crystal micro-nano controlled polarization device under different external voltages Vn is arctan(Iy Vn / Ix Vn ).

[0021] Accordingly, the present invention further provides an image restoration method, which is applied to any of the above medium-wave infrared polarization imaging systems, and the method comprises:

[0022] S10, debugging the medium-wave infrared polarization imaging system so that it can acquire a target grayscale image;

[0023] S20, turning on the controllable power supply, and collecting the measured images of the target under different external voltages through the medium-wave focal plane detector;

[0024] S30, calculating the corresponding polarization rotation angles under different external voltages according to calibration data of the corresponding relationship between the external voltage and the polarization rotation angle;

[0025] S40, converting the measured target images corresponding to different polarization rotation angles into corresponding polarization angle images according to the calibration data;

[0026] S50 , converting the polarization angle image into a linear polarization degree image of the target scene according to the corresponding relationship between the Stokes components.

[0027] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides a medium-wave infrared polarization imaging system, a laser beam calibration system, and an image restoration method. The medium-wave infrared polarization imaging system does not require complex optical path debugging and microstructure design. It only needs to directly couple a liquid crystal micro-nano polarization control device with a medium-wave focal plane detector. Based on the modulation effect of the liquid crystal micro-nano polarization control device on the polarization state of the incident light of the target scene under the action of an external voltage, and through the calibration data of the incident light rotated by the liquid crystal micro-nano polarization control device under a laser environment, the corresponding relationship between the polarization rotation angle and the external voltage is obtained, and finally the linear polarization degree image of the target scene is inverted, thereby realizing the use of the polarization rotation angle instead of the traditional polarization angle to analyze the target scene. The above-mentioned liquid crystal micro-nano optical control component is simple to manufacture and low in cost. It can effectively realize the electrical control adjustment of the polarization direction of the incident light by low voltage drive, which is achieved only by adjusting the size of the external drive voltage. There are no mechanical rotating parts during use, and the use requirements are low. At the same time, this medium-wave infrared polarization imaging system is different from traditional polarization imaging systems when obtaining polarization images corresponding to polarization angles. It uses polarization rotation angle instead of polarization angle for parameter analysis, so that the obtained polarization images reflect polarization information on the basis of higher energy utilization, and can realize electronically controlled polarization detection of target scenes without sacrificing resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the overall architecture of the medium-wave infrared polarization imaging system provided in Example 1 of the present invention;

[0029] Figure 2 A schematic diagram of the optical path of the laser beam calibration system provided in Example 1 of the present invention;

[0030] Figure 3a Schematic diagram of the change in calibration light intensity in the X direction under typical voltages of 0, 1.4 Vrms, and 2.1 Vrms in the laser beam calibration system provided in Example 1 of the present invention;

[0031] Figure 3b Schematic diagram of the change in calibration light intensity in the Y direction under typical voltages of 0, 1.4 Vrms, and 2.1 Vrms in the laser beam calibration system provided in Example 1 of the present invention;

[0032] Figure 3c A schematic diagram of the change in calibration light intensity without distinguishing directions at typical voltages of 0, 1.4 Vrms, and 2.1 Vrms in the laser beam calibration system provided in Example 1 of the present invention;

[0033] Figure 4 A schematic diagram showing the relationship between the polarization rotation angle of a liquid crystal micro-nano polarization control component and voltage obtained by the laser beam calibration system provided in Example 1 of the present invention;

[0034] Figure 5Flowchart of the image restoration method provided in Example 1 of the present invention;

[0035] Figure 6a The measured target image of the medium-wave focal plane detector at a typical voltage of 0 Vrms in the image restoration method provided in Example 1 of the present invention;

[0036] Figure 6b The measured target image of the medium-wave focal plane detector under a typical voltage of 1.3 Vrms in the image restoration method provided in Example 1 of the present invention;

[0037] Figure 6c The measured target image of the medium-wave focal plane detector at a typical voltage of 1.4 Vrms in the image restoration method provided in Example 1 of the present invention;

[0038] Figure 6d The measured target image of the medium-wave focal plane detector under a typical voltage of 2.0 Vrms in the image restoration method provided in Example 1 of the present invention;

[0039] Figure 6e The Stokes vector S0 image of the target scene in the image restoration method provided in Example 1 of the present invention;

[0040] Figure 6f The Stokes vector S1 image of the target scene in the image restoration method provided in Example 1 of the present invention;

[0041] Figure 6g The Stokes vector S2 image of the target scene in the image restoration method provided in Example 1 of the present invention;

[0042] Figure 6h The linear polarization degree image of the target scene in the image restoration method provided in Example 1 of the present invention;

[0043] In the figure: 100 - medium-wave infrared polarization imaging system; 11 - liquid crystal micro-nano polarization device; 12 - medium-wave focal plane detector; 121 - medium-wave infrared band adapter lens; 122 - medium-wave infrared detection CMOS focal plane array; 13 - controllable power supply; 14 - data storage and analysis module; 15 - device support frame; 16 - precision gimbal stabilizer; 17 - second substrate; 200 - laser beam calibration system; 21 - medium-infrared optical parametric oscillation laser; 22 - polarizer; 23 - analyzer; 24 - objective lens; 25 - attenuator; 26 - light quality analyzer. DETAILED DESCRIPTION

[0044] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] The purpose of the present invention is to address the shortcomings of the existing technology and provide a medium-wave infrared polarization imaging system 100, a laser beam calibration system 200 and an image restoration method. The medium-wave infrared polarization imaging system 100 is different from traditional polarization imaging systems in that it uses polarization rotation angle instead of polarization angle for parameter analysis when obtaining polarization images corresponding to polarization angles, so that the obtained polarization images reflect polarization information on the basis of higher energy utilization, and can realize electronically controlled polarization detection of target scenes without sacrificing resolution.

[0046] The technical solution of the present invention will now be described with reference to specific embodiments.

[0047] Example 1:

[0048] See also Figure 1 , Figure 1 Schematic diagram of the overall device structure of the medium-wave infrared polarization imaging system 100 provided in Example 1 of the present invention; Figure 1 It can be seen that the medium-wave infrared polarization imaging system 100 includes a controllable power supply 13, a liquid crystal micro-nano polarization control device 11 electrically connected to the controllable power supply 13, a medium-wave focal plane detector 12 arranged closely to the light-emitting side of the liquid crystal micro-nano polarization control device 11, and a data storage and analysis module 14 electrically connected to the medium-wave focal plane detector 12;

[0049] Among them, the controllable power supply 13 is used to output an external voltage, the liquid crystal micro-nano polarization control device 11 is used to adjust the polarization rotation angle of the outgoing light compared to the incident light in the target scene after the external voltage is applied, and the medium-wave focal plane detector 12 is used to obtain the target measured image of the target scene corresponding to different external voltages; the data storage and analysis module 14 is used to invert the linear polarization degree image of the target scene based on the calibration data of the correspondence between the external voltage and the polarization rotation angle, the external voltage and the light intensity data of the target measured image.

[0050] In this embodiment 1, the controllable power supply 13 is an AC power supply or a square wave power supply, preferably a square wave power supply, whose square wave power supply frequency is 1 kHz and the duty cycle is 1:1; wherein, the square wave power supply is a common periodic power supply signal form, and its output voltage periodically switches between a high level and a low level, presenting a waveform similar to a rectangle.

[0051] Specifically, a higher frequency can enable the liquid crystal micro-nano polarization control device 11 to respond relatively quickly to voltage changes at different times, and then more quickly adjust the polarization rotation angle of the outgoing light compared to the incident light in the target scene, which helps to obtain more light signals in different polarization states per unit time, thereby improving the dynamic response capability of the imaging system and the timeliness of data acquisition as a whole, so as to more efficiently obtain relevant image information of the target scene in multiple polarization states.

[0052] Specifically, the duty cycle is 1:1, indicating that within a complete cycle, the square wave's high-level and low-level periods are equal. For the liquid crystal micro-nanopolarization control device 11, this symmetrical duty cycle provides a more balanced driving state. At a high level, the device adjusts the polarization rotation angle according to the corresponding high-level voltage value, while at a low level, it can reset its state or prepare for the next high-level drive response. This ensures the stability and regularity of polarization rotation angle regulation, making the changes in the target measured image acquired by the medium-wave focal plane detector 12 within different cycles more repeatable and regular. This also facilitates the subsequent data storage and analysis module 14 to accurately invert the linear polarization image of the target scene based on stable and regular data, ensuring the accuracy and reliability of the entire imaging system.

[0053] In this embodiment 1, the liquid crystal micro-nano controlled polarization device 11 includes a first substrate, a first electrode layer, a first alignment layer, a liquid crystal layer, a second alignment layer, a second electrode layer, and a second substrate in sequence along the propagation direction of the incident light; wherein, the thickness of the liquid crystal micro-optical device is on the millimeter level, which can greatly reduce the thickness of the medium-wave infrared polarization imaging system 100 after overall integration.

[0054] Specifically, the liquid crystal micro-nano polarization control device 11 primarily utilizes the electro-optical properties of liquid crystals to operate. Before an external electric field is applied, the liquid crystal molecules in the liquid crystal layer have their initial arrangement state. When an external electric field is applied, the orientation of the liquid crystal molecules changes. Because the arrangement direction of the liquid crystal molecules is closely related to the polarization state of light, this change in orientation will adjust the polarization state of the incident light passing through the liquid crystal micro-nano polarization control device 11. For example, changes in the degree of twisting of the liquid crystal molecules, the orientation angle, etc., can cause the polarization direction of the incident linearly polarized light to rotate by a certain angle, thereby changing the polarization state of the light.

[0055] Specifically, both the first and second substrates are transparent to light in the 3-5 μm mid-wave infrared band. This provides a fundamental guarantee for incident light to smoothly enter and exit the liquid crystal micro-nano polarization control device 11. They serve as the outer support structure of the entire assembly, supporting the various internal functional layers and ensuring the stability of the assembly structure, allowing the internal optical and electrical processes to proceed normally.

[0056] Specifically, the liquid crystal molecules in the liquid crystal layer are positive nematic liquid crystals, which possess unique electro-optical properties. Under the influence of an external electric field, the liquid crystal molecules can flexibly change their orientation, thereby affecting the polarization state of the incident light passing through. This ability to change polarization state is the core of the medium-wave infrared polarization imaging system 100100's different operating modes and light intensity modulation capabilities.

[0057] Specifically, neither the first nor the second electrode layer requires a patterned design. The material used is an ITO material with a thickness of 25 nm. With these parameters, the first and second electrode layers have little absorption of the target infrared band and provide good electrical conductivity. Furthermore, conductive tape with good electrical conductivity is used to electrically connect to the external electric field, enabling the liquid crystal micro-nano polarization control device 11 to flexibly control the polarization state of incident light.

[0058] Specifically, the molecular orientation of the first alignment layer is perpendicular to that of the second alignment layer. This orthogonal arrangement plays a key role in guiding the liquid crystal molecules in the liquid crystal layer. Based on the orientation of these two alignment layers, the liquid crystal molecules will assume a specific initial arrangement when no external voltage is applied. This typically results in a twisted structure, for example, where the liquid crystal molecules may gradually twist at a certain angle from top to bottom, laying the foundation for subsequent adjustment of the polarization state of light through the electric field.

[0059] In this embodiment 1, the medium-wave focal plane detector 12 includes a medium-wave infrared band adapter lens 121, a medium-wave infrared detection CMOS focal plane array 122, and an electronic component in sequence along the propagation direction of the incident light. One end of the electronic component is electrically connected to the medium-wave infrared detection CMOS focal plane array 122, and the other end of the electronic component is electrically connected to the data storage and analysis module 14. The medium-wave infrared detection CMOS (Complementary Metal-Oxide-Semiconductor) focal plane array is a HgCdTe infrared focal plane array, and the medium-wave infrared detection band is 3.7μm~4.8μm.

[0060] Specifically, the electronic component plays a key connecting role. One end of the electronic component is electrically connected to the medium-wave infrared detection CMOS focal plane array 122 and can receive electrical signals from the focal plane array. The other end is electrically connected to the data storage and analysis module 14 and is responsible for transmitting the collected signals to the data storage and analysis module 14, thereby ensuring a smooth signal transmission link in the entire imaging system and laying the foundation for subsequent image generation and analysis processing.

[0061] Specifically, the mid-wave infrared detection CMOS focal plane array 122 is a HgCdTe infrared focal plane array. HgCdTe (mercury cadmium telluride) material possesses excellent optoelectronic properties and high quantum efficiency in the mid-wave infrared band, effectively converting received infrared light signals into electrical signals. It exhibits excellent responsiveness to light in the mid-wave infrared band and can more sensitively detect light radiated or reflected by the target scene within this wavelength range. This improves the imaging system's detection sensitivity and imaging resolution for the target scene, enabling the captured target image to more clearly and accurately reflect the detailed features of the target scene.

[0062] Specifically, the mid-wave infrared detection band is set to 3.7μm to 4.8μm. This band has unique infrared spectral characteristics that can help distinguish targets from backgrounds or identify different types of targets. For the mid-wave infrared polarization imaging system 100, focusing on this band for detection and combining it with polarization characteristic analysis can obtain richer and more valuable target scene information, further improving the system's application efficiency in target detection, identification, and scene analysis.

[0063] In this embodiment 1, the medium-wave infrared polarization imaging system 100 also includes a device support frame 15 and a precision gimbal stabilizer 16. One end of the device support frame 15 is fixedly connected to the medium-wave infrared band adapter lens 121, and the precision gimbal stabilizer 16 is used to carry the medium-wave focal plane detector 12.

[0064] Specifically, the device support frame 15 can ensure that the lens can maintain a fixed position and angle under various usage environments (for example, when there is a certain external force interference, vibration, etc.), so that the incident light can accurately enter the lens in the expected direction, thereby ensuring the normal progress of a series of processes such as subsequent light propagation, polarization adjustment and detection, ensuring that the optical system is always in a good calibration state, and helping to improve the accuracy of the final measured target image and the inverted linear polarization image.

[0065] Specifically, the precision gimbal stabilizer 16 effectively offsets external vibrations such as wind, device vibration, and slight human movement through its internal stabilization mechanisms (e.g., using high-precision gyroscopes and motors for real-time attitude adjustment and compensation), allowing the MWFPD 12 to operate in a relatively stable state. In addition to its stabilization function, the precision gimbal stabilizer 16 also provides the MWFPD 12 with flexible pointing capabilities. It can rotate and adjust its angle in various directions as needed, facilitating imaging and detecting targets in various locations. Furthermore, when tracking dynamic targets, the precision gimbal stabilizer 16 precisely controls the pointing direction of the MWFPD 12 based on the target's trajectory, ensuring the detector remains aligned with the target. This allows for continuous and accurate acquisition of image information of the target at different times and in different polarization states, further enhancing the applicability and practicality of the entire MWIR polarization imaging system 100 in practical applications.

[0066] Furthermore, the device support frame 15 has a receiving cavity, in which the liquid crystal micro-nano polarization control device 11 is arranged. The angle between the liquid crystal micro-nano polarization control device 11 and the medium-wave infrared band adapter lens 121 is 10°~45°, preferably 30°.

[0067] Specifically, the accommodating cavity of the device support frame 15 provides a relatively stable installation space for the liquid crystal micro-nano polarization control device 11. This helps protect the liquid crystal micro-nano polarization control device 11 from external environmental factors (such as dust and moisture), ensuring its stable and reliable performance. Furthermore, because the accommodating cavity is located within the device support frame 15, the liquid crystal micro-nano polarization control device 11 and other components of the entire imaging system (such as the mid-wave infrared band adapter lens 121) are more compact in spatial location, which helps reduce optical signal loss during transmission and ensures efficient and accurate transmission of optical signals between various components.

[0068] Specifically, the angle between the liquid crystal micro-nano polarization control device 11 and the mid-wave infrared band adapted lens 121 can greatly reduce the adverse effects of cold reflection on the imaging quality during the imaging process.

[0069] The medium-wave infrared polarization imaging system 100 provided in this embodiment 1 does not require complex optical path debugging and microstructure design. The medium-wave infrared polarization imaging system 100 directly couples the liquid crystal micro-nano polarization device 11 with the medium-wave focal plane detector 12. Based on the modulation effect of the spiral structure formed in the twisted nematic phase liquid crystal box on the polarization state of the incident light, the target scene is analyzed using the polarization rotation angle instead of the traditional polarization angle. By controlling the calibration data of the incident light to rotate the liquid crystal micro-nano polarization device 11 with a controllable power supply 13 under a laser environment, the corresponding relationship between the polarization rotation angle of the outgoing light and the incident light and the voltage is obtained, thereby inverting the linear polarization degree image of the target scene. The medium-wave infrared polarization imaging system 100 adopts low-signal drive as a whole, with high integration, small size and low energy consumption.

[0070] Specifically, compared with the polarization components in traditional infrared polarization imaging systems, the liquid crystal micro-nano polarization component of the medium-wave infrared polarization imaging system 100 has a simpler structure, is easy to plug and unplug, is easy to couple, and has high energy utilization. The medium-wave infrared polarization imaging system 100 adopts a support coupling mode with a simple optical path. The polarization control of the target scene does not sacrifice resolution. It has good spatial consistency and can realize dynamic adjustment of the polarization state of the target scene. It has a long observation distance and can achieve long-distance polarization detection of 5km.

[0071] See also Figure 2 , Figure 2 Schematic diagram of the optical path of the laser beam calibration system 200 provided in Example 1 of the present invention; wherein, this Example 1 further provides a laser beam calibration system 200 for calibrating calibration data of any of the above medium-wave infrared polarization imaging systems 100, wherein the laser beam calibration system 200 includes, from the optical signal input end to the optical signal output end, a mid-infrared optical parametric oscillator laser 21, a polarizer 22, a liquid crystal micro-nano polarization control device 11, an analyzer 23, an objective lens 24, an attenuator 25, and an optical quality analyzer 26;

[0072] The laser beam calibration system 200 further includes a controllable power supply 13 , which is electrically connected to the liquid crystal micro-nano deflection control device 11 .

[0073] Specifically, the laser beam calibration system 200 arranges multiple key components in sequence from the optical signal input end to the optical signal output end along the transmission path of the optical signal. The first is the mid-infrared optical parametric oscillator laser 21, which, as the source of the optical signal, can generate mid-infrared light with specific wavelength, intensity and other parameters, providing a stable and controllable optical input for the subsequent calibration process. The light then passes through the polarizer 22. The function of the polarizer 22 is to convert non-polarized light such as natural light into polarized light with a specific polarization direction, so that subsequent operations are all based on light with a determined polarization direction. The light then reaches the liquid crystal micro-nano polarization control device 11, which can adjust the polarization rotation angle of the light under the action of the controllable power supply 13 electrically connected to it, which is an important link in achieving control of different polarization states. The light then passes through the analyzer 23, objective lens 24, and attenuator 25. The analyzer 23 further filters and detects light of a specific polarization state. The objective lens 24 performs optical operations such as focusing the light to meet the reception requirements of subsequent components. The attenuator 25 regulates the light intensity to prevent damage to the subsequent optical quality analyzer 26 caused by excessive light intensity. Finally, the light enters the optical quality analyzer 26, which performs a detailed analysis of the quality and polarization characteristics of the processed light, obtaining relevant data and completing the calibration process.

[0074] In Example 1, the medium-wave infrared laser adopts a medium-wave infrared optical parametric oscillator laser with a central wavelength of 4.1 μm; the polarizer 22 and the analyzer 23 adopt a wire grid structure with a transmittance of more than 70% in the transmission direction in the 3-5 μm band and an extinction ratio of 300:1; when the transmission directions of the polarizer 22 and the analyzer 23 are the same, an extinction ratio of 20000:1 can be achieved; the optical quality analyzer 26 adopts a high-sensitivity, high-resolution, ultra-wideband wavelength coverage spot analyzer, which is used to measure the dynamic energy distribution of the spot in the continuous or pulsed laser generation optical path.

[0075] In Example 1, the laser beam calibration system 200 uses a beam quality analyzer to record light intensity, and the data is accurate and highly analyzable. The proposed target scene polarization image recovery method is simple to calculate, easy to understand and implement, and the laser beam calibration system 200 has a simple optical path and is highly feasible.

[0076] In Example 1, the laser beam calibration system 200 calibrates the electrically tunable polarization characteristics of the liquid crystal micro-nano polarization control component as follows:

[0077] Step 1: First, Figure 2 The laser beam calibration system 200 is aligned with the optical path and various components are installed so that the polarization direction of the output light of the mid-infrared optical parametric oscillation laser 21, the transmission direction of the polarizer 22, and the orientation direction of the liquid crystal micro-nano polarization control component close to the laser beam are all arranged along the X axis;

[0078] Step 2: Make the transmission direction of the analyzer 23 along the X-axis, adjust the square wave voltage 4 of the controllable power supply 13 from small to large, observe the light spot shape and light intensity obtained by the beam quality analyzer, and record them as the X-direction voltage adjustment range;

[0079] Step 3: Based on the state of the polarizer 23 in the previous step, the voltage is precisely adjusted in the recorded X-direction voltage adjustment range with a step size of 0.5Vrms. The pixel light intensity of the beam quality analyzer CMOS surface at each voltage value is recorded, and the average light intensity value Ix is taken. Vn ;

[0080] Step 4: Adjust the square wave voltage of the analyzer 23 along the Y-axis, and observe the spot shape and light intensity obtained by the beam quality analyzer. Record this as the Y-direction voltage adjustment range.

[0081] Step 5: Based on the state of the analyzer 23 in the previous step, the voltage is precisely adjusted in the Y direction voltage adjustment range with a step size of 0.5 Vrms. The pixel light intensity of the beam quality analyzer CMOS surface at each voltage value is recorded, and the average light intensity value Iy is taken. Vn ;

[0082] Step 6, repeat three times;

[0083] Step 7: Calculate the polarization angle AOP of the liquid crystal polarization control device at each voltage. Vn The calculation formula is as follows:

[0084] AOP Vn =arctan(Iy Vn / Ix Vn )(1).

[0085] Specifically, in step one, the polarization direction of the output light of the mid-infrared optical parametric oscillation laser 21, the transmission direction of the polarizer 22, and the orientation direction of the liquid crystal micro-nano controlled polarization component close to the laser beam are all set along the X-axis. This ensures that the initial polarization state of the light is clear and uniform, avoiding interference in the subsequent measurement of the polarization rotation angle adjustment of the liquid crystal micro-nano controlled polarization component under different voltages due to inconsistent initial polarization directions, making the subsequently obtained data more comparable and accurate.

[0086] Specifically, in step 2, the changes in the light spot shape and light intensity reflect the changes in the polarization state of the liquid crystal micro-nano polarization control component under different voltage driving conditions. Determining the voltage adjustment range in the X direction can clarify the approximate range of the subsequent precise voltage adjustment, avoiding voltage adjustment beyond a reasonable range and affecting the accuracy and effectiveness of the calibration.

[0087] Specifically, in step 3: the voltage is precisely adjusted in steps of 0.5 Vrms. This small step adjustment can more accurately capture the details of the light intensity changing with voltage. Record the pixel light intensity at each voltage and take the average surface light intensity Ix Vn The purpose is to obtain more representative and stable data, reduce the error in the final result caused by factors such as fluctuations in individual pixels, and make the subsequent results calculated based on this data more reliable.

[0088] Specifically, in step six: repeating the above process from determining the voltage adjustment range to precisely adjusting the voltage and recording the light intensity data multiple times makes the final accumulated data set richer and more comprehensive. When calculating key parameters such as the polarization rotation angle in the subsequent calculation, a comprehensive analysis can be performed based on multiple sets of data, thereby obtaining accurate results that can better reflect the true performance of the liquid crystal micro-nano polarization control component.

[0089] Specifically, in step 7, the polarization rotation angle formula is based on the ratio of light intensities in the X and Y directions, using inverse trigonometric functions to determine the polarization rotation angle. This calculated polarization rotation angle intuitively reflects the actual polarization rotation adjustment effect of the liquid crystal micro-nano polarization control component under different driving voltages, providing precise calibration data for accurately using this component in the medium-wave infrared polarization imaging system 100 to perform polarization adjustment and accurately obtain linear polarization images of the target scene.

[0090] See also Figure 3a to Figure 3b , Figure 3a Schematic diagram of the change of calibration light intensity in the X direction at typical voltages of 0, 1.4 Vrms, and 2.1 Vrms in the laser beam calibration system 200 provided in Example 1 of the present invention; Figure 3b Schematic diagram of the change of the calibration light intensity in the Y direction under the typical voltages of 0, 1.4 Vrms, and 2.1 Vrms in the laser beam calibration system 200 provided in Example 1 of the present invention; Figure 3a to Figure 3b It can be seen that the initial light intensity response of the light spot in the X direction is almost 0, and it increases from zero to a certain level after the voltage is applied. However, the change pattern of the light intensity collected in the Y direction is just the opposite, indicating that when there is no voltage drive, the liquid crystal polarization control device rotates the originally X-direction polarized light to the Y direction. However, under voltage drive, the optical rotation effect of the liquid crystal polarization control component on the polarization plane of the incident light gradually disappears, and its polarization direction changes from the Y direction back to the X direction.

[0091] See also Figure 3c , Figure 3c Schematic diagram of the change of calibration light intensity without distinguishing direction at typical voltages of 0, 1.4 Vrms, and 2.1 Vrms in the laser beam calibration system 200 provided in Example 1 of the present invention; Figure 3c It can be seen that when the analyzer 23 and the liquid crystal micro-nano polarization control components are removed, the overall light intensity is slightly reduced and there is always a response.

[0092] See also Figure 4 , Figure 4 Schematic diagram of the relationship between the polarization rotation angle of the liquid crystal micro-nano controlled polarization component and the voltage obtained by the laser beam calibration system 200 provided in Example 1 of the present invention; Figure 4 As can be seen, when no voltage is applied, the liquid crystal polarization control element rotates incident linearly polarized light by 90°. When an external square wave voltage is applied, the polarization rotation gradually disappears when the voltage reaches the operating threshold of 0.9 Vrms (the voltage at which the liquid crystal begins to twist), until it is almost completely gone at 1.6 Vrms. The typical polarization rotation angle reading and voltage relationship are as follows: 90° corresponds to a voltage before 0.9 Vrms, 60° to 1.3 Vrms, 30° to 1.4 Vrms, and 0° to a voltage after 1.6 Vrms.

[0093] See also Figure 5 , Figure 5 This is a flow chart of the image restoration method provided in Example 1 of the present invention; wherein the specific steps of the above-mentioned image restoration method are as follows:

[0094] S10 , debugging the medium-wave infrared polarization imaging system 100 so that it can capture a target grayscale image.

[0095] Specifically, step S10 further includes:

[0096] First, provide a medium-wave infrared polarization imaging system 100 and connect it to a computer image acquisition card to capture images. Second, turn on the computer power supply and wait for cooling. After cooling for about 8 minutes, the computer image acquisition card can capture the target grayscale image.

[0097] S20 , turning on the controllable power supply 13 , and collecting the measured images of the target under different external voltages through the medium-wave focal plane detector 12 .

[0098] S30 , calculating corresponding polarization rotation angles under different external voltages according to calibration data of the corresponding relationship between the external voltage and the polarization rotation angle.

[0099] Specifically, step S30 further includes:

[0100] Specifically, the external square wave power supply connected to the liquid crystal polarization control component is adjusted according to the calibration data provided by the laser beam calibration system 200, and the measured images of the target under four typical calibration voltages of 0 Vrms, 1.3 Vrms, 1.4 Vrms and 2 Vrms are collected respectively, and the corresponding polarization rotation angles under different external voltages are calculated.

[0101] At this time, the polarization rotation angle corresponding to the 0Vrms target measured image is 90°, the polarization rotation angle corresponding to the 1.3Vrms target measured image is 60°, the polarization rotation angle corresponding to the 1.4Vrms target measured image is 30°, and the polarization rotation angle corresponding to the 2Vrms target measured image is 0°.

[0102] S40, converting the measured target images corresponding to different polarization rotation angles into corresponding polarization angle images according to the calibration data.

[0103] Specifically, step S40 further includes:

[0104] The above four images are converted into corresponding 0° polarization angle images, 30° polarization angle images, 60° polarization angle images, and 90° polarization angle images according to the light intensity data calibrated by the laser beam calibration system 200 .

[0105] Furthermore, in the laser calibration environment, the conversion of the measured target image corresponding to the polarization rotation angle of 30° in step S30 into the image with a polarization angle of 30° is used as an example to illustrate:

[0106] When the polarization rotation angle is set to 30°, the overall average light intensity of the spot is a (a known quantity, provided by the calibration data provided by the laser beam calibration system 200), and the average light intensity of the spot at a polarization angle of 30° is b (a known quantity, related to the incident light intensity and transmittance). During actual imaging, image A is obtained at a polarization rotation angle of 30°, which is converted into image B at a polarization angle of 30° according to the light intensity ratio. The corresponding relationship satisfies B=A*b / a. The light intensity of each pixel point in image B (represented by the grayscale value of the grayscale image) can be converted according to the light intensity ratio to obtain an image with a polarization angle of 30°.

[0107] S50 , converting the polarization angle image into a linear polarization degree image of the target scene according to the corresponding relationship between the Stokes components.

[0108] Specifically, step S50 further includes:

[0109] The Stokes vector is a four-dimensional vector that completely describes the polarization state of light: S = (S0, S1, S2, S3). S0 represents the total intensity of light, which is the sum of the intensities of light in all polarization directions; S1 is related to the horizontal and vertical linear polarization components; S2 is related to the ±45° linear polarization component; and S3 is related to the left-handed and right-handed circular polarization components. In the present invention, the circular polarization component S3 is ignored, and the Stokes vector becomes S = (S0, S1, S2). This means that in this calculation method, the focus is on the linear polarization characteristics of light, without considering the influence of circular polarization.

[0110] Specifically, the light intensity ratio conversion relationship between S0, S1, S2, degree of linear polarization DoLP and 0°, 30°, 60° and 90° polarization angle images is as follows:

[0111] (2);

[0112] (3);

[0113] (4);

[0114] (5);

[0115] Among them, I0, I 30 , I 60 and I 90 They represent the outgoing light intensities of the polarization angles of 0°, 30°, 60°, and 90°, respectively.

[0116] See also Figures 6a to 6d , Figure 6a The measured image of the target at a typical voltage of 0 Vrms of the medium-wave focal plane detector 12 in the image restoration method provided in Example 1 of the present invention; Figure 6b The measured target image of the medium-wave focal plane detector 12 at a typical voltage of 1.3 Vrms in the image restoration method provided in Example 1 of the present invention; Figure 6c The measured target image of the medium-wave focal plane detector 12 at a typical voltage of 1.4 Vrms in the image restoration method provided in Example 1 of the present invention; Figure 6d The measured target image of the medium-wave focal plane detector 12 under a typical voltage of 2.0 Vrms in the image restoration method provided in Example 1 of the present invention; wherein, Figures 6a to 6d It can be seen that the grayscale values ​​at several voltages on different materials (such as the car body) vary significantly, but the overall light intensity does not change much, indicating that the polarization imaging system achieves polarization control of the target with low energy loss.

[0117] See also Figures 6e to 6h , Figure 6e The Stokes vector S0 image of the target scene in the image restoration method provided in Example 1 of the present invention; Figure 6f The Stokes vector S1 image of the target scene in the image restoration method provided in Example 1 of the present invention; Figure 6g The Stokes vector S2 image of the target scene in the image restoration method provided in Example 1 of the present invention; Figure 6h The linear polarization degree image of the target scene in the image restoration method provided in Example 1 of the present invention; wherein Figures 6e to 6h It can be seen that timely extraction of target contours can reflect the surface characteristics of different materials and reduce image glare.

[0118] The polarization image restoration method for a target scene provided by this invention uses calibration data from a liquid crystal micro-nano polarization device in a laser environment and images directly obtained by a medium-wave infrared polarization imaging system 100 to recover a polarization image with polarization characteristics. The method is simple in principle and utilizes the rotation angle control properties of the liquid crystal micro-nano polarization device to achieve polarization resolution of the target scene.

[0119] Different from the prior art, the medium-wave infrared polarization imaging system 100, laser beam calibration system 200, and image restoration method provided by the present invention have the following advantages:

[0120] (1) The liquid crystal micro-nano polarization device in the medium-wave infrared polarization imaging system 100 is simple to manufacture and low in cost. It can effectively realize the electrical control adjustment of the polarization direction of the incident light by driving it with a small voltage. This is achieved only by adjusting the size of the external driving voltage. There are no mechanical rotating parts during use, and the use requirements are low.

[0121] (2) The medium-wave infrared polarization imaging system 100 is different from the traditional polarization imaging system in that it does not only consider certain polarization angles (50% energy loss) when acquiring polarization images corresponding to polarization angles. Instead, it uses polarization rotation angles instead of polarization angles for parameter analysis, so that the acquired polarization images reflect polarization information on the basis of higher energy utilization.

[0122] (3) The medium-wave infrared polarization imaging system 100 can realize electrically controlled polarization detection of the target scene without sacrificing resolution.

[0123] (4) The laser beam calibration system 200 has reliable data, strong analyzability and high repeatability.

[0124] (5) The proposed target scene polarization image restoration method has simple principle, simple calculation and strong understandability.

[0125] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0126] The above embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A medium-wave infrared polarization imaging system, characterized in that: include: A controllable power supply for outputting external voltage; a liquid crystal micro-nano polarization control device, electrically connected to the controllable power supply, for adjusting the polarization rotation angle of outgoing light relative to incident light in a target scene after the external voltage is applied; A medium-wave focal plane detector is provided close to the light-emitting side of the liquid crystal micro-nano controlled polarization device, and is used to obtain measured images of the target scene corresponding to different external voltages; a data storage and analysis module, electrically connected to the medium-wave focal plane detector, for inverting and obtaining a linear polarization degree image of the target scene based on pre-stored calibration data of the corresponding relationship between the external voltage and the polarization rotation angle, the external voltage, and the light intensity data of the measured target image; Among them, the medium-wave focal plane detector includes a medium-wave infrared band adapter lens, a medium-wave infrared detection CMOS focal plane array and an electronic component in sequence along the propagation direction of the incident light. One end of the electronic component is electrically connected to the medium-wave infrared detection CMOS focal plane array, and the other end of the electronic component is electrically connected to the data storage and analysis module; the medium-wave infrared detection CMOS focal plane array is a HgCdTe infrared focal plane array, and the medium-wave infrared detection band is 3.7μm~4.8μm.

2. The medium-wave infrared polarization imaging system according to claim 1, characterized in that: The controllable power supply is a square wave power supply with a frequency of 1 kHz and a duty cycle of 1:

1.

3. The medium-wave infrared polarization imaging system according to claim 1, characterized in that: The liquid crystal micro-nano controlled polarization device comprises a first substrate, a first electrode layer, a first alignment layer, a liquid crystal layer, a second alignment layer, a second electrode layer and a second substrate in sequence along the propagation direction of the incident light.

4. The medium-wave infrared polarization imaging system according to claim 1, characterized in that: The medium-wave infrared polarization imaging system also includes a device support frame and a precision gimbal stabilizer. One end of the device support frame is fixedly connected to the medium-wave infrared band adapter lens, and the precision gimbal stabilizer is used to carry the medium-wave focal plane detector.

5. The medium-wave infrared polarization imaging system according to claim 4, characterized in that: The device support frame has an accommodating cavity, in which the liquid crystal micro-nano polarization control device is arranged. The angle between the liquid crystal micro-nano polarization control device and the medium-wave infrared band adapted lens is 10°~45°.

6. A laser beam calibration system for calibrating the calibration data of the medium-wave infrared polarization imaging system according to any one of claims 1 to 5, characterized in that: The laser beam calibration system includes a mid-infrared optical parametric oscillator laser, a polarizer, the liquid crystal micro-nano polarization control device, an analyzer, an objective lens, an attenuator, and an optical quality analyzer in sequence from the optical signal input end to the optical signal output end; Wherein, the laser beam calibration system further includes the controllable power supply, and the controllable power supply is electrically connected to the liquid crystal micro-nano deflection control device.

7. The laser beam calibration system according to claim 6, characterized in that: The polarization direction of the outgoing light of the mid-infrared optical parametric oscillation laser and the orientation direction of the liquid crystal micro-nano controlled polarization device on the side close to the incident light are both along the X-axis.

8. The laser beam calibration system according to claim 7, characterized in that: When the polarizer transmission direction is along the X axis, the pixel light intensity of the CMOS surface of the light quality analyzer under different external voltages is recorded within the X direction voltage adjustment range, and the average surface light intensity is taken as Ix Vn When the polarizer transmission direction is along the Y axis, the pixel light intensity of the CMOS surface of the light quality analyzer is recorded at different external voltages within the Y direction voltage adjustment range, and the average light intensity is taken as Iy Vn ; The polarization rotation angle AOP of the liquid crystal micro-nano controlled polarization device under different external voltages Vn is arctan(Iy Vn / Ix Vn ).

9. An image restoration method, applied to the medium-wave infrared polarization imaging system according to any one of claims 1 to 5, characterized in that: The method comprises: S10, debugging the medium-wave infrared polarization imaging system so that it can capture a target grayscale image; S20, turning on the controllable power supply, and collecting measured images of the target under different external voltages respectively through the medium-wave focal plane detector; S30, calculating the polarization rotation angle corresponding to different external voltages according to calibration data of the corresponding relationship between the external voltage and the polarization rotation angle; S40, converting the target measured images corresponding to different polarization rotation angles into corresponding polarization angle images according to the calibration data; S50 , converting the polarization angle image into a linear polarization degree image of the target scene according to the correspondence between the Stokes components.

Images