Mid-wave infrared interference spectral imagers possess unique advantages in gas detection and identification due to their wide characteristic spectral coverage,high-throughput detection capability,and multi-channel sampling.Particularly in daily inspection and early warning of chemical gases and rapid emergency response to leakage scenarios,they can provide early warnings of disasters at the initial stage of gas leakage,preventing the situation from escalating.After a gas leak occurs,without requiring personnel to enter the site,they can quickly identify the type of leaking gas and the distribution of its diffusion concentration,providing first-hand on-site data for the evaluation of emergency response plans.However,traditional point-scan and area-scan interference spectral imaging configurations face significant limitations in enhancing lightweight,compact design,and stability.It is of great significance to research and design interference spectral imaging instruments that meet the high demands for mobility,adaptability to complex environments,field of view coverage,and lightweight compactness in specific application scenarios.Additionally,as interference spectral imagers require high precision in detector pixel intensity detection,it is necessary to study the analysis and suppression methods of infrared stray radiation in complex scenarios. This paper proposes a spectral imaging system based on static interference modulation using a stepped micro-mirror.The optical configuration of the system is shown in Figure 1.The scanning telescope imaging lens assembly achieves wide-field one-time convergence imaging onto the stepped micro-mirror for interference modulation,and the image is then relayed onto the detection focal plane through the relay imaging lens group.A cylindrical design is introduced to compensate for the high-order astigmatism introduced by the interference beam-splitting system.Achromatic broadband design and athermalization across a wide temperature range are achieved through hybrid refractive-diffractive and aspheric designs,resulting in a static Modulation Transfer Function(MTF)better than 0.7 at the cutoff frequency.To analyze infrared stray radiation,a stray radiation model for the interference spectral imaging system was constructed.The materials and surface radiation scattering characteristics of the optomechanical structure were defined,and ray tracing was performed.Based on the tracing results,a stray radiation suppression structure was designed,achieving infrared radiation suppression at the level of 10⁻⁵. The telescope imaging lens group was optimized with an image-space telecentric design,while the relay imaging lens group adopted an object-space telecentric design,achieving a perfect match in a dual-high telecentric optical system.By employing hybrid refractive-diffractive and aspheric designs,the system demonstrated excellent performance in the mid-wave infrared band of 3 μm-5 μm across a temperature range of-40℃to 60℃.The static MTF exceeded 0.7 at 17 lp/mm,distortion was controlled within 0.2%,and the RMS radius of the imaging spot was less than 5.9 μm,meeting all imaging quality requirements.A stray radiation simulation model for the interference spectral imaging optomechanical system,as illustrated in Figure 7,was constructed.Stray radiation tracing was performed for typical field light paths,and based on the analysis results,efficient suppression was achieved through blackbody extinction treatment and dedicated stray radiation suppression structures.This reduced the infrared stray radiation energy ratio from an initial level of 10⁻² to 10⁻⁵.Imaging detection experiments on long-distance target scenes using an engineering prototype demonstrated excellent image quality.The MTF test of the prototype of high-precision alignment principle shows that the actual MTF of the designed imaging system is better than 0.32 at the cut-off frequency. The infrared spectral imaging system based on static interference modulation with a stepped micro-mirror successfully achieves high-quality remote sensing imaging,identification and analysis of gases.The adoption of achromatic methods using cylindrical lenses and hybrid refractive-diffractive lenses,together with the stray radiation suppression method proposed in this paper,has all yielded the expected effects in optimizing imaging quality,which is proven to be effective and can serve as a reference for research in the same field.In addition,the instrument's volume is reduced by a quarter and its weight by approximately 60%,which also provides a valuable contribution to the miniaturization process of such imaging systems.
Intense solar activities(such as coronal mass ejections and solar flares)release a large number of high-energy charged particles.When these particles reach Earth,they interact with the magnetosphere and trigger magnetic storms through processes like particle precipitation.The duration of magnetic storms can range from several hours to days.During this period,they cause ionospheric disturbances and drastic changes in the geomagnetic field,leading to disruptions in on-orbit satellite communications and shortwave broadcasting,significant degradation or even loss of lock in the positioning accuracy of global navigation satellite systems,and an increased risk of accelerated orbital decay for low-orbit satellites due to sudden increases in atmospheric drag. During magnetic storms,precipitating particles collide with the upper atmosphere at the poles along magnetic field lines,exciting the generation of auroras.The radiation characteristics of auroras are directly related to the flux and energy of the incident particles.Therefore,detecting the morphology of auroras in specific wavelength bands has become a key method for studying solar activities.During magnetic storms,precipitating high-energy particles collide with neutral atmospheric components(such as atomic oxygen and nitrogen molecules)above Earth's poles.Through excitation and ionization processes,these collisions produce auroral radiation covering wavelengths from visible light to the far ultraviolet.Among this radiation,the emission intensity of the LBH band of nitrogen molecules(N₂)—located in the far ultraviolet range of 160～180 nm—has a direct and sensitive quantitative relationship with the energy flux of the precipitating particles. Far ultraviolet radiation is effectively absorbed by the upper atmosphere,enabling its observation even in sunlight.However,achieving high-precision imaging of N₂ LBH band auroral radiation faces two core technical challenges.Firstly,the dynamic range of auroral brightness under natural conditions is extremely wide.Imaging across a range from approximately 100 Rayleigh(R)to over 30 000 Rayleigh(30 kR)during intense activity periods requires the instrument to have an extremely high linear dynamic range.Secondly,in the far ultraviolet band,stray light interference from non-target sources(such as the Sun and geocoronal background)is extremely strong,which can easily overwhelm weak auroral signals.This places extremely stringent requirements on the system's internal stray light suppression capability. To capture the full dynamic range(100 R～30 kR)of N₂ LBH band(160～180 nm)auroral radiation and overcome the challenges of weak far ultraviolet signals and strong background interference,this study developed an optical system based on a coaxial four-reflection structure.The core of the instrument's performance lies in its large dynamic range detection capability and high stray light suppression level.Through targeted optical design,simulation,and testing,the system ultimately achieved a signal-to-noise ratio(SNR)>1.5 for extremely weak signals(100 R),ensuring the reliable extraction and detectability of weak signals.For strong signals(30 kR),the SNR reached>30,guaranteeing measurement accuracy and the upper limit of dynamic range during intense auroral activity.Meanwhile,the stray light suppression level reached 10-3 within the 160～180 nm operating band and exceeded 10-9 in the non-operating band of 200～1 000 nm,thereby effectively extracting real auroral signals from complex optical backgrounds. This instrument can continuously monitor the spatiotemporal evolution of the position,morphology,scale,and intensity distribution of the auroral oval.Through inversion and analysis of these high-quality image data,we can quantitatively obtain core parameters such as information on precipitating particles and their energy flux.This deepens the scientific understanding of magnetic storm triggering mechanisms,energy coupling processes,and evolution laws.It provides crucial data support and technical backing for accurate magnetic storm forecasting,space weather modeling,and ensuring the stable operation of on-orbit satellites and ground communication systems,boasting significant scientific value and broad application prospects.
Intraocular Lens(IOL)is a medical device implanted into the eye,commonly utilized in the treatment of ophthalmic conditions such as cataracts.In clinical practice,implanted IOLs frequently exhibit varying degrees of decentration and tilt.These positional deviations from the ideal alignment can significantly compromise the eye's optical performance.Among the widely adopted monofocal IOLs,which are primarily designed to restore distance vision,two main categories exist:spherical and aspherical monofocal IOLs.Aspherical monofocal IOLs can be further subdivided into two types:Aberration-correcting Intraocular Lens(ACIOL)and Aberration-free Intraocular Lens(AFIOL).ACIOL is specifically designed to neutralize the cornea's inherent positive spherical aberration,thereby enhancing the quality of distance vision.Under perfect centration conditions,these lenses are capable of delivering optimal optical outcomes.In contrast,AFIOL,while not altering the overall spherical aberration of the eye,demonstrate superior performance in the presence of decentration or tilt.Under such non-ideal positional conditions,they are usually superior to ACIOL.However,while numerous studies have evaluated the optical performance of misaligned IOLs,the underlying causes of performance variations among different aspherical monofocal IOL types remain inadequately explored—a challenge that persists in the field.Some investigations have focused on compensating for refractive errors resulting from IOL tilt or axial shift,whereas others have derived analytical expressions to estimate the specific aberration terms that require correction under given decentration conditions.Despite these valuable efforts,a critical gap remains:the absence of a comprehensive theoretical model capable of simultaneously characterizing the aberrations of the human eye's optical system in the presence of both decentration and tilt.This limitation ultimately hinders a systematic analysis of the factors responsible for optical performance differences among misaligned IOLs. To address these challenges,this study introduces several key improvements.First,the computational model incorporates the thickness of both the cornea and the IOL.Under realistic implantation conditions,the anterior surface of the IOL may not be perfectly aligned with the iris and can exhibit a measurable offset.This misalignment significantly increases the complexity of aberration calculations,requiring repeated application of the pupil-shift law to both optical surfaces.To enable efficient computation and analysis,the wave aberration coefficients corresponding to primary spherical aberration and primary coma in the pseudophakic eye are explicitly derived.Then,based on functional differences,different axial lengths,and functional principles,three types of ACIOL and three types of AFIOL were designed respectively.The validity of both ACIOL and AFIOL is confirmed through a comprehensive analysis of their Modulation Transfer Function(MTF),spot diagrams,simulated imaging,and aberration characteristics.The accuracy of these aberration coefficients is subsequently verified using numerical software.During the development of the misaligned pseudophakic eye model,we clarify why the primary spherical aberration field remains invariant under lateral misalignments.Subsequently,we establish the relationship between the primary coma field and the aberration field decenter vector.A mathematical formula for determining the coordinates of the primary coma field center is derived,revealing that under misaligned conditions,the pseudophakic eye possesses only one nodal point for primary coma—a position that is demonstrably influenced by lateral misalignments.Moreover,a comparison was made between the designed IOL and a commercial ACIOL,which showed similar MTF,thus demonstrating the universality of the conclusions drawn in this study. Based on the misaligned pseudophakic eye model,this study investigates the primary coma field centers of both ACIOL and AFIOL under misaligned conditions.Analytical results indicate that a larger shift in the primary coma field center is associated with a lower MTF.Under decentered conditions,the primary coma field center shift of ACIOL is significantly greater than that of AFIOL.Since the posterior surface spherical aberration is consistent between the two types of IOLs,and the absolute value of the anterior surface spherical aberration in ACIOL is significantly higher than that of the posterior surface,reducing the anterior surface spherical aberration becomes necessary to achieve zero overall spherical aberration.However,as both IOL types share the same dioptric power,their spherical contributions to anterior surface spherical aberration are comparable.Consequently,the reduction of anterior surface spherical aberration must be achieved by decreasing its aspherical contribution,specifically by reducing the conic constant of the anterior surface.This adjustment ensures that the total spherical aberration of the IOL is zero for AFIOL.Once the conic constant of the IOL anterior surface is reduced,the aspherical contribution of the primary coma coefficient of the anterior surface decreases.Given that the aspherical contribution of the posterior surface's primary coma coefficient is zero,this reduction leads to a diminished aspherical contribution to the primary coma field center under decentered conditions.Then,the accuracy of calculating the center of the aberration field is verified through numerical software.Furthermore,by discussing the differences in refractive index between corneal and intraocular structures at different wavelengths and their impact on aberration calculation,the rationality of eye model selection can be enhanced.Finally,by discussing the potential impact of a single parameter such as corneal aberration and thickness,the applicability of the conclusions drawn in this study is demonstrated. By integrating nodal aberration theory with primary aberration theory,we establish a mathematical model that systematically relates IOL misalignments to the primary aberrations of the entire eye.This analytical framework offers a clear advantage over purely numerical approaches,allowing for a principled evaluation of how IOL decentration and tilt influence overall ocular aberrations.Consequently,the model provides a theoretical basis for explaining the performance differences between the two types of aspherical monofocal IOLs under misaligned conditions.The following conclusion can be drawn:1)Decentration and tilt of an IOL cause displacement of the primary coma field center from the field center.This displacement is collectively influenced by factors such as the magnitude of IOL misalignment,geometry of lens surface,and refractive index.Moreover,the magnitude of the primary coma field center shift demonstrates a negative correlation with the system's MTF;2)In the design of aspherical monofocal IOLs,appropriately reducing the conic constant can significantly diminish the primary coma field center shift induced by decentration,thereby enhancing optical performance under misaligned conditions.When the primary coma field center shift is sufficiently minimized,the system's MTF can be maintained nearly unchanged.In summary,the misaligned pseudophakic eye model provides a comprehensive framework for understanding how decentration and tilt influence the performance of aspherical IOLs.This approach offers valuable theoretical guidance for future IOL design and evaluation criteria.
Phase unwrapping serves as a critical step in high-precision optical measurement, aiming to recover the absolute phase from its wrapped counterpart. While current deep learning-based approaches for absolute phase extraction have achieved improvements in both accuracy and computational efficiency, critical challenges persist, including excessively large network parameter counts and low accuracy in resolving discontinuous phases. To overcome these limitations, this paper introduces the Attentive Directional Encoder-Decoder Network (ADE-Net) for structured light phase unwrapping applications. The primary objective is to develop a lightweight, efficient, and robust deep learning framework that achieves consistently high unwrapping accuracy under complex conditions such as noise corruption, phase discontinuities, and aliasing artefacts, thereby providing a practical, engineering-ready solution capable for reliable development in real-world optical measurement systems. The proposed ADE-Net is built upon a concise and efficient encoder-decoder backbone architecture. The encoder consists of four feature extraction stages, each comprising a convolutional block and a Haar Wavelet Down-sampling (HWD) module. The HWD structure preserves high-frequency directional details, such as phase jump edges, during down-sampling, providing a more complete feature foundation for subsequent processing. The decoder employs a symmetric up-sampling structure based on transposed convolutions, with skip connections to fuse multi-scale features from the encoder, ensuring effective detail recovery. To enhance feature representation, two innovative modules are integrated: the Adaptive Clockwork Long Short-Term Memory (AC-LSTM) module and the Depthwise-separable-convolution Efficient Multi-Scale Attention (DEMA) module. The AC-LSTM module is designed to capture multi-scale contextual and direction-sensitive features simultaneously. It consists of two parallel branches: an Atrous Spatial Pyramid Pooling (ASPP) branch for multi-scale context aggregation, and a bidirectional LSTM (Bi-LSTM) branch enhanced with Context Anchor Attention (CAA) to model long-range dependencies along horizontal and vertical directions with spatial awareness. The outputs of both branches are fused to produce rich, direction-aware features. The DEMA module is an improved version of the Efficient Multi-Scale Attention (EMA) mechanism. It introduces depthwise separable convolution to replace standard 3 & times;3 convolutions, significantly reducing computational complexity while maintaining receptive field coverage. Additionally, Batch Matrix Multiply (BMM) is adopted for more efficient parallel processing of batch data. DEMA operates by grouping input features, performing adaptive height and width pooling, and applying depthwise separable convolution in parallel branches, followed by cross-branch fusion via BMM and element-wise multiplication with the original features. This design enhances the model's ability to focus on critical information across scales while optimizing computational efficiency. To comprehensively evaluate the performance of ADE-Net, systematic experiments were conducted using both simulated and real-world datasets. For simulation, three distinct datasets were constructed, each comprising 2 000 pairs of wrapped and absolute phase images with a size of 256 & times;256. Dataset 1 simulated noise interference by introducing Gaussian noise with signal-to-noise ratios of 0, 5, 20, 40, and 80 dB. Dataset 2 simulated phase discontinuities by randomly generating 1 to 2 rectangular jump regions with random positions, sizes, and phase values. Dataset 3 combined both noise and discontinuities to emulate aliasing effects. Additionally, the public real dataset 'Single-input dual-output 3D shape reconstruction' was adopted to assess generalization capability, which contains 1 500 real-scene samples acquired by a structured-light 3D measurement system. The evaluation was performed using three metrics: Normalized Root Mean Square Error (NRMSE), Mean Absolute Error (MAE), and Structural Similarity Index Measure (SSIM). Benchmark comparisons were carried out against mainstream models such as U-Net, Res-UNet, Perera's Net, and TNUNet. In the comparative experiments, ADE-Net achieved the best performance across all three simulated datasets. On the discontinuous dataset, it attained an NRMSE of 4.35 degrees o, an MAE of 1.094 5 rad, and an SSIM of 0.871 4. On the random-noise dataset, the results were 4.58 degrees o NRMSE, 1.216 5 rad MAE, and 0.838 9 SSIM. On the aliased dataset, ADE-Net reached 4.34 degrees o NRMSE, 1.137 7 rad MAE, and 0.834 0 SSIM. Cross-validation on the public dataset demonstrated excellent generalization ability, with a Root Mean Square Error (RMSE) of 0.505 2, an MAE of 0.180 9 rad, and an SSIM of 0.997 1. Ablation studies further confirmed the individual performance contributions of both the AC-LSTM and DEMA modules. Moreover, while maintaining the aforementioned high accuracy, ADE-Net also exhibited remarkable computational efficiency advantages. With only 2.012 M parameters and 2.655 GFLOPs, it is significantly lighter than the compared models. The inference time per single image is only 12.71 ms, meeting real-time processing requirements without compromising accuracy, thereby achieving an effective balance between model complexity and computational performance. In conclusion, ADE-Net presents a lightweight, efficient, and highly accurate deep learning framework for phase unwrapping in structured light 3D measurement. By integrating the AC-LSTM module for capturing direction-sensitive multiscale features and the DEMA module for computationally streamlined attention-driven feature refinement, the models achieve an ideal balance between performance and computational complexity. It demonstrates superior resilience in challenging conditions involving noise corruption, phase discontinuities, and aliasing artefacts, outperforming leading benchmark models in both accuracy and processing efficiency. Rigorous validation on real-world datasets confirms its robust generalization capability, while its fast inference speed and low resource footprint make it well-suited for high-precision phase reconstruction tasks. By addressing practical constrains in deployment, this work promotes the feasibility of structured light 3D measurement system for real-world, resource-aware applications.
Ionic liquids, as a new type of molten salts with high thermal stability, low vapor pressure, and strong designability, have important application value in cutting-edge fields such as electrochemistry, catalytic synthesis, and biomedicine. However, the accuracy and efficiency of ionic liquid type identification still need to be continuously explored and optimized. Traditional characterization methods, such as infrared spectroscopy and nuclear magnetic resonance, usually rely on large precision instruments, which have limitations such as complex operating procedures, high equipment costs, and long analysis cycles. At the same time, the inherent strong hygroscopicity of ionic liquids makes the control of sample purity more stringent, and existing moisture detection methods find it difficult to achieve rapid and precise measurement. Against this background, metasurfaces, as two-dimensional artificial materials that can flexibly control the amplitude, phase, and polarization of electromagnetic waves, provide a new technical path for the development of high-performance sensing technologies. This type of structure has both high sensitivity and non-contact detection advantages, and has shown significant potential in dielectric property analysis and substance identification. However, existing metasurface sensors still have certain limitations in practical applications, such as being easily affected by external electromagnetic interference or requiring direct contact with samples. These issues not only reduce measurement accuracy but may also cause sensor contamination, thereby limiting their widespread application in practical scenarios. Aiming at the technical bottlenecks of ionic liquid type identification and moisture content detection mentioned above, this paper proposes a metasurface microwave sensor based on a dielectric substrate integrated with a double-layer metal resonant structure. The sensor converts the dielectric properties of ionic liquids into significant changes in resonant frequency shift and resonance linearity through its unique electromagnetic field localization and enhancement mechanism, providing a new way to achieve rapid and precise sensing analysis. To deeply study the working mechanism of the sensor, this study adopted a multi-level research method: from the physical mechanism level, the formation and energy distribution of electromagnetic resonance were intuitively presented through surface current distribution analysis; from the model construction level, the physical structure was transformed into circuit parameters through equivalent circuit analysis, and the regulation law of resonant frequency was quantitatively revealed; from the performance prediction level, the electromagnetic response characteristics of the sensor were accurately obtained through full-wave numerical simulation, and the structure was optimized; from the final verification level, experimental tests confirmed that the sensor can not only accurately distinguish six different types of ionic liquids but also achieve high-precision detection of trace moisture content. Before conducting experimental characterization, this study first compared and analyzed the reflection characteristic changes of the sensor before and after loading ionic liquids in the 7 similar to 10 GHz frequency band based on electromagnetic simulation software. The simulation results show that the introduction of ionic liquids not only changed the original resonant mode of the sensor but also induced a stronger electromagnetic response through the dielectric regulation mechanism, thereby verifying that the metasurface sensor has excellent dielectric sensitivity and electromagnetic regulation capabilities. Subsequently, six representative ionic liquids were selected as the measured samples for actual measurement analysis. The experimental measurement results show that when the sample to be tested in the sample holder is changed from [EMIm][BF4] to [OMIm][BF4], the resonant peak position of the reflection spectrum shifts from 8.37 GHz to 8.86 GHz, resulting in a significant frequency shift of 490 MHz. Calculations show that the sensor's average sensitivity to dielectric constant changes can reach 185.42 MHz/epsilon '. In addition, this study systematically evaluated the sensor's ability to detect trace moisture content. Experimental data show that when the water content increases from 0% to 10%, the resonant peak of the reflection spectrum shows a significant frequency shift of 180 MHz (8.22 GHz -> 8.40 GHz), proving that the sensor can effectively detect moisture changes in ionic liquids at the ppm level. In summary, this paper successfully designed and verified a metasurface microwave sensor based on a double-layer metal resonant unit. By using a three-layer structure constructed with an FR4 epoxy resin substrate, combined with an open sample holder and a fully copper-plated bottom plate design, the sensor exhibits excellent detection performance in the 7 similar to 10 GHz working frequency band, achieving non-contact and high-precision detection of ionic liquid types and their moisture content. Simulation and experimental results show that the sensor has different characteristic frequency responses for six typical ionic liquids (including [EMIm][BF4], [BMIm][SCN], [BMIm][OTf], [BMIm][BF4], [HMIm][NTf2], and [OMIm][BF4]), with a maximum frequency shift of 490 MHz and a detection sensitivity of 185.42 MHz/epsilon '. In terms of moisture detection, the sensor shows a good resonant response to 0 similar to 10% moisture content changes in [EMIm][BF4] solutions, with a resonant frequency shift of 180 MHz. The metasurface sensor designed in this study has high sensitivity and good measurement repeatability, providing an effective technical means for ionic liquid purity detection and deterioration monitoring, and has important engineering application prospects in fields such as chemical process control and real-time monitoring in hazardous environments.
