像素刻划偏振相机的高精度像素级偏振非均匀性矫正

Error analysis and correction of a photoelastic method based on a pixelated polarization camera

We present a novel phase-based filtering algorithm designed to retrieve the Degree of Linear Polarization (DoLP) and Angle of Linear Polarization (AoLP) by leveraging the intrinsic properties of a pixelated polarization camera. Unlike conventional intensity-based filters, our approach utilizes complex phase values to estimate polarization parameters, offering a flexible and computationally efficient alternative. Each point is treated as an independent measurement, dependent solely on the kernel size, which enables the potential for real-time processing. Experimental and simulation evaluations under Gaussian noise conditions validate the robustness of our approach, demonstrating a high degree of consistency with standard methods. The ANOVA analysis results reflect this consistency across datasets, as indicated by the sum of squares (SS), mean squares (MS), and F-statistic values. This reinforces the reliability of the proposed algorithm and highlights its practical applicability in noise-affected environments. Our findings suggest that the proposed method provides a stable and adaptable solution for polarization parameter extraction, making it well-suited for applications in fields such as biomedical imaging, remote sensing, and industrial inspection, where real-time performance and noise resilience are critical.

Ellipsometric Surface Plasmon Resonance (SPR) sensors are known for their relatively simple optical configuration compared to interferometric and optical heterodyne phase interrogation techniques. However, most of the previously explored ellipsometric SPR sensors based on intensity measurements are limited by their real-time applications because phase or polarization shifts are conducted serially. Here we present an ellipsometric SPR sensor based on a Kretschmann-Raether (KR) diverging beam configuration and a pixelated microgrid polarization camera. The proposed methodology has the advantage of real-time and higher precision sensing applications. The short-term stability of the measurement using the ellipsometric parameters tanψ and cos(Δ) is found to be superior over direct SPR or intensity measurements, particularly with fluctuating sources such as laser diodes. Refractive index and dynamic change measurements in real-time are presented together with Bovine Serum Albumin (BSA)-anti-BSA antibody binding to demonstrate the potential of the developed sensor for biological sensing applications with a resolution of sub-nM and down to pM with additional optimization. The analysis shows that this approach may provide the ultimate detection limit for SPR sensors.

The development of the pixelated polarization camera is enabling dynamic interferometry, a new metrology technique that is insensitive to vibration and suits use in an industrial environment.

We report variable shear interferometers employing liquid-crystal-based geometric-phase (GP) gratings. Conventional grating-based shear interferometers require two lateral shifts of the gratings to enable phase-shifting capabilities in x- and y- direction and two axial shifts of the gratings to adjust the shear amount in x- and y- direction, i.e., these systems need control of four axes mechanically. Here we show that the GP gratings combined with a pixelated polarization camera give instantaneous-phase shifting so that no mechanical movement is necessary to obtain phase shifts. Furthermore, we show that a single fixed shear with a rotational shear axis provides a more robust selection of shears while requiring the control of only one mechanical axis. We verify this statement using spatial domain and frequency domain criteria. We further show that the resolution of the reconstructed wavefield depends not only on the numerical aperture of the imaging system, the pixel size of the detector, or the spatial coherence of the source but also on the ability to determine the shear amount accurately. To improve this, we report a methodology to accurately detect the shear amounts using the second derivative of the autocorrelation function of the measured holograms, which further relaxes the requirements on mechanical stability.

Phase analysis by differential interference contrast microscope using pixelated polarization camera

This work presents a dynamic electronic speckle pattern interferometry (ESPI) system with out-of-plane sensitivity based on a pixelated polarization camera. The approach employs polarization-encoded phase-shifting interferometry, enabling the simultaneous acquisition of multiple phase-shifted speckle interferograms and allowing the temporal tracking of deformation fields induced by mechanical loading. From the four polarization-resolved interference patterns, the phase is retrieved using a Fourier-based phase demodulation approach, from which the out-of-plane displacement field is reconstructed. Experimental results obtained on galvanized steel plates, including samples with and without structural defects such as cracks, demonstrate the capability of the method to resolve spatial variations in dynamic deformation, which were introduced by a piezoelectric actuator to assess the temporal stability and repeatability of the proposed system. These results indicate that the proposed approach is suitable for non-destructive evaluation and dynamic deformation monitoring of metallic components under mechanical stress.

Inner surface micro-scale topography is a concerned aspect in precise pipe-type workpiece manufacturing. To realize nondestructive measurement of pipe-type workpieces, in this paper a compact side-viewing interference microscope (CSIM) is proposed and a prototype is developed. Based on the Michelson-type configuration, a special interference objective is designed, in which the object plane is placed at the side of the objective to realize side viewing. To avoid mechanical scanning and reduce the measuring head size, a polarization interferometric method is employed by using a pixelated polarization camera to achieve phase shifting. The response of four polarization channels is calibrated with a simple spatial carrier method, and the surface reconstruction error is reduced by half with least-squares fittings compensation. Experiments verify that the CSIM achieves high axial resolution and roughness measurement accuracy up to the sub-nanometer level. Two pipe-type workpieces made of different materials, of which the minimum diameter is 42 mm, are successfully measured with the developed CSIM.

In this investigation, we propose a simple and effective lateral shearing interferometer based on a polarization grating. In the lateral shearing device, an incident beam is split into two beams by a polarization grating, and the returning beams can be laterally shifted after reflecting off a flat mirror and passing through the polarization grating again. These two beams are not only laterally shifted, but also their polarization states are orthogonal to each other as circular polarizations. With a single image obtained by a pixelated polarization CMOS camera, the proposed LSI can obtain the phase map corresponding to the x-sheared interferogram, and the other phase map can be calculated from another single image obtained by 90° rotation of the shearing device. Then, the original wavefront corresponding to the surface figure of the specimen can be reconstructed by wavefront reconstruction algorithms. In the experiments, various wavefronts generated by concave mirrors and a deformable mirror were measured and compared with those of a commercial Shack-Hartmann sensor.

Rural environmental protection and governance is an important link for the sustainable development of township economy, the sustainable utilization of resources and the realization of short-term and long-term interests. Many villages in Western China show the characteristics of many points and a wide range. The objects of rural environmental protection and treatment are mainly domestic waste and sewage. In order to save resources and reasonably set the site selection of environmental protection facilities, it is necessary to obtain a large number of rural topographic maps in advance. However, there are many villages in Northwest China, and traditional means can not obtain drawings and data quickly and accurately. UAV aerial survey has high speed, high precision and high operation efficiency, but the cost of industrial UAV is high. Thanks to the development of sensor technology, the non measurement camera pixels carried by consumer UAV basically meet the industry requirements. With the help of phantom 4 Pro UAV platform, this paper has completed the rural topographic map mapping of a certain area in the northwest, which has passed the verification, its accuracy fully meets the design requirements of facility location, and provides technical support for scattered regional aerial survey.

Fringe projection profilometry has emerged as a widely used non-contact three-dimensional (3D) measurement technique due to its full-field acquisition, high precision, and rapid measurement capabilities. However, its performance degrades significantly when measuring objects with complex surface reflection characteristics, as light undergoes inter-reflection and subsurface scattering during measurement, generating indirect light signals that lead to reconstruction errors. Dual profilometry, a computational 3D profilometry based on dual photography theory, overcomes this limitation by treating each camera pixel as a single-pixel detector to isolate the direct light signals. While theoretically effective, existing implementations need the reconstruction of millions of dual images. To overcome this limitation, we present an efficient reconstruction method that avoids dual image reconstruction. Experimental validation demonstrates that the reconstruction speed can be substantially improved compared to existing dual profilometry implementations, achieved without compromising reconstruction accuracy. The proposed method effectively resolves the efficiency bottleneck that has hindered the practical adoption of dual profilometry, enabling its deployment in practical applications such as industrial inspection and high-resolution biomedical surface characterization.

Wide Field Camera 3 (WFC3) is the most used instrument on board the Hubble Space Telescope. Providing a broad range of high quality imaging capabilities from 200 to 1700mn using Silicon CCD and HgCdTe IR detectors, WFC3 is fulfilling both our expectations and its formal requirements. With the re-establishment of the observatory level "spatial scan" capability, we have extended the scientific potential ofWFC3 in multiple directions. These controlled scans, often in combination with low resolution slit-less spectroscopy, enable extremely high precision differential photometric measurements of transiting exo-planets and direct measurement of sources considerably brighter than originally anticipated. In addition, long scans permit the measurement of the separation of star images to accuracies approaching 25 micro-arc seconds (a factor of 10 better than prior FGS or imaging measurements) enables direct parallax observations out to 4 kilo-parsecs. In addition, we have employed this spatial scan capability to both assess and improve the mid­ spatial frequency flat field calibrations. WFC3 uses a Teledyne HgCdTe 1014xl014 pixel Hawaii-lR infrared detector array developed for this mission. One aspect of this detector with implications for many types of science observations is the localized trapping of charge. This manifests itself as both image persistence lasting several hours and as an apparent response variation with photon arrival rate over a large dynamic range. Beyond a generally adopted observing strategy of obtaining multiple observations with small spatial offsets, we have developed a multi-parameter model that accounts for source flux, accumulated signal level, and decay time to predict image persistence at the pixel level. Using a running window through the entirety of the acquired data, we now provide observers with predictions for each individual exposure within several days of its acquisition. Ongoing characterization of the sources on infrared background and the causes of its temporal and spatial variation has led to the appreciation of the impact of He I 1.083 micron emission from the earth's atmosphere. This adds a significant and variable background to the two filters and two grisms which include this spectral feature when the HST spacecraft is outside of the earth's shadow. After nearly five years in orbit, long term trending of the scientific and engineering behavior of WFC3 demonstrates excellent stability other than the expected decline in CCD charge transfer efficiency. Addition of post-flash signal to images is shown to markedly improve the transfer efficiency for low level signals. Combined with a pixel based correction algorithm developed at STScl, CCD performance is stabilized at levels only slightly degraded from its initial values.

<title>Abstract</title> Detection of traffic participants is one of the core tasks in environmental perception for autonomous driving. However, accurately identifying small sized and occluded objects in complex traffic scenarios remains a pressing challenge. To address these issues, a high precision multi-scale perception architecture named DCD-YOLO is proposed based on YOLOv11n, which integrates multi-branch feature extraction, attention guided enhancement, and task decoupled prediction mechanisms.A Dynamic Fusion Block (DFB) is introduced to partially replace the original C3k2 structure, enhancing feature extraction for small objects and complex backgrounds. In addition, the Content Guided Attention (CGA) module is incorporated in the Neck to emphasize key object regions through the collaborative effects of channel, spatial, and pixel level attentions.Meanwhile, a Dynamic Shared Enhanced Head (DSEH) combines reparameterizable detail enhanced convolutions, shared convolutional weights, and Group Normalization to improve multi-scale object localization and classification performance while maintaining a lightweight architecture.Experimental results demonstrate that DCD-YOLO improves mAP@0.5 by 2.9% on the KITTI dataset. Furthermore, the proposed model is deployed on a real vehicle platform and tested under realistic driving scenarios, which further verifies its deployment feasibility and practical significance for autonomous driving systems.

To achieve the high precision measurement of the complicated deep-hole profile geometric parameters, the detection system for the profile based on the structured light was established. However the images collected by the camera had larger geometric distortion compared with the plane images from the profile because of the curvy surface features of the deep-hole profile. The geometric distortion affected the calculation accuracy of the geometric parameters directly. Firstly, the models were established indiscriminately for the deep-hole profile and its plane structure to analyze the space coordinate transformation between each other. Then, the ideas of the cubic spline interpolation and discrete mapping were referred to propose the deep-hole profile correction algorithm based on the discrete mapping considering the precision and speed of the distortion correction comprehensively. The purpose of correcting the deep-hole profile distortion online was achieved through the algorithm. The test precision reached the sub pixel level and the error was less than 0.1 mm.

Abstract. Sugarcane is an important source of food, biofuel, and farmer income in many countries. At the same time, sugarcane is implicated in many social and environmental challenges, including water scarcity and nutrient pollution. Currently, few of the top sugar-producing countries generate reliable maps of where sugarcane is cultivated. To fill this gap, we introduce a dataset of detailed sugarcane maps for the top 13 producing countries in the world, comprising nearly 90 % of global production. Maps were generated for the 2019–2022 period by combining data from Global Ecosystem Dynamics Investigation (GEDI) and Sentinel-2 (S2). GEDI data were used to provide training data on where tall and short crops were growing each month, while S2 features were used to map tall crops for all cropland pixels each month. Sugarcane was then identified by leveraging the fact that, among all non-tree species grown in cropland areas, sugarcane is typically tall for the largest fraction of time. Comparisons with field data, pre-existing maps, and official government statistics all indicated high precision and high recall of our maps. Agreement with field data at the pixel level exceeded 80 % in most countries, and subnational sugarcane areas from our maps were consistent with government statistics. Exceptions appeared mainly due to problems in underlying cropland masks or due to under-reporting of sugarcane area by governments. The final maps should be useful in studying the various impacts of sugarcane cultivation and producing maps of related outcomes such as sugarcane yields. The dataset is available on Zenodo at https://doi.org/10.5281/zenodo.10871164 (Di Tommaso et al., 2024a).