三相机同时偏振成像系统设计及标定

Design and calibration of three-camera simultaneous polarization imaging system

  • 摘要: 同时偏振成像系统可实时获取运动目标的偏振图像,具有广泛的应用前景。然而,现有棱镜分束型同时偏振成像系统存在光学结构复杂、制造和维修成本高、集成度低、对环境稳定性要求严苛等问题,极大地制约了其在小型无人机遥感探测、工业检测等复杂场景中的推广应用。针对这一现状,研究提出了一种低成本、集成化的三相机同时偏振成像系统。该系统采用并行光学成像架构,集成多组件,实现偏振图像采集与处理一体化。为保证系统性能,进一步分析了系统误差来源,并针对通道像元响应一致性、各通道辐射响应一致性、偏振片角度一致性和图像几何像差四个方面提出了相应的标定和校正方法。经校正,系统像元响应非一致性平均值降至0.94%,辐射响应相对差异率平均值降至−0.17%,图像几何像差平均值降至0.53 pixel。标定校正测试和实际场景应用实验结果均表明,系统在保证测量精度的前提下,实现了多角度同时偏振成像系统的低成本化、小型化和集成化,极大地提高了其在小型无人机遥感探测、工业检测、教育教学等对成本敏感的偏振成像方面推广应用的可能性。

     

    Abstract:
    Objective Simultaneous polarization imaging system can obtain real-time polarization images of moving targets, which has a wide range of applications. However, existing beam-splitting simultaneous polarization imaging systems have problems such as complex optical structures, high manufacturing and maintenance costs, low integration, and strict requirements for environmental stability, which greatly restrict their promotion and application in complex scenarios, such as small unmanned aerial vehicle remote sensing detection and industrial inspection. Therefore, it is crucial to develop a low-cost, miniaturized, and highly integrated simultaneous polarization imaging system to meet the demands of cost-sensitive applications.
    Methods A three-camera simultaneous polarization imaging system with a parallel optical imaging architecture was designed. The system utilizes three miniature USB industrial camera modules and linear polarizers with fixed angles to construct a multi-channel optical framework. It utilizes 3D printing technology to deeply integrate polarization optical components, CMOS image sensors, an embedded Linux processing unit, and an MIPI touchscreen, achieving integration of polarization image acquisition and processing. To address system error sources, four calibration and correction methods were proposed: a multi-point correction method to resolve the non-consistency of pixel responses caused by fixed-pattern noise in camera modules; a linear response model-based method to correct radiation response non-consistency between channels; Malus' Law to calibrate polarizer angle errors; and the Scale-Invariant Feature Transform (SIFT) algorithm for image registration to correct geometric aberrations.
    Results and Discussions After calibration and correction, the system performance was significantly optimized: the average polarization imaging non-uniformity was reduced to 0.94%; the average relative difference rate of radiation response between channels was lowered to −0.17%; polarizer angle calibration results showed an average error of 5.00° for the 45° polarizer and 0.00° for the 0° and 90° polarizers (Tab.2), and this error has been incorporated into Stokes parameter calculations for correction; the average image geometric aberration was reduced to 0.53 pixel (Tab.3). Meanwhile, comparison experiments with the prism beam-splitting simultaneous polarization imaging systems from Fluxdata (Fig.10-Fig.11, Tab.5) demonstrated that, while ensuring basic measurement accuracy, the proposed system achieves low-cost, miniaturized, and integrated multi-angle simultaneous polarization imaging, greatly enhancing its potential for promotion and application in cost-sensitive polarization imaging fields such as unmanned aerial vehicle remote sensing, industrial inspection, and education.
    Conclusions To address the application limitations of traditional beam-splitting simultaneous polarization imaging systems, a three-camera simultaneous polarization imaging system with a parallel optical imaging architecture was successfully designed and implemented. By analyzing system error sources and implementing four calibration and correction methods, issues such as polarization imaging non-uniformity, inter-channel radiation response inconsistency, polarizer angle deviation, and geometric aberration were effectively suppressed. Experimental results showed that the system not only accurately captures target polarization information but also significantly reduces manufacturing costs and improves integration, environmental robustness, and modular maintainability compared to traditional systems. This system provides a feasible solution for the lightweight and popularization of multi-channel simultaneous polarization imaging technology, greatly enhancing its potential for application in cost-sensitive fields, including unmanned aerial vehicle remote sensing, industrial inspection, and education.

     

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