基于偏振调制的激光三维成像方法研究

发布时间：2018-03-17 07:06

本文选题：激光雷达　切入点：三维成像　出处：《中国科学院光电技术研究所》2017年博士论文　论文类型：学位论文

【摘要】：三维成像激光雷达因其具有分辨率高,信息量大,快速成像以及全天时工作等突出特性,成为目标三维形态识别的重要手段,广泛应用于空间碎片监视和识别、大尺寸精密测量、非接触式精密无损检测以及微振动测量等基础前沿领域。但是现有激光三维成像方法仍然存在以下不足:(1)扫描成像体制的激光雷达,其成像速度受限于机械扫描机构,难以满足对高动态目标的实时三维成像需求;(2)APD阵列成像体制的激光雷达,其横向分辨率受限于探测器件及其配套的高速读出电路;(3)ICCD相机成像体制的激光雷达,其横向分辨率和灵敏度受限于相机本身的“光-电-光-电”多重转换和耦合结构。上述缺点使三维成像激光雷达难以满足高分辨率动态成像领域的探测需求。因此,研究一种高分辨率、快速成像、作用距离远且数据量低的激光三维成像方法,是目前激光主动探测领域亟待解决的重要课题。为此,本论文提出了基于偏振调制的激光三维成像方法。首先在完成对大口径电光晶体的偏振调制特性研究的基础上,建立了基于偏振调制的脉冲测距理论;其次,建立了基于偏振调制的面阵三维成像仿真系统,利用仿真系统对测距理论进行了数值分析和仿真验证,从而确立了激光三维成像系统的详细技术方案和指标体系;最后,搭建了基于偏振调制的激光三维成像实验系统,在完成三维重建算法的基础上实现对远距离静态和动态目标的三维成像及显示。论文的主要特色和创新之处在于:提出了基于偏振调制的高灵敏度高分辨率三维成像方法。利用偏振调制技术将时间信息转换为灰度信息,为高灵敏度高分辨率EMCCD相机用于激光三维成像提供了可能。由于EMCCD相机的成像信号直接完成“光-电”一次转换,省去了现有激光三维成像系统中ICCD相机的“光-电-光-电”多重转换过程,提高了探测灵敏度和横向分辨率。另外,系统仅需发射一次脉冲即可获得一幅三维图像,具备闪光三维成像能力,并且其曝光时间达到亚微秒量级,能够满足平台运动或动态目标的三维成像需求。提出了自适应的距离选通三维成像方法。根据测距精度与选通距离成反比的特性,首先在较大的选通距离内搜索目标并粗略测距,然后根据目标的概略位置自适应地调整选通距离的基准和宽度,实现精细测距。这样使得激光三维成像系统既能实现较高的测距精度,又能保持较宽的选通距离。在目标场景的三维重建方面,提出了适用于三维成像系统的高效图像配准算法。根据激光三维成像系统对实时三维重建和亚像素级配准精度的特定需求,提出了基于第一主成分分析的高效图像配准算法,与现有的亚像素级图像配准算法相比,该方法既保持了配准精度和稳健性,又提高了算法效率,有利于实时三维重建及显示。另外,利用灰度图像的信噪比甄别距离图像中的噪声并加以抑制,从而能够从模糊难辨的距离图像中准确地识别目标的三维形态特征。该方法简单且效果显著,同样有利于实时三维重建及显示。综上所述,本论文提出的激光三维成像方法具备了高分辨率、快速响应、作用距离远且数据量低的特性,为激光三维成像领域开辟了一条新的技术路径。
[Abstract]:The 3D imaging laser radar because of its high resolution, large amount of information, fast imaging and all day long work and other prominent characteristics, has become an important means of 3D pattern recognition, are widely used in space debris monitoring and identification of large size precision measurement, non-contact precision non-destructive detection and micro vibration measurement based but Frontiers. There are still the following deficiencies of the existing 3D laser imaging methods: (1) laser scanning imaging system, the imaging speed is limited by the mechanical scanning mechanism, it is difficult to meet the needs of real-time three-dimensional imaging of high dynamic targets; (2) APD array imaging laser radar system, the lateral resolution is limited by the detection device and supporting high speed readout circuit; (3) ICCD camera imaging laser radar system, its transverse resolution and sensitivity is limited by the camera itself "o-e-o electric" multiple conversion and coupling structure. Structure. These shortcomings make 3D imaging laser radar is difficult to meet the need of the detection of high resolution dynamic imaging field. Therefore, fast imaging of a high-resolution, three-dimensional laser imaging method, the role of distance and the amount of the data is low, is an important task for active laser detection field to be solved. Therefore, this paper puts forward a three-dimensional laser imaging method based on polarization modulation. Based on the research on polarization modulation characteristics of large aperture optical crystals on a pulse ranging theory based on polarization modulation; secondly, to establish the three-dimensional polarization modulation array imaging simulation system based on the ranging theory is studied by numerical analysis and simulation using simulation system. In order to establish a detailed technical scheme of three-dimensional laser imaging system and index system; finally, build a polarization modulated laser 3D imaging experiment system based on The realization of three-dimensional imaging to distant targets and the static and dynamic display based 3D reconstruction algorithm. The main features and innovations in this thesis are: put forward the high sensitivity and high resolution 3D imaging method based on polarization modulation. Using polarization modulation technology to convert the time information to the gray information, provides the possibility for high sensitivity and high resolution EMCCD camera for 3D laser imaging. The imaging signal of EMCCD camera directly to complete the "light electric conversion", eliminating the existing 3D laser imaging system ICCD camera "o-e-o electric" multiple conversion process, improve the detection sensitivity and lateral resolution. In addition, the system only need to launch a the pulse can obtain a three-dimensional image, with flash 3D imaging, and the exposure time to achieve sub microsecond, can satisfy the kinematic or dynamic target platform The 3D imaging needs. The adaptive range gated three-dimensional imaging method. According to the range accuracy and gating is inversely proportional to the distance characteristic, first in the larger range gated search target and rough location, then according to the approximate position of target adaptive adjustment of the strobe distance datum and width, so that to achieve precise ranging. Laser 3D imaging system can achieve high accuracy, and can keep a wide distance. In the 3D reconstruction of the target scene, propose an efficient image registration algorithm for 3D imaging system. According to the specific needs of the laser 3D imaging system for real-time 3D reconstruction and sub-pixel registration accuracy, proposed an efficient image registration algorithm based on principal component analysis first, compared with sub-pixel image registration algorithms, this method not only maintains the registration accuracy and robustness, and The high efficiency of the algorithm and is conducive to real-time 3D reconstruction and display. In addition, the noise in the image distance than screening and suppress by gray image noise, which can accurately identify the three-dimensional morphological features of target from the image blurred in the distance. This method is simple and effective, also conducive to real-time 3D reconstruction and display 3D laser imaging. In summary, the proposed method has high resolution, fast response characteristics, the role of distance and the amount of the data is low, has opened up a new path for 3D laser imaging technology field.

【学位授予单位】：中国科学院光电技术研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN958.98

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