距离选通超分辨率激光三维成像反降晰研究

Three-dimensional range-gated active imaging with super resolution is an active optical 3D imaging, and has higher real time than three dimensional scanning LiDAR and higher spatial resolution than Flash LiDAR. Meanwhile, this technique maintains the advantages of range-gated imaging such as high suppression of backscatter from fog and other obscurants, high signal-to-noise ratio, long detection range and so on. Therefore, it has large potential in the applications of low contrast target detection, remote identification, terrain mapping and target capture on obit. However, echo broadening effect and ambient noise blurs the edges of space slices, which impacts on the 3D information deduction, especially for the range-gated super-resolution imaging based on trapezoid range-intensity profile with a small dynamic range of gray level ratio. As a result, the blurring of space slices reduces range resolution of imaging. To solve this problem, an angular algorithm for range deblurring is proposed with a large dynamic range of gray level ratio, and furthermore a spatial deblurring filter is given to reshape space slices and solve the blurring of space slices..Under the trapezoid algorithm of 3D information deduction, the dynamic range of gray level ratio is small. To enlarge the dynamic range, we propose an angular algorithm of 3D information deduction. In this method, space slices with angular range-intensity profiles are established based on echo broadening effect, which reduces the impacts of ambient noise and improve the range resolution of three-dimensional range-gated super-resolution imaging..For echo broadening effect, it results from the convolution of laser pulse and gate pulse. When the laser-pulse shape is not rectangular, the blurring of space slices is strengthened, especially under the degradations caused by speckle effects due to atmospheric turbulence, ambient light and sensor noise. Under the blurring, the depth of viewing and the operation range of range-gated imaging are not given precisely, which impacts on the range accuarcy in 3D imaging. To solve this problem, we propose a spatial deblurring filter to reshape image slices by spatial difference and develop filtering algorithm. Under the method, space interval imaged is weakly influenced by laser-pulse shape. After filtering, the edge of viewing area for an image slice is clear even suffering from atmospheric turbulence, ambient light pollution and sensor noise, which also helps to improve precision of delay time control and realize the deblurring of three-dimensional range-gated super-resolution imaging.

距离选通超分辨率激光三维成像技术是一种新型主动光学三维成像技术，与激光扫描三维成像相比具有更高的时效性，与闪光成像激光雷达相比则具有更高的空间分辨率，同时保留了距离选通成像所特有的在雾雨雪及低照度环境下有效工作的特点，在低对比度目标探测、远距离身份识别、地形地貌测绘、航天测控等领域具有重要的应用前景。但是，在回波展宽效应及环境干扰因素的作用下，该技术反演目标距离所需的空间切片会出现边界模糊，甚至强背景噪声，致使空间切片的梯形距离能量包络畸变，造成三维成像降晰（距离分辨率降低），从而限制了其面向远距离、高距离分辨率技术需求领域的应用。针对此本项目将开展超分辨率三维成像反降晰（deblurring）研究，利用回波展宽效应构造具有三角形距离能量包络的空间切片，从而扩展图像灰度比动态范围，提高距离分辨率，并通过空间降模糊滤波实现空间切片空域整形，解决上述边界模糊问题，实现反降晰超分辨率三维成像。

距离选通超分辨率激光三维成像技术是一种新型主动光学三维成像技术，与激光扫描三维成像相比具有更高的时效性，与闪光激光成像雷达相比则具有更高的空间分辨率，在低对比度目标探测、远距离身份识别、地形地貌测绘、水下成像等领域具有重要的应用前景。但是，在回波展宽效应及环境噪声的影响下，三维重建所需的空间切片图像的距离能量包络发生畸变，造成三维成像降晰，从而限制了其在远距离、高距离分辨率成像方面的应用。针对此本项目开展了超分辨率三维成像反降晰研究，主要研究内容如下：.1、开展了回波展宽效应及背景噪声对距离选通空间切片的影响研究，分析了不同时域参数下回波展宽效应对选通切片的影响。通过匹配激光脉宽和选通门宽可构建出三角形和梯形距离能量包络，用于距离选通三维成像。.2、提出了三角形包络超分辨率三维成像技术，利用具有三角形距离能量包络的空间切片图像建立距离能量比映射关系，实现三维重建，相比于传统梯形包络的方法（Optics Letters, 2007, Vol. 32(21), 3146-3148），距离分辨率提高约3倍。.3、提出了一种多脉冲延时积分整形技术，解决了距离选通超分辨率三维成像中固体激光器矩形脉冲难以获得及脉宽不可调的难题，推进了该成像技术在水下成像、全天候工作的实用化应用。.4、提出了一种帧相关距离选通实时三维成像技术，通过时序编码获取AB型视频流，实现实时三维成像。实验上获得了200m处像素数696×520、帧频10fps的两人互抛篮球的三维视频。.5、提出了一种空间降模糊滤波法，可实现空间切片整形，获得清晰的空间切片边界，并将激光脉宽等效压窄一半，从而提高距离分辨率。.6、提出了一种基于数字移相的在线编码同步控制技术，并研制了时序控制器，实现1ns级精度延时控制及脉宽控制，满足超分辨率三维成像时序控制要求。此外，为开展实验研究，本项目还研制了激光驱动器和激光照明镜头等硬件模块，并开发了系统控制软件。. 本项目相关成果已应用到中国科学院重点部署项目、中科院科研装备研制项目，并得到法德圣路易斯研究院、白俄罗斯科学院、莫纳什大学等国际同行的关注。. 综上所述，通过本项目的实施突破了三角形包络超分辨率三维成像、多脉冲延时积分整形、帧相关实时三维成像、空间降模糊滤波以及在线编码同步控制等关键技术，可为距离选通超分辨率三维成像的应用提供技术支撑。