关联成像系统多维信息测量和性能提高的研究

发布时间：2018-07-27 13:59

【摘要】：在过去二十多年中,关联成像有了蓬勃的发展。关联成像诞生之初,人们认为其物理本质是基于双光子的非局域相关。然而随后的研究表明赝热光源同样可以实现关联成像,使得关联成像得以进一步发展。关联成像使用普通热光源或赝热光源进行主动照明,有着传统成像探测手段所不具备的优势,例如工作波段限制小、探测距离远、易于小型化、复杂环境适用性强等方面。关联成像由于其抗大气湍流能力强,不受瑞利衍射极限限制等优势,迅速成为激光雷达、空间遥感等领域研究的热点。然而关联成像系统仍然存在着很多问题,例如:二维关联成像的成像速度较慢,受大气湍流影响成像分辨率会降低,三维关联成像的测距精度较低等。这些难点极大地制约了关联成像激光雷达系统的实际应用。此外关联成像目前能够测量目标的信息较为单一,现有的关联成像系统大多只能够得到目标的强度信息和距离信息,而在复杂的探测环境下,仅仅依靠这两个维度的信息无法有效地对目标进行测量,需要开展目标多维信息的测量,如偏振这个信息维度。针对关联成像系统目前所面临的问题,有必要开展关联成像性能提高的相关研究,并扩宽关联成像系统的可测量信息维度,使关联成像系统能够测量的维度从二维、三维信息拓展到多维信息。针对关联成像系统所面临的问题,本论文首先分析了在湍流大气存在的情况下,2D关联成像系统的成像分辨率受哪些因素的影响,并推导了湍流大气条件下该系统的成像公式。其次,提出了可以利用双曲余弦高斯光束替代传统的高斯光束,进而提高2D关联成像激光雷的成像分辨率。通过数值仿真,证明了利用双曲余弦高斯光束替代高斯谢尔型光束作为光源能够提高系统的成像分辨率。此外提出了多波长关联成像系统来解决2D关联成像系统的成像速度慢的问题,该系统对光斑光场进行分波长调制,有效地提高单位时间内的系统采样数,进而提高了2D关联成像激光雷达的成像速度,并通过实验证明了多波长关联成像系统的有效性。针对3D关联成像测距精度的研究,以基于质心算法的3D关联成像测距公式以及测距精度的表达式为基础,分析了强度像切片数对3D关联成像系统的测距精度的影响。发现单纯地提高切片个数并不能够一直提高测距精度,存在一个所谓的最佳切片数,当强度像切片数高于这个最佳切片数的时候,3D关联成像系统的测距精度会有所降低。并基于此提出了最佳切片数法的3D关联成像。针对最佳切片数法3D关联成像进行了相关实验,并对比了基于传统方法、质心算法、最佳切片算法的3D关联成像系统的得到的距离像的结果,用距离均方根误差来定量地比较三种方法的测距精度的差别。针对在数据采集系统的采样率较低的情况下,3D关联成像的测距分辨率较低的问题,设计了外差3D关联成像系统,该系统采用外差的手段对目标的距离信息进行测量。该系统采用连续波激光作为光源,用电光晶体对光场的强度进行调制,之后再利用空间光调制器对光场的强度分布做进一步的调制。并利用单点探测器接收从不同距离处目标反射回来光的强度,单点探测器探测得到的反射回波强度信号与加载在电光晶体上的调制信号进行时间相关,从而得到目标的距离信息;而利用测得的目标反射回波光场的强度值与空间光调制器调制的光斑分布进行空间相关,可以得到目标的强度分布信息。结合距离信息和强度分布信息,可以得到目标的距离像。分析了该系统的距离分辨率,发现其距离分辨率不受数据采集系统的采样率的影响,只与电光晶体中调制信号的调制带宽有关。仿真结果表明,在数据采集系统的采样频率相同时,外差3D关联成像系统得到的距离像的距离分辨率优于传统3D关联成像系统得到的距离像的距离分辨率。为了解决传统关联成像系统无法判别相同反射率的不同材质目标的弊端,改进了传统2D关联成像系统,提出了偏振关联成像系统。该系统能够实现对目标的偏振信息的测量,通过关联成像的成像方式对目标物体反射光的偏振态分布进行探测。同时引入偏振色度值的概念,利用这个偏振色度值来描述目标反射回波光场的偏振特性。通过仿真实验证明了偏振关联成像系统能够获得目标的偏振像,使得关联成像系统能够应用于目标材质的判别。
[Abstract]:Associated imaging has developed rapidly over the past more than 20 years. At the beginning of the birth of associated imaging, it was believed that its physical nature was based on the non local correlation of two photons. However, the subsequent study showed that the pseudo heat source could also achieve associated imaging, making the associated imaging a step forward. The associated imaging uses a common hot source or a pseudopotential. The active illumination of the heat source has the advantages that the traditional imaging detection means do not have, such as the small limitation of the working band, the far distance, the miniaturization and the strong applicability of the complex environment. The associated imaging is rapidly becoming a laser radar and space remote sensing because of its strong ability to resist atmospheric turbulence and not limited by the limit of Rayleigh diffraction limit. However, there are still many problems in the related imaging system, such as the slow imaging speed of the two-dimensional correlation imaging, the reduction of imaging resolution by the influence of atmospheric turbulence and the lower precision of the three-dimensional correlation imaging, which greatly restrict the practical application of the closed imaging laser radar system. The information of the target is relatively simple at present. Most of the existing related imaging systems can only get the intensity information and distance information of the target. In the complex detection environment, only the information of the two dimensions can not be effectively measured on the target. It is necessary to measure the multi-dimensional information of the target, such as polarization. In view of the problems facing the associated imaging system, it is necessary to carry out the related research on the enhancement of related imaging performance and broaden the measurable information dimension of the associated imaging system, so that the dimensions of the associated imaging system can be measured from two-dimensional, three-dimensional information to multidimensional information. This paper first analyzes the influence of the imaging resolution on the imaging system of 2D associated imaging system under the presence of turbulent atmosphere, and derives the imaging formula of the system under the turbulence atmosphere. Secondly, it is proposed that the hyperbolic cosine Gauss beam can be used instead of the traditional Gauss beam, and then the 2D associated imaging laser ray can be improved. Through numerical simulation, it is proved that using the hyperbolic cosine Gauss beam instead of Gauss Schell beam as a light source can improve the imaging resolution of the system. In addition, a multi wavelength correlation imaging system is proposed to solve the problem that the imaging speed of 2D associated imaging system is slow. The system is used to modulate the light field of the light spot. The system sampling number in unit time is improved, and the imaging speed of 2D associated imaging lidar is improved. The effectiveness of the multi wavelength correlation imaging system is proved by experiments. Based on the research of the range accuracy of the 3D associated imaging, based on the formula of 3D correlation imaging ranging based on the centroid algorithm and the expression of distance precision, The influence of the number of intensity image slices on the ranging accuracy of the 3D associated imaging system is analyzed. It is found that the number of slices can not improve the distance accuracy by simply raising the number of slices. There is a so-called best slice number. When the number of intensity images is higher than the best slice number, the distance precision of the 3D related imaging system will be reduced. In this paper, the 3D correlation imaging of the best slice method is proposed. The correlation experiments of 3D associated imaging with the best slice number method are carried out, and the result of the distance image obtained by the 3D correlation imaging system based on the traditional method, the centroid algorithm and the best slice algorithm is compared. The distance mean square error is used to quantitatively compare the distance precision of the three methods. In the case of low sampling rate of the data acquisition system, the range resolution of 3D associated imaging is low, the heterodyne 3D correlation imaging system is designed. The system uses heterodyne to measure the distance information of the target. The system uses continuous wave laser as the light source and the intensity of the light field with the electrooptic crystal. After modulation, the intensity distribution of the light field is further modulated using a spatial light modulator. The intensity of the reflected light from the target is received by the single point detector. The reflection echo intensity signal obtained by the single point detector is related to the time correlation of the modulated signal loaded on the electro-optic crystal, thus obtaining the target. The intensity distribution of the measured target reflected light field is related to the spatial distribution of the light spot modulated by the spatial light modulator. The intensity distribution information of the target can be obtained. The distance image of the target can be obtained by combining the distance information and the intensity distribution information. The distance resolution of the system is analyzed and its distance is found. The detection rate is not affected by the sampling rate of the data acquisition system and is only related to the modulation bandwidth of the modulated signal in the electro-optic crystal. The simulation results show that the distance resolution of the distance image obtained by the heterodyne 3D associated imaging system is better than the distance resolution of the traditional 3D associated imaging system when the sampling frequency is the same. In order to solve the problem that the traditional correlation imaging system can not distinguish the different material targets with the same reflectivity, the traditional 2D imaging system is improved, and the polarization correlation imaging system is proposed. The system can measure the polarization information of the target, and the polarization distribution of the reflected light of the target object through the imaging mode of the associated imaging. The polarization chromaticity value is introduced to describe the polarization characteristics of the target reflected echo light field. The polarization correlation imaging system can obtain the polarization image of the target by simulation experiments, and the correlation imaging system can be applied to the discrimination of the target material.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN958.98

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