摘要
为了剔除闪光式激光雷达白天工作时太阳光对目标的光污染,采用基于形态学开运算的强度图像预处理方法,对闪光式激光雷达在白天接收到的原始强度图像预处理,随后采用相邻帧差法对预处理后的强度图像进行三维重建,可以有效地将目标从太阳光污染中提取出来。为了验证该方法的可行性,用闪光式激光成像雷达在白天对距离500 m外的目标建筑物进行了成像实验,并与高斯滤波预处理、中值滤波预处理和阈值分割预处理进行对比,随后采用相邻帧差法并根据四种方法预处理后的强度图像来获取目标的距离信息。经过计算,形态学开运算预处理与高斯滤波预处理、中值滤波预处理和阈值分割预处理的结构相似度分别为0.78、0.83和0.85,他们之间的结构相似图分析结果充分说明采用形态学开运算的预处理方法在去除由太阳光引起的干扰的同时,可以完整获取目标的距离信息。
Optical detection and ranging techniques based on range-gated active imaging systems have been greatly developed.Flash lidar obtains slice images of targets by accurately measuring the time of flight of laser pulses,and effectively reduces the influence of backscattering on imaging results through range gating technology.It has the ability to work in the harsh environments.Therefore,flash lidar is widely used in various fields.However,in the flash lidar daytime measurement,since sunlight dominates the backscattered noise,when the backscattered sunlight is received by the lidar detector,there is a huge amount of energy due to the wide wavelength range of solar radiation.The huge energy will make the target mixed with the sunlight.Even if the range gating technology is used,the influence of sunlight on the intensity image received by the lidar cannot be avoided.As a result,the flash lidar cannot obtain target distance information during the daytime,severely limiting the application of flash lidar.In order to eliminate the light pollution of sunlight on the target,this paper adopts the intensity image preprocessing method based on morphological opening operation to preprocess the original intensity image received by the flash lidar during the day,and then uses the adjacent frame difference method to get the distance information of the target.First of all,a structural element is selected according to the principle of selecting structural elements for morphological opening operation.Secondly,the chosen structural element is used to preprocess the target slice images received by the flash lidar imaging system using morphological opening operation,while the preprocessing results are evaluated by average intensity image.Thirdly,the adjacent frame difference method is used to obtain the distance information of the target from these preprocessed intensity images.In order to verify the feasibility of this method,we use a self-developed flash lidar to conduct imaging experiments on a target building at a distance of 500 m during the daytime.The raw average intensity image obtained from the raw slice image received by the flash lidar system shows that the sunlight scattered by the surrounding target is mixed with the laser echo signal reflected back from the target building,making it difficult to distinguish the target building.Therefore,we can only obtain the distance information of the target by preprocessing the raw slice image obtained by the flash lidar system.Based on the principle of preprocessing the original intensity images with morphological opening operation,in this experiment,a 3 × 3 cross-shaped structural element is selected by the structural element selection principle.The chosen structural element is then used to preprocess the raw sliced images of the building target at 500 m received by the flash lidar system with morphological opening operation,while compared with binarized average intensity image from Gaussian filtering preprocessing,median filtering preprocessing and threshold segmentation preprocessing.The results of the comparison amply demonstrate that preprocessing based on morphological opening operations can extract the target from sunlight pollution.After that,the adjacent frame difference method is used to obtain the distance information of the target from the preprocessed intensity images based on these four methods.Using structural similarity to evaluate the distance information of the reconstructed target building,the morphological opening operation preprocessing is compared with Gaussian filtering preprocessing,median filtering preprocessing and threshold segmentation preprocessing,and the structural similarity is 0.78,0.83,and 0.85,respectively.By analyzing the structural similarity between them,the result fully demonstrated that the preprocessing method using the morphological opening operation could completely obtain the distance information of the target while removing the isolated noise caused by sunlight.
作者
杨刚
毕宗杰
崔子浩
田兆硕
YANG Gang;BI Zongjie;CUI Zihao;TIAN Zhaoshuo(Institute of Marine Optoelectronic Equipment,Harbin Institute of Technology at Weihai,Weihai,Shandong 264209,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2022年第11期265-273,共9页
Acta Photonica Sinica
基金
国家重点研发计划(No.2020YFE0201500)。
关键词
激光雷达
成像系统
图像重构
形态学开运算
三维图像采集
Lidar
Imaging system
Image reconstruction
Morphological opening operation
Threedimensional image acquisition
