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。

In this Letter, a method for shape visualization of small objects (microscopic) in the form of a hologram is presented. It consists of a standard optical set-up for small object registration (i.e., stereoscopic or biological microscope). The focus stacking technique is used to obtain a series of images with increased depth of field and on them a shape reconstruction procedure (structure from motion, SfM) is made. With use of a dense cloud of points, a sequence of parallax-related images suitable for Geola’s digital holographic printing is generated. The holographic printer produces single-parallax holographic (full three-dimensional) images of real or virtual objects.

We proposed a three-dimensional (3D) image authentication method using binarized phase images in double random phase integral imaging (InI). Two-dimensional (2D) element images obtained from InI are encoded using a double random phase encryption (DRPE) algorithm. Only part of the phase information is used in the proposed method rather than using all of the amplitude and phase information, which can make the final data sparse and beneficial to data compression, storage, and transmission. Experimental results verified the method and successfully proved the developed 3D authentication process using a nonlinear cross correlation method.

The work proposes a three-laser-beam streak tube imaging lidar system. Besides the main measuring laser beam, the second beam is used to decrease the error of time synchronization. The third beam has n+0.5 pixels’ difference compared to the main measuring beam on a CCD, and it is used to correct the error caused by CCD discrete sampling. A three-dimensional (3D) imaging experiment using this scheme is carried out with time bin size of 0.066 ns (i.e., corresponding to a distance of 9.9 mm). An image of a 3D model is obtained with the depth resolution of <2 mm, which corresponds to ～0.2 pixel.

In this Letter, we propose an on-line inspection method based on a plenoptic camera to detect and locate flaws of optics. Specifically, due to the extended depth of field of the plenoptic camera, a series of optics can be inspected efficiently and simultaneously. Moreover, the depth estimation capability of the plenoptic camera allows for locating flaws while detecting them. Besides, the detection and location can be implemented with a single snapshot of the plenoptic camera. Consequently, this method provides us with the opportunity to reduce the cost of time and labor of inspection and remove the flaw optics, which may lead to performance degradation of optical systems.

An endoscopic imaging system using a plenoptic technique to reconstruct 3-D information is demonstrated and analyzed in this Letter. The proposed setup integrates a clinical surgical endoscope with a plenoptic camera to achieve a depth accuracy error of about 1 mm and a precision error of about 2 mm, within a 25 mm×25 mm field of view, operating at 11 frames per second.

Streak tube imaging lidar (STIL) is an active imaging system that has a high range accuracy with the use of a pulsed laser transmitter and streak tube receiver to produce 3D range images. This work investigates the effect of the time bin size on the range accuracy of STIL systems based on the peak detection algorithm. The numerical simulation indicates that the time bin size has a significant effect on the range accuracy, resulting in a modified analytical estimate of the range error. An indoor experiment with a planar target is carried out to validate the theory that shows the linear relationship between the range error and the time bin size. Finer 3D depth images of a fist model are acquired by using a smaller time bin size and the best range error of 0.003 m is achieved with the optimal time bin size of 0.07 ns.

Because the bottom of the cavity has the shadow and occlusion, the angle between the projection system and imaging system is limited. So the traditional fringe projection technique based on the principle of optical triangulation is inapplicable. This Letter presents a 3D shape measurement method of using the light tube for the cavity. The method can measure an object from two opposite views at the same time, which means it will obtain two different groups of 3D data for the same object in a single measurement. The experimental results show the feasibility and validity of the 3D shape measurement method.