The propagation characteristics of the circular Airy beam (CAB) modified with low-pass filtering is investigated in details in this paper. Based on a modification of the angular spectrum of CAB, we get a new kind of CAB constructed with low frequency spectrum, which is called “LCAB” for short. A suitable low-pass filter is introduced to cut off the high frequency angular spectrum and maintain the low frequency domain mainly affecting the front light rings of CAB. Two apodization parameters are employed to optimize the low-pass filtering, which influence the propagation characteristic of the LCAB. Fortunately, the abruptly autofocusing property, the most important property of CAB, is still maintained in LCAB. What is more, the initial ring number and the focal spot length can be controlled by adjusting the two apodization parameters. If the two apodization parameters are appropriately chosen, one can form an elegant optical needle which plays an important role in optical manipulations. The numerical results show that the less front light rings are, the longer the optical needle is. It should be noted that the width of the optical needle will increase as long as the length increases, and lead to the decline of the maximum intensity of the optical needle.
We demonstrated a single-shot quasi-on-axis digital holography which is capable of simultaneously capturing two-step phase-shifting interferences. A dual-channel interferometer was employed to monitor the Gouy phase-shifting between two orthogonal polarized references which was introduced by two confocal lenses. A new algorithm was derived for reconstruction the complex field of the object’s wavefront according to the feature of Gouy phase-shifting. Simulation was carried out and recover software was also made. The proposed approach can also be applied to single-shot quasi-onaxis digital holography for real time measurement.
Mesh simplification is an efficient method to reduce the time of computer handling complicated models. It requires the
algorithm with less processing time and space complexity, while the quality of simplification and the consistency of the
simplified triangles are quite well. This paper presents a mesh simplification algorithm of three-dimensional models
defined by triangle-mesh. In this algorithm, the gradient of the curvature of surface is used as the simplification condition,
the manner of simplification is edge collapse and the error metrics is the distance between vertex before simplifying and
the related surface after simplifying. Experiment results indicate that this algorithm can be applied to any topological
mesh and has the advantages of speediness and efficiency.
In this paper, we proposed a new method, controllable rectangle filter, to improve the resolution of reconstruction in
multi-frame digital holography. In this method, the entire process needs only one hologram with multi-frame digital
holographic interference and the different images' spectrum can be obtained separately without mutual influence.
Therefore the size limiting of the recording objects is reduced and the frame amounts can be increased. Moreover, the
nonessential information of zero-order and the conjugate image can be eliminated well, and the resolution of the
reconstructed images is enhanced. Theoretical analysis and experimental results show that it is a realistic and practical
This paper analyses a disparity correction of an advanced multi-sparkle camera system. This system is also called
Cranz-Schardin camera, which a method to achieve extreme high-speed photography. The camera axis in this system
have an angle with principal optical axis, so each image taking by different cameras in system is formed by different
orientation projections of the object, and this process generates parallax among the different cameras. In order to solve
this problem, camera calibration method is setting up after a detailed analysis of this system. A planar calibration is used
as standard reference object in experiment. And image corresponding relationship among different cameras can be built
through learning the position changes of feature points in different cameras. Then, grab pictures from transient
phenomenon which need to be analyzed, and after image processing on these pictures with the image corresponding
relationship, the disparity influence on experiment images in this advanced multi-sparkle camera system would be
Rotating scan is a common 360-degrees measurement method in 3D measure system which based on line-structure light.
In this system, the calibration for rotary axis of the rotary platform is an important section. It will be affecting the
measurement results. In known methods, precision and expensive auxiliary instruments are required to ensure that the
rotation axis is located in the plane of line-structure light. In this paper, a simple, flexible and real-time calibration
method is proposed. Firstly, a plane calibration board with tessellated pattern is placed incline on the rotating stage.
Secondly, recoded several pictures of the calibration board while the stage rotating several angles. Thirdly, the
parameters of camera (include the intrinsic parameters and the extrinsic parameters, such as rotating matrixes and
transform vectors between the local coordinates of these planes and the global coordinate of sensor) can be estimated
from these pictures. Then, the global coordinates of these control points were calculated according to these parameters.
Finally, the axis parameters of the working stage can be optimized with these control points because the global
coordinates of same control point in different position are in circle. This method is proved by experiment, and the
root-mean-square error is 0.04mm.
A simple, flexible and real-time calibration method is proposed to solve the calibrating problems of line structure light sensor such as requirement of high accurate calibration model, complicated calibrating procedure and so on. First, a 2D calibration plane with tessellated pattern is placed at several arbitrary places in the measurement range of sensor, and the pictures of calibration board on these positions are recoded. The parameters of camera are estimated from these pictures. Secondly, the line structure light is turned on, and projected on the surface of calibration board. Several pictures are captured while the board is being moved along the direction of line structure light. Thirdly, the rotating matrixes and transform vectors between the local coordinates of these planes and the global coordinate of sensor are estimated. The global coordinates of the control points falling on the line structure light plane were calculated according to these matrixes and vectors. Finally, the model parameters of the sensor at working state are optimized with these control points. The cost of calibration equipment is greatly reduced and the calibrating procedure is simplified with the proposed approach. So it can promote the engineering applications of the line structure light sensor. It shows that this method is practical for surface measurement. The height error (RMS) of the measured object reaches 0.03mm in the region of 200mm x 150mm.