Nanjing University of Science and Technology

Hohai University

Yan Hu

Liang Zhang

Qian Chen

Chao Zuo

Shijie Feng

Wei Yin

Tianyang Tao

Jiaming Qian

Jiasong Sun

Kai Liu

Zhen Zhang

Yan Ding

Chunxia Yang

Jiaye Wang

Mingzhu Xu

Huiwen Liu

Mengshang Zhao

Shuaijie Wu

Disclosed is a high-precision dynamic real-time 360-degree omnidirectional point cloud acquisition method based on fringe projection. The method comprises: firstly, by means of the fringe projection technology based on a stereoscopic phase unwrapping method, and with the assistance of an adaptive dynamic depth constraint mechanism, acquiring high-precision three-dimensional (3D) data of an object in real time without any additional auxiliary fringe pattern; and then, after a two-dimensional (2D) matching points optimized by the means of corresponding 3D information is rapidly acquired, by means of a two-thread parallel mechanism, carrying out coarse registration based on Simultaneous Localization and Mapping (SLAM) technology and fine registration based on Iterative Closest Point (ICP) technology. By means of the invention, low-cost, high-speed, high-precision, unconstrained and rapid-feedback omnidirectional 3D real-time molding becomes possible, and a new gate is opened into the fields of 360-degree workpiece 3D surface defect detection, rapid reverse forming, etc.

High-precision dynamic real-time 360-degree omnidirectional point cloud acquisition method based on fringe projection

A calibration method for fringe projection systems based on plane mirrors. Firstly, two mirrors are placed behind the tested object. Through the reflection of mirrors, the camera can image the measured object from the front and other two perspectives, so as to obtain 360-degree two-dimensional information of the measured object. The projector projects three sets of phase-shifting fringe patterns with frequencies of 1, 8, and 64. The camera captures the fringe image to obtain an absolute phase map with a frequency of 64 by using the phase-shifting method and the temporal phase unwrapping algorithm. By using the calibration parameters between the projector and the camera, the absolute phase map can be converted into three-dimensional information of the measured object. Then, the mirror calibration is realized by capturing a set of 3D feature point pairs, so that the 3D information from different perspectives is transformed into a unified world coordinate system. The calibration method does not need to artificially fix the feature pattern on plane mirrors, only needs to capture a set of 3D feature point pairs by the camera to directly realize the mirror calibration that it avoids the loss of measurement accuracy and realizes high-precision panoramic three-dimensional measurement.

Calibration method for fringe projection systems based on plane mirrors

A convex type guide plate waterwheel energy increasing device with gradually dense holes is provided. The convex type guide plate waterwheel energy increasing device comprises fixed devices, a main diversion plate and auxiliary diversion plates, wherein an upwards convex arc structure is arranged on the top surface of the main diversion plate, gradually dense first through holes are formed in the main diversion plate from the middle to the two ends, the diameters of the first through holes are gradually increased, the auxiliary diversion plates are connected to the two sides of the main diversion plate, second through holes are formed in the auxiliary diversion plates, fixed devices are fixed to the two sides of the auxiliary diversion plates, and the fixed devices are used for fixing the main diversion plate and the auxiliary diversion plates to the riverbed. Through the convex type main diversion plate with the gradual dense holes with different heights, the device adapts to the condition that the distance between the waterwheel and the bottom of the riverbed is different along with the change of the phase angle, kinetic energy of low-velocity air at the bottom of the riverbed is conveyed to the impeller area of the waterwheel, the effective acceleration area in the river channel is large, the average velocity of water flow in the impeller area of the waterwheel is increased, and the output power of the unit is improved.

Convex type guide plate waterwheel energy increasing device with gradually dense holes

Growing community of inventors

Nanjing, China

Yan Hu