Research On Key Technology Of Handheld Photography Scanning System Based On Structured Light

Three-dimensional surface measurement techniques have been widely used in many fields, including reverse engineering, product quality inspection, object recognition etc, but they are mostly static measurements and can not be used for three-dimensional measurements and surface reconstruction dynamically or handheldly. In addition, due to the measurement conditions and measurement environment constraints, using the widely used non-contact three-dimensional measurement techniques to reconstruct complex objects will produce the surface point cloud holes by the outline occlusion (blind areas), which lead to the resulting surface point cloud model incompletely. Meanwhile, the resolution and measurement scope achieved by only one measurement method is limited, thus its applicable scope is restricted.Aim at solving these problems, combining with the optical photography scanning principle, a handheld photography scanning solutions based on structured light was presented in this paper. After the analysis of the characteristics of handheld photography scanner, and combining projection grating encoding technology based on structured light with digital photogrammetry technology, a hardware system consist of a single camera-microprojector was designed based on the principle of reducing system cost, volume and weight, replace of expensive hand-held laser scanner and the bulky, heavy stereo vision three-dimensional measurement system based on structured light. A handheld three-dimensional scanning software system based on color structured light was researched and developed for acquiring the three-dimensional point clouds of occlusion area high precision and quickly, assisting other three-dimensional information acquisition means such as three-dimensional laser scanner to complete the whole three-dimensional model reconstruction of the complex object with outline occlusion.Main research contents and achievements in this paper are as follows:1) Research status and development trends of three-dimensional measurement techniques at home and abroad were introduced and analyzed, including research status of static three-dimensional measurement, dynamic three-dimensional measurement techniques and development trends of three-dimensional measurement technologies. 2) Handheld photography scanning hardware system was built. After analyzing the characteristics of handheld photography scanning systems, we built the handheld photography scanning hardware system using single camera-microprojector based on the principle of high-precision, high-speed, and cost reduction, which reduced the cost, size and weight of hardware system, so that it can be used to scan objects handheldly.3) Hardware system calibration. We classified the current camera calibration methods, described the camera’s imaging model, focusing on the principle and method of projector calibration, and then gave the implementation process of camera and projector calibration. The detailed analysis about the mark design of plan calibration board and projected pattern design for projector calibration was made in the hardware system calibration. The feasibility and accuracy levels of camera-projector calibration methods were tested by the real image datas acquired with camera-projector measurement system.4) Research the principles and methods of handheld photography scanning based on structured light. We have designed a kind of color hybrid coding raster based on color-coded principle, which can obtain dense three-dimensional point cloud model of target object by projecting only one raster image. After analyzing a decoding method based on single projected raster image, and executing the global optimization matches between the code information decoded and code information designed, the three-dimensional surface information from a viewpoint can be got.5) Research a stable algorithm about acquiring initial value of point clouds registration automaticlly, and improved ICP registration algorithm, to realize the registration between the object point cloud from single viewpoint acquired by handheld scanned system and whole point cloud precisely, and complete the whole three-dimensional reconstruction of target object.6) Propose a scattered data fast surface reconstruction algorithm based on tangent plane projection, which can reconstruct the triangular network model of the three-dimensional point cloud of complex object surface quickly, stably and automatically, to achieve the three-dimensional surface measurement.