Research On Related Techniques Of Portable Stereo Measuring System

This thesis documents the research into the design and development of an effective portable vision system for measuring and modeling. The system achieves depth information by stereo vision system without laser or raster. It meets most of the needs of rapid measuring and modeling in engineering entertainment and business. Portable stereo measuring system based photogrammetry is small in capacity, cheap and easy-developed.It also documents the research into related techniques which include device composition, system configuration and assembly, system accuracy analysis, calibration, image acquisition, image processing, stereo match, depth data extraction and data storage. Examples are provided to verify the correctness and feasibility of the system and key techniques that are created. The accuracy can meet the need of measuring and 3D reconstruction area.In summary, the research has made following contribution:(1)Modifies the accuracy estimation models by adding in digital quantization effect, computes the effective visual workspace, analyzes system measuring accuracy, and optimizes the system structure. With these works, measuring errors can be estimated with parameters of camera, length of baseline and measuring range in the engineering. The system can also be redesigned with these models.(2)Promotes stereo matching algorithm for monotone texture, expands application range of vision system in some extent. This thesis sets the matching and searching constraints by edge detecting, epipolar geometry and correlation of stereo pairs, then achieves the matching result by iterative area match from coarse to fine. Experiments have verified that this algorithm can not only enhance matching accuracy, the results are more accurate and reliable and can be employed for 3D reconstruction in reverse engineering.(3)Proposes filtering and compression algorithm for cloud data achieved in photogrammetry. Pulse noise and random noise present simultaneously, while single point is difficult to tell from features and noises. The thesis presents a method of noise filtering for data cloud based on morphology. Morphology based filtering is verified effective for the data cloud processing in photogrammetry. It not only filters noises but also repair some flaws. The depth data is very large. One piece of image contains tens of million of bytes. It is difficult for information transformation or surface reconstruction. The thesis reduces cloud data based on image processing methods. Experimental test shows that the data can be reduced to 60% without losing vital information, especially the most important features. This has been used to conceive and elaborate the following up research for example, surface reconstructions. Cloud data compression and reduction based image processing technologies is creative in this area. Template computing, histogram, threshold segmentation and uniform grid are composed together.(4)Improves 3D reconstruction flows based 2D images. This research composes image and depth information into one image file format, which is called 3D image. Reduction, compression and recoding make the image pair more slender and depth data can be saved in image for ever, which implements images as data blocks. The 3d image not only can be used as common image for display, but also can be used for facilitating 3d reconstruction. It has features of both raster images and vector graphics, preceded to the transforming of two objects and wide application for image based on modeling and reconstruction.(5)One portable vision system is developed for 3D measuring and reconstruction of mechanical parts. Several key techniques are overcome in new solutions. Examples prove that the algorithms and theories are right and suitable for this system.This system will have more users and more application for its low price and smart developping styles. It can be used in 3D measuring and reconstruction of scene and mechanical parts. Examples are provided as tests to verify the theory and application of the system, which proves that this system can be used in virtual engineering, reverse engineering and modeling of rapid prototyping.