Development And Application Of Three-dimensional Measurement System For Tiny Objects Based On Structured Light

Three-dimensional contour measurement for small objects is an important branch of modern three-dimensional shape measurement.Since being first proposed abroad in the 1960 s,domestic and foreign research scholars have been researching and developing for decades,and their related measurement techniques and measuring equipment have also achieved rapid development.After entering the 21 st century,it has been widely used,such as Defect detection,precision manufacturing,virtual reality(VR),machine vision,medical engineering,video games,3D printing,and modern education.However,compared with the existing measurement technology and equipment in foreign countries,our country is still in a relatively backward situation.Therefore,it is extremely urgent to develop a three-dimensional measurement system for small objects with high measurement accuracy,fast measurement speed,miniaturization and more intelligence.According to the above situation,this thesis studies the three-dimensional measurement of tiny objects from two directions.On the one hand,research about three-dimensional measurement methods based on sinusoidal grating fringe projection and optical triangulation.On the other hand,it focuses on the design and construction of hardware measurement systems based on stereo-microscopes and dual telecentric lenses.The specific research contents are as follows:(1)The existing methods and research status of three-dimensional contour measurement for micro-objects have been systematically investigated.The existing problems of traditional methods were summarized,and the difficulties and challenges faced by the measurement of micro objects were clarified.This thesis would study this progress from two aspects: hardware system construction and algorithm implementation.(2)A hardware measurement system based on a stereo-microscope and a double telecentric lens have been designed and built.Stereoscopic microscopy can achieve stereo imaging of objects,and the observable area is large.Because of high resolution and low distortion,dual telecentric lens has large depth of field,so it can restore the shape information of objects to the maximum extent when imaging.Therefore,the measurement system used a stereo-microscope and a double telecentric lens as the main structure to design and built a measurement system,combined with the optical triangulation principle based sinusoidal grating stripe projection three-dimensional measurement method,after the system calibration,could successfully obtain the measured object 3D contour information.The field of view of the measuring system can reach 1.8cm * 1.6cm.(3)The three-dimensional measurement method based on sinusoidal grating fringe projection and optical triangulation has been studied.In this thesis,the sinusoidal grating fringe projection with no damage,high precision,fast speed and easy implementation was combined with optical triangulation to measure the three-dimensional contour of the surface of tiny objects.The measurement principle was elaborated in detail,and an improved phase-encoding algorithm based on mass map guidance was proposed--reliable path tracking algorithm.Improve the overall measurement speed of the system while meeting the measurement accuracy requirements.For the system calibration,the camera calibration and system calibration method were introduced based on the general imaging model.The method theory of camera calibration and system calibration was elaborated,and the overall calibration of the measurement system was completed.The related algorithms were implemented based on C++ and MATLAB.A large number of related experiments have been carried out to verify the stability and effectiveness of the measurement method.The experimental results show that the maximum measurement accuracy of the system can reach 10?m.