3d Shape Measurement Based On Structured Light

Three-dimensional surface measurement has wide application prospects in biological,industry,science,security and other fields.Optical shape reconstruction which is based on the coding structured is considered to be one of the most reliable methods to achieve three-dimensional measurement of the measured object.Coding structured light measurement system uses computer and one pair of the projector,camera with calibrated.The camera captures the coding light pattern of the projected object,and the match relation between corresponding feature point can be gotten by computer decoding,then three-dimensional information can be extracted.In this paper,we use the Sinusoidal Phase-Shifted Structure Optical Coding,which belongs to the continuous time phase encoding in the coded structured light,phase shift determines the solution of wrapped phase.Sinusoidal phase-shift optical coding obtains the absolute phase to realize corresponding,So the key is how to get high-precision absolute phase quickly.High-precision absolute phase is inseparable from the accurate wrapped phase and the accurate phase unwrapping.Therefore,this paper proposes the indirect mixed periodic phase encoding to achieve the accurate phase unwrapping,while analyzing and regulating the source of the absolute phase accuracy,the main contents of this paper are as follows:Firstly,the paper introduces the procedure and principle of light measurement for sinusoidal fringe projection,building the mathematical model about phase and height.And the paper analyses the phase extraction method and phase unwrapping method,in order to be able to complete the phase unwrapping of the discontinuous objects and the objects which surface change dramatically,determining the research direction of temporal phase unwrapping.Secondly,the paper researches two kinds of time phase unwrapping algorithm which are used commonly,and according to the sinusoidal phase shift model,in order to increase the measuring speed,proposing the direct mixed period encoding,analyzing its shortage about measurement range,further combining phase encoding,proposing the indirect mixed period-shifting coding to achieve absolute phase calculation.Thirdly,in order to improve the measure accuracy about the absolute phase,the paper analyzes the source of measuring system errors,setting up the mathematical model of Gamma Distortion module which considers the defocusing effect,and Gamma pre-correction is used to reduce the error,raising two-step calibration method to correct the cycle error of the indirect fusion period-shifting coding.Finally,the paper uses the indirect mixed period-shifting coding measuring the object based on four-step phase-shifting measuring method,and the three-dimensional reconstruction is realized with the aid of Gamma pre-correction and two-step calibration,testing and verifying the feasibility of indirect mixed period-shifting coding and correction meathod.