Research Of Three-dimensional Measurement Method Based On Structured-light With Error Correction Coding

The three-dimensional measurement using encoded structured-light is a branch ofthree-dimensional measurement. It has become a hot research topic in this field because of itshigh reliability measurement results. Currently, the study of three-dimensional measurementmethod based on encoded structured-light is mainly focus on improving the accuracy, speedand application range of measurement. A number of key techniques have emerged aroundthese aspects. This study was focused on improving the accuracy of three-dimensionalmeasurement by using the key technique of phase unwrapping.In the measurement of encoded structured-light, the phase unwrapping algorithm basedon projection grating includes key steps of calculating the order and principal value of phase.During calculating the order of phase, grating stripe encoding method is the key factor inimproving the accuracy of the phase order. Because of the influence of noise and backgroundlight intensity on the measuring environment, the traditional method of phase ordercalculation based on gray code has pixels encoding errors at the junction of projection codinggrating stripe. It will produce phase order calculation errors. Aiming at this problem, thispaper proposed a grating structured-light coding method with error correction.The structured-light grating coding method with error correction was based on theprinciple of Hamming error correcting codes. This method could correct the error coding atthe junction of grating fringe to getting correct order of phase by increasing the projection ofHamming code check digit coding grating fringe. Then it could get the correction phase order.The use of structured light coding method with error correction and four-step phase-shiftingtechnique enhanced the accuracy of the phase unwrapping from the aspect of structured lightgrating coding. Therefore the accuracy of three-dimensional measurement was improved. The calibration of camera system is also involved in three-dimensional measurement.The calibration method of binocular camera system used in this paper was studied, itsprinciple was based on Zhengyou Zhang classic camera calibration method. This methodcalibrated a monocular camera firstly, and then completed the calibration of binocularcameras on this basis.Finally, camera calibration experiment and phase unwrapping experiment werecompleted on basis of theoretical study. The error of camera calibration results was within therange of0.2pixels, the calibration results had a high accuracy. The phase unwrappingexperimental results showed that the method could solve the problem of error coding atgrating junction effectively. It helped to improve the accuracy of phase unwrapping andverified the feasibility and effectiveness of this method.