Study On Triple-frequency Multi-period Analog Encoded Structured Light 3D Measurement Method

Three-dimensional measurement technology which has the features of intelligence,convenience and rapid measurement plays an irreplaceable role in industrial production,medical,aerospace and many other areas.Among all the measurements,the time-coded structured light measurement has become the main concerned focus in 3D measurement method due to its high accuracy.In particular,the analog coded light measurement method which takes the phase shift method as representatively has become the most promising measurement method in the field of3 D measurement due to its high resolution and high sampling density.However,applying one-cycle analog code to measure will generate the matters of low anti-interference ability without the requirement of a high intensity difference between adjacent pixels,also in using the multi-period analog code will bring the problem of phase unwrapping.Therefore,in this paper,we propose triple-frequency multi-period analog coded light 3D measurement method based on triple-frequency phase unwrapping,which includes the calibration and correction of the combined gamma value of the system,in order to improve the anti-jamming capability of analog coded light and to ensure phase unwrapping without error.In this paper,the multi-period analog coded light is adopted to enhance the intensity difference between adjacent pixels,also to reduce the quantization error and improve the anti-interference ability at the existing basis of the multi-step cosine phase shift method;Aiming at the situation of two meanings of phase value in measurement,the article established the triple-frequency analog light phase unwrapping model,analyzed and derived of the mathematical formula,.This paper confirmed the wrapping phase error tolerance of phase unwrapping method according to the theoretical analysis;Finally,the combined gamma value of thethree-dimensional measurement system is calibrated,so that it can correct the non-linear error,and the gamma calibration technique were used in 3D measurement experiment which were combined with triple-frequency multi-period phase shift method and triple-frequency phase unwrapping method.The experiment includes the combined gamma calibration and correction experiments,and the complex surface measurement experiments;The method of this paper is compared with the dual-frequency method and heterodyne method.According to the results of the experimental,the effectiveness of the method can be evaluated.The theoretical analysis and experimental results show that this method is more accurate than the dual-frequency method while the mean value of the measurement increases by 70.6%;the method has better anti-interference ability and shows a higher precision accuracy compared with the heterodyne method under the same coding fringe combination while the mean square deviation increased by 68.24%,also the curve change rate of its unwrapped phase residual reveals stable and the method has a higher precision in unwrapping phase.The method reduces the phase jumping error caused by the enlargement of phase error on principle.In this paper,the triple-frequency phase unwrapping method has a simple algorithm,and a large expansion range.It can expand without deviations within the error tolerance,which provides the theoretical and experimental basis for the analog coded light three-dimensional measurement.