Research On High Dynamic Range Surface Three Dimensional Topography Measurement Technology

Structured light three-dimensional shape measurement technology is widely used in industry.Phase measurement profilometry is one of the most effective methods to obtain three-dimensional shape information of object surface.However,for the high dynamic range object surface with large surface reflectivity variation,the traditional fringe projection technology is difficult to achieve high-precision shape measurement in high reflectivity and low reflectivity regions.In order to solve this problem,firstly,an algorithm based technique is proposed for the scene where the saturation is not obvious.This technique uses reverse fringes to compensate the truncated intensity value of the saturation region,so as to reduce the saturation error.Then,an adaptive fringes projection method based on recursion is proposed.Firstly,the algorithm solves the problem that the pixels between the camera and the projector cannot be mapped one by one The traditional mapping method is improved,which greatly improves the mapping accuracy.The algorithm can analyze the pixels with saturation and insufficient brightness in the collected image,and adaptively adjust the brightness of the projection pattern according to the coordinate mapping relationship,so that the projection brightness of each pixel recursively dichotomizes to the best projection brightness,so as to avoid saturation and improve the signal-to-noise ratio.Finally,the multi exposure image fusion technology is applied to the high dynamic 3D measurement,using a small number of image sequences under different exposures can be fused into an image without saturation and dark pixels,and the fused image is used for 3D data calculation.Based on the proposed method,several high dynamic scenes are built for experiments.The experimental results show that the reverse fringe compensation method is effective for unsaturated high dynamic scenes,and the multi exposure image fusion technology can greatly reduce the errors caused by saturation and low signal-to-noise ratio.The proposed adaptive fringe projection method can accurately adjust the projection brightness.With only a small amount of recursion,99.3% of the pixels with unreasonable projection brightness can be corrected,which can improve the 3D display effect of high dynamic range surface and the measurement accuracy of 3D topography.