Color Fringe Projection 3D Measurement Method Based On Improved Three-step Phase Shif

Optical three-dimensional(3D)profile measurement technology has been widely used and developed in many fields such as intelligent manufacturing,virtual reality,medical plastic surgery,face recognition,cultural relic protection and so on.Fringe projection 3D measurement system has the advantages of non-contact,non-destructive nature,high measurement accuracy and high resolution,which has become a research hotspot in the field of 3D profile measurement.With the rapid development of digital optical projection technology and imaging sensor technology,people have put forward higher requirements on the speed and accuracy of measurement technology in industrial applications.Therefore,based on the 3D measurement method of gray fringe projection,a 3D measurement method of color fringe projection based on improved three-step phase shifting is developed in this paper.This method can quickly and accurately calculate the height information of the object only with a pair of color fringe,so as to reconstruct the 3D profile of the object.The specific research content is as follows:(1)The principle and structure of the fringe projection 3D measurement system are deeply analyzed.The fringe image encoded by computer software is projected onto the surface of the measured object by a projector.The 3D profile of the object will cause the fringe to be deformed to different degrees,and the deformed fringe image is captured by camera.The improved color image vector median filtering method is used to filter the noise effectively.(2)The Hilbert transform is introduced into the traditional three-step phase shifting method,and the DC component of the fringe image is obtained by using the Hilbert transform,and a cosine fringe image is replaced by a flat image of the captured light intensity distribution of DC component,so the improved three-step phase shifting method is obtained.The improved three-step phase shifting method has low sensitivity to external noise and can effectively improve the measurement accuracy.Combined with RGB color model,an improved color fringe phase shifting method is proposed,which can measure the phase of objects only by projecting a color fringe image,which greatly improves the measurement speed.(3)In order to avoid the influence of wrapped phase change too fast,a four directions least-square phase unwrapping method based on lateral shearing interometry is designed in this paper.Experimental results show that this method can effectively reduce the phase error transmission,and effectively improve the speed and accuracy of full-field phase recovery.The continuous phase of the object is obtained by the phase unwrapping method,and the 3D profile of the object is measured by combining the result of system parameter calibration.(4)The color fringe projection 3D measurement system is successfully built,and the phase-height parameter calibration experiment of the system is completed on the hardware platform,and the measurement experiment of the real object is carried out,and the measurement efficiency of the 3D measurement system designed in this paper is analyzed in detail.The experimental results show that this measurement system increases the reliability of the system while ensuring the measurement efficiency,and is suitable for real-time online 3D measurement of objects.