Parameter Optimization And Accuracy Improvement Of Full-Frequency Phase Profilometry Based On Multi-Frequency Heterodyne

With the concept of “Industry 4.0” and “Made in China 2025”,the demand for more accurate and efficient 3D measurement technology is increasing.As an important branch of optical 3D measurement,surface structured light 3D measurement technology based on phase measurement profilometry has been widely used in the field of industrial measurement.Since the measurement accuracy of phase measurement profilometry is limited by the physical properties and processing accuracy of optical and electronic components,the error analysis and method improvement of phase measurement profilometry have important theoretical significance and wide application value.Based on the phase error analysis,an improved method of phase measurement profilometry is proposed,which is full-frequency phase profilometry based on multi-frequency heterodyne.In order to improve the measurement accuracy of full-frequency phase profilometry,the parameter optimization and error compensation methods are proposed.Firstly,the paper establishes the phase error model according to the application process of phase measurement profilometry,including analog-to-digital conversion discrete error,projector nonlinear response error,projector defocus error and ambient light error.Based on the error analysis,the constraint relationship between phase error and phase unwrapping algorithm based on multi-frequency heterodyne principle is derived and verified by simulation analysis.Then,this paper proposes a full-frequency phase unwrapping algorithm based on the multi-frequency heterodyne principle,which uses the redundant phase information in the multi-frequency heterodyne principle to improve the measurement accuracy.A complete parameter optimization and error compensation method is proposed to further improve the measurement accuracy.In order to reduce the defocus effect of the projector,the optical transfer function of the projector's defocusing effect is estimated,and the projector focal length,the camera focal length,and the measured distance of the measured object are adjusted to make the measured object at the optimal measurement position.The gray-scale modulation coefficient and the average gray value of the surface structure light are optimized according to the nonlinear response curve of the projector.Predistortion compensation is performed by estimating the projector gamma distortion parameter.After the parameter optimization and error compensation,the maximum phase error calculated according to the phase error model.The appropriate number of sinusoidal fringe periods is estimated by the constraint equation of the phase unwrapping algorithm.The effects of the above parameter optimization and error compensation are verified by simulation.Finally,based on the theoretical analysis,this paper builds a 3D measurement experimental platform for monocular surface structure.After calibrating the internal and external parameter matrices of the camera and the projector,the parameter optimization and error compensation of the surface structured light are carried out according to the theoretical analysis.The 3D measurement is performed using the surface structure light before optimization and the optimized surface structure light,respectively.The 3D measurement experimental results of this method are compared with the traditional methods to prove the effectiveness of the proposed method.