Research On Wavefront Measurement System Based On Transmassive Fringe Deflectometry

Optical free-form lens has a higher degree of design freedom than traditional lens,and is an important development direction of modern optical system design.Free-form surfaces from design to applications require extremely high machining accuracy.Therefore it is essential to test the free-form lenses machined to find whether they meet the requirements of design.Transmissive fringe deflectometry(TFD)wavefront measurement system consists of a computer monitor displaying fringes and a camera receiving distorted fringes,which has the advantages of simple structure,large measuring range of curvature,fast measuring speed and high precision,and is suitable for the measurement of free-form lenses.In this paper,the method of TFD is studied,a measurement system of free-form lens is designed and developed based on TFD.The main contents of this paper are as follows:1.The working principle of TFD is introduced.The calibration model of system parameters is established to realize the conversion from the monitor screen phase coordinate system to the camera coordinate system.The initial phase of the fringes is restored using phase shifting method and phase unwrapping techniques.The wavefront is reconstructed using poisson reconstruction method.2.The measurement process of TFD measurement system is modeled and simulated.By comparing the simulation results,the influence of using non-parallel light on the measurement accuracy is discussed.Meanwhile,by comparing the simulation results with and without position calibration error of lens,the effect of lens' position calibration accuracy on the lens' diopter measurement accuracy is discussed.3.The TFD measurement system is set up to carry out experiments on a single vision lens,two F-Theta lenses of different sizes and a progressive lens.Measurement results of wavefront slopes,integral reconstruction of wavefront,spherical and astigmatic power of the lenses are obtained and discussed.