Beam Deflection Technology Of EWOD-based Liquid Prism And Its Application

Beam deflection technology plays an indispensable role in holographic projection,laser radar scanning,free space communication,solar lighting and many other fields.Traditional mechanical beam deflection technology relies on the vibration and rotation of optical devices to realize large-angle beam deflection,which has problems such as large volume,low accuracy,complicated structure and high energy consumption.The beam deflection technology based on electrowetting has the characteristics of high response speed,small volume,low energy consumption and easy array,etc.In this work,the spatial beam modulator based on electrowetting liquid prism array is designed to adjust various beams(parallel light,converging light and diverging light)in three-dimensional space.The Optical Transfer Function(OTF)is derived according to geometric optics,matrix optics and electrowetting theory.The physical model of spatial beam modulator is established by using the simulation software COMSOL,and the beam control performance of it is simulated and analyzed.The results show that the spatial beam modulator can translate,expand,shrink,converge and diverge the parallel beam.When the parallel beam is incident on the spatial beam modulator,the maximum translation distance is 0.71 mm,and the focal length f of the outgoing beam can be adjusted in the range of 15.8mm ～ ∞(biconvex liquid interface)or-∞ ～-38.1mm(biconcave liquid interface).In addition,the spatial beam modulator can converge,diverge and collimate non-parallel beam.A beam scanner based on electrowetting liquid prism is designed,whose structure and working principle is presented in detail.The formula of its beam scanning path and the relationship between beam scanning radius and liquid interface inclination angle is derived.The results show that the double-layer liquid interface can freely rotate 360°on all axes,and the inclination angle of the liquid interface can be adjusted freely in 0°～ 45°.Finally,the scanning path patterns of double-layer liquid interface are simulated by MATLAB.The results show that when scanning in the same direction,the larger the scanning frequency ratio k is,the less blind areas in the field of view are.On the contrary,when scanning in reverse direction,the larger the scanning frequency k is,the more blind spots on the edge of the field of view,but the scanning effect of the center field is excellent.