Fabrication And Applications Of Aspherical Liquid Micro Lens And Lens Array

Micro lenses and lens arrays are significant devices of micro optics and have been widely applied on fiber coupling, beam shaping, integral imaging and optical neural network, et al. Aspherical lenses have increasing market needs because their comparative smaller optical aberrations. In this thesis, a novel method of fabricating aspherical micro lens and lens array with shape manipulation by electrostatic field is proposed. An experiment setup which can fabricate aspherical micro lens by electrostatic shape manipulation, in situ measurement and Ultra Violet (UV) curing is developed. The aspherical lens array fabricating technology is theoretically and experimentally studied and summarized. Aspherical lens and lens array with nice optical performance are fabricated and their optical aberrations are calculated and evaluated. The aspherical liquid lens is applied on Laser Diode (LD) collimation and compound eye fabrication.The main research contents of this thesis are listed as follows:1. A novel method of fabricating aspherical micro lens and lens array is proposed. UV curable polymer is selected as the material of the liquid lens. Electrostatic field is employed to manipulate the lens shape from initial spherical to aspherical. The surface profile and focus spot images of the liquid lens are in situ measured and used to calculate its aberrations. When appropriate surface profile and focus spot are detected, aspherical liquid lens is cured and solid aspherical lens with good performance is achieved. An experiment setup which can fabricate aspherical micro lens by electrostatic shape manipulation, in situ measurement and UV curing is developed, including the developments of its mechanical structure, optical system, controlling circuit and software system. And the setup can work for the fabrication of aspherical liquid lens and lens array.2. The aspherical lens array fabricating technology is theoretically and experimentally studied and summarized. The interaction of fluidic field and electrostatic filed is theoretically analyzed and numerical calculated. The shape variation of liquid lens in electrostatic field is resolved. The numerical calculation results well fit the experimental results. Experimental results show that the lens shape is manipulated by electrostatic field from initial spherical to parabolic and to even conic. The surface profiles and focus spots images of a liquid lens in different electrostatic fields are in situ measured. The variations of principal curvature, focal length and focal spot size are calculated by imaging process and polynomial fitting. The parameters of many kinds of UV curable polymers are studied and selected. The distortion of the aspherical liquid lens while UV curing is investigated and compared. The reasons why the distortion happens, its influence on lens's optical quality and how it can be solved are discussed.3. The optical aberrations of the fabricated aspherical lens are calculated and its imaging performance is evaluated. The polynomial of the aspherical liquid lens is achieved by imaging process and polynomial fitting from the lens surface profile image. Associated with Zemax software, the geometrical aberrations and the imaging quality evaluating parameters, such as wave aberration, spot diagram, Strehl ratio and MTF, are calculated by ray tracing method. A probe scanning microscope with high optical resolution is developed. The focus spot of the fabricated aspherical lens is precisely measured and its PSF, MTF and Strehl ratio are calculated. Therefore, the imaging quality of the aspherical lens is evaluated. The actual imaging experiment of the fabricated aspherical lens is accomplished and has good results.4. Applications of the fabricated aspherical lens are discussed. An experiment setup of fabricating LD collimating lens is developed. A polymer drop is dropped on the LD emitting window. Its wetting shape is controlled and its shape is manipulated by electrostatic field. Its divergence angles vary following its shape distortion. When a collimated emitting beam is in situ investigated, the liquid collimating lens is cured and the integral LD collimating lens is achieved. A novel structure design of spherical compound eye is proposed. Aspherical lenses are fabricated on a spherical shell substrate and serve as channel lenses of the spherical compound eye. Each channel lens incepts lights of certain field of view (FOV) and focuses on a planar photodetector. The spherical compound eye can achieve a large FOV. The channel lens is tunable aspherical lens fabricated by dropping UV curable polymer on a double-concave glass substrate lens. The lens shape and its focal length are manipulated by electrostatic field and keep small aberration to satisfy the demand of spherical compound eye. At last, aspherical solid immersion lens is fabricated and beam steering experiment using fabricated lens array is accomplished and have good results.