Approaches for realizing a small scale tunable liquid-crystal microlens array (LCMLA) with several independent driving channels of applying voltage signal has been investigated in recent year. However, current requirements based on electrically tuning focus function are further increasing array scale of LCMLA and continuously improving driving efficiency of electric-signal setup so as to acquire more optical information of objects. The conventional point-to-point electrically driving (PTPED) method, which has disadvantages such as high power dissipation, lots of external wirings connections, and complicated electric-structure matching, cannot be used to accomplish a real-time independent driving control of arbitrary electrode end in a patterned electrode array of a LCMLA. In this paper, an addressably electric-scanning driving (ESD) approach for a 4×4 zoned LCMLA with sixteen electrode zone divided so as to reduce the number of driving signal lines, is proposed. Simultaneously, key functions such as the amplitude and frequency of a square-wave voltage signal for driving arbitrary electrode with needed RMS voltage value, which can be programmable processed so as to independently control zoned electrodes, can be effectively achieved. The principle of ESD of LCMLA, the simulation and design of hardware circuit, and the fabrication of ESD device are presented. According to our experiences in LCMLA, the ESD approach will exhibit possibility for construction and application of large-scale LCMLA. Besides, scene scanning automatically and three-dimension object reconstruction based on addressable LCMAL with multi-focuses is also predicted.
Liquid-crystal material demonstrates a special property of optical anisotropy. So far, it is widely used in many fields including flat panel displaying and other various optoelectronic devices. Electrically controlled liquid-crystal microlenses have presented some unique capabilities such as swinging focus over the focal plane and tuning focal length only by electrical signals applied over them. According to the typical electro-optical characteristics of nematic liquid-crystal materials, a liquid-crystal microlens array (LCMLA) with a featured zoned quasi-single-microhole electrode with more controlling area than the past microelectrode structure developed by us, which is applied by a multiplexed controlling signals according to an electrically scanning fashion, is proposed for realizing a new type of dual-mode imaging including one addressable wavefront measurement and correction through sensor array zoned by LCMLA, and another intensity image. Each sub-electrode in a quasi-single-microhole electrode can be individually driving and adjusting. So, two operations of adjusting focus and swinging focus can be achieved only by applying suitable voltage signals over each subelectrode. However, to successfully achieve a dynamic compensation of the aberrated wavefront measured so as to minimize target image distortion, hundreds of LC microlenses are needed for measuring and reconstructing wavefront corresponding to realtime image acquired. This will lead to a problem: a large number of conductive wires cannot be effectively arranged and connected to the LC microlens. In this paper, a LCMLA based on an electrically scanning approach is proposed. An "active matrix" for applying voltage signal over different structural unit is used so as to realize a active control of wavefront measurement and correction corresponding to a target image.
In this study, a kind of electronically controlled liquid-crystal microlens array (LCMLA) with plane swing focus and tunable focal length instead of a commonly microlens array with a fixed focal length and then focus distribution for highresolution image acquisition, wavefront measurement, and distortion wavefront correction, is proposed. The LCMLA mainly consists of two glass substrates coated with a film of indium-tin-oxide (ITO) transparent material on one side. Each sub-unit top layer is composed of four sub-square electrodes, and the bottom layer is a circular electrode. The key technological steps in electrode fabrication contain an ultraviolet lithography, a dry etching (ICP etching), and final electron beam evaporation and overlay. The current LCMLA can be realized in three operating modes under external driving circuitry, including intensity image acquiring, wavefront measurement and distortion wavefront correction. The LCMLA is only in the image acquisition mode under the condition of no driving electrical signal. As the same driving electrical signals are applied onto the top four sub-electrodes of each sub-unit, the LCMLA is in the wavefront measurement mode. The LCMLA is in the key wavefront correction mode when different driving electrical signals are simultaneously applied onto the top four sub-electrodes of each sub-unit. Experiments show that the focal point of the LCMLA can be moved along the optical axis and over the focal plane by applying appropriate driving voltage signals.
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