To focusing ion beam etching (FIB) machine, the maximum effective processing size in x- and y-direction is still in ~100 micron scale during a single manufacturing cycle, generally. Considering the performances of existing equipments, it is a core operation that a high-precision and small-volume stepping displacement microplatform with a larger manufacturing size of more than that of existing equipments, is constructed effectively for fabricating optical antenna with a size in centimeter scale. The designed setup can be used to conduct a two-dimensional displacement with very high precision of few tens of nanometers for processing sample with structural size scope in centimeter level or even more, is to attach to the working plate of the FIB machine. In this paper, the 80C51 single-chip microcomputer is used as the control setup. Based on the analysis of the three closed-loop DC speed regulation system, the key parameters of the controller are designed according to the dynamic and static performance indicators of the system. Using Matlab's Simulink and Power System toolbox, a three-mode closed-loop DC speed control system for positioning and current generating is built. The model and the key parameter setting of the positioning loop, the speed loop and the current generating loop, are introduced. The simulation model and results of the DC reversible speed control system are given. The simulations verify the model, which can be effectively utilized to correct the parameter setting. It should be noted that the current change rate is suppressed while maintaining a maximum allowable changing rate, so as to make the entire current waveform being closer to the ideal waveform.
We propose a foveated imaging system (FIS) implementing by effectively correcting wavefront aberration, which mimics the human visual system to obtain a high resolution image for the regions of interest (ROI) while keeping a wide field of view (FOV). It is flexibly tuning the variation of the refractive index of liquid-crystal (LC) materials through adding variable AC voltage signals. A novel liquid-crystal microlens array (LCMLA) with three concentric ringelectrodes are presented, where three different AC voltage signals can be applied to corresponding ring-electrodes. There are three hexagon arrangement patterned electrode arrays with different diameters (equivalent to 98μm, 112μm and 140μm from the center to the periphery) in the concentric circles. The diameter of the MLA in the central field is the smallest, where the spatial resolution may be the highest. If appropriate AC voltage signals are added, the wavefront aberration of the incident light of ROI could be well adjusted. An experiment is developed to validate the performance of the FIS using LCMLA. The example images show that the proposed FIS can obtain local high resolution image of the ROI by dynamically controlling AC voltage signals and a total low resolution image over a wide FOV.
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.
This paper presents a polarization insensitive infrared filter based on a liquid-crystal Fabry-Perot (LC-FP) developed for electrically tunable spectrum and performing high efficient imaging detection. Generally, the LC-FP filters are polarization sensitive optical devices, which means that filtering effect will be enormously influenced by ray polarization so as to lead to a low utilizing efficiency of incident energy. Therefore, it is of great significance to find an approach to improve or even solve the problem. The new type of infrared filter designed by us is mainly consists of a FP resonant cavity with a layer of zinc selenide (ZnSe) material as its substrate and a thin film of nano-aluminum (Al) material acting as its electrode and high-reflection mirror. Particularly, compared to the common filters, it has a multi-directional layer of ployimide (PI) film which can make the LC distributed along two mutually perpendicular directions so that the incident infrared light in different polarization orientations are able to be modulated. The experiment results indicate that the filter’s polarization insensitivity is substantially improved, thus it can work well in various polarized infrared radiations, and obviously will have a broader prospect of application.
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 paper, a new type of electrically controlled liquid-crystal microlens arrays (ECLCMAs) based on plane nonuniform spiral microcoils (PNSMs) is proposed. The microlens array is based on a nematic liquid-crystal material, which presents a special characteristics of optical anisotropy and birefringence, and is fabricated by common ultraviolet lithography and dry ICP etching process to form needed PNSMs pattern. In the ECLCMAs, a glass substrate precoated by a film of indium tin oxide (ITO) on both surfaces of substrate is adopted. The key center electrode for shaping each functioned LC cell is drilled using a laser etching and emery polishing process. Metallic indium particles are selected to connect the upper and lower ITO layers. The design can guarantee the continuity of the upper and lower plates and does not affect the electric and magnetic fields generated by spiral microcoils, which are utilized to drive LC film to present needed functions of further controlling and adjusting incident microbeam distribution, which is preprocessed by main objective lens system. After an AC voltage signal is applied across the microcoil, an effective electromagnetic field can be formed in LC cell so as to drive LC molecules to rotate and thus demonstrates an electrically tuning focus. The simulations show that the design of patterned PNSMs can be effectively used to form a sufficient electric and magnetic fields that are directly used to rotate LC molecules and thus form a gradient refractive index distribution for converging incident microbeams so as to show a higher controlling-light efficiency than that of traditional patterned microelectrodes. The proposed method laid a solid foundation for future smart ECLCMAs.
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.
In this paper, a kind of electronically controlled liquid crystal microlens arrays (LCMAs) with non-uniform coil electrodes arrays (NCEAs) is presented. The focal length of the electronically controlled LCMAs can be easily adjusted by applying the appropriate AC signal. The structure of the LCMAs is designed as a NCE array, which can then produce non-uniform electric field to drive liquid crystal molecules. The top electrode is fabricated by depositing an indium-tinoxide (ITO) semiconductor transparent conductive film based on a non-uniform electrode coil, and the bottom electrode is a conventional plate electrode. Due to the design of non-uniform electrode coil array is small, in addition to the traditional lithography process, the etching process we used is dry etching (ICP etching). The simulation results show that, the focal length of the LCMAs with the NCEAs can be tuned easily by applying the appropriate AC signal.
In this paper, a new liquid-crystal microlens array (LCMLA) with patterned ring-electrode arrays (PREAs) is investigated, which has an ability to acquire multiple-mode two-dimensional images with better electrically tunable efficiency than common liquid-crystal devices. The new type of LCMLA can be used to overcome several remarkable disadvantage of conventional liquid-crystal microlens arrays switched and adjusted electrically by relatively complex mechanism. There are two layer electrodes in the LCMLA developed by us. The top electrode layer consists of PREAs with different featured diameter but the same center for each single cell, and the bottom is a plate electrode. When both electrode structures are driven independently by variable AC voltage signal, a gradient electric field distribution could be obtained, which can drive liquid-crystal molecules to reorient themselves along the gradient electric field shaped, so as to demonstrate a satisfactory refractive index distribution. The common experiments are carried out to validate the performances needed. As shown, the focal length of the LCMLA can be adjusted continuously according to the variable voltage signal applied. According to designing, the LCMLA will be integrated continuously with an image sensors to set up a camera with desired performances. The test results indicate that our camera based on the LCMLA can obtain distinct multiple-mode two-dimensional images under the condition of using relatively low driving signal voltage.
Previous studies have presented the usefulness of typical liquid-crystal Fabry-Perot (LC-FP) infrared filters for spectral imaging detection. Yet, their infrared transmission performances still remain to improve or even rise. In this paper, we propose a new type of electrically tunable LC-FP infrared filter to solve the problem above. The key component of the device is a FP resonant cavity composed of two parallel plane mirrors, in which the zinc selenide (ZnSe) materials with a very high transmittance in the mid-long-wavelength infrared regions are used as the electrode substrates and a layer of nano-aluminum (Al) film, which is directly contacted with liquid-crystal materials, is chosen to make high reflective mirrors as well as the electrodes. Particularly, it should be noted that the directional layer made up of ployimide (PI) used previously is removed. The experiment results indicate that the filter can reduce the absorption of infrared wave remarkably, and thus highlight a road to effectively improve the infrared transmittance ability.
Under the condition of existing intense turbulence, the object's wavefront may be severely distorted. So, the wavefront sensors based on the traditional microlens array (MLA) with a fixed focal length can not be used to measure the wavefront effectively. In order to obtain a larger measurement range and higher measurement accuracy, we propose a liquid-crystal microlens array (LCMLA) with needed ability of swing focus over the focal plane and further adjusting focal length, which is constructed by a dual patterned ITO electrodes. The main structure of the LCMLA is divided into two layers, which are made of glass substrate with ITO transparent electrodes. The top layer of each liquid-crystal microlens consists of four rectangular electrodes, and the bottom layer is a circular electrode. In common optical measurements performed, the operations are carried out such as adding the same signal voltage over four electrodes of each microlens to adjust the focal length of the lens cell and adding a signal voltage with different RMS amplitude to adjust the focus position on the focal plane. Experiments show that the LCMLA developed by us demonstrate a desired focal length adjustable function and dynamic swing ability, so as to indicate that the method can be used not only to measure wavefront but also correct the wavefront with strong distortion.
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