Abstract
An electrically tunable-focusing liquid crystal (LC) microlens array exhibiting a wide-range tunable focal length is proposed. The lower substrate has strip indium tin oxide (ITO) electrodes, the upper substrate has periodic ITO electrodes with a certain gap coated on the inner surface., and an LC microlens is generated between the two strip electrodes. For each LC microlens, the gap between the top planar electrodes is directly above the center of the microlens. Unlike the conventional LC lens, the individual LC microlens is not coated with ITO electrodes on the central part of its upper and lower substrates, which helps to maintain the LC’s horizontal orientation. In the voltage-off state, the focal length of the microlens array is infinity because of the homogeneous LC alignment. At a given operating voltage, an ideal gradient refractive index distribution is induced over the homogeneous LC layer, which leads to the focusing effect. The simulation result shows that the focal length of the LC microlens could be gradually drawn to 0.381 mm with a change of voltage.
Highlights
A microlens array is a key part for optical information processing, optical interconnection, optic fiber switches [1,2,3,4], ophthalmic application [5], three-dimensional display systems [6,7,8,9,10,11,12,13], and so on.A tunable liquid crystal (LC) microlens array has been investigated for 40 years
We propose a LC microlens array with a simple electrode structure that behaves as a cylindrical lens
We proposed an electrically tunable-focusing LC microlens array with a simple electrode structure
Summary
A microlens array is a key part for optical information processing, optical interconnection, optic fiber switches [1,2,3,4], ophthalmic application [5], three-dimensional display systems [6,7,8,9,10,11,12,13], and so on.A tunable LC microlens array has been investigated for 40 years. To obtain a LC lens, various devices such as a multi-strip or hole-patterned electrode [8,14,15,16,17], LC lens with switchable positive and negative focal lengths [18], optically hidden dielectric structure [19,20], and polymer-stabilized blue phase LC [21,22,23,24,25] have been studied in recent years. The optically hidden dielectric structure enables finer phase control for generating a nearly ideal parabolic phase profile, it has Fresnel reflections between dielectric layers, which will affect the image quality
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