This study presents an innovative approach to create a tunable multifocal LC microlens array (TMLCMA) that can switch between convex and concave modes. The TMLCMA is constructed using nematics and a triple-electrode structure comprising a top large-hole electrode, a middle small-hole array, and a bottom planar ITO electrode. A ZTO modal film is applied to the large-hole electrode on the top substrate to aid in distributing the electric field across the large-hole area. Various voltage control methods can manipulate the TMLCMA. Under the influence of voltage, the axially symmetric fringing electric field generated by the top large-hole electrode leads to a gradual and radial adjustment of the microlens's focal length from the TMLCMA's periphery to its center. This electrically tunable gradient in focal length is achieved. Practical demonstrations of the imaging functions of the TMLCMA are provided.
The development of multifocal microlens array has paid many attentions recently with the applications of plenoptic cameras, stereoscopic displays, and beam homogenizers. A variety of technologies have been explored and applied to produce multifocal microlens arrays, however, most multifocal microlens arrays are limited due to structural modification, long fabrication time, and lack of tunability. In this study, we present a novel method of fabricating a tunable multifocal liquid crystal microlens array (TMLCMA) using the three-electrode structure composed of a large hole, small-hole array, and planar electrodes. Liquid crystals with positive dielectric anisotropy were filled in the TMLCMA sample and aligned planar with antiparallel rubbing treatment. A modal layer was deposited on the surface of the large hole electrode to assist in extending the fringing electric field into the TMLCMA center. The fringing electric field induced by the large hole electrode results in the microlenses have different focal lengths from the TMLCMA border to the center. The TMLCMA can be worked in concave and convex modes on the basis of signal control schemes. The beam patterns through the TMLCMA are observed and the phase shifts of the microlenses at various positions are reported. The optical imaging of the TMLCMA has been demonstrated practically. The results reveal that the proposed method is able to produce a tunable multifocal microlens array via a simple fabrication and addressing scheme. This study has proposed a strong basis for the further development of microlens array, and the optical characteristics of the TMLCMA are promising to applications of optical fields.
In this presentation, a rubbing-free LC device fabricated with organic Single-Crystal Rubrene (SCR) substrate has been investigated. The LC orientation on SCR is determined with capillary flowing direction of LCs, the SCR-coated LC cell has a homogeneous alignment with low pretilt angle. The SCR-based LC cell performs a wider thermal tolerance than that of the PI-based cell, owing to the strong anchoring property of SCR surface. SCR-based LC cell performs a lower operation voltage, faster response time, and higher voltage holding ratio than the PI-based LC cell. A rubbing-free modal LC device based on SCR layer is under development.
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