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.
By controlling the deposition time of indium–tin–oxide (ITO) film, a high resistance of ultra-thin ITO (UTITO) layer can be realized. The UTITO layer is then deposited at the interface between the dielectric and LC layers in the hole-patterned liquid crystal (LC) lens. The UTITO application spreads the fringing field into the aperture hole center of LC lens and thus assists the LC reorientation therein. That considerably decreases the addressing voltage and switching-on time of LC lens. The UTITO LC lens also provides a wide tunable focus function, and preserves the lens quality and imaging performance as the conventional hole-patterned LC lens.
A three-dimensional/two-dimensional (3-D/2-D) convertible display was proposed. The display system offers 2-D images via the traditional display technology and offers 3-D images via the computer-generated hologram (CGH) technology. In this system, 2-D and 3-D images are generated from the same amplitude-modulated spatial light modulator (SLM). In the 2-D display mode, the panel displays an amplitude-modulated image and the 2-D image is projected on a polarization-dependent diffuser (PD) screen. In the 3-D display mode, the SLM panel displays CGHs to generate 3-D images. The zero-order diffraction of the amplitude-type CGH will be blocked by a spatial filter (SF), which is designed by a polarizer. Furthermore, a liquid crystal element was employed to modulate the polarization state of the reconstructed light to let the 3-D image quality not to be reduced by the PD. Finally, the proposed system can offer 2-D and 3-D images both clearly. The system suppresses the zero-order diffraction noise of the amplitude-type CGH system successfully.
Liquid crystal (LC) lenses have attracted much attention, owing to the light weight and an adjustable focal length without mechanically moving parts. Among the developed LC lenses, the hole-patterned LC lens has a convenient fabrication process, a simple addressing scheme, and widely tunable focal range. Nonetheless, a thick dielectric layer (TDL) has to be inserted between the hole-patterned electrode and the LC layer to distribute the fringing electric field throughout the center of the aperture hole (AH). However, the inserted TDL significantly increases the operation voltage of the LC lens. In this paper, we propose a hole-patterned LC lens with a wide diameter of 6 mm. In our design, a floating ring electrode (FRE) is embedded into the interface between the dielectric layer and the LC layer. This structure confines the electric field in the hole patterned area, therefore assists in distributing the fringing electric field throughout the LC layer and thus assists in tilting the LCs in the AH center of the lens. Therefore, the dielectric layer used in the conventional hole-patterned LC lens can be effectively decreased. The decreased thickness of the dielectric layer provides the FRE LC lens with the advantages of lower operation voltage and large tunable focal range. With a voltage of 40 V, the introduced floating ring electrode modulates the phase retardation of the LC lens in a nearly perfect quadratic form with wavefront error approaching 0.07 . The design principle, simulation and fabrication of the LC lens are demonstrated in this paper.
Previously, we have established hole-patterned liquid crystal (LC) lens consisted of a floating ring electrode (FRE LC lens).
However, while the applied voltage is given across the FRE LC lens, the disclination lines are induced as conventional hole-patterned
LC lens, degrading the lens quality. To avoid the appearrance of disclination lines, the polymer stabilization is adopted to construct
the FRE LC lens. The polymer stabilized FRE LC lens not only excludes the occurrence of the disclination lines during applied
voltages but also preserves optical properties similar to the ordinary FRE LC lens.
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