Se-Um Kim

Physical mechanism for flat-to-lenticular lens conversion in homogeneous liquid crystal cell with periodically undulated electrode

A convertible lenticular liquid crystal (LC) lens architecture is demonstrated using an index-matched planarization layer on a periodically undulated electrode for the homogeneous alignment of an LC. It is found that the in-plane component of the electric field by the undulated electrode plays a primary role in the flat-to-lens effect while the out-of-plane component contributes to the anchoring enhancement of the LC molecules in the surface layer. Our LC device having an index-matched planarization layer on the undulated electrode is capable of achieving the electrical tunability from the flat surface to the lenticular lens suitable for 2D/3D convertible displays.

Lenticular lens array based on liquid crystal with a polarization-dependent focusing effect for 2D–3D image applications

Demonstrated herein is a liquid-crystal-(LC)-based lenticular lens array with a polarization-dependent focusing effect, fabricated through a simple imprinting process. The input polarization dependence of the proposed LC lenticular lens array arises mainly from the index matching scheme between the polymer lenticular lens and the LC on it. For the input polarization perpendicular to the LC director, the focal length of the lenticular lens is about 3.1 mm. The focusing and non-focusing properties depending on the input polarization are useful for realizing autostereoscopic 2D/3D convertible displays combined with polarization selection elements.

Optically switchable grating based on dye-doped ferroelectric liquid crystal with high efficiency

We demonstrate an all-optically switchable ferroelectric liquid crystal (FLC) grating constructed in an alternating binary configuration with different optical properties from domain to domain. A dye-doped FLC is uniformly aligned in one type of domains whereas it is infiltrated into the photo-polymerized networks of reactive mesogens in the other. Compared to conventional nematic LC cases, our FLC grating allows more efficient all-optical modulation and faster diffraction switching between the 0th and the 1st orders in subsecond since the optical response associated with the dye molecules in the layered state is less hindered than in the orientationally ordered state. Our dye-doped FLC grating with periodically infiltrated structures will be useful for designing a new class of all-optically switching systems.

Concept of active parallax barrier on polarizing interlayer for near-viewing autostereoscopic displays

We proposed a concept of an active parallax barrier using a liquid crystal-on-polarizing interlayer (LPI) for near-viewing autostereoscopic displays. In contrast to a conventional two-panel configuration where two independent panels are stacked together for displaying and parallaxing purposes, a monolithic one-panel architecture was demonstrated with the help of the LPI. The LPI was constructed using a polarizer sheet, one side of which provided the support for the active parallax barrier and the other served as the substrate for the image panel. For the active parallax barrier, an array of periodically patterned indium-tin-oxide electrodes was first prepared on the LPI and bi-level structures were subsequently fabricated for the cell gap and the liquid crystal alignment. Our monolithic one-panel architecture allows the near-viewing distance property which is essential for mobile applications.

Design and fabrication of liquid crystal-based lenses

ABSTRACT Liquid crystal (LC)-based lenses are promising for a wide range of applications from optical communications and signal processing to three-dimensional displays. Among a variety of the LC-based lenses, several classes including the Fresnel type and the lenticular type are comprehensively reviewed from the standpoints of the basic concepts and the device architectures. The underlying mechanisms for the focusing effect and the tuning capability inherent to the lens configuration are described. Recent progress on the LC-based lenses for reconfigurable optical processing and autostereoscopic displays is also presented. The lens architecture combined with the intrinsic anisotropy of the LC provides a versatile platform to build up high-performance LC-based lenses with the tuning capability. Graphical Abstract

Reduction of gamma distortions in liquid crystal display by anisotropic voltage-dividing layer of reactive mesogens

ABSTRACT We demonstrate a new concept of reducing the off-axis gamma distortions in a liquid crystal display by the formation of an anisotropic voltage-dividing layer (AVDL) on the alignment layer. The AVDL was prepared using reactive mesogens (RMs) by simple spin-coating, followed by the photo-polymerisation under the exposure of ultraviolet light (UV) through a photomask and the removal of residual RMs. The UV exposure time for the photo-polymerisation was found to be critical for the uniform alignment of the liquid crystal molecules on the AVDL. Owing to the capacitance difference between the sub-domains produced by the AVDL, the threshold voltage shift was naturally appeared in sub-domain by domain so that the reduction of the gamma distortions in the off-axis was achieved in a simple way. GRAPHICAL ABSTRACT

The domain mixing effect on the electro-optical properties of liquid crystals using polyimide doped with reactive mesogen

ABSTRACT This paper investigates the enhancement of the electro-optic (EO) properties of liquid crystal (LC) devices by the domain mixing effect of vertical-alignment polyimide (PI) doped with reactive mesogen (RM). The mixture of PI and RM on a glass substrate was exposed to ultraviolet light and was thermally annealed to produce circular microdomains of the LC polymer (LCP) in the PI background. Due to the appearance of such LCP microdomains depending on the RM doping concentration, the EO properties such as the threshold voltage and the response times were significantly improved in a vertically aligned configuration of the LCs.

Precise Lens-On-Lens Architecture Using Selective Wettability for Image-Depth Representation

We demonstrate a precise lens-on-lens architecture using the concept of the selective wettability for the image-depth representation. Two focal lengths realized by the difference between two geometrical curvatures of the primary convex lens and the secondary convex lens in a lens-on-lens manner enable to produce two image planes. Such lens architecture was spontaneously produced through the selective wetting process of a photo-reactive polymer during dip-coating, followed by the irradiation of ultraviolet light for polymerization. Our selective wettability approach is capable of building various sizes and shapes of the lens-on-lens patterns over large-area without using a photo-lithography or a wet-chemical etching process.

P‐126: Tunable Lenticular Lens Array Using Liquid Crystal on Periodically Undulated Electrodes for Autostereoscopic 2D/3D Convertible Displays

We developed an electrically tunable lenticular lens array using a liquid crystal on periodically undulated electrodes for autostereoscopic 2D/3D convertible displays. The undulated electrodes fabricated through an imprinting and planarization process provide the focal length tenability of the liquid crystal lens. For 2D images, the uniform LC layer under no applied voltage produces no variations of the phase retardation over the whole area. For 3D images, the focusing capability arising from the electric field gradient generated by the undulated electrodes is achieved.

New architectures of liquid-crystal-based lenticular lenses in index matching approach for display applications

Within the index matching framework, the overview of two architectures of liquid crystal (LC)-based lenticular lens arrays developed previously is given. The first type exhibits the polarization-dependent focusing effect which comes from the index matching between a polymer convex lens structure on the bottom substrate and a LC on it. It shows the high quality two-dimensional image and the focusing effect depending on the polarization of the incident light. The second type is capable of laterally shifting the focusing effect in a complementary geometry of a convex lens on the bottom substrate and a concave lens on the other. The lateral offset between the centers of both lenses was one half of lens pitch such that the lateral shift of the focusing effect is spontaneously achieved at either the interface of LC-concave lens or that of LC-convex lens. The two architectures of the LC-based lenticular lenses would be applicable for devising a new class of advanced 2D-3D convertible systems.