In this paper, we present world-first TFT liquid crystal glasses (TFT-LCG) that display images to the passersby and have limited obstruction to the vision of wearers. By the concept of manipulating the polarization state of incident light with the liquid crystal, the appearance at the world side of the glasses is electrically controlled. The glasses display colored images with resolution of 36 pixels per inch and contrast ratio over 15. The viewing angle of wearer is almost the same as existing glasses and keep high MTF performance with TFT pixel traces. The driving power of the TFT-LCG is lower than 100mW with frame rate of 10 fps. Integrated with virtual platform and wireless control, the glasses can serve as a novel interaction medium between individuals. It opens a new path for how people connect with each other.
We proposed a reflowable liquid crystal (LC) geometric phase element for vertical cavity surface emitting laser (VCSEL) projector. By photo alignment technology and LC one drop fill process, we realized an active LC geometric phase element and pattern switchable VCSEL projector. According to geometric phase distribution, the incident light was transformed into different light distribution, such as flood pattern, beam multiplication, or wider illumination. When voltage was applied, all LC directors aligned perpendicularly to substrates and the geometric phase distribution vanished. Therefore, the output light remained as the original projecting pattern. Due to narrow wavelength range of the VCSEL, the optical performance, such as diffraction efficiency and phase difference, was not decayed by the dispersion of geometric phase. We made a record of 3 × 3 mm LC cell with our in-house ink-jet printing system. The transmittance was over 95%, and the switching time was <5 ms.
We propose a novel 2-in-1 pattern projector, which consists of a Dot projector and an LC diffuser. The LC diffuser is made of switchable Microlens Arrays (MLA) based on geometric phase. The LC diffuser can switch between “no lens power” and “MLA” mode. In “no lens power” mode, the Dot pattern is not affected by the LC diffuser. In “MLA” mode, the focused Dot pattern is “blurred” by the MLA, which generates the Flood pattern. The eigen mode of geometric phase MLA is carefully designed to achieve polarizer free modulation. We implement this novel modulation concepts with the world smallest and 1st ever reflowable LC cell. We made a record of 3x3mm LC cell with our in-house IJP system. The optical efficiency is over 95%, and the switching time is less than 5ms.
The anisotropic properties of nematic liquid crystals result in polarization dependency which leads to requirement of at least a polarizer in liquid crystal photonic devices. To develop polarizer free phase modulation, Kerr effect is one of the path. The phase modulation in polymer dispersed liquid crystals (PDLCs) is shown to have two parts: Kerr phase, which is the optical phase modulation linearly proportional to a square of electric field, and orientational phase. However, many puzzles are still under investigation: the origins of Kerr phase, the relation between Kerr phase and orientational phase, and how two-steps of electro-optical (EO) response relates to Kerr phase and orientational phase. We investigated the origins of Kerr phase and orientational phase in PDLC and their connection to two-step EO response. In our study, the Kerr phase is a result of LC orientation in the center of LC droplets. The orientational phase attribute to orientation of LC molecules near LC-polymer interfaces. The two phase in PDLC samples are adjustable depending on droplet size. We also found that two-steps EO response existing in small droplet (<33 nm) is related to Kerr phase and orientational phase. A modified PDLC model related to the Kerr phase and orientational phase is also proposed. Besides the conventional features of PDLC, such as polarization independent optical phase shift and response time independent of cell gap, we believe the Kerr phase and orientational phase with different response times (~ msec) in PDLC pave a way for designing versatile photonic devices with pure optical phase modulation.
We have developed a bistable negative lens by integrating a polarization switch of ferroelectric liquid crystals (FLCs) with a passively anisotropic focusing element. The proposed lens not only exhibits electrically tunable bistability but also fast response time of sub-milliseconds, which leads to good candidate of optical component in optical system for medical applications. In this paper, we demonstrate an optical system consisting of two FLC phase retarders and one LC lenses that exhibits both of electrically tunable wavelength and size of exposure area. The operating principles and the experimental results are discussed. The tunable spectrum, exposure area size and tunable irradiance are illustrated. Compared to conventional lenses with mechanical movements in the medical light therapy system, our electrically switchable optical system is more practical in the portable applications of light therapy (LLLT).
Motion blur is one of the major factors decreasing the image quality of a hand-held optical imaging system while the system is under shakes or vibrations during exposure. Optical image stabilization (OIS) is a technique to reduce such a blurring. The basic principle of OIS is to stabilize the recorded image in a camera by varying the optical path to the sensor under vibrations during exposure. In this paper, we demonstrate optical image stabilization (OIS) for an imaging system using a droplet manipulation on a liquid crystal and polymer composite film (LCPCF) that reduces the motion blur. The mechanism is based on manipulation of position of the liquid lens on LCPCF by means of electrically adjusting orientations of liquid crystals. The change of the position of the liquid lens compensates the deviation of light when the image system is under a handshake vibration. Therefore, the imaging system forms a clear image with a droplet on different position to overcome handshake vibration. The concept in this paper can also be extended to design other optical components for modulating the direction of light.
A polarized liquid crystal (LC) lens composed of a LC layers as a polarization switch and a liquid crystal and polymer composites lens (LCPC lens) is demonstrated with electrically switching (ES) mode and optically rewritten (ORW) mode. The lens power of LCPC lens is related to a polarization state of light modulated by the LC layer whose orientations are manipulated either electrically or optically. As a result, the LC lens is not only electrically switchable, but also optically rewritable. Each mode, ES mode or ORW mode, exhibits two discrete lens powers (-1.39 Diopter and +0.7 Diopter). The demonstrated aperture size is 10 mm. The detail optical mechanism is also discussed. The Modulation Transfer Function (so-called MTF) of the lens is measured as well. In addition, the image performance and the dispersion of the LC lens are investigated. Such a polarized LC lens could be a special switch in optical systems due to dual operation modes.
Liquid crystal (LC) lenses offer novel opportunities for applications of ophthalmic lenses, camera modules, pico projectors, endoscopes, and optical zoom systems owing to electrically tunable lens power. Nevertheless, the tunable lens power and the aperture size of LC lenses are limited by the optical phase resulting from limit birefringence of LC materials. Recently, we developed a liquid crystal and polymer composite film (LCPCF) as a separation layer and an alignment layer for a multi-layered structure of LC lenses in order to enlarge the polarization-independent optical phase modulation. However, the physical properties and mechanical properties of the LCPCF are not clearly investigated. In this paper, we show the mechanical and physical properties of the LCPCF. The anchoring energy of the LCPCF is comparable with the standard rubbing-induced alignment layer. The transmission efficiency is around 97% neglecting the Fresnel reflection. The surface roughness is under 2 nm by using AFM scanning. The bending strength test indicates that the LCPCF can hold the LC material with reasonable deformation. We believe this study provides a deeper insight to the LC lens structure embedded with LCPCF.
Large aperture and polarizer-free liquid crystal lenses (LC lenses) based on a double-layered structure for ophthalmic applications are demonstrated. The polarizer-free LC lens functions as both of a positive lens and a negative lens with large aperture size of 10mm. The lens power is electrically and continuously tunable ranging from -1.32 Diopter to 1.83 Diopter. To demonstrate the polarization independency, the wavefronts of the LC lenses under different polarized light were measured and discussed. The detail operations of the applied voltage and frequency are also discussed. The imaging performance of the LC lens is also evaluated. This study provide a detail understanding of the polarizer-free LC lenses based on a double-layered structure.
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