Browsing by Author "Chen, Hung-Shan"

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A large bistable negative lens by integrating a polarization switch with a passively anisotropic focusing element
(2014-06-02)
Chen, Hung-Shan
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Lin, Yi-Hsin
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Srivastava, Abhishek Kumar
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Chigrinov, Vladimir Grigorievich
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Chang, Chia-Ming
A bistable negative lens with a large aperture size (similar to 10mm) by integrating a polarization switch of ferroelectric liquid crystals (FLCs) with a passively anisotropic focusing element is demonstrated. The proposed lens not only exhibits electrically tunable bistability but also fast response time of sub-milliseconds. The tunable lens power is from 0 to -1.74 Diopters. The electro-optical properties and imaging performances are demonstrated. The impact of this study is to provide a solution of electrically bistable liquid crystal lenses for the applications of portable devices, wearable devices and colored ophthalmic lenses. (C) 2014 Optical Society of America
A liquid crystal and polymer composite film for liquid crystal lenses
(2015-01-01)
Lin, Yi-Hsin
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Chen, Hung-Shan
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Wang, Yu-Jen
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Chang, Chia-Ming
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光電工程學系
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.
A polarized bifocal switch based on liquid crystals operated electrically and optically
(2015-01-28)
Chen, Hung-Shan
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Lin, Yi-Hsin
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Chang, Chia-Ming
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Wang, Yu-Jen
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Srivastava, Abhishek Kumar
A polarized bifocal switch based on liquid crystals (LC) operated electrically and optically is demonstrated. The bifocal switch mainly consists of two parts: a LC layer as a polarization switch and two polymeric layers for modulation of polarization dependent spatial phase difference which results in a positive or a negative lensing effect. The orientations of the LC molecules in the polarization switch are manipulated either in electrically switching (ES) mode or optically rewritten (ORW) mode. The bifocal switch with an aperture size of 10mm exhibits two discrete lens powers (-1.39 Diopter and +0.7 Diopter) with different polarization states no matter in ES mode or in ORW mode. ORW mode is also a bistable mode. The related mechanism and electro-optical performance are discussed and demonstrated. Such a versatile optical switch is capable of not only switching between a positive lens power and a negative lens power, but also switching between two linear polarization states which can be useful in optical systems. The potential applications are for optical systems, wearable devices and ophthalmic lenses. (C) 2015 AIP Publishing LLC.
A polarized liquid crystal lens with electrically switching mode and optically written mode
(2015-01-01)
Chen, Hung-Shan
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Lin, Yi-Hsin
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Chang, Chia-Ming
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Wang, Yu-Jen
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Srivastava, Abhishek Kumar
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.
A polarizer-free flexible display using dye-doped liquid-crystal gels
(2009-10-01)
Lin, Yi-Hsin
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Yang, Chih-Ming
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Lo, Chun-Hsiang
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Chen, Hung-Shan
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Wu, Yung-Hsun
A reflective-type polarizer-free flexible display using a dye-doped liquid-crystal (LC) gels is demonstrated. Compared to the conventional guest-host LC mode, it has high contrast ratio and brightness due to the combining of both scattering and absorption. Such a gel-like flexible display is bendable and trimable. In this paper, a three-step switch using distinct dye-doped LC gels is also demonstrated. The potential applications are e-paper and decorative displays.
A Polarizer-Free Liquid Crystal Lens Exploiting an Embedded-Multilayered Structure
(2015-04-15)
Chen, Hung-Shan
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Wang, Yu-Jen
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Chang, Chia-Ming
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Lin, Yi-Hsin
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光電工程學系
Development of liquid crystal (LC) lenses is limited by the power law. The aperture size of LC lenses is traded for the lens power. In this letter, we prove theoretically and experimentally that the aperture size is not limited by the power law based on a polarizer-free LC lens exploiting an embedded-multilayered structure. By adding numbers of LC layers, the aperture size of the LC lens can be enlarged without lowering the tunable lens power. The optical theory of the polarization independence of the LC lens is derived. The wavefronts are measured after light propagates through the LC lens to discuss the polarization independence and image adjustment. The impact of this study is to show the possibility of LC lenses with large aperture size for wearable devices and ophthalmic applications.
A reflective polarizer-free display using dye-doped polymer-stabilized blue-phase liquid crystals
(2012-06-01)
Lin, Yi-Hsin
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Chen, Hung-Shan
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Chiang, Tsung-Han
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光電工程學系
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Department of Photonics
A reflective polarizer-free display using dye-doped polymer-stabilized blue-phase liquid crystal (DDPSBP-LC) has been demonstrated. The mechanism is a combination of electrically tunable light absorption and Bragg reflection. In this paper, the influence of light absorption in DDPSBP-LC by changing the dye concentration and absorption paths has been studied. Increased dye concentration can improve the contrast ratio of DDPSBP-LC; however, the response time is the tradeoff. Increasing the cell gap can improve the contrast ratio of DDPSBP-LC; however, the response time remains the same. The study of DDPSBP-LC can help in shutter-glass applications of 3-D displays and electronic paper.
A reflective polarizer-free electro-optical switch using dye-doped polymer-stabilized blue phase liquid crystals
(2011-01-31)
Lin, Yi-Hsin
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Chen, Hung-Shan
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Chiang, Tsung-Han
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Wu, Chun-Hung
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Hsu, Hsu-Kuan
We demonstrate a reflective polarizer-free electro-optical switch using dye-doped polymer-stabilized blue phase liquid crystals (DDPSBP-LC). At the voltage-off state, the dye molecules and liquid crystals form the structure of the double twist cylinders. As a result, the DDPSBP-LC is in dark state due to the combination of Bragg reflection and light absorption. At the voltage-on state, the blue phase structure is unwound locally. The DDPSBP-LC is then in bright state because of the small light absorption only. The applications of such a switch are shutter glass of 3D displays, and electronic papers. (C) 2011 Optical Society of America
An electrically tunable depth-of-field endoscope using a liquid crystal lens as an active focusing element
(2013)
Chen, Hung-Shan
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Chen, Ming-Syuan
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Lin, Yi-Hsin
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光電工程學系
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Department of Photonics
An electrically tunable depth-of-field (DOF) endoscope using a liquid crystal lens (LC lens) as an active focusing element is demonstrated. The optical mechanism of the electrically-tunable DOF endoscope adopting a two-mode switching LC lens is introduced. The two-mode switching LC lens provides not only a positive lens power but also a negative lens power. Therefore, we could extend the range of DOF originally from 27 mm similar to 55 mm to 12.4 mm similar to 76.4 mm by using the two-mode switching LC lens as an active focusing element. The detail derivations of the optical mechanism of the endoscopic system adopting a LC lens are invistgated. The more detail experimental results are demonstrated. We believe this study can provide a more detail understanding of an endoscopic system adopting a tunable focusing lens.
An endoscopic system adopting a liquid crystal lens with an electrically tunable depth-of-field
(2013-07-29)
Chen, Hung-Shan
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Lin, Yi-Hsin
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光電工程學系
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Department of Photonics
Conventional endoscopic systems consisting of several solid lenses suffer from a fixed and limited depth-of-field (DOF). For practical applications, conventional endoscopes mechanically change the distance between the solid lenses of a lens module in order to change the focusing plane and DOF to see clearly in a scene. In this paper, we demonstrate an electrically tunable endoscopic system adopting a liquid crystal lens. By means of tunable focusing properties of the LC lens as a positive lens and a negative lens, the object at different objective distances can be imaged to the image sensor clearly and the corresponding depth-of-field can also help to enlarge the total spatial depth perception in a scene. The optical mechanism is discussed. In the experiments, under adjustment of three discrete lens powers of the LC lens, the viewing range or total spatial depth perception of the endoscopic system is from 76.4 mm to 12.4 mm which is 2x improved compared to the conventional one without LC lens. We believe this study can be extended to the applications of industrial and medical endoscopes. (C) 2013 Optical Society of America
An experimental investigation of electrically induced-birefringence of Kerr effect in polymer-stabilized blue phase liquid crystals resulting from orientations of liquid crystals
(2012-08-27)
Chen, Hung-Shan
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Ni, Shih-Ya
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Lin, Yi-Hsin
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光電工程學系
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Department of Photonics
The electrically induced-birefringence (EIB) of Kerr effect of polymer-stabilized blue phase liquid crystals (PSBP-LCs) is experimentally investigated by discussing the orientations of liquid cryastal (LC) molecules. The results show that the EIB of Kerr effect of PSBP-LCs mainly results from the orientations of LC molecules when the voltage is larger than the voltage of disappearance of the lattice deformation; otherwise, lattice deformation is also involved in the contribution of EIB besides the orientations of LC molecules. This study proves that the orientations of liquid crystals indeed play roles in the EIB of Kerr effect in PSBP-LCs. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748117]
An optical image stabilization using a droplet manipulation on a liquid crystal and polymer composite film
(2015-01-01)
Wang, Yu-Jen
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Chang, Chia-Ming
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Tsou, Yu-Shih
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Chen, Ming-Syuan
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Chen, Hung-Shan
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.
An optical system adopting liquid crystals with electrical tunability of wavelength and energy density for low level light therapy
(2015-01-01)
Chang, Chia-Ming
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Wang, Yu-Jen
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Chen, Hung-Shan
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Lin, Yi-Hsin
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Srivastava, Abhishek Kumar
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).
Electrically adjustable location of a projected image in augmented reality via a liquid-crystal lens
(2015-11-02)
Chen, Hung-Shan
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Wang, Yu-Jen
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Chen, Po-Ju
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Lin, Yi-Hsin
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光電工程學系
An augmented reality (AR) system involving the electrically tunable location of a projected image is implemented using a liquid-crystal (LC) lens. The projected image is either real or virtual. By effectively doubling the LC lens power following light reflection, the position of a projected virtual image can be made to vary from 42 to 360 cm, while the tunable range for a projected real image is from 27 to 52 cm on the opposite side. The optical principle of the AR system is introduced and could be further developed for other tunable focusing lenses, even those with a lower lens power. The benefits of this study could be extended to head-mounted display systems for vision correction or vision compensation. We believe that tunable focusing LC optical elements are promising developments in the thriving field of AR applications. (C) 2015 Optical Society of America
Electrically assisting crystal growth of blue phase liquid crystals
(2014-05-01)
Chen, Michael
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Lin, Yi-Hsin
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Chen, Hung-Shan
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Chen, Hung-Yuan
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光電工程學系
We proposed an electrically assisting crystal growth of blue phase liquid crystals (BP-LCs) to generate uniform crystal orientation of BP-LCs. With an applied electric field, a phase transition from BP-LCs to focal conic state and homeotropic state occurs. As the electric field is removed, the crystal orientation of [220] quickly dominates the crystal growth process and other crystal orientations grow less at the same time. The BP-LCs with a single crystal orientation can be achieved with multiple cycles of the electrical treatment. We also provide a possible mechanism of crystal growth with electrical treatment which is applicable for both BP-LCs and PSBP-LCs. In addition, we conclude that the hysteresis effect is mainly affected by the domain size of PSBP-LCs rather than uniformity of crystal orientation. This study helps further understanding of the origin of hysteresis effect in PSBP-LCs which is important for development of many BP-LCs based photonic devices, such as micro lenses, displays, and lasers. (C) 2014 Optical Society of America
Electrically Tunable Liquid Crystal Lenses and Applications
(2014-06-13)
Lin, Yi-Hsin
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Chen, Hung-Shan
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Chen, Ming-Syuan
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交大名義發表
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光電工程學系
Electrically tunable liquid crystal (LC) lenses have been studied for over 30years. Three main problems of LC lenses hinder the applications: 1) the paradox between the response time and tunable focusing range, 2) polarization dependency, and 3) large aperture size for ophthalmic lenses. In this paper, we introduce the two mode switching method of the LC lenses to solve the paradox of the LC lenses. The basic optical principles for designing polarization independent LC lenses are discussed and several polarizer-free LC lenses we developed are reviewed. Several applications of LC lenses are also introduced, including auto-focusing imaging systems, auto-focusing projection systems, optical zoom systems, endoscopic systems, solar cells, ophthalmic lenses for myopia-presbyopia.
Electrically tunable microlens arrays based on polarization-independent optical phase of nano liquid crystal droplets dispersed in polymer matrix
(2015-06-29)
Yu, Ji Hoon
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Chen, Hung-Shan
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Chen, Po-Ju
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Song, Ki Hoon
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Noh, Seong Cheol
Electrically tunable focusing microlens arrays based on polarization independent optical phase of nano liquid crystal droplets dispersed in polymer matrix are demonstrated. Such an optical medium is optically isotropic which is so-called an optically isotropic liquid crystals (OILC). We not only discuss the optical theory of OILC, but also demonstrate polarization independent optical phase modulation based on the OILC. The experimental results and analytical discussion show that the optical phase of OILC microlens arrays results from mainly orientational birefringence which is much larger than the electric-field-induced birefringence (or Kerr effect). The response time of OILC microlens arrays is fast similar to 5.3ms and the tunable focal length ranges from 3.4 mm to 3.8 mm. The potential applications are light field imaging systems, 3D integrating imaging systems and devices for augment reality. (C) 2015 Optical Society of America
Electrically Tunable Ophthalmic Lenses for Myopia and Presbyopia Using Liquid Crystals
(2014-06-13)
Chen, Hung-Shan
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Chen, Ming-Syuan
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Lin, Yi-Hsin
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交大名義發表
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光電工程學系
In this paper, an electrically tunable-focusing and polarizer-free liquid crystal (LC) lens for ophthalmic lenses is demonstrated. The optical operating principles of the LC lens in a human eye system are introduced and the optical principle of the polarization independent of the double-layered LC lens is investigated. The polarization dependency, image quality and the response time of the double-layered LC lens are measured. The continuously tunable-focusing properties of the LC lenses are more practical in applications for different visional conditions of people. The concept in this paper can also be extensively applied to imaging systems, and projection systems, such as cameras in cell phones, pico projectors, and endoscopes.
Electrically tunable-focusing and polarizer-free liquid crystal lenses for ophthalmic applications
(2013-04-22)
Lin, Yi-Hsin
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Chen, Hung-Shan
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光電工程學系
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Department of Photonics
An electrically tunable-focusing and polarizer-free liquid crystal (LC) lens for ophthalmic applications is demonstrated. The optical mechanism of a LC lens used in human eye system is introduced. The polarizer-free LC lens for myopia-presbyopia based on artificial accommodation is demonstrated. The continuously tunable-focusing properties of the LC lenses are more practical in applications for different visional conditions of people. The concept we proposed can also be applied to another types of lenses as long as the focusing properties are tunable. The concept in this paper can also be extensively applied to imaging systems, and projection systems, such as cameras in cell phones, pico projectors, and endoscopes. (C) 2013 Optical Society of America
Electrically-tunable liquid crystal lenses and applications
(2013-01-01)
Lin, Yi-Hsin
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Chen, Hung-Shan
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Chen, Ming-Syuan
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光電工程學系
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Department of Photonics
In this paper, the electrically-tunable liquid crystal (LC) lenses and the applications are reviewed. We introduce the basic mechanism of LC phase modulation first. LC lenses are categorized based on different operating principles: 1) Gradient Index (GRIN) LC lenses with a homogeneous cell gap, 2) non-GRIN LC lenses with an inhomogeneous cell gap, 3) diffractive LC lenses, and 4) LC lenses controlled by polarizations. To remove the polarization independency, we also summarize polarization independent LC phase modulations. Many promising applications based on LC lenses are also summarized, such as imaging system, pico projectors, optical zoom systems, ophthalmic applications, and solar systems.