Browsing by Author "Ren, Hongwen"

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Electrically actuated liquid iris
(2015-03-01)
Xu, Miao
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Ren, Hongwen
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Lin, Yi-Hsin
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光電工程學系
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Department of Photonics
We report an adaptive iris using dielectric liquids and a radial-interdigitated electrode. A black liquid is confined by a circular gasket with a donut shape. The surrounding of the black liquid is filled with an immiscible liquid. In the relaxing state, the black liquid obtains the largest clear aperture. By applying a voltage, the surface of the black liquid is stretched by the generated dielectric force, resulting in a reduction of its aperture. For the demonstrated iris, the diameter of the aperture can be changed from similar to 4.7 mm to similar to 1.2 mm when the voltage is applied from 0 to 70 V-rms. The aperture ratio is similar to 94%. Owing to the radial-interdigitated electrode, the aperture size of the iris can be effectively switched with a reasonably fast response time. The optical switch is polarization-insensitive. The potential applications of our iris are light shutters, optical attenuators, biomimicry, and wearable devices. (C) 2015 Optical Society of America
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
;
Chen, Hung-Shan
;
Chen, Po-Ju
;
Song, Ki Hoon
;
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 wettability of liquid crystal/polymer composite films
(2008-10-27)
Lin, Yi-Hsin
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Ren, Hongwen
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Wu, Yung-Hsun
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Wu, Shin-Tson
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Zhao, Yue
An electrically tunable wettability in a liquid crystal/polymer composite film is demonstrated, in which liquid crystal molecules are anchored among polymer grains. The tunable wettability of the composite films originates from the reorientation of the anchored liquid-crystal molecules, which is switched by an in-plane electric field with squared pulses of voltages. These liquid crystal/polymer composite films with electrically tunable wettability have potential applications in polarizer-free displays, ink-jet printing, microfluidic devices, and lab-on-a-chip. (C) 2008 Optical Society of America
In situ observation of fringing-field-induced phase separation in a liquid-crystal-monomer mixture
(2008-03-21)
Ren, Hongwen
;
Wu, Shin-Tson
;
Lin, Yi-Hsin
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光電工程學系
;
Department of Photonics
Fringing-field-induced phase separation dynamics in liquid-crystal-(LC-)monomer mixtures is investigated via a microscope. At a low LC concentration, the fringing field converts the randomly dispersed LC droplets to an ordered droplet array, while at a high LC concentration the fringing field converts the amorphous LC-monomer system to a composite film. Because the LC and monomer are immiscible, the converted morphologies are stable even after the voltage is removed. Using the fringing field-induced phase separation, it is possible to prepare different polymer-dispersed LC morphologies.
Single glass substrate liquid crystal device using electric field-enforced phase separation and photoinduced polymerization
(2007-05-07)
Ren, Hongwen
;
Wu, Shin-Tson
;
Lin, Yi-Hsin
;
光電工程學系
;
Department of Photonics
An in-plane switching liquid crystal (LC) cell using a glass substrate and a photoinduced polymer layer is demonstrated. The fabrication process is based on the electrodynamics of dielectric fluids. When the fringing field is present, the LC molecules tend to aggregate in the strong electric field regions while the monomers diffuse to the weak field regions. After photopolymerization, the LC molecules are confined by a thin polymer layer and polymer walls which define the cell gap. This approach enables single-substrate large panel display devices to be fabricated. (C) 2007 American Institute of Physics.