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Varifocal augmented reality adopting electrically tunable uniaxial plane-parallel plates
(2020-07-20)
Wang, Yu-Jen
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Lin, Yi-Hsin
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Cakmakci, Ozan
;
Reshetnyak, Victor
;
光電工程學系
Vergence-accommodation conflict (VAC) is a major challenge in optical-see through augmented reality (AR) system. To resolve this conflict, many approaches are proposed, for instance, by means of adjustment of the projected virtual image to coincide with the surroundings, called image registration, which is more often referred to as varifocal function. In this paper, a varifocal AR system is demonstrated by adopting electrically tunable liquid crystal (LC) plane-parallel plates to solve VAC problem. The LC plates provide electrically tunable optical paths when the directors of LC molecules are re-orientated with applied voltages, which leads to a corresponding change of light speed for an extraordinary wave. To provide a sufficient tunable optical path, three pieces of multiple-layered LC structures are used with the total thickness of the active LC layers (similar to 510 mu m). In experiments, the projected virtual image can be adjusted from 1.4 m to 2.1 m away from the AR system, while the thickness of LC plane-parallel plates are only less than 3 mm without any mechanical moving part. When light propagates in the uniaxial LC layers, the wave vector and the Poynting vector are different. The longitudinal displacement of the image plane is determined by Poynting vectors rather than wave vectors. As a result, the analysis of the AR system should be based on Poynting vectors during geometrical optical analysis. Surprisingly, the tunable range of the longitudinal displacement of Poynting vectors is 2-fold larger than the tunable range of the wave vectors. Moreover, the virtual image shifts in opposite directions with respect to the Poynting vectors and wave vectors. The proposed AR system is not only simple but also thin, and it exhibits a large clear aperture. The investigation here paves the way to a simple solution of the VAC problem for augmented reality systems. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Modeling Liquid Crystal Lenses
(2020-01-01)
Reshetnyak, V. Yu.
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Sova, O.
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Wang, Yu-Jen
;
Lin, Yi-Hsin
;
光電工程學系
Liquid crystal based lenses with variable focal length are of broad interest due to their wide area of applications ranging from techniques to medicine. We present the modeling approaches and results for a couple of tunable liquid crystal based lenses, namely: curved electrode lens, lens with hole patterned electrode and high resistivity layer, lens based on modulated anchoring and contact lens. We also discuss the current challenges associated with the modeling of LC lenses and possible ways to overcome them.
Phase modulators with tunability in wavefronts and optical axes originating from anisotropic molecular tilts under symmetric electric field II: experiments
(2020-03-16)
Wang, Yu-Jen
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Lin, Yi-Hsin
;
Cakmakci, Ozan
;
Reshetnyak, Victor
;
光電工程學系
We demonstrate, for the first time, an electrically-tunable and physically-planar freeform optical element made up of nematic liquid crystals (LCs). Continued on numerical study in previous paper (Part I), experimental results here show that it is possible to break the rotational symmetry of the wavefront through the use of uneven tilt angles of the LC molecules even though the electric potential is rotationally symmetric. Our optical element offers the ability to electrically tune the direction of the optical axis, the wavefront deviation, as well as the Zernike polynomials for general descriptions of wavefronts. Corresponding Zernike coefficients of a Zernike polynomial that are related to defocus and spherical aberration, which can be adjusted individually or together. The minimum wavefront deviation is >lambda/16. The Zernike coefficients related to coma aberration or the tilt of the optical axis are also electrically tunable. By incorporating our LC phase modulator with tunability of freeform wavefronts into a simple reflective optical system, we demonstrate convincing image performance for off-axis image aberration correction. This approach will inspire further development and design of LC optical elements for applications, such as hyperspectral imagers in aerospace optics, augmented reality, virtual reality, quantum information systems, innovative miniaturized reflective telescopic systems for astrophysics, planetary science, and earth science. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Polarization aberrations of electrically tunable liquid crystal mirrors
(2020-04-13)
Wang, Yu-Jen
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Lin, Yi-Hsin
;
Cakmakci, Ozan
;
Reshetnyak, Victor
;
光電工程學系
Curved mirrors are able to fold optical paths and play important roles in compact optical systems in general. In this paper, we investigate the polarization aberrations of electrically tunable liquid crystal (LC) mirrors with two kinds of configurations (flat and curved ones). The LC mirrors exhibit spatially-continuous tunable wavefronts. The detailed wavefronts of two LC mirrors are related to angles of incidence, polarization of light, and the alignment direction of LC molecules. The key contribution of this paper is the development and characterization of a tunable liquid crystal mirror. The tunability of polarization aberration of LC mirrors should be able to provide extra parameters for optical engineers to design versatile optical systems. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Electrically tunable gradient-index lenses via nematic liquid crystals with a method of spatially extended phase distribution
(2019-10-28)
Wang, Yu-Jen
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Hsieh, Huai-An
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Lin, Yi-Hsin
;
光電工程學系
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Department of Photonics
The dilemma between tunable range of a lens power and an aperture size in gradient-index (GRIN) type of liquid crystal (LC) lenses is well known due to the limitation of birefringence of LC martials and the nature of soft matters. In order to overcome the dilemma of the power law, a multi-layered LC lens was previously proposed by us. However, the aperture size of GRIN LC lenses is still difficult to exceed 10 mm. In this paper, we proposed an electrically tunable GRIN LC lens via nematic liquid crystals with a method of spatially extended phase distribution. A GRIN LC lens with an aperture size of 20 mm is achieved. The proposed GRIN LC lens consists of two LC elements modulating wavefronts at different regions of the lens aperture extending to 20 mm. The lens power of the GRIN LC lens is continuously tunable, while the LC lens can function as a positive lens, a negative lens, and a bifocal lens. The proposed GRIN LC lens not only overcomes the dilemma of the power law but also provides a more practical approach that could benefit the ophthalmic applications and augmented reality systems. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
An optical system for augmented reality with electrically tunable optical zoom function and image registration exploiting liquid crystal lenses
(2019-07-22)
Wang, Yu-Jen
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Lin, Yi-Hsin
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光電工程學系
;
Department of Photonics
An optical-see-through augmented reality (AR) system assists our daily work by augmenting our sense with computer-generated information. Two of optical challenges of AR are image registration and vision correction due to fixed optical properties of the optical elements of AR systems. In this paper, we demonstrated an AR system with optical zoom function as well as a function of image registration via two LC lenses in order to help people see better by magnifying the virtual image and adjusting the location of virtual image. The operating principles are introduced, and experiments are performed. The concept demonstrated in this paper could be further extended to other electro-optical devices as long as the devices exhibit the capability of phase modulations. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Liquid crystal beyond displays: feature introduction
(2019-07-22)
Lin, Yi-Hsin
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Hu, Wei
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Lin, Tsung-Hsien
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d'Alessandro, Antonio
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交大名義發表
The editors introduce the feature issue on liquid crystal beyond displays. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
A polarization-independent liquid crystal phase modulation using polymer-network liquid crystal with orthogonal alignment layers
(2012-01-01)
Chen, Ming-Syuan
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Lin, Wei-Chih
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Tsou, Yu-Shih
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Lin, Yi-Hsin
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光電工程學系
A polarization-independent liquid crystal (LC) phase modulation using polymer-network liquid crystals with orthogonal alignments layers (T-PNLC) is demonstrated. T-PNLC consists of three layers. LC directors in the two layers near glass substrates are orthogonal to each other. In the middle layer, LC directors are perpendicular to the glass substrate. The advantages of such T-PNLC include polarizer-free, larger phase shift (similar to 0.4 pi rad) than the residual phase type (< 0.05 pi rad), and low operating voltage (< 30V(rms)). It does not require bias voltage for avoiding scattering because the refractive index of liquid crystals matches that of polymers. The phase shift of T-PNLC is affected by the cell gap and the curing voltages. The potential applications are laser beam steering, spatial light modulators and electrically tunable micro-lens arrays.
Electrically-tunable liquid crystal lenses and applications
(2013-01-01)
Lin, Yi-Hsin
;
Chen, Hung-Shan
;
Chen, Ming-Syuan
;
光電工程學系
;
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.
The Dynamics of Human Sperm Droplets on a Liquid Crystal and Polymer Composite Film
(2010-01-01)
Lu, Farn
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Lin, Yi-Hsin
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Tsai, Wan-Chen
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Li, Jiong-Juan
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Chu, Ting-Yu
A switchable surface using a liquid crystal and polymer composite film (LCPCF) based on phase separation between liquid crystals (LC) and polymers after photopolymerization is developed recently. The wettability of LCPCF is electrically tunable because of the orientation of liquid crystal directors anchored among the polymer grains under an in-planed electric field. A water droplet on the top of LCPCF can be manipulated under an inhomogeneous electric field on the LCPCF owning to the wettability gradient. The dynamics of a droplet of human sperms on the LCPCF is demonstrated as well. Three motions of sperm droplets are observed: the droplet collapse and the droplet stretch,. We found that the dynamics, concentrations, and activities of spermatozoa, affect the motions of a sperm droplet. The potential applications of LCPCF are polarizer-free displays, liquid lenses, and the microfluidic device in assisted reproductive technology (ART)

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