Browsing by Author "Wang, Yu-Jen"

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A fast algorithm and its VLSI architecture for fractional motion estimation for H.264/MPEG-4 AVC video coding
(2007-05-01)
Wang, Yu-Jen
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Cheng, Chao-Chung
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Chang, Tian-Sheuan
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper presents a fast algorithm and its VLSI architecture for H.264 fractional motion estimation. Motivated by the high correlation of cost between neighboring fractional pel position, the proposed algorithm efficiently explores the neighborhood position around the minimum one and thus skips other unlikely ones. Thus, the proposed search pattern and early termination under constant quantization parameter can reduce about 50% of computation complexity compared to that in reference software but only with 0.1-0.2 dB peak signal-to-noise ratio degradation and less than 2% of bit rate increase. The VLSI architecture of the proposed algorithm thus can save 40% of area cost due to only half of the processing elements and save 14% of searching time when compared with the previous design.
A fast fractional pel motion estimation algorithm for H.264/MPEG-4 AVC
(2006)
Wang, Yu-Jen
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Cheng, Chao-Chung
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Chang, Tian-Sheuan
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper presents a fast algorithm for H.264 fractional ME. Motivated by the highly correlation of cost between neighboring fractional pel position, the proposed algorithm efficiently explores the neighborhood position around the minimum one and thus skips other unlikely ones. Thus, the proposed algorithm can complete the search by only examining 8 or 9 search points instead of 17 search points in the search algorithm of reference software. Early termination technique is applied in every single search point The simulation result shows that the proposed algorithm can reduce about 50% of computation complexity compared to that in reference software but only with 0.1-0.2 dB PSNR degradation and less than 2% of bit rate increase.
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 New Method for Calibrating a Six-DOF Joint Force/Torque Sensor
(2014-01-01)
Tran Trong Hieu
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Chao, Paul C-P
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Wang, Yu-Jen
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Wang, Chun-Chieh
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電機工程學系
A Novel 6-DOF Force/Torque Sensor for COBOTs and its Calibration Method
(2018-01-01)
Tan-Phat Phan
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Chao, Paul C. -P.
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Cai, Jia-Jun
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Wang, Yu-Jen
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Wang, Sheng-Ching
This paper intends to design a 6-DOF force/torque sensor along with its readout circuit for collaborative robots (Cobots) working environment. There are two major technologies to develop by this paper. The first technology is the capability of sensing contact forces and torques by a newly-designed six degrees-of-freedom (DOF) force/torque sensor at a fast speed to facilitate feedback control towards anti-collision for the Cobots with wide measurement range, precision, with a smaller size and lower costs. For the force/torque sensor structure, the finite element method (FEM) is established. The sensor is designed and optimized based on finite element analysis (FEA) while " maximum likelihood estimation (MLE)" is utilized to increase accuracy in estimation of force/torque by using appropriate statistical model. The second technology is the anti-collision control. If the collision occurs, the Cobot has an ability to response safely and instantaneously. The proposed control scheme and assisting 6-DOF sensor are capable of performing Cobots anti-collision in welding, grinding, polishing, assembling, etc. with high precision.
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 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 SIX-DOF FORCE/TORQUE SENSOR FOR COLLABORATIVE ROBOT AND ITS CALIBRATION METHOD
(2017-01-01)
Trong-Hieu Tran
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Tan-Phat Phan
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Chao, Paul C. -P
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Wang, Yu-Jen
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Wang, Chun-Chieh
This study presents a new six-DOF force/torque sensor and its calibration method for a "collaborative robot or cobot". This new calibration method applies the so-called "maximum likelihood estimation (MLE)". MLE is used to determine and identify the parameters related to applied torques/forces and resulted deformations at varied locations of the sensor structure. Formulating the relations in a vector-matrix form, such parameters are captured as the coefficients in a matrix relating torques/forces to angular/linear deformations in different directions. In addition to applying MLE, finite element (FEM) modeling and analysis are conducted to generate realistic-like empirical data for the aforementioned calibration computation based on MLE. The matrix formed by these coefficients can then predict forces and torques with good accuracy via deformations detected by strain gauges. Seen in simulation results, the worst sum of error for three forces is less than 0.04%, while that for three torques is less than 0.00005%. Very small values of sum of error demonstrate a strong correlation of the model with the results obtained from MLE, indicating high precision in sensing forces and torques without decoupling matrix. The developed sensor is highly suitable for real-time sensing of multidimensional interactive forces/torques in industrial robots.
A value-at-risk analysis of carry trades using skew-GARCH models
(2013)
Wang, Yu-Jen
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Chung, Huimin
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Guo, Jia-Hau
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交大名義發表
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資訊管理與財務金融系註：原資管所+財金所
We carry out a value-at-risk (VaR) analysis of an extremely popular strategy in the currency markets, namely, "carry trades," whereby a position purchased in high interest rate currencies is funded by selling low interest rate currencies. Since the natural outcome of the truncated normal distribution of interest-rate spreads combined with the normal distribution of exchange rate returns is a skew-normal distribution, we consider a skew-normal innovation with zero mean for our analysis of carry trade returns using generalized autoregressive conditional heteroskedasticity (GARCH) models. The stress testing results reveal that skew-normal or densities are suitable for the measurement of VaR for carry trade returns involving, for example, taking up a long position in Australian Dollars or Argentine Peso which are funded by selling Japanese Yen.
An optical image stabilisation using a droplet manipulation on a liquid crystal and polymer composite film
(2016-10-12)
Wang, Yu-Jen
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Tsou, Yu-Shih
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Chen, Ming-Syuan
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Lin, Yi-Hsin
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光電工程學系
We demonstrate an image system with an optical image stabilisation using a droplet manipulation on a liquid crystal (LC) and polymer composite film (LCPCF) to reduce motion blur while preserve image quality. Such an image system adopts a liquid lens on an LCPCF and the mechanism is on a basis of droplet movement on LCPCF whose position changes because electrically tunable orientations of LC molecules on the surface of LCPCF. The change of position of the liquid lens compensates the deviation of light as the image system is under a handshake vibration. As a result, the image system under handshake vibrations could keep a clear image. The operating principles are introduced, and the experiments are performed and discussed. The concept in this paper can also be extended to design other optical components for modulating direction of light. [GRAPHICS] .
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).
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
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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
Augmented reality with image registration, vision correction and sunlight readability via liquid crystal devices
(2017-03-27)
Wang, Yu-Jen
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Chen, Po-Ju
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Liang, Xiao
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Lin, Yi-Hsin
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光電工程學系
Augmented reality (AR), which use computer-aided projected information to augment our sense, has important impact on human life, especially for the elder people. However, there are three major challenges regarding the optical system in the AR system, which are registration, vision correction, and readability under strong ambient light. Here, we solve three challenges simultaneously for the first time using two liquid crystal (LC) lenses and polarizer-free attenuator integrated in optical-see-through AR system. One of the LC lens is used to electrically adjust the position of the projected virtual image which is so-called registration. The other LC lens with larger aperture and polarization independent characteristic is in charge of vision correction, such as myopia and presbyopia. The linearity of lens powers of two LC lenses is also discussed. The readability of virtual images under strong ambient light is solved by electrically switchable transmittance of the LC attenuator originating from light scattering and light absorption. 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 and amplitude modulations.
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 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
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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
Extended depth-of-field 3D endoscopy with synthetic aperture integral imaging using an electrically tunable focal-length liquid-crystal lens
(2015-08-01)
Wang, Yu-Jen
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Shen, Xin
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Lin, Yi-Hsin
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Javidi, Bahram
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光電工程學系
Conventional synthetic-aperture integral imaging uses a lens array to sense the three-dimensional (3D) object or scene that can then be reconstructed digitally or optically. However, integral imaging generally suffers from a fixed and limited range of depth of field (DOF). In this Letter, we experimentally demonstrate a 3D integral-imaging endoscopy with tunable DOF by using a single large-aperture focal-length-tunable liquid crystal (LC) lens. The proposed system can provide high spatial resolution and an extended DOF in synthetic-aperture integral imaging 3D endoscope. In our experiments, the image plane in the integral imaging pickup process can be tuned from 18 to 38 mm continuously using a large-aperture LC lens, and the total DOF is extended from 12 to 51 mm. To the best of our knowledge, this is the first report on synthetic aperture integral imaging 3D endoscopy with a large-aperture LC lens that can provide high spatial resolution 3D imaging with an extend DOF. (C) 2015 Optical Society of America
Extended depth-of-focus 3D micro integral imaging display using a bifocal liquid crystal lens
(2015-02-15)
Shen, Xin
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Wang, Yu-Jen
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Chen, Hung-Shan
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Xiao, Xiao
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Lin, Yi-Hsin
We present a three dimensional (3D) micro integral imaging display system with extended depth of focus by using a polarized bifocal liquid crystal lens. This lens and other optical components are combined as the relay optical element. The focal length of the relay optical element can be controlled to project an elemental image array in multiple positions with various lenslet image planes, by applying different voltages to the liquid crystal lens. The depth of focus of the proposed system can therefore be extended. The feasibility of our proposed system is experimentally demonstrated. In our experiments, the depth of focus of the display system is extended from 3.82 to 109.43 mm. (C) 2015 Optical Society of America