Browsing by Author "Tien, Chung-Hao"

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A localized partition approach for high-dynamic-range display
(2007)
Lu, Yen-Hsing
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Cheng, Yu-Kuo
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Tien, Chung-Hao
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光電工程學系
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Department of Photonics
A mosaic-form backlight system for high-dynamic-range display was introduced. The backlight unit consisting of a side-emitting LED, a quadratic light guide, and a concentric prism sheet can form an isolated square super-Gaussian distribution over the local area of liquid crystal panel. By means of our approach, high-dynamic-range display system can reduce the time required for processing compensated image signal.
A Novel Anti-Spoofing Solution for Iris Recognition Toward Cosmetic Contact Lens Attack Using Spectral ICA Analysis
(2018-03-01)
Hsieh, Sheng-Hsun
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Li, Yung-Hui
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Wang, Wei
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Tien, Chung-Hao
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光電工程學系
In this study, we maneuvered a dual-band spectral imaging system to capture an iridal image from a cosmetic-contact-lens-wearing subject. By using the independent component analysis to separate individual spectral primitives, we successfully distinguished the natural iris texture from the cosmetic contact lens (CCL) pattern, and restored the genuine iris patterns from the CCL-polluted image. Based on a database containing 200 test image pairs from 20 CCL-wearing subjects as the proof of concept, the recognition accuracy (False Rejection Rate: FRR) was improved from FRR = 10.52% to FRR = 0.57% with the proposed ICA anti-spoofing scheme.
A scanning backlight module for FSC-LCD using tandem light-guides with micro line-prism structures
(2008)
Lu, Yen-Hsing
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Yao, Yuan-Jung
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Hsiao, Jen-Chang
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Tien, Chung-Hao
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光電工程學系
A spatially partitioned backlight system composed of tandem wedge-shaped light-guides with micro line-prism arrays was developed for scanning held-sequential-color (FSC) LCD in large size. The light-guides combined with LED light-bars have been designed and fabricated to well distinguish each region and decrease the light leakage. By means of our approach, the volume of backlight system can be reduced down to 25 mm without sacrifice of the optical performance. As a result, 2750 nits average luminance subject to 50% duty cycle and 83% uniformity can be achieved. The leakages into the continuous adjacent blocks are well suppressed to 11.86%.
A skew freeform reflector design method for prescribed off-axis irradiance
(2019-06-01)
Su, Jian-Jia
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Tien, Chung-Hao
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Tsai, Yu-Lin
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Wu, Chin-Tien
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應用數學系
In this paper we proposed a new methodology for designing freeform reflectors tailored to redistribute the radiant flux emitted by a point light source onto a target plane with the prescribed irradiance pattern. Based on the laws of reflection and energy conservation, a skew freeform model with a set of second-order ordinary differential equations formulating the ray tracing between the source and target domain was presented. A 3D freeform reflector was constructed by using such skew freeform model with quadric surface fitting accordingly. Proposed scheme is applicable for arbitrary geometric-based mapping without the restrictions subject to the target, source, collective solid angle, or target topography, respectively.
Accessing Refractive Errors via Eccentric Infrared Photorefraction Based on Deep Learning
(2019-01-01)
Yang, Chia-Chi
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Su, Jian-Jia
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Li, Jie-En
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Zhu, Zhi-Yu
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Tseng, Jin-Shing
Eccentric infrared photorefraction is an attractive vision screening method which is widely used for uncooperative subjects, such as infants and toddlers. Unlike conventional slope-based photorefraction, a deep neural network is used to predict refractive error in this study. Total 1216 ocular image were collected by a homemade photorefraction device, whose corresponding refractive error was measured by a commercial autorefractor device, to create a series of dataset for our deep neural network. The mean squared error of the preliminary result is +/- 0.9 diopter, which indicates its feasibility and can be improved with bigger database.
An iterative model of diffuse illumination from bidirectional photometric data
(2009-01-19)
Tien, Chung-Hao
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Hung, Chien-Hsiang
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光電工程學系
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顯示科技研究所
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光電工程研究所
This paper presents a methodology for including the photometric raw data sets into the diffuse illumination design process. The method is based on computing the luminance distribution on the outgoing side of diffusing elements from measured bidirectional scattering distribution functions (BSDFs). The model is limited to specimens that create rotationally symmetric scattering distribution. The calculation procedure includes the linear superposition and the correcting feedback. As an application example, the method is verified by a commercially available diffusing sheet illuminated by a 32-inch backlighting module. Close agreement (correlation coefficient = 98.6%) with the experimental measurement confirmed the validity of the proposed procedure. (C) 2009 Optical Society of America
Approach to analytically minimize the LCD moire by image-based particle swarm optimization
(2015-10-01)
Tsai, Yu-Lin
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Tien, Chung-Hao
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光電工程學系
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Department of Photonics
In this paper, we proposed a methodology to optimize the parametric window of a liquid crystal display (LCD) system, whose visual performance was deteriorated by the pixel moire arising in between multiple periodic structures. Conventional analysis and minimization of moire patterns are limited by few parameters. With the proposed image-based particle swarm optimization (PSO), we enable a multivariable optimization at the same time. A series of experiments was conducted to validate the methodology. Due to its versatility, the proposed technique will certainly have a promising impact on the fast optimization in LCD design with more complex configuration. (C) 2015 Optical Society of America
Automatic Organic Light-emitting Diode Display Mura Detection Model based on Human Visual Perception and Multi-resolution
(2019-01-01)
Zhu, Zhi-Yu
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Li, Jie-En
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Hsieh, Po-Yuan
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Su, Jian-Jia
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Tien, Chung-Hao
Organic light emitting diode generally has serious non-uniformity phenomena due to the instability of organic processing, called Mura. In this paper, we propose an automatic Mura detection model to mimic the human perception and detect Mura pixel-wisely. First, we extract regions of interest from the original image with different sizes of windows, and then we verify these regions by SEMU criterion. Consequently, we implement human visual properties based on the contrast sensitivity function filtering and ModelFest matching to segment Mura regions. As the result, our approach can successfully detect Mura with various sizes and shapes, which could have a great impact on the display industry.
Biometric iris image acquisition system with wavefront coding
(2013)
Hsieh, Sheng-Hsun
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Yang, Hsi-Wen
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Huang, Shao-Hung
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Li, Yung-Hui
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Tien, Chung-Hao
Biometric signatures for identity recognition have been practiced for centuries. Basically, the personal attributes used for a biometric identification system can be classified into two areas: one is based on physiological attributes, such as DNA, facial features, retinal vasculature, fingerprint, hand geometry, iris texture and so on; the other scenario is dependent on the individual behavioral attributes, such as signature, keystroke, voice and gait style. Among these features, iris recognition is one of the most attractive approaches due to its nature of randomness, texture stability over a life time, high entropy density and non-invasive acquisition. While the performance of iris recognition on high quality image is well investigated, not too many studies addressed that how iris recognition performs subject to non-ideal image data, especially when the data is acquired in challenging conditions, such as long working distance, dynamical movement of subjects, uncontrolled illumination conditions and so on. There are three main contributions in this paper. Firstly, the optical system parameters, such as magnification and field of view, was optimally designed through the first-order optics. Secondly, the irradiance constraints was derived by optical conservation theorem. Through the relationship between the subject and the detector, we could estimate the limitation of working distance when the camera lens and CCD sensor were known. The working distance is set to 3m in our system with pupil diameter 86mm and CCD irradiance 0.3mW/cm(2). Finally, We employed a hybrid scheme combining eye tracking with pan and tilt system, wavefront coding technology, filter optimization and post signal recognition to implement a robust iris recognition system in dynamic operation. The blurred image was restored to ensure recognition accuracy over 3m working distance with 400mm focal length and aperture F/6.3 optics. The simulation result as well as experiment validates the proposed code apertured imaging system, where the imaging volume was 2.57 times extended over the traditional optics, while keeping sufficient recognition accuracy.
Broad Detecting Range of Objective-Based Surface Plasmon Resonance Sensor via Multilayer Structure
(2011-09-01)
Lan, Tzu-Hsiang
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Chung, Yi-Kuan
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Tien, Chung-Hao
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光電工程學系
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顯示科技研究所
The demand of pursuing higher resolution drives the instrumental development of a surface plasmon resonance (SPR) sensor to shift from Kretchmann to objective-based configuration. However, its maximum sensing refractive index is restricted by the numerical aperture of an objective lens. Based on the mode conversion, we proposed a multilayer structure to extend the detecting range up to 11% (from 1.28 to 1.42) for a 1.45 objective lens via a transformed SPR mode. This technique not only overcomes intrinsic constraint but also reduces the cost. (C) 2011 The Japan Society of Applied Physics
Cladding Effect on Hybrid Plasmonic Nanowire Cavity at Telecommunication Wavelengths
(2013-05-01)
Cheng, Pi-Ju
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Weng, Chen-Ya
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Chang, Shu-Wei
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Lin, Tzy-Rong
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Tien, Chung-Hao
In this paper, we investigate the effect of cladding layers on a hybrid plasmonic nanowire cavity. A decent confinement factor and moderate modal loss can be achieved for lasing. Within a certain index range of the cladding layer, the fundamental hybrid plasmonic mode is well confined inside the narrow gain region and becomes the most promising lasing mode. Our results also indicate that the mirror loss can be reduced if the refractive index of the cladding layer is properly chosen. An estimated cold-cavity quality factor of 87, corresponding to a threshold gain of about 1072 cm(-1), is achievable at a cavity length of 10.13 mu m for the lasing mode.
Cluster LEDs mixing optimization by lens design techniques
(2011-07-04)
Chien, Ming-Chin
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Tien, Chung-Hao
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光電工程學系
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顯示科技研究所
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Department of Photonics
This paper presents a methodology analogous to a general lens design rule to optimize step-by-step the spectral power distribution of a white-light LED cluster with the highest possible color rendering and efficiency in a defined range of color temperatures. By examining a platform composed of four single-color LEDs and a phosphor-converted cool-white (CW) LED, we successfully validate the proposed algorithm and suggest the optimal operation range (correlated color temperature = 2600-8500 K) accompanied by a high color quality scale (CQS > 80 points) as well as high luminous efficiency (97% of cluster's theoretical maximum value). (C) 2011 Optical Society of America
Computational Ghost Image via Controlling Pseudothermal Light Source
(2019-01-01)
Hong, Xuan-En
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Chen, Chen-Chi
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Tien, Chung-Hao
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光電工程學系
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Department of Photonics
In this study, we implemented a two-step setup to validate the ghost image through the coherent argument. Here we applied a SLM-based pseudothermal point source and sequentially scanned through the object. By means of 2nd - order VCZ theory, we can retrieve the original object subject to different propagation distances.
Computational Lighting by a LED-based System
(2012)
Chien, Ming-Chin
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Tien, Chung-Hao
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光電工程學系
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Department of Photonics
A methodology analogous to a general lens design rule was proposed to step-by-step optimize the spectral power distribution (SPD) of a composite light-emitting diodes (LEDs) cluster. The computation is conducted for arbitrary SPD combination for the applications in radiometry, photometry and colorimetry, respectively. Based on the matrix computation, a spectrally tunable source is implemented to strategically manipulate the chromaticity, system efficiency and light quality according to all kinds of operational purposes. By the R/G/B/A/CW light engine with graphic utility interface, the cluster engine was experimentally validated to offer a wide-ranged operation in ambient temperature (T-a = 10 degrees C to 100 degrees C) with high color quality scale (CQS > 85 points) as well as high luminous efficiency (LE > 100 lm/watt) over the chromaticity point from 2800K to 8000K.
Coupled nanowire-based hybrid plasmonic nanocavities on thin substrates
(2014-11-28)
Cheng, Pi-Ju
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Chiang, Chih-Kai
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Chung, Yi-Cheng
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Tien, Chung-Hao
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Lin, Tzy-Rong
We theoretically analyze nanowire-based hybrid plasmonic nanocavities on thin substrates at visible wavelengths. In the presence of thin suspended substrates, the hybrid plasmonic modes, formed by the coupling between a metal nanowire and a dielectric nanowire with optical gain, exhibit negligible substrate-mediated characteristics and overlap better with the gain region. Consequently, the confinement factor of the guided hybrid modes is enhanced by more than 42%. However, the presence of significant mirror loss remains the main challenge to lasing. By adding silver coatings with a sufficient thickness range on the two end facets, we show that the reflectivity is substantially enhanced to above 50%. For a coating thickness of 50 nm and cavity length of about 4 mu m, the quality factor is above 100.
Design and Evaluation of Light Spread Function for Area-Adaptive LCD System
(2009-01-01)
Cheng, Yu-Kuo
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Lu, Yen-Hsing
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Tien, Chung-Hao
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Shieh, Han-Ping
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光電工程學系
A methodology, based on two-dimensional super-Gaussian light spread functions (LSFs), was studied for the light-emitting-diode (LED) backlighting system in the high dynamic range (HDR) liquid crystal displays (LCDs). We proposed a novel LED-based optomechanical configuration to implement the desirable luminous pattern. A dual-liquid-crystal-panel system was constructed as a pseudo-HIE)R LCD to evaluate the super-Gaussian illumination. The proposed HDR scheme was verified via the current platform: overall luminance uniformity, contrast ratio and processing speed could be improved by factors of 1.55, 1.95-4.15, and 4.82, respectively. The design flexibility made the methodology applicable to any panel dimension and backlight division of the HDR LCDs, and to the conventional full-on backlighting LCDs as well.
Design of catadioptric lens with servo optical mechanism in holographic recording system
(2008-07-01)
Lan, Yung-Sung
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Tien, Chung-Hao
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光電工程學系
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顯示科技研究所
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Department of Photonics
In this paper, we present a catadioptric telecentric objective for a holographic recording system. The lens was made of Zeonex, whose aspherical surfaces were formed by diamond-turning machining. A least-squares method was used to solve a set of linear equations for the spot size of charge-coupled device (CCD). The data were obtained to generate an S curve, which was used in the pupil obscuration method, for the control of the system operated in a linear range of +/- 0.3 mm.
Design of mosaic-form LED backlight module
(2007)
Lu, Yen-Hsing
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Tien, Chung-Hao
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光電工程學系
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Department of Photonics
A quadratic light-guide with micro-prismatic bump structures for illumination of the liquid crystal display (LCD) system has been developed. The functional light-guide combining with a side-emitting light-emitting-diode (LED) and a concentric prism sheet (CPS) is able to illuminate a uniformly square distribution over the LC panel. Through the assembly of these kinds of optical elements, the mosaic-form LED backlight module can be applied to any dimension of a panel associated with relational parameters with proportional quantities. According to our simulation, the proposed system can increase the output efficiency from roughly 50 % (without any optical elements) to 75 % and maintain the brightness uniformity of 88. 3 % as well.
Direct measurement of versatile surface plasmon polaritons excited by split polarization
(2011-02-21)
Lan, Tzu-Hsiang
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Ho, Chen-Yeh
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Tien, Chung-Hao
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光電工程學系
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顯示科技研究所
We report on the concept, generation, and observation of versatile excited surface plasmon polariton (SPP) patterns via focused split polarization. Unlike the conventional subwavelength features such as holes array, grating, or other protrusion to satisfy the phase matching condition for SPP excitation, we utilized a structured focus to form either counterpropagating interference or a multiple casting plasmonic pattern by means of the arrangement of split polarization and corresponding focus position. The characteristics of the near-field SPP image are in close agreement with the finite-difference time-domain calculation and confirm its feasibility associated with SPP excitations in many areas. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552673]
Dual-probe near-field fiber head with gap servo control for data storage applications
(2007-10-29)
Fang, Jen-Yu
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Tien, Chung-Hao
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Shieh, Han-Ping D.
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光電工程學系
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Department of Photonics
We present a novel fiber-based near-field optical head consisting of a straw-shaped writing probe and a flat gap sensing probe. The straw-shaped probe with a C-aperture on the end face exhibits enhanced transmission by a factor of 3 orders of magnitude over a conventional fiber probe due to a hybrid effect that excites both propagation modes and surface plasmon waves. In the gap sensing probe, the spacing between the probe and the disk surface functions as an external cavity. The high sensitivity of the output power to the change in the gap width is used as a feedback control signal. We characterize and design the straw-shaped writing probe and the flat gap sensing probe. The dual-probe system is installed on a conventional biaxial actuator to demonstrate the capability of flying over a disk surface with nanometer position precision. (C) 2007 Optical Society of America.