Browsing by Author "Chiang, Che-Wen"

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Design and demonstration of high efficiency anti-glare LED luminaires for indoor lighting
(2015-02-09)
Chiang, Che-Wen
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Hsu, Yu-Kai
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Pan, Jui-Wen
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光電系統研究所
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照明與能源光電研究所
An anti-glare luminaire design is proposed to reduce the effect of glare and the multi-shadow while preserving high optical efficiency, high illumination uniformity and low unified glare rating (UGR). Comparison to the traditional direct light emitting diode (LED) luminaire in optical simulations showed an enhancement of the illumination uniformity from 64.9% to 80.0%. The optical efficiency was 79.5%, and the UGR value was controlled under 18.8. For the actual measurement, the finished product had an illumination uniformity of 77.0%, optical efficiency of 76.0%, UGR value of 19.0, and efficacy of 81.4 lm/w. Through this design, the lighting performance was greatly enhanced. (C) 2014 Optical Society of America
Dual view capsule endoscopic lens design
(2015-04-06)
Sheu, Ming-Jen
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Chiang, Che-Wen
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Sun, Wen-Shing
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Wang, Jhi-Joung
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Pan, Jui-Wen
A dual view capsule endoscopic (DVCE) lens is proposed with front view and back view functions. This is a hybrid lens with a catadioptric mirror and an aspherical surface to support both view functions. The field of view (FOV) for the front view function is 90 degrees. The FOV for the back view function is 260 to 290 degrees. The TV distortion for the front view and back view function is under 30% and 25%. The corner relative illuminations for the two view functions are above 0.53. The Modulation Transfer Function (MTF) performance at the Nyquist Frequency for the two view functions can be kept above 0.35, even under tolerance they can remain above 0.2. Moreover, the telecentric conditions at the image plane of the DVCE system can support constant magnification through focusing. This condition can reduce the measurement error by slightly defocusing of the lens. Thus, the two view functions can offer physicians a wide viewing angle to deal with lesions over the fold. (C)2014 Optical Society of America
Entanglement-free determination of pretilt angles of twisted nematic liquid-crystal cells by phase measurement
(2017-08-10)
Chiang, Che-Wen
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Lin, Ping-Chun
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Yang, Kei-Hsiung
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光電系統研究所
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影像與生醫光電研究所
The pretilt angle of a twisted nematic (TN) liquid crystal display has a strong effect on viewing angles and response times of the display as well as shifting the light-leaking disclination lines into the black-matrix area within pixels of a thin-film-transistor driven TN panel for a high contrast ratio. In this Letter, we develop an optical method to determine the TN pretilt angle based on heterodyne measurements of the phase versus the incident angle of a thin TN cell subjected to out-of-plane rotations. We believe that our method of measuring phases has advantages of simpler setup and calculations, better stability, and less sensitive to ambient electromagnetic interference than the commonly used method of measuring intensities.
Optics of light scattering caused by liquid-crystal-director fluctuations
(2019-01-02)
Chiang, Che-Wen
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Yang, Kei-Hsiung
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光電學院
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College of Photonics
We have applied the light-scattering equation caused by liquid-crystal (LC)-director fluctuations as derived by De Gennes [1] to the case where the polarization direction of the incident light is at an arbitrary angle with respect to the LC directors within the cell. Based on the De Gennes's equation, we have used an out-of-plane (OPR) cell-rotation method to measure the pretilt angles of a tilted-homogeneously aligned LC cell. Our measured pretilt angles are in good agreement with that obtained by the published OPR-rotation method [2] based on a different mechanism. Our method is simple in setup and requires no complicated data-fitting calculations when the pretilt angles are below about 30 degrees. In addition, there is no need to know cell parameters except the ordinary and extraordinary refractive indices of the LC medium at the wavelength of incident light. [GRAPHICS] .