Browsing by Author "Chern, Jyh-Long"

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Aberration analysis of a wedge-plate display system
(2007-08-01)
Cheng, Yi-Kai
;
Chung, Sen-Nien
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
The aberration characteristics of a wedge-plate display optical system are analyzed. The study shows that a kink-like feature is inherent in the ray-intercept curve due to either the onset of the dark zone in imaging or the coincidence of the ray direction with the vertex. Third-order aberration coefficients are deduced, and the total amount of aberration is investigated to illustrate the basic limitations of image quality in this type of display. The issue of design optimization is also investigated based on the aberration characteristics. A numerical example of a 50 in. display with a 1:10 thickness and a diagonal screen length ratio is also provided. (c) 2007 Optical Society of America.
Analysis and reduction of dark zone in ultra-thin wedge-plate displays
(2006-09-01)
Cheng, Yi-Kai
;
Chung, Sen-Nien
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A wedge plate can be used as the screen of a display, and the thickness of the display can be incredibly thin. In this paper, a basic formula for ray tracing in such a wedge plate is deduced. The fundamental limitation on the display quality of a wedge plate is explored, and the formation of a dark zone on the display screen is analyzed and verified numerically. Experimental exploration and confirmation of one 14-in. acrylic wedge plate with a white-light-emitting diode is also provided. Two approaches to eliminate the dark zone are proposed, and the corresponding numerical demonstration of a 52-in. wedge-plate display is also shown.
Application of a global optimization process to the design of pickup heads for compact and digital versatile disks
(2006-10-01)
Tsao, Chao-Hsi
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Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A global optimization process is developed for designing an objective lens for multiple-configuration applications. As a demonstration, it is shown that diffraction-limit performance can be achieved for a pickup head used for both compact disks (wavelength 780 nm) and digital versatile disks (wavelength range 635 to 650 nm) with different working distances and focal lengths, at a numerical aperture of 0.6. (c) 2006 Society of Photo-Optical Instrumentation Engineers.
Application of global optimization to design of an aspheric pickup head for multiple wavelengths
(2006-01-01)
Tsao, Chao-Hsi
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
An optimization process combining of global optimization algorithm and further optimization treatment is proposed and demonstrated with application to the objective lenses of multiple-wavelength configurations. Based on the optimal variable set of aspheric coefficients obtained by the proposed global optimization strategy, singlet objective lens for different operational configurations, i.e., for CD and DVD, and for DVD and HDDVD, can be deduced.
Application of global optimization to design of an aspheric pickup head for multiple wavelengths - art. no. 63422G
(2006)
Tsao, Chao-Hsi
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
An optimization process combining of global optimization algorithm and further optimization treatment is proposed and demonstrated with application to the objective lenses of multiple-wavelength configurations. Based on the optimal variable set of aspheric coefficients obtained by the proposed global optimization strategy, singlet objective lens for different operational configurations, i.e., for CD and DVD, and for DVD and HDDVD, can be deduced.
Characterization of one-dimension edge roughness from far-field irradiance at subwavelength-scale precision
(2008-04-15)
Chu, Shu-Chun
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
It is proposed and numerically verified that the one-dimensional edge roughness of test sample can be characterized by far-field irradiance measurement at subwavelength-scale precision with a constructed aperture playing as an optical ruler. The precision of the proposed scheme of measurement could be better than 3%, even when the edge roughness is in subwavelength-scale. The influence of sample thickness on the proposed measurement scheme is also investigated and considered. (C) 2007 Elsevier B.V. All rights reserved.
Design of a dual-f-number illumination system and its application to DMD (TM) projection displays
(2006-09-01)
Cheng, Chu-Ming
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A dual-f/# optical system is evaluated and considered for illumination. Etendue theory has been employed to increase the optical throughput and collection efficiency. A classical Cooke triplet with a dual f/# is included for illustration. As a demonstration of the potential application to projection displays, an elliptically shaped illumination-pupil system is proposed to increase the optical collection efficiency in the DMD(TM) (Digital Micromirror Device(TM))-based projection system. With a dual-f/# configuration, this design can eliminate the f/2.4 constraint that was caused by the light-steering action of the narrow +/- 12 degrees tilt angles on the DMD(TM). The percentage of increase in the optical collection efficiency is 6.2% in the dual f/2.0 x f/2.4 optical projection system by using ray-tracing simulation. This method enables a lower than f/2.4 optical design with a high brightness and an adequate contrast ratio in the DMD(TM)-based projectors.
Design of a wedge plate for polarization-preserving angular shifter
(2009-03-01)
Cheng, Yi-Kai
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
It is shown that by using a wedge plate, the incident direction of light propagation can be rotated as necessary while still preserving beam polarization. The basic conditions of these preservations of polarization are deduced. For numerical demonstration, it is shown that a collimated beam with +45A degrees linear polarization can be guided to any pre-settled direction where the square of ellipse ratio variation in the polarization is less than 0.0001%, while the variation of squared ellipse ratio of a right circular polarization beam is kept under 0.1%.
Design of aspheric lens to collimate and uniform irradiance of a light source with Lambertian angular distribution
(2006-01-01)
Cheng, Chieh-Jen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A design of aspheric lens is proposed to collimate a light source of Lambertian angular distribution and generate homogenous irradiance. Two numerical solutions were calculated. One used even orders of general aspheres to describe the aspheric surfaces and the performance was evaluated by commercial optical software package Tracepro. Both of high numerical aperture (NA) of 0.79 and good RMS uniformity within 95% of designed area in the second surface of lens could be obtained. The reverse of this lens would be used in focusing and the simulated point spread function (PSF) is almost diffraction-limited. The other fitted both of aspheric surface with radial spline surface and the performance was evaluated by commercial optical software package OSLO. With the radial spline surface representation, the aspheric lens has a higher NA of 0.9; meanwhile, the uniformity was still good enough and PSF is also near diffraction-limited.
Design of aspheric lens to collimate and uniform irradiance of a light source with Lambertian angular distribution - art. no. 63422F
(2006)
Cheng, Chieh-Jen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A design of aspheric lens is proposed to collimate a light source of Lambertian angular distribution and generate homogenous irradiance. Two numerical solutions were calculated. One used even orders of general aspheres to describe the aspheric surfaces and the performance was evaluated by commercial optical software package Tracepro. Both of high numerical aperture (NA) of 0.79 and good RMS uniformity within 95% of designed area in the second surface of lens could be obtained. The reverse of this lens would be used in focusing and the simulated point spread function (PSF) is almost diffraction-limited. The other fitted both of aspheric surface with radial spline surface and the performance was evaluated by commercial optical software package OSLO. With the radial spline surface representation, the aspheric lens has a higher NA of 0.9; meanwhile, the uniformity was still good enough and PSF is also near diffraction-limited.
Design of Circular-shape No-loss Bent Lightpipe with a Novel Transform of Elliptical Form
(2008)
Peng, Yi-Wen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
Designs for optimizing depth of focus and spot size for UV laser ablation
(2010-11-01)
Wei, An-Chi
;
Sze, Jyh-Rou
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
The proposed optical systems are designed for extending the depths of foci (DOF) of UV lasers, which can be exploited in the laser-ablation technologies, such as laser machining and lithography. The designed systems are commonly constructed by an optical module that has at least one aspherical surface. Two configurations of optical module, lens-only and lens-reflector, are presented with the designs of 2-lens and 1-lens-1-reflector demonstrated by commercially optical software. Compared with conventional DOF-enhanced systems, which required the chromatic aberration lenses and the light sources with multiple wavelengths, the proposed designs are adapted to the single-wavelength systems, leading to more economical and efficient systems.
Designs for optimizing depth of focus and spot size for UV laser ablation
(2010-11-01)
Wei, An-Chi
;
Sze, Jyh-Rou
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
The proposed optical systems are designed for extending the depths of foci (DOF) of UV lasers, which can be exploited in the laser-ablation technologies, such as laser machining and lithography. The designed systems are commonly constructed by an optical module that has at least one aspherical surface. Two configurations of optical module, lens-only and lens-reflector, are presented with the designs of 2-lens and 1-lens-1-reflector demonstrated by commercially optical software. Compared with conventional DOF-enhanced systems, which required the chromatic aberration lenses and the light sources with multiple wavelengths, the proposed designs are adapted to the single-wavelength systems, leading to more economical and efficient systems.
Equiangular-spiral bent lightpipes with arbitrary bent angle
(2009-05-15)
Chu, Shu-Chun
;
Cheng, Yi-Kai
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A recent study proposed the concept of a leakage-free bent lightpipe with an equiangular-spiral shape [S.-C. Chu, J.-L Chern, Opt. Lett. 30 (2005) 3006]. This paper extends the design of a leakage-free equiangular-spiral bent lightpipe with arbitrary-bend-angle and addresses in detail the mathematical formalism required to build such an equiangular-spiral bent lightpipe. Furthermore, a comparison of the proposed equiangular-spiral bent lightpipe and a conventional circular bent lightpipe is provided. Numerical verifications are discussed, and experimental explorations with different bent shapes and angles are carried out for comparison. Results show that equiangular-spiral bent lightpipes with different bent angles exhibit a theoretical 100% transmission with more than 76% efficiency when practically propagating, which is much better than conventional circular bent lightpipes. The output irradiance distributions of bent lightpipes with different bent shapes are also investigated. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
Equiangular-spiral non-loss bent lightpipe and its applications
(2006-01-01)
Chu, Shu-Chun
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A novel bending lightpipe operation scheme with an arbitrary bent angle without light leakage is illustrated in details. Possible applications to a light-splitting element that could split light flux with specified separation ratio, and a light-mixing element that could mix light fluxes from several ports of entrance without light leakage are also shown with case demonstration.
Equiangular-spiral non-loss bent lightpipe and its applications - art. no. 63420S
(2006)
Chu, Shu-Chun
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A novel bending lightpipe operation scheme with an arbitrary bent angle without light leakage is illustrated in details. Possible applications to a light-splitting element that could split light flux with specified separation ratio, and a light-mixing element that could mix light fluxes from several ports of entrance without light leakage are also shown with case demonstration.
Global distributions and occurrence rates of transient luminous events
(2008-08-15)
Chen, Alfred B.
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Kuo, Cheng-Ling
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Lee, Yi-Jen
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Su, Han-Tzong
;
Hsu, Rue-Ron
We report the global transient luminous event (TLE) distributions and rates based on the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) experiment onboard the FORMOSAT-2 satellite. ISUAL observations cover 45 degrees S to 25 degrees N latitude during the northern summer and 25 degrees S to 45 degrees N latitude during the northern winter. From July 2004 to June 2007, ISUAL recorded 5,434 elves, 633 sprites, 657 halos, and 13 gigantic jets. Surprisingly, elve is the dominant type of TLEs, while sprites/halos are a distant second. Elve occurrence rate jumps as the sea surface temperature exceeds 26 degrees Celsius, manifesting an ocean-atmosphere-ionosphere coupling. In the ISUAL survey, elves concentrate over the Caribbean Sea, South China Sea, east Indian Ocean, central Pacific Ocean, west Atlantic Ocean, and southwest Pacific Ocean; while sprites congregate over central Africa, Japan Sea, and west Atlantic Ocean. The ISUAL experiment observed global rates of 3.23, 0.50, 0.39, and 0.01 events per minute for elves, sprites, halos, and gigantic jets, respectively. Taking the instrumental detection sensitivity and the restricted survey area into account, the corrected global occurrence rates for sprites and elves likely are a factor of two and an order of magnitude higher, respectively. ISUAL observations also indicate that the relative frequency of high peak current lightning (> 80 kA) is 10 times higher over the oceans than over the land. On the basis of the corrected ISUAL elve global occurrence rate, the total electron content at the lower ionosphere above elve hot zones was computed to be elevated by more than 5%.
Illuminance formation and color difference of mixed-color light emitting diodes in a rectangular light pipe: an analytical approach
(2008-01-20)
Cheng, Chu-Ming
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Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
We developed an analytical method of illuminance formation for mixed-color LEDs in a rectangular light pipe in order to derive American National Standards Institute (ANSI) light uniformity, ANSI color uniformity, and color difference of light output using photometry, nonimaging, and colorimetry. The analytical results indicate that the distributions of illuminance and color difference vary with different geometric structures of light pipes and the location of the light sources. It was found that both the ANSI light and the ANSI color uniformity on the exit plane of the light pipe are reduced exponentially with the increase in length of the light pipe. It is evident that a length scale L/A greater than unity assures that the mixed-color LED sources on the entrance plane are uniformly illuminated with acceptable uniform brightness and color on the exit plane of the rectangular light pipe, where L is the length of the light pipe, and A is a constant, which is a geometric parameter for the scale unit of the light pipe's input face. Furthermore, the ANSI light uniformity can be minimized, and the ANSI color uniformity can be maximized under the condition of multilight-source locations P = Q = +/- A/4, where P and Q are the coordinates along the long axis and the short axis, respectively, with one being the entrance plane of the light pipe. We can conclude that the optimum form factor of the light pipe is a square shaped cross section, with the length scale L/A being equal to unity and with multilight sources located individually on positions of A/4 in order to achieve very uniform illuminations with the highest light efficiency and compact package for the optical system with mixed-color LEDs, where L is the length of the light pipe. (C) 2008 Optical Society of America.
Irradiance formations of on-axis Lambertian pointlike sources in polygonal total-internal-reflection straight light pipes
(2007-09-01)
Cheng, Yi-Kai
;
Wang, Meng-Hua
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
Different geometric shapes of light pipes cause different irradiance distributions. We analytically explore the irradiance distributions of on-axis Lambertian pointlike sources in polygonal total-internal-reflection (TIR) straight light pipes. lt is analytically shown that the irradiance of pentagonal light pipes concentrates on the center of the exit plane. Numerical verifications are also provided, and experimental explorations with different shapes of acrylic light pipes are carried out for comparison. We also analyze the influence of light-pipe length on distribution uniformity and deduce the smallest uniform-mixing length/circumradius ratios for polygonal light pipes. (c) 2007 Optical Society of America.
LEDs on curved ceramic substrate with primary optics for modification of luminous intensity
(2011-01-01)
Wei, An-Chi
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Sze, Jyh-Rou
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
Unlike the conventional LED luminary with a planar substrate and only the forward emission, the proposed LED luminary with a curved ceramic substrate can perform both the forward and the backward emissions. Assembled with the proper primary optics, an illustrated LED bulb has been designed, fabricated and measured. The measured luminous intensity of the LED bulb has shown the backward emission and designed distribution with the beam-angle of 133. To broaden the application areas, such a LED bulb on a curved substrate has been modularized as a streetlight. The measured results of the proposed streetlight have shown that the beam angle of the luminous intensity and the luminaire efficiency are 132 degrees and 86%, respectively. Meanwhile, its luminous characteristics also fit the standard for lighting design of urban roads.