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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Chern, Jyh-LongHas files: No

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Now showing 1 - 9 of 9
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    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.
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    Symmetry property of a generalized Billet's N-split lens
    (2010-10-01)
    Cheng, Chieh-Jen
    ;
    Chern, Jyh-Long
    ;
    光電工程學系
    ;
    Department of Photonics
    This study examines the diffraction properties of a generalized split N-sector lens originating from Billet's split bi-sector lens. The intensity distributions vary dramatically as the number of split sectors increases, and especially compared with those of the classical Billet's split lens. Nevertheless, the type of lens splitting selected causes the interference pattern of equidistant straight lines in the original Billet's lens to form an N-fold angularly distributed pattern with an angle difference of 2 pi/N. For an odd number of splitting N, there is an additional angle shift of pi/N for the azimuthally distributed patterns of equidistant straight lines. In other words, there are two kinds of symmetry even for simple splitting operations. On the other hand, the peak intensity distribution in the central portion resembles a concentric-circle-like pattern, when N is large as a result of N-beam interference. (C) 2010 Elsevier B.V. All rights reserved.
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    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.
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    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.
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    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.
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    Retrieving two-dimensional information of the subwavelength variation from far-field irradiance
    (2006-10-01)
    Chu, Shu-Chun
    ;
    Chern, Jyh-Long
    ;
    光電工程學系
    ;
    Department of Photonics
    An eigenvalue-problem approach of blind deconvolution is developed to retrieve the information of two-dimensional subwavelength variation from far-field irradiance with an embedded-aperture configuration with three detectors. A reference signal has been implemented to determine the scaling issue, and hence it allows the exact order of magnitude of the retrieved signals to be estimated correctly. It is shown that the subwavelength variations of a two-dimensional aperture can be identified with a precision of better than a 1% error ratio. (c) 2006 Optical Society of America.
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    Optical transfer functions for specific-shaped apertures generated by illumination with a rectangular light pipe
    (2006-12-01)
    Cheng, Chu-Ming
    ;
    Chern, Jyh-Long
    ;
    光電工程學系
    ;
    Department of Photonics
    We investigated the pupil functions of specific-shaped apertures generated by Lambertian illumination with a rectangular light pipe to derive the corresponding optical transfer functions (OTFs) in aberration-free and defocused optical systems. The semianalytical results indicate that the curves of the OTF of the optical system vary with the form of the shaped apertures that are generated by illumination with different geometric structures of light pipes and light sources. It was found that the OTF values of even-peak frequencies decrease when the Lambertian light source decreases. If there are a total of n X n individual apertures within a pupil, then n near-periodical peaks will appear on the OTF curve. It is evident that the values of the OTF remain almost unchanged even when the lengths of the light pipes are different. Furthermore, the geometric structure of the light pipe does not affect the resolution limit of the optical system, and under the condition of a larger defocused coefficient omega(20), the results of the defocused system can coincide with those of the aberration-free systems. (c) 2006 Optical Society of America.
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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.
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    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.