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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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🏛️國立陽明交通大學機構典藏

Access type: Open accessAuthor: search.filters.author.Cheng, Chu-Ming

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    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
    ;
    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.
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    Programmable apodizer in incoherent imaging systems using a digital micromirror device
    (2010-02-01)
    Cheng, Chu-Ming
    ;
    Chern, Jyh-Long
    ;
    光電工程學系
    ;
    Department of Photonics
    We propose a programmable apodizer using a digital micromirror device and the total-internal-reflection prism subsystem for incoherent imaging systems. It is shown that the proposed programmable apodizer can extend the depth of focus with the specific shaped aperture generated by the digital micromirror device. With a scale ratio of K <= 0.05, one can achieve almost the same level of imaging quality as provided by the conventional annular apodizer, where K represents the ratio between the integer multiple of the micromirror's square pixel size and the diameter of the effective aperture stop. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3314306]
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    Projection quality improvement with embedded illumination modulator in projector system
    (2010-06-01)
    Cheng, Chu-Ming
    ;
    Chern, Jyh-Long
    ;
    光電工程學系
    ;
    Department of Photonics
    We demonstrate an approach for improving the image quality for a projector system with a shape-programmable pupil, which could be generated by an illumination modular in which a digital micromirror device is embedded. Essentially, the shaped pupil from the illumination modulator is developed with a dynamically programmable approach to provide aberration compensation for the projection system. By analyzing the optical transfer function, the resolution limit of an imaging system with specific defocus, spherical aberration and coma are shown to be improved significantly with a binary-shaped pupil. It is found that the improvement of the projection quality could be characterized by the scale ratio of K = c/D, defined as the ratio between the resolution scale of structured light, c, and the size scale of the aperture stop, D. When K is equal to 0.05, the low-frequency components of the image could be improved, while if K is equal to 0.3, the imaging quality of the image at high-frequency components can be enhanced in a defocused system. Furthermore, as K ranges from 0.05 to 0.3, the imaging performance of the optical contrast could be enhanced in a projector system with large coefficients of defocused, spherical aberration and coma. (c) 2010 Optical Society of America