教師著作

Permanent URI for this collectionhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/31266

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Author: search.filters.author.Yeh, Zong-Mu

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Now showing 1 - 10 of 46
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    Contrast compensation for back-lit and front-lit color face images via fuzzy logic classification and image illumination analysis
    (2008-07-12) Tsai, Chun-Ming; Yeh, Zong-Mu; Wang, Yuan-Fang
    Conventional contrast enhancement methods have two shortcomings. First, most of them do not produce satisfactory enhancement results for face images with back-lit or front-lit. Second, most of them need transformation functions and parameters which are specified manually. Thus, this paper proposes an automatic and parameter-free contrast compensation algorithm for color face images. This method includes: RGB color space is transformed to YIQ color space. Fuzzy logic is used to classify the color images into back-lit, normal-lit, and front-lit categories. Image illumination analysis is used to analyze the image distribution. The input image is compensated by piecewise linear based compensation method. Finally, the compensation image is transformed back to RGB color space. This novel compensation method is automatic and parameter-free. Our experiments included back-lit and front-lit images. Experiment results show that the performance of the proposed method is better than other available methods in visual perception measurements.
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    A Problem-based Learning Management System Using Fuzzy Petri Net
    (2008-03-03) Chang, Wan-Jen; Chen, Hung-Pin; Yeh, Zong-Mu; Yeh, Po-Chun
    The e-learning system has been proposed in many collaborative learning environments to help learners. This study enhances e-learning system to computer-assisted problem-based learning system, investigates its effectiveness for gender communication in undergraduate students, and develops six learning phases to produce a workflow-based course definition in Gender communication. To manage these complex learning activities, a problem-based learning management system (PBLMS) based on fuzzy Petri nets (FPN) was proposed. In this study, we completed a problem-based learning project of gender communication with a sample of ninety undergraduates who register for the common course and empirically demonstrated results. Using the PBLMS-FPN system, the academic load of teachers in mass course environments can be reduced and higher quality education can be achieved.
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    Contrast Compensation for Back-lit and Front-lit Color Face Image via Fuzzy Logic Classification and Image Illumination Analysis
    (Institute of Electrical and Electronics Engineers (IEEE), 2008-07-12) Tsai, Chun-Ming; Yeh, Zong-Mu; Wang, Yuan-Fang
    Conventional contrast enhancement methods have two shortcomings. First, most of them do not produce satisfactory enhancement results for face images with back-lit or front-lit. Second, most of them need transformation functions and parameters which are specified manually. Thus, this paper proposes an automatic and parameter-free contrast compensation algorithm for color face images. This method includes: RGB color space is transformed to YIQ color space. Fuzzy logic is used to classify the color images into back-lit, normal-lit, and front-lit categories. Image illumination analysis is used to analyze the image distribution. The input image is compensated by piecewise linear based compensation method. Finally, the compensation image is transformed back to RGB color space. This novel compensation method is automatic and parameter-free. Our experiments included back-lit and front-lit images. Experiment results show that the performance of the proposed method is better than other available methods in visual perception measurements.
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    Design and Implementation of Confocal Imaging Systems with a Generalized Theoretical Framework
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2007-02-17) Chang, Gao-Wei; Liao, Chia-Cheng; Yeh, Zong-Mu
    Confocal imaging is primarily based on the use of apertures in the detection path to provide the acquired three-dimensional images with satisfactory contrast and resolution. For many years, it has become an important mode of imaging in microscopy. In biotechnology and related industries, this technique has powerful abilities of biomedical inspection and material detection with high spatial resolution, and furthermore it can combine with fluorescence microscopy to get more useful information. The objective of this paper is first to present a generalized theoretical framework for confocal imaging systems, and then efficiently to design and implement such systems with satisfactory imaging resolutions. In our approach, a theoretical review for confocal imaging is given to investigate this technique from theory to practice. Also, computer simulations are performed to analyze the imaging performance with varying optomechanical conditions. For instance, the effects of stray light on the microscopic systems are examined using the simulations. In this paper, a modified optomechanical structure for the imaging process is proposed to reduce the undesired effects. From the simulation results, it appears that the modified structure highly improves the system signal-to-noise ratio. Furthermore, the imaging resolution is improved through the investigation on the tolerance of fabrication and assembly of the optical components. In the experiments, it is found that the imaging resolution of the proposed system is less sensitive than that of common microscopes, to the position deviations arising from installations of the optical components, such as those from the pinhole and the objective lens.
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    White-light interferometric profile measurement system using spectral coherence
    (SPIE, 2007-01-23) Chang, Gao-Wei; Lin, Yu-Hsuan; Yeh, Zong-Mu
    It is well known that white light interferometry (WLI) is important to nano-scale 3-D profile measurement technology. To archive cost-effective and accurate measurements, the researches for WLI are widely spreading. Our objective is to build up a 3-D micro-structure profile measurement system based on WLI, for micro-mechatronic, micro-optical, and semi-conductor devices. This paper briefly reviews related WLI theory and then the principle of spectral coherence is employed to improve the system design. Specifically, proper spectral filters can be used to extend the coherence length of the light source to the order of several ten micrometers. That is, the coherence length of the filtered light source is longer than that of the original source. In this paper, Michelson interference experiments are conducted with filtered and unfiltered white light sources, to show the feasibility of the concept of spectral coherence. The Michelson interferometer is adopted due to its convenience of optical installation and its acceptable tolerance to noise. The experiment results indicate that our approach is feasible and thus it can improve the WLI measurement performance.
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    High-accuracy and cost-effective photodiode spectral response measurement system
    (SPIE, 2007-02-09) Chang, Gao-Wei; Lin, Yu-Hsuan; Yeh, Zong-Mu
    With the rapid growth of optoelectronics technologies, photodiodes (PDs) has been widely used in optical measurement systems, color measurement and analysis systems, etc. To meet most of the measurement requirements, the determination of PD spectral responses is very important. The goal of this paper is to develop a high-accuracy and cost-effective spectral response measurement system for PDs. In this paper, the proposed system contains a grating-based spectral filtering module, an amplifier module, and a digital-signal-processing (DSP) based platform. In the spectral filtering module, a single-grating monochromator based on a Czerny-Turner configuration is first analyzed and simulated, and then the experiments are conducted to check if the measurement accuracy is satisfactory. In the measurement system, optoelectronic signals from the PD under test are acquired from the amplifier module and the DSP-based platform is developed to communicate and manipulate the measured data. Through comparison with the measurement data from a commercially available system, it is found that our approach gives quite satisfactory results.
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    Accurate and cost-effective MTF measurement system for lens modules of digital cameras
    (SPIE, 2007-01-30) Chang, Gao-Wei; Liao, Chia-Cheng; Yeh, Zong-Mu
    For many years, the widening use of digital imaging products, e.g., digital cameras, has given rise to much attention in the market of consumer electronics. However, it is important to measure and enhance the imaging performance of the digital ones, compared to that of conventional cameras (with photographic films). For example, the effect of diffraction arising from the miniaturization of the optical modules tends to decrease the image resolution. As a figure of merit, modulation transfer function (MTF) has been broadly employed to estimate the image quality. Therefore, the objective of this paper is to design and implement an accurate and cost-effective MTF measurement system for the digital camera. Once the MTF of the sensor array is provided, that of the optical module can be then obtained. In this approach, a spatial light modulator (SLM) is employed to modulate the spatial frequency of light emitted from the light-source. The modulated light going through the camera under test is consecutively detected by the sensors. The corresponding images formed from the camera are acquired by a computer and then, they are processed by an algorithm for computing the MTF. Finally, through the investigation on the measurement accuracy from various methods, such as from bar-target and spread-function methods, it appears that our approach gives quite satisfactory results.
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    Accurate Spectral Response Measurement System for Digital Color Camera
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2007-01-30) Chang, Gao-Wei; Yeh, Zong-Mu
    In imaging systems, color plays an essential role in conveying and recording visual information from the real world. To faithfully represent colors acquired from digital cameras, a spectral responsivity measurement system is proposed for those devices in this paper. For estimating spectral responsivities of digital color cameras, a filter-based optical system is designed with proper filter selections. Since the spectral filters primarily prescribe the optical characteristics of the system, the filter consideration is important to the optical design of the system with the presence of noise. A theoretical basis is presented to confirm that sophisticated filter selections can make this system as insensitive to noise as possible. Also, we propose a filter selection method based on the orthogonal-triangular (QR) decomposition with column pivoting (QRCP). To investigate the noise effects, we assess the estimation errors between the actual and estimated spectral responsivities, with the different signal-to-noise ratio (SNR) levels of an eight-bit/channel camera. To demonstrate the effectiveness of this approach, the experimental results from the filter-based optical system with the spectral filters selected from the QRCP-based method is much less sensitive to noise than those with other filters from different selections. It is found that the measurement accuracy is fairly satisfactory.
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    Design and Implementation of Real-Time LED Spatial Radiance Measurement Systems
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2007-02-13) Chang, Gao-Wei; Yeh, Zong-Mu; Liao, Chia-Cheng
    Light-emitting diodes (LEDs) have been recognized as a generation of new light sources because they possess the properties of energy-saving, environmental protection, long lifetime, and those lacking in conventional lighting. To satisfy the requirements for different applications (e.g., for large-scale displays), determining the spatial radiances of LEDs is important to identifying their viewing angle and utilizing their lighting efficiency. The objective of this paper is to build up a real-time spatial radiance measurement system for LEDs, on the basis of digital signal processing (DSP) techniques. In this paper, the system analysis is given to show the feasibility of this work. Two primary subsystems are devised to perform the real-time measurements. First, in the optoelectronic sensing and signal processing subsystem, a wide-bandwidth photodiode sensing circuit is employed to acquire optical signals at a high speed, and an automatic gain control (AGC) circuit is designed to increase the measurement range. To support high-speed data processing, a DSP-based platform is developed in the subsystem. Second, a light-source rotation scheme is used in the optomechanical subsystem. For performance evaluations, we adopt a standard calibrating light source to test and verify our system. Experimental results indicate that the proposed system gives satisfactory results.