Browsing by Author "Cheng, Wei-Chung"

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A visualization tool for evaluating angular-dependent colorimetric performance of LCD
(2006)
Lin, Jane-Jhe
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Cheng, Wei-Chung
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應用化學系
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Department of Applied Chemistry
We have developed an interactive visualization tool that emulates the visual effect of an LCD when viewed at a specific angle such that the user can easily assess its colorimetric performance such as color shift, saturation degradation, and contrast/luminance reduction. The target LCD has to be characterized to generate its colorimetric parameters at different viewing angles. The proposed tool then calculates the resulting image by table-lookup and interpolation. This tool is particularly useful when evaluating multiple LCDs simultaneously or remotely.
An EOG-assisted Contingent Display for Suppressing Saccadic Color Breakup
(2009)
Cheng, Wei-Chung
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Wu, Chih-Nan
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光電工程學系
;
Department of Photonics
A contingent field sequential display reduces chroma to inhibit saccadic color breakup on-the-fly when saccadic eye movement is detected by an electro-oculogram (EOG) sensing circuit.
An experimental platform for evaluating color breakup phenomenon
(2007)
Hsu, Chih-Fu
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Wu, Chih-Nan
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Cheng, Wei-Chung
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光電工程學系
;
Department of Photonics
An RGB-LED-backlit LCD was implemented for psychophysical study of color breakup phenomenon. The backlight module can generate colors either sequentially or simultaneously to assess human subject's detectability of color breakup phenomenon.
An experimental platform for evaluating color breakup phenomenon
(2007)
Hsu, Chih-Fu
;
Wu, Chih-Nan
;
Cheng, Wei-Chung
;
光電工程學系
;
Department of Photonics
An RGB-LED-backlit LCD was implemented for psychophysical study of color breakup phenomenon. The backlight module can generate colors either sequentially or simultaneously to assess human subject's detectability of color breakup phenomenon.
An experimental platform for evaluating color breakup phenomenon
(2007-01-01)
Hsu, Chih-Fu
;
Wu, Chih-Nan
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Cheng, Wei-Chung
;
光電工程學系
;
顯示科技研究所
An RGB-LED-backlit LCD was implemented for psychophysical study of color breakup phenomenon. The backlight module can generate colors either sequentially or simultaneously to assess human subject's detectability of color breakup phenomenon.
Color Management for Flexible Cholesteric-LCD
(2009)
Chen, Huang-Ming P.
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Cheng, Cheng-Fu
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Liu, Yuh-Ferng
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Cheng, Wei-Chung
;
Huang, Jih-Fon
The reflective cholesteric liquid crystal display suffers from voltage-induced color shift and viewing angle-dependent color shift. In this paper, two solutions are presented to overcome these problems. First, four types of cholesteric liquid crystals were synthesized and characterized to find the best mixture with the lowest voltage-induced color shift and reflectance reduction. Secondly, 5-primary (red, yellow, green, cyan and blue) cholesteric liquid crystals were synthesized such that the color gamut and reflectance were enhanced.
Color Management for Flexible Cholesteric-LCD under LED Illumination
(2009-01-01)
Cheng, Wei-Chung
;
Chen, Huang-Ming P.
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Huang, Jih-Fon
;
交大名義發表
;
National Chiao Tung University
The reflective cholesteric liquid crystal display suffers from voltage-induced color shift and viewing angle-dependent color shift. In this paper, three solutions are presented to overcome these problems. First, four types of cholesteric liquid crystals were synthesized and characterized to find the best mixture with the lowest voltage-induced color shift and reflectance reduction. Secondly, 5-primary (red, yellow, green, cyan and blue) cholesteric liquid crystals were synthesized such that the color gamut and reflectance were enhanced. Finally, the viewing angle-dependent color shift was characterized and then compensated by adjusting the chromaticity of the red/green/blue LED light sources.
Discovering monotonic stemness marker genes from time-series stem cell microarray data
(2015-01-21)
Wang, Hsei-Wei
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Sun, Hsing-Jen
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Chang, Ting-Yu
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Lo, Hung-Hao
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Cheng, Wei-Chung
Background: Identification of genes with ascending or descending monotonic expression patterns over time or stages of stem cells is an important issue in time-series microarray data analysis. We propose a method named Monotonic Feature Selector (MFSelector) based on a concept of total discriminating error (DEtotal) to identify monotonic genes. MFSelector considers various time stages in stage order (i.e., Stage One vs. other stages, Stages One and Two vs. remaining stages and so on) and computes DEtotal of each gene. MFSelector can successfully identify genes with monotonic characteristics. Results: We have demonstrated the effectiveness of MFSelector on two synthetic data sets and two stem cell differentiation data sets: embryonic stem cell neurogenesis (ESCN) and embryonic stem cell vasculogenesis (ESCV) data sets. We have also performed extensive quantitative comparisons of the three monotonic gene selection approaches. Some of the monotonic marker genes such as OCT4, NANOG, BLBP, discovered from the ESCN dataset exhibit consistent behavior with that reported in other studies. The role of monotonic genes found by MFSelector in either stemness or differentiation is validated using information obtained from Gene Ontology analysis and other literature. We justify and demonstrate that descending genes are involved in the proliferation or self-renewal activity of stem cells, while ascending genes are involved in differentiation of stem cells into variant cell lineages. Conclusions: We have developed a novel system, easy to use even with no pre-existing knowledge, to identify gene sets with monotonic expression patterns in multi-stage as well as in time-series genomics matrices. The case studies on ESCN and ESCV have helped to get a better understanding of stemness and differentiation. The novel monotonic marker genes discovered from a data set are found to exhibit consistent behavior in another independent data set, demonstrating the utility of the proposed method.
Minimization for LED-backlit TFT-LCDs
(2006)
Cheng, Wei-Chung
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Chao, Chain-Fu
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光電工程學系
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Department of Photonics
This paper presents an algorithm for minimizing power consumption of LED backlights in transmissive TFT-LCD monitors. The proposed algorithm reduces power consumption by scaling the luminous intensity of the red, green, and blue LED backlights independently according to the image histograms of each color channel. The algorithm consists of two phases. The first phase, chromaticity scaling, finds the optimal ratios of red, green, and blue backlights subject to a perceived color difference constraint. The second phase, luminance scaling, finds the optimal dimming factor subject to a perceived lightness difference constraint. The perceived color and lightness differences are measured by the CIELAB Color Difference Equation 2 Delta E-ab* standard metric for measuring color variation. Psychophysical experiments were performed with 35 observers to uncover the optimal luminance scaling function, An experimental LED backlight module was implemented and installed on a 19" side-lit TFT-LCD monitor to replace the original CCFL backlight. Within limited perceivable difference 2 Delta E-ab*, up to 76% of power consumption can be reduced for the benchmark images.
Temporal vision-guided energy minimization for portable displays
(2006)
Cheng, Wei-Chung
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Hsu, Chih-Fu
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Chao, Chain-Fu
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光電工程學系
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Department of Photonics
This paper presents a novel backlight driving technique for liquid crystal displays. By scaling the intensity, frequency, and duty cycle of the backlight, this technique not only increases the perceived brightness but also prolongs the service time Of rechargeable batteries. The increased brightness comes from a perceptual effect of temporal vision - a brief flash appears brighter than a steady light of the same intensity, called Brucke brightness enhancement effect. The prolonged service time comes from the relaxation phenomenon - a lithium-ion battery lasts longer by pulsed discharge. Combining these two effects, a great amount of service time can be obtained at the cost of flickering. We performed visual experiments to parameterize the Brucke effect and derived an optimization algorithm accordingly. To demonstrate the potential energy savings of this technique, we profiled the power consumption of an Apple iPod and fabricated an LED driving module. Based on experimental data, 75% of energy consumption can be saved and the service time can be extended to 300%.
Theoretic bounds on panel size of flicker-free field sequential liquid crystal displays
(2007)
Hsu, Chih-Fu
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Cheng, Wei-Chung
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光電工程學系
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Department of Photonics
The Field sequential liquid crystal display (FSLCDs) technology synthesizes color in the temporal domain. However, the temporal property of human visual perception perceives flickering when the refresh rate is not sufficiently high. To estimate the perceivable flickering on FSLCDs, we conducted visual experiments to characterize the critical flicker fusion frequency for different FSLCD panel sizes.
Variation-Aware and Adaptive-Latency Accesses for Reliable Low Voltage Caches
(2013)
Wang, Po-Hao
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Cheng, Wei-Chung
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Yu, Yung-Hui
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Kao, Tang-Chieh
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Tsai, Chi-Lun
Contemporary cache is known for consuming a large part of total power in microprocessors. Voltage scaling had been used to reduce the power consumption of the cache. However, due to the impact of variations, SRAM cells of the cache could potentially fail when voltage dropping. To against variations, we need to increase the supply voltage for the safety margin, thus the cache costs large energy consumption. For eliminating the voltage safety margin, some prior works for SRAM failure tolerance designs were proposed. These schemes will result in worse energy consumption and cannot deal with dynamic variations. They still have a safety margin to resist dynamic variations. With the supply voltage scaling down, we find out that the major reason of failures is that some slow cells have longer latency. We call these cell faults as "latency fault". If each cache line can be accessed in an appropriate access time, the slower cells could be reused but not disable them. We propose a VAL-Cache adapting the access time to tolerate latency faults and which is able to scale down the voltage. And we also propose the latency-fault detector to detect latency faults at run-time so as to tolerate both static and dynamic variations. Our experimental results on Mibench and 0xbench benchmarks demonstrate that the energy consumption can be reduced 10%similar to 18% in average at a cost of acceptable performance loss.
Viewing angle-aware color correction for LCDs
(2007)
Wu, Chih-Nan
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Cheng, Wei-Chung
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光電工程學系
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Department of Photonics
Viewing angle-dependent color shift is one of the major drawbacks of liquid crystal displays (LCD). As the viewing angle increases, not only the luminance but also the color saturation reduces and compromises the image quality. In this paper, we characterize the viewing angle-dependent color shift of an LCD and propose a compensation method of adjusting the backlights and panel transmittance simultaneously. By increasing the panel transmittance, the color shift and luminance attenuation can be minimized. By increasing or decreasing the backlight intensity, the original luminance can be preserved or the power consumption can be reduced. Similar to previous approaches, the proposed method requires a video camera to capture the user's location for calculating the viewing angle. We have also implemented an emulator for reproducing the viewing angle-dependent visual effects.
Viewing Direction-Aware Backlight Scaling
(2007)
Wu, Chih-Nan
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Cheng, Wei-Chung
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光電工程學系
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Department of Photonics
High power consumption and limited viewing angles are the two major drawbacks of liquid crystal displays (LCDs). This paper models the angular-dependent luminance attenuation of a twisted nematic LCD and incorporates user's viewing direction into a backlight scaling framework such that the power consumption can be minimized while preserving the optimal image quality. We also studied the human factors of viewing direction variation, and developed an emulator for visualizing luminance attenuation and color shift in different viewing directions.
Zero-Counting and Adaptive-Latency Cache Using a Voltage-Guardband Breakthrough for Energy-Efficient Operations
(2016-10)
Wang, Po-Hao
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Cheng, Wei-Chung
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Yu, Yung-Hui
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Kao, Tang-Chieh
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Tsai, Chi-Lun
In modern embedded processor systems, energy efficiency is a critical issue. Unfortunately, to avoid cache memory (SRAM) faults from dynamic variations, caches generally operate at an elevated voltage to build a safety guardband that decreases energy efficiency. To address this issue, tolerating SRAM faults to eliminate the safety of a guardband without frequency scaling may be a viable solution. This study investigates the characteristics of low-voltage 8 T SRAM faults and demonstrates that most SRAM faults are typically caused by insufficient access times with variation effects and significantly reduced voltages. Thus, we propose an access-time fault-tolerant cache design based on a type of 8 T SRAM known as zero-counting and adaptive-latency cache (ZCAL cache), which can tolerate numerous access-time faults. ZCAL caches detect access-time faults dynamically using a lightweight error detection code ("0" counting) because access-time faults occur only when reading "0" bits on the 8 T SRAM; the cache then adapts its access time to tolerate the access-time faults with new cache management processes. With the ZCAL cache, the experimental results from the MiBench benchmarks indicate that the energy efficiency is improved by 17% on average and that the energy consumption is reduced by 22% from 0.76 to 0.63 V.