Browsing by Author "Shieh, Han-Ping David"

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Ambient-light-adaptive image quality enhancement for full-color e-paper displays using a saturation-based tone-mapping method
(2018-03-01)
Qin, Zong
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Chen, Yi-Wen
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Lin, Fang-Cheng
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Hung, Chi-Mao
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Shieh, Han-Ping David
Full-color e-paper displays that have a small color gamut encounter image tone distortions and contour artifacts in high-saturation regions. To solve these issues, in this paper, we comprehensively measure the colorimetric responses of input image signals and demonstrate that the perceptual colorfulness in terms of chroma abnormally declines when the input saturation is beyond a certain value. Accordingly, saturation-based tone-mapping curves are developed to map the abnormal high saturation to the range that the display is able to normally render. By testing several test charts and natural images, the recoveries of the original image tones and the removals of the contour artifacts are experimentally verified. More important, by discussing how to conduct a database of tone-mapping curves for different ambient lights and utilize the database for an unknown ambient light, the proposed method is proven to be completely ambient light adaptive.
Color Breakup Reduction by 180 Hz Stencil-FSC Method in Large-Sized Color Filter-Less LCDs
(2010-03-01)
Lin, Fang-Cheng
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Huang, Yi-Pai
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Shieh, Han-Ping David
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光電工程學系
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顯示科技研究所
Field-sequential color (FSC) is a high optical throughput technique for future green liquid crystal displays (LCDs). However, the FSC-LCD faces a lethal issue, color breakup (CBU) which degrades image clarity and prevents high level LCD-TV productions. We proposed the "180 Hz Stencil Field-Sequential-Color" method to redistribute intensities of the three primary color field-images to suppress CBU. By applying local color-backlight-dimming technology to FSC-LCDs, a low resolution colorful backlight panel combined with a high resolution color filter-less LC panel generated a "green-based multi-color" field-image which showed the most image luminance in the first field. Therefore, residual red and blue field-image intensities were reduced and effectively suppressed CBU when compared to field-rate increasing methods. In addition, to further implement hardware, the number of backlight divisions of 32 24 and a proper Gaussian point spread function profile were optimized via simulations while considering CBU reduction and image fidelity. Using optimized hardware parameters, the CBU phenomenon was suppressed by 50% of traditional RGB driving in simulation and was demonstrated on a 120 Hz 46-inch MVA LCD-TV.
Color Breakup Reduction by 180 Hz Stencil-FSC Method in Large-Sized Color Filter-Less LCDs (vol 6, pg 107, 2010)
(2010-06-01)
Lin, Fang-Cheng
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Huang, Yi-Pai
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Shieh, Han-Ping David
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光電工程學系
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顯示科技研究所
Compact and High Resolution Virtual Mouse Using Lens Array and Light Sensor
(2016-01-01)
Qin, Zong
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Chang, Yu-Cheng
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Su, Yu-Jie
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Huang, Yi-Pai
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Shieh, Han-Ping David
Virtual mouse based on IR source, lens array and light sensor was designed and implemented. Optical architecture including lens amount, lens pitch, baseline length, sensor length, lens-sensor gap, focal length etc. was carefully designed to achieve low detective error, high resolution, and simultaneously, compact system volume. System volume is 3.1mm (thickness) x 4.5mm (length) x 2, which is much smaller than that of camera-based device. Relative detective error of 0.41mm and minimum resolution of 26ppi were verified in experiments, so that it can replace conventional touchpad/touchscreen. If system thickness is eased to 20mm, resolution higher than 200ppi can be achieved to replace real mouse.
Electrical and Photosensitive Characteristics of a-IGZO TFTs Related to Oxygen Vacancy
(2011-04-01)
Yao, Jianke
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Xu, Ningsheng
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Deng, Shaozhi
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Chen, Jun
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She, Juncong
The electrical and photosensitive characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) related to the oxygen vacancies V(O) are discussed. With the filling of V(O) of ratio from 14 to 8, the electron density of the a-IGZO channel decreases from 7.5 to 3.8 (x10(16) cm(-3)); the saturation mobility of the TFT decreases from 3.1 to 1.4 cm(2)/(V . s); the threshold voltage increases from 7 to 11 V for the TFT with a lower on-current; and the subthreshold slope increases from 2.4 to 4.4 V/dec for the TFT with a higher interface defect density of 4.9 x 10(11) cm(-2), the worst electrical stability of Delta V(th) similar to 10 V, and a hysteresis-voltage decrease from 3.5 to 2 V. The photoreaction properties of a-IGZO TFTs are also sensitive to the oxygen-content-related absorption of the a-IGZO channel. With the lowest content of oxygen in the channel, the TFT has the largest photocurrent gain of 50 mu A (V(g) = 30 V; V(d) = 10 V) and decrease in V(th) (|Delta V(th)| similar to 5 V) at a high light intensity. The light-induced change of TFT characteristics is totally reversible with the time constant for recovery of about 2.5 h.
High Ambient Contrast Ratio OLED Display with Microlens Array and Cruciform Black Matrices
(2015)
Qin, Zong
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Yeh, Yen-Wei
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Huang, Yi-Pai
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Shieh, Han-Ping David
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Lee, Kuo-Ch\'ang
Microlens array and cruciform black matrices were adopted to reduce ambient light reflection by 87.8% in OLED display for a 21mm by 21mm eye box while only 19.8% of reflective layer\'s area was occupied.
Image content adaptive color breakup index for field sequential color displays using a dominant visual saliency method
(2018-02-01)
Qin, Zong
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Lin, Ying-Ju
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Lin, Fang-Cheng
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Kuo, Chia-Wei
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Lin, Ching-Huan
An index that can predict the perceptual visibility of color breakup for varying image content is valuable in field sequential color displays, whereas the current indices are usually for fixed patterns. To solve this problem, an image database containing 25 diverse reference images and 125 test cases with various color breakup visibility was first established. Next, visual experiments using a 240-Hz liquid crystal display were performed to acquire the subjective color breakup scores of the test cases. A theorem based on visual saliency theory was proposed that the color breakup perception is mainly determined by the image regions with visual saliency values higher than a certain threshold, called the dominant visual saliency regions. A computational model based on this theorem was developed to obtain objective color breakup scores of the test cases from retinal images with and without color breakup. An analysis of the objective and subjective results revealed a Pearson linear correlation coefficient as high as 0.82, which matches the top-level image quality assessment algorithms. Finally, the proposed color breakup index was used to benchmark against several mainstream field sequential color algorithms to determine their performances in color breakup suppression.
Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants
(2006-01-01)
Chen, Huang-Ming Philip
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Tsai, Yun-Yen
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Lin, Chi-Wen
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Shieh, Han-Ping David
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光電工程學系
A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 degrees C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 mu m pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.
Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants - art. no. 63320G
(2006)
Chen, Huang-Ming Philip
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Tsai, Yun-Yen
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Lin, Chi-Wen
;
Shieh, Han-Ping David
;
光電工程學系
A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 degrees C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 mu m pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.
Photosensitivity of amorphous IGZO TFTs for active-matrix flat-panel displays
(2008-01-01)
Chuang, Chiao-Shun
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Fung, Tze-Ching
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Mullins, Barry G.
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Nomura, Kenji
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Kamiya, Toshio
We studied the optical and electrical properties of the amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs). To develop a-IGZO density-of-states model, intrinsic a-IGZO optical properties such as optical band gap and Urbach energy, and TFT characteristics under illumination are investigated During the a-IGZO TFTs illumination with the wavelengths ranging from 460 to 660 nm, the off-state drain current only slightly increases while a large increase was observed for the wavelength below 400 nm. Threshold voltage and subthreshold swing are also only slightly modified between 460 to 660 nm, while field-effect mobility is almost unchanged in the investigated photon energy range. The observed results are consistent with the a-IGZO optical energy band gap of about 3.05 eV. This study suggest that the a-IGZO TFTs are light sensitive above 3.0 eV and photogenerated electrons are more mobile than holes within device channel region.
See-Through Image Blurring of Transparent Organic Light-Emitting Diodes Display: Calculation Method Based on Diffraction and Analysis of Pixel Structures
(2016-11)
Qin, Zong
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Tsai, Yu-Hsiang
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Yeh, Yen-Wei
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Huang, Yi-Pai
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Shieh, Han-Ping David
In this paper, the issue of see-through image blurring of transparent organic light-emitting diodes display is demonstrated, and a systematic method is proposed to calculate blurred see-through image based on diffraction theory. In the calculation, distances of background object and the viewer are considered to correct Fresnel diffraction and chromatic image can be finally synthesized. Calculated and actually captured see-through images match well by using different background distances and pixel structures to verify, as error ratio of only 2.3% and 4.3%, respectively, in the term of blurred image\'s fringe length. Based on the calculation results, see-through image qualities corresponding to four pixel structures are evaluated and two structures are verified to have better image quality. Finally, higher resolutions that lead to much more significant see-through image blurring are discussed.