Browsing by Author "Liaw, MJ"

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Color characterization of an LC projection system using multiple-regression matrix and look-up-table with interpolation
(1998)
Liaw, MJ
;
Chen, CY
;
Shieh, HPD
;
光電工程學系
;
Department of Photonics
A forward model of an LC projector is studied to predict its colorimetric attribution. To identify color characteristics of the projector, 729 colors were measured in a dark room. The forward model was built using three methods: (I) a 3x11 multiple-polynomial regression matrix, (2) a 3-dimensional(3-D) look-up table(LUT) viith cubic interpolation, and (3) a one dimensional(I-D) LUT with linear interpolation. In addition, 216 colors were also measured to evaluate the prediction accuracy of the forward model. All methods can be used to obtain acceptable predictions of calorimetric attributions on the LC projector. When the 3x11 multiple-polynomial regression matrix was used, the average and maximum prediction differences were 2.18 and 6.68 Delta E-uv*, respectively. For the 3-D LUT method, those values were 3.3 and 16.4 Delta E-uv*, respectively. The results of the 1-D LUT are comparable with those of the 3-D LUT if die sampling points per channel of these two approaches are the same. If the sampling points per channel are dense enough, for example 16 points per channel, the performance of the I-D LUT is better than that of the 3x11 multiple-polynomial regression matrix.
Color characterization of twist nematic LC panels by using empirical functions
(1998)
Liaw, MJ
;
Shieh, HPD
;
光電工程學系
;
Department of Photonics
An empirical exponential equation is proposed to characterize the transfer functions of the image signals to tristimulus values of twist nematic (TN) liquid crystal displays(CDs). Parameters of the empirical equation can be determined according to the colorimetric measurements of the test panel without knowing the panel's physical details. A two-stage forward model is also proposed to model the color characteristics of TN LCDs by using the empirical function. Moreover, a backward model is derived to reproduce desired colors accurately on TN LCDs. The main benefit of the study is that only 12 colors should be measured to characterize color rendering on TN LCDs.
Color rendering of cathode ray tube (CRT) by digital driving
(1997-08-01)
Liaw, MJ
;
Shieh, HPD
;
光電工程研究所
;
Institute of EO Enginerring
Color rendering by digital driving methods of equal voltage change (EVC) and equal color difference (ECD) were studied. A CRT was assumed to be driven by 262,144 (64 x 64 x 64) RGB digital combinations. The number of ''effective'' colors which can be discriminated one another were calculated. It reveals that ECD supports more digital combinations (78.9% for ECD and 68.0% for EVC, respectively) to produce effective colors. ECD driving also supports higher color resolution except in the region of color gamut with lightness value below 20. In the dark region, EVC supports higher color resolution. Color images can be shown with higher fidelity by choosing proper digital driving methods.
Color rendering of cathode ray tube (CRT) by digital driving
(1997-08-01)
Liaw, MJ
;
Shieh, HPD
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
Color rendering by digital driving methods of equal voltage change (EVC) and equal color difference (ECD) were studied. A CRT was assumed to be driven by 262,144 (64 x 64 x 64) RGB digital combinations. The number of ''effective'' colors which can be discriminated one another were calculated. It reveals that ECD supports more digital combinations (78.9% for ECD and 68.0% for EVC, respectively) to produce effective colors. ECD driving also supports higher color resolution except in the region of color gamut with lightness value below 20. In the dark region, EVC supports higher color resolution. Color images can be shown with higher fidelity by choosing proper digital driving methods.
Color reproduction of twist nematic LCD by polynomial regression applied in primary-invariance model
(1999)
Tsai, CY
;
Liaw, MJ
;
Shieh, HPD
;
光電工程學系
;
Department of Photonics
As primary-shifts on LCDs is non-negligible, primary-invariance model, widely used to characterize the color reproduction on CRT monitors, can not be applied well on LCDs. To obtain average color difference of less than 3 Delta E-uv* for LCDs, primary-invariance forward model should be modified by at least a 3x9 regression analysis matrix. In backward model, polynomial regression method can transfer data in both RGB and XXZ domains. However, only in XYZ domain, desired colors can be reproduced sufficiently.
Colorimetric calibration of CRT monitors using modified Berns' model
(1996-11-01)
Liaw, MJ
;
Shieh, HPD
;
光電工程研究所
;
Institute of EO Enginerring
Analytic methods based on Berns' model and its reverse model are proposed to characterize a CRT's colorimetric characteristics. The methods rake primary shift and channel interaction into consideration to predict and reproduce colors on a CRT more accurately. Average prediction error of 729 test colors is reduced to less than 1 Delta E* defined in L* u* v* color space by using both forward and reverse models. Percentage of colors whose prediction errors are less than 1 Delta E* is large than 75%. The maximum prediction error is of less than 3 Delta E*.
Colorimetric calibration of CRT monitors using modified Berns' model
(1996-11-01)
Liaw, MJ
;
Shieh, HPD
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
Analytic methods based on Berns' model and its reverse model are proposed to characterize a CRT's colorimetric characteristics. The methods rake primary shift and channel interaction into consideration to predict and reproduce colors on a CRT more accurately. Average prediction error of 729 test colors is reduced to less than 1 Delta E* defined in L* u* v* color space by using both forward and reverse models. Percentage of colors whose prediction errors are less than 1 Delta E* is large than 75%. The maximum prediction error is of less than 3 Delta E*.
Empirical tone reproduction curve equation applied for color characterization of LCDs
(1999)
Liu, HJ
;
Liaw, MJ
;
Shieh, HPD
;
光電工程學系
;
Department of Photonics
An empirical function is proposed to characterize the transfer functions of the image signals to tristimulus values of twist nematic liquid crystal displays (TN LCDs). This empirical equation can be applied for Color additive model and Primary-shift backward model of LCDs' characterizations. A notebook PC was used to examine the fitting accuracy and color difference with different transfer functions. The main benefit of the work is that only 12 colors are required to accurately characterize the color rendering of LCDs.