<title>Color characterization issues for TFTLCD displays</title>

Abstract

This paper describes few issues related to TFTLCD display color rendition and characterization. The paper points out specific aspects of color rendition on TFTLCD devices that differentiate the traditional CRT self luminous devices from the TFTLCD transmissive devices. Two TFTLCD technologies are discussed, TN (Twisted Nematic) and IPS (In Plane Switching) with and without dual domain improvement. The paper discusses specific aspects of color rendering for TN and IPS technologies, the display primaries, color gamut and brightness, the transfer function, the white point, some viewing angle issues and the color model. The paper explains why the TFTLCD displays offer perceptually a larger gamut than the CRT displays, even if chromatically their gamut triangle is smaller in the CIE chromaticity diagram than the one of a typical CRT. The paper also explains the hue shift effect of the primaries with the input voltage and the effect of luminance variation with the viewing angle, both encountered in some TN TFTLCD displays. The paper confirms that despite their advantages due to high brightness, high contrast, high sharpness, virtually no geometric image distortion, in terms of color capability, with few exceptions, TFTLCD devices have not yet surpassed the CRT devices with larger chromatic gamut and no color variation with the viewing angle.

The PLVC display color characterization model revisited

“…2(a),2(b),2(e), and 2(f)] we can notice the same effect as in the work of Marcu et al, 40 the black level chromaticity is bluish because of the poor filtering power of the blue filter in the low wavelength.…”

Gray tracking correction for TFT-LCDs

“…The chromaticity variation of the primaries can be observed even after the flare compensation is performed (as suggested in [2]). This variation reported earlier [3], [4] may be explained by two interacting factors. First, the transmittance of the liquid crystal cell depends on the wavelength of the transmitted light and on the input level of the signal, as it is illustrated in figure 2 [5] [6].…”

Device characterization

“…This is largely due to the non-smooth spectral characteristics of the backlight and its interaction with the color filters. 45 Kwak et al 47 compensate for the lack of chromaticity constancy by introducing cross terms in the nonlinear calibration functions to capture interactions among R, G, and B. They claim a significant improvement in overall accuracy as a result of this extension.…”

“…Recent developments such as in-plane switching technology 45 overcome these problems to some extent.…”

“…The same geometry should be used for viewing images. For further details on LCD characterization, the reader is referred to the works by Marcu, 45 Sharma, 46 and Kwak. 47 …”