Modeling motion-induced color artifacts from the temporal step response Kees Teunissen Xiaohua Li Lin Chai Ingrid Heynderickx Abstract — LCD motion blur is a well-known phenomenon, and a lot of research is attributed to characterize and improve it. Until recently, most studies were focused on explaining the effects visible in black-and-white patterns, and hence color effects were ignored. However, when a colored pattern is moving over a colored background, an additional motion-induced artifact becomes visible, which is referred to as chromatic aberration. To describe this phenomenon, our model to characterize the appearance of moving achromatic patterns is extended in such a way that it now calculates the apparent image from the temporal step response of the individual primary colors. The results of a perception experiment indicate that there is a good correspondence between the apparent image pre- dicted with the model and the actual image perceived during motion. Keywords — Motion artifacts, LCD, motion-induced chromatic aberration, temporal step response, motion-picture response curve, human-visual perception. 1 Introduction The major advantage of liquid-crystal displays (LCDs) over cathode-ray tubes (CRTs) is their reduced thickness and weight. Huge investments in LCD factories and a signifi- cant research effort to improve the display quality resulted in a dominant position of LCDs in today’s display industry. It is actually the form factor (thin design) that made LCDs very well suitable to replace the bulky CRT monitors in office environments, where a reduced viewing angle and a slow response time were, initially, acceptable. Improvements in viewing angle, response time, and contrast, together with large-scale investments, to bring down the production costs, enabled LCDs to be introduced in television (TV) sets. In the TV market, next to the thin design, the increased TV size (32 in. and above) combined with an acceptable product weight is highly appreciated. The acceptance of LCDs in this market does not necessarily mean that their quality is on par with that of CRTs. Especially in the case of LCDs with continuous backlight intensity, the sample-and-hold effect reduces the dynamic resolution, which becomes visible as blurred edges in moving objects. 1 Already some years ago, Kurita and his colleagues 2 explained motion blur as the result of smooth-pursuit eye tracking and temporal integra- tion of the light at the retina. To evaluate, quantify, and reduce this artifact, four methods are proposed: (1) direct visual judgment with specific moving test patterns, (2) a time-based image integration system, 3,4 (3) pursuit-camera methods, 5 and (4) moving-picture simulation. 6,7 A recent study 8 shows that both the pursuit-camera method and the simulation method produce similar results, where the latter is judged to be more accurate. Until now, these methods mainly concentrate on characterizing LCD motion blur for achromatic images. Next to motion blur in black-and-white (B&W) patterns, an additional motion artifact appearing in LCDs is the occurrence of wrongly colored edges, also referred to as chromatic aberration. In the VESA FPDM standard, motion-induced chromatic aberration is defined as a motion artifact, in which the blur region appears to contain anoma- lous colors which are not part of the blend between the mov- ing color and the reference background. 9 Some traits and considerations are included in this standard, but a full understanding and characterization of this artifact is still lacking. Some attempts to characterize it with the pursuit- camera system can be found in Ref. 10, but the correlation between the obtained results with this system and percep- tion is reported as their subject for further research. In our earlier publications, 11–13 a system is described that accurately measures the LCD temporal response curves for several luminance transitions, and from these curves calculates the apparent image, for a given motion speed, with a model that includes the assumptions of smooth-pursuit eye tracking and temporal light integration (temporal low-pass filter, which is implemented by averag- ing over a frame time). The model is designed for, and vali- dated with, achromatic images, and perceptual experiments show a good correspondence between the apparent image, obtained via the model, and the image, perceived during actual motion. In the case of chromatic objects, moving over a differently colored background, chromatic aberration may be perceived. This phenomenon is analyzed and charac- terized using the same measurement system and model described in our previous publications. 11–13 However, in this case the temporal step responses of the luminance tran- sitions need to be measured for each of the primary colors [red (R), green (G), and blue (B)] individually, instead of for the combination R = G = B in the achromatic case. Slight Extended revised version of a paper presented at the SID Symposium, Seminar & Exhibition (SID ‘07) held in Long Beach, California, May 20–25, 2007. K. Teunissen is with Philips Consumer Electronics, Innovation Laboratory, High Tech Campus 37, HTC37 (WY) 8.010, Eindhoven, Noord Brabant 5656AE, Netherlands; telephone +31-653-938-847, kees.teunissen@philips.com. X. Li and L. Chai are with Southeast University, Nanjing, P. R. China. I. Heynderickx is with Philips Research Laboratories and the Technical University Delft, The Netherlands. © Copyright 2007 Society for Information Display 1071-0922/07/1512-1065$1.00 Journal of the SID 15/12, 2007 1065