It is not uncommon to calculate very high required display luminances on the order of 3000cd/m2 out of the TFT for dead-front touch-lens systems. This value is much larger than typical automotive TFT luminances of 500-850cd/m2 that do not have a “dead front” neutral density lens in front of the TFT. The luminance reduction of the display at center stack viewing angles also needs to be considered for different backlight brightness enhancement film configurations. By considering thermal maintenance from a system level, high luminance 3000 cd/m2 displays can be achieved, which dissipate approximately 20 Watts of backlight power for an 8” TFT.
Predictive Display Visibility Analysis:
Once the total reflected background luminance is determined, the required display luminance can be estimated using historical human factor studies. The required display luminance is a straight visibility line on a log-log plot. Figure 14 shows how various film configurations may be studied to determine the best solution to stay above the visibility line. This solution can then be used for a cost-driven optimized system.
Summary
The conflict between the aesthetics of a dead-front curved touch lens, display visibility need, and the functional aspects of the display interface create a dynamic new area of development for the automotive supplier. To be productive in this space will require the ability to assess optical performance and develop the best system solution.
References:
[1] Weindorf, P., Hayden, B., 3.4 Anti-glare Film Sharpness Measurement Investigations, SID 2012 Vehicle Displays and Interfaces Symposium Digest of Technical Papers.
[2] Information Display Measurements Standard, Version 1.03