Analytical equation for the motion picture response time of display devices

Abstract

Motion picture response time (MPRT) affects the image blurs of thin-film transistor (TFT) liquid crystal displays and organic light emitting diode (OLED) displays. We derive an analytical equation to correlate MPRT with the liquid crystal (LC)/OLED response time and TFT frame rate. Good agreement between our physical model and experimental results is obtained. Based on our model, we find that if the LC's response time is 2 ms or less, then its MPRT is nearly the same as that of OLED, even if OLED's response time is assumed to be 0. To achieve MPRT comparable to OLEDs, we developed an ultra-low viscosity LC mixture for the vertical alignment mode operation. The measured average gray-to-gray response time is 0.93 ms, and its MPRT at 120 Hz is 6.88 ms. In comparison, OLED's MPRT is 6.67 ms. To further shorten MPRT, we could either increase the frame rate or reduce the backlight duty ratio. Pros and cons of these approaches are discussed.