Measurement and characterization of the halo effect for mini-LED backlit LCDs

The continuous upgrading of partition backlight technology has brought new competitive advantages to LCD, making it comparable to OLED in display performance, such as high contrast. Because the LCD does not have an ideal turn-off characteristic, there will be a halo phenomenon when local dimming is turned on. Due to the low luminance value of the halo and glare interference of the luminance meter, the actual light distribution is difficult to measure, so previous studies on halo effect characterization were mostly based on simulation or qualitative analysis. This paper first gives a method to accurately measure the halo distribution by using a mask to cover the center luminous region to avoid glare interference generated by the normal luminance meter. Based on the measured halo distribution and its correlation with the subjective assessment on halo visibility, a halo visibility estimation model was established, which quantifies the impact of display luminance, panel transmittance, and backlight unit (BLU) size. The predicted value of this model was highly correlated with the subjective experiment data, with a good fit of R²=0.92. With this model, the halo visibility with any combination of panel sizes, initial contrast ratios, and BLU numbers can be easily calculated.