Measuring Flicker in Display
Flicker in display is a phenomenon whereby visible fluttering in brightness can be seen on the screen of a display. The cause of flicker varies according to the type of display technology. Generally, a display screen refresh at regular time intervals. When there is no change in the light emission intensity during those intervals and frames as shown in figure 1, flicker does not occur. As seen in figure 2, if there is no light emission within each interval, or figure 3, when the intensity between frames varies, flicker occurs.
When light emission intensity fluctuates consistently between each frame, high-frequency flicker occurs. As this frequency is higher than our visible frequency, it is hardly noticeable. Some of the potential factors that cause fluctuation within frames are:
- No light emission during refresh
- Pulse-Width Modulation (PWM)
- Intensity control (low brightness) in organic EL (OLED) displays
- Leakage of light emitting circuit
For liquid-crystal display (LCD), flicker is caused by polarity reversal as they respond to both positive and negative voltages, hence, the polarity of image signal input to LCD is reversed on every frame (vertical synchronization period).
Flicker can be measured using the following two methods:
- Contrast Method – determine the ratio of AC to DC components to obtain flicker value
- JEITA Method – analyze the frequency component of the fluctuation and determine flicker from the ratio between DC and maximum AC components at up to 60hz.
When attempting to measure flicker, Konica Minolta Display Color Analyzer CA-410, capable of both the contrast and JEITA methods, would be helpful. The CA-410 series, with increased color accuracy and luminance range, is also capable of evaluating the luminance and chromaticity uniformity, white balance, color gamut, gamma and contrast ratio of today’s display technology with ease.
Interested to find out more about CA-410 or need help finding the right display measurement and testing solution? Contact us for a free consultation or product demonstration.