Flicker refers to the continuous alternating on and off of the screen. Although we may not be aware of flickering, physiologically the eye still responds to flickering, and the iris expands and contracts in response to changes in brightness. This involuntary physiological response can explain the cause of headaches, especially after prolonged viewing of the screen. The eyes will feel tired because the eyes have been working hard. This is especially true when viewing the screen in a dark environment.
The reason for the flickering
Unfortunately, flickering on mobile phone screens (especially screens OLED) is still a problem for many users. So, why is the smartphone screen flickering? Smartphone display equipment is based on LCD (liquid crystal display) or OLED (organic light emitting diode) technology. The LCD display itself does not emit light, but uses a very bright LED as a source of illumination. This compensates for the decrease in brightness caused by the low transmittance of the LCD panel (mainly caused by the RGB color filter). In contrast, in an OLED screen, each pixel is itself an OLED that can emit light by itself.
As we all know, smartphone screens are made of diodes (OLED, or LEDs of LCD screens). Due to the inherent physical characteristics of the diode, ie when the LED is dimmed by a change in current (mA), it will definitely affect the color of the LED. Therefore, to darken the screen, smartphone manufacturers use a technique called pulse width modulation (PWM) to turn the LEDs on and off with different pulse rates. However, we usually don't see the LED switching between on/off (in other words, flickering). In general, we only experience blackout of the screen. The degree of dimming depends on the duration of turning off and on the LED. The longer the shutdown time, the darker the screen will appear.
Therefore, although LCD screens and OLED screens have different methods of powering light sources, both technologies will have flickering effect. However, the flickering effect of OLED screens is generally more pronounced than that of LCD displays. First of all, the frequency range of an OLED display and an LCD display are different. The PWM frequency range of an OLED screen is ~ 50 ~ 500 Hz, while an LCD starts at around 1000 Hz or higher. Second, since the human eye is sensitive to flickering up to 250 Hz (at least for most people), it's no surprise that OLED displays are more likely to cause eye strain than LCD displays.
