Analysis of the impact of screen technology on eye protection, which should not be missed by heavy mobile phone users

As a heavy mobile phone user, eye swelling, eye pain, eye discomfort, and eye fatigue are almost unavoidable. Choosing a phone screen that has less impact on the eyes is a concern for many people. The frequently mentioned concepts in daily life include OLED screens, LCD screens, circularly polarized light, linearly polarized light LTPS、LTPO、 High frequency PWM dimming, DC like dimming, true color display, natural light simulation, and eye protection mode, etc. How they affect eye protection needs to be comprehensively judged from the perspectives of flicker, blue light, polarization processing, and backplate technology.

From the perspective of comprehensive eye protection, especially for people with flicker sensitivity, the ultimate way to protect their eyes is still to look less at their phones. If only sorted by screen technology, LCDs with full DC dimming are usually superior to high-quality OLEDs with high-frequency PWM or DC like dimming, while OLEDs with low-frequency PWM dimming, especially LTPO, often require more caution when working in low brightness and low-frequency regions.

The fundamental difference between OLED and LCD determines the different emphasis on eye protection. Each pixel of OLED emits self light, and when displaying black, the pixel can be completely turned off, resulting in extremely high contrast and theoretically more energy-efficient. But its controversy over eye protection mainly comes from flicker. The vast majority of OLEDs use PWM dimming at low brightness levels, adjusting brightness through rapid screen flickering. When the frequency is too low, such as 240Hz, although the human eye and brain cannot directly perceive it, the ciliary muscle will constantly tense and adjust, which may cause visual fatigue, dryness, and headaches. In terms of blue light, the peak wavelength of OLED blue light is usually slightly longer than LCD, with slightly lower energy, but the difference is not significant, and anti blue light measures are still needed. LCD adjusts brightness by changing the backlight current or voltage, usually using full range DC dimming, without flicker issues, and is more friendly to flicker sensitive individuals. Its pain points lie in backlight uniformity and blue light. LCD requires a backlight layer, and when displaying black, the backlight still lights up, which may cause light leakage. The peak energy of blue light from LED backlight sources may also be high, and some low-end screens may have more obvious blue light overflow. Long term viewing of LCD may also cause fatigue, but the main cause is usually not flicker, but blue light. Overall, LCD is usually superior to OLED in terms of flicker issues, while both require hardware or software filtering optimization for blue light issues.

LTPS and LTPO belong to backplane technologies and are closely related to dimming strategies. LTPS is a mature technology with high electron mobility and the ability to achieve high refresh rates, such as 120Hz. On OLEDs, it is typically tied to a fixed PWM dimming frequency, such as global 480Hz or 360Hz. LTPO is a newer technology with the biggest feature of supporting adaptive refresh rates ranging from 1Hz to 120Hz, which greatly saves energy. But the eye protection trap is also here. In order to maintain display and balance power consumption at extremely low refresh rates such as 1Hz, many LTPO screens significantly reduce the PWM dimming frequency at low brightness and low refresh rates, possibly dropping to 60Hz to 240Hz, entering the low-frequency flashing area that is more stimulating to the human eye. This is also the root of the claim that LTPO is more eye damaging. To be precise, LTPO technology itself does not necessarily harm the eyes, the real problem lies in the low-frequency PWM strategy adopted for power saving. LTPS technology is relatively stable, and high-frequency PWM is also easier to implement.

Circularly polarized light and linearly polarized light are mainly used for screen surface treatment processes and are not related to light source flicker. Linear polarized light is commonly found on ordinary screens and sunglasses, with a single direction of light vibration. When the screen rotates or the user wears polarized sunglasses, it is easy to cause the screen to turn black or color distortion. The vibration direction of circularly polarized light rotates in a spiral shape, which can effectively reduce the reflection and glare of ambient light on the screen, and is not affected by screen rotation or polarizing lenses, making viewing more comfortable and clearer under strong light. It can significantly reduce environmental light interference, alleviate the burden of eye adjustment caused by glare, and indirectly play a role in protecting the eyes. This is also the reason why high-end displays or privacy screens commonly use this technology.

There are currently two main methods for addressing the low-frequency PWM flicker issue in OLED: high-frequency PWM dimming and DC like dimming. High frequency PWM dimming significantly increases the frequency to higher than 1250Hz, such as 1440Hz, 1920Hz, or even 2880Hz. The higher the frequency, the harder it is for the human body to perceive flicker, which can effectively reduce visual fatigue of sensitive people. It is currently the preferred solution that balances display effect and eye protection. The disadvantage is that ultra-high frequency may cause slight power consumption increase. Class DC dimming, also known as analog DC dimming or low flicker mode, does not change the current to achieve pure DC at low brightness, but simulates brightness changes through pixel micro brightness or algorithm jitter. Essentially, it is still a very high-frequency PWM or mixed dimming. It can significantly reduce low-frequency flicker, which is helpful for sensitive users, but it may lead to uneven display under low brightness, such as cloth screen and color distortion. The optimization level of algorithms varies greatly among different manufacturers. For OLED screens, high-frequency PWM dimming is usually better than well optimized DC like dimming, which is significantly better than low-frequency PWM dimming.

If the degree of eye protection is comprehensively ranked, the top choice for eye protection is usually LCD screen phones or displays that use full DC dimming, hardware level low blue light technology such as TUV Rheinland certification, and undergo circularly polarized light treatment. High quality balanced selection refers to OLED screens that use high-frequency PWM dimming, above 1440Hz, or optimized DC like dimming, preferably non LTPO or LTPO models that do not reduce the frequency in the low-frequency range. A cautious choice is to use low-frequency PWM dimming, especially for OLED screens below 480Hz, especially those LTPO models that trigger extremely low frequency flicker at low brightness, such as 60Hz models.

For ordinary users, understanding their own sensitivity is important. If you experience eye strain and headaches when watching OLED screen phones, it is likely that you belong to the flicker sensitive population and should prioritize LCD or ultra-high frequency PWM OLED. Querying specific parameters is also crucial. Don't just look at OLED or LTPO, you must find out what Hertz the PWM dimming frequency of the model is and whether it changes under different brightness levels. Professional review websites or videos are important sources of information. Many phones provide anti flicker mode in developer options or display settings, which is usually achieved by enabling DC dimming and can be turned on if necessary. Usage habits are equally important. Avoid using your phone in extremely dark or bright environments, and avoid using your phone on moving vehicles. Turn on automatic brightness to match the screen brightness with the ambient light. Using night mode or dark themes can reduce white light stimulation. Follow the 20-20-20 rule, take regular breaks, and move your body after excessive eye use.

Eye protection is a systematic project, and screen technology is only a crucial part. At present, there is no perfect eye protection screen, only a technology combination that is more suitable for individual physique. For the vast majority of users, an OLED screen with high-frequency PWM dimming or a high-quality full DC dimming LCD screen, combined with good usage habits, can provide a relatively comfortable visual experience. It's better to personally experience the actual product than to look at the parameters and comparisons; It's better to feel the effects of different settings than to look at the settings and analysis. After one or two days, the experience of the eyes will not lie.