PWM dimming frequency
The PWM dimming frequency should be above 100Hz to avoid the LED flicker phenomenon observed by human eyes. When PWM dimming, set the maximum and minimum led average current as iled (MA) The maximum duty cycle and minimum duty cycle were respectively [) M. X、Dmin。
Eye injury caused by PWM dimming
PWM dimming the eye, this is a lot of people make complaints about things, but some people do not agree. When someone is perplexed and looks at the screen carefully, they feel that the PWM dimming screen is still OK, and will not feel the irritation of eye injury, and the human eye can not distinguish more than a certain frequency of light, so the conclusion of eye injury seems unreasonable.
In fact, eye injuries do not occur when you look at the screen carefully, but when your visual center shifts. When your visual focus moves on the screen, your eyes will receive such information:
The left side is PWM screen and the right side is non flashing screen
Where there should be dynamic blurring effect, clear outline violation information appears
And the image is still a dizzy overlap:
Images of dizziness
Take a look at the picture of PWM dimming
Moving the visual center is because the brain needs information from other places, and the violation generated in this process is covered up by the current processing of the brain. People often don’t pay attention to this, only feel that the eyes are getting tired during the whole process.
(the object of the eye injury in this article is the area of the brain that processes visual information. If you classify it as an eye, just like the hardware driver in a computer, the software can also be regarded as a part of the hardware. Therefore, the title map represents the visual processing area. And although blue light is considered to be a cause of eye injuries, most people’s discomfort is mainly caused by stroboscopic lighting after lowering the brightness)
How to avoid this kind of situation?
1. Try to keep the eyeball and screen not moving and turning relative (close the eyes when moving the eyes).
2. Reduce vision switching between screen and other objects. (this is also the reason why some people are tired of watching videos and taking notes, but watching subtitles (movies) is OK. PWM screen hinders human progress.
3. The most important thing is to change a screen that doesn’t flash and has low blue light.