OPPO Shen Yiren: At present OLED “DC” dimming is not hardware DC dimming

OPPO will launch a new series of smartphones called Reno on April 10th. According to the official news, Reno will be equipped with Snapdragon 855 processor, using 10x hybrid optical zoom and 4065mAh battery. The combination. On March 24th, OPPO Vice President Shen Yiren said that the Reno new machine’s DC dimming has been arranged (can not catch up with the release software version, to ensure stability), but it must be displayed.

Today, OPPO Vice President continued on Weibo that the current OLED “DC” dimming is not hardware DC dimming, this is determined by the hardware itself, and the screen manufacturers are also developing how to implement real hardware on OLED. “DC” dimming. Now it’s a soft way to reduce the low-brightness strobe. OPPO did it, and it was also seen under high-speed cameras, but the principle is still clear.

As can be seen from the above, hardware DC dimming is the fundamental solution to the problem of screen flashing. Currently, it is software DC dimming.

What is DC dimming ?

According to the definition of CIE TN006-2016 of the International Lighting Association Technical Report, the flicker can be divided into three types: “flicker, flicker effect and phantom effect”. The latter two refer to the physical effects of the observed object and the observer moving respectively.

Different humans have great differences in sensitivity to stroboscopic, and even have the saying that “flashing sensitive physique”. The most sensitive frequency for humans is 8.8 Hz, which then continues to drop. Most people don’t see flicker after 80Hz, but even so, some people will feel tired and have pain in their eyes.

At present, the main focus of smart phones is DC dimming and PWM dimming.

LCD screens rely on LED backlights to illuminate. In the field of smart phones, LCD screens mostly use DC dimming. This is a technique to adjust the brightness by directly controlling the current on both sides of the LED. When the LED backlights are on both sides, the current is higher. Small, the lower the brightness.

DC dimming itself is a very straightforward method, but the disadvantages are also very obvious – due to the different wavelengths of the three primary colors, DC dimming can lead to inevitable color casts in extreme low brightness conditions, such as early DC modulation. The light LCD display, at low brightness, can cause significant color loss problems.

Unlike DC dimming, PWM dimming takes a clever approach. We all know that the switching light source will cause flickering. The faster the switch speed, the faster the screen flicker will be, but when the frequency of the switching light source exceeds the limit of the human eye, since the brightness information of all the pictures overlaps each other in the human eye, The speed of the frequency only affects the brightness of the screen. This technique of controlling the brightness by quickly switching the screen light source is called PWM dimming (pulse width modulation).

PWM dimming (pulse width modulation).

PWM dimming

PWM dimming

However, since PWM dimming is a technique for adjusting brightness by fast flickering, even if the human eye cannot perceive the change of the picture during the switching process, we will react to this phenomenon in our brains. Frequent flickering is easier on both sides of the eyes. The muscles cause fatigue, which stimulates the refractive system to link and accelerate the aging of vision.

Since all current Samsung AMOLED displays use 250Hz low-frequency PWM dimming technology, the lower the screen brightness, the lower the strobe rate, the greater the possibility that the human eye can perceive, so it is easier for sensitive people. Make an impact.

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