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Why Do OLED Screens Require Higher Resolution?

Jun 22, 2018

With the rapid development of the smart phone industry, OLED screens have moved to the center of the historical stage. Currently, most of the flagship smart phones on the market use OLEDs, including but not limited to iPhone X, Samsung S9+ Huawei Mate 10 Pro, etc. Its thin and colorful features make it the flagship of choice.

However, we will often hear a word, that is, OLED has a grainy (or jagged) sense, especially the screen resolution with a resolution of about 1080P will be more apparent, as the saying goes, no 2K is not A screen, then why AMOLED screen Need a higher resolution?

Why do AMOLED screens require higher resolution? In fact, we must start with the pixel arrangement. The traditional LCD screens use the RGB (red, green, blue) standard arrangement. The RGB three sub-pixels are the same regardless of their size or number. . For AMOLED, the Pentile diamond pixel arrangement is used. The number of green pixels is 2 times that of the red and blue pixels, that is, the RGBG arrangement. The single red and blue pixel area is larger than the green pixel.


Pentile array of red and blue pixels are arranged in a straight line at an angle of 45°, not horizontally vertical. When the screen pixel density PPI is not high, there will be a sawtooth sensation when displaying horizontal and vertical fonts or pictures, which is due to the red and blue The pixels are arranged in a straight line at an angle of 45°.


And if the RGB red, green and blue sub-pixels are displayed separately, you can find the OLED screen sub-pixel arrangement is not the same, the picture below is the OLED screen shot under the magnifying glass display three primary colors real shot map, you can see the RED red and The BLUE blue subpixels are diagonally aligned at a 45° angle, while the GREEN green pixels are horizontally and vertically arranged.


It can be seen from the above figure that the number of green pixels is 2 times that of red and blue pixels. This difference is the root cause of the inefficiency of OLED screens.

Here we must first mention the PPI (Pixels Per Inch) unit pixel density of the concept, the higher the PPI, the screen display more delicate, and the screen pixel density formula is PPI = √ (X ^ 2 + Y ^ 2) / Z ( X: number of length pixels; Y: number of width pixels; Z: screen size). Due to the special nature of the Pentile arrangement, the pixel density is also discounted to √(2/3), and √(2/3) is approximately 81.65%. This discount is due to the fact that the green pixel is twice as large as the red and blue pixels.

81.65% means that √ (2/3) is after the integrated green pixel point. When the picture color is relatively average, the graininess is in fact determined by the roughest part. Pentile is in the best case (the picture green is Main), PPI can be wireless near normal RGB array 100%, in extreme cases (red or blue-based, and red and blue light purple at the same time the three cases) PPI is 70.71%, which is √ 0.5.

In a word, the OLED screen is more sensitive to the resolution due to the Pentile arrangement. The LCD screen with the same resolution is more delicate than the OLED. The only solution to the OLED is to enhance the resolution. Rate, when the screen pixel density PPI reaches 450 or more, people will not feel a clear sense of sawtooth.