https://qooah.com/2012/07/29/%e6%9c%89%e5%82%b3%e8%81%9e%e6%8c%87-samsung-%e5%af%a6%e7%8f%be-350ppi-%e9%a1%af%e7%a4%ba%e6%8a%80%e8%a1%93%e8%ae%93-oled-%e5%aa%b2%e7%be%8e-retina/