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High Pixel Density

Pixel Density

Fineness of a display is expressed by pixel density (ppi = pixels per inch). On a high pixel density (= high definition) display, the pixels constituting the display are not recognizable. Therefore, images look clear and characters look smooth.

Comparison of picture quality (example)

Comparison of character font

Japanese font "shueitai"
http://www.dnp.co.jp/shueitai/ 別ウィンドウ

Low Temperature Poly-silicon

TFTs (= thin film transistors) used in a TFT LCD are made of silicon as semiconductor material. It is, however, very difficult to fabricate crystaline silicon onto glass, and only amorphous silicon (a-Si) could be fabricated in the past. Since electron’s mobility in a-Si is low to drive TFT fast, there are limitations to pixel density of displays.

In contrast, a low temperature poly-silicon (LTPS) TFT LCD, prepared by forming polycrystalline silicon on a glass substrate at relatively low temperatures, achieves high carrier mobility in TFT. Therefore, LTPS TFT LCD realizes a high resolution and high density display that cannot be achieved with a-Si by integrating part of the display drive circuitry on the glass substrate. JDI has developed LTPS displays, and has introduced one of the world’s highest density display prototypes.

Prototype of 651ppi high definition display
Screen size 2.3-inch (5.9cm) diagonal
Number of pixels 1280×800 (WXGA)
Resolution density 651ppi
Pixel pitch 39μm
Number of colors 16,777,216 colors

Closeup of display image