Three years ago tech geeks all over the world were awestruck when Apple (NASDAQ:AAPL) unveiled its high resolution “Retina” display boasting of a pixel density of 326 pixels per inch (ppi) for the iPhone 4.   Since then many other phone companies have come up with models that best that figure. Sony (NYSE:SNE) and HTC (TPE:2498) for example both have 5-inch 1080p smartphones with pixel densities of around 440 ppi.   Samsung however looks set to up the ante. According to a Digitimes report Samsung (PINK:SSNLF) is looking at eschewing the conventional side-by-side pixel layout and developing hexagon- and ...