Toshiba has unveiled a prototype of a display which makes the iPhone's retina screen seem no big deal: a 6.1in LCD which offers a massive 498 pixels per inch resolution.

By contrast, Apple's existing 'retina display' - as used in the iPhone 4 and iPhone 4S smartphones - sits around the 326 pixels per inch mark, making Toshiba's compact creation the highest resolution display around.

The 6.1in LCD panel features a native resolution of 2560x1600, almost double that of the 1920p 'Full HD' standard used in HDTVs.

The prototype display, which uses a thin-film transistor technology for ease of production, promises a contrast ration of 1000:1, a 176-degree viewing angle, and support for a wide colour gamut up to 16.7 million colours.

The result? A screen which is pin-sharp, no matter how close you get to it.

The size of the prototype device suggests that Toshiba is going for an interesting market: had the screen been five inches or lower, a smartphone home would have been indicated; seven inches or above, a tablet.

At just over six inches, it seems likely that Toshiba's initial market will be eReader manufacturers looking to upgrade from electrophoretic displays to something capable of full-colour images and full-motion video.

With such a high resolution, it won't be long before the tablet and smartphone makers start demanding different sizes. With over four million pixels to drive, that's going to take some serious hardware - suggesting that we won't see such devices until quad-core ARM chips are the standard in the market.

Toshiba has yet to offer a clue as to when the prototype display might yield a production model.