Rohm is demonstrating a prototype full-colour OLED screen that's smaller than a fingernail, yet offers resolution of 320 pixels by 240 pixels, at this week's Ceatec exhibition.

The tiny display, which measures approximately 4mm by 3mm, is embedded in a prototype chip and is designed for use in a video-camera viewfinder, said Yasufumi Ueno, a Rohm spokesman.

Rohm OLEDThe full-colour image on the OLED display is barely visible to the naked eye and requires a magnifying glass to be seen clearly. Under a magnifying glass, the prototype screen showed a detailed image of a woman dressed in a kimono, standing outside a traditional Japanese home surrounded by trees with colourful autumn foliage. Plans to commercialise the prototype display are not yet confirmed, Ueno said.

The company is also developing a tiny OLED display with a resolution of 640 pixels by 480 pixels, but did not offer a date for when it will be ready.

OLED displays are produced using carbon-based materials that emit light when an electrical field is applied. They don't require a backlight, which makes them thinner than other displays. And they offer better colours and higher contrast than LCDs and other technologies.