Technology world

Small-Screen Technologies: Portable and Hand-held Devices

by techno world on 30/06/09 at 8:47 am

Two basic technologies exist in the world of portable and hand-held devices. While not common household phrases, organic light-emitting diodes (OLEDs) and interferometric modulator displays (iMoDs) are at the forefront of the applications in tiny devices we cannot live without.

Briefly, OLEDs are based on carbon-based semiconductors that emit photons when charged. They can be screen-printed so they are usable in flat, flexible applications. In 2007, Samsung came out with OLED technology “immediately useful for cellphones, portable media players and other devices that browse the web, per an article at Electronista
(http://www.electronista.com/articles/07/10/09/samsung.wide.handheld.oled/). In the last two years, this technology has continued to advance and it is believed that the market will soon reflect the newest research (http://www.eetindia.co.in/ART_8800515163_1800010_TA_23becaac.HTM#related_div) with India and China in the hundreds of millions each of mobile phone users.

In the iMoD world, a reflective membrane is suspended over a layer of thin-film electronics on a glass substrate. In the on position, a gap exists between the two. By passing a constant voltage through both membrane and electronics, the membrane reflects light. In the off position, the gap is closed. Counterintuitively, the voltage must actually increase to pull the membrane and the electronics together to close the gap. Because of this, these devices have limited lifetimes, however the technology may advance to the point where the problem will be solved with reflective displays like this.

These technologies as yet cannot compete in the big device worlds of plasma technology and LCDs, but perhaps the future will hold more in store for them. Plasma tv technology has some downsides — it’s power hungry, heavy, and has limited longevity. Contrast ratio, the difference between lit and unlit elements comprising the picture, can lose as much as 50% in five years, making the picture looked washed out. Plasma sets don’t work well at high altitudes, either, due to differences in the ambient pressure from their internal gases. LCDs on the other hand, while reliable work horses, house fluorescent tubes which age over time, and the color on the TV changes slightly. A new technology, called SED (surface-conduction electron-emitter display) is emerging on the horizon for big screen adaptation with Canon and Toshiba leading the way.

Whether big or small applications, the technologies of image reproduction are a fascinating thing to watch as it progresses.