As your cellphone allows you to capture high-resolution pictures and videos, there arises the need for a big screen to show them.Don't worry, with miniaturisation in projection technologies and optics, you can now carry in your pocket a screen as big as 127 cm (60 inches).The built-in projectors of cellphones allow you to project large images directly from your phone.This is a great way of sharing and enjoying digital content.

At last year's Consumer Electronics Show (CES), Texas Instruments (TI) had demonstrated digital light processing (DLP) based pico projector chips. This year's CES in January saw Samsung's W7900 has an inbuilt DLP projector chipset, while LG's eXpo has an add-on pico-projector.Both the phones project images with resolution of 480 x 320 pixels.

Mobile World Congress (MWC) experienced more flavours of micro-projection technologies that can be built into the cellphones.Samsung's Android operating system based Beam or I8520 Halo was one of the highlights.It uses TI's latest pico-projector chipset to give off an 800 x 600 projection with 10 lumens of brightness.

Moble projection technologies

Innovations in semiconductor technologies and optical electronics, and their integration in mobile devices to render large-screen experience, have started gaining attention from the manufacturers.

Projection requires a combination of several different technologies, ranging from scanning the image to translating it onto a big screen, so every player has something different to offer.

Microvision's PicoP uses a single micro-electromechanical system (MEMS) based light-scanning platform with coloured laser diodes for displaying the image.This system uses optimal power as the intensity of each laser diode-red,green and blue-is adjusted to the requirement of every pixel.

In contrast to Microvision's single MEMS, TI's DLP uses anarray of millions of MEMS sensors.For every pixel , a corresponding MEMS mirror acts as a switch to turn the pixel 'on' and 'off'.This results in extremely high quality of the image.TI's DLP technology is known for giving a high contrast, fast switching and high optical efficiency .

Liquid-Crystal-on-Silicon (LCos) technology from Light Blue Optics uses an innovative approach to projection with its miniature light engines.By using an algorithm, its holographic laser projection method converts the image into diffracted patterns or holograms that are displaed on the LCos microdisplay.As the holograms are illuminated by coherent red,green and blue sources of laser light, a 2-D image is formed.This technique requires no moving part or projection lens, and is therefore suitable for miniaturisation.

Some Projector Phones Available Today

• Samsung Show W7900 in Korea and i7410 in Europe
• Samsung i8520 Halo (uses a DLP projector running on Android OS)
• Samsung W9600 (uses TI's new WVGA DLP chip)
• LG eXpo (with a pico-projector 'add-on')