Aimed at solving the problem of how to get a big picture out of a small device, micro-projectors cast a large image (typically about 125 centimeters wide) onto a nearby wall or surface to show photos, documents, maps, or video. Several micro-projectors are now available (see reviews of three on the next page), and forthcoming technology will allow the devices to be squeezed into the latest cell phones.

The first projector-equipped cell phone may be shown off by Samsung later this year at the Consumer Electronics Show in Las Vegas. But like existing micro-projectors, it is expected to employ a traditional optics-based approach. This involves using a white light source, image reflectors known as liquid crystal on silicon (LCoS), and a lens system that focuses the image.

While this approach works well enough, it carries with it the limitations of traditional projectors: it requires darkened lighting conditions, and the image needs focusing.

Later this year, Microvision, based in Redmond, WA, plans to launch a laser-based micro-projector. Using solid-state lasers and MEMS-based mirrors allows the technology to be miniaturized further. Laser projectors also promise to deliver more-vibrant and -colorful images. Microvision’s micro-projector can also refocus automatically.

A slightly different approach, developed by Light Blue Optics, based in Cambridge, U.K., uses a technique called holographic projection. This should produce even brighter images because instead of using a process of selective reflection or filtering to generate an image, it employs holographic principles to steer light, so more light actually reaches the surface.

Light Blue Optics says that it will be possible to place the device flat and cast an image on the surface in front. The company is also developing technology to let the device sense when a user touches different parts of the projected image, turning the surface into a touch screen.

Aiptek V10+

This micro-projector works with a range of portable gadgets: cell phones, DVDs, and video cameras. It comes with speakers and two gigabytes of built-in memory, which can be extended up to eight gigabytes with its internal SD/MMC memory card slot. This allows images or a presentation to be loaded onto one single handheld device. The built-in memory allows a user to share content by recording it directly from another device while also projecting it. The V10+ supports AVI, ASF, MEPG4, and JPEG file formats and displays images with a resolution of 640 X 480.

3M MPro110

This projector is designed more for business users who don’t want to lug around a heavy projector. It’s particularly good for PowerPoint presentations and can cast a 125-centimeter image from just 1.2 meters away, with a resolution of 640 x 480. Unlike other micro-projectors, the MPro110 comes with its own miniature tripod, which is handy if you don’t want to balance the device on books or hold it. On the downside, it doesn’t come with speakers or an audio-out socket.

Adapt Pico Projector

The Pico Projector, made by Taipei-based Adapt, features a Video/VGA cable input and no speakers, so it also seems that it is aimed at professional or business users. Under the hood, however, the Pico packs more punch than its competitors, offering 17 lumens–the perceived intensity of light–compared with the 10 lumens offered by the other two projectors. As a result, the image appears much clearer in lighter conditions, or at least requires less-dark conditions for viewing. The Pico will display 125-centimeter-wide images at a 640 x 480 resolution, features one gigabyte of built-in memory, and will run for about an hour on its lithium-ion batteries.