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.