Pico projectors are tiny battery powered projectors - as small as a mobile phone - or even smaller: these projectors can even be embedded inside phones or digital cameras.
A Philips pico-projector
Pico-projectors are small, but they can show large displays (sometimes up to 100"). While great for mobility and content sharing, pico-projectors offer low brightness and resolution compared to larger projectors. It is a new innovation, but pico-projectors are already selling at a rate of about a million units a year (in 2010), and the market is expected to continue growing quickly.
How do pico projectors work?
There are several companies developing and producing pico projectors, and there are 3 major technologies: DLP, LCoS and Laser-Beam-Steering (LBS).
DLP and LCoS use a white light source, and some sort of filtering technique to create a different brightness and color on each pixel:
- DLP (Digital Light Processing) - pioneered by TI, the idea behind DLP is to use tiny mirrors on a chip that direct the light. Each mirror controls the amount of light each pixel on the target picture gets (the mirror has two states, on and off. It refreshes many times in a second - and if 50% of the times it is on, then the pixel appears at 50% the brightness). Color is achieved by a using a color wheel between the light source and the mirrors - this splits the light in red/green/blue, and each mirror controls all thee light beams for its designated pixel.
- LCoS (Liquid Crystal on Silicon): an LCoS projector uses a small liquid-crystal display (LCD) to control how much light each pixel gets. There are two basic designs to get color: Color-Filter (CF-LCoS) which uses 3 subpixels, each with its own color (RGB) and a Field-Sequential-Color (FSC) which uses a faster LCD with a color filter - so you split the image for the 3 main colors (RGB) sequentially and you refresh the LCD 3 times (once for each color). The light source for the LCoS can be LED or diffused laser.
Pico projector module
Laser-Beam-Steering (LBS) projectors are different, creating the image one pixel at a time, using a directed laser beam. You start with 3 different lasers (Red/Green/Blue), each at its required brightness, which are combined using optics, and guided using a mirror (or two mirrors in some designs). If you scan the image fast enough (usually at over 60Hz), you do not notice this pixel-by-pixel design.
Microvision is currently the only company with commercialized LBS projectors, offering both stand alone projectors (the Show WX Plus) and embeddable modules. There are several other companies developing their own LBS modules, and we expect them to be commercialized within a year or two. There are several theoretical advantages to LBS over DLP and LCoS:
- Focus free - the image is always focused, even on curved surfaces. A laser-based LCoS is also focus-free, by the way
- Low power consumption - especially since pixels that are darker require less energy, and a 'black' pixel requires no energy at all
- Small size
There are some disadvantages to lasers, though:
- Laser is expensive
- Speckle: a random intensity pattern produced by the mutual interference of a set of wavefronts. It basically means that there are shiny black dots visible all over the image, (it's mostly on static images, videos suffer much less). You can see the speckle dots with any laser-pointer as well.
- Eye-safety concerns
Currently the major problem with laser projectors is the fact that there is no commercial 'direct' green laser, and so companies has to use the expensive, in-efficient and bulky frequency-doubled green laser. Direct green lasers are expected by 2011-2012 and these should help bring the price, size and power consumption down.
Another method to create a pico-projector is called Holographic Laser Projection - in which a hologram is used to diffract a laser. This is explained here.
There are 4 basic types of pico projectors:
- Stand-alone: these receive the input via a cable (A/V, USB, etc) and cannot display anything unless you use another device to stream the video signal.
- USB projector: stand alone projectors that use USB for both power and data, and so require a laptop (or tablet). They are the smallest projectors as they do not include a battery.
- Media-player: projectors that include on-board memory (or a memory-card slot) and can play files directly from the memory (usually photos, videos and sometimes office documents too). This is really useful for some people, but file format support and lack of convenient controls sometimes make media player projectors less useful then they could have been.
- Embedded projector: in this case the light-engine is embedded inside a mobile device such as a phone, camera, laptop, tablet or PDA.
What's on the market today?
There are many pico projectors already available - from companies such as 3M, Philips, Samsung, Optoma, AAXA and Aiptek - ranging in price from $99 to about $400, depending on features and brand. You can read our buyer's guide and use our tools to find the best projector for you.
Embedded projectors are also starting to appear - projector-phones from Samsung, LG and others, projector cameras, camcorders and other devices.
Samsung projector phone