Introduction to Pico Projectors

Pico projectors are tiny projectors - so small that they are the size of a small cellphone. Indeed the projectors can even be embedded inside mobile devices such as phones, cameras or video players.

3M Micro Professional Projector

These players are small, can show large displays (sometimes up to 100"). Usually, as with most projectors, they require a dark room.

There are already several such products available on the market, and Samsung already showed their first phone that includes such a projector inside.

How do pico projectors work?

There are several companies making these tiny 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) - this technology is pioneered by TI. The idea is to use a light source and tiny mirrors 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 pixel.
• LCoS (Liquid Crysal on Silicon): an LCoS projector is rather similar to a DLP, but it uses liquid-crystal to control how much light each pixel gets, instead of mirrors. To achieve color, we place 3 different chips, one for each color (RGB), and direct the light beam through filters or using dichroic mirrors (that only allow certain wavelengths to pass through). The light source can be a LED, or a diffused laser.

Laser-Beam-Steering (LBS) projectors are different. The create the image one pixel at a time. You start with 3 different laser beams (Red/Green/Blue), each at its required brightness, you combine them using optics, and guide them 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.

LBS projection is a new technology, and we're still waiting for the first such projector to hit the market (which will probably be Microvision's Show WX, which started shipping to distributors in September 2009) There are several advantages to LBS over DLP and LCoS:

• No need to focus - the image is always focused, even on curved surfaces. If you use a laser to light an LCoS projector, it doesn't need focus either, by the way.
• Image is brighter, and it's possible to get a better resolution
• Power consumption is lower (especially since pixels that are darker require less energy, and a 'black' pixel requires no energy at all)
• Overall size of the projector module is smaller

There are some disadvantages to lasers, obviously:

• Higher price
• Some people are concerned with eye-safety
• Speckle. Speckle is 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.

Here's a photo showing the difference in image quality between an LCoS projector and a laser one (from bTendo):

Laser (right) and LCoS (left)

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.

Pico-Projector types

There are 3 basic types of pico projectors:

• Stand-alone: These are devices that are essentially just a projector. They receive the input via a cable (A/V, USB, etc) and cannot display anything unless you use another device to stream the video signal.
• Media-player: These projectors also include on-board memory (or a memory-card slot) and can play files directly from the memory. Obviously the projector needs to support the file type you want to view, whether it is photos, videos or audio files. Some projectors even support office documents and other types.
• Embedded projector: in this case the light-engine is added to an existing product (mobile phone, camera, laptop, PDA, etc.) as an accessory. 

What's on the market today?

There are many pico projectos already available - from companies such as 3M, Samsung, Optoma, AAXA and Aiptek. You can check our on-line store for prices and details. Many more devices are also coming soon.

Samsung has announced the world's first projector-phone, and Nikon is the first to offer a Projector-Camera, the CoolPix S1000pj (available now). In the near future we are likely to hear of more and more such embedded projectors in phones, cameras, laptops, etc.

Samsung show