Projectors (beamers) allow an image to be produced of almost any size usually from 20″ – 300″. The differences between the different models are important in what you look for if you are trying to choose a certain projector:
Lumen Rating (Brightness):
This rating tells how bright the projector will be. Most projectors are between 1000-3000 lumen. The larger the number the brighter the image will be. There are also settings on most projectors to turn the bulb on econo mode, which dims the brightness, but adds more life to the bulb, which need to be replaced when it reaches the end of its life. Pico projectors which are becoming popular now have very low lumen rating, usually a couple hundred lumen. This means that in a room that is not totally or nearly dark, the image will be hard to make out. The lumen rating is important when you are designing your table for certain environments, where the image will need to be brighter than the ambient light so that it can be well seen.
This number tells how well the optics inside the projector are at throwing an image at a certain distance. Useful tools to use with this are projection calculators and image-mirror tools which calculate the final image after the image from a projector is reflected or “bent” by mirrors. There are projectors known as Short Throw Projectors which are able to produce larger images at a closer distance which are popular in building smaller multi-touch setups, though usually more expensive.
The resolution for projectors is just like TV and computer monitors. Standard Definition (SD) is the lowest resolution and is not HD. An example of SD resolution is 800×600. High Definition (HD) resolution is a much better image: 720p is anything that has a 720 or 768 in the last number. So for example, 1280×720, 1280×768, 1024×720, 1024×768 are all 720p HD resolution; 1080i (or 1080p) is anything that has a 1080 or higher as the last number. So for example, 1920×1080 and 1900×1200 are both capable of 1080 HD resolution.
There are two formats for resolution: they are 4:3 (which I call “square”) and 16:9 (which I call “rectangle”). When deciding on a projector the native resolution is important because that is the resolution that will give you the truest quality. For instance if your native resolution is 800×600, but it has the ability to go up to 1280×768, you would be enlarging the pixels and creating a simulated HD image. Simulated since the pixels wont really be creating an HD image due to the enlarged pixels, and you may get noticable pixelation in fast video/animations. For most people working on multitouch tables, they usually get low-end 800×600 projectors since they are cheaper and easier to find. The low resolution is usually fine for most basic animations that arnt coded for HD screens. The problem with the low resoltion projectors though is that the above categories like throw ratio and lumen aren’t usually very good.
When buying a projector, I look at the spec sheets for the above things, and then I figure out the limitations in the image size due to the throw ratio on the projector by using a projection calculator. Then I go look at as many reviews as I can, noting little things like db rating (how loud the projector is when on) and over all quality of the image.
Playstation 3 Eye Webcam(New Weapon)
The PS3 Eye Web camera was built to be used only on the Playstation 3 System, but thanks to AlexP from the NUI Group forums, it is now able to be used on computer systems.
- Very inexpensive. Retails for $40 USD, but can be found for cheaper at places like Amazon.com
- Capable of 320×240 resolution at 125fps, and 640×480 resolution at 75fps.
- Easily able to take the camera apart and remove/insert neccessary filters
- Uses the USB port, which is more common than the Firewire port used on more expensive camera
Infrared Light Sources
Single through-hole LEDs are a cheap and easy to create LED frames when making FTIR, DSI, and LED-LP MT setups. They require a knowledge in soldering and a little electrical wiring when constructing. LED calculators like here and here make it easy for people to figure out how to wire the LEDs up.The most common through-hole IR LED used are the OSRAM SFH 485 P.
If you are trying to make a LCD FTIR, you will need brighter than normal IR LEDs, so these are probably your best bet.
The easiest solution for making LED frames instead of soldering a ton of through-hole LEDs, LED ribbons are FFC cables with surface mount IR LEDs already soldered on them as seen here. They come with an adhesive side that can be stuck into a frame and wrapped around a piece of acrylic with a continuous LED ribbon. All that is required is wrap and plug the ribbon into the power adapter and done.The best quality ribbons can be found at environmentallights.com.
When making Rear DI or Front DI setups, pre-built IR emitters are much easier than soldering a ton of single through-hole LEDs together. For most Rear DI setups, 4 of these are usually all that is needed to completely cover the insides of the box. By buying the grouped LEDs, you will have to ellimate “hot spot” IR blobs caused by the emitters by bouncing the IR light off the sides and floor of the enclosed box.
Infrared lasers are an easy and usually inexpensive way to create a MT setup using the LLP method.
Most setups go with 2-4 lasers, postioned on the corners of the touch surface.The laser wattage power rating (mW,W) is related to the brightness of the laser, so the more power the brighter the IR plane will be.The common wavelenght to use is 780nm and 940nm as those are the wavelengths available on the Aixiz.com website where most people buy their laser modules.
Laser modules need to have line lenses on them to create a light plane. The 120 degree line lens is usually the common one used.
You can check out the data sheet on an Aixiz 780nm laser
*Safety when using lasers of any power is important, so excersize common sense and be mindful of where the laser beams are traveling
Buying acrylic depends on the MT setup that you are trying to make. Acrylic is usually favored over lexan and plexiglass.
- 8-10mm thick optically clear acrylic
8-10mm thick Endlighten or similar composition acrylic. Endlighten acrylic has mirror-like particles suspended throughout to frustrate the light over the whole surface. Below are three pdfs on explaining about Endlighen acrylic.