Cameras
When looking for a camera to act as a sensor, be sure to check out the native resolution (sometimes measured in lines), the light sensitivity (measured in lux) and the type of lens mount (CS is best). In general, black and white cameras are best unless your application requires color. While there are cameras that are called "Infrared cameras", they really are just black and white cameras with built in IR LED's around the lens. Canal Alarm Devices is a great source for cameras and will match internet prices. also has a large number of cameras, many of which are their own brand. A good camera will cost between $50 and $150. Avoid webcams since they generally use low quality CCD's and they do automatic white balancing which cannot be disabled.
Lenses
Getting the right camera lens for your application is essential. In general, you should purchase a fixed focus, manual iris lens of a specific focal length. The manual iris will let you adjust light levels and works much better than the camera's built in white balancing. This page http://www.supercircuits.com/resources/tools/lens-calculator has a lens calculator that will help you figure out the focal length required given the distance of the camera to the surface and the size of the surface itself. Lower focal length means wider field of view. Always add at least 6" on all sides of the active surface when choosing a lens, since the calculations are not 100% accurate. Avoid zoom lens since they are more costly and are hard to lock down to a set focal length. http://www.supercircuits.com is a good place to find inexpensive lenses, though there are many websites that sell similar products.
Infrared-Pass Film
There are not a lot of options for infrared-pass films. I recommend Kodak's 87 Opaque Infrared Wratten 2 Optical Gel Filter. It comes in sheets from 3" x 3" to 12" x 12". Unfortunately, it's not cheap. A 3" x 3" piece costs about $70. The good news is that you only need a circle about 3/4" across per camera, so a 3" x 3" sheet can be cut up and shared by many people. The B&H online store http://www.bhphotovideo.com/ has this in stock and can deliver it quickly. In addition to these flexible films, there are solid discs and squares that can be purchased from the Edmund Optics website. These tend to be more expensive and harder to fit behind the lens.
Infrared Illuminators
Any incandescent lightbulb is a great source of infrared light. The problem is that it also puts out a lot of other frequencies of light as well, making for washed out projections. An infrared illuminator only emits infrared light. While in the past, IR illuminators were incandescent (they resembled french fry warmers), most new models are now based on LED technology. The best indicators of how much light a given illuminator emits are the amount of power they require and the number of LED's used. Also, consider the angle of illumination. Most LED's project a narrow beam (about 15 degrees) forward, but some illuminators claim to offer a wider angle than others. If your illuminator is producing too narrow a beam, just mount translucent film or paper to the front and the light will become far more diffuse. A good source for IR illuminators is , which is a security products website. There are several excellent and compact illuminators that cost between $50 and $100.
Translucent Surfaces for Under-Sensing
There are all kinds of translucent films and surfaces but it's hard to find ones that diffuse light in a way that works well for diffuse illumination. If you're just looking for shadows, almost any translucent surface will work just fine. But if you're looking for a material will work well for diffuse illumination or diffuse shadow techniques, consider the products below.
1/16" Translucent acrylic
This works quite well for under-sensing purposes, but is a pretty poor projection surface because the image is blurred by the thickness of the material. This is fine if you're dealing with abstract imagery or with a very large display, but does not work well for smaller displays that feature text or fine lines. This product is available at Canal Plastics or T & T Plastic Land and can be laser-cut to non-rectangular shapes if requested, though this is expensive. Please remember that plastic does not biodegrade and will be around for 10,000 years after your midterm project.
Cromatica Translucent Vellum in White
This is actually a translucent paper that works very well for under-sensing and acts as a very good rear-projection surface. It's also quite cheap. Unfortunately, it only comes in 25" x 38" sheets, so you may need to tile it for a larger display. Also, you will probably need a clear surface to support it such as glass or plastic. This product is available at the single-sheet paper counter at Pearl Paint.
3mm or 5mm Drafting Film
This is a very thin plastic film that works somewhat well for under-sensing, though it does not diffuse as much as the options above. It does serve as a very good rear-projection surface and is relatively cheap. It is available by the yard at Canal Plastics.
General Hardware
The best source for hard-to-find parts and materials is the McMaster-Carr website, http://www.mcmaster.com. If they don't have it, there's a good chance it doesn't exit. Their prices are very reasonable and almost all deliveries arrive the next day even when ground freight is selected,
