Day 3
Beginning with the Multitouch input
I purchased a Logitech QuickCam Communicate STX cheap from a local computer retailer and removed the IR Filter by prying the sides off the camera and unscrewing the body, unscrewing the lens assembly from the board and removing the small rectangular section of glass that had a red sheen and then reassembling the whole thing. I ordered a large 140 LED IR spotlight from Hong Kong and while I was waiting for delivery the next weekend rolled around... and I had seemingly little to do so I purchased two small 32 LED IR spotlight kits from Jaycar Electronics and assembled them to use for testing.
On the left we can see the IR LEDs in the remote which shows us that the camera is sensitive to IR. In the middle, after I have removed the IR filter we can see the improved pickup of IR light and on the right we can see the Visible Light filter blocking out the light from everything except the IR on the remote and from the Halogen down lights in the background.
I initially cut an IR filter from magnetic interior of a 3.5" floppy diskette (I had to borrow one of these... there were none in my house :) only to find with my test IR lights that it blocked too much IR light. I assumed that the spotlights weren't bright enough however after further investigation not only did I find that without the filter they lit up the entire screen but I also found that the camera in fact uses a CMOS sensor instead of a CCD sensor which is less sensitive to IR light and further to that in dark lighting conditions it has quite a lot of noise. Without an IR filter in place the camera more or less registered white over the entire picture and with it in place only the absolute faintest of reflections was visible with both spotlights focused on the one spot.
At this point I was going to get a roll of film and get it overexposed and developed however I decided that ultimately I may as well try and do the whole thing properly. I was quite happy with the output prototype and was sure that once the whole thing was running I would make a final version using shaped glass and a permanent frame. So I decided to take it head on and use the right equipment from the start, I managed to find a Philips SPC900NC CCD web camera which is designed for use in low light and is very popular among amateur astrologists for taking photos through telescopes because of this and the fact that it has an MR12x0.5 standard lens fitting. This meant that for my purposes I could simply buy a new lens with a visible light filter or at the very least one without an IR filter in place and proceed from there.
I purchased a clear 4.3mm lens with an MR12 fitting from an eBay store and a Long Pass light filter from another eBay store, the Long Pass light filter has a transmission rate of ~90% for all light of a wavelength greater than about 780nm.Since the light I wanted the camera to see was about 800nm onward (depending on what IR LEDs I ended up using) and visible light stops at the mid 700's then it would be perfect for the job.
While I was purchasing gear for this project I decided that I may as well order a graphics card for the computer that I had to hook up to the system and a new lamp for the projector which is at least 100 hours past the rated lifetime.
After the online spending spree and the obviousness that I would be waiting another weekend or two before being able to continue working on the project I pencilled out a few ideas for a final coffee table design and then mocked one up in Cinema 4D (now at the top of this page).
I played around a little with the computer hooked up to the projector and webcam to get a feel for where the camera belongs, a few shots here for posterity.
The above was taken with the flash on and the screen is actually very bright as you will see in the next couple.
This one was taken with the flash off in a dark room.
This one was taken with my lighting on, each of those lights are 50w halogen down lights on at full brightness.