As part of my MEE program at Rice University I decided to take a Computer vision course that was centered largely around a course project. I told the professor that I didnt want my project to be tied up with wires at some workstation, rather a completely mobile embedded system. It added more work for me but it was well worth it. So lets talk about the hardware involved.
In order for structured light to work you need a light source. Resolution was sacrificed for the incredibly small form factor. The TI DLP Pico Projector will run you about $200, but its pretty cool. Heck if you dont have anything to take 3D pictures of you have a portable movie player at your disposal. Here are the specs.
- Resolution: HVGA [480 x 320]
- Brightness: 7 lumens
- Dimesions: 44 x 67 x 14 mm
- Low Power consumption (5V in)
- Sync signal output to camera (really fast refresh rate possible)
The Leopardboard 365 VGA Camera board is the only camera I could find at the time, that had the right hardware connector and available device drivers. Its only $28 for the module, but they nail you with a $20 shipping charge. The problem introduced with this camera is its short focal length of 1.34. With the camera and projector side by side, only 1/4 of the captured image is light from the projector, the rest is wasted space. We need to zoom in! Luckily photojojo makes small 2x telephoto lenses for cellphones that attach with a magnetic base. I rigged up a mount to our camera board by hotgluing a thick metal washer around the camera module.
This was actually a last minute find and the guys at photojojo expressed it over faster than advertised. Great Customer service!
I had been wanting to learn how to use the BeagleBoard since I first heard of it. Tapping into the world in linux in an embedded platfrom is very attractive. Once I figured out how to install the OS I felt right at home and Ill discuss that process in the next post, but for now lets look at the important hardware features for this project. The camera header has 34 pins and mates with the aforementioned camera. The pico projector will use the available HDMI header. We will need a 5v source to connect to the barrel jack.
In this build I actually used two separate USB battery packs, one for the BeagleBoard and the other for the Pico. The two battery approach was a combination of what was available and kept the BeagleBoard from reseting when the projector was turned on. A proper battery could have been selected that would have enough source current to supply both devices simultaneously. As is the system will run for just under two hours with the projector and beagle board running.