1. It depends how big the code is. It needs to be able to clearly make out the whole code. I find mine is best with the code is around 1/8th size of the video window.

2. Yes but the camera will need them far enough apart so it knows which to track. If it detects two at once then you will run in to recognition problems.

3. Yes, upside down, 90 degrees either way all work

Thanks for the feedback Rich , impeccable as always. I will print some examples. Any suggestions to fashion a "zoom" ?

I think lighting would be more important, if it can see it clearly then size probably is less of an issue. I just tested a couple out and at 2m away in my dim living room it could just about read them (they were about 3 inch by 3 inch in size though).

Stick them to some plexi, stuff a few LEDs behind, let the white paper diffuse the light and the black ink of the QR code should block it. The camera should pick it up very easily (and it could be passed off as some artistic form of ceiling light).

This is a neat idea! you could use it to tell the rob ot if it is in a certain room and then open a floor map file to tell it where to go.

Using discrete placement of QR Codes was mentioned in the topic on automatic charging and autonomous finding of the charging dock as a means of navigation however it wasn't in too much detail for reasons that are apparent if you read that topic. I have a few ideas scribbled down in one of my many notebooks somewhere which I'll try and dig out when I get chance (now that the idea wont be argued and belittled immediately).

@Josh, if it's for navigation, you could always use an IR beacon based system (northstar) like the rovio uses if QR isn't going to cut it.

Josh this sounds like a neat idea. I have been searching a long time for the best method of room ID. I want something simple that does not require a ton of complex programing. Lighting at or near the ceiling would however be a problem in my house. I very much hope your plans are successful. Would it be helpful if the QR code was in some way IR reflective? Then use an IR spotlight to shine up at the ceiling. Would the camera then see a crisp image of the QR code? Just throwing this out there. Don't know if the camera would pick this up the way I am thinking. The spot light may just cause the image to be washed out. Anyone know?

I am still planning on pursuing the IR beacon method to help my bot find its way to the charger. One of my Christmas presents arrived yesterday. It is the Pololu IR Beacon Transceiver Pair. Claims to have a 15ft range. Looks promising.

IR Beacon

Greetings all! Sometimes crazy ideas from out of no where will add a fresh perspective. the answer may be underneath your feet! Josh, maybe you have already thought about placing the QR on the !floor! and having the camera pointed down. The QR may then be very small and perhaps no bigger then a stamp . Just my 2 canadian cents worth!

First Robotics uses Retro Reflective Tape to mark targets and for line tracking on the floor to get high contrast images.

http://www.3m.com/product/information/Scotch-Reflective-Tape.html

If you can't get enough contrast from light in the room, try putting a light source near the camera on the robot and using retro reflective tape on the white areas of the QR Code. The tape should allow you to light up the QR code when needed and not need exceptionally bright room lighting. The light source must be near the camera lens. First Robotics recommends a ring around the camera lens. Haven't tried it with QR Codes, but the retro reflective tape lights up targets from a good 15 to 20 feet away with 10 or so Ultrabright narrow angle LEDs in a ring around the camera lens.