Does anyone know where you can find a cheap downward-facing optical flow sensor for measuring odometry on a general-purpose mobile robot?
I've read a few stories of people using hacked optical mice, but these don't usually work well since the lenses are designed to be used within a few millimeters of a very flat surface.
The paper Outdoor Downward-facing Optical Flow Odometry with Commodity Sensors uses this technique in an outdoor domain by using multiple optical mouse sensors fitted with custom lenses to work on varying terrain. However, I can't find anyone who's selling these sensors.
I've used OpenCV's optical flow code to effectively function as an optical mouse sensor using a commodity webcam. Has anyone tried this approach on a mobile robot, or are aware of any pitfalls? Are there alternative solutions?