I noticed that there were several posts on building a sewing machine stitch regulator.I am modifying a standard sewing machine to convert it into a machine for free motion quilting, I will use a led mouse sensor to measure fabric displacement and apply a stitch. My goal is to allow the machine to stitch at a slow enough rate that my wife can move the fabric and still have uniform stitch spacing. I noticed that there are previous posts on the topic and am wondering how successful the authors were. Also, any info on interfacing a led mouse with ARDUINO?
http://code.google.com/p/arducopter/wiki/AC2_OptFlow
You'll have some luck with Google if you use the term "optical flow".
Never used one myself -- just know they're out there.