use appropriate filters like a PDI filter, it will be able to recognize the black lines a lot more accurately. If not then make the ambient light really strong so that the reflection of your sensor is less apparent.
do you hav the download file for the soduko solver still cuz i need it i cnt figure out how to program it if you do contact me @ Chikara.power@yahoo.com
Ya. Figuring out where each number goes is the easy part. The hard part is reading (and recognizing) all of the starting numbers and writing your answers, translating the physical location on the the paper to a block on a puzzle, etc... Any code monkey could write code to figure out the answer.
This is really some interesting stuff, but what prooves me that the robot hasn't been "preprogrammed" before to just rewrite the numbers wich have been solved by human?