"with this I presume that Leo already has the binary string (the correct one I mean) and its only a matter of converting it"

I have already queried this:
http://www.8052.com/forum/read.phtml?id=54593
no reply yet! :-(

It is unclear what he means by "the binary string:"
If he means that it gives a '1' while it's "seeing" white, and a '0' while it's "seing" black then, as Craig just said, it is not a trivial matter to convert this to thick & thin bars & spaces - because of the speed variation problem.

Once you have got to the thick & thin bars & spaces, and understood the required symbology, decoding the text/number string is not difficult.