William,

sorry for answering late, I think that you are looking for a very simple
phototransistor reader focused at 25mm or so (or at infinity, with a
narrow beam), fixed-mounted to an inclined table (inclined in 2
dimensions). You put the book on, it slides to the guide edge, down across
the phototransistor following it, and stops on the other side. Very
economical ;-)

Peter

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