Starting to look into different ways for transport/sprocket detection and came across this patent. DE102009032943B4 - Flash film scanner with optical perforation detection - Google Patents
In the prior art, there are a few interesting methods for detecting including light reflection or light through (as the patent).
Was wondering if something like a capacitive or RF sensor would work. I have to confess I do not have the RF expertise to make something that small (looking to do it for Super 8 film). In any case, for frame-by-frame scanners, I think a good stepper driver like the TMC2208 with microsteps would provide the accuracy to eliminate the light sensor on the patent, and move the film off the stepper. Thoughts?