I’m interested in scanning some old books in microfilm format (and later, on microfiche cards with an XY platform) for OCR/preservation at Project Gutenberg. It’s generally stored on small reels, 35mm (sometimes 16mm), usually unperforated, usually black and white. Material generally has significant space between pages, but the spacing is not super consistent, and it often doesn’t fill the frame. Eventual target is 300-600 DPI equivalent.
I’ve been planning this off and on for years; I have a CHDK-compatible 20MP compact camera (which should enable inexpensive raw usb tethered capture), a raspberry pi to run the capture interface (CHDKPTP), and a basic arduino/ramps control system for motion control. I am looking to do some initial feasibility tests in the next month or two; determine if the camera’s macro capability is sufficient, or if I need additional optics/z-axis control.
My current plan is to use a stepper on the take up reel, and a standard DC motor on an H-bridge for tensioning / rewind on the supply reel. Optical encoder wheel on the first spindle to measure linear velocity as the take up reel fills. Start/stop operation for initial design, but may be possible to move to continuous later. I have a 10W white COB LED for backlight (will need to print a diffuser).
Any comments? Am I reinventing the wheel unnecessarily? The kinograph film transport looks quite useful, but my resolution target is much higher.