As a tinkerer let me tell you, that, had I been confronted with the problem, would probably have taken apart one of the old Logitech Scanman handheld scanners s

As a tinkerer let me tell you, that, had I been confronted with the problem, would probably have taken apart one of the old Logitech Scanman handheld scanners still collecting dust in my attic. A little bit of mechanical modification should do the trick. These are essentially line scan cameras and they come with a high resolution rotary encoder.