The lighting module must meet the following criteria:

It must evenly and uniformly illuminate the page surface.

It must have a white balance that can be easily calibrated.

It must not send light where things need to be dark.

It shouldn’t disturb or be disturbed by the presence of an operator.

It should not block access to any other part of the system.

Here are some fun images from when I was designing and prototyping the Archivist. The CAD modeling I did predicted the ideal illumination height to be about 46″ from the bottom of the scanner. In the end, it turned out to be 48″ due to some off-axis effects from the lenticular lenses. You can easily see that in this setup, where I moved an illumination source vertically and captured the glare problems it caused as it moved.

Although some of the information in these videos is a bit stale, this was the first instance (in 2011) of me systematically exploring lighting issues and trying to determine what effect lighting and camera focal length had on the ideal platen angle. The Archivist employs a 100 degree platen, which in the end turns out to be just a few degrees off the ideal of 106 (search the DIY Book Scanner forums for more on that).