I can't find the link, but there was a Stackoverflow question about ripping a cdrom by using a flatbed scanner, the conclusion was that the scanner would've required 2-3X the DPI currently available on a commercial device to correctly parse the gaps, given that a cdrom laser size is roughly 800nm.
On the other hand I'm still puzzled why there are no homebrew projects for a dumb dumping device that simply reads all the data on a cdrom, error correction, subchannels completely raw. There are a lot of CDs with a very weird data structure (Console Games, Early Copy Protected pc games, AKAI sample discs, some Hybrid Macintosh discs, in other words anything not using the iso9660 standard) which are at risk of Disc Rot[1], and simply storing them as Iso or Bin/Cue files (including proprietary variants like Alcohol 120%/Daemon Tools mdf files) is basically useless both for archival and real world usage purposes.