I’ve been playing around with the DLP projector setup with its 1080p resolution. I measured the smallest features I’ve printed to be around 0.25 mm. Its small but not that small. I wonder what else could be done to get better resolution. Probably adding an aperture.
Today I put together a rough focusing idea. First I got an old fluorescent blue sharpie and I dissolved the ink cartridge in IPA. Then I made a CMC mix and coated a paper with the fluorescent mix. Next I bought a really inexpensive Chinese filter on eBay “Various sizes ZB2 BG3 UV IR Dual-band 380nm Pass Filter Violet Glass”. Using my super photonics engineering power I deduced that this filter would cut off all visible light except for deep blue and then allow UV to pass relatively freely. Having those two things I made a CMC cyanotype today that was the sharpest thing I ever printed so far and indeed the CMC formula allows for the printing of fine lines almost as small as the full resolution of my DLP projector. I will try this at lower scale to see if the details become finer.