A small project I recently worked on using DLP. I haven't actually used it to print photos so I think I shouldn't start a separate thread, but based on the parameters, it might serve as a useful reference.
The device utilizes TI's DLP4710LC (0.47", 1920x1080), controlled by dual DLPC3479 chips, with power management handled by a DLPA3005. It drives a Luminus CBM-50X-UV 385nm LED. We followe TI’s reference design—specifically the DLP4710EVM-LC evaluation module (manufactured by Young Optics). If you're just looking to start experiment, you can skip the circuit part and simply buy the module to modify its LED and optical components.
The optical path starts from the UV LED with an aspheric collimator lens, followed by a fly-eye lens for light homogenization, then directed to the DMD via a TIR prism. We were lucky to find some components that, while rated only down to 420nm, maintained decent transmittance in the 385nm range (though it drops significantly at 365nm, it remains acceptable). The final stage is a short-throw macro lens (from a photography perspective), which creates a 2x magnified real image of the DMD at the object plane.
Added: I think the easiest way to try is to modify TI's evaluation modules, such as the 4K resolution DLPDLCR471TPEVM (1080p DMD and Pixel Shifting Actuator Technology) and the 1080p DLP4710EVM-LC. Lower resolutions are also available (DLPDLCR160CPEVM, 360x640), but these have bad image quality. It's generally believed that these can directly replace the blue LED (455nm) with a similar 405nm near-UV LED. However, the situation with 385nm depends on the module components, and 365nm are almost impossible to use properly, requiring custom UV components.
If the process allows for 455nm blue light, then the original module might be quite nice. For example, the DLP4710EVMLC's LED model is OSRAM OSTAR™ P1W, operating at a maximum current of 16A (~48W! Impressive for its size). Just need to ask a monochrome projection firmware that only enables the blue LED, Ti likes to support developers.
The cheapest option is to modify a commercial DLP projector(second-hand or obsolete items are better). which can provide high power blue light(~450 nm) by default, but UV application of them is unreliable. The optical path will likely contain various cost-cutting plastic components. The lens also needs some consideration, as commercial projectors may not allow focusing to small areas (such as A4 or A3 size) at close range.
Some test patterns are shown in the images; the UV light is projected onto a fluorescent plastic film, giving it an appearance similar to an old-fashioned CRT monitor.The final projection size is approximately 20mm x 10mm at 1920x1080 resolution. With the 385nm LED running at 5A (35W), the measured irradiance is 1100 W/m2, which is roughly 20 times the intensity of UV radiation in midday sunlight.
I'm not doing just for hobby, so my next step might be to further reduce the projection area (which would correspondingly increase the UV intensity, the current value is still not enough) to make it easier for some photochemical induced material deposition (in a sense, an kind of alternative process?). Finding a macro lens with a smaller magnification is easy (the difficulty in macro photography usually in larger magnification), the main problem is that they may not be suitable for those UV wavelengths.
