Making a UV projector for alt-process prints

[calebarchie]

I recall not too long ago a light engine available out of China for a far more reasonable price.

DSP engine - Kirin

DSP engine - Kirin

www.hitry3d.com

 

[Yezishu]

I suspect Kirin use a commercial grade(not UV-grade) DMD chip with XPR technology, which explains its long lifespan at 405nm and not using 365nm. TI’s DLPDLCR471TPEVM evaluation module (native 1080p, 4K via XPR at 1/4 light intensity) retails for $999. I expect mass-produced UV engines based on this can eventually hit that $500–$1000 range. Hope in 5–10 years, DIYers can buy affordable DMD kits like the LCD kits here, for high-power DLP mods. Currently, high-power & large-area for some alt-process remains a challenge for these evaluation modules or light engines.

An example: Let's see a current $4000 (385nm, 4k via XPR, commercial grade DMD, 12mw/cm2 in 192x108 mm area) commercial light engine. It will give ~3.6mw/cm2 for a A4 photo, and need ~10 min for a 2000mJ/cm2 cyanotype process. It can offer some industrial advantages, such as low power dissipation (requiring only 120W of power input, as well as a long lifespan and output stability), but this exposure time doesn't offer much advantage, and they may not cost-effective enough at this moment (The OP's work likely cost less than $1,000?).

 

[AndrewBurns]

I suspect Kirin use a commercial grade(not UV-grade) DMD chip with XPR technology, which explains its long lifespan at 405nm and not using 365nm. TI’s DLPDLCR471TPEVM evaluation module (native 1080p, 4K via XPR at 1/4 light intensity) retails for $999. I expect mass-produced UV engines based on this can eventually hit that $500–$1000 range. Hope in 5–10 years, DIYers can buy affordable DMD kits like the LCD kits here, for high-power DLP mods. Currently, high-power & large-area for some alt-process remains a challenge for these evaluation modules or light engines.

An example: Let's see a current $4000 (385nm, 4k via XPR, commercial grade DMD, 12mw/cm2 in 192x108 mm area) commercial light engine. It will give ~3.6mw/cm2 for a A4 photo, and need ~10 min for a 2000mJ/cm2 cyanotype process. It can offer some industrial advantages, such as low power dissipation (requiring only 120W of power input, as well as a long lifespan and output stability), but this exposure time doesn't offer much advantage, and they may not cost-effective enough at this moment (The OP's work likely cost less than $1,000?).

Yeah I went through all of this before building my projector, I got quotes from a number of DMD/DLP suppliers. I was 'happy' with 4k resolution but there was nothing available on the market that could exceed the performance I could get with an LCD-based system in terms of exposure time, they were all approaching $5-10k USD and none could handle shorter wavelengths than 405nm without rapid deterioration. As you say the LCD based system was significantly cheaper, and even if the LCD requires replacement every few hundred or thousand hours it's still going to come out ahead over any realistic scenario.

One thing that might be interesting as a future development in the LCD space is separating the polarising films from the LCD itself. I've read that back when normal video and theater projectors used LCD screens rather than DMD chips they had both polarising screens physically separate from the LCD itself. This is because a significant amount of the energy dissipated is at the polarisers, and so having them separate from the LCD means they can be independently cooled and they also don't head up the LCD itself which is more temperature sensitive. It also makes glass-plate polarisers can be used rather than plastic films, which again are more resistant to damage from high-energy light. I wonder if it would be possible to get one of the LCD manufacturers to supply a screen without any polarisers...

On another note, I've modified my projector code so that it turns the LED off every 20 seconds and flips the screen between black and white for a few seconds, and so far I haven't noticed any evidence of image persistence, so I think that should be an acceptable fix (doesn't increase overall exposure times that much).

 

[AndrewBurns]

I recall not too long ago a light engine available out of China for a far more reasonable price.

DSP engine - Kirin

DSP engine - Kirin

www.hitry3d.com

Just had a look at that, and from what I can tell that's an LCD-based unit rather than DMD, but it's really hard to tell?. They talk about it being "DLP-like" however they call it DSP (digital surface projection) which as far as I can tell is a term they invented to account for their ability to dynamically change focal point.

So basically it's a 4k LCD-based UV projector similar to what I made, however mine is 8k, significantly more powerful and able to project an image over a much larger area.

That said, if it is just an LCD unit I don't see how they can claim such massively increased print times AND also longer lifetime vs. LCD-based printers, so who knows...

Still looks like it could be a good option for somebody who wants to buy a pre-made projector for alt-process printing however, as long as you're happy with the limited print size and resolution.