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3LCD vs DLP Projectors for Resin Printing

Posted by Don McLean 
3LCD vs DLP Projectors for Resin Printing
October 17, 2017 05:53PM
I may end up with a 3LCD projector. I've been thinking of how to modify it for resin printing. I looked at some examples of people who made their own 4K projectors using a single UHD LCD with good results, but this wasn't for 3d printing, just for viewing in UHD.

For a printer, only monochrome is needed. So only one of the 3 LCDs would be needed. The white light is separated by wavelength filters in Red, Green, and Blue before it is supplied to the respective LCD's. I'm guessing these also filter out UV light. Seems pretty easy to me, to take out these filters / prisms, and replace with mirrors to focus all of the light through the center LCD. Then either use a UV pass filter in front of the bulb so the one LCD that is being used doesn't now have to process three times as much light, or do a ballast bypass and replace with a UV Led around 405nm. The filters/prisms are just flat pieces of what looks like glass. Easy enough to cut some mirrors the same size.

If this burns out LCD's quicker, that's OK, there are two more sitting there as spares, not being used.

I've heard that DLP mirrors do not like UV light, and burn out much faster, resulting in spots on the screen. Also, I've heard that LCD's can "bleed" light. I don't know if I should try the 3LCD. Has anyone else tried it in a way similar to the method I described above? It seems intuitive to me that this would be a good way to do it, however I don't know if anyone has succeeded. It seems like everyone is using DLP projectors.


If you look at the first picture in the above document, my guess is that you would remove "A" and replace "B" with a mirror instead of the dichroic filter.


Also, the prism that joins the RGB streams is made from dichroic filters. So that would need to be removed also.

Lastly, the polarizing filters before and after the lcds, well those are specific for each colour, and it is my understanding that they also act as filters to remove unwanted wavelengths (like UV) for each of the 3 colours.

So I would replace the polarizers on the center led with generic lcd polarizing film instead of the specific colour polarizing film used in these projectors. Does polarizing film need to be matched to the LCD specs or will generic polarizing film work with any LCD pannel? Does anyone know?

I haven't heard definitively that generic polarizing filters will filter UV, although it is my understanding that some can (like perhaps the ones normally used in 3LCD projectors). People are making printers using large lcd panels for bottom up builds with UV led arrays to replace the backlight, so I am guessing this would also work?

These mods seem straight forward to me. I don't see why they wouldn't work well. I was looking for a cheap setup to try this out on and do some tests.

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