Tips for cleaning optical mirrors (Snorkel Mirrors on Lens)?

[Ryan Gallagher]

So we have one of those weird steep angle installs with two snorkel mirrors on our CP2200.

Cleaning those mirrors (and getting to the lens) has been on the bucket list. I think everyone has been afraid of them and all they have received is air dusting. Actual cleaning is overdue because we run haze etc.

My initial research on 1st surface optical mirror cleaning (such as with telescope mirrors) is that submersion cleaning and swabbing is best and least likely to scratch anything.

But anyone got any tips on cleaning them in situ without dismantling? Cleaning the inverted one seems the most tricky.

I am tempted by these polymer cleaning products. Paint them on, let them set, and then peel away.
https://www.newport.com/f/polymer-optic-cleaning-kits

I'm willing to take the snorkel apart if I have to and is best practice. Already recorded the mirror angles with a digital angle finder.

[Carsten Kurz]

Interesting, but pricey. If you clean rarely, as usually suggested, I think alcohol and swabs are completely okay. Just change swabs often during the process. And just relax leaving some remnants on the surface instead of trying to get it 100% perfect. It will never be 100% perfect. The moment bright light hits the surface, you WILL see something.

[Ryan Gallagher]

Both Alcohol and Acetone are safe on uncoated (unprotected) front surface mirrors, but it's really a question of the swabbing method. That and I have no idea if these are coated or uncoated mirrors. If there is any optical coating acetone and alcohol are riskier. Ammonia based products are no-go in all cases of course. Perhaps I'm overly paranoid on this front. It's not a telescope after all.

Christie DUO mirrors are a related mirror product, but couldn't find any recommended cleaning tips in the manuals.

My main worry swabbing in place would be keeping the process wet enough, as both mirrors are slanted at a 45-ish-deg, one inverted of course. The telescope community is pretty quick to say don't use cotton balls/swabs on unprotected aluminum 1st surface mirrors, cause even the cotton can scratch them, let alone particles you might drag. I do have kimwipes but wetting one on an inverted mirror to drag wipe without rubbing seems tricky! And I've read in lens cleaning forums that even Kimwipes, while being lint free, are still less desirable than purpose made lens wipes.

On the other hand the telescope folks also swear by submersion swabbing in distilled water and a little dish soap. Cheap, provided i take the damn thing apart!

Since you were intrigued...

1st Contact Polymer does not appear marketed to our price point. Apparently LIGO (Gravity Wave Observatory) cleaned their test masses with it. That is quite a testimony, but perhaps overkill for me.

Apparently Universal Photonics "Precote Num33 Blue" is a somewhat more affordable competing product to 1st Contact Polymer (which yes, is ridiculously expensive)
https://universalphotonics.com/UPIPr...5/Default.aspx
a Precote price shown here:
https://firstsurfacemirror.com/produ...pray-laminate/

Precote is actually designed to protect optics for transport or storage, but works on same principle. Apparently it also easily lifts off dust etc, but is a little less effective on grease and oils etc according to 1st hand reports. Think of that blue film that might ship with new optics. They both start out pretty liquid though, probably best on horizontal surfaces to achieve needed thickness, but at least some 1st Contact demos suggests it's possible even on vertical surfaces (perhaps via enough layering).

And then I suppose the OBVIOUS answer is to ask Christie. ;-)

[Marco Giustini]

on a Christie the fold mirror at the bottom is important. That faces up and collects quite some dust. Remove it by carefully removing the brass clips, clean it and put it back. You might need to re-align it after doing that. The procedure is in the manual and it's very important you put it back on the right side - the one with no glass on top.

The manual might have some recommendation but I'd say dust it with some good quality duster (office equipment use might leave microscopic particles behind) then I feel kimwipes are ok - though not my favourites. I used to use some microfiber cloths which were provided by Sony for their projectors - sorry Sony!

When cleaning optics, I found that sometimes you need a water-based quality lens cleaner to remove some of the contaminants. I usually wipe with isopropyl first (gently, first pass just to remove the dust, then fold the cloth and go on again) then I apply the water-based liquid on the cloth (suitable for coated lenses, Zeiss makes a good one) which removes what alcohol could not. That probably does not apply to the fold mirror though as that mirror does not have glass on top.

If you see haze on high-contrast patterns, that's likely happening AFTER the DMDs though. Cleaning the fold mirror will give you more light.

Christie engines are not sealed and the LAD filters are a joke. Eventually - particularly in dusty rooms and particularly if maintenance was skipped - dust will accumulate on the DMDs, you'll see haze and there is nothing you can do to clean that.

I'd leave alone the integrator rod, anything there WILL be seen on screen.

Good luck

[Ryan Gallagher]

Marco, I wasn't going that deep at all. I'm comfortable cleaning lenses... 1st surface mirrors that we have mounted in front of the Lens is the topic at hand.

Fold mirror doesn't need touching as far as I can tell. ;-)

(I know, most people don't have extra mirrors involved in their setup... i'll post a picture for those curious Friday).

[Marco Giustini]

Ah, you have mirrors in front of the projector? Oh no! I've worked on a few, I know the pain!

[Steve Guttag]

Most would call those mirror "periscope" not "snorkel."

[Ryan Gallagher]

Cheers Steve. Proper language is helpful for sure. Periscope for Optics, Snorkel for Breathing. Makes sense. ;-)