Leica DM IL Light Source Optics Window

[microb]

Just above the phase contrast slide, there are some circular planar windows. One is frosted. And one has on both sides some stuff that seems to slowly dissolve in acetone. That window does not come out despite removing its mounting ring. So that stuff has glued it or it was cemented. Not certain.

Any ideas what this stuff is. There is aspheric lens and the frosted window sandwiching it, so I don't see how stuff could have gotten onto. It has a crack, so I think someone tried to remove it before and gave up maybe.

Any ideas appreciated.

Thanks,
Ted

[Hobbyst46]

I would try to wipe that glass with a damp Kimwipe or damp soft cloth (or Q-tip for the underside) and see what happens.

The suspect might be any water-soluble salt that precipitated after solution drops were left to "dry out" with time.
Another, less likely possibility is corrosion of the glass by alkali. Soda caustic for example corrodes glass. Such corrosion signs will stay even after wiping with a damp cloth.

[microb]

I got the optics window way cleaner. It still has smudges that are not coming off without a lot of q-tip scrubbing. The glass seems smooth, but has a crack. Maybe the crack was from a high temperature change. Don't know.

Since it's crack, I'd like to replace it. But it seems glued in there even though it had a holding ring.

How do you remove something that might be cemented?

[Scarodactyl]

You never know what has happened to components. I got a head for a high end Chinese stereo (nikon smz 1000 clone) which had huge brown smudges on one prism. When I opened it up I could see it was covered in fingerprints made in a hard grease that I couldn't remove with alcohol, but acetone (tried as a last resort) would loosen up. The same guy had also flipped the front element in both eyepieces. The worst part was it was fine once I cleaned it off, so what was this moron even doing in there???

[Hobbyst46]

I got the optics window way cleaner. It still has smudges that are not coming off without a lot of q-tip scrubbing. The glass seems smooth, but has a crack. Maybe the crack was from a high temperature change. Don't know.

Since it's crack, I'd like to replace it. But it seems glued in there even though it had a holding ring.

How do you remove something that might be cemented?

Potential solvents for cement:
1. Water
2. Hot water
3. Ethanol (ethyl alcohol; 96% alcohol;)
4. Iso-propanol (rubbing alcohol)
5. Light petrol (white gasoline, lighter fluid etc)
6. Acetone, or nail polish remover

There are stronger solvents, e.g. chloroform, but they are quite toxic and less available.
Whatever you use - use it sparingly. Apply the minimum amount of liquid to the rim of the "cemented" item, wait a minute and very gently pry it off with a spatula. Flooding the area with solvent might do more harm than benefit.

[microb]

So this is what it looks like so far. You can see the crack. An almost closed holding C metal ring snaps next to it from the short side. So a ~3mm gap is milled into the black holder for the glass and ring. The glass is glued somehow. So why a ring?
Also the surface seems pitted. It feels smooth, but maybe from damage, it has a 2mm diameter wavy distortion to it.
But why have this? It didn’t seem to be coated for anything, like UV or IR. I can try a spectrometer, but it’s just glass.
Here’s the order of the optics, so it’s use seems unclear:

LIGHT SOURCE
--------------------
ASPHERIC LENS
\----------------/

-------------- broken glass

--------------- slightly frosted glass, frost side away form light

[Roldorf]

Maybe the gunge that was on the glass has glued the glass to the holder.