Cleaning excitation filtres

[Polymerase]

Thanks to everyone who has contributed to my many questions about epifluorescense. Being new to this modality, new issues keep coming up.

One pf my filtre cubes has an excitation filtre that has accumulated something on the internal surface, to a degree where it is completely opaque, and no light is transmitted throught it. Disassembling two other cubes, I came to realize the excitation filtre on another one has a lot of white spots on ots interior surface.

I know these filtres are very delicate. Is it possible to clean them, or should they be discarded? If they can be restored, what is the best approach to cleaning?

Also, I wonder how to do imaging in epifluorescense. My dedicated camera (an hdmi digital camera connected to a trinocular port with an NFK 2.5x in a PMTVC on a BHS scope with apochromats) seemingly cannot pick up enough light to show anything on my screen. I managed to take a few photos with my phone through the eyepieces, but that is not a desirable method for the future.
Any thoughts on this?

[Hobbyst46]

Thanks to everyone who has contributed to my many questions about epifluorescense. Being new to this modality, new issues keep coming up.

One pf my filtre cubes has an excitation filtre that has accumulated something on the internal surface, to a degree where it is completely opaque, and no light is transmitted throught it. Disassembling two other cubes, I came to realize the excitation filtre on another one has a lot of white spots on ots interior surface.

I know these filtres are very delicate. Is it possible to clean them, or should they be discarded? If they can be restored, what is the best approach to cleaning?

Also, I wonder how to do imaging in epifluorescense. My dedicated camera (an hdmi digital camera connected to a trinocular port with an NFK 2.5x in a PMTVC on a BHS scope with apochromats) seemingly cannot pick up enough light to show anything on my screen. I managed to take a few photos with my phone through the eyepieces, but that is not a desirable method for the future.
Any thoughts on this?

Can you post a close up photo of the filter ? it all depends on its composition. If absorbent glass, it can be cleaned. Some such UV filters do look bad after years of use, but they remain useful. If it is the filter is an interference filter, and the outer surface of the coating is dirty, extremely gentle wiping with a wetted Kimwipe can be tried, with low chances of success.

Your camera is likely not sensitive enough for fluorescence, where sensitivity is the important feature, rather than sensor size. That is why dedicated fluorescence microscope cameras (Olympus DP-73, for example) are very expensive, although their sensors are pretty small. Problem is, that such cameras are usually supported by proprietary software (meaning $$$$). Our eye is a great sensitive sensor, and has a high dynamic range !

[Polymerase]

Hobbyst46, you are a lifesaver.

I haven’t quite figured out how to post images, but I’ll see what I can do.

[Polymerase]

I am not on track with uploading images, but I think this link will allow you to see pictures of the Olympus BH2 G cube, and its opaque inner surface of the BP545 excitation filtre. It is blocking absolutely all light projected to it. The dichroic mirror and emission filtre seem good.

https://photos.app.goo.gl/Hs1zDQ7K3pMsV

My B cube is working, but the BP490 filtre has some white spots on the inner surface. Maybe that is why it is a bit dimmer than the last cube - which by the way I managed to identify. It had a sticker on its back, saying “Omega XF 102-2.” This is not a standard Olympus cube, as far as I understand. It has the following configuration:

Exciter: XF1067 (560AF55)
Dichroic: XF2029 (595DRLP)
Emitter: XF3081 (645AF75)

Here is a link to it: http://www.glenspectra.co.uk/glen/filte ... F102-2.pdf

[Hobbyst46]

I am not on track with uploading images, but I think this link will allow you to see pictures of the Olympus BH2 G cube, and its opaque inner surface of the BP545 excitation filtre. It is blocking absolutely all light projected to it. The dichroic mirror and emission filtre seem good.

https://photos.app.goo.gl/Hs1zDQ7K3pMsV

Could not open the link. So the G stands for green, namely 545nm. Lo and behold, here is a brochure for the accessory and cubes: https://www.opticalservice.cz/download/ ... 2_v_aj.pdf. The dichroic mirror cutoff is at 570nm, for red fluorescence. The BP545 is very probably an interference filter, so should be gently handled as mentioned. Or might need replacement.

My B cube is working, but the BP490 filtre has some white spots on the inner surface. Maybe that is why it is a bit dimmer than the last cube - which by the way I managed to identify. It had a sticker on its back, saying “Omega XF 102-2.” This is not a standard Olympus cube, as far as I understand. It has the following configuration:

Exciter: XF1067 (560AF55)
Dichroic: XF2029 (595DRLP)
Emitter: XF3081 (645AF75)

Here is a link to it: http://www.glenspectra.co.uk/glen/filte ... F102-2.pdf

Omega is a well known supplier of optical interference filters. This specific cube is described as optimized to the fluorescent stain Texas Red.

Note: all interference filters are expensive but there is no way around it - yet sometimes, if the required specs are not very high, far less expensive absorption filters (not dichroic mirrors though) can be used instead. Provided the appropriate diameter and thickness are found (they come in many sizes).

[Polymerase]

Could not open the link. So the G stands for green, namely 545nm. Lo and behold, here is a brochure for the accessory and cubes: https://www.opticalservice.cz/download/ ... 2_v_aj.pdf. The dichroic mirror cutoff is at 570nm, for red fluorescence.

Ok! I'll try to find another way to post the images. Thanks for trying.
Need to take care of a few other things first.

[Polymerase]

Finally figured it out:

IMG_1569 by Dagfinn Rosnes, on Flickr

IMG_1570 by Dagfinn Rosnes, on Flickr

IMG_1571 by Dagfinn Rosnes, on Flickr

IMG_1572 by Dagfinn Rosnes, on Flickr

IMG_1573 by Dagfinn Rosnes, on Flickr

[Hobbyst46]

Perhaps I am utterly stupid but could it be that there are actually two glass filters, in two separate metal holders in series ?
One holder contains nice violet-reflecting glass, probably the BP545 filter. It passes green and reflects violet.
The other holder contains what looks like a green-reflecting, rough surface absorption filter. This could be a heat filter, fitted to block
IR radiation from the excitation lamp, which was probably a ~100W high pressure mercury lamp.

Otherwise, if the photos show just the two surfaces of a single glass piece, probably one surface has been severely damaged by heat
so much that its color has changed to opaque green and cannot be repaired. Just a far fetched conjecture. Not likely.

[Polymerase]

Perhaps I am utterly stupid but could it be that there are actually two glass filters, in two separate metal holders in series ?
One holder contains nice violet-reflecting glass, probably the BP545 filter. It passes green and reflects violet.
The other holder contains what looks like a green-reflecting, rough surface absorption filter. This could be a heat filter, fitted to block
IR radiation from the excitation lamp, which was probably a ~100W high pressure mercury lamp.

Otherwise, if the photos show just the two surfaces of a single glass piece, probably one surface has been severely damaged by heat
so much that its color has changed to opaque green and cannot be repaired. Just a far fetched conjecture. Not likely.

If there are two separate filtres, they are glued together in one holder. I do not think so.
The only filtre-containing part in the assembly when detached from the cube, is a metal ring with the inscription "XF 1005 365WB50 71353."
Maybe two filtres have been fitted together in this ring - but it seems unlikely.

I am at a loss of what happened to this filtre. I suppose it can't be restored? You are right about the excitation lamp. It is a 100W mercury arc lamp.

[Hobbyst46]

Perhaps I am utterly stupid but could it be that there are actually two glass filters, in two separate metal holders in series ?
One holder contains nice violet-reflecting glass, probably the BP545 filter. It passes green and reflects violet.
The other holder contains what looks like a green-reflecting, rough surface absorption filter. This could be a heat filter, fitted to block
IR radiation from the excitation lamp, which was probably a ~100W high pressure mercury lamp.

Otherwise, if the photos show just the two surfaces of a single glass piece, probably one surface has been severely damaged by heat
so much that its color has changed to opaque green and cannot be repaired. Just a far fetched conjecture. Not likely.

If there are two separate filtres, they are glued together in one holder. I do not think so.
The only filtre-containing part in the assembly when detached from the cube, is a metal ring with the inscription "XF 1005 365WB50 71353."
Maybe two filtres have been fitted together in this ring - but it seems unlikely.

I am at a loss of what happened to this filtre. I suppose it can't be restored? You are right about the excitation lamp. It is a 100W mercury arc lamp.

Nobody glues filters together. But they could be just placed and retained within the same sleeve.
Yet the XF 1005 365WB50 71353 is interesting. What if it means a UV filter, 365nm peak transmission, 50nm peak width... but that contradicts
the BP545 mark... sorry, clueless. BTW, a BP 365nm filter would look totally opaque, since it hardly passes any visible light.
Can try holding that filter towards a very strong light (say, a 17W ordinary home LED light - not the sun and not a laser source!!)
look through and see the color of transmitted light. An UV filter would pass a very faint dark violet light.

[Polymerase]

Nobody glues filters together. But they could be just placed and retained within the same sleeve.
Yet the XF 1005 365WB50 71353 is interesting. What if it means a UV filter, 365nm peak transmission, 50nm peak width... but that contradicts
the BP545 mark... sorry, clueless. BTW, a BP 365nm filter would look totally opaque, since it hardly passes any visible light.
Can try holding that filter towards a very strong light (say, a 17W ordinary home LED light - not the sun and not a laser source!!)
look through and see the color of transmitted light. An UV filter would pass a very faint dark violet light.

This is very strange indeed!
I think I will need to give up on this cube (I've ordered another G cube....).
But I would very much like to know what this is. I got it from a third party surplus vendor in England (whom I shall not name), who did a very poor job in packaging a BHS scope with an RFCA unit and power supply. The RFCA broke in transport, and I had to get a new one. Of three objectives, only one was in a working state. And now it proves that 2 out of three cubes are in a deteriorated state. The BHS, however, was in a remarkably good state, so receiving a good partial refund, I am satisfied after all. But it is annoying that the cubes aren't working as expected, now that I finally have a working RFCA unit....

Thanks for enlightening me. Upon your last suggestion, I am afraid no light passes through the filter at all....It is completely blocking everything.

[Polymerase]

I can't get any light to come through....

I noticed the back of the cube is labeled "Omega XF06." This describes the following setup:

Exciter: XF1005 (365WB50)
Dichroic: XF2001 (400DCLP)
Emitter: XF3002 (450DF65)

as described here: http://www.glenspectra.co.uk/glen/filters/pdfs/XF06.pdf

But the Olympus G cube should contain something like:

Exciter: 545
Dichroic: 570
Emitter: 590

Is it possible that someone has just modified an Olympus cube, and didn't bother to remove the "G" on the casing and the "BP545" from the sleeve? This is a mystery to me....

[Hobbyst46]

I can't get any light to come through....

I noticed the back of the cube is labeled "Omega XF06." This describes the following setup:

Exciter: XF1005 (365WB50)
Dichroic: XF2001 (400DCLP)
Emitter: XF3002 (450DF65)

as described here: http://www.glenspectra.co.uk/glen/filters/pdfs/XF06.pdf

But the Olympus G cube should contain something like:

Exciter: 545
Dichroic: 570
Emitter: 590

Is it possible that someone has just modified an Olympus cube, and didn't bother to remove the "G" on the casing and the "BP545" from the sleeve? This is a mystery to me....

So possibly your cube was modified to UV. The XF06 is a UV set. Easy to check the emission filter. If it is the 450DF65, it should pass blue light. If Olympus G, it should pass orange-red light (590nm and up). And the dichroic mirror: if it is the 400DCLP, it should reflect violet and pass green. If it is the 570nm, it should reflect yellow-orange or yellow-green (I am not sure) and pass orange-red.

[Polymerase]

So possibly your cube was modified to UV. The XF06 is a UV set. Easy to check the emission filter. If it is the 450DF65, it should pass blue light. If Olympus G, it should pass orange-red light (590nm and up). And the dichroic mirror: if it is the 400DCLP, it should reflect violet and pass green. If it is the 570nm, it should reflect yellow-orange or yellow-green (I am not sure) and pass orange-red.

That settles it. This is not an olympus G cube. It emits blue light. That probably means I have a UV cube with a defective excitation filtre. If I could get the XF1005 filtre, that means I have a working UV cube. Individual filtres seem hard to find in the second hand market, and very expensive when new.

Thanks for helping me sort this out.