Odd apearence in the microscope.

[Kennethhp]

Hello !
This is not about materials, but hopefully some of you have seen this before when looking into microscopes.

Here where I am an intern we have an old Carl Zeiss Jena microscope that im using regularly.
Out of nowhere, yesterday, some dark shades appeared over the screen. I have tried to localize where they come from and from what makes sense its from the glass where the view is split into the ocular and the camera and to right before the magnification lenses.
I have tried to lighty dust of any possible glass/filters from the bulb to the magnification lenses but they still apear and it is like they form a "filter" over all images and magnifications.

I have attached 1 photo where you can see the dark shades, and a seconond one where i tried to focus on the shades. To me it looks like cracks.

Anyone who can come with an input about this ?

 

[yirmidokuz]

Could it be the room lightning from the ceiling ?

I had a similar issue before, and when I block the light that hits on oculars the effect was cleared.
It also looks like wave interference pattern.

 

[IRstuff]

Really? It looks more like a light bulb filament to me. Is the light from the microscope really dim?

TTFN
I can do absolutely anything. I'm an expert!
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[EdStainless]

Or it could be a failure of the coating, all of the optics are coated.
But do try in a dark room first, and also look into alignment of the light and mirrors.

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P.E. Metallurgy, Plymouth Tube

 

[Kennethhp]

@ Yirmidokuz. We havent changed anything in the room according to ceiling lights so i highly doubt it. But i will try to block the occulars and see if it has any effect.

@IRstuff. Yes i was trying to catch the best picture of the "flaw" but even when i turn up the light its still there. We have recently changed the buld to a un original bulb. It worked fine until yesterday, but it might be the bulb.

@EdStainless. Sounds logic with what im thinking looking at the microscope. It is an old lady so im leaning towards something in the lane. I will try later in dark and see what happens.

Thank for your quick respons !

 

[redpicker]

We have recently changed the bulb to a un original bulb. It worked fine until yesterday, but it might be the bulb.

Ding! Ding! Ding!
We have a winner!

The location of the bulb in the housing can be very important. Usually, there is an adjustment so the bulb can be moved forward, backward, up, and down. You need to adjust the bulb so the filament is "out of focus" with respect to the focal plane of the microscope lenses.

This happened to me the first time I replaced the bulb in a metallograph. It was doing just fine, but I noticed similar shadows on the photographs. I discovered that by moving the bulb, the shadows moved. From there, it was easy to determine how I had to move the bulb to eliminate the shadows.

 

[IRstuff]

Oh, are those dark-field images?

TTFN
I can do absolutely anything. I'm an expert!
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[Kennethhp]

@Redpicker, i would asume that too. but it has been working fine for a whole month and i had it dialed in when replaced. Thats why im questioning it is the bulb ?

@IRstuff, Im not so familiar with dark field microscopy but i dont think it is ? i just had the light turned down a bit to make the flaw stand out

 

[IRstuff]

While it might have been working, that's not to say that someone didn't bump or tweak it accidentally

TTFN
I can do absolutely anything. I'm an expert!
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[IRstuff]

Oh, So do you see anything unusual with the light turned up? It's possible that it's just more obvious with the light turned down, since otherwise, the intensity swamps out your retina.

TTFN
I can do absolutely anything. I'm an expert!
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[EdStainless]

Or the support wires in the bulb have sagged and the filament moved. Check alignment.

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P.E. Metallurgy, Plymouth Tube

 

[Kennethhp]

An update to this!.

The bulb was faulty, there was nothing to see on the bulb visually but another one made the "scratches" go away. We also found that some of the dark spot was spots on one of the deep internal lenses, we have been able to clean it a bit but some of the spots are almost burned into the glass.

But thanks to you all for your help, its useable for now.