A question concerning resolution

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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Greg Howald
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A question concerning resolution

#1 Post by Greg Howald » Sat Jun 26, 2021 7:59 pm

We were all excited when we learned earlier in the month about a new lighting technique that allowed for higher resolution in light microscopy. I found that article most interesting.
Today I've been working on bright field at 100x. I will be using 100x for the next couple of months to run certain experiments. Don't tell OPEC. If they find out how much oil I'm using they'll raise the price!. ...
So while I was in the process of looking at several slides with oblique, polarized and phase contrast I took a look at a window film called Funfox. This material is in sheet form, very thin. Comes in a roll. Mirror surface on both sides but you get your eye close to it you can see through it. It's purpose is to reduce the amount of heat coming through your window on a bright and sunny day.
I took a small piece of this and examined it under the scope. It has a bit of a darkening effect, eliminates all glare, and is riddled with pin holes that seem random at first before you notice a repeating pattern.
I slid that thin slice of material under the slide on the scope. The image became even and clear. Not layered as much as usual. Not having to continually refocus.
I liked the result very much even though it dimmed the image slightly.
I wonder if anyone else has been dumb enough to do this, and I wonder if this result is an improvement in resolution. Comments appreciated. A lot of you folks are smarter and have more experience and knowledge than I will ever have and your input is cherished.

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Re: A question concerning resolution

#2 Post by c-krebs » Mon Jun 28, 2021 4:10 am

Never tried anything like this nor am I familiar with the material you mentioned. But your post really makes me think of an opticians diagnostic tool called an "pinhole occluder". There are even pinhole eyeglasses available (stenopeic glasses) that some people find useful. If you do some searching on these I suspect you will find some useful information pertaining to your observations.


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Re: A question concerning resolution

#3 Post by Hobbyst46 » Mon Jun 28, 2021 8:16 am

A "Funfox" home window coating is advertised as a privacy protection translucent (according to the photos) PVC layer, that electrostatically clings to clean flat windows and attenuates UV. Pin-holes or partial mirror surface are not mentioned AFAIK. Perhaps there are variants of this product ?

A 1-2 decades ago, thermochromic films, that became reflective at high ambient temperatures and retained transparency otherwise, to block infrared radiation and maintain a cooler home, were developed. But the FunFox I see appears to be something different.

If the Funfox you experimented with looks like the advertised, it might function as diffuser, and make the FOV brightness more uniform, at the expense of brightness level. Perhaps it is also a polarizer so might attenuate glare.

Another question about the film you mention is thickness. The above mentioned Funfox is detachable and reusable. So unlikely to be much thinner than, say, 0.5mm or so. How does that affect performance ?
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Phill Brown
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Re: A question concerning resolution

#4 Post by Phill Brown » Mon Jun 28, 2021 9:13 am

If the slide is raised, the subject is raised as with moving the stage height.
I get light travels in straight lines through pinholes and UV end of the spectrum scatters more than the red end.
Images of the effect would be helpful if possible.

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Re: A question concerning resolution

#5 Post by MicroBob » Mon Jun 28, 2021 9:37 am

The camera accessory company Novoflex used to sell a macro photo system based on a multi pinhole disc that increased depth of field. This here is probably the same effect.
With enough light available and modern manufacturing it might be useful for microscopy.

Con you post photos to compare the effect it gives?


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Re: A question concerning resolution

#6 Post by patta » Mon Jun 28, 2021 3:58 pm

Can you try to close the condenser and see what happens?

My guess is that this Funfox pinhole layer works as a "diffraction diffuser". If you close or remove the condenser, it will get dim, but still keep the same high (or small?) NA.
Maybe also with progressive dimming, like with "smooth bokeh" apodization filter, so the nicer image.

This should work if the holes are small (<< 1 micron, less than wavelength) and at some distance from the subject (funfox under the slide).
Similar result by using a frosted glass slide instead of the Funfox. Well, the frosted slide does that "frosted illumination". The Funfox, maybe?

Greg Howald
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Re: A question concerning resolution

#7 Post by Greg Howald » Tue Jun 29, 2021 2:27 am

I'll try to duplicate and photograph during tomorrow's morning lab session.

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Re: A question concerning resolution

#8 Post by Lilanza » Sun Nov 21, 2021 5:07 pm

I love posts like this. Pretty cool and useful

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Re: A question concerning resolution

#9 Post by DonSchaeffer » Wed Nov 24, 2021 2:22 am

Can you post a link to the retailer?

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Re: A question concerning resolution

#10 Post by alicejenny » Thu Jun 23, 2022 9:44 am

What an excellent post! Thank you so much. I am looking forward to reading more your posts in the future.

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Re: A question concerning resolution

#11 Post by MichaelG. » Thu Jun 23, 2022 10:52 am

Greg Howald wrote:
Sat Jun 26, 2021 7:59 pm

… and I wonder if this result is an improvement in resolution. Comments appreciated.
My gut-feeling is that this will actually reduce the resolution … but it might well improve the visual appearance of typical ‘real world’ subjects.

Most grateful if you could share some images of ‘technical’ subjects, so that we can attempt some quantitive analysis.

Too many 'projects'

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