Sciencemadness Discussion Board

The kitchen sources of polarized light for microphotography

Antoncho - 22-12-2011 at 04:38

Hi guys!

Will you please excuse me - I should've made an extensive Web search bee4 starting this topic, but this time I decided to just go via the easy route :)

So, have anyone on this site ever had an experience with taking pictures with the help of simple digital camera and microscope?

The particular topic of interest for me is the microphotography of crystals in polarized light. It so happened that I've come into posession of some real weird, rare, juuuuicy chemicals - of which I have no use in my kitchen lab and which I evidently cannot bring myself to just throw away (you guys must understand me on this :-))

So, the only use of I can make of them is through photography :) - making these reeeeal cool colorful pictures like the ones you can see on the Web -- only taken from crystals of this truly enigmatic, obscure stuff :)


The technology itself is pretty straightforward, but I have no clue of what kitchen sources of polarized light I can employ, and whether there are any special requirements for the apparatus itself - such as protection from the outer light etc.


Iа anyone of you has got a hint to share with me and my youger enthusiastic comrades (hehe), then - well, it would bee real nice of you, and we will bee your friends forever ;-)





Antoncho

[Edited on 22-12-2011 by Antoncho]

[Edited on 22-12-2011 by Antoncho]

fledarmus - 22-12-2011 at 04:50

If you are just looking for plane polarized light, wouldn't a lens from a pair of polarized sunglasses work?

kavu - 22-12-2011 at 04:52

Few months back Journal of Chemical education (J. Chem. Educ., 2011, 88 (12), pp 1692–1693) published an article describing the use of iPad (any other gadged producing polarized light works too) as a source of polarized light. This might be of some interest to you.

Neil - 22-12-2011 at 06:26

Find an old LCD TV/computer screen, gut said screen. you will find at least one large sheet of polarized plastic.

Wizzard - 22-12-2011 at 08:32

Yeah, dead LCDs from laptops are a great source for polarizers :D

unionised - 22-12-2011 at 08:37

The thing about microscopes is that they magnify images.
One effect of that is that you can't see much of any big thing through one. The field of view is quite restricted.
So you don't need a big polariser - just one as big as the hole in the microscope stage.

Danger!

Sedit - 22-12-2011 at 13:47

Quote: Originally posted by Wizzard  
Yeah, dead LCDs from laptops are a great source for polarizers :D



I just extracted the polarizer screens and I have to say it was a royal pain in the ass that could have ended in disaster so read this before attempting it...

The sheets of polarizer are glued to a very thin piece of glass very well and half way it broke into a million glass knifes, I only got a small knick but it had the potential to be much worse. Please be careful, also the glue makes them hard to see through so I suggest that you heat it well with a hair dryer before attempting to remove the screens so that the glass does not break. Then you are going to have to remove the glue some how so perhaps some solvent will be good.

I'm just glad I did not end up with a large glass shard in my hand.

peach - 22-12-2011 at 18:29

Quote: Originally posted by kavu  
Few months back Journal of Chemical education (J. Chem. Educ., 2011, 88 (12), pp 1692–1693) published an article describing the use of iPad (any other gadged producing polarized light works too) as a source of polarized light.


Thirty five dollars a read.

Here's a free youtube video from 2009:

<iframe sandbox width="640" height="360" src="http://www.youtube.com/embed/FkXwNQwrxZ4" frameborder="0" allowfullscreen></iframe>

That video has 4,500 hits, so that's $150k's worth of information by the journal standard.

How about a 3 cent craig tube to replace the expensive glass ones. $35 a read. A cotton swab and a disposable pipette.

Student fees are tripling this year, whilst the private owners of the journals are creaming the cash in for these peer reviewed DIY innovations; R&D is on the students and taxpayer too!

[Edited on 23-12-2011 by peach]

Neil - 23-12-2011 at 05:17

I've found the newer LCD screens are not as good of light sources as the older ones, I don't have an Ipad but I have tried newer and older LCD monitors.

I've never had an issue gutting screens. Normally the glass has been two sheets which together were thick enough that I could lightly pull the film off with no fuss. :( glad you weren't hurt.

3D glasses, and calculators have bits of the same polarized material minus the large amounts of glass. cell phone screens also have a number of Fresnel lenses, which can be useful for light diffusion

Sedit - 23-12-2011 at 11:06

The glass was a single sheet (Very thin at that one mm at best) and on either side the polarizer screens where glued with a very pain in the ass glue. I suspect that a hair drier or perhaps a solvent would help a alot but IpOH did little good.

peach - 23-12-2011 at 11:55

They can be a pain to get off and the glass is extremely thin on the new LCDs. It's not just it being thin, it's the size of the sheet as well, making it so easy to snap. Lying it down flat and pinning it down would help.

A big glass scraping razor blade helps, the 100mm kind, and taking ten minutes to do it, gently peeling and cutting at the back.

The solvent suggestion is also good. If not only to get it off more easily but because the sheets end up covered in dust bunnies. I think I might have tried an alcohol as well (or even acetone), and didn't have much luck.

DCM would get it off. And melt the sheet too.

It might be best to get two screens. Peel one of the polarisers off and bin it, then clean the bare glass with the polariser on the other side and repeat for the other monitor. That way, aggressive solvents would be fine and the DIY'er would end up with a nice clean, rigid sheet for each.

Neil - 23-12-2011 at 18:10

hmm I have a sheet freshly removed sitting suspiciously close to a microscope... lets see -IPA, ethanol, hand sanitizer(ethanol,glycerine and water) and acetone do not remove the glue, cold cream does.

Hot water from the tap made the plastic sheet start to curl.

The only problem with keep both screens attached is that you still have pixels but if you are just using it to cover a lamp w/e.

I've just noticed that different chrome finishes show purple/blue/or red through the polarizer so now I have a full evening of excitement:D

Antoncho - 23-12-2011 at 21:30

It turns out that I was somewhat a 'naive young lad from Chukotka', as Russian saying goes. Polarized light microscopy is more complicated than simply sticking a sheet of plastic under the specimen.

First of all, there is a need for two polarization filters: one beefore the specimen (polarizer), and one - at some point after - doesn't really matter where, could bee even after the eyepiece, and it's called analyzer. These filters must bee strictly parallel to each other and perpendicular to the optic axis. Hence, one problem with making a polarized light microscope from an ordinary school-grade one (which is the obly one I have) is to find a way of placing a piece of plastic into the optic tube.

Another thing is the need for a light condenser in the microscope (otherwise there's too little light since polarizers absorb light waves with the vibration plane angles different from their own) - and that is another obstacle, my microscope doesn't have one, it's the most basic model, I'm afraid :-)

Lastly, there is a need for the highest-grade optics: all lenses must bee stain- and stress- free, otherwise their own optical inhomogenities add to the picture in form of colored veils etc.

There are quite a bit of other improvements in the 'real' polarized light microscopes - such as rotating stage, optic compensators, Bertrand's lense - but to my knowlendge thus far these are not so essential for means of photography.


So, my plan at this point is to:

1. Find a way to neatly shove a plastic circle into the scope's tube;

2. Find a powerful source of light - I think of some high-power LED (my only fear is that its light would have some unwanted characteristics - e.g., being too blue or maybee even already polarized, what do you think?)

3. And then just settle with the optics' quality I have and the resulting artefacts (hopefully, they won't bee too huge and still allow us to have fun :))



Antoncho



P.S. By the way, all I printed above was originated from this article: http://micro.magnet.fsu.edu/primer/techniques/polarized/pola...

peach - 24-12-2011 at 00:50

Thanks for taking the time to check those Neil. I also had a laugh at the idea of you wandering around all night looking at the appliance finishes.

Antoncho...

Using LED's may produce some weird, but perhaps not so pleasant, pictures. The different colours and rainbows seen in polarised photography are caused by the differing wavelengths of the light source being filtered by differing amounts. LEDs emit an almost pure, single wavelength. I would suggest using a bright halogen lamp, or something similar, if you wish to see the pretty colours.

You are correct that you'll see the optics own artifacts if the viewing side polariser is behind one or more of them. There are two things I can suggest.

Just start with a normal digital camera and take photos of the crystals using the macro mode, preferably with big crystals.

Or, you could perhaps use some photoshoppery / GIMP trickery. Put a sample under the modified microscope, focus it until you're happy, capture an image, store it. Remove the sample, without touching the focus at all, and capture another image; this will be your baseline, or null.

Via the wonderous magic of the shop, you should be able to layer the photographs over each other and subtract the metaphorical tare image from the actual sample image, removing the artifacts caused by the optics. You may need to do some playing around with the colour and intensity values when subtracting the tare image.

It'd definitely be worth having a quick check of the camera and microscope before worrying too much, as the results may not be too bad with either. The microscopes used in university biology labs are serious business and designed for cellular work. Even moderately sized crystals are far larger than that.

Neil - 24-12-2011 at 14:50

Many LED's use a driver and run essentially push pull to get the voltage high enough to run the LED. Any bright white LED flash light that I have tried produced too much of a strobe to allow a digital camera to take a picture. Any of the white LED lights that I tried which were dimmer seemed okay (no strobe) but they were so dim that there was no point in using them.

If you can get a set of passive 3D glasses, the polarizers on them might make a suitable eye pieces cover, failing that you can actually get a polarized filter lens for your camera.

Peach (as usual) already has everything else covered.

@Peach - so far the best are really white chrome finishes which turn pink when viewed just right, I think it has to do with light coming through the filter and then reflecting off the shiny stuff and going back through the filter so that it gets filtered incestuously.