About polarized light

General Discussion
1

The filters can be cheap from a place like Edmunds Scientific where they are just film.

One goes immediately above the light source - which is below the stage and slide.

The other goes somewhere on the line of sight after the objective.

The lower one ends up having to be manually adjusted to totally darken the backgound field.

Because the light (now limited to one orientation of transmission) hits the pollen, it gets jumbled going through the pollen so when it reaches the other/second polarized filter some of it will continue to be transmitted.

(A text book that describes rock thin sections might cover this better than I have.)

2

Hi Ann, in May, I purchased a Bausch and Lomb microscope that is set up for polarization studies, it has a rotatable stage with attached polarization unit and a second polarization unit below the eyepiece (e-bay $9.50 plus $18.77 shipping - 2 bids). All I have done with it so far is to check it out. I will have to try it with some pollen. (The reason that I mention the purchase cost is so people will realize how inexpensive Doctors’ quality microscopes (usually from the 1950s) can be on e-bay. Of course if you enter the search term “microscope”, you will see many very expensive microscopes listed. I enter an upper search limit of $50. and then, when somthing comes up that I am interested in put in low bids so that the shipping plus purchase price is between $30. and $50. I then replace the light source with the LED head of a 21-31 LED flashlight (under $10. on e-bay), and I replace the eyepiece with an inexpensive webcam ($10 - $15 from e-bay).

3

Henry,

If you’ve got some diatomaceous earth, that’s IMO the best way to learn about dark field photography.

Sometime I’ll rant about the decline in quality of objectives from the 40s onward. That you got it so frugally is really both wonderful and sad that something that can such a door opener for a whole new world for anyone can be had so frugally.

(I love science, so I guess I’ve been a geek for quite a while now.)

Ann

4

I did William Baffin pollen before as it was a difficult one. Here is an “easy” one, John Davis pollen viewed with IR light:

http://picasaweb.google.com/lh/photo/EbMrbPHUDaCiBQSWdm13TQ?feat=directlink

Link: picasaweb.google.com/lh/photo/EbMrbPHUDaCiBQSWdm13TQ?feat=directlink

5

This link is to John Davis pollen that was stained with methylene blue.

http://picasaweb.google.com/lh/photo/aS0NM_ju9u6AoKYXOpDxug?feat=directlink

I also tried some polarization experiments. Using visible light, I did not see any resolution improvement; using IR light - it appears that the polarizers do not work with infrared light.

Link: picasaweb.google.com/lh/photo/aS0NM_ju9u6AoKYXOpDxug?feat=directlink

6

The links below are to slides of John Davis pollen that was stained with methylene blue and observed with a 20 X lens, a 5 megapixel webcam, and a Bausch and Lomb microscope that came equipped with a Bausch and Lomb darkfield condenser.

Pictures using a darkfield condenser and infrared light (I do not know why the color is different):

http://picasaweb.google.com/lh/photo/Sdl1fx1uwTHvOeVqbB-zeA?feat=directlink

http://picasaweb.google.com/lh/photo/1uYQuiRDwhQLkjImWeMecw?feat=directlink

Pictures using a darkfield condenser and visible light (same pollen grain as above):

http://picasaweb.google.com/lh/photo/T5bgxPewMwxqVvWPQPF9Jw?feat=directlink

http://picasaweb.google.com/lh/photo/UUjszCDcOOjADXE3e6XS6g?feat=directlink

Regular condenser, regular light (same pollen grain as above):

http://picasaweb.google.com/lh/photo/BbsagCBd1YIQxcCr8_eAjA?feat=directlink

Notice that infrared light gave better resolution than the visible light both in the darkfield condenser and regular condenser pictures. I am surprised that the regular light, regular condenser picture has such a low resolution. I do not know if it is due to the stain used or possibly due to the time that had passed between its picture and the others). I will have to repeat these experiments with John Davis pollen stained with acetocarmine instead of with methylene blue.

7

These are pictures of John Davis pollen using acetocarmine as the stain, and either a regular white light LED or an infrared light LED, and either a darkfield or a regular condensor. Both 20X and 30 X magification lenses were used.

Regular white LED light, 20X lens, regular condensor, John Davis rose pollen, primary 5 megapixel webcam 2009-08-03-acetocarmine-0001

http://picasaweb.google.com/lh/photo/nQyazoJ_-PsexvDtr6ziPQ?feat=directlink

Infrared LED light, 20X lens, darkfield condensor, John Davis rose pollen, primary 5 megapixel webcam 2009-08-03-acetocarmine-0001

http://picasaweb.google.com/lh/photo/wbimiWpq0eF22NruckfF-Q?feat=directlink

Regular white LED light, 30X lens, regular condensor, John Davis rose pollen, primary 5 megapixel webcam 2009-08-03-acetocarmine-0001

http://picasaweb.google.com/lh/photo/QBuHluT1MBc_j-Kq4MWiMg?feat=directlink

Infrared LED light, 30X lens, regular condensor, John Davis rose pollen, primary 5 megapixel webcam 2009-08-03-acetocarmine-0001

http://picasaweb.google.com/lh/photo/pdJzv2aBjk1HHSPAQz94Qw?feat=directlink

Infrared LED light, 30X lens, darkfield condensor, John Davis rose pollen, primary 5 megapixel webcam 2009-08-03-acetocarmine-0001

http://picasaweb.google.com/lh/photo/NxCnb_fUxRvat9MqZ9l7Iw?feat=directlink

Infrared LED light, 30X lens, darkfield condensor, John Davis rose pollen, primary 5 megapixel webcam 2009-08-03-acetocarmine-0002

http://picasaweb.google.com/lh/photo/G18ajOYPORCRDoPOpLuppw?feat=directlink