Polarization (Olympus BH2-KP and crystals)

Planapo · Post by **Planapo** » Sun Oct 16, 2011 3:34 am

To be honest

, I was not aware that there is a polarizer built in already, I thought it would be an extra piece to be inserted into one of the five positions, like the prisms or the darkfield stop. Now, even though a bit embarrassing, it's good news!

So thanks much for the pointer, Charlie!

Admittedly, there are a few curled knobs and wheels and a second iris diaphragm the functions of which still elude me. I guess one of them is to rotate this polarizer? And while we are at it: Could you please tell me how the built-in polarizer is (dis)engaged?

In a desperate attempt to save my honour, I hastily wish to add

that the condenser came without a manual, and I haven't yet been able to retrieve one elsewhere.

--Betty

NikonUser · Post by **NikonUser** » Sun Oct 16, 2011 5:21 am

Rik: If you are reading this - perhaps this topic should be moved to techniques and title changed to Polarization or something similar.

Charles Krebs · Post by **Charles Krebs** » Sun Oct 16, 2011 1:38 pm

Betty,
As you sit facing the microscope, on the bottom of the condenser toward the back on the left (at about 10 o'clock looking down on it from the top) you can see two silver knurled wheels. One of these will rotate the built in polarizer through 360 degrees. The other is used to lock the rotational dial for the times when you do not want it to move.

For DIC the polarizer must be in the proper orientation. There is a light click detent at that location. But for crossed polarization you will typically rotate it (and the subject, and the analyzer) until you get the desired effect.

Also, it is possible to move the larger disk holding the polarizer so that the polarizer is completely out of the light path. This is very helpful when doing darkfield or phase contrast (with a stop or annulus placed in one of the turret positions) since it provides about two more stops of light (and the polarizer is not used for those lighting methods... unless you are trying something really funky

)

rjlittlefield · Post by **rjlittlefield** » Sun Oct 16, 2011 2:02 pm

NikonUser wrote:Rik: If you are reading this - perhaps this topic should be moved to techniques and title changed to Polarization or something similar.

OK, done. I left a "shadow topic" in Beginners Micro since this seems like something that other people may want to run into by browsing.

--Rik

Charles Krebs · Post by **Charles Krebs** » Sun Oct 16, 2011 3:32 pm

On the BH2-UCD there are three layered concentric control rings. The upper one changes to the different turret positions (Nomarski filters, annuli for phase, darkfield stop and brightfield position... whatever you've put in there).

The middle one changes the condenser aperture size.

The lower one has two large notches, and moves the polarizer into and out of the light path.

Planapo · Post by **Planapo** » Mon Oct 17, 2011 12:39 am

Aww Charlie, thank you very much indeed for that instructive explanation!

Now I am much more confident to touch the valuable thing. Before, I had feared I could cause some damage... I seem to have a special gift to do so...

--Betty