Phase contrast, whats the deal?

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GreenLarry
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Phase contrast, whats the deal?

Post by GreenLarry »

I know a bit about microscopy, and have made my own dark field stop for my student scope, but what exactly is phase contrast, and what is its purpose? Is polarization involved as I see lots of colours.

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piotr
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Post by piotr »

Hi Larry, and welcome to the group! :-)

Basically, phase contrast is a microscopy contrast enhancement technique that allows visualizing transparent objects, e.g. live cells. Various objects can retard (delay) light wave in a different way, and phase contrast technique helps to visualize this difference. The technique was invented in 1930s by a Dutch scientist Frits Zernike, who later was awarded a Nobel Prize for this discovery.

It is a bit more complicated than dark field microscopy. Two elements are required: a phase stop (annulus) in a substage condenser, and a specialized phase objective that includes a phase ring at a back focal plane.

My explanation is far from being clear, so you may wish to read a great description of phase contrast technique on Molecular Expressions website: Phase Contrast Microscopy.

One of our group members, Graham, has made a phase contrast setup by himself. He has got pretty impressive results. Check out his website: A very big small world.
Piotr

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GreenLarry
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Post by GreenLarry »

Ah thanks Piotr, this rings a bell!
Two elements are required: a phase stop (annulus) in a substage condenser, and a specialized phase objective that includes a phase ring at a back focal plane.
I seem to remember reading up on something like this a few years ago!

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