One week…   Leave a comment

The cells have been growing all week without any contamination…. I’ve moved some cells into the differentiation incubator, so there should be ciliated cells in another week- if everything remains sterile.

So, in the meantime, I took a few images demonstrating how a certain type of imaging works: differential interference contrast imaging (DIC).

Usually, DIC is performed in transmission- most of the wiki pics are in transmission mode. However, it’s possible to perform reflection DIC as well on surfaces that are highly reflective. Without getting into too much detail about how it works (the wiki article has it all), in reflection mode DIC converts the slope of the surface into color. For example, a steep slope may be red, but a gradual slope may be blue, and as the color turns from blue -> green -> yellow -> red the slope gets steeper.

Razor blades are the *perfect* object to show this effect: this was taken at 16X

This is a clean single-edge blade used in boxcutters. What you are seeing is where the tapered part of the blade starts- the vertical stripes are from the grinding process. Realize this is bare shiny metal, and the color comes from the lens (and other optical components)- it’s not a rainbow-hued Photoshop job.

Making images like this is fairly straightforward, but there is some ‘art’ to getting really colorful images. Here’s another example, imaging the front lens of a 16X Epiplan HD objective.

‘HD’ means the lens is made for darkfield imaging and the lens is actually similar to a catadioptric lens. The front lens is very flat- perfect for DIC imaging.

Good lenses have a special thin coating on them to prevent unwanted reflections from occurring- plain glass reflects about 7% of the light, and if you have 3 or 4 lenses, about 50% of the light is lost to these reflections. These coatings have special optical properties and on most coated lenses, if you look at the lens the right way with your eye, you can see a deep purple color.

I exploited the optical properties of the coating using DIC imaging to make the coating change color:

For some technical reasons, I had to correct the overall brightness of each image to make them all appear similar, but the effect is clear.

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Posted September 24, 2010 by resnicklab in Physics, Physiology, pic of the moment, Science

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