Orbis non sufficit
Friday, April 14, 2006
Another World
I've just been writing up my report for physics on the SEM, or Scanning Electron Microscope. In the course of my research I naturally found my way to wikipedia, where I found some awesome pictures taken with an SEM. The one used must have been so much better than the one steve and I used, some of the stuff had a resolution of 36000x. Steve and I were amazed when we got a clear picture at 5000x. Check out the wikipedia article on it sometime, for the pictures if nothing else. Also follow a few of the external links to pictures, there are some great ones there too. Here's a couple of my favourites (be sure to click for enlarged versions):
Snowflake magnification series
Assorted Pollen
Ant
The way the SEM works is actually pretty interesting, and also quite simple in principle, I'd say most non-physics people should still be able to understand it pretty easily (simple, but pretty freaking tricky to actually constuct I'd say). It's also quite brilliant.
Basically it shoots a beam of electrons down on a sample, focused really, really tightly (focused onto a spot approx 1-5 nm across) using magnetic fields, which causes some interactions to occur and electrons to be emitted from the sample. These are then detected by an instrument which decides how bright that particular pixel of the image should be based mostly on how many electrons it counts. Yes, just the one pixel. The beam is then moved a tiny bit to repeat the process for the next pixel, doing this again and again (like a tv), scanning over a section of the sample. Of course it does all this very quickly, scanning the whole section around 30 times per second. Pretty impressive really. Surface angles and different elevations affect the number of electrons that come flying off the surface, giving good surface contrast, so you get a really nifty 3D looking image.
Actually when you take the final image it does the scanning a lot more slowly, so you get a much higher resolution picture than the one on the tiny real-time monitor.
I've just been writing up my report for physics on the SEM, or Scanning Electron Microscope. In the course of my research I naturally found my way to wikipedia, where I found some awesome pictures taken with an SEM. The one used must have been so much better than the one steve and I used, some of the stuff had a resolution of 36000x. Steve and I were amazed when we got a clear picture at 5000x. Check out the wikipedia article on it sometime, for the pictures if nothing else. Also follow a few of the external links to pictures, there are some great ones there too. Here's a couple of my favourites (be sure to click for enlarged versions):
Snowflake magnification series
Assorted Pollen
Ant
The way the SEM works is actually pretty interesting, and also quite simple in principle, I'd say most non-physics people should still be able to understand it pretty easily (simple, but pretty freaking tricky to actually constuct I'd say). It's also quite brilliant.
Basically it shoots a beam of electrons down on a sample, focused really, really tightly (focused onto a spot approx 1-5 nm across) using magnetic fields, which causes some interactions to occur and electrons to be emitted from the sample. These are then detected by an instrument which decides how bright that particular pixel of the image should be based mostly on how many electrons it counts. Yes, just the one pixel. The beam is then moved a tiny bit to repeat the process for the next pixel, doing this again and again (like a tv), scanning over a section of the sample. Of course it does all this very quickly, scanning the whole section around 30 times per second. Pretty impressive really. Surface angles and different elevations affect the number of electrons that come flying off the surface, giving good surface contrast, so you get a really nifty 3D looking image.
Actually when you take the final image it does the scanning a lot more slowly, so you get a much higher resolution picture than the one on the tiny real-time monitor.
Comments:
That pollen one enlarged looks awesome, near the top right is that some sorta of electrical occurance? cool pics tho (Y)
nah you can't capture electrical disturbances with an SEM, they buggerise the image. It's just some organic stringy thing. And yeah, the pollen rocks, I was pretty amazed at how spherical and symmetric it was. It looks like someone has computer modelled it, not taken a real picture.
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