Terminological Confusion
A confocal microscope is one of the best applications that I know to the principle of spatial filtering.
The idea is simple: you take a normal light microscope, pass the light that is reflected from the sample through a lens, and then put an aperture with a small pinhole near the focal point of the lens, and look only at the light that went through. This allows you to slice the picture according to different heights, so you get a 3D image of the sample, instead of the 2D images normal microscopes give you. A simple trick, that revolutionized biological imaging in the past few decades.
In my spare time, I recently played a bit with confocal microscopes. The simple principle I just described is transformed into very expensive systems, with multiple channels, beam spliters, filters, lasers, and more. The systems give the opportunity to use fluorescent dyes and paint the samples in differerent colours, collecting each colour to a different path. The system is, of course, computerized, and you can play with filters and stuff.
I noticed many filters are marked in things like “LP 546″. This means, that the filter lets through light with wavelength greater then 546nm. At first, it confused me. In electrical engineering the term “LP” is a technical term, used to indicate “Low Pass” - meaning that anything below the specified number should go through. Then I explained to myself that the higher wavelengthes have shorter frequency - so they just mixed up the term for frequency with the number that indicates wavelength (which is reasonable, because nobody related to light in terms of frequencies - it is much more common to relate colours to the wavelength, in the technical world).
Then, I talked with some biologists. “It is easy,” they explained to me “the term, as we study it, is actually long pass, not low pass, so what is your problem?”
Well, I guess that’s how it goes when you try to speak in several of the scientific languages at the time. Confusion in the terminology always rise.
August 8th, 2008 at 14:54
BTW - I’ve read a sci-fi story a while back where an alien species was described that only has a single eye (a very large one though) but uses rapid focus changes to achieve depth perception. I wonder if it was modeled after such a microscope.