Imaging Without Lenses

Extract

In the past 10 or so years lens-less microscopies have proliferated tremendously, because they promise (and in many cases already deliver) substantial gains in performance when compared to other approaches to imaging. One of the perceived advantages is the superlative resolution which most of these techniques are (at least theoretically) capable of delivering. Another is that one can map any physical property for which there is a sufficiently sensitive detection system. Microscopists are no longer limited to imaging only regions of the sample which can be made to modulate light absorption or emission. All the simple nomograms showing what part of the spectrum to use if one wishes to see amoebae, bacteria or molecules will now have to be revised because of the advent of Scanned Probe Microscopes.

According to one of the dictionaries on my desk, a microscope is “an instrument containing one or more lenses for magnifying near objects”. The other says a microscope is “an optical instrument having a magnifying lens or a combination of lenses for inspecting objects too small to be seen, or to be seen distinctly in detail, by the naked eye”. So is it appropriate to call a lens-less machine a “microscope”? Should one disregard the “scholars, specialists and editors who worked to meet the essential needs of the reader, speaker, and writer who want to know, the meaning of a word”? Perhaps it would be better not to offend these distinguished and devoted linguists and instead call the new machines “Scanned Probe Instruments”, abbreviated SPI. SPI would obviously to be pronounced “spy”-reminding us that with SPIs we can indeed spy on the most intimate details of materials and, perhaps, of living things as well.