Laser Microscopy

Laser microscopy (or laser scanning microscopy) is a class of techniques for generating microscopic images of some sample by raster scanning it with a diffraction-limited laser beam. Scanning may be achieved by moving either the laser beam or the sample. Typically, the laser beam excites fluorescence in its focus, and the intensity of that fluorescence light is recorded for each point in the sample (→ fluorescence microscopy). From these data, images can be produced on a computer, and of course they can be stored in electronic form. Numerical methods can be applied to process the images, e.g. to enhance the contrast.

A frequently used imaging technique is based on a confocal geometry, where the light from the focus in the sample is imaged (e.g. with a microscope objective) onto a pinhole, behind which the optical power is detected. This geometry suppresses the influence of light coming from other regions in the sample, e.g. from before or after the focus, because such light can not efficiently pass through the pinhole. In effect, mainly the depth resolution is improved. The confocal principle is emphasized in the term confocal laser scanning microscopy, and discussed in more detail in the article on fluorescence microscopy.

Instead of fluorescence, one may exploit acoustic effects of pulsed laser beams; the resulting method is called optoacoustic or photoacoustic microscopy.

Jesús Ramirez
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