Confocal Laser Scanning Microscopy (CLSM) is an optical imaging technique based on laser beam scanning over the specimen. The confocal principle makes possible to produce an image of exclusively the focal plane. This is due to a pinhole positioned in front of the detection system which rejects all light that originates from the outside of the detection volume defined by the focal plane (Fig. 1). Contrary to it, in ordinary microscope, the light that comes from place other than focusing position is overlapped with image forming light at focusing position and whole image Tums blurry.
The image is reconstructed point-by-point in the CLSM as the laser beam, focused to a very small spot, scans point-by-point over the specimen in X-Y directions. Thanks to the optical sectioning behavior, unique for the confocal light microscope, 3-dimensionally resolved images of the specimen surface or the internal structure of semi-transparent specimen under investigation are produced. The optical slicing is possible due to the confocal principle because part where light was repelled is truly darkened in the image and particular plane scans are
This is done by computational technique gathering images of recorded focal planes obtained by scanning the specimen in a direction of light axe. The contrast mechanisms conventionally used are based on reflection (ordinary Fresnel reflection as well as generation of scattered light due to local variations of the refractive index) and fluorescence. The first mechanism is used in materials science; the latter one is widely used in biological applications.
The CLSM is relatively new nondestructive method, fast and easy to operate. It over bridges the gap existing between traditional optical microscopy (OM)and scanning electron microscopy (SEM). The reason is high resolution and contrast and no special requirement for sample treatment and size. The scanning is carried out at room temperature under atmospheric pressure.
The method obtained the primacy in the field of biology where possibilities of morphology study are successfully improved thanks to the fluorescent dyes and selective markers. The observed objects are usually small (proteins, various cell part, tissues) therefore it is possible to scan the whole volume of sample and create its spatial image. But nowadays, the CLSM is more and more uses also in materials science. It is successfully used for investigation of topography and morphology of polymers, ceramics, wood, fibers, bones or teeth; it is used for investigation of changes of polymers or composites due to an applied mechanical stress, and so on.