New developments in light microscopy

Digital microscopes are a newly advance in light microscopy. Alternatively of objective and eyepiece lenses a CCD camera produces a digital image of a specimen that is produced on an images and screen can be viewed annotated and stored on the computer. Other recent improvements in light microscopy include differential interference microscopy, atomic force microscopy and confocal scanning microscopy. All these methods can create 3-dimensional images with improved depth of field over those of conventional light microscopy.

                                               Figure.  Phase contrast microscopy.

                                                Figure .  Dark field microscopy


Differential interference contrast microscopy uses a polarized beam of light which is split into two and both light beams are passed by the specimen. The beams are then reunited in the goal lens.  The image they produce is established from an interference effect caused through small changes in phase caused through passage by the specimen. The Cell organelles viewed with DIC which is known as differential interference contrast microscopy have a 3- dimensional quality.

In atomic force microscopy a living hydrated specimen is scanned using a microscopic stylus so small which it records minute repulsive forces that exist among it and the specimen. The stylus records changes in topography as it scans across the specimen in Figure 5. Data are then processed through computing to established detailed 3-dimensional images. No chemical fixatives or coatings required to be used with this method and thus the artifacts seen in SEM which is also known as scanning electron microscopy are avoided.

Confocal scanning laser microscopy CSLM uses a laser light source and computing to create 3-dimensional digital images of thick specimens. The precision of the laser beam, focused by a pinhole, insures which is only a single plane of a specimen is illuminated at one time in Figure 6. By adjusting focus, different layers of a specimen can be complex and viewed images can be created from digital data. Artificial colors and Fluorescent staining linked to depth or density differences in the specimen can be used to enhance the image. CSLM is particularly useful in the study of microbial ecology of soils and biofilms.

                              Figure .  Confocal scanning laser microscopy