Microscope:Definition,Function,Structure,Classification and different observation methods

A microscope is an optical instrument consisting of a lens or a combination of several lenses, mainly used to magnify tiny objects into instruments that can be seen by the human eye. 

Structure and names of microscope:

Classification of microscope:

• Biological microscope: a common type of microscope, can be divided into orthostatic and inverted. Magnification can be up to 1000x.

  Orthostatic microscope: can be used to observe biological sections, biological cells, bacteria, and living tissue culture, fluid precipitation and other observation and research, and at the same time can observe other transparent or translucent objects, as well as powders, fine particles and other objects.

  Inverted microscope: the imaging is the same as ordinary microscope, except that the objective lens and illumination system are reversed, the former is under the stage, the latter is on top of the stage, used for observing cultured living cells, with phase contrast objective lens.

• Stereomicroscope:Also known as "stereomicroscope" or "operating and dissecting microscope". It is generally able to see samples at magnifications of 8 to 56 times. It is a kind of microscope with stereoscopic sense of positive image, which is widely used in industrial fields such as macroscopic surface observation of materials, and is widely used in various sectors of biology, medicine, agriculture, forestry, industry and marine biology.

• Polarising microscope: Also known as "mineral microscope" or "ore microscope", it is a kind of microscope used to study substances with birefringence. For example, to look at the composition of traditional Chinese medicine, you need to look at the crystals, which are samples with diametrical properties, that is, birefringent substances. There are important applications in geology and other scientific and technical disciplines.

• Metallographic microscope: mainly observe metal or material samples, mostly irregular or opaque substances.Used to identify and analyse the phase and tissue constituents of the constituent materials, grains, non-metallic inclusions and even the number of certain crystal defects, morphology, size, distribution, orientation, spatial arrangement of the state and so on. Mostly used for electronic component analysis, measurement.

Different microscopic observation methods:

• Brightfield: the most common way of observation, the light from the illuminator is directed vertically through the objective lens and incident on the specimen, the direct reflected light from the specimen is observed through the objective lens. Mainly look at conventional stained film, such as HE staining, etc.

• Dark Field: In contrast to bright field observation, the illuminating light is directed obliquely through the periphery of the objective lens onto the specimen, and the interfering and diffracted light from the specimen is observed. It is mainly used to look at the appearance of small particles, such as bacterial counts, etc.

• Phase contrast: also known as "phase contrast", enhances contrast and shows the difference between light and dark that is clearly visible to the naked eye; often used with an inverted microscope. Mainly seen in live cell specimens, such as cell cultures, membrane clamps, etc.. Between the cell body and the liquid, there is a distinct halo. 

• Fluorescence: fluorescent labelling of samples for observation, mainly for substance identification, such as antibodies, antigens, fluorescence in situ hybridisation (FISH), etc.