Since its invention, compound microscopes made a remarkable contribution to the advancement of science. Compound means that microscope uses more than one lenses. Microscope is a combination of two Greek words, micron which means small and skopein meaning to look at. The modern compound light microscope was widely known for its importance in the field of biology. The discovery of bacteria and microorganism paid the way to one the greatest inventions of all time. Another equally important discovery was by Robert Hooke who was credited by his discovery of cell. In the world of medicine, Louis Pasteur of France discovered a yeast fungus and in the middle of the 19th century a German Bacteriologist, Karl J. Ebert made his discovery of Eberthella Thyphosa. Similar instrument was used by Robert Koch when he discovered tubercle and cholera bacilli. Composed of two optical elements this extraordinary instrument has a primary magnifying lens and a secondary lens system which is similar to a telescope which commonly referred as the ocular.

The primary or the objective lens is located close to the object which forms a magnified picture of the specimen and then the secondary lens will serve as the eye piece will act as a magnifier and produces an enlarged image of the image produced by the objective lens. Images produced by a compound microscope are two-dimensional and most images are upside down and backward compared to the actual reflection of the object. The same basic construction is being used in today’s microscope except that the primary and the secondary lenses are not single simple lenses but more are made of two or more optical elements. It maybe inverted or upright, compound microscopes can magnify through several of its objectives from about 4x to 100x, and its eyepieces can result to 10x to its total magnifications of 40x to 1000x (Objective x Eyepiece). A compound light microscope with a 2000x magnification can view bacteria, algae, protozoa and a range human/animal cells.

There are special types of compound microscopes; the first one is stereoscopic microscope which gives three-dimensional erectal image of the object. It’s like giving the viewer a different perspective of the specimen. These types of compound microscope are widely used in biological laboratories in experimenting tiny biological specimens. Another type is metallurgical microscope; this instrument illuminates normal specimen thicknesses of metals, minerals and ores. Since they are all opaque to brightness and cannot transmit light, all of them can reflect to a greater or lesser extent of light. To illuminate such specimens, there’s a light source attached to the body and to the other parts of the microscope. Next is polarizing microscope; this type has two additional elements – a polarizer and an analyzer. The polarizer send out light whose waves vibrate in one direction and the analyzer which is located between the specimen and the eye piece, is a second polarizing element.

This two elements block out the light coming from the specimen that does not affect the state of polarization. Fluorescence microscope made it possible to see biological specimens through mercury-vapor lamps. These lamps are loaded with light in the blue region of the spectrum and equipped with special light filters. The last type is the phase contrast and differential interference contrast (DIC) microscope, this type made it possible to see practically invisible structures without any deceptive chemical treatment and often times reveal better results than any conventional techniques.