A light microscope is an instrument that can be used to display the smallest structures in a recognizable way. These are magnified accordingly by the action of lenses.
What is a microscope?
A light microscope is understood to be an instrument with which the smallest structures can be recognizably displayed. By using a light microscope, it is possible to magnify images extremely. The smallest objects, organisms or living beings can be easily recognized by the human eye through the magnification. The light microscope achieves magnification through various optical effects. The name light microscope includes the ancient Greek terms “micron” and “scopein”. In German translation, this means “to look at something small”. The light microscope has the property of magnifying the objects to be examined by exposure to light in such a way that the observer can look at them. Magnifying lenses were used as early as the 16th century. The physiological principles for the light microscope, which are still valid today, were developed around 1873 by the German physicist and optician Ernst Abbe (1840-1905). They made it possible to construct more efficient microscopes. Thus, the production of objectives now took place whose resolution limit was no longer determined by the quality of the material, but instead by the physical laws of diffraction. The physical resolution limit was given the name Abbe limit. The production of the corresponding microscopes took place in the optical workshops of Carl Zeiss (1816-1888).
Shapes, types and types
The light microscope can be divided into several types. For example, among others, there is the reflected light microscope, in which the light comes from the same side on which the observation is made. It is mainly used in fluorescence microscopy and for the examination of opaque objects. Another form is the stereo microscope, which has separate beam paths for both eyes. In this way, the object can be viewed from several angles, giving a three-dimensional impression. The surgical microscope is used by doctors specifically to perform surgical procedures, while the trichinoscope is used for examinations that detect trichinae (threadworms). A measuring microscope is a light microscope equipped with an additional device that can be used to measure objects. A modern variant is the computer microscope. With a USB cable, it is connected to a computer that displays the image of the object. A distinction must also be made between simple and compound light microscopes. Simple microscopes have optical lenses through which high magnification is achieved. There is a smooth transition to the magnifying glass, whose principle works in the same way, although its magnification is significantly weaker. Nowadays, compound light microscopes are mainly used. They consist of two lens systems. The lens marking the foremost optical element creates an intermediate image. Re-magnification of this image takes place through the eyepiece.
Structure and operation
Built up a light microscope from the lens system, the eyepiece, objectives, a deflecting prism, a tube as well as a tube carrier. Furthermore, the microscope has a so-called objective nosepiece at its upper end. This revolver holds the objectives, which are selected and locked in place by means of a rotating wheel. For the presentation of an object to be examined, an object stage and object clamps are used. In its lower section, the light microscope is also equipped with a light source, an aperture, and a condenser. To provide stability to the light microscope, it is supported by a base. The foot allows the instrument to be moved or lifted. With the aid of the aperture, the user sets the optimum exposure for the object under examination. The diaphragm can be opened or closed by means of a control slider. The condenser focuses the light radiation and directs it onto the object. The light sources of the microscope are usually located at its base. This may be a mirror that makes sunlight usable for microscopy. However, electric lamps are considered to be more uniform and reliable. The objective of the light microscope has the effect of a converging lens.It provides magnification of the image to be examined and generates an intermediate image in the tube in a first step. The eyepiece, which acts like a magnifying glass, provides significant magnification of the intermediate image in the second step. Using this method, a light microscope can produce magnifications of up to 1400 times. In a sense, the function of the light microscope is based on viewing an object in backlight. The light starts at the light source on the underside of the microscope. The object is penetrated by the light, resulting in an intermediate image in the tube through the objective, which is then magnified by the eyepiece.
Medical and health benefits
The light microscope is one of the most important medical instruments. For example, the microscope made it possible to elucidate numerous fundamental scientific questions. In addition, it enabled medicine to make important modern developments. In medical use, the light microscope is primarily used to evaluate microorganisms, body cells, blood components or tissue samples. Before carrying out special therapies, it is often indispensable to microscopically determine the causative pathogens such as bacteria or fungi. Precise detection of the pathogens is also possible using the light microscope. This involves a laboratory examination of samples such as blood, pus or wound secretions, through which the responsible bacterium can be precisely identified. One disadvantage of the light microscope, however, is that it can hardly detect viruses. An electron microscope is better suited for this purpose. The light microscope also plays an important role in microsurgery and minimally invasive surgical procedures.
