These parameters fundamentally depend on the construction of the lens. In practice, the values ​​for a specific lens are usually written on the side of the body (mount) of the lens itself.

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Similar to lenses, a larger number of lenses will provide better correction of optical defects; so-called plan eyepieces provide the best correction of optical defects.

Schematic of the appearance of almost completely open (a) and half-closed (b) field diaphragms when viewed through the eyepiece.

Scheme of chromatic aberration - a) simple lens: rays of different wavelengths create three different foci, b) diplet lens: rays of different wavelengths meet at a common focus.

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The Eyepieces are the last part of the microscope through which the light rays from the light source pass. They participate in the final adjustments of the image. Similar to lenses, they consist of several lenses that work together as a connecting lens; but the number of lenses in the eyepiece is significantly smaller. The eyepiece lenses collectively produce an apparent, magnified, non-inverted image; the overall image produced by the microscope is therefore apparent, magnified and inverted.

The light microscope is mainly used for its relatively easy production and the ability to observe preparations dynamically, without damaging them (unlike microscopes using other types of electromagnetic radiation) and with preservation of color (unlike electron microscopes).

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The lighting apparatus is used to illuminate the object plane as perfectly as possible (that is, the plane of the table on which the specimen is located). The main function is to ensure the correct direction and intensity of the light rays to adequately illuminate the preparation (without unwanted reflections, so that the features and structures of the preparation are as clear as possible). This function is best fulfilled when applying the so-called Köhler lighting principle, which will be described below.

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When choosing an eyepiece, it is essential to choose an eyepiece that best matches the given lens - the main factors are the brightness , focal length and numerical aperture of the lens.

Köhler's lighting principle is the principle of setting the light apparatus in such a way as to achieve the best possible results in the contrast of the specimen. Applying Köhler's principle, the condenser projects a field diaphragm into the object plane, and the condenser diaphragm allows light to flow only into the field of view of the objective [4].

After being directed by the lighting apparatus, the light first passes through the observed specimen and then through the objective and eyepiece. Angled mirrors can be placed between the individual components of the lighting apparatus, which direct the light rays in the desired direction, but do not adjust the shape of the light cylinder/cone.

Scheme of coma/astigmatism - light rays do not point parallel to the optical axis, thus creating an asymmetric image (yellow ellipse) in the projection plane (blue circle).

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These parts are supplemented by a mechanical system into one functional unit. In developmentally older microscopes, it was common to use only one biconvex connecting lens and a kahan or candle light [1].

Optical components

Diagram of light flow through a light microscope: 1) light source, 2) collector lens, 3) mirror, 4) field diaphragm, 5) condenser and condenser diaphragm, 6) stage with specimen, 7) objective

In the preparation of specimens, dyes are often used , which cover the true color of the sample; however, different shades and depths of color are still preserved in places with different chemical and physical properties.

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The objective is the most important part of the microscope - the quality of the objective determines the resulting magnification of the microscope and the resulting image quality. It is also the most difficult to construct. It usually contains a large number of lenses of different shapes and in different groups (in triplets, doublets or individually) fixed in the lens barrel. The layout, number and shape of the lenses is individual for each type of lens and significantly affects all lens parameters. The entire lens system of the objective functions together as a connecting lens.

In practice, the mechanical system is the system with which the user comes into contact the most. A properly designed mechanical system is a necessary condition for a high-quality microscope: it ensures firm anchoring of the lenses and apertures, the correct angle of the light rays and the object plane, and a very fine mutual displacement of the optical systems and the object plane ("focusing").

A light microscope is a complex optical device that, with the help of several optical systems, enlarges the eye of vision and thereby improving its Resolution up to a thousand times.

In total, we distinguish three basic construction types of lenses: achromatic lens, fluorite lens and the most complex apochromatic lens. Achromatic and fluorite lenses have a smaller number of lenses at the same magnification value and thus a significantly worse correction of optical defects [5].

In addition to lenses, eyepieces also have an eyepiece diaphragm. According to the position of the eyepiece diaphragm in relation to the lenses, we distinguish two basic design types of eyepieces: the positive eyepiece, in which the diaphragm is located in front of the lenses (closest to the object plane), and the negative eyepiece, where the diaphragm is usually located behind the first lens. The simplest type of positive eyepiece with two lenses is called a Ramsden piece; the simplest type of negative eyepiece is called a Huygens eyepiece.

This high-quality 2/3" lens is suited for demanding machine vision applications at short working distances. When combined with the CMV 2000, IMX 249 and IMX 174 sensors increased vignetting can occur depending on the application.

Diagram of the appearance of the cone of light when the condenser diaphragm is open (a) and closed (b) - the condenser is located at the bottom, the light is directed into the lens.