Features
General purpose of a microscope.
Nowadays, there are 4 main options for the appointment:
children's,
educational,
laboratory and
specialized microscopes. At the same time, different options (at least from the first three) may well be combined in one model — for example, the simplest and most inexpensive educational microscopes may well be positioned as children's, and the most advanced as laboratory ones. Here is a detailed description of the different destinations:
— Children's. The most simple and inexpensive microscopes, designed primarily for children who are taking their first steps in the natural sciences (as well as for other undemanding users who do not need particularly advanced functionality). Accordingly, such devices lack advanced features such as focus lock, Keller lighting, video outputs (for digital and opto-digital models), a trinocular with the ability to connect a camera, etc. In addition, the body can be made in bright colours, and in plastic is usually used as the body material. However, many children's microscopes are equipped with turrets for quick re-tuning of magnification, and the total magnification factor may well exceed 600x out of the box and 1000x in the top configuration.
— Educational. Microscopes well suited for teaching applications; sometimes such an appointment is even di
...rectly indicated by the manufacturer. The specific functionality of such models is quite diverse, the type can also be different (both biological and stereoscopic). In general, devices of this specialization occupy an intermediate position between simple and inexpensive children's microscopes and advanced laboratory equipment. At the same time, there are many models that have a combined purpose — "children's / educational" or "training / laboratory". The first variety is simple and inexpensive, for educational purposes it is suitable mainly for school; the second option, in turn, can be useful even at the university faculty of natural sciences.
— Laboratory. The most advanced type of modern microscopes, designed for full-fledged laboratory research and other serious tasks. Accordingly, such models are not cheap, but they provide a high-quality image and, in general, have the most extensive functionality (although the specific set of features, of course, may be different). Among the features found in laboratory microscopes are a movable stage, installation of light filters, 2 types of illumination (lower and upper), Keller illumination, suitability for special microscopy methods (fluorescence, phase contrast), etc.
— Specialized. Microscopes of a specific design and purpose, one way or another different from more traditional models. These differences may vary; accordingly, the specific specialization also differs. So, recently, portable models for smartphones have gained quite significant popularity: with the help of a special clothespin, such a device is attached directly to the gadget opposite the main camera, and the smartphone screen plays the role of an eyepiece. Another popular variety is compact digital microscopes without their own screens, connected to PCs or laptops via USB, and even to smartphones via Wi-Fi (including via the Internet). This also includes professional equipment with a fairly narrow specialization: stereoscopes with special mounts for dental prosthetics, for soldering microcircuits, etc.; microscopes for metallurgical research; devices on a tripod with a remote rod, designed to inspect individual areas on general objects; comparative microscopes for ballistic and trace investigations in forensics; and etc.Magnification
The range of magnifications provided by the device is from minimum to maximum.
The magnification of the microscope is calculated by the formula "the magnification of the eyepiece is multiplied by the magnification of the objective." For example, a 20x objective with a
10x eyepiece will give a magnification of 10*20 = 200x. Modern microscopes can be equipped with multi-objective turrets, zoom lenses (see below) and interchangeable eyepieces — so that in most models the magnification can be adjusted. This allows you to adjust the device to different situations: when you need to consider small details, a high degree of magnification is used, but to expand the field of view, the magnification must be reduced.
Detailed recommendations on optimal multiplicities for different tasks can be found in special sources. Here we note that many manufacturers go to the trick and indicate the maximum value of the magnification by the degree of magnification achieved with an additional Barlow lens. Such a lens can indeed give a serious increase in magnification, but it is not a fact that the image will turn out to be of high quality; for more details, see "Complete set".
Object table
The design of the object stage provided in the microscope.
— Stationary. Subject table, fixed motionless; focus in such microscopes is carried out by moving up and down the tube with the objective and the eyepiece. Such systems are simple and inexpensive, but focus while looking through a constantly moving eyepiece is not very convenient. In addition, for advanced biological microscopes (see "Type") with binoculars and trinoculars (see "Eyepiece"), this option is also poorly suited for some design reasons. But the vast majority of stereomicroscopes are equipped with stationary tables — this is the most reasonable design, taking into account the specifics of the application.
—
Movable. In microscopes of this type, the entire optical system is fixedly fixed on a tripod, and the stage can be moved up and down to focus the optics. This design is found exclusively in biological microscopes (see "Type"). It is somewhat more complicated and expensive than with a fixed table, but at the same time it is much more convenient: when focus, the eyepiece does not move, which allows you to comfortably adjust the image without looking up. In addition, it is the movable stage that is most suitable for advanced devices with binoculars and trinoculars (see "Eyepiece"), almost all such microscopes have such equipment.
Light filters
The presence of
light filters in the scope of delivery of the microscope.
Light filters are installed in the lighting system; they can be interchangeable or built-in (usually on a turret). Anyway, such devices change the characteristics of light, adjusting it to the specifics of the situation. The types and purpose of light filters can be different, as well as their range in the kit; here are some of the most common options:
— Blue colour. Useful in cases where light from an incandescent or "halogen" lamp is used for illumination. Such a filter equalizes the colour temperature (white balance), making the shades of colours colder and providing natural colour reproduction; this is especially important for microphotography, since a properly set white balance is critical to obtaining high-quality images.
— Yellow colour. Kind of the opposite of blue: lowers the colour temperature, giving the image a warmer tint. It is also sometimes useful for adjusting white balance, but yellow filters have another important use: they are well suited for detecting imperfections in metallic surfaces.
— Green colour. Achromatic and planachromatic objectives, which are installed in most modern microscopes, are best at eliminating aberrations in the green part of the spectrum. With this in mind, similar filters are applied: an image painted in a green tint has the least visible distortion. In addition, most objectives
...for phase contrast microscopy are also most effective in the green part of the spectrum (although exceptions are possible).
— Matte (diffuser). White colour filters that do not change the colour of the light, but provide additional dispersion. This can be useful, in particular, when working with low magnification lenses.
— Neutral. Filters in different shades of grey. Used to reduce the intensity of lighting without changing its other characteristics. Such devices can be especially useful when taking photographs — namely, if the camera does not have a sufficiently fast shutter speed. Note that a similar effect can be achieved using a microscope diaphragm, but this is not always the best option when shooting. So, narrowing the aperture reduces the field of view and increases the depth of field (the latter is also not always desirable), while filters do not affect these parameters; besides, in some situations, even the narrowest aperture may not be “dark” enough.
— Light filters for coloured preparations. Improve the visibility of elements painted in a particular colour. Such fixtures are especially popular in biological studies, as they are the most commonly stained specimens and are also the most susceptible to dye fading, making it difficult to view under normal lighting conditions. Note that filters of this type, in contrast to the colour filters described above, do not colour the entire image in a certain colour, but only muffle all other colours, except for their “native”.
— Fluorescent. Filters used in fluorescence microscopy. They are divided into two types — exciting (they separate UV radiation from the general backlight spectrum to illuminate the drug) and closing (protect the user's eyes from ultraviolet radiation and at the same time let the fluorescent glow of the drug pass through).
