The forensic and microbiological labs include a variety of microscopes that may be used. The value of microscopes is increased by how widely they may be used and modified.
A sharp dividing line in the eyepiece, which may be monocular or binocular in design, allows the user to observe a portion of the field of vision from each microscope, side by side while using two identical microscopes with the same optical system to provide the same magnification. In a single tiny area, the examiner can see a piece of two separate bullets or cartridges at once. Through the microscope’s shared eyepiece, light rays reflecting from the surfaces of both bullets are seen. The reflected lights from the primary markings of the two bullets are moved into the same line and inspected to see whether they tally by adjusting the placements of the two bullets.
It may be used to examine the surfaces of weapons or firearm parts as well as the surfaces of bullets, cartridges, gunpowder, and other cartridge components. This produces a three-dimensional view by using two eyepieces to capture images of the material being studied in two planes. This reflection microscope provides a surface view of any traces of components that may be present on the surface of another item. Because of the greater field of view, a larger surface may be inspected. Magnification ranges from 15 to 125.
Only specified types of items may be investigated using this microscope. In order to make the emitted rays visible due to the presence of the fluorescent agent, the specimen treated with the fluorescent agent causes the emission of rays of longer wavelength and reduced frequency after absorption of invisible short wavelength, high-frequency rays (such as UV rays).
By examining and analyzing in image contrast or colour, polarising microscopes, also known as petrology or geology microscopes, are used to observe the birefringent characteristics of anisotropic objects. To observe chemicals, rocks, and minerals, polarising light is combined with either transmitted or reflected light.
A cross-line reticle built into one of the polarising microscope’s eyepieces is handy for measuring and segmenting the specimens.
A Bertrand Lens is used by the microscope body to examine interference patterns in the objective’s rear focal plane.
One of the main functions of a polarising microscope is to detect variations in the optical path of the item under examination, enabling examiner to collect additional information about the specimen’s absorbance colour and optical path limits. A polarizer in the substage and compensator and retardation plates are used to improve this. In order to enhance image contrast and boost interference reflection quality by lowering disturbances at the glass-air interfaces, strain-free objectives and condensers are particularly constructed and chosen without inclusions.
Scanning Electron Microscope (SEM)
In order to identify an object or any trace materials up to the level of elements, this is utilised while studying the surface of various things. The usage of S.E.M. provides an incredibly detailed image of the surface of the material being tested for trace elements as well as a visual presentation of the electrons released by the element present in the testing substance, both of which allow for the easy identification of the trace elements. A heated tungsten filament emits an electron beam. Electromagnets are used to concentrate these electron beams on the surface of the test material. The main electrons that are concentrated create electron emission from the testing material’s surface. These released electrons are turned into focused images on a screen by being scanned, amplified, and fed into a cathode ray tube. The picture may be up to one lakh times larger than the actual size of the test particles. The enlarged image of the surface of the testing material seems to be in three dimensions and has a depth that is about 300 times greater than that of other surface microscopes. This aids in the identification of tiny trace components that are present on the surface of matter and whose precise nature must be recognised. When electrons strike a substance under test, X-ray is also produced and is reflected off the surface. The amount of X-rays released and their characteristics may be determined with the use of an X-ray analyser and recorder, allowing the elements present on the surface of the investigated sample to be identified.
Paints, metals, fibres, and other comparable materials are all analysed using it. SEM is the ideal tool for examining and identifying a paint layer’s uniformity and imperfections.
Along with X-ray fluorescence, it can be utilized. It is possible to detect very tiny particles and collect information about their basic elements. It is possible to examine the edges of paint chips, identify variances in their elemental composition, and compare them to those of other paint chips.
Transmission Electron Microscope (TEM)
The TEM is an electron microscope that can provide pictures of bulk materials and nanomaterials at almost the atomic level. Highly concentrated electron beams are employed in the TEM technique to pass through extremely thin nanoscale structures of organic and inorganic materials, as well as minuscule biological specimens including viruses, bacteria, DNA, and other elements. The thin specimen is exposed to electrons, which then impact a fluorescent screen and provide a picture of the item from top to bottom, both inside and outside. Depending on the uses, structures, and kinds of materials, TEM equipment has imaging and diffraction modes.
A compound microscope uses a single eyepiece and multiple “objectives” on a rotating ring that allow switching from one to another to increase magnification power. This type of microscope is also sometimes referred to as a “biological microscope,” though technically stereo microscopes are also included in this category. They are frequently employed in medical research and other professions where a high level of optical magnification is necessary, and are frequently found in schools, especially at higher levels.
The most frequent range of magnification for compound microscopes is 40x, followed by 100x, 400x, and even 1000x.
Biological Inverted Microscopes and metallurgical inverted microscopes are the two main types of inverted microscopes.
Biological inverted microscopes may typically magnify between 40x and 100x, and occasionally up to 200x or 400x. These can very handy for examining biological samples in petri dishes on a flat stage with the objective lens located underneath the stage. Invitro fertilisation, live cell imaging, developmental and cell biology, neurology, and microbiology are among the fields where they are often employed in business and research.
As the name implies, Metallurgical Inverted Microscopes are frequently employed in metallurgical industry and research. They are employed to identify flaws and fractures in surfaces and objects made of metal. Usually referred to as “pucks,” smooth, polished samples are put on the stage for viewing via an objective positioned below.
A digital microscope is an adaptation of a conventional optical microscope where the image output is shown on a screen and/or monitor due to a connection to a digital/microscope camera. Most models come with software and a usable PC.
Software enables the user to concentrate on and capture still and moving pictures of the material being studied. The resulting images can be utilised and saved just like any other digital picture file.
A method for observing live, unstained cells and microorganisms is known as dark-field microscopy. This microscope has a dark background and a bright lighted specimen. It is one of several types of light microscopes, including fluorescence, bright-field, phase-contrast, and differential interface contrast.
Using a light microscope with an additional opaque disc underneath the condenser lens or a unique condenser with a centrally blacked-out section, dark-field microscopy prevents light from the source from passing straight into the objective.
The light’s path is designed so that it can strike the sample at an oblique angle while passing through the condenser’s outer edge at a broad angle. For visualisation, only the light that is dispersed by the sample reaches the objective lens. The specimen is strongly lit against a dark background because any additional light that enters the specimen but misses the objective will not be seen.
A light microscopy method called phase contrast is used to improve the contrast in pictures of clear and colourless materials. It makes it possible to examine cells and cell parts that are difficult to see using a standard light microscope.