Uses Of Bright Field Microscope
Brightfield Microscopes: Uses, Advantages and Limitations
The bright field microscope is the most common type of light microscope used for magnification and observation of specimens. This is the simplest and earliest type of microscopy that is used in a variety of settings, including classrooms, clinics, hospitals and research facilities. It uses a source of bright light for examination, where a specimen can either be stained or unstained. Inexpensive models of Brightfield Microscopes typically use a sub stage mirror to provide illumination while other models use a light source that is built into the unit.
Common components of the bright field microscope
The bright field microscope is made up of several parts. They are:
The base – the structure that supports the unit and contains the control for the adjustment of light intensity, which is usually an illuminator or electrical source of light.
Arm – the structure that provides support for the base and the lens system.
Objective lenses – these lenses are located nearest the object or specimen and enlarge the image using a combination of different magnification powers. The objective lens provides the aerial or primary image of the specimen.
Oculars – these are the lenses that magnify an image. These lenses are located nearest to the viewer. The ocular lens magnifies the image to put the primary image in focus. This helps provide the virtual or final image, which is the product of the ocular and objective lenses.
Revolving nosepiece – allows rotation of the objective lenses for better viewing position.
Stage – the platform where the microscope slide is laid and viewed.
Adjustment knobs – consist of the coarse adjustment and the fine adjustment knobs. The coarse adjustment focuses the image using the 4X and 10X objective lenses. The fine adjustment lenses focus the image using the high dry and oil immersion objective lenses (40X and 100X).
Condenser – this may be raised or lowered to focus the light for better viewing of the specimen.
Uses of the bright field microscope
Brightfield Microscopes provide images that appear dark-colored against a bright field. They are used extensively in classroom settings for the examination of specimen in biology and chemistry. This type of microscope may be used for either stained or unstained specimens. In microbiology, for example, simple stains such as crystal violet and methylene blue as well as differential stains such as flagellar stains, negative stains and endospore stains are often used to enhance details in a specimen for observation. Images of microorganisms may be magnified to a maximum of 400X. When specimens are stained, they can be further magnified with an oil immersion lens to a maximum of 1200X. Brightfield Microscopes are also effective in bacteriological microscopy because the oil immersion lens allows for increase in resolving power.
Advantages of Brightfield Microscopes
Brightfield Microscopes are not only easy to use, their setup is also simple, requiring only the most basic equipment. They also allow easy viewing and observation of live cells because there usually is no need to prepare the sample. For images that require viewing enhancements, a bright field microscope may be adjusted manually, allowing manipulation of the light source through the condenser, effectively reducing the resolution. Polarising filters may also be used with the light source to help enhance specimen features that are not apparent when under a white light. This makes Brightfield Microscopes also excellent viewing and magnification tools for mineral samples. They also perform excellently for magnification of transparent, opaque or semi-transparent specimens.
Limitations of Brightfield Microscopes
The bright field microscope is advantageous for images that are either dark or those which have significant refraction because the white background can effectively enhance the image. For other images, a bright field microscope may not provide the best view. The resolution of diffraction is limited to about 0.2 micrometer. Lights that are out of focus located in the external area of the focal plane further reduce the clarity of the image. Some images also do not have the natural contrast that allows them to be studied and viewed successfully using the bright field microscope. Some live specimens may also prove difficult to view using a bright field microscope, limiting imaging in real time.
This is why some specimens have to be stained in order to provide or increase the contrast of the different structural details. Be that as it may, staining may also introduce certain details into the specimen that are not part of the specimen itself, but are instead a caused by the processing. The apparent details may be misconstrued as a feature when in truth, they are not. However, background illumination may be corrected when using the device.
