When choosing a microscope, it can be overwhelming wading through a wide range of information. There are also a a lot of microscopes being sold. One may end up with a poor quality microscope, which will not meet their required needs.
However, there are several factors to consider before actually purchasing a microscope including the lighting options, the type of specimens to be observed as well as the type and construction of the microscope among others.
The stereo microscope, also referred to as the dissecting or stereoscopic microscope, typically use two different paths of light which allows the user to see a specimen in 3D.
Although these microscopes have a high depth perception, they have the disadvantage of low resolution and magnification. They are excellent for the purposes of dissecting, viewing insect specimens and fossils.
The best models of these types of microscopes are composed of a built in light source as well as zoom capabilities.
A digital microscope may either be a stereo or compound microscope. These types of microscopes enable the user to capture still images and video images, which can then be displayed on to the computer monitor.
This is made possible by the presence of optics as well as a charge coupled device (CCD) moreover, these microscopes contain imaging software that allows the user to zoom, create special effects as well as time lapse images and editing.
Typically, these types of microscopes have an inbuilt led light source. A digital microscope differs from the stereo microscope due to the fact that a digital microscope has no provision that Allows direct viewing through an eyepiece.
Once an individual has considered which type of microscope to purchase for given purposes, it is important to consider a number of other variables, most importantly being the quality of the microscope. The quality of the microscope will depend on a number of factors that include:
The Quality of Construction
There are a wide range of microscopes from those made of plastic which would be considered a toy to the cheaply constructed imported scopes. A majority of these are have inferior structure that can break easily in addition to giving minimal optical quality. This can be avoided by purchasing from a reputable vendor. With regards to construction, sturdiness is one of the most important qualities to consider when purchasing a microscope. This should be solidly constructed and composed of a sturdy metallic allow. A strong construction would be important since it would possess a certain degree of durability and will last longer as compared to that of plastic.
The majority of microscopes have a built in light source either use a fluorescent, tungsten or halogen bulb. Those with a fluorescent bulb system tend to be more expensive as compared to the tungsten system.
However, their light quality is brighter and they give out lesser heat as compared to halogen or tungsten bulb systems.
LED illuminators are going for almost the same prices as the fluorescent systems are today becoming more and more popular in microscopy. Although they have similar color rendition problems as those of fluorescent systems, they have a variety of benefits given that they can draw in lesser power and essentially emit no heat.
For example in the case of a battery powered microscope, they would be the ideal choice since they use less power.
The quality of optics will largely depend on the quality of the objective lenses in addition to the quality of the eyepiece, but this is secondary. An achromatic lens is used as the standard for good quality objective lenses.
Achromatic lens- this is the lens that corrects for the fact that different colors refract through curved, glass lenses at varying angles.
It is also important to ensure that the objectives are DIN (Deutsch Industry Norm) compatible. This is because DIN objectives become useful given that they are interchangeable from a DIN compatible microscope to another. In this case, the user can replace a damaged objective rather than purchasing a new microscope.
With eyepieces, a wider eyepiece allows for easier viewing. Some of the best ones include wide field (WF) or super wide field eyepieces (SWF).
However, it is important to keep in mind that the lens width will decrease relative to the size of the magnification power.
Some of the other factors to consider would include:
Abbe Condenser and Iris Diaphragm
When purchasing a compound microscope, it is critical to ensure that it has a good quality condenser and iris diaphragm. Typically, the best Abbe condenser will allow for greater level of adjustments.
The two are found in the sub-stage of a microscope and are typically used to adjust the base illumination. Some of the compound microscopes will have an iris diaphragm as well as an Abbe condenser as a standard.
This is a useful part of the microscope. When viewing at high magnifications, the mechanical stage becomes very important.
With a good mechanical stage, it would be much easier to move the slide in a fine differential, and thus following a moving organism across the slide is much more effective.
The Focusing System
The focusing system allows for the movement of the stage. For high power use, it is necessary that the user have a fine adjustment system that works effectively in addition to the course adjustment knob.
It would be wise to ensure that the knobs have no backlashes. During observation, the user may need to turn the fine adjustment knob both directions, and thus it has to respond well without problems.
When purchasing a microscope, it would be wise to purchase a brand that is of higher quality than a mediocre instrument that will eventually cost the user more in replacements and upgrades.
Research has also shown that some of the most high quality microscopes include those from Japan and Germany. However, they are more expensive as compared to others.
The user should always
take into account their needs (for home or school purposes or advanced
research) in addition to considering the instrument as an investment, thinking
long term, so as to avoid purchasing the wrong microscope initially.
Paul E. Nothnagle, William chambers, and Michael W. Davidson, Nikon microscopy. "introduction to stereomicroscopy"
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