CHOOSING A MICROSCOPE

 

Our philosophy "fitness for purpose" certainly rings true when choosing a microscope.  It is simply a question of getting the right instrument for the task at hand and not going overboard!  We hope the following will help you understand about the different types of microscope and also understand how the microscopes we offer can be used.  If you need some advice on which microscope will best suit your needs, fill out the form on our home page and we will match you with the right microscope!

 

Applications

 

In our opinion, the most important factor when choosing a microscope is your application.  What do you want to look at; what are the most appropriate magnifications and lastly, what type of lighting will help you to see what you want to see?

 

A common misconception is that the higher the magnification the better.  This could not be further from the truth!  It all depends on what you are looking at!  The more the microscope magnifies an object, the smaller the part of it (also referred to as the "field of view") that can be seen at any one time.  The small this field of view, the more difficult it is to work out what the object is.  For example, an insect magnified at 400x may be completely unrecognisable, however at a magnification of say 20x, this will yeild more information and provide greater perspective - the image can be recognised as an insect.  On the other hand, looking at blood cells at 20x will yield little information.  Increase the magnification to 400x to 500x however, and the individual cells can be clearly seen.

 

Two types of microscope

 

There are basically two types of optical microscope: the stereo (not to be confused with binocular) and compound.  If you need to look at circuit boards or other relatively large objects, you would probably use a stereomicroscope.  If you need higher magnifications to view structures of cells, etc., you would most likely use a compound microscope.

 

Stereomicroscopes 

 

 Stereomicroscopes give a viewer an erect (upright and unreversed) "stereoscopic" (3-dimensional) image using two distinct optical systems, very

  much like our own eyes.  At this point it is 

  important to point out a common misconception. 

  Just because a microscope has two eyetubes, it

  does not mean it is a stereomicroscope.  A

  compound microscope (which we will talk about

  next) can also have two eyetubes (making it

  binocular as opposed to monocular).  A

  stereomicroscope is particularly useful for those

  performing dissections, technicians repairing

  circuit boards or anyone who needs to work with

  their hands on smaller objects.  Most stereomicroscopes are used at magnifications from 5x to 50x, but with proper stereomicroscope and accessory optics, magnifications up to 400x can be achieved for certain applications.

 

This type of instrument has a much greater "depth of focus" (i.e. what is in focus at any one time) than the compound microscope, so it is very useful for those doing inspection work.

 

For the above reasons, we recommend that younger people who are making their first foray into the wonders of the magnified world, be introduced to this type of instrument.  Children can put everyday objects and samples collected from outside quickly and easily under the instrument and observe at a relatively low magnification.  All too often we hear of parents purchasing a "microscope" from a toy store (boasting magnifications of 600x, 800x plus and requiring slide preparation) and being disappointed when the images are poor and unrewarding.  For beginners we recommend our models S-10-P or ST-30R-DL

 

These instruments will certainly introduce the wonders of the magnified world.  For those users requiring slightly more sophisticated instruments or with a larger range of accessories, we offer a comprehensive range or laboratory and research quality instruments. 

 

Compound Microscopes

 

Compound microscopes are normally what people picture when they think about a microscope.  They have a number of objectives of varying magnifications mounted in a nosepiece that rotates.  Typically the range of magnification of a compound microscope is between 40x and 1000x; the standard range of magnifications for a student microscope in New Zealand schools is between 40x and 400x (in fact three magnifications - 40x, 100x and 400x).  Because only one objective is used at a time, the viewer sees a two-dimensional image of the specimen.  This is different from the three-dimensional image produced by a stereomicroscope.  Whereas a stereomicroscope will have two eyetubes/eyepieces, the compound microscope can be monocular or binocular (or even trinocular for image capture - e.g. our B3-302TR).  A binocular compound microscope provides no additional information, however it is recommended if the instrument 

for very long periods.  For beginners and students, we generally recommend the monocular instruments to be perfectly adequate.  Examples are our 100F and 100FL models.

 

Compound microscopes can, themselves, be divided into a number of categories, depending on the type of material being examined or the type of illumination required to examine that material.  Compound biological microscopes are used for examining biological material, cut extremely thin and sandwiched between and microscope slide and coverslip.  The normal illumination method employed is "transmitted light" (i.e. light is transmitted through the specimen) and the contrast method is normally "brightfield".  Other contrast techniques are available for transmitted light such as "darkfield", "oblique illumination" or "polarised light" and these can be extremely useful, depending on the particular specimen being imaged.

Polarising microscopes, although they are usually used to examine very thin slide preparations of rock samples, also use transmitted light.  

 

Other types of compound microscopes, such a "metallurgical" or "incident/reflected light" instruments employ a method of "incident light" (i.e. the light is reflected down onto the specimen and back up to the objective) to image specimens such as plastics, polished metal samples, rock samples etc.  It is also possible to use transmitted light as an option also (e.g. polarising microscopes) depending on the type of sample and the type/quality of information required.  The standard contrast technique is brightfield but others (as mentioned above) can be used.

 

The Macroscope

 

There is another type of microscope - the macroscope - a cross between the compound and stereomicroscope.  A macroscope utilises a single, vertical optical system similar to a compound microscope, but with a relatively high depth of field, similar to a stereomicroscope.  We offer the Meiji Techno range of macroscopes and our microEYE DISCOVERY interactive videomicroscope.  A single, vertical optical system has the additional advantage of being very useful if precise measuring tasks are required.

 

Image Capture

 

Capturing an image from a microscope (using the traditional 35mm SLR camera, digital SLR camera or digital or video CCD/CMOS cameras) can be carried out on virtually all microscopes in our range.  For further information, please contact us.

 

So, talk to us about what you need or want.  We will make sure you choose the right microscope for your application.    

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