Types of microscope light sources
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Resolution increases with the quality of the light that passes through  your specimen.   

That is why old or cheap microscopes that use a rotating mirror to catch ambient light lead to unsatisfactory images  especially at higher magnifications.  

You will need a built-in, dimmable electric light source, as shown on point A of the above diagram.

Resolution is improved when shorter wavelengths of light are used to illuminate your specimen because shorter wavelengths are more intense.  Different type of light have different wave lengths.

Tungsten globes

A hot light, like a tungsten globe is likely to dry out the specimen. Tungsten globes are cheap but are often hard to replace in older microscope models because they were not standardised when they became popular for built in microscope lighting.

Fluorescent and LED globes  are cool, cheap to run and  long-lasting.

  • Fluorescent globes produce more natural  looking images. 

LED globes

  • Are usually dimmable

  • Are available in various versions of white light with those having more violet light  having the  shortest wavelengths.

  • But LED globes are often wired into their own circuit making them hard to replace.
Halogen globes

  • Medical and research microscopes are likely to have halogen bulbs.

  • Their light is intense but produce natural colours.

  • They usually have dimmer controls. 

  • A  binocular scope is best with halogen or LED lighting  because of the extra brightness needed to light  both tubes.
Other Pointers
  • Check that the microscope globe and fitting is a standard type that preferably can be purchased for common applications.

  • Otherwise  you may not be able to replace the globe when it fails some years down the track.
     
  • Make sure the light is dimmable rather than just having an on and off  switch.

    There should be a moveable diaphragm  called a Field Diaphram, located near  the light source as in the diagram point  b.  

    It will allow you to  control the diameter of the light beam  to eliminate stray light and send all the light upwards toward your specimen. 

Click here to learn about other factors that increase the quality of microscope light and hence the resolution of observed images.
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