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What Are the Two Light Sources of a Microscope?

Your microscope is made up of several parts, including a light source. This light source, referred to as an illuminator, is used to reflect light. While the eyepiece and objective lenses might appear to be the main lenses used in conjunction with the light source in producing a specimen's image for your viewing, it is really the condenser lens that helps direct the light source onto the microscopic specimen to be viewed.

Types
- Your microscope essentially has two light source options: a mirror or a bulb. Using a mirror will give you an illumination source that does not have to be replaced as often as a bulb light source. This means the mirror option is more economical in the long run. In addition, it will not require the need for electricity, so you can use it more easily in the field. However, using a mirror as your microscope light source can be problematic for work conducted in a darkened area, away from a secondary light source.
Significance
- When choosing a light source for a microscope that does not have a built-in illuminator, you should select one that has a wide light range. You want to be able to have higher illumination intensity when viewing objects through higher magnification and lower illumination capability during lower magnification uses. When selecting a microscope for purchase, choose one that contains a built-in illuminator with controls for light intensity as well as the shape of the beam projected.
Bulb
- You need a steady lighting source for your microscope and a lightbulb designed for microscope use is a good option. This lighting source is sometimes already built into the microscope, only requiring replacement at the end of its useful life. Bulbs types available for microscope use will vary based upon the type of microscope being purchased -- and its manufacturer -- but can be found in the following types: fluorescent, halogen, incandescent, reflector style and short-arc lamp bulbs. Voltage (110 to 120 AC) and wattage (50 to 100) will vary between the types somewhat.
Mirror
- Even microscopes using a mirror for illumination require an external light source. This external light source, which in the past has included clouds and the blue sky according to the Olympus Microscopy Resource Center, can result in poor illumination and distorted sample coloration. Before the use of bulbs, however, mirrors were the only way to capture the light needed to view items microscopically. Daylight and oil lamp light are the other examples of external light sources still being used with mirror light source microscopes.

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