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  • Microscopes
  • microscope accessories

Abbe Condenser - Compensated eyepiece

1. Abbe Condenser

A condenser is a sub stage lens that focuses light on the specimen. The Abbe condenser is the most widely used condenser system in use on microscopes today. It is typically used with an adjustable iris, in effect allowing the operator to change the diameter and focal point of the light entering the slide. By moving the condenser up and down and changing the opening on the iris, the contrast and detail in the specimen can be precisely set for best image quality. All microscopes at magnifications over 400x will require an Abbe condenser or the equivalent.

The potential N.A, (numerical aperture) of a system is only as good as its weakest link. Any objective with an N.A. of 0.4 or more will require a condenser and oil and water objectives will require a condenser in keeping with their higher N.A. The typical Abbe condenser has a numerical aperture (N.A.) of 1.25 and will thus allow the use of objectives with an N.A. up to 1.25. Higher N.A. objectives will require a higher N.A. condenser system.

2. Aberration

An optical flaw, usually associated with a particular lens design, though it can also be produced through improper lens grinding.

3. Achromatic Objectives

Different colors of light (wavelengths) come to a different focus point when they emerge from a lens. The color fringe around the specimen thus produced is known as chromatic aberration. This optical defect causes loss of detail and resolution. Achromatic objectives or achromats focus two wavelengths (red and blue), but not the green, thus reducing chromatic aberration, but not eliminating it. However, for most applications, achromats are suitable and if well made, will do an excellent job at a relatively affordable price. The achromat, for this reason, remains the most common type of objective in use today.

4. Aperture

This is simply the diameter or width of a lens. All else equal, the greater the aperture, the higher the resolution. In a microscope, however, there are other factors that must be considered. See numerical aperture (NA)

5. Apochromatic Objectives

To bring all wavelengths to the same focus point requires an apochromatic objective, often referred to as an APO. These high performance objectives employ complex lens systems and are thus expensive, but for serious research they remain the design of choice.

6. Arm

The section of the microscope body that connects the eyepiece tube to the rest of the body.

7. Articulated Arm

An articulated arm is a hinged arm, which allows the user to set the angle of the eyepiece tube for the sake of comfort.

8. Asbestos Microscope

An asbestos microscope is typically a specialized version of a polarized light microscope modified to asbestos counts for legal work. Requires the use of a compensated eyepiece.

9. Base

The part of the microscope that comes in contact with the table or other surface used to support it.

10. Bertrand Lens

This is a small lens used in the tube of a polarized light microscope and is used to study interference patterns for the sake of identification and analysis.

11. Binocular Head

Monocular head microscopes (microscopes offering only one ocular) produce eyestrain and fatigue over extended viewing sessions. For this reason, all serious microscopes use a binocular head offering two eyepieces. Fatigue and eyestrain are greatly reduced.

12. Bright field Microscope

This is the most common microscope system used in classrooms and for many applications, a bright field is adequate. In a bright field microscope, objects appear dark against a bright background. Illumination is sub stage via a mirror on inexpensive models or more typically, a built in light source using a bulb of various types. Best used for opaque, semi-transparent or transparent specimens that have been stained.

13. C-mount

The standard 25.4mm thread size used on camcorders and video cameras with interchangeable lenses. A C-mount equipped microscope has a tube or adapter that allows photography with a camcorder.

14. Chromatic Aberration

Different colors of light (wavelengths) come to a different focus point when they emerge from a lens. The color fringe around the specimen thus produced is known as chromatic aberration. This optical defect causes loss of detail and resolution. Chromatic aberration is partially corrected with an achromat objective and fully corrected with an apochromat.

15. Coarse Focus

This knob is used at low power to bring the specimen to focus quickly. The use of the coarse focus knob should be restricted to lower magnification objectives which offer greater working distances. High magnification objectives have very short working distance and in order to prevent damage to the slide, specimen and possibly the objective, high magnification objectives should only be used with fine focus.

16. Coaxial Focus

A common arrangement of focusing knobs featuring a knob within a knob, most often with the smaller knob the fine focus.

17. Compensated eyepiece

For most visual work, knowing the approximate magnification delivered by a system is sufficient. Applications requiring counts, however, require the operator to know the exact magnification of the system. Compensated eyepieces are designed to work with specific objectives to deliver an exact magnification.

Microscope Glossary of Terms