Compound Microscope Parts

Compound Microscope Parts
A high power or compound microscope achieves higher levels of magnification than a stereo or low power microscope. It is used to view smaller specimens such as cell structures which cannot be seen at lower levels of magnification.
Essentially, a compound microscope consists of structural and optical components. However, within these two basic systems, there are some essential components that every microscopist should know and understand.
These key microscope parts are illustrated and explained below.
STRUCTURAL COMPONENTS
The three basic structural components of a compound microscope are the head, base and arm.
•Head/Body houses the optical parts in the upper part of the microscope
•Base of the microscope supports the microscope and houses the illuminator
•Arm connects to the base and supports the microscope head. It is also used to carry the microscope.
When carrying a compound microscope always take care to lift it by both the arm and base, simultaneously.

OPTICAL COMPONENTS
There are two optical systems in a compound microscope: Eyepiece Lenses and Objective Lenses:
Eyepiece or Ocular is what you look through at the top of the microscope. Typically, standard eyepieces have a magnifying power of 10x. Optional eyepieces of varying powers are available, typically from 5x-30x.
Eyepiece tube holds the eyepieces in place above the objective lens. Binocular microscope heads typically incorporate a diopter adjustment ring that allows for the possible inconsistencies of our eyesight in one or both eyes. The monocular (single eye usage) microscope does not need a diopter. Binocular microscopes also swivel (Interpupillary Adjustment) to allow for different distances between the eyes of different individuals.
Objective Lenses are the primary optical lenses on a microscope. They range from 4x-100x and typically, include, three, four or five on lens on most microscopes. Objectives can be forward or rear-facing.
Nosepiece houses the objectives. The objectives are exposed and are mounted on a rotating turret so that different objectives can be conveniently selected. Standard objectives include 4x, 10x, 40x and 100x although different power objectives are available.
Coarse and Fine Focus knobs are used to focus the microscope. Increasingly, they are coaxial knobs - that is to say they are built on the same axis with the fine focus knob on the outside. Coaxial focus knobs are more convenient since the viewer does not have to grope for a different knob.
Stage is where the specimen to be viewed is placed. A mechanical stage is used when working at higher magnifications where delicate movements of the specimen slide are required.
Stage Clips are used when there is no mechanical stage. The viewer is required to move the slide manually to view different sections of the specimen.
Aperture is the hole in the stage through which the base (transmitted) light reaches the stage.
Illuminator is the light source for a microscope, typically located in the base of the microscope. Most light microscopes use low voltage, halogen bulbs with continuous variable lighting control located within the base.
Condenser is used to collect and focus the light from the illuminator on to the specimen. It is located under the stage often in conjunction with an iris diaphragm.
Iris Diaphragm controls the amount of light reaching the specimen. It is located above the condenser and below the stage. Most high quality microscopes include an Abbe condenser with an iris diaphragm. Combined, they control both the focus and quantity of light applied to the specimen.
Condenser Focus Knob moves the condenser up or down to control the lighting focus on the specimen.

Microscope Parts

Microscope Parts
Eyepiece Lens:  the lens at the top that you look through.  They are usually 10X or 15X power.
Tube:  Connects the eyepiece to the objective lenses
Arm:  Supports the tube and connects it to the base
Base:  The bottom of the microscope, used for support
Illuminator:  A steady light source (110 volts) used in place of a mirror.  If your microscope has a mirror, it is used to reflect light from an external light source up through the bottom of the stage.
Stage:  The flat platform where you place your slides.  Stage clips hold the slides in place.  If your microscope has a mechanical stage, you will be able to move the slide around by turning two knobs.  One moves it left and right, the other moves it up and down.
Revolving Nosepiece or Turret:  This is the part that holds two or more objective lenses and can be rotated to easily change power.
Objective Lenses:  Usually you will find 3 or 4 objective lenses on a microscope.  They almost always consist of 4X, 10X, 40X and 100X powers.  When coupled with a 10X (most common) eyepiece lens, we get total magnifications of 40X (4X times 10X), 100X , 400X and 1000X.  To have good resolution at 1000X, you will need a relatively sophisticated microscope with an Abbe condenser.  The shortest lens is the lowest power, the longest one is the lens with the greatest power.  Lenses are color coded and if built to DIN standards are interchangeable between microscopes.  The high power objective lenses are retractable (i.e. 40XR).  This means that if they hit a slide, the end of the lens will push in (spring loaded) thereby protecting the lens and the slide.  All quality microscopes have achromatic, parcentered, parfocal lenses.
Rack Stop:  This is an adjustment that determines how close the objective lens can get to the slide.  It is set at the factory and keeps students from cranking the high power objective lens down into the slide and breaking things.  You would only need to adjust this if you were using very thin slides and you weren't able to focus on the specimen at high power. (Tip: If you are using thin slides and can't focus, rather than adjust the rack stop, place a clear glass slide under the original slide to raise it a bit higher)
Condenser Lens:  The purpose of the condenser lens is to focus the light onto the specimen.  Condenser lenses are most useful at the highest powers (400X and above).  Microscopes with in stage condenser lenses render a sharper image than those with no lens (at 400X).  If your microscope has a maximum power of 400X, you will get the maximum benefit by using a condenser lenses rated at 0.65 NA or greater.  0.65 NA condenser lenses may be mounted in the stage and work quite well.  A big advantage to a stage mounted lens is that there is one less focusing item to deal with.  If you go to 1000X then you should have a focusable condenser lens with an N.A. of 1.25 or greater.  Most 1000X microscopes use 1.25 Abbe condenser lens systems.  The Abbe condenser lens can be moved up and down.  It is set very close to the slide at 1000X and moved further away at the lower powers. 
Diaphragm or Iris:  Many microscopes have a rotating disk under the stage.  This diaphragm has different sized holes and is used to vary the intensity and size of the cone of light that is projected upward into the slide.  There is no set rule regarding which setting to use for a particular power.   Rather, the setting is a function of the transparency of the specimen, the degree of contrast you desire and the particular objective lens in use.