What is Microscope?
Microscope is derived from Ancient Greek words and composed of mikrós, “small” and skopeîn,”to look” or “see”.
It is one of the most revolutionized scientific instruments used to observe or examine minute structures not clearly visible from naked eyes.
In 1665, for the first time Robert Hooke made an impressive Micrographic illustration using microscope.
Antonie van Leeuwenhoek, another scientist made significant contribution in microscope research by magnifying the simple single lens microscope 300 times.
What Microscope does?
Microscopes magnify or enlarge small objects such as cells, microbes, bacteria, viruses, microorganisms etc. at a viewable scale for examination and analysis.
Microscopes consist of one or more magnification lenses to enlarge the image of the microscopic objects placed in the focal plane.
The magnification power of simple laboratory microscope is 1250x.
Types of Microscope
There is various type of microscope such as transmission electron microscopes (TEMs), scanning electron microscopes (SEMs), atomic force microscopes (AFM), near-field scanning optical microscopes (MSOM or SNOM, scanning near-field optical microscopy, and scanning tunneling microscopes (STM).
However, the most common type of microscope is optical microscope.
Microscope Parts and their Functions
In general, microscopes are made up of supporting parts to hold the structure of Microscopes and optical parts, consist of lenses used to magnify the specimens.
The description given below summarize the brief description of microscope parts used to visualize the microscopic specimens such as animal cells, plant cells, microbes, bacteria, viruses, microorganisms etc.
The Microscopes parts divided into three different structural parts Head, Base, and Arms.
Head/Body: It contain the optical parts in the upper part of the microscope.
Arm: It supports the tube and connects it to the base.
Base: The bottom of the microscope, used for support.
Optical Components of Microscope
Eyepiece Lens: the lens at the top that you look through, usually 10x or 15x power.
Tube: Connects the eyepiece to the objective lenses.
Illuminator: Illuminator is the most important microscope parts and it serve as light source for a microscope during slide specimen visualization.
It is a continuous source of light (110 volts) used in place of a mirror. The mirror of microscope is used to reflect light from the external light source up through the bottom of the stage.
Usually, the Illuminator located in the base of the microscope. Most light microscopes use low voltage, halogen bulbs with continuous variable lighting control located within the base.
Stage with Stage Clips: The stage of a microscope is a flat platform where you place your subject slides. Stage clips hold the slides in place.
The mechanical stage of your microscope will help you to move the slide around by turning two knobs. One knobs moves it left and right, the other knobs moves it up and down.
Revolving Nosepiece or Turret: Turret is the part of the microscope that holds two or multiple objective lenses and helps to rotate objective lenses and also helps to easily change power.
Objective Lenses: Three are 3 or 4 objective lenses on a microscope. The objective lenses almost always consist of 4x, 10x, 40x and 100x powers.
The most common eyepiece lens is 10x and when it coupled with others, total magnification is 40x (4x times 10x), 100x , 400x and 1000x. Objectives can be forward or rear-facing.
Microscope Rack Stop Rack Stop: Rack Stop is an important microscope parts that determines how close the objective lens can get to the slide.
It keeps the students from damaging the high power objective lens down into the slide. If you cann’t able to focus on the specimen at high power while using very thin slides then slight adjustment helps you to adjust the focus.
Diaphragm or Iris: Most of the laboratory microscopes have a rotating disk under the stage known as diaphragm or iris.
Iris Diaphragm controls the amount of light reaching the specimen. The Iris Diaphragm is located above the condenser lens and below the microscope stage.
The different sized holes in the diaphragm helps to vary the size of the cone and intensity of light that is projected upward into the slide. However, there is no set rule regarding which setting to use for a particular power.
The specimen transparency, degree of contrast and particular objective lens in use decide the Diaphragm or Iris setting. Majority of high quality microscopes used in laboratory include an Abbe condenser with an iris diaphragm.
When iris diaphragm is combined with Abbe condenser, it control both the quantity of light applied as well as focus on the specimen.
Aperture: It is the hole in the stage through which the base (transmitted) light reaches the stage.
Condenser: Condenser lenses are used to collect and focus the light from the illuminator on to the specimen.
Usually the Condenser lenses are located under the stage in conjunction with an iris diaphragm. Condenser lenses helps in ensuring clear and sharp images are produced with a high magnification of 400X and above.
Magnification power of the condenser is directly realted to the image clarity.
Most of the sophisticated microscopes in the laboratory come with an Abbe condenser that has a high magnification of about 1000X.
Condenser Focus Knob moves the condenser up or down to control the lighting focus on the specimen.
How to Focus Your Microscope?
The most appropriate way to focus a microscope in the laboratory is to start with the lowest power objective lens.
While looking from the eyepiece lens, crank the lens down as close to the specimen as possible without touching it.
Once everything is then, look through the eyepiece lens and focus upward only until the image is sharp.
If you can’t get it in focus, repeat the whole process again.
Once the image is sharp with the low power lens, then only you should change high power lens and do minor adjustments with the focus knob.
If your microscope has a fine focus adjustment, turning it a bit should be all that’s necessary.
Continue with subsequent objective lenses and fine focus each time.