A microscope (from the Greek: mikrós, "small" and skopeîn, "to look" or "see") is an instrument used to see objects that are too small for the naked eye.

MICROSCOPY:

The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.

It was in the 16th century when the first compound microscope was discovered by and credited to Zacharias Janssen. Through placing an object at the end of a tube, and placing two lenses on top and bottom of the tube, Zacharias and his father Hans, realized that the object became magnified. Thanks to this discovery, more breakthroughs and innovations were developed that lead to the microscopes we are using today.

MAGNIFICATION:

For calculation of the total magnification when viewing an image with a light microscope, first take the power of the objective lens which is at 4x, 10x or 40x and then multiply it by the power of the eyepiece which is generally 10x. It means, a 10x eyepiece used with a 40x objective lens, will produce a magnification of 400x. Magnification is a measure of increase in diameter of an object.

RESOLUTION:

Resolution means the degree of detail. Resolving Power may be described as the ability to measure the separation of images that are close together. The shorter wavelength ensures increased resolution.

PRINCIPLE OF WORKING:

MAGNIFICATION SYSTEM:

Stereo microscopes have two major types of magnification systems. One fixed magnification and other zoom magnification. Primary magnification is a part of fixed magnification which is achieved by set of objective lenses with a set degree of magnification. While with Zoom magnification, range of magnification is already set and magnification can be continuously changed within that range. If one wants more magnification of the object, it can be achieved by using auxiliary objectives that increase total magnification by a set factor. By changing the eyepiece, one can increase or decrease total magnification of both fixed and zoom system. In between these two magnifications, there are fixed-focus convex lenses that are arranged so to achieve the fixed magnification. This system is called "Galilean optical system". But the difference to fixed magnification is that if same arrangement of these convex lenses is physically inverted one will get the different magnification. So to get two different magnifications, same set of lenses can be used; two sets of lenses will provide four magnifications and so on. Galilean optical system is a good replacement of expensive zoom magnification system.

ILLUMINATION:

Fiber optic light source with halogen lamps is used to illuminate specimen which gives high light output for a given power input. Many other light stalks are also used for the same specimen, so increasing the illumination yet further.

VIEWING HEADS:

  • MONOCULAR
  • BINOCULAR
  • TRI-NOCULAR

1. MONOCULAR

The use of only one eyepiece when viewing the specimen. The monocular microscopes are light weight and inexpensive.

2. BINOCULAR

A microscope having two eyepieces. It is most comfortable to use as a common choice.

3.TRINOCULAR

It has a third eyepiece tube that can be used by another person simultaneously or by a CCD camera. The trinocular option is more expensive than monocular or binocular.

HOW DO MICROSCOPES WORK? 

The most basic microscopes used in various institutions today make use of a series of lenses that collect, reflect, and focus light into the specimen, which is the object under inspection. Without the presence of light, microscopes won’t work. This kind of microscope is typically used in research centers, schools, and hospitals.

The use of different microscope lenses promotes magnification without altering the quality of the image produced. Also, most microscopes have binocular lenses consisting of two lenses and a prism to split the image on both oculars where you’ll peek through. 

On another end of the microscope are objective lenses which are responsible for collecting and concentrating light into the specimen. These objective lenses have varying strengths which can be used one at a time by adjusting the revolving nose-piece. 

An instrument called an eyepiece magnifies the object by changing the wavelength of light that is used in the instrument to make it function. There are many types of eyepieces, each capable of different tasks. The most common eyepieces are those which use gas-displacement technology to supply light. The next common eyepiece is the gas-corrected model. The third common eyepiece is the photocell model. 

Other types of eyepieces exist and are used depending on the needs of the experiment being conducted. By learning how a microscope works, researchers will be able to use these eyepieces in their experiments, thus providing better ways to study nature and its workings.

Microscopes are usually powered by batteries or by mechanical mechanisms to allow the observation of objects up to 10 times smaller than their original size. If a microscopic specimen is not handled correctly or in an inappropriate way, it can distort the image and give misleading results. Therefore, using the right type of microscope and handling it properly is important for viewing your chosen object. 

Here are five types of microscope, their specific qualities, and uses:


1.    SIMPLE MICROSCOPE

A simple microscope is simply a large magnifying glass with a shorter focal length that has a convex mirror with a small focal area. The most common examples of this type of device are the handheld lens and eyepiece lens. 

When a material is held close to the lens of the microscope, its focus is created, and the original object becomes magnified and more erect. Then, it focuses on a portion of the material by bringing together the two edges of the lens. This creates a smaller, more focused image of the material than the larger area. 

Since it’s only a simple microscope, it only has one magnification level depending on what lens is used. Therefore, simple microscopes are only used for reading and magnifying non-complex items. For instance, you can use a magnifying glass to zoom in the details of a map. 


2.    COMPOUND LIGHT MICROSCOPE 

A compound microscope is the most common type of microscope used today, which mechanism is explained earlier. It is basically a microscope that has a lens or a camera on it that has a compound medium in between. This compound medium allows for magnifications in a very fine scale. 

While the simple microscope only requires natural light to see the object, a compound light microscope needs an illuminator to view the specimen. These are the basic specifications of a compound microscope: 

Magnification: This pertains to making the specimen look larger through the microscope through zooming in the lenses. Magnification is a quantified property which ranges from 40x, 100x, 400x, and up to 1000x. 

Resolution: This refers to how good the image is captured by the compound microscope lens. A higher resolution means that the image will be clearer and more detailed. Also, it has an improved visual clarity as it has more layers of magnifications. 

Contrast: Like in photography, the background’s darkness relative to the focus or specimen is referred to as contrast. Excellent contrast is typically achieved through staining the specimen so its colors would stand out when viewed in the microscope. 

Compound microscopes are extremely useful for research on different areas. It has made a big impact on science and technology in general. Some of its popular uses are when viewing a scientific specimen for educational and research purposes.  

3.    STEREO MICROSCOPE

The stereo microscope, dissecting or stereoscopic microscope, is an optical microscopy version designed specifically for low magnification imaging of a biological specimen. It works through reflecting light off the specimen’s surface rather than transmitted through its medium. 

This type of microscope is often used in chemistry laboratories where more detailed, three-dimensional images are required that would be possible with an electron microscope or other high-powered microscope. While the stereo microscopy technology has existed for over 100 years, stereo microscopes only recently have come into being in the laboratory and can produce higher quality images than ever before.

Many people choose stereoscopes over other microscope models because it can produce better quality images depending on one’s needs. In addition, these microscope models require less maintenance and are inexpensive. Stereo microscope applications involve less thorough microscopic requirements, such as viewing manufacturing materials, circuit board work, dissection, and inspection.


4.    SCANNING ELECTRON MICROSCOPE (SEM)

A scanning electron microscope is a very popular type of scanning electron microscopes, which produces images of a material by scanning the sample with a high-powered beam of electrons. The electrons interacting with atoms within the sample create different signals which contain data about the structure and topography of the material. The images that are produced using these microscope instruments are highly accurate as well as they can be viewed in high resolution using a microscope eyepiece or magnifier. 

To obtain appropriate results from an SEM, the sample or specimen should have electrical conduction for the electrons to bounce off on its surface, thus producing a clear image. For the sample to become electrically conductive enough, they’re coated in a thin layer of metals like gold. 

Several techniques can be employed to enhance the image quality of SEM, such as: fluorescence imaging, tip electron microscopy, multi-beam scanning and the use of colloidal crystals. 

Additionally, it’s important to use the microscope in good working condition as this will reduce the quality of images that you receive. With all these things in place, you can have a great instrument that will allow you to view and examine the smallest sample possible. 

Listed below are the best applications and uses of a scanning electron microscope:

  • Semiconductor inspection
  • Materials science
  • Medical science
  • Soil and rock sampling
  • Nanowires for gas sensing
  • Art 

5.    TRANSMISSION ELECTRON MICROSCOPE (TEM)

Transmission electron microscopy is an optical microscopy method in which an electrical beam of electrons is transmitted through an unstained sample to create an optical image of the sample. Instead of sending electrons to scan and bounce off the specimen as what SEMs do, TEMs allow the electrons to pass through the thin sample. The sample is usually an ultrathin slice less than 50 micrometers thick or an electrolyte suspension suspended on a grid of grid-like plates.

In contrast to ordinary compound microscopes, TEMs have amazing magnification that’s possibly 10,000 times more than what optical microscopes do, allowing researchers to view exceptionally small specimens. It can even illustrate the arrangement of the atoms within a sample. 

Because of the sophistication of TEMs, they’re extremely technical and expensive. Students usually don’t have access to this type of microscope as they’re for scientists doing demanding work involving the field of nanotechnology, medical research, life sciences, biological research, material research, gemology, and metallurgy.  

However, the samples require detailed preparation where it must be placed in a vacuum chamber. Thus, living samples such as protozoa can’t be examined under TEM. While the samples can be stained or coated with chemicals to protect their structure, there are higher chances that the microscope will still destroy the sample. Despite these drawbacks, the contributions of transmission electron microscopes are unrivaled. 

CARE AND WISE USE OF MICROSCOPES

Ever hold a microscope firmly by the stand, only. Don’t catch it by the eyepiece holder.

When to unplug the illuminator; hold the plug (not the cable).

After completion of lab work, turn the illuminator off.

The stage and lenses should be cleaned before putting away the microscope.

Always use a good quality lens tissue or a cotton swab (100% natural cotton) to clean an optical surface. Appropriate lens cleaner or distilled water may be used to help remove dried material. Organic solvents will damage the lens coatings.