Dissecting/Stereo microscope | Principle, Parts, working, and applications of Stereo microscope

What is a stereo microscope

Microscopes are used widely nowadays for researches as well as academic experiments in schools and colleges. While Simple microscope and Compound microscope are used commonly for studies but stereo microscope is no less.

There are a lot of microscopes in the market right now and stereo microscope like others is different and beneficial in its way to the scientists. It is known for low magnification but serves many different and important purposes.

Stereo microscope also known as Dissecting microscope is an optical instrument used for the observation of objects in low magnification, in which the instrument uses the light reflected from the surface rather than using the transmitted light from the object. It helps in examining the objects in 3D such as rocks, fibers, soil, electronic items, etc.

The 3D examination of objects by Stereo microscope makes it unique than other microscopes. Here, in this article we will talk about its principle, working and applications.

What is a Stereo microscope?

There are two types of light microscope i.e., Compound microscope and Stereo microscope. Both have their own characteristics and have certain advantages over each other.

Stereo microscope is a variant of optical microscope that uses the light reflected from the surface for examination in 3-Dimension. It also uses two separate optical paths so that the object is viewed from different angles.

The microscope also has a characteristic feature of photography to record and examine the samples for a detailed examination. They have two light sources among which one is above the sample reflected onto the eyepiece while the other is below sample for illumination.

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History of Stereo microscope

The first stereoscopic microscope was built by Cherubin d Orleans in 1671 which had two eyepieces and matching objectives. However, the design had major flaws such that the image erection was done only by the use of supplemental lenses.

Another flaw included the projection of image. This flaw projected the right side of image to the left eyepiece while the left side of image was projected to the right side.

In the mid-19th century, Francis Herbert Wenham from London designed a true stereo microscope in which he used the achromatic prism to split the beam of light at the rear of single objective.

In early 1890’s, Horatio S. Greenough of America invented the modern Stereo microscopic design and convinced the Zeiss company of Jena, Germany to produce the microscope. The company accepted the offer and produced the microscope with little modification with the help of company’s engineers.

Instead of using the Greenough’s Lens erecting system they produced it by inverting the prisms that produces an erect image. This particular design of stereo microscopes is still used.

Parts of Stereo microscope

Parts of stereo microscope

The different parts of stereo microscope includes:

  1. Stand/Arm: It can be considered as the backbone due to the fact that it supports the upper part of microscope by connecting it with the base.
  2. Base: It is the lower part of the microscope that holds the other parts of microscope thus providing stability during the examination.
  3. Stage: The stage in stereo microscope is the base. The sample is kept on the base to examine. They are large and can hold large specimens.
  4. Light Source: Most of these microscopes use LED illuminators as their light source.
  5. Focus Knob: These kind of microscopes have a single focus knob that moves head up and down for exact focus.
  6. Objective lens: It has different objective lens with different magnification powers.
  7. Eyepiece: It consist of two eye lens with its own magnification.
  8. Diopter settings: It helps in the focusing difference between the left and the right eye.
  9. Digital Camera: These microscopes include a digital camera for recording and capturing the images of specimens.
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The stereo microscopes also include Prism, Relay lens and Reticle. Prism is used for bending light and changing the orientation of the image whereas Relay lens is used to invert the image while Reticle is a small piece of glass that is used to make measurements.

Working Principle of Stereo microscope

  • The principle of stereo microscope depends on the 2 different paths of light from objective lens and the eyepiece. Both these lights provides a different angle of viewing in which the bottom light is used for viewing the samples while the top light is used during dissecting.
  • The two eyepieces enables in this microscope enables a comforting view of the sample from different angles simultaneously.
  • It also consists of a digital camera that is used for viewing the images of the samples in the computer for a close observation. The image produced is a little larger than normal and is recorded.
  • The dissecting microscope has two magnifications known as Fixed magnification and Zoom magnification. Fixed magnification is used in eyepiece to provide a degree of magnification while Zoom magnification offers different magnifications at different ranges.
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Ray diagram of stereo microscope

Magnification of Dissecting/Stereo microscope

The total magnification power of dissecting microscope is the combination of both the lenses present in the microscope i.e., the objective lens and the eyepiece.

If the objective lens is of 10x and the eyepiece is of 6x then the total magnification power of dissecting microscope is:

M = 10x * 6x = 60x

Applications of Stereo microscope

Like any other optical instrument, dissecting microscope is also used in various fields of medicine, manufacturing, quality control, etc. Some of its applications include:

  • It is used for dissection of samples.
  • It is used for inspection of fractures.
  • It is used for microsurgery in hospitals.
  • It is used to clean and analyze fossils.
  • It is used by biologists for dissection.
  • It is used in all kinds of industries for quality control.
  • It is used by dermatologists for examining skin diseases.
  • It is used by watch-makers due to the small components of the watches.
  • It is used to study flowers and other plants.
  • It is used in studying insects.
  • It is used in Forensic engineering.
  • It is used to study the topography of solid samples.
  • It is used by technicians to repair circuit boards.

Conclusion

Stereo microscope or Dissecting microscope is used widely in various departments of researches and has a lot of applications. It has many more advantages over other microscopes due to which it has brought wonders in microscopy.

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