BY- K. Sai Manogna (MSIWM014)

 

The microscope is an instrument that creates enlarged photographs of small objects, enabling the viewer to display minute structures in a too near manner at a scale that is convenient for observation and study. Although optical microscopes are the focus of this article, many other types of wave, like acoustic, X-ray, or electron beam, can also enlarge the image and receive it by direct or digital imaging or a combination of these methods. The microscope can give a dynamic picture (as with traditional optical instruments) or a static one (as with conventional scanning electron microscopes).

The Compound Light Microscope - ppt video online download

The Resolution (or) Magnification: 

1. The magnification of a microscope tests the amount of times the object tends to increase in size and the magnification ratio.

2. It is typically expressed in the 10-fold form (for a 10-fold magnified image), often misrepresented as “ten eks,” as though the algebraic symbol were an algebraic symbol, rather than the correct “ten times.” form.

3. A microscope’s resolution is a measure of the smallest object detail that can be observed. Resolution is expressed in linear units, which usually are micrometers.

Different types of microscopes: 

Optical Microscope or Light Microscope:

The optical, or light microscope, consists of glass lenses used to shape the image, which is the most familiar microscope type. Optical microscopes, consisting of a single lens or compound consisting of many in-line optical components, may be straightforward.

Optical Microscope - an overview | ScienceDirect Topics

a. The Resolution: 

The hand magnifying glass will magnify approximately 3 to 20 points. Single-lensed simple microscopes, though compound microscopes can magnify up to 2,000, can magnify up to 300, and can expose bacteria. Under 1 micrometer (μm; one-millionth of a meter), a simple microscope can resolve; a compound microscope can resolve down to around 0.2 μm.

b. Image of Interest: 

1. By photography through a microscope, a process is known as photomicrography, photographs of interest may be captured.

2. This has been done with film since the 19th century, but digital photography is now used widely instead. Some optical microscopes have dispensed with an eyepiece and view images on the computer screen directly.

3. A modern series of low-cost digital microscopes with a wide variety of imaging possibilities, including time-lapse microscopy, has made previously challenging and costly tasks much easier for the beginner or amateur microscopist.

Other types of microscopes use the wave nature of different physical processes. The electron microscope uses an electron beam in its image creation, which is the most important. There are magnifying powers of more than 1,000,000 in the transmission electron microscope (TEM). In a near-vacuum, TEMs shape images of thin specimens, usually parts. A scanning electron microscope typically has a lower resolution than a TEM, which produces a mirrored image of relief in a contoured specimen, but can display concrete surfaces in a way that the traditional electron microscope cannot. Microscopes that use lasers, sound, or X-rays are also available. The Scanning Tunnelling Microscope (STM) can generate atoms, and the Environmental Scanning Electron Microscope (ESEM), which produces images of specimens using electrons in a gaseous atmosphere, use other physical effects to broaden further the types of objects that can be examined.

History of Microscopes:

1. The theory of magnification has been established for a long time. “About 1267 In Perspectiva, English philosopher Roger Bacon wrote, “Because of the greatness of the angle under which we can see them, we can number the smallest particles of dust and sand,” and in 1538 in Homocentrica, Italian physician Girolamo Fracastoro wrote, “If someone can look through two spectacle lenses, one superimposed on the other, the image seems something much larger”. 

2. Hans Jansen and his sons, Zacharias Jansen and Hans Lippershey, three Dutch spectacle makers, received credit for inventing the compound microscope around 1590.

3. The first illustration of a microscope was drawn in the Netherlands around 1631. It was a compound microscope with an oculus and an objective lens. In the mid-17th century, this kind of instrument, which came to be made of wood and cardboard, often decorated with polished fish skin, became increasingly popular and was used by the English natural philosopher Robert Hooke to provide the new Royal Society with frequent demonstrations.

4. These demonstrations began in 1663, and Hooke published a folio volume titled Micrographia two years later, which offered a wide variety of microscopic views of recognizable objects such as fleas, lice, and nettles. He coined the word cell in this book.

5. The description of how a single high-powered lens could be made into a serviceable microscope is concealed in the unnumbered pages of Micrographia’s preface. Using this template, the Dutch civil servant Antonie van Leeuwenhoek began his pioneering observations of freshwater microorganisms in the 1670s.

6. He made his postage-stamp-sized microscopes by hand, and details of about 0.7 μm could be resolved by the best of them. More than three centuries later, his fine specimens found at the Royal Society in excellent condition show what a great technician he was.

7. Leeuwenhoek’s simple microscopes launched microbiology in 1674, and single-lensed microscopes remained popular until the 1850s.

8. The Scottish botanist Robert Brown used them in 1827 to illustrate the ubiquity of the cell nucleus, a phrase he invented in 1831.

9. Using single lenses, simple microscopes can produce fine images; but they can also produce spurious colors in which various wavelengths of light do not come to the same focus due to chromatic aberration.

10. In the compound microscopes of the time, the aberrations were worse than magnifying the images.

11. They produced inferior images, although the compound microscopes were beautiful objects that bestowed status on their owners.

12. In 1733, by trial and error, the amateur English optician Chester Moor Hall discovered that a combination of a convex crown-glass lens and a concave flint-glass lens could help correct chromatic aberration in a telescope. 

13. In 1774, Benjamin Martin of London designed an important set of color-corrected lenses for a microscope.

14. In the 19th century, the advent of new optical glasses stimulated continued microscope growth, and substantial advances were made to understand image forming’s geometric optics.

15. In 1791, Dutch optician Francois Beeldsnijder eventually introduced the idea of an achromatic (non-color-distorting) microscope target, and in 1830 the English scientist Joseph Jackson Lister published a work outlining a theoretical approach to the complete design of microscope goals.

16. The German physicist Ernst Abbe studied the physics of lens design. He developed an apochromatic lens system in 1868, which had even better color correction than achromatic lenses, and he published a detailed lens theory study in 1873.

17. The successful limits of optical microscopy were reached by light microscopes developed in the closing quarter of the 19th century.

18. Subsequent methods, such as phase-contrast microscopes, confocal microscopes, and interference microscopes, solved particular problems while examining specimens such as living cells.

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