Microscope History and Development

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Microscope History and Development
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Hans and Zacharias Janssen, 1590, Dutch
Eyeglass Makers, Inventors

• The first compound microscopes produced by the
  Janssen's was simply a tube with lenses at each
  end. The magnification of these early scopes
  ranged from 3X to 9X, depending on the size of
  the diaphragm openings.

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Background

• 14th century lenses were used in spectacles
• Late 16th century the Dutch refined the art of
  lens grinding ? significant magnification.
• 1600s lenses first mounted on permanent
  frameworks (so distance could be changed) This is
  important to focus the image

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• Next, lenses were paired together.
• These formed the earliest compound microscopes
  and telescopes. This increases the magnification.

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Robert Hooke

• In 1665, the English physicist Robert Hooke
  looked at a sliver of cork through a microscope
  lens and noticed some "pores" or "cells" in it.
• Hooke was the first person to use the word
  "cell" to identify microscopic structures when he
  was describing cork.

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Illustration of Cork Cells by Robert Hooke
http//askabiologist.asu.edu/research/buildingbloc
ks/rhooke.html
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• In Micrographia (1665), Hooke used the word cell
  to describe the features of plant tissue (cork
  from the bark of an oak tree) he was able to
  discover under the microscope.

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Early Microscopes - Anton Van Leeuwenhoek

• (1632-1723).
• Anton Van Leeuwenhoek was the first to see and
  describe bacteria (1674), yeast plants, the
  living things in a drop of water, and the
  circulation of blood corpuscles in capillaries.

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Anton van Leeuwenhoek, 1632-1723,

• Leeuwenhoek made simple (one lens) microscopes.
  He was not the first person to build a
  microscope, but the microscopes that he did build
  were the best ones for that time period.
  Leeuwenhoek was the first person to describe
  bacteria (from teeth scrapings), protozoans (from
  pond water), helped to prove the theory of blood
  circulation. He gained much of his inspiration
  from reading Hooke's Micrographia.

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Anton van Leeuwenhoek

• refined lens grinding so that living things could
  be seen through the microscope.
• Then there was little change until the industrial
  revolution

Leeuwenhoeks primitive one lens microscope.
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Technological Advances in Microscopes

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Compound Light Microscopes

• Uses light
• Has two lenses
• Magnification limited to 2000x (400x at LHHS)

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Monocular Compound Microscope http//www.ascoindia
.com/pcat-gifs/products-small/ms-351.jpg
Binocular Compound Microscope http//www.labessent
ials.com/Rev3.jpg
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Transmission Electron Microscope (TEM)

• Uses beams of electrons
• Magnification of 2 000 000x
• Has two limitations
• Good only for thin specimens
• Only dead cells can be observed

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Scanning Electron Microscope (SEM)

• Electrons are reflected from the surface of the
  specimen
• Produces a 3-d image
• Good for the thicker specimens
• Lacks the magnification and resolution of the
  transmission electron microscope

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Magnification

• Magnification Objective lens X Ocular lens
• (4x, 10x, 40x) (10x)

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• Van Leeuwenhoek used his new instrument, which
  was ten times more powerful than Hookes (he
  reached the amazing power of 300 times with a
  single lens) to discover startling microscopic
  things, such as protozoa and spermatozoa, which
  thus far were completely unknown to science, or
  to discover the microscopic structure of known
  things, such as fleas and plant leaves.

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Changes of the Industrial Revolution

• standardized parts (which were interchangeable
  with other microscopes) lead to mass production
• This triggered a drop in price ? increased access
  ? new discoveries ? clearer images
• In approx. 1880 ? modern microscopes were being
  used

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Electron Microscope

• Developed in the 1930s
• the electron microscope allowed for higher
  magnification
• used electron beams (instead of light) and
  focused with an electromagnet (no lenses)
• the light microscope produces magnifications up
  to 2000X
• the electron microscope produces images that are
  magnified up to 50 000X or higher
• The electron microscope allowed scientists to see
  better quality images at higher magnification

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Electron Microscope
Termite Head http//alfa.ist.utl.pt/cvrm/staff/v
ramos/SIP.html
http//www.phy.cuhk.edu.hk/centrallaboratory/CM120
/CM120.html
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Spider ---- http//semguy.com/gfx/spidey.jpg