Microscope History and Development

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.

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

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

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.

Illustration of Cork Cells by Robert Hooke http://askabiologist.asu.edu/research/buildingblocks/rhooke.html

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.

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.

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.

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 Leeuwenhoek’s primitive one lens microscope.

Technological Advances in Microscopes

Compound Light Microscopes Uses light Has two lenses Magnification limited to 2000x (400x at LHHS)

Monocular Compound Microscope http://www.ascoindia.com/pcat-gifs/products-small/ms-351.jpg Binocular Compound Microscope http://www.labessentials.com/Rev3.jpg

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

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

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

Van Leeuwenhoek used his new instrument, which was ten times more powerful than Hooke´s (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.

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

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

Electron Microscope Termite Head: http://alfa.ist.utl.pt/~cvrm/staff/vramos/SIP.html http://www.phy.cuhk.edu.hk/centrallaboratory/CM120/CM120.html

Spider ---- http://semguy.com/gfx/spidey.jpg