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http://inventors.about.com/od/mstartinventions/a/mi croscope.htm During that historic period known as the Renaissance, after the "dark" Middle Ages, there occurred the inventions of printing, gunpowder and the mariner's compass, followed by the discovery of America. Equally remarkable was the invention of the light microscope: an instrument that enables the human eye, by means of a lens or combinations of lenses, to observe enlarged images of tiny objects. It made visible the fascinating details of worlds within worlds. The definition of a microscope: An instrument for viewing objects that are too small to be seen easily by the naked eye. Invention of Glass Lenses Long before, in the hazy unrecorded past, someone picked up a piece of transparent crystal thicker in the middle than at the edges, looked through it, and discovered that it made things look larger. Someone also found that such a crystal would focus the sun's rays and set fire to a piece of parchment or cloth. Magnifiers and "burning glasses" or "magnifying glasses" are mentioned in the writings of Seneca and Pliny the Elder, Roman philosophers during the first century A. D., but apparently they were not used much until the invention of spectacles, toward the end of the 13th century. They were named lenses because they are shaped like the seeds of a lentil. Circa 1000AD – The first vision aid was invented (inventor unknown) called a reading stone. It was a glass sphere that magnified when laid on top of reading materials. Circa 1284 - Italian, Salvino D'Armate is credited with inventing the first wearable eye glasses. 1590 – Two Dutch eye glass makers, Zaccharias Janssen and son Hans Janssen experimented with multiple lenses placed in a tube. The Janssens observed that viewed objects in front of the tube appeared greatly enlarged, creating both the forerunner of the compound microscope and the telescope. Birth of the Light Microscope About 1590, two Dutch spectacle makers, Zaccharias Janssen and his son Hans, while experimenting with several lenses in a tube, discovered that nearby objects appeared greatly enlarged. That was the forerunner of the compound microscope and of the telescope. In 1609, Galileo, father of modern physics and astronomy, heard of these early experiments, worked out the principles of lenses, and made a much better instrument with a focusing device. The earliest simple microscope was merely a tube with a plate for the object at one end and, at the other, a lens which gave a magnification less than ten diameters -- ten times the actual size. These excited general wonder when used to view fleas or tiny creeping things and so were dubbed "flea glasses." Types of scopes Microscopes are used both in classrooms and in making important evaluations in medical laboratories and other microtechnologies. The different types of microscopes are designed for these different uses, and therefore will vary based on their resolution, magnification, depth of field, field of view, illumination method, degree of automation, and type of image they produce. There are essentially three categories of microscopes: electron, confocal, and compound. 1665 – English physicist, Robert Hooke looked at a sliver of cork through a microscope lens and noticed some "pores" or "cells" in it. 1674 – Anton van Leeuwenhoek built a simple microscope with only one lens to examine blood, yeast, insects and many other tiny objects. Leeuwenhoek was the first person to describe tiny cells and bacteria invented and he invented new methods for grinding and polishing microscope lenses that allowed for curvatures providing magnifications of up to 270 diameters, the best available lenses at that time. Robert Hooke Robert Hooke, the English father of microscopy, re- confirmed Anton van Leeuwenhoek's discoveries of the existence of tiny living organisms in a drop of water. Hooke made a copy of Leeuwenhoek's light microscope and then improved upon his design. Anton van Leeuwenhoek (1632-1723) The father of microscopy, Anton van Leeuwenhoek of Holland, started as an apprentice in a dry goods store where magnifying glasses were used to count the threads in cloth. He taught himself new methods for grinding and polishing tiny lenses of great curvature which gave magnifications up to 270 diameters, the finest known at that time. These led to the building of his microscopes and the biological discoveries for which he is famous. He was the first to see and describe bacteria, yeast plants, the teeming life in a drop of water, and the circulation of blood corpuscles in capillaries. During a long life he used his lenses to make pioneer studies on an extraordinary variety of things, both living and non living, and reported his findings in over a hundred letters to the Royal Society of England and the French Academy. 18th century – Technical innovations improved microscopes, leading to microscopy becoming popular among scientists. Lenses combining two types of glass reduced the "chromatic effect" the disturbing halos resulting from differences in refraction of light. Compound microscopes are mostly used in biology. They give a 2-D slice of an object, yet can attain a high enough magnification to see parts of eukaryotic cells, a hair strand, or pond scum. Unfortunately, they do not have excellent resolution, so the image may be blurry. On the other hand, stereoscopic microscopes, as the name implies, provide a 3-D picture of bisected items, like muscle tissue or an organ. In this case, magnification is poor, so you can't make out separate cells, but resolution is much improved. Finally, there are the simplest types of microscopes found in classrooms across the world: compound microscopes. These are entirely operated by hand and use the ordinary ambient light from the sun or a light bulb to illuminate the specimen. Whatever you want to look at is mounted between two glass slides and clipped beneath the main lens. You use a dial to focus the image. These tools use a simple series of magnifying lenses and mirrors to bring the image up to an eyepiece, much like a telescope. 1830 – Joseph Jackson Lister reduces spherical aberration or the "chromatic effect" by showing that several weak lenses used together at certain distances gave good magnification without blurring the image. This was the prototype for the compound microscope. Beyond the Light Microscope A light microscope, even one with perfect lenses and perfect illumination, simply cannot be used to distinguish objects that are smaller than half the wavelength of light. White light has an average wavelength of 0.55 micrometers, half of which is 0.275 micrometers. (One micrometer is a thousandth of a millimeter, and there are about 25,000 micrometers to an inch. Micrometers are also called microns.) Any two lines that are closer together than 0.275 micrometers will be seen as a single line, and any object with a diameter smaller than 0.275 micrometers will be invisible or, at best, show up as a blur. To see tiny particles under a microscope, scientists must bypass light altogether and use a different sort of "illumination," one with a shorter wavelength. 1872 – Ernst Abbe then research director of the Zeiss Optical Works, wrote a mathematical formula called the "Abbe Sine Condition". His formula provided calculations that allowed for the maximum resolution in microscopes possible. Your scope has an Abbe condenser 1903 – Richard Zsigmondy developed the ultramicroscope that could study objects below the wavelength of light. He won the Nobel Prize in Chemistry in 1925. 1932 – Frits Zernike invented the phase-contrast microscope that allowed for the study of colorless and transparent biological materials for which he won the Nobel Prize in Physics in 1953. A confocal microscope is a step down from the previous types. It uses a laser beam to illuminate a specimen whose image is then digitally enhanced for viewing on a computer monitor. The specimen is often dyed a bright color so the laser gives a more contrasting image. It is mounted on a glass slide just like in high school biology. Confocal microscopes are controlled automatically, and motorized mirrors help with auto-focus. 1931 – Ernst Ruska co-invented the electron microscope for which he won the Nobel Prize in Physics in 1986. An electron microscope depends on electrons rather than light to view an object, electrons are speeded up in a vacuum until their wavelength is extremely short, only one hundred-thousandth that of white light. Electron microscopes make it possible to view objects as small as the diameter of an atom. 1981 – Gerd Binnig and Heinrich Rohrer invented the scanning tunneling microscope that gives three-dimensional images of objects down to the atomic level. Binnig and Rohrer won the Nobel Prize in Physics in 1986. The powerful scanning tunneling microscope is the strongest microscope to date. Electron microscopes are extremely sophisticated types of magnification devices. These are used in archaeology, medicine, and geology to look at surfaces and layers of objecs such as organs and rocks. Instead of using light, these devices point a stream of electrons at the specimen and attached computers analyze how the electrons are scattered by the material. The specimen must be suspended within a vacuum chamber. With transmission electron microscopes, a scientist gets a view of 2-D slices of the object at different depths. Of course, with such powerful instruments, both the degree of magnification and the resolution, or sharpness of the image, are very high. Scanning electron microscopes are slightly different in that they scan a gold-plated specimen to give a 3-D view of the surface of an object. This view is in black and white, yet gives an amazing picture of, for example, the minute hills and valleys of a dinosaur bone. Charles A. Spencer Later, few major improvements were made until the middle of the 19th century. Then several European countries began to manufacture fine optical equipment but none finer than the marvelous instruments built by the American, Charles A. Spencer, and the industry he founded. Present day instruments, changed but little, give magnifications up to 1250 diameters with ordinary light and up to 5000 with blue light. Electron Microscope < Introduction: History of Early Light Microscopes The introduction of the electron microscope in the 1930's filled the bill. Co-invented by Germans, Max Knott and Ernst Ruska in 1931, Ernst Ruska was awarded half of the Nobel Prize for Physics in 1986 for his invention. (The other half of the Nobel Prize was divided between Heinrich Rohrer and Gerd Binnig for the STM.) In this kind of microscope, electrons are speeded up in a vacuum until their wavelength is extremely short, only one hundred-thousandth that of white light Beams of these fast-moving electrons are focused on a cell sample and are absorbed or scattered by the cell's parts so as to form an image on an electron-sensitive photographic plate. Power of the Electron Microscope If pushed to the limit, electron microscopes can make it possible to view objects as small as the diameter of an atom. Most electron microscopes used to study biological material can "see" down to about 10 angstroms--an incredible feat, for although this does not make atoms visible, it does allow researchers to distinguish individual molecules of biological importance. In effect, it can magnify objects up to 1 million times. Nevertheless, all electron microscopes suffer from a serious drawback. Since no living specimen can survive under their high vacuum, they cannot show the ever-changing movements that characterize a living cell. Light Microscope Vs Electron Microscope Using an instrument the size of his palm, Anton van Leeuwenhoek was able to study the movements of onecelled organisms. Modern descendants of van Leeuwenhoek's light microscope can be over 6 feet tall, but they continue to be indispensable to cell biologists because, unlike electron microscopes, light microscopes enable the user to see living cells in action. The primary challenge for light microscopists since van Leeuwenhoek's time has been to enhance the contrast between pale cells and their paler surroundings so that cell structures and movement can be seen more easily. To do this they have devised ingenious strategies involving video cameras, polarized light, digitizing computers, staining and other techniques that are yielding vast improvements in contrast, fueling a renaissance in light microscopy.