The light microscope is also known as an “optical microscope”. It is a device that makes use of light to detect and study organisms or objects that are too tiny to be seen by the naked eye. It is the simplest and earliest form of microscope, and it is often used in laboratories for scientific research.
Before the light microscope was invented in the 16th century, optical lenses were already being used for various purposes. The history of the lens dates back to about 3,000 years ago, when the Assyrians used Nimrud lenses as burning glasses to make fire. Evidence has been found that the ancient Egyptians had made use of lenses as early as 8th century BC. Around 424 BC, the Greeks invented biconvex lenses, which were also used as burning glasses. The Romans were probably the first to use corrective lenses to enhance vision. It was reported that Nero used an emerald to watch gladiatorial fights.
The first comprehensive treatise on optics, Book of Optics, was written by Ibn al-Haytham during the 11th century, and the book inspired many innovations in optical science. Two centuries later, Englishman Robert Bacon revealed the magnifying properties of lenses, and the first spectacles were invented in Italy by Salvino D’Amate. In the year 1872, Ernst Abbe’s discovery of the Abbe Sine Condition changed the way optical instruments were made.
The first compound microscope was invented in the 1590s by father-and-son opticians Hans and Zacharias Janssen. The Dutchmen developed a simple device that had a magnification power of three to nine times. It was made up of two tubes and two lenses. One of the tubes was placed in the other tube, and each tube had a lens attached to it. The lens that was closer to the eye was a bi-convex lens, and the lens at the other end was a plano-convex lens. The focus of this compound microscope could be altered by sliding one of the tubes.
Improvements were made to the Janssens’ microscope in the 17th century. Anton von Leeuwenhoek and Robert Hooke discovered that greater magnification could be achieved by reducing focal lengths. Their microscopes featured spherical lenses and extreme double convex lenses, which were made of quartz to produce clearer images. Von Leeuwenhoek’s microscope had a magnification ability of 270 times, and he used it to study bacteria and other small organisms.
In the 18th century, more microscopic technical innovations were introduced, and more and more scientists began to study microscopy. The greatest innovation of this century was perhaps the achromatic lens of John Dollard. This new lens, which was patented in 1758, made use of two different types of glass to eliminate the chromatic effects that were caused by the refraction of light.
English surgeon Joseph Jackson Lister made a significant improvement to the microscope in the year 1830. By placing a number of weak lenses at certain distances in a microscope, he could magnify the image of an object without blurring it. This discovery led to the perfection of the compound microscope. Ernst Abbe’s formulation of the Abbe Sine Condition in 1872 enabled microscopes to reach maximum resolution.
Today, microscopes are much more advanced than those that were developed two centuries ago. The most powerful microscope to date is the scanning tunneling microscope that was invented by Gerd Binnig and Heinrich Rohler in 1981. This microscope can reveal the atomic structure of objects in three-dimensional form. Present-day microscopes do not only use light to magnify images; they are able to use electrons to study an object and produce a high-resolution image of it. These microscopes can magnify the image of an object up to 200,000 times.
A light microscope makes use of light to magnify the image of a specimen. The light comes from a light bulb that is located under the stage where the specimen is placed, and it will travel through the objective lens and the ocular lens before it reaches the eye. The objective lens has a short focal length and it puts the image into focus at the lower part of the microscope’s tube. The image will then be enlarged by the ocular lens. The focal length of the objective lens can be adjusted with the focus knobs on the microscope.