The story of the microscope needs to start from the Mesopotamian plains in 3500 BC. Archaeological evidence shows that people in coastal areas unintentionally produced the first piece of glass in history during metal processing. Beautiful glass has become a valuable ornamental object since then, and its manufacturing technology has been passed down. Around the 4th century AD, the Romans finally discovered other functions of glass besides viewing: they began to use glass to make doors, windows, cups and other practical things. At the same time, the technology of using crystal stones to polish lenses has appeared in my country, but this is usually only used as an ornament. In the 13th century, Marco Polo brought this crystal lens back to Europe, and Europeans learned how to polish the lens. The development of the manufacturing industry has made glass a cheap material. Therefore, the glasses manufacturing industry has been booming.
At that time, most of the people who wore glasses were very old and rich people. What they needed was reading glasses, that is, convex lenses. People quickly discovered that convex lenses can magnify the image of an object. As a result, some curious people began to use convex lenses to observe small objects, and the microscope was born at this time. There are two types of microscopes, one is a single convex lens, also called a magnifying glass or a single microscope; the other is a combination of multiple convex lenses, also called a compound microscope.
In the beginning, people used a single convex lens to observe objects. This has a fatal disadvantage: the focal length of the convex lens is directly proportional to the diameter of the lens, and the focal length is inversely proportional to the magnification, that is to say, if you want to obtain a larger magnification, the diameter of the lens must be small. If you want to obtain an image with a magnification of 100 times, then the diameter of the lens should be as small as 0.33 mm-a lens smaller than a pin could not be manufactured at that time. Therefore, the magnification of the convex lens at that time was no more than 25 times. This magnification is at the toy level, and only allows children to observe bugs. If they want to observe more subtle things, they can only seek other tools.
In the 1690s, the first microscope in human history was born in Middelburg, Netherlands. The record of a specific year was lost in an explosion that occurred in Middelburg on May 17, 1940 during World War II. It is speculated that the year of the microscope's invention should be between 1590 and 1505. At that time, the inventor Zacharias Janssen (Zacharias Janssen) is probably just a child about ten years old (his birth year is also unknown, about 1580~1585), following his father Hans. Hans Janssen sells his polished lenses on the street. Perhaps inspired by playing in his father's studio, Zakarias has become a person in the world who can combine multiple convex lenses. It is this move that opens the door to the microcosm for mankind. Father Hans helped him make the world's first compound microscope, which looked like a flashlight.
The structure of the compound microscope of Jensen and his son is very simple: it is composed of three lens barrels connected, the middle lens barrel is relatively thick and suitable for hand holding; the other two lens barrels are inserted into its two ends respectively, and they can be retracted. Adjust to achieve the purpose of focusing. When the two movable lens barrels of this compound microscope are fully closed, its magnification is 3 times; when they are fully extended, the magnification is 10 times. Although this magnification seems to be inferior to a single-type convex lens, its significance is that it is an early zoom lens, and at the same time it is just an immature prototype. With the structural foundation of the compound lens combination, the magnification will soon begin. leap. In addition, the manufacturing process is also very simple, people no longer need to work hard to grind small lenses.
Unfortunately, although the invention of the microscope by Johnson and his son opened the door to the microscopic world for mankind, no one was able to step into it in that era. Due to technical limitations, the magnification of compound microscopes in the 16th century was still not high enough, and human beings did not have any exciting discoveries in exploring the microscopic world. In that era, the microscope was not so much a scientific instrument as it was a work of art. Its beautiful brass appearance and exquisite decoration are sought after by the society, and most people only regard the microscope as an elegant and noble collection.
Half a century later, a great microscope man was born in the Netherlands. On October 24, 1632, Antonie van Leeuwenhoek (Antonie van Leeuwenhoek) was born in Delf, the Netherlands. Due to family difficulties, he only went to school for a short time and was sent to the Dutch capital at the age of 16. Apprentice in a cloth shop in Amsterdam. In 1654, the 22-year-old Levinhoek returned to his hometown of Delf and opened a small cloth shop of his own. In the beginning, he tried to use convex lenses to magnify and appraise the quality of fabrics. The cloth shop was not busy. He quickly developed an interest in lenses and tried to polish the lenses himself. Relying on interest and perseverance, this young man who has not studied for a few years has polished and manufactured the world's lenses in his own shop. Their thickness is only 1 mm, the radius of curvature is 0.75 mm, and they have a very high magnification. And resolution.
After mastering the lens grinding technology, Leeuwenhoek assembled the lenses into compound microscopes and used them to discover cells that have never been seen by humans. A typical Leeuwenhoek microscope is very small and has a very clever structure. It consists of a flat and wide lens body, a lens, a needle-shaped stage, and two screws. The lens is inlaid between two brass plates with small holes, and the screw can be used to adjust the distance between the specimen and the lens to adjust the focal length. When using, first fix the specimen on the tip of the needle, pick up the microscope to aim at the light source, adjust the screw to make the image reach a good state and observe.
In 1677, he observed protozoa in pond water, red blood cells in salmon blood. In 1683, he discovered bacteria in tartar and wrote a report to send to the Royal Society of England, which was affirmed by the latter, thus pioneering microbiology. He also correctly described the shape of microorganisms as rod-shaped, spiral-shaped, etc. By observing the capillaries, he confirmed the existence of the blood circulatory system and ended many years of scientific disputes. The door to the microcosm was opened to him alone. He wandered through it with lenses, constantly discovering various shocking facts and changing people's perceptions.
Leeuwenhoek personally polished 550 lenses and assembled 247 microscopes in his lifetime, creating a lot of precious wealth for mankind. Nine units have been preserved so far, all of which are properly kept in museums around the country. The microscope in the Utrecht University Museum in the Netherlands has a magnification of 270 times and a resolution of 1.4 microns, which is almost the limit of optical microscopes. Leeuwenhoek's method of making lenses has been lost, and the quality of his hand-made microscopes is so high that no one can reproduce them with his hands until now.