The working principle and development history of optical microscope
Optical Microscope (abbreviated as OM) is an optical instrument that uses optical principles to magnify and image tiny objects that cannot be resolved by the human eye, so that people can extract microstructure information.
As early as the first century BC, people have discovered that when observing tiny objects through spherical transparent objects, they can make them magnify into images. Later, I gradually came to understand the law that the spherical glass surface can make objects magnified and imaged. In 1590, Dutch and Italian eyeglass makers had created magnifying instruments similar to microscopes. Around 1610, while studying telescopes, Galileo in Italy and Kepler in Germany changed the distance between the objective lens and the eyepiece to obtain a reasonable microscope optical path structure. Optical craftsmen at that time were engaged in the manufacture, promotion and improvement of microscopes.
In the middle of the 17th century, Robert Hooke in England and Leeuwenhoek in the Netherlands both made outstanding contributions to the development of microscopes. Around 1665, Hooke added coarse and fine focus adjustment mechanisms, illumination systems and a workbench for carrying specimens to the microscope. These components have been continuously improved and become the basic building blocks of modern microscopes.
During the period from 1673 to 1677, Levin Hooke made high-power microscopes of the single-unit magnifying glass type, nine of which have been preserved to this day. Hooke and Levin Hooke made outstanding achievements in the study of the microscopic structure of animals and plants using self-made microscopes. In the 19th century, the appearance of high-quality achromatic immersion objective lenses greatly improved the ability of microscopes to observe fine structures. In 1827 Amici was the first to use a liquid immersion objective. In the 1870s, the German Abbe laid the classical theoretical foundation of microscope imaging. These have promoted the rapid development of microscope manufacturing and microscopic observation technology, and provided powerful tools for biologists and medical scientists, including Koch and Pasteur, to discover bacteria and microorganisms in the second half of the 19th century.
While the structure of the microscope itself is developing, the microscopic observation technology is also constantly innovating: polarized light microscopy appeared in 1850; interference microscopy appeared in 1893; in 1935, Dutch physicist Zernik created phase contrast microscopy. technique, for which he was awarded the Nobel Prize in Physics in 1953.
The classical optical microscope is just a combination of optical components and precision mechanical components, and it uses the human eye as a receiver to observe a magnified image. Later, a photographic device was added to the microscope, and photosensitive film was used as a receiver that could be recorded and stored. In modern times, optoelectronic components, TV camera tubes and charge couplers are generally used as the receiver of the microscope, and a complete image information acquisition and processing system is formed after being equipped with a microcomputer.
Optical lenses made of curved glass or other transparent materials can magnify objects into images. Optical microscopes use this principle to magnify tiny objects to a size sufficient for human eyes to observe. Modern optical microscopes usually use two stages of magnification, which are completed by the objective lens and eyepiece respectively. The object to be observed is located in front of the objective lens. It is magnified by the objective lens in the first stage and becomes an inverted real image. Then the real image is magnified by the eyepiece in the second stage to form a virtual image. What the human eye sees is a virtual image. The total magnification of the microscope is the product of the magnification of the objective lens and the magnification of the eyepiece. Magnification refers to the magnification ratio of linear dimensions, not the area ratio.
