What is a microscope? This definition is actually very vague. Microscopes, telescopes, and magnifying glasses are classified according to their specific uses, not by a certain parameter index, and there are intersections between uses, and the boundaries are not so clear, which leads to the use of telescopes. It becomes a microscope (this can be tried with your own telescope, only careful users will find interesting phenomena). In terms of optical structure design, microscopes, magnifying glasses, and telescopes are essentially the same, and can be described by a 4-f system, which is why the above-mentioned phenomenon of using the telescope with the microscope in the opposite direction occurs. By definition, a magnification greater than 1 is called a microscope/magnifying glass, and a magnification less than 1 is called a telescope. Among them, objects that can magnify visible objects are called magnifying glasses, and objects that can magnify invisible objects are called microscopes. It can be seen that the definition has nothing to do with the imaging resolution, only the magnification, then 200nm, 1um, 10um can be microscopic, and academically, there are some subdivisions in order to distinguish from the perspective of resolution, such as microscopic microscopy, mesoscopic microscopy and many more.
