There are three main different types of microscopes, each of which work in a slightly different way. These three types are the optical microscope, the electron microscope and the scanning probe microscope. The most commonly used is the optical microscope and the way in which is magnifies an object is described below.
An optical microscope, or light microscope, is one that uses visible light and a system of lenses in order to magnify images of small samples. Within a modern microscope the optical components are very complex and in order for the microscope to work well, the optical path has to be set up accurately. Once the optical path is controlled, the basic operating principles of an optical microscope are reasonably simple. The objective lens is a high-powered magnifying glass. This means that it is a lens with a very short focal length.
This lens is brought very close to the object that is being examined so that the light that is coming from the object comes to focus about 160 millimeters inside the microscope tube. When this is in place it creates a much larger image of the object, which is the inverted. This real image can be seen by taking the eye piece off the microscope and placing a piece of paper, preferably tracing, over the end of the tube. The eyepiece within the microscope is a compound lens. It has one component lens near the front of the tube and another near the back. These lenses form an air-separated couplet in the tube, bringing the real image to focus on the first lens and the second lens enabling the eye to focus on the virtual image. Most microscopes are meant to be used with the eye being focused on infinity.
To summarize, a microscope has an objective lens that has a short focal length to form a real image of the object being examined. A second lens then makes it possible for the human eye to see the object by inverting the real image and creating a virtual one.
An optical microscope, or light microscope, is one that uses visible light and a system of lenses in order to magnify images of small samples. Within a modern microscope the optical components are very complex and in order for the microscope to work well, the optical path has to be set up accurately. Once the optical path is controlled, the basic operating principles of an optical microscope are reasonably simple. The objective lens is a high-powered magnifying glass. This means that it is a lens with a very short focal length.
This lens is brought very close to the object that is being examined so that the light that is coming from the object comes to focus about 160 millimeters inside the microscope tube. When this is in place it creates a much larger image of the object, which is the inverted. This real image can be seen by taking the eye piece off the microscope and placing a piece of paper, preferably tracing, over the end of the tube. The eyepiece within the microscope is a compound lens. It has one component lens near the front of the tube and another near the back. These lenses form an air-separated couplet in the tube, bringing the real image to focus on the first lens and the second lens enabling the eye to focus on the virtual image. Most microscopes are meant to be used with the eye being focused on infinity.
To summarize, a microscope has an objective lens that has a short focal length to form a real image of the object being examined. A second lens then makes it possible for the human eye to see the object by inverting the real image and creating a virtual one.
