<P> Scanning optical and electron microscopes, like the confocal microscope and scanning electron microscope, use lenses to focus a spot of light or electrons onto the sample then analyze the signals generated by the beam interacting with the sample . The point is then scanned over the sample to analyze a rectangular region . Magnification of the image is achieved by displaying the data from scanning a physically small sample area on a relatively large screen . These microscopes have the same resolution limit as wide field optical, probe, and electron microscopes . </P> <P> Scanning probe microscopes also analyze a single point in the sample and then scan the probe over a rectangular sample region to build up an image . As these microscopes do not use electromagnetic or electron radiation for imaging they are not subject to the same resolution limit as the optical and electron microscopes described above . </P> <P> The most common type of microscope (and the first invented) is the optical microscope . This is an optical instrument containing one or more lenses producing an enlarged image of a sample placed in the focal plane . Optical microscopes have refractive glass (occasionally plastic or quartz), to focus light on the eye or on to another light detector . Mirror - based optical microscopes operate in the same manner . Typical magnification of a light microscope, assuming visible range light, is up to 1250x with a theoretical resolution limit of around 0.250 micrometres or 250 nanometres . This limits practical magnification to ~ 1500x . Specialized techniques (e.g., scanning confocal microscopy, Vertico SMI) may exceed this magnification but the resolution is diffraction limited . The use of shorter wavelengths of light, such as ultraviolet, is one way to improve the spatial resolution of the optical microscope, as are devices such as the near - field scanning optical microscope . </P> <P> Sarfus is a recent optical technique that increases the sensitivity of a standard optical microscope to a point where it is possible to directly visualize nanometric films (down to 0.3 nanometre) and isolated nano - objects (down to 2 nm - diameter). The technique is based on the use of non-reflecting substrates for cross-polarized reflected light microscopy . </P>

Name a type of microscope that does not use light to produce an image