Focusing is the concentration or bundling techniques of light, radio waves, or electron beams onto a point or plane. The term focusing is used in photography, in optical transmission technology and optical storage technology, in radio transmission and in cathode ray tubes as used in oscilloscopes, televisions and color televisions.
Focusing is used in the focusing of digital cameras and film scanners, where the object to be captured is brought into focus on the image sensor, or in projectors, where the image to be projected is brought into focus on the projection surface.
The term focusing is also used in optical transmission technology; in optical fibers, for example, divergent light beams are bundled with focusing lenses, such as the Selfoc lens. In addition, in radio and satellite technology, microwaves are focused on the transmitting and receiving sides with a parabolic antenna, and the same applies to directional radio links. In electron tubes, focusing is used to bundle the electron beam. So in oscilloscopes, where the cathode ray tube has special focusing electrodes to make the incident beam as sharp as possible, and also in color television tubes, where it is important that the electron beams for red, green and blue activate the corresponding phosphors, and not the neighboring phosphor points.