Light-emitting diode of their major uses until their price drops low enough to make signaling and illumination uses more economically feasible. Barcode scanners are the most common example of machine vision applications, and many of those scanners use low-cost products red LEDs instead of laser-based LEDs. Optical computer mice are an example of LEDs in machine vision, as it is used to provide an even light source on the surface for the miniature camera within the mouse. LEDs constitute a nearly ideal light source for machine vision systems for several reasons: The light from LEDs can be modulated very quickly so they
Light-emitting diode thousands of hours) at which a given LED reaches 70% and 50% of initial light output, respectively. Whereas in most previous sources of light (incandescent lamps, discharge lamps, and those that burn combustible fuel, e.g. candles and oil lamps) the light results from heat, LEDs only operate if they are kept cool enough. The manufacturer commonly specifies a maximum junction temperature of 125 or 150 °C, and lower temperatures are advisable in the interests of long life. At these temperatures, relatively little heat is lost by radiation, which means that the light beam generated by an LED is cool. The