An illumination unit, having a channel having a first end and a second end, wherein the illumination unit encompasses a housing by which the channel is formed, having a first and a second light source (16, 18), having a first cooling unit, arranged at the first end of the channel, for cooling the first and the second light source (16, 18), and having a second cooling unit, arranged at the second end of the channel, for cooling the first and the second light source (16, 18), a light exit opening being provided in the channel, a displaceable reflection element with the aid of which, depending on the position of the reflection element, light radiated selectably from the first or the second light source (16, 18) is directed through the light exit opening, being provided in the channel, and the first and the second light source (16, 18) are arranged one behind another in the channel, wherein the first and the second light source (16, 18) are arranged one behind another with respect to a longitudinal axis of the channel, characterized in that the first and/or the second cooling unit (30, 32) have several fans, the illumination unit encompasses a switching apparatus for controlling the illumination unit, and in that the illumination unit is configured such that, in a regular operating state, the fans of the first and the second cooling unit (30, 32) are operated at a first rotation speed, and upon failure of one of the fans of the first or the second cooling unit (30, 32), the fans of the other cooling unit (30, 32) are operated at a second rotation speed, wherein the second rotation speed is higher than the first rotation speed. having a channel having a first end and a second end, wherein the illumination unit encompasses a housing by which the channel is formed, having a first and a second light source (16, 18), having a first cooling unit, arranged at the first end of the channel, for cooling the first and the second light source (16, 18), and having a second cooling unit, arranged at the second end of the channel, for cooling the first and the second light source (16, 18), a light exit opening being provided in the channel, a displaceable reflection element with the aid of which, depending on the position of the reflection element, light radiated selectably from the first or the second light source (16, 18) is directed through the light exit opening, being provided in the channel, and the first and the second light source (16, 18) are arranged one behind another in the channel, wherein the first and the second light source (16, 18) are arranged one behind another with respect to a longitudinal axis of the channel, the first and/or the second cooling unit (30, 32) have several fans, the illumination unit encompasses a switching apparatus for controlling the illumination unit, and in that the illumination unit is configured such that, in a regular operating state, the fans of the first and the second cooling unit (30, 32) are operated at a first rotation speed, and upon failure of one of the fans of the first or the second cooling unit (30, 32), the fans of the other cooling unit (30, 32) are operated at a second rotation speed, wherein the second rotation speed is higher than the first rotation speed.