Abstract: Infrared radiation from a light source such as a laser diode illuminates the field of view of a surveillance camera. The amount of illumination is varied in intervals, which may for example, be about 3/4 of a second, by varying the power applied to the light source. The radiation may emanate from optical fibers surrounding a camera lens, or through other ports. The power to the laser diode may be altered in response to background light sensed by a photo cell. A filter on the camera preferentially passes reflected illumination of the source while alternating background illumination.

Abstract: Infrared radiation from a light source such as a laser diode illuminates the field of view of a surveillance camera. The amount of illumination is varied in intervals, which may for example, be about 3/4 of a second, by varying the power applied to the light source. The radiation may emanate from optical fibers surrounding a camera lens, or through other ports. The power to the laser diode may be altered in response to background light sensed by a photo cell.

Abstract: A light unit has a strobe operated flash tube and a non-strobe peripheral lamp immediately beneath the flash tube; a switch can turn the unit off, operate either light or enable the pilot of an aircraft to signal the light unit to operate the flash tube or to turn off the flash tube and operate the non-strobe peripheral lamp, by means of a radio receiver having a local oscillator midway between two standard distress frequencies. The light unit may have infrared or other color lenses. A ribbon assists establishing a pattern of light and/or colors to mark a landing site and indicate wind direction.