Drum camera
A drum camera is a high-speed camera with a drum-shaped or circular disk-shaped film carrier around which the unexposed film is wrapped.
Before the exposure, the film carrier is rotated by an (electric) motor around its longitudinal axis up to a certain speed, which then remains constant during the exposure of the film. If the diameter of the film carrier is large enough and the speed is adjusted accordingly, up to 10,000 images per second can be achieved. If a camera shutter is not feasible at this high recording frequency, the moving object to be filmed must be exposed by means of a light pulse generator that emits high-frequency light pulses (in otherwise darkened surroundings). An exactly uniform light pulse frequency must be guaranteed. An electrical spark gap is suitable as a light pulse generator because the individual light pulses each have a pulse duration of only one hundred millionth of a second at a constant pulse frequency. This enables excellent image sharpness. The object to be filmed is expediently positioned between the light pulse generator and the lens of the drum camera. A suitable lens system and possibly a (semitransparent) mirror can also be arranged between the light pulse generator and the object to be filmed. The exposed film is removed from the film carrier, developed and can then be shown with a commercially available film projector . Due to the extremely high recording frequency, the movements of the filmed object can be displayed in super slow motion.
Application example
A drum camera can e.g. B. be used for the investigation of the turbulent jet breakup and cavitation in (especially under high pressure) sprayed and atomized liquids.