Spark flash camera (1974)
Around 1974, the spark flash system was designed for the Commission of trials of the Royal Netherlands Army to photograph projectiles in flight. The schematic design of the camera system is shown in the accompanying diagram. The camera C, the flash unit F and the semi-transparent mirror 50/50 form one entity. The flash F with a source diameter of 1 millimeter has a mirror image in the centre of the camera lens. When it flashes, it looks like the flashlight is coming out of the camera. The light reflected by the retro-reflector R largely returns to the camera lens.
The mechanical shutter of the camera is opened during the flash. If a projectile in the flight (perpendicular to the plane of the drawing) passes the camera, the shadow image thereof is displayed together with the shock wave pattern.