The rapatronic camera is a high-speed camera

High speed photography

High speed photography is the science of taking pictures of very fast phenomena. In 1948, the Society of Motion Picture and Television Engineers defined high-speed photography as any set of photographs captured by a camera capable of 128 frames per second or greater, and of at least three...

 capable of recording a still image with an exposure time as brief as 10 nanosecond

Nanosecond

A nanosecond is one billionth of a second . One nanosecond is to one second as one second is to 31.7 years.The word nanosecond is formed by the prefix nano and the unit second. Its symbol is ns....

s (billionths of a second).

The camera was developed by Harold Edgerton in the 1940s and was first used to photograph the rapidly-changing matter in nuclear explosion

Nuclear explosion

A nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two, though to date all fusion based weapons have used a fission device...

s within millisecond

Millisecond

A millisecond is a thousandth of a second.10 milliseconds are called a centisecond....

s of ignition. To overcome the speed limitation of a conventional camera's mechanical shutter

Shutter (photography)

In photography, a shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing photographic film or a light-sensitive electronic sensor to light to capture a permanent image of a scene...

, the rapatronic camera uses two polarizing filters and a Kerr cell

Kerr effect

The Kerr effect, also called the quadratic electro-optic effect , is a change in the refractive index of a material in response to an applied electric field. The Kerr effect is distinct from the Pockels effect in that the induced index change is directly proportional to the square of the electric...

. The two filters are mounted with their polarization angles at 90° to each other, to block all incoming light. The Kerr cell between the filters, which changes the polarization plane of light passing through it depending on the level of voltage applied, acts as shutter when it is energized at the right time for a very short amount of time, allowing the film to be properly exposed.

For a film

Film

A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

-like sequence of high-speed photographs, as used in the photography of nuclear and thermonuclear tests

Nuclear testing

Nuclear weapons tests are experiments carried out to determine the effectiveness, yield and explosive capability of nuclear weapons. Throughout the twentieth century, most nations that have developed nuclear weapons have tested them...

, arrays of up to 12 cameras were deployed, with each camera carefully timed to record a different time frame.

External links

• Rapatronic Shutter technique description at the Edgerton Digital Collections website