In the Blink of an Eye
November 16January 12, 1997
HighSpeed Photography from the University of California, San Diego and the designers of the fastest cameras in the world: Dr. John E. Starrett and Dr. Albert T. Ellis
During the early 1970s, at a time before desktop computers and video equipment were commonplace in science labs, John E. "Skip" Starrett, Jr. (19421990) was completing research on his doctoral dissertation at UCSD on "cavitation," the sudden formation and collapse of lowpressure bubbles in liquids by mechanical force, as those resulting from rotation of a marine propeller. In order to complete his research, Starrett required highspeed photographs to visually measure the location, size and shape of an individual bubble from the beginning to the end of its life.
To resolve his problem, Starrett needed to redesign and improve a very unusual camera. He drew upon the designs of the highspeed 1952 Ellis Camera, invented by his friend and colleague Professor Albert T. Ellis (19171991). Typically, as a photograph is taken the camera's film moves past the shutter winding onto a take up spool. This mechanical procedure requires time, something that Professor Ellis had in short supply. Ironically, Ellis resolved the problem of mechanical duration by creating a camera in which the film remained stationary. The fastest shutter speed on most thirty-five millimeter cameras is one thousandth of a second; the shutter speed of the Ellis Camera is one millionth of a second.
In the Ellis Camera a mirror rotating at up to one thousand revolutionsper minute sweeps an image across an eightfoot strip of film. A specially designed ruby laser strobe light is synchronized with the mirror to establish the correct framing on the film. Each individual flash of light lasts only twentybillionths of a second. In creating his camera, Professor Ellis had two major problems to solve after fashioning the rotating mirror design for his camera. A mechanical shutter was not fast enough; so he chose the Kerr Cell, a device that when electrically charged would allow light to pass through. But to use the Kerr Cell as a shutter required a very intense light source. A colleague of "Doc" Edgerton, Dr. Kenneth J. Germeshausen, was working at Cal Tech on pulsing flash lamps. Professor Ellis consulted with Dr. Germeshausen on different ways to resolve the problem. By 1952, pictures taken with the Ellis Camera were published. Later, Professor Ellis patented the first high power ruby laser capable of emitting uniform light pulses with a duration of only one billionth of a second.
Unfortunately, as it was initially designed, the Ellis Camera was not entirely suitable for Starrett's experiments. Drawing upon the innovative concepts of the Ellis Camera, Starrett made several improvements. To record the complete event, in this case the life of a bubble, Starrett extended the film length. By manipulating the camera's design, the backlit images were rendered sharper and the film's framing was more clearly defined. Through the adding of a Pockels Cell to the laser design, Starrett increased control over the light source so that the camera could be operated with an open shutter. By covering the lens with a narrow band filter to block all light except for laser light, the camera could be used in a lighted room.
The newly designed Starrett Camera (1976) held a 100 foot roll of 35 millimeter Kodak Tri-X film; twelve experimental runs could be filmed with each roll. Like his colleague Albert Ellis, Starrett used what was at hand to resolve design issues. For example, the Starrett Camera's film was time and date coded by the LED display of a digital watch. In a unique design decision, the 915 millimeter focal length aerial telephoto lens was mounted backwards. Focusing was then accomplished with an adjustable mirror (made from a modified dental mirror) inside the camera. The main rotating mirror design was also enhanced to improve image quality and experimental sequencing.
To have all of the pertinent information to study cavitation required a complete record of the life of the bubble. Starrett's design modifications made possible the image clarity and definition that was crucial to the identifying of shock wave location and the complete measuring of bubble size and shape. His contributions to the scientific study of cavitation and to visual technology resulted in the awarding of his Ph.D. in engineering in 1982.
Dr. Starrett's widow, Jane Starrett proudly explains that "The final filmed records could only be achieved by careful alignment and calculated sequencing of the laser light source, the experiment and the camera. Skip was able to do this consistently, like a symphony conductor making beautiful music."
From November 16 through January 12, 1997 UCR/CMP will present the exhibition In the Blink of an Eye . Here museum visitors can view for themselves these unusual cameras. In addition to the display of the Ellis Camera and the Starrett Camera, In the Blink of an Eye also includes a video presentation that illustrates and explains these amazing highspeed cameras, and a print made from film taken by the Starrett Camera. This exhibition is made possible through the cooperative efforts of Professors M. Lea Rudee and Sia Nemat-Nasser of the University of California, San Diego and the families of John E. Starrett and Albert T. Ellis. The Starrett and Ellis Cameras have been maintained and restored by David W. Lischer. An opening night reception for In the Blink of an Eye and UCR/CMP's other Winter exhibitions will be held at the museum on Saturday, November 16 from 7:009:00 pm.
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