Emmett Leith

American physicist and electrical engineer

• Born: March 12, 1927
• Birthplace: Detroit, Michigan
• Died: December 23, 2005
• Place of death: Ann Arbor, Michigan

Leith and Juris Upatnieks presented the first three-dimensional hologram at a conference in 1964. Holography has been applied in many fields, including data storage, credit card security, art, and interferometry.

Primary fields: Electronics and electrical engineering; optics; physics

Primary invention: Three-dimensional holography

Early Life

Emmett Norman Leith (leeth) was born on March 12, 1927, in Detroit, Michigan. Little is known about his childhood. He attended Wayne State University in Detroit, where he graduated with a bachelor of science degree in physics in 1949 and received his master of science degree in physics in 1952.

Life’s Work

After finishing his master’s degree, Leith took a job with the University of Michigan’s Radar Laboratory, part of its Willow Run facilities. He worked for the university during his entire fifty-two-year career. The laboratory had an Army contract to develop synthetic aperture radar (SAR), a scanning radar system to be used by aircraft to create topographic maps. Many thought that the project for this high-quality imaging radar system would fail because airplanes could not carry the necessary massive antenna. With SAR, an aircraft could be outfitted with a five-foot antenna, which acted as a much larger one. The antenna would send out a signal that hit objects on the ground and bounced back. The data would then be captured as a line on photographic film, and the lines would produce images when a computer developed the film. The early computers of the early 1950’s were not able to handle the volume of data needed for SAR. While other scientists worked on improving computer technology, Leith began working with physical optics solutions.

By 1957, Leith had created a new version of SAR based on his optics research. He later described the system as a “holographic viewpoint.” At first, it seemed that Leith’s method was valid only in theory; the first eight trials failed. The ninth test flight, however, produced startling results, successfully mapping the Michigan terrain. Leith’s work with SAR eventually led to his research in holography. British scientist Dennis Gabor first introduced the idea of holograms in 1947. Gabor’s holograms looked fuzzy and had double images, in part because he was working with a mercury lamp. He had hoped that his research would be used to improve the resolution of electron microscopes. By 1955, most scientists felt that holography could not be accomplished successfully and abandoned the field.

Leith began thinking about applying certain optics principles used in SAR to holography. In 1960, Leith told coworker Juris Upatnieks about his theory of how to build holograms. Leith planned to produce an unfocused image on a transparency and use the recorded image to get a clear picture. Upatnieks was not interested at first but was eventually convinced that Leith’s idea might work. Leith and Upatnieks used a continuous-wave laser as their light source, a crucial device for creating clear holograms. Based on Gabor’s theory, their method—called carrier-frequency, or off-axis, holography—split two beams of light from one coherent beam. One of the beams (the object beam) is shone onto the object to be recorded, and the other (the reference beam) is deflected by a mirror onto the photographic film behind the object. The object beam reflects off the object and converges with the reference beam on the photographic plate, resulting in a negative that looks like a random collection of blobs and specks. This “hodgepodge,” as Leith called it, is actually the hologram.

A second step must be taken in order for the hologram to be viewable. In the reconstruction stage, the hologram is illuminated with a replica of the reference beam. The result is two separate images, a virtual one that appears behind the plate and a real one that appears in front of the plate. Together these two images form a hologram. In optics, a real image is produced when the rays of light exiting a lens actually converge at a point. This image can be produced on a screen, such as a movie screen. A virtual image is created when light rays shown through a lens only appear to intersect at a point. This image (such as a reflection seen in a mirror) cannot be produced on a screen.

The two men refined their method in 1961 and published their work in the journal of the Optical Society of America the following year. They had proven the critics wrong; holography was possible. In 1963, their work was known as lensless photography, simply because no lens was used. Having successfully found a way to make holograms of any object, Leith and Upatnieks began working on further refining their method. The next goal was to create a three-dimensional (3-D) hologram. In 1964, they presented a paper at an Optical Society of America conference, having successfully created the world’s first 3-D hologram. Again, their success was due in part to the newly developed laser, which allowed them to use coherent light to make the hologram three-dimensional. When the two scientists showed their colleagues a hologram of a toy train, the image appeared so real that many of the men thought it was a trick done with mirrors. Leith told Michigan Engineer magazine that a few of the scientists even had asked him where the train was. He told them it was back in Ann Arbor. Viewing the hologram was like seeing the toy train in person. It was even possible to look behind the train.

Leith and Upatnieks filed for the first holography patent on April 23, 1964. It was titled “Wavefront Reconstruction Using a Coherent Reference Beam.” The term “wavefront reconstruction” had been Gabor’s initial name for holography. Leith eventually held more than fourteen patents. During the 1960’s, he also played a major role in setting up an optics program for the University of Michigan Physics Department.

The toy train hologram created a lot of buzz within the optics community. News of it spread to nonscientists around the world through press releases, newspapers, and magazines. Life magazine covered the story of Leith and the hologram; articles in Scientific American, naturally, focused on the science. Holography became a popular field of study for scientists around the world. By 1970, hundreds were working on improving techniques, materials, and applications. Many of these researchers were not optical scientists. Applications for holograms in medical imaging, data storage, and entertainment were being investigated.

In 1978, Leith received his Ph.D. in electrical engineering from Wayne State University. The following year, he was given the National Medal of Science by President Jimmy Carter for his work in holography. Over the course of his career, Leith received several other commendations, including (with Upatnieks) the Inventor of the Year Award (1976).

Leith continued to teach physics, optics, and computer science at the University of Michigan until his death in 2005. He also continued his research in optics and imaging. He suffered a stroke on December 22, 2005, and died the following day from an internal hemorrhage. Leith was to retire on December 31. He was survived by June, his wife of forty-nine years, and two daughters and three grandchildren.

Impact

Leith’s work in optics and holography has had great influence. His early work on the SAR program for the Army helped create a radar system capable of producing high-quality maps of enemy terrain from a safe distance. His work on SAR piqued his interest in optics, which started his career in holography.

Much of his later work dealt with biomedical imaging. Leith and one of his former graduate students, Dr. David Dilworth, collaborated from 1987 to 2005 to create improved biomedical imaging. Together they held a patent related to methods of early detection for breast cancer.

Photon migration, or imaging through human tissue, has become a whole new field of optics. Leith is among the field’s pioneers, becoming involved in the research in the late 1980’s. His goal was to make human tissue transparent, allowing doctors to look through the tissue to spot tumors. In the 1990’s, Leith began working on a joint project with the Michigan Center for Biological Information and the University of Michigan that aimed to produce a virtual 3-D human, visible without 3-D glasses. The image would be used for education, dissections, and virtual surgery.

Leith also influenced a number of students, many of whom pursued fields dealing with optics or holography. Leith was influential in creating the University of Michigan’s optics program. His Friday lectures were always filled with demonstrations. Students found themselves drawn in by Leith’s enthusiasm for optics.

Bibliography

Benton, Stephen, and V. Michael Bove, Jr. Holographic Imaging. Hoboken, N.J.: Wiley-Interscience, 2008. Explains the basics of how holograms work. Also includes a history of the field and advanced holographics. Suitable for undergraduate and graduate students and scientists.

Caulfield, H. John, ed. The Art and Science of Holography: A Tribute to Emmett Leith and Yuri Denisyuk. Bellingham, Wash.: SPIE, 2004. An introductory chapter discusses Leith and other pioneers in the field. An in-depth technical and mathematical analysis of various forms of holograms and their applications.

Johnson, Sean. Holographic Visions: A History of New Science. New York: Oxford University Press, 2006. A good introductory work covering the history of holography through 2005. Also explores how holography has affected other sciences and the role it plays in American society.

Kasper, Joseph, and Stephen Feller. The Complete Book of Holograms: How They Work and How to Make Them. Mineola, N.Y.: Dover, 2001. Explains various types of holograms without discussing complicated mathematics. Includes step-by-step directions.