How Holography Took a Giant Step Forward at the College of Engineering

By Paul Gargaro

This hologram of a toy train represents a process that has found numerous applications in aerospace, archeology, credit-card security and popular art, to name just a few.

As we begin Michigan Engineering's 150th-anniversary year, it's fitting to look back at the milestones that so many CoE researchers and alumni have left along the road from yesterday to today. The list, both exhaustive and impressive, contains household names, objects and technologies that people see and use every day but rarely think about. One of the most common is the holographic image.

When college of Engineering researchers Emmett Leith and Juris Upatnieks (MSE EE '65) displayed their revolutionary laser transmission hologram of a toy train at the Optical Society's 1964 Spring Conference, they shed new light on a nascent scientific principle that, in the following years, has found numerous applications in aerospace, archaeology, credit-card security and popular art, to name just a few.

"They had never seen anything like it," Leith said, referring to attendees at that Washington, D.C., conference 39 years ago. "There was a mass exodus from the room after Juris delivered our paper and invited the audience to come look at our hologram in a nearby suite. Many of them thought it was done with mirrors. A few wanted to know where the train was. I said, 'It's back in Ann Arbor.'"

Leith, Schlumberger Professor of Engineering, Electrical Engineering and Computer Science, said that in general, the creation of a hologram involves a number of steps. (See Figure 1.) This image is unlike 3-D or virtual-reality images that appear in a two-dimensional plane such as a computer display.

Figure 1: The creation of a hologram begins with the splitting of a beam of light (a). A mirror (b) redirects one beam so that it reflects off an object (c). A second mirror (d) redirects the second beam. The two beams combine, creating an interference pattern (e) which is captured on film, transforming the film into a hologram. Later, shining a laser through the hologram (the film) creates a three- dimensional, free-standing image.

While holography has become a common resource in today's commercial and research arenas, it was a largely undeveloped technology when Leith and Upatnieks presented their findings to the Optical Society. Their work helped refocus the scientific community's attention on the work of Dennis Gabor, a Hungarian/British scientist, who had his breakthrough brainstorm as he waited for a tennis court in Rugby, England, in 1947. The technological constraints of the day limited his work to badly distorted images.

Leith uncovered the principles of holography for himself in the mid-1950s while working on a military radar program at the University of Michigan's Institute of Science and Technology at Willow Run. Leith was a member of a group that was trying to produce images with resolution comparable to that of aerial photography.

"It came close to paralleling Gabor's original work," Leith said, noting that he was unaware of Gabor's initial research and "a little disappointed" to learn that he had "rediscovered" the principles of holography. Nevertheless, it gratified Leith to find that there was credible theory behind his research.

Between 1961 and 1964, Leith and Upatnieks made a series of presentations to the Optical Society of America describing three major advances in holography. The first was the use of the off-axis reference beam to capture, on a single piece of photographic film, the complete record of the light wave, resulting for the first time in holographic images of excellent quality. (Of the three major advances, this advance has by far the greatest scientific significance.) The second advance was the use of diffused coherent illumination, which gave the hologram some new properties, including a high degree of immunity to defects in the optical system, such as dust and scratches on the optical elements. The third advance was the use of the newly invented laser, which was able to record holograms that produced images of solid, reflecting, three-dimensional objects. This was an advance over previous methods, in which the traditional mercury arc light, with its far inferior coherence, could only make holograms that produced transparent images rather than fully three-dimensional images with solid, reflecting surfaces.

"Holography as we know it today stems from their off-axis technique," said Paul Barefoot, president of Holophile Inc., a Connecticut-based company that provides three-dimensional imagery for trade shows and conferences. "I'm not sure where holography would be today without this development. It's simply the way things are done."

Subsequent advances in the technology have made holography an invaluable tool. Leith and Upatnieks thought of all kinds of applications for their work. "But," Leith said, "who would have thought of (phone) cards at the time? With all of these new ideas and products, we simply had no idea." -E

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Paul Gargaro is a freelance writer whose work has appeared in such publications as The New York Times and Detroit Monthly. He has held staff positions with The Bridgeport Post, Crain's Detroit Business and Bloomberg News.