Inventor's Voice: He Made Holography Practical

“One day we came across Gabor’s paper and simply out of curiosity decided to duplicate it.”

Nobel prize-winning physicist Dennis Gabor was inducted posthumously into the National Inventors Hall of Fame in 2012 for his “research in electron optics that led to the invention of holography.” The brief citation went on to note that Gabor’s 1947 invention of “a new microscopic principle” (1) saw numerous applications because of his efforts “and also the efforts of researchers after him.”

Emmett N. Leith was one of those less-well-remembered researchers. The University of Michigan physicist was memorialized as  “inventor of practical holography” in a tribute published by the University’s EE and Computer Science Dept. shortly after his death in December 2005 at age 78(2). The department chair eulogized him as “a phenomenal thinker…who came within a whisker of winning a Nobel prize.”

Leith had joined the University’s Radar Laboratory in 1952 and began working on a classified military project to build an airborne radar system for mapping enemy terrain. Leith made important theoretical contributions to what became a highly successful synthetic aperture radar (SAR) capable of mapping territory from safe distances (hence the name side-looking radar).

The new radar had been tested with “startling results” by 1960 when Leith was joined in the lab by 24-year-old Juris Upatnieks, regarded by colleagues as an extremely meticulous experimentalist.

Discovering a Fascinating Field

Leith related what followed in a 1969 interview (3):

“One day we came across Gabor’s paper and simply out of curiosity decided to duplicate it. We did, and right then and there decided that this was a most fascinating field to be in. It’s a fairly striking thing—you see this sharp image hanging in space with no object in the entire system that looks as if it could produce it. There’s just an unintelligible smear on a transparency.

“So at odd moments, in a corner of the laboratory, we started investigating holography. In particular, we tried various ways of removing the twin image, which appeared in Gabor’s holograms as identical to the reconstructed image but considerably out of focus.”

“That was when we introduced the off-axis reference beam, whereby you essentially modulate the diffraction pattern by bringing in a second beam at an oblique angle via a prism or mirror.

“This idea of the off-axis reference beam, by which we were able to preserve very precisely all the phase and amplitude information in the scene, is very common in radar and communication systems. It worked very well and did improve the imagery.”

“Their Results Were Brilliant”

Gabor acknowledged the significance of Leith’s earlier radar work in his 1971 Nobel address (4). He explained that the solution Leith and his collaborators devised “was in fact two-dimensional holography with electromagnetic waves, a counterpart of electron holography…Their results were brilliant.”

In his 1969 interview, Leith said that the U of M bought its first lasers in 1962 (two years after the gas laser was invented at Bell Labs) “and this made things quite a bit easier.” With lasers they were able to make holograms of solid three-dimensional objects rather than just of transparencies. “There was a lot of failure along the way but finally by December 1963 we made some very good holograms of solid objects.”

Scientists Get Excited

Leith and Upatnieks published several important papers between 1961 and 1964. However, it wasn’t until they showed the toy-train hologram you see on page 15 to hundreds of attendees waiting in line at the April 1964 Optical Society of America meeting that the scientific community got excited over holography’s potential.

“After the meeting we were deluged with phone calls and letters requesting information on how to make holograms,” Leith recalled, adding how there was “an explosion of activity” in his now-20-man optics group. “Everyone wanted to work in holography, and it wasn’t too long before we were able to get enough money from government and industry to support eight to ten people in it.”

In his 1971 Nobel lecture, Gabor related how back in 1950 he thought about ”the desirability of a strong source of coherent light” (i.e., a laser) .He told about offering his “best student” the idea for a pulsed laser “but he declined it, as too risky, and I could not gainsay it, as I could not be sure that we would find a suitable crystal.”

“Around 1955” Gabor continued, “holography went into a long hibernation. The revival came suddenly and explosively in 1963, with the publication of the first successful laser holograms by Emmett N. Leith and Juris Upatnieks…. Their success was due not only to the laser, but to the long theoretical preparation of Emmett Leith, which started in 1955.

It’s About Great, True Ideas

A former student of Leith’s, Rod Alferness, remembered his teacher differently in the 2006 memorial tribute. Then a Bell Labs research executive, Alferness said his work with Leith taught him that, “It’s about ideas. It’s about coming up with great, true ideas… His ideas and the things that he made possible from them were very powerful.”

Many applications have certainly flowed from that 1963 invention. By 2009, the market for viewable holographic products had grown 470% in the prior decade to  $3,201 million, a trade newspaper estimated. Document and identity protection were the biggest growth areas.

In November 2010, Nature published a letter from Arizona State University scientists who reported “a practical method of producing truly three-dimensional images that do not require the viewer to wear special eyewear.” Their “holographic three-dimensional telepresence” realized one of Gabor’s long-held dreams. In 1969 he received U.S. patent 3,479,111 for “Three-Dimensional Picture Projection.” He admitted, however, that the funding necessary to develop the idea was so large that it might have to wait until the 21st century.

The Lucky Physicist

In concluding his 1971 Nobel lecture, Gabor, by then the recipient of many other honors and awards, observed that, “I am one of the few lucky physicists who could see an idea of theirs grow into a sizeable chapter of physics.” Emmett Leith would surely have agreed.

References

1. D. Gabor; “A New Microscopic Principle.” Nature 161, 1948, pp.777-778.

2. Emmett Leith (1927-2005) Inventor of Practical Holography; University    of Michigan EECS News, Spring/Summer 2006.

3. Michael Wolff. “The Birth of Holography; Innovation No. 7, 1969, pp.4-15.

4. Dennis Gabor. HOLOGRAPHY, 1948-1971; Nobel Lecture, December 11, 1971 

Michael F. Wolff
Editor, IMR
mwolff3877@aol.com

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