With its appearances in TV and movies, holography belongs to science fiction as well as reality. It’s part of the human imagination. Perhaps it’s surprising to learn, then, that holography is a science rooted in the earliest years of the 20th century, with more than one human parent. Hungarian-born British scientist Dennis Gabor is widely credited with being the “father of holography” in 1947, but before him Gabriel Lippmann is credited with being the first to come up with the idea of a holographic camera, which he dubbed “radiance photography.” Lippmann won the Nobel Prize in Physics in 1908 for his two-step method for recording and reproducing natural color in photography.
In 1908, Lippman also introduced a way to photograph a scene that he dubbed “integral photography.” The technique used a plane array of closely spaced, small spherical lenses to record images of the scene from slightly different horizontal and vertical locations. The resulting image, viewed through a similar lens array, would allow the left eye and right eye to see different images, each composed of small portions of all of the originally recorded images. “The position of the eye determines which parts of the small images it sees,” Lippmann wrote. “The effect is that the visual geometry of the original scene is reconstructed so that the limits of the array seem to be the edges of a window through which the scene appears life-size and in three dimensions, realistically exhibiting parallax and perspective shift with any change in the position of the observer.” This principle gave birth to the concept of a light field, an image composed of recordings from numerous lenses. It is the foundation of today’s light field cameras and microscopes and is the fundamental principle underlying Light Field Lab’s development of truly holographic displays.
Gabor gave the phenomenon a name, combining the Greek words for “whole” (holos) and “message” (gramma). Gabor (née Günszberg) was born in Budapest in June 1900, when it was part of the Austro-Hungarian Empire. He served with the Hungarian artillery in World War I and began studying engineering in 1918, first at the Technical University of Budapest and then at the Charlottenburg Technical University (now the Technology University of Berlin) in Germany. He developed an interest in electron optics early in his career when he analyzed the properties of high-voltage electric transmission via cathode-beam oscillographs. After obtaining a diploma in electrical engineering in 1924, he went on to obtain his engineering doctorate in 1927, with a thesis (“Recording of Transients in Electric Circuits with the Cathode Ray Oscillograph”) related to the development of one of the first high-speed cathode ray oscillographs. [1]
His first job was in one of the physical laboratories of Siemens & Halske in Berlin. When Hitler came to power, Gabor (whose family had converted to Lutheranism) was deemed Jewish and his contract was not renewed. He left Germany by accepting an invitation to work at the development department of the British Thomson-Houston company, an engineering and heavy industrial subsidiary of the New York-based General Electric Company. Prior to World War II, Thomson-Houston played a major role in developing the first prototype jet engine. What Gabor did at the company during that time is unknown, but after the war, in 1947, he developed the theory of holography while working on improving the electron microscope. While the electron microscope had dramatically improved the resolution of the best optical microscopes, there was still room for improvement, according to Dr. Augusto Beléndez, a professor of applied physics at the University of Alicante in Spain. “Its main limitation was related to the spherical aberration of the magnetic lenses of the microscope,” writes Beléndez. “To solve the problem, Gabor asked himself, ‘Why not take a bad electron picture, but one which contains the whole information and correct it by optical means?’” [2]
Gabor developed the idea of a two-step process involving interference (the recording step) and diffraction (the reconstruction step) in 1947. He described the process in a paper published in 1949 titled “Microscopy by Reconstructed Wave-Fronts”:
“In a first step, the object is illuminated with a coherent monochromatic wave, and the diffraction pattern resulting from the interference of the coherent secondary wave issuing from the object with the strong coherent background is recorded on a photographic plate. If the photographic plate, suitably processed, is replaced in the original position and illuminated with the coherent background alone, an image of the object will appear behind it, in the original position.” [2]
Gabor named the interference pattern a hologram because it contained the whole information (holos) of amplitude and phase of the object wave. In the second step, the reconstruction, Beléndez explains, “the hologram is illuminated with visible light and the original wavefront is reconstructed, so that the aberrations of the electronic optics can be corrected by optical methods.” [3]
Gabor made his first hologram in 1948 using a mercury arc lamp with a narrow-band green filter as his light source. Beléndez calls it “one of the best coherent light sources before the laser.” The object of his photo was a tiny, 1.4mm-diameter circular transparency with lettering spelling the names of Huygens, Young and Fresnel, three physicists he considered important because their work informed his wavefront reconstruction technique.
Gabor published “A New Microscopic Principle” in Nature magazine that same year, and “Microscopy by Reconstructed Wave-Fronts” subsequently appeared in the Proceedings of the Royal Society of London. The paper prompted an immediate global response and was well received by Nobel physics laureates Lawrence Bragg and Max Born. Perhaps most crucially, National Physical Laboratory director Charles Darwin, grandson of the more famous Darwin, also approved. That led to Gabor’s 1949 appointment to the new position of Mullard Readership in Electronics at the Imperial College of London and his directorship of a new electronics lab. [3]
According to an article by University of Glasgow Professor/Affiliate Research Fellow Sean F. Johnston in Historical Studies in the Physical and Biological Sciences, Bragg also arranged for Gabor to demonstrate the technology at the September annual meeting of the British Association for the Advancement of Science (BAAS), which, Johnston writes, “brought Gabor’s technique to its widest audience and produced the most public result” — a New York Times article introducing the idea of holography to the public. [4]
Gabor’s wave-reconstruction technique became a topic of study by numerous scientists worldwide, including Gordon Rogers in the U.K., Adolf Lohmann in Germany, and Patrick Kirkpatrick at Stanford University in the U.S.; all told, about 50 articles on the technique were published between 1948 and 1955. Even so, Johnston reported that “many of [Gabor’s] scientific contemporaries” regarded Gabor’s wave-reconstruction idea (also dubbed holoscopy, interference microscopy, diffraction microscopy and Gaboroscopy) to be “unintuitive and baffling … of dubious practicality and, at best, constrained to a narrow branch of science. By the late 1950s, Gabor’s subject had been assessed by its handful of practitioners to be a white elephant,” says Johnston. [4]
By 1954, only a handful of small, blurry images had been created, and Rogers, one of Gabor’s most enthusiastic research supporters, wrote to a colleague in 1956 that he was “quite happy to let Diffraction Microscopy die a natural death. I see relatively little future for it, and am looking forward to doing something else.” [5] At about the same time, Gabor abandoned his research.
Less than 10 years later, holography was reborn, thanks to the invention of the laser in 1960 and contributions of researchers in the U.S. and Russia. In 1962, at the University of Michigan, Emmett Leith and Juris Upatnieks read Gabor’s paper and decided to duplicate his technique, this time using a laser and an “off-axis” approach they borrowed from their own work in developing side-reading radar. They successfully achieved the first laser transmission hologram of two 3D objects: a toy train and a bird, both of them images with realistic depth and clarity. In the same year, Dr. Yuri Denisyuk of the State Optical Institute in Leningrad relied on Lippmann’s earlier work in natural color photography, combined with holography, to produce a white-light reflection hologram. For the first time, the hologram could be viewed in light “from an ordinary incandescent light bulb.” [6]
When Denisyuk’s research became known in the U.S., three research groups—one at University of Michigan, another at Bell Labs and yet another at Batelle Memorial Institute—decided to take his off-axis recording technique and “apply it to reflection holography.” By fall 1965, all three groups had succeeded; the U.S. patent was issued to the Batelle Memorial Institute’s N. Hartmann. After that, other scientists pushed the research on holography forward, with experiments and published papers from Robert Powel and Karl Stetson (1965, on holographic interferometry) and T.A. Shankoff and K.S. Pennington (1967, on the use of a dichromated gelatin as a holographic recording medium). [7]
Holography was still produced in the laboratory, but the 1967 World Book Encyclopedia Science Yearbook contained what is believed to be “the first mass-distributed hologram,” a 4-inch-by-3-inch transmission view of chess pieces on a board. In 1967, Conductron Corporation’s Larry Sieberg used a pulsed laser to make the first hologram of a person, which “played an important role in the early days of commercial display holography.” In 1968, Dr. Stephen Benton furthered display holography by inventing white-light transmission holography while he was researching the potential of holographic television at Polaroid Research Laboratories. [7]
With the advent of the laser and all the groundbreaking work done by multiple research teams, Dennis Gabor’s work was no longer the white elephant of Johnston’s story. In 1971, he was awarded a Nobel Prize in Physics for his pioneering holographic work in 1947. In his Nobel Lecture, Gabor recognized the “contributions of other researchers” that led to his award. “I am one of the few lucky physicists who could see an idea of theirs grow into a sizeable chapter of physics,” he said. “I am deeply aware that this has been achieved by an army of young, talented and enthusiastic researchers.”
FOOTNOTES
[1] https://en.wikipedia.org/wiki/Dennis_Gabor
[2] https://royalsocietypublishing.org/doi/10.1098/rspa.1949.0075
[3] https://www.bbvaopenmind.com/en/science/leading-figures/dennis-gabor-father-of-holography/
[4] http://eprints.gla.ac.uk/2891/1/from_white_elephant1.pdf
[5] https://www.jstor.org/stable/10.1525/hsps.2005.36.1.35
[6] http://mathdragon.net/kml/math/MESA/Holograms/research.htm
[7] http://www.holophile.com/history.htm