Raisin Bread in Space

as related by Robert Nichols

The science editor of the Orange County Register News visited us to do a special article on Orange County Companies who are involved in space research. He first interviewed me for about half an hour. One of our more interesting space projects, which I attempted to explain to him was the three-dimensional recording and analysis of particle fields in space using holography. He was having considerable trouble understanding what I was explaining so I called in Robert and Frank, who are doing some experiments and asked them to show the reporter some examples and explain to him. They took him to the lab and I forgot all about the story until the next day, when I saw Robert at the coffee pot.

Robert explained how difficult it had been to explain to the reporter. They would scan through a three dimensional image produced by the holograms we had made in space, focusing on particles one by one until they scanned the whole volume, showing how we could track particles precisely in three-D, measuring microgravity effects on particle motion. The reporter had considerable difficulty understanding what we were doing, until Frank came forth with a good analogy that cleared things up.

Frank said, "Consider if you had a loaf of raisin bread and wanted to find the distribution of raisins in the bread. You could slice it off in thin slices one by one until you had located each raisin. How we can do the same sort of thing optically with lasers, slicing a three-dimensional image up optically until we find all of the raisins, and we don't have to touch the space where the bread is. "Oh, I see now," said the reporter, "That clears up everything". Today, we got the galley proof of the MetroLaser portion of his article. It read something like the following.

"Not all of the Orange County Companies involved in space are large. Take MetroLaser Inc., for example, a thirty-five man company in Irvine. This group of scientists produce extremely high tech and esoteric solution to all kinds of measurement problems using advanced optics and lasers. These brilliant, if a bit nerdy, scientists are providing solutions that make life easier for astronauts in space. They have developed an advanced method for slicing raisin bread in microgravity that is so sophisticated that they can tell where the raisins are even before the bread is sliced." My first reaction was "Robert...............tell him it's perfect. Print it." Unfortunately, Robert had already explained to the reporter that MetroLaser does not slice bread in space.

Smoke and Mirrors

In the early days of laser applications, many scientists still smoked. It was common practise to use cigarette smoke to align and trace laser beams in laboratory set ups. Some people said you couldn't work with lasers unless you smoked. Joe O'Hare, an AEDC engineer I worked with, was a cigar smoker and he always had a cigar going when working with a laser setup. Eventually, I followed suit and switched to cigars because they lasted longer and produced more smoke. Often when working with large setups we would leave cigar butts in the rafters or other remote places that beams of light were passed. We often joked that someday, people all over the US would begin to wonder where all the cigar butts came from. Before long we began to recognize that our mirrors and lenses were scattering more and more light and finally it dawned upon us that we were coating the optics with tobacco films. This put a halt to using cigar and cigarette smoke for laser alignment. After that we used various, non polluting aerosols to visualize laser beams. Various optical engineers discovered this problem at different times, but eventually, the word got around to everyone. Even so, years later, I still occasionally encountered a group using  tobacco smoke for beam tracing.

 

Holographic Tire Testing-As told by Jim Trolinger

 By the early 1980’s I had made holograms of just about everything except tires, which at that time appeared to be one of the few success stories in commercial holography. Not long after we had started MetroLaser I finally got the chance to do tires. It came with a phonecall from a plant manager, I will refer to as Mike, at Michelin Tires in Cerritos, which was about 30 miles from MetroLaser. Mike was in somewhat a panic because a holographic tire tester that he had purchased from GRC had stopped producing holograms. On a previous occasion when this had happened he had hired George Grant to come and repair it, which not only cost him a lot of money, but also caused several weeks of delay in the process and created a huge backlog of recapped aircraft tires that were required by law to be holographically inspected.

 Newport Corporation had purchased GRC and no longer offered the tire tester as a product, but friends at Newport had given Mike my name as someone who might be able to help. He expressed the desire to have someone in the area that he could put on a retainer to call whenever problems arose. “The system has worked quite well and we rarely have problems with it, but when we do, it causes serious production delays. There are however, a lot of little things that should be refined, realigned, and adjusted regularly, and you could do that as part of the service we contract you for.”

 I drove to Cerittos the next day and met with the Mike who showed me the holography inspection room. “Everything was working well until summer got here, then without warning, we stopped getting holograms on the developed film. It probably has to do with temperature,” he added.

 Mike ran the system through its routine, produced a strip of holograms and showed me that nothing could be seen in the holograms. The system was pretty dirty, not well aligned and in bad need of general maintenance, but none of these problems would cause a complete failure to produce a hologram. I immediately suspected a vibration problem, which is usually only reason for getting not even a bad hologram. So I started looking for a source. It was then I realized that there was a huge floor fan blowing across the apparatus. “How long has that fan been there?” I asked.

 “Oh, the guys just moved it in last week. It gets really hot in here in the summer.”

 “That is most likely your problem,” I told him. “Let’s turn if off and try again.” Sure enough, the holograms came out not perfect, but usable.

 Mike was elated that the problem had been solved so easily and he could get on with production. I recommended that I do a complete system maintenance. “Okay, put together a little proposal and I’ll submit it to my management,” he responded, thanking me profusely as I left. But thanks was all I received from the visit.

 Weeks passed after I had submitted a proposal with no response when finally I gave Mike a call to inquire about this “retainer” idea he had mentioned. His response was not what I wanted to hear.

 “Well, Jim, we moved the fan and all the problems went away. We haven’t had any problems since, so I don’t think we will need you after all.” So I wrote the whole thing off as a bad screwing that we have to accept every now and then just to be in the business.

 Almost a year passed when Mike called again. He began by apologizing for what he had done before, and then told me that the system had stopped producing holograms again. He promised to pay me for my time and have me do a general maintenance on the system if I could just get it working again.

 At the time I was extremely busy and did not have time to work on the system maintenance so I called Don Broadbent, another holographer, who lived nearby, to help. Don and I drove to Cerritos together, and I related my previous experience at Michelin Tire recapping.

 Once again, Mike described how the system had been working perfectly until they recently cleaned up the laboratory, after which it was incapable of producing holograms. He ran the system through a recording cycle and once again produced exposed pieces of film that clearly were not holograms.  “I think they must have knocked something out of alignment,” he suggested. Don and I both were already concluding that a new source of vibration had been inadvertently added in the cleaning process.  

We walked around the table, and both saw it at the same time. Someone had propped a block of wood under the umbilical cord to the system, which sat otherwise isolated on the stable table, essentially connecting the floor mechanically to the table top. We looked at each other, smiled, and said not a word. I made a lot of notes and estimated that Don could maintenance it and get in working in an estimated three days of work. Mike insisted on having a fixed price to get the system working, and he happily signed a fixed price purchase order with an extra day thrown in just in case unseen difficulties arose.

 Don returned, cleaned up and realigned the system and removed the board propping up the umbilical cord. According to Mike, he had never seen the system work as well before and he was happy even though Don finished in two days and Mike had paid for four. 

 Even after that he still never gave us a retainer.

 

 

by

James D. Trolinger, B.S., M.S., Ph.D, Holoknight, WWT

May , 2004

Holography was purportedly invented by Dennis Gabor in 1947. I was in the second grade, just entering my first art contest, fully convinced that I would be an artist when I grew up. By the time of high school graduation, reality had set in, the Soviets had launched Sputnik, the space race was on, and I was accepting a scholarship to the University of Tennessee to study physics. Better yet, accompanying the scholarship was an immediate internship at the Arnold Engineering Development Center (AEDC) in nearby Tullahoma, Tennessee, the primary U.S. Air Force test center for aircraft and spacecraft. The center operates wind tunnels for flight simulation, rocket stands for testing, engine cells for simulating jet engine flight, vacuum cells for simulating space, and launchers to simulate ballistics.

My father had helped build the center, with several of the facilities comprising captured, World War II German hardware. With an entire nation being focused on space and competition with the Soviet Union, this was, for a high school student, like heaven on earth. If I could maintain a high grade point average at the University of Tennessee, I could alternate work at AEDC and school and rub elbows with the new elite class of scientists and engineers.

I began with a non destructive test group and eventually moved into a group that provided the optical instrumentation for wind tunnels and shock tubes, experiences that shaped my career as much as the scholarship and the formal education that went with it. I loved optics, high-speed cameras, schlieren systems, and interferometers, and had decided early on that optics had a good future for me, even before lasers had arrived on the scene, and their invention in my third year of college enhanced the opportunity even more. We could only read about lasers at first since none were commercially available for a few years, but I began imagining how to use them long before I could own one.

Following undergraduate work I spent two years at Louisiana State University (They paid better) learning quantum mechanics and that high-energy physics was much less exciting than optics. So I returned to Tennessee to pursue a PhD at the University of Tennessee Space Institute (which had been established near AEDC to support space science) while continuing to work at AEDC in the Center's elite research group of the Director of Engineering. An advantage of this position was that I could work in any laboratory in the entire center. All of these are instrumented with the best diagnostics possible, and I had landed in a group tasked to find new generations of advanced diagnostics. I was in the first PhD group of three to receive degrees at UTSI.

The timing could not have been better. My first involvement with holography began in 1967 when I chose to make it one of the new diagnostics to implement in the center. My colleagues in holography at AEDC were Joe O’Hare, Mike Farmer, and Ronald Belz. Both Mike and Ron did Ph.D. dissertations at the University of Tennessee Space Institute in holography applications, and I was a member of their committees.

The aerospace industry was prime territory for applying lasers and holography. Part of the reason may have been because the aerospace industry was booming in the late fifties through the seventies, having been boosted by Sputnik. Optical instrumentation groups in the aerospace industry were some of the first people sufficiently funded to be able to afford lasers. The two major fronts were powered by NASA, in a race to put satellites into orbit and to go to the moon and beyond, and the military, who were trying to build defenses as well as offensive weapons in a race against the Soviets. Funds were fairly easy to come by for new research, and especially my friends in NASA had practically unlimited materials budgets, so much that they sometimes had difficulty spending the money. (The NASA Marshal Space Flight Center is in Huntsville, Alabama, about 70 miles Southwest of AEDC and the UT Space Institute.)

Advanced optics was already in use, when lasers and holography were invented, and optical engineers were always pushing the limits. The theory of coherent optics was already highly developed simply because it was simpler and easier than incoherent optics. Lasers just made the theory practical for the first time since usable amounts of coherent light had not been available before. This is one of the few examples in science where an almost fully developed theory was ready and waiting for the experimental hardware to arrive. Usually, experiments lead the way and provide observations needing theories. The availability of a good theory made experimental advancements happen much faster, and the field of applied optics benefited greatly.

Almost every optical theory and method that had been produced experienced a quantum leap when high intensity coherent light became available. There were so many possibilities that it was hard sometimes to maintain focus on any one of them. Many NASA groups and DOD groups began to look at holography as a way to make revolutionary improvements in diagnostics and inspection. At NASA Marshal Space Flight Center in Huntsville, a group sprang up around 1969 that included John Williams, Bob Kurtz, Bob Owen, and William Witherow. At least two these are still doing holography after thirty years. (William Witherow helped develop a new holocamera that is slated ultimately to fly in space.)

Holography provided a capability to record in 3-D and make all kinds of intereferometry possible, where it was not practical before. The basic idea was that one could record the wavefront and decide later what kind of diagnostics to employ, because the wavefront had all of the optical information in it. This feature offered a huge payoff for short-lived events, events spread out over a large volume, and events occurring in remote places, where diagnostics equipment could not be operated.

In the late 1960's and '70's, spurred on by the invention of lasers and lots of money in the sciences, applied laser and optical component companies sprang up everywhere. These often grew out of university groups where graduate students made their own equipment to save money. Some grew out of government laboratories. Optical component companies like Jodon (offspring of University of Michigan, started by John and Don Gillespie) made significant innovations both in utility and lower cost than older established companies like Gaetner.

A huge market in versatile components and optical tables emerged with Newport Corporation (offspring of Caltech, started by Dr. Milton Chang and associates), who popularized self-leveling, air supported, honeycomb tables with screw holes every inch. Stable tables at that time largely comprised huge granite tables that were extremely expensive and not very versatile. The self-leveling, relative low cost, honeycomb table of Newport became ubiquitous after 1970 in holography labs all over the world because they offered an affordable solution to the vibration problem for laboratory holography as well as other fields.

Before 1970, three major aerospace companies to get involved with holography in a big way were Hughes Research, where the first operating laser was invented by Theodore Maiman, TRW, a major military contractor, and MacDonnell Douglas, who had bought Conductron, an earlier failed effort to commercialize holography.

Among other applications, Don Close and his group at Hughes developed, under a NASA contract, a holocamera to place on the moon in planned lunar explorations. The idea was that surface details could be recorded in holograms and brought back for detailed analysis easier than the materials themselves. In the end the holocamera results were not good enough to allow it not make the cut in the lunar exploration toolbox.

Maiman had left Hughes and started a ruby laser company, Korad, which was soon purchased by Union Carbide, who produced the crystals. In 1967, AEDC purchased our first ruby lasers from Korad to be used in optical diagnostics and we took laser classes from Maiman and his group at the company in Santa Monica. I was introduced to Maiman in one of my visits, and thought of him as just another guy selling lasers. I think I was not even aware of his importance in the field, since Schawlow and Townes were the guys I had heard about most. Other ruby laser companies, i.e. Optics Technology, did not last very long because their lasers were expensive and not very reliable.

Interestingly, while history is in the making, the historical importance of specific people and companies is not always obvious.

In 1968 I attended the first SPIE conference in holography in San Francisco, sponsored by the Air Force, and met Brian Thompson, Ralph Wuerker and other heavy weights for the first time. For me this meeting was especially inspiring, having met both of my heroes in holography. I exploded with pride when Thompson, during his talk, actually mentioned my work at AEDC on holographic particle velocimetry(1) This was a landmark meeting, bringing aerospace scientists together with the founders of holography, including Lieth, Thompson, and Upatnieks. Of course I had respect for Leith, Upatnieks, and even Stroke, but to me they were academicians. I was interested in field applications.

The controversy between Stroke and Leith was at its peak at this time and the politics of the meeting were already obvious. The first speaker was Kirkpatrick, the oldest American holographer. Next came Lieth, then Stroke. I imagined how much thought the organizer, Brian Thompson, must have put into this arrangement since the battle was known by most people by this time. Kirkpatrick gave a history of holography that was rather curious and he failed to even mention Leith or Stroke.

This meeting began my friendship with Ralph Wuerker and Brian Thompson that was active for many years. Especially, Ralph Wuerker and I visited each other, crossed paths, and compared notes many times during the subsequent years. Nearly twenty years later we worked together in designing the first holocamera that America would fly in space^,(2)

One of the highlights of the 68 SPIE meeting was a banquet talk by Arthur Schawlow. He was an excellent and very funny speaker, appearing as though he enjoyed his own speech as much as we did. He opened his talk by holding up a small HeNe laser (about 18X4 inches was considered small) and then projecting an overhead with a diagram describing how a laser works. He described the laser as a solution looking for a problem and commented that he, Charles Townes, and others sat around at first and wondered what possible use there would be for such a device. Then he non-challantly began using the laser as a pointer, which drew a big laugh from the audience. No one had ever seen a laser pointer, and his appearance of just now discovering the problem to be solved was really funny. He then pulled out a hand held pulsed ruby laser that he used to pop a black Mickey Mouse balloon inside a clear one. After mentioning the military thoughts on death rays, with tongue in cheek, he described a counter measure called a DASER (Dark Amplification by Stimulated Emission of Radiation), with an associated viewgraph showing a black beam leaving the daser, which drew another big laugh. Finally he moved to holography, the subject of the conference, and he concluded that holography must be the problem for which the laser was the solution.

By 1970 Ralph Weurker and his group at TRW, having constructed their own ruby laser, began an almost endless stream of potential applications of holography and came up with ways to apply ruby lasers even before they were very good coherent sources. They did this by matching reference wave pathlength (relaxes temporal coherence requirement) and ray to ray mixing (relaxes spatial coherence requirement). I always admired and tried to imitate Ralph’s abilities to field ruby laser holography in the wildest of field applications. By 1980, he had placed a holocameras in a simulated nuclear explosions in the New Mexico desert, rocket motor exhausts, and had even produced holograms of medieval paintings.

TRW Group members included Ralph Weurker, Bob Brooks, Lee Heflinger, Arvel Witte, Bob Apprahamian, Sam Zivi, and others. They built a series of holocameras that were used in flow diagnostics and spray diagnostics. I think they were the first to use double-pulsed holographic interferometry. I often heard the claim that the first double pulsed holographic interferogram was the result of an accidental double pulsing of the laser (That was a common occurrence. Ruby laser holographers got holographic interferograms whether they wanted them or not.) TRW looked at military, biological, medical, and industrial applications. Holographic interferometry offered new ways to do non-destructive testing and new possibilities for analyzing flows around aircraft models, and analyzing three dimensional particle fields of all types.

The first holography application at AEDC (1967) was holographic particle image velocimetry (Tullahoma, TN. USAF) to measure flow fields. This technique was used extensively but was never sufficiently automated and was ultimately replaced largely by digital particle image velocimetry, or PIV, a non-holographic procedure that has become an industry standard and a great commercial success. A few researchers still persist in using holographic PIV. We have even made plans to fly a holographic PIV system in space.

Other particle holography applications at AEDC were for the study of sprays, fuel injectors, and a never-ending array of particle fields^,. We could use inline (Gabor) holography for this, making it very easy to apply. My first hero in this area was Dr. Brian J. Thompson, who had already used the methods in developing a commercial fog analyzing system of Tech Ops Inc, known as a fog disdrometer. During the same period I began to study the work of Dr. Ralph Wuerker and began planning to apply these methods at AEDC^,,.

Pulsed holography in such applications would be a must. The only laser candidate was ruby, which was not a very good coherent sources at first, having both poor spatial and temporal mode structure. Since I was one of the first people planning on doing holography with a Korad laser, I managed to get special treatment, help and advice from the Korad group, who included Marti Phillips, Ed Gregor, James Boyden, and Hal Walker.

Making the laser sufficiently coherent was a non-trivial exercise. Being a three level laser made it inefficient and unstable when operating near threshold where a single mode might be expected to lase. Cleaning up the coherence required unstable, unpredictable, cryptocyanine dye cell q switches and etalons in the cavity. These were not well developed for several years and required a lot of trial and error. Tricks, like inserting a transverse mode-selecting aperture that are common now, represented major breakthroughs at the time. Equally important was the discovery that we could spatial filter the pulsed laser beam to improve spatial coherence and beam uniformity even more. Eventually, diamond pinholes became available removing the requirement of replacing the pinhole regularly. Temperature controlled, tunable etalons were not commercially available. Fortunately Union Carbide had learned how to grow high quality ruby crystals. In buying a laser, we had to pay a lot more to get the best ruby rods.

Another severe problem was recording materials. At first Kodak 649F was the only game in town. It was very slow and not very usable with the ruby laser wavelength. When Agfa Gaveart came out with sensitized emulsions, holography took a great leap forward. Kodak introduced a few other films, like Kodak SO173 that were extremely useful with ruby laser holography. Even Polaroid PN film was usable to some extent.

At AEDC we set speed records recording holograms of particles and projectiles in flight at hypersonic speeds. One unique facility was a dust erosion facility that simulated a missile reentry through a dust cloud at hypersonic speed. The challenge was to measure the dust density, size, and velocity hitting the model. We had to invent a double-barreled ruby laser that could fire twice and produce two holograms in less than a microsecond. The data we collected was used in designing nose tip shields.

In cooperation with the U.S. Army, we installed windows in a diesel engine and made the first holograms inside an operating diesel engine to observe fuel sprays. We repeated this application in the laboratories of Detroit Diesel Allison Division.

Detroit Diesel Allison (now part of General Motors?) maintained a holography group that continued applying holography for at least 10 years, headed by Bob McClure and Dave Monnier.

There seemed to be no end to different kinds of particle fields one could examine. The excitement about viewing dynamic things microscopically in 3-D was a driving force. I never ran out of different kinds of particle fields to record usefully with holography with a list of over 100 different kinds of applications that took me to around the world. The amount of work and complexity in reducing the data to something really useful was largely overlooked at first. In many cases we would do it once then move on to another application when reducing the data for a given problem became too overwhelming for the method to become routine. We were simply solving one of a kind problems over and over. We measured particle size, velocity, and density in rocket exhausts, fuel sprays, icing test facilities, and reentry facilities.

During the same period Joe O'hare and I began applying holographic interferometry to examine flows in wind tunnels. Joe was the head of an optics group in the Center's hypersonic wind tunnel facilities and had ready access to a wide range of testing. Our first efforts were largely "bootlegged" attempts made unofficially during tests that were run at night. Eventually, holographic interferometry became a popular method for experimental tests. Most of Wuerker's applications used diffused light since he could cover larger fields with rather poor quality optics. We had high quality, large schleiren mirrors already available that we exploited building upon already highly developed schlieren and interferometry procedures and developed the first uses of holographic schlieren systems. We also had a continuing supply of high visibility test articles, like the Space Shuttle, that gave us an opportunity to provide necessary data that engineers were happy to see.

Being a part of the U.S. Air Force provided me the opportunity to apply holography in other aerospace facilities around the country on location in such companies as Boeing, Northrop, and McDonald Douglas. This also gave me access to the work in other Air Force and NASA laboratories. At Wright Patterson AF Base a holography group was run by Gene Maddux, who was applying holography to test turbine blades. The Wright Laboratories also did some groundbreaking work in producing holographic interferometry of rotating turbine blades by derotating the blade image. George Havener duplicated one of the systems we had developed at AEDC and made many classic holograms in the Wright Patterson AF Base wind tunnels. Being an aerodynamicist by training, he was able to better popularize the applications to aerodynamicists.

Holography was always difficult to employ in such studies and we could never seem to hand off the measurements to others. After the original specialists left AEDC, holography was largely abandoned and is rarely used there today.

In 1968 while working at AEDC I was also an associate professor of physics at the University of Tennessee Space Institute, and worked with two professors there, Dr. F.M. Shofner and T.H. Gee to develop a short course in holography to help kick off a holography group at the university. Among the lecturers were Juris Upatnieks and John Devilis (author of one of the first books on holography) as lecturers to give depth to the course. During the next few years we continued the short courses and taught regular courses in coherent optics and holography to provide an academic background to engineers at AEDC.

In the beginning of the space era, all of the services and NASA sponsored some kind of space program so there was a lot of money in space. The Space Institute benefited from this greatly since in addition to money some of the astronauts came there for schooling. Possibly the strongest student in any of the classes I taught was Henry Hartsfield, an astronaut who came to the Space Institute after his program "Manned Orbiting Laboratory" or MOL was cancelled by the Air Force. He went on to fly several space shuttle missions and headed the astronaut program for many years.

The big university plan was to make a major optical holography institute within the university. Within a few years Shofner left to start a new company and Gee succumbed to cancer, so the dream never came to pass.

Our university team gave me my first exposure to European holography in 1971 with a meeting we helped organize at the Von Karmen Institute in Brussels Belgium, through NATO's AGARD (Advisory Group for Aerospace Research and Development). Holography applications in aerospace seemed quite rare at the time in Europe. I believe that the only holography talks were given by Americans.

As a result of that meeting I took on a commission from AGARD to write an "AGARDograph" reviewing optical diagnostics throughout the NATO countries, giving me a good look all over Europe. The commission gave me a red carpet visit to places like Rolls Royce in England (Rick Parker, Bernard Hockley, and Peter Bryanston Cross were doing holography inside jet engines to observe flow fields and blade vibration: Loughborough University (John Tyrer was doing holographic interferometry for vibration analysis and Nick Phillips was developing advance bleaching methods); The German French Institute of Saint Louis (Paul Smigielski, Gunter Smeets, Bernard Kock, Hans Pfeifer, were doing similar work to my own work at AEDC) and ONERA (The Office of Aerospace Research) in France (Claude Veret was doing holographic interferometry of flow fields). I was stunned at the amount of work being done in Europe by this time by very strong research teams. Some of these people are still at it thirty years later, i.e. Nick Phillips at DeMontfort University in Leicester, Peter Bryanstan-Cross in Warwick University, Paul Smigielski in a private company he started, John Tyrer, still at Loughborough.

A strong effort in holography was under way at Ford Research in the early '70's headed by Karl Stetson, one of the first to graduate from Emmett Leith's group and the first person to produce a holographic interferogram. The Ford research applied holographic interferometry to a wide range of vibrational mode studies and to tire testing. Holography got major publicity for a role in solving a Ford (Linx?) transmission noise problem by locating modes that could be dampened with stiffeners. Karl hired Jon Sollid, who, with Gordon Brown and Mitch Marchie, continued the work at Ford after Karl left to join United Technologies, where his contributions to aerospace holography intensified. For the next twenty plus years, he developed a wide range of applications of holography, including derotated image holography of turbine blades. In studies supported by Wright Patterson Air Force base, he developed optical devices that could essentially freeze the image of a rotating object by derotating the image, allowing holographic interferometry of blades rotating at very high RPM's. He was one of the first to recognize and exploit the difference between electronic speckle pattern interferometry and true TV holography.   Stetson started his own holography company, PCHOLO http://www.pcholo.com/ , which continues today,  Sollid is a consultant in Santa Fe, New Mexico, Brown is retired in Florida, and Marchie is a consultant.

The first Gordon Conference on Holography, held in 1972, included representatives of the core of the world's scientific holography community. It was organized by John Caulfield. Here is a picture of the group and a list of attendees. I gave a talk on applications in particle field diagnostics.

These conferences are possibly the most unique of all conferences. Meetings are set up so that attendees live, eat, and socialize together intensively for a week. Attendees agree to show their latest work and nothing can be quoted or referenced to the meeting so that raw, immature ideas can flow freely. I made friendships at this meeting that lasted forever. One of the friendships was with Kenneth Haines, the first of Leith's team to get a PhD from the University of Michigan (He actually got his PhD before Leith did). I persuaded Ken to come and join the staff at the University of Tennessee Space Institute the following year.

I detected a pessimistic feeling about holography in the meeting with attendees already expressing a belief that holography had been oversold. Other Gordon Conferences on holography were held in '74 and '76, and a similar pessimism seemed to persist. The Gordon conferences were not continued for holography.

During my years at AEDC and the Space Institute, I had met a lot of industry people who made tempting offers to move into the world of private industry. 1970 was an especially good year for me. I made quite a hit applying holography in the missile field to answer a critical question in reentry simulation. Three centers in the US were running reentry simulations through ice and dust clouds. These were at AEDC, Boeing in Seattle, Washington, and Northrop in Hawthorne. These were hypersonic wind tunnels that launched dust and ice clouds at models to see how the models would interact with hypersonic particles and survive. The question was, "What kind of shielding should our missiles have?" and what kind of dust can we launch to burn up an incoming missile?" The problem was that no one knew for sure what was actually hitting the models, since the processes tended to burn up the dust. I proposed making double exposure particle holograms to measure dust size, number density and velocity. High speed photography was not applicable because the particles were small and dispersed over a large volume.

After some politicking and failed in-house efforts to produce holograms at Northrop, the Air Force sent Joe O’Hare and I with our equipment to Northrop where we produced, not only a complete particle field characterization, but discovered a new heating phenomena, known as augmented heating, that would have destroyed a shield that was then being deployed for the Minuteman missile system. We went on to calibrate the facilities at Boeing and at AEDC producing the first really usable particle field data for those simulating facilities.

These successes combined with other technologies developed at AEDC provided me an opportunity to move more into a commercial market. One of the offers promised a high potential for applying holography in some rather spectacular applications. Funding in the reentry ballistic missile industry was extremely loose at the time and I began looking at the possibility of flying holocameras in airplanes and space ships.

I left AEDC in 1973 to start an office of Science Applications International Corporation in Tullahoma Tennessee. Almost immediately we were awarded a large contract from the USAF Space and Missiles Systems Organization to fly holocameras in airplanes to analyze ice clouds. Here again, competing particle instruments could not provide the kind of crystal habit data needed for modelers. We flew a holocamera in the nose of a B57 high altitude aircraft over Albuquerque, NM then Guam and collected thousands of holograms of high altitude cloud ice crystals. Two years later we installed a similar system in a Cessna Citation jet and flew experiments over the Kwajalein Missile Range in the Marshal Islands where reentry tests are conducted by the Air Force. It appears that air borne holography was never fully accepted as a necessary diagnostic, and apparently no other such measurements have been made.

Kenneth Haines left the Space Institute and joined me at SAIC along with Mike Farmer from AEDC. Ken continued to develop holography, eventually starting Eidetic Images, which ultimately produced the first commercial embossed holography applications that ultimately turned into the most successful commercial application of holography to date.

I took one of the holocameras to the top of Elk Mountain Wyoming in 1974 and again in 1975 to record holograms of snow and ice cloud crystals. NASA employee Bob Owen took the system up a third time a year later. Professor Gabor Valley, who headed the department of Meteorology of the University of Wyoming (owner of the Elk Mountain weather observatory) told us to come back again only if we got the system weight down by an order of magnitude. Gabor loved the holographic ice crystal data, but was not happy with the logistics. Getting the required equipment up Elk Mountain in the dead of winter was no mean task. It took about 12 hours and three vehicle changes to conquer the changes in terrain. On one of the trips up the mountain, the additional weight had slowed us down so badly that we had to leave the heaviest items halfway down the mountain face until the following day.

We delivered a holocamera to the U.S. Army Cold Regions Research Laboratory in New Hampshire for the study of snow formation. Apparently after a few years use this system was deemed too bulky and difficult to apply and the analysis of data was not straightforward. Uses of holography in meteorology have not flowered as one might have expected.

By the early 1980’s YAG lasers had provided a better overall pulsed holography laser. My first experiences were with International Laser Systems in Orlando Florida. Fred Way of ILS pioneered the YAG laser holography application and our work together began a friendship that has never ceased to be valuable. Some years later he joined Spectron and operated an Albuquerque office for several years before breaking out on his on to form Decade Optics, which has become a successful supplier of rugged YAG lasers. Fred was such an aficionado of holography that he named his cocker spaniel Gabor. Gabor the dog outlived Gabor the Nobel Prize winner.

Having learned how to get contract business, I soon decided to leave SAIC and start my own company, Spectron Development Laboratories with another SAIC friend/employ. One of Spectron's key areas of business became applied holography. At Spectron I was able to attract several great holography associates to work with including James Craig, Bernard Hockley (formerly Rolls Royce and Diffracto), Will Bachalo, and Percy Hildebrand, another of the Leith team. It was during this period that Percy and I helped NASA design the first American space holocamera that actually flew.

Dr. Milton Chang at Newport Corporation, which was located one mile from Spectron, was a huge fan of holography and put millions of dollars into commercializing holography. He was one of the best things ever to happen to holography. Newport Corporation purchased holography company, GC Optronics (founded by George Grant and ? to market holographic tire testers). The plan was to commercialize holographic inspection systems. That turned out to be a very bad investment, with little of value coming out of it, since George Grant immediately formed another holographic tire testing company that soon switched to the simpler shearography methods.

The Newport Corporation played a role as a major benefactor of holography, also purchasing the patent license rights from the bank who was administering them and financing years of research to produce holocameras, including one of the first user-friendly thermoplastic devices that allowed electronic, in-place processing. David Rosenthal and Rudy Garza were key players for Newport in popularizing the applications. Holography ads appeared in many technical magazines and vendor shows during the years from 1975 to 1990, and that was extremely beneficial in keeping the field alive.

At one point, Newport attempted to collect royalties from companies like Spectron who were employing holography. The problem was that they were selling most of the hardware to the people doing the holography and could not afford to anger their customers. I think that Newport did not make money on their patent rights.

As long as holograms were confined to photographic materials, a long time passed between hologram recordings and viewings, often requiring several attempts to get an acceptable one. These involved set up time and film development, and washing and drying before anything useful could be extracted. In a good day, we could collect a few dozen holograms. Getting the data out of them could take months.

With time and technology this improved. Using film and vacuum platens or liquid gates that allowed development in place eliminated some of the time. A major breakthrough seemed to be the emergence of the thermoplastic recording devices that allowed holograms to be produced and examined immediately. Two companies, Rottenkolber in Germany and Newport Corporation in California led the way. Rottenkolber produced a film device and Newport produced a truly user-friendly write and erase device. This would seem to have been the answer to commercialization prayers. Both systems revolutionized holographic interferometry. One could make a hologram and process it in place electronically and view the reconstructed image immediately. This made a lot of non-destructive applications practical that had previously been extremely limited by film processing requirements. Although hundreds of these cameras were sold, they did not become a major, lasting product and both companies discontinued production. Other companies have attempted to fill the void in Newport’s thermoplastic holocamera, but, so far, none has the marketing muscle that Newport had to promote these devices.

Rottenkolber produced a holographic tire tester that sold well throughout Europe and to a lesser extent in the US. It employed 70 mm film and was not rewritable so each new hologram was rolled up on a reel and saved. He had a strong business in the Soviet Block of countries. Rottenkolber had a protégé, Hans Steinbiecler, who broke away and started Steinbiekler Laboratories selling essentially the same technology. Rottenkolber, believing that the Soviet part of the business was key focused on that area, which unfortunately collapsed along with the Soviet Union. Steinbieckler Laboratories is a strong company today, having moved into electronic holography. Rottenkolber is still pursuing tire-testing holography with an electronic holography system.

Spectron marketed pulsed ruby laser holocameras for particle and flow applications, sold about a dozen systems, and made field measurements for many customers. One system of particular interest was sold to China in 1980 just as the country was opening up to the west. By this time Korad had disappeared from the scene and ruby laser companies, Apollo and Holobeam were our suppliers. Ralph Page of Apollo and I personally delivered the holocamera to China and trained the employees of the Nanjing Gas Turbine Institute.

One of our systems was purchased by Rockwell International's Rocketdyne division to view flow fields in high powered chemical lasers. Another was purchased by the University of Michigan to study fuel sprays. Yet another was purchased by Kimberly Clark to study production of tissue paper.

One interesting field application of the Spectron Holocamera placed a holocamera in the fuel cloud of a Fuel Air Explosive (FAE) bomb to determine fuel droplet size. Another was using holography to study the processes in mineral and glass fiber production. We produced holograms of the process in the plant of U.S. Gypsom in Tacoma Washington.

In another unusual application in Guardian Fiber Glass Incorporated we helped settle a patent infringement lawsuit by proving that the process that had been patented did not work the way the patent claimed.

Will Bachalo played a major role in making successful holography applications at the NASA Ames Research Center, including flow visualization in several wind tunnels and in a helicopter facility where we succeeded in doing tomography with a large ruby laser holography system.

Jim Craig and I installed holocameras in a variety of aerodynamic facilities around the country. Perhaps the greatest achievement was in flying a YAG laser holocamera in a KC135 aircraft to produce holographic interferograms of turbulent boundary layers. The U.S. Air Force was developing high-powered laser weapons systems to project from aircraft. One of the serious issues was (and still is) the effect of the turbulent boundary layer on projected beam quality and the ability to focus energy on a distant target. Holographic interferometry allowed us to observe a range of aero optical effects for the first time, and played a major role in identifying and understanding such effects.

Craig and Bachalo left Spectron and formed other companys (Aerometrics Inc. and Stratonics Inc.). Jim continues to apply holography in hypersonic flow diagnostics facilities. Bachalo gave up holography entirely.

I left Spectron in 1985 after it was acquired by the Titan Corporation and formed MetroLaser, another applied laser company where I now work in 2004. During these years I had the privilege to work with excellent holographers, including David Rosenthal (formerly of Newport Corporation), David Weber and James Millerd (who became holographers after joining MetroLaser and Vladimir Markov, who had been the Director of the Institute of Optics in Kiev, Ukraine and his colleague Anatoliy Khizhnyak. Again, holography applications of varied types continue to show up, some made possible by continuing advances in computers, laser, and image processing technology. Some of these are one of kind applications to make a specific measurement.

In 1986 David Weber and I showed that holography had an application in earthquake engineering^, and started a worldwide fad to use holography to assess structures in earthquakes. We produced holographic interferograms with a ruby laser holocamera of large liquid storage tanks showing how to measure earthquake damage. Although we had impressive holographic data on large structures the system did not prove highly versatile since it still relied on film. Today's electronic holography still has a chance in such applications as described below.

In 1986 MetroLaser formed a teaming alliance with Newport Corporation to act as an applications company for referred customers. This worked well until Milton Chang left Newport Corporation and applied holography was abandoned at Newport. MetroLaser bought out the entire experimental holography laboratory and hired David Rosenthal who had been in charge of the laboratory. When Newport ceased the holography advertising campaign that they had maintained for years, holography visibility quickly diminished.

We have investigated many possibilities in holographic storage, holographic security, new materials, electronic holography, particle holography flow visualization holography, and holography in non-linear materials. We also do a large amount of military research that employs holography. Holography continues to have potential in many possible applications, but it also faces stiff competition from the many other options that often win out.

In 1995 MetroLaser built a large mobile ruby laser holocamera for the U.S. Air Force for monitoring shrapnel and debris clouds. The system was used in field tests at Eglin Air Force Base and other Air Force facilities. Again the complexity of maintenance and data reduction have resulted in the systems lack of widespread use.

We flew experiments that used holography successfully in two different spaceflight experiments, and in 1998 I was selected by NASA as a principal investigator for a space flight experiment (SHIVA, Spaceflight Holography Investigation in a Virtual Apparatus) that would feature digital holography in a particle and fluid mechanics study^,. The system was developed and tested to record digital holograms for both particle and flow diagnostics and to downlink data from the International Space Station. The experiment has been delayed for various reasons such as the Columbia space shuttle disaster. This application employs holography in the concept of acting as a remote window into a distant experiment. One can peer into a holographic window in the laboratory and see into the experimental chamber located on the moon.

One of the holography technologies we developed has resulted in a successful spin off product, known as "The PhaseCam" that is now produced by Four D Technologies, in Tucson Arizona. The system combines phase shifting interferometry, holographic optical elements, and electronic holography to make instantaneous wavefront phase maps. It has a very good chance of becoming a widely used product. Electronic holography as a variant of Electronic speckle pattern interferometry offers new possibilities that may eventually push holography back to the forefront in diagnostics. One promising system now under exploration at MetroLaser employs electronic holography to detect buried land mines.

For many years real time holography has been explored as a candidate for producing phase conjugate mirrors for various purposes. Markov and Khizhnyak are currently developing such a system in MetroLaser for space communications. A laser beam can be projected through a turbulent environment and then be corrected by employing such phase conjugate mirrors.

The growth of aerospace holography in Europe continued and still thrives in many universities and organizations. Examples not already mentioned are:

BIAS in Bremen Germany (headed by Prof. Werner Jueptner) where digital holography has been developed and applied extensively.

University of Oldenburg (Headed by Professor Klaus Hench) has developed methods for wind tunnel diagnostics as well as non destructive testing for use in art preservation.

University of Warwick (Headed by Prof. Peter Brianstan-Cross).

University of Stuttgart (Headed by Prof. Wolfgang Osten).

University of Loughborough (Headed by Prof. Niel Haliwell.)

University of Warsaw (Headed by Prof. Malgorzata Kujawinska)

Europeans have managed to continue high level professional meetings and organizations that emphasize holography with conferences like "Fringe" that is held every three years. The international organization of holoknights was founded founded in 1988 to promote holography by Dr. Hans Rotenkolber, a well known holographer who pioneered industrial holography in Germany. Members take a vow to promote the optical sciences in every way and to always offer friendship and help to all HOLO-Ritters in personal and business matters. It is the personal right of the last elected HOLO-Ritter to choose the next one. He vows to carefully select someone who is a leading international holographic scientist deserving of the honor and who is also a widely recognized contributor to international friendship, hospitality, and cooperation. A sword, symbol of membership in the society, is used in the knighting ceremony and is a personal gift of the foregoing HOLO-Ritter to the new member. A scroll, in the language of the awarding holoknight and signed by other holoknights is presented during the ceremony. New members are chosen no more than twice each year in conjunction with an international optics conference, and the selection is kept secret until the moment of the knighting ceremony. The following is the current list of holoknights.

Aerospace holography in the former Soviet Union was not visible to the west before 1990. They had significant efforts underway especially in military applications. From my recent associations with Vladimir Markov, clearly the Soviets had plans for holography in advanced applications like four wave mixing.

Aerospace holography has been developed and applied in Japan in more recent years. One example is the work of Professor Takeyama in shock wave research facilities of the Tohoku University of Sendai, Japan.

Industrial holography has seemed stalled many times with obstacles like difficulty, expense, and tedium of data extraction. Each time a death knell tolls, some breakthrough provides hope that finally holography is ready to take off, and a new enthusiasm springs up with another generation of holographers.

In the early days a hologram of almost anything would help sell a contract to apply holography to something else. Everyone in the business kept a small collection of holograms of the most novel things to show off when marketing a new idea for applying holography. Holography was so novel that almost any engineer or scientist would show up to a talk if he heard that holograms would be shown. You couldn't ask for a better attention-getter.

In some ways it was misleading since the limitations were not always apparent, and the holograms were often irrelevant to the application under discussion. Many charlatans who had never made a hologram themselves marketed with the holograms produced by others. We could show a potential customer a hologram of a few chess pieces and then explain how we would make similar holograms of ice crystals in clouds. This gave the impression that one would be able to look into a hologram and see an ice crystal microscopically in 3-D. There are several reasons why this is not so straightforward that were not obvious. To see microscopic detail required looking through a microscope. If direct light was used, this was not easy. If diffused light was used, then speckle led to a very noisy image. Most scientific studies employed TV cameras to examine the particles so this took away some of the excitement in viewing the holographic image.

One could publish a paper or give a talk simply by applying holography to something new. Papers often had a title like "Application of holography to the Measurement of ..." It was easy to assemble a meeting with a holography focus. NASA sponsored meetings at the Marshal Spaceflight Center in Huntsville, Alabama, and Ames Research Center, in Mountain View, CA. The US Air Force assembled them at Wright Patterson Air Force Base, in Ohio, AEDC, in Tennessee, and Air Force Cambridge Research Labs in Boston.

After many failed promises holography actually took on a stigma of charlatanism during some periods and the word holography in a proposal could mean instant death. This state of affairs has come and gone several times in my career as new breakthroughs offer to breath new life into holography.

The latest "real breakthrough", would seem to be the emergence of digital holography in the late twentieth and early twenty first century. In the first week that I began producing digital holograms on a CCD array, I determined that I had made more holograms than in the entire rest of my career. Only time will tell if digital holography can act as the ultimate "holy grail" for holography.

1.  J.D. Trolinger, “Multiple exposure holography of time varying three dimensional fields” Applied Optics, August, vol 7, no. 8, pp 1640 (1968).

2.  R.B. Lal, M.D. Aggarwal, A.K. Batra, (Al A&M), R.L. Kroes, (NASA/MSFC), W.R. Wilcox, J.D. Trolinger, (SDL), P. Cirino, (BEC), "Growth of Triglycine Sulfate (TGS) Crystals Aboard Spacelab-3," Crystal Technology, 1988.

3.  J.D. Trolinger & B.R. Hildebrand, "Statistical Analysis of a Holographic System Intended for the Space Shuttle",  Applied Optics, Vol. 22, No. 14, p. 2124, 15 July, 1983.

4.  J. D. Trolinger, W. Farmer, and R. Belz, Holographic Techniques for the Study of Three Dimensional Dynamic Particle Fields”, Applied Optics, 8, 967, (1969)

5.  J.D. Trolinger, "Particle Field Holography", Optical Engineering, Vol. 14 No. 5, p. 383, September/October 1975.

6.  J.D. Trolinger and J.E. O'Hare, "Holographic Color Schlieren," Applied Optics, October 1969.

7. J.D. Trolinger & T.H. Gee, "Resolution Factors in Edgeline Holography", Applied Optics, Vol. 10, No. 6, p. 1319, June 1971

8.  J.D. Trolinger, "Flow Visualization Holography," Optical Engineering, Vol. 14, No. 5, p. 470, September/October 1975.

9.  J.D. Trolinger, "Multiple-Cavity Lasers for Holography," Optical Engineering, Vol.23, No.1, January/February 1984.

10.  J.D. Trolinger, H.T. Bentley, A.E. Lennert and R.E. Sowls, "Application of Electro-Optical Techniques in Diesel Engine Research," SAE Journal, 1971.

11.  J.D. Trolinger and J.E. O'Hare, "Holographic Color Schlieren," Applied Optics, October 1969.

12. J.D. Trolinger, "Laser Instrumentation for Flow Field Diagnostics," AGARDograph No. 186, published by North Atlantic Treaty Organization, March 1974.

13.  J.D. Trolinger, "An Airborne Holography System for Cloud Particle Analysis in Weather Studies", ISA Reprint 74-627, presented at International Instrument-Automation Conference & Exhibit, New York City, NY, 28-31 October 1974.J.D. Trolinger,

14.  "Airborne Holography Techniques for Particle Field Analysis", Annals of the New York Academy of Sciences, Vol. 267, pp. 448-459, January 1976.

15.  J.D. Trolinger, "Aero-Optical Characterization of Aircraft Optical Turrets by Holography Interferometry and Shadowgraph," in Aero-Optical Phenomena, Vol. 80, Progress in Astronautics and Aeronautics, edited by K.G. Gilbert and J. Otten, 1982. Also presented at the Symposium on Aero-Optics, NASA Ames Research Center, Moffett Field, California, 14-15 August, 1979.

16.  J.D. Trolinger, D.C. Weber, (ML),  G. Pardoen, G.T. Gunnarsson, (UCI) and W. Fagan, (Lasermet), "Application of Long Range Holography in Earthquake Engineering," SPIE paper number 1162-17, pp. 132-142, SPIE International Conference on Laser Interferometry:  Quantitative Analysis of Interferograms, San Diego, California, 7-9 August 1989

17.  D.M. Rosenthal, J.D. Trolinger, and D.C. Weber, "The use of double pulsed ESPI for earthquake mitigation of large structures." Presented at SPIE's International Symposium on Optical Applied Science and Engineering, San Diego, California, July 1991.

18.  Markov, V.B., Weber, D., and Trolinger, J.D., “Volume Hologram with Random Encoded Reference Beam for Secure Data Encryption”, SPIE Proc., Vol. 3973, pp. 266-275 (2000).

19.  Markov, V.B., Millerd, J., Trolinger, J.D., Norrie, M., Downie ,J., and Timuchin, D., “Multiyear Holographic Optical Memory”, Opt. Lett., Vol. 24, No. 4, pp. 265-267 (1999).

20.  Markov, V.B., Millerd, J., and Trolinger, J.D., “Volume Holographic Memory with a Speckle-encoded Reference Beam”, SPIE Proc., Vol. 3749, pp. 773-774 (1999).

21.  N.J. Brock, J.E. Millerd, J.D. Trolinger “A simple and versatile, real-time interferometer for quantitative flow visualization” AIAA99-0770; 37^th Aerospace Sciences Meeting and Exhibit, Reno, NV, January 1999.

22.  J. D. Trolinger, “New Techniques in Aeroballistic Range Holography” Invited Talk, AIAA 99-0563; 37th Aerospace Sciences Meeting and Exhibit, Reno, NV, January, 1999

23. Lal, A., Rohrbacher, A., Markov, V.B., Millerd, J., and Trolinger, J.D., “Characterization of the Bacteriorhodopsin Gelatin Films Used for Optical Data Storage in Image Processing”, SPIE Proc., Vol. 3793, pp. 103-122 (1999).

24.  J.D. Trolinger, R.B. Lal, D. McIntosh and W.K. Witherow “Holographic Particle Image Velocimetry Aboard the Space Shuttle Discovery”, Applied Optics, Vol. 35, No. 4, pp. 681-689 1996.)

25.  Trolinger, J.T., L’Esperance, D., Rangel, R., Coimbra, C., Witherow, W. “Design and preparation of a particle dynamics space flight experiment, SHIVA”, ECI: MTP-03-86: Proceedings of the Microgravity Transport Processes in Fluid, Thermal, Biological and Materials Sciences III, S. Sadhal, ed. Davos, (To be published in Annals of The New York Academy of Sciences ) Switzerland (September 14-19, 2003.)

26.  Trolinger, J., L’Esperance, D., Rangel, R., Coimbra, C., Witherow, W., Bodiford, M., and Patterson, W.; “Ground Based and Mock Up Experiments to Support the ISS Flight Definition Program SHIVA”; Proceedings of the 2003 IEEE Aerospace Conference, Big Sky MT (8-16 March 2003).

27. Trolinger, J.T., L’Esperance, D., Rangel, R., Coimbra, C., Witherow, W. “Design and preparation of a particle dynamics space flight experiment, SHIVA”, ECI: MTP-03-86: Proceedings of the Microgravity Transport Processes in Fluid, Thermal, Biological and Materials Sciences III, S. Sadhal, ed. Davos, (To be published in Annals of The New York Academy of Sciences ) Switzerland (September 14-19, 2003.)

28.  Trolinger, J.D., “High Speed Digital Wavefront Sensing for Aero-Optics and Flow Diagnostics”, ICIASF 2003 Record; 20^th International Congress on Instrumentation in Aerospace Simulation Facilities; Goettingen Germany, IEEE no. 0-7803-8149-1/03; Aug. 25-29, 2003.