KARL A. STETSON
Our usual Business Forum interviews by Milton Chang will resume in July.
The last quarter of 2014 marks the 50th anniversary of a set of experiments Robert Powell and I performed at the University of Michigan’s Institute of Science and Technology that defined the ability to record incoherent optical fields and reconstruct them coherently, forming the basis for double-exposure and time-average holographic interferometry. The following April, we used a hologram as a beamsplitter between the reference and object fields to allow real-time interferometry on diffusely reflecting objects. I have worked in this area for the entire 50 years and find myself thinking back over all that happened in this half-century.
One area in particular is patents—holographic interferometry was my first patent. Two applications were filed. The first was titled “Wavefront reconstruction” serial no. 503,993 filed on October 23, 1965, with six names: Emmett N. Leith, Juris Upatnieks, Bernard P. Hildebrand, Kenneth A. Haines, Karl A. Stetson, and Robert L. Powell. The second one was titled “Method and apparatus for analyzing structures using wavefront reconstruction,” serial no. 514,482 filed on December 17, 1965, with four names: Bernard P. Hildebrand, Kenneth A. Haines, Karl A. Stetson, and Robert L. Powell.
Sometime during 1970, when I was at the National Physical Laboratory (NPL) in Teddington, UK, an English solicitor contacted me about the University of Michigan patent applications. Three applications were to be filed in place of the originals. In particular, the invention of holographic vibration analysis was being filed by Leith and Upatnieks, based on their disclosure in April of 1964. I believe that Powell and I were to be credited with real-time interferometry between an object and its hologram reconstruction, and Haines and Hildebrand with holographic contouring by varying laser wavelengths. Leith, Upatnieks, Haines, and Hildebrand had all signed the necessary documents, but Powell was objecting.
To credit holographic vibration analysis to Leith and Upatnieks, they provided me with a copy of their initial disclosure. This document contained no reference to interference within the reconstruction of a hologram, nor it did not mention fringes within the hologram reconstruction–in particular the zero-order Bessel function fringes that Powell and I first identified. Their disclosure described a hologram reconstruction analogous to a Chladni pattern where small particles on a vibrating surface migrate away from vibration antinodes and collect at vibration nodes. It would be bright at the nodes and dark in the antinodes.
Before I would sign their documents, I required removal from their claims of all reference to fringes and all mention of how to measure vibration amplitude of a vibrating object via its holographic reconstruction. Although it was issued (patent No. 3548643), this removal effectively neutered it. Fringes are mentioned once in the discussion section, and there are drawings sketching the results that Powell and I obtained, but none of this is claimed.
In retrospect, I should have insisted on expunging all mention of fringes and any of our work from the entire document, but since the legal teeth of a patent are its claims, I let it go. Powell accepted the modifications obtained and also signed the documents. So far as I know, the application for Powell and me was never awarded a patent, nor do I know it was ever filed. A patent for holographic contouring was awarded to Haines and Hildebrand (No. 3,552,858). Whether our patent was abandoned because of the restrictions we placed on the Leith and Upatnieks patent, there is no way to know.
Assertions have been published that Emmett Leith and Juris Upatnieks were the first to discover holographic interferometry.1,2 Unquestionably, they first observed phenomena that, in retrospect, were explained as holographic interferometry; however, had there been any way the Leith–Upatnieks disclosure or anything in their notebooks could have been used to argue that they understood the concepts of holographic interferometry, I could never have imposed the restrictions I did on their patent.
For this reason, I feel justified in saying that Robert Powell and I were the first to discover holographic interferometry. Juris Upatnieks recently confirmed this for me in an email communication regarding their observations: “We observed the effect and noted it, but did not get into any detail. Our main interest was image quality [of holograms].”
Beside our work, the year 1965 saw a number of independent discoveries of holographic interferometry.3-6
Twenty-five or 30 years ago, when I was working at United Technologies Research Center, I received a telephone call from a woman at a West Coast company that had acquired all the patents from the University of Michigan relating to holographic interferometry as well as a number of others including those from NPL. She asked what they could do with them.
I remember that I laughed, which upset her, and I explained my reaction in terms of the experience related above. The United States Patent Office website shows 17 patents with the term “holographic interferometry” in their titles, and over 3000 more with “hologram” or “holographic.” How many of all these patents have yielded any economic value to their assignees?
In the case of holographic interferometry, a number of patents assigned to GCO (Grant Crafton Optronics) did establish a viable business in holographic tire testing, and those patents probably deterred potential competitors to some extent. With regard to holographic vibration analysis, numerous companies and laboratories have used it. Pratt & Whitney and Westinghouse, for example, have used it since the early 1970s to identify vibration modes of turbine blades, but I don’t believe they or any other companies ever paid a royalty.
In the March 10, 2014 issue of the Wall Street Journal, I read an article on the Patent Trial and Appeal Board, which was launched in September 2012 and was described as “a little known but powerful authority that often allows a company embroiled in a law suit to skip the question of whether it infringed a patent and challenge whether the patent should have been issued in the first place.”
This is an interesting development that may influence the corporate policy of “file first and ask questions later” regarding patents. Many issued patents are vague, ill-conceived, and describe a device that would be impossible for anyone skilled in the art to create. Many others patent something for which there is no real practical application. It will be interesting to see what the future holds.
References
1. K. A. Haines, “Emmett Leith: Misconceptions and Realities,” J. Holog, Speckle, 3, 35–41 (2006).
2. Sean F. Johnston, Holographic Visions (Oxford U. Press, 2006), pp. 191–200.
3. M. H. Horman, “An application of wavefront reconstruction to interferometry,” Appl. Opt., 4, 333–336 (1965).
4. R. J. Collier, E. T. Doherty, and K. S. Pennington, “Application of moiré techniques to holography,” Appl. Phys. Lett., 7, 223–225 (1965).
5. R. E. Brooks, L. O. Heflinger, and R. F. Wuerker, “Interferometry with a holographically reconstructed comparison beam,” Appl. Phys. Lett., 7, 248–249 (1965).
6. J. M. Burch, “The application of lasers in production engineering,” (The 1965 Vicount Nuffield Memorial Paper), Prod. Eng., 44, 431–442 (1965).
KARL A. STETSON discovered the phenomenon of holographic interferometry together with Robert L. Powell. He spent two years at the UK’s National Physical Laboratory, and eventually two decades at the United Technologies Research Center in East Hartford, CT. Since 1994, he has operated Karl Stetson Associates (Coventry, CT), manufacturing and selling equipment for digital electronic holography. He received his bachelor’s degree from the University of Massachusetts at Lowell, his master’s degree from the University of Michigan, and doctoral degree from the Royal Institute of Technology in Stockholm. You can contact him at [email protected]; www.holofringe.com.