H l S T O R I C A L P A R A L L A X

Bjelkhagen Hans

Holographic Portraits Made by Pulse Lasers

A B S T R A C T

The author presents the history of holographic portraits made with pulse lasers and briefly discusses the work of some of the scientists and artists working in this field. He then describes the recording technique that is used for making pulse portraits at Holicon Corporation (Evanston, Illinois) and the transfer setup that is used for making reflection copies of pulse masters at Holovision AB (Stockholm, Sweden). An extensive list of references relating to the art and technique of making holographic portraits is also provided.

A holographic portrait by definition is a recording of a human face whereby the final product is a hologram of some sort. Often holographic portraits are referred to as pulse portraits, which means that the original recording (the master plate, or Hl) of the subject is made holographically. For another type of holographic portrait, the actual recording of the subject is made using conventional photographic techniques, and then holograms are made from these recordings, e.g. Multiplex holograms or stereograms, which are often rainbow holograms (white light transmission holograms). These types of holograms have also been successfully made into embossed holograms, which sometimes even show a natural color image at a certain viewing position. In this paper, however, I use the term 'holographic portrait' to refer only to those portraits that are completely holographic, i.e. where both the master plate and the white-light viewable copy are made using lasers. Laser-recorded holographic portraits have been made since 31 October 1967, when Lawrence D. Siebert (Conductron Corporation) made the first hologram of a human subject—himself (Fig. 1 ) [ 1 ] . This laser transmission hologram was recorded with a ruby laser. Another historic holographic portrait of the laser transmission type is the hologram of l:Dennis Gabor (Fig. 2) made in 1971 by R. Rhinehaart (McDonnell Douglas Electronics Co.). The portrait was made to celebrate Gabor's Nobel Prize in physics, which he was awarded that year for the invention of holography. The technique for making a transmission master for a holographic portrait is very much the same today as it was in the beginning. The main difference between now and then is that nowadays the image is normally copied to another holographic plate to make an imageplane hologram—normally, a reflection hologram that is white light viewable. Occasionally, the image is copied as a rainbow-transmission hologram. The copies are usually made without changing the image magnification; however, reduced-size hologram copies can be made from a pulse master. In the early days, the laser-transmission hologram (the master) was exhibited using lasers or mercury lamps. Another difference is that nowadays reliable, high-quality pulse lasers are being produced, which facilitates the recording process. The most commonly used pulse laser today is the ruby laser; however, an advantage of the frequncy-doubled neodymium-YAG (Nd:YAG) laser's 530-nm wavelength is that light of this wavelength does not penetrate the human epidermis as much as the ruby laser's 69nm light does. Unfortunately, the quality of commercial Nd:YAG lasers is not comparable to that of ruby lasers. As holographic portraits are expensive, the market for them is rather limited; thus only a few commercial companies and holographic studios around the world are producing them. Since the recording of the first holographic portrait more than 20 years ago, a number of papers on the art and the technique of making holographic portraits have been published [Y-36]. The technique for pulse portrait master recording does not differ much from holographer to holographer. During the years since the first portraits were made, quite a few scientists have continued to work in this field. In particular, I note the work of John Webster, who has been responsible for setting up many pulse recording facilities around the world. He has also been working together with artists to create interesting pulse portraits [37,38] . Other scientists who have been or are currently engaged in holographic portraiture include P. Smigielski [39], P. Fiala [40], R. Rallison [41],V. Bryskin [42] and P. Boone [43-45]. Boone has introduced a Denisyuk recording setup for holographic portraits that uses a diffuser with a small scatter angle between the subject and the holographic plate. According to Boone's papers, this onestep technique makes it possible to produce safe pulse portraits very quickly. Other scientists such as D. Fargion, N. Phillips, R. Lessing, M. Marhic, H. Steinbichler, J. C. Vienot and R. Wuerker have also made important contributions to the field of pulse portraiture. The first person to attempt to use pulse portraiture for art purposes was Bruce Nauman in 1968: Making Faces (Fig. 3), a laser transmission portrait, was recorded in the laboratory of Conductron Corporation, Ann Arbor, Michigan.

During the late l 1970s, Peter and Ana Maria Nicholson worked in Hawaii, where they recorded many transmission pulse portraits One of these, .Sourld of the Sea (Fig. 4) is a portrait made for the Children of Hawaii exhibition held at the Honolulu Academy of Art in 1979. A year earlier, many of Peter Nicholson's pulse portraits had been included in the Alice in the I.Light World exhibition held at the Clover Hall of the Isetan department store, Tokyo, during August 1978. At first, Peter Nicholson used the McDonnell Douglas laser that had been used for the recording of the Gabor portrait. The laser was donated to the Smithsonian Institute after McDonnell Douglas ceased its holography operation in 1975, but Peter Nicholson was able to use it for some time after that. This laser, originally built by Siebert, was one of the few good pulse ruby lasers at that time. Peter Nicholson was actually the first artist to explore pulse portraiture seriously. His interest began while he was at the Brookhaven National Laboratories, Brookhaven, New York, where he worked with Bill Molteni and Bruce Goldberg [46]. Later, when he felt his recording technique was working well, he moved his laser and optics operation to Hawaii, where he worked for a few years [47]. Because of the difficulties involved in exhibiting laser transmission holograms, which was one of the reasons his enterprise did not become the commercial success he was dreaming about, Nicholson suspended his holographic activities to concentrate on sculpture.

Ana Maria Nicholson has continued to work with pulse portraiture in the New York area, producing portraits that are transferred to reflection copies, which offer more convenient replay conditions than do transmission holograms [48,49]. For her new operation, she bought one of the first high-quality JK lasers jointly developed by Nick Phillips and the then-British laser manufacturer. K. Lasers (now Lumonics, Inc., Canada). Many of her reflection holograms are very good examples of holographic portraits. Not only is her image a recording of the person's face but she is actually able to bring something about the subject's personality into the picture as well. An example of her recent work is the portrait f Diane Dixon (Fig. 5), the World Champion runner and Olympic star. In the early 1980s, I recorded a number of holographic portraits in Sweden with the artist Carl Fredrik Reuterswärd. One of the more interesting portraits to which I lent technical assistance is Cross Reference (Fig. 6), for which Reuterswärd took on the identity of Salvador Dali. His mustaches were shaped to form the letters C and R, which are the initials both of the work and of his first and last names. Other portraits that I recorded in Sweden during his period include one of the- movie star Gösta Ekman (Fig. 7) and one of Ki Siegbahn, winner of the l9XI Nobel Prize in physics [.0,51]. Edwina Orr and David Trayner in England have produced many holographic portraits over the years, a famous one being their portrait of Boy George (Fig. 8). Recently, they have produced holographic black-and-white portraits [52-54], of which Kle McGouar with .Stephen Jones Hat is an outstanding example (Fig. 9). Margaret Benyon, also from England, has produced special types of portraits: by placing a gouache painting underneath the holographic plate, she creates unique and beautiful art pieces (see Color Plate A No. 3) [55]. Ana;t Stephens, who is from the United States, is one of the few artists to have a pulse laser in her own studio. She has been active in the field of pulse holography since the early 1970s, making several different types of pulse holograms, including some holographic portraits. Other interesting pulse portraits that I feel are worthy of mention have been made by Nicole Aebischer, Gerard Al lon, Patrick Boyd, Melissa Crenshaw, Rebecca Deem, Sydney Dinsmore, Robert Munday, George Niedzialkowski, Martin Richardson, Per Skande, Michael Snow, Michael Sowdon, Fred Unterseher and Ed Wesly. Currently, several artists are working at the Royal College of Art in I.London, where they are producing holographic portraits of high technical and high artistic quality. Recently, a pulse studio has been established at Fringe Research Holographics in Toronto, Canada, from which interesting work can be expected.

In the following sections, I describe the recording and copying setups that I have designed. I use the master recording studio at Holicon Corporation in Evanston, Illinois, U.S.A., and the copying facility at Holovision AB in Stockholm, Sweden, as examples of holographic pulse portrait operations.

MASTER RECORDING SETUP

The recording of a transmission master hologram at Holicon is arranged according to the setup shown in Figs 10 and 11. The laser used is a ruby laser from I.umonics ( 1 joule JK laser, model Y000), operating at = 694 nm. The laser is equipped with an oscillator, an internal spatial filter, one amplifier and a Q-switch. A 10-mW helium-neon (HeNe) laser is attached to the pulse laser for alignment purposes. The ruby laser head and part of the optics are mounted on a table in a separate room, where the water-cooled power supply is also located. The output beam from the ruby laser is spread by a negative lens, in front of which is positioned a beam-splitting prism. About 10% of the beam is reflected from one surface of the prism and used as the reference beam. Two first-surface plane mirrors are used to direct the reference beam to the holographic plate in the room next to the laser room. The other 90% of the laser beam, which passes through the prism, is used as the object light. This divergent object beam hits a 20-x-20-cm ground glass (scatter plate) positioned in a hole in the wall between the laser room and the studio. The diameter of the beam on the ground glass is about 15 cm. Even if the person whose portrait is being made (the 'subject') is looking directly at the diffusing screen, or the ground glass, when the laser is fired, it is completely safe [56]. In the studio, part of the scattered light from the ground glass is directed by mirrors to illuminate the subject from different directions, while another part directly illuminates the subject's face. The subject is then illuminated from two to three additional directions. The reference beam, passing through another hole in the wall, is directed by an overhead mirror and hits the plate at an angle of about 45° from above the subject's head.It is important that the reflected part of the light from the holographic plate not be allowed to hit the subject's eyes. It must hit far below the subject's face. Part of the reference beam also illuminates the subject's hair from behind. The distance between the subject and the holographic plate is about 35 cm. A black curtain normally serves as the background, but the curtain can be removed and the white-painted wall used instead. The holographic plate is not exposed in complete darkness—a suitable green safelight is provided in the studio. In addition, a spotlight with a green filter is directed toward the subject's eyes to reduce the size of the pupils so that they are not wide open when exposed. (The safelight is green because red-light-sensitive plates are not very green-light sensitive . If a greenlight laser were used [e.g. Nd:YAG] a red safelight is suitable.) By eliminating the 'fixed look', a more natural portrait is obtained. To make the portraits more lifelike and to avoid a waxlike or 'death mask' effect, it is important to use some makeup, e.g. cosmetic face powder and green lipstick. The plates used for the transmission master are Agfa-Gevaert Holotest 8E75 HD, 30 x 40 cm. They are developed in a special pulse developer, which is suitable for the extremely short exposure time used, and then fixed and bleached in the ferric nitrate bleach first described by Phillips and Porter [57]. This processing technique produces high quality masters while requiring only a minimum of exposure energy.

REFLECTION COPYING SETUP

The setup for making copies from the master hologram is shown in Fig. 12. The whole arrangement is placed directly on the concrete floor in the transfer laboratory at Holovision AB in .Sweden. The laser pulsed is a 5-W krypton laser (Spectra Physics, model 171) equipped with a temperature-regulated etalon and a polarization-plane rotating device. The latter is used to obtain a horizontal plane of polarization in order to reduce internal reflections in the plates when the plate is oriented in such a way that the laser light hits the plate at the Brewster angle. The wavelength used is 647 nm and an output power of about 1 W, single-mode operation, can be obtained. The beam from the laser is divided into two beams by means of a variable beamsplitter. One beam is pulsed to illuminate the master plate in such a way that the beam travels in the opposite direction from the one traveled by the reference beam used for the recording. An off-axis parabolic mirror is used to create the time-reversed reference beam f or the master (H ) . A pseudoscopic, real image of the face is then obtained. The other beam from the laser, directed by another off-axis parabolic mirror, is arranged in a similar way to act as a reference beam for the transfer plate (H2), which is positioned about 35 cm in front of and parallel to the Hl plate. The H2 plate is normally adjusted to a position where the eyes are sharply focused, i.e. the level of the eyes in the pseudoscopic image. It is necessary to adjust the variable beamsplitter so that a suitable ratio between the reference beam (illuminating the copy) and the object beam (illuminating the master) is obtained. The ratio has to be varied due to different diffraction efficiencies of various masters. Depending on the quality of the master, exposure times of between 5 and 30 secs are typical. The holographic material used or the copies, which measure 30 x 40 cm, is the same as the master material (Agfa-Gevaert, Holotest 8E75 HD) . The processing of the plates is made using a pyrogallol-based developer (Holodev 60Y) and a reversal bleach (Pyrochrome bleach) [58]. The shrinkage introduced in the reversal bleaching process gives a s subtle hue for the monochrome holographic portrait copy when reconstructed in white light. The emulsion side of the glass plate are painted black, using a silk-screen technique, and then sealed with another glass plate in order to prevent color changes due to humidity variations. The white light used to illuminate the final reflection hologram travels in the opposite direction from that traveled by the krypton reference beam during the recording of the copy plate, which means that an orthoscopic image with little distortion is obtained. An example of a portrait I made at the Holicon studio is Iron Mike (Fig. 13), a hologram of Mike Ditka, coach of the Chicago Bears. Several portraits o holographers have been recorded at Holicon, for example, Emmett Leith, Yuri Denisyuk (Fig. 14) and T. H.Jeong. In addition, the father of high-speed photography, Harold Edgerton, has been captured by a 10-ns pulse (Fig. 15). A final example of a Holicon portrait is the hologram made in 1987 of Donna F.dmundson, a Playboy bunny (Fig. 16) . The hologram is titled Bella Donna (Beautiti:ll Donna), a play on words that alludes to the well-known drug as well as to the plant known as the deadly nightshade (Atropa belladonna). The plant contains several important medical alkaloids, the chief one being atropine, which is used to dilate the pupils of the eyes during eye exams. As I mentioned earlier, green light is used during the recording of a hologram to reduce the size of the subject's pupil the reverse of the dilation effect of the drug belladonna. Using this reverse effect, I produced the holographic bella Donna.

Acknowledgments

Jonny Custafssoll, president of Holovision AB, Stockholm, Sweden, is responsible for the transfer set-up and the copies of master holograms made by Holicon Corporation. The early development of portrait holography in Sweden was carried out by the author in cooperation with Per Skande, who also made some of the early reflection copies of' recorded at Holicon Corporation arc made by the author in cooperation with Michel Marhic.