|NDT.net - April 2002, Vol. 7 No.04|
Toys and tools are separated by a very large distance nowadays. Long ago, e.g. in Renaissance, or even earlier, in classic Greece and Rome, or still earlier in Egypt or Mesopotamia toys and tools were generally united in one object. Today they seem to go separate paths: tools for grown-up people, toys for children. Holography is an exception: you have the possibility to make a job out of a hobby, and a hobby out of your job.
Holography, toys, aesthetics, applied science, tools.
When I was first confronted with the title Dr. Osten allocated me, I had to take a serious look in the Oxford Advanced Learners Dictionary in order to try to understand what he asked me. Results are shown here:
Toy (toi) n 1 thing to play with, esp for a child. 2 (usu derog) thing intended for amusement
rather than for serious use: His latest toy is a personal computer, or executive toys. toy adj.
[attrib] 1 made in imitation of the specified thing and used for playing with: a toy car, gun,
telephone o toy (ie model) soldiers. 2 (of a dog) of a small breed or variety kept as a pet: a toy
toy v (phr v) toy with sth 1 consider idly or without serious intent: Ive been toying with the idea of moving abroad. 2 handle or move sth carelessly or absent-mindedly: toying with a pencil o She was just toying with her food, as if she wasnt really hungry.
Tool /tu:l/ n 1 instrument held in the hand and used for working on sth: A screwdriver and a hammer are they only tools you need. o garden tools, eg spade, rake, etc. 2 anything used to do or archive sth: The computer is now an indispensable tool in many businesses. ŢUsage at MACHINE. 3 person used or exploited by another, esp for selfish or dishonest purposes: The prime minister was a mere tool in the hands of the countrys president. 4 (D sl) penis. 5 (idm) down tools Ţ DOWN3.
tool v 1 [Tn esp passive] make a design on (the cover or binding of a book) by pressing with a heated tool(s): hand-tooled leather o The spine is tooled in gold. 2 (phr v) tool along (infml) drive in a casual and relaxed way. Tool sth up equip (a factory) with the necessary machine tools.
Rogets Thesaurus gives some examples of how tools is used but ignores completely
toys. So : again no help.
Finally, looking on the Web Word Net 1.6 Vocabulary Helps has even more problematic outcomes: 7 pages for tool, 8 pages for toy, but also nothing really practical.
Having done my literature excursion, I had to conclude that I would never be capable of doing my task properly, so I turned over to a classical engineering option: the KISS approach, an acronym for "for keep it small and simple". I thus will only speak about some occasionally occurring interactions in various practical situations. As it is almost compulsary nowadays to adopt a holistic or at least a mindmapping (eventually virtual) approach, I am sure I am allowed to make a number of loosely related or even unrelated remarks in the framework of this paper, leaving to the recipient the task of choosing a linear order between them.
The author started working in holography, in the early sixties, 1965 if remembered well. The advantage of the situation was that one was able to become a "specialist" after having read three articles, the only that existed at that time about holography. If in addition to that one had the luck of seeing and using one of the first European lasers, and applying it to a practical problem (also three papers at that time), one became a "world specialist". But specialists are serious people, and serious people dont play, or only during weekends. While children are forbidden to play with tools, as they could hurt themselves. In holography, you will have to do both, in order to get satisfaction and results.
Although probably the most productive manufacturer of silver halide holographic materials was Belgium for more than 30 years, it was quite difficult to persuade Belgian people that holography existed at all. The author, who was making relatively good holograms since 1967, has an engineering background and mainly applied holography to technical problems. He felt increasingly disappointed with the years passing, and after a decade finally about the fact that very few people knew about what holography can do, and even ignored holography completely. As a scientist he had also to be logical, and the logic was to do something against it. So exhibitions were organised and lectures were given, as it was thought that bringing holography out of the lab sphere would suffice to give the great impetus everybody was waiting for. A couple of years and a number of exhibitions later, one had to admit that, although some improvement could be noted, still a large portion of the population was unaware of the existence of holography, not to speak about its applications.
For that purpose, some more spectacular things were organised, as the Herbarium Holographicum project (Fig. 1), the recording of portraits during a Technology Fair, and some large size holographic entertainment interactive projects. In this way, we also came in contact with a number of interesting and interested people: artistic, photographers, but also museum conservators and technical laymen loving the 3D reconstrutions without spectacles. (Fig. 2, 3) there again, half of the satisfaction is due to the fun one has doing the production.
Normally, nobody stands (-or better, sits-) still in a movie theatre about the fact that, in the
movie they are watching, it are merely human parodies of real situations that are presented,
fixed in a completely technical-scientific manner and reproduced through image and sound
carriers, through sophisticated technology with emulsions, apparatus and the like to produce
natural impressions in "industrial" proportions.
Still bigger is the influence of electricians on music rendition, and synthesiser musicians are sometimes called the harp players of the future. In music, there is collaboration between people knowing how a musical score is conceived, with others knowing the "secrets" of producing suitable sound.
In those two specialities, there is little left for amusement: it is really work, and the technical part is only a tool to achieve goals, and no fun (toy) on itself.
Such interactions do not occur often in holography, where people seemingly prefer to work
alone. In holography we can consider interaction between "pure" (i.e. almost contemplative,
or theoretical, or fundamental) science, with production on three (artistic) levels. As stated in
the same Random House unabriged dictionary, Art can be considered as:
Three concepts have been mentioned: aesthetics, physical phenomena, art. When something is appealing, it may develop an aesthetic impression on men. The potential of understanding the concept of beauty can be elaborated upon by assuming that the aesthetic impressions are produced whenever the particular thing exhibits some peculiar effects. Holography became practical in the mid-sixties; and from the very beginning, a number of people tried to use it in the artistic context. Evolution has been continuous: in the early stages, the mere fact of being holographic was synonymous to artistic; in a second stage, reactionary people claimed a hologram could only be named artistic if it was made by an artist with a diploma, giving rise to the other extremum that any hologram made by the certified artist was a piece of art. For the time being, things have cooled down a little; first came demystification, afterwards a number of people tried debanalisation. Holography is now more used as just another technique, just as oil paint in the 14th century where tempera was king. Here too, a number of experimental circumstances can lead to results that can be called pleasant and appealing, but again, it is both the action of the "generator" coupled to the awareness and the training of the public that will lead to a general appreciation. Here again, both technique (tool) and joy on reaction and result (toy) are complementary.
Around 1980, rainbow holograms became familiar to the general public by their appearance a credit cards and magazines. As proud as holographers were to see these images gain worldwide recognition, it needs to be said that their image quality falls somewhat short of our hopes. Because the stickers reflect a great deal of background light into the image, making it sometimes difficult to see, the subject matter must be easily identifiable. The practical necessity that the hologram be visible in any light severely restricts the depth that can be used. Thus the design of images for these holograms has its own special set of aesthetics and the creation of these holograms presents its own technical challenges. We therefore decided that it would be more logical to work with reflection holograms (as they are simpler to reconstruct properly) and not in the second-generation mode but in the direct one-step Denisyuk mode, for reasons that will be explained later.
The projects mentioned above stem primarily from the fact that almost nobody even the
most enthusiastic hologram fan has a hologram hung in its living room. Hologram
exhibitions attract thousands of visitors, holography is a good conversation item, one finds
rainbow stickers on magazines every month, but almost inevitably even a good reflection
hologram ends its life in a drawer because nobody likes to see the black square hole on ones
wall when the hologram is not illuminated by the suitable halogen source. We therefore
looked for a solution for this problem in terms of trying to find relatively simple objects, that
would allow for reconstruction by ambient light; objects should be recognizable by
everybody, but preferably also pleasant to the eye, occasionally even beautiful, and we began
Why plants? People recognize them directly, a lot find them beautiful; they have been used as ornament since the very early times of civilisation (see the Lascaux caves, the Egyptian tombs, the Greek and Roman pillar ornaments, the precolumbian Middle-American civilisations ..). Both real plants and "copies" were used through the times, and special emphasis should be laid on the trials to use the real object as a "matrix" to make the copies: see the experiments with nature-printing in the sixteenth and seventeenth centuries; a more general survey of different methods used are given in (6).
Of course, a number of artists try to continue their views on art with holography as a medium.
On the other hand, some holographers think they are chosen by God or other Supreme
Creatures to make the final piece. In my opinion, a hologram is not necessarily an art piece if:
But it resembles classical photography where:
Summarizing, I think we can accept that holography is merely some kind of alchemy people who are doing it seriously mainly develop themselves, trying to improve knowledge and by that way are helping others. Making gold out of nothing didnt seem to work in the Middle Ages; here too, very little people seem to become holo-millionnaires, well on the contrary. The enrichment comes from the exchanges of information, from the cross-fertilisation, from the shock of ideas that generates the light. And probably this is art too but once again as a result of some kind of serendipity, mixing toy and tool, giving a result larger than the sum of components
The third aspect of interaction of knowledge and amusement by holography has in fact been treated in an undercover way. To make a hologram and a good one, we have to learn techniques, underlying fundamentals, theory, but also the limitations of what is available in practice. Holography itself can be considered as an art and most of us are living examples that it can take more than a quarter of a century for fully mastering even the principles.
To end this quasi-philosophical discussion, I can say that although doing all this is a lot of
fun, not at least by the people one learns to know, it is thought that I will return to my old love
of purely mechanical applications of holography once a generation is persuaded that
holography not only exists but also can be practical importance. But before this goal is
achieved, a lot of work remains to be done. Even if the goal is achieved once, it is hoped that
the fruitful discussions and the cross-fertilisation of different approaches between the
different users of this type of image presentation will continue: it certainly was, probably is
and hopefully will be one of the lasting bridges between science and arts, work and play, I
believe that this will be true even when holography will have turned, like electricity,
telephone, audio, television, from technical curiosity to irreplaceable part of daily life.
And it must be noted that the technique is so appealing that a number of my colleague holographers even continue to make experiments at home during weekends in order to improve their skills and their results (Fig. 4)
The work reported here was supported by the Belgian National Foundation for Scientific Research through grants 2900878, 2001275 and 2004486, and the author also gratefully acknowledges the personal grant placed at this disposal by the same institute. The technical skills and the fruitfully discussions with Dr. Ludo Joly, Maurice De Caluwé, Octave Landuyt, Paul Jacobs and Frank Mortier were of invaluable help.
The in-line reflection recording scheme named after Deniyuk, is by far the most simple of the
holographic schemes and it can be used as well for metrological and interferometrical
purposes (piggyback setup [8,9,10]), as for single shot display applications. Apart from its
simplicity, this setup, where laser, sensitive materials and object are almost in-line, is also
very economical with light: the available energy is effectively used twice; the viewing angle
at reconstruction is very large, approaching 180° when the object is close to the hologram
plane; the distortions introduced are minimal: they are due to slope variations in the recording
materials (small if relative humidity is between 40 and 60 %), and to colour discrepancies
between reconstruction and recording wavelength. Normally, records are made with ruby
laser (l = 694,3 nm) or Helium-Neon (l = 632,8), and now also stabilised diodes while
reconstruction is wavelength shifted by processing between 580 and 550 nm, optimum for the
human eye sensitivity.
The main drawbacks of the Denisyuk scheme are the extreme requirements that must be met by the sensitive material and by its processing, and the fact that the ratio of object to reference beam intensity can only be altered by treating the object surface (e.g. painting).
The lack of constraints in the building stage allows one to excert all ones creativity, without having to think about lenses and mirrors ; at the other hand, from the artistic viewpoint , one can state that each recording is an original one : no copies are made, each of the records is unique and can be signed as orig..
Phenomena involved in the processing of silver halide holograms are still not fully
understood. Most holographers apply photographic-type processing, almost everyone having
his own pet-developer, as result of experience bUT also of temperature and relative
humidity in his specific darkroom. True holographic developers, based on a well-considered
hypothesis of holographic image formation, are not published. Probably, some scientists have
a lot of knowledge about his subject, but little is given free.
Quality of holograms is generally described in terms of diffraction efficiency, signal-to-noise (S/N)ratio, and resolution. However, it is felt that subjective factor also play an important role in the judgment of the result : color accepted by the viewer, acceptability of small defects, optimal amount of light, contrast rendition, etc. At the moment, there is no measuring standard ; our experience is that people like wavelengths between 580 nm (yellowish orange) to 530 nm (not so yellowish green), the peak of the Gaussian lying aroung 560 nm. In the first contact, the amount of light is very important, while, when people get used to holograms, more attention is paid to contrast and resolution, and a heavily reflecting background or flare (noise) are percieved as defects. At the time being, we use the metol ascorbic acid superadditive developer, using baths of very simple formulations and a Kodak R9 type of bleach. It has the advantage that acceptable quality is produced consistently ; other development schemes, involving very rapid developers (extremely basic) and/or rehalogenating bleaches can give better results in terms of diffraction efficiency, but are normally accompanied by a higher flare or noise, and are also more prone to variations in result due to intrabatch differences in the emulsions and/or the age of the material. Since AGFA stopped production of holographic emulsions, it is quite difficult to find consistent quality in the open market.
This Paper was presented at Fringe 2001 "The 4th International Workshop on Automatic Processing of Fringe Patterns" held in Bremen, Germany, 17-19 September 2001. Proceedings edited by Wolfgang Osten, BIAS, Germany. Please contact Wolfgang Osten for full set of proceedings at email@example.com.
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