Commercial display holography is approaching a critical stage where the ability to compete with other graphic media will dictate its future. Factors involved will be cost, technical quality and, in particular, design. The tenuous commercial success of display holography has relied heavily on its appeal to an audience with little or no previous experience in the medium. Well designed images were scarce, leading many commercial designers to avoid holography. As the public became more accustomed to holograms, the excitement dissipated, leaving a need for strong visual design if the medium is to survive in this marketplace. Drawing on the vast experience of TV, rock music and magazine advertising, competitive techniques such as video walls, mural duratrans, laser light shows and interactive videos attract a professional support structure far greater than does holography. This paper will address design principles developed at Holographics North for large format commercial holography. Examples will be drawn from a number of foreign and domestic corporate trade exhibitions. Recommendations will also be made on how to develop greater awareness of a holographic design.
An optical system is described which is capable of recording multicolour white-light-viewable holograms in a single recording stage. The hologram can be of the transmission or the reflection type, exhibits no chromatic aberrations and very low geometric distortions and third-order aberrations. Factors affecting the choice of optimum recording wavelengths are discussed, and a possible method of generating suitable wavelengths is suggested.
The methods for obtaining the sharp image are briefly surveyed for Lippmann hologram and the characteristics of the point image obtained by the method of wavelength dispersion compensation are analyzed using imaging equations and coupled wave theory. The two Lippmann holograms are used in this method, one is the hologram grating and the other is the ordinary hologram. The experimental results are also shown.
We discuss a method for producing high quality true color reflection holograms in silver halide based on multiple wavelength recording in a sandwiched emulsion layer. From a consideration of the literature on color theory and an experiment conducted in psychophysics, we determined optimum available laser wavelengths for color holography: 458 nm blue, 528 nm green and 647 nm red (a combination not used in the past). We then used these wavelengths to record true-color white light reflection display holograms of a set of Munsel colored papers. Ilford SP672T and SP673T emulsions provided the high spatial frequency response necessary for blue recordings. The hologram and object were measured and compared using a spot spectro-radiometer to determine the fidelity of color reproduction. The techniques were then used to record holograms of a three dimensional colored object.
A new method of full color rainbow hologram which can reconstruct a natural color image is developed and has been shown in Applied Optics. This method uses a technique of achromatic holographic stereogram invented by Benton and is realized by only one wavelength of Argon-ion laser and a photoresist plate. It is found from the result of experiments that the reconstructed image has sufficient contrast and wide range of color reproduction in both bright and dark area.
The ideal holographic material would have the sensitivity and spatial resolution of silver halide emulsion, the efficiency of dichromated gelatine, the self developing feature of photorefractive crystals, and useful at all laser wavelengths. Unfortunately, no such material exists; those that do exist are characterized in the table below. Photoresist materials have proved especially disappointing. In spite of years of effort, the sensitivity, resolution, efficiency and ease of processing leave almost everything to be desired!
The chemical processes involved at development and bleach stages sometimes show variations that are difficult to explain. The paper describes some work about those effects (e.g. amount of developer, influence of exhaustion, safetight used, ...) and some efforts to minimize variations by the use of microprocessor-controlled automatic development machinery. Some minor problems caused by commercially available and affordable items will be presented; some major problems when trying to build one's own equipment are discussed.
A general review is given on the archival permanence of high resolution images and holograms recorded in silver halide emulsions, together with the influences of expected degradations on the image quality that may occur in stored holograms. Emphasis is placed on silver image absorption (amplitude) holograms which have been subjected to incubation experiments to simulate and accelerate ageing conditions, employing an elevated temperature of 600C and 70% relative humidity for periods of upto 30 days, in the presence of varying amounts of residual thiosulphate ion. Degradations in image quality have been quantified in terms of signal-to-noise ratio and resolution changes. Changes in morphology of the image have been demonstrated by changes in optical density and spectral density. The effects of oxidizing gases have also been investigated using extreme conditions to simulate microspot or redox blemishes, employing 500 ppm of hydrogen peroxide at 50°C. and 80% relative humidity for periods of upto 7 days. Image quality has also been quantified for. these conditions in terms of signal-to-noise and resolution changes. The archival limits for residual thiosulphate ion are discussed and some preliminary recommendations are made for minimising problems of image deterioration in stored holograms.
Volume holographic recording materials are modeled on a PC for the case of a conformal reflector geometry. The model is used to help describe the physical structure of holographic mirrors made in (3) popular materials. Experimentally determined properties of each material that affect preparation, exposure, processing, tuning and protection are discussed. Examples of possible applications and limitations of each material are given.
DMP-128 Photopolymer Holographic Optical Elements are stable to natural environmental conditions. The DMP-128 holograms may also be specially treated so as to withstand the harsh conditions and chemical environments involved in some manufacturing processes. This treatment involves filling the air voids in the photopolymer structure with a low refractive index monomer which is then polymerized in place. Void filled samples were laminated into glass structures, including a polyvinylbutyral interlayer, at high temperature and pressure. The resulting glass laminates were then stored at high temperature; in every case only small, predictable and reproducible changes in the optical properties were observed.
A method for monitoring the humidity incubation or activation procedure of Polaroid photopolymer DMP-128 will be described. The technique involves water absorption measurements with an infrared helium neon laser. Advantages of the activation monitor to the fabrication of holographic optical elements will be discussed.
Changes in the structure of photopolymer holograms during environmental testing were studied with two techniques: (1) Scanning electron microscopy of freeze-fracture cross-sections and (2) modeling the refractive index profile. The profile was estimated using optical data: reflectivities corresponding to the fundamental spatial frequency and the second harmonic. We chose to use holograms that had not been through the normal stabilization treatments for the material, in order to study the properties of the basic structure. The changes are interpreted within the context of the void model for this photopolymer's structure.
Holograms recorded in dichromated gelatin can easily be destroyed when subjected to high temperatures. In this work, a new treatment of holographic dichromated gelatin layers that improves remarkably the hologram life time under adverse thermal conditions, is presented: exposing the developed hologram to microwave radiaton. Similar holograms were subjected to microwave radiation for variable timelengths and then subjected to heating. The resultant angular and spectral bandwidths were measured after different heating time intervals. Some preliminary results will be presented. The role of water in holograms made with dicromated gelatin will be discussed, in this new context.
The effects of varying the concentration of the ammonium dichromate sensitizing solution on the gelatin film properties were investigated quantitatively. The film thicknesses were measured following preparation, sensitization and processing. The refractive indices of the film surfaces were measured following sensitization and processing. The absorbances of the films were measured following sensitization. The results indicated that following sensitization the refractive indices of the films increased and the film thicknesses decreased for low ammonium dichromate concentrations and increased for high concentrations. Subsequent to processing, the refractive indices decreased and the film thicknesses increased for films sensitized at low concentrations and decreased for films sensitized at high concentrations. The expected shifts in the reconstruction wavelengths were determined from the changes in the film thicknesses and refractive indices and were found to agree well with the wavelength shifts measured using a spectrophotometer. The reconstruction wavelengths were determined to vary linearly with the specific absorbance. The diffraction efficiencies and bandwidths of the holograms produced increased as the concentration of the ammonium dichromate in the sensitizing bath was increased. The implications of the results for the production of highly efficient volume holograms were discussed.
Proc. SPIE 1051, An Integrated Approach To Production Line Nondestructive Testing Using A Customized Newport Research Corporation Holographic Inspection Station, 0000 (25 May 1989); doi: 10.1117/12.951465
Production line techniques of nondestructive testing have been streamlined and automated with the use of a customized Newport Research Corporation Holographic Inspection Station. The nondestructive evaluation of the glue joints in XM785 rocket motor bodies has been performed totally by remote control; the operator requires no specialized knowledge of part handling or of holographic techniques. The holocamera was modified with a pneumatic part-handling fixture which could rotate a part to produce 12 real-time holograms of the rocket motor body in different positions. By heating the sample with a remotely controlled heat gun, the samples could be checked for voids in the bonding layer of silicon-based adhesive between the insulating phenolic liner and the titanium rocket motor body. Defects greater than 1/4" in diameter have been successfully located by observing the fringe pattern produced by this method. The fringe pattern produced is a characteristic bull's-eye pattern, quite different from the solid rigid body fringes produced in places where the glue is successfully joining the inner liner to the massive titanium structure. The results were repeatable during sample reheatings, and suspected defects on the edges of the visible region could be reexamined by rotating the sample along its axis to a better viewing angle. During evaluation, the fringes were viewed in real time by a video camera focused through the thermoplastic plate onto the sample, and recorded by a VCR for off-line examination. Still photos could be taken either by replacing the video camera with a 35 mm camera, or by obtaining a hard copy from the VCR unit.
The human visual system is often equated to a photographic camera. This is a poor analogy because the differences are far greater than the similarities. The processing of the human visual system is complex and non-linear so that even optical transfer function concepts must be applied with caution. Holographic optics offers some extra degrees of freedom with respect to refractive optics. Unlike refractive optics, diffractive effects are not, in the first order, dependent on material and geometric shape and require no significant volume. On the other hand they may suffer from fractional efficiencies and strong wavelength dependencies. The Pilkington 'Diffrax' lens invented by the author is an example of a product which steers between the disadvantages and maximises the advantages to provide the world's first diffractive bifocal contact lens. Indications for other visual applications are not very propitious although time and development may show this to be incorrect. This paper will review the interaction between the preferences and antipathies of the human visual system and the optical effects of diffractive systems.
The fingerprint sensor that we developed uses a hologram. Two requirements are important for actual use; laser safety and high-contrast images. The illumination method we developed uses total reflection and a new type of detection. For safety, total-reflection lighting ensures that laser beams cannot enter an operator's eyes. To obtain high-contrast images, signal and noise light were separated.
Waveguide grating couplers have been actively investigated for several years for application as read-out heads for optical data storage. Fabrication by optical holography has generally been considered to be very difficult because the grating is used in the near infrared but must be made at blue-green wavelengths where good holographic materials are suitable. As is typical of all gratings, operation at a wavelength different from the construction wavelength causes severe aberrations. While, in principal, the aberrations may be precompensated by special fabrication optics, the design and construction of such systems is extremely difficult because of the unusual aberrations and the lack of rotational symmetry in the construction optics. The highly unusual aspects of the waveguide grating make conventional optical design difficult. In this paper we show a simple configurations which is rotationally symmetrical and relatively easy to fabricate. In addition, the design may be readily done on a conventional lens design program without modifications.
The diffraction characteristics of multiplexed holographic gratings are investigated using a rigorous coupled-wave approach. The effect of the angular separation between the multiplexed holograms on the diffraction efficiency, the direct cross-talk, and the indirect cross-coupling between the two holograms is determined. It is shown that the indirect cross-coupling could cause serious limitations on the maximum diffraction efficiency of the multiplexed holograms and on the total number of holograms that can be multiplexed.
Recent progress in UV and XUV optics has been accelerated as a result of development of new holographic materials based on graft concept. Using the new polymeric materials, holographic optical elements (HOEs) can be recorded in the visible and reconstructed in the UV and XUV region, with diffraction efficiencies higher than 95% for UV HOEs and 25% for XUV HOEs. The new series of high resolution (20,000 1/mm) and high refractive index modulation (Δn = 0.2) materials consist of extremely dense photochemical crosslinking network of hydroxyalkyl acrylate-methacrylates, hard dichromated gelatin, and transparent PVA.
Ambient lighting seldom produces optimum illumination for display holograms. This paper describes some considerations for producing compact illuminator packages for transmission holograms that guarantee optimum illumination. An application of the illuminator in a hybrid display that uses both a holographic image and a liquid crystal display as a user interface for a business machine will be described.
Solar holoconcentrators based on transmission holograms as well as reflection holograms have been designed. In the first case we have shown that silver-halide gelatin, which has a light sensitivity ≈103 times better than dichromated gelatin, is an alternative. In the second case we have developed methods to make broad-band violet spectrally responsive holoconcentrators.
Modern scientific data sets require new algorithms and hardware for display and interpretation tasks. We present a discussion of the new display requirements and of techniques currently under developed for this purpose. Special emphasis is placed on holographic and interactive devices. We also present examples of the application of these new techniques to fluid mechanics data.
This paper describes a new family of displays which combine the versatility of liquid crystal displays with the 3-D perception and look-around conveyed by holograms. Results obtained with computer generated stereograms, coupled to dynamic scattering and twisted nematic displays, will be discussed together with possible applications.
The plane type white light reconstructed holographic stereogram (PW-HS) is useful when portrait or other objects,which can riot be taken hologram directlytare chosen to the objects and are used for the cover of the books or the demonstration on the wall. In this method usually the object or camera is moved transversely to make the object film photographically. But, in this method the projected image moves on the screen and it limits the number of element hogram. Consequently it limits the field of view of HS. For these reasons we propose the rotation method to take photograph of 3 dimensional object. The reconstructed image obtained in this method usually contain the distortion depending on the scanning angle of the object.
Multiplrex Holograms are printed by using a liquid-crystal television receiver as a spatial light modulator instead of silver-halide movie film. Reconstructed 3-D images of wire-frame model can be observed with high contrast. But, some noise which is caused by LCTV is also observed.
Deliberate variations of the emulsion thickness between holographic exposures and reconstruction produce a range of output wavelengths from a fixed exposure wavelength, a technique known as "pseudo-color" multi-color reflection holography. Usual methods require the removal of the film or plate from the holographic setup between exposures for imbibition of a swelling agent, followed by drying and replacement, so that a retention of the swelling agent forces a physical increase in the thickness of the emulsion. The density (and hence the thickness) of the gelatin binder can also be varied by changing its electrolytic environment. By immersing the holographic emulsion in a suitable solution, allowing it to come to a new equilibrium thickness, and exposing with a long-wavelength laser, shorter wavelength reconstructions can be obtained without removing the film or plate from the setup. Accurate changes of solution can make a precise sequence of swellings possible, producing multiple reconstruction colors from a set of constant-wavelength recordings. Here we describe pre-treatments of the emulsion that make rapid and stable equilibria possible, and swelling bath sequences that produce color primaries suitable for full-color computer-graphic holographic imagery.
An important feature for an effective display hologram is a wide viewing angle so that the autostereoscopic aspects of holography are dramatically evident. A short conjugate distance between the light source and the hologram can simplify the problem of supplying optimum illumination for display holograms and provide higher illumination intensity. These two desirable features, wide viewing angle and nearby point source illumination, have been incorporated simultaneously in planar format white light-illuminated transmission holographic stereograms made from computer graphics. This talk will discuss design considerations related to these two issues. We have achieved conjugate distances of 15 cm for illumination with a tungsten light bulb and viewing angles >70°.
The inclusion of animation in holographic stereograms introduces errors in the perceived location of moving objects. Consider, for example, a hologram of a road with a moving car. When each view of this hologram is recorded the car is in a different position. When the hologram is viewed, each eye sees an image recorded at a different time. Because the brain expects both eyes to see the scene at the same instant in time it misinterprets the position of the moving car. If the car is moving from left to right (in the same direction as the camera) it will appear to be behind its correct position. If it is moving from right to left it will appear to be closer to the viewer than it should. If the car is moving toward or away from you there is error in both its left to right position and its in and out position which changes with viewer location. The magnitude of these errors is highly dependent on the object's velocity. The perceived position error of an object moving at moderate velocity can easily be greater than the distance that it moves in the hologram. We have derived, using a simple geometric model, a set of formulas which predict the perceived position and perceived position error of moving objects in holographic stereograms. Using these formulas designers of animated holographic stereograms will be able to compensate for errors in the perceived locations of moving objects. This will enable them to place moving objects in the correct positions relative to other moving and stationary objects. For example, the designer will be able to design a hologram where a car travels along a street without driving up on the sidewalk.