Amplitude Holograms Research Articles

Sensitometric and holographic data of Kodak 120-02 and llford He-Ne 1 plates

The macroscopic transfer characteristics of Kodak 120-02 and llford He-Ne/1 plates exposed to diffused laser light at 633 nm and processed in different developers for various times are reported. Diffraction efficiency and signal-to-noise ratio of amplitude holograms recorded in these materials have been checked and compared with the results obtained from other holographic emulsions.

On the Diffraction Efficiency of Synthetic Binary Holograms

The diffraction efficiency of synthetic amplitude and phase holo grams has been studied as a function of the ratio of the line-width to the grating period (s/d). A strong dependence of the diffraction efficiency on s/d results in a reconstructed wave with non-uniform amplitude. This behaviour will restrict the applications of synthetic holograms as optical components.

Relative Phase Shift of Images Reconstructed by Phase and Amplitude Holograms

Relative Phase Shift of Images Reconstructed by Phase and Amplitude Holograms

Advances in Bleaching Methods for Photographically Recorded Holograms

A new, dry method for converting photographically recorded amplitude holograms to high diffraction efficiency phase holograms is described. The dry method involves the application of elemental bromine or chlorine. The bromine vapor bleaching of transmission holograms produced efficiencies of 70.8% in dry film and 75.5% in water swelled layers. Index modulations of 0.033 have been observed. Reflection hologram efficiencies of 73% were obtained. The stability of the bromine vapor bleached holograms to printout is superior to all previous methods.

Thick Amplitude Holograms: Effect of Nonlinear Recording

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Cynthia R. Bendall, B. D. Guenther, and R. L. Hartman, "Thick Amplitude Holograms: Effect of Nonlinear Recording," Appl. Opt. 11, 2992-2993 (1972) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Point Efficiency and Signal-to-Background Ratio in Exponential Holograms for Optical Memories

The reconstruction of a point matrix by holograms with an exponential exposure characteristic is exactly calculated in dependence on exposure parameters, geometry, and position of a point in the image field. Linear and nonlinear distortion of the reconstruction is described in terms of the signal-to-background ratio (SBR). The variation of the SBR across the image field is demonstrated for both phase holograms and exponential amplitude holograms. The results, derived for point holograms in optical memories, are also applicable to the more generalized case of holograms of diffuse objects.

Kontrasterhöhung von phasenhologrammen durch beschichtung der platten

Phase holograms of diffusely illuminated objects produced by bleaching have lower contrast than amplitude holograms. By convering such phase holograms with a lacquer of a gelatin layer, the refractive index of which is not considerably differenct from the refractive index of the photographic layer, it is possible to improve the contrast by a factor of approximately 2.

Electron micrographs of hologram cross sections

The cross sections of both amplitude and phase holograms are observed by electron microscopy. Holograms were recorded on Kodak 649F and Scientia 14C75 sheet films by using a He–Ne laser beam (6328 Å). It is shown that the holograms are recorded throughout the whole thickness of the emulsion layer and the developed grains are enlarged by bleaching (about 1.5 times by length). This enlargement can be correlated with the thickness change of the emulsion layer during the chemical processing in making holograms.

Effect of Emulsion Thickness on the Diffraction Efficiency of Amplitude Holograms

The diffraction efficiency of amplitude holograms recorded on photographic emulsions is shown to be independent of the thickness of the emulsion layer. This can be explained theoretically under the assumption that the exposure modulation is not too high, i.e., for high and moderate beam ratios K. With this assumption it is possible to demonstrate the equivalence of Kogelnik’s equation using a coupled-wave theory for thick holograms and the equations derived by Kaspar and Lamberts for thin holograms. This is true even though the former contains an explicit dependence on thickness and the latter equation includes only the MTF of the emulsion and the slope of the amplitude-transmittance log-exposure characteristic of the emulsion. This conclusion is demonstrated experimentally by measuring the diffraction efficiency for two series of very-fine-grain emulsions, which differ only in the thickness of the emulsion layer.

Attempts to Increase the Holographic Exposure Index of Photographic Materials

The holographic exposure index (HEI) relates the radiant energy necessary for recording a hologram to the diffraction efficiency to be achieved. In addition to the sensitometric speed of the recording material, the HEI takes into account that the modulation transfer function and macroscopic transfer characteristics, depolarization, and losses in the object beam path determine the share of the laser flux to be split off for the object beam. Several techniques expected to save exposure are examined. Extended development may increase the HEI by a factor of about 2, but light scattering due to granularity increases more. Combining a hologram exposure with incoherent preexposure or postexposure is governed by quite different characteristics, depending upon which of the exposures is variable or whether both are proportional. The characteristics alpha(E),beta(E) for amplitude holograms and gamma(E),delta (E) for bleached holograms are used for the analysis and verified experimentally. Preexposure or postexposure is of use only if extreme underexposure is unavoidable. When superimposing several holograms a decrease in diffraction efficiency in the order of exposure was found. Finally, Scientia 8E70 and 10E70 plates and 10E70 film were hypersensitized by bathing. Distilled water and a relatively diluted ammonia bath yield the best results by increasing both the sensitometric speed and the values of the macroscopic transfer characteristics, the gain in HEI becoming up to 3 for the slowest plate.

High-efficiency Phase-hologram Gratings

Optimum conditions for the generation of high-efficiency hologram gratings are presented. The most efficient phase holograms were obtained for exposures 10 to 20 times larger than those for optimally exposed amplitude holograms. Hologram gratings produced on Agfa Gevaert 8 E 70 recording plates diffracted 40 percent of the incident radiation into the holographic image. This experimentally obtained efficiency is 60 percent of the theoretical maximum for a hologram with a geometric parameter Q of 4.6.

Properties and Limitations of Hologram Recording Materials

The role of the recording material in holographic imaging is reviewed. Following a general classification of holograms into four basic types, the thick and thin amplitude and phase holograms, a discussion is given of the diffraction efficiency and other intrinsic characteristics of each of these types. The effects of zero spread nonlinearities in hologram recording are examined, and the limitations they impose on the usable diffraction efficiency of the various hologram types are discussed. The effect of the recording material modulation transfer function is treated by means of a fictitious mask model which facilitates prediction of the recordable object field and resolution. The noise characteristics of recording media are discussed in terms of their effect on holographic recording. Some examples of noise limitations on holographic information recording by silver halide emulsions are examined, as are the effects of such limitations on the dynamic range of holography. The effects of silver halide grain noise in conventional and holographic recording are compared, showing the conditions under which better performance can be achieved in the latter by a given emulsion. The characteristics of several nonsilver halide hologram recording materials are briefly summarized.

Three Dimensional Hologram Reconstruction and Image Speckle

It is known that three dimensional objects form three dimensional images by using the hologram technique and it has recently been shown that when the photographic record (hologram) is bleached to make a phase hologram, three dimensional images also result. The purpose of this paper is to demonstrate, theoretically these experimental observations. In particular a three dimensional boundary value problem is considered and the resulting three dimensional image is derived both for amplitude and phase holograms and for reflecting and transmitting objects. The speckling that appears superimposed upon the image is also derived from the same model by assuming that rough surfaces in the optical system are random noise generators.