Production Of Holograms Research Articles

Near-infrared holography by two-photon photochemistry

The applicability of the technique of two-photon four-level photochemistry for the production of near-IR holograms is critically evaluated. Although the current best system (biacetyl in a polycyanoacrylate matrix) has low recording sensitivity, several applications of the material have been demonstrated. Hologram efficiencies of up to 70% recorded at 752 nm are shown. Recording of extended holographic images and production of holographic optical elements are demonstrated. Finally, we have recorded holograms directly with GaAlAs diode lasers.

Improved Integrating Exposure-Control System For Color Holography

The exposure-control system described in this paper has been found extremely useful in the production of multicolor holograms, which require precise repetition of exposures at different laser wavelengths. It permits rapid measurements of the irradiances of the object and reference beams in the hologram plane for adjustments of the beam ratio, as well as summation of these irradiances and automatic determination of the exposure time for a desired radiant exposure. A separate detector continuously monitors the laser power and automatically adjusts the exposure time to compensate for varia-tions in laser output during the exposure. A simple interlock ensures the correct combination of settings of detector sensitivity and radiant exposure when changing from one wavelength to another.

UV hologram recording with an excimer laser

Ultraviolet hologram production using 353-nm radiation from an e-beam-pumped XeF laser is reported. Mode selection was accomplished via an unstable resonator. A description of the holographic optical configuration is detailed and the simplicity of the arrangement noted. Reconstruction was accomplished with a low-power He-Ne laser. Scene and reference optical path length differences of up to 15 cm produced no detectable change in hologram quality. Some advantages in using excimer lasers for UV holographic recording are presented.

Production of holograms with shearing interferometers using a wide light source

Interferograms with narrow fringes obtained with grating and polarization interferometers using a wide source allow the use of some processes of holographic interferometry and schlieren techniques for investigating a reconstructed wavefront. The reconstructed interference patterns of a sphere's supersonic flow are presented. A scheme for obtaining colour schlieren patterns is described.

POLARIZATION EFFECTS IN HOLOGRAPHY

The review considers the recording and reproduction of complete as well as partial information concerning the vector characteristics of a field. The principal methods and features of producing a complete recording of the wave polarization are indicated, namely the use of two reference beams with orthogonal polarizations, coding the reference beam with random wave fronts, and the use of three-dimensional holograms. Different aspects of the use of holographic recording of partial information concerning field polarization are considered. In such a procedure, the information on the polarization characteristics of the object wave is coded by means of other field characteristics, the amplitude and the phase. In this connection, in analogy with the phase-contrast method, the concept of polarization contrast is introduced and defined as the transformation of the changes of the state of polarization over the object into variation of the intensity of the image reconstructed from the hologram. The production of holograms by this procedure is described consistently with the aid of the correlation-matrix formalism, and also with Stokes parameters. The intensity of the virtual image is expressed in terms of the coherence matrix of the object and reference waves, or else with the aid of corresponding Stokes parameters. It is shown that the polarization state of the reference wave serves as the analyzer of the vector characteristics of the object field. The method of double exposure using orthogonally linearly polarized waves for different exposures is compared with the method of single exposure with circularly polarized fields. Certain limitations imposed on the objects and conditions of the experiment, under which both methods coincide, are indicated. Experiments with a very simple object, illustrating the procedure, are described.

Holography using a train of mode-locked pulses

Reports the production of holograms of a rapidly moving object using a train of mode-locked pulses. The reconstructions display high finesse velocity fringes.

Holography Using a Fundus Camera

Modifications to a Zeiss fundus camera to enable production of holograms of selected sites of an optic fundus are described. Resolution near the resolution limit of the camera has been obtained in holograms of the fundi of anaesthetized cats. Laser intensities on the retina are below injury levels.

Phase holograms in photographic emulsions for digital data storage

Holography offers a way to develop permanent computer memories with large capacities and short access times. We analysed the influence of imaging properties and statistical light scattering of phase holograms on their storage capacity and optical signal-to-noise ratio at readout. We found that above a certain value of reconstruction efficiency to scattering efficiency ratio the hologram store performs as if it were free from scattering. We measured this ratio for holograms bleached with mercuric chloride and potassium bichromate. In the first case it is below, and in the second above, the threshold. This shows that photographic emulsions allow production of holograms which fulfil the most important requirements of optical data storage.

Computer-generated Binary Holograms

Holograms synthesized by computer are used for constructing optical wavefronts from numerically specified objects. Elimination of the need for a physical object has made new applications possible, for example, three-dimensional computer output displays, synthetic prototypes for interferometric testing, and filters for various optical data processing operations. Our computer holograms differ from a normal hologram in that the transmittance is binary, yet they are able to construct general wavefronts and images efficiently and have several practical advantages over holograms with a continuous range of transmittance. Recent improvements that simplify the production of binary holograms and improve their performance are described and experimental work showing reconstruction of two- and three-dimensional images is presented.

Ultrasound camera system for viewing acoustical holograms

A system for the simultaneous production and reconstruction of acoustical holograms is proposed. It uses electron beam scanning techniques to produce a variable transmittance hologram that can be reconstructed by the usual laser techniques.

Holograms of the aerial image of a lens

Wave front reconstruction imaging technique for hologram production of aerial image of lens

9A9 - Pulsed laser holograms

The limited coherence of most pulsed lasers is the principle difficulty in making pulsed holograms. This paper describes techniques used for the production of quality holograms of back lighted subjects, using ordinary pulsed lasers. The arrangements used achieve a temporal and spatial matching of the scene and reference beams to the degree required by the laser coherence cell. Techniques are described which prevent the destruction of the spatial match when using a diffusing screen. The use of lenses to permit the recording of large subjects on small holograms with limited pulsed energy is described. The limitations on subject motion are described. Experimental examples of the techniques are illustrated by holographic recordings of bullets in flight. The technique of double exposure holographic interferometry is also illustrated.

Simplification of Holographic Procedures

The present state of the holographic art has set many stringent parameters on the production of holograms, such as extreme mechanical, temperature, and air stability for long periods of time, and slow film emulsions with extremely high resolution. The Physical Sciences Laboratory of the U.S. Naval Training Device Center has investigated, experimented, and produced many clear high resolution holograms in a ground-level Butler Building without close temperature controls and using other than expensive, massive, and extremely rigid optical mounts and equipment.