POSSIBILITIES AND PROSPECTS OF HOLOGRAPHY

Welcome to the holography and holographic interferometry pages

Authors: Cernecky Jozef – Pivarciova Elena

Introduction

Experimental methods play a significant role in both the basic and applied research. They are used to verify the results of theoretical computations or to specify mathematical models, and are often the only way to solve the tasks. To these methods also belong the optical methods of holography and holographic interferometry.

The global view on the optical visualisation methods is described in papers by (Zacharevskij, 1952), (Cholder, Nort, 1966), (Vasiliev, 1968),
(Pavelek, Janotková, 2001).

Holography is an optical imaging method that started to develop intensively in the half of the 60s in the last century. It was developed as a sort of photography that takes three-dimensional images on a film by laser light reflected from the object and incident on the film. After the film is developed it is illuminated and the observer can see a three-dimensional image looking as if it were floating in the space. At present, holography belongs to interesting technologies and is used for studying processes and events in different disciplines, in practice and also to prepare art works and protect objects against counterfaiting (Fiala et al, 1998), (Fontelera, 2005).

Holographic interferometry makes it possible to obtain information in the form of an observable (macroscopic) interference image where information characterising at least one physical state of the observed object is encoded. Practical understanding of the holographic interferometry methods is connected with solution of a number of tasks. In some cases the character of interference image as such enables us to draw conclusions about resonance frequencies and oscillation shapes of the objects (Powell, Stetson, 1965), (Agren, Stetson, 1972) as well as defects in structure of materials (Kudrin et al, 1982), (Kozačok, 1984), makes it possible to compare the observed objects with standard ones and solve other qualitative and quantitative tasks. It is necessary to obtain quantitative information about the objects or processes in many experimental studies, which requires an analysis of interferograms (Briers, 1976).

Based on of the first theoretical papers in the field of holography published by Gabor (Gabor, 1948), (Gabor, Goss, 1966), Denisjuk and also by Leith and Upatnieks (Leith, Upatnieks, 1963) in the middle of the 60s, the holographic interferometry was verified by many scientists (Brooks, Heflinger, 1965), (Burch, 1965), (Collier et al, 1965). A much more detailed description of the holographic interferometry is given in papers by (Aleksandrov, Bonč–Brujevič, 1967), (Zajdel et al, 1967), (Vlasov, Štaňko, 1976), (Jones, Wykes, 1989).

Over the last decades many papers presenting applications of the holographic interferometry and development of its methods appeared (Ostrovskij et al, 1977), (Vest, 1979), (Ostrovskij et al, 1988) and new ways of three-dimensional phase objects research were developed (Hauf, Grigull, 1970), (Beketova et al, 1979).

In their papers (Hauf, Grigull, 1970), (Panknin, 1977) demonstrated the possibilities of holographic interferometry utilisation in the study of heat and material transmission on various models. They also described the methods of holographic interferogram analysis.

A detailed review of the holographic inerferometry development from its beginning up to 1975 was elaborated by Briers (Briers, 1976). He classified the applied techniques from the viewpoint of interference image interpretation and studied the conditions of localisation of the interference fringes occurring during the reconstruction of the record. A review of the holographic interferometry methods utilisation during measurements of transfers, deformations and tensions was presented by Boone (Boone, 1976). From the viewpoint of the holography application in the mechanics of solid bodies Ebbeni (Ebbeni, 1979) elaborated the following classification:

• Measurement of displacements on the surface of diffusive objects,

• Direct measurement of deformations,

• Investigation of vibrations of the objects,

• Applications in holographic photoelasticimetry,

• Non-destructive testing.

Many methodological questions of holographic interferometry utilisation and examples of other particular tasks solution are mentioned in papers by (Pavelek et al, 1976), (Pavelek et al, 1977), (Keprt et al, 1984), (Zemánek, 1984), (Černecký, 1992), (Keprt et al, 1996), (Pavelek, Štětina, 1997), (Berkeš, 2001), (Urgela, 2002), (Javorková, 2003), (Pigošová, 2004), and others.

In the last decade, holographic interferometry has been successfully used also to solve special practical tasks (Jansson et al, 1994), (Keprt et al, 1995), (Gopalakrishna, 1996). It has been developed in various applied measurements in mechanical engineering and wood-working research (investigation of resonance frequencies of circular saw blades, penetration of the cutting wedge into wood, creation of particles during a cutting operation, applications in the design of musical instruments – violins, in aerodynamics of drying processes, thermal characteristics of various materials, investigation of tensions in the gullet of sawing instruments (Černecký, 1992), (Černecký, Siklienka, 1995), (Černecký, Pivarčiová, 1997), (Černecký, Dubovská, 1998), (Černecký, Marčok, 1998), (Molin, 2002), etc.

The importance of experiments has been increasing in new and non traditional areas such as refraction mechanics, optimisation of designing, dynamic and random processes, rheologic characteristics of materials, influence of inhomogenity of materials, diagnostic and defectoscopic material quality control, and others.

The present state of publications suggests that holographic interferometry as a method of scientific and technical research has been continuously extending its influence in solving new special tasks, for example applications in agricultural engineering (Brozman, 1999), projection of the three-dimensional local atom structure (Korecki, Korecki, 2002), study of non-linear optical processes in a molecule (Korchemskaya et al, 2005) or acoustic diagnosing of different ranges of frequency (Alexander, 2005).

Practical application of the holographic interferometry methods meets with certain difficulties as it is substantially conditioned by a sufficiently high standard of knowledge in various fields of science such as the coherent optics, laser technique, experimental mechanics, applied mathematics, computer programming skills and, of course, in the particular research area studied.

Their advantage lies mainly in the possibility to obtain an integrated image of the investigated object, information about point displacements on the whole surface of the illuminated object even without direct contact with the object. The obtained results offer information about the real state of the object enabling us to learn more about connections between the investigated events and about the development of non-stationary actions. The method is exact and does not require the entrance of a mechanical scanner that could influence the observed field.

By application of digital scanning it is possible to ensure the continuity between the classical technique and digital processing implementation (Repetto et al, 2004). The digital processing of holographic interferograms is presented in papers by (Vejbor, Zapletálek, 1996), (Pavelek, Janotková, 2001), (Pivarčiová, 2002), (Siláči, 2004).

By utilising computers the holography enters a completely new age as a display technique.

Instead of a film, computer controlled micromirrors can be used to create a sequence of holographic images. Yves Gentet, the optical technician, invented a portable holographic camera for face scanning and a holographic film (Kunzig, 2002). Drs. Huebschman and Garner in the Southwestern Medical Centre at the University in Texas used the idea to create a simple two-minute film (Hill, 2005).

The present publication involves an analysis of physical bases of holography, holographic interferometry and its individual methods with the examples of their particular applications aimed mainly at the mechanical engineering and wood-working research.