Television holography (TVH) can be defined as `the family of optical measurement techniques based on the electronic recording and processing of holograms'. Image-plane TVH was introduced in the early 1970s with the name `electronic speckle-pattern interferometry' (ESPI). Since then, TVH has undergone an impressive development and become one of the most promising optical techniques for non-destructive testing and industrial inspection. The aim of this review is to propose an original scheme for the systematic treatment of TVH and to review the existing techniques according to it. In this approach we split the measurement process into four highly independent stages (illumination and observation geometry, temporal treatment, secondary-correlogram generation and fringe-pattern analysis) and establish a common notation to formulate the corresponding techniques. Such a strategy allows the free combination of the techniques proposed for each stage as building blocks to obtain every particular variant of the whole TVH measurement process, whether it has already been reported or not, and also the incorporation of new techniques while retaining compatibility with the existing variants of the previous and following stages.

/pdf/a-systematic-approach-to-tv-holography-44h8p1g35o.pdf

A systematic approach to TV holography

Recent developments in digital speckle pattern interferometry

A dual-function ESPI system for the measurement of out-of-plane displacement and slope

Divergent laser illumination is commonly used in current designs of commercial electronic speckle pattern shearing interferometry (ESPSI) or shearography, for qualitative non-destructive testing (NDT) of material defects. The growing demand for quantitative out-of-plane (OOP) and more recently in-plane (IP) ESPSI, is determining the quality of optical system design and analysis software. However, little attention is currently being given to understanding, quantifying and compensating for the numerous error sources. Data describing the measurement inaccuracy due to the divergence of the object illumination wavefront for an OOP interferometer is presented. The errors are measured by comparing divergent object illumination with collimated illumination, with respect to illumination angle, lateral shear and shearing direction. Results indicate that the magnitude of the relative error increases by approximately a power function as the distance from the illumination source decreases.

Wavefront divergence: a source of error in quantified speckle shearing data

Recent developments in holographic optical elements (HOEs)

An imaging system with its aperture fully open or with a multiaperture mask in front has been used for carrying out speckle shear interferometry. The shearing is achieved by installing shear elements in front of the imaging system. The multiaperture configuration has built-in in-plane displacement sensitivity, and hence shear fringes obtained from multiaperture shear interferometer always carry the in-plane displacement contribution. This problem does not arise when the full aperture of the lens is used. A three-aperture speckle shear interferometric technique is introduced here to separate the in-plane displacement and slope contributions from the shear interferogram. Detailed theoretical and experimental results are presented.

Separation of the influence of in-plane displacement in multiaperture speckle shear interferometry

This paper presents the use of holographic optical elements for the measurement of slope and curvature by video techniques. the curvature fringes occur as moire between two speckle slope patterns. A good agreement between theory and experimental results is demonstrated.

Electronic speckle pattern interferometry with holo-optical element

The integrated optics waveguide devices should have low coupling losses with optical fibers. We present a procedure for determining the ion-exchange process parameters for fabrication of such low loss waveguides in glass and discuss the single mode waveguide fabrication by the inverse ion-exchange.

Design and fabrication of single-mode waveguides in glass by inverse ion exchange

The inverse ion-exchange process in glass is studied with the aim of fabricating single mode waveguide devices. Single mode channel waveguides arc fabricated by ion-exchange. The process is modeled using finite difference technique and the effects of various experimental parameters on the refractive index profile of the waveguide are studied.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Prafulla J. Masalkar

Papers

Separation of the influence of in-plane displacement in multiaperture speckle shear interferometry

Electronic speckle pattern interferometry with holo-optical element

Design and fabrication of single-mode waveguides in glass by inverse ion exchange

Fabrication of singlemode waveguide devices by inverse ion-exchange in glass