Digital Speckle Pattern Interferometry and Related Techniques

Abstract

Three decades have passed since Butters and Leendertzpublished their ground-breaking articles on electronicspeckle-pattern interferometry (ESPI). However, it has beenduring the last 15 years that ESPI, boosted by the availabilityof affordable and increasingly powerful digital image processingsystems, has grown into one of the leading opticalmeasurement techniques, receiving new names such as TV holography ordigital speckle-pattern interferometry. Nowadays, it deserves achapter in almost every book that is published on speckletechniques, holographic interferometry or optical metrology.Despite this, a monograph on DSPI has long been awaited,and here it is.Pramod Rastogi has edited this comprehensive review that coversmost of the concepts, methods and techniques in the field ofDSPI. The authors have conveniently classified these items,giving concise descriptions of them, and they provide anextensive set of references for further reading within the scopeof each chapter. The contents are fully up-to-date, includingsuch recent developments as temporal phase unwrapping, incrementalmeasurement methods, compact fibre optic systems, techniques fortransient analysis using pulsed lasers and high speed cameras,digital holography, etc.The book is organized into six chapters. The first, by MathiasLehmann, presents an overview of the statistical properties ofspeckle that affect the behaviour of electronic speckleinterferometers. Besides the usual statistics of the intensityin speckle fields and speckle interferograms, it treats thestatistics of decorrelation-induced phase-errors and theoptimization of the interferometer parameters using statisticalcriteria.The second, third and fourth chapters are dedicated todescribing the different techniques of `classical' DSPI.Jonathan Huntley makes a remarkably neat approach to theautomated analysis of speckle interferograms, describing bothtemporal and spatial phase evaluation and phase unwrappingtechniques, as well as post-processing methods to convert theoptical phase maps into measurements of the parameter understudy. Pramod Rastogi reviews the interferometricgeometries that provide sensitivity to displacements,derivatives of displacement, shape and slope attending to staticmeasurands. A respectable number of schemes and picturesillustrates the multiple configurations, and many examples ofapplications give a view of the possibilities of thesetechniques. The measurement of dynamic events is treated byAndrew Moore, Julian Jones and Jesús Valera. They introducethe principles of the techniques that allow the measurement ofperiodic and transient vibrations, disclosing somepracticalities about the use of continuous and pulsed lasers,fibre optics and diverse types of CCD cameras.The fifth chapter, by Mikael Sjödahl, is dedicated to digital specklephotography with special emphasis on the measurement of speckledisplacements by numerical correlation and on the influence of digitalsampling over the error sources.Finally, in the last chapter, Giancarlo Pedrini and Hans Tizianipresent an introduction to what is nowadays the most fashionabletechnique in the DSPI bunch: digital holographicinterferometry. The fundamentals and variants (quasi-Fourier,Fresnel and image-plane) of digital recording and reconstructionof holograms are described, as well as their application to themeasurement of displacements, shapes and phase objects.From my point of view, this book keeps a good balance between theoreticaland formal aspects and those more applied or technical. It will be anexcellent guide for newcomers to the field of DSPI - either scientists,engineers or postgraduate students - as well as a valuable source ofreference for those already involved in the development or application ofthese rapidly evolving techniques.Ángel F Doval