Optics and Lasers in Engineering 8 (1988) 109-121 Use of High Resolution Real-time Image Processing Techniques in Generation and Analysis of ESPI Fringe Patterns D. Kerr and J. Tyrer Loughborough University of Technology, Loughborough, Leicestershire, UK (Received 19 January 1987; revised version received 8 July 1987; accepted 10 July 1987) ABSTRACT A high resolution (1024 × 1024) image processing system has been employed in the analysis of ESPI fringe patterns. This machine utilises real-time, high bandwidth digitisation and recursive video techniques to produce high quality surface displacement fringes requiring a minimum of enhancement. Operational parameters of the system are discussed and a basic processing methodology is outlined. A flexible set of software algo- rithms has been developed and results from typical image fields are presented. A technique of phase stepping has been evaluated and the effects of reduced modulation and signal-to-noise ratio on the resulting phase difference maps are examined. 1 INTRODUCTION Electronic Speckle Pattern Interferometry (ESPI) is by now a well documented and established technique in the field of engineering surface metrology. 1'2 Akin to holographic interferometry, ESPI is a very powerful whole-field surface displacement measurement technique which is finding application within the engineering industry in a variety of areas ranging from quality assurance through NDT to research and development. One major constraint which is at present preventing a more widespread industrial application of this technique is the inherent 109 Optics and Lasers in Engineering 0143-8166/88/$03-50 © Elsevier Applied Science Publishers Ltd, England, 1988. Printed in Northern Ireland