<title>Electronic system for real-time display and quantitative analysis of hologram interference fringes</title>

Abstract

A system has been developed for display in real-time of dynamic and static holographic interference fringes and for quantitative data output. Although the optics are similar to a conventional Electronic Speckle Pattern Interferometer (ESPI), a 90° phase shift is introduced between the reference and object beams after each TV frame. A pipeline image processor subtracts alternate frames and processes pairs of these results to obtain the square root of the sum of their squares. A true holographic image results whose speckles correspond only to image speckles on the original object. Dynamic displacements, such as vibration, are displayed in real-time Jo fringes. Static displacements are displayed as cosine fringes obtained by adding four current TV frames to four stored frames. Provision is made for speckle averaging by changing the object illumination. Image data fields can be transferred to the host computer for displacement analysis.A system has been developed for display in real-time of dynamic and static holographic interference fringes and for quantitative data output. Although the optics are similar to a conventional Electronic Speckle Pattern Interferometer (ESPI), a 90° phase shift is introduced between the reference and object beams after each TV frame. A pipeline image processor subtracts alternate frames and processes pairs of these results to obtain the square root of the sum of their squares. A true holographic image results whose speckles correspond only to image speckles on the original object. Dynamic displacements, such as vibration, are displayed in real-time Jo fringes. Static displacements are displayed as cosine fringes obtained by adding four current TV frames to four stored frames. Provision is made for speckle averaging by changing the object illumination. Image data fields can be transferred to the host computer for displacement analysis.