ESPI ― The ultimate holographic tool for vibration analysis?

Holographic interferometry opened new worlds of research by making possible accurate, global mapping of small dynamic surface displacements in a two-step process. A technique, called Electronic Speckle Pattern Interferometry or ESPI, has been developed in various forms to provide similar results instantly. ESPI’s principal capabilities, and some practical applications in industry, biomedicine, and acoustical research are described in an overview in the hope of encouraging its use by researchers who were deterred by the relatively cumbersome process of holography. In various forms, ESPI is shown to be capable of measuring phase and amplitude of dynamic displacements between 0.01 nm and 10 μm over an area of up to 1 m2.