Electronic Speckle Pattern Interferometry techniques for non-destructive evaluation: a review

Age-Related Differences in the Elasticity of the Human Cornea

“…Optical interferometric techniques are well suited to measuring corneal biomechanical properties because they are noncontact, highly sensitive, and capable of simultaneously recording information from across the whole test surface. 14,15 Holographic interferometry (HI) has been used to qualitatively assess keratoplasty wound integrity in vivo 16 and to quantitatively investigate the effect of radial keratotomy incisions in the laboratory. 17 Our group has described how electronic speckle pattern interferometry (ESPI) can be used to quantify the effect of microkeratome flap creation on the displacement response of the sheep cornea.…”

“…The differential magnification between the two images allows a mathematical analysis that detects changes in radial strain. 15 The purpose of this study was to develop a RSSP interferometer for corneal measurement and to use the device to determine the biomechanical properties of the human cornea as a function of age.…”

Application of ESPI for the NDE of low-modulus materials using mechanical loading

“…The phase change δ due to the surface displacement of the specimen is given as [18] : where w and u are displacement components in the Z and X direction and θ the angle of illumination. The equation (1) gives both in-plane and out-of-plane displacement components.…”

“…ESPI permits measurement of deformations in the micrometer and sub-micrometer range, which are caused by very small stress applied to the specimen under test. This technique is most suited since it offers real-time inspection for quality assurance and is less affected by rigid body motion [18] .…”

Path independent demodulation method for single image interferograms with closed fringes within the function space C2

“…Applications of optical interferometry in areas such as digital contouring or strain analysis in mechanics are very important because they are non-invasive techniques and gives full field measurements [1]. For example, the electronic speckle pattern interferometry technique (ESPI), is widely used in this areas [2].…”