Deformation and shape measurement using multiple wavelength microscopic TV holography

Abstract

Characterization of deformation and surface shape is an important parameter in quality testing of micro-objects in view of the functionality, reliability, and integrity of the components. Single-wavelength TV holography is widely used for deformation analysis. However, the single-wavelength TV holographic configuration suffers from overcrowding of fringes for large deformation that sets a limitation due to speckle decorrelation for quantitative fringe analysis. Furthermore, shape cannot be determined when using single wavelength. In this paper, we describe a multiple-wavelength microscopic TV holographic configuration that uses sequentially recorded phase-shifted frames at three different wavelengths before and after deformation of the specimen for evaluation of relatively large deformation fields at the effective wavelengths. Use of multiple wavelengths for deformation and shape evaluation is discussed. The design of the system along with the experimental results on smallscale rough specimens under static load is presented.

Red-Green-Blue wavelength interferometry and TV holography for surface metrology

“…Using the 8-phase step algorithm [15,16], the phase distribution can be written in terms of arctan function as…”

“…Two wavelength electronic speckle pattern interferoemty (ESPI) [14], and multiple wavelength techniques for deformation and shape measurement [15] have been used to overcome these problems. Multiple wavelength techniques can be applied in (a) sequential [13][14][15], or (b) simultaneous [12] mode of operation. Regular single-chip monochromatic CCD cameras can be used for sequential illumination method.…”

“…The same motion of the PZT introduces a phase-step miscalibration at the other wavelengths. Almost perfect compensation can be obtained by the use of the 8-step algorithm [15,16]. LABVIEW based programs suitable for colour CCD camera have been developed for visualization of fringes and storing the phase shifted frames.…”

“…The colour RGB interferograms are decomposed into its monochromatic components. An 8-step phase shifting algorithm which is suitable for RGB wavelength analysis is used for phase evaluation at individual wavelengths [13,15]. A fringe order method which can provide the resolution of phase shifting interferometry is used for surface profiling on an etched silicon sample with microstructures.…”

Use of two wavelengths in microscopic TV holography for nondestructive testing

“…[9][10][11][12][13] In this method, deformation phases measured at two different wavelengths (λ 1 and λ 2 ) are subtracted to generate a phase at an effective wavelength. Single wavelength TV holography is a widely used whole-field noncontacting optical method for nondestructive testing (NDT) of engineering structures.…”