, Volume 28, Issue 4, pp 329-335

The influence of grating characteristics on moiré fringe multiplication

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Coherent optical techniques of fringe multiplication can be used to enhance the sensitivity of moiré measurements. However, for some coherent optical-processing systems, the significance of the resulting interference pattern is influenced by the characteristics of the gratings being processed. Analysis of one commonly used system for fringe multiplication involving two bar and space amplitude gratings reveals that accuracy of displacements and strains calculated from a fringe pattern is very sensitive to the transmission ratios of the gratings being processed. For variations of the transmission ratio of only 10 percent from the ideal case of 50 percent, the interference patterns produced by optical processing no longer correspond to multiplied moiré-fringe patterns.

Subscriptst andi refer to transmitted and incident respectively. Symbol * is used to represent convolution. Symbol ⋌ is used to represent the multiplicative inverse of the quantity under the symbol.
Paper was presented at the 1986 SEM Spring Conference on Experimental Mechanics held in New Orleans, LA on June 8–13.