Citation:
Ian A. Bledowski, Thomas O. H. Charrett, Daniel Francis, Stephen W. James, and Ralph P. Tatam, Frequency-division multiplexing for multicomponent shearography, Applied Optics, 2013, Volume 52, Issue 3, Pages 350-358.
Abstract:
A new method of multiplexing the speckle patterns needed in multicomponent digital shearography systems is presented. Frequency-division multiplexing (FDM) of the measurement channels is achieved by recording speckle patterns from objects illuminated by intensity-modulated sources. Each source is modulated at a discrete frequency, which is less than half of the camera frame rate, and a bank of images of the modulated speckle patterns is captured. This allows for pixel-by-pixel Fourier-based extraction of the individual speckle patterns from peaks in the power spectra. The approach is demonstrated with a two-component in-plane shearography instrument.