Wavelet-Based Terahertz Coherent Local Tomography

In the previous chapter we explored wavelet-based coherent tomography, and in this chapter we now build on this approach to specifically perform local tomography. With traditional CT techniques such as X-ray tomography, full exposure data are needed for use in the IRT to produce cross-sectional images. This remains true even if the ROI is a small subset of an entire image. For time-domain terahertz measurements, the requirement for full exposure data is impractical due to the slow measurement process. Here, we apply a wavelet-based algorithmto reconstruct THz CT images with a significant reduction in the required measurements when the ROI is small. Instead of inverting the Radon transform, the approach uses modified wavelet and scaling ramp filters along with the traditional back-projection algorithm to obtain the resultant reconstruction.