Fig. 5.

(a) Side-view photograph of the test object showing the embedded square silicone-TiO₂ test object. THz and OCT were incident on the top surface. (b) B-scan from the OCT image of the test object, showing a scattered signal from the top surface of the test object and increased scatter from the embedded square. (c) B-scan THz image showing reflections from the top surface of the test object, the top surface of the embedded square, and the bottom surface of the test object. (d) The co-registered overlay of the THz and OCT images showing the agreement between the two imaging methods, where the OCT image is in ‘hot’ colourmap for contrast.