Figure 2. OIRD images of a sandstone core in which a random region was scanned by OIRD.
(a) 2-D image of Re{Δp − Δs} of sandstone. No striation was observed. In most areas, the signal intensities were uniform; in addition, several peak points existed, but they were not connected. (b) 2-D image of Im{Δp − Δs} of sandstone. No striation was observed. In most areas, the signal intensities were uniform; in addition, several peak points existed, but they were not connected. (c) 3-D images of Re{Δp − Δs} and Im{Δp − Δs} of six selected regions with areas of 100 μm × 100 μm. Areas No. 1, 2 and 3 are shown in (a), and No. 4, 5 and 6 are shown in (b). The information gathered by this technique indicated the surface properties of the sandstone.