Olympus TG-3 has a 16.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features TruePic VII processor. On the other hand, Nikon S1200pj has a 14.0MP 1/2.3" (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the TG-3 and S1200pj sensor size comparison.
Olympus TG-3 and Nikon S1200pj have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Nikon S1200pj has 14% larger pixel area (2.01µm2 vs 1.76µm2) compared to Olympus TG-3, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.