Olympus TG-4 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, Pentax WG-10 has a 14.0MP 1/2.3" (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the TG-4 and WG-10 sensor size comparison.
Olympus TG-4 and Pentax WG-10 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 Pentax WG-10 has 15% larger pixel area (2.04µm2 vs 1.76µm2) compared to Olympus TG-4, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.