Pentax WG-10 has a 14.0MP 1/2.3" (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, 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.
Below you can see the WG-10 and TG-4 sensor size comparison.
Pentax WG-10 and Olympus TG-4 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 compared to Olympus TG-4, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.