Both Fujifilm XQ2 and Olympus TG-630 iHS have 12.0 MP resolution sensors but Fujifilm XQ2's sensor is 2/3' (8.8 x 6.6 mm ) and Olympus TG-630 iHS's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Fujifilm XQ2's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Olympus TG-630 iHS.
Below you can see the XQ2 and TG-630 iHS sensor size comparison.
As seen above, Fujifilm XQ2 has a 2.1x Larger sensor area than Olympus TG-630 iHS. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.