Nikon L31 has a
16.0MP 1/2.3' (6.17 x 4.55 mm ) sized CMOS sensor . On the other hand, Olympus VR-320 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features TruePic III processor.
Below you can see the L31 and VR-320 sensor size comparison.
Nikon L31 and Olympus VR-320 have the same 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 Olympus VR-320 has 15% larger pixel area (2.04µm2 vs 1.76µm2) compared to Nikon L31, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.