Leica D-Lux Typ 109 has a 13.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor . On the other hand, Leica D-Lux 7 has a 17.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor .
Below you can see the D-Lux Typ 109 and D-Lux 7 sensor size comparison.
Leica D-Lux Typ 109 and Leica D-Lux 7 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 Leica D-Lux Typ 109 has 32% larger pixel area compared to Leica D-Lux 7, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.