Measuring the perceived resolution of a lens is a much more complicated and subtle thing than a single number. David linked to various sites explaining MTF (modulation transfer frequency) because that is the best empirical measurement system we have, and the one lens manufacturers use when publishing specifications on their lenses. It factors in both resolution and contrast, as well as centre versus edge performance. There are even different graphs for sagittal and meridional MTF, because lenses often resolve a line that radiates out from the centre of the image differently to one that circles around the centre.
As a starting point, this webpage is a short but decent example of trying to extrapolate meaning from a test chart like yours using line pairs/mm and MTF:
It's worth remembering that this kind of test is actually measuring the 'system' resolution of the camera/lens combination.