An apparatus for photometric measurement of biological liquids and a method of simultaneously measuring the presence or quantity of an analyte in a sample region are disclosed. The apparatus includes a plurality of spaced apart sample regions; a light source adapted to emit light including at least one frequency; a lens system including a light coupling system, wherein the light coupling system is disposed between the light source and the plurality of sample regions. A method is also disclosed including illuminating the sample region with a light beam emitted from a light source, wherein said light beam passes a light coupling system, the light coupling system including a telecentric element and a plurality of light mixing rods, wherein the light coupling system is disposed between the light source and the sample region such that the light beam is directed into the sample region.