Optical device for quantitative determination of the concentration of an analyte in a liquid sample comprising a mask member between first and second chambers

An optical device for the quantitative determination of the concentration of an analyte in a liquid sample, the liquid sample provided in one or more assay devices, each comprising a lateral flow membrane, the one or more assay devices providing a plurality of test regions for retaining tagging particles in the plurality of test regions in dependence on the concentration of the analyte in the liquid sample, the optical device comprising:

• a housing defining a first chamber and a second chamber;
• a sample port defined in the first chamber, the sample port for receiving light from the plurality of test regions of the assay device(s) when the optical device is engaged with the assay device(s);
• a plurality of optical detectors provided in the second chamber;
• and
• a mask member interposed between the first chamber and the second chamber and having an aperture defined therein configured to direct light from the sample port onto the optical detectors.