Optical measuring device for test strips

An optical measuring device for detecting the coloring of test fields of a test strip to be wetted with a liquid for detecting substances in said liquid, whereupon the reflectivity of the test fields changes depending on the concentrations of the substances to be detected, comprising:

• a measuring plane upon which said test strip is to be placed;
• an illumination device for illuminating the measuring plane and the test strip;
• a planar image sensor;
• an optical system for providing an image of the test strip onto said planar image sensor;
• an electronic evaluation unit for evaluating at least one signal generated by said planar image sensor, wherein said illumination device comprises at least two light sources of different colors to alternatively illuminate said test strip in said different colors such that said electronic evaluation unit detects the coloring of said test fields under different color illuminations;
• and
• an adjustable reference surface that is movable between a first position in which it takes on the position of a test strip during measurement and a second position in which it cannot be imaged by said optical system onto said image sensor.