The present invention relates generally to the field of biochemical laboratory instrumentation for different applications of measuring properties of samples on e.g. microtitration plates and corresponding sample supports. The object of the invention is achieved by providing an optical measurement instrumentation wherein a sample (281-285) is activated (212AS, 218AS) and the emission is detected (291, 292), wherein between the activation and detection phases of measuring the sample, a shift is made in the relative position between the sample and means (218) directing the activation radiation to the sample as well as in the relative position between the sample and the means (293) receiving the emission radiation from the sample. This can be implemented e.g. by moving (299) the sample assay plate and/or a measuring head between the activation and emission phases of a sample. The invention allows a simultaneous activation of a first sample and detecting emission from a second sample thus enhancing efficiency of the measurement.