Patent DE 10 2024 138 869

In the field of medical diagnostics (in vitro diagnostics), the concentration of analytes such as proteins or DNA can be determined using time-resolved fluorescence measurement. To test different analytes simultaneously, so-called microarrays with individual test wells are used. During the measurements, the microarrays are usually illuminated by a laser, which excites an added fluorescent dye to emit light depending on the concentration of an analyte. The concentration of an analyte can be determined from the ratio of excitation light to fluorescence light.

Single-photon avalanche diodes (SPAD arrays) are suitable for measuring the fluorescence light; these allow individual photons to be detected with high temporal resolution (time-correlated single-photon counting, TCSPC). An SPAD array comprising one or more SPADs corresponds to a test field.

The excitation light is not distributed homogeneously across the entire microarray. However, the intensity of the excitation light must be known at every position on the microarray in order to enable the determination of the molar concentration of an analyte. Due to the properties of the excitation light, SPADs are not suitable for measuring it. Consequently, in the prior art, the excitation light is homogenised using complex and costly homogenisation optics.

The invention provides a cost-effective solution by eliminating the need for homogenisation and placing additional photodiodes between the individual SPAD arrays to determine the intensity of the excitation light. Through interpolation, the light can be calculated precisely for each test well. This enables targeted correction of inhomogeneity, and a large number of test wells on a given microarray can be examined and analysed accurately simultaneously.