LED die-on-chip integration for fluorescence-detection applications

Conventional fluorescence-detection systems typically involve a separate laser excitation source shining directly down towards the photodetectors, with the fluorescent sample in-between. A major issue with such systems is the strong excitation light signal that can saturate detection circuitry and/or make detection of the fluorescent signal difficult, even with optical filtering. A fluorescence-detection system is described consisting of light emitting diode dies bonded on top of a CMOS imaging chip. Such a system facilitates a high level of integration while potentially reducing the excitation light hitting the photodetectors. Model results are used to predict the shape of the imager response to excitation light. Experimental results confirm the validity of the model.