Optical interrogation device

An interrogation device for detecting luminescent light produced by analytes in a sample excited by multiple excitation light beams each having individual spectral contents, comprising:

• a plurality of light sources each generating one of said multiple excitation light beams, the excitation light beams being projected on the sample to excite the analytes;
• at least one detector for detecting the luminescent light produced by the sample;
• and
• an optical assembly defining distinct and fixed excitation light paths for each of the excitation light beams from the light sources to a common excitation site on the sample and defining a shared luminescence light path for the luminescent light from the excitation site on sample to the at least one detector, said excitation light paths and said luminescence light path being on a same side of said sample, said optical assembly including sample-side optics projecting the excitation light towards the sample and collecting luminescent light from said sample, said optical assembly providing said sample-side optics in all of said excitation light paths and in said shared luminescence light path.