An apparatus for detecting labeled beads is provided. The apparatus can include: one or more irradiation sources disposed for irradiating the one or more detection zones with radiation; at least one detector disposed for collecting charges corresponding to light signals emitted from labeled beads in the one or more detection zones, which have been excited by the radiation; and a system coupled to the at least one detector for effecting time delay integration of the charges by accumulating the charges before reading the charges at the output of the at least one detector.