beam splitter 17 is designed such that the fluorescence signal 15 u2032 is reflected laterally a dichroic mirror is preferably used as the beam splitter 17 and will transmit the excitation light while reflecting the emitted longer wavelength fluorescence signal the reflected fluorescence signal 15 u2032 is then sensed by a detector 18 the detector 18 is fitted with an optical device 19 that can reproduce the fluorescence signal 15 u2032 onto a light sensitive sensor 27 in lieu of the typical large area lens element the collimator in the optical device 19 is an array of optic fibers 20 the optical fiber array catches the light from the wells 12 reflected by the beam splitter 17 by means of the mutually spaced light input areas 21 and harnessing optic fibers 20 so as to transmit the light through parallel harness ends at 23 contrary to a collimator composed of lens elements the collimator configuration of a bundle of optic fibers 20 offers the feature that the light exiting the bundle optic fibers at 23 is collimated more narrowly that feature is especially advantageous when for instance interference filters offering a spectral transfer function that depends on the light 39 s angle of incidence are configured subsequently.