sample by means of an excitation lens 72 any reflected stray laser light having the excitation wavelength is reflected again by the dichroic mirror or beam splitter 70 whereas the fluorescence luminance is passed through the mirror beam splitter 70 to the detector 22 a band pass filter can provide further filtering for rejection of the excitation light and the filtered light is focused on the detector 22 by an imaging lens 74 which images the sample onto the detector 22 the read out can be implemented in a quasi confocal mode by introducing a pinhole in the focal point of the collecting lens in the read out path or using the pixelated detector as a quasi pinhole to suppress luminance from other parts outside the binding array however no pinhole arrangement is required when an evanescent field is present only at an excitation spot the examples above have fixed magnetic and optical components and the magnetic and optical functions are performed with the same cartridge position in an arrangement shown in fig7 the coaxial arrangement of magnetic and optical elements replaced with a parallel arrangement with the advantage of having a better imaging quality the arrangement of fig7 has an actuated sledge 80 containing the magnet arrangement 82 and the imaging and detection optics 18 22 next to each other fig7 a shows the device in side view and top view fig7 b shows the two positions of the sledge 80 the top part of.