or more sources of light each source covering a different frequency range e g visible and infra red or infra red and ultra violet etc and the imaging device 325 c includes two or more imaging devices one sensitive to one frequency range and the other sensitive to another frequency range in one embodiment illustrated in fig6 the light source 325 a consists of two sources of light and the imaging device 325 c is as discussed with respect to fig5 in the embodiment shown in fig6 the light source 325 a is on the same side of the analysis section channel 305 and the light reflects off a mirrored surface that is either part of a wall of the analysis section channel 305 or is separate from and outside the analysis section channel 305 in one embodiment illustrated in fig7 the light source 325 a includes two sources of light and the imaging device 325 c consists of two imaging devices as discussed with respect to fig5 and two optical masks 705 710 are present in one embodiment shown in fig8 light pipes 805 810 carry light from the analysis section channel 305 to the imaging device 325 c in one embodiment shown in fig9 the imaging device 325 c includes a large number only four are shown of imaging devices and a large number only three are shown of light pipes 805 810 815 to convey light from the analysis section channel 305 to the imaging device 325 c in another arrangement for collecting images illustrated in fig1 parabolic reflecting mirrors 1005 and 1010 collect the light from the light source 325 a and direct it to the imaging device 325 c the parabolic reflecting mirrors 1005 and 1010 are designed so that each compensates for the.