out under total reflection application_number US 45349099 A description referring now to fig1 to 3 it is initially seen that fig1 is a schematic diagram of an apparatus for spectroscopic analysis of fluid mediums according to the invention it shows the specific case of an atr probe where measurement is carried out polarization independently at two different angles of incidence light from a lamp 11 is coupled into a first optical fiber 12 which in a y branch 13 diverges into two optical fibers 14 15 for the incident first and second light beams respectively the optical fibers are guided into a probe 16 which in the illustrated example is configured as a dip probe and is equipped at one end with an atr prism 17 at whose boundary 18 with the medium 19 the two light beams are totally reflected at different angles the atr probe 16 is illustrated in fig1 and 2 in section along the plane of incidence of the first light beam the plane of incidence of the second beam is essentially perpendicular to the plane of incidence of the first beam the reflected beams pass via optical fibers 20 21 to a spectrometer 22 which includes two diode arrays not depicted which record the spectra produced at a grating likewise not depicted a further optical fiber 23 leads directly from the lamp 11 to the spectrometer 12 where the spectral intensity distribution of the light source 11 is recorded via a third diode array likewise not depicted the amplified signals from the diode arrays in the present example are read out via a multiplexer and processed by a personal computer 24 fig2 illustrates a sectional view of the upper part 25 and the lower part.