which fails on the filter 138 passes to the polarizer 140 and the control 142 is adjusted to pass the maximum intensity of light for rotating its plane of polarization the lens 144 focuses the light onto a single detector 146 and its output is applied to band pass amplifiers 148 150 152 154 156 158 160 and 162 that are respectively tuned to pass one of the frequencies of equation 9 such as those shown in case a infra furthermore the gains of the amplifiers 148 162 are adjusted so that all the mueller matrix elements are normalized and bound between 1 and 1 the amplifiers 148 162 are respectively coupled via ad 39 s 148 39 162 39 to a processor 164 for each of the cases a b c and d the eight frequencies are assigned to different mueller coefficients u03c844 u03c843 u03c842 u03c841 u03c844 u03c834 u03c833 u03c832 u03c831 u03c824 u03c823 u03c822 u03c821 u03c814 u03c813 and u03c812 which respectively can have values of 1 1 or 0 by setting up the axial rotation of the polarizers 54 and 30 and the pem 39 s 48 and 36 as required by each of the cases a b c and d the outputs of the a d 39 s 148 39 162 39 for each case can be determined i e each of the cases have a known pattern of 1 39 s 1 39 s and 0 39 s a processor 164 recognizes these patterns and outputs a different signal for each that can be displayed on a display 166 thus in order to send a message the controller 61 of.