29 of the configuration illustrated in fig5 b the 100 u03bcm thick polyimide foil is provided on one side with an aluminium foil 1 u03bcm thick and is cut into strips which form the electrodes 27 a pressure roller 30 presses the strips between the apertures 31 of the metal plate 29 which is covered with a polyamide solution it is alternatively possible to provide the polyamide solution on the strips 27 in this manner the strip 36 having lens electrodes is obtained of the configuration illustrated in fig5 c the strip 36 is guided with the aid of guide rolls 32 through a high frequency furnace 33 in which the polyamide is converted into polyimide after leaving the furnace a knife 34 cuts the strip 36 into plates 35 the plates possibly after a drawing process in which they are drawn in a curved shape constitute the color selection means 7 it is also possible first to cut the electrode assembly 36 into plates 35 and then treat them in a furnace the parallel electrodes 27 in each plate 35 are connected together electrically by a connection strip not shown the connection of the supports between the apertures 31 in the.