GB1002809A - Improvements in and relating to devices for modulating electromagnetic wave energy - Google Patents

Abstract

A device for electrically controlling or modulating electromagnetic wave energy at or near the visible spectrum wave lengths comprises a cell holding electrolyte having a boundary wall, which will allow the passage of said energy therethrough and of which wall an inner surface portion is electrically conductive, electro chemically stable to electrolyte and electrically accessible from outside the cell so that it can receive an electroplated deposit, whereby to inhibit the said passage of said energy, said electrolyte comprising a substance itself adapted chemically to remove the elctroplated deposit. Silver bromide dissolved in a solution of lithium bromide and silver iodide dissolved in a solution <PICT:1002809/C6-C7/1> <PICT:1002809/C6-C7/2> of sodium iodide are referred to as suitable electrolytes. It is stated that oxygen should be added by aerating the electrolyte. Reference is also made (without giving details) to electrolytes based on sodium, copper and tin. One construction of device is illustrated in Figs. 9 and 11 where glass or plastic plates 71 and 72 are spaced by a gasket 73 to form a suitable container for electrolyte 70. The inner faces of the plates carry conductive transparent layers 75 and 76 of a metal oxide, e.g. tin oxide. Connection to the layers is made by wires 78, 80 carried in grooves in the plates. The conductive layers extend into the grooves as shown in Fig. 12 and are held in contact with the wires by conductive paint 83. The grooves are closed by synthetic strips 84. The grooves in plate 71 are staggered in relation to those in plate 72. A metal film 88 is plated on to layer 75 by charging a capacitor 92 from battery 91 and then discharging the capacitor through the cell by appropriate operation of switches 74. The film is maintained against the self-erasing action of the electrolyte by battery 94 until switches 74 are returned to the left-hand side. Film 88 causes an impinging beam of radiation 86, which normally pases through the device, to be absorbed and/or reflected as shown at 89. Other constructions are described with reference to Figs. 3-6 (not shown). In these constructions the control circuit is arranged to provide a reverse current to aid the chemical erasing process.