GB375639A - Improvements in or relating to photo-electric cells - Google Patents

Abstract

375,639. Photo-electric cells. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven, Holland. Oct. 1, 1931, No. 27341. Convention date, Oct. 1, 1930. [Class 39 (i).] In a photo-electric cell, particularly for photography, having a photo-electric electrode and an electrode consisting at least in part of a fluorescent substance, a screen, arranged between the electrodes, allows the passage of electrons but not of fluorescent rays. As shown in Fig. 1, the cathode 5 consists of an alkali metal such as caesium deposited on a thin transparent layer 4 of calcium fluoride. The anode 8 consists of a fluorescent substance such as zinc sulphide, willemite (zinc silicate), scheelite (calcium tungstate), or barium platinocyanide applied to a layer 7 of metal such as platinum, transparent to fluorescent rays, for example by evaporation in a vacuum ; the conductivity of the layer may be improved by the inclusion of conducting particles. The screen 10 consists of a sheet of black paper in a metal frame. In the cell shown in Fig. 2, the screen 16 consists of a thin metal plate which may be connected by a switch 19 so that a positive or negative potential may be applied to the screen in order to accelerate or retard the passage of electrons. A shaft 23, carrying a drum for a film 22, is provided with lugs 24 engaging with a lever 25 to operate the switch 19 at intervals, so as to apply a positive potential to the screen during the periods when the film is exposed to the fluorescent rays, and a negative potential for other periods. Specifications 326,200, [Class 39 (i), Electric lamps, Arc &c.], and 366,883 also are referred to.