GB1426011A - Photoresistive arrangements - Google Patents

Abstract

1426011 Photo-conductive devices; variable resistors INSTITUT POLYPROVODNIKOV AKADEMII NAUK UKRAINSKOI SSR 10 Jan 1973 1332/73 Headings H1K and HIS [Also in Division G1] A photo-responsive device, e.g. for use as a contactless theostat or potentiometer comprises a pair of series connected photoconductive regions and a light beam different parts of which illuminate respective parts of the two regions. In the Fig. 1 arrangement, disposed on insulating substrate 1, the illuminated parts 8 of photoconductive layers 4, 7 provide a path from earth to a tapping point on resistive layer 2 connected as a potentiometer across the supply voltage. Thus the voltage developed across layer 7 acting as load resistor is linearly related to the beam position but independent of temperature and probe width and intensity. In the Fig. 2 arrangement electrode 12 is effectively a tapping fixed in relation to one end of a potentiometer the length of which, represented by the part of the illuminated portion of photo-conductive layer 9 between electrodes 11 and 13, varies. Output voltage is again a function of beam position but independent of temperature and probe characteristics. Similar considerations apply in Fig. 3 where constant and varying width portions of photo-conductive layer 18 underlying transparent electrodes 19, 20 exposed to the light beam via transparent sections 23 of mask 22 define the potentiometer. In another arrangement (Fig. 4, not shown) comprising an elongate fixed beam aligned with a corresponding elongate photo-conductive layer, an interposed opaque mask movable normal to the beam has two transparent sections one of varying width traversing a part of the layer disposed between a distributed resistance layer and a first electrode and the other, of constant width, traversing a part defined between the first and further electrode.