GB603321A - Target direction finding apparatus - Google Patents

Abstract

603,321. Photo-electric apparatus for direction finding. FARNSWORTH TELEVISION & RADIO CORPORATION. Oct. 22, 1945, No. 27764. Convention date, Sept. 29, 1944. [Class 40 (iii)] [Also in Group XL (a)] In a direction-finding system, light from a target is projected, with intermittent interruption, on to a photosensitive cathode in such a manner as to produce a circular trace the location of the centre of which is representative of the target direction. In Fig. 1, the photo - sensitive cathode 12 of a photocell is divided into quadrants I, II, III, IV (see also Fig. 2), contained-in an evacuated envelope 11. Light from a distant target is projected on to the cathode through a lens 25 mounted eccentrically in an otherwise opaque disc 26 (see also Fig. 3), which is rotated about an axis common to the photocell to produce a circular trace 33 (see Fig. 2), the position of the centre 34 of which is representative of target direction relative to the common axis. To discriminate between the standing currents of the photocell and those due to the target the latter are made intermittent by arranging a disc 27 containing alternate opaque and transparent sectors to rotate with disc 26 (see also Fig. 3) and fixing a similar stationary disc 30 (see also Fig. 4) on the common axis between the lens carrier and the photocell. Each cathode quadrant is associated with an electron multiplier, e.g. 13, 14, the electrode potentials of which are supplied by separate sources, e.g. 17, 18. The A.C. components of the voltages across electron multiplier load resistances, e.g. 19, 20, are applied through capacitors, e.g. 23, 24, to amplifiers, e.g. 20, 21. The relative outputs of the four amplifiers are thus dependent on target direction and are equal if the target is on the common axis. The following modifications are referred to : (a) a single supply source for the electron multiplier electrodes; (b) tuned circuits resonant at the interruption frequency in place of the resistive loads of the electron multipliers; (c) division of the photo-sensitive cathode into a number of segments other than four; (d) operation without electron multipliers ; (e) positioning of the interrupting discs between the target and the lens.