Patent GB-634143-A (GB)
Title: Improvements in radio location systems
IPC: G01S7/20
Filed: 1945-06-01
Abstract: 634,143. Cathode ray oscillographs. WESTERN ELECTRIC CO., Inc. June 1, 1945, No. 13870. Convention date, April 1, 1944. [Class 37] [Also in Group XL (c)] In a radiolocation system having a twodimensional scanning arrangement azimuth and elevation data are displayed on each of two cathode-ray tubes and the azimuth scanning means of the tubes are differentially biassed to an extent depending on the distance away of the object presented so that when the displays are viewed each by a corresponding eye of an observer an illusion of depth is created. According to another aspect of the invention, the azimuth and elevation data are presented on a single cathode-ray oscillograph as before and the range information used to bias the deflecting means so that the representation of a distant object is displaced by an amount inversely related to the distance of the object whereby the apparent viewpoint is changed from that of the oscillograph itself. The two aspects of the invention may be combined in one apparatus. A pulse radar transmitter 2 and receiver 4 (Fig. 1) have an antenna 1 scanning in azimuth and elevation, the horizontal and vertical sweep voltages of cathoderay tubes 8, 8a are provided by generator 6 synchronized over circuits 11, 10 from the antenna scanning means. Received impulses are used to modulate the cathode ray to present type " C " displays. A pulse synchronizing voltage derived from that portion of the transmitted pulse leaking past T.R. box 3 is applied to range sweep circuit 18; this consists of a condenser C1 (Fig. 2) charged to the pulse voltage through diode 22 and whose charge leaks away exponentially through resistor R1. The voltage across R1 is applied in push-pull through mixer circuit 16 to the horizontal deflection plates. The effect of this range sweep voltage is to cause the indication of nearby objects to be moved to the right on the left-hand tube and to the left on the righthand tube whereas objects further away are moved very little owing to the decay in the voltage across R1. The distorted displays when viewed through eyepieces 21 of stereoscopic optical system 20 thus give the illusion of depth. It is stated that the exponential decay provided is an adequate substitute in practice to the hyperbolic decay theoretically required. In order to provide a means of measuring range, a scale may be marked on the screen or artificial impulses at predetermined time intervals introduced into the system. The synchronizing pulse voltage may be subjected to an adjustable delay, Fig. 3 (not shown), which .has the effect of moving the apparent viewpoint nearer the objects observed; the magnitude of this voltage may also be adjusted to change the apparent depth of the picture. An arrangement in which the apparent viewpoint may be displaced horizontally or vertically or both is described for a single oscilloscope display with reference to Fig. 4 (not shown) and for a stereoscopic system with reference to Fig. 5. In this embodiment common D.C. supply voltage is provided for the sweep circuits and is applied, together with the range sweep voltage, across potentiometers 25 and 26 and the taps A are moved in synchronism with the aerial scan to provide the normal. sweep. Potentiometer 27 gives a displacement of apparent viewpoint, by varying the taps thereon the position on the screen from which the range sweep voltage appears to spread the images is controlled. This is due to the relatively long time constants of the resistance capacitance networks producing a component of the range voltage across the potentiometer. In the horizontal deflection circuit potentiometers 30 and 31 jointly provide an exactly similar effect to that of potentiometer 27, centre-tapped resistor 33 merely being introduced to provide a D.C. path. Rheostat 34 causes a variable difference in the horizontal displacement voltages applied to the two tubes so that when these are viewed with a stereoscopic optical system an illusion of depth is obtained. Specification 616,520, [Group XL (c)], is referred to.