Patent GB-839558-A (GB)
Title: A system for displaying the position of a craft
IPC: G01S1/02
Filed: 1956-09-20
Abstract: 839,558. Course recorders. STANDARD TELEPHONES & CABLES Ltd. (International Telephone & Telegraph Corporation). Sept. 20, 1956, No. 28743/56. Class 97(2) [Also in Group XL(c)] A system for displaying the position of a craft comprises means for producing optical representations of the craft and of a map, with relative movement controlled by a navigation system, and means, such as a television link, including a light sensitive screen and a display device, for reproducing the combined representation. The optical system shown in Fig. 2 comprises a lamp 52, reflector 54 and condenser lenses 50, 51, the latter carrying an aircraft silhouette and being rotatable by a compass operated servomotor 56. An image of the silhouette is projected by the objective 53 on to the film 58 by reflection from a mirror 59, the film carrying a sequence of map images 58a &c. A field lens 57 in front of the film images the objective 53 on the objective 61 which images the film on the television camera tube 63. the light beam being reflected from a mirror 60. A Dove prism 62 rotated at half the speed of the condenser 51 maintains the final image with the aircraft silhouette vertical. A scale change in the final image is produced by exchanging the objective 61 for another 66 or by conjugated movements of the objective and camera tube. The silhouette image is moved on the film in the X direction by pivoting the mirror 59 and in the Y direction by vertical movement of the objective 53, the necessary drives to the shafts 92c, 93c being produced by the computer shown in Fig. 3. In the computer shown the "X" and "Y" input voltages represent rates of movement in the co-ordinate directions and are fed to the Mercator step attenuators 80, 81 which reduce the voltages in proportions depending on the latitude in use. The resulting voltages are balanced against the voltage outputs of generators 84, 85 to produce inputs to the amplifiers 82, 83 feeding the servo-motors 86, 87 driving the generators. The servo-motor systems thus act as velodynes running at rates proportional to the input voltages and so integrating the input data. The X and Y servomotors drive differentials 90, 91, the outputs from which drive the shafts 92c, 93c which feed the X and Y movements to the optical system. When the movement has been such that the silhouette image reaches say a side margin of the map in use, a cam driven from the appropriate servo-system closes the "right" or "left limit switch". This energizes the "right" or "left" relay 103R or 103S from a D.C. source and causes and energizes the "single frame transport motor" which is also energized from a "quadrature phase source" and runs in a direction depending on which relay was energized. The "single frame indexing cam" closes a switch 107 which holds the relay closed until the motor has run to feed one film frame. As the motor runs it drives into the differential 90 to turn the shaft 92c to position the aircraft silhouette in the opposite margin of the new map. The film carries a sequence of say 25 maps forming an E-W strip followed by 25 forming an adjacent strip. Therefore, to move from any map to an adjacent map to the North or South, it is necessary to feed the film 25 frames. This is done when the extent of the Y movement produced by the Y servo is such as to close the "top" or "bottom limit switch" and close the relay 102R or 102S and energize the "frame transport motor" Which then runs, the relay being held on by switches 106, 110 until the necessary number of frames has been fed. The motor also drives the differential 91 through reduction gearing 112 to rotate the shaft 93c to reset the silhouette to the opposite margin of the new map. The drives from the two film feed motors are joined in a differential 108. A steering control, not shown, is provided to permit the aircraft silhouette to be aligned initially with a selected point. The map required initially may be selected manually using switches 114, 115, 116, 117. Friction clutches 92, 93 prevent possible damage during these operations. Friction clutches 162, 163 prevent possible damage during map changing.