Patent GB-1355327-A (GB)
Title: Missile steering device
IPC: F41G7/22
Filed: 1962-08-22
Abstract: 1355327 Missile tracking PLUGGERATEWERK BODENSEE GmbH 22 Aug 1962 4582/65 Divided out of 1,355,326 Heading H4D [Also in Divisions G3 and F3] A missile target seeker includes a target area  scanner and means for aligning the seeker on to the target, the sensitivity of the scanner gradually increasing with decreasing off-target position and then decreasing rapidly from a maximum. Thus once the seeker has become aligned with the target it will not be disturbed by another target displaced from the centre of the scanner. Further, should there be initially a number of identical targets the seeker will align itself with that target nearest to the centre of the scanner. As shown, a target seeker mounted in a missile comprises a gyro rotor 514 supported for rotation on a sleeve 521 by bearings 528 and pivotally supported on the sleeve about two axes mutually at right angles by inner and outer gimbal frames 538, 534. A magnet 522 on the rotor coacts with a coil 548, signals supplied to the latter enabling the gyro to be processed to align the seeker with a target T. Radiation from the target T impinges on a concave mirror . 506 fixed to the rotor 514 and is reflected by a plane mirror 508 also fixed to the rotor on to a chopper disc 516 rotating with the rotor. From the chopper disc the radiation passes through an infra-red filter 517 and impinges on a receiver 520 supported by the sleeve 521. The signals from the receiver 520 modulated by the disc 516 are applied to the coil 548. The chopper disc 516, Fig. 3, produces the variable sensitivity feature by the chequer board half-section 702 comprising light-transmitting and opaque portions. The radial dimensions of the successive chequer board rings 712 714, 716 ... &c. decrease gradually from the centre outwards and decrease rapidly through rings 710, 708 to the centre 706. Since the image of a target has a finite size the radiation will be most strongly modulated when it lies wholly within a specific ring and does not overlap adjacent rings owing to the cancelling out effect of "black" and "white". This tendency for overlapping increases with departure of the target image from the ring 712 having the greatest radial dimension. Fig. 5 shows the variation of the signal amplitudes 708A . . . 730A corresponding to the rings 708. . . 730, there being zero amplitude 706A at the centre 706 corresponding to the condition when the target seeker has been aligned with the missile so that the image falls at the centre. Maximum amplitude 712A occurs when the target image is slightly offcentre in ring 712. The tendency to overlap adjacent rings also increases with the size of the target image and hence the target seeker has a preference for small targets. Clouds do not produce any modulation since the image is so large that its affect is completely cancelled out by the transmitting and opaque portions of the disc. In a modification, Fig. 6, the gyro rotor comprises a complete instrument 400 freely supported and rotating about the axis of its casing 404, nutation damping being provided by outriggers 440 and masses 438. A chopper disc 410, as shown in Fig. 3, is fixed to the casing in the focal plane of an objective 408, modulations of the target image producing signals in a radiation receiver 412. These signals are applied to an electromagnet 428 through an amplifier and demodulator 414 to control the position of a tube 424 pivotally mounted at 426. The tube is supplied with compressed gas from a source 418 and hose 422 and supplies the gas selectively to nozzles 430, 434 connected, respectively, to oppositely facing reaction jets 432, 436 whereby the instrument 400 is processed until the target is aligned with the axis of the objective 408 and disc 410.