A receiver

Abstract: An optical receiver is divided into two receiver portions (5, 6). Each respective receiver portion is operative to receive an associated strobe (3, 4, respectively) or group of strobes. The receiver units are connected to an electric signal initiation circuit (5'', 6''; B) which, in response to reception by the receivers of each respective strobe, generates signals, for instance pulses (P1, P2) representative of each respective receiver unit. With the assistance of such signals, sensing means (7, 8) indicate that one of the receiver units which, on the actual occasion, is activated by the strobe (3, 4) in question.

Description: TECHNICAL FIELD The present invention relates to an optical receiver adapted for mounting in a unit, having an elongate shape, with a central axis of symmetry, such as a missile, projectile or the like. When operating, the receiver receives two or more optical strobes reflected from a target object, which optical strobes are incident at mutually different angles of incidence on the unit. The receiver comprises first and second receiver sections mounted at respective locations on the unit, which said receiver sections operate cooperatively, and receive respectively the optical strobes incident thereon. Each said first and second receiver sections comprises an electrical signal initiation circuit including photodetection means, each said signal initiation circuit generating and outputting a respective electric signal in response to reception therein of incident optical strobes, a first photodetection means receiving optical strobes incident on said first receiver section , and a second photodetection means receiving optical strobes incident on said second receiver section, said electrical signals occurring at mutually displaced times, due to the different mounting locations of the receiver sections with respect to the incident strobes. The optical receiver further including sensing means which senses said electrical signals and produces an indication signal which indicates reception by a receiver section of an optical strobe. BACKGROUND ART An optical receiver according to the above is known from US-A-4 015 530 in which two optical channels are included in a fuzing system. The two channels, one forward looking channel and one rearward looking channel, involve a receiver operation. The fuzing system will only be activated if the forward looking channel detects a target and the rearward looking channel sees the same target in a specific time interval. In such a system a target may be detected but the direction to the target is not determinable from the channel information. In the receiver operation the infrared energy radiated by an enemy target is detected by the fuzing system. Receivers according to the preamble may also form part of so-called proximity fuses of the type which emits electromagnetic radiation in the form of narrow lobes and receives lobes reflected on the target on which the unit is homing for the purpose of realizing target detection for control of functions within the unit. Proximity fuses are well known in this art and it is also well known in the art to cause the proximity fuse to operate with narrow part lobes which together cover the entire circumference of the unit such that all-round sensing may be effected. It is further previously known in this art to signal process a received signal in the proximity fuse from each part lobe individually. The division of emitted energy into narrow part lobes and individual signal processing of the part lobe signals affords advantages in that the so-called return dispersion may be kept to a minimum despite the desired high level of emission power. In associated types of receivers, there is a need to increase the level of tolerance in respect of return dispersion in relation to prior-art performance. Moreover, wishes have been expressed within the art that the equipment as such must be able to operate with relatively few components. OBJECT OF THE PRESENT INVENTION The present invention has for its object to solve the above and other disclosed problems, and that which may substantially be considered as characterizing the novel receiver according to the present invention is that the receiver sections are mounted at locations on the surface of said unit distributed around the central axis of the unit, and that the first and second photodetection means have polarised electrical connections and are inversely interconnected through these electrical connections such that the polarities of said electrical signals are mutually inverted, said sensing means comprising means for adding together the said electrical signals output from said receiver sections. In further developments of the inventive concept as herein disclosed, account is taken of the mutual placings of the receiver sections around the central axis of the unit. The major requirement, in this instance, is that the receiver must be directed in such a manner from each other that one receiver section cannot receive a strobe which is intended for the other receiver section. Viewed around the central axis of the unit, it is advantageous if the angle between the receiver sections is of greater magnitude, preferably between ±90-180°. Further embodiments of the present invention indicate in greater detail how the receiver sections are to cooperate in the signal initiation circuit. The device sensing the pulses following the signal initiation circuit may comprise two parallel threshold devices. The photodetectors of the receiver sections are mutually interconnected to potentials such that pulses of different polarities are obtained. The threshold devices are, in this instance, arranged such that the first threshold device is activated for pulses from the first receiver section and the second threshold device is activated for pulses from the second receiver section. The single-out feature is obtained in such a manner that one of the threshold devices will be activated. The receiver may comprise two or more pairs of receiver sections. Within each respective pair of receiver units, these may operate independently of remaining receiver sections. As a result of the above-proposed arrangement, advantages will be achieved on receipt of pulsed optical strobes received in the unit. The electrical signal initiation and signal processing will be manifestly simple, at the same time as return dispersion may effectively be kept at a low level. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS One currently proposed embodiment of a receiver displaying the significative characterizing features of the present invention will be described in greater detail below with reference to the accompanying drawing, in which: Fig. 1 is a schematic side elevation showing the application of the receiver in a missile body, shown in part. DESCRIPTION OF PREFERRED EMBODIMENT In the Figure, the missile fuselage is indicated by reference numeral 1 and its centre axis by reference numeral 2. The missile is fitted with a proximity fuse which is illustrated only in those parts which are dealt with in the present invention. Hence, the transmitter means of the proximity fuse are not shown, it being presupposed that these are of such type as emit the electromagnetic radiation in the form of narrow part lobes which, together, cover the entire circumference of the missile so that the emitted optical energy radiates outwardly in full circle. The number of part lobes may vary without in any manner effecting the inventive concept of the principles for receptive function as described in the following presentation. In the Figure, two received strobes 3 and 4 are shown, these having been emitted from the emitter devices and reflected on a target (not shown). The receiver in the proximity fuse/missile is divided into at least two receiver units 5 and 6, the first receiver unit being intended to receive the first strobe 3 which impinges upon the robot in a direction R1, and the second receiver 6 is intended to receive the strobe 4 which impinges in a direction R2. In the illustrated embodiment, the directions R1 and R2 are diametrically opposed to one another. Generally however, the present invention functions for other mutual angles of incidence between the directions R1 and R2. The requirement is that the receivers must be directed in such a manner away from one another that the one receiver is not capable of receiving the part lobe of the other receiver when this is reflected on its largest imaginary target. Each respective receiver unit includes a collimator lens 5' and 6', respectively, and a photodetector 5'', and 6'', respectively. The anode A1 in the first detector 5'' is interconnected, at a junction point S, with the cathode K2 in the detector 6''. The cathode K1 in the detector 5'' is coupled to plus potential and the anode A2 in the detector 6'' is coupled to minus potential. These potentials are obtained from a battery B in the unit, this battery being provided with per se known earth J. As a result of the illustrated interconnection of the detectors 5'' and 6'', activation of the receiver units 5 and 6 will generate pulses P1 and P2, respectively, of different signs. In that but a single lobe is reflected on one and the same occasion in the target, the pulses P1 and P2 cannot occur simultaneously. An operational amplifier 7 of per se known type is connected, with its input 7a, to the above-mentioned interconnection point S. The output 7b of the operational amplifier is, in its turn, connected to a threshold circuit 8. This latter includes two threshold devices 8a, 8b of per se known type. In the illustrated case, the threshold devices are in the form of comparators with two inputs, the first inputs 8a' and 8b', respectively, being connected to the output 7b on the amplifier 7. The inputs 8a'' and 8b'' are each connected to their reference voltage which is realized by battery B' and B'', respectively. Hence, the input 8a" is connected to plus potential and the input 8b'' to minus potential. On incoming signals on the inputs 8a' and 8b'', respectively, which exceed a certain amplitude preset by means of the reference voltage on 8a'' and 8b'', respectively, there will be obtained activations of the outputs 8a''' and 8b''', respectively, of the comparator 8a and 8b. In brief, the apparatus functions as follows. On an incoming strobe 3 from the direction R1, the receiver 5 is activated, in whose detector 5" the pulse P1 then occurs. This pulse is amplified in the amplifier 7. The amplified pulse is impressed upon the input 8a'. If the amplitude in the pulse P1 exceeds a predetermined level, a signal will be obtained on the output 8a"'. Using this signal, it is thus possible to single out the receiver section 5 activated on this particular occasion. If, instead, a strobe 4 occurs in the direction R2, the receiver section 6 will be correspondingly activated, whose detector 6" gives the pulse P2. This latter pulse has a sign which is opposed to the sign in the pulse P1. The pulse P2 is amplified correspondingly in the amplifier 7 and the amplified pulse is impressed upon the input 8b'. Correspondingly, the threshold 8b emits a signal on the output 8b"'. The activated output thus singles out the receiver section 6 every time this is activated by an incoming strobe 4. The single-out function may also be employed within the missile for controlling its internal functions. In that the pulses P1 and P2 are counterdirected in relation to one another, a subtraction effect of the return dispersion will be obtained in the illustrated connection. This makes for greater possibilities to realize a higher signal/background contrast relationship.

Claims: An optical receiver adapted for mounting in a unit, having an elongate shape, with a central axis of symmetry, such as a missile, projectile or the like, which receiver when operating, receives two or more optical strobes (3, 4) reflected from a target object, which optical strobes are incident at mutually different angles of incidence (R1, R2) on the unit, the receiver comprising first and second receiver sections (5, 6), mounted at respective locations on the unit, which said receiver sections operate cooperatively, and receive respectively the optical strobes incident thereon, said first and second receiver sections each comprising an electrical signal initiation circuit (5", 6", B), including photodetection means (5", 6"), each said signal initiation circuit generating and outputting a respective electric signal (P1, P2) in response to reception therein of incident optical strobes, a first photodetection means (5") receiving optical strobes incident on said first receiver section (5), and a second photodetection means (6") receiving optical strobes incident on said second receiver section (6), said electrical signals (P1, P2) occurring at mutually displaced times, due to the different mounting locations of the receiver sections (5, 6) with respect to the incident strobes, said optical receiver further including sensing means (7, 8) which senses said electrical signals (P1, P2) and produces an indication signal which indicates reception by a receiver section of an optical strobe, characterized in that the receiver sections (5, 6) are mounted at locations on the surface of said unit distributed around the central axis of the unit, and that the first and second photodetection means (5", 6") have polarised electrical connections and are inversely interconnected through these electrical connections such that the polarities of said electrical signals (P1, P2) are mutually inverted, said sensing means (7, 8) comprising means for adding together the said electrical signals (P1, P2) output from said receiver sections. The receiver as claimed in Claim 1, characterized in that the receiver sections (5, 6) are operative to receive strobes having a narrow spatial pattern and are allocated mutual disposition around the central axis of the unit such that one receiver section has its major direction (R1, R2) directed beside a maximum target detectable by the other receiver section. The receiver as claimed in Claim 1 or 2, characterized in that the two receiver sections are mutually rotated ±90-180° around the central axis of the unit. The receiver as claimed in Claim 3, characterized in that the two reciever sections are mutually rotated ±180° or close to ±180° around the central axis of the unit. The receiver as claimed in any of the preceding Claims, characterized in that the anode (A1) of the first photodetection means (5") is interconnected at an interconnection point (S) with the cathode (K2) of the second photodetection means (6"); that the cathode (K1) of the first photodetection means (5'') is connected to a plus potential; and that the anode (A2) of the second photodetection means (6") is connected to a minus potential. The receiver as claimed in Claim 5, characterized in that the sensing means (7, 8) for sensing the electric signals (P1, P2) are connected to the interconnection point (S) and comprises two parallel-disposed threshold devices (8a, 8b) each allocated their receiver section (5, 6) respectively. The receiver as claimed in claim 6, characterized in that the threshold devices (8a, 8b), disposed in parallel, sense , by the intermediary of their first inputs (8a', 8b') occuring signals at the interconnection point (S) and have their other inputs (8a", 8b") coupled to such potentials that the first threshold device (8a) reacts to a signal (P1) coming from the first receiver section, and the second theshold device (8b) reacts to a signal (P2) coming from the second receiver section, indication of the activated receiver section consisting of activation of the output (8a", 8b") of the corresponding threshold device. The receiver as claimed in Claim 6 or 7, characterized in that there is connected, between the interconnection points (S) and said threshold devices (8a, 8b), an amplifier device (7). The receiver as claimed in Claim 8, characterized in that the amplifier device is of the operational amplifier type. The receiver as claimed in any of the preceding claims, characterized in that the first and second receiver sections are each divided respectively into two or more pairs of receiver sections; and that said pairs of receiver sections operate independently of one another.

Inventors: SKAGERLUND LARS-ERIK, SKAGERLUND, LARS-ERIK,
Applicants: BOFORS AB
Application year: 1988
Main classification: G01S7
IPC codes: G01S7, F42C13