IL28305A - Optical system for the simultaneous guidance of a plurality of moving bodies - Google Patents

Description

i The present invention relates to a system for the simultaneous guidance of a plurality of moving bodies by multiple director beams with coherent or natural optical radiation situated in the infra-red, visible or ultraviolet region.

The system makes it possible for each moving body moving inside a given field that may reach 10 or so degrees, to detect, evaluate and then eliminate the angular displacement of its position in relation to the assigned path which, however, may not be exactly the same as that of the neighbouring moving body.

With a single very discreet, optical link, the system in conformity with the invention is particularly suited to AIR-GROUND or GROUND-AIR guidance and capable of directing a single or a very large number of craft to their respective destinations.

The greater part of the current procedures which make use of the various very high frequency techniques are not easily adapted to the requirements of missile guidance tactics. In fact, these systems on the one hand make use of relatively complex equipment and on the other hand, requiring a wide transmission band, can, owing to this fact, be easily detected and jammed.

The recent methods using the optical technique, as, for s eafta/vbqA/' example, that described in the French Patent A-p-lluat/lon filed on the 1st June 1966, PTLJ-te-sSfTS?! , by the Applicant , lead to a working equipment that is light and not cumbersome. This method uses during transmission, apart from the optical ,. beams, a radio-electrical pulse of very short duration covering by its radiation the whole of the solid angle of the area monitored. On reception, the radio-electric wave reference instant. If the optical beams by their form provide the discretion required for missile guidance, the radio-electric pulse, on the other hand, by its weakly directive radiation pattern is liable to make a transmission centre detectable, and thus also vulnerable.

This brief survey shows the difficulties which are encountered in trying to satisfy simultaneously all the requirements imposed by firing triggers or guided weapons. In order to be operational, the equipment used must be light, not cumbersome, must not interfere with the aerodynamic qualities of the missile and, at the same time, be characterised by a stable and reliable functioning. This latter requirement becomes imperative where one is dealing with missiles carrying high volume explosive charges for which particularly rigorous operational safety measures are indispensible. In order to attain the required degree of safety, the .tactics employed must locate the object with great precision and high separating power.

In order to fulfil these conditions and remedy the drawbacks mentioned, the present invention applies new means to the known methods and, in particular, to that described in the French Patent^referred" to earlier.

Thus it is accepted that upon transmission, a scanning device with a well-defined temporal law, as for example the symmetrical saw-tooth law, causes the elevation and bearing planes to be explored respectively by two optical beams with flat and narrow lobes. The holding on course of the missile is ensured by the receiver on board which makes use of a device for detecting the intensity of light preceded by an optical system and followed by a tuned electronic amplifier the output signals of which make it possible to' evaluate the by the transmission centre. These latter serve to devise signals which, acting on the direction orders of the missiles, rectify the protectory followed and swiftly align the moving body on the path laid down.

The deviation measurement made by means of such optical beams, which in the direction of propulsion of the weapons have lobes of narrow width ensures simultanesouly a precise angular location and the desired discretion. However, this latter, as has been indicated, is compromised by the almost .. omni directional radiation of the reference signal required by displacement measurement.

The new methods applied ensure in particular complete discretion of transmission, an increased range associated with a greater signal-to-noise ratio when the weapon follows the assigned path, the possibility of directing simultaneously a plurality of missiles onto different targets and an equipment at the same time more compact and lighter.

The discretion is obtained by the suppression of the reference signal upon transmission. This fact leads at the reception on the one hand to the suppression of the channel attributed to the reference signal, and on the other hand to the constitution in the displacement measurement device of the receiver of a reference duration controlled by the recurrence period of the scanning law created on transmission.

In order to ensure an effective guidance of missiles when they are near the target but far from the transmitter, the range of the director beams and signal-to-noise ratio in the axis must be increased. To this end, on the one hand the optical channels from the transmission centre comprise primarly sources with high luminosity and long duration of life. On the other hand, the receiver on board comprises an internal noise by establishing a lower threshold of reception and immunises. the receiver against any fortuitous or systematic jamming.

The path assigned to a given missile, established prior to its launching, is ensured in flight b a calibrated device which, following the scanning law, modifies the reference period device elaborated angular displacement measurement unit of the receiver on board.

Given that the transmission centre is supposed to be airborne, it is important that almost the whole of the equip-ment be fixed, that is to say that the equipment comprises the smallest possible number of mobile units. To this end, the present invention replaces the temporal modulation of the luminous intensity of the director beams, made most frequently in transmission by the rotary elements, by a spatial modulation carried out on board the carrying weapon automatically and without supplementary units. This spatial modulation consists in replacing, by means of a fixed coding device, each director beam by a multiple beam composed of a certain number of elementary beams. These latter in travelling past in front of the receiver engender a sequence of pulses the 1 number of which, since it may vary for elevation and bearing beams, is evaluated by the counting device which lies in front of the angular displacement measurement unit oh board.

Thus the important feature of the present invention relates to the construction of an improved optical guidance system which directs simultaneously and with great precision a plurality of missiles towards the advance targets designated by means of two director beams. The improvements made are concerned with the optical paths from the transmission centre and the receivers on board each missile. transforming the director beam transmitted by the primary source into a specific multiple beam which, in scanning one of the pjanes, elevation or bearing, of the area moniioxeci , modulates the receiver spatially when it is illuminated.

Each photo-sensitive receiver on board is constituted by an electro-optical device for spatial section which distinguishes the coincidence between the direction of the multiple beam and the path assigned, by an angular displacement measurement unit composed of a controlled device, delivering a signal the duration of which serves as a reference, and of a precalibrated device modifying the reference duration in accordance with the angle made, in the plane envisaged, elevation and bearing, by the path imposed in relation to the. optical axis of the scanning unit.

In accordance with another feature of the invention, the two director beams are determined by the same angular speed (v ) of scanning and by distinct widths (e and e_) bringing s g about different lengths of time of the travelling past (&a s and Θ ) of the beams in front of the lens of the receiver on board.

Each specific width (e) of the beam may, moreover, be composed of a number that is well defined but different for each of the beams, of regularly spaced elementary widths e) of the same dimensions.

In accordance with another feature of the invention, the spatial selection device comprises, preceded by the optical receiver system, a unit for detecting the optical radiation constituted by a mosaic of photo-sensitive cells connected to the electronic devices using the selective properties of band filters. The central cell of the mosaic, covering only a field of several mils of steradiams, ensures an increased ,,οί the system.

The features enumerated materialise the invention and specify the new means applied to systems for the guidance by two optical beams of a plurality of weapons travelling in a group towards different targets or all onto the same target.

The invention can just as well be applied to AIR-GROUND systems, where the transmission centres are airborne and the targets located on the ground as to GROUND-AIR equipment where the targets pursued are space vehicles.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of two director beams; Figure 2 is an example of a configuration of moving bodies in the area monitored; Figure 3 shows the diagrammatic structure of the transmission centre; Figure 4- and 5 show the network of elevation and bearing slips; Figure 6 shows the temporal diagrams of elevation and bearing scanning; Figures and 8 are graphs showing the different paths assigned; ' Figure 9 is the synoptic diagram of the receiver on board; Figure 10 shows the angular displacement measurement and clock control devices; Figure 11 shows the temporal diagrams of the angular displacement signals ; Figure 12 shows primary the clock and its control system; and Figure 13 is a varient of the angular displacement measurement device. conformity with the invention, the transmission centre projects into space two optical beams with flat and narrow lobes which scan respectively two planes at right angles with the solid angle monitored. In order to ensure a certain functioning and avoid any hesitation in the determination of the director beam which illuminates the receiver of the moving body, the two elevation and bearing planes are not scanned simultaneously, but alternatively, one after the other.

Figure 1 shows in diagrammatic form the lobes of two director beams 20 and 30. One, the beam 50, covering a large sector (Ogh) in the vertical plane, explores with its narrow width (gh) the bearing plane. Thus, in the course of scanning, the moving bodies situated on the same vertical, as, for example, the moving bodies illustrated at points A^, Aj or A2 A^ are illuminated at the same' moment. The second lobe constituted by the beam 20, covering the large sector (Oab), explores with its narrow width (ab) the elevation plane. This lobe illuminates at the same instant all the moving bodies situated on the same horizontal, as, for example, the vehicles A^, or A^, A^. By way of example, these moving bodies have been taken disposed symmetrically around the axis OC. Figure 2 illustrates this particular configuration.

Figure 3 shows diagrammatically, by way of a non-restrictive example, the transmission centre which comprises the two optical paths 2 and 3» a d the control unit of the mobile mechanisms 4. The paths 2 and 3 generate the optical beams 20 and 30 which scan respectively the elevation and bearing planes.

A certain number of methods applied by the present invention are similar to some of the devices described in 28305/2 example, the optical channels 2 and 3 each use a primary source Ls(Lg), a condenser Gs (Cg), an alternating mechanism V2 (VI), 'a large-opening lens 27 (37)» a scanning mechanism constituted preferably by a plurality of diasporametres 25 (35) and a uhit for controllin the mobile mechanisms 4. In the text that follows, the functioning of these devices is only given very briefly. Throughout this specification and unless otherwise stated the term "condenser" refers to an optical condenser.

The system in conformity with the present invention comprises, however, important distinctive methods characterising notably the transmission centre, the receivers on board and the optical channels 2 and 3.

The text that follows describes the use and functioning of the new methods applied. The references which apply more particularly to the new devices are notably for the primary sources 22 (Ls) and 32 (Lg) of Figure 3» for the coding device - Fs (Fg) of Figure 3 and Figures 4 and 5» for the spatial selection device - the moslac R21 acting together with the electro-optical unit R27 of Figure 9, for the autonomous angular displacement measurement unit - H24 controlled by the unit R26 o Figures 9 and 10 and for the variant - the unit R28 of Figure 12, and for the units determining the path imposed - the devices 261 of Figure 10, 276 of Figure 12 and 286 of Figure 13.

As has been mentioned, for reasons of discretion the transmission centre, and consequently the receivers on board no longer comprise the electro-magnetic channels transmitting and receiving the radio-electric reference signal. Consequently, each receiver on board elaborates through its own means a 28305/2 time base, which it uses as a reference, making it possible to evaluate the angular displacements of its actual trajector in relation to the path traced.

As for the optical channels 2 and 3» each i3 distinguished by a primary source and by the fixed coding device leading to - a - •the suppression of the electro-mechanical modulation. This last feature makes the system particularly interesting in applications where the weapons are guided from an airborne transmission centre.

In order to produce flat and narrow director beams, the primary source may be constituted by a thread-like filament of tungsten brough to a high temperature. This solution, can, however, give rise to drawbacks in particular when the transmission centre is placed on board an aeroplane. In effect, the filament, being for the requirements of angular displacement measurement long and thin, becomes mechanically fragile owing to both the high temperature and vibrations* These vibrations and accelerations induce, principally at the middle point in the length of the filament, troublesome oscillations which bring about an imprecise aim of the director beams.

Depending on the use and the location of the transmission centres, the present invention uses preferably hot sources 22 (32) constituted either by high pressure zirconium or xenon arcs or by incandescent tungsten. These hot sources have a considerable luminance in the spectral band used and a fairly large transmission surface which adapts itself to the elongated form of the beams.

The concentrated zirconium arc has a colour temperature of 32000I£ and has numerous lines situated in the close infrared. Its transmission surface, is relatively small, has, however, a fairly great luminosity making possible the use of this hot source.

The high pressure xenon arc has a colour temperature of 6000° so that the brilliant parts of the arc may obtain a luminosity as high as 3000 to 4000 cd/mm . The very intense Applications, however, the use of such arcs is a delicate matter since their length and consumption are considerable and, moreover, their position may not be indiscriminate.

Although the filaments in incandescent tungsten do not attain the luminosity of the arcs mentioned previously, they have however, the advantage of possessing a large surface in elongated form, as, for example, the filaments in ribbon or cylindrical,, shape. Such a filament associated with the condenser Cg (Cs) makes it possible to light uniformly the secondary source iFg (Fs) constituted by the slits situated in the focus of the optical system 27 (37).

The temperature of the filament must be as high as possible, o With ordinary lamps, it is scarecely possible to exceed 3000 otherwise the length of life becomes very reduced. In order substantially to increase both the longevity and the luminosity the system in accordance with the present invention uses as primary source "quartz-iodine" lamps where the temperature of the filament may reach 34-00°K. These iodine lamps are characterised by their regenerative cycle. The tungsten which is deposited on the wall of the bulb is transmuted '. into a volatile compound, thanks to the temperature of the wall which reaches 600°C. In its turn, this volatile compound decomposes on the filament or in the vicinity of it. The regenerative cycle of the code lamps thus procures appreciable advantages concerning duration in time and the range of the director beams. In effect, on the one hand, whatever may be the service time of the lamp, the bulb wall remains free from blackening and, on the other hand, the tungsten filament is only subject to a slight weight loss. Consequently, there results from this an increased longevity which permits it to be heated to vt¾ry high temperatures. Moreover, it should envelopes these lamps have in the infra-red an. improved transmission factor, thanks to their walls of melted silica.

Using the elongated form of the filaments, the lamps Ls and Lg of the channels 2 and 3 are placed perpendicularly one to the other. The lamp Ls which equips the channel 2 that projects the beam exploring the elevation plane, is placed in such a way that the length of the filament 22, perpendicular to the optical axis, is situated in the bearing plane. Similarly, the lamp Lg is placed in such a way that the length 32, remaining always perpendicular to the optical axis, is in the elevation plane, that is to say in the plane of figure 3· Another distinctive feature in the present invention, as has been stated earlier, lies in the fixed coding which characterises individually the elevation and bearing beams, Each of these beams is, thanks to the coding device, replaced by a multiple beam composed respectively of Ns or r Ng elementary beams. These elementary beams fixed spatially, emerge from the lens 27 (37) > illuminating the scanning device 25 (35)» and then scanning the area, one after the other. In order to effect the transformation of the incident beam into a multiple beam, the coding device comprises, by optical channel, a system of fixed slits regularly spaced out. Figure 4- shows diagrammatic lly the system of silts Ps comprising Ns slits, narrow and long; the length of each slit being laid parallel to the length 22 of the filament of the primary source Ls. These slits constitute both the uniformly lighted secondary source of the channel 2 and the coding device printing on the elevation beam its distinctive code.

Figure 5 illustrates the system of slits for the bearing channel 3· These slits to the number of Ng, perpendicular The elementary beams of each multiple beam cross the scanning device 25 (35)» then explore the area and illuminate, one after the other, the moving bodies. Each receiver on board thus receives a sequence of pulses composed of Ns (Ng) optical signals with a well-defined repetition frequency, proportional to the angular speed of exploration. The number of pulses Ns or Ng contained in the sequence makes it possible for the receiver to differentiate the elevation and beaming beams.

Thanks to the multiple beam created by the fixed coding device, each luminous beam is modulated spatially instead of temporally by means of moving parts controlled by the control unit .

Figure 6 shows the action. of the alternating mechanism VI (V2) and that of the scanning devices 25 (35) ensuring, for example, a temporal law β (t) in symmetical saw-tooth form with period T. The upper diagram/? g(t) shows the exploration as a function of the time of the director beam scanning the bearing plane, and the lower diagram y# s(t) the exploration of the elevation plane. As has been mentioned, this latter, making a maximum angle of deviation (Ds), is interposed between two consecutive diagrams of the bearing plane, the angular excursion of which is Dg. In the course of the exploration the elevation and bearing beams point in the direction of the optical axis respectively to the instants Tl (61) during the outward scanning and to the instants T2 (G2) during the return scanning. Given that the multiple director beams have a different number of elementary beams, the length of time taken for travelling past ©s (©g) in front of any illuminated moving body are also different.

In order to show that the angular displacement measurement position. of the moving body, Figure 6 represents the instants where the moving bodies Al to A4- of Figure 2, distributed symmetrically around the optical axis, are illuminated by the director beams. In particular it is noticeable that the interval of time that separates the instants where a given moving body is illuminated by the same beam in the course of a scanning cycle, depends on the angular position of the said moving body in relation to the optical axis. Thus for missies such as Al, A3, which in the bearing plane make a negative angl xl3» since they are too far to *e left on the optical axis, the interval of time is greater than the period Gl, G2, while the moving bodies A2 and A which are to the right of the axis, making a positive angle x24, the interval of time is less than the period Gl, G2. Similarly, it may be seen in the elevation plane, that the weapons Al and A2, which are above the optical axis, show, by comparison/the reference period Tl and T2, too short intervals of time , while the missiles A3 and AM- which make a negative angle y34, show too long intervals. Any angular position of a moving body moving in the area::surveyed is thus well determined by means of its.'temporal co-ordinates related to the reference period Gl, G2 (Tl, T2) . asurement which hai6{just been set out pre-suppose implicity that the path to be followed coincides with that of the optical axis. However, it is easy to image that the path imposed may take any other direction than that of the optical axis. Figure 7 shows, by way of example, such. a case where the path assigned OR in the bearing plane makes an angle /3o with the optical axis OP. Figure 8 shows, corresponding to the path, the interval of time Rl , R2 , traced on the diagram illustrating the temporal law β g (t) of scanning -in the bearing plane. ,the temporal displacement are applied in the same way to the . reference period Rl, R2, as to that of Gl, and G2 described above.

Thus it may be noted that the system of angular displacement measurement in accordance with the invention directs with the two directive beams, groups of missiles or other moving bodies by aligning them on the paths assigned which may be different and must reach distinct targets.

Figure 9 represents diagrammatically the structure of the receiver on board. The description that follows briefly describes its functioning.

The multiple director beams illuminating the moving body are picked up by the optical unit E20 which concentrates the incident luminous flux, modulated by the succession of elementary beams, onto the unit of photo sensitive detectors R21. The modulated useful signals delivered by these latter, previously ■ amplified in the selective unit R22 centred on the modulation frequency, are directed on to the decodin device R23 which, according tp the number of pulses Ns (Ng) , i contained in the sequence, isolates the elevation and bearing signals. The signals thus separated are directed by their own channels (s) (g) on to the displacement measurement device R2 . After having evaluated in each plane the error of the trajectory followed in relation to the path assigned, the displacement measurement device R24- delivers correction signals to the direction control device R25.

In conformity with the invention, the spacial selection device favouring the direction of the path assigned is formed by the combination of methods procurred by the optical and photo electric units. In effect, the said spatial selection device is constituted by the optical unit R20 composed o^— the optical field imposed, which may reach 10 or so degrees. This mosaic is composed of at least three cells with unequal photo-sensitive surfaces, each of the cells being connected to an electronic pre-amplifier incorporated in the preselection unit Ε27· The central cell, having a sensitive layer with a very weak surface, only covers by itself a very limited field around the optical axis, in the order of several mils of steradians. When the trajectory followed by the moving body coincides with optical axis, this cell, illuminated by the elementary beams which succede at a regular rhythm, delivers a sequence of pulses at a constant repetition frequency. The marginal cells of larger surfaces are connected to the associated pre-amplifiers , which are preferably connected in opposition, and form a differential electronic structure.

This constitution makes it possible, on the one hand, to immunise the receiver against an extensive external parasitic force and on the other hand to reduce the quantic noise on the central cell, ensuring by this. fact an increased precision and signal-to-noise ratio in the axis, that is to say in the direction of the path assigned. This result is particularly appreciable when the missile is near to the target , thus far from the transmission centre.

The pre-selection unit R27 comprises by way of a photosensitive cell, a bottom clipping device and a pre-amplifier. The bottom clipping device establishes a lower threshold which determines the normal reception level as a function of value of the active surface of the associated cell.

The acting elements composing each pre-amplifier are preferably semi-conductors electrically interconnected in such a way that the input impedance of the said pre-amplifier seen by the associated detector is very high and the output • rlow value.

In many applications and in particular when the beams are in infra-red light, it is useful, in order to ensure the maximum sensitivity on reception, to maintain the photo sensitive cells at a very low temperture . To this end, the cooling device R26, maintaining the required temperature in the , atmosphere surrounding the mosaic R21, is constituted by a Peltier effect battery or by a jet of liquid helium or nitrogen.

The useful signals delivered by the pre-selection device E27, feed the selective amplifier R22 centred on the recurrent frequency of the elevation and bearing pulse sequences ^ The decoding device R23 using binary counters searches the sequences according to their number Ns (Ng) of pulses and the routing on the separated channels s and g connected electrically to the angular displacement measurement device R24-.

In the course of the scanning cycle, bearing or elevation, this latter receives two signals elaborated after the passage of each sequence picked-up. Thus, for example, the bearing channel g delivers the signal gl after the sequence received in the course of a "outward" scanning (GoGl) and the signal g2 during the "return" (GO G2) of the bearing director beam. •The signals for Gl and G2 represented on figure 9 are also reproduced on Figures 10 and 11. These two figures show the functioning of the displacement measurement unit. .

On Figure 10, and also on Figure 9» it may be seen that the pairs of signals glg2 and sls2 after having crossed the device R24- give rise to series of pulses which feed through the respective terminal G and S the direction control device R25« Figure 11 shows the temporal position of the signals gl, g2, as well as the formation of the pulses which, by displacement between the actual trajectory of the moving body xl3 and the direction of the assigned path Rl, R2, making a angle with the axis ot of the system. ' In order to specify the diagram of Figure 11, it has been supposed that the scanning law is of a symmetrical sawtooth shape and that the moving body occupying the position of Al (or A3) of Figures 1, 2 and 6 elaborates the signals gl - g2.

The device R24, in order to evaluate angular displacement (X13 -βο) first determines the interval of time which separates the reception of the signals of gl, g2, and then compares this period with the interval To which the signals must make if the moving body were following the axis Rl, R2 imposed.

From now onwards for the sake of brevity, the interval of time To is called "reference time To" and the interval of time separating the reception of the signals gl - g2 "interval gl - g2". The comparison between the two intervals is effected by the comparator 244· which is fed both by the clock 246 and by the bistable trigger circuit 240.

The signal gl delivered by the decoder R23 triggers off simultaneously the clock delivering the pulse D the duration of which approximates to the reference time To and the trigger circuit which provides the pulse El having a duration equal to the interval gl, g2. Thus fed, the comparator 244 $>ol lAT i†\i delivers at each scanning cycle a pulse HI the plurality and duration of which characterise the angular displacement (xl3 ~β o) . The pulse HI, by the intermediary of the device R25* acts on the orders of the moving body in order to bring it nearer to the direction Rl, R2 and by this fact to reduce the displacement (xl3 -β o) . The successive pulses HI have This latter, as may he seen on Figure 11, is proportional to the reference time To with a value; Tr a 4T = KTo where T designates the scanning period evaluated along the x - axis Ot.

The pulses HI only invert their polarities f the moving body goes beyond the path assigned by placing the interval gl , g2 above the axis El , R2. Such pulses act in a reverse direction on the orders which bring back the moving body in the direction imposed.

It may thus be noted that the duration of the path HI is a direct function of the absolute value of the angular 'displacement (xl3 - β o) and that the polarity of the amplitude indicates the sign of this displacement.

The return signal g2 acting on the trigger circuit 2 0 determines the rear edge of the pulse of El. So that the signal g2 shall not trigger off the clock 246, the "gate" device 2 5, shown on Figure 10 is fed by the trigger circuit 240. The pulse. El thus blocks the gate 245 which by this fact prevents access by the clock during the whole of the interval gl - g2.

The elevation channel (s) of the angular displacement measurement unit R24 receiving from the decoder R23 the signals si and s2 comprises similar devices to those of the bearing channel which have just been described.

In order to be able to guide simultaneously a plurality of weapons aiming at targets that are sometimes different, it is necessary for the reference time To to be not only " · constant but also controlled by the scanning period T. . This latter, imposed by the speed of rotation of the scanning device 25 - 35 of Figure 3, is liable to vary fortuitously in the course of functioning, or even deliberately. These variations modify the scanning diagrams shown on Figure 6, βο of the moving body is maintained constant. The control of the clock 246 is effected by means of the device R26.

Figure 10 shows by way of a non-exclusive example the constitution of the control device R26. Its functioning is based on the observation, made and illustrated by the diagram (D) of Figure 11, that the clock 246 delivers a series of pulses, each of duration (To + *£), which follow each other with a repetition period Tr. This latter, as has been explained, is proportional to the scanning time T, that also to the actual reference time To.

In order to control the clock while annulling the temporal error *£, the units R26 uses on the one hand the devices 263 to 265 which deliver a signal V (To) proportional to the repetition period Tr of the series of pulses, and on the other hand the devices 260 to 262 which provide a signal V (To +X,) proportional to the duration (To + "£) of the pulse of the clock which is derived from . The level comparator 266 comprise these two signals and elaborates a resulting signal, difference which constitutes the error signal V (¾. This latter, acting on the clock 246, modifies its duration . in the direction of the cancellation of the drift X..

The channel giving the signal V (To) comprises the bistable trigger circuit 263, the upper threshold device 264 and the integrator 265· This channel being connected after the "gate" 245, the trigger circuit 263 is triggered off by the first pulse g, and stopped by the first pulse gll of the following cycle, shown on Figure 11. The interval of time . which separates gl and gll being equal to the period Tr, the pulse delivered by the trigger 263 has, owing to this fact, the same duration. The threshold device 264 limits this pulse, consequently the device 265 integrates a pulse of ,the integrator being (CR) the signal V (To) delivered by the integrator to the compaisfcor 266 takes a level Mtr, that is to say equal to mkTo, where the factor m has a value Uo/CR.

The channel delivering the signal KV(To+t ) comprises the threshold device 260, the pulse transformer 261 with a predetermined transformation ratio equal to k:and the integrator 262.. As this channel is connected to the output of the clock 246, the threshold device 260 delivers a normal amptitude pulse Uo of duration (To +'¾_.), which, after having passed through the transformer 261, feeds the integrator 262. This latter having a time constant RC and acting in the peak integrator, delivers to the comparator 266 a voltage kV(To equal to mk(To + Ό.

The comparator device 266 fed by the signals delivered · by the two channels provide an error signal V(*t- equal to km* » proportional to the temporal shift * . This signal being amplified k times render the servo-control very energetic so that the drift of the clock 2 6 is very quickly annulled.

The functioning of the device R26 is identical if the pulse transformer 261 is replaced by an amplifier with calibrated gain.

From what has gone before, it can be seen that in order to attribute different paths to groups of moving bodies, it is sufficient to furnish the receiver with devices having a transformation ratio kn which corresponds to the angles/ n and reference time Tn imposed, knowing that each product kn. Tn is a constant equal to the scanning period Tr.

The clock 246, the duration of which is automatically adjustable by the voltage of error V (*£) may by way of a non-restrictive example , be the same as the generator of rectangular signals described in the French Patent No.1.018.132 ' The clock 2 6 may also be constituted by an integrator which charges a capacity with constant current followed by an electronic switch making possible the triggering of the, clock when the fixed voltage is reached. The capacitor of the clock is instantaneously discharged and takes up a charging cycle again until the following discharge. Such a clock gives a trail of pulses in saw-tooth shape. The error voltage of error V( .) modifying the current which charges the condenser alters the duration of each pulse, and in consequence the frequency of repetition of the sequence of . pulses generated.

The control system explained above requires in order to synchronise the clock 246 an interval of time at least equal to Tr. One may, however, if necessary, shorten this period by taking as a reference the repetition period r of the elementary pulses Ng and No in sequences created by the passage of the multiple director beams. These sequences may be picked-up at the output of the selective amplifier R22 . shown on Figure 9. In effect, the number of pulses N i each sequence is equal to the product of the modulation frequency-': f by the temporal width ©■ of the multiple beam, a width shown on Figure 6. In consequence the repetition period (ΘΓ) of the elementary pulses is expressed by ; ©r a 1/f « e/tT = A.T. where the factor A is a constant which depends on the angular width oC o of each elementary slit of the codes shown on Figures 4 and 5 and on the maximum angle of exploration D of the scanning law represented by Figure 6.

On Figure 12 there is shown diagrammatically the control unit R29 which regulates the clock 270 having a repetition , period of approximately θτ, thus considerably shorter than the period Tr. The sequences of pulses delivered by the ...· .:! directed in the form of a series of short pulses on to the coincidence device 272. This latter also receives another succession of short pulses transmitted by the pulse transformer 274- which is fed at the primary by the pulses generated by the clock to be regulated 270 and then differentiated by the device 273· In this manner, the coincidence device is fed both by a series of pulses having the repetition frequency f and by another approximate repetition frequency train imposed by the clock 270. For ever two successive pulses received by the coincidence device, this latter delivers a pulse of a width corresponding to the interval of time which separates the two incident pulses. When the pulse coming from the receiver R22 precedes that of the clock 270 , the pulse delivered by the device 272 takes on a well defined polarity. This polarity is reversed when the two pulses follow each other in the reverse order.

The integrator 275 receiving the coincidence signals transforms the sequence into a ΰ.Ο. voltage of amplitude proportional to the time of opening of the pulse and of a sign identical to the latter. This D.C. voltage acting as an error signal, serves as a base voltage to the charge circuit for the clock 270. It modifies the recurrence period of the clock in order to bring it back into exact coincidence with the period 6r of the sequence delivered .by the amplifier R22.

The clock 270 may be used as a primary clock, the period of which synchronizes the clock 246 on the reference period T imposing as a navigational path the axis Ot shown on · Figure 11.

The clock 270 may also control the principal clock 246 on a reference duration To different from the period T, in with the axis OP, as shown on Figure 7· To this end, in conformity with Figure 12 the pulses generated by the clock 270 feed the amplification device 276. The pulses delivered by. this latter are' integrated in the device 277 which delivers an error voltage proportional to the required duration To. This voltage acts on the control circuit of the principal clock 246, imposing on it the imposed periodicity. The synchronisation of the primary clock 270 renders the control unit R26 superfluous .

Figure 13 shows a variant of the angular displacement measurement unit which needs only a single clock for its functioning, noteably the clock 270 ; the clock 246 and the control unit R26 becoming by this fact redundant. In this assembly the structure of the displacement measurement device R28 comprises the level comparator 283 which receives both a signal translating the interval gl, g2 and another V(To) proportional to ½e imposed reference time To.

The channel evaluating the interval gl g2, being fed by the bearing channel (g) of the decoder R23, comprises the bistable trigger circuit 240, the limiter device 281 followed by the integrator 282 connected to the level comparator 283. The channel assessing the reference time To, fed by the clock 270 , is composed of the limiter device 284 followed by the integrator 285 connected to the amplifier with calibrated amplification 286 which feeds the level compaistor 283.

The bistable trigger circuit 240 fed by the two signals gl, g2.which are consecutive, delivers a pulse of duration equal.: to the interval of gl, g2. After limiting in the device 281, this pulse is integrated in the unit 282 which supplies to the comparator 283 a D.C. voltage equal to m(tg2 - tgl), proportional to the interval gl, g2. In the /■limited by the device 284, then integrated by .the device 285 which delivers a D.C. voltage of value m (ΝΘ r) , proportional to the total duration (M&r) of the sequence of pulses supplied by the clock, This voltage feeds the amplifier 286 with calibrated amplification (k) which delivers to the level comparator 283 a voltage of value mk (N r) equal to mTo.

Fed by the two incident signals, the level comparator 283 delivers to the direction control unit R25. a voltage equal to m times £7tg2 - tgl) - To~J. It is easy to see that this voltage is proportional to the angular displacement to be corrected (xl3 -β ) of Figure 11.

The variant has the advantage of being able to control the clock 270 twice per scanning cycle and each time on a succession of pulses a repetition period ©r proportional to the scanning period T.

The description given shows that the present invention, remedying the difficulties at present met with, makes it possible to constitute an optical system with director beams which guides simultaneously, with precision, discretion and protected from any jamming, a plurality of moving bodies o assigned paths which may be distinct from each other.

The present invention leads to an equipment that is robust and not cumbersome, particularly adapted to guidance links of , the AIR-GROUND or GROUND-AIR type.

. The new methods used insure the- robustness, the precision of angular displacement measurement and the discretion of radiation of the optical projector, noteably by the primary optical forces selected, the fixed coding applied to the director beams, the electronic and photo - optical selection of the parameters characterising the optical beams reference time base controlled both by the scanning period of the director beam and by the imposed direction of the path to be followed.

. The director beams with practically uniform luminous intensity, generated by primary forces with great luminance and duration of life, are, by means of fixed spacial coding devices , transformed into multiple beams . Each elementary lobe of these latter is very narrow and has a well defined angle of divergence which may be in the order of some tenths of arc-seconds. In scanning the surveyed area without discontinuity, the said multiple beams insure a characteristic spacial modulation that replaces with advantage the temporal modulation or modulations determined by mobile mechanisms. The periodic succession of elementary lobes and that of the scanning cycles procure the precise means for controlling on board the reference time base by the scanning period which may be subject to accidental or deliberate changes. In a parallel fashion, the new means immunise the receiver on board against parasitic signals by using electronic devices and photo-optical units which select the useful signals.

The photo-optical means favour these latter when the moving body follows the assigned path noteably reducing the parasites due both to the quantic noise of the photo-sensitive detectors and to extensive jamming forces.

It will be understood that various modifications may be made without departing from the scope of the invention.

Claims (1)

1. reception instants and delivering' to the device for controlling the directions of the moving body signals measuring the angular displacements between the trajectory1 followed and the path Imposed. · Optical guidance ' system in accordance ' with Claim , characterised in that the receiver on board comprises a photo-sensitive detector constituted by a mosaic of cells, ■ each connected to an electronic pre-selection circuit, an optical unit and by a device maintaining at a very high level the, sensitivity of the cells, the optical unit being composed of an optical system with elements which are preferably refringent and a condenser comprising in its focal plane the mosaic of cells. Optical guidance system in accordance with Claim $, characterised in that the mosaic of cells has an overall surface determining the optical field imposed which may attain ten or so degrees and in that it is constituted by at least one central cell and two marginal cells, the central cell having a photo-sensitive layer, the surface dimensions of which cover around the optical axis a very limited field of a few mils of steradians consequently ensuring a very low quantic noise, and a signal to noise ratio increasing in the direction of the axis, the marginal cells each having a sensitive layer whose dimensions are of the order of ten or so times greater than those of the central cell. @. Optical guidance system in accordance with Claim characterised in that the pre-selection circuits connected to the cell are constituted by a bottom-clipping device, establishing a lower threshold which determines the minimal • reception level as a function of the value of the active surface of the said cell, and by a pre-amplifier comprising preferably transistors and field effect semi-conductors •V- interconnected in electronic structures ensuring a very high input impedance, seen by the associated cell, and a very weak output impedance seen by the selective amplifier that follows . °Ί 5®. Optical guidance system in accordance with Claims, and Q characterised in that the pre-amplifiers associated with the marginal cells are preferably interconnected in opposition by forming a differential electronic structure which ensures the protection of the receiver against an extensive parasitic cell. 10. Optical guidance system in accordance with Claim 0, characterised in that it comprises a device which maintains the maximum sensitivity of the photo-sensitive cells and, in particular, those sensitive to ,the infra-red radiation constituted either by a jet of liquid Helium or nitrogen, or by a Peltier effect battery. l . Optical guidance system in accordance with Claim characterised in that in the angular displacement measurement unit the unit evaluating the time gap that separates the reception signals' from the director' beam is constituted by a bistable trigger circuit triggered and arrested respectively by the first and second signals of the decoder, in that the clock is triggered by the first signal from the decoder and in that a duration comparator effects the difference between the two pulses of the trigger circuit and the clock and delivers to the unit for controlling the directions of the moving body a pulse defining by its duration and its polarity the value and the direction of the angular displacement of the moving body to be picked up. l^. Optical guidance system in accordance with Claim ^ characterised in that the principal clock generating the reference time base is constituted by a monostable trigger circuit of adjustable duration or by a saw tooth generator, and in that it is servo controlled by a servo control device or by a primary clock which is also- servo controlled, lj^. Optical guidance system in accordance with Claim l^, characterised in that the control unit of the principal clock comprises two channels and a level comparator, one of the channels, fed by the pulses delivered by the clock being composed of a limiting device with upper threshold, a pulse transformer and of an integrator delivering a voltage proportional to the duratio of the clock, -the other channel fed only by the first signal delivered by the. decoder through a gate being composed of a bistable trigger circuit delivering a pulse of duration equal to the repetition period of the scannin cycles, an upper threshold device and an integrator delivering a voltage proportional to the reference time base, the level comparator effectin the difference between the voltages delivered by the two channels and supplying the clock with an error voltage proportional to its temporal drift ensuring the adjustment of the duration of the clock to that imposed. ΐ . Optical guidance system in accordance with Claim l^j characterised in that the primary clock which is servo-controlled comprises a coincidence device, two channels which feed it, and a servo-control loop; one of the channels comprising a differentiation. device connected to the selective amplifier of the receiver, the other channel being composed of a generator of adjustable duration, and a differentiation device followed by a pulse transformer; the servo-control loop comprising an integration device, connected by its input terminals to the output terminals of the coincidence device and by its output terminals to the control circuit of the generator of variable duration in such a way that the pulses synchronise the principal clock. Optical guidance system in accordance with Claim ΐ , characterised in that the primary clock is" connected to a pulse amplification device connected by its input terminals to the output terminals of the primary clock, an integration device connected after the amplification device delivering to the control circuit of the principal clock a voltage determining its reference time. lQ. Optical guidance system in , accordance with Claims J|f and l characterised in .that a modification of the angular displacement measurement discriminator comprises a level comparator device and two channels which feed it, one of the channels being constituted by a bistable trigger circuit triggered and arrested respectively by the first and second signal delivered by the decoder, by an upper threshold device and by an integration device connected to the level comparator, the other channel, connected by its input to the output of the primary clock, comprising in cascade an upper threshold device, an integration device and an amplifier connected by its output terminals to the level comparator, said level comparator supplying the channel of the device for controlling the directions of the moving body. 1 · Optical guidance systems substantially as hereinbefore described with reference to the accompanying drawings. . Dated this 11th da of July, 1967 ■ For -he. Applica ts -