Abstract:
The invention concerns a rotating missile emitting light pulses. The invention is characterized in that means are provided to interrupt said light pulses ( 5 ) when the rotational movement ( 3 ) of the missile ( 2 ) about its longitudinal axis (L-L) stops.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a rotating missile provided with an emitter of light pulses, addressed to a receiver disposed at a fixed post (the firing post of said missile) and able to serve in the location and guiding of said missile, as is for example described in document U.S. Pat. No. 4,710,028 (FR-2 583 523). 
   BACKGROUND OF THE RELATED ART 
   It is known that such an emitter can comprise a voluminous flash lamp consuming significant energy, or else, preferably, a laser source. However, in the latter case, the laser energy emitted must be significant in order to ensure a long-range optical link resistant to possible jamming. This therefore results in significant ocular risks to the operators of said missiles, especially in the eventuality that the missile, for example following a motor fault occurring immediately after the firing thereof, were to fall to the ground in the vicinity of the firing post where said receiver and said operators are situated. 
   SUMMARY OF THE INVENTION 
   The present invention is aimed at remedying this drawback. 
   To this end, according to the invention, the missile provided with an emitter of light pulses addressed to a receiver disposed at a fixed post, said missile receding from said receiver while being impressed with a rotational motion about its longitudinal axis, is noteworthy in that it comprises means for interrupting said light pulses when said rotational motion of said missile stops. 
   Thus, by virtue of the invention, since, when said missile falls to the ground, its rotation is no longer possible, there is no longer any ocular risk to the operators of the missile in case of premature and accidental landing of the latter in the vicinity of the firing post. 
   Said means for interrupting the light pulses may act in various ways. For example, they may mask said emitter. However, preferably, they halt the operation of said emitter, either by direct action on it, or by indirect action. In the latter case, when the said emitter is controlled by an electronic control device, said means of interruption may disable either said device, or the control link between said electronic control device and said emitter. 
   In the case where, in a known manner, said missile comprises a roll detector emitting roll pulses each of which corresponds to a specific angular position of said missile about its longitudinal axis, it is advantageous for said roll detector to control said means for interrupting the light pulses. 
   Preferably, said means of interruption interrupt said light pulses with delay with respect to the detection of the first missing roll pulse. For example, this interruption occurs after a duration corresponding to at least two periods of the roll pulses, said duration being metered starting from the last roll pulse detected by said detector. 
   In an advantageous embodiment, said means for interrupting said light pulses comprise a systematic meter permanently metering at a higher frequency than the frequency of said roll pulses, said systematic meter being reset to zero and reinitialized by each roll pulse that it receives, whereas, in case of absence of roll pulse, said systematic meter emits a signal after metering up to a predetermined number, starting from the last roll pulse received. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The figures of the appended drawing will elucidate the manner in which the invention may be embodied. In these figures, identical references denote similar elements. 
       FIG. 1  diagrammatically illustrates the guiding of a rotating missile from a fixed firing post. 
       FIG. 2  diagrammatically shows a roll detector for the missile of  FIG. 1 . 
       FIG. 3  is a chart diagrammatically showing, as a function of time t, the sequence of roll pulses generated by the detector of  FIG. 2 . 
       FIGS. 4 to 6  are schematic diagrams respectively illustrating three variant embodiments of the device for interrupting the light pulses emitted by a missile, in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Represented diagrammatically in  FIG. 1  is a firing post  1 , able to guide a missile  2  with respect to a reference axis X-X (line of aim). The missile  2  recedes from the firing post  1  while being impressed with a rotational motion about its longitudinal axis L-L. This rotational motion has a speed Vr of for example 5 to 10 revolutions per second and is symbolized by the arrow  3 . The missile  2  carries a laser emitter  4 , for example a VCSEL laser or laser diode emitter  4 A (see  FIGS. 4 to 6 ), able to emit laser pulses  5  toward the firing post  1 . The latter comprises a receiver  6  for receiving said laser pulses  5 . 
   As shown diagrammatically in  FIG. 2 , inside the missile  2  is provided a gyroscopic system  7 , defining a fixed direction V-V. On this gyroscopic system  7  of fixed orientation are fixed a light source  8  and a corresponding receiver  9 . Furthermore, around the gyroscopic system  7  is provided an envelope  10 , tied to the missile  2  in its rotation about the axis L-L. This envelope  10  carries several point-like reflecting surfaces  11 , able to receive the incident light beam  12  emitted by the source  8  and to address the corresponding reflected beam  13  onto the receiver  9 . The reflecting surfaces  11  are regularly distributed around the envelope  10 , for example every 120° (as represented) or every 45°. 
   Thus, each time a reflecting surface  11  cuts the incident beam  12 , the receiver  9  receives a light pulse, which it transforms into an electrical roll pulse  14  and, with each revolution of the missile  2  about its longitudinal axis L-L, are generated as many electrical roll pulses  14  as the envelope  10  comprises reflecting surfaces  11 . Of course, the period T between two successive pulses  14  is equal to T=1/Vrxn, Vr being the speed of rotation of the missile  2  about itself (as mentioned above) and n being the number of reflecting surfaces (see  FIG. 3 ). 
   Furthermore, as shown in  FIGS. 4 to 6 , the receiver  9  is connected to a meter  15 , while the laser emitter  4  is controlled by the electronic device  16 , to which it is connected by a link  17 . The meter  15  systematically meters at a higher frequency than the frequency 1/T of the roll pulses  14  and it is reset to zero and reinitialized by each of said roll pulses  14  that it receives from the receiver  9 . 
   Thus, while the missile  2  is rotating about its axis L-L, the meter  15  is permanently reset to zero and reinitialized by the successive roll pulses  14 . 
   On the other hand, if the missile  2  ceases rotating about its axis L-L, for example because it has touched the ground, the roll pulses  14  disappear and the meter  15  meters starting from the last roll pulse  14   d  received—without being reset to zero or reinitialized by any pulse  14 —up to a predetermined number corresponding to a duration D greater than the time T separating the last pulse  14   d  received from the first, referenced  14 M 1 , of the missing pulses  14 , referenced  14 M in  FIG. 3 . As is represented in  FIG. 3 , the duration D is preferably greater than 2T. 
   When this predetermined number is metered by the systematic meter  15 , the latter addresses a control signal to means of actuation  18 , by way of a link  19 . 
   Upon receipt of this latter control signal, said means of actuation  18  interrupt the emission of the laser pulses  5  by controlling:
         either a flap  20 , which masks the laser diode or the VCSEL laser  4 A ( FIG. 4 );   or the halting of the electronic control device  16  through a link  21  or the halting of the emitter  4  through a link  22  ( FIG. 5 );   or else the opening of an interrupter  23  disposed in the link  17  between the electronic control device  16  and the emitter  4  ( FIG. 6 ).