EP0165170B1 - Device for sighting, recognising and tracking a target - Google Patents

Description

The present invention relates to an optical sighting, designation and objective tracking assembly.

The sets of this type allow the designation of a target by means of a laser transmitter (generally a rangefinder) whose radiation, generally infrared radiation, is directed by the operator towards the target which the latter observes and pursues thanks to optical sighting means. More specifically, a collimator is provided capable of forming a visible image of a reticle materializing the direction of sight, and superimposed on the image of the target, the reference direction (that is to say the pointing direction). of the laser rangefinder) must coincide with the direction of sight when the image of the target is placed in the center of the reticle.

When a projectile is fired at the target, the radiation from its tracer is received and directed towards a deviation measurement device (also referred to below as "locating means"), which also receives a signal representative of the direction of the target, thus defining for the latter a "location direction" which is that in which the locator "imagines" the target (except in the case of a laser emitter also forming an illuminator, the locator does not have 'no radiation returned by the target). The spatial position of the two directional information is analyzed, and the locator derives therefrom a differenceometric signal representative of the angular difference between the location direction -which, ideally, coincides with the direction of the target as designated by the laser beam ( reference direction) - and the direction of the projectile. This information can then be used to remote control the projectile in order to bring its trajectory towards the target.

Furthermore, the laser transmitter generally cooperates with telemetric means, which also receive the radiation reflected by the target, so as to derive a telemetric signal of distance and, if necessary, of relative speed of the target, from time. propagation of the returned laser pulse.

One of the difficulties encountered with this type of device lies in the precise adjustment of coincidence between the reference or sighting direction (that is to say the real direction of the target), the direction indicated by the crosshair of the collimator. (hereinafter referred to as "collimation direction", which is the apparent direction of the target, as it appears to the operator's eye), and the location direction, (which is the fictitious direction of the target considered by the locator) .It is indeed essential that, when the operator aims at a target, the center of his reticle corresponds exactly to the reference and location directions; if this condition were not fulfilled, it would not be the targeted target that would be taken into account for the telemetry and the variometry, but a point close to this one, more or less distant.

This adjustment, known as "harmonization", has already been envisaged in the prior art.

In the case of aiming by purely electronic means (projection of the target field on a cathode ray tube analyzer or equivalent, the target being automatically continued), it is possible to carry out this harmonization by modifying the scanning of the analyzer tube. Such a harmonization technique is for example described in patent FR-2,475,208 (or EP-A-0033 679).

The invention, on the contrary, relates to the case of a purely optical aiming with reticle, that is to say where it is the operator himself who designates the target by centering his collimator, and who pursues it in his field of view.

In such a case, the difficulty is increased by the fact that the rangefinder-devometer assembly - which is an electronic assembly - and the aiming assembly - which is a purely optical assembly - form two separate blocks. Harmonization is generally carried out by a very fine adjustment of the angular position of the beam emitted by the rangefinder relative to the aiming block which transmits it, which supposes precise means of adjustment and a very rigid mechanical structure to avoid any misalignment ulterior.

• . des moyens désignateurs, aptes à émettre, selon une direction de référence, un rayonnement monochromatique vers une cible désignée,
• . un bloc de visée permettant l'observation de la cible par un opérateur selon une direction de visée coïncidant avec la direction de référence, et orientable de manière à modifier simultanément ces directions pour les amener sur la cible,
• . des moyens collimateurs, aptes à former une image visible d'un réticule matérialisant la direction de visée, et à émettre cette image en direction du bloc de visée, selon une direction de collimation, représentative de la direction de visée,
• . des moyens localisateurs, aptes à recevoir d'une part, selon une direction de localisation, un signal représentatif de la direction de la cible, et d'autre part le rayonnement émis par un projectile tiré en direction de la cible, et à en comparer les directions de propagation respectives pour en dériver un signal écartométrique relatif au projectile et à la cible.

To overcome this difficulty, the invention proposes a new means of harmonization used in combination with the aforementioned structure, the latter comprising more precisely:

• . designating means, capable of emitting, in a reference direction, monochromatic radiation towards a designated target,
• . an aiming block allowing the observation of the target by an operator according to an aiming direction coinciding with the reference direction, and orientable so as to simultaneously modify these directions to bring them onto the target,
• . collimating means, capable of forming an image visible from a reticle materializing the aiming direction, and emitting this image towards the aiming block, in a collimation direction, representative of the aiming direction,
• . locating means, capable of receiving on the one hand, in a localization direction, a signal representative of the direction of the target, and on the other hand the radiation emitted by a projectile fired towards the target, and to compare it the respective directions of propagation to derive therefrom a deviation signal relating to the projectile and the target.

• . des moyens harmonisateurs, interposés entre les moyens collimateurs et le bloc de visée, aptes à ajuster l'orientation angulaire de la direction de collimation, et recevant un signal d'harmonisation fourni par les dits moyens localisateurs
     de manière à faire coïncider la direction de collimation, en sortie du bloc de visée, avec les directions de référence et de visée, de manière invariante avec l'orientation du bloc de visée,
• . des moyens pour renvoyer vers les moyens localisateurs une partie du rayonnement émis par les moyens collimateurs, après traversée des moyens harmonisateurs, ainsi que des moyens pour, simultanément, renvoyer vers les moyens localisateurs une partie du rayonnement émis par les moyens désignateurs,
     de manière que, au cours d'une phase d'étalonnage, les moyens localisateurs puissent délivrer ledit signal d'harmonisation représentatif de l'écart angulaire entre la direction de localisation et la direction de collimation.

According to the invention, provision is made:

• . harmonizing means, interposed between the collimating means and the aiming block, capable of adjusting the angular orientation of the collimation direction, and receiving a harmonization signal supplied by said locating means
  so as to make the collimation direction coincide, at the output of the aiming block, with the reference and aiming directions, invariantly with the orientation of the aiming block,
• . means for returning part of the radiation emitted by the collimating means to the locating means, after crossing the harmonizing means, as well as means for simultaneously returning part of the radiation emitted by the designating means to the locating means,
  so that, during a calibration phase, the locator means can deliver said harmonization signal representative of the angular difference between the location direction and the collimation direction.

A first advantage arising from this arrangement lies in the decoupling which is thus carried out between the aiming block, which is an autonomous optical assembly, and the rangefinder-variometer-harmonizer assembly, essentially electronic, without modifying the harmonization of the assembly. Adaptation to any existing aiming block is thus facilitated, insofar as the harmonizing means are optically and mechanically external to it. In addition, the interchangeability of the aiming block is ensured without difficulty.

A second advantage lies in the dual function provided by the collimator: on the one hand, a classic reticle function allowing the operator to center his field of vision on the target, and, on the other hand, a reference source function to ensure immediate harmonization, integrated into the system. It is indeed the image of the reticle returned to the locator which defines the aforementioned "direction of location".

It will also be noted that this harmonization can be carried out at any time, in the absence of a target and without requiring any return of the laser beam.

Advantageously, one can provide servo means, for controlling the harmonizing means so as to cancel the harmonization signal delivered by the locating means.

Preferably, the harmonizing means comprise a diasporameter interposed on the optical path of the light rays at the output of the collimating means.

Furthermore, the part of the radiation emitted by the collimating means and returned to the locating means is preferably formed by the image of a pair of source points, of predetermined spacing, further allowing, during the calibration phase, an adjustment of the proportionality factor of the locating means.

Preferably also, the radiation of the illuminating means and that of the source points of the collimator are included in a spectral band not visible by the operator, the image of the reticle being on the other hand radiated in a visible spectral band.

The two aforementioned functions fulfilled by the collimator means are thus fulfilled in two different spectral bands: harmonization in the invisible infrared band, corresponding moreover to the emission band of the laser and to the best sensitivity of the locator means; and formation of a sighting reticle in visible light, thus not risking to interfere with the harmonization process.

Other characteristics and advantages of the invention will appear on reading the detailed description below, made with reference to the single appended figure, which schematically illustrates an embodiment of the invention.

In this figure, there is shown a laser transmitter 100, for example a laser rangefinder delivering a telemetric signal ST, a locator assembly 200, capable of providing a deviation signal SE, a sighting block 300 which constitutes an optical invariant, a collimator 400 allowing the formation of the reticle and the source points, as well as means of harmonization 500.

The rangefinder 100, provided with its afocal optical group 110, comprises an output window 111 for the emission of the monochromatic beam, and a window input 112 for the analysis of this same beam after its reflection on the target.

The locator module 200 includes an input window 210, which allows two rays to illuminate a cathode ray tube image analyzer, or an equivalent device (for example a charge transfer device). The computation circuit 220 of the deviation meter then determines, from this information, the angular deviation of the directions of propagation of the two radiations striking the window 210.

The aiming block 300 is, in the example shown, a periscopic viewfinder comprising a frame 310 surmounted by a pivoting cover 320 supporting a gyrostabilized mirror 370. The cover and the mirror are controlled so as to move together on command of the operator.

The aiming block includes an exit window 330 transmitting the visible image of the target to the operator, and located opposite another window 340 also transmitting to the operator, in superposition, the image of the reticle formed by the collimator 400. A window 350, in the lower part, allows the transmission of the radiation (infrared) emitted by the range finder 100, as well as the radiation emitted by the tracer of the projectile towards the locator 200.

The aiming block accommodates a separating prism 360 allowing the distribution or the regrouping of the different radiations between the windows of the viewfinder.

• . image visible de la cible retransmise à l'opérateur : trajet A₁ B₁ C₁ D₁ (le point C₁ correspond à une réflexion sur une face dichroïque 361 réfléchissant le rayonnement visible, mais laissant passer le rayonnement infrarouge).
• . faisceau monochromatique émis par le télémètre 110 vers la cible : trajet E₂ F₂ G₂ B₂ A₂ ; les lignes A₁ B₁ (direction de visée) et A₂ B₂ (direction de référence) ont été représentées distinctes pour la clarté de la figure, mais elles coïncident en réalité, tout comme la direction A₄ B₄ (direction en retour laser), comme il sera expliqué par la suite.
• . réception du faisceau réfléchi par la cible consécutivement à l'émission laser du télémètre : trajets A₄ B₄ G₄ F₄ E₄ (retour vers la fenêtre 112 du télémètre).

More specifically, the following optical paths have been represented:

• . visible image of the target retransmitted to the operator: path A₁ B₁ C₁ D₁ (point C₁ corresponds to a reflection on a reflecting dichroic face 361 visible radiation, but letting infrared radiation pass).
• . monochromatic beam emitted by the range finder 110 towards the target: path E₂ F₂ G₂ B₂ A₂; the lines A₁ B₁ (direction of sight) and A₂ B₂ (reference direction) have been shown distinct for clarity of the figure, but they coincide in reality, just like the direction A₄ B₄ (direction in laser return), as it will be explained later.
• . reception of the beam reflected by the target following the laser emission from the range finder: paths A₄ B₄ G₄ F₄ E₄ (return to window 112 of the range finder).

The separator-deflector assembly formed by the semi-reflecting dichroic mirror 230 and the prism 240 is supported by a single body 250 which allows perfect alignment of its different optical elements, which are the optical elements associated with the rangefinder-locator assembly. , independently of the optics of the aiming block itself There is thus an interchangeable sub-assembly which behaves by optical invariant and therefore does not require rigorous positioning compared to electronic detectors (rangefinder and locator).

• . rayonnement émis par le traceur du projectile tiré sur la cible : trajet A₅ B₅ G₅ F₅ J₅ F₅. D'après l'écartement entre les points K₆ (rayonnement en provenance du collimateur) et K₅ (projectile tiré), le localisateur pourra élaborer un signal écartométrique relatif au projectile et à la cible.

This sub-assembly also includes a retroreflector 540, an attenuator 530, as well as an optical square 520 used for harmonization, the role of which will be described below.

• . radiation emitted by the tracer of the projectile fired at the target: path A₅ B₅ G₅ F₅ J₅ F₅. According to the spacing between the points K₆ (radiation coming from the collimator) and K₅ (projectile fired), the locator will be able to develop a deviation signal relating to the projectile and the target.

The collimator means 400 have, as indicated above, a double function of forming a firing reticle in visible light and of emitting at least one source point for harmonization, in infrared light. These two elements are materialized by construction on the same reticle glass 422, however they radiate in different spectral bands: the visible lighting is produced by a halogen lamp lighting 410, heat and spectral shape filter 411 and condenser 412. On the other hand, the illumination of the points of the reticle used for harmonization is carried out by a light-emitting diode 420 whose infrared light is brought to the corresponding zone of the reticle by a fiber optic network 421. Finally, a lens 430 is placed at the output of the collimator.

The harmonizing means 500 consist of a diasporameter, located at the outlet of the collimator, which makes it possible to slightly deflect the light rays coming from the latter to make them parallel to the axis of emission of the laser beam. It consists of two prisms 501, 502 with a very small apex angle, each driven by an electric motor 511, 512 under the control of a servo-control 550, and according to a harmonization signal (SH) delivered by the locator during a preliminary adjustment phase.

• . prélèvement d'une fraction très faible (moins de 1 ppm] du rayonnement laser émis par l'illuminateur : trajet E₂ F₂ H₃ I₃ J₃ K₃, par réflexion sur le coin de cube 540 via l'atténuateur 530. On dispose ainsi sur le localisateur d'un point K₃ représentatif de la direction de référence.
• . image des points de référence émis en lumière infrarouge par le collimateur 400 : trajet L₆ M₆ N₆ F₆ J₆ K₆, par l'intermédiaire de l'équerre optique 520. On dispose ainsi d'un second point K₆ sur le localisateur, représentatif de la direction de collimation, puisque le signal est prélevé en sortie du diasporamètre 500.
• . réticule visible renvoyé vers l'opérateur : trajet L₇ O₇ D₇. On notera - et c'est là l'une des caractéristiques essentielles de l'invention - que, dans la mesure où le verre réticule 422 est unique et où le rayonnement pour l'harmonisation est prélevé en sortie du diasporamètre, tout variation angulaire de la direction O₇ D₇ (c'est-à-dire de la direction apparente de visée) se traduira par une modification simultanée de la direction J₆ K₆.

Harmonization involves the following optical paths:

• . sampling of a very small fraction (less than 1 ppm] of the laser radiation emitted by the illuminator: path E₂ F₂ H₃ I₃ J₃ K₃, by reflection on the corner cube 540 via the attenuator 530. There is thus on the locator a point K₃ representative of the reference direction.
• . image of the reference points emitted in infrared light by the collimator 400: path L₆ M₆ N₆ F₆ J₆ K₆, via the optical square 520. There is thus a second point K₆ on the locator, representative of the direction collimation, since the signal is taken at the output of the diasporameter 500.
• . visible reticle returned to the operator: path L₇ WHERE D₇. It will be noted - and this is one of the essential characteristics of the invention - that, insofar as the reticle glass 422 is unique and where the radiation for harmonization is taken at the output of the diasporameter, any angular variation in the direction O₇ D₇ (that is to say the apparent direction of sight) will result in a simultaneous modification of the direction J₆ K₆.

It then suffices to adjust the diasporameter so that the points K₆ and K₃ are confused, that is to say in other words that the direction O₇ D₇ (apparent direction of aiming) and C₁ D₁ (real direction of aiming or of reference) coincide.

This adjustment can be carried out automatically by a servo control 550 controlling the motors 511 and 512 of the diasporameter, so as to cancel the harmonization signal SH delivered by the locator.

Note that the optical paths identified with letters bearing the indices 3 and 6, which are those which allow harmonization, are entirely internal to the apparatus - they therefore do not require the illumination of a standard target for the surgery - and never pass through the optical unit 300 - it is therefore an optical invariant external to the system, which ensures perfect interchangeability.

Claims (6)

1. A optical aiming assembly for designating and tr acking a target, the assembly being of the type comprising :
      designator means (100) suitable for emitting monochromatic radiation along a reference direction (E₂G₂, B₂A₂) towards a designated target;
      an aiming block (300) enabling the target to be observed by an operator along an aiming direction (A₁B₁, C₁D₁) coinciding with the reference direction (A₂B₂), and orientable in such a manner as to simultaneously modify said directions to direct them to a target;
      collimator means (400) suitable for forming a visible image of a reticle (422) indicative of the aiming direction and for sending said image to the aiming block, in a collimation direction (O₇D₇) representative of the aiming direction (C₁D₁); and
      localization means (200) suitable for receiving firstly (K₃) a signal representative of the direction to the target along a localization direction, and secondly (K₅) radiation emitted by a projectile fired towards the target, and for comparing the respective propagation directions (J₃K₃, J₅K₅) to derive an angle signal (SE) relating to the projectile and to the target;
      wherein the optical aiming assembly further comprises :
      harmonization means (500) interposed between the collimator means and the aiming block and suitable for adjusting the angular orientation of the collimation direction, and receiving a harmonization signal (SH) provided by said localization means, in such a manner as to cause the collimation direction (O₇D₇) at the outlet from the aiming block to coincide with the reference (A₂B₂) and aiming (A₁B₁, C₁D₁) directions in a manner which does not vary with the orientation of the aiming block; and
      means (520) for sending a portion of the radiation emitted by the collimator means to the localization means (200) after passing through the harmonization means (500), together with means (230, 530, 540, 240) for simultaneously sending a portion of the radiation emitted by the designator means to the localization means, in such a manner that during a setting-up phase the localization means are capable of delivering a harmonization signal (SH) representative of the angular difference between the localization direction and the collimation direction.
2. An assembly according to claim 1 further including servo-control (550, 511, 512) means for controlling the harmonization means in such a manner as to cancel the harmonization signal (SH) delivered by the localization means.
3. An assembly according to claim 1, wherein the portion of the radiation emitted by the collimator means and returned to the localization means is constituted by the image of a pair of point sources at a predetermined distance apart, thereby additionally enabling the scale factor of the localization means to be adjusted during a setting up phase.
4. An assembly according to claim 1, wherein the harmonization means (500) include a crossed-prism defflector (501, 502) interposed on the optical path of the light rays at the outlet from the collimator means.
5. An assembly according to claim 3, wherein the radiation from the designator means and the radiation from the point sources of the reticle ly in a portion of the spectrum which is not visible to the operator, whereas the image of the reticle is formed by radiation lying in a visible portion of the spectrum.
6. An assembly according to claim 1, wherein the designator means (100) include telemeter means, and the optical block is suitable for returning monochromatic radiation reflected from the target to the telemeter means in such a manner as to derive a telemeter signal (ST) based on the propagation time of said radiation.

Images