EP0356303B1 - Firing control system with compensation of aiming errors - Google Patents

Description

The present invention relates to fire control installations for a barrel which can be oriented and pointed by a servant. It is particularly applicable to installations comprising a weapon or several twin weapons, of small or medium caliber.

There are already known fire control installations of the type having a sight carried by the barrel of the weapon, with a reticle movable relative to the axis of the weapon and means for evaluating the angle of offset controlling the position of the reticle. The offset angle, i.e. the distance between the direction of the crosshair and the axis of the weapon, is determined so that, if the direction of the crosshair is oriented towards the current target, the weapon is aimed at the "future goal". The offset angle is determined by taking into account the angular speed of movement of the target, the speed of the ammunition and the appreciated distance between the target and the weapon. The distance between the target and the weapon is generally estimated or measured, while the speed of the ammunition is memorized. The angular speed of movement of the target with respect to a fixed mark is assimilated to the angular speed of the weapon controlled by the servant who keeps it pointed at the target. Because of this assimilation, the measurement of the angular speed of the target is marred by noise due to pointing errors by the servant and possibly to the instabilities of the support.

GB-A-1605027 describes a rifle whose sight is equipped with a wide field camera.

The invention aims in particular to provide a firing control installation allowing a better determination of the offset angle to be given to the reticle.

To this end, the invention provides a firing pipe installation for a barrel with an adjustable barrel which can be pointed by a serving, comprising a sight carried by the barrel of the weapon, with reticle movable relative to the axis of the weapon, and a wide field camera, linked to the weapon, characterized in that it also comprises means for calculating an offset angle between an aiming axis materialized by the reticle and the axis of the weapon, to control the position of the reticle in the viewfinder so that when the aiming axis is aligned with the target, the axis of the weapon is aligned with an estimated position that the target will have at the moment when the ammunition fired by the weapon will pass close to the target, the angle of offset (α) being calculated from variations in the aiming angle of the weapon, measured by sensors, and a correction signal supplied by means for measuring the apparent movement of the target in the field of the camera.

This achieves a function equivalent to that of a stabilized remote pager serving as a control station for a weapon system, but in a much simpler manner. Measuring the apparent movement in the field of the camera simply provides a pointing correction term, eliminating the noise caused by the servant's inability to continuously and rigorously follow the movement of the target. In other words, the trajectory of the target becomes independent of the quality of pursuit of the target. Filtering to minimize the influence of pointing errors can be simplified.

In addition, the couplings between pointing and introduction of the shot correction have no effect on the calculation of the latter.

The invention also aims to give a shooting installation a stadimetry capacity by using only simple means. For this, the invention uses a wide field camera (which can be the camera used for measuring pointing errors) and means for measuring the apparent diameter of the target in the image supplied by this camera. A simple treatment makes it possible to determine, from the apparent diameter of the target, the value of the focal length of the camera and the actual pre-displayed dimensions of the target, the distance from the latter.

We can especially use, to highlight The invention implements a camera using a matrix of load-coupled sensors (less expensive than a "Vidicon" camera). This camera can be, for night use, coupled to a light intensifier tube. The installation can then be used both day and night.

It is important to note that the stadimetric measurement can be maintained continuously, on the only condition that the target remains in the field of the camera. The camera does not have to be pointed exactly at the target, whereas this is necessary in the case of a laser rangefinder with low field for example.

The invention also aims to provide a movable reticle for fire control installations, making it possible to define the line of sight at the weapon pointer precisely, using only simple means.

For this, the invention provides a sighting shooting installation whose reticle is constituted by a liquid crystal matrix and a matrix display, making it possible to give at least one pixel a particular brightness.

The matrix can also be used to present to the pointer the image seen by a wide field camera, such as that necessary for the functions mentioned above. This use is particularly advantageous when the camera is intended to operate with a low level of light, for example when it uses a light intensifier or a matrix of sensitive elements "NOCTICON": night shooting then becomes possible.

• la Figure 1 est un schéma de principe destiné à faire apparaître les paramètres qui interviennent pour la mise en oeuvre de l'invention ;
• la Figure 2 est un synoptique montrant les composants d'une installation suivant l'invention ;
• la Figure 3 montre un exemple de variation de la direction d'une arme pointée sur la cible, dans un repère fixe, en fonction du temps, faisant apparaître l'écart de pointage calculée par analyse de l'image fournie par une caméra liée au fût de l'arme ;
• la Figure 4 est un schéma montrant l'image fournie par un moniteur associé à la caméra de télévision portée par le fût de l'arme.

The invention will be better understood on reading the following description of a particular embodiment given by way of non-limiting example. The description refers to the accompanying drawings, in which:

• Figure 1 is a block diagram for showing the parameters involved in the implementation of the invention;
• Figure 2 is a block diagram showing the components of an installation according to the invention;
• Figure 3 shows an example of variation of the direction of a weapon aimed at the target, in a fixed reference, as a function of time, showing the aiming deviation calculated by analysis of the image provided by a camera linked to the was of the weapon;
• Figure 4 is a diagram showing the image provided by a monitor associated with the television camera carried by the barrel of the weapon.

The pointing installation shown diagrammatically in FIGS. 1 and 2 is intended for a small caliber weapon 10, such as a 20 mm twin-barrel cannon, with manual aiming by rotation about a bearing axis 12 and an axis of site 14. The axis Xa of the weapon must be directed not towards the instantaneous position of the target at the instant of the shooting, which one will call thereafter "real goal", but towards the position which will have the target at the moment when the ammunition passes nearby, that is to say towards the "future goal", indicated in dashes in Figure 1. To facilitate the aiming by the servant, the telescopic sight fixed to the weapon is provided with a reticle shift system in a direction and an amplitude such that, when the line of sight Xr is aligned with the real goal, the axis Xa of the weapon is aligned with the future goal . The use of an offset system involves estimating or calculating the angle of offset α between Xr and Xa, and of course that of the direction of the offset.

The means shown in FIGS. 1 and 2 for defining the amplitude and the direction of α comprise a block for measuring the angle (or the angular speed) of pointing and a camera equipped with a deviation measurement device. The measuring block 16 can have a conventional constitution. In the case shown in FIG. 2, it is carried by the weapon and comprises for example two gyrometers which permanently supply the angles or the speeds to the calculation member 18. When the mount of the weapon is perfectly stationary, instead of gyros, tachometric or angular sensors can be used.

Due to the imperfections and time constants of the lookout motorization system and the inherent limitations of manual aiming, the pursuit of a target whose angular position varies over time as indicated by a straight line in Figure 3, can be represented by an irregular line, such as line 20. In a conventional installation, the influence of the pointing difference e is reduced by low-pass filtering of the signal, which is not without drawbacks. The installation according to the invention eliminates this need. For this, it includes a camera 22 carried by the weapon and whose field ϑ is coaxial with the direction of the weapon. The field of view of this camera must be sufficient so that the real goal does not come out even when the difference between real goal and future goal is maximum.

The video signal supplied by the camera 22 is applied to an image processing circuit 24 whose function is to provide, on an output 26, the characteristics (module and orientation) of the position and the speed of the goal in the field , i.e. optical deviation data.

By combining the speed or position measurements provided by the block 16 and by the circuit 24, as well as an indication of the distance from the goal, the calculating member 18 determines the angle α (Figure 1). The distance can be supplied manually to the calculation unit on an output 28 of a desk 30. It can also be given by the image processing circuit 24, as will be seen further: the desk 30 can then include an output 32 for selecting the operating mode, allowing the calculation unit 18 to take into account either a distance pre-displayed on the desk, or a distance provided by the processing circuit picture.

It will often be unnecessary to assist the image processing circuit by manually designating the target in the field. In fact, the calculating member 18 can provide the image processing circuit 24, on a channel 34, with an approximate indication of the location where the target must be in the field, which allows discrimination.

The image processing circuit 24 can be provided for analyzing the image of the target, extracting its geometrical dimensions (apparent diameter) and supplying them to the calculating member 18 on an output 36. It then suffices to store in the calculation unit the dimensions of standard targets, for the various orientations where they may occur, so that the calculation unit has the elements necessary for stadimetry. A few standard dimensions are sufficient. It therefore suffices to provide a manual selector on the console 30.

It is possible to use reticles of a very varied nature; however, in an advantageous embodiment of the invention, the reticle comprises a matrix, in particular with liquid crystals. To display the reticle, the arrangement shown schematically in FIG. 1 can be used. A semi-reflecting plate 42 makes it possible to superimpose the real target and the graphics provided by the matrix 44. The calculating member 18 then excites at least one line and a column of the matrix, so as to reveal two brilliant perpendicular lines, or a pixel. This arrangement can be reversed, so that the reticle appears in black on an illuminated background, a switching of contrast inversion can be provided by modification. control of the matrix or reversing the direction of the polarizer involved in the implementation of the liquid crystal matrix. The calculation unit then determines the position of the column and of the row to be excited. It is in particular advantageous to excite two rows 48 and two columns 50 to constitute a rectangular reticle usable for a stadimetric evaluation by the servant.

It is also possible, especially for night shooting, with a light intensifier camera, to use the matrix to reveal the reticle and the image provided by the camera (Figure 4). Night shooting is thus made possible.

The invention is susceptible of numerous modes of implementation. One can for example use, instead of a matrix addressable by line and by column, two orthogonal bars; to allow time multiplexing of the control circuit without loss of contrast, the matrix may include transistors for storing the excitation between two refreshes.

Claims (6)

1. A fire control system for a weapon having an operator-aimed barrel, comprising a sighting piece carried by the barrel of the weapon (10), having a reticle movable with respect to the axis of the weapon, and a large field camera (22) fast with the weapon (10), characterized in that it further comprises means for computing and offset angle (α) between a sighting axis (Xr) materialized by the reticle and the axis (Xa) of the weapon, for controlling the position of the reticle in the sighting piece so that, when the sighting axis (Xr) is aligned with the target, the axis (Xa) of the weapon is aligned with an estimated position which the target will have when the ammunition fired by the weapon is close to the target, the offset angle (α) being computed from the variations of the aiming angle of the weapon, measured by sensors, and from a correction signal delivered by means (18,24) for measuring the apparent movement of the target in the field of the camera.
2. A system according to claim 1, characterized by comprising a large field camera, means for measuring the apparent diameter of the target in the image delivered by the camera, and computing means (18) for determining the distance of the target from the apparent diameter of the target, the focal length of the camera and actual preset dimensions of the target.
3. A system according to claim 2, characterized in that it comprises a common large field camera (22) for both measuring the distance of the target and measuring the apparent movement of the target.
4. A system according to claim 1, 2 or 3, characterized in that the reticle consists of a liquid cristal matrix display having means for energizing at least one pixel or at least one line and one column of the matrix.
5. A system according to claim 4, characterized in that it comprises means for displaying the image of the field of the camera by means of the matrix.
6. A system according to any one of the preceding claims, characterized in that the large field camera has a light intensifier tube permitting night firing.

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