EP1632743A1

EP1632743A1 - Device for a laser simulator

Info

Publication number: EP1632743A1
Application number: EP04020757A
Authority: EP
Inventors: Per Cederwall
Original assignee: Saab AB
Current assignee: Saab AB
Priority date: 2004-09-01
Filing date: 2004-09-01
Publication date: 2006-03-08

Abstract

A device for a laser simulator (1) for simulating the firing of a weapon with a parabolic, homing or otherwise guided high ammunition trajectory or combinations thereof. A barrel (2) constitutes a launch ramp for the missile weapon and is elevated at an angle of elevation α relative to the line of sight (I) in connection with the firing of the missile weapon. The laser simulator (1) contains a laser unit (3) arranged in the barrel (2) with a mechanical and optical axis (x_a) in a known relationship relative to one another and relative to a center axis for the barrel (2). An optical aiming unit (4) containing an optical wedge (6) is arranged in front of an optical outlet (9) on the laser unit (3). The optical wedge (6) is disposed so as to deflect a beam of light emitted from the laser unit (3) at an angle of deflection φ corresponding to the angle of elevation α.

Description

TECHNICAL AREA

This invention concerns a device for a laser simulator for simulating the firing of a weapon with a parabolic, homing or otherwise guided high ammunition trajectory or combinations thereof as described in the preamble to claim 1.

BACKGROUND OF THE INVENTION

The use of simulator devices is known in the training of gunners in the firing of missiles. These devices make it possible to conduct tactical training and train the gunners in that they learn to aim and fire at a target without using real projectiles or missiles. The projectile in these simulator devices is generally a fictive projectile: a computer determines the position of the fictive projectile, compares this position with that of the target being aimed at and then estimates the quality of the firing by, among other ways, determining the extent to which the aiming (or sighting) of the firing would have enabled the projectile to hit the target if the firing had been real. One common type of similar device for simulating missile firing is a so-called "laser simulator," wherein the fictive projectile can consist of a laser beam that can strike a target with a hit pattern that corresponds to that of a real missile. One problem associated with this type of laser simulator is that a laser beam cannot be caused to follow a missile trajectory when it is not rectilinear, as in the case of, e.g. a parabolic missile trajectory. Simulation can instead be achieved by aiming the laser beam in a direction that deviates from the direction of elevation for the laser simulator in such a way that the hit point for the laser beam corresponds to the hit point for the missile. The laser beam can thereby represent, e.g. a missile weapon with a homing warhead that continuously searches for and locks onto the heat signature given off by the target being engaged. To achieve optimum effect, such missiles fly with high, parabolic trajectories. The missile can then terminate its flight by turning down toward the target and, e.g. striking the roof of a tank. This can also be relevant with respect to ballistic weapons whose projectile trajectories conform to a ballistic parabola, or other types of guided missiles.
In order for a missile/projectile to be able to assume a parabolic trajectory, the barrel/launch ramp must be elevated at a large angle relative to the horizontal plane and "Line of Sight" at the moment of firing. This can be achieved by tilting the barrel/launch ramp relative to the "line of sight" of the sight. The sight is connected mechanically to the launch ramp via a sight mounting so that this angle is maintained. A laser simulator for such a missile weapon should have its laser beam oriented in line with the "line of sight" of the sight to achieve the best possible performance. This is realized in current solutions in that the laser unit in the laser simulator is mounted in line with the "line of sight" and thereby angled relative to the center axis of the barrel or launch ramp. The beam orientation of the laser unit can then easily be aligned so that it coincides with the sighting orientation of the sight.
However, one problem with this known solution consists in that the space inside the barrel is limited, which can cause problems in achieving sufficient tilting of the laser unit when it is arranged inside the barrel. Problems with mechanical interference have been encountered when the laser unit is angled at a large angle in order to correspond to a high angle of elevation of the missile weapon. Such interference can result in degradation of the quality of the simulation to such an extent that the laser simulator does not deliver the desired training results.
There are also requirements with respect to the robustness of the suspension of the laser unit inside the missile weapon to ensure that the system can withstand a harsh environment involving vibrations, impacts and jolts without the unit altering its orientation. This suspension is rendered more difficult when the laser unit is to be aligned in an orientation that differs from the center axis of the missile weapon.
Another solution involves expanding the replica weapon to create room for the laser unit. However, this solution has the disadvantage that the simulator equipment thereby assumes an appearance that deviates from that of the missile weapon, which in and of itself degrades the training results obtained with the equipment. Furthermore, it is difficult to realize such an expansion without problems arising with projecting portions that disrupt both appearance and handling and/or get in the way of other peripheral equipment. There is also a risk that the simulator equipment will not fit into permanent installations adapted for the weapon, such as vehicles racks, shipping boxes, etc.

DESCRIPTION OF THE INVENTION

The invention provides a device for a laser simulator for simulating missile firing in a missile weapon for a parabolic, homing, or otherwise guided missile trajectory or combinations thereof. The laser simulator simulates a missile weapon in which a barrel consists of a launch ramp. The barrel is elated at an angle of elevation α relative to the line of sight during a firing of the missile weapon. The laser simulator contains a laser unit arranged in the barrel with a mechanical and optical axis in a known relationship relative to one another and relative to a center axis for the barrel. An optical aiming unit comprising an optical wedge arranged in front of an optical outlet on the laser unit so that a beam of light emitted from the laser unit passes through the optical wedge. The optical wedge is intended to deflect the beam of light emitted from the laser unit at an angle of deflection φ corresponding to the angle of elevation α.
The optical wedge in one embodiment of the invention is arranged so as to deflect the emitted beam of light in the vertical plan of the beam path.
In another embodiment of the invention, the optical wedge has a first surface facing toward the muzzle of the barrel and a second surface facing toward the laser unit. The second surface is angled relative to the first surface at a wedge angle β, which is chosen so that an incident beam of light from the second surface emanates from the first surface of the optical wedge at the deflection angle φ.
In a preferred embodiment of the invention, the first surface is arranged so that its perpendicular direction points in the same direction as the center axis of the barrel. The surface can thereby constitute an orthogonal muzzle glass for the laser unit.
In a special embodiment of the invention, the optical wedge is arranged so that a so-called "extreme cross-section", a plane cross-section through the center of gravity of the optical wedge and through the part of the wedge that gives the longest optical path and through the part of the wedge that gives the shortest optical path is arranged so as to coincide with the vertical plane.
In yet another embodiment of the invention, the wedge angle β is dimensioned with respect to the refractive index of the wedge relative to the refractive index of the media adjacent to the first and second surface of the optical wedge and the desired optical tilt.
In yet another preferred embodiment of the invention, the wedge angle β is selected within the range 13.8°<β<35.8° when the angle of elevation α for the barrel is within the range 10°<α<28°. The refractive index for the optical wedge should, under these angular conditions, fall within the range 1.716<nD<1.718, while the effective wavelength of the laser should fall within the range 880 nm<λ<930 nm.
In a preferred embodiment of the laser simulator, the laser unit is arranged so as to receive reflections of the emitted beam of light in an optical inlet that coincides with the optical outlet. By analyzing the received reflection in relation to the emitted beam of light, software in the laser simulator can be arranged so as to correct the image distortion that arises in connection with the refraction of light in the optical lens.
In yet another preferred embodiment of the invention, the optical aiming unit contains a cylindrical seat in which the optical wedge is fixedly mounted. A gas-tight cylindrical glue joint is arranged between the seat and the optical wedge. A gas-tight volume is created thereby between the laser unit and the optical wedge when the optical aiming unit is sealed by means of an 0-ring that clamps against the laser unit.
In a supplemental embodiment of the invention, the cylindrical seat is arranged in a front wall disposed facing the laser unit. This front wall can be releasably secured to the laser unit by means of bolt and/or a friction joints.
In an alternative embodiment of the invention, the optical wedge is arranged in a unit that is freestanding from the laser unit, which freestanding unit is fixed relative to the optical axis of the laser unit in the rotational direction.
In an alternative embodiment of the invention, two or more optical wedges are arranged sequentially in the optical beam path in an integrated unit or in a unit that is freestanding from the laser unit. The optical wedges are fixed relative to the optical axis of the laser unit in the rotational direction. This embodiment occurs mainly in connection with large angles of elevation α>28°.
Additional advantages and features of the invention are defined in the claims and presented further in the following description of preferred embodiments, which are provided with reference to the accompanying figures. The invention is however not limited to the embodiments described below.

BRIEF FIGURE DESCRIPTION

Fig. 1: shows a laser simulator
Fig. 2 a: shows a side view of a laser unit and optical aiming unit connected thereto
Fig. 2 b: shows a frontal view of the laser unit and the optical aiming unit
Fig. 3: shows an exploded diagram of an optical aiming unit with optical wedge and cylindrical seat
Fig. 4: shows a laser unit with optical aiming unit and scattered-light protection in perspective

PREFERRED EMBODIMENTS

Figure 1 shows a perspective view of a laser simulator 1 according to the invention. In the preferred embodiment, the laser simulator 1 comprises a replica of a missile weapon. Alternative embodiments of the laser simulator 1 are naturally also possible within the scope of the idea of the invention. In alternative embodiments, the laser simulator can also be intended for other types of ammunition such as projectiles, shells, guided missiles and rockets. It is advantageous to have the laser simulator consist of a copy of the actual weapon, since this enables, e.g. the installation of the laser simulator 1 in holders intended for the missile weapon, such as vehicle racks, shipping boxes, etc. It also imparts a realistic feel and experience during exercises with the simulator if it is as precise a copy of the actual weapon as possible.
The laser simulator 1 comprises a tubular barrel 2 and a sight 5 arranged beneath the barrel 2. The sight can be a simulator sight, or it can be identical with the sight used on the actual weapon. The sight can be coupled to and uncoupled from the barrel by means of a simple handle, and this can be included as part of the simulator exercise. In the case of a missile weapon of the type simulated by the laser simulator 1 shown in the figure, the barrel 2 comprises the launch ramp for a fired missile. In a ballistic weapon, the direction of elevation direction in combination with the propulsive capacity of the missile yields a projectile trajectory consistent with a ballistic parabola. The hit point for the missile weapon, i.e. the point where the projectile trajectory terminates, is simulated via the laser simulator

1. The laser simulator 1 shown in Figure 1 corresponds to a missile weapon that is elevated at a relatively large angle of elevation α when fired. The barrel 2 in the depicted embodiment is elevated at an angle of elevation α = 18° relative to a line of sight I for the missile weapon. The invention is not limited to an angle of elevation of this size, but rather is applicable to angles of elevation within the range 0<α<90°, even if angles of elevation α>45° are unlikely for currently known weapon systems. For large angles α>28°, a plurality of sequentially arranged optical wedges 6 is usually required, which wedges are arranged in the optical beam path so as to refract the laser light to the desired direction in stepwise fashion.

A laser unit 3 is arranged inside the barrel 2 of the laser simulator 1. In the embodiment shown in the figure, the laser unit 3 is entirely enclosed inside the barrel 2 in order that the laser simulator 1 will resemble the missile weapon to the greatest extent possible. The laser unit 3 is cylindrical in shape and is arranged in the barrel 2 in such a way that the mechanical axis x_m for the laser unit 3 coincides with a center axis for the replica weapon. The laser unit 3 comprises a laser emitter to emit a laser beam of coherent monochromatic light. A beam of light emitted from the laser unit 3 has an optical axis x_a which, in the embodiment shown, coincides with the mechanical axis x_m. Minor angular displacements of the optical axis x_a relative to the mechanical axis x_m are also possible within the scope of the idea of the invention. An optical aiming unit 4 is further arranged in connection to the laser unit 3 inside the barrel 2. The optical aiming unit lies in abutment to against an optical outlet 9 from the laser unit 3. In the example shown in the figure, this optical outlet also comprises an optical inlet through which the re-reflected laser beam can be received. By receiving reflected radiation, software in the detector can be adapted so that minor image distortion can be compensated for in the laser simulation.
The laser unit 3 is suspended in frame sections arranged in the barrel 2 of the laser simulator 1. These frame sections consist of linear aluminum sections with specially designed V-grooves that suspend the laser unit 3 by means of vibration-damping rubber strips. The mechanical axis x_m of the laser unit 3 is oriented in line with the center axis of the replica weapon frame. Other alternative means of suspending the laser unit 3 are naturally also possible within the scope of the idea of the invention.
The laser unit 3 and optical aiming unit 4 are shown in side view in Figure 2a. The optical aiming unit in the figure is arranged as a front wall that is arranged integrated with the laser unit. The optical aiming unit can however also be realized as a unit that is freestanding from and mechanically connected to the laser unit 3, and arranged in front of its outlet. It is important that the mechanical connection be fixed and stable in such an embodiment.
The optical aiming unit contains a cylindrical seat 10 and an optical wedge 6 arranged therein that tilts the optical orientation of the laser beam emitted from the laser unit 3. The laser beam is tilted at an angle of deflection φ that corresponds to the angle of elevation α of the barrel 2. The outgoing laser beam thus travels in a direction that is illustrated in the figure by a corrected optical axis x_o. When the laser unit 3 is centered in the barrel 2 as shown in the figure, the angle of deflection φ is equal to the angle of elevation α. In an embodiment where the laser unit 3 is secured in the barrel 2 with a given angular relationship between the optical axis x_a of the laser unit 3 and the center line for the barrel 2, the angle of deflection corresponds to the difference between the tilt of the optical axis x_a of the laser unit and the angle of elevation.
The optical wedge 6 is positioned in the cylindrical seat in such a way that the optical beam path can freely pass through the optical wedge 6. The wedge 6 deflects the beam in the vertical plane. In the embodiment shown in the figure, the optical wedge 6 is centered in front of the optical outlet of the laser unit 3.
Figure 2b shows a frontal view of the unit. The optical wedge is secured in a mounting component that comprises the front wall of the laser unit 3. The wedge is secured by, e.g. gluing. The wall also comprises three T-grooves for insulating rubber strips that enable stable and vibration-damped mounting in the frame sections. These T-grooves can be seen in the exploded diagram of an optical aiming unit 4 shown in Figure 3.
The optical aiming unit further comprises a cylindrical seat 10, one end of which opens out in an axial stop for the optical wedge 6. The other end engages a recess in the front wall. The front wall lies in abutment to the laser unit 3 with an O-ring that lies in a tilted O-ring groove. Two bolts secure the front wall to the laser unit 3 and are used to clamp the front wall to the laser unit 3. The front wall is positionally and rotationally controlled by the two bolts in combination with the O-ring, which controls and centers on a protruding window flange at the optical inlet and outlet of the laser unit 3. The bolt joint also forms a friction joint in the rotational direction, since the O-ring is held against the laser unit 3 under pressure. The O-ring also forms the seal between the optical aiming unit and the laser unit 3.
Figure 3 shows an exploded diagram of the optical aiming unit. The optical wedge 6 is made of glass with a known refractive index. The optical wedge 6 has a first surface which, in the embodiment of the invention shown in Figure 2, is arranged so that its perpendicular direction points in the same direction as the center axis of the barrel 2.
The first surface 7 constitutes the muzzle glass for the laser unit 3. A second surface (8) of the optical wedge 6 is faced toward the optical outlet from the laser unit 3. This surface is angled at a wedge angle β in relation to the first surface 7. The wedge angle is chosen based on the desired angle of deflection and the refractive index. At an elevation of the laser simulator having the direction of elevation α = 18°, the angle of deflection φ = 18° for the embodiment shown in Figure 2. The wedge angle is then β = 24.2° at a refractive index nD = 1.717. At angles of deflection φ in the range 10°<φ><28° the wedge angle β will fall within the range 13.8°<β<35.8°, as the refractive index nD will be on the order of 1.716<nD<1.7.18. This correlation is determined by the law of refraction for optical media transitions such as between air/glass/nitrogen. Other gases with known refractive indices can also be relevant, as can other optical materials with known refractive indices in the wedge. In calculating the wedge angle β according to the preferred embodiment, the refractive index for nitrogen is assumed to be very close to the refractive index for air, nD = 1. It is naturally also possible to turn the optical wedge 6 so that the side angled at wedge angle β is faced toward the muzzle of the barrel 2. It is however advantageous to have the angled second side 8 turned toward the laser unit 3, since this yields favorable angles of incidence and reflection in the beam path, and less distortion of the laser beam during its passage through the wedge 6.
In the preferred embodiment, the effective wavelength of the laser should fall within the range 880 nm<λ<930 nm. The laser wavelength is chosen based on the wavelength range of one of the commercially available laser diodes. The preferred embodiment uses a laser diode with the nominal wavelength λ = 905 nm. The principle is however the same for other common laser wavelengths, such as λ = 780 nm, λ = 850 nm and λ = 1550 nm.
The optical wedge 6 is fixedly mounted in the cylindrical seat against an axial stop in the mounting component. The cylindrical seat is equipped with a cylindrical glue gap with glue-filling channels distributed around the wedge 6. The cylindrical glue joint secures the wedge 6 and forms a gas-tight glue joint against the outside world. The unit thus comprises an encapsulation and creates a gas-tight volume between the laser unit 3 and the optical aiming unit. The gas-tight volume between the optical wedge 6 and the outlet of the laser unit 3 is gas-filled via a valve 11; the space can alternatively be placed under vacuum. Removing all types of moisture from the space eliminates the risk of condensation problems when the laser simulator 1 is used at, e.g. low temperatures. The seal also provides effective protection against dirt and impurities on the optical wedge 6 and the outlet of the laser unit 3.
The wedge 6 is oriented so that an extreme cross-section through the wedge coincides with the vertical plane. The extreme cross-section constitutes a plane cross-section through the part of the wedge 6 that yields the longest optical path, the part of the wedge 6 that yields the shortest optical path, and a center of gravity for the wedge 6. The part of the wedge 6 that yields the longest optical path is oriented downward in the barrel 2.
The optical wedge 6 is antireflection-treated to reduce reflections and transmission losses. The range of the laser beam from the laser unit 3 is thus essentially the same as in an embodiment without no optical wedge 6.
Finally, Figure 4 shows a view of the laser simulator 1 with a portion of the barrel 2 removed to reveal the units arranged inside the barrel 2. Scattered-light protection 12 is oriented with the center axis at an angle corresponding to the angle of elevation α in relation to the center axis of the barrel 2. It is naturally also possible to use a laser simulator 1 according to the invention without this type of scattered-light protection 12.

Claims

A device for a laser simulator (1) for simulating the firing of a weapon with a parabolic, homing or otherwise guided high ammunition trajectory, wherein a barrel (2) comprises a launch ramp for the weapon and is elevated at an angle of elevation α relative to the line of the sight (I) in connection with a firing of the weapon, which laser simulator (1) contains a laser unit (3) arranged in the barrel (2) and having a mechanical (x_m) and optical axis (x_a) in a known relationship relative to one another and relative to a center axis for the barrel (2), characterized in that an optical aiming unit (4) comprising an optical wedge (6) is arranged in front of an optical outlet (9) on the laser unit (3), which optical wedge (6) is arranged so as to deflect a beam of light emitted from the laser unit (3) at an angle of deflection φ corresponding to the angle of elevation α.
A device according to claim 1, wherein the optical wedge (6) is arranged so as to deflect the emitted beam of light in the vertical plane of the beam path.
A device according to claim 1 or 2, wherein the optical wedge (6) has a first surface (7) facing toward the muzzle of the barrel (2) and a second surface (8) facing toward the laser unit (3), which second surface (8) is angled relative to the first surface (7) at a wedge angle β arranged so that an incident beam of light striking the second surface (8) emanates from said first surface (7) at an angle of deflection φ.
A device according to claim 3, wherein the first surface (7) is arranged so that its perpendicular direction points in the same direction as the center axis of the barrel (2).
A device according to claim 4, wherein the first surface (7) comprises a muzzle glass for the laser unit (3).
A device according to claim 5, wherein a plane cross-section through the center of gravity of the optical wedge (6) and through the part of the wedge (6) that yields the longest optical path and through the part of the wedge (6) that yields the shortest optical path, an extreme cross-section, is oriented so as to coincide with the vertical plane.
A device according to claim 5 or 6, wherein the wedge angle β is dimensioned with respect to the refractive index of the optical wedge (6) relative to a gas contained in a volume between the second surface (8) and the laser unit (3) and the desired optical tilt.
A device according to claim 7, wherein the wedge angle β is further dimensioned based on the transition between the optical lens and air.
A device according to claim 3, wherein the wedge angle β is chosen within the range 13.8°<β<35.8° when the angle of elevation of the barrel (2) falls within the range 10°<α<28°.
A device according to claim 9, wherein the optical wedge (6) has a refractive index within the range 1.716<nD<1.718 in connection with laser light with a wavelength λ in a range 880 nm<λ<930 nm.
A device according to any of the foregoing claims, wherein the first surface (7) and the second surface (8) of the optical wedge (6) are antireflection-treated.
A device according to any of the foregoing claims, wherein the laser unit (3) is arranged so as to receive a reflection of the emitted laser beam in an optical inlet, which coincides with the optical outlet.
A device according to any of the foregoing claims, wherein the laser simulator (1) contains software arranged so as to correct image distortion in connection with light refraction.
A device according to any of the foregoing claims, wherein the optical aiming unit contains a cylindrical seat (10) in which the optical wedge (6) is fixedly mounted.
A device according to claim 14, wherein the cylindrical seat contains a glue joint that is gas-tight so that a gas-tight volume is formed between the laser unit (3) and the optical wedge (6).
A device according to any of the foregoing claims, wherein in the optical aiming unit is disposed in a front wall arranged facing the laser unit (3).
A device according to claim 16, which front wall is releasably fastened to the laser unit (3) by means of bolt and/or friction joints.
A device according to any of claims 1 - 13, where the optical aiming unit is arranged in a unit that is freestanding from the laser unit (3), which freestanding unit is fixed relative to the optical axis (x_a) of the laser unit (3) in the rotational direction.
A device according to any of the foregoing claims, wherein at least one additional optical wedge (6) is arranged in the optical beam path, which optical wedges (6) are fixed relative to one another and fixed relative to the optical axis (x_a) of the laser unit (3) in the rotational direction.
A device according to any of the foregoing claims, wherein the laser simulator is intended to simulate the firing of missiles, projectiles, shells, guided missiles or rockets.