GB2036936A - Target training apparatus - Google Patents

Abstract

In target training apparatus a projector projects on to a screen a target image at which in use a trainee marksman aims a weapon and fires a projectile which forms a shot-hole in the screen. To compensate for trajectory drop of the projectile over the apparent range of the target a trajectory compensation system is provided which comprises light refracting means arranged in the path of the light beam transmitting the target image from the projector to the screen and effective to refract the beam on or following the firing of the weapon to elevate the target image on the screen by an amount to compensate for trajectory drop. In the preferred embodiment the compensation system comprises a pair of relatively rotatable prisms 33, 38. The prisms are held in support rings 32, 37, each carrying a crown wheel 36, 41 and rotatable in opposite directions about an axis 22 by a carrier pinion 42. The amount of rotation of the pinion is such that the prisms relatively rotate to deflect the image the desired amount. <IMAGE>

Description

SPECIFICATION Target training apparatus The present invention relates to target training apparatus and is particularly concerned with apparatus in which a projector projects on to a screen a target image at which, in use, a trainee marksman aims a weapon and fires from the weapon a projectile which forms a shot-hole in the screen.

Such apparatus is usually provided for indoor training, the projector, the screen and the trainee marksman all being housed in a suitable enclosure. While the apparatus provides a generally realistic and practical aid for training marksmen in fast and accurate shooting, there is the disadvantage that the marksman fires the weapon at an image of a target having an apparent range which is usually greater and often much greater than the distance of the marksman from the screen.

To overcome the above mentioned disadvantage, it has been proposed to bring the target image on the screen, on or after firing of the weapon, to an assessment position by a displacement which comprises or includes an elevation of the target image to compensate for trajectory drop of the projectile over the apparent range of the target and it is an object of the present invention to provide target training apparatus embodying a trajectory compensation system which provides for elevation of the target image.

According to the present invention, there is provided target training apparatus comprising a projector for projecting on to a screen a target image at which, in use, a trainee marksman aims a weapon and fires from the weapon a projectile which forms a shot-hole in the screen, and ballistic compensation means for bringing the target image on the screen, on or after the firing of the weapon, to an assessment position by a displacement which comprises or includes a trajectory elevation of the target image which compensates for trajectory drop of the projectile over the apparent range of the target, the ballistic compensation means including a trajectory compensation system comprising light refracting means which is arranged in the path of the light beam transmitting the target image from the projector to the screen and which is effective to refract the beam on or following firing of the weapon by such an amount as to produce the said trajectory elevation of the target image.

The projector may be a slide projector for projecting on to the screen an image of a stationary target or a projector such as a cinematograph projector for projecting an image of a moving target on to the screen.

Where the projector projects an image of a moving target, the apparatus further includes means responsive to firing of the weapon to arrest the projector so that it holds projected on to the screen the image of the moving target at the time of firing of the weapon, and the ballistic compensation means further includes a flight time compensation system which is effective to delay the arrest of the projector by a time interval which is equal to the projectile flight time from the weapon to the target at the apparent range of the target, whereby displacement of the target image to the assessment position also provides compensation for the projectile flight time.

The light refracting means may comprise first and second transparent members so arranged that the target image light beam passes first through the first member, entering by passage through a first surface thereof and leaving by passage through a second surface thereof and then through the second member, entering by passage through a first surface thereof and leaving by 'passage through a second surface thereof, one or each of the members being movable relatively to the other to effect a relative displacement of them in which one of the first and second surfaces of the first member remains equi-spaced from one of the first and second surfaces of the second member while the inclination of the other of the surfaces of the first member to the other of the surfaces of the second member varies with the relative displacement, whereby the relative displacement is effective to refract the beam and produce the trajectory elevation of the target image.

In a preferred embodiment of the invention, the first and second surfaces of the transparent members are planar surfaces. The members are so arranged that the second surface of the first member is adjacent and parallel to the first surface of the second member. Furthermore, the surfaces of each member are inclined to each other at equal angles of inclination and the two members are arranged for rotation about a rotary axis passing through them at right angles to the second surface of the first member and the first surface of the second member. Drive means may then be provided for rotating the two members in opposite directions from a predetermined datum position by equal amounts to produce the required relative displacement of the members.

In an embodiment of the invention hereinafter to be described in detail, the transparent members are fixedly mounted in supports rotatably mounted in a housing for rotation about the rotary axis and the drive means comprises a crown gear mounted on each support and concentric with the rotary axis and a pinion drivingly engaging the two crown gears and effective to turn the two supports about the rotary axis in opposite directions by equal amounts. The drive means may include a drive motor drivingly connected to the pinion and responsive to a displacement signal.

The first surface of the first member and the second surface of the second member are in a null position arranged parallel to each other with a perpendicular to each plane lying in a vertical plane and the arrangement is such that the null position of the members lies at or toward the end of the range of relative displacement of the members from their datum position.

The apparatus according to the invention may include a ballistics information store in respect of the weapon in use and responsive to a range signal applied thereto and representative of the apparent range of the target to generate a trajectory signal representative of the trajectory elevation for that weapon at that range, and a trajectory control circuit responsive to the trajectory signal and the firing of the weapon to generate the displacement signal for application to the drive means. The ballistics information store may be one of a plurality of stores for a plurality of different weapons so that any one of the stores can be selected for supplying a trajectory signal based on the ballistics of the weapon in use and the apparent range of the target.

In the preferred embodiment of the invention, the trajectory control circuit is responsive to the trajectory signal to generate a displacement signal in the form of pulses, the number of which is representative of the trajectory elevation and the drive motor is a step motor which is stepped forward in response to each pulse of the displacement signal.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is a schematic plan view of a target training apparatus according to the'invention, Fig. 2 is a side elevation of a projector and trajectory compensation system of the apparatus shown in Fig. 1, Fig. 3 is a end elevation of the projector and trajectory compensation system shown in Fig. 2, Fig. 4 is a section of the trajectory compensation system shown in Fig. 2, taken on the line lV-IV in Fig. 2 and drawn to an enlarged scale, - Fig. 5 is a section taken on the line V-V in Fig.

4 showing part of the trajectory compensation system illustrated in Fig. 4 and, Fig. 6 is a section taken on the line VI--VI in Fig. 4 showing a further part of the trajectory compensation system illustrated in Fig. 4.

Referring first to Fig. 1, the training apparatus shown comprises a cinematograph projector 11 for projecting on to a screen 12 from a cinematograph film the image of a moving target at which trainee marksmen 13 aim their weapons and fire from them prqjectiles which form shotholes in the screen 12. Lamps (not shown) are arranged behind the screen 12 and are illuminated after shots have been fired so that light passes through the shot-holes in the screen 1 2 to identify their positions.The screen 12 comprises a first sheet 14 which is movable horizontally from a supply roller 1 5 to a take up roller 16, a further sheet 1 7 also movable horizontally but in the opposite direction to the sheet 14 from a supply roller 18 to a take up roller 19 and a third sheet 20 which is movable vertically downwardly from a supply roller (not shown) at the top of the screen to a drive roller (not shown) at the bottom of the screen. After the accuracy of the shots has been assessed, the sheets 14, 7 and 20 are moved relative to each other by small amounts to bring the shot-holes in them out of alignment so as to prevent subsequent shots from being confused with any previous shots.

Referring now to Figs. 2 and 3, the cinematograph projector 11 includes projection lens 21 which projects an image transmitting light beam along a projection axis 22 shown in chain-dot line. A light refracting unit 23 is fixedly mounted in front of the projection lens 21 on an upstanding bracket 24. The unit 23 is of generally cylindrical form and arranged concentric with the projection axis 22 of the projection lens 21.

The light refracting unit 23 is shown to an enlarged scale and in section in Fig. 5. The unit 23 includes a main housing portion 25 which is fitted with end caps 26 and 27 and which rotatably supports in bearings 28 and 29 prism support assemblies 30 and 31. The assembly 30 comprises a support ring 32 which supports a prism 33 which is held in place therein by a retaining ring 34 and an O-ring 35. The assembly 30 further includes a crown gear 36 which extends circumferentially round the support ring 32 and which is rotatably supported by the bearing 28. The prism assembly 31 comprises a support ring 37 which supports a prism 38 which is held in place by a retaining ring 39 and an 0ring 40. A crown wheel 41 is fixedly mounted on the support ring 37 and is likewise supported by the bearing 29.The crown wheels 36 and 41 are engaged by a pinion 42 which is fixed on the upper end of a shaft 43 and which upon rotation turns the crown wheels in opposite directions by equal amounts.

Referring now to Fig. 4, the shaft 43 of the pinion 42 is arranged to be rotatably dirven by a motor 44 through a position sensing unit 45. As shown, an output shaft 46 of the motor 44 imparts a drive through gears 47 and 48 to a shaft 49 carrying a cam 50 and drivably coupled to the pinion shaft 43 by a coupling 51 known by the trade name "Panamech".

The motor 44 is a step motor responsive to pulses applied thereto to turn the output shaft 46 in incremental steps equal to the number of pulses received. As hereinafter described in detail, a trajectory control unit is provided for supplying to the motor 44 pulses, the number of which is representative of the trajectory drop of the projectile at the apparent range of the target. The drive of the motor shaft 46 is transmitted through gears 47 and 48 to the pinion 42 which causes the prism assemblies 30 and 31 to turn in opposite directions through equal angles.

As best seen in Fig. 6, the position sensing unit 45 includes limit switches 52 and 53 which are arranged to cooperate with a profile 54 on the cam 50.

The two prisms 33 and 38 are of solid cylindrical form with planar end surfaces 55, 56, 57 and 58. The adjacent end surfaces 56 and 57 are arranged parallel to each other and at right angles to the projection axis 22 of the projection lens 21. The surface 55 of the prism 33 is, as shown, inclined to the surface 56 and the face 58 of the prism 38 is likewise inclined to the surface 57. The two inclined surfaces 55 and 58 are, in the disposition shown in Fig. 5, parallel to each other with their perpendiculars in vertical planes.

In this disposition, light from the projection lens 21 is refracted first in one direction by the prism 33 and then in the opposite direction by the prism 38 to produce no net angular deviation of the beam from the projection axis 22 of the projection lens 21.

The relationship between the amount of rotation of the prisms required for a desired displacement of the target image on the screen is calcuiated as follows. If the deviating power of each of the prisms 33 and 38 is a, and the angle turned through by each prism from the null position is b, then the resultant deviation by refraction of the light beam passing throug the two prisms is 2a sin b. If b is limited to + 200 then sin b is approximately proportional to b. With prisms giving an angular deviation of 2+0 between b = -200 and +200, the resultant error on the screen due to the departure of sin b from linearity is only 0.07 inches (1.78 mm) which can be regarded as negligible.This error is reduced by arranging for the prisms 33 and 38 to occupy an initial position, before the firing of the weapon, in which the light beam is refracted downwardly by them and then turning them toward and, if necessary, beyond the null position. If desired, however, compensation for this error could be made. Generally, the linear relationship is sufficient to allow the necessary movement of the prisms to be determined and the circuits producing the motor drive pulses matched to the prisms.

In a specific embodiment of the invention, the prisms 33 and 38 are arranged in an initial position in which the light beam is refracted downwardly at an angle of about 40 to the projection axis 22 and the step motor arranged to rotate the prisms toward and if necessary beyond the null position.

The glass used for the prisms 33 and 38 is so chosen as to minimize chromatic errors due to variation in refraction with wavelength. This difference can be reduced to 1/64.4 of the overall deviation of the prisms 33 and 38, producing an invisible difference between red and green refractions on a screen at a distance of 30 feet (9.14 metres) from the projector. The glass prisms 33 and 38 may furthermore be coated with an anti-reflection coating to reduce losses of light due to reflection to as little as 2.5%.

In a preferred form of displacement control system for advancing the step motor 44, which will now be described, the projector 11 is provided with film for projection, which carries along the edge of the film optical serial range data indicating the apparent range of the target, the image of which is being projected. The projector 11 is provided with an optical film reader which reads the range data and produces a range signal which is converted by a serial-to-parallel converter to produce a digital range signal representative of the apparent range of the target. The digital range signal is applied to a selected one of a plurality of weapon store modules each of which contains a programmed memory holding ballistic information on a particular weapon, the store module selected corresponding to that for the weapon in use.The weapon store module generates in response to the range signal a projectile flight time digital signal which represents the flight time of the projectile for that range and a trajectory digital signal representative of the trajectory angle at which the projectile needs to be fired to hit the target at that range.

The projectile flight time signal is applied to a flight time control circuit and the trajectory signal is applied to a trajectory control circuit.

When a weapon is fired a gun-shot sensor produces a sensor signal which starts an oscillator in the flight time control circuit which feeds output pulses to a digital comparator to which the flight time digital signal is also applied. The comparator is arranged to generate an output control signal when the pulse count of the oscillator equals the light time digital signal number, the output control signal being applied to open an control gate which then passes a delayed sensor signal to the projector 11 to arrest it in a stop motion mode following a delay equal to the projectile flight time over the apparent range of the target.

The delayed sensor signal from the flight time control circuit is applied to enabling switch which is switched on by the delayed sensor signal to start a drive oscillator in the trajectory control circuit. The oscillator generates drive pulses which are fed through a forward drive control gate to the step motor 44 to advance it in steps equal in number to the number of pulses applied to it. The drive pulses are also applied to a digital comparator to which is applied the trajectory digital signal from the selected weapon store module.When the drive pulse count equals the trajectory digital signal number, the comparator switches off the enabling switch, which in turn switches off the oscillator, whereupon the step motor 44 is arrested at a position in which the prisms 33 and 38 deflect the projector light beam through an angle representing the trajectory angle at which the projectile needs to be fired to hit the target at its apparent range.

The delayed sensor signal, in addition to switching the projector 11 to its stop motion mode, starts an assessment timer which in turn switches on the lamps to illuminate the rear of the screen for assessment of the shot. When the assessment timer stops the screen lamps are extinguished, the screen sheets 14, 17 and 20 displaced as hereinbefore described and a signal applied to the trajectory control circuit to restart the drive oscillator for generating drive pulses which are then fed through a reverse drive control gate to drive the step motor 44 in the reverse direction and bring the prisms 33 and 38 back to their datum position. Upon reaching the datum position, the cam profile 54 of the cam 50 in Fig. 6 activates one of the limit switches 52 and 53 to generate a null position signal and other of the switches to generate a null direction signal.The null position signal controls a null sense oscillator in the trajectory control circuit, which generates null correction pulses which are applied to the step motor 44 through the forward or reverse drive control gates in dependence upon the null direction signal, so that any deviation of the step motor from its null position in either direction is corrected.

The displacement of the screen sheets 1 4, 1 7 and 20 may be controlled by a timer which upon cutting off the drive motors for the screen sheets restarts the projector 11. The assessment timer can be overridden and the screen movement timer independently controlled from an instructor's hand control box.

The range signal produced by the optical film reader may, if desired, be replaced by a range signal set manually, for use for example when the projector is in the form of a slide projector.

Furthermore, the projectile flight time digital signal and the trajectory digital signal can be set in manually when required and displays of both trajectory and flight time can be provided.

A crosswind compensation system (not shown) may also be provided by the use of a further light refracting unit which is identical to the light refracting unit 23 as hereinbefore described and which is mounted in the path of the projector light beam either between the projection lens 21 and the light refracting unit 23 or on the other side of the unit 23. The further light refracting unit would, however, be mounted so that when the prisms are contra-rotated from their datum positionthey refract the light beam sideways in a horizontal plane.

Allowance for cross-wind requires a sideways displacement of the target image on the screen which is proportional to the crosswind velocity, but substantially independent of range.

Displacement of the prisms of the further light refracting unit to allow for crosswind can be made manually either direct or by a servo-motor.

It will be appreciated that trajectory compensation and cross-wind compensation can be applied simultaneously by one light refracting unit 23 if a single resultant deflection is calculated in polar coordinate from the required trajectory deflection and the required cross-wind deflection.

The prisms 33 and 38 would then need to be rotated in opposite directions by an amount representing the magnitude of the polar vector and rotated as a pair from a datum position through an angle equal to the polar angle. The calculation of the polar coordinates for the combined deflection can be made by means of analogue or digital electronic circuits.

While the prisms 33 and 38 in the embodiment of the invention hereinbefore described with reference to the drawings are formed with adjacent end surfaces 55 to 58 which are planar sufaces, prisms of other forms may, if desired, be employed in apparatus according to the invention.

For example, one of the adjacent surfaces of the two prisms may be made plano-convex and the other adjacent surface plano-concave, the two surfaces being equi-spaced from each other and having a common centre of curvature. The two outer surfaces of the prisms may then be planar surfaces arranged, in a null position, parallel to each other and at right angles to the projection axis 22. In the null position, the light beam on the projection axis passes through the two prisms with no net refraction of the beam and deflection of the beam by refraction is obtained by moving one of the prisms about the common centre of curavature relative to the other prism to bring the planar outer surface of the one prism to a position in which it is inclined to the planar outer surface of the other prism. The prism which is made movable may be made larger than the other prism.

Claims (13)

1. Target training apparatus comprising a projector for projecting on to a screen a target image at which in use a trainee marksman aims a weapon and fires from the weapon a projectile which forms a shot-hole in the screen, and ballistic compensation means for bringing the target image on the screen on or after the firing of the seapon to an assessment position by a displacement which comprises or includes a trajectory elevation of the target image which compensates for trajectory drop of the projectile over the apparent range of the target, the ballistic compensation means including a trajectory compensation system comprising light refracting means which is arranged in the path of the light beam transmitting the target image from the projector to the screen and which is effective to refract the beam on or following firing of the weapon by such an amount as to produce the said trajectory elevation of the target image.

2. Apparatus according to claim 1, wherein the projector is operative to project an image of a moving target and includes means responsive to firing of the weapon to arrest the projector so that it holds projected on to the screen the image of the moving target at the time of firing of the weapon, and wherein the ballistic compensation means further includes a flight time compensation system which is effective to delay the arrest of the projector by a time interval which is equal to the projectile flight time from the weapon to the target at the apparent range of the target, whereby displacement of the target image to the assessment position also provides compensation for the projectile flight time.

3. Apparatus according to claim 1 or 2, wherein the light refracting means comprises first and second transparent members so arranged that the target image of light beam passes first through the first member, entering by passage through a first surface thereof and leaving by passage through a second surface thereof, and then through the second member1 entering by passage through a first surface thereof and leaving by passage through a second surface thereof, and wherein one or each of the members is movable relatively to the other of the members to effect a relative displacement of them in which one of the first and second surfaces of the first member remains equispaced from one of the first and second surfaces of the second member, while the inclination of the other of the surfaces of the first member to the other of the surfaces of the second member varies with the relative displacement, whereby the said relative displacement is effective to refract the beam and produce the said trajectory elevation of the target image.

4. Apparatus according to claim 3, wherein the first and second surfaces of the transparent members are planar surfaces, wherein the members are so arranged that the second surface of the first member is adjacent and parallel to the first surface of the second member, wherein the first and second surfaces of the first member are inclined to each other and the first and second surfaces of the second member are inclined to each other by the same angle of inclination as the first and second surfaces of the first member, and wherein the two members are arranged for rotation about a rotary axis passing through them at right angles to the second surface of the first member and the first surface of the second member.

5. Apparatus according to claim 4, wherein the first surface of the first member and the second surface of the second member are, in a null position, arranged parallel to each other with a perpendicular to each plane lying in a vertical plane and wherein the null position of the members lies at or toward an end of a range of relative displacement of the members.

6. Apparatus according to claim 4 or 5, wherein drive means are provided responsive to a displacement signal to rotate the two members in opposite directions from a predetermined datum position by equal amounts to produce the said relative displacement of the members.

7. Apparatus according to claim 6, wherein the members are fixedly mounted in supports rotatably mounted in a housing for rotation about the rotary axis, and wherein the drive means includes a crown gear mounted on each support and concentric with the rotary axis and a pinion drivingly engaging the two crown gears and effective to turn the supports about the rotary axis in opposite directions by equal amounts.

8. Apparatus according to claim 7, wherein the drive means includes a drive motor drivingly connected to the pinion and responsive to the displacement signal.

9. Apparatus according to claim 6, 7 or 8, includinga ballistics information store in respect of the weapon in use and responsive to a range signal applied thereto and representative of the apparent range of the target to generate a trajectory signal representative of the trajectory elevation for that weapon and that range and a trajectory control circuit responsive to the trajectory signal and the firing of the weapon to generate the displacement signal.

10. Apparatus according to claim 9, wherein the ballistics information store is one of a plurality of ballistic information stores for a plurality of different weapons, whereby any one of the stores can be selected for supplying a trajectory signal based on the ballistics of the weapon in use and the apparent range of the target,

11. Apparatus according to claim 9 or 10, as appendant to claim 8, wherein the trajectory control circuit is responsive to the trajectory signal to generate a displacement signal in the form of pulses, the number of which is representative of the trajectory elevation and wherein the drive motor is a step motor which is stepped forward in response to each pulse of the displacement signal.

12. Apparatus according to claim 9, 10 or 11, wherein the projector is a cinematograph projector for projecting a cinematograph film of a moving target, wherein the film carries a record of the apparent range of the target as it appears an the film, and wherein a reader device is provided which is responsive to said record to generate the range signal.

13. Apparatus according to claim 12, wherein the ballistics information store or the selected ballistics information store is responsive to the range signal to generate a flight time signal representative of the flight time of the projectile for that weapon at that range and wherein the flight time compensation system includes a fight time control circuit responsive to the flight time signal and the firing of the weapon to generate a delayed stop signal to arrest the projector following a delay after the firing of the weapon equal to the projectile flight time from the weapon to the target at the apparent range of the target.

1 4. Target training apparatus substantially as hereinbefore described with reference to the accompanying drawings.