GB2067273A - Target Training Apparatus - Google Patents

Abstract

Target training apparatus comprises a projector, a screen and a weapon fitted with an image intensifier. The image intensifier is responsive to infra-red radiation to produce a visible image and the projector includes beam generating means for generating a beam of radiation which has a visual component and an infra-red component and which transmits a target image to the screen and light control means for reducing the intensity of the visual component in the beam relative to the intensity of the infra-red component, whereby radiation emitted by the target image on the screen can be made representative of that emitted by a target at night or in poor visibility and so that the target image can be used in practice by a trainee marksman who aims the weapon at the target image using the image intensifier and fires from the weapon a projectile which forms a shot hole in the screen. In a preferred embodiment, the projector beam passes through the plane polarizing elements 30, 31, 32 which in the uncrossed condition transmit light to simulate daylight conditions and in a variety of crossed conditions transmit light to simulate a variety of dusk or night conditions. <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. A realistic view may be provided for the marksman by projecting on to the screeen a composite image of a target and a background scene. For most target training it is sufficient to provide on the screen a composite image of a target and its background as seen in daylight and there is usually no difficulty in providing for the marksman an image which closely simulates that which he would see in an actual daylight situation. There is, however, a need for training marksmen in night firing using sights embodying image intensifiers which not only intensify the visible light emitted by the scene being viewed, but also convert infra-red radiation emitted from the scene into a visible image.

It has been proposed to simulate night firing in target training apparatus as above described simply by reducing the intensity of illumination of the composite image being displayed on the screen. While this provides the marksman with a view simulating conditions of poor visibility, such as conditions at dusk or at night, it does not produce conditions simulating those to which the image intensifier is responsive. In particular, the amount of infra-red radiation reflected from the screen would be far below that which would be emitted from a target and background at night. As a result, a marksman would not receive in the intensifier an image simulating that which would be obtained during actual night firing.

It is an object of the present invention to provide target training apparatus for use in training marksmen in night firing, which does not suffer from the above-mentioned disadvantage.

According to the present invention, there is provided target training apparatus comprising a projector, a screen and a weapon fitted with an image intensifier, the image intensifier being responsive to infra-red radiation to produce a visible image, and the projector including beam generating means for generating a beam of radiation which has a visual component and an infra-red component and which transmits a target image to the screen and light control means for reducing the intensity of the visual component in the beam relative to the intensity of the infra-red component, whereby radiation emitted by the target image on the screen can be made representative of that emitted by a target at night or in poor visibility and so that the target image can be used in practice by a trainee marksman who aims the weapon at the target image using the image tensifier and fires from the weapon a projectile which forms a shot hole in the screen.

It can be shown that when a beam of radiation is passed through plane polarising elements arranged with their planes of polarisation inclined to each other, the visual component of the beam transmitted by them becomes more or less severely attenuated, whereas the infra-red component of the beam does not.

In accordance with a preferred embodiment of the invention, the light control means comprises polarising means through which the beam is caused to pass in its passage to the screen. In this way, the relative amounts of visible and infra-red radiation forming a target image on the screen and reflected by the screen can then readily be adjusted or set to simulate very closely radiation emitted in real situations at night or in poor visibility.

The polarising means may comprise first and second plane polarising elements through which the beam passes, in succession, in its passage to the screen and which occupy or are movable to occupy dispositions in which their planes of polarisation are inclined at a predetermined angle to each other. The elements are preferably relatively rotatable between a first disposition in which the planes of polarisation of the two elements are co-planar with each other and a second disposition in which the planes of polarisation of the two elements are inclined to each other, whereby the transmittance of the visible component of the beam can be varied between a predetermined maximum transmittance and a predetermined minimum transmittance.

In a preferred embodiment ofthe invention, the polarising means further comprises a third polarising element located between the first and second polarising elements and rotatable between a first disposition in which the plane of polarisation of the third polarising element is coplanar with the plane of polarisation of the first polarising element and a second disposition in which the plane of polarisation of the third polarising element is inclined to the planes of polarisation of the first and second polarising elements.

The first and second poiarising elements are preferably relatively rotatable to their second disposition in which their planes of polarisation are inclined at 900 to each other. Preferably, the first polarising element occupies a fixed position and the second polarising element is rotatable relative thereto.

The third polarising element is preferably rotatable to its second disposition in which its plane of polarisation is inclined at 450 to the plane of polarisation of the first polarising element, whereby when the polarising planes of the first and second elements are at 900 to each other rotation of the third polarising element from its first disposition to its second disposition results in an increase in the transmittance of the visible component by the three elements.

It is not unusual with cinematograph and slide projectors to include an infra-red blocking filter between the projection lamp and the film or slide to prevent overheating of the latter. Where a projector of this kind is to be used in apparatus according to the present invention, the blocking filter should be removed. It has, however, been found that with conventional projection lamps the infra-red component in the projected beam can be too strong, giving rise to saturation of the image intensifier, and in this situation an infra-red filter for reducing the intensity of the infra-red component to an acceptable level can be provided.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic plan view of target training apparatus according to the invention; Figure 2 is a side elevation of a cinematograph projector forming part of the apparatus shown in Figure 1 and embodying a light control device according to the invention; Figure 3 is a horizontal section of the light control device forming part of the projector shown in Figure 2, taken on the line Ill-Ill in Figure 2 and drawn to an enlarged scale; Figure 4 is a section taken on the line IV-IV in Figure 3; Figure 5 is a side elevation of the light control device shown in Figure 1, and drawn to an enlarged scale;; Figure 6 is a section of the device shown in Figure 5, taken on the line VI--VI in Figure 5; Figure 7 is a section of the device shown in Figure 5, taken on the line VIl-VIl in Figure 5; and Figure 8 is a vertical section of the device shown in Figure 5, taken on the line VIll-VIll in Figure 7.

Referring first to Figure 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 projectiles which form shot-holes in the screen 12. Controls are provided for arresting the projector 11 following the firing of one of the weapons so that the target image at the instant of firing is held displayed on the screen 12. Lamps (not shown) are arranged behind the screen 12 and are illuminated after shots have been fired and the projector 11 arrested so that light passes through the shotholes in the screen 12 to identify their positions in relation to the target image.The screen 1 2 comprises a first sheet 14 which is movable horizontally from a supply roller 1 5 to take-up roller 16, a further sheet 17 aiso 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, 1 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. The projector 11 is then switched back to its motion picture mode.

Referring now to Figure 2, the projector 11 comprises an assembly of a projection lens mount 21, a polarising device 22 which is screwed to the projection lens mount 21, and an anamorphic lens mount 23 which is in turn screwed on to the device 22, the assembly serving to project an image-transmitting light beam along a beamprojection axis 24 shown in chain-dot line.

The polarising device 22 is shown to an enlarged scale in Figure 5 and in horizontal and vertical sections in Figures 3 and 8. It comprises an annular body 25 provided with an externally screw-threaded end portion 26, which is screwthreaded into an internally screw-threaded end portion 27 of the projection lens mount 21, and an internally screw-threaded end portion 28 into which is screwed a retaining ring 29 in turn provided with an internal screw thread, into which is screwed the anamorphic lens mount 23.

As best seen in Figure 8, the body 25 of the polarising device 22 carries first, second and third plane polarising elements 30, 31 and 32. The first polarising element 30 is mounted in a recess formed in the body 25 and is held against rotation relative thereto by a pin 33 passing through a radial slot 34 formed in the element 30 and engaging in a blind hole formed in the body 25.

The polarising element 31 is likewise mounted in a recess formed in a mounting ring 35 and held against rotation relative thereto by a pin 36 passing through a radial slot in the element 31 and engaging in a blind hole in the ring 35. The polarising element 32 is likewise mounted in a recess formed in a mounting ring 37 and held against rotation relative thereto by a pin 38 passing through a radial slot in the element 32 and engaging in a blind hole in the ring 37.

The three polarising elements 30, 31 and 32 and the two mounting rings 35 and 37 carrying the elements 31 and 32 are held against axial displacement by the retaining ring 29 which is screwed into the end portion 28 of the body 25, where the ring 29 abuts against an internal shoulder which is formed in the body 25 and which is so positioned as to provide a small axial clearance for the two rings 35 and 37, enabling them to be turned within the body 25, whilst nevertheless holding all the elements 30,31 and 32 axially in place as shown. Diametrically opposed holes 39, 40 are provided in the retaining ring 29 for engagement by a tool used for screwing the ring 29 into place.

As best seein the horizontal section of Figure 3, the mounting rings 35 and 37 are provided with radially projecting pins 41 and 42 which are screw-threaded into radial holes in the rings and project from the body 25 through arcuate slots 43 and 44 as shown in Figure 5. By this means, the mounting rings 35 and 37 can be turned in opposite directions from the positions shown in the drawings by manually engaging the pins 41 and 42 and moving them along the slots 43 and 44. The slot 43 extends to provide for the turning of the ring 35 and the polarising element 31 through 900, while the slot 44 provides for the turning of the ring 37 and the polarising element 32 through 900 in a direction opposite to that of the polarising element 31.

Each of the polarising elements 30,31 and 32 is such as to plane polarise light transmitted by it and may be of the type manufactured by Polarizers (UK) Limited of High Wycombe, Bucks, under the type No. KN36. The first polarising element 30 is fixediy mounted in the body 25 of the device 22 so that light transmitted by it is polarised in a fixed plane of polarisation, which in the embodiment now to be described may be either the vertical or the horizontal plane, but which for convenience of description will be assumed to be the vertical plane.The third polarising element 32 is so mounted within its mounting ring 37 that in the position illustrated in the drawings with the pin 42 at the position shown in Figure 6, light transmitted by it is polarised in a vertical plane and can be turned from the position shown in Figure 6 through 900 to a crossed position with the element 30 in which the plane of polarisation of the element 32 is at right angles to the vertical plane of polarisation of the element 30. Finally, the polarising element 31 is so mounted in the mounting ring 35 that with the ring in the position shown in Figure 7 and the pin 41 at the lower-most end of the arcuate slot 43, light transmitted by the element 31 is polarised in a vertical plane of polarisation and can be turned from the position shown in Figure 7 through 900 to a crossed position with the element 30.

In the absence of the polarising element 31, light transmitted by the two polarising elements 30 and 32 can be represented by the following formula: T=(TmaxTmin)CO520+Tmin where T=transmittance Tmax=maximum transmittance in uncrossed positioned of the polarising elements 30 and 32 Tm,n=minimum transmittance in the crossed positions of the polarising elements 30 and 32, and 0=the angle between the planes of polarisation of the two polarising elements.

By turning the polarising element 32 from its uncrossed position with the element 30 to its crossed position by moving the pin 42 in the slot 44, the transmittance can be changed progressively from the maximum transmittance TmaX to the minimum transmittance Twin.

If it is now assumed that the element 32 is set in a crossed position in relation to the polarising element 30 and the polarising element 31 interposed, the latter will, in the position shown in the drawings, occupy an uncrossed position with the element 30 and a crossed position with the element 32 and have only a small effect on the transmittance. Likewise, in the other extreme position of the element 31, in which the pin 41 is at the other end of the slot 43 from that shown in Figure 7, the element 31 takes up a crossed position in relation to the element 30 and an uncrossed position in relation to the element 32, thereby producing the same transmittance for the three elements as that produced in its other extreme position.By turning the element 31 from one of its two extreme positions to the other it becomes only partially crossed with both the elements 30 and 32 and provides for an increase in the transmittance of the three elements, a maximum transmittance being reached when the element 31 is midway between its two extreme positions, that is to say, with its plane of polarisation at 450 to the polarising planes of the elements 30 and 32.

The image-transmitting beam of radiation projected by the projection lens 21 comprises a visual component and an infra-red component.

With the polarising elements 30, 31 and 32 in their uncrossed positions the visual component of the beam is transmitted with some degree of attenuation, together with the infra-red component which is transmitted substantially unattenuated. By providing a beam of appropriate intensity, a target image can be projected onto the screen 12, which closely simulates a view observed by a marksman under actual daylight conditions. To simulate conditions at dusk or at night, the polarising element 32 is turned from the uncrossed position with the element 30 to the crossed or a partially crossed position in relation thereto. The visual component of the beam is thereby attenuated to simulate different degrees of visibility from normal daylight to night time.

The infra-red component in the beam is however left substantially unattenuated so that the image projected on to the screen is one obtained mainly from infra-red radiation.

Referring again to Figure 1, each marksman 13 is provided with a weapon 45 fitted with an image intensifier sight 46. The marksman 13 when viewing the screen direct with the naked eye will find that he is unable to see the target image on the screen or will see it only with great difficulty depending upon the extent to which the polarising elements 30 and 32 are crossed.

When, however, he takes aim by viewing the screen 1 2 through the image intensifier sight 46 he then receives in the sight a visible image of the target produced by the infra-red radiation transmitted in the projected beam and reflected from the screen 12. With the target image in the image intensifier sight, he fires the weapon 45 and produces a shot hole in the screen 12. The marksman is thereby provided with firing conditions closely simulating actual night firing using an image intensifier sight.

In response to the firing of the weapon 45, the projector 11 is automatically arrested so that an assessment can be made of the accuracy of the shot. The target image on the screen is however not visible to the naked eye and some adjustment of the polarising device 22 needs to be made to bring back on to the screen a visible target image.

To this end, the instructor controlling the sequence of firing turns the polarising element 31 from the position shown in Figure 7 to a position in which the transmittance by the three elements is increased sufficiently to produce a visible image of the target on the screen 12, maximum transmittance being obtained at the 450 position, with the pin 41 intermediate the two ends of the slot 43. When a proper assessment has been made of the shot, the components 14, 17 and 20 of the screen 12 are advanced as hereinbefore described to bring the aligned shot holes in them out of alignment and the polarising element 31 is returned to the position shown in Figure 7 to restore attenuation of the visual component of the target image.

The slot 43 in the body 25, which controls the limit of turning movement of the polarising element 31, may, if desired, be limited to an arc subtending an angle of 450 only, so that for assessment of a shot an instructor may simply move the pin 41 from one extreme position in the slot to the other.

It will furthermore be appreciated that, if desired, the poiarising element 31 may be omitted from the polarising device 22 and a reduction in the degree of attenuation of the visual component obtained by turning the element 32 to an uncrossed or partially crossed position in relation to the polarising element 30.

Claims (9)

Claims

1. Target training apparatus comprising a projector, a screen and a weapon fitted with an image intensifier, the image intensifier being responsive to infra-red radiation to produce a visible image, and the projector including beam generating means for generating a beam of radiation which has a visual component and an infra-red component and which transmits a target image to the screen and light control means for reducing the intensity of the visual component in the beam relative to the intensity of the infra-red component, whereby radiation emitted by the target image on the screen can be made representative of that emitted by a target at night or in poor visibility and so that the target image can be used in practice by a trainee marksman who aims the weapon at the target image using the image intensifier and fires from the weapon a projectile which forms a shot hole in the screen.

2. Apparatus according to claim 1 , wherein the light control means comprises poiarising means through which the beam is caused to pass in its passage to the screen.

3. Apparatus according to claim 2, wherein the polarising means comprises first and second plane polarising elements through which the beam passes in succession in its passage to the screen and which occupy or are movable to occupy dispositions in which their planes of polarisation are inclined at a predetermined angle to each other.

4. Apparatus according to claim 3, wherein the first and second plane polarising elements are relatively rotatable between a first disposition in which the planes of polarisation of the two elements are co-planar with each other and a second disposition in which the planes of polarisation of the two elements are inclined to each other, whereby the transmittance of the visible component of the beam can be varied between a predetermined maximum transmittance and a predetermined minimum transmittance.

5. Apparatus according to claim 5, wherein the first and second polarising elements are relatively rotatable to their second disposition in which their planes of polarisation are inclined at 900 to each other.

6. Apparatus according to claim 5, wherein the first polarising element occupies a fixed position and the second polarising element is rotatable relative thereto.

7. Apparatus according to claim 4, 5 or 6, wherein the polarising means comprises a third polarising element located between the first and second polarising elements, and wherein the third poiarising element is rotatable between a first disposition in which the plane of polarisation of the third polarising element is co-planar with the plane of polarisation of the first polarising element and a second disposition in which the plane of polarisation of the third polarising element is inclined to the planes of polarisation of the first and second polarising elements.

8. Apparatus according to claim 7 as appendent to claim 6, wherein the third polarising element is rotatable to its second disposition in which its plane of polarisation is inclined at 450 to the plane of polarisation of the first polarising element, whereby when the first and second polarising elements occupy their second disposition rotation of the third polarising element from its first disposition to its second disposition results in an increase in the transmittance of the visible component by the three elements from a predetermined minimum transmittance to a predetermined maximum transmittance.

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