AU1152499A

AU1152499A - Measuring head

Info

Publication number: AU1152499A
Application number: AU11524/99A
Authority: AU
Inventors: Dieter Malsbender; Klaus Schmidt
Original assignee: STN Atlas Elektronik GmbH
Current assignee: Atlas Elektronik GmbH
Priority date: 1997-10-17
Filing date: 1998-10-10
Publication date: 1999-05-10
Also published as: WO1999020972A1; KR20010015537A; CA2293561A1; DE19745971C1; NO20001264L; NO20001264D0; EP1023571A1

Description

Measuring head Description The invention concerns a measuring head for a simulator for simulating the firing of especially long-range weapons, like 5 ballistic barrel weapons or firing devices for rockets and guided missiles, of the type defined in the generic part of claim 1. In the case of a known measuring head of this type (DE 31 14 0 000 Al) the illumination emitter emitting a pulsed laser beam has a series of, for example, five laser diodes, which can be triggered by a control equipment, a focusing optical system and a pair of wedge prisms which rotate in opposing directions about the optical axis. The pulsed laser beam is deflected by 5 the sequential triggering of the laser diodes horizontally and by the rotating wedge prisms vertically in such a manner that it will scan line-by-line a measuring field situated in a spatial angle sector, point-by-point. By means of the control equipment a pulse-coded triggering of the individual diodes can 0 also be carried out for the purpose of imposing an information on the laser beam. The laser light reflected at the target reaches a receiving element via a beam distributor provided in the path of the beam of the optical system. To the receiving element a device to determine the time necessary to travel by 5 the laser light reflected by the target is connected enabling the calculation of the distance of the target. In addition, a device to determine the horizontal angular position of the target, based on the allocation of the reflected laser light to the respective triggered laser diode, is connected to the 0 receiving element. From that and the momentary rotated position of the wedge prisms a computer calculates the position of the target from the optical axis, and consequently from the axis of the bore of the tube of the ballistic weapon, in elevation and in the azimuth. 1 Such a measuring head is not suitable for the fast recording of the azimuth and the elevation of one or several targets in a large measuring field at great distances, e.g. 4-5 km, with a high resolution. Because of the sequential scanning of the measuring field point-by-point in each of the vertically superposed lines, the measuring head requires quite a long scanning time, since the following laser diode can be activated only when the light emitted by the previous laser diode has reached the receiving element after having been reflected by the target. In addition, the horizontal and vertical resolutions of the measuring head are weak, as they depend directly on the aperture angle of the laser beam and in the case of greater distances to the target, e.g. 5 km, it cannot be below 5 m even in the case of a small aperture angle of, for example, 1 mrad, which does not satisfy the requirements for the purpose of simulated firing and indicating hits. The object of the invention is to improve a measuring head of the type mentioned in the introduction with regard to the resolution when the distance to the target is great and faster target determination of several targets in a relatively large measuring field is required. According to the invention this objective is achieved with a measuring head for a simulator for simulating the firing of the type stated in the generic part of claim 1 by the features of the characterising part of claim 1. The measuring head according to the invention has the advantage that the measuring field is illuminated in the vertical direction by the laser line of the illumination emitter and the laser line is deflected horizontally only. Thus the scanning time for a complete measuring field at a great distance is drastically reduced. The location resolution of the targets by the measuring head is independent from the aperture angle of the laser beam and in the azimuth it is determined by the time interval of consecutive emitter pulses and in the elevation by the number of vertical superposed detector elements in the 2 detector line, which, for example, when using the preferred silicon diodes may be sixty and more. Since each detector element has its allocated own individual channel for signal processing, the target positioning in the elevation from the 5 optical axis of the measuring head can be extremely accurately determined on-line in the detector line based on the position of the light-sensitive detector element on the one hand and on the other the delay periods in the signal processing do not influence the emission frequency of the illumination emitter o and, consequently, the horizontal resolution of the target positioning through the measuring head. Altogether, with the measuring head according to the invention a large measuring field of targets can be monitored from a 5 great distance and several targets in the measuring field can be registered fast. The resolution is extremely high, for example less than 1 m at a distance of 4-5 km, so that targets closely adjacent to each other can also be separated. 0 Useful executions of the measuring head according to the invention with advantageous refinements and developments of the invention become apparent from the following claims. According to an advantageous embodiment of the invention the optical path of the beam from the emitter and the receiver is guided through a common objective and for the horizontal deflection of the emittance angle and viewing angle two wedge plates constantly rotating opposing each other about the axis of the objective are allocated to the objective, which wedge plates are preferably driven by a DC motor and their rotated positions are registered by means of an encoder or a resolver. According to an advantageous embodiment of the invention the emitter operates with polarised laser light and the combining of the optical paths of the beam from the emitter and the receiver is carried out by means of a polarisation beam distributor and a X/4 plate is provided in the path of the beam of the common objective from the emitter to the receiver. 3 By using polarised light the problem of the scattered light in the optical path of the beam are minimised on the one hand and the proportion of the external light, e.g. sunlight, impacting on the receiver is halved on the other. By means of the ,/f4 plate the reflected and received laser light is rotated in the plane of the polarisation beam distributor by 900 relative to the emitted laser light and almost completely deflected to the detector line by the polarisation beam distributor, while only 50 % of the received non-polarised external light is diverted to the detector line. To further reduce the external light reaching the receiver an interference filter is connected upstream from the detector line, the interference filter harmonised with the wave length of the emitted laser light, the wave length tolerances and the aperture angle of the path of the beam in the plane of the interference filter. By virtue of the extreme reduction of the external light, achieved by these measures, highly sensitive detector elements can be used, consequently the emitting capacity of the illumination emitter can be reduced and the measuring head remains operational also in bright sunlight. At the same time the interference filter can be vapour-coated directly on the detector line. According to an advantageous embodiment of the invention the vertical laser line of the illumination emitter, i.e. the emittance angle and the viewing angle of the detector line, can be additionally vertically deflected step-by-step, for which purpose tiltable lenses or two wedge plates rotating about the axis of the objective in opposing directions are provided in the path of the beam of the common objective, which wedge plates are driven by a stepping motor. By means of this additional vertical deflection of the laser line an ammunition specific and weapon specific vertical gunsight of the weapon as well as a maximum permissible vertical target positioning, for example during ranging or simulating guided missiles, is compensated for, for which purpose the laser line is moved upward or downward from its normal position. 4 According to an advantageous embodiment of the invention a monitor diode is allocated to the illumination emitter, which registers the light emitted by the illumination emitter. on this occasion the monitor diode can be so arranged that it measures the scattered laser light reflected by the polarisation beam distributor or the laser light radiated rearward by the illumination emitter (backlight). The monitor diode serves the purpose of determining the moment of emission and monitoring the emitted energy of the illuminating laser. In a preferred embodiment of the invention a code emitter is allocated to the illumination emitter, which code emitter transmits data by means of a pulsed laser beam to a target receiver provided on the target. The code emitter comprises at least one emitter line having several independently triggerable code emitter cells, which are provided adjacent to each other in such a manner that their beam exit areas arranged in a row extend at right angle and preferably centrally to the vertical laser line produced by the illumination emitter. The code emitter provides the possibility to emit data and information photo-optically to one or several chosen targets, which are received and evaluated by the target receiver. To minimise the spatial angle of the laser pulse emitted by the code emitter the data for a specific target is emitted via only one to two code emitter cells. The illumination emitter and the code emitter are preferably combined into one laser module with a common optical path of the beam. By virtue of this construction of the code emitter a longer lasting time period of data transfer to the target is assured, even in the case of progressing horizontal beam deflection. At the same time only that code emitter cell is activated, i.e. is placed in emission readiness mode, in the spatial illumination angle of which the target is actually situated. The speed with which the code emitter cells, commencing with the code emitter cell situated closest to the vertical laser line, are placed in emission readiness mode one after another, is the result of the 5 actual horizontal beam deflection speed and the relative movement of the chosen target to the measuring head. The invention is described below in detail based on an embodiment illustrated in the drawing. Schematically illustrated they show in: Fig.1 - the opto-mechanical construction of a measuring head for a simulator for shooting simulation of long-range weapons, Fig.2 - a top view on the beam exit area of the laser module in the focal plane of the emitting objective in the measuring head according to Fig.l. The opto-mechanical construction of the measuring head for a simulator for the simulation of the firing of long-range weapons, which is schematically sketched in Fig.1, e.g. of ballistic barrel weapons or firing devices for rockets and guided missiles, has an illumination emitter 10 which illuminates a target with a pulsed laser beam for the purpose of firing simulation, a receiver 11 for the laser light reflected by the target and a signal processor 12 to determine the spatial and temporal position of the target and to define the target position in the azimuth and elevation from the optical axis 13 of the measuring head as well as the distance of the target from the measuring head. As laser beam the illumination emitter 10 emits a longitudinally extended vertical laser line, which homogeneously illuminates a defined spatial angle, the so called emittance angle and is horizontally continuously deflected, so that the vertical laser line moves horizontally over the measuring field in the plane of the target. The receiver 11 has a vertically aligned, high resolution detector line 14, which is made up from a plurality of superposed detector elements 141 and has a spatial viewing angle which is identical with the emittance angle. The detector elements 141 are preferably constructed as silicon diodes and an independent channel 121 of the signal processing is provided 6 downstream to each detector element 141. By means of the optical system of the measuring head the receiver 11 is so synchronised with the illumination emitter 10, that the emittance angle and the viewing angle are congruent at all times and consequently the detector line 14 always records the total image of the vertical laser line in the measuring field. In particular, the illumination emitter 10 has a pulse-driven illumination laser (not illustrated) which forms a laser line which in the longitudinal direction provides a homogeneous illumination which is widened defined by an optical system. The beam exit area of the illumination laser, which in Fig.2 is designated by 15, is formed by one or several light guides 16 or internally reflectively coated light guide channels, while behind each light guide 16 or light guide channel a laser diode is provided. The illumination laser, together with a triggerable energy supply, a trigger circuit and a programmable high voltage source is integrated in a laser module 17. An emitting objective 18 is arranged upstream from the laser module 17, the optical axis of the emitting objective coinciding with the optical axis 13 of the measuring head. A receiving objective 19 and an interference filter 20 are provided upstream from the detector line 14. By means of a flat mirror 21 the optical path of the beam of the receiver 11 is deflected by 900 and by means of a beam distributor 22 it is united with the beam path of the illumination emitter 10. Both beam paths are then guided through a common main objective 23. The axis of the main objective 23 forms the optical axis 13 of the measuring head. For the horizontal deflection of the laser line emitted by the illumination emitter 10, a pair of optical wedges 24 is allocated to the main objective 23, the optical wedges having two optical wedge plates 241, 242 or optical wedge prisms rotating constantly in opposing directions about the optical axis 13 of the measuring head, which are driven by a DC motor 25. The momentary rotated position of the optical wedge plates 241, 242 is registered by an encoder 26. Instead of an encoder 26 a resolver may also be used. To reduce the 7 problem of scattered light and to reduce the external light, e.g. sunlight, falling on the detector line 14, the illumination laser operates with polarised laser light and the beam distributor 22 is constructed as a polarisation beam distributor 22. In addition, a ) /4 plate 27 is provided in the path of the beam of the main objective 23. The laser light emitted by the laser module 17 after passing through the polarisation beam distributor 22 is linearly polarised in a defined manner and is circularly polarised through the X/4 3 plate. The circularly polarised laser light reflected by the target and received through the main objective 23 is linearly polarised by the X/4 plate 27. This laser light is linearly polarised in the plane of the polarisation beam distributor 22 rotated by 90" to the emitted laser light and is deflected to the detector line 14 almost completely through the polarisation beam distributor 22. In contrast, only 50 % of the non polarised external light, received through the main objective 23, is diverted to the detector line 14. The remaining portion of the external light deflected in the direction of the ) detector line 14 is further reduced through the interference filter 20 in the path of the beam of the receiver 11, which is harmonised with the wave length of the illumination laser, the wave length tolerance and the aperture angle of the path of the beam in the plane of the interference filter 20. A monitor diode 28 is also provided in the measuring head, which detects the emission of the laser light through the laser module 17. In the embodiment of Fig.1 the monitor diode 28 is so arranged that it measures the scattered laser light ) reflected through the polarisation beam distributor 22. Alternatively, the monitor diode 28 may be provided in the laser module 17 and measure the rearward radiated laser light (backlight). The monitor diode 28 serves the purpose of determining the moment of emission of the illumination emitter 5 and monitoring the emitted laser energy. To compensate for an ammunition specific or weapon specific vertical gunsight of the original weapon as well as for a 8 maximum permissible vertical target positioning during ranging or when simulating guided missiles a step-by-step deflection of the laser line, emitted by the illumination emitter 10, is provided upward or downward in the vertical direction. For this purpose a further pair of optical wedges 29 comprising two opposite wedge plates 291, 292 rotating in opposing directions is provided in the path of the beam of the main objective 23, the wedge plates driven by a stepping motor 30. Thus the laser line can be moved vertically upward or downward by a definite amount. Instead of the pair of optical wedges at least one tiltable lens may be used. The modus operandi of the measuring head is as follows: The targets are illuminated with the horizontally continuously deflected and vertically aligned laser line of the illumination emitter 10. The vertically aligned detector line 14 looks over the common path of the beam with the illumination emitter 10 always in the same spatial angle as the illumination emitter 10. Therefore the emittance angle and the view angle of the detector line 14 are congruent with the horizontal deflection of the laser line at all times. After a delay, corresponding to twice the travel time of the light to the target, the detector line 14, viewing in the emittance angle of the illumination emitter 10, i.e. in the illuminating spatial angle of the illumination laser, receives the laser beam reflected by a retro-reflector at the target, which laser beam is sharply imaged on the detector line 14 through the main objective 23 and the receiving objective 19. To each individual triggerable detector element 141 its own electric channel 121 to prepare and process the signals as well as its own low-resistance output is allocated. The electric channels 121 are combined into an ASIC. The vertical position of the target relative the optical axis 13 of the measuring head is calculated from the position of the illuminated detector element 141 of the detector line 14. At the same time the achievable location resolution is determined by the number of the detector elements 141. The horizontal position of the target relative the optical 9 axis 13 of the measuring head is calculated from the position of the horizontal beam deflection, for which purpose the output signals of the encoder 26 are utilised. The achievable horizontal location resolution is determined, inter alia, by the temporal laser pulse intervals of the pulse-driven illumination laser. On this occasion the horizontal width of the laser line has no influence at all on the achievable horizontal location resolution. For an unambiguous target allocation the individual illumination laser pulse received after the reflection the minimum temporal laser pulse interval of consecutive laser pulses of the illumination laser has to be longer than twice the travel time of the light to the target. The moment of receiving the reflected illumination laser beam is determined by the illuminated detector element 141 of the detector line 14. The moment of emission of the illumination laser beam is determined by the monitor diode 28. The distance to the target is calculated from the time difference between the moments of emission and reception in conjunction with the speed of light. A code emitter is also allocated to the illumination emitter 10, which code emitter transmits data photo-optically by means of a pulsed laser beam to a target receiver allocated to the target. The code is pulse-pause modulated. The code emitter has a code emitter laser (not illustrated) which is integrated in the laser module 17 and, incidentally, makes use of the emitting optics of the illumination emitter 10, i.e. the emitting objective 18, the polarisation beam distributor 22, the main objective 23, the rotating pairs of optical wedges 24, 29 as well as of the /4 plate 27. The code emitter laser is constructed from several individually triggerable code emitter cells 33 (Fig.2), wherein the rectangular cross-section of the beam exit area 32 of a code emitter cell 33 is formed by one or several light guide or an internally reflectively coated light guide channel. There is a laser diode situated behind each light guide or internally reflectively coated light guide channel of a code emitter cell 33. The beam exit area of the code emitter laser, designated in Fig.2 by 31, is made up from 10 the rectangular beam exit areas 32 of the single individually triggerable code emitter cells 33. The code emitter cells 33 arranged next to each other form an emitter line, while the code emitter cells 33 are so arranged next to each other that the adjacent arrangement of their beam exit areas 32 extends at right angle to the beam exit area 15 of the illumination laser. In the embodiment illustrated in Fig.2 two optical fibres, each with a laser diode, are used to produce the rectangular beam exit area 32, while both laser diodes are triggered always simultaneously. The two optical fibres of a code emitter cell 33 are designated by 331 and 332. The beam exit area 31 of the code emitter laser and the beam exit area 15 of the illumination laser, the relative arrangement of which is unchangeable, form a lying T. To assure a reliable data transmission, the data transmission is carried out only during that horizontal deflecting direction, at which the illumination laser first contacts the chosen target. Therefore in the arrangement of the beam exit areas 31, 15, illustrated in Fig.2, the data transmission is carried out with the illumination laser deflected to the right. By virtue of this the target position is controlled immediately prior to the data transmission, and a vertical position correction of the code emitter laser is feasible by means of the vertical beam deflection. To minimise the spatial angle of the laser beam of the code emitter the data for a specified target is emitted only via one to two code emitting cells 33. To ensure a longer lasting data transmission to the target with progressing horizontal beam deflection, that code emitter cell 33 is activated for the data transmission in the spatial illuminating angle of which the target is actually situated. The code emitter cells 33 are activated opposing the horizontal beam deflection, commencing with that code emitter cell 33 which is the closest to the beam exit area 15 of the illumination laser. Accordingly, the activation is carried out similarly to a running light, whereby during the transition from a code emitter cell 33 to the next one both code emitter cells are activated. The speed with which the code emitter 11 cells 33 are activated for the data transmission one after another, results from the actual horizontal beam deflection speed and the relative movement of the chosen target to the measuring head, which is calculated at the commencement of the 5 data transfer. The activation of a code emitter cell 33 means that this code emitter cell 33 is ready to emit. Whether and when an activated code emitter cell 33 emits a coded laser beam depends on the pulse-pause modulation used in this case, from the emitted data content and the code used. The invention is not limited to the embodiment described. Thus the beam exit areas 15 and 31 from the illumination emitter 10 and the code emitter may be arranged cross-shaped in the plane extending perpendicularly to the axis 13 of the measuring head. 5 Alternatively, the illumination emitter 10 may have two beam exit areas 15 which are parallel and at a distance from each other, each producing a vertical laser line, while the beam exit area 31 of the code emitter extends between the two beam exit areas 15. On this occasion an H-shaped arrangement of the beam exit areas 15 and 31 is produced. Whereas in the case of the T-shaped arrangement of the beam exit areas 15, 31, in fact in the lying form, a data transmission to the target is carried out only during one pivoting movement of the vertical laser line, in the case of the above described two alternative arrangements of the beam exit areas 15, 31 data can be transmitted to the chosen targets during both the forward and rearward movements of the pivoting laser line, since in this case always the illumination emitter 10 contacts first the chosen target in both pivoting directions. In any case the cost of the hardware is somewhat greater, since in the case of the cross-shaped arrangement one half only of the beam exit area 31 of the code emitter can be used and in the case of the H-shaped arrangement two identically constructed beam exit areas 15 of the illumination emitter have to be provided. 12

Claims

1. A measuring head for a simulator for simulating the firing of especially long-range weapons, like ballistic barrel weapons or firing devices for rockets and guided missiles, with an illumination emitter (10) which for the purpose of simulating the firing illuminates a target with a pulsed laser beam, with a receiver (11) for the laser light reflected in the target and with a signal processor (12) to determine the spatial and temporal position of the target and to define the target position in the azimuth and elevation from the optical axis of the measuring head and the distance of the target from the measuring head, characterised in that the laser beam is a vertical laser line which can be horizontally deflected, which homogeneously illuminates a defined spatial angle (emittance angle), that the receiver (11) has a vertically aligned high resolution detector line (14) with a spatial viewing angle which is identical with the emittance angle wherein the detector line comprises a plurality of individual superposed detector elements (141), preferably silicon diodes, that the illumination emitter (10) and the receiver (11) are so synchronised with each other that the emittance angle and the viewing angle of the detector line (14) are congruent at all times, and that an independent channel (121) for signal processing is provided downstream to each detector element (141) of the detector line (14).

2. A measuring head according to claim 1, characterised in that the optical path of the beam from the illumination emitter (10) and the receiver (11) is guided through a common objective (23) and that for the horizontal deflection of the emittance angle and viewing angle two wedge plates (241, 242) constantly rotating opposing each other about the axis of the objective are allocated to the objective (23). 13

3. A measuring head according to claim 2, characterised in that the wedge plates (241, 242) are driven by a DC motor (25) and the rotated positions of the wedge plates (241, 242) are registered by means of an encoder (26) or a resolver.

4. A measuring head according to claim 2 or 3, characterised in that the illumination emitter (10) emits polarised laser light, that the combining of the optical paths of the beam from the illumination emitter (10) and the receiver (11) is carried out with a polarisation beam distributor (22) and a X/4 plate (27) is provided in the path of the beam of the common objective (23).

5. A measuring head according to any one of claims 2 to 4, characterised in that an interference filter (20) is provided in the optical path of the beam of the receiver (11) and preferably the interference filter (20) is vapour coated directly on the detector line (14).

6. A measuring head according to any one of claims 2 to 5, characterised in that the vertical laser line can be additionally vertically deflected step-by-step and for this purpose at least one tiltable lens or a pair of wedges (29) of wedge plates (291, 292) rotating in opposing directions is allocated to the common objective (23), which wedge plates are driven by a stepping motor (30).

7. A measuring head according to any one of claims 1 to 6, characterised in that a monitor diode (28) is allocated to the illumination emitter (10) which detects the laser light emitted by the illumination emitter (10). 14

8. A measuring head according to any one of claims 1 to 7, characterised in that a code emitter is allocated to the illumination emitter (10), which code emitter transmits data by means of a pulsed laser beam to a target receiver provided on the target, and that the code emitter has a plurality of independently triggerable code emitter cells (33), which are provided adjacent to each other in such a manner that their adjacent beam exit areas (32) extend at right angle and preferably centrally to the beam exit areas (15) of the illumination emitter (10) producing the laser line.

9. A measuring head according to claim 8, characterised in that the code emitter is integrated in the illumination emitter (10).

10. A measuring head according to claim 8 or 9, characterised in that the code of the code emitter is pulse-pause modulated.

11. A measuring head according to any one of claims 8 to 10, characterised in that for the data transfer only those code emitter cell (33) or code emitter cells (33) is/are placed in emission readiness mode, in the spatial illumination angle of which the target is situated at the moment.

12. A measuring head according to any one of claims 8 to 11, characterised in that the code emitter is so synchronised with the illumination emitter (10) that the code emitter cells (33) are activated only when first the illumination emitter (10) contacts the target. 15