WO2006134202A1

WO2006134202A1 - Laser System and Method

Info

Publication number: WO2006134202A1
Application number: PCT/FI2006/000187
Authority: WO
Inventors: Karri Palovuori
Original assignee: Iprbox Oy
Priority date: 2005-06-17
Filing date: 2006-06-09
Publication date: 2006-12-21
Also published as: FI20050655A; FI20050655A0

Abstract

The present invention relates to a transmitter and receiver used in a tactical combat simulation, a system formed by these and a method for locating the hit point. The system comprises a transmitter for transmitting at least three intensity-profiled laser beams. The beams travel along different optical axes, intersect each other and are distinguishable from each other. The receiver comprises at least one detector and a data processing unit. The detector is sensitive to the laser beams produced by the shooter and is attached to the data processing unit arranged to determine the location of the detector in relation to the optical axes of the beams. By means of the invention the aiming line of the shot in the vicinity of the target can be precisely determined.

Description

Laser System and Method

The present invention relates to a method and system for locating the hit point in tactical engagement simulator training. In such a system the weapons of the shooting combatants send signals which can be detected by receivers carried by the target combatants.

Tactical engagement simulation systems (TESS) have been developed for a more efficient and realistic training of soldiers and policemen. A traditionally popular method has been to use laser transmitters attached to the weapons and laser receivers attached to the targets for indicating the hits by simulated shots. The MILES 2000 system developed by the United States armed forces represents the newest state of the art (Multiple Integrated Laser Engagement system, http://www.peostri.army.mil/PRODUCTS/MILES/). The MILES standard enables encoding a number of data with the laser beam, the data making the combat more realistic. Such data are, for example, data about the weapon and about the location of the shooter. The data can be used for assessing the damage caused to the target combatant or target vehicle by the possible hit and for following the development of the engagement in a more general manner. The transmitters of the MILES system can be installed on a number of weapons and, for example, on tanks and helicopters.

EP publication 1359386 discloses a system in which the location of the shooter is encoded into the transmitted laser signal by modulating the signal. In the receiving end the signal is decoded, whereby the shooting location of the shot can be known and the degree of damage can be better assessed.

WO 0008405 discloses a helmet designed for tactical training simulation use, the helmet including a GPS positioning apparatus connected to the weapon of the user of the helmet for transmitting the position data from via the laser beam emitted by the gun. The helmet also comprises detectors for detecting hits on the wearer.

WO 95/30125 discloses a harness comprising a number of detectors and an amplifier for detecting hits. The methods referred to above have a number of limitations, the most severe of which probably is that they can not precisely indicate a hit. Thus, detecting a shot always includes a great uncertainty whether the shot were injuring or lethal in a real situation. Because of this, the current systems train combatants to partly incorrect practices. For example, the effect of movement by the target or the distance of the target to the actual shooting can not be realistically estimated. Even knowing the location of the shooter and the target by means of, for example, a GPS system, does not improve determining the hit accuracy, in case there is a great uncertainty in the determining accuracy of the aiming line. In US 4229103, there is disclosed a device for transmitting several identifiable laser beams separately towards the target. However, there is not disclosed a technique for determining the hit point accurately by using the beams.

US 4063368 discloses a similar device, wherein the beams are directed such that they partly overlap. Assessing of the hit point is made only on grounds of the sub-sector the detector is located in. Thus, the technique is not suitable for accurate determining of the hit point without increasing the number of the beams unreasonably much.

Other known systems have been disclosed in DE 2727841, US 4781593 and DE 4213209. Accurate determination of the hit point is not disclosed in them either.

The problem associated with the low bit accuracy detection is basically that indication is carried out by means of detecting one laser beam by combining data from a number of receivers. Thus, the only data produced is about whether the aiming line has passed near one receiver. The beam cluster has widened as it has travelled from the source to the target and the intensity of the beam is distributed in the radial direction of the beam (on a level perpendicular to the propagation direction of the beam). Depending on the width and intensity profile of the laser beam, the distance to the target and the position of the target and the optical connection between the source and the target, the system will either leave some hits unindicated or - more typically - will indicate some misses as hits. As the indication of a hit is based on just the detection of the laser beam and the data contained by it, near misses are often not indicated at all. This does not correspond at all to a real situation, where a missing bullet will usually cause a loud boom due to its supersonic speed. This will naturally have an effect on the behaviour of the target. The above-mentioned limitation of prior art is illustrated in figures Ia and Ib. Figure Ia illustrates a situation, in which a narrow beam 12 is shot just above the target 10. Five detectors 16 are located on the target. Each detector will effectively see laser impulses shot within a distance from it, whereby a detection zone is formed, i.e. the area producing a hit indication, as shown in 14. A narrow beam does not fall within the detection zone, whereby the detectors do not detect it and the miss will not be registered, either, as the case should be. On the other hand, in figure Ib the shot 12' (beam 12') hits the detection zone, i.e. its beam hits at least one detector with a sufficient intensity. The shot is incorrectly registered as a hit. In case the beam is so close to the target 10 that more than one detector 16 detects the shot, detection accuracy can be mathematically improved by comparing the intensities indicated by the detectors. Even in this case a missed shot can be interpreted as a hit. In figure Ib the shot 12" does not hit the detection zone, but it is a near miss instead. Such a shot remains totally undetected.

Figure Ic illustrates a detection zone 14' around the target 10, the zone corresponding well to the form of the target. Such a detection zone is desirable, if one wishes to accomplish a more realistic engagement simulation. According to prior art, the detection zone can only be narrowed by increasing the number of detectors on the target and by reducing the opening angle of the laser beams. This will significantly increase the amount of gear to be car- ried by the target combatant and it will also be more expensive.

The aim of the invention is to improve the accuracy of the hit detection of engagement simulation systems.

The invention is based on the idea that one laser pulse sent by the shooting party is replaced by at least three directed laser pulses distinguishable from each other. Thus, instead of one beam, the shooting party sends three beams travelling to slightly differing directions so that they, however, intersect each other. The receiving party must have at least one detector (sensor). As the beams hit the detectors, the distance of each detector from the opti- cal axis of each beam, thus also the location of the aiming line, can be determined by using the intensity data and distinguishability of the various beams. The laser transmitter according to the invention comprises means for producing at least three distinguishable intensity-profiled laser beams essentially in the direction of the aiming line of the shooter. The beams are directed in the transmitter so that they are propagated slightly overlapping (intersecting each other), but still so that their optical axes differ from each other, i.e. they do not converge. In the vicinity of the shooter the beams might be propagated separately, but as the beams widen, they intersect each other. Thus, the aiming line of the shooter is arranged so that it is within the intersection area of the beams starting from at least a certain distance.

The receiver apparatus according to the invention comprises at least one detector for detecting a laser beam hitting the detector and indicating the intensity thereof. The receiver further comprises a data processing unit connected to the detector. The data processing unit is arranged to determine the distance of the detector from the optical axis of each beam on the basis the intensity of the least three distinguishable laser beams hitting the detector.

Thus, a system according to the invention comprises first means for producing at least three laser beams travelling along different optical axes, intersecting each other and are distinguishable from each other on the basis of one of their properties. The aiming line of the shooter thus remains essentially in the intersection area of the beams. The system fur- ther has second means, including at least one detector arranged to indicate the intensity of the laser pulses hitting it and to transmit the intensity data to the data processing unit. The data processing unit includes means for determining the location of the detector in relation to the optical axes of the beams.

In a method according to the invention at least three intensity-profiled laser beams are transmitted, the beams being distinguishable from each other, travelling along separate optical axes and intersecting each other so that the aiming line remains essentially within the intersection area of the beams. The intensity of the beams is indicated and the beams are individually identified in at least one observation point. The location of the observation point in relation to the aiming line is determined on the basis of the intensities of the beams. The radial intensity profiles of the beams are such that on the intersection area of the beams the distance between the observation point and the optical axis of each beam can be unambiguously determined.

More specifically, the transmitter according to the invention is characterized by what is disclosed in the characterizing part of claim 1.

On the other hand, the receiver according to the invention is characterized by what is disclosed in the characterizing part of claim 14.

The system according to the invention is characterized by what is disclosed in the characterizing part of claim 20.

The method according to the invention is further characterized by what is disclosed in the characterizing part of claim 23.

A number of advantages are achieved by the various embodiments of the invention. The detection zone around the target can be better focussed to more closely correspond with the target and both hitting and missed shots can be more accurately distinguished. Further, better information about the accurate hit or miss line of the shot can be obtained. Thus the engagement simulation is more realistic and combatants can be more effectively trained.

The invention can be applied to, for example, training of soldiers and policemen as well as to leisure use.

Typically the system does not demand a great number of detectors for the target. Even use of only one detector allows determination of the distance from the aiming line with a good accuracy. However, using a number of detectors increases the determining accuracy of the hit point while producing even more information about the arrival direction of the "shot". However, even a single sensor can provide enough data to make assumptions about the arrival direction of the shot, and together with the assumed position of the weapon even this single measurement result can be used for more accurately controlling the hit data. Because even near misses can be detected and measured, they can be indicated to the target by means of, for example, sound, whereby e.g. simulation of critically important fire- opening situations can be done much more realistically.

Information can be embedded in one or more laser impulses. The information can comprise, for example, data about the shooter, the weapon used by the shooter, location, time of day or the time of firing the shot. Preferably the MCC coding method (MILES Commu- nication Code), based on code words, according to MILES or MILES 2000 system is used, whereby the system according to the invention can be integrated with most existing MILES systems with small efforts. In case information is embedded in parallel in all impulses, the impulses can be made shorter.

If data about the location of the shooter and the target are available by means of, for example, a GPS system and data transfer network, the calculated trajectory of the bullet can be used for determining the hit instead of aiming line, whereby the bullet drop and even the advance needed for a moving target can be taken into account, whereby a very accurate and versatile shooting simulation can be realized.

In the following the invention is described in more detail with reference to the accompanying drawings, in which figures Ia and Ib illustrate the shape of the hit detection area in prior art systems, figure Ic illustrates a desirable shape of hit detection area. figure 2 shows an example of forming the laser beam cluster making it possible to locate the hit point, figures 3 a and 3b illustrate the desirable shape of the hit detection area when the target is in two different positions, figure 4 illustrates as a block diagram a practical solution according to one embodiment, figure 5 illustrates as a block diagram a practical solution according to another embodiment, and figure 6 is plan view of a beam arrangement according to a preferable embodiment.

Referring to figure 4, according to one embodiment each laser beam produced by the transmitter 40 is produced by its dedicated laser source. In figure 4, three laser sources are indicated by reference numbers 43, 43' and 43".

According to one embodiment the laser sources use different wave lengths, whereby no special procedures are needed at transmission step for distinguishing each beam, but the detector of the receiver must be able to reliably detect all these wave lengths.

According to one embodiment the laser sources use the same wave length and the beams are modulated by different frequencies or other identifiable code. The modulation step is shown in figure 4 with reference numbers 46, 46' and 46". The modulation can be applied to, for example, the intensity, phase or polarization of the beam. Thus a simple frequency analysis performed in the receiver can be used for distinguishing between the beams for determining the hit point, hi addition to frequency coding other coding methods can be used.

The modulation of the beams (beams) can be carried out by directly modulating the laser source or by means of a suitable electro-optical, magneto-optical or acousto-optical element, hi direct modulation a voltage regulator circuit, for example, can be used as a modu- lator for regulating the operating voltage of the laser. In direct modulation the response time of the laser source must be short enough in relation to the used modulation frequency or the properties of the modulation code.

An optical modulator can be realized as a filter-type element located on the path of one or more beams . The element can comprise a thin film. The modulator can also consist of fi- ber optics. Methods commonly used for modulating a laser beam in interferometrics or optical data transfer can be used for carrying out the modulation.

The operation of an electro-optical modulator can be based on, for example, piezoelectric- ity.

According to one embodiment, the lasers use the same wavelength, but the beams are shot one after the other. This can be accomplished so that the subsequent beams are triggered slightly delayed in relation to the first beam, whereby the phase difference of the signals indicates which impulse the current one is, or so that the impulses are triggered fully one after the other, whereby the detector only detects one beam at a time. The delay can be realized by directly controlling a number of laser sources or by delaying the signals by means of, for example, fiber optics.

With reference to figure 5, according to one embodiment the laser light of the transmitter 50 is produced in one laser source 54 and split into three different beams by means of optical methods in step 55. The laser beam can be split by means of, for example, semitrans- parent mirrors or prisms. The split beams can thereafter be modulated and/or delayed and/or data can be encoded into them in steps 54, 54' and 54", as has been described above. If the same data is to be coded in all beams, the coding can be carried out even prior to splitting the laser.

According to one preferable embodiment three laser beams with gaussian intensity distribution are modulated, each with its own frequency or code, whereby the relative strength of each signal can be measured from the signal received by the sensor. In a correctly designed system the relative strengths of intensities unambiguously define the location of the sensor in the laser beam bundle.

Figure 2 illustrates an example of using three laser beams. Five detectors 21-25 are visible in the target. In the example of figure 2, the intensity profiles of the laser beams are decreasing in radial direction. In this example, the aiming line 29 is in the geometrical center of the beams. The intersection area 201 of the beams in the level of the target is here emphasized by means of a hatch pattern. To one skilled in the art it is obvious that also more intersecting beams can be directed in a corresponding way. Generally, a certain point is included in the intersection area of the beams when the intensity of each beam at this point is sufficient for detecting it. Should more beams be utilized, in this disclosure the intersection area means an area in which at least three beams intersect each other, thus enabling the determination of the aiming point. Thus, by using more beams intersection areas with widely differing cross-sections can be formed.

The intensity profile of the laser beams can in principle be widely varying as long as the relation of the radiation intensities unambiguously determines the location of the detector. It is thus preferable that the beams be intensity profiled in a level perpendicular to the optical axis thereof so that the intensity profiles of the beams follow the essentially monotonous distribution in the radial direction of the beams (towards the edges of the beam from the optical axis thereof). The mathematically most simple profile would be a linear one, optically the most easily realizable one would be a gaussian profile.

Figures 3 a and 3 b show a detection zone made possible by, for example, the beam arrangement according to figure 2. As the target turns, the position of the detectors 36, 36' having received the signals can be used for determining the direction of arrival of the shot and thereby further make the detection zone 34, 34' more precisely correspond with the outline of the target 30, 30'.

In the following reference is made to figure 6 showing the beam group formed by three laser beams. The figure corresponds roughly with the beam group of figure 2 as seen from above or below. The optical axes of beams A, B and C are accordingly referred to with reference numbers 66, 67 and 68. The opening angles are correspondingly marked by reference numbers 63, 64, 65, and the angles between the optical axes of the beams are referred to with reference numbers 60, 60 and 62. The intersection area of the beams is dark- ened and it is denoted by reference number 601. The aiming line is denoted by reference number 69. According to one embodiment the beams are arranged to open in a certain opening angle and the angle between the optical axes and the aiming line is 0-49%, preferably 20-40% of this angle. The opening angle can, for example, be 0.01-10 degrees, preferably 0.05-5 degrees, typically 0.5-3 degrees.

The preferable magnitudes of the angles depend on both the weapon used and the shooting distance. With sniper rifles having a range of possibly over one kilometer, the beams open in a very narrow angle, for example 0.05-1 degrees, and their optical axes are near each other. Thus the cross-section of the intersection area remains relatively small even with long distances and the hit point can be accurately determined in this area. With assault rifles having a typical combat range of 30-300 meters, the beams can open in angle of, say, 0.5-2 degrees. The angle between the optical axes of the beams can in this case be, for example, 0.2-1.8 degrees. With handguns the beams can open in even larger angles, whereby a large detection zone is accomplished even at short ranges.

The optical axes of the beams can be arranged to travel in the same direction, but separate from each other. Thus, the distance between the initial points (the laser sources or the initial points of the optical splitting means) of the beams is preferably comparable to the dimensions of the target. This embodiment is especially useful in, for example, vehicles and long-range weapons, because then the opening angles can be kept smaller and yet achieve a relatively large intersection area of the beams and a good definability of the aiming line.

The opening angle of the beams must be kept so small that with the chosen target distance the radiation intensity of the beams is sufficient in the intersection area for reliably detect- ing the beams independently of each other.

On the other hand, the dimensions of the intersection area of the beams in the assumed (most probable in the training situation) distance between the target and the source are preferably of the magnitude of the dimensions of the target, such as 50-150%, typically 70- 130% of the dimensions of the target. When estimating the direction of the beams, the largest horizontal and vertical dimension of the intersection area and the target or the areas of the intersection area and the target, for example, can be used as a guideline. A preferable beam pattern also depends on the amount and positioning of the detectors in the target. The aiming line can in principle be located anywhere at the intersection area of the beams, but preferably it is arranged to essentially go along the geometric center line of the optical axes.

Digital information is preferably encoded into at least one beam. The information can be at least partly encoded according to the MILES or MILES 2000 code word system. For this purpose the transmitter is provided with an encoder. Information can also be coded into a number of beams or all beams. Thus the shot impulses can be kept shorter, because information can be transmitted in parallel.

Preferably the digital information includes also data about the number of beams and/or opening angles and/or the angles between the optical axes and/or the location of the aiming line in relation to the optical axes, i.e. information about the shape of the beam group. This embodiment makes it possible that all information about all possible weapons (beam groups) are not input into the target end in advance, but all necessary information can be deduced from the received signal. Further, at the transmitter end, the opening angles of the beams and the angles between optical axes can be steplessly changed during combat de- pending on the shooting distance. This feature can be connected to, for example, the adjustment of the sights of the weapon at various shooting distances. This will further make the combat simulation even more realistic.

In case the initial points of the beams do not exactly converge, as can happen in a number of practical solutions, there can be an area in front of the barrel of the weapon, where the beams do not intersect. The length of this area depends on the distance between the laser sources as well as the direction and the opening angle of the beams. Thus, the hit point can not be detected at this area. If necessary, an extra close-range combat beam or beam group can be used for covering this shadow area. According to another embodiment the actual beam group is scattered by optical means so that no shadow area is formed in front of the weapon. Referring again to figures 4 and 5, the detector 42, 52 of the receiver 41, 52 must be sensitive to at least three distinguishable laser beams. This means that the sensitivity range of the receiver must be sufficient for identifying all beams and determining their intensities. The output signal or signals of the detector must thus be of sufficiently good quality so that the data processing unit can determine the hit point in steps 48 or 56. It must be noted that radiation power many times larger than that in prior art single beam solutions can be exerted on the detector. If all beams have the same wavelength, one radiation indicator is usually enough for one detector. Especially when using multiple wavelengths, the detector can comprise a number of indicators. On the other hand, even one wide-band indicator can be used for identifying and distinguishing a number of wavelengths. The wavelengths used in the transmitter can vary from ultraviolet through visible light to infrared.

The laser detectors can comprise one or more light-sensitive elements, in which the optical signal is transformed into an electrical signal (optoelectronic element). The element can be selectively sensitive to the wavelength used in the transmitter (such as a suitable semiconductor detector) or it can have wider bandwidth. The detector can also comprise a photo- element based on thick or thin film technology. The element can also be manufactured as a flexible one and thus well suitable for field use. The simplest solution of the detector is a light dependent resistor (LDR). hi a preferred embodiment the photoelement is based on semiconductors, such as a photodiode. Fiber-optical sensors and light conductors can also be used. In some solutions it is also possible to use photo multipliers. In case the sensor is a wide bandwidth one, it can be preferable to filter the incoming light in an optical filter prior to its arrival on the photo element.

The signals emitted by the detectors can be amplified in an amplifier prior to any further processing.

hi the data processing unit of the receiver the distance of the detector from the optical axis of each beam and further the position of the detector in relation to the aiming line of the shot can be calculated on the basis of the given angle and intensity profile data of the laser beams. In case there is a number of detectors, the accuracy of the determination of the hit point can be improved in the data processing unit by means of the data transmitted from the number of detectors. The most probable aiming line of the shot can thus be determined as, for example, an average of the number of possibly varying hit points. It is obvious that in this case only data from detectors that successfully received all the data necessary for determining the hit point is used. Some detectors can namely be in a partly or totally shadowed for one or more beams behind, e.g., parts of the body or obstacles in the ground. The quality of the signal can also be so weak that the detection is not reliable anymore.

In a very simple system the sum signal produced by a number of detectors can be used. Because the aiming point is determined on the basis of the relations of the intensities of the beams, and their average produces an approximation in the right direction about the position of the aiming point. This will work especially well with laser beams having a linear intensity modulation.

According to one embodiment the data processing unit has the data concerning the position of the detectors in the target and/or data about the outer dimensions of the target. By means of these data the data processing unit can accurately determine, for example, the position of the target in relation to the aiming line of the shot (arrival direction of the shot) or the trajectory of the aiming line in relation to the dimensions of the target. The receiver apparatus can further include data about the different areas of the target (such as easily damaged or specially resistant areas) that can be utilized when assessing the damage done to the target upon a shot hitting the target. The arrival direction of the shot can be simply determined by comparing the phases of the signal received by one or more detectors. The time difference between the signals can be used for determining the distance difference of the detectors to the shooter and thereby also the position of the target. For determining the direction the data processing unit can use signals from, for example, detectors that have successfully received only one of the number of beams, the signal of which is therefore not sufficient for assessing the hit point. Such a signal can also be used for indicating missed shots.

The data processing unit preferably comprises a processor taking care of all necessary digi- tal data processing and the calculation needed for determining the hit point. The processor can also take care of other tasks necessary for the combat simulation. The apparatus preferably also comprises a memory into which data about the combat is saved. Detectors can be located on the head, torso, arms and legs or the weapon of the target so that they cover the target from directions most important for the combat. The number of detectors can be 1-20, preferably 4-16, specially 6-12. The target can also be, for example, a practice target, building, an animal, vehicle, aeroplane or a marine vessel. For example, in range, practical or police shooting, where the shooting direction in relation to the target is usually known well or relatively well, one detector is usually enough for the target. When the shooting direction is known, even one detector is sufficient for determining the hit point (the route of the aiming line) in the vicinity of the target within a few centimeters or even more accurately, hi the field, where the target and the shooter can move more freely in relation to each other, it is preferable to use a number of detectors, whereby the direction of the shot can be determined as described above.

According to one embodiment the system takes into account the movement of the target (advance of the shot) and/or the ballistic behaviour of the imaginary bullet. This is possible if the aiming line can be accurately determined. The necessary advance can be calculated by using the distance data between the shooter and the target, the speed data of the target and data about the weapon. For example, if the target moves to the left from the shooter and the receiver of the target notices the aiming line of the shot slightly to the left of the target, the shot can be interpreted as a hit, if, for example, the above-mentioned data is available. The speed of the target can be determined by means of a GPS system or the like, by means of acceleration sensors fastened on the receiver or by some other means. When calculating ballistics, data concerning the movement of the target is not necessary, but the intersection area of the beams must cover a sufficient area below the aiming line. It can therefore be preferable to direct the beams in some embodiments so that the actual aiming line runs above the geometric centerline of the beams. The effect of ballistics to the realism of the simulation can also be taken into account by directing the beams at slightly different heights when shooting at different distances. The direction can, for example, be connected to the adjustment of the sight of the weapon.

This document discloses laser cones having a circular cross-section, but it is optically possible to produce beams having a different shape, the intensity profiles of which produce an unambiguous intersection pattern. The beams can be e.g. triangular, square or elliptical. In some embodiments the shape of the intersection area can be optimised so as to suit the situation by changing the shape of the beams.

Example:

The example discloses the determining of a hit point by means of a cone arrangement according to figure 2.

Table 1. The relative signal strengths S detected by the sensors 21-25 (location (x,y)) and the location of the hit point estimated on the basis of them. The co-ordinates are shown in a rectangular co-ordinate system, the origo of which is in the center line and shoulder level of the target. The scale is arbitrary.

Table 1 lists the intensities detected by five sensors on the basis of a shot. The table also lists the estimated locations of hit points (in an arbitrary co-ordinate system). The sensors 24 and 25 did not receive enough information for completely determining the hit point, because beam A did not reach them. By averaging the hit co-ordinates the final hit point is (12, 29), which in this case is in the throat area of the target. Thus the hit can be interpreted as lethal. In this example, using a number of detectors and beams is useful, because if one were to trust only the signal from, say, detector 22, the shot could have been interpreted as slightly missing the target on the right side. On the other hand, had prior art method been used, thus utilizing the signal emitted by only one beam, the only possible estimate would have been to roughly estimate on which side of the target the shot went and a rough estimate whether the shot hit. It would have been impossible to accurately determine the hit point. Had only one detector detected the beam, it would have been impossible to determine just about anything about the hit. Thus, the use of multiple beams increases the hit point determining accuracy.

Claims

Claims:

1. An apparatus for transmitting a shot signal in a tactical engagement simulation, the apparatus comprising a laser transmitter (40, 50), characterized in that the laser transmitter comprises means for producing at least three intensity profiled laser beams (A, B, C) so that the laser beams are distinguishable from each other, travel along different optical axes (66, 61, 68) and intersect each other, whereby the aiming line (69) of the shot is arranged to pass through the intersection area (201, 601) of the beams.

2. An apparatus according to claim 1, characterized in that the number of beams is three.

3. An apparatus according to claim 1 or 2, characterized in that the beams are arranged to open in a certain opening angle (63, 64, 65) and that the angle between the optical axes (66, 61, 68) and the aiming line is 0-49%, preferably 20-40 % of this angle.

4. An apparatus according any of the preceding claims, characterized in that the beams are arranged to open in an opening angle of 0.01-10, preferably 0.05-5, typically 0.5-3 degrees.

5. An apparatus according any of the preceding claims, characterized in that the means for producing at least three intensity-profiled laser beams comprises at least three laser sources (43, 43,', 43"), each of which produces one beam.

6. An apparatus according to claim 5, characterized in that the laser sources are arranged to produce light at different wavelengths for accomplishing the distinguishability of the beams.

7. An apparatus according to any of claims 1-4, characterized in that the means for producing at least three directed laser beams comprise one laser source (54), the laser beam produced therewith is optically (55) split into at least three beams.

8. An apparatus according any of the preceding claims, characterized in that the apparatus comprises a modulator (46, 46', 46", 54, 54', 54") for modulating the intensity of the beams for accomplishing the distinguishability of the beams.

9. An apparatus according any of the preceding claims, characterized in that the apparatus comprises means for emitting laser impulses temporally one after the other for accomplishing the distinguishability of the beams.

10. An apparatus according any of the preceding claims, characterized in that the apparatus comprises an encoder for including digital information into at least one beam.

11. An apparatus according to claim 10, characterized in that the digital information comprises information about the opening angles of the beams and the angles between the opti- cal axes and the aiming line.

12. An apparatus according to claim 10 or 11, characterized in that the encoder is arranged to encode the information according to the MILES or MILES 2000 (Multiple Integrated Laser Engaged Simulation) code word system.

13. An apparatus according any of the preceding claims, characterized in that the beams are intensity-profiled in a level perpendicular to their optical axis so that the intensity profiles of the beams follow the essentially monotonous distribution of the beams in radial direction, preferably a gaussian or linear distribution.

14. An apparatus for detecting a shot in a tactical engagement simulation, the apparatus comprising

- at least one detector (21-25, 41, 51) for detecting a laser beam and for indicating intensity, - a data processing unit being operationally attached to the detector for assessing the hit, characterized in that

- the detector (21-25, 41, 51) is sensitive to at least three distinguishable laser beams (A, B, C),

- the data processing unit is arranged to determine (48, 56) on the basis of at least three laser beams hitting the detector and being distinguishable from each other the distance of the detector from the optical axes (66 61, 68) of the beams.

15. An apparatus according to claim 14, characterized in that the data processing unit is arranged to calculate the location of the detector in relation to the aiming line of the shot on the basis of the given angle and intensity profile data.

16. An apparatus according to claim 14 or 15, characterized in that there is a number of detectors and the data processing unit is arranged to determine the most probable aiming line (29, 69) of the shot on the basis of the intensities detected by each detector.

17. An apparatus according to any of claims 14-16, characterized in that the data about the location of each detector (21-25, 41, 51) on the target can be included in the data proc- essing unit and that the data processing unit is arranged to determine the position of the target in relation to the aiming line (29, 69) of the shot by using these data.

18. An apparatus according to claim 17, characterized in that the data processing unit can also include data about the dimensions of the target and that the data processing unit is arranged to determine the dimensions of the target in relation to the aiming line (29, 69) of the shot by using these data.

19. An apparatus according to any of claims 14-18, characterized in that the number of detectors is 2-20, preferably 4-16, specifically 6-12.

20. A system tor tactical engagement simulation, the engagement simulation having at least one shooter and at least one target, the system comprising

- shooter's means (40, 50) for producing a directed and intensity-profiled laser beam, and - the target's means (42, 52) for detecting the laser beam and for indicating the intensity of the laser beam, characterized in that

- the shooter's means (40, 50) comprise means for producing at least three laser beams (A, B, C) travelling along different optical axes (66, 67, 68), intersecting each other and being distinguishable from each other, and

- the target's means (42, 52) comprise at least one detector (21-25, 29, 69) sensitive to the laser beams (A, B, C) produced by the shooter and being attached to the data processing unit arranged to determine (48, 56) the location of the detector in relation to the optical axes (66, 61, 68) of the beams (A, B, C).

21. A system according to claim 20, characterized in that the shooter's means comprise an apparatus according to any of claims 1-13.

22. A system according to claim 20 or 21, characterized in that the target's means com- prise an apparatus according to any of claims 14-19.

23. A method of determining the aiming line at a tactical engagement simulation, characterized in that

- at least three intensity-profiled laser beams (A, B, C) are transmitted, the beams being distinguishable from each other, travelling along different optical axes (66,

67, 68) and intersecting each other so that the aiming line (29, 69) essentially remains within the intersection area (201, 601) of the beams,

- laser beams are detected (47, 47', 47", 55, 55', 55") and identified and their intensities are indicated in at least one observation point, and - the position of the observation point in relation to the aiming line is determined (48, 56) on the basis of the intensities of the beams.

24. A method according to claim 23, characterized in that the laser beams are modulated (46, 46', 46", 54, 54', 54") independently of each other for accomplishing their distin- guishability.

25. A method according to claim 23 or 24, characterized in that there is a number of observation points (21-25) and the most probable location of the aiming line (201, 601) in relation to the number of observation points is determined.