Device and method for electronic evaluation of hits

0001The invention relates to a device and a method for detecting the position of an object flying through an evaluation surface, in particular a projectile or arrow, wherein the device and the method can be used in particular for shooting ranges, especially for sport shooters.

0002In the <patcit id="pcit0001" dnum="DE4415944A1"><text>DE 44 15 944 A1</text></patcit> describes an electronic target and a method for evaluating it, a light source illuminating a focusing screen via optics. The optics represent a shadow projection of a projectile on the focusing screen onto a target sensor. The target sensor exchanges the information obtained with a system control by means of a line. Slotted disks are introduced into the beam path of the light source.

0003A disadvantage of this method is that the light signal is weakened by the additional screen or screen, which can give rise to an increased technical outlay given the short exposure times required. In addition, the distance between the camera and the measuring field must be observed, which results in a large design. In addition, the point light source is expanded by the lens, which additionally requires a further distance between the light source and the evaluating surface with the lens arranged in between.

0004One object of the invention is to implement a device and a method for detecting the position of an object, in particular a projectile or arrow, flying through an evaluation surface, which have a very compact design and a high evaluation accuracy.

0005The object is achieved according to the features of the independent claims. The dependent claims show advantageous embodiments and further developments of the invention.

0006The device according to the invention and the method according to the invention can be used for shooting ranges, especially for sports shooters. The projectile or arrow can penetrate two light curtains which are preferably arranged orthogonally (90 °) to one another. The two light curtains can be arranged one above the other or overlapping in the flight direction of the shot, so that no parallax errors can occur. That of, for example, rod-shaped or Light emitted in the form of strips can be forwarded to a respective camera device via a respective lens, wherein the camera device can contain, for example, a line scan camera. A lens of this camera can form a telecentric lens together with the associated lens. Furthermore, the beam path directly behind the lens can be redirected twice, for example by 90 °, so that the camera device can be arranged on the same side as the light source, as a result of which a very compact design can be achieved.

0007According to the invention, the device for optically detecting the position of an object flying through an evaluation surface, in particular a projectile or arrow, has at least one light source emitting a light strip which emits light into an evaluation plane, at least one lens through which the light emitted by the light source is guided at least one camera device into which the light is guided after the lens and / or an evaluation device, which evaluates a signal from the camera device and outputs a position of the object. The method according to the invention can use an evaluation device to determine position values ​​which correspond to x-axis values ​​and y-axis values, from which a position in the x and y directions of an object passing through the evaluation plane is determined.

0008Furthermore, at least one deflection device can be provided, which is arranged behind the lens and deflects the light in such a way that it is guided again through the lens, the light after the lens being in a return plane. Instead of using one lens that is irradiated twice, two lenses can also be used, for example the light radiating to the deflection device is guided through the one lens and the light returned by the deflection device is guided through the other lens.

0009A very compact device can be achieved by providing the deflection device and using the lens twice. In addition, position values ​​can also be used to further increase the detection accuracy, which are obtained when the object flies through the return plane. Furthermore, on the basis of the number of images captured by the camera device, on which a shadow of the object can be seen, a conclusion can be drawn about a speed of the object, wherein the speed can be used as a plausibility check for the detected signal. This makes it possible to distinguish the fast-flying projectiles to be detected from other bodies and particles which may move through the detection device, in order to thereby filter out false signals. Two light sources, two lenses, two deflection devices and two camera devices can be provided. The light emitted by the two light sources can preferably be arranged at an angle of essentially 90 ° to one another. The light emitted by the light sources can penetrate the evaluation plane uniformly with homogeneous light and strikes a respective lens on the other side. From the respective lens, the light strikes the respective deflection device, which then in turn reflects the light through the respective lens back in the return plane onto the respective camera device. The lenses and the objects of the camera device are designed in such a way that a telecentric lens is obtained, ie that the opening angle of the lenses is corrected by the lenses in such a way that a parallel beam path results. This applies to the x and y or to the horizontal and vertical directions (see FIG. 1).

0010The light emitted by the two light sources can preferably overlap in the evaluation plane and / or in the return plane. However, it is also possible for the light from the two light sources to be emitted in different planes. The same applies to the light in the return level, which can also be sent back to different levels. However, the distance between these different levels should only be small so as not to reduce the evaluation accuracy too much.

0011The disadvantage of the large size described in the aforementioned prior art results from the fact that, depending on the focal length of the lens, the distance from the camera to the converging lens must be approximately the same size as the firing field to be evaluated, i.e. the complete apparatus would be at least four times the area of ​​the firing field to be evaluated exhibit. According to the invention, this disadvantage can be eliminated in that the light behind the converging lens is deflected by, for example, two mirrors. These mirrors in the deflection device create two light curtains, a parallel, telecentric light curtain and a non-telecentric light curtain. The side facing the shooter has the telecentric area. The twice deflected beam path in the return plane can have an angle which corresponds to the opening angle of the lens of the camera device.

0012The distance between the telecentric and the non-telecentric light curtain should be at least so large that the projectile does not fly through both light curtains during an integration time of a sensor of the evaluation device, i.e. the projectile flying through (the moving object) on the camera chip creates a shadow twice in succession, whereby only the first (telecentric) light curtain in the evaluation level is of primary importance. As already briefly explained above, the second light curtain can also be used to increase the measuring accuracy. However, this is only possible if the projectile is in the center area of ​​the device.

0013It is also advantageous to guide the beam path twice through the corresponding lens. This enables the necessary focal length of the lens to be doubled, ie the lens thickness can be almost halved.

0014Furthermore, the converging lens can be designed as a Fresnel lens. The deflection mirrors mentioned above can also be replaced by a 90 ° prism with total reflection.

0015According to a further possibility, the two deflecting mirrors can be made concave in order to achieve the telecentric effect of the lens.

0016In order to make the light emitted from the light source to the lens as homogeneous as possible, a scattered light means can also be provided. This scattered light means can be provided in the beam path after a transparent rod, can be integrated into the rod, and / or can be realized by the rod. The rod can be provided in the beam path after light-generating elements, for example light-emitting diodes. The light source can be the light-generating elements, the rod and / or the or contain the scattered light.

0017The invention will now be explained in more detail using exemplary and schematic figures.

0018Show it<ul id="ul0001" list-style="none" compact="compact"><li>1 is a schematic view of individual components of the invention with a converging lens,</li><li>2 shows a schematic view of the invention with a Fresnel lens,</li><li>3 and 3a are schematic views of the invention with two beam paths,</li><li>4 shows a schematic section through the device according to the invention in one direction (x or y direction),</li><li>5 shows a schematic arrangement of the optical elements in the x and y directions,</li><li>6 is a schematic view of the electrical control of the invention.</li></ul>

00191 shows a preferably linear or rod-shaped light source 1, which emits its light in the direction of the lens. The light source 1 can be designed such that the light is emitted as a light strip. The angle of the light 2 is changed by a converging lens 3 or a parabolic mirror 23, 24 such that a beam path 10 is obtained which corresponds to an opening angle of a lens 5 of a camera device 4. The objective 5 focuses the incident light on a position-sensitive photosensitivity area of ​​a preferably semiconductor component or sensor 6, such as a CCD or C-MOS line sensor. In Fig. 1 only one beam path is shown schematically in one direction (x or y direction of the detection device).

0020In contrast to FIG. 1, FIG. 2 shows a Fresnel lens 7 instead of the converging lens 3.

0021The converging lens 3 and / or the Fresnel lens 7 together with the camera device 4 form a telecentric lens which has a parallel beam path on the respective left side of the lens 3, 7 and a triangular beam path on the right side.

00223 shows an advantageous embodiment of the invention for space optimization. To optimize space, the beam path behind the lens 3 is deflected via, for example, two mirrors 8, 9 of the deflection device and reflected back in the direction of the light source 1 against the parallel light curtain (primary light curtain). The reflected light curtain 10 is at a predetermined distance from the primary light curtain 2. The primary light curtain 2 is located in an evaluation level 16 and the reflected light curtain 10 is located in a return level (see FIG. 4).

00234 is the basic structure of an inventive. Detection or scanning unit shown in one direction (x or y direction). Light is emitted via, for example, light-emitting diodes 18, which can be arranged in a row. This light strikes an at least partially transparent, preferably rotationally symmetrical rod 19 which focuses the light in the direction of the lens. The rod can be made of glass, for example.

0024In order to make the light emitted to the lens as homogeneous as possible, a scattered light means can also be provided. This scattered light means can be provided in the beam path after the rod 19 or can be integrated into the rod 19 and / or realized by the rod 19. The scattered light can be made of milky, transparent material. The features of the light source explained above can be used for all the embodiments described, in particular also for realizations of the invention without a deflection device.

0025The rod 19 transmits the beam path 2 in the evaluation plane 16 to the converging lens 7. The light runs from the collecting lens 7 to the deflection device 8, 9, which consists of a mirror 8 and a mirror 9. At this point it should be noted that a Fresnel lens 7 can also be provided instead of the converging lens 3. Behind the corresponding lens 3, 7 is the mirror 8 which is inclined by 45 ° and which deflects the incident light onto a second mirror 9. This mirror is also inclined at 45 °. The light is guided through the two mirrors 8, 9 of the deflection device into a return plane 17, which can be parallel to the evaluation plane 16. The deflected light curtain in the return plane 17 has such a distance from the first parallel light curtain 2 in the evaluation plane 16 that during the exposure time of the camera device 4 a projectile 20 only passes through the first light curtain 2 and has not yet reached the second light curtain 10. The distances between the two light curtains 2, 10 or the evaluation level 16 and the return level 17 are preferably between 10 and 30 mm. Exposure times can be, for example, 60,000 frames / s.

0026When the projectile 20 passes through the evaluation plane 16, the camera device 4 can detect a corresponding shadow. This shadow can then be detected by an evaluation device. Since the arrangement shown in FIG. 4 is provided both in the x-direction and in the y-direction, an accurate position detection of the projectile 20 or of the moving object becomes possible.

00275, the optical elements of the device according to the invention are shown schematically in the x and y direction or in the vertical and horizontal direction. The first light source 1 and the second light source 1 'emit their light in the x and y directions. These parallel beam paths meet corresponding converging lenses 3, 3 'on the other side of an active evaluation surface 21. Instead of the collecting lenses 3, 3 'shown, Fresnel lenses 7, 7' can also be used. The active evaluation surface 21 is located in the intersection of the beam paths 2 and 2 '.

0028The light is reflected by the mirrors 8, 9; 8 ', 9' of the deflection device are reflected back and directed back in the direction of the respective light source 1, 1 '. However, the light is returned in a return plane 17 which is different from the evaluation plane 16. The lenses 3, 3 'and 7, 7' (not shown) are designed such that the light path passes the corresponding lens twice. As a result, the necessary focal length of the corresponding lens is twice as large, i.e. that is, the lens can be made about half as thick. The light 10, 10 'reflected back by the aforementioned lenses in the direction of the camera device 4, 4' is arranged behind the parallel (telecentric) light field, as seen in the firing direction. The projectile or the moving object penetrates the returning light curtain 10, 10 'only after the hit position has been evaluated.

0029It should be expressly mentioned here that the use of parabolic mirrors is possible instead of the aforementioned lenses or Fresnel lenses and mirrors. This possibility is in the figure. 3a shown. Here, two parabolic mirrors 23, 24 are provided, which can also be aligned twice at 45 ° to one another, so that here too the second light curtain is reflected in the return plane 17 behind the first primary light curtain 2, 2 '. Would in Fig. 4th If the two mirrors 8, 9 are designed parabolically, the converging lens 3, 7 could be omitted, as shown in FIG. 3a. The radii of the concave mirror (concave mirror) can be determined using the following formula:<maths id="math0001" num=""><math display="block"><mi mathvariant="normal">f</mi><mo mathvariant="normal">=</mo><mi mathvariant="normal">r</mi><mo mathvariant="normal">/</mo><mn mathvariant="normal">2</mn></math><img file="EP1892495A2_D0001.tif" /></maths> f stands for the focal length of the light and r for the radius of the mirror.

0030It can be seen from FIG. 5 that a projectile 20 passing through the primary light curtains 2 and 2 'results in an x ​​and y position in the corresponding camera devices 4 and 4', since a respective shadow is detected in both camera devices 4 and 4 '. This shadow can be evaluated accordingly in order to output corresponding position signals (see FIG. 6).

0031An example of an electrical control of the device according to the invention is shown in FIG. 6. An evaluation device or a controller 11 sets a light intensity of the linear light sources 1 and 1 'via two corresponding outputs 22. Furthermore, sensors 6, 6 'are read in by controller 11. These sensors 6, 6 'are preferably line sensors. The controller 11 continues to generate pixel and line clock signals 12. The light sources 1 and 1 'are controlled by the signals returned by the line sensors 6 and 6', so that closed control loops are created. The two sensors 6 and 6 'are illuminated uniformly by the optical arrangement. If, for example, a projectile 20 flies through the two light curtains 2 and 2 ', corresponding sectors on the sensors 6 and 6' are darkened. The x and y values ​​calculated in this way by the controller 11 are forwarded via a network, for example to a visualization which can be arranged during the protection. Furthermore, the signals can be received directly with a central computer, so that, for example, a competition can be evaluated online. A data transmission can advantageously take place through a BUS system 13 or a radio network 14. In addition, a coding device 15 can be provided, which allows a data record to belong to a specific shooting range if several corresponding devices are provided.

0032The aforementioned features and embodiments can be combined with one another in any manner.