DE102018100417A1 - Method and device for optical target tracking of target object that can be irradiated with a high-energy laser - Google Patents

Abstract

The invention relates to a method and a device (1) for optical target tracking of a target object (5) which can be irradiated with a high energy laser (2), wherein the target object (5) is illuminated by an illumination laser (6).
In order to enable a precise alignment of the laser beam (4) of the high-energy laser (2) on the target object (5) even if on the target object (5) triggered by the laser beam (4) flame and / or smoke development or self-lighting ( Disturbance), the invention proposes a differential image determination. For this purpose, synchronously and with the same exposure time two camera images (22, 24) of the target object (5) are recorded and stored in different wavelength ranges, each with a separate camera (14, 15), wherein the first wavelength range is selected such that the radiation of the illumination laser (6) is measurable. The second wavelength range is slightly shifted with respect to the first wavelength range, such that although not the radiation of the illumination laser (6) itself but the interference (23) caused by the irradiation with the high energy laser (2) is measured. If the second camera image (24) is now electronically subtracted from the first camera image (22), a difference image (25) with a target object freed from the interference (23) is produced.

Description

The invention relates to a method and a device for optical target tracking of a high-energy laser irradiated target object, wherein the target object is illuminated with a illumination laser.

In laser weapons, the laser beam of a high-energy laser (Wirklaser) is usually aligned by an optical tracking method on a target object. In this case, an image of the target object is usually generated on a camera with an imaging optics. By appropriate software, the spatial position of the target object is determined and aligned the laser beam to the target object. The alignment of the laser beam is done mechanically by the movement of a support platform or optically e.g. by the controlled movement of a deflecting mirror.

For fast moving targets, the control loop will run for a correspondingly short period of time, i. with a suitably high clock rate, from, wherein the image recording frequencies can be up in the kHz range.

Laser guns using high energy lasers have high precision, so precise beam alignment is particularly important. In particular, in the case of extended target objects, the laser beam can be aligned with a defined object point, which is particularly vulnerable. The illumination laser usually has a larger beam cone than the active laser and is also aligned in the direction of the target object.

If the laser beam of the active laser is exactly aligned with the target object and acts on it, it often results in a strong flame and / or smoke development of the target object. Likewise, the material of the target object is heated by the laser irradiation, so that the target object emits thermal radiation or optical radiation is generated by chemical reactions. Due to these effects, a strong disturbance of the camera image occurs because the target object is at least partially obscured by flames and smoke and in the evaluation area of the image very bright areas arise (flame, intrinsic lighting), which distort the evaluation. A further precise alignment of the laser beam of the active laser on the target object is then no longer possible (track loss).

From the DE 32 30 068 C2 For example, a method for accurately positioning the laser beam of an active laser is known. In this case, the respective angular position of the laser beam reflected from the target object and the angular position of the thermal radiation emitted by the laser beam and heated body of the target object, measured and obtained by a comparison of these two angular positions a filing signal, which then nachsteuert the effective fiber and thus the latter Laser beam is aimed at the heated spot of the target object.

With this method, however, a subsequent accurate positioning of the active laser on a new target point of the target object - because the initially irradiated target point was chosen wrong - difficult to realize, because the target object is at least partially obscured by the flames and the smoke of the already heated target area or thermal radiation is emitted from locations other than the target point.

The invention has for its object to provide a method with which the influence of interference is reduced or suppressed, so that a precise alignment of the laser beam of the active laser on the target object is also possible if on the target object triggered by the laser beam flame and / or smoke or self-lighting occurs. Furthermore, a device for carrying out the method should be specified.

This object is achieved with regard to the method by the features of claim 1 and with respect to the device by the features of claim 4. Further, particularly advantageous embodiments of the invention disclose the dependent claims.

The invention is based essentially on the idea of suppressing or significantly reducing the influence of the disturbances caused by flames, smoke and / or intrinsic lighting on an accurate positioning of the laser beam of the active laser by means of a special image recording technique. For this purpose, a difference image is determined from two camera shots of the target object in which the interference does not occur. This image is then used to determine the position of the object and is used to track the laser beam.

To obtain the difference image, two images of the target object in different wavelength ranges, each with a separate camera, are recorded synchronously and with the same exposure time, wherein the first wavelength range is selected such that the radiation of the illumination laser can be measured. The corresponding camera image then reflects the target object superimposed by the fault. The second wavelength range is slightly displaced from the first wavelength range, such that although not the radiation of the illumination laser itself, but the radiation caused by the irradiation with the high energy laser by flame formation and / or self-illumination of the surface material of the Target object (fault) is measured. This camera image contains only the disturbance. If the second camera image is now electronically subtracted from the first camera image, a difference image is produced with a target object freed from the interference.

The difference image is then evaluated with respect to the position of the target object and the direction of the laser beam is controlled. Subsequently, the image acquisition starts again in the manner described above.

Thus, a method and an apparatus for optical target tracking of a target object which can be irradiated with a high energy laser are proposed, wherein the target object is illuminated with a illumination laser. In order to enable precise alignment of the laser beam of the high-energy laser on the target object even if on the target object triggered by the laser beam flame and / or smoke or intrinsic (disturbance) occurs, the invention proposes a difference image determination. For this purpose, two camera images of the target object in different wavelength ranges, each with a separate camera are recorded synchronously and with the same exposure time and stored. The first wavelength range is selected such that the radiation of the illumination laser can be measured. The second wavelength range is slightly shifted relative to the first wavelength range, such that, although not the radiation of the illumination laser itself but a disturbance caused by the irradiation with the high-energy laser is measured. If the second camera image is now electronically subtracted from the first camera image, a difference image is produced with a target object freed from the disturbance. The advantage lies, i.a. in that also disturbances caused by other light sources, such as solar radiation and reflections of solar radiation, are suppressed.

• 1 die schematische Darstellung einer Vorrichtung (Laseranordnung) zur Durchführung des erfindungsgemäßen Verfahrens mit Wirklaser, Strahlführungssystem, Beleuchtungslaser, Kameras und Rechner;
• 2 das mit einer ersten Kamera aufgenommene Bild eines Zielobjektes, bei dem der Wellenlängenbereich derart gewählt ist, dass das Licht des Beleuchtungslasers messbar ist;
• 3 das zeitlich gleichzeitig mit einer zweiten Kamera aufgenommene Bild, bei dem der Wellenlängenbereich derart gewählt ist, dass nur die Störung sichtbar ist;
• 4 das aus der Differenz der Kamerabilder gem. 2 und 3 sich ergebende Kamerabild des Zielobjektes.

Further details and advantages of the invention will become apparent from the following, with reference to figures explained embodiments. Show it:

• 1 the schematic representation of a device (laser assembly) for carrying out the method according to the invention with active laser, beam guiding system, illumination laser, cameras and computers;
• 2 the captured with a first camera image of a target object, wherein the wavelength range is selected such that the light of the illumination laser is measurable;
• 3 the temporally recorded simultaneously with a second camera image, wherein the wavelength range is selected such that only the disturbance is visible;
• 4 the gem of the difference of the camera images. 2 and 3 resulting camera image of the target object.

In 1 1 denotes a laser arrangement which is a high-energy laser 2 (Weapon or real fiber), at least one of the real fiber 2 downstream beam guidance system 3 for focusing the laser beam 4 of the Wirklaser 2 on a moving target 5 , a lighting laser 6 and an electronic calculator 7 includes. The laser arrangement can be arranged on a support platform, not shown.

The beam guiding system 3 , also called radiation guide module, can also include mirrors as optical elements in addition to lenses.

The real fiber 2 is over a fiber optic cable 8th with the beam guidance system 3 connected. The latter consists essentially of a collimating lens 9 , a first deflection mirror 10 and a pivotable second deflecting mirror 11 as well as two telescope lenses 12 and 13 ,

In addition, the beam guiding system 3 two cameras 14 . 15 associated with taking an image of the target object 5 with both cameras 14 . 15 using the same beam path (same optical axis) takes place. For this purpose, the first deflection mirror 10 as well as another deflection mirror 16 formed as dichroic beam splitters, which thus have a wavelength-dependent reflection or transmisson.

The target object 5 is constantly using the illumination laser 6 illuminated, this being the moving target object 5 is also traceable and this example, with a corresponding drive 17 connected is.

Both the real laser 2 and the illumination laser 6 as well as the cameras 14 . 15 , a drive 18 for the swiveling mirror 11 and the drive 17 for the illumination laser 6 are via appropriate electrical lines to the computer 7 connected. For the rough pursuit of the target object 5 In addition, the carrier platform becomes the target object 5 tracked.

For the wavelength-dependent recording of the two images of the target object 5 with the two cameras 14 and 15 are accordingly narrow band optical filter 20 . 21 connected upstream with different transmission properties.

In front of the first camera 14 there is a narrow band filter 20 that the wavelength of the lighting laser 6 well transmitted. The corresponding camera image contains this through the illumination laser 6 generated image superimposed with the interference (flame, intrinsic light), which in the spectral range of the optical filter 20 lie.

In front of the second camera 15 there is an optical filter 21 , which does not transmit the illumination laser, but the light of the interference in a slightly offset spectral range with the same spectral width as the filter 20 Has.

The central wavelength of the optical filter 20 the first camera 14 corresponds to the wavelength of the illumination laser 6 , The central wavelength of the optical filter 21 in front of the second camera may be larger or smaller than the central wavelength of the optical filter 20 the first camera 14 , The wavelength distance is freely selectable. The wavelength of the illumination laser 6 may be in the visible or near infrared range. Adapted to this are filters and cameras.

The dichroic mirror 16 is done so that the mirror 16 the first wavelength reflects (for the camera 14 ) and the second wavelength (for the camera 15 ).

Below is with the help of 2 to 4 on the operation of the laser array 1 received. It is assumed that the target object 5 moved in the direction of the designated 100 directional arrow.

Is from the illumination laser 6 the target object 5 recorded, so evaluates the calculator 7 the corresponding signals of the two cameras 14 . 15 out. The camera delivers 14 this in 2 illustrated camera image 22 one of the error 23 partially hidden target object 5 , On the other hand, the camera delivers 15 this in 3 reproduced camera image 24 the disorder 23 without target 5 ,

Now become the data of the camera picture 24 from the data of the first camera image 22 with the help of the computer 7 subtracted electronically, the result is a difference image 25 with one of the error 20 liberated target object 5 ( 4 ).

Based on the difference image 25 can the laser beam 4 now precisely to the destination 19 be aligned.

Subsequently, the image acquisition starts again in the manner described above.

Preferably, the same imaging lenses are used for the generation of the camera images, so that the image sizes are the same and the difference formation provides a clear image directly. It is also advantageous to use cameras of the same type, ie with the same sensor size, with the same sensitivity, etc. To increase the quality of the difference image 25 For example, image processing tools can be used to compensate for differences in image size or signal strength. Such image processing is well known.

In a preferred embodiment, the illumination laser wavelength was 980nm. The optical filter 20 was therefore chosen such that the central wavelength is also 980nm and the spectral transmission width is 10nm. The optical filter 21 had a central wavelength of 970nm and a spectral transmission width of 10nm. The dichroic beam splitter 16 in this case has its spectral edge at 975nm.

The optics for imaging on the cameras 14 . 15 can be independent of the beam guidance system 3 and be independent optics.

LIST OF REFERENCE NUMBERS

1

Device, laser arrangement

2

High energy laser, active laser

3

Beam guidance system

4

laser beam

5

target

6

laser lighting

7

calculator

8th

Fiber Optic cable

9

collimating lens

10

first deflection mirror

11

second deflection mirror

12.13

telescope lenses

14

first camera

15

second camera

16

deflecting

17

drive

18

drive

19

Endpoint

20, 21

optical filters

22

camera image

23

disorder

24

camera image

25

difference image

100

arrow

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3230068 C2 [0006]

Claims (11)

Method for optical target tracking of target object (5) which can be irradiated with a high energy laser (2), wherein the target object (5) is illuminated by an illumination laser (6), characterized in that two camera images (22, 24) of the Target object (5) in different wavelength ranges, each with a separate camera (14, 15) are recorded and stored, wherein the first wavelength range is selected such that the radiation of the illumination laser (6) is measured, and that the second wavelength range relative to the first wavelength range is selected to be slightly shifted such that, although not the radiation of the illumination laser (6) itself, but the interference (23) caused by the irradiation with the high energy laser (2) is measured; in that subsequently the two stored camera images (22, 24) are electronically subtracted by means of a computer (7), so that a difference image (25) results which disturbances (23) resulting from the irradiation of the target object (5) with the laser beam (4), not or barely perceptible contains, and that the data of the difference image (25) evaluated with respect to the respective target position and used to determine the direction of the laser beam (4) of the high-energy laser (2). Method according to Claim 1 , characterized in that the central wavelength of an optical filter (20) of a first camera (14) corresponds to the wavelength of the illumination laser (6). Method according to Claim 1 or 2 , characterized in that the central wavelength of an optical filter (21) in front of a second camera (15) may be larger or smaller than the central wavelength of an optical filter (20) of a first camera (14). Method according to one of Claims 1 to 3 , characterized in that light of the wavelength 980 nm is used for illuminating the target object (5), that the wavelength range received by the first camera (14) has a central wavelength of 980 nm and a spectral transmission width of 10 nm and that the second camera (15 ) received second wavelength range has a central wavelength of 970nm and a spectral transmission width of also 10nm. Apparatus for carrying out the method according to one of Claims 1 to 4 , characterized in that at least a part of the means (10-13) of the beam guiding system (3) required for beam guidance of the laser beam (4) of the high energy laser (2) are arranged such that they are also used as imaging optics for the two cameras (14, 15 ), so that light beams are received by the two cameras (14, 15), which pass through the same beam path between the beam guiding system (3) and the target object (5), such as the laser beam (4) of the high energy laser (2) and that Wavelength-dependent recording of the two camera images (22, 24) the two cameras (14, 15) corresponding narrow-band optical filters (20, 21) are connected upstream. Device after Claim 5 , characterized in that the optical filters (20, 21) each have a spectral transmission width of ≤ 10nm. Device after Claim 5 or 6 , characterized in that means of image processing can be used to increase the quality of the difference image (25). Device according to one of Claims 5 to 7 , characterized in that in the beam guidance system (3) as optical elements in addition to lenses and mirrors can be used. Device according to one of Claims 5 to 8th , characterized in that the optics for the cameras (14, 15) can be independent of the beam guidance system (3). Device according to one of Claims 5 to 9 , characterized in that the optics of the cameras (14,1 15) can be independent optics. Use of the method according to one of Claims 1 to 4 to suppress interference caused by other sources of light.

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