LASER WEAPON SYSTEM AND METHOD FOR RANGE MEASUREMENT

Description

[0001] The present invention relates to a laser weapon system and methods for measuring the distance between such a laser weapon system and a target.

[0002] Typical systems for influencing a target object using directed electromagnetic radiation use a high-energy laser beam to disrupt and / or damage the target. To achieve high system efficiency, precise knowledge of the system's distance to the target object is essential, e.g., to focus the effective laser on the target object. Separate rangefinders are typically used to determine the distance. Depending on their operating principle, these devices use their own radiation sources to emit electromagnetic radiation.

[0003] A widely used method for distance determination uses a separate pulsed laser beam directed at the target, see, for example, document DE 10 2010 053 896 A1. The reflected radiation pulse can be detected with a detector, and a time-of-flight measurement can be performed based on this. By measuring the time it takes a light pulse to travel from the measuring device to the target object and back, the distance between the source and the target object is determined using the speed of light.

[0004] Laser weapon systems are also known from US 8,218,589 B1 and EP 3 118 561 A1.

[0005] Against this background, the present invention is based on the object of finding simpler yet precise solutions for a laser weapon system with a rangefinder.

[0006] According to the invention, this object is achieved by a laser weapon system having the features of patent claim 1 and by a method having the features of patent claim 6.

[0007] Accordingly, a laser weapon system is provided. The laser weapon system comprises an effective laser configured to irradiate a target with a continuous-wave laser beam having a predetermined beam intensity; and a radiation detector configured to detect reflected laser radiation reflected by the target with a reflected intensity. The effective laser is configured to impart a modulation pulse to the beam intensity of the continuous-wave laser beam, and the radiation detector is configured to detect the modulation pulse in the reflected intensity of the detected reflected laser radiation and to determine a distance of the target from the laser weapon system via a time-of-flight measurement of the modulation pulse.

[0008] Furthermore, a method for measuring the distance between a laser weapon system and a target is provided. The method comprises irradiating the target with a continuous-wave laser beam of an effective laser of the laser weapon system at a predetermined beam intensity, wherein a modulation pulse is applied to the beam intensity of the continuous-wave laser beam; detecting reflected laser radiation with a radiation detector of the laser weapon system, which is reflected by the target with a reflected intensity; detecting the modulation pulse in the reflected intensity of the detected reflected laser radiation; and determining the distance of the target from the laser weapon system via a time-of-flight measurement of the modulation pulse.

[0009] One idea underlying the present invention is to use the actual effective laser simultaneously for distance measurement, thereby eliminating the need for a second laser for distance measurement. The effective laser operates in continuous wave mode, being modulated with one or more short, characteristic pulses. This only minimally reduces the duty cycle of the effective laser. The pulses can be identified in the reflected radiation using the radiation detector based on their characteristic properties. The radiation detector can, for example, continuously measure the reflected radiation. Once the pulse(s) have been identified, the distance to the target can be determined based on the time between transmission and reception of the respective pulse.

[0010] In summary, the present invention offers a significantly simpler design than conventional laser weapon systems with a separate laser-based rangefinder. Typical effective lasers also offer a very long range compared to conventional rangefinders. With the present system, range measurement can be performed at high, e.g., constant, repetition rates. Alternatively or additionally, the range measurement can also be triggered only sporadically as needed.

[0011] Advantageous embodiments and further developments emerge from the further subclaims and from the description with reference to the figures.

[0012] According to the invention, the effective laser is designed to generate the modulation pulse by decreasing and / or increasing the beam intensity over a pulse duration. The method accordingly comprises generating the modulation pulse by decreasing and / or increasing the beam intensity over a pulse duration.

[0013] There are various options available for modulating the effective laser. For example, in a simple case, a short-term (e.g. <1 ms) reduction in the intensity / power of the effective laser can occur. Such a pulse can have any pulse shape, e.g. rectangular, Gaussian, Sech2, sawtooth, Lorentz curve, etc. In principle, modulation pulses within the meaning of the invention also include more complex short-term modulations of the beam intensity of the effective laser, e.g. an oscillation of the beam intensity with a modulation amplitude around a standard value of the beam intensity, which indicates the value at which the effective laser is operated in continuous wave mode outside the short pulse window. A modulation pulse within the meaning of the invention is a short-term, ieChange in the intensity and / or power of the effective laser for a negligible length of time relative to the continuous wave operation of the effective laser, in which the intensity / power is increased by one modulation height and / or decreased by one modulation depth.

[0014] According to the invention, the modulation pulse has a pulse duration of less than 1 ms. For example, the pulse duration can be 0.5 ms.

[0015] According to the invention, the effective laser is designed to generate the modulation pulse by briefly operating the effective laser in an overload range and / or an underload range. The method accordingly comprises generating the modulation pulse in an overload range and / or an underload range.

[0016] The laser diodes commonly used in effective lasers can typically be driven briefly (<1 ms) into an overload range. The power or intensity can be temporarily increased by up to 50% above the standard value. However, the intensity of the effective laser can also be modulated in such a way that the effective laser is driven not only into the overload range but also into an underload range. In general, the modulation pulse can exhibit a complex intensity profile, which can, for example, include an oscillation or multiple changes between the overload range and the underload range.

[0017] According to a further development, the effective laser can be configured to impose a plurality of modulation pulses on the beam intensity. The effective laser can further be configured to adaptively adjust a modulation amplitude of the modulation pulses. The method can accordingly comprise imposing a plurality of modulation pulses on the beam intensity. The method can further comprise adaptively adjusting a modulation amplitude of the modulation pulses.

[0018] A modulation depth and / or modulation height, i.e., a deviation from a standard intensity of the effective laser, is therefore not necessarily fixed, but can be adaptively adjusted. For example, the modulation depth or modulation height can be reduced if the modulation pulse is well detected in the receiver. Modulation amplitude is defined as the amount of change in the intensity or power of the effective laser around the standard value.

[0019] According to a further development, the radiation detector can be configured to detect the modulation pulse by comparing a signal profile of the reflection intensity of the detected reflection laser radiation with a signal profile of the beam intensity of the continuous-wave laser beam. The method can accordingly comprise detecting the modulation pulse by comparing a signal profile of the reflection intensity of the detected reflection laser radiation with a signal profile of the beam intensity of the continuous-wave laser beam.

[0020] The characteristic modulation of the received signal is generally not compared with a target signal (signal at a modulation input), but with an actual value (measured optical power of the active laser), i.e., with the output signal of the corresponding laser diodes. Inaccuracies such as fluctuations ("jitter") or the like are thus automatically taken into account.

[0021] According to a further development, the radiation detector can be configured to perform the time-of-flight measurement by means of edge detection in the signal waveforms of the intensities. The method can accordingly comprise performing the time-of-flight measurement by means of edge detection in the signal waveforms of the intensities.

[0022] With a "simple" modulation, the detection of a falling / rising edge in the optical power curve can be used. The difference between the times of the falling / rising edges determines the time period for determining the distance.

[0023] According to a further development, the modulation pulse can have a characteristic amplitude variation in a modulation amplitude. The radiation detector can be configured to perform the runtime measurement by measuring the correlation between the signal waveforms of the intensities. The method can accordingly comprise performing the runtime measurement by measuring the correlation between the signal waveforms of the intensities.

[0024] For more complex modulations, the duration can be determined, for example, by measuring the correlation of the signal waveforms of the transmitted and received optical power. Autocorrelation, for example, enables subsampling and thus an even better distance estimation compared to the modulation time. Especially with slow current regulators of the laser diodes (of the high-energy laser), such techniques enable significantly improved edge and signal resolution and thus improved distance estimation.

[0025] The above embodiments and developments can be combined with one another as desired, where appropriate. Further possible embodiments, developments, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention.

[0026] The present invention is explained in more detail below with reference to the exemplary embodiments shown in the schematic figures. In the figures: Fig. 1 schematic view of a laser weapon system according to an embodiment of the invention; Figs. 2 to 7 schematic intensity curves of modulation pulses with the laser weapon system of Fig. 1; and Fig. 8 schematic flow diagram of a method for distance measurement with the laser weapon system from Fig. 1 .

[0027] The accompanying figures are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the noted advantages will be apparent upon consideration of the drawings. Elements of the drawings are not necessarily shown to scale relative to one another.

[0028] In the figures of the drawing, identical, functionally identical and acting elements, features and components are provided with the same reference symbols, unless otherwise stated.

[0029] Figure 1 shows a schematic view of a laser weapon system 1 according to an embodiment of the invention. Fig. 8shows a schematic flow diagram of a method for distance measurement with the laser weapon system from Fig. 1 .

[0030] Conventional distance measurements to a target object over longer distances (e.g., over 1 m) often work according to the time-of-flight principle. These rangefinders are usually constructed from a transmitter (light source / laser with optics), a receiver (optics and receiving diode(s)), and additional electronics for evaluation and control. Typically, a single or multiple separate light pulses are emitted from a transmitter toward the target object, and the time it takes for the pulse(s) to travel from the transmitter to the target object and back to the receiver is measured. This ultimately allows the distance to be determined.

[0031] In systems designed to damage or disrupt an object using directed electromagnetic radiation ("high-energy laser systems," "defensive radiation," "directed energy," etc.), a (high-energy) laser beam ("effective laser") is directed at a target object. For such a system to be effective, precise knowledge of the distance to the target object is helpful or necessary, e.g., to focus the effective laser on the target object and / or to focus the image for observation or tracking. Separate rangefinders are typically used to determine the distance. Depending on their operating principle, these devices then use their own sources to emit a light pulse.

[0032] In the Fig. 1The laser weapon system 1 shown uses a completely different approach, requiring no dedicated source. Instead, a continuous-wave laser 2 is used as a rangefinder. The only additional component required is a suitable receiver for detection (radiation detector 3).

[0033] Specifically, the laser weapon system 1 in Fig. 1 thus an effective laser 2, which is designed to irradiate a target 4 with a continuous-wave laser beam 5 having a predetermined beam intensity 6. Furthermore, the laser weapon system 1 comprises a radiation detector 3, which is designed to detect reflected laser radiation 7 reflected by the target 4 with a reflection intensity 8.

[0034] The effective laser 2 is designed to impress a modulation pulse 9 on the beam intensity 6 of the continuous wave laser beam 5. For this purpose, the effective laser 2 increases or decreases the beam intensity 6 over a short pulse duration 10, according to the invention less than 1 ms. For example, a short-term reduction in the intensity or power of the effective laser 2 can lead to the Fig. 2 and 3 shown intensity curves.

[0035] This is achieved according to the invention by briefly driving laser diodes of the effective laser 2 (not shown) into an overload range and / or underload range (e.g. 10%, 20% or up to 50% relative to a standard value). The modulation can therefore, for example, Fig. 5 take the form shown, where the dashed line represents a standard value as set during continuous wave operation.

[0036] However, more complex modulation pulses 9 are also possible and provided. For example, Fig. 6 a modulation pulse 9 with a complex time course, in which one or more laser diodes of the effective laser 2 are moved into an overload range.

[0037] Fig. 7 represents another example in which the active laser 2 is driven not only into the overload range, but also into an underload range. The intensity or power fluctuates or oscillates around the standard value (dashed line). The modulation pulse 9 thus acquires a characteristic shape. This characteristic shape characterizes the modulation pulse 9 and can be recognized in the reflected radiation to simplify the detection of the pulse.

[0038] Referring again to Fig. 1The radiation detector 3 is further configured to detect the modulation pulse 9 in the reflection intensity 8 of the detected reflection laser radiation 7 and to determine a distance of the target 4 from the laser weapon system 1 via a time-of-flight measurement of the modulation pulse 9. For this purpose, a signal profile of the reflection intensity 8 of the detected reflection laser radiation 7 can be compared with a signal profile of the beam intensity 6 of the continuous-wave laser beam 5.

[0039] For example, the radiation detector 3 can be designed to carry out the transit time measurement by means of an edge detection in the signal curves of the intensities 6, 8, e.g. in the case of a simple modulation, as in Fig. 2, 3 and 5In another example, the radiation detector 3 can be designed to carry out the transit time measurement by means of a correlation measurement in the signal curves of the intensities 6, 8, e.g. in the case of a complex modulation, as shown in Figs. 6 and 7 can be seen.

[0040] In embodiments, the effective laser 2 can further be configured to impart a plurality of (regular or merely sporadic) modulation pulses 9 to the beam intensity 6. The depth and / or height of the individual modulation pulses 9 above a standard value of the intensity / power can be adaptively adjusted, e.g., depending on a detection quality. Fig. 4 shows an example in which a pulse depth is gradually reduced.

[0041] The described principle for distance measurement thus inverts, in a sense, a conventional laser rangefinder: Instead of emitting and detecting individual pulses, a continuous laser beam is subjected to characteristic modulation pulses, which are then used to measure the time of flight. This offers the significant advantage that the effective laser itself can simultaneously function as a rangefinder, simplifying the entire design of the laser weapon system.

[0042] In the foregoing detailed description, various features have been combined into one or more examples for clarity of illustration. It should be understood, however, that the above description is merely illustrative and not restrictive. It is intended to cover all alternatives, modifications, and equivalents of the various features and embodiments. Many other examples will be readily apparent to those skilled in the art based on their skill in the art in light of the above description.

[0043] The embodiments were chosen and described in order to best illustrate the principles underlying the invention and their possible practical applications. This will enable those skilled in the art to optimally modify and utilize the invention and its various embodiments with respect to the intended purpose. In the claims and the description, the terms "including" and "having" are used as neutral language terms for the corresponding term "comprising." Furthermore, the use of the terms "a," "an," and "an" is not intended to exclude a plurality of such described features and components. List of reference symbols

[0044] 1 Laser weapon system 2 Effective laser 3 Radiation detector 4 Target 5 Continuous wave laser beam 6 Beam intensity 7 Reflected laser radiation 8 Reflected intensity 9 Modulation pulse 10 Pulse duration 11 Modulation amplitude 1 Intensity t Time M Procedure M1-M4 Procedure steps

Claims

1. Laser weapon system (1), having: an active laser (2), which is designed to irradiate a target (4) with a continuous-wave laser beam (5) at a predetermined beam intensity (6); and a radiation detector (3), which is designed to detect reflected laser radiation (7) which is reflected by the target (4) with a reflection intensity (8); wherein the active laser (2) is designed to impose a modulation pulse (9) on the beam intensity (6) of the continuous-wave laser beam (5) in continuous-wave operation, and wherein the radiation detector (3) is designed to detect the modulation pulse (9) in the reflection intensity (8) of the detected reflected laser radiation (7) and to determine a distance of the target (4) from the laser weapon system (1) via a time-of-flight measurement of the modulation pulse (9); wherein the active laser (2) is designed to produce the modulation pulse (6) by lowering and / or increasing the beam intensity (6) over a pulse duration (10) of less than 1 ms by operating the active laser (2) in an overload range and / or an underload range in which the beam intensity (6) deviates by a modulation amplitude (11) from a standard intensity of the active laser (2).

2. Laser weapon system (1) according to claim 1, wherein the active laser (2) is designed to impose a plurality of modulation pulses (9) on the beam intensity (6) and wherein the active laser (2) is designed to adaptively adjust a modulation amplitude (11) of the modulation pulses (9).

3. Laser weapon system (1) according to claim 1 or 2, wherein the radiation detector (3) is designed to detect the modulation pulse (9) by comparing a signal profile of the reflection intensity (8) of the detected reflected laser radiation (7) with a signal profile of the beam intensity (6) of the continuous-wave laser beam (5).

4. Laser weapon system (1) according to one of claims 1 to 3, wherein the radiation detector (3) is designed to perform the time-of-flight measurement by means of an edge detection in the signal profiles of the intensities (6, 8).

5. Laser weapon system (1) according to one of claims 1 to 4, wherein the modulation pulse (9) has a characteristic amplitude variation in a modulation amplitude (11) and wherein the radiation detector (3) is designed to perform the time-of-flight measurement by a correlation measurement in the signal profiles of the intensities (6, 8).

6. Method (M) for measuring a distance between a laser weapon system (1) and a target (4), including: irradiating (M1) the target (4) with a continuous-wave laser beam (5) of an active laser (2) of the laser weapon system (1) at a predetermined beam intensity (6), wherein a modulation pulse (9) is imposed on the beam intensity (6) of the continuous-wave laser beam (5); detecting (M2) reflected laser radiation (7) with a radiation detector (3) of the laser weapon system (1), which is reflected by the target (4) with a reflection intensity (8); detecting (M3) the modulation pulse (9) in the reflection intensity (8) of the detected reflected laser radiation (7); and determining (M4) the distance of the target (4) from the laser weapon system (1) via a time-of-flight measurement of the modulation pulse (9); wherein the modulation pulse (9) is produced by lowering and / or increasing the beam intensity (6) over a pulse duration (10) of less than 1 ms by operating the active laser (2) in an overload range and / or an underload range in which the beam intensity (6) deviates by a modulation amplitude (11) from a standard intensity of the active laser (2).

7. Method (M) according to claim 6, wherein a plurality of modulation pulses (9) are imposed on the beam intensity (6) and wherein a modulation amplitude (11) of the modulation pulses (9) is adaptively adjusted.

8. Method (M) according to claim 6 or 7, wherein the modulation pulse (9) is detected by comparing a signal profile of the reflection intensity (8) of the detected reflected laser radiation (7) with a signal profile of the beam intensity (6) of the continuous-wave laser beam (5).

9. Method (M) according to one of claims 6 to 8, wherein the time-of-flight measurement is performed by means of an edge detection in the signal profiles of the intensities (6, 8).

10. Method (M) according to one of claims 6 to 9, wherein the modulation pulse (9) has a characteristic amplitude variation in a modulation amplitude (11) and wherein the time-of-flight measurement is performed by a correlation measurement in the signal profiles of the intensities (6, 8).