Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41H—ARMOUR; ARMOURED TURRETS; ARMOURED OR ARMED VEHICLES; MEANS OF ATTACK OR DEFENCE, e.g. CAMOUFLAGE, IN GENERAL
  • F41H13/00—Means of attack or defence not otherwise provided for
  • F41H13/0043—Directed energy weapons, i.e. devices that direct a beam of high energy content toward a target for incapacitating or destroying the target
  • F41H13/005—Directed energy weapons, i.e. devices that direct a beam of high energy content toward a target for incapacitating or destroying the target the high-energy beam being a laser beam
  • F41H13/0062—Directed energy weapons, i.e. devices that direct a beam of high energy content toward a target for incapacitating or destroying the target the high-energy beam being a laser beam causing structural damage to the target
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41H—ARMOUR; ARMOURED TURRETS; ARMOURED OR ARMED VEHICLES; MEANS OF ATTACK OR DEFENCE, e.g. CAMOUFLAGE, IN GENERAL
  • F41H5/00—Armour; Armour plates
  • F41H5/20—Turrets
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
  • H01S3/0071—Beam steering, e.g. whereby a mirror outside the cavity is present to change the beam direction
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
  • H01S3/06—Construction or shape of active medium
  • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
  • H01S3/067—Fibre lasers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
  • H01S3/2383—Parallel arrangements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping

Definitions

• the present invention relates to directed energy weapons and, in particular, it concerns directed energy weapons based on fiber lasers.
• Fiber lasers i.e., lasers in which the active gain occurs within an optical fiber
• Fiber lasers are compact and avoid use of dangerous chemicals. Although output powers of more than 1 kW are available, output from a single fiber laser using current technology does not provide sufficient output power for implementation of an optimal directed energy weapon.
• the present invention is a directed energy weapon based on fiber lasers.
• a directed energy weapon for use against a target, the weapon comprising: (a) a plurality of laser units, each of the laser units comprising: (i) a fiber laser generating an output beam from a fiber, the output beam conveying power of at least 1 kW, (ii) an objective lens arrangement for focusing the output beam into a focused beam directed towards the target, and (iii) a fine adjustment mechanism for adjusting a direction of the focused beam; (b) for each of the laser units, a beam deflector arrangement deployed to deflect a portion of the focused beam as a deflected beam in a direction in predefined relation to a direction of the focused beam; (c) an angle sensing unit deployed for receiving the deflected beams and generating an output indicative of a current direction of the deflected beam for each of the laser units; and (d) a controller associated with the angle sensing unit and the fine adjustment mechanisms, the controller being configured to actuate the fine adjustment
• the fine adjustment mechanism comprises at least one actuator deployed for varying an angular position of a mirror.
• a focus adjustment mechanism including at least one actuator deployed for displacing a fiber tip of the fiber laser so as to vary a length of an optical path from the fiber tip to the objective lens arrangement.
• the sensing arrangement comprises: (a) a first sensing system deployed for focal-plane sensing of the part of the output beam reflected from the element of the optical arrangement so as to be indicative of a direction of propagation of the focused beam; and (b) a second sensing system deployed for focal-plane sensing of radiation arriving at the optical arrangement from the target so as to allow tracking of the target.
• the output beam has a given wavelength conveying at least a majority of the power, and wherein the part of the output beam reflected from the element shares the given wavelength.
• the optical arrangement includes a corner reflector deployed for reflecting a part of the focused beam back through the optical arrangement.
• the element of the optical arrangement reflecting part of the output beam is a surface of an objective lens of the optical arrangement.
• the fine adjustment mechanism comprises at least one actuator deployed for varying an angular position of a mirror.
• FIG. 2 is a. front view of the directed energy weapon of FIG. 1;
• FIG. 3B is an enlarged view of a region of FIG. 3A designated III, illustrating alignment beam deflecting elements associated with individual laser units;
• the present invention is a directed energy weapon based on fiber lasers.
• FIG. 1 and 2 illustrate a directed energy weapon, generally designated 10, constructed and operative according to an embodiment of the present invention, employing a plurality of fiber laser units 12 arranged in an array within a housing 14 which is mounted on a gimbal mount 16 providing elevation-over- azimuth coarse direction control. Also integrated into housing 14 are a coarse tracking imaging sensor 18, such as a FLlR, a fine tracking sensor 20, which may optionally be integrated as part of a CATC unit 60 according to the second aspect of the present invention, and an angular sensing unit 34, the function of which will be described below.
• a coarse tracking imaging sensor 18 such as a FLlR
• a fine tracking sensor 20 which may optionally be integrated as part of a CATC unit 60 according to the second aspect of the present invention
• an angular sensing unit 34 the function of which will be described below.
• directed energy weapon 10 includes an arrangement for inter-beam alignment to facilitate correct relative alignment of the beams from laser units 12.
• each laser unit 12 has a beam deflector (or "beam sampler") arrangement deployed to deflect a portion of the focused beam as a deflected beam in a direction in predefined relation to a direction of the focused beam.
• the beam deflector arrangement includes a pentaprism 32 associated with each objective lens arrangement 28, either attached thereto or spaces in front of the objective lens arrangement, which generates a once-deflected beam perpendicular to the focused beam emerging from the objective lens.
• An angle sensing unit (ASU) 34 is deployed for receiving the deflected beams, optionally after one or more further deflection (as will be exemplified below), and generates an output indicative of a current direction of the deflected beam for each of the laser units. This indication is then processed by a controller 36 to determine a. required alignment correction for the corresponding laser units. Controller 36 generates outputs to actuate the fine adjustment mechanism for each laser unit to maintain a desired relative alignment between the directions of the focused beams.
• optical lens is used herein to refer to the outermost optical component from which an outgoing beam is issued (not including a beam deflector), or the first optical component encountered by incoming radiation for imaging or sensing functions.
• the objective lens typically also defines an optical aperture of the corresponding optical arrangement.
• controller processing system
• processor processing system
• the intention is typically to refer to a processing system including one or more processors configured, by hardware, software or any combination thereof, and by addition of any required interfaces or the like, to perform the recited functions.
• multiple functions performed by a processing system may be performed by a single processing system, or may be distributed between multiple processing systems which may be physically separate and even remote from one another. All such arrangements fall within the intended scope of the terms “controller”, “p rocessor " and “processing system”, whether used in the singular or in the plural.
• each laser unit 12 is fed by a fiber laser 25 which delivers an output beam from a fiber 26.
• the output from fiber 26 typically emerges via a suitable fiber terminator or "end cap", which achieves some initial spreading of the beam.
• the fiber laser feeds into the optical arrangement of the laser unit, which includes objective lens arrangement 28 and optionally other optical components.
• the optical arrangement achieves broadening of the beam and collimation to form a final beam which is referred to as a "focused beam" directed towards a target.
• typical ranges for use of the directed energy weapon of the present invention are typically from hundreds of meters up to several kilometers, such that the focused beam has a very small convergence, and for longer ranges is effectively a collimated parallel beam.
• Each laser unit 12 has its own fine adjustment mechanism for adjusting a direction of the focused beam.
• the option illustrated in FIG. 7 employs a fiber tip displacement mechanism 30, which can conveniently be implemented using a piezo-electric actuator deployed to displace the fiber tip (or fiber terminator) in two dimensions perpendicular to the optical axis of the laser unit. Since coarse alignment is controlled by gimbal mount 16, the range of fine adjustment required is typically small, and linear displacements of less than a millimeter, or at most a few millimeters, in each direction are typically sufficient.
• the laser units 12 also include a focal length adjustment mechanism, typically implemented by employing at least one actuator deployed for displacing the tip of fiber 26 in a direction parallel to an optical axis of the laser unit so as to vary a length of an optical path from the fiber tip to the objective lens arrangement. This motion is used to vary an effective focal distance of the system to correspond to the estimated distance to the current target.
• the focal adjustment may optionally be integrated with the alignment adjustment.
• simpler or lower cost adjustment actuators may be used.
• One non-limiting example is use of a linear stage operated by a stepper motor.
• each laser unit 12 is provided with a small pentaprism 32 deployed for deflecting a small proportion of the outgoing focused beam through 90°.
• the pentaprism preferably deflects no more than 1 percent of the energy of the focused beam, and typically much less.
• the deflected intensity is determined primarily by the dimensions of the pentaprism, which is preferably small compared to the optical aperture.
• the present invention preferably deploys staggered arrays of pentaprisms to deflect beams from a row of laser units into a set of once-deflected beams in generally parallel relation. This is best illustrated in FIGS. 313 and 4.
• the example of a two-dimensional array illustrated here thus generates, for each row, a set of horizontal once-deflected beams which are in a closely spaced vertical row.
• This set of beams is preferably spaced apart by less than a diameter of the objective lens arrangement of the laser units, and typically arranged in a close-packed bundle of rays with inter-beam spacing of less than 1 cm.
• a preferred beam deflection arrangement as illustrated includes an additional pentaprism 38 for each of the rows deployed to deflect the set of once-deflected beams to form an array of deflected beams from a plurality of the rows.
• additional pentaprisms 38 as presented here is best understood from the view of FIG. 5 shows staggering of successive rows of laser units so that each additional pentaprism 38 deflects its group of beams from its corresponding row upwards in a plane parallel to those of the other rows.
• the overall result is to generate a two-dimensional array of parallel beams in closely spaced relation corresponding to the two dimensional array of laser units, but all aligned within a cross- section sufficiently small to be delivered to a single angle sensing unit.
• Angle sensing unit 34 may be implemented as a conventional sensing unit for determining direction of incidence of laser beams of the appropriate wavelength.
• the lateral offsets between the incoming beams are typically not significant, since the device detects the incident angle of the beam but is insensitive to lateral offsets.
• the incoming beams are typically focused onto an array of sensors and the position of the beam falling on the focal plane indicates the direction of incidence.
• a simplest implementation employs a shutter 42 (FIG. 7) associated with each laser unit. 12 and deployed to selectively block or allow transmission of the beam deflected from the corresponding pentaprism 32.
• controller 36 preferably actuates shutters 42 so as to sequentially open one shutter at a time and to retrieve from ASU 34 the angle measurement for the beam from the corresponding laser unit 12.
• Other options include, but are not limited to, adding a distinctive frequency or time-varying signal as a modulation to the deflected beam, and employing selective detection techniques to allow the ASU to lock onto a given beam even in the presence of other incident beams.
• modulation may be introduced by shutters 42 operating as modulators.
• the output of ASU 34 for each laser unit 12 is typically an angular offset from a default "correct" direction for that laser unit. It should be noted that the "correct" directions are not necessarily exactly parallel, since the focused beams are intended to combine at the target onto a small region of the target. Furthermore, slight misalignments of elements in the beam deflecting arrangement may lead to the "correct" beam alignment being slightly away from the expected beam alignment measurement. All such factors are preferably taken into consideration during an initial calibration process performed after manufacture, and optionally repeated periodically, which defines the ASU output direction for each laser unit which corresponds to the corresponding laser unit's "correct" default beam direction. The real time ASU outputs are then indicative of any unintended deviation from the default direction, as well as measuring any currently applied fine steering correction.
• this shows schematically closure of the control loop for maintaining correct alignment and fine steering of the focused beam from each laser unit.
• the line-of-sight (LOS) deviation measured by the ASU 34 is provided to controller 36 which generates a beam steering correction command winch is delivered to the fine adjustment mechanism (e.g., fiber displacement mechanism 30) to achieve the correction.
• controller 36 also employs input from a fine tracking sensor (details of which will be discussed further below) which indicates any fine tracking correction which is required to the overall beam direction of the directed energy weapon to optimize its position on the target.
• a fine tracking sensor (details of which will be discussed further below) which indicates any fine tracking correction which is required to the overall beam direction of the directed energy weapon to optimize its position on the target.
• the approach of this aspect of the present invention allows compact juxtaposition of a relatively large number of laser units in a one-dimensional or more preferably two-dimensional array.
• the combination of at least ten laser units 12 into a single weapon using inter-beam alignment is envisaged.
• Gimbal mount 16 operating under control of controller 36 based on input from coarse tracking image sensor 18 aligns housing 14 facing towards a designated target, typically maintaining this alignment to a sufficient accuracy to allow fine alignment correction within the range of adjustment of the fine adjustment mechanism, and typically to an accuracy of significantly better than one degree.
• the fiber lasers are actuated to generate a set of focused beams all converging on the target.
• the beam exiting each laser unit 12 is sampled via the beam deflection arrangement which directs the beam to ASU 42, and any line-of-sight correction required in order to maintain inter-beam alignment with the other laser units is implemented by fine adjustment mechanism of each laser unit.
• fine tracking sensor 20 assesses the precision of the combined beam alignment with the target, and provides fine alignment correction inputs to controller 36 which are implemented together with the inter-beam alignment correction.
• directed energy weapon 60 includes a fiber laser 62 generating an output beam from a fiber 64 that conveys a power of at least 1 kW, and more preferably at least 10 kW.
• An optical arrangement 66 focuses the output beam into a focused beam directed towards the target.
• Weapon 60 also includes a fine adjustment mechanism, here exemplified by a fast steering mirror 68, associated with optical arrangement 66 and deployed to adjust a direction of the focused beam.
• FIGS. 9 and 10A-10C A first preferred but non-limiting exemplary implementation of the above principles of operation is illustrated in FIGS. 9 and 10A-10C.
• FIG. 9 shows a combined view of the various different optical paths
• FIGS. 10A- 10C are views of the same device but showing separately the optical paths for different wavelengths, and showing only those components which are relevant to each optical path, as will now be detailed.
• the output from optical fiber 64 includes a first wavelength component, designated (1 ) in FIG. 9 and illustrated in.
• FIG. 10A which is the high- energy laser (HEL) component, conveying power of at least 1 kW.
• HEL high- energy laser
• This is combined within the same fiber 64 with a second wavelength component, designated (2), that conveys a power at least two orders of magnitude smaller than the first wavelength component.
• the two components are at distinct wavelengths, typically originating from separate fiber lasers, and are coupled into a single fiber by conventional fiber coupling arrangements.
• the HEL itself may be configured by use of dichroic mirrors to simultaneously generate guide beam of a different wavelength within a single fiber.
• at least one component of the optical arrangement is configured by suitable use of layered coatings to be transparent (i.e., transmitting at least 98%, and preferably over 99%, of the incident radiation intensity) to the first wavelength while being an at least partial reflector (i.e., reflecting at least 5%, and preferably at least 10%, of the incident radiation intensity) to the second wavelength.
• the coatings to achieve at least partial reflection of the second wavelength are applied to a rear surface of the objective lens, with the surface being shaped to focus the reflected component (2) towards first sensing system 70.
• fine alignment correction of the HEL beam (1) is achieved by adjusting an angle of fast steering mirror 68, which is configured to be highly reflective to the first wavelength so as to direct substantially all of the HEL beam outwards towards the target.
• the HEL optical path is illustrated separately in FIG. 10A.
• fast steering mirror 68 is preferably also configured to have significant reflectivity (at least 10%) and significant transmission (at least 10%) for the second, wavelength, thereby allowing a proportion of second wavelength component (2) to follow a path from fiber 64 through a reflection at fast steering mirror 68, reflection at the rear surface of an objective lens of optical arrangement 66, transmission through fast steering mirror 68 and transmission through a dichroic beam splitter 74 to reach sensor 70.
• fast steering mirror 68 has a transmittance in the range of 50% (+/- 20%) transmission of the second wavelength, thereby ensuring that the signal following the above optical path arrives with sufficient intensity to facilitate measurement at sensor 70. despite the proportions of the beam lost at each reflection/transmission.
• the design of the fast steering mirror is chosen such that the positioning of the actuators does not obstruct a transmitted beam in the direction towards sensor 70.
• directed energy weapon 60 additionally serves as an imaging device for incoming radiation (3) arriving via optical arrangement 66 from the target for the purpose of tracking the target.
• the range of wavelengths employed for target tracking preferably excludes the first and second wavelengths, and may be any suitable range of wavelengths with a corresponding choice of sensor 72, including but not limited to, visible light, NIK or SW1R wavelengths of one or more range, for example, for image sensing via a CCD or CMOS image sensor.
• dichroic mirror 74 is configured to reflect a majority of the radiation at the wavelengths used for imaging, while a majority of radiation of the second wavelength passes through, although a reversed layout could clearly be implemented.
• additional optical components such as a lens 76 complete the target tracking imaging optical arrangement for forming an image at sensor 72.
• the overall optical path of the target tracking channel is illustrated in FIG. 20C.
• the operation of directed energy weapon 60 will be understood. Since the first and second wavelength components emerge from the same fiber 64 and are reflected at the same fast steering mirror 68, the second wavelength component necessarily follows exactly the same direction as the outgoing HEL channel, such that the resulting position of the sensed dot on sensor 70 is a reliable indication of the HEL beam direction.
• the same objective optics is used in deriving a target image at sensor 72. By performing an initial production calibration for the device (optionally repeated intermittently), a known mapping of the sensed beam direction to pixels of the tracking sensor can be determined, thereby allowing subsequent verification of the alignment of the beam with a tracked target.
• Fast steering mirror 68 is then operated under closed loop control by a line-of-sight controller 78 to maintain the outgoing beam direction aligned with the tracked target.
• directed energy weapon 60 in using a common aperture for both HEL transmission and target tracking, a number of such directed energy weapons may be combined, for example by mounting in a common gimbaled housing, to form a directed energy weapon of substantially any desired power output.
• fine tracking sensor 20 may be implemented as directed energy weapon 60 so as to simultaneously provide the required fine tracking functionality and to contribute to the transmitted HEL output.
• the output beam of directed energy weapon 60 is preferably sampled by a pentaprism of the inter-beam alignment system in order to ensure correct alignment between the outgoing beams of the two subsystems.
• a small portion of the outgoing focused beam beyond the objective optics of optical arrangement 66 is reflected by a small corner reflector 82.
• Corner reflectors formed by three mutually perpendicular mirrors meeting at a corner, are well knows in optics, and have the property of reflecting incident radiation back along a path parallel to its incident path.
• the reflected portion of the beam which is less than 1 % of the focused beam intensity (and more typically a small proportion of a percent), passes back through optical arrangement 66 and impinges on fast steering mirror 68.
• FSM 68 is configured to reflect as high a proportion of the HEL beam as possible, a small proportion, typically in the region of 0.2%, "leaks" through the mirror.
• the objective lens system can be designed such that the very small proportion of the HEL beam reflected off the rear surface (or some other surface) of the objective lens is directed towards sensor 70 in a manner analogous to the geometry of the FIG. 9 beam alignment optical path.
• FIG. 11B shows the target tracking channel, which is fully equivalent to that of directed energy weapon 60 as described above with reference to FIG. 1OC.
• Other details, such as the control system, as well as the overall function of the device, are also equivalent to that described above with reference to directed energy weapon 60, and for conciseness of presentation, are not described again here.

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• 2014
  • 2014-08-10 IL IL234036A patent/IL234036B/en active IP Right Grant
• 2015
  • 2015-07-02 WO PCT/IL2015/050682 patent/WO2016024265A1/en active Application Filing
  • 2015-07-02 US US15/502,786 patent/US10337841B2/en active Active

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