IL300562A - Optical phased array dynamic beam shaping with noise correction - Google Patents

Description

OPTICAL PHASED ARRAY DYNAMIC BEAM SHAPING WITH NOISECORRECTION FIELD OF THE INVENTIONThe present invention relates generally to laser coherent beam combining and more particularly to optical phased arrays.

BACKGROUND OF THE INVENTIONVarious types of optical phased arrays are known in the art.

SUMMARY OF THE INVENTION The present invention seeks to provide systems and methods relating to noise correction in dynamically shaped beams produced by laser optical phased arrays.There is thus provided in accordance with a preferred embodiment of the present invention a laser system including a seed laser, a laser beam splitting and combining subsystem receiving an output from the seed laser and providing a combined laser output having noise and a noise cancellation subsystem operative to provide a noise cancellation phase correction output based on taking into consideration the noise at intermittent times, the laser beam splitting and combining subsystem varying a phase of the combined laser output during time interstices between the intermittent times.There is additionally provided in accordance with another preferred embodiment of the present invention a laser system including a seed laser, a laser beam splitting and combining subsystem receiving an output from the seed laser and providing a combined laser output having noise and a noise cancellation subsystem operative to provide a noise cancellation phase correction output, based on taking into consideration the noise at a noise sampling rate, the laser beam splitting and combining subsystem varying a phase of the combined laser output at a phase varying rate which exceeds the noise sampling rate.Preferably, at least one of the noise sampling rate and the phase varying rate changes over time.Preferably, the noise sampling rate is predetermined.Preferably, the laser beam splitting and combining subsystem varies a phase of the combined laser output to provide spatial modulation of the combined laser output.Preferably, the spatial modulation of the combined laser output is provided in combination with mechanical spatial modulation of the combined laser output, the spatial modulation in combination with the mechanical spatial modulation being faster than the mechanical spatial modulation in the absence of the spatial modulation.

Additionally or alternatively, the spatial modulation of the combined laser output is provided in combination with mechanical spatial modulation of the combined laser output, the spatial modulation in combination with the mechanical spatial modulation being more precise than the mechanical spatial modulation in the absence of the spatial modulation.Preferably, the spatial modulation includes modulation of at least one of a shape and a diameter of the combined laser output.Preferably, the laser beam splitting and combining subsystem provides laser beam amplification downstream of the splitting and upstream of the combining.In accordance with a preferred embodiment of the present invention, the noise cancellation phase correction output is calculated based on sequentially applying at least two phase changes to at least one constituent beam of the combined laser output and identifying one phase change of the at least two phase changes corresponding to a maximum output intensity of the at least one constituent beam.Preferably, the system also includes at least one detector cooperatively coupled to the noise cancellation subsystem for detecting at least a portion of the combined laser output.Preferably, the at least one detector performs the detecting continuously.In accordance with a preferred embodiment of the present invention, the noise cancellation phase correction output cancels intensity noise in the combined laser output.Preferably, the system also includes at least one intensity modulator for varying an intensity of the combined laser output.Additionally or alternatively, the noise cancellation phase correction output cancels position noise in the combined laser output.Preferably, the system also includes at least one position modulator for varying a position of the combined laser output.In accordance with a preferred embodiment of the present invention, a laser cutting system includes the laser system of the present invention.In accordance with another preferred embodiment of the present invention, a laser additive manufacturing system includes the laser system of the present invention.

In accordance with yet another preferred embodiment of the present invention, a laser welding system includes the laser system of the present invention.In accordance with yet a further preferred embodiment of the present invention, a free-space optical communication system includes the laser system of the present invention.There is additionally provided in accordance with still another preferred embodiment of the present invention a method for performing noise correction on a phase varied laser output including receiving an output from a seed laser, splitting and combining the output to provide a combined laser output having noise, applying a noise cancellation phase correction output to the combined laser output based on taking into consideration the noise at intermittent times and varying a phase of the combined laser output during time interstices between the intermittent times.There is also provided in accordance with a still further preferred embodiment of the present invention a method for performing noise correction on a phase varied laser output including receiving an output from a seed laser, splitting and combining the output to provide a combined laser output having noise, applying a noise cancellation phase correction output to the combined laser output, based on taking into consideration the noise at a noise sampling rate and varying a phase of the combined laser output at a phase varying rate which exceeds the noise sampling rate.Preferably, at least one of the noise sampling rate and the phase varying rate changes over time.Preferably, the noise sampling rate is predetermined.Preferably, the varying of the phase provides spatial modulation of the combined laser output.Preferably, the spatial modulation of the combined laser output is provided in combination with mechanical spatial modulation of the combined laser output, the spatial modulation in combination with the mechanical spatial modulation being faster than the mechanical spatial modulation in the absence of the spatial modulation.

Additionally or alternatively, the spatial modulation of the combined laser output is provided in combination with mechanical spatial modulation of the combined laser output, the spatial modulation in combination with the mechanical spatial modulation being more precise than the mechanical spatial modulation in the absence of the spatial modulation.Preferably, the spatial modulation includes modulation of at least one of a shape and a diameter of the combined laser output.Preferably, the method also includes amplifying the output, downstream of the splitting and upstream of the combining.In accordance with a preferred embodiment of the present invention, the method also includes calculating the noise cancellation phase correction output based on sequentially applying at least two phase changes to at least one constituent beam of the combined laser output and identifying one phase change of the at least two phase changes corresponding to a maximum output intensity of the at least one constituent beam.Preferably, the method also includes detecting at least a portion of the combined laser output.Preferably, the detecting is performed continuously.In accordance with a preferred embodiment of the present invention, the noise cancellation phase correction output cancels intensity noise in the combined laser output.Preferably, the method also includes modulating an intensity of the output, downstream of the splitting and upstream of the combining.In accordance with another preferred embodiment of the present invention, the noise cancellation phase correction output cancels position noise in the combined laser output.Preferably, the method also includes modulating a position of the output, downstream of the splitting and upstream of the combining.In accordance with a preferred embodiment of the present invention, a method for laser cutting includes the method of the present invention.In accordance with another preferred embodiment of the present invention, a method for additive manufacturing includes the method of the present invention.

In accordance with yet another preferred embodiment of the present invention, a method for laser welding includes the method of the present invention.In accordance with still a further preferred embodiment of the present invention, a method for free space optical communication includes the method of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully based on the following detailed description taken in conjunction with the drawings in which:Fig. 1A is a simplified schematic illustration of an optical phased array laser system for noise corrected dynamic beam shaping, constructed and operative in accordance with a preferred embodiment of the present invention;Figs. IB and IC are graphical representations of phase variation and noise correction in a system of the type illustrated in Fig. 1 A;Fig. 2A is a simplified schematic illustration of an optical phased array laser system for noise corrected dynamic beam shaping, constructed and operative in accordance with another preferred embodiment of the present invention;Figs. 2B and 2C are graphical representations of phase variation and noise correction in a system of the type illustrated in Fig. 2A;Fig. 3 A is a simplified schematic illustration of an optical phased array laser system for noise corrected dynamic beam shaping, constructed and operative in accordance with a further preferred embodiment of the present invention;Figs. 3B and 3C are graphical representations of phase variation and noise correction in a system of the type illustrated in Fig. 3 A;Fig. 4A is a simplified schematic illustration of an optical phased array laser system for noise corrected dynamic beam shaping, constructed and operative in accordance with a further preferred embodiment of the present invention;Figs. 4B and 4C are graphical representations of phase variation and noise correction in a system of the type illustrated in Fig. 4A; andFigs. 5A - 5G are simplified illustrations of possible far-field motion of an output of an optical phased array laser system of any of the types illustrated in Figs. 1A-4C.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference is now made to Fig. 1 A, which is a simplified schematic illustration of an optical phased array laser system for noise corrected dynamic beam shaping, constructed and operative in accordance with a preferred embodiment of the present invention; and to Figs. IB and IC, which are simplified graphical representations of phase variation and noise correction in a system of the type illustrated in Fig. 1 A.As seen in Fig. 1A, there is provided an optical phased array (OPA) laser system 100, here shown to be employed, by way of example, within a laser cutting system 102. Laser cutting system 102 may include OP A laser system 1mounted in spaced relation to a multi-axis positioning table 104, upon which table 104 an item, such as an item 106, may be cut using laser system 100, as is detailed henceforth. It is understood that although laser cutting system 102 is illustrated herein in the context of table 104, system 102 may be embodied as any type of laser cutting system, as will be appreciated by one skilled in the artAs best seen at an enlargement 110, OP A laser 100 preferably comprises a seed laser 112 and a laser beam splitting and combining subsystem 114. Splitting and combining subsystem 114 preferably receives an output laser beam from seed laser 112 and splits the output laser beam into a plurality of sub-beams along a corresponding plurality of channels 116. Here, by way of example only, an output from seed laser 112 is shown to be split into ten sub-beams along ten channels 1although it is appreciated that splitting and combining subsystem 114 may include a fewer or greater number of channels along which the output of seed laser 112 is split, and typically may include a far greater number of channels such as 32 or more channels.The relative phase of each sub-beam may be individually modulated by a phase modulator 118, preferably located along each of channels 116. Each phase modulated sub-beam produced by the splitting and subsequent phase modulation of the output of seed laser 112 preferably propagates towards a collimating lens 119. The individually collimated, phase modulated sub-beams are subsequently combined, for example at a focal lens 120, to form an output beam 122.

Splitting and combining subsystem 114 may also provide laser amplification of the sub-beams, preferably following the splitting of the output beam of seed laser 112 into sub-beams and prior to the combining of the sub-beams to form output beam 122. Here, by way of example, splitting and combining subsystem 114 is shown to include a plurality of optical amplifiers 124 located along corresponding ones of channels 116 for amplifying each sub-beam. It is appreciated, however, that such amplification is optional and may be omitted, depending on the power output requirements of OP A laser 100.The phase of output beam 122, and hence the position and shape of the far- field intensity pattern thereof, is controlled, at least in part, by the relative phases of the constituent sub-beams combined to form output beam 122. In many applications, such as laser cutting as illustrated in Fig. 1A, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This may be achieved in laser system 100 by laser splitting and combining subsystem 114 dynamically varying the relative phases of the individual sub- beams and thereby varying the phase of the combined laser output 122 so as dynamically to control the position and shape of the far-field intensity pattern thereof.The relative phases of the sub-beams are preferably predetermined in accordance with the desired laser output pattern for the cutting of item 106. Particularly preferably, the varying relative phases are applied by a phase control subsystem 130. Phase control subsystem 130 preferably forms a part of a control electronics module 132 in OP A laser 100 and preferably controls each phase modulator 118 so as to dynamically modulate the relative phases of the sub-beams along channels 116.Due to noise inherent in OP A system 100, output beam 122 has noise. Noise in output beam 122 is typically phase noise created by thermal or mechanical effects and/or by the amplification process in the case that optical amplifiers 1are present in OP A system 100. It is a particular feature of a preferred embodiment of the present invention that laser system 100 includes a noise cancellation subsystem 140 operative to provide a noise cancellation phase correction output in order to cancel out the noise in output beam 122 in a manner detailed henceforth.Particularly preferably, noise cancellation subsystem 140 employs an algorithm to sense and correct phase noise in the combined laser output. The noise cancellation phase correction output is preferably provided by noise cancellation subsystem 140 to phase modulator 118 so as to correct phase noise in output beam 122 and thus avoid distortion of the shape and position of the far field intensity pattern of output beam 122 that would otherwise be caused by the noise. Noise cancellation subsystem 140 may be included in control electronics module 132.It is understood that output beam 122 may be additionally or alternatively affected by types of noise other than phase noise, including intensity noise. In the case of output beam 122 having intensity noise, noise cancellation subsystem 1may be operative to provide a noise cancellation phase correction output in order to cancel out the intensity noise in output beam 122. In such a case, OP A laser system 100 may optionally additionally include intensity modulators 142 along channels 116 for modulating the intensity of each of the sub-beams along channels 116.It is understood that output beam 122 may be additionally or alternatively affected by mechanical noise which may affect the relative position of the sub- beams. In the case of output beam 122 having position noise, noise cancellation subsystem 140 may be operative to provide a noise cancellation phase correction output in order to cancel out the position noise in output beam 122. In such a case, OP A laser system 100 may optionally additionally include position modulators 144 along channels 116 for modulating the position of each of the sub-beams along channels 116.In order to facilitate application of phase variation and noise correction to output beam 122, a portion of the output of OP A laser 100 is preferably extracted and directed towards at least one detector, here illustrated as a single detector 150. The extracted portion of the output beam preferably functions as a reference beam, based on characteristics of which the required noise correction and/or phase variation may be calculated. In the embodiment shown in Fig. 1A, plurality of sub-beams along channels 116 are directed towards a beam splitter 160. Beam splitter 160 preferably splits each sub-beam into a transmitted portion 162 and a reflected portion 164 in accordance with a predetermined ratio. For example, beam splitter 160 may split each sub-beam with a 99.9% transmitted: 0.01% reflected ratio.The transmitted portion 162 of the sub-beams preferably propagates towards focal lens 120, at which focal lens 120 the sub-beams are combined to form output beam 122 having a far-field intensity pattern 166 incident on a surface of item 106. The reflected portion 164 of the sub-beams is preferably reflected towards an additional focal lens 168, at which additional focal lens 168 the sub-beams are combined to form an output reference beam 170 having a far-field intensity pattern 172 incident on a surface of detector 150.It is understood that the particular structure and configuration of beam splitting and recombining elements shown herein, including beam splitter 160 and focal lenses 120 and 168, is exemplary only and depicted in a highly simplified form. It is appreciated that OP A laser system 100 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers and coherent free-space far- field combiners.As described hereinabove, the shape and position of far-field intensity pattern 166 of the output beam 122 and correspondingly of far-field intensity pattern 1of the reference beam 170 are constantly changing, due to the ongoing variation of the relative phases of the sub-beams. As a result, far-field intensity pattern 172 is not fixed upon detector 150 but rather is constantly being moved around with respect to detector 150 depending on the combined relative phases of the constituent sub-beams. However, in order for detector 150 to provide the required noise cancellation phase correction output, far-field intensity pattern 172 must be incident upon detector 150 in order for detector to measure the intensity of far- field intensity pattern 172 and hence apply a noise correction accordingly, resulting in a fixed output beam.The conflict between the dynamic nature of far-field intensity pattern 172 due to the phase-variation thereof and the fixed nature required of far-field intensity pattern 172 in order to derive and apply noise correction thereto, is advantageously resolved in the present invention by providing the noise cancellation and phase variation at mutually different times and rates.The noise cancellation phase correction output is provided based on taking into consideration noise measured at detector 150 at a noise sampling rate. The output beam 122 is controlled in such a way that the far-field intensity pattern 172 is incident upon detector 150 during the course of the dynamic changes to the shape and position of output and reference far-field intensity patterns 166, 172 at a rate that is equal to or higher than the required noise sampling rate. The noise in reference beam 170 is taken into consideration during those intermittent times at which the far-field intensity pattern 172 is returned to detector 150.At time interstices between the intermittent times at which far-field intensity pattern 172 is incident upon detector 150, the phase of the combined output beams 122, 170 is varied in order to dynamically change the shape and position of the far-field intensity pattern thereof as required to perform laser cutting of item 106. The combined laser output is varied at a phase varying rate which exceeds the noise sampling rate, in order to rapidly change the phase and hence shape and position of the far-field intensity pattern. By way of example, the noise sampling rate may be of the order of 10 - 1000 Hz whereas the phase varying rate may be greater than 10,000 Hz.The different rates and time scales over which the noise cancellation and phase variation are preferably performed in embodiments of the present invention may be best understood with reference to a graph 180 seen in Fig. 1A and an enlarged version thereof shown in Fig. IB.As seen most clearly in Fig. IB, graph 180 includes an upper portion 1displaying variation in intensity over time of far-field intensity pattern 172 as measured at detector 150 and a lower portion 184, displaying variation over the same time period of the relative phases of a number of sub-beams contributing to output beam 122 and reference beam 170. For the sake of simplicity, the relative phases of ten sub-beams are displayed in graph 180, although it is appreciated that OP A system 100 and hence the explanation provided herein is applicable to a fewer or, more typically, a far greater number of sub-beams.

As seen in upper portion 182, intensity peaks 186 represent measured intensity of the reference beam 170 when the far field intensity pattern 172 passes over detector 150. As seen in lower portion 184, intensity peaks 186 occur at intermittent times Ti at which the relative phase of each sub-beam is zero, meaning that there is no shift in phase between the sub-beams, the position of the combined output beam is therefore not being changed and the far field intensity pattern 172 is hence directly incident on the detector 150. It is understood that detector 150 may alternatively be positioned such that the relative phase of the sub-beams thereat is non-zero. Furthermore, more than a single detector may be employed so as to allow measurement of the far field intensity pattern 172 at more than one location therealong.Between intensity peaks 186 the measured intensity is close to zero, as the far- field intensity pattern 172 is moved to the either side of detector 150 and thus is not directly incident on the detector 150. As appreciated from consideration of upper portion 182, the magnitude of intensity peaks 186 is not constant due to the presence of noise in the laser output beam, which noise degrades the far field intensity pattern 172.As seen in lower portion 184, the relative phases of the sub-beams are varied at time interstices Tbetween between intermittent times Ti. In the phase variation function illustrated herein, the relative phases of the sub-beams are shown to be varied in a periodic, regularly repeating pattern, with equal phase shifts being applied in the positive and negative directions. It is appreciated that such a simplistic pattern is illustrative only and that the phase variation is not necessarily regularly repeating, nor necessarily symmetrical in positive and negative directions. Furthermore, it is understood that time interstices Tbetween preferably but not necessarily do not overlap with intermittent times Ti. Additionally, it is appreciated that at least one of the phase varying rate and the noise sampling rate may be constant or may change over time.Noise cancellation subsystem 140 preferably operates by taking into consideration the noise at intermittent times Ti and providing a noise cancellation phase correction output based on the noise sensed at intermittent times Ti. Noise cancellation subsystem 140 preferably employs an algorithm in order to sense noise and correct for the sensed noise accordingly.According to one exemplary embodiment of the present invention, noise cancellation subsystem 140 employs an algorithm in which the relative phase of one channel is changed in such a way that the relative phase is modified by a given phase change A(p during each cycle of travel of the far-field intensity pattern 172 with respect to detector 150. Following a number of such cycles, in which a different phase change Atp is applied to the selected sub-beam over each cycle, the algorithm ascertains the maximum output intensity over all of the cycles and finds the optimum phase change Atp that produced this maximum intensity. The phase change of the selected sub-beam is then fixed at the optimum phase change A(p for subsequent cycles and the algorithm proceeds to optimize another sub-beam.Graph 180 illustrates noise cancellation according to this exemplary algorithm in three sub-beams or channels A, B and C of the total of 10 sub-beams. Sub- beams A, B and C are displayed alone in Fig. IC for the sake of clarity. It is appreciated that the line style of the traces representing phase variation and noise correction of sub-beams A, B and C respectively is modified in Fig. IC in comparison to Figs. 1A and IB, in order to aid differentiation between the various sub-beams for the purposes of the explanation hereinbelow.As seen initially in the case of channel A, and appreciated most clearly from consideration of an enlargement 190, the dashed trace represents the pattern of variation in relative phase of sub-beam A, as would be applied by phase control sub-system 130 in the absence of any noise correction. This trace may be termed Auncorrected. The dotted-and dashed trace represents the actual relative phase of sub- beam A as modified by the noise correction algorithm in order to find the optimum phase noise correction. ,This trace may be termed Acorrected. The modified relative phase of Acorrected is shifted with respect to the non-modified relative phase of Auncorrected by a different Aq>A over the first five cycles of sub-beam A. The intensity 186 measured at detector 150 varies over the first five cycles of optimization of sub-beam A due to the deliberate change in relative phase shift.Following the first five cycles of sub-beam A, the algorithm ascertains the maximum intensity and finds the phase change Aq)A that produces the maximum intensity. In this case, the maximum intensity is seen to be IAmax produced by the second phase shift AA. The phase change applied to relative phase variation of sub-beam A is thus fixed at the second phase shift A output beam intensity and correct for intensity degradation thereof due to phase noise in sub-beam C.Detector 150 may operate continuously in order to continuously optimize the relative phases of the sub-beams and correct for phase noise therein. However, due to a finite response time of detector 150, detector 150 only takes into consideration the noise in reference beam 170 at intermittent times, at a relatively slow noise sampling rate. Hie noise sampling rate is preferably but not necessarily predetermined. The noise sampling rate may alternatively be random.It is appreciated that the particular parameters of the noise correction algorithm depicted in graph 180 are exemplary only and may be readily modified, as will be understood by one skilled in the art. For example, the phase shift A(p may be optimized over a greater or fewer number of cycles than illustrated herein, each sub-beam may be fully optimized each time the sub-beam passes over detector 150 or several sub-beams or all of the sub-beams may be optimized during each cycle in which the far-field intensity pattern passes over detector 150. Furthermore, non-sequential noise correction optimization algorithms may alternatively be implemented, including, but not limited to, Stochastic parallel gradient descent optimization algorithms.The use of dynamically shaped, noise corrected optical phased array output beams for laser cutting is highly advantageous and enables rapid beam steering, fast power modulation, fast beam focusing and beam shape tailoring. Both the speed and quality with which a material may be cut are improved using dynamically shaped, noise corrected optical phase array output in comparison to conventional laser cutting methods. It is appreciated that but for the provision of noise correction, in accordance with preferred embodiments of the present invention, the shape and position of the optical phased array output beam would be degraded, thereby degrading the quality, speed and precision of the laser cutting process.In order to maintain output beam intensity as the far-field intensity pattern of the beam moves, as is advantageous in certain laser cutting applications, movement of the output beam may be controlled such that the beam spends more time at lower-intensity positions so as to compensate for reduced power delivery thereat. Additionally or alternatively, an intensity profile mask such as an ND filter may be applied to the output beam in order to modify the intensity thereof.Reference is now made to Fig. 2A, which is a simplified schematic illustration of an optical phased array laser system for noise corrected dynamic beam shaping, constructed and operative in accordance with another preferred embodiment of the present invention; and to Figs. 2B and 2C, which are simplified graphical representations of phase variation and noise correction in a system of the type illustrated in Fig. 2A.As seen in Fig. 2A, there is provided an optical phased array (OPA) laser system 200, here shown to be employed, by way of example, within an additive manufacturing system 202. Additive manufacturing system 202 may include OP A laser system 200 mounted in spaced relation to a scanning mirror 203 and multi- axis positioning table 204, upon which table 204 an item, such as an item 206, may be additively manufactured using laser system 200, as is detailed henceforth. It is understood that although additive manufacturing system 202 is illustrated herein in the context of scanning mirror 203, system 202 may be embodied as any type of additive manufacturing system, as will be appreciated by one skilled in the art.As best seen at an enlargement 210, OP A laser 200 preferably comprises a seed laser 212 and a laser beam splitting and combining subsystem 214. Splitting and combining subsystem 214 preferably receives an output laser beam from seed laser 212 and splits the output laser beam into a plurality of sub-beams along a corresponding plurality of channels 216. Here, by way of example only, an output from seed laser 212 is shown to be split into ten sub-beams along ten channels 2although it is appreciated that splitting and combining subsystem 214 may include a fewer or greater number of channels along which the output of seed laser 212 is split, and typically may include a far greater number of channels such as 32 or more channels.The relative phase of each sub-beam may be individually modulated by a phase modulator 218, preferably located along each of channels 216. Each phase modulated sub-beam produced by the splitting and subsequent phase modulation of the output of seed laser 212 preferably propagates towards a collimating lens 219. The individually collimated, phase modulated sub-beams are subsequently combined, for example at a focal lens 220, to form an output beam 222.Splitting and combining subsystem 214 may also provide laser amplification of the sub-beams, preferably following the splitting of the output beam of seed laser 212 into sub-beams and prior to the combining of the sub-beams to form output beam 222. Here, by way of example, splitting and combining subsystem 214 is shown to include a plurality of optical amplifiers 224 located along corresponding ones of channels 216 for amplifying each sub-beam. It is appreciated, however, that such amplification is optional and may be omitted, depending on the power output requirements of OP A laser 200.The phase of output beam 222, and hence the position and shape of the far- field intensity pattern thereof, is controlled, at least in part, by the relative phases of the constituent sub-beams combined to form output beam 222. In many applications, such as laser additive manufacturing as illustrated in Fig. 2A, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This may be achieved in laser system 200 by laser splitting and combining subsystem 214 dynamically varying the relative phases of the individual sub-beams and thereby varying the phase of the combined laser output 222 so as dynamically to control the position and shape of the far-field intensity pattern thereof.The relative phases of the sub-beams are preferably predetermined in accordance with the desired laser output pattern for the 3D printing of item 206. Particularly preferably, the varying relative phases are applied by a phase control subsystem 230. Phase control subsystem 230 preferably forms a part of a control electronics module 232 in OP A laser 200 and preferably controls each phase modulator 218 so as to dynamically modulate the relative phases of the sub-beams along channels 216.Due to noise inherent in OP A system 200, output beam 222 has noise. Noise in output beam 222 is typically phase noise created by thermal or mechanical effects and/or by the amplification process in the case that optical amplifiers 2are present in OP A system 200. It is a particular feature of a preferred embodiment of the present invention that laser system 200 includes a noise cancellation subsystem 240 operative to provide a noise cancellation phase correction output in order to cancel out the noise in output beam 222 in a manner detailed henceforth.Particularly preferably, noise cancellation subsystem 240 employs an algorithm to sense and correct phase noise in the combined laser output. The noise cancellation phase correction output is preferably provided by noise cancellation subsystem 240 to phase modulator 218 so as to correct phase noise in output beam 222 and thus avoid distortion of the shape and position of the far field intensity pattern of output beam 222 that would otherwise be caused by the noise. Noise cancellation subsystem 240 may be included in control electronics module 232.It is understood that output beam 222 may be additionally or alternatively affected by types of noise other than phase noise, including intensity noise. In the case of output beam 222 having intensity noise, noise cancellation subsystem 2may be operative to provide a noise cancellation phase correction output in order to cancel out the intensity noise in output beam 222. In such a case, OP A laser system 200 may optionally additionally include intensity modulators 242 along channels 216 for modulating the intensity of each of the sub-beams along channels 216.It is understood that output beam 222 may be additionally or alternatively affected by mechanical noise which may affect the relative position of the sub- beams. In the case of output beam 222 having position noise, noise cancellation subsystem 240 may be operative to provide a noise cancellation phase correction output in order to cancel out the position noise in output beam 222. In such a case, OP A laser system 200 may optionally additionally include position modulators 244 along channels 216 for modulating the position of each of the sub-beams along channels 216.In order to facilitate application of phase variation and noise correction to output beam 222, a portion of the output of OP A laser 200 is preferably extracted and directed towards at least one detector, here illustrated as a single detector 250. The extracted portion of the output beam preferably functions as a reference beam, based on characteristics of which the required noise correction and/or phase variation may be calculated. In the embodiment shown in Fig. 2A, plurality of sub-beams along channels 216 are directed towards a beam splitter 260. Beam splitter 260 preferably splits each sub-beam into a transmitted portion 262 and a reflected portion 264 in accordance with a predetermined ratio. For example, beam splitter 260 may split each sub-beam with a 99.9% transmitted: 0.01% reflected ratio.The transmitted portion 262 of the sub-beams preferably propagates towards focal lens 220, at which focal lens 220 the sub-beams are combined to form output beam 222 having a far-field intensity pattern 266 incident on scanning mirror 203. The reflected portion 264 of the sub-beams is preferably reflected towards an additional focal lens 268, at which additional focal lens 268 the sub-beams are combined to form an output reference beam 270 having a far-field intensity pattern 272 incident on a surface of detector 250.It is understood that the particular structure and configuration of beam splitting and recombining elements shown herein, including beam splitter 260 and focal lenses 220 and 268, is exemplary only and depicted in a highly simplified form. It is appreciated that OP A laser system 200 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers and coherent free-space far- field combiners.As described hereinabove, the shape and position of far-field intensity pattern 266 of the output beam 222 and correspondingly of far-field intensity pattern 2of the reference beam 270 are constantly changing, due to the ongoing variation of the relative phases of the sub-beams. As a result, far-field intensity pattern 272 is not fixed upon detector 250 but rather is constantly being moved around with respect to detector 250 depending on the combined relative phases of the constituent sub-beams. However, in order for detector 250 to provide the required noise cancellation phase correction output, far-field intensity pattern 272 must be incident upon detector 250 in order for detector to measure the intensity of far- field intensity pattern 272 and hence apply a noise correction accordingly, resulting in a fixed output beam.The conflict between the dynamic nature of far-field intensity pattern 272 due to the phase-variation thereof and the fixed nature required of far-field intensity pattern 272 in order to derive and apply noise correction thereto, is advantageously resolved in the present invention by providing the noise cancellation and phase variation at mutually different times and rates.The noise cancellation phase correction output is provided based on taking into consideration noise measured at detector 250 at a noise sampling rate. The output beam 222 is controlled in such a way that the far-field intensity pattern 272 is incident upon detector 250 during the course of the dynamic changes to the shape and position of output and reference far-field intensity patterns 266, 272 at a rate that is equal to or higher than the required noise sampling rate. The noise in reference beam 270 is taken into consideration during those intermittent times at which the far-field intensity pattern 272 is returned to detector 250.At time interstices between the intermittent times at which far-field intensity pattern 272 is incident upon detector 250, the phase of the combined output beams 222, 270 is varied in order to dynamically change the shape and position of the far-field intensity pattern thereof as required to perform additive manufacturing of item 206. The combined laser output is varied at a phase varying rate which exceeds the noise sampling rate, in order to rapidly change the phase and hence shape and position of the far-field intensity pattern. By way of example, the noise sampling rate may be of the order of 10 - 1000 Hz whereas the phase varying rate may be greater than 10,000 Hz.The different rates and time scales over which the noise cancellation and phase variation are preferably performed in embodiments of the present invention may be best understood with reference to a graph 280 seen in Fig. 2A and an enlarged version thereof shown in Fig. 2B.As seen most clearly in Fig. 2B, graph 280 includes an upper portion 2displaying variation in intensity over time of far-field intensity pattern 272 as measured at detector 250 and a lower portion 284, displaying variation over the same time period of the relative phases of a number of sub-beams contributing to output beam 222 and reference beam 270. For the sake of simplicity, the relative phases of ten sub-beams are displayed in graph 280, although it is appreciated that OP A system 200 and hence the explanation provided herein is applicable to a fewer or, more typically, a far greater number of sub-beams.

As seen in upper portion 282, intensity peaks 286 represent measured intensity of the reference beam 270 when the far field intensity pattern 272 passes over detector 250. As seen in lower portion 284, intensity peaks 286 occur at intermittent times Ti at which the relative phase of each sub-beam is zero, meaning that there is no shift in phase between the sub-beams, the position of the combined output beam is therefore not being changed and the far field intensity pattern 272 is hence directly incident on the detector 250. It is understood that detector 250 may alternatively be positioned such that the relative phase of the sub-beams thereat is non-zero. Furthermore, more than a single detector may be employed so as to allow measurement of the far field intensity pattern 272 at more than one location therealong.Between intensity peaks 286 the measured intensity is close to zero, as the far- field intensity pattern 272 is moved to the either side of detector 250 and thus is not directly incident on the detector 250. As appreciated from consideration of upper portion 282, the magnitude of intensity peaks 286 is not constant due to the presence of noise in the laser output beam, which noise degrades the far field intensity pattern 272.As seen in lower portion 284, the relative phases of the sub-beams are varied at time interstices Tbetween between intermittent times Ti. In the phase variation function illustrated herein, the relative phases of the sub-beams are shown to be varied in a periodic, regularly repeating pattern, with equal phase shifts being applied in the positive and negative directions. It is appreciated that such a simplistic pattern is illustrative only and that the phase variation is not necessarily regularly repeating, nor necessarily symmetrical in positive and negative directions. Furthermore, it is understood that time interstices Tbetween preferably but not necessarily do not overlap with intermittent times Ti. Additionally, it is appreciated that at least one of the phase varying rate and the noise sampling rate may be constant or may change over time.Noise cancellation subsystem 240 preferably operates by taking into consideration the noise at intermittent times Ti and providing a noise cancellation phase correction output based on the noise sensed at intermittent times Ti. Noise cancellation subsystem 240 preferably employs an algorithm in order to sense noise and correct for the sensed noise accordingly.According to one exemplary embodiment of the present invention, noise cancellation subsystem 240 employs an algorithm in which the relative phase of one channel is changed in such a way that the relative phase is modified by a given phase change A(p during each cycle of travel of the far-field intensity pattern 272 with respect to detector 250. Following a number of such cycles, in which a different phase change Atp is applied to the selected sub-beam over each cycle, the algorithm ascertains the maximum output intensity over all of the cycles and finds the optimum phase change Atp that produced this maximum intensity. The phase change of the selected sub-beam is then fixed at the optimum phase change Acp for subsequent cycles and the algorithm proceeds to optimize another sub-beam.Graph 280 illustrates noise cancellation according to this exemplary algorithm in three sub-beams or channels A, B and C of the total of 10 sub-beams. Sub- beams A, B and C are displayed alone in Fig. 2C for the sake of clarity. It is appreciated that the line style of the traces representing phase variation and noise correction of sub-beams A, B and C respectively is modified in Fig. 2C in comparison to Figs. 2A and 2B, in order to aid differentiation between the various sub-beams for the purposes of the explanation hereinbelow.As seen initially in the case of channel A, and appreciated most clearly from consideration of an enlargement 290, the dashed trace represents the pattern of variation in relative phase of sub-beam A, as would be applied by phase control sub-system 230 in the absence of any noise correction. This trace may be termed Auncorrected. The dotted-and dashed trace represents the actual relative phase of sub- beam A as modified by the noise correction algorithm in order to find the optimum phase noise correction. This trace may be termed Acorrected. The modified relative phase of Acorrected is shifted with respect to the non-modified relative phase of Auncorrected by a different Aq>A over the first five cycles of sub-beam A. The intensity 286 measured at detector 250 varies over the first five cycles of optimization of sub-beam A due to the deliberate change in relative phase shift.Following the first five cycles of sub-beam A, the algorithm ascertains the maximum intensity and finds the phase change Aq)A that produces the maximum intensity. In this case, the maximum intensity is seen to be IAmax produced by the second phase shift AA. The phase change applied to relative phase variation of sub-beam A is thus fixed at the second phase shift Aq)A for subsequent cycles and the algorithm proceeds to optimize sub-beam B.It is appreciated that during the sequential cycles of optimization of sub-beam A, the relative phases of the remainder of the sub-beams are varied as usual, each at a phase varying rate that far exceeds the noise sampling rate at which the noise in sub-beam A is taken into consideration.As seen further in the case of sub-beam B, and appreciated most clearly from consideration of an enlargement 292, the thicker trace during optimization of channel B represents the pattern of variation in relative phase of sub-beam B, as would be applied by phase control sub-system 230 in the absence of any noise correction. This trace may be termed Buncortected. The thinner trace during optimization of channel B represents the actual relative phase of sub-beam B as modified by the noise correction algorithm in order to find the optimum phase noise correction. This trace may be termed Bcorrected. The modified relative phase of Bcorrected is shifted with respect to the non-modified relative phase of Buncorrected by a different A(pe over five cycles of optimization sub-beam B. The intensity 2measured at detector 250 varies over these five cycles of optimization sub-beam B due to the deliberate change in relative phase shift.Following these five cycles of sub-beam B, the algorithm ascertains the maximum intensity and finds the phase change Acps that produces the maximum intensity. In this case, the maximum intensity is seen to be IABmax produced by the fourth phase shift A(pe. The phase change applied to relative phase variation of sub-beam B is then fixed at the fourth phase shift A(p8 for subsequent cycles and the algorithm proceeds to optimize sub-beam C.It is appreciated that during the five cycles of optimization of sub-beam B, the relative phases of the remainder of the sub-beams are varied as usual, each at a phase varying rate that far exceeds the noise sampling rate at which the noise in sub-beam B is taken into consideration.A similar optimization process is preferably implemented for sub-beam C, in which a phase change A(pc is applied over several cycles in order to optimize the output beam intensity and correct for intensity degradation thereof due to phase noise in sub-beam C.Detector 250 may operate continuously in order to continuously optimize the relative phases of the sub-beams and correct for phase noise therein. However, due to a finite response time of detector 250, detector 250 only takes into consideration the noise in reference beam 270 at intermittent times, at a relatively slow noise sampling rate. Hie noise sampling rate is preferably but not necessarily predetermined. The noise sampling rate may alternatively be random.It is appreciated that the particular parameters of the noise correction algorithm depicted in graph 280 are exemplary only and may be readily modified, as will be understood by one skilled in the art. For example, the phase shift A(p may be optimized over a greater or fewer number of cycles than illustrated herein, each sub-beam may be fully optimized each time the sub-beam passes over detector 250 or several sub-beams or all of the sub-beams may be optimized during each cycle in which the far-field intensity pattern passes over detector 250. Furthermore, non-sequential noise correction optimization algorithms may alternatively be implemented, including, but not limited to, Stochastic parallel gradient descent optimization algorithms.The use of dynamically shaped, noise corrected optical phased array output beams for laser additive manufacturing is highly advantageous and enables rapid beam steering, fast power modulation, fast beam focusing and beam shape tailoring. Both the speed and quality with which an item may be manufactured are improved using dynamically shaped, noise corrected optical phase array output in comparison to conventional laser 3D printing methods. It is appreciated that but for the provision of noise correction, in accordance with preferred embodiments of the present invention, the shape and position of the optical phased array output beam would be degraded, thereby degrading the quality, speed and precision of the laser additive manufacturing process.In order to maintain output beam intensity as the far-field intensity pattern of the beam moves, as is advantageous in certain additive manufacturing applications, movement of the output beam may be controlled such that the beam spends more time at lower-intensity positions so as to compensate for reduced power delivery thereat. Additionally or alternatively, an intensity profile mask such as an ND filter may be applied to the output beam in order to modify the intensity thereof.Reference is now made to Fig. 3A, which is a simplified schematic illustration of an optical phased array laser system for noise corrected dynamic beam shaping, constructed and operative in accordance with a further preferred embodiment of the present invention; and to Figs. 3B and 3C, which are simplified graphical representations of phase variation and noise correction in a system of the type illustrated in Fig. 3 A.As seen in Fig. 3A, there is provided an optical phased array (OPA) laser system 300, here shown to be employed, by way of example, within a free space optical communication system 302. Free space optical communication system 3may include OP A laser system 300 mounted at an outdoor location, such as on a building, in spaced relation to a receiver 303 for receiving optical signals emanating from OP A laser 300. It is understood that although free space optical communication system 302 is illustrated herein in the context of communication between two fixed points, free-space optical communication system 302 may be adapted for use in communications between two locations that are moving relative to one another, as will be appreciated by one skilled in the art. It is further understood that although free space optical communication system 302 is illustrated herein in the context of terrestrial communications, free-space optical communication system 302 may be adapted for use in extraterrestrial communications, as will be appreciated by one skilled in the art.It is appreciated that free space optical communication system 302 is illustrated in Fig. 3A as including only a single OPA laser 300 and receiver 3for the sake of simplicity only, and may include a greater number of each, depending on the communication requirements of system 302. It is further appreciated that receiver 303 may also be an OPA laser of a type resembling OPA laser 300 and having receiving functionality. Furthermore, OPA laser 300 may include receiving functionality so as to allow duplex operation of OPA lasers 3and 303, for transmission and reception of optical signals therebetween.

As best seen at an enlargement 310, OP A laser 300 preferably comprises a seed laser 312 and a laser beam splitting and combining subsystem 314. Splitting and combining subsystem 314 preferably receives an output laser beam from seed laser 312 and splits the output laser beam into a plurality of sub-beams along a corresponding plurality of channels 316. Here, by way of example only, an output from seed laser 312 is shown to be split into ten sub-beams along ten channels 3although it is appreciated that splitting and combining subsystem 314 may include a fewer or greater number of channels along which the output of seed laser 312 is split, and typically may include a far greater number of channels such as 32 or more channels.The relative phase of each sub-beam may be individually modulated by a phase modulator 318, preferably located along each of channels 316. Each phase modulated sub-beam produced by the splitting and subsequent phase modulation of the output of seed laser 312 preferably propagates towards a collimating lens 319. The individually collimated, phase modulated sub-beams are subsequently combined, for example at a focal lens 320, to form an output beam 322.Splitting and combining subsystem 314 may also provide laser amplification of the sub-beams, preferably following the splitting of the output beam of seed laser 312 into sub-beams and prior to the combining of the sub-beams to form output beam 322. Here, by way of example, splitting and combining subsystem 314 is shown to include a plurality of optical amplifiers 324 located along corresponding ones of channels 316 for amplifying each sub-beam. It is appreciated, however, that such amplification is optional and may be omitted, depending on the power output requirements of OP A laser 300.The phase of output beam 322, and hence the position and shape of the far- field intensity pattern thereof, is controlled, at least in part, by the relative phases of the constituent sub-beams combined to form output beam 322. In many applications, such as free space optical communications as illustrated in Fig. 3 A, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This may be achieved in laser system 300 by laser splitting and combining subsystem 314 dynamically varying the relative phases of the individual sub-beams and thereby varying the phase of the combined laser output 322 so as dynamically to control the position and shape of the far-field intensity pattern thereof.The relative phases of the sub-beams are preferably predetermined in accordance with a desired laser output pattern for transmission to receiver 303. Particularly preferably, the varying relative phases are applied by a phase control subsystem 330. Phase control subsystem 330 preferably forms a part of a control electronics module 332 in OPA laser 300 and preferably controls each phase modulator 318 so as to dynamically modulate the relative phases of the sub-beams along channels 316.Due to noise inherent in OPA system 300, output beam 322 has noise. Noise in output beam 322 is typically phase noise created by thermal or mechanical effects and/or by the amplification process in the case that optical amplifiers 3are present in OPA system 300. It is a particular feature of a preferred embodiment of the present invention that laser system 300 includes a noise cancellation subsystem 340 operative to provide a noise cancellation phase correction output in order to cancel out the noise in output beam 322 in a manner detailed henceforth.Particularly preferably, noise cancellation subsystem 340 employs an algorithm to sense and correct phase noise in the combined laser output. The noise cancellation phase correction output is preferably provided by noise cancellation subsystem 340 to phase modulator 318 so as to correct phase noise in output beam 322 and thus avoid distortion of the shape and position of the far field intensity pattern of output beam 322 that would otherwise be caused by the noise. Noise cancellation subsystem 340 may be included in control electronics module 332.It is understood that output beam 322 may be additionally or alternatively affected by types of noise other than phase noise, including intensity noise. In the case of output beam 322 having intensity noise, noise cancellation subsystem 3may be operative to provide a noise cancellation phase correction output in order to cancel out the intensity noise in output beam 322. In such a case, OPA laser system 300 may optionally additionally include intensity modulators 342 along channels 316 for modulating the intensity of each of the sub-beams along channels 316.

It is understood that output beam 322 may be additionally or alternatively affected by mechanical noise which may affect the relative position of the sub- beams. In the case of output beam 322 having position noise, noise cancellation subsystem 340 may be operative to provide a noise cancellation phase correction output in order to cancel out the position noise in output beam 322. In such a case, OP A laser system 300 may optionally additionally include position modulators 344 along channels 316 for modulating the position of each of the sub-beams along channels 316.In order to facilitate application of phase variation and noise correction to output beam 322, a portion of the output of OP A laser 300 is preferably extracted and directed towards at least one detector, here illustrated as a single detector 350. The extracted portion of the output beam preferably functions as a reference beam, based on characteristics of which the required noise correction and/or phase variation may be calculated. In the embodiment shown in Fig. 3A, plurality of sub-beams along channels 316 are directed towards a beam splitter 360. Beam splitter 360 preferably splits each sub-beam into a transmitted portion 362 and a reflected portion 364 in accordance with a predetermined ratio. For example, beam splitter 360 may split each sub-beam with a 99.9% transmitted: 0.01% reflected ratio.The transmitted portion 362 of the sub-beams preferably propagates towards focal lens 320, at which focal lens 320 the sub-beams are combined to form output beam 322 having a far-field intensity pattern 366. The reflected portion 364 of the sub-beams is preferably reflected towards an additional focal lens 368, at which additional focal lens 368 the sub-beams are combined to form an output reference beam 370 having a far-field intensity pattern 372 incident on a surface of detector 350.It is understood that the particular structure and configuration of beam splitting and recombining elements shown herein, including beam splitter 360 and focal lenses 320 and 368, is exemplary only and depicted in a highly simplified form. It is appreciated that OP A laser system 300 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers and coherent free-space far- field combiners.As described hereinabove, the shape and position of far-field intensity pattern 366 of the output beam 322 and correspondingly of far-field intensity pattern 3of the reference beam 370 are constantly changing, due to the ongoing variation of the relative phases of the sub-beams. As a result, far-field intensity pattern 372 is not fixed upon detector 350 but rather is constantly being moved around with respect to detector 350 depending on the combined relative phases of the constituent sub-beams. However, in order for detector 350 to provide the required noise cancellation phase correction output, far-field intensity pattern 372 must be incident upon detector 350 in order for detector to measure the intensity of far- field intensity pattern 372 and hence apply a noise correction accordingly, resulting in a fixed output beam.The conflict between the dynamic nature of far-field intensity pattern 372 due to the phase-variation thereof and the fixed nature required of far-field intensity pattern 372 in order to derive and apply noise correction thereto, is advantageously resolved in the present invention by providing the noise cancellation and phase variation at mutually different times and rates.The noise cancellation phase correction output is provided based on taking into consideration noise measured at detector 350 at a noise sampling rate. The output beam 322 is controlled in such a way that the far-field intensity pattern 372 is incident upon detector 350 during the course of the dynamic changes to the shape and position of output and reference far-field intensity patterns 366, 372 at a rate that is equal to or higher than the required noise sampling rate. The noise in reference beam 370 is taken into consideration during those intermittent times at which the far-field intensity pattern 372 is returned to detector 350.At time interstices between the intermittent times at which far-field intensity pattern 372 is incident upon detector 350, the phase of the combined output beams 322, 370 is varied in order to dynamically change the shape and position of the far-field intensity pattern thereof as required to perform additive manufacturing of item 206. The combined laser output is varied at a phase varying rate which exceeds the noise sampling rate, in order to rapidly change the phase and hence shape and position of the far-field intensity pattern. By way of example, the noise sampling rate may be of the order of 10 - 1000 Hz whereas the phase varying rate may be greater than 10,000 Hz.The different rates and time scales over which the noise cancellation and phase variation are preferably performed in embodiments of the present invention may be best understood with reference to a graph 380 seen in Fig. 3A and an enlarged version thereof shown in Fig. 3B.As seen most clearly in Fig. 3B, graph 380 includes an upper portion 3displaying variation in intensity over time of far-field intensity pattern 372 as measured at detector 350 and a lower portion 384, displaying variation over the same time period of the relative phases of a number of sub-beams contributing to output beam 322 and reference beam 370. For the sake of simplicity, the relative phases of ten sub-beams are displayed in graph 380, although it is appreciated that OP A system 300 and hence the explanation provided herein is applicable to a fewer or, more typically, a far greater number of sub-beams.As seen in upper portion 382, intensity peaks 386 represent measured intensity of the reference beam 370 when the far field intensity pattern 372 passes over detector 350. As seen in lower portion 384, intensity peaks 386 occur at intermittent times Ti at which the relative phase of each sub-beam is zero, meaning that there is no shift in phase between the sub-beams, the position of the combined output beam is therefore not being changed and the far field intensity pattern 372 is hence directly incident on the detector 350. It is understood that detector 350 may alternatively be positioned such that the relative phase of the sub-beams thereat is non-zero. Furthermore, more than a single detector may be employed so as to allow measurement of the far field intensity pattern 372 at more than one location therealong.Between intensity peaks 386 the measured intensity is close to zero, as the far- field intensity pattern 372 is moved to the either side of detector 350 and thus is not directly incident on the detector 350. As appreciated from consideration of upper portion 382, the magnitude of intensity peaks 386 is not constant due to the presence of noise in the laser output beam, which noise degrades the far field intensity pattern 372.

As seen in lower portion 384, the relative phases of the sub-beams are varied at time interstices Tbetween between intermittent times Ti. In the phase variation function illustrated herein, the relative phases of the sub-beams are shown to be varied in a periodic, regularly repeating pattern, with equal phase shifts being applied in the positive and negative directions. It is appreciated that such a simplistic pattern is illustrative only and that the phase variation is not necessarily regularly repeating, nor necessarily symmetrical in positive and negative directions. Furthermore, it is understood that time interstices Tbetween preferably but not necessarily do not overlap with intermittent times Ti. Additionally, it is appreciated that at least one of the phase varying rate and the noise sampling rate may be constant or may change over time.Noise cancellation subsystem 340 preferably operates by taking into consideration the noise at intermittent times Ti and providing a noise cancellation phase correction output based on the noise sensed at intermittent times T؛. Noise cancellation subsystem 340 preferably employs an algorithm in order to sense noise and correct for the sensed noise accordingly.According to one exemplary embodiment of the present invention, noise cancellation subsystem 340 employs an algorithm in which the relative phase of one channel is changed in such a way that the relative phase is modified by a given phase change A(p during each cycle of travel of the far-field intensity pattern 372 with respect to detector 350. Following a number of such cycles, in which a different phase change Acp is applied to the selected sub-beam over each cycle, the algorithm ascertains the maximum output intensity over all of the cycles and finds the optimum phase change A(p that produced this maximum intensity. The phase change of the selected sub-beam is then fixed at the optimum phase change A(p for subsequent cycles and the algorithm proceeds to optimize another sub-beam.Graph 380 illustrates noise cancellation according to this exemplary algorithm in three sub-beams or channels A, B and C of the total of 10 sub-beams. Sub- beams A, B and C are displayed alone in Fig. 3C for the sake of clarity. It is appreciated that the line style of the traces representing phase variation and noise correction of sub-beams A, B and C respectively is modified in Fig. 3C in comparison to Figs. 3A and 3B, in order to aid differentiation between the various sub-beams for the purposes of the explanation hereinbelow.As seen initially in the case of channel A, and appreciated most clearly from consideration of an enlargement 390, the dashed trace represents the pattern of variation in relative phase of sub-beam A, as would be applied by phase control sub-system 330 in the absence of any noise correction. This trace may be termed Auncorrected. The dotted-and dashed trace represents the actual relative phase of sub- beam A as modified by the noise correction algorithm in order to find the optimum phase noise correction. This trace may be termed ACOrrected. The modified relative phase of ACOrrected is shifted with respect to the non-modified relative phase of Auncorrected by a different A؟>a over the first five cycles of sub-beam A. The intensity 386 measured at detector 350 varies over the first five cycles of optimization of sub-beam A due to the deliberate change in relative phase shift.Following the first five cycles of sub-beam A, the algorithm ascertains the maximum intensity and finds the phase change A©A that produces the maximum intensity. In this case, the maximum intensity is seen to be IAmax produced by the second phase shift AA. The phase change applied to relative phase variation of sub-beam A is thus fixed at the second phase shift AcpA for subsequent cycles and the algorithm proceeds to optimize sub-beam B.It is appreciated that during the sequential cycles of optimization of sub-beam A, the relative phases of the remainder of the sub-beams are varied as usual, each at a phase varying rate that far exceeds the noise sampling rate at which the noise in sub-beam A is taken into consideration.As seen further in the case of sub-beam B, and appreciated most clearly from consideration of an enlargement 392, the thicker trace during optimization of channel B represents the pattern of variation in relative phase of sub-beam B, as would be applied by phase control sub-system 330 in the absence of any noise correction. This trace may be termed Buncorrected. The thinner trace during optimization of channel B represents the actual relative phase of sub-beam B as modified by the noise correction algorithm in order to find the optimum phase noise correction. This trace may be termed Bcorrected. The modified relative phase of Bcorrected is shifted with respect to the non-modified relative phase of Buncorrected by a different Alps over five cycles of optimization sub-beam B. The intensity 3measured at detector 350 varies over these five cycles of optimization sub-beam B due to the deliberate change in relative phase shift.Following these five cycles of sub-beam B, the algorithm ascertains the maximum intensity and finds the phase change Acpe that produces the maximum intensity. In this case, the maximum intensity is seen to be IABmax produced by the fourth phase shift A(pe. The phase change applied to relative phase variation of sub-beam B is then fixed at the fourth phase shift A(ps for subsequent cycles and the algorithm proceeds to optimize sub-beam C.It is appreciated that during the five cycles of optimization of sub-beam B, the relative phases of the remainder of the sub-beams are varied as usual, each at a phase varying rate that far exceeds the noise sampling rate at which the noise in sub-beam B is taken into consideration.A similar optimization process is preferably implemented for sub-beam C, in which a phase change A(pc is applied over several cycles in order to optimize the output beam intensity and correct for intensity degradation thereof due to phase noise in sub-beam C.Detector 350 may operate continuously in order to continuously optimize the relative phases of the sub-beams and correct for phase noise therein. However, due to a finite response time of detector 350, detector 350 only takes into consideration the noise in reference beam 370 at intermittent times, at a relatively slow noise sampling rate. The noise sampling rate is preferably but not necessarily predetermined. The noise sampling rate may alternatively be random.It is appreciated that the particular parameters of the noise correction algorithm depicted in graph 380 are exemplary only and may be readily modified, as will be understood by one skilled in the art. For example, the phase shift A(p may be optimized over a greater or fewer number of cycles than illustrated herein, each sub-beam may be fully optimized each time the sub-beam passes over detector 350 or several sub-beams or all of the sub-beams may be optimized during each cycle in which the far-field intensity pattern passes over detector 350. Furthermore, non-sequential noise correction optimization algorithms may alternatively be implemented, including, but not limited to, Stochastic parallel gradient descent optimization algorithms.The use of dynamically shaped, noise corrected optical phased array output beams for free-space optical communication is highly advantageous and enables rapid beam steering, fast power modulation, fast beam focusing and beam shape tailoring. Both the speed and quality of communication are improved using dynamically shaped, noise corrected optical phase array output in comparison to conventional free space optical communication methods. It is appreciated that but for the provision of noise correction, in accordance with preferred embodiments of the present invention, the shape and position of the optical phased array output beam would be degraded, thereby degrading the quality, speed and precision of the transmitted laser output.In order to maintain output beam intensity as the far-field intensity pattern of the beam moves, as is advantageous in certain optical communication applications, movement of the output beam may be controlled such that the beam spends more time at lower-intensity positions so as to compensate for reduced power delivery thereat. Additionally or alternatively, an intensity profile mask such as an ND filter may be applied to the output beam in order to modify the intensity thereof.Reference is now made to Fig. 4A, which is a simplified schematic illustration of an optical phased array laser system for noise corrected dynamic beam shaping, constructed and operative in accordance with yet another preferred embodiment of the present invention; and to Figs. 4B and 4C, which are simplified graphical representations of phase variation and noise correction in a system of the type illustrated in Fig. 4A.As seen in Fig. 4A, there is provided an optical phased array (OPA) laser system 400, here shown to be employed, by way of example, within a laser welding system 402. Laser welding system 402 may include OP A laser system 400 mounted on or within a portion of a laser welding robot 404. An item, such as an item 406, may be welded by laser welding robot 404, as is detailed henceforth. It is understood that although laser welding system 402 is illustrated herein in the context of welding robot 404, system 402 may be adapted for use in any welding setup, as will be appreciated by one skilled in the art.As best seen at an enlargement 410, OP A laser 400 preferably comprises a seed laser 412 and a laser beam splitting and combining subsystem 414. Splitting and combining subsystem 414 preferably receives an output laser beam from seed laser 412 and splits the output laser beam into a plurality of sub-beams along a corresponding plurality of channels 416. Here, by way of example only, an output from seed laser 412 is shown to be split into ten sub-beams along ten channels 4although it is appreciated that splitting and combining subsystem 414 may include a fewer or greater number of channels along which the output of seed laser 412 is split, and typically may include a far greater number of channels such as 32 or more channels.The relative phase of each sub-beam may be individually modulated by a phase modulator 418, preferably located along each of channels 416. Each phase modulated sub-beam produced by the splitting and subsequent phase modulation of the output of seed laser 412 preferably propagates towards a collimating lens 419. Hie individually collimated, phase modulated sub-beams are subsequently combined, for example at a focal lens 420, to form an output beam 422.Splitting and combining subsystem 414 may also provide laser amplification of the sub-beams, preferably following the splitting of the output beam of seed laser 412 into sub-beams and prior to the combining of the sub-beams to form output beam 422. Here, by way of example, splitting and combining subsystem 414 is shown to include a plurality of optical amplifiers 424 located along corresponding ones of channels 416 for amplifying each sub-beam. It is appreciated, however, that such amplification is optional and may be omitted, depending on the power output requirements of OP A laser 400.The phase of output beam 422, and hence the position and shape of the far- field intensity pattern thereof, is controlled, at least in part, by the relative phases of the constituent sub-beams combined to form output beam 422. In many applications, such as laser welding as illustrated in Fig. 4A, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This may be achieved in laser system 400 by laser splitting and combining subsystem 414 dynamically varying the relative phases of the individual sub- beams and thereby varying the phase of the combined laser output 422 so as dynamically to control the position and shape of the far-field intensity pattern thereof.The relative phases of the sub-beams are preferably predetermined in accordance with the desired laser output pattern for the welding of item 406. Particularly preferably, the varying relative phases axe applied by a phase control subsystem 430. Phase control subsystem 430 preferably forms a part of a control electronics module 432 in OP A laser 400 and preferably controls each phase modulator 418 so as to dynamically modulate the relative phases of the sub-beams along channels 416.Due to noise inherent in OP A system 400, output beam 422 has noise. Noise in output beam 422 is typically phase noise created by thermal or mechanical effects and/or by the amplification process in the case that optical amplifiers 4are present in OP A system 400. It is a particular feature of a preferred embodiment of the present invention that laser system 400 includes a noise cancellation subsystem 440 operative to provide a noise cancellation phase correction output in order to cancel out the noise in output beam 422 in a manner detailed henceforth.Particularly preferably, noise cancellation subsystem 440 employs an algorithm to sense and correct phase noise in the combined laser output. The noise cancellation phase correction output is preferably provided by noise cancellation subsystem 440 to phase modulator 418 so as to correct phase noise in output beam 422 and thus avoid distortion of the shape and position of the far field intensity pattern of output beam 422 that would otherwise be caused by the noise. Noise cancellation subsystem 440 may be included in control electronics module 432.It is understood that output beam 422 may be additionally or alternatively affected by types of noise other than phase noise, including intensity noise. In the case of output beam 422 having intensity noise, noise cancellation subsystem 4may be operative to provide a noise cancellation phase correction output in order to cancel out the intensity noise in output beam 422. In such a case, OP A laser system 400 may optionally additionally include intensity modulators 442 along channels 416 for modulating the intensity of each of the sub-beams along channels 416.It is understood that output beam 422 may be additionally or alternatively affected by mechanical noise which may affect the relative position of the sub- beams. In the case of output beam 422 having position noise, noise cancellation subsystem 440 may be operative to provide a noise cancellation phase correction output in order to cancel out the position noise in output beam 422. In such a case, OP A laser system 400 may optionally additionally include position modulators 444 along channels 416 for modulating the position of each of the sub-beams along channels 416.In order to facilitate application of phase variation and noise correction to output beam 422, a portion of the output of OP A laser 400 is preferably extracted and directed towards at least one detector, here illustrated as a single detector 450. The extracted portion of the output beam preferably functions as a reference beam, based on characteristics of which the required noise correction and/or phase variation may be calculated. In the embodiment shown in Fig. 4A, plurality of sub-beams along channels 416 are directed towards a beam splitter 460. Beam splitter 460 preferably splits each sub-beam into a transmitted portion 462 and a reflected portion 464 in accordance with a predetermined ratio. For example, beam splitter 460 may split each sub-beam with a 99.9% transmitted: 0.01% reflected ratio.The transmitted portion 462 of the sub-beams preferably propagates towards focal lens 420, at which focal lens 420 the sub-beams are combined to form output beam 422 having a far-field intensity pattern 466 incident on item 406. The reflected portion 464 of the sub-beams is preferably reflected towards an additional focal lens 468, at which additional focal lens 468 the sub-beams are combined to form an output reference beam 470 having a far-field intensity pattern 472 incident on a surface of detector 450.It is understood that the particular structure and configuration of beam splitting and recombining elements shown herein, including beam splitter 460 and focal lenses 420 and 468, is exemplary only and depicted in a highly simplified form. It is appreciated that OP A laser system 400 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers and coherent free-space far- field combiners.As described hereinabove, the shape and position of far-field intensity pattern 466 of the output beam 422 and correspondingly of far-field intensity pattern 4of the reference beam 470 are constantly changing, due to the ongoing variation of the relative phases of the sub-beams. As a result, far-field intensity pattern 472 is not fixed upon detector 450 but rather is constantly being moved around with respect to detector 450 depending on the combined relative phases of the constituent sub-beams. However, in order for detector 450 to provide the required noise cancellation phase correction output, far-field intensity pattern 472 must be incident upon detector 450 in order for detector to measure the intensity of far- field intensity pattern 472 and hence apply a noise correction accordingly, resulting in a fixed output beam.The conflict between the dynamic nature of far-field intensity pattern 472 due to the phase-variation thereof and the fixed nature required of far-field intensity pattern 472 in order to derive and apply noise correction thereto, is advantageously resolved in the present invention by providing the noise cancellation and phase variation at mutually different times and rates.The noise cancellation phase correction output is provided based on taking into consideration noise measured at detector 450 at a noise sampling rate. The output beam 422 is controlled in such a way that the far-field intensity pattern 472 is incident upon detector 450 during the course of the dynamic changes to the shape and position of output and reference far-field intensity patterns 466, 472 at a rate that is equal to or higher than the required noise sampling rate. The noise in reference beam 470 is taken into consideration during those intermittent times at which the far-field intensity pattern 472 is returned to detector 450.At time interstices between the intermittent times at which far-field intensity pattern 472 is incident upon detector 450, the phase of the combined output beams 422, 470 is varied in order to dynamically change the shape and position of the far-field intensity pattern thereof as required to perform laser welding of item 406. The combined laser output is varied at a phase varying rate which exceeds the noise sampling rate, in order to rapidly change the phase and hence shape and position of the far-field intensity pattern. By way of example, the noise sampling rate may be of the order of 10 - 1000 Hz whereas the phase varying rate may be greater than 10,000 Hz.The different rates and time scales over which the noise cancellation and phase variation are preferably performed in embodiments of the present invention may be best understood with reference to a graph 480 seen in Fig. 4A and an enlarged version thereof shown in Fig. 4B.As seen most clearly in Fig. 4B, graph 480 includes an upper portion 4displaying variation in intensity over time of far-field intensity pattern 472 as measured at detector 450 and a lower portion 484, displaying variation over the same time period of the relative phases of a number of sub-beams contributing to output beam 422 and reference beam 470. For the sake of simplicity, the relative phases of ten sub-beams are displayed in graph 480, although it is appreciated that OP A system 400 and hence the explanation provided herein is applicable to a fewer or, more typically, a far greater number of sub-beams.As seen in upper portion 482, intensity peaks 486 represent measured intensity of the reference beam 470 when the far field intensity pattern 472 passes over detector 450. As seen in lower portion 484, intensity peaks 486 occur at intermittent times Ti at which the relative phase of each sub-beam is zero, meaning that there is no shift in phase between the sub-beams, the position of the combined output beam is therefore not being changed and the far field intensity pattern 472 is hence directly incident on the detector 450. It is understood that detector 450 may alternatively be positioned such that the relative phase of the sub-beams thereat is non-zero. Furthermore, more than a single detector may be employed so as to allow measurement of the far field intensity pattern 472 at more than one location therealong.Between intensity peaks 486 the measured intensity is close to zero, as the far- field intensity pattern 472 is moved to the either side of detector 450 and thus is not directly incident on the detector 450. As appreciated from consideration of upper portion 482, the magnitude of intensity peaks 486 is not constant due to the presence of noise in the laser output beam, which noise degrades the far field intensity pattern 472.As seen in lower portion 484, the relative phases of the sub-beams are varied at time interstices Tbetween between intermittent times Ti. In the phase variation function illustrated herein, the relative phases of the sub-beams are shown to be varied in a periodic, regularly repeating pattern, with equal phase shifts being applied in the positive and negative directions. It is appreciated that such a simplistic pattern is illustrative only and that the phase variation is not necessarily regularly repeating, nor necessarily symmetrical in positive and negative directions. Furthermore, it is understood that time interstices Tbetween preferably but not necessarily do not overlap with intermittent times Tl Additionally, it is appreciated that at least one of the phase varying rate and the noise sampling rate may be constant or may change over time.Noise cancellation subsystem 440 preferably operates by taking into consideration the noise at intermittent times Ti and providing a noise cancellation phase correction output based on the noise sensed at intermittent times Ti. Noise cancellation subsystem 440 preferably employs an algorithm in order to sense noise and correct for the sensed noise accordingly.According to one exemplary embodiment of the present invention, noise cancellation subsystem 440 employs an algorithm in which the relative phase of one channel is changed in such a way that the relative phase is modified by a given phase change Acp during each cycle of travel of the far-field intensity pattern 472 with respect to detector 150. Following a number of such cycles, in which a different phase change Acp is applied to the selected sub-beam over each cycle, the algorithm ascertains the maximum output intensity over all of the cycles and finds the optimum phase change Acp that produced this maximum intensity. The phase change of the selected sub-beam is then fixed at the optimum phase change Acp for subsequent cycles and the algorithm proceeds to optimize another sub-beam.Graph 480 illustrates noise cancellation according to this exemplary algorithm in three sub-beams or channels A, B and C of the total of 10 sub-beams. Sub- beams A, B and C are displayed alone in Fig. 4C for the sake of clarity. It is appreciated that the line style of the traces representing phase variation and noise correction of sub-beams A, B and C respectively is modified in Fig. 4C in comparison to Figs. 4A and 4B, in order to aid differentiation between the various sub-beams for the purposes of the explanation hereinbelow.As seen initially in the case of channel A, and appreciated most clearly from consideration of an enlargement 490, the dashed trace represents the pattern of variation in relative phase of sub-beam A, as would be applied by phase control sub-system 430 in the absence of any noise correction. This trace may be termed Auncorrected. The dotted-and dashed trace represents the actual relative phase of sub- beam A as modified by the noise correction algorithm in order to find the optimum phase noise correction. This trace may be termed ACOrrected. The modified relative phase of Acorrected is shifted with respect to the non-modified relative phase of Auncorrected by a different AA over the first five cycles of sub-beam A. The intensity 486 measured at detector 450 varies over the first five cycles of optimization of sub-beam A due to the deliberate change in relative phase shift.Following the first five cycles of sub-beam A, the algorithm ascertains the maximum intensity and finds the phase change A©A that produces the maximum intensity. In this case, the maximum intensity is seen to be IAmax produced by the second phase shift AA. The phase change applied to relative phase variation of sub-beam A is thus fixed at the second phase shift AcpA for subsequent cycles and the algorithm proceeds to optimize sub-beam B.It is appreciated that during the sequential cycles of optimization of sub-beam A, the relative phases of the remainder of the sub-beams are varied as usual, each at a phase varying rate that far exceeds the noise sampling rate at which the noise in sub-beam A is taken into consideration.As seen further in the case of sub-beam B, and appreciated most clearly from consideration of an enlargement 492, the thicker trace during optimization of channel B represents the pattern of variation in relative phase of sub-beam B, as would be applied by phase control sub-system 430 in the absence of any noise correction. This trace may be termed Buncorrected. The thinner trace during optimization of channel B represents the actual relative phase of sub-beam B as modified by the noise correction algorithm in order to find the optimum phase noise correction. This trace may be termed BCOrrected. The modified relative phase of Bcorrected is shifted with respect to the non-modified relative phase of Buncorrected by a different A(pe over five cycles of optimization sub-beam B. The intensity 4measured at detector 450 varies over these five cycles of optimization sub-beam B due to the deliberate change in relative phase shift.Following these five cycles of sub-beam B, the algorithm ascertains the maximum intensity and finds the phase change Alps that produces the maximum intensity. In this case, the maximum intensity is seen to be IABmax produced by the fourth phase shift A(pe. The phase change applied to relative phase variation of sub-beam B is then fixed at the fourth phase shift A(pe for subsequent cycles and the algorithm proceeds to optimize sub-beam C.It is appreciated that during the five cycles of optimization of sub-beam B, the relative phases of the remainder of the sub-beams are varied as usual, each at a phase varying rate that far exceeds the noise sampling rate at which the noise in sub-beam B is taken into consideration.A similar optimization process is preferably implemented for sub-beam C, in which a phase change A(pc is applied over several cycles in order to optimize the output beam intensity and correct for intensity degradation thereof due to phase noise in sub-beam C.Detector 450 may operate continuously in order to continuously optimize the relative phases of the sub-beams and correct for phase noise therein. However, due to a finite response time of detector 450, detector 450 only takes into consideration the noise in reference beam 470 at intermittent times, at a relatively slow noise sampling rate. The noise sampling rate is preferably but not necessarily predetermined. The noise sampling rate may alternatively be random.It is appreciated that the particular parameters of the noise correction algorithm depicted in graph 480 are exemplary only and may be readily modified, as will be understood by one skilled in the art. For example, the phase shift A(p may be optimized over a greater or fewer number of cycles than illustrated herein, each sub-beam may be fully optimized each time the sub-beam passes over detector 450 or several sub-beams or all of the sub-beams may be optimized during each cycle in which the far-field intensity pattern passes over detector 450. Furthermore, non-sequential noise correction optimization algorithms may alternatively be implemented, including, but not limited to, Stochastic parallel gradient descent optimization algorithms.The use of dynamically shaped, noise corrected optical phased array output beams for laser welding is highly advantageous and enables rapid beam steering, fast power modulation, fast beam focusing and beam shape tailoring. Both the speed and quality with which a material may be cut are improved using dynamically shaped, noise corrected optical phase array output in comparison to conventional laser cutting methods. It is appreciated that but for the provision of noise correction, in accordance with preferred embodiments of the present invention, the shape and position of the optical phased array output beam would be degraded, thereby degrading the quality, speed and precision of the laser cutting process.In order to maintain output beam intensity as the far-field intensity pattern of the beam moves, as is advantageous in certain laser cutting applications, movement of the output beam may be controlled such that the beam spends more time at lower-intensity positions so as to compensate for reduced power delivery thereat. Additionally or alternatively, an intensity profile mask such as an ND filter may be applied to the output beam in order to modify the intensity thereof.Reference is now made to Figs. 5A - 5G, which are simplified illustrations of possible far-field motion of an output of an optical phased array laser system of the types illustrated in Figs. 1A - 4C.As detailed hereinabove, the use of dynamically shaped, noise corrected optical phased array output beams in various laser applications, including but not limited to laser cutting, laser additive manufacturing, laser welding and laser free- space optical communication, is highly advantageous and enables rapid beam steering, fast power modulation, fast beam focusing and beam shape tailoring.Exemplary far-field patterns illustrating rapid beam steering in accordance with embodiments of the present invention are shown in Figs. 5A and 5B. These beam steering patterns may be provided in combination with and so as to compliment mechanical spatial modulation of the beam, such as mechanical beam steering. Mechanical beam steering may be due to motion provided by positioning table 104 shown in Fig 1A; due to mirror scanning, such as in an additive manufacturing system of the type shown in Fig. 2A; due to mechanical motion between laser system 300 and receiver 303 shown in Fig 3A; due to motion provide by robot 404 shown in Fig 4A, or due to any other source of mechanical motion.The mechanical motion may be desired or undesired motion. Preferably, the far-field rapid beam steering provided by embodiments of the present invention compliments the mechanical motion so as to achieve the desired combined beam motion. The desired combined motion may be faster and/or more precise than would be produced as a result of mechanical beam modulation alone.As seen in Fig. 5A, dynamically shaped, noise corrected optical phased array output beams may exhibit rapid multipoint jumping, as illustrated by first beam paths 502, which rapid multipoint jumping compliments beam motion due to mechanical scanning, represented by a second beam path 504.By way of example, such multipoint jumping may be advantageous in material processing, wherein time is taken for energy to be absorbed at each point of the material being processed. Multipoint jumping allows the beam to jump between points, returning to each point multiple times, thus facilitating the processing of many points in parallel. Further by way of example, such multipoint jumping may be advantageous in communication systems by allowing transmission to multiple locations in parallel.As seen in Fig. 5B, the use of dynamically shaped, noise corrected optical phased array output beams also facilitates rapid scanning, as illustrated by a third beam path 506, which rapid scanning compliments beam motion due to mechanical scanning represented by a fourth beam path 508. Such rapid scanning facilitates continuous, smooth mechanical beam motion, fine features of which may be provided by far-field dynamic shaping in accordance with embodiments of the present invention. Furthermore, dynamic noise corrected far field modulation may be provided in combination with mechanical beam motion in order to correct inaccuracies that may be present in the mechanically modulated beam patterns.An exemplary far field beam pattern illustrating electro-optical beam wobble in accordance with preferred embodiments of the present invention is shown in Fig. 5C. As seen in Fig. 5C, the dynamically shaped, noise corrected optical phased array output beam is controlled so as to exhibit a rapid beam wobble 5along a direction of beam motion 512, particularly useful, for example, in a laser welding system such as that illustrated in Fig. 4A.Exemplary far-field beam patterns illustrating dynamic modification of depth of focus in accordance with preferred embodiments of the present invention are shown in Figs. 5D - 5F. As seen in Figs. 5D - 5F, the depth of the beam focus may be dynamically changed by systems of the present invention, allowing variable beam focal length for scanning (Fig. 5E) and for deep cutting (Figs. 5D and 5F), particularly useful, for example, in cutting, additive manufacturing and welding systems of the types illustrated in Figs. 1 A, 2 A and 4 A.Exemplary far-field beam patterns illustrating dynamic beam shaping in accordance with preferred embodiments of the present invention are shown in Fig. 5G. As seen in Fig. 5G, the shape of the beam may be dynamically changed to create a desired beam shape output. This may be particularly useful, for example, in cutting, additive manufacturing and welding systems of the types illustrated in Figs. 1 A, 2A and 4A, as well as in other contexts. As is well known in the art, the quality and speed of laser cutting, welding and 3D printing are typically influenced by beam size and shape. The present invention allows dynamic adaptation of the beam to the optimum shape at any point.It is appreciated that the various far-field beam motion patterns illustrated in Figs. 5A - 5G are all preferably produced by systems of the present invention using digital electronic controls and without requiring any moving parts.It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly claimed hereinbelow. Rather, the scope of the invention includes various combinations and subcombinations of the features described hereinabove as well as modifications and variations thereof as would occur to persons skilled in the art upon reading the forgoing description with reference to the drawings and which are not in the prior art.

Claims (32)

1.CLAIMS 1. A laser system comprising: a seed laser; a laser beam splitting and combining subsystem receiving an output from said seed laser and providing a combined laser output having noise; and a noise cancellation subsystem operative to provide a noise cancellation phase correction output based on taking into consideration said noise at intermittent times and to apply said noise cancellation phase correction output to different sub-beams of said combined laser output at different ones of said intermittent times, said laser beam splitting and combining subsystem varying a phase of said combined laser output during time interstices between said intermittent times, for purposes other than noise cancellation, for use in at least one of laser cutting, laser welding, free-space optical communications and laser additive manufacturing.

2. A laser system comprising: a seed laser; a laser beam splitting and combining subsystem receiving an output from said seed laser and providing a combined laser output having noise; and a noise cancellation subsystem operative to provide a noise cancellation phase correction output, based on taking into consideration said noise at a noise sampling rate, and to apply said noise cancellation phase correction output to different sub-beams of said combined laser output at different times, said laser beam splitting and combining subsystem additionally varying a phase of said combined laser output at a phase varying rate which exceeds said noise sampling rate, for purposes other than noise cancellation, for use in at least one of laser cutting, laser welding, free-space optical communications and laser additive manufacturing.

3. A laser system according to claim 2 and wherein at least one of said noise sampling rate and said phase varying rate changes over time.

4. A laser system according to claim 2 or claim 3, wherein said noise sampling rate is predetermined.

5. A laser system according to any one of the preceding claims and wherein said laser beam splitting and combining subsystem varies a phase of said combined laser output to provide spatial modulation of said combined laser output.

6. A laser system according to claim 5, wherein said spatial modulation of said combined laser output is provided in combination with mechanical spatial modulation of said combined laser output, said spatial modulation in combination with said mechanical spatial modulation being faster than said mechanical spatial modulation in the absence of said spatial modulation.

7. A laser system according to claim 5 or claim 6, wherein said spatial modulation of said combined laser output is provided in combination with mechanical spatial modulation of said combined laser output, said spatial modulation in combination with said mechanical spatial modulation being more precise than said mechanical spatial modulation in the absence of said spatial modulation.

8. A laser system according to any one of claims 5 – 7, wherein said spatial modulation comprises modulation of at least one of a shape and a diameter of said combined laser output.

9. A laser system according to any one of the preceding claims and wherein said laser beam splitting and combining subsystem provides laser beam amplification downstream of said splitting and upstream of said combining.

10. A laser system according to any one of the preceding claims, wherein said noise cancellation phase correction output is calculated based on sequentially applying at least two phase changes to at least one constituent beam of said combined laser output and identifying one phase change of said at least two phase changes corresponding to a maximum output intensity of said at least one constituent beam.

11. A laser system according to any one of the preceding claims, and also comprising at least one detector cooperatively coupled to said noise cancellation subsystem for detecting at least a portion of said combined laser output.

12. A laser system according to claim 11, wherein said at least one detector performs said detecting continuously.

13. A laser system according to any one of the preceding claims and wherein said noise cancellation phase correction output cancels intensity noise in said combined laser output.

14. A laser system according to claim 13 and also comprising at least one intensity modulator for varying an intensity of said combined laser output.

15. A laser system according to any one of the preceding claims and wherein said noise cancellation phase correction output cancels position noise in said combined laser output.

16. A laser system according to claim 15, and also comprising at least one position modulator for varying a position of said combined laser output.

17. A method for performing noise correction on a phase varied laser output comprising: receiving an output from a seed laser; splitting and combining said output to provide a combined laser output having noise; applying a noise cancellation phase correction output to said combined laser output based on taking into consideration said noise at intermittent times, said applying comprising applying said noise cancellation phase correction output to different sub-beams of said combined laser output at different ones of said intermittent times; additionally varying a phase of said combined laser output during time interstices between said intermittent times for purposes other than noise cancellation; and using said combined laser output in at least one of laser cutting, laser welding, free-space optical communications and laser additive manufacturing.

18. A method for performing noise correction on a phase varied laser output comprising: receiving an output from a seed laser; splitting and combining said output to provide a combined laser output having noise; applying a noise cancellation phase correction output to said combined laser output, based on taking into consideration said noise at a noise sampling rate, said applying comprising applying said noise cancellation phase correction output to different sub-beams of said combined laser output at different times; varying a phase of said combined laser output at a phase varying rate which exceeds said noise sampling rate, for purposes other than noise cancellation; and using said combined laser output in at least one of laser cutting, laser welding, free-space optical communications and laser additive manufacturing.

19. A method according to claim 18 and wherein at least one of said noise sampling rate and said phase varying rate changes over time.

20. A method according to claim 18 or claim 19, wherein said noise sampling rate is predetermined.

21. A method according to any one of claims 17 - 20 and wherein said varying of said phase provides spatial modulation of said combined laser output.

22. A method according to claim 21, wherein said spatial modulation of said combined laser output is provided in combination with mechanical spatial modulation of said combined laser output, said spatial modulation in combination with said mechanical spatial modulation being faster than said mechanical spatial modulation in the absence of said spatial modulation.

23. A method according to claim 21 or claim 22, wherein said spatial modulation of said combined laser output is provided in combination with mechanical spatial modulation of said combined laser output, said spatial modulation in combination with said mechanical spatial modulation being more precise than said mechanical spatial modulation in the absence of said spatial modulation.

24. A method according to any one of claims 21 - 23, wherein said spatial modulation comprises modulation of at least one of a shape and a diameter of said combined laser output.

25. A method according to any one of claims 17 – 24, and also comprising amplifying said output, downstream of said splitting and upstream of said combining.

26. A method according to any one of claims 17 - 25, and also comprising calculating said noise cancellation phase correction output based on sequentially applying at least two phase changes to at least one constituent beam of said combined laser output and identifying one phase change of said at least two phase changes corresponding to a maximum output intensity of said at least one constituent beam.

27. A method according to any one of claims 17 - 26, and also comprising detecting at least a portion of said combined laser output.

28. A method according to any one of claims 17 - 27, wherein said detecting is performed continuously.

29. A method according to any one of claims 17 – 28, and wherein said noise cancellation phase correction output cancels intensity noise in said combined laser output.

30. A method according to claim 29, and also comprising modulating an intensity of said output, downstream of said splitting and upstream of said combining.

31. A method according to any one of claims 17 – 30, and wherein said noise cancellation phase correction output cancels position noise in said combined laser output.

32. A method according to claim 31, and also comprising modulating a position of said output, downstream of said splitting and upstream of said combining.