Interlock systems and methods for optical power beaming

Abstract

Embodiments of the present disclosure may include a power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having radius R1 and a second constituent beam having radius R2, the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P; a power receiver movable at a maximum speed S relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to-electrical power conversion; and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration based on (R1-R2-P) / S.

Description

INTERLOCK SYSTEMS AND METHODS FOR OPTICAL POWER BEAMINGCROSS-REFERNCES TO RELATED APPLICATIONS

[0001] The present application claims convention priority to Australian patent application no. 2024901138 filed on 23 April 2024, entitled “SAFETY SYSTEMS AND METHODS FOR OPTICAL POWER BEAMING”, Australian patent application no. 2025900301 filed on 4 February 2025, entitled “SAFETY SYSTEMS AND METHODS FOR OPTICAL POWER BEAMING”, and Australian patent application no. 2025900408 filed on 14 February 2025, entitled “SAFETY SYSTEMS AND METHODS FOR OPTICAL POWER BEAMING”, the entire disclosure of each of which is incorporated herein by reference.

[0002] The present application is related to the PCT applications entitled “STEERING SYSTEMS AND METHODS FOR OPTICAL POWER BEAMING”, “SAFETY SYSTEMS AND METHODS FOR OPTICAL POWER BEAMING”, and “BEAM CONTROL SYSTEMS AND METHODS FOR OPTICAL POWER BEAMING”, each filed in the name of the present applicant and sharing the same filing date as the present application, and each also claiming convention priority to Australian patent application numbers 2024901138, 2025900301, and 2025900408. The entire disclosure of each of these related PCT applications is incorporated herein by reference.TECHNICAL FIELD

[0003] The present disclosure generally relates to systems and methods for power beaming via free-space optical means, and in particular, optical power beaming systems and methods with safety pre-cautions.BACKGROUND OF THE DISCLOSURE

[0004] The knowledge described in this section is known to the inventors or applicants. However, unless otherwise indicated, it should not be taken that any of the described knowledge in this section qualify as prior art or common general knowledge, in any jurisdiction, merely by virtue of their inclusion in this section, or that the described knowledge is known to a person of ordinary skill in the art.

[0005] In optical power beaming (i.e. power delivery via frees-space optical means), a harmfully high amount of optical power is typically found in the power delivery optical beam that propagates unguided in air / free-space. Safety considerations, such as eye safety, injury to wildlife, stray reflections, or otherwise entry of any intervening obstacles into the beam path, can limit the deployment of optical power beaming as a safe power transfer option.

[0006] In optical power beaming, it is known to send a radio-frequency (RF) signal, from the power receiver to the power transmitter, to provide feedback to the power transmitter regarding status of power receipt. The RF feedback can be indicative of the level of received power, such that the power transmitter responsive to receiving the feedback can determine whether it is to continue (or stop) power delivery, for example, based on the received power matching (or mismatching) the transmitted power, taking into account attenuation. However, RF techniques can be limited in range. Further, the broadcasting nature of RF techniques can be susceptible to interception and thus hacking by malicious actors.

[0007] US 10816694 titled “light curtain safety system” depicts a safety system where the power transmitter emits light at two wavelengths to be received at a power receiver. The power receiver includes a wavelength filter designed to suppress light at one wavelength and pass-through light at another wavelength. The system also includes a retroreflector to retro- reflect the passed-through wavelength back to the power transmitter. The transmitter’s continued operation is based on the receipt of the passed-through wavelength combined with the non-receipt of the suppressed wavelength back at the transmitter. Otherwise, the transmitter’s operation is ceased due to indication of an obstacle. In particular, receipt of both wavelengths back at the transmitter indicates a reflective obstacle, whereas non-receipt of both wavelengths back at the transmitter indicates a non-reflective obstacle.

[0008] There is therefore a need for improving safety considerations of optical power beaming associated with entry of obstacles into the optical beam path, and / or at least provide an alternative to optical power beaming systems and methods.BRIEF SUMMARY OF THE DISCLOSURE

[0009] The present disclosure makes use of transmission of light with dual wavelengths, with one wavelength used for power delivery to a power receiver and another wavelength used for safety piloting from, and / or safety interlock at, a power transmitter. Safetypiloting involves transmitting, for piloting purposes, light at a first wavelength (e.g. eye-safe wavelength), and then transmitting, for power delivery purposes, light at a second wavelength (e.g. power delivery wavelength) upon receipt of return light at the first wavelength back at the transmitter. Safety interlock involves cessation of light transmission at the second wavelength, responsive to reduction or non-receipt of return light at the first wavelength back at the transmitter.

[0010] Described are embodiments of a power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam at a first wavelength and a second constituent beam at a second wavelength, distinct from the first wavelength, the power transmitter including a photodetector assembly configured to provide a measure of return optical power; a power receiver configured to return at least part of the first constituent beam to the photodetector assembly at the power transmitter and receive the second constituent beam for optical-to-electrical power conversion; and one or more processors configured to influence operation of the system based on (a) changes in return optical power and (b) a determination of whether, based on the measure of the return optical power, the changes in optical power are indicative of one or more defined events of: (i) obstacle intrusion or (ii) beam misalignment or realignment, or (iii) both.

[0011] In embodiments, the measure of return optical power includes a measure of temporally resolved optical power, and the determination of whether the changes in optical power are indicative of the one or more defined events includes a first recursive detection of obstacle intrusion and a second recursive detection of beam misalignment. The first recursive detection may recur at a rate greater than that of the second recursive detection. The first recursive detection may recur at a rate at least 10 times that of the second recursive detection.

[0012] In embodiments, the measure of return optical power includes a measure of spatially resolved optical power. The determination may be based on presence or absence of spatially abrupt or uneven changes in the return optical power. The influenced operation of the system may include a first action responsive to the absence of spatially abrupt or uneven changes in the return optical power. The absence of spatially abrupt or uneven changes in return optical power may correspond to misalignment or realignment of the transmitted optical beam towards the power receiver, and the first action includes steering adjustment of the transmitted optical beam towards the power receiver. The steering adjustment may include iterative steering adjustment based on increasing the return optical power. The iterative steeringadjustment may include maximising the return optical power by way of gradient ascent. The iterative steering adjustment may include iterations of steering adjustment at no less than 10 kHz. The power transmitter may include beam steering optics to facilitate the steering adjustment of the transmitted optical beam. The beam steering optics may include a piezoelectric-actuated reflector. The piezoelectric-actuated reflector may be configured to steer the transmitted optical beam with angular resolution of less than or equal to 1 rad, preferably less than or equal to 0.2 rad. The influenced operation may include a second action responsive to the presence of spatially abrupt or uneven changes in the return optical power. The presence of spatially abrupt or uneven changes in return optical power nay correspond to obstacle intrusion of the transmitted optical beam, and the second action includes cessation of light transmission at the power transmitter.

[0013] Also described is a method of operating a power beaming system, the system including: a power transmitter including a photodetector assembly configured to provide a measure of return optical power, a power receiver, and one or more processors, the method including: transmitting, by the power transmitter, an optical beam, the optical beam including a first constituent beam at a first wavelength and a second constituent beam at a second wavelength, distinct from the first wavelength; returning, by the power receiver, at least part of the first constituent beam to the photodetector assembly at the power transmitter and receive the second constituent beam for optical-to-electrical power conversion; and influencing, by the one or more processors, operation of the system based on (a) changes in return optical power and (b) a determination of whether, based on the measure of the return optical power, the changes in optical power are indicative of one or more defined events of: (i) obstacle intrusion, (ii) beam misalignment, and (iii) both obstacle intrusion and beam misalignment. The measure of return optical power may include a measure of temporally resolved optical power, and the determination of whether the changes in optical power are indicative of the one or more defined events may include a first recursive detection of obstacle intrusion and a second recursive detection of beam misalignment. Alternatively, the measure of return optical power may include a measure of spatially resolved optical power. The determination may be based on presence or absence of spatially abrupt or uneven changes in the return optical power.

[0014] Also described are embodiments of a power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam at a first wavelength and a second constituent beam at a second wavelength,distinct from the first wavelength, the power transmitter including a photodetector assembly; a power receiver configured to receive the optical beam for optical-to-electrical power conversion, the power receiver including a plurality of reflectors that are: (i) positioned to intercept respective spatial portions of the first constituent beam and avoid at least a substantial portion of the second constituent beam; and (ii) configured to return the respective spatial portions of the first constituent beam to the power transmitter for receipt by the photodetector assembly, and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter.

[0015] In embodiments, the plurality of the reflectors are further configured to cause each returned spatial portion of the first constituent beam to at least partially overlap with at least a neighbouring returned spatial portion. The partial overlap nay occur at at least 5% of peak intensity, preferably at at least 10% of peak intensity, more preferably at at least 20% of peak intensity, and even more preferably at at least 50% of peak intensity. The photodetector assembly may be a single photodetector assembly configured to detect at least two returned spatial portions. The power transmitter may include a beam combiner for combining the first constituent beam with the second constituent beam to form an aggregate beam. The plurality of reflectors may be unevenly spaced to facilitate determination of pose of the power receiver. The power beaming system may further include one or more spacer positions to unevenly space the plurality of reflectors. The power beaming system, wherein the one or more spacer position each may include an optical signal emitter to emit an optical signal for receipt by the photodetector assembly at the power transmitter. One or more of the plurality of reflectors may each be a dichroic reflector configured to reflect light at the first wavelength and pass through light at the second wavelength. The dichroic reflector may be positioned to pass through a circumferential portion of the second constituent beam

[0016] Also described are embodiments of a power beaming system including: (a) a power transmitter configured to transmit an outgoing optical beam, the outgoing optical beam including light at a first wavelength and light at a second wavelength, distinct from the first wavelength, (b) a power receiver configured to receive the outgoing optical beam, the power receiver including a wavelength discriminator configured to return the transmitted light at the first wavelength in an incoming beam for receipt by the power transmitter, and to accept the transmitted light at the second wavelength for the optical-to-electrical power conversion, and(c) one or more processors configured to influence operation of the system based on the return light received at the power transmitter.

[0017] In embodiments, the wavelength discriminator includes a dichroic retroreflector. Referring to FIG. 2, the dichroic retroreflector may be configured to retroreflect substantially the transmitted light at the first wavelength back to the power transmitter, and to pass through substantially the transmitted light at the second wavelength. The dichroic retroreflector may include a dichroic comer cube reflector.

[0018] In embodiments, the influenced operation of the system includes at least partial cessation of light transmission by the power transmitter based on a first predetermined condition of the return light received at the power transmitter. The first predetermined condition may include defined changes in the return light received at the power transmitter, such as non-receipt or reduction of the return light. The at least partial cessation of light transmission may include cessation of light transmission at the second wavelength. Alternatively or additionally the at least partial cessation of light transmission may include cessation of light transmission at the first wavelength.

[0019] Alternatively or additionally, the influenced operation of the system includes commencement of transmission of light at the second wavelength, based on a second predetermined condition of the return light received at the power transmitter. The second predetermined condition may be maximised return light at the first wavelength received at the power transmitter.

[0020] In embodiments, the system includes a photovoltaic assembly configured to convert optical power contained in the transmitted light at the second wavelength to electrical power.

[0021] In embodiments, the outgoing optical beam includes a first constituent beam including the light at the first wavelength and a second constituent beam, distinct from the first constituent beam, including the light at the second wavelength. The first constituent beam may be axially aligned with the second constituent beam, and may have a larger beam diameter than the second constituent beam along at least a portion of the axially aligned constituent beams. The first constituent beam may have a larger beam diameter than the second constituent beam along all portion of the axially aligned constituent beams. For example, the first constituent beam has an at least 1.5 times larger beam diameter than the second constituent beam. Asanother example, the first constituent beam has an at least 2 times larger beam diameter than the second constituent beam. In yet another example, the first constituent beam has an at least 2.5 times larger beam diameter than the second constituent beam. In still yet another example, the first constituent beam has an at least 3 times larger beam diameter than the second constituent beam.

[0022] In embodiments, the system includes an optical combiner configured to combine the first constituent beam with the second constituent beam to provide the outgoing optical beam. The optical combiner may include at least one or more of the following: a beam splitter, dichroic mirror, a wavelength-division multiplexer.

[0023] In embodiments, the system includes beam shaping optics for beam shaping the outgoing optical beam. The beam shaping optics may include a first set of optics for beam shaping the first constituent beam, and a second set of optics for beam shaping the second constituent beam. The beam shaping optics may include one or more beam expanders to increase a beam diameter of any one or more of the following: the outgoing optical beam, the first constituent beam, and the second constituent beam. The beam shaping optics may include one or more converging optics to converge the outgoing optical beam.

[0024] In embodiments, the system includes one or more laser sources to generate the light at the first wavelength and the light at the second wavelength. The one or more laser sources source may comprise two laser sources, one for each of the first wavelength and the second wavelength. The first wavelength may be within an eye-safe wavelength band. The eye-safe wavelength band may be centred around 1550nm. The second wavelength may be within an atmospherically least absorptive wavelength band. The atmospherically least absorptive wavelength band may be centred around 1080nm.

[0025] Also described are embodiments of a method of operating a power beaming system, the method including the steps of: (a) transmitting, by a power transmitter, an optical beam, the optical beam including light at a first wavelength and light at a second wavelength, distinct from the first wavelength; (b) receiving, by a power receiver including a wavelength discriminator, the optical beam; (c) returning, by the power receiver, the transmitted light at the first wavelength for receipt by the power transmitter; (d) accepting, by the power receiver, the transmitted light at the second wavelength for optical-to-electrical power conversion; and (e)influencing, by one or more processors, operation of the power transmitter based on the return light received at the power transmitter.

[0026] Also described are embodiments of a power beaming initialisation method, the method including the steps of: (a) at a power transmitter, transmitting a first constituent beam including light at a first wavelength; (b) at a power receiver, via a wavelength discriminator, returning the transmitted light at the first wavelength for receipt at the power transmitter; (c) at the power transmitter, based on and subsequent to receipt of return light at the first wavelength, transmitting a second constituent beam including light at a second wavelength, distinct from the first wavelength; and (d) at the power receiver, via the wavelength discriminator, accepting the transmitted light at the second wavelength for optical- to-electrical power conversion.

[0027] In embodiments, the step of transmitting the second constituent beam including light at the second wavelength includes continuing transmission of the first constituent beam including light at the first wavelength. The method may further include the step of, at the power transmitter, ceasing light transmission at the second wavelength responsive to non-receipt or reduction of the return light at the first wavelength receiving at the power transmitter.

[0028] Also described are embodiments of a power beaming interlock method, the method including the steps of: (a) at a power transmitter, transmitting an optical beam including light at a first wavelength and light at a second wavelength, distinct from the first wavelength; (b) at a power receiver, via a wavelength discriminator, returning the transmitted light at the first wavelength for receipt by the power transmitter, and accepting the transmitted light at the second wavelength for optical-to-electrical power conversion; and (c) at the power transmitter, responsive to a predetermined condition of the return light at the first wavelength received at the power transmitter, ceasing light transmission at the second wavelength. The predetermined condition may include non-receipt or reduction of the return light at the first wavelength receiving at the power transmitter.

[0029] Also described are embodiments of a power beaming system like those described in paragraph

[0012]

[0014] or paragraph

[0016] but from the perspective of the power transmitter. These embodiments relate to a power transmitter of a power beaming system.

[0030] Also described are embodiments of a power beaming system like those described in paragraph

[0012]

[0014] or paragraph

[0016] but from the perspective of the power receiver. These embodiments relate to a power receiver of a power beaming system, power beaming system including a power transmitter configured to transmit an outgoing optical beam for receipt by the power receiver, the outgoing optical beam including light at a first wavelength and light at a second wavelength, distinct from the first wavelength, the power receiver including a wavelength discriminator configured to return the transmitted light at the first wavelength in an incoming beam for receipt by the power transmitter, and to accept the transmitted light at the second wavelength for the optical-to-electrical power conversion.

[0031] Also described are embodiments of a power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius Rl and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is AR = R1 - R2 (in metres), the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P (in metres); a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to-electrical power conversion; and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tailored based on (AR- ) / S, such that the allowed or allowable duration Tailored is greater than or equal to an actual duration to undertake the influenced operation.

[0032] In embodiments, the influenced operation includes extinguishment of the power transmitter. The extinguishment of the power transmitter may include reducing output power of the power transmitter to zero. The power transmitter and the power receiver may be separated by a separation distance D and the allowed or allowable duration T based on (AR- ) / S increases as the separation distance D increases. AR may increase as the separation distance D increases. The first beam radius Rl may increase as the separation distance D increases. The first beam radius Rl may increase at a faster rate than R2 increases as the separation distance D increases. The maximum allowable speed S may be less than or equal to 20 m / s. The second beam radius R2 may be quantified based on maximum permissibleexposure. The maximum permissible exposure may be 90 W / m2. The separation distance D may be less than or equal to 400 metres.

[0033] In embodiments, the one or more processors may further be configured to sample an output of the photodetector at a sampling frequency f related to a sampling interval AT= lf and wherein the allowed or allowable duration Tallowed is additionally based on AZ. The allowed or allowable duration Tallowed may be based on (AR-P) / S - T.

[0034] Also described are embodiments of a method of assessing a power beaming system, the power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius Rl and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is R = Rl - R2 (in metres), the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by P (in metres); a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to- electrical power conversion; and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tallowed based on (AR-P) / S, the method including the step of: determining whether an actual duration Tactual to undertake an influenced operation is less than or equal to the allowed or allowable duration Tallowed.

[0035] Also described are embodiments of a method of configuring or reconfiguring a power beaming system, the power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius Rl and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is AR = Rl -R2 (in metres), the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P (in metres); a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent opticalbeam for optical-to-electrical power conversion; and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tailored based on (AR- ) / S, the method including the steps of: determining whether an actual duration Tactual to undertake an influenced operation is less than or equal to the allowed or allowable duration Tailored,' and if it is determined that the actual duration Tactual to undertake the influenced operation is greater than the allowed or allowable duration Tallowed, configuring or reconfiguring operational parameters of the power beaming system such that the actual duration Tactual to undertake the influenced operation is less than or equal to the allowed or allowable duration Tallowed-

[0036] Also described are embodiments of a method of configuring or reconfiguring a power beaming system, the power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius R1 and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is AR = R1 - R2 (in metres), the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P (in metres); a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to-electrical power conversion; and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tailored based on (AR- ) / S, the method including the step of: configuring or reconfiguring operational parameters of the power beaming system such that the actual duration Tactual to undertake the influenced operation is less than or equal to the allowed or allowable duration Tailored.

[0037] In embodiments, the influenced operation may include extinguishment of the power transmitter of the power beaming system. The extinguishment may last for an extinguishment duration based on the laser decay time. The influenced operation may include defined direction of an output of the power transmitter. The defined direction may be based on mechanical direction.

[0038] As used herein, unless context requires otherwise, the words “comprise”,“comprises”, “comprising” and their variations are intended to be interpreted in the inclusive sense, rather than the exhaustive sense.

[0039] As used herein, the terms “first”, “second” and so forth are used to distinguish one entity from another and are not used to indicate or require any particular sequencing, in time, position or otherwise. For example, “a first wavelength and a second wavelength” has the same meaning as “a wavelength and another wavelength”.

[0040] As used herein, “light” and “optical beam” each refer to electromagnetic radiation having optical frequencies, including far-infrared radiation, infrared radiation, visible radiation and ultraviolet radiation.

[0041] As used herein, “intensity” and “power” when referring to light or an optical beam are interchangeable terms unless the context requires otherwise.

[0042] As used herein a designation of a view or orientation, for instance a top view, a side view, horizontal or vertical is arbitrary for the purposes of illustration and does not suggest any required orientation.

[0043] When an element is referred to as being "connected" or "coupled" to or with another element, or when an element is referred to as “receiving” or “providing” a signal or light from or to another element, using those or words of the same or similar meaning, unless the context requires otherwise, the element can be directly connected or coupled to the other element, or intervening elements may be present. In other words, the element is not necessary directly connected or coupled to the other element without any intervening elements.

[0044] Further aspects of the present disclosure and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings. It should be understood that the following description and accompanying drawings are not intended to limit the disclosure to the particular form disclosed.BRIEF DESCRIPTION OF THE FIGURES

[0045] FIGs. lA(i) and (ii) are block diagrams each illustrating a power beaming system, according to embodiments of the present disclosure.

[0046] FIG. IB is a pictorial diagram illustrating a power beaming system, according to another embodiment of the present disclosure.

[0047] FIG. 1C is a pictorial diagram illustrating a power beaming system, according to yet another embodiment of the present disclosure.

[0048] FIGs. 2A and 2B display a front view and a perspective rear view, respectively, of an example of a retroreflector.

[0049] FIG. 2C displays a front view of an example of an annulus of retroreflectors.

[0050] FIGs. 2D-2F are block diagrams each illustrating a power transmitter having a photodetector assembly.

[0051] FIG. 2G(a)-(c) illustrates various examples of photodetector arrays. FIG 2G(d) illustrate an example of directional information and intensity information associated with the embodiment illustrated in FIG. 2G(c).

[0052] FIGs. 3A and 3B illustrate staggered monitoring time windows and nonstaggered monitoring time windows for monitoring photocurrent output.

[0053] FIG. 4A is a collection of diagrams illustrating a spatial buffer provided by a safety beam around a power beam, according to still yet another embodiment of the present disclosure.

[0054] FIG. 4B is a collection of diagrams illustrating an obstacle intruding the spatial buffer of FIG. 4 A.

[0055] FIG. 4C is a collection of diagrams illustrating a spatial buffer provided by a safety beam around a power beam, according to an alternative embodiment of the present disclosure.

[0056] FIG. 4D is a collection of diagrams illustrating an obstacle intruding the spatial buffer of FIG. 4C.

[0057] FIG. 4E is a collection of diagrams illustrating a spatial buffer provided by a safety beam around a power beam, according to yet an alternative embodiment of the present disclosure.

[0058] FIG. 4F is a collection of diagrams illustrating an obstacle intruding the spatial buffer of FIG. 4E.

[0059] FIG. 4G(a) to (f) is a collection of intensity plots illustrating reflected portions of the outgoing optical beam by the annulus of retroreflectors of FIG. 2C at increasing return distance.

[0060] FIG. 5 is a flowchart illustrating a power beaming safety method, according to some embodiments of the present disclosure.

[0061] FIG. 6 is a flowchart illustrating a power beaming initialization method, according to some embodiments of the present disclosure.

[0062] FIG. 7 is a flowchart illustrating a power beaming interlock method, according to some embodiments of the present disclosure.

[0063] FIG. 8A is a flowchart illustrating a method of determining safety of a power beaming system, according to some embodiments of the present disclosure.

[0064] FIGs. 8B and 8C are flowcharts illustrating methods of configuring or reconfiguring a power beaming system, according to some embodiments of the present disclosure.DETAILED DESCRIPTION

[0065] FIGs. lA(i) and (ii) are block diagrams that depict power beaming systems 10-1 and 10-2 (hereinafter power beaming system 10), according to embodiments of the present disclosure. FIG. IB is a pictorial diagram that depicts another power beaming system 100, according to another embodiment of the present disclosure. Like elements of FIGS. 1A and IB are labelled with like references. The power beaming system 10, 100 includes a power transmitter 11, 110 configured to transmit an outgoing optical beam 135 A including light at a first wavelength and light at a second wavelength. The light at a first wavelength may be contained in a first constituent beam of the outgoing optical beam 135 A. Similarly the light ata second wavelength may be contained in a second constituent beam of the outgoing optical beam 135 A. In contexts, a constituent beam may be understood to mean an optical beam with spatial coherence, such as an optical beam emitted from a single laser. An optical beam with spatial coherence allows its properties, such as beam propagation or intensity distribution in the far field, to be simulated, predicted or otherwise estimated. In some embodiments, the first wavelength may be within an eye-safe wavelength band, for example centred around 1550 nm. The second wavelength may be within an atmospherically least absorptive wavelength band, for example within the spectral region of 700 to 1150 nm, such as around 1080 nm. In embodiments, most optical power is contained in the atmospherically least absorptive wavelength band (e.g. at or around 1080 nm) for power delivery by the optical transmitter 11, 110. In contrast, optical power in the eye-safe wavelength band (e.g. at 1550 nm) is limited, by design. In some embodiments, the power transmitter 11, 110 is ground-based or stationary.

[0066] In the embodiment of FIGS. 1A and IB, the power beaming system 10, 100 also includes a power receiver 12, 120 for receiving the outgoing optical beam 135A. In some implementations, as illustrated in FIG. lA(i), the power receiver 12, 120 further includes a wavelength discriminator 13 configured to return the transmitted light at the first wavelength in an incoming optical beam 135B for receipt by the power transmitter 11, 110. The wavelength discriminator 13 is also configured to accept the transmitted light at the second wavelength for optical -to-electrical power conversion. In other implementations, as illustrated in FIG. 1 A(ii), the power receiver 12, 120 includes, instead of or in addition to the wavelength discriminator, a plurality of reflectors 16 that are configured to return respective spatial portions of the first constituent beam to the power transmitter 11, 110. The reflectors are positioned to avoid the second constituent beam to be received by the power receiver 12, 120 for optical -to-electrical power conversion. In some embodiments, the power receiver 12, 120 is airborne or mobile, for example installed on an aircraft. In use, the power receiver 12, 120 may be moving at a speed of at least 1 m / s, or in some cases at least 5 m / s, or in other cases at least 10 m / s.

[0067] Herein, the labels “outgoing” and “incoming” optical beams are used from the perspective of the system 10, 100, and coincides with the perspective of the optical transmitter 11, 110. Unless the context requires otherwise, for consistency purposes, the same labels remain even if the description is from the perspective of the power receiver 12, 120 or otherwise of the power beaming system 10, 100. That is, an “outgoing” optical beam is associated with an optical beam propagating from the optical transmitter towards the optical receiver 12, 120.Similarly, an “incoming” optical beam is associated with an optical beam propagating from the optical receiver 12, 120 towards the optical transmitter 11, 110.

[0068] For clarity purposes, in FIG. IB, the outgoing optical beam 135A and the incoming optical beam 135B are depicted as offset light paths. The depicted offset is however not representative of the actual light paths. In practice, the outgoing optical beam 135 A and the incoming optical beam 135B may overlap substantially in space.

[0069] In some embodiments, the power receiver 12, 120 include one or more reflectors, such as retroreflectors. One or more or the one or more retroreflectors may each include a dichroic retroreflector. . To return light at the first wavelength, the retroreflector(s) may be configured to retroreflect substantially the transmitted light at the first wavelength back to the power transmitter 11, 110. Use of a retroreflector allows for a wider acceptance angle for the outgoing beam 135 A, 135C and still re-directs the incoming beam 135B, 135D back at the power transmitter 11, 110. FIGs. 2A and 2B display a front view and a perspective rear view, respectively, of an example of a retroreflector 200. Referring to FIG. 2A, the retroreflector 200 includes a corner cube reflector 202. The corner cube reflector 202 may be constructed with three surfaces 202A, 202B, 202C. For simplicity, description and features of outgoing beam 135 A is equally applicable, with no or minor modifications, to outgoing beam 135C. Similarly, description and features of incoming beam 135B is equally applicable, with no or minor modifications, to outgoing beam 135D.

[0070] Referring to FIG. 2B, which illustrates the embodiment with a wavelength discriminator 13, the retroreflector 200 may be adjustably mounted for alignment with the outgoing beam 135A. For example, the retroreflector 200 is gimbal-mounted. The retroreflector 200 may be operatively coupled with a gimbal 204. For the embodiment with a plurality of reflectors 16 (not shown), the reflector holder securing the plurality of reflectors 16 may be gimbal -mounted. In either embodiment, the gimbal 204 may in turn be operatively coupled with a mounting assembly 206 for support. The gimbal 204 may be adjusted in two dimensions, for example, in its azimuth angle and / or its elevation angle. Gimbal adjustment may be beneficial in improving the acceptance angle of the retroreflector 200. In some embodiments, the gimbal 204 is dynamically adjusted by the power receiver 120. The power receiver 120 may be configured to adjust the azimuth angle and / or the elevation angle based on received optical power of the transmitted light. The power receiver 120 may be configured to be gimballed towards the power transmitter 110, for example within a defined angle, suchas less than 4 degrees, or preferably less than 2 degrees, or more preferably less than 1 degree, or even more preferably less than 0.5 degree. For example, the angle may be dynamically adjusted (e.g. to be dynamically corrected within the defined angle) by maximising the received optical power of the transmitted light. The received optical power may be measured by way of an optical splitter (e.g. 99 / 1 splitter) followed by a photodetector assembly (e.g. one or more photodetectors). An output of the photodetector assembly may be provided to one or more processors or microcontrollers for determining the received optical power. The one or more processors or microcontrollers may be configured to determine a target azimuth angle and / or a target elevation angle based on kinematic GPS data (such as real-time kinematic of RTK GPS data. As a result, deviations in amount of return signal may be confined within 0.2%, or preferably within 0.1%, or more preferably within 0.05%.

[0071] In embodiments with the wavelength discriminator 13, as depicted in FIG. 2B, the retroreflector 200 may be a dichroic retroreflector. To accept light at the second wavelength, the dichroic retroreflector may be additionally configured to pass through substantially the transmitted light at the second wavelength. In embodiments with the plurality of reflectors 16, as depicted in FIG. 2C, the plurality of reflectors may form an annulus of reflectors, such as a ring of retroreflectors 260. Each retroreflector 260 may be in the form of a retroreflector, such as the corner cube reflector 202. The annular positioning of the reflectors 16 avoids intercepting at least a substantial portion the second constituent beam. Instead, the annular positioning allows the second constituent beam to pass unimpeded or almost unimpeded through the inner open area of the ring. One or more of the reflectors 16 may each include a dichroic reflector, such as a dichroic retroreflector. Each dichroic reflector may be configured to reflect light at the first wavelength and pass through light at the second wavelength. The dichroic reflector(s) may be positioned to pass through one or more circumferential portions of the second constituent beam. The power receiver 12, 120 may include one or more beam stoppers or absorbers located behind the one or more dichroic reflectors. The beam stopper(s) or absorber(s) are configured to stop or absorb the second constituent beam. While circumferential portions of an optical beam carry less optical energy than other portions of the optical beam, they still carry some optical energy. By stopping absorbing any energy contained in the circumferential portions of the second constituent beam, stray light or unwanted reflections may be reduced. Further, the reflectors 16 in the annular position are configured to intercept different portions of the first constituent beam and reflect the intercepted portions back to the power transmitter 11, 110 for detection by the one or more photodetectors.

[0072] In either of these embodiments, the surfaces of the retroreflector may be optically coated (e.g. double-coated) to provide dichroic properties. For example, the surfaces may be optically coated to provide at least 90% reflectivity, preferably at least 95% reflectivity and more preferably at least 98.5% reflectivity, at the first wavelength. Alternatively or additionally, the surfaces may be optically coated to provide at most 1% reflectivity, preferably at most 0.5% reflectivity and more preferably at most 0.4% reflectivity, at the second wavelength. Where the wavelength discriminator includes a dichroic comer cube reflector, the effective reflectivity at the second wavelength after reflection off its three surfaces is the cube of its surface reflectivity. For example, if the surface reflectivity at the second wavelength is at most 1%, then the effective reflectivity is (1%)A3 = 0.0001%. As an another example, if the surface reflectivity at the second wavelength is at most 0.4%, then the effective reflectivity is (0.4%)A3 = 0.0000064%. Use of a corner cube reflector therefore enhances safety by dramatically reducing the reflected power of the power beam towards the power transmitter.

[0073] In embodiments, the power beaming system 10, 100 further includes a photovoltaic (PV) assembly configured to convert optical power contained in the transmitted light at the second wavelength to electrical power. The PV assembly may include one or more PV cells. The one or more PV cells may be selected to be absorptive, ideally most absorptive, to the wavelength in which the optical power is contained. For example, if the wavelength of light accepted by the wavelength discriminator 13 for optical -to-electrical power conversion purposes is 1080 nm, then PV cell(s) with absorption spectrum that peaks at or near a 1080 nm band is / are selected. For example, the PV cells may correspond to III-IV semiconductor alloy whose band-gap is tuned to have activation energy near 1080 nm photons. The converted power may be used to power a power-consuming apparatus, such as an aerial vehicle 150, on which the power receiver 12, 120 may be supported or installed. Alternatively or additionally, the converted power may be used to recharge a power storage device, such as a battery on the aerial vehicle 150, on which the power receiver 12, 120 is supported or installed. In the embodiments with the annulus of reflectors 16, the PV assembly may be positioned within or substantially within the inner open area.

[0074] For aerial vehicles, such as drones or electric aircrafts, power provision may be achieved by way of installing a power receiver 12, 120 on such an aerial vehicle and charging it or its battery in-flight from a ground-based optical transmitter 11, 110 via a group- to-air optical beam 135 A. The present disclosure may provide added safeguards to a power beaming system that provides wireless energy to, and hence extending the inherent range of, such aerial vehicles.

[0075] The power beaming system 10, 100 further includes one or more processors14, 140 configured to influence operation of the system 10, 100 based on the return light. The one or more processors 14, 140 are operatively coupled to the power transmitter 11, 110. The one or more processors 14, 140 may be collocated with, part of, or remote from the power transmitter 11, 100. The one or more processors 14, 140 may include a controller, such as a micro-controller, for controlling one or more operations of the system 10, 100. The one or more processors 14, 140 may take the form of a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC). The one or more processors 14, 140 may include or be operatively coupled to a memory, such as volatile or non-volatile memory, for storing data or instructions. Where the memory store processor-readable instructions, the processor- readable instructions may be adapted to control the one or more operations of the system 10, 100 or any of its components, such as the power transmitter 11, 110, and / or the power receiver 12, 120.

[0076] To receive the return light, the power transmitter 11, 110 may include a photodetector assembly 207, as depicted in FIGs. 2D-2F. The photodetector assembly 207 includes one or more photodetectors (e.g. photodiodes). Each photodetector provides a photocurrent output responsive to a light input. The power transmitter 11, 110 may include an emitter assembly 230, including one or more emitters, to emit the outgoing optical beam 135 A for at least partial return by the power receiver 12, 120 in the incoming optical beam 135B for detection by the photodetector assembly 207. Each emitter may be configured to emit light of a designated wavelength. For example, the emitter assembly 230 may include a first emitter configured to emit light at the first wavelength and a second emitter configured to emit light at the second wavelength. The first emitter and / or the second emitter may each be a single emitter emitting a single constituent optical beam. The single constituent optical beam may have a designated intensity profile, such as a Gaussian intensity profile or a flat-top intensity profile. The emitter assembly 230 may include an optical combiner to combine the emitted light at the different wavelengths to form the outgoing optical beam 135 A.

[0077] In an embodiment, as depicted in FIG. 2D, the photodetector assembly 207 includes a single photodetector 208. In another embodiment, as depicted in FIG. 2E, the photodetector assembly 207 includes a photodetector array 210 (e.g. a photodiode array). In yet another embodiment, as depicted in Fig. 2F, the photodetector assembly 207 includes both a single photodetector 208 and a photodetector array 210. The photodetector assembly 207 mayinclude a beam splitter 214, such as a 50 / 50 splitter, to separate the incoming optical beam 135B into two portions, one for each of the single photodetector 208 and a photodetector array 210. Each of the one or more photodetectors may be configured to provide a measure of temporally-resolved optical power. That is, the one or more photodetectors may be responsive to, and thereby detect, changes in optical power over time. Correspondingly, the one of more processors 14, 140 may be configured to sample the detected changes in optical power over time at a sufficiently fast sampling rate(s). In these embodiments, the single photodetector 208 may be configured to provide a measure of the overall optical power. The photodetector array 210 may also be configured to provide a measure of the overall optical power, for example by summing, or applying a weighted sum or a linear combination of, the individual photocurrent values from respective photodiodes. Additionally or alternatively, the photodetector array 210 may be configured to provide a measure of spatially-resolved optical power. The measure of spatially-resolved optical power provides the optical beam profile over one or two dimensions. The optical beam profile may be indicative of intensity as a function of orthogonal axes (e.g. x-axis and y-axis, or radial-axis and angular-axis). The photodetector array 210 may be in the form of a beam profiler, a digital or analogue camera, a charge-coupled device (CCD) array, an image sensor, or otherwise an array of spatially arranged photodetectors.

[0078] Where the outgoing optical beam 135 A is in alignment or near-alignment with the power receiver 12, 120, the photodetector array 210 is configured to receive at least part of the incoming optical beam 135B on return to provide a measure of spatially-resolved return optical power. The measure of spatially-resolved return optical power may include directional information and intensity information characterising the incoming optical beam 135B. The directional information and intensity information may be a paired set of information. FIG. 2G(d) illustrates an example of a paired set of information 250 in tabular form, indicative of a measure of spatially resolved optical power detected by the photodetector array 204c illustrated in FIG. 2G(c), as further described below.

[0079] In this example, the paired set of information 250 includes 8 pairs of directional information 252 and intensity information 254. The intensity information 254 may be in arbitrary units (a.u.). The directional information 252 is in polar coordinates (r, 9) in the units of mm and degrees. As illustrated, the first four items of the paired set of directional information 252 and intensity information 254 correspond to the four detectors arranged in an inner (e.g. innermost) ring of photodetector array 204c. The last four items of the paired set ofdirectional information 252 and intensity information 254 correspond to the four detectors arranged in an outer (e.g. outermost) ring of photodetector array 204c. In other examples (not shown), the photodetector array may further include one or more intervening rings in between an innermost ring and an outermost ring. In the first four items, the intensity information 254 indicates the spatially resolved optical power is evenly distributed. Similarly, in the last four items, the intensity information 254 indicates the spatially resolved optical power is evenly distributed, but reduced to about a quarter compared to the spatially resolved optical power in the first four items. The intensity information 254 may be based on the photocurrent outputs of the photodetector array 210. For example, the intensity information includes one or more photocurrent values indicative of the amount of light input collected by respective one or more photodetectors of the photodetector array 210. The photocurrent outputs may be representative of a one-dimensional or two-dimensional image of the incoming optical beam 135B. The directional information may be based on the positions of the photodetectors relative to one another in the array 210. The directional information may be fixed, such as the fixed relative positions of the photodetectors. For example, if the photodetectors are arranged in one dimension or linearly, the directional information may be indicative of photodetector positions along a linear axis (e.g. x-axis, y-axis or radial axis). If the photodetectors are arranged in two dimensions, the directional information may be indicative of photodetector positions in paired coordinates, such as cartesian coordinates along the x-axis and y-axis or polar coordinates along the radial axis and angular axis. The electronic circuitry 212 may include a memory for storing the directional information. The directional information may be accessible by the one or more processors 14, 140. In combination, the intensity information and the directional information is indicative of the intensity profile and the position of the incoming optical beam 135B. The position of the incoming optical beam 135B may be based on the location of the centre of the incoming optical beam 135B. The one or more processors 14, 140 may be configured to influence alignment of the outgoing optical beam 135 A and / or the incoming optical beam 135B based on the directional information and the intensity information.

[0080] In embodiments, the transmitter 11, 110 includes electronic circuitry 212, such as an optical sensor board, operatively coupled to the photodetector assembly 207. The electronic circuitry 212 may be part of, or separate from the one or more processors 14, 140. The electronic circuitry 212 may be configured to receive photocurrent outputs of the photodetector array 210. The electronic circuitry 207 may include analogue-to-digital converter (ADC) for sampling the photocurrent outputs to provide photocurrent values. The electroniccircuitry 212 may include gain circuitry to electronically amplify the sampled outputs of the photodetector array 210. The electronic circuitry 207 may be configured to provide feedback signals, based on the spatially resolved return optical power, to other components of system 10, 100.

[0081] In embodiments, the one or more processors 14, 140 includes a beam steering controller for controlling beam steering mechanisms, such as beam steering optics. The beam steering controller may be operatively coupled to the electronic circuitry 212. For example, the electronic circuitry 212 provides the feedback signals to beam steering controller. The feedback signals may include intensity information, such as the sampled outputs, amplified or unamplified, of the photodetector array 210. The feedback signals may further include directional information, such as the relative positions of the photodetectors in the array. The beam steering controller may be operatively coupled to mechanical actuation, such as piezoelectric reflectors, and configured to steer the optical beam 135 A based on the spatially resolved return optical power.

[0082] Further, the gain circuitry of the electronic circuitry 212 may include a gain control input configured to receive a gain control signal derived from the beam steering controller. The gain control input is configured to control the level of amplification of the gain circuitry based on the gain control signal. For example, if more than a first predetermined number of photodetectors in the array 210 (e.g. more than half) produce a photocurrent above a first threshold (e.g. 90% saturation), then the gain control signal may be associated with decreasing the amplification level of the gain circuitry. Alternatively and additionally, if more than a second predetermined number of photodetectors in the array 210 (e.g. more than a third) produce a photocurrent below a second threshold (e.g. 20% saturation), then the gain control signal may be associated with increasing the amplification level of the gain circuitry. The gain circuitry may be configured such that the level of amplification is repeatedly or iteratively adjusted. Repeated or iterative adjustment of the amplification level facilitates more accurate characterisation of the incoming optical beam 135B, thereby improving sensitivity and responsiveness of the safety system 10, 100.

[0083] Where the photodetector array is representative of a two-dimensional image, the photodetectors of the array may be arranged in a matrix pattern of rows and columns of photodetectors, such as being evenly spaced along both the x-axis and the y-axis. Alternatively, the photodetectors of the array may be arranged in an annular or ring-like pattern, such as beingspaced along the radial-axis and the angular-axis. FIG. 2G illustrates examples of the photodetector arrays 240a, 240b, 240c in annular patterns. Each photodetector is represented by a circle in solid line indicating its photosensitive area. The underlying annular pattern is represented by one or more dashed lines. In some embodiments, an annular pattern may include a single ring. In other embodiments, an annular pattern may include multiple rings, such as an inner ring and an outer ring, such as concentric inner and outer rings. For example, as illustrated in FIG. 2G(a), the array 240a of photodetectors 241 includes photodetectors arranged in an outer ring 242 and photodetectors 241 arranged in an inner ring 244. Photodetectors arranged in one or two dimensions, such as in a matrix or annular pattern, allows for measuring or estimating alignment or misalignment of the outgoing and / or incoming optical beams 135 A, 135B. In other examples (not shown), the array of photodetectors may further include one or more intervening rings of photodetectors in between an inner ring and an outer ring. It is expected that fewer photodetectors are required to provide equivalent level of alignment information if the photodetectors are arranged in an annular pattern than in a matrix pattern.

[0084] As foreshadowed above, alignment or re-alignment of the outgoing and / or incoming optical beams 135 A, 135B may be based on the return optical power, such as the spatially resolved or temporally resolved return optical power. In embodiments, the electronic circuitry 212 provides sampled outputs of the photodetector array 210 to the beam steering controller of the one or more processors 14, 140. The beam steering controller may be further operatively coupled to mechanical actuation, such as piezoelectric reflectors, and configured to steer the optical beam 135 A based on the directional information and the intensity information.

[0085] In the case of proper beam alignment, annularly arranged (being directional information) photodetectors are expected to detect evenly distributed optical power (being intensity information) around one or more of its one or more rings. The even distribution of return optical power over annularly arranged photodetectors is due to rotational symmetry of an optical beam, such as a Gaussian beam or flat-top beam. Further, for annular patterns that have an inner ring and an outer ring, higher optical power is expected to be detected in the inner ring than the outer ring.

[0086] Conversely, in the case of beam misalignment, the annularly arranged photodetectors are expected to detect unevenly distributed optical power around one or more of its one or more rings. The uneven distribution of return optical power is due to an off-centredincoming optical beam. Further, for annular patterns having an inner ring and an outer ring, higher optical power may in some cases be detected in the outer ring than in the inner ring. A higher return optical power detected in the outer ring indicates that the outgoing optical beam 135 A is sufficiently misaligned that the beam centre coincides more with the outer ring than with the inner ring.

[0087] The one or more processors 14, 140 may be configured to facilitate optical beam alignment or re-alignment based on a weighted sum of the photocurrent outputs. For example, one or more processors 14, 140 may be configured to apply a linear combination of the photocurrent values. Alternatively or additionally, the one or more processors 14, 140 may be configured to apply a neural network to facilitate optical beam alignment or re-alignment. The neural network may include one or more input nodes based on the spatially-resolved return optical power. The neural network may include one or more output nodes to estimate a position of the optical incoming beam 135B. Alternatively or additionally, position estimation may be useful where there is a limited number of photodetectors in the photodetector array 210, or otherwise it is difficult to accurately define the beam centre based on beam intensity profile. The one or more processors 14, 140 may be configured to facilitate alignment or re-alignment of the outgoing optical beam 135 A based on the estimated position of the incoming optical beam 135B. For example, the beam steering controller may mechanically actuate the beam steering optics to adjust the angle of the outgoing optical beam 135 A until the incoming optical beam 135B is estimated to be centred.

[0088] Arrangement of the photodetectors in each of an inner ring and an outer ring facilitates directional detection. The number of photodetectors in the outer ring 242 may equal the number of photodetectors in the inner ring 244. Alternatively, the number of photodetectors in the outer ring 242 may differ from the number of photodetectors in the inner ring 244. The number of photodetectors in each of the inner ring and the outer ring may range from 3 to 20 inclusive, preferably from 4 to 15 inclusive, more preferably from 5 to 10 inclusive. In the example of FIG. 2G(a), there are 8 photodetectors in each of the outer ring 242 and the inner ring 244. In the example of FIG. 2G(b), there are also 8 photodetectors in each of the outer ring and the inner ring, but compared to FIG. 2G(a), the photodetectors are arranged closer together to reduce the gaps between the active area. In the example of FIG. 2G(c), there are 4 photodetectors in each of the outer ring and the inner ring. In one or more examples, the photodetectors in each of the inner ring and outer ring are evenly spaced or arranged with acircular symmetry. For example, the photodetector arrangements depicted in FIGs. 2G(a) and (b) each have a 8-fold symmetry. The photodetector arrangement depicted in FIG. 2G(c) has a 4-fold symmetry. The photodetectors in the outer ring 242 may be arranged with an angular offset from the photodetectors in the outer ring 244. For example, as illustrated in FIG.2G(a), the outer ring 242 of 8 photodetectors 241 are angularly offset the inner ring 244 of 8 photodetectors 241 by 360 / 8 / 2 = 22.5 degrees. Alternatively, the photodetectors in the outer ring 242 may be arranged without any angular offset from the photodetectors in the outer ring 244. For example, as illustrated in FIG.2G(c), the outer ring of 4 photodetectors are aligned radially with the inner ring of 4 photodetectors.

[0089] The photocurrent output may be provided to the one or more processors 14,140, for example, for monitoring the photocurrent output. The response of one or more the photodetectors is proportional to, or at least monotonically correlated to, the amount of light input. For example, a steady amount of the return light received by the power transmitter 11, 110 corresponds to a steady photocurrent. An increased amount of the return light corresponds to an increased photocurrent. Similarly, a reduced amount of the return light corresponds to a reduced photocurrent. Any change in the photocurrent output is indicative of the changes in the amount of the return light. Accordingly, based on the photocurrent, the one or more processors 14, 140 may be configured to determine any defined changes associated with changes in the return light. The one or more processors 14, 140 may be configured to influence operation of the power transmitter 11, 110 based on the changes in the return light. Further, the power transmitter 11, 110 may include a circulator. The circulator includes at least three ports or apertures: an input port or aperture, a bi-directional port or aperture and an output port or aperture. The input port or aperture may be optically coupled to the one or more laser sources for receiving outgoing light. The bidirectional port or aperture is optically coupled to air or free-space, for transmitting outgoing light and receiving return light. The output port or aperture is optically coupled to, and provide return light, to the one or more photodetectors.

[0090] In embodiments, the one or more processors 14, 140 are configured to sample the photocurrent output at a sampling interval. For example, the sampling interval is no greater than a 1 ms, or preferably no greater than 0.1 ms, or more preferably no greater than 0.02 ms. These sampling intervals correspond to, respectively, sampling frequencies of no less than 1 kHz, or preferably no less than 10 kHz, or more preferably no less than 50 kHz. Changes in the amount of return light may be due to atmospheric fluctuations, such as presence of dust,fog, cloud or other atmospheric particles. Such fluctuations are understood to vary in the order of milliseconds. As such, a sampling interval of no greater than 1-10 ms is considered suitable in filtering out most if not all atmospheric fluctuations. Further, the one or more processors 14, 140 are configured to determine that a predetermined condition occurs. For example, the one or more processors 14, 140 are configured to monitor for defined changes (e.g. defined percentage changes) in the sampled photocurrent output over a defined duration, such as a monitoring time window. For example, the monitoring time window is no more than 2 ms, preferably no more than 1 ms, or more preferably no more than 0.5 ms. The monitoring time window has a start time and an end time. In embodiments where the power transmitter 11, 110 includes a photodetector array, the photocurrent output includes multiple time series of photocurrent values, with each time series representing the light input of one pixel.

[0091] In some embodiments, the monitoring time window re-starts after each sampling interval. For example, referring to FIG. 3 A, at a sampling interval 302 of 0.1 ms, the one or more processors 14, 140 may monitor over a monitoring time window 300 A of 1 ms (i.e. from the 1stsampling point to the 10thsampling point) for changes in the photocurrent output 304. As the one or more processors 14, 140 completes sampling the next sample (i.e. the 11thsample 306A), the one or more processors 14, 140 may monitor over a monitoring time window 308A of the immediately preceding 1 ms (i.e. from the 2ndsampling point to the 11thsampling point) for changes in the photocurrent. Thereafter, the one or more processors 14, 140 completes sampling the next sample (i.e. the 12thsample), the one or more processors 14, 140 may monitor over a monitoring time window of the immediately preceding 1 ms (i.e. from the 3rdsampling point to the 12thsampling point) for changes in the photocurrent, and so on. Accordingly, in these embodiments, the successive monitoring time windows 300 A, 308 A are staggered. In alternative embodiments, the monitoring time window re-starts after the previous monitoring time window ends. Referring to FIG. 3B, and continuing with the example of a sampling interval 302 of 0.1 ms and a monitoring time window 300B of 1 ms, here, the one or more processors 14, 140 are configured to sample the next 10 samples (i.e. the 11thto 20thsamples) before re-starting the next monitoring time window 308B of 1 ms. Accordingly, in these alternative embodiments, the successive monitoring time windows are non-staggered. Use of staggered monitoring time windows allows for more regular monitoring, such as rolling mean received power. Conversely, use of non-staggered monitoring time windows lowers processor requirement. Further, the shorter the monitoring time window, the quicker the one or more processors 14, 140 may respond to influence operation of the system 10, 100, such asceasing transmission of the power transmitter 11, 110. In embodiments, consistent with the duration of the monitoring time window, the response time of the transmission cessation is no more than 2 ms, preferably no more than 1 ms, more preferably no more than 0.5 ms, or even more preferably no more than 0.25 ms.

[0092] In embodiments having the wavelength discriminator 13, because the wavelength discriminator 13 is configured to return light at the first wavelength and accept light at the second wavelength, the return light received at the power transmitter 11, 110, is mostly light at the first wavelength. For this reason, the one or more photodetectors of the power transmitter 11, 110 are selected to be sensitive to the first wavelength. For example, if the wavelength of light returned by the wavelength discriminator 13 for receipt by the power transmitter 11, 110 is at is 1550 nm, then photodetector(s) sensitive to a 1550 nm wavelength band is / are selected.

[0093] In embodiments, the influenced operation of the system 10, 100 includes adjusting direction of the outgoing beam 135A, 135C towards the power receiver 12, 120. The one or more processors 14, 140 may cause adjustment to the direction of the outgoing beam 135A, 135C based on changes in the return light. For example, the power transmitter 11, 110 may include a piezoelectric mirror to re-direct the outgoing beam 135 A, 135C. The one or more processors 14, 140 may cause actuation of the piezoelectric mirror based on changes in the return light. The one or more processors 14, 140 may determine an optimum direction of the outgoing beam 135 A, 135C by maximising the amount of return light, using, for example, a gradient ascent algorithm. Determining the optimum direction allows the power transmitter 11, 110 to direct the outgoing beam 135A, 135C towards the power receiver 12, 120. Where the power receiver 12, 120 is moving, the determination may be repeated regularly to track the moving power receiver 12, 120.

[0094] In embodiments, the influenced operation of the system 10, 100 includes at least partial cessation of light transmission by the power transmitter 11, 110. Cessation of light transmission, even partially, may reduce potential harm caused by an intense optical beam. In other embodiments, the influenced operation of the system 10, 100 may include full cessation of light transmission by the power transmitter 11, 110. The at least partial cessation of light transmission may be based on a predetermined condition, such as non-receipt or reduction, of the return light received at the power transmitter 11, 110. For example, the one or more processors 14, 140 may monitor the return light (e.g. its intensity or power) by monitoring thephotodetector current output. Upon determining that the received return light deviates from the predetermined condition, the one or more processors 14, 140 may influence operation of the system 10, 100. Light transmission may be ceased at the second wavelength. Light transmission may continue at the first wavelength. Alternatively light transmission may be ceased at both the first wavelength and the second wavelength. To cease light transmission, the one or more processors 14, 140 may cause actuation of a solid state relay that switches the power transmitter 11, 110. The actuation may be based on amplitude-shift keying, however other modulation methods may also be used. Further, the actuation may be based on triple modular redundancy to improve fault-tolerance of the transmission cessation. The solid state relay allows rapid cessation in transmission of the power transmitter 11, 110. In embodiments, the cessation of transmission occurs within no more than 2 ms, preferably no more than 1 ms, more preferably no more than 0.5 ms, and even more preferably no more than 0.25 ms.

[0095] In embodiments, the predetermined condition is one or more defined power changes. Power changes may be as a result of any one or more of: an obstacle intruding the optical beam path, the outgoing beam deviating from or not fully received by the power receiver, the outgoing beam not fully returned by the power receiver, and the incoming beam deviating from or not fully received by the power transmitter. A defined power change may be presented as a defined percentage change, such as at least 0.5%, at least 1%, at least 1.5%, or at least 2%. The defined power change may be measured relative to one or more defined power levels. In some embodiments, the defined power level includes the average received power of the return light measured during any monitoring time window (e.g. rolling mean received power for staggered monitoring time windows). For example, the one or more processors 14, 140 may determine whether or not there is a defined percentage change from the average received power. Alternatively or additionally, the defined power level includes the range of power of the return light measured during the monitoring time window. For example, the one or more processors 14, 140 may determine whether or not there is a defined percentage change in the range of return power. Still alternatively or additionally, the defined power level is based on telemetric information. For example, the system 10, 100 is configured to obtain and reconcile telemetric information, such as power reception telemetry data and / or kinematic GPS data (such as realtime kinematic of RTK GPS data), with the photodetector output. The system 10, 100 may determine whether or not there is a defined percentage discrepancy between the telemetric information and photodetector output.

[0096] FIG. 1C is a pictorial diagram that depicts yet another power beaming system 102, according to yet another embodiment of the present disclosure. The power beaming system 102 of FIG. 1C is similar to the power beaming system 100 of FIG. IB. Identical and like elements of FIGS. IB and 1C are labelled with identical and like references, respectively. The power beaming system 102 is different from the power beaming system 100 in that the former includes a second power transmitter 112, also operatively coupled to the one or more processors 140. The second power transmitter 112, like the (first) power transmitter 110, is configured to transmit an outgoing optical beam 135C including light at the first wavelength and light at the second wavelength. Upon receiving the outgoing optical beam 135C by the power receiver 120, the wavelength discriminator 13 is configured to return the transmitted light at the first wavelength in an incoming optical beam 135D to the second power transmitter 112, and accept the transmitted light at the second wavelength for optical-to-electrical power conversion.

[0097] While FIG. 1C depicts two outgoing beams 135 A and 135C, in practice, at least in some embodiments, only one of the two outgoing beams is active. In other words, where the power beaming system has multiple power transmitters, hence multiple outgoing beams, the power receiver may be configured to receive only one of the multiple outgoing beams at a time. For example, in FIG. 1C, the dichroic retroreflector of the power receiver 120 is gimbal mounted. The gimbal-mounted dichroic retroreflector may be controllably adjusted, for example in its azimuth angle and / or elevation angle for alignment with the desired power transmitter, such as power transmitter 112, instead of power transmitter 110.

[0098] In this embodiment, the same set of one or more processors 140 are configured to also influence operation of the second optical transmitter 112. In an alternative embodiment, a different set of one or more processors (not shown) is configured to also influence operation of the second optical transmitter 112. Regardless, the multiple power transmitters, including at least the first power transmitter 110 and the second power transmitter 112, may form a network of power transmitters that are remote from one another. Each power transmitter in the network of power transmitters may cover a respective zone of ground area or air space. By locating the network of power transmitters in accordance with the respective zones of ground area or air space, for example slightly overlapping neighbouring zones, the network of power transmitters may extend the range of power delivery or charging by way of installing morepower transmitters. The wavelength discriminator 13 has a limited angle of acceptance, which in turn limits the separation of between neighbouring power transmitters in the network.

[0099] Referring to FIGs. 4A-4F, in some embodiments, the outgoing optical beam 135 A, 135C includes a first constituent beam 404 including the light at the first wavelength and a second constituent beam 402, distinct from the first constituent beam 404, including the light at the second wavelength. The first constituent beam may be referred herein to as the “safety beam”, whereas the second constituent beam may be referred herein to as the “power beam”. It shall become apparent that the safety beam is intended for safety purposes, whereas the power beam is intended for power delivery purposes. The safety beam may contain optical power in the order of 1 W, whereas the power beam may contain optical power in the order of 2 kW. The first wavelength may be an eye-safe wavelength, for example within the 1550 nm wavelength band. The second wavelength may be an atmospherically less or least absorptive wavelength, for example within the 1080 nm wavelength band.

[0100] FIGs. 4A-4F illustrate examples of the respective beam widths of the safety beam 404 and the power beam 402, in both the outgoing beam 135 A, 135C and incoming the beam 135B, 135D. FIGs. 4A-4D correspond to embodiments with a wavelength discriminator 13, such as that in FIG. lA(i), whereas FIGs. 4E and 4F correspond to embodiments with a plurality of reflectors 16, such as that in FIG. lA(ii). Subsets (a) and (b) plots their intensity profile over radial distance x and / or y at two different propagating distances, one at around the beam waist, where Gaussian-profile coherent light (M2factor of 1) converges to the narrowest beam width, and another away from the beam waist, close to or at the power transmitter. Also plotted in subsets (a) and (b) are the contour plots of their full-widths at half maximum (FWHM). Subset (c) plots their FWHM over propagating distance z.

[0101] In FIGs. 4A-4F, beam waist locations for the safety beam 404 and the power beam 402 are depicted to be the same. In practice, the beam waist location may be different. The beam waist location may be dependent on, and / or adjusted by, beam divergence 0 = k / %w0, which scales directly proportionally with wavelength A. and inversely proportionally with beam waist wO. In this example, the wavelengths of the safety beam and the power beam are selected to be approximately 1550 nm and approximately 1080 nm, that is a ratio of approximately 1.5 to 1. Accordingly, as will be further described below, a safety beam size of around 1.5 times, for example between 1.2 times and 2 times, of a power beam size will result in similar divergence and beam waist locations for the safety beam 404 and the power beam 402. Thesafety beam 404 may be approximately 50 mm in diameter (FWHM), such as between 25 mm and 100 mm. For example, at their beam waists, where the power beam 402 is approximately 50 mm in diameter (FWHM), the safety beam 404 is approximately 60 to 100 mm in diameter (FWHM). As another example, at their beam waists, where the power beam 402 is approximately 100 mm in diameter (FWHM), the safety beam 404 is approximately 120 to 200 mm in diameter (FWHM). As yet another example, at their beam waists, where the power beam 402 is approximately 25 mm in diameter (FWHM), the safety beam 404 is approximately 30 to 50 mm in diameter (FWHM). Because of beam divergence, the safety beam 404 and the power beam 402 will expand in size away from their beam waists. The beam size of the safety beam 404 and the power beam 402 away from their beam waists may be between 1.1 and 4 times the beam waist, or between 1.5 to 3.5 times the beam waist, or between 2 and 3 times their respective beam waist. The beam sizes exemplified in absolute terms are for illustrative purposes only, and are not intended to limit the scope of the present disclosure.

[0102] In some embodiments, as illustrated in FIGs. 4A and 4B, the power transmitter110, 112 is configured to converge the outgoing beam 135A, 135C, at least initially. The outgoing beam 135A, 135C is converged to a beam waist and then diverges in an opposite manner. In the illustrated scenario of FIG. 4A, the power receiver 120 is located at a target maximum range of the power beaming system 100, 102. The target maximum range may be in the vicinity of one to a few hundred meters, such as no less than 100 m, no less than 200m, or no less than 400 m. In this scenario, the power receiver 120 coincides with, or coincides approximately with, the beam waist of outgoing beam 135A, 135C. Upon return by the power receiver 120, the incoming beam 135B, 135D diverges towards the power transmitter 110, 112. Here, the outgoing beam 135 A, 135C converges and the incoming beam 135B, 135D diverges in an opposite manner. The beam width of incoming beam 135B, 135D received at the power transmitter 110, 112 is approximately the same as the beam width of the outgoing beam 135A, 135C transmitted at the power transmitter 110, 112.

[0103] In another scenario (not shown), where the power receiver 120 is located closer than the target maximum range, the outgoing beam 135 A, 135C is still converging when received by the power receiver 120. Upon return by the power receiver 120, the incoming beam 135B, 135D continues to converge, at least initially, towards the power transmitter 110, 112. The beam width of incoming beam 135B, 135D received at the power transmitter 110,112 is smaller than the beam width of the outgoing beam 135A, 135C transmitted at the power transmitter 110, 112.

[0104] In alternative embodiments, as illustrated in FIGs. 4C and 4D, the power transmitter 110, 112 is configured to diverge the outgoing beam 135A, 135C, at least initially. Identical and like elements between FIGs. 4A and 4B and FIGs. 4C and 4D are labelled with identical and like references, respectively. In this scenario, the power transmitter 110, 112 coincides with, or coincides approximately with, the beam waist of outgoing beam 135A, 135C. Upon return by the power receiver 120, the incoming beam 135B, 135D is converged towards the power transmitter 110, 112. For example, the power receiver 120 may include converging optics to converge the incoming beam 135B, 135D. The converging optics may include one or more lenses, such as focussing lens(es) and / or de-focussing lens(es). Here, the outgoing beam 135 A, 135C diverges and the incoming beam 135B, 135D converges in an opposite manner. The beam width of incoming beam 135B, 135D received at the power transmitter 110, 112 is approximately the same as the beam width of the outgoing beam 135 A, 135C transmitted at the power transmitter 110, 112. In some cases, the converging optics may be dynamically adjusted. For example, the dynamic adjustment may be to adjust the beam convergence of the incoming beam 135B, 135D such that the beam waist coincides or approximately coincide with the power transmitter 110, 112. Adjustment to the beam convergence may be based on the beam width of the outgoing beam 135A, 135C received at the power receiver 120, 122. For example, a greater received beam width at the power receiver 120, 122 corresponds to an adjustment of a greater convergence. The adjustment of the beam convergence may be by way of re-positioning of the one or more lenses, such as by mechanical actuation (e.g. one or more stepper motors). The adjustment of the beam convergence allows for dynamic re-focussing of the incoming beam 135B, 135D. Alternatively or additionally, the adjustment of the beam convergence may be way of controlling one or more fluidic adaptive lenses, such as based on pressure actuation, using for example one or more pressure actuators.

[0105] In yet alternative embodiments, as illustrated in FIGs. 4E and 4F, the power transmitter 110, 112, as in the embodiment in FIGs. 4A and 4B, is configured to converge the outgoing beam 135 A, 135C, at least initially. Identical and like elements between FIGs. 4A and 4B and FIGs. 4E and 4F are labelled with identical and like references, respectively. Unlike the embodiment in FIGs. 4A and 4B, the incoming beam 135B, 135D of the embodiment in FIGs. 4E and 4F includes multiple beamlets. These beamlets correspond to the intercepted andreturned spatial portions of the first constituent beam. Further, as the returned spatial portions propagate over distance, each returned spatial portion may become at least partially overlap with at least a neighbouring returned spatial portion. The at least partial overlap extends in the radial direction, and continues over the axial direction. The at least partial overlap may be caused by divergence of individual beamlets (as depicted by the flare-like patterns in FIG. 4E) or steering the multiple beamlets to become closer together (as depicted by a progressively smaller diameter of the incoming beam in FIG. 4G), or both. FIGs. 4G(a) to (e) illustrate, in another embodiment, intensity plots of the incoming beam 135B, 135D at increasing distances (specifically at 0, 100, 200, 300 and 400 metres, respectively) from the power receiver 12, 120. As illustrated, the at least partial overlap causes the incoming beam 135B, 135D to exhibit an anuular intensity profile.

[0106] In embodiments of FIGs. 4E and 4F, the partial overlap my occur at at least5% of peak intensity, preferably at at least 10% of peak intensity, more preferably at at least 20% of peak intensity, and even more preferably at at least 50% of peak intensity. As depicted in FIG. 4G, neighbouring returned spatial portions at least partially overlap to form a ring-like beam profile. Such a beam profile reduces the gaps between the beamlets to avoid masking obstacle intrusion, especially small obstacles that might otherwise hide between the beamlets. Further, by steering the multiple beamlets to become closer together, the overall diameter of the incoming beam 135B, 135D becomes smaller. This allows the photodetector assembly 207 to consist of a single photodetector array configured to detect at least two returned spatial portions, such as adjacent returned spatial portions. Accordingly a single photodetector array may possibly detect all returned spatial portions.

[0107] In embodiments of FIGs. 4E and 4F, the power transmitter 11, 110 includes a beam combiner for combining the first constituent beam with the second constituent beam to form an aggregate beam. In embodiments, the transmitted optical beam is symmetric and includes an intensity gradience suited to a gradient ascent algorithm. For example, the radial intensity of the transmitted optical beam decreases monotonically, such as in a Gaussian intensity profile. Alternatively or additionally, the radial intensity changes gradually, rather than abruptly. In embodiments, the plurality of reflectors 16 are positioned with at least partial rotational asymmetry to facilitate determination of a pose of the power receiver 12, 120. The plurality of reflectors 16 may be secured in position by a reflector holder 261. For example, as illustrated in FIG. 2C, the reflectors 16 may be unevenly spaced at or around one or more spacerpositions 262. Each spacer position 262 may correspond to an absence of a reflector 16. The one or more processors 14, 140 may be configured to determine a pose of the power receiver 12, 120 based on a lack of return optical power at one or more spatial directions. For example, as illustrated in FIG. 4G(c), the return optical power upon spatially resolved exhibits gaps 440, 442, 444 corresponding to the spacer positions 262. Based on the angular position of the gaps 440, 442, 444 along the annular intensity profile, the pose of the power receiver 12, 12 may be determined. Additionally, each spacer position 262 may include an optical signal emitter, such as a LED, to emit an optical signal for receipt by the photodetector assembly at the power transmitter. The emitted optical signal may act as a pilot signal for the power transmitter 11, 110 to locate the power receiver 12, 120 in the absence of any incoming beam 135B, 135D.

[0108] In embodiments, the safety beam 404 may be axially aligned with the power beam 402, as shown in subsets (a) and (b) of FIGs. 4A-4F. For example, the safety beam 404 and the power beam 402 may share, along at least a portion of either beam, a common optic axis 405. Alternatively, the safety beam 404 may be axially mis-aligned with the power beam 402. The safety beam 404 may have, or may be configured to have, a larger beam diameter than the power beam 402 along at least a portion of the constituent beams 404, 402, whether axially aligned or axially mis-aligned. For example, the safety beam 404 has a larger beam diameter than the power beam 402 along all portion of the constituent beams 404, 402. The safety beam 404 and power beam 402 may each have circular beam shape, as illustrated in FIGs. 4A-4D. Alternatively, the safety beam 404 and power beam 402 may each have a beam shape other than circular, such as elliptical (not shown). In case of an elliptical beam shape, the diameter of the safety beam may be larger than that of the power beam in both axes.

[0109] The safety beam 404, having a larger diameter than the power beam 402, provides a spatial buffer 406 around the power beam 402. The spatial buffer 406 allows for detection of obstacle intrusion into the light path of the outgoing beam 135 A, 135C before breaching the power beam 402. Referring to FIGs. 4B 4D and 4E, corresponding to the scenario in FIGs. 4A,4C and 4E, respectively, where an obstacle 408 (e.g. a bird, dust cloud, an aircraft) enters the light path of outgoing beam 135 A, 135C, the obstacle 408 first enters the light path of the safety beam 404, before potentially entering the light path of the power beam 402. The initial entry of the obstacle 408 into the light path of the safety beam 404 allows the present power beaming system to react before the obstacle 408 makes entry (or further entry) into the light path of the power beam 402.

[0110] Where an obstacle at least partially blocked the outgoing beam 135 A, 135C, a shadow region 410 is created. The shadow region 410 corresponds to periphery of the safety beam 404. The blocked periphery of the safety beam 404 in turn corresponds to a decrease in power of the safety beam 404 upon return. Therefore, light at the first wavelength reaching the power receiver 120 and returned to the power transmitter 110 is at least reduced or at worst not received. The decrease in return power of the safety beam 404 is such that the decrease is detectable by the photodetector. The one or more processors 14, 140 are configured to determine a defined change, such as a defined percentage change over a defined duration, in return power of the safety beam 404, based on detection by the photodetector. Accordingly, based on reduction or non-receipt of the return light received at the power transmitter (e.g. the one that is active in providing power), the one or more processors 140 may influence operation of the present power beaming system, such as ceasing light transmission of the power transmitter to address obstacle intrusion.[OHl] In some cases, the shadow region 410 additionally corresponds to periphery of the power beam 402. However, any peripheral power being blocked in the power beam 402 is designed to be negligible or lower than required by safety standards. For example, the spatial buffer 406 may be adjusted in size to contain the peripheral power blockage in the power beam 402. For a given a detectable decrease in the power of the safety beam 404, a larger spatial buffer 406 corresponds to a smaller (hence safer) peripheral power blockage in the power beam 402.

[0112] In embodiments, the size of the spatial buffer 406 may be adjusted based on tolerance of obstacle intrusion. A larger spatial buffer 406 allows for more sensitive detection of obstacle intrusion. In other words, A larger spatial buffer 406 allows for a larger shadow region 410 (or a smaller periphery) before the power beam 402 is, or is significantly, breached. However the size of the spatial buffer 406 may be limited by the numerical aperture of the power receiver and / or sensitivity of the photodetector.

[0113] To adjust the size of the spatial buffer 406, the system 10, 100, 112 may include beam shaping optics for beam shaping the optical beam. Beam shape may include any one or more of: beam size, beam diameter, and beam ellipticity. Beam size is a measure of the area occupied by an optical beam. Beam diameter is a measure of the transverse extent of the optical beam in one or both longitudinal dimensions (e.g. x and / or y). Beam ellipticity is the ratio of the radial extent between the longitudinal dimensions (e.g. x and y) of the optical beam. Eachof beam size, beam diameter and beam ellipticity may be quantified based on the full-width at half maximum (FWHM). Further, beam shape of the two constituent beams may be separately adjustable. To separately adjust the beam shape for the two constituent beams, the beam shaping optics may include a first set of optics for beam shaping the first constituent beam, and a second set of optics for beam shaping the second constituent beam. The beam shapes may be adjustable by adjusting relative positions of optical elements of the beam shaping optics. The relative positions of the optical elements may be adjustable by way of mechanical actuation, for example, by one or more stepper motors. For example, the beam shaping optics includes one or more beam expanders or compressors to increase a beam diameter. A beam expander or compressor includes two converging lenses, longitudinally separated based on a desired magnification factor. The longitudinal separation may be adjusted by way of the above- mentioned mechanical actuation. As another example, the beam shaping optics includes one or more beam ellipticity adjustors. A beam ellipticity adjustor includes the same of different set of two converging lenses, axially offset by a defined offset based on desired ellipticity. The axial offset may be adjusted by way of the above-mentioned mechanical actuation.

[0114] As mentioned, the one or more processors 14, 140 are configured to determine any changes in the return light, for example changes in the amount of return light. In the following examples, it is assumed that the one or more processors 14, 140 are configured to determine that there is a 1% drop in safety beam power detected by the photodetector:

[0115] As a first example, the safety beam may have an at least 1.25 times larger beam diameter than the power beam. In this case, assuming that the power and safety beams are axially aligned and having a Gaussian beam profile with l / eA2 half-widths of G and more than 1 ,25s, respectively, the safety beam power will drop by 1% if an obstacle intrudes within about 2.9 Is of the centre of the aligned beams, at which point the power beam power will drop by less than 0.18%, which may be absorbed by the obstacle and / or scattered to the surroundings.

[0116] As a second example, the safety beam may have an at least 1.5 times larger beam diameter than the power beam. In this case, assuming that the power and safety beams are axially aligned and having a Gaussian beam profile with l / eA2 half-widths of G and more than 1.5c, respectively, the safety beam power will drop by 1% if an obstacle intrudes within about 3.49G of the centre of the aligned beams, at which point the power beam power will drop by less than 0.024%, which may be absorbed by the obstacle and / or scattered to the surroundings.

[0117] As a third example, the safety beam may have an at least 1.75 times larger beam diameter than the power beam. In this case, assuming that the power and safety beams are axially aligned and having a Gaussian beam profile with l / eA2 half-widths of c and more than 1.75o, respectively, the safety beam power will drop by 1% if an obstacle intrudes within about 4.07o of the centre of the aligned beams, at which point the power beam power will drop by less than 0.00235%, which may be absorbed by the obstacle and / or scattered to the surroundings.

[0118] As a fourth example, the safety beam may have an at least 2 times larger beam diameter than the power beam. In this case, assuming that the power and safety beams are axially aligned and having a Gaussian beam profile with l / eA2 half-widths of s and more than 2o, respectively, the safety beam power will drop by 1% if an obstacle intrudes within about 4.65o of the centre of the aligned beams, at which point the power beam power will drop by less than 0.00016%, which may be absorbed by the obstacle and / or scattered to the surroundings.

[0119] As a fifth example, the safety beam may have an at least 2.25 times larger beam diameter than the power beam. In this case, assuming that the power and safety beams are axially aligned and having a Gaussian beam profile with l / eA2 half -widths of s and more than 2.25o, respectively, the safety beam power will drop by 1% if an obstacle intrudes within about 5.23 o of the centre of the aligned beams, at which point the power beam power will drop by less than 0.0000084%, which may be absorbed by the obstacle and / or scattered to the surroundings.

[0120] As a sixth example, the safety beam may have an at least 2.5 times larger beam diameter than the power beam. In this case, assuming that the power and safety beams are axially aligned and having a Gaussian beam profile with l / eA2 half -widths of s and more than 2.5o, respectively, the safety beam power will drop by 1% if an obstacle intrudes within about 5.82o of the centre of the aligned beams, at which point the power beam power will drop by less than 0.000000295%, which may be absorbed by the obstacle and / or scattered to the surroundings.

[0121] As a seventh example, the safety beam may have an at least 3 times larger beam diameter than the power beam. In this case, assuming that the power and safety beams are axially aligned and having a Gaussian beam profile with l / eA2 half -widths of s and morethan 3o, respectively, the safety beam power will drop by 1% if an obstacle intrudes within about 9.3o of the centre of the aligned beams, at which point the power beam power will drop by a negligible amount.

[0122] The power transmitter 11, 110, 112 may include a multi -wavelength source to generate light at the first wavelength and light at the second wavelength. Alternatively, where a multi -wavelength source at the desired first and second wavelengths is unavailable, the power transmitter 11, 110, 112 may include one or more laser sources to generate the light at the first wavelength and the light at the second wavelength. For example, the one or more laser sources source comprises two laser sources, one for each of the first wavelength and the second wavelength. In embodiments with the one or more laser sources, the system 10, 100, 102 includes an optical combiner configured to combine the first constituent beam at the first wavelength with the second constituent beam at the second wavelength to provide the outgoing optical beam 135 A, 135C. The optical combiner may include one of the following: a beam splitter, dichroic mirror, a wavelength-division multiplexer.

[0123] Another aspect of the present disclosure relates to responding to, such as disambiguating between the needs for, different actions responsive to changes in return optical power. Since changes in photocurrent output can be indicative of one or more different defined events, such as either or both of obstacle intrusion and misalignment of outgoing optical beam 135A, 135C to the power receiver 12, 120, any ambiguity may misdirect the one or more processors 14, 140 as to what appropriate action is to be taken. The one or more processors 14, 140 may be configured to influence operation of the system 10, 100 based on (a) changes in return optical power and (b) a determination of whether, based on the measure of the return optical power, the changes are indicative of (i) obstacle intrusion or (ii) beam misalignment or (iii) both. The measure of return optical power may include a measure of spatially-resolved optical power, such as that measured by an array of photodetectors. Alternatively or additionally, the measure of return optical power may include a measure of temporally-resolved optical power, such as an optical power over time, examples of which are illustrated in FIGs. 3 A and 3B.

[0124] In the case of an obstacle intruding the outgoing optical beam 135 A, 135C, the return optical power may exhibit spatially abrupt or spatially uneven changes. As illustrated in FIG. 4G(f), a solid object intrusion causes a spatially abrupt drop 450 in return optical power, due to a shadow region 460 being created by the solid object. Similarly, atmospheric intrusion,such as rain, snow or fog may cause spatially uneven changes in return optical power, due to random particulate scattering. Conversely, in the case of beam misalignment, the return optical power may exhibit a lack of such spatially abrupt or spatially uneven changes. Instead, the return optical power may exhibit spatially smooth or even changes. For example, due to beam misalignment, the return optical power may evenly decrease across the cross section of the incoming beam 135B, 135D. Accordingly, the determination of whether the changes in return optical power are indicative of obstacle intrusion and / or beam misalignment may be based on presence or absence of spatially abrupt or uneven changes in the return optical power.

[0125] In the case of temporally resolved return optical power, the determination may include a first recursive detection of obstacle intrusion and a second recursive detection of beam misalignment. A recursive detection includes repeated attempts to detect a defined event. In embodiments, a defined event includes a detectable condition that requires or benefits from a corrective or otherwise responsive action to be taken. Examples of a defined event include any one or more of: obstacle intrusion and beam misalignment. The recursive detection, upon detection of a defined event, triggers a detection alert. The detection alert may be in the form of an electric signal. A recursive detection may be implemented as an algorithmic “loop” in the instructions executed by the one or more processors 14, 140. The rate difference between the two recursive detection may be based on the severity of the potential consequence associated with the respective defined events. For example, the potential consequence of obstacle intrusion (e.g. laser-induced damage) can be more catastrophic than the potential consequence of beam misalignment (e.g. reduced delivered power). In some embodiments, the first recursive detection recurs at a greater rate than the second recursive detection. However, in other embodiments, the first recursive detection may recur at a lower rate than the second recursive detection. The first recursive detection may recur at at least 2, at least 5, at least 10 or at least 20 times greater rate than the second recursive detection. Generally, the first recursive detection of obstacle intrusion may recur at 10-100 kHz, whereas the second recursive detection of beam misalignment may recur at 1-10 kHz. For example, where the first recursive detection of obstacle intrusion recurs at 10 kHz or above, the second recursive detection of beam misalignment may recur at 1 kHz. As another example, the first recursive detection of obstacle intrusion may recur at 100 kHz, whereas the second recursive detection of beam misalignment may recur at 10 kHz or lower.

[0126] In embodiments, the influenced operation of the system may include a first action responsive to the absence of spatially abrupt or uneven changes in the return optical power. The absence of spatially abrupt or uneven changes in return optical power may correspond to misalignment of the transmitted optical beam towards the power receiver. The first action may include realignment or steering adjustment of the transmitted optical beam towards the power receiver. Realignment may include adjusting direction of the outgoing beam 135A, 135C towards the power receiver 12, 120. The one or more processors 14, 140 may cause adjustment to the direction of the outgoing beam 135 A, 135C based on changes in the return light. For example, the power transmitter 11, 110 may include a piezoelectric mirror to re-direct the outgoing beam 135A, 135C. The one or more processors 14, 140 may cause actuation of the piezoelectric mirror based on changes in the return light. The one or more processors 14, 140 may determine an optimum direction of the outgoing beam 135A, 135C by maximising the return optical power, using, for example, a gradient ascent algorithm. Determining the optimum direction allows the power transmitter 11, 110 to direct the outgoing beam 135A, 135C towards the power receiver 12, 120.

[0127] Where the power receiver 12, 120 is moving, the determination may be repeated regularly to track the moving power receiver 12, 120. The steering adjustment may include iterative steering adjustment based on increasing the return optical power. For example, the iterative steering adjustment may include maximising the return optical power by way of a gradient ascent algorithm. In some instances, the iterative steering adjustment includes iterations of steering adjustment at no less than 10 kHz.

[0128] In embodiments, the power transmitter 11, 110 includes beam steering optics to facilitate the steering adjustment of the transmitted optical beam. The beam steering optics may include a piezoelectric-actuated reflector. The piezoelectric-actuated reflector may be configured to steer the transmitted optical beam with angular resolution of less than or equal to 1 rad, preferably less than or equal to 0.2 rad. In one embodiment, the beam steering optics are configured to receive the outgoing optical beam 135 A following or subsequent to combination of the first and second constituent. For example, the beam steering optics may be positioned downstream in the outgoing beam direction from the optical combiner or beam combiner. In this embodiment, an adjustment to the beam steering optics simultaneously adjusts steering of both the first constituent beam and the second constituent beam. Such a simultaneous adjustment allows relative alignment between the first constituent beam and the secondconstituent beam to be maintained. In another embodiment, the beam steering optics are configured to receive the outgoing optical beam 135 A before or prior to combination of the first and second constituent. For example, the beam steering optics may be positioned upstream in the outgoing beam direction from the optical combiner or beam combiner. In this embodiment, there may be more flexibility to individually adjust the first and second constituent.

[0129] In embodiments, the influenced operation of the system may include a second action responsive to the presence of spatially abrupt or uneven changes in the return optical power. The presence of spatially abrupt or uneven changes in return optical power may correspond to obstacle intrusion of the transmitted optical beam. The second action may include cessation of light transmission at the power transmitter.

[0130] Another aspect of the present disclosure relates to a power beaming system configured with a defined set of operational parameters, such as in accordance with a defined standard. In embodiments, this aspect of disclosure provides for a power beaming system with sufficient spatial buffer 406 to deem the system safe. A related aspect of the present disclosure relates to assessing a power beaming system in accordance with a defined set of operational parameters, such as a defined standard. In embodiments, this related aspect provides for a method of determining safety of a power beaming system, such as assessing whether there is sufficient spatial buffer 406 to deem the system safe. Other corresponding aspects of the present disclosure relate to methods of configuring and / or reconfiguring a power beaming system, such as configuration or reconfiguration that provides sufficient spatial buffer 406 to, for example, deem the system safe or adhering to a defined standard. The defined standard may be a standard in the field of power beaming. Such a system may include a power transmitter 11, 110 configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius R1 and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is AR = Rl - R2 (in metres). In some cases, the power transmitter includes a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P (in metres). The system may further include a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to-electrical power conversion. In some embodiments, the power transmitter is stationary while the power receiver is movable. In some other embodiments, the power transmitter is movable while the power receiver is stationary. In yet some other embodiments, both the power transmitter and the power receiver are movable. The system may further include one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tallowed derived from (AR-P) / S.

[0131] In some cases, the one or more processors 14, 140 are further configured to sample an output of the photodetector at a sampling frequency related to a sampling interval T= / f. In these cases, the allowed or allowable duration Tailored may additionally be based on AZ. AZ represents the longest possible duration between an obstacle intrusion event and commencement of the influenced operation. Accordingly, as the worst-case scenario, the allowed or allowable duration may be shortened by AZ. In other words, the allowed or allowable duration Tailored may be based on (AR-P) / S - AZ.

[0132] FIG. 8A illustrates a method 800 of assessing a power beaming system. The power beaming system may include a set of operational parameters as defined above. The assessment method 800 may be used to determine safety of the power beaming system and / or its compliance in accordance with a standard, such as a power beaming standard. As illustrated in FIG. 8A, the method 800 includes the step 802 of determining whether an actual duration Tactual to undertake an influenced operation is less than or equal to the allowed or allowable duration Tailored. The allowed or allowable duration Tailored may be derived as above. The influenced operation may include extinguishment of a power transmitter of the power beaming system.

[0133] In embodiments, as illustrated in FIG. 8B, the method 825 of configuring and / or reconfiguring a power beaming system includes the step 802 of determining whether an actual duration Tactual to undertake an influenced operation is less than or equal to the allowed or allowable duration Tailored. The allowed or allowable duration Tailored may be derived as above. The influenced operation may include extinguishment of a power transmitter of the power beaming system. The method 825 may additionally include the step 804 of, if it is determined that the actual duration Tactual to undertake the influenced operation is greater than the allowed or allowable duration Tallowed, configuring or reconfiguring operational parameters of the power beaming system such that the actual duration Tactual to undertake the influenced operation is less than or equal to the allowed or allowable duration Tailored. In alternative embodiments, asillustrated in FIG. 8C, step 802 may be omitted. That is, a method 850 of configuring and / or reconfiguring a power beaming system may instead include the step 804 of, such as without determining that the actual duration Tactual to undertake the influenced operation is greater than the allowed or allowable duration Tallowed, configuring or reconfiguring operational parameters of the power beaming system such that the actual duration Tactual to undertake the influenced operation is less than or equal to the allowed or allowable duration Tailored. For example, it is determined that the actual duration Tactual to undertake the influenced operation is less than or equal to Tailored, then the power beaming system is deemed safe or adhering to a defined standard. Alternatively or additionally, this aspect of the present disclosure relates to a method of configuring or reconfiguring operational parameters of a power beaming system to facilitate operational safety. The operational parameters may include any one or more of Rl, R2, R, P, S, / and AT.

[0134] The power beaming system is deemed safe if, or is configured with operational parameters such that, the allowed or allowable duration Tallowed is greater than or equal to an actual duration Tactual to undertake the influenced operation. The influenced operation includes extinguishment of the power transmitter. The extinguishment may last for an extinguishment duration based on the laser decay time, such as equal to or at least the laser decay time. In some cases, the laser decay time may be approximately 0.1 ms, such as between 0.05 ms and 0.2 ms. Alternatively or additionally, the influenced operation may include defined direction of an output of the power transmitter, for example redirection to an internal beam stop or absorber. As another example, the defined direction may be based on mechanical direction such as actuation of a shutter or a reflective mirror. In particular, the influenced operation includes reducing output power of the power transmitter to zero within a defined time period.

[0135] For example, in a particular power beaming system, Rl = 49 mm, R2 = 12.5 mm, P = 20 mm, and S = 20 m / s, so that the allowed or allowable duration Tallowed to undertake the influenced operation can be derived from (A7?- ) / S, which is 0.85 ms, Further, if it is determined that the actual duration Tactual to undertake the influenced operation is 0.1 ms, the power beaming system is deemed safe. Here, Tallowed > Tactual so there is sufficient spatial buffer 406 for the system to facilitate safe operation. Alternatively, if it is determined that the actual duration Tactual to undertake the influenced operation is greater than Tallowed, then the power beaming system is configured or reconfigured by way of adjusting one or more defined operational parameters to facilitate operational safety. For example, if it is determined that theactual duration Tactual to undertake the influenced operation is 0.9 ms, Tailored < Tactual so there is insufficient spatial buffer 406 for the system to be deemed safe. The second beam radius of the second constituent beam R2 may be increased until Tallowed AL Tactual-

[0136] In some instances, the power transmitter and the power receiver are separated by a separation distance D and the allowable duration Tailored based on (AR- ) / S can be increased as the separation distance D increases, for example when AR increases as the separation distance D increases. Alternatively or additionally, first beam radius R1 increases as the separation distance D increases. Still alternatively or additionally, the first beam radius R1 increases at a faster rate than R2 increases as the separation distance D increases. The operational parameters may further include D.

[0137] In embodiments, the maximum allowable speed S is less than or equal to 20 m / s. In these or alternative embodiments, the second beam radius R2 is based on maximum permissible exposure. For example, the maximum permissible exposure is 90 W / m2. In these or alternative embodiments, the separation distance / ) is less than or equal to 400 metres.

[0138] Described embodiments of the power beaming system according to the present disclosure are suited for implementing one or more power beaming methods, which will now be described. These power beaming methods are directed to the three distinct operating phases of the power beaming system: (a) a method 500 for operating a power beaming system, which relates to regular operations of the power beaming system, (b) an initialisation method 600 for a power beaming system, which relates to the initial operations of the power beaming system, and (c) an interlocking method 700 for a power beaming system, which relates to the interlocking operations of the power beaming system.

[0139] FIG. 5 is a flowchart that depicts a method 500 for operating a power beaming system, such as the power beaming system 10, 100, 102, according to some embodiments of the present disclosure. The method 500 corresponds to the power beaming system 10, 100, 102 operating under continuing conditions, such as in the midst of delivering wireless power. The method 500 includes the steps of: (a) transmitting 510, by a power transmitter, an optical beam, the optical beam including light at a first wavelength and light at a second wavelength, distinct from the first wavelength; (b) (i) receiving 520, by a power receiver including wavelength discriminator, the optical beam, (ii) returning 522 the transmitted light at the first wavelength for receipt by the power transmitter, and (iii) 524 accepting the transmitted light at the secondwavelength for optical-to-electrical power conversion; and (c) influencing 530 operation, by one or more processors, of a power beaming system, based on the return light received at the power transmitter.

[0140] The method 500 may include performing further steps or actions, in correspondence with the embodiments described in respect of the power beaming system 10, 100, 102. For example, where embodiments of the power beaming system are configured to cease transmission of light based on a predetermined condition, the power beaming safety method 500 may perform corresponding steps or actions, such as ceasing transmission of light based on the predetermined condition. As another example, where embodiments of the power beaming system are configured to provide a spatial buffer by way of a safety beam around a power beam, the power beaming safety method 500 may perform corresponding steps or actions, such as providing the spatial buffer by way of the safety beam around the power beam.

[0141] FIG. 6 is a flowchart that depicts an initialisation method 600 for operating a power beaming system, such as the power beaming system 10, 100, 102, according to some embodiments of the present disclosure. The initialisation method 600 corresponds to the power beaming system 10, 100, 102 operating initially, such as in the lead up to delivering wireless power.

[0142] The initialisation method 600 includes the steps of: (a) at a power transmitter, transmitting 610 a first constituent beam including light at a first wavelength; (b) at a power receiver, via a wavelength discriminator, returning 620 the transmitted light at the first wavelength for receipt at the power transmitter; (c) at the power transmitter, based on and subsequent to receipt of return light at the first wavelength, commencing 630 transmission of a second constituent beam including light at a second wavelength, distinct from the first wavelength; and (d) at the power receiver, via the wavelength discriminator, accepting 640 the transmitted light at the second wavelength for optical-to-electrical power conversion.

[0143] Before the step of transmitting a second constituent beam including light at a second wavelength, the initialisation method further includes the step of maximizing the receipt of return light at the first wavelength.

[0144] In embodiments, the step of transmitting the second constituent beam including light at the second wavelength includes continuing transmission of the first constituent beam including light at the first wavelength. The method may further include thestep of, at the power transmitter, ceasing light transmission at the second wavelength responsive to non-receipt or reduction of the return light at the first wavelength receiving at the power transmitter.

[0145] FIG. 7 is a flowchart that depicts an interlocking method 700 for a power beaming system, according to some embodiments of the present disclosure. The interlocking method 700 corresponds to the power beaming system 10, 100, 102 operating interruptedly, such as in the lead up to terminating wireless power delivery.

[0146] The method 700 includes the steps of: (a) at a power transmitter, transmitting710 an optical beam including light at a first wavelength and light at a second wavelength, distinct from the first wavelength; (b) at a power receiver, via a wavelength discriminator, returning 720 the transmitted light at the first wavelength for receipt by the power transmitter, and accepting the transmitted light at the second wavelength for optical-to-electrical power conversion; and (c) at the power transmitter, responsive to a predetermined condition of the return light at the first wavelength received at the power transmitter, 730 ceasing light transmission at the second wavelength. The predetermined condition may include non-receipt or reduction of the return light at the first wavelength receiving at the power transmitter.

[0147] Having now described various embodiments and examples of the present disclosure, it should be apparent that the power beaming systems and methods present the following advantages:• All-optical means of initialising and interlocking power delivery can avoid use of RF feedback, hence avoiding limitations in RF range and interception.• Upon initialisation of power beaming, the optical beam path can be determined as cleared even before power delivery is commenced.• During continuing operation of power beaming, an eye-safe safety beam can provide continuing assurance of a clear path.• If an obstacle intrudes the optical beam path, an interlocking procedure allows rapid shut-off of the optical transmitter, especially where a spatial buffer is provided to protect the power beam from intrusion.

[0148] Those skilled in the art will appreciate that the present disclosure described herein is susceptible to variations and modifications other than those specifically described. For example, parameters such as beam diameters, sampling intervals, and monitoring time window may assume values that are different from what are described or exemplified. All such variations and modifications are to be considered within the scope of the present disclosure the nature of which is to be determined from the foregoing description.

Claims

CLAIMS1. A power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius Rl and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is AR = Rl - R2 (in metres), the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P (in metres); a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to-electrical power conversion ;and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tailored based on (AR- ) / S, such that the allowed or allowable duration Tailored is greater than or equal to an actual duration to undertake the influenced operation.

2. The power beaming system of claim 1, wherein the influenced operation includes extinguishment of the power transmitter.

3. The power beaming system of claim 2, wherein the extinguishment of the power transmitter includes reducing output power of the power transmitter to zero.

4. The power beaming system of any one of claims 1-3, wherein power transmitter and the power receiver is separated by a separation distance D and the allowed or allowable duration allowed based on (AR- ) / S increases as the separation distance D increases.

5. The power beaming system of claim 4, wherein AR increases as the separation distance D increases.

6. The power beaming system of claim 4 or 5, wherein the first beam radius Rl increases as the separation distance D increases.

7. The power beaming system of any one of claims 4-6, wherein the first beam radius R1 increases at a faster rate than R2 increases as the separation distance D increases.

8. The power beaming system of any one of claims 1-7, wherein the maximum allowable speed S is less than or equal to 20 m / s.

9. The power beaming system of claim any one of claims 1-8, wherein the second beam radius R2 is quantified based on maximum permissible exposure.

10. The power beaming system of claim 9, wherein the maximum permissible exposure is 90 W / m2.

11. The power beaming system of any one of claims 4-10, wherein the separation distance D is less than or equal to 400 metres.

12. The power beaming system of any one of claims 1-11, wherein the one or more processors are further configured to sample an output of the photodetector at a sampling frequency f related to a sampling interval T= / f and wherein the allowed or allowable duration Tailored is additionally based on AZ.

13. The power beaming system of claim 12, wherein the allowed or allowable duration Tailored is based on (AR-P) / A - AZ.

14. A method of assessing a power beaming system, the power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius R1 and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is AR = R1 -R2 (in metres), the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P (in metres); a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to-electrical power conversion ;andone or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tailored based on ( R-PyS, the method including the step of determining whether an actual duration Tactual to undertake an influenced operation is less than or equal to the allowed or allowable duration Tallowed-15. A method of configuring or reconfiguring a power beaming system, the power beaming system including: a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius R1 and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is AR = R1 - R2 (in metres), the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P (in metres); a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to-electrical power conversion ;and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tallowed based on (AR- ) / S, the method including the steps of a. determining whether an actual duration Tactual to undertake an influenced operation is less than or equal to the allowed or allowable duration Tallowed,' and b. if it is determined that the actual duration Tactual to undertake the influenced operation is greater than the allowed or allowable duration Tallowed-, configuring or reconfiguring operational parameters of the power beaming system such that the actual duration Tactual to undertake the influenced operation is less than or equal to the allowed or allowable duration Tallowed-16. A method of configuring or reconfiguring a power beaming system, the power beaming system including:a power transmitter configured to transmit an optical beam, the optical beam including a first constituent beam having a first beam radius R1 and a second constituent beam having a second radius R2 that is smaller than the first beam radius Rl, such that the difference in their radii is AR = R1 - R2 (in metres), the power transmitter including a photodetector having a photodetection resolution corresponding to an obstacle intrusion into the first constituent beam by intrusion distance P (in metres); a power receiver movable at a maximum speed S (in m / s) relative to an intruding obstacle or the power transmitter, and configured to return at least a portion of the first constituent beam to the power transmitter for receipt by the photodetector and receive the second constituent optical beam for optical-to-electrical power conversion ;and one or more processors configured to influence operation of the system based on the return light detected at the power transmitter within an allowed or allowable duration Tailored based on (AR- ) / S, the method including the step of configuring or reconfiguring operational parameters of the power beaming system such that the actual duration Tactual tO undertake the influenced operation is less than or equal to the allowed or allowable duration Tallowed-17. The method of any one of claims 14-16, wherein the influenced operation includes extinguishment of the power transmitter of the power beaming system.

18. The method of claim 17, wherein the extinguishment lasts for an extinguishment duration based on the laser decay time.

19. The method of any one of claims 14-16, wherein the influenced operation includes defined direction of an output of the power transmitter.

20. The method of claim 19, wherein the defined direction is based on mechanical direction.

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