Dual Contrafocal Homogenizer

Abstract

The power receiver includes a beam homogenizer that takes portions of the power beam and spreads them out to cover a substantial portion (or all) of the power converter surface, respectively. The beam homogenizer may not have reflective sidewalls and may have an aspect ratio as low as 2-5. The normalized deviation of the beam irradiance at the surface may be reduced by a factor of 2-5 or more.

Description

[Technical Field]

[0001] <Background technology> Power beaming is an emerging method of transmitting power to locations that are difficult or inconvenient to access using wires by sending a beam of electromagnetic energy to a specially designed receiver that converts it into electricity. Power beaming systems can be free-space (where the beam is sent through air, vacuum, liquid, or other non-optically designed medium) or power-over-fiber ("PoF"), where power is transmitted via optical fiber. While the latter may share certain drawbacks with wire in some situations, it may also offer improved transmission efficiency, electrical isolation, and / or safety. Free-space power beaming may be more flexible but may present more challenges in precisely targeting the receiver and avoiding hazards such as reflections and objects that may intrude into the power beam.

[0002] All of the subject matter discussed in the "Background" section is not necessarily prior art and should not be assumed to be prior art merely as a result of its discussion in the "Background" section. Along these lines, recognition of problems in the prior art discussed in the Background section or related to such subject matter should not be treated as prior art unless expressly stated to be prior art. Instead, the discussion of any subject matter in the Background section should be treated as part of the inventors' approach to a particular problem and may itself be inventive. Summary of the Invention [Means for solving the problem]

[0003] <Summary> In one aspect, the beam homogenizer includes a compound lens configured to reshape an incident power beam. The compound lens includes a first optical surface configured to focus the incident power beam at a focal length and a second optical surface including a plurality of optical elements. Each of the plurality of optical elements is configured to expand a respective portion of the focused power beam toward a collection region, where the directed portions of the focused power beam overlap one another at the collection region to form a homogenized power beam. In a related aspect, the power receiver includes the beam homogenizer described above and a power converter positioned to receive the homogenized power beam.

[0004] In another aspect, a method for homogenizing a power beam includes receiving an incident power beam, splitting the received beam into a plurality of beam portions, and directing each beam portion toward a beam target area, the directing step including changing the size of the beam portion at the target area to a selected size, the plurality of beam portions overlapping each other at the target area. [Brief explanation of the drawings]

[0005] The drawings illustrate one or more implementations in accordance with the present teachings by way of example only, and not by way of limitation. In the drawings, like reference numbers refer to the same or similar elements. Further, it should be understood that the drawings are not necessarily to scale. [Figure 1] FIG. 1 is a schematic diagram of a power beaming transmitter and receiver. [Figure 2] FIG. 2 is a functional diagram of the power beaming transmitter of FIG. 1, showing the interrelationships between the transmitter components. [Figure 3]FIG. 3 is a functional diagram of the power receiver of FIG. 1, showing the interrelationships between the components of the power receiver. [Figure 4] FIG. 4 is a schematic diagram showing the operating principle of a homogenization lens. [Figure 5] FIG. 5 is a first stage hybrid homogenizing lens. [Figure 6] FIG. 6 is a schematic diagram including a homogenizing lens, which differs from the lens of FIG. 4 by using convex (converging) lenslets instead of concave (diverging) lenslets. [Figure 7] FIG. 7 shows the response of the lens of FIG. 6 when light is incident off-axis. [Figure 8] FIG. 8 shows a module including a homogenizing lens and a concentrator. [Figure 9] Figure 9 is a quadratic polygonal concentrator that relies on a single reflection at grazing incidence to match the size of the PV cell and minimize losses. [Figure 10] Figure 10(a) shows an incident collimated beam with a Gaussian distribution. Figure 10(b) shows the beam just before it enters the concentrator, and Figure 10(c) shows the beam just before it enters the PV cell. These three figures are sometimes collectively referred to herein as Figure 10. [Figure 11] Figure 11(a) shows an incoming collimated beam with a Gaussian distribution that is significantly shifted relative to its optical axis before entering the module shown in Figure 8. Figure 11(b) shows the beam just before entering the concentrator, and Figure 11(c) shows the beam just before entering the PV cell. These three figures are sometimes collectively referred to herein as Figure 11. [Figure 12] Figure 12(a) shows an incident collimated beam with a Gaussian distribution entering the 3x3 catadioptric array of the module shown in Figure 8. Figure 12(b) shows the beam just before entering the concentrator, and Figure 12(c) shows the beam just before entering the PV cell. These three figures are sometimes collectively referred to herein as Figure 12. [Figure 13]Figure 13(a) shows an incident collimated beam with a Gaussian distribution entering the 3x3 catadioptric array of the module shown in Figure 8, which differs from the beam shown in Figure 12(a) only in that it is offset from the center of the array. Figure 13(b) shows the beam just before entering the concentrator, and Figure 13(c) shows the beam just before entering the PV cell. These three figures are sometimes collectively referred to herein as Figure 13. DETAILED DESCRIPTION OF THE INVENTION

[0006] <Detailed explanation> In the following detailed description, numerous specific details are set forth by way of example to provide a thorough understanding of the relevant teachings. However, it will be apparent that the present teachings may be practiced without such details. In other instances, well-known methods, procedures, components, and / or circuits have been described at a relatively high level, without detail, to avoid unnecessarily obscuring aspects of the present teachings. Nevertheless, those skilled in the art will understand the features of these methods, procedures, components, and / or circuits and how they may be used in the following description. Other relevant material may be found in other patents and applications, such as: TIFF0007733826000001.tif184169

[0007] Each of these related applications and patents is incorporated herein by reference to the extent not inconsistent herewith.

[0008] As mentioned above, power beaming is becoming a viable method of delivering power to objects in situations where running wires is inconvenient or difficult. For example, free-space power beaming can be used to deliver power via a ground-based power transmitter to power remote sensors, recharge batteries, or power unmanned aerial vehicles (UAVs) such as dronecopters, allowing them to remain airborne for extended periods of time. Power-over-fiber (PoF) systems typically require optical fiber (or equivalent) to be run from the power source to the receiver, but may offer electrical isolation and / or other advantages over traditional copper wire, which carries electricity instead of light.

[0009] It will be understood that the term “light source” is intended to encompass all forms of electromagnetic radiation that can be used to transfer energy, not just visible light. For example, a light source (e.g., a diode laser, fiber laser, light-emitting diode, magnetron, or klystron) can emit ultraviolet, visible, infrared, millimeter-wave, microwave, radio, and / or other electromagnetic waves, any of which may be generally referred to herein as “light.” The term “power beam” is used interchangeably with “light beam” herein to generally refer to an inherently directional, high-irradiance transmission that may be single-wavelength or multiple-wavelength, coherent or incoherent, and pulsed or continuous. A power beam may be free-space, PoF, or may include each component. For example, a transmitter can transmit a free-space power beam to a receiver surface, which may conduct it as light over an optical fiber to a photovoltaic (PV) cell that converts it to electricity. For ease of reading, the description may use the term "laser" to describe the light source, although other light sources such as (but not limited to) light emitting diodes, magnetrons, or klystrons may nevertheless be contemplated unless the context dictates otherwise.

[0010] In many applications, a power receiver is configured to receive a free-space or PoF power beam and convert it to electricity, for example, using a PV cell or other component for converting light to electricity (e.g., a rectenna for converting microwave power, or a heat engine for converting heat generated by the light beam to electricity). For ease of reading, this application may refer to a "PV cell" with the understanding that other components having similar functionality (such as, but not limited to, those listed above) may be substituted without departing from the scope of this application.

[0011] <Power beaming system> FIG. 1 is a schematic diagram of a power beam transmitter 102 and receiver 104. A laser 106 directs a power beam 108 (shown as a dotted line throughout the figure) toward an optical unit 110, which directs the beam toward a beam steering assembly, such as a mirror assembly 112. The optical unit 110 may include various lenses, mirrors, and other optical elements, as described further below. The steering mirror assembly 112 directs the power beam 108 toward the power receiver 104. An optional chiller 114 is shown connected to the laser 106, although other components of the transmitter 102 may also have separate or connected thermal management systems, as desired. FIG. 1 also shows a tracking system 116 and a safety system 118 as part of the transmitter 102. While these systems are shown in the figures as being internal to the optical unit 110, those skilled in the art will recognize that in some implementations, they may be external to the optical unit 110, part of the steering mirror assembly 112, or elsewhere in the transmitter system. Also shown are a TX controller 120, a user interface 122, and a TX communications unit 124, all of which are further described below in connection with FIG. 2. It should be understood that the transmitter 102 may include other elements, such as a beam shaper, guard beams, or other suitable accessory elements, which are omitted from FIG. 1 for simplicity. Some of these elements are shown schematically below in FIG. 2, but those skilled in the art will understand how to combine optical and control elements in a power transmitter.

[0012] The receiver 104 includes a PV array 130 that includes a plurality of individual PV cells 132 (not all PV cells are labeled to avoid unnecessarily cluttering the figure). The PV cells 132 convert the input power beam 108 into electricity, as described further below. The receiver 104 also shows a tracking emitter 134, which in some implementations may be used by a tracking system 116 to monitor the position of the PV array 130 for beam tracking or other purposes. The receiver 104 also shows a safety emitter 136, which in some implementations may be used by a safety system 118 to monitor the power beam 108 for potential intrusion, reflection, or other safety hazards. The RX communication unit 138 (as indicated by the dashed line) communicates with the TX communication unit 124 and may be used for safety, tracking, telemetry, feedback control, or any other purpose for which it may be desirable for the transmitter 102 and receiver 104 to communicate. While the illustrated embodiment provides communication over a separate channel, such as a wireless link, between the transmitter 102 and the receiver 104, it is also contemplated that communication may be achieved via modulation of the power beam 108, tracking emitter 134, safety emitter 136, or other existing components of the power beaming system. The receiver 104 may also include an optional RX sensor 140, which is described further below in connection with FIG. 3. As shown in FIG. 1, the PV array 130 is mounted to an optional mast 142, which may elevate the receiver 104 to allow the power beam 108 to avoid people or other obstacles.

[0013] Figure 2 is a summary diagram illustrating the functional relationships between transmitter components. Transmitter 102 includes laser 106, although it should be understood that in some implementations, other light-generating components, such as an LED or magnetron, can be used in place of laser 106. Laser 106 is connected to controller 120, power supply unit (PSU) 202 (connected to input power 204), and thermal management system (chiller) 114. Throughout Figures 2 and 3, heat flow is indicated by thick dotted lines, while power beam 108 is indicated by thick solid lines, sensor signals are indicated by thick dashed lines, data and / or control signals are indicated by dash-dot lines, and power is indicated by thin solid lines. For clarity, not all internal electrical connections are shown.

[0014] The controller 120 controls the operation of the laser 106 and may be manual (e.g., using a user interface 122), partially automated, or fully automated, depending on the system's design constraints. In particular, the controller 120 may receive input from a safety system, such as those described in commonly owned U.S. Patent Nos. 10,634,813 and 10,816,694, U.S. Patent Application Nos. 15,574,659 and 16 / 079,073, International Patent Application No. PCT / US20 / 34104, and U.S. Provisional Application No. 63 / 140,236. The safety system may be designed, for example, to attenuate (or turn down) or shut off (or turn off) the beam when an uninterrupted optical path from the transmitter 102 to the receiver 104 cannot be guaranteed or when other unsafe conditions may be associated with the continuation of the beam power. The controller 120 may also receive input (data) from other components, for example, to monitor the health or temperature of the laser. PSU 202 draws power from input power 204, which may be, for example, a power grid, a generator, or a battery, and provides it to laser 106. While controller 120 and chiller 114 are shown directly connected to input power 204, in other embodiments these or other components may receive power from power supply unit 202. Chiller 114 monitors the temperature of laser 106 (and / or other components of the transmitter, as needed) to ensure that it does not exceed safe values.

[0015] As shown in FIG. 2 , power beam 108 exits light source 106 and enters optical unit 110. While light 108 maintains the same reference numerals throughout FIG. 2 , it will be understood that the properties of light 108 may change in various ways (e.g., polarization, convergence / divergence angle, beam profile, or intensity) as it passes through different optical and other components. Optical unit 110 may include beam integrator 206 and other optical systems such as lenses, mirrors, phased arrays, or any other suitable components for managing the light direction, divergence, and beam irradiance profile or for merging different optical power beams and / or signals. Beam integrator 206 is typically selected to match the wavelength range of light source 106 and may be used to change the size, shape, or intensity distribution of the power beam. For example, when beaming power to a receiver, in some implementations it may be desirable to match the beam width to the size of the receiver and possibly "flatten" the beam irradiance profile to be relatively uniform across the surface of the receiver, e.g., converting a substantially Gaussian beam profile to a "top hat" or super-Gaussian profile. Beam direction and beam profile shaping are discussed in more detail in co-pending, commonly owned International Patent Application No. PCT / US20 / 34095. In particular, mechanisms described therein for monitoring the placement of the power beam on the receiver and using the monitored data to provide feedback to the controller 120 and / or steering assembly 112 may be incorporated into the present system.

[0016] In some implementations, the steering (or steering / direction) assembly 112 may include steering optics 210 and / or sensors 212, which may be used to measure beam characteristics, such as direction or irradiance profile, to provide feedback information for tracking the receiver and directing the beam to its position, or to monitor for potential intrusions into the optical path. The steering assembly 112 may also include merging optics. Merging optics are typically used to combine multiple optical paths, or in some cases, to separate them when the optical flow is in opposite directions. For example, as shown, the outgoing power beam 108 for transmitting power may be combined with an incoming optical beacon 208 used to track the receiver. As shown, a beacon is used in the steering assembly 112 for tracking, although in other implementations, the signal 208 may propagate through the optical unit 110 or beyond.

[0017] The transmitter 102 may also include a sensor 214 that can be used to monitor ambient conditions. The sensors 212, 214 may be used to adjust the beam integrator 206 and / or the steering optics 210. For example, the sensor 212 may monitor the position of a focusing lens or other optical component in the steering assembly 112, and the sensor 214 may be used to monitor the ambient temperature and / or the temperature of other components. Data from the sensors 212, 214 may be fed back to the controller 120 to control the steering optics 210 and / or the steering assembly 112, for example, to adjust the laser 106 for safety considerations or to direct the beam 108 onto the receiver. Control and data signals may be passed between the controller 120 and other components, as shown by the dashed-dotted lines in FIG. 2, and the controller 120 may control communications with the receiver, for example, using the transmitter communication unit 124.

[0018] After passing through the optical unit 110, the power beam 108 is directed in a desired direction away from the transmitter 102 by a steering assembly 112. In some implementations, the steering assembly 112 may include steering optics 210, motors for adjusting mirrors or other components (not shown), and / or more shaping optics (not shown). Those skilled in the art will understand that different implementations may require different arrangements of optical elements (such as the order in which components the light passes through) without changing the fundamental nature of the transmitter system.

[0019] FIG. 3 illustrates the functional relationships among the components of a power receiver 104, such as the receiver shown in FIG. 1. The illustrated receiver 104 includes a power converter 302 that includes a PV array 130 of PV cells 132. The power converter 302 is configured to convert the power beam 108 from the laser 106 into electricity (or, in some implementations, into another useful form of energy). The receiver 104 may also include optics 304 that can shape or modify the received beam before it reaches the PV array 130, for example, as described in International Application No. PCT / US20 / 34093. In many embodiments, the PV array 130 includes a thermal management system 306. This system may include passive or active cooling and may be configured to send a signal back to the transmitter 102 (e.g., via the RX communication unit 138) if any portion of the PV array 130 exceeds a safe temperature limit.

[0020] The power converter 302 may further be connected to a power management and distribution (PMAD) system 308. The PMAD system 308 may provide power to a user device 310, a power bus 312, and / or an energy storage device 314. The PMAD system 308 may be connected to a controller 316, which may monitor the PV array 130 via sensors 140, such as the voltage, current, and / or temperature of individual photovoltaic cells, cell clusters, or the entire array, the voltage and / or current of the PMAD, or individual loads. The controller 316 may also include maximum power point tracking (MPPT) for the PV array 130, or MPPT may be processed by the PMAD system 308. The PMAD system 308 may also include a DC / DC converter, for example, to provide power to the devices 310, 312, 314 with preferred voltage and current characteristics. The telemetry unit 318 may transmit any or all of the above data back to the transmitter, for use in controlling the light beam 108, for example, via the RX communication unit 138. In some implementations, the controller 316 may be in communication with a receiver user interface 320, which may allow a user of the power receiver to locally view and / or control receiver operation.

[0021] 3 also shows a signal 208 (e.g., an optical signal) sent by the receiver 104 back to the transmitter 102, which may be transmitted along the same path as the power beam 108, as shown. In some implementations, for example, the signal 208 may include a safety signal used to ensure an uninterrupted path from the transmitter 102 to the receiver 104. In some implementations, this signal may be sent from a safety emitter 136. Further details of safety systems can be found in, for example, commonly owned U.S. Patent Nos. 10,580,921, 10,634,813, 10,816,694, and 11,105,954, U.S. Patent Application No. 16 / 079,073, and International Patent Application No. PCT / US20 / 34104. In some implementations, the signal 208 may include a tracking signal used to position the power beam 108 over the power converter 302, such as a signal sent from a tracking emitter 134. Although the signal 208 shown in the figure is an “active” signal, in other implementations the emitters 134, 136 may be replaced by fiducial marks (not shown) that are identified by the transmitter 102 or other suitable components in the power transmission system.

[0022] Any receiver components requiring power, such as, but not limited to, thermal management system 306, RX communication unit 138, PMAD system 308, controller 316, telemetry unit 318, and / or user interface 320, may be powered by power converter 302 (either directly or via PMAD 308) as needed. If components are powered by converter 302, the system may include a battery (either as part of energy storage 314 or as a separate component) to power these components during startup or at other times when converter 302 is not providing power.

[0023] <Beam Reshaping> Although it is preferable to deliver a beam with a super-Gaussian or nearly “flat-top” intensity profile at the receiver, in some cases, for example, due to the distance to the receiver, a “plain” Gaussian beam may be delivered instead. Even super-Gaussian beams have “tails” in their intensity profile, which can limit array performance because PV cells near the periphery of the PV array may receive little or no light. Overfilling the array and illuminating all of them reduces efficiency due to wasted light and potentially poses a safety hazard due to light spilling beyond the receiver. Cells have a per-cell input power level beyond which they lose efficiency and can eventually overheat; therefore, the beam’s peak power intensity (usually near the center of the beam) can drive the total number of cells required for a given power output. Furthermore, scintillation can cause individual PV cells to register rapidly and widely varying intensities, both above and below their nominal intensity, which can reduce efficiency for various reasons. The present design at least partially homogenizes the beam so that the range of intensities on individual cells in the array is effectively reduced by shifting some light to the outermost cells, which allows for higher array power output for a given number of cells.

[0024] FIG. 4 is a schematic diagram for understanding the present invention. Angles and distances are not necessarily drawn to scale. As shown, assembly 400 includes a square compound refractive lens 402 (shown in cross section in FIG. 4 and in perspective in FIG. 5) that receives incident collimated light 404 (e.g., from a laser power beam). Lens 402 has a width d, and its top surface has a convex shape with a focal length f (hence the f-number f / d). Therefore, ignoring the effects of the bottom surface, it focuses light 404 onto a surface 406 that is a distance f away from the lens, as indicated by the thick dashed line 408. In the example shown in FIG. 4, focal length f and working distance L are equal, although, as discussed below, this is not a requirement. Working distance L may differ from the focal length in other implementations, and the top shape may be any suitable shape (e.g., spherical, aspherical, or freeform). In the embodiment shown in FIG. 4, the bottom surface of lens 402 is tiled with an array of square concave lenslets with negative f-numbers approximately the same size as the top surface. Each of these lenses therefore returns light expanded to approximately the width of the original beam at a plane a distance L from the lens, as indicated by a pair of dotted and dash-dotted lines 410, 412, and 414. This combination effectively homogenizes the beam, as each lenslet on the bottom surface spreads a portion of the incident beam across (or nearly across) the entire target plane, as the beam portion from each individual lenslet is angled toward the center of target surface 406 due to its refraction from the first surface. The overall effect of the lenslet array is therefore to flatten the beam profile and mitigate the effects of scintillation or other beam non-uniformities (i.e., inhomogeneity). In particular, even without side reflectors, very little light escapes the width of a right cylinder projected downward from the cross section of lens 402, and the light reaching the target plane is closer to perpendicular to the plane than would be the case with a standard diffuser system, which tends to widen the beam.This is important because PV cells may have a limited acceptance angle for light, or at least improved efficiency when the light is as close to normal to their surface as possible. In some embodiments, the f-number of the concave lenslet is slightly larger, so that the light diverges more slowly but still reaches the overlapping area at working distance L. As shown, target surface 406 has approximately the same width as lens 402, although of course in some embodiments it could be narrower, as long as it is at least wide enough to capture most or all of the incident beam.

[0025] In some implementations, the target surface 406 may be somewhat larger or smaller than the lens 402, but the target surface is still shaped according to the same principle that each lenslet spreads its own section of the incident light 404 over an overlapping target area that is approximately the same size as the lens 402, as shown in FIG. 4. In some implementations, the target area is at least 25%, at least 50%, at least 75%, at least 90%, or at least 95% of the width of the target surface 406. The target area 406 may also be wider (e.g., 110% or 125%) than the lens 402, although in these cases the degree of homogenization may be somewhat reduced at the periphery of the target surface 406, and assembling multiple modules may be more difficult, as discussed below in connection with FIGS. 12 and 13.

[0026] FIG. 6 shows an assembly 600 including an alternative refractive lens 602 that uses a convex lenslet on its bottom surface. The top surface still has the same focal length (here marked f1), but the lenslets have a smaller positive focal length f2 selected so that the light (610, 612, 614) coming from each lenslet converges to a sufficient point before reaching the target surface 406, then diverges and spreads out over the same target area of ​​the surface. In this illustration, f2 is selected to reach a smaller overlap area than shown in FIG. 4, i.e., approximately 35% of the width of the target surface 406 (and thus approximately 12% of the area above). It will be apparent to those skilled in the art that various implementations can include concentrating (as shown) or spreading the incident light to different degrees without altering the principles of the present invention.

[0027] Those skilled in the art will further understand how to select the f-number of the lenses 402, 602 to contain the light on the target surface 406 and spread the light evenly across the target plane without losing light from the edges. While this is most easily illustrated and understood in the context of lenses such as those shown in FIGS. 4-6, those skilled in the art will also understand that the same principles can be applied to reflective optics or diffractive optical elements (DOEs), which may provide a lighter and / or more compact system and may also improve the light-induced damage threshold for the system. Lenslets may be somewhat larger than typical microlenses, for example, about 0.1-3 cm wide. An advantage of the system is that slight changes in the angle of the collimated light 404 entering the system shift the position of the light projected onto the target surface 406 while maintaining the overlap area, as can be seen more clearly in FIG. 7. The lens 602 has the same shape as in FIG. 6, but the incident light 404 is shifted 3 degrees away from normal. This change shifts the target area to the left, but each lenslet still spreads its portion of the beam over the target area. Because the size of the beam in Figure 7 at the plane of the target surface 406 is less than the full width of the target surface 406, the shifted beam does not spill off the target surface 406 because this shift in beam position is less than the width of the blank / unilluminated area, allowing the system to accommodate some amount of pointing error. The shift in the position of the beam (but not its angle) is discussed below in connection with Figure 11.

[0028] FIG. 8 shows a module 800 including a lens 402, a group of concentrators 802 (not all numbered for clarity), and a PV cell 132. The concentrator shown is a compound parabolic concentrator (CPC), although other non-imaging concentrators are contemplated. Incident light 404 enters the lens 402 and is directed toward the concentrator 802, which is positioned at a location equivalent to the target surface 406 as described above and focuses the light 404 toward the PV cell 132, similar to the beam splitting device described in co-pending and co-owned U.S. patent application Ser. No. 17 / 613,015. A cross section of one concentrator 802 is shown in FIG. 9. It is a hollow section with a polygonal geometric shape, e.g., a square or hexagonal cross section, which may be close-packed in some preferred embodiments. In some implementations, the output angle of the concentrator 802 can be selected to correspond to the maximum acceptance angle of the PV cell 132 for improved coupling. While the hollow reflective profile shown in Figure 9 is selected to reduce receiver mass and aid in internal radiative cooling, other types of concentrators are contemplated within the scope of the present invention. Figure 8 also includes three lines A, B, and C that intersect the path of light 404 as it passes through the lens 402 to the PV cell 132. These represent the viewing planes of Figures 10-13, described below.

[0029] <Efficacy indicators> FIG. 10 shows how irradiance changes as light travels through module 800. A Gaussian light beam incident on line A in FIG. 8 is shown in FIG. 10(a). This figure includes a heat map with overlaid contour lines showing the beam irradiance (in arbitrary units), as well as a graph of irradiance along a single line at the point of highest intensity. FIG. 10(b) shows how the light beam profile is homogenized at line B just before it enters the concentrator, and FIG. 10(c) shows the light distribution at line C just before it enters the PV cell. (FIGS. 10-13 each show the same combination of a heat map with contours and a 2D graph along the line of highest intensity in each section, except that the profile at point C has its contour omitted to improve the clarity of the illustration.) It can be clearly seen that the light is substantially homogenized by the system, and the optical power on each of the PV cells is qualitatively equalized compared to what it would have been without the homogenizer. A quantitative analysis of the degree of homogenization is provided below.

[0030] Figure 11 shows how the system responds to a somewhat off-center beam. Figure 11(a) shows an incident beam offset 25 mm in the x and y directions from the center of a 100 mm square module. Figure 11(b) shows how the light beam profile is homogenized at line B just before entering the concentrator, and Figure 11(c) shows the light distribution at line C just before entering the PV cell. While spatial homogenization of the incident beam can be optimized by compound lenses when the beam is centered along the optical axis, the inherent shift-invariant properties of the optical system can nevertheless mitigate decentering and ensure uniform filling of the second-stage optics. It can be seen that even though only a portion of the optical elements receive the light (see Figure 11(a)), the light is still spread fairly evenly across most of the target plane when it reaches the PV cell (see Figure 11(c)).

[0031] In some implementations, the complete optical element shown in FIG. 8 may include multiple modules 800 shown in FIG. 8, for example, in a 3×3 or 4×4 array. While in some implementations, each microlens array may be shaped as shown and discussed in FIGS. 4-6 , in other implementations, the lenslets may be shaped such that each lenslet spreads its respective portion of light 404 over a larger portion of the target surface. In such implementations, light from different elements of the multiple modules described above may overlap at the target surface. An advantage of the former configuration is that the modules 800 may all be substantially identical, providing construction efficiency. An advantage of the latter configuration is that the incident light may be more completely equalized across the entire plane. For simplicity, the following description assumes that each module 800 is substantially identical, but those skilled in the art will understand how modules within the array may be arranged to spread light to adjacent modules to further equalize the harvested beam.

[0032] The modular array design is catadioptric and includes an array of nine square optical modules arranged in a 3 × 3 pattern, with each module containing an assembly 800 as shown in Figure 8. Module-to-module uniformity at the PV cells is achieved in two stages: a first-stage refractive optic (e.g., lens 402) provides some weak focusing (in addition to homogenization) of the optical radiation at the entrance to the second stage, and a secondary non-imaging optic 802 (e.g., a hollow concentrator, Köhler concentrator, or simple lens) focuses the light onto the individual PV cells. The function of the staged optics is to shape the quasi-collimated laser input into a spatially homogenized beam within the angular acceptance limits matching the secondary non-imaging optic, which ensures the final concentration ratio at each individual PV cell.

[0033] Figure 12 shows the system response to a central high-power Gaussian beam that fills most of the 3 × 3 aperture of the catadioptric array. For a 300 × 300 mm array, the full-width half-max of the beam is 119 mm. Little light spills from the edges of the PV array, and each of the nine first-stage optics homogenizes its portion of the incident beam. Figure 12(a) shows the beam irradiance as it enters the array (line A), Figure 12(b) shows the beam irradiance as it enters the concentrator (line B), and Figure 12(c) shows the beam irradiance as it reaches the PV cell (line C).

[0034] Even when the incident beam is not centered on the array, the system produces uniform irradiance of the PV cells within each individual module that forms the array of modules, as shown in Figure 13. Figure 13(a) shows the beam irradiance as it enters the array (line A), Figure 13(b) shows the beam irradiance as it enters the concentrator (line B), and Figure 13(c) shows the beam irradiance as it reaches the PV cell (line C).

[0035] Qualitatively, the most efficient and cost-effective laser power delivery systems tend to have light that is relatively evenly spread across the array, with most PV cells receiving roughly the same amount of light, and little light that misses the array entirely or enters at such high angles that the PV cells do not efficiently convert it to energy. We can evaluate an array to see how well it matches this qualitative description by modeling the standard deviation of the irradiance measured across the array. This parameter is converted to a dimensionless normalized deviation (or normalized deviation) by dividing by the average irradiance, eliminating any arbitrary units. For the system described in the previous section, we can model the normalized deviation for a single module (e.g., the homogenizing lens and 4 × 4 array of PV cells modeled in Figure 10) and make various assumptions about the incident light beam. We can then calculate the normalized deviation at the point where the light enters the concentrator.

[0036] The normalized deviation varies depending on the beam profile directed at the module. Figure 10 is based on a centered Gaussian beam with a full width at half maximum of 39.25 mm over a 100 mm array width, while Figure 11 shows a beam of the same size offset from the array center by 25 mm in the x- and y-axes, respectively. We report the normalized deviations for both the centered and offset beams in planes A and B of Figure 8. The obtained data are shown in the first two rows of Table 1. The normalized deviation of the irradiance is reduced by at least a factor of four by the beam homogenizer. TIFF0007733826000002.tif36169

[0037] For the array of modules shown in FIG. 12 (and FIG. 13), the normalized deviation (averaged across the entire array) will typically be higher for a Gaussian beam reaching the full array because each module tends to direct most of the incident light onto its own array of PV cells, and therefore different modules may experience significantly different irradiance levels. These differences are qualitatively apparent in FIG. 12. In some implementations, the differences may mean that it is more efficient or cost-effective to use different PV cells, electronics, and / or other components for different modules in the array. For these reasons, the normalized deviation for each module is a more manageable metric. As shown in Figure 12, for a 3 × 3 array of 100 mm square modules and a centered Gaussian beam with a full width at half maximum of 119 mm, we calculate the normalized deviation for three of the nine modules: the single central module, one of the four edge modules (orthogonally adjacent to the central module), and one of the four corner modules (diagonally adjacent to the central module). The other six have virtually identical values ​​due to the symmetry of the overall system, so they were not modeled separately. These data are reported in Table 1 under the column labeled "Large Beam." It can be seen that for the central module, the homogenizer makes the beam slightly nonuniform (since the homogenizer slightly reduces the beam area, but the "dark edges" are included in the calculation of the normalized deviation), but for the edge and corner modules (where the initial distribution of irradiance is less uniform), the homogenizer reduces the normalized deviation by approximately three or four times.

[0038] The inventors also confirm that the concentrator 802 does not adversely affect irradiance at the PV cells by modeling the amount of power entering each PV cell within a single module (using both centered and offset beams). For the centered beam, the normalized luminous flux at each PV cell (total power at a PV cell divided by the average power across all PV cells) ranges from 0.832 at the corners to 1.29 for the central four cells, with a normalized deviation of 0.177. For the offset beam, the normalized luminous flux ranges from a minimum of 0.679 to a maximum of 1.38, with a normalized deviation of 0.210. This relatively narrow range means that the mismatch between PV cells is smaller than without the homogenizer (normalized deviation of 1.215 for the centered case and 1.475 for the offset case), thereby improving PV cell utilization and effectiveness.

[0039] In some implementations, the PV cells of the modules shown in FIGS. 12 and 13 may be wired in a series-parallel configuration, as discussed in our co-pending and commonly owned International Application No. PCT / US22 / 13570, although in other implementations homogenization across each module may obviate this type of wiring.

[0040] The same optical function modeled and described above can also be achieved with a DOE (e.g., a sub-wavelength DOE), which can be thinner and therefore much lighter. In one implementation of a two-lens Kohler-type optic (which does not homogenize the beam across multiple PV cells), a power beam receiver module (10 cm x 10 cm) includes optics weighing 228 grams, plus a metal support frame weighing 363 grams, for a total of 591 grams. We estimate that replacing the optics and mounts with the two stages described above reduces the mass to ~115 grams per module, a five-fold reduction.

[0041] Further features, characteristics, and advantages are described below under the following headings: Item 1: A beam homogenizer includes a compound lens configured to reshape an incident power beam. The compound lens includes a first optical surface configured to focus the incident power beam at a focal length and a second optical surface including a plurality of optical elements. Each of the plurality of optical elements is configured to expand a respective portion of the focused power beam toward a focusing region, where the directed portions of the focused power beam overlap one another to form a homogenized power beam. Item 2: The beam homogenizer described in Item 1, wherein the compound lens has a width and the compound lens is positioned at a distance from the focusing region between about half the width and about six times the width. Item 3: The beam homogenizer described in Item 2, wherein the compound lens is positioned at a distance from the focusing region between about the width (or approximately the width / roughly the width) and about four times the width. Item 4: The beam homogenizer of item 3, wherein the compound lens is positioned at a distance from the focusing region between about two times the width and about three times the width. Item 5: A beam homogenizer as described in Item 1, wherein the compound lens has an axis, the homogenized power beam has a final width that is smaller than the width of the compound lens, and the focusing region is sufficiently wide so that the homogenized power beam is positioned within the focusing region when the incident power beam forms an angle of less than 2 degrees with respect to the axis. Item 6: A beam homogenizer as described in Item 5, wherein the focusing region is sufficiently wide so that the homogenized power beam is positioned within the focusing region when the incident power beam forms an angle of less than 5 degrees with respect to the axis. Item 7: A beam homogenizer as described in Item 5, wherein the focusing region is sufficiently wide so that the homogenized power beam is positioned within the focusing region when the incident power beam forms an angle of less than 10 degrees with respect to the axis. Item 8: A beam homogenizer as described in Item 1, wherein the incident power beam has an unshaped beam irradiance profile and the homogenized power beam has a reshaped beam irradiance profile, and the reshaped beam irradiance profile is flatter than the unshaped beam irradiance profile. Item 9: The beam homogenizer of item 8, wherein the unshaped beam irradiance profile is approximately Gaussian. Item 10: The beam homogenizer of item 9, wherein the reshaped beam irradiance profile is approximately flat across at least half of the collection area. Item 11: The beam homogenizer of item 8, wherein the reshaped beam irradiance profile has a normalized deviation that is less than half the normalized deviation of the unshaped beam irradiance profile. Item 12: The beam homogenizer of item 11, wherein the normalized deviation of the reshaped beam irradiance profile is less than 0.3 times the normalized deviation of the unshaped beam irradiance profile. Item 13: A beam homogenizer as described in Item 11, wherein the normalized deviation of the reshaped beam irradiance profile is less than 0.25 times the normalized deviation of the unshaped beam irradiance profile. Item 14: A beam homogenizer as described in Item 11, wherein the normalized deviation of the reshaped beam irradiance profile is less than 0.2 times the normalized deviation of the unshaped beam irradiance profile. Item 15: The beam homogenizer of item 1, wherein the optical element has a width that is approximately 1 / 20 of the width of the beam homogenizer. Item 16: The beam homogenizer of item 1, wherein the optical element has a width that is approximately one-tenth the width of the beam homogenizer. Item 17: The beam homogenizer of item 1, wherein the optical element has a width that is approximately one-fifth the width of the beam homogenizer. Item 18: The beam homogenizer of item 1, wherein the optical element has a width of less than 1 mm. Item 19: The beam homogenizer of item 1, wherein the optical element has a width of less than 5 mm. Item 20: The beam homogenizer of item 1, wherein the optical element has a width of less than 20 mm. Item 21: The beam homogenizer according to item 1, wherein the optical element is convex. Item 22: The beam homogenizer of item 1, wherein the optical element is concave. Item 23: The beam homogenizer according to item 1, wherein the optical element is a lenslet. Item 24: A beam homogenizer according to item 1, wherein the first side (or the first surface) has a first f-number, the second side (or the second surface) has a second f-number, and the first f-number and the second f-number have absolute values ​​within 10% of each other. Item 25: A power receiver includes the beam homogenizer of item 1 and a power converter positioned to receive the homogenized power beam. Item 26: The power receiver of item 25, further comprising a concentrator positioned to direct at least a portion of the homogenized power beam toward the power converter. Item 27: The power receiver of item 26, wherein the concentrator is a reflective concentrator. Item 28: The power receiver of item 26, wherein the concentrator has an output angle less than or equal to a maximum acceptance angle of the power converter. Item 29: The power receiver of item 25, further comprising a plurality of concentrators, each concentrator positioned to direct at least a portion of the reshaped power beam to a particular location within the concentration region. Item 30: The power receiver of item 29, wherein the multiple concentrators are packed together to collect at least 90% of the reshaped power beam. Item 31: The power receiver of item 25, wherein the power converter includes a photovoltaic (PV) cell. Item 32: The power receiver of item 25, wherein the power converter includes a plurality of PV cells. Item 33: The power receiver of item 32, wherein the power receiver includes a plurality of concentrators, each concentrator positioned to receive at least a portion of the homogenized power beam, and each concentrator positioned to direct a respective portion of the homogenized power beam to at least one PV cell. Item 34: A method for homogenizing a power beam includes receiving an incident power beam, splitting the received beam into multiple beam portions, and directing each beam portion toward a beam target area, wherein directing each beam portion includes changing the size of the beam portion at the target area to a selected size, and wherein the multiple beam portions overlap one another at the target area. Item 35: The method of item 34, wherein splitting the beam into multiple beam portions and directing each beam portion toward a beam target area includes passing the power beam through a compound lens. Item 36: The method of item 35, wherein the compound lens has an entrance surface and an exit surface, the exit surface comprising a plurality of lenslets. Item 37: The method of item 36, wherein the lenslets are convex. Item 38: The method of item 36, wherein the lenslets are concave. Item 39: The method of item 36, wherein the entrance surface is aspheric. Item 40: The method of Item 36, wherein the entrance surface has a first f-number and the exit side has a second f-number, and the first f-number and the second f-number have absolute values ​​within 10% of each other. Item 41: The method of item 34, wherein the incident power beam has an incident normalized deviation of beam irradiance, and the overlapping beam portions at the target area have a homogenized normalized deviation of beam irradiance, and the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 2. Item 42: The method of Item 41, wherein the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 3. Item 43: The method of Item 41, wherein the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 4. Item 44: The method of Item 41, wherein the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 5. Item 45: The method of item 34, wherein the plurality of beam portions includes 9 to 10,000 beam portions. Item 46: The method according to Item 34, wherein the plurality of beam portions includes 25 to 400 beam portions. Item 47: The method according to Item 34, wherein the plurality of beam portions includes 64 to 225 beam portions. Item 48: The method of item 34, wherein the overlapping beam portions form a homogenized beam. Item 49: The method of item 48, further comprising focusing at least a portion of the homogenized beam. Item 50: The method of item 49, further comprising directing a focused portion of the homogenized beam to a power converter. Item 51: The method of Item 50, wherein concentrating at least a portion of the power beam includes passing the beam through a concentrator having an output angle less than or equal to a maximum acceptance angle of the power converter. Item 52: The method of item 34, further comprising directing the homogenized power beam toward a power converter. Item 53: The method of item 52, wherein the power converter includes a photovoltaic (PV) cell. Item 54: The method of item 52, wherein the power converter includes a plurality of PV cells.

[0042] While the above has set forth what is considered to be the best mode and / or other examples, it should be understood that various modifications can be made herein, that the subject matter disclosed herein can be implemented in various forms and examples, and that the teachings can be applied to numerous applications, only a few of which have been described herein. It is intended that the following claims claim any and all applications, modifications, and variations that fall within the true scope of the present teachings.

[0043] Unless otherwise specified, all measurements, values, estimates, positions, dimensions, sizes, and other specifications set forth in this specification, including the following claims, are approximate rather than exact and are intended to have a reasonable range consistent with the function to which they relate and that which is customary in the technical field to which they pertain.

[0044] The scope of protection is limited only by the claims that follow. That scope is intended to be as broad as possible, consistent with the ordinary meaning of the language used in the claims when interpreted in light of this specification and the following prosecution history, to encompass all structural and functional equivalents. Nevertheless, no inclusion of subject matter that does not meet the requirements of 35 U.S.C. §§ 101, 102, or 103 is intended, and should not be so construed. Any unintended inclusion of such subject matter is hereby disclaimed.

[0045] Except as set forth in the preceding paragraph, nothing described or shown, whether claimed or not, is intended to or should be construed to cause appropriation of any element, step, feature, object, benefit, advantage, or equivalent to the public.

[0046] It will be understood that the terms and expressions used herein have the ordinary meanings ascribed to such terms and expressions with respect to their corresponding respective fields of inquiry and research, unless a specific meaning is otherwise stated herein. Relative terms such as first and second may be used only to distinguish one entity from another, without necessarily implying any relationship or order between such entities. The terms "comprise" and "include," in all their grammatical forms, are intended to cover non-exclusive inclusions; thus, a process, method, article, device, or composition that includes or includes a list of elements may also include other elements not expressly listed. An element preceded by "a" or "An" does not, without further constraints, exclude the existence of additional identical or similar elements.

[0047] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It should be understood that the Abstract is not used to interpret or limit the scope of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features may be grouped together in various examples for clarity of explanation. This method of disclosure should not be interpreted as reflecting an intention that the claims require more features than are expressly recited in each claim. Furthermore, features from one example may be freely included in another, or substituted for one another, without departing from the overall scope and spirit of the present application.

[0048] The following is the invention as originally described in the present application. <Claim 1> 1. A beam homogenizer comprising a compound lens configured to reshape an incident power beam, The compound lens is a first optical surface configured to focus the incident power beam at a focal length; a second optical surface including a plurality of optical elements each configured to expand a respective portion of the focused power beam toward a focusing region, wherein the directed portions of the focused power beam overlap one another at the focusing region to form a homogenized power beam. <Claim 2> 10. The beam homogenizer of claim 1, wherein the compound lens has a width, and the compound lens is positioned at a distance from the focusing region that is between about half the width and about six times the width. <Claim 3> 3. The beam homogenizer of claim 2, wherein the compound lens is positioned at a distance from the focusing region between about the width and about four times the width. <Claim 4> 4. The beam homogenizer of claim 3, wherein the compound lens is positioned at a distance from the focusing region between about two times the width and about three times the width. <Claim 5> the compound lens has an axis; the homogenized power beam has a final width that is less than a width of the compound lens; 10. The beam homogenizer of claim 1, wherein the focusing region is sufficiently wide so that the homogenized power beam is located within the focusing region when the incident power beam forms an angle of less than 2 degrees with respect to the axis. <Claim 6> 6. The beam homogenizer of claim 5, wherein the focusing region is sufficiently wide that the homogenized power beam is located within the focusing region when the incident power beam forms an angle of less than 5 degrees with respect to the axis. <Claim 7> 6. The beam homogenizer of claim 5, wherein the focusing region is sufficiently wide that the homogenized power beam is located within the focusing region when the incident power beam forms an angle of less than 10 degrees with respect to the axis. <Claim 8> 10. The beam homogenizer of claim 1, wherein the incident power beam has an unshaped beam irradiance profile and the homogenized power beam has a reshaped beam irradiance profile, the reshaped beam irradiance profile being flatter than the unshaped beam irradiance profile. <Claim 9> 9. The beam homogenizer of claim 8, wherein the unshaped beam irradiance profile is approximately Gaussian. <Claim 10> 10. The beam homogenizer of claim 9, wherein the reshaped beam irradiance profile is approximately flat across at least half of the collection area. <Claim 11> 9. The beam homogenizer of claim 8, wherein the reshaped beam irradiance profile has a normalized deviation that is less than half the normalized deviation of the unshaped beam irradiance profile. <Claim 12> 12. The beam homogenizer of claim 11, wherein the normalized deviation of the reshaped beam irradiance profile is less than 0.3 times the normalized deviation of the unshaped beam irradiance profile. <Claim 13> 12. The beam homogenizer of claim 11, wherein the normalized deviation of the reshaped beam irradiance profile is less than 0.25 times the normalized deviation of the unshaped beam irradiance profile. <Claim 14> 12. The beam homogenizer of claim 11, wherein the normalized deviation of the reshaped beam irradiance profile is less than 0.2 times the normalized deviation of the unshaped beam irradiance profile. <Claim 15> 10. The beam homogenizer of claim 1, wherein the optical element has a width that is approximately 1 / 20th the width of the beam homogenizer. <Claim 16> 10. The beam homogenizer of claim 1, wherein the optical element has a width that is approximately one-tenth the width of the beam homogenizer. <Claim 17> 10. The beam homogenizer of claim 1, wherein the optical element has a width that is approximately one-fifth the width of the beam homogenizer. <Claim 18> 10. The beam homogenizer of claim 1, wherein the optical element has a width of less than 1 mm. <Claim 19> 10. The beam homogenizer of claim 1, wherein the optical element has a width of less than 5 mm. <Claim 20> 10. The beam homogenizer of claim 1, wherein the optical element has a width of less than 20 mm. <Claim 21> 10. The beam homogenizer of claim 1, wherein the optical element is convex. <Claim 22> 10. The beam homogenizer of claim 1, wherein the optical element is concave. <Claim 23> 10. The beam homogenizer of claim 1, wherein the optical element is a lenslet. <Claim 24> 2. The beam homogenizer of claim 1, wherein the first side has a first f-number and the second side has a second f-number, the first f-number and the second f-number having absolute values ​​within 10% of each other. <Claim 25> The beam homogenizer according to claim 1; a power converter positioned to receive the homogenized power beam. <Claim 26> 26. The power receiver of claim 25, further comprising a concentrator positioned to direct at least a portion of the homogenized power beam toward the power converter. <Claim 27> 27. The power receiver of claim 26, wherein the concentrator is a reflective concentrator. <Claim 28> 27. The power receiver of claim 26, wherein the concentrator has an output angle less than or equal to a maximum acceptance angle of the power converter. <Claim 29> 26. The power receiver of claim 25, further comprising a plurality of concentrators, each concentrator positioned to direct at least a portion of the reshaped power beam to a particular location within the concentration region. <Claim 30> 30. The power receiver of claim 29, wherein the plurality of concentrators are packed together to collect at least 90% of the reshaped power beam. <Claim 31> 26. The power receiver of claim 25, wherein the power converter includes a photovoltaic (PV) cell. <Claim 32> 26. The power receiver of claim 25, wherein the power converter includes a plurality of PV cells. <Claim 33> 33. The power receiver of claim 32, wherein the power receiver comprises a plurality of concentrators, each concentrator positioned to receive at least a portion of the homogenized power beam, and each concentrator positioned to direct a respective portion of the homogenized power beam toward at least one PV cell. <Claim 34> 1. A method for homogenizing a power beam, comprising: receiving an incident power beam; splitting the received beam into a plurality of beam portions; directing each beam portion toward a beam target area; directing each beam portion includes changing the size of the beam portion at the target area to a selected size; wherein the multiple beam portions overlap one another at the target area. <Claim 35> 35. The method of claim 34, wherein splitting the beam into a plurality of beam portions and directing each beam portion toward a beam target area comprises passing the power beam through a compound lens. <Claim 36> 36. The method of claim 35, wherein the compound lens has an entrance surface and an exit surface, the exit surface comprising a plurality of lenslets. <Claim 37> 37. The method of claim 36, wherein the lenslets are convex. <Claim 38> 37. The method of claim 36, wherein the lenslets are concave. <Claim 39> 37. The method of claim 36, wherein the entrance surface is aspheric. <Claim 40> 37. The method of claim 36, wherein the entrance surface has a first f-number and the exit surface has a second f-number, the first f-number and the second f-number having absolute values ​​within 10% of each other. <Claim 41> the incident power beam has an incident normalized deviation of beam irradiance; the overlapping beam portions at the target area have a homogenized normalized deviation of beam irradiance; 35. The method of claim 34, wherein a ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 2. <Claim 42> 42. The method of claim 41, wherein the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 3. <Claim 43> 42. The method of claim 41, wherein the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 4. <Claim 44> 42. The method of claim 41, wherein the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 5. <Claim 45> 35. The method of claim 34, wherein the plurality of beam portions comprises between 9 and 10,000 beam portions. <Claim 46> 35. The method of claim 34, wherein the plurality of beam portions comprises between 25 and 400 beam portions. <Claim 47> 35. The method of claim 34, wherein the plurality of beam portions comprises between 64 and 225 beam portions. <Claim 48> 35. The method of claim 34, wherein the overlapping beam portions form a homogenized beam. <Claim 49> 49. The method of claim 48, further comprising focusing at least a portion of the homogenized beam. <Claim 50> 50. The method of claim 49, further comprising directing the focused portion of the homogenized beam to a power converter. <Claim 51> 51. The method of claim 50, wherein concentrating at least a portion of the power beam comprises passing the beam through a concentrator having an output angle less than or equal to a maximum acceptance angle of the power converter. <Claim 52> 35. The method of claim 34, further comprising directing the homogenized power beam towards a power converter. <Claim 53> 53. The method of claim 52, wherein the power converter comprises a photovoltaic (PV) cell. <Claim 54> 53. The method of claim 52, wherein the power converter comprises a plurality of PV cells.

Claims

1. 1. A beam homogenizer comprising a compound lens configured to reshape an incident collimated power beam, The compound lens is a first optical surface having a first f-number and configured to focus the incident power beam at a focal length; a second optical surface including a plurality of optical elements, each optical element of the plurality of optical elements configured to expand a respective portion of the focused power beam toward a collection region; each optical element of the plurality of optical elements has an associated f-number having an absolute value within 10% of the first f-number; the second optical surface, wherein the expanded portions of the focused power beam overlap each other at the focused region to form a homogenized power beam.

2. 10. The beam homogenizer of claim 1, wherein the compound lens has a width, and the compound lens is positioned at a distance from the focusing region that is between half the width and six times the width.

3. the compound lens has an axis; the homogenized power beam has a final width that is less than a width of the compound lens; 10. The beam homogenizer of claim 1, wherein the focusing region is sufficiently wide that the homogenized power beam is located within the focusing region when the incident power beam forms an angle of less than 10 degrees with respect to the axis.

4. 10. The beam homogenizer of claim 1, wherein the incident power beam has an unshaped beam irradiance profile and the homogenized power beam has a reshaped beam irradiance profile, the reshaped beam irradiance profile being flatter than the unshaped beam irradiance profile.

5. 5. The beam homogenizer of claim 4, wherein the reshaped beam irradiance profile has a normalized deviation that is less than half the normalized deviation of the unshaped beam irradiance profile.

6. 6. The beam homogenizer of claim 5, wherein the normalized deviation of the reshaped beam irradiance profile is less than 0.2 times the normalized deviation of the unshaped beam irradiance profile.

7. 10. The beam homogenizer of claim 1, wherein the optical elements each have a width of less than 20 mm.

8. The beam homogenizer of claim 1 , wherein the optical element is a lenslet.

9. The beam homogenizer of claim 1; a power converter positioned to receive the homogenized power beam.

10. The power receiver of claim 9 , further comprising a concentrator positioned to direct at least a portion of the homogenized power beam toward the power converter.

11. 10. The power receiver of claim 9, further comprising a plurality of concentrators, each concentrator positioned to direct at least a portion of the reshaped power beam to a particular location within the concentration region.

12. The power receiver of claim 9 , wherein the power converter includes a photovoltaic (PV) cell.

13. The power receiver of claim 9 , wherein the power converter includes a plurality of PV cells.

14. 1. A method for homogenizing a power beam, comprising: receiving an incident collimated power beam; splitting the received beam into a plurality of beam portions; directing each beam portion toward a beam target area; directing each beam portion includes changing the size of the beam portion at the target area to a selected size; the plurality of beam portions overlap one another at the target area; the step of splitting the received beam into a plurality of beam portions and directing each beam portion toward a beam target area includes passing the power beam through a compound lens; the compound lens having an entrance surface and an exit surface, the exit surface including a plurality of optical elements; the entrance surface has a first f-number, and each element of the plurality of optical elements has a respective f-number having an absolute value within 10% of the first f-number.

15. the incident power beam has an incident normalized deviation of beam irradiance; the overlapping beam portions at the target area have a homogenized normalized deviation of beam irradiance; 15. The method of claim 14, wherein the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 2.

16. 16. The method of claim 15, wherein the ratio of the homogenized normalized deviation to the incident normalized deviation is less than 1 / 5.

17. The method of claim 14, wherein the plurality of beam portions comprises between 9 and 10,000 beam portions.

18. The method of claim 14 , wherein the overlapping beam portions form a homogenized beam.

19. 20. The method of claim 18, further comprising the steps of: focusing at least a portion of the homogenized beam; and directing the focused portion of the homogenized beam to a power converter.

20. 20. The method of claim 18, further comprising directing the homogenized power beam toward a power converter.

21. The method of claim 20 , wherein the power converter comprises a photovoltaic (PV) cell.

22. The method of claim 20 , wherein the power converter comprises a plurality of PV cells.

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