Transmission device, information processing device, optical wireless power transfer system, information processing method, and program

Abstract

The present invention provides a transmission device in an optical wireless power transfer system provided with the transmission device and a reception device, the transmission device comprising a a modulation unit and a light source unit for outputting a combination of a plurality of Gaussian beams outputted from the transmission device in such a manner that the combination of the plurality of Gaussian beams becomes a flat-top beam after propagating through space to the reception device.

Description

Transmitting device, information processing device, optical wireless power supply system, information processing method, and program

[0001] The present invention relates to optical wireless power supply technology.

[0002] Optical wireless power transfer technology uses, for example, a laser as an energy medium. Laser light (also called a laser beam or beam) is transmitted from the laser toward a target to be powered, and the target converts the laser light into electricity using a photoelectric conversion element such as a solar cell. Note that, here, the light source (light source element) that outputs the laser light is called a "laser." A "laser" may also be called a laser medium, a laser oscillator, or the like.

[0003] Diffractive optical element (DOE) and glass diffuser, https: / / www.agc.com / products / electoric / detail / doe_and_diffuser.html, retrieved June 1, 2023. Spatial light modulator (SLM), https: / / www.symphotony.com / products / ultrashort / ultrashortmenu / slm / , retrieved June 1, 2023. Overview of laser beam shaping, https: / / www.edmundoptics.jp / knowledge-center / application-notes / optics / laser-beam-shaping-overview / , retrieved June 1, 2023.

[0004] To supply high-power electricity, it is expected that a multi-cell type photoelectric converter equipped with multiple cells (photoelectric conversion elements) will be used as a photoelectric conversion unit that converts received light into electricity. In a multi-cell type photoelectric conversion unit, it is desirable that light be uniformly incident on each cell to avoid reducing the efficiency of photoelectric conversion.

[0005] However, with conventional technology, it is difficult to make light uniformly incident on each cell, which causes a problem of reduced photoelectric conversion efficiency.

[0006] The present invention has been made in view of the above points, and an object of the present invention is to provide a technique for improving the efficiency of photoelectric conversion in an optical wireless power supply system.

[0007] According to the disclosed technology, there is provided a transmitting device in an optical wireless power supply system including a transmitting device and a receiving device, the transmitting device including a light source unit and a modulation unit for outputting a combination of a plurality of Gaussian beams so that the combination of the Gaussian beams output from the transmitting device becomes a flat-top beam after propagating through space to the receiving device.

[0008] The disclosed technology provides a technology for improving the efficiency of photoelectric conversion in an optical wireless power supply system.

[0009] 12 is a diagram for explaining a problem when a Gaussian beam is used. FIG. 13 is a diagram for explaining a problem when a Gaussian beam is used. FIG. 14 is a diagram illustrating an example of a configuration of an optical wireless power supply system according to an embodiment of the present invention. FIG. 15 is a diagram illustrating an example of a configuration of a transmitting device 100. FIG. 16 is a diagram illustrating an example of a configuration of a receiving device 200. FIG. 17 is a diagram illustrating an example of a configuration of an information processing device 300. FIG. 18 is a diagram illustrating a flat-top beam. FIG. 19 is a diagram illustrating the intensity distribution of a beam after counterpropagation. FIG. 20 is a diagram illustrating the intensity distribution of a beam before and after counterpropagation. FIG. 21 is a diagram illustrating the intensity distribution of a beam after counterpropagation, using multiple Gaussian beams to reproduce the intensity distribution of a counterpropagated beam. FIG. 22 is a diagram illustrating a beam after phase modulation has been applied to the beam of FIG. 11 and then propagated 1 km. FIG. 23 is a diagram illustrating the intensity distribution of a beam before and after propagation. FIG. 24 is a diagram illustrating an example of a configuration of a transmitting device 100 and a receiving device 200. FIG. 25 is a diagram illustrating an example of a configuration of the transmitting device 100. FIG. 26 is a diagram illustrating an example of a hardware configuration of the device.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0011] In the embodiment described below, it is assumed that a laser is used as the light source in the transmitting device, but using a laser as the light source is merely one example. The light source to which the technology according to the present invention can be applied is not limited to a specific type of light source. Any light source that can output light (electromagnetic waves from infrared to ultraviolet) may be used. Hereinafter, an entity that outputs light may be referred to as a "light source element" or "light source unit." As mentioned above, the light source is not limited to a laser, but in this embodiment, it is preferable to use a laser as the light source.

[0012] In the following, first, the problems associated with the technology of the present embodiment will be described in detail, and then the technology of the present embodiment will be described. Note that the content of the following description of the problems is not publicly known.

[0013] (Regarding the Problem) Generally, a beam output from a laser is called a Gaussian beam, and the light intensity distribution in a plane perpendicular to the optical axis is a Gaussian distribution.

[0014] Optical wireless power transfer technology is available in two types: a single-cell type with a single photoelectric conversion element cell as the photoelectric conversion unit that converts received light into electricity, and a multi-cell type with multiple cells. The voltage that can be extracted from a single cell is determined by the band gap of the element, and is 0.5 V for a typical solar cell. Therefore, when attempting to supply high-power electricity, the current value becomes large, making the single-cell type unsuitable.

[0015] On the other hand, in the case of a multi-cell type, connecting the cells in series makes it possible to increase the voltage and thus the power that can be extracted. However, if there is a cell among the multiple cells that does not receive enough light, the current value of that cell becomes a bottleneck, limiting the overall current value and preventing high power from being obtained. Furthermore, the light energy that enters other cells cannot be extracted as power, but rather turns into heat, which reduces the efficiency of photoelectric conversion. Therefore, in optical wireless power transfer, it is desirable for light to be uniformly incident on each cell in the photoelectric conversion section.

[0016] The above-mentioned problems that arise when a Gaussian beam is used will be explained more specifically with reference to FIGS.

[0017] In the configuration shown in Figures 1 and 2, a laser 1, which is a light source element, and a photoelectric conversion unit 2 on the light receiving side are shown. For the laser 1, a surface 3 (light emitting surface) on the side from which the laser 1 outputs light is also shown. For the photoelectric conversion unit 2, a surface (light receiving surface) on the side from which light is received is also shown. As shown in Figures 1 and 2, the photoelectric conversion unit 2 has a plurality of cells arranged in a lattice pattern. Furthermore, in Figures 1 and 2, the beam output from surface 3 is input to the optical path, so surface 3 is described as "input." Furthermore, the output from the optical path becomes the input to the photoelectric conversion unit 2.

[0018] As described above, the intensity distribution of the Gaussian beam is a Gaussian distribution, and therefore, as shown in FIG. 1, it is difficult to uniformly apply light to each cell constituting the photoelectric conversion unit 2.

[0019] Furthermore, as shown in Figure 2, if a laser 1 that outputs laser light (beam) from a wider area is used in order to apply light as uniformly as possible to each cell, the base of the Gaussian beam will extend beyond the light-receiving surface of the photoelectric conversion unit 2, resulting in increased loss.

[0020] To address this issue, it is conceivable to use a beam with a constant intensity distribution, such as a flat-top beam. However, when a flat-top beam propagates over a long distance, the beam pattern is distorted due to diffraction, and the intensity distribution is no longer constant when the beam enters the photoelectric conversion unit 2.

[0021] Therefore, beam shaping can be considered to ensure a constant intensity distribution after propagation. However, when propagating over distances of the order of m or more, such as in energy transmission, it is difficult to obtain a desired beam, such as a flat-top beam, using phase modulation alone, and intensity modulation is required. Conventional intensity modulation beam shaping methods (such as SLMs (Spatial Light Modulators)) inevitably result in a decrease in efficiency when modulating intensity, making them unsuitable for optical wireless power transfer, which is intended for energy transmission. Furthermore, SLMs have low power tolerance and are unsuitable for high-power energy transmission. Therefore, improving the efficiency and power tolerance of beam shaping is a challenge for optical wireless power transfer.

[0022] The configuration and operation of a system that solves the above-mentioned problems will be described in detail below.

[0023] (Configuration Example of System / Device) A configuration example of an optical wireless power supply system according to this embodiment is shown in Fig. 3. As shown in Fig. 3, the optical wireless power supply system according to this embodiment includes a transmitting device 100 and a receiving device 200.

[0024] In this embodiment, an information processing device 300 is used that performs numerical calculations for beam shaping, as shown in Fig. 3. The details of the numerical calculations for beam shaping will be described later.

[0025] FIG. 4 shows an example configuration of the transmitting device 100. As shown in FIG. 4, the transmitting device 100 includes a light source unit 110 and a modulation unit 120. In this embodiment, the light source unit 110 includes a plurality of lasers (light source elements). The modulation unit 120 can shape a beam by modulating the phase or intensity of light, partially cutting the intensity of light, or superimposing light. For example, a diffractive optical element (DOE) or a spatial light modulator (SLM) can be used as the modulation unit 120.

[0026] Fig. 5 shows an example configuration of the receiving device 200. As shown in Fig. 5, the receiving device 200 includes a photoelectric conversion unit 210. The photoelectric conversion unit 210 has, for example, a configuration in which a plurality of photoelectric conversion elements (each photoelectric conversion element is called a cell) are arranged in a lattice pattern.

[0027] (Outline of Processing by Information Processing Device 300) In this embodiment, the intensity distribution and phase distribution of the beam before propagation are calculated by backpropagating the flat-top beam by the propagation distance in a numerical calculation so that the intensity distribution of the beam output from the transmitting device 100 becomes a flat-top beam after propagating through space. The information processing device 300 performs this numerical calculation.

[0028] In this numerical calculation, the information processing device 300 adjusts the beam width so that the propagation distance of the beam exceeds the Rayleigh length (so that it falls within the Fraunhofer diffraction region).

[0029] The intensity distribution obtained by back propagation through numerical calculations by the information processing device 300 is reproduced in the transmitting device 100 by using a light source unit 110 that combines multiple lasers with different intensities. Regarding the phase, the phase obtained by back propagation is reproduced using a modulation unit 120 (a phase modulation device such as a DOE).

[0030] (Configuration example of information processing device 300) Fig. 6 shows a configuration example of the information processing device 300. As shown in Fig. 6, the information processing device 300 has an input unit 310, a back propagation calculation unit 320, an intensity distribution reproduction unit 330, and an output unit 340. The "back propagation calculation unit 320 and the intensity distribution reproduction unit 330" may be called a calculation unit. Furthermore, the information processing device 300 may not be provided with the intensity distribution reproduction unit 330. In this case, the calculation of intensity distribution reproduction is performed by a separate device.

[0031] (Example of Operation of Information Processing Device 300) An example of operation of the information processing device 300 having the above configuration will be described below. Here, a detailed description will be given using a specific example.

[0032] Consider a situation in which the wavelength of the laser light output from the transmitting device 100 is 1.06 μm and the propagation distance is 1 km. The propagation distance is the distance between the transmitting device 100 and the receiving device 200. Both the wavelength of the laser light and the propagation distance are examples of conditions for back propagation calculation.

[0033] First, as shown in FIG. 7, a flat-top beam (a beam with a constant intensity) having a beam diameter of 3 cm is prepared.

[0034] Here, in the case of a Gaussian beam, the beam diameter (intensity is 1 / e ２ If the total beam width is 3 cm, the Rayleigh length is 174 m, so it can be said that a propagation distance of 1 km is sufficiently long for a beam diameter of 3 cm.

[0035] The above conditions (wavelength, propagation distance, "flat-top beam with a beam diameter of 3 cm", etc.) are input from the input unit 310 of the information processing device 300.

[0036] The backpropagation calculation unit 320 performs numerical calculations equivalent to backpropagating the prepared flat-top beam 1 km. Backpropagating the flat-top beam 1 km is equivalent to propagating the flat-top beam −1 km. The backpropagation calculation unit 320 obtains the intensity distribution and phase distribution after backpropagation. The intensity distribution and phase distribution may be output from the output unit 340.

[0037] 8 and 9 show the intensity distribution of the beam after counterpropagation, and FIG. 10 shows the phase distribution of the beam after counterpropagation.

[0038] Figures 8 and 10 show the intensity and phase distributions, respectively, in a plane perpendicular to the beam. Figure 9 shows a cross section of the intensity distribution at y = 0. Figure 9 shows the cross section of the intensity distribution of the beam before backpropagation as Input, and the cross section of the intensity distribution of the beam after backpropagation as Output.

[0039] As shown in Figure 9, the intensity distribution after back propagation consists of a central main lobe and multiple side lobes. Because the propagation distance is sufficiently longer than the Rayleigh length and falls within the Fraunhofer diffraction region, this intensity distribution can be considered to be a flat-top beam, that is, a sinc function, which is the Fourier transform of a rectangular function.

[0040] Next, the intensity distribution reproducing section 330 reproduces the intensity distribution obtained by the backpropagation calculating section 320 by superimposing a plurality of Gaussian beams. The calculation contents performed by the intensity distribution reproducing section 330 will be explained below.

[0041] First, one Gaussian beam is placed at the origin, and one or more Gaussian beams (Gaussian beams corresponding to side lobes) whose intensity decreases toward the periphery are prepared around it.

[0042] The coordinates of the zero points of the sinc function are ±m(λz / 2w) (λ: wavelength, z: propagation distance, w: rectangular width, m: integer). The intensity distribution reproducing unit 330 places the center of the Gaussian beam, which corresponds to the side lobe, at the center between the zero points. Specifically, this is as follows:

[0043] The intensity distribution reproducing unit 330 calculates the central coordinates of the Gaussian beam corresponding to the side lobes as (±((2m-1) / 2)·(λZ / 2w), 0), (0, ±((2m-1) / 2)·(λZ / 2w)).

[0044] Furthermore, the intensity distribution reproducing unit 330 calculates the width of each Gaussian beam as λz / ((√(2 log 2) · 2w)) and the central intensity as (2√2) / ((2m-1)π). Note that "√(2 log 2)" is the root of (2 log 2).

[0045] The beams obtained by the above calculation when m=2, 3, and 4 are shown in Fig. 11. That is, Fig. 11 shows the intensity distribution of a beam that reproduces the intensity distribution of a counter-propagated beam using multiple Gaussian beams.

[0046] FIG. 12 shows the beam of FIG. 11 that has been given the phase modulation of FIG. 10 using the modulation section 120 and then propagated for 1 km.

[0047] FIG. 13 shows a cross section of the intensity distribution at y=0 of the beam before propagation (FIG. 11) (Input) and a cross section of the intensity distribution at y=0 of the beam after propagation (FIG. 12) (Output).

[0048] 12 and 13, it can be seen that the beam becomes nearly uniform after propagation and the intensity of the beam drops off at a right angle. As a result, by using this method, it is possible to obtain a beam that can be photoelectrically converted with high efficiency and without loss.

[0049] (Configuration Example) Fig. 14 shows configuration examples of a transmitting device 100 and a receiving device 200 that realize the counter-propagated beam calculated as described above using multiple Gaussian beams. As shown in Fig. 14, the transmitting device 100 is provided with multiple lasers and phase modulators. The receiving device 200 is provided with a photoelectric conversion element.

[0050] The lasers are arranged to output the Gaussian beams shown in Fig. 11, and the phases are modulated by the phase modulators. The homogenized beams are incident on the photoelectric conversion element.

[0051] 15 shows a front view of the light source unit 110. As shown in Fig. 15, a plurality of lasers are arranged in the light source unit 110 so as to reproduce the intensity distribution shown in Fig. 11.

[0052] (Example of Hardware Configuration of Information Processing Device 300) The information processing device 300 described in this embodiment can be realized, for example, by causing a computer to execute a program. This computer may be a physical computer or a virtual machine on the cloud.

[0053] That is, the device can be realized by executing a program corresponding to the processing performed by the device using hardware resources such as a CPU and memory built into a computer. The program can be recorded on a computer-readable recording medium (such as a portable memory) and stored or distributed. The program can also be provided via a network such as the Internet or email.

[0054] Fig. 16 is a diagram showing an example of the hardware configuration of the computer. The computer in Fig. 16 includes a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, and the like, all of which are interconnected by a bus BS. The computer may further include a GPU.

[0055] The program that realizes the processing on the computer is provided by a recording medium 1001, such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the program does not necessarily have to be installed from the recording medium 1001, but may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files, data, etc.

[0056] The memory device 1003 reads and stores the program from the auxiliary storage device 1002 when an instruction to start the program is received. The CPU 1004 realizes functions related to the information processing device 300 in accordance with the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network, etc. The display device 1006 displays a GUI (Graphical User Interface) or the like according to the program. The input device 1007 is composed of a keyboard, mouse, buttons, a touch panel, etc., and is used to input various operation instructions. The output device 1008 outputs the results of calculations.

[0057] (Summary of the embodiment) As described above, in this embodiment, a flat-top beam is reverse-propagated over the propagation distance and reproduced by beam shaping so that it becomes a flat-top beam after propagation. Although beam shaping using intensity modulation is necessary for long-distance propagation, conventional intensity modulation devices such as SLMs are not used because of their low efficiency and low tolerance for high intensity. Instead, a combination of multiple lasers with different intensities reproduces the intensity distribution when a flat-top beam is reverse-propagated without reducing efficiency.

[0058] For phase modulation, a conventional phase modulation device such as a DOE is used to reproduce the phase when the flat-top beam is propagated backward.

[0059] (Advantages of the Technique According to the Embodiments) By shaping the beam so that the intensity becomes uniform after propagation, the conversion efficiency of the photoelectric conversion element can be improved. Furthermore, by combining multiple Gaussian beams, the decrease in efficiency caused by conventional intensity modulation can be resolved and the power tolerance limitations can be eliminated.

[0060] The following additional notes are provided regarding the above-described embodiments.

[0061] <Supplementary Notes> (Supplementary Item 1) An optical wireless power supply system including a transmitting device and a receiving device, the transmitting device comprising a light source unit and a modulation unit for outputting a combination of multiple Gaussian beams output from the transmitting device so that the combination of the multiple Gaussian beams becomes a flat-top beam after propagating through space to the receiving device. (Supplementary Item 2) The transmitting device according to Supplementary Item 1, wherein the light source unit reproduces the intensity distribution of the intensity distribution and phase distribution of the flat-top beam before propagation, and the modulation unit reproduces the phase distribution. (Supplementary Item 3) The transmitting device according to Supplementary Item 2, wherein the intensity distribution and the phase distribution are distributions obtained by propagating the flat-top beam backward by a propagation distance. (Supplementary Item 4) The transmitting device according to Supplementary Item 2, wherein the multiple Gaussian beams in the transmitting device are arranged to reproduce the intensity distribution. (Supplementary Item 5) An information processing device including: a memory; and at least one processor connected to the memory, wherein the processor inputs conditions related to propagation in an optical wireless power supply system including a transmitting device and a receiving device, calculates an intensity distribution and a phase distribution of the beam before propagation based on the conditions so that the beam transmitted from the transmitting device becomes a flat-top beam after propagating through a space to the receiving device, and calculates an arrangement of a plurality of Gaussian beams in the transmitting device so as to reproduce the intensity distribution. (Supplementary Item 6) An optical wireless power supply system including the transmitting device according to any one of Supplementary Items 1 to 4, and a receiving device including a photoelectric conversion element that receives the flat-top beam. (Supplementary Item 7) An information processing method executed by an information processing device, comprising: an input step of inputting conditions related to propagation in an optical wireless power supply system including a transmitting device and a receiving device; and a calculation step of calculating an intensity distribution and a phase distribution of a beam before propagation based on the conditions so that the beam transmitted from the transmitting device becomes a flat-top beam after propagating through a space to the receiving device, and calculating an arrangement of multiple Gaussian beams in the transmitting device so as to reproduce the intensity distribution.(Supplementary Item 8) A non-transitory storage medium storing a program for causing a computer to function as each unit in the information processing device according to Supplementary Item 5.

[0062] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0063] REFERENCE SIGNS LIST 100 Transmitting device 110 Light source unit 120 Modulation unit 200 Receiving device 210 Photoelectric conversion unit 300 Information processing device 310 Input unit 320 Backpropagation calculation unit 330 Intensity distribution reproduction unit 340 Output unit 1000 Drive device 1001 Recording medium 1002 Auxiliary storage device 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input device 1008 Output device

Claims

1. A transmitting device in an optical wireless power supply system comprising a transmitting device and a receiving device, the transmitting device comprising a light source unit and a modulation unit for outputting a combination of multiple Gaussian beams so that the combination of the multiple Gaussian beams output from the transmitting device becomes a flat-top beam after propagating through space to the receiving device.

2. The transmitting device according to claim 1, wherein the light source section reproduces the intensity distribution of the intensity distribution and phase distribution of the flat-top beam before propagation, and the modulation section reproduces the phase distribution.

3. The transmitting device according to claim 2, wherein the intensity distribution and the phase distribution are distributions obtained by propagating the flat-top beam in a reverse direction over a propagation distance.

4. The transmitting device according to claim 2, wherein a plurality of Gaussian beams in said transmitting device are arranged so as to reproduce said intensity distribution.

5. An information processing device comprising: an input unit for inputting conditions related to propagation in an optical wireless power supply system having a transmitting device and a receiving device; and a calculation unit for calculating the intensity distribution and phase distribution of the beam before propagation based on the conditions so that the beam transmitted from the transmitting device becomes a flat-top beam after propagating through a space to the receiving device, and for calculating the arrangement of multiple Gaussian beams in the transmitting device so as to reproduce the intensity distribution.

6. An optical wireless power supply system comprising a transmitting device according to any one of claims 1 to 4 and a receiving device having a photoelectric conversion element for receiving the flat-top beam.

7. An information processing method executed by an information processing device, comprising: an input step of inputting conditions related to propagation in an optical wireless power supply system including a transmitting device and a receiving device; and a calculation step of calculating the intensity distribution and phase distribution of the beam before propagation based on the conditions so that the beam transmitted from the transmitting device becomes a flat-top beam after propagating through a space to the receiving device, and calculating the arrangement of multiple Gaussian beams in the transmitting device so as to reproduce the intensity distribution.

8. A program for causing a computer to function as each unit in the information processing device according to claim 5.

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