Shaping device

Abstract

This shaping device for shaping a beam includes a beam shaper functioning as a lens in which a central portion of an axicon lens is formed as a concave lens.

Description

plastic surgery device

[0001] The present invention relates to beam shaping techniques.

[0002] Optical wireless power transfer technology uses light, such as a laser, as an energy medium. The laser beam is emitted from the laser toward the target, where it is converted into electricity using a photoelectric conversion element, such as a solar cell.

[0003] Methods for shaping laser beams include diffractive optical elements (DOEs) and spatial light modulators (SLMs). By using DOEs and SLMs, it is possible to obtain the desired beam by modulating the phase and intensity of light, cutting off parts of the light intensity, or superimposing it.

[0004] https: / / www.cqpub.co.jp / hanbai / books / 41 / 41291 / 41291_p23-114.pdfC. Guo, et.al., "Large aperture flat-top beam shaping and long-distance transmission based on off-axis reflective free-form surface optical system," Proc. of SPIE, 12765 127650K-1-127650K-9 (2023).Z. Hu, et.al., "Performance research on flat-topped beam-based small satellites free space optical communication," Opt. Commun. 487, 126802 (2021).P. Barcik, et.al., "Optical Wireless Communication Transmitter with a Refraction Beam Shaper," 9th International Symposium on Communication Systems, Networks & Digital Sign (2014).Z. Zhai, et.al., "Flattop Beam Shaping Using Hybrid Gratings," IEEE Photonics J. 14, 4, 7440605 (2022).https: / / www.edmundoptics.jp / knowledge-center / application-notes / optics / laser-beam-shaping-overview /

[0005] In high-power optical wireless power transfer, a panel consisting of multiple photovoltaic cells connected in series is used to suppress the current value after photovoltaic conversion and increase the voltage. However, if there is a cell that is not sufficiently exposed to light, the current value of that cell becomes a bottleneck, limiting the overall current value and leading to a decrease in photovoltaic conversion efficiency. Therefore, it is desirable to uniform the intensity distribution of the beam incident on the photovoltaic panel. In other words, it is necessary to shape the beam so that the intensity distribution is uniform after propagation.

[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 shaping a beam so that the intensity distribution becomes uniform after propagation.

[0007] According to the disclosed technology, there is provided a beam shaping device for shaping a beam, comprising a beam shaper having a lens function in which the central portion of an axicon lens is a concave lens.

[0008] The disclosed techniques provide techniques for shaping a beam so that it has a uniform intensity distribution after propagation.

[0009] FIG. 1 is a diagram for explaining the problem. FIG. 2 is a diagram for explaining the problem. FIG. 3 is a configuration diagram of an optical wireless power supply system according to an embodiment of the present invention. FIG. 4 is a configuration diagram of a light transmitting device 100. FIG. 5 is a configuration diagram of a beam shaper 10. FIG. 6 is a configuration diagram including the beam shaper 10 and an enlargement / reduction optical system 20. FIG. 7 is a configuration diagram including the beam shaper 10 and an enlargement / reduction optical system 20. FIG. 8 is a diagram for explaining Example 1. FIG. 9 is a diagram for explaining Example 2. FIG. 10 is a diagram for explaining Example 3.

[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] Below, as an example, an embodiment will be described in which the beam shaping technology according to the present invention is applied to the field of optical wireless power supply. However, the beam shaping technology according to the present invention can be applied to various fields such as optical wireless communication and laser processing.

[0012] In the following, first, the problems associated with the technology of the present embodiment will be described in more 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 Problems) Generally, a beam output from a laser medium 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 includes a single-cell type that has only one cell, which is a photoelectric conversion element, as the photoelectric conversion unit that converts received light into electricity, and a multi-cell type that has multiple cells. The voltage that can be extracted from one cell is determined by the band gap of the element, and is, for example, 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 solar cell, connecting the cells in series increases the voltage and therefore the amount of 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. In addition, the light energy that enters the other cells cannot be extracted as power, but rather turns into heat, which deteriorates the characteristics of the photoelectric conversion section.

[0016] The above-mentioned problem in the case of using a Gaussian beam will be explained more specifically with reference to FIG.

[0017] In the configuration shown in FIG. 1, a laser medium 1, which is a light source element, and a photoelectric conversion unit 2 on the light receiving side are shown. For the laser medium 1, a surface 3 (light emitting surface) on the side from which the laser medium 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 FIG. 1, the photoelectric conversion unit 2 has a plurality of cells arranged in a lattice pattern. Furthermore, in FIG. 1, 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 mentioned above, the intensity distribution of a Gaussian beam is a Gaussian distribution, and therefore it is difficult to uniformly apply light to each cell that constitutes the photoelectric conversion unit 2, as shown in Figure 1. In a Gaussian beam, in accordance with the Gaussian distribution, in a circular shape, the light is strong in the center and becomes weaker towards the periphery.

[0019] Therefore, it is desirable to be able to shape the beam so that the intensity distribution becomes constant (uniform) after the beam propagates. However, in long-distance propagation of the order of m or more, such as in optical wireless power transfer, it is difficult to flatten the beam due to the laser diffraction phenomenon (Non-Patent Document 1).

[0020] Flat-top beam shaping technology for 1-meter and 1-km propagation has also been reported in the field of optical wireless communication (Non-Patent Documents 3 and 4), but the beam does not drop sharply at the base, resulting in significant loss in optical wireless power transfer. This situation is shown in Figure 2. As shown particularly on the right side of Figure 2 (the light-receiving surface of the photoelectric conversion unit 2), the outer cells are not exposed to much light, and the current value of these unexposed cells limits the overall current value.

[0021] Conventional techniques include a highly flat beam using a diffraction grating (Non-Patent Document 5) and a beam shaping method in which a Gaussian beam is physically cut off using an aperture (Non-Patent Document 6). However, these techniques have low beam shaping efficiency and are unsuitable for the field of optical wireless power transfer.

[0022] The following describes a technique according to the present embodiment for solving the above problems.

[0023] (System Configuration Example) 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 light transmitting device 100 and a light receiving device 200.

[0024] Fig. 4 shows an example of the configuration of the light transmitting device 100. As shown in Fig. 4, the light transmitting device 100 includes a light source unit 110 and a shaping unit 120. The light source unit 110 includes a light source element that emits laser light. The shaping unit 120 includes a beam shaper 10, as will be described later. The shaping unit 120 may also be called a shaping device. Furthermore, the shaping unit 120 (shaping device) may be a standalone device.

[0025] The light receiving device 200 is equipped with a photoelectric conversion panel in which cells are connected in series. The surface of the photoelectric conversion panel serves as the light receiving surface. Below, a first embodiment and a second embodiment will be described as beam shaping methods using the shaping unit 120. The first embodiment is a basic example, and the second embodiment has an additional mechanism in addition to the first embodiment.

[0026] First Embodiment In the first embodiment, an axicon lens with a concave lens at the center is used as the beam shaper 10 in the shaping unit 120. That is, as shown in Fig. 5 , beam shaping is performed by combining the effects of the axicon lens and the concave lens.

[0027] An axicon lens is a lens having one conical surface and one flat surface, and in this embodiment, the central part of the conical part is a concave lens.

[0028] By making the center part of the axicon lens a concave lens, the outer part of the beam becomes a ring-shaped beam, and the central part is diffused by the concave lens. Note that the "outer part of the beam" refers to the part near the outer periphery of the circle that represents the beam when the beam is cut by a plane perpendicular to its direction of travel.

[0029] Depending on the propagation distance and the desired beam thickness after propagation, the original Gaussian beam can be shaped to obtain a desired flat beam by adjusting the focal length of the axicon lens, the focal length of the concave lens, and the width of the concave lens, as shown in Fig. 5. In this embodiment, diffracted light is not used and the beam is not physically truncated, so a highly efficient beam shaping method can be realized.

[0030] The beam shaper 10 may be a processed physical lens (a physical axicon lens with the central portion thereof turned into a concave lens), or may be something other than a physical lens.

[0031] Other than a physical lens, for example, any one or more of a DOE, an SLM, and a hologram can be used to realize the function of a lens with the central part of the axicon lens being a concave lens.

[0032] When using one or more of a DOE, an SLM, and a hologram as the beam shaper 10, it is also possible to give the beam shaper 10 lens power instead of giving the input Gaussian beam a wavefront curvature.

[0033] When a physical lens is used as the beam shaper 10, it can be used in a wider band than wavelength-dependent systems such as DOE, SLM, and hologram. Therefore, in systems that use multiple wavelengths, it is desirable to use a physical lens as the beam shaper 10. Furthermore, when a variable beam shaping device such as an SLM or hologram is used as the beam shaper 10, the beam shape can be adjusted by adjusting one or more of the focal length of the axicon lens, the focal length of the concave lens, and the width of the concave lens.

[0034] Second Embodiment Next, a second embodiment will be described. In the second embodiment, as shown in Fig. 6, the shaping unit 120 includes an expansion / reduction optical system 20, which expands or reduces the beam using a beam expander, a lens system, or the like, in front of the beam shaper 10.

[0035] By adjusting the lens power or magnification in the magnification / reduction optical system 20, it is possible to change the propagation distance from the light transmitting device 100 to the target 30 (a photoelectric conversion panel in the case of optical wireless power supply) (FIG. 7), and to change the beam diameter and intensity profile (FIG. 8).

[0036] 7 shows a case where lens power is applied to the enlargement / reduction optical system 20 to shorten the distance to the target 30. Fig. 8 shows a case where lens power or magnification is changed to increase the beam diameter at the target 30 in the enlargement / reduction optical system 20. Examples of the operation of the enlargement / reduction optical system 20 and its effects are as follows.

[0037] (Example 1) When the beam is focused by the magnification / reduction optical system 20, the focal length of the outer ring-shaped beam is closer to the front, so the beam diameter after 100 m is wider. The degree of divergence of the central beam is smaller, so the beam diameter after 100 m is smaller.

[0038] Therefore, a gap occurs between the beam in the outer ring portion and the beam in the center portion, but by increasing the diameter of the incident beam (by increasing the magnification of the expander or expansion system), the beam in the outer ring becomes thicker, and a flat beam can be maintained at the target 30. Note that the "expander or expansion system" used here may be the expansion / reduction optical system 20, or an expander other than the expansion / reduction optical system 20.

[0039] (Example 2) When the beam is diverged by the magnification / reduction optical system 20, the focal length of the outer ring-shaped beam becomes farther back, and the beam diameter after 100 m propagation becomes smaller. The degree of divergence of the central beam becomes greater, and the beam diameter after 100 m propagation becomes larger.

[0040] Therefore, the intensity of the overlapping portion of the ring-shaped beam and the central beam becomes strong, but by narrowing the diameter of the incident beam (reducing the magnification of the expander or expansion system), the outer ring beam becomes thinner, and it is possible to maintain a flat beam on the target 30. Note that the "expander or expansion system" used here may be the expansion / reduction optical system 20, or an expander other than the expansion / reduction optical system 20.

[0041] (Example of a specific design method) Here, an example of a specific design method will be described. Note that the design method here is just an example and is not limited to this design method.

[0042] Adjust the parameters so that the width (outer diameter) of the beam expanded into a ring shape by the axicon lens and the width of the beam expanded by the central concave lens are approximately the same. Here, as shown in Figure 5, the width of the input Gaussian beam is set to w ｂ , propagation distance is L, width of the flat beam to be shaped is w ｆ Then, the beam shaping parameter, the focal length of the axicon lens, f ａ , the focal length of the concave lens f ｃ , the width of the central concave lens w ｃ can be determined using the following equations (1) and (2).

[0043]

[0044] If the wavefront of the input Gaussian beam has curvature, or if the beam shaping itself is to have lens power, the design should take this curvature into consideration.

[0045] Example 1 A more specific example (simulation) will be described as Example 1. In Example 1, the width of the input Gaussian beam is set to 1 / e ２ The beam shaper 10 was designed so that the beam diameter after propagation of 100 m would be about 60 cm.

[0046] The axicon lens design is defined as ａ = 10 m, f ｃ = 8.3 m, w ｃ= 40 mm, and the entire system was given a lens power with a wavefront curvature of 35 m. Figure 9(a) shows the simulated beam profile after propagation of 100 m. Figure 9(b) shows the cross section of the beam intensity at y = 0. It can be seen that the proposed method produces a flatter beam compared to a Gaussian beam. The beam also has a steeper base, which reduces loss in optical wireless power transmission.

[0047] Next, a second embodiment will be described, which is an example of the above-mentioned "(Example 1) When the beam is focused by the magnification / reduction optical system 20." In the second embodiment, the axicon lens is designed as follows, as in the first embodiment: ａ = 10 m, f ｃ = 8.3 m, w ｃ = 40 mm, and the entire lens is given a lens power of wavefront curvature 35 m.

[0048] FIG. 10 shows a simulated beam profile after propagation of 100 m and a cross section of the beam intensity at y=0 in Example 2.

[0049] FIG. 10A shows the simulation results for the basic design for comparison, in which the diameter of the incident Gaussian beam is 7.52 cm and the wavefront curvature of the incident Gaussian beam is infinite (collimated light).

[0050] In FIG. 10B, the diameter of the incident Gaussian beam is set to 7.52 cm, the same as in the basic design, and the wavefront curvature of the incident Gaussian beam is set to −200 m.

[0051] In Figure 10(c), the diameter of the incident Gaussian beam is increased to 9 cm, which is larger than the basic design. The wavefront curvature of the incident Gaussian beam is -200 m, the same as in Figure 10(b).

[0052] If the wavefront curvature of the incident beam is set to -200 m, the focal length will be closer to the front, which will increase the ring diameter and make the beam larger (Fig. 10(a) → (b)). If the incident beam diameter is expanded to 9 cm, the ring diameter will become thicker and the beam will approach flat (Fig. 10(b) → (c)).

[0053] Next, a third embodiment will be described, which is an example of the above-mentioned "(Example 2) When the beam is diverged by the magnification / reduction optical system 20." In the third embodiment, the axicon lens is also designed in the same way as in the first embodiment, as follows: ａ = 10 m, f ｃ = 8.3 m, w ｃ = 40 mm, and the entire lens is given a lens power of wavefront curvature 35 m.

[0054] FIG. 11 shows a simulated beam profile after propagation of 100 m and a cross section of the beam intensity at y=0 in Example 3.

[0055] FIG. 11A shows the simulation results for the basic design for comparison, in which, as in Example 2, the diameter of the incident Gaussian beam is 7.52 cm and the wavefront curvature of the incident Gaussian beam is infinite (collimated light).

[0056] In FIG. 11B, the diameter of the incident Gaussian beam is set to 7.52 cm, the same as in the basic design, and the wavefront curvature of the incident Gaussian beam is set to 140 m.

[0057] In Fig. 11(c), the diameter of the incident Gaussian beam is set to 5 cm, which is smaller than the basic design. The wavefront curvature of the incident Gaussian beam is set to 140 m, the same as in Fig. 11(b).

[0058] If the wavefront curvature of the incident beam is 140 m, the focal length moves further back, so the ring diameter becomes smaller and the beam can be made smaller (Fig. 11(a) → (b)). Here, if the incident beam diameter is narrowed to 5 cm, the central Gaussian component becomes larger, so the beam approaches flat (Fig. 11(b) → (c)).

[0059] (Summary, Effects, etc. of the Embodiments) As described above, according to the technology of the present embodiments, it is possible to efficiently shape a beam into a flat beam during long-distance propagation and to suppress a decrease in photoelectric conversion efficiency due to intensity non-uniformity in optical wireless power transfer. Furthermore, flat-top beams are required in fields other than optical wireless power transfer, such as optical wireless communication and laser processing, and the technology of the present embodiments can be applied thereto.

[0060] Furthermore, as described in the second embodiment, the propagation distance, beam width, and intensity profile can be adjusted by combining the lens optical system 20, such as a beam expander, with the beam shaper 10. In optical wireless power feeding to a moving object with a variable propagation distance or in optical wireless power feeding to a variable (multiple) power feeding target, this adjustment mechanism makes it possible to shape the beam suitable for each system.

[0061] The following additional notes are provided regarding the above-described embodiments.

[0062] <Appendix> (Appendix 1) A beam shaping device for shaping a beam, comprising: a beam shaper having a lens function in which the central portion of an axicon lens is a concave lens. (Appendix 2) The shaping device according to appendix 1, in which the focal length of the axicon lens, the focal length of the concave lens, and the width of the concave lens are adjusted to homogenize the intensity distribution of the beam after propagation. (Appendix 3) The shaping device according to appendix 1, further comprising an optical system that expands or contracts the beam. (Appendix 4) The shaping device according to appendix 1, in which the beam shaper has a physical lens, a DOE (Diffractive Optical Element), an SLM (Spatial Light Modulator), or a hologram. (Appendix 5) The shaping device according to appendix 1, in which a variable beam shaper is used as the beam shaper to adjust any one or more of the focal length of the axicon lens, the focal length of the concave lens, and the width of the concave lens.

[0063] 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.

[0064] 10 Beam shaper 20 Magnification / reduction optical system 100 Light transmitting device 200 Light receiving device

Claims

1. A beam shaping device that is equipped with a beam shaper that functions as a lens, with the central part of an axicon lens being a concave lens.

2. The shaping device according to claim 1, wherein the focal length of the axicon lens, the focal length of the concave lens, and the width of the concave lens are adjusted to make the intensity distribution of the beam uniform after propagation.

3. The shaping device according to claim 1, further comprising an optical system for expanding or contracting the beam.

4. The beam shaping device according to claim 1, wherein the beam shaper comprises a physical lens, a DOE (Diffractive Optical Element), an SLM (Spatial Light Modulator), or a hologram.

5. The beam shaping device according to claim 1, wherein a variable beam shaper is used as the beam shaper, and any one or more of the focal length of the axicon lens, the focal length of the concave lens, and the width of the concave lens are adjusted.

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