Light condensing unit and sunlight receiving device

Abstract

A light condensing unit 1 according to the present invention comprises: a spherical lens 10 that receives a light beam 60; and a first ellipsoid 22a that guides the light beam emitted from the spherical lens 10. The first ellipsoid 22a is formed from a material the refractive index of which increases by light irradiation, and the spherical lens 10 and the first ellipsoid 22a are disposed such that the center C of the spherical lens 10 and a first focus f1 of the first ellipsoid 22a match.　According to this light condensing unit 1, sunlight can be condensed with high light condensing efficiency.

Description

Light collecting unit and sunlight receiving device Cross Reference

[0001] This application claims priority based on Japanese Patent Application No. 2023-149081 filed in Japan on September 14, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a light collecting unit and a sunlight receiving device.

[0003] An example of a sunlight receiving device that receives sunlight is the sunlight receiving device (sunlight concentrating lighting device) described in Patent Document 1. FIG. 41 is a diagram illustrating a sunlight receiving device 910 described in Patent Document 1. The sunlight receiving device 910 includes a concentrating unit body (reference numeral omitted) that integrates multiple lenses 911 facing the sun and a sensor 912 that detects the position of the sun, and a driving unit 913 that corrects the orientation of the lenses 911. The output of the sensor 912 is processed by a signal processing unit 914. The processing result is transmitted to the driving unit 913, which corrects the orientation of the lenses 911 of the concentrating unit body. This allows the lenses 911 to track the sun. Furthermore, the sunlight receiving device 910 is placed inside a transparent dome 915 to ensure waterproofing while allowing sunlight to pass through.

[0004] On the other hand, an example of a sunlight receiving device (sunlight concentrating device) that collects sunlight without tracking the sun is the sunlight receiving device described in Patent Document 2.

[0005] Fig. 42 is a diagram for explaining a sunlight receiving device 930 described in Patent Document 2. In the sunlight receiving device 930, one end of an optical fiber 932 is arranged facing upward as a light receiving surface 933, and a plurality of condensing lenses (convex lenses) 931 are arranged inclined sequentially above the light receiving surface 933 to form a substantially dome-shaped concentrator 940. Any of the condensing lenses 931 included in the concentrator 940 is configured to form a focal point on the light receiving surface 933 of the optical fiber 932 in response to the sun moving due to its diurnal motion and annual motion.

[0006] JP-A-6-300925 JP-A-10-68904

[0007] However, the solar light receiving device described in Patent Document 1 has the problem that the light collection efficiency cannot be increased unless the lens is constantly and accurately tracked to the sun. Furthermore, the tracking mechanism for tracking the lens to the sun needs to be installed inside a transparent dome to ensure waterproofing and wind resistance. Another problem is that regular maintenance is required to ensure the reliability of the circuit control unit and drive unit.

[0008] On the other hand, the solar light receiving device described in Patent Document 2 has the advantage of not having a mechanism for tracking the sun, but has the problem that the light collecting efficiency of the sunlight that falls on the entire device is extremely low due to changes in the angle of incidence on the light collecting surface of the device caused by the diurnal and annual motion of the sun.

[0009] Therefore, the present invention aims to solve such problems and to provide a light collecting unit or a sunlight receiving device that can collect sunlight with high light collecting efficiency even when the light collecting unit or the sunlight receiving device does not have a tracking mechanism for tracking the sun.

[0010] [1] The focusing unit of the present invention comprises a spherical lens that receives light rays and a first ellipsoid that guides the light rays emitted from the spherical lens, the first ellipsoid being formed from a material whose refractive index increases when irradiated with light, and the spherical lens and the first ellipsoid being arranged so that the center of the spherical lens coincides with the first focal point of the first ellipsoid.

[0011] [2] According to the focusing unit of this application example, it is preferable that the first ellipsoid has an incident surface onto which the light rays emitted from the spherical lens are incident, and that the incident surface has a spherical surface centered at the center position of the spherical lens.

[0012] [3] According to the light collecting unit of this application example, it is preferable that the spherical lens and the first ellipsoid are disposed apart from each other.

[0013] [4] According to the light collecting unit of this application example, it is preferable that the light collecting unit further includes a light receiving section, and that the light receiving section is disposed at a position including the second focal point of the first ellipsoid.

[0014] [5] According to the focusing unit of this application example, it is preferable that the first ellipsoid further has an exit surface near the second focal point of the first ellipsoid that emits light rays guided by the first ellipsoid, the exit surface forms a curved surface surrounding the second focal point of the first ellipsoid, and the refractive index of the region between the exit surface and the light receiving unit is smaller than the refractive index of the light receiving unit.

[0015] [6] According to the focusing unit of this application example, it is preferable that the exit surface of the spherical lens and / or the entrance surface of the first ellipsoid have a convex portion, the convex portion is arranged on the major axis of the first ellipsoid, and is configured in a shape that focuses light that has passed through the center of the spherical lens at the position of the second focal point of the first ellipsoid.

[0016] [7] According to the light collecting unit of this application example, it is preferable that the first ellipsoid has an ellipsoidal surface of the first ellipsoid and a plane including a major axis of the first ellipsoid.

[0017] [8] According to this application example, the light collecting unit preferably further includes a light receiving section and a second ellipsoid that guides the light guided by the first ellipsoid to the light receiving section.

[0018] [9] According to the focusing unit of this application example, it is preferable that the first ellipsoid and the second ellipsoid are arranged so that the second focal point of the first ellipsoid coincides with the first focal point of the second ellipsoid, and the light receiving unit is arranged at a position that includes the second focal point of the second ellipsoid.

[0019]

[10] According to the light collecting unit of this application example, it is preferable that the light receiving portion is a light receiving portion of a light guiding device, a light receiving portion of a photovoltaic device, or a light receiving portion of a light heating device.

[0020]

[11] According to the focusing unit of this application example, it is preferable that the spherical lens receives sunlight incident from different angles due to the annual and diurnal motion of the sun and directs the sunlight to the first ellipsoid, and the first ellipsoid guides the sunlight incident from the spherical lens and directs it to the position of a second focal point of the first ellipsoid.

[0021]

[12] The solar light receiving device of the present invention is a solar light receiving device in which a plurality of focusing units are arranged, and the spherical lens included in one of the focusing units abuts against the spherical lens included in another of the focusing units.

[0022]

[13] According to the solar light receiving device of this application example, it is preferable that the spherical lens included in the one focusing unit and the spherical lens included in the other focusing unit are in face-to-face contact.

[0023]

[14] According to the solar light receiving device of this application example, it is preferable that the spherical lens has a regular hexagonal shape when viewed from the optical axis direction of the focusing unit, and that the plurality of spherical lenses are arranged in a close-packed configuration.

[0024]

[15] According to the sunlight receiving device of this application example, it is preferable that the optical axes of the plurality of light collecting units are arranged in different directions.

[0025] According to the present invention, it is possible to provide a light collecting unit that can collect sunlight with high light collecting efficiency even when it does not have a tracking mechanism that tracks the sun.

[0026] Furthermore, according to the present invention, it is possible to provide a sunlight receiving device that can receive sunlight with high light collection efficiency even when it does not have a tracking mechanism that tracks the sun.

[0027] FIG. 1 is a cross-sectional view shown for explaining a light collecting unit 1 according to embodiment 1. FIG. 2 is a perspective view shown for explaining a light collecting unit 1 according to embodiment 1. FIG. 3 is a ray tracing diagram shown for explaining the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 1 according to embodiment 1. FIG. 4 is a ray tracing diagram shown for explaining the behavior of a light ray 60 when the light ray 60 is incident on a spherical lens 10. FIG. 5 is a diagram showing an illuminance distribution on an incident surface 24 of a first ellipsoid 22a. FIG. 6 is a diagram showing an illuminance-refractive index characteristic of a material constituting the first ellipsoid 22a. FIG. 7 is a diagram showing a refractive index characteristic of a material constituting the first ellipsoid 22a. FIG. 8 is a diagram showing a case where a light ray 60 is incident on the light collecting unit 1 according to embodiment 1 at an incident angle θ ０9 is a ray tracing diagram when a light ray 60 is incident at an angle of .gtoreq.30°. FIG. 10 is a graph showing the refractive index characteristics of the material constituting the first ellipsoid 22a in the light collecting unit 1 shown in FIG. 8. FIG. 11 is a graph showing the refractive index characteristics of the material constituting the first ellipsoid 22a. FIG. 12 is a diagram showing the relationship between the distance from the center of the spherical lens 10 and the shape of the light ray 60 when the light ray 60 is incident on the spherical lens 10. FIG. 13 is a ray tracing diagram when the spherical lens 10 and the first ellipsoid 22a are arranged at a distance from each other in the light collecting units 1A to 1C according to the first embodiment. FIG. 14 is a cross-sectional view shown for explaining the light collecting unit 1D according to the first embodiment. FIG. 15 is a ray tracing diagram showing the behavior of the light ray 60 when the light ray 60 is incident on the light collecting unit 1D according to the first embodiment. FIG. 16 is a ray tracing diagram showing the behavior of the light ray 60 when the light ray 60 is incident on the light collecting unit 1D according to the first embodiment, and is an enlarged view of the coupling portion between the exit surface 29 and the light receiving unit 30. FIG. 17 is a cross-sectional view shown for explaining the light collecting unit 2 according to the second embodiment. 1 is a schematic view showing a light collecting unit 2 according to a second embodiment; FIG. 2 is a ray tracing diagram showing the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 2 according to the second embodiment; FIG. 3 is a cross-sectional view showing a light collecting unit 3 according to a third embodiment; FIG. 4 is a schematic view showing a light collecting unit 3 according to the third embodiment; FIG. 5 is a ray tracing diagram showing the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 3 according to the third embodiment; FIG. 6 is a cross-sectional view showing a light collecting unit 3A according to the third embodiment; FIG. 7 is a ray tracing diagram showing the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 3A according to the third embodiment; FIG. 8 is a perspective view showing a light collecting unit 3C according to the third embodiment; FIG. 9 is a cross-sectional view showing a light collecting unit 4 according to a fourth embodiment; FIG. 10 is a ray tracing diagram showing the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 4 according to the fourth embodiment; FIG. 11 is a diagram showing an application example of the light collecting unit 3A according to the third embodiment. 1 is a perspective view showing an external appearance of a solar light receiving device 6 according to an embodiment of the solar light receiving device. ０1 is a ray tracing diagram when a ray of light 60 is incident at an incident angle θ = 30°. FIG. 2 is a diagram for explaining a solar light receiving device 7 according to another embodiment of the solar light receiving device. ０ 1 is a ray tracing diagram when a ray of light 60 is incident at an incident angle θ = 30° with respect to the optical axis 40 of the light collecting unit 1 disposed at the center of the solar light receiving device 8. ０ 1 is a diagram showing the results of a ray tracing simulation when a ray of light 60 is incident at an angle θ of 30°. FIG. 2 is an external view of the sunlight receiving device 8 when the tilt angle of the light collecting unit 1 is set to 30°. ０ FIG. 1 is a diagram showing the results of a simulation in which the above-mentioned condition is changed. FIG. 2 is a diagram shown to explain a light collecting unit 4a according to a modified example 1. FIG. 3 is a diagram shown to explain a light collecting unit 4b according to a modified example 2. FIG. 4 is a diagram shown to explain a light collecting unit 4c according to a modified example 3. FIG. 5 is a diagram shown to explain a solar light receiving device 9 according to a modified example 5. FIG. 6 is a diagram shown to explain a solar light receiving device 910 described in Patent Document 1. FIG. 7 is a diagram shown to explain a solar light receiving device 930 described in Patent Document 2.

[0028] The following describes the light collecting unit and the solar light receiving device of the present invention based on the embodiments. Note that the embodiments described below do not limit the invention according to the claims. Furthermore, not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

[0029] Furthermore, in the description of the embodiments, the light collecting unit or the sunlight receiving device may be placed in an xyz coordinate system and the description may be made using terms such as "when viewed from the x direction."

[0030] 1. Embodiment 1 A light collecting unit 1 according to embodiment 1 will be described below. Fig. 1 is a cross-sectional view shown for explaining the light collecting unit 1 according to embodiment 1. Fig. 2 is a perspective view shown for explaining the light collecting unit 1 according to embodiment 1.

[0031] 1.1 Light-Concentrating Unit 1 As shown in FIGS. 1 and 2, the light-condensing unit 1 includes a spherical lens 10, a first ellipsoid 22a, and a light-receiving unit 30.

[0032] The spherical lens 10 is a lens whose entrance and exit surfaces for light rays 60 are formed as spherical surfaces, and receives light rays 60 (incident light) that enter the light focusing unit 1. The light rays 60 that enter the spherical lens 10 are, for example, sunlight. The light rays 60 are focused by the spherical lens 10. The light rays 60 are focused at positions in front of and behind the entrance surface 24 of the first ellipsoid 22a.

[0033] The first ellipsoid 22a guides the light emitted from the spherical lens 10. The first ellipsoid 22a is made of a transparent material whose refractive index increases when irradiated with light. The transparent material whose refractive index increases when irradiated with light will be described in detail later.

[0034] The first ellipsoid 22a forms a part of a shape of a spheroid. In this specification, the term "spheroid" does not necessarily have to have a shape of a complete spheroid, but includes a three-dimensional object in which a part of a spheroid has been cut away, as shown in FIG. 1. In other words, the first ellipsoid 22a does not have to have a shape of a complete spheroid, as long as it forms a part of a spheroid and the part that forms the part of the spheroid includes the ellipsoid surface 26. The first ellipsoid 22a has a first focal point f1 and a second focal point f2.

[0035] In the following description, the straight line connecting the first focal point f1 and the second focal point f2 of the first ellipsoid 22a, which is the central axis of rotation of the first ellipsoid 22a, will be referred to as the "optical axis 40."

[0036] As shown in Fig. 1, the spherical lens 10 and the first ellipsoid 22a are arranged so that the center C of the spherical lens 10 and the first focal point f1 of the first ellipsoid 22a coincide. Specifically, the first ellipsoid 22a has a shape in which a portion including the first focal point f1 is cut out of a spheroid of revolution. The spherical lens 10 is arranged in the cut-out portion of the first ellipsoid 22a. In this case, the spherical lens 10 and the first ellipsoid 22a are arranged so that the center C of the spherical lens 10 and the first focal point f1 of the first ellipsoid 22a coincide.

[0037] The first ellipsoid 22a has an incident surface 24 onto which light rays 60 exiting the spherical lens 10 are incident. The incident surface 24 is a curved surface of the first ellipsoid 22a that faces the spherical lens 10. Herein, the terms "curved surface" and "spherical surface" are intended to include a surface that is formed by a collection of multiple flat and / or curved surfaces and functions as a curved or spherical surface as a whole. It is preferable that the incident surface 24 has a spherical surface centered at the center C of the spherical lens 10.

[0038] By having the incident surface 24 be a spherical surface centered at the center C of the spherical lens 10, the light rays 60 incident on the first ellipsoid 22a that pass through the center C of the spherical lens 10 will be incident at a right angle to the incident surface 24 when they enter the first ellipsoid 22a, and will travel straight without being refracted at the incident surface 24, be reflected by the ellipsoidal surface 26 of the first ellipsoid 22a, and reach the second focal point f2.

[0039] That is, since the incident surface 24 has a spherical surface centered at the position of the center C of the spherical lens 10, the light that passes through the center C of the spherical lens 10 among the light rays 60 incident on the spherical lens 10 is incident at an incident angle θ ０ In the following description, the incident angle θ ０ " is simply referred to as "incident angle θ ０ " is sometimes written as ".

[0040] It is preferable to determine the distance between the incident surface 24 of the first ellipsoid 22a and the exit surface (symbol omitted) of the spherical lens 10 taking into consideration the refractive index of the spherical lens 10 and the degree of change in refractive index when light is irradiated onto the first ellipsoid 22a.

[0041] The first ellipsoid 22a further has a surface 27. The surface 27 intersects with the optical axis 40 (the major axis of the first ellipsoid 22a) of the light-collecting unit 1 at the position of the second focal point f2. The light-receiving unit 30 is disposed on the surface 27. Specifically, the light-receiving unit 30 is disposed on the surface 27 at a position including the second focal point f2. As will be described in detail later, the light ray 60 incident on the spherical lens 10 is guided to the position of the second focal point f2. By disposing the light-receiving unit 30 at a position including the second focal point f2 of the first ellipsoid 22a, the light ray 60 can be efficiently received.

[0042] The shape of the surface 27 is not limited as long as it includes the second focal point f2 of the first ellipsoid 22a and allows the light receiving unit 30 to be disposed thereon. That is, the surface 27 may be a flat surface or a curved surface. Furthermore, the surface 27 may be perpendicular to the major axis of the first ellipsoid 22a or may intersect with the major axis at a specific angle.

[0043] Of the light rays 60 incident on the spherical lens 10, those that pass through the center C of the spherical lens 10 continue to travel straight after passing through the spherical lens 10 and enter the first ellipsoid 22a, as shown in FIG. 1 . After being reflected by the ellipsoidal surface 26, the light is guided to the second focal point f2 of the first ellipsoid 22a. The light receiving unit 30 is disposed at the second focal point f2. As a result, of the light rays 60, those that pass through the center C of the spherical lens 10 are received by the light receiving unit 30.

[0044] Light that does not pass through the center C of the spherical lens 10 is refracted in the direction of travel of the light that passes through the center C of the spherical lens 10 when it enters the spherical lens 10 and when it exits the spherical lens 10. The light ray 60 passes through the region (space) between the spherical lens 10 and the first ellipsoid 22a and enters the first ellipsoid 22a from the entrance surface 24.

[0045] The first ellipsoid 22a is formed from a transparent material whose refractive index increases with light irradiation. Therefore, the first ellipsoid 22a has a refractive index distribution in which the refractive index is greatest at the position where the illuminance is greatest (see FIG. 7 ). As a result, light that does not pass through the center C of the spherical lens 10 travels in the first ellipsoid 22a along the light that has passed through the center C of the spherical lens 10. Note that the phenomenon in which the refractive index increases with light irradiation in the first ellipsoid 22a and the behavior of light that does not pass through the center C of the spherical lens 10 traveling along the light that has passed through the center C of the spherical lens 10 will be described in detail later.

[0046] The first ellipsoid 22a preferably has a convex portion 25 (hereinafter referred to as the "first convex portion 25"). The first convex portion 25 is configured in a shape that focuses light that has passed through the center C of the spherical lens 10 and is incident on the first convex portion 25 at the position of a second focal point f2 of the first ellipsoid 22a.

[0047] The first convex portion 25 is provided at a position where the incident surface 24 intersects with the major axis of the first ellipsoid 22 a, i.e., a position where the incident surface 24 intersects with the optical axis 40 of the light collecting unit 1. A light ray 60 incident on the first convex portion 25 is incident at an incident angle θ ０ By providing the first convex portion 25, the incident angle θ ０ The light beam 60 having a relatively small diameter can be focused at the second focal point f2 of the first ellipsoid 22a and can be efficiently received by the light receiving section 30 (see FIG. 3B).

[0048] The ellipsoidal surface 26 of the first ellipsoid 22a reflects light guided inside the first ellipsoid 22a. A reflective film (not shown) may be formed on the ellipsoidal surface 26. The reflective film here refers to a film formed on the ellipsoidal surface 26 that reflects light guided inside the first ellipsoid 22a. The reflective film is not particularly limited as long as it reflects light guided inside the first ellipsoid 22a. An example of the reflective film is a thin metal film. The reflective film is provided to prevent light guided inside the first ellipsoid 22a from passing through the ellipsoidal surface 26 and exiting the first ellipsoid 22a. In this sense, it is preferable that the reflectivity of the reflective film is high.

[0049] The light receiving unit 30 is disposed at the position of the second focal point f2 of the first ellipsoid 22a. As described above, the light ray 60 guided inside the first ellipsoid 22a is incident on the spherical lens 10 at an incident angle θ ０ By disposing the light receiving unit 30 at the position of the second focal point f2, the incident angle θ when the light ray 60 is incident on the spherical lens 10 is ０ Regardless of the above, the light ray 60 incident on the light collecting unit 1 can be received by the light receiving section 30.

[0050] The light receiving section 30 may be, for example, a light receiving section of a light guide device, a light receiving section of a photovoltaic device, or a light receiving section of an optical heating device. Alternatively, the light receiving section 30 may be a light guide 31 having a cladding section 34 and a core section 33 having a refractive index higher than that of the cladding section. Examples of the light guide 31 include an optical fiber and a liquid light guide.

[0051] 1.2. Optical Simulation of the Light Collecting Unit 1 When the light collecting unit 1 according to the first embodiment is subjected to an incident angle θ ０ An optical simulation was performed on the behavior of the light ray 60 when the light ray 60 is incident on the optical disk 1. The results of the optical simulation will be described below.

[0052] Fig. 3 is a ray tracing diagram showing the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 1 according to the first embodiment. Fig. 4 is a ray tracing diagram showing the behavior of a light ray 60 when the light ray 60 is incident on the spherical lens 10. Fig. 5 is a diagram showing the illuminance distribution on the incident surface 24 of the first ellipsoid 22a. Fig. 6 is a diagram showing the illuminance-refractive index characteristics of the material constituting the first ellipsoid 22a. Fig. 7 is a diagram showing the refractive index characteristics of the material constituting the first ellipsoid 22a.

[0053] The optical simulation was performed using LightTools (registered trademark) from Synopsys, Inc., USA. LightTools is software that uses geometric optics to calculate the optical path in an optical element composed of multiple media with defined shapes and refractive indices. It is generally accepted in the development of optical instruments and lighting devices that it guarantees experimental results equivalent to those obtained by experiments in which optical paths are measured using prototype optical elements. For simplicity, the light receiving unit 30 in the simulation was a cylindrical optical duct with a mirror-finished inner surface.

[0054] FIG. 3A shows a case in which a light ray 60 is incident at an angle θ ０ 10 is a diagram showing a simulation result when a light ray 60 is incident on the focusing unit 1 at an angle f = 30°. A light ray 60 emitted from the spherical lens 10 is incident on the first ellipsoid 22a from the incident surface 24, reflected by the ellipsoidal surface 26 of the first ellipsoid 22a, and received by the light receiving unit 30 located at the second focal point f2.

[0055] FIG. 3B shows that the light ray 60 is incident at an angle θ ０ 10 shows the results of a simulation in which light enters the focusing unit 1 at an angle f = 10°. The first ellipsoid 22a has a first convex portion 25 at the position where the entrance surface 24 intersects with the major axis of the first ellipsoid 22a. The first convex portion 25 is configured in a shape that focuses light that is incident on the first convex portion 25, out of light rays 60 that have passed through the center C of the spherical lens 10, at the position of the second focal point f2 of the first ellipsoid 22a.

[0056] Therefore, the incident angle θ of the light ray 60 incident on the light collecting unit 1 ０ When is small, the light ray 60 emitted from the spherical lens 10 passes through the first convex portion 25 formed on the incident surface 24 of the first ellipsoid 22a, and is then directly received by the light receiving unit 30 located at the position of the second focal point f2.

[0057] Here, a phenomenon will be described in which a light ray 60 incident on the spherical lens 10 enters the first ellipsoid 22a and travels along the direction of travel of the light that passed through the center C of the spherical lens 10.

[0058] Fig. 4 is a ray tracing diagram showing the behavior of a parallel ray 60 incident on the spherical lens 10 placed in air (refractive index 1.0). Fig. 5 is a diagram showing the illuminance distribution on the incident surface 24 of the first ellipsoid 22a. In Fig. 4, r ０ denotes the radius of the spherical lens 10, and r １ denotes the radius of the entrance surface 24 of the first ellipsoid 22a.

[0059] The light ray 60 that has passed through the spherical lens 10 has spherical aberration, as shown in Fig. 4. Therefore, the illuminance distribution of the light ray 60 on the incident surface 24 of the first ellipsoid 22a exhibits a maximum value (peak) at the position where the light ray 60 that has passed through the center C of the spherical lens 10 is incident on the incident surface 24, as shown in Fig. 5, as an example of the illuminance distribution.

[0060] The material constituting the first ellipsoid 22a may be, for example, a transparent material that, when irradiated with light, generates a charge imbalance due to photoinduced electron transfer, increasing the refractive index (see FIG. 6). Specifically, the refractive index changes reversibly when irradiated with light, increasing the refractive index when irradiated with high-intensity light, and spontaneously recovering to the value before the light irradiation when the light irradiation is stopped.

[0061] For example, the first ellipsoid 22a may be made of a material whose molecular structure changes reversibly through the photoisomerization reaction of diarylethene (Reference 1), or a material whose refractive index increases locally due to charge imbalance caused by photoinduced electron transfer upon irradiation with light (Reference 2). [Reference 1] Jae-Wook Kang, et al., Optical Material 21(2002) 543-548 [Reference 2] M. Maaza et al., Optics Communications 285(2012) 1190-1193

[0062] More specifically, the material constituting the first ellipsoid 22a can be, for example, a material in which specific semiconductor nanoparticles are dispersed in inorganic glass such as Pyrex (registered trademark). Here, the specific nanoparticles refer to semiconductors capable of absorbing ultraviolet light or the like and undergoing electron transition, as will be described later. For example, composite nanoparticles of titanium oxide and tin oxide can be exemplified.

[0063] When sunlight is irradiated onto the first ellipsoid 22a as the light beam 60, an electronic transition occurs in semiconductors such as titanium oxide and tin oxide. Because this electronic transition is a quantum chemical electronic transition, it depends not on the light intensity (the number of photons per unit time per unit area) but on the energy of the photons. In other words, even light that is not as intense as laser light can cause electronic transitions as long as the photons have high energy. Ultraviolet light and violet light from the visible light are absorbed from the sunlight, inducing charge separation. As a result, the refractive index of the portion of the first ellipsoid 22a irradiated with sunlight is increased.

[0064] The semiconductor nanoparticles are adjusted to have a size on the order of several tens of nanometers, which makes it possible to suppress scattering of visible light. The sunlight incident on the first ellipsoid 22 a is guided through the interior of the first ellipsoid 22 a while the refractive index of the first ellipsoid 22 a is gradually increased.

[0065] The degree to which the refractive index of the material forming the first ellipsoid 22a increases upon exposure to light is determined taking into consideration the amount of ultraviolet light contained in sunlight, the amount of purple light in visible light, the reflectivity of the ellipsoid surface 26, and the optical path length of sunlight in the first ellipsoid 22a, but is preferably 0.05 or more, more preferably 0.10 or more, and even more preferably 0.17 or more.

[0066] By using a transparent material whose refractive index increases with light irradiation as the material for forming the first ellipsoid 22a, a local deviation in the refractive index occurs due to light irradiation, and as a result, the refractive index distribution on the incident surface 24 of the first ellipsoid 22a becomes a refractive index distribution that has a maximum value (peak) at the position where light passes through the center C of the spherical lens 10, corresponding to the illuminance distribution on the incident surface 24.

[0067] 7 is a diagram showing the refractive index distribution on the incident surface 24 of the first ellipsoid 22a. As shown in Fig. 7, the refractive index distribution on the incident surface 24 of the first ellipsoid 22a exhibits a refractive index distribution having a maximum value (peak) at the position where light passing through the center C of the spherical lens 10 passes.

[0068] The first ellipsoid 22a is made of a transparent material whose refractive index increases with light irradiation. Therefore, the light ray 60 guided inside the first ellipsoid 22a is guided in the direction of the larger refractive index, similar to the light traveling through a general GI optical fiber. In other words, among the light rays 60 incident on the first ellipsoid 22a, the light that does not pass through the center C of the spherical lens 10 also travels along the light that has passed through the center C of the spherical lens 10.

[0069] Here, the light that passes through the center C of the spherical lens 10 reaches the second focal point f2 of the first ellipsoid 22a. As a result, the light ray 60 incident on the spherical lens 10, both the light that passed through the center C of the spherical lens 10 and the light that did not pass through the center C of the spherical lens 10, travels along the light that passed through the center C of the spherical lens 10 and reaches the light receiving unit 30.

[0070] Optical Simulation Using LightTools (1) Next, an optical simulation was performed using LightTools to examine the behavior of light in the first ellipsoid 22a made of a material whose refractive index changes when irradiated with light, and the light collection efficiency of the light collection unit 1 at this time.

[0071] FIG. 8 shows a light beam 60 incident on the light collecting unit 1 according to the first embodiment at an incident angle θ ０ 9 is a ray tracing diagram when the light is incident at an angle of 30°. Fig. 9 is a graph showing the refractive index characteristics of the material that forms the first ellipsoid 22a in the light collecting unit 1 shown in Fig. 8.

[0072] The light collecting unit 1 according to the first embodiment is provided with an incident angle θ ０ A simulation was performed using LightTools to determine how light ray 60 is guided when light ray 60 is incident at an angle of θ = 30°. The conditions for spherical lens 10, first ellipsoid 22a, light receiving unit 30, and light ray 60 (incident light) were as follows:

[0073] Spherical lens 10 Refractive index: 1.5 Diameter: 100 mm (r ０ = 50 mm) First ellipsoid 22a Material constituting the first ellipsoid 22a: Transparent material having the refractive index characteristics shown in FIG. 9 (normal refractive index n ０ = 1.50, peak refractive index n １ = 1.67, normal refractive index n ０ and the peak refractive index n １ The refractive index difference Δn between the first ellipsoid 22a and the incident surface 24 is Δn=0.17. The minor axis of the first ellipsoid 22a is 100 mm, the major axis is 200 mm, and the radius r of the incident surface 24 is 58 mm. The light receiving surface of the light receiving unit 30 is a circle with a diameter of 10 mm. Incident light is a parallel ray with a diameter of 100 mm. The incident angle θ is ０ : 30°

[0074] The results of simulation (1) are shown in Figure 8. Of the light rays 60 incident on spherical lens 10, those that were incident at positions close to the outer periphery of spherical lens 10 had large spherical aberration and were therefore unable to reach light receiving unit 30, as shown in Figure 8. Of the light rays 60, those that were located close to the position where the light that passed through center C of spherical lens 10 passes travel along the light that passed center C of spherical lens 10, and reach light receiving unit 30, becoming effective light.

[0075] As a result of ray tracing simulation (1), it was found that when 1006 uniformly distributed light rays 60 were incident on the spherical lens 10 of the light-collecting unit 1, 593 light rays reached the light-receiving unit 30. The light-collecting efficiency was a high 58.9%.

[0076] Optical Simulation by LightTools (2) The light collection efficiency, i.e., the number of light rays reaching the light receiving unit 30, is determined by the refractive index n ０ and the peak refractive index n １ It is known that the refractive index difference Δn between the first and second layers (hereinafter, sometimes simply referred to as "refractive index difference Δn") is highly dependent on the refractive index difference Δn between the first and second layers.

[0077] Therefore, the number of light rays reaching the light receiving unit 30 and the light collection efficiency were simulated for a light collecting unit 1 having a first ellipsoid 22a made of a material in which the refractive index difference Δn of the material constituting the first ellipsoid 22a is smaller than the refractive index difference Δn of the material constituting the first ellipsoid 22a used in optical simulation (1).

[0078] The conditions of the spherical lens 10, the first ellipsoid 22a, the light receiving unit 30, and the incident light (light ray 60) used in simulation (2) were the same as those in simulation (1), except for the following:

[0079] First ellipsoid 22a Material constituting the first ellipsoid 22a: transparent material having the refractive index characteristics shown in FIG. 10 (normal refractive index n ０ = 1.50, peak refractive index n １ = 1.60, normal refractive index n ０ and the peak refractive index n １ Refractive index difference Δn = 0.10) Radius r of incident surface 24: 60 mm

[0080] As a result of ray tracing simulation (2), it was found that when 1006 light rays 60 with a uniform distribution and a diameter of 100 mm are incident on the spherical lens 10 of the focusing unit 1, 437 light rays reach the light receiving unit 30 with a diameter of 10 mm. It was confirmed that a high focusing efficiency of 43.4% can be obtained even with a refractive index difference Δn = 0.10.

[0081] 1 and 2, the light collecting unit 1 includes a spherical lens 10, a first ellipsoid 22a, and a light receiving unit 30. The spherical lens 10 receives sunlight incident from different angles due to the annual and diurnal motion of the sun and directs the sunlight to the first ellipsoid 22a. The first ellipsoid 22a guides the sunlight incident from the spherical lens 10 to the position of a second focal point f2 of the first ellipsoid 22a.

[0082] According to the light collecting unit 1, even if a tracking mechanism for tracking the sun is not provided, it is possible to provide a light collecting unit that can collect sunlight with high light collecting efficiency.

[0083] 1.3 Light Collecting Units 1A to 1C Fig. 12 is a ray tracing diagram when the spherical lens 10 and the first ellipsoid 22a are arranged apart from each other in the light collecting unit 1 according to the first embodiment.

[0084] In the light-concentrating unit 1, the spherical lens 10 and the first ellipsoid 22a are preferably arranged at a distance from each other, as shown in Figures 1 and 12. By arranging the incident surface 24 and the spherical lens 10 at a distance from each other, it is possible to adjust the size of a light flux concentration region of the light rays 60 that are emitted from the spherical lens 10 and enter the first ellipsoid 22a. Here, the "light flux concentration region" refers to a region where the illuminance of the light rays 60 suddenly increases (a region where the illuminance rises) on a plane perpendicular to the traveling direction of the light rays 60.

[0085] 11 is a diagram illustrating the relationship between the distance from the center of the spherical lens 10 and the light intensity distribution of the light ray 60 when the light ray 60 is incident on the spherical lens 10. The light ray 60 incident on the spherical lens 10 is refracted at the entrance surface and the exit surface of the spherical lens 10, as shown in FIG.

[0086] Assuming that the spherical lens 10 and the first ellipsoid 22a are positioned so that the incident surface 24 of the first ellipsoid 22a is located at a distance Z from the center C of the spherical lens 10 (radius 50 mm), the light intensity distribution of the light ray 60 at the position of the incident surface 24 was obtained by simulation for a number of distances Z. Figure 11 shows the results for (a) Z = 56 mm, (b) Z = 60 mm, (c) Z = 65 mm, (d) Z = 70 mm, and (e) Z = 75 mm.

[0087] The horizontal axis indicates the distance (unit: mm) of the light ray 60 from the center of the spherical lens 10, and the vertical axis indicates the ratio (illuminance magnification) of the illuminance at the incident surface 24 to the illuminance before incidence on the spherical lens 10. For example, if the illuminance before incidence is 100,000 lux and the illuminance magnification is 1,000 times, this indicates that the illuminance at the incident surface 24 is 100,000 lux x 1,000 times.

[0088] When the distance Z from the center C of the spherical lens 10 to the incident surface 24 is relatively small, i.e., (a) Z = 56 mm, (b) Z = 60 mm, or (c) Z = 65 mm, the light intensity distribution of the light ray 60 at the incident surface 24 has a light flux concentration region where the light intensity in the central portion is high, and a region where the light intensity is lower than in the central portion and the illuminance rises sharply.

[0089] When the distance Z from the center C of the spherical lens 10 to the incident surface 24 increases, i.e., when Z=70 mm (d) and Z=75 mm (e), only a light flux concentration region with a high central light intensity is observed. However, when the light intensity distribution when Z=70 mm (d) is compared with the light intensity distribution when Z=75 mm (e), the light intensity in the light flux concentration region is high (approximately 13,000 times) and the distribution shape is sharp when Z=70 mm (d), whereas when Z=75 mm (e), the light intensity in the light flux concentration region is not as high (approximately 2,300 times) as when Z=70 mm, and the distribution shape is broader than when Z=70 mm.

[0090] As described above, by arranging the incident surface 24 and the spherical lens 10 at a distance from each other and selecting the position at which the incident surface 24 is arranged, the size of the light beam concentration area of ​​the light rays 60 incident on the first ellipsoid 22a can be adjusted.

[0091] The region between the spherical lens 10 and the first ellipsoid 22a may be filled with space, in other words, air, or may be filled with a material that transmits visible light. There are no particular restrictions on the material that can be placed in the region between the spherical lens 10 and the first ellipsoid 22a, as long as it has the property of transmitting visible light and its refractive index is independent of illuminance. Alternatively, the region between the spherical lens 10 and the first ellipsoid 22a may include both a region filled with air and a region filled with a material that transmits visible light.

[0092] 12A and 12B are ray tracing diagrams of a light collecting unit 1 according to the first embodiment, in which the spherical lens 10 (refractive index: 1.56) and the first ellipsoid 22a are arranged at a distance from each other. Fig. 12A is a ray tracing diagram of a light collecting unit 1A in which air (refractive index: 1.0 at 20°C and 1 atmosphere) is placed between the spherical lens 10 and the first ellipsoid 22a. Fig. 12B is a ray tracing diagram of a light collecting unit 1B in which a transparent member 73 with a refractive index of 1.45 is placed between the spherical lens 10 and the first ellipsoid 22a. Fig. 12C is a ray tracing diagram of a light collecting unit 1C in which air and a transparent member 73 with a refractive index of 1.45 are placed between the spherical lens 10 and the first ellipsoid 22a.

[0093] In any of light collecting units 1A to 1C, the size of the light flux concentration area of ​​light ray 60 when it enters first ellipsoid 22a is smaller than the size of the light flux concentration area of ​​light ray 60 when it exits spherical lens 10. In other words, by arranging spherical lens 10 and first ellipsoid 22a at a distance from each other, the size of the light flux concentration area of ​​light ray 60 exiting spherical lens 10 can be adjusted to be small, and light ray 60 can be incident on first ellipsoid 22a.

[0094] Here, if the refractive index of the region between the spherical lens 10 and the first ellipsoid 22a is made smaller than the refractive index of the spherical lens 10, the size of the luminous flux concentration region of the light rays 60 on the incident surface 24 of the first ellipsoid 22a can be reduced. On the other hand, the amount of light that is diffused on the exit surface of the spherical lens 10 also increases.

[0095] Therefore, by optimizing the refractive index of the region between the spherical lens 10 and the first ellipsoid 22a and the distance of the region between the spherical lens 10 and the first ellipsoid 22a, it is possible to reduce the size of the light flux concentration region of the light rays 60 on the incident surface 24 of the first ellipsoid 22a while keeping the amount of light diffused at the exit surface of the spherical lens 10 low.

[0096] 1.4. Light collecting unit 1D Next, a light collecting unit 1D according to the first embodiment will be described. Fig. 13 is a cross-sectional view shown for explaining the light collecting unit 1D according to the first embodiment. Fig. 14 is a ray tracing diagram shown for explaining the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 1D according to the first embodiment.

[0097] 15A and 15B are ray tracing diagrams illustrating the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 1D according to the first embodiment, and are enlarged views illustrating a coupling portion between the exit surface 29 and the light receiving unit 30. Fig. 15A illustrates a case in which the exit surface 29 forms a curved surface that surrounds the second focal point f2 of the first ellipsoid 22a. Fig. 15B illustrates a case in which the exit surface 29 does not form a curved surface that surrounds the second focal point f2 of the first ellipsoid 22a.

[0098] The light collecting unit 1D differs from the light collecting unit 1 in the structure of the portion of the first ellipsoid 22a where the light receiving unit 30 is arranged. In the following description of the light collecting unit 1D, the portions that differ from the light collecting unit 1 will be described, and overlapping portions will be omitted as appropriate.

[0099] 13 , the first ellipsoid 22a included in the light collecting unit 1D has an exit surface 29 that exits the light ray 60 guided by the first ellipsoid 22a near the second focal point f2 of the first ellipsoid 22a. The exit surface 29 forms a curved surface that surrounds the second focal point f2 of the first ellipsoid 22a. The curved surface may be a spherical surface centered at the position of the second focal point f2 of the first ellipsoid 22a.

[0100] The refractive index of a region 29a between the light exit surface 29 and the light receiving surface 32 of the light receiving unit 30 is configured to be smaller than the refractive index of the first ellipsoid 22a. The light that has traveled through the first ellipsoid 22a is directed toward the second focal point f2 of the first ellipsoid 22a at the light exit surface 29, as shown in FIG.

[0101] When the light guide 31 is used as the light receiving section 30, it is preferable that the refractive index of the region between the light exit surface 29 and the light receiving surface 32 is smaller than the refractive index of the material constituting the core section 33. As a result, the light ray 60 incident on the light receiving surface 32 of the light guide 31 is refracted at the light receiving surface 32 in the direction in which the light guide 31 extends. As a result, the light guiding efficiency of the light ray 60 in the light guide 31 can be improved.

[0102] The material constituting the region 29a between the light-emitting surface 29 and the light-receiving surface 32 of the light-receiving unit 30 is not particularly limited as long as it has a smaller refractive index than the material constituting the light-receiving unit 30. The region 29a between the light-emitting surface 29 and the light-receiving unit 30 may be filled with air or may be a vacuum.

[0103] 14 and 15(a) are ray tracing diagrams illustrating the behavior of a light ray 60 when the light ray 60 is incident on a light collecting unit 1D according to a preferred embodiment. The first ellipsoid 22a included in the light collecting unit 1D shown in Fig. 15(a) has an exit surface 29 near the second focal point f2 of the first ellipsoid 22a, from which the light ray 60 that has traveled through the first ellipsoid 22a exits. The exit surface 29 forms a curved surface that surrounds the second focal point f2 of the first ellipsoid 22a.

[0104] The refractive index of a region 29a between the exit surface 29 and the light receiving surface 32 of the light receiving unit 30 is smaller than the refractive index of the light receiving unit 30. When the light emitted from the first ellipsoid 22a enters the light guide 31, it is refracted so as to follow the center line of the core portion 33 of the light guide 31, which has a high refractive index. As a result, the light guide efficiency of the light ray 60 in the light guide 31 can be improved.

[0105] 15(b), which does not have the above-described configuration, when a light ray 60 enters the light guide 31, a small proportion of the light travels along the center line of the core portion 33, which has a high refractive index, in the light guide 31. This reduces the angle of incidence of the light ray 60 when it enters the interface between the core portion 33 and the cladding portion 34, causing light to leak into the cladding portion 34 and deteriorating the light guide efficiency of the light guide 31.

[0106] 2. Embodiment 2 A light collecting unit 2 according to embodiment 2 will be described. Fig. 16 is a cross-sectional view shown for explaining the light collecting unit 2 according to embodiment 2. Fig. 17 is an overview diagram shown for explaining the light collecting unit 2 according to embodiment 2. Fig. 18 is a ray tracing diagram shown for explaining the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 2 according to embodiment 2.

[0107] The light-collecting unit 2 according to the second embodiment differs from the light-collecting unit 1 according to the first embodiment in the shape of the first ellipsoid 22b and the structure of the coupling portion between the first ellipsoid 22b and the light-receiving unit 30. The other parts are the same as those of the light-collecting unit 1 according to the first embodiment. The basic operating principle and behavior of the light-collecting unit 2 are the same as those of the light-collecting unit 1 according to the first embodiment. Therefore, the light-collecting unit 2 will be described in terms of the differences from the light-collecting unit 1 according to the first embodiment, and descriptions of the common parts will be omitted as appropriate.

[0108] As shown in FIGS. 16, 17, and 18, the light collecting unit 2 includes a spherical lens 10, a first ellipsoid 22b, and a light receiving section 30.

[0109] The first ellipsoid 22b condenses the light rays 60 emitted from the spherical lens 10. The first ellipsoid 22b constitutes a part of a shape of a spheroid. Like the first ellipsoid 22a in the first embodiment, the first ellipsoid 22b constitutes a part of a spheroid, and does not have to have a shape of a complete spheroid as long as the part constituting the part of the spheroid includes the ellipsoid surface 26. The first ellipsoid 22b has the ellipsoid surface 26 of the first ellipsoid 22b and a surface 28 including the major axis of the first ellipsoid 22b.

[0110] In the light-collecting unit 2, the light-receiving unit 30 is disposed at a position on the surface 28 that includes the second focal point f2 of the first ellipsoid 22b. This allows the light-collecting unit 2 to extract the light ray 60 guided by the first ellipsoid 22b in a direction perpendicular to the major axis of the first ellipsoid 22b, in other words, in a direction perpendicular to the surface 28.

[0111] FIG. 18 shows a light beam 60 incident on the light collecting unit 2 at an incident angle θ ０1 is a ray tracing diagram simulating the behavior of a light ray 60 when the light ray 60 is incident at an angle f2=30°. It can be seen that in the light focusing unit 2 as well, by forming the first ellipsoid 22b from a transparent material whose refractive index increases upon light irradiation, the light ray 60 can be focused with high efficiency at the position of the second focal point f2 of the first ellipsoid 22b.

[0112] Furthermore, the light collecting unit 2 can extract the light ray 60 in a direction perpendicular to the major axis of the first ellipsoid 22b. This allows the length of the light collecting unit 2 in the z-axis direction (see FIG. 16 ) to be shortened without impairing the light collecting efficiency, even if the distance between the two focal points f1 and f2 of the first ellipsoid 22b is shortened. As a result, the light collecting unit 2 can be made thinner.

[0113] 3. Embodiment 3 3.1. Light collecting unit 3 A light collecting unit 3 according to embodiment 3 will be described. Fig. 19 is a cross-sectional view shown for explaining the light collecting unit 3 according to embodiment 3. Fig. 20 is an overview diagram shown for explaining the light collecting unit 3 according to embodiment 3. Fig. 21 is a ray tracing diagram shown for explaining the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 3 according to embodiment 3.

[0114] The light-collecting unit 3 according to the third embodiment differs from the light-collecting unit 2 according to the second embodiment in that it further includes a second ellipsoid 23. Other parts are the same as the light-collecting unit 2 according to the second embodiment. Therefore, the light-collecting unit 3 according to the third embodiment will be described focusing on the differences from the light-collecting unit 1 according to the first embodiment and the light-collecting unit 2 according to the second embodiment, and descriptions of the common parts will be omitted as appropriate.

[0115] As shown in FIGS. 19, 20, and 21, the light collecting unit 3 includes a spherical lens 10, a first ellipsoid 22b, a second ellipsoid 23, and a light receiving section 30.

[0116] The first ellipsoid 22b collects the light emitted from the spherical lens 10. The second ellipsoid 23 receives the light guided by the first ellipsoid 22b and guides the light to the light receiving unit 30. The first ellipsoid 22b and the second ellipsoid 23 are made of a transparent material whose refractive index increases when irradiated with light.

[0117] The second ellipsoid 23 constitutes a part of a shape of a spheroid. Similar to the first ellipsoid 22b in the second embodiment, the second ellipsoid 23 constitutes a part of a spheroid, and does not have to have a shape of a complete spheroid as long as the part constituting the part of the spheroid includes an ellipsoid surface (reference numeral omitted). The second ellipsoid 23 has a first focal point f3 and a second focal point f4.

[0118] The first ellipsoid 22b and the second ellipsoid 23 are arranged so that the position of the second focal point f2 of the first ellipsoid 22b coincides with the position of the first focal point f3 of the second ellipsoid 23. In addition, the light receiving unit 30 is arranged at a position including the second focal point f4 of the second ellipsoid 23.

[0119] The first ellipsoid body 22b and the second ellipsoid body 23 may be made of the same material. When the first ellipsoid body 22b and the second ellipsoid body 23 are made of the same material, the first ellipsoid body 22b and the second ellipsoid body 23 may be made of an integral member or may be made of separate members.

[0120] In the light-collecting unit 3, light that has passed through the center C of the spherical lens 10 travels straight through the incident surface 24 of the first ellipsoid 22b and is incident on the first ellipsoid 22b, as shown in FIG. 19 . The light that has entered the first ellipsoid 22b is reflected by the ellipsoidal surface 26 of the first ellipsoid 22b, passes through the second focal point f2 of the first ellipsoid 22b (the first focal point f3 of the second ellipsoid 23), and is incident on the second ellipsoid 23. The light that has entered the second ellipsoid 23 is reflected by the ellipsoidal surface (reference numeral omitted) of the second ellipsoid 23, and is then guided to the second focal point f4 of the second ellipsoid 23. A light-receiving unit 30 is disposed at a position including the second focal point f4 of the second ellipsoid 23, and the guided light is received by the light-receiving unit 30.

[0121] The first ellipsoid 22b is made of a transparent material whose refractive index increases with light irradiation. Therefore, when the light that does not pass through the center C of the spherical lens 10 enters the first ellipsoid 22b, it travels along the light that has passed through the center C of the spherical lens 10 while being guided through the first ellipsoid 22b.

[0122] As a result, of the light ray 60, both the light that has passed through the center C of the spherical lens 10 and the light that has not passed through the center C of the spherical lens 10 travel along the light that has passed through the center C of the spherical lens 10 while being guided through the first ellipsoid 22b, and are received by the light receiving unit 30.

[0123] FIG. 21 shows a light beam 60 incident on the light collecting unit 3 at an incident angle θ ０ 1 is a ray tracing diagram simulating the behavior of a ray 60 when the ray 60 is incident at an angle f4 of 45°. The focusing unit 3 can also focus the ray 60 with high efficiency at the position of the second focal point f4 of the second ellipsoid 23.

[0124] 3.2. Light collecting unit 3A Fig. 22 is a cross-sectional view shown to explain the light collecting unit 3A according to embodiment 3. Fig. 23 is a ray tracing diagram shown to explain the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 3A according to embodiment 3.

[0125] The light-collecting unit 3A differs in the arrangement of the second ellipsoid 23 relative to the first ellipsoid 22b. The light-collecting unit 3A also differs from the light-collecting unit 3 in that it further includes a protrusion 71. The other parts are the same as the light-collecting unit 3. Therefore, the light-collecting unit 3A will be described focusing on the differences from the light-collecting unit 1 according to the first embodiment and the light-collecting units 2 and 3 according to the second embodiment, and descriptions of the common parts will be omitted as appropriate.

[0126] The light collecting unit 3A includes a second ellipsoid 23. The first ellipsoid 22b and the second ellipsoid 23 are arranged so that the position of the second focal point f2 of the first ellipsoid 22b and the position of the first focal point f3 of the second ellipsoid 23 coincide with each other.

[0127] As shown in Fig. 22, the position of the second focal point f4 of the second ellipsoid 23 is disposed above the xz plane, which is a plane including the x-axis and z-axis (above the z-axis in Fig. 22). The position of the second focal point f4 of the second ellipsoid is not limited to being above the xz plane, and is not particularly limited as long as the light receiving unit 30 disposed at the second focal point f4 can appropriately receive the light ray 60. The second focal point f4 of the second ellipsoid may be disposed on the z-axis or below the xz plane (below the z-axis in Fig. 22).

[0128] The light guide 31 serving as the light receiving unit 30 is disposed at a position including the second focal point f4 of the second ellipsoid 23. The light guide 31 is disposed at an angle that allows it to receive both the light ray 60 that is reflected by the ellipsoidal surface 26 of the first ellipsoid 22b and then reflected by the ellipsoidal surface (reference numeral omitted) of the second ellipsoid 23, and the light ray 60 that is directly incident on the light guide 31 without being reflected by the ellipsoidal surface 26 of the first ellipsoid 22b.

[0129] The first ellipsoid 22b has a protrusion 71 that protrudes downward with respect to the xy plane. The surface of the protrusion 71 that faces the spherical lens 10 constitutes a part of the incident surface 24. The protrusion 71 constitutes a part of the shape of the ellipsoid, and guides the light ray 60 that is incident from the incident surface 24 to the light receiving unit 30. By having the protrusion 71 on the first ellipsoid 22b, the incident angle θ ０ When the angle .theta. is small, it is possible to prevent a part of the light ray 60 from straying from the edge of the incident surface 24 of the first ellipsoid 22b, and it is possible to make the light ray 60 efficiently incident on the first ellipsoid 22b. This makes it possible to improve the light collection efficiency.

[0130] FIG. 23A shows the incident angle θ ０ 23B is a ray tracing diagram when a light ray 60 is incident on the light collecting unit 3A at an incident angle θ ０ 23(c) is a ray tracing diagram when a light ray 60 is incident on the light collecting unit 3A at an incident angle θ ０ 10 is a ray tracing diagram when a ray 60 is incident at an angle of 2°.

[0131] Incident angle θ ０ 23A, when the incident angle θ is 27°, the light ray 60 incident on the first ellipsoid 22b is reflected by the ellipsoid surface 26 and travels toward the second focal point f2 of the first ellipsoid 22b (the first focal point f3 of the second ellipsoid). Thereafter, the light ray 60 is reflected by the ellipsoid surface (reference numeral omitted) of the second ellipsoid, travels toward the second focal point of the second ellipsoid, and is incident on the light guide 31 serving as the light receiving unit 30. ０ = 27°, the light ray 60 is incident substantially parallel to the direction in which the core portion 33 of the light guide 31 extends.

[0132] Incident angle θ ０23B, when the incident angle θ is 54°, the light ray 60 incident on the first ellipsoid 22b is reflected by the ellipsoid surface 26 and travels toward the second focal point f2 of the first ellipsoid 22b (the first focal point f3 of the second ellipsoid). The light ray 60 is reflected by the ellipsoid surface of the second ellipsoid, travels toward the second focal point of the second ellipsoid, and then enters the light guide 31. ０ = 54°, the light ray 60 enters at an angle relative to the direction in which the core portion 33 of the light guide 31 extends, but due to the difference in refractive index between the core portion 33 and the clad portion 34, the light ray 60 propagates inside the light guide 31 while being reflected at the interface between the core portion 33 and the clad portion 34.

[0133] Incident angle θ ０ 23C, when the incident angle θ is 2°, the light ray 60 incident on the first ellipsoid 22b is directly received by the light receiving unit 30 without being reflected by the ellipsoid surface 26. ０ Even when angle .omega.=2°, the light ray 60 enters at an angle relative to the direction in which the core portion 33 of the light guide 31 extends, but due to the difference in refractive index between the core portion 33 and the clad portion 34, the light ray 60 propagates inside the light guide 31 while being reflected at the interface between the core portion 33 and the clad portion 34.

[0134] The protrusion 71 has an incident angle θ ０ When the incident angle .theta..sub.1 is small, the protrusion 71 serves to efficiently allow the light ray 60 to be incident on the first ellipsoid 22b. In the above description, the protrusion 71 is described as constituting a part of the elliptical shape of the first ellipsoid 22b, but the shape is not limited as long as it does not prevent the light ray 60 from being incident on the first ellipsoid 22b. The protrusion may be, for example, a conical shape or another shape.

[0135] As described above, by arranging the second focal point f2 of the second ellipsoid 23 at an upward tilt and by arranging the light receiving unit 30 at the position of the second focal point f2, it is possible to reduce the numerical aperture of the light receiving unit 30. In other words, even when the light collecting unit 3A is combined with a light receiving unit 30 having a small numerical aperture, it is possible to collect sunlight with high light collecting efficiency.

[0136] 3.3 Light Collecting Unit 3B Fig. 24 is a cross-sectional view shown for explaining a light collecting unit 3B according to the third embodiment.

[0137] The light collecting unit 3B differs from the light collecting unit 3A in that the size of the first ellipsoid 22b is different from the size of the spherical lens 10. The other parts are the same as the light collecting unit 3B. Therefore, the explanation of the light collecting unit 3B will focus on the differences from the light collecting unit 3A, and explanation of the common parts will be omitted as appropriate.

[0138] In the light collecting unit 3B, the first ellipsoid 22b has a minor axis length r ３ is the radius r of the spherical lens 10 ０ The longer first ellipsoid 22b is used, so that a higher proportion of the output surface of the spherical lens 10 is covered by the input surface 24 of the first ellipsoid 22b.

[0139] As can be seen from a comparison between FIG. 24 and FIG. 22, the light collecting unit 3B has a larger incident angle θ than the light collecting unit 3 and the light collecting unit 3B. ０ It can respond to.

[0140] That is, the light collecting unit 3B can increase the maximum angle of incidence of the light beam 60. Therefore, the light collecting unit 3B can accommodate, for example, large changes in elevation angle and azimuth angle of the sun's diurnal and annual motions.

[0141] 3.4. Light-Concentrating Unit 3C. Figure 25 is a perspective view illustrating a light-condensing unit 3C according to embodiment 3. The light-condensing unit 3C includes one spherical lens 10, a first light-receiving unit 5a, and a second light-receiving unit 5b. The first light-receiving unit 5a and the second light-receiving unit 5b each include a first ellipsoid 22b, a second ellipsoid 23, and a light-receiving unit 30.

[0142] The spherical lens 10, the first ellipsoid 22b included in the first light receiving unit 5a, and the first ellipsoid 22b included in the second light receiving unit 5b are arranged so that the center of the spherical lens 10 (symbol omitted), the first focal point (symbol omitted) of the first ellipsoid 22b included in the first light receiving unit 5a, and the first focal point (symbol omitted) of the first ellipsoid 22b included in the second light receiving unit 5b coincide.

[0143] In the first light receiving unit 5a and the second light receiving unit 5b, the first ellipsoid 22b and the second ellipsoid 23 are arranged so that the second focal point (reference numeral omitted) of the first ellipsoid 22b coincides with the first focal point (reference numeral omitted) of the second ellipsoid 23. In addition, the light receiving unit 30 is arranged at the position of the second focal point (reference numeral omitted) of the second ellipsoid 23.

[0144] The first light receiving unit 5a and the second light receiving unit 5b are disposed in a positional relationship rotated, for example, 180 degrees around the z-axis, 12 degrees around the y-axis, and 7 degrees around the x-axis with respect to the center of the spherical lens 10. Note that the positional relationship between the first light receiving unit 5a and the second light receiving unit 5b described above is an example. The first light receiving unit 5a and the second light receiving unit 5b may be disposed in any position as long as the first focal point of the first ellipsoid 22b of the first light receiving unit 5a and the first focal point of the second light receiving unit 5b coincide with the center of the spherical lens 10 and the elements included in the first light receiving unit 5a and the elements included in the second light receiving unit 5b do not interfere with each other.

[0145] The light collecting unit 3C includes a first light receiving unit 5a and a second light receiving unit 5b for one spherical lens 10. This increases the time during which light can be received by the light collecting unit 3C in response to fluctuations in elevation angle and azimuth angle due to the diurnal and annual motion of the sun.

[0146] 4. Embodiment 4 4.1. Light collecting unit 4 A light collecting unit 4 according to embodiment 4 will be described. Fig. 26 is a cross-sectional view shown for explaining the light collecting unit 4 according to embodiment 4. Fig. 27 is a ray tracing diagram shown for explaining the behavior of a light ray 60 when the light ray 60 is incident on the light collecting unit 4 according to embodiment 4.

[0147] The light-collecting unit 3 according to the third embodiment differs from the light-collecting unit 2 according to the second embodiment in that it includes a first convex portion 25. The other parts are the same as the light-collecting unit 2 according to the second embodiment. Therefore, the light-collecting unit 4 according to the fourth embodiment will be described focusing on the differences between the light-collecting unit 4 according to the fourth embodiment and the light-collecting unit 1 according to the first embodiment and the light-collecting unit 2 according to the second embodiment, and descriptions of the common parts will be omitted as appropriate.

[0148] The light collecting unit 4 has a first convex portion 25. The first convex portion 25 is configured in a shape that collects light that has passed through the center C of the spherical lens 10 and is incident on the first convex portion 25 at the position of the second focal point f2 of the first ellipsoid 22a. By having the first convex portion 25, the incident angle θ ０ The light beam 60 having a relatively small diameter can be condensed at the second focal point f2 of the first ellipsoid 22a and can be efficiently received by the light receiving unit 30.

[0149] FIG. 27( a ) shows the incident angle θ ０ 27B is a ray tracing diagram when a light ray 60 is incident on the light collecting unit 4 at an incident angle θ ０ 27(c) is a ray tracing diagram when a light ray 60 is incident on the light collecting unit 4 at an incident angle θ ０ 4 is a ray tracing diagram when a ray 60 is incident at an angle of .theta.=5.degree.. FIG.

[0150] Incident angle θ to the light collecting unit 4 ０ But θ ０ = 43° or θ ０ When the incident angle is relatively large, such as θ = 15°, the light ray 60 is reflected by the ellipsoidal surface 26 and reaches the light receiving section 30, as shown in FIGS. 27(a) and 27(b). ０ When the angle is small, such as .gtoreq.5.degree., the light passes through the first convex portion 25 and is guided directly to the light receiving portion 30, as shown in FIG.

[0151] 28A and 28B are diagrams illustrating an application example of the light collecting unit 3A according to embodiment 3. Fig. 28A is a layout diagram of the light collecting unit 3A as viewed from the south in an example where the light collecting unit 3A is installed, and Fig. 28B is a layout diagram of the light collecting unit 3A as viewed from the east in an example where the light collecting unit 3A is installed.

[0152] In the following explanation, an example will be described in which the light collecting unit 3A is installed in Nagano Prefecture, Japan (latitude 36 degrees north, longitude 138 degrees east). As shown in Figures 28(a) and 28(b), the light collecting unit 3A is positioned so that the direction of its optical axis (z-axis) is aligned with the direction of the sun at summer solstice noon. The elevation angle of the sun at summer solstice noon in Nagano Prefecture is 77°. Furthermore, the elevation angle at vernal and autumnal equinox noon is 54°, and the elevation angle at winter solstice noon is 31°, so the light collecting unit 3A can effectively cover the diurnal and annual motion of the sun.

[0153] When installing outside Nagano Prefecture, the optimum location can be selected depending on the diurnal and annual motion of the sun at the installation location and the intended use.

[0154] 6. Sunlight Receiver Next, a sunlight receiver according to a fifth embodiment will be described. The sunlight receiver can be configured by combining a plurality of light collecting units 1. Fig. 29 is a perspective view showing an external image of a sunlight receiver 6 according to one embodiment of the sunlight receiver. Fig. 30 shows a sunlight receiver 6 at an incident angle θ ０ 4 is a ray tracing diagram when a ray 60 is incident at an angle of .theta.=30.degree.. FIG.

[0155] 29 , the sunlight receiving device 6 can be configured by combining two concentrating units 1. The two concentrating units 1 included in the sunlight receiving device 6 can have the same configuration as the concentrating units 1 according to the first embodiment described above. The sunlight receiving device 6 is arranged so that the direction in which the optical axes 40 of the two concentrating units 1 extend is parallel to the z-axis. The two concentrating units 1 are also stacked in the y-axis direction, with part of the spherical lens 10 abutting part of the spherical lens 10 of the concentrating unit 1 arranged adjacently.

[0156] When viewed from the z-axis direction, the spherical lens 10 may have the portion that abuts an adjacent spherical lens 10 scraped off, so that the adjacent spherical lens 10 abuts face-to-face, as shown in Figures 29 and 30.

[0157] This further reduces the proportion of light that escapes to the rear of the focusing unit 1 without entering the spherical lens 10. As a result, the light-collecting efficiency can be increased. Furthermore, because the spherical lens 10 has spherical aberration, light that is incident near the outermost periphery of the spherical lens 10 contributes little to light collection. By cutting the outermost periphery of the spherical lens 10 and configuring adjacent spherical lenses 10 to abut face-to-face, it becomes possible to collect more light that is incident at a position closer to the center of the spherical lens 10. As a result, the sunlight-collecting efficiency can be further increased.

[0158] 30, a light ray 60 is incident on the sunlight receiving device 6 at an incident angle θ ０ 2 shows a ray tracing diagram when the light is incident at an angle of 0° = 30°. Of the light rays 60, the light irradiated onto the spherical lens 10 of the upper collecting unit 1 of the solar light receiving device 6 is incident onto the spherical lens 10 of the upper collecting unit 1, is guided through the first ellipsoid 22a, and is received by the light receiving unit 30. On the other hand, the light irradiated onto the spherical lens 10 of the lower collecting unit 1 is incident onto the spherical lens 10 of the lower collecting unit 1, is guided through the first ellipsoid 22a, and is received by the light receiving unit 30.

[0159] The spherical lens 10 is configured such that the portion that comes into contact with the spherical lens 10 of the adjacent light-collecting unit 1 is cut away, so that they come into face-to-face contact, thereby increasing the light-collecting efficiency.

[0160] Fig. 31 is a diagram for explaining a solar light receiving device 7 according to another embodiment of the solar light receiving device. Fig. 31(a) is a perspective view showing an external appearance of the solar light receiving device 7. Fig. 31(b) is a diagram of the solar light receiving device 7 as seen from the incident side of the spherical lens 10 on which a ray 60 of light is incident. Fig. 32 is a diagram showing a solar light receiving device 7 having an incident angle θ ０ 4 is a ray tracing diagram when a ray 60 is incident at an angle of .theta.=30.degree.. FIG.

[0161] 31 , the solar light receiving device 7 can be configured by combining seven light collecting units 1. The light collecting units 1 included in the solar light receiving device 7 can have the same configuration as the light collecting unit 1 according to the first embodiment described above.

[0162] The seven concentrating units 1 are arranged so that the direction in which the optical axis 40 (see FIG. 32) of the concentrating unit 1 extends is parallel to the z-axis. Furthermore, of the seven concentrating units 1, six of the concentrating units 1 are arranged so that the centers C (see FIG. 1) of the spherical lenses 10 are located at the vertices of regular hexagons H when the solar light receiving device 7 is viewed from the side on which the spherical lenses 10 are arranged, i.e., from the -z direction, as shown in FIG. 31( b). Of the seven concentrating units 1, the remaining one concentrating unit 1 is arranged so that the center C of the spherical lens 10 is located at the center of gravity of the regular hexagon H when the solar light receiving device 7 is viewed from the side on which the spherical lenses 10 are arranged.

[0163] 31(a) and 31(b), when viewed from the direction of the optical axis 40 of the light-collecting unit 1, the spherical lenses 10 have a regular hexagonal shape, with the portions thereof cut away where they come into contact with the spherical lenses 10 of adjacent light-collecting units 1. The spherical lenses 10 are also arranged in a close-packed configuration.

[0164] This reduces the proportion of light that escapes to the rear of the focusing unit 1 without entering the spherical lens 10. Furthermore, because the spherical lens 10 has spherical aberration as described above, light that is incident near the outermost periphery of the spherical lens 10 contributes little to focusing. By cutting the outermost periphery of the spherical lens 10 and forming a close-packed structure with adjacent spherical lenses 10, it becomes possible to focus more light that is incident at a position close to the center of the spherical lens 10. As a result, the sunlight focusing efficiency can be further improved.

[0165] 32, a light ray 60 is incident on the sunlight receiving device 7 at an incident angle θ ０ 1 shows the results of a ray tracing simulation when the light ray 60 is incident at an angle of 30°. As the simulation results show, it can be seen that the light ray 60 is collected on the light receiving section 30 with high collection efficiency.

[0166] 33 is an external view of a solar light receiving device 8 according to another embodiment of the solar light receiving device. ０10 is a diagram showing the results of a ray tracing simulation when a light ray 60 is incident at an angle of 30°.

[0167] 35 is an external view of the sunlight receiving device 8 when the tilt angle of the light collecting unit 1 is set to 30°. ０ 36(a) shows the results of a simulation performed by changing the incident angle θ of sunlight. ０ 36(b) is a diagram showing the ray tracing results when the incident angle θ of sunlight is 60°. ０ 36(c) is a diagram showing the ray tracing results when the incident angle θ of sunlight is 0°. ０ 10 is a diagram showing the ray tracing results when the angle is −60°.

[0168] As shown in Fig. 33 , the sunlight receiving device 8 is configured by combining a plurality of collecting units 1. The plurality of collecting units 1 included in the sunlight receiving device 8 can have the same configuration as the collecting units 1 according to the above-described first embodiment. The optical axes 40 of the collecting units 1 included in the sunlight receiving device 8 are tilted relative to each other as shown in Fig. 33 .

[0169] The angle of incidence of sunlight varies greatly with the diurnal and annual motion of the sun. For this reason, it is desirable for a sunlight receiving device to be able to accommodate as wide an angle of incidence as possible. As shown in Figure 33, by tilting the optical axes 40 (major axes of the first ellipsoids 22a) of the concentrating units 1 included in the sunlight receiving device 8 relative to each other, it becomes possible to accommodate variations in the angle of incidence.

[0170] 34 shows the incident angle θ ０ 1 shows the results of a ray tracing simulation when a ray 60 is incident at an angle of 30°. It can be seen that a wide range of incident angles can be accommodated because the optical axes 40 of the multiple light collecting units 1 are arranged so as to be tilted relative to each other.

[0171] FIG. 35 is an external view showing a sunlight receiving device 8 configured so that the tilt angle of the light collecting unit 1 is increased to 30° and can accommodate large fluctuations in the incident angle.

[0172] 36 shows the incident angle θ of a light ray 60 relative to the optical axis 40 of the light collecting unit 1 at the center of the sunlight receiving device 8. ０ =60°, (b) incident angle θ ０ =0°, (c) incident angle θ ０ 36 shows the results of ray tracing simulation when the sunlight is incident at an angle θ = -60°. ０ It can be seen that even when the tilt angle (Δθ) changes over a wide range from −60° to 60°, at least one of the three light collecting units 1 receives and collects sunlight. In other words, it can be seen that by increasing the tilt angle (Δθ), it is possible to cope with large fluctuations in the incident angle.

[0173] [1] Modification 1 A light collecting unit 4a according to Modification 1 will be described. Fig. 37 is a diagram for explaining a light collecting unit 4a according to Modification 1.

[0174] The light-collecting unit 4a differs from the light-collecting unit 1 according to the first embodiment in that the spherical lens 10 has a convex portion 15 (hereinafter referred to as a "second convex portion 15"). In other respects, the light-collecting unit 4a is the same as the light-collecting unit 1 according to the first embodiment.

[0175] In FIG. 37, a light ray 60a is incident at an angle θ ０ The light ray 60b has an incident angle θ ０ indicates a small ray.

[0176] In the focusing unit 4a, the exit surface of the spherical lens 10 has a recess 12. The recess 12 has a circular shape when viewed from the +z direction (the right side in the figure). As shown in FIG. 37 , the bottom surface of the recess 12 protrudes in the +z direction to form a second convex portion 15. The second convex portion 15 functions as a lens that focuses the light ray 60b. Specifically, the second convex portion 15 is configured in a shape such that the light ray 60b that passes through the center C of the spherical lens 10 is refracted by the second convex portion 15 and focused at the position of the second focal point f2 of the first ellipsoid 22a.

[0177] The first ellipsoid 22a is made of a transparent material whose refractive index increases with light irradiation. Therefore, the light (not shown) of the light ray 60b that does not pass through the center C of the spherical lens 10 travels along the light that has passed through the center C of the spherical lens 10 while being guided inside the first ellipsoid 22a, and is guided to the second focal point f2.

[0178] That is, by forming the second convex portion 15 on the output side of the spherical lens 10, the incident angle θ of the light ray 60b incident on the light collecting unit 4a with respect to the optical axis 40 of the light collecting unit 4a is ０ Even if the angle .theta. is small, the light ray 60b can be guided to the light receiving section 30 with high light collection efficiency.

[0179] [2] Modification 2 A light collecting unit 4b according to Modification 2 will be described. Fig. 38 is a diagram for explaining a light collecting unit 4b according to Modification 2.

[0180] In the light-collecting unit 4b, there is no space between the spherical lens 10 and the incident surface 24 of the first ellipsoid 22a. In other words, the exit surface of the spherical lens 10 and the incident surface 24 of the first ellipsoid 22a are arranged in close contact with each other. In other respects, the light-collecting unit 4b is the same as the light-collecting unit 4a according to the second modification.

[0181] If the spherical lens 10 is made using a material with a relatively high refractive index, the spherical aberration of the spherical lens 10 will be large. As a result, light that does not pass through the center C of the spherical lens 10 will converge at a position close to the outer periphery of the spherical lens 10. In other words, by making the spherical lens 10 using a material with a relatively high refractive index, the first ellipsoid 22a and the spherical lens 10 can be arranged in close contact with each other.

[0182] By closely contacting the spherical lens 10 with the incident surface 24 of the first ellipsoid 22a, the accuracy of the spatial distance between the first ellipsoid 22a and the spherical lens 10 can be improved, and the long-term durability of the light receiving device can be increased. As a result, variations in light collection efficiency can be suppressed. In addition, the intrusion of foreign matter such as dust into the gap between the first ellipsoid 22a and the spherical lens 10 can be suppressed, improving reliability. Furthermore, there is an effect of facilitating the assembly of the spherical lens 10 and the first ellipsoid 22a.

[0183] [3] Modification 3 A light collecting unit 4c according to Modification 3 will be described. Fig. 39 is a diagram for explaining a light collecting unit 4c according to Modification 3.

[0184] The spherical lens 10 included in the light collecting unit 4c has an incident side radius r ０ and the exit radius r ２ The radius of the incident side r is set to a different value. ０ is the radius of the exit side r ２ is set to a smaller value (r ０ <r ２ ). This allows light that does not pass through the center C of the spherical lens 10 to be converged at a position close to the outer periphery of the spherical lens 10. This allows the exit surface of the spherical lens 10 and the entrance surface 24 of the first ellipsoid 22a to be arranged in close contact with each other.

[0185] Furthermore, by adopting a structure in which the exit surface of the spherical lens 10 and the entrance surface 24 of the first ellipsoid 22a are in close contact with each other, the accuracy of the spatial distance between the first ellipsoid 22a and the spherical lens 10 can be improved, and the long-term durability of the light receiving device can be enhanced. As a result, variations in light collection efficiency can be suppressed. Furthermore, the intrusion of foreign matter such as dust into the gap between the first ellipsoid 22a and the spherical lens 10 can be suppressed, improving reliability. Furthermore, the spherical lens 10 and the first ellipsoid 22a can be easily assembled.

[0186] [4] Modification 4 In Modifications 1 to 3, examples have been shown in which the second convex portion 15 is disposed on the exit side of the spherical lens 10, but as shown in Embodiment 1, it is also possible to dispose the convex portion on the incident surface 24 of the first ellipsoid 22a, or to dispose the convex portion on both the exit side of the spherical lens 10 and the incident surface 24 of the first ellipsoid 22a. In either case, the shape of the first convex portion 25 should be designed so that light passing through the center C of the spherical lens 10 passes through the second focal point f2 of the first ellipsoid 22a.

[0187] [5] Modification 5 Fig. 40 is a diagram for explaining a solar light receiving device 9 according to Modification 5. In the solar light receiving device 9, the spherical lenses 10 included in a plurality of light collecting units 1 are formed as a single component, a composite spherical lens 11. Other configurations of the solar light receiving device 9 are the same as those of the solar light receiving device 7 etc. described as the embodiment.

[0188] By replacing the plurality of spherical lenses 10 with a compound spherical lens 11 having the functions of the plurality of spherical lenses 10, it becomes possible to improve assembly accuracy and reduce costs.

[0189] Although the light collecting unit and the solar light receiving device according to the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit and scope of the present invention.

[0190] The effects achieved by the light collecting unit and the sunlight receiving device described as the embodiment will be described below.

[0191] 1 and other figures, the light collecting unit 1 according to the first embodiment has a first ellipsoid 22a that guides light emitted from a spherical lens 10. Here, the spherical lens 10 and the first ellipsoid 22a are arranged so that the center C of the spherical lens 10 and the first focal point f1 of the first ellipsoid 22a coincide with each other. As a result, of the light rays 60 incident on the light collecting unit 1, the light that has passed through the center C of the spherical lens 10 is reflected at an incident angle θ ０ Regardless of the angle, the light can be guided to the second focal point f2 of the first ellipsoid 22a.

[0192] 6, the first ellipsoid 22a is made of a transparent material whose refractive index increases when irradiated with light, so that light that does not pass through the center C of the spherical lens 10 also travels through the first ellipsoid 22a along the light that has passed through the center C of the spherical lens 10.

[0193] That is, in the light collecting unit 1 according to the first embodiment, for the light ray 60 incident on the light collecting unit 1, both the light that has passed through the center C of the spherical lens 10 and the light that has not passed through the center C of the spherical lens 10 are incident at an incident angle θ ０As a result, even if the light-concentrating unit 1 does not have a sun-tracking mechanism, it is possible to concentrate sunlight with high light-concentration efficiency.

[0194] 1 and the like, the light collecting unit 1 according to the first embodiment has an incident surface 24, and the incident surface 24 preferably has a spherical surface centered on the position of the center C of the spherical lens 10. As a result, the light ray 60 incident on the light collecting unit 1 is incident at an incident angle θ ０ Regardless of the position of the first ellipsoid 22a, the light can be guided to the position of the second focal point f2 of the first ellipsoid 22a.

[0195] According to a preferred embodiment of the light collecting unit 1 of the first embodiment, the spherical lens 10 and the first ellipsoid 22a are preferably arranged apart from each other, as shown in Fig. 1 etc. This makes it possible to adjust the size of the light flux concentration region of the light rays 60 that are emitted from the spherical lens 10 and enter the first ellipsoid 22a.

[0196] 1 etc., the light collecting unit 1 according to the first embodiment further includes a light receiving unit 30, which is preferably disposed at a position including the second focal point f2 of the first ellipsoid 22 a. By disposing the light receiving unit 30 at a position including the second focal point f2 of the first ellipsoid 22 a, the light ray 60 guided by the first ellipsoid 22 a can be efficiently received.

[0197] According to a preferred embodiment of the light collecting unit 1 of the first embodiment, as shown in FIG. 13 and other figures, the first ellipsoid 22a further has an exit surface 29 near the second focal point f2 of the first ellipsoid 22a, which emits the light ray 60 guided by the first ellipsoid. The refractive index of a region 29a between the exit surface 29 and the light receiving unit 30 is smaller than the refractive index of the light receiving unit. As a result, when the light emitted from the first ellipsoid 22a enters the light receiving unit 30, it enters the light receiving unit 30 along the center line of the light receiving unit. As a result, when the light receiving unit 30 is a light guide 31, the light guide efficiency of the light ray 60 in the light guide 31 can be improved.

[0198] 1 and other figures, the incident surface 24 of the first ellipsoid 22a has a first convex portion 25. The first convex portion 25 is disposed on the major axis of the first ellipsoid 22a and is configured in a shape that focuses light that has passed through the center C of the spherical lens 10 at the position of the second focal point f2 of the first ellipsoid 22a.

[0199] As a result, as shown in FIG. 3B, the incident angle θ ０ The light ray 60, which has a relatively small diameter, can be focused at the second focal point f2 of the first ellipsoid 22a and efficiently received by the light receiving unit 30. Note that instead of or in addition to the first convex portion 25, a second convex portion 15 may be formed on the exit surface of the spherical lens 10.

[0200] 16 etc., the light focusing unit 2 according to the second embodiment preferably further includes an ellipsoidal surface 26 of the first ellipsoid 22 b and a surface 28 including the major axis of the first ellipsoid 22 b. This allows the light ray 60 guided by the first ellipsoid 22 b to be extracted in a direction perpendicular to the major axis of the first ellipsoid 22 b.

[0201] 19 and the like, the light collecting unit 3 according to the third embodiment preferably further includes a second ellipsoid 23. This allows light to be guided with high efficiency at the position of the second focal point f4 of the second ellipsoid 23.

[0202] 19 and other figures, the light collecting unit 3 according to the third embodiment is preferably arranged so that the position of the second focal point f2 of the first ellipsoid 22b coincides with the position of the first focal point f3 of the second ellipsoid 23, and the light receiving unit 30 is arranged at the position of the second focal point f4 of the second ellipsoid 23. This allows light to be received with high efficiency at the position of the second focal point f4 of the second ellipsoid 23.

[0203] The light receiving portion of the light collecting unit 1 is preferably a light receiving portion of a light guide device, a light receiving portion of a photovoltaic device, or a light receiving portion of a light heating device, thereby enabling the light collecting unit 1 to collect light with high efficiency.

[0204] 29 and other figures, a sunlight receiving device 6 according to a fifth embodiment is a sunlight receiving device in which a plurality of concentrating units 1 are arranged, and it is preferable that the spherical lenses 10 included in one concentrating unit 1 abut against the spherical lenses 10 included in the other concentrating units 1. This makes it possible to reduce the proportion of light that escapes to the rear of the concentrating units 1 without entering the spherical lenses 10.

[0205] 29 and other figures, in the solar light receiving device 7 according to the fifth embodiment, it is preferable that one spherical lens 10 and another spherical lens 10 are in face-to-face contact with each other. This makes it possible to reduce the proportion of light that escapes to the rear of the light collecting unit 1 without being incident on the spherical lens 10.

[0206] 31 , in the solar light receiving device 8 according to the fifth embodiment, the spherical lenses 10 have a regular hexagonal shape when viewed from the direction of the optical axis 40 of the light collecting unit 1, and the spherical lenses 10 are preferably arranged in a close-packed arrangement. This makes it possible to further reduce the proportion of light that escapes to the rear of the light collecting unit 1 without entering the spherical lenses 10.

[0207] In the solar light receiving device 9 according to the fifth embodiment, as shown in Fig. 33 etc., it is preferable that the optical axes 40 of the plurality of light collecting units 1 are arranged in different directions. This makes it possible to provide a solar light receiving device 9 that can accommodate changes in the angle of incidence.

[0208] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D, 2, 3, 3A, 3B, 3C, 4a, 4b, 4c...light collecting unit, 6, 7, 8, 9...sunlight receiving device, 10...spherical lens, 11...composite spherical lens, 12...concave portion, 15...second convex portion, 22a, 22b...first ellipsoid, 23...second ellipsoid, 24...incident surface, 25...first convex portion, 26...ellipsoid surface, 28...surface including the major axis of the first ellipsoid 22b, 29...exit surface, 30...light receiving portion, 31...light guide, 32...light receiving surface, 33...core portion, 34...cladding portion, 40...optical axis of light collecting unit 1, 60, 60a, 60b...light ray, 71...protrusion portion, 73...transparent member, C...center of spherical lens 10, f1...first focus of first ellipsoids 22a, 22b, f2...second focus of first ellipsoids 22a, 22b, f3...first focus of second ellipsoid 23, f4...second focus of second ellipsoid 23

Claims

1. A focusing unit comprising: a spherical lens that receives light rays; and a first ellipsoid that guides the light rays emitted from the spherical lens, wherein the first ellipsoid is formed from a material whose refractive index increases when exposed to light; and the spherical lens and the first ellipsoid are positioned so that the center of the spherical lens and a first focal point of the first ellipsoid coincide with each other.

2. A focusing unit as described in claim 1, characterized in that the first ellipsoid has an incident surface on which the light beam emitted from the spherical lens is incident, and the incident surface has a spherical surface centered on the center position of the spherical lens.

3. A light collecting unit according to claim 2, characterized in that the spherical lens and the first ellipsoid are arranged at a distance from each other.

4. A light collecting unit as claimed in claim 1, further comprising a light receiving section, the light receiving section being arranged at a position including a second focal point of the first ellipsoid.

5. A focusing unit as described in claim 4, characterized in that the first ellipsoid further has an exit surface in the vicinity of the second focal point of the first ellipsoid, which emits light rays guided by the first ellipsoid, the exit surface forms a curved surface surrounding the second focal point of the first ellipsoid, and the refractive index of the region between the exit surface and the light receiving unit is smaller than the refractive index of the light receiving unit.

6. A focusing unit as described in claim 1, characterized in that the exit surface of the spherical lens and / or the entrance surface of the first ellipsoid have a convex portion, the convex portion is arranged on the major axis of the first ellipsoid, and is configured in a shape that focuses light that has passed through the center of the spherical lens at the position of the second focal point of the first ellipsoid.

7. A light collecting unit according to claim 1, characterized in that the first ellipsoid has an ellipsoidal surface of the first ellipsoid and a plane including the major axis of the first ellipsoid.

8. A light collecting unit as claimed in claim 1, further comprising: a light receiving section; and a second ellipsoid that guides the light guided by the first ellipsoid to the light receiving section.

9. A focusing unit as described in claim 8, characterized in that the first ellipsoid and the second ellipsoid are arranged so that the second focal point of the first ellipsoid coincides with the first focal point of the second ellipsoid, and the light receiving unit is arranged at a position including the second focal point of the second ellipsoid.

10. A light-collecting unit according to claim 4 or 8, characterized in that the light-receiving portion is a light-receiving portion of a light-guiding device, a light-receiving portion of a photovoltaic device, or a light-receiving portion of a photoheating device.

11. A focusing unit as described in claim 1, characterized in that the spherical lens receives sunlight incident from different angles due to the annual and diurnal motion of the sun and makes the sunlight incident on the first ellipsoid, and the first ellipsoid guides the sunlight incident from the spherical lens and directs it to the position of a second focal point of the first ellipsoid.

12. A solar light receiving device in which a plurality of the focusing units according to claim 1 are arranged, characterized in that the spherical lens included in one of the focusing units is in contact with the spherical lens included in another of the focusing units.

13. A solar light receiving device as described in claim 12, characterized in that the spherical lens included in the one focusing unit and the spherical lens included in the other focusing unit are in face-to-face contact.

14. A solar light receiving device as described in claim 13, characterized in that the spherical lens has a regular hexagonal shape when viewed from the optical axis direction of the focusing unit, and the plurality of spherical lenses are arranged in a close-packed configuration.

15. A solar light receiving device according to claim 12, characterized in that the optical axes of the plurality of light collecting units are arranged in different directions.

Images