JPWO2016051530A1 - Optical element and illumination device - Google Patents

Abstract

The transparent optical element (10) has a light guide member (14) having a diffusion part (15) for diffusing light. Each of the second rods (12a, 12b, 12c) guides light from the light source 1 from a direction inclined toward the diffusing unit.

Description

  Embodiments of the present invention relate to, for example, an optical element that can emit light that appears to be spot-like in a wide light distribution, and an illumination device such as a light bulb including the optical element.

  Conventionally, there has been known an optical element of a type in which a scatterer is arranged at a position away from a light source and light emitted from the light source is guided to the scatterer via a light guide member. This optical element can illuminate the scatterer at a position away from the light source.

  For example, when this type of optical element is arranged in a transparent globe and the optical element is arranged so that the scatterer is located in the center of the transparent globe, it can function as a light bulb-type lighting device. At this time, by making the scatterer as small as possible and using it as a pseudo point light source, it can be expected to be close to how the incandescent bulb shines (retrofit). In this case, considering the size of a general light bulb, it is preferable to use an LED as the light source.

US 6,350,041

  However, when an LED is used as the light source of the optical element described above, the light distribution angle of the light bulb becomes narrow because the directivity of light emitted from the LED is strong. For this reason, it is difficult to realize a pseudo point light source having a wide light distribution like an incandescent bulb.

  The optical element according to the embodiment is formed of a material transparent to visible light, and diffuses light transmitted through the optical element; a first air layer in contact with the first diffusion surface; And a second portion provided integrally with the first portion and extending in a direction inclined with respect to the first diffusion surface. The first air layer includes a side surface in a direction intersecting with the first diffusion surface.

  According to the embodiment of the present invention, it is possible to provide an optical element and an illumination device that can realize a pseudo-point light source with a wide light distribution.

FIG. 1 is a schematic diagram illustrating an example of a light bulb including the optical element according to the first embodiment. FIG. 2 is an external perspective view showing the optical element according to the first embodiment arranged in the globe of the light bulb shown in FIG. FIG. 3 is a top view of the optical element of FIG. 2 viewed from the direction of arrow F3. FIG. 4 is a side view of the optical element of FIG. 2 viewed from the direction of arrow F4. FIG. 5 is a bottom view of the optical element of FIG. 2 viewed from the direction of the arrow F5. FIG. 6 is a cross-sectional view of the optical element taken along line F6-F6 in FIG. FIG. 7 is a chart for explaining the light distribution characteristics of the optical element according to the first embodiment. FIG. 8 is an external perspective view showing an optical element according to the second embodiment. FIG. 9 is an exploded perspective view of the optical element of FIG.

Hereinafter, embodiments will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a light bulb 100 that is an example of a lighting device including an optical element 10 according to the first embodiment. The light bulb 100 includes a metal heat dissipating housing 102, a base 104 for electrical connection to a ceiling socket (not shown), a spherical globe or a spherical globe 106 that covers the optical element 10, and is not shown here. A lighting circuit 108 that supplies power to the light source 1 to light it and an optical element 10 are provided. For example, the light bulb 100 is attached to a ceiling socket in a state where the posture shown in FIG.

  The heat dissipating casing 102 has one end (the lower end in the figure) to which the base 104 is connected and the other end (the upper end in the figure) to which the globe 106 is attached. The heat radiating housing 102, the base 104, and the globe 106 have axes that are along the rotational symmetry axis of the light bulb 100.

  Here, the rotational symmetry means that when the object is rotated with respect to the rotational symmetry axis, the rotation angle is less than 360 ° and coincides with the original object (before rotation). For example, a cylinder, a cone, a polygonal column, and a polygonal guess are rotationally symmetric.

  The heat dissipating casing 102 has a substantially frustoconical outer shape whose diameter gradually increases from one end to the other end. The heat dissipating case 102 is thermally connected to a light source 1 (not shown here) via a support member 20 (not shown here), and dissipates heat from the light source 1 to the outside of the heat dissipating case 102. Have For this reason, the heat radiating housing 102 may include a plurality of heat radiating fins on the outer peripheral surface 102a.

  Hereinafter, the optical element 10 of the first embodiment will be described with reference to FIGS. 2 to 7. Here, the vertical and horizontal directions will be described with reference to the orientation of the optical element 10 in FIG.

  2 is an external perspective view of the optical element 10, FIG. 3 is a top view of the optical element 10, FIG. 4 is a side view of the optical element 10, and FIG. 5 is a bottom view of the optical element 10. It is. In FIG. 3, the scatterer 16 described later is not shown. 6 is a cross-sectional view of the optical element 10 taken along F6-F6 in FIG. 4, and FIG. 7 is a chart showing the light distribution characteristics of the optical element 10. FIG. 6 shows a cross section of the optical element 10 cut along a plane passing through the central axis of the second rod 12a described later.

  The optical element 10 includes a light guide member 14 shaped like a tetrapot having a cylindrical bottomed receiving recess 13 and a substantially columnar scatterer 16 having a cavity 17. The scatterer 16 is housed and disposed in the housing recess 13 of the light guide member 14, and a part thereof is bonded and fixed to the inner surface of the housing recess 13. The optical element 10 is attached via a support member 20 (FIG. 6), which will be described later, in such a posture that the center axis of the first rod 11 described later and the center axis of the scatterer 16 overlap the rotational symmetry axis of the bulb 100.

  The optical element 10 of this embodiment, that is, the light guide member 14 and the scatterer 16 is formed of transparent acrylic. The material of the optical element 10 is not limited to acrylic, but may be, for example, polycarbonate or glass that is transparent to visible light and has heat resistance. In addition, the light guide member 14 and the scatterer 16 may be formed of different types of transparent materials.

  The light guide member 14 includes a substantially cylindrical first rod 11 having an accommodation recess 13 coaxially, and three second rods that are integrally continuous with an angle at one end (lower end in FIG. 2) of the first rod 11. 12a, 12b, 12c (hereinafter, collectively referred to as the second rod 12). The first rod 11 functions as a first portion of the optical element 10. Further, the second rod 12 functions as a second portion of the optical element 10, and the scatterer 16 functions as a third portion. Here, the second portion is composed of a plurality of second rods 12. Each second rod 12 is provided so as to be rotationally symmetric with respect to the central axis of the first rod 11.

  The first rod 11 has an outer peripheral surface 11a that is curved so that the diameter gradually decreases from one end to the other end. The three second rods 12 a, 12 b, 12 c have the same structure and are connected to the first rod 11 at the same angle. That is, the central axes of the three second rods 12 a, 12 b, and 12 c intersect on the central axis of the first rod 11. The first rod 11 has a larger diameter than the second rod 12.

  The housing recess 13 has a circular opening 13a on the other end side of the first rod 11, and has a peripheral wall 13b extending from the opening 13a toward the one end side in parallel with the central axis. In addition, a flat diffusion portion 15 that functions as a first diffusion surface for diffusing light is provided on the bottom portion of the accommodation recess 13 that is spaced from the opening 13a. The diffusion unit 15 is disposed along a plane orthogonal to the central axis of the first rod 11. The housing recess 13 includes a first air layer. Further, the inner surface of the peripheral wall 13 b is rotationally symmetric with respect to the central axis passing through the diffusing portion 15 and becomes a surface in a direction intersecting with the diffusing portion 15. Thereby, the side surface of the first air layer intersects with the diffusing portion 15.

  In the present embodiment, the diffusion portion 15 is formed by applying a white paint with a constant film thickness to the bottom wall of the housing recess 13. In addition to this, the diffusing portion 15 may be formed by subjecting the surface of the bottom wall of the housing recess 13 to a rough surface by sandblasting. Moreover, the same process may be given also to the surrounding wall 13b of the accommodation recessed part 13, In that case, it functions to diffuse the light to permeate | transmit.

  The three second rods 12a, 12b, 12c are inclined outward in a direction away from one end of the first rod 11, and are provided at equal intervals (every 120 degrees) along the circumferential direction of the first rod 11. (See FIGS. 3 and 5). A circular incident surface 12d (incident plane) on which light emitted from the light source 1 (FIG. 6) is incident is provided at the end of each of the second rods 12a, 12b, and 12c spaced from the first rod 11. ing. The light sources 1 disposed so as to face the respective incident surfaces 12d have different emission spectra.

  As shown in FIG. 6, the scatterer 16 has an outer diameter smaller than the inner diameter of the housing recess 13 of the light guide member 14. That is, a cylindrical gap S is formed between the peripheral wall 13 b of the storage recess 13 and the outer peripheral surface 16 a of the scatterer 16 in a state where the scatterer 16 is coaxially stored in the storage recess 13. This gap S functions as a second air layer. The length of the scatterer 16 in the axial direction is designed such that the scatterer 16 does not protrude from the opening 13 a of the housing recess 13 in a state where the scatterer 16 is housed in the housing recess 13. However, it is not limited to this and may protrude. The scatterer 16 is provided with a bottom surface that faces the diffusion portion 15.

  In the present embodiment, the cavity 17 is a bottomed hole formed coaxially with the peripheral wall 13 b of the housing recess 13, and extends from the other end of the scatterer 16 toward the diffusion portion 15 of the housing recess 13. Yes. The cavity 17 has a cylindrical peripheral surface 17a parallel to the peripheral wall 13b of the housing recess 13, and a diameter gradually decreases from one end (lower end in the figure) of the peripheral surface 17a toward the diffusion portion 15, and then gently curves and closes. A bottom surface 17b. In other words, the bottom surface 17 b of the accommodation recess 13 is curved so as to be convex toward the diffusion portion 15. The other end (the upper end in the figure) of the peripheral surface 17a is open, and the other end of the cavity 17 is open. The peripheral surface 17a and the bottom surface 17b function as a second diffusion surface.

  The peripheral surface 17a and the bottom surface 17b are subjected to processing (white coating or sandblasting) for scattering transmitted light, and function as a scattering surface. Alternatively, the cavity 17 may be filled with a scattering material that can scatter light.

  As shown in FIG. 6, the optical element 10 described above is fixed to the heat dissipation housing 102 via the support member 20. The support member 20 is made of a metal material such as aluminum having good thermal conductivity. The optical member 10 is, for example, applied to one end of the first rod 11 between the three second rods 12a, 12b, and 12c, and is bonded and fixed to the support member 20 through the adhesive. In this way, by fixing the optical element 10 to the support member 20 on one end side of the first rod 11, the support member 20 hardly blocks light emitted from the optical element 10. The support member 20 may have a notch 21 so that it does not exist on the optical path of the light emitted through the optical element 10.

  In addition, the support member 20 includes three support surfaces 22 that support the three light sources 1 so as to face the above-described three incident surfaces 12 d of the optical element 10. The light source 1 is, for example, one in which at least one LED is mounted on the surface of a substrate and sealed with resin. Each light source 1 is attached with the back surface of the substrate in contact with the support surface 22 of the support member 20. In this case, the support surface 22 is provided at a position where the light source 1 faces the incident surface 12d through a certain gap. In the present embodiment, the light emission plane of the light source 1 and the incident surface 12d are separated from each other in a non-contact state, but a silicone resin mixture containing a white pigment or the like may be filled therebetween.

  For example, if three types of light sources 1 that emit light of three colors of RGB are prepared and arranged to face each of the three incident surfaces 12 d of the optical element 10, the light of the three colors is mixed by the diffusing portion 15 of the optical element 10. The peripheral surface 17a and the bottom surface 17b of the cavity 17 of the scatterer 16 can be illuminated in white. In the present embodiment, as shown in FIG. 1, since the cavity 17 of the optical element 10 is arranged at the center of the globe 106, illumination light close to an incandescent bulb can be emitted.

  Next, how light is transmitted in the optical element 10 having the above structure will be described with reference to FIG. Since the light emitted from the three light sources 1 travels in the optical element 10 in the same manner, here, how to propagate the light will be described by paying attention to the light emitted from one light source 1 facing the incident surface 12d of the second rod 12a. To do.

  The light emitted from the light emission plane of the light source 1 enters the second rod 12a of the optical element 10 through the incident surface 12d. Most of the light incident on the second rod 12 a is totally reflected by the outer peripheral surface of the second rod 12 a and guided to the diffusion unit 15. The light applied to the diffusing unit 15 is transmitted through the Lambert scattering with the normal direction (that is, the direction parallel to the central axis of the first rod 11) perpendicular to the diffusing unit 15 passing through the irradiation position as the central axis. The transmitted light is diffused as indicated by the arrows in the figure. That is, in this case, the diffusing unit 15 functions as a secondary light emitting unit that emits light upon receiving light from the light source 1.

  The light incident on the diffusing unit 15 is Lambert-transmitted with the normal direction perpendicular to the diffusing unit 15 as the central axis regardless of the incident angle with respect to the diffusing unit 15. The scatterer 16 is designed to guide Lambert scattered light from the light emitting surface to the scattering surface of the cavity 17 when the light emitting surface is disposed opposite the bottom surface. As described above, the light that is Lambert scattered by the diffusing unit 15 and enters the scatterer 16 is guided to the scattering surface of the cavity 17 and diffusely reflected.

  At this time, in order to efficiently guide light to the diffusing unit 15, it is important to guide as much light as possible emitted from the light source 1 to the diffusing unit 15. Therefore, first, it is desirable that the contour shape of the light source 1 is a circle having a smaller diameter than the circular incident surface 12d. That is, it is desirable that the size of the light source 1 is such that almost all the light emitted from the light source 1 enters the incident surface 12d. As a matter of course, it is advantageous that the area of the diffusion portion 15 is large.

  In addition, it is desirable to lay out the position of the diffusion portion 15 along the central axis direction of the first rod 11 at an appropriate position so that as much light as possible is guided to the diffusion portion 15. For example, if the diffusing unit 15 is laid out at a position offset from the position shown in FIG. 6 toward the other end side (the upper side in the drawing) of the first rod 11, much of the light transmitted through the second rod 12 a can be guided to the diffusing unit 15. looks like. However, if the diffusion portion 15 is shifted to the other end side (upward in the figure), the ratio of the light transmitted through the second rod 12a to the other two adjacent second rods 12b and 12c increases, resulting in diffusion. The light guided to the part 15 is reduced. Therefore, it is desirable to design the position of the diffusing unit 15 in the axial direction at a position where the most light emitted from the three light sources 1 is guided to the diffusing unit 15.

  Further, if the diffusing portion 15 is not provided at the bottom of the housing recess 13, the light is emitted from the light source 1 even if the depth of the housing recess 13 is set to an appropriate depth and the bottom position is laid out at an appropriate position. The light is totally reflected at the bottom of the housing recess 13. This is because the optical element 10 of the present embodiment has three second rods 12 a, 12 b, and 12 c provided to be inclined with respect to the first rod 11, and therefore the diffusion portion 15 is not provided at the bottom of the housing recess 13. This is because much of the light emitted from the light source 1 is totally reflected at the bottom of the housing recess 13. That is, due to the structure of the optical element 10 of the present embodiment, it is necessary to provide the diffusing portion 15 at the bottom of the accommodating recess 13.

  As described above, the diffused light that is secondarily emitted from the diffusing unit 15 enters the scatterer 16 via the bottom surface 16 b of the scatterer 16. The diffused light incident on the scatterer 16 repeats total reflection at the outer peripheral surface 16a of the scatterer 16, and is irradiated on the inner surface (that is, the peripheral surface 17a and the bottom surface 17b) of the cavity 17 functioning as the scattering surface. Hereinafter, the peripheral surface 17a and the bottom surface 17b may be referred to as scattering surfaces 17a and 17b. Alternatively, the diffused light incident on the scatterer 16 is directly applied to the scattering surfaces 17 a and 17 b of the cavity 17 to shine the inner surface of the cavity 17.

  As described above, the gap S (second air layer) is provided between the outer peripheral surface 16 a of the scatterer 16 and the inner surface of the peripheral wall 13 b of the housing recess 13. For this reason, the light guided through the scatterer 16 is easily totally reflected by the outer peripheral surface 16a. If there is no gap S, that is, if the outer peripheral surface 16a of the scatterer 16 is in close contact with the peripheral wall 13b of the housing recess 13, the light incident on the scatterer 16 is diffused by the scattering surfaces 17a and 17b ( The amount of light that passes through the outer peripheral surface 16a without being scattered) and is emitted to the outside of the optical element 10 increases. In this case, the light emitted from the optical element 10 does not have a wide light distribution.

  Further, as described above, since the bottom surface 17b of the cavity 17 of the scatterer 16 is curved so as to be convex toward the diffusing portion 15, the light reflected by the bottom surface 17b and returning to the diffusing portion 15 is reduced. it can. That is, the secondary light emitted from the diffusing portion 15 can be effectively collected on the scattering surfaces 17 a and 17 b of the cavity 17 by the above-described gap S and the convex shape of the bottom surface 17 b.

  The light collected on the scattering surfaces 17a and 17b of the cavity 17 is diffused and reflected by the scattering surfaces 17a and 17b and is emitted to the outside of the optical element 10 by refractive transmission. In this case, the illumination light visible from the outside of the optical member 10 is affected by the shapes of the inner surfaces 17 a and 17 b of the cavity 17. That is, by changing the shape of the inner surface of the cavity 17, the optical characteristics of the illumination light can be controlled.

  The diffuse reflection by the scattering surfaces 17a and 17b is ideally Lambert scattering. When the diffuse reflection by the peripheral surface 17a is regarded as Lambert scattering, the light diffusely reflected by the peripheral surface 17a tends to be diffused in a direction perpendicular to the peripheral surface 17a. That is, the intensity of light emitted from the peripheral surface 17a increases in the direction orthogonal to the central axis of the optical element 10. Therefore, when the optical element 10 of the present embodiment is used, light in a direction orthogonal to the central axis of the optical element 10 can be generated, and illumination such as an incandescent bulb having a large light distribution angle (wide light distribution). Light can be obtained.

  FIG. 7 is a chart showing a light distribution when the optical element 10 of the first embodiment described above is used. Here, the result calculated using a ray tracing simulation (LightTools) (registered trademark) is shown. In addition, this simulation result is a thing at the time of forming the spreading | diffusion part 15 which functions as a secondary light emission part by white coating with a thickness of 100 micrometers. According to this, the 1/2 light distribution angle is about 320 °, and it can be seen that wide light distribution can be realized.

  When the thickness of the diffusing portion 15 is made thinner than 100 μm, the light totally diffused without being diffused by the diffusing portion 15 increases. For example, if the thickness of the diffusing unit 15 is less than 50 μm, the light diffused by the diffusing unit 15 is reduced, the light distribution angle of the optical element 10 is narrowed, and cannot be used as a point light source. In particular, since the second rod 12 is inclined with respect to the first rod 11 in the present embodiment, the problem of total reflection becomes large when the diffusion portion 15 is thinned. That is, in this case, the diffusing unit 15 does not function normally as a secondary light emitting unit.

  On the other hand, when the thickness of the diffusion portion 15 is increased to about 300 μm, almost no light is transmitted through the diffusion portion 15 as it is, and more light is diffused by the diffusion portion 15. In this case, the light distribution angle of the optical element 10 is increased, and the light bulb 100 can be illuminated like an incandescent light bulb. That is, the film thickness of the diffusion portion 15 is desirably 50 μm or more and 300 μm or less, and retrofit can be realized when the diffusion portion 15 is about 300 μm (± 50 μm). In addition, when the film thickness of the diffusion part 15 greatly exceeds 300 μm, the light is blocked by the diffusion part 15 and the absorbed light increases, so that the instrument efficiency is lowered.

  As described above, according to the present embodiment, the central axis of the first rod 11 of the light guide member 14 is obtained by collecting and scattering the diffused light secondarily emitted from the diffusing unit 15 on the scattering surfaces 17a and 17b. It is possible to generate light components in a direction orthogonal to the direction of light, and to increase the light distribution angle of illumination light. For this reason, when the optical element 10 is incorporated in the light bulb 100 as in this embodiment, illumination light that realizes a pseudo-point light source with a wide light distribution like an incandescent light bulb can be obtained.

  Further, according to the present embodiment, since the three second rods 12a, 12b, and 12c are provided to be inclined with respect to the first rod 11, it is not necessary to arrange the three light sources 1 on the same plane. Can be arranged obliquely with respect to each other, and the apparatus configuration can be reduced in size. For this reason, it can adapt to the size of a general light bulb and can be used as a substitute for a conventional incandescent light bulb.

  Further, according to the present embodiment, the light from the three light sources 1 is irradiated to the diffusing unit 15 so that the light is emitted, so that, for example, RGB three colors of light can be mixed by the diffusing unit 15. After that, the diffused light emitted from the diffusing unit 15 as the secondary light emitting unit is collected on the scattering surfaces 17a and 17b, whereby white light with uniform and wide light distribution can be emitted. If the way of viewing is changed, illumination light of a desired color can be formed by combining the three light sources 1, and convenience can be improved.

  Moreover, according to this embodiment, since the three light sources 1 are each attached to the three support surfaces 22 of the support member 20, the heat of each light source 1 can be thermally radiated efficiently. That is, the heat of the light source 1 is transmitted from the back surface of the substrate of the light source 1 to the support member 20 via the support surface 22 and is transmitted to the heat dissipation housing 102 via the support member 20. Then, the heat transmitted to the heat radiating housing 102 is released to the outside through the outer peripheral surface 102 a of the heat radiating housing 102. In addition, according to the present embodiment, the three light sources 1 can be attached to the support member 20 in a state of being separated from each other, and heat dissipation can be further improved.

  Next, an optical element 30 according to the second embodiment will be described with reference to FIGS. FIG. 8 is an external perspective view of the optical element 30, and FIG. 9 is an exploded perspective view showing a state where the scatterer 32 is separated from the light guide member 14 of the optical element 30. This optical element 30 has the same structure as the optical element 10 of the first embodiment described above except that the shape of the scatterer 32 is different. Therefore, here, the same reference numerals are given to components that function in the same manner as in the first embodiment, and detailed description thereof will be omitted.

  As shown in FIG. 8, the scatterer 32 of the present embodiment has an axial length such that the end on the other end side slightly protrudes from the opening 13 a of the housing recess 13 of the light guide member 14. That is, the length of the scatterer 32 in the axial direction is slightly longer than that of the scatterer 16 of the first embodiment. Moreover, as shown in FIG. 9, the scatterer 32 of this embodiment is reduced in diameter from the one end side facing the diffusion part 15 in the bottom of the accommodation recessed part 13 of the light guide member 14 toward the other end side in the axial direction. It has the outer peripheral surface 32a to do.

  According to this embodiment, since the edge part of the scatterer 32 protrudes from the opening part 13a of the accommodating recessed part 13, the axial direction length of the cavity 17 can be lengthened to that extent. Thereby, the area of the peripheral surface 17a of the cavity 17 can be increased, and the areas of the scattering surfaces 17a and 17b can be increased. If the area of the scattering surfaces 17a and 17b of the cavity 17 is small, the light emission intensity per unit area becomes strong, and it may be dazzling when viewing the illumination light. For this reason, when the area of the scattering surfaces 17a and 17b is increased as in this embodiment, light that is gentle to the eyes can be emitted.

  Although several embodiments have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  For example, in the above-described embodiment, the optical elements 10 and 30 including the three second rods 12 corresponding to the three light sources 1 have been described. However, the present invention is not limited to this, and the number of the second rods 12 is arbitrarily set. It can be changed.

  DESCRIPTION OF SYMBOLS 1 ... Light source 10, 30 ... Optical element 11 ... 1st rod, 11a ... Outer peripheral surface, 12a, 12b, 12c ... 2nd rod, 12d ... Incident surface, 13 ... Housing recessed part, 13a ... Opening part, 13b ... Peripheral wall , 14: Light guide member, 15: Diffusing portion, 16, 32: Scattering body, 16a, 32a ... Outer peripheral surface, 16b ... Bottom surface, 17 ... Cavity, 17a ... Peripheral surface (scattering surface), 17b ... Bottom surface (scattering surface) 20 ... support member, 22 ... support surface, S ... gap.

Claims (11)

An optical element formed of a material transparent to visible light,
A first portion having a first diffusion surface for diffusing light transmitted through the optical element, and a first air layer in contact with the first diffusion surface;
A second portion provided integrally with the first portion and extending in a direction inclined with respect to the first diffusion surface;
The first air layer includes a side surface in a direction intersecting the first diffusion surface.
Optical element. The side surface of the first air layer is rotationally symmetric with respect to a central axis passing through the first diffusion surface;
The optical element according to claim 1. The first portion includes an accommodation recess, the first air layer is included in the accommodation recess, the first diffusion surface is provided at the bottom of the accommodation recess, and the third portion is accommodated in the accommodation recess. The third portion has a second diffusion surface;
The optical element according to claim 1 or 2. The second diffusion surface of the third portion is rotationally symmetric with respect to the central axis, and has a shape that is gradually reduced in diameter toward the first diffusion surface and closed.
The optical element according to claim 3. Having a second air layer between the outer peripheral surface of the third portion and the inner surface of the housing recess,
The optical element according to claim 3. An optical element according to any one of claims 1 to 5,
The light source;
A glove covering this light source,
A base for supplying power to the light source;
A lighting device. The light source includes a plurality of light sources spaced apart from each other,
The optical element guides light from different directions emitted from the light sources to the first diffusion surface;
The lighting device according to claim 6. The light source includes a plurality of light sources spaced apart from each other,
Each light source has a light emission plane;
Each light source has a different emission spectrum;
The end of the second part has an incident plane;
Guiding light emitted from each light source and having a different emission spectrum to the first diffusion surface;
The lighting device according to claim 7. The second portion has a plurality of portions extending in a direction inclined with respect to the first diffusion surface.
The optical element according to claim 1. The second portion is rotationally symmetric with respect to a central axis passing through the first diffusion surface.
The optical element according to claim 9. The second diffusion surface of the third portion has a surface along a central axis passing through the first diffusion surface;
The optical element according to claim 3.

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