JP2019050208A - Optical element and luminaire - Google Patents

Abstract

To develop an optical element which can emit light of wide light distribution efficiently, and to develop a luminaire including the optical element.SOLUTION: A luminaire uses an optical element 50 formed by a material transparent with respect to visible light and having a shape rotationally symmetry with respect to a central axis, and inside the optical element, a hole 1 in which the transparent material does not exist is provided. An inner surface of the hole has a shape which includes a curved portion in which a boundary line L of the hole where a plane including the central axis C and the inner surface cross with each other swells outward of the optical element. Also, when an original point O is in the hole and the direction advancing clockwise along the boundary line with respect to the original point is defined as a normal direction, in the case where a first tangent vector V1 is given on a first point A on the boundary line and a second tangent vector V2 is given on a second point B adjacent to the first point in the normal direction, an angle formed by making the clockwise direction of the second tangent vector with respect to the first tangent vector positive is always equal to or greater than 0 degrees, and the inner surface of the hole does not include a surface recessed inside.SELECTED DRAWING: Figure 2

Description

  Embodiments of the present invention relate to a lighting device used in general homes, stores, offices, etc., and an optical element incorporated in the lighting device.

  For LED lighting devices for general lighting, it may be desirable to have a shape and light like an incandescent bulb (retrofit). In particular, there are many requests for a wide light distribution (1/2 light distribution angle: about 270 °) from a point light source inside the glove, such as a clear type incandescent light bulb (an incandescent light bulb using a clear glass glove) . However, when the LED is used as a light source as it is, the light distribution angle becomes narrow, and the half light distribution angle becomes about 120 °. Then, the device which extends a light distribution angle is made | formed using optical elements, such as a wide light distribution lens.

  As such an optical element, for example, one having a scattering member at the tip of a light guide rod is known. When this optical element is used, the LED is disposed opposite to the bottom surface of the light guide rod facing away from the scattering member. Then, light emitted from the LED is propagated by total internal reflection in the light guiding rod and is guided to the scattering member. The light beam reaching the scattering member is scattered by the scattering member and emitted to the outside of the optical element. In this way, light beams of wide light distribution are created.

US Patent US6350041

  However, when the above-described optical element is used, some of the light beams scattered by the scattering member propagate again through the light guiding rod and return to the LED. The light returned to the LED is almost absorbed. That is, as the percentage of light returning to the LED increases, the loss of light increases and the fixture efficiency decreases.

  Therefore, development of an optical element capable of efficiently emitting wide light distribution light and a lighting apparatus provided with the optical element is desired.

  The optical element according to the embodiment is formed of a transparent material, and provided at a cylindrical light guide having one end on the light source side along the central axis, and at the other end along the central axis of the light guide. A hemispherical scattering portion, and a hole connecting the cylindrical interior of the light guiding portion and the hollow interior of the scattering portion.

FIG. 1 is an external perspective view showing an optical element according to the first embodiment. FIG. 2 is a partially enlarged cross-sectional view in which a main portion of the optical element of FIG. 1 is partially enlarged. FIG. 3 is a simulation result of light distribution of the optical element of FIG. FIG. 4 is an external view showing an optical element according to the second embodiment. FIG. 5 is a partially enlarged cross-sectional view in which a main part of the optical element of FIG. 4 is partially enlarged. FIG. 6 is a schematic view showing a lighting device provided with the optical element of FIG. FIG. 7 is an external view showing an optical element according to the third embodiment. FIG. 8 is a cross-sectional view cut along a plane including the central axis of the optical element of FIG. FIG. 9A is an external view showing an optical element according to a fourth embodiment. FIG. 9B is a bottom view showing the optical element of FIG. 9A.

  Hereinafter, embodiments will be described with reference to the drawings.

First Embodiment
FIG. 1 is an external perspective view showing an optical element 10 according to the first embodiment. FIG. 2 is a partially enlarged cross-sectional view in which a cross section obtained by cutting the optical element 10 in FIG. 1 along a plane including the central axis C is partially enlarged. FIG. 3 is a radar chart diagram showing calculation results of simulation of light distribution of the optical element 10 of FIG. In FIG. 1, in addition to the optical element 10, a plurality of light emitting elements 11 facing one end (the lower end in the drawing) of the optical element 10 in the longitudinal direction are also illustrated. Each light emitting element 11 is obtained by, for example, sealing an LED chip (not shown) with a resin.

  As shown in FIG. 1, the optical element 10 is a rotating body having a shape that is rotationally symmetrical with respect to the central axis C. The optical element 10 is formed of a material (acrylic in this embodiment) transparent to visible light. The material of the optical element 10 may be any material as long as it is transparent to visible light, and the optical element 10 may be formed of, for example, polycarbonate, glass or the like in addition to acrylic.

  Moreover, the optical element 10 is provided with the void | hole 1 in which the said transparent material does not exist in the inside. In the present embodiment, the air holes 1 also have a shape that is rotationally symmetrical with respect to the central axis C. Further, the air holes 1 of the present embodiment are provided over substantially the entire length of the optical element 10 in the longitudinal direction.

  That is, the optical element 10 has a structure in which the cylindrical light guide portion 2 and the hemispherical scattering portion 3 are integrally connected. The outer diameter of the light guide 2 and the outer diameter of the scattering portion 3 are the same. Then, the inside of the cylinder of the light guide portion 2 and the hollow inside of the scattering portion 3 are smoothly connected to form the air hole 1. That is, the air hole 1 of the present embodiment is a space having a shape in which a hemisphere of the same diameter is connected to one end (upper end in the drawing) of a cylinder. In other words, the holes 1 extend through the entire length of the light guide 2 to the inside of the scattering unit 3.

  Among the inner surfaces of the holes 1, the inner surface (hemispherical surface) of the scattering portion 3 is a diffusion surface 3a for scattering light. The inner surface (that is, the cylindrical surface) of the air holes 1 other than the diffusion surface 3a is a mirror surface. As described above, by setting the inner surface of the scattering portion 3 provided near the tip of the optical element 10 as the diffusion surface 3 a, light with a wide light distribution angle can be emitted.

  The diffusion surface 3a inside the scattering portion 3 may be white-painted on the inner surface of the hole 1, for example. Alternatively, the diffusion surface 3a may be a rough surface where the inner surface of the hole 1 is partially sandblasted. Further, instead of providing the diffusion surface 3a, a scattering member (not shown) for scattering light may be filled in the air holes 1 of the scattering portion 3.

  The diffusion surface 3 a may extend to a position slightly behind the cylindrical inner surface of the light guide 2. When the scattering member is filled, the scattering member may be filled to a position slightly inside the light guide 2. That is, the size of the diffusion surface 3a can be arbitrarily changed.

  The light guide portion 2 includes a bottom surface 21 having a circular outer peripheral edge at one end side in the longitudinal direction separated from the scattering portion 3 along the central axis C. Further, the light guide portion 2 has a cylindrical side surface 22 connected from the outer peripheral edge of the bottom surface 21 toward the other end side in the longitudinal direction. On the other end side of the side surface 22 separated from the bottom surface 21, the hemispherical surface 31 serving as the outer surface of the scattering portion 3 is smoothly continuous.

  That is, the bottom surface 21, the side surface 22, and the hemispherical surface 31 become the outer surface of the optical element 10, and these surfaces are all mirror surfaces. However, not limited to this, these surfaces 21, 22, 31 may include diffusion surfaces. The bottom surface 21 is orthogonal to the central axis C of the optical element 10, and the side surface 22 extends in parallel to the central axis C.

  One end (the lower end in the figure) of the air hole 1 is connected to the bottom surface 21 to form a circular opening 23 concentric with the bottom surface 21. The inner surface of the hole 1 has a shape that spreads toward the bottom surface 21 along the central axis C. Here, the spreading shape means one that is not a narrowing shape, and includes a shape such as a cylindrical surface. That is, since the inner surface (the diffusion surface 3a) of the scattering portion 3 is a hemispherical surface, the air holes 1 have a shape that does not include the surface recessed inward.

  The above-mentioned rotational symmetry means that when the object is rotated with respect to the central axis C, the object conforms to the original shape and the rotation angle around the central axis C is less than 360 °. means.

  Each of the plurality of light emitting elements 11 has a light emitting surface (not shown). Each light emitting element 11 is disposed such that its light emitting surface faces the annular bottom surface 21 of the optical element 10. In the present embodiment, the plurality of light emitting elements 11 are arranged annularly at equal intervals in the circumferential direction of the bottom surface 21. The plurality of light emitting elements 11 are mounted on, for example, the surface of a substrate (not shown). In the present embodiment, the plurality of light emitting elements 11 are arranged on the same plane. However, the present invention is not limited to this, and the plurality of light emitting elements 11 can be three-dimensionally arranged.

  Hereinafter, the inner surface shape of the hole 1 described above will be described in more detail with reference to FIG. Note that FIG. 2 is a partially enlarged view (in the vicinity of the diffusion surface 3a) of a cross section obtained by cutting the optical element 10 along a plane including the central axis C.

  Since the air hole 1 of the present embodiment is rotationally symmetrical with respect to the central axis C, when the optical element 10 is cut at a plane including the central axis C, a line where the cut surface intersects the inner surface of the air hole 1 The shape of L (hereinafter, this line is referred to as a boundary line L) uniquely represents the inner surface shape of the hole 1. That is, by defining the shape of the boundary line L, the inner surface of the hole 1 can be defined.

  The boundary line L includes a curved portion having a shape that bulges outward of the optical element 10. In the present embodiment, a line at which the inner surface (the diffusion surface 3a) of the scattering portion 3 intersects with the cut surface is a curved portion. In addition to this, the boundary line L includes a straight line at which the inner surface of the light guide 2 intersects with the cut surface. In other words, the boundary line L does not have a portion that is recessed inward toward the hole 1.

  For example, in the cross section of FIG. 2, an origin O is taken in the hole 1, and a direction along the boundary L is defined as a positive direction clockwise around the origin O in the figure. The origin O can be any point not including the inner surface in the hole 1. Here, the origin O is temporarily placed at the center of the curvature of the scattering portion 3 on the central axis C.

  Next, an arbitrary point A is taken on the boundary line L, and a tangent at the point A is made a tangent vector V1 that is directed in the positive direction. As described above, the positive direction is defined as the direction of going clockwise on the boundary L with respect to the origin O. Further, a point B moved on the boundary L in the positive direction from the point A is taken, and a tangent at the point B is set as a tangent vector V2 directed in the positive direction. At this time, an angle formed by making the clockwise rotation of the tangent vector V2 with respect to the tangent vector V1 positive is a tangent rotation angle θ.

  When the boundary line L is defined based on the above conditions, the tangent rotation angle θ can be a shape that is always 0 degree or more.

  Next, the function of the optical element 10 will be described.

  The light emitted from the plurality of light emitting elements 11 (FIG. 1) is propagated through the optical element 10 as shown in FIG. The light emitted from each optical element 10 can be classified as parallel rays. As such, the discussion of ray groups does not lose generality below.

  The light beam group is emitted through the light emitting surface of each light emitting element 11 and then enters the bottom surface 21 of the optical element 10. A group of light beams incident on the optical element 10 from the bottom surface 21 is guided by being repeatedly totally reflected between the side surface 22 of the light guide 2 and the hemispherical surface 31 of the scattering unit 3 and the inner surface of the air hole 1.

  At this time, in the light group scattered (primary scattering) by the diffusion surface 3a on the inner surface of the hole 1, the transmission / reflection component changes in accordance with the incident angle of the light group to the diffusion surface 3a. That is, when the incident angle to the diffusion surface 3a is large, the reflection component (diffuse reflection component) increases and the transmission component (diffuse transmission component) decreases. On the contrary, when the incident angle to the diffusion surface 3a is small, the reflection component decreases and the transmission component increases. Here, the incident angle means the angle formed by the incident light beam and the normal direction of the diffusion surface 3a at the point where the light beam incident on the diffusion surface 3a hits the diffusion surface 3a.

  On the other hand, when the scattering member is packed in the air hole 1 without providing the diffusion surface 3a on the inner surface of the scattering portion 3, the transmission component of light transmitted through the inner surface of the scattering portion 3 becomes the absorption component. The same applies to the components. That is, in any case, when the incident angle of the light beam to the inner surface of the hole 1 is large, the reflected component increases, and when the incident angle to the inner surface is small, the reflected component decreases.

  The light beam reflected by the inner surface of the hole 1 is refracted and transmitted from the side surface 22 or the hemispherical surface 31 of the optical element 10 to the outside, or is reflected again by the side surface 22 or the hemispherical surface 31 and returned toward the diffusion surface 3a. The light beam returned to the diffusion surface 3a is again scattered (secondary scattering) by the diffusion surface 3a. However, a part of the light beam scattered by the diffusion surface 3 a is returned to the light guide 2.

  In FIG. 2, for example, reference numeral 41 denotes an example of a ray refracted and transmitted from the side surface 22, and reference numeral 42 denotes an example of a ray returned to the light guide 2. The light beam 42 returning to the light guide 2 is finally absorbed back to the light emitting element 11. However, most of the light rays secondarily scattered by the diffusion surface 3 a are finally refracted and transmitted through the side surface 22 of the optical element 10. Therefore, it is possible to prevent the light rays diffusely reflected by the diffusion surface 3a from being primarily returned to the light guide 2 and reduce the light rays to be absorbed back into the light emitting element 11 by scattering again by the diffusion surface 3a. .

  In the optical element 10 of this type, in order to improve the efficiency of the instrument, it is desirable to minimize the number of rays scattered by the diffusion surface 3 a and returned to the light guide 2. In order to reduce the number of light beams returning to the light guide 2, it is only necessary to create a situation in which the light primarily reflected by the diffusion surface 3a is likely to enter the diffusion surface 3a again. For this purpose, the light beam may be scattered in a region as far as possible from the light emitting element 11 out of the entire region of the diffusion surface 3a.

  Most of light rays scattered in a region far from the light emitting element 11 are refracted and transmitted through the hemispherical surface 31 of the scattering portion 3 or the side surface 22 of the light guiding portion 2. Then, a part of light rays that are not refracted and transmitted do not directly return to the light guide 2, and are likely to be incident again on the diffusion surface 3a. As described above, most of the light beam secondarily scattered by the diffusion surface 3 a is finally refracted and transmitted through the side surface 22 of the optical element 10.

  On the other hand, when a large amount of light is scattered in a region near the light emitting element 11, this primary scattered light is likely to be returned to the light guide 2 and finally absorbed by the light emitting element 11.

  The optical element 10 according to the first embodiment described above has a configuration capable of scattering most of light rays emitted from the light emitting element 11 in a region as far as possible from the light emitting element 11. Hereinafter, the function of this configuration will be described with reference to FIG.

  Of the parallel light beams emitted from the light emitting element 11, the light beam 43 is diffusely reflected at the point A on the inner surface of the hole 1, and the light beam 44 is also diffusely reflected at the point B. At this time, the light beam 43 incident to the point A and the light beam 44 incident to the point B have different incident angles with respect to the inner surface of the hole 1.

  As described above, in the present embodiment, since the tangent rotation angle θ defining the inner surface shape (the shape of the boundary L) of the hole 1 is always 0 degree or more, the incident angle of the light beam 43 with respect to the point A in FIG. On the other hand, the incident angle of the light beam 44 to the point B is larger. That is, in this case, the diffuse reflection component of the light ray 44 at the point B is larger than the diffuse reflection component of the light ray 43 at the point A.

  From another point of view, in the present embodiment, in order to increase the diffuse reflection component of the light beam in a region as far as possible from the light emitting element 11, the inner surface shape of the hole 1 is a shape in which the tangent rotation angle θ is always 0 degrees or more. . Thereby, the light beam returning to the light emitting element 11 can be reduced, and the efficiency of the optical element 10 can be enhanced.

  In addition, since the tangential rotation angle continuously changes or becomes constant along the boundary L, the direction of the diffuse reflection can be changed gently. From this, the light distribution can be made to be a gentle distribution like an incandescent lamp.

  The light distribution of the optical element 10 described above can be calculated using Light Trace Simulation (LightTools) (registered trademark). The calculation results are shown in FIG. This figure shows the light intensity of the light beam according to the light distribution angle in the form of a radar chart. As can be seen from this figure, in the case of the optical element 10 of the present embodiment, it can be seen that the half light distribution angle is approximately 310 degrees, which exceeds 300 degrees.

  As described above, according to the present embodiment, it is possible to provide the optical element 10 capable of emitting light with wide light distribution and high efficiency even though the LED is used as the light source.

Second Embodiment
Next, an optical element 50 according to a second embodiment will be described with reference to FIGS. 4 and 5. In the optical element 50, the air holes 51 are not connected to the bottom surface 52 of the optical element 50 and form a closed space closed inside the optical element 50. The configuration other than this is substantially the same as that of the above-described first embodiment, and therefore, the components functioning in the same manner as the first embodiment are denoted by the same reference numerals, and the detailed description thereof is omitted.

  The inner surface shape of the air hole 51 of the optical element 50 is a spheroidal surface based on two fixed points (not shown) separated from each other on the central axis C. That is, a surface obtained by continuing arbitrary points is the inner surface of the hole 51 such that the sum of the distances from these two fixed points to any point on the inner surface of the hole 51 is equal. The two fixed points may overlap, and in this case, the inner surface of the hole 51 is a spherical surface. Alternatively, when the two fixed points are sufficiently separated, the inner surface of the hole 51 is a paraboloid of revolution. In any case, the air holes 51 of the present embodiment also have a shape in which the tangent rotation angle θ is always 0 degrees or more, and does not include a surface that is recessed inward.

  The holes 51 are laid out near the tip of the optical element 50 which is separated from the bottom surface 52 of the optical element 50 along the central axis C. A diffusion surface 51 a is provided on the inner surface of the hole 51 by white paint or sand blast. In this case, the optical element 50 is divided at a plane including the central axis C, and after the diffusion surface 51a is formed in the holes 51, both are bonded. Alternatively, when using a 3D printer, the holes 51 are filled with a support material (for example, white acrylic).

  As shown in FIG. 6, the optical element 50 is incorporated in a light bulb 100 which is an example of a lighting device. Although the description is omitted here, the optical elements of the other embodiments can also be incorporated in the light bulb 100 as shown in FIG.

  The light bulb 100 is supplied with power by lighting the metallic heat radiation housing 102, the base 104 for electrically connecting to the socket of the ceiling (not shown), etc., the substantially spherical transparent globe 106 covering the optical element 50, and the light emitting element 11. The lighting circuit 108 and the optical element 50 are provided. The light emitting element 11 has a substrate 11 a and is attached to the upper surface 110 a of the substrate support 110 with the back surface of the substrate 11 a in contact. The lighting circuit 108 is connected to the light emitting element 11 and the base 104 via a wire not shown here. The lower end side of the substrate support 110 is thermally connected to the heat dissipation housing 102. The optical element 50 is attached to the light emitting surface of the light emitting element 11 so that the bottom surface 52 faces the light emitting surface. For example, the light bulb 100 is attached to the socket of the ceiling with the cap 104 turned up with the posture shown in FIG. 6 reversed.

  The heat dissipation housing 102 has one end (lower end in the drawing) to which the base 104 is connected and the other end (upper end in the drawing) to which the globe 106 is attached. The heat dissipation housing 102, the base 104, and the globe 106 have an axis that overlaps the tube axis of the light bulb 100. The optical element 50 is mounted such that its central axis C coincides with the tube axis of the light bulb 100.

  The heat dissipation housing 102 has a substantially frusto-conical outer shape whose diameter gradually increases from one end to the other end. The heat dissipation housing 102 is thermally connected to the light emitting element 11 through the substrate support 110, and functions to radiate the heat of the light emitting element 11 to the outside of the heat dissipation housing 102. For this reason, the heat dissipation housing 102 may be provided with a plurality of heat dissipation fins on the outer peripheral surface 102a.

  The globe 106 is not limited to a spherical shape as illustrated, but may be a chandelier type.

  A light group emitted from the light emitting surface of the light emitting element 11 is incident from the bottom surface 52 of the optical element 50. The ray group incident on the bottom surface 52 is propagated through the optical element 50 through the light guiding unit 2 and the scattering unit 3. The light propagated through the optical element 50 is collected and scattered by the diffusion surface 51 a of the air hole 51, and the illumination light having a light distribution angle similar to that of the incandescent lamp is emitted. That is, when the optical element 50 of the present embodiment is used, the center of the globe 106 can be illuminated, and the effect of retrofit can be exhibited.

  As described above, also in the second embodiment, as in the first embodiment described above, it is possible to provide the optical element 50 capable of emitting light with wide light distribution and high efficiency, and the heat of the light emitting element 11 is effective. Can dissipate heat.

Third Embodiment
Next, an optical element 60 according to a third embodiment will be described with reference to FIGS. 7 and 8. Also in the present embodiment, the components functioning in the same manner as in the first embodiment described above are denoted by the same reference numerals, and the detailed description thereof is omitted.

  The optical element 60 has an annular inclined bottom surface 62 facing the plurality of light emitting elements 11 at one end side. The inclined bottom surface 62 is inclined with respect to a plane orthogonal to the central axis C of the optical element 60. The light emitting surfaces of the plurality of light emitting elements 11 are arranged to face the inclined bottom surface 62 and arranged at equal intervals along the circumferential direction of the inclined bottom surface 62. For this reason, the light emitting surface of each light emitting element 11 is not orthogonal to the central axis C of the optical element 60. That is, the light emitting surfaces of the light emitting elements 11 are not arranged on the same surface, and a three-dimensional layout is obtained.

  As described above, the three-dimensional arrangement of the light emitting elements 11 makes it possible to make the device configuration compact and to increase the degree of freedom in design. Further, the plurality of light emitting elements 11 can be disposed in a dispersed manner, so that concentration of the heat source can be suppressed and the heat dissipation characteristics can be improved.

  Further, the optical element 60 of the present embodiment has a hole 61 opened on the other end side separated from the light emitting element 11. A diffusion surface 61 a is provided on the inner surface of the hole 61. The inner surface of the air hole 61 also has a shape such that the above-mentioned tangential rotation angle θ is always 0 degrees or more. Therefore, also in the present embodiment, the same effects as those of the first and second embodiments described above can be obtained.

  Although not illustrated here, the inner surface of the hole opened on the other end side of the optical element may be gradually expanded toward the opening as in the present embodiment. In this case, the die can be removed when the optical element is molded, and the manufacture of the optical element can be facilitated.

Fourth Embodiment
Next, an optical element 70 according to a fourth embodiment will be described with reference to FIGS. 9A and 9B. Here too, the components that function in the same manner as the embodiment described above are given the same reference numerals, and detailed descriptions thereof will be omitted.

  The optical element 70 has a conical surface 72 at one end along the central axis C. The conical surface 72 is formed by recessing the bottom of the optical element 70. Aluminum is vapor-deposited on the conical surface 72 to be a mirror surface. A plurality of light emitting elements 11 are provided opposite to the conical surface 72. That is, the light emitting element 11 is provided in the direction in which the light emitting surface faces the side surface 22 of the optical element 70.

  Then, the light beam group emitted from the light emitting surface of the light emitting element 11 is reflected by the conical surface 72, propagates through the light guide 2, and is guided to the air hole 71. The holes 71 have the same inner surface shape as the holes 51 of the second embodiment. Therefore, the optical element 70 is also divided and formed in a plane including the central axis C.

  As described above, also in the present embodiment, the same effects as those of the first to third embodiments described above can be obtained, and wide light distribution can be efficiently emitted.

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

Hereinafter, the invention described in the claims at the beginning of the application of the present application is appended.
[1]
An optical element formed of a material transparent to visible light and having a shape that is rotationally symmetrical with respect to a central axis,
A hole is provided inside the optical element,
The inner surface of the void has a shape such that the boundary between the void where the plane including the central axis intersects the inner surface includes a curved portion that bulges outward of the optical element; The origin is taken in the hole, the direction which proceeds clockwise along the boundary with respect to the origin is positive, and the first tangent vector at the first point on the boundary is taken, the first point When the second tangent vector at the second point adjacent to the positive direction is taken, the clockwise positive angle with respect to the first tangent vector of this second tangent vector is always 0 degrees. Or more,
Optical element.
[2]
A bottom surface at one end of the central axis,
And a side surface along the central axis connected to the bottom surface,
The side surface has a shape tapered toward the other end of the central axis,
Optical element of [1].
[3]
The void is disposed inside the tapered shape,
Optical element of [2].
[4]
The inner surface of the cavity includes a diffusing surface that scatters light,
Optical element of [1].
[5]
In the holes, a scattering member for scattering light is provided.
Optical element of [1].
[6]
The cavity has an opening connected to the bottom surface, and the inner surface of the cavity has a shape that gradually spreads toward the opening along the central axis.
Optical element of [2].
[7]
The void is a closed space closed inside the optical element.
Optical element of [1].
[8]
The inner surface shape of the hole is an ellipsoid of revolution in which, when two fixed points are placed in the hole, the sum of distances from each of the fixed points to any point on the inner surface is equal.
Optical element of [7].
[9]
The inner surface shape of the hole is a spherical surface on which the two fixed points overlap.
The optical element of [8].
[10]
The air hole has an opening on the other end side away from the bottom surface of the optical element, and has an inner surface having a shape gradually expanding along the central axis toward the opening.
Optical element of [2].
[11]
Any one of the optical elements of [1] to [10],
A light source having a light emitting surface;
The light source is disposed such that the light emitting surface faces the bottom surface at one end side along the central axis of the optical element.
Lighting device.
[12]
It further has a substrate in which a plurality of the light sources are arranged in a circle,
The substrate is disposed such that the light emitting surface of each of the plurality of light sources faces the bottom surface of the optical element,
The lighting device of [11].
[13]
The bottom surface of the optical element includes an inclined surface inclined with respect to a plane orthogonal to the central axis,
The plurality of light sources are arranged such that the respective light emitting surfaces face the inclined surfaces.
The lighting device of [12].
[14]
Any one of the optical elements of [1] to [10],
A light source having a light emitting surface;
A light-transmitting globe covering the light source and the optical element;
The light source is disposed such that the light emitting surface faces the bottom surface at one end side along the central axis of the optical element.
Lighting device.

  Reference Signs List 1 void 2 light guide portion 3 scattering portion 3 a diffusion surface 10, 50, 60, 70 optical element 11 light emitting element L boundary line V1, V2 tangent vector θ ... tangent rotation angle.

The optical element according to the embodiment is an optical element having a shape that is rotationally symmetrical with respect to a central axis and made of a material transparent to visible light, and one end on the light source side along the central axis And a hole which is provided on the other end side along the central axis separated from the light entrance surface and which forms a closed space closed inside the optical element.

Claims (1)

A cylindrical light guide formed of a transparent material and having one end on the light source side along the central axis;
A hemispherical scattering portion provided at the other end of the light guiding portion along the central axis;
A hole connecting the inside of the cylinder of the light guide and the inside of the hollow of the scattering portion;
An optical element having