Light guide body and vehicle interior lighting device

Abstract

To provide a rod-shaped light guide body having a Fresnel lens structure at an edge section thereof, which can efficiently capture light directly from a light source through the edge section, and which exhibits high uniformity of captured light within a plane perpendicular to a length direction thereof and to provide a vehicle interior lighting device incorporating the light guide body.SOLUTION: In a light guide body 1, at least one end in a longitudinal direction of a rod-shaped light guide main body 10 has a Fresnel lens structure which includes a convex lens section 131 and an annular lens section 132 formed of a plurality of concentric annular lenses surrounding the convex lens section 131. The height of the outermost annular lens in the annular lens section 132 is greater than the height of the convex lens section 131.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a light guide and a lighting device for vehicle interiors. [Background technology]

[0002] BACKGROUND ART Conventionally, a light source unit is known that controls the light distribution of light emitted from a light source by using a TIR-Fresnel composite lens, which is a linear Fresnel lens (see Patent Document 1).

[0003] The TIR-Fresnel composite lens included in the light source unit described in Patent Document 1 can control the light distribution in the longitudinal direction by using multiple linear prisms arranged in the longitudinal direction on its light incident surface, and can also control the light distribution in the lateral direction by using multiple linear prisms arranged in the lateral direction on its light exit surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-207790 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the TIR-Fresnel composite lens included in the light source unit described in Patent Document 1 controls the light distribution only in two axial directions, that is, the longitudinal direction and the lateral direction, and therefore the uniformity of the light distribution of the light emitted from the TIR-Fresnel composite lens in the in-plane direction of the TIR-Fresnel composite lens is not high.

[0006] Furthermore, the light source unit described in Patent Document 1 requires a specular reflective film surrounding the space between the light source and the TIR-Fresnel composite lens in order to guide the light emitted from the light source to the TIR-Fresnel composite lens.

[0007] An object of the present invention is to provide a rod-shaped light guide having a Fresnel lens structure at its end, which can directly and efficiently take in light from a light source from the end, and which has high uniformity in the light taken in within a plane perpendicular to its length, and to provide a vehicle interior lighting device equipped with such a light guide. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the present invention provides the following light guide and vehicle interior lighting device.

[0009] [1] A light guide in which at least one of the longitudinal ends of a rod-shaped light guide body has a Fresnel lens structure including a convex lens portion and an annular lens portion consisting of a plurality of concentric annular lenses surrounding the convex lens portion, and the height of the outermost annular lens in the annular lens portion is greater than the height of the convex lens portion. [2] The light guide according to [1] above, wherein the heights of the plurality of annular lenses in the annular lens portion increase sequentially from the inside to the outside. [3] When the refractive index of the light guide body is N2, the angle γ of the tips of the plurality of annular lenses satisfies the relationship expressed by the following formula (1): 3. The light guide according to claim 1 or 2.

number

Advantages of the Invention

[0010] According to the present invention, there can be provided a rod-shaped light guide body having a Fresnel lens structure at an end portion, which can directly and efficiently take in light from a light source, and has high uniformity of the light taken in within a plane perpendicular to the longitudinal direction thereof, and a vehicle interior lighting device including the light guide body.

Brief Description of the Drawings

[0011] [Figure 1] FIGS. 1(a), (b), and (c) are a perspective view, a side view, and a bottom view of a light guide body 1 according to an embodiment of the present invention. [Figure 2] FIGS. 2(a) and (b) are cross-sectional views around an end portion of the light guide body. [Figure 3] FIGS. 3(a), (b), and (c) are schematic views showing the relationship between the shape of the Fresnel lens structure at the end portion and the light rays from a light source for supplying light to the light guide body. [Figure 4] FIGS. 4(a) and (b) are schematic views showing an example of the light rays of the light emitted from the light source and entering the inside of the light guide body from the end portion. FIG. 4(c) is a schematic view showing an example of the light rays when the reflecting surface is curved outward. [Figure 5] FIGS. 5(a) and (b) are a perspective view and a cross-sectional view of a vehicle interior lighting device including the light guide body.

Embodiments for Carrying Out the Invention

[0012] FIGS. 1(a), (b), and (c) are a perspective view, a side view, and a bottom view of a light guide body 1 according to an embodiment of the present invention. FIG. 2(a) is a cross-sectional view around an end portion 13 of the light guide body 10.

[0013] In the light guide 1, at least one of the longitudinal ends of the rod-shaped light guide main body 10 has an end 13 having a Fresnel lens structure including a convex lens portion 131 and an annular lens portion 132 consisting of multiple concentric annular lenses (annular prisms) surrounding the convex lens portion 131.

[0014] The light guide 1 takes in light supplied from an external light source through the end 13 of the light guide body 10. Taking in light through the end 13 having a Fresnel lens structure reduces angular variation in the light beam (light path) traveling inside the light guide body 10. This makes it easier for the angle of incidence of light entering the interface between the inside and outside of the light guide body 10 to become larger than the critical angle, resulting in total reflection, and makes it less likely for the light to diverge to the outside.

[0015] Furthermore, suppressing the angular variation of the light rays reduces the brightness caused by differences in the optical path length, which can be expected to result in uniform light emission from the light guide 1. Furthermore, since the light travels parallel to the longitudinal direction of the light guide body 10, the light rays become shorter relative to the longitudinal distance of the light guide body 10, and therefore attenuation due to absorption by the light guide body 10, which is a medium, is reduced, allowing light to be guided efficiently.

[0016] Furthermore, the Fresnel lens structure can suppress variations in orientation in all directions of 360° as viewed from the center, and therefore the uniformity of the captured light in the plane perpendicular to the length direction of the light guide body 10 is improved compared to when a linear Fresnel lens structure is used, which suppresses variations in orientation in one direction.

[0017] In each of the multiple annular lenses constituting the annular lens section 132, the inner surface is a refractive surface 132a for refracting light from the light source, and the outer surface is a reflective surface 132b for reflecting the light refracted by the refractive surface 132a. After being refracted and reflected by the annular lens section 132, the light emitted from the light source travels in the length direction of the light guide body 10. This suppresses angular variation in the light rays traveling inside the light guide body 10.

[0018] Each of the plurality of annular lenses constituting the annular lens portion 132 has a height of, for example, 0.3 to 1.3 mm. The height of the plurality of annular lenses is the height based on the position of the bottom of the deeper one of the inner concave portion (the concave portion between the annular lens and another annular lens adjacent to the inner side) and the outer concave portion (the concave portion between the annular lens and another annular lens adjacent to the outer side) of each annular lens (the concave portion having a larger distance in the direction parallel to the optical axis 100 (described later) from the light source at the bottom).

[0019] Note that, as shown in FIG. 2(b), the end portion 13 having the Fresnel lens structure may be separated from the light guide body 10.

[0020] The light guide 1 preferably has a V-groove-shaped lens cut 12 on the side surface of the rod-shaped light guide body 10 for reflecting the light propagating along the length direction of the light guide body 10 inside the light guide body 10 and emitting it outside the light guide body. Typically, as shown in FIGS. 1(a) and (c), a plurality of lens cuts 12 are provided side by side along the length direction of the light guide body 10.

[0021] Since the lens cut 12 reflects the light traveling along the length direction of the light guide body 10, the length direction of the lens cut 12 (the direction of the linear V-groove pattern) is substantially perpendicular to the length direction of the light guide body 10.

[0022] The light guide body 10 is made of, for example, a transparent resin such as an acrylic resin or glass. The light guide body 10 has, for example, a cylindrical shape as shown in FIGS. 1(a), (b), and (c), and a plane 11 extending in the length direction of the light guide body 10 on a part thereof. In this case, the lens cut 12 is provided on the plane 11. Further, the light guide body 10 may have another shape such as a polygonal prism shape. When the light guide body 10 has a polygonal prism shape, the lens cut 12 is provided on one of the plurality of planes constituting the side surface of the polygonal prism. The light guide body 10 has, for example, a diameter of 3 to 10 mm and a length of 400 to 1000 mm.

[0023] Figs. 3(a), (b), and (c) are schematic diagrams showing the relationship between the shape of the Fresnel lens structure of the end portion 13 and the light rays from the light source 21 for supplying light to the light guide 1.

[0024] In the end portion 13 shown in Fig. 3(a), the height of the outermost annular lens in the annular lens portion 132 is higher than the height of the convex lens portion 131. On the other hand, in the end portion 13 shown in Fig. 3(b), the height of the outermost annular lens in the annular lens portion 132 is lower than the height of the convex lens portion 131.

[0025] Comparing Fig. 3(a) and Fig. 3(b), it can be seen that the range of light that can be taken in from the end portion 13 changes due to the difference in the height of the outermost annular lens in the annular lens portion 132.

[0026] Generally, there is a minimum distance (for example, 0.5 mm or more and 2 mm or less) between the light guide and the light source to prevent them from contacting and interfering with each other. For example, when the distance between the light source 21 and the convex lens portion 131 in the structure shown in Fig. 3(b) is the above-mentioned minimum distance, the light source 21 and the convex lens portion 131 cannot be brought closer to take in the light on the wide-angle side (outer side) from the end portion 13. Also, depending on the use and installation location of the light guide 1, etc., there may be cases where the diameter of the light guide body 10 cannot be increased, for example, it cannot be accommodated in the housing of the light source unit using the light guide 1.

[0027] Even in such a case, by making the height of the outermost annular lens in the annular lens portion 132 higher than the height of the convex lens portion 131 to such an extent that it does not contact the light source, like the structure shown in Fig. 3(a), it is possible to take in the light on the wide-angle side from the end portion 13 without bringing the light source 21 and the convex lens portion 131 closer or increasing the diameter of the light guide body 10.

[0028] That is, since the height of the outermost annular lens in the annular lens portion 132 is higher than the height of the convex lens portion 131, the light from the light source 21 can be directly and efficiently taken in from the end portion 13. And when the distance between the light source 21 and the convex lens portion 131 is equal to or less than the minimum distance, for example, 2 mm or less, that effect becomes particularly important.

[0029] Also, in the end portion 13 shown in FIG. 3(a), the heights of the plurality of annular lenses in the annular lens portion 132 increase in order from the inside to the outside. On the other hand, in the end portion 13 shown in FIG. 3(c), the heights of the plurality of annular lenses in the annular lens portion 132 decrease in order from the inside to the outside.

[0030] Comparing FIG. 3(a) and FIG. 3(c), it can be seen that the density of the light rays of the light taken into the light guide body 10 from the end portion 13 changes due to the difference in the configuration of the heights of the plurality of annular lenses in the annular lens portion 132.

[0031] In the structure shown in FIG. 3(c), since the distance from the light source 21 to the end portion 13 (refracting surface 132a) of the light guide body 10 is larger for the light rays on the wide-angle side, the density of the light rays inside the light guide body 10 becomes sparser on the outside compared to the inside, and the uniformity decreases. In this case, for example, since the light hits the plurality of lens cuts 12 arranged in the length direction of the light guide body 10 unevenly, unevenness is likely to occur in the light emission of the light guide 1.

[0032] On the other hand, in the structure shown in FIG. 3(a), since the heights of the plurality of annular lenses in the annular lens portion 132 increase in order from the inside to the outside, the difference in the distance from the light source 21 to the end portion 13 between the light rays on the wide-angle side and the light rays on the narrow-angle side (inside) becomes smaller, and the uniformity of the density of the light rays inside the light guide body 10 becomes higher. As a result, for example, since the light hits the plurality of lens cuts 12 evenly, unevenness in the light emission of the light guide 1 can be suppressed. Also, by making the light rays passing through the outside inside the light guide body 10 dense, the light can be efficiently applied to the lens cuts 12, and the light emission efficiency of the light guide 1 can be increased.

[0033] Figs. 4(a) and 4(b) are schematic diagrams showing an example of the light rays emitted from the light source 21 and entering the inside of the light guide body 10 from the end portion 13.

[0034] For the orientation control of illumination using the light guide 1, it is effective to suppress the angular variation of the light rays inside the light guide body 10. In particular, when the light rays inside the light guide body 10 are aligned parallel to the optical axis 100, the optical path length becomes the shortest, absorption due to the material of the light guide body 10 is suppressed, and attenuation of the light quantity can be suppressed. Here, the optical axis 100 is a straight line passing through the center of the light source 21 and the center of the light guide body 10.

[0035] Hereinafter, the angle γ of the tip of each annular lens in the annular lens portion 132 is obtained such that the direction of the light ray L after being reflected by the reflecting surface 132b of the annular lens becomes parallel to the optical axis 100.

[0036] Assuming that the incident angle of the light passing through the light ray L to the refracting surface 132a of the annular lens is α, the refraction angle is β, the refractive index of air is N1, and the refractive index of the light guide body 10 is N2, the following Equation 2 holds according to Snell's law.

[0037]

Equation

[0038] Further, when the light ray L after being reflected by the reflecting surface 132b is parallel to the optical axis 100, the following Equation 3 holds.

[0039]

Equation

[0040] Also, assuming that the inclination angle of the light ray L from the optical axis is θ, the following Equation 4 holds.

[0041]

Equation

[0042] Then, from the above formulas 2 to 4, the following formula 5 is derived.

[0043]

Equation

[0044] Assuming that the light distribution of the light source 21 is up to 180°, since the range of θ is 0° or more and 90° or less, if the refractive index N1 of air is set to 1, the range of the angle γ at which the direction of the light ray L after being reflected by the reflecting surface 132b of the annular lens becomes parallel to the optical axis 100 is represented by the following formula 1.

Equation

[0045] For example, when the light guide body 10 is made of acrylic, with the refractive index N2 being 1.49, the range of the angle γ at which the direction of the light ray L after being reflected by the reflecting surface 132b of the annular lens becomes parallel to the optical axis 100 is obtained from formula 1 to be approximately 23° or more and 45° or less.

[0046] Also, by increasing the angles γ of the tips of the plurality of annular lenses in the annular lens portion 132 in order from the inside to the outside, it is easier to align the directions of the light rays inside the light guide body 10.

[0047] In order to suppress the variation in the incident angle of light on the refractive surface 132a, it is preferable that the refractive surface 132a is close to being parallel to the optical axis 100. On the other hand, from the viewpoint of mold release from the mold when the light guide 1 is formed by injection molding and the physical strength of the annular lens, it is preferable that the refractive surface 132a has a draft angle. For this reason, the refractive surface 132a is preferably inclined by about 0.1 to 2° from a direction parallel to the optical axis 100 in a direction away from the center of the light guide body 10 as it approaches the tip of the annular lens.

[0048] FIG. 4(c) is a schematic diagram showing an example of light rays when the reflecting surface 132b is curved outward. Since the light emitted from the light source 21 spreads radially, as shown in FIG. 4(c), the bundle of light rays entering the annular lens from one refracting surface 132a has continuously changing angles rather than a single angle. Therefore, in order to efficiently reflect these light rays by the reflecting surface 132b, it is preferable that the reflecting surface 132b is a curved surface curved outward.

[0049] In the light guide 1, both end portions in the length direction of the light guide main body 10 may be end portions 13 having a Fresnel lens structure. In this case, in order to take in light from both sides in the length direction of the light guide main body 10, the lens cut 12 has an inclined surface capable of reflecting light from both sides.

[0050] FIGS. 5(a) and 5(b) are a perspective view and a cross-sectional view of the vehicle interior lighting device 2 including the light guide 1. The cross-section shown in FIG. 5(b) is a cross-section parallel to the length direction of the light guide main body 10 of the light guide 1 and perpendicular to the plane 11.

[0051] The vehicle interior lighting device 2 includes a light guide 1 and a light emitting device 20 that allows light to enter the inside of the light guide main body 10 from an end portion 13 having a Fresnel lens structure of the light guide main body 10.

[0052] The light emitting device 20 includes a light source 21 such as an LED element mounted on a substrate 22, and a housing 23 composed of components 231 and 232 that houses these.

[0053] In the example shown in FIGS. 5(a) and 5(b), the end portion 13 of the light guide main body 10 is fitted into the opening of the housing 23, and the light guide 1 and the light emitting device 20 are fixed in a state where the light source 21 and the end portion 13 face each other.

[0054] Light emitted from the light source 21 of the light-emitting device 20 enters the inside of the light guide body 10 from the end portion 13. Specifically, the light emitted from the light source 21 of the light-emitting device 20 is refracted and reflected by the annular lens portion 132, and then travels in the length direction of the light guide body 10. That is, the light emitted from the light source 21 of the light-emitting device 20 is directed in the length direction of the light guide body 10 by the Fresnel lens structure of the end portion 13. The light traveling inside the light guide body 10 in the length direction of the light guide body 10 is reflected by, for example, the lens cuts 12, and extracted to the outside from a region on the side of the light guide body 10 opposite to the region where the lens cuts 12 are provided.

[0055] The vehicle interior lighting device 2 may be provided with two light-emitting devices 20 that respectively introduce light into the interior of the light guide body 10 from both longitudinal ends of the light guide body 10, in cases where both longitudinal ends of the light guide body 10 are end portions 13 having a Fresnel lens structure.

[0056] The light guide 1 and the vehicle interior lighting device 2 using the same can be attached to, for example, a door panel or an instrument panel inside the vehicle.

[0057] (Effects of the embodiment) According to the light guide 1 and vehicle interior lighting device 2 of the above-described embodiment of the present invention, light is taken into the light guide body 10 from the end portion 13 having the Fresnel lens structure, and therefore the light taken into the light guide body 10 has high uniformity in a plane perpendicular to the longitudinal direction of the light guide body 10. Furthermore, since the height of the outermost annular lens in the annular lens portion 132 is greater than the height of the convex lens portion 131, light can be taken in directly and efficiently from the light source 21.

[0058] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications can be made without departing from the spirit of the invention. Furthermore, the components of the above-described embodiments can be combined in any manner without departing from the spirit of the invention.

[0059] Furthermore, the above-described embodiments do not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments are essential means for solving the problems of the invention.

Description of Reference Numerals

[0060] 1 Light guide 10 Light guide body 13 End portion 132 Annular lens portion 132a Refracting surface 132b Reflecting surface 2 Interior lighting device for vehicle 20 Light emitting device 21 Light source

Claims

1. At least one of the ends in the length direction of the rod-shaped light guide body has a Fresnel lens structure including a convex lens portion and an annular lens portion composed of a plurality of concentric annular lenses surrounding the convex lens portion, wherein the height of the outermost annular lens in the annular lens portion is higher than the height of the convex lens portion, a light guide.

2. wherein the heights of the plurality of annular lenses in the annular lens portion increase in order from the inside to the outside, the light guide according to Claim 1.

3. Let the refractive index of the light guide body be N ２ When this is the case, the angle γ at the tip of the plurality of annular lenses satisfies the relationship represented by the following formula (1). the light guide according to Claim 1 or 2. 【Number 1】

4. wherein the light guide body is made of acrylic, and the angle γ is 23° or more and 45° or less, the light guide according to Claim 3.

5. in each of the plurality of annular lenses, the inner surface is a refracting surface for refracting light from a light source, and the outer surface is a reflecting surface for reflecting the light refracted by the refracting surface, the light guide according to Claim 1 or 2.

6. wherein the reflecting surface is curved outward, the light guide according to Claim 5.

7. the light guide according to Claim 1 or 2, and a light emitting device that allows light to enter the inside of the light guide body from at least the end having the Fresnel lens structure among the ends in the length direction of the light guide body, comprising a vehicle interior lighting device.

8. wherein the distance between the light emitting element, which is the light source of the light emitting device, and the convex lens portion is 2 mm or less, the vehicle interior lighting device according to Claim 7.

9. wherein the light emitted from the light emitting device is refracted and reflected by the annular lens portion and then travels in the length direction of the light guide body, the vehicle interior lighting device according to Claim 7.

Images