Light-emitting device and road surface marking device

Abstract

To enable strongly emitting light when emitting light in a specific direction with a small elevation angle by using refraction.SOLUTION: A light-emitting device 10 includes a light guide body 12 and a light source 14. The light guide body 12 is a rectangular column having an isosceles trapezoidal bottom surface, and the side surface of the rectangular column is the upper surface 12a of the light emitting device 10 and a road surface. Light from the light sources 14 enters the incident part 16 and enters the upper surface 12a. A part of the incident light 22a is refracted and becomes refracted light 23a in a direction of a large refraction angle, and reflection light 24b which is the remaining light is totally reflected inside the light guide 12 and is incident again on the upper surface 12a as the incident light 22c at the same incident angle as the first incident angle, a part of the light is radiated as refracted light 23b with the same refraction angle as that of the refracted light 23a. The light reflected by the upper surface 12a is repeatedly incident on the upper surface 12a as incident light in the same manner.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light-emitting device and a road marking device, and more particularly to light-emitting devices that utilize refracted light. [Background technology]

[0002] Conventionally, light-emitting diodes have been buried near center lines on roads, intersections, or pedestrian crossings, and are illuminated at night to guide and alert drivers and pedestrians.

[0003] For example, Patent Document 1 proposes a light irradiation device that can irradiate light at a small angle of elevation by arranging a resin with a right-angled triangular cross section so that its hypotenuse is underground, its long side is the road surface, and its short side is perpendicular to the road surface, and by irradiating light from the short side in a direction parallel to the road surface. More specifically, when light is incident from the short side in a direction parallel to the road surface, the incident light repeatedly reflects off the hypotenuse and the road surface, decreasing the angle of incidence, and when the angle of incidence on the road surface becomes smaller than the critical angle, part of the light is refracted in a direction closer to the road surface (with a large refraction angle). In other words, light can be emitted at a small angle of elevation.

[0004] When road studs, which are light-emitting bodies, are installed on the road surface, pedestrians can trip over the road studs and vehicles can rattle every time they step over a road stud. However, in Patent Documents 1 and 2, the light can be emitted without the light irradiation device having to protrude from the road surface. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3982174 specification [Patent Document 2] Patent No. 2857974 specification Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, light that is incident on the road surface and is reflected without being refracted is reflected by a surface that corresponds to the hypotenuse of a right triangle in a vertical cross section, and is thereby made to re-enter the road surface.

[0007] However, because the angle of incidence of the re-incident light is smaller than the initial angle of incidence, the refraction angle is also smaller. In this case, the number of refractions is small at a large refraction angle. When the refraction angle is large, a large proportion of light is reflected without being refracted, and as a result, the refracted light in the direction of the large refraction angle is weaker. In a structure that uses refraction for light emission, increasing the refraction angle increases the amount of light that is reflected without being refracted, resulting in weaker emitted light.

[0008] An object of the present invention is to make it possible to emit light more strongly in a specific direction including a small elevation angle by utilizing refraction. [Means for solving the problem]

[0009] The light emitting device according to the present invention comprises a light source means, and a light guide having a predetermined three-dimensional shape formed from a first medium consisting of a transparent solid or liquid, having an incident portion into which light from the light source means is incident, wherein the light guide is configured such that light from the light source means passing through the incident portion is incident on an interface with a second medium having a refractive index relatively smaller than that of the first medium at a predetermined incident angle according to the relative refractive index of the first medium with respect to the second medium, thereby radiating the refracted light at the interface at a refraction angle at which it reaches a predetermined target position, and the reflected light at the interface is totally reflected by being incident on an inner surface other than the interface at an incident angle equal to or greater than the critical angle, thereby becoming incident light that is incident on the interface at the predetermined incident angle, thereby radiating the refracted light at the interface at a refraction angle at which it reaches the predetermined target position.

[0010] The boundary surface may also form a part of a planar surface of an object when the light guide is embedded in the object.

[0011] The light guide is also characterized in that the predetermined three-dimensional shape is formed by a prism having an isosceles trapezoidal bottom surface, and the side surface of the prism including the longer of the two parallel sides of the isosceles trapezoid is the boundary surface.

[0012] The shape of the isosceles trapezoid is set in accordance with the magnitudes of the incident angle and the critical angle.

[0013] A road marking device according to the present invention includes the light-emitting device described above, and is installed so that the boundary surface forms part of the road surface. [Effects of the Invention]

[0014] According to the inventions set forth in claims 1 and 4, when light is emitted in a specific direction including a small angle of elevation by utilizing refraction, it is possible to emit light more intensely.

[0015] According to the inventions recited in claims 2 and 3, the second medium can be provided without protruding from the boundary surface with the second medium.

[0016] According to the invention as set forth in claim 5, it is possible to emit strong light at a small angle of elevation from the road surface. [Brief explanation of the drawings]

[0017] [Figure 1] 1A, 1B, and 1C are schematic diagrams showing an embodiment of a light emitting device according to the present invention, in which FIG. 1A is a top view of the light emitting device, FIG. 1B is a front view of the light emitting device, and FIG. 1C is a right side view of the light emitting device. [Figure 2] 1 is a diagram for explaining refraction and reflection of light at the boundary surface between different media; [Figure 3] FIG. 1 is a graph showing the relationship between the refraction angle and the transmittance of p-waves and s-waves. [Figure 4] FIG. 2 is a vertical cross-sectional view of the light guide according to the present embodiment. [Figure 5] FIG. 2 is a vertical cross-sectional view of the light guide according to the present embodiment. [Figure 6] 1 is a diagram showing an example of the structure of a road marking device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0019] <Structure of light-emitting device> Fig. 1 is a schematic diagram showing an embodiment of a light emitting device according to the present invention. In Fig. 1, (a) is a top view of a light emitting device 10 according to this embodiment, (b) is a front view of the light emitting device 10, and (c) is a right side view of the light emitting device 10. The light emitting device 10 according to this embodiment includes a light guide 12 and a light source 14.

[0020] In this embodiment, the light guide 12 is formed into a predetermined three-dimensional shape using a first medium made of a transparent solid or liquid. More specifically, as shown in Fig. 1(b), the light guide 12 is formed into a predetermined three-dimensional shape as a quadrangular prism having an isosceles trapezoidal base.

[0021] In this embodiment, a light guide 12 having a rectangular prism shape with an isosceles trapezoidal bottom surface is used by tilting it so that the surface of the rectangular prism including the longer of the two parallel sides of the isosceles trapezoid becomes the top surface of the light emitting device 10. In terms of the three-dimensional shape, the surface of the isosceles trapezoid shown in FIG. 1(b) is the bottom surface. However, in this embodiment, since the rectangular prism is tilted and used as the light emitting device 10 as described above, the surface of the light emitting device 10 opposite to the "top surface" shown in FIG. 1(a) (the downward direction in FIG. 1(b)) becomes the "bottom surface" (or "lower surface"). In the following description, the respective surfaces of the light emitting device 10 will be referred to as the top surface 12a, the left slope (or left side surface) 12b, the lower surface (or bottom surface) 12c, and the right slope (or right side surface) 12d.

[0022] When the light-emitting device 10 of this embodiment is used as a road marking device, which will be described later, the light guide 12 is embedded in the road. In this case, the upper surface 12a of the light guide 12 forms part of the planar road surface. The upper surface 12a of the light guide 12 also serves as the boundary surface with air, which is a second medium present on the road. Therefore, in the following description, the "upper surface," which is one of the side surfaces of the light guide 12, and the "boundary surface" with the second medium are used synonymously. Air is a medium whose refractive index is relatively smaller than that of the first medium that forms the light guide 12.

[0023] It should be noted that the second medium when the light emitting device 10 of this embodiment is applied to a road marking device is basically air. In this embodiment, it is sufficient that light from the light source 14 is refracted at the boundary surface with the second medium and emitted from the light emitting device 10. In other words, the second medium does not have to be limited to air as long as it is a medium whose refractive index is relatively smaller than that of the first medium. For example, a vacuum may also be used. However, in this embodiment, the description will be given assuming that the light emitting device 10 is applied to a road marking device, and therefore, unless otherwise specified, "air" will be used synonymously with the second medium.

[0024] In this embodiment, the light source 14 provided as the light source means is installed at one obtuse-angled portion of the bottom surface 12c of the light guide 12 (the obtuse-angled portion on the right side in FIG. 1(b)), and emits light toward the light guide 12. Incidentally, although the light source means is illustrated as one light source 14 in FIG. 1, the light source 14 may be configured as a light source group including a plurality of light sources. In this case, the plurality of light sources are arranged side by side in the thickness direction of the light guide 12 (the vertical direction in FIG. 1(a) and the horizontal direction in FIG. 1(c)).

[0025] A slit-shaped entrance section 16 is provided in a portion of the light guide 12 facing the light source 14 so that light from the light source 14 can enter the interior of the light guide 12. In this embodiment, the entrance section 16 is formed by cutting an obtuse-angled portion of the bottom surface 12c of the light guide 12 facing the boundary surface with the second medium, as shown in FIG. 1 . However, as will be described in detail later, it is sufficient that the refracted light at the boundary surface is emitted at a refraction angle that reaches a predetermined target position. Therefore, the location of the entrance section 16 does not need to be limited to the obtuse-angle portion as long as the refracted light can be irradiated at this refraction angle. Furthermore, the entrance section 16 may be formed and arranged in an appropriate shape depending on the arrangement and size of the light source 14, the direction of light emitted from the light source 14, the number of light sources 14 constituting the light source means, and the like.

[0026] In FIG. 1(b), the optical path is shown by a broken line, but the optical path will be described later.

[0027] <Refraction and reflection of incident light on a boundary surface> The basic principles of when light incident on a boundary surface of a medium is refracted and emitted and when it is reflected will be explained using Fig. 2. Here, the explanation will be given with a specific example assuming that the light emitting device 10 of the present embodiment is applied to a road marking device.

[0028] As an example of a case where light is emitted in a specific direction including a small elevation angle using refraction, when light is emitted from the road surface toward the driver of a vehicle approaching a road marking point, in order for the driver to see the light, it is necessary to emit the light toward the eye height of the driver, which is the target position of the light, that is, at a very small elevation angle from the road marking point. In this embodiment, the height from the ground and the distance from the road marking point are used as information indicating the predetermined target position to which the light is to be delivered. Here, when the height of the driver's eyes is H [m] and the distance from the road marking point to the driver is L [m], the elevation angle θ E Between the two, tanθ E =H / L (1) For example, when L=30m and H=1.5m, θ E teeth, tanθE =1.5 / 30 (2) θ E =arctan(1.5 / 30) =2.86° A small elevation angle θ E As a method of emitting light from the road surface, it is not realistic to dig a groove in the road surface to let the light pass through, install a light source in the groove, and emit light from the light source at a small angle of elevation. For example, if a light source with a size H=1.5 cm is installed in the groove, the angle θ that satisfies equation (1) is E If light is emitted from the surface of the earth, the required groove length L is 30 cm, which is calculated using an equation equivalent to equation (2). If part of the groove becomes filled with dust or dirt over time, light will no longer be emitted to the ground.

[0029] Small elevation angle θ E As another method for emitting light, there is a method using refraction of light. As shown in Fig. 2, a light guide 12 is a transparent solid container filled with a transparent solid such as glass or a transparent liquid such as water, and is buried in a road so that one side of the light guide 12, specifically the upper surface of the light guide 12, faces the road surface 21. When light 22 is incident obliquely onto the road surface 21 from the light guide 12 side, it is refracted by the road surface 21 and is emitted at a small elevation angle θ E The dashed-dotted line is an auxiliary line indicating the direction perpendicular to the road surface 21. In the following drawings, the auxiliary lines are also indicated by dashed-dotted lines. In this case, the incident angle θ I , refraction angle θ T (=90°-θ E ) and the refractive index n of the light guide, n=sinθ T / sinθ I ···(3) For example, when using S-BSL7, a type of radiation-resistant optical glass with a refractive index of n=1.518, the θ calculated by equation (2) E =2.86°, i.e., the refraction angle θ T To emit light at =87.14°, from equation (3), sinθ I =sinθ T / n ···(4) =sin(87.14°) / 1.518 =0.658 θ I =arcsin0.658 =41.14° That is, in this embodiment, the incident light 22 corresponding to the light from the light source 14 is incident at a predetermined incident angle θ corresponding to the refractive index (more specifically, the relative refractive index of the material of the light guide 12 with respect to air) n and a predetermined target position (here, the height of the driver's eyes) where the emitted light 23 is to reach. I By making the light incident on the road surface 21, the light can be irradiated onto the driver.

[0030] The road marking uses refracted light and is directed at the driver of a vehicle heading towards the road marking point at a very small elevation angle θ E , in other words, a large refraction angle θ T When light 23 is irradiated from the road surface 21, the intensity of the light 23 received by the driver is weakened by two factors in addition to the long distance to the road marking. The two factors are that the light spreads due to refraction, and that the proportion of the light 22 that is refracted out of the light 22 incident on the road surface 21 from the light guide 12 side is small. The former can be exemplified as follows. From equation (3), θ T =arcsin(n sinθ I ) ···(5) For example, the incident angle θ that satisfies Equation (4) I Refraction angle θ at ±0.05° of 41.14° T From equation (5), it is 86.16°(θ I =4.14°-0.05°) and 88.72°(θ I = 41.14° + 0.05°) Therefore, when light with an illumination angle of ±0.05°, i.e., 0.1°, is incident at an angle of θ I When the incident angle of the light beam 23 to the road surface 21 is 41.09° to 41.19°, the refracted light beam 23 is T The irradiation angle is 2.56°, from 86.16° to 88.72°, and the light 23 is expanded by approximately 26 times due to refraction. In order to irradiate the driver of a vehicle heading towards the road marking point with refracted light 23 with a small irradiation angle, a light source with a very small irradiation angle (for example, 0.1° or less) can be used.

[0031] The latter point where the proportion of the refracted light 22 incident on the road surface 21 from the light guide 12 is small can be determined as follows. When the light 22 is refracted at a boundary surface such as the road surface 21, a part of the light 24 is reflected at the boundary surface. The refraction angle θ T When the angle is close to 90°, the ratio of reflected light 24 is high and the ratio of refracted light 23 is low. The ratio of both can be calculated by the Fresnel formula shown below.

[0032] Light can be divided into p-waves and s-waves. In the case of Figure 2, the component of light 22 parallel to the plane of the drawing is p-wave, and the component perpendicular to the plane of the drawing is s-wave. In this explanation, "refraction" will be expressed as "transmission." The amplitude transmittance t of p-waves is p and amplitude reflectance r p , and the s-wave amplitude transmittance t s and amplitude reflectance r s are respectively, t p =2sinθ T cosθ I / {sin(θ I +θ T )cos(θ I -θ T )} ···(6) r p =tan(θ I -θ T ) / tan(θ I +θ T ) ···(7) t s =2sinθ T cosθ I / sin(θ I +θ T ) ···(8) r s =-sin(θ I -θ T ) / sin(θ I +θ T ) ···(9) and the transmittance of p-waves T p and reflectance R p , s-wave transmittance T S and reflectance R S are respectively, T p =t p 2 tanθ I / tanθ T ···(10) R p =r p 2 ···(11) T S =t s 2 tanθ I / tanθ T ···(12) R S =r s 2 ···(13) In the above-mentioned S-BSL7 (refractive index n=1.518), the refraction angle θ calculated from the formulas (4) and (6) to (13) shown in FIG. T and the p-wave transmittance T p , and the refraction angle θ T and s-wave transmittance T S From the relationship, θ T In the vicinity of =90°, the refraction angle θ T With the increase in transmittance (T p and T S ) both decrease rapidly and approach 0. The refraction angle θ at S-BSL7 T = 87.14°, the angle of incidence θ I = 41.14°, and from equations (4) and (6) to (13), T p =0.332, R p =0.668, T S =0.160 and R S =0.840, and only 33.2% of the p-wave and 16.0% of the s-wave of the incident light 22 are refracted.

[0033] In this specific example, S-BSL7 (refractive index n=1.518) is used as the first medium, and the predetermined incident angle θ I is determined according to the relative refractive index of the first medium to the second medium (air in the above example).

[0034] <Isosceles Trapezoid Shape of Light Guide 12> A feature of this embodiment is that when using refraction to emit light, the light reflected from the boundary surface 21 is effectively utilized. In particular, to accommodate cases where the predetermined target position for the light is at a low position, a method of emitting strong light at a small elevation angle from the road surface 21, in other words, a method of emitting strong light at a large refraction angle, is to repeatedly cause the light reflected from the boundary surface 21 to be incident on the boundary surface 21 at the same incident angle. Increasing the incident angle of the light incident on the boundary surface 21 to emit light at a larger refraction angle reduces the proportion of the incident light that is refracted, resulting in a relatively weaker light intensity per emission. Therefore, in this embodiment, the structure of the light-emitting device 10 is designed so that the light reflected from the boundary surface 21 can be repeatedly incident on the boundary surface 21 at the same predetermined incident angle, allowing the light-emitting device 10 to emit strong light, i.e., at high brightness.

[0035] The light guide 12 in this embodiment is a quadrangular prism with an isosceles trapezoidal base, and is embedded in the road so that the bottom is perpendicular to the road surface and the side that contacts the longer of the two parallel sides of the isosceles trapezoidal base is on the road surface. Here, the optical path formed by the light emitting device 10 in this embodiment will be described with reference to Fig. 1(b).

[0036] First, light from the light source 14 enters the light guide 12 through the incident portion 16. To suppress reflection at the incident portion 16 and increase the amount of light transmitted through the light guide 12, it is desirable to have light enter the light guide 12 perpendicular to the incident portion 16. Incident light 22a that passes through the incident portion 16 is incident on the top surface 12a, which serves as the boundary surface with air, at a predetermined angle of incidence corresponding to the relative refractive index of the light guide 12 with respect to air. A portion of the incident light 22a is refracted at the boundary surface and becomes refracted light 23a that is emitted in a direction with a relatively large refraction angle and reaches a predetermined target position. The remainder is reflected by the top surface 12a and becomes reflected light 24b that travels inside the light guide 12. The reflected light 24b at the boundary surface is totally reflected by the inner surfaces of the light guide 12 other than the boundary surface, as it is incident at an angle of incidence greater than the critical angle. 1(b), reflected light 24b is totally reflected by left slope 12b, bottom surface 12c, and right slope 12d of light guide 12, and becomes incident light 22c that is incident on the boundary surface at the same predetermined angle of incidence as incident light 22a. Therefore, refracted light 23b of incident light 22c at the boundary surface is emitted at the same refraction angle as first refracted light 23a, reaching the predetermined target position. The reflected light from top surface 12a repeatedly enters top surface 12a at the same angle of incidence along the same optical path as above.

[0037] As described above, in light-emitting device 10 according to the present embodiment, total reflection occurs at surfaces other than the boundary surfaces, and therefore there is no need to cover light guide 12 with a reflective material. Incident portion 16 is disposed at the lower right corner of the isosceles trapezoidal cross section, but it may also be disposed at the lower left corner so that light from light source 14 is incident toward right slope 12d and the reflected light that is totally reflected at right slope 12d is incident on top surface 12a.

[0038] Next, the reason why the angle of incidence of light on the upper surface 12a is the same every time when the shape of the vertical cross section is an isosceles trapezoid with the upper base longer than the lower base will be explained below.

[0039] Fig. 4 is a vertical cross-sectional view of the light guide 12 in this embodiment. This figure shows the light guide 12 shown in Fig. 1 in combination with the relationship of the optical paths of light explained with reference to Fig. 2. Note that in Fig. 4, hatching indicating a cross section has been omitted for the sake of convenience so as to clearly show the optical paths and the like indicated by dashed lines. Furthermore, the incident portion 16 has been omitted from the figure. This also applies to the following figures.

[0040] As described above, the light guide 12 in this embodiment has a prismatic shape with an isosceles trapezoidal cross section in the vertical direction. The top surface 12a corresponds to the road surface 21 shown in Fig. 2. With respect to the isosceles trapezoid ABCD of the vertical cross section of the light guide 12, the point where the light beam is incident on the top surface 12a including the side AB for the mth time and the point where the light beam is incident on the surfaces including the sides BC, CD, and DA thereafter (the left slope 12b, the bottom surface 12c, and the right slope 12d, respectively) are respectively referred to as a m , b m , c m , d m Let a m The angle of incidence at α m Point a m The light reflected by m , c m , d m , a m+1 The incident angle is the angle with respect to the perpendicular line of the boundary surface 21, and since the incident angle and the reflection angle are equal, the light reaches point a m The angle ("□") between the reflected light and the boundary surface 21 is 90°-α m In addition, the sum of the interior angles of the vertices on both sides of the two non-parallel sides of an isosceles trapezoid (B and C, and D and A in Figure 4) is 180°, and the angles of the vertices on both sides of the two parallel sides (A and B, and C and D in Figure 4) are equal. Here, to satisfy the above, the angle of vertices A and B ("●") is set to 90°-Δ, and the angle of vertices C and D ("◎") is set to 90°+Δ. b m The angle of incidence and the angle of reflection at are equal, and △a m Bb m Since the sum of the interior angles is 180°, ∠c m b m C=∠a m b m B=180°-(90°-Δ)-(90°-α m )=αm +Δ ···(14) Similarly, equation (14) and c m The angle of incidence and the angle of reflection at are equal, and △b m Cc m Since the sum of the interior angles is 180°, ∠d m c m D=∠b m c m C=180°-(90°+Δ)-(α m +Δ)=90°-α m -2Δ ···(15) In addition, equation (15) and d m The angle of incidence and the angle of reflection at are equal, and △c m Dd m Since the sum of the interior angles is 180°, ∠a m+1 d m A=∠c m d m D=180°-(90°+Δ)-(90°-α m -2Δ)=α m +Δ (16) Then, equation (16) and △d m Aa m+1 Since the sum of the interior angles is 180°, ∠d m a m+1 A=180°-(90°-Δ)-(α m +Δ)=90°-α m ···(17) This becomes:

[0041] Equation (17) is a m+1 The angle of incidence at m , i.e., a m It indicates that the angle of incidence at point b on the left slope 12b is equal to the angle of incidence at point b on the left slope 12b. Since the angle of incidence at point b on the left slope 12b is equal to the angle of incidence at point b on the left slope 12b, it can be said that the angle of incidence at point b on the left slope 12b is equal to the angle of incidence at point b on the left slope 12b. m and point d on the right slope 12d mThis shows that the angles of incidence to the

[0042] Next, the condition for Δ that determines the angle of the vertex of the isosceles trapezoid is as follows: When light in the light guide 12 is incident on the boundary surface 21, the incident angle is equal to the critical angle θ C In the above cases, no refraction occurs at the boundary surface 21, and total reflection occurs. C is the refractive index n, sinθ C =1 / n (18) The condition under which the incident light on the upper surface 12a of the light guide 12 is not totally reflected is as follows: α<θ C ···(19) The condition for total reflection at the left and right slopes 12b and 12d is given by the following equation (14) or (16): 90°-(α+Δ)≧θ C ···(20) The condition for total reflection at the bottom surface is given by equation (15): 90°-(90°-α-2Δ)=α+2Δ≧θ C ···(twenty one) From equation (20) and equation (19), 90°-Δ≧θ C +α>2α (22) However, when emitting light at a low elevation angle, the incident angle α is equal to the critical angle θ C Since it is a neighborhood of 90°-Δ≧2θ C ∴Δ≦90°-2θ C ···(twenty three) The value of Δ must be determined so that: Also, since Δ is positive, 2θ C <90°, i.e., θ C <45°, and if this condition is not met, it is difficult to emit light efficiently at low elevation angles. Δ≧(θ C -α) / 2 (24) and emits light only at low elevation angles, and the incident angle α and critical angle θ C If the difference between the incident angle α and the critical angle θ is small, there is no problem. CWhen the angle of elevation is sufficiently smaller than Δ and light is emitted in a direction with a high elevation angle, Δ must be set to a large value to satisfy equation (24).

[0043] As explained above, Δ, which determines the angle of the vertex of an isosceles trapezoid, is the ratio of the incident angle α to the critical angle θ C Set according to the size of

[0044] As a specific example, we will explain the case where S-BSL7 with a refractive index n=1.518 is used. From equation (18), θ C =arcsin(1 / n)=arcsin(1 / 1.518)=41.2055° ···(twenty five) and θ C <45° is satisfied. From equation (23), Δ≦90°−2×41.2055°=7.589° (26) As a result, Δ is limited to a small range of 7.5° or less. For example, when Δ=5°, from equation (21), θ C -α≦2Δ=10° (27) and α is θ C θ from 10° smaller than C It can be set in a wide range up to near .

[0045] Fig. 5 is a vertical cross-sectional view of light guide 12 in this embodiment, similar to Fig. 4. The incident portion is also omitted in Fig. 5. Here, the shape of the isosceles trapezoid in the vertical cross section, specifically the relationship between the length of the sides and the height, will be described with reference to Fig. 5.

[0046] The length of the upper base of the isosceles trapezoid is u, the length of the lower base is u-2δ, and the height is h. In Figure 5, if the intersection of the upper base and the perpendicular line drawn from vertex D to the upper base is a0, then Aa0 = δ and Ba0 = u-δ. As in Figure 4, the angle of vertex A is 90°-Δ, and the angle of incidence to the upper surface is α. Consider the case where light enters light guide 12 from vertex D at the right end of the lower surface as shown in Figure 5, strikes a1 on upper surface 12a at angle of incidence α, and the reflected light at a1 is totally reflected by b1 on left slope 12b, and then strikes c1 on lower surface 12c. ■a0=h, ∠A■a0=Δ, so δ (=Aa0) is found between Δ and h as follows: δ=htanΔ (28) The following relationship holds. If the intersections of perpendicular lines drawn from b1 to the upper surface 12a and the lower surface 12c are a1' and c1', respectively, then the quadrilateral Da0a1'c1' is a rectangle with 90-degree angles at all vertices, so a1'c1'=Da0=h, and a1'a0=c1'D. If auxiliary lines are drawn perpendicular to the upper surface 12a and the lower surface 12c from a1 and c1, the angles can be found as shown in Figure 5 using alternate angles of two parallel lines. △Da0a1 and △b1a1'a1 are similar because the angles of the corresponding vertices are equal, Da0:a0a1=b1a1':a1' a1...(29) From the above, a1' a1=a1' a0-a0a1=CD+Cc1'-a0a1, so if we set b1a1'=X and Cc1'=Y, equation (29) becomes h:htanα=X:u-2htanΔ+Y-htanα ···(30) And Xtanα=u-2htanΔ+Y-htanα ···(31) Also, △Da0A and △b1c1'C are similar because the angles of the corresponding vertices are equal, so Da0:a0A=b1c1':c1'C=a1' c1'-b1a1':c1'C ···(32) twist, h:htanΔ=hX:Y (33) holds true, Y = (hX) tan Δ (34) Substituting equation (34) into equation (31), we finally obtain X=(u-htanΔ-htanα) / (tanα+tanΔ) ···(35) Y=tanΔ(2htanα+2htanΔ-u) / (tanα+tanΔ) ···(36) The condition that c1 is on the lower surface 12c is c1' c1 <c1’Dであり、 c1' c1=c1' b1tan(α+2Δ)=(a1' c1'-b1a1')tan(α+2Δ)=(hX)tan(α+2Δ) ···(37) and c1'D=Cc1'+CD=Y+u-2htanΔ...(38) twist, (hX)tan(α+2Δ) <Y+u-2htanΔ ···(39) Then, by substituting equations (35) and (36) into equation (39), we finally get u / h>2(tanα+tanΔ)tan(α+2Δ) / {tanα+tan(α+2Δ)} ···(40) is obtained.

[0047] For example, when the above-mentioned S-BSL7 is used as the light guide, and the incident angle α is 40 degrees, which satisfies the formulas (23) to (27), and the angle Δ of the isosceles trapezoid of the bottom surface is 5 degrees, the formula (40) becomes: u / h>2(tan40+tan5)tan(40+2·5) / {tan40+tan(40+2·5)}=1.087 ···(41) The upper base must be at least 1.09 times the height.

[0048] As explained above, the ratio of the side length to the height of the isosceles trapezoid is set according to the incident angle α and the angle of the vertex of the isosceles trapezoid. C As a result, the shape of the isosceles trapezoid is determined by the magnitude of the incident angle α and the critical angle θ C It will be set according to the size of

[0049] Note that equation (40) does not take into account the incident portion 16 provided at the vertex D. If the incident portion 16 is taken into account, u / h needs to be set to a value slightly larger than the value obtained from the right side of equation (40).

[0050] <Structure of road marking device> The road marking device of this embodiment can be used as is, for example, with the light emitting device 10 shown in FIG. 1 as its basic structure.

[0051] FIG. 6 is a diagram showing an example of the structure of a road marking device 30 in this embodiment. The road marking device 30 is used in places where it is desired to draw the attention of drivers and the like with road markings, for example, by installing it on both sides of a crosswalk. In this embodiment, a plurality of road marking devices 30 may be installed side by side. For example, a plurality of road marking devices 30 may be installed at desired locations to form a single road marking. Even when a plurality of road marking devices 30 are installed, each road marking device 30 may be embedded in the road in a similar manner, as shown in FIG. 6 as an example.

[0052] The road marking device 30 is installed so that the entire device is buried in a groove 26 formed in the road. Specifically, the installation is carried out in the following procedure.

[0053] That is, first, a groove 26 for installing the road marking device 30 is formed. In FIG. 6, the shape of the groove 26 is shown by a thick line. In this embodiment, the groove 26 is formed so that its cross section is shaped like a pot with shoulders. Then, a buffer material 32 is fixed around below the shoulder of the groove 26. Then, wiring for the light source 14 (not shown) is laid, and the light guide 12 is installed. By embedding the light guide 12 in the groove 26, the left and right slopes 12b, 12d of the light guide 12 correspond to the positions of the buffer materials 32 on both sides. Furthermore, as will be described later, a cover 36 is installed on the light guide 12 as necessary.

[0054] A space 34 is formed below the light guide 12 supported by the buffer material 32. The light source 14 is disposed in the space 34, and electrical wiring and the like (not shown) are also installed therein to supply power to the light source 14.

[0055] When total reflection occurs repeatedly inside the light guide 12 and the optical path inside the light guide 12 becomes long, it is desirable that the material of the light guide 12 be a material with high transparency (internal transmittance), such as optical glass typified by S-BSL7 as exemplified above.

[0056] If the road marking device 30 is installed in a place such as a sidewalk where the downward load on the road surface 21 is small, and there is no concern that the light guide 12 will be damaged by the load, then, unlike in Fig. 6, a groove 26 of the same shape as the light guide 12 can be provided in the road surface 21 and the road marking device 30 can be fitted into the groove 26. Even if there is a space 34 below the groove 26 for installing the light source 14, for example, the road marking device 30 can be fixed to the road surface 21 at a position where the left and right inclined surfaces 12b, 12d of the light guide 12 contact the groove 26. This is an advantage of making the vertical cross section of the light guide 12 an isosceles trapezoid whose upper base is longer than its lower base.

[0057] For example, if the vertical cross section of a light guide is a parallelogram (including a rectangle), the light guide will slip through the groove if it is simply placed in a groove of the same shape. If there is space below the groove, the light guide will not be fixed to the groove and will fall into the space. For this reason, a separate mechanism is required to fix the light guide to the groove.

[0058] When the road marking device 30 is installed in a location such as a roadway where a large downward load is applied to the road surface 21, and there is a concern that the light guide 12 may be damaged by the load, it is desirable to take measures to prevent damage to the light guide 12. Figure 6 shows two measures to prevent damage to the light guide 12.

[0059] The first measure is to provide buffer materials 32 between the left and right slopes 12b, 12d of the light guide 12 and the groove 26, as shown in FIG. 6 . When a downward load is applied to the light guide 12, the buffer materials 32 cause the light guide 12 to sink. The buffer materials 32 are compressed toward the groove 26 and become thinner, thereby distributing the load to areas other than the light guide 12. In this way, damage to the light guide 12 can be avoided. Note that the interfaces 12b, 12d between the light guide 12 and the buffer materials 32 may not undergo total reflection because the relative refractive index n of the light guide 12 with respect to the buffer materials 32 is smaller than the relative refractive index of the light guide with respect to air. In this case, the interfaces 12b, 12d may be covered with reflectors, or an air layer may be created by cutting the buffer materials 32 at the positions where light enters the interfaces 12b, 12d.

[0060] If the buffer material 32 alone is not sufficient to protect against the downward load and there is still concern that the light guide 12 may be damaged, a cover 36 made of a transparent, unbreakable material such as polycarbonate may be disposed on the upper surface 12a as a second measure. Even if the cover 36 elastically deforms downward due to the vehicle load, the light guide 12 can be sunk by the buffer material 32 with an equal amount of deformation, thereby reducing the load on the light guide 12.

[0061] The light guide 12 has very high transparency, and the strong cover 36 generally has lower transparency than the light guide 12. To efficiently refract and radiate light from the road surface 21, it is desirable to thin the cover 36 to shorten the optical path length within the cover 36 and reduce light loss due to the cover 36. On the other hand, if the cover 36 is too thin, there is a concern that the cover 36 itself may be damaged by the vehicle load. Therefore, it is desirable to make the cover 36 as thin as possible within a thickness range that does not cause damage. If the cover 36 is thick, it is desirable for the material of the cover 36 to have a small difference in refractive index from the light guide 12. If the refractive indexes of the cover 36 and the light guide 12 are equal, the ratio of the refractive indexes of the two, corresponding to n in Equation (3), is 1. According to Equation (3), the angle of incidence and the angle of refraction between the light guide 12 and the cover 36 are equal, and light travels straight at the interface between the light guide 12 and the cover 36. Furthermore, because the angle of incidence and the angle of refraction are equal, the right-hand sides of equations (7) and (9) become 0, and all light is transmitted (travels straight) without reflection at the boundary surface between the light guide 12 and the cover 36. In this case, u / h can be set under the condition of equation (40), where u is the upper base of the cover 36 and h is the sum of the heights of the cover 36 and the light guide 12. If the difference in refractive index between the cover 36 and the light guide 12 cannot be ignored, the shapes of both must be designed taking into account the refraction and reflection at the boundary surface between them.

[0062] Alternatively, a buffer material may be provided in the space 34 to support the sunken light guide 12 from below. In this case, the interface 12c between the light guide 12 and the buffer material may not undergo total reflection because the relative refractive index n of the light guide 12 with respect to the buffer material is smaller than the relative refractive index of the light guide 12 with respect to air. Therefore, the interface 12c may be covered with a reflector, or a layer of air may be provided by cutting out the buffer material at the position where light enters the interface 12c.

[0063] In this embodiment, a groove 26 is formed in the road, and buffer material 32, electrical equipment such as light source 14, light guide 12, and cover 36 are installed in the groove 26 in this order. However, a unit integrating these components may be precast and buried in a groove 26 provided on the road.

[0064] <Other> In the above embodiment, the light emitting device 10 has been described as being applied to a road marking device. However, the light emitting device may be installed in other locations. For example, the light emitting device may be embedded in the side wall of a building. In this case, there is no risk of pedestrians or vehicles tripping over the light emitting device 10, but it is preferable that the top surface of the light emitting device 10 be formed as part of the flat wall surface of the building.

[0065] Furthermore, when a light source 14 with a large irradiation angle is used to emit light in a wide range of refraction angles, even if the light guide 12 has a certain thickness, a part of the light 22 may be incident on surfaces other than the upper surface 12a (including the surfaces of the isosceles trapezoid) at a critical angle θ c Since there is a possibility that light may be incident at an angle smaller than the angle θ, surfaces other than the upper surface 12a (including the isosceles trapezoidal surface) may be covered with a reflective material such as a reflector. The light reflected by the reflective material may be irradiated in directions other than the intended target position.

[0066] [Configuration of the present invention] Configuration 1: a light source means; a light guide having an incident portion to which light from the light source means is incident and having a predetermined three-dimensional shape formed from a first medium made of a transparent solid or liquid; Equipped with The light guide is The light from the light source means passing through the incident portion is incident on an interface with a second medium having a refractive index relatively smaller than that of the first medium at a predetermined incident angle according to the relative refractive index of the first medium with respect to the second medium, so that the refracted light at the interface is emitted at a refraction angle that reaches a predetermined target position, and On an inner surface other than the boundary surface, light is totally reflected by the boundary surface when incident at an incident angle equal to or greater than the critical angle, and the reflected light becomes incident light that is incident on the boundary surface at the predetermined incident angle, and the refracted light of the incident light at the boundary surface is emitted at a refraction angle that reaches the predetermined target position. A light-emitting device characterized by: Configuration 2: 2. The light emitting device of claim 1, wherein the boundary surface forms part of a planar surface of an object when the light guide is embedded in the object. Configuration 3: The light-emitting device according to configuration 1 or 2, characterized in that the light guide is formed as a prism having an isosceles trapezoidal bottom as the predetermined three-dimensional shape, and the side of the prism including the longer of the two parallel sides of the isosceles trapezoid is the boundary surface. Configuration 4: 4. The light emitting device according to any one of configurations 1 to 3, wherein the shape of the isosceles trapezoid is set in accordance with the magnitudes of the incident angle and the critical angle. Configuration 5: A light-emitting device according to any one of configurations 1 to 4, A road marking device characterized in that the boundary surface is installed so as to form a part of the road surface. [Explanation of symbols]

[0067] 10 Light emitting device, 12 Light guide, 12a Top surface, 12b Left slope, 12c Bottom surface, 12d Right slope, 14 Light source, 16 Incident part, 22,22a,22c Incident light, 24,24b,24d Reflected light, 23,23a,23b Refracted light, 21 Road surface (boundary surface), 26 Groove, 30 Road marking devices, 32 buffers, 34 spaces, 36 covers.

Claims

1. a light source means; a light guide having an incident portion to which light from the light source means is incident, the light guide having a predetermined three-dimensional shape formed of a first medium made of a transparent solid or liquid; Equipped with The light guide is The light from the light source means passing through the incident portion is incident on an interface with a second medium having a refractive index relatively smaller than that of the first medium at a predetermined incident angle according to the relative refractive index of the first medium with respect to the second medium, so that the refracted light at the interface is emitted at a refraction angle that reaches a predetermined target position, and On an inner surface other than the boundary surface, light is totally reflected by the boundary surface when incident at an incident angle equal to or greater than the critical angle, and the reflected light becomes incident light that is incident on the boundary surface at the predetermined incident angle, and the refracted light of the incident light at the boundary surface is emitted at a refraction angle that reaches the predetermined target position. A light-emitting device characterized by:

2. 2. The light emitting device according to claim 1, wherein the boundary surface forms part of a planar surface of an object when the light guide is embedded in the object.

3. The light-emitting device according to claim 1, characterized in that the light guide is formed as a prism having an isosceles trapezoidal base as the predetermined three-dimensional shape, and the side of the prism including the longer of the two parallel sides of the isosceles trapezoid is the boundary surface.

4. 2. The light emitting device according to claim 1, wherein the shape of the isosceles trapezoid is set in accordance with the magnitudes of the incident angle and the critical angle.

5. A light emitting device according to claim 1, A road marking device characterized in that the boundary surface is installed so as to form a part of the road surface.

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