JP-2026075292-A - Light-emitting devices and road surface display devices

JP2026075292AJP 2026075292 AJP2026075292 AJP 2026075292AJP-2026075292-A

Abstract

[Problem] To enable illumination over a wide range, from a low elevation angle assuming a vehicle driver to a medium elevation angle assuming a pedestrian on a crosswalk on the opposite side of the vehicle. [Solution] A light-emitting device comprising a light source X having an irradiation angle of 15° or more, and a light guide 100 formed of a first medium and having an incident surface for light from the light source X, causes light from the light source X passing through the incident surface to be incident on the first interface between the first medium and the second medium at a predetermined first incident angle including an angle greater than or equal to a critical angle determined by the relative refractive index of the first medium with respect to the second medium, thereby causing the light guide 100 to emit first refracted light at a first refraction angle corresponding to the first incident angle less than the critical angle, and causing the first reflected light generated inside the light guide 100 at a first reflection angle equal to the first incident angle greater than or equal to the critical angle to be incident on the second interface between the first medium and the second medium at a predetermined second incident angle less than the critical angle, thereby causing the light guide 100 to emit second refracted light at a second refraction angle. [Selection Diagram] Figure 7

Inventors

竹川秀人
村瀬守正
林知三夫
市毛敬介
早川喜三郎

Assignees

株式会社豊田中央研究所

Dates

Publication Date: 20260508
Application Date: 20241022

Claims (9)

A light source having an illumination angle of 15° or more, A light guide formed of a first medium and having an incident surface for light from the light source, A light-emitting device equipped with, The light guide body is By causing light from the light source passing through the incident surface to be incident on the first interface between the first medium and the second medium at a predetermined first incident angle that includes an angle greater than or equal to a critical angle determined by the relative refractive index of the first medium with respect to a second medium having a different refractive index than the first medium, first refracted light is emitted from the light guide at a first refraction angle corresponding to the first incident angle less than the critical angle, and first reflected light is generated within the light guide at a first reflection angle equal to the first incident angle greater than or equal to the critical angle. By reflecting the first reflected light within the light guide body, the light is incident on the second interface between the first medium and the second medium at a predetermined second incident angle less than the critical angle, causing the light guide body to emit second refracted light at a second refraction angle corresponding to the second incident angle. A light-emitting device characterized by the following features.
A light-emitting device according to claim 1, The light-emitting device is characterized in that the first interface surface is provided with an inclined portion that protrudes from the surface on which the light guide is arranged, and the first refracted light is emitted from the inclined portion.
A light-emitting device according to claim 1 or 2, A light-emitting device characterized in that the angle between the surface on which the first reflected light is reflected and the direction of incidence of the first reflected light to the second interface is set within the light guide body such that the second incident angle is less than the critical angle.
A light-emitting device according to claim 3, If the surface in the light guide that reflects the first reflected light is the surface facing the first interface, the surface is tilted such that the angle of incidence of the first reflected light onto that surface is smaller than the first angle of incidence. A light-emitting device characterized in that, when the surface on which the first reflected light is reflected within the light guide body is a surface that does not face the first interface, the surface is tilted such that the angle of incidence of the first reflected light onto that surface is greater than (90° - the first angle of incidence).
A light-emitting device according to claim 1, A light-emitting device characterized by comprising optical path changing means for changing the direction of light from the light source before it passes through the incident surface, thereby limiting the direction of light passing through the incident surface.
A light-emitting device according to claim 5, The light-emitting device is characterized in that the optical path changing means increases the amount of light passing from the light source to the incident surface compared to when the direction of the light is not changed, by changing the direction of the light from the light source, thereby increasing the amount of light emitted by the first refracted light.
A light-emitting device according to claim 6, A light-emitting device characterized in that it increases the amount of light incident on the inclined portion by utilizing the light at the end of the emission direction range limited by the optical path changing means from the light source for the first refracted light from the inclined portion, thereby causing the first refracted light from the inclined portion to emit light at a greater intensity.
The light-emitting device is provided as described in claim 1, A road surface display device characterized in that the light guide is embedded in the road surface such that the first boundary surface forms a part of the road surface.
A road surface display device according to claim 8, The road surface display device is characterized in that the first medium is polycarbonate or a material possessing transparency and strength equivalent to or greater than that of polycarbonate.

Description

This invention relates to a light-emitting device and a road surface display device used for purposes such as emitting light on roads. Lighting devices are used to warn and guide the eyes of drivers and pedestrians by emitting light from the center line of a road, the center of an intersection, or a crosswalk. When emitting light from the road surface at a warning point such as a crosswalk, directed towards drivers of approaching vehicles, the distance from the light source to the vehicle is several tens of times greater than the height from the road surface to the driver's eyes, so the light needs to be emitted at a low angle. Road studs are an example of a product that emits light at a low angle from the road surface. By installing multiple light sources on both sides of a road stud, it becomes possible to illuminate both drivers of vehicles approaching the road stud and pedestrians on the crosswalk on the opposite side of the road. As prior art, various forms utilizing a transparent light guide plate with a right-angled triangular cross-section have been shown (Patent Document 1). When Embodiment 4 in that document is applied to a road, the right-angled triangle is positioned so that the hypotenuse is in the ground, the long side is on the road surface, and the short side is perpendicular to the road surface, and light is incident from the short side in a direction parallel to the road surface. In this case, the angle of incidence decreases as the light is repeatedly reflected between the hypotenuse and the road surface, and when the angle of incidence to the road surface becomes less than or equal to the critical angle, some of the light is refracted onto the road at a low elevation angle. The light that is reflected within the light guide plate without refraction is reflected by the hypotenuse and then incident on the road surface at an even smaller angle of incidence, and some of it is refracted. Embodiment 17 is a configuration that irradiates light in two different directions. When this configuration is applied to a road, the short sides of two light guide plates are joined to form a vertical cross-section of an isosceles triangle with a small ratio of height to base, and a light source is embedded in the lower part of the joint of the light guide plates and installed on the road. Furthermore, by cutting the upper part of the joint directly above the light source to create a low slope in the center, and using the sloped section as a reflective surface, light incident from the light source onto the sloped section is reflected into the light guide plate, ultimately enabling refraction at a low elevation angle. Although this configuration uses two light sources, refraction at a low elevation angle is also possible with a single light source in two different directions. Japanese Patent Publication No. 2001-229703 This figure illustrates the principle of a road surface display device according to an embodiment of the present invention.This figure shows the relationship between the refraction angle θT , the p-wave transmittance Tp , and the s-wave transmittance Ts .This diagram shows the difference in the light path when light is emitted from a road surface and an inclined surface.This is a vertical cross-sectional view showing the basic configuration of the light guide and the optical path of the light included in the road surface display device according to an embodiment of the present invention.This figure shows an example of the arrangement of a road surface display device in an embodiment of the present invention.This is a cross-sectional view showing an example of the configuration of the light source unit in an embodiment of the present invention.This is a vertical cross-sectional view showing the configuration of the road surface display device and the optical path of light in an embodiment of the present invention.This figure shows the results of an optical simulation for a road surface display device in an embodiment of the present invention.This figure shows the results of an optical simulation for a road surface display device in an embodiment of the present invention. [Principle in this embodiment] Figure 1 is a diagram illustrating the principle of a road surface display device according to an embodiment of the present invention. When using light for road surface display and emitting light from the road surface towards the driver of a vehicle approaching the display point, it is necessary to emit light at a very small elevation angle from the display point. When the height of the driver's eyes from the road surface is H [m] and the distance from the display point to the driver is L [m], the elevation angle θE satisfies the relationship given by equation (1) between the two. (Math 1) tanθ E =H/L...(1) For example, the elevation angle θE when L = 40 m and H = 1.2 m can be expressed by equation (2). (Math 2) tanθ E =1.2/40 Elevation angle θ E = arctan0.03 = 1.72°...(2) As a method for emitting