Road display device, installation method, and projection method

Abstract

A road display device 10 comprises a lighting device 30 that irradiates a road surface 95 with light so as to project a display having a width at least in a first direction. The display has a first end portion 90a located on a first side S11 in a first direction D1. In observation from a vertical direction DN, an angle Φ1 formed by a first light beam L1 and a virtual line segment L3 is smaller than 90°, the first light beam L1 being emitted from the lighting device 30 to the first end portion 90a, the virtual line segment L3 extending from the first end portion 90a to the first side S11 along the first direction D1. In observation from a second direction D2 perpendicular to the first direction D1 and perpendicular to the vertical direction DN, an angle θ1 formed by the first light beam L1 and a perpendicular line L4 to the road surface 95 is larger than 0° and is 83.15° or smaller.

Description

Road display device, installation method, and projection method

[0001] The present disclosure relates to a road display device, an installation method, and a projection method.

[0002] Conventionally, a technique for projecting a light display on a road surface has been known. In particular, a technique for projecting a linear light display on a road surface by a lighting device has been known (for example, Patent Documents 1 and 2). With such a light display, for example, a sign that contributes to vehicle safety can be shown to passengers in a vehicle traveling on the road surface. In particular, even in the case of snow accumulation, a sign that contributes to vehicle safety can be shown.

[0003] Japanese Patent No. 5982325, Japanese Patent No. 6860905

[0004] When an observer visually recognizes a display projected on a road surface by a lighting device, a part of the display may be missing due to unevenness of the road surface. For example, when an observer visually recognizes a line display projected on a road surface by a lighting device, a line display with a part missing may be visually recognized due to unevenness of the road surface. In particular, when an observer who is a passenger in a vehicle traveling on the road surface visually recognizes a line display projected on the road surface along the direction in which the vehicle is traveling, a line display with a part missing may be visually recognized due to unevenness of the road surface.

[0005] The present disclosure has been made in consideration of the above points, and an object thereof is to project a display in which missing is difficult to be visually recognized.

[0006] Embodiments of the present disclosure relate to the following [1] to

[25] .

[0007] [1] A road display device comprising an illumination device that emits light to project a display having a width in at least a first direction onto a road surface, wherein the display has a first end located on the first side in the first direction, and when viewed from a vertical direction, the angle Φ1 between a first ray emitted from the illumination device and reaching the first end and a virtual line segment extending from the first end to the first side along the first direction is less than 90°, and when viewed from a second direction that is perpendicular to the first direction and perpendicular to the vertical direction, the angle θ1 between the first ray and a perpendicular line to the road surface is greater than 0° and 83.15° or less.

[0008] [2] The road display device according to [1], wherein the display is a line display extending in the first direction.

[0009] [3] The road display device according to [1] or [2], wherein the angle Φ1 is greater than 0°.

[0010] [4] The road display device according to [2], wherein the length of the line display in the first direction is 8 m or more.

[0011] [5] The road display device according to [2] or [4], wherein the length of the line display in the second direction is 105 mm or less.

[0012] [6] The road display device according to any one of [1] to [5], wherein the angle θ2 between the first ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

[0013] [7] The road display device according to any one of [1] to [6], further comprising a holder for holding the lighting device so as to fix the position of the lighting device with respect to the road surface.

[0014] [8] The lighting device is held by a moving body that moves along the road surface, as described in any one of [1] to [7].

[0015] [9] The road display device according to any one of [1] to [8], wherein the angle Φ1 is less than 45°.

[0016]

[10] A road display device comprising an illumination device that extends in the direction of the road and irradiates light onto the road surface of a road on which a moving body moves from the first side of the road in the direction of the road to the second side of the road in the direction of the road, wherein the display has a first end in the direction of the road located on the first side of the road in the direction of the road, and the angle Φ2 between a second ray emitted from the illumination device and reaching the first end in the direction of the road and a virtual line segment extending along the direction of the road from the first end in the direction of the road to the first side of the road is less than 90° when viewed from a vertical direction.

[0017]

[11] The road display device according to

[10] , wherein the display is a line display extending in the direction of the road.

[0018]

[12] The road display device according to

[10] or

[11] , wherein, when observed from the width direction which is perpendicular to the road direction and perpendicular to the vertical direction, the angle θ3 between the second ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

[0019]

[13] The road display device according to any one of

[10] to

[12] , wherein the angle θ4 between the second ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

[0020]

[14] Installation method for installing a road display device on the road surface of a road that extends in the direction of the road and on which a moving body moves from a first side of the road in the direction of the road to a second side of the road in the direction of the road, the installation method comprising an installation step of installing the road display device such that the first direction is along the direction of the road, the first end of the display faces the first side of the road, and when observed from a vertical direction, the angle Φ1 between a first ray emitted from the illumination device and reaching the first end and a virtual line segment extending from the first end to the first side along the first direction is less than 90°.

[0021]

[15] The installation method according to

[14] , wherein the display is a line display extending in the first direction.

[0022]

[16] The installation method according to

[14] or

[15] , wherein in the installation step, the road display device is installed such that, when observed from a second direction which is perpendicular to the first direction and perpendicular to the vertical direction, the angle θ1 between the first ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

[0023]

[17] The installation method according to any one of

[10] to

[16] , wherein in the installation step, the road display device is installed such that the angle θ2 between the first ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

[0024]

[18] The installation method according to

[15] , wherein the length of the line marking in the first direction is 8 m or more.

[0025]

[19] The installation method according to

[15] or

[18] , wherein the length of the line marking in a second direction that is perpendicular to the first direction and perpendicular to the vertical direction is 105 mm or less.

[0026]

[20] A projection method for projecting a line display onto the road surface of a road that extends in the direction of the road and on which a moving body moves from a first side of the road in the direction of the road to a second side of the road in the direction of the road, the road display device comprising an illumination device that emits light to project the line display, the line display having a first end that extends in a first direction and is located on a first side in the first direction, and a second end that is located on a second side in the first direction, the projection step comprising projecting the line display such that the first direction is along the direction of the road, the first end of the line display faces the first side of the road, and when observed from a vertical direction, the angle Φ1 between a first ray emitted from the illumination device and reaching the first end and a virtual line segment extending from the first end to the first side along the first direction is less than 90°.

[0027]

[21] The projection method according to

[20] , wherein the display is a line display extending in the first direction.

[0028]

[22] The projection method according to

[20] or

[21] , wherein, in the projection step, the display is projected such that, when observed from a second direction which is perpendicular to the first direction and perpendicular to the vertical direction, the angle θ1 between the first ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

[0029]

[23] The projection method according to any one of

[20] to

[22] , wherein in the projection step, the display is projected such that the angle θ2 between the first ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

[0030]

[24] The projection method according to

[21] , wherein the length of the line display in the first direction is 8 m or more.

[0031]

[25] The projection method according to

[21] or

[24] , wherein the length of the line display in a second direction that is perpendicular to the first direction and perpendicular to the vertical direction is 105 mm or less.

[0032] [Effects of the Invention] According to the embodiments of this disclosure, it is possible to project a display in which defects are difficult to see.

[0033] Figure 1 is a perspective view showing an example of a road display device according to this embodiment. Figure 2 is a perspective view showing an example of a lighting device according to this embodiment. Figure 3 is a perspective view showing another example of a lighting device according to this embodiment. Figure 4 is a cross-sectional view showing yet another example of a lighting device according to this embodiment. Figure 5 is a plan view showing an example of a road display device according to this embodiment. Figure 6 is a side view showing an example of a road display device according to this embodiment. Figure 7 is a side view showing an example of a road display device according to a comparative example. Figure 8 is a side view showing an example of a road display device according to a comparative example. Figure 9 is a diagram illustrating the effects of the road display device according to this embodiment. Figure 10 is a diagram illustrating the effects of the road display device according to this embodiment. Figure 11 is a side view showing an example of a road display device according to modification 1.

[0034] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that, for the sake of illustration and ease of understanding, the scale and aspect ratios of the drawings attached to this specification have been appropriately altered and exaggerated from those of the actual objects.

[0035] To clarify directional relationships between drawings, some drawings show the first direction D1, the second direction D2, and the third direction D3 (described later) as common directions across the drawings, indicated by arrows. Arrows aligned perpendicular to the plane of the drawing are indicated by a symbol consisting of an "x" inside a circle, as shown in Figure 5, for example.

[0036] In this specification, terms such as "parallel," "orthogonal," and "identical," as well as values ​​of length and angle, which specify shapes, geometric conditions, and their degrees, should not be interpreted in a strict sense, but rather to include a range that can be expected to function similarly.

[0037] Figure 1 is a perspective view showing an example of the road display device 10 of this embodiment. The road display device 10 in this embodiment includes a lighting device 30. The lighting device 30 irradiates light LA ​​onto the road surface 95 of the road 94 to project a display. The display has a width in at least a first direction D1. In the example shown in Figure 1, the display is a line display 90 extending in the first direction D1. It can also be said that the display has a width in at least a road direction DR. In the example shown in Figure 1, the display is a line display 90 extending in the road direction DR. The line display 90 is a line-shaped light display. Details of the line display 90, the first direction D1 and the road direction DR will be described later. The display projected by the lighting device 30 onto the road surface 95 of the road 94 may be a display other than a line display 90. The display may be, for example, a display of characters such as "10km" or "10km / h".

[0038] The following description will focus on the case where the display projected by the lighting device 30 onto the road surface 95 of the road 94 is a line display 90, unless otherwise specified. The description given regarding the line display 90 can also be applied to displays other than the line display 90 projected by the lighting device 30, as long as they do not contradict each other.

[0039] Observer 5 can observe the line markings 90 on the road surface 95. The road display device 10 of this embodiment is designed to make it difficult for observer 5 to see any gaps in the line markings 90. In the example shown in Figure 1, the road display device 10 further includes a holder 60 for holding the lighting device 30.

[0040] In the following, one embodiment will be described with reference to a specific example shown in the drawings.

[0041] The road surface 95 on which the line markings 90 are projected is a surface on which a moving body 51 is expected to move. The road surface 95 on which the line markings 90 are projected is, for example, an outdoor road surface on which automobiles or the like travel. The road surface 95 may also be an indoor road surface in a factory or warehouse on which industrial vehicles travel. The road surface 95 may have irregularities, as will be described later. Even if the road surface 95 has irregularities, the directions parallel to the road surface 95 and the perpendiculars to the road surface 95 are determined based on the approximate shape of the road surface 95, ignoring the irregularities of the road surface 95.

[0042] The mobile unit 51 is a machine that moves along the road surface 95 by direct or indirect instructions from a human. The mobile unit 51 may include all vehicles that travel on the road surface 95. For example, the mobile unit 51 is a manned machine. In this case, the mobile unit 51 may be a manned automobile that travels on an outdoor road surface. The mobile unit 51 may be an unmanned machine. In this case, the mobile unit 51 may have a camera that photographs the road surface 95. In this case, the camera may photograph line markings 90 projected onto the road surface 95. The mobile unit 51 may be remotely controlled by a user of the mobile unit 51 who refers to the condition of the road surface 95 as captured by the camera. The mobile unit 51 may drive automatically based on the condition of the road surface 95 as captured by the camera. The mobile unit 51 may be an industrial vehicle that travels on an indoor road surface such as a factory or warehouse. The mobile unit 51 may be an aircraft such as a drone that flies on the road surface 95 at a height below the height of the driver's eye level in a typical automobile. The mobile body 51 may be an aircraft that flies at a height of 2.4 m or less above the road surface 95. The mobile body 51 may be an aircraft that flies at a height of 1.2 m or more above the road surface 95.

[0043] In this embodiment, unless otherwise specified, the road surface 95 is an outdoor road surface on which vehicles and the like travel, and the case where the moving body 51 is a vehicle driven by a human will be described.

[0044] In the example shown in FIG. 1, the road 94 having the road surface 95 on which the line display 90 is projected extends in the road direction DR. The road direction DR is a direction assumed as the direction in which the moving body 51 travels on the road surface 95 of the road. The road 94 in the example shown in FIG. 1 is a road on which it is assumed that the moving body 51 travels from the road first side SR1 in the road direction DR to the road second side SR2 in the road direction DR. The road direction DR can be specified, for example, by referring to road signs by display boards, road surface markings by paint applied on the road surface 95, and the like.

[0045] The lighting device 30 will be described. The lighting device 30 irradiates light LA to the illuminated area 96 of the road surface 95. The observer 5 recognizes the illuminated area 96 as the line display 90. The line display 90 has the same shape as the shape of the illuminated area 96.

[0046] In the example shown in FIG. 1, the line display 90 and the illuminated area 96 have a linear shape. In the example shown in FIG. 1, the line display 90 extends in the first direction D1. That is, the line display 90 has a longitudinal direction in the first direction D1. The first direction D1 is a direction parallel to the road surface 95. The line display 90 has a lateral direction in the second direction D2. The second direction D2 is perpendicular to the first direction D1 and perpendicular to the vertical direction DN. The line display 90 has a first end 90a located on the first side S11 in the first direction D1 and a second end 90b located on the second side S12 in the first direction D1.

[0047] The lighting device 30 emits light to project a line marking 90 extending in the road direction DR onto the road surface 95. The line marking 90 has a first end portion 90c in the road direction located at the first road side SR1 in the road direction DR, and a second end portion 90d in the road direction located at the second road side SR2 in the road direction DR. The position of the lighting device 30 relative to the road surface 95 is determined so that the first direction D1 of the line marking 90 is aligned with the road direction DR. In other words, the position of the lighting device 30 relative to the road surface 95 is determined so that the first direction D1 of the line marking 90 is parallel to the road direction DR. By determining the position of the lighting device 30 as described above, the lighting device 30 can emit light to project a line marking 90 extending in the road direction DR onto the road surface 95. Furthermore, the position of the lighting device 30 relative to the road surface 95 is determined such that the first end 90a of the line indicator 90 faces the first side SR1 of the road in the road direction DR, and the second end 90b of the line indicator 90 faces the second side SR2 of the road in the road direction DR. By determining the position of the lighting device 30 as described above, the first end 90a becomes the first end 90c in the road direction, and the second end 90b becomes the second end 90d in the road direction.

[0048] When the outline of the line display 90 is not clear and thus the first end 90a, the second end 90b, the first road-direction end 90c, and the second road-direction end 90d are not clear, the first end 90a, the second end 90b, the first road-direction end 90c, and the second road-direction end 90d are defined as follows. Among the points where the illuminance becomes 1 / 20 of the maximum value within the illuminated area 96, the point located on the most first side S11 in the first direction D1 is defined as the first end 90a. Among the points where the illuminance becomes 1 / 20 of the maximum value within the illuminated area 96, the point located on the most second side S12 in the first direction D1 is defined as the second end 90b. Among the points where the illuminance becomes 1 / 20 of the maximum value within the illuminated area 96, the point located on the most road first side SR1 in the road direction DR is defined as the first road-direction end 90c. Among the points where the illuminance becomes 1 / 20 of the maximum value within the illuminated area 96, the point located on the most road second side SR2 in the road direction DR is defined as the second road-direction end 90d. The measurement of the illuminance is performed in accordance with JIS C7612:1985 using a spectral irradiance meter (product name "CL-500A", manufactured by Konica Minolta Co., Ltd.) as the measuring instrument. When the line display 90 is projected onto the outdoor road surface 95, the measurement of the illuminance is performed at night. When the line display 90 is projected onto the indoor road surface 95, the measurement of the illuminance is performed in a state where no external light enters the room and other lighting in the room is turned off. When the line display 90 is projected onto the outdoor road surface 95, the measurement of the illuminance is performed under the condition that the illuminance at a location on the road surface 95 where the illuminated area 96 is not present (a location where it can be recognized that the clear display (line display 90) is not displayed) is 100,000 lx or less.

[0049] In the example shown in FIG. 1, the portion of the road 94 onto which the line display 90 is projected extends linearly. In this case, the line display 90 and the illuminated area 96 are linear. Although not shown, the portion of the road 94 onto which the line display 90 is projected may be curved. In this case, the road direction DR is a direction along the direction in which the portion of the road 94 onto which the line display 90 is projected extends. Further, in this case, the line display 90 and the illuminated area 96 have a shape curved along the portion of the road 94 onto which the line display 90 is projected.

[0050] Line markings 90 are, for example, indicators that allow observer 5 to recognize the road direction DR. Line markings 90 may also be indicators that allow observer 5 to recognize the range of the road surface 95 that the mobile vehicle 51 on which observer 5 is riding can travel. Line markings 90 may also indicate signs that contribute to vehicle safety. Line markings 90 may indicate the boundary between the pedestrian area and the vehicle area of ​​the road surface 95. Line markings 90 may also be indicators that guide the mobile vehicle 51 to proceed in a specific direction. Line markings 90 may also be indicators that guide the mobile vehicle 51 into facilities around the road 94. Line markings 90 may also be indicators that guide the mobile vehicle 51 not to proceed in a specific direction. Line markings 90 may also indicate signs that contribute to vehicle safety, especially during snowfall.

[0051] The length W1 of the line marking 90 in the first direction D1 is preferably 8 m or more. More preferably, the length W1 is 20 m or more. By having a length W1 of 8 m or more, the line marking 90 is projected onto the road surface 95 such that the first direction D1 is aligned with the road direction DR, allowing the observer 5 of the line marking 90 to recognize the line marking 90 as a line with sufficient clarity. In particular, when the moving object 51 is a car traveling on an outdoor road surface 95, and the observer 5 is a passenger in the car, for example, the driver, the observer 5 can recognize the line marking 90 as a line with sufficient clarity. In particular, the observer 5 of the line marking 90 can recognize the road direction DR with sufficient clarity. This allows the driver of the car to drive while referring to the line marking 90.

[0052] Although not shown in the figures, the lighting device 30 projects the line display 90 by irradiating the illuminated area 96 with light LA, and may also project additional displays by irradiating areas on the road surface 95 other than the illuminated area 96 with light. In this case, the additional displays are not particularly limited. The additional displays may include a single area. The additional displays may include multiple areas that are separated from each other. The additional displays may include one or more of the following: letters, pictures, geometric patterns, symbols, marks, illustrations, characters, and pictograms. The additional displays may display information. In this embodiment, unless otherwise specified, the case in which the lighting device 30 irradiates only the illuminated area 96 with light LA ​​will be described.

[0053] As an example, the lighting device 30 projects illumination light in a specific wavelength range onto the road surface 95. The illumination light may be coherent light. Coherent light is light with the same wavelength and phase. The illumination light may include coherent light of a single wavelength. The illumination light may be green light with a wavelength of 520 nm. The illumination light may be green light with a wavelength of 530 nm. The illumination light may be red light with a wavelength of 635 nm. The illumination light may be red light with a wavelength of 638 nm. The illumination light may include coherent light of multiple wavelengths.

[0054] Next, the specific configuration of the lighting device 30 will be described.

[0055] Figure 2 is a perspective view showing an example of an illumination device 30. In the example shown in Figure 2, the illumination device 30 includes a light source 40, a shaping optical system 45, and a diffractive optical element 50. The light source 40 emits illumination light. The light source 40 is not particularly limited. The light source 40 may emit coherent light with a constant wavelength and phase. The coherent light emitted from the light source 40 has excellent directivity. Therefore, the light source 40 is suitable for an illumination device 30 that illuminates distant areas. Various types of light sources can be used as the light source 40. A laser light source that emits laser light may be used as the light source 40. A semiconductor laser light source can be exemplified as a laser light source. In the example shown in Figure 2, the light source 40 includes a single coherent light source. Therefore, in the example shown in Figure 2, the illuminated area 96 is illuminated with coherent light of a color corresponding to the wavelength range of the coherent light emitted from the light source 40. The following describes an example in which the light source 40 emits coherent light.

[0056] The shaping optical system 45 shapes the light emitted from the light source 40. For example, the shaping optical system 45 shapes the shape of the illumination light in a cross section perpendicular to the optical axis, or the three-dimensional shape of the coherent illumination light. The shaping optical system 45 may also enlarge the cross-sectional area of ​​the coherent light in a cross section perpendicular to the optical axis of the coherent light.

[0057] In the example shown in Figure 2, the shaping optical system 45 shapes the light emitted from the light source 40 into a widened parallel beam. That is, the shaping optical system 45 functions as a collimating optical system. In the example shown in Figure 2, the shaping optical system 45 has a first lens 46 and a second lens 47 arranged along the optical path. The first lens 46 shapes the light emitted from the light source 40 into a divergent beam. The second lens 47 shapes the divergent beam generated by the first lens 46 into a parallel beam. In this example, the second lens 47 functions as a collimating lens.

[0058] The diffractive optical element 50 changes the direction of propagation of coherent light from the light source 40. The coherent light diffracted by the diffractive optical element 50 is irradiated onto the illuminated area 96 on the road surface 95. The diffractive optical element 50 diffracts the coherent light from the light source 40 and directs it towards the illuminated area 96 on the road surface 95. As a result, the road surface 95 is irradiated with diffracted light from the diffractive optical element 50. The road surface 95 has a line display 90 projected onto it that corresponds to the diffraction pattern of the diffractive optical element 50.

[0059] The diffractive optical element 50 may be a holographic element. By using a holographic element as the diffractive optical element 50, it becomes easier to design the diffraction characteristics of the diffractive optical element 50. A holographic element that can illuminate only the entire area of ​​a desired region on the road surface 95 with a predetermined position, contour shape, size, and orientation can be designed relatively easily. The area on the road surface 95 that is illuminated by coherent light becomes the illuminated area 96.

[0060] When designing the diffractive optical element 50, the illuminated area 96 is set in real space at a predetermined position relative to the diffractive optical element 50, with a predetermined contour shape, size, and orientation. The position, contour shape, size, and orientation of the illuminated area 96 on the road surface 95 depend on the diffraction characteristics of the diffractive optical element 50. By adjusting the diffraction characteristics of the diffractive optical element 50, the position, contour shape, size, and orientation of the illuminated area 96 on the road surface 95 can be arbitrarily adjusted. Therefore, when designing the diffractive optical element 50, first the position, contour shape, size, and orientation of the illuminated area 96 on the road surface 95 are determined. Next, the diffraction characteristics of the diffractive optical element 50 should be adjusted so that light can be irradiated over the entire determined illuminated area 96.

[0061] The diffractive optical element 50 can be fabricated as a computer-generated hologram (CGH). A computer-generated hologram is fabricated by calculating a structure with arbitrary diffraction characteristics on a computer. Therefore, by using a computer-generated hologram as the diffractive optical element 50, it is possible to eliminate the need to generate object light and reference light using a light source and optical system, and to record interference fringes on the hologram recording material by exposure. The illumination device 30 is intended to irradiate illumination light onto an illuminated area 96 with a predetermined contour shape, size, and orientation at a predetermined position relative to the illumination device 30. By inputting information about the illuminated area 96 as parameters into the computer, a structure with diffraction characteristics capable of projecting diffractive light onto the illuminated area 96, such as an uneven surface, can be identified by computer calculations. By forming the identified structure, for example, by resin molding, the diffractive optical element 50 as a computer-generated hologram can be fabricated at low cost using a simple procedure.

[0062] For the design of the diffractive optical element 50, for example, the iterative Fourier transform method may be used. When the iterative Fourier transform method is used, the process is carried out assuming that the illuminated area 96 is far from the diffractive optical element 50, and the line display 90 projected onto the road surface 95 may be used as the Fraunhofer diffraction pattern. Therefore, the road surface 95 may not be parallel to the diffraction plane of the diffractive optical element 50.

[0063] As shown in Figure 3, the diffractive optical element 50 may include a plurality of elemental diffractive optical elements 55. Each elemental diffractive optical element 55 is, for example, a hologram element and can be configured in the same way as the diffractive optical element 50 described above. In the example shown in Figure 3, the coherent light diffracted by the plurality of elemental diffractive optical elements 55 is directed to the same illuminated area 96. That is, the light diffracted by each elemental diffractive optical element 55 is directed to the entire illuminated area 96 on the road surface 95. With such a diffractive optical element 50, light directed towards each position in the illuminated area 96 can be emitted in a dispersed manner from the plurality of elemental diffractive optical elements 55 included in the diffractive optical element 50. This suppresses excessive brightness at each position on the diffractive optical element 50 and improves laser safety.

[0064] Each elemental diffractive optical element 55 may be configured to have the same diffraction characteristics as the others. However, in order to achieve higher precision illumination, each elemental diffractive optical element 55 may be given separately designed diffraction characteristics depending on its position within the diffractive optical element 50. In this example, by adjusting the diffraction characteristics of each elemental diffractive optical element 55 according to the difference in its position relative to the other elemental diffractive optical elements 55, the diffractive light can be directed with high precision only to the entire illuminated area 96 on the road surface 95.

[0065] Incidentally, with an illumination device 30 having a light source 40 that emits coherent light and a diffractive optical element 50 that diffracts coherent light, it is possible to illuminate a large area of ​​the road surface 95 or an area of ​​the road surface 95 that extends far from the illumination device 30. That is, an elongated line display 90 can be projected onto the road surface 95. At this time, the angle of incidence α of the coherent light to each position within the area of ​​the road surface 96 varies greatly. The angle of incidence α to the area of ​​the road surface 96 that is far from the illumination device 30 becomes very large, for example, close to 90°. The diffraction plane of the diffractive optical element 50 comes to form a large angle with respect to the road surface 95 and the area of ​​the road surface 96. Here, the angle of incidence α to the area of ​​the road surface 96 is the angle that the direction of propagation of the illumination light makes with respect to the vertical direction DN. In the illustrated example, the vertical direction DN is parallel to the third direction D3 which is perpendicular to both the first direction D1 and the second direction D2. In the illustrated example, the vertical direction DN is perpendicular to the road surface 95 and parallel to it.

[0066] In this lighting device 30, the diffractive optical element 50 adjusts the optical path of the coherent light. The optical path adjustment function of the diffractive optical element 50 is highly accurate. Therefore, the optical path of the coherent light can be adjusted by the diffractive optical element 50 toward the illuminated area 96 of a desired shape. As a result, the illuminated area 96 can be set even at positions far away from the lighting device 30, or at positions where the incident angle α of the coherent light becomes large, without being strongly constrained by the relative position to the lighting device 30. In other words, the degree of freedom in setting the line display 90 and the road surface 95 can be greatly improved. As a result, coherent light can be irradiated onto the illuminated area 96 with high accuracy. The line display 90 can be accurately projected onto the road surface 95.

[0067] For example, a diffractive optical element 50 made of a computer-generated hologram can adjust the direction of propagation of coherent light incident from a certain direction with an accuracy of ±0.01° in angular space. By using such a diffractive optical element 50, it is possible to illuminate areas 96 located at a distance of 1 m to 120 m from the diffractive optical element 50, or areas 96 where the incident angle α of coherent light onto the illuminated area 96 is at least 30° and at most 89.99°, with high precision. Therefore, the illumination device 30 can irradiate areas 96 located on the road surface 95 with high precision coherent light. As a result, the edges of the line display 90 can be made clear, and the operator can observe the line display 90 located at a distance.

[0068] Figure 4 shows a specific configuration example of the lighting device 30. The lighting device 30 shown in Figure 4 is portable. That is, the lighting device 30 shown in Figure 4 can be carried by an operator without the use of special means. The lighting device 30 has a casing 70. In the lighting device 30 shown in Figure 4, the light source 40, the shaping optical system 45, and the diffractive optical element 50 are fixed to the casing 70. In normal use, the light source 40, the shaping optical system 45, and the diffractive optical element 50 are not intended to be removed from the casing 70. The light source 40, the shaping optical system 45, and the diffractive optical element 50 are not removable from the casing 70. This maintains the relative positions of the light source 40, the shaping optical system 45, and the diffractive optical element 50. This allows for high-precision and stable projection of the line display 90 onto a position on the road surface 95 that is in a predetermined relative positional relationship with the lighting device 30. Furthermore, it suppresses displacement of the light source 40, the shaping optical system 45, and the diffractive optical element 50 from their predetermined positions, thereby improving laser safety.

[0069] In the example shown in Figure 4, the shaping optical system 45 includes a first lens 46, a second lens 47, and a third lens 48. The casing 70 includes a cylindrical portion 71 that holds the light source 40 and the shaping optical system 45, and a lid portion 72 fixed to the cylindrical portion 71. The cylindrical portion 71 is a cylinder with one end closed. The light source 40 is fixed to the closed end of the cylindrical portion 71. The internal dimensions of the cylindrical portion 71 change via stepped portions 71a. The internal diameter increases from the upstream side to the downstream side along the optical path of the coherent light emitted from the light source 40. The first lens 46 and the second lens 47 are mounted on each of the two stepped portions 71a. A spacing ring 73 is provided inside the cylindrical portion 71 that allows for high-precision control of the distance between the lenses. The spacing ring 73 is positioned between the first lens 46 and the second lens 47. The spacing ring 73 is positioned between the second lens 47 and the third lens 48. Furthermore, a spacing ring 73 is positioned between the lid portion 72 and the third lens 48. The spacing ring 73 suppresses relative positional displacement of each lens due to vibrations and shocks applied to the lighting device 30. The spacing ring 73 may be, for example, an annular or cylindrical member. The spacing ring 73 may be made of a metal such as aluminum, or of resin. The resin may be mixed with an inorganic material such as glass fiber to reduce its thermal expansion coefficient. The spacing ring 73 suppresses the shift in the parallelism of the collimated light caused by vibrations and shocks applied to the lighting device 30. In other words, it is possible to suppress blurring of the line markings 90 on the road surface 95. This makes it possible to maintain high visibility of the line markings 90.

[0070] In order to maintain a constant relative position of the light source 40, the shaping optical system 45, and the diffractive optical element 50, the light source 40, the shaping optical system 45, and the diffractive optical element 50 may be fixed to the casing 70 by fixing with adhesive, in combination with fixing by fitting.

[0071] To make fine adjustments to the relative positions of the light source 40, the shaping optical system 45, and the diffractive optical element 50, for example, spacers may be used. Thin metal plate-like materials may be used as spacers. Spacers may be used in combination with spacing rings 73 or adhesives.

[0072] Furthermore, components such as the light source 40, the shaping optical system 45, and the diffractive optical element 50 may be held by a position adjustment holder that allows for fine adjustment of their arrangement. The position adjustment holder may allow for fine adjustment of the position of the components by operating an adjustment part such as a screw. The components may be fixed to the casing 70 via the position adjustment holder. When using a position adjustment holder, the adjustment part such as a screw may be fixed with adhesive or the like after the adjustment of the position of the components is complete. In addition, the position adjustment holder may be used in combination with the spacing ring 73 described above and other members for maintaining the relative positions of the finely adjusted components.

[0073] The casing 70 may be made non-disassemblable, thereby maintaining the relative positions of components such as the light source 40, the shaping optical system 45, and the diffractive optical element 50. For example, the relative positions of components positioned by the manufacturer of the lighting device 30 may be maintained. For example, adhesive may be applied to the screw fastening or fitting parts of the casing 70 to make it non-disassemblable.

[0074] In the example shown in Figure 4, the lighting device 30 includes a battery 74, a circuit 75, and a switch 76. The battery 74 may be a primary battery or a rechargeable secondary battery. The circuit 75 is electrically connected to the battery 74 and the switch 76. When the switch 76 is operated, the circuit 75 switches between supplying power from the battery 74 to the light source 40 and stopping the power supply.

[0075] The lighting device 30 may be powered by an external power source. For example, a connector for electrically connecting to an external power source may be provided in the casing. In this example, the lighting device 30 may or may not include a primary battery or a secondary battery. A lighting device 30 that does not include a primary battery or a secondary battery is lighter and therefore has superior resistance to vibration and shock.

[0076] The lighting device 30 and the casing 70 may be waterproof. To provide waterproofing to the lighting device 30, waterproofing materials such as rubber or gaskets may be provided at the joints and fitting portions of the casing 70.

[0077] The lighting device 30 may have a temperature control mechanism. The temperature control mechanism may maintain the light source 40 and the circuit 75 at a temperature within a predetermined range. The temperature control mechanism may heat or cool the light source 40 and the circuit 75. The temperature control mechanism may be installed inside the casing 70. Examples of temperature control mechanisms include fans, heaters, and coolers. A heating element or Peltier element may also be used as the temperature control mechanism.

[0078] The lighting device 30 of this embodiment is installed on the road surface 95 such that its positional relationship with the road surface 95 and the line display 90 is as described below. Figure 5 is a plan view showing the road display device 10 of this embodiment as observed from the vertical direction DN. In Figure 5, and in Figures 6 to 8 and 11 described later, the holder 60 is not shown. The light ray emitted from the lighting device 30 and reaching the first end 90a, as shown in Figures 1 and 5, is called the first light ray L1. The first light ray L1 is, in particular, a light ray emitted from the light-emitting surface 31 of the lighting device 30, which is the surface that emits light, and reaching the first end 90a. Furthermore, consider the imaginary line segment L3 shown in Figure 5, which extends from the first end 90a to the first side S11 along the first direction D1. When observed from the vertical direction DN, the angle Φ1 between the first light ray L1 and the imaginary line segment L3 is less than 90°. In particular, angle Φ1 is defined as the angle between the first ray L1 that makes the largest angle with the imaginary line segment L3 when observed from the vertical direction DN, and the imaginary line segment L3. Angle Φ1 may be less than 60° or less than 45°. In this embodiment, angle Φ1 is greater than 0°.

[0079] Figure 6 is a side view showing the road display device 10 of this embodiment as observed from a second direction D2. The second direction D2 is perpendicular to the first direction D1 and perpendicular to the vertical direction DN. When observed from the second direction D2, the angle θ1 between the first ray L1 and the perpendicular L4 to the road surface 95 is greater than 0° and less than or equal to 83.15°. In particular, the angle θ1 is defined as the angle between the ray that makes the largest angle with the perpendicular L4 among the first rays L1 when observed from the second direction D2, and the perpendicular L4.

[0080] Let us consider the angle θ2 between the first ray L1 and the perpendicular L4 to the road surface 95, as shown in Figure 1. The angle θ2 is determined from the three-dimensional positional relationship between the first ray L1 and the perpendicular L4. The angle θ2 may be greater than 0° and less than or equal to 83.15°. In particular, the angle θ2 is defined as the angle between the ray that makes the largest angle with the perpendicular L4 among the first rays L1, and the perpendicular L4, in a three-dimensional observation. "Three-dimensional observation" means determining the angle θ2 based on the positional relationship between the first ray L1 and the perpendicular L4 in three-dimensional space, rather than determining the angle θ2 based on the two-dimensional observation results observed when the road display device 10 is observed from a specific direction, such as the "observation from the second direction D2" described above.

[0081] As shown in Figures 1, 5, and 6, the light rays emitted from the lighting device 30 and reaching the first end 90c in the road direction are referred to as the second light rays L2. The second light rays L2 are, in particular, light rays emitted from the light-emitting surface 31 of the lighting device 30, which is the surface that emits light, and reaching the first end 90c in the road direction. In this embodiment, as described above, the position of the lighting device 30 with respect to the road surface 95 is determined such that the first direction D1 of the line indicator 90 is aligned with the road direction DR. Furthermore, the position of the lighting device 30 with respect to the road surface 95 is determined such that the first end 90a of the line indicator 90 faces the first side SR1 of the road in the road direction DR, and the second end 90b of the line indicator 90 faces the second side SR2 of the road in the road direction DR. For this reason, the first end 90a becomes the first end 90c in the road direction, and the first light ray L1 becomes the second light ray L2. In observations from the vertical direction DN, the angle Φ2 between the second ray L2 and the imaginary line segment L3 is less than 90°. In particular, angle Φ2 is defined as the angle between the ray of the second ray L2 that makes the largest angle with the imaginary line segment L3 in observations from the vertical direction DN, and the imaginary line segment L3. In the example shown in Figure 5, angle Φ2 coincides with angle Φ1.

[0082] The direction perpendicular to the road direction DR and perpendicular to the vertical direction DN is referred to as the width direction DW. In this embodiment, the width direction DW is parallel to the second direction D2. Therefore, Figure 6 corresponds to a side view showing the road display device 10 of this embodiment as observed from the width direction DW. When observed from the width direction DW, the angle θ3 between the second ray L2 and the perpendicular L4 to the road surface 95 is greater than 0° and less than or equal to 83.15°. In particular, the angle θ3 is defined as the angle between the ray of the second ray L2 that makes the largest angle with the perpendicular L4 when observed from the width direction DW and the perpendicular L4. In the example shown in Figure 6, the angle θ3 coincides with the angle θ1.

[0083] Let's consider the angle θ4 between the second ray L2 and the perpendicular L4 to the road surface 95, as shown in Figure 1. Angle θ4 is determined from the three-dimensional positional relationship between the second ray L2 and the perpendicular L4. Angle θ4 may be greater than 0° and less than or equal to 83.15°. In particular, angle θ4 is determined as the angle between the ray of the second ray L2 that makes the largest angle with the perpendicular L4 in a three-dimensional observation, and the perpendicular L4. In the example shown in Figure 1, angle θ4 coincides with angle θ2.

[0084] The road display device 10 of this embodiment further comprises a holder 60. The holder 60 holds the lighting device 30 so as to fix the position of the lighting device 30 with respect to the road surface 95. The form of the holder 60 is not particularly limited as long as the lighting device 30 can be installed with respect to the road surface 95 such that the positional relationship between the lighting device 30 and the road surface 95 is as described above. The holder 60 may be a device installed on the road surface 95. The holder 60 may be a device installed on the ground surface near the road surface 95. The holder 60 may be a device attached to a structure installed on the road surface 95 or on the ground surface near the road surface 95. The holder 60 may be a device attached to a structure or house with a pole, such as a utility pole or sign, installed on the road surface 95 or on the ground surface near the road surface 95. In the example shown in Figure 1, the holder 60 is a columnar device installed on the ground surface near the road surface 95.

[0085] A method for installing the road display device 10 of this embodiment on the road surface 95 of the road 94 will now be described. The installation method for installing the road display device 10 includes an installation step for installing the road display device 10. In the installation step, the road display device 10 is installed so that the first direction D1 of the display (line display 90) is aligned with the road direction DR. In the installation step, the road display device 10 is installed so that the first end 90a of the display (line display 90) faces the first side SR1 of the road. Furthermore, in the installation step, the road display device 10 is installed so that the angle Φ1 described above is less than 90°. In the installation step, the road display device 10 may be installed so that the positional relationship between the lighting device 30 and the road surface 95 is as described above.

[0086] A projection method for projecting a display (line display 90) onto the road surface 95 of a road 94 using the road display device 10 of this embodiment will be described. The projection method for projecting a display (line display 90) using the road display device 10 comprises a projection step of projecting the display (line display 90). In the projection step, the display (line display 90) is projected such that the first direction D1 of the display (line display 90) is aligned with the road direction DR. In the projection step, the display (line display 90) is projected such that the first end 90a of the display (line display 90) faces the first side SR1 of the road. Furthermore, in the projection step, the display (line display 90) is projected such that the angle Φ1 described above is less than 90°. In the projection step, the display (line display 90) may be projected such that the positional relationship between the lighting device 30 and the display (line display 90) is as described above.

[0087] The effects and advantages of the road display device 10 of this embodiment, the installation method for the road display device 10, and the projection method for projecting a display (line display 90) using the road display device 10 will be described below.

[0088] First, let's explain the effects of an angle Φ2 being less than 90°. Let's consider the case where the angle Φ2 is 90° or greater. In this case, as shown in Figure 7, it is conceivable to install the lighting device 30 between the first end 90c and the second end 90d in the road direction DR. However, in this case, the angle β formed by the straight line L5 connecting the light-emitting surface 31 of the lighting device 30 and the first end 90c in the road direction, and the straight line L6 connecting the light-emitting surface 31 of the lighting device 30 and the second end 90d in the road direction, becomes larger. That is, in order to project the line display 90, it becomes necessary to make the lighting device 30 wider angle. In this case, it becomes difficult to ensure sufficient illuminance over the entire illuminated area 96 while making the lighting device 30 wide angle. In particular, when the length of the line display 90 in the road direction DR is increased, the angle β tends to become larger, making it difficult to install the lighting device 30 between the first end 90c and the second end 90d in the road direction DR. When the length of the line display 90 in the road direction DR is increased while the angle β is reduced, it becomes necessary to install the lighting device 30 at a higher position. This makes it difficult to install the lighting device 30. Furthermore, when the lighting device 30 is installed between the first end 90c and the second end 90d in the road direction DR, as shown in Figure 7, light LB directed toward the first road side SR1 and light LC directed toward the second road side SR2 are generated. As will be described later, the road surface 95 may have irregularities 97 including protrusions 97a and recesses 97b. If the road surface 95 has irregularities 97, a shadow area 98 may be formed on the road side SR1 of the protrusions 97a that is not illuminated by light from the lighting device 30, around the area of ​​the road surface 95 that is illuminated by light LB directed toward the first road side SR1. In this case, the observer 5 of the line marking 90, who is the occupant of the moving body 51 moving along the road surface 95 from the first road side SR1 to the second road side SR2, can perceive the shadowed area 98 as a gap in the line marking 90. In particular, the observer 5 may perceive the shadowed area 98 as a break in the line marking 90 and not perceive the line marking 90 as a continuous line.

[0089] Next, as another example when the angle Φ2 is 90° or more, as shown in Figure 8, the lighting device 30 can be installed on the SR2 on the second side of the road, rather than the second end 90d in the road direction. However, even in this case, the following problems may arise. The road surface 95 may have irregularities 97 including convex portions 97a and concave portions 97b, as shown in Figure 8. The irregularities 97 of the road surface 95 are formed, for example, by snow accumulated on the road surface 95 during snowfall. The irregularities 97 of the road surface 95 may also be formed by remaining snow, gravel, curbs, road surface inclines, obstacles on the road surface 95, etc. If the road surface 95 has irregularities 97, a shadow area 98 is formed on the SR1 on the first side of the road of the convex portion 97a, where light from the lighting device 30 is not irradiated. In this case, the observer 5 of the line marking 90, who is the occupant of the moving body 51 moving along the road surface 95 from the first road side SR1 to the second road side SR2, can perceive the shadowed area 98 as a gap in the line marking 90. In particular, the observer 5 may perceive the shadowed area 98 as a break in the line marking 90 and not perceive the line marking 90 as a continuous line.

[0090] In contrast, because the angle Φ2 is less than 90°, as shown in Figures 5 and 6, the lighting device 30 is installed on the first road side SR1 rather than the first road end 90c. In this case, the shadow area 98 is formed on the second road side SR2 of the protrusion 97a. Such a shadow area 98 is difficult to see for the observer 5 of the line display 90, who is the occupant of the moving body 51 moving on the road surface 95 from the first road side SR1 to the second road side SR2. Therefore, because the angle Φ2 is less than 90°, it is possible to project a line display 90 in which the gaps caused by the shadow area 98 are not easily visible. In particular, it is possible to project a line display 90 in which the gaps caused by the shadow area 98 are not easily visible. Furthermore, it becomes unnecessary to make the lighting device 30 wide-angle, making it easier to secure a large illuminance over the entire illuminated area 96. In particular, even when the length of the line display 90 in the road direction DR is large, for example, when the length is 8m or more, it becomes easier to secure a large illuminance over the entire illuminated area 96. Furthermore, by using a lighting device 30 in which the angle Φ2 is less than 90° and which has a light source 40 that emits the aforementioned coherent light and a diffractive optical element 50 that diffracts the coherent light, a large amount of illuminance can be secured over the entire illuminated area 96. In particular, a large amount of illuminance can be secured over the entire illuminated area 96 while keeping the height of the lighting device 30 from the road surface 95 low.

[0091] The above explanation of the effects and benefits can also be applied when the display projected by the lighting device 30 onto the road surface 95 of the road 94 is not a line display 90. That is, if the angle Φ2 is less than 90°, a display can be projected that is less likely to be visible as having a gap.

[0092] Furthermore, by positioning the lighting device 30 such that the first direction D1 of the line marking 90 is aligned with the road direction DR and the first end 90a of the line marking 90 faces the first side SR1 of the road, the angle Φ2 can be made smaller than 90°. This allows for the projection of a line marking 90 in which gaps, especially breaks, are less visible. In other words, by positioning the angle Φ1 smaller than 90°, a line marking 90 in which breaks are less visible can be projected to an observer 5 who is a passenger on a moving body 51 moving along the road surface 95 from the first side S11 to the second side S12.

[0093] In particular, because the angle Φ1 is less than 45°, a shadow area 98 that can be seen by the observer 5 is less likely to form laterally in the second direction D2 of the protrusion 97a. As a result, a line display 90 that is less likely to be seen as having a break by the observer 5 can be projected.

[0094] The above explanation of the effects and benefits also applies when the display projected by the lighting device 30 onto the road surface 95 of the road 94 is not a line display 90. That is, if the angle Φ1 is less than 90°, a display that is less likely to be seen as having a gap can be projected. In particular, if the angle Φ1 is less than 45°, a display that is even less likely to be seen as having a gap by the observer 5 can be projected.

[0095] Next, we will explain the effects of the angle θ3 being greater than 0° and less than or equal to 83.15°.

[0096] When the angle θ3 is 0°, the lighting device 30 will be installed at the position of the first end 90c in the road direction DR. In this case, as shown in Figure 7 and described above, when the lighting device 30 is installed between the first end 90c and the second end 90d in the road direction DR, it becomes necessary to make the lighting device 30 wider angle. In this case, it becomes difficult to ensure a large illuminance over the entire illuminated area 96 while making the lighting device 30 wide angle. In contrast, when the angle θ3 is greater than 0°, it becomes unnecessary to make the lighting device 30 wide angle, and it becomes easier to ensure a large illuminance over the entire illuminated area 96. In particular, it is possible to ensure a large illuminance over the entire illuminated area 96 while keeping the height of the lighting device 30 from the road surface 95 low.

[0097] The effects of having an angle θ3 of 83.15° or less will be explained. Consider the case where the shadow region 98 is formed on the second road side SR2 of the protrusion 97a as shown in Figure 6, and the driver of the mobile body 51 is instructed to drive while referring to the line markings 90. In this case, for the driver to drive while referring to the line markings 90, it is important that the driver can recognize the line markings 90 as a line when the first road-direction end 90c comes into the driver's field of view.

[0098] When the observer is positioned on the first road side SR1 relative to the first road-direction end 90c of the line display 90, the higher the observer's viewpoint, the easier it is for the observer to see the shadow area 98 formed on the second road-side SR2 of the protrusion 97a. In addition, the closer the observer's viewpoint is to the first road-direction end 90c in the road-direction DR, the easier it is for the observer to see the shadow area 98 generated on the second road-side SR2 of the protrusion 97a.

[0099] The height from the road surface 95 of the viewpoint of a vehicle driver, for example, is typically 2.4m or less. Furthermore, a vehicle driver, for example, does not normally drive the vehicle while looking directly below it. The driver of the vehicle usually drives with an area of ​​vision at least 20m ahead of the vehicle.

[0100] Therefore, in order for the driver to recognize the line marking 90 as a line when the first end 90c in the direction of the road enters the driver's field of view of the moving body 51, the shadow area 98 should not be visible to the driver when the driver's viewpoint is at a height of 2.4 m above the road surface 95 and located 20 m on the first side SR1 of the road from the first end 90c in the direction of the road. To achieve this, the following conditions must be met. Consider the angle θ5 between the driver's line of sight L7 and the perpendicular L4 to the road surface 95 when the driver observes the first end 90c in the direction of the road from a viewpoint that is at a height of 2.4 m above the road surface 95 and located 20 m on the first side SR1 of the road from the first end 90c in the direction of the road. In this case, if angle θ3 is less than or equal to angle θ5, the shadow area 98 will not be visible to the driver.

[0101] The angle θ5 is calculated to be approximately 83.15°. Therefore, by setting the angle θ3 to 83.15° or less, the angle θ3 can be made to be less than or equal to the angle θ5. This allows the driver of the mobile vehicle 51 to recognize the line display 90 as a line when the first end 90c in the direction of the road comes into the driver's field of vision. As a result, the driver of the mobile vehicle 51 can be made to drive while referring to the line display 90.

[0102] The above explanation of the effects and benefits can be partially applied even when the display projected by the lighting device 30 onto the road surface 95 of the road 94 is not a line display 90. That is, if the angle θ3 is greater than 0° and 83.15° or less, the shadow area 98 becomes less visible to the driver, and a display with no visible gaps can be projected.

[0103] Furthermore, the angle θ2 determined from the three-dimensional positional relationship between the first ray L1 and the perpendicular L4 is greater than 0° and less than or equal to 83.15°, which provides the following effect: The shadow region 98 is less likely to form laterally in the width direction DW of the protrusion 97a. This makes it easier for the driver of the moving body 51 to recognize the line display 90 as a line.

[0104] The above explanation of the effects and benefits can be partially applied even when the display projected by the lighting device 30 onto the road surface 95 of the road 94 is not a line display 90. That is, if the angle θ2 is greater than 0° and 83.15° or less, the shadow area 98 becomes less visible to the driver, and a display with fewer visible gaps can be projected.

[0105] Furthermore, by positioning the lighting device 30 such that the first direction D1 of the line indicator 90 is aligned with the road direction DR and the first end 90a of the line indicator 90 faces the first road side SR1, the angle θ3 becomes greater than 0° and 83.15° or less. In other words, by positioning the lighting device 30 such that the angle θ1 is greater than 0° and 83.15° or less, the driver of the mobile vehicle 51 can operate the vehicle while referring to the line indicator 90.

[0106] The above explanation of the effects and benefits can be partially applied even when the display projected by the lighting device 30 onto the road surface 95 of the road 94 is not a line display 90. That is, if the angle θ1 is greater than 0° and 83.15° or less, the shadow area 98 becomes less visible to the driver, and a display with no visible gaps can be projected.

[0107] Furthermore, the angle θ4 determined from the three-dimensional positional relationship between the second ray L2 and the perpendicular L4 is greater than 0° and less than or equal to 83.15°, which provides the following effect: The shadow region 98 is less likely to form laterally in the second direction D2 of the convex portion 97a. This makes it easier for the driver of the moving body 51 to recognize the line display 90 as a line.

[0108] The above explanation of the effects and benefits can be partially applied even when the display projected by the lighting device 30 onto the road surface 95 of the road 94 is not a line display 90. That is, if the angle θ4 is greater than 0° and 83.15° or less, the shadow area 98 becomes less visible to the driver, and a display that is less likely to be seen by the driver can be projected.

[0109] The road display device 10 of this embodiment is a road display device 10 that includes an illumination device 30 that irradiates light onto the road surface 95 to project a display having a width at least in a first direction D1. The display has a first end 90a located at the first side S11 in the first direction D1. When observed from the vertical direction DN, the angle Φ1 between the first ray L1 emitted from the illumination device 30 and reaching the first end 90a and a virtual line segment L3 extending from the first end 90a to the first side S11 along the first direction D1 is less than 90°. When observed from a second direction D2 which is perpendicular to the first direction D1 and perpendicular to the vertical direction DN, the angle θ1 between the first ray L1 and the perpendicular L4 to the road surface 95 is greater than 0° and less than or equal to 83.15°. The display may also be a line display 90 extending in the first direction D1.

[0110] The length of the line marker 90 in the first direction D1 is, for example, 8 m or more. The effect of this will be explained. Figure 9 is a diagram showing an example of how the line marker 90 and the driver of the mobile body 51, who is the observer 5 of the line marker 90, are observed from the second direction D2.

[0111] The greater the length of the line display 90 visible to the driver of the mobile body 51 in the first direction D1, the easier it is for the driver to recognize the line display 90 as a line extending in the first direction D1. The lower the driver's viewpoint of the mobile body 51, the smaller the length of the line display 90 visible to the driver in the first direction D1 tends to be. On the other hand, the height of the driver's viewpoint from the road surface 95 of a vehicle, for example, a car, is usually 1.2m or more. In order for the driver to recognize the line display 90 as a line when the first end 90c in the road direction comes into the driver's field of view of the mobile body 51, the length of the line display 90 visible to the driver in the first direction D1 should be sufficiently large when the driver's viewpoint is 1.2m above the road surface 95 and 20m from the first side SR1 of the road relative to the first end 90c in the road direction. Thus, by ensuring that the length of the line display 90 visible to the driver in the first direction D1 is sufficiently large, the driver can perceive the line display 90 as a line extending in the first direction D1. To ensure that the length of the line display 90 visible to the driver in the first direction D1 is sufficiently large, the viewing angle θ6 of the line display 90 projected onto the driver's eye when observed from the second direction D2, as shown in Figure 9, should be 1° or more. The inventors of this invention have found through calculations that when the driver's viewpoint is at a height of 1.2m above the road surface 95 and located 20m from the first end 90c in the road direction on the first side SR1 of the road, the viewing angle θ6 can be made 1° or more if the length of the line display 90 in the first direction D1 is 8m or more. Therefore, by making the length of the line display 90 in the first direction D1 8m or more, the viewing angle θ6 can be sufficiently large, making the length of the line display 90 visible to the driver in the first direction D1 sufficiently large, and allowing the driver to perceive the line display 90 as a line.

[0112] When the above conditions are met, a display (line display 90) with imperfections that are difficult to see can be projected. In particular, the driver of a moving object 51 traveling on the road surface 95 can recognize the line display 90 as a line. Furthermore, even when the length of the line display 90 in the first direction D1 is large, for example, when the length is 8 m or more, it becomes easier to ensure a high level of illumination across the entire illuminated area 96.

[0113] The length of the line indicator 90 in the second direction D2 is 105 mm or less. The effect of this will be explained. Figure 10 is a diagram showing an example of how the line indicator 90 and the driver of the moving body 51, who is the observer of the line indicator 90, are observed from the third direction D3. The straight line L8 shown in Figure 10 is a hypothetical straight line that passes through the center of the line indicator 90 in the second direction D2 and extends along the first direction D1.

[0114] The smaller the width of the line display 90 visible to the driver of the moving object 51 (length in the second direction D2), the larger the ratio of the length of the line display 90 in the first direction D1 to the length of the line display 90 in the second direction D2. Therefore, the smaller the length of the line display 90 in the second direction D2, the easier it is for the driver to perceive the line display 90 as a line extending in the first direction D1. On the other hand, when the position of the driver's viewpoint in the second direction D2 is changed, the width of the line display 90 visible to the driver increases as it approaches the straight line L8. The width of the line display 90 visible to the driver is maximized when the driver's viewpoint is located on the straight line L8. When the first end 90c in the road direction comes into the driver's field of view of the moving body 51, in order for the driver to recognize the line display 90 as a line extending in the first direction D1, the width of the line display 90 visible to the driver should be sufficiently small when the driver's viewpoint is located on the straight line L8 and 20 m from the first end 90c in the road direction to the first side SR1 of the road. To make the width of the line display 90 visible to the driver sufficiently small, the viewing angle θ7 of the line display 90 projected to the driver's eye when observed from the third direction D3, as shown in Figure 10, should be 0.3° or less. The inventors of this invention have found through calculations that when the driver's viewpoint is located on the straight line L8 and 20 m from the first end 90c in the road direction to the first side SR1 of the road, the viewing angle θ7 can be made 0.3° or less if the length of the line display 90 in the second direction D2 is 105 mm or less. Based on the above, by making the length of the line display 90 in the second direction D2 105 mm or less, the viewing angle θ7 is made sufficiently small, the length of the line display 90 visible to the driver in the second direction D2 is made sufficiently small, and the driver can recognize the line display 90 as a line.

[0115] In the road display device 10 of this embodiment, the angle θ2 between the first light ray L1 and the perpendicular L4 to the road surface 95 is greater than 0° and 83.15° or less. This makes it easier for the driver of the mobile vehicle 51 to recognize the line display 90 as a line.

[0116] The road display device 10 of this embodiment further includes a holder 60 that holds the lighting device 30 so as to fix the position of the lighting device 30 relative to the road surface 95. This makes it possible to fix the position of the lighting device 30 relative to the road surface 95.

[0117] The road display device 10 of this embodiment is a road display device 10 that includes an illumination device 30 that extends in the road direction DR and illuminates the road surface 95 of a road 94, on which a moving body 51 travels from the first road side SR1 in the road direction DR to the second road side SR2 in the road direction DR, so as to project a display having a width of at least in the road direction DR. The display has a first road direction end 90c located at the first road side SR1 in the road direction DR. When observed from the vertical direction DN, the angle Φ2 between the second light ray L2 emitted from the illumination device 30 and reaching the first road direction end 90c and a virtual line segment L3 extending along the road direction DR from the first road direction end 90c to the first road side SR1 is less than 90°. The display may be a line display 90 extending in the road direction DR.

[0118] By satisfying the above conditions, it becomes possible to project a display (line display 90) in which the defects are less easily visible. Furthermore, even when the length of the line display 90 in the first direction D1 is large, it becomes easier to ensure a high level of illumination across the entire illuminated area 96.

[0119] In the road display device 10 of this embodiment, when observed from the width direction DW, which is perpendicular to the road direction DR and perpendicular to the vertical direction DN, the angle θ3 between the second ray L2 and the perpendicular L4 to the road surface 95 is greater than 0° and 83.15° or less. This allows the driver of a moving body 51 traveling on the road surface 95 to recognize the line display 90 as a line.

[0120] In the road display device 10 of this embodiment, the angle θ4 between the second light ray L2 and the perpendicular L4 to the road surface 95 is greater than 0° and 83.15° or less. This makes it easier for the driver of the mobile vehicle 51 to recognize the line display 90 as a line.

[0121] The installation method of this embodiment involves installing the road display device 10 on the road surface 95 of a road 94 that extends in the road direction DR, and on which a mobile body 51 moves from the first side SR1 of the road in the road direction DR to the second side SR2 of the road in the road direction DR. The road display device 10 includes an illumination device 30 that emits light to project a display having a width at least in the first direction D1. The display has a first end portion 90a located at the first side S11 in the first direction D1. The installation method includes an installation step. In the installation step, the road display device is installed such that the first direction D1 is along the road direction DR and the first end portion 90a of the display faces the first side SR1 of the road. In the installation process, the road display device 10 is installed such that, when observed from the vertical direction DN, the angle Φ1 between the first ray L1 emitted from the lighting device 30 and reaching the first end 90a and a virtual line segment L3 extending from the first end 90a to the first side S11 along the first direction D1 is less than 90°. The display may be a line display 90 extending in the first direction D1.

[0122] The installation method described above allows the angle Φ2 to be smaller than 90°. This makes it possible to project a display (line display 90) where the imperfections are less noticeable.

[0123] The projection method of this embodiment is a projection method that uses a road display device 10 to project a display having a width at least in the first direction D1 onto the road surface 95 of a road 94 that extends in the road direction DR, and on which a moving body 51 moves from the first side SR1 of the road in the road direction DR to the second side SR2 of the road in the road direction DR. The road display device 10 includes an illumination device 30 that irradiates light to project the display. The display has a first end portion 90a located at the first side S11 in the first direction D1. The projection method includes a projection step. In the projection step, the display is projected such that the first direction D1 is along the road direction DR and the first end portion 90a of the display faces the first side SR1 of the road. In the projection process, the display is projected such that, when observed from the vertical direction DN, the angle Φ1 between the first ray L1 emitted from the illumination device 30 and reaching the first end 90a, and a virtual line segment L3 extending from the first end 90a to the first side S11 along the first direction D1, is less than 90°. The display may be a line display 90 extending in the first direction D1.

[0124] The projection method described above allows the angle Φ2 to be made smaller than 90°. This makes it possible to project a display (line display 90) where the imperfections are less noticeable.

[0125] In the installation method of this embodiment, the road display device 10 may be installed in the installation step such that, when observed from a second direction D2 which is perpendicular to the first direction D1 and perpendicular to the vertical direction DN, the angle θ1 between the first ray L1 and the perpendicular L4 to the road surface 95 is greater than 0° and 83.15° or less. In the projection method of this embodiment, the display may be projected in the projection step such that, when observed from a second direction D2 which is perpendicular to the first direction D1 and perpendicular to the vertical direction DN, the angle θ1 between the first ray L1 and the perpendicular L4 to the road surface 95 is greater than 0° and 83.15° or less. By performing the installation and projection steps described above, a display that is difficult for drivers to see as having any defects can be projected.

[0126] In the installation method of this embodiment, the road display device 10 may be installed in the installation step such that the angle θ2 between the first light ray L1 and the perpendicular L4 to the road surface 95 is greater than 0° and 83.15° or less. In the projection method of this embodiment, the display may be projected in the projection step such that the angle θ2 between the first light ray L1 and the perpendicular L4 to the road surface 95 is greater than 0° and 83.15° or less. The above-described installation and projection steps make it possible to project a display that is less likely to be seen as having defects by drivers.

[0127] In the installation and projection methods of this embodiment, the length of the line display 90 in the first direction D1 may be 8 m or more. This allows the driver to recognize the line display 90 as a line.

[0128] In the installation and projection methods of this embodiment, the length of the line display 90 in the second direction D2, which is perpendicular to the first direction D1 and perpendicular to the vertical direction DN, may be 105 mm or less. This allows the driver to recognize the line display 90 as a line.

[0129] The effects of the road display device 10, installation method, and projection method of this embodiment have been described from the perspective of whether the driver of the mobile device 51 can recognize the line display 90 as a line, assuming that the mobile device 51 is a manned machine. However, even if the mobile device 51 is an unmanned machine and has a camera that photographs the road surface 95, the effects corresponding to those described above can be obtained. That is, the camera can be made to photograph the line display 90 as a line. In particular, when the height of the camera from the road surface 95 is less than or equal to the height of the driver's viewpoint in a typical automobile, the camera can be made to photograph the line display 90 as a line. That is, when the height of the camera from the road surface 95 is 2.4 m or less, the camera can be made to photograph the line display 90 as a line. Furthermore, when the height of the camera from the road surface 95 is 1.2 m or more, the length of the line display 90 photographed by the camera can be made sufficiently long.

[0130] The road display device 10, installation method, and projection method of this embodiment can also be used on the road surface 95 of a road 94 having multiple lanes. When the road display device 10, installation method, and projection method are used on the road surface 95 of a road 94 having multiple lanes, the display may be shown on the first lane (the lane closest to the edge of the road 94), or on the second lane, third lane, etc. The road display device 10, installation method, and projection method of this embodiment can be used not only outdoors but also on indoor road surfaces 95 such as tunnels.

[0131] Various modifications can be made to the embodiments described above. An example of such a modification will be described below with reference to the drawings. In the following description and the drawings used therein, parts that can be configured similarly to the specific examples described above will be given the same reference numerals as those used for the corresponding parts in those specific examples, and redundant explanations may be omitted. Furthermore, if it is clear that the effects and advantages obtained in the embodiments described above can also be obtained in the modified versions, the explanation may be omitted.

[0132] (Modification 1) In the above-described embodiment, a road display device 10 was described in which the lighting device 30 is held by a holder 60 that fixes the position of the lighting device 30 relative to the road surface 95. However, the form of the road display device 10 is not limited to this. Figure 11 is a side view showing the road display device 10 of Modification 1.

[0133] In the example shown in Figure 11, the lighting device 30 is held by a moving body 51 that moves along the road surface 95. In the example shown in Figure 11, the lighting device 30 and the road display device 10 equipped with the lighting device 30 move along the road surface 95 together with the moving body 51. Regardless of the position of the moving body 51 on the road surface 95, the road display device 10 projects a line display 90 onto the second road side SR2 (second side S12) of the moving body 51. Even with such a road display device 10, it is possible to project a display (line display 90) that is difficult to see due to gaps. Furthermore, even with such a road display device 10, the driver of the moving body 51 can be made to drive while referring to the display (line display 90).

[0134] The multiple components disclosed in the above embodiments and variations can be combined as needed. Alternatively, some components may be removed from all the components shown in the above embodiments and variations.

[0135] 10 Road display device 30 Lighting device 51 Mobile body 60 Holder 90 Line display 90a First end 90b Second end 90c First end in road direction 90d Second end in road direction 94 Road 95 Road surface

Claims

1. A road display device comprising an illumination device that emits light to project a display having a width in at least a first direction onto a road surface, wherein the display has a first end located on the first side in the first direction, and when viewed from a vertical direction, the angle Φ1 between a first ray emitted from the illumination device and reaching the first end and a virtual line segment extending from the first end to the first side along the first direction is less than 90°, and when viewed from a second direction that is perpendicular to the first direction and perpendicular to the vertical direction, the angle θ1 between the first ray and a perpendicular line to the road surface is greater than 0° and less than or equal to 83.15°.

2. The road display device according to claim 1, wherein the display is a line display extending in the first direction.

3. The road display device according to claim 1, wherein the angle Φ1 is greater than 0°.

4. The road display device according to claim 2, wherein the length of the line display in the first direction is 8 m or more.

5. The road display device according to claim 2, wherein the length of the line display in the second direction is 105 mm or less.

6. The road display device according to claim 1, wherein the angle θ2 between the first ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

7. The road display device according to claim 1, further comprising a holder for holding the lighting device so as to fix the position of the lighting device with respect to the road surface.

8. The road display device according to claim 1, wherein the lighting device is held by a moving body that moves along the road surface.

9. The road display device according to any one of claims 1 to 8, wherein the angle Φ1 is less than 45°.

10. A road display device comprising an illumination device that extends in the direction of the road and irradiates light onto the road surface of a road on which a moving body travels from a first side of the road in the direction of the road to a second side of the road in the direction of the road, wherein the display has a first end in the direction of the road located on the first side of the road in the direction of the road, and the angle Φ2 between a second ray emitted from the illumination device and reaching the first end in the direction of the road and a virtual line segment extending along the direction of the road from the first end in the direction of the road to the first side of the road is less than 90° when observed from a vertical direction.

11. The road display device according to claim 10, wherein the display is a line display extending in the direction of the road.

12. The road display device according to claim 10, wherein, when observed from the width direction which is perpendicular to the road direction and perpendicular to the vertical direction, the angle θ3 between the second ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

13. The road display device according to any one of claims 10 to 12, wherein the angle θ4 between the second ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

14. Installation method for installing a road display device on the road surface of a road that extends in the direction of the road and on which a moving body moves from a first side of the road in the direction of the road to a second side of the road in the direction of the road, wherein the road display device comprises an illumination device that emits light to project a display having width in at least in a first direction, the display has a first end located on the first side in the first direction, and the installation step comprises installing the road display device such that the first direction is along the direction of the road, the first end of the display faces the first side of the road, and when observed from a vertical direction, the angle Φ1 between a first ray emitted from the illumination device and reaching the first end and a virtual line segment extending from the first end to the first side along the first direction is less than 90°.

15. The installation method according to claim 14, wherein the display is a line display extending in the first direction.

16. The installation method according to claim 14, wherein in the installation step, the road display device is installed such that, when observed from a second direction which is perpendicular to the first direction and perpendicular to the vertical direction, the angle θ1 between the first light ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

17. The installation method according to claim 14, wherein in the installation step, the road display device is installed such that the angle θ2 between the first light ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

18. The installation method according to claim 15, wherein the length of the line display in the first direction is 8 m or more.

19. The installation method according to claim 15, wherein the length of the line display in a second direction that is perpendicular to the first direction and perpendicular to the vertical direction is 105 mm or less.

20. A projection method for projecting a display having a width in at least a first direction onto the road surface of a road that extends in the direction of the road and on which a moving body moves from a first side of the road in the direction of the road to a second side of the road in the direction of the road, the road display device comprising an illumination device that emits light to project the display, the display having a first end located on the first side in the first direction, the projection step comprising projecting the display such that the first direction is along the direction of the road, the first end of the display faces the first side of the road, and, when observed from a vertical direction, the angle Φ1 between a first ray emitted from the illumination device and reaching the first end and a virtual line segment extending from the first end to the first side along the first direction is less than 90°.

21. The projection method according to claim 20, wherein the display is a line display extending in the first direction.

22. The projection method according to claim 20, wherein, in the projection step, the display is projected such that, when observed from a second direction which is perpendicular to the first direction and perpendicular to the vertical direction, the angle θ1 between the first ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

23. The projection method according to claim 20, wherein in the projection step, the display is projected such that the angle θ2 between the first ray and the perpendicular to the road surface is greater than 0° and 83.15° or less.

24. The projection method according to claim 21, wherein the length of the line display in the first direction is 8 m or more.

25. The projection method according to claim 21, wherein the length of the line display in a second direction that is perpendicular to the first direction and perpendicular to the vertical direction is 105 mm or less.

Images