JP7744402B2 - display device - Google Patents

Description

This disclosure relates to a display device.

A display device has been proposed that includes a display unit in which multiple stacked display panels are arranged, each display panel displaying patterns such as pictures, letters, or symbols that are illuminated by light entering from the side (see, for example, Patent Document 1). Stacked panels are also called multi-layered panels. This display device is capable of displaying multiple display patterns on a transparent display unit by arranging multiple stacked display panels.

JP 2017-211498 A

However, with the above-mentioned conventional display devices, each independent display panel can only display one type of display pattern, which means the variety of display patterns that the display device can display is insufficient. Furthermore, in order to increase the number of display patterns, stacked display panels must be used, which results in a complex structure.

The objective of this disclosure is to provide a display device that can simplify its configuration and display a variety of display patterns on a transparent display panel.

The display device of the present disclosure is a device for displaying a display object, and includes a plurality of light sources that each emit light of a different wavelength, and a transparent display board, and is configured to have a plurality of display patterns, each of which has a different peak wavelength of scattered light, on at least one of the front and back surfaces of a single display board in order to display the display object in response to the light emitted by the light sources, and includes a display unit that, when the light source emits light that is scattered by the display pattern, puts the display pattern into a visible display state, and when the light source does not emit light that is scattered by the display pattern, puts the display pattern into a transparent non-display state; and and a lighting control circuit that controls the plurality of light sources to switch the wavelength of light entering the single display panel and independently switch between display and non-display of each of the plurality of display patterns, wherein the plurality of light sources include a light source that emits light of a first wavelength among the light of different wavelengths, the plurality of display patterns are formed by transparent ink containing multiple types of light scattering particles that have different peak wavelengths of scattered light, the light of the first wavelength is scattered more significantly by the first display pattern than by the second display pattern , and the display pattern has a plurality of divided tiny regions, and the wavelength of light scattered in adjacent regions of the plurality of regions is different .

The display device disclosed herein allows for a simplified configuration and is capable of displaying a variety of display patterns on a transparent display panel.

1 is a diagram schematically illustrating a configuration of a display device according to an embodiment. FIG. 2 is a perspective view schematically illustrating a configuration of the display device shown in FIG. 1 . 2 is a side view showing a display pattern of the display device shown in FIG. 1 and light traveling inside the display panel. FIG. 10 is a front view schematically showing another example of a display pattern of the display device according to the embodiment. 1 is a side view showing a display pattern of a display device according to an embodiment and light traveling inside a display panel. 1A and 1B are a front view and a side view, respectively, schematically illustrating the configuration of a display device according to a first embodiment. 1A and 1B are a front view and a side view schematically illustrating a configuration of a display device according to a first modification of the first embodiment. 10A and 10B are a front view and a side view, respectively, schematically illustrating the configuration of a display device according to a second modification of the first embodiment. 10A and 10B are a front view and a side view schematically illustrating a configuration of a display device according to a third modification of the first embodiment. 10A and 10B are a front view and a side view schematically illustrating a configuration of a display device according to a fourth modification of the first embodiment. 10A and 10B are a front view and a side view schematically illustrating a configuration of a display device according to a fifth modification of the first embodiment. 13A and 13B are front views schematically illustrating a configuration of a display device according to a sixth modification of the first embodiment. FIG. 13 is a front view including a partially enlarged view showing a display device according to a sixth modification of the first embodiment. 13A to 13C are diagrams showing examples of decoration of each display pattern according to a sixth modification of the first embodiment. 13A and 13B are diagrams showing examples of decoration of a plurality of display patterns according to a sixth modification of the first embodiment; FIG. 13 is a front view including another example of an enlarged partial view showing a display device according to the sixth modification of the first embodiment. 13A and 13B are front views schematically illustrating a configuration of a display device according to a seventh modification of the first embodiment. 13A, 13B, 13C, and 13D are perspective views schematically illustrating a configuration of a display device according to an eighth modification of the first embodiment. 10A and 10B are a front view and a side view schematically showing the configuration of a display device according to a second embodiment. 10A and 10B are a side view and a perspective view schematically showing the configuration of a display device according to a third embodiment. 10 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a third embodiment, and light rays. FIG. 10 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a third embodiment, and light rays. FIG. 13 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a first modification of the third embodiment, and light rays. FIG. 13 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a second modification of the third embodiment, and light rays. FIG. 13 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a second modification of the third embodiment, and light rays. FIG. 13A and 13B are a side view and a perspective view showing the structure of a light distribution control element and a display panel of a display device according to a third modification of the third embodiment, and light rays. FIG. 10 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a third modification of the third embodiment, and light rays. FIG. 10 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a third modification of the third embodiment, and light rays. FIG. 11 is a side view schematically showing the configuration of a light distribution control element and a display panel of a display device according to a fourth modification of the third embodiment. 13A and 13B are a side view and a perspective view showing the structure of a light distribution control element and a display panel of a display device according to a fifth modification of the third embodiment. FIG. 11 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a fifth modification of the third embodiment, and light rays. FIG. 11 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a fifth modification of the third embodiment, and light rays. FIG. 11 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a fifth modification of the third embodiment, and light rays. 13A and 13B are a side view and a perspective view showing the structure of a light distribution control element and a display panel of a display device according to a sixth modification of the third embodiment. FIG. 13 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a sixth modification of the third embodiment, and light rays. FIG. 13 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a sixth modification of the third embodiment, and light rays. FIG. 13 is a side view showing the structure of a light distribution control element and a display panel of a display device according to a sixth modification of the third embodiment, and light rays. 13A and 13B are a side view and a perspective view of a light distribution control element and a display panel of a display device according to a sixth modification of the third embodiment. 10A is a perspective view showing a part of the configuration of a display device according to a fourth embodiment, and FIG. 10B is a perspective view showing a schematic configuration of the display device according to the fourth embodiment. FIG. 10 is a side view schematically showing the configuration of a display device according to a fifth embodiment. FIG. 13 is a diagram schematically illustrating a configuration of a display device according to a sixth embodiment. FIG. 22 is a diagram schematically illustrating a configuration of a display device according to a first modification of the sixth embodiment. FIG. 22 is a diagram schematically illustrating a configuration of a display device according to a second modification of the sixth embodiment.

Display devices according to embodiments will be described below with reference to the drawings. The following embodiments are merely examples, and the embodiments can be combined and modified as appropriate.

The figure shows the coordinate axes of an XYZ Cartesian coordinate system. The X and Y axes are the horizontal and vertical (or vertical and horizontal) coordinate axes in the human field of vision when viewing the display device. The Z axis is the coordinate axis in the thickness direction of the display panel. In addition, the same symbols are used in the figure to designate identical or similar components.

Overview of the embodiment
Fig. 1 is a diagram schematically showing the configuration of a display device 100 according to an embodiment. Fig. 2 is a perspective view schematically showing the configuration of the display device 100 shown in Fig. 1. Fig. 3 is a side view schematically showing the configuration of the display device 100 shown in Fig. 1.

The display device 100 comprises a light source 10 and a display unit 40. The display unit 40 comprises a transparent display panel 20 that guides light, and a display object. The display object is, for example, a display pattern 30 or multiple display patterns (for example, as shown in Figure 6(a) below) that are interchangeably arranged on the display panel 20. The light source 10 is a light source that emits directional light. The display panel 20 is a rectangular plate-shaped member having a front surface 201 as a first surface, a back surface 202 as a second surface opposite the front surface 201 (i.e., rear surface) as a second surface, and four side surfaces 203 connecting these. However, the shape of the display panel 20 is not limited to the shape shown in the figure. The first surface may be the rear surface and the second surface may be the front surface.

When the lighting control circuit 90, which is a control device that controls the operation of the light source 10, turns on the light source 10, light L0 emitted from the light source 10 enters the interior of the display board 20, is guided, and exits the display board 20 via the display pattern 30, causing the display pattern 30 to enter a display state. In FIG. 3, the light L0 is scattered by the display pattern 30 provided on the back surface 202 of the display board 20 and exits the display board 20 from the front surface 201 of the display board 20. However, the front surface 201 and back surface 202 of the display board 20 may be reversed. The display state is a visible state in which a person can see the display pattern 30. The non-display state is a state in which the light source 10 is not lit, and the display pattern 30 is either invisible or barely visible to a person. In the non-display state, the display unit 40 is transparent.

The light source 10 includes, for example, one or more light-emitting elements. The multiple light-emitting elements may be arranged one-dimensionally, for example, in the X-axis direction. The light-emitting element is, for example, a solid-state light source. The solid-state light source is a directional light source. The solid-state light source is, for example, a semiconductor light source. The light-emitting element is, for example, a light-emitting diode (LED). The solid-state light source may be an organic electroluminescence light source or a laser diode. The solid-state light source may also have a structure that emits light by irradiating excitation light onto a phosphor coated on a flat surface. The light source may be a white light source that emits white light, a full-color light source that emits light of red (R), green (G), and blue (B), or a monochrome light source.

The display unit 40 includes, for example, a single display panel 20 and a display pattern 30. The display panel 20 is a member filled with a refractive material. The display panel 20 may be stacked, or multiple display panels 40 may be arranged horizontally, vertically, or in both directions when viewed from the front. Stacking is also referred to as multi-layering. The display panel 20 is a transparent member. In this application, "transparent" refers to the ability to transmit light, including being nearly transparent. The display panel 20 is made of a plastic such as acrylic. Examples of plastic that can be used include PMMA (polymethyl methacrylate) and PC (polycarbonate). The display panel 20 may also be made of glass. A display pattern 30 is provided on at least one of the front surface 201 and back surface 202 of the display panel 20. The display pattern 30 may be a single-color or multi-color pattern.

The light source 10 is disposed opposite the side surface 203 of the display board 20. However, if a structure that allows light to enter the interior of the display board 20 (described in embodiment 3 below) is adopted, the position of the light source 10 is not limited to the position shown in the figure. Light emitted from the light source 10 enters the side surface 203 of the display board 20 and is guided inside the display board 20.

When forming the display pattern 30 on the display board 20 (e.g., when decorating the display board 20), the display pattern 30 is printed by applying ink to at least one of an area on the front surface 201 of the display board 20 corresponding to the planned portion of the display pattern 30 (here, a rightward arrow mark) and an area on the back surface 202 of the display board 20 corresponding to the planned portion of the display pattern 30. The ink is, for example, a transparent ink. The transparent ink contains, for example, light-scattering particles. The printing method is, for example, silkscreen printing. When printing on the front surface 201 of the display board 20, the display pattern 30 is likely to become dirty or damaged, so it is preferable to print on the back surface 202 of the display board 20. Here, the front surface 201 of the display board 20 is the surface of the display board 20 that constitutes the display unit 40 and that faces a person observing the display unit 40.

The painted areas in the display pattern 30 are printed as a dot pattern, allowing the background to show through when the display is not lit, thereby increasing transparency.

The color intensity of the display pattern 30 can be adjusted by designing the dot diameter, pitch, or both. However, to increase resolution, it is desirable to make the pitch as small as possible. To make the color darker, simply increase the dot area per unit area. To make the color lighter, simply decrease the dot area per unit area.

4 is a front view schematically illustrating another configuration of the display pattern of the display device 101 according to the embodiment. FIG. 4 illustrates an example in which transparent ink is not applied to the area of the front surface 201 or back surface 202 of the display board 20 of the display unit 40a where the display pattern 30a is to be formed (here, a rightward arrow mark), but is applied to the background area other than this area (i.e., the peripheral area). Light guided through the interior of the display board 20 is scattered by light-scattering particles contained in the transparent ink. Some of the scattered light does not satisfy the total reflection condition at the boundary of the front surface 201 of the display board 20 and is emitted to the outside through the front surface 201 of the display board 20. The display pattern 30a is displayed according to the above principle. When the light source 10 is on, the viewer can see the display pattern 30a because the peripheral area of the display pattern 30a emits light. When the light source 10 is off, the peripheral area of the display pattern 30a cannot be seen, and as a result, the display pattern 30a cannot be seen.

Because transparent ink does not adhere well to glass, if transparent ink is used to form the display pattern 30a, it is preferable to use a plastic such as acrylic for the display panel 20.

Furthermore, if the light source 10 is a laser light source, speckles can be generated when the display pattern 30a is illuminated, further improving the visibility of the display pattern 30a.

As a method for decorating the display pattern on the display board 20, a method of applying prism processing to the portion of the back surface 202 of the display board 20 where the display pattern 30b is to be formed may be employed. Figure 5 is a side view schematically illustrating the display pattern 30b of the display device 102 according to an embodiment. Light guided through the interior of the display board 20 is reflected by the inclined portion (i.e., the prism-shaped portion) formed by prism processing on the back surface 202. A portion of the light reflected by the inclined portion does not satisfy the total reflection condition at the front surface 201 of the display board 20 (i.e., the boundary with air) and is emitted to the outside through the front surface 201 of the display board 20. The display state of the display pattern 30b is achieved by this principle. The display pattern 30b is visible when the light source 10 is on and is invisible when the light source 10 is off. Note that the number of elongated convex shapes extending in the X-axis direction formed by prism processing is not limited to the number shown. Furthermore, the shape of the processed display pattern 30b is not limited to a prism shape, and can be other structures that have a surface facing in a different direction from the surface on which the display pattern 30b is formed.

First Embodiment
6A and 6B are front and side views illustrating a schematic configuration of the display device 1 according to the first embodiment. The display unit 40c of the display device 1 includes two directional light sources 10c and 10d and two display patterns 30c and 30d provided on the display board 20 and configured to be independently display-controllable. The light sources 10c and 10d and the display patterns 30c and 30d are arranged in corresponding positions. Light L1 emitted from the light source 10c enters the interior of the display board 20 from the side surface 203, is guided, and exits from the front surface 201 of the display board 20 via the display pattern 30c, thereby displaying only the display pattern 30c. Light L2 emitted from the light source 10d enters the interior of the display board 20 from the side surface 203, is guided, and exits from the front surface 201 of the display board 20 via the display pattern 30d, thereby displaying only the display pattern 30d.

In other words, the display device 1 is provided with multiple display patterns provided on the front surface 201 or back surface 202 of the display board 20, and at least one light source corresponds to each display pattern. The multiple display patterns do not overlap with each other, for example, when the decorated areas of the display board 20 are viewed in the Y-axis direction. For example, on the surface of the display board 20 on which display pattern 30c is provided, light source 10c is arranged so that the area through which light is guided inside the display board 20 includes only the area on which display pattern 30c is provided (i.e., does not include the area decorated with display pattern 30d). For example, light source 10d is arranged on the surface of the display board 20 on which display pattern 30d is decorated so that the area through which light is guided inside the display board 20 includes only the area decorated with display pattern 30d (i.e., does not include the area decorated with display pattern 30c).

In order to reduce the distance between display patterns 30c and 30d on the display board 20, it is preferable to increase the directivity of light L1, L2 emitted from light sources 10c, 10d. The spread angle of light L1 emitted from light source 10c corresponding to display pattern 30c is preferably set narrow enough so that it does not enter the area of adjacent display pattern 30d. The spread angle of light L2 emitted from light source 10d corresponding to display pattern 30d is preferably set narrow enough so that it does not enter the area of adjacent display pattern 30c. To increase directivity, for example, laser light sources that emit highly directional laser light may be used as light sources 10c, 10d.

The display device 1 allows multiple display patterns to be displayed independently using a single display panel 20.

Furthermore, since multiple display patterns can be displayed using a single display panel 20, the structure of the display device 1 can be simplified.

Furthermore, by forming the multiple display patterns 30c and 30d by printing, there is no need to deform or process the display board 20.

The number of display patterns and light sources may be three or more.

First Modification of First Embodiment
7(a) and 7(b) are front and side views schematically illustrating the configuration of a display device 1a according to a first modification of the first embodiment. FIGS. 7(a) and 7(b) illustrate an example in which cylindrical lenses 50c and 50d are provided as optical elements between the light sources 10c and 10d and the display board 20. The cylindrical lenses 50c and 50d are, for example, lenses filled with a refractive material. The cylindrical lenses 50c and 50d have curvature only in the long-side direction (X-axis direction) of the side surface 203 of the display board 20. The cylindrical lenses 50c and 50d can narrow the spread angle of the light beams L1 and L2 emitted from the light sources 10c and 10d in the X-axis direction. Anamorphic aspherical lenses or rotationally symmetric lenses may also be used instead of the cylindrical lenses 50c and 50d.

The display device 1a can increase the directivity of light L1 and L2. Furthermore, light sources other than laser light sources can be used as light sources 10c and 10d. In all other respects, the display device 1a is the same as the display device 1 described above.

<<Modification 2 of First Embodiment>>
8(a) and 8(b) are front and side views schematically illustrating the configuration of a display device 1b according to Modification 2 of Embodiment 1. FIGS. 8(a) and 8(b) illustrate an example in which anamorphic lenses 50e and 50f are provided as optical elements between the light sources 10e and 10f and the display board 20. The anamorphic lenses 50e and 50f are, for example, lenses filled with a refractive material. The anamorphic lenses 50e and 50f have a curvature in the long-side direction (X-axis direction) of the side surface 203 of the display board 20 and also in the thickness direction (Z-axis direction) of the side surface 203 of the display board 20. The anamorphic lenses 50e and 50f can narrow the divergence angle of the light beams L1 and L2 emitted from the light sources 10e and 10f. The optical elements may be hollow reflectors, for example, as long as they focus light beams diverging at least in the long-side direction of the side surface of the display board 20.

Display device 1b can increase the directivity of light L1 and L2. Furthermore, light sources other than laser light sources can be used as light sources 10e and 10f. In all other respects, display device 1b is the same as display device 1 described above.

Third Modification of First Embodiment
9(a) and 9(b) are a front view and a side view schematically illustrating the configuration of a display device 1c according to Modification 3 of Embodiment 1. The display device 1c differs from the display device 1 shown in FIGS. 6(a) and 6(b) in that the light source 10g is arranged to face the side surface 204 opposite to the side surface 203. In all other respects, the display device 1c is the same as the display device 1 shown in FIGS. 6(a) and 6(b).

With display device 1c, light sources 10d and 10g can be positioned facing different sides 203 and 204 of the display board 20, increasing the degree of freedom in the installation position of light sources 10d and 10g. In all other respects, display device 1c is the same as display device 1 described above.

Fourth Modification of First Embodiment
6(a) and (b) to 9(a) and (b), examples have been described in which the directionality of light traveling inside the display board 20 is high, and as a result, the distance between two display patterns can be narrowed. In Variation 4 of Embodiment 1, a case will be described in which a boundary surface 23 that can change the traveling direction of light inside the display board 20 is provided between two display patterns 30c and 30d.

Figures 10(a) and 10(b) are a front view and a side view showing a schematic configuration of a display device 1d according to Variation 4 of Embodiment 1. The boundary surface 23 is formed of a material with a different refractive index from that of the display panel 20. The boundary surface 23 is, for example, a cavity that is a region with a low refractive index. Means for providing a boundary surface that changes the direction of travel of light in part of the gap may, for example, be to apply a reflective finish to the boundary surface. Alternatively, the boundary surface may be optically polished. Alternatively, the boundary surface may be subjected to a scattering finish. Alternatively, the boundary surface may be subjected to an absorption finish. By providing a region with a lower refractive index than the display panel 20, light is totally reflected at the boundary due to the difference in refractive index, preventing it from entering the region with the lower refractive index.

In the display device 1d, the display patterns 30h and 30i are separated by the boundary surface 23, so even if low-directivity light sources 10h and 10i are used, the display patterns 30h and 30i can be independently controlled.

If the boundary surface 23 between the areas of the display board 20 decorated with the display patterns 30h and 30i is formed as a hollow space, it is possible to reduce the weight of the display device 1d. Furthermore, in this case, it is possible to improve wind resistance against winds perpendicular to the display device. In all other respects, the display device 1d is the same as the display device 1 described above.

Fifth Modification of First Embodiment
11(a) and 11(b) are front and side views schematically illustrating the configuration of a display device 1e according to Variation 5 of Embodiment 1. Figures 11(a) and 11(b) show an example in which a display panel 20 is divided into four grid-like sections by boundary surfaces 23 and 24. If the arrangement of the light-emitting surfaces makes it difficult to achieve total reflection due to differences in refractive index at the boundary surfaces 23 and 24, the direction of travel of light rays is changed by performing any of the following processing on the boundary surfaces: reflection, scattering, or absorption.

In display device 1e, light sources 10h, 10i, 10j, and 10k irradiate light L1, L2, L3, and L4 onto display patterns 30h, 30i, 30j, and 30k, respectively. Display patterns 30h, 30i, 30j, and 30k are separated by boundary surfaces 23 and 24, so even if a light source with low directivity is used, it is possible to independently control the display of display patterns 30h, 30i, 30j, and 30k.

If the boundary surfaces 23 and 24 of the display panel 20 are formed as hollows, it is possible to reduce the weight of the display device 1e. In all other respects, the display device 1e is the same as the display device 1 described above.

Sixth Modification of First Embodiment
6(a) and 6(b) to 11(a) and 6(b) have been described above with reference to examples in which the positions of the display patterns are different in order to independently control the display of the plurality of display patterns on a single display board 20. However, the display of the plurality of display patterns may be independently controlled on a single display board 20 by varying the wavelength of light emitted from the light-emitting elements corresponding to the display patterns and entering the interior of the display board 20.

Figures 12(a) and (b) are front views schematically illustrating the configuration of a display device 1f according to Variation 6 of Embodiment 1. In Figures 12(a) and (b), the light source 10m emits multiple types of light with different wavelengths in order to independently control the display of multiple display patterns 30c, 30d on a single display board 20.

Furthermore, display patterns 30c and 30d are formed using transparent ink. The transparent ink contains multiple types of light-scattering particles that have different peak wavelengths of scattered light. In other words, the transparent ink used contains light-scattering particles that have wavelength selectivity in scattering light.

The wavelength range of light emitted from the light-emitting element corresponding to display pattern 30c (or 30d) and entering display board 20 overlaps with the wavelength range scattered by the transparent ink of the same display pattern 30c (or 30d) when white light enters display board 20.

The spectrum of light emitted from the light-emitting element corresponding to display pattern 30c (or 30d) and entering display board 20 is different from, and does not overlap with, the spectrum scattered by the clear ink when white light enters another non-corresponding display pattern 30d (or 30c). In other words, light emitted from the light-emitting element corresponding to display pattern 30c and entering display board 20 is scattered by display pattern 30c but not by display pattern 30d, and light emitted from the light-emitting element corresponding to display pattern 30d and entering display board 20 is scattered by display pattern 30d but not by display pattern 30c.

When there are two types of display patterns 30c, 30d, one of the display patterns 30c, 30d may be provided on the front surface 201 and the other on the back surface 202. In this way, when display patterns 30c, 30d are formed on both the front surface 201 and the back surface 202 of the display board 20, the output light from the light-emitting element corresponding to the display pattern on the back surface 202 may be greater than the output light from the light-emitting element corresponding to the display pattern on the front surface 201, so that the brightness of the display pattern on the front surface 201 and the brightness of the display pattern on the back surface 202 are equivalent.

Multiple display patterns 30c, 30d may be printed overlapping one another on the same surface. Figure 13 is a front view including a partially enlarged view of a display device 1f. In this case, as shown in the partially enlarged view of Figure 13, regions R1, R2, each partitioned sufficiently small relative to the size of the display pattern, may be printed in a staggered pattern. Figure 14 is a diagram showing an example of decoration for each display pattern 30c, 30d. Figure 15 is a diagram showing an example of decoration for multiple display patterns. Figure 16 is a front view including another partially enlarged view of a display device 1f. As shown in Figure 16, regions R1, R2 may be, for example, a grid of squares arranged so that adjacent regions are different colors. Regions R1, R2 may be a grid of rectangles, triangles, and circles arranged so that adjacent regions are different colors. Furthermore, in areas where multiple display patterns 30c, 30d overlap, the spectrum scattered by the transparent ink when white light enters may include all or part of the spectrum of light emitted from the light-emitting elements corresponding to the overlapping display patterns 30 and entering the display board 20. Furthermore, light emitted from light source 10m may enter from any of the side surfaces of the display board 20. However, the number of multiple display patterns is not limited to two, and three or more types may be used. In the case of three or more types, sufficiently small partitioned regions may be arranged. For example, in the case of three types, hexagonal regions may be arranged so that adjacent regions are different colors.

The display device 1f allows for independent display control of multiple display patterns 30c, 30d on a single display board 20.

In addition, display device 1f allows for a simplified structure while ensuring a variety of display pattern designs.

Furthermore, by forming the multiple display patterns 30c and 30d by printing, there is no need to deform or process the display board 20.

It is also possible to independently control the display of multiple display patterns 30c and 30d in the same area.

In the case of variant 6, for example, if visibility is low due to the difference in the density of the two colors in multiple display patterns 30c and 30d, visibility may be improved by adjusting the dot diameter, pitch, or both. However, to increase resolution, it is desirable to make the pitch as small as possible.

Seventh Modification of First Embodiment
17(a) and 17(b) are front views schematically illustrating the configuration of a display device 1g according to Variation 7 of Embodiment 1. FIGS. 17(a) and 17(b) illustrate an example in which a wavelength-selective filter 11n is provided between a light source 10n and a side surface 203 of the display board 20 to differentiate the wavelengths of light entering the display board 20 corresponding to the display patterns 30c and 30d. In this example, the colors of the display patterns 30c and 30d may be a single color or multiple different colors. Furthermore, the colors of the light emitted from the light-emitting elements corresponding to the display patterns 30c and 30d and entering the display board 20 may be a single color or multiple different colors. Furthermore, the multiple display patterns 30c and 30d may overlap each other on the display board 20.

The effects of display device 1g are similar to those of display device 1f.

Eighth Modification of First Embodiment
By controlling the lighting of the light sources with the lighting control circuit 90, lighting of the display patterns can be controlled individually, enabling dynamic display on the display board 20. For example, current control of a light source corresponding to at least one display pattern can be performed, and the light can be flashed or the light intensity can be varied to create a highlighting effect.

Furthermore, by controlling multiple display devices in a coordinated manner, it can be used, for example, to display guidance on expressways or on roads under construction.

Figures 18(a), (b), (c), and (d) are perspective views schematically illustrating the configuration of a display device according to Variation 8 of Embodiment 1. Figures 18(a), (b), (c), and (d) illustrate an example in which multiple display devices are stacked, with each display pattern partially overlapping and controlled to be illuminated in a time-division manner. Figures 18(a), (b), and (c) show stacked display devices a, b, and c, respectively. Display devices a, b, and c are decorated with display patterns a1, a2, and a3, display patterns b1, b2, and b3, and display patterns c1, c2, and c3, respectively. Figure 18(d) shows display devices a, b, and c stacked in the z-axis direction. Here, display patterns a3 and b1, and display patterns b3 and c1 overlap in the same position on the XY plane when viewed from the -Z-axis direction. For example, if the display pattern is an arrow, by controlling the lighting of the arrows in a time-division manner so that they overlap in part, the arrows will not light up intermittently but will instead appear to light up continuously (smoothly). Among the multiple display units (display patterns a1, a2, and a3, or display patterns b1, b2, and b3, or display patterns c1, c2, and c3), the display patterns (display patterns a3 and b1, and display patterns b3 and c1) of adjacent display units (display unit A and display unit B, or display unit B and display unit C) may be arranged so that they overlap each other. Note that, assuming that the display patterns are viewed from the -Z-axis direction, they may overlap in the Z-axis direction. In other words, the display patterns may overlap in a direction perpendicular to the display panel.

Dynamic display on the display board 20 improves the expressiveness of the display and improves visibility. Furthermore, flashing or varying the intensity of the light emission creates a highlighting effect.

Second Embodiment
In the above embodiment, the display pattern 30 has been described as being used to decorate the display board 20. However, the display unit 40d may be configured by attaching the film 25 having the display pattern 30 to the front surface 201 or the back surface 202 of the display board 20. The film 25 of the second embodiment can also be applied to the other embodiments.

Figures 19(a) and (b) are front and side views that schematically illustrate the configuration of a display device 2 according to embodiment 2. Figures 19(a) and (b) show an example in which a decorated film 25 is attached to a display board 20.

The film 25 is a plastic film made of, for example, acrylic or other plastic. The display board 20 is made of, for example, a plastic material such as acrylic. The display board 20 may also be made of glass. The film 25 is attached to the display board 20, for example, with an adhesive. By making the refractive indexes of the film 25, adhesive, and display board 20 similar, total reflection is less likely to occur at the interface between the film and adhesive, and at the interface between the adhesive and display board 20. Multiple display boards 20 with films 25 attached may be arranged in the X-axis direction, the Y-axis direction, or both. Furthermore, display boards 20 with films 25 attached may be stacked in the Z-axis direction. Furthermore, it is preferable to use an adhesive that allows the film 25 to be peeled off.

Furthermore, the display pattern 30 of the display unit shown in any of Figures 6 to 17 may be formed using film 25.

With the display device 2, the display pattern 30 can be easily replaced by simply replacing the film 25.

In addition, while it is relatively difficult to directly process the curved display board 20, using the film 25 makes it easy to form the display pattern 30 on the curved display board 20, and makes it easy to manufacture the display device 2.

Third Embodiment
In the above-described embodiments, a case has been described in which light emitted from a light source enters the interior of display board 20 from side surface 203 or 204 of display board 20. In embodiment 3, a case will be described in which light emitted from a light source enters the interior from front surface 201 or rear surface 202 of display board 20 via a light distribution control element, which is an incident optical element (i.e., a refractive optical element) attached to front surface 201 or rear surface 202 of display board 20. The structure of embodiment 3 can be applied to other embodiments.

The display device according to embodiment 3 may have a structure in which a plurality of display panels 20 each equipped with a light distribution control element are arranged in the X-axis direction, the Y-axis direction, or both directions. The display device according to embodiment 3 may also have a structure in which a plurality of display panels 20 each equipped with a light distribution control element are stacked in the Z-axis direction.

Figures 20(a) and (b) are a side view and a perspective view showing the schematic configuration of a display device 3 according to embodiment 3. Figure 21 is a side view showing the structure of the light distribution control element 60 and display panel 20 of the display device 3, and the light rays LTC1, LTT1, and LTB1. Figure 22 is a side view showing the structure of the light distribution control element 60 and display panel 20 of the display device 3, and the light rays LBC1, LBT1, and LBB1.

In the display device 3, a light distribution control element 60 is bonded to the display board 20 at the adhesive interface 60a. Light emitted from the light source 10 enters the interior of the display board 20 via the light distribution control element 60 and is guided inside the display board 20 in the -Y-axis and ±Z-axis directions.

The display board 20 is made of transparent plastic, such as PMMA. For example, the length of the display board 20 in the X-axis direction is 300 mm, and the length of the display board 20 in the Y-axis direction is 600 mm. The thickness of the display board 20 in the Z-axis direction is 6 mm. The display pattern 30 may be formed on either the front surface 201 or the back surface 202 of the display board 20.

The light source 10 has, for example, multiple 1 mm square light-emitting diodes (LEDs). The LEDs are arranged in an array in the X-axis direction. The light source 10 is also positioned toward the display board 20 with respect to the optical axis AX of the light distribution control element 60. This allows the light from the light source 10 to be guided inside the display board 20 in the -Y-axis direction with high efficiency. This point will be described in more detail later.

The light distribution control element 60 is formed from a transparent plastic such as PMMA, and is installed with its optical axis AX tilted at an angle β of 40 degrees, for example, with respect to the Y-axis direction, which is parallel to the front surface 201 of the display board 20. By minimizing the difference in refractive index between the display board 20 and the light distribution control element 60 at the adhesive interface 60a, it is possible to reduce interfacial reflection.

Figure 21 shows the behavior of light rays emitted from the end of light source 10 in the -Z axis direction. In Figure 21, light ray LTT1 emitted from the end of light source 10 in the -Z axis direction generally in the -Y axis direction is shown by a dashed line, light ray LTC1 emitted from the end of light source 10 in the -Z axis direction generally parallel to the optical axis AX is shown by a solid line, and light ray LTB1 emitted from the end of light source 10 in the -Z axis direction generally in the +Z axis direction is shown by a dashed line.

Light ray LTT1 is emitted from the end of light source 10 in the -Z-axis direction, generally in the -Y-axis direction, is refracted at incident surface T1, and is totally reflected at optical surface T1a, traveling in a direction generally parallel to the optical axis AX. The traveling light ray is then totally reflected at the rear surface 202 of display panel 20, traveling in the -Y-axis direction. Note that optical surface T1b may be tilted toward the optical axis AX so that a portion of light ray LTT1 reaches the rear surface 202. However, the tilt angle of optical surface T1b with respect to the optical axis AX must be determined so as to satisfy the condition for total reflection at the rear surface 202. By tilting optical surface T1b toward the optical axis AX, the length of adhesive interface 60a in the Y-axis direction can be shortened.

Light ray LTC1 is emitted from the end of light source 10 in the -Z-axis direction in a direction generally parallel to the optical axis AX, is refracted by convex surface 60b, and travels as a light ray generally parallel to the optical axis AX. A portion of the traveling light ray is totally reflected by optical surface B1b, and after reaching the rear surface 202 of display board 20, is totally reflected again and travels in the -Y-axis direction. Most of light ray LTC1 is totally reflected by the rear surface 202 of display board 20, and the light ray travels in the -Y-axis direction.

Light ray LTB1 is emitted from the end of light source 10 in the -Z-axis direction, generally in the +Z-axis direction, refracted at incident surface B1, and totally reflected at optical surface B1b, traveling as parallel light at an angle of approximately 13 degrees with respect to optical axis AX. A portion of the traveling light ray LTB1 is totally reflected at optical surface B1b, then totally reflected at the rear surface 202 of display board 20, traveling in the -Y-axis direction. Most of light ray LTB1 is totally reflected at the rear surface 202 of display board 20, traveling in the -Y-axis direction. Optical surface B1b is tilted toward the optical axis AX. This is because light ray LTB1 travels at an angle of approximately 13 degrees with respect to optical axis AX, and tilting it to shorten the length of adhesive interface 60a in the Y-axis direction does not affect the travel of light ray LTB1. In Figures 21 and 22, optical surface B1b is tilted by more than 13 degrees with respect to optical axis AX. For example, optical surface B1b is tilted approximately 18 degrees with respect to the optical axis AX.

Figure 22 shows the behavior of light rays emitted from the end of light source 10 in the +Z-axis direction. In Figure 22, light ray LBT1 emitted from the end of light source 10 in the +Z-axis direction generally in the -Y-axis direction is shown by a dashed line, light ray LBC1 emitted from the end of light source 10 in the +Z-axis direction in a direction generally parallel to the optical axis AX is shown by a solid line, and light ray LBB1 emitted from the end of light source 10 in the +Z-axis direction generally in the +Z-axis direction is shown by a dashed line.

Light ray LBT1 is emitted from the end of light source 10 in the +Z-axis direction, generally in the -Y-axis direction, refracted at incident surface T1, and totally reflected at optical surface T1a, traveling at an angle to the optical axis AX (i.e., gradually approaching the optical axis AX). The traveling light ray is then totally reflected at the rear surface 202 of display panel 20, and travels in the -Y-axis direction.

Light ray LBC1 is emitted from the end of light source 10 in the +Z-axis direction in a direction roughly parallel to optical axis AX, is refracted, focused, and diffused by convex surface 60b, and is totally reflected by rear surface 202 of display panel 20, traveling in the -Y-axis direction.

Light ray LBB1 is emitted from the end of light source 10 in the +Z-axis direction, is refracted at incident surface B1, and is totally reflected at optical surface B1b, becoming a light ray tilted with respect to optical axis AX (i.e., traveling in a direction gradually approaching optical axis AX). A portion of the traveling light ray LBB1 is totally reflected at rear surface 202 of display board 20 and travels in the -Y-axis direction. Most of light ray LBB1 is totally reflected at optical surface B1b, then totally reflected at rear surface 202 of display board 20 and travels in the -Y-axis direction.

As such, it is necessary to take into account the light rays emitted from the end of the light source 10 in the -Z-axis direction and the end in the +Z-axis direction. The optical surface B1a shortens the length of the adhesive interface 60a in the Y-axis direction by tilting the light rays with respect to the optical axis AX. Furthermore, the optical surface B1b needs to be designed so that the light rays emitted from the end in the -Y-axis direction satisfy the total reflection condition on the rear surface 202 of the display panel 20. Here, for example, when the refractive index n1 of PMMA is 1.49, the refractive index n2 of air is 1, and α is the critical angle, the total reflection condition with the air interface can be calculated from the following formula:
sin(α)=1/1.49
From this equation, α≈42.15 degrees is obtained. Therefore, when the rear surface 202 of the display panel 20 is used as a reference,
90-α=90-42.15≒47.8
In other words, when the light ray reaches the rear surface 202 of the display panel 20 at an inclination angle of 47.8 degrees or less with respect to the rear surface 202, the total reflection condition is satisfied.

Thus, in the examples shown in Figures 21 and 22, the optical axis AX of the light distribution control element 60 is tilted by β = 40 degrees with respect to the Y axis, but this angle β can be changed.

<<First Modification of Third Embodiment>>
FIG. 23 is a side view showing the structure and light rays of the light distribution control element 61 and display panel 20 of the display device 3a according to Variation 1 of Embodiment 3. FIG. 23 illustrates the case where β=43 degrees. With β=43 degrees, the optical surface T2b is slightly tilted toward the optical axis AX to shorten the adhesive interface 61a of the light distribution control element 61 in the Y-axis direction (i.e., the end of the optical surface T2b in the −Y-axis direction is moved in the +Y-axis direction). The length of the adhesive interface 61a in the Y-axis direction can be set as appropriate. It is necessary to prevent the light ray L61b refracted by the convex surface 61b, which is the incident surface of the light distribution control element 61, from being refracted by the optical surface T2b and emitted in the −Y-axis direction. In other words, it is necessary to ensure that the light ray refracted by the convex surface 61b reaches the front surface 201 of the display panel 20 and is directed toward the front surface 201 by total reflection at the back surface 202. From the above, it is considered preferable that the angle β between the display panel 20 and the optical axis AX is 43 degrees or less when the light distribution control element 61 and the display panel 20 are made of PMMA.

Furthermore, if the display panel 20 is made of glass, refraction at the adhesive interface must be taken into consideration. Note that when the light distribution control element 61 is made of glass, the characteristics of each surface are the same as when it is made of PMMA.

<<Modification 2 of Embodiment 3>>
Figure 24 is a side view showing the structures of light distribution control element 62 and display panel 20 of display device 3b according to Variation 2 of Embodiment 3, and light ray L62b. Figure 24 shows a case where β = 29 degrees, as an example of a case where angle β is smaller than 40 degrees. Light distribution control element 62 has substantially the same shape as that shown in Figures 21 and 22, but differs from those shown in Figures 21 and 22 in the angle β of optical axis AX relative to the Y axis and the height of light distribution control element 62. Light ray L62b refracted by convex surface 62b, which is the incident surface of light distribution control element 62, reaches front surface 201 of display panel 20 and is directed toward front surface 201 due to total reflection at back surface 202.

Furthermore, in the examples of Figures 21 and 22, if the thickness of the display panel 20 is changed from 6 mm to 5 mm, it becomes difficult to guide light with high efficiency in the -Y axis direction. However, in the example of Figure 24, by tilting the optical surface T1b with respect to the optical axis AX (i.e., by moving the end of the optical surface T1b in the +Y axis direction in the -Y axis direction), it becomes possible to guide light with high efficiency even with a thickness of 5 mm.

Figure 25 is a side view showing the structure of the light distribution control element 62 and display board 20 of the display device 3b2, and the light ray L62bT. Figure 25 shows the case where the thickness of the display board 20 is 5 mm. The optical surface T3b has a larger inclination with respect to the optical axis AX than the optical surface T1b shown in Figure 24. Therefore, in the example of Figure 25, the length of the adhesive interface 60a in the Y-axis direction is shorter.

Even if the angle β is less than 29 degrees, it is possible to guide light inside the display board 20 with high efficiency. However, as the length of the adhesive interface 62a increases, the displayable area of the display board 20 becomes narrower, so it is preferable that the adhesive interface 62a be short in the Y-axis direction. Therefore, it is preferable that the angle β be 29 degrees or greater.

<<Modification 3 of Embodiment 3>>
26(a) and 26(b) are a side view and a perspective view schematically showing the configuration of a display device 3c according to embodiment 3. Fig. 27 is a side view showing the structure of a light distribution control element 70 and a display panel 20 of the display device 3c, and light rays.

The display panel 20 is made of transparent plastic, such as PMMA. The display panel 20 is 300 mm long in the X-axis direction and 600 mm long in the Y-axis direction. It is 5 mm thick in the Z-axis direction. The display pattern 30 may be formed on either the front surface 201 or the back surface 202. The light source 10 has, for example, multiple 1 mm square LEDs, which are arranged in a multiple array in the X-axis direction.

The light distribution control element 70 is made of a transparent plastic such as PMMA, and is installed with its optical axis AX tilted at an angle of, for example, β = 40 degrees relative to the display panel 20. By adhering it so as to eliminate the refractive index difference at the adhesive interface 70a, it is possible to reduce interfacial reflection.

The light ray LCT2 emitted from the center of the light source 10 in approximately the -Y axis direction is shown by a dashed line, and the light ray LCB2 emitted from the center of the light source 10 in approximately the +Z axis direction is shown by a broken line.

After being emitted from the light source 10, the light ray LCT2 is refracted by the curved surface (e.g., a free-form surface) of the incident surface T2, suppressing the spread of the light, and is totally reflected by the optical surface T2a. The totally reflected light ray LCT2 becomes a light ray roughly parallel to the optical axis AX, and some of the light ray LCT2 is totally reflected by the optical surface T2b and then by the rear surface 202 of the display panel 20, traveling in the -Y-axis direction. Most of the light ray LCT2 is totally reflected by the optical surface T2a, then totally reflected by the rear surface 202, traveling in the -Y-axis direction.

Optical surface T2b is parallel to the optical axis AX, but because the parallelism of light ray LCT2 is low, part of it reaches optical surface T2b.

After emitting from the light source 10, light ray LCB2 is refracted by the curved surface (e.g., a free-form surface) of incident surface B2, suppressing the spread of the light and undergoing total reflection at optical surface B2a. The totally reflected light ray LCB2 is inclined at approximately 13 degrees with respect to the optical axis AX, becoming a roughly parallel ray, and some of the light ray LCB2 is totally reflected at optical surface B2b and then at the rear surface 202 of the display panel 20, traveling in the -Y-axis direction. Most of the light ray LCB2 is totally reflected at optical surface B2a, then at the rear surface 202, traveling in the -Y-axis direction. Optical surface B2b is inclined at 18 degrees with respect to the optical axis AX to shorten the length of the adhesive interface 70a in the Y-axis direction.

Figure 28 is a side view that schematically illustrates the configuration of the light distribution control element 70 and display panel 20 of the display device 3c. Figure 28 shows the behavior of light rays emitted from the ends of the light source 10 in the ±Z-axis directions. Light ray LT2 emitted from the end of the light source 10 in the -Z-axis direction is shown by a dotted-dash line, and light ray LB2 emitted from the end of the light source 10 in the +Z-axis direction is shown by a dashed line. It can be seen that both light rays are guided inside the display panel 20 in the -Y-axis direction.

Unlike the light distribution control element 60 in Figure 21, the light distribution control element 70 does not have a convex surface 60b. The light distribution control element 70 guides light rays emitted from the light source 10 to the display board 20 via the incident surface T2 and the incident surface B2. Furthermore, the recess 70b forming the boundary between the incident surface T2 and the incident surface B2 is offset in the -Z-axis direction from the optical axis AX of the light distribution control element 70. This increases the number of light rays emitted from the light source 10 that enter the incident surface B2 rather than the incident surface T2, thereby shortening the length of the adhesive interface 70a in the Y-axis direction. With this shape, when the light distribution control element 70 is tilted at β = 40 degrees with respect to the front surface 201 of the display board 20, it is possible to guide light rays in the -Y-axis direction even if the thickness of the display board 20 is 5 mm.

<<Fourth Modification of Third Embodiment>>
FIG. 29 is a side view schematically illustrating the configuration of a light distribution control element 71 and a display panel 20 of a display device 3d according to Variation 4 of Embodiment 3. FIG. 29 illustrates a case where the angle β of the optical axis AX of the light distribution control element 70 is 29 degrees. FIG. 29 illustrates a light ray LT3 emitted from the end of the light source 10 in the −Z-axis direction by a dashed line, and a light ray LB3 emitted from the end of the light source 10 in the +Z-axis direction by a broken line. A light ray LC3 emitted from the center of the light source 10 is illustrated by a solid line. It can be seen that both light rays are guided inside the display panel 20 in the −Y-axis direction. With the configuration of FIG. 29 , as with the display devices shown in FIGS. 21 and 22 , it can be seen that light can be guided inside the display panel 20 in the −Y-axis direction with high efficiency even when the angle β is 29 degrees.

The configuration in Figure 29 differs from that in Figure 28 in that the shapes of the incident surface B2 and optical surface B2a of the light distribution control element 70 have been changed. Light ray LC3 emitted from the center of the light source 10 in the +Z-axis direction is totally reflected by optical surface B3a, and then travels in the -Y-axis direction at an angle of approximately 14 degrees with respect to the optical axis AX.

Even when β is 29 degrees or less, it is possible to guide light inside the display panel 20 with high efficiency, but it is preferable to shorten the length of the adhesive interface 71a in the Y-axis direction to widen the image display area of the display panel 20.

As in the examples of Figures 21 and 22, even when the angle β between the optical axis AX of the display board 20 and the light distribution control element 70 is 43 degrees, the light emitted by the light source 10 is guided with high efficiency inside the display board 20 in the -Y axis direction.

The display devices according to embodiment 3 and its variations 1 to 4 can direct light into the interior of the display board 20 when it is difficult to install the light source 10 in a position facing the side surface 203 of the display board 20.

Furthermore, by laminating the film 25 to a transparent member (e.g., glass) such as a shop window in an existing store, laminating the light distribution control element 70, and arranging a light source, it is possible to install a display device on the existing transparent member. This has the effect of making it possible to install a new display device without renovating existing facilities.

Note that the structure of establishing a new display device by laminating film 25 to a transparent member and arranging a light source can also be applied to other variations of embodiment 3 and other embodiments.

Fifth Modification of Third Embodiment (Light Source 1 mm Square)
Figures 30(a) and 30(b) are a side view and a perspective view schematically illustrating the configuration of a display device 3e according to embodiment 3. Figures 31, 32, and 33 are side views showing the structure and light rays of the light distribution control element 72 and the display panel 20 of the display device 3e. In Modifications 1 to 4 of embodiment 3, the light distribution control element was formed with a configuration including multiple incident surfaces, but Modification 5 differs in that it has only one incident surface. This makes it possible to reduce the size of the light distribution control element compared to Modifications 1 to 4.

In the display device 3e, a light distribution control element 72 is bonded to the display board 20 at the adhesive interface 72a. Light emitted from the light source 10 enters the interior of the display board 20 via the light distribution control element 72 and is guided inside the display board 20 in the -Y-axis and ±Z-axis directions.

The display board 20 is made of transparent plastic, such as PMMA. For example, the length of the display board 20 in the X-axis direction is 300 mm, and the length of the display board 20 in the Y-axis direction is 600 mm. The thickness of the display board 20 in the Z-axis direction is 5 mm, for example. The display pattern 30 may be formed on either the front surface 201 or the back surface 202 of the display board 20.

The light source 10 has, for example, multiple 1 mm square LEDs. The LEDs are arranged in the X-axis direction. The center of the light source 10 is also located on the optical axis AX of the light distribution control element 72.

The light distribution control element 72 is formed from a transparent plastic such as PMMA, and is installed with its optical axis AX tilted at an angle β of, for example, 11.5 degrees with respect to the Y-axis direction, which is parallel to the front surface 201 of the display board 20. The length of the incident surface IS72 in the direction perpendicular to the optical axis AX, i.e., the direction parallel to the double-headed arrow indicating the length of the light source 10 in Figure 31 (1 mm in the figure), is, for example, 2 mm. By minimizing the difference in refractive index between the display board 20 and the light distribution control element 72 at the adhesive interface 72a, it is possible to reduce interfacial reflection.

Figure 31 shows the behavior of light rays emitted from the end of light source 10 in the -Z-axis direction. Light ray LT51a1 is emitted from the end of light source 10 in the -Z-axis direction at an angle of -60 degrees relative to the plane formed by optical axis AX and the X-axis, approximately in the -Y-axis direction. Light ray LT51a2, light ray LT51a3, light ray LT51a4, and light ray LT51a5 are shown by dashed dotted lines, in the order of emission at an angle in the +RX direction from light ray LT51a1. Light ray LT51a5 is emitted approximately in the -Y-axis direction at an angle of +60 degrees relative to the plane formed by optical axis AX and the X-axis. Here, clockwise rotation around the X-axis is +RX rotation, clockwise rotation around the Y-axis is +RY rotation, and clockwise rotation around the Z-axis is +RZ rotation.

The behavior of each ray will be explained. Light ray LT51a1 is totally reflected by the upper surface TS72 of the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LT51a2 is totally reflected twice by the upper surface TS72 of the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LT51a3 is totally reflected by the upper surface TS72 of the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LT51a4 is guided within the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LT51a5 is totally reflected by the lower surface BS72 of the light distribution control element 72, then totally reflected by the upper surface TS72, and then totally reflected by the rear surface 202 of the display board 20, traveling in the -Y axis direction.

Light ray LT51a4 passes near the junction between the lower surface BS72 of the light distribution control element 72 and the front surface 201 of the display panel 20, and reaches the rear surface 202 directly. If twice the distance D51 in the Y-axis direction from the junction between the lower surface BS72 and the front surface 201 to the rear surface 202 of light ray LT51a4 is shorter than the distance D72a in the Y-axis direction of the adhesive interface 72a, light ray LT51a4 will be refracted at the upper surface TS72 of the light distribution control element 72 and emitted to the outside, and therefore, from the perspective of light utilization efficiency, it is preferable that twice the distance D51 in the Y-axis direction be longer than the distance D72a in the Y-axis direction of the adhesive interface 72a.

The angle γ between front surface 201 of display board 20 and lower surface BS72 of light distribution control element 72 is 13.5 degrees. The angle β between front surface 201 of display board 20 and optical axis AX is 11.5 degrees. Therefore, lower surface BS72 of light distribution control element 72 is inclined by 2 degrees in the +RX rotation direction with respect to optical axis AX. Note that if angle γ satisfies the following formula (1) or formula (2), light can be efficiently guided within display board 20. If adhesive interface 72a is narrowed in consideration of light leakage due to scattering by the adhesive layer at adhesive interface 72a, it is preferable to reduce angle γ. Furthermore, if installation stability is important, it is preferable to increase angle γ in order to widen adhesive interface 72a.
7.5 degrees < γ < 14.1 degrees...(1)
β-4 degrees < γ < β + 2.6 degrees…(2)

The size of the light distribution control element 72 in Figure 31 (Variant 5) is, for example, a length W72 in the Y-axis direction of 23.9 mm and a length D72 in the Z-axis direction of 3.3 mm. For example, in Figure 21, the length W60 in the Y-axis direction is 32.3 mm and the length D60 in the Z-axis direction is 17.2 mm; in Figure 23, the length W61 in the Y-axis direction is 26.4 mm and the length D61 in the Z-axis direction is 14.8 mm; in Figure 24, the length W62 in the Y-axis direction is 34.2 mm and the length D62 in the Z-axis direction is 11.8 mm; in Figure 27, the length W70 in the Y-axis direction is 46.1 mm and the length D70 in the Z-axis direction is 26.7 mm; and in Figure 29, the length W71 in the Y-axis direction is 50.1 mm and the length D71 in the Z-axis direction is 18.9 mm. It can be seen that the size of the light distribution control element 72 in Figure 31 (Variant 5) can be made smaller than the sizes of the light distribution control elements 72 in Variations 1 to 4.

Figure 32 shows the behavior of light rays emitted from the center of light source 10. Light ray LC51b1 is emitted from the center of light source 10 at an angle of -60 degrees relative to the plane formed by optical axis AX and X axis, approximately in the -Y axis direction. Solid lines show light ray LC51b2, light ray LC51b3, and light ray LC51b4, which are emitted at an angle in the +RX direction from light ray LC51b1. Light ray LC51b4 is emitted at an angle of +60 degrees relative to the plane formed by optical axis AX and X axis, approximately in the -Y axis direction. Light ray LC51b3 is emitted at an angle parallel to optical axis AX.

The behavior of each ray will be explained. Light ray LC51b1 is totally reflected by the upper surface TS72 of the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LC51b2 is totally reflected by the upper surface TS72 of the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LC51b3 is guided within the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LC51b4 is totally reflected by the lower surface BS72 of the light distribution control element 72, then totally reflected by the upper surface TS72, and then totally reflected again by the rear surface 202 of the display board 20, and travels in the -Y axis direction.

Figure 33 shows the behavior of light rays emitted from the +Z-axis direction end of light source 10. Light ray LB51c1 is emitted from the +Z-axis direction end of light source 10 at an angle of -60 degrees relative to the plane formed by optical axis AX and the X-axis, approximately in the -Y-axis direction. Light ray LB51c2, light ray LB51c3, and light ray LB51c4 are shown in dashed lines, in that order, emitted at an angle in the +RX direction from light ray LB51c1. Light ray LB51c4 is emitted approximately in the -Y-axis direction at an angle of +60 degrees relative to the plane formed by optical axis AX and the X-axis.

The behavior of each ray will be explained. Light ray LB51c1 is totally reflected by the upper surface TS72 of the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LB51c2 is totally reflected by the upper surface TS72 of the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LB51c3 is guided within the light distribution control element 72, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LB51c4 is totally reflected by the lower surface BS72 of the light distribution control element 72, then totally reflected by the upper surface TS72, and then totally reflected again by the rear surface 202 of the display board 20, and travels in the -Y axis direction.

The above is for a display panel 20 with a thickness of 5 mm, but a thickness of 4 mm is also possible. In that case, the size of the light distribution control element 72 can be, for example, 27.5 mm in the Y-axis direction (W72) and 4.3 mm in the Z-axis direction (D72). Although the size of the light distribution control element 72 will be slightly larger, it is possible to increase light utilization efficiency even when the thickness of the display panel 20 is reduced.

Furthermore, as shown in FIG. 32, the upper surface TS72 of the light distribution control element 72 is shaped such that on the +Y-axis direction side, an incident ray of light at an angle AI51a (e.g., absolute value 35.4 degrees) is totally reflected at an angle AO51a (e.g., absolute value 12.2 degrees) in a direction that reduces the angle with respect to the optical axis AX, and on the -Y-axis direction side, an incident ray of light at an angle AI51b (e.g., absolute value 6.3 degrees) is totally reflected at an angle AO51b (e.g., absolute value 11.1 degrees) in a direction that increases the angle with respect to the optical axis AX. Here, angle AO51b may be greater than angle AI51b so that the light ray is incident at an angle of incidence that satisfies the total reflection condition on the rear surface 202 of the display board 20. As a result, light rays with a large emission angle relative to the optical axis AX are totally reflected by the back surface 202 of the display board 20 at a smaller angle relative to the optical axis AX, and light rays with a small emission angle relative to the optical axis AX are totally reflected by the back surface 202 of the display board 20 at a larger angle relative to the optical axis AX. In other words, it is possible to efficiently make light emitted from the light source 10 incident on the back surface 202 of the display board 20 at an incident angle that satisfies the conditions for total reflection on the back surface 202 of the display board 20.

Furthermore, by shaping the -Y-axis direction side of the upper surface TS72 of the light distribution control element 72 so that angle AO51b is larger than angle AI51b, the point of contact between the upper surface TS72 and the front surface 201 of the display panel 20 moves in the +Y-axis direction, making it possible to shorten the distance D72a of the adhesive interface 72a in the Y-axis direction and improving light utilization efficiency.

Sixth Modification of Third Embodiment (Light Source 3 mm Square)
From the above, it has been found that in Modification 5, it is possible to reduce the size of light distribution control element 72 and the thickness of display panel 20. Therefore, Modification 6 shows an example of light distribution control element 73 when the light source size is increased.

Figures 34(a) and (b) are a side view and a perspective view showing the schematic configuration of a display device 3f according to embodiment 3. Figures 35, 36, and 37 are side views showing the structure and light rays of the light distribution control element 73 and the display panel 20 of the display device 3f.

In display device 3f, a light distribution control element 73 is bonded to the display board 20 at the adhesive interface 73a. Light emitted from light source 10b enters the interior of the display board 20 via the light distribution control element 73 and is guided inside the display board 20 in the -Y-axis and ±Z-axis directions.

The display board 20 is made of transparent plastic, such as PMMA. For example, the length of the display board 20 in the X-axis direction is 300 mm, and the length of the display board 20 in the Y-axis direction is 600 mm. The thickness of the display board 20 in the Z-axis direction is 5 mm, for example. The display pattern 30 may be formed on either the front surface 201 or the back surface 202 of the display board 20.

Light source 10b has, for example, multiple 3 mm square LEDs. The LEDs are arranged in the X-axis direction. The center of light source 10b is located on the optical axis AX of light distribution control element 73. By using 3 mm square LEDs, it is possible to increase the amount of light emitted compared to when the LEDs are 1 mm square.

The light distribution control element 73 is formed from a transparent plastic such as PMMA, and is installed so that its optical axis AX is tilted at an angle β of 11.5 degrees, for example, with respect to the Y-axis direction, which is parallel to the front surface 201 of the display board 20. The length of the incident surface IS73 in the direction perpendicular to the optical axis AX (parallel to the length of the light source 10b) is, for example, 4 mm. By minimizing the difference in refractive index between the display board 20 and the light distribution control element 73 at the adhesive interface 73a, it is possible to reduce interfacial reflection.

Figure 35 shows the behavior of light rays emitted from the end of light source 10b in the -Z axis direction. Light ray LT53a1 is emitted from the end of light source 10b in the -Z axis direction at an angle of -60 degrees relative to the plane formed by optical axis AX and the X axis, approximately in the -Y axis direction. Light ray LT53a2, light ray LT53a3, light ray LT53a4, and light ray LT53a5 are shown by dashed dotted lines, in the order of emission at an angle in the +RX direction from light ray LT53a1. Light ray LT53a5 is emitted approximately in the -Y axis direction at an angle of +60 degrees relative to the plane formed by optical axis AX and the X axis. Here, clockwise rotation around the X axis is +RX rotation, clockwise rotation around the Y axis is +RY rotation, and clockwise rotation around the Z axis is +RZ rotation.

The behavior of each ray will be explained. Light ray LT53a1 is totally reflected by the upper surface TS73 of the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LT53a2 is totally reflected twice by the upper surface TS73 of the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LT53a3 is totally reflected by the upper surface TS73 of the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LT53a4 is guided within the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LT53a5 is totally reflected by the lower surface BS73 of the light distribution control element 73, then totally reflected by the upper surface TS73, and then totally reflected by the rear surface 202 of the display panel 20, traveling in the -Y axis direction.

Light ray LT53a4 passes near the junction between the lower surface BS73 of the light distribution control element 73 and the front surface 201 of the display panel 20, and reaches the rear surface 202 directly. If twice the distance D53 in the Y-axis direction from the junction between the lower surface BS73 and the front surface 201 to the rear surface 202 of light ray LT53a4 is shorter than the distance D73a in the Y-axis direction of the adhesive interface 73a, light ray LT53a4 will be refracted at the upper surface TS73 of the light distribution control element 73 and emitted to the outside, and therefore, from the perspective of light utilization efficiency, it is preferable that twice the distance D53 in the Y-axis direction be longer than the distance D73a in the Y-axis direction of the adhesive interface 73a.

The angle γb between the front surface 201 of the display board 20 and the lower surface BS73 of the light distribution control element 73 is 10.9 degrees. The angle β between the front surface 201 of the display board 20 and the optical axis AX is 11.5 degrees. Therefore, the lower surface BS73 of the light distribution control element 72 is tilted by 0.6 degrees in the -RX rotation direction with respect to the optical axis AX. By reducing the angle γb, the distance D73a in the Y-axis direction of the adhesive interface 73a is shortened, suppressing light from being refracted at the upper surface TS73 of the light distribution control element 73 and emitting to the outside.

The size of the light distribution control element 73 in Figure 31 (Variant 6) is, for example, a length W73 in the Y-axis direction of 30.2 mm and a length D73 in the Z-axis direction of 6.1 mm. For example, in Figure 21, the length W60 in the Y-axis direction is 32.3 mm, the length D60 in the Z-axis direction is 17.2 mm; in Figure 23, the length W61 in the Y-axis direction is 26.4 mm, the length D61 in the Z-axis direction is 14.8 mm; in Figure 24, the length W62 in the Y-axis direction is 34.2 mm, the length D62 in the Z-axis direction is 11.8 mm; in Figure 27, the length W70 in the Y-axis direction is 46.1 mm, the length D70 in the Z-axis direction is 26.7 mm; and in Figure 29, the length W71 in the Y-axis direction is 50.1 mm, the length D71 in the Z-axis direction is 18.9 mm. It can be seen that the length in the Z-axis direction of the light distribution control element 73 in Variation 6 can be made smaller than in Variations 1 to 4. Furthermore, considering that the length in the Y-axis direction is approximately 14% longer than the shortest length in Figure 23, but the length in the Z-axis direction is less than half, it can be seen that even though the size of the light source 10b is tripled, the size of the light distribution control element 73 can be made smaller than in Variations 1 to 4.

Figure 36 shows the behavior of light rays emitted from the center of light source 10b. Light ray LC53b1 is emitted from the center of light source 10b at an angle of -60 degrees relative to the plane formed by optical axis AX and the X axis, approximately in the -Y axis direction. Solid lines show light ray LC53b2, light ray LC53b3, and light ray LC53b4, which are emitted at an angle in the +RX direction from light ray LC53b1. Light ray LC53b4 is emitted at an angle of +60 degrees relative to the plane formed by optical axis AX and the X axis, approximately in the -Y axis direction. Light ray LC53b3 is emitted at an angle parallel to the optical axis AX.

The behavior of each ray will be explained. Light ray LC53b1 is totally reflected by the upper surface TS73 of the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LC53b2 is totally reflected by the upper surface TS73 of the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LC53b3 is guided within the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LC53b4 is totally reflected by the lower surface BS73 of the light distribution control element 73, then totally reflected by the upper surface TS73, and then totally reflected again by the rear surface 202 of the display board 20, and travels in the -Y axis direction.

Figure 37 shows the behavior of light rays emitted from the +Z-axis direction end of light source 10b. Light ray LB53c1 is emitted from the +Z-axis direction end of light source 10b at an angle of -60 degrees relative to the plane formed by optical axis AX and the X-axis, approximately in the -Y-axis direction. Light ray LB53c2, light ray LB53c3, and light ray LB53c4 are shown in dashed lines, in that order, emitted at an angle in the +RX direction from light ray LB53c1. Light ray LB53c4 is emitted approximately in the -Y-axis direction at an angle of +60 degrees relative to the plane formed by optical axis AX and the X-axis.

The behavior of each ray will be explained. Light ray LB53c1 is totally reflected by the upper surface TS73 of the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LB53c2 is guided within the light distribution control element 73, then totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LB53c3 is totally reflected by the lower surface BS73 of the light distribution control element 73, then totally reflected by the upper surface TS73, and again totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction. Light ray LB53c4 is totally reflected by the lower surface BS73 of the light distribution control element 73, then totally reflected by the upper surface TS73, and again totally reflected by the rear surface 202 of the display board 20, and travels in the -Y axis direction.

Furthermore, as shown in FIG. 36, the upper surface TS73 of the light distribution control element 73 is shaped such that, on the +Y-axis direction side, an incident ray of light is totally reflected at an angle AI53a (e.g., absolute value 35.4 degrees) at an angle AO53a (e.g., absolute value 16.2 degrees) in a direction that reduces the angle with respect to the optical axis AX, and on the -Y-axis direction side, an incident ray of light is totally reflected at an angle AI53b (e.g., absolute value 4.0 degrees) at an angle AO53b (e.g., absolute value 26.3 degrees) in a direction that increases the angle with respect to the optical axis AX. Here, angle AO53b may be greater than angle AI53b so that the light is incident at an angle of incidence that satisfies the total reflection condition on the rear surface 202 of the display board 20. As a result, light rays with a large emission angle relative to the optical axis AX are totally reflected by the back surface 202 of the display board 20 at a smaller angle relative to the optical axis AX, and light rays with a small emission angle relative to the optical axis AX are totally reflected by the back surface 202 of the display board 20 at a larger angle relative to the optical axis AX. In other words, it is possible to efficiently make light emitted from the light source 10b incident on the back surface 202 of the display board 20 at an incident angle that satisfies the conditions for total reflection on the back surface 202 of the display board 20.

In other words, the light distribution control element 73, which is a refractive optical element, reflects first light that reaches a first region of the upper surface TS73 closer to the light source 10b at a first exit angle that is smaller than the first angle of incidence of the first light, and reflects second light that reaches a second region of the upper surface TS73 farther from the light source 10b than the first region at a second exit angle that is larger than the second angle of incidence of the second light. In this case, the first angle of incidence is larger than the second angle of incidence, and the first light and second light are reflected and guided to the second surface, which is the front or back surface opposite the first surface (front or back surface).

Furthermore, by shaping the -Y-axis direction side of the top surface TS73 of the light distribution control element 73 so that angle AO53b is larger than angle AI53b, the point of contact between the top surface TS73 and the front surface 201 of the display panel 20 moves in the +Y-axis direction. This makes it possible to shorten the distance D73a in the Y-axis direction of the adhesive interface 73a, thereby improving light utilization efficiency.

Figures 38(a) and (b) show an example of a side view and a perspective view of the light distribution control element 73 and display panel 20 of a display device 3f according to Variation 6 of Embodiment 3. This differs in that a light-shielding cover SH73 is provided to cover the light distribution control element 73.

Due to inaccuracies in the installation of light source 10b or errors in the shape of the light distribution control element 73, there is a possibility that unwanted light may be emitted from the upper surface TS73 of the light distribution control element 73. Therefore, by providing a light-shielding cover SH73 that covers the light distribution control element 73, it is possible to prevent unwanted light from entering the observer's eyes as glare.

The light-shielding cover SH73 extends in the +X-axis direction and is preferably black to block light, but any other color that blocks light may be used. Furthermore, since the light distribution control element 73 is outside the display area, it is preferable that it is not visible to the viewer, and therefore the presence of the light-shielding cover SH73 is desirable.

A light-shielding cover or light-shielding sheet may also be provided on the +Z side of the display board 20. This will prevent the light distribution control element 73 from being observed from the +Z axis direction, and will also block unwanted light emitted from the back surface 202 of the display board 20. Note that a similar effect can be achieved in variant 5 by providing a light-shielding cover.

Fourth Embodiment
In the above embodiment, the display unit 40 of the display device has been described as having a single display panel 20. However, the display unit 40 may also include a visibility improving member, which is a substantially transparent member for improving visibility, in addition to the display panel 20. The structure of embodiment 4 can also be applied to the other embodiments.

Figure 39(a) is a perspective view showing a portion of the configuration of a display device 4 according to embodiment 4, and Figure 39(b) is a perspective view showing a schematic configuration of the display device 4 according to embodiment 4. The visibility improving member 80 is preferably installed behind the display board 20 so as not to impair the visibility of the display pattern 30. The visibility improving member 80 may be, for example, a transparency adjusting member having a lower transmittance than a normal transparent body.

The transparency adjustment member is, for example, processed as a neutral density filter. Alternatively, the transparency adjustment member may be a polymer dispersed liquid crystal. Neutral density filters can be either transmissive or reflective, with transmissive neutral density filters being preferred as they have the advantage of being less affected by total reflection. The transmittance of the transparency adjustment member is, for example, 60% or less.

The visibility-enhancing member 80 may be, for example, a diffusion plate with a diffusion treatment applied to its front surface, back surface, or both the front and back surfaces. It is also possible to provide a visibility-enhancing member 80 when the display panel 20 is stacked.

In the display device 4, by applying a neutral density filter to the transparency adjustment member that constitutes the visibility improvement member 80, the brightness (luminance) of the background is reduced and the contrast ratio of the display board 20 is improved, thereby improving the visibility of the display pattern 30.

Furthermore, if the transparency-adjusting member that constitutes the visibility-enhancing member 80 is made of polymer-dispersed liquid crystal, the contrast ratio of the background decreases, improving the visibility of the display pattern 30.

When a visibility-enhancing member 80 made of a transparent material with a diffusion coating is used, the visibility of the display pattern 30 is improved by illuminating the display pattern 30 against a blurred background.

Fifth Embodiment
In the above embodiment, an example in which the display unit 40 includes a single display panel 20 has been described. However, the display unit 40 may also include stacked display panels 20. However, when stacked display panels 20 are included, moire may occur due to periodic decoration in the multiple display patterns 30. The periodic structure may be, for example, dots in printing. To reduce moire, for example, the display patterns 30 (e.g., decorative areas) of the stacked display panels 20 may be decorated so that they do not overlap each other when viewed from the observation position. Furthermore, to reduce moire, the planar periods of the decorations of the multiple display panels 20 may be matched, and the decorated surfaces may overlap (i.e., the display patterns may be overlapped so that they are in contact with each other). The structure of embodiment 5 can also be applied to other embodiments.

Figure 40 is a side view schematically illustrating the configuration of a display device 5 according to embodiment 5. Figure 40 shows an example of stacking display panels 20 to minimize the impact of moire on visibility. For example, if the thickness of the display panel 20 (i.e., the length of the short side of the side surface 203 in the Z-axis direction) is 4 mm or less, as shown in Figure 40, the impact of moire on visibility is minimal if two display patterns 30 are stacked on top of each other with the decorative surface of another layer facing inward, up to three layers in total. This is because, by matching the planar periods, no spatial periodic shift occurs between the two overlapping decorative surfaces (i.e., two display patterns in contact with each other), and therefore moire is not visible. Furthermore, because the third display pattern 30 (i.e., the topmost display pattern 30 in Figure 40) is positioned 4 mm away from the other display patterns, some spatial periodic shift occurs, but the impact on visibility is minimal.

The display device 5 is equipped with stacked display panels 20 and multiple display patterns 30, allowing it to display a variety of display patterns.

In addition, because the decorative surfaces of the two display patterns 30 are overlapped, the impact of moire on visibility can be reduced.

Sixth Embodiment
In the above-described embodiments, examples have been described in which the display device is mainly composed of a light source and a display unit. In the sixth embodiment, the display device includes a sensor unit disposed behind the display unit 40 in addition to the light source 10 and the display unit 40.

Figure 41 is a diagram showing a schematic configuration of a display device according to embodiment 6. In addition to the light source 10 and display unit 40, the display device shown in Figure 41 includes a sensor unit that detects the presence of an object (e.g., a finger 606) near the display panel 20 of the display unit 40. The display device according to embodiment 6 is applicable to a non-contact control panel, which is an operating device for operating equipment or facilities.

The sensor unit of the display device according to embodiment 6 includes, for example, a sensor light source 602 that emits light (sensor light), a light receiving unit 603 that has a light receiving element that detects the light, and a bandpass filter 601 that passes light in a predetermined wavelength band. The display panel 20 that constitutes the display unit 40 is made of a material that transmits the light emitted from the sensor light source 602.

The sensor light source 602 is, for example, a semiconductor laser. The light emitted from the sensor light source 602 is not visible light, but, for example, near-infrared light (e.g., wavelength 850 nm). An optical element such as a lens may be provided immediately after the sensor light source 602.

The light receiving unit 603 receives light coming from the direction of the display unit 40. The light receiving unit 603 is, for example, a photodiode, a CCD (Charge Coupled Device) image sensor, or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. An optical element such as a lens may be provided immediately in front of the light receiving unit 603.

The bandpass filter 601 selectively transmits light in the wavelength band of the sensor light source 602. The bandpass filter 601 may be designed to pass light within a full width at half maximum of 50 nm, centered on the peak wavelength of the sensor light source 602, for example.

In the display device of Figure 41, light is emitted from the sensor light source 602, passes through the bandpass filter 601, passes through the display board 20 from the back to the front, is reflected by the target object, the finger 606, passes through the display board 20 from the front to the back, and passes through the bandpass filter 601, and then enters the light receiving unit 603.

Figure 42 is a diagram schematically illustrating the configuration of a display device according to Variation 1 of Embodiment 6. The display device shown in Figure 42 includes a sensor light source 602, a light receiving unit 603, a bandpass filter 601, and a beam splitter 604. By including the beam splitter 604, the optical axis of the sensor light source 602 and the optical axis of the light receiving unit 603 can be aligned.

In the display device of Figure 42, light is emitted from the sensor light source 602, passes through the beam splitter 604 and bandpass filter 601, passes through the display board 20 from the back to the front, is reflected by the target object, the finger 606, passes through the display board 20 from the front to the back, passes through the bandpass filter 601, and is reflected by the beam splitter 604, and is incident on the light receiving unit 603.

Figure 43 is a diagram schematically illustrating the configuration of a display device according to Variation 2 of Embodiment 6. The display device shown in Figure 43 includes a sensor light source 602, a light receiving unit 603, a bandpass filter 601a, and a dichroic mirror 605. The dichroic mirror 605 transmits light in the visible wavelength band (e.g., 380 nm to 780 nm) and reflects light in the wavelength band of the sensor light source 602. Depending on the color displayed by the display unit 40 or the combination of wavelengths used by the display unit 40 and the sensor light source 602, the dichroic mirror 605 can deflect light to make optical components such as the sensor light source 602 and the light receiving unit 603 less visible to the observer (at the position of the finger 606). Furthermore, if the display unit 40 and the dichroic mirror 605 are transparent, a see-through structure can be achieved, allowing objects behind them (such as other displays and guide signs) to be visible.

In the display device of Figure 43, light is emitted from the sensor light source 602, passes through the bandpass filter 601a, is reflected by the dichroic mirror 605, passes through the display board 20 from the back to the front, is reflected by the target finger 606, passes through the display board 20 from the front to the back, is reflected by the dichroic mirror 605, and passes through the bandpass filter 601a, and then enters the light receiving unit 603.

When a finger 606 is brought close to the display board 20 of any of the display devices shown in Figures 41 to 43, light emitted from the sensor light source 602 is reflected by the finger 606, and the reflected light is received by the light receiving unit 603. The control unit 610 can determine whether or not an input operation has been performed by the finger 606 based on changes in the intensity of the detected light at the light receiving unit 603. The control unit 610 may also determine whether or not an input operation has been performed by the finger 606 using ToF (Time of Flight). The control unit 610 may also perform lighting control and switching control of the display pattern 30 based on the input determination. The control unit 610 is composed of a processing circuit. The processing circuit may be composed of a processor that executes a program as software stored in memory.

It is desirable that the color of the display pattern 30 on the display board 20 has a sufficiently high brightness contrast ratio with the color of the bandpass filters 601, 601a. For example, if the light emitted from the sensor light source 602 is near-infrared light, the color of the bandpass filters 601, 601a is black. In contrast, the color of the display pattern 30 is a high-brightness color, such as white.

The display devices shown in Figures 41 to 43 are expected to save space by integrating a structure for displaying information with a sensor unit that detects objects such as a finger 606 without contact.

Furthermore, by using any of the display devices shown in Figures 41 to 43, the configuration of the sensor unit can be made invisible from the outside, thereby improving the design.

Note that the configuration of the sensor unit of any of the display devices shown in Figures 41 to 43 can be applied to any of the above embodiments.

1, 1a to 1g, 2, 3, 3a to 3c, 3b2, 4, 5 display device, 10, 10c, 10d, 10e, 10f, 10h, 10i, 10m, 10n light source, 20 display board, 30, 30c, 30d, 30h, 30i, 30j, 30k display pattern, 40, 40c, 40d display section, 201 front, 202 back, 203, 204 side, L0 to L4, L6, L7 light.

Claims (13)

In a display device for displaying a display object,
a plurality of light sources each emitting light of a different wavelength;
a display unit having a transparent display plate, configured to have a plurality of display patterns with different peak wavelengths of scattered light on at least one of the front and back surfaces of the single display plate in order to display the display target in response to light emitted by the light source, the display pattern being in a visible display state when the light source is emitting light scattered by the display pattern, and the display pattern being in a transparent non-display state when the light source is not emitting light scattered by the display pattern;
a lighting control circuit that controls the plurality of light sources so as to switch between light sources to be turned on among the plurality of light sources, thereby switching the wavelength of light incident on the single display panel and independently switching between display and non-display of each of the plurality of display patterns;
Equipped with
the plurality of light sources include a light source that emits light of a first wavelength among the light of different wavelengths,
the plurality of display patterns are formed by transparent ink containing a plurality of types of light scattering particles having different peak wavelengths of scattered light, and the light of the first wavelength is scattered more significantly by the first display pattern than by the second display pattern ;
the display pattern has a plurality of divided minute regions,
The wavelengths of light scattered in adjacent regions among the plurality of regions are different.
A display device characterized by: The replaceable display pattern is provided on a film attached to at least one of the front and back surfaces of the display plate with an adhesive,
The display device according to claim 1 , wherein the display panel, the adhesive, and the film have substantially the same refractive index. 3. The display device according to claim 1, wherein the plurality of display patterns are formed by transparent ink containing a plurality of types of light scattering particles that scatter light with different peak wavelengths. Further comprising a refractive optical element bonded to the display panel,
The light emitted from the light source passes through the refractive optical element and enters the inside of the display panel from the front or rear surface of the display panel, and is guided in a direction along the front or rear surface,
The refractive optical element is
a first incident surface that refracts light emitted toward the display panel;
a first reflecting surface having a curved shape that reflects light refracted by the first incident surface;
a second reflecting surface having a planar shape extending from the first reflecting surface;
a second incident surface that refracts light emitted to the opposite side of the display panel;
a curved third reflecting surface that reflects the light refracted by the second incident surface;
4. The display device according to claim 1 , further comprising: a fourth reflecting surface having a planar shape and extending from the third reflecting surface. 5. The display device according to claim 4 , wherein an angle of the second reflecting surface relative to the surface of the display panel is smaller than an angle of the optical axis of the refractive optical element relative to the surface of the display panel. Further comprising a refractive optical element bonded to the display panel,
The light emitted from the light source passes through the refractive optical element and enters the inside of the display panel from the front or rear surface of the display panel, and is guided in a direction along the front or rear surface,
the refractive optical element has an incident surface onto which light emitted from the light source is incident, an upper surface, a lower surface opposite to the upper surface, and an adhesive interface opposite to the upper surface;
The adhesive interface is bonded to a first surface, which is the front surface or the back surface, of the display panel;
3. The display device according to claim 1, wherein the upper surface is a free-form surface. The refractive optical element is configured such that, among the light emitted from the end portion on the upper surface side of the light source, the light passes through the contact point on the light source side of the adhesive interface and travels toward a second surface which is the back surface or the front surface opposite the first surface,
The display device according to claim 6, characterized in that twice the distance in a first direction, which is a direction parallel to the second surface, from the contact point on the light source side to the position of the second surface of the display panel that is first reached after passing through the adhesive interface is longer than the length of the adhesive interface in the first direction. The refractive optical element is
When the angle between the optical axis of the refractive optical element and the incident light is defined as an incident angle, and the angle between the optical axis of the refractive optical element and the incident light is defined as an exit angle,
a first light beam reaching a first region of the upper surface closer to the light source is reflected at a first exit angle that is smaller than a first incident angle that is an incident angle of the first light beam;
reflecting second light reaching a second region of the upper surface that is farther from the light source than the first region at a second exit angle that is larger than a second incident angle that is an incident angle of the second light;
the first angle of incidence is greater than the second angle of incidence;
8. The display device according to claim 6 , wherein the first light and the second light are guided by the reflection to a second surface, which is the rear surface or the front surface opposite the first surface. The display device according to claim 6 , further comprising a light-shielding cover that covers the refractive optical element. a plurality of the light sources and a plurality of the display units are stacked;
The display patterns of adjacent display sections among the plurality of display sections are arranged so as to contact and overlap each other,
the plurality of display patterns are arrows,
3. The display device according to claim 1, wherein the plurality of display patterns are independently controlled to be illuminated in a time-division manner. The light source has two light sources,
The display unit has two of the above-mentioned displays,
The two display units are stacked,
3. The display device according to claim 1, wherein the display patterns of the two display sections are arranged so as to overlap each other in a direction perpendicular to the display sections. a sensor unit on at least one of the front and back surfaces of the display board that detects an object present on the opposite side of the one surface of the display board;
The sensor unit
a sensor light source that emits sensor light;
a light receiving unit that detects the sensor light that has passed through the display plate from the one surface to the opposite side of the one surface, been reflected by the object, passed through the display plate from the opposite side of the one surface to the one surface, and been reflected by a dichroic mirror;
12. The display device according to claim 1 , wherein the dichroic mirror reflects light in a wavelength band of the sensor light source and transmits light in a visible wavelength band between the display panel and the sensor light source and light receiving unit. 13. The display device according to claim 12 , wherein visible light incident on the surface of the dichroic mirror opposite to the display panel and exiting from the surface of the dichroic mirror facing the display panel travels straight and is incident on the display panel.