JP3365528B2 - Holographic display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be applied to a high mount stop lamp for automobiles, a turn signal indicator, a display of a show window, or the like, and a transparent plate-shaped member near one end of the transparent plate-shaped member. Light from the provided light source is introduced through a prism or a hologram for introduction, and while being totally reflected inside the transparent plate, the hologram for display adhered to the transparent plate is irradiated, and its diffraction The present invention relates to a light guide type holographic display device for displaying by.

[0002]

2. Description of the Related Art As a high mount stop lamp for automobiles, a display hologram is provided on the rear window glass, and light from the light source is introduced through a prism to display the light while totally reflecting the window glass. Illuminate the hologram,
A light guide type display device for diffracting backward is disclosed in Japanese Patent Application Laid-Open No. Hei 4
Although it has been proposed as No. 228329, etc., the plate glass has a sharp edge portion ground (siming) for easy handling, but when light is incident on this portion on the side opposite to the light source. Another type of holographic display device is also proposed, which has the drawback of irregular reflection and light leakage, and a hologram is attached to a transparent plate different from the window glass for display, but the hologram is not diffracted by the hologram. Is totally reflected at the interface between the air and the air, reaches the end face on the side opposite to the light source, and there is light transmitted and reflected from the end face at this part, and the transmitted light is unnecessary because it is radiated to the ceiling of the automobile, etc. The reflected light is incident on the hologram again and is diffracted to the inside of the vehicle to hinder the driver or the like. Especially, at night, the unnecessary light is not preferable for safety. Is a new look However it is intended that no present invention aims to provide a holographic display device of the light guide type which prevents such unwanted light leaks.

[0003]

According to the present invention, light from a light source disposed in the vicinity of one end of the transparent plate is introduced into the transparent plate through a prism or an introduction hologram. While irradiating the display hologram adhered to the transparent plate while total reflection is performed with the total reflection angle being θ and the incident angle into the hologram being θ ′ in the transparent plate, the irradiation is performed.
In a holographic display device in which light is diffracted backward to be visually recognized and displayed, the light incident on the hologram is not diffracted but is totally reflected at the interface between the hologram and air, and is totally reflected on the plate-like body surface. End face opposite to light source
The light that reaches the end point is reflected by the end face and re-enters the hologram at an incident angle smaller than θ ′ and larger than the critical angle to reduce the diffraction efficiency, and the light from the light source is gradually reduced to a negligible level. As described above, the end face of the transparent plate-shaped body is characterized by being cut obliquely from the vertical plane of the transparent plate-shaped body, and when the end face of the transparent plate-shaped body is cut obliquely,
It is preferable to form a reflective layer on the end face.

[0004]

The operation of the present invention will be described with reference to FIG .
While the light a ₁ , a ₂ , a ₃ etc. from the light source is totally reflected,
The light radiated to the hologram 2 at the incident angle θ is diffracted rearward as a ₁₂ , a ₂₂ , a _32, etc., and is visually recognized by a following vehicle, etc., but the end face opposite to the light source is shown by a dotted line. Thus, when the light is not cut perpendicularly to the transparent plate-like member, the light which is not diffracted is totally reflected at the interface between the hologram and the air, A ₁ , A ₂ , A ₃ etc., and the light a ₁ becomes B _{1 on the} plate-like member surface. At the end face C ₁ ′, the light a ₂ directly reaches the end face B ₂ ′, and the light a ₃ directly reaches the end face B ₃ ′.

On these end faces C ₁ ', B ₂ ' and B ₃ ', a _{14 s} , a _{24 s} and a _{34 s} are partially transmitted to the outside, which is a problem if the space in the transmission direction is large, such as outdoors. However, when the space is small, such as in a room, it is not preferable because the ceiling is irradiated. On the other hand, for the remaining light, the light a ₃ is C indicated by the dotted line.
₃ ', D _3' returns while being totally reflected transparent plate-shaped body in the path through the, but rarely a problem because attenuated,
The light a ₁ re-enters the hologram 2 at an incident angle θ ″ and is totally reflected at the interface D ₁ ′ between the hologram 2 and the air, and this light is incident from the direction completely opposite to the light a ₁ . According to the diffraction efficiency, the light diffracts to the inside of the room as a ₁₂ ′, which hinders the driver. Similarly, the light a ₂ re-enters the hologram 2 at the incident angle θ ″, is totally reflected at the interface C ₂ ′ between the hologram 2 and the air, and is diffracted as a ₂₂ ′ toward the inside of the room, which may hinder the driver. Become.

Therefore, in the present invention, when the end face on the side opposite to the light source is absorbed with light, for example, a black absorption film is coated or a reflection film is coated, the light transmitted from the end face to the outside can be almost ignored. When the end face is covered with the absorption film, the light reflected from the end face and returning to the transparent plate can be reduced to a negligible level. The shape of the end surface may be vertical to the transparent plate-like member as in the conventional case, may be cut by being inclined from the vertical, or may be a shape in which corner portions are seamed.

The end face on the side opposite to the light source is inclined and cut from the vertical face of the transparent plate, and the reflection film 3 is formed on the cut end face.
In the case of coating with the light, as shown in FIG. 2, while the lights a ₁ , a ₂ , a ₃ from the light source are totally reflected, the incident angle θ ′ (strictly speaking, in FIG. Since there is a difference in the refractive index of the hologram, it is refracted at the interface, and the angle at that time is θ ', but the difference in the refractive index is actually small, so the light irradiated by (not shown) is almost Light that is diffracted backwards as a ₁₂ , a ₂₂ , a _32, etc. and is visually recognized by the following vehicles, etc., but the light that is not diffracted is totally reflected at the interface between the hologram and air, A ₁ , A ₂ , A _3, etc. , Light a ₁ is a plate
The light is totally reflected by B ₁ on the surface of the sheet and reaches the end face C ₁ , the light a ₂ directly reaches the end face B ₂ , and the light a ₃ directly reaches the end face B ₃ .

On the end faces C ₁ , B ₂ and B ₃ , most of the light is reflected by the reflecting film 3, and the light a ₂ and the light a ₃ are a ₂₃ and a ₃₃ , respectively, and the transparent plate-like body has a plate shape. Since it returns substantially parallel to the body surface, it is attenuated and causes almost no problem, and the light a ₁ is incident on the hologram 2 at an incident angle θ ′ (strictly speaking, since there is a difference in refractive index between the glass and the hologram in FIG. The light is refracted, and the angle at that time is θ ′, but since the difference in refractive index is actually small, it is smaller than (not shown) and is incident at an angle θ ″ larger than the critical angle. The light a ₁₃ is totally reflected at the interface D ₁ with the air, and this light a ₁₃ is the light a ₁
Since the diffraction efficiency is reduced and the light of the light source is gradually reduced to, for example, about 0.5% at an angle different from the incident angle θ of, the diffracted light at this time can be ignored.

In this case, if there is surface irregularity on the end face, there is a risk that light will leak due to scattering at this part, so it is better to make it a smooth surface. If there is no problem even if light is transmitted from this end face, the end face is It is not necessary to cover the reflective film, but when the display device is installed indoors, the light transmitted through the end face is generally unpleasant. However, if the light is reflected almost at this end face, there is almost no diffraction by the hologram, and the light returning to the light source side while totally reflecting the transparent plate-like body without re-incident on the hologram is attenuated on the way, so it can be ignored. ,
Unwanted light does not leak into the room or from the end face.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. 1 is a schematic view of a main part showing a holographic display device in a first embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part showing a light path in the second embodiment, and FIG. 3 is an incident angle to a hologram in the second embodiment. It is a figure which shows the relationship between and diffraction efficiency.

Embodiment 1 Referring to FIG. 1, apart from a rear window glass for a vehicle,
A holographic display device in which a transparent plate-like body 1 such as a plate glass to which a hologram 2 is attached is applied as a separately mounted type high mount stop lamp, and an end face of the transparent plate-like body 1 is covered with a light absorbing film 4. Will be illustrated.

The light absorbing film 4 is formed by applying black paint or the like to the upper end surface of the transparent plate-shaped body 1 such as a plate glass having a thickness of 4 mm. On the other hand, a dry plate obtained by applying a photosensitive material such as a photopolymer onto a base film such as polyethylene terephthalate is divided into two light beams from a laser light source (not shown) that oscillates, for example, green, and is irradiated with light from two directions.
Interference fringes are formed, and thereafter, the hologram 2 having a length of 80 mm and a width of 200 mm obtained by a normal development process is adhered to the transparent plate-shaped body 1 so that polyethylene terephthalate becomes the uppermost portion (protective layer).

The transparent plate 1 thus obtained is mounted in the vicinity of the rear window glass 5 for a vehicle, and is hidden under the rear parcel 6 to be a reflection mirror, a filter for transmitting red light, etc. Is provided with a light source 7 including a prism 8
Is provided so as to be in close contact with the transparent plate 1.

In the holographic display device thus constructed, when red light is emitted from the light source, it is introduced into the transparent plate through the prism 8 and the total reflection angle θ is critical in the transparent plate. The light travels while totally reflecting at an angle exceeding 41.8 °, is diffracted in the direction of the arrow by the display hologram 2, and red light is visually recognized by the eyes 9 of the following vehicle.

At this time, the light not totally diffracted by the hologram 2 but totally reflected at the interface between the hologram 2 and the air reaches the end face, but is absorbed by the almost black light absorbing film 4 to prevent light leakage. You can

Embodiment 2 With reference to FIG. 2, a holographic display device applied as a separately mounted high mount stop lamp as in Embodiment 1, in which an end face of a transparent plate 1 is cut obliquely. The case where the end face is coated with a reflective film will be exemplified.

One end face of the transparent plate-like body 1 such as a plate glass having a thickness of 4 mm is formed from the vertical plane of the transparent plate-like body (φ).
=) Tilt by 10 °, cut, cut, and polished multiple cut surfaces, and mask the surfaces of the leading and trailing transparent plates that are not adjacent to another transparent plate. A chromium film is coated on all of the end faces of the chromium film with a chromium film 3 by an ordinary sputtering method.

On the other hand, a hologram 2 having a length of 80 mm and a width of 200 mm obtained by the same method as in Example 1 is used.
Is adhered to the transparent plate-like body 1 with a double-sided adhesive tape so that polyethylene terephthalate may be the uppermost part (protective layer).

The transparent plate 1 thus obtained was mounted in the vicinity of the rear window glass 5 for a vehicle in the same manner as in Example 1, and was concealed under the rear parcel 6 so as to conceal it with a reflecting mirror and a red color. A light source including a filter that transmits light is provided, and a prism is provided in close contact with the plate glass 1.

In the holographic display device thus constructed, the total reflection angle θ in the transparent plate is 70 °,
The angle between the transparent plate and the rear parcel is set to 30 °, and the backward diffraction is set to the horizontal direction.
The change in the diffraction efficiency depending on the incident angle is obtained by the well-known theoretical formula of Cogelnic as shown in FIG.

When the red light is emitted from the light source, it is introduced into the transparent plate through the prism, and the total reflection angle θ in the transparent plate is 70 ° which exceeds the critical angle of 41.8 ° (for holograms). If the refractive index is 1.5 and the refractive index of the plate glass is 1.52, the incident angle θ'on the hologram will be 72.2 °.
While the lights a ₁ , a ₂ , a ₃ etc. are totally reflected at 87% of the light incident on the hologram 2 at an incident angle of 72.2 ° is diffracted backwards as a ₁₂ , a ₂₂ , a ₃₂ etc. Te, but is visible in such vehicle behind the interface 13 percent of the light that is not diffracted and the hologram and the _{air, a 1, a 2, a} 3 light a ₁ is totally reflected at such an end face C via B _{1 1} , the light a ₂ directly reaches the end face B ₂ , and the light a ₃ directly reaches the end face B ₃ .

This end face C₁, B₂, B₃Then most of that
Light, 90% or more of the light, is reflected by the reflection film 3 and the light a
₂And light a₃Is a_{twenty three}, A₃₃As in the transparent plate
It returns almost parallel to the plane of the plate, so it is attenuated and almost becomes a problem.
Not light a₁Is 51 ° smaller than θ'on hologram 2
It is incident at (= θ ″) and the interface D between the hologram 2 and air ₁
Is totally reflected by, and the diffraction efficiency of this light is clear from Fig. 3.
Since it is almost 1.5%, the light from the light source is set to 1.
The diffracted light is 0.13 × 0.9 × 0.015 = 0.0
01755, ie 0.2% or less, completely ignored
It is gradually reduced to the extent possible. In fact, in the transparent plate
Since there is attenuation due to absorption, it is further reduced.

The light that escapes from the reflective film on the end face to the outside of the transparent plate is also absorbed by the reflective film and can be ignored. The preferred examples have been described above, but the present invention is not limited to these, and various applications are possible.

Regarding the reflection film, in addition to the chromium film, an aluminum film formed by a vacuum deposition method, silica (SiO ₂ ) having a refractive index of 1.4 and titania (TiO ₂ having a refractive index of 2.2).
It is possible to use a wavelength selection film that reflects light of a specific wavelength formed by a sol-gel method or the like by appropriately selecting the mixing ratio of ₂ ).

With respect to the color of the light absorbing film, black is the most absorbing of light. Therefore, it is preferable to use a color close to black, which has a large absorption amount, such as gray or brown. Colors that absorb the light of, for example, colors that have a relationship of complementary colors,
When reproducing in red as in the embodiment, most of blue can be absorbed.

With respect to the transparent plate-shaped body, various transparent plate-shaped bodies such as transparent acrylic plates and plastic materials such as polycarbonate plates other than the plate glass can be used, and the application is also for window glass for vehicles such as vehicles, Alternatively, the invention can be applied to the case where a hologram is adhered to a window glass for construction, a partition, etc., and the display can be a solid display as well as a three-dimensional display of characters and figures.

Therefore, various kinds of lamps can be adopted as the light source, and the installation place may be installed above. When it is applied to building window glass, it can also be installed under the ceiling or under the floor. .

[0028]

INDUSTRIAL APPLICABILITY The present invention is a light guide type holographic display device, which can prevent unnecessary light from leaking at the time of reproduction, and is also preferable in terms of safety.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a holographic display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a key portion showing a light path according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between an incident angle on a hologram and diffraction efficiency in Example 2.

[Explanation of symbols]

1 transparent plate 2 hologram 3 reflective film 4 Light absorbing film 5 Rear window glass for vehicles 6 rear parcel 7 light source 8 prism 9th

Claims (2)

(57) [Claims] 1. Light from a light source disposed in the vicinity of one end of the transparent plate member is introduced into the transparent plate member through a prism or a hologram for introduction, and the entire inside of the transparent plate member is introduced. The hologram for display adhered to the transparent plate is irradiated while being totally reflected with the reflection angle being θ and the incident angle in the hologram being θ ′, and the irradiated light is diffracted backward and is visually recognized.
In a holographic display device in which the hologram is displayed, the light incident on the hologram is not diffracted but is totally reflected at the interface between the hologram and air, and is totally reflected by the plate-like surface.
The light that reaches the end face on the opposite side of the light source from the light source is reflected by the end face and re-enters the hologram at an angle of incidence smaller than θ ′ and larger than the critical angle to reduce the diffraction efficiency. A holographic display device characterized in that an end face of a transparent plate-like member is cut by being inclined from a vertical plane of the transparent plate-like member so as to be gradually reduced to a negligible level. 2. A reflective layer is formed on the cut end surface of the transparent plate.
The holographic display device of claim 1, wherein the form has.