Optical: systems and elements – Holographic system or element – Head up display
Reexamination Certificate
2001-10-15
2003-04-08
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Holographic system or element
Head up display
C359S015000, C359S008000, C359S014000
Reexamination Certificate
active
06545778
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a holographic display device which has a hologram to be used for e.g. a combiner provided to a fixed substrate.
2. Discussion of Background
As a method of displaying information to e.g. a driver in a vehicle, a head-up display (hereinafter referred to as HUD) has become used in recent years. HUD is such a device that a display image containing information of instruments, projected from a light-emitting display means such as a liquid crystal display device, is reflected on a combiner consisting of e.g. a half mirror or a reflection hologram provided to a wind-proof glass which is a windshield fixed on a forward portion of a vehicle as a fixed substrate, so that a display virtual image is visually recognized by a driver.
According to HUD, a driver can read information substantially without moving line of sight in a driving state.
Particularly one which employs a reflection hologram as a combiner is effective as a combiner of HUD, since it has such characteristics that a display image containing information from a light-emitting display means can be diffracted toward a driver and formed on an optional position on the forward portion of a hologram, and a high brightness virtual image display can be obtained without impairing brightness in the forward field of view, i.e. foreground brightness.
However, in the case of a combiner employing a reflection hologram, it is a virtual image that a driver observes, and the position of the display virtual image changes when the position of the eyes move, and how the image deforms also changes. Accordingly, the shape of the display virtual image variously changes during driving, and not only does a driver feel uncomfortable but also visual recognizability of the display significantly decreases.
FIG. 14
is a cross-sectional view illustrating a display device for a vehicle using a conventional reflection hologram. With a conventional display device for a vehicle as disclosed in JP-A-8-91094, as illustrated in
FIG. 14
, a reflection diffusion hologram
15
is used for a combiner provided to a wind-proof glass
1
, light containing information from a display element
2
is formed as an image on the surface of the reflection diffusion hologram
15
by means of an imaging optical component
3
such as a lens, and the image is diffracted by the reflection diffusion hologram
15
so that a real image is visually recognized by an observer
5
. Visual recognizability is high when the display image is a real image as compared with a virtual image.
However, in a case where the above reflection diffusion hologram is used, light having a certain wavelength of external light such as solar light is reflected on the reflection diffusion hologram, and a portion of the reflection diffusion hologram may look colored from the outside of the vehicle in some cases, and such is unfavorable in view of design of a vehicle. Further, simultaneously, since the hologram portion reflects light having a certain wavelength of external light, complementary color to the reflected color may be observed by a person in a vehicle, thus making the person feel uncomfortable.
Further, there is such a problem that external light such as solar light is reflected on the interface with the air on the vehicle inner side of the wind-proof glass, and the reflected light is diffracted by a hologram and reaches the eyes of a driver (hereinafter this phenomenon will be referred to as external light noise), and such a phenomenon significantly decreases visual recognizability of the driver.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the above-described drawbacks of the prior art and to provide a holographic display device which can improve visual recognizability.
The present invention provides a holographic display device which forms a display image of light containing information projected from a light-emitting display means, on a diffusion hologram provided on a fixed substrate, wherein the above diffusion hologram is a transmission diffusion hologram, and the above display image transmission-wise diffracted by the above diffusion hologram is reflected on the surface of the above fixed substrate for visual recognition.
The present invention further provides the above-mentioned holographic display device, wherein the above fixed substrate is a window glass of a vehicle.
The present invention further provides the above-mentioned holographic display device, wherein the visible light transmittance is at least 70% when the above transmission diffusion hologram is provided to the above fixed substrate.
The present invention further provides the above-mentioned holographic display device, wherein the above fixed substrate is a glass of a show window.
The present invention further provides the above-mentioned holographic display device, wherein a transparent substrate having non-reflection coating applied thereto is provided to the light-emitting display means side of the above transmission diffusion hologram.
The present invention further provides the above-mentioned holographic display device, wherein a high-reflection coating is applied to the glass of a show window on the side to which no transmission diffusion hologram is provided.
The present invention further provides the above-mentioned holographic display device, wherein the hologram is recorded on an acrylic photopolymer.
The present invention further provides the above-mentioned holographic display device, wherein the light-emitting display means is a liquid crystal display element.
The present invention further provides a method for producing a transmission diffusion hologram, which comprises disposing a diffusion optical component having light diffusion properties on one side of a hologram photosensitive material so as to produce a hologram only by a diffused light transmitted through or reflected on the above diffusion optical component.
The present invention further provides the above-mentioned method for producing a transmission diffusion hologram, wherein the above diffusion optical component has an angle of light diffusion within ±20°.
The present invention further provides the above-mentioned method for producing a transmission diffusion hologram, wherein the above diffusion optical component and the above hologram photosensitive material are disposed so that they are parallel to each other, and the distance between them is within 30 mm.
The present invention further provides the above-mentioned method for producing a transmission diffusion hologram, wherein a deep color glass which absorbs light is disposed in order of diffusion optical component/hologram photosensitive material/deep color glass.
The present invention further provides the above-mentioned method for producing a transmission diffusion hologram, wherein the above diffusion optical component is a frosted glass.
The present invention still further provides the above-mentioned method for producing a transmission diffusion hologram, wherein the above hologram photosensitive material is an acrylic photopolymer.
When a holographic display device of the above constitution is applied to a vehicle, a color of reflection toward the outside of the vehicle and a complementary color toward the inside of the vehicle are eliminated at a hologram installation portion, and a desirable display device in view of design and visual recognizability can be realized, and external light noise can be reduced. Such is preferred to use in view of safety when a wind-proof glass is used as a window glass. Further, by using the above-described transmission diffusion hologram, halation which is a phenomenon such that light is generated around a light source when external light falls thereon, can be prevented and the visible light transmittance improves. The diffusion angle of the above diffusion optical component is preferably within ±20°, more preferably within ±10°, taking both prevention of the halation and improvement of the visible light transmittance
Nakazawa Norihito
Ono Motoshi
Asahi Glass Company Limited
Lavarias Arnel C.
Spyrou Cassandra
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