JPH05178120A - Head up display for vehicle - Google Patents

Abstract

PURPOSE:To provide a holographic head-up display which is clear and has no chromatic aberration. CONSTITUTION:Light beams emitted from an information display source 3 are diffracted by a correction hologram 1 to be subjected to wave-band selection and be converged in the direction different from the direction of regular reflection. The light beams are once converged on a point F and then applied to a combiner hologram 2 to be diffracted and visually confirmed by an observer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle head-up display (HUD).

[0002]

2. Description of the Related Art HUD has recently been used as a method of displaying information to a driver in a vehicle. This is to display optical information projected from a display information source such as a liquid crystal display device on a combiner composed of a half mirror,
The driver can read the information from the driving state without moving the line of sight.

Recently, as the above combiner, due to its simplicity as an optical element and the abundance of added functions,
Holograms are gaining attention. Since this holographic combiner can have not only a reflection function (diffraction function) but also a lens function and the like, it can diffract optical information in the driver's visual field direction, or use other optical systems such as lenses. It is possible to form an image at an arbitrary position without using it. Another feature is that a high-luminance display image can be obtained without impairing the foreground luminance.

FIG. 5 is a conceptual diagram showing the structure of such a vehicle HUD. Here, 31 is a driver's observation position, 32 is a holographic combiner, 33 is a light beam containing information, 34 is a lens system that is a collimator, 35 is a transmissive liquid crystal display element that is a display, and 36 is a halogen lamp or the like. Is a light source, 37 is a windshield, and 38 is a vehicle body.

The light emitted from the light source 36 passes through the transmissive liquid crystal display element 35 through the lens system 34, and the holographic combiner 32 provided on the windshield 37 of the vehicle.
It is irradiated on the vehicle and reflected (diffracted) to the driver at the observation position 31.
Is visible in.

In FIG. 5, if the holographic combiner 32 is provided with a lens function, it is possible to form a distant image on the display. Further, the holographic combiner 32 can be provided with the function of the lens system 34 which is the collimator.

[0007]

Conventionally, in a vehicle holographic head-up display, a single hologram for a combiner has various problems such as chromatic aberration, image distortion, and blurring. There is also an attempt to reduce chromatic aberration by using a hologram for correction once and then diffracting it by a combiner to reduce chromatic aberration. However, in order to avoid a specular reflection image and a high-order diffraction image from the correction hologram. It was very difficult to match the combiner hologram and the correction hologram, and the setting was limited.

[0008]

The present invention has been made to solve the above problems, and is a vehicle in which a light beam containing information emitted from a display information source is diffracted by a hologram toward a viewer. The display for display comprises a first hologram for diffracting a light beam containing information in the viewer direction, and a second hologram for diffracting the light generated from the information display source into the first hologram, and the information Rays containing
And a second hologram for substantially condensing the first-order diffracted light of the hologram of (1) to a vehicle head-up display.

The present invention also provides the above vehicle head-up display in which a diaphragm is installed in the vicinity of the condensing position of a light beam containing information.

Here, the display information is appropriately selected according to its display application, and examples thereof include a vehicle speedometer and a tachometer.

The viewer is mainly the driver of the vehicle,
In addition, passengers such as the passenger seat and other passengers, or all of these passengers can be targeted.

The hologram usually has an area of about several tens mm square to several hundred mm square and a thickness of several tens of μm, and has a light diffraction function. As this hologram, emboss type, Lippmann type, rainbow type, and other holograms can be widely used. As the hologram material, various photosensitive materials such as polyvinyl cabazole, gelatin dichromate, photoresist, photopolymer, and silver salt can be used. The following description will be given for a volume hologram having a diffraction grating as a refractive index distribution in the hologram.

It is preferable that the peak wavelength of the diffraction intensity of the hologram substantially matches the peak wavelength of the intensity of the light source in order to improve the diffraction efficiency. Further, the hologram may be formed by performing multiple exposure with light having different properties.

Although the hologram for combiner may be provided separately from the windshield, it is preferably used by being attached to the windshield of a vehicle because of its simple structure. Especially, from the viewpoint of hologram protection, it is a laminated glass. It is good to use it by enclosing it inside a windshield.

In this case, the laminated glass is formed by laminating and adhering a synthetic resin film such as a polyvinyl butyral film and a polyurethane film on at least one glass, and examples of its form include a glass plate / synthetic resin film and a glass. Plate / synthetic resin film / glass plate, glass plate / synthetic resin film / glass plate / synthetic resin film / synthetic resin film. The hologram may be enclosed in the boundary between these glass plates or the synthetic resin film or inside the synthetic resin film. The glass plate on which the hologram is mounted may be colored, or the surface thereof may be provided with a heat ray reflective film or the like.

The information display source in the present invention has a function of emitting light to display, and as a typical example, a so-called light-receiving type display element such as a liquid crystal display element is used as a hot cathode tube (H).
There is a combined use of a light source including a CT), a fluorescent display tube (VF), a tungsten lamp, a halogen lamp, and an LED. As the liquid crystal display element, a transmission type twisted nematic type liquid crystal display element, a super twisted nematic type liquid crystal display element or the like can be preferably used. In the case where such a light receiving type display element is also used with the above light source, an appropriate light beam collimating means such as a lens system and an appropriate light guiding means such as a light guide plate are arranged between the light receiving type display element and the light source. May be.

Further, as a light emitting display means, a plasma display, an electroluminescence display,
A light emitting display element such as a CRT may be used. Alternatively, instead of using a display element, the light source itself may be patterned and arranged to generate specific information as light.

Further, in the optical path until the light is projected on the holographic combiner, if necessary, a light changing means such as a mirror or KNbO ₃ , β-BaB ₂ O.
_4, KTiOPO _4, the non-linear optical element made of KH ₂ PO ₄ and the like may be disposed.

In the present invention, the correction hologram and the combiner hologram are used, and the focus position of the first-order diffracted light of the combiner hologram (first hologram) is
It is characterized in that a light beam containing information is substantially condensed by a correction hologram (second hologram).

Since the incident angle of the hologram diffracted by the wavelength is limited, the position where the diffracted light of the hologram is focused is also limited if the wavelength of the light source is determined. Here, it is characterized in that such a condensing point is substantially matched by two holograms.

[0021]

In the present invention, the light emitted from the information display source is diffracted by the correction hologram to be wavelength-selected and diffracted in a direction different from that of the specular reflection image. The diffracted light is once condensed and then diverged. The converging point is preferably installed at the position of the point light source of the reference light at the time of hologram production,
Aberrations such as image distortion and blurring can be solved by matching the states of the wavefronts that enter the hologram for the combiner between the reference light during hologram production and the reproduction light during reproduction. Furthermore, a specular reflection image, a high-order diffraction image, unnecessary reflection light from the lens interface, and the like can be easily removed by installing a diaphragm at the focal point during reproduction. For this reason, it is not necessary to consider the influence of the above-mentioned unnecessary image and unnecessary reflection in the installation of the optical system, so that the design restrictions are extremely reduced.

[0022]

[Embodiment] Especially, when the exposure wavelength and the reproduction wavelength are matched with each other, the arrangement of the optical system during the exposure of the hologram becomes simple. So, in the following case,
An example will be described.

First, a method of manufacturing a combiner hologram will be described. FIG. 2 is a conceptual diagram thereof. The light emitted from the laser oscillator 7 is split into two lights by the beam splitter 9, and then reflected by the mirrors 8a and 8b, respectively, and then spreads through the objective lenses 10a and 10b.
One of the two light beams that becomes the object light is the distance to be displayed,
The lens 11d appropriately changes the spread of the wavefront of the light flux according to the size. Further, the light source that serves as the reference light is located at a position where the display light source during reproduction is apparently arranged. That is, when the light from the display light source during reproduction enters the hologram through the lens system or the like, the position of the light source of the reference light is determined in consideration of the existence of this lens system. A pinhole may be provided after the objective lenses 10a and 10b to remove foreign matter on the lens and unnecessary reflected light due to the interface of the combined lens.

Next, a method of manufacturing the correction hologram will be described with reference to FIG. Similarly to the above, the light emitted from the laser oscillator 7 is divided into two lights by the beam splitter 9 and then reflected by the mirrors 8a and 8b, respectively, and then the objective lens 10
The luminous flux is expanded through a and 10b. The lens 14a changes the wavefront of the object light into convergent light.
The reference light is used as parallel light or divergent light by the lens 14b.

The photosensitive material 12 for hologram exposed by the above method is developed and dried to form a hologram. FIG. 1 is a conceptual diagram showing the configuration of the head-up display. The light emitted from the information display source 3 is the hologram for correction 1
The light is diffracted by, the wavelength is selected, and the light is condensed in a direction different from the specular reflection direction. Once the light is condensed at the point F, it is irradiated onto the combiner hologram 2, diffracted and visually recognized by the viewer 4. The converging point F is a common converging point at the light source wavelength of the correction hologram 1 and the combiner hologram 2, and is the position of the apparent light source when the combiner hologram is produced. In this way, the incident angles of the reproduction light and the reference light used for exposure with respect to the hologram for the combiner can be made to coincide with each other, and distortion such as image distortion and blurring can be prevented. In addition,
When the hologram photosensitive material has expansion and contraction, it is possible to manufacture a hologram in consideration of the deviation of the diffraction grating interval due to the expansion and contraction.

Further, by installing the diaphragm 5 near the focal point F during reproduction, the specular reflection image and the high-order diffraction image 15 can be easily removed, and a clear image can be seen.

As the hologram for correction, not only the reflection type but also the transmission type can be used. FIG. 4 is a conceptual diagram showing the arrangement at that time. The reference numerals are the same as those used in FIG. In the figure, 1a is a transmissive correction hologram that replaces the reflective correction hologram in FIG.

[0028]

According to the present invention, the chromatic aberration is reduced by once diffracting the light emitted from the information display source with the correction hologram and selecting the wavelength. In addition, the correction hologram temporarily collects light. By matching the focus point of the combiner hologram to this focus point, image distortion,
It is possible to prevent aberration such as blurring.

Further, by installing the diaphragm 5 near the converging point, the specular reflection image, the high-order diffraction image, and unnecessary reflection can be easily removed, and the degree of freedom in the arrangement of the optical system can be increased and a clear image can be obtained. be able to.

Further, the correction hologram can be made small and the combiner hologram can be made large. Furthermore, since the light is focused once, the frontage can be reduced at the stop. From the above, the on-vehicle holographic head-up display in which the optical system is arranged in the dashboard can be made large for the display part, and the optical system in the dashboard becomes compact,
Furthermore, the frontage of the dashboard can be made smaller.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an arrangement of a head-up display of the present invention.

FIG. 2 is a conceptual diagram showing a method for exposing a hologram for a combiner used in the present invention.

FIG. 3 is a conceptual diagram showing an exposure method for a correction hologram used in the present invention.

FIG. 4 is a conceptual diagram showing another example of the arrangement of the head-up display of the present invention.

FIG. 5 is a conceptual diagram showing the arrangement of a head-up display.

[Explanation of symbols]

 1, 1a Second hologram (correction hologram) 2 First hologram (combiner hologram) 3 Information display source 4 Viewer 5 Aperture

Claims (2)

[Claims] 1. A vehicle display comprising a hologram, which diffracts a light beam containing information emitted from a display information source in the viewer direction, wherein a first light beam diffracts the light beam containing information in the viewer direction. A hologram and a second hologram for diffracting the light generated from the information display source into the first hologram are provided, and the light beam containing the information is provided at a position where the first-order diffracted light of the first hologram is condensed. A head-up display for a vehicle, which is substantially condensed by the hologram of No. 2. 2. The head-up display for a vehicle according to claim 1, wherein a diaphragm is installed in the vicinity of a position where a light ray containing information is condensed.