JPH04345537A - Automotive head-up display - Google Patents

Abstract

PURPOSE:To provide a holographic head-up display free from much dispersion in diffraction efficiency. CONSTITUTION:A luminous display means 6 is provided near the windshield glass of an automobile, and has such beam as incident slantingly on the surface of the glass. The beam is transmitted and diffracted with the predetermined angle via the second transmission type hologram 4 sealed within the glass, and further made incident on the first reflective type hologram 5. Then, the beam is reflected and diffracted toward a driver's field of view 7 through the first hologram 5. In this case, the first hologram 5 has diffraction lattice surface inclined 30 degrees or more with hologram surface.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art HUDs have recently come into use as a method of displaying information to drivers and the like inside a vehicle. This system projects optical information projected from a light-emitting display means such as a liquid crystal display onto a combiner such as a half mirror, allowing the driver to read the information without having to move his or her eyes while driving. .

Recently, the above-mentioned combiner has been used because of its simplicity as an optical element and the richness of added functions.
Holograms are gaining attention. This holographic combiner has not only a reflection function (diffraction function) but also a lens function, so it can diffract optical information in the direction of the driver's field of vision, or it can be used to incorporate other optical systems such as lenses. It becomes possible to form an image at any position without using it. Another feature is that a high-brightness display image can be obtained without impairing foreground brightness.

FIG. 5 is a conceptual diagram showing the configuration of such an in-vehicle HUD. Here, 31 is the observation position of the driver, 32 is a holographic combiner, 33 is a light beam containing information, 34 is a lens system that is a collimator, 35 is a transmission type liquid crystal display element that is a display body, 36 is a halogen lamp, etc. 37 is a windshield, and 38 is a vehicle body.

The light emitted from the light source 36 passes through a transmission type liquid crystal display element 35 via a lens system 34, and then passes through a holographic combiner 32 provided in a windshield 37 of the vehicle.
is reflected (diffracted) and presented to the driver at observation position 31.
is visible.

In FIG. 5, if the holographic combiner 32 is provided with a lens function, it becomes possible to form a display image at a distance. In addition, the function of the lens system 4, which is the collimator, is transferred to the holographic combiner 32.
It is also possible to have it.

[0007]

FIG. 2 shows a conventional example of a hologram recording method for forming a reproduced image of such a display device at a distance. A reference beam 9 that is a diverging spherical wave and an object beam 10 that is a diverging spherical wave are each irradiated with a single wavelength laser beam onto a photosensitive material 8 for forming a hologram, and the photosensitive material 8 is exposed. The center of the diverging spherical wave of the reference light 9 is the position where the display should be placed if the photosensitive material 8 is placed parallel to the windshield surface, and the center of the diverging spherical wave of the object light 10 is the position where the display device should be placed, assuming that the photosensitive material 8 is placed parallel to the windshield surface. is the position to be imaged.

By the way, when encapsulating a hologram in a laminated glass, it is preferable that the thickness of the hologram be as thin as possible in order to reduce perspective distortion of the laminated glass. Further, even if the hologram is not enclosed in a laminated glass, if the hologram is thick, the parting lines will be noticeable, which is not preferable. On the other hand, the above-mentioned holographic combiner usually uses a reflective type, but the direction of the light beam is almost determined depending on the position of the observer and the position of the holographic combiner attached to the windshield (approximately horizontal - 10° to +10°).

Furthermore, if the diffraction grating surface is made at a large angle with respect to the hologram surface (approximately equal to the inclination of the windshield, usually 20° to 40°), the light source position will be near the driver's position, It gets in the way of driving. Therefore, the diffraction grating recorded in the hologram must be nearly parallel to the hologram surface. Therefore, in order to increase the number of interference fringes (diffraction gratings) and obtain sufficient diffraction efficiency, it is necessary to make the hologram thicker.

[0010] Furthermore, when displaying a long distance as described above, at least one of the reference light and the object light becomes a spherical wave, so the angle formed by these lights differs depending on each point within the photosensitive material, and the photosensitive The diffraction grating pattern formed as a refractive index gradient within the material has a three-dimensional curvature. For this reason, when the hologram is thin, the number of diffraction gratings is small, so the diffraction efficiency often varies at each point on the surface of the hologram, making it even more difficult to make the hologram thinner.

[0011] The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a new structure for a vehicle head-up display that has not been previously known. It is something to do.

0012

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and includes a light-emitting display means that generates information to be displayed as a light beam, and a light-emitting display means that diffracts the light beam toward a viewer. a reflective first hologram having a diffraction grating, and between the light emitting display means and the first hologram,
a transmission-type second hologram that diffracts the light beam containing the information to be displayed in the direction of the first hologram, wherein the diffraction grating surface of the first hologram is in the first hologram direction; The present invention provides an in-vehicle head-up display that is tilted at an angle of 30° or more with respect to a hologram surface.

[0013] The information to be displayed here is appropriately selected depending on its display purpose, and examples thereof include a vehicle speedometer and tachometer. What is a viewer?
The target is mainly the driver of the vehicle, but can also include passengers in the front passenger seat and other passengers, and all of these.

[0014] The hologram functions as a combiner for the HUD. It usually has an area of several tens to several hundred mm square, a thickness of several tens of micrometers, and has a light diffraction function. As this hologram, not only the embossed type that is widely used at present, but also Lippmann type, rainbow type, and other so-called holograms can be widely used. In addition, as a hologram material,
Various photosensitive materials such as polyvinyl cabazole, dichromate gelatin, photoresist, photopolymer, and silver salt can be used. The following description will be made regarding a volume hologram having a diffraction grating as a refractive index distribution within the hologram.

The peak wavelength of the diffraction intensity of the hologram can be made to substantially match the peak wavelength of the intensity of the light source.
This is preferable in terms of increasing diffraction efficiency. Further, the hologram may be formed by performing multiple exposures with light having different properties.

[0016] The holographic combiner made of such holograms may be provided separately from the windshield, but due to its simple structure, it is preferably used by being attached to the windshield of a vehicle, especially from the viewpoint of protecting the hologram. is preferably used by being sealed inside a windshield glass that is laminated glass. In the present invention, two types of holograms are used, and both of them may be enclosed in the windshield, or only the hologram that diffracts light toward the viewer may be enclosed.

[0017] In this case, the laminated glass is made by laminating and adhering a synthetic resin film such as a polyvinyl butyral film or a polyurethane film to at least one sheet of glass. Examples include glass plate/synthetic resin film/glass plate, glass plate/synthetic resin film/glass plate/synthetic resin film, and glass plate/synthetic resin film/synthetic resin film. The hologram may be encapsulated at the boundary of these glass plates or synthetic resin films or inside the synthetic resin film. The glass plate on which the hologram is mounted may be colored, or may have a heat ray reflective film or the like provided on its surface.

The light-emitting display means of the present invention has the function of emitting light to display a display, and representative examples thereof include:
Hot cathode tubes (
HCT), fluorescent display tube (VF), tungsten lamp,
Some use light sources such as halogen lamps and LEDs. As this liquid crystal display element, a transmission type twisted nematic type liquid crystal display element, a super twisted nematic type liquid crystal display element, etc. can be preferably used.

Alternatively, the light sources themselves may be patterned and arranged to generate specific information as light without using a light-receiving display element. In the case of a light-receiving type display element that uses the above-mentioned light source in combination, an appropriate light beam collimating means such as a lens system, or an appropriate light-guiding means such as a light guide plate may be placed between the light-receiving type display element and the light source. good.

Furthermore, in the optical path until the light is projected onto the holographic combiner, optical deflection means such as a mirror, or KNbO3, β-BaB
A nonlinear optical element made of 2O4, KTiOPO4, KH2PO4, etc. may be arranged.

[0021]

[Example] The present invention will be explained below according to an example.

FIG. 1 shows a sectional view of the basic structure of the holographic combiner of the present invention sealed in laminated glass. The glass surface of an automobile opening (for example, a windshield glass) is a laminated glass made of two sheets of glass, and in the figure, 1 is an inner glass, 2 is an outer glass, and 3 is an interlayer film. There is a predetermined light emitting display means 6 in the automobile instrument panel near the glass surface, and this light beam is transmitted through a diffraction grating formed in a transmission hologram 4 (second hologram) enclosed within the glass surface. 4a to be transmitted and diffracted at a predetermined angle and incident on the reflection hologram 5 (first hologram), and then the reflection hologram 5
The diffraction grating surface 5a formed therein reflects and diffracts the light in the direction of the driver's field of view.

[0023] In this way, the second hologram, which diffracts the information to be displayed so that the light beam enters the first hologram, is placed between the first hologram, which diffracts the light beam toward the viewer, and the light emitting display means. By arranging the light source, the inclination of the interference fringes in the first hologram plane can be brought closer to the normal direction of the hologram plane without moving the position of the light source, and the number of interference fringes can be increased. Efficiency becomes uniform. That is, in the present invention, since the angle between the diffraction grating surface of the first hologram and the hologram surface is 30 degrees or more, the hologram can be easily formed without making the first hologram too thick. Since the number of diffraction gratings in the hologram can be increased, diffraction efficiency can be improved and variations in diffraction efficiency within the hologram plane can be suppressed.

In addition to the above configuration, it is preferable to adjust the diffraction angle of the second hologram so that the light is incident on the first hologram almost perpendicularly to the hologram surface. By doing so, during exposure for creating a hologram, the photosensitive material is exposed from a direction substantially perpendicular to the photosensitive material, which facilitates alignment during exposure. Additionally, if the hologram is tilted with respect to the optical axis during exposure, the interference intensity of the exposure light on the hologram surface will be asymmetrical with respect to the optical axis, which may cause the intensity of the reconstructed image to be uneven. However, such non-uniformity can be suppressed.

[0025] Exposure methods for producing each of these holograms are shown in FIGS. 3 and 4.

First, in order to create a second hologram (transmission type hologram), as shown in FIG. Object light 13 in the form of a plane wave is simultaneously irradiated onto the photosensitive material 11 from different directions for exposure.

In addition, as shown in FIG. 4, in order to create a first hologram (reflection type hologram) for making the transmitted diffracted light by the second hologram visible as if it were formed as a distant image in front of the driver, a reference hologram is used. A reference beam 15 in the form of a plane wave from the same direction as the direction in which the light enters the first hologram with respect to the photosensitive material surface and an object beam 16 in the form of a diverging spherical wave centered at a distant imaging point are simultaneously exposed. The material 14 is irradiated and exposed.

By the way, in FIGS. 3 and 4, we have described the case of manufacturing a hologram mirror with a lens function for performing distant imaging, but if the divergent spherical waves in the figures are replaced with plane waves, it is possible to form distant images ( It is possible to create a hologram mirror that does not have the effect of enlarging or reducing the image. It should be noted that it is easier to manufacture and advantageous if the holograms are mounted on two glass plates as shown in Figure 1, but it is better to have the holograms 4 and 5 in close contact with each other so that they can pass through media with different refractive indexes. This is desirable for obtaining clear images because the number of times the image is removed is reduced.

[0029]

Effects of the Invention According to the present invention, it is possible to reduce the distortion of a holographic reproduced image, and even for a relatively thin hologram, the in-plane diffraction efficiency of the hologram can be made uniform. .

[Brief explanation of drawings]

[Fig. 1] Cross-sectional view showing the basic configuration of the present invention

[Figure 2] Conceptual diagram showing the conventional exposure method during hologram production

[Fig. 3] Conceptual diagram showing the exposure method during hologram production of the present invention

[Fig. 4] Conceptual diagram showing the exposure method during hologram production of the present invention

[Figure 5] Conceptual diagram of holographic HUD

[Explanation of symbols]

1 Inner plate glass 2 Exterior glass 3 Intermediate film 4 Transmission hologram 5 Reflection hologram 6. Luminous display means 7 Driver's field of view 8, 11, 14 Photosensitive material

Claims (1)

[Claims] 1. A first hologram of a reflective type having a light emitting display means for generating information to be displayed as a light beam, a diffraction grating for diffracting the light beam toward a viewer, and a first hologram comprising: a light emitting display means and a first light emitting display means; a transmission-type second hologram that is located between the holograms and diffracts the light beam containing the information to be displayed in the direction of the first hologram, the vehicle head-up display comprising: An in-vehicle head-up display characterized in that a grating plane is inclined by 30 degrees or more with respect to a first hologram plane.