JPH04303812A - Headup display - Google Patents

Abstract

PURPOSE:To display a sharp image as keeping a function by forming a holographic optical device in a set of element holograms which reproduce a different one point. CONSTITUTION:The element hologram 25a that is a hologram with small area is photographed as the position 23a of the point light source of reference light and the position 27a of the point light source of a material, and similarly, the element hologram 25b is photographed by placing the point light source on positions 23b, 27b. Therefore, adjacent element holograms 25a, 25b perform the stigmatic reproduction of the points 23a, 23b neighboring to each other on a display screen at the positions 27a, 27b. By using the holographic optical device 25 manufactured in such way as the combiner of a head-up display, an observer can observe one part 27a of an virtual image on the display screen via a certain one element hologram 25a in the holographic optical device, and observe the part 27b via the element hologram 25b.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffractive optical head-up display using a hologram, and more particularly to a head-up display that reduces aberrations and enables clear image display with less blur. Head-up displays can be installed in aircraft, automobiles, ships, trains, etc. as devices that reduce the burden on drivers.

0002

2. Description of the Related Art In recent years, head-up displays have been put into practical use in aircraft, automobiles, etc. as a means to prevent accidents caused by elderly drivers or when driving at high speeds.

There are various types of head-up displays, one of which is a diffractive optical head-up display using a holographic optical element. In other words, in a head-up display, light from the display surface is reflected by a combiner (a device that overlaps the display surface and the foreground) so that the viewer can see a virtual image on the display surface. The head-up display used is called a diffractive optical head-up display. Diffractive optical head-up displays using holograms can have a high transmission efficiency of 90% in the entire visible range, but can also have high reflection efficiency for specific wavelengths, and can also function as a wavefront conversion element such as a long-distance convergence function. It has the feature that it is possible to have

[0004] The diffractive optical head-up display is
Typically, this head-up display has a configuration as shown in FIG. 3, in which light emitted from a display surface 31 is reflected and diffracted by a mirror 32 and a holographic optical element 33, and then enters the viewer's eyes 35. .

[0005] The holographic optical element 33 is a volume phase reflection type hologram produced by interference between a divergent spherical wave and a plane wave or between divergent spherical waves. Therefore, the light emitted from one point on the display surface 31 is reflected and diffracted by the holographic optical element 33 and reproduced as a spherical wave with different curvatures, so that the image on the display surface 31 is converted into a virtual image 34. It will be created far away within the field of view of the observer 35.

[0006]

By the way, it is generally desired that image information displayed on a head-up display has less blur. However, in the above-mentioned head-up display, since off-axis imaging is performed, wavefront aberration cannot be avoided. In other words, the holographic optical element 33, which is a combiner of a head-up display, is a volume phase type hologram, and if light is incident on it under the same conditions as the reference light during hologram production, it will be reproduced without aberration, but if it deviates from the conditions If this happens, aberrations will occur. In other words, the central part of the display surface 31 is close to the light source position of the reference light during hologram production, so there is little blurring due to aberrations;
Near the outer periphery of the display surface 31, the reproduction light is incident from a position different from that of the light source of the reference light, resulting in increased blur due to aberrations. Therefore, the virtual image 34 on the display surface becomes blurred and unclear as it goes from the center to the periphery. This becomes more noticeable as the area of the combiner increases.

[0007] Due to the above-mentioned circumstances, it has conventionally been difficult to reduce blur due to aberrations in diffractive optical head-up displays. The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a head-up display that can display clear images with less blur, regardless of the size of the combiner.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a holographic optical element in a head-up display that includes a plurality of small-area holograms (
Hereinafter, this is a volume phase type hologram consisting of holograms (hereinafter referred to as elemental holograms), and each elemental hologram is manufactured so as to reproduce one point on the corresponding display surface without blurring.

In other words, when manufacturing a holographic optical element, each element hologram was photographed while changing the position of the point light source of the reference light and the position of the point light source of the object light, as shown in FIG.
, the element hologram 25a is photographed with the point light source of the reference light at 23a and the point light source of the object light at 27a, and similarly the element hologram 25b is photographed at 23b, 27b.
This is a hologram taken with a point light source placed at the position.

Therefore, the adjacent element holograms 25a
and 25b are adjacent points 23a and 23b on the display surface.
are reproduced at positions 27a and 27b, respectively, without aberration. Holographic optical element 2 produced in this way
5 as a combiner in a head-up display, the viewer can
1 on the virtual image of the display surface through the two element holograms 25a.
Since part 27a is observed and 27b is observed through 25b, there is no blur due to aberration. Furthermore, even if the observer's viewpoint position changes, the observation is made through the element hologram that was created to reproduce one point in the immediate vicinity, so blurring of the image due to aberrations can be suppressed to a minimum.

[0011]

According to the present invention, the holographic optical element as a combiner in a head-up display is composed of a plurality of element holograms photographed under different conditions. As a result, it is possible to relatively easily realize a head-up display that can display clear images with less blur caused by aberrations.

0012

[Embodiment] In the present invention, in order to reduce blur caused by aberration in a head-up display, the holographic optical element is composed of small-area element holograms, and each element hologram is designed to reproduce points at different positions without aberration. It is manufactured in

An embodiment of the present invention based on the above concept will be described below with reference to the drawings. Figure 1
1 is a schematic explanatory diagram showing an example of the overall configuration of a head-up display according to the present invention. The light emitted from the display surface 11 is
It is reflected by the mirror 12 and the holographic optical element 13
reach. And this holographic optical element 1
3 is reflected and diffracted, and is visible to the observer 15. Observer 1
The light seen at 5 is visually recognized as a virtual image 14 on the display surface.

Here, one portion 11a on the display surface 11 is an element hologram 13a in the holographic optical element 13.
On the other hand, another portion 11 on the display surface 11
rays b and 11c are reflected and diffracted by element holograms 13b and 13c, respectively. Each element hologram reproduces a corresponding point without aberration, so when the observer 15 observes within a certain range, a clear image with less blur due to aberration can be displayed.

Next, an example of a method for manufacturing the holographic optical element according to this embodiment will be explained. In FIG. 2, the photosensitive material 25 for the holographic optical element is covered with a light shielding plate 26 having slits cut to match the size of the element holograms on both the front and back surfaces, and the photosensitive material 25 is fixed. The light shielding plate 26 is located on a stage 24 that is movable in vertical and horizontal directions. The point light sources of the reference light and object light each consist of a microscope objective lens and a pinhole, and are also located on the moving stage 22. Element hologram 25a
23a corresponding to a certain point on the display surface is the light source position of the reference light, and the point 23a on the virtual image of the display surface corresponding to this 23a is the light source position of the reference light.
Photographing is performed by interference of two spherical waves with point 27a as the light source position of the object light. Next, the two point light sources are moved to 23b and 27b by the stage 22, and at the same time, the slit is also moved to 25b to photograph the element hologram 25b. A holographic optical element is manufactured by sequentially performing the same operation on all the element holograms.

In addition to the manufacturing method described above, it is also possible to use a two-dimensional lens array, a computer hologram, or the like to manufacture a holographic optical element having a similar effect by one photographing process. The thus manufactured holographic optical element reproduces light from one point on the display surface using the corresponding element hologram, and thus becomes an imaging system with almost no aberration.

[0017]

As explained above, according to the present invention, the holographic optical element in the head-up display is made up of a collection of elemental holograms each made to reproduce one different point. functions, and prevents image blurring due to aberrations.
It becomes possible to display clear images.

[0018]

[Brief explanation of drawings]

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

FIG. 2 is an explanatory diagram showing an example of a method for manufacturing a holographic optical element in the same example.

FIG. 3 is an explanatory diagram showing an example of a conventional head-up display.

[Explanation of symbols]

11, 31... Display surface 12, 32... Mirror 13, 33... Holographic optical element (combiner)
14, 34... Virtual image 15, 35... Observer 21... Laser oscillator 22, 24... Moving stage 23... Light source position of reference light 25... Photosensitive material 26... Light shielding plate 27... Light source position of object light

Claims (1)

[Claims] 1. A head-up display using a volume phase reflection type holographic optical element as a combiner, wherein the holographic optical element consists of a small-area hologram divided into a plurality of parts, each hologram comprising:
A head-up display is characterized by being designed to reproduce points on the display surface corresponding to the hologram without aberration.