WO2012156124A1

WO2012156124A1 - Hud comprising holographic optical elements

Info

Publication number: WO2012156124A1
Application number: PCT/EP2012/054788
Authority: WO
Inventors: Jan Weingarten
Original assignee: Robert Bosch Gmbh
Priority date: 2011-05-16
Filing date: 2012-03-19
Publication date: 2012-11-22
Also published as: CN103534632A; DE102011075884A1

Abstract

A display device (1), more particularly a head-up display, comprising a light-emitting image source (3) and comprising optical elements (4, 5, 6, 7, 8, 9) forming a beam path (12) for beams is presented. In this case, the optical elements (4, 5, 6, 7, 8, 9) comprise a holographic optical element (8) having a predefined optical imaging function and a reflector (5). The holographic optical element (8) is positioned in a manner spatially separated from the reflector (5) in the beam path (12). Moreover, the holographic optical element (8) is arranged in the beam path (12) in such a way that beams in a first section of the beam path are directed onto the holographic optical element (8) in order to deflect them under the influence of the imaging function of the holographic optical element (8) into a second section of the beam path in a new direction. The reflector (5) and the holographic optical element (8) are arranged relative to one another in such a way that beams emitted by the reflector (5) into a third section of the beam path (12) can at least partly transilluminate the holographic optical element, wherein illumination angles of transilluminating beams in the third section of the beam path (12) substantially deviate from angles of incidence at which an influence of the imaging function of the holographic optical element (8) is effective.

Description

description

title

HUP with holographic optical elements The invention relates to a display device according to the preamble of claim 1.

State of the art

As technology advances, ever smaller and more energy efficient optical systems are becoming increasingly popular

Display systems are used in vehicles. This favors in particular the development of head-up displays, with which vehicle data such as speed, speed, fuel level or weather conditions z. B. in the field of view of a driver can be superimposed on lying in the direction of travel traffic situations. Therefore, in recent years, a lot of new

Solutions and improvements for display devices known.

From the physical and technical optics [1] holographic optical elements are known. A known application of holographic optical elements in display systems is, for. B. to correct aberrations of an optical beam path or a single optical element. For example, DE 103 44 688 A1 presents a head-up display, in which an optical imaging element is combined with a holographic optical element in order, for. B. on a transparent coated mirror optical aberrations using a holographic optical element formed in the coating to correct.

WO 2009/156752 A1 introduces a display system which, in a broader sense, takes up holographic concepts. It consists of a spatial light modulator, e.g. a micromirror display illuminated by an expanded laser beam. A computer unit generates data for controlling the spatial

Light modulator, which is the spatial light modulator in hologram-like

Interference pattern can be implemented so that information as a diffraction image on a screen or directly on the retina of a viewer can be seen. One Disadvantage of the system, however, is that the visibility of the displayed information is relatively sensitive depending on the viewing direction due to the strong angular dependence of diffraction patterns. Another disadvantage of this technique is the comparatively high and thus expensive computing power which is necessary for the control in order to convert conventional image data into interference patterns.

Disclosure of the invention

The object of the present invention is the space requirement of

Display devices, in particular of head-up displays to reduce in vehicles with relatively simple means.

This object is achieved by a display device, in particular a head-up display, with the features of claim 1.

Preferred and advantageous embodiments of the invention are in the

Subclaims presented.

The invention is based on a display device, in particular a head-up display, with a light-emitting image source and with optical elements which form a beam path for radiation bundles. The optical elements include a reflector and a holographic optical element having a predetermined optical imaging function. The essence of the invention is that the holographic optical element in

Beam path is spatially separated from the reflector and that the

holographic optical element is arranged in the beam path such that

Beams of a first portion of the beam path are directed to the holographic optical element to redirect them under the influence of the imaging function of the holographic optical element in a second portion of the beam path in a new direction, and that the reflector and the holographic optical element are arranged to each other, that radiation beams emitted by the reflector into a third section of the beam path can at least partially illuminate the holographic optical element, wherein the

Illumination angle of radiating beams essentially from

Incidence angles at which an influence of the imaging function of the holographic optical element is effective differ.

The holographic optical element is on a transparent, especially clear transparent body, for example, made of a mineral glass. Of the

transparent body serves as a support for the holographic optical element.

Preferably, the transparent body has large surface areas, e.g. are just. A preferred embodiment of the invention is that the transparent body is a particular thin disc on which the holographic optical element is formed. The thickness of the disc is mainly in the

Compared to a length of the third portion of the beam path is thin and is preferably less than one-tenth of a beam length in the third section. in the

Compared to the beam diameter at the installation location or to the largest surface diagonal of the disk, the disk thickness is e.g. at most one quarter of this diameter, more preferably less than one fifth, preferably not more than one-eighth, in particular not more than one-tenth. Thereby, the holographic optical element is relatively inexpensive to produce and can be relatively easily attached to a designated position in the display device. The minimum thickness may be determined by providing a predetermined stiffness of the disk to it

Avoidance of e.g. Natural vibration is achievable.

Large opposing surface areas of the transparent body may be e.g. be arranged in parallel or e.g. to form a prism at an angle to each other. The clear-transparent body may for example consist of several, e.g. two, layers with different refractive indices can be constructed. As a result, the holographic optical element can advantageously be produced as a phase hologram. Hereinafter, an optical element will be referred to as conventional if it is an optical image by refraction on a surface after

Laws of geometric optics effected. Examples of conventional optical elements are mirrors, lenses and prisms. A holographic optical element is a hologram, i. a holographic one

Recording, a conventional optical element or a combination of several conventional optical elements. The optical imaging function of the holographic optical element is determined by the conventional optical element, which is recorded as a hologram in the holographic optical element. In this case, the optical imaging function can also correspond to a combination of conventional optical elements. The optical imaging function is in

Holographic optical element formed as a diffraction structure, which may be formed in a spatial periodic modulation, for example, a reflection coefficient or, for example, a refractive index in the transparent body of a carrier. A Diffraction efficiency describes a relative proportion of the light incident on a diffraction structure, which is diffracted, for example, overall or, for example, in a predetermined direction. The diffraction efficiency can be influenced by an amplitude and a strength of the spatial modulation, for example a reflection coefficient.

A diffraction structure for the holographic optical element may be formed, for example, by exposure and development of a photographic layer, or e.g. be embossed in the form of a structuring on a boundary or surface of a transparent support. For producing a diffraction structure, e.g. an optical structure for exposure to an interference image or e.g. starting from a numerical calculation, a diffraction pattern e.g. be transferred by laser processing in a transparent photorefractive polymer. Preferably, the diffraction structure is formed in an at least approximately planar layer, wherein preferably this layer is arranged parallel to an approximately flat large surface of the transparent body. This offers the advantage that the holographic optical element can be aligned comparatively easily.

The optical imaging function of the holographic optical element is available only on condition that the diffraction conditions for a

Image are satisfied by the holographic optical element. At the

The display device according to the invention, the diffraction conditions are met by the fact that angle of incidence of the first portion of the beam path, angle of reflection of the second portion of the beam path, a wavelength of the light used and the holographic optical element matched. The angles of reflection of the second section of the beam path correspond to the new direction of the

Beam after its deflection at the holographic optical element.

For good image reproduction by the holographic optical element, it is preferred that the image source is adapted to emit substantially coherent light, in particular monochromatic coherent light. This is

by, for example, obtaining the image source from e.g. one

Liquid crystal display is provided with a. expanded or e.g. scanning laser beam is illuminated. Preferably, the holographic optical element and the image source, in particular a light source of the image source, are matched to one another, at least with regard to a wavelength or a wavelength range of available light.

When a beam hits the holographic optical element with wiggles, which do not conform to the diffraction conditions, can pass substantially unbent through the holographic optical element and its transparent body. The diffraction structure of the holographic optical element can cause a reduction in the light intensity at a passing beam.

In the display device according to the invention, therefore, the holographic optical element is positioned in the third section of the beam path in such a way that bundles of rays which are irradiated into the third section of the beam path in

Illumination angles impinge on the holographic optical element that the

Diffraction conditions for a holographic image do not meet and therefore can pass through the holographic optical element hardly influenced in their propagation direction. The display device according to the invention thus advantageously uses the lighted

Space area in the third section of its beam path for a space-saving

Housing the holographic optical element whose optical

Imaging function is essentially only effective when deflecting light beams from the first portion of the beam path in the second section. The display device according to the invention thus enables a comparatively more compact construction and thereby facilitates its placement in a vehicle, in particular in an instrument panel.

The holographic optical element can be arranged in different ways in the third section of the beam path. Beams of the third section may pass through the holographic optical element continuously and / or only temporarily during operation of the display device. In this case, entire bundles of rays and / or parts of bundles of rays in the third section can completely and / or only partially cover a region of the holographic optical element

illuminate.

In order to avoid that an edge or another edge region of the transparent body, which serves as a carrier of the holographic optical element, interfering with cross sections of bundles of rays of the third portion of the beam path, it is particularly preferred that a surface of the transparent body, in particular a transparent thin disc, is designed such that it is attached to a

Installation position in the display device beams of the third section with a maximum beam cross section completely surmounted. A preferred embodiment of the invention provides that the reflector, the

Beam directs into the third gate of the beam path, a mirror is. This offers the advantage that the deflection or imaging hardly or no

Intensity losses at the beam bundles, which the reflector reflects in the third section, arise. In addition, a specular reflector can additionally be designed for an optical enlargement of the image display.

In addition to the reflector, the display device may comprise further optical elements, in particular conventional optical elements. For example, the display device may have another, e.g. Own mirror to the beam path through

Deflection of the beam direction to fold so that the display device can be accommodated in a vehicle comparatively cheaper. Furthermore, a display device according to the invention can have a diffusing screen for generating real images, with which, for example, the light of real images can be directed into the first section of the beam path and onto the holographic optical element.

Preferably, the third portion of the beam path between the reflector and another optical element, in particular a mirror, the

Display device. Thereby, the third portion and thus also the holographic optical element can be housed in a housing of the display device and protected against disturbances of their arrangement, which the

Conditions of the optical imaging function adversely affect. In addition, the holographic optical element can be advantageously protected from disturbing radiation from an environment of the display device and from contamination.

A preferred embodiment of the invention provides that the holographic optical element is arranged in the display device such that radiation beams of the second section of the beam path are directed onto the reflector. In this case, the reflector directs radiation beam of the second section of the beam path directly into the third section. In this case, it is arranged in the display device such that only a comparatively small, negligible part of the light beams of the third section of the beam path can strike the holographic optical element at illumination angles at which diffraction by the holographic optical element occurs. This can be done by a comparatively simpler

Structure advantageous to save optical components. In order to reduce the influence of the holographic optical element in the third section of the beam path on rays with an unfavorable illumination angle, it is preferred that a

Diffraction efficiency of the holographic optical element on the reflector such is agreed that in a direct radiation of the holographic optical element with light radiation originating from the reflector, no significant

Weakening of the Liches takes place. In this case, the diffraction efficiency may be less than 90 percent, better still less than 80 percent, preferably less than 70 percent, in particular less than 60 percent and particularly preferably about 50 percent. The comparatively lower diffraction efficiency can be achieved by a correspondingly increased intensity of light emission by the image source

be balanced. A further preferred embodiment of the invention consists in that at least one further optical element is provided for deflecting radiation beams from the second section of the beam path such that the reflector guides them

Beam deflects in the third section of the beam path. This advantageously facilitates an arrangement of the holographic optical element and the

Reflectors to each other in a way that beam of the third section of the

Beam path, the holographic optical element substantially always without diffraction loss. Therefore, it is preferred that the

Diffraction efficiency of the holographic optical element is comparatively high, e.g. over 60 percent, better over 70 percent, especially over 80 percent and most preferably over 90 percent.

In the beam path, only the order of the first section before the second section is determined, because the first section forms the beam section incident on the holographic optical element and the second section corresponds to the emergent beam section generated by the optical imaging function of FIG

holographic optical element influenced by beam. Therefore, the third section can not only directly or indirectly follow the second section, but it is also conceivable that the third section of the beam path lies indirectly or immediately before the first section, so that imaging

Beam initially the holographic optical element unaffected in the third

Illuminate section of the beam path before they hit the reflector and finally pass through the first and the second section of the beam path.

According to a preferred embodiment of the invention, the holographic optical element is designed as a reflective hologram. The optical effect works here

Imaging function on beams that are reflected by the holographic optical element in those half-space from which the radiation beams arrive. As a result, the holographic optical element can be replaced by a comparatively strong one

Change of direction in the beam path contribute to a more compact beam guidance. Likewise, it is preferable that the holographic optical element is formed as a transmissive hologram. This offers the advantage that comparatively lower intensity losses occur at the holographic optical element. Preferably, a display device according to the invention with several

equipped with holographic optical elements, e.g. on different

Wavelengths are tuned for a multicolor display.

On the basis of exemplary embodiments of the invention, details and further advantages are described below and explained in more detail by means of drawings. Show it:

Figure 1 a a section of a vehicle in a schematic side

Sectional view with a head-up display according to the prior art,

Figure 1 b a section of a vehicle in a schematic lateral

Sectional view with a head-up display according to the prior art,

Figure 2 shows a detail of a vehicle in a schematic lateral

Section view with a head-up display according to the invention,

Figure 3 shows a detail of a vehicle in a schematic lateral

Sectional view with a head-up display according to the invention.

Figures 1a and 1b each show a vehicle 20 with a head-up display 10 according to the prior art, the driver 30 when looking in the direction of travel

Can display information. The driver 30 is symbolically represented in all FIGS. 1 a, 1 b, 2 and 3 by a head 31 with eyes 32.

Figures 1a and 1b show an arrangement of the head-up display 10 in the vehicle 20, which is similarly applicable to a head-up display 1 according to the invention, which is shown in Figures 2 and 3.

The head-up display 10 is housed in the vehicle 20 below a lower portion of a sloped windshield 21. Looking through the

Windscreen 21, the driver 30 looks into a portion 12 a of a

Beam path 12, wherein a projector 3 of the head-up display 10 light beam to Display of images in the beam path 12 can send. At a virtual image distance 13, the driver 30 can recognize a virtual image 16 of displayed information only when the eyes 32 of the driver 30 are located in a vertical region 14. Because the beam path 12 is divided by reflective optical elements 4, 5 and 6 and by the windshield 21 into a plurality of sections 12a-12e

By the reflective optical elements 4,5,6 light in the beam path 12 is deflected several times and thus the beam path 12 folded several times. The reflective optical elements used so far for folding the beam path are conventional mirrors 4, 5 and lenses 6. They often also have a magnifying imaging function. This allows the light path for an optical

Illustration through the beam path with several sections on more

Distribute spatial directions and shorten them by enlarging the image.

The reflective elements 4, 5, 6 are intended to reflect irradiated light as completely as possible, in particular at almost every angle of incidence. They therefore form end points of the sections of the beam path on which

Beams are diverted from one section to the next. Due to their reflective properties, they essentially reflect light from arbitrary directions, which is why display devices are usually protected from unfavorable light radiation from their surroundings by means of diaphragms. Because of their reflection at any Einstrahlwinkeln Wrkung must not protrude into a portion of the beam path in which they are not intended for deflection or imaging. Because these reflective elements 4, 5, 6, 6 substantially reflect any incident light, none is allowed to protrude into a portion 12a-12e for which it is not intended to be the starting or ending point of the section.

The folding of the beam path 12 makes it possible to adapt the head-up display 10 with regard to shape and size to an installation location in the vehicle 20. However, a shortening of a beam path by means of conventional optical elements are limited in that e.g. a larger number of e.g. Mirroring or e.g. a stronger optical magnification at the same time disadvantages such. larger

Can cause manufacturing costs or greater optical aberrations. These are therefore a further reduction of the head-up display 10 by known means in the way.

FIG. 1 b shows how the size of the head-up display 10 can affect the display of information for the driver 30. By moving the head-up display 10 in the direction of the arrow A, the virtual image area 17 of the head-up display could either be moved into the area 18 (arrow B) or around the Area 18 are enlarged. However, the housing 2 of the head-up display 10 requires at the shifted position, a volume 2a, which is already partially occupied by other parts, in particular by a handlebar 22, which can hardly be positioned differently.

FIG. 2 shows a vehicle 20 with a first embodiment of a vehicle

Head-up displays 1 according to the invention, which is also arranged in a region below a windshield 21. From a main mirror 4, the head-up display 1 radiates beams into a section 12 b of the beam path 12 to the windshield 21. This reflects the beams coming out of the head-up

Display exit, in a portion 12 a of the beam path 12 and thus in the direction of the eyes 32 of a driver 30th

Within the head-up display 1 are next to the main mirror 4 and a

Projector 3 further optical elements 5, 7, and 8 are arranged, which the beam path 12 in further sections, for. B. 12c, 12d and 12e, subdivide. For example, the projector may include a laser (not shown) and an LCD display (not shown), the light beam of the laser continuously scanning the surface of the LCD display and passing through pixels. The projector 3 illuminates one

Deflection mirror 7, the beam onto a holographic optical element 8, e.g. a holographic lens. Thus, the portion 12e of the optical path corresponds to the first portion in which radiation beam on the

Holographic diffuser 8 occur. The support of the holographic optical element 8 is preferably a thin planar disk of a clear transparent glass material, for example Plexiglas or polycarbonate. The holographic optical element 8 is designed to be reflective and thus contributes to the space-saving folding of the beam path 12. The am

transparent carrier formed diffraction structure can e.g. from a

consist of reflective material of a developed photographic layer.

The optical imaging function of the holographic optical element 8 is only available if further optical elements are suitably positioned with respect to the holographic optical element. Therefore, the deflection mirror 5, the holographic optical element 8 and the deflection mirror 7 are in a manner in the

Head-up display 1 incorporated that a predetermined angle of incidence and a predetermined angle of reflection in accordance with the diffraction conditions of the holographic optical element 8 of the sections 12e and 12d of the beam path through the arrangement of the deflection mirrors 7 and 5 with respect to the holographic optical Elements 8 are complied with. The section 12d corresponds to a second section of the beam path. At the deflection mirror 5, therefore, intermediate images are formed by a combination of reflection, diffraction and interference, whereby at a given wavelength the angle of incidence and the angle of reflection with respect to the holographic optical element is determined for optical imaging.

The deflecting mirror 5 is provided to direct light irradiated from the holographic optical element 8 toward the main mirror 4. there

The light emitted by the deflecting mirror 5 illuminates the holographic optical element 8 and can at least partially illuminate the area of the holographic optical element 8. Therefore, the portion 12c corresponds to the third portion of the beam path. The carrier of the holographic optical element, e.g. a plastic glass pane, preferably protrudes beyond a maximum possible beam cross section of the portion 12 c to image distortion of

to avoid continuous edges of the carrier of the holographic optical element.

In order to prevent the transilluminating light on the holographic optical element from being influenced again, the deflecting mirror 5 directs light rays in directions onto the holographic optical element 8 and its carriers which deviate from the diffraction conditions of the holographic optical element 8 with respect to their angles of incidence. Since this is only possible to a limited extent in the arrangement shown in FIG. 2, the diffraction efficiency of the holographic optical element 8 is preferably reduced in such a way that diffraction losses in the

Section 12c have only a negligible effect on the visibility of the display. The reduced diffraction efficiency of the holographic optical element 8 also causes intensity losses between the beams of the sections 12e and 12d, which can be compensated by the projector 3, for example, by a more intense light emission.

FIG. 3 shows a second embodiment of a device according to the invention

Head-up displays 1. The arrangement of the head-up display 1 in the vehicle 20 relative to a Wndschutzscheibe 21 and a driver 30 agrees with that previously described with respect to Figure 2, which is why hereinafter only on the internal structure of the head-up display 1 is received.

The head-up display 1 has a projector 3, of which several

Deflection mirror 5, 7, 9 and via a holographic optical element 8 imaging beam to a main mirror 4 pass. The main mirror 4 directs that Light-imaging beam on the windshield 21st

To display information, the projector 3 radiates light beam onto the mirror 7, which preferably has an image-enlarging effect. The mirror 7 redirects irradiated light beams to the holographic optical element 8. In this case, the mirror 7 and the holographic optical element 8 are arranged such that light rays emanating from the mirror 7 on the holographic optical element 8 with

Incident angles which correspond to the diffraction conditions for a holographic reproduction of the optical imaging function of the holographic optical

Elements 8 correspond. Likewise, the mirror 9 is arranged with respect to the holographic optical element 8 such that at its mirror surface by

Reflection, diffraction and interference the optical imaging function, e.g. a

Mirroring an irradiated image, the holographic optical element 8 is displayed as a virtual image.

However, the deflection mirror deflects 9 imaging beam to the next deflection mirror 5 and only the deflection mirror 5 is intended to direct imaging light beams at such an angle to the holographic optical element 8 that they are not diffracted when passing the holographic optical element 8.

Compared with the embodiment shown in FIG. 2, the advantage of this head-up display according to the invention is that the deflection mirror 5 can be arranged more favorably on the deflection mirror 9 by means of an additional deflection of imaging beam bundles, in order to ensure that the deflection mirror 5 is in the third

Section 12c of the beam path 12 radiated beam only with

Illuminate angles at the holographic optical element 8, which differ sufficiently from the diffraction conditions of the holographic optical element 8 to avoid diffraction effects. This allows the

Image source with a comparatively low intensity images for display in the

Beam radiation 12, which can keep energy consumption and heat generation to advantageously low values.

[1] Bergmann, Ludwig; Shepherd, Clemens; Low, Heinz (ed.); Textbook of Experimental Physics, Volume 3: Optics; Walter de Gruyter; 10th edition; Berlin; 2004

Claims

Display device (1), in particular head-up display, with a light-emitting image source (3), with optical elements (4,5,6,7,8,9) which form a beam path (12) for beams of rays, the optical elements (4,5,6,7,8,9) comprise a holographic optical element (8) with a predetermined optical imaging function and a reflector (5), characterized in that the holographic optical element (8) in the beam path (12 ) is positioned spatially separated from the reflector (5), and that the holographic optical element (8) is arranged in the beam path (12) in such a way that beams of rays of a first section of the beam path are directed at the holographic optical element (8) in order to accommodate them Influence of the imaging function of the holographic optical element (8) in a second section of the beam path in a new direction, and that the reflector (5) and the holographic optical element (8) are arranged relative to one another in such a way that from the reflector (5) into one Third section of the beam path (12) can at least partially illuminate the holographic optical element, the illumination angle of illuminated beams of the third section of the beam path (12) being essentially of angles of incidence at which an influence of the imaging function of the holographic optical element (8) is effective , differ.

Display device (1) according to claim 1, characterized in that the holographic optical element (8) is formed on a disk made of transparent material.

Display device (1) according to claim 2, characterized in that a surface of the disk is designed such that it completely protrudes beyond beams of rays of the third section of the beam path (12) with a maximum beam cross section at an installation position in the display device (1).

Display device (1) according to one of the preceding claims, characterized in that the holographic optical element (8) is a reflective holographic optical element (8).

5. Display device (1) according to one of the preceding claims, characterized in that the holographic optical element (8) is designed as a phase hologram.

6. Display device (1) according to one of the preceding claims, characterized in that the optical imaging function of the holographic optical element (8) corresponds to that of a lens.

7. Display device (1) according to one of the preceding claims, characterized in that the optical imaging function of the holographic optical element (8) corresponds to that of a mirror.

8. Display device (1) according to one of the preceding claims, characterized in that the optical imaging function of the holographic optical element (8) corresponds to that of a combination of a lens and / or a mirror and / or a lens and / or a prism.

9. Display device (1) according to one of the preceding claims, characterized in that the holographic optical element (8) and the reflector (5) are arranged in the beam path (12) in such a way that imaging light is transmitted over the second section of the beam path (12). is directed from the holographic optical element (8) to the reflector (5).

10. Display device (1) according to one of the preceding claims, characterized in that a diffraction efficiency of the holographic optical element is coordinated with the reflector in such a way that when the holographic optical element is irradiated directly with light rays that come from the reflector, there is no significant weakening of the light takes place.

1 1. Display device (1) according to one of the preceding claims, characterized in that the reflector (5) is a mirror.

12. Display device (1) according to one of the preceding claims, characterized in that the third section of the beam path (12) is delimited by the reflector (5) and a further conventional optical element (4) of the display device (1), the holographic optical Element (8) is arranged at least partially between the delimiting optical elements (4,5) of the third section of the beam path (12) and spatially separated from both.