Head-up display with an arrangement for producing a bundled light flux

0001The invention relates to a head-up display with a device for generating a bundled luminous flux.

0002In order to convey information to drivers without their having to avert their gaze from the road to be traveled or the airspace to be served, so-called head-up displays have become known with which an image representing the information is superimposed on the windshield of a vehicle. To ensure that it is still visible in bright ambient light, this requires a high luminance of the image. Bundled luminous fluxes are also required for other lighting purposes, for example as reading lamps or as spotlights for shop windows and exhibitions.

0003Displays with a device for generating a bundled luminous flux are already known from the patents <patcit id="pcit0001" dnum="US5836676A"><text>US 5,836,676</text></patcit> and <patcit id="pcit0002" dnum="US5043716A"><text>US 5, 043, 716</text></patcit> and the publication <patcit id="pcit0003" dnum="JPH07130256B"><text>JP H07-130256</text></patcit>, each known in an application for an advertisement. A display with a light valve-containing image display device is disclosed in the publication<patcit id="pcit0004" dnum="WO0217405A"><text>WO 02/17405</text></patcit> known. A luminaire with bundling of the light beam is from the patent<patcit id="pcit0005" dnum="US4935665A"><text>US 4,935,665</text></patcit> known. However, due to their respective bundling and stray characteristics, the arrangements shown are unlikely to be suitable for use in a head-up display.

0004The object of the invention is therefore to produce a luminous flux with facilities which in particular have a small size and low weight, absorb as little power loss as possible and give off as heat and thus are also suitable for operation in a vehicle.

0005This object is achieved by the features cited in claim 1.

0006In the device according to the invention, it has proven to be advantageous if in each case a matrix point is formed by a plurality of light-emitting diodes, which may also be different colors.

0007A cost-effective production of the device according to the invention is possible in that the converging lenses of all the light channels are integrally connected to a plate arranged between the light source and the lattice-shaped reflector.

0008An advantageous embodiment of the invention is that the radii of curvature of the lens are different in different directions (astigmatic lenses). As a result, the light distribution can be improved, in particular in elongate light exit openings.

0009The image display device comprising light valves arranged at the light exit opening enables a compact device for generating high-resolution images with high luminance and uniform luminance distribution over the entire image area. In this case, the device for focusing and scattering ensures that the light generated by the light-emitting diodes is concentrated on the surface of the image-reproducing device without disturbing the individual light-emitting diodes. A preferred field of application of the device according to the invention are graphic head-up displays for vehicle applications.

0010With the image reproduction device, the device according to the invention still has some advantages listed below. Thus, the coordination between the RGB light source and the color display makes it possible to display graphic color images in a head-up display with sufficient luminance. In conjunction with the reflector and the lens, a uniform color and luminance distribution of the backlighting on the surface of the liquid crystal display is achieved.

0011In the liquid crystal color display configurable image content can be displayed in color. The image content can thus be adapted to the driving situation. The space for the entire imaging device is in the practical example only a few cubic centimeters. By choosing the colors of the light-emitting diodes and the associated display, the color space to be displayed in each case can be influenced. For example, instead of an RGB light-emitting diode grid, a red-green light-emitting diode grid can be selected, and the blue filter elements are correspondingly replaced by green in the liquid crystal display. Then there is a limited color space with again significantly increased luminance.

0012The invention allows numerous embodiments. Several of them are shown schematically in the drawing with reference to several figures and described below. It shows:<dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>a section through an embodiment,</dd><dt>Fig. 2</dt><dd>a plan view of the grid-shaped reflector in the embodiment according to <figref idref="f0001">Fig. 1</figref>.</dd><dt>Fig. 3</dt><dd>a section through a non-inventive example,</dd><dt>Fig. 4</dt><dd>an enlarged view of a section from <figref idref="f0001">Fig. 1</figref> to explain different details,</dd><dt>Fig. 5</dt><dd>an enlarged view of a section of another embodiment and</dd><dt>Fig. 6</dt><dd>a part of a non-inventive lenticular grid.</dd></dl>

0013In the embodiment of the <figref idref="f0001">FIGS. 1 and 2</figref> is provided as a light source, a grid of 4 x 8 groups of four light-emitting diodes 1, which are mounted on a support 2. Between the groups are webs 3, whose inclined surface serves as a reflector.

0014Above the light source 1, 2, 3 is a lenticular grid 4, to which a grid-shaped reflector 5 is connected.

0015The webs 3, the lenticular grid 4 and the inclined surfaces 6 of the grid-shaped reflector 5 cause a uniform light distribution. To avoid shadowing by the webs 7 of the reflector 5, a frame 8 is provided, which causes a distance between the reflector 5 and the liquid crystal display 9. Below the liquid crystal display 9 is a diffuser 10 to further improve the uniformity of the backlighting of the liquid crystal display 9.

0016The frame 8 causes an inclination of the liquid crystal display, so that incident light from above is not reflected in the same direction in which the light leaves the liquid crystal display to reach the viewer.

0017<figref idref="f0001">Fig. 2</figref> shows the device <figref idref="f0001">Fig. 1</figref> with removed liquid crystal display 9 and with removed lens 10. The LEDs 1 are in the presentation after <figref idref="f0001">Fig. 2</figref> visible by the lenticular 4. For the sake of simplicity, however, a corresponding distortion of the LEDs 1 has not been shown.

0018The embodiment according to <figref idref="f0002">Fig. 3</figref> represents a lighting device in which the light exit opening consists of a glass plate 18 which rests on a frame 17. Otherwise, this embodiment is like the one after<figref idref="f0001">Fig. 1</figref> built up.

0019<figref idref="f0002">Fig. 4</figref> essentially represents an enlarged detail <figref idref="f0001">Fig. 1</figref> and is illustrative of details of the liquid crystal display and the light source. The liquid crystal display 9 has between two glass plates 11, 12 a liquid crystal 13 and a color filter 14. The latter consists of a grid of three different colored dots, which is in<figref idref="f0002">Fig. 4</figref> characterized by different hatching. Correlating with the grid of the color filter control electrodes, not shown, are provided which each form a light valve with the liquid crystal. Outside the glass plates 11, 12 are polarizers 15, 16 with mutually perpendicular polarization planes.

0020The related to <figref idref="f0001">Fig. 1</figref> briefly described light source is in <figref idref="f0002">Fig. 4</figref> also shown in more detail.

0021Four light emitting diodes 1 are arranged elevated in the middle of a hole formed by webs 3 on a submount 20. The LEDs are connected via bonding wires 21 with lines 25, which are shown only schematically by hatching the area occupied by them. In a preferred embodiment, one of the LEDs is red, two are green and the fourth is blue. In this arrangement, the light mixes to white. The space between the submount 20 and the webs 3 is filled with a white potting compound 22, whose surface 24 serves as a reflector for the emitted light from the side of the LEDs 1. A transparent potting compound 23 prevents the formation of a cavity.

0022The connection between the light source 1, 2, 3 and the lenticular grid 4 takes place in the in <figref idref="f0002">Fig. 4</figref> illustrated embodiment of a layer 26 of silicone gel, a PCF layer 27 and a suitable adhesive 28th

0023The PCF layer 27 causes only the light generated by the light emitting diodes to pass therethrough, which is polarized toward the lower polarizer 15, so that no light is lost by the polarization in the PCF layer 27. The differently polarized light is reflected by the PCF layer 27 and then remitted from the surface 24. From this, in turn, the proportion with the corresponding polarization additionally passes through the PCF layer 27, so that the PCF layer as a whole contributes to an increase in the brightness.

0024<figref idref="f0003">Fig. 5</figref> shows an embodiment without a PCF layer. It is also located in<figref idref="f0003">Fig. 5</figref> the section shown on the edge of the device.

0025<figref idref="f0003">Fig. 6</figref> shows a non-inventive lenticular grid 31 with eight lenses, which are held together by webs 32.