Head-up display with curved screen

Abstract

The invention relates to a head-up display (1) comprising: - a screen (22) adapted to generate a light beam through an output face (22B), and - an image transmission device (30) adapted to receive the light beam generated by the backlit screen and to direct it towards a partially transparent blade (80). According to the invention, the output face of the screen has a non-zero radius of curvature. (Shorthand figure: Figure 1)

Description

Description Title of the invention: Head-up display with curved screen

[0001] Technical field to which the invention relates

[0002] — The present invention relates generally to the field of head-up displays high.

[0003] It relates more particularly to a head-up display comprising:

[0004] - a screen adapted to generate a light beam by means of an output face, and,

[0005] - an image transmission device adapted to receive the light beam generated by the backlit screen and to send it towards a partially transparent blade.

[0006] The invention finds a particularly interesting application as a display head held high in a motor vehicle. Technological background

[0007] — For the driver of a motor vehicle, it is particularly comfortable to view information related to vehicle operation and traffic conditions, or others, without having to take one's eyes off the road in front of the vehicle.

[0008] It is known for this purpose to equip a motor vehicle with a so-called display "Heads-up display" such as the one described in the introduction.

[0009] = In such a head-up display, the backlit screen generates a re- light beam presenting a virtual image containing the information to be displayed and the device Image reflection sends the generated light beam back towards the blade by- fully transparent, located in front of the driver, in order to visually overlay the virtual image represented by the light beam to the environment facing to the vehicle.

[0010] = For the driver's comfort, it is advisable that the virtual images thus created in front of him must be of good quality, and in particular, must have the least amount of Possible defects.

[0011] = To do this, it is known to anticipate the defects of the virtual image seen by the driver, such as distortions or jagged edges, and to compensate digitally these defects by calculating opposing defects and generating at the screen level a a light beam creating a virtual image with opposing defects.

[0012] It is particularly known that the virtual image seen by the driver is distorted by the curvature of the partially transparent blade onto which it is sent by the image transfer device. This phenomenon is better known as "Warping" in English. To avoid this phenomenon, the final deformation is anticipated and digitally corrected during image generation by the screen, of so that the screen initially generates a beam of light forming an image in- distorted payment. It is also known that the virtual image seen by the driver exhibits aliasing, meaning the driver perceives the virtual image as pixelated. To avoid this phenomenon, also known as "aliasing," it is common to digitally remove the pixelation, for example, by increasing the brightness of fully illuminated pixels on the screen and darkening the partially illuminated pixels. These two known digital corrections require complex calculations for the head-up display. Furthermore, they do not allow for correction of the sharpness of the virtual image seen by the driver. However, the virtual image seen by the driver is generally blurry at the edges, because, to prevent stray rays illuminating an output face of the screen from being reflected towards the partially transparent blade and superimposed on the virtual image, the screen is preferably not positioned in a plane perpendicular to the optical axis of the image transmission device. Object of the invention In order to remedy the aforementioned drawback of the prior art, the present invention proposes a head-up display that improves the sharpness of the virtual image seen by the driver. More particularly, the invention proposes a display as defined in the introduction, in which the output face of the screen has a non-zero radius of curvature. Thus, the screen physically corrects and compensates for blurring problems associated with the tilt of the screen and / or the curvature of other optical elements of the head-up display. Other non-limiting and advantageous features of the head-up display according to the invention, taken individually or in all technically possible combinations, are as follows: - the screen is backlit, on one input side, by a light source; - the concavity of the screen's output face is turned towards the image transmission device; - the concavity of the screen's output face is turned away from the image transmission device, i.e. towards the light source; - the exit face of said screen has a first radius of curvature along a first principal direction of the screen, and a second radius of curvature along a second principal direction of the screen, perpendicular to said first principal direction; - the exit face of said screen has a first radius of curvature along an arbitrary direction relative to a first principal direction of the screen, and a second radius of curvature along a second arbitrary direction relative to a second principal direction of the screen, the two directions of curvature being able to present any cone angle between them, for example between -45° and +45°: - the radius of curvature of the output face of the screen is determined as a function of the radius of curvature of at least one of the optical elements of the image transmission device and / or the radius of curvature of the partially transparent blade; - the radius of curvature of the screen's output face is such that each point of said output face is equidistant from an object focal plane associated with said screen; - the radius of curvature of the screen's output face is between 10 cm and 50 mm; - a plane tangent to the output face of the screen, at the level of the intersection between said screen and an optical axis associated with the image transmission device, is inclined at a non-zero angle with respect to a plane perpendicular to said optical axis; - the screen has a plurality of pixels, all the pixels of the screen having the same size; - it is planned that the image transmission device will include at least one curved magnifying mirror; -the absolute value of the ratio between the radius of curvature of the screen's output face and the radius of curvature of the magnifying mirror is between 0.5 and 2; - the magnifying mirror is interposed between the screen and the partially transparent blade in the path of the light beam; - the partially transparent blade is formed by a separate blade located between a windshield of the vehicle equipped with said head-up display and the eyes of the driver of that vehicle; - the partially transparent blade is formed by a windshield of the vehicle equipped with said head-up display. Detailed description of a project example The description that follows, with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out. Regarding the attached drawings: [fig.1] is a schematic representation of a first embodiment of the head-up display according to the invention in a motor vehicle; [fig.2] is a schematic representation of a second embodiment of the head-up display according to the invention in a motor vehicle; and, [fig.3] is a schematic representation illustrating the formation of the virtual image by the screen of such a head-up display. It should also be noted that identical or similar elements of the different embodiments of the invention shown in the different figures will, as far as possible, be referenced by the same reference symbols and will not be described each time. Figure ! schematically represents the main elements of a head-up display 1 intended to equip a vehicle, for example a motor vehicle, a train, a boat such as a barge, a tram, a bus or an aircraft. The following description will focus more specifically on a head-up display 1 fitted to a motor vehicle. The head-up display 1 includes, more specifically, an image generation unit 20, comprising a backlighting device 21 and a screen 22 illuminated by this backlighting device 21. The screen 22 is, for example, a thin-film transistor (TFT) liquid crystal display (LCD), backlit by a light source 110 comprising, for example, LEDs. The screen 22 can then be constructed on rigid but curved glass plates. More specifically, the backlighting device 21 is here a light source backlighting the screen 22, that is to say illuminating said screen 22 on an input face 22A of the latter. The 22-inch screen contains a plurality of pixels (arranged in a pixel matrix), each capable of transmitting varying amounts of the light with which it is backlit. All the pixels of the 22-inch screen are identical in size. Alternatively, a technology can be used in which the screen contains light-emitting pixels, such as OLED (Organic Light-Emitting Diode) or AMOLED (Active-Matrix Organic Light-Emitting Diode). This technology is based, for example, on thin-film deposition and encapsulation through evaporation. This technology allows for the production of curved screens. The image generation unit 20 is thus adapted to generate, via the output face 22B of the screen 22, a light beam towards an image return device 30 also included in the head-up display 1. The image transmission device 30 is adapted to send the light beam generated by the image generation unit 20 towards a partially transparent blade 80 in order to form, with the partially transparent blade 80, a virtual image (VIM) in the field of vision of a driver. The virtual image (VIM) is thus formed according to the composition of the light beam generated at the level of the image generation unit 20, and more precisely at the level of the screen 22. This allows information to be displayed in the driver's field of vision without the driver having to take their eyes off the road. As shown in figure |, the image transfer device 30 here includes a plane folding mirror 31. As shown in Figures 2 and 3, the image transfer device 30 can also include, in addition to the flat folding mirror 31, a curved magnifying mirror 32, also called a magnification mirror, for example, whose reflecting surface has the shape of a polynomial of several degrees. According to a variant not shown, a curved magnifying mirror could replace the flat folding mirror. Such a magnifying mirror 32 makes it possible to display in the driver's field of vision a virtual image IMV magnified compared to that generated by the light beam in the image generation device 20, so that said virtual image IMV is of sufficient size to be clearly visible to the driver at a certain distance. In particular, the larger the radius of curvature of the magnifying mirror 32, the closer the final virtual image IMV is to the image generated by the screen 22, i.e. it is sharper closer to the driver. According to a first variant shown in Figure 2, it is possible to foresee that the image transfer device 30 comprises a first folding mirror 31 flat, followed by a magnifying mirror 32 curved, in that order, between the screen 22 and the partially transparent blade 80. According to a second variant not shown, it is conceivable that the image transmission device comprises a first curved magnifying mirror followed by a second curved magnifying mirror, each with its own radius of curvature (therefore its own magnification), to reflect the light beam generated by the screen towards the partially transparent blade. Alternatively, the image transmission device could include other mirrors and / or other optical elements, in addition to or in place of those previously described. In general, the optical axis X of the image transfer device 30 is defined as the axis connecting the center of the light source with the center of the first mirror of the image transfer device 30 encountered by the optical ray from said light source. Here, the optical axis X of the image transfer device 30 passes through the center of the folding mirror 31 and the center of the light source. The output face 22B of the screen 22 is arranged at an angle with respect to this optical axis, that is to say, a tangent plane T to the output face 22B of the screen 22, at the level of the intersection between said output face 22B of the screen 22 and the optical axis X associated with the image transmission device 30, is inclined at a non-zero angle A with respect to a plane perpendicular P to said optical axis (see figure 3). Thus, any stray rays accidentally illuminating the screen 22 through its output face 22B are not reflected by the output face 22B of the screen 22 towards the image transmission device 30, so that they do not reach the partially transparent blade 80 and do not degrade the quality of the virtual image IMV seen by the driver. As shown in Figure |, the partially transparent blade 80 is formed here by a combiner, that is, a thin, partially transparent plate, positioned between the windshield 2 of the vehicle and the driver's eyes 3. The partially transparent blade 80 is therefore a separate blade from the windshield 2. Alternatively, as shown in Figure 2, the image transmission device 30 can project the light beam generated by the image generation unit 20 directly towards the windscreen 2 of the vehicle, the aforementioned combiner being omitted. In this case, the partially transparent blade 80 is formed by the windscreen 2 of the vehicle itself. In addition to being partially transparent, this blade is partially reflective, and thus allows at least part of the light beam generated by the image generation unit 20 to be reflected back towards the conductor, as shown schematically in Figure 1. The virtual image MV, formed in the driver's field of vision by the folding mirror 31, possibly the magnifying mirror 32, and the partially transparent blade 80, is located opposite the driver with respect to the partially transparent blade 80, for example a few meters in front of the partially transparent blade 80, outside the vehicle (see figures 1 and 2). Remarkably, the output face 22B of the screen 22 has, according to the invention, a non-zero radius of curvature. The screen 22 can in particular be concave (see figures 1 or 2) or convex (see figure 3), that is to say that the concavity of the screen 22 is turned towards the image transfer device 30 (figures 1 or 2) or, on the contrary, towards the backlighting device 21 (figure 3). In particular, it can be predicted that all points of the screen 22, in particular all pixels, are equidistant from an image focal plane F associated with said screen 22 (see figure 3), even though the output face 22B of the screen 22 is not positioned orthogonally to the optical axis X associated with the image transmission device 30. This prevents the virtual image (IMV) seen by the driver from being blurry, particularly at the edges of the image. Indeed, as shown in Figure 3, in which the partially transparent blade is omitted, the fact that the output face 22B The curved shape of screen 22 ensures that all pixels of screen 22 are equidistant from the image focal plane F, while also allowing screen 22 to be tilted relative to the optical axis X. This configuration advantageously rectifies the virtual image IMV generated by screen 22 so that it is entirely contained within a so-called "sharp" zone Z1 and does not spill over into adjacent so-called "blurred" zones Z2. In addition, the curved configuration of the output face 22B of the screen 22 makes it possible to anticipate and compensate for the distortions of the virtual image IMV caused by the curvatures of the other optical elements of the head-up display 1, for example by the partially transparent blade 80 or by the magnifying mirror 32. Here, as shown in Figure 1, the input face 22A and the output face 22B of the screen 22 are both curved. Advantageously, the radius of curvature of the output face 22B of the screen 22 is determined as a function of the radius of curvature of at least one of the other optical elements of the head-up display 1, in particular the radius of curvature of at least one of the optical elements 31 of the image transmission device 30 (magnifying mirror 32 in particular) and / or the radius of curvature of the partially transparent blade 80 (whether it is a combiner or directly from the windshield). For example, we can predict that the radius of curvature of the exit face 22B of the screen 22 is in a ratio within the interval [-2 ; -0.5] or within the interval [0.5 ; 2] with respect to the radius of curvature of the magnifying mirror 32, that is to say that the absolute value of the ratio between the radius of curvature of the exit face 22B of the screen 22 and the radius of curvature of the magnifying mirror 32 is between 0.5 and 2. More specifically, the screen 22 extends along two principal directions perpendicular to each other. The first principal direction is a generally horizontal direction when the head-up display 1 is in place in the vehicle, for example a direction parallel to the ground, while the second principal direction is a direction including a vertical component when the head-up display 1 is in place in the vehicle, i.e. a direction perpendicular to the ground. According to a first embodiment of the screen, the screen's exit face is curved along a straight line, called the "axis of greatest deflection," which corresponds to the maximum deformation of the screen with respect to a plane formed by two screen edges parallel to this axis of greatest deflection. Thus, when the axis of greatest deflection is vertical, the maximum deformation of the screen is measured with respect to the plane formed by the screen edges parallel to the aforementioned second principal direction (including the vertical component), while when the axis of greatest deflection is horizontal, the maximum deformation is measured with respect to the plane formed by the screen edges parallel to the aforementioned first principal direction (horizontal). The axis of The largest arrow is not necessarily a central axis of the screen. More generally, according to another embodiment of the screen 22, the axis of greatest arrow defining the curvature of the output face of the screen can be oriented along any axis, comprising a component along the first principal direction and a component along the second principal direction. In other words, advantageously, the output face 22B of the screen then has, on the one hand, a first radius of curvature along the first principal direction of the screen 22, that is to say, the edges of the output face 22B of the screen 22 extending mainly along this first principal direction, as well as all lines parallel to these edges, have said first radius of curvature, and, on the other hand, a second radius of curvature along the second principal direction of the screen 22, that is to say, the edges of the output face 22B of the screen 22 extending mainly along this second principal direction, as well as all lines parallel to these edges, have said second radius of curvature. Preferably, the two radii of curvature are different. More specifically, the first and second radii of curvature of the output face 22B of the screen are each between 10 cm and 50 cm. Preferably, the first radius of curvature is greater than the second radius of curvature. The first radius of curvature along the first direction of the screen 22 (horizontal) makes it possible to compensate mainly for the distortions caused by the radius of curvature of the curved magnifying mirror 32 of the image transmission device 30, while the second radius of curvature along the second direction of the screen 22 (including a vertical component) makes it possible to compensate mainly for the blur caused by the inclination of the screen 22 with respect to the optical axis X associated with the image transmission device 30. According to another possible embodiment, the exit face of the screen has a first radius of curvature along an arbitrary direction relative to a first principal direction of the screen, and a second radius of curvature along a second arbitrary direction relative to a second principal direction of the screen; the two directions of curvature can then have an arbitrary cone angle between them, for example between -45° and +45°. According to yet another screen embodiment, it is conceivable that the deformation of the screen's output face follows the equation of a sphere, a torus, or any Cartesian equation, in order to correct the aforementioned optical aberrations as precisely as possible. In this situation, the screen's output face exhibits a point of maximum deflection, meaning that the maximum deformation of the screen's output face, relative to a plane of the screen passing through two of its parallel edges, said screen, is located at a single point. In the case where the output face of the screen is curved according to the equation of a sphere, the point of maximum deflection of the screen is located at the intersection of the diagonals connecting two by two opposite corners of said output face of the screen. Thus, thanks to the curved screen according to the invention, the quality of the virtual IMV image seen by the driver is improved.

Claims

Demands

1. Head-up display (1) comprising: - a screen (22) adapted to generate a beam of light through one face of exit (22B), and, - an image transmission device (30) adapted to receive the beam light generated by the backlit screen (22) and to send it towards of a partially transparent blade (80), characterized in that the output face (22B) of the screen (22) has a non-zero radius of curvature.

2. Head-up display (1) according to claim 1, wherein the the concavity of the exit face (22B) of the screen (22) is turned towards the image transmission device (30).

3. Head-up display (1) according to claim 1, wherein the the concavity of the exit face (22B) of the screen (22) is rotated to the opposite of the image return device (30).

4. Head-up display (1) according to any one of claims 1 to 3, in which the output face (22B) of said screen (22) has a first radius of curvature along a first principal direction of the screen (22), and a second radius of curvature along a second principal direction of the screen (22), comprising a component perpendicular to said first main direction.

5. Head-up display (1) according to any one of claims 1 to 4, in which the radius of curvature of the output face (22B) of the screen (22) is determined based on the radius of curvature of at least one of the elements optical (31) of the image transmission device (30) or of the beam of partially transparent blade curvature (80).

6. Head-up display (1) according to any one of claims 1 to 5, in which the radius of curvature of the output face (22B) of the screen (22) is such that each point of said exit face (22B) is equidistant from a focal plane object associated with audit screen (22).

7. Head-up display (1) according to any one of claims 1 to 6, in which the radius of curvature of the output face (22B) of the screen (22) is between 10 cm and 50 mm.

8. Head-up display (1) according to any one of claims 1 to 7, in which a plane tangent to the output face (22B) of the screen (22), at the level of the intersection between said screen (22) and an optical axis (X) associated with the image transfer device (30), is inclined at a non-zero angle by relative to a plane perpendicular to said optical axis.

9. Head-up display (1) according to any one of claims 1 to 8, in which The screen (22) contains a plurality of pixels, all the pixels of the screen of identical size.

10. Head-up display (1) according to any one of claims 1 to 9, in which the image transfer device (30) includes at least one mirror of curved magnification.

11. Head-up display (1) according to claim 10, wherein the value absolute ratio of the radius of curvature of the exit face (22B) of the screen (22) and the radius of curvature of the magnifying mirror (32) is between 0.5 and 2.

12. Head-up display (1) according to any one of claims 1 to 11, in in which the partially transparent blade (80) is formed by a blade distinct location between a windshield of the vehicle equipped with said head-up display high and the eyes of the driver of this vehicle.

13. Head-up display (1) according to any one of claims 1 to 11, in in which the partially transparent blade (0) is formed by a windscreen (2) of the vehicle equipped with said head up display (1).

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