Method for determining a mounting position of a head-up display in a vehicle

Abstract

The invention relates to a method for determining a mounting position of a head-up display (20) in a vehicle (10), wherein the vehicle comprises a projection assembly (11) comprising a windshield (13) and a support (12), the support being intended to receive the head-up display, and wherein the head-up display is designed, when it is positioned on the support, to project a light beam (30, 31) onto the windshield in order to form a virtual image (3) visible to a driver (1) of the vehicle, wherein the method comprises the steps of: - measuring an optical characteristic of the head-up display in a test environment separate from the vehicle; - measuring an optical characteristic of the projection assembly using a light source separate from the head-up display; - determining the mounting position on the basis of the optical characteristic of the head-up display and the optical characteristic of the projection assembly, such that, when the head-up display is mounted on the support, the light beam reflected by the windshield has a predetermined direction (5) in the vehicle.

Description

Description Title of the invention: Method for determining a mounting position of a head-up display in a vehicle Technical field

[0001] The present invention relates generally to the technical field of display systems.

[0002] It relates more particularly to a method for determining a mounting position of a head-up display in a vehicle.

[0003] The invention finds a particularly advantageous application in the assembly of a vehicle comprising a head-up display. Technological background

[0004] A head-up display for a motor vehicle generally comprises an image generator adapted to produce a light beam and an optical system arranged to guide this light beam towards the windshield of the vehicle. The light beam is then partially reflected towards the eyes of the driver of the vehicle. This forms a virtual image visible to the driver superimposed on an external scene, typically the roadway located in front of the vehicle and the objects located there.

[0005] The position of the light beam reflected by the windshield characterizes, in a reference frame linked to the vehicle, both the position of the virtual image and the position of an observation zone from which the virtual image is visible with sufficient intensity. This means that the driver's eyes must be located in this observation zone so that he can correctly see the virtual image.

[0006] The accuracy of the interaction, i.e. in practice the superposition, between the external scene and the virtual image is important, for example so that the head-up display can annotate objects in the external scene or indicate routes to follow. It is therefore necessary to correctly calibrate the position of the virtual image.

[0007] However, the virtual image and the observation area are objects that are optically intrinsically linked since they are both characterized by the beam light reflected by the windshield. It is therefore not possible to reposition only the virtual image without also modifying the observation area.

[0008] Thus, a calibration step, which typically takes place during vehicle assembly, is conventionally provided to adjust the positions of the virtual image and the observation zone. This step therefore aims both to place the virtual image in an adequate position, so that it is correctly superimposed on the external scene, and to place the observation zone in an adequate position, in practice so that it corresponds to an average location of the eyes of the driver seated in the vehicle.

[0009] To do this, the head-up display is installed in the vehicle. Then, the position of the virtual image and the observation area are determined using a camera placed approximately (initially) in the observation area and oriented towards the virtual image. The camera thus makes it possible to estimate what the driver of the vehicle will see. The camera is then moved to measure the extent of the observation area (the observation area is scanned) and the corresponding position of the virtual image. If the position of the virtual image or the observation area is not satisfactory, the arrangement of the head-up display relative to the vehicle is changed and the positions of the virtual image and the observation area are rechecked. This process is repeated until the positions of the virtual image and the observation area are satisfactory.

[0010] Determining the position of the head-up display in the vehicle therefore appears to be long and tedious. In practice, it requires at least fifteen minutes, which represents a considerable amount of time on a motor vehicle assembly line. Summary of the invention

[0011] In this context, the present invention provides a method for determining a mounting position of a head-up display in a vehicle, the vehicle comprising projection equipment comprising a windshield and a support, the support being intended to receive the head-up display, the head-up display being adapted, when positioned on the support, to project a light beam onto the windshield in order to form a virtual image visible to a driver of the vehicle, the method comprising the following steps: - measuring an optical characteristic of the head-up display in a test environment separate from the vehicle; - measurement of an optical characteristic of the projection equipment using a light source separate from the head-up display; - determination of the mounting position, depending on the optical characteristic of the head-up display and the optical characteristic of the projection equipment, so that, when the head-up display is placed on the support, the light beam reflected by the windshield has a predetermined direction in the vehicle.

[0012] The fact that the light beam reflected by the windshield has the predetermined direction means here that at least one of the rays forming the reflected light beam is substantially parallel to the predetermined direction.

[0013] Thus, thanks to the invention, the head-up display is characterized on one side while the projection equipment is characterized on the other. On the basis of these two characterizations, it is then possible to determine the mounting position of the head-up display on the support even before carrying out this mounting. This therefore saves valuable time on the vehicle assembly line.

[0014] As a simple example, the optical characteristics of the head-up display and the projection equipment can be deviations. For example, measurements determine that the head-up display inherently deviates two degrees to the left and the projection equipment inherently deviates one degree to the right. Thus, it is calculated that the head-up display must be positioned one degree to the right on the support so that the light beam it emits is parallel to the front-rear axis of the vehicle after reflection on the windshield.

[0015] Furthermore, each characterization (of the head-up display on the one hand and of the projection equipment on the other) can be carried out quickly since they do not require changing the annoyance of the head-up display or changing the arrangement of the light source. The determination of the optical characteristics are in fact simple measurement steps which are not iterative.

[0016] Advantageously, the head-up display and the projection equipment each having their own optical characteristic, independently of one another, it is for example possible to replace the head-up display with a new head-up display without having to characterize the projection equipment again. Measuring the optical characteristic of the new head-up display is sufficient to determine its mounting position in the vehicle since the projection equipment is already characterized.

[0017] Other advantageous and non-limiting characteristics of the method according to the invention, taken individually or in all technically possible combinations, are the following: - the test environment comprises a test support and a test windshield reproducing respectively the support and the windshield of the vehicle, the test environment being constructed on the basis of a manufacturing plan of the projection equipment; - the optical characteristic of the head-up display is representative of a direction of at least one ray of interest of the head-up display which is reflected by the test windshield, when the head-up display is placed on the test support; - the at least one ray of interest comprises at least one of a main ray of the head-up display passing through the center of a reference surface when the head-up display is placed on the support and at least one marginal ray of the head-up display passing through an edge of the reference surface; - the test environment includes a mask designed to allow only at least one ray of interest to pass through; - when measuring the optical characteristic of the projection equipment, the light source is positioned on the support and illuminates the windshield; - the optical characteristic of the projection equipment is representative of a direction of a test light beam emitted by the light source and which is reflected by the windshield; - the light source is designed so that the test light beam passes through a reference surface; - the predetermined direction of the light beam reflected by the windshield is characterized by a predetermined position of the virtual image and a predetermined position of an observation surface in a reference frame linked to the vehicle; - the method comprises a step of arranging at least one element between the support and the head-up display so that the head-up display is positioned in accordance with the mounting position.

[0018] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Description of the invention

[0019] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0020] On the attached drawings:

[0021] [Fig. 1] is a schematic side view representation of a vehicle including a head-up display adapted to project a virtual image.

[0022] [Fig. 2] is a block diagram of a sequence of steps for determining a mounting position for the head-up display in the vehicle of Fig. 1.

[0023] [Fig. 3] is a schematic side view representation of the head-up display of Figure 1 placed in a test environment to determine, according to a first embodiment of the method of Figure 2, an optical characteristic of the head-up display.

[0024] [Fig. 4] is a schematic side view representation of projection equipment of the vehicle of Fig. 1 and a light source for determining, according to the first embodiment, an optical characteristic of the projection equipment.

[0025] [Fig. 5] is a schematic side view representation of the head-up display of Figure 1 placed in the test environment to determine, according to a second embodiment of the method of Figure 2, the optical characteristic of the head-up display.

[0026] [Fig. 6] is a schematic side view of the projection equipment and the light source for determining, according to the second embodiment, the optical characteristic of the projection equipment.

[0027] Figure 1 illustrates a vehicle 10, here a motor vehicle, in which a head-up display 20 is mounted. Figure 1 represents the head-up display 20 installed in a mounting position which has been determined using the method shown in Figure 2.

[0028] The vehicle 10 comprises projection equipment 11. The projection equipment 11 includes in particular a support 12 which is designed to receive the head-up display. high 20 and the windshield 13 of the vehicle 10. As described below, the position of the head-up display 20 on the support 12 is adjustable. The support 12 is here positioned behind the steering wheel, relative to the driver 1, and under the windshield 13. The support 12 is for example connected to a cross member of the vehicle 10. As shown in FIG. 1, the support 12 here has a hollow shape designed to receive the head-up display 20. A reference frame RI linked to the vehicle 10 is defined, which is here a three-dimensional orthogonal reference frame.

[0029] The head-up display 20 is adapted to project an incident light beam 30 towards the windshield 13. Here, the incident light beam 30 is therefore emitted generally upwards, as shown in FIG. 1. The windshield 13, which then constitutes a partially transparent blade, then reflects a portion of the incident light beam 30 into a reflected light beam 31 towards an eye 2 of the driver 1 of the vehicle 10. The reflected light beam 31 thus forms a virtual image 3 visible to the driver 1 superimposed on an exterior scene located at the front of the vehicle 10. In FIG. 1, the light beams 30, 31 are represented by their envelope corresponding to the edges of the virtual image 3.

[0030] As shown in Figure 3, the head-up display 20 comprises in particular an image generator 21, an optical system 22 and a housing 23 in which the image generator 21 and the optical system 22 are mounted. The housing 23, which is for example made of plastic material, thus delimits an external structure of the head-up display 20. The image generator 21 is designed to emit the incident light beam 30. For this, it here comprises a liquid crystal screen and a backlighting surface of the screen. The optical system 22 comprises an aspherical mirror 24 adapted to shape the incident light beam 30, and therefore to shape the virtual image 3. The optical system 22 also comprises a covering window 25, arranged at an opening provided in the housing 23, which allows the incident light beam 30 to exit the head-up display 20, preferably without deformation.

[0031] As shown in Figure 1, the virtual image 3 is intrinsically linked to an observation surface 4, located in the passenger compartment of the vehicle 10, at which the virtual image 3 is visible. The observation surface 4 corresponds to the positions that the eye 2 of the driver 1 can take to correctly observe the virtual image 3.

[0032] This observation surface 4 is for example defined geometrically on the basis of all the points in space, in the reference frame RI linked to the vehicle, for which the intensity of the virtual image 3 is greater than a threshold value. This threshold value is for example a given proportion of the maximum intensity of the virtual image, such as half or 70% of the maximum intensity. The intensity of the virtual image 3 is maximum at the focal point 32 of the reflected light beam 31. The observation surface 4 can for example be defined as the largest flat rectangular surface for which the intensity of the virtual image 3 is greater than half or 70% of the maximum intensity.

[0033] When designing the vehicle 10, the positions of the virtual image 3 and the observation surface 4 are adjusted so that the observation surface 4 corresponds to the eye positions of a majority of potential drivers while ensuring correct superposition of the exterior scene with the virtual image 3. The position of the observation surface 4 preferably complies with the characteristics of the vehicle 10 (e.g. a seat height) and with automotive standards, in particular standards relating to observation areas, such as the ECE R125 standard.

[0034] The virtual image 3 and the observation surface 4 here define a predetermined direction 5, passing for example through the center of the virtual image 3 and the center of the observation surface 4. It is also possible to define a predetermined vector field comprising a set of directions (including for example the predetermined direction 5) passing through the virtual image 3 and the observation surface 4. When the observation surface 4 is rectangular, the set of directions can comprise the direction between the center of the virtual image 3 and the center of the observation surface 4 and the four directions between each corner of the virtual image 3 and each corner of the observation surface 4 (see figure 5).

[0035] The objective of the method according to the invention is to determine the mounting position so that the reflected light beam 31 extends in this predetermined direction 5 when the head-up display 20 is placed on the support 12. In other words, it is sought that at least one ray of the reflected light beam 31 is parallel to the predetermined direction 5 when the head-up display 20 is placed on the support 12. Preferably, the ray of the reflected light beam 31 having the predetermined direction is a central ray 31' of the reflected light beam 31 coming from the center of the virtual image 3. This central ray 31' thus corresponds here to the reflected main ray 34 described later.

[0036] Subsequently, a mounting position of the head-up display 20 comprises an “orientation”, defined by rotations around reference axes, and / or a “location”, defined by translations relative to these reference axes. Thus, determining a mounting position means determining an orientation and / or a location of the head-up display 20 in the reference frame RI linked to the vehicle. The orientation is for example given by three angles relative to the three orthogonal axes of the reference frame RI linked to the vehicle 10. The location is for example given by three coordinates relative to the three orthogonal axes of the reference frame RI linked to the vehicle 10.

[0037] The mounting position of the head-up display 20 in the vehicle 10 can be defined relatively to a nominal position representing a theoretical position, based on manufacturing plans, of the head-up display 20 in the vehicle 10. In practice, the mounting position most often differs from the nominal position due to manufacturing tolerances for the head-up display 20 and for the vehicle 10. The mounting position can also be defined directly by coordinates in the linked reference frame RI linked to the vehicle 10. The mounting position of the head-up display 20 in the vehicle 10 is here more particularly representative of the position of the head-up display 20 relative to the support 12.

[0038] As shown in Figure 2, the method of determining the mounting position includes the following main steps: - a first step E1 of measuring an optical characteristic of the head-up display 20 in a test environment 40; - a second step E2 of measuring an optical characteristic of the projection equipment 11 by means of a light source 50; - a third step E3 of determining the mounting position, as a function of the optical characteristic of the head-up display 20 and the optical characteristic of the projection equipment 11.

[0039] A first embodiment of the method is first described in detail with reference to Figures 3 and 4. This first embodiment allows a simple and rapid characterization of the head-up display 20 and the projection equipment 11.

[0040] The first step E1 makes it possible to measure an optical characteristic specific to the head-up display 20. For this purpose, it is implemented in the test environment 40 which is separate from the vehicle 10.

[0041] As shown in Figure 3, the test environment 40 reproduces the projection equipment 11 of the vehicle 10. The test environment 40 thus comprises a test support 41 reproducing the support 12 of the vehicle 10 and a test windshield 42 reproducing the windshield 13 of the vehicle 10. The test environment 40 is here constructed with great precision on the basis of a manufacturing plan of the vehicle 10. It is in particular constructed with greater precision than that of the construction of the head-up display 20. The test environment 40 thus represents an environment simulating the protective equipment 11 and the characteristics of which are known with great precision.

[0042] The test windshield 42 is for example made of aluminum, which allows it to be manufactured and positioned with very high precision. The shape of the test windshield 42 is thus produced with an accuracy of less than 10 μm, or even less than 5 μm, and it is positioned with an accuracy of less than 0.1 mm. The test support 41 is also produced and positioned with identical precision. For comparison, the support 12 and the windshield 13 of the vehicle 10 are conventionally manufactured with an accuracy that is only less than 300 μm. It is indeed more difficult to control the manufacture of a glass object (the windshield 13) than of an aluminum object (the test windshield 42).

[0043] To measure the optical characteristic of the head-up display 20, the first step E1 firstly comprises placing the head-up display 20 on the test support 41, as shown in FIG. 3.

[0044] The first step E1 then comprises the positioning of a mask 43 on the optical path of the incident light beam 30 or the optical path of the reflected light beam 31. The mask 43 is here part of the test environment 40. The mask 43 is specially designed to allow only a ray of interest of the head-up display 20 to pass, which is here the main ray 33 of the head-up display 20. Here, the term "ray" is understood to mean a globally collimated light beam of very small diameter, for example less than 3 mm. As described below, the rays are here formed by means of diaphragms (the openings of the mask 43).

[0045] The main ray 33 is here the central ray of the incident light beam 31. When the head-up display 20 is placed in the vehicle 10, the main ray 33 is the ray connecting the center of the virtual image 3 and the center of the observation zone 4. The main ray 33 comes from one or more pixels corresponding to the center of the virtual image 3. The main ray 33 comes for example from the central pixel or a group of central pixels of the screen of the image generator 21.

[0046] In the example of Figure 3, the mask 43 is positioned on the covering glass 25 of the head-up display 20. The mask 43 has a single small opening whose position is predetermined, here by simulation on an optical design plane of the head-up display 20, to allow only the main ray 33 to pass. The mask 43 thus forms a diaphragm whose diameter is for example between 1 mm and 5 mm. By "only let through" is meant that the rays coming from the center of the screen of the image generator 21 forming an angle greater than 0.1 degrees with the main ray 33 are blocked by the mask 43. Thus, as shown in FIG. 3, the other rays 36 coming from the center of the screen of the image generator 21 are blocked by the mask 43. Alternatively, the mask can be placed at different locations in the test environment 40, for example on a dedicated bench, and adapted accordingly.

[0047] The first step E1 finally comprises the measurement of the direction of the main ray 33 reflected by the test windshield 42 in a reference frame R2 linked to the test environment 40. After reflection on the test windshield 42, the main ray is referenced 34 in figure 3 and is called reflected main ray 34.

[0048] The direction of the reflected main ray 34 is for example represented by a three-dimensional vector (i.e. three coordinates) in the reference frame R2 linked to the test environment 40. The measurement is carried out here by means of a photosensitive detector 44.

[0049] For this, the main ray 33 is emitted by the central pixel or the central group of pixels of the screen of the image generator 21, the other pixels remaining off. In practice, a group of ten by ten central pixels can be lit to obtain sufficient intensity for the measurement.

[0050] The photosensitive detector 44 is here an image capture device and more specifically a camera whose position, that is to say the orientation and location, is known and precisely modifiable in the R2 reference frame linked to the test environment 40. The camera 44 is for example mounted on a robotic arm. To determine the direction of the reflected main ray 34, the camera 44 is then translated and oriented so as to maximize the received light. The orientation giving the maximum intensity then provides information on the direction of the reflected main ray 34. Other known uses of the photosensitive detector 44 for measuring the direction of rays can also be implemented.

[0051] Alternatively, it is possible to measure the direction of the main ray without a photosensitive detector by means of a scattering surface moved along the path of the main ray reflected by the test windshield. Since the position of the scattering surface is known in the reference frame linked to the test environment, the coordinates of the point of incidence of the main ray on the scattering surface can be located. Two sets of coordinates, for two positions of the scattering surface, are acquired. The direction of the main ray is then calculated by taking the difference between the two sets of coordinates.

[0052] In this first embodiment, the optical characteristic of the head-up display 20 may correspond to the direction of the reflected main ray 34 itself. The optical characteristic of the head-up display 20 is then a three-dimensional vector. The coordinates of this vector are first expressed in the reference frame R2 linked to the test environment 40 and then expressed in the reference frame RI linked to the vehicle 10 by means of a change of base. The optical characteristic of the head-up display 20 may also be an indication representative of a deviation of the main ray 33 by the test windshield 43, the deviation being represented relative to a reference direction. This deviation is for example expressed in the form of an angle and a direction. Such an optical characteristic of the head-up display 20 indicates for example that the head-up display 20 deviates two degrees upwards.

[0053] Preferably, the optical characteristic of the head-up display 20 comprises the direction of the reflected main ray 34 as well as its location in the reference frame R2 linked to the test environment 40 and in the reference frame RI linked to the vehicle 10. Thus, the optical characteristic of the head-up display 20 also comprises the coordinates of a point in space through which the reflected main ray 34 passes.

[0054] The second step E2 makes it possible to measure an optical characteristic specific to the projection equipment 11. For this purpose, it is implemented by means of the light source 50 which is distinct from the head-up display 20. The optical characteristic of the projection equipment 11 depends on the shapes and relative positions of the support 12 and the windshield 13.

[0055] The light source 50 is here a tool specifically designed to characterize the projection equipment 11. The light source 50 comprises a base 51 and at least one light emitting source, here a laser source 52 such as a laser diode. In this first embodiment, the light source 50 comprises a single laser source 52, as shown in FIG. 4. The base 51 is designed to fit into the hollow shape of the support 12.

[0056] In the manner of the test environment 40, the light source 50 is manufactured with high precision, which is at least higher than the manufacturing precision of the projection equipment 11.

[0057] The light source 50 is here designed so that, once placed on the support 12, the windshield 13 partially reflects an incident laser beam 53 produced by the laser source 52 into a reflected laser beam 54 in the direction of a potential placement zone of the eye 2 of the driver 1. The potential placement zone of the eye 2 of the driver 1 corresponds here to the desired position of the observation zone 4. Thus, the laser source 52 is for example positioned on the base 51 so that the position of the incident laser beam 53 is close to a theoretical position of the main beam 33 corresponding to the nominal position of the head-up display 20.

[0058] Preferably, the light source 50, for example, is designed so that the point of incidence of the incident laser beam 53 on the windshield 13 is included in a theoretical surface of incidence of the light beam 31 on the windshield 13. The theoretical surface of incidence is, for example, determined on the basis of the manufacturing plans of the vehicle 10 and the head-up display 20. The theoretical surface of incidence is in fact the zone of the windshield 13 which best allows the projection equipment 11 to be characterized.

[0059] To measure the optical characteristic of the projection equipment 11, the second step E2 firstly comprises the placement of the light source 50 on the support 12, as shown in FIG. 4.

[0060] The second step E2 then comprises measuring the direction of the reflected laser beam 54 in the reference frame RI linked to the vehicle 10. The direction of the reflected laser beam 54 is for example represented by a three-dimensional vector (i.e. three coordinates) in the reference frame RI linked to the vehicle 10.

[0061] As for the main beam 33, the direction of the reflected laser beam 54 is measured here by means of a photosensitive detector 55, here a camera 55. The position of the camera 55, i.e. the orientation and location, is known and can be modified precisely relative to the support 50. The camera 55 is for example mounted on a robotic arm.

[0062] The position of the camera 55 is also determined in the RI reference frame linked to the vehicle 10, here with an accuracy of between 1 mm and 2 mm. For this, it is for example possible to scan the passenger compartment of the vehicle 10 using a LIDAR system. The camera 55 can also be trained by a learning algorithm to detect certain elements of the passenger compartment such as the dashboard or the steering wheel.

[0063] Similarly, as a variant, the direction of the reflected laser beam can be measured without a photosensitive detector by means of a diffusing surface whose position is determined in the reference frame linked to the vehicle.

[0064] In this first embodiment, the optical characteristic of the projection equipment 11 may correspond to the direction of the reflected laser beam 54 itself. The optical characteristic of the projection equipment 11 is then a three-dimensional vector. The optical characteristic of the projection equipment 11 may also be an indication representative of a deviation of the reflected laser beam 54 relative to a reference direction. This deviation is for example expressed in the form of an angle and a direction. Such an optical characteristic of the projection equipment 11 indicates for example that the projection equipment 11 deviates by one degree downwards.

[0065] Preferably, the optical characteristic of the projection equipment 11 also includes the location of the reflected laser beam 54 in the reference frame RI linked to the vehicle 10.

[0066] Once the optical properties of the head-up display 20 and the projection equipment 11 have been measured, the third step E3 of determining the mounting position can be implemented. The third step E3 is for example implemented digitally by means of a computer processing unit receiving as input the optical properties of the head-up display 20 and the projection equipment 11.

[0067] The mounting position of the head-up display 20 is here determined in the reference frame RI linked to the vehicle 10, which makes it possible to determine the position of the head-up display 20 relative to the support 12.

[0068] Determining the mounting position so that the reflected light beam 31 has (i.e., complies with) the predetermined direction 5 means here mathematically solving a system of equations. Here, "has" or "complies with" the main direction 5 means that the central ray 31' of the reflected light beam 31 and the predetermined direction 5 are substantially parallel, i.e., form an angle of less than 0.1 degrees and preferably less than 0.05 degrees.

[0069] Depending on the number of degrees of freedom chosen, the determination may consist of finding the mounting position so that the reflected light beam 31 exactly respects the predetermined direction 5 or of optimizing the mounting position so as to find the best possible alignment between the reflected light beam 31 and the predetermined direction 5.

[0070] Here, the determination of the mounting position is for example made according to three degrees of freedom: an orientation of the head-up display 20 in a vertical plane, an orientation of the head-up display 20 in a horizontal plane and a distance between the head-up display 20 and the windshield 13, considering a reference point for each. These three degrees of freedom make it possible in practice to align the direction of the reflected light beam 31 with the predetermined direction 5.

[0071] For example, when the optical properties of the head-up display 20 and the projection equipment 11 are deviations, the third step E3 may comprise the calculation of an intermediate deviation summing the deviation of the head-up display 20 and the deviation of the projection equipment 11. The mounting position is then calculated so as to compensate for the intermediate deviation so that the light beam reflected 31 has a predetermined direction. With the above examples (deviation of two degrees upwards for the head-up display 20 and one degree downwards for the projection equipment 11), the intermediate deviation is then one degree upwards. The mounting position then indicates that the head-up display 20 must be mounted in the support 12 oriented 1 degree downwards relative to the nominal position.

[0072] As another example, when the optical properties of the head-up display 20 and the projection equipment 11 are vectors, the third step E3 may comprise a step of calculating an intermediate vector making the sum of the vector representative of the main ray 33 and the vector representative of the laser beam of the deflection of the head-up display 20 and the deflection of the projection equipment 11. The mounting position is then calculated so as to align the intermediate vector with the predetermined direction 5.

[0073] Preferably, the mounting position is determined so that the reflected light beam 31 respects, in addition to the predetermined direction, a predetermined location. This means that the mounting position is determined so that the central ray 31' of the reflected light beam 31 passes through a predetermined point in the reference frame RI linked to the vehicle (or as close as possible to this point). For this, the computer processing unit takes into account the location of the main ray 33 as well as the location of the reflected laser beam 54.

[0074] In a second embodiment, shown in Figures 5 and 6, the optical characteristics of the head-up display 20 and the projection equipment 11 correspond to vector fields. These vector fields allow a very precise determination of the mounting position.

[0075] Thus, this second embodiment differs from the first embodiment in that several rays of interest are characterized for the head-up display 20 and in that several laser beams are characterized for the projection equipment 11.

[0076] In this second embodiment, in the first step E1, several rays of interest are studied. Here, the mask 43 (not shown in FIG. 5) is designed to allow only the main ray 33 and four marginal rays 35 of the head-up display 20 to pass.

[0077] As shown in Figure 5, the four marginal rays 35 considered here are those passing through the corners of the observation zone 4 when the head-up display 20 is placed in the vehicle 10. The four marginal rays 35 correspond here to the four corners of the virtual image and are for example derived from pixels at the four corners of the screen of the image generator 21. In Figure 5, a test observation zone 45 which is equivalent to the observation zone 4 in the test environment 40 is represented.

[0078] The mask 43 then comprises five openings: one for the main ray 33 and four for the marginal rays 35. The mask 43 is also positioned on the covering glass 25 of the head-up display 20.

[0079] As in the first embodiment, the direction of the main ray 33 reflected by the test windshield 43 and the respective directions of the marginal rays 35 reflected by the test windshield 43 are measured in the reference frame R2 linked to the test environment 40.

[0080] In this second embodiment, the optical characteristic of the head-up display 20 then corresponds to the directions of the five rays of interest 33, 35 considered. The optical characteristic of the head-up display 20 is then a set of three-dimensional vectors, i.e. a vector field. This vector field allows a very precise characterization of the head-up display 20.

[0081] In this second embodiment, in the first step E2, the light source 50 comprises several laser sources 52. The light source 50 here comprises five laser sources 52, two of which are visible in section in FIG. 6. The laser sources 52 are for example positioned on the base 51 so that the positions of the incident laser beams 53 that they emit are close to the theoretical positions of the main ray 33 and the marginal rays 35.

[0082] As in the first embodiment, the direction of the reflected laser beams 54 are measured in the RI reference frame linked to the vehicle 10.

[0083] In this second embodiment, the optical characteristic of the projection equipment 11 then corresponds to the directions of the five reflected laser beams 54. The optical characteristic of the projection equipment 11 is then a set of three-dimensional vectors, i.e. a vector field. This vector field allows a very precise characterization of the projection equipment 11.

[0084] In this second embodiment, the third step E3 then comprises the calculation of a superposition of the vector fields of the head-up display 20 and the projection equipment 11. This calculation is carried out digitally by the computer processing unit. The computer processing unit then determines the mounting position so that the superposition of the vector fields corresponds, exactly or as closely as possible, to the predetermined vector field.

[0085] Whatever the embodiment, once determined, the mounting position can then be recorded and / or transmitted to subsequently carry out the installation of the head-up display 20 in the vehicle 10.

[0086] Here, whatever the embodiment, the method here comprises a fourth step E4 of positioning the head-up display 20 in the vehicle 10 and more particularly on the support 12.

[0087] The fourth step E4 more specifically comprises the arrangement of at least one element 60 between the support 12 and the head-up display 20 so that the latter is in the mounting position. The at least one element 60 comprises, for example, one or more shims 60, for example of parallelepiped shape. Such a shim 60 is shown in FIG. 1. These shims 60 may be placed in corners of a lower surface 26 of the housing 23 so as to modify the orientation and / or the distance to the windshield 13 of the head-up display 20. The at least one element 60 may also comprise spacers, or spacers, of adjustable sizes, for example based on screw-nut systems or screws coupled to springs.

[0088] In this context, the mounting position determined in step E3 may be directly indicative of a number of shims (having predetermined sizes and shapes) to be installed and their location, for example relative to the support 12. This indication then constitutes an installation guide allowing simple and rapid mounting of the head-up display 20 on the support 12.

[0089] Remarkably, the first step E1 and the second step E2 can be carried out independently of each other, spatially and temporally. The first step E1 is for example carried out by the manufacturer of the head-up display 20 and the second step E2 by the manufacturer of the vehicle 10, which is in practice often distinct from the manufacturer of the head-up display 20. Similarly, the fourth assembly step E4 can be carried out by yet another operator, for example a mechanic.

[0090] The present invention is in no way limited to the embodiments described and shown, but those skilled in the art will be able to provide any variation in accordance with the invention.

[0091] For example, the determination of the mounting position can be done according to one to six degrees of freedom (maximum three in rotation and three in translation).

[0092] The test environment and the light source may be made of materials other than those described above. The light source may include light sources other than lasers.

[0093] The head-up display may be different from that shown in the figures. The method according to the invention applies to all head-up displays as long as they are adapted to project an incident light beam towards the windshield.

Claims

Claims

1. A method for determining a mounting position of a head-up display (20) in a vehicle (10), the vehicle (10) comprising projection equipment (11) comprising a windshield (13) and a support (12), the support (12) being intended to receive the head-up display (20), the head-up display (20) being adapted, when positioned on the support (12), to project a light beam (30, 31) onto the windshield (13) in order to form a virtual image (3) visible to a driver (1) of the vehicle (10), the method comprising the following steps: - measuring an optical characteristic of the head-up display (20) in a test environment (40) separate from the vehicle (10); - measuring an optical characteristic of the projection equipment (11) by means of a light source (50) separate from the head-up display (20); - determining the mounting position, depending on the optical characteristic of the head-up display (20) and the optical characteristic of the projection equipment (11), so that, when the head-up display (20) is placed on the support (12), the light beam (30, 31) reflected by the windshield (13) has a predetermined direction (5) in the vehicle (10).

2. A method according to claim 1, wherein the test environment (40) comprises a test support (41) and a test windshield (42) respectively reproducing the support (12) and the windshield (13) of the vehicle (10), the test environment (40) being constructed on the basis of a manufacturing plan of the projection equipment (11).

3. A method according to claim 1 or 2, wherein the optical characteristic of the head-up display (20) is representative of a direction of at least one ray of interest (33, 34, 35) of the head-up display which is reflected by the test windshield (42), when the head-up display (20) is placed on the test support (41).

4. The method of claim 3, wherein the at least one ray of interest (33, 34, 35) comprises at least one of a main ray (33, 34) of the head-up display (20) passing through the center of a reference surface (4) when the head-up display (20) is placed on the support (12) and at least one marginal ray (35) of the head-up display (20) passing through an edge of the reference surface (4).

5. A method according to claim 3 or 4, wherein the test environment (40) comprises a mask (43) designed to allow only the at least one ray of interest (33, 34, 35) to pass through.

6. Method according to one of claims 1 to 5, wherein, when measuring the optical characteristic of the projection equipment (11), the light source (50) is positioned on the support (12) and illuminates the windshield (13).

7. A method according to claim 6, wherein the optical characteristic of the projection equipment (11) is representative of a direction of a test light beam (53, 54) emitted by the light source (50) and which is reflected by the windshield (13).

8. A method according to claim 7, wherein the light source (50) is configured such that the test light beam (53, 54) passes through a reference surface (45).

9. Method according to one of claims 1 to 8, in which the predetermined direction (5) of the light beam (30, 31) reflected by the windshield (13) is characterized by a predetermined position of the virtual image (3) and a predetermined position of an observation surface (4) in a reference frame (RI) linked to the vehicle (10).

10. Method according to one of claims 1 to 9, comprising a step of arranging at least one element (60) between the support (12) and the head-up display (20) so that the head-up display (20) is positioned in accordance with the mounting position.

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