METHOD AND SYSTEM FOR SELECTIVE ALIGNMENT OF PIXELS IN AN OPTICAL MODULE TO COMPENSATE FOR GEOMETRIC ERRORS DUE TO MANUFACTURING TOLERANCES

Description

[0001] The present invention relates to vehicle lighting, using a spatially decomposed pixel modulator, for example in the form of a micromirror matrix (or DMD, for "Digital Micromirror Device") whose micromirrors are controllable. More particularly, in the automotive field, the invention relates to a method and a system for adjusting the pixels of the projected image in order to compensate for geometric defects in the design or assembly of the shaping optics.

[0002] A lighting and / or signaling device for motor vehicles is known to comprise a light source, a micromirror array, or a similar modulating device that decomposes a light beam into pixels distributed in two dimensions. The micromirror array is generally used to reflect light rays from the light source to a beam-shaping optic, which projects the pattern formed on the micromirror array as an output beam. This beam can, for example, illuminate the roadway on which the motor vehicle equipped with this lighting and / or signaling device is traveling, or fulfill a signaling function.

[0003] Such lighting devices are designed using mass production methods. There is necessarily some play between the constituent elements of the lighting and / or signaling device, firstly to allow for easy assembly, and secondly because the parts are generally not machined but rather molded in plastic, which helps to reduce production costs.

[0004] Document DE 10 2016 103649 A1 discloses a lighting device enabling pixelated light emission, with individual pixel control, in order to produce a luminous output image in the device's environment.

[0005] It is particularly important to emphasize the difficulty of perfectly aligning a spatial pixel-based modulator (also called a high-definition spatial pixel modulator, given the very large number of pixels that can be activated or deactivated) with the optical projection component, which is generally in the form of at least one lens. Due to the large numerical aperture of the lens used for the projection function, the image projection quality degrades significantly as soon as the lateral offset of the optical axis reaches 50 µm. Furthermore, dynamically aligning the positions of the elements (including the micromirror array or similar modulating device) during the manufacturing of an optical module is practically complicated.

[0006] Manufacturing and positioning tolerances of the elements that make up the optical system can then lead to geometric defects, perceptible on the projection screen internal to the lighting and / or signaling device if the latter has one, or on a screen placed outside when the lighting and / or signaling device is designed to project a beam directly onto the road and does not have an internal projection screen.

[0007] Additionally, the projection lens often generates other aberrations that blur the images. This phenomenon is exacerbated by the aforementioned positional shift.

[0008] These geometric flaws become more pronounced when a large numerical aperture is required, for example with a factor close to or on the order of 0.7 (wide-angle lenses). Therefore, there is a need to provide better optical systems, particularly for large numerical apertures, without resorting to complex and expensive components or imposing tedious and costly adjustment operations to align the elements.

[0009] The invention therefore aims to prevent manufacturing tolerances, which are incurred during production, from resulting in geometric defects (significant deformations or excessive displacement relative to the optical axis) of the shaped light beam as it arrives on the projection screen before exiting the vehicle or as projected directly onto the road.

[0010] To this end, the invention relates to a method for correcting geometric defects in a light beam projected by an optical module for a motor vehicle, the optical module comprising: an imaging device, equipped with a high-definition pixelated spatial modulator and projection optics, a light source to generate light for the modulator, and optionally, a projection screen adapted to receive a light beam transmitted by the projection optics, the process comprising the steps consisting essentially of: receiving a first command to display an image to be projected, intended for the high-definition pixelated spatial modulator; transforming the first display command into a second display command which takes into account correction parameters, the correction parameters being predefined on the basis of an identification of geometric defects which are specific to the projection optics, by which means the modulator is controlled so that the image actually projected by using the imaging device corresponds better to the image to be projected than without taking into account said correction parameters, in which the projection optics defines a numerical aperture greater than 0.5.

[0011] These features allow for the control and adaptation of lighting, compensating for defects that disrupt certain parts of the beam and / or distort its appearance. This process enables adaptation through the selective activation or deactivation of modulator pixels, and potentially the modulation of their activation time, without the need for any mechanical devices or additional components that would increase the overall size.

[0012] It is understood that the geometric defects inherent in projection optics correspond to all the defects that occur downstream, following the direction of light propagation within the optical module, from the high-definition pixelated spatial modulator. These include slight misalignments of one or more components of the projection optics (defects related to tolerances, particularly lateral ones) and inherent structural defects linked to the complex shape of the projection lens. The process allows for an efficient method for the mass production of optical modules, maintaining a degree of tolerance that facilitates assembly operations and minimizing manufacturing constraints and the cost of optical elements (a perfect lens being expensive, for example, especially if it is designed for a large numerical aperture).

[0013] The best possible match to the desired image results, of course, from reducing discrepancies or anomalies affecting the perception of the projected image. Typically, geometric deviations or variations in line thickness, measured on portions of the image, are reduced.

[0014] Another advantage of the process is that the identification of geometric defects is carried out only once, and therefore no further comparison steps are required during operation.

[0015] According to one option, the second display command differs from the first display command in particular by the selective activation of all or part of a row of pixels, defined in a margin area (at the edge or on the side of an edge) by the modulator.

[0016] Depending on one particular feature, the correction parameters are adapted to modify the activation status of pixels in order to compensate for at least one of the following defects: a lateral shift of the contour of the light beam transmitted by the projection optics; a deformation of the contour of the light beam transmitted by the projection optics.

[0017] One particular feature is that the correction parameters compensate for distortion effects by determining positional shifts within the modulator. These shifts are selectively applied to areas of pixels previously identified during a calibration phase, which allows for the identification of geometric defects. In practice, these are typically stretching or contraction effects that, due to the discrete nature of the modulator, ultimately result in shifts, but also in variations in luminance—that is, variations in grayscale levels in digital imaging. It should be noted that the term "grayscale levels" applies to the variation in luminance independently of the actual color of the light beam. Thus, it corresponds to an indication of the beam's luminance, whether the beam is white or colored, for example, red, amber, or any other color.

[0018] Another distinctive feature is that the correction parameters and / or the second display command are stored in memory accessible to a control unit. Typically, this control unit is used to activate the second display command.

[0019] It is understood that the memory available to the control unit can store data representative of the calibration, in particular the correction parameters, and / or one or more predefined images that correspond to the result of the correction.

[0020] Depending on one particularity, the correction parameters are obtained after: obtaining, by using at least one target, a determined series of offset information, relating to the differences in position and shape affecting the target as projected (projection onto a projection screen internal to the module, adapted to receive a light beam transmitted by the projection optics, or projection directly to the outside), calculation of correction parameters to be applied to the light beam transmitted from the modulator according to the determined series of offset information, activation or deactivation of one or more pixels of the modulator according to the correction parameters; this typically relies on a reserve of unused pixels when the system is properly adjusted, pixels which are used for corrections when they require moving (offsets, tolerances) and / or enlarging the image (distortion) which will be projected.

[0021] Depending on one particular feature, to compensate for distortion (related to the optical design or lateral play), the modulator pixels are divided into zones, and the offset to be applied to each zone to obtain the correct projected shape is calculated. This zone division can define at least four zones (optionally of equal size), and preferably at least nine zones, for example.

[0022] According to one particular feature, a command to display a target is stored in a memory available to the control unit, the target being displayed in a prior step of identification and definition of correction parameters.

[0023] According to a particular feature of the modulator, the test pattern preferably extends over a central sector and at least four complementary sectors of equal size, formed around the central sector. It is understood that the test pattern extends, in part, beyond a central area of ​​the modulator pixels, which allows for the identification of certain defects to which correction parameters correspond.

[0024] In one particular case, to compensate for blurring, a test pattern defining the desired patterns is used. The reduction in the number of "active" pixels to be applied to the modulator is calculated to project a test pattern with the same pattern boundaries as the desired patterns, as well as the "active / inactive" pixel ratio to be applied to compensate for the decrease in light output due to the reduction in pixels used. More generally, some lines are thinned so that, once projected, they have the desired thickness. This can improve certain contours, particularly those parallel to the lines of the test pattern.

[0025] A method according to the invention may include one or more of the following characteristics: The modulator has a single power input and allows the selective activation of up to 1000 pixels. Activation is optionally achieved by controlling the movement of a movable element within each micromirror of a micromirror array (each movable micromirror having at least two positions, one active and the other inactive for illumination). Correction parameters are adjusted to modify pixel activation durations or frequencies to compensate for a loss of sharpness in the projected image, particularly near the periphery of the light beam transmitted by the projection optics (it is possible to manipulate luminance or grayscale levels). This loss of sharpness can most often be defined as a widening of the image with the appearance of at least one blurred edge.The identification of all or part of the geometric defects comprises the following steps: a) turning on the light source; b) activating a series of pixels defined by the modulator to create a target distributed across different pixel areas of the module, the series of pixels having a contour, continuous or discontinuous, allowing a predefined shape parameter of the target to be defined; and c) using the target to define all or part of the correction parameters. Step c) comprises at least one of the following substeps: i) comparing the shape parameter of the target as projected to the predefined shape parameter; ii) defining the correction parameters based on the comparison results obtained in substep i).Step c) includes the following sub-steps: estimating a parameter representative of blur in the target as projected, using at least one blur compensation in the correction parameters depending on whether or not the estimated parameter exceeds a sharpness threshold.

[0026] According to one particular feature, the beam transmitted from the modulator is of the segmented type, exhibiting at least one break.

[0027] Depending on one particularity, the beam exiting the optical module is a segmented code type beam (the cut is a horizontal code type cut, for example formed by one or more upper edges of one or more segments of the beam) or a segmented road type beam (the cut is a vertical cut, for example formed by one or more lateral edges of one or more segments of the beam).

[0028] According to one option, the segmented beam includes at least one line of light segment resulting, for example, from horizontally juxtaposed or partially superimposed segments, each light segment being associated with all or part of a row of selectively activatable pixels, the activation of this row or portion of a row of pixels causing the lighting of said light segment.

[0029] Depending on one characteristic, the light source is an electroluminescent element or a group of electroluminescent elements, for example one or more LEDs. Each of these elements can be connected to a control circuit belonging to the control unit.

[0030] Pixel control by the control unit provides adjustment flexibility, and it is understood that this control allows for fine adjustment of the projected image (an image that can be projected infinitely from the projection optics or from the projection screen).

[0031] Another object of the invention is to propose a lighting system to correct at least in part the undesirable distortions in the projected beam, caused by certain manufacturing tolerances of an optical module of the high-definition pixelated spatial modulator type.

[0032] To this end, a lighting system for motor vehicles is proposed, enabling the implementation of the process described above, the system comprising: an optical module comprising: an imaging device, equipped with a high-definition pixelated spatial modulator and a projection optic, a light source to generate light for the modulator, and optionally a projection screen adapted to receive a light beam transmitted by the projection optic (screen not provided when the light beam is intended to be projected to infinity, i.e. at a great distance from the light system, a distance at least 10 times greater, in particular 20 times greater, notably 100 times greater than the dimensions of the light system); a modulator control unit, designed and arranged to control the modulator and adapted to receive initial display commands, each initial display command being representative of an image to be projected;

[0033] the control unit including adjustment means to convert each first display command into a second display command which takes into account correction parameters, the correction parameters being predefined on the basis of an identification of geometric defects which are specific to the projection optics, the control unit driving the modulator according to the second display commands so that the image actually projected by the imaging device corresponds better to the image to be projected than without taking into account the correction parameters, in which the projection optics defines a numerical aperture greater than 0.5.

[0034] According to one particular feature, the high-definition pixelated spatial modulator includes a micromirror matrix, the micromirrors of the micromirror matrix being movable, each between: a first position in which the micro-mirror is arranged to reflect, in the direction of the projection optics, light rays arriving from the light source or from a light-emitting unit that includes said light source; and a second position in which the micro-mirror is arranged to reflect light rays arriving from the light source or from a light-emitting unit that includes said light source, away from the projection optics (outside the entrance pupil of the projection optics).

[0035] According to a particular feature, the projection optics defines a large opening angle, preferably with a numerical aperture greater than 0.5 and preferably greater than 0.7.

[0036] A lighting system according to the invention may include one or more of the following characteristics: The high-definition pixelated spatial modulator is illuminated by the light source in an illuminated area and defines a determined plurality of pixels distributed in parallel rows of pixels, at least one first row of pixels possibly being initially located outside the illuminated area due to oversizing of the spatial modulator. A margin area to allow for oversizing corresponds to a peripheral area with a frame format, in order to define an excess of pixels at the top, bottom, left and right of the nominal surface which is sufficient to create the desired image in the absence of geometric defects (in the case of a micro-mirror matrix, an advantage associated with oversizing is also the possibility, if desired, of limiting the heating caused by illumination on the non-reflective edge of the matrix).The active area where the pixels are defined may have, in one or more margin areas, an excess of pixels compared to a pixel format defined in each of the initial display commands (this allows for the correction of off-center distortion or barrel distortion, for which the image must be enlarged in the corners, or pincushion distortion, for which the image must be stretched towards the center of its edges). The control unit is adapted to selectively control the high-definition pixelated spatial modulator in order to selectively activate one or more margin areas located along the edges or portions of edges of the active area where the pixels are defined, depending on the correction parameters (of course, the term "activate" can simply mean that one or more pixels / mirrors are put into the active state).The imaging device is adapted to project a segmented beam of light with at least one cutoff. The pixels of the high-definition pixelated spatial modulator are distributed along or parallel to a first axis and define rows parallel to the first axis, which are distributed at different levels along a second axis perpendicular to the first axis. The first axis typically corresponds to a horizontal axis and the second axis to a substantially vertical axis, in a vehicle lighting system operating configuration. The control unit has memory storing correction parameters and / or information representing the second display commands.

[0037] Another distinctive feature is that the lighting system comprises two optical modules, each containing: an imaging device, equipped with a high-definition pixelated spatial modulator and a projection optic, and a light source to generate light for the modulator, each light beam transmitted by one of the projection optics being received on at least one projection screen.

[0038] Preferably, the control unit is configured to drive the modulator of each of the two optical modules, taking into account a first set of correction parameters associated with one of the two optical modules and a second set of correction parameters associated with the second of the two optical modules. Typically, the correction parameters of the first set are predefined based on the identification of geometric defects specific to the projection optics in the first optical module, while the correction parameters of the second set are predefined based on the identification of geometric defects specific to the projection optics in the second optical module.

[0039] In addition, a motor vehicle lighting and / or signaling light may be proposed, to project at least one beam of light, the light comprising: a case; a closing glass; and a lighting system according to the invention.

[0040] It may also be possible to create a luminous assembly, which has a first component and a second component formed by: two lights; two spotlights; or one light and one spotlight, the light assembly being provided with a light system with two optical modules as above, the two optical modules being distributed one in the first component and the other in the second component.

[0041] Other features and advantages of the invention will become apparent from the following description of several embodiments thereof, given by way of non-limiting examples, with reference to the accompanying drawings in which: there figure 1 schematically represents an example of a vehicle headlight comprising an optical module and implementing a system for compensating for geometric defects; the figure 2 schematically represents in cross-section a detail of a micro-mirror matrix forming the high-definition pixelated spatial modulator, used in the optical module of the figure 1 ; there figure 3 illustrates in a simplified way the parameterization of the modulator pixels by locating, along two axes, the modulator surface that is active for producing the beam exiting the optical module, in order to allow adjustment of the image actually projected; the figure 4 is a diagram of the steps implemented according to a method for correcting geometric defects according to the invention; the figures 5A et 5B These diagrams schematically illustrate, respectively, a light distribution that would be correct in the absence of significant geometric defects in the optics, and the light distribution that must actually be parameterized to obtain the desired photometric rendering, taking into account the geometric defects. figure 6A This illustrates an example of distortion observed between the ordered image and the image appearing on the optical module's projection screen, in the absence of correction. figure 6B illustrated by a detailed view of the figure 6A , an example of distortion observed with a blurring effect that makes certain patterns in the projected image appear thicker.

[0042] In the various figures, the same references designate identical or similar elements. Some elements may have been enlarged in the drawings to facilitate understanding.

[0043] There figure 1 represents a first embodiment of an optical module 1 that can form or be part of a lighting system 5 of a motor vehicle, for example a front or rear light. The optical module 1 forms a light-emitting device configured to implement one or more functions, some of which may be subject to photometric regulations.

[0044] The optical module 1 comprises, as illustrated, a light-emitting unit 20, a micromirror array 6 (or DMD, for "Digital Micromirror Device"), a control unit 16, for example in the form of a controller 16, for controlling the micromirrors 12 of the micromirror array 6, and a projection optic 18 (or shaping optic). The control unit 16 can optionally be located remotely, for example, to allow the control of several optical modules 1. It is understood that the lighting system 5 for motor vehicles can receive centrally initiated commands corresponding, for example, to a command for a lighting and / or signaling function or another photometric function.

[0045] A preferred photometric function associated with optical module 1 is a lighting and / or signaling function visible to the human eye. These photometric functions may be subject to one or more regulations establishing requirements for colorimetry, intensity, spatial distribution according to a so-called photometric grid, or even visibility ranges of the emitted light.

[0046] Optical module 1 is, for example, a lighting device constituting a vehicle projector 10 - or headlight. It is then configured to implement one or more photometric functions, for example, chosen from a dipped beam function called "dipped beam function", a main beam function called "main beam function", and a fog light function.

[0047] Alternatively or in parallel, optical module 1 is a signaling device intended to be arranged at the front or rear of the motor vehicle.

[0048] When intended to be arranged at the front, the photometric functions that can be implemented by using optical module 1 (possibly in addition to those it implements as a lighting device) include a direction change indication function, a daytime running light function known by the English acronym DRL, for "Daytime Running Light", a front light signature function, a position light function, a "Side-marker" function, which comes from English and can be translated as side signaling.

[0049] When intended to be fitted at the rear, these photometric functions include a reversing indicator function, a stop function, a fog light function, a turn signal indicator function, a rear light signature function, a lantern function, and a side signal function.

[0050] A light source 2, which is part of unit 20, is provided to generate the light rays that form a radiation R1 directed towards the micromirror array 6. The light source 2 can consist of an electroluminescent element such as a light-emitting diode (LED) or an LED array. In the case of a group of electroluminescent elements, these are preferably concentrated in a single area that can be considered a single light source. A laser diode, possibly coupled with a collimator system and possibly a wavelength conversion device, can also be used to generate the radiation R1.

[0051] In the case of a rear light signaling function, the light source 2 may be red. In the case of a front light function, the light source 2 is preferably white.

[0052] Although the drawings show a micromirror array 6, it is understood that the light rays emitted by the light source 2 can be directed, using suitable optics, to any type of high-definition pixelated spatial modulator 3, which allows the received radiation R1 to be decomposed into pixels. In one embodiment, a pixel array with optically active surfaces in the form of pixels, of the "LCD" (Liquid Crystal Display) type, can be used. A transmissive LCD screen device can indeed be suitable, and in this case, the optical path of the radiation R1 can be replaced by an optical path internal to the LCD device, possibly without detours. More generally, it is understood that a first radiation R1 can be received on a very finely subdivided surface to define high-definition pixels, typically with more than 1280 by 720 pixels, and whose configurations can be modulated.State change is preferably allowed for each pixel, in a way that is known per se.

[0053] The light beam emission unit 20 can also be equipped with the collimation lens 4 adapted to direct the radiation R1 onto the modulator 3. We can also have, in this unit 20, "imaging" optics giving a convergent beam.

[0054] In the example shown on the figure 1 , we prefer to use a collimating lens 4 or a set of collimating lenses to receive the light from the light source 2, so that the collimated light is received on an active, substantially rectangular face of the micro-mirror matrix 6.

[0055] By way of non-limiting example, a converging lens can be used to achieve collimation. In this case, the light source 2 is advantageously positioned near the object focus of the converging lens to ensure that the light rays of the radiation R1 propagating between the light-emitting unit 20 and the micromirror array 6 are substantially beam-shaped. Alternatively, or in addition, the light-emitting unit 20 includes a reflecting mirror. In this case, the light source 2 is advantageously positioned near the object focus of this reflecting mirror.

[0056] The 10-inch motor vehicle projector shown in the image figure 1 can be housed in a casing 14 or be enclosed by such a casing 14. The casing 14, as illustrated, comprises a body 14a forming a hollow interior space that at least partially receives the optical module 1. A cover 14b, at least partially transparent, is coupled to the body 14a to close the interior space. As illustrated, the cover 14b also forms a hollow space, partially receiving the optical module 1, in particular all or part of the projection optics 18.

[0057] The cover 14b is, for example, made of plastic resin or other suitable plastic material. The lighting projector 10 can include several optical modules 1 which are then adapted to emit adjacent beams, the beams preferably partially overlapping. In particular, the lateral ends of adjacent beams can be superimposed. The lower edge of one can also be superimposed with the upper edge of another in a different beam distribution, for example, to make digital beam modifications and obtain adaptive driving beam (ADB) and dynamic bending light (DBL) functions.

[0058] Here the projection optics 18 allows the shaping of the reflected radiation R2 after reflection on the micro-mirror matrix 6, allowing the definition of an outgoing beam 40. More generally, the imaging device provided in the optical module 1 includes the high-definition pixelated spatial modulator 3 and the projection optics 18.

[0059] The micro-mirror matrix 6, for example, is rectangular, as illustrated in the figures 1 And 3 The micro-mirror matrix 6 thus extends mainly along a first direction of extension, between lateral extremities 6a, 6b of the micro-mirror matrix 6. Along a second direction of extension, which can correspond to a vertical dimension (height), we also find two opposite end edges 6c, 6d which are typically parallel to each other.

[0060] As seen on the figure 2 The micromirror array 6 can optionally be coated with a transparent CP layer to protect the micromirrors 12. The pivot axis of each micromirror 12 can, for example, allow a rotation of plus or minus 10° from a nominal, non-rotating position.

[0061] With reference to the figure 1 The micromirror array 6 is essentially defined here by an electronic chip 7, attached to a printed circuit board 8 via a suitable socket 9. A cooling device, here a heatsink 11, is attached to the printed circuit board 8 to cool the printed circuit board 8 and / or the chip 7 of the micromirror array 6. To cool the chip 7 of the micromirror array 6, the heatsink 11 may have a raised section extending through an opening in the printed circuit board 8 to make contact with this chip 7, the socket 9 providing a passage for this raised section. Thermal paste or any other means of facilitating heat transfer, readily available to those skilled in the art, may be interposed between the raised section and the micromirror array 6.

[0062] The control unit 16 is connected here to the micromirror array 6 or other type of high-definition pixelated spatial modulator 3, for example through the printed circuit board 8. The control unit 16 can control changes in the position of each of the micromirrors 12 of the micromirror array 6. In the case of an LCD-type pixel array, the pixel states are also similarly controllable by the control unit 16. Such a control unit 16 can be part of the projector 10 by being integrated into the housing 14, or it can be separate and located remotely from the optical module 1.

[0063] It can be considered that the control unit 16 is part of the lighting system 5 which combines the functions of light projection and correction of display commands.

[0064] There figure 6A This shows an example of distortion observed in the prior art between the image F1 sent to modulator 3 and the image F3 that appears on the projection screen E1 of the optical module, in the absence of correction. figure 6B It further illustrates the problem of blurring with particularly inhomogeneous lighting, creating thinned sub-zones 21 and widened sub-zones 22.

[0065] As illustrated on the figure 1 The control unit 16 is configured to at least partially correct the distortions caused by the imaging optics, by generating a display command F2 which distorts the pixel pattern to be normally activated on the modulator 3 (pattern corresponding to the initial display command, or first display command F1, a representation of which is visible at the top of the figure 1 ). The second display command F2 takes into account correction parameters to compensate for distortions, usually caused by curvature defects of a lens or other optical element.

[0066] For example, a normally vertical line, such as that appearing in the number "1", could be curved concave to the left by such distortions when projected onto the projection screen E1. To correct this type of distortion, the relevant pixels on the modulator 3 that are activated to form this vertical line are changed from pixels that are straight to pixels that are curved concave to the right (or concave to the left, if other optical elements are present that reverse the direction of curvature perceived by the driver). This change is incorporated, as a correction parameter, into the display control F2.

[0067] The degree of "curvature" or distortion compensation of the imaging optics which is programmed in the pixels of the modulator 3 can be obtained by using a target M, during an initial calibration phase 50 (cf. figure 4 ) allowing the identification and definition of correction parameters.

[0068] To compensate for the centering error (and possibly the perimeter distortion), implementing compensation for this type of image distortion may require a pixel distribution with a greater number of pixels than would be necessary if no image distortion correction were applied.

[0069] Indeed, while the high-definition pixelated spatial modulator 3 is illuminated by the light source 2 within an illuminated area delimited by a perimeter, this modulator 3 can define a specific plurality of pixels 30 arranged in parallel rows, with a surplus of pixels such that at least one first row of pixels can be found outside the perimeter of the illuminated area. The modulator 3 is then oversized, for example by a few tens or a hundred micrometers, so as to present this type of pixel row at the edge. This first row of pixels, distal to a central point of symmetry of the modulator 3, cannot be used. However, due to the oversizing, another distal row of pixels, parallel and opposite to the first row, can be used if necessary to compensate for geometric defects, particularly a centering defect, affecting the projection.Thus, the second display command F2 can differ from the first display command F1 by selectively activating all or part of such another distal row of pixels. This is applicable for compensating for a centering error of the illuminated area on the modulator 3. The control unit 16 can also compensate for centering errors of the projection optics (and not of the upstream elements 4 and 2). In this case, the entire matrix 6 is illuminated, including the spare pixels (which can then be used to correct the distortion).

[0070] With reference to the figure 1 The control unit 16 may have a memory 16a and adjustment means 17 for modifying the operating state of the pixels defined by the modulator 3. In the case of a micromirror array 6, the adjustment means 17 allow the movement of the micromirrors 12 to be controlled. As schematically illustrated in the figure 2 , only part of the micro-mirrors 12 which have a first position effectively deflect the radiation R1, coming from the light source 2 or from a light ray emission unit 20, to transmit the light energy in the reflected radiation R2 which is directed towards the projection optic 18. The other micro-mirrors 12 are in a second inactive position (position ineffective for recovering the light radiation in the projection optic 18) or possibly are located outside the illuminated area of ​​the modulator 3.

[0071] Here, in the micro-mirror matrix 6, each of the micro-mirrors 12 is movable between: the first position in which the micro-mirror 12 reflects incident light rays from the radiation R1 towards the projection optic 18, and the second position in which the micro-mirror 12 transmits by reflection the incident light rays from the radiation R1 away from the projection optic 18, for example towards a radiation absorption device 19 which has a light-absorbing surface.

[0072] With reference to the figure 3 The control unit 16 can define a display command corresponding to a figure or pattern 25 on the matrix 6. Here it is a cross, but it could be a ring shape, an alphanumeric character, or any other geometric element easily identifiable in the form of coordinates (horizontal coordinates H1, H2, H3, H4, etc. and vertical coordinates V1, V2, V3, V4, etc.) as briefly illustrated on the figure 3 ) or vectors. Depending on correction parameters taken into account by the control unit 16, the routine applied by the adjustment means 17 can consist of modifying the position, shape and / or adjusting the lighting on the peripheral areas of the pattern 25 in order to compensate for distortions and aberrations identified and calibrated during the identification of geometric defects.

[0073] A vector table can typically be determined during such a step, in order to selectively modify the state of the pixels of the modulator 3. Such a vector table can list micro-mirrors 12 whose activation is to be selectively removed, which have been determined as corresponding to areas of light reflection "extra" in an initial calibration step, micro-mirrors 12 to be selectively activated in addition can also be specified in this table, corresponding to the determination of areas of light reflection "missing" in the initial calibration step.

[0074] In the case of using a micromirror array 6, the adjustment means 17 thus take into account the vector table so that the active pixels are readjusted. Typically, the memory 16a of the control unit 16 stores data representing the positional shifts induced by the geometric defects inherent in the projection optics 18. This data may already incorporate compensations to be applied to correct such shifts, or a program may be included in the adjustment means 17 to deduce the compensation to be applied from this data. Such positional shift data constitutes all or part of the correction parameters.

[0075] This data may be accompanied by factors to be applied to the gray levels, or even by coefficients of linear combinations of the gray level values ​​of neighboring pixels to determine the gray level to be assigned to the new pixel (the displaced pixel). Typically, the displacements, as well as the factors to be applied to the gray levels, can be calculated for each pixel individually by interpolating the values ​​found on the few points of the target M.

[0076] Regarding the centering defect, the figure 1 schematically illustrates the inverse distortion needed to be applied in the second display command F2, in order to simultaneously compensate for the distortion of the type shown on the figure 6A , observed in the absence of correction.

[0077] With reference to the figure 4 The method for correcting geometric defects in the light beam projected by the optical module 1 may include a calibration phase 50, preferably implemented before the first actual use of the optical module 1 in a motor vehicle. In this non-limiting example, the calibration phase 50 is initiated following a step 60 of switching on the optical module 1, in which an initial display command is transmitted to the modulator 3b. This initial command corresponds to a default command, designed without taking into account the inherent assembly or structural variations of the projection optics 18, and therefore only appropriate in the absence of geometric defects.

[0078] The calibration phase 50 begins with step 51, which involves receiving the first command from the modulator 3. This is followed by step 52, which generates a pixel usage configuration. figure 4 This illustrates a case where the first display command essentially results in a shift due to a centering error. A step 53 for identifying the errors can then begin, preferably using a test pattern M which can be observed on the projection screen E1.

[0079] The term "target" is used here in its usual optical sense. Considering the context of illumination broken down into 30 pixels, a target generally corresponds to a set of lines / elements of patterns of varying widths and orientations. Target M is used here to study, in particular, the limits of sharpness, deformations, and distortion effects observed during the projection of radiation R2 by the projection optics 18.

[0080] During calibration phase 50, the collection and analysis of positional shift information and other aberrations is preferably automated, for example, using sensors and an image processing and defect identification program, by comparing the expected position of the notable points of the target M with the position actually obtained. The target M is generated, for example, by activating a predefined series of pixels that have at least one contour, continuous or discontinuous, allowing a shape parameter of the target M to be defined.

[0081] Optionally, a target M can be generated that extends over the entire micromirror array 6, in order to identify defects as comprehensively as possible. In such a target M, transitions between dark or black pixels and light pixels are preferably numerous and distributed throughout all pixel areas, which can then allow the generation of a pattern 25 that is obviously more extensive and typically more complex than the one shown as an illustration on the figure 3 .

[0082] In step 53 of fault identification, offset information is identified and a determined series of offset information is generated, relating to the differences in position and shape affecting the target M as projected onto the projection screen E1. Then, the correction parameters can be obtained in a step 54 during which the correction parameters, to be applied to allow modification of the light beam to be transmitted from the modulator 3, are calculated as a function of the determined series of offset information.

[0083] Memory 16a can then store information representing these correction parameters. For subsequent requests to the optical module 1, these correction parameters will be systematically taken into account, so as to modify the activation or deactivation of certain pixels of the modulator 3.

[0084] Typically, in steps 53 and 54, one or more shape parameters of the projected target M can be compared to the predefined shape parameter(s) of the target. The results of this comparison allow for the definition of at least some of the correction parameters. A distortion of the image contour, for example, a local change in curvature, orientation, or thickness (blur), can also be compensated for. It is thus possible to estimate a parameter representative of blur in the projected target M. Depending, for example, on whether the estimated parameter exceeds a sharpness threshold, an associated compensation can be integrated into the correction parameters. This type of compensation can be applied zone by zone.If the number of "active" pixels is reduced to limit blurring in a specific area, the "active / inactive" pixel ratio can be recalculated in that area to compensate for the reduced bandwidth resulting from the reduced number of pixels used. The thickness of certain lines can also be corrected, which is useful, for example, for line drawings or text.

[0085] The correction parameters can also allow, where appropriate, the modification of the durations or frequencies of activation of the pixels 30 of the modulator 3 in order to compensate for a loss of luminance of the projected image F3, in particular near the periphery of the light beam transmitted by the projection optics 18.

[0086] After these steps, the calibration phase 50 can be completed. Alternatively, the relevance of the correction parameters can be tested by repeating steps 52 and 53, which may allow for further refinement of the correction parameters. The calibration phase can also be broken down into several sub-phases, particularly when the optical module 1 exhibits multiple operating modes that affect the shape, segmentation, or homogeneity of the desired output beam 40.

[0087] Next, the optical module 1 can operate in a vehicle, in particular a motor vehicle, by having a control unit 16 which drives the modulator 3, so as to systematically convert the first display command into a second display command which takes into account the correction parameters determined during the calibration phase 50.

[0088] Thus, in the non-limiting case of figure 4 As can be seen, following steps 60 and 61, respectively the activation of optical module 1 and the reception by modulator 3 of the first command (i.e., a command without taking into account geometric defects), the control unit 16 retrieves, in step 55, from memory 16a, the information representing the correction parameters. This allows the modulator 3 to be controlled in a precisely adjusted manner during step 56, the execution of the second display control function.

[0089] Step 62, which generates a pixel usage configuration and is functionally similar to step 52, then leads to customizing the use of modulator 3 to compensate for the geometric defects specifically identified during calibration phase 50.

[0090] With reference to figures 5A And 6A, a visible distortion effect can be seen which may affect the projection of a horizontal boundary or cut 35. The projected image F3 may exhibit a lighting defect, for example in the corners of the projection screen E1 (offset at the edges, visible on the figure 6A When the optical module 1 exhibits such geometric defects, as seen here with a segmented beam, the method can be implemented to reorganize the use of pixels 30 by blurring the boundaries between the active pixels (forming the R2 radiation) and the inactive pixels. In this non-limiting example, the pixels 30 are sufficiently numerous to achieve a resolution of less than 1°, preferably on the order of 0.1° or less. Furthermore, the upper zone of the modulator 3 may have a surplus of pixels 30 compared to the initially planned pixel requirements, in order to provide the necessary margin for applying the corrective effect.

[0091] The process illustrated on the figure 4 or a similar process is then applied to take into account the correction parameters, in order to compensate for the distortion effect shown to the right of the figure 6A In practice, here for a corner area of ​​the micro-mirror matrix 6, the pixel lighting that was planned with the horizontal boundary at a height level A0, as visible on the figure 5A , is modified. By converting the first display command into a second display command, we can then obtain, for the same corner area, a very different pixel distribution 30, illustrated on the figure 5B Here, the separation at height level A0 is replaced by a gradient with a gradual increase in the height level of the 30 active rendered pixels, up to a maximum height level A1. The added row segments LP1, LP2, and LP3 compensate for the localized lighting defect in the corner areas. In reference to the figure 5B The margin zone Z1 that was added results from the definition of the correction parameters obtained during calibration phase 50. This example for the margin zone Z1 is taken from the upper left corner of what is represented in figure 6A .

[0092] Of course, other areas of the micromirror array 6 can be processed by subtracting pixels 30, to avoid over-illumination. Indeed, the control unit 16 associated with the optical module 1 can also remove or add pixels 30, for example in the form of rows or portions of rows of pixels LP1, LP2, LP3, or columns or portions of columns of pixels.

[0093] After implementation and consideration of correction parameters, particularly during each use of optical module 1 in a motor vehicle, the image F3 projected onto the screen E1 more closely matches the desired image from the initial display command F1. In certain cases where optical module 1 is used for lighting purposes (particularly for high beams or low beams), neutralizing or attenuating pixels 30 ensures that distortions or glare do not cause dazzling of road users, or only within regulatory limits.

[0094] Memory 16a can optionally store a default configuration state for the micromirrors 12, and this state can be modified by applying correction parameters. Such a change then corresponds to a modification of the display command. Of course, the method for adjusting the distribution between active and inactive pixels, by modifying the display command, can be implemented in numerous ways.

[0095] The geometric defect correction / recovery process can work to correct both a decentering and one or more distortions, and where appropriate some more localized aberrations.

[0096] One of the advantages of the optical module 1 is that it allows the projection of a light beam which can be homogeneous, so that the projection optics 18 of this optical module 1 is perceived as perfectly assembled, without actually resorting to a production and assembly method which would be tedious or excessively expensive.

[0097] It should be obvious to persons versed in the art that the present invention permits embodiments in many other specific forms without departing from the field of application of the invention as claimed.

[0098] Thus, while the optical module 1 has been illustrated for a case in which the projection screen E1 is defined internally with respect to the transparent wall forming the glass of the transparent cover 14b, it is understood that a portion of the transparent cover 14b or another element forming part of the external housing 14 can define the projection screen. The projection optics 18 can, for example, be focused on a film formed on the external side of the glass rather than on a separate screen.

[0099] Additional functions can also be implemented as needed. For example, in the context of wide-angle optical imaging (numerical aperture of 0.5, 0.6, or 0.7, by way of non-limiting example), it is understood that an indication or marking can be added within the outgoing light beam 40. The use of a high-definition pixelated spatial modulator 3 and the correction of aberrations makes it possible to form characters (letters, numbers, or similar) with sufficient resolution to display messages or pictograms to people outside the vehicle, which are, for example, representative of the activation of a function or an operating context of the vehicle.

Claims

1. Method for amending geometric defects in a light beam projected by an optical module (1) of a motor vehicle, the optical module (1) including: - an imaging device, provided with a high-definition pixelated spatial modulator (3) and a projecting optic (18), and - a light source (2) for generating light intended for the modulator (3), the method comprising steps essentially consisting in: - receiving a first command (F1) to display an image to be projected, intended for the modulator (3); and - converting the first display command (F1) into a second display command (F2) that takes into account correction parameters, the correction parameters being predefined on the basis of an identification of geometric defects that are specific to the projecting optic (18), by virtue of which the modulator (3) is controlled so that the image (F3) actually projected using the imaging device corresponds better to the image to be projected than without said correction parameters taken into account, wherein the projection optics defines a numerical aperture greater than 0.5.

2. Method according to Claim 1, wherein the second display command (F2) in particular differs from the first display command (F1) in the selective activation of all or some of a row (LP3) of pixels (30), said row being defined in a marginal zone by the modulator (3).

3. Method according to Claim 1 or 2, wherein the correction parameters are suitable for modifying activation statuses of the pixels (30) defined by the modulator (3), in order to compensate for at least one among the following defects: - a lateral shift of the outline of the light beam transmitted by the projecting optic (18); and - a deformation of the outline of the light beam transmitted by the projecting optic (18).

4. Method according to any one of the preceding claims, wherein the correction parameters are suitable for modifying the durations or frequencies of activation of the pixels (30) of the modulator (3) in order to compensate for a loss of clearness in the projected image (F3), in particular close to the periphery of the light beam transmitted by the projecting optic (18).

5. Method according to any one of the preceding claims, wherein the correction parameters and / or the second display command (F2) are stored in a memory (16a) accessible to a control unit (16), the control unit (16) being suitable for activating the second display command (F2).

6. Luminous system (5) for a motor vehicle, allowing the method according to any one of the preceding claims to be implemented, the system (5) including: - an optical module (1) comprising: - an imaging device, provided with a high-definition pixelated spatial modulator (3) and a projecting optic (18), and - a light source (2) for generating light intended for the modulator (3), and - a control unit (16) designed and arranged to control the modulator (3) and suitable for receiving first display commands (F1), each of the first display commands (F1) being representative of an image to be projected, the control unit (16) comprising adjusting means (17) for converting each first display command (F1) into a second display command (F2) that takes into account correction parameters, the correction parameters being predefined on the basis of an identification of geometric defects that are specific to each projecting optic (18), the control unit (16) controlling the modulator (3) depending on second display commands (F2) in order that the image (F3) actually projected by the imaging device corresponds better to the image to be projected than without the correction parameters taken into account, wherein the projection optics defines a numerical aperture greater than 0.5.

7. System according to Claim 6, wherein the high-definition pixelated spatial modulator (3) comprises a digital micromirror device (6), the micromirrors (12) of the digital micromirror device (6) each being movable between: - a first position in which the micromirror (12) is arranged to reflect light rays (R1) that come thereto from the light source (2) or from a light-ray emitting unit (20) that includes said light source (2), in the direction of the projecting optic (18), - and a second position in which the micromirror (12) is arranged to reflect the light rays (R1) that come thereto from the light source (2) or from a light-ray emitting unit (20) that includes said light source (2), away from the projecting optic (18).

8. System according to Claim 7, wherein the control unit (16) has access to a memory (16a) storing the correction parameters and / or information representative of the second display commands (F2).

9. System according to Claim 7 or 8, wherein the imaging device is suitable for projecting a segmented output light beam (40) containing at least one cut-off.

10. System according to any one of Claims 7 to 9, comprising two optical modules (1) each including: - an imaging device, provided with a high-definition pixelated spatial modulator (3) and a projecting optic (18), and - a light source (2) for generating light intended for the modulator (3), each light beam transmitted by one of the projecting optics (18) being received on at least one projecting screen (E1), the control unit (16) being suitable for controlling the modulator (3) of each of the two optical modules (1) while taking into account a first set of correction parameters that is associated with a first of the two optical modules (1) and a second set of correction parameters that is associated with a second of the two optical modules, the correction parameters of the first set being predefined on the basis of an identification of geometric defects that are specific to the projecting optic (18) in the first optical module, whereas the correction parameters of the second set are predefined on the basis of an identification of geometric defects that are specific to the projecting optic (18) in the second optical module.

11. Lighting and / or signalling lamp of a motor vehicle for projecting at least one light beam, the lamp comprising: - a housing; - a closing outer lens; and - a luminous system according to any one of Claims 6 to 10.

12. Luminous assembly having a first component and a second component that are formed by: - two lamps; - two headlamps; or - a lamp and a headlamp, the luminous assembly comprising a system according to Claim 10, said two optical modules (1) being distributed one in the first component and the other in the second component.