Lighting device for vehicles and procedures

Abstract

Lighting device for vehicles containing - a high-resolution light source module (1) with a plurality of light source elements arranged spatially separated from each other in a first section (10') and in a second section (10''), - a secondary optical unit (15) arranged downstream of the high-resolution light source module for imaging a light field (14') formed on the output side of the first section (10') to a first image (17') in a projection surface (18) in which a predetermined light distribution is generated, and for imaging a light field (14'') formed on the output side of the second section (10'') to a second image (17'') in the projection surface (18), - a control unit (13) configured such that the light source elements arranged in the first section and in the second section (10'') are controlled, characterized in that - an adjustment device (21) is provided for avoiding and / or reducing a spatial offset (20) between the first image (17') and the second image (17'') in the projection surface (18), wherein the adjustment device (21) has offset correction means (24) which, depending on calibration data and / or correlation data, control the number of light source elements of the first section (10') and / or the number of light source elements of the second section (10'') such that the spatial offset (20) between the first image (17') and the second image (17'') falls below a predetermined threshold.

Description

[0001] The invention relates to a lighting device for vehicles according to the preamble of claim 1.

[0002] From DE 10 2015 115 339 A1, a lighting device for vehicles is known, comprising a light source unit, a liquid crystal unit, a secondary optics unit, and a polarization filter for separating the unpolarized light generated by the light source unit into a first light component containing waves with a first polarization direction and a second light component containing waves with a second polarization direction perpendicular to the first polarization direction. A mirror is associated with this polarization filter, so that the first and second light components are directed via different light paths onto different liquid crystal sections of the liquid crystal unit. Each of the spatially distinct liquid crystal sections is assigned an identical secondary optics element, so that the specified light distribution is generated by superimposing the first and second light components.By utilizing two polarization directions of light in two light paths, the luminous efficacy of the lighting device can be increased. For optimal light distribution quality, it is desirable that the light images generated along each light path focus on a single projection surface. Otherwise, the two light images will be offset, resulting in double images with a deterioration in sharpness and contrast of the superimposed projected image (resulting light distribution).

[0003] From DE 10 2014 209 824 A1, a lighting device for vehicles is known, comprising a light source unit, a liquid crystal unit, and a polarizing filter. The polarizing filter is arranged downstream of the liquid crystal unit in terms of luminous flux and is intended to suppress the generation of double images on a projection surface designed as a windshield. These double images are multiple reflections on the windshield and are not comparable to double images generated by the lighting device for producing light distributions on the road.

[0004] The object of the present invention is to provide a lighting device for vehicles with multiple light paths and a method for reducing image offset, such that a light distribution can be generated in a simple and cost-effective manner, which consists of optimally superimposed light images, and the occurrence of double images is largely avoided.

[0005] To solve this problem, the invention has the features of claim 1.

[0006] The particular advantage of the invention lies in the fact that, by means of an adjustment device, the light source elements (liquid crystal elements) of a first and / or second section (liquid crystal section) of a high-resolution light source module, in particular liquid crystal elements of a first and / or second liquid crystal section of a liquid crystal unit, are controlled in such a way that light fields projected via a secondary optics unit from the respective sections (liquid crystal sections) are focused into images on a projection surface, largely avoiding the occurrence of double images. The adjustment device uses calibration data of the illumination device and / or correlation data to determine the offset of the images produced by the currently controlled light source elements (liquid crystal elements) of the sections (liquid crystal sections).Depending on the determined image offset, light source elements (liquid crystal elements) of the first and / or second section (liquid crystal section) are then controlled such that light fields are formed at each section (liquid crystal section), which are then projected sharply onto the projection surface by the secondary optics unit. The image offset between the projected light fields is less than a predefined threshold. If the image offset were zero, no double images would occur. Optimal reduction of double images would be achieved if the light images from individual light source elements (liquid crystal elements) of different sections (liquid crystal sections) overlapped with at least 50% on the projection surface. The required degree of this overlap can be specified by selecting the predefined threshold.Preferably, the threshold is chosen such that the geometric overlap of light source elements (liquid crystal elements) of different light paths is greater than 50%, wherein the light source elements (liquid crystal elements) are designed to fill the same geometric light pattern in the projection surface.

[0007] According to a further development of the invention, the offset correction means for controlling the sections (liquid crystal sections) are determined based on calibration data of the lighting device. The calibration data is available during the presetting of the lighting device and contains all the information required for the optimal adjustment of a conventional spotlight, for example, the optical properties of the light source unit, the primary optics unit, and the secondary optics unit. Advantageously, the image offset compensation can be calculated in this way using fixed, predefined data.

[0008] According to a further development of the invention, the offset correction means for controlling the first and / or second section (liquid crystal section) are determined as a function of correlation data, whereby images of the different light paths intended for the same geometric location in the projection surface are compared with one another. The images exhibit optical structures that are detected by means of a detection unit, in particular a camera, and then compared with one another. The determined image offset is compensated for by appropriately controlling the light source elements (liquid crystal elements). By again checking the image offset with the detection unit and determining the image offset, it can be further reduced by controlling the high-resolution light source module (liquid crystal unit).

[0009] According to a further development of the invention, the detection unit is designed as a camera that is installed in a vehicle. Advantageously, the function of the camera, which is used as a functional component for an assistance system for distance detection, for example when parking the vehicle, can also be used.

[0010] According to a further development of the invention, the images from the different light paths are identical, with the images exhibiting an optical structure perpendicular to the offset direction. This optical structure can, for example, be formed by a horizontal light / dark boundary in the light distribution. The offset direction is vertical. In this way, the correlation data can be determined more easily and the image offset reduced.

[0011] According to a further development of the invention, the first and second sections (liquid crystal section) are designed to be switched on and off separately, so that a step-by-step acquisition of the photographic images and a step-by-step compensation of the photographic image offset is ensured.

[0012] According to a further development of the invention, the offset correction means can be determined depending on the projection of the photographic images onto a roadway, whereby the image offset is compensated for by taking into account at least partial compression and / or stretching of the photographic images of the first and second light paths. Advantageously, this takes into account the distance and inclination of the road compared to a vertically oriented measuring screen. This allows for further improvement of the image display on the road. In particular, symbols are easier to recognize. The contrast and sharpness of the photographic images are increased.

[0013] To solve the problem, the invention has the features of claim 9.

[0014] According to the inventive method, the spatial offset between images from different light paths is reduced stepwise. Individual frames of the respective images are compared, and then the image offset is reduced by a predetermined step length. The step length is preferably the same, which simplifies the calculation of the correction data. Thus, the image offset is reduced iteratively until it falls below a predetermined threshold and / or is approximately zero.

[0015] According to a further development of the inventive method, the acquisition and comparison of the photographic images can be repeated in predetermined operating cycles of the lighting device. In this way, a dynamic correction of the image offset is made possible during the service life of the lighting device.

[0016] The polarizing filter can be designed as a wire-grid polarizer. The advantage is low manufacturing costs. A mirror is associated with the polarizing filter designed as a separation polarizer, so that the first and second light components are directed via a first and second light path, respectively, which are arranged parallel and offset from each other.

[0017] Preferably, a polarization filter is assigned to each light path downstream of the liquid crystal unit, wherein the polarization filters are arranged rotated relative to each other about an optical axis according to the difference between the first and second polarization directions. Depending on the control of the individual light source elements (liquid crystal elements), light is thus absorbed or transmitted via the polarization filters.

[0018] Preferably, the light source elements (liquid crystal elements) of the section (liquid crystal section) assigned to the first light component and the section (liquid crystal section) assigned to the second light component are of the same size. This allows for the cost-effective use of a single type of light source element (liquid crystal element).

[0019] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings.

[0020] They show: Fig. 1 a block diagram of a lighting device according to the invention, in which the light pattern of two liquid crystal elements of different liquid crystal sections, which do not focus in the projection plane, is shown by way of example, Fig. 2 a representation of corrected controlled liquid crystal elements of the different liquid crystal sections according to Fig. 1, which focus on the projection surface, Fig. 3 a flowchart according to a first embodiment of the invention, Fig. 4 a representation of two offset photographs of the different liquid crystal sections and Fig. 5 a flowchart according to a second embodiment of the invention.

[0021] A lighting device according to the invention can be used as a headlight to generate different light distributions, for example low beam, city light, motorway light, high beam distribution or the like.

[0022] The lighting device comprises a high-resolution light source module that includes a plurality of light source elements (pixels). The light source elements are preferably arranged in a matrix. For example, several high-resolution light source modules can be provided, the light from which is projected onto a projection plane via a common or individually assigned secondary optical unit.

[0023] As an embodiment, a high-resolution light source module comprising essentially a light source unit and a liquid crystal unit is described below. The liquid crystal unit can, for example, form a single unit together with the light source unit, thus creating the high-resolution light source module.

[0024] The lighting device can comprise a light source unit 1 with a plurality of light sources 2 for emitting unpolarized light 3. The light sources 2 are arranged on a common, preferably rigid, support plate. The light sources 2 are arranged in a matrix-like configuration within a planar light source field. The light sources 2 can be configured as LED light sources, laser light sources, or other semiconductor-based light sources.

[0025] In the main emission direction H in front of the light source unit 1, a primary optics unit 4 is arranged with a plurality of primary optics elements 5, each assigned to a light source 2. The primary optics elements 5 are arranged parallel to each other and each preferably has differently designed optical surfaces on the light output side. The primary optics elements 5 thus deflect the light in different directions, so that, depending on the control of the light sources 2, the center of light of the beam 3 emitted by the primary optics unit 4 can be shifted in the horizontal plane. The primary optics elements 5 can, for example, be designed as lenses or reflectors.

[0026] In the main emission direction H in front of the primary optics unit 4, a polarizing filter 6 and a deflecting mirror 7 are arranged. The polarizing filter 6 serves as a beam-splitting filter for polarizing the incoming unpolarized light 3. The beam-splitting filter 6 splits the light 3 coming from the primary optics unit 4 into a first light component 3' with a first polarization direction, which passes through the beam-splitting filter 6 without changing direction, and a second light component 3" with a second polarization direction, which is deflected laterally by the beam-splitting filter 6. The first light component 3' is, for example, polarized parallel to the plane of incidence, while the second light component 3" is polarized perpendicular to the plane of incidence. The first polarization direction is thus oriented at a 90° angle to the second polarization direction.

[0027] The second light component 3" strikes the deflecting mirror 7, by which it is deflected in the main emission direction H. This results in two light paths: the first light component 3' is guided along a first light path 8, and the second light component 3" is guided along a second light path 9, which runs perpendicular to the main emission direction H. The first light component 3' and the second light component 3" exhibit linear polarization, with the polarization of the second light component 3" being rotated by 90° relative to the polarization of the first light component 3'.

[0028] In the main emission direction H, upstream of the polarizing filter 6 and the deflecting mirror 7, a liquid crystal unit 10 with a plurality of liquid crystal elements 11 is arranged. The liquid crystal elements 11 can be considered liquid crystal pixels arranged in a matrix and which, depending on an applied electrical voltage, rotate the polarization direction of the light 3', 3". Depending on the electrical voltage applied to the liquid crystal elements 11, a rotation of the liquid crystal elements occurs or not. In conjunction with the main emission direction H, upstream of the liquid crystal unit 10, another polarizing filter 12 is arranged, which serves as an analyzer. Through the interaction of the polarizing filter 6, the liquid crystal unit 10, and the other polarizing filter 12, light is transmitted or blocked at the locations of the polarizing filter 12 corresponding to the locations of the liquid crystal elements 11.

[0029] The liquid crystal unit 10 is divided into two spatially separated liquid crystal sections 10', 10". In the present embodiment, a first liquid crystal section 10' is arranged within the first light path 8 and a second liquid crystal section 10" is arranged within the second light path 9.

[0030] The lighting unit 1 also has a control unit 13, by means of which the liquid crystal elements 11 of the first liquid crystal section 10' and the second liquid crystal section 10" are individually controlled.

[0031] Depending on the control of the individual liquid crystal elements 11, a light field 14', 14" can thus be generated on the light output side of the liquid crystal sections 10', 10" which can be imaged into the vehicle forecourt (road) by means of a secondary optical unit 15 arranged in the main emission direction H in front of the polarization filter 12.

[0032] The additional polarization filter 12 is preferably arranged in the main emission direction H in front of the liquid crystal unit 10. Alternatively, the polarization filter 12 can also be arranged in the main emission direction H behind the liquid crystal unit 10.

[0033] A first polarizing filter 12' is assigned to the first light path 8, and a second polarizing filter 12" is assigned to the second light path 9. The first polarizing filter 12' is arranged rotated by 90° relative to the second polarizing filter 13" with respect to the main emission direction H, so that the polarization caused by the separating polarizing filter 6 is compensated. The degree of light transmission to the secondary optical unit 15 can thus be controlled solely by activating or deactivating or controlling the liquid crystal elements 11.

[0034] The secondary optics unit 15 has an imaging optic 16 assigned to each of the light paths 8, 9. The imaging optics 16 and the liquid crystal sections 10', 10" are preferably identical.

[0035] The first light path 8 has the first light component 3' that passes through the first liquid crystal section 10' of the liquid crystal unit 11, and the second light path 9 has the second light component 3'' that passes through the second liquid crystal section 10'' of the liquid crystal unit 11.

[0036] The first liquid crystal section 10' and the second liquid crystal section 10'' have geometrically identical liquid crystal elements 11, preferably with the same number of these elements. The first liquid crystal section 10' is thus identical to the second liquid crystal section 10''. The difference lies in the fact that the second liquid crystal section 10'' is offset perpendicular to the main emission direction H and / or arranged adjacent to the first liquid crystal section 10'.

[0037] The imaging optics 16 of the secondary optics unit 15 are designed such that when the locally identical liquid crystal elements 11 of the respective liquid crystal sections 10' and 10'' are actuated, an identical light image or light distribution is produced, i.e., in the case of two light paths, a second light image 17'' of the second light path 9 is produced that is identical to a first light image 17' of the first light path 8.

[0038] As from Fig. As can be seen in Figure 1, it can happen that when imaging light rays intended for the same location in the projection plane 18 from the liquid crystal elements 11 of the first and second light paths 8, 9 do not meet in the projection plane 18, but in a focal plane 19, which is arranged at a distance from the projection plane 18. This results in an offset 20 of images 17', 17''. Fig. Figure 4 shows the offset 20 between the light patterns 17', 17'' designed as dipped beam distribution.

[0039] To reduce this offset 20, which would lead to double images, an adjustment device 21 is provided in the control unit 13. This device acts on a control input 22 of the control unit 13 such that liquid crystal elements 11 of the first liquid crystal section 10' are controlled in relation to liquid crystal elements 11 of the second liquid crystal section 10'', with the effect that the image offset 20 between the first image 17' of the first light path 8 and the second image 17'' of the second light path 9 is smaller than a predetermined threshold value. For this purpose, the adjustment device 21 has corresponding offset correction means 24, which are applied as a correction signal to the input of the control input 22.

[0040] As from Fig. As can be seen in Figure 2, by controlling an alternative liquid crystal element 11' of the second liquid crystal section 10'', compared to the control according to Figure 2, the following can be achieved: Fig. 1. A balance is created so that the images 17', 17'' of the first light path 8 and the second light path 9 meet in the projection plane 18.

[0041] According to a first embodiment of the invention, the offset correction means 24 are determined from calibration data of the illumination device. The calibration data defines the settings of the optical units for the two light paths 8, 9, so that the light image 17', 17'' of the respective light paths 8, 9 can be calculated. If, in addition, the distance of the illumination device to the projection plane 18 is known, the offset correction means 24 can be calculated and the liquid crystal elements 11 of the liquid crystal sections 10', 10'' can be controlled accordingly.

[0042] If the projection distance, i.e. the distance of the lighting device to the projection plane 18, is not known, this can be determined by additional sensors, for example radar, lidar, ultrasound.

[0043] According to the first embodiment of the invention, in a first step S1 the calibration data is evaluated and in a second step S2 the liquid crystal elements are controlled11, see Fig. 3.

[0044] According to a second embodiment of the invention, the offset correction means 24 are determined as a function of correlation data. For this purpose, a detection unit 25 is provided, by means of which photographic images 17', 17'' can be captured on a measuring screen or on a road. The photographic images 17', 17'' of the different light paths 8, 9 are compared with each other and the offset correction means 24 are calculated from this. As shown Fig. As can be seen in Figure 5, the first sub-step of step A1 involves the alternating deactivation of light paths. For example, the second light path 9 is first deactivated and the first light path 8 is activated. The light image 17' of the first light path 8 is then captured. Afterward, the first light path 8 is deactivated and the second light path 9 is activated, so that another light image 17'' of the second light path 9 is captured. Thus, the light images 17', 17'' of the first light path 8 and the second light path 9 are selectively captured, with the light images 17', 17'' of the first and second light paths 8, 9 having the same shape (see Figure 5). Fig. 4.

[0045] In a further sub-step of step A1, the captured light images 17', 17'' from different light paths are compared.8, 9 For example, in Fig. As shown in section 4, an image offset of 24 in the vertical direction V has been detected, which needs to be corrected. Fig. Figure 4 shows the light fields 17', 17'' as low beam with an asymmetrical light / dark boundary. A horizontal part of the light / dark boundary can be used as an optical reference structure (optical structure) that runs perpendicular to an offset direction V.

[0046] In a further step A2, the offset correction means 24 are calculated such that the image offset 20 is reduced by a step size Δd. Fig. Figure 4 shows photographs 17', 17'' of liquid crystal elements (pixels) 11 of the two liquid crystal sections 10', 10'', in which a single imaged pixel P' of the first light path 8 and a single pixel P'' of the second light path 9, which are intended for the same photograph location in the projection surface 18, are shown enlarged.

[0047] In a further step A3, the light path images are again captured and compared, i.e., the light images 17', 17'' of the first light path 8 and the second light path 9.

[0048] In a further step A4, it is checked whether the image offset 20 is smaller than the threshold value. If this is confirmed, the control of the liquid crystal unit can be fixed in a final step A5. If the image offset 20 is equal to or greater than the threshold value, the image offset 20 is further reduced by the step size Δd in step A2. Steps A2 and A3 are repeated until the image offset 20 is smaller than the threshold value. In this way, the image offset 20 is gradually reduced until the images 17', 17'' of the first and second light paths 8, 9 are aligned.

[0049] The detection unit 25 is preferably designed as a camera that is installed in the vehicle and is used for other assistance functions, for example distance determination when packing and unpacking the vehicle.

[0050] According to a further embodiment of the invention, the offset correction means 24 are determined as a function of a projection of the photographic images 17', 17'' onto a road, wherein the image offset 20 is compensated taking into account any compression and / or stretching of the photographic images 17', 17''. Thus, when projecting the photographic images 17', 17'' onto the road, any compression and / or stretching of the photographic images 17', 17'' is factored in during the control of the liquid crystal unit 10.

[0051] It should be noted that the polarizing filter 6 can be designed as a wire mesh polarizer.

[0052] According to an alternative embodiment of the invention (not shown), the light source unit 1 can also be configured such that the light paths 8, 9 are not supplied by the same light source 2. Thus, a different light source can be assigned to the first liquid crystal section 10' than to the second liquid crystal section 10''. Crucially, the first liquid crystal section 10' is supplied with perpendicularly polarized light compared to the second liquid crystal section 10''.

[0053] If necessary, more than two light paths 8, 9 can be provided. Reference symbol list 1 light source unit 2 light sources 3.3',3'' light components 4 Primary optical unit 5 Primary optical element 6 polarization filters 7 deflecting mirrors 8 1. Light path 9 2. Light path 10 liquid crystal units 10', 10'' liquid crystal section 11 Liquid crystal element 12 polarization filters 13 Control unit 14',14'' light field 15 Secondary optical unit 16 Imaging optics 17', 17'' photograph 18 Projection plane 19 Focus level 20 offset 21 Adjustment device 22 Control 24 Offset correction agents 25 recording units H Main radiation direction Δd step size V Vertical direction P', P'' Pixel S1,S2 steps A1, A2, A3 steps A4, A5 steps

Claims

[1] Lighting device for vehicles containing - a high-resolution light source module (1) with a plurality of light source elements arranged spatially separated from each other in a first section (10') and in a second section (10''), - a secondary optical unit (15) arranged downstream of the high-resolution light source module for imaging a light field (14') formed on the output side of the first section (10') to a first image (17') in a projection surface (18) in which a predetermined light distribution is generated, and for imaging a light field (14'') formed on the output side of the second section (10'') to a second image (17'') in the projection surface (18), - a control unit (13) configured to control the light source elements arranged in the first section and in the second section (10''), characterized by , that - an adjustment device (21) is provided for avoiding and / or reducing a spatial offset (20) between the first image (17') and the second image (17'') in the projection surface (18), wherein the adjustment device (21) has offset correction means (24) which, depending on calibration data and / or correlation data, control the number of light source elements of the first section (10') and / or the number of light source elements of the second section (10'') such that the spatial offset (20) between the first image (17') and the second image (17'') falls below a predetermined threshold. [2] Lighting device according to claim 1, characterized by, that the calibration data are determined by presetting the lighting device, that depending on the specified or determined distance of the high-resolution light source module to the projection plane (18) the spatial offset (20) between the first and second light images (17', 17'') can be calculated, and that the offset correction means (24) for light path-dependent control of the light source elements can be derived from the calibration data, so that the spatial offset (20) of the light images (17', 17'') is smaller than the specified threshold. [3] Lighting device according to claim 1, characterized by, that a detection unit (25) is provided for the provision of photographic images (17', 17'') of the different light paths (8, 9), so that correlation data can be determined from the comparison of individual images of the first photograph (17') and the second photograph (17''), by means of which the offset correction means (24) for controlling the corresponding sections (10', 10'') can be determined. [4] Lighting device according to claim 3, characterized by , that the detection unit (25) is designed as a camera installed in a vehicle. [5] Lighting device according to any one of claims 1 to 4, characterized by , that the first and second images (17', 17'') are identical, with each image (17', 17'') having optical structures perpendicular to a direction of the offset (20). [6] Lighting device according to any one of claims 3 to 5, characterized by, that the first section (10') and the second section (10'') can be switched on and off separately, so that a stepwise acquisition of the first and second photograph (17', 17'') takes place. [7] Lighting device according to any one of claims 1 to 6, characterized by , that the offset correction means (24) can be determined depending on a projection of the first and second photographs (17', 17'') onto a roadway in such a way that the offset (20) is compensated taking into account at least partial compression and / or stretching of the first and second photographs (17', 17''). [8] Lighting device according to any one of claims 1 to 7, characterized by , that the high-resolution light source module (1) has: - a light source unit (1) with a number of light sources (2), - a liquid crystal unit (10) containing a plurality of liquid crystal elements (11) which are spatially separated from each other in a first liquid crystal section (10') and in a second liquid crystal section (10''), - a polarizing filter (6) arranged upstream of the liquid crystal unit (10) for converting light (3) generated by the light source unit (1) into polarized light (3', 3''), wherein a first component (3') of the light (3) is polarized in a first polarization direction and a second component (3'') of the light is polarized in a second polarization direction perpendicular to the first polarization direction, so that the first component (3') reaches the first liquid crystal section (10') via a first light path (8) and the second component (3'') reaches the second liquid crystal section (10'') via a second light path (9), - that the secondary optical unit (15) is configured to image a light field (14') formed on the output side of the first liquid crystal section (10') into a first image (17') in a projection surface (18) in which a predetermined light distribution is generated, and to image a light field (14'') formed on the output side of the second liquid crystal section (10'') into a second image (17'') in the projection surface (18), - a control unit (13) which is configured such that the liquid crystal elements (11) of the second liquid crystal section (10'') are controlled in an inverting manner to the liquid crystal elements (11) of the first liquid crystal section (10'), - that the adjustment device (21) is provided to avoid and / or reduce a spatial offset (20) between the first image (17') and the second image (17'') in the projection surface (18), wherein the adjustment device (21) has offset correction means (24) which, depending on calibration data and / or correlation data, control the number of liquid crystal elements (11) of the first liquid crystal section (10') and / or the number of liquid crystal elements (11) of the second liquid crystal section (10'') such that the spatial offset (20) between the first image (17') and the second image (17'') falls below a predetermined threshold. [9] Method for reducing a spatial offset between photographic images (17', 17'') of several light paths (8, 9) of a lighting device according to any one of claims 1 to 7, characterized by , - the sequentially identically shaped light images (17', 17'') of a first light path (8) and a second light path (9) are captured on a projection surface (18), - that a photograph (17') of the first light path (8) is compared with a photograph (17'') of the second light path (9) for agreement, wherein agreement exists if a spatial offset (20) between the first photograph (17') and the second photograph (17'') is less than a specified threshold, and mismatch exists if the spatial offset (20) between the first photograph (17') and the second photograph (17'') is greater than or equal to the specified threshold, - that if the first image (17') does not match the second image (17''), the liquid crystal elements (11) of the first section (liquid crystal section 10') and / or of the second section (liquid crystal section 10'') are controlled in such a way that the offset (20) is reduced by a predetermined step size (Δd), - that the first photograph (17') and the second photograph (17'') are repeatedly captured separately and checked for agreement until the determined spatial offset (20) between the photographs (17', 17'') is smaller than the threshold value. [10] Method according to claim 9, characterized by , that the recording and comparison of the photographic images (17', 17'') of the different light paths (8, 9) are repeated in predetermined operating cycles of the lighting device. [11] Method according to claim 9 or 10, characterized by, that when projecting the photographic images (17', 17'') onto a roadway, a local compression and / or stretching of the photographic images (17', 17'') is calculated.

Images