Procedure for automated headlight calibration

Abstract

Method for calibrating at least one headlight of a vehicle, comprising the following steps: Providing images of the light field produced by the at least one spotlight, wherein each of the provided images of the light field is correlated with a different position of the at least one spotlight; Determining calibration values ​​by evaluating the provided images of the light field, wherein the calibration values ​​indicate a misalignment of at least one spotlight; and Transmitting the calibration values ​​to a headlight control unit to control at least one headlight; wherein at the beginning of determining the calibration values, the status of conditions of a first group and the status of conditions of a second group are checked, wherein the status of the conditions of the second group is only checked if all conditions of the first group are met and the procedure is aborted if any of the conditions are not met, and wherein, during the further determination of the calibration values, the status of the conditions of the first group and the second group is monitored and the procedure is aborted if at least one of the conditions of the first group or the second group is no longer met.

Description

[0001] Methods are known in the art for calibrating the main headlights (hereinafter referred to as headlights) of a vehicle based on images of the light pattern produced by the headlights. The necessary images are provided by a driver assistance camera. By evaluating and comparing the images of the light pattern, any misalignment of the headlights can be determined. To correct the misalignment, calibration values ​​are determined that describe the horizontal and vertical misalignments of the headlights. These calibration values ​​can then be transmitted to the lighting control unit and used by its integrated lighting algorithm to adjust the headlights to the correct alignment.

[0002] The present invention aims to further develop the method known from the prior art in such a way that it can be carried out safely and reliably.

[0003] This objective is achieved by a method having the features of claim 1, wherein further preferred embodiments result from the dependent claims.

[0004] The inventive method for calibrating at least one headlight of a vehicle comprises the following steps: providing images of the light field generated by the at least one headlight, wherein each of the provided images of the light field is correlated with a different position of the at least one headlight; determining calibration values ​​by evaluating the provided images of the light field, wherein the calibration values ​​indicate a misalignment of the at least one headlight; and transmitting the calibration values ​​to a headlight control unit for controlling the at least one headlight.The procedure is further designed such that, at the beginning of the calibration value determination process, the status of conditions in a first group and a second group are checked. The status of the second group is only checked if all conditions in the first group are met, and the procedure is terminated if any of the conditions are not met. Additionally, during the further determination of the calibration values, the status of the conditions in both the first and second groups is monitored, and the procedure is terminated as soon as at least one of the conditions in either the first or second group is no longer met.

[0005] In this context, headlight calibration refers to an automated process in which the headlight is adjusted from an incorrect position to the correct one. This adjustment is achieved using actuators (e.g., stepper motors) controlled by the lighting control unit based on calibration values. In other words, calibration adjusts the headlight to its correct resting position. This differs from setting the headlight's basic alignment, which is done during vehicle production and then as needed, for example, during a vehicle inspection, by adjusting the headlight's vertical and horizontal alignment using appropriate mechanical adjustment screws.This initial headlight alignment adjustment, typically performed by production or inspection personnel, serves to set the headlight's mechanical resting position and is not the same as headlight calibration as described here. The headlight calibration procedure described here can be understood as an automatically performed fine-tuning of the headlight from this mechanical resting position, which, at least temporarily, corrects the headlight's initial alignment using actuators. This process allows the headlight position to be adjusted to the vehicle's current condition without intervention from qualified personnel. Such an adjustment can be useful, for example, if the vehicle's bodywork changes due to mechanical wear of its components.Specifically, calibrating a headlight does not refer to adjusting it to implement basic lighting functions or adaptive lighting concepts beyond these, such as automatic headlight range control or dynamic cornering lights. Rather, correct implementation of both basic and adaptive lighting concepts requires a correctly aligned headlight. Calibration can also be achieved through a non-mechanical intervention in the form of an offset in the light algorithm.

[0006] The method according to the invention is characterized by the fact that its execution depends on the status of the conditions in the first group and the status of the conditions in the second group. For the purposes of this description, the status of a condition means whether the condition is fulfilled or not, and consequently, checking the status of a condition means checking whether the condition is fulfilled. According to the invention, the conditions to be checked are divided into (at least) two groups. At the start of the determination of the calibration values, the status of each condition in the first group is checked first. The method continues only if all conditions in the first group are fulfilled; otherwise, the method is terminated and can be restarted at a later time or immediately after termination. If the method is continued, the status of each condition in the second group is checked first.The process continues only if all conditions of the second group are also met; otherwise, it is aborted and can be restarted later or immediately after the abort. In the initial phase, the groups of conditions are checked hierarchically, one after the other, for their status. Although the procedure described here refers to at least one headlight, it can expediently be carried out by simultaneously including both front headlights of a vehicle.

[0007] The conditions of the first group can relate to the vehicle's technical or peripheral environment and can be verified regardless of the availability or quality of the provided images. In particular, the conditions of the first group can relate to conditions whose verification does not require evaluation of the provided light field images. Evaluation of one or more light field images can refer to a data analysis used to determine characteristic features of an image, such as the progression of the light-dark boundary, using predefined image processing steps. The conditions of the second group can relate to matters that, for example, require more complex verification processes and / or are based on information obtained by evaluating the provided light field images.Therefore, the verification of the conditions of the first group can begin in parallel with the provision of a first image of the light field generated by the at least one spotlight, in particular even before the first image to be provided has been evaluated / processed. Regardless of the assignment of a condition to a group, the finding that a condition is not fulfilled is equivalent to the statement that a prerequisite required for the successful execution of the method according to the invention is classified as not fulfilled, and thus the method cannot be completed with a usable result. Consequently, in such a case, the method is terminated.

[0008] Following the initial cascaded verification of the (at least) two groups of conditions, the status of each condition is monitored for any potential non-fulfillment during the further determination of the calibration values ​​of the inventive method. This subsequent monitoring of the conditions is performed in parallel and on an equal footing, i.e., independently of the group membership of a condition. For example, all conditions can be checked for their status at regular intervals, with the interval being individually adjustable for each condition—depending, for instance, on the complexity and duration of the underlying verification process. As soon as it is determined that a condition is not fulfilled, the method is terminated. The parallel and equal verification of the conditions can immediately follow the single cascaded verification of the conditions of the first and second groups.

[0009] For the purpose of automatic calibration of the at least one illuminator, each image of the light field produced by the at least one illuminator is captured with the illuminator in a different orientation. For this purpose, the at least one illuminator can be adjusted for each image in a predetermined manner (rotation / tilt by predetermined angles and / or translation by predetermined distance). Based on the evaluation of one or more images with regard to characteristic features (e.g., cut-off line) of the depicted light fields, a misalignment of the at least one illuminator can be determined. The misalignment of a illuminator can be quantified using calibration values, which specify the misalignment of the illuminator with respect to its degrees of freedom, usually the horizontal and vertical misalignment.To compensate for the detected misalignment, the calibration values ​​are then transmitted to the lighting control unit to control at least one headlight. The lighting control unit can thus perform correct light control based on the calibration values ​​determined from the current basic alignment of at least one headlight. This prevents the use of unsuitable standard or otherwise outdated and therefore incorrect calibration values, which ultimately lead to faulty lighting functions.

[0010] According to a further embodiment of the method, providing an image of the light field can involve retrieving an image of the light field captured by an image acquisition unit of the vehicle. The vehicle's image acquisition unit can be a camera that is part of a driver assistance system. Furthermore, the method can involve synchronization or other correlation between the position of the at least one headlight and the image retrieved by the image acquisition unit. For example, an adjustment of the at least one headlight can be requested via the vehicle's on-board electronics. Successful adjustment of the headlight can be confirmed with a corresponding signal, whereupon an image of the light field is captured by the image acquisition unit and subsequently provided within the framework of the method according to the invention.

[0011] According to a further embodiment of the method, before retrieving the images of the light field from the image acquisition unit, and in particular before retrieving a first image of the light field from the image acquisition unit, the status of the conditions of the first group can be checked, whereby the actual retrieval of the images is only carried out if all conditions of the first group are met. In this embodiment of the method, images of the light field are thus selectively retrieved from the image acquisition unit only if the minimum requirements for the successful execution of the method, which are formulated in the conditions of the first group, are met. As soon as it has been determined that the conditions of the first group are met, a first image can, in principle, already be retrieved, and the checking of the conditions of the second group can begin.Alternatively, after the (positive) verification of the status of the conditions for the first group, the second group can be checked immediately, and the first image can only be retrieved if these conditions are also met. In other words, the hierarchical verification of the conditions according to their group affiliation can be performed at the beginning of image retrieval from the image acquisition unit, instead of at the beginning of determining the calibration values.

[0012] According to a further embodiment of the method, analogous to checking the status of the conditions of the first and second groups, the status of a third condition can also be checked at the beginning of determining the calibration values, but only if all conditions of the second group are met. During the further determination of the calibration values, the status of the third condition can also be monitored together with the conditions of the first and second groups, in which case the third condition is treated as equivalent to the conditions of the first and second groups. The method is terminated as soon as at least one of the conditions of the first group, the second group, or the third condition is no longer met.The third condition, the fulfillment of which is also required for the execution of the method according to the invention, can be understood in the context of the method according to the invention as a third group of conditions, which, however, comprises only one condition. Alternatively, the third condition can also be assigned to the second group of conditions. Likewise, the verification of the third condition, in accordance with the hierarchical sequence, can be carried out at the beginning of the image retrieval from the image acquisition unit, as explained in the previous paragraph.

[0013] According to another embodiment of the method, checking the status of the third condition can include verifying whether a suitable projection surface is available for executing the method. For example, the distance to and size of the projection surface or a corresponding projection object can be taken into account when checking the status of the third condition. In particular, checking whether a suitable projection surface is available for executing the method can be based on characterizing specific points in a basic configuration of the light field (e.g., low beam or city light).

[0014] In one embodiment, checking whether the conditions of the first group are met can include checking at least one of the following conditions: i) whether the vehicle's state of motion corresponds to a standstill or at least to movement below a certain speed; ii) whether the stepper motors responsible for headlight range control are in a suitable position; iii) whether a rotary light switch position corresponds to a predefined position; iv) whether a high beam / flash-to-pass request has not been made; and v) whether the light sensor reports darkness. Condition i) can, for example, be caused by the fact that, above a certain speed, the captured images are too strongly influenced by the vehicle's dynamics.Condition iii) is contingent upon the procedure only being executable if at least one headlight is switched on and, according to condition v), the area around the vehicle is sufficiently darkened so that the generated light field can be optimally recognized on the captured images during evaluation and processed using image processing methods.

[0015] In one embodiment, checking whether the conditions of the second group are met can include checking at least one of the following conditions: i) whether there are interfering objects in the light field that could impair the correct capture of the light field by an image acquisition unit; ii) whether the headlight control unit allows automated headlight calibration at the time the procedure is executed; and iii) whether the vehicle's image acquisition unit is ready to capture a sequence of images of the light field. Condition i) may not be met, for example, if people, vehicles, trees, or other objects with a curved surface are in the light field and cause, for example, perspective distortion of the light field in the captured images. Highly reflective objects in the light field or objects that themselves generate light, such as taillights or headlights of other vehicles, can also adversely affect the image processing that takes place during the evaluation of the images.

[0016] According to a further embodiment, the method can also include controlling the headlight by means of the headlight control unit based on the transmitted calibration values, thereby ensuring a correct implementation of the light functions based on the at least one headlight.

[0017] Further details, features, and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not limit the essential concept of the invention. Fig. Figure 1 schematically shows an interaction of basic components in a vehicle during headlight calibration, including the extension according to the invention. Fig. Figure 2 shows a flowchart illustrating the process of the method according to the invention.

[0018] In Fig. Figure 1 illustrates the interaction of several basic vehicle components during headlight calibration, as well as the extension according to the invention. The area enclosed by the dashed rectangle 15 illustrates a standard headlight calibration ring. The basis for headlight calibration is information about the light field generated by the at least one headlight 13. This information can be provided, for example, in the form of images 3, which are captured by the image acquisition unit 1 and transmitted to a determination unit 5 for determining calibration values ​​or the misalignment of the headlights. The determination unit 5 can, for example, be implemented as a functional unit (e.g., FPGA or integrated circuit) within the vehicle electronics or as a program unit in the main module of the vehicle electronics.The images 3 can be provided together with, or may contain, information indicating the position of the headlight at which the respective image was captured. The detection unit 5 can further be configured to evaluate the captured images 3 using appropriate image processing methods, i.e., for example, to segment them, extract relevant areas, and perform pattern recognition within these areas. The evaluation yields a calibration result 7, e.g., the horizontal and vertical misalignment of the headlight 13, which is then transmitted to the lighting control unit 9. The lighting control unit 9 has a lighting algorithm that serves to control the at least one headlight 13. Based on the calibration result 7, the lighting control unit 9 can transmit a corresponding control signal 11 to the headlight 13 and control it in such a way that the surroundings are always correctly illuminated.This ensures that the headlight 13 always produces a correct light field despite being misaligned compared to its basic orientation.

[0019] The modification of the standard headlight calibration 15 according to the invention is described in Fig. 1 is represented by an additional unit 19, which is configured to communicate with the target unit 5 via a communication channel 17 and thus influence its operation. The additional unit 19 can be implemented analogously to the target unit 5 using the vehicle electronics, for example, as a program module in the main module of the vehicle electronics, or it can be an additional electronic module that is part of the vehicle electronics. Three groups of conditions are indicated in the additional unit 19: a first group 21 of conditions, a second group 22 of conditions, and a third group 23 of conditions, the presence of the third group 23 of conditions being optional.The dashed arrows between groups 21, 22, and 23 of conditions indicate the initial cascaded verification procedure at the beginning of the process, in which the status of the conditions in groups 21, 22, and 23 is checked once in succession. Only if all conditions are met at the end is the determination of calibration values ​​carried out by the determination unit 5.

[0020] In one embodiment, the determination unit 5 can be configured such that it only begins evaluating the images 3 of the light field after the auxiliary unit 19 has confirmed the existence of the conditions from at least the first group 21. A corresponding message can be transmitted from the auxiliary unit 19 to the determination unit 5 for this purpose.

[0021] After a successful initial check of the status of the conditions of the first group 21, the second group 22, and the third group 23, the status of each condition is monitored in parallel and uniformly, along with all others. If, during this phase, while the image acquisition unit 1 is providing the images 3 and / or while the determination unit 5 is determining calibration values, it is detected that one of these conditions is not met, the headlight calibration 15 is aborted. The corresponding instruction can be transmitted to the determination unit 5 via communication channel 17.Since a headlight calibration can take approximately between a few tens of seconds and a minute, the headlight calibration procedure 15 can be a nested process in the sense that between the provision / retrieval of an image of the light field at a certain position of the at least one headlight 13 and the provision / retrieval of a subsequent image at a different position of the headlight 13, the older image is fully processed as part of the evaluation.

[0022] Although the additional unit 19 in the schematic representation in Fig. The fact that unit 1 is represented as a separate unit does not constitute a fundamental technical requirement. In actual implementation, the functionality of unit 19 can also be implemented within unit 5 or considered as a functional extension. In other words, the functionality of unit 5 can be extended by the functions of unit 19 such that both the invocation and the subsequent execution of determining calibration values ​​are subject to the conditions already described in detail.

[0023] The procedure for calibrating at least one headlight of a vehicle is further described in the Fig.The process is illustrated in the flowchart shown in Figure 2. In a first step 31, the method comprises providing images of the light field generated by the at least one headlight, wherein each of the provided images of the light field is correlated with a different position of the at least one headlight. In a further step 33, the method comprises determining calibration values ​​by evaluating the provided images of the light field, wherein the calibration values ​​indicate a misalignment of the at least one headlight. Furthermore, in step 35, the method comprises transmitting the calibration values ​​to a headlight control unit for controlling the at least one headlight.

[0024] As already explained, the method is characterized by the fact that, during the provision of the light field images (corresponding to step 31) and the determination of the calibration values ​​(corresponding to step 33), the status of conditions of a first group and the status of conditions of a second group are checked, whereby the status of the conditions of the second group is checked only if all conditions of the first group are met. This conditional check takes place only once at the beginning of the method. Thereafter, in the method according to the invention, during the provision of the light field images and the determination of the calibration values, the status of the conditions of the first and second groups is monitored, and the method is terminated as soon as at least one of the conditions of the first or the second group is no longer met.In other words, the initial check of the conditions in groups is carried out once sequentially, after which, if all conditions are detected as fulfilled, the conditions merge into a single group of conditions that are monitored in parallel and on an equal footing.

Claims

[1] Method for calibrating at least one headlight of a vehicle, comprising the following steps: Providing images of the light field produced by the at least one spotlight, wherein each of the provided images of the light field is correlated with a different position of the at least one spotlight; Determining calibration values ​​by evaluating the provided images of the light field, wherein the calibration values ​​indicate a misalignment of at least one spotlight; and Transmitting the calibration values ​​to a headlight control unit to control at least one headlight; wherein at the beginning of determining the calibration values, the status of conditions of a first group and the status of conditions of a second group are checked, wherein the status of the conditions of the second group is only checked if all conditions of the first group are met and the procedure is aborted if any of the conditions are not met, and wherein, during the further determination of the calibration values, the status of the conditions of the first group and the second group is monitored and the procedure is aborted if at least one of the conditions of the first group or the second group is no longer met. [2] Method according to claim 1, wherein providing an image of the light field comprises retrieving an image of the light field captured by an image acquisition unit of the vehicle. [3] Method according to claim 2, wherein the status of the conditions of the first group is checked before the images of the light field are retrieved by the image acquisition unit and the retrieval of the images is only carried out if all conditions of the first group are met. [4] Method according to any one of claims 1 to 3, wherein at the beginning of determining the calibration values ​​the status of a third condition is further checked, but only if all conditions of the second group are met, and wherein during the further determination of the calibration values ​​the status of the third condition is monitored together with the conditions of the first and the second group and the method is terminated as soon as at least one of the conditions of the first group, the second group or the third condition is no longer met. [5] Method according to claim 4, wherein checking the status of the third condition comprises checking whether a suitable projection surface is available for carrying out the method. [6] Method according to claim 5 wherein checking whether a suitable projection surface is available for carrying out the method comprises characterizing specific points at a basic configuration of the light field. [7] Method according to any one of claims 1 to 6, wherein checking whether the conditions of the first group are met comprises checking at least one of the following conditions: i) whether the state of motion of the vehicle corresponds to a standstill or at least to movement below a certain speed; ii) whether the position of stepper motors responsible for headlight range control is in a suitable position; iii) whether a rotary light switch position corresponds to a predefined position; iv) whether a high beam / flash-to-pass request was not made; v) whether the light sensor reports darkness. [8] Method according to any one of claims 1 to 7, wherein checking whether the conditions of the second group are met comprises checking at least one of the following conditions: i) whether there are interfering objects in the light field which impair the correct detection of the light field by an image acquisition unit; ii) whether the headlight control unit allows automated headlight calibration at the moment the procedure is carried out; iii) whether the vehicle's image acquisition unit is ready to acquire a sequence of images of the light field. [9] Method according to any one of claims 1 to 8, further comprising: Controlling the headlight via the headlight control unit based on the transmitted calibration values.

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