Focal adjustment of automotive camera

Abstract

To provide a method for focal adjustment.SOLUTION: For focal adjustment of a camera (3), a first image is captured during a first frame period (F1), where multiple rows (P) of a sensor array (11) are exposed according to a rolling shutter mode, and a second image is captured after the first frame period (F1). Areas on the sensor array (11) corresponding to regions of interest (6a, 6b, 6c, 7a, 7b, 7c) are determined; a subset (P1) of the multiple rows (P) including the areas is determined; and a focal adjustment period (Ta) which starts when or after all rows of the subset (P1) are exposed is determined. At least one focal parameter is adjusted during the focal adjustment period (Ta) according to a predefined focal setting.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The invention relates to a method for focusing of a motorized vehicle camera, whereby a first image is acquired by an imaging device of the camera during a first frame period and multiple rows of a sensor array of the imaging device are exposed according to a rolling shutter mode, whereby a second image is acquired by the imaging device during a second frame period after the first frame period. The invention further relates to a corresponding motorized vehicle camera, an electronic vehicle guidance system including the motorized vehicle camera, and a computer program product. Summary of the Invention

[0002] In photography and other applications of cameras, the term focusing refers to the adjustment of the respective camera and / or lens settings to the object distance in order to bring the object being represented or a certain part of the environment being represented into focus. Such adjustment is hereinafter also referred to as focus adjustment or focus adjustment.

[0003] In the context of motorized vehicle applications of cameras, image or video streams comprising multiple successive camera images according to successive frames may be acquired, displayed and / or processed to realize various driving assistance functions or other functions for automatically or partially automatically guiding the vehicle. Corresponding frame rates may be, for example, on the order of a few frames or tens of frames per second, fps. Typically, frame rates between 15 fps and 60 fps may be used.

[0004] In motor vehicle applications, dynamically changing the focus setting of the camera can be beneficial in various cases. For example, for various functions, objects at different distances from the camera are typically relevant. For example, for driver assistance functions that assist the driver of the vehicle in reversing, for example for parking the vehicle, nearby objects may be most relevant, whereas for computer vision algorithms that detect other vehicles, pedestrians or further road users in the environment, the most relevant objects may typically be located far from the camera.

[0005] Adjusting the focus setting while the sensor array of the imaging device is exposed may have undesirable effects and may reduce the quality of the corresponding image. Furthermore, adjusting the relevant focus parameters of the camera takes some time. In general, there are various known ways of achieving focus adjustment. In principle, the position of the object-side principal surface of the lens unit of the camera may be changed with respect to the image plane provided by the surface of the sensor array. For this purpose, the sensor array or the entire imaging device may be physically moved with respect to the lens unit. Alternatively or additionally, the optical parameters or properties of the lens unit may be changed by moving the individual lenses of the lens unit with respect to each other or by changing the shape of one or more lenses, for example by applying an electrical voltage.

[0006] In digital cameras, particularly in motor vehicle cameras, it is known to use electronic shutters rather than mechanical shutters as used, for example, in conventional digital single-lens reflex cameras. In the case of an electronic shutter, the sensor pixels of the sensor array are electronically controlled such that only photoelectrons generated by light falling on each sensor pixel during a defined exposure period, also referred to as an integration period, contribute to an accumulated charge or voltage that is read out to determine the corresponding pixel value of a raw image. However, there are no mechanical parts and light only falls on a pixel during the exposure period as in the case of a mechanical shutter.

[0007] On the other hand, the electronic shutter can be implemented as a global shutter, where all sensor pixels of the sensor array are exposed at the same time. In other words, the exposure period starts and ends at the same time for all pixels of the sensor array. On the other hand, the electronic shutter can be implemented as a rolling shutter, where the sensor pixels of the sensor array are grouped into multiple rows, also referred to as lines, and the exposure period starts and ends at the same time for all sensor pixels of a row. However, the exposure periods for different rows start and end at different times. For example, there may be a predetermined time offset between the start of the respective exposure for adjacent rows. As a result, the exposure period starts for each of the multiple rows one after the other, and the exposure of the entire sensor array is completed when the last row is exposed. For completeness, it is also noted that the rolling shutter can be performed mechanically.

[0008] Advantages of the rolling shutter compared to the global shutter include a simplified pixel architecture of the imaging device, since the rolling shutter principle requires less intermediate buffering of data and less complex readout electronics. Furthermore, less heat is dissipated and less electronic noise is generated, and thermal noise can be smaller than that for a global shutter.

[0009] Document DE102016124089A1 describes the use of a camera in rolling shutter mode in a motorized vehicle.

[0010] It is an object of the present invention to provide a method for focusing a camera for a motor vehicle operating in rolling shutter mode, in which the adverse effects of the focusing on the acquired image are avoided for at least a part of the image.

[0011] This object is achieved by the subject matter of the respective independent claims. Further implementations and preferred embodiments are the subject matter of the dependent claims.

[0012] The invention is based on the idea of ​​using a predefined region of interest, ROI, to identify those rows of the sensor array that are exposed row by row in rolling shutter mode, which rows comprise the area of ​​the sensor array that corresponds to the region of interest. Then the focus adjustment period during which the focus parameters are adjusted is calculated such that it starts after the region of interest has been captured. In other words, a certain part of the exposure period that does not affect the region of interest is used to adjust the focus parameters.

[0013] According to one aspect of the invention, a method for focusing of a motorized vehicle camera is provided, whereby a first image is acquired by an imaging device of the camera during a first frame period. To acquire the first image, a plurality of rows of a sensor array of the imaging device are exposed according to a rolling shutter mode, in particular a rolling shutter mode of the camera or imaging device, respectively. A second image is acquired by the imaging device during a second frame period after the first frame period. A first area in the sensor array is determined, in particular by at least one control unit of the motorized vehicle camera, the first area corresponding to a region of interest that is predefined for the first frame period. A first subset of the plurality of rows is determined, in particular by the at least one control unit, whereby the first subset of rows comprises the first area, in particular completely comprises the first area. A focusing period is determined, in particular calculated, for example by the at least one control unit, whereby the focusing period starts when or after all rows of the first subset of rows have been exposed to acquire the first image during the first frame period. At least one focus parameter of the camera is adjusted during a focus adjustment period with a predefined focus setting for acquiring the second image, in particular by a focus adjustment arrangement of the camera, which focus adjustment arrangement is, for example, controlled for this purpose by at least one control unit.

[0014] The method for focusing can also be expressed as a method for acquiring at least a first image and a second image, where focusing is performed to acquire the second image.

[0015] A motorized vehicle camera may be considered as a camera suitable to be mounted on a vehicle, in particular on a motorized vehicle, such as a front camera, a rear camera, a side camera, etc. The motorized vehicle camera is mounted on the vehicle while the method according to the invention is carried out.

[0016] The first and second frame periods may correspond, for example, to two consecutive frames of an image or video stream generated by a camera. As a result, the second frame period may start immediately after the first frame period ends. However, before the first frame period ends, exposure of the entire sensor array may already be completed for the first image and / or readout of the data, e.g., data storage, may already be completed.

[0017] The plurality of rows may correspond to the entire sensor array, in other words the plurality of rows may include all sensor pixels of the sensor array. However, in other implementations the plurality of rows may include only a portion of all sensor pixels of the sensor array, for example the top half or the bottom half of the sensor array. This may be beneficial in terms of electronic control of image acquisition and / or readout. However, in both cases the first subset is a real subset of the plurality of rows, in other words the first subset of rows does not include all of the plurality of rows. In other words, the method is applicable to situations where at least one row of the plurality of rows does not include any pixels corresponding to the first area and, as a result, does not include any pixels corresponding to the region of interest in the first frame period.

[0018] Here and in the following, the region of interest, and in particular the region of interest for the first frame period, may be considered as a three-dimensional volume in the environment of the camera, which in the real world is represented for example as a cubic volume or a cubic-shaped volume or other three-dimensional volume. Then, points in the three-dimensional volume are mapped onto the two-dimensional surface of the sensor array in a predetermined manner, in particular given by the intrinsic parameters of the camera. Then, the sensor pixels in the sensor array onto which the region of interest is mapped correspond to a certain area in the sensor array, which is the first area in the case of the region of interest for the first frame period. In particular, the region of interest is a connected three-dimensional volume, and the first area is a connected part of the surface of the sensor array. Alternatively, the region of interest, and in particular the region of interest for the first frame period, may be directly given as a connected two-dimensional area in image coordinates, in other words in coordinates on the surface of the sensor array. In this case, the region of interest for the first frame period is identical to the first area.

[0019] The sensor array is in particular a rectangular array of sensor pixels arranged in pixel rows and pixel columns, such that each sensor pixel is uniquely identified by its pixel row and pixel column. Each of the rows associated with the rolling shutter mode, or in other words, the rows of the plurality of rows, may correspond to one or more adjacent or consecutive pixel rows or pixel columns. For example, a row of the plurality of rows may include tens, hundreds or thousands of pixel rows or pixel columns.

[0020] In the following, a row of a plurality of rows corresponds to a plurality of pixel rows instead of a pixel column, but all the descriptions can be carried over analogously to the case where a row includes a plurality of pixel columns instead of pixel rows.

[0021] The length of each of the plurality of rows is equal to the length of each of the pixel rows. In other words, each row includes a sensor pixel of each of the pixel columns of the sensor array. As a result, the first subset of rows including the first area generally covers an area larger than the first area, because the latter does not necessarily include the sensor pixels of all the pixel columns.

[0022] The first subset of rows may, for example, include only those rows of the plurality of rows that overlap the first area, in other words, the first subset of rows may be considered as the smallest subset of the plurality of rows that includes the first area.

[0023] An imaging device may be understood as an electronic device including a sensor array corresponding to an array of photodetectors. A sensor pixel may be understood as one of the photodetectors or a group of two or more adjacent photodetectors. The sensor array may be designed as a CCD sensor, a CMOS sensor, in particular an active pixel sensor or a passive pixel sensor, or other sensor array sensitive to light, in particular to visible light. In addition to the sensor array, the imaging device may also include further electronic components, such as for example for readout of the sensor array and / or for pre-processing purposes. The imaging device may be implemented on a single semiconductor chip and therefore may also be represented as an imaging device chip. Alternatively, the sensor array and the further electronic components may be implemented on two or more different semiconductor chips, which may for example be implemented on a common circuit board. In particular, the imaging device may include one or more of at least one control unit.

[0024] The at least one focus parameter depends on how the focus adjustment is actually performed. For example, if the focus adjustment is performed by adjusting the distance between the lens unit and the sensor array of the camera, the at least one focus parameter may include or consist of the distance between the sensor array and the lens unit. The at least one focus parameter may also include at least one control parameter for operating the focus adjustment configuration, or may include a relative distance change between the sensor array and the lens unit, etc. The at least one focus parameter may also include a focal length of the lens unit, if the focal length may be changed to perform the focus adjustment. A relative difference in focal length may represent the at least one focus parameter. In general, the at least one focus parameter includes one or more parameters that directly or indirectly affect or change the distance between the image plane of the camera provided by a surface including the surface of the sensor array and the object-side principal surface of the lens unit.

[0025] In particular, no focus adjustment, in particular no change of at least one focus parameter of the camera, is performed while the first subset of rows is being exposed, in other words after the first row of the first subset has started to be exposed and before the last row of the first subset has been completely exposed.

[0026] The predefined focus settings for acquiring the second image correspond to a predefined set of values ​​for at least one focus parameter, which may be focus settings for acquiring the entire second image or focus settings for acquiring a portion of the second image.

[0027] In the case of a mechanical shutter, exposure occurs when mechanical parts allow light to enter the interior area of ​​the camera from outside the camera through the lens unit and strike a respective portion of the sensor array. In the case of an electronic shutter, exposure can be understood as the period during which charge carriers generated by the corresponding sensor pixel due to the impinging light contribute to the accumulated or integrated charge or voltage that is read out from the sensor pixel to determine the respective pixel value. That is, the exposure period corresponds to the integration time in this case.

[0028] The rolling shutter is preferably an electronic shutter, but in principle the method according to the invention can also be applied in the case of a mechanical shutter, and unless otherwise stated it is assumed here and below that the rolling shutter is an electronic shutter.

[0029] In particular, the focus adjustment period begins before all rows of the plurality of rows have been exposed to obtain a first image during a first frame period, based on the premise that exposure of a first subset of rows is completed before exposure of all rows of the plurality of rows is completed. The focus adjustment period begins between those two times.

[0030] That is, if the plurality of rows includes N consecutive rows labelled 1, 2, ..., N, then when acquiring a first image, the plurality of rows are exposed such that the exposure period of row 1 starts first, then the exposure period of row 2 starts after a predefined offset or delay time after the exposure period of row 1 starts, and so on. Finally, the exposure period of row N begins. In other words, the exposure period of row N starts last and ends last. And in the scenario in which the method according to the invention is performed, the first subset of rows does not include row N. The method according to the invention can be understood as allowing it to be applied to situations in which this assumption holds.

[0031] The invention does not concern the exceptional case where row N is also included in the first subset of rows. In this case, there are various possibilities on how to handle the focus adjustment for acquiring the second image. For example, the second frame period may be deliberately delayed until the focus parameters are adjusted, the focus adjustment may be omitted, or it may be acceptable to start the focus adjustment after all rows of the plurality of rows have been exposed.

[0032] According to the invention, it is ensured that no focusing occurs before all rows of the first subset are exposed, while allowing focusing to occur while the remaining rows not included in the first subset are exposed. That is to say, it is ensured that the mapping of the area of ​​interest for the first frame period is not affected by the focusing, while allowing image areas outside the area of ​​interest for the first frame period to be affected by the focusing. In other words, subsequent vehicle functions using the first image can use the parts of the first image that correspond to the area of ​​interest for the first frame period without any image quality loss due to focusing, while image quality loss outside the area of ​​interest for the first frame period is allowed and is not relevant for the corresponding function, for example.

[0033] In some designs, there may be an intermediate period after the last row of the plurality of rows, denoted row N, is exposed in the first frame period and before the first row of the plurality of rows, denoted row 1, begins to be exposed. The focus adjustment period may include this intermediate period. However, because the focus adjustment period already starts before the last row of the plurality of rows is exposed, the time available to perform focus adjustment is increased beyond the intermediate period. As a result, the range of focus adjustment achievable in one step is increased. In other implementations, there may not be a suitable intermediate period between the end of the exposure of the last row N in the first frame period and the start of the exposure of the first row 1 in the second frame period. In this case, the invention nevertheless allows focus adjustment without adversely affecting the mapping of the region of interest in the first frame period.

[0034] According to some implementations of the method for focusing according to the invention, the plurality of rows are exposed according to a rolling shutter mode for acquiring a second image. A second area in the sensor array is determined, in particular by the at least one control unit, the second area corresponding to a predetermined region of interest for a second frame period. A focusing period is determined depending on the second area.

[0035] The predetermined focus setting for acquiring the second image may correspond to the predetermined focus setting for acquiring the ROI for the second frame period.

[0036] The regions of interest of the first frame period and the second frame period may be the same or different from each other. If they are the same, the first area is the same as the second area. On the other hand, if the ROI of the first frame period and the ROI of the second frame period are different, the first area and the second area may be different, especially when the regions of interest are defined as respective three-dimensional volumes in the real world as described above. However, even if the ROIs for the first frame period and the second frame period are given by three-dimensional volumes in the real world and are different from each other, the first area may still be coincidentally the same as the second area, since different three-dimensional volumes may be mapped to the same area on the sensor array by the camera, especially the lens unit. If the ROIs of the first frame period and the second frame period are given directly by two-dimensional portions of the surface of the sensor array and are different from each other, the first area and the second area are different from each other.

[0037] According to some implementations, if the second area is identical to the first area, the focus adjustment period ends before exposure of any of the first subset of rows to acquire the second image during the second frame period begins.

[0038] In other words, if the first area is identical to the second area, it is guaranteed that no focus adjustment occurs in the second frame period after the exposure of the first subset of rows is started. In such a case, the first subset of rows covers not only the ROI or the mapped ROI of the first frame period, but also the ROI or the mapped ROI of the second frame period. Nevertheless, the focus parameters of the second frame period, in other words the predetermined focus settings, are generally different from the respective settings for the first frame period. In such an implementation, it is achieved that the imaging of the ROI for the second frame period is not adversely affected by the focus adjustment.

[0039] For example, the focus adjustment period may end at a time instance when the exposure of the first subset of rows in the second time period begins. However, in another implementation, there may be a time difference between the end of the focus adjustment period and the start of the exposure of the first subset of rows in the second frame period. The time difference may be equal to or greater than a predetermined non-zero buffer period. The non-zero buffer period may, for example, take into account the determination of the at least one focus parameter after the adjustment. In this way, undesired variations of the at least one focus parameter during the exposure of the first subset of rows in the second frame period may be avoided.

[0040] According to some implementations, if the second area is different from the first area, a second subset of the plurality of rows is determined, particularly by the at least one control unit, the second subset of rows includes the second area, particularly completely includes the second area, and the focus adjustment period ends before any of the second subset of rows are exposed to light to acquire a second image during a second frame period.

[0041] The above explanation regarding the case where the first area and the second area are identical also applies analogously to this case.

[0042] Also, in such implementations, there may be a time difference between the end of the focus adjustment period and the start of the exposure of the second subset of rows that is equal to or greater than a predetermined non-zero buffer period as described above.

[0043] According to some implementations, the first subset of rows corresponds to a smallest set of rows of the plurality of rows that includes the first area.

[0044] According to some implementations, if the second area is different from the first area, the second subset of rows corresponds to a further minimal subset of rows of the plurality of rows that includes the second area.

[0045] In this case, the first subset of rows and possibly the second subset of rows contain only the number of rows actually required to cover the first area or the second area, respectively, thereby maximizing the time available for the focus adjustment period.

[0046] According to some implementations, adjusting at least one focus parameter includes changing the distance between an image plane provided by the sensor array, in particular a plane including the surface of the sensor array, and an object-side principal plane of the camera, in particular of the lens unit.

[0047] According to some implementations, adjusting the at least one focus parameter includes changing the distance between the sensor array, and in particular the image plane, and the lens unit of the camera.

[0048] The lens unit includes one or more lenses. To change the distance between the sensor array and the lens unit, the lens unit and the sensor array are moved relative to each other. In particular, the lens unit may remain stationary while the sensor array is moved, for example while the entire imaging device is moved, or the imaging device and the sensor array remain stationary while the lens unit, in particular the entire lens unit with all of its one or more lenses, is moved.

[0049] By varying the distance between the sensor array and the lens unit, in particular mechanically, the distance between the object-side principal plane of the lens unit and the image plane is changed accordingly.

[0050] According to some implementations, adjusting the at least one focus parameter includes changing a focal length of a lens unit of the camera.

[0051] Also, by changing the focal length, for example by changing the optical properties of one or more lenses or their relative positions with respect to each other or their shapes, the position of the object-side principal surface with respect to the image plane is changed.

[0052] In some implementations, adjusting the at least one focus parameter includes changing a distance between the sensor array and the lens unit and also includes changing a focal length of the lens unit.

[0053] According to a further aspect of the invention there is provided a method for at least partly automatically guiding a vehicle, in particular a motorized vehicle, in which the vehicle is equipped with a motorized vehicle camera and a method according to the invention for focusing the motorized vehicle camera is performed, and the vehicle is at least partly automatically guided depending on the first image and / or the second image.

[0054] One or more computer vision functions may be performed in response to the first image and / or the second image in order to at least partially automatically steer the vehicle. A further control unit of the vehicle may generate at least one control signal in response to a result of the one or more computer vision functions in order to at least partially automatically steer the vehicle. The one or more control signals may for example be provided to one or more actuators of the vehicle, which in response to the one or more control signals affect lateral and / or longitudinal control of the vehicle in order to at least partially automatically steer the vehicle.

[0055] Alternatively or additionally, one or more human vision functions may be performed in response to the first image and / or the second image, and for this purpose the first image and / or the second image may be displayed or first processed and thereafter displayed on a display device of the vehicle so as to assist a driver of the vehicle to guide the vehicle.

[0056] For use cases or situations that may arise in the method but are not explicitly described herein, error messages and / or prompts for user feedback may be output and / or default settings and / or predetermined initial states may be set according to the method.

[0057] According to a further aspect of the invention, a motorized vehicle camera is provided. The motorized vehicle camera includes an imaging device, and in particular a lens unit. The motorized vehicle camera comprises at least one control unit, configured to control the imaging device to acquire a first image during a first frame period during which a plurality of rows of a sensor array of the imaging device are exposed according to a rolling shutter mode, and to acquire a second image during a second frame period after the first frame period. The motorized vehicle camera comprises a focus adjustment arrangement configured to adjust at least one focus parameter of the camera. The at least one control unit is configured to determine a first area of ​​the sensor array corresponding to a predetermined region of interest for the first frame period, to determine a first subset of the plurality of rows such that the first subset of rows includes the first area, and to determine a focus adjustment period. The at least one control unit is configured to determine the focus adjustment period such that it starts when or after all rows of the first subset of rows have been exposed during the first frame period, for example before all rows of the plurality of rows have been exposed during the first frame period. The at least one control unit is configured to control the focus adjustment arrangement to adjust at least one focus parameter of the camera during a focus adjustment period according to a predetermined focus setting for acquiring the second image.

[0058] The control units of the at least one control unit may also be represented as respective computing units. The at least one control unit may be partly or entirely comprised by the imaging device or may be implemented separately from the imaging device.

[0059] An arithmetic unit may in particular be understood as a data processing device including processing circuits, and may therefore in particular be capable of processing data to perform arithmetic operations, which may also include operations performing indexed accesses to data structures, such as look-up tables, LUTs, etc.

[0060] In particular, the computing unit may comprise one or more computers, one or more microcontrollers, and / or one or more integrated circuits, such as one or more application specific integrated circuits, ASICs, one or more field programmable gate arrays, FPGAs, and / or one or more systems on chips, SoCs. The computing unit may also comprise one or more processors, such as one or more microprocessors, one or more central processing units, CPUs, one or more graphics processing units, GPUs, and / or one or more signal processors, in particular one or more digital signal processors, DSPs. The computing unit may also comprise a cluster of physical or virtual computers or other such units.

[0061] In various embodiments, a computing unit includes one or more hardware and / or software interfaces and / or one or more memory units.

[0062] The memory unit may be implemented as a volatile data memory, such as, for example, Dynamic Random Access Memory, DRAM, or Static Random Access Memory, SRAM, or as a non-volatile data memory, such as, for example, Read Only Memory, ROM, Programmable Read Only Memory, PROM, Erasable Programmable Read Only Memory, EPROM, Electrically Erasable Programmable Read Only Memory, EEPROM, Flash memory or Flash EEPROM, Ferroelectric Random Access Memory, FRAM, Magnetoresistive Random Access Memory, MRAM, or Phase Change Random Access Memory, PCRAM.

[0063] To control the focusing arrangement, the at least one control unit may generate at least one focus control signal and provide it to the focusing arrangement accordingly.

[0064] According to some implementations of a motor vehicle camera according to the invention, the focus adjustment arrangement is configured to move the sensor array relative to a lens unit of the camera to adjust at least one focus parameter.

[0065] According to some implementations, the focus adjustment arrangement is configured to change a focal length of a lens unit of the camera to adjust at least one focus parameter.

[0066] Further implementations of the motorized vehicle camera according to the invention can be derived directly from the various embodiments of the method according to the invention and vice versa. In particular, the individual features and corresponding descriptions and advantages related to the various implementations of the method according to the invention can be transferred analogously to the corresponding implementations of the motorized vehicle camera according to the invention. In particular, the motorized vehicle camera according to the invention is designed or programmed to carry out the method according to the invention. In particular, the motorized vehicle camera according to the invention carries out the method according to the invention.

[0067] According to a further aspect of the invention there is provided an electronic vehicle guidance system for a vehicle, comprising a camera for a motorized vehicle according to the invention and a further control unit configured to generate one or more control signals for at least partially automatically guiding the vehicle in response to the first image and / or the second image and / or configured to perform a method for at least partially automatically guiding a vehicle according to the invention.

[0068] An electronic vehicle guidance system may be understood as an electronic system configured to guide a vehicle in a fully automated or fully autonomous manner, in particular without manual intervention or control by a driver or user of the vehicle. The vehicle performs all necessary functions, such as steering, deceleration and / or acceleration operations, and also automatically monitors and records road traffic and the corresponding reactions. In particular, the electronic vehicle guidance system may implement a fully automated or fully autonomous driving mode according to level 5 of the SAE J3016 classification. The electronic vehicle guidance system may also be implemented as an advanced driver assistance system, ADAS, that assists the driver for partially automated or partially autonomous driving. In particular, the electronic vehicle guidance system may implement a partially automated or partially autonomous driving mode according to levels 1 to 4 of the SAE J3016 classification. Here and below, SAE J3016 refers to the respective standard dated June 2018.

[0069] Thus, guiding the vehicle at least partially automatically may include guiding the vehicle according to a fully automated or fully autonomous driving mode according to Level 5 of the SAE J3016 classification. Guiding the vehicle at least partially automatically may also include guiding the vehicle according to a partially automated or partially autonomous driving mode according to Levels 1-4 of the SAE J3016 classification.

[0070] According to a further aspect of the invention there is provided a first computer program comprising first instructions which, when executed by a motorized vehicle camera according to the invention, for example by at least one control unit, cause the motorized vehicle camera to execute a method for focus adjustment according to the invention.

[0071] According to a further aspect of the invention there is provided a second computer program comprising second instructions which, when executed by the electronic vehicle guidance system according to the invention, in particular by at least one control unit of the motorized vehicle camera and / or a further control unit of the electronic vehicle guidance system, cause the electronic vehicle guidance system to execute the method for at least partially automatically guiding a vehicle according to the invention.

[0072] The first instructions and / or the second instructions may be provided as program code, for example as binary code or assembler and / or as source code in a programming language, for example C, and / or as a program script, for example Python.

[0073] According to a further aspect of the invention there is provided a computer readable storage device storing a first computer program and / or a second computer program according to the invention.

[0074] The first computer program, the second computer program, and the computer readable storage device may each be referred to as a respective computer program product including the first instructions and / or the second instructions.

[0075] Further features of the invention are evident from the claims, the drawings and the description of the drawings. Features and combinations of features mentioned above in the specification and those mentioned below in the description of the drawings and / or shown in the drawings may be included in the invention not only in the respective combinations described but also in other combinations. In particular, embodiments and combinations of features that do not comprise all the features of the claims initially defined may also be included in the invention. Moreover, embodiments and combinations of features that go beyond or deviate from the combinations of features described in the claims may be included in the invention. [Brief description of the drawings]

[0076] The invention will now be described in detail with reference to specific exemplary implementations and respective schematic drawings in which identical or functionally identical elements may be designated with the same reference numerals. Descriptions of identical or functionally identical elements are not necessarily repeated with respect to different drawings.

[0077] In the drawings: [Figure 1] FIG. 1 shows a schematic diagram of a vehicle with an exemplary implementation of an electronic vehicle guidance system according to the invention, including an exemplary implementation of a camera for a motorized vehicle according to the invention. [Diagram 2] FIG. 2 shows a schematic representation of a region of interest in the environment of a motor vehicle camera. [Diagram 3] FIG. 3 shows diagrammatically further areas of interest in the environment of a motor vehicle camera. [Figure 4] FIG. 4 shows a schematic block diagram of a visualisation of an exemplary implementation of the method for focus adjustment according to the invention. [Diagram 5] FIG. 5 illustrates diagrammatically the exposure of a number of rows according to a rolling shutter mode in two successive frame periods according to a further exemplary implementation of the method for focus adjustment according to the invention. [Figure 6]FIG. 6 illustrates diagrammatically the exposure of a number of rows according to a rolling shutter mode in two successive frame periods according to a further exemplary implementation of the method for focus adjustment according to the invention. [Figure 7] FIG. 7 illustrates diagrammatically the exposure of multiple rows in rolling shutter mode in two successive frame periods according to a further exemplary implementation of the method for focus adjustment according to the invention. [Figure 8] FIG. 8 illustrates, in terms of a flow diagram, a use case for applying the method for focus adjustment according to the invention. [Figure 9] FIG. 9 illustrates, in schematic terms in a flow diagram, a further use case for applying the method for focus adjustment according to the invention. [Figure 10] FIG. 10 illustrates, in schematic terms in a flow diagram, a further use case for applying the method for focus adjustment according to the invention. [Figure 11] FIG. 11 illustrates, in terms of a flow diagram, a further use case for applying the method for focus adjustment according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] 1 shows a schematic representation of a vehicle 1 equipped with an electronic vehicle guidance system 2 according to the invention. The vehicle guidance system 2 includes one or more cameras implemented as a motorized vehicle camera 3 according to an exemplary implementation of the invention. The motorized vehicle camera 3 is shown diagrammatically as a block diagram in the inset of FIG. 1.

[0079] The motor vehicle camera 3 comprises an imaging device 10, which is disposed, for example, inside a housing 8 of the camera 3. The motor vehicle camera 3 also comprises a lens unit 9 including one or more lenses (not shown). Furthermore, a sensor array 11 of the imaging device is disposed relative to the lens unit 9 such that light passing through the lens unit 9 may impinge on a surface of the sensor array 11. The camera 3 comprises one or more control units 13a, 13b. The one or more control units 13a, 13b may be part of the imaging device 10, as shown for control unit 13a in FIG. 1, or may be implemented in addition to the imaging device 10, as shown for control unit 13b in FIG. 1.

[0080] Furthermore, the motor vehicle camera 3 comprises a focus adjustment arrangement 12 controllable by at least one control unit 13a, 13b to change or adjust at least one focus parameter of the camera 3. For this purpose, the focus adjustment arrangement may be controlled by the at least one control unit 13a, 13b to change the distance between a surface of the sensor array 11 corresponding to the image plane of the camera and the object-side principal surface of the lens unit 9. This may be achieved by moving the position of the sensor array 11 relative to the position of the lens unit 9. For example, the imaging device 10 and the sensor array 11 may remain fixed while the position of the lens unit 9 may be changed by the focus adjustment arrangement, or vice versa. Alternatively or additionally, the focus adjustment arrangement 12 may electronically change the optical properties of the lens unit, for example the focal length.

[0081] The electronic vehicle guidance system 2 may include a further control unit 4, which may for example be implemented as an electronic control unit, ECU, connected to a camera 3. The camera 3 is configured to generate a stream of camera images comprising at least a first image and a second image, and to provide said stream or a pre-processed version of said stream to the further control unit 4. The further control unit 4 may then generate, in response to the stream of camera images, one or more control signals for at least partially automatically guiding the vehicle 1, and may provide the one or more control signals to respective actuators (not shown) of the vehicle, which in response to the one or more control signals affect longitudinal and / or lateral control of the vehicle 1.

[0082] To adjust the focus setting of the camera 3, the camera 3 may implement a method for focus adjustment of a camera for a motor vehicle according to the invention, details of which are described below with reference to Figures 2 to 7.

[0083] At least one control unit 13a, 13b is configured to determine a first area in the sensor array 11, in other words a connected subset of pixels of the sensor array 11, which corresponds to a predetermined region of interest 6a, 6b, 6c, 7a, 7b, 7c for a first frame period F1 in which a first image is acquired by the imaging device 10.

[0084] 2 shows a schematic example of three different regions of interest 6a, 6b, 6c in an environment 5 of a camera 3. The three different regions of interest 6a, 6b, 6c may be defined by different sizes and / or horizontal angles from the viewpoint of the camera. The regions of interest 6a, 6b, 6c may for example correspond to a three-dimensional volume in the environment 5, which is a rectangular parallelepiped volume or an approximately rectangular parallelepiped volume. If the camera 3 is a non-rectilinear camera, such as a fisheye camera, the lines or planes that delimit the rectangular parallelepiped volume are distorted as shown in FIG. 2.

[0085] The different regions of interest 6a, 6b, 6c may for example be related to different functions of the electronic vehicle guidance system 2. The central region of interest 6a may for example be used to assist the driver when driving backwards of the vehicle 1, by displaying a corresponding part of the image acquired by the camera 3 on a display (not shown) of the vehicle 1. On the other hand, the lateral regions of interest 6b, 6c may for example be used by computer vision functions, such as object detection functions aimed at detecting other vehicles located further away from the vehicle 1. As a result, it may be desirable to have different focus settings for the different ROIs 6a, 6b, 6c. The invention allows for example to switch between optimal settings for the different ROIs, using different frames of the image stream with different focus settings. Each ROI 6a, 6b, 6c may be directly mapped to a corresponding area, which is part of the surface of the sensor array 11.

[0086] 3 shows a further example of different ROIs 7a, 7b, 7c in the environment 5 of the camera 3. In this example, the largest ROI 7a contains a smaller ROI 7b, which in turn contains an even smaller ROI 7c. For these ROIs 7a, 7b, 7c, different focus settings may also be desirable depending on the different expected distances of relevant objects in the environment 5 from the camera 3.

[0087] In the course of the method according to the invention, at least one control unit 13a, 13b controls the imaging device 10 to acquire a first image in a first frame period F1, as shown diagrammatically in Fig. 5 to Fig. 8. The camera 3, i.e. the imaging device 10, is operated in a rolling shutter mode, for example as shown in Fig. 5. Therein, a number of rows P of the sensor array 11 are exposed R1, R2, ..., R3, R4, ..., R5, R6, ..., R7, ..., R8, ..., R9, ..., R10, ..., R11, ..., R12, ..., R13, ..., R14, ..., R15, ..., R16, ..., R17, ..., R18, ..., R19, ..., R20, ..., R21, ..., R22, ..., R23, ..., R24, ..., R25, ..., R26, ..., R27, ..., R28, ..., R29, ..., R30, ..., R31, ..., R32, ..., R33, ..., R34, ..., R35, ..., R36, ..., R37, ..., R38, ..., R39, ..., R40, ..., R41, ..., R42, ..., R43, ..., R44, ..., R45, ..., R46, ..., R47, ..., R48, ..., R49, ..., R50, ..., R51, ..., R52, ..., R53, ..., R54, ..., R65, ..., R66, ..., R70, ..., R71, ..., R72, ..., R85, ..., R91, ..., R92, ..., R10, ..., R111, ..., R121, ..., R132, ..., R141, ..., R151, ..., R i , R i+1 , ..., R j , R j+1 , ..., R NFor each row of the image sensor 10, a reset period during which the corresponding buffer is cleared is followed by an exposure period or, i.e., an integration period, and after the exposure period is finished, a respective readout period during which all pixels of the respective row are read out. The reset and readout periods are represented in Fig. 6 by differently shaded blocks, while the exposure periods are represented by blank blocks. As is known in the rolling shutter principle, the individual exposure periods of adjacent rows are offset with respect to each other by a predefined offset time. In a second frame period F2 after the first frame period F1, the at least one control unit 13a, 13b controls the imaging device 10 to acquire a second image in the same way by exposing a number of rows P according to the rolling shutter mode.

[0088] At least one control unit 13a, 13b determines a first area in the sensor array 11 corresponding to the first ROI 6a, 6b, 6c, 7a, 7b, 7c that is predetermined with respect to the first frame period F1, and determines a first subset P1 of the plurality of rows P that includes the first area. i , row R j+1 ~row R N is not included in the first subset P1. The first subset P1 is the row R i+1 ~R jAnalogously, the at least one control unit 13a, 13b may determine a second subset P2 of the plurality of rows P including a second area, the second area corresponding to the predetermined ROI 6a, 6b, 6c, 7a, 7b, 7c for the second frame period F2, where the ROI 6a, 6b, 6c, 7a, 7b, 7c of the first frame period F may be identical or different from the ROI 6a, 6b, 6c, 7a, 7b, 7c of the second frame period F2. As a result, the first area may be identical or different from the second area in the sensor array 11. If the first area is identical to the second area, the first subset P1 is identical to the second subset P2, as shown diagrammatically in FIG. 5. On the other hand, if the first area is different from the second area, the first subset P1 may be different from the second subset P2, as shown diagrammatically in FIG. 7. In this case, the first subset P1 is the row R i+1 ~R j and the second subset P2 includes row R k+1 ~R l where k≠I and / or l≠j.

[0089] In the example of Fig. 6, the first subset P1 is identical to the second subset P2 as described for Fig. 5, except that in the example of Fig. 5, the exposure of the first row R1 in the second frame period F2 is the same as the exposure of the last row R1 in the first frame period F1. N On the other hand, in the examples of FIG. 6 and FIG. 7, the exposure of the last row R in the first frame period F1 is started immediately after the exposure of the last row R N There is an intermediate period between the end of the exposure of row R1 and the start of the exposure of the first row R2 in the second frame period F2.

[0090] At least one control unit 13a, 13b determines the focus adjustment period T in response to the first subset P1 and in particular in response to the second subset P2. a and determining a focus adjustment period T according to a predetermined focus setting for acquiring the second image, in particular the ROIs 6a, 6b, 6c, 7a, 7b, 7c for the second frame period F2. aThe focus adjustment arrangement 12 is controlled to adjust at least one focus parameter of the camera 3 during the focus adjustment period T a starts when or after all rows of the first subset P1 of rows have been exposed, in this example the last row R of the first subset P1. j The focus adjustment period T a In particular, the exposure period F1 starts before all rows of the plurality of rows P are exposed during the first frame period F1, in other words, in this example, the exposure period R N The focus adjustment period T a 5 ends before any row of the second subset P2 is exposed during the second frame period F2, or the first row R i+1 In the example of FIG. 7, the focus adjustment period T a Accordingly, the first row R of the second subset P2 k+1 is terminated before the exposure begins.

[0091] In other words, the maximum period available for focus adjustment T a ' is the last row of the first subset P1, in this example row R j , and the end of the exposure of the first row of the second subset P2, row R in the example of Figs. i+1 And in the example of Figure 7, row R k+1 , is given by the time difference between the start of the exposure of the focus adjustment period T a is the maximum available period T a ' than a non-zero buffer period T b The buffer period T b may correspond to or include a period of time provided for determining at least one focus parameter adjusted by the focus adjustment arrangement 12.

[0092] Fig. 4 shows a block diagram that shows a schematic example implementation of a method for focus adjustment according to the invention. The references S1, S2, S3, S4 correspond to respective method steps executed by at least one control unit 13a, 13b. In step S1, a first subset P1 and optionally a second subset P2 of a plurality of rows P is calculated. To calculate the subsets P1, P2, the at least one control unit 13a, 13b may use respective predetermined intrinsic and extrinsic camera parameters 16 of the camera 3 and a predetermined definition 18 of the ROIs 6a, 6b, 6c, 7a, 7b, 7c for the first and second frame periods F1, F2. In step S2, a focus adjustment period T a is calculated based on the first and second subsets P1, P2. For this purpose, the at least one control unit 13a, 13b may use predetermined imaging device configuration data 17 and / or predetermined image quality data 15 obtained from an image quality manager circuit (not shown) of the camera 3, said predetermined image quality data 15 defining respective settings for automatic white balance, image brightness etc. The focus adjustment period T a To calculate (F1), the at least one control unit 13a, 13b may alternatively or additionally use a frame-level or row-level exposure duration signal from the imaging device 10. It is noted that the at least one control unit 13a, 13b does not necessarily need all of the exposure duration signal, the imaging device configuration data 17 and the image quality data 15 from the imaging device 10. As for the at least one control unit 13a, 13b, 13c, it is sufficient that it has suitable predetermined information, which allows it to directly estimate or estimate the time instance at which the exposure of the first subset P1 ends in the first frame period F1 and the exposure of the second subset P2 of rows starts in the second frame period F2.

[0093] In some implementations, the imaging device 10 may also provide vertical and horizontal synchronization signals to at least one control unit 13a, 13b. The horizontal synchronization signal, also denoted HSYNC, is output whenever a row has been fully exposed and read out, and the vertical synchronization signal, also denoted VSYNC, is output whenever all rows of the plurality of rows P have been exposed.

[0094] In step S3, the at least one control unit 13a, 13b may calculate, from a predefined focus setting for the first and / or second frame periods F1, F2, which may for example be obtained from focus setting logic 14 of the camera 3, how to adjust at least one focus parameter to achieve a desired setting. In step S4, in some implementations, the adjustment may optionally be divided into multiple smaller adjustments. The adjustment control signal is then provided to the focus adjustment arrangement 12, which performs the focus adjustment T a and adjusting at least one focus parameter accordingly during the period. The at least one control unit 13a, 13b may also provide one or more feedback signals to the focus setting logic 14, e.g. providing an information signal regarding the current focus setting and / or that a certain focus adjustment has been made.

[0095] In Figures 8 to 11, different use cases are depicted as schematic flow diagrams, with the time direction running from left to right.

[0096] FIG. 8 shows a basic example, where the first line corresponds to the steps of image acquisition, the second line corresponds to the human vision (HV) function, and the third line corresponds to the computer vision (CV) function. In block 800, parameters, including at least one focus parameter, are set for the required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n. If multiple ROIs are involved, a common focus parameter may be used. In block 801, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n. In block 802, parameters are set for the required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+1. In block 803, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+1. In block 804, parameters are set for the required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+2. In block 805, respective raw images containing the required ROIs 6a, 6b, 6c, 7a, 7b, 7c are acquired for frame n+2. In block 806, parameters are set for the required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+3. In block 807, respective raw images containing the required ROIs 6a, 6b, 6c, 7a, 7b, 7c are acquired for frame n+3.

[0097] At block 810, the output for the HV function is updated based on the capture of frame n-1, and at block 820, the output for the CV function is updated based on the capture of frame n-1. At block 811, the output for the HV function is updated based on the capture of frame n, and at block 821, the output for the CV function is updated based on the capture of frame n-1. At block 812, the output for the HV function is updated based on the capture of frame n+1, and at block 822, the output for the CV function is updated based on the capture of frame n+1. At block 813, the output for the HV function is updated based on the capture of frame n+2, and at block 823, the output for the CV function is updated based on the capture of frame n+2.

[0098] 9 shows a further example for handling the transition of the HV function from one output view to another, where each output view requires a different parameter set including at least one focus parameter. The transition between parameter sets is immediate.

[0099] In block 900, parameters including at least one focus parameter are set for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n, specifically for view m. In block 901, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n. In block 900, parameters are set for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+1, specifically for view m+1. In block 901, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+1. In block 904, parameters are set for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+2, specifically for view m+1. In block 905, respective raw images containing the required ROIs 6a, 6b, 6c, 7a, 7b, 7c are acquired for frame n+2. In block 906, parameters are set for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+3, specifically for view m+1. In block 907, respective raw images containing the required ROIs 6a, 6b, 6c, 7a, 7b, 7c are acquired for frame n+3.

[0100] In block 910, the output for the HV function is updated based on the capture of frame n-1 and view m. In block 911, the output for the HV function is updated based on the capture of frame n and view m. In block 912, the output for the HV function is updated based on the capture of frame n+1 and view m+1. In block 913, the output for the HV function is updated based on the capture of frame n+2 and view m+1.

[0101] 10 shows a further example for handling the transition in the HV function from one output view to another, where each output view requires a different parameter set including at least one focus parameter. The transition between parameter sets is done gradually, i.e. over several frames.

[0102] In block 1000, parameters including at least one focus parameter are set for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n, specifically for view m. In block 1001, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n. In block 1002, the parameters are partially adapted for view m+1 for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+1. In block 1003, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+1. In block 1004, the parameters are further partially adapted for view m+1 for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+2. In block 1005, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+2. In block 1006, the parameters are further partially adapted for view m+1 for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+x, where x>2. In block 1007, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+x. In block 1008, the parameters are finally set for view m+1 for ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+x+1. In block 1009, each raw image including the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+x+1.

[0103] In block 1010, the output for the HV function is updated based on the capture of frame n-1 and view m. In block 1011, the output for the HV function is updated based on the capture of frame n and view m. In block 1012, the output for the HV function is updated based on the capture of frame n+1 and view m+1. In block 1013, the output for the HV function is updated based on the capture of frame n+x-1 and view m+1. In block 1013, the output for the HV function is updated based on the capture of frame n+x and view m+1.

[0104] FIG. 11 shows a further example for handling seamless toggling between two computational CV functions, CV1 and CV2, where each CV function requires its own parameter set including at least one focus parameter.

[0105] In block 1100, parameters including at least one focus parameter are set for required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n according to the requirements of CV1. In block 1101, respective raw images including required ROIs 6a, 6b, 6c, 7a, 7b, 7c are acquired for frame n. In block 1102, parameters are set for required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+1 according to the requirements of CV2. In block 1103, respective raw images including required ROIs 6a, 6b, 6c, 7a, 7b, 7c are acquired for frame n+1. In block 1104, parameters are set for required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+2 according to the requirements of CV1. In block 1105, each raw image containing the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+2. In block 1106, parameters are set for the required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+x, where x>2, according to the requirements of CV2. In block 1107, each raw image containing the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+x. In block 1108, parameters are set for the required ROIs 6a, 6b, 6c, 7a, 7b, 7c for frame n+x+1, according to the requirements of CV1. In block 1105, each raw image containing the required ROIs 6a, 6b, 6c, 7a, 7b, 7c is acquired for frame n+x+1.

[0106] In block 1110, the output for CV1 is updated based on the capture of frame n. In block 1120, the output for CV2 is updated based on the capture of frame n-1. In block 1111, the output for CV1 is updated based on the capture of frame n+x-1. In block 1121, the output for CV2 is updated based on the capture of frame n+1. In block 1122, the output for CV2 is updated based on the capture of frame n+x.

[0107] As will be described with particular reference to the drawings, the invention provides a method for focusing a motor vehicle camera operating in rolling shutter mode, whereby the negative effects of focusing on a captured image are avoided for at least a portion of the image.

[0108] For example, focus adjustments may be treated as background activity that does not affect foreground activity, i.e., capture of a predefined frame-specific ROI. Frame-to-frame variations, including variations in frame rate, exposure duration, and ROI, may be taken into account. Image quality control may be performed at frame boundaries using standard mechanisms provided by the imaging device, such as a group set of imaging device register settings. Changes in ROI may occur due to, for example, planned changes in the viewpoint of human vision functions, periodic changes in ROI to support parallel multitasking of human vision functions and / or computer vision functions, or dynamic adaptation of ROI for image stabilization.

[0109] In some implementations, the invention maximizes the operating window for focus adjustments, for example, by increasing the chance that an adjustment can occur in a single frame-to-frame transition and / or by minimizing the number of frame-to-frame adjustments required to complete a larger focus adjustment that cannot be completed in a single frame-to-frame transition, both factors beneficial to the operation of the focus control loop.

[0110] It also assists in focus control by making overall focus adjustments more predictable: since these adjustments are made in the background, especially at frame boundaries, when important rows of the sensor array are not exposed, large focus adjustments are intentionally broken down into a sequence of smaller successive adjustments if it is beneficial.

[0111] To calculate the focus adjustment period, in some implementations, the row-specific exposure period can be determined in different ways: for example, the imaging device may indicate the exposure period at the row level or at the frame level, and / or the exposure can be controlled or effected at the frame level, and / or the exposure period of a particular row can be calculated or at least estimated with a high degree of accuracy.

[0112] The time available for focus adjustment may be maximized in some implementations while simultaneously ensuring that focus adjustment does not occur during exposure of a row corresponding to a predetermined ROI and therefore does not affect the exposure of the ROI.

[0113] In some implementations, the settling time of the focus adjustment arrangement may also be taken into account. For example, a settling time may be specified for each adjustment of the focus. The specification may include a predetermined settling time for each operation of the focus adjustment arrangement, taking into account environmental and lifetime factors. This may be based on parameterized formulas and / or look-up tables. The specification may alternatively or additionally include an online learning element based on historical monitoring of the settling time, and / or a safety margin that can be designed to account for inaccuracies in other elements of the characterization.

Claims

1. A method for adjusting the focus of a camera (3) for a powered vehicle, wherein the first frame period (F １ During the first frame period (F), a first image is acquired by the imaging device (10) of the camera (3), and multiple rows (P) of the sensor array (11) of the imaging device (10) are exposed based on the rolling shutter mode, and the first frame period (F １ ) the second frame period (F ２ During this time, the imaging device (10) acquires a second image. - The aforementioned first frame period (F １ A first area in the sensor array (11) corresponding to a predetermined region of interest (6a, 6b, 6c, 7a, 7b, 7c) is determined with respect to the following: - The first subset (P) of the aforementioned multiple rows (P) １ ) is determined, and the first subset of rows (P １ ) includes the aforementioned first area; - Focus adjustment period (T ａ ) is determined, and the focus adjustment period (T ａ ) starts during or after all rows of the first subset (P １ ) of the rows are exposed during the first frame period (F １ ); - At least one focus parameter of the camera (3) is set to the focus adjustment period (T ａ ) during which the focus is adjusted based on a predetermined focus setting for acquiring the second image, A method characterized by the following:

2. - In order to obtain the second image, the plurality of rows (P) are exposed based on the rolling shutter mode, - The second area in the sensor array (11) is determined, and the second area is defined as the second frame period (F ２ Corresponding to predetermined areas of interest (6a, 6b, 6c, 7a, 7b, 7c) regarding ), - said focus adjustment period (T ａ ) is determined according to the two preceding areas, The method according to feature 1.

3. If the second area is the same as the first area, the focus adjustment period (T ａ ) is the second frame period (F ２ ) the first subset of rows (P １ Ends before any of the exposures () begin. The method according to feature 2.

4. The focus adjustment period (T ａ The end of the aforementioned period and the second frame period (F ２ The first subset of rows between (P １ The time difference (T) between the start of exposure and the start of exposure. ｂ ) is equal to or greater than a predetermined non-zero buffer period. The method according to feature 3.

5. If the second area is different from the first area, - The second subset (P) of the aforementioned multiple rows (P) ２ ) is determined, and the second subset of the row (P ２ ) includes the aforementioned second area; - said focus adjustment period (T ａ ) is the second frame period (F ２ ) between the second subset of rows (P ２ The process ends before any of the ) are exposed. The method according to feature 2.

6. The focus adjustment period (T ａ The aforementioned end of ) and the aforementioned second subset of the row (P ２ The time difference (T) between the start of exposure and the start of exposure. ｂ ) is equal to or greater than a predetermined non-zero buffer period. The method according to specification 5.

7. The first subset of the row (P １ ) corresponds to the smallest set of rows of the plurality of rows (P) including the first area, The method according to feature 1.

8. - Adjusting the at least one focus parameter includes changing the distance between the sensor array (11) and the lens unit (9) of the camera (3); or - Adjusting the at least one focus parameter includes changing the focal length of the lens unit (9) of the camera (3). The method according to feature 1.

9. The focus adjustment period (T ａ ) is the first frame period (F １ It is determined that this begins before all rows of the plurality of rows (P) are exposed during the interval, The method according to feature 1.

10. A method for automatically guiding a vehicle (1) at least partially, - A method for adjusting the focus of the power vehicle camera (3) of the vehicle (1) is performed according to claim 1; - The vehicle (1) is at least partially automatically guided in accordance with the first image and / or the second image. method.

11. A camera (3) for a powered vehicle, which includes an imaging device (10), - A first frame period (F) in which multiple rows (P) of the sensor array (11) of the imaging device (10) are exposed based on the rolling shutter mode. １ The first image is acquired during the first frame period (F １ ) the second frame period (F ２ The system includes at least one control unit (13a, 13b) configured to control the imaging device (10) to acquire a second image during the following period: - A focus adjustment configuration (12) configured to adjust at least one focus parameter of the camera (3); The at least one control unit (13a, 13b) is - The aforementioned first frame period (F １ The first area in the sensor array (11) corresponding to a predetermined region of interest (6a, 6b, 6c, 7a, 7b, 7c) is determined with respect to the following: - The first subset (P) of the aforementioned multiple rows (P) １ ) determines the first subset of rows (P １ ) includes the aforementioned first area; - Focusing period (T ａ ) is determined, and the focus adjustment period (T ａ ) is the first subset of the row (P １ All rows of ) are within the first frame period (F １ When exposed during or after exposure; - Control the focus adjustment configuration (12) to control the focus adjustment period (T ａ ) During this time, the camera (3) adjusts at least one focus parameter based on a predetermined focus setting for acquiring the second image. It is configured in such a way. A camera for powered vehicles (3) characterized by the following:

12. The focus adjustment configuration (12) is configured to move the sensor array (11) relative to the lens unit (9) of the camera (3) to adjust the at least one focus parameter. The camera for a powered vehicle (3) according to claim 11.

13. The focus adjustment configuration (12) is configured to change the focal length of the lens unit (9) of the camera (3) to adjust the at least one focus parameter. The camera for a powered vehicle (3) according to claim 11.

14. An electronic vehicle guidance system (2) for a vehicle (1), comprising a power vehicle camera (3) as described in claim 11, and a further control unit (4) configured to generate one or more control signals for at least partially automatically guiding the vehicle (1) in accordance with the first image and / or the second image.

15. A computer program product that includes instructions, the instructions are - When performed by a power vehicle camera (3) according to any one of claims 11 to 13, cause the power vehicle camera (3) to perform the method described in any one of claims 1 to 9; or - When performed by the electronic vehicle guidance system (2) described in claim 14, the electronic vehicle guidance system (2) is instructed to perform the method described in claim 10. Computer program product.

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