Patent Description:
An increasing number of modern vehicles have advanced driver-assistance systems, ADAS, to increase vehicle safety and more generally road safety. ADAS - which for instance may be represented by lane departure avoidance, adaptive cruise control, ACC, collision avoidance system, forward collision warning, etc. - are electronic systems that may aid a vehicle driver while driving. To function as intended, ADAS may rely on inputs from multiple data sources, such as e.g. LIDARs, radars, ultrasonics, cameras, automotive imaging, image processing, computer vision, and/or in-car networking. Moreover, in a not too distant future, autonomous or automated driving systems, AD systems, will to greater extent find their way into modern vehicles. An AD system is a complex combination of various components that can be defined as systems where perception, decision making, and operation of the vehicle are performed by electronics and machinery instead of a human driver, and as introduction of automation into road traffic. This includes handling of the vehicle, destination, as well as awareness of surroundings. While the automated system has control over the vehicle, it allows the human operator to leave all responsibilities to the system. An AD system commonly combines a variety of sensors to perceive the vehicle's surroundings, such as e.g. radar, LIDAR, sonar, camera, navigation and/or positioning system e.g. GNSS such as GPS, odometer and/or inertial measurement units, upon which advanced control systems may interpret sensory information to identify appropriate navigation paths, as well as obstacles and/or relevant signage.

In current ADAS and AD systems, a safety level of features is commonly propagated top down towards all components contributing to a function. For one or more on-board image capturing devices such as cameras - e.g. comprised in a surround camera system - that often implies reaching an Automotive Safety Integrity Level, ASIL, level such as an ASIL B level. Reaching such a functional safety goal may require ensuring that respective image capturing device - or rather imagers thereof - is functioning properly. Accordingly, voltage and clock monitoring is commonly required for detection of abnormal voltages that can cause abnormal luminance in captured images - a state insinuating improper functioning of said image capturing device(s) or its imager(s) which in turn may result in non-compliance with reaching said safety goal. Such voltage monitoring is, however, commonly done with specialized integrated circuit, IC, components, that may add to complexity and/or to overall system cost. <CIT> (<CIT>) discloses a stereo camera failure detection apparatus of a vehicle by comparing luminance levels in an overlapping imaging area of the image pairs. A wiper is considered as a luminance affecting element and images with the wiper are not used for the camera failure detection purposes in order to avoid or reduce false-positives.

It is therefore an object of embodiments herein to provide an approach for in an improved and/or alternative manner monitor on-board vehicle image capturing device functionality compliance with a predeterminable requirement level. The object above may be achieved by the subject-matter disclosed herein. Embodiments are set forth in the appended claims, in the following description and in the drawings.

The disclosed subject-matter relates to a method performed by a luminance assessment system of a vehicle for monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level. The vehicle comprises two or more image capturing devices adapted to capture surroundings of the vehicle, wherein a first image capturing device has a first field of view and a second image capturing device has a second field of view with a primary region thereof at least partly overlapping the first field of view. The luminance assessment system obtains at respective one or more time instants, a respective first image with support from the first image capturing device and a respective second image with support from the second image capturing device, wherein a first section of the respective first images and a second section of the respective second images respectively cover the primary region. The luminance assessment system further measures for respective first image a respective first luminance value of the first section, and for respective second image a respective second luminance value of the second section. Moreover, the luminance assessment system determines a luminance deviation based on comparing at least one of the respective first luminance values to at least one of the respective second luminance values. The luminance assessment system furthermore determines, when the luminance deviation exceeds a deviation threshold, that the first image capturing device or the second image capturing device fails to function according to the requirement level.

The disclosed subject-matter further relates to a luminance assessment system of a vehicle for - and/or adapted for - monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level. The vehicle comprises two or more image capturing devices adapted to capture surroundings of the vehicle, wherein a first image capturing device has a first field of view and a second image capturing device has a second field of view with a primary region thereof at least partly overlapping the first field of view. The luminance assessment system comprises a primary image obtaining unit for obtaining at respective one or more time instants, a respective first image with support from the first image capturing device and a respective second image with support from the second image capturing device, wherein a first section of the respective first images and a second section of the respective second images respectively cover the primary region. The luminance assessment system further comprises a primary luminance measuring unit for measuring for respective first image a respective first luminance value of the first section, and for respective second image a respective second luminance value of the second section. Moreover, the luminance assessment system comprises a primary deviation determining unit for determining a luminance deviation based on comparing at least one of the respective first luminance values to at least one of the respective second luminance values. The luminance assessment system furthermore comprises a failure identifying unit for determining, when the luminance deviation exceeds a deviation threshold, that the first image capturing device or the second image capturing device fails to function according to the requirement level.

Furthermore, the disclosed subject-matter relates to a vehicle comprising a luminance assessment system as described herein. Moreover, the disclosed subject-matter relates to a computer program product comprising a computer program containing computer program code means arranged to cause a computer or a processor to execute the steps of a luminance assessment system described herein, stored on a computer-readable medium or a carrier wave. The disclosed subject-matter further relates to a non-volatile computer readable storage medium having stored thereon said computer program product.

Thereby, there is introduced an approach enabling detection of improper functioning of an image capturing device, such as of an imager thereof, which subsequently may imply non-compliance with a set requirement level. That is, since there is obtained at respective one or more time instants, a respective first image with support from the first image capturing device and a respective second image with support from the second image capturing device, wherein a first section of the respective first images and a second section of the respective second images respectively cover the primary region, there is derived at one or more time points from respective first and second image capturing device one or more images respectively comprising the overlapping region of the first and second fields of view. Moreover, that is, since there is measured for respective first image a respective first luminance value of the first section and for respective second image a respective second luminance value of the second section, luminance values are derived for each time point for the areas of the images covering the primary region, i.e. covering the section where the fields of view for the first and second image capturing devices overlap. Accordingly, luminance values applicable for the same area - i.e. the primary region - at one or more points in time, are gathered not only from images obtained by the first image capturing device, but also from images obtained by the second image capturing device. Furthermore, that is, since there is determined a luminance deviation based on comparing at least one of the respective first luminance values to at least one of the respective second luminance values, there may be detected potential discrepancy between on one end one or more luminance values applicable for the overlapping primary region obtained by the first image capturing device and on the other end one or more luminance values applicable for the overlapping primary region obtained by the second image capturing device. Moreover, that is, since there is determined, when the luminance deviation exceeds a deviation threshold, that the first image capturing device or the second image capturing device fails to function according to the requirement level, it is concluded provided that the determined luminance difference - applicable for the overlapping primary region - between luminance values derivable from the first image capturing device and luminance values derivable from the second image capturing device is greater than a predeterminable limit set in view of a predeterminable requirement level, that either the first or the second image capturing device fails to function in accordance therewith. That is, with the introduced concept, there may be detected abnormal image luminance values - which may equate to abnormal voltages - pertinent either the first image capturing device or an imager thereof, or the second image capturing device or an imager thereof. Such abnormal image luminance values and subsequently abnormal voltages in turn insinuate improper functioning, and - should the deviation threshold be exceeded - then non-compliance with the set requirement level, for instance a safety goal such as commonly known ASIL B level, is detected. Accordingly, with the introduced concept according to which image luminance values are monitored, commonly known voltage and clock monitoring by means of IC components - which may add to complexity and/or overall system cost - may be omitted.

For that reason, an approach is provided for in an improved and/or alternative manner monitor on-board vehicle image capturing device functionality compliance with a predeterminable requirement level. The technical features and corresponding advantages of the above mentioned method will be discussed in further detail in the following.

Non-limiting embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Dashed lines of some boxes in the figures indicate that these units or actions are optional and not mandatory. In the following, according to embodiments herein which relate to monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level, there will be disclosed an approach enabling detection of improper functioning of an image capturing device, such as of an imager thereof, which subsequently may imply non-compliance with said requirement level.

Referring now to the figures, there is depicted in <FIG> schematic views of an exemplifying luminance assessment system <NUM> according to embodiments of the disclosure, and in <FIG> a schematic block diagram illustrating an exemplifying luminance assessment system <NUM> according to embodiments of the disclosure. The luminance assessment system <NUM> is for monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level. The predeterminable requirement level may be represented by any feasible functional goal and/or mission, such as a safety level, for instance a commonly known ASIL level such as an ASIL B level. Moreover, the luminance assessment system <NUM> may be comprised - or at least partly comprised - in and/or provided on-board a vehicle <NUM>. The exemplifying vehicle <NUM> may be represented by any arbitrary - e.g. known - manned or unmanned vehicle, for instance an engine-propelled or electrically-powered vehicle such as a car, truck, lorry, van, bus and/or tractor. Moreover, the term "vehicle" may refer to "autonomous and/or at least partly autonomous vehicle", "driverless and/or at least partly driverless vehicle", and/or "self-driving and/or at least partly self-driving vehicle". The vehicle <NUM> may thus comprise, and/or be adapted to support an optional ADAS and/or AD system <NUM>, i.e. an advanced driver-assistance system and/or an automated driving system. Such an ADAS and/or AD system <NUM> may refer to any arbitrary ADAS and/or AD system, e.g. known in the art and/or yet to be developed. The vehicle <NUM> and/or the ADAS or AD system <NUM> may comprise, be provided with and/or have on-board an optional perception system <NUM> and/or similar system and/or functionality adapted to estimate surroundings of the vehicle <NUM>, and subsequently adapted to estimate world views of the surroundings e.g. with support from a - e.g. commonly known - digital map <NUM> such as a high definition, HD, map, and/or an equivalent and/or successor thereof. Such an exemplifying perception system <NUM> or similar system may refer to any commonly known system and/or functionality, e.g. comprised in one or more electronic control modules, ECUs, and/or nodes of the vehicle <NUM> and/or the ADAS or AD system <NUM>, adapted and/or configured to interpret sensory information - relevant for driving of the vehicle <NUM> - to identify e.g. obstacles, vehicle lanes, relevant signage, appropriate navigation paths etc. The exemplifying perception system <NUM> or similar system - which may be adapted to support e.g. sensor fusion, tracking, localization etc. - may thus be adapted to rely on sensory information. Such exemplifying sensory information may for instance be derived from one or more - e.g. commonly known - sensors comprised in and/or provided on-board the vehicle <NUM> adapted to sense and/or perceive the vehicle's <NUM> whereabouts and/or surroundings, for instance represented by one or a combination of one or more of a positioning system <NUM>, odometer, inertial measurement units, radar, lidar, ultrasonics, and/or surrounding detecting sensors such as image capturing devices.

The phrase "luminance assessment system" may refer to "luminance monitoring system", "compliance assessment system", "abnormal luminance assessment system" and/or merely "assessment and/or monitoring system", and further according to an example to "abnormal voltage assessment system". The phrase "for monitoring", on the other hand, may refer to "adapted for monitoring", whereas "for monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level" may refer to "for on-board vehicle image capturing device luminance monitoring", "for on-board vehicle image capturing device functionality monitoring", "for detecting abnormal on-board vehicle image capturing device luminance", "for detecting abnormal on-board vehicle image capturing device voltages" and/or "for detecting improper on-board vehicle image capturing device functioning". Moreover, according to examples, the phrase "for monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level" may further refer to "for on-board vehicle image capturing device imager luminance monitoring", "for on-board vehicle image capturing device imager functionality monitoring", "for detecting abnormal on-board vehicle image capturing device imager luminance", "for detecting abnormal on-board vehicle image capturing device imager voltages" and/or "for detecting improper on-board vehicle image capturing device imager functioning". Furthermore, the phrase "requirement level" may refer to "functional requirement level" and/or "requirement goal and/or mission", and according to examples further to "safety requirement" and/or "requirement level such as ASIL level requirement, e.g. ASIL B level".

The vehicle <NUM> comprises two or more image capturing devices <NUM> adapted to capture surroundings of the vehicle <NUM>, such as at a respective field of view <NUM>. Respective field of view <NUM> may be of any feasible extent, dimensions and/or degrees, for instance dictated by the implementation at hand and/or by characteristics associated with respective image capturing device <NUM>. The two or more image capturing devices <NUM> - which may be distributed in any arbitrary feasible manner e.g. to capture a section of or even up to <NUM> degrees of the vehicle's <NUM> surroundings - may be represented by any - e.g. known - sensors, functionality and/or systems adapted to capture images of vehicle surroundings, for instance in the visible wavelength range, for instance represented by one or more cameras. Moreover, the two or more image capturing devices <NUM> may respectively comprise at least a first imager (not shown), such as an image sensor, as known in the art. According to an example, the two or more image capturing devices <NUM> may be comprised in an optional surround camera system (not shown). Out of the one or more image capturing devices <NUM>, a first image capturing device <NUM> has a first field of view <NUM> and a second image capturing device <NUM> has a second field of view <NUM> with a primary region <NUM> thereof at least partly overlapping the first field of view <NUM>. The primary region <NUM> may be of any feasible extent, dimensions and/or degrees, for instance dictated by a position of the first image capturing device <NUM> relative a position of the second image capturing device <NUM>. In exemplifying <FIG>, the first image capturing device <NUM> is depicted to be positioned near and/or comprised in the rear-view mirror with its field of view <NUM> in an essentially forward direction of the vehicle <NUM>, whereas the second image capturing device <NUM> is depicted to be positioned near and/or comprised in the right-hand side mirror with its field of view <NUM> in an essentially right-hand side direction of the vehicle <NUM>. It should be noted, however, that the first and second image capturing devices <NUM>, <NUM> - given the condition that at least a portion referred to as the primary region <NUM> of the second field of view <NUM> at least partly overlaps the first field of view <NUM> - may be positioned in any feasible manner, such as alternated and/or at other positions of the vehicle <NUM> covering other fields of view such as in a rearward direction and/or in a left-hand side direction of the vehicle <NUM>. The region making up the primary region <NUM> may be identified and/or determined - and/or have been identified and/or determined - in any feasible manner, for instance during calibration such as during factory calibration. "Having a first field of view" may refer to "supporting and/or covering a first field of view", and correspondingly, "having a second field of view" may refer to "supporting and/or covering a second field of view". Moreover, "second field of view with a primary portion thereof at least partly overlapping said first field of view" may refer to "second field of view with a primary portion thereof at least partly and/or to some extent coinciding with said first field of view". The phrase "primary region", on the other hand, may refer to "first region" and/or merely "region", and further to "primary field", "primary section" and/or "primary portion".

As depicted in exemplifying <FIG>, the luminance assessment system <NUM> is - e.g. by means of a primary image obtaining unit <NUM> - adapted and/or configured for obtaining at respective one or more time instants t<NUM>, t<NUM>, t<NUM>, a respective first image <NUM>, <NUM>, <NUM> with support from the first image capturing device <NUM> and a respective second image <NUM>, <NUM>, <NUM> with support from the second image capturing device <NUM>, wherein a first section <NUM> of the respective first images <NUM>, <NUM>, <NUM> and a second section <NUM> of the respective second images <NUM>, <NUM>, <NUM> respectively cover the primary region <NUM>. Thereby, there is derived at one or more time points t<NUM>, t<NUM>, t<NUM> from respective first and second image capturing device <NUM>,<NUM>, one or more images <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> respectively comprising the overlapping region <NUM> of the first and second fields of view <NUM>, <NUM>.

Obtaining at respective one or more time instants t<NUM>, t<NUM>, t<NUM>, a respective first image <NUM>, <NUM>, <NUM> and a respective second image <NUM>, <NUM>, <NUM> may be accomplished in any feasible - e.g. known - manner, for instance with support from imagers of said image capturing devices <NUM>, <NUM>. The one or more time instants t<NUM>, t<NUM>, t<NUM> may occur at any feasible points in time, for instance at predeterminable time intervals and/or at predeterminable irregular time points. The respective first images <NUM>, <NUM>, <NUM> may accordingly be represented by consecutive and/or non-consecutive images and/or image frames captured by the first image capturing device <NUM>, and correspondingly, the respective second images <NUM>, <NUM>, <NUM> may accordingly be represented by consecutive and/or non-consecutive images and/or image frames captured by the second image capturing device <NUM>. In exemplifying <FIG>, a first time instant t<NUM>, a second time instant t<NUM> and a third time instant t<NUM> are depicted, it may however be noted that the one or more time instants t<NUM>, t<NUM>, t<NUM> may be represented by any feasible number of time instants. The first section <NUM> of the respective first images <NUM>, <NUM>, <NUM> and the second section <NUM> of the respective second images <NUM>, <NUM>, <NUM> respectively covering the primary region <NUM>, may be represented by any feasible area and/or portion of said images <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> comprising said primary region <NUM>, and may accordingly be of any dimensions in accordance therewith. The first section <NUM> and the second section <NUM> may be identified and/or determined - and/or have been identified and/or determined - in any feasible manner, for instance during calibration such as during factory calibration. In exemplifying <FIG>, the first section <NUM> and the second section <NUM> are respectively depicted with rectangular shape, although other shapes and/or dimension also may apply. It may be noted that positioning and dimensions of respective first section <NUM> in respective first image <NUM>, <NUM>, <NUM> remain unchanged, and correspondingly, that positioning and dimensions of respective second section <NUM> in respective second image <NUM>, <NUM>, <NUM> remain unchanged. The phrase "obtaining at respective one or more time instants" may refer to "deriving and/or capturing at respective one or more time instants", whereas "one or more time instants" may refer to "one or more predeterminable time instants". "A respective first image with support from said first image capturing device", on the other hand, may refer to "a respective first image and/or image frame of a first vehicle surrounding with support from said first image capturing device" and/or "a respective first image utilizing and/or with input from said first image capturing device", and correspondingly, "a respective second image with support from said second image capturing device" may refer to "a respective second image and/or image frame of a second vehicle surrounding with support from said second image capturing device" and/or "a respective second image utilizing and/or with input from said second image capturing device". Moreover, "a first section" may refer to "a first overlapping section" and/or merely "an overlapping section", and correspondingly, "a second section" may refer to "a second overlapping section" and/or merely "an overlapping section". The phrase "respectively covering said primary region", on the other hand, may refer to "respectively essentially covering said primary region" and/or "respectively comprising, reproducing and/or capturing said primary region".

Furthermore, the luminance assessment system <NUM> is - e.g. by means of a primary luminance measuring unit <NUM> - adapted and/or configured for measuring for respective first image <NUM>, <NUM>, <NUM> a respective first luminance value <NUM>, <NUM>, <NUM> of the first section <NUM>, and for respective second image <NUM>, <NUM>, <NUM> a respective second luminance value <NUM>, <NUM>, <NUM> of the second section <NUM>. Thereby, for each time point t<NUM>, t<NUM>, t<NUM>, luminance values <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are derived for the areas <NUM>, <NUM> of the images <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> covering the primary region <NUM>, i.e. covering the section <NUM> where the fields of view <NUM>, <NUM> for the first and second image capturing devices <NUM>, <NUM> overlap. Accordingly, luminance values <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> applicable for the same area <NUM> - i.e. the primary region <NUM> - at one or more points in time t<NUM>, t<NUM>, t<NUM>, are gathered not only from images <NUM>, <NUM>, <NUM> obtained by the first image capturing device <NUM>, but also from images <NUM>, <NUM>, <NUM> obtained by the second image capturing device <NUM>.

Respective luminance value <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be measured in any feasible - e.g. known - manner, for instance with support from image processing, and further such as for instance described in Measuring Luminance with a Digital Camera by <NPL>. Moreover, said measuring may refer to measurements for at least a portion of respective first section <NUM> and second section <NUM>, and/or of one or more pixels of said respective first section <NUM> and second section <NUM>. The phrase "measuring [. ] a respective first luminance value, and [. ] a respective second luminance value" may refer to "detecting, gathering, deriving, obtaining, monitoring and/or determining [. ] a respective first luminance value, and [. ] a respective second luminance value", whereas "luminance value" throughout the disclosure may refer to "luminance value, or range and/or set of luminance values" and according to an example further to "pixel luminance value". Moreover, "respective first luminance value of said first section" may refer to "respective first luminance value of at least a portion - and/or of one or more pixels - of said first section", and correspondingly, "respective second luminance value of said second section" may refer to "respective second luminance value of at least a portion - and/or of one or more pixels - of said second section". The phrase "respective second luminance value of said second section" may further refer to "respective second luminance value of a corresponding second portion and/or pixels of said second section".

Moreover, the luminance assessment system <NUM> is - e.g. by means of a primary deviation determining unit <NUM> - adapted and/or configured for determining a luminance deviation based on comparing at least one of the respective first luminance values <NUM>, <NUM>, <NUM> to at least one of the respective second luminance values <NUM>, <NUM>, <NUM>. Thereby, there may be detected potential discrepancy between on one end one or more luminance values <NUM>, <NUM>, <NUM> applicable for the overlapping primary region <NUM> obtained by the first image capturing device <NUM> and on the other end one or more luminance values <NUM>, <NUM>, <NUM> applicable for said overlapping primary region <NUM> obtained by the second image capturing device <NUM>.

To determine the luminance deviation, one or more of the respective first luminance values <NUM>, <NUM>, <NUM> may be compared to one or more of the respective second luminance values <NUM>, <NUM>, <NUM> in any feasible manner. For instance a first luminance value <NUM> - and/or a range of first luminance values <NUM> - applicable for the first time instant t<NUM> may be compared to a second luminance value <NUM> - and/or a range of second luminance values <NUM> - applicable for said first time instant t<NUM>. Similarly, additionally or alternatively, for instance a first luminance value <NUM> - and/or a range of first luminance values <NUM> - applicable for the second time instant t<NUM> may be compared to a second luminance value <NUM> - and/or a range of second luminance values <NUM> - applicable for said second time instant t<NUM>, and/or a first luminance value <NUM> - and/or a range of first luminance values <NUM> - applicable for the third time instant t<NUM> may be compared to a second luminance value <NUM> - and/or a range of second luminance values <NUM> - applicable for said third time instant t<NUM>. Optionally, however, determining a luminance deviation may comprise comparing an average - such as a median, mean and/or weighted value - of two or more of the respective first luminance values <NUM>, <NUM>, <NUM> to an average - such as a median, mean and/or weighted value - of two or more of the respective second luminance values <NUM>, <NUM>, <NUM>. Thereby, potential e.g. glitches may be compensated for, in that a smoothed and/or representative first luminance value may be compared to a representative and/or smoothed second luminance value. The phrase "determining a luminance deviation" may refer to "identifying and/or detecting a luminance deviation", whereas "based on comparing at least one of said respective first luminance values to at least one of said respective second luminance values" may refer to "by determining and/or calculating a difference between at least one of said respective first luminance values and at least one of said respective second luminance values". Moreover, the phrase "comparing at least one of said respective first luminance values to at least one of said respective second luminance values" may refer to "comparing at least one of said respective first luminance values representative for said first luminance value to at least one of said respective second luminance values representative for said second luminance value".

The luminance assessment system <NUM> is further - e.g. by means of a failure identifying unit <NUM> - adapted and/or configured for determining, when the luminance deviation exceeds a deviation threshold, that the first image capturing device <NUM> or the second image capturing device <NUM> fails to function according to the requirement level. Thereby, provided that the determined luminance difference - applicable for the overlapping primary region <NUM> - between luminance values <NUM>, <NUM>, <NUM> derivable from the first image capturing device <NUM> and luminance values <NUM>, <NUM>, <NUM> derivable from the second image capturing device <NUM>, is greater than a predeterminable limit set in view of a predeterminable requirement level, then it is concluded that either the first or the second image capturing device <NUM>, <NUM> fails to function in accordance therewith. That is, with the introduced concept, there may be detected abnormal image luminance values - which may equate to abnormal voltages - pertinent either the first image capturing device <NUM> or an imager thereof, or the second image capturing device <NUM> or an imager thereof. Such abnormal image luminance values and subsequently abnormal voltages in turn insinuate improper functioning, and - should the deviation threshold be exceeded - then non-compliance with the set requirement level, for instance a safety goal such as commonly known ASIL B level, is detected. Accordingly, with the introduced concept according to which image luminance values <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are monitored, commonly known voltage and clock monitoring by means of IC components - which e.g. may add to complexity and/or overall system cost - may be omitted.

The deviation threshold may be represented by any feasible limit and/or limits - which for instance may vary with varying luminance ranges - and may further be set for instance in view of the implementation at hand and/or desired - e.g. regulatory - requirements and/or goals. Moreover, the deviation threshold may be expressed in any feasible manner, for instance indicating a difference and/or differences expressed in absolute values, additionally or alternatively as a percentage, such as a difference and/or differences greater than e.g. <NUM> percent, <NUM> percent, <NUM> percent or <NUM> percent. The phrase "determining [. ] that said first image capturing device or said second image capturing device fails" may according to an example refer to "determining [. ] that an imager of said first image capturing device or an imager of said second image capturing device fails". "Fails to function according to said requirement level", on the other hand, may throughout the disclosure refer to "fails to perform according to said requirement level", "is functioning and/or performing inadequately" and/or "renders and/or demonstrates abnormal luminance values and/or abnormal voltages". Moreover, "when said luminance deviation exceeds a deviation threshold" may refer to "when said luminance deviation exceeds a predeterminable deviation threshold" and/or "when said luminance deviation exceeds a deviation threshold set based on, reflecting and/or being pertinent a predeterminable requirement level", and according to an example further to "when said luminance deviation exceeds a deviation threshold set based on, reflecting and/or being pertinent a predeterminable functional requirement level and/or safety level such as an ASIL level, for instance an ASIL B level". "Deviation threshold" may further refer to "first deviation threshold", whereas "when said luminance deviation exceeds a deviation threshold" further may refer to "should, if and/or provided that said luminance deviation exceeds a deviation threshold".

Optionally, as depicted in exemplifying <FIG>, the vehicle <NUM> may comprise - out of the one or more image capturing devices <NUM> - a third image capturing device <NUM> having a third field of view <NUM> with a secondary region <NUM> thereof at least partly overlapping the first field of view <NUM>. The secondary region <NUM> may be of any feasible extent, dimensions and/or degrees, for instance dictated by a position of the first image capturing device <NUM> relative a position of the third image capturing device <NUM>. In exemplifying <FIG>, the third image capturing device <NUM> is depicted to be positioned near and/or comprised in the left-hand side mirror with its field of view <NUM> in an essentially left-hand side direction of the vehicle <NUM>. It should be noted, however, that the third image capturing device <NUM> - given the condition that at least a portion referred to as the secondary region <NUM> of the third field of view <NUM> at least partly overlaps the first field of view <NUM> - may be positioned in any feasible manner, such as at other positions of the vehicle <NUM> covering another field of view. The region making up the secondary region <NUM> may be identified and/or determined - and/or have been identified and/or determined - in any feasible manner, for instance during calibration such as during factory calibration. "Having a third field of view" may refer to "supporting and/or covering a third field of view", whereas "third field of view with a secondary portion thereof at least partly overlapping said first field of view" may refer to "third field of view with a secondary portion thereof at least partly and/or to some extent coinciding with said first field of view". The phrase "secondary region", on the other hand, may refer to "second region" and/or merely "region", and further to "secondary field", "secondary section" and/or "secondary portion".

As depicted in exemplifying <FIG>, optionally, the luminance assessment system <NUM> may then - e.g. by means of an optional secondary image obtaining unit <NUM> - be adapted and/or configured for obtaining at respective one or more time instants t<NUM>, t<NUM>, t<NUM>, a respective third image <NUM>, <NUM>, <NUM> with support from the third image capturing device <NUM>, wherein a third section <NUM> of the respective third images and a first secondary section <NUM> of the respective first images <NUM>, <NUM>, <NUM> respectively cover the secondary region <NUM>. Thereby, there is additionally derived at the one or more time points t<NUM>, t<NUM>, t<NUM> - from the third image capturing device <NUM> - one or more images <NUM>, <NUM>, <NUM> - which along with the one or more images <NUM>, <NUM>, <NUM> captured by the first image capturing device <NUM> - respectively comprises the overlapping secondary section <NUM> of the third and first fields of view <NUM>, <NUM>. Obtaining at the respective one or more time instants t<NUM>, t<NUM>, t<NUM>, a respective third image <NUM>, <NUM>, <NUM> may be accomplished in any feasible - e.g. known - manner, for instance with support from one or more imagers of the image capturing devices <NUM>. Since the one or more time instants t<NUM>, t<NUM>, t<NUM> may occur at any feasible points in time, for instance at predeterminable time intervals and/or at predeterminable irregular time points, the respective third images <NUM>, <NUM>, <NUM> may accordingly be represented by consecutive and/or non-consecutive images and/or image frames captured by the third image capturing device <NUM>. The first secondary section <NUM> of the respective first images <NUM>, <NUM>, <NUM> and the third section <NUM> of the respective third images <NUM>, <NUM>, <NUM>, respectively covering the secondary region <NUM>, may be represented by any feasible area and/or portion of said images <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> comprising said secondary region <NUM>, and may accordingly be of any dimensions in accordance therewith. The first secondary section <NUM> and the third section <NUM> may be identified and/or determined - and/or have been identified and/or determined - in any feasible manner, for instance during calibration such as during factory calibration. In exemplifying <FIG>, the first secondary section <NUM> and the third section <NUM> are respectively depicted with rectangular shape, although other shapes and/or dimension also may apply. It may be noted that positioning and dimensions of respective first secondary section <NUM> in respective first image <NUM>, <NUM>, <NUM> remain unchanged, and correspondingly, that positioning and dimensions of respective third section <NUM> in respective third image <NUM>, <NUM>, <NUM> remain unchanged. The phrase "a respective third image with support from said third image capturing device" may refer to "a respective third image and/or image frame of a third vehicle surrounding with support from said third image capturing device" and/or "a respective third image utilizing and/or with input from said third image capturing device". Moreover, "a first secondary section" may refer to "a first overlapping secondary section" and/or merely "an overlapping section", and correspondingly, "a third section" may refer to "a third overlapping section" and/or merely "an overlapping section". The phrase "respectively covering said secondary region", on the other hand, may refer to "respectively essentially covering said secondary region" and/or "respectively comprising, reproducing and/or capturing said secondary region".

Further optionally, the luminance assessment system <NUM> may then - e.g. by means of an optional secondary luminance measuring unit <NUM> - be adapted and/or configured for measuring for respective third image <NUM>, <NUM>, <NUM> a respective third luminance value <NUM>, <NUM>, <NUM> of the third section <NUM>, and for respective first image <NUM>, <NUM>, <NUM> a respective first secondary luminance value <NUM>, <NUM>, <NUM> of the first secondary section <NUM>. Thereby, for each time point t<NUM>, t<NUM>, t<NUM>, luminance values <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are derived for the areas <NUM>, <NUM> of the images <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> covering the secondary region <NUM>, i.e. covering the section <NUM> where the fields of view <NUM>, <NUM> for the first and third image capturing devices <NUM>, <NUM> overlap. Accordingly, luminance values <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> applicable for the same area <NUM> - i.e. the secondary region <NUM> - at one or more points in time t<NUM>, t<NUM>, t<NUM>, are gathered not only from images <NUM>, <NUM>, <NUM> obtained by the first image capturing device <NUM>, but also from images <NUM>, <NUM>, <NUM> obtained by the third image capturing device <NUM>. Respective luminance value <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be measured in any feasible - e.g. known - manner, such as - as indicated above - for instance with support from image processing, and further such as for instance described in Measuring Luminance with a Digital Camera by <NPL>. Moreover, said measuring may refer to measurements for at least a portion of respective first secondary section <NUM> and third section <NUM>, and/or of one or more pixels of said respective first secondary section <NUM> and third section <NUM>. The phrase "measuring [. ] a respective third luminance value, and [. ] a respective first secondary luminance value" may refer to "detecting, gathering, deriving, obtaining, monitoring and/or determining [. ] a respective third luminance value, and [. ] a respective first secondary luminance value". Moreover, "respective third luminance value of said third section" may refer to "respective third luminance value of at least a portion - and/or of one or more pixels - of said third section", and correspondingly, the phrase "respective first secondary luminance value of said first secondary section" may refer to "respective first secondary luminance value of at least a portion - and/or of one or more pixels - of said first secondary section". The phrase respective first secondary luminance value of said first secondary section" may further refer to "respective first secondary luminance value of a corresponding secondary portion and/or pixels of said first secondary section".

Further optionally, the luminance assessment system <NUM> may then - e.g. by means of an optional secondary deviation determining unit <NUM> - be adapted and/or configured for determining a secondary luminance deviation based on comparing at least one of the respective third luminance values <NUM>, <NUM>, <NUM> to at least one of the respective first secondary luminance values <NUM>, <NUM>, <NUM>. Thereby, there may be detected potential discrepancy between on one end one or more luminance values <NUM>, <NUM>, <NUM> applicable for the overlapping secondary region <NUM> obtained by the first image capturing device <NUM> and on the other end one or more luminance values <NUM>, <NUM>, <NUM> applicable for said overlapping secondary region <NUM> obtained by the third image capturing device <NUM>. To determine the secondary luminance deviation, one or more of the respective first secondary luminance values <NUM>, <NUM>, <NUM> may be compared to one or more of the respective third luminance values <NUM>, <NUM>, <NUM> in any feasible manner. For instance a first secondary luminance value <NUM> - and/or a range of first secondary luminance values <NUM> - applicable for the first time instant t<NUM> may be compared to a third luminance value <NUM> - and/or a range of third luminance values <NUM> - applicable for said first time instant t<NUM>. Similarly, additionally or alternatively, for instance a first secondary luminance value <NUM> - and/or a range of first secondary luminance values <NUM> - applicable for the second time instant t<NUM> may be compared to a third luminance value <NUM> - and/or a range of third luminance values <NUM> - applicable for said second time instant t<NUM>, and/or a first secondary luminance value <NUM> - and/or a range of first secondary luminance values <NUM> - applicable for the third time instant t<NUM> may be compared to a third luminance value <NUM> - and/or a range of third luminance values <NUM> - applicable for said third time instant t3. Optionally, however, determining a secondary luminance deviation may comprise comparing an average - such as a median, mean and/or weighted value - of two or more of the respective third luminance values <NUM>, <NUM>, <NUM> to an average - such as a median, mean and/or weighted value - of two or more of the respective first secondary luminance values <NUM>, <NUM>, <NUM>. Thereby, potential e.g. glitches may be compensated for, in that a smoothed and/or representative third luminance value <NUM>, <NUM>, <NUM> may be compared to a representative and/or smoothed first secondary luminance value <NUM>, <NUM>, <NUM>. The phrase "determining a secondary luminance deviation" may refer to "identifying and/or detecting a secondary luminance deviation", whereas "based on comparing at least one of said respective third luminance values to at least one of said respective first secondary luminance values" may refer to "by determining and/or calculating a difference between at least one of said respective third luminance values and at least one of said respective first secondary luminance values". Moreover, the phrase "comparing at least one of said respective third luminance values to at least one of said respective first secondary luminance values" may refer to "comparing at least one of said respective third luminance values representative for said third luminance value to at least one of said respective first secondary luminance values representative for said first secondary luminance value".

Further optionally, the luminance assessment system <NUM> may then - e.g. by means of an optional device identifying unit <NUM> - be adapted and/or configured for identifying, when the secondary luminance deviation exceeds a secondary deviation threshold, that it is the first image capturing device <NUM> that fails to function according to the requirement level, and/or when the secondary luminance deviation does not exceed the secondary deviation threshold, that it is the second image capturing device <NUM> that fails to function according to the requirement level. Thereby, provided that the secondary determined luminance difference - applicable for the overlapping secondary region <NUM> - between luminance values <NUM>, <NUM>, <NUM> derivable from the first image capturing device <NUM> and luminance values <NUM>, <NUM>, <NUM> derivable from the third image capturing device <NUM>, is greater than a predeterminable second limit - which potentially may be equal to the deviation threshold discussed above and/or set in view of the predeterminable requirement level - then it is concluded that the first image capturing device <NUM> is the device out of the first and second image capturing devices <NUM>, <NUM> that fails to function in accordance with the requirement level. That is, since the first image capturing device <NUM> is involved in luminance values comparison in view of both the deviation threshold - i.e. in consideration of the overlapping primary region <NUM> and subsequently the second image capturing device <NUM> - and the secondary deviation threshold - i.e. in consideration of the overlapping secondary region <NUM> and subsequently the third image capturing device <NUM> - and since it then is established that both these thresholds are exceeded, it may be concluded that it is the first image capturing device <NUM> or an imager thereof that demonstrates abnormal luminance values <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. On the other hand, provided that the secondary determined luminance difference not is greater than said predeterminable second limit, then it is concluded that the second image capturing device <NUM> is the device out of the first and second image capturing devices <NUM>, <NUM> that fails to function in accordance with the requirement level. That is, since the first image capturing device <NUM> as indicated above is involved in luminance values comparison in view of both the deviation threshold and the secondary deviation threshold, and since it is established that the secondary deviation threshold then not is exceeded thus implying that the first image capturing device <NUM> or an imager thereof does not demonstrate abnormal luminance values <NUM>, <NUM>, <NUM> as compared to luminance values <NUM>, <NUM>, <NUM> of the third image capturing device <NUM>, it may be concluded that it rather than the first image capturing device <NUM> is the second image capturing device <NUM> or an imager thereof that demonstrates abnormal luminance values <NUM>, <NUM>, <NUM>.

The secondary deviation threshold may potentially, although not necessarily, be set to be equal to - or at least to some extent be equal to - the deviation threshold discussed above in view of the second primary region <NUM>. Accordingly, the secondary deviation threshold may be represented by any feasible limit and/or limits - which for instance may vary with varying luminance ranges - and may further be set for instance in view of the implementation at hand and/or desired - e.g. regulatory - requirements and/or goals. Moreover, the secondary deviation threshold may be expressed in any feasible manner, for instance indicating a difference and/or differences expressed in absolute values, additionally or alternatively as a percentage, such as a difference and/or differences greater than e.g. <NUM> percent, <NUM> percent, <NUM> percent or <NUM> percent. The phrase "identifying [. ] that is it" may refer to "determining and/or concluding [. ] that it is". The phrase "that it is said first image capturing device that fails", on the other hand, may refer to "that it is an imager of said first image capturing device that fails", and correspondingly, the phrase "that it is said second image capturing device that fails" may refer to "that it is an imager of said second image capturing device that fails". Moreover, the phrase "when said secondary luminance deviation exceeds a secondary deviation threshold" may refer to "when said secondary luminance deviation exceeds a predeterminable secondary deviation threshold" and/or "when said secondary luminance deviation exceeds a secondary deviation threshold set based on, reflecting and/or being pertinent a predeterminable requirement level", and according to an example further to "when said secondary luminance deviation exceeds a secondary deviation threshold set based on, reflecting and/or being pertinent a predeterminable functional requirement level and/or safety level such as an ASIL level, for instance an ASIL B level". Furthermore, "when said secondary luminance deviation exceeds a secondary deviation threshold" may further refer to "should, if and/or provided that said secondary luminance deviation exceeds a secondary deviation threshold". "Secondary deviation threshold" may further refer to "second deviation threshold", whereas "when said secondary luminance deviation does not exceed said secondary deviation threshold" may further refer to "should, if and/or provided that said secondary luminance deviation does not exceed said secondary deviation threshold". The phrase "and/or when said secondary luminance deviation does not exceed said secondary deviation threshold, that it is said second image capturing device that fails to function according to said requirement level", on the other hand, may refer to "otherwise, that it is said second image capturing device that fails to function according to said requirement level".

It may be noted that the vehicle <NUM> may comprise any further arbitrary number of image capturing devices <NUM>, such as - as depicted in exemplifying <FIG> - a fourth image capturing device <NUM> having a fourth field of view <NUM>. In exemplifying <FIG>, the fourth field of view <NUM> - in combination with the first, second and third fields of view, <NUM>, <NUM>, <NUM> - enable for <NUM> degrees vehicle surroundings to be covered. It may be noted, however, that any other combination and/or number of image capturing devices <NUM> may be used to accomplish the same or similar effect. It may further be noted that the optional fourth image capturing device <NUM> and/or any further image capturing device <NUM>, may - with respective overlapping field of view regions - contribute to and/or support the inventive concept presented herein. the luminance assessment system <NUM> may - e.g. by means of an affecting element determining unit <NUM> - be adapted and/or configured for determining whether there is presence of an image luminance affecting element (not shown), such as e.g. a tunnel and/or overpass, within image capturing device range of the vehicle <NUM>. Determining that the first image capturing device <NUM> or the second image capturing device <NUM> fails to function according to the requirement level, as described above, then comprises determining, when the luminance deviation exceeds a luminance deviation threshold and when there is determined no presence of an image luminance affecting element, that the first image capturing device <NUM> or the second image capturing device <NUM> fails to function according to the requirement level. Thereby, provided that the determined luminance difference - applicable for the overlapping primary region <NUM> - between luminance values <NUM>, <NUM>, <NUM> derivable from the first image capturing device <NUM> and luminance values <NUM>, <NUM>, <NUM> derivable from the second image capturing device <NUM>, is greater than the predeterminable limit set in view of the predeterminable requirement level, and in addition thereto provided that there is established absence in vicinity the vehicle <NUM> of elements which potentially may affect luminance in captured images <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, then it is concluded that either the first or the second image capturing device <NUM>, <NUM> fails to function in accordance therewith. That is, should it be determined that an image luminance affecting element is present within range of the vehicle <NUM>, then said image luminance affecting element, e.g. a tunnel and/or overpass, may potentially - e.g. by casting shadows and/or darkness - affect the measured luminance values <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in the captured images <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> - a situation that for instance may occur if the image capturing devices are provided at different positions of the vehicle <NUM>, such as at differing longitudinal positions of the vehicle <NUM>. Consequently, in such a case, the measured respective first luminance values <NUM>, <NUM>, <NUM> may potentially differ from the measured respective second luminance values <NUM>, <NUM>, <NUM> to such extent that the deviation threshold is exceeded due to impact from said image luminance affecting element rather than due to the first or second image capturing device <NUM>, <NUM> failing to function according to the requirement level. Thus, according to this embodiment, should it be determined that there is presence of an image luminance affecting element within image capturing device range of the vehicle <NUM>, then the luminance assessment system <NUM> refrains from determining that the first image capturing device <NUM> or the second image capturing device <NUM> fails to function according to the requirement level, even though the luminance deviation may exceed the requirement level.

The image luminance affecting element may refer to any feasible element and/or object potentially having impact on luminance of images captured by the image capturing devices <NUM>, such as a tunnel, overpass, bridge etc. Determining whether there is presence of an image luminance affecting element may be accomplished in any feasible - e.g. known - manner. For instance, absence or presence thereof may for instance be determined by means of commonly known object detection and/or image processing. however, the luminance assessment system <NUM> - e.g. by means of an vehicle position determining unit <NUM> - is adapted and/or configured for determining, with support from a positioning system <NUM>, a position of the vehicle <NUM>, and further - e.g. by means of an vehicle localization unit <NUM> - be adapted and/or configured for localizing, based on the vehicle position, the vehicle <NUM> in view of a digital map <NUM>. Determining whether there is presence of an image luminance affecting element, as described above, then comprises determining whether there in the digital map <NUM> is presence of an image luminance affecting element within image capturing device range of the vehicle <NUM>. Thereby, by localizing the vehicle <NUM> in view of a digital map <NUM>, and further analysing map data thereof , it may be derived whether there is - within range of the in the digital map <NUM> mapped vehicle <NUM> location - an element in said digital map <NUM> which is deemed to potentially affect image luminance. Determining the position of the vehicle <NUM>, and further localizing the vehicle <NUM> in view of a digital map <NUM>, may be accomplished in any feasible - e.g. known - manner, with support from a positioning system and further e.g. with support from an optional perception system <NUM> or similar system and/or functionality described above. The phrase "determining whether there is presence of an image luminance affecting element" may refer to "identifying, estimating and/or deriving whether there is presence of an image luminance affecting element" and/or "determining whether an image luminance affecting element is present", whereas "image luminance affecting element" may refer to "image luminance affecting object", "image luminance affecting stationary and/or dynamic element" and/or "element potentially affecting and/or impacting image luminance". Moreover, the phrase "within image capturing device range of said vehicle" may refer to "within a predeterminable distance from said vehicle, such as within <NUM>, <NUM> or <NUM> meters from said vehicle", "within image capturing device range of said first image capturing device and/or said second image capturing device", and according to an example further to "within said primary region". The phrase "when there is determined no presence of an image luminance affecting element" may refer to "should it be, provided that there is and/or if there is determined no presence of an image luminance affecting element".

As further shown in <FIG>, the luminance assessment system <NUM> comprises a primary image obtaining unit <NUM>, a primary luminance measuring unit <NUM>, a primary deviation determining unit <NUM>, a failure identifying unit <NUM>, an optional secondary image obtaining unit <NUM>, an optional secondary luminance measuring unit <NUM>, an optional secondary deviation determining unit <NUM>, an optional device identifying unit <NUM>, a vehicle position determining unit <NUM>, a vehicle localization unit <NUM>, an affecting element determining unit <NUM>, all of which already have been described in greater detail above. Furthermore, the embodiments herein for monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level, may be implemented through one or more processors, such as a processor <NUM>, here denoted CPU, together with computer program code for performing the functions and actions of the embodiments herein. Said program code may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the luminance assessment system <NUM>. One such carrier may be in the form of a CD ROM disc and/or a hard drive, it is however feasible with other data carriers. The computer program code may furthermore be provided as pure program code on a server and downloaded to the luminance assessment system <NUM>. The luminance assessment system <NUM> may further comprise a memory <NUM> comprising one or more memory units. The memory <NUM> may be arranged to be used to store e.g. information, and further to store data, configurations, schedulings, and applications, to perform the methods herein when being executed in the luminance assessment system <NUM>. For instance, the computer program code may be implemented in the firmware, stored in FLASH memory <NUM>, of an embedded processor <NUM>, and/or downloaded wirelessly e.g. from an off-board server. Furthermore, said units <NUM>-<NUM>, the optional processor <NUM> and/or the optional memory <NUM>, may at least partly be comprised in one or more nodes <NUM> e.g. ECUs of the vehicle <NUM>, e.g. in and/or in association with the optional ADAS or ADS system <NUM> and/or one or more image capturing devices <NUM>. Those skilled in the art will also appreciate that said units <NUM>-<NUM> described above as well as any other unit, interface, system, controller, module, device, element, feature, or the like described herein may refer to, comprise, include, and/or be implemented in or by a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in a memory such as the memory <NUM>, that when executed by the one or more processors such as the processor <NUM> perform as described herein. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry, ASIC, or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a System-on-a-Chip, SoC.

<FIG> is a flowchart depicting an exemplifying method performed by a luminance assessment system <NUM> according to embodiments of the disclosure. Said method is for monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level. The exemplifying method, which may be continuously repeated, comprises one or more of the following actions discussed with support from <FIG>. Moreover, the actions may be taken in any suitable order and/or one or more actions may be performed simultaneously and/or in alternate order where applicable. For instance, Action <NUM> and optional Action <NUM> may be performed simultaneously and/or in alternate order. Similarly, Action <NUM> and optional Action <NUM>, and/or Action <NUM> and optional Action <NUM>, may be performed simultaneously and/or in alternate order, whereas Actions <NUM>-<NUM> and one or more of Actions <NUM>-<NUM> in a similar manner may be performed simultaneously and/or in alternate order.

In Action <NUM>, the luminance assessment system <NUM> obtains - e.g. with support from the primary image obtaining unit <NUM> - at respective one or more time instants t<NUM>, t<NUM>, t<NUM>, a respective first image <NUM>, <NUM>, <NUM> with support from the first image capturing device <NUM> and a respective second image <NUM>, <NUM>, <NUM> with support from the second image capturing device <NUM>, wherein a first section <NUM> of the respective first images <NUM>, <NUM>, <NUM> and a second section <NUM> of the respective second images <NUM>, <NUM>, <NUM> respectively cover the primary region <NUM>.

Optionally, a third image capturing device <NUM> has a third field of view <NUM> with a secondary region <NUM> thereof at least partly overlapping the first field of view <NUM>. Accordingly, in optional Action <NUM>, the luminance assessment system <NUM> may obtain - e.g. with support from the optional secondary image obtaining unit <NUM> - at respective one or more time instants t<NUM>, t<NUM>, t<NUM>, a respective third image <NUM>, <NUM>, <NUM> with support from the third image capturing device <NUM>, wherein a third section <NUM> of the respective third images <NUM>, <NUM>, <NUM> and a first secondary section <NUM> of the respective first images <NUM>, <NUM>, <NUM> respectively cover the secondary region <NUM>.

In Action <NUM>, the luminance assessment system <NUM> measures - e.g. with support from the primary luminance measuring unit <NUM> - for respective first image <NUM>, <NUM>, <NUM>, a respective first luminance value <NUM>, <NUM>, <NUM> of the first section <NUM>, and for respective second image <NUM>, <NUM>, <NUM> a respective second luminance value <NUM>, <NUM>, <NUM> of the second section <NUM>.

In optional Action <NUM>, which may follow upon optional Action <NUM>, the luminance assessment system <NUM> may measure - e.g. with support from the optional secondary luminance measuring unit <NUM> - for respective third image <NUM>, <NUM>, <NUM> a respective third luminance value <NUM>, <NUM>, <NUM> of the third section <NUM>, and for respective first image <NUM>, <NUM>, <NUM> a respective first secondary luminance value <NUM>, <NUM>, <NUM> of the first secondary section <NUM>.

In Action <NUM>, the luminance assessment system <NUM> determines - e.g. with support from the primary deviation determining unit <NUM> - a luminance deviation based on comparing at least one of the respective first luminance values <NUM>, <NUM>, <NUM> to at least one of the respective second luminance values <NUM>, <NUM>, <NUM>.

Optionally, Action <NUM> of determining a luminance deviation may comprise - and/or the primary deviation determining unit <NUM> may be adapted and/or configured for - comparing an average of two or more of the respective first luminance values <NUM>, <NUM>, <NUM> to an average of two or more of the respective second luminance values <NUM>, <NUM>, <NUM>.

In optional Action <NUM>, which may follow upon optional Action <NUM>, the luminance assessment system <NUM> may determine - e.g. with support from the optional secondary deviation determining unit <NUM> - a secondary luminance deviation based on comparing at least one of the respective third luminance values <NUM>, <NUM>, <NUM> to at least one of the respective first secondary luminance values <NUM>, <NUM>, <NUM>.

Optionally, Action <NUM> of determining a secondary luminance deviation may comprise - and/or the optional secondary deviation determining unit <NUM> may be adapted and/or configured for - comparing an average of two or more of the respective third luminance values <NUM>, <NUM>, <NUM> to an average of two or more of the respective first secondary luminance values <NUM>, <NUM>, <NUM>.

In Action <NUM>, the luminance assessment system <NUM> determines - e.g. with support from the vehicle position determining unit <NUM> - with support from a positioning system <NUM>, a position of the vehicle <NUM>.

In Action <NUM>, which may follow upon Action <NUM>, the luminance assessment system <NUM> localizes - e.g. with support from the vehicle localization unit <NUM> - based on the vehicle position, the vehicle <NUM> in view of a digital map <NUM>.

In Action <NUM>, the luminance assessment system <NUM> determines - e.g. with support from the affecting element determining unit <NUM> - whether there is presence of an image luminance affecting element, such as e.g. a tunnel and/or overpass, within image capturing device range of the vehicle <NUM>.

Optionally, should Action <NUM> follow upon Action <NUM> of localizing the vehicle <NUM> in view of a digital map <NUM>, then Action <NUM> may comprise - and/or the optional affecting element determining unit <NUM> may be adapted and/or configured for - determining whether there in the digital map <NUM> is presence of an image luminance affecting element within image capturing device range of the vehicle <NUM>.

In Action <NUM>, the luminance assessment system <NUM> determines - e.g. with support from the failure identifying unit <NUM> - when the luminance deviation exceeds a deviation threshold, that the first image capturing device <NUM> or the second image capturing device <NUM> fails to function according to the requirement level. should Action <NUM> follow upon Action <NUM> of determining whether there is presence of an image luminance affecting element, then said determining of Action <NUM> may comprise - and/or the failure identifying unit <NUM> is adapted and/or configured for - determining, when the luminance deviation exceeds a luminance deviation threshold and when there is determined no presence of an image luminance affecting element, that the first image capturing device <NUM> or the second image capturing device <NUM> fails to function according to the requirement level.

In optional Action <NUM>, which may follow upon optional Action <NUM>, the luminance assessment system <NUM> may determine - e.g. with support from the optional device identifying unit <NUM> - when the secondary luminance deviation exceeds a secondary deviation threshold, that it is the first image capturing device <NUM> that fails to function according to the requirement level, and/or when the secondary luminance deviation does not exceed the secondary deviation threshold, that it is the second image capturing device <NUM> that fails to function according to the requirement level.

Claim 1:
A method performed by a luminance assessment system (<NUM>) of a vehicle (<NUM>) for monitoring of on-board vehicle image capturing device functionality compliance with a predeterminable requirement level, said vehicle (<NUM>) comprising two or more image capturing devices (<NUM>) adapted to capture surroundings of said vehicle (<NUM>), a first image capturing device (<NUM>) having a first field of view (<NUM>) and a second image capturing device (<NUM>) having a second field of view (<NUM>) with a primary region (<NUM>) thereof at least partly overlapping said first field of view (<NUM>), said method comprising:
obtaining (<NUM>) at respective one or more time instants (t<NUM>, t<NUM>, t<NUM>), a respective first image (<NUM>, <NUM>, <NUM>) with support from said first image capturing device (<NUM>) and a respective second image (<NUM>, <NUM>, <NUM>) with support from said second image capturing device (<NUM>), a first section (<NUM>) of said respective first image (<NUM>, <NUM>, <NUM>) and a second section (<NUM>) of said respective second image (<NUM>, <NUM>, <NUM>) respectively covering said primary region (<NUM>);
measuring (<NUM>) for respective first image (<NUM>, <NUM>, <NUM>) a respective first luminance value (<NUM>, <NUM>, <NUM>) of said first section (<NUM>), and for respective second image (<NUM>, <NUM>, <NUM>) a respective second luminance value (<NUM>, <NUM>, <NUM>) of said second section (<NUM>);
determining (<NUM>) a luminance deviation based on comparing at least one of said respective first luminance values (<NUM>, <NUM>, <NUM>) to at least one of said respective second luminance values (<NUM>, <NUM>, <NUM>);
determining (<NUM>) with support from a positioning system (<NUM>) a position of said vehicle (<NUM>);
localizing (<NUM>) based on said vehicle position, said vehicle (<NUM>) in view of a digital map (<NUM>);
determining (<NUM>) whether there in said digital map (<NUM>) is presence of an image luminance affecting element, such as e.g. a tunnel and/or overpass, within image capturing device range of said vehicle (<NUM>); and
determining (<NUM>), when said luminance deviation exceeds a deviation threshold and when there is determined no presence of an image luminance affecting element, that said first image capturing device (<NUM>) or said second image capturing device (<NUM>) fails to function according to said requirement level.