Camera system, method for controlling camera system, and image evaluation unit comprising camera system

Abstract

To provide a camera system, a method for controlling a camera system, and an image evaluation unit comprising a camera system.SOLUTION: A camera system comprises a camera (34) and a control unit (38), the camera (34) being configured to capture a sequence of successive images of a person of interest within a field of view of the camera (34), the camera system (30) being configured to determine intensity of light upon the person of interest, the control unit (38) being configured to control camera settings of the camera (34) based on the intensity of light determined by the camera system (30), the control unit (38) being configured to change the camera settings of the camera (34) only at defined points in time (tx1, tx2, ...txn).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a camera system, a related method for controlling the camera system, and an image evaluation unit comprising the camera system.

Background Art

[0002] Physiological parameters are often determined in order to determine a person's mental state, i.e., whether the person is sleepy, tired, or drowsy. Such information is often used, for example, in vehicles that may output a warning if it is determined that a person is not suitable for driving. In this way, the risk of (fatal) accidents can be significantly reduced. For example, physiological parameters such as heart rate, pulse, blood pressure, respiratory rate, and respiratory pattern can be determined in many different ways. Some methods for determining physiological parameters require attaching one or more sensors to the person being monitored. This can be inconvenient, for example, for the driver of a vehicle. A very simple method for determining physiological parameters involves capturing an image of the person being monitored and determining the physiological parameters by detecting slight changes in the pixel intensity of subsequent images. However, especially in a moving vehicle, the lighting conditions can change (rapidly), which can generate unwanted noise, which can have an adverse effect on the accuracy of physiological parameter determination.

[0003] There is a need for a camera system, a method for controlling the camera system, and an image evaluation unit comprising the camera system that can significantly reduce the impact of changing lighting conditions.

Summary of the Invention

Means for Solving the Problems

[0004] The camera system includes a camera and a control unit. The camera is configured to capture a series of consecutive images of a target person within the field of view of the camera. The camera system is configured to determine the intensity of light on the target person. The control unit is configured to control the camera settings of the camera based on the intensity of light determined by the camera system. The control unit is configured to change the camera settings of the camera only at defined time points. When it is detected that the intensity of light on the target object changes between two defined time points, the current camera settings are maintained until the next defined time point.

[0005] The image evaluation unit includes a camera system and a physiological parameter determination unit. The physiological parameter determination unit is configured to determine a change in pixel intensity in at least a defined target area of an image captured by the camera system and to determine one or more physiological parameters of the target person based on the change in pixel intensity.

[0006] The method includes capturing, by a camera, a series of consecutive images of a target person within the field of view of the camera, determining the intensity of light on the target person, and controlling, by a control unit, the camera settings of the camera based on the determined intensity of light. The camera settings of the camera are changed only at defined time points. When it is detected that the intensity of light on the target object changes between two defined time points, the current camera settings are maintained until the next defined time point.

[0007] Other systems, features, and advantages of the present disclosure will be or will become apparent to those of ordinary skill in the art upon examination of the following specification and drawings. All such additional systems, methods, features, and advantages are included within this specification, are within the scope of the present invention, and are intended to be protected by the following claims. The present invention provides, for example, the following items. (Item 1) A camera system (30) comprising a camera (34) and a control unit (38), The camera (34) is configured to capture a series of consecutive images of a target person within the field of view of the camera (34). The camera system (30) is configured to determine the intensity of light on the target person. The control unit (38) is configured to control the camera settings of the camera (34) based on the intensity of the light determined by the camera system (30). The control unit (38) is configured to change the camera settings of the camera (34) only at defined time points (tx1, tx2,... txn), and when it is detected that the intensity of the light on the target object changes between two defined time points (tx1, tx2,... txn), the current camera settings are maintained until the next defined time point (tx1, tx2,... txn), for the camera system (30). (Item 2) The camera system (30) according to the above item, wherein the interval between two directly consecutive defined time points (tx1, tx2,... txn) is at least 10 seconds, at least 15 seconds, or at least 30 seconds. (Item 3) The camera settings controlled by the control unit (38) include at least one of an exposure time and an F-value, for the camera system (30) according to any of the above items. (Item 4) An image evaluation unit (200), The camera system (30) according to any of the above items, And a physiological parameter determination unit (32), The physiological parameter determination unit (32) is configured to determine a change in pixel intensity of at least a defined target area of the image captured by the camera system (30), and to determine one or more physiological parameters of the target person based on the change in pixel intensity, for the image evaluation unit (200). (Item 5) The one or more physiological parameters determined by the physiological parameter determination unit (32) include at least one of the heart rate and the heart rate variability, and the image evaluation unit (200) according to any one of the above items. (Item 6) The physiological parameter determination unit (32) is configured to determine the one or more physiological parameters by an evaluation algorithm, and the algorithm is temporarily stopped at the defined time points (tx1, tx2,... txn), or the sensitivity of the algorithm decreases at the defined time points (tx1, tx2,... txn), and the image evaluation unit (200) according to any one of the above items. (Item 7) The physiological parameter determination unit (32) receives the image captured by the camera (34) of the camera system (30), The physiological parameter determination unit (32) further receives information from the control unit (38) of the camera system (30) regarding the changes made by the control unit (38) to the camera settings at the defined time points (tx1, tx2,..., txn), The evaluation algorithm compensates for the changes in the camera settings made at the defined time points (tx1, tx2,..., txn), and the image evaluation unit (200) according to any one of the above items. (Item 8) The physiological parameter determination unit (32) receives the image captured by the camera (34) of the camera system (30), The image evaluation unit (200) is configured to estimate the changes made by the control unit (38) to the camera settings at the defined time points (tx1, tx2,..., txn), The evaluation algorithm compensates for the changes in the camera settings made at the defined time points (tx1, tx2,..., txn), and the image evaluation unit (200) according to any one of the above items. (Item 9) The image evaluation unit (200) is configured to estimate the change made to the camera settings by evaluating an image captured immediately before a defined time point (tx1, tx2,..., txn) and an image captured immediately after the defined time point (tx1, tx2,..., txn), the image evaluation unit (200) according to any of the above items. (Item 10) The image evaluation unit (200) is disposed in the vehicle (10), and the target person is the driver (40) of the vehicle (10), the image evaluation unit (200) according to any of the above items. (Item 11) Capturing, by a camera (34), a series of consecutive images of a target person within the field of view of the camera (34), Determining the intensity of light on the target person, Controlling, by a control unit (38), the camera settings of the camera (34) based on the determined light intensity, including, The camera settings of the camera (34) are changed only at defined time points (tx1, tx2,...txn), and when it is detected that the intensity of the light on the target object changes between two defined time points (tx1, tx2,..., txn), the current camera settings are maintained until the next defined time point (tx1, tx2,...txn), a method. (Item 12) Determining a change in pixel intensity within at least a defined target area of the captured image, Determining one or more physiological parameters of the target person based on the change in pixel intensity, Further including, the method according to any of the above items. (Item 13) Processing the one or more physiological parameters, Determining the mental state of the target person based on the physiological parameters, Further including, the method according to any of the above items. (Item 14) The method according to any one of the above items, wherein the one or more physiological parameters include at least one of heart rate and heart rate variability. (Abstract) The camera system includes a camera (34) and a control unit (38). The camera (34) is configured to capture a series of consecutive images of a target person within the field of view of the camera (34). The camera system (30) is configured to determine the intensity of light on the target person. The control unit (38) is configured to control the camera settings of the camera (34) based on the intensity of light determined by the camera system (30). The control unit (38) is configured to change the camera settings of the camera (34) only at defined time points (tx1, tx2,... txn). When it is detected that the intensity of light on the target object changes between two defined time points (tx1, tx2,..., txn), the current camera settings are maintained until the next defined time point (tx1, tx2,..., txn).

[0008] This configuration and method can be understood more deeply with reference to the following description and drawings. The components in the drawings are not necessarily drawn to scale; instead, emphasis is placed on illustrating the principles of the present invention. Further, in the drawings, the same reference numerals refer to the same components throughout different figures.

Brief Description of the Drawings

[0009]

Figure 1

[0010]

Figure 2

[0011]

Figure 3

[0012]

Figure 4

[0013]

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0014] A camera system and a related method for controlling the camera system can significantly reduce the influence of rapidly changing lighting conditions when determining physiological parameters of a target person in an image captured by the camera system. When analyzing an image captured by the camera system (e.g., by an image evaluation unit) to determine physiological parameters of a target person (e.g., a driver of a vehicle), the result of the determination is quite accurate.

[0015] FIG. 1 schematically shows a vehicle 10 including an image evaluation unit 200 according to an embodiment of the present disclosure. The image evaluation unit 200 includes a camera system 30 and a physiological parameter determination unit 32. The camera system 30 includes a camera 34 (see, e.g., FIG. 3) and is configured to capture a series of consecutive images of a target person within the field of view of the camera 34. When disposed in the vehicle 10, the camera 34 of the camera system 30 can be directed, for example, towards the driver's seat 102 of the vehicle 10. As schematically shown in FIG. 3, the camera 34 has a defined field of view, and by directing the camera 34 (i.e., the field of view of the camera 34) towards the driver's seat 102, the face of the driver 40 sitting on the driver's seat 102 enters the field of view of the camera 34. The image evaluation unit 200 further includes a physiological parameter determination unit 32, and the physiological parameter determination unit 32 is configured to determine changes in pixel intensities of at least a defined target area of an image captured by the camera system 30 and to determine one or more physiological parameters of the target person based on the changes in pixel intensities.

[0016] Physiological parameters are often determined in order to judge a person's mental state, i.e., whether the person is sleepy, tired, or dazed. Such information is often used in vehicles that can output a warning, for example, when it is determined that a person (i.e., the driver 40 of vehicle 10) is not considered suitable for driving. In this way, the risk of (fatal) accidents can be significantly reduced. Physiological parameters can include, for example, heart rate, pulse, blood pressure, respiratory rate, and breathing pattern. A very simple method for determining physiological parameters includes capturing a plurality of images of the person being monitored (the subject person) and determining one or more physiological parameters by detecting slight changes in the pixel intensity of subsequent images.

[0017] Referring to FIG. 2, a method for determining a person's mental state (e.g., whether the driver 40 of vehicle 10 is sleepy, tired, or dazed) is schematically shown by a flowchart. The method includes determining a physiological parameter of the person of the subject (e.g., heart rate and / or heart rate variability) (step 201). Next, one or more physiological parameters are processed (step 202), and the mental state of the subject person is determined based on the one or more physiological parameters (step 203). The first step (step 201) of such a method can be performed using the image evaluation unit 200. That is, the image evaluation unit 200 can be used to determine one or more physiological parameters of the subject person. Optionally, the image evaluation unit 200 can also perform subsequent steps of the method (steps 202 and 203). However, such subsequent steps can alternatively be performed by other units separate and different from the image evaluation unit 200.

[0018] A method for determining physiological parameters of a target person by evaluating an image captured by a camera 34 is generally known. However, such a method can be inaccurate because it involves determining another physiological parameter by detecting slight changes in the pixel intensity of subsequent images. Especially in a moving vehicle, the lighting conditions can change (rapidly), generating unwanted noise, which can adversely affect the accuracy of physiological parameter determination. This will be explained in more detail with respect to FIG. 4. FIG. 4 schematically shows a vehicle 10 moving on a road. For example, as shown on the right side of FIG. 4, the vehicle 10 can travel through a tunnel. While traveling through the tunnel (vehicle positions (A) and (B)), the lighting conditions can be insufficient, and it is necessary to apply the camera settings to match the insufficient lighting conditions. For example, a relatively long exposure time and a low F value can be set by the control unit 38. As long as the vehicle 10 is moving inside the tunnel, the lighting conditions can be essentially stable. However, because the lighting inside the tunnel is irregular, the lighting conditions can still change to some extent inside the tunnel. For example, when the vehicle 10 passes a lamp, the lighting conditions can become somewhat better, and when the vehicle 10 is between two subsequent lamps, the lighting conditions can become somewhat worse. When the vehicle 10 exits the tunnel, especially when there is bright sunlight outside the tunnel, the lighting conditions can change significantly. However, when the vehicle 10 is outside the tunnel, for example, it can pass objects such as trees or buildings, and as a result, the lighting conditions can change rapidly between bright sunlight (vehicle position (C)) and shade (vehicle position (D)).

[0019] Each time the lighting condition changes, the camera settings are adjusted (automatically) to avoid the image being underexposed or overexposed. Camera settings that can be adjusted to avoid underexposure or overexposure can include, for example, automatic iris adjustment where the aperture controls the flow of light from the camera's optical subsystem to the light receiving element. Reducing the aperture reduces the flow of light to the light receiving element of the camera 34, and thus reduces the pixel brightness in the case of a digital camera. Additionally or alternatively, camera settings that can be adjusted to avoid underexposure or overexposure can include, for example, automatic exposure control. The total amount of energy reaching the light receiving element is determined by the exposure amount, or the time the light receiving element is exposed to the incident light, and as a result, the pixel brightness is determined. The exposure time and the F-value are generally related to automatic exposure control. Additionally or alternatively, camera settings that can be adjusted to avoid underexposure or overexposure can include various other techniques for amplifying the signal received from the light receiving element, either analogically or digitally, in order to obtain an appropriate pixel brightness value with respect to human perception or processing algorithms. Generally, any of the approaches mentioned above "multiplies" the pixel brightness by a factor, resulting in either amplification or attenuation of the resulting signal. Generally speaking, if the pixels of an image are too dark and thus have low brightness or are indistinguishable from each other and are not suitable for further analysis, using any of such adjustment techniques eliminates the effect of underexposure, or if the pixels are too bright and at the same time have strong brightness and are indistinguishable from each other and are not suitable for further analysis, overexposure is eliminated, thereby providing an acceptable dynamic range of the captured object.

[0020] Changes in pixel intensity caused by changes in lighting conditions and the resulting changes in camera settings are generally much larger than those caused by changes in skin color due to the blood pulsation of the subject person. When automatically adjusting the camera settings, the characteristics of all pixels or at least a subset of pixels in the captured image change rapidly (e.g., the brightness increases or decreases). The amplitude of the change is relatively large and is often much larger than one unit of pixel brightness. A heart rate estimation system generally calculates the change in skin reflectance caused by the pulsation of blood in blood vessels. The pulsation causes changes in the "color" and pixel intensity of the part of the image representing the skin. Such a system can be based on both digital signal processing algorithms and systems using machine learning and artificial neural networks. With standard levels of camera technology, such changes in pixel intensity caused by changes in skin color due to the blood pulsation of the subject person often hardly match the dynamic range of the camera 34. In other words, the changes in pixel intensity related to the determination of physiological parameters are generally equivalent to or even have an amplitude smaller than the unit of change in pixel brightness. For example, in the encoding of the photometric component of an 8-bit standard camera corresponding to a photometric range of 0 to 255, such changes are often less than 1 / 255 or one unit of the photometric range defined by the camera. Averaging and using information from all relevant pixels (or at least a subset of pixels) in the image generally results in the possibility of constructing a system with sufficient characteristics for useful applications. An algorithm for evaluating pixel intensity to determine the physiological parameters of a subject person cannot provide reliable results when the lighting conditions change rapidly and the camera settings are adjusted quickly accordingly.

[0021] Rather than the physiological parameter itself being monitored, changes in pixel luminance caused by adjustments to the camera settings are generally considered noise. As explained above, this noise can have an amplitude significantly greater than the changes caused by the monitored physiological parameter. Noise caused by adjustments to the camera settings is generally transient and thus cannot be easily removed by appropriate processing techniques (e.g., by averaging pixel luminance across a single image).

[0022] A camera system 30 (see, e.g., FIG. 3) according to an embodiment of the present disclosure includes a camera 34 and a control unit 38. The camera 34 is configured to capture a series of consecutive images of a target person within the field of view of the camera 34. The camera system 30 is configured to determine the intensity of light on the target person, and the control unit 38 is configured to control the camera settings of the camera 34 based on the intensity of light determined by the camera system 30. To reduce the impact of noise caused by automatic adjustment of the camera settings, the control unit 38 is configured to change the camera settings of the camera 34 only at defined time points tx1, tx2, ... txn. When it is detected that the intensity of light on the target person is changing between two defined time points tx1, tx2, ..., txn, the current camera settings are maintained until the next defined time point tx1, tx2, ..., txn. The intensity of light on the target person can be determined in any suitable manner. Most current cameras can determine the intensity of light on a target person (or target object), for example, by means of appropriate sensors and evaluation circuits. For example, the intensity of light on the target person can be determined by appropriately evaluating camera parameters such as pixel luminance, exposure time, iris, amplification, etc. According to another example, the camera 34 included in the camera system 30 can have an integrated exposure meter, exposure meter, or photometer configured to determine the intensity of light on the target person. However, the camera system 30 can also include an exposure meter, exposure meter, or photometer 36 separate from the camera 34.

[0023] Referring to FIG. 4, for example, the automatic adjustment of camera settings would be performed by a conventional system at time point t1 when the vehicle 10 exits the tunnel and the lighting conditions change. However, time point t1 in the example of the present invention does not correspond to any of the defined time points tx1, tx2, tx3, tx4, etc. In order to avoid too many changes in camera settings within a short time frame (for example, changes in camera settings every 1 to 4 seconds), the camera settings remain the same regardless of whether the lighting conditions change until the next defined time points tx1, tx2,...txn. That is, in the example shown in FIG. 4, the camera settings will change only at time point tx3. Also, further changes at time points t2 and t3 due to changes in lighting conditions will be suppressed. The next change in camera settings will occur at time point tx4. Therefore, between time point tx3 and time point tx4, there may be an underexposed image (in this example, due to the shadow caused by the tree). In other situations, there may also be overexposed images until the camera settings are changed again at each of the next defined time points tx1, tx2,...txn.

[0024] The defined points in time tx1, tx2, ... txn at which the camera settings can be changed are known to the physiological parameter determination unit 32 of the image evaluation unit 200. The evaluation algorithm used to determine physiological parameters based on the captured images can be temporarily stopped at the defined points in time tx1, tx2, ... txn, or the sensitivity of the evaluation algorithm can be reduced, for example, at the defined points in time tx1, tx2, ... txn. In this way, the impact caused by the change in camera settings can be significantly reduced. There is an interval of image parameter stability between two subsequent defined points in time tx1, tx2, ... txn (the image parameters / camera settings are stable), which significantly improves the accuracy of physiological parameter determination based on the captured images. The interval between two directly consecutive defined points in time tx1, tx2, ..., txn can be, for example, at least 10 seconds, at least 15 seconds, or at least 30 seconds. Generally, increasing the time between two directly consecutive defined points in time tx1, tx2, ... txn simplifies the internal structure of the noise. This makes it possible to more efficiently filter out unwanted noise.

[0025] As described above, the evaluation algorithm may depend on the fact that the camera settings are fixed over the interval between two consecutively defined points in time tx1, tx2, ..., txn. However, in general, it is also possible for the evaluation algorithm to compensate for any changes in the camera settings made at the defined points in time tx1, tx2, ..., txn. For example, the control unit 38 may provide the physiological parameter determination unit 32 with information regarding any changes made by the control unit to the camera settings. The physiological parameter determination unit 32 can then take this information into account when determining the physiological parameters. That is, in addition to the images captured by the camera 34, the camera system 30 can provide the physiological parameter determination unit 32 with additional information regarding the camera settings for further consideration when determining the physiological parameters.

[0026] Generally, it is possible to select the intervals between two continuously defined time points tx1, tx2, ... txn to be long. For example, the intervals between two directly consecutive time points tx1, tx2, ..., txn can be several minutes or even several hours. For example, the camera settings may not change at all throughout the driving session of the vehicle. The camera settings can be set once at the start of the driving session and maintained throughout the remaining driving. In this case, the camera settings can be considered constant. The automatic camera setting adjustment can be essentially disabled. Thus, the noise caused by the adjustment of the camera settings is completely removed. However, if the interval between two continuously defined time points tx1, tx2, ... txn is set too long, when the lighting conditions change frequently, significant underexposure and / or overexposure can occur in many images. Next, it may no longer be possible to accurately detect the head position of the target person and identify the target person by an appropriate face recognition algorithm. That is, when choosing a long time interval between two continuously defined time points tx1, tx2, ..., txn, certain drawbacks will need to be accepted.

[0027] The control unit 38 may, in some cases, be unable to provide information regarding changes in camera settings to the physiological parameter determination unit 32. In such cases, the image evaluation unit 200 may be configured to estimate changes made to the camera settings by means of an appropriate algorithm. The defined time points tx1, tx2, ... txn are further known. Thus, the image evaluation unit 200 may estimate the changes made to the camera settings by appropriately evaluating the images captured immediately before the defined time points tx1, tx2, ..., txn and the images captured immediately after the defined time points tx1, tx2, ..., txn. According to one example, the image evaluation unit 200 may comprise, or be coupled to, a near-infrared camera configured to generate a near-infrared flash. Such a flash is not visible to the person being targeted. However, the image evaluation unit 200 knows the characteristics of the artificial light generated to produce the flash. The reference object may be placed near the person being targeted. For example, a reference object of a defined color (e.g., white) may be attached to or integrated into the headrest of the vehicle 10. Next, the head of the driver 40 of the vehicle 10 is directly adjacent to such a reference object (e.g., a simple white circle on the headrest, or an entirely white headrest), and both the head of the person being targeted and the reference object (or at least one reference object) are captured in the image. The characteristics of the reference object (e.g., a specific color) are known to the image evaluation unit 200. Based on the known characteristics of the near-infrared flash, the known characteristics of the reference object, and the captured image, the image evaluation unit 200 may then determine the changes in the camera settings by means of an appropriate algorithm. In other words, the image evaluation unit 200 estimates the camera settings from the appearance of the reference object in the captured image (e.g., bright or dark). Instead of being on the headrest, the reference object may be placed on any other suitable element within the vehicle (e.g., on a part of the steering wheel visible in the image, or on a part of the seat backrest visible in the image, etc.).

[0028] As described above, the algorithms used to determine physiological parameters are capable of compensating for any changes in camera settings made at defined time points tx1, tx2, ..., txn. Examples of ways in which such compensation can be implemented are provided below. The effect of changes in camera settings is generally sufficiently predictable, at least to a first approximation. For example, doubling the exposure increases the total energy received by the light-receiving elements by a factor of two, which in turn doubles their average luminance. The same applies to gain control and iris aperture.

[0029] If the exposure value of frame f is E(f), the aperture is D(f), and the gain is G(f), their changes between frames f1 and f2 are determined by Equation (1) respectively.

Number

[0030] The total coefficient of variation of pixel luminance by adjustment (optimization) is determined by Equation (2).

Number

[0031] Depending on the configuration, if it is possible to obtain other parameters that affect the considered changes in exposure, aperture, gain, and pixel luminance, such parameters can be used to calculate the luminance correction factor. For an arbitrarily acquired pixel of an image P(x, y, f) having coordinates (x, y) in frame f, it is possible to obtain, for example, the luminance normalized with respect to the first frame of the video stream.

Number

[0032] As can be seen from the above formulas (1), (2), and (3), this normalization compensates for fluctuations in pixel luminance due to parameter adjustment, and the image stabilizes with respect to such fluctuations.

[0033] Possible extensions or generalizations of the compensation are as follows. - Instead of for the first frame, normalize with respect to another frame selected by the internal logic of the physiological parameter determination algorithm, for example, bound at the moment of algorithm calibration. - Periodic selection of frames for normalization (e.g., done when the reference frame for normalization is selected every 10 seconds). - As an extreme example of a previous extension, the inter-frame compensation when the difference between two consecutive frames is compensated is obtained by formula (4).

Number

Number

Number

[0034] The camera system 30 and the image evaluation unit 200 have been described above as being arranged in the vehicle 10. In the vehicle 10, physiological parameters of the driver 40 or any other passenger can be determined for different purposes, for example, to determine the mental state of the driver 40 (i.e., whether the driver 40 is suitable to drive). In the vehicle 10, the lighting conditions can change rapidly. However, in general, the camera system 30 and the image evaluation unit 200 can be used in an environment other than a vehicle.

[0035] According to an embodiment of the present disclosure, the method, as schematically shown in FIG. 5, includes capturing, by a camera 34, a series of consecutive images of a target person within the field of view of the camera 34 (step 501), determining the intensity of light on the target person (step 502), and controlling, by a control unit 38, the camera settings of the camera 34 based on the determined light intensity (step 503), wherein the camera settings of the camera 34 are changed only at defined time points tx1, tx2,... txn, and when it is detected that the intensity of light on the target object changes between two defined points of the time points tx1, tx2,... txn, the current camera settings are maintained until the next defined time points tx1, tx2,... txn.

[0036] The method may further include determining a change in pixel intensity of at least a defined target area of the captured image, and determining one or more physiological parameters of the target person based on the change in pixel intensity. The one or more physiological parameters can then be processed, and the mental state of the target person can be determined based on the physiological parameters. The one or more physiological parameters can include, for example, at least one of a heart rate and a heart rate variability.

[0037] It can be understood that the illustrated systems and methods are merely examples. Although various embodiments of the present invention have been described, it will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the present invention. In particular, those skilled in the art will recognize the interchangeability of various features from different embodiments. Although these technologies and systems are disclosed in the context of specific embodiments and examples, it is understood that these technologies and systems can be extended beyond the specifically disclosed embodiments to other embodiments and / or uses and their obvious modifications. Therefore, the present invention is not limited except as considered in the appended claims and their equivalents.

[0038] The description of the embodiments is presented for purposes of illustration and description. Appropriate modifications and variations to the various embodiments can be made in view of the above description, or obtained from practicing the method. The configurations described are exemplary in nature and can include additional elements and / or omit elements. As used in this application, elements recited in the singular and starting with the word "a" or "an" are to be understood as not excluding their plurals unless otherwise stated to exclude them. Further, references to "one embodiment" or "one example" of the present disclosure are not intended to be construed as excluding the existence of additional embodiments that also incorporate the recited features. Terms such as "first", "second", and "third" are used merely as labels and are not intended to impose numerical requirements or an order of particular positions on those objects. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions, and / or characteristics disclosed. The following claims specifically point out the subject matter regarded as novel and non-obvious from the above disclosure.

Claims

1. A camera system (30) comprising a camera (34) and a control unit (38), wherein the camera (34) is configured to capture a series of consecutive images of a target person within the field of view of the camera (34), the camera system (30) is configured to determine the intensity of light on the target person, the control unit (38) is configured to control the camera settings of the camera (34) based on the intensity of light determined by the camera system (30), the control unit (38) is configured to change the camera settings of the camera (34) only at defined points in time (tx1, tx2,..., txn), and when it is detected that the intensity of light on the target object changes between two defined points in time (tx1, tx2,..., txn), the current camera settings are maintained until the next defined point in time (tx1, tx2,..., txn), the camera system (30).

2. The camera system (30) according to claim 1, wherein the interval between two directly consecutive defined points in time (tx1, tx2,..., txn) is at least 10 seconds, at least 15 seconds, or at least 30 seconds.

3. The camera system (30) according to claim 1 or 2, wherein the camera settings controlled by the control unit (38) include at least one of an exposure time and an F-value.

4. An image evaluation unit (200), comprising the camera system (30) according to claim 1, and a physiological parameter determination unit (32), wherein the physiological parameter determination unit (32) is configured to determine a change in pixel intensity of at least a defined target area of the image captured by the camera system (30), and to determine one or more physiological parameters of the target person based on the change in pixel intensity, the image evaluation unit (200).

5. The image evaluation unit (200) according to claim 4, wherein the one or more physiological parameters determined by the physiological parameter determination unit (32) include at least one of a heart rate and a heart rate variability.

6. The physiological parameter determination unit (32) is configured to determine the one or more physiological parameters by an evaluation algorithm, and the algorithm is temporarily stopped at the defined time points (tx1, tx2,..., txn), or the sensitivity of the algorithm is reduced at the defined time points (tx1, tx2,..., txn). The image evaluation unit (200) according to claim 4 or 5.

7. The physiological parameter determination unit (32) receives the image captured by the camera (34) of the camera system (30). The physiological parameter determination unit (32) further receives information regarding the changes made by the control unit (38) to the camera settings at the defined time points (tx1, tx2,..., txn) from the control unit (38) of the camera system (30). The evaluation algorithm compensates for the changes in the camera settings made at the defined time points (tx1, tx2,..., txn). The image evaluation unit (200) according to claim 6.

8. The physiological parameter determination unit (32) receives the image captured by the camera (34) of the camera system (30). The image evaluation unit (200) is configured to estimate the changes made by the control unit (38) to the camera settings at the defined time points (tx1, tx2,..., txn). The evaluation algorithm compensates for the changes in the camera settings made at the defined time points (tx1, tx2,..., txn). The image evaluation unit (200) according to claim 6.

9. The image evaluation unit (200) is configured to estimate the changes made to the camera settings by evaluating the image captured immediately before the defined time points (tx1, tx2,..., txn) and the image captured immediately after the defined time points (tx1, tx2,..., txn). The image evaluation unit (200) according to claim 8.

10. The image evaluation unit (200) is arranged in a vehicle (10), and the target person is the driver (40) of the vehicle (10). The image evaluation unit (200) according to claim 4.

11. The camera (34) captures a series of consecutive images of a target person within the field of view of the camera (34), determines the intensity of light on the target person, and the control unit (38) controls the camera settings of the camera (34) based on the determined light intensity, wherein the camera settings of the camera (34) are changed only at defined times (tx1, tx2,..., txn), and when it is detected that the intensity of the light on the target object changes between two defined times (tx1, tx2,..., txn), the current camera settings are maintained until the next defined time (tx1, tx2,..., txn).

12. determining a change in pixel intensity within at least a defined target area of the captured image, determining one or more physiological parameters of the target person based on the change in pixel intensity, The method according to claim 11, further comprising:

13. processing the one or more physiological parameters, determining the mental state of the target person based on the physiological parameters, The method according to claim 12, further comprising:

14. The method according to any one of claims 11 to 13, wherein the one or more physiological parameters include at least one of a heart rate and a heart rate variability.

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