WO2017088963A1

WO2017088963A1 - Method and device for reducing a brightness of an object perceivable by a passenger of a vehicle

Info

Publication number: WO2017088963A1
Application number: PCT/EP2016/001920
Authority: WO
Inventors: Jürgen Röder
Original assignee: Jürgen Röder
Priority date: 2015-11-23
Filing date: 2016-11-18
Publication date: 2017-06-01

Abstract

The inventive method for reducing a brightness of an object perceivable by a passenger of a vehicle through a screen comprises the steps of determining a degree of tiredness T of the passenger, determining a hazard parameter H characteristic of a hazard potential related to a situation of the vehicle and/or the passenger, monitoring the occurrence of a glare situation and, when a glare situation is detected, reducing a transmittance of the screen in at least a part of the screen, wherein the reduction of transmittance depends on the degree of tiredness T of the passenger and on the hazard parameter H, and wherein the hazard parameter H is determined based on a degree of autonomy of the vehicle. The invention also relates to a device for reducing a brightness of an object perceivable by a passenger of a vehicle.

Description

Method and Device for Reducing a Brightness of an Object Perceivable by a

Passenger of a Vehicle

The present invention relates to a method for reducing a brightness of an object perceivable by a passenger of a vehicle through a screen. The present invention further relates to a corresponding device for reducing a brightness of an object.

In DE 198 14 094 Al a method and a device for darkening a transparent screen are disclosed, the device having selectively electrically controllable darkening elements for darkening the screen in a passage region of a disturbing source. A position of the disturbing source and an eye position of a person are determined for calculating the passage region on the screen.

According to DE 10 2014 203 321 Al a glare protection device in a vehicle comprises at least one transparent layer with a multiplicity of elements, the transmittance of which is separately alterable. In a method for selectively reducing the light from a glare source for an eye of an observer an element is selected such that it is on a light trajectory from the glare source to a predicted eye position of the observer, and the light transmittance of the selected element is reduced. In DE 10 2005 007 427 Al a motor vehicle is disclosed that comprises a windscreen having segments having adjustable transparency, and a glare sensor for measuring an eyelid position and/or a pupil size of a passenger of the vehicle. The vehicle further comprises a control for automatically adjusting the transparency of a segment of the screen depending on an output signal of the glare sensor.

DE 10 2012 100 698 Al discloses a method and a driver assistance system for detecting tiredness and/or for evaluating the attention of a driver of a vehicle. In the method or system a distance and/or a relative speed to a vehicle running ahead is taken into account. GB 2 421 828 A discloses a traffic hazard management system for a vehicle that comprises a hazard management processor, sources of information feeding the hazard management processor, a communications system for wirelessly communicating with sources of data, and a communications system for communicating with other vehicles. The processor is capable of sending signals for controlling the travel of the vehicle and of sending alert signals to a driver of the vehicle. Passenger related risk factors include drowsiness of the driver.

According to US 2013/0286177 Al, in a localized glass glare reduction a processor is to determine a head position of a person, to determine a field of view of the person in response to the determined head position, to identify areas of brightness in the field of view of the person, and to dim the areas of brightness in the field of view of the person in a localized manner. US 2009/0027759 Al discloses an automatic electronic shading system comprising light sensors and a display element attached to a part of a transparent body and a control unit controlling the operation of the display element. As described in DE 10 2005 015 960 Al, a glare protection device of a front screen of a motor vehicle comprises a sensor device for detecting incident light and a device on the front screen having a multiplicity of segments that can be switched between transparent and opaque. Further, an eye position detection device is provided, and such a segment is darkened that is located between a light source and the eye position of the driver. Presently known glare protection methods and devices in vehicles, however, have proven not optimal in relation to comfort and/or safety.

It is an object of the present invention to provide an improved method for reducing a brightness of an object perceivable by a passenger of a vehicle through a screen, in particular a method that provides enhanced comfort and/or safety. Further it is an object of the invention to provide a corresponding improved device for reducing the brightness of an object perceivable by a passenger of a vehicle. These objects are met by a method according to claim 1 and by a device according to claim 15.

According to the present invention a brightness of an object as perceivable by a passenger of a vehicle can be reduced. The vehicle may be, for example, a car or another kind of motor vehicle such as a motor coach, a boat or an airplane. In particular, the vehicle is configured for at least partially autonomous operation. The term "passenger" in the following means any passenger of the vehicle, which may be a person controlling the vehicle such as the driver of a car or a boat or the pilot of an airplane. The term "passenger" may as well denote any other passenger of the vehicle, for ex- ample a co-driver or a co-pilot, or any other front or rear passenger. The present invention may also be employed to reduce the brightness of an object perceivable by several passengers, for example by the driver and the co-driver of a car, or by several passengers of a motor coach. The object the perceivable brightness of which is to be reduced may be an object within a scene viewed by the passenger, in particular an object seen in front of the vehicle, such as the headlights of an oncoming car seen by a car driver. The object typically is a light source bright enough to dazzle the passenger; such an object is also denoted a "glare source". The object is perceivable by the passenger through a screen. The vehicle may comprise a multiplicity of screens through one of which the object is perceived by the passenger. The screen in particular is a windscreen of the vehicle or a layer on an inner or outer side of the windscreen, through which a scene in front of the vehicle is observed by the passenger. The screen may as well be any other front, side or rear window or a glass sunroof of the vehicle or a layer of such a window or sunroof. The screen is electrically controllable to alter its transmission at least in a part of the screen. Such screens are known and comprise, for example, a screen or layer of electrochromic glass or a liquid crystal layer or some other kind of electrically switchable smart glass. A glare source shining through a side window into a vehicle may glare the passenger although it is not necessarily part of the scene observed. A glare source may also shine into the passenger's eyes through a rear- view mirror and dazzle the passenger. A glare effect may even be due to bright light from a diffuse source, which is here also comprised by the term "object".

According to the present invention a degree of tiredness of the passenger is determined. Methods for automatically detecting tiredness are known in themselves. Alternatively, the degree of tiredness may be entered manually. The degree of tiredness may be characterized by a tiredness parameter. In a simple case, the tiredness parameter may be taken to be 0 if there is no indication of tiredness of the passenger, and 1 if there is any such indication. The tiredness parameter may as well be defined to have a variety of values providing a quantitative measure of the degree of tiredness of the passenger. Preferably, the degree of tiredness is monitored continuously or at a repetition rate of a few seconds or minutes and stored to be immediately available.

Moreover, a parameter is determined that is characteristic of a hazard potential related to a situation of the vehicle and/or the passenger. This parameter is denoted "hazard parameter" in the following. The hazard parameter may be characteristic of a degree of attention required to control the vehicle in that situation, which degree of attention in the following also is comprised by the term "hazard". In particular, the hazard parameter may be determined to represent a likelihood of occurrence of an incident and/or a severity of an incident that may occur due to incorrect or insufficient reaction of the driver of the vehicle, for example caused by impeded recogni- tion of objects in front of the vehicle due to the glare situation and/or caused by delayed reaction by the driver in case of tiredness. The hazard parameter may take account of, for example, a risk of injury of the passenger and/or other persons in the current situation of the vehicle. The hazard parameter may be pre-determined or may be evaluated based on sensor signals that characterize the situation of the vehicle and/or the passenger. Preferably the hazard parameter is evaluated continuously based on such sensor signals.

Further, according to the present invention, the occurrence of a glare situation is monitored. In the following, the term "glare situation" in particular means a situation or an event in which the passenger is being glared or in which due to sensor signals or other information it is considered likely that the passenger feels glared. Such a glare situation may be due to a glare source shining into the eyes of the passenger, for example a bright object shining up in the scene viewed by the passenger through the screen. A glare situation may be detected automatically, for example by means of one or several optical or other sensors, or by a signal from a manual control element that can be operated by the passenger. Preferably, parameters and/or sensor signals that are indicative of a glare situation are continuously monitored and evaluated in order to detect a glare situation with minimal delay.

When a glare situation is detected, a transmittance of the screen in at least a part of the screen is reduced to reduce the object's brightness perceivable by the passenger. I.e., in response to the glare situation, preferably immediately after detecting the glare situation, the screen is controlled for reducing its transmittance in at least such a part of the screen that the brightness of the object perceivable by the passenger is reduced. In this way, a glare source can be darkened in the perception of the passenger to protect the passenger against being glared. If the vehicle comprises a multi- plicity of screens, transmittances of more than one screen may be reduced. Preferably, when it is detected that the glare situation no longer persists, the screen transmittance is controlled to return to normal or initial transmittance, which usually is the maximal transmittance of the screen. According to the present invention, the reduction of transmittance depends on the degree of tiredness of the passenger and on the hazard parameter. In particular, a degree of reduction of transmittance of the screen with respect to its normal or initial transmittance is chosen in accordance with the degree of tiredness as currently determined, and in accordance with the hazard parameter. The darkening of at least the part of the screen may depend on one or more further parameters. At least for one combination of parameters, the reduction of transmittance is thus chosen different for different degrees of tiredness, and different for different values of the hazard parameter.

Further according to the invention, the hazard parameter is determined based on a degree of autonomy of the vehicle. In fully autonomous driving, no action by the driver of a vehicle is required for controlling the vehicle. On the other hand, in non- autonomous driving, the vehicle is under full driver control. The degree of autonomy of the vehicle characterizes the degree to which driver control currently is exerted for operating the vehicle. The passenger may be identified to be a driver, a co-driver, or another passenger of the vehicle. If the passenger is the driver, the hazard parameter depends on the degree of control that currently is exerted by the driver on the vehicle, the hazard parameter having a higher value at a higher degree of control, i.e. a lower degree of autonomy, and a lower value at a lower degree of control, corresponding to a higher degree of autonomy. If the passenger is a co-driver or another passenger who has no control of the vehicle, the hazard parameter typically is lower than that of the driver. The hazard parameter may take account of other parameters related to the situation of the vehicle and/or the passenger.

By darkening the screen depending on the tiredness of the passenger account can be taken of the fact that the perception of glare by a human depends on fatigue. A dark- ening that is adequate for a person in normal or alert condition may not be optimal if the person is tired. In particular, a tired passenger may feel uncomfortable with a degree of darkening that would be suitable in normal condition. The present invention thus permits controlling the screen to increase the passenger's viewing comfort. Similarly, distraction of a driver by a glare source may depend on the degree of tiredness of the driver, and thus safety may be increased by taking account of the driver's tiredness. Further, consideration of the hazard parameter in determining the reduction of transmittance of the screen permits controlling the screen to minimize risk due to glare and/or tiredness in potentially hazardous situations, while in less hazardous situations the screen can be controlled to optimize comfort. Furthermore, an increase of tiredness which may be supported by darkening of the screen can be avoided. By darkening the screen depending on the hazard parameter, the hazard parameter taking account of the degree of autonomy of the vehicle, essential parameters bearing on the risk of operating the vehicle can be taken into account such that, for example, the screen transmission is controlled to minimize risk at high speed under driver control, while the screen can be controlled to maximize comfort in case of highly autonomous driving controlled by a driver assistance system. This aspect of the invention is particularly advantageous if the passenger is the driver or co-driver of the vehicle. The present invention therefore provides an anti-glare method that permits increasing comfort and/or safety.

The degree of tiredness may be determined, for example, based on physiological parameters such as pulse frequency and/or blood pressure, on electroencephalograph- ic data, on other sensor data and/or on a pattern and/or frequency of willful actions taken by the passenger. In an advantageous manner, the degree of tiredness T of the passenger is determined by means of one or more wearable devices. In particular, relevant parameters and/or data may be captured by a smartwatch, by an activity tracker, by smartglasses, by smart clothing or other wearable devices or by in-ear phones, and transmitted to a control unit for evaluation. In this way, relevant parameters and/or data that can be employed for determining the degree of tiredness of the passenger can be captured without limiting the passenger's ability to move or reducing the passenger's comfort.

According to a preferred embodiment of the invention, the degree of tiredness of the passenger is determined by registering and evaluating a pattern and/or a frequency of eye and/or eyelid movements of the passenger and/or on a pupil diameter of the passenger and/or on an eyelid position of the passenger. Data on eye and/or eyelid movements and/or pupil diameter and/or eyelid position may be registered by means of a camera observing the passenger's eyes. In particular, if the pupil diameter is smaller than is to be expected with respect to a light intensity shining into the pas- senger's eyes, this may be taken as an indication of tiredness. In this way, a simple determination of tiredness is made possible, which may be based on optical sensors only. Preferably, the glare situation is detected based on a light intensity of the object or another glare source shining on the passenger's eyes and/or on an angular or surface brightness of the object, which can be detected, for example, by a light sensor or by evaluating an image received by a camera. Such light intensity employed for detecting the glare situation is denoted "glare light intensity" in the following. The light sensor and/or the camera can be advantageously placed in the vehicle, close to the passenger's eyes or on the screen. Alternatively or additionally, the glare situation may be detected by registering and evaluating a pattern and/or a frequency of eye movements of the passenger and/or on a pupil diameter of the passenger. Such data may be registered by means of a camera observing the passenger's eyes. In this way the glare situation can be detected reliably and with a simple sensor arrangement, possibly with the same sensor arrangement that is provided for determining the degree of tiredness of the passenger.

If the glare situation is detected in a way which is independent from the transmission of the screen, such as by a light sensor or a camera placed outside the screen, an end of the glare situation can be detected by a corresponding decrease of the glare light intensity. If the glare situation is detected by a sensor or a camera receiving light through the screen, a corresponding correction may be made. If the glare situation is detected based on observing the passenger's eyes, after some time the screen may be controlled to gradually return to initial transmittance and the passenger's eye monitored to detect whether the glare situation persists.

The vehicle may comprise a multiplicity of screens through which an object may be perceivable by the passenger. The screen, the transmittance of which is reduced, may be predetermined, depending on the passenger, such as the windscreen if the passenger is the driver of the vehicle. Preferably, however, the screen is selected out of the multiplicity of screens depending on a position of a glare source with respect to the passenger. In particular, if the object is a glare source, the glare source is detected, a line of sight from the passenger's eyes to the glare source is determined, and the screen is selected out of the multiplicity of screens such that the selected screen comprises a passage point of the line of sight through the screen. In this case, the transmittance of the selected screen is reduced in at least a part of the screen as described above. In a car or a motor coach, for example, a passenger may be dazzled by a glare source shining through one or another one of the windows of the car or the motor coach. By reducing the transmission of that window screen through which the glare source shines on the passenger, comfort can be increased while maintaining unimpeded view through the other windows.

According to a preferred embodiment, the transmittance of the screen is reduced in substantially an entire area of the screen or in a predetermined partial area of the screen, for example in an upper part of the screen. In this way the passenger and oth- er passengers can be protected reliably and comprehensively against being dazzled by any kind of bright light shining through the screen.

According to a further preferred embodiment of the invention, if the object is a glare source, the glare source is detected, a passage point of a line of sight from the pas- senger's eyes to the glare source through the screen is calculated and the transmittance of the screen is reduced in a partial area of the screen that encompasses the passage point. The partial area includes the passage point and may comprise a predetermined radius or area surrounding that point. In particular, the direction to the center of the glare source is determined and the passage point is determined to be that point in which the line of sight from the middle point between the passenger's eyes to the center of the glare source passes through the screen. This embodiment is particularly advantageous if the glare source has an angular size that is small as compared to the angular size of the screen, as viewed by the passenger. In such a case the glare effect due to the glare source may be largely avoidable, while the passenger maintains substantially unimpeded sight to other parts of the scene. Advantageously, the reduction of transmittance depends in such a way on the degree of tiredness of the passenger that the darkening generally is higher when the degree of tiredness is higher. This does not exclude that under certain circumstances the reduction of transmittance is the same for different degrees of tiredness or even is lowered with increasing degree of tiredness. In this way account can be taken of the fact that a sensitivity of being glared increases with the degree of tiredness, such that an increased level of comfort and safety can be achieved.

According to a particularly preferred embodiment of the invention, the degree of reduction of transmittance is increased if the degree of tiredness increases. I.e. the at least partial darkening of the screen is intensified if an increased tiredness of the passenger is detected. Alternatively or additionally, there may be a glare threshold relating to a light intensity, the transmittance of the screen being reduced if the light intensity exceeds the glare threshold, and the glare threshold is reduced if the degree of tiredness increases. I.e. the at least partial darkening is switched on at a lower level of glare light intensity if an increased tiredness of the passenger is found. The glare light intensity may be measured by an optical sensor or a camera. If another parameter is employed for detecting a glare situation, such as a reduction of pupil parameter, the glare threshold may as well relate to that other quantity and be reduced in a simi- lar manner. Thus a simple and effective method for reducing a glare effect is provided.

In addition to the hazard parameter being determined based on a degree of autonomy of the vehicle, advantageously the hazard parameter may be determined based on an overall light intensity, for example in order to take account of a difference between day and night driving, and/or the hazard parameter may depend on a current velocity of the vehicle and may be chosen to increase with increasing velocity, and/or the hazard parameter may depend on a situation of the passenger who may be identified to be a driver, a co-driver, or another passenger of the vehicle. If the vehicle is a car or a motor coach, the hazard parameter may depend on a condition of the road on which the vehicle is driving or on the class of the road. For example, the hazard parameter may be generally higher on a single-lane or double-lane road than on a dual carriageway. The data evaluated for determining the hazard parameter may be provided by corresponding sensors or by a control system of the vehicle. In this way, further parameters bearing on the risk of operating the vehicle can be taken into account such that, for example, the screen transmission is controlled to minimize risk at high speed, while the screen can be controlled to maximize comfort at low speed or at rest of the vehicle.

Preferably, the reduction of transmittance depends in such a way on the hazard parameter that the darkening generally is lowered when the hazard is higher. This does not exclude that under certain circumstances the reduction of transmittance is the same for different values of the hazard parameter. In this way account can be taken of the fact that in case of a potentially hazardous situation safety can be increased by controlling the screen transmission accordingly. According to a particularly preferred embodiment of the invention, the degree of reduction of transmittance is lowered if the hazard parameter indicates an increased hazard. I.e. the at least partial darkening of the screen is reduced if the situation involves a higher hazard or, which as mentioned is comprised by this term, an increased level of attention required. Alternatively or additionally, there may be a glare threshold relating to a light intensity, the transmittance of the screen being reduced if the light intensity exceeds the glare threshold, and the glare threshold is increased if the hazard increases. I.e. the at least partial darkening is switched on only at a higher level of light intensity if the situation is more hazardous. The glare threshold may as well relate to another quantity indicative of the glare situation, in which case the glare threshold is reduced in a similar manner. In this way account can be taken of the fact that a perception of objects viewed in a scene in front of the vehicle by the driver of the vehicle needs to be maintained or improved in case of a potentially hazardous situation. According to a particularly preferred embodiment of the invention, the reduction of transmittance of at least part of the screen depends in such a way on the degree of tiredness of the passenger and on the hazard parameter that in case of high hazard there is no darkening of the screen or only a reduced darkening, while in case of low hazard the darkening of the screen is controlled in a way to optimize comfort by reducing or avoiding the glare effect. This can be achieved, in particular, by reducing the degree of reduction of transmission and/or by raising the glare threshold, as de- scribed above, depending on the hazard parameter. There may be a predefined hazard threshold, and when the hazard parameter exceeds the hazard threshold the degree of reduction of transmission is lowered and/or the glare threshold is increased. Most preferably, the degree of reduction of transmittance is only increased and/or the glare threshold is only reduced if the hazard parameter is less than the predefined hazard threshold. In this way a glare protection method is provided that not only improves the passenger's comfort, but also reduces risk due to reduced vision or increased tiredness, in particular if the passenger is the driver of a vehicle. The reduced or switched-off darkening of the screen may even serve to increase attention of the driver by increasing the total light intensity shining into the driver's eyes.

According to a preferred embodiment of the invention, the reduction of transmittance depends on a personal sensitivity function and/or on one or more passenger-specific threshold values. Preferably, the degree of reduction of transmittance and/or the glare threshold as described above are calculated based on personalized data of the pas- senger, who in particular is the driver of the vehicle. Such personalized function and/or threshold values may be pre-defined or be continuously adapted due to reactions of the passenger registered by sensors, for example by the optical sensors for measuring eye movements and/or pupil diameter. In this way further improvements of comfort and safety are achievable.

Preferably, the passenger is alerted at or before the end of a period of a high degree of autonomy of the vehicle and/or at or before arrival at a destination of the vehicle. The end of highly autonomous driving may be determined based on geographical data stored in a control unit, combined with current position data as derived by a global positioning system receiver, for example. The same pertains to arrival at a destination of a trip of the vehicle, with corresponding position data being stored in the control unit. At or a short time period before the end of highly autonomous driv- ing or the arrival at the destination, an alert signal is generated perceivable by the passenger. For example, about 1 min or less before the end of a phase of high autonomy or before arrival, the signal may be generated, alerting the passenger. The signal may be an acoustic signal, an optical signal, or a vibration alarm, for example. In particular, if the passenger is the driver, the alert signal serves to increase attention of the driver after a period of low attention to enable the driver to resume increased control of the vehicle. Thus, for example, a short time period before the vehicle will leave a dual carriageway and enter on a single- or double-lane road, the driver is alerted by means of the alert signal. Regardless of whether the passenger is the driver or another passenger than the driver, the alert signal may be generated a short time period before arrival in order to enable the passengers of the vehicle to prepare for leaving the vehicle. In this way, further increased safety and/or comfort may be achieved. If more than one passenger is present in the vehicle, the above mentioned steps may be performed for one or more of the passengers. In this case, preference may be given to the driver of the vehicle. Thus the transmittance of one or more screens through which objects are perceivable by the driver may be controlled according to the above described method with the passenger being the driver. On the other hand, the trans- mittance of screens irrelevant to the driver's perception may be reduced relating to one or more other passengers that are not actively controlling the vehicle. In a motor coach, for example, the front screen and/or the front side windows may be darkened if a glare situation pertaining to the driver is detected and depending on a degree of tiredness of the driver only, while the rear side windows and/or a glass sunroof may be darkened depending on a glare situation and a degree of tiredness of one or more rear passengers.

According to a particularly preferred embodiment of the invention, the above mentioned steps are performed relating to the driver of the vehicle. Thus, the screen is a screen allocated to the driver, i.e. a screen usable by the driver to view objects outside the vehicle, in particular a screen through which a light source, which may be a glare source, is perceivable by the driver. The driver may be assumed to be any per- son on a driver's seat of the vehicle. The screen may be, for example, a windscreen, a front side window or a rear window of the vehicle. As mentioned above, depending on a position of a glare source with respect to the driver, the screen may be selected out of a set of screens comprising the windscreen, at least one front side window and a rear window of the vehicle. A degree of tiredness T of the driver is determined, and a hazard parameter characteristic of a hazard potential related to a situation of the vehicle and/or the driver is determined. The occurrence of a glare situation is monitored and, when a glare situation relating to the driver is detected, a transmittance of the screen in at least a part of the screen allocated to the driver is reduced, wherein the reduction of transmittance depends on the degree of tiredness of the driver and on the hazard parameter, and wherein the hazard parameter depends on a degree of control of the vehicle currently exerted by the driver in driving the vehicle.

Moreover, according to this embodiment of the invention, a degree of tiredness of a further passenger of the vehicle is determined, the further passenger generally being any passenger that is not on the driver's seat of the vehicle or that has no control over the vehicle. Further, occurrence of a glare situation relating to the further passenger is monitored and, when a glare situation relating to the further passenger is detected, a transmittance of a screen allocated to the further passenger is reduced in at least a part of the screen, wherein the reduction of transmittance of the screen allocated to the further passenger depends on the degree of tiredness of the further passenger. The screen is a screen through which the further passenger can view objects outside the vehicle and, in particular, through which a glare source may be perceived by the further passenger. Preferably the screen is not a screen that is also allocated to the driv- er; if the screen also can be used by the driver for perceiving objects outside the vehicle, the transmittance of the screen preferably is reduced depending on the detection of a glare situation relating to the driver and on the degree of tiredness of the driver, not having regard to a glare situation relating to the further passenger or a degree of tiredness of the further passenger. The reduction of transmittance may or may not depend on a hazard parameter determined with respect to the further passenger, the hazard parameter being typically lower than that determined with respect to the driver. For example, a trip may comprise autonomous and non-autonomous driving phases. In a non-autonomous driving phase, the hazard parameter relating to the driver may be comparatively high. In such a period the windscreen and other screens may be darkened as described above, employing a comparatively low reduction of transmit- tance, while screens not relevant to the driver's vision may be darkened employing a higher reduction of transmittance. In a period of highly autonomous driving, the higher reduction of transmittance may be employed with respect to all screens of the vehicle. In this way comfort of the passengers can be further increased without af- fecting safety of driving.

According to a further aspect of the invention a device for reducing a brightness of an object perceivable by a passenger of a vehicle comprises a screen having electronically controllable transmittance, a passenger tiredness detection device, a glare sit- uation detection device and a control unit. The control unit is configured for determining a degree of tiredness of the passenger and, when a glare situation is detected, controlling the screen to reduce the transmittance of the screen in at least a part of the screen depending on the degree of tiredness of the passenger. Further, the device is configured for determining a hazard parameter based on data provided, in particular, by the vehicle control system, the hazard parameter being determined based on a degree of autonomy of the vehicle, and for controlling the reduction of transmittance depending on the degree of tiredness and on the hazard parameter. The vehicle may be, for example, a car or another kind of motor vehicle, a boat or the airplane, being configured for at least partially autonomous operation. In particular, the vehicle may be equipped with a driver assistance system for at least partially autonomous driving. The passenger preferably is the driver of the car or boat or the pilot of an airplane. The screen preferably is a windscreen or front window or a side or rear window or a glass sunroof of the vehicle through which light from light sources outside the vehicle can shine into the passenger's eyes. The screen is electronically controllable by the control unit to alter the transmission at least of part of the area of the screen. The screen may be or comprise, for example, electrically switchable smart glass such as electrochromic glass or have a liquid crystal layer to electronically control the trans- mission of the screen. The vehicle may comprise more than one such electronically controllable screen. The passenger tiredness detection device preferably comprises a sensor arrangement, in particular an arrangement of one or more optical sensors directed towards the eyes of the passenger who may be the driver of the vehicle. The glare detection device preferably comprises an arrangement of one or more optical sensors, for example a camera arranged for viewing a scene in front of the vehicle. The control unit is configured for controlling the transmission of the screen. The control unit may also be configured for evaluating data provided by sensors of the passenger tiredness detection device and by sensors of the glare detection device and/or by a vehicle control system to determine the degree of tiredness of the passenger and to detect a glare situation. The screen, the passenger tiredness detection device, the glare situation detection device, and the control unit are preferably arranged on or within the vehicle. The control unit may be part of a vehicle control system. Preferably, the device is configured for executing the above described method for reducing the brightness of an object perceivable by a passenger of the vehicle. Most preferably, the device is configured for executing the above described method, the passenger being the driver of the vehicle, and for determining a degree of tiredness of a further passenger of the vehicle, for monitoring the occurrence of a glare situation relating to the further passenger and, when a glare situation relating to the further passenger is detected, for reducing a transmittance of a screen allocated to the further passenger in at least a part of the screen, wherein the reduction of transmittance of the screen allocated to the further passenger depends on the degree of tiredness of the further passenger.

The features of the invention as mentioned above and as described below apply not only in the combinations mentioned but also in other combinations or alone, without leaving the scope of the present invention. Further aspects of the present invention will be apparent from the figure and from the description of a particular embodiment that follows. Fig. 1 shows a flow diagram of a method according to a preferred embodiment of the invention.

As shown in Fig. 1, in a simple embodiment of the present invention in a normal state the screen has high transmission. The screen may be, for example, a windscreen of a car. Data from a control system of the car are continuously evaluated in order to determine and update a hazard parameter H. The hazard parameter H in the simple example shown has only two possible values, which are H = 0 in case of autonomous driving controlled by a driver assistance system or in case of standstill of the vehicle for more than a few minutes, and H = 1 in all other cases. Moreover, data from a camera arrangement observing the driver's eyes are continuously evaluated to determine a degree of tiredness T of the driver, which, in the simple case described here, only has two values. If an indication of tiredness is detected or an increased degree of tiredness is manually indicated, the degree of tiredness is set to

T = 1 . Such indication of tiredness may be, for example, changes in a pattern or frequency of eye movements or a reduced pupil diameter as compared to the light intensity impinging on the driver's eyes, or changes in physiological parameters detected by a wearable device of the driver. If no such indication is found, the degree of tiredness is set to

T = 0 , i.e. the driver is assumed to be alert.

Further, data from a scene camera observing a scene in front of the car, the camera being placed outside the screen, are continuously evaluated for detecting a glare situation. Such a glare situation is detected, for example, if the total registered light intensity and/or the light intensity originating from an angular region typically corresponding to the headlights of an oncoming car exceeds a pre-determined glare threshold. ,

If a glare situation has been detected, the degree of tiredness T of the driver and the hazard parameter H are checked in order to control the screen transmission accordingly. If there is no indication of tiredness, i.e.

T = 0 , the screen transmission is set to an intermediate value. In particular, the screen transmission may be reduced substantially uniformly to an intermediate value. Thus, in response to the glare situation, the screen is darkened in order to reduce or avoid the driver being glared. If the driver is tired, i.e.

T = 1 and the hazard parameter H = 0 indicates that the vehicle is in extended standstill or the vehicle is being moved under control of a driver assistance system, the screen transmission is set to a low value in order to further reduce the glare effect. In this way, account is taken of the increased sensitivity for glare light when the driver is tired. Thus, the driver's comfort can be increased. Moreover, the hazard parameter indicates that currently not a high level of recognition of objects in front of the vehicle is required. On the other hand, if the driver is tired

T = 1 and the hazard parameter is H = l , i.e. the driver is driving the vehicle under full driver control and the vehicle currently is moving, the screen transmission is also set to the intermediate value. The aforementioned steps are regularly repeated. When the camera signal indicates that the light intensity no longer exceeds the glare threshold, the transmission is set to its initial value, which is high transmission.

At the same time, a further screen that is not relevant to the driver's perception of objects outside the vehicle may be darkened upon detection of a glare situation relevant to a further passenger that can perceive the glare source through the further screen. For such a glare detection a dedicated camera placed outside the further screen may be provided. The transmission of the further screen is reduced depending on a degree of tiredness of the further passenger of the vehicle, which may be determined in a similar manner as mentioned above with respect to the driver. The reduction of transmission of the further screen may be independent of the degree of tiredness T of the driver and the hazard parameter determined as described above.

In this way, comfort of the driver can be improved in glare situations, without reducing safety.

Claims

1. Method for reducing a brightness of an object perceivable by a passenger of a vehicle through a screen, comprising the steps of determining a degree of tired- ness T of the passenger, determining a hazard parameter H characteristic of a hazard potential related to a situation of the vehicle and/or the passenger, monitoring the occurrence of a glare situation and, when a glare situation is detected, reducing a transmittance of the screen in at least a part of the screen, wherein the reduction of transmittance depends on the degree of tiredness T of the passenger and on the hazard parameter H, and wherein the hazard parameter H is determined based on a degree of autonomy of the vehicle.

2. Method according to claim 1, characterized in that the degree of tiredness T of the passenger is determined by means of one or more wearable devices and/or the degree of tiredness T of the passenger is determined based on a pattern and/or frequency of eye movements of the passenger and/or on a pupil diameter of the passenger and/or on an eyelid position of the passenger.

3. Method according to claim 1 or 2, characterized in that a glare source is detect- ed, a line of sight from the passenger to the glare source is determined, and the screen is selected out of a multiplicity of screens of the vehicle to comprise a passage point of the line of sight.

4. Method according to any one of the preceding claims, characterized in that the transmittance of the screen is reduced in substantially an entire area of the screen or in a predetermined part of the screen area.

5. Method according to any one of claims 1-3, characterized in that a glare source is detected, a passage point of a line of sight from the passenger to the glare source through the screen is determined and the transmittance of the screen is reduced in a part of the screen encompassing the passage point.

6. Method according to any one of the preceding claims, characterized in that a degree of reduction of transmittance is increased if the degree of tiredness T increases.

7. Method according to any one of the preceding claims, characterized in that the transmittance of the screen is reduced if a light intensity exceeds a glare threshold and that the glare threshold is reduced if the degree of tiredness T increases.

8. Method according to any one of the preceding claims, characterized in that in determining the hazard parameter H account is taken of an overall light intensity, a velocity of the vehicle and/or a situation of the passenger.

9. Method according to any one of the preceding claims, characterized in that a degree of reduction of transmittance is reduced if the hazard parameter H indicates an increased hazard.

10. Method according to any one of the preceding claims, characterized in that the transmittance of the screen is reduced if a light intensity exceeds a glare threshold and that the glare threshold is raised if the hazard parameter H indicates an increased hazard.

11. Method according to claim 9 or 10 in combination with claim 6 or 7, characterized in that the degree of reduction of transmittance is only increased and/or the glare threshold is only reduced if the hazard parameter H is less than a hazard threshold.

12. Method according to any one of the preceding claims, characterized in that the reduction of transmittance depends on a personal sensitivity function and/or one or more threshold values specific to the passenger.

13. Method according to any one of the preceding claims, characterized in that the passenger is alerted at or before the end of a period of high autonomy of the vehicle and/or at or before arrival at a destination.

14. Method according to any one of the preceding claims, characterized in that the passenger is the driver of the vehicle, that the screen is a screen allocated to the driver, and the glare situation is a glare situation relating to the driver, wherein further a degree of tiredness T of a further passenger of the vehicle is determined, the occurrence of a glare situation relating to the further passenger is monitored and, when a glare situation relating to the further passenger is detected, a trans- mittance of a screen allocated to the further passenger is reduced in at least a part of the screen, wherein the reduction of transmittance of the screen allocated to the further passenger depends on the degree of tiredness T of the further passenger.

15. Device for reducing a brightness of an object perceivable by a passenger of a vehicle, comprising a screen having electronically controllable transmittance, a passenger tiredness detection device, a glare situation detection device and a control unit, the control unit being configured for determining a degree of tiredness T of the passenger and for determining a hazard parameter H characteristic of a hazard potential related to a situation of the vehicle and/or the passenger, the hazard parameter H being determined based on a degree of autonomy of the vehicle, and, when a glare situation is detected, for controlling the screen to reduce the transmittance of the screen in at least a part of the screen depending on the degree of tiredness T of the passenger and on the hazard parameter H.