Method for calibrating an optical sensor

Abstract

A method for calibrating an optical sensor and / or a camera for a motor vehicle, wherein the optical sensor and / or the camera detects ambient light through a first pane (10) for the motor vehicle, the method comprising the following steps: receiving a first attenuation value of a first reference light beam reflected in a second pane (50) for a motor vehicle; receiving a second attenuation value of a second reference light beam passed through the second pane (50); transmitting a measuring light beam from a first side (12) of the first pane (10) into the first pane (10); receiving the measuring light beam reflected in the first pane (10) on the first side (12) of the first pane (10); determining a third attenuation value of the measuring light beam in the first pane (10) based on the transmitted measuring light beam and the received measuring light beam;and calibrating the optical sensor and / or the camera based on the first attenuation value of the second disc (50), the second attenuation value of the second disc (50) and the third attenuation value of the first disc (10);

Description

The invention relates to a method for calibrating an optical sensor and / or a camera for a motor vehicle.Prior ArtOptical sensors, for example ambient light sensors or cameras, which are arranged behind a window of a motor vehicle, must be calibrated individually for different windows, since the windows have different thicknesses and designs (angles of inclination) and ambient light or light from the outside is attenuated to different extents by the windows. This is technically complicated and causes high costs, in particular since there are a large number of different panes.DE 10 2008 030 611 A1 discloses an optical sensor for measuring visibility according to the runtime method according to the prior art.Disclosure of the InventionThe invention is based on the object of carrying out the calibration of an optical sensor and / or a camera which receives light through a window of a motor vehicle in a technically simple manner.This object is achieved by a method for calibrating an optical sensor and / or a camera according to claim 1.In particular, the object is achieved by a method for calibrating an optical sensor and / or a camera for a motor vehicle, wherein the optical sensor and / or the camera captures light of the environment through a first pane for the motor vehicle, wherein the method comprises the following steps:receiving a first attenuation value of a first reference light beam reflected in a second window for a motor vehicle;receiving a second attenuation value of a second reference light beam that has passed through the second plate;transmitting a measuring light beam from a first side of the first pane into the first pane;receiving the measurement light beam reflected in the first pane on the first side of the first pane;determining a third attenuation value of the measurement light beam in the first slice based on the transmitted measurement light beam and the received measurement light beam;and calibrating the optical sensor and / or the camera based on the first attenuation value of the second slice, the second attenuation value of the second slice, and the third attenuation value of the first slice.One advantage of this is that the calibration of the optical sensor and / or of the camera can be carried out in a technically simple manner depending on the attenuation or absorption of the light by the respective pane. In addition, the calibration can be carried out without human intervention or manual intervention. In this way, the optical sensor and / or the camera can be calibrated automatically or automatically. Thus, the optical sensor or camera need not be calibrated manually for each type of disk, but rather the sensor can be calibrated automatically after the sensor is placed on the disk. In addition, the reliability and / or safety of the optical sensor or of the optical camera is thereby increased. Also, no attributes of the pane, CAD data or the like are required for determining the attenuation or absorption of the light by the respective pane.The object is also achieved by a calibration system according to claim 10.In particular, the object is also achieved by a calibration system for calibrating an optical sensor and / or a camera for a motor vehicle, wherein the optical sensor and / or the camera captures light from the environment through a first pane for the motor vehicle, wherein the calibration system comprises the following: a receiving device for receiving a first attenuation value of a first reference light beam reflected in a second pane for a motor vehicle and for receiving a second attenuation value of a second reference light beam that has passed through the second pane, a transmitting device for transmitting a measurement light beam from a first side of the first pane into the first pane, a measuring device for measuring the measurement light beam reflected in the first pane on the first side of the first pane, a determining device for determining a third attenuation value of the measurement light beam in the first pane on the basis of the transmitted measurement light beam and the measured measurement light beam, and a calibrating device for calibrating the optical sensor and / or the camera on the basis of the first attenuation value of the second pane, the second attenuation value of the second pane and the third attenuation value of the first pane.It is advantageous here that the optical sensor or the camera can be calibrated automatically. In particular, no data about the structure (e.g. CAD data) or the like is required. Moreover, no manual intervention or the like is necessary for calibration. The calibration system is technically simple and cost-effective, in particular since under certain circumstances no additional sensors other than those which are present in any case in most disks are required. Moreover, the calibration can be performed quickly.A disc with such a calibration system is also claimed. A motor vehicle with such a pane (with calibration system) is also claimed.According to one embodiment of the method, the third attenuation value is determined by means of a rain sensor arranged on the first pane. It is advantageous here that the third damping value can be determined in a technically simple manner and without additional sensors, since a rain sensor is often or usually arranged on windows for motor vehicles. This reduces the costs and the outlay of the method. In addition, the third attenuation value can be determined experimentally in this way in a technically particularly reliable manner.According to one embodiment of the method, the third attenuation value is determined by means of a reference path in the first pane by means of a reflected light beam comprising visible light. One advantage of this is that the third attenuation value is determined with visible light (for the human being). Thus, the determination of the third attenuation value can be carried out with light which is similar to or identical to the light whose initially unknown fourth attenuation value is to be determined in the first pane for the calibration.According to one embodiment of the method, the thicknesses and / or the color properties of the first pane and the second pane differ from one another. It is advantageous here that the optical sensor and / or the camera is calibrated in a technically simple manner for very different panes.According to one embodiment of the method, the first attenuation value is determined by means of a rain sensor arranged on the second pane. One advantage of this is that the first damping value can be determined in a technically simple manner without an additional sensor, since a rain sensor is often or usually arranged on windows for motor vehicles. In addition, the first attenuation value can be determined precisely.According to one embodiment of the method, the first pane and / or the second pane comprises or is a windshield and / or rear window for a motor vehicle. One advantage of this is that the calibration can be carried out in a technically simple manner, in particular for specially designed windows for a motor vehicle, since the windshield or the rear window often has e.g. plastic films and / or heating elements.According to one embodiment of the method, in the step of calibrating, the third attenuation value is set in relation to the first attenuation value for determining an attenuation ratio between the first pane and the second pane, in order to determine a fourth attenuation value of the first pane, which indicates how much light that passes through the first pane is attenuated, the second attenuation value is multiplied by the attenuation ratio, and the optical sensor and / or the camera is calibrated by means of the fourth attenuation value. As a result, the attenuation of the light incident through the first panes for the optical sensor and / or the camera can be determined particularly easily and reliably in technical terms.According to one embodiment of the method, the first attenuation value is determined by setting the radiation power of a light beam emitted from a first side of the second pane with respect to the radiation power of the light beam reflected on the second side of the second panes and received in a sensor on the first side of the second pane. It is advantageous here that the first attenuation value can be determined particularly reliably and with little computing effort.According to one embodiment of the method, the second attenuation value is determined by setting the radiation power of light incident on a second side of the second pane with respect to the radiation power of light received from a sensor arranged on the first side of the second pane and / or from a camera arranged on the first side of the second pane and having passed through the second pane. One advantage of this is that the second attenuation value can be calculated with little computing effort. In addition, this determination of the second attenuation value is particularly precise.An attenuation value or attenuation can be, in particular, the absorption of the light or light beam by the respective pane. The absorption can depend in particular on the respective properties of the pane, e.g. thickness, design, angle of inclination, color or tint, material composition, surface treatment, further elements (e.g. plastic films and / or heating elements) on or in the pane, etc.The optical sensor and / or the camera can capture light visible to the human and / or light invisible to the human (e.g. infrared and / or ultraviolet).The calibration can be carried out by means of software or by means of a computer. The calibration system may include software or a computer for calibrating the optical sensor and / or the camera.The receiving device may be part of a computer. The attenuation values may be received from, for example, a memory (e.g., a hard disk, an SSD, or the like).By calibration, in particular the optical sensor and / or the camera or the measurement signals thereof can be set in relation to the actual light on the other side of the pane (which is the outer side of the pane in the motor vehicle). It is possible to determine, so to speak, which part or proportion of the light which is present before or upon entering the pane arrives at the optical sensor or in the camera. It can thus be determined which part or proportion of the light which would be received by the optical sensor or the camera without the presence of the pane is received in the presence of the respective pane.The motor vehicle can be, for example, a car, a truck, a bus, a motorcycle, an aircraft, a helicopter, a scooter, a fork lift truck, a rail vehicle or railway vehicle, an excavator or the like.The optical sensor may comprise or be a sensor for light visible to humans. It is also conceivable that the optical sensor can receive or measure light that is not visible to the human. A combination of visible light and non-visible light is also conceivable. The optical sensor may be part of a lidar or ladar system. In particular, the lidar system or ladar system can be an active optical sensor. The optical sensor may be an active optical sensor.The camera can comprise or be a camera for light visible to humans. The camera can comprise or be a camera for observing the environment, for example for capturing road signs. It is conceivable that the camera captures invisible light (e.g. infrared light) to the human. It is also conceivable for the camera to comprise or be a TOF camera.Preferred embodiments are evident from the dependent claims. The invention is explained in more detail below with reference to drawings of exemplary embodiments. Shown here are: FIG. 1 is a schematic view of a second window for a motor vehicle; and FIG. 2 shows a schematic view of a first pane for a motor vehicle.In the following description, the same reference numerals are used for the same and identically acting parts.The damping or absorption or the third damping value of a first pane 10 for a motor vehicle is intended to be determined.FIG. 1 shows a schematic view of a second pane 50 for a motor vehicle.The pane 10, 50 is shown only in sections or sections in the respective drawing. Typically, the (first and / or second) pane 10, 50 is bent, which is not shown in the drawings, however.The first pane 10 and / or the second pane 50 can be, for example, a windshield or front pane for a motor vehicle or a motor vehicle. It is also conceivable for the first pane 10 and / or the second pane 50 to be a rear window for a motor vehicle or a motor vehicle.The second pane 50 can also be referred to as a reference pane, since the first attenuation value and the second attenuation value are determined by means of this pane 50, and an optical sensor or a camera of another pane (first pane 10) is subsequently calibrated therewith.The second pane 50 has a first side 52 (lower side in FIG. 1 ) and a second side 54 (upper side in FIG. 1 ) opposite the first side 52.On the first side 52 of the second pane 50, a rain sensor 80 is arranged. The rain sensor 80 may be disposed directly on the first side 52 of the second pane 50. The rain sensor 80 includes a light emitting device, e.g., an LED 82, and a light receiver (e.g., photodiode 88). The light emitting device emits a light beam 84 into the second pane 50 at an angle in the direction of the second side 54 of the second pane 50. At the second side 54 of the second pane 50, (if no liquid is present at this location on the second side 54 of the second pane 50), the light beam is substantially totally reflected. The reflected light beam 86 is detected by a light receiver or light sensor.The light of the rain sensor 80 may include or be infrared light. It is possible that the emitted and received light of the rain sensor 80 comprises or is pulsed light. It is also conceivable that the light of the rain sensor 80 comprises or is visible light.The attenuation or absorption of the light beam of the rain sensor 80 can be detected or determined. Based on the radiation power of the emitted light beam from the light emitting device of the rain sensor 80 and the radiation power of the received reflected light beam in the light receiver, the attenuation of the second disk 50 can be calculated. For example, it can be established that only approximately 90% of the radiation power or of the emitted light beam is received in the light receiver. Thus, the attenuation or absorption of the second pane is 10%. This is the first attenuation value. Instead of or in addition to the radiation power, the radiation intensity can also be used to determine the first attenuation value.An optical sensor (e.g., ambient light sensor 60) or a camera is arranged on the first side 52 of the second pane 50 (shown on the left in FIG. 1 ). The sensor or the camera can be arranged directly on the first side 52 of the second pane 50. Light from the environment or from the second side 54 of the second pane 50 radiates through the second pane 50 and reaches the optical sensor or the camera. The light entering the second pane 50 from the second side 54 is attenuated or partially absorbed by the second pane 50. This means that (even in the case of vertically incident) light or ambient light 62 on the second side 54 of the second pane 50, not all of the light reaches the optical sensor or the camera on the first side 52 of the second pane 50. By means of a reference light beam (with a predetermined radiation power or radiation intensity) from the second side 54 of the second pane 50 through the second pane 50 onto the optical sensor or into the camera, the attenuation by the second pane 50 when the light or the light beam 64 passes through the second pane 50 can be determined. This attenuation or absorption in the second pane 50 is the second attenuation value.The light of the reference beam for the optical sensor or the camera can comprise or be visible light. It is conceivable that the light of the reference beam for the optical sensor or the camera comprises invisible light (e.g. infrared and / or ultraviolet).The first attenuation value and the second attenuation value for the tested second slice 50 (reference slice) may be stored and / or sent.FIG. 2 shows a schematic view of a first pane 10 for a motor vehicle.The first pane 10 can differ from the second pane 50 in terms of its properties. Theoretically, it is of course conceivable for the second pane 50 to be completely structurally identical to the first pane 10.The first pane 10 of FIG. 2 is thicker than the second pane 50 in FIG. 1 ; this is only a difference, shown by way of example, between the properties of the first pane 10 and the second pane 50. The attenuation or absorption for a light beam which passes through the first pane 10 is initially unknown.The first pane 10 has a first side 12 (lower side in FIG. 1 ) and a second side 14 (upper side in FIG. 1 ) opposite the first side 12. The second side 14 is located on the outside of the motor vehicle after the first pane 10 has been installed in a motor vehicle. The first side 12 of the first pane 10 faces the interior of the motor vehicle after installation in a motor vehicle.A rain sensor 40 is disposed on the first side 12 of the first pane 10. The rain sensor 40 of the first pane 10 can be identical in construction to the rain sensor 80 of the second pane 50. The rain sensor 40 comprises, for example, an LED 42 which emits a light beam 44. The rain sensor 40 of the first pane 10 thus also measures a light beam 46 reflected on the second side 14 of the first pane 10. Any different sizes of the sensor surfaces of the rain sensor 80 of the second pane 50 and of the rain sensor 40 of the first pane 10 can be taken into account during the calibration or during the determination of the respective attenuation values.An optical sensor and / or a camera is arranged on the first side 12 of the first pane 10. The optical sensor may, for example, comprise or be an ambient light sensor 20 for detecting ambient light 22. The optical sensor and / or camera receives light from the second side 14 of the first pane 10 that passes through the first pane 10. When the first pane 10 is irradiated, the light 24 is attenuated or partially absorbed by the first pane 10. This absorption of the light or light beam 24 by the first pane 10 can be different from the absorption of the second pane 50.The optical sensor may be an active optical sensor. This may mean in particular that the light received by the active optical sensor and having passed through the first pane 10 is or comprises light which was initially emitted or radiated by the active optical sensor (through the first pane 10) and was subsequently reflected by objects in the environment (i.e. objects which are on the other side of the first pane 10 as seen from the sensor, wherein the objects may be spaced apart from the first pane 10). The same can apply accordingly to the optical sensor in the second pane 50.This can be caused in particular by different thicknesses of the two panes 10, 50, different materials of the panes 10, 50, different shades of the panes 10, 50, different further elements on or in the panes 10, 50, etc.A third attenuation value is determined by setting the radiation power of the light beam emitted from the light emitting device of the rain sensor 40 with respect to the radiation power of the light beam received or measured by the light receiver (e.g., photodiode 44) or measuring device of the rain sensor 40. For example, a ratio between the radiation power or intensity emitted into the first pane 10 and the radiation power or intensity received in the light receiver or measuring device can be formed. Thus, it can be established, for example, that only about 90% of the emitted radiation power is received in the rain sensor 40 by the light receiver or by the measuring device (in this region in the case of a dry second side 14 of the first pane 10). This means that the third attenuation value of the first pane 10 is thus 10% (100% minus the received 90% light intensity). Thus, in this example, 10% of the light of the rain sensor 40 is absorbed by the first pane 10 or the light is attenuated accordingly. Instead of or in addition to the radiation power, the radiation intensity can also be used to determine the third attenuation value.Based on the first attenuation value and the second attenuation value of the second pane 50, as well as the third attenuation value of the first pane 10, the fourth attenuation value or the attenuation of the light through the first pane 10 to the optical sensor or to the camera can be determined. This can be determined, for example, by setting the third attenuation value in relation to the first attenuation value. Thus, for example, if the third attenuation value divided by the first attenuation value is 1.2, it means that the first disk 10 has an attenuation value larger than the second disk 50 by 20%, and thus it is assumed that the fourth attenuation value (attenuation of light when passing through the first disk 10 to the optical sensor) is also 20% larger than the second attenuation value. According to this fourth attenuation value, the optical sensor or the camera can be calibrated. Thus, for example, the measured values or signal values of the optical sensor or of the camera of the first pane 10 can be correspondingly amplified at 20% greater attenuation by the first pane 10 (in comparison to the second pane 50) (e.g. division of the measured values or signal values by 0.8). The measured values or signal values of the optical sensor or of the camera of the first pane 10 then substantially correspond to the measured values or signal values of the optical sensor or of the camera of the second pane 50 (with the same incidence of light on the respective pane 10, 50).The procedure of the method is thus that the first attenuation value and the second attenuation value are received (e.g. retrieved from a memory by radio, via Internet). The third attenuation value is determined at the first disk 10. The fourth attenuation value, i.e. the absorption or attenuation for a beam passing through the first pane 10, can now be determined or calculated and the optical sensor or the camera can be set or calibrated to the determined or calculated absorption of the first pane 10. The optical sensor may comprise or be, for example, an ambient light sensor 20.The memory can be part of an evaluation device (e.g. a computer or an IC) of the optical sensor 20, for example.In determining the fourth attenuation value, it can be taken into account that the path of the reflected beam increases more (namely approximately by the factor 2) in the case of a thicker pane than the path of the beam passing through the pane in the case of a thicker pane. The path of the light beam passing through increases by 10% for a 10% thicker pane, while the path of the reflected light beam increases by approximately 20% for a 10% thicker pane.By taking into account the third attenuation value (actually measured in the first pane 10), different colors or tints or the like can also be taken into account during the calibration. The region of the respective pane in which the rain sensor 40 and the optical sensor or the camera are arranged is usually not tinted or colored.Usually, the sensor or the optical camera is not located far away from the rain sensor, so that the assumption is correct that the region through which the light beam of the rain sensor passes in the pane 10, 50 and the region through which the light passes through the pane 10, 50 on the way to the optical sensor or to the camera has substantially the same properties, in particular substantially identical attenuation values or absorption values. Differences in this case can of course be taken into account in the calibration.It is conceivable that instead of or in addition to the rain sensor 40, 80 a reference path is used in the first pane 10 and / or in the second pane 50 for determining the first attenuation value of the second pane 50 and / or the third attenuation value of the first pane 10. The reference path may include a light emitting device on the first side 52 of the second pane 50, and a light receiver on the first side 52 of the second pane 50 for receiving the light beam reflected on the second side 54 of the second pane 50. In the case of the first pane 10 as well, a correspondingly constructed reference section can be present. The reference path may use visible light. The color of the light can comprise or be, for example, red, green, blue and / or yellow.List of reference numbers:10 The following are also described: first pane 12 first side of first pane 14 second side of first pane 20 ambient light sensor of first pane 22 ambient light outside first pane 24 light entered the first pane 40 rain sensor of first pane 42 LED of first pane 44 light emitted by the LED in first pane 46, light reflected in first pane 48 photodiode of first pane 50 second pane 52 first side of second pane 54 second side of second pane 60 ambient light sensor of second pane 62 ambient light outside second pane 64 light entered the second pane 80 rain sensor of second pane 82 LED of second pane 84 light reflected by the LED in second pane 86 light reflected in second pane 88 photodiode of the second pane

Claims

A method for calibrating an optical sensor and / or a camera for a motor vehicle, wherein the optical sensor and / or the camera captures light of the environment through a first pane (10) for the motor vehicle, wherein the method comprises the steps of: receiving a first attenuation value of a first reference light beam reflected in a second pane (50) for a motor vehicle; receiving a second attenuation value of a second reference light beam that has passed through the second pane (50); transmitting a measurement light beam (44) from a first side (12) of the first pane (10) into the first pane (10); receiving the measurement light beam (46) reflected in the first pane (10) on the first side (12) of the first pane (10); determining a third attenuation value of the measurement light beam in the first pane (10) based on the transmitted measurement light beam and the received measurement light beam; and calibrating the optical sensor and / or the camera based on the first attenuation value of the second pane (50), the second attenuation value of the second pane (50), and the third attenuation value of the first pane (10).Method according to Claim 1, wherein the third attenuation value is determined by means of a rain sensor (40) arranged on the first pane (10).Method according to claim 1 or 2, wherein the third attenuation value is determined by means of a reference distance in the first pane (10) by means of a reflected light beam comprising visible light.Method according to any of the preceding claims, wherein the thicknesses and / or the colour properties of the first pane (10) and the second pane (50) differ from each other.Method according to one of the preceding claims, wherein the first attenuation value is determined by means of a rain sensor (80) arranged on the second pane (50).Method according to one of the preceding claims, wherein the first pane (10) and / or the second pane (50) comprises or is a windshield and / or rear window for a motor vehicle.Method according to any of the preceding claims, wherein in the step of calibrating, the third attenuation value is set in relation to the first attenuation value for determining an attenuation ratio between the first pane (10) and the second pane (50), for determining a fourth attenuation value of the first pane (10), which indicates how much light that passes through the first pane (10) is attenuated, the second attenuation value is multiplied by the attenuation ratio, and the optical sensor and / or the camera is calibrated by means of the fourth attenuation value.Method according to one of the preceding claims, wherein the first attenuation value is determined by setting the radiation power of a light beam emitted by a first side (52) of the second pane (50) with respect to the radiation power of the light beam reflected on the second side (54) of the second panes (50) and received in a sensor on the first side (52) of the second pane (50).Method according to any of the preceding claims, wherein the second attenuation value is determined by setting the radiation power of light incident on a second side (54) of the second pane (50) with respect to the radiation power of a sensor arranged on the first side (52) of the second pane (50) and / or of a light received on the first side (52) of the second pane (50) and having passed through the second pane (50).Calibration system for calibrating an optical sensor and / or a camera for a motor vehicle, wherein the optical sensor and / or the camera captures light from the environment through a first pane (10) for the motor vehicle, wherein the calibration system comprises: a receiving device for receiving a first attenuation value of a first reference light beam (86) reflected in a second pane (50) for a motor vehicle and for receiving a second attenuation value of a second reference light beam (64) that has passed through the second pane (50), a transmitting device for transmitting a measurement light beam (44) from a first side (12) of the first pane (10) into the first pane (10), a measuring device for measuring the measurement light beam (46) reflected in the first pane (10) on the first side (12) of the first pane (10), a determination device for determining a third attenuation value of the measurement light beam in the first pane (10) on the basis of the transmitted measurement light beam (44) and the measured measurement light beam (46), and a calibration device for calibrating the optical sensor and / or the camera on the basis of the first attenuation value of the second pane (50), the second attenuation value of the second pane (50) and the third attenuation value of the first pane (10).A vehicle window pane having a calibration system according to claim 10.Motor vehicle having a window according to Claim 11.

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