DE102019130316B3 - Vehicle with a camera system for optically scanning an environment of the vehicle - Google Patents

Abstract

The invention relates to a vehicle with a camera system for optically scanning an environment of the vehicle. The vehicle has a heated window with heating wires. The heating wires are arranged in the field of view of the camera system. The camera system has a lens, the lens having a hyperfocal distance of at least 1 m, an aperture number of at most 8.0 and an effective focal length of at least 3 mm. The field of view of the camera system is at least 50 ° in a horizontal orientation.

Description

The invention relates to a vehicle with a camera system for optically scanning an environment of the vehicle.

With such an optical scanning, an image of the surroundings of the vehicle is generated. Nowadays, vehicles often use a camera system with multiple cameras to create a 360 ° all-round view. However, it is particularly important to map the area in front of the vehicle in the direction of travel.

The optical scanning of the surroundings can have various reasons, e.g. recording this optical scan to log an accident. Even when autonomous driving is gaining in importance, as support for parking, as a lane departure warning system or for traffic sign recognition, an optical scanning of the vehicle surroundings by camera systems is important.

With so-called dash cams, the light field in front of the vehicle can be recorded while a vehicle is traveling. A camera is attached in the area of the rear-view mirror and the camera looks through the windscreen of the vehicle onto the road. The driving behavior of the driver and other road users is recorded so that it can be presented later as evidence.

Furthermore, camera systems for facilitating navigation are known. Images taken by the camera are overlaid with navigation information and shown on a display. Here, too, a camera is attached to the center of the windscreen. Navigation is made easier by the fact that the driver can compare his view with the navigation display.

The problem with the camera systems described above is that under certain temperature conditions, such as frost in winter or increased air humidity, the pane can freeze and / or mist up. If the windshield is fogged up, water or steam condenses on the windshield. This obscures the view of the camera.

Water condensed and / or frozen on a windshield of a vehicle can be evaporated with a warm air flow provided by a window ventilation. However, such a window ventilation is usually set such that the windows are dehumidified in a lower area of the window. The area in which camera systems are installed is only dehumidified at a later time, if at all. In addition, warm air can only be provided with a considerable delay after the start of the journey.

Disc heaters are also known which cause the disc to be dehumidified or defrosted quickly and reliably. Two different disc heaters are used. On the one hand, pane heating can be realized by energized, applied metallic layer. The advantage of this heating technology is that it is barely visible. However, a metallic heating layer applied over a large area is expensive and prone to errors.

Most disc heaters are designed as heating wires. These are either printed on the pane or integrated between two layers of the pane. Such heating wires are robust and can deliver a high heating output to the surrounding pane. A disadvantage of these heating wires is that they are visible and are also recorded by the camera systems described above. These then appear as lines in the captured image. This is disturbing for a viewer of the picture and hinders the autonomous evaluation of the pictures. In the worst case, an observer can also miss important information.

One possibility would be to remove these recorded heating wires digitally, for example by digital brightening or interpolation. However, these digital filters require very powerful control devices and, depending on the optical properties of the heating wires, typically cannot correct some scenarios without visible degradation or artifacts.

From the WO 2009/012771 A1 an optical detection system for monitoring the vehicle environment emerges. A camera system is arranged in front of a vehicle window. Heating wires run around a field of view of the camera without being arranged in the field of view of the camera. The disadvantage here is that the center of the viewing area receives the lowest heating power, which, for example, considerably increases the defrosting time, with this center being the most critical for detection.

In the DE 10 2018 22 27 40 A1 discloses a camera with a heater for vehicles. The heating device is a heating plate and is arranged opposite a disc. The camera is laterally offset between the pane and the heater. This means that the field of vision is not affected by the heating plate. The heating plate heats the pane and the camera by heat radiation. It is disadvantageous that only a small amount of heating power reaches the pane. The construction of the heating device is expensive compared to classic heating wires.

In the DE 10 2006 010 672 A1 a camera arrangement for a motor vehicle is known which has a camera directed at a vehicle window and at least one electrical conductor structure which is connected directly or indirectly to the vehicle window. The conductor structure is arranged in the detection area of the camera.

In the DE 10 2010 023 591 A1 describes a stereo camera system which is designed for use in motor vehicles behind an inclined windshield. At least one of, for example, two camera modules has an additional, partially arranged, temporarily supplied or acting as a beam splitter optical element. As a result, it can be used as a bifocal optical camera module with at least two different depth of field ranges on an image sensor.

The object of the invention is to create a vehicle with a camera system in which the camera system reliably monitors the surroundings of the vehicle in a cost-effective and temperature-independent manner without impairing the view.

The object is achieved by the subject matter of the independent claim. Advantageous further developments and preferred embodiments form the subject of the subclaims.

A vehicle with a camera system for optically scanning an environment of the vehicle has a heated window with heating wires. The heating wires are arranged in the field of view of the camera system. The camera system has a lens, the lens having a hyperfocal distance of at least 1 m, an aperture number of at most 8.0 and an effective focal length of at least 3 mm.

Due to the fact that the hyperfocal distance is at least 1 m, the maximum number of f-stops is 8.0 and the effective focal length is at least 3 mm, objects, such as the heating wires, are displayed in a close-up range. The close range is the area in the immediate vicinity of the lens (e.g. at a distance of less than 10 cm) in which the disc with the heating wires can be arranged. The rays of light that shine into the vehicle from the outside continue to be blocked by the heating wires. The images of the heating wires are so blurred that they fill up a large part of the image in width or even go beyond it. The less sharp the heating wires are, the wider and more translucent they appear in the resulting image. Surprisingly, it has been found that if the lens has a hyperfocal distance of at least 1 m, an aperture of maximum 8.0 and an effective focal length of at least 3 mm, the image of the heating wires is so wide and translucent that it is one of forms a gray film that is no longer perceptible to a viewer. So that the camera system can be used for the optical scanning of the surroundings of the vehicle, it is sufficient to display objects that are at least 1 m away from the camera system in sharp focus. The inventors of the present invention have recognized this.

The robust, reliable and powerful heating wires ensure rapid evaporation and / or defrosting of the glass in the area of the camera. Due to the setting of the camera system described above, the recorded images of the camera system are not disturbed by the heating wires that are also included. Optical scanning of the surroundings of the vehicle is therefore independent of weather and temperature.

The distance between the lens and the pane is preferably not greater than 100 mm, preferably not greater than 75 mm and in particular not greater than 50 mm. The distance is defined here between the outer edge of the lens and the inside of the lens.

The objective can also have an aspherical lens. Aspherical lenses are optical lenses in which at least one refractive surface deviates from the spherical or flat shape. In the present objective, the edge region of the aspherical lens can be more curved at least in the horizontal direction, as a result of which the focal length in this edge region decreases and the field of vision increases. Due to the aspherical lens, the field of vision of the camera system can be at least 50 ° in a horizontal orientation. If the field of view were smaller, this would not be sufficient for optically scanning an environment. There would be a risk that important areas in the area, such as pedestrian paths, could no longer be recorded by the camera system, which would mean that the danger from there could not be detected. The aspherical image of the camera system is curved unnaturally by an aspherical lens, i.e. different from the lens of the human eye. The advantage here, however, is that the field of view of the camera system increases in both horizontal and vertical alignment. A captured image appears squashed in the peripheral areas.

The viewing area preferably has an aspect ratio between horizontal and vertical alignment of at least 64:27, preferably of at least 16: 9 and in particular of at least 1: 1. As a result, the area surrounding the vehicle can be monitored over a large area.

The pane can be a front pane of the vehicle. Here, the camera is arranged in the front part of the vehicle and the camera system records approximately the same area as a driver of the vehicle sees.

The camera system can be arranged in the upper quarter, preferably in the upper fifth and in particular in the upper sixth of the pane and in particular in the center. This corresponds approximately to the position of the rear-view mirror in the vehicle. A driver is distracted little or not at all by a camera system in this position and his visual range is not affected.

An optical axis of the camera system preferably hits the pane at an angle of at most 90 °, preferably at most 60 ° and in particular at most 30 °. The optical axis of the camera system is an axis of symmetry which extends approximately across the surfaces of one or more lenses contained in the camera system. The angle arises primarily from the fact that the front window of a vehicle is oblique with respect to a horizontal, while the camera system is oriented essentially horizontally.

A heating surface, in which the heating wires are arranged in the pane, preferably has a size which corresponds to a maximum of 300%, preferably a maximum of 200% and in particular a maximum of 150% of the viewing area, the viewing area being the area of the pane which is in the visible range of the Camera system lies. As a result, the heating wires are only arranged in the area of the camera. A driver and / or front passenger is therefore not irritated by the heating wires. Nevertheless, quick defrosting or dehumidification is possible in the area of the camera system.

The lens of the camera system preferably has an effective focal length of at most 20 mm, preferably at most 15 mm, preferably at most 10 mm and in particular at most 7 mm in a central area. The smaller the focal length in the central area, the greater the field of view of the camera system.

Since the objective preferably has an aspherical lens, the focal length in the edge region can be smaller, at least in the horizontal direction, than in the central region. As described above, this allows the viewing area in the edge area to be enlarged.

In the central area, the aspherical lens has refractive surfaces that are essentially spherical or planar. At the edge regions arranged on the right and left in the horizontal direction, the aspherical lens has sections in which the refractive surfaces are aspherical, i.e. that is, they deviate from the spherical shape or planar shape. The size of the central area can be selected such that at least 40%, preferably at least 60% and in particular at least 80% of the image recorded by the camera system was imaged with the focal length of the central area.

The lens of the camera system can have an aperture of at most 5.6, preferably at most 2.8 and in particular at most 1.8. The smaller the f-number, the more objects in the close-up area are blurred. Furthermore, more light falls through the lens onto the camera sensor.

The camera system preferably has a circle of confusion diameter of at most 0.010 mm, preferably at most 0.007 mm and preferably at most 0.004 mm. The circle of confusion diameter describes the maximum tolerable diameter of the circle of confusion. The circle of confusion is created by blurring. If a point of an object at the hyperfocal distance is not imaged exactly on a sensor level of the camera system, but shortly before or after, this point appears as a circle on the sensor level. This is called the circle of confusion. Due to the spatial distance between two sensor points, a certain diameter of the circle of confusion can be tolerated.

The objective is preferably configured at a hyperfocal distance of at least 2 m and in particular at least 4 m and preferably at least 6 m. The hyperfocal distance is the distance between the camera system and the foremost point of depth of field when the camera system is focused on infinity.

The greater the hyperfocal distance, the more objects in the close range are displayed as out of focus.

The effective focal length of the objective is preferably at least 4 mm, preferably at least 5 mm and in particular at least 6 mm. The longer the focal length of the lens is, the more objects in the close-up range are blurred.

The field of vision of the camera system preferably has at least 50 °, at least 60 ° and in particular at least 70 ° in a horizontal orientation.

The invention is explained in more detail below using the examples shown in the drawings.

• 1 ein Kraftfahrzeug in einer Seitenansicht,
• 2 ein Ausschnitt eines Kraftfahrzeuges aus 1 mit Kamerasystem, Scheibe und Heizdrähten,
• 3 ein Diagramm über ein Bildkontrast gegen die vertikale Richtung von einem perfekt abgebildeten Heizdraht und das vom Kamerasystem aufgenommene Bild eines Heizdrahtes, und
• 4 beispielhaftes aufgenommenes Bild durch das Kamerasystem.

The drawings show schematically:

• 1 a motor vehicle in a side view,
• 2nd a section of a motor vehicle 1 with camera system, disc and heating wires,
• 3rd a diagram of an image contrast against the vertical direction of a perfectly imaged heating wire and the image of a heating wire recorded by the camera system, and
• 4th exemplary image taken by the camera system.

The following is an embodiment of a vehicle 1 explained ( 1 and 2nd ).

The vehicle 1 has a camera system 2nd and a disc 3rd on which to the neighboring camera system 2nd is arranged. The disc 3rd is a windshield in this embodiment and is in the front area of the vehicle 1 arranged. The camera system 2nd is inside the vehicle 1 arranged directly in front of the pane in the center of a rear-view mirror.

In other exemplary embodiments, however, a camera system can also be used 2nd adjacent to other disks 3rd , such as a rear window or side window.

The disc 3rd has several horizontal heating wires 4th on. The heating wires are in the disk in this embodiment 3rd arranged between two composite panes. In other embodiments, the heating wires 4th also on the disc 3rd be printed. The heating wires 4th have a width of ≤ 0.4 mm. The heating wires 4th are heating resistors and convert electrical energy into thermal energy (Joule heat) through their electrical resistance.

The camera system 2nd has a lens 5 on. At least one lens of the lens 5 is an aspherical lens. The aspherical lens has an effective focal length of f _central = 6.25 mm in a central area. In the central area, the aspherical lens has refractive surfaces that are essentially spherical or planar. At the edge regions arranged on the right and left in the horizontal direction, the aspherical lens has sections in which the refractive surfaces are aspherical, ie that they deviate from the spherical shape or planar shape. The spherical sections are designed such that the focal length remains constant in the vertical direction (f _edge , _v = 6.25 mm), that is to say that an infinitesimally thin lens segment which is cut out in the vertical direction from the aspherical edge region of the lens, this focal length owns. In the horizontal direction, however, the deviation of the refractive surfaces from the spherical shape increases the focal length to the outside up to a maximum value f _{edge, h} = 3 mm. Corresponding horizontal infinitesimally thin line segments have refractive surfaces, with an increasingly greater curvature with respect to a sphere.

Due to this special configuration of the aspherical lens, the images generated with the lens are compressed in the horizontal direction at the edge area, as shown in FIG 4th based on the outer trees 7 compared to the inner trees 8th is recognizable.

In other embodiments, the focal length of the vertical edge area may differ from the focal length of the central area and e.g. be equal to the focal length of the vertical edge area.

The camera system 2nd has an optical axis 6 , which runs approximately horizontally. The disc 3rd is opposite to the optical axis 6 at a disc angle γ inclined. In this exemplary embodiment, the disk angle γ is approximately 65 °. The distance of the camera system 2nd to the disc 3rd is described by a disc distance D lying in the horizontal direction. The lens distance D is between the outer edge of the lens 5 and the inside of the disc 3rd measured. In that the disc 3rd is at a disk angle γ <90 ° to the optical axis, the disk distance D is in a range between a minimum disk distance Dmin and a maximum disk distance Dmax. The minimum disc distance Dmin is 3 mm. The maximum disc distance Dmax is 2 cm.

An area along the optical axis 6 , in which the disc with the heating wires is located, is called near range N.

A viewing area of the camera system 2nd is α = 50 ° in the horizontal orientation and β = 40 ° in the vertical orientation ( 4th ). The camera system 2nd is set such that there is a hyperfocal distance H of at least 4 m. This means that objects that are at a distance of H / 2 = 2 m to infinity from the camera system 2nd are arranged, are shown sharply.

From the focal length f _{central of} the central area, the f-number k and the hyperfocal Distance H, a circle of confusion diameter Z can be calculated using the following formula: $$\text{Z}=\left({\text{f}}_{\text{Central}}\cdot {\text{f}}_{\text{Central}}\right)/\left(\left(\text{H}*\text{k}\right)-\left({\text{f}}_{\text{Central}}*\text{k}\right)\right).$$

In this exemplary embodiment, the focal length f _central = 6.25 mm, the f-number k = 1.9 and the hyperfocal distance H = 4 m. This results in a circle of confusion diameter Z = 0.005 mm.

A blur circle diameter U can be calculated with a similar formula, where M is any distance: $$\text{U}=\left({\text{f}}_{\text{Central}}*{\text{f}}_{\text{Central}}\right)/\left(\left(\text{M}*\text{k}\right)-\left({\text{f}}_{\text{Central}}*\text{k}\right)\right).$$

In order to be able to estimate the blurring of a point in the close range, M = Dmax is chosen. This results in a blur circle diameter Umax = 1.495 mm.

The uncertainty circle diameter Umax describes how large the diameter of the image of a point at the maximum disc distance Dmax on the camera sensor is. The circle of uncertainty diameter is similar to the circle of confusion diameter. However, the circle of confusion diameter is limited to a point at which the distance N is equal to the hyperfocal distance H.

In the case of a smaller distance, for example the minimum disk distance Dmin = 3 mm, the amount of the unsharpness circle diameter is | U _min | = 6.326 mm.

A point in the near area thus appears 300 to 1250 times larger in diameter than a point at the hyperfocal distance.

The distance between two light sensor points on a camera sensor is typically around 0.005 mm. Thus, a point on the hyperfocal distance is sharply imaged. A point in the close range, however, is detected by at least Pi * (0.5 * (1.495 mm / 0.005 mm)) ^ 2 = 70 215 light sensor points. This also means that the mapping of the point per light sensor point, i.e. which light information reaches the light sensor point, is weakened by a factor of 70 215. The point is therefore sufficiently out of focus.

A typical camera sensor has a height of 5.4 mm, the height representing the dimension perpendicular to the alignment of the heating wires. This means that a single point in the close range already covers 28% to 117% of the sensor height.

Due to the small slice distance D in comparison to the hyperfocal distance H, objects in the near range N, such as the heating wires, become 4th , very blurred.

Heating wires 4th can then no longer be recognized as such in an image. As in 3rd is shown schematically, is the contrast difference between a real heating wire 4th and an illustration of the heating wire 4th at less than 20%. The image of the camera system 2nd appears to a viewer as if there were no heating wires 4th in the field of view of the camera system 2nd would be present.

Below is the use of the vehicle described above 1 or the intended camera system 2nd explained.

Through the heating wires 4th an electric current flows. They give thermal energy to the surrounding pane 3rd from. As a result, the visual area of the camera system can be cleared of ice and dew.

The camera system 2nd depicts the front area of the vehicle ( 4th ). The camera system 2nd generated image can be fed to an automatic image processing, which of different functional elements in the vehicle 1 can be used. Such functional elements are, for example, automatic traffic sign recognition, automatic collision detection, parking assistance and / or a system for autonomous driving of the vehicle.

Objects farther than half the hyperfocal distance H / 2 from the camera system 2nd are sharp from the camera system 2nd pictured. The closer objects are to the camera system, the less clear they are shown in the picture.

Through the aspherical lens of the lens 5 the generated image is compressed in the horizontal direction at the edge. Objects appear narrower than they actually are. This compression can be eliminated by an equalization calculation.

The camera system according to the invention 2nd is therefore quickly usable even in situations where the windscreen 3rd of the vehicle 1 is fogged up or iced over, since both the fogging and the ice can be quickly removed by heating up the section of the windscreen that is in the field of view of the camera system. Due to the special design of the lens, the heating wires interfere 4th not the image created in this way. There can be relatively wide heating wires 4th are used, which are inexpensive to manufacture and have a long life and good heating performance.

The values mentioned in the exemplary embodiment mentioned above are only examples. The values may vary depending on the application. For example, is the camera system 2nd farther away from the disk than in the exemplary embodiment explained above, so that the disk distance D is greater, the near range N also changes. So that the heating wires remain so blurred that they are not recognizable, the focal lengths f _Central , f _{edge, v} and f _{edge, v} must be adjusted accordingly. This can also be the case if the disc angle γ changes, since the minimum and maximum disc spacing D and the width of the close range are then changed.

Are the heating wires 4th thinner than indicated above, correspondingly larger focal lengths, smaller focal lengths and / or lower hyperfocal distances can also be selected. The illustrations of the heating wires 4th are nevertheless so wide and translucent that they form a gray film that is no longer perceptible to a viewer.

The parameters of the hyperfocal distance H, focal length f _{central of} the central area, the f-number k and the circle of confusion diameter Z are linked using the above-mentioned formula. If one or more of these parameters are changed, the remaining parameters may have to be adjusted so that the field of vision is not restricted too much or the hyperfocal distance H becomes too great.

Depending on the camera system 2nd , in particular depending on the aspherical lens, the field of view of the camera system 2nd vary both horizontally and vertically.

In particular, the position of the camera system 2nd be modified in the vehicle. So can camera systems 2nd also be installed in the side windows or the rear window of the vehicle. But they are also camera systems 2nd conceivable the own washers with heating wires 4th have at any position on the vehicle 1 are attached. For example, there are camera systems for reversing that are mounted in the area of a rear bumper. Another example is camera systems for capturing 360-degree views from a street perspective.

Reference list

1

vehicle

2nd

Camera system

3rd

disc

4th

Heating wire

5

lens

6

optical axis

7

tree

8th

tree

α

Viewing area of the camera system in the horizontal direction

β

Viewing area of the camera system in the vertical direction

γ

Disc angle

N

Close range

D _min

minimum disc distance

D

Disc spacing

D _max

maximum disc distance

H

Hyperfocal removal

Claims (13)

Vehicle with a camera system for optically scanning an environment of the vehicle, the vehicle having a heated window with heating wires, which is arranged in the field of view of the camera system, wherein the camera system has a lens, and the lens has a hyperfocal distance of at least 1 m, an aperture of maximum 8.0 and an effective focal length of at least 3 mm. Vehicle after Claim 1 , characterized in that the distance between the lens and the disc is not greater than 100 mm, preferably not greater than 75 mm and in particular not greater than 50 mm. Vehicle after Claim 1 or 2nd , characterized in that the lens has an aspherical lens and a viewing area of the camera system in the horizontal orientation is at least 50 °. Vehicle according to one of the Claims 1 to 3rd , characterized in that the field of view of the camera system has an aspect ratio between horizontal alignment and vertical alignment of at least 64:27, preferably of at least 16: 9 and in particular of at least 1: 1. Vehicle according to one of the Claims 1 to 4th , characterized in that the window is a front window of the vehicle. Vehicle according to one of the Claims 1 to 5 , characterized in that the camera system is arranged in the upper quarter, preferably in the upper fifth and in particular in the upper sixth in front of the pane. Vehicle according to one of the Claims 1 to 6 , characterized in that an optical axis of the camera system strikes the window at an angle of at most 90 °, preferably at most 60 ° and in particular at most 30 °. Vehicle according to one of the Claims 1 to 7 , characterized in that the lens of the camera system has a focal length of at most 20 mm, preferably at most 15 mm, preferably at most 10 mm and in particular at most 7 mm in a central area. Vehicle according to one of the Claims 1 to 8th , characterized in that the lens of the camera system has an aperture of at most 5.6, preferably at most 2.8 and in particular at most 1.8. Vehicle according to one of the Claims 1 to 9 , characterized in that the camera system has a circle of confusion diameter of at most 0.010 mm, preferably at most 0.007 mm and preferably at most 0.005 mm. Vehicle according to one of the Claims 1 to 10th , characterized in that the lens is set to a hyperfocal distance of at least 2 m and in particular at least 4 m and preferably at least 6 m. Vehicle according to one of the Claims 1 to 11 , characterized in that the focal length is at least 4 mm, preferably at least 5 mm and in particular at least 6 mm. Vehicle according to one of the Claims 1 to 12th , characterized in that the field of view of the camera system has at least 50 °, preferably at least 60 ° and in particular at least 70 ° in a horizontal orientation.

Images