WO2009018907A2

WO2009018907A2 - Night vision system for motor vehicles

Info

Publication number: WO2009018907A2
Application number: PCT/EP2008/005840
Authority: WO
Inventors: Helmuth Eggers; Jörg Moisel
Original assignee: Daimler Ag
Priority date: 2007-08-06
Filing date: 2008-07-17
Publication date: 2009-02-12
Also published as: WO2009018907A3; DE102007037091A1

Abstract

The invention relates to night vision systems for motor vehicles, comprising a camera that is located behind a suitable window (1) of the motor vehicle and a planar transparent element (6) which is arranged between the window and the camera within the light path of the camera. In order to prevent the night vision system from being dazzled by oncoming vehicles that are equipped with the same systems, the planar transparent element is adequately disposed and designed, e.g. by resting the planar transparent element against the window without leaving an optical boundary surface therebetween and by providing the planar transparent element with an anti-reflective coating.

Description

Night vision system for motor vehicles

The invention relates to night vision systems for motor vehicles, which have a camera arranged behind an inclined disc of the motor vehicle and a flat transparent element which is arranged in the light path of the camera between the disc and the camera, according to the preambles of the independent claims.

Such a system - albeit not exclusively for night vision - is known from DE 102 37 608 A1. The sheet-like transparent element is an additional disk arranged parallel to it at a distance from the disk. The trapped between the disc and the additional disc air layer to prevent fogging of the disc (s).

A similar system is known from DE 101 60 669 B4. The sheet-like transparent member is disposed at a distance from the disk parallel thereto and has a relatively large thickness. It breaks the coming of the objects to be detected light that has passed through the disc, twice, in order to arrange the camera closer to the disc can.

From DE 103 42 837 Al a camera system in motor vehicles is also known, which has a camera arranged behind an inclined disc of the motor vehicle and an optical prism, approximately the same Refractive index as the disc has, is glued to the lens in the light path of the camera and has a light exit surface, which is substantially perpendicular to the optical axis of the camera system. This prevents reflections or refraction in the inclined disk. Loud

The introduction of the application mentioned above has previously been proposed to provide the disc with an anti-reflection coating, which, however, requires a complex treatment of the disc.

The present invention is based on the following problem. It has been found that when two vehicles equipped with IR deference systems meet, the IR headlights of the oncoming vehicle generate or "bloom" in the image captured by the camera. This effect can be so strong that important details like e.g. People on the road in the picture are no longer recognizable.

The present invention has for its object to provide a night vision system for motor vehicles with the simplest possible means of glare by oncoming vehicles with just such systems.

This object is achieved in generic night vision systems in each case by the characterizing features of the independent claims.

The invention is based on the finding that although there are several factors which may be responsible for the observed glare, the presumed predominant factor or the most likely cause is double images and possibly multiple images due to multiple reflections within the pane. The While intensities of such multiple images are small compared to the direct transmitted light, the multiple images appear much brighter than they actually are due to the logarithmic sensitivity characteristic of the imaging chip in the CCD camera in the captured image, and the superimposed multiple images appear as " Flourishing "of the spotlight images predominantly in the vertical direction.

Reflections of the incident light within the disk could indeed be eliminated with a prism arrangement as in DE 103 42 837 A1 or with an antireflection coating of the disk. However, both conventional solutions are relatively complex, and in particular it is hardly possible to retrofit existing night vision systems with it.

In the invention, the sheet-like transparent member may be a glass or plastic sheet or foil of constant thickness, which is much easier to manufacture than a prism.

In the embodiment in which the sheet-like transparent element has an antireflection coating, it can be applied with little effort in the production of the transparent element.

Also requires little effort, the embodiment in which the sheet-like transparent element is inclined at a small angle of, for example, some degrees to the disc of the motor vehicle flat additional disc, either with a suitable holder or preferably by means of a transparent filler such as refractive index-matched epoxy resin, a wedge-shaped space between the disc and the auxiliary disc fills, is attached to the disc. This inclined additional disc may additionally have an antireflection coating, but need not.

In modern motor vehicles, the disc may be inclined backwards by up to 60 ° or more. At an inclination of 60 °, the angle of incidence of the light received by the headlights of oncoming vehicles is near the Brester angle at which the light reflected from a glass-air interface is completely polarized, in the direction that is perpendicular to the plane of incidence. In the case of multiple reflections within the disk, this can lead to double images becoming more intense and / or having a different polarization distribution than the direct passing light. Both effects can be unfavorable in the CCD camera. Therefore, it may be advantageous if the planar transparent element is polarizing or if there is a polarization filter at any other point in the light path of the camera between the pane and the camera. In fact, even a polarizing filter between the lens and the camera alone can help reduce the glare of the forbearance system.

The invention is particularly suitable for cases in which the inclined disc of the motor vehicle is the windshield, the camera is a CCD infrared camera and the indulgence system comprises at least one mounted on the motor vehicle infrared headlamp, the planar transparent element must of course be transparent to infrared light.

The following is a description of embodiments of the invention with reference to the drawing. It shows: 1 is an enlarged sectional view of a windshield with a main jet incident from the front and partial beams thereof which are refracted or reflected at boundary surfaces of the windshield;

Figure 2 is a sectional view corresponding to Figure 1 through a windshield, the inside of which is covered with a glass plate which carries on its facing the vehicle interior surface an anti-reflection coating.

Fig. 3 is a sectional view corresponding to Figure 1 through a windshield with a glass behind it, which is arranged at a small angle to the windshield, so that it forms an upwardly open wedge-shaped space. and

Fig. 4 is a Fig. 1 corresponding sectional view through a windshield with a glass behind it, which is arranged at a small angle to the windshield, so that it forms a downwardly open wedge-shaped space.

Fig. 1 shows a tilted by 60 ° to the vertical rear windshield 1, on which a light beam 2 impinges horizontally from the front. The light beam 2 is partially refracted on the outside of the windshield 1 and reflected to a lesser extent away from the windshield 1. The broken and transmitted partial beam is partially broken at the vehicle interior facing inside of the windshield 1 and reflected to a lesser extent back into the windshield 1 into. The partial beam which is refracted towards the vehicle interior on the inside of the windshield 1 is a horizontal main partial beam 3, which enters a camera, not shown, which is arranged behind the windshield 1. The partial beam reflected back into the windshield 1 is repeatedly refracted and / or reflected and generates inter alia a first double image corresponding to a first-order partial beam 4 and a second double image corresponding to a second-order partial beam 5. Because the sub-beams 4 and 5 appear on the CCD chip of the camera at locations other than the main sub-beam 3, "blooming" of the image of the light beam 2 in the image generated by the camera is caused. This "blooming" is stronger in the vertical direction than in the horizontal direction.

At each interface of the windshield 1, is reflected or reflected at the light beam 2, its light intensity is distributed to about 90% on the transmitted partial beam and about 10% on the reflected partial beam when the light beam 2 is unpolarized and the windshield 1 off Glass exists. Thus, the first partial beam 4 still has a relative intensity of 1/100 of that of the main partial beam 3 corresponding to an attenuation of 2OdB, while the second partial beam 5 still has a relative intensity of 1/10000 corresponding to an attenuation of 4OdB. Due to the logarithmic sensitivity characteristic of the CCD chip of the camera, however, the double images generated by the partial beams 4 and 5 appear much brighter in the image produced thereby. Especially in the range of high light levels, as they occur when the camera is hit by headlights, the CCD chip operates almost in the saturation range, and differences in intensity of some 1OdB are barely noticeable on the display of the night vision system. In Fig. 1 and in all other figures, in which the same or corresponding elements as in Fig. 1 are denoted by the same reference numerals, it is assumed for simplicity that the mentioned luminous intensity distribution of 90% to 10% of the refracted partial beams for all occurring refractions and reflections, and it is neglected that reflected partial beams can be more or less polarized at the angle ratios shown. Furthermore, it is neglected that even within the windshield 1 certain reflections and / or scattering may occur, namely at the embedded therein PVB film. Any adverse effects of the PVB film can also be mitigated by the measures described below for damping the double images.

In the embodiment of Fig. 2, a thin plane-parallel glass pane 6 is glued to the inside of the windshield 1, for example by means of refractive index matched, curing under ultraviolet light epoxy resin. The glass sheet 6 has only a fraction of the thickness of the windshield 1, for example a tenth of it, and forms a window in the light path of the camera, which has a size corresponding to the field of view of the camera. The vehicle interior facing surface of the glass sheet 6 is provided with an anti-reflection coating. Depending on the quality of the antireflection coating, the reflection coefficient is then reduced from previously 10% to 1% or significantly less. An easily achievable reduction of the reflection coefficient to 1% leads to an improvement in the attenuation of the first partial beam 4 from 2OdB to 3OdB and of the second partial beam 5 from 4OdB to 6OdB. Thus, the light intensities of the first and second double images are only one tenth or one hundredth the light intensities of the corresponding double images without the glass sheet 6 as in Fig. 1st

In the embodiment of Fig. 3 is located on the inside of the windshield 1, a thin plane-parallel glass plate 7, which is inclined at an angle of more than 0 °, but less than 90 ° to the window of the motor vehicle and the lower and front edge of the windshield 1 is present. A wedge-shaped free space 8 formed between the windshield 1 and the glass pane 7 is filled with a refractive index-matched material, for example an epoxy resin, which also holds the glass pane 7 against the windshield 1. Thus, a wedge-shaped transparent element or prism is formed, which causes the main partial beam 3 and the first-order partial beam 4 to be no longer parallel, as in FIGS. 1 and 2, but to diverge, as shown in FIG. 3 detects. Also, the sub-beam 5 second order is divergent (not shown in Fig. 3), and the partial beams 4 and 5 can no longer reach the camera. Unlike in the

Embodiment of Fig. 2, no antireflection coating is required in the embodiment of Fig. 3 to turn off the double images or at least substantially mitigate, although an additional

Antireflection coating may be helpful. The drawn in Fig. 3 wedge angle of about 6 ° is shown only for illustration. Which wedge angle is optimal in the concrete application can be calculated or determined by tests.

The embodiment of Fig. 4 differs from the embodiment of Fig. 3 only in that the glass sheet 7 rests with its upper and rear edge on the windshield 1, so that the between trained wedge-shaped space 8 is open at the top or rear. This clearance 8 is also filled with a refractive index matched material, and the partial beams 4 and 5 produced by reflections are also broken away from main partial beam 3, as can be seen in FIG.

Claims

claims

1. Night vision system for motor vehicles, which has a camera arranged behind an inclined disc of the motor vehicle and a planar transparent element, which is arranged in the light path of the camera between the disc and the camera, characterized in that the planar transparent element (6) substantially without optical interface between them on the disc (1) is applied and that the camera facing surface of the sheet-like transparent element a

Has anti-reflection coating.

2. Night vision system for motor vehicles, which has a camera disposed behind an inclined disc of the motor vehicle and a planar transparent element which is arranged in the light path of the camera between the disc and the camera, characterized in that the planar transparent element (7) an additional disc is inclined at an angle of more than 0 °, but less than 90 ° to the disc (1) of the motor vehicle.

3. night vision system for motor vehicles, according to claim 2, characterized in that the disc (1) and the additional disc (7) form a wedge-shaped free space (8) between them, which is filled with a transparent material, which also the additional disc on the disc holds.

4. Night vision system for motor vehicles, according to claim 2 or 3, characterized in that the camera facing surface of the sheet-like transparent element (6; 7) has an antireflection coating.

5. Night vision system for motor vehicles, according to one of the preceding claims, characterized in that the sheet-like transparent element (6; 7) is a glass or plastic plate or film with a constant thickness.

6. Night vision system for motor vehicles, according to one of the preceding claims, characterized in that the sheet-like transparent element (6; 7) and possibly the transparent filler material have a refractive index which is substantially equal to the refractive index of the disc (1) of the motor vehicle.

7. Night vision system for motor vehicles, according to one of the preceding claims, characterized in that the planar transparent element (6; 7) is polarizing or that is located at any other point in the light path of the camera between the disc and the camera, a polarizing filter.

8. Night vision system for motor vehicles, which has a camera arranged behind an inclined disc of the motor vehicle and a planar transparent element, which is arranged in the light path of the camera between the disc and the camera, characterized in that the transparent element is a polarizing filter.

9. Night vision system for motor vehicles, according to one of the preceding claims, characterized in that the inclined disc (1) of the motor vehicle whose windshield is.

10. Night vision system for motor vehicles, according to one of the preceding claims, characterized in that the camera is a CCD camera.

11. Night vision system for motor vehicles, according to one of the preceding claims, characterized in that the camera is an infrared camera, the forbidden system comprises at least one mounted on the motor vehicle infrared headlights and the sheet-like transparent element (6; 7) is transparent to infrared light.