DE102020120626A1 - Glare-reduced camera monitor system - Google Patents

Abstract

Camera monitor system in which the emitted or reflected luminous flux of a field of view is reflected via a mirror onto a camera sensor, characterized in that the camera sensor is arranged outside of the expected main direction of reflection of the light beams reflected by the mirror for capturing a virtual image of the field of view , where the main direction of reflection is the direction of the rays of the light rays reflected by the mirror from an external light source with the highest luminous flux.

Description

The invention relates to a glare-reduced camera monitor system for vehicles, in particular for digital rear-view mirrors.

State of the art

The utility model DE 20 2016 005 453 U1 discloses a vehicle exterior mirror system that includes an exterior vehicle portion having a lens and a prism and an interior vehicle portion having a mirror. The prism is designed to reflect light from the outside of the vehicle onto the mirror. Vehicle interior and exterior portions form a cavity that extends from the interior of the vehicle to the exterior of the vehicle. The vehicle exterior mirror system has a protective window made of glass, polymer or composite panes at both ends of the cavity. The protective windows may include an electro-optical element to help reduce glare. The mirror may also include an electro-optical element that can help reduce glare.

The problem of glare is not solved satisfactorily. Local dimming, which requires a very complex method of determining the glare source angle of incidence and the driver's eye position in order to work at all, does not solve one of the main glare problems, namely a strong contrast reduction due to the optical-physical phenomenon of haze luminance. Although large-area dimming can reduce direct glare, it is inherently associated with a reduction in contrast.

The utility model DE 297 05 054 U1 describes a rear-facing camera arrangement at fender height to replace the exterior mirrors. Alternatively, the camera monitor system (CMS) can be replaced by an optical system made up of light deflection devices such as mirrors and light guides. Both systems can also be combined so that the camera records the redirected image. Technical effects that could have a negative impact on glare are not disclosed per se, with the exception of the existence of extraneous light sources. The only way to reduce glare is to regulate the brightness of the monitor (display) using filters. As a result, this has the same effect as the local or large-area dimming of the electro-optical elements mentioned above in the mirror, each with the same disadvantages.

The vehicle exterior mirrors can therefore be replaced by a camera monitor system (KMS) and are therefore also called "digital rear-view mirrors". The rearward field of vision is transmitted into the vehicle interior via monitors or displays. The advantages of a CMS are higher degrees of freedom in the design of the vehicle, the improvement of the cd value (drag coefficient) of the vehicle body and thus the improvement of the acoustics due to less air turbulence, the reduction of the necessary drive energy due to the lower air resistance as well as the possibility of integrating the camera images and /or the monitor displays in the existing driver assistance systems (FAS). However, from an ophthalmic point of view, it should be viewed critically that such a system should have at least as small minimum contrasts and at least as high dynamics in luminance detection as a healthy human eye, so that it can perceive at least as well even under difficult lighting conditions.

object of the invention

It is therefore the object of the invention to improve a camera monitor system (CMS), in particular to ensure a high level of perception even under difficult lighting conditions.

Presentation and advantages of the invention

The task is solved by a camera monitor system according to the subject features of independent claim 1 .

First, a brief explanation of the optical background follows in order to understand the effect of the invention.

$$C\stackrel{!}{=}\text{max}$$

An object emits or reflects light. The resulting luminous flux depends on location and direction and is referred to as luminance L. An object with the luminance Lo must have a certain minimum contrast to its surroundings with the luminance Lu in order to be recognized. The higher the contrast C of the object to its surroundings, the higher the probability that the object will be detected or perceived. (2) must be satisfied for maximum detectability. $$C=\frac{L_O-L_u}{L_u}$$

$$C\stackrel{!}{=}\text{Max}$$

$$C_W\le C$$

$$C_W\stackrel{!}{\to }C$$

A glaring light source causes stray light in the eye. The stray light is referred to as the "equivalent veil luminance" _Lsaq and reduces the perceived contrast C _w . In order to keep detectability as high as possible, condition (5) should be met. $$C_W=\frac{L_O-L_u}{L_u+L_{S\ddot{a}q}}$$

$$C_W\le C$$

$$C_W\stackrel{!}{\to }C$$

The equivalent veil luminance is proportional to the illuminance E _B on the eye. The illuminance E indicates the light on a surface, e.g. B. the eye, incident luminous flux again and is also referred to as luminous flux density. $$L_{S\ddot{a}q}=f\left(In\mathrm{i.e}ivi\mathrm{i.e}\mathrm{and}\mathrm{and}m,GeOmet\mathrm{right}ie\right)\cdot E_B$$

The function f depends on the individual and on the blend geometry. Glare illuminance must be minimized to meet (5). $$E_B\stackrel{!}{=}\text{at least}$$

This also applies to a camera, since the structure of a camera and the eye are similar (objective = eye lens and vitreous body, aperture = iris, photodetector = retina). Even with a camera, the detected contrast is reduced by stray light penetrating the lens.

The invention relates to a camera monitor system (CMS), preferably for detecting and displaying a rear or front field of view for a vehicle. CMS are known from the prior art. Cameras are preferably digital cameras that capture and store, forward or display individual images by means of light sensors, also known as image sensors. Image sensors can differ according to the principle of the sensors and the readout of the data, e.g. B. CCD sensors or CMOS sensors, and are known in principle to those skilled in the art. In addition to the known image-presenting displays, a monitor is also understood to mean vehicle-integrated data processing or evaluation, by means of which the image data are output to the driver directly or in processed form. A processed form is, for example, the integration into a driver assistance system, which warns the driver by means of optical, haptic and/or acoustic output.

Information on orientation, such as the rear or front, relates to the longitudinal axis of the vehicle. The front field of vision thus corresponds to the view of the scenery in front of the vehicle, that is to say what the driver sees through the windscreen, with the field of vision to be recorded not having to match the driver's natural field of vision. The driver's main line of sight is the direction of travel, although the opposite direction, in most cases to see the rear view, should also be monitored regularly. In these two viewing directions, oncoming or following road users are regularly present, which is why these two directions are correspondingly susceptible to glare situations. In principle, the CMS according to the invention can also be used for other viewing directions, for example downwards from a truck driver's cab. However, these viewing directions are not critical with regard to possible glare.

The camera monitor system has a mirror chamber with a vehicle interior portion and a vehicle exterior portion, making it partly inside and partly outside the vehicle shell, z. B. body panel, is arranged, but without having to be physically divided from the vehicle shell.

The camera monitor system further includes input optics associated with the vehicle exterior portion for receiving light from outside the vehicle into the mirror chamber. The input optics can be a lens, a mirror, a prism, a transparent pane or have means for adjusting the transmission or reflection of the received light. The input optics are used to shape and/or guide the received or incident light and are basically known from the prior art.

The camera-monitor system also has a mirror arranged in the mirror chamber. The mirror, which lies behind the entrance optics in the beam path of the light incident through the entrance optics into the mirror chamber, is preferably a flat mirror, but can also be a curved or other type of mirror, which can mainly be used for reflection, but also for shaping the incident light . The mirror is arranged in such a way that the light incident from the direction of the vehicle's outer section is reflected in the direction of the vehicle's inner section. The mirror can be designed as a fully reflecting mirror, as a splitter mirror, as a one-way mirror and/or as an interference mirror. The mirror reflects incident light optically in a very defined way with little diffusely reflected portion.

The CMS also has one located in the mirror chamber and those of the mirror camera sensor detecting reflected light rays. This corresponds to the image sensor described above.

The camera monitor system also has a display unit for displaying the incidence of light detected by the camera sensor. The incidence of light, also referred to as an image, displayed on the display unit, which corresponds to the monitor described above, can be processed and/or displayed. Editing can be the targeted manipulation of original image components, e.g. B. Brightness adjustments of particularly light or dark areas, or the addition of new information, e.g. B. in the form of a (colored) frame around an object of interest. Processing can be the targeted interpretation or extraction of information from the image, with further processing in other systems being possible. Of course, an image can be edited as well as processed, e.g. if identified objects in the image are visually highlighted. The treatment and/or processing of the incidence of light detected by the camera sensor can be object recognition, such as road user or lane line recognition, transmission to a driver assistance system arranged inside the vehicle, transmission to a display or reception unit arranged outside the vehicle, or also recording include for subsequent display. Accordingly, the representation is not limited to the pure (not edited or processed) image reproduction, but can also be edited or processed.

The CMS is characterized in that the camera sensor is arranged outside the expected main direction of reflection of the light rays reflected by the mirror for capturing a virtual image of the field of view, the main direction of reflection being the direction of the rays of the light rays reflected by the mirror from an external light source with the highest luminous flux.

The main direction of reflection is the (theoretical) direction in which, due to the geometry, the largest proportion of the incident illuminance (luminous flux per surface) is reflected by the mirror. It can be expressed vectorially as a single ray or as a solid angle. When the illuminance of the main reflection direction hits a driver's eye or the lens of a camera, it acts as a glare illuminance and reduces the perceived contrast. The expected main direction of reflection is the most probable direction of reflection according to the vehicle design, e.g. B. mounting height and angle of the mirrors, the vehicle equipment, z. B. Height of the seats or arrangement of the steering wheel, as well as the vehicle environment, such as the road layout and other fixed or moving light sources.

A virtual image is a mirror-reflected image of the rear or front field of vision, which is perceptible outside the main direction of reflection of the incident light rays. It is perceived in the line of sight as lying behind the mirror.

In other words, the CMS is characterized in that the camera sensor is not arranged in the expected maximum illuminance for capturing the virtual mirror image.

Advantageously, the CMS according to the invention enables the reflected field of view to be recorded with a higher contrast range, since the glare illuminance which is incident on the image sensor and is the main cause of the veiling luminance is minimized. This leads to an improvement in the perceptiveness of the camera-monitor system, even under difficult lighting conditions, which in turn contributes to a significant increase in safety and the range of functions made possible by driver assistance systems.

In an advantageous development of the camera-monitor system, the mirror and/or the camera sensor are arranged so that they can move. Accordingly, both the mirror and the camera sensor can be rotatable, pivotable and/or displaceable, that is to say their position relative to one another, relative to the vehicle and relative to the vehicle environment can be changed. The adjustment can be incremental or continuous. Advantageously, this allows the geometric arrangements of the components to be adapted to one another and thus a shift in the expected main direction of reflection relative to the camera sensor or a shift in the camera sensor relative to the expected main direction of reflection. This brings about a further increase in safety in assisted or autonomous driving, since the glare illuminance can be deflected even more reliably from the camera sensor and the detectable contrast can be further increased.

In a further embodiment of the invention, the mirror and/or the camera sensor can be moved as a function of an environment determined by an expectation unit. The expectation unit can be embodied in the form of a control unit, which receives signals or data from an environment detection unit, processes them and/or forwards them to a driver assistance system or warnings to a driver in the form of control commands. The anticipation unit is designed to assess the current glare situation based on recognized and localized light sources, e.g. B. other vehicles, stationary light sources or the sun to interpret. This is done using data from the vehicle's own surroundings detection devices, such as cameras, data from other vehicles, which is received via vehicle-to-vehicle communication, or data from digital maps and calendars, in order to select areas with expected light sources from the course of the road, or, for example, to determine the time and location-dependent position of the sun.

Advantageously, the mirror and/or the camera sensor can thus be adjusted, depending on the actual position of the external light source and with knowledge of the optical and geometric relationships, in such a way that the camera sensor is not arranged in the main direction of reflection of the light source and the virtual image is therefore recognized with high contrast.

In a particularly advantageous development of the camera-monitor system according to the invention, the mirror chamber has openings for receiving stray light. The mirror chamber can be provided with openings so that the stray light cannot be reflected in the direction of the camera sensor. The entire structure of the light-detecting section of the CMS can be made compact and partially sunk into the vehicle's outer shell, so that the camera is no more bulky than in the previous structure and takes up space.

In a further particularly advantageous development of the invention, at least one additional light sensor, preferably a plurality of additional light sensors, is arranged in the mirror chamber. This additional light sensor in addition to the camera sensor can be designed as a simple light sensor in the form of a photodiode or a photoresistor. The additional light sensor, or illumination sensor, is designed to detect stray light in the mirror chamber and/or the light reflected by the mirror. In situations in which the position of the external light source changes quickly or frequently, or in special geometric cases of the position of the external light source in relation to the vehicle, the additional light sensor can be used to detect even more precisely if the camera sensor is in the field with high illuminance (main reflection direction). Mirror and camera sensor can move the camera sensor out of the main direction of reflection by sole or coordinated position changes. The shifting of the main direction of reflection can also be detected early, so that a preventive adjustment of the mirror and/or camera sensor can take place.

In a further embodiment of the invention, the entrance optics can be changed in their refraction property and/or the mirror in its reflection property (curved) for shaping the received and/or reflected light. The refractive property of the entrance optics can be changed by a lens with variable curvature. This results in a different exit and/or refraction angle of the incoming and outgoing light as well as a change in the focal length. The reflection property of the mirror can also be adjusted by changing the curvature. This can also be done using a micro-mirror array (DMD—Digital Micromirror Device). Advantageously, the incident luminous flux can thus be shaped, bundled and/or deflected in a targeted manner in order to further reduce stray light and to move the camera sensor even more reliably out of the main direction of reflection.

example

Further features, application possibilities and advantages of the invention result from the following description of exemplary embodiments of the invention with reference to the schematically illustrated drawings.

• 1 eine Teilansicht des erfindungsgemäßen Kamera-Monitor-Systems mit dem erfindungsgemäßen Wirkprinzip und
• 2 eine vorteilhafte Ausgestaltung mit Störlichtöffnungen und weiteren Lichtsensoren.

Here show:

• 1 a partial view of the camera-monitor system according to the invention with the active principle according to the invention and
• 2 an advantageous embodiment with stray light openings and other light sensors.

1 shows the part of the light detection system of the camera-monitor system according to the invention in the form of a vehicle exterior mirror (1). The monitor is not shown. This can be done professionally. The vehicle exterior mirror (1) is partially arranged outside the vehicle outer shell (10). Behind the vehicle, not shown, is a glare source (2), for example the headlights of another vehicle driving behind. The luminous flux (4) emitted by the glare light source (2) enters the mirror chamber of the vehicle exterior mirror (1) through the input optics (7) (dash-dot line) and hits the mirror (3) there. This reflects the incident luminous flux (4), with the mirror (3) being positioned in such a way that the largest proportion of the incident luminous flux or the proportion with the highest illuminance or luminous flux density is reflected in the direction of the reflected luminous flux (5) shown. The reflected luminous flux (5) represents the main direction of reflection given the geometric conditions shown, i.e. the position of the glare light source (2) and the angle of the mirror (3).

It can be seen that the camera sensor (8) is not arranged in the main direction of reflection. The largest part of the luminous flux (4, 5) emitted and reflected by the glare light source (2) therefore does not hit the camera sensor (8) and does not cause any veiling of luminance and thus no loss of contrast. The field of view (9) of the camera (8) is still directed towards the mirror (3). This enables the virtual image (6) of the glare light source (2) or the field of view to be recorded. The avoidance of glare thus enables a high-contrast and detailed detection of the glare light source (2) and associated or surrounding objects.

2 shows an advantageous embodiment of the camera-monitor system according to the invention with stray light openings (11) and other light sensors (12). The stray light openings (11) can direct stray light out of the vehicle exterior mirror without it hitting the camera sensor (8). The stray light openings (11) are preferably arranged on the side of the shell of the vehicle exterior mirror (1) that is inside the vehicle shell (10) and can be designed to be adjustable. The other light sensors (12) are arranged inside the shell of the vehicle exterior mirror (1) and are data-connected to the CMS.

The additional light sensors (12) can be arranged around the camera sensor (8) in order to detect a movement in the main direction of reflection in the direction of the camera sensor (8) in good time and to preventive adjustment of the input optics, the mirror (3) or the positioning unit of the camera sensor (8 ) trigger. The additional light sensors (12) can also be distributed within the mirror chamber of the vehicle exterior mirror (1) in order to record the entire light situation in the mirror chamber. Alternatively or additionally, further light sensors (12) can be arranged in the main direction of reflection in order to detect deviations from the expected direction at an early stage and, if necessary, to initiate corrective measures.

Reference List

1

vehicle exterior mirror

2

glare source

3

mirror

4

emitted luminous flux

5

reflected luminous flux

6

virtual image of the field of view

7

input optics

8th

camera sensor

9

field of view camera

10

vehicle shell

11

stray light openings

12

light sensors

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 202016005453 U1 [0002]
• DE 29705054 U1 [0004]

Claims (6)

Camera-monitor system, preferably for detecting and displaying a rear or front-side field of view for a vehicle, comprising: - a mirror chamber with a vehicle interior section and a vehicle exterior section, - input optics assigned to the vehicle exterior section for receiving light from outside the vehicle into the mirror chamber, - a mirror arranged in the mirror chamber, - a camera sensor arranged in the mirror chamber and detecting the light beams reflected by the mirror, and - a display unit for displaying the incidence of light detected by the camera sensor, characterized in that the camera sensor is outside of the expected main direction of reflection of the the mirror reflected light rays is arranged for capturing a virtual image of the field of view, wherein the main reflection direction is the beam direction of the mirror reflected light rays of an external light source with the highest Lic htstrom is. camera monitor system claim 1 , characterized in that the mirror and/or the camera sensor are movably arranged. camera monitor system claim 2 , characterized in that the mirror and/or the camera sensor can be moved as a function of an environmental situation determined by an expectation unit. Camera monitor system according to one of the preceding claims, characterized in that the mirror chamber has openings for receiving stray light. Camera monitor system according to one of the preceding claims, characterized in that at least one further light sensor is arranged in the mirror chamber. Camera monitor system according to one of the preceding claims, characterized in that the input optics can be changed in terms of their refractive property and/or the mirror can be changed in terms of its reflection property.

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