Camera arrangement behind an inclined pane

A camera arrangement includes a camera having a lens pointed at a pane and being separated from the pane. A light-guiding element is between the camera lens and the pane. The light-guiding element guides at least light which is incident on the pane in a grazing manner from a direction of incidence to the camera.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a camera arrangement having a camera directed onto a pane with a light-guiding element being between the camera and the pane.

2. Background Art

A camera arrangement includes a camera and a pane. The pane separates an outside region from an inside region. For example, the pane is a vehicle window pane such that the outside region is the environment outside of the vehicle and the inside region is the vehicle interior. The camera is located in the inside region (i.e., behind the pane) for protection from the outside region and is directed towards the pane to detect images in the outside region (i.e., to detect light rays incident to the pane). The detection region of the camera is a function of the optics of the camera and the configuration of the arrangement. Because of space requirements of the camera, it is generally not possible to align the camera relative to the pane such that the detection region extends along the surface of the pane. Consequently, the camera has a blind region in which the camera cannot detect light rays which are incident to the pane at an angle nearly parallel to the surface of the pane (i.e., light rays which have a glancing angle of incidence).

U.S. Pat. No. 7,322,755, which is hereby incorporated by reference, describes a camera arrangement having a camera and a pane. A light-guiding element fills the space between the camera and the pane. The camera may be cast within the light-guiding element. The camera arrangement is configured such that the camera has a detection region along a horizontal viewing direction. Due to the refractive properties of the transmitting medium (e.g., air on the outer region of the pane, the pane, the light-guiding element), light rays incident onto the pane at shallow angles (i.e., at angles between the normal angle of incidence and glancing angles of incidence) are deflected in the direction of the camera.

SUMMARY OF THE INVENTION

An object of the present invention is a camera arrangement having a camera directed onto a pane in which the camera has a detection region large enough to detect light rays which are incident to the pane at angles nearly parallel to the surface of the pane such that the camera can detect objects located in a viewing direction nearly parallel to the surface of the pane through which light passes. Consequently, the camera has a relatively reduced blind angle such that the camera can detect objects visible in the neighborhood of the surface of the pane (i.e., the camera is capable of imaging the detection of objects at a shallow (i.e., glancing) angle with respect to the surface of the pane).

In carrying out the above object and other objects, the present invention provides a camera arrangement having a camera and a light-guiding element. The camera has a lens pointed at a pane and separated from the pane. The light-guiding element is between the camera lens and the pane. The light-guiding element guides at least light which is incident on the pane in a grazing manner from a direction of incidence to the camera.

Further, in carrying out the above object and other objects, the present invention provides another camera arrangement having a camera and a light-guiding element. The camera includes a lens pointed at a pane and separated from the pane. The pane divides an outside region from an inside region with the camera being in the inside region. The light-guiding element is between the camera lens and the pane. The light-guiding element guides light from the outside region that is incident to the pane and is substantially perpendicular to the normal of the pane to the camera lens.

Also, in carrying out the above object and other objects, the present invention provides another camera arrangement having a camera and a light-guiding element. The camera includes a lens pointed at a pane and separated from the pane. The pane divides an outside region from an inside region with the camera being in the inside region. The light-guiding element is between the camera lens and the pane. The light-guiding element guides light from the outside region that is incident to the pane and is substantially parallel with the pane to the camera lens.

In embodiments of the present invention, a light-guiding element guides light incident on the pane, at least from a glancing angle of incidence, to the camera.

A light ray incident on a pane having parallel faces from a non-perpendicular direction continues to pass in the direction of incidence, having undergone a slight parallel displacement after passing through the pane, because the refraction of the light ray toward the perpendicular at the point of entry into the pane is cancelled by refraction away from the perpendicular as the light ray exits the pane. Thus, the angular region detected by a camera through the pane is insignificantly altered. For various reasons such as minimizing space requirements, prevention of reflections on the inner sides of the panes, protection against vandalism and environmental effects, etc., it is necessary to mount the camera near the pane and to screen the camera and the region of light passage between camera and the pane by a housing. These requirements can generally be fulfilled in cases where the camera points almost perpendicularly through the pane. However, when a part of the outside space near the pane surface is to be detected, the camera must be pointed at a shallow angle to the plane. This is often disadvantageous due to the space requirement of the camera and the resulting large screening.

In embodiments of the present invention, a light-guiding element is between the camera and the pane. The light-guiding element include a prism or a combination of prisms. The light-guiding element cancels the refraction effect behind the pane such that light rays emanating from a comparatively large angular region in front of the pane are transmitted into a comparatively small angular region behind the pane and can thus be detected by the camera.

In an embodiment of the present invention, the light-guiding element and the pane are integrally joined together. In another embodiment of the present invention, the pane is formed integrally with the light-guiding element. The external surface of the pane is thereby formed by the outer surface of the light-guiding element, which is mostly designed to be flat. The light-guiding element thus fulfills the pane function of separating inner and outer regions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now toFIG. 1, a schematic representation of a camera arrangement10in accordance with an embodiment of the present invention is shown. Camera arrangement10includes a camera12, a pane14, and a light-guiding element16. Camera12includes a lens18. Pane14separates an outside region20from an inside region22. Pane14has an outer surface24facing outside region20and an inner surface26facing inside region22. Outer and inner surfaces24,26of pane14are parallel to one another such that pane14is a flat parallel pane. Pane14may be a window pane of a vehicle or a building.

Camera12is arranged in inside region22with camera lens18being oriented in a slanted direction towards pane14. Light-guiding element16is arranged between camera12and pane14. Forward side28of light-guiding element16is connected to inner surface26of pane14and opposite rearward side30of light-guiding element16is connected to camera lens18. The connections of light-guiding element16to inner surface26of pane14and to camera lens18is as seamless as possible.

Light-guiding element16includes a prism or a combination of prisms. Light-guiding element16has a refraction index that is substantially the same as the refraction index of pane14. Preferably, pane14and light-guiding element16are made of the same material. For example, pane14is a glass pane and light-guiding element16is a glass prism. Edge surfaces32and34of light-guiding element16may be colored mat black to prevent distracting reflections and penetration by ambient light.

Pane14and light-guiding element16may be formed integrally with one another. Similarly, light-guiding element16and camera lens18may be formed integrally with one another. Other configurations for fabricating and designing camera arrangement10in which camera12is connected to pane14via a light-guiding element16are described in U.S. Pat. No. 7,322,755, which is hereby incorporated by reference.

Camera12located on inside region22is intended to record an image of outside region20passing through pane14. As shown inFIG. 1, light rays incident on camera lens18from outside region20are refracted during transition. The angle of refraction depends on the incident angle of light rays impinging on pane14. As an example of light ray trajectories,FIG. 1illustrates (as continuous lines) three light rays38,40,42incident on camera lens18.FIG. 1further illustrates (as dashed lines) the apparent light paths39,41,43and thus the directions from which corresponding light rays38,40,42appear to originate by straight line propagation, i.e., without refraction. The difference between the actual (38,40,42) and corresponding apparent (39,41,43) light ray trajectories are manifested by a distortion of the image detected by camera lens18. The difference between the actual trajectory and apparent trajectory of a light ray becomes larger as the angle of incidence, measured with respect to the normal36of pane14, of the light ray becomes larger. For instance, the difference between the actual trajectory of light ray38and its apparent trajectory39is relatively small as light ray38has a relatively small angle of incidence relative to pane normal36whereas the difference between the actual trajectory of light ray42and its apparent trajectory43is relatively large as light ray42has a relatively large angle of incidence relative to pane normal36.

As further seen inFIG. 1, light rays (e.g., light ray42) which fall onto pane14at a glancing angle (i.e., at an angle that is almost perpendicular to pane normal36or, put another way, at an angle that is almost parallel with outer surface24of pane14) are deflected by light-guiding element16into camera lens18. This feature of camera12being able to detect an image from directions that are almost parallel to the surface of pane14is made possible by light-guiding element16in conjunction with camera12being tilted with respect to pane14as shown inFIG. 1.

Camera arrangement10further includes an evaluation device44. Evaluation device44is connected to camera12for receiving a camera signal indicative of the image detected by camera12. Evaluation device44processes the camera signal for display on a monitor48. Evaluation device44can be integrated in camera12. Evaluation device44includes a computer46or the like for processing the signal output to equalize the image detected by camera12.

Numerous advantageous applications are possible for the image acquisition process described here. For example, pane14can be a window pane of a building with camera12and light-guiding element16being attached to pane14and thereby being protected inside the building. Camera12enables the monitoring of the area below pane14without camera12being accessible or even visible from outside region20. Thus, for example, camera12arranged above a door can be pointed downward at a steep angle and thereby cover the region directly in front of the door.

Pane14can likewise be a side window of a vehicle. In this case,FIG. 1indicating a view from above onto the edge of side window14. Camera12initially detects a side region of the vehicle, while the incident direction parallel to pane14can be provided for detecting the rear side of the vehicle. Camera12thereby assumes the function of a side mirror characterized by an extremely small blind spot.

In addition, camera arrangement10can be located on the rear window of a vehicle, whereby it is possible to achieve a wide view of the rear vehicle region, for example, as a backup or parking aid, or for monitoring a trailer hitch.