DE102008027307A1 - Camera arrangement for a motor vehicle - Google Patents

Abstract

The invention relates to a camera arrangement for a motor vehicle having a vehicle window through a camera, wherein in the beam path between the vehicle window and the camera lens is introduced a prism arrangement having at least two successively arranged prisms of optically transparent materials, which cooperatively color error compensating properties, wherein the Prisms are oriented so that they have opposite refractive directions and their facing surfaces are non-parallel and wherein the beam path passes through a non-condensed optical medium located between the prisms.

Description

The The invention relates to a camera arrangement for a motor vehicle with a vehicle window looking through a camera, wherein in the beam path between the vehicle window and the camera lens a prism assembly is placed, the at least two consecutively arranged prisms of optically transparent materials, the have cooperative color-error compensating properties.

camera arrangements for example, with a camera looking through a vehicle window used for lane and / or traffic sign recognition. In a modern motor vehicle stands as a windshield designated front vehicle window under a relatively flat Angle (about 20 ° to 25 °) to the horizon. Therefore becomes a horizontally incident light beam at Entry into such a vehicle window strongly broken.

In order to the light beam at the exit from the vehicle window again is broken, it is known a prismatic light guide refraction-free or with only a small refraction to the inside of the Coupling the vehicle window. Such light guide However, geometric distortions and annoying ones can Cause color aberrations. When the geometric distortions act these are both vertical compressions and bends the camera pictures.

The Use of the light guide in combination with the strong refraction on the outer surface of a vehicle window In addition to an angular deflection leads to an enlargement beam cross-section after refraction. This is desired because thereby the coupling surface on the vehicle window can be kept small.

In the European patent specification EP 1 651 469 B1 a camera arrangement is described in which the light guide is formed of a solid composite of at least two prisms, which form an achromatisch acting arrangement according to the flint crown glass principle.

adversely here is that of the needed different Prism materials usually at least one is relatively expensive, which contributes significantly to the cost of the entire camera assembly.

adversely is further that the color error compensation only for a few wavelengths succeed well. A further improved Color error compensation requires the use of additional Prisms made of other materials, resulting in another Cost leads.

This Prisms are optically coupled to each other and are usually together glued, wherein the adhesive material in terms of its optical Properties must meet high requirements, otherwise considerable reflection losses occur.

Of Furthermore, the previously known prism arrangement geometric distortions do not correct, so that an image defect correction later, about through digital equalization.

It Therefore, the task arose, a camera arrangement for to create a motor vehicle, which is a particularly cost-effective and at the same time efficient color error compensating prism combination and in addition by a lesser degree distinguishes geometric distortions.

These The object is achieved according to the invention that the prisms are oriented so that they are opposite Have refractive directions and their facing surfaces non-parallel run and that the beam path through a between the prisms located non-condensed optical medium runs.

The facing each other surfaces of the prisms are thus under an offset angle ≠ 0 ° to each other, wherein in the space between these prism faces Gas, gas mixture or a vacuum is located. For an efficient Color aberration requires that the optical medium there is little or no dispersion between the prisms, why provided here a non-condensed optical medium is.

Especially advantageous is that by a suitable arrangement of two prisms in an optimized offset angle to each other a very good color error compensation for a large wavelength range becomes possible, giving a qualitatively excellent color representation allows.

The camera assembly according to the invention sets, in contrast to that of the EP 1 651 469 B1 known camera arrangement, no prisms of different materials ahead. This makes it possible to manufacture both prisms from a single inexpensive glass or plastic material.

It is particularly advantageous that the angles between the optically acting surfaces of the two prisms or even the entire shape and size of both prisms can match. As a result, a single prism type can be used for both prisms be used. Since a lower unit price can be achieved through higher production quantities of the same prisms, this results in further cost savings.

alternative can also be provided, the two prisms by a molded Connecting connecting element with each other. The prism arrangement can also be used, for example, as an integrally formed light guide body, which provides an air gap between the two prisms formed be. Such a prism arrangement with fixedly arranged Prisms is particularly inexpensive to produce and requires no adjustment effort during assembly.

The Prism arrangement made possible by shaping the beam path the construction of a particularly compact camera arrangement. this will by the counter-rotating beam deflection by reached the two prisms.

by virtue of the offset angle between the two prisms results in a anamorphic distortion, namely a vertical compression of the picture. This can be advantageous depending on the purpose of the camera may be and may be displayed on a screen through the camera or an evaluation device connected to the camera by electronic means, in particular by a digital computer, easily reversed. The single prism observed curvature of the camera image is against compensated by the prism arrangement.

in the The following is an embodiment of the invention based the drawing shown and explained in more detail become.

The 1 shows the basic arrangement of the components of a camera arrangement according to the invention. Since the structure and function principle is to be clarified, the components shown in terms of a real constructive implementation neither size nor angle to each other shown.

The arrangement consists in its minimal configuration of two prisms ( 3 . 5 ) and a camera 7 , where the camera 7 the vehicle window 2 looks through, so light from the outside of the vehicle window 2 receives. The beam path runs here 1 from the vehicle window 2 to the camera 7 through both prisms ( 3 . 5 ) and through, between the prisms ( 3 . 5 ) located optical medium 4 ,

The term "camera" is to be understood in this document an arrangement consisting of at least one lens 6 and a light-sensing sensor chip 8th consists. The objective 6 has at least one focusing lens. Of course, further optical, electronic or mechanical components, in particular a separate housing, also components of the camera 7 be.

The term "prism" here refers to a body having mutually non-parallel, optically refracting surfaces. In the simplest case, the prisms ( 3 . 5 ), as shown in the figure, be designed as simple triangular prisms, which are perpendicular to the beam path 1 have a triangular cross-sectional area.

It is advantageous if the prisms ( 3 . 5 ) consist of the most cost-effective materials, it being particularly advantageous if both prisms ( 3 . 5 ) consist of the same material and also have the same shape and size, so are designed to be identical overall, so that can be used in large quantities cheap to produce prisms. It should be noted that the properties of the prisms (see 3 . 5 ) are by no means to be regarded as mandatory for the function of the arrangement, so that in a suitable adaptation prisms of different shapes, sizes and materials can be connected to form a prism group. Important here is the achievement of the desired beam deflection with the best possible color compensation.

The important thing is that the beam path between the prisms ( 3 . 5 ) through an optical medium 4 which has a different refractive index than the prisms ( 3 . 5 ). As this refractive index of the optical medium 4 It must be smaller than the refractive index or refractive indices of the prisms and the dispersion of the optical medium should be as low as possible, it is advantageous an uncondensed optical medium 4 provide, so a gas or gas mixture, in particular air. In addition, a non-material optical medium can also be used 4 , so a vacuum between the prisms ( 3 . 5 ) be provided.

To explain the principle of operation of the arrangement shown is in the 1 the course of three parallel rays of light 1 represented, approximately horizontally on the outside of a vehicle window inclined towards the direction of incidence 2 to meet. When entering the vehicle window, the light rays 1 Broken towards the Scheibenlot.

On the inside of the vehicle window 2 is a first prism 3 arranged. This first prism 3 has a same or similar refractive index as the vehicle window 2 , and is visually to the vehicle window 2 coupled, so that in the transition region between the vehicle window 2 and the first prism 3 virtually no angular deflection of the light rays 1 he follows.

The two prisms ( 3 . 5 ) are with their prism angles ( 3a . 5a ) are oriented opposite to each other so that they pass through the light beams 1 deflect in opposite directions of refraction. The beam deflection of the first prism 3 becomes so through the second prism 5 at least partially compensated. The beam path is defined by a default of the offset angle 4a between the prisms ( 3 . 5 ), which is advantageous in the construction of a particularly compact camera arrangement.

The after passing through the second prism 5 still parallel to each other light beams 1 be through the camera lens 6 on the sensor chip 8th the camera 7 focused.

The principle of color error compensation is described below with reference to 2 and 3 explained. The 2 illustrates first in a highly simplified, purely qualitative representation, the emergence of color aberrations, in an arrangement with only one prism.

On the entrance surface of the prism 3 ' meet two parallel white beams 1' on. The different color components of these rays 1' are known to pass through the prism 3 ' due to the dispersion properties of the prism material broken to different degrees. This is indicated here by the fact that the incoming light rays 1 split into two beams (b ₁ ', r ₁ ', b ₂ ', r ₂ '), wherein the rays (r ₁ ', r ₂ ') shown in dashed lines represent the red color components here, while the beams (b ₁ ', b ₂ ') represent the blue color components.

As rays of the same colors (b ₁ ', b ₂ ', or r ₁ ', r ₂ ') through the prism 3 ' are equally strong, the same color rays (b ₁ ', b ₂ ', or r ₁ ', r ₂ ') each parallel to each other in the lens 6 ' , here symbolically represented by a single convex lens, and through the lens 6 ' focused on one pixel (B or R). Pixels of different color (B or R) are thus in the image plane of the camera next to each other, resulting in color fringes or in a only sensing the brightness sensor chip ("black and white camera") to blurred images.

The compensation of these color errors occurs, as in the 3 outlined by a second prism 5 , The second prism 5 breaks the incoming rays of light 1 like the first prism 3 , but because of his first prism 3 opposite arrangement in the opposite direction. This is especially true for the different degrees of refraction of different colors, so that the rays of different colors are aligned parallel to each other after passing through the second prism. These parallel rays are created by the focusing lens 6 combined in a single pixel P, resulting in no more color separation in the image plane of the camera.

In the event that the offset angle 4a of the two prisms ( 3 . 5 ) Becomes zero, you get the special case that the two prisms form a plane-parallel plate. In this special case results in a distortion-free and completely chromatic aberration-free image, but lacks the desired deflection of the beam path. This deflection is only by a suitable offset angle 4a of the two prisms ( 3 . 5 ) reachable. With increasing offset angle 4a also the beam deflection becomes larger. In principle, the color error increases, but to a much smaller extent than with only one prism as in 2 shown. In particular, it is possible by suitable simultaneous selection of the refractive indices of the media 3 . 4 and 5 , the prism angle ( 3a . 5a ) and the offset angle ( 4a ) for a certain angle of incidence range of the light beams 1 to achieve a very good color compensation.

1, 1'

light rays (Optical path)

2

vehicle window

3, 3 '

first prism

3a

prism angle

4

optical medium

4a

offset angle (between the prisms)

5

second prism

5a

prism angle

6 6 '

lens

7

camera

8th

sensor chip

b ₁ , r ₁ ', b ₂ ', r ₂ '

radiate

R B, P

pixels

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1651469 B1 [0005, 0014]

Claims (9)

Camera arrangement for a motor vehicle with a vehicle window through a camera, wherein in the beam path between the vehicle window and the camera lens is introduced a prism arrangement having at least two successively arranged prisms of optically transparent materials, which cooperatively color error compensating properties, characterized in that the prisms ( 3 . 5 ) are oriented such that they have opposite directions of refraction and their faces facing each other are non-parallel and that the beam path through a between the prisms ( 3 . 5 ) located non-condensed optical medium ( 4 ) runs. Camera arrangement according to claim 1, characterized in that the prisms ( 3 . 5 ) consist of the same material. Camera arrangement according to claim 1, characterized in that the prisms ( 3 . 5 ) the same prism angle ( 3a . 5a ) exhibit. Camera arrangement according to claim 3, characterized in that the prisms ( 3 . 5 ) have the same shape. Camera arrangement according to claim 1, characterized in that the prism arrangement exactly two prisms ( 3 . 5 ) having. Camera arrangement according to claim 1, characterized in that the optical medium ( 4 ) is formed by a gas or gas mixture. Camera arrangement according to claim 1, characterized in that the optical medium ( 4 ) is designed as a vacuum. Camera arrangement according to claim 1, characterized in that the prisms ( 3 . 5 ) are integrally connected. Camera arrangement according to claim 1, characterized in that the angles ( 3a . 5a ) between the optically acting surfaces of the prisms ( 3 . 5 ) and at the same time the offset angle ( 4a ) between the prisms ( 3 . 5 ) are selected so that the color error resulting from this arrangement is minimized.