METHOD FOR CALIBRATING AN ASSEMBLY USING AT LEAST ONE OMNIDIRECTIONAL CAMERA AND AN OPTICAL DISPLAY UNIT

• US 20100214412A1
• Filed: 09/23/2008
• Published: 08/26/2010
• Est. Priority Date: 10/16/2007
• Status: Active Grant

• Current Assignee: Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler AG (Mercedes-Benz Group AG)
• Inventors: Ehlgen, Tobias
• Granted Patent: US 8,599,258 B2
• Time in Patent Office: Days
• US Class Current: 348/148
• CPC Class Codes: G06T 3/047 Fisheye or wide-angle transformations
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle

Abstract

A method for calibrating an assembly consisting of an omnidirectional camera (2) located on a vehicle (1) and an optical display unit. An image displayed by the display unit reproduces a perspective of an imaginary virtual camera above the object (1), an image from the virtual camera is projected into an object coordinate system and resulting coordinates (X_W, X_W.Y) are projected into the omnidirectional camera. During the projection of the image of the virtual camera into the object coordinate system, pixels (x_p) of the image of the virtual camera within an imaginary circle or ellipse (1) around the object are projected onto an imaginary plane, while pixels (x_p) of the image outside the circle or ellipse are transformed by the virtual camera into the object coordinate system in such a way that they are projected onto an imaginary surface that rises from the edge of the circle or ellipse.

Claims

1. A method for calibrating an assembly having at least one omnidirectional camera (2) that is arranged on an object (1) and an optical display unit, in which an image that is displayed by the display unit reproduces a perspective of an imaginary virtual camera above the object (1), wherein an image from the virtual camera is projected into an object coordinate system and wherein the resulting coordinates (X_W, X_W.Y) are projected into the omnidirectional camera, the method comprising, during the projection of the image of the virtual camera into the object coordinate system:

projecting onto an imaginary plane pixels (x_p) of the image of the virtual camera within an imaginary circle or ellipse around the object (1),

while transforming pixels (x_p) of the image outside the circle or ellipse by the virtual camera into the object coordinate system in such a way that they are projected onto an imaginary surface that rises from the edge of the circle or ellipse,

wherein a height of the coordinates (X_W, X_W.Y) on the surface in the object coordinate system is proportional to a distance of the coordinate (X_W) to a center of the circle or the ellipse.

2. The method according to claim 1, wherein the surface has the form of a casing of a truncated cone.

3. The method according to claim 1, wherein the omnidirectional camera (2) is calibrated with regard to intrinsic parameters with the help of a calibration body, which comprises the entire field of view of the omnidirectional camera (2).

4. The method according to claim 3, wherein the calibration body has the form of a barrel, whose inner side is provided with circular markings.

5. The method for the image processing and image display by means of an assembly with at least one omnidirectional camera (2) arranged on an object (1), especially a vehicle (1) and an optical display unit, wherein the assembly is calibrated by means of a method according to claim 1, wherein an environment of the object (1) is recorded with the omnidirectional camera (2) and is reproduced in the display unit corresponding to the calibration.

6. The method according to claim 5, wherein images of two omnidirectional cameras (2) are recorded, which are arranged at a rear side of the vehicle (1).

7. The method according to claim 6, wherein a region with regard to the vehicle (1) detected by the omnidirectional cameras (2) is divided asymmetrically onto the omnidirectional cameras (2).

8. The method according to claim 5, wherein, with a reversing vehicle (1) and/or an engaged reverse gear, a drive movement is predicted in dependence on a steering angle (δ

_R) and is superposed over the image in the display unit.

9. The method according to claim 8, wherein the prediction is based on a single track model (6), where respectively two wheels of an axle are modelled by a virtual wheel (7) in the center of the axle.

10. The method according to claim 1, wherein the object (1) on which the at least one omnidirectional camera (2) is arranged is a vehicle.