Method for dynamically calibrating vehicular cameras

  • US 10,640,041 B2
  • Filed: 02/04/2019
  • Issued: 05/05/2020
  • Est. Priority Date: 04/25/2011
  • Status: Active Grant
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First Claim
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1. A method of dynamically calibrating without manual intervention a forward viewing vehicular camera with respect to its three rotational degrees of freedom, the method comprising:

  • disposing a forward viewing camera at a vehicle, the forward viewing camera, when disposed at the vehicle, having a field of view exterior and forward of the vehicle;

    providing a control having a processor operable for processing image data captured by the forward viewing camera;

    driving the vehicle so that the vehicle is in motion;

    wherein driving the vehicle comprises steering the vehicle so as to establish a plurality of vehicle steering angles;

    operating the forward viewing camera to acquire multiple frames of image data captured by the forward viewing camera while the vehicle is in motion and steered within at least two ranges of steering angles, wherein each frame of captured image data defines an image plane having a horizontal axis and a vertical axis;

    determining, via processing at the control of a first image frame of image data captured by the forward viewing camera, first and second feature points in the first image frame of captured image data;

    tracking, via processing at the control of image frames of image data captured by the forward viewing camera subsequent to the first image frame, a motion trajectory of the first feature point and of the second feature point while the vehicle is moving and steered within a first range of steering angles;

    determining a first vanishing point based on the tracked first feature point and second feature point;

    determining, via processing at the control of a second image frame of image data captured by the forward viewing camera, third and fourth feature points in the second image frame of captured image data;

    tracking, via processing at the control of image frames of image data captured by the forward viewing camera subsequent to the second image frame, a motion trajectory of the third feature point and of the fourth feature point while the vehicle is moving and steered within a second range of steering angles that is different from the first range of steering angles;

    determining a second vanishing point based on the tracked third feature point and fourth feature point;

    determining a vanishing line based on the first and second vanishing points;

    determining whether the vanishing line is non-parallel to the horizontal axis of the image plane; and

    responsive to determining that the vanishing line is non-parallel to the horizontal axis of the image plane, adjusting at least one selected from the group consisting of pitch of the forward viewing camera, roll of the forward viewing camera and yaw of the forward viewing camera to correct for rotational misalignment of the forward viewing camera.

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