US 11,875,535 B2
Method, apparatus, electronic device and computer readable medium for calibrating external parameter of camera
Zhikang Zou, Beijing (CN); Xiaoqing Ye, Beijing (CN); Xiao Tan, Beijing (CN); and Hao Sun, Beijing (CN)
Assigned to Beijing Baidu Netcom Science and Technology Co., Ltd., Beijing (CN)
Filed by Beijing Baidu Netcom Science and Technology Co., Ltd., Beijing (CN)
Filed on Jun. 4, 2021, as Appl. No. 17/339,177.
Claims priority of application No. 202011375196.4 (CN), filed on Nov. 30, 2020.
Prior Publication US 2021/0358169 A1, Nov. 18, 2021
Int. Cl. G06T 7/80 (2017.01); G06T 7/73 (2017.01)
CPC G06T 7/80 (2017.01) [G06T 7/74 (2017.01); G06T 2207/10028 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A method for calibrating an external parameter of a camera, the method comprising:
acquiring a data set of three-dimensional point clouds and a two-dimensional image time-synchronized with the data set, of a calibration reference object, the two-dimensional image being acquired by the camera with a to-be-calibrated external parameter;
establishing a transformation relationship between a point cloud coordinate system and an image coordinate system, the transformation relationship comprising a transformation parameter;
back-projecting the data set of the three-dimensional point clouds onto a plane where the two-dimensional image is located through the transformation relationship to obtain a set of projection points of the three-dimensional point clouds;
adjusting the transformation parameter to map the set of projection points onto the two-dimensional image to obtain an adjusted transformation parameter; and
obtaining the to-be-calibrated external parameter of the camera based on the adjusted transformation parameter and the data set of the three-dimensional point clouds,
wherein the adjusting the transformation parameter to map the set of projection points onto the two-dimensional image, comprises:
initializing the transformation parameter; and
increasing or decreasing a value of the transformation parameter until the set of projection points is mapped onto the two-dimensional image, in response to detecting that the set of projection points is not mapped onto the two-dimensional image.