Portable visual metrology without traditional self-calibration measurement model

To improve the 3D measurement accuracy of portable visual metrology using generic digital SLRs, deficiencies related to the traditional self-calibration model are analyzed, and a novel calibration method of generic digital SLRs is proposed. The collinear equations are established using the orientation angles of the targets, which are determined using a non-parameterized calibration platform. After calibration, the camera maps the orientation angles of incoming scene rays to the corresponding pixels on the image plane, becoming a goniometer. Additionally, the implementation and error analysis of the non-parameterized calibration model are investigated. The image points matching method, external station orientation method and bundle adjustment algorithm, which are based on orientation angles of image points, are studied. Finally, the calibration and 3D measurement accuracy are verified, along with the variation in the measurement accuracy with different calibration rotation intervals and LED intervals of the straight line target. The experimental results show that our calibration method is efficient to improve the 3D measurement accuracy of generic digital SLRs.