Simultaneous All-Parameters Calibration and Assessment of a Stereo Camera Pair Using a Scale Bar

Abstract

Highly accurate and easy-to-operate calibration (to determine the interior and distortion parameters) and orientation (to determine the exterior parameters) methods for cameras in large volume is a very important topic for expanding the application scope of 3D vision and photogrammetry techniques. This paper proposes a method for simultaneously calibrating, orienting and assessing multi-camera 3D measurement systems in large measurement volume scenarios. The primary idea is building 3D point and length arrays by moving a scale bar in the measurement volume and then conducting a self-calibrating bundle adjustment that involves all the image points and lengths of both cameras. Relative exterior parameters between the camera pair are estimated by the five point relative orientation method. The interior, distortion parameters of each camera and the relative exterior parameters are optimized through bundle adjustment of the network geometry that is strengthened through applying the distance constraints. This method provides both internal precision and external accuracy assessment of the calibration performance. Simulations and real data experiments are designed and conducted to validate the effectivity of the method and analyze its performance under different network geometries. The RMSE of length measurement is less than 0.25 mm and the relative precision is higher than 1/25,000 for a two camera system calibrated by the proposed method in a volume of 12 m × 8 m × 4 m. Compared with the state-of-the-art point array self-calibrating bundle adjustment method, the proposed method is easier to operate and can significantly reduce systematic errors caused by wrong scaling.

Correcting Decalibration of Stereo Cameras in Self-Driving Vehicles

“…The introduction of high definition cameras and related inexpensive hardware had a similar effect, which called for efficient calibration of high-definition stereo rigs [19]. The consequence of stereo imaging systems entering widespread use is indeed the search for methods that are easy to operate and still provide high-quality stereo calibration, one of such methods is presented in work by Sun et al [20]. Interesting common point with our system is that they specifically target large calibration volumes, which cannot be efficiently calibrated by the conventional checkerboard pattern methods.…”

Correcting Decalibration of Stereo Cameras in Self-Driving Vehicles

“…The introduction of high definition cameras and related inexpensive hardware had a similar effect, which called for efficient calibration of highdefinition stereo rigs [1]. The consequence of stereo imaging systems entering widespread use is indeed the search for methods that are easy to operate and still provide highquality stereo calibration, one of such methods is presented in work by Sun et al [13]. Interesting common point with our system is that they specifically target large calibration volumes, which cannot be efficiently calibrated by the conventional checkerboard pattern methods.…”

Sensor-aided camera calibration for three dimensional digital image correlation measurements

“…Due to the separability of a stereovision system's intrinsic and extrinsic parameters, researchers are currently looking for alternative ways to compute the extrinsic parameters. Some examples include using a single image of multiplanar 15 or cylindershaped 16 calibration objects, collecting multiple images of a scale bar 17 , measuring the phase-shift of active targets 18,19 , and relying on the detection of single feature points 20 . However, those procedures are still affected by the drawbacks of a traditional image-based calibration, such as the loss of calibration after the cameras are moved relatively to each other.…”