Global Calibration of Multi-Cameras Based on Refractive Projection and Ray Tracing

Abstract

Multi-cameras system is widely applied in 3D computer vision especially when multiple 11 cameras are distributed on both sides of the measured object. The calibration methods of multi-12 cameras system are critical to the accuracy of vision measurement and the key is to find an 13 appropriate calibration target. In this paper, a high-precision camera calibration method for multi- 14cameras system based on transparent glass checkerboard and ray tracing is described, which is used 15 to calibrate multiple cameras distributed on both sides of the glass checkerboard. Firstly, the

Perspective Camera Model With Refraction Correction for Optical Velocimetry Measurements in Complex Geometries

“…In (9) the dependences of the refractive distortion function F F upon the model parameters have been explicitly reported. In this regard, it should be noted that the optical ray distortion dj j depends only on the refractive intrinsic parameters (g and r r) and the relative position of the focus C with respect to the body (j j C ), and not on the relative position and orientation of the body with respect to the world reference frame (refractive extrinsic parameters).…”

“…In this paper, an experimental verification of the method was also provided for a planar acrylic window separating air from water and mean reprojection errors between 0.1 and 0.2 pixels were reported as a function of the number of cameras employed. More recently, Feng et al [9] used a similar raytracing technique to develop a multi-camera calibration method based on the use of a refractive transparent glass calibration board. Beyond analogies with these methods, the model proposed herein adopts a slightly different principle for 3D point projection, i.e., the computation of the optical ray distortion which is implicitly defined by the relative position and orientation of the pinhole focus, the object point and the refractive body.…”

Optimisation of camera positions for optical coordinate measurement based on visible point analysis

“…Characterisation of the intrinsic and extrinsic camera parameters is critical for accurate measurement [19]. Camera calibration is a research topic in its own right and is beyond the scope of this work (for more details see [19][20][21][22][23]). Barazzetti points out [10] that as optical coordinate measurement, particularly photogrammetry, has become more accessible, inexperienced users with little measurement experience often produce crude reconstructions at the cost of metric accuracy.…”