tailieunhanh - Robot Vision 2011 Part 9

Tham khảo tài liệu 'robot vision 2011 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 312 Robot Vision The polynomial function is used both to determine the focal distance at the center of the image and to correct the diffraction angle produced by the lens. With the tested lenses the actual focal distance for the 4mm lens obtained by this method is while for the 6mm lens the actual focal distance is mm. Polynomial coefficients K0 K1 K2 and K3 calculated for the two tested lenses are respectively 0 0 .0045 and 0 0 . CCD Plane Fig. 4. Correction of radial distortion as a function of 0. Using this method we will also assume that the pinhole model can provide an accurate enough approach for our practical setup therefore disregarding any other distortion of the lens. Instead of elaborating on the general problem from the beginning we will start by applying some restrictions to it that will simplify the initial solution. Later on these restrictions will be relaxed in order to find a general solution. Initial approach Let s start by assuming a restricted setup as depicted in Fig. 5. Assumptions applied to this setup are as follows The origin of the coordinate system is coincident with the camera pinhole through which all light rays will pass i j and k are unit vectors along axis X Y and z respectively The Y axis is parallel to the mirror axis of revolution and normal to the ground plane CCD major axis is parallel to the X system axis CCD plane is parallel to the XZ plane Mirror foci do not necessarily lie on the Y system axis The vector that connects the robot center to its front is parallel and has the same direction as the positive system Z axis Distances from the lens focus to the CCD plane and from the mirror apex to the XZ plane are htf and mtf respectively and can be readily available from the setup and from manufacturer data Point Pm mcx 0 mcz is the intersection point of the mirror axis of revolution with the XZ plane Distance unit used throughout this discussion will be the millimeter. Calibration