Haldimann, R., "3D Countersink Measurement," SAE Technical Paper 2015-01-2510, 2015, doi:10.4271/2015-01-2510.
Accurate measurement of countersinks in curved parts has always been a challenge. The countersink reference is defined relative to the panel surface which includes some degree of curvature. This curvature thus makes accurate measurements very difficult using both contact and 2D non-contact measurements. By utilizing structured light 3D vision technologies, the ability to very accurately measure a countersink to small tolerances can be achieved. By knowing the pose of the camera and projector, triangulation can be used to calculate the distance to thousands of points on the panel and countersink surface. The plane of the panel is then calculated using Random Sample Consensus (RANSAC) method from the dataset of points which can be adjusted to account for panel curvatures. The countersink is then found using a similar RANSAC method. As the full geometric definition of the countersink and the plane are known, the radius and angle of the countersink can be calculated by intersecting of the two geometries to find the countersink diameter and depth. By inspecting the fit of each set of point to their respective geometric entities a confidence factor can be generated for the overall countersink measurement. Utilization of this technique would allow for more detailed measurement of countersink features.