Image Noise Compensation in Industrial Implementation of the SFF Method Using Controllable Optics

To keep up with increasing production efficiency and rising consumer demands, the industry is increasingly implementing quality control systems. Vision systems are starting to play an increasingly important role in quality control. Such systems allow the assessment of the geometry and surface of a part in an autonomous and non-contact manner. 3D vision systems are a particular case of vision systems. 3D vision systems allow the measurement of a scene, including depth information. As a result, a broader analysis of dimensions and defects is possible which for 2D systems may remain neglected. Only a few 3D imaging methods are applicable in industrial conditions. Scanners based on laser triangulation, stereovision and time of flight technologies are available. This article discusses the industrial implementation of another 3D image acquisition method - Shape From Focus. Shape from focus estimates the scene depth by comparing local sharpness in the image during the movement of the image plane. Usually image plane position is changed by the movement of the vision system. The novel approach is the use of electrically controlled optics to replace the movement of the system. It recognizably improves 3D scene acquisition performance. Electrically controlled optics also introduces the undesirable implications of changing the focusing power and magnification during acquisition. This results in noise in the 3D image. The article proposes a compensation algorithm to reduce the impact of the mentioned factors on the final 3D image. The paper discusses the structure of the stand used in the research. Factors affecting the quality of the 3D image obtained are presented and compensation algorithm is proposed. The study focuses on images of actual industrial materials.