Efficient Optical Metrology for Industrial Inspection

Optical metrology for the characterization and inspection of objects has become increasingly popular and mature in recent years [1]. The principles of various optical metrology methods may be quite different. Among the large variety of optical measurement technologies, the phase-aided active stereoscopy (PAAS) based on sinusoidal fringe structured illumination becomes one of the most attractive approaches [2]. The PAAS can acquire the range images with high accuracy and dense point cloud thus it is widely used for surface profile measurement. Nevertheless, the inspection task with single three-dimensional (3D) optical sensor will be confronted with a serious of challenges, such as the limitation of the field of view (FOV), the contradiction between measurement accuracy and volume. To measure large and complex surface with single 3D optical sensor, it should be recognized that employing a relatively small FOV and multiple viewpoints to cover the entire surface area would be a simple and effective process to get a 3D surface model with high relative accuracy and spatial resolution. However, in the case of industrial inspection, if the objects cannot be moved and rotated freely, it would be a complex and cost solution to change the viewpoint automatically.