Abstract
Fast optical 3D inline inspection sensors are a powerful tool to advance factory automation. Many of these visual inspection tasks require high speeds, high resolutions, and repeatability. Stereo vision, photometric stereo, light sectioning, and structured light are the most common principles for inline imaging in the several micrometers to sub-millimeter resolution range. Selecting the correct sensor principle can be challenging as manufacturers’ datasheets frequently use different values to describe their systems and do not stick to proposed characterizations defined by the “Initiative Fair Data Sheet” or the VDE/VDI standards. With the help of standardized parameters, this paper aims to compare four different measurement principles, namely AIT’s own single sensor light field camera method, a structured light pattern projector, a laser triangulation sensor, and a stereo camera system, with an approximate field of view of $100\times 100$ mm. We demonstrate simple yet meaningful experiments to determine lateral resolution, temporal noise, and calibration accuracy to enable an objective system comparison. Additionally, the reproduction of small surface structures and an overall performance on a challenging test object is evaluated. Results show that the measurement principles partly serve different application areas. The provided methods will help end users to select the correct sensor for specific applications.
Highlights
IntroductionVision systems are a crucial part in many manufacturing and quality control processes
To assist inspection tasks, vision systems are a crucial part in many manufacturing and quality control processes
In this paper we focus on inline 3D inspection tasks with a Field of View (FOV) of approximately >100 mm and a lateral sampling of around 50 μm/pixel, which are capable of being used in inline processes, and for inspection of objects moving across the FOV
Summary
Vision systems are a crucial part in many manufacturing and quality control processes. Production demands challenging requirements on the optical inspection system, namely high throughput, detection of small defects, both glossy and dark inspection surfaces, and precise 3D height measurements of moving objects [1]–[3]. There are a huge number of optical 3D imaging methods, which generally differ in speed and quality depending on environmental conditions [4], [5]. The pros and cons of different metrology methods are often difficult to grasp by the user. Technical terms are frequently used differently when comparing product data sheets. This problem is addressed by the ‘‘Initiative Fair Data Sheet’’ [6] (http://www.optassyst.de/fairesdatenblatt/) supported by numerous partners from research and industry. Acquisition techniques strongly differ in their robustness to different object types, surrounding illumination
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