cost effective quality assessment in industrial parts manufacturing via optical acquisition

Abstract We tackle the problem of dimensional verification via optical acquisition systems in the context of industrial manufacturing processes. Optical methods for quality inspection play a crucial part in the transition process to industry 4.0 and, despite the lack of international standardization, several solutions are available to industries that need to provide dimensional verification to their customers. Unfortunately most of these solutions are still economically unavailable to the majority of small or medium companies. In this paper we present an optical system based on low-cost components and we demonstrate that it provides useful and reliable information in quality inspection procedures

High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques

This video describes the fundamentals of digital fringe projection techniques, which provide dense 3D measurements of dynamically changing surfaces. It also demonstrates the design and operation of a high-speed binary defocusing system based on these techniques

BUDDHIST STELE OF SWAT VALLEY: POINT CLOUD ANALYSIS AND INTERPRETATION

Abstract. With recent advancements on 3D sensors and cloud computing, high-speed, high-accuracy 3D measurement at micrometer level have been increase by scientists community and digital humanities researchers.The methodology proposed in this project aims to test some of the algorithms used in remote-sensing to the Buddhist sculptures from Swat Valley (Pakistan); these algorithms use high-resolution topographic data to identify, from DEMs, specific features like valleys, ridges, peaks, pits or surface anomalies.In the carved stone, the surface is analysed like a landscape, where carved areas are valleys bordered by slopes and crests. One of the simplest tools, the commonly used analytical hill-shading, which simulates artificial illumination on the DEM surface, is based on the same principle as the use of an oblique light source to highlight incisions in classic photography. Other families of algorithms that can be divided into three main groups (Slope and Curvature, Local Relief Model and Sky View Factor, Positive and Negative Openness and Geomorphons) are tested here

Reduction of systematic errors in structured light metrology at discontinuities in surface reflectivity

In measuring 3D shape with structured light techniques, systematic errors arise in the neighbourhood of discontinuities in reflectivity or geometry. A mechanism for this phenomenon is proposed, based on the finite size of the imaging system’s point spread function. A theoretical analysis for the phase errors in a phase-shifting projected fringe system is given, from which a correction algorithm to minimise the systematic errors is presented. In this algorithm, a closed form expression for the errors based on the intensity values and the phase values in a neighbourhood excluding the affected region is used to remove the estimated error from the measured phase values within the affected region. Experiments on samples with both linear and circular discontinuities in reflectivity demonstrated respective reductions in systematic errors by factors of 2.5× and 3×

A grid-point detection method based on U-net for a structured light system

Accurate detection of the feature points of the projected pattern plays an extremely important role in one-shot 3D reconstruction systems, especially for the ones using a grid pattern. To solve this problem, this paper proposes a grid-point detection method based on U-net. A specific dataset is designed that includes the images captured with the two-shot imaging method and the ones acquired with the one-shot imaging method. Among them, the images in the first group after labeled as the ground truth images and the images captured at the same pose with the one-shot method are cut into small patches with the size of 64x64 pixels then feed to the training set. The remaining of the images in the second group is the test set. The experimental results show that our method can achieve a better detecting performance with higher accuracy in comparison with the previous methods.Comment: http://airccse.org/csit/V10N16.htm

A Coded Structured Light System Based on Primary Color Stripe Projection and Monochrome Imaging

Coded Structured Light techniques represent one of the most attractive research areas within the field of optical metrology. The coding procedures are typically based on projecting either a single pattern or a temporal sequence of patterns to provide 3D surface data. In this context, multi-slit or stripe colored patterns may be used with the aim of reducing the number of projected images. However, color imaging sensors require the use of calibration procedures to address crosstalk effects between different channels and to reduce the chromatic aberrations. In this paper, a Coded Structured Light system has been developed by integrating a color stripe projector and a monochrome camera. A discrete coding method, which combines spatial and temporal information, is generated by sequentially projecting and acquiring a small set of fringe patterns. The method allows the concurrent measurement of geometrical and chromatic data by exploiting the benefits of using a monochrome camera. The proposed methodology has been validated by measuring nominal primitive geometries and free-form shapes. The experimental results have been compared with those obtained by using a time-multiplexing gray code strategy