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Using the optimal combined index weight ratio to improve the probability of anomaly detection in big area additive manufacturing

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VIRTUAL AND PHYSICAL PROTOTYPING 2025年第1期20卷

作者： Mcclain, Monique S. Chowdhury, Dhrubajit Eldaghar, Omar Villez, Kris Purdue Univ Sch Mech Engn W Lafayette IN 47907 USA Oak Ridge Natl Lab Mfg Demonstrat Facil Oak Ridge TN USA Purdue Univ Dept Math W Lafayette IN USA

Big Area Additive Manufacturing (BAAM) of composites requires significant time, energy, and material, so it is critical to reduce production inefficiencies to make functional parts without multiple iterations. Statistical process control coupled with Principal Component Analysis (PCA) is a powerful technique that provides a quick, computationally inexpensive, and intuitive way for operators to detect defects that form in a manufacturing process without massive datasets. Recently, a combined index that is a weighted sum of the Hotelling's $T<^>2$T2 and squared residual error statistics has been proposed that can be monitored in one chart, improving interpretation accuracy and simplicity. However, the literature does not offer a formal method to optimise the weights. Here, we introduce two new approaches to the traditional weight selection approach using simulated and BAAM image data. Approach 1 uses a theoretically motivated optimum inspired by probabilistic principal component analysis. Approach 2 systematically varies the ratio of the weights to find the optimum. We show that approach 1 delivers optimal anomaly detection performance in select cases while approach 2 fares better in practice. Surprisingly, we also show that choosing a more complex PCA model has a minimal negative impact on anomaly detection performance compared to a more simplistic model.

关键词： 3-Dimensional printing digitization and image capture machine learning biomanufacturing extrusion

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Assisted color acquisition for 3D models

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COMPUTERS & GRAPHICS-UK 2017年 68卷 119-128页

作者： Coutinho, Daniel Marroquim, Ricardo Dellepiane, Matteo Scopigno, Roberto Univ Fed Rio de Janeiro Comp Graph Lab BR-21941 Rio De Janeiro Brazil CNR ISTI Visual Comp Lab Pisa Italy

Capturing surface appearance precisely is paramount for modeling realistic materials. Nevertheless, the spatially varying nature of most materials is difficult to measure. State-of-the-art methods often rely on complex apparatus and controlled environments, and even if they are able to acquire reliable SVBRDFs, the whole process usually takes a long time and generates a large amount of data, that is often redundant. In this work, we propose a method for fast and assisted acquisition of material properties on-site. The system has a simple setup, requiring only a generic camera and a light source. Consequently, it is also very portable and appropriate for a broad range of object sizes and scenarios. The system guides the acquisition process, allowing for a fast capture session while at the same time producing high-quality per vertex diffuse colors. To help in achieving a complete coverage it suggests missing light directions, reducing the amount of necessary input images and the acquisition time. The system is designed to work in situ, therefore the whole acquisition process works with immediate feedback and interactive integration of new data. We show results for a variety of objects differing in size and materials. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： digitization and image capture Reflectance

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Convolutional Sparse Coding for High Dynamic Range Imaging

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COMPUTER GRAPHICS FORUM 2016年第2期35卷 153-163页

作者： Serrano, Ana Heide, Felix Gutierrez, Diego Wetzstein, Gordon Masia, Belen Univ Zaragoza E-50009 Zaragoza Spain Stanford Univ Stanford CA 94305 USA MPI Informat Saarbrucken Germany

Current HDR acquisition techniques are based on either (i) fusing multibracketed, low dynamic range (LDR) images, (ii) modifying existing hardware and capturing different exposures simultaneously with multiple sensors, or (iii) reconstructing a single image with spatially-varying pixel exposures. In this paper, we propose a novel algorithm to recover high-quality HDRI images from a single, coded exposure. The proposed reconstruction method builds on recently-introduced ideas of convolutional sparse coding (CSC);this paper demonstrates how to make CSC practical for HDR imaging. We demonstrate that the proposed algorithm achieves higher-quality reconstructions than alternative methods, we evaluate optical coding schemes, analyze algorithmic parameters, and build a prototype coded HDR camera that demonstrates the utility of convolutional sparse HDRI coding with a custom hardware platform.

关键词： Categories and Subject Descriptors (according to ACM CCS) I 4 1 [image Processing and Computer Vision] digitization and image capture

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Multisampling Compressive Video Spectroscopy

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COMPUTER GRAPHICS FORUM 2016年第2期35卷 467-477页

作者： Jeon, Daniel S. Choi, Inchang Kim, Min H. Korea Adv Inst Sci & Technol Seoul South Korea

The coded aperture snapshot spectral imaging (CASSI) architecture has been employed widely for capturing hyperspectral video. Despite allowing concurrent capture of hyperspectral video, spatial modulation in CASSI sacrifices image resolution significantly while reconstructing spectral projection via sparse sampling. Several multiview alternatives have been proposed to handle this low spatial resolution problem and improve measurement accuracy, for instance, by adding a translation stage for the coded aperture or changing the static coded aperture with a digital micromirror device for dynamic modulation. State-of-the-art solutions enhance spatial resolution significantly but are incapable of capturing video using CASSI. In this paper, we present a novel compressive coded aperture imaging design that increases spatial resolution while capturing 4D hyperspectral video of dynamic scenes. We revise the traditional CASSI design to allow for multiple sampling of the randomness of spatial modulation in a single frame. We demonstrate that our compressive video spectroscopy approach yields enhanced spatial resolution and consistent measurements, compared with the traditional CASSI design.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.4.1 [Computer Graphics]: image Processing and Computer Vision&mdash digitization and image capture

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Chroma key without color restrictions based on asynchronous amplitude modulation of background illumination on retroreflective screens

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JOURNAL OF ELECTRONIC IMAGING 2016年第2期25卷 023009-023009页

作者： Vidal, Borja Lafuente, Juan A. Univ Politecn Valencia Escuela Politecn Super Gandia C Paranimf 1 Gandia 46370 Spain Univ Politecn Valencia Nanophoton Technol Ctr C Paranimf 1 Gandia 46370 Spain

A simple technique to avoid color limitations in image capture systems based on chroma key video composition using retroreflective screens and light-emitting diodes (LED) rings is proposed and demonstrated. The combination of an asynchronous temporal modulation onto the background illumination and simple image processing removes the usual restrictions on foreground colors in the scene. The technique removes technical constraints in stage composition, allowing its design to be purely based on artistic grounds. Since it only requires adding a very simple electronic circuit to widely used chroma keying hardware based on retroreflective screens, the technique is easily applicable to TV and filming studios. (C) 2016 SPIE and IS&T

关键词： chroma keying video segmentation image processing digitization and image capture

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Design and Fabrication of Faceted Mirror Arrays for Light Field capture

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COMPUTER GRAPHICS FORUM 2013年第8期32卷 246-257页

作者： Fuchs, Martin Kachele, Markus Rusinkiewicz, Szymon Univ Stuttgart Stuttgart Germany Univ Ulm D-89069 Ulm Germany Princeton Univ Princeton NJ 08544 USA

The high resolution of digital cameras has made single-shot, single-sensor acquisition of light fields feasible, though considerable design effort is still necessary in order to construct the necessary collection of optical elements for particular acquisition scenarios. This paper explores a pipeline for designing, fabricating and utilizing faceted mirror arrays which simplifies this task. The foundation of the pipeline is an interactive tool that automatically optimizes for mirror designs while exposing to the user a set of intuitive parameters for light field quality and manufacturing constraints. We investigate two manufacturing processes for automatic fabrication of the resulting designs: one is based on CNC milling, polishing, and plating of one solid work piece, while the other involves assembly of CNC-cut mirror facets. We demonstrate results for refocusing in a macro photography scenario. In addition, we observe that traditional photographic parameters take novel roles in the faceted mirror array setup and discuss their influence.

关键词： catadioptric fabrication light field recording mirror design 2012 Computing Methodologies Artificial Intelligence Computer Vision image and Video Acquisition Computational Photography I 4 1 image Processing and Computer Vision digitization and image capture Imaging geometry

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Color invariant chroma keying and color spill neutralization for dynamic scenes and cameras

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VISUAL COMPUTER 2010年第9期26卷 1167-1176页

作者： Grundhoefer, Anselm Kurz, Daniel Thiele, Sebastian Bimber, Oliver Bauhaus Univ Weimar D-99423 Weimar Germany JKU Inst Comp Graph A-4040 Linz Austria

In this article we show how temporal backdrops that alternately change their color rapidly at recording rate can aid chroma keying by transforming color spill into a neutral background illumination. Since the chosen colors sum up to white, the chromatic (color) spill component is neutralized when integrating over both backdrop states. The ability to separate both states additionally allows to compute high-quality alpha mattes. Besides the neutralization of color spill, our method is invariant to foreground colors and supports applications with real-time demands. In this article, we explain different realizations of temporal backdrops and describe how keying and color spill neutralization are carried out, how artifacts resulting from rapid motion can be reduced, and how our approach can be implemented to be compatible with common real-time post-production pipelines.

关键词： Chroma keying Color spill image processing digitization and image capture

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Modeling Repetitive Motions Using Structured Light

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2010年第4期16卷 676-689页

作者： Xu, Yi Aliaga, Daniel G. Purdue Univ Dept Comp Sci W Lafayette IN 47907 USA

Obtaining models of dynamic 3D objects is an important part of content generation for computer graphics. Numerous methods have been extended from static scenarios to model dynamic scenes. If the states or poses of the dynamic object repeat often during a sequence (but not necessarily periodically), we call such a repetitive motion. There are many objects, such as toys, machines, and humans, undergoing repetitive motions. Our key observation is that when a motion-state repeats, we can sample the scene under the same motion state again but using a different set of parameters;thus, providing more information of each motion state. This enables robustly acquiring dense 3D information difficult for objects with repetitive motions using only simple hardware. After the motion sequence, we group temporally disjoint observations of the same motion state together and produce a smooth space-time reconstruction of the scene. Effectively, the dynamic scene modeling problem is converted to a series of static scene reconstructions, which are easier to tackle. The varying sampling parameters can be, for example, structured-light patterns, illumination directions, and viewpoints resulting in different modeling techniques. Based on this observation, we present an image-based motion-state framework and demonstrate our paradigm using either a synchronized or an unsynchronized structured-light acquisition method.

关键词： Three-dimensional graphics and realism digitization and image capture geometric modeling

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A Self-Calibrating Method for Photogeometric Acquisition of 3D Objects

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 2010年第4期32卷 747-754页

作者： Aliaga, Daniel G. Xu, Yi Purdue Univ Dept Comp Sci W Lafayette IN 47907 USA

We present a self-calibrating photogeometric method using only off-the-shelf hardware that enables quickly and robustly obtaining multimillion point-sampled and colored models of real-world objects. Some previous efforts use a priori calibrated systems to separately acquire geometric and photometric information. Our key enabling observation is that a digital projector can be simultaneously used as either an active light source or as a virtual camera ( as opposed to a digital camera, which cannot be used for both). We present our self-calibrating and multiviewpoint 3D acquisition method, based on structured light, which simultaneously obtains mutually registered surface position and surface normal information and produces a single high-quality model. Acquisition processing freely alternates between using a geometric setup and using a photometric setup with the same hardware configuration. Further, our approach generates reconstructions at the resolution of the camera and not only the projector. We show the results of capturing several high-quality models of real-world objects.

关键词： digitization and image capture scene analysis geometric modeling

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An Adaptive Correspondence Algorithm for Modeling Scenes with Strong Interreflections

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2009年第3期15卷 465-480页

作者： Xu, Yi Aliaga, Daniel G. Purdue Univ Dept Comp Sci W Lafayette IN 47907 USA

Modeling real-world scenes, beyond diffuse objects, plays an important role in computer graphics, virtual reality, and other commercial applications. One active approach is projecting binary patterns in order to obtain correspondence and reconstruct a densely sampled 3D model. In such structured-light systems, determining whether a pixel is directly illuminated by the projector is essential to decoding the patterns. When a scene has abundant indirect light, this process is especially difficult. In this paper, we present a robust pixel classification algorithm for this purpose. Our method correctly establishes the lower and upper bounds of the possible intensity values of an illuminated pixel and of a nonilluminated pixel. Based on the two intervals, our method classifies a pixel by determining whether its intensity is within one interval but not in the other. Our method performs better than standard method due to the fact that it avoids gross errors during decoding process caused by strong interreflections. For the remaining uncertain pixels, we apply an iterative algorithm to reduce the interreflection within the scene. Thus, more points can be decoded and reconstructed after each iteration. Moreover, the iterative algorithm is carried out in an adaptive fashion for fast convergence.

关键词： Three-dimensional graphics and realism digitization and image capture geometric modeling

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