HD-RTI: An adaptive multi-light imaging approach for the quality assessment of manufactured surfaces

Nurit, Marvin; Goïc, Gaëtan Le; Lewis, David E.; Castro, Yuly; Zendagui, Abir; Chatoux, Hermine; Favrelière, Hugues; Maniglier, Stéphane; Jochum, Pierre; Mansouri, Alamin

doi:10.1016/j.compind.2021.103500

Cited by 14 publications

(13 citation statements)

References 26 publications

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“…The human–machine interface of LightBot is simple and completely built over a HTTP webserver. Hence, with the API of the LightBot, which gives access to various functionalities of the system, it is convenient to develop new methods in RTI acquisition, such as NBLP [ 15 ], HD-RTI [ 22 ], data stitching, etc. The key benefits of this system design are demonstrated in this paper.…”

Section: Discussionmentioning

confidence: 99%

LightBot: A Multi-Light Position Robotic Acquisition System for Adaptive Capturing of Cultural Heritage Surfaces

et al. 2022

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Multi-light acquisitions and modeling are well-studied techniques for characterizing surface geometry, widely used in the cultural heritage field. Current systems that are used to perform this kind of acquisition are mainly free-form or dome-based. Both of them have constraints in terms of reproducibility, limitations on the size of objects being acquired, speed, and portability. This paper presents a novel robotic arm-based system design, which we call LightBot, as well as its applications in reflectance transformation imaging (RTI) in particular. The proposed model alleviates some of the limitations observed in the case of free-form or dome-based systems. It allows the automation and reproducibility of one or a series of acquisitions adapting to a given surface in two-dimensional space.

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Section: Discussionmentioning

confidence: 99%

LightBot: A Multi-Light Position Robotic Acquisition System for Adaptive Capturing of Cultural Heritage Surfaces

et al. 2022

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“…The system is motorized, allowing the selection of adjustable illumination angles and number of positions. High Dynamic Range RTI (HD-RTI) was selected to compensate for under-or over-saturated pixels due to the various illumination an- gles [25]. 150 to 170 images were acquired for each data set in each case study to obtain an adequate amount of information accounting for computational time and data quality [26].…”

Section: Data Acquisitionmentioning

confidence: 99%

Appearance segmentation and documentation applied to cultural heritage surfaces

Saha¹,

Σιάτου²,

Degrigny³

et al. 2023

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This paper describes the application of a novel supervised segmentation technique used for conservation documentation based on visible appearance changes of Cultural Heritage (CH) metal surfaces. The technique employs a linear discriminant analysis model to classify Reflectance Transformation Imaging (RTI) reconstruction coefficients. The Hemispherical Harmonics (HSH) reconstruction coefficients for each pixel are first calculated and then normalized. This normalization enhances the robustness and invariance of the application, making it possible to apply it for documenting different surfaces at different time intervals. This paper presents three cases related to surface appearance changes due to corrosion that provokes low or high topographic changes. Tarnishing of silver and filiform corrosion on steel are examined. For each case study, a supervised data set is constructed, teaching the algorithm to recognize as distinct a specified appearance characteristic (such as corrosion, metal, etc.) by comparing it to the reconstruction coefficients of each pixel through Linear Discriminant Analysis (LDA). A simplified color map visualizes the segmented information. The calculated results are afterward verified by visible inspection from conservation-restoration experts. The method can segment surfaces with changes in micro-geometry, creating accurate cartographies of the object's condition. However, limitations are met on surfaces with minimal topography and high specularity.

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“…The principle of this technique is illustrated in Figure 1, where PTM, HSH, and DMD are RTI reconstruction models and stand for Polynomial Texture Mappings, Hemispherical Harmonics, and Discrete Modal Decomposition, respectively. Many new RTI acquisition modalities have recently been developed, including multispectral approaches [34,35], approaches to measure the complete luminance dynamic (HD-RTI, [36][37][38]) self-adaptive approaches to determine the relevant lighting directions (NBLP-RTI, [39]), and even robot-based RTI systems [40]. Within the framework of this research, we focus on the RTI acquisition parameters associated with the conventional approach.…”

Section: Reflectance Transformation Imagingmentioning

confidence: 99%

“…The lower lens and other optic components are fully modular, allowing one to cover a very wide range of the measurement scale, the main limitation being the difference between the maximum and minimum magnification ([×1, ×12]) and the space available to position the samples to be measured (maximum of approximately 10 × 10 cm). The device can be fully controlled with a user interface, allowing one to adjust all the RTI acquisition parameters [38]. In addition, the system is modular, and a specific light wavelength for RTI acquisition on particular surfaces, such as transparent or semi-transparent (varnished) surfaces, can easily be implemented.…”

Section: Experimental Surface Samples and Rti Acquisition Set-upmentioning

confidence: 99%

Reflectance Transformation Imaging as a Tool for Computer-Aided Visual Inspection

et al. 2022

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This work investigates the use of Reflectance Transformation Imaging (RTI) rendering for visual inspection. This imaging technique is being used more and more often for the inspection of the visual quality of manufactured surfaces. It allows reconstructing a dynamic virtual rendering of a surface from the acquisition of a sequence of images where only the illumination direction varies. We investigate, through psychometric experimentation, the influence of different essential parameters in the RTI approach, including modeling methods, the number of lighting positions and the measurement scale. In addition, to include the dynamic aspect of perception mechanisms in the methodology, the psychometric experiments are based on a design of experiments approach and conducted on reconstructed visual rendering videos. The proposed methodology is applied to different industrial surfaces. The results show that the RTI approach can be a relevant tool for computer-aided visual inspection. The proposed methodology makes it possible to objectively quantify the influence of RTI acquisition and processing factors on the perception of visual properties, and the results obtained show that their impact in terms of visual perception can be significant.

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HD-RTI: An adaptive multi-light imaging approach for the quality assessment of manufactured surfaces

Cited by 14 publications

References 26 publications

LightBot: A Multi-Light Position Robotic Acquisition System for Adaptive Capturing of Cultural Heritage Surfaces

LightBot: A Multi-Light Position Robotic Acquisition System for Adaptive Capturing of Cultural Heritage Surfaces

Appearance segmentation and documentation applied to cultural heritage surfaces

Reflectance Transformation Imaging as a Tool for Computer-Aided Visual Inspection

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