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Fastener identification and assembly verification via IR tracking

ASSEMBLY AUTOMATION 2012年第3期32卷 262-275页

作者： Rusli, Leonard Luscher, Anthony Ohio State Univ Dept Mech & Aerosp Engn Columbus OH 43210 USA

Purpose - The purpose of this paper is to create an assembly verification system that is capable of verifying complete assembly and torque for each individual fastener. design/methodology/approach - The 3d position of the tool used to torque the fastener and the assembly pallet will be tracked using an infrared (IR) tracking system. A set of retro-reflective markers are attached to the tool and assembly while being tracked by multiple IR cameras. Software is used to triangulate the relative position of the tool in order to identify the fastener being torqued. The torque value is obtained from the tool controller device. By combining the location of the tool and the torque value from the tool controller, assembly of each individual fastener can be verified and its achieved torque recorded. Findings - The IR tracking is capable of tracking within 2-3 mm for each tracking ball, with a resulting practical resolution of 24 mm distance between fasteners while maintaining 99.9999 per cent reliability without false positive fastener identification. Research limitations/implications - This experiment was run under simulated assembly line lighting conditions. Practical implications - By being able to verify assembly reliably, the need for manual torque check is eliminate and hence yield significant cost savings. This will also allow programming electric tools according in real time based on the fastener in proximity identification. Originality/value - Currently, assembly verification is only done using the torque values. In automated assembly line, each process might involve fastening multiple fasteners. Using this system, a new level of assembly verification is achieved by recording the assembled fastener and its associated torque.

关键词： Assembly Sensors image processing 3-d image processing Sensor review Flaw detection Intelligent sensors Inspection Industrial robotics Automotive industry

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Adaptive Speckle Reduction in OCT Volume data Based on Block-Matching and 3-d Filtering

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IEEE PHOTONICS TECHNOLOGY LETTERS 2012年第20期24卷 1802-1804页

作者： Wang, Longzhi Meng, Zhuo Yao, X. Steve Liu, Tiegen Su, Ya Qin, Mingliang Tianjin Univ Coll Precis Instrument & Optoelect Engn Tianjin 300072 Peoples R China Tianjin Univ Minist Educ Key Lab Optoelect Informat Tech Sci Tianjin 300072 Peoples R China Suzhou Optoring Co Ltd Suzhou 215123 Peoples R China

An adaptive speckle denoising method called Volume-BM3d is developed for optical coherence tomography (OCT) volume data processing, including an adaptive noise level estimation algorithm and a denoising strategy based on block-matching and filtering in a highly sparse local 3-d transform domain. Noise level estimation, an important step for denoising, is obtained from estimating signal fluctuations among neighboring A-Scans. Unlike 2-d denoising approaches, the Volume-BM3d considers the similarities of tissue structures either in a single 2-d image or in a volume data simultaneously. It not only effectively suppresses speckle noise, but also improves the visualization of small morphological features, such as sweat glands in finger images. Application of this proposed method to the OCT volume data of a human finger tip shows an 18.4-dB signal-to-noise ratio improvement in speckle noise reduction with little edge blurring. It outperforms other filtering methods in suppressing speckle noises and revealing attenuated subtle features.

关键词： 3-d image processing image enhancement optical coherence tomography

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Histogram approaches for lossy compression of digital holograms of three-dimensional objects

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IEEE TRANSACTIONS ON image processing 2007年第6期16卷 1548-1556页

作者： Shortt, Alison E. Naughton, Thomas J. Javidi, Bahram Natl Univ Ireland Dept Comp Sci Maynooth Kildare Ireland Oulu Univ RFMedia Lab Ylivieska 84100 Finland Univ Connecticut Dept Elect & Comp Engn Storrs CT 06269 USA

We present a novel nonuniform quantization compression technique-histogram quantization-for digital holograms of 3-d real-world objects. We exploit a priori knowledge of the distribution of the values in our data. We compare this technique to another histogram based approach: a modified version of Max's algorithm that has been adapted in a straightforward manner to complex-valued 2-d signals. We conclude the compression procedure by applying lossless techniques to our quantized data. We demonstrate improvements over previous results obtained by applying uniform and nonuniform quantization techniques to the hologram data.

关键词： digital holography image compression nonuniform quantization 3-d image processing

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Free view 3-d visualization of occluded objects by using computational synthetic aperture integral imaging

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JOURNAL OF dISPLAY TECHNOLOGY 2007年第1期3卷 64-70页

作者： Hwang, Yong Seok Hong, Seung-Hyun Javidi, Bahram Univ Connecticut Dept Elect & Comp Engn Storrs CT 06269 USA Pusan Natl Univ Pusan 609735 South Korea

In this paper, we present computational methods for reconstructing a free view of a partially occluded object using integral imaging. To obtain unobstructed images with high resolution, low focus error, and large depth of focus, synthetic aperture integral imaging utilizing a digital camera has been adopted. Two novel algorithms are proposed: 1) an algorithm for reconstructing volumetric perspective images and 2) an algorithm for scaling reconstructed images at arbitrary distances.

关键词： geometrical optics integral imaging optical data processing 3-d image processing

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Representative elementary volume analysis of sands using X-ray computed tomography

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GEOTECHNICAL TESTING JOURNAL 2007年第3期30卷 212-219页

作者： Reza Razavi, Mohammad Muhunthan, Balasingam Al Hattamleh, Omar Washington State Univ Dept Civil & Environm Engn Pullman WA 99164 USA Hashemite Univ Dept Civil Engn Zarqa 13115 Jordan

The concept of a representative elementary volume (REV) provides an effective means of developing macroscopic measures in the description of granular materials. However, due to the difficulties associated with the measurement and characterization of granular microstructure the existence and size of an REV has remained largely conjectural. This study presents a systematic method to examine the characteristics of the REV using X-ray computed tomography images. The 3-d images of spherical glass beads., Silica sand, and Ottawa sand have been characterized using advanced image processing techniques. An interactive computer program is developed to study porosity variation within a sphere with increasing radius from the images of these materials. The porosity variation of Silica sand and Ottawa sand showed three characteristic regions: an initial fluctuation region due to microscopic variations, a constant plateau region, and a region with a monotonic increase/decrease due to heterogeneity. The homogenous medium of glass beads did not show the last region. The results show that for a random packing of spherical glass beads the REV is about two to three times of the identical average diameter. The radius for Silica sand composed mainly of elongated particles is between 5 to 11 times of d(50), and for Ottawa sand composed mainly of subrounded particles is between 9 to 16 times of d(50).

关键词： granular materials representative elementary volume porosity X-ray computed tomography 3-d image processing

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Analysis of 3-d Integral Imaging displays Using the Wigner distribution

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JOURNAL OF dISPLAY TECHNOLOGY 2006年第2期2卷 180-185页

作者： Furlan, Walter d. Martinez-Corral, Manuel Javidi, Bahram Saavedra, Genaro Univ Valencia Dept Opt E-46100 Valencia Spain Univ Connecticut Dept Elect & Comp Engn Storrs CT 06269 USA

Integral imaging is a promising technology for 3-d TV and 3-d display. In this paper, a theoretical analysis of 3-d integral imaging systems is performed in the frame of the Wigner distriburion formalism. It is shown that the entire intensity distribution in the pick-up image plane of these systems can be obtained from a single 2-d Wigner distribution function of a single lenslet pupil. This result reveals the Wigner distribution function as a powerful tool for analysis of 3-d integral imaging systems with different pupil functions. As an example, the extension of the depth of field of an integral imaging system with lenslets having amplitude modulation (central obscuration) is proposed.

关键词： Multiple perspective imaging three-dimensional (3-d) image acquisition 3-d image processing

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Three-dimensional object recognition using x-ray imaging

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OPTICAL ENGINEERING 2005年第2期44卷 027201-1-027201页

作者： Yeom, S Javidi, B Roh, YJ Cho, HS Univ Connecticut Dept Elect & Comp Engn Storrs CT 06269 USA Korea Adv Inst Sci & Technol Dept Mech Engn Taejon 305701 South Korea

This paper presents a distortion-tolerant 3-d volume object recognition technique. Volumetric information on 3-d objects is reconstructed by x-ray imaging. We introduce 3-d feature extraction, volume matching, and statistical significance testing for the 3-d object recognition. The 3d Gabor-based wavelets extract salient features from 3-d volume objects and represent them in the 3-d spatial-frequency domain. Gabor coefficients constitute feature vectors that are invariant to translation, rotation, and distortion. distortion-tolerant volume matching is performed by a modified 3-d dynamic link association (dLA). The dLA is composed of two stages: rigid motion of a 3-d graph, and elastic deformation of the graph. Our 3-d dLA presents a simple and straightforward solution for a 3-d volume matching task. Finally, significance testing decides the class of input objects in a statistical manner. Experiment and simulation results are presented for five classes of volume objects. We test three classes of synthetic data (pyramid, hemisphere, and cone) and two classes of experimental data (short screw and long screw). The recognition performance is analyzed in terms of the mean absolute error between references and input volume objects. We also confirm the robustness of the recognition algorithm by varying system parameters. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

关键词： 3-d image processing image reconstruction image recognition image classification x-ray imaging systems

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Hybrid optical encryption of a 3-d object using a digital holographic technique

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OPTICAL ENGINEERING 2004年第10期43卷 2228-2232页

作者： Nomura, T Uota, K Morimoto, Y Wakayama Univ Dept Optomechatron Wakayama 6408510 Japan Wakayama Univ Grad Sch Syst Engn Wakayama 6408510 Japan

An encryption method of a 3-d object based on the phase modulation of an object wave is proposed. The phase of the object wave is modulated by a virtual optical random phase mask using a digital holographic technique. The keys of an encryption step are both a phase distribution and a position of the virtual optical phase mask. If either of them is not correct, we cannot decrypt the 3-d object. Owing to a characteristic of a hologram, we can see some parallax of a reconstructed 3-d object. Experimental results are presented to confirm the proposed method. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

关键词： optical encryption digital holography 3-d image processing

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Automated segmentations of skin, soft-tissue, and skeleton from torso CT images

Automated segmentations of skin, soft-tissue, and skeleton f...

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Medical Imaging 2004 Conference

作者： Zhou, XR Hara, T Fujita, H Yokoyama, R Kiryu, T Hoshi, H Gifu Univ Grad Sch Med Dept Intelligent Image Informat Div Regenerat & Adv Med Sci Gifu 5011193 Japan

ISBN: (纸本)0819452831

We have been developing, a computer-aided diagnosis (CAd) scheme for automatically recognizing human tissue and organ regions from high-resolution torso CT images. We show some initial results for extracting skin, soft-tissue and skeleton regions. 139 patient cases of torso CT images (male: 92, female: 47, age: 12-88) were used in this study. Each case was imaged with a common protocol (120kV/320mA) and covered the whole torso with 0.63 (mm) isotopic spatial resolution and 12 (bits) density resolution. A gray-level thresholding based procedure was applied to separate the human body from background. The density and distance features to body surface were used to determine skin, and separate soft-tissue from the other regions. A 3-d region growing based method was used to extract skeleton. We applied this system to 139 cases and found that the skin, soft-tissue and skeleton regions were recognized correctly for 93% patient cases. The accuracy of segmentation results was acceptable by evaluating the results slice by slice. This scheme will be included in a CAd system for detecting and diagnosing the abnormal lesions in multi-slice torso CT images.

关键词： mult-slice torso CT images 3-d image processing organ region segmentations CAd

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3d image sensing and reconstruction with time-division multiplexed computational integral imaging (CII)

3D image sensing and reconstruction with time-division multi...

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Conference on Three-dimensional TV Video and displayII

作者： Stern, A Javidi, B Univ Connecticut Dept Elect & Elect Engn Storrs CT 06269 USA

ISBN: (纸本)0819451266

We present a method to compute high-resolution three-dimensional (3-d) images based on integral imaging. In order to overcome optical limitation on the spatial resolution of reconstructed 3-d image, we suggest performing time-division multiplexing by which a sequence of II's is captured with a slightly different location of the lenslet array. The II image sequence obtained by the detector array is processed digitally with super-resolution reconstruction algorithms to obtain a reconstructed image, appropriate to a viewing direction, which has a spatial resolution beyond the optical limitation.

关键词： 3-d image acquisition 3-d image processing superresolution multiple imaging image reconstruction-restoration

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