3D Data Acquisition System Research Articles

Motion-based microwave tomographic measurement device for three-dimensional coverage in a magnetic resonance system.

We have developed a fully 3D data acquisition system for microwave breast imaging which can operate simultaneously inside a magnetic resonance imaging (MRI). MRI is used regularly for breast imaging to distinguish tumors from normal tissue. It generally has poor specificity unless used with a gadolinium contrast agent. Microwave imaging could fill this need because of the good endogenous tumor:normal tissue property contrast, especially in light of safety concerns for gadolinium. The antenna array consists of 16 monopole antennas positioned in a horizontal circle surrounding the breast which can then be moved vertically for 3D coverage of the breast. The tank system materials were chosen to minimize artifacts in the MR image within the specific shared imaging zone. The support rods are stainless steel, albeit positioned sufficiently far from the imaging target to have little effect. The mechanical motion parts are all 3D printed plastic. Unlike many conventional antennas, the monopoles consist of just the center conductor and insulator of the coaxial cable, making it one of the least possible metallic structures. Data were acquired both inside and outside of the MR bore to confirm that the MR bore did not have adverse effects on the microwave imaging process. The imaging tank was filled with a mixture of glycerin and water to both provide a reasonable property match to the phantom and to highly attenuate the fields which also acted to suppress multi-path signals. Microwave images were reconstructed using our Gauss-Newton scheme combined with a log transformation for a more linear convergence. MR images were also acquired to assess the effects of the microwave tank structures on the imaging. The microwave measurement data were acquired in log magnitude and phase format at 200 MHz increments from 700-1900 MHz. Each antenna acted sequentially as a transmitter while the complement of 15 acted as a receiver. The single frequency images were reconstructed using a Gauss-Newton iterative technique with a standard log transformation to linearize the process. The data showed that the signal strengths were between 7-10 dB lower for the case when the array was inside the MRI versus when not. Notwithstanding, the image quality was still high because of the significant signal to noise ratio. The reconstructed images in both situations demonstrated good 3D object recovery of the vertically size and shaped varying object. The MR images were not adversely affected by the presence of antennas or feed structures. We have demonstrated that our technique can recover high-quality images of a 3D varying object within an MRI system. Compatibility issues have been addressed for both the microwave and MRI systems. The reduced SNR for the case operating in the MRI did not adversely affect the images. To the best of our knowledge, this is the first example of a microwave imaging system operating in an MRI with full 3D volumetric capability.

Real-Time 3D Reconstruction Method for Holographic Telepresence

This paper introduces a real-time 3D reconstruction of a human captured using a depth sensor and has integrated it with a holographic telepresence application. Holographic projection is widely recognized as one of the most promising 3D display technologies, and it is expected to become more widely available in the near future. This technology may also be deployed in various ways, including holographic prisms and Z-Hologram, which this research has used to demonstrate the initial results by displaying the reconstructed 3D representation of the user. The realization of a stable and inexpensive 3D data acquisition system is a problem that has yet to be solved. When we involve multiple sensors we need to compress and optimize the data so that it can be sent to a server for a telepresence. Therefore the paper presents the processes in real-time 3D reconstruction, which consists of data acquisition, background removal, point cloud extraction, and a surface generation which applies a marching cube algorithm to finally form an isosurface from the set of points in the point cloud which later texture mapping is applied on the isosurface generated. The compression results has been presented in this paper, and the results of the integration process after sending the data over the network also have been discussed.

Pro-Cam SSfM: projector–camera system for structure and spectral reflectance from motion

Image-based reconstruction of an object’s 3D shape having the wavelength-by-wavelength spectral reflectance property enables higher-fidelity object 3D modeling compared with typical RGB-based modeling. In this paper, we propose a novel projector–camera system for practical and low-cost acquisition of a dense object 3D model with the spectral reflectance property. Different from existing spectral 3D data acquisition systems that use a dedicated multispectral camera or light, we use a standard RGB camera and an off-the-shelf projector as active illumination for both the 3D reconstruction and the spectral reflectance estimation. We first propose a calibration-free multi-view structured-light method to reconstruct the 3D points while estimating the intrinsic parameters and the poses of both the camera and the projector, which are alternately moved around the object during our image acquisition procedure. We then exploit the projector for multispectral imaging and estimate the spectral reflectance of each 3D point based on a novel spectral reflectance estimation method considering the geometric relationship between the reconstructed 3D points and the estimated projector positions. Experimental results on both synthetic and real data demonstrate that our system can precisely acquire a dense spectral 3D model using off-the-shelf devices.

ACCURATE 3D RECONSTRUCTION USING A VIDEOGRAMMETRIC DEVICE FOR HERITAGE SCENARIOS

Abstract. In recent years, handheld laser scanning systems have been developed for documenting architectural heritage, among other applications. In this article we present a new alternative for the 3D documentation of historical heritage based on videogrammetry. For this purpose, a prototype has been designed with two cameras, a high resolution camera and a VGA camera which, when connected to a tablet, allow the user to establish a guidance system to ensure that the trajectory is not lost and enables highly flexible and long-lasting movements over time. This paper unveils the operation of the filtering and image selection system to finally proceed to an evaluation of the prototype in three areas of an archaeological site, called “Casa del Mitreo” in the city of Mérida (Spain). The results are compared to the Faro Focus 3D X330 laser scanner, yielding very similar accuracies and a capture time about 17 times faster than the 3D laser scanner. The article therefore proposes a real alternative to 3D data acquisition systems in applications for the graphic documentation of architectural and archaeological heritage.

Geometrical defect detection for additive manufacturing with machine learning models

This study proposed a scheme based on Machine Learning (ML) models to detect geometric defects of additively manufactured objects. The ML models are trained with synthetic 3D point clouds with defects and then applied to detect defects in actual production. Using synthetic 3D point clouds rather than experimental data could save a huge amount of training time and costs associated with many prints for each design. Besides distance differences of individual points between source and target point clouds, this scheme uses a new concept called “patch” to capture macro-level information about nearby points for ML training and implementation. Numerical comparisons of prediction results on experimental data with different shapes showed that the proposed scheme outperformed the existing Z-difference method in the literature. Five ML methods (Bagging of Trees, Gradient Boosting, Random Forest, K-nearest Neighbors and Linear Supported Vector Machine) were compared under various conditions, such as different point cloud densities and defect sizes. Bagging and Random Forest were found the two best models regarding predictability; and the right patch size was found to be at 20. The proposed ML-based scheme is applicable to in-situ defect detection during additive manufacturing with the aid of a proper 3D data acquisition system.

Editorial for the Special Issue “Estimation of Crop Phenotyping Traits using Unmanned Ground Vehicle and Unmanned Aerial Vehicle Imagery”

High-throughput crop phenotyping is harnessing the potential of genomic resources for the genetic improvement of crop production under changing climate conditions. As global food security is not yet assured, crop phenotyping has received increased attention during the past decade. This spectral issue (SI) collects 30 papers reporting research on estimation of crop phenotyping traits using unmanned ground vehicle (UGV) and unmanned aerial vehicle (UAV) imagery. Such platforms were previously not widely available. The special issue includes papers presenting recent advances in the field, with 22 UAV-based papers and 12 UGV-based articles. The special issue covers 16 RGB sensor papers, 11 papers on multi-spectral imagery, and further 4 papers on hyperspectral and 3D data acquisition systems. A total of 13 plants’ phenotyping traits, including morphological, structural, and biochemical traits are covered. Twenty different data processing and machine learning methods are presented. In this way, the special issue provides a good overview regarding potential applications of the platforms and sensors, to timely provide crop phenotyping traits in a cost-efficient and objective manner. With the fast development of sensors technology and image processing algorithms, we expect that the estimation of crop phenotyping traits supporting crop breeding scientists will gain even more attention in the future.

Design of 3D Data Acquisition System on Handicrafts

Design of 3D Data Acquisition System on Handicrafts

선형 레이저 광 영상기반 다면 3차원 스캐너

In light of recently developed 3D printers for rapid prototyping, there is increasing attention on the 3D scanner as a 3D data acquisition system for an existing object. This paper presents a prototypical 3D scanner based on a striped laser light image. In order to solve the problem of shadowy areas, the proposed 3D scanner has two cameras with one laser light source. By using a horizontal rotation table and a rotational arm rotating about the latitudinal axis, the scanner is able to scan in all directions. To remove an additional optical filter for laser light pixel extraction of an image, we have adopted a differential image method with laser light modulation. Experimental results show that the scanner’s 3D data acquisition performance exhibited less than 0.2 mm of measurement error. Therefore, this scanner has proven that it is possible to reconstruct an object’s 3D surface from point cloud data using a 3D scanner, enabling reproduction of the object using a commercially available 3D printer.

레이저 구조광 영상기반 3차원 스캐너 개발

This paper addresses the development of 3D data acquisition system (3D scanner) based laser structured-light image. The 3D scanner consists of a stripe laser generator, a conventional camera, and a rotation table. The stripe laser onto an object has distortion according to 3D shape of an object. By analyzing the distortion of the laser stripe in a camera image, the scanner obtains a group of 3D point data of the object. A simple semiconductor stripe laser diode is adopted instead of an expensive LCD projector for complex structured-light pattern. The camera has an optical filter to remove illumination noise and improve the performance of the distance measurement. Experimental results show the 3D data acquisition performance of the scanner with less than 0.2㎜ measurement error in 2 minutes. It is possible to reconstruct a 3D shape of an object and to reproduce the object by a commercially available 3D printer.

STUDY ON THE LINE SCAN CCD CAMERA CALIBRATION OF VEHICLE-BORNE 3D DATA ACQUISITION SYSTEM

Abstract. Based on the characters of the line scan CCD camera and the Vehicle-borne 3D data acquisition system, it presented a novel method to calibrate the line Scan Camera (LSC) based on the laser scanner. Using the angle information in the original laser scanner data, combing the principle of the line scan camera, it built a calibration model for LSC and designed some experiment methods to implement that. Using the new model and the special experiment methods it computed out high precision LSC calibration parameters, which provides basis for the fusion of image and point cloud data and gives references to the similar sensors calibration.

A bismuth activation counter for high sensitivity pulsed 14 MeV neutrons

We have built a fast neutron bismuth activation counter that measures activation counts from pulsed 14-MeV neutron generators for incident neutron fluences between 30 and 300neutrons/cm2 at 15.2cm (6in.). The activation counter consists of a large bismuth germanate (BGO) detector surrounded by a bismuth metal shield in front of and concentric with the cylindrical detector housing. The 14MeV neutrons activate the 2.6-millisecond (ms) isomer in the shield and the detector by the reaction 209Bi (n,2nγ) 208mBi. The use of millisecond isomers and activation counting times minimizes the background from other activated materials and the environment. In addition to activation, the bismuth metal shields against other outside radiation sources. We have tested the bismuth activation counter, simultaneously, with two data acquisition systems (DASs) and both give similar results. The two-dimensional (2D) DAS and three dimensional (3D) DAS both consist of pulse height analysis (PHA) systems that can be used to discriminate against gamma radiations below 300keV photon energy, so that the detector can be used strictly as a counter. If the counting time is restricted to less than 25ms after the neutron pulse, there are less than 10 counts of background for single pulse operation in all our operational environments tested so far. High-fluence neutron generator operations are restricted by large dead times and pulse height saturation. When we operate our 3D DAS PHA system in list mode acquisition (LIST), real-time corrections to dead time or live time can be made on the scale of 1ms time windows or dwell times. The live time correction is consistent with nonparalyzable models for dead time of 1.0±0.2μs for our 3D DAS and 1.5±0.3μs for our 2D DAS dominated by our fixed time width analog to digital converters (ADCs). With the same solid angle, we have shown that the bismuth activation counter has a factor of 4 increase in sensitivity over our lead activation counter, because of higher counts and negligible backgrounds.

Upgrading of the PETRA-2 beamline at HASYLAB for materials science analyses

The high energy synchrotron radiation beamline PETRA-2 at HASYLAB has been extended by two 2D-position sensitive multi-wire Xe/CO 2 detectors with an active area of (300 mm) 2 and a detection probability of ∼10% for 100 keV photons. The detectors may be placed at distances between ∼1 m and 8 m from the sample in order to cover large space angles or to measure with high resolution, respectively. Fast 3D-data acquisition systems allow for analyses of continuous processes with excellent time resolution and sample movements during measurements with continuously operating detectors. The experimental set up will be especially used for analyses of residual stresses, local textures and kinetics of phase transformations.