Hand-held Laser Scanner Research Articles

Growing images: generating 3D digital models to investigate archaeological Moriori carvings on live trees

Three-dimensional (3D) digital models have been used globally to investigate archaeological carvings on natural surfaces. However, the associated capital costs and technical requirements can discourage the uptake of digital modelling for primary field analysis. One solution is to employ lightweight handheld laser scanners to generate basic 3D models of selected object areas for visual examination and immediate feedback. This targeted approach is illustrated in the investigation of a novel, threatened type of archaeological art form: carvings indented into live trees by Moriori people of the southern Polynesian Chatham Islands. In this investigation, variously lighted and rotated 3D models and paired photographs of Moriori tree carvings are examined to address research questions and assist in conservation planning.

Three-dimensional facial distances of Northern Sudanese persons from childhood to young adulthood

No current age- and gender-related normative data exist for the dimensions of facial structures in Northern Sudanese subjects. In the current study information about normal sex- and age-related linear distances is provided. The three-dimensional coordinates of 14 landmarks on the facial soft tissues were obtained using a hand-held laser scanner in 653 healthy Northern Sudanese subjects (326 males and 327 females) aged 4–30 years. From the landmarks, 13 linear distances were calculated, and averaged for age and sex. Comparisons were performed by factorial analysis of variance. All analyzed linear soft tissue facial dimensions were significantly larger in men than in women (p < 0.01), except mouth width (ch-ch), upper facial height (n-sn), mandibular body length (pg-go) and width (go-go). All measurements underwent significant modifications as a function of age (p < 0.01), with significant age × sex interactions (p < 0.01) for all linear dimensions except lower face height (sn-pg). Overall, when compared to literature data for African and Caucasoid subjects, several differences were found, pointing to the necessity of ethnic-specific data. Data collected in the present investigation could serve as a database for the quantitative description of human facial morphology during normal growth and development.

Measurement of Gravel-Bed Topography: Evaluation Study Applying Statistical Roughness Analysis

In this two-part study, experiments are conducted to evaluate available topography measurement techniques for gravel beds in a laboratory flume and to study their suitability for statistical roughness analysis. The available instruments for this study include (1) an acoustic bed profiler; (2) a hand-held laser scanner; and (3) two digital consumer cameras forming a stereophotogrammetric system, and are employed to obtain digital elevation models (DEMs) of water-worked gravel beds. In the first part of the study, the three measurement techniques are reviewed and their feasibilities for future grain-scale roughness work assessed, based on the obtained elevation datasets. Water-worked gravel-bed topographies are measured with all three available measurement techniques. The analysis of the DEMs concentrates on using probability distribution functions (PDFs) and second-order structure functions of bed elevations. Roughness coefficients are determined and used as a benchmark for comparison of the three measurement techniques. Although, visually, differences in the DEMs obtained with different measurement techniques are observed, the results of the chosen statistical analysis do not disclose the visual differences to the same extent. It is shown that the used stereophotogrammetric system, although theoretically allowing a fast and high-resolution recording process, lacks behind in accuracy. Thus, the second part of the study identifies and presents steps to improve the quality of the obtained stereophotogrammetric DEMs. A checklist is provided, highlighting the improvements made in the follow-up study, in order to obtain a high-quality stereophotogrammetric DEM. The overview will be useful for other researchers to make use of available low-cost and high-quality consumer camera equipment, to setup their own, non-proprietary stereophotogrammetric system.

Correlation between stereoradiography and 3D topographic measurements

Background The EOS is al ow-dose digital stereoradiography system that can produce highly reproducible spine measurements. The Milwaukee Topographic System (MTS) has reliably detected the 3-dimensional (3D) back surface contour changes. The correlation between Cobb angles and the MTS analog to Cobb angles in both the sagittal and coronal planes have been studied, but data are limited for comparisons of axial vertebral rotation measures derived from the MTS and X ray system. Purpose The goal of this study was to evaluate the correlations between EOS-derived axial rotation and MTS-registered axial surface rotation at each vertebral level. Methods A case control study design was performed, and four subjects with adolescent idiopathic scoliosis (ages 10 to 17) had measurements taken using both the MTS and EOS system. The MTS used a handheld laser scanner to gather the subjects’ back geometry while standing. Markers were placed on the subjects’ spinal processes so they could be identified in the scans and a custom software package was used to calculate 3D back measures. The EOS system took bi-planar images of the subjects’ torsos while standing and then calculated spine measurements by semi-automatically making a 3D reconstruction of the spine. The vertebral axial rotations from the MTS and EOS system were compared for the thoracic and lumbar vertebrae. The Pearson correlation coefficient was calculated for all the vertebrae. Results Only one vertebral level measurement, the third lumbar vertebrae (r=0.95, p<0.049), had a significant correlation, although the eighth (r=0.94, p<0.06) and ninth (r=0.92, p<0.08) thoracic vertebrae had high correlations that were close to significance. Conclusions and discussion In this limited study, the MTS predicts for the transverse rotations of the spinal segments, especially in the thoracolumbar and proximal lumbar region. Our current experience may indicate that the larger the vertebral body, the better the 3D reconstructive process using EOS.

Development of a 3-Dimensional Back Contour Imaging System for Monitoring Scoliosis Progression in Children

Study DesignControl study. ObjectivesTo present a new surface topography system capable of taking 3-dimensional (3D) spine measurements, to establish baseline values for the measured parameters in a typically developing population, and to determine the intra-rater and inter-rater reproducibility of these parameters. Summary of Background DataCumulative exposure to radiation from diagnostic radiographs increases patient risk for cancer development. There is a need for noninvasive and non-radiographic tools to accurately and reproducibly measure spine deformity and track scoliosis progression. MethodsWe measured 10 typically developing subjects with the new Milwaukee Topography System, which is composed of 2 electromagnetic markers, an electronic processing unit, a handheld laser scanner, a software package, and a desktop computer. Two investigators separately scanned the same subjects multiple times, yielding a total of 4 scans per subject per investigator. We measured 17 3D back parameters in each scan. We performed a multivariate analysis of variances to test the hypothesis of no difference for all variables, measured intra-rater and inter-investigator reliability with intra-class correlation (ICC) coefficients, and calculated mean values. ResultsThere were highly reproducible ICC values between investigators for 6 parameters (ICC > 0.75), moderate ICC values for 8 parameters (0.75 > ICC > 0.4), and poor ICC values for 3 parameters (ICC < 0.4), all at p < .05. Intra-investigator ICCs were moderate to excellent for almost all parameters. ConclusionsThe Milwaukee Topography System can be used to monitor and measure 3D back contours in children. The 3D back parameters values measured in the typically developing population can be considered baseline values that can be compared with parameters measured in children with idiopathic scoliosis.

Morphometry of the soft tissues of the orbital region in Northern Sudanese persons

The orbital region plays a predominant role in the evaluation of the craniofacial complex. No current normative data exist for Northern Sudanese subjects. In the current study information about normal sex- and age-related dimensions of the orbital region was provided. The three-dimensional coordinates of ten landmarks on the orbital soft tissues were obtained using a hand-held laser scanner in 654 healthy Northern Sudanese subjects aged 4–30 years. From the landmarks, biocular and intercanthal widths, paired height and inclination of the orbit relative to both the true horizontal (head in natural head position) and Frankfurt plane, length and inclination of the eye fissure, the relevant ratios, were calculated, and averaged for age and sex. Comparisons were performed by factorial analysis of variance. All analysed linear soft-tissue orbital dimensions, except intercanthal width and left orbital height, were significantly larger in men than in women (p<0.01). A significant sexual dimorphism was found also for the height-to-width ratios (larger in women in most age groups), the orbital inclinations vs. the true horizontal and Frankfurt plane (both measurements were almost always larger in men than in women), and the right side inclination of the eye fissure vs. the true horizontal (larger in women than in men), while no sex-related differences were observed for the left side inclination of the eye fissure vs. the true horizontal. All measurements but the right side inclination of the eye fissure vs. the true horizontal underwent significant modifications as a function of age, with several significant age×sex interactions. Biocular and intercanthal widths, orbital height, length of the eye fissure, all increased from childhood to young adulthood; in the second decade of life all age-related increments were larger in men than in women. Overall, when compared to literature data for African and Caucasoid subjects, several differences were found, pointing to the necessity of ethnic-specific data. Data collected in the present investigation could serve as a database for the quantitative description of human orbital morphology during normal growth and development. Forensic applications (evaluations of traumas, craniofacial alterations, teratogenic-induced conditions, facial reconstruction, ageing of living and dead people, personal identification) may also benefit from age- and sex-based data banks.

Methods for Quantitative Assessment of Femoral Antroposcopic Landmarks Using Hand‑held Laser Scanner

Purpose : This study is focused on an innovative approach to the numerical assessment of gluteal tuberosity through 3D visualization and its use as sex discriminant. Materials and methods : The study was based on an aggregate of 40 right femora, male and female in equal proportion. The surface of tuberositas glutea femoris is captured in a 3D image, using a Hand-held Laser Scanner (FastSCAN). Afterwards, the assessment contains three ways. Firstly, the result is a 3D shape comprising two tetrahedrons with common base. Therefore, the volume of the roughness is approximately equal to the total of the volumes of these two tetrahedrons (volume). Secondly, several points /markers/ are placed on the surface of the roughness of the 3D image. After that we create two-dimensional shape which is a function of the three-dimensional one. The area of the formed shape is measured (area) as well as its greatest elevation (elevation). Thirdly, we assess the position angle of gluteal tuberosity (angle C). The results were processed with SPSS 17.0 using Discriminant Function Analysis. Results : If the predictors (volume, area, elevation and angle) are included in the model, than the percentage of cases classified correctly is 95%. Conclusion : This score coincides with world results based on various anthropometric indices of the femur.

3D shape modeling using a self-developed hand-held 3D laser scanner and an efficient HT-ICP point cloud registration algorithm

Firstly, we develop a cost-efficient hand-held three-dimensional (3D) laser scanner for optical 3D laser scan data acquisition. Then, an automatic registration algorithm is used for 3D laser scanning based 3D shape modeling. Inspired by the use of twist to parameterize rigid motion in workpiece localization, we present the Hong–Tan based ICP (Iterative Closest Point) automatic registration algorithm (named HT-ICP) for partially overlapping point clouds. Using the point clouds from Stanford 3D Scanning Repository, we compare HT-ICP with the original ICP algorithm and its main variants, and experimental results show that the HT-ICP algorithm improves both the speed and accuracy of registration. Then we give the performance analysis with increasing amount of noise, and show the power of the “4PCS”+“HT-ICP” strategy for working directly on the raw noisy data. Furthermore, in the process of complete 3D shape modeling of Venus-head-statue, we demonstrate the effectiveness of the HT-ICP algorithm when aligning the actually acquired noisy point clouds from our self-developed low-precision hand-held scanner.

HIGH-RESOLUTION SURFACE RECONSTRUCTION FROM IMAGERY FOR CLOSE RANGE CULTURAL HERITAGE APPLICATIONS

Abstract. The recording of high resolution point clouds with sub-mm resolution is a demanding and cost intensive task, especially with current equipment like handheld laser scanners. We present an image based approached, where techniques of image matching and dense surface reconstruction are combined with a compact and affordable rig of off-the-shelf industry cameras. Such cameras provide high spatial resolution with low radiometric noise, which enables a one-shot solution and thus an efficient data acquisition while satisfying high accuracy requirements. However, the largest drawback of image based solutions is often the acquisition of surfaces with low texture where the image matching process might fail. Thus, an additional structured light projector is employed, represented here by the pseudo-random pattern projector of the Microsoft Kinect. Its strong infrared-laser projects speckles of different sizes. By using dense image matching techniques on the acquired images, a 3D point can be derived for almost each pixel. The use of multiple cameras enables the acquisition of a high resolution point cloud with high accuracy for each shot. For the proposed system up to 3.5 Mio. 3D points with sub-mm accuracy can be derived per shot. The registration of multiple shots is performed by Structure and Motion reconstruction techniques, where feature points are used to derive the camera positions and rotations automatically without initial information.

Scanning and Modeling of Large Thin-Walled Curved Surface Part

The large sandwich structure composed of thin-walled aluminum alloy panels, and variable thickness of honeycomb or Polymethacrylimide (PMI) foam core is usually manufactured by pre-bonded forming process, that is pre-forming panels and sandwich core, and then curing adhesive them to be sandwich structure. Welding process of large thin-walled panel causes the panel surface to be irregular and have greater errors relative to the design surface. Simply CNC machining the sandwich core according to the design surface cannot guarantee an exact match sandwich core consistent with the panels. The actual topography of the panels must be scanned. It is proposed that the use of a new hand-held laser scanner, Handyscan to scan large thin-walled curved surface parts, of Geomagic software to handle the acquired point clouds and construct the surface model.

A hand-held 3D laser scanning with global positioning system of subvoxel precision

In this paper we propose a hand-held 3D laser scanner composed of an optical head device to extract 3D local surface information and a stereo vision system with subvoxel precision to measure the position and orientation of the 3D optical head. The optical head is manually scanned over the surface object by the operator. The orientation and position of the 3D optical head is determined by a phase-sensitive method using a 2D regular intensity pattern. This phase reference pattern is rigidly fixed to the optical head and allows their 3D location with subvoxel precision in the observation field of the stereo vision system. The 3D resolution achieved by the stereo vision system is about 33 microns at 1.8 m with an observation field of 60cm x 60cm.

EEG–MRI Co-registration and Sensor Labeling Using a 3D Laser Scanner

This paper deals with the co-registration of an MRI scan with EEG sensors. We set out to evaluate the effectiveness of a 3D handheld laser scanner, a device that is not widely used for co-registration, applying a semi-automatic procedure that also labels EEG sensors. The scanner acquired the sensors' positions and the face shape, and the scalp mesh was obtained from the MRI scan. A pre-alignment step, using the position of three fiducial landmarks, provided an initial value for co-registration, and the sensors were automatically labeled. Co-registration was then performed using an iterative closest point algorithm applied to the face shape. The procedure was conducted on five subjects with two scans of EEG sensors and one MRI scan each. The mean time for the digitization of the 64 sensors and three landmarks was 53s. The average scanning time for the face shape was 2min 6s for an average number of 5,263 points. The mean residual error of the sensors co-registration was 2.11mm. These results suggest that the laser scanner associated with an efficient co-registration and sensor labeling algorithm is sufficiently accurate, fast and user-friendly for longitudinal and retrospective brain sources imaging studies.

A comparative study of methods for surface area and three‐dimensional shape measurement of coral skeletons

The three‐dimensional morphology and surface area of organisms such as reef‐building corals is central to their biology. Consequently, being able to detect and measure this aspect of corals is critical to understanding their interactions with the surrounding environment. This study explores six different methods of three‐dimensional shape and surface area measurements using the range of morphology associated with the Scleractinian corals: Goniopora tenuidens, Acropora intermedia, and Porites cylindrica. Wax dipping; foil wrapping; multi‐station convergent photogrammetry that used the naturally occurring optical texture for conjugate point matching; stereo photogrammetry that used projected light to provide optical texture; a handheld laser scanner that employed two cameras and a structured light source; and X‐ray computer tomography (CT) scanning were applied to each coral skeleton to determine the spatial resolution of surface detection as well as the accuracy of surface area estimate of each method. Compared with X‐ray CT, wax dipping provided the best estimate of the surface area of coral skeletons that had external corallites, regardless of morphological complexity. Foil wrapping consistently showed a large degree of error on all coral morphologies. The photogrammetry and laserscanning solutions were effective only on corals with simple morphologies. The two techniques that used projected lighting were both subject to skeletal light scattering, caused by both gross morphology and meso‐coral architecture and which degraded signal triangulation, but otherwise provided solutions with good spatial resolution. X‐ray CT scanning provided the highest resolution surface area estimates, detecting surface features smaller than 1000 µm2.

Real-time triangulation of point streams

Hand-held laser scanners are commonly used in industry for reverse engineering and quality measurements. In this process, it is difficult for the human operator to scan the target object completely and uniformly. Therefore, an interactive triangulation of the scanned points can assist the operator in this task. In this paper, we describe the technical and implementational details of our real-time triangulation approach for point streams, presented at the 17th International Meshing Roundtable. Our method computes a triangulation of the point stream generated by the laser scanner online, i.e., the data points are added to the triangulation as they are received from the scanner. Multiple scanned areas and areas with a higher point density result in a finer mesh and a higher accuracy. On the other hand, the vertex density adapts to the estimated surface curvature. To guide the operator, the resulting triangulation is rendered with a visualization of its uncertainty and the display of an optimal scanning direction.

MEMS-based handheld confocal microscope for in-vivo skin imaging

This paper describes a handheld laser scanning confocal microscope for skin microscopy. Beam scanning is accomplished with an electromagnetic MEMS bi-axial micromirror developed for pico projector applications, providing 800x600 (SVGA) resolution at 56 frames per second. The design uses commercial objective lenses with an optional hemisphere front lens, operating with a range of numerical aperture from NA=0.35 to NA=1.1 and corresponding diagonal field of view ranging from 653 μm to 216 μm. Using NA=1.1 and a laser wavelength of 830 nm we measured the axial response to be 1.14 μm full width at half maximum, with a corresponding 10%-90% lateral edge response of 0.39 μm. Image examples showing both epidermal and dermal features including capillary blood flow are provided. These images represent the highest resolution and frame rate yet achieved for tissue imaging with a MEMS bi-axial scan mirror.

Outside In

This article discusses reverse engineering software is slowly changing the way design engineers do their everyday jobs. With the pervasiveness of computer-aided design packages, reverse engineering technology has become a practical tool to create a 3D virtual model of an existing physical part. This model is then available to be used in 3D CAD, computer-aided manufacturing, or other computer-aided engineering applications. The reverse engineering process needs hardware and software that work together. The hardware is used to measure an object, and the software reconstructs it as a 3D model. The physical object can be measured using 3D scanning technologies such as a coordinate measuring machine, laser scanner, structured light digitizer, or computed tomography. The wider accessibility of handheld-laser scanners and portable CMMs like the one used at Excel Foundry means more companies can afford reverse engineering for their own unique ends. The scanner has turned out to be equally useful for engineering and for local archeological and preservation projects; and so far, it has been used to help preserve endangered artifacts.

Motion Compensation in Hand-held Laser Scanning for Surface Modeling in Plastic and Reconstructive Surgery

The purpose of this work is to develop a new integrated methodology for breast morphology assessment in plastic and reconstructive surgery. Such a methodology comprises hand-held laser scanning with active compensation of breathing motion and involuntary movements, in order to obtain a thorough and artifacts-free representation of patient breast shape. This was obtained by tracking surface motion with a configuration of passive markers fitted on the patient's thoraco-abdominal region. The proposed method, based on a mapping procedure, has been compared with respiratory gating, that is commonly used in radiotherapy and biomedical imaging applications. The results show that the implemented procedure is adequately able to compensate for motion, resulting in quantitative surface description to be used for clinical evaluation.

Facial recognition and laser surface scan: a pilot study

Surface scanning of the face of a suspect is presented as a way to better match the facial features with those of a perpetrator from CCTV footage. We performed a simple pilot study where we obtained facial surface scans of volunteers and then in blind trials tried to match these scans with 2D photographs of the faces of the volunteers. Fifteen male volunteers were surface scanned using a Polhemus FastSCAN Cobra Handheld Laser Scanner. Three photographs were taken of each volunteer's face in full frontal, profile and from above at an angle of 45 degrees and also 45 degrees laterally. Via special software (MIMICS and Photoshop) the surface scans were matched with the photographs in blind trials. The matches were graded as: a good fit; possible fit; and no fit. All the surface scans and photos were matched correctly, although one surface scan could be matched with two angled photographs, meaning that the discriminatory value was 86.7%. We also tested the surface scanner in terms of reliability in establishing point measures on skulls, and compared with physical measurements performed by calipers. The variation was on average 1 mm for five cranial measures. We suggest how surface scanning might be applied in forensic facial identification.

FORWARD-LOOKING SESSIONS FEATURED IN EDUCATIONAL PROGRAM IN DALLAS

FORWARD-LOOKING SESSIONS FEATURED IN EDUCATIONAL PROGRAM IN DALLAS

Facial acquisition by dynamic optical tracked laser imaging: a new approach

Three-dimensional capture of the surface of soft tissue is a desirable support for documentation and therapy planning in plastic and reconstructive surgery concerning the complex anatomy of the face, particularly cleft lip and palate (CLP). Different scanning systems are used for capturing facial surfaces. These systems are mostly based on a static linear measuring arrangement. Established systems work on the basis of coded white light or linear laser triangulation and digital stereophotogrammetric approaches. Shadowing effects occur with these devices. These effects may be avoided by a radical new approach first used in automotive industries that employs a mobile, flexible handheld laser scanner with simultaneous registration by optical tracking. The aim of this study was to assess the suitability of this scanner for surgical procedures on the human face in operating theatre. Five babies aged about 3 months with cleft deformities (one CLP, one bilateral CLP, three isolated cleft lips) were captured directly: twice preoperatively, twice postoperatively and twice after 7 days. An industrial standard specimen and two plaster cast masks of CLP babies were taken and subsequently measured to assess reliability and validity of the device. Masks were measured to reflect the complex surface of the cleft deformity. Data evaluation was done with respect to completeness of the data sets, as well as reliability and validity of the system. Missing data caused by shadowing could be avoided in all images. Even complex areas with undercuts could be reproduced completely and precisely with an accuracy in the sub-millimetre range.