Structured Light Scanning System Research Articles

3D Morphological Scanning and Environmental Correlates of Bufo gargarizans in the Yellow River Basin

Morphology plays a crucial role in understanding the intricacies of biological forms. Traditional morphometric methods, focusing on one- or two-dimensional geometric levels, often fall short of accurately capturing the three-dimensional (3D) structure of organisms. The advent of 3D scanning techniques has revolutionized the study of organismal morphology, enabling comprehensive and accurate measurements. This study employs a 3D structured light scanning system to analyze the morphological variations in the Chinese toad (Bufo gargarizans Cantor, 1842) along the Yellow River Basin. The 3D digital model obtained from the scan was used to calculate various morphological parameters including body surface area, volume, fractal dimensions, and limb size. The research explores geographic variability patterns and identifies environmental drivers affecting the 3D phenotypic variation of B. gargarizans. Results reveal a bimodal pattern of variation in the toad population, with higher elevations exhibiting smaller body sizes, greater appendage proportions, and more complex body structures. Linear regression analyses highlight the influence of elevation and annual mean temperature on the morphological variation of B. gargarizans, with elevation playing a significant role. This study underscores the significance of 3D morphometric analysis in unraveling the intricacies of organismal morphology and understanding the adaptive strategies of species in diverse environments.

Accuracy of digital implant impressions using a novel structured light scanning system assisted by a planar mirror in the edentulous maxilla: An invitro study.

This study aimed to develop a structured light scanning system with a planar mirror to enhance the digital full-arch implant impression accuracy and to compare it with photogrammetry and intraoral scanner methods. An edentulous maxillary stone cast with six scan bodies was scanned as the reference model using a laboratory scanner. Three scanning modalities were compared (n = 10): (1) self-developed structured light scanning with a mirror (SSLS); (2) intraoral scanner (IOS); and (3) photogrammetry system (PG). The scanners were stopped for 1 min after each scan. Six scan bodies were analysed within each scan model. Linear deviations between the scan bodies (1-2, 1-3, 1-4, 1-5, and 1-6) and 3D mucosal deviations were established. The overall deviation was calculated as the mean of all linear deviations. "Trueness" represented the discrepancy between the test and reference files, while "precision" denoted the consistency among the test files. Kruskal-Wallis and Mann-Whitney U tests were used for statistical analyses. Significant overall linear discrepancies were noted among the SSLS, PG, and IOS groups (p < .001). SSLS showed the best overall trueness and precision (6.6, 5.7 μm), followed by PG (58.4, 6.8 μm) and IOS (214.6, 329.1 μm). For the 3D mucosal deviation, the trueness (p < .001) and precision (p < .001) of the SSLS group were significantly better than those of the IOS group. The SSLS exhibited higher accuracy in determining the implant positions than the PG and IOS. Additionally, it demonstrated better accuracy in capturing the mucosa than IOS.

Structured light scanning artifact-based performance study

Structured light scanning is used to create a digital twin of a manufactured part, where features are extracted to determine if the part meets the designer’s intent and required tolerances. This paper describes repeatability and reproducibility analyses for a commercially-available structured light scanning system and measurement artifact. The repeatability study used five repeated scans at 15 measurement positions. Repeatability was assessed by randomly selecting one of the five scans at each of the 15 positions and creating a part mesh. This process was performed 50 times and the statistics for the dimension variations were calculated to isolate the scanning effects only. The same sequence was then performed for 10 of the 15 positions and five of the 15 positions to evaluate the repeatability sensitivity to the number of measurement positions. Reproducibility was assessed by selecting 15 positions to create a mesh and repeating the 15-position measurement sequence 10 times using different positions for each mesh construction. The statistics for the dimension variations were then calculated. This incorporated the effects of both scanning and the position and orientation of the part relative to the scanner. This sequence was repeated for 10-position and five-position scans to evaluate the corresponding sensitivity. Finally, the artifact dimensions from structured light scanning were compared to coordinate measuring machine measurements of the same features.

A Cross-Line Structured Light Scanning System Based on a Measuring Arm

The measurement system proposed in this paper, using a measuring arm and line structured light, has a wide range of applications. To improve the scanning efficiency, the system outlined in this paper uses two single-line structured lights to form crosshair structured light, which we combine with a measuring arm to form a comprehensive scanning measurement system. The calibration method of Zhengyou Zhang and a calibration board are used to complete parameter calibration of the sensors and cameras, as well as hand–eye calibration of the measuring arm. For complex curved-surface objects, this system extracts the cross-line structured light optical center location, which suffers from ambiguity. Therefore, we introduce the use of periodic control of the two line structured light sources in order to resolve the light extraction polysemy. Our experimental results indicate that the proposed system can effectively satisfy the function of crosshair structured light scanning of large, complex surfaces.

Preliminary Study on Structured Light Strip Center Extraction Method Based on Underwater Structured Light Scanning System

Preliminary Study on Structured Light Strip Center Extraction Method Based on Underwater Structured Light Scanning System

Better precision of a new robotically assisted system for total knee arthroplasty compared to conventional techniques: A sawbone model study.

The purpose of this study was to compare the accuracy of this new HURWA robotic-assisted total knee arthroplasty (TKA) technique to the accuracy of the conventional technique in a sawbone model. The HURWA robotic-assisted TKA system was applied in the robotic group. After bone resection, all of these sawbones were scanned by the use of a structured light scanning system. Measurements of bone resections, femoral coronal and sagittal measurements, and tibial coronal and sagittal measurements were recorded. Compared to the conventional technique, the HURWA robotic-assisted system significantly improved the accuracy of the bone resection levels and angles. In the robotic group, the accuracy of all of the bone resection levels was below 0.6mm (with standard deviation [SD] below 0.6mm), and all of the bone resection angles were below 0.6° (with SD below 0.4°). Our data suggest that this novel HURWA robotic-assisted system can significantly improve the accuracy of bone resection levels and angles.

Filling cavities in point clouds representing human body surface using Bezier patches

In this paper we introduce a cavity reconstructing algorithm for 3D surface scans (CRASS) developed for filling cavities in point clouds representing human body surfaces. The presented method uses Bezier patches to reconstruct missing data. The source of input data for the algorithm was an 8-directional structured light scanning system for the human body. Typical 3D scan representing human body consists of about 1 million points with average sampling density of 1 mm. The paper describes the complete scan processing pipeline: data pre-processing, boundary selection, cavity extraction and reconstruction, and a post-processing step to smooth and resample resulting geometry. The developed algorithm was tested on simulated and scanned 3D input data. Quality assessment was made based on simulated cavities, reconstructed using presented method and compared to original 3D geometry. Additionally, comparison to the state-of-the-art screened Poisson method is presented. Values’ ranges of parameters influencing result of described method were estimated for sample scans and comprehensively discussed. The results of the quantitative assessment of the reconstruction were lower than 0,5 of average sampling density.

Calibration of Structured Light Scanning System

Abstract On the basis of studying the calibration method of the camera and the rotating platform, we designed an automatic camera calibration scheme based on four azimuth circles, which can realize the automatic sorting of the mark points. In order to improve the efficiency of identifying the center of the calibration plate, this paper uses RANSAC to improve the RED ellipse center detection algorithm. Experimental verification shows that the improved RED algorithm has increased 29.34% in anti-noise interference ability and 30.10% in center detection accuracy, which effectively guarantees the measurement stability and accuracy of the measurement system. Then, with the aid of the designed calibration board, we fit the rotation center of the turntable using the principle of three points in a circle, which provides a basis for the subsequent point cloud splicing. Experiments show that the back-projection error of the calibration method in this paper is less than 1 pixel, and the calibration accuracy is better than Zhang’s algorithm.

3D Reconstruction Based on Fusing Active Structured Laser and Passive Stereo Techniques

Three-dimensional reconstruction of real objects comprises capturing the appearance and the shape for these objects and determining the three-dimensional coordinates for their profiles. This reconstruction process can be accomplished either by using active or passive techniques. In this paper, a new fusion method is proposed for 3D reconstruction. This method exploits the advantages of both stereo-based passive and laser-based active techniques and overcomes their limitations to improve the performance of 3D reconstruction. With this method, a hybrid laser-based structured light scanning system is designed and implemented. This system captures the required information using passive and active techniques and uses the proposed fusion method for 3D reconstruction. The performance of the proposed method and its scanning system were experimentally evaluated. The evaluation results show high reconstruction performance for the proposed fusion method over the traditional 3D reconstruction techniques. The results also show the effectiveness of the hybrid laser scanning system and its ability to scan and reconstruct the shape and the appearance for real objects using the proposed fusion method.

Monitoring and modeling of part thickness evolution in vacuum infusion process

The main hurdles in Vacuum Infusion (VI) are the difficulty in achieving complete mold filling and uniform part thickness. This study integrates process monitoring by full field thickness measurements and resin flow modeling that accounts for compaction and permeability characterizations of fabric reinforcements to assess the evolution of part thickness during filling and post-filling stages of VI process. A Structured Light Scanning system is used for full field thickness monitoring in experiments and a Control Volume Finite Element Method solver is implemented to couple resin flow with fabric’s compaction and permeability. Two cases are studied both experimentally and numerically. Evolutions of thickness and pressure validate the developed flow solver, its accuracy in terms of predicting fill times and fill patterns, suitability and limitations of the elastic compaction models for thickness modeling.

Evaluating the accuracy of hand models obtained from two 3D scanning techniques

The aim of this study was to identify an efficient approach for 3D imaging of hand. The 3D photographs of hand were taken with Gemini structured-light scanning system (SL scanning) and CT scanning. The 3D photographs, average time of scanning and reconstruction were compared between these two indirect techniques. The reliability, reproducibility and accuracy were evaluated in these two indirect techniques and the direct measurement (DM). Statistical differences in the measurements were assessed by 99% probability, with clinical significance at > 0.5 mm. The Gemini structured-light scanning system established a complete and smooth 3D hand photograph with shorter scanning and reconstruction time. Reproducibility of CT scanning and SL scanning methods was better (P < 0.01, both) than the DM, but did not differ significantly from each other (P = 0.462). Of the 19 (31.58%) measurements obtained, 6 showed significant differences (P < 0.01). Significant differences were observed more often for circumference dimensions (5/9, 55.56%) than for length dimensions (1/10, 10%). Mean absolute error (AE) of the 10 subjects was very low for 3D CT (0.29 ± 0.10 mm) and SL scanning (0.30 ± 0.11 mm). Absolute percentage error (APE) was 4.69 ± 2.33% and 4.88 ± 2.22% for 3D CT and SL scanning, respectively. AE for the PIP circumference between the 3rd finger (0.58 mm) and 4th finger (0.53 mm) scan was > 0.5 mm, indicating significant difference between DM and CT scanning at the level of 99% probability. In this study, the Gemini structured-light scanning system not only successfully established a complete and smooth 3D hand photograph, but also shortened the scanning and reconstruction time. Compared to the DM, measurements obtained using the two indirect techniques did not show any statistically or clinically insignificant difference in the values of the remaining 17 of 19 measurements (89.47%). Therefore, either of the two alternative techniques could be used instead of the direct measurement method.

Quantifying quality of 3D printed clay objects using a 3D structured light scanning system

Three-dimensional (3D) printing, or additive manufacturing, has been increasingly used in many fields, including the medicine, food, sensing, metal, automotive, and construction industries. Regardless of its growing applications, there are few of methods, guidelines, and specifications for measuring and quantifying the qualities of 3D printed objects. This is particularly so for objects those are too small, too large, and/or too fragile to be handled manually. In this study, for the first time, a non-contact, and non-destructive measurement method, a 3D structured light scanning system (3D-SLSS), was employed for evaluating the printing qualities of clay objects with different levels of visual defects (e.g., roughness and distortion). 3D scanned images of these clay samples were developed using 3D-SLSS. Then, they were sliced along their sides (perpendicular to the base) to generate a number of two-dimensional (2D) plots, from which various parameters (e.g., sample total height [Htotal], outer diameter [DMouter], layer thickness [TL], layer width, [(WL], surface angle [Sα], semi-cross-sectional area [XA], and surface roughness [R]) were measured. These measurements were then compared with the designed values. The percentages of the differences between the measured and designed values were used to develop a diagnosed area of deficiency, by which the overall qualities of the printed samples were quantified. The results illustrated that all the printed samples exhibited certain differences between their measured and designed values, even for those that appeared well printed. Compared with the designed object, the printed samples generally had reduced total height, diameter, and layer thickness; increased layer width; measurable distortion; and visible surface roughness. Many of these were largely because the freshly printed clay deformed under the weight of the layers above. The distortion angle and area are two necessary parameters for quantifying the degree of distortion of a printed sample. The diagnosed area of deficiency can well describe the overall qualities of the printed samples. 3D-SLSS is a relatively simple, fast, and inexpensive characterization method. Moreover, it can be conveniently extended to various industries for quality control of diverse 3D printing products.

Three dimensional evaluation of soft tissue after orthognathic surgery

BackgroundTo evaluate the nasolabial soft tissue change three-dimensionally after orthognathic surgery, using a structured light scanner.MethodsThirty-two malocclusion patients, who underwent orthognathic surgery, were evaluated. CBCT and 3D facial scans were obtained before surgery and 3 months after surgery. The 3D changes in the 26 landmarks, and the relative ratio of the soft tissue movement to the bony movement, were evaluated.ResultsIn the Le Fort I advancement patients, the nasal tip moved 17% forward, compared to the maxillary bony movement, but the nasal prominence decreased 15%. The alar width increased 4 mm after the advancement, and the width decreased 4.7 mm after Le Fort I setback. The relative ratio of the soft tissue movement to the bony movement after bilateral sagittal split osteotomy was about 66% at the Li point in the anteroposterior direction, and it was 21% in the Le Fort I advancement and 14% in Le Fort I setback at the Ls point.ConclusionAlar cinch suturing may not be sufficient to overcome the effect of the maxilla advancement compressing the nasal complex. Alar width widening was prevented in Le Fort I setback. However, it is uncertain that the alar cinch suturing was solely responsible. The soft tissue around the mandible tends to accompany the bony movement more than the maxillary area. In addition, structured light scanning system proved to be a useful tool to evaluate the nasolabial soft tissue.

Robust technique for 3D shape reconstruction

In this paper a robust and simple scheme is presented for three dimensional (3D) shape reconstruction of real object. A novel composite pattern technique is proposed for projecting the light pattern on the object of interest. The proposed scheme reduces the number of patterns by combining the primary color coded channels into one composite format. Our approach uses both spatial and temporal intensity variation for calibration and construction phase. Gamma calibration is considered with the propose scheme. High quality depth map is obtained from the linear light reflected by the shape of object without complex calculations. Experimental results demonstrated that proposed technique is fast and exhibit high level of precision. In addition hardware cost is minimized as compare to current calibration procedures used in structured light scanning system. Our scheme requires a digital camera, flashlight and mask of pattern only.

Scanning the H.L. Hunley: Employing a structured-light scanning system in the archaeological documentation of a unique maritime artifact

In 2008, the Warren Lasch Conservation Center acquired a Breuckmann OptoTOP-HE structured-light scanning system to begin the 3D documentation of the American Civil War submarine H.L. Hunley. The choice of this particular system was determined by the interests of the archaeological team and the particular research goals of the project. High resolution 3D surface topography and integrated photographic data were considered equally necessary, suggesting an optical-based scanning system. However, maritime artifacts, or artifacts from a marine environment, are necessarily stored in water or other aqueous solutions prior to completing the conservation process. Using structured-light technology on the H.L. Hunley submarine itself, as well as other artifacts kept in a wet condition, presented the team with some unique difficulties in terms of three-dimensional documentation.This paper will discuss the use of structured-light scanning on the H.L. Hunley, and highlight some of the specific problems and challenges encountered when employing this technology on maritime archaeological material. In particular, we would like to present a brief study of the effectiveness of optical scanning to record surface details, including issues of reflectivity, color, and surface darkness. Moreover, we intend to address the challenges of using the 3D data to reconstruct the submarine into an accurate, color 3D model. It is hoped that this study will both illustrate the problems associated with recording maritime artifacts and suggest further avenues for research and the development of strategies useful for better data collection.

Removal of noise and radial lens distortion during calibration of computer vision systems.

The calibration of computer vision systems that contain the camera and the projector usually utilizes markers of the well-designed patterns to calculate the system parameters. Undesirably, the noise and radial distortion exist universally, which decreases the calibration accuracy and consequently decreases the measurement accuracy of the related technology. In this paper, a method is proposed to remove the noise and radial distortion by registering the captured pattern with an ideal pattern. After the optimal modeled pattern is obtained by registration, the degree of freedom of the total calibration markers is reduced to one and both the noise and radial distortion are removed successfully. The accuracy improvement in a structured light scanning system is over 10(24) order of magnitude in the sense of mean square errors. Most importantly, the proposed method can be readily adopted by the computer vision techniques that use projectors or cameras.

A flexile and high precision calibration method for binocular structured light scanning system.

3D (three-dimensional) structured light scanning system is widely used in the field of reverse engineering, quality inspection, and so forth. Camera calibration is the key for scanning precision. Currently, 2D (two-dimensional) or 3D fine processed calibration reference object is usually applied for high calibration precision, which is difficult to operate and the cost is high. In this paper, a novel calibration method is proposed with a scale bar and some artificial coded targets placed randomly in the measuring volume. The principle of the proposed method is based on hierarchical self-calibration and bundle adjustment. We get initial intrinsic parameters from images. Initial extrinsic parameters in projective space are estimated with the method of factorization and then upgraded to Euclidean space with orthogonality of rotation matrix and rank 3 of the absolute quadric as constraint. Last, all camera parameters are refined through bundle adjustment. Real experiments show that the proposed method is robust, and has the same precision level as the result using delicate artificial reference object, but the hardware cost is very low compared with the current calibration method used in 3D structured light scanning system.

A High-Precision Registration Technology Based on Bundle Adjustment in Structured Light Scanning System

The multiview 3D data registration precision will decrease with the increasing number of registrations when measuring a large scale object using structured light scanning. In this paper, we propose a high-precision registration method based on multiple view geometry theory in order to solve this problem. First, a multiview network is constructed during the scanning process. The bundle adjustment method from digital close range photogrammetry is used to optimize the multiview network to obtain high-precision global control points. After that, the 3D data under each local coordinate of each scan are registered with the global control points. The method overcomes the error accumulation in the traditional registration process and reduces the time consumption of the following 3D data global optimization. The multiview 3D scan registration precision and efficiency are increased. Experiments verify the effectiveness of the proposed algorithm.

A practical coordinate unification method for integrated tactile–optical measuring system

To meet the requirement of both high speed and high accuracy 3D measurements for dimensional metrology, multi-sensor measuring systems have been developed to measure, analyse and reverse engineer the geometry of objects. This paper presents a new development in coordinate unification called the “centroid of spherical centres” method, which can be used instead of the traditional method which uses three datum-points to perform the geometric transformation and unification of tactile and optical sensors. The benefits of the proposed method are improved accuracy in coordinate unification and the method is used to integrate a coordinate measuring machine (CMM) and optical sensors (structured light scanning system and FaroArm laser line probe). A sphere-plate artefact is developed for data fusion of the multi-sensor system and experimental results validate the accuracy and effectiveness of this method.

Three-dimensional facial anthropometry of unilateral cleft lip infants with a structured light scanning system

Cleft lip in the presence or absence of a cleft palate is a major public health problem. However, few studies have been published concerning the soft-tissue morphology of cleft lip infants. Currently, obtaining reliable three-dimensional (3D) surface models of infants remains a challenge. The aim of this study was to investigate a new way of capturing 3D images of cleft lip infants using a structured light scanning system. In addition, the accuracy and precision of the acquired facial 3D data were validated and compared with direct measurements. Ten unilateral cleft lip patients were enrolled in the study. Briefly, 3D facial images of the patients were acquired using a 3D scanner device before and after the surgery. Fourteen items were measured by direct anthropometry and 3D image software. The accuracy and precision of the 3D system were assessed by comparative analysis. The anthropometric data obtained using the 3D method were in agreement with the direct anthropometry measurements. All data calculated by the software were 'highly reliable' or 'reliable', as defined in the literature. The localisation of four landmarks was not consistent in repeated experiments of inter-observer reliability in preoperative images (P<0.05), while the intra-observer reliability in both pre- and postoperative images was good (P>0.05). The structured light scanning system is proven to be a non-invasive, accurate and precise method in cleft lip anthropometry.