Structured Light Measurement Research Articles

Using a three-dimensional optical simulation to investigate uncertainty in image-based dimensional measurements

Many advanced dimensional measurements exist that incorporate two-dimensional images of the object to be measured, such as structured-light measurements and photogrammetry. The measurements are quite complex and often suitable calibration artifacts are not available; consequently, a traceable uncertainty analysis is difficult. Advanced optical simulation packages can be used to assess important aspects of the uncertainty. These packages can simulate a virtual object to be measured, simulate a virtual camera, and trace rays as they leave a light source, scatter from the object, propagate through the camera, and arrive at the camera image plane. The result is a virtual image of the object whose dimensions are known. The virtual image(s) can then be processed as part of a dimensional measurement and the results compared to the known dimensions of the object. This allows different uncertainty aspects to be isolated and explored. It can be used to validate and understand the current methods of estimating measurement uncertainty, explore optimal measurement conditions, and/or test data analysis algorithms. These types of measurements involve a camera calibration process and the technique can also be used to check this step. This paper demonstrates the approach as applied to a photogrammetry measurement of a box.

3-Step-Calibration of 3D Vision Measurement System Based-on Structured Light

In structured light 3D vision measurement system, calibration tasks are key steps. Aiming at a special application of line structured light measurement, namely computer hard-disk surface planeness measurement at a precision equipment manufacturing company in Singapore, and combining with the structured light measurement model, determined three calibration tasks of the system. The three calibrating tasks concluded: calibrating the camera parameters; calibrating the light plane pose and calibrating the movement pose. At the same time, according to the three calibration results, measured the computer hard disk, and reconstructed the 3D model of the computer hard disk. The experimental results show that, the whole system of three calibration process is simple and reliable, the method does not need any auxiliary adjustment and realize the measurement accuracy about 0.023 mm. The work laid the better foundation for hard disk planeness vision measurement.

Research on Color Gray Code Encoding and Color Components Correction in 3D Measurement for Color Object

The existing structured light measurement technologies mainly focus on the single color objects, especially for measuring white object. Mainly because of in the process of threedimensional measurement for color objects, color object’s surface has a great influence on color components of structured light, leading to the color of structured light changing, this will cause serious errors in the decoding process. To solve this problem, combined with the actual measurements for colored objects, this paper adopts a color Gray code for encoding and decoding structured light, and presents an obtaining technical for color components of structured light, which first through regression analysis builds a mathematical model, and then uses the least squares method for solving it, at last restores the color of the projected stripes to ensure the correctness of decoding, to achieve the measurement for color object and to improve the measurement accuracy. The experimental results show that this method has a good effect on decoding.

Geometrical Shape Analysis for Investment Casting Turbine Blade Based on Optical Measurement

Turbine blade is one of the key components of the aero engine. It needs to be inspected comprehensively and carefully during its production stage. The methods for investment turbine blade geometrical shape analysis based on optical scanning measurement were presented, including optical measurement data collection, blade model reliable alignment and geometrical shape deviation fast calculation and visualization. Real measurement data from a structure light measurement device for a turbine blade was used to validate the discussed methods.

Research of Automatic Coding Algorithm in Calibration Target Dot Serialization

A kind of automatic coding algorithm in calibration board dot serialization used in structure light measurement system calibration process is introduced by this paper. The method includes five steps. The first step is getting dot coordinate and radius by the least square method, the second step is getting reference direction by fives big points serialization, the third step is getting selection region by reference direction, the fourth step is to accomplish base points serialization, the last step is to accomplish other points serialization. This algorithm proves to be stable and robust, and it has simplified the system operation and improved the camera calibration precision.

Lower body kinematics evaluation based on a multidirectional four-dimensional structured light measurement

We report on a structured light-scanning system, the OGX|4DSCANNER, capable of capturing the surface of a human body with 2 mm spatial resolution at a 60 Hz frame-rate. The performance of modeling the human lower body dynamics is evaluated by comparing the system with the current gold standard, i.e., the VICON system. The VICON system relies on the application of reflective markers on a person's body and tracking their positions in three-dimensional space using multiple cameras [optical motion capture (OMC)]. For the purpose of validation of the 4DSCANNER, a set of "virtual" markers was extracted from the measured surface. A set of musculoskeletal models was built for three subjects based on the trajectories of real and virtual markers. Next, the corresponding models were compared in terms of joint angles, joint moments, and activity of a number of major lower body muscles. Analyses showed a good overall agreement of the modeling outcome. We conclude that the 4DSCANNER within its limitations has the potential to be used in clinical gait analysis instead of optical marker-based systems. The advantage of the 4DSCANNER over OMC solutions is that it does not burden patients with time-consuming marker application. This study demonstrates the versatility of this measurement technique.

Calibration of the Structured Light Measurement System with Bundle Adjustment

In the structured light 3D measurement system,calibration is a key to the measurement accuracy.Especially the calibration accuracy of projector is low or the calibration procedure is complex.To reduce the effect of calibration point errors,bundle adjustment is applied to the calibration of the camera and projector.And plane projective transformations and error compensation method is also proposed to map the image coordinates of the calibration points from camera image plane to projector image plane.Thus,it not only solves the issue of low calibration accuracy and complicated calibration process on projector,but also overcomes the difficulty of directly optimizing the projector and camera together with bundle adjustment method.Then the bundle adjustment method is applied to calibration of camera and projector to reduce the impact of calibration point errors.In addition,the most rigorous adjustment optimization model is established to optimize the camera,projector and the calibration points.The experimental results show that the calibration accuracy can be effectively improved by this method.

基于畸变规律的三维结构光测量系统标定

基于畸变规律的三维结构光测量系统标定

Study on the Error of the Three-Dimensional Structure Light Measurement Based on Triangulation Principle

The error of the three-dimensional structure light measurement is analyzed in the paper. The experiment is done to verify the presence of measurement error. The error of data is analyzed and some conclusions are gotten. The three-dimensional structure light measurement is based on the triangulation principle. The error distribution is different because of the view angle of measurement equipment relative to the part to be inspected, the effect of the external environment light and the effect of the data processing software system. Finally, the corresponding compensation measures are put forward in the paper according to different errors.

PMP-Based Micro-3D Dental Measuring Technology

Based on the structured light measurement principle, digital fringes projection technology and phase-shifting measuring technology, specific to the 3D profile of some tiny objects like teeth, in this paper we proposes a 3D scanning system which was directly used for intraoral dental measurement utilizing the merits of flexible and long distance signal transmission of the fiber image bundle. The structured light is projected out from DLP LightCommander produced by Texas Instruments Company, shrunk via telecentric imaging lens, conveyed in fiber image bundle. Utilizing the transformational relation between single-camera and projector, afterwards, the 3D profile of teeth is obtained by reconstructing the acquisition images in electronic endoscope. The feasibility of this system has been testified in our experiments. It satisfies the requirements of miniaturization, directness and flexibility; expands the scope of application of micro-3D measurement with structured light in dental clinical practice.

Intraoral 3D optical measurement system for tooth restoration

In this paper we present a new miniaturized 3D optical measurement system for tooth restoration. The system is designed for scanning tooth within human mouth. The measuring process is based on the structured light measurement principle. The novelty in the approach is characterized by the following features: a flexible optimization convergence algorithm is taken as the calibration of the special miniaturized system, a rapid phase-shifting method is used to measure the tooth shape, multi-view 3D registration is completed based on matching between scale invariant features of 2D image and the miniaturized device is constituted with the LCoS micro-display module and camera. Some experiments are performed to validate the availability and reliability of the developed system. This miniaturized measurement system has a wide applications for dental CAD/CAM restoration system.

基于射影变换的结构光测量系统中投影仪标定方法

基于射影变换的结构光测量系统中投影仪标定方法

Data Registration Method Based on Three Dimensional Target

Data registration method using special three dimensional target to track the structured light measurement system is discussed. Optical scanning device, tracking target and stereo vision system are integrated together to fulfill profile inspection of large-scale free-form surface objects without extra mark points. System architecture and processing steps are introduced and layout optimization methods of three dimensional target are illustrated. Experimental results are showed to evaluate the validity of the registration method and suggests are given to improve the accuracy of the system.

结构光测量技术中的投影仪标定算法

结构光测量技术中的投影仪标定算法

3-D Modeling for Teeth Correction on the Basis of Optical Measurement

In this paper, a teeth correction 3-D data modeling technology based on the basis of optical measurement is proposed. Using structured light measurement, the STL data of the teeth plaster model are obtained. Based on STL data, the topological relationship model of vertices and planes is constructed. The data of single tooth is separated with separation algorithm, and using matrix transform, geometrical transformation of teeth model is realized. Then, after establishing frame curves, the 3-D solid modeling of corrected tooth socket is constructed. At last, using the SLA technology, the colophony model of the remedying device is produced.

Enhancing structured-light measurement for 3D metrology

Enhancing structured-light measurement for 3D metrology