基于线结构光扫描的结冰冰形三维测量

现有三维扫描仪进行结冰冰形测量时需喷涂显影剂,无法满足结冰生长过程3D冰形在线测量需求。为此,基于线结构光扫描,提出了结冰冰形三维测量方法,搭建了基于传送带的线结构光扫描冰形测量装置,对线结构光视觉测量系统进行标定,获取了摄像机和激光平面方程参数,采用改进的梯度重心法实现了低对比度冰体图像激光光带亚像素中心位置提取,结合标定结果计算了冰体轮廓线三维坐标,再根据传送带运动距离,对冰体轮廓线逐行拼接,得到整个冰体三维测量点云。实验结果表明,对半径已知的圆柱形冰块进行轮廓线测量,相对误差为0.157 mm。     

基于激光反射投影原理的重叠玻璃尺寸测量方法研究

论文在激光投影法的基础上,结合重叠玻璃的投影特性提出了一种新的测量重叠玻璃平面尺寸的方法---基于激光反射投影原理的移动式测量方法,解决了使用非接触测量法测量重叠玻璃平面尺寸存在的难题。该方法通过获取经玻璃反射后的激光投影线段图像,分析被反射后激光线的投影特性,提取了反映玻璃平面尺寸的特征,并利用该特征分析计算出了重叠玻璃的平面尺寸。论文根据此方法设计了一套重叠玻璃平面尺寸测量实验系统。实验数据表明：这个测量方法能达到生产的精度要求,对于重叠玻璃的平面尺寸测量具有可行性,可应用于流水线上的重叠玻璃平面尺寸在线测量。     

基于单目视觉几何构建的三维扫描系统

为构建基于单目视觉的快速便捷式三维扫描系统,提出一种高精度的单目视觉几何投影的场景建模方法,并开发一种低成本高精度的三维扫描系统。首先,获取平面标定点的图像坐标,经投影变换将其转换为摄像坐标系下的三维空间位置坐标,分别建立平移台面和底座的三维空间平面方程;其次,通过移动平移台面求取同名标定点的空间坐标,求解平移台面的平移向量,并通过落在平移台面和底座上的激光线条求解激光平面;最后,提取图像中的激光光条中心点并将其变换为物体表面的三维点云数据。实验结果表明,投影变换求得的平面方程误差小于0．2％,扫描结果误差低于0．05mm。     

A high-speed 3-D image measurement method

With the recent popularization of digital cameras and projectors, practical applications of three-dimensional (3-D) image measurements based on intensity-modulation pattern projection are eagerly anticipated. Such an approach would permit a projection pattern to contain more measurement data, allowing 3-D data to be calculated with greater accuracy. However, to achieve a high level of accuracy using this approach, it is essential that an ideal observation pattern image should be obtained with a certain minimum number of stripes and a certain intensity distribution. To satisfy these requirements, an intensity correction method with two observation pattern images has previously been used. It is difficult to measure a fast-moving object in such calculations because the correspondence relation of the measured object is not established between the two photographic images, and consequently the pattern intensity is not corrected accurately. This study proposes an image analysis method for correcting intensity using an image synthesis technique that extracts precise stripes from a single observation pattern image. This analysis method allows 3-D shape measurements to be performed from a single projection pattern and a single image capture.     

2D/3D image registration using regression learning

In computer vision and image analysis, image registration between 2D projections and a 3D image that achieves high accuracy and near real-time computation is challenging. In this paper, we propose a novel method that can rapidly detect an object’s 3D rigid motion or deformation from a 2D projection image or a small set thereof. The method is called CLARET (Correction via Limited-Angle Residues in External Beam Therapy) and consists of two stages: registration preceded by shape space and regression learning. In the registration stage, linear operators are used to iteratively estimate the motion/deformation parameters based on the current intensity residue between the target projection(s) and the digitally reconstructed radiograph(s) (DRRs) of the estimated 3D image. The method determines the linear operators via a two-step learning process. First, it builds a low-order parametric model of the image region’s motion/deformation shape space from its prior 3D images. Second, using learning-time samples produced from the 3D images, it formulates the relationships between the model parameters and the co-varying 2D projection intensity residues by multi-scale linear regressions. The calculated multi-scale regression matrices yield the coarse-to-fine linear operators used in estimating the model parameters from the 2D projection intensity residues in the registration. The method’s application to Image-guided Radiation Therapy (IGRT) requires only a few seconds and yields good results in localizing a tumor under rigid motion in the head and neck and under respiratory deformation in the lung, using one treatment-time imaging 2D projection or a small set thereof.     

Complete 3D Foot Scanning System Using 360 Degree Rotational and Translational Laser Triangulation Sensors

This paper proposes a new type of 3D foot scanning system using rotational and translational 3D scanning stages. Commercial 3D foot scanning systems (or scanners) mostly employ the laser triangulation method and three or more linear stages to scan the entire 3D shape of the foot. We introduce a new foot scanning method using only two laser-camera triangulation sensors. The proposed scanning system consists of a 360° rotational and a linear translational 3D sensors. The rotational sensor employs two line lasers with a vision camera to solve an occlusion problem of the rotational stage and acquires the 3D shape of the upper part of the foot. The translational sensor consists of a line laser and a vision camera and acquires the 3D shape of the foot sole. The performance of the proposed scanning technique is verified using plastic models and human feet. In average, about 0.5 mm reconstruction accuracy is obtained by the proposed technique.

     

Diffractive optical element based sensor for roughness measurement

A roughness sensing system, based on the fringe projection technique, is introduced. Roughness parameters are estimated from the fringe pattern projected on the target. The system employs a new projection unit in which light, coming from a laser diode, is coupled to a fiber optic and then impinges on a diffractive optical element (DOE) to produce sinusoidal fringes. The proposed sensor is simple, small and cheap and its sensitivity is easily adjustable. Fringes generated by the DOE are analyzed by a fast fourier transform (FFT) based algorithm, which can work also on curved surfaces.

Experimental results, obtained on varying spark erosion surface roughness standards, showed the capability of the system to perform roughness measurements with a resolution of about 0.5 μm.     

A high-speed and continuous 3D measurement system

A new system for high-speed and continuous 3D measurement is presented. It is based on the slit-ray projection method. The key component is the image plane constructed by a position-sensitive device (PSD) array that is horizontally un segmented and linear, but vertically numbered. All PSD row elements are attached to their respective analog signal processors. The analog signals are multiplexed and digitized by multiplexers and A/D converters at appropriate sampling intervals and stored in memory. By virtue of this configuration of the image plane, basis data for 3D measurement are acquired during only one scan of the slit ray at high speed in the form of memory addresses and data. Moreover, if we use large capacity and/or dual port memories, we can continuously obtain 3D range data for as many scenes as needed. The trial system has been implemented with a newly designed 128-channel PSD array and has verified our method, enabling us to obtain successive 3D range data at video rates with an error within±0.3%.     

两面多框可构视图中存在不可构表面的条件

对两面多框可构视图中存在不可构表面的条件进行了研究,指出当两面多框可构视图中存在有对称同类形图框,则该对称同类形图框分别为形体上两个不可构表面;当两面多框可构视图中存在不含有同面点集的对应同类形图框时,则该对应同类形图框亦为形体上一个不可构表面;当两面多框可构视图中存在含有同面点集的对应多边形图框(非三角形),且该图框线中至少有一对应边与同面点集同向倾斜或斜交时,则该对应同类形图框亦为形体上一个不可构表面;当一投影直线与一封闭图框对应,且该封闭图框线不与视图中两同面点集出现部分重合时,则该封闭图框亦为不可构表面。     

Modeling Surperspective Projection of Landscapes for Geographical Guide-Map Generation

It is still challenging to generate hand-drawn pictures because they differ from ordinary photographs in that they are often drawn as seen from multiple viewpoints. This paper presents a new approach for modeling such surperspective projection based on shape deformation techniques. Specifically, surperspective landscape images for guide-maps are generated from 3D geographical elevation data. Our method first partitions a target geographical surface into feature areas to provide designers with landmarks suitable for editing. The system takes as input 2D visual effects, which are converted to 3D geometric constraints for geographical surface deformation. Using ordinary perspective projection, the deformed shape is then transformed into a target guide-map image where each landmark enjoys its own vista points. An algorithm for calculating such 2D visual effects semi-automatically from the geographical shape features is also considered.     

Three-Dimensional Measurement Using Structured Light Based on Deep Learning

Three-dimensional (3D) reconstruction using structured light projection has the characteristics of non-contact, high precision, easy operation, and strong real-time performance. However, for actual measurement, projection modulated images are disturbed by electronic noise or other interference, which reduces the precision of the measurement system. To solve this problem, a 3D measurement algorithm of structured light based on deep learning is proposed. The end-to-end multi-convolution neural network model is designed to separately extract the coarse- and fine-layer features of a 3D image. The point-cloud model is obtained by nonlinear regression. The weighting coefficient loss function is introduced to the multi-convolution neural network, and the point-cloud data are continuously optimized to obtain the 3D reconstruction model. To verify the effectiveness of the method, image datasets of different 3D gypsum models were collected, trained, and tested using the above method. Experimental results show that the algorithm effectively eliminates external light environmental interference, avoids the influence of object shape, and achieves higher stability and precision. The proposed method is proved to be effective for regular objects.     

一种无标记点三维点云自动拼接技术

基于相位投影和双目的三维光学测量系统已经广泛应用于各领域.受投影光测量系统单次测量范围大小的限制,对大型物体的测量需要在表面粘贴圆形标记点进行多次拼接的缺点,探讨一种基于SIFT的无标记点自动拼接技术.该技术采用SIFT方法获取两次测量的特征点,其次结合RANSAC求出图像特征点的匹配关系,再根据立体匹配中图像特征点与三维点云之间的对应关系,将二维特征点的对应关系映射到三维点云的对应关系上,最后由SVD奇异值分解算法求得旋转和平移矩阵实现拼接.实验证明:该方法可以避免在被测量对象上粘贴标记点,能够快速准确地实现自动拼接.     

最大投影栅缝法检测文档图像倾斜角

针对由照相机扫描仪等文档获取设备拍摄的文档图像可能存在倾斜,进而导致光学字符识别（OCR）软件不能正确识别的情况,采用了一种以文档图像投影栅缝宽为目标函数的优化方法,栅缝宽最大值对应的投影角度的相反数即为文档图像的倾斜角。利用栅线宽函数扩大了检测范围,并提高了检测速度;利用反投影法和均布列预投影等方法,减少了计算量;利用二分法提高了算法的检测精度。通过一些包含少量插图的文档图像的倾斜角检测实验,验证了该方法的有效性。     

3D reconstruction of specular surfaces using a calibrated projector–camera setup

Structured light is widely used for shape measurement of beamless surfaces using the triangulation principle. In the case of specular surfaces deflectometry is an appropriate method. Hereby the reflection of a light pattern is observed by a camera. The distortion of the reflected pattern is evaluated to obtain information about the reflecting surface. An important requirement for a 3d reconstruction of a specular surface by deflectometry is a calibrated measurement setup. We propose a method for the overall calibration of a setup consisting of a structured light source, a projection screen and a camera. We consider all extrinsic and intrinsic parameters for the optical mapping including a distortion model for the projector and for the camera, respectively. Given the deflectometric data obtained by the calibrated setup two methods are described which allow the 3d reconstruction of points on a specular surface. This is not trivial as a reconstruction using solely deflectometric data shows ambiguity. In the first method screen displacement between two deflectometric measurements is used to overcome this ambiguity. In the second method curvature-like features on the surface are determined to serve as starting points for a region growing approach. Results of the reconstruction of a specular surface are shown and the performance of the described reconstruction methods are compared to each other.     

基于最小区域的快速CT图像重建

由于工业CT重建目标的形状差异较大,针对传统CT图像重建算法均选取矩形重建区域,提出一种基于最小区域的图像重建方法.首先由扫描到的投影数据通过直线生成算法构建重建目标的最小区域包络图;然后提出一种快速区域填充算法,生成图像重建的最小区域.该方法将重建区域限定在最小区域内,减少了不必要的计算,提高了重建速度.最后通过仿真实验与传统的重建方法进行比较,表明了文中方法的有效性.     

Determining surface orientation by projecting a stripe pattern

A method is presented for determining the surface orientations of an object by projecting a stripe pattern on to it. Assuming orthographical projection as a camera model and parallel light projection of the stripe pattern, the method obtains a 2 1/2-D representation of objects by estimating surface normals from the slopes and intervals of the stripes in the image. The 2 1/2-D image is further divided into planar or singly curved surfaces by examining the distribution of the surface normals in gradient space. A simple application to finding a planar surface and determining its orientation and shape is shown. The error in surface orientation is discussed     

Models for low resolution slit scan measurements based on high resolution laser scanning image analysis: DNA and nuclear dimensions

A laser scanning microscope has been developed and employed to make high precision measurements of cells from clinical cervical samples. These specimens have been stained with the DNA specific fluorochrome mithramycin and the fluorescent images analyzed to give information on nuclear size, DNA content and nuclear shape. This information has been used to develop low resolution parameters as measured with flow cytometers, thus permitting some comparisons between high resolution and low resolution features as measured from the same cells. The results indicate that both low resolution flow slit scan and high resolution pattern recognition techniques yield the same average cellular information. However, low resolution methods are insensitive to shape and the influence of shape on the broadening of low resolution features is now under investigation.     

三维人脸数据的获取及人脸特征自动定位

介绍了一种快速获取人脸三维面貌数据的结构光相移测量技术,并利用这种高速的相移技术在获取三维面貌数据的同时获得人脸纹理背景图像,结合二维人脸图像中的人脸特征识别手段,应用到三维人脸图像中,可以让计算机自动提取人脸图像的主要特征点.首先介绍了高速相移技术的基本原理,介绍了二维人脸图像中的积分投影方法来求取人脸轮廓粗略位置的方法,接着介绍了将二维图像做纹理映射到三维数据里面的方法,结合三维高度信息的曲线分析、曲率判断等,快速的提取出了人脸的三维特征.经实验验证,此方法对于三维人脸特征的自动定位有很高的准确性和通用性.     

基于VR技术的三维图像景区救助人员定位仿真

为了解决传统技术易受外界干扰,造成三维图像景区救助人员视觉特征存在缺失,导致后续定位精度偏低的问题,提出基于VR技术(虚拟现实技术)的三维图像景区救助人员定位方法。对真实景区环境利用激光测量技术(LMS)进行平扫,获得景区三维扫描点云;采用VR技术进行景区图像三维重建,从中设置几何投影模型表示在现实环境中的透视转换模型,通过非线性算法提取描述救助人员的视觉特征;利用Euler距离实现景区救助人员视觉特征匹配与定位。实验结果表明,将本文的方法应用于三维图像景区救助定位,大大提高了救助人员定位的准确性和效率,证明了上述方法相对于传统的定位方法更具鲁棒性,能够稳定快速地完成三维图像景区救助人员目标的定位。     

Range sensing by projecting multiple slits with random cuts

A method for range sensing that projects a single pattern of multiple slits is described. Random dots are used to identify each slit. The random dots are given as randomly distributed cuts on each slit. Thus, each slit is divided into many small line segments. Segment matching between the image and the pattern is performed to obtain 3-D data. Using adjacency relations among slit segments, the false matches are reduced, and segment pairs whose adjacent segments correspond with each other are extracted and considered to be correct matches. Then, from the resultant matches, the correspondence is propagated by exploiting the adjacency relationships to get an entire range image