本文選題：三維測量 + 結(jié)構(gòu)光��； 參考：《廣東工業(yè)大學》2017年博士論文

【摘要】：結(jié)構(gòu)光三維測量技術(shù)目前在工業(yè)檢測/質(zhì)量控制、逆向工程(復雜自由曲面的數(shù)字化)、物體識別、文物保護、醫(yī)學和虛擬現(xiàn)實等領(lǐng)域得到了廣泛應用。通過該技術(shù)可以準確獲得工件的幾何形貌信息,為先進制造、自動裝配、表面檢測等提供有效的指導;另一方面,將工件的三維點云與CAD模型或已有三維數(shù)據(jù)進行比對,可檢測出工件的形變,為質(zhì)量控制、應力分析、碰撞測試等提供更加完整和更容易理解的可視化分析手段。然而,現(xiàn)有的結(jié)構(gòu)光三維測量技術(shù)在應用中仍然存在一些問題,比如要求測量時環(huán)境光照限制在一定范圍內(nèi),被測物體必須是漫反射表面,且表面反射率變化范圍不大。而工業(yè)生產(chǎn)中有大量金屬工件以銑削加工為主,經(jīng)過加工處理后工件的表面會變得十分光亮,若直接對這種光亮表面進行測量,則鏡面反射之后的光會太強,造成相機圖像傳感器飽和,丟失條紋圖像高光區(qū)域的條紋信息,以致難以正常進行測量;另一方面,由于相機的動態(tài)范圍有限,對于反射率較低的區(qū)域,則會造成條紋過暗,大幅降低測量精度。針對這些問題,本文系統(tǒng)地研究了結(jié)構(gòu)光圖案編碼、相位誤差補償、系統(tǒng)標定和高動態(tài)范圍條紋圖像的獲取等多個關(guān)鍵技術(shù),提出一種自適應、高動態(tài)范圍結(jié)構(gòu)光三維測量新方法,包括線移法編碼結(jié)構(gòu)光圖案、基于特征點映射的系統(tǒng)標定算法、自適應調(diào)節(jié)條紋圖案的最佳投射灰度值和基于平滑樣條擬合的相位誤差補償算法,有效地解決了光亮表面結(jié)構(gòu)光三維測量中數(shù)據(jù)丟失的難題,為高動態(tài)范圍光亮表面的三維測量,特別是復雜機加工零件的三維測量,提供了有效的解決途徑。本文主要內(nèi)容概括如下:(1)深入調(diào)研國內(nèi)外光亮表面的三維形貌測量方法,對現(xiàn)有的方法進行歸納,比較,分析,同時指出該領(lǐng)域仍然存在的難點問題,明確本文的研究內(nèi)容。(2)針對目前廣泛使用的相移法在測量光亮表面時面臨圖像飽和、互反射和噪聲靈敏度高等問題,在深入研究空間編碼方法、時間編碼方法、相移法等結(jié)構(gòu)光圖案編碼原理的基礎(chǔ)上,提出一種面向光亮表面的快速、魯棒、高空間分辨率的線移法。為了使生成的圖案比正弦條紋圖案更可靠,使用格雷碼生成正反黑白條紋圖案,并像相移法一樣進行線移。而在圖案解碼時,對采集的條紋圖像邊緣的非線性輪廓做線性插值,通過求解交點得到亞像素精度的邊緣坐標,由此達到較高的空間分辨率。(3)測量系統(tǒng)標定是個復雜且耗時的過程,針對基于參考平面的系統(tǒng)標定算法存在約束過強、標定精度不高、可操作性差、需要定制特殊的標定板等問題,提出一種基于特征點映射的系統(tǒng)標定算法。把數(shù)字投影儀當作逆向的相機,通過建立相機圖像像素和數(shù)字投影儀圖像像素之間的精確對應關(guān)系,將相機拍攝的標定板圖像中的特征點坐標映射為數(shù)字投影儀圖像坐標,從而將數(shù)字投影儀參數(shù)標定轉(zhuǎn)化為成熟的相機標定,進而將整個結(jié)構(gòu)光三維測量系統(tǒng)的參數(shù)標定轉(zhuǎn)化為雙目立體視覺系統(tǒng)的參數(shù)標定。(4)針對目前在光亮表面三維形貌測量方面存在的自適應測量問題,提出一種自適應、高動態(tài)范圍的結(jié)構(gòu)光三維測量算法。通過建立光亮表面條紋圖案成像的數(shù)學模型,分析被測物體表面反射率、表面互反射和環(huán)境光照等因素對采集的條紋圖像的影響,提出兩種生成條紋圖案最佳投射灰度值算法,實現(xiàn)自適應調(diào)節(jié)條紋圖案中每個像素點的最佳投射灰度值,以克服由于被測物體表面反射率、表面互反射和環(huán)境光照等因素引起的高光和黑暗,從而獲得清晰的條紋圖像,恢復被測物體的三維形貌。(5)在解相位過程中,針對條紋圖像的灰度分布非正弦化引起的相位誤差,通過對系統(tǒng)的非線性效應進行建模,在分析系統(tǒng)非線性響應及相位空間分布特征的基礎(chǔ)上,提出一種基于平滑樣條擬合的相位誤差補償算法。從平面標定板的條紋圖像中提取相位誤差并構(gòu)建相位誤差查找表,并在后續(xù)測量過程中,用于補償求得的相位。對補償后仍然存在的殘余相位誤差,使用平滑樣條擬合的方法對相位進一步做光順處理。(6)在前述理論與技術(shù)研究的基礎(chǔ)上,設(shè)計、開發(fā)面向高動態(tài)光亮表面測量的結(jié)構(gòu)光三維測量系統(tǒng)。采用Qt應用程序開發(fā)框架和OpenCV計算機視覺庫開發(fā)測量軟件,實現(xiàn)系統(tǒng)各項功能模塊。最后通過具體的應用實例,驗證本系統(tǒng)的檢測功能及相關(guān)算法的有效性。
[Abstract]:The three-dimensional measurement technology of structured light has been widely used in the fields of industrial detection / quality control, reverse engineering (digitalization of complex free-form surface), object recognition, cultural relics protection, medical and virtual reality. Through this technology, the geometrical information of the workpiece can be obtained accurately, and it is provided for advanced manufacturing, automatic assembly, surface detection and so on. On the other hand, the 3D point cloud of the workpiece is compared with the CAD model or the existing three dimensional data, which can detect the deformation of the workpiece and provide a more complete and more understandable visual analysis method for quality control, stress analysis and collision testing. However, there are still some structural optical three-dimensional measurement techniques in its application. Some problems, such as the limit of ambient light in a certain range when the measurement is required, the measured object must be diffuse surface, and the surface reflectivity varies little. In industrial production, a large number of metal pieces are mainly used for milling. After processing, the surface of the workpiece will become very bright, if the surface is directly on the bright surface. In the measurement, the light after the mirror reflection will be too strong, causing the camera image sensor to saturate and lose the stripe information in the high light region of the stripe image so that it is difficult to carry out the normal measurement. On the other hand, due to the limited dynamic range of the camera, the stripe is too dark to reduce the measurement accuracy for the lower reflectivity area. This paper systematically studies the key technologies of structural light pattern coding, phase error compensation, system calibration and high dynamic range stripe image acquisition, and proposes an adaptive, high dynamic range structure light three-dimensional measurement method, including the line shift coding structured light graph, the system calibration algorithm based on the feature point mapping, and the adaptive algorithm. The optimal projection gray value of the stripe pattern and the phase error compensation algorithm based on the smoothing spline fitting can effectively solve the problem of data loss in the three-dimensional measurement of the bright surface structure light, and provide an effective solution for the three-dimensional measurement of the bright surface of the high dynamic range, especially the three-dimensional measurement of the complex machined parts. The main contents are summarized as follows: (1) in-depth investigation of three dimensional topography measurement methods on the bright surface at home and abroad. The existing methods are summarized, compared and analyzed. At the same time, the difficult problems still exist in this field are pointed out, and the content of this paper is clarified. (2) the current widely used phase shifting method faces the saturation of the image when measuring the bright surface. On the basis of the deep study of the spatial coding method, time coding method and phase shift method, a fast, robust, high spatial resolution line shift method for the bright surface is proposed. In order to make the generated graph more reliable than the sinusoidal pattern, the gray code is used to generate the positive. The anti black and white stripe pattern and line shift like phase shift. While the pattern decode, the nonlinear contour of the fringe image edge is interpolated linearly. By solving the intersection point, the edge coordinates of the sub-pixel precision are obtained. (3) the calibration of the measurement system is a complicated and time-consuming process. The system calibration algorithm of the reference plane has the problems of too strong constraint, low calibration precision, poor operability and special calibration board. A system calibration algorithm based on feature point mapping is proposed. The digital projector is used as a reverse camera, and the accuracy between the pixel of a camera image and the image pixel of a digital projector is established. Corresponding relation, the coordinates of feature points in the camera calibration board image are mapped to the digital projector image coordinates, thus the calibration of the digital projector parameter calibration is converted to the mature camera calibration, and then the parameters calibration of the whole structure optical three-dimensional measurement system is converted to the parameter calibration of the binocular stereo vision system. (4) aiming at the current in the light. An adaptive, high dynamic range of structural light three-dimensional measurement algorithm is proposed in the measurement of bright surface three-dimensional topography. By establishing a mathematical model of the pattern image of the bright surface stripe pattern, the influence of the surface reflectivity, the surface reflection and the ambient light on the Striped image are analyzed. Two kinds of gray value algorithm for the best projection of the pattern pattern are proposed to achieve the best projection gray value of each pixel in the adaptive stripe pattern, so as to overcome the high light and darkness caused by the surface reflectivity, surface reflection and environmental illumination of the measured object, so as to obtain a clear image of the stripe and restore the three of the measured object. (5) (5) in the phase process, the phase error caused by the non sinusoidal distribution of the stripe image is modeled. On the basis of analyzing the nonlinear response of the system and the characteristics of the phase spatial distribution, a phase error compensation algorithm based on the smoothing spline fitting is proposed. The phase error is extracted from the Striped image of the plate and the phase error lookup table is constructed. In the subsequent measurement, the phase error is compensated. The residual phase error still exists after the compensation. The smoothing spline fitting method is used to further smooth the phase. (6) on the basis of the previous theoretical and technical research, the design and development of the phase error are designed and developed. The three-dimensional measurement system of structural light for high dynamic light surface measurement is made by using the Qt application development framework and the OpenCV computer vision library to develop the measurement software to realize the various functional modules of the system. Finally, the detection function and the validity of the related calculation method are verified by specific application examples.
【學位授予單位】：廣東工業(yè)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TP391.41

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