摘要
数字条纹投影技术由于其非接触、测量精度高等特点在生物医学监测、虚拟现实以及计算机视觉等领域中应用越来越广泛。但其仍存在一定局限性,例如测量深度范围受限和投影仪存在非线性误差。二值离焦技术很好地克服了条纹投影三维测量中的非线性问题,但二值图像的高次谐波分量会造成测量误差。文中提出一种基于抖动算法的多频相位选择方法,该方法利用离焦抖动技术减少二值图像的高次谐波,避免投影仪非线性误差的影响;同时采用不同抖动算法及扫描方向调制得到二值图像,通过对比周期为12~60 pixel范围内的条纹图像在25个离焦程度下的展开相位误差分布,筛选出相应图像频率的离焦选择范围,最终确定不同离焦程度下条纹频率的最优选择。对于深度为22.5 cm被测物体进行了实验,正确恢复了大深度物体的三维形貌。实验结果表明:文中所提出的方法能有效地扩展测量深度范围,从而实现大深度范围被测物体的三维形貌测量。
Objective With the rapid development of modern information technology,optical three-dimensional(3D)profiling measurement technology has gradually matured.Among numerous optical 3D profiling measurement technologies,due to its non-contact and high-accuracy measurement,digital fringe projection(DFP)technology is increasingly applied in the fields such as biomedical monitoring,virtual reality,and computer vision,and has broad prospects for development due to its non-contact and high measurement accuracy.However,this technology still faces some technical challenges:1)Due to the limited depth of field of the system equipment(such as cameras and projectors),only the 3D shape of objects within a limited depth of field can be reconstructed;2)Nonlinearity problems caused by theγ-effect of commercial projectors may affect measurement accuracy. To overcome these problems, this paper proposes a method to extend the measurement depth range,which can achieve high-accuracy measurement of multiple objects at different depths or objects with a large depthrange.Methods The paper proposes a novel method for measuring the 3D shape of objects with a large depth range.Firstly, defocus technique is used to measure the dithering pattern in a simulated sinusoidal mode, avoiding theinfluence of projector non-linear errors on 3D measurement of fringe projection and increasing the measurementspeed. Then, by analyzing the relationship between the degree of defocusing of the fringe and the depth (Fig.1-2),this paper analyses the relationship between fringe defocus and depth and finds that the defocus degree of fringesat different frequencies is inconsistent with the depth variation nodes. Based on this, a multi-frequency phaseselection method is proposed in this paper. The optimal frequency mode determination algorithm (Fig.4) is usedto select the bayer dithering algorithm and the floyd-steinberg dithering algorithm to generate dithering patterns.After comparing the phase error distribution of the fringe images within the range of 12-60 pixel in period at 25defocus levels, the defocusing selection range of the corresponding fringe frequency is screened to determine theoptimal selection of fringe frequency at different defocusing degrees. Then, in order to obtain a binary patternwith the highest quality sinusoidal structure, 8 different scanning orders are used based on the selection results ofthe optimal frequency mode which is to select the optimal dithering mode for the current frequency (Tab.1).Finally, the method uses the selected dithering fringe pattern within the optimal frequency range to obtain the 3Dshape of the object. The proposed method can extend the measurement range of object depth by selecting multifrequencydithering fringe and determining the optimal frequency at different defocus degrees.Results and Discussions This paper presents qualitative and quantitative comparison experiments between thestandard sinusoidal fringe and the proposed method. In the qualitative experiment, both methods are used toreconstruct the 3D shape of an object with a depth of 22.5 cm (Fig. 9). The measurement results of the proposedmethod are better than those of the standard sinusoidal fringe method with complete shape, clear details andwithout ripple phenomenon. Moreover, in the quantitative experiment, the maximum absolute error of theproposed method is 0.033 mm (Tab.2), which is comparable to the measurement accuracy of traditional DFPtechnology. Therefore, the proposed method not only ensures measurement accuracy but also extends themeasurement depth range, and effectively solves the problem of measuring the 3D shape of objects with a largedepth in the DPF field.Conclusions This paper proposes a MFPS method based on dithering algorithms to solve the limitedmeasurement depth range and nonlinearity problem of the existing DFP technology. By using defocusingdithering techniques, the impact of projector nonlinearity error is overcome. Moreover, the MFPS method is usedto generate dithering fringe patterns for measurement, which extends the measurement depth range. Experimentalresults demonstrate that the proposed method effectively extends the measurement depth range and achieve 3Dshape measurements of objects in a large depth range.
作者
杨静雯
张宗华
付莉娜
李雁玲
高楠
高峰
Yang Jingwen;Zhang Zonghua;Fu Lina;Li Yanling;Gao Nan;Gao Feng(School of Mechanical Engineering,Hebei University of Technology,Tianjin 300130,China;Centre for Precision Technology,University of Huddersfield,Huddersfield HD13DH,UK)
出处
《红外与激光工程》
EI
CSCD
北大核心
2023年第8期167-176,共10页
Infrared and Laser Engineering
基金
国家自然科学基金项目(52075147)
河北省研究生创新资助项目(CXZZXX2022053)
河北省科学技术厅外专引才引智项目。
关键词
三维测量
条纹投影
离焦
抖动
相移法
three-dimensional measurement
fringe projection
defocusing
dithering
phase shift
作者简介
杨静雯,女,硕士生,主要从事三维形貌测量等方面的研究;通讯作者:张宗华,导师,男,教授,博士,主要从事光学检测、三维数字成像和造型、条纹自动分析等方面的研究。
