初始图像对选取是增量式从运动中恢复结构的一个关键环节,但传统方法中存在计算效率低、对特殊场景不鲁棒的问题。因此,提出基于多任务学习的初始图像对选取网络以提高该过程的效率,并针对某些特殊场景容易出现初始图像对位于场景边缘...初始图像对选取是增量式从运动中恢复结构的一个关键环节,但传统方法中存在计算效率低、对特殊场景不鲁棒的问题。因此,提出基于多任务学习的初始图像对选取网络以提高该过程的效率,并针对某些特殊场景容易出现初始图像对位于场景边缘的问题,提出结合场景连接图的初始对选取策略。该策略首先构建图像间的拓扑结构,通过图像间连接的疏密程度判断初始图像对是否处于场景中心,从而避免初始图像对处于场景边缘导致重建不完整的问题。对比传统SfM(structure from motion)中的初始图像对选取方法,结果表明:所提出的方法在多种不同场景中的选取速度提升5倍以上;同时,提出的结合场景图的选取策略可使得特殊场景中重建的空间点数量增加10倍,且重投影误差下降0.05 px,显著提升了在特殊场景中初始图像对选取的鲁棒性,证明了所提方法的有效性,在提高了效率的同时,能够很好地保证特殊场景重建的完整性和稳定性。展开更多
We have obtained the high-resolution threshold photoelectron （TPE） spectra of chlorobenzene C6HaCl （X1A1）, propargyl radical C3H3 （X2B1）, and allyl radical C3H5 （X2A1） by employing the vacuum ultraviolet （VUV...We have obtained the high-resolution threshold photoelectron （TPE） spectra of chlorobenzene C6HaCl （X1A1）, propargyl radical C3H3 （X2B1）, and allyl radical C3H5 （X2A1） by employing the vacuum ultraviolet （VUV） laser velocity-map-imaging-TPE （VUV-VMI-TPE） method. The photoelectron energy resolution of 1-2 cm^-1 observed for the VUV-VMI-TPE method is comparable to that achieved in VUV laser pulsed-field ionization-photoelectron （VUV-PFI-PE） measurements. Similar to VUV-PFI-PE measurements, the energy resolutions for VUV-VMI-photoelectron （VUV-VMI-PE） and VUV-VMI-TPE measurements are found to depend on the dc electric field F in V/cm used at the photoionization region for electron extraction. The decrease of the ionization thresholds of C6H5Cl and C3H3 observed as a function of F shows that the Stark shift correction for VUV-VMI-TPE measurements is governed by the formula -3.1√F in cm^-1, which is half of the classical prediction of -6.1v/F in cm^-1. We have also measured the VUV-VMI-PE spectra of C6H5Cl and C3H5 at VUV energies near their ionization thresholds. The cationic vibrational bands observed in the VUV-VMI-PE measurements were assigned to be the vibrational progression, nv7＋ （n=0-3）, for C3H＋. The higher experimental sensitivity and similar energy resolutions achieved in VUV-VMI-TPE compared to VUV-PFI-PE measurements make the VUV-VMI- TPE method an excellent alternative for high-resolution VUV-PFI-PE measurements.展开更多
文摘初始图像对选取是增量式从运动中恢复结构的一个关键环节,但传统方法中存在计算效率低、对特殊场景不鲁棒的问题。因此,提出基于多任务学习的初始图像对选取网络以提高该过程的效率,并针对某些特殊场景容易出现初始图像对位于场景边缘的问题,提出结合场景连接图的初始对选取策略。该策略首先构建图像间的拓扑结构,通过图像间连接的疏密程度判断初始图像对是否处于场景中心,从而避免初始图像对处于场景边缘导致重建不完整的问题。对比传统SfM(structure from motion)中的初始图像对选取方法,结果表明:所提出的方法在多种不同场景中的选取速度提升5倍以上;同时,提出的结合场景图的选取策略可使得特殊场景中重建的空间点数量增加10倍,且重投影误差下降0.05 px,显著提升了在特殊场景中初始图像对选取的鲁棒性,证明了所提方法的有效性,在提高了效率的同时,能够很好地保证特殊场景重建的完整性和稳定性。
基金This work was supported by the National Science Foundation under CHE-0910488 and CHE-1462172. C. Y. Ng also acknowledges the support by the Chemi- cal Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, （US） Department of Energy （DOE） under Contract No.DEFG02-02ER15306.
文摘We have obtained the high-resolution threshold photoelectron （TPE） spectra of chlorobenzene C6HaCl （X1A1）, propargyl radical C3H3 （X2B1）, and allyl radical C3H5 （X2A1） by employing the vacuum ultraviolet （VUV） laser velocity-map-imaging-TPE （VUV-VMI-TPE） method. The photoelectron energy resolution of 1-2 cm^-1 observed for the VUV-VMI-TPE method is comparable to that achieved in VUV laser pulsed-field ionization-photoelectron （VUV-PFI-PE） measurements. Similar to VUV-PFI-PE measurements, the energy resolutions for VUV-VMI-photoelectron （VUV-VMI-PE） and VUV-VMI-TPE measurements are found to depend on the dc electric field F in V/cm used at the photoionization region for electron extraction. The decrease of the ionization thresholds of C6H5Cl and C3H3 observed as a function of F shows that the Stark shift correction for VUV-VMI-TPE measurements is governed by the formula -3.1√F in cm^-1, which is half of the classical prediction of -6.1v/F in cm^-1. We have also measured the VUV-VMI-PE spectra of C6H5Cl and C3H5 at VUV energies near their ionization thresholds. The cationic vibrational bands observed in the VUV-VMI-PE measurements were assigned to be the vibrational progression, nv7＋ （n=0-3）, for C3H＋. The higher experimental sensitivity and similar energy resolutions achieved in VUV-VMI-TPE compared to VUV-PFI-PE measurements make the VUV-VMI- TPE method an excellent alternative for high-resolution VUV-PFI-PE measurements.
