相衬成像中的空间滤波研究
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摘要
相衬成像基于空间滤波方法将物体的相位信息转化为相应的振幅信息,实现透明相位物体的衬度显示。相衬成像的关键在于改变频谱的相位,它的本质是空间频域滤波。
本文从空间频域滤波和光学系统空间频率响应特性的角度去探究相衬成像。相衬成像系统中空间频域滤波所使用的滤波器是相位滤波器,传统的做法是对零级衍射光产生一定的相位补偿,但不改变光波振幅。在此基础上我们提出了两种不同于传统做法的新思路。一是给非零级衍射光一定的相位补偿,等效代替对零级衍射光的相位改变,这种方法能够获得与传统做法相同的衬度图像,并且有利于相位滤波器的工艺制作；二是给零级衍射光一定的相位补偿的同时,给零级和非零级衍射光一定的振幅衰减,经模拟验证,改进后的滤波器可使成像衬度大大提高。
衍射受限系统是一个低通滤波器,系统的频率响应特性决定了光学系统的成像能力,系统传递函数能够全面地评定系统的频率响应特性,与星点法和分辨率法相比具有优越性。我们将相衬成像系统视作衍射受限系统,求出了相干照明下相衬成像系统的相干传递函数,它有利于相衬成像系统频率特性分析。
照明光源相干性是影响相衬成像质量的另一个重要因素,现有的相衬成像研究中通常将相干光源作为照明光源。然而实际光源均有一定大小和谱线宽度,当这些影响因素大到一定程度时,相干理论不再适用于相衬系统成像的分析,而应使用部分相干理论来解释。我们定性地描述了部分相干光照明下的相衬成像,通过数值模拟初步比较了相干和部分相干光照明下相衬成像的差别。
本文最后对文中所述方法进行了实验验证,实验实现了观测样品的相衬成像。我们还结合实验的具体情况进行分析,分析讨论了一种相衬成像方法——遮挡零频法,它与干涉相衬成像法思想相同,但该方法对实验环境要求更低,便于实现。
Phase contrast imaging system transforms phase distributions of objects into corresponding intensity distributions based on spatial filtering, so as to realize the visualization of phase objects. Phase-retardation of the spectrum is the key to phase contrast imaging. The essence of the phase contrast imaging is spatial spectrum filtering.
In this paper, the phase contrast imaging is studied from the spatial spectrum filtering point of view and spatial frequency response of optical systems. Spatial spectrum filtering of phase contrast imaging system utilizes the phase filter. The traditional approach provide a certain phase compensation for zero-order diffracted light but does not change the amplitude. On this basis, we propose two new ideas which different from the traditional approach. First of all, using a certain phase-retardation for non-zero-order diffracted light substitutes for phase-retarding of zero-order diffraction equivalently. By this method a same contrast images can be obtained as traditional approach and one phase filter can be fabricated easily. Second, during a certain phase-retardation acts on zero-order diffracted light, the amplitudes of the zero-order and non-zero-order diffraction light are attenuated. After simulation verification, the modified filter can greatly improve imaging contrast.
Diffraction-limited system is a low-pass filter. The imaging ability of the optical system is determined by the frequency response characteristics. The system coherent transfer function which has advantages compared to the star-point method and the resolution method can fully assess the system's frequency response. We regard phase contrast imaging system as a diffraction-limited system and have deduced coherent transfer function of phase contrast imaging system. It is conducive to analyze the frequency characteristics of phase contrast imaging system.
The coherence of illuminating light is another important factor which affects the quality of phase contrast imaging. Existing phase contrast imaging studies usually take coherent light as illuminating light. However, the actual illuminating source has a certain size and spectral line width. When these factors reach a significant degree, coherence theory no longer applies to the analysis of phase contrast imaging. Instead, we should use partially coherent theory to explain it. We qualitatively describe phase contrast imaging under the partially coherent illuminating light. By numerical simulation, the differences between coherent illumination and partially coherent illumination are compared preliminary.
Finally, the method presented in this article is proved by experiments. The experiment demonstrated the phase-amplitude transformation of sample can be achieved and the method is valid. We also analyze the specific situation of experiment, a novel method is proposed for phase contrast imaging by zero-order-block method, which is equivalent to the idea of interference contrast imaging. In addition, this method requires only simple conditions for experiment, so the experimental validation is very easy.
本文从空间频域滤波和光学系统空间频率响应特性的角度去探究相衬成像。相衬成像系统中空间频域滤波所使用的滤波器是相位滤波器,传统的做法是对零级衍射光产生一定的相位补偿,但不改变光波振幅。在此基础上我们提出了两种不同于传统做法的新思路。一是给非零级衍射光一定的相位补偿,等效代替对零级衍射光的相位改变,这种方法能够获得与传统做法相同的衬度图像,并且有利于相位滤波器的工艺制作；二是给零级衍射光一定的相位补偿的同时,给零级和非零级衍射光一定的振幅衰减,经模拟验证,改进后的滤波器可使成像衬度大大提高。
衍射受限系统是一个低通滤波器,系统的频率响应特性决定了光学系统的成像能力,系统传递函数能够全面地评定系统的频率响应特性,与星点法和分辨率法相比具有优越性。我们将相衬成像系统视作衍射受限系统,求出了相干照明下相衬成像系统的相干传递函数,它有利于相衬成像系统频率特性分析。
照明光源相干性是影响相衬成像质量的另一个重要因素,现有的相衬成像研究中通常将相干光源作为照明光源。然而实际光源均有一定大小和谱线宽度,当这些影响因素大到一定程度时,相干理论不再适用于相衬系统成像的分析,而应使用部分相干理论来解释。我们定性地描述了部分相干光照明下的相衬成像,通过数值模拟初步比较了相干和部分相干光照明下相衬成像的差别。
本文最后对文中所述方法进行了实验验证,实验实现了观测样品的相衬成像。我们还结合实验的具体情况进行分析,分析讨论了一种相衬成像方法——遮挡零频法,它与干涉相衬成像法思想相同,但该方法对实验环境要求更低,便于实现。
Phase contrast imaging system transforms phase distributions of objects into corresponding intensity distributions based on spatial filtering, so as to realize the visualization of phase objects. Phase-retardation of the spectrum is the key to phase contrast imaging. The essence of the phase contrast imaging is spatial spectrum filtering.
In this paper, the phase contrast imaging is studied from the spatial spectrum filtering point of view and spatial frequency response of optical systems. Spatial spectrum filtering of phase contrast imaging system utilizes the phase filter. The traditional approach provide a certain phase compensation for zero-order diffracted light but does not change the amplitude. On this basis, we propose two new ideas which different from the traditional approach. First of all, using a certain phase-retardation for non-zero-order diffracted light substitutes for phase-retarding of zero-order diffraction equivalently. By this method a same contrast images can be obtained as traditional approach and one phase filter can be fabricated easily. Second, during a certain phase-retardation acts on zero-order diffracted light, the amplitudes of the zero-order and non-zero-order diffraction light are attenuated. After simulation verification, the modified filter can greatly improve imaging contrast.
Diffraction-limited system is a low-pass filter. The imaging ability of the optical system is determined by the frequency response characteristics. The system coherent transfer function which has advantages compared to the star-point method and the resolution method can fully assess the system's frequency response. We regard phase contrast imaging system as a diffraction-limited system and have deduced coherent transfer function of phase contrast imaging system. It is conducive to analyze the frequency characteristics of phase contrast imaging system.
The coherence of illuminating light is another important factor which affects the quality of phase contrast imaging. Existing phase contrast imaging studies usually take coherent light as illuminating light. However, the actual illuminating source has a certain size and spectral line width. When these factors reach a significant degree, coherence theory no longer applies to the analysis of phase contrast imaging. Instead, we should use partially coherent theory to explain it. We qualitatively describe phase contrast imaging under the partially coherent illuminating light. By numerical simulation, the differences between coherent illumination and partially coherent illumination are compared preliminary.
Finally, the method presented in this article is proved by experiments. The experiment demonstrated the phase-amplitude transformation of sample can be achieved and the method is valid. We also analyze the specific situation of experiment, a novel method is proposed for phase contrast imaging by zero-order-block method, which is equivalent to the idea of interference contrast imaging. In addition, this method requires only simple conditions for experiment, so the experimental validation is very easy.
引文
[1]陈家壁,苏显渝.光学信息技术原理及应用[M].北京：高等教育出版社,2002.7
[2]邓大鹏.光纤通信原理[M].北京：人民邮电出版社,2009.9
[3]李镜,刘文杰,朱佩平等.基于光栅相衬成像的扇束螺旋CT重建算法[J].光学学报,2010,30(2)：421-427
[4]潘卫清,朱勇建,郎海涛.基于系统标定的相衬显微数字全息方法[J].中国激光.2010,37(7)：1812-1820
[5]谢敬辉,廖宁放,曹良才.傅里叶光学与现代光学基础[M].北京：北京理工大学出版社,2007.9
[6]J. Gluckstad. Phase contrast image synthesis [J]. Optics Commum.,1996,130:225-230
[7]周常河,刘立人,王淮生.可实现任意形状的高效Zernike照明器[J].强激光与粒子束.1996,,11(3)：295-298
[8]刁麓弘,李华,于斌等.基于Zernike相衬法的相衬成像探索[J].工程图学学报.2006,4：100-104
[9]P.C. Mogense, J. Gluckstad. Dynamic array generation and pattern formation for optical Tweezers[J]. Opt. Commun.,2000,175:75-81
[10]R.L. Eriksen, P.C. Mogensen, J. Gluckstad. Multiple-beam optical tweezers generated by the generalized phase-contrast method[J]. Opt. Let.,2002,27(4):267-269
[11]C. Preza. Rotational-diversity phase estimation from differential interference contrast microscopy images[J]. J. Opt. Soc. Am. A.,2000,(3):415-424
[12]P. Marquet, B. Rappaz, P.J. Magistretti, etal. Digital holographic microscopy: noninvasive contrast imaging technique allowing quantitative visualization of living cells with subwavelength axial accuracy [J]. Opt. Lett.,2005,30:468-470
[13]刘战存.泽尼克是如何发明相衬显微镜的[J].物理实验.1999,20(8)：42-44
[14]C. Mann, L. Yu, C.M. Lo, etal. High-resolution quantitative phase-contrast micro-scopy by digital holography [J]. Opt. Express,2005,13(22):8693-8698
[15]李俊昌,熊秉衡.信息光学理论与计算[M].北京：科学出版社,2009.6
[16]唐福元.泽尔尼克与相衬显微镜[J].物理与工程.2004,14(4)：45-47
[17]M. Teschke, S. Sinzinger. Phase contrast imaging-a generalized perspective [J]. Optical Society of America A,2009,26(4):1015-1021
[18]P. Langehanenberg, B. Kemper, D. Dirksen, etal. Autofocusing in digital hologra-phic phase contrast microscopy on pure phase. Appl. Opt.2008,47(19):D176-D182.
[19]J. W. Kang, C. K. Hong. Precise Phase-contrast image using in-line phase-shifting digital holographic microscopy[J]. Frontiers in Optics.2006:JSuA44
[20]张雪蓉,李劲松.相衬技术在现代光学中的应用[J].激光杂志.2009,30(3)：6-7
[21]Rene Lynge Eriksen, Vincent Ricardo Daria, Jesper Gluckstad. Fully dynamic multiple-beam optical tweezers[J]. Optics express.2002,10(14):597-602
[22]K.A. Nugent. T.E. Gureyev, D.F. Cookson, etal. Quantitative phase imaging using hard X rays. Phys. Rev. Lett..1996,77:2961
[23]陈建文,高鸿奕,李儒新等.X射线相衬成像[J].物理学进展.2005,225(2)：175-193
[24]陈博.X射线相位衬度成像相关光学问题研究：[博士学位论文].合肥：中国科学技术大学,2007
[25]P.J. Bostick, A.E. Giuliano. Vital dyes in sentinal node localization[J]. Semin Nucl Med.2000,30:18-24
[26]高鸿奕,谢红兰,陈建文.硬X射线相位衬度成像的实验研究[J].中国激光.2005,32[2]：167-169
[27]朱佩平,吴白玉.X射线相位衬度成像[J].物理.2007,36(6)：443-451
[28]Talbot. Facts relating to optical science[J]. Phios. Mag..1836,9(4):401-407
[29]P. Cloctens. Hard x-ray phase imaging using simple propagation of a coherent synchrotron radiation beam[J]. Appl. Phys..1999,32:145-151
[30]苏显渝,李继陶.信息光学[M].北京：科学出版社,1999.9
[31]Joseph W. Goodman. Introduction to Fourier Optics[M]. Beijing:Publishing Hou-se of Electronics Industry,2006,9
[32]何钰.阿贝成像原理和空间滤波实验及计算机模拟实验[J].物理与工程,2006,16(2)：19-23
[33]李林,林家明,王平等.工程光学[M].北京：北京理工大学出版社,2003.8
[34]郁道银,谈恒英.工程光学[M].北京：机械工业出版社,2008.1
[35]林强.部分相干激光：产生、传输及其应用[J].红外与激光工程.2007,36：442
[36]徐延亮.部分相干光模式分解和传输特性的研究：[硕士学位论文].成都：西南交通大学,2008
[37]文侨.部分相干光的传输特性研究：[硕士学位论文].成都：四川大学,2005
[38]蓝信钜.激光技术[M].北京：科学出版社,2000.8
[39]赵建林.高等光学[M].北京：国防工业出版社,2003,5
[40]赵朋,夏海瑞.孙大亮等.利用全息相衬干涉显微术研究EDTA和KDP对晶体生长习性的影响[J].人工晶体学报.2003,32(1)：31-34
[41]于锡玲,魏爱俭.研究晶体生长的全息相衬显微术[J].人工晶体学报.1987,16(2)：165-169
[42]Pan Liping, Li Chongguang. Novel Measurement Method of Small Phase with Interference Phase Contrast[C]. In:Advanced Measurement and Test Part 1. Switzer land,2011
[2]邓大鹏.光纤通信原理[M].北京：人民邮电出版社,2009.9
[3]李镜,刘文杰,朱佩平等.基于光栅相衬成像的扇束螺旋CT重建算法[J].光学学报,2010,30(2)：421-427
[4]潘卫清,朱勇建,郎海涛.基于系统标定的相衬显微数字全息方法[J].中国激光.2010,37(7)：1812-1820
[5]谢敬辉,廖宁放,曹良才.傅里叶光学与现代光学基础[M].北京：北京理工大学出版社,2007.9
[6]J. Gluckstad. Phase contrast image synthesis [J]. Optics Commum.,1996,130:225-230
[7]周常河,刘立人,王淮生.可实现任意形状的高效Zernike照明器[J].强激光与粒子束.1996,,11(3)：295-298
[8]刁麓弘,李华,于斌等.基于Zernike相衬法的相衬成像探索[J].工程图学学报.2006,4：100-104
[9]P.C. Mogense, J. Gluckstad. Dynamic array generation and pattern formation for optical Tweezers[J]. Opt. Commun.,2000,175:75-81
[10]R.L. Eriksen, P.C. Mogensen, J. Gluckstad. Multiple-beam optical tweezers generated by the generalized phase-contrast method[J]. Opt. Let.,2002,27(4):267-269
[11]C. Preza. Rotational-diversity phase estimation from differential interference contrast microscopy images[J]. J. Opt. Soc. Am. A.,2000,(3):415-424
[12]P. Marquet, B. Rappaz, P.J. Magistretti, etal. Digital holographic microscopy: noninvasive contrast imaging technique allowing quantitative visualization of living cells with subwavelength axial accuracy [J]. Opt. Lett.,2005,30:468-470
[13]刘战存.泽尼克是如何发明相衬显微镜的[J].物理实验.1999,20(8)：42-44
[14]C. Mann, L. Yu, C.M. Lo, etal. High-resolution quantitative phase-contrast micro-scopy by digital holography [J]. Opt. Express,2005,13(22):8693-8698
[15]李俊昌,熊秉衡.信息光学理论与计算[M].北京：科学出版社,2009.6
[16]唐福元.泽尔尼克与相衬显微镜[J].物理与工程.2004,14(4)：45-47
[17]M. Teschke, S. Sinzinger. Phase contrast imaging-a generalized perspective [J]. Optical Society of America A,2009,26(4):1015-1021
[18]P. Langehanenberg, B. Kemper, D. Dirksen, etal. Autofocusing in digital hologra-phic phase contrast microscopy on pure phase. Appl. Opt.2008,47(19):D176-D182.
[19]J. W. Kang, C. K. Hong. Precise Phase-contrast image using in-line phase-shifting digital holographic microscopy[J]. Frontiers in Optics.2006:JSuA44
[20]张雪蓉,李劲松.相衬技术在现代光学中的应用[J].激光杂志.2009,30(3)：6-7
[21]Rene Lynge Eriksen, Vincent Ricardo Daria, Jesper Gluckstad. Fully dynamic multiple-beam optical tweezers[J]. Optics express.2002,10(14):597-602
[22]K.A. Nugent. T.E. Gureyev, D.F. Cookson, etal. Quantitative phase imaging using hard X rays. Phys. Rev. Lett..1996,77:2961
[23]陈建文,高鸿奕,李儒新等.X射线相衬成像[J].物理学进展.2005,225(2)：175-193
[24]陈博.X射线相位衬度成像相关光学问题研究：[博士学位论文].合肥：中国科学技术大学,2007
[25]P.J. Bostick, A.E. Giuliano. Vital dyes in sentinal node localization[J]. Semin Nucl Med.2000,30:18-24
[26]高鸿奕,谢红兰,陈建文.硬X射线相位衬度成像的实验研究[J].中国激光.2005,32[2]：167-169
[27]朱佩平,吴白玉.X射线相位衬度成像[J].物理.2007,36(6)：443-451
[28]Talbot. Facts relating to optical science[J]. Phios. Mag..1836,9(4):401-407
[29]P. Cloctens. Hard x-ray phase imaging using simple propagation of a coherent synchrotron radiation beam[J]. Appl. Phys..1999,32:145-151
[30]苏显渝,李继陶.信息光学[M].北京：科学出版社,1999.9
[31]Joseph W. Goodman. Introduction to Fourier Optics[M]. Beijing:Publishing Hou-se of Electronics Industry,2006,9
[32]何钰.阿贝成像原理和空间滤波实验及计算机模拟实验[J].物理与工程,2006,16(2)：19-23
[33]李林,林家明,王平等.工程光学[M].北京：北京理工大学出版社,2003.8
[34]郁道银,谈恒英.工程光学[M].北京：机械工业出版社,2008.1
[35]林强.部分相干激光：产生、传输及其应用[J].红外与激光工程.2007,36：442
[36]徐延亮.部分相干光模式分解和传输特性的研究：[硕士学位论文].成都：西南交通大学,2008
[37]文侨.部分相干光的传输特性研究：[硕士学位论文].成都：四川大学,2005
[38]蓝信钜.激光技术[M].北京：科学出版社,2000.8
[39]赵建林.高等光学[M].北京：国防工业出版社,2003,5
[40]赵朋,夏海瑞.孙大亮等.利用全息相衬干涉显微术研究EDTA和KDP对晶体生长习性的影响[J].人工晶体学报.2003,32(1)：31-34
[41]于锡玲,魏爱俭.研究晶体生长的全息相衬显微术[J].人工晶体学报.1987,16(2)：165-169
[42]Pan Liping, Li Chongguang. Novel Measurement Method of Small Phase with Interference Phase Contrast[C]. In:Advanced Measurement and Test Part 1. Switzer land,2011