基于偏折术的角膜地形图测量方法研究

为了提高获取角膜地形图的测量精度，将相位测量偏折术和传统Placido盘法相结合，研究了一种新型的人眼角膜地形图获取方法。将人眼顶点处的法线与相机光轴共线，且与显示器的法线平行。显示器上显示的二维正交条纹图经人眼反射后，被相机接收。利用相位提取算法和迭代算法得到显示器和人眼角膜的坐标，再根据两者的几何关系，进而得到人眼角膜地形图。数值模拟表明模型眼的曲率半径和屈光度的测量精度理论上可达±14.7 μm和±0.07D。最后实验上对曲率半径与人眼接近的球面元件进行了测量验证，结果表明，本方法具有测量精度高、装置简单、成本低等优点。

Abstract

In order to improve the accuracy， a new method is proposed to obtain the corneal topography based on phase measurement deflectometry and the traditional placido disk system. The proposed method utilizes a geometry configuration where the normal at the apex of the human eye is collinear with the optical axis of the camera and parallel with the normal of the screen.Two-dimensional orthogonal fringe pattern displayed on the screen is reflected off the human eye， and the deformed fringe image is recorded by camera. Then the coordinates of the screen and human cornea are calculated by phase extraction algorithm and iterative algorithm， respectively. According to the geometric relationship between them， the corneal topography can be obtained. The numerical simulation demonstrates that the measurement accuracy of the radius of curvature and diopter of the model eye can theoretically reach ±14.7 μm and ±0.07D， respectively. Finally， experiments are conducted to measure a spherical element with a radius of curvature close to that of the human eye. The results show that this method has the advantages of highaccuracy， simple deviceand low cost.

参考文献

[1] S A Klein. Corneal Topography： A review， new ANSI standards and problems to solve[J]. Optical Society of America， 2000， (5)： 286-296.

[2] Rao S K， Padmanabhan P. Understanding corneal topography[J]. Current Opinion in Ophthalmology， 2000， 11(4)：248.

[3] Watanabe T， Gekka T， Watanabe A， et al. Analysis of changes in corneal topography after 27-gauge transconjunctival microincision vitrectomy combined with cataract surgery[J]. Journal of Ophthalmology， 2019， (3)： 1-5.

[4] Thornton， Spencer P. Clinical evaluation of corneal topography[J]. Journal of Cataract & Refractive Surgery， 1993， 19 Suppl： 198.

[5] Yobani Mejía-Barbosa， Daniel Malacara-Hernández. A review of methods for measuring corneal topography[J]. Optometry & Vision ence Official Publication of the American Academy of Optometry， 2001， 78(4)： 240-53.

[6] Doss J D， Hutson R L， Rowsey J J， et al. Method for calculation of corneal profile and power distribution[J]. Arch Ophthalmol， 1981， 99(7)： 1261-1265.

[7] Klyce S D. Computer-assisted corneal topography. High-resolution graphic presentation and analysis of keratoscopy[J]. Investigative Ophthalmology & Visual Science， 1985， 25(12)： 1426-1435.

[8] Micali J D， Greivenkamp J E， Primeau B C. Dynamic measurement of the corneal tear film with a Twyman-Green interferometer[C]// Interferometry Xvii： Advanced Applications. International Society for Optics and Photonics， 2014.

[9] Micali J D， Greivenkamp J E. Dual interferometer for dynamic measurement of corneal topography[J]. Journal of Biomedical Optics， 2016， 21(8)： 085007.

[10] H T Kasprzak， K Waldemar， J Jaronski. Interferometric measurements of fine corneal topography[J]. Proceedings of SPIE- The International Society for Optical Engineering， 1995， (3)： 32-39.

[11] Jongsma F H M， Laan F C， Stultiens B A T， et al. Moire-based corneal topographer suitable for discrete Fourier analysis[J]. 1994， 2126： 185-192.

[12] Kawara T. Corneal topography using moire contour fringes[J]. Applied Optics， 1979， 18(21)： 3675-8.

[13] Ortega J C P， Moreno J W R， Rodriguez L B， et al. Image processing for 3D reconstruction using a modified Fourier transform profilometry method[J]. 2007， (8)： 10-13.

[14] Warnicki J W， Rehkopf P G， Curtin D Y， et al. Corneal topography using computer analyzed rasterstereographic images[J]. Applied Optics， 1988， 27(6)： 1135-1140.

[15] Braaf B， Dubbelman M， Van d H R G L， et al. Performance in specular reflection and slit-imaging corneal topography[J]. Optometry and Vision Science， 2009， (5)： 86.

[16] CARVALHO， Alberto L. Absolute accuracy of Placido-based videokeratographs to measure the optical aberrations of the cornea[J]. Optom. Vis.， 2004， 81(8)： 616-628.

[17] Klein S A. Corneal topography reconstruction algorithm that avoids the skew ray ambiguity and the skew ray error. [J]. Optometry & Vision ence Official Publication of the American Academy of Optometry， 1997， 74(11)： 945.

[18] Gong D W， Chen J H， Yuan C， et al. A new method for reconstruction of corneal topography with Placido disk system[J]. Advanced Materials Research， 2014， 974： 373-378.

[19] Yoder P R， Macri T F， Telfair W B， et al. Precision measurement of corneal topography[C]. SPIE， 1989， 1036： 99.

[20] Rand R H， Howland H C， Applegate R A. Mathematical model of a Placido disk keratometer and its implications for recovery of corneal topography[J]. Optometry & Vision ence Official Publication of the American Academy of Optometry， 1997， 74(11)： 926-30.

[21] CAMPBELL， CHARLES. Reconstruction of the corneal shape with the MasterVue corneal topography system[J]. Optometry & Vision ence Official Publication of the American Academy of Optometry， 1997， 74(11)： 899-905.

[22] Carvalho L A， Tonissi S A， Castro J C. Preliminary results of a computerized Placido disk surgical corneal topographer[C]. SPIE， 1999， 3591： 53-62.

[23] Huang L， Ng C S， Asundi A K. Fast full-field out-of-plane deformation measurement using fringe reflectometry[J]. Optics and Lasers in Engineering， 2012， 50(4)： 529-533.

[24] Florindo， J. B， Soares， et al. Mumford-Shah algorithm applied to videokeratography image processing and consequences to refractive power values[J]. Comput Methods Programs Biomed， 2007，87(1)：61-67.

[25] Knauer M C， Kaminski J， Hausler G. Phase measuring deflectometry： a new approach to measure specular free-form surfaces[C]. SPIE， 2004， (5457)： 366-376.

[26] Bothe T， Li W， Kopylow C V， et al. High-resolution 3D shape measurement on specular surfaces by fringe reflection[C]. SPIE， 2004， 5457： 411-422.

[27] Liang H， Olesch E， Yang Z， et al. Single-shot phase-measuring deflectometry for cornea measurement[J]. Advanced Optical Technologies， 2016， (5)： 5-6.

[28] Luo P， Li D， Wang R， et al. Phase-extraction algorithm for a single-shot spatial-carrier orthogonal fringe pattern with least squares method[J]. Optical Engineering， 2020， 59(2)： 1.

[29] Wang R， Li D， Zhang X. Systematic error control for deflectometry with iterative reconstruction[J]. Measurement， 2020： 108393.

[30] Graves L R， Heejoo C， Wenchuan Z， et al. Model-free deflectometry for freeform optics measurement using an iterative reconstruction technique[J]. Optics Letters， 2018， 43(9)： 2110-2113.

[31] Lotmar W. Theoretical eye model with aspherics[J]. Journal of the Optical Society of America， 1971， 61(11)：1522-1529.

[32] Liou H L， Brennan N A. Anatomically accurate， finite model eye for optical modeling[J]. Journal of the Optical Society of America Optics Image ence & Vision， 1997， 14(8)： 1684-95.

[33] Lindsay R， Smith G， Atchison D. Descriptors of corneal shape[J]. Optom. Vis.， 1998， 75(2)： 156-158.

[34] Guo H， Wang Z， Zhao Q， et al. Individual eye model based on wavefront aberration[J]. Optik- International Journal for Light and Electron Optics， 2005， 116(2)： 80-85.

[35] M Campos-garcía， Cossio-Guerrero C， Moreno-Oliva V I， et al. Surface shape evaluation with a corneal topographer based on a conical null-screen with a novel radial point distribution[J]. Applied Optics， 2015， (5)： 10-13.

刘肖萧, 李大海, 刘鑫, 洪铁鑫, 张新伟, 王瑞阳, 刘春玲, 黄永志. 基于偏折术的角膜地形图测量方法研究[J]. 光学与光电技术, 2021, 19(3): 100. LIU Xiao-xiao, LI Da-hai, LIU Xin, HONG Tie-xin, ZHANG Xin-wei, WANG Rui-yang, LIU Chun-ling, HUANG Yong-zhi. Study of Corneal Topography Measurement Method Based on Deflectometry[J]. OPTICS & OPTOELECTRONIC TECHNOLOGY, 2021, 19(3): 100.

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