角膜曲率计的优化设计及实现
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摘要
为实现简化的角膜曲率测量系统,提出一种以角膜反射成像为原理的角膜曲率计,其测量方法是将六个呈正六边形排布的点光源准直后投射到角膜前表面,角膜反射图像经物方远心光路成像在CMOS上;利用重心算法求出角膜反射图像中位于正六边形长对角线上的两个点光源的距离,进而求得角膜曲率。本文对系统的成像质量、测量范围和测量精度进行了理论分析,并且采用标准模拟眼和人眼进行实验,以验证理论分析结果。结果表明:本文设计的测量系统的角膜曲率半径测量范围为5.5 mm～11 mm(对应角膜屈光度30 m-1～60m-1),测量误差为±0.02mm。这将为自动角膜曲率计的设计及优化提供技术支持。
To realize a simplified keratometer, we proposed a design proposal based on corneal reflex imaging. Six pointolites which arranged in a regular hexagon were used to emit parallel light to the surface of a cornea and were reflected by the cornea. Then the image was captured by a telecentric optical system in the object space to a CMOS camera. In order to obtain the corneal curvature, the distance between two pointolites located on the regular hexagonal diagonal in the corneal reflection images were calculated by using the center of gravity algorithm. The imaging quality, measuring range and measuring precision of the system were theoretically analyzed, and the Ziess' s model eye and human eyes were used to conduct experiments to verify the theoretical analysis results. The experiment results have shown that the precision of the measurement error is ±0.02 mm and the measurement range is from 5.5 mm to 11.6 mm(30 m-1 to 60 m-1 in diopter of cornea). The research will provide technical supports for the design and optimization of automatic keratometer.
To realize a simplified keratometer, we proposed a design proposal based on corneal reflex imaging. Six pointolites which arranged in a regular hexagon were used to emit parallel light to the surface of a cornea and were reflected by the cornea. Then the image was captured by a telecentric optical system in the object space to a CMOS camera. In order to obtain the corneal curvature, the distance between two pointolites located on the regular hexagonal diagonal in the corneal reflection images were calculated by using the center of gravity algorithm. The imaging quality, measuring range and measuring precision of the system were theoretically analyzed, and the Ziess' s model eye and human eyes were used to conduct experiments to verify the theoretical analysis results. The experiment results have shown that the precision of the measurement error is ±0.02 mm and the measurement range is from 5.5 mm to 11.6 mm(30 m-1 to 60 m-1 in diopter of cornea). The research will provide technical supports for the design and optimization of automatic keratometer.
引文
[1]Gutmark R,Guyton D L.Origins of the keratometer and its evolving role in ophthalmology[J].Survey of Ophthalmology,2010,55(5):481-497.
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[3]Wang Y L.Analysis of corneal curvature meter(B)[J].China Glasses Science-Technology Magazine,2017(5):172-174.王英丽.角膜曲率计浅析(下)[J].中国眼镜科技杂志,2017(5):172-174.
[4]Tao Y,Fan D J,Kang Y S.Discussion on problems and solutions in the verification of keratometer[J].China Glasses Science-Technology Magazine,2013(7):124-126.陶瑛,范冬娟,康玉霜.角膜曲率计检定中常见问题及解决方法探讨[J].中国眼镜科技杂志,2013(7):124-126.
[5]Cai J Q,Liu Y.Discussion on principle and detection method of keraometer[J].China Metrology,2010(1):89-90.蔡建奇,刘毅.角膜曲率计测量原理和检测方法探讨[J].中国计量,2010(1):89-90.
[6]Xu T,Qin A L,Li Y Z,et al.A new formula of corneal refractive power and the corneal refractive powers of myopia eyes after laser in situ keratomileusis[J].Journal of Nanjing University(Natural Sciences),2011,47(1):91-96.徐唐,秦爱玲,李一壮,等.角膜屈光力新公式与近视眼准分子激光角膜原位磨镶术后的角膜屈光力[J].南京大学学报(自然科学),2011,47(1):91-96.
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[9]He Y Q,Wang Y,Wang Z Q,et al.Design of imaging keratometer with annular object and charge-coupled device detector[J].Applied Optics,2013,52(35):8532-8539.
[10]Yan J,Meng P H,Zhao J Q.Research of curvature measuring system of eyes cornea[J].Journal of Basic Science and Engineering,2011,19(S1):254-261.闫洁,孟鹏花,赵俊奇.人眼角膜曲率测量系统的研究[J].应用基础与工程科学学报,2011,19(S1):254-261.
[11]Zhao J Q,Duan P H,Guo Z Y,et al.Design of subpixel algorithm of dioptric paramater measurement system for eye cornea[J].Journal of North University of China(Natural Science Edition),2011,32(3):362-366.赵俊奇,段培华,郭智勇,等.人眼角膜曲率参数亚像素测量系统的设计[J].中北大学学报(自然科学版),2011,32(3):362-366.
[12]Zhao J Q,Guo Z Y,Chen A S,et al.Auto-ophthalmometer of eye based on image processing[J].Chinese Journal of Biomedical Engineering,2011,30(1):100-104.赵俊奇,郭智勇,陈安世,等.一种基于图像处理的人眼全自动角膜曲率计研究[J].中国生物医学工程学报,2011,30(1):100-104.
[13]He Y Q,Liu Y J,Zhai Y.Optical design of imaging keratometer[J].Chinese Optics,2014,7(6):956-961.何远清,刘永基,翟奕.成像角膜曲率计的光学设计[J].中国光学,2014,7(6):956-961.
[14]Zheng S L,Liu Y J,Wang Z Q,et al.Design of optical system for a novel imaging keratometer[J].Acta Optica Sinica,2013,33(5):0522004.郑少林,刘永基,王肇圻,等.新型成像角膜曲率仪的光学系统设计[J].光学学报,2013,33(5):0522004.
[2]Wang Y L.Analysis of corneal curvature meter(A)[J].China Glasses Science-Technology Magazine,2016(21):136-137.王英丽.角膜曲率计浅析(上)[J].中国眼镜科技杂志,2016(21):136-137.
[3]Wang Y L.Analysis of corneal curvature meter(B)[J].China Glasses Science-Technology Magazine,2017(5):172-174.王英丽.角膜曲率计浅析(下)[J].中国眼镜科技杂志,2017(5):172-174.
[4]Tao Y,Fan D J,Kang Y S.Discussion on problems and solutions in the verification of keratometer[J].China Glasses Science-Technology Magazine,2013(7):124-126.陶瑛,范冬娟,康玉霜.角膜曲率计检定中常见问题及解决方法探讨[J].中国眼镜科技杂志,2013(7):124-126.
[5]Cai J Q,Liu Y.Discussion on principle and detection method of keraometer[J].China Metrology,2010(1):89-90.蔡建奇,刘毅.角膜曲率计测量原理和检测方法探讨[J].中国计量,2010(1):89-90.
[6]Xu T,Qin A L,Li Y Z,et al.A new formula of corneal refractive power and the corneal refractive powers of myopia eyes after laser in situ keratomileusis[J].Journal of Nanjing University(Natural Sciences),2011,47(1):91-96.徐唐,秦爱玲,李一壮,等.角膜屈光力新公式与近视眼准分子激光角膜原位磨镶术后的角膜屈光力[J].南京大学学报(自然科学),2011,47(1):91-96.
[7]Li B Z,Liang C,Dong X C,et al.Comparison and evaluation of four different techniques of keratometric measurements[J].Chinese Journal of Practical Ophthalmology,2014,32(4):450-455.李炳震,梁晨,冬雪川,等.四种不同方法测量角膜曲率比较研究[J].中国实用眼科杂志,2014,32(4):450-455.
[8]Miller J M.A handheld open-field infant keratometer(an american ophthalmological society thesis)[J].Transactions of the American Ophthalmological Society,2010,108:77-95.
[9]He Y Q,Wang Y,Wang Z Q,et al.Design of imaging keratometer with annular object and charge-coupled device detector[J].Applied Optics,2013,52(35):8532-8539.
[10]Yan J,Meng P H,Zhao J Q.Research of curvature measuring system of eyes cornea[J].Journal of Basic Science and Engineering,2011,19(S1):254-261.闫洁,孟鹏花,赵俊奇.人眼角膜曲率测量系统的研究[J].应用基础与工程科学学报,2011,19(S1):254-261.
[11]Zhao J Q,Duan P H,Guo Z Y,et al.Design of subpixel algorithm of dioptric paramater measurement system for eye cornea[J].Journal of North University of China(Natural Science Edition),2011,32(3):362-366.赵俊奇,段培华,郭智勇,等.人眼角膜曲率参数亚像素测量系统的设计[J].中北大学学报(自然科学版),2011,32(3):362-366.
[12]Zhao J Q,Guo Z Y,Chen A S,et al.Auto-ophthalmometer of eye based on image processing[J].Chinese Journal of Biomedical Engineering,2011,30(1):100-104.赵俊奇,郭智勇,陈安世,等.一种基于图像处理的人眼全自动角膜曲率计研究[J].中国生物医学工程学报,2011,30(1):100-104.
[13]He Y Q,Liu Y J,Zhai Y.Optical design of imaging keratometer[J].Chinese Optics,2014,7(6):956-961.何远清,刘永基,翟奕.成像角膜曲率计的光学设计[J].中国光学,2014,7(6):956-961.
[14]Zheng S L,Liu Y J,Wang Z Q,et al.Design of optical system for a novel imaging keratometer[J].Acta Optica Sinica,2013,33(5):0522004.郑少林,刘永基,王肇圻,等.新型成像角膜曲率仪的光学系统设计[J].光学学报,2013,33(5):0522004.