[1] D S Fong, L Aiello, T W Gardner, et al.. Retinopathy in diabetes [J]. Diabetes Care, 2004, 27(s1): s84-s87.

[2] K Alsabti, S Raizada, V B Wani, et al.. Efficacy and reliability of fundus digital camera as a screening tool for diabetic retinopathy in Kuwait [J]. Journal of Diabetes and its Complications, 2003, 17(4): 229-233.

[3] Zhang Yunhai, Zhao Gaina, Zhang Zhonghua, et al.. Accurate focusing of non-mydriatic fundus camera [J]. Optics and Precision Engineering, 2009, 17(5): 1014-1018.

[4] Pan Lin. Research on Tele-Screening System for Diabetic Retinopathy and Its Image Processing Key Technologies [D]. Fuzhou: Fuzhou University, 2011. 59-76.

[5] R Zeimer, S Zou, T Meeder, et al.. A fundus camera dedicated to the screening of diabetic retinopathy in the primary-care physician′s office [J]. Investigative Ophthalmology & Visual Science, 2002, 43(5): 1581-1587.

[6] M Moscaritolo, H Jampel, F Knezevich, et al.. An image based auto-focusing algorithm for digital fundus photography [J]. IEEE Transactions on Medical Imaging, 2009, 28(11): 1703-1707.

[7] A Marrugo, M Millán, G Cristóbal, et al.. No-reference quality metrics for eye fundus imaging [C]. Computer Analysis of Images and Patterns, 2011, 6854: 486-493.

[8] Huang Yang. Near-Infrared Fundus Camera Design [D]. Nanjing: Nanjing University of Science & Technology, 2011. 13-19.

[9] Zhai Yongping, Zhou Dongxiang, Liu Yunhui. Large range autofocusing algorithm for microscopy with small depth of field [J]. Acta Optica Sinica, 2012, 32(4): 0418001.

[10] Wang Zhongxun, Pan Yiming, Yin Shaoyun, et al.. Laser processing lens of long focal depth and high resolution [J]. Acta Optica Sinica, 2013, 33(2): 0222004.

[11] J Jeon, I Yoon, D Kim, et al.. Fully digital auto-focusing system with automatic focusing region selection and point spread function estimation [J]. IEEE Transactions on Consumer Electronics, 2010, 56(3): 1204-1210.

[12] X Xu, Y Wang, J Tang, et al.. Robust automatic focus algorithm for low contrast images using a new contrast measure [J]. Sensors, 2011, 11(9): 8281-8294.

[13] S Lee, J Yoo, Y Kumar, et al.. Reduced energy-ratio measure for robust autofocusing in digital camera [J]. Signal Processing Letters, 2009, 16(2): 133-136.

[14] C Shen, H H Chen. Robust focus measure for low-contrast images [C]. Digest of Technical Papers. International Conference on Consumer Electronics, 2006. 69-70.

[15] Zhang Yatao, Ji Shupeng, Wang Qiangfeng, et al.. Definition evaluation algorithm based on regional contrast [J]. Journal of Applied Optics, 2012, 33(2): 293-299.

[16] Han Ruiyu, Wang Jinjiang, Nie Kai, et al.. Adaptive autofocus technique under different contrast [J]. Acta Photonica Sinica, 2012, 41(2): 222-227.

[17] Gao Shiyi, Zhao Mingyang, Zhang Lei, et al.. Improved algorithm about subpixel edge detection of image based on Zernike orthogonal moments [J]. Acta Automation Sinica, 2008, 34(9): 1163-1168.

[18] Qu Yingdong, Li Rongde, Bai yanhua, et al.. A high-speed Zernike momnets edge operator based on 9×9 masks [J]. Journal of Optoelectronics·Laser, 2010, 21(11): 1683-1687.

[19] Wang Yaoming. Moment Function for Image: Principle, Algorithm and Application [M]. Shanghai: East China University of Science and Technology Press, 2002. 32-35.

[20] Shi Jinfeng, Wu Qingwen, Zhang Jianping, et al.. Thermal-optical analysis for optical window of high-altitude and high-speed aerial camera [J]. Acta Optica Sinica, 2012, 32(4): 0422004.

[21] S Ghosal, R Mehrotra. Detection of composite edges [J]. IEEE Transactions on Image Processing, 1994, 3(1): 14-25.

[22] Han Ke, Zhu Xiuchang, Feng Quan. Research on auto-focusing approaches for different object distance [J]. Journal of Nanjing University of Posts and Telecommunications (Natural Science), 2007, 27(6): 44-48.

[23] Wang Yong, Tan Yihua, Tian Jinwen. A new kind of sharpness evaluation function of image [J]. Journal of Wuhan University of Technology, 2007, 29(3): 124-126.

[24] Li Lihong, Zhang Minglu. Research of focusing evaluation function under a strong shot-noise background [J]. Laser & Optoelectronics Progress, 2012, 49(11): 111103.

[25] Shi Hongwei, Shi Yaowu, Yang Shuang. Evaluation and selection of estimating function for auto-focus system of optical microscope [J]. Journal of Computer-Aided Design & Computer Graphics, 2013, 25(2): 235-240.

[26] Zhai Yongping, Zhou Dongxiang, Liu Yunhui, et al.. Design of evaluation index for auto-focusing function and optimal function selection [J]. Acta Optica Sinica, 2011, 31(4): 0418002.