[1] [1] Fujii Kenichi. Present state of the solid and liquid density standards [J]. Metrologia(S0026-1394),2004,41:S1-S15.

[2] [2] LUO Zhi-yong,YANG Li-feng,GU Ying-zi,et al. A study on solid density primary standard [J]. Chinese Science Bulletin (S1001-6538),2007,52(21):2881-2886.

[3] [3] LUO Zhi-yong. The progress and development trend of mass natural standard [J]. Acta Metrologica Sinica,2004,25(2):138-141.

[4] [4] Becker Peter. History and progress in the accurate determination of the Avogadro constant [J]. Report on Progress in Physics (S0034-4885),2001,64:1945-2008.

[5] [5] Fujii K,Tanaka M,Nezu Y,et al. Determination of the Avogadro constant by accurate measurement of the molar volume of a silicon crystal [J]. Metrologia(S0026-1394),1999,36:455-464.

[6] [6] KANG Yan-hui,ZHU Ji-gui,LUO Zhi-yong,et al. Impact analysis of Gaussian beam on measurement of single crystal silicon sphere diameter [J]. Acta Optica Sinica,2008,28(11):2148-2152.

[7] [7] Saunders J B. Ball and cylinder interferometer [J]. J. Res. Nat. Bur. Stand. Sect. C(S0022-4316),1972,76:11-20.

[8] [8] LUO Zhi-yong,YANG Li-feng,GU Ying-zi,et al. The absolute measurement of density of silicon crystals for determining Avogadro constant [J]. Acta Metrologica Sinica,2008,29(3):211-215.

[9] [9] Fujii K,Tanaka M,New Y,et al. Interferometric measurements of the diameters of a single-crystal silicon sphere [J]. Rev. Sci. Instrum(S0034-6748),1992,63(11):5320-5325.

[10] [10] Kuramoto Naoki,Fujii Kenichi. Interferometric determination of the diameter of a silicon sphere using a direct optical frequency tuning system [J]. IEEE Transactions on Instrumentation and Measurement(S0018-9456),2003,52(2):631-635.

[11] [11] WEI Zhen-zhong,GAO Ming,ZHANG Guang-jun,et al. Sub-pixel extraction method for the center of light-spot image[J]. Opto-Electronic Engineering,2009,36(4):7-12.

[12] [12] LI Chun-yan,XIE Hua,LI Huai-feng,et al. Centroiding algorithm for high-accuracy star tracker [J]. Opto-Electronic Engineering,2006,33(2):41-44.

[13] [13] TANG Guan-qun. Analysis and comparison of several calculation methods of beam spot center [J]. Journal of Beijing Institute of Machinery,2009,24(1):61-64