A method for measuring focal length based on Talbot effect is put forward, which suits determining focal length of long-focus lens. The variation of Moiré fringes occurs after typical phase object of measuring lens is laid between two gratings. The images of fringes taken by CCD camera are processed with MATLAB. The focal length of measuring lens is figured out accurately after calculating the slope of fringes, the separation angle between two grating lines and measuring the distance between lens and the second grating. Experimental data indicate that, for a system with laser wavelength of 0.65μm, measuring lens wth focal length of 420mm, the measurement accuracy is 0.10%.So this method has advantages of simple device, fast processing speed and high precision. It satisfies focal length determination of long focal-length lens used in SG - III Facility.

Date Published: 20 May 2009
PDF: 5 pages
Proc. SPIE 7283, 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 72834H (20 May 2009); doi: 10.1117/12.828827

Published in SPIE Proceedings Vol. 7283:
4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment
Yudong Zhang; James C. Wyant; Robert A. Smythe; Hexin Wang, Editor(s)