A new formula for the lens index has been reported which is independent of the lens parameters. This proposed innovative nondestructive liquid-immersion technique is based on a coherent optical-processing configuration, and it is superior to the existing methods because the lens aperture, air equivalent factors for the glass cell and the liquids, lens aberrations, focusing errors, etc. are not of concern. The Fourier transform spectra of a grating as well as of a double slit have been employed to determine the lens index. The comparator and the x-y recorder have been separately used to calculate the distance between two successive diffraction orders in the back focal plane of the test lens. The present technique is quick to perform and easy to handle.
© 1984 Optical Society of America
R. S. Kasana, S. Boseck, and K.-J. Rosenbruch, "Use of a grating in a coherent optical-processing configuration for evaluating the refractive index of a lens," Appl. Opt. 23, 757-761 (1984)