Analysis of the lateral shearing interferograms of human tear film using modified FFT techniques

Tomasz J. Licznerski; Henryk T. Kasprzak; Waldemar Kowalik

doi:10.1117/12.328314

22 October 1998 Analysis of the lateral shearing interferograms of human tear film using modified FFT techniques

Tomasz J. Licznerski, Henryk T. Kasprzak, Waldemar Kowalik

Proceedings Volume 3579, Ophthalmic Measurements and Optometry; (1998) https://doi.org/10.1117/12.328314
Event: Ophthalmic Measurements and Optometry, 1997, Kazimierz Dolny, Poland

Abstract

The paper presents a modified method of the Shearing interferogram analysis by the use of the Fast Fourier Transform. The interference fringes are obtained in Shearing interferometer and are related to a wavefront reflected from the tear film over the cornea. The method is based on the measurement of interference fringes disturbances by calculation of the 2^nd momentum of Fourier spectra of the interferogram. The less smooth tear film covering the cornea the more disturbed interference fringes and higher value of the 2^nd momentum calculated from its Fourier spectra. The interferograms obtained from the proposed setup can differ also in the shape of fringes and in its density. This is caused by the differences in distance between the interferometer objective and the eye. Since the living eye is a continuously moving object, the fixation of this distance is difficult to achieve in practice. Obviously the fringes variations affect the Fourier spectra distribution and results of the numerical analysis based on FFT. The proposed method compensates the variations by applying the correcting factor determined from spectra distance from the origin of Fourier domain.

Citation Download Citation

Tomasz J. Licznerski, Henryk T. Kasprzak, and Waldemar Kowalik "Analysis of the lateral shearing interferograms of human tear film using modified FFT techniques", Proc. SPIE 3579, Ophthalmic Measurements and Optometry, (22 October 1998); https://doi.org/10.1117/12.328314

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