| 摘要 |
Quantitative measurement of corneal surface topography is obtained by processing a two-dimensional image of the surface which reflects a quasi-periodic illuminated pattern, such as series of concentric rings, from a Placido disk source. The local spatial phases exhibited by the image of the illuminated pattern when reflected from the corneal surface and when reflected from standard specular surfaces are obtained by processing the images which includes use of specially filtered Fourier and inverse transforms. The distances at which predetermined local spatial phases are observed in the image from the cornea are compared with the distances at which these same phases are observed in the images of the standard surfaces. The distances are also compared with certain corresponding distances on the Placido disk source and converted to reveal the dioptric powers of refraction of the corneal surface without the need for parametric interpolation. Results are obtained to a finer degree of granularity than the number of rings in the pattern or even the actual number of pixels in the pattern. During the processing, any mislocation of the apex of the corneal surface along the optical axis is compensated for.
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