Optical surface reconstruction technique through combination of zonal and modal fitting

Abstract

Abstract. Videokeratometers and Scheimpflug cameras permit accurate estimation of corneal surfaces. From height data it is possible to adjust analytical surfaces that will be later used for aberration calculation. Zernike polynomials are often used as adjusting polynomials, but they have shown to be not precise when describing highly irregular surfaces. We propose a combined zonal and modal method that allows an accurate reconstruction of corneal surfaces from height data, diminishing the influence of smooth areas over irregular zones and vice versa. The surface fitting error is decreased in the considered cases, mainly in the central region, which is more important optically. Therefore, the method can be established as an accurate resampling technique.

A Study for Parametric Morphogeometric Operators to Assist the Detection of Keratoconus

“…Both surfaces and the peripheral surface (the bonding surface between both sides in the Z-axis direction) were then joined to obtain the final 3D solid model of the studied cornea. functions to generate reconstruction surfaces [26,27]. In this study, the Rhinoceros' surface from the point grid function was applied to the imported point cloud, creating a rectangular grid of 21 rows and 256 columns that was deformed to minimise the nominal distance between the spatial points and the grid surface.…”

“…This software enables to use non-uniform rational B-spline (NURBS) In a second step (Figure 2), the point clouds representative of both corneal surfaces were imported into the surface reconstruction CAD software Rhinoceros ® V 5.0 (McNeel and Associates, Seattle, WA, USA) [25]. This software enables to use non-uniform rational B-spline (NURBS) functions to generate reconstruction surfaces [26,27]. In this study, the Rhinoceros' surface from the point grid function was applied to the imported point cloud, creating a rectangular grid of 21 rows and 256 columns that was deformed to minimise the nominal distance between the spatial points and the grid surface.…”

Multifocal multiphoton microscopy with adaptive optical correction

“…Fitting over many zones diminishes the affect of smoothing while providing the analytical advantage of Zernike modes (Espinosa et al, 2010). However, an alternative approach demonstrates how reconstruction based on the use of Zernike polynomials does not require a mask (Bowman et al, 2010).…”

“…Overlapping regionalized scanning of the sample provides diverse local phase calculations which are then fitted to Zernike polynomials to appropriately characterize the amplitude of the various distortions present (Espinosa et al, 2010).…”

“…The mask is suitably displaced over the entire surface providing a zonal approach with a modal fit. Unlike a microlens array, the masked region does not necessarily need to correspond to any specific region.Fitting over many zones diminishes the affect of smoothing while providing the analytical advantage of Zernike modes (Espinosa et al, 2010). However, an alternative approach demonstrates how reconstruction based on the use of Zernike polynomials does not require a mask (Bowman et al, 2010).…”