Bará Salvador
Area de Optica, Facultade de Física, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galiza, Spain.
J Opt Soc Am A Opt Image Sci Vis. 2003 Dec;20(12):2237-45. doi: 10.1364/josaa.20.002237.
A usual approximation in Hartmann-Shack aberrometry is that the centroid displacements are proportional to the spatial averages of the wave-front slopes at the sampling subapertures. However, these spatial averages are actually weighted by the local irradiance distribution across each microlens. The irradiance across the eye pupil is not uniform in usual reflectometric aberrometers, which is due to several factors including retinal scattering and cone waveguiding directionality. It is shown that neglecting this fact in usual least-squares reconstruction procedures gives rise to a biased estimation of the aberration coefficients. The magnitude of this bias depends on the actual irradiance distribution across the eye pupil, the mode being estimated, the detailed modal composition of the aberrated wave front, and the geometry of the wave-front sampling array. Order-of-magnitude calculations suggest that this bias may well be in the range 5%-10% for relatively smooth irradiance distributions. The systematic nature of this error makes it advisable to check for its presence and, if required, to compensate for it by an adequate choice of the least-squares reconstruction matrix.
在哈特曼-夏克像差仪中，通常的一种近似是，质心位移与采样子孔径处波前斜率的空间平均值成正比。然而，这些空间平均值实际上是由每个微透镜上的局部辐照度分布加权的。在通常的反射式像差仪中，穿过眼瞳的辐照度并不均匀，这是由包括视网膜散射和视锥波导方向性在内的几个因素造成的。结果表明，在通常的最小二乘重建过程中忽略这一事实会导致像差系数的估计有偏差。这种偏差的大小取决于穿过眼瞳的实际辐照度分布、所估计的模式、像差波前的详细模式组成以及波前采样阵列的几何形状。量级计算表明，对于相对平滑的辐照度分布，这种偏差很可能在5% - 10%的范围内。这种误差的系统性使得有必要检查其是否存在，并在需要时通过适当选择最小二乘重建矩阵来对其进行补偿。
