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Depth-of-Focus and its Association with the Spherical Aberration Sign. A Ray-Tracing Analysis

机译：景深及其与球差符号的关系。射线追踪分析

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Purpose To investigate the relationship between the sign of spherical aberration (SA) and the corresponding depth-of-focus (DoF) values around best focus, at three different spatial frequencies (SF). Additionally, to study the influence of the Stiles-Crawford effect (SCE) on DoF. Methods We modeled schematic eyes having a range of SA values, C (4, 0), from -0.20 to 0.20?μm, at 6?mm pupil, in a ray-tracing software (Zemax). The through-focus optical performance was obtained via Modulation Transfer Function (MTF) calculations using thin paraxial lenses in-front of the model eye, from -2.00 to+2.00 D in 0.05D steps. Through-focus full-width (defocus) occurring at the half maximum of MTF value was considered as DoF, in diopters. Results For the low-SF configuration, +SA and –SA results were close to being mirror symmetries of one another. However, for midand high- SF targets, in the SA range spanning from -0.15 to 0.15?μm, models of equal SA magnitude but opposite sign produced similar DoF measures, but those with SA more negative than -0.15?μm showed marginally higher DoF than their positive counterparts. The SCE improved DoF for low SF (10 cycles/mm), while for mid and higher SF (>30 cycles/mm) mixed results were observed. Conclusions As regards presbyopic-correction strategies that use deliberately induced aberrations to increase the depth of focus, the current study suggests that both positive and negative SA have equal potential. However, practical considerations will probably limit the useful DoF achievable through the utilization of SCE in presbyopes. for reference to a contemporary record detailing refractive history.
机译：目的研究在三个不同空间频率（SF）时，球差（SA）的符号与最佳聚焦附近的相应景深（DoF）值之间的关系。此外，研究Stiles-Crawford效应（SCE）对DoF的影响。方法我们在光线追踪软件（Zemax）中，对瞳孔6？mm处具有-0.20至0.20？μm的SA值C（4，0）范围的示意性眼睛建模。透过焦点的光学性能是通过使用模型眼前方的近轴薄透镜通过调制传递函数（MTF）计算而获得的，以0.05D为步长从-2.00到+2.00D。在MTF值的一半最大值处出现的全焦点全焦（散焦）被视为DoF（以屈光度为单位）。结果对于低SF配置，+ SA和–SA结果几乎是彼此的镜像对称。但是，对于中，高SF目标，在SA范围从-0.15到0.15？m的SA范围内，相同SA幅值但符号相反的模型产生了类似的DoF量度，但是SA负于-0.15？μm的那些模型显示出略高的DoF。比他们的积极同行。对于较低的SF（10个循环/毫米），SCE改善了DoF，而对于中等和较高的SF（> 30个循环/毫米），则观察到混合结果。结论关于使用故意引起的像差来增加焦深的老花眼矫正策略，当前研究表明，正负SA具有相同的潜力。但是，实际考虑可能会限制通过老花眼中SCE的使用实现的有用DoF。参考详细记录屈光史的当代记录。

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