School of Optometry, Indiana University, Bloomington, USA.
Ophthalmic Physiol Opt. 2014 May;34(3):331-45. doi: 10.1111/opo.12110. Epub 2014 Mar 4.
To examine the separate and combined influences of zone geometry, pupil size, diffraction, apodisation and spherical aberration on the optical performance of concentric zonal bifocals.
Zonal bifocal pupil functions representing eye + ophthalmic correction were defined by interleaving wavefronts from separate optical zones of the bifocal. A two-zone design (a central circular inner zone surrounded by an annular outer-zone which is bounded by the pupil) and a five-zone design (a central small circular zone surrounded by four concentric annuli) were configured with programmable zone geometry, wavefront phase and pupil transmission characteristics. Using computational methods, we examined the effects of diffraction, Stiles Crawford apodisation, pupil size and spherical aberration on optical transfer functions for different target distances.
Apodisation alters the relative weighting of each zone, and thus the balance of near and distance optical quality. When spherical aberration is included, the effective distance correction, add power and image quality depend on zone-geometry and Stiles Crawford Effect apodisation. When the outer zone width is narrow, diffraction limits the available image contrast when focused, but as pupil dilates and outer zone width increases, aberrations will limit the best achievable image quality. With two-zone designs, balancing near and distance image quality is not achieved with equal area inner and outer zones. With significant levels of spherical aberration, multi-zone designs effectively become multifocals.
Wave optics and pupil varying ocular optics significantly affect the imaging capabilities of different optical zones of concentric bifocals. With two-zone bifocal designs, diffraction, pupil apodisation spherical aberration, and zone size influence both the effective add power and the pupil size required to balance near and distance image quality. Five-zone bifocal designs achieve a high degree of pupil size independence, and thus will provide more consistent performance as pupil size varies with light level and convergence amplitude.
研究同心环带形双焦点的区域几何形状、瞳孔大小、衍射、消像差和球差分别和共同对光学性能的影响。
双焦点的眼和眼科矫正的区域瞳孔函数是通过双焦点不同光学区域的波前交错来定义的。用可编程区域几何形状、波前相位和瞳孔传输特性配置了两区域设计（一个中央圆形内区，周围是一个由瞳孔限定的环形外区）和五区域设计（一个中央小圆形区，周围是四个同心环）。利用计算方法，我们研究了衍射、斯提尔-克劳福德（Stiles Crawford）消像差、瞳孔大小和球差对不同目标距离的光学传递函数的影响。
消像差改变了每个区域的相对权重，从而改变了近距和远距光学质量的平衡。当包括球差时，有效距离矫正、附加光焦度和像质取决于区域几何形状和斯提尔-克劳福德效应消像差。当外区宽度较窄时，聚焦时衍射限制了可用的图像对比度，但随着瞳孔扩大和外区宽度增加，像差会限制最佳可实现的图像质量。对于两区域设计，用相等面积的内区和外区不能达到近距和远距像质的平衡。在存在显著的球差时，多区域设计实际上成为多焦点。
波光学和瞳孔变化的眼光学对同心双焦点的不同光学区域的成像能力有显著影响。对于两区域双焦点设计，衍射、瞳孔消像差、球差和区域尺寸影响有效附加光焦度和平衡近距和远距像质所需的瞳孔大小。五区域双焦点设计达到了高度的瞳孔尺寸独立性，因此在瞳孔尺寸随光照水平和会聚幅度变化时将提供更一致的性能。
