Hofer H, Artal P, Singer B, Aragón J L, Williams D R
Center for Visual Science, University of Rochester, New York 14627, USA.
J Opt Soc Am A Opt Image Sci Vis. 2001 Mar;18(3):497-506. doi: 10.1364/josaa.18.000497.
It is well known that the eye's optics exhibit temporal instability in the form of microfluctuations in focus; however, almost nothing is known of the temporal properties of the eye's other aberrations. We constructed a real-time Hartmann-Shack (HS) wave-front sensor to measure these dynamics at frequencies as high as 60 Hz. To reduce spatial inhomogeneities in the short-exposure HS images, we used a low-coherence source and a scanning system. HS images were collected on three normal subjects with natural and paralyzed accommodation. Average temporal power spectra were computed for the wave-front rms, the Seidel aberrations, and each of 32 Zernike coefficients. The results indicate the presence of fluctuations in all of the eye's aberration, not just defocus. Fluctuations in higher-order aberrations share similar spectra and bandwidths both within and between subjects, dropping at a rate of approximately 4 dB per octave in temporal frequency. The spectrum shape for higher-order aberrations is generally different from that for microfluctuations of accommodation. The origin of these measured fluctuations is not known, and both corneal/lenticular and retinal causes are considered. Under the assumption that they are purely corneal or lenticular, calculations suggest that a perfect adaptive optics system with a closed-loop bandwidth of 1-2 Hz could correct these aberrations well enough to achieve diffraction-limited imaging over a dilated pupil.
众所周知，眼睛的光学系统表现出时间上的不稳定性，其形式为焦点的微波动；然而，对于眼睛其他像差的时间特性却几乎一无所知。我们构建了一个实时哈特曼-夏克（HS）波前传感器，以测量高达60 Hz频率下的这些动态变化。为了减少短曝光HS图像中的空间不均匀性，我们使用了低相干光源和扫描系统。在三名正常受试者自然调节和麻痹调节的情况下收集HS图像。计算了波前均方根值、赛德尔像差以及32个泽尼克系数各自的平均时间功率谱。结果表明，眼睛的所有像差中都存在波动，而不仅仅是散焦。高阶像差的波动在受试者内部和之间具有相似的频谱和带宽，在时间频率上以大约每倍频程4 dB的速率下降。高阶像差的频谱形状通常与调节微波动的频谱形状不同。这些测量到的波动的起源尚不清楚，角膜/晶状体和视网膜方面的原因都在考虑之中。假设它们纯粹是角膜或晶状体引起的，计算表明，一个闭环带宽为1 - 2 Hz的完美自适应光学系统能够很好地校正这些像差，从而在散瞳情况下实现衍射极限成像。
