Large dynamic range autorefraction with a low-cost diffuser wavefront sensor

Abstract

Wavefront sensing with a thin diffuser has emerged as a potential low-cost alternative to a lenslet array for aberrometry. Diffuser wavefront sensors (DWS) have previously relied on tracking speckle displacement and consequently require coherent illumination. Here we show that displacement of caustic patterns can be tracked for estimating wavefront gradient, enabling the use of incoherent light sources and large dynamic-range wavefront measurements. We compare the precision of a DWS to a Shack-Hartmann wavefront sensor (SHWS) when using coherent, partially coherent, and incoherent illumination, in the application of autorefraction. We induce spherical and cylindrical errors in a model eye and use a multi-level Demon's non-rigid registration algorithm to estimate caustic displacements relative to an emmetropic model eye. When compared to spherical error measurements with the SHWS using partially coherent illumination, the DWS demonstrates a ∼5-fold improvement in dynamic range (-4.0 to +4.5 D vs. -22.0 to +19.5 D) with less than half the reduction in resolution (0.072 vs. 0.116 D), enabling a ∼3-fold increase in the number of resolvable prescriptions (118 vs. 358). In addition to being 40x lower-cost, the unique, non-periodic nature of the caustic pattern formed by a diffuser enables a larger dynamic range of aberration measurements compared to a lenslet array....

Quantitative Phase and Intensity Microscopy Using Snapshot White Light Wavefront Sensing

“…Our method only requires minor modifications to a conventional microscope and works under white light illumination. Wavefront sensing using speckle tracking technique was first proposed in X-ray phase imaging 32,35–38 , and then for optical wavefront retrieval 34,39 , adaptive optics 40 , and trial lens metrology 41 . Simultaneous reconstruction for absorption, phase, and dark field images from one single speckle-pattern measurement image have also been shown 42–44 .…”

Modeling classical wavefront sensors

“…For slope tracking sensors, due to mm level distance z, wavefront resolution is fundamentally limited as in Fig. 3, and hence we suggest classical slope tracking sensors be applicable to large-scale smooth aberrations, e.g., large-scale adaptive optics [42] and autorefraction metrology [43]. If higher resolution is desired, possible workarounds are scanning optics [44,45] for ptychography, combining spatial light modulators for computational sensing [46] beyond simple optics, or using numerical propagation based inversion [47,48].…”

Advanced Optical Wavefront Technologies to Improve Patient Quality of Vision and Meet Clinical Requests

“…A weak diffuser at distinct angles of illumination has been adopted by Gunjala et al to reconstruct the aberration profiles from multiple images by a statistical approach [ 65 ]. Recently, McKay et al have developed a diffuser wavefront sensor (DWFS) for ocular aberrometry with a larger dynamic range with respect to a Shack–Hartmann wavefront sensor (SHWFS) for wavefront measurements [ 24 ] ( Figure 7 ).…”