An ocular wavefront sensor based on binary phase element: design and analysis

A modal wavefront sensor for ocular aberrations exhibits two main advantages compared to a conventional Shack-Hartmann sensor. As the wavefront is detected in the Fourier plane, the method is robust against local loss of information (e.g. local opacity of ocular lens as in the case of cataract), and is not dependent on the spatial distribution of wavefront sampling. We have proposed a novel method of wavefront sensing for ocular aberrations that directly detects the strengths of Zernike aberrations. A multiplexed Fourier computer-generated hologram has been designed as the binary phase element (BPE) for the detection of second-order and higher-order ocular aberrations (HOAs). The BPE design has been validated by comparing the simulated far-field pattern with the experimental results obtained by displaying it on a spatial light modulator. Simulation results have demonstrated the simultaneous wavefront detection with an accuracy better that similar to lambda/30 for a measurement range of +/- 2.1 lambda with reduced cross-talk. Sensor performance is validated by performing a numerical experiment using the City data set for test waves containing second-order and HOAs and measurement errors of 0.065 mu m peak-to-valley (PV) and 0.08 mm (PV) have been obtained, respectively.