Direct phase measurement in zonal wavefront reconstruction using multidither coherent optical adaptive technique

Abstract

In traditional zonal wavefront sensing for adaptive optics, after local wavefront gradients are obtained, the entire wavefront can be calculated by assuming that the wavefront is a continuous surface. Such an approach will lead to sub-optimal performance in reconstructing wavefronts which are either discontinuous or undersampled by the zonal wavefront sensor. Here, we report a new method to reconstruct the wavefront by directly measuring local wavefront phases in parallel using multidither coherent optical adaptive technique. This method determines the relative phases of each pupil segment independently, and thus produces an accurate wavefront for even discontinuous wavefronts. We implemented this method in an adaptive optical two-photon fluorescence microscopy and demonstrated its superior performance in correcting large or discontinuous aberrations.

Multiplexed aberration measurement for deep tissue imaging in vivo

“…2 ), with an overall signal integration time of 2× N R × T . Followed by either phase reconstruction algorithms or phase measurement methods 4 , we then obtain the corrective wavefront. Depending on the sample, N R varies between 100 and 256 (10×10 to 16×16 2D grid), and T varies between 45 and 360 ms (and can be smaller if higher signal level is used).…”

“…Repeating the procedure for all light rays ( Fig. 1a ), we get the local wavefront gradients, from which the entire corrective wavefront can be obtained and applied to the SLM for aberration correction 3 , 4 . This method, however, is slow: the interference between rays at a small pupil segment and the rest leads to only small signal variations (~1–2% for edge segments in Fig.…”

Multi-plane Imaging of Neural Activity From the Mammalian Brain Using a Fast-switching Liquid Crystal Spatial Light Modulator

“…However, we anticipate a decrease of the acceptable axial range of the point spread function (PSF) degradation when using a higher effective NA. Therefore, to maintain the optical performance of the system over an extended axial range in this scenario, adaptive optics procedures have to be employed to correct for those defocus induced aberrations [29,30]. By replacing lens L3 with one of different focal lengths, the overall beam expansion ratio from the SLM to the back focal plane of the objective can be adjusted to achieve different effective excitation NAs.…”

Multidither coherent optical adaptive technique for deep tissue two-photon microscopy

“…Liu et al have pointed out that this overlap is avoidable by certain speci¯c frequency choosing method under single-photon condition. 36 However, when it comes to two-photon circumstance, the overlap can hardly be eliminated completely by conventional frequency choosing method, which is e®ective under singlephoton condition.…”