The crosstalk effect considerably limits the capability of holography-based modal wavefront sensing (HMWS) when measuring wavefronts with large aberrations. In this contribution, we introduce a curvature-based measurement technique into HMWS to extend the dynamic range and the sensitivity of HMWS via a compact holographic design. If the input aberrations are large, the dominating aberration modes are first detected via curvature sensing and compensated using a wavefront correcting device, e.g. a membrane mirror. The system then switches to HMWS to obtain better sensitivity and accuracy with reduced aberrations. Different approaches for the reconstruction of the wavefront have been tested and extensive simulations for different aberrations have been analyzed.
The linearity and accuracy of holography-based modal wavefront sensing (HMWS) is reduced when large aberrations
are present in the incoming wavefront. In this contribution, a combination of HMWS and a low-resolution Shack-
Hartmann sensor (LRSHS) is introduced to extend the dynamic range of HMWS via a compact holographic design. The
typically dominating low-order modes in the incoming wavefront are first corrected by the LRSHS. The system then
switches to HMWS after one or two corrections to obtain better sensor sensitivity and accuracy. First experimental
results are shown for validating the method.
The crosstalk problem inherent in holography based modal wavefront sensing (HMWS) becomes more severe with
increasing aberrations of the incident beam. In this paper, the cause of crosstalk is theoretically revealed and then
demonstrated using simulations. For extending the use of HMWS in correcting atmospheric turbulence introduced
aberration, the sensor response is statistically analyzed with random aberrations created in accordance with the
atmosphere turbulence model. The system parameters are optimized considering the turbulence strength and calibrated
response curves are further used to improve the sensor performance. The simulation and first preliminary experimental
results are shown for validating the method.
As a crucial part of active three dimensional(3D) vision system based on fringe projection technique, correspondence
search between two adjacent range images would directly influence on the accuracy of matching and fusion procedure of
the depth data. The conventional sub-pixel matching method by means of phase correlation can achieve a high level of
accuracy while it would also be associated with a time consuming procedure due to the requirement of capturing two
orthogonal series of sinusoidal fringes. Another technique utilizing linear interpolation algorithm based on the fringe
projection with single direction might cause accuracy declination as a result of the simplification in imaging model. A
novel method under the framework of linear interpolation was proposed. This approach makes use of absolute phase
values and parameters of epipolar line as two kinds of feature points for correspondence search, leading to a significant
improvement on the measurement accuracy of the depth data. Theoretical analysis and experiment results demonstrate
the validity of presented approach.
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