Cause of the non-zero ML-LLOWFS residual at zero aberration

Determine the cause of the non-zero ML-LLOWFS modal prediction observed when no aberration is applied to the deformable mirror, and establish whether detector noise is responsible for the residual.

Background

During the ML-LLOWFS linearity test, the convolutional-neural-network reconstructor produced a non-zero modal prediction even when no aberration was applied to the deformable mirror. The authors suggest that detector noise could account for this residual and indicate that its magnitude should decrease with increased source flux, but they do not establish the actual cause. Resolving this issue is relevant to the sensor’s accuracy near the zero-wavefront-error reference point.

References

The non-zero prediction in the reference, when no aberration was applied to the DM, could be due to detector noise and should decrease if the source flux is increased. We will investigate the cause of the non-zero residual at the zero point in future work.

— Addressing the low-wind effect with the Lyot-based low-order wavefront sensor on SCExAO  (2609.00737 - Singh et al., 1 Sep 2026) in Section 3, Results, paragraph discussing the ML-LLOWFS linearity test