Rolling shutter detector data flow strategies to push the limits of AO performance

Adaptive Optics (AO) improves the image quality of ground-based telescopes, by compensating in real-time for the blurring effects of atmospheric turbulence. AO systems of future Extremely Large Telescopes (ELTs) will have to operate at much bigger scales (in terms of degrees of freedom) and faster control rates (in terms of loop frequency) to realise their full potential. We have investigated and simulated an AO control methodology to stream pixels “as they come” using a rolling-shutter sCMOS camera to reconstruct 2D images. Compared to a traditional global shutter implementation, the initial results indicate the rolling shutter can reduce control loop latency by a factor of two to four, using existing hardware. This means we can detect twice the number of photons while sampling twice as slowly. Nevertheless, significant technical challenges remain in implementing the rolling functionality, especially when integrating off-the-shelf software and hardware, which is often constricted by a closed-source code base. Furthermore, as the rolling shutter readout is asynchronous, questions remain about coupling and aliasing of telescope vibrations into the imaging system, causing distortions of time and space. If successfully implemented in practice, the rolling shutter approach has the potential to allow astronomers and engineers to capture better scientific observations closer to the diffraction limit.