Focusing scattered light using wavefront shaping provides interesting perspectives to image deep in opaque samples, as e.g. in nonlinear fluorescence microscopy. Applying these technics to in vivo imaging remains challenging due to the short decorrelation time of the speckle in depth, as focusing and imaging has to be achieved within the order of the decorrelation time. In this paper, we experimentally study the focus lifetime after focusing through dynamical scattering media, when iterative wavefront optimization and speckle decorrelation occur over the same timescale. We show experimental situations with heterogeneous stability of the scattering sequences, where the focus presents significantly higher stability than the surrounding speckle.

The extremely low surface brightness sensitivity required to observe the ultra-low-surface brightness universe lead us to propose MESSIER, a space mission designed to drift-scan the entire sky in 6 filters covering the 200-1000 nm range and reaching unprecedented surface brightness levels of 34 and 37 mag arcsec 2 in the optical and UV, respectively. Here, we present the ground-based MESSIER pathfinder aimed at testing several breakthrough technologies involved (e.g. curved detectors) and carrying out observations. We present here a detailed analysis of the optical quality achievable through photon Monte Carlo simulations of the system, including atmospheric effects.

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In the present paper, we discuss the design of a projection system with curved display and its enhancement by variably adjusting the curvature. We demonstrate that the focal surface curvature varies significantly with a change of the object position and that it can easily be computed with the Seidel aberration theory. Using this analytically derived curvature value as the starting point, we optimise a refocusable projection system with 90 • field of view and F/# = 6.2. It is demonstrated that such a system can provide stable image quality and illumination when refocusing from infinity to 1.5 m. The gain in spatial resolution is as high as 1.54 times with respect to a flat focal surface. Furthermore, we prove that a silicon die can be curved to the required shape with a safety factor of 4.3 in terms of the mechanical stress. Finally, it is shown that the developed system can be used in a virtual reality headset providing high resolution, low distortion and a flexible focusing mode.

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