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Precise polarisation imaging requires two key aspects – imaging resolution and vector information correctness. Errors in the state of polarisation (SOP) can disrupt these two aspects hence leading to imperfect interference at the focus, and incorrect vector states in the illumination or detection. Those issues will therefore lead to detrimental problems for high resolution polarisation sensitive optical systems, such as Stokes/Mueller confocal microscopes. The SOP errors can be introduced in different ways, which include pre-measurement processes, such as denoising, optimisation, and calibration, which are built on matrix calculation processes which would introduce an error amplification; or, other errors sources in optical systems such as focusing through stressed optical elements, due to Fresnel’s effects, or induced via polarising effects in materials or biological tissues
Here we put forward two techniques to deal with those errors, including next generation polarimetry and next generation adaptive optics techniques. We first show a new polarimetry method that has the ability to map all polarisation analyser states into a single vectorially structured light field, hence all vector components are analysed in a single-shot. We extract the vectorial state through inference from a physical model of the resulting image, providing a single-step sensing procedure. These methods in effect circumvent these method-related error amplification, accumulation and complex preprocessing steps. We then show a new adaptive optics technology that can correct both phase and polarisation aberrations within the optical systems. We validate improvements in both vector field state and the focal quality of an optical system, through correction for commonplace vectorial aberration sources.
Surrey Satellite Technology Ltd. (SSTL) has already demonstrated low-cost 1m GSD imagery from the Carbonite-2 platform, but the deployable telescope solution presented here provides the opportunity to build on this capability by significantly improving revisit time, without the typical increase in cost.
SSTL is developing, alongside the Surrey Space Centre (SSC) and the Dynamic Optics and Photonics Group at the University of Oxford, a telescopic deployable structure and a fine alignment system to align the Cassegrain-type telescope in-orbit. The three-concentric barrel deployable structure and mechanisms are discussed including the associated requirements and trade-off study that led to this design.
The dynamic nature of this system exacerbates traditional optical challenges such as alignment and stray light control; solutions to these are proposed, the optical design rationale is explained and predicted imaging performance shown. The novel autonomous fine alignment system, both algorithms and mechanisms, is presented. The last section deals with the spacecraft level implications and accommodation. Then finally the constellation level system design is shown with regards to the launch vehicle options and orbit configuration for coverage optimization; both global and target-specific.
Towards an efficient spin-photon interface with near-deterministically engineered defects in diamond
Aberrations can be suppressed by implementing sensorless adaptive optics techniques, whereby aberration correction is achieved by maximising a certain image quality metric. In confocal microscopy for example, one can employ the total image brightness as an image quality metric. Aberration correction is subsequently achieved by iteratively changing the settings of a wavefront corrector device until the metric is maximised. This simplistic approach has limited applicability to isoSTED microscopy where, due to the complex interplay between the excitation and depletion foci, maximising the total image brightness can lead to introducing aberrations in the depletion foci. In this work we first consider the effects that different aberration modes have on isoSTED microscopes. We then propose an iterative, wavelet-based aberration correction algorithm and evaluate its benefits.
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