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This Letter introduces a technique for performing binary adaptive optics, which is carried out by optical components only, without the help of any electronic or optoelectronic device. In this technique, the interferogram produced by a point diffraction interferometer modulates a light-driven crystal. The modulated light-driven crystal may produce pupil-plane only-phase or only-amplitude binary masks to mitigate phase aberrations. The capability of working unsupported makes it suitable for application in hard-to-reach or hazardous locations such as satellites, underwater, or contaminated places. The Letter includes an experimental validation where the ability of the technique to produce pupil amplitude masking is confirmed.

HARMONI is the adaptive optics assisted, near-infrared and visible light integral field spectrograph for the Extremely Large Telescope (ELT). A first light instrument, it provides the work-horse spectroscopic capability for the ELT. As the project approaches its Final Design Review milestone, the design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument's capabilities from a user perspective, provide a summary of the instrument's design, including plans for operations and calibrations, and provide a brief glimpse of the predicted performance for a specific observing scenario. The paper also provides some details of the consortium composition and its evolution since the project commenced in 2015.

We present a new Point Diffraction Interferometer (PDI). Binary adaptive optics (BAO) and Quaternary Adaptive Optics (QAO) can be performed with the help of this PDI as a wavefront sensor. The PDI interferogram, once binarized, is used in two consecutive steps to produce a quaternary mask with phase values 0, π/2, π and 3π/2. The addition of the quaternary mask compensates for the aberrated wavefront and allows us to reach a Strehl ratio of about 0.81. We have verified through computer simulations that the use of QAO depends on the number of actuators of the compensating device to achieve effective compensation. The technique was successfully validated through an experiment. Ministerio de Economía y Competitividad (MINECO) (AYA2016-78773-C2-1-P).

The detection of faint stellar companions requires high contrast techniques such as coronagraphy. To achieve such high contrast coronagraphs must work with the aid of adaptive optics or be mounted on space telescopes. We propose a new coronagraphic technique that consists of the digital processing of non-coronagraphic images. The only requirement is a priori knowledge of the telescope amplitude point spread function. This digital coronagraph algorithm presents the advantage that it avoids problems associated with manufacture, implementation, and alignment of optical coronagraphs. The digital coronagraph algorithm is successfully checked with laboratory generated images. Moreover, numerical simulations show that the digital coronagraph presents contrast curves similar to that of the optical coronagraph. Finally, speckle noise can be cancelled out as effectively as in optical coronagraphs.

Trabajo presentado en SPIE Astronomical Telescopes, celebrado en San Diego (California), del 26 de junio al 1 de julio de 2016, HARMONI is the E-ELT's first light visible and near-infrared integral field spectrograph. It will provide four different spatial scales, ranging from coarse spaxels of 60 × 30 mas best suited for seeing limited observations, to 4 mas spaxels that Nyquist sample the diffraction limited point spread function of the E-ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers (R 3500, 7500 and 20000) and instantaneous wavelength coverage spanning the 0.5 - 2.4 ¿m wavelength range of the instrument. In autumn 2015, the HARMONI project started the Preliminary Design Phase, following signature of the contract to design, build, test and commission the instrument, signed between the European Southern Observatory and the UK Science and Technology Facilities Council. Crucially, the contract also includes the preliminary design of the HARMONI Laser Tomographic Adaptive Optics system. The instrument's technical specifications were finalized in the period leading up to contract signature. In this paper, we report on the first activity carried out during preliminary design, defining the baseline architecture for the system, and the trade-off studies leading up to the choice of baseline.

A new technique for high resolution wavefront sensing has been introduced. It is based on the Optical Differentiation wavefront sensor, however its application has required the development of a diffractive element that provides four or five copies of the original wavefront. It some aspect the result is similar to that provide by the Pyramid sensor although from a theoretical point of view is more close to the Modified Hartmann sensor. Here we introduce the theoretical background and principles along with an example of phase derivative estimate based on a computer simulation. The technique looks very promising since it is simple, with high resolution, without moving parts and allows us an easy post processing to recover Zernike coefficients. Nevertheless, a lot of work has to be completed to a proper evaluation of its actual capabilities, noise, resolution, etc.

In this paper we show new ways to improve the performance of ground-based coronagraphy. We introduce adaptive coronagraphic masks whose profile is a binary version of the instantaneous atmospherically degraded star image. We also propose the hyper-Gaussian profile masks obtained by averaging adaptive masks. In addition, adaptive Lyot stops and hyper-Gaussian Lyot stops are analyzed. Computer simulations show that all these masks outperform the circular hard-edged mask and that a proper mask and stop combination significantly reduces the angular separation at which a faint companion can be detected.

In this paper we introduce a simple diffractive optics technique to improve images distorted by propagating through an inhomogeneous medium. Diffractive elements are used to generate a series of slightly displaced overlapping replicas of the incoming wavefront which produces a local averaging of the field. We propose two different configurations depending on whether the field aberration is produced before or after (or in the pass through) the focussing or imaging optics. Furthermore, the aberration correction is achieved without the need of prior wavefront sensing or complex active compensating elements in contrast to adaptive optics (AO) and holographic techniques. Both numerical simulations and laboratory experiments show that the different kinds of proposed diffractive masks (DMs) (amplitude and phase) work efficiently in the two configurations. Since this technique is particularly suitable for compensating the highest spatial frequencies it seems to be appropriate to be combined with AO systems.

We introduce the use of Super-Gaussian apodizing functions in the telescope pupil plane and/or the coronagraph Lyot plane to improve the imaging contrast in ground-based coronagraphs. We describe the properties of the Super-Gaussian function, we estimate its second-order moment in the pupil and Fourier planes and we check it as an apodizing function. We then use Super-Gaussian function to apodize the telescope pupil, the coronagraph Lyot plane or both of them. The result is that a proper apodizing masks combination can reduce the exoplanet detection distance up to a 45% with respect to the classic Lyot coronagraph, for moderately aberrated wavefronts. Compared to the prolate spheroidal function the Super-Gaussian apodizing function allows the planet light up to 3 times brighter. An extra help to increase the extinction rate is to perform a frame selection (Lucky Imaging technique). We show that a selection of the 10% best frames will reduce up to a 20% the detection angular distance when using the classic Lyot coronagraph but that the reduction is only around the 5% when using an apodized coronagraph.