Free-space optical communication systems always require a precise focusing on the receiver to maximize the fiber coupling efficiency. Unfortunately, atmospheric turbulence causes scintillation at the receiver. Ground to ground receivers over short distances (up to 500m) have usually small aperture (about 50mm). In this case the main aberration is tip/tilt and its correction is of fundamental importance for high bandwidth data transmission. We present a new concept of Fast Steering Prism (FSP) for the correction of tilt, suitable for optical communication and optical tracking. The system consists in the use of a novel design of a tunable prism with a variable angle based on the usage of piezoelectric actuators. A system with a FSP has the advantage to be more compact and simpler with respect to the one with a fast-steering mirror. The entire setup has been tested in a 200m outdoor transmission with promising results.
Free-space optical communication systems always require a precise focusing on the receiver to maximize the fiber coupling efficiency. Unfortunately, atmospheric turbulence causes scintillation at the receiver. Ground to ground receivers over short distances (up to 500m) have usually small aperture (about 50mm). In this case the main aberration is tip/tilt and its correction is of fundamental importance for high bandwidth data transmission.
We present a new concept of Fast Steering Prism (FSP) for the correction of tilt, suitable for optical communication and optical tracking. The system consists in the use of a novel design of a tunable prism with a variable angle based on the usage of piezoelectric actuators. A system with a FSP has the advantage to be more compact and simpler with respect to the one with a fast-steering mirror. The entire setup has been tested in a 200m outdoor transmission with promising results.
SHARK-NIR is a high-contrast camera for the LBT, it has been conceived and designed to fully exploit the high Strehl ratio adaptive optics correction delivered by the FLAO module, which is being upgraded to SOUL, and will implement different coronagraphic techniques, with contrast as high as 10-6 down to 5 mas from the star. To maximize the achievable contrast, SHARK-NIR implements a couple of peculiar features, namely a fast internal TT loop to minimize the residual jitter and a local non-common path aberration correction, applied through an internal deformable mirror. To derive instrumental aberrations, one option is to use the phase diversity technique, which allows wavefront sensing by using two images in intrafocus and extrafocus positions. To calibrate this sensor, we initially assembled a dedicated optical bench equipped with a deformable mirror and a fast IR camera. To characterize phase diversity under more general conditions and independently from the SHARK-NIR setup, we focused then on a new simple test bench, implementing a new (multi-actuator) deformable lens able to reproduce low order aberrations up to 4th order of Zernike polynomials, as an aberration generator. The optical design is simpler and cheaper than using a deformable mirror, which requires a folded optical path and more optics. In this case we used an interferometer to characterize the linearity of the aberration generator and the phase diversity is used for sensing non-common path aberrations (NCPA) in SHARK-NIR.
Although adaptive optics (AO) systems have been developed to compensate for atmospheric turbulence, their application is mostly limited to large size (1.5 to 8 m) telescopes due to high cost and complexity. In particular, for small to medium aperture telescopes for which the need for AO correction is critical, AO systems have different requirements such as compactness and transportability. We report on the realization and the on-sky test of an extremely small adaptive optics module (XSAO) based on a multiactuator adaptive lens. Observations were performed on an 11-in. commercial telescope and a 1-m scientific telescope with minimal modifications. The results show a strong improvement of the acquired images for different types of observed objects, such as bright stars, double stars, planets, and deep sky objects.
Optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) are two state-of-the-art imaging technologies commonly used to study retina. Adaptive Optics (AO) methodologies enable high-fidelity correction of ocular aberrations, resulting in improved resolution and sensitivity for both SLO and OCT systems. Here we present work integrating OCT into a previously described mouse retinal AO-SLO system, allowing simultaneous reflectance and fluorescence imaging. The new system allows simultaneous data acquisition of AO-SLO and AO-OCT, facilitating registration and comparison of data from both modalities. The system has data acquisition speed of 200 kHz A-scans/pixel, and high volumetric resolution.
Adaptive Optics (AO) is a key technology for ground-based astronomical telescopes, allowing to overcome the limits imposed by atmospheric turbulence and obtain high resolution images. This technique however, has not been developed for small size telescopes, because of its high cost and complexity. We realized an AO system based on a Multi-actuator Adaptive Lens and a Shack-Hartmann wavefront sensor (WFS), allowing for a great compactness and simplification of the optical design. The system was integrated on a 11” telescope and controlled by a consumer-grade laptop allowing to perform Closed-Loop AO correction up to 400 Hz.
Adaptive Optics (AO) is a key technology for ground-based astronomical telescopes, allowing to overcome the limits imposed by atmospheric turbulence and obtain high resolution images. This technique however, has not been developed for small size telescopes, because of its high cost and complexity. We realized an AO system based on a Multi-actuator Adaptive Lens and a Shack-Hartmann wavefront sensor (WFS), allowing for a great compactness and simplification of the optical design. The system was integrated on a 11” telescope and controlled by a consumer-grade laptop allowing to perform Closed-Loop AO correction up to 400 Hz.
The use of adaptive lenses instead of deformable mirrors can simplify the implementation of an adaptive optics system. The recently introduced Multi-actuator Adaptive Lens (MAL) can be used in closed loop with a wavefront sensor to correct for time-variant wavefront aberrations. The MAL can guarantee a level of correction and a response time similar to the ones obtained with deformable mirrors. The adaptive lens is based on the use of piezoelectric actuators and, without any obstruction or electrodes in the clear aperture, can guarantee a fast response time, less than ~10ms. Our tests show that the MAL can be used both in combination with a wavefront sensor in a “classical” adaptive optics closed loop, or in a wavefront sensorless configuration. The latter has allowed us to design more compact and simple imaging systems for different microscopy platforms. We will show that the Multi-actuator Adaptive Lens has been successfully used for in-vivo OCT ophthalmic imaging in both mice and humans, as well as confocal and two photon microscopy. We tested and compared different optimization strategies such as coordinate search and the DONE algorithm. The results suggest that the MAL optimization can correct for eye aberrations with a pupil of 5mm or sample induced aberrations in microscopy.
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