Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userINGOT Wavefront Sensor: from the optical design to a preliminary laboratory test
115
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The Ingot wavefront sensor is a novel pupil-plane wavefront sensor, specifically designed to cope with the elongation typical of the extended nature of the Laser Guide Star (LGS). In the framework of the ELT, we propose an optical solution suitable for a Laser launch telescope, located outside the telescope pupil. In this paper, we present the current optical design, based on a reflective roof-shaped prism, which, at the level of the focal plane, splits the light from an LGS producing three beams. The three images of the telescope pupils can be then used for the retrieval of the first derivative of the wavefront. The 3D nature of such a device requires new alignment techniques to be determined theoretically and verified in the real world. A possible fully automated procedure, relying solely on the illumination observed at the three pupils, to align the prism to the image of the LGS is discussed. Careful attention needs to be put both on the telecentricity of the system and on the reference systems of the Ingot adjustments in the 3D space. This is crucial in order to disentangle all the possible misalignment effects. In this context, we devised a test-bench able to reproduce, in a scaled manner, the 3D illumination that the Ingot will face at the ELT, in order to validate the design and to perform preliminary tests of phase retrieval.
rate research
Read More
The ingot wavefront sensor (I-WFS) has been proposed, for ELT-like apertures, as a possible pupil plane WFS, to cope with the geometrical characteristics of a laser guide star (LGS). Within the study and development of such a WFS, on-going in the framework of the MAORY project, the final purpose of the I-WFS simulation is to estimate its performance in terms of wavefront aberration measurement capability. The first step of this analysis is to translate incoming wavefronts into the three pupil images, produced by the optical system. The intrinsic geometrical characteristics of the ingot optical element, designed to be coupled with the LGS elongated image, make the system conceptually different with respect to other pupil WFSs (like the Pyramid WFS, P-WFS) also in terms of the simulation technique to be selected, within the ones which can be found in literature. In this paper, we aim to report the considerations and derivations which led to the selection of a ray-tracing method for ingot pupil images simulation, and the geometrical assumptions and approach made to optimize the computing time.
Adaptive optics systems correct atmospheric turbulence in real time. Most adaptive optics systems used routinely correct in the near infrared, at wavelengths greater than 1 micron. MagAO- X is a new extreme adaptive optics (ExAO) instrument that will offer corrections at visible-to- near-IR wavelengths. MagAO-X will achieve Strehl ratios greater than 70% at H-alpha when running the 2040 actuator deformable mirror at 3.6 kHz. A visible pyramid wavefront sensor (PWFS) optimized for sensing at 600-1000 nm wavelengths will provide the high-order wavefront sensing on MagAO- X. We present the optical design and predicted performance of the MagAO-X pyramid wavefront sensor.
We revisit one class of z-invariant WaveFront sensor where the LGS is fired aside of the telescope aperture. In this way there is a spatial dependence on the focal plane with respect to the height where the resonant scattering occurs. We revise the basic parameters involving the geometry and we propose various merit functions to define how much improvement can be attained by a z-invariant approach. We show that refractive approaches are not viable and we discuss several solutions involving reflective ones in what has been nicknamed ingot wavefront sensor discussing the degrees of freedom required to keep tracking and the basic recipe for the optical design.
Wavefront sensing and control are important for enabling one of the key advantages of using large apertures, namely higher angular resolutions. Pyramid wavefront sensors are becoming commonplace in new instrument designs owing to their superior sensitivity. However, one remaining roadblock to their widespread use is the fabrication of the pyramidal optic. This complex optic is challenging to fabricate due to the pyramid tip, where four planes need to intersect in a single point. Thus far, only a handful of these have been produced due to the low yields and long lead times. To address this, we present an alternative implementation of the pyramid wavefront sensor that relies on two roof prisms instead. Such prisms are easy and inexpensive to source. We demonstrate the successful operation of the roof prism pyramid wavefront sensor on a 8-m class telescope, at visible and near infrared wavelengths ---for the first time using a SAPHIRA HgCdTe detector without modulation for a laboratory demonstration---, and elucidate how this sensor can be used more widely on wavefront control test benches and instruments.
Extremely Large Telescopes have overwhelmingly opted for the Pyramid wavefront sensor (PyWFS) over the more widely used Shack-Hartmann WaveFront Sensor (SHWFS) to perform their Single Conjugate Adaptive Optics (SCAO) mode. The PyWFS, a sensor based on Fourier filtering, has proven to be highly successful in many astronomy applications. However, it exhibits non-linearity behaviors that lead to a reduction of its sensitivity when working with non-zero residual wavefronts. This so-called Optical Gains (OG) effect, degrades the close loop performance of SCAO systems and prevents accurate correction of Non-Common Path Aberrations (NCPA). In this paper, we aim at computing the OG using a fast and agile strategy in order to control the PyWFS measurements in adaptive optics closed loop systems. Using a novel theoretical description of the PyFWS, which is based on a convolutional model, we are able to analytically predict the behavior of the PyWFS in closed-loop operation. This model enables us to explore the impact of residual wavefront error on particular aspects such as sensitivity and associated OG. The proposed method relies on the knowledge of the residual wavefront statistics and enables automatic estimation of the current OG. End-to-End numerical simulations are used to validate our predictions and test the relevance of our approach. We demonstrate, using on non-invasive strategy, that our method provides an accurate estimation of the OG. The model itself only requires AO telemetry data to derive statistical information on atmospheric turbulence. Furthermore, we show that by only using an estimation of the current Fried parameter r_0 and the basic system-level characteristics, OGs can be estimated with an accuracy of less than 10%. Finally, we highlight the importance of OG estimation in the case of NCPA compensation. The proposed method is applied to the PyWFS.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
