A simple new way of obtaining absolute wavefront measurements with a laboratory Fizeau interferometer was recently devised. In that case, the observed wavefront map is the difference of two cavity surfaces, those of the mirror under test and of an unknown reference surface on the Fizeau’s transmission flat. The absolute surface of each can be determined by applying standard wavefront reconstruction techniques to two grids of absolute surface height differences of the mirror under test, obtained from pairs of measurements made with slight transverse shifts in X and Y.
Adaptive optics systems typically provide an actuated periscope between wavefront sensor (WFS) and common-mode optics, used for lateral registration of deformable mirror (DM) to WFS. This periscope permits independent adjustment of either pupil or focal spot incident on the WFS. It would be used to give the required lateral pupil motion between common and non-common segments, analogous to the lateral shifts of the two phase contributions in the lab Fizeau.
The technique is based on a completely new approach to calibration of phase. It offers unusual flexibility with regard to the transverse spatial frequency scales probed, and will give results quite quickly, making use of no auxiliary equipment other than that built into the adaptive optics system. The new technique may be applied to provide novel calibration information about other optical systems in which the beam may be shifted transversely in a controlled way.
This work was done by Eric E. Bloemhof of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48060
This Brief includes a Technical Support Package (TSP).
Transverse Pupil Shifts for Adaptive Optics Non-Common Path Calibration
(reference NPO-48060) is currently available for download from the TSP library.
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Overview
The document titled "Transverse Pupil Shifts for Adaptive Optics Non-Common Path Calibration" is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL), detailing advancements in adaptive optics (AO) technology. It focuses on the calibration of non-common-path phases in AO systems, which are crucial for improving the performance of optical systems used in astronomical observations and other applications.
Adaptive optics systems are designed to correct distortions in the wavefront of light caused by atmospheric turbulence, allowing for clearer images of celestial objects. The document discusses the mechanisms involved in this process, particularly the use of a Fast Steering Mirror (FSM) and a Deformable Mirror (DM). The FSM corrects low-order tip/tilt errors, while the DM addresses higher-order phase distortions, enhancing the overall image quality.
A key feature of the technology described is the ability to separate two-dimensional phase maps into common and non-common paths. The common path refers to the light traveling from the star to the dichroic beam splitter, while the non-common paths involve the light traveling from the dichroic to the wavefront sensor and the science camera. This separation is essential for accurately calibrating the system and ensuring that the corrections applied by the AO system are effective.
The document also emphasizes the importance of calibrating non-common-path phases to achieve optimal performance in AO systems. By accurately measuring and compensating for these phases, researchers can significantly improve the quality of astronomical images, enabling more detailed observations of distant celestial bodies.
The Technical Support Package is part of NASA's Commercial Technology Program, aimed at disseminating aerospace-related developments with broader technological, scientific, or commercial applications. It serves as a resource for those interested in the latest advancements in adaptive optics and related fields.
For further inquiries or assistance, the document provides contact information for the Innovative Technology Assets Management team at JPL, encouraging collaboration and exploration of these innovative technologies. Overall, this document represents a significant contribution to the field of adaptive optics, highlighting the ongoing efforts to enhance imaging capabilities in astronomy and beyond.
