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…simplifies and accelerates the wavefront-sensing process NASA Goddard Space Flight Center invites companies to license this new optical design that simplifies and accelerates the data collection process for focus-diverse wavefront sensing (WFS). Accurate image-based WFS requires collecting multiple defocused point source images, which currently requires careful measurement with direct human intervention for calibration at each defocus value. This innovative technology simplifies that process by using a fixed-lens technique, resulting in a simpler, faster, and more cost-effective method for introducing defocus diversity for image-based WFS. See also, supplemental technology "Hybrid Diversity Algorithm for Image-based Wavefront Sensing" (GSC-14879-1)
This technology offers an alternative to interferometry for the purpose of optical system performance testing in addition to wavefront sensing and control applications required by adaptive and active optical systems. It can also function as an optical subsystem to a phase-retrieval camera. Specific applicable areas include:
Phase retrieval (PR) is a general term used in optics to describe the estimation of optical imperfections or aberrations from the image of a point source object such as a star or a laboratory point source such as a pinhole. It is image-based in the sense that data is collected by a science camera or other charge coupled device. Image-based WFS refers to a general class of algorithms that recover optical phase information, and PR algorithms constitute a subset of this general class. Focus-diverse PR requires defocused images of a point source as input to the WFS algorithm. Conventional focus-diverse PR collects data via the linear motion of the imaging camera from its nominal focus position. Because accurate image-based WFS requires the collection of multiple diversity defocus images, careful measurements must be taken of all intermediate camera positions. This procedure is difficult to implement without direct human intervention since calibration of the images is required for each defocus value. Additional latency is also introduced as the camera is translated to various defocus positions. How it works
The optical design implementation is based on the insertion of weak lenses into a converging beam path. Using low power optics (i.e., the focal lengths are large), significant defocus can be realized with negligible variation in focal ratio and minimal perturbation of the wavefront. Why it is better This innovative design eliminates the need for translation of the camera as well as additional manual calibration, which simplifies and accelerates the WFS process. The filter wheel/lens mechanism uses readily available commercial catalog components, making it cost effective to build. The rotation of the wheel can also be automated with a motor drive without requiring further calibration. Additionally, the optical hardware can be used on a variety of optical systems without requiring redesign by varying the defocus magnitude with filter wheel stage positions.
This technology is part of NASA's Innovative Partnerships Program, which seeks to transfer technology into and out of NASA to benefit the space program and U.S. industry. NASA invites companies to consider licensing this Fixed Lens Wavefront Sensing Design (GSC-14901-1) for commercial applications. For information and forms related to the technology licensing and partnering process, please visit the Licensing and Partnering page. (link opens a new browser window) If you are interested in more information or want to pursue transfer of this technology, please contact: Innovative Partnerships Program Office
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This innovation is unique in that no motion of the imaging camera is required to generate a known diversity defocus. This optical design introduces diversity defocus into the optical beam path using a fixed-lens WFS technique. The linear motion traditionally required by the imaging camera is replaced by the insertion of individual lenses (corresponding to specific defocus values) into the converging beam path using the rotational motion of a filter wheel. The filter wheel positions are occupied with the diversity defocus lenses—one for each defocus position.
