Shaping the PSF to nearly top-hat profile: CHEOPS laboratory results

Magrin, Demetrio; Farinato, Jacopo; Umbriaco, Gabriele; Kumar Radhakrishnan Santhakumari, Kalyan; Bergomi, Maria; Dima, Marco; Greggio, Davide; Marafatto, Luca; Ragazzoni, Roberto; Viotto, Valentina; Munari, Matteo; Pagano, Isabella; Scandariato, Gaetano; Scuderi, Salvatore; Piotto, Giampaolo; Beck, Thomas; Benz, Willy; Broeg, Christopher; Cessa, Virginie; Fortier, Andrea; ... (2 August 2014). Shaping the PSF to nearly top-hat profile: CHEOPS laboratory results. In: Oschmann, Jacobus M.; Clampin, Mark; Fazio, Giovanni G.; MacEwen, Howard A. (eds.) Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave. Montréal, Quebec, Canada. 10.1117/12.2055858

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Spreading the PSF over a quite large amount of pixels is an increasingly used observing technique in order to reach extremely precise photometry, such as in the case of exoplanets searching and characterization via transits observations. A PSF top-hat profile helps to minimize the errors contribution due to the uncertainty on the knowledge of the detector flat field. This work has been carried out during the recent design study in the framework of the ESA small mission CHEOPS. Because of lack of perfect flat-fielding information, in the CHEOPS optics it is required to spread the light of a source into a well defined angular area, in a manner as uniform as possible. Furthermore this should be accomplished still retaining the features of a true focal plane onto the detector. In this way, for instance, the angular displacement on the focal plane is fully retained and in case of several stars in a field these look as separated as their distance is larger than the spreading size. An obvious way is to apply a defocus, while the presence of an intermediate pupil plane in the Back End Optics makes attractive to introduce here an optical device that is able to spread the light in a well defined manner, still retaining the direction of the chief ray hitting it. This can be accomplished through an holographic diffuser or through a lenslet array. Both techniques implement the concept of segmenting the pupil into several sub-zones where light is spread to a well defined angle. We present experimental results on how to deliver such PSF profile by mean of holographic diffuser and lenslet array. Both the devices are located in an intermediate pupil plane of a properly scaled laboratory setup mimicking the CHEOPS optical design configuration. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Item Type:

Conference or Workshop Item (Paper)


08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences > Theoretical Astrophysics and Planetary Science (TAPS)
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
10 Strategic Research Centers > Center for Space and Habitability (CSH)

UniBE Contributor:

Beck, Thomas, Benz, Willy, Broeg, Christopher, Cessa, Virginie, Fortier, A., Piazza, Daniele


500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 620 Engineering


Proc. SPIE




Cléa Serpollier

Date Deposited:

21 Aug 2015 14:27

Last Modified:

05 Dec 2022 14:49

Publisher DOI:



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