A new technique of characterization of the intrapixel response of astronomical detectors

Ketchazo, Christian; Viale, T.; Boulade, O.; Druart, Guillaume; Moreau, Vincent; Mugnier, Laurent M.; Dubreuil, Didier; Derelle, Sophie; Ronayette, S.; Guérineau, Nicolas

doi:10.1117/12.2055721

Cited by 3 publications

(8 citation statements)

References 15 publications

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“…Note, however, that the measured pixel response variations inside the pixel active area may not necessarily be silicon related, but could be due to microlens imperfections. In many of the prior studies ( [6], [7], [8], [9]), the IPS variation is extracted by the deconvolution method. We therefore compare our forward modeling method with the deconvolution method.…”

Section: Resultsmentioning

confidence: 99%

“…In [4], Bryson et al reported a study of the Kepler pixel response function. [6] presents a new Continuous Self-Imaging Grating (CSIG) technique to measure the IPS map of the CCD in the framework of Euclid mission. Most prior publications studied extensively the IPS variation profiles of front and back illuminated CCDs [7], [8], [9], [10], but so far, few studies have been done on CMOS image sensors [11].…”

Section: Introductionmentioning

confidence: 99%

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Measuring Intra-Pixel Sensitivity Variations of a CMOS Image Sensor

Mahato

Meynants²,

Raskin

et al. 2018

IEEE Sensors J.

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Some applications in scientific imaging, like spacebased high-precision photometry, benefit from a detailed characterization of the sensitivity variation within a pixel. A detailed map of the intra-pixel sensitivity (IPS) allows to increase the photometric accuracy by correcting for the impact of the tiny sub-pixel movements of the image sensor during integration. This paper reports the measurement of the sub-pixel sensitivity variation and the extraction of the IPS map of a front-side illuminated CMOS image sensor with a pixel pitch of 6 µm. Our optical measurement setup focuses a collimated beam onto the imaging surface with a microscope objective. The spot was scanned in a raster over a single pixel to probe the pixel response at each (sub-pixel) scan position. We model the optical setup in ZEMAX to cross-validate the optical spot profile described by an Airy diffraction pattern. In this work we introduce a forward modeling technique to derive the variation of the IPS. We model the optical spot scanning system and discretize the CMOS pixel response. Fitting this model to the measured data allows us to quantify the spatial sensitivity variation within a single pixel. Finally, we compare our results to those obtained from the more commonly used Wiener deconvolution.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Measuring Intra-Pixel Sensitivity Variations of a CMOS Image Sensor

Mahato

Meynants²,

Raskin

et al. 2018

IEEE Sensors J.

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“…A detailed description of the test bench has been presented in a precedent paper. 1 In this section we will describe the principal characteristics of the components, and the principle of the inversion software.…”

Section: General Description Of the Experimentsmentioning

confidence: 99%

“…This interferogram, as a self-image of the CSIG, is designed to explore the pixel's EUCLID CCD (pitch 12 µm) MTF to 500 mm −1 , which corresponds to explore the pixel response with an accuracy of 1 µm (or a twelfth of pixel). 1 Nevertheless, the pixel pitch under-samples the interferogram, cutting the MTF to a spatial frequency of 83 mm −1 , it is then necessary to microscan the CSIG to over-sample the interferogram. This microscan step consists in moving the CSIG at a pitch of 1 µm to ensure that a pixel -or a restrained zone of pixels on the detector -observes a complete period of the interferogram.…”

Section: Introductionmentioning

confidence: 99%

High accuracy measurements of the intrapixel sensitivity of VIS to LWIR astronomical detectors: experimental demonstration

et al. 2016

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The reduction of systematic effects is necessary to improve the accuracy in imaging and astrometry. For example, in Euclid Mission which aims at carrying out accurate measurements of dark energy and quantifying precisely its role in the evolution of the Universe, systematic effects need at be controlled to a level better than 10 −7 (Euclid, Science Book). To achieve this goal, a high-level of knowledge of the system point spread function (PSF) is required. This paper follows the concept-paper presented at the last SPIE conference 1 and gives the recent developments achieved in the design of the test bench for the intrapixel sensitivity measurements. The measurement technique we use is based on the projection of a high spatial resolution periodic pattern on the detector using the self-imaging property of a new class of diffractive objects named continuously self-imaging gratings (CSIG) and developed at ONERA. The principle combines the potential of global techniques, which make measurements at once on the whole FPA, and the accuracy of spot-scan-based techniques, which provide high local precision.

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“…To mitigate the speed issue, a team located at CEA Saclay is currently developing a different calibration technique using spot arrays (Ketchazo et al 2014) generated by self imaging gratings (Guérineau et al 2001). The goals for the calibration are more general than precision astrometry, it includes for example photometry of diffuse objects.…”

Section: Detector Interferometric Calibration Experiments (Dice)mentioning

confidence: 99%

A detector interferometric calibration experiment for high precision astrometry

Crouzier

Malbet

Hénault

et al. 2016

A&A

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Context. Exoplanet science has made staggering progress in the last two decades, due to the relentless exploration of new detection methods and refinement of existing ones. Yet astrometry offers a unique and untapped potential of discovery of habitable-zone lowmass planets around all the solar-like stars of the solar neighborhood. To fulfill this goal, astrometry must be paired with high precision calibration of the detector. Aims. We present a way to calibrate a detector for high accuracy astrometry. An experimental testbed combining an astrometric simulator and an interferometric calibration system is used to validate both the hardware needed for the calibration and the signal processing methods. The objective is an accuracy of 5 × 10 −6 pixel on the location of a Nyquist sampled polychromatic point spread function. Methods. The interferometric calibration system produced modulated Young fringes on the detector. The Young fringes were parametrized as products of time and space dependent functions, based on various pixel parameters. The minimization of function parameters was done iteratively, until convergence was obtained, revealing the pixel information needed for the calibration of astrometric measurements. Results. The calibration system yielded the pixel positions to an accuracy estimated at 4×10 −4 pixel. After including the pixel position information, an astrometric accuracy of 6 × 10 −5 pixel was obtained, for a PSF motion over more than five pixels. In the static mode (small jitter motion of less than 1 × 10 −3 pixel), a photon noise limited precision of 3 × 10 −5 pixel was reached.

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A new technique of characterization of the intrapixel response of astronomical detectors

Cited by 3 publications

References 15 publications

Measuring Intra-Pixel Sensitivity Variations of a CMOS Image Sensor

Measuring Intra-Pixel Sensitivity Variations of a CMOS Image Sensor

High accuracy measurements of the intrapixel sensitivity of VIS to LWIR astronomical detectors: experimental demonstration

A detector interferometric calibration experiment for high precision astrometry

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