Dr. Hannah P. Earnshaw Profile

Dr. Hannah P. Earnshaw

at Caltech

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Author

Publications (5)

Proceedings Article | 27 September 2023 Presentation

Ultraviolet CMOS sensors with integrated filter coatings for the UVEX mission

John Hennessy, Robin Rodríguez, April Jewell, Michael Hoenk, Shouleh Nikzad, Brian Grefenstette, Timothee Greffe, Roger Smith, Hannah Earnshaw, Fiona Harrison

Proceedings Volume 12678, 126780K (2023) https://doi.org/10.1117/12.2677968

KEYWORDS: Optical coatings, Ultraviolet radiation, Tunable filters, CMOS sensors, Atomic layer deposition, Far ultraviolet, Optical sensors, Fabrication, Dielectrics, Coating thickness

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Proceedings Article | 29 August 2022 Presentation + Paper

High dynamic range techniques for astronomical applications of CMOS devices

Hannah Earnshaw, Timothee Greffe, Roger Smith, Brian Grefenstette, Fiona Harrison, John Hennessy, Shouleh Nikzad, Charles Shapiro

Proceedings Volume 12191, 121910G (2022) https://doi.org/10.1117/12.2630367

KEYWORDS: Signal to noise ratio, High dynamic range imaging, Sensors, CMOS sensors, Point spread functions, Astronomy, High dynamic range image sensors, CMOS devices, Detection and tracking algorithms, Signal detection

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Proceedings Article | 29 August 2022 Presentation + Paper

Characterization of low light performance of a CMOS sensor for ultraviolet astronomical applications

Timothee Greffe, Roger Smith, Myles Sherman, Fiona Harrison, Hannah Earnshaw, Brian Grefenstette, John Hennessy, Shouleh Nikzad

Proceedings Volume 12191, 121910E (2022) https://doi.org/10.1117/12.2629198

KEYWORDS: Sensors, Cadmium sulfide, Photons, CMOS sensors, Ultraviolet radiation, Video, Charge-coupled devices, Monte Carlo methods, Interference (communication), Astronomy

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SPIE Journal Paper | 22 April 2022

Characterization of low light performance of a complementary metal-oxide semiconductor sensor for ultraviolet astronomical applications

Timothee Greffe, Roger Smith, Myles Sherman, Fiona Harrison, Hannah Earnshaw, Brian Grefenstette, John Hennessy, Shouleh Nikzad

JATIS, Vol. 8, Issue 02, 026004, (April 2022) https://doi.org/10.1117/12.10.1117/1.JATIS.8.2.026004

KEYWORDS: Sensors, Semiconductors, Cadmium sulfide, Ultraviolet radiation, Charge-coupled devices, CMOS sensors, Photons, Video, Astronomy, Switches

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Complementary metal-oxide semiconductor (CMOS) detectors offer many advantages over charge-coupled devices (CCDs) for optical and ultraviolet (UV) astronomical applications, especially in space where high radiation tolerance is required. However, astronomical instruments are most often designed for low light-level observations demanding low dark current and read noise, good linearity, and high dynamic range, characteristics that have not been widely demonstrated for CMOS imagers. We report the performance, over temperatures from 140 to 240 K, of a radiation hardened SRI 4k × 2k back-side illuminated CMOS image sensor with surface treatments that make it highly sensitive in blue and UV bands. After suppressing emission from glow sites resulting from defects in the engineering grade device examined, a 0.077 me − / s dark current floor is reached at 160 K, rising to 1 me − / s at 184 K, rivaling that of the best CCDs. We examine the trade-off between readout speed and read noise, finding that 1.43 e − median read noise is achieved using line-wise digital correlated double sampling at 700 kpix / s / ch corresponding to a 1.5 s readout time. The 15 ke − well capacity in high gain mode extends to 120 ke − in dual gain mode. Continued collection of photogenerated charge during readout enables a further dynamic range extension beyond 106 e − effective well capacity with only 1% loss of exposure efficiency by combining short and long exposures. A quadratic fit to correct for non-linearity reduces gain correction residuals from 1.5% to 0.2% in low gain mode and to 0.4% in high gain mode. Cross-talk to adjacent pixels is only 0.4% vertically, 0.6% horizontally, and 0.1% diagonally. These characteristics plus the relatively large (10 μm) pixel size, quasi 4-side buttability, electronic shutter, and sub-array readout make this sensor an excellent choice for wide field astronomical imaging in space, even at far-UV wavelengths where sky background is very low.

SPIE Journal Paper | 22 February 2022 Open Access

Reconstruction of the NuSTAR point spread function using single-laser metrology

Hannah Earnshaw, Kristin Madsen, Karl Forster, Brian Grefenstette, Murray Brightman, Andreas Zoglauer, Fiona Harrison

JATIS, Vol. 8, Issue 01, 014009, (February 2022) https://doi.org/10.1117/12.10.1117/1.JATIS.8.1.014009

KEYWORDS: Point spread functions, Laser metrology, Metrology, Transform theory, Telescopes, Sensors, Space operations, X-ray telescopes, Distortion, Time metrology

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