DCDS weighted averaging theory and development for improved noise filtering in scientific CCD applications

Clapp, Matthew; Mihalcea, Ionut; Morse, T.; Salter, Mike; Waltham, Nick

doi:10.1117/12.2231619

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…Finally, a good correlation has been shown between the measured and modelled results providing good confidence in the future performance of this technology. Previous work [6] has demonstrated that the use of DCDS weighted averaging may further reduce the system noise at low pixel frequencies due to the attenuation of 1/f noise. Whilst a 50 kHz pixel frequency is on the borderline of the frequency range at which this technique is most effective, it is possible that some reduction in system noise will be observed with this method.…”

Section: Conclusion and Future Plansmentioning

confidence: 99%

“…A further trade-off has been required between design complexity and video settling time. Previous work [6] has found that using samples from the settling period of the pixel waveform may degrade the noise performance and therefore it is important to avoid using these samples for the DCDS averaging. As a consequence, the video harness has been kept as short as possible within the mechanical constraints of the system.…”

Section: Dcds Designmentioning

confidence: 99%

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Development of digital correlated double sampling (DCDS) camera electronics for the space-based world space observatory ultra-violet spectrograph mission

Clapp

Salter

Patel

et al. 2017

International Conference on Space Optics — ICSO 2016

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Digital correlated double sampling (DCDS) is an emerging technology for CCD imaging systems in space-based applications. DCDS technology not only provides the low readout noise electronics required by many applications but also offers a range of flexible readout modes that allows the readout noise and pixel frequency to be dynamically adjusted even in operation. This paper describes the DCDS implementation used within the World Space Observatory Ultraviolet (WSO-UV) mission. The latest theoretical and measured noise performance results are presented alongside detailed performance results for the camera electronics including linearity, crosstalk, transient response and gain stability. STFC RAL Space has developed the DCDS implementation for WSO-UV as part of the camera electronics boxes (CEBs) which house the CCD drive electronics for the WSO Ultraviolet Spectrograph Subsystem (WUVS). WSO-UV is a major Russian-led international collaboration to develop a large space-borne telescope and instrumentation to study the universe at ultraviolet wavelengths between 115 nm and 310 nm. The WUVS is led by the Institute of Astronomy of the Russian Academy of Sciences. WUVS consists of two high resolution spectrographs covering the far-UV range of 115-176 nm and the near-UV range of 174-310 nm, and a long-slit spectrograph covering the wavelength range of 115-305 nm. RAL Space is providing the camera electronics that will interface with the custom-designed CCD sensor and cryostat assembly developed by e2v technologies (UK). This paper describes the implementation of DCDS within the constraints of a space-based application that imposes challenging technical requirements. We discuss the key design trade-offs with particular emphasis on those relating to the baseline readout noise requirement of < 3 electrons rms read out at 50 kpixels/s. The results presented illustrate the performance achieved by this novel design now that the CEB has passed the critical design review. Finally, we present our plans for the next stage in this development including the use of weighted averaging for even lower readout noise in the future. I. INTRODUCTIONWorld Space Observatory Ultraviolet (WSO-UV) is a major Russian-led international collaboration to develop a large space-borne 1.7 m Ritchey-Chrétien telescope and instrumentation to study the universe at ultraviolet wavelengths between 115 nm and 320 nm. There are a number of key science drivers for the mission, including the study of galaxy formation, the evolution of the Milky Way and the atmospheres of extrasolar planets [1]. There are two primary sets of instrumentation on the satellite [1]; the Field Camera Unit (FCU) and the WSO Ultraviolet Spectrographs (WUVS). The FCU is a UV imager with two channels; a far ultraviolet (FUV) channel covering 115-175 nm wavelengths and a near ultraviolet (NUV) channel covering 185-320 nm wavelengths. The WUVS instrument set consists of three spectrographs:• Vacuum Ultraviolet Echelle Spectrograph (VUVES): 115-176 nm, R=50000 • Ultraviolet Echelle Spectrogr...

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Section: Conclusion and Future Plansmentioning

confidence: 99%

Section: Dcds Designmentioning

confidence: 99%

Development of digital correlated double sampling (DCDS) camera electronics for the space-based world space observatory ultra-violet spectrograph mission

Clapp

Salter

Patel

et al. 2017

International Conference on Space Optics — ICSO 2016

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Time Domain Noise Analysis of Oversampled CMOS Image Sensors

Süss

Wilhelmsen

Zuo

et al. 2022

IEEE Trans. Electron Devices

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Charge-coupled device readout by digital-correlated double sampling

Cruz,

De Vicente

2024

Front. Detect. Sci. Technol.

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Charge-coupled devices (CCDs) play crucial roles in astronomy owing to their widespread use in the optical band, offering high sensibility, low noise, high dynamic range, and high spatial resolution. Recent advancements in CCDs have focused on improving the sub-electron noise levels for particle detection and enhancing readout speeds through simulation studies. The main objective of this study is to replace the analog processing of CCD signals using the digital-correlated double sampling (DCDS) technique. DCDS allows post-acquisition noise correction through intermittent sampling of an internal reference voltage to provide compact and flexible performance. In this study, DCDS was evaluated using two digital processing systems, namely, a 2.5 mega-samples per second (MSPS) 24-bit analog-to-digital converter (ADC) board and a 250 MSPS 16-bit ADC field-programmable-gate-array( FPGA)-based buffer memory board. The readout noise value at 74 kpix/s (7.1 e) was a significant improvement over that obtained with analog processing (9.7 e). The DCDS implementation demonstrates optimal signal-to-noise ratio for a wide range of readout speeds. Parameters such as the sample positions per pixel, number of samples, and number of pixels were identified to be essential in achieving an accurate gain value. Finally, hardware implementation of the DCDS IP core algorithm on a Xilinx Zynq-7000 AP system-on-a-chip (SoC) showed a significant improvement in power dissipation (7.1 W) compared to the analog Monsoon correlated double sample (CDS) circuit (13.6 W). The DCDS IP core implementation also showed a background noise reduction of up to 34% compared to DCDS offline readout processing using a Python algorithm.

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DCDS weighted averaging theory and development for improved noise filtering in scientific CCD applications

Cited by 3 publications

References 6 publications

Development of digital correlated double sampling (DCDS) camera electronics for the space-based world space observatory ultra-violet spectrograph mission

Development of digital correlated double sampling (DCDS) camera electronics for the space-based world space observatory ultra-violet spectrograph mission

Time Domain Noise Analysis of Oversampled CMOS Image Sensors

Charge-coupled device readout by digital-correlated double sampling

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