Low-Power CMOS Laser Doppler Imaging Using Non-CDS Pixel Readout and 13.6-bit SAR ADC

Denis Guangyin Chen, Man Kay Law, Yong Lian, Amine Bermak

Research output: Contribution to journalArticle

3 Citations (Scopus)


Laser Doppler imaging (LDI) measures particle flows such as blood perfusion by sensing their Doppler shift. This paper is the first of its kind in analyzing the effect of circuit noise on LDI precision which is distinctively different from conventional imaging. Based on this result, it presents a non-correlated-double-sampling (non-CDS) pixel readout scheme along with a high-resolution successive-approximation-register (SAR) analog-to-digital-converter (ADC) with 13.6b effective resolution (ER). Measurement results from the prototype chip in 0.18 μm technology confirm the theoretical analysis and show that the two techniques improve LDI sensing precision by 6.9 dB and 4.4 dB (compared to a 10b ADC) respectively without analog pre-amplification. The sensor's ADC occupies 518 μu × 84 μu and is suitable for fast column parallel readout. Its differential non-linearity (DNL), integral non-linearity (INL), and input referred noise are +3.0/-2.8 LSB, +24/-17 LSB, and 110 μVrms respectively, leading to a Figure-of-Merit (FoM) of 23 fJ/state which makes it one of the most energy efficient image sensor ADCs and an order of magnitude better than the best reported LDI system using commercial high-speed image sensors.

Original languageEnglish
Article number6985687
Pages (from-to)186-199
Number of pages14
JournalIEEE Transactions on Biomedical Circuits and Systems
Issue number1
Publication statusPublished - 1 Feb 2016
Externally publishedYes



  • CMOS image sensor
  • correlated double sampling (CDS)
  • flowmetry
  • laser Doppler imaging (LDI)
  • perfusion
  • successive-approximation-register analog-to-digital-converter (SAR ADC)
  • time-domain comparator

ASJC Scopus subject areas

  • Biomedical Engineering
  • Electrical and Electronic Engineering

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