Multi-resolution low-power Gaussian filtering by reconfigurable focal-plane binning

J. Fernández-Berni, R. Carmona-Galána, F. Pozas-Flores, Á Zarándy, Á Rodríguez-Vázquez

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Citations (Scopus)

Abstract

Gaussian filtering is a basic tool for image processing. Noise reduction, scale-space generation or edge detection are examples of tasks where different Gaussian filters can be successfully utilized. However, their implementation in a conventional digital processor by applying a convolution kernel throughout the image is quite inefficient. Not only the value of every single pixel is taken into consideration sucessively, but also contributions from their neighbors need to be taken into account. Processing of the frame is serialized and memory access is intensive and recurrent. The result is a low operation speed or, alternatively, a high power consumption. This inefficiency is specially remarkable for filters with large variance, as the kernel size increases significantly. In this paper, a different approach to achieve Gaussian filtering is proposed. It is oriented to applications with very low power budgets. The key point is a reconfigurable focal-plane binning. Pixels are grouped according to the targeted resolution by means of a division grid. Then, two consecutive shifts of this grid in opposite directions carry out the spread of information to the neighborhood of each pixel in parallel. The outcome is equivalent to the application of a 3×3 binomial filter kernel, which in turns is a good approximation of a Gaussian filter, on the original image. The variance of the closest Gaussian filter is around 0.5. By repeating the operation, Gaussian filters with larger variances can be achieved. A rough estimation of the necessary energy for each repetition until reaching the desired filter is below 20nJ for a QCIF-size array. Finally, experimental results of a QCIF proof-of-concept focal-plane array manufactured in 0.35μm CMOS technology are presented. A maximum RMSE of only 1.2% is obtained by the on-chip Gaussian filtering with respect to the corresponding equivalent ideal filter implemented off-chip.

Original languageEnglish
Title of host publicationBioelectronics, Biomedical, and Bioinspired Systems V; and Nanotechnology V
DOIs
Publication statusPublished - Jun 10 2011
EventBioelectronics, Biomedical, and Bioinspired Systems V; and Nanotechnology V - Prague, Czech Republic
Duration: Apr 18 2011Apr 20 2011

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume8068
ISSN (Print)0277-786X

Other

OtherBioelectronics, Biomedical, and Bioinspired Systems V; and Nanotechnology V
CountryCzech Republic
CityPrague
Period4/18/114/20/11

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Keywords

  • Binomial filter mask
  • Focal-plane processing
  • Gaussian kernels
  • Low-power smart image sensors

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

Cite this

Fernández-Berni, J., Carmona-Galána, R., Pozas-Flores, F., Zarándy, Á., & Rodríguez-Vázquez, Á. (2011). Multi-resolution low-power Gaussian filtering by reconfigurable focal-plane binning. In Bioelectronics, Biomedical, and Bioinspired Systems V; and Nanotechnology V [806806] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 8068). https://doi.org/10.1117/12.886555