New autofocusing technique using the frequency selective weighted median filter for video cameras

Kang Sun Choi, Jun Suk Lee, Sung-Jea Ko

Research output: Contribution to journalArticle

162 Citations (Scopus)


Most conventional autofocusing techniques based on the gradient estimator are very sensitive to noise. In this paper, a new autofocusing technique which is resistive to noise generated by the CCD of video cameras is proposed. In the proposed scheme, the frequency selective weighted median (FSWM) filter is utilized to estimate the degree of focus and the fast hill-climbing search (HCS) strategy is exploited to determine the best focused image. Since the FSWM filter can not only extract high frequency components from the image, but also eliminate impulsive noise, the proposed autofocusing method employing the FSWM criterion function can estimate the degree of focus precisely. Furthermore, the proposed real-time HCS algorithm enables the video camera to continuously focus on dynamic images. Experimental results demonstrate that the proposed technique outperforms existing techniques by enhancing the accuracy of the focus value of the video camera without the influence of noise.

Original languageEnglish
Pages (from-to)820-827
Number of pages8
JournalIEEE Transactions on Consumer Electronics
Issue number3
Publication statusPublished - 1999 Aug 1



  • Autofocusing
  • Criteria function
  • Hill-climbing search
  • The frequency selective weighted median filter

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Computer Networks and Communications

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