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

Kang Sun Choi, Jun Suk Lee, Sung Jae Ko

    Research output: Contribution to journalArticlepeer-review

    177 Citations (Scopus)

    Abstract

    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
    Volume45
    Issue number3
    DOIs
    Publication statusPublished - 1999 Aug

    Bibliographical note

    Funding Information:
    This work was performed as a part of ASIC Development Project supported by Korean Ministry of Commerce, Industry and Energy, Ministry of Science and Technology, and Ministry of Information and Communications.

    Keywords

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

    ASJC Scopus subject areas

    • Media Technology
    • Electrical and Electronic Engineering

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