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.
Bibliographical noteFunding 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.
- Criteria function
- Hill-climbing search
- The frequency selective weighted median filter
ASJC Scopus subject areas
- Media Technology
- Electrical and Electronic Engineering