Abstract
The auto-focus is a fundamental function of a camera system which is required to photograph a clear image of an object. To obtain the optimal focus of a specific region within an image, the sharpness of the region must be measured. Since the sharpness represents the difference between a pixel and its neighbors, multiple pixel references occur while evaluating each pixel. To compensate for the processing bottleneck caused by this repetitive memory reference, this paper presents a dedicated hardware architecture for real-time auto-focusing. The proposed system processes the incoming pixel simultaneously with its neighboring pixels based on its parallelized window processing architecture. In addition, the proposed system performs an adaptive thresholding-based sharpness function with multiple windows to achieve accuracy and robustness. The proposed system is compared to several conventional pixel-based auto-focusing systems under various environmental conditions.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Lee, S.Y. et al.: Low-power auto focus algorithm using modified DCT for the mobile phones. In: International Conference on Consumer Electronics, pp. 67–68 (2006)
Sohn, S.M. et al.: SoC design of an auto-focus driving image signal processor for mobile camera application. In: International Conference on Consumer Electronics 73–74 (2006)
Allegro S., Chanel C., Jacot J.: Autofocus for automated microassembly under a microscope. Proc. Int. Conf. Image. Process. 2, 677–680 (1996)
Chern N.K., Neow P.A., Ang M.H. Jr: Practical issues in pixel-based autofocusing for machine vision. Proc. IEEE Int. Conf. Robot. Autom. 3, 2791–2796 (2001)
Choi K.-S., Lee J.-S., Ko S.-J.: New autofocus technique using the frequency selective weighted median filter for video cameras. IEEE Trans. Consumer Electron. 45, 820–827 (1999)
Song, Y., Li, M., Sun, L.: A new auto-focusing algorithm for optical microscope based automated system. In: International Conference on Control, Automation, Robotics and Vision (2006)
Yeo T.T.E., Ong S.H., Jayasooriah S.R.: Autofocusing for tussue microscopy. Image Vis. Comput. 11(10), 629–639 (1993)
Nayar S.K., Nakagawa Y.: Shape from focus. IEEE Trans. Pattern Anal. Mach. Intell. 16(8), 824–831 (1994)
Gonzalez, R.C., Woods, R.E.: Digital Image Processing, pp. 600–607. 2nd edn. Prentice-hall, New Jersey (2002)
Jin, S.H. et al.: The dynamic thresholding circuit of a real-time window-based image processing structure. Asia Pacific System on a Chip, pp. 631–634 (2004)
Li F., Jin H.: A fast auto focusing method for digital still camera. Proc. Int. Conf. Mach. Learn. Cybern. 8, 18–21 (2005)
Subbarao M., Choi T., Nikzad A.: Focusing techniques. J. Optical Eng. 32(11), 2824–2836 (1993)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Jin, S., Cho, J., Kwon, K.H. et al. A dedicated hardware architecture for real-time auto-focusing using an FPGA. Machine Vision and Applications 21, 727–734 (2010). https://doi.org/10.1007/s00138-009-0190-2
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00138-009-0190-2