Practical issues in pixel-based autofocusing for machine vision

Different autofocusing methods exist for many cameras today. While not ignoring commercially available methods requiring specialized hardware, this paper focuses mainly on pixel based autofocusing algorithms as applied to CCD camera systems. Different measures of image sharpness are compared. For each of these, different algorithms for searching the best lens setting are assessed in terms of performance as well as their applicability to various situations. In addition, several other factors potentially affecting camera focusing are also discussed. Based on the information obtained, this research attempts to formulate a robust autofocusing algorithm.