An improved clarity evaluation function for precise focusing and its application on vision measuring machine

Abstract

Four clarity evaluation functions are introduced. Their merits and deficits in sensitivity and speed were tested by using four photos with different clarity. Based on the test, a new evaluation function was proposed, which is adopted by Fourier spectrum evaluation function. Test results show that the new function has the better sensitivity on clarity evaluation compared to the Fourier spectrum evaluation function. This new function was applied to the vision measuring machine for clarity evaluation. Gauss curve fitting method is used to get the exact focusing position after acquiring the evaluation value of each position. It’s shown that the new evaluation function has good performance on machine’s auto-focusing action. It’s suitable to be used for the precise focusing situation.

Keywords

Precise focusing clarity evaluation function fourier spectrum function gauss curve fitting

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