Selecting the Optimal Focus Measure for Autofocusing and Depth-From-Focus
IEEE Transactions on Pattern Analysis and Machine Intelligence
IEEE Transactions on Pattern Analysis and Machine Intelligence
Evaluation of focus measures in multi-focus image fusion
Pattern Recognition Letters
A passive auto-focus camera control system
Applied Soft Computing
Multi-focus image fusion based on salient edge information within adaptive focus-measuring windows
SMC'09 Proceedings of the 2009 IEEE international conference on Systems, Man and Cybernetics
Developing robust vision modules for microsystems applications
Machine Vision and Applications
Low-Light Auto-Focus Enhancement for Digital and Cell-Phone Camera Image Pipelines
IEEE Transactions on Consumer Electronics
Removing the blocking artifacts of block-based DCT compressed images
IEEE Transactions on Image Processing
Enhanced Autofocus Algorithm Using Robust Focus Measure and Fuzzy Reasoning
IEEE Transactions on Circuits and Systems for Video Technology
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A number of contrast measurements have been investigated and compared in the literature. Each of them exhibits an ideal curve with a well defined peak standing for the best focused image. However, a focused image obtained in low light conditions possesses a small contrast value, which may be easily influenced by noise. In this case, contrast measurements may generate fluctuant curves with many local peaks. This paper presents a comparison among six contrast measurements in passive autofocus systems towards a non-previously researched object of low contrast images. The criterium to evaluate the performance of each measurement is unimodality. And we assess the similarity of the resulting curves with an ideal focus curve which exhibits a single peak and an absence of plateau. Experimental results from six typical image sequences indicate that Tenengrad and CMAN approaches yield the best performance, but it is still necessary to derive a more elaborated method because both methods fail to generate a single sharp peak in some circumstances.