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Disparity servoing based fast autofocusing method for stereomicroscope

Liu Y., Yu M., Cui L., Jiang G., Wang G., Fan S.

Optica Applicata

2016

Vol. 46, nr 4

651--663

A disparity servoing based fast autofocusing method is proposed for stereomicroscopes according to linear relationship between the disparity change in stereomicroscopic images and the move distance of a motorized translation stage. For a certain stereomicroscope, the calibration of a disparity range of clear images at each magnification is implemented offline. After that, the disparity of the stereomicroscopic image is used as an index to represent the sharpness of an arbitrary image. If the disparity does not satisfy the requirement, move steps and direction of a step motor are calculated by utilizing the linear relationship between the disparity change and the move distance of the stage. The iteration will be continued until the disparity of the captured stereomicroscopic image approximates to the clearest disparity. The experimental results show that the proposed method only requires a few iterations and less time to reach the focus position, and the disparity error is less than 0.5 pixel.

Improved Roberts focusing evaluation method for an autofocusing system

Yin A., Dai Z., Chen B., Li K.

Optica Applicata

2013

Vol. 43, nr 3

529--538

In this paper, a new focusing evaluation method based on local 2/8 center windows is proposed for an autofocusing system. We have proposed an evaluation function which improved the Roberts function with eight-neighborhood or four-neighborhood. The approximate optimal criteria window is selected by a 2/8 rule. Comparative experiments implemented with other methods have shown that the 2/8 rule method not only can find the approximate optimal evaluation window quickly, but also has better generality. This evaluation function of improved Roberts’ function has higher sensitivity and better real-time performance.

Autofocusing with the help of orthogonal series transforms

Śliwiński P.

International Journal of Electronics and Telecommunications

2010

Vol. 56, No. 1

33-39

An autofocus algorithm employing orthogonal series expansions is proposed. Several instances of the generic algorithm, based on discrete trigonometric, polynomial and wavelet series, are reviewed. The algorithms are easy to implement in the transform coders used in digital cameras. Formal analysis of the algorithm properties is illustrated in experiments. Some practical issues are also discussed.