Properties of degenerate four-wave mixing in a Ce:KNSBN photorefractive fiber-like crystal under the conditions that the angle between the pump beam and the signal beam is smaller and bigger was studied. It is found that there are two interaction regions of degenerate four-wave mixing in the sample when the angle is bigger, and four-times enhancement of the maximum phase-conjugate reflectivity compared with that in smaller angle condition is obtained. The experimental results of the phase-conjugate reflectivity versus the intensity of signal beams, and versus the ratio of the pump beams are presented, which are numerically fitted by theoretical equations. They are coincident quite well. The property of the four-wave mixing gratings and the phase-conjugate response time of Ce:KNSBN photorefractive fiber-like crystal were studied. The response time could be faster, in an order of second in our experimental conditions.
IN this paper, the advantage and disadvantage of several seal imprint recognition methods have been compared, and an approach for seal imprint recognition based on ring- projecting template matching is proposed. Firstly, the seal important in divided into some rings, and the local and global intrinsic features are extracted. The, the recognition is made, with the border and the words of seal imprint separated, by 1D template matching. The experimental results show that the proposed approach is of adaptability and reliability.
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