提出一种利用光折变二波耦合放大原理实现图像边缘增强的新方法.在用Cr:SBN晶体作记录介质的实时傅里叶变换全息读写装置中,物光中相对分离的高、低空间频率成分分别与参考光波在晶体中发生二波耦合.由于代表图像边缘信息的高频分量强度远低于低频分量,耦合的结果使得相对较弱的高频分量得到增强,从而使再现的全息像边缘凸出.文中详细讨论了晶体光轴取向及参物比对图像边缘增强效果的影响,分析了不同能量转移方向下实现边缘增强的物理机制.实验结果表明,Cr:SBN晶体有可能成为一种用于图像边缘增强的光折变晶体动态滤波器.

A new method is presented to enhance the image edge using photorefractive two wave coupling. In the setup for real time writing and reading, the Fourier transform hologram using Cr:SBN crystal as the recording medium, the spatially separated high and low frequency components of the object beam will couple with the reference beam individually. The coupling results in the enhancement of the relatively weak high frequency component, because the intensity of the high frequency carrying the edge information of the object is much weaker than that of the low frequency. It discussed that the influences of the crystal axis orientation and the intensity ratio of the reference beam to object beam on the image edge enhancement. The physical mechanism of the image edge enhancement under different reference object ratio is analyzed. This Cr:SBN crystal can be used as a model of optical dynamic filtering for image edge enhancement.