微弱光学图像的光参量放大特性的研究

Parametric Amplification Characteristics of Weak Image

研究了微弱光学图像在光参量图像放大中的放大特性,分析了相位匹配和晶体的空间频率带宽对图像信号增益的影响,从实验上验证了不同的相位匹配时输入图像信号在傅里叶平面上的增益分布.结果表明,当晶体的空间频率带宽大于输入图像信号的空间频率带宽且完全相位匹配时,光参量图像放大器能够对输入图像信号实现无失真、高增益的理想放大;有相位失配时,图像信号的增益峰值向高空间频率范围移动,并且在峰值附近范围变窄,随相位失配量大小的变化能够对图像信号光场中某特定空间频率实现放大,对图像信号进行滤波处理,突出图像特定频率的信息,实现图像边缘增强.

The image amplification characteristics in optical parametric image amplification are investigated. The phase-match condition, the spatial frequency bandwidth of crystal and the image signal gain are simulated. The numerical simulation results are validated in optical parametric image amplification experiment with BBO （b-BaB2O4） typed crystal. Theoretical and experimental results show that when the spatial frequency bandwidth of crystal than the band of the input image signal and the perfectly phase match,the weak optical image are amplified without distortion. The gain peak shifts to higher spatial frequencies and spatial bandwidth narrows, this effect occurs when a small phase mismatch is induced. As the magnitude of this mismatch is increased, optical parametric image amplification could be used to selectively amplify the given spatial-frequency of the weak image.