频率变换 meaning in English
channel rotation
frequency change
frequency conversion
frequency tra lation
frequency transformation
frequency translation
frequency transposition
frogging
Examples
- The chaos sequence was applied in these two algorithms to increase its security and was served separately as the random watermark generator and the watermark image encryption techniques . due to the analysis of the image characteristics , we determined the watermark strength by the classification of the image content and obtained better robustness and imperceptibility . new algorithms of meaningful digital watermarking in svd domain with chaotic transform encryption are proposed
混沌序列在这两类算法中分别作为随机水印信号发生器和二值图像水印的混沌加密手段，具有安全性高、形式简单的优点；利用hvs特性，分别在时空域和dct频率变换域中计算图像内容的自适应嵌入强度，增强了算法的稳健性；水印的嵌入和检测计算复杂度小，算法简单。 - It shows that when walk - off and diffraction effects could be ignored approximately estimation of the phase distribution of second - harmonic wave could be done . the far field divergent angle and second moment radius of harmonic wave will vary with the aberration of fundamental wave , but the far field divergent angle will be obviously smaller than that of fundamental wave . the phase distribution of both fundamental and harmonic wave is measured using hartmann - shack wave front sensor in the experiment with 1064nm and 790nm lasers , respectively
这说明利用非线性光学频率变换方法拓宽波前传感器件的响应波段是很难实现的，但是，通常三波相互作用过程的研究均是建立在平面波和理想高斯光束之上，因此我们对于位相畸变倍频过程的研究是非线性光学领域一个重要而有意义的新课题，它有助于人们更加深入理解非线性光学效应，为进一步合理利用之奠定了理论和实验的基础。 - The basic principle and characteristics of optical frequency conversion technology based on the photonic crystals are firstly summarized in the paper ; then , the current developments of frequency conversion of photonic crystals are also presented ; finally , its importance are pointed out in the tunable laser and other application fields
摘要文章首先介绍了光子晶体光学频率变换技术的基本原理和技术特点；然后简述光子晶体光学频率变换技术研究进展情况；最后指出了光子晶体变频技术在可调谐激光器和其它领域中的应用前景。 - At present , people usually use birefrigence and quasi - phase - matching methods to achieve higher effiency in the process of conversion . a significant advantage of quasi - phase - matching method is that the interaction is occurred through the largest element of the x ( 2 ) tensor ; the period of optical superlattice can be designed randomly , and any interaction can be matched without walk - off angle ; they are fitted to be used in frequency conversion of lower power especially . the quasi - phase - matching method has some advantages over birefrigence method , improving the efficiency of frequency conversion ; the range of frequency conversion covers its whole transperant wavelength
由于准相位匹配技术有其独特的优势，可以利用非线性光学晶体的最大二阶极化张量，如ppln 、 pplt 、 ppktp用的非线性极化张量都是d _ ( 33 ) ,其有效非线性系数高出普通非线性光学介质(如bbo 、 lbo 、 ktp )一个数量级，而且可以人为灵活设计调制周期，通过周期设计其频率变换范围可以覆盖准相位匹配介质的整个透明波段，选择无走离效应，解决了常规pm难以解决的问题，拓宽了非线性晶体的应用范围，极大地提高了频率转换效率，已成为非线性光学材料和固体激光器的研究热点之一。