One color contrast enhanced infrared and visible image fusion method

Color constancy (Toet and Franken, 2003 [2]; Toet, 2003 [7]) and color contrast (Scribner et al., 2000 [21]; Lee et al., 2005 [23]) are two important topics for color image fusion. The paper focuses on the low color contrast problem of linear fusion algorithms with color transfer method. Color transfer technology is popular in infrared (IR) and visible image fusion to give the fused image a natural day-time color appearance (Toet, 2003 [7]; Wang et al., 2007 [8]; Zheng and Essock, 2008 [9]). However, in the color transfer step, all three channels of the color space are processed with the same linear mapping without color enhancement, resulting in low color contrast between the target and the background (Wang et al., 2007 [8]). Based on the characteristics of the IR image, we introduce a ratio of local to global divergence of the IR image to improve the color contrast. The enhancement ratios for both hot and cold targets are larger than one, while it tends to one for the background. As a result, the proposed method pops out both hot and cold targets in color, where hot targets will appear intense red, and cold targets will appear cyan. Subjective results show visible color contrast enhancement effects. Target detection experiments through hue and saturation components of the fused image show an improvement in the hit rate for target detection, owing to larger color distance between the target and the background.     

Widely phase-matched tunable difference-frequency generation in periodically poled LiNbO3 crystal

We report on the development of a laser source in the mid-infrared spectral region based on difference-frequency generation (DFG) in a periodically poled LiNbO₃ (PPLN) crystal. Continuously tunable coherent radiation from 2.75 to 4.78 μm was produced by optical parametric interaction between a diode-pumped monolithic continuous-wave (CW) Nd:YAG laser operating at 1.064 μm and a CW Ti:Sapphire laser tunable from 767 to 871 nm. Temperature-dependent quasi-phase-matched DFG wavelength acceptance bandwidth was studied and characterized. An empiric formula is given to estimate the phase-matched wavelength acceptance bandwidth as a function of the crystal temperature at Λ = 22.5 μm. A large frequency scan of 128 cm⁻¹ (about 78 cm⁻¹ above 1 μW) near 4.2 μm was achieved. The whole absorption spectrum of the P and R branches of the ν₃ band of atmospheric carbon dioxide has been recorded with a single phase-matched frequency scan.     

LaOBr:Ce3+,Tb3+中Ce3+与Tb3+间能量传递

本文利用毫微秒技术在ns秒量级测量了不同浓度组分的LaOBr:Ce3+,Tb3+中Ce3+发射带的衰减常数τCe值和时间分辨光谱,确立了Ce3到Tb3+能量传递过程模型,建立了动力学方程和导出能量传递的计算公式。据此计算出Ce3+到Tb3+的能量传递几率和效率,得出Ce3+,Tb3+的最佳浓度。     

轴对称低雷诺数空塞流动的有限元解法

管道中的空塞流动问题,由于其自由面上边界条件的非线性性质,使问题的求解困难很大。本文用罚函数有限元方法,数值计算了无重力的低雷诺数空塞流动问题。对非线性的自由面边界条件,本文采用了一种基于流线的迭代方法。数值计算的结果与实验相吻合,且收敛速度较快。     

Variational principles for two kinds of extended Korteweg—de Vries equations

Variational principles are constructed using the semi-inverse method for two kinds of extended Korteweg—de Vries (KdV) equations, which can be regarded as simple models of the nonlinear oceanic internal waves and atmospheric long waves, respectively. The obtained variational principles have also been proved to be correct.     

Intersubband transitions in Al0.82In0.18N/GaN single quantum well

The influence of the width of a lattice-matched Al_0.82In_0.18N/GaN single quantum well (SQW) on the absorption coefficients and wavelength of the intersubband transition (ISBT) has been investigated by solving the Schrödinger and Poisson equations self-consistently. The wavelength of 1—2 ISBT increases with L, the thickness of the single quantum well, ranging from 2.88 μm to 3.59 μm. The absorption coefficients of 1—2 ISBT increase with L at first and then decrease with L, with a maximum when L is equal to 2.6 nm. The wavelength of 1—3 ISBT decreases with L at first and then increases with L, with a minimum when L is equal to 4 nm, ranging from approximately 2.03 μm to near 2.11 μm. The absorption coefficients of 1—3 ISBT decrease with L. The results indicate that mid-infrared can be realized by the Al_0.82In_0.18N/GaN SQW. In addition, the wavelength and absorption coefficients of ISBT can be adjusted by changing the width of the SQW.     

掺Er光纤飞秒激光器载波包络位相偏移的探测

本文介绍了基于掺Er光纤飞秒激光器光学频率梳中光学部分的研制. 实验上采用重复频率为230 MHz的掺Er光纤飞秒激光器,通过放大、光谱展宽以及单臂f—2f系统,在优化及分析相关参数影响的基础上,获得了~30 dB信噪比f₀的输出,为光纤光学频率梳的建立奠定了基础. 关键词： 掺Er光纤激光器 光学频率计量 光纤光学频率梳 光谱展宽     

微颗粒样品X射线定量分析Monte Carlo模拟计算软件

基于作者前文[1,2]的物理模型和计算方法,编制了适用于多元微颗粒样品x射线定量分析的Monte Carlo程序软件,给出了对颗粒中电子散射,x射线激发、吸收和荧光效应等复杂物理过程进行严格计算的一系列公式,程序中建立了数据文件,具有较强的自动处理数据功能,本程序还适用于平厚块样品及薄膜样品的定量分析计算。     

摩擦点火Ti-V-Cr阻燃钛合金燃烧产物的组织特征

采用摩擦氧浓度实验方法, 结合原位观察、扫描电镜、能谱仪和X-射线衍射分析, 系统研究Ti-V-Cr 阻燃钛合金燃烧产物的微观组织形貌、燃烧反应过程的合金元素分布规律及微观机理. 结果表明: Ti-V-Cr 阻燃钛合金燃烧过程发出闪亮耀眼的白光, 具有典型金属燃烧的火焰特征. 燃烧产物主要有TiO₂, V₂O₅和Cr₂O₃三种氧化物, 该混合氧化物以分散颗粒和致密连续体存在. 分散颗粒为规则的球形; 致密连续燃烧产物的微观组织具有分区特征, 从合金基体至燃烧表面依次为过渡区、热影响区、熔凝区和燃烧区. 其中, 过渡区存在一些微小的颗粒状凸起, 且有一定方向性; 热影响区中形成大量V基固溶体相和少量的Ti基固溶体相, V基固溶体相上存在Ti的含量远高于基体的针状析出物; 熔凝区中, 大量的Ti基固溶体中存在少量的V基固溶体; 燃烧区主要为Ti, V和Cr的氧化物混合物. 热影响区的V基固溶体相降低了Ti元素向熔凝区的迁移速率, 减慢了燃烧区Ti与O的优先反应; 燃烧区形成的TiO₂, V₂O₅和Cr₂O₃混合氧化物和熔凝区O在Ti中大量固溶共同终止了O向合金基体的继续扩散, 从而使Ti-V-Cr阻燃钛合金表现出优异的阻燃功能性.