针对固定红外摄像机视频监控在夜雾天况下获得的成像效果差、监控范围有限等问题,运用带云台的LED红外摄像机,结合红外成像与可见光成像的特点,提出一种变焦式夜雾天彩色视频构建的方法。该方法在天气状况良好的白天利用可见光成像特点实现全景图像接拼,然后将红外图像与全景图像配准,从而构建出视场角一致的可见光背景图像。在能见度较低的夜雾下利用红外成像系统提取运动目标,然后通过掩模融合算法和配准参数,将运动目标同比例发融合到可见光背景图像相同位置中,最终实现变焦式彩色视频构建。实验结果表明,该方法能够满足大范围监控和夜雾天全天候彩色视频实时监控的要求。

In accordance with nonperturbative quantum scattering theory, we investigate photoelectron angular distributions (PADs) from above-threshold detachment (ATD) of negative ions irradiated by circularly polarized few-cycle laser fields. Electrons ejected on the polarization plane demonstrate distinct anisotropies in angular distributions which distinctly vary with the carrier-envelope (CE) phase. The anisotropy is caused by interference between transition channels; it also depends strongly on laser frequency, pulse duration, and kinetic energy of photoelectrons. Optimal emission of photoelectrons, which varies with CE phase, makes it possible to control photoelectron motion.

Photoelectron angular distributions (PADs) from two-photon ionization of atoms in linearly polarized strong laser fields are obtained in accordance with the nonperturbative quantum scattering theory. We also study the influence of laser wavelength on PADs. For two-photon ionization very close to the ionization threshold, most of the ionized electrons are vertically ejected to the laser polarization. PADs from two-photon ionization of atoms are determined by the second order generalized phased Bessel function at which the ponderomotive parameter plays a key role. In terms of dependence of PADs on laser wavelength, corresponding variations for the ponderomotive parameter are demonstrated.