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首页> 外文期刊>Optical engineering >Effects of practical aerosol forward scatter of infrared and visible light on atmospheric coherence diameter
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Effects of practical aerosol forward scatter of infrared and visible light on atmospheric coherence diameter

机译：实际的红外和可见光气溶胶前向散射对大气相干直径的影响

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A correction to the definition of the atmospheric coherence diameter is suggested here, based on the existence of a practical instrumentation-based aerosol modulation transfer function (MTF), which is often the dominant ingredient of the atmospheric MTF. As defined classically by Fried about 25 yr ago, atmospheric MTF and coherence diameter were related to turbulence MTF only. Lutomirski considered diffractive aerosols, too, but did not consider effects of instrumentation on scattering angles actually recorded in the image. These are limited in the real world by instrumentation to milliradians, rather than by the broad angular spread of diffraction to radians. In the case of a Gaussian approximation of the practical aerosol MTF, an analytical expression is derived for the practical aerosol-derived coherence diameter. This parameter is related to the practical aerosol MTF's cutoff frequency, and to its asymptotic value at high spatial frequencies. Thus, a more general concept of atmospheric coherence diameter is proposed here, which is relevant to actual real-world imaging systems, whether they are passive or active. Quantitative validation of the theory is presented, based on both simulations and actually measured atmospheric MTFs in both the visible and thermal infrared spectral ranges. Overall atmospheric coherence diameter is determined generally by the smaller of the turbulence and practical aerosol coherence diameters, depending on optical depth. The results here appear applicable particularly to cost-effective thermal imaging system design, although applications are considered, too, for the visible and near infrared. For example, blur deriving from aerosol scatter should have much less effect in coherent detection laser radar (LIDAR) than in direct detection imaging.
机译：根据实际的基于仪器的气溶胶调制传递函数（MTF）的存在，在此建议对大气相干直径的定义进行校正，而这通常是大气MTF的主要成分。正如弗里德（Fried）在大约25年以前经典定义的那样，大气MTF和相干直径仅与湍流MTF有关。 Lutomirski也考虑了衍射气溶胶，但没有考虑仪器对实际记录在图像中的散射角的影响。在现实世界中，这些限制是通过仪器检测到的弧度，而不是衍射到弧度的广角传播。在实际气溶胶MTF的高斯近似情况下，可以得出实际气溶胶相干直径的解析表达式。此参数与实际气溶胶MTF的截止频率有关，并且与高空间频率下的渐近值有关。因此，在此提出了大气相干直径的更一般的概念，这与实际的现实世界成像系统有关，无论它们是被动的还是主动的。基于模拟和实际测量的可见光和热红外光谱范围内的大气MTF，对理论进行了定量验证。总的大气相干直径通常由湍流和实际气溶胶相干直径中较小者决定，具体取决于光学深度。尽管考虑了可见光和近红外光的应用，但这里的结果似乎特别适用于具有成本效益的热成像系统设计。例如，与直接检测成像相比，由气溶胶散射引起的模糊对相干检测激光雷达（LIDAR）的影响应小得多。

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