Tohsing Korntip, Schrempf Michael, Riechelmann Stefan, Schilke Holger, Seckmeyer Gunther
Institut für Meteorologie und Klimatologie, Leibniz Universität Hannover, Hannover, Germany.
Appl Opt. 2013 Mar 10;52(8):1564-73. doi: 10.1364/AO.52.001564.
We describe how sky luminance can be derived from a newly developed hemispherical sky imager (HSI) system. The system contains a commercial compact charge coupled device (CCD) camera equipped with a fish-eye lens. The projection of the camera system has been found to be nearly equidistant. The luminance from the high dynamic range images has been calculated and then validated with luminance data measured by a CCD array spectroradiometer. The deviation between both datasets is less than 10% for cloudless and completely overcast skies, and differs by no more than 20% for all sky conditions. The global illuminance derived from the HSI pictures deviates by less than 5% and 20% under cloudless and cloudy skies for solar zenith angles less than 80°, respectively. This system is therefore capable of measuring sky luminance with the high spatial and temporal resolution of more than a million pixels and every 20 s respectively.
我们描述了如何从新开发的半球形天空成像仪（HSI）系统中得出天空亮度。该系统包含一台配备鱼眼镜头的商用紧凑型电荷耦合器件（CCD）相机。已发现该相机系统的投影几乎是等距的。已计算出高动态范围图像的亮度，然后用CCD阵列光谱辐射计测量的亮度数据进行了验证。对于无云和完全阴天的天空，两个数据集之间的偏差小于10%，对于所有天空条件，偏差不超过20%。对于太阳天顶角小于80°的情况，从HSI图片得出的全球照度在无云和多云天空下的偏差分别小于5%和20%。因此，该系统能够以分别超过一百万个像素的高空间分辨率和每20秒的高时间分辨率测量天空亮度。
