云相机绝对辐射定标技术研究

Absolute Radiometric Calibration Technique of Cloud Camera

云相机用于对目标区域进行云识别和云覆盖率的判别,其采用阈值法进行云判。为满足云判的准确性,确定探测器响应值与辐亮度之间的关系尤为重要。以云相机采用的基于拜耳阵列的面阵彩色CCD相机为研究对象,分析其成像过程,发现其红(R)、绿(G)、蓝(B)通道的辐射响应光谱存在重叠;以此为基础,建立了多通道CCD探测器辐射响应定标模型。针对云相机使用的R和B通道,使用747 nm LED和443 nm LED作为积分球的光源,设置光谱辐亮度的最小值、典型值、最大值,在单光源条件下进行云相机的绝对辐射响应定标实验以确定相应的绝对辐射响应系数,在双光源条件下验证了提出的辐射响应定标模型的正确性。该方法消除了探测器响应混叠带来的定标不确定性,有效提高了绝对辐射定标的准确度。

Cloud camera is designed to perform cloud recognition and cloud coverage discrimination of the target area,and it adopts the threshold method for cloud detection.To satisfy the accuracy of cloud detection,it is important to determine the relationship between the response value of the detector and the radiance.We take the Bayer array based plane array color CCD camera adopted by the cloud camera as the research object,analyze its imaging process,and find that the radiation response spectra of R,G,and B channels overlap.Based on this phenomenon,a multi-channel CCD detector radiation response calibration model is established.For the R and B channels used by the cloud camera,the 747 nm LED and 443 nm LED are used as the light sources of the integrating sphere,and the minimum,typical,and maximum values of spectral radiance are set.The absolute radiation response calibration experiment of the cloud camera is carried out under the single light source condition to determine the corresponding absolute radiation response coefficients,and the correctness of the proposed radiation response calibration model is verified under the dual light source condition.This method eliminates the calibration uncertainty caused by the detector response aliasing and effectively improves the accuracy of absolute radiation calibration.