平场定标是空间相机研制过程中必不可少的定标项目。目前,普遍使用均匀照明目标进行空间相机的平场定标,而该方法由于依赖于目标的均匀性,其应用存在一些缺陷。提出了一种基于非均匀目标的平场定标方法,摆脱了对目标均匀性的依赖,具有实际应用价值。首先,基于多幅非均匀目标图像像元灰度的相关性,建立了相机像面响应度分布计算模型;采用最小二乘迭代法对该模型进行了求解,并编写程序进行仿真验证,验证结果表明,在图像信噪比高于25 dB的情况下该方法定标精度优于0.5%;最后,根据该方法的特点,给出了实际定标试验的操作流程。

Flat field calibration is an essential calibration project for space camera. At present the uniform illumination target is generally used to fulfill space camera′s flat field calibration, but this method is limited in application because it relies on the uniformity of the target. A new flat field calibration method was proposed based on the non-uniform target. This method has a great practical value as it is no longer dependent on the uniform target. At first, a responsivity distribution calculation model of the camera image plane was established based on the pixels gray correlation of multiple non-uniform target images. Then by using the least-squares iteration method, the calculation model was solved. Meanwhile, a simulation program had been developed to test this calibration method. The test results show that the new calibration method′s precision is better than 0.5% when the image signal-to-noise ratio is higher than 25 dB. Finally, based on the characteristics of this method, a practical calibration process has been proposed.