空间相机焦平面CCD交错拼接重叠像元数计算

Calculation of overlapping pixels in interleaving assembly for CCD focal plane of space camera

针对大视场空间相机焦平面采用的多片CCD交错拼接,提出了一种适用于多种姿态模式的重叠像元数解析计算方法,以保证空间相机成像视场中不出现漏缝。分析了CCD交错拼接的成像特性和产生漏缝的原因;基于空间坐标系变换和中心投影共线方程建立了重叠像元数计算模型,对像点、相机摄像中心、地面景物点建立动态数学关系,通过追踪像点在像面上的运动轨迹计算了拼接缝像元重叠情况。结合实际工程样例,计算和分析了空间相机机动角度、星下点纬度、视场位置等因素对重叠像元数的影响,并将各工况下计算的最多漏像元数作为最终拼接量。结果表明:重叠像元数理论误差小于1pixel;对比侧摆,俯仰成像时所需拼接像元数更多;该计算模型可扩展应用于其他类型空间相机在任何姿态模式下的重叠像元数计算。

The focal plane of a wide-field space camera is comprised of several staggered Charge Coupled Device（CCD） detectors. To eliminate the gap in imaging field of the space camera,this paper proposes an analytic calculation method for overlapping pixels applied to multiple maneuvering angle modes. The imaging characteristics of CCD interleaving assembly and the reason that imaging gaps appear were analyzed. Then, the calculation model for overlapping pixels was established by combining space coordinate transformation with a collinearity equation. The dynamic mathematical relationship of the image point, camera center and the ground point was established. The overlapping pixels between adjacent CCDs were calculated by tracing the locus of image point on the image plane. With an engineering example, the influence of maneuvering angle , subastral latitude and the field location of the space camera on overlapping pixels was calculated and analyzed and the maxmum number of gap pixels calculating among different working situations were considered as mechanical assembly numbers. The result shows that the theoretical error of the number overlapping pixels is less than 1 pixel. Comparing with scrolling imaging, the pitching imaging needs more number of assembly pixels. The computing model can be applied to other space cameras of different types, and the overlapping pixels can be calculated at any attitude mode.