On-Orbit Real-Time Variational Image Destriping: FPGA Architecture and Implementation

On-orbit real-time image processing is of increasing demands due to requirements for quick-response missions. Image destriping is usually an important pre-processing step to improve image quality in practice. The unidirectional variational models have shown impressive destriping performance. However, they are not easy for real-time implementation for high-computation complexity and there are few attempts for hardware implementation. This article is the first hardware implementation of variational image destriping algorithm, which achieves high throughput for large-swath remote-sensing images. In this article, a fully pipelined hardware architecture is proposed. First, the involved iteration loop is unrolled and a coarse-grained parallelism is obtained. Second, for each deployed iteration computation blocks (ICBs), a dedicated timing arrangement is designed to alleviate the bottleneck caused by the data dependency within each ICB, obtaining a fine-grained parallelism. Moreover, to further optimize the critical path, an approximate simplification scheme is proposed, saving the resource usage and reducing computing delay. The proposed architecture is implemented and verified on a XILINX 6vcx240t field programmable gate array (FPGA); it achieves a maximum frame rate up to 41.9 frames/s with delay of only tens of row cycles for 8-bit ${{2048}} \times {{2048}}$ images. It performs all the processing on the pixels in raster scan order on- the-fly as they are being transmitted from camera payload, which significantly facilitates on- orbit real-time processing of large-swath remote-sensing images with high data rate.