星上多通道遥感图像的实时合成压缩

Composition and compression of satellite multi-channel remote sensing images

针对星上图像整合电路工作频率过高而造成的成像系统工作不稳定的问题,讨论了相机结构的改进,提出了一种基于现场可编程门阵列(FPGA)平台实现星上时间延迟积分CCD(TDICCD)遥感图像实时合成压缩的方法。介绍了星上多通道遥感图像实时合成压缩的原理。针对TDICCD线阵推扫成像模式的特点,使用改进的JPEG-LS压缩算法;通过自适应量化动态地控制码率,在FPGA硬件平台上实现了图像数据的实时合成压缩。试验验证结果表明,在无损压缩和2倍压缩时,系统主时钟从原来的100MHz分别降低为80MHz和64MHz,整合电路的工作稳定,恢复图像的峰值信噪比(PSNR)满足大于80dB的要求。提出算法的存储量小,处理每行的平均时间为57.5μs,小于相机的最小行周期63μs,满足实时性要求。本文系统可靠性高,算法稳定,实现了星上多通道时间延迟积分CCD相机内部的实时合成压缩。

To improve the understable imaging system caused by the high work frequency of image composing circuit on a satellite,the structure of a camera was innovated.A composion and compression method of Time Delay Integration CCD（TDICCD） based on a Field Programming Gate Array（FPGA） platform was proposed for satellite remote sensing data.The principle of real-time compostion and compression for multi-channel satellite remote sensing data was introduced.Then,based on the characteristics of TDICCD linear array push-broom imaging mode,the improved JPEG-LS was used.By taking adaptive quantization to control the coding rate dynamically,composion and compression of image data were simultaneously achieved on the FPGA.At last,an experiment platform was established for the validation.Experimental results indicate that the system clock has reduced to 80 MHz and 64 MHz,respectively,from the original 100 MHz in the lossless and 2-time compression and the Peak Signal Noise Ratio（Reconstruct PSNR） of the image is higher than 80 dB.As the proposed algorithm has low storage capacity,the average processing time of one line image is 57.5 μs,smaller than the smallest line period of the camera.The proposed algorithm is stable and the system is reliable and achieves the composion and compression of multi-channel TDICCD remote image within the camera.