衛星遙測系統之影像處理軟體與介面硬體設計

Abstract

在現今的衛星遙測系統上高解析度影像重組與處理技術扮演很重要的角色。本研究展示一個影像重組與處理系統，具有處理多個一維(直條狀)的CMOS影像感測器之能力。此系統的優點在於可隨衛星線性移動特性來控制CMOS影像感測器合理的曝光時間並提供即時的高解析度影像。 此系統的主要功能包含使用ICAI (Image Combiner and Acquisition Interface) 晶片來處理CMOS影像感測器的原始資料、於顯示器即時顯示影像、儲存影像與影像後處理軟體。ICAI晶片的功能在於同時處理多個直條狀的CMOS影像感測器資料流以及控制CMOS影像感測器動作。顯示與儲存影像是由一個FPGA 開發板以硬體完成。此FPGA 開發板同時整合了ICAI與其他週邊裝置，成為一個簡單的嵌入式系統，此嵌入式系統可獨立完成從影像擷取到存檔的動作。 此系統的另一個部份為影像後處理軟體。因為此系統使用多個CMOS影像感測器以建構高解析度影像，在封裝多個CMOS影像感測器的過程中，會造成一些影像的失真，主要原因在不同CMOS影像感測器之間的特性差異與封裝誤差。此影像後處理軟體提供一個在PC上運作的解決方案。 此軟體也提供了影像壓縮的功能，主要是可將嵌入式系統儲存的Bitmap檔案轉換為HD Photo檔案，HD Photo是由微軟提出的高壓縮比與高影像品質的影像格式，應當非常適合使用在此具有高存儲容量需求的衛星影像上。

High resolution image combination and processing plays an important role in today’s satellites’ remote sensing application. The study presents an image recombination and processing system for one-dimensional multi-strip CMOS image sensors. The proposed system takes advantage of satellites’ linear moving property to control exposed time of CMOS image sensors and provide the real-time ability to generate high resolution image. Briefly, the main functions of the system are processing image raw data by ICAI (Image Combiner and Acquisition Interface) chip, displaying image to VGA port, saving image file and post-processing image file in software. The multi-strip CMOS image sensors capture image and send signals to ICAI chip. The data stream and control of CMOS image sensors are dominated by ICAI chip. The VGA output and data processing are implemented on a FPGA development board. The FPGA development board integrates ICAI and necessary peripherals as an embedded system. The embedded system could independently complete the job from capturing to saving image. The other part of the system is a software of image post-processing. Because the system uses multiple CMOS image sensors to construct larger image, there are some issues after packaging multiple sensors. The main issues are characteristics variation among sensors and package mismatch. The post-processing software provides a PC-based solution to overcome these problems. The software also provides a function of image compression. The function is converting bitmap file to HD Photo file. HD Photo is a high compression rate and high quality image format developed by Microsoft Corporation. The advantages of HD Photo are very suitable for lager storage request in satellites’ application.