OK, thank you guys, your replies do help me, in fact, I have a crazy idea, I'm considering to build a "fusion type night vision", like the "nanovision" in Crisis for my personal interests, I plan to use the following hardware:
1. A HMD, for main display, must be HD and wide-angled.
2. 2 webcams, one front as main camera, one for rear sight, both for capturing real-time scene around. Front one must be HD and wide-angled, can detect both visible light and near-infrared, maybe autofocus for better image.
3. A thermal image camera, for capturing far-infrared, I want it to be 320*240@30Hz or higher, wider FOV is better.
4. A console, using to process images from 3 cameras, combine the image from the front webcam and thermal imager together to show a fusion image, zoom to real size as human eye sight, show rear camera scene on the corner, perform digital zoom for cameras, recording videos, mark objects in the image(people faces for example), and display system information(such as battery, tempreture...). I'm not sure whether I should use a UMPC like OQO, or use a raspberry Pi, but I know little on programming so maybe I can't run these on a ras PI.
5. A helmet, mounting the cameras.
This is just in planning now, I have to wait to have enough money, and the software maybe also a problem for me. I'm happy to hear your guys opinions.