An improved image restoration method for the high definition panoramic camera system

Abstract

An improved panoramic annular camera system with very high spatial bandwidth while at compact size that images the surrounding environment through an annular lens to an image sensor in quasi-real time is described here. The image improvements are realized by using a larger annular lens and a larger CCD array. The flat cylinder perspective method, which is adopted by the annular lens, and the mapping relationship between the three-dimensional object spaces and the two-dimensional annular imageries were investigated. The annular images can be transformed into rectangular by an improved panoramic image restoration method proposed here. The calculating basis of that method is the circular image at 90 ∘ viewing angle in the object space, which is always included in the field of view of annular lenses. As the large format CCD requires a light shutter to make it function properly, a dual-layer twisted nematic liquid crystal box was adopted to switch the incident light on and off as a camera shutter built inside the lens assembly. It was the first attempt, to the best of our knowledge, to extend the usage of a liquid crystal box to the camera as a light shutter. The induced lens resolution degradation by the liquid crystal light shutter is not evident and the supporting experimental results are provided. Subsequent digital image processing methods, which are necessary due to that imperfect liquid crystal light shutter, are described here to suppress the transfer smears occurred on the CCD array. At last, a calibration experiment was set up to verify the image restoration method and several outdoor experiments were taken to demonstrate the high quality and rich information in the result images.