TDI CCD全景航空相机行转移信号产生方法

Generation method of line transfer signal in TDI CCD panorama aerial camera

TDI CCD全景相机照相时需要给TDI CCD施加行转移信号,为了达到相机照相分辨率要求,需保证像速度与电荷转移速度匹配,一般采用固定频率行转移信号或者采用编码器随动产生行转移信号。分析了上述2种方法的不足,提出了以速率陀螺值为基准的行转移信号产生的方法,即根据速率陀螺数据计算分频倍率,依此对高频时钟分频产生行转移信号,并分析了行转移信号的频率偏差对像移的影响。在环境实验室对该方法进行了验证:利用长焦距精密平行光管模拟目标,把相机固定在振动平台上模拟载体的振动环境,相机对靶标成像,分辨率达到62 lp/mm。对比了振动平台静止、振动2种情况下相机拍照图像的分辨率,验证了该方法的可行性。

TDI CCD panoramic camera requires charge transfer signals in one line to finish the TDI transfer. In or- der to achieve the requirements of camera resolution, the image speed and charge transfer speed should be matched synchronously. Generally, it adopts fixed frequency line transfer signal or servo charge transfer signal in one line generated by the encoder. This paper analyzes the shortcomings about the two methods, and proposes new charge transfer signal in one line generation method based on the gyro value, namely by calculating the divider ratio accord- ing to the gyro data and producing charge transfer signal in one line of high frequency clock divider by ratio. Final- ly, the relation between the frequency error of line transfer signal and image motion is analyzed. This new method is verified by Environmental Laboratory. By using long focal length to simulate the target and the camera fixed on a vi- brating platform to simulate carrier vibration environment, the imaging resolution reaches more than 62 lp/mm. This result shows the feasible by comparing image resolutions with static and vibration states of the vibration platform.