Abstract
In this paper, the performance of the electronic conventional image motion compensation (IMC) method based on the time delay integration (TDI) mode was analyzed using the optical injection formula of charge coupled devices (CCDs). The result shows that the non-synchronous effect of charge packet transfer caused by line-by-line transfer during exposure makes the compensated image dissatisfying. Then an improved electronic IMC method based on the CCD multiphase structure was proposed. In this method, a series of proper driving clocks were applied to drive the charge packet to move electrode-by-electrode during the exposure time, which results in a minimum non-synchronous effect of charge packet transfer. The mismatch of velocity between charge packet transfer and image motion was decreased. The performance of the improved electronic IMC method was also analyzed using the optical injection formula. The modulation degrees of the two methods were compared. The average value of the modulation degree of the improved electronic IMC method was 47/96, greater than the conventional electronic IMC method, which was 1/3. To achieve the improved electronic IMC, the driver timing diagram of the improved electronic IMC method was proposed. This paper presented an improved hardware implementation method for the improved electronic IMC method. Based on the basic FTF4052M drive circuit system, an IMC pulse pattern generator that worked together with the main pulse pattern generator (SAA8103) was added to achieve the improved electronic IMC. Then, the internal structure of the IMC pulse pattern generator was given. A dual pulse pattern generator drive circuit system was proposed. After computer simulation and indoor real shot verification, the compensation effect of the improved electronic IMC method was better than the compensation effect of the conventional electronic IMC method.
Highlights
When a charge coupled devices (CCDs) aerial camera takes an aerial photograph, given the high-speed flight of the aircraft, there is relative motion between the camera and the target during the exposure time, which causes the image of the target on the focal plane to change, that is, image motion
The reasons for the displacement can be divided into the forward image motion caused by the forward flight of the aircraft; the random image motion caused by changes in the attitude of the aircraft; aircraft components; camera platforms; and the vibration of the camera itself due to the operation or impact; and the vibration image motion caused by the fluctuation of the air flow
The key problem of the transformation is the design of the Image Motion Compensation (IMC) pulse pattern generator
Summary
When a CCD aerial camera takes an aerial photograph, given the high-speed flight of the aircraft, there is relative motion between the camera and the target during the exposure time, which causes the image of the target on the focal plane to change, that is, image motion. The reasons for the displacement can be divided into the forward image motion caused by the forward flight of the aircraft; the random image motion caused by changes in the attitude (such as pitch, yaw, and rolling) of the aircraft; aircraft components (such as propellers and engine blocks); camera platforms; and the vibration of the camera itself due to the operation or impact; and the vibration image motion caused by the fluctuation of the air flow. In a vertically-photographing aerial camera, the amount of forward image motion is one order of magnitude higher than that of other image motions, so the main consideration with this type of camera is to compensate for the forward image motion [2].
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