| As the main component of controlling exposure time, the aerial camera shutter is a key factor to decide the imaging quality. Under the traction of aerial imaging demand, the aerial camera shutter is increasingly mature and has now developed into a variety of shutter to meet the requirements of the camera imaging components. Due to the development of a late start, there is a large lap compared with foreign, especially in the demand of focal plane shutter in the array CCD camera. In fact, the focal plane shutter has become the bottleneck of the development of plane array CCD camera.According to the different of assembly position and motion characteristics in the optical system, the camera shutter can be divided into two types of objective lens shutter and focal plane shutter. An electromagnetic vertical-travel focal plane shutter is developed for a certain plane array CCD camera, which can be used to solve the high-frequency and large format shutter problem. The shutter frequency is 3 frame per second, the shortest exposure time is 1/500 seconds, and the exposure uniformity is better than 10%. The shutter has a small, wide-format(48mm×36mm), high-frequency, long life and other characteristics, and with automatic tightening, automatic release, automatically adjusts the exposure time and other functions. The shutter is mainly composed of two sets of front and rear curtain, each consisting of four blades. The exposure slit can expose the photosensitive medium which is formed by the edge of the front curtain and the rear curtain blade group.In this paper, the structure parameters and the driving spring parameters have a great influence on the movement characteristics of the shutter, which directly determines the exposure time and exposure uniformity of the shutter. The shutter blade motion mathematical model and exposure time mathematical model are deduced, and the shutter exposure time distribution and light efficiency in each position of the entire imaging format is given by the simulation analysis. The dynamic analysis of the shutter is carried out by ABAQUS software and the motion of shutter blade is simulated. The shutter blade motion mathematical model is further validated, the stress changes of the shutter blade is analyzed, and the vulnerable parts of the shutter blade are predicted, which provides the basis for the design of shutter structure, parameter optimization and modification.In order to analysis the influence of the shutter exposure on optical transfer function, the static optical transfer function of the optical system in different position is analyzed, and the influence of illumination changes and shutter motion on the optical transfer function are analyzed. The analysis results show that the influence factors which can reduce the impact of the shutter movement on the optical transfer function are the shutter curtain can be as close as possible to the image plane, the increase of the exposure slit and the speed of the shutter movement.The influence of shutter slit on the image distortion in the exposure process is analyzed, combined with the work characteristic of the curtain shutter, the image distortion of camera is as a result of image motion compensation residual and time-exposure. when there is no variation of the attitude angle of the camera, the image motion compensation velocity residuals and image distortion mathematical model are deduced in the vertical, roll, pitch three imaging mode. When the attitude angle of the camera is changed, the image motion compensation velocity residuals and image distortion mathematical model are deduced. And the distribution of the image motion compensation velocity residuals and image distortion in each position of the entire imaging format is given by MATLAB software.Finally, the shutter exposure time is tested and the analysis method and results are verified through the shutter exposure time test and the image distortion test. The test results show that the performance of the shutter can meet the requirements of the camera. |
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