采用单帘式快门配合CCD增益控制曝光量的调光方法, 设计了面阵CCD相机的调光系统, 以使面阵CCD相机在宽照度视场范围和较短的拍照周期内获得正确的曝光量。分析了航空成像传输过程中的影响因素, 结合单帘式快门的曝光原理推导出曝光量的数学表达式。通过确定CCD的最佳曝光量, 建立了快门狭缝速度、CCD增益和目标照度之间的对应关系。然后, 由光电池采集地面目标的照度信号, 根据采集的信号控制狭缝速度和CCD增益。最后, 测试了快门辊轴的稳速精度。结果表明, 对系统分别输入6 300、4 170和1 200 r/min的阶跃输入信号时, 快门的稳速精度达到0.033。根据得到的稳速精度并考虑快门的曝光量误差, 得到快门的曝光精度为0.091。在实验室进行了地面照相试验, 测试系统获得的曝光量为1 833 DN, 计算得到的系统曝光精度为0.066。结果显示利用单帘式快门和CCD增益相结合的方法能够使CCD获得正确的曝光量, 捕获的图像满足使用要求。

To obtain the perfect exposure in a wide illuminance range at a short period, an adjustable exposure system was designed for an area CCD camera in combination of a single curtain type shutter with controlling exposure by CCD gain. The effect factor on aero photographing process was analyzed, and a exposure expression was work out according to exposure principle of the single curtain type shutter. After confirming the optimized exposure amount of a CCD, the relationship among the slip rate, CCD gain and the illuminance of the ground target was established according to the exposure expression. Furthermore, the signal of a ground target illuminance was collected by a photosensitive resistance, then the signals were used to control the slip rate and the CCD gain. Finally, the rate accuracy of shutter roll shaft was tested at the input rates of 6 300, 4 170 and 1 200 r/min, respectively. The result shows that the rate accuracy of shutter is 0.033, and the exposure accuracy is 0.091 according to combination of the computation results and exposure errors. A ground test on photographing was performed in a laboratory, and the results indicate that the exposure amount obtained is 1 833 DN and the exposure accuracy is 0.066. These results demonstrate that the method proposed can allow the CCD to obtain a proper exposure and captured images can meet the demands of CCD cameras.