航空相机的自准直自动检焦方法研究

Autofocusing method with automatic calibration for aerial camera

针对航空照相在高空中会由于温度、气压等环境参数的变化引起光学系统离焦的现象,设计了一种利用自准直原理实现自动检焦的结构。分析了光栅常数与反射镜摆扫速率、接收元件响应时间的关系,研究了光栅的刻线方向在焦平面上的摆放位置和不同光源参数对检焦精度的影响。试验结果表明,自动检焦的焦平面位置与实验室光学标定的焦平面位置的偏差<1/3半焦深,满足使用要求,并在动态飞行试验中获得了良好的图像。该方法可推广于带有扫描反射镜的航空相机的检焦设计与研究中。

For the defocusing phenomenon caused by the changes of temperature, pressure and other environment parameters in optical system for a aerial camera in the air, an autofocusing method with automatic calibration was introduced, and the relationships of grating constant,the whiskbroom velocity of reflector and the response time of received component were analyzed, The effect of the position of grating direction on focal plane and the difference of light-house performance on calibration precision was researched. Experimental results indicate that the focal plane position tested by proposed autofocusing method is close to that tested by other automatic calibration methods in lab, the error is less than 1/3 half focal depth（0.05 mm）. A vivid image has been acquired in dynamic imaging test,which shows proposed method can be used in autofocusing for various aerial cameras with scanning mirror.