大幅宽长波红外变帧频变焦成像

为了验证变焦扫描大幅宽成像时扫描方向边缘视场图像畸变的矫正效果,并降低扫描镜控制难度。首先分析了变焦成像时扫描镜扫描速度与扫描视场角间非线性变化关系;针对扫描镜变速扫描稳定性低且控制难度大的问题,在结合探测器变帧频分析与实现的基础上,提出采用扫描镜匀角速度扫描结合探测器变帧频变焦成像方法。推导了扫描镜匀角速度扫描时,光学系统焦距、相机实时帧频与扫描成像视场角的关系式。最后基于课题组已有的可连续变焦长波红外光学系统,搭建了一套基于扫描镜扫描成像的大幅宽长波红外变焦实验系统,并利用该系统进行了成像验证。成像结果表明,采用变帧频结合变焦成像方法,可有效抑制大幅宽成像时扫描方向边缘视场图像畸变问题。变帧频成像方法降低了变焦扫描时扫描镜扫描复杂度,证明了变焦扫描方法具备图像畸变矫正能力。

Wide-swath and long-wave infrared zoom imaging method with variable frame rate

This study aims to verify the effect of image-distortion correction on the edge-field-of-view scanning direction in the case of zoom-scanning wide-swath imaging and to simplify the scanning mirror control. First, the nonlinear relationship between the scanning speed of a scanning mirror and the imaging angle of view during zoom imaging is analyzed. With respect to the problem of low stability and the difficulty of realizing control of the variable-speed scanning of the mirror, uniform angular-velocity scanning with a scanning mirror combined with a variable-frame-rate zoom-imaging detector is proposed based on the analysis and realization of a variable-frame-rate detector. Based on the experimental system, the relationship between the focal length of the optical system, the real-time frame rate of the camera, and the imaging field angles at the time of the uniform angular velocity scanning are determined in order to achieve variable-frame-rate zoom scanning imaging. Finally, a wide-swath long-wave infrared (IR) zoom experiment system based on mirror-scanning imaging is constructed using the pre-existing continuous zooming long-wave IR optical system, and the system is used for imaging verification. The results show that by employing a variable frame rate combined with zoom imaging, the image distortion of the edge-field-of-view can be effectively suppressed in the scan direction in wide-swath imaging. The variable frame rate imaging method simplifies the scan-mirror scanning in zoom scanning, and it is confirmed that the zoom-scanning method is able to eliminate the image distortion.