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实验方案示意图如图3所示,系统和实验设置的参数如表1所示。采用
$ 512\times 512 $ 中波红外探测器进行验证(响应波段3~5 μm),分别对自由下落的水滴和运动的烙铁成像。通过水滴成像实验验证开窗减小成像帧间间隔和降低占用数据带宽的性能,通过烙铁成像实验验证文中所提DW方法的目标运动轨迹预测性能。配置探测器采用双通道、边积分边读出的工作模式下,并将阈值信噪比设置为3。Parameter Value Parameter Value Pixel/μm 30 Angular velocity/(°)·s-1 290 IFOV/μrad 345 Radius/cm 10 Readout noise/e- 3174 Focal length/mm 87 Full well capacity/Me- 13 Object distance/cm 83 Table 1. Parameters of detector and optical system & parameters of experimental setup
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设置探测器分别工作在
$ 512\times 512 $ 全视场和$ 256\times 32 $ 开窗两种方式下,对自由下落的水滴成像,减去背景后的图像输出结果如图4所示。其中图(a)为帧频30 Hz时连续4帧(0.13 s)的成像结果,图(b)为帧频810 Hz时连续12帧(0.015 s)的成像结果。目标的帧间运动距离和占用数据传输带宽对比如图5所示,全视场成像时相邻两帧的目标平均运动距离为102.84 pixel,开窗后相邻两帧的目标平均运动距离为2.38 pixel,平均距离减小了43倍。相较于全视场,开窗可获取更为密集的目标运动轨迹坐标。而开窗后数据量从16.15 MB/s下降到13.24 MB/s,去除了冗余数据2.91 MB,占用带宽降低了18%。Figure 4. Detection imaging results of water droplets. (a) Full field of view imaging; (b) High frame rate imaging with window openning
全视场与DW方法对烙铁成像的实验结果对比如图6所示,图中(a)为传统全视场探测30 Hz。目标的质心坐标和运动轨迹分别如图7(a)、(b)所示,图中的纵轴代表目标质心位置的坐标,横轴表示该坐标来自探测器获取到的第N帧图像。全视场探测时相邻两帧图像间目标的运动距离较大,在
$ {T}_{0}\sim{T}_{1} $ 时间段内仅能获取一组目标位置坐标,获取的目标运动坐标较为稀疏,而采用文中提出的DW方法,系统平均工作帧频为480 Hz,在$ {T}_{0}\sim{T}_{1} $ 时刻可获取15组目标位置坐标。相邻帧的平均目标运动距离分别为64.13 、4.81 pixel,点密度扩展了约16倍,探测时间灵敏度有了较大提升。且传输数据量为12 MB/s,占用带宽降低了25%。Figure 6. Detection imaging results of electric soldering iron. (a) Full field of view imaging; (b) DW method imaging
Figure 7. Target centroid coordinates and predicted trajectory error. (a) Target centroid coordinates acquired by the full field of view method; (b) Target centroid coordinates acquired by the DW method; (c) Error of trajectory prediction of the full field of view method; (d) Error of trajectory prediction of the DW method
运动轨迹预测曲线如图7(c)、(d)所示,为了更直观地展示预测误差随时间的变化情况,将预测误差的数值放大了100倍。采用文中提出的DW方法在预测运动轨迹时,前10帧的估计误差较大,但随着获取到的目标信息增加,较高的轨迹点密度为预测器提供了更多的迭代次数,使得误差降低了一个数量级。经过多次迭代修正后运动轨迹水平和垂直方向的预测误差分别从0.395、0.789下降到0.084、0.014。
为进一步评估文中方法对目标运动轨迹预测的性能,采用最小二乘和RANSAC算法对获取的目标质心坐标进行拟合[19],RANSCA的假设模型为圆周的运动模型,对所有轨迹点随机抽样得到支持率最高的模型并舍弃外点以去除图像质心提取时引入的误差。得到的参考目标运动方程如公式(15)所示,分别将传统全视场和DW方法获取的坐标代入运动方程(21),利用公式(19)计算目标圆周运动半径估计值的均方根误差。
利用两种方法获取的坐标分别拟合得到其各自的运动轨迹如图8所示,生成1000组坐标计算预测运动方程与目标实际运动方程(21)的弗雷歇距离计算结果如图9所示,采用文中提出的DW方法,使得圆周运动半径的估计误差由0.82838降为0.05697,估计精度提升了14.5倍;预测的目标运动轨迹与实际轨迹的弗雷歇距离由8.89711下降到3.37335,轨迹预测精度提升了2.6倍。
Fast motion target information acquisition method based on dynamic window opening
doi: 10.3788/IRLA20210164
- Received Date: 2021-02-27
- Rev Recd Date: 2021-06-03
- Publish Date: 2022-04-07
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Key words:
- infrared detection /
- dynamic windowing(DW) /
- fast moving targets /
- trajectory prediction
Abstract: The trajectory prediction of infrared moving target is widely used in military and civilian fields such as monitoring and space-based remote sensing detection. When the relative velocity of the target is much higher, influenced by the fixed readout rate and integration time, the target trajectory points obtained by the traditional full field of view imaging information acquisition method are sparse, and it’s difficult to meet the accuracy requirements of target trajectory predication. To address this problem, an information acquisition method for fast moving targets based on dynamic windowing(DW) was proposed. The observation area was first imaged with full field of view, and after capturing the moving target, the target and its neighbors were imaged with a window to increase the frame rate. The discriminant matrix was obtained by analyzing the influence of the radiation characteristics of the detection scene on the working parameters of the system, and the dynamic adjustment of the window opening parameters was realized and the density of target trajectory points was enhanced. Finally, the window openning position was updated using the target trajectory prediction results to achieve the full-field coverage monitoring of a single target. The experimental results show that for the mid-wave infrared demonstration system, the method increases the target trajectory point density by 16 times and the system trajectory prediction accuracy by 2.6 times compared with the full field of view imaging information acquisition method. And the required data transmission bandwidth is reduced by 25%. This study can provide useful reference for the design of intelligent infrared sensing systems.