Quantitative Image Quality Improvement Method Based on On-Orbit MTF Test
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原文链接
NETL
NSTL
维普
万方数据
针对TDI推扫型光学遥感载荷在轨工作时可能出现的垂轨或沿轨方向图像质量下降现象,提出一种基于在轨MTF测试的单方向可定量图像质量提升方法.首先,采用刃边法测试得到沿轨和垂轨两个方向的MTF曲线,选取从零频到奈奎斯特频率范围内的n个不同频率点,根据MTF目标值与实测值的比值确定各选定频率点的MTF提升倍数,依据频域响应特性并以提升倍数作为频域响应幅值构建空域卷积函数,同时结合在轨实测信噪比(Signal to Noise Ratio,SNR)构建抑噪函数,在确保SNR的前提下实现的MTF的定量提升.根据在轨试验验证结果表明,按照所提方法进行图像质量提升,在噪声抑制阈值 0.5 dB范围内,垂轨方向MTF基本不变,沿轨方向奈奎斯特频率点的MTF提升 2.51 倍,获取的图像清晰度提升 8.33%,证明该方法可有效实现定量图像质量提升.
In this paper,a single direction quantitative image quality improvement method based on on-orbit MTF test is proposed to improve the image quality due to the phenomenon that the image quality of the TDI push-sweep optical remote sensing camera may decrease in along-track or vertical track.Firstly,the MTF curves in both directions were tested by the edge bar method.N different frequency points in the range from zero frequency to Nyquist frequency were selected to determine the MTF improvement multiple of each selected frequency point according to the ratio of the MTF target value to the measured value.The spatial convolution function was constructed according to the frequency domain response characteristics and the lift multiple was taken as the amplitude of the frequency domain response.At the same time,the noise suppression function is constructed based on the on-orbit measured signal-to-noise ratio(SNR),and the quantitative improvement of MTF is realized under the premise of ensuring SNR.According to the verification results of the on-orbit test,the image quality is improved according to the proposed method.Within the noise suppression threshold of 0.5 dB,the MTF of the vertical rail direction is basically unchanged,the MTF of the Nyquist frequency point along the rail direction is increased by 2.51 times,and the clarity of the obtained image is improved by 8.33%,which proves that the method can effectively achieve quantitative image quality improvement.
NETL
NSTL
维普
万方数据
