MTF Evaluation
The modulation transfer function (MTF) is defined as the discrete Fourier transform of the line spread function. Thus, given the LSF, the MTF is approximated numerically. This data is graphed against the spatial frequency data. A sixth order polynomial is fitted to the MTF vs. spatial frequency curve to remove any trends. The 50% cutoff frequency is determined to yield the corresponding spatial frequency. Thus, the approximate position of best focus of the unit under test is determined from this data.
Read more about this topic: Modulation Transfer Function (infrared Imaging)
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