my US4000 DQE update , MTF same to Niko's US4000, but NPS quite a big difference
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the new version can work well for my US4000 data, but compare to the NPS curve of Niko's US4000, my NPS too low, that's maybe abnormal. my pixel dose is 56e/pixel. 300kV FEG.
How can I improve it? lower dose and longer exposure time?
The first think I would check
The first thing I would check is your calibration of the exposure. Secondly, make sure that the software you use does not secretly apply a scale factor to your image after it is read out of the detector.
negative NPS-fit number?
In reply to The first think I would check by niko
Why are there some negative NPS-fit number? like below:
******************************************************
Frequency MTF NPS NPS-Fit DQE
0.000000 1.000000 2.000000 1.000000 0.005349
0.000488 0.999927 2.000000 0.877498 0.006095
0.000977 0.999707 2.000000 0.764801 0.006990
0.001465 0.999343 2.000000 0.661547 0.008075
0.001953 0.998838 2.000000 0.567376 0.009406
0.002441 0.998193 2.000000 0.481926 0.011059
0.002930 0.997414 1.513050 0.404837 0.013144
0.003418 0.996506 0.589235 0.335748 0.015820
0.003906 0.995475 0.419322 0.274297 0.019324
0.004395 0.994327 0.111012 0.220125 0.024025
0.004883 0.993069 0.116879 0.172869 0.030515
0.005371 0.991709 0.069121 0.132170 0.039802
0.005859 0.990256 0.056090 0.097666 0.053705
0.006348 0.988717 0.073075 0.068996 0.075785
0.006836 0.987100 0.049601 0.045792 0.113816
0.007324 0.985416 0.054642 0.027606 0.188151
0.007812 0.983671 0.064607 0.013948 0.371064
0.008301 0.981875 0.042433 0.004328 1.191367
0.008789 0.980035 0.029872 -0.001744 -2.945979
0.009277 0.978160 0.033248 -0.004759 -1.075316
0.009766 0.976258 0.023643 -0.005209 -0.978774
0.010254 0.974335 0.021880 -0.003582 -1.417697
0.010742 0.972398 0.023499 -0.000370-13.680303
The noise power spectrum
In reply to negative NPS-fit number? by Kunpeng
The noise power spectrum estimate at very low resolution is quite noisy due to the small number of Fourier pixels that contribute there. This does not affect the DQE calculation at higher resolution that most people care about.