Flowchart of the iterative nonlinear filtering algorithm for denoising HR(S)TEM images.
4. Performance of the nonlinear filter
4.1. Simulated images
Tests were made to investigate the performance of the nonlinear filter in noise Aprotinin and quantification of the simulated HR(S)TEM micrographs. Fig. 4a shows the nonlinear filtered image of the testing HRTEM image of the MgO super cell (Fig. 1c). No noticeable peak attenuation and artifacts are seen in the error image (Fig. 4b). For comparison, Fig. 4c shows the details at the dislocation core from the Poisson noise included (S+N), noise-free (S), nonlinear (NL), Wiener (W), and Gaussian low-pass (G) filtered images. All images are in the same scale, except for the image with noise (S+N) the scale is Casparian strip set for optimal contrast. The Wiener filtered image exhibits obvious artifacts around the dislocation core (Fig. 4c), whereas profile analysis reveals profound peak intensity attenuation in the Gaussian low-pass filtered image (Fig. 4d). In contrast, the nonlinear filtered image is more accurately representing the noise-free image even at the dislocation core.