Ptychography

What it tells you: as with DPC you get an image of your overall sample, with added resolution

Ptychography uses overlapping measurements and computation to produce a higher resolution image. For this technique, we automatically place the sample at ~800 µm out of focus, generating a bigger (but less coherent) beam of ~1.5 µm ² size.

This image is based on phase contrast and can be helpful for imaging structures that can be seen in DPC at higher resolution. Due to the mathematical retrieval algorithms used, the pixel size of the phase reconstructed image is not limited to the size of the beam, what may lead to the acquisition high resolution images, down to ~20 nm per pixel (energy dependent!).

Please note that ptychography is not a routine technique yet, but we encourage users with different samples to acquire some ptychography scans on their samples, should the DPC images described above look fine.

Things to consider:

Post-processing – Getting the best image can be highly sample specific. You may need to do some re-processing to optimise the computation. Nonetheless, we currently offer a “user friendly” system that automatically triggers different post-processing retrieval algorithms all at once. That allows the users to visualise several phase images in about ~1 hour after submission.

Signal – Too thick or too thin samples can result in a poor reconstruction.