X-Ray and Laser Imaging using iterative methods by Osman Omar

On my in2scienceUK Placement, I studied ptychography and worked with laser imaging with a PhD student, Stefanos Chalkidis. During my placement, I scanned various different things such as a piece of mica, glass, a sample from a colleague and a wing from a dead fly.

First, we set up the sample by attaching it to a glass substrate using tape and then mounted it to the sample stage which was in a blackout box along with the camera used to capture the image, a diffuser and the laser itself. Next, we received a live feed of the sample on a computer from which we then took various different types of scans, such as ROI scan, which takes images of the sample in a circular pattern within a region of interest, a flat scan which takes images of the background alone without any sample present and a dark scan which takes images with the laser turned off.

Next, we used the data from the scans and by running various different python scripts, we formed reconstructions of our scanned object which we then further analysed. The reconstructions were performed by using two algorithms in succession for which we could choose how many iterations we wanted to run. We used two different amounts, 500 of each algorithm for one reconstruction and 2000 for another, and compared the differences. We also changed the position of the diffuser to see how that would affect our results and what changes we would get.

Here is one set of our results: The insect wing; diffuser at 250mm, original position, closest to laser.


The left image shows the transmission image of the object, whilst the middle image is the phase change of the object and the right image depicts the phase change of the illumination. We also moved the diffuser to 240mm and here are our results:


Here are our set of results when analysing the mica:


I also went to the Diamond Light Source, located in Harwell, which is a synchrotron. Electrons are sped up and accelerated there in a circular pattern to near light speed, from which then X-rays and other lights are emitted. These beams are then directed off into laboratories or beamlines so they can be used for experiments and research such as new medicines or cutting-edge technology. I was given a tour of the building and met scientists who worked with my supervisor in his field of research, which is near-field ptychography.