Centred static image as post processing material

How can I create a post process material similarly to the one shown in the attached pictures? It contains an immobile image at the center of the screen. Whatever the angle you look at the scene, the image remains at the same position.

The reasons why I need that are difficult to explain. I can only say it’s for a scientific experiment.

Nice and simple.

This would have been quite easy to figure out if you had googled the term, screen aligned texture in UE4. Good luck next time!