The lobster eye consists of square channels arranged into a spherical array.
Light reflecting down the channels forms a cross shaped image.
The geometry behind the reflections is shown below. In order to apply lobster eye optics to some x-ray applications, we must make a spherically curved array of square channels. It is also convenient if the size of individual channels is small. Using the same technology, square channel MCP's are now being made with channel sizes down to 10 microns. In the lobster eye geometry it is possible to arrange for the x-ray reflections to occur at very small angles.