Optical phenomenon when using DOF

[kosso_olli]

Hey guys,
I have an issue here where I'm sure there is a physically plausible explanation for it, but I did not find it yet.
This is a render of some cylinders randomly stacked into the distance, rendered with DOF. As you can see, along the intersection there is this strange "interference", which kinda looks odd. There's also a render without DOF to make it clear. What is this effect called?

[fixeighted]

That's very weird but I just tried and I can see it with 2 pens in an X and held close to my eyes, like a 'cross-eyed' sort of thing, so maybe it's related to that.