Camera falls into a character pawn mesh

I have a pawn and a camera into its blueprint, binded to pawn mesh by spring-arm component.
Player can rotate camera around the pawn at any direction. distance (== min spring arm length) was equal to a bounding sphere radius. And I had no problems.

Problem: But now I want to set distance from pawn to a value which is less than those sphere radius (I need it to let the player to examine small elements of the pawn).
So now camera at some its positions may falls into a pawn mesh.

Question: How to prevent this falling into a mesh?
I searched some option in camera or it pawn mesh. But did not find anthing useful.

In details of mesh there is Collision section. But even if I choose Block Camera (see screenshot) it does not give me wanted effect.