Question overlay effect a UI

Hi there!

I really want to do something like this


I want to make this UI image can overlay other 2D Sprite game objects, especially UI things
and take it to blur or something.

is this possible?

I know that we have a render target right, for blur a texture next,
But my game is 2D sprite and a camera is only draw sprites Not UI,
But I also want a UI in my texture too.

Thanks!!!