The double slit experiment and the delayed choice quantum eraser experiment.?

Can anyone explain HOW physicists eliminated the "measuring device" from being the cause of the collapsing wave function? I understand the conclusion, "observation" caused the change from wave band pattern to 2 single bands in the double slit experiment, but how did they eliminate the photon detector as being the cause? And can anyone explain the "delayed choice quantum eraser" experiment and the implications of it. There is just too much crap to sort through in WIKI and of all my physics books, none of them explain the quantum eraser experiment (and delayed choice q.e.). I am studying physics and quantum physics in my spare time but would really love these 2 concepts explained a little better.