  Bohr's principle of complementarity predicts that in a welcher weg
("which-way") experiment, obtaining fully visible interference pattern should
lead to the destruction of the path knowledge. Here I report a failure for this
prediction in an optical interferometry experiment. Coherent laser light is
passed through a dual pinhole and allowed to go through a converging lens,
which forms well-resolved images of the respective pinholes, providing complete
path knowledge. A series of thin wires are then placed at previously measured
positions corresponding to the dark fringes of the interference pattern
upstream of the lens. No reduction in the resolution and total radiant flux of
either image is found in direct disagreement with the predictions of the
principle of complementarity. In this paper, a critique of the current
measurement theory is offered, and a novel nonperturbative technique for
ensemble properties is introduced. Also, another version of this experiment
without an imaging lens is suggested, and some of the implications of the
violation of complementarity for another suggested experiment to investigate
the nature of the photon and its "empty wave" is briefly discussed.
