Perspective and Vision

[sakekasi]

I have managed to get code working to recognize the reflective tape rectangles working with the NI labview assistant, but have no idea how to proceed with the problem of side(azimuthal) angle. The assistant provides no way for me to recognize trapezoids and I cannot correct for the perspective in the image as far as I know. How would I go about recognizing the targets from a reasonable angle to the left or right?