Just found this also:
http://electronicdesign.com/components/consider-all-factors-when-selecting-proper-inductive-proximity-sensor
This article definitely helps me realize I have to utilize the right sensor and design. I have a specific goal of detecting one type of object, so it should be pretty easy :~. I just have to understand the principles on how these types of sensors work, and go from there. Any insight would be appreciated!