What is the doctrine of equivalents?
The doctrine of equivalents relates to the issue of whether some product infringes a patent. For a product to be infringing, it must contain every element of at least one of the patent’s claims. However, the doctrine of equivalents slightly broadens this requirement by stating that a patent can be infringed, even if every element of the claim is not present in the invention, if the invention does the same thing as the patented invention in substantially the same way (thus, the infringing product and the patented invention are equivalent). The purpose of this doctrine is to ensure that someone does not try to avoid patent infringement by making an insignificant alteration to the patented product. However, a substantial change to the product may be enough to avoid application of the doctrine of equivalents.