There are two types of patent infringement: literal infringement and Infringement under doctrine of equivalents.

If a product has differences from the patented invention, the working of the product does not literally infringe the patent right according to the patented invention. However, provided that it is estimated that the product is substantially identical with the patented product, the patent right would be infringed by the product under the doctrine of equivalents. (see H6 (O) 1083)