Say I saw the present state of a technology not change much in 20 years as a result of a patent. That is, the patent holders failed to innovate. Is there a way for me to start the innovation process? What sort of agreement would I need with the patent holder? And could I get a new patent if my invention was based on but much better than the patented version?
Patents do not stagnate innovation. Innovation rarely (if ever) happens in a vacuum and usually (always?) builds on what's known before. If you can improve on what's is known and the improvement is novel and not obvious, then you can get a patent. In fact, most granted patents are improvement of prior patent.
Usually, innovation starts with
- Building (improving) on patents that you own or already expired, and
- Work around existing patents from competitors
The later is an important skill because companies want to avoid paying licensing fee. Even if you cannot work around an existing patent, there may be incentive to improve on it. For example, if multiple vendors are licensees of the same patent, the vendors will try to make patentable improvement so to differentiate with others.
The definition of "non-obviousness" varies from one field to another. In a crowded field, getting a granted patent becomes difficult, and the patent is usually more limited. Whereas in a field that is relatively new or neglected, getting a patent with broad claims may be possible. It may be worthwhile to read some patents in your field to get general understanding of the state of the art.