Linearity analysis by quadrupole convolution originated (to the best of the author’s knowledge after a careful web search) in the mid 1980s, when the author’s daytime employer was seeking to diversify its work. The employer set up a group to seek unsolved problems that were important to society. The group was to find innovative solutions for them, that would be suitable targets for the excellent scientific staff. The author, because of his reputation for innovative thinking, was diverted from work as a reactor physicist to work on this group.
A challenge was put to this group, to create a portable device that would read printed text aloud to blind persons. The most difficult part of this challenge was character recognition, and the author developed quadrupole convolution in response to that challenge.
The resources were not available to make the reader, or even to make a complete character recognition algorithm from quadrupole convolution. As the employer sought other applications for the technique, it was kept a trade secret for a couple of years. However, as the legal climate became more favorable to patenting mathematically based inventions, a patent was obtained for the technique.
The employer then shifted its focus more to its core business. The author resumed working full-time as a reactor physicist. When the patent became due for renewal, the employer instead abandoned it. Linearity analysis by quadrupole convolution entered the public domain.
According to web searches, no research has been done on quadrupole analysis, and no use has been made of it, unless it is referred to by very different terms, or kept as a trade secret.
Up to Quadrupole Convolution.