I read a US utility patent for some technology where the first claim was a method claim consisting of multiple parts a), b), c), etc. One of those parts specified the range of radiation in which the invention works as something like "wavelengths between about 500nm and about 1000nm" (bolded emphasis mine). My understanding is that whether or not a patent is violated depends on whether any of the claims of the patent are, strictly, infringed upon. But if, as in this case, one of the parts of a claim is worded ambiguously as "between 'about' some value and 'about' another value", then, since this seems subjective ("about" has no technical meaning), how can this be valid, and how are we to interpret this? For instance, would using the same device (that is, a device that strictly satisfies all of the other parts of the method claim) with a wavelength of 1010nm (so does not literally infringe upon one of the parts of the method claim, but fully infringes upon all of the other parts) infringe upon the claim of the patent? What about 1030nm? 1100nm? Etc. And, with regards to the doctrine of equivalents (see my edit), at what point is the doctrine no longer valid, even though you're still violating the triple identity test? Surely there is some value outside of the range of 500 - 1000nm where, even though you're still violating the triple identity test of the doctrine of equivalents, you're not infringing upon the patent? Otherwise, what would be the point of having the patent say "wavelengths between about 500nm and about 1000nm", with those values specifically?

EDIT: I just came across the doctrine of equivalents, from this answer. So, if I'm interpreting this correctly, even if you're not in strict infringement of the patent claim, if your device achieves the same functionality by some “insubstantial” deviation from the claim (see the “triple identity test”), then that is still a violation?


"About" is found in many claims, including range claims like the one you point out. There is a very rich case law and commentary about "about". The first issue would be the meaning of about in the context of the patent. If an alleged infringer was outside whatever that was determined to be then the doctrine of equivalents could come into play.

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