I recently came across a journal article that included and referenced a figure (photograph) from a US patent. I found the patent, and I would like to use the same figure, and I'm wondering who the copyright holder is. Might it be free to use since the patent itself is public, or do I need to ask around until I find the copyright holder?
It depends on how the figure is being used. If it is for non-commercial purposes -- e.g., in a scientific journal to support a study -- then it will likely fall under the 'fair use' provision. If it is for commercial purposes, such as a book that you are seeking to publish, then it is likely considered commercial purposes, and you will need to work out the permissions.
I have always felt that directly re-using (i.e., copying) anyone's figures in any work, including student papers, is dubious practice even if cited. If students re-draft figures and cite them properly, this seems just about acceptable for undergraduate work. For almost any other purpose, however, I think substantial modification of the figure is necessary.