Here is another, (but similar,) approach... but combining both possible definitions of "objet" in the original context:
An expression transformed into an object
(used to surreal effect, in avant-garde art.)
Note: "surreal" is used here to demonstrate a different approach for that part of the translation, though, something having to do more with the word "illusion" would probably be more accurate.
Also, (and as already noted in the comments on the question,) this part:
It depends on the represented target, doesn't seem to be in the original writing.
As long as the definition fits with the definition of "objet" in French, the translation into English should be fine.