  In this technical note, we complete the PhD work of A. Esterle about
determining the image of any Artin group of finite Coxeter type inside the
associated Hecke algebra over a finite field, when the latter is semisimple.
The only remaining case was the 48-dimensional irreducible representation in
type $H_4$, for which the image is proven here to be $\Omega_{48}^+$.
