  We consider a quantization of relativistic wave equations which allows to
treat quantum fields together with interacting particles at a finite time. We
discuss also a dissipative interaction with the environment. We introduce a
stochastic wave function whose dynamics is determined by a non-linear
Schr\"odinger-type evolution equation in an additional time parameter.
  The correct classical limit requires the proper time interpretation of the
time parameter. An average over the proper time leads to the conventional
quantum field theory of particles which are free at an infinite space
separation. We consider models with scalar and vector fields on a
pseudoriemannian manifold. A quantization of the Einstein gravity in this
approach is briefly discussed.
