  In this paper we generalize the quantum mechanical model of three coupled
oscillators because of its usage in the crystal optical activity. Using this
model we can include the influence of all essential couplings between single
oscillators which represent the molecules or atoms of optically active crystals
belonging for example to the space groups of symmetry D(3,4) or D(3,6). The
single oscillators are damped and therefore we can include both parts of the
optical activity - optical rotatory dispersion and circular dichroism - into
computations. We present more universal formulas for description of the above
mentioned parts.
