  We describe quantization designs which lead to asymptotically and order
optimal functional quantizers. Regular variation of the eigenvalues of the
covariance operator plays a crucial role to achieve these rates. For the
development of a constructive quantization scheme we rely on the knowledge of
the eigenvectors of the covariance operator in order to transform the problem
into a finite dimensional quantization problem of normal distributions.
Furthermore we derive a high-resolution formula for the $L^2$-quantization
errors of Riemann-Liouville processes.
