This last equation is a condition, derived from wave optics, on light-ray fields.

His theorem proves the equivalence of classical wave optics to quantum optics.

In wave optics, a phase change of shift can occur upon reflection (as with thin film interference).

This more general wave optics accurately explains the operation of Fourier optics devices.

This behavior of rays has an analogy in wave optics.

When we calculate the uncertainty in position, Ax, we use formulae for resolving power which are derived from wave optics.

In scalar wave optics a lens is a part which shifts the phase of the wave-front.

In wave optics this is expressed by the eigenvalue degeneration of the modes.

In wave optics, the latter is the k-vector of the incoming wave.

His research area is wave optics and he is President of the Estonian Physical Society.