Holographic optical scanning elements: analytical method for determining the phase function

A laser beam is deflected and focused by a holographic optical element (HOE). The hologram can be described by a phase function Φ(x, y). While displacing the HOE, the incident beam moves along a line x(s) in the hologram plane, and the image point describes another line y(t) in space. We present a method to calculate the phase function Φ, which is necessary to generate a particular line y(t) in space. It can be shown analytically, using second-order (paraxial) approximation, that a circular motion x(s) cannot generate a straight line y(t) in space without astigmatism of the focal spot.